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 "4.94"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
58 . /////////////////////////////////////////////////////////////////////////////
59 . Additional xfpt markup used by this document, over and above the default
60 . provided in the xfpt library.
61 . /////////////////////////////////////////////////////////////////////////////
63 . --- Override the &$ flag to automatically insert a $ with the variable name.
65 .flag &$ $& "<varname>$" "</varname>"
67 . --- Short flags for daggers in option headings. They will always be inside
68 . --- an italic string, but we want the daggers to be in Roman.
70 .flag &!! "</emphasis>†<emphasis>"
71 .flag &!? "</emphasis>‡<emphasis>"
73 . --- A macro for an Exim option definition heading, generating a one-line
74 . --- table with four columns. For cases when the option name is given with
75 . --- a space, so that it can be split, a fifth argument is used for the
85 .itable all 0 0 4 8* left 6* center 6* center 6* right
86 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
90 . --- A macro for the common 2-column tables. The width of the first column
91 . --- is suitable for the many tables at the start of the main options chapter;
92 . --- a small number of other 2-column tables override it.
94 .macro table2 196pt 254pt
95 .itable none 0 0 2 $1 left $2 left
98 . --- A macro that generates .row, but puts &I; at the start of the first
99 . --- argument, thus indenting it. Assume a minimum of two arguments, and
100 . --- allow up to four arguments, which is as many as we'll ever need.
104 .row "&I;$1" "$2" "$3" "$4"
108 .row "&I;$1" "$2" "$3"
116 . --- Macros for option, variable, and concept index entries. For a "range"
117 . --- style of entry, use .scindex for the start and .ecindex for the end. The
118 . --- first argument of .scindex and the only argument of .ecindex must be the
119 . --- ID that ties them together.
122 &<indexterm role="concept">&
123 &<primary>&$1&</primary>&
125 &<secondary>&$2&</secondary>&
131 &<indexterm role="concept" id="$1" class="startofrange">&
132 &<primary>&$2&</primary>&
134 &<secondary>&$3&</secondary>&
140 &<indexterm role="concept" startref="$1" class="endofrange"/>&
144 &<indexterm role="option">&
145 &<primary>&$1&</primary>&
147 &<secondary>&$2&</secondary>&
153 &<indexterm role="variable">&
154 &<primary>&$1&</primary>&
156 &<secondary>&$2&</secondary>&
162 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
166 . use this for a concept-index entry for a header line
168 .cindex "&'$1'& header line"
169 .cindex "header lines" $1
171 . ////////////////////////////////////////////////////////////////////////////
174 . ////////////////////////////////////////////////////////////////////////////
175 . The <bookinfo> element is removed from the XML before processing for ASCII
177 . ////////////////////////////////////////////////////////////////////////////
181 <title>Specification of the Exim Mail Transfer Agent</title>
182 <titleabbrev>The Exim MTA</titleabbrev>
186 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
187 <authorinitials>EM</authorinitials>
188 <revhistory><revision>
190 <authorinitials>EM</authorinitials>
191 </revision></revhistory>
194 </year><holder>University of Cambridge</holder></copyright>
199 . /////////////////////////////////////////////////////////////////////////////
200 . This chunk of literal XML implements index entries of the form "x, see y" and
201 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
202 . at the top level, so we have to put the .chapter directive first.
204 . These do not turn up in the HTML output, unfortunately. The PDF does get them.
205 . /////////////////////////////////////////////////////////////////////////////
207 .chapter "Introduction" "CHID1"
210 <indexterm role="variable">
211 <primary>$1, $2, etc.</primary>
212 <see><emphasis>numerical variables</emphasis></see>
214 <indexterm role="concept">
215 <primary>address</primary>
216 <secondary>rewriting</secondary>
217 <see><emphasis>rewriting</emphasis></see>
219 <indexterm role="concept">
220 <primary>Bounce Address Tag Validation</primary>
221 <see><emphasis>BATV</emphasis></see>
223 <indexterm role="concept">
224 <primary>Client SMTP Authorization</primary>
225 <see><emphasis>CSA</emphasis></see>
227 <indexterm role="concept">
228 <primary>CR character</primary>
229 <see><emphasis>carriage return</emphasis></see>
231 <indexterm role="concept">
232 <primary>CRL</primary>
233 <see><emphasis>certificate revocation list</emphasis></see>
235 <indexterm role="concept">
236 <primary>delivery</primary>
237 <secondary>failure report</secondary>
238 <see><emphasis>bounce message</emphasis></see>
240 <indexterm role="concept">
241 <primary>dialup</primary>
242 <see><emphasis>intermittently connected hosts</emphasis></see>
244 <indexterm role="concept">
245 <primary>exiscan</primary>
246 <see><emphasis>content scanning</emphasis></see>
248 <indexterm role="concept">
249 <primary>failover</primary>
250 <see><emphasis>fallback</emphasis></see>
252 <indexterm role="concept">
253 <primary>fallover</primary>
254 <see><emphasis>fallback</emphasis></see>
256 <indexterm role="concept">
257 <primary>filter</primary>
258 <secondary>Sieve</secondary>
259 <see><emphasis>Sieve filter</emphasis></see>
261 <indexterm role="concept">
262 <primary>ident</primary>
263 <see><emphasis>RFC 1413</emphasis></see>
265 <indexterm role="concept">
266 <primary>LF character</primary>
267 <see><emphasis>linefeed</emphasis></see>
269 <indexterm role="concept">
270 <primary>maximum</primary>
271 <seealso><emphasis>limit</emphasis></seealso>
273 <indexterm role="concept">
274 <primary>monitor</primary>
275 <see><emphasis>Exim monitor</emphasis></see>
277 <indexterm role="concept">
278 <primary>no_<emphasis>xxx</emphasis></primary>
279 <see>entry for xxx</see>
281 <indexterm role="concept">
282 <primary>NUL</primary>
283 <see><emphasis>binary zero</emphasis></see>
285 <indexterm role="concept">
286 <primary>passwd file</primary>
287 <see><emphasis>/etc/passwd</emphasis></see>
289 <indexterm role="concept">
290 <primary>process id</primary>
291 <see><emphasis>pid</emphasis></see>
293 <indexterm role="concept">
294 <primary>RBL</primary>
295 <see><emphasis>DNS list</emphasis></see>
297 <indexterm role="concept">
298 <primary>redirection</primary>
299 <see><emphasis>address redirection</emphasis></see>
301 <indexterm role="concept">
302 <primary>return path</primary>
303 <seealso><emphasis>envelope sender</emphasis></seealso>
305 <indexterm role="concept">
306 <primary>scanning</primary>
307 <see><emphasis>content scanning</emphasis></see>
309 <indexterm role="concept">
310 <primary>SSL</primary>
311 <see><emphasis>TLS</emphasis></see>
313 <indexterm role="concept">
314 <primary>string</primary>
315 <secondary>expansion</secondary>
316 <see><emphasis>expansion</emphasis></see>
318 <indexterm role="concept">
319 <primary>top bit</primary>
320 <see><emphasis>8-bit characters</emphasis></see>
322 <indexterm role="concept">
323 <primary>variables</primary>
324 <see><emphasis>expansion, variables</emphasis></see>
326 <indexterm role="concept">
327 <primary>zero, binary</primary>
328 <see><emphasis>binary zero</emphasis></see>
330 <indexterm role="concept">
331 <primary>headers</primary>
332 <see><emphasis>header lines</emphasis></see>
338 . /////////////////////////////////////////////////////////////////////////////
339 . This is the real start of the first chapter. See the comment above as to why
340 . we can't have the .chapter line here.
341 . chapter "Introduction"
342 . /////////////////////////////////////////////////////////////////////////////
344 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
345 Unix-like operating systems. It was designed on the assumption that it would be
346 run on hosts that are permanently connected to the Internet. However, it can be
347 used on intermittently connected hosts with suitable configuration adjustments.
349 Configuration files currently exist for the following operating systems: AIX,
350 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
351 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
352 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
353 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
354 Some of these operating systems are no longer current and cannot easily be
355 tested, so the configuration files may no longer work in practice.
357 There are also configuration files for compiling Exim in the Cygwin environment
358 that can be installed on systems running Windows. However, this document does
359 not contain any information about running Exim in the Cygwin environment.
361 The terms and conditions for the use and distribution of Exim are contained in
362 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
363 Public Licence, a copy of which may be found in the file &_LICENCE_&.
365 The use, supply, or promotion of Exim for the purpose of sending bulk,
366 unsolicited electronic mail is incompatible with the basic aims of Exim,
367 which revolve around the free provision of a service that enhances the quality
368 of personal communications. The author of Exim regards indiscriminate
369 mass-mailing as an antisocial, irresponsible abuse of the Internet.
371 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
372 experience of running and working on the Smail 3 code, I could never have
373 contemplated starting to write a new MTA. Many of the ideas and user interfaces
374 were originally taken from Smail 3, though the actual code of Exim is entirely
375 new, and has developed far beyond the initial concept.
377 Many people, both in Cambridge and around the world, have contributed to the
378 development and the testing of Exim, and to porting it to various operating
379 systems. I am grateful to them all. The distribution now contains a file called
380 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
384 .section "Exim documentation" "SECID1"
385 . Keep this example change bar when updating the documentation!
388 .cindex "documentation"
389 This edition of the Exim specification applies to version &version() of Exim.
390 Substantive changes from the &previousversion; edition are marked in some
391 renditions of this document; this paragraph is so marked if the rendition is
392 capable of showing a change indicator.
395 This document is very much a reference manual; it is not a tutorial. The reader
396 is expected to have some familiarity with the SMTP mail transfer protocol and
397 with general Unix system administration. Although there are some discussions
398 and examples in places, the information is mostly organized in a way that makes
399 it easy to look up, rather than in a natural order for sequential reading.
400 Furthermore, this manual aims to cover every aspect of Exim in detail, including
401 a number of rarely-used, special-purpose features that are unlikely to be of
404 .cindex "books about Exim"
405 An &"easier"& discussion of Exim which provides more in-depth explanatory,
406 introductory, and tutorial material can be found in a book entitled &'The Exim
407 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
408 (&url(https://www.uit.co.uk/exim-book/)).
410 The book also contains a chapter that gives a general introduction to SMTP and
411 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
412 with the latest release of Exim. (Note that the earlier book about Exim,
413 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
415 .cindex "Debian" "information sources"
416 If you are using a Debian distribution of Exim, you will find information about
417 Debian-specific features in the file
418 &_/usr/share/doc/exim4-base/README.Debian_&.
419 The command &(man update-exim.conf)& is another source of Debian-specific
422 .cindex "&_doc/NewStuff_&"
423 .cindex "&_doc/ChangeLog_&"
425 As Exim develops, there may be features in newer versions that have not
426 yet made it into this document, which is updated only when the most significant
427 digit of the fractional part of the version number changes. Specifications of
428 new features that are not yet in this manual are placed in the file
429 &_doc/NewStuff_& in the Exim distribution.
431 Some features may be classified as &"experimental"&. These may change
432 incompatibly while they are developing, or even be withdrawn. For this reason,
433 they are not documented in this manual. Information about experimental features
434 can be found in the file &_doc/experimental.txt_&.
436 All changes to Exim (whether new features, bug fixes, or other kinds of
437 change) are noted briefly in the file called &_doc/ChangeLog_&.
439 .cindex "&_doc/spec.txt_&"
440 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
441 that it can easily be searched with a text editor. Other files in the &_doc_&
445 .row &_OptionLists.txt_& "list of all options in alphabetical order"
446 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
447 .row &_exim.8_& "a man page of Exim's command line options"
448 .row &_experimental.txt_& "documentation of experimental features"
449 .row &_filter.txt_& "specification of the filter language"
450 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
451 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
452 .row &_openssl.txt_& "installing a current OpenSSL release"
455 The main specification and the specification of the filtering language are also
456 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
457 &<<SECTavail>>& below tells you how to get hold of these.
461 .section "FTP site and websites" "SECID2"
464 The primary site for Exim source distributions is the &%exim.org%& FTP site,
465 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
466 website, are hosted at the University of Cambridge.
470 As well as Exim distribution tar files, the Exim website contains a number of
471 differently formatted versions of the documentation. A recent addition to the
472 online information is the Exim wiki (&url(https://wiki.exim.org)),
473 which contains what used to be a separate FAQ, as well as various other
474 examples, tips, and know-how that have been contributed by Exim users.
475 The wiki site should always redirect to the correct place, which is currently
476 provided by GitHub, and is open to editing by anyone with a GitHub account.
479 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
480 this to report bugs, and also to add items to the wish list. Please search
481 first to check that you are not duplicating a previous entry.
482 Please do not ask for configuration help in the bug-tracker.
485 .section "Mailing lists" "SECID3"
486 .cindex "mailing lists" "for Exim users"
487 The following Exim mailing lists exist:
490 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
491 .row &'exim-users@exim.org'& "General discussion list"
492 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
493 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
496 You can subscribe to these lists, change your existing subscriptions, and view
497 or search the archives via the mailing lists link on the Exim home page.
498 .cindex "Debian" "mailing list for"
499 If you are using a Debian distribution of Exim, you may wish to subscribe to
500 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
503 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
505 Please ask Debian-specific questions on that list and not on the general Exim
508 .section "Bug reports" "SECID5"
509 .cindex "bug reports"
510 .cindex "reporting bugs"
511 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
512 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
513 whether some behaviour is a bug or not, the best thing to do is to post a
514 message to the &'exim-dev'& mailing list and have it discussed.
518 .section "Where to find the Exim distribution" "SECTavail"
520 .cindex "HTTPS download site"
521 .cindex "distribution" "FTP site"
522 .cindex "distribution" "https site"
523 The master distribution site for the Exim distribution is
525 &url(https://downloads.exim.org/)
527 The service is available over HTTPS, HTTP and FTP.
528 We encourage people to migrate to HTTPS.
530 The content served at &url(https://downloads.exim.org/) is identical to the
531 content served at &url(https://ftp.exim.org/pub/exim) and
532 &url(ftp://ftp.exim.org/pub/exim).
534 If accessing via a hostname containing &'ftp'&, then the file references that
535 follow are relative to the &_exim_& directories at these sites.
536 If accessing via the hostname &'downloads'& then the subdirectories described
537 here are top-level directories.
539 There are now quite a number of independent mirror sites around
540 the world. Those that I know about are listed in the file called &_Mirrors_&.
542 Within the top exim directory there are subdirectories called &_exim3_& (for
543 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
544 distributions), and &_Testing_& for testing versions. In the &_exim4_&
545 subdirectory, the current release can always be found in files called
549 &_exim-n.nn.tar.bz2_&
551 where &'n.nn'& is the highest such version number in the directory. The three
552 files contain identical data; the only difference is the type of compression.
553 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
554 most portable to old systems.
556 .cindex "distribution" "signing details"
557 .cindex "distribution" "public key"
558 .cindex "public key for signed distribution"
559 The distributions will be PGP signed by an individual key of the Release
560 Coordinator. This key will have a uid containing an email address in the
561 &'exim.org'& domain and will have signatures from other people, including
562 other Exim maintainers. We expect that the key will be in the "strong set" of
563 PGP keys. There should be a trust path to that key from the Exim Maintainer's
564 PGP keys, a version of which can be found in the release directory in the file
565 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
566 such as &'pool.sks-keyservers.net'&.
568 At the time of the last update, releases were being made by Jeremy Harris and signed
569 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
570 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
571 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
573 The signatures for the tar bundles are in:
575 &_exim-n.nn.tar.xz.asc_&
576 &_exim-n.nn.tar.gz.asc_&
577 &_exim-n.nn.tar.bz2.asc_&
579 For each released version, the log of changes is made available in a
580 separate file in the directory &_ChangeLogs_& so that it is possible to
581 find out what has changed without having to download the entire distribution.
583 .cindex "documentation" "available formats"
584 The main distribution contains ASCII versions of this specification and other
585 documentation; other formats of the documents are available in separate files
586 inside the &_exim4_& directory of the FTP site:
588 &_exim-html-n.nn.tar.gz_&
589 &_exim-pdf-n.nn.tar.gz_&
590 &_exim-postscript-n.nn.tar.gz_&
591 &_exim-texinfo-n.nn.tar.gz_&
593 These tar files contain only the &_doc_& directory, not the complete
594 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
597 .section "Limitations" "SECID6"
599 .cindex "limitations of Exim"
600 .cindex "bang paths" "not handled by Exim"
601 Exim is designed for use as an Internet MTA, and therefore handles addresses in
602 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
603 simple two-component bang paths can be converted by a straightforward rewriting
604 configuration. This restriction does not prevent Exim from being interfaced to
605 UUCP as a transport mechanism, provided that domain addresses are used.
607 .cindex "domainless addresses"
608 .cindex "address" "without domain"
609 Exim insists that every address it handles has a domain attached. For incoming
610 local messages, domainless addresses are automatically qualified with a
611 configured domain value. Configuration options specify from which remote
612 systems unqualified addresses are acceptable. These are then qualified on
615 .cindex "transport" "external"
616 .cindex "external transports"
617 The only external transport mechanisms that are currently implemented are SMTP
618 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
619 transport is available, and there are facilities for writing messages to files
620 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
621 to send messages to other transport mechanisms such as UUCP, provided they can
622 handle domain-style addresses. Batched SMTP input is also catered for.
624 Exim is not designed for storing mail for dial-in hosts. When the volumes of
625 such mail are large, it is better to get the messages &"delivered"& into files
626 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
629 Although Exim does have basic facilities for scanning incoming messages, these
630 are not comprehensive enough to do full virus or spam scanning. Such operations
631 are best carried out using additional specialized software packages. If you
632 compile Exim with the content-scanning extension, straightforward interfaces to
633 a number of common scanners are provided.
637 .section "Runtime configuration" "SECID7"
638 Exim's runtime configuration is held in a single text file that is divided
639 into a number of sections. The entries in this file consist of keywords and
640 values, in the style of Smail 3 configuration files. A default configuration
641 file which is suitable for simple online installations is provided in the
642 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
645 .section "Calling interface" "SECID8"
646 .cindex "Sendmail compatibility" "command line interface"
647 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
648 can be a straight replacement for &_/usr/lib/sendmail_& or
649 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
650 about Sendmail in order to run Exim. For actions other than sending messages,
651 Sendmail-compatible options also exist, but those that produce output (for
652 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
653 format. There are also some additional options that are compatible with Smail
654 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
655 documents all Exim's command line options. This information is automatically
656 made into the man page that forms part of the Exim distribution.
658 Control of messages in the queue can be done via certain privileged command
659 line options. There is also an optional monitor program called &'eximon'&,
660 which displays current information in an X window, and which contains a menu
661 interface to Exim's command line administration options.
665 .section "Terminology" "SECID9"
666 .cindex "terminology definitions"
667 .cindex "body of message" "definition of"
668 The &'body'& of a message is the actual data that the sender wants to transmit.
669 It is the last part of a message and is separated from the &'header'& (see
670 below) by a blank line.
672 .cindex "bounce message" "definition of"
673 When a message cannot be delivered, it is normally returned to the sender in a
674 delivery failure message or a &"non-delivery report"& (NDR). The term
675 &'bounce'& is commonly used for this action, and the error reports are often
676 called &'bounce messages'&. This is a convenient shorthand for &"delivery
677 failure error report"&. Such messages have an empty sender address in the
678 message's &'envelope'& (see below) to ensure that they cannot themselves give
679 rise to further bounce messages.
681 The term &'default'& appears frequently in this manual. It is used to qualify a
682 value which is used in the absence of any setting in the configuration. It may
683 also qualify an action which is taken unless a configuration setting specifies
686 The term &'defer'& is used when the delivery of a message to a specific
687 destination cannot immediately take place for some reason (a remote host may be
688 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
691 The word &'domain'& is sometimes used to mean all but the first component of a
692 host's name. It is &'not'& used in that sense here, where it normally refers to
693 the part of an email address following the @ sign.
695 .cindex "envelope, definition of"
696 .cindex "sender" "definition of"
697 A message in transit has an associated &'envelope'&, as well as a header and a
698 body. The envelope contains a sender address (to which bounce messages should
699 be delivered), and any number of recipient addresses. References to the
700 sender or the recipients of a message usually mean the addresses in the
701 envelope. An MTA uses these addresses for delivery, and for returning bounce
702 messages, not the addresses that appear in the header lines.
704 .cindex "message" "header, definition of"
705 .cindex "header section" "definition of"
706 The &'header'& of a message is the first part of a message's text, consisting
707 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
708 &'Subject:'&, etc. Long header lines can be split over several text lines by
709 indenting the continuations. The header is separated from the body by a blank
712 .cindex "local part" "definition of"
713 .cindex "domain" "definition of"
714 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
715 part of an email address that precedes the @ sign. The part that follows the
716 @ sign is called the &'domain'& or &'mail domain'&.
718 .cindex "local delivery" "definition of"
719 .cindex "remote delivery, definition of"
720 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
721 delivery to a file or a pipe on the local host from delivery by SMTP over
722 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
723 host it is running on are &'remote'&.
725 .cindex "return path" "definition of"
726 &'Return path'& is another name that is used for the sender address in a
729 .cindex "queue" "definition of"
730 The term &'queue'& is used to refer to the set of messages awaiting delivery
731 because this term is in widespread use in the context of MTAs. However, in
732 Exim's case, the reality is more like a pool than a queue, because there is
733 normally no ordering of waiting messages.
735 .cindex "queue runner" "definition of"
736 The term &'queue runner'& is used to describe a process that scans the queue
737 and attempts to deliver those messages whose retry times have come. This term
738 is used by other MTAs and also relates to the command &%runq%&, but in Exim
739 the waiting messages are normally processed in an unpredictable order.
741 .cindex "spool directory" "definition of"
742 The term &'spool directory'& is used for a directory in which Exim keeps the
743 messages in its queue &-- that is, those that it is in the process of
744 delivering. This should not be confused with the directory in which local
745 mailboxes are stored, which is called a &"spool directory"& by some people. In
746 the Exim documentation, &"spool"& is always used in the first sense.
753 . ////////////////////////////////////////////////////////////////////////////
754 . ////////////////////////////////////////////////////////////////////////////
756 .chapter "Incorporated code" "CHID2"
757 .cindex "incorporated code"
758 .cindex "regular expressions" "library"
761 A number of pieces of external code are included in the Exim distribution.
764 Regular expressions are supported in the main Exim program and in the
765 Exim monitor using the freely-distributable PCRE library, copyright
766 © University of Cambridge. The source to PCRE is no longer shipped with
767 Exim, so you will need to use the version of PCRE shipped with your system,
768 or obtain and install the full version of the library from
769 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
771 .cindex "cdb" "acknowledgment"
772 Support for the cdb (Constant DataBase) lookup method is provided by code
773 contributed by Nigel Metheringham of (at the time he contributed it) Planet
774 Online Ltd. The implementation is completely contained within the code of Exim.
775 It does not link against an external cdb library. The code contains the
776 following statements:
779 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
781 This program is free software; you can redistribute it and/or modify it under
782 the terms of the GNU General Public License as published by the Free Software
783 Foundation; either version 2 of the License, or (at your option) any later
785 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
786 the spec and sample code for cdb can be obtained from
787 &url(https://cr.yp.to/cdb.html). This implementation borrows
788 some code from Dan Bernstein's implementation (which has no license
789 restrictions applied to it).
792 .cindex "SPA authentication"
793 .cindex "Samba project"
794 .cindex "Microsoft Secure Password Authentication"
795 Client support for Microsoft's &'Secure Password Authentication'& is provided
796 by code contributed by Marc Prud'hommeaux. Server support was contributed by
797 Tom Kistner. This includes code taken from the Samba project, which is released
801 .cindex "&'pwcheck'& daemon"
802 .cindex "&'pwauthd'& daemon"
803 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
804 by code taken from the Cyrus-SASL library and adapted by Alexander S.
805 Sabourenkov. The permission notice appears below, in accordance with the
806 conditions expressed therein.
809 Copyright © 2001 Carnegie Mellon University. All rights reserved.
811 Redistribution and use in source and binary forms, with or without
812 modification, are permitted provided that the following conditions
816 Redistributions of source code must retain the above copyright
817 notice, this list of conditions and the following disclaimer.
819 Redistributions in binary form must reproduce the above copyright
820 notice, this list of conditions and the following disclaimer in
821 the documentation and/or other materials provided with the
824 The name &"Carnegie Mellon University"& must not be used to
825 endorse or promote products derived from this software without
826 prior written permission. For permission or any other legal
827 details, please contact
829 Office of Technology Transfer
830 Carnegie Mellon University
832 Pittsburgh, PA 15213-3890
833 (412) 268-4387, fax: (412) 268-7395
834 tech-transfer@andrew.cmu.edu
837 Redistributions of any form whatsoever must retain the following
840 &"This product includes software developed by Computing Services
841 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
843 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
844 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
845 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
846 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
847 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
848 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
849 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
854 .cindex "Exim monitor" "acknowledgment"
857 The Exim Monitor program, which is an X-Window application, includes
858 modified versions of the Athena StripChart and TextPop widgets.
859 This code is copyright by DEC and MIT, and their permission notice appears
860 below, in accordance with the conditions expressed therein.
863 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
864 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
868 Permission to use, copy, modify, and distribute this software and its
869 documentation for any purpose and without fee is hereby granted,
870 provided that the above copyright notice appear in all copies and that
871 both that copyright notice and this permission notice appear in
872 supporting documentation, and that the names of Digital or MIT not be
873 used in advertising or publicity pertaining to distribution of the
874 software without specific, written prior permission.
876 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
877 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
878 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
879 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
880 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
881 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
886 .cindex "opendmarc" "acknowledgment"
887 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
888 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
889 derived code are indicated in the respective source files. The full OpenDMARC
890 license is provided in the LICENSE.opendmarc file contained in the distributed
894 Many people have contributed code fragments, some large, some small, that were
895 not covered by any specific license requirements. It is assumed that the
896 contributors are happy to see their code incorporated into Exim under the GPL.
903 . ////////////////////////////////////////////////////////////////////////////
904 . ////////////////////////////////////////////////////////////////////////////
906 .chapter "How Exim receives and delivers mail" "CHID11" &&&
907 "Receiving and delivering mail"
910 .section "Overall philosophy" "SECID10"
911 .cindex "design philosophy"
912 Exim is designed to work efficiently on systems that are permanently connected
913 to the Internet and are handling a general mix of mail. In such circumstances,
914 most messages can be delivered immediately. Consequently, Exim does not
915 maintain independent queues of messages for specific domains or hosts, though
916 it does try to send several messages in a single SMTP connection after a host
917 has been down, and it also maintains per-host retry information.
920 .section "Policy control" "SECID11"
921 .cindex "policy control" "overview"
922 Policy controls are now an important feature of MTAs that are connected to the
923 Internet. Perhaps their most important job is to stop MTAs from being abused as
924 &"open relays"& by misguided individuals who send out vast amounts of
925 unsolicited junk and want to disguise its source. Exim provides flexible
926 facilities for specifying policy controls on incoming mail:
929 .cindex "&ACL;" "introduction"
930 Exim 4 (unlike previous versions of Exim) implements policy controls on
931 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
932 series of statements that may either grant or deny access. ACLs can be used at
933 several places in the SMTP dialogue while receiving a message from a remote
934 host. However, the most common places are after each RCPT command, and at the
935 very end of the message. The sysadmin can specify conditions for accepting or
936 rejecting individual recipients or the entire message, respectively, at these
937 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
940 An ACL is also available for locally generated, non-SMTP messages. In this
941 case, the only available actions are to accept or deny the entire message.
943 When Exim is compiled with the content-scanning extension, facilities are
944 provided in the ACL mechanism for passing the message to external virus and/or
945 spam scanning software. The result of such a scan is passed back to the ACL,
946 which can then use it to decide what to do with the message.
948 When a message has been received, either from a remote host or from the local
949 host, but before the final acknowledgment has been sent, a locally supplied C
950 function called &[local_scan()]& can be run to inspect the message and decide
951 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
952 is accepted, the list of recipients can be modified by the function.
954 Using the &[local_scan()]& mechanism is another way of calling external scanner
955 software. The &%SA-Exim%& add-on package works this way. It does not require
956 Exim to be compiled with the content-scanning extension.
958 After a message has been accepted, a further checking mechanism is available in
959 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
960 runs at the start of every delivery process.
965 .section "User filters" "SECID12"
966 .cindex "filter" "introduction"
967 .cindex "Sieve filter"
968 In a conventional Exim configuration, users are able to run private filters by
969 setting up appropriate &_.forward_& files in their home directories. See
970 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
971 configuration needed to support this, and the separate document entitled
972 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
973 of filtering are available:
976 Sieve filters are written in the standard filtering language that is defined
979 Exim filters are written in a syntax that is unique to Exim, but which is more
980 powerful than Sieve, which it pre-dates.
983 User filters are run as part of the routing process, described below.
987 .section "Message identification" "SECTmessiden"
988 .cindex "message ids" "details of format"
989 .cindex "format" "of message id"
990 .cindex "id of message"
995 Every message handled by Exim is given a &'message id'& which is sixteen
996 characters long. It is divided into three parts, separated by hyphens, for
997 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
998 normally encoding numbers in base 62. However, in the Darwin operating
999 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
1000 (avoiding the use of lower case letters) is used instead, because the message
1001 id is used to construct filenames, and the names of files in those systems are
1002 not always case-sensitive.
1004 .cindex "pid (process id)" "re-use of"
1005 The detail of the contents of the message id have changed as Exim has evolved.
1006 Earlier versions relied on the operating system not re-using a process id (pid)
1007 within one second. On modern operating systems, this assumption can no longer
1008 be made, so the algorithm had to be changed. To retain backward compatibility,
1009 the format of the message id was retained, which is why the following rules are
1013 The first six characters of the message id are the time at which the message
1014 started to be received, to a granularity of one second. That is, this field
1015 contains the number of seconds since the start of the epoch (the normal Unix
1016 way of representing the date and time of day).
1018 After the first hyphen, the next six characters are the id of the process that
1019 received the message.
1021 There are two different possibilities for the final two characters:
1023 .oindex "&%localhost_number%&"
1024 If &%localhost_number%& is not set, this value is the fractional part of the
1025 time of reception, normally in units of 1/2000 of a second, but for systems
1026 that must use base 36 instead of base 62 (because of case-insensitive file
1027 systems), the units are 1/1000 of a second.
1029 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1030 the fractional part of the time, which in this case is in units of 1/200
1031 (1/100) of a second.
1035 After a message has been received, Exim waits for the clock to tick at the
1036 appropriate resolution before proceeding, so that if another message is
1037 received by the same process, or by another process with the same (re-used)
1038 pid, it is guaranteed that the time will be different. In most cases, the clock
1039 will already have ticked while the message was being received.
1042 .section "Receiving mail" "SECID13"
1043 .cindex "receiving mail"
1044 .cindex "message" "reception"
1045 The only way Exim can receive mail from another host is using SMTP over
1046 TCP/IP, in which case the sender and recipient addresses are transferred using
1047 SMTP commands. However, from a locally running process (such as a user's MUA),
1048 there are several possibilities:
1051 If the process runs Exim with the &%-bm%& option, the message is read
1052 non-interactively (usually via a pipe), with the recipients taken from the
1053 command line, or from the body of the message if &%-t%& is also used.
1055 If the process runs Exim with the &%-bS%& option, the message is also read
1056 non-interactively, but in this case the recipients are listed at the start of
1057 the message in a series of SMTP RCPT commands, terminated by a DATA
1058 command. This is called &"batch SMTP"& format,
1059 but it isn't really SMTP. The SMTP commands are just another way of passing
1060 envelope addresses in a non-interactive submission.
1062 If the process runs Exim with the &%-bs%& option, the message is read
1063 interactively, using the SMTP protocol. A two-way pipe is normally used for
1064 passing data between the local process and the Exim process.
1065 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1066 example, the ACLs for SMTP commands are used for this form of submission.
1068 A local process may also make a TCP/IP call to the host's loopback address
1069 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1070 does not treat the loopback address specially. It treats all such connections
1071 in the same way as connections from other hosts.
1075 .cindex "message sender, constructed by Exim"
1076 .cindex "sender" "constructed by Exim"
1077 In the three cases that do not involve TCP/IP, the sender address is
1078 constructed from the login name of the user that called Exim and a default
1079 qualification domain (which can be set by the &%qualify_domain%& configuration
1080 option). For local or batch SMTP, a sender address that is passed using the
1081 SMTP MAIL command is ignored. However, the system administrator may allow
1082 certain users (&"trusted users"&) to specify a different sender addresses
1083 unconditionally, or all users to specify certain forms of different sender
1084 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1085 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1086 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1087 users to change sender addresses.
1089 Messages received by either of the non-interactive mechanisms are subject to
1090 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1091 (either over TCP/IP or interacting with a local process) can be checked by a
1092 number of ACLs that operate at different times during the SMTP session. Either
1093 individual recipients or the entire message can be rejected if local policy
1094 requirements are not met. The &[local_scan()]& function (see chapter
1095 &<<CHAPlocalscan>>&) is run for all incoming messages.
1097 Exim can be configured not to start a delivery process when a message is
1098 received; this can be unconditional, or depend on the number of incoming SMTP
1099 connections or the system load. In these situations, new messages wait on the
1100 queue until a queue runner process picks them up. However, in standard
1101 configurations under normal conditions, delivery is started as soon as a
1102 message is received.
1108 .section "Handling an incoming message" "SECID14"
1109 .cindex "spool directory" "files that hold a message"
1110 .cindex "file" "how a message is held"
1111 When Exim accepts a message, it writes two files in its spool directory. The
1112 first contains the envelope information, the current status of the message, and
1113 the header lines, and the second contains the body of the message. The names of
1114 the two spool files consist of the message id, followed by &`-H`& for the
1115 file containing the envelope and header, and &`-D`& for the data file.
1117 .cindex "spool directory" "&_input_& sub-directory"
1118 By default, all these message files are held in a single directory called
1119 &_input_& inside the general Exim spool directory. Some operating systems do
1120 not perform very well if the number of files in a directory gets large; to
1121 improve performance in such cases, the &%split_spool_directory%& option can be
1122 used. This causes Exim to split up the input files into 62 sub-directories
1123 whose names are single letters or digits. When this is done, the queue is
1124 processed one sub-directory at a time instead of all at once, which can improve
1125 overall performance even when there are not enough files in each directory to
1126 affect file system performance.
1128 The envelope information consists of the address of the message's sender and
1129 the addresses of the recipients. This information is entirely separate from
1130 any addresses contained in the header lines. The status of the message includes
1131 a list of recipients who have already received the message. The format of the
1132 first spool file is described in chapter &<<CHAPspool>>&.
1134 .cindex "rewriting" "addresses"
1135 Address rewriting that is specified in the rewrite section of the configuration
1136 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1137 both in the header lines and the envelope, at the time the message is accepted.
1138 If during the course of delivery additional addresses are generated (for
1139 example, via aliasing), these new addresses are rewritten as soon as they are
1140 generated. At the time a message is actually delivered (transported) further
1141 rewriting can take place; because this is a transport option, it can be
1142 different for different forms of delivery. It is also possible to specify the
1143 addition or removal of certain header lines at the time the message is
1144 delivered (see chapters &<<CHAProutergeneric>>& and
1145 &<<CHAPtransportgeneric>>&).
1149 .section "Life of a message" "SECID15"
1150 .cindex "message" "life of"
1151 .cindex "message" "frozen"
1152 A message remains in the spool directory until it is completely delivered to
1153 its recipients or to an error address, or until it is deleted by an
1154 administrator or by the user who originally created it. In cases when delivery
1155 cannot proceed &-- for example when a message can neither be delivered to its
1156 recipients nor returned to its sender, the message is marked &"frozen"& on the
1157 spool, and no more deliveries are attempted.
1159 .cindex "frozen messages" "thawing"
1160 .cindex "message" "thawing frozen"
1161 An administrator can &"thaw"& such messages when the problem has been
1162 corrected, and can also freeze individual messages by hand if necessary. In
1163 addition, an administrator can force a delivery error, causing a bounce message
1166 .oindex "&%timeout_frozen_after%&"
1167 .oindex "&%ignore_bounce_errors_after%&"
1168 There are options called &%ignore_bounce_errors_after%& and
1169 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1170 The first applies only to frozen bounces, the second to all frozen messages.
1172 .cindex "message" "log file for"
1173 .cindex "log" "file for each message"
1174 While Exim is working on a message, it writes information about each delivery
1175 attempt to its main log file. This includes successful, unsuccessful, and
1176 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1177 lines are also written to a separate &'message log'& file for each message.
1178 These logs are solely for the benefit of the administrator and are normally
1179 deleted along with the spool files when processing of a message is complete.
1180 The use of individual message logs can be disabled by setting
1181 &%no_message_logs%&; this might give an improvement in performance on very busy
1184 .cindex "journal file"
1185 .cindex "file" "journal"
1186 All the information Exim itself needs to set up a delivery is kept in the first
1187 spool file, along with the header lines. When a successful delivery occurs, the
1188 address is immediately written at the end of a journal file, whose name is the
1189 message id followed by &`-J`&. At the end of a delivery run, if there are some
1190 addresses left to be tried again later, the first spool file (the &`-H`& file)
1191 is updated to indicate which these are, and the journal file is then deleted.
1192 Updating the spool file is done by writing a new file and renaming it, to
1193 minimize the possibility of data loss.
1195 Should the system or Exim crash after a successful delivery but before
1196 the spool file has been updated, the journal is left lying around. The next
1197 time Exim attempts to deliver the message, it reads the journal file and
1198 updates the spool file before proceeding. This minimizes the chances of double
1199 deliveries caused by crashes.
1203 .section "Processing an address for delivery" "SECTprocaddress"
1204 .cindex "drivers" "definition of"
1205 .cindex "router" "definition of"
1206 .cindex "transport" "definition of"
1207 The main delivery processing elements of Exim are called &'routers'& and
1208 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1209 number of them is provided in the source distribution, and compile-time options
1210 specify which ones are included in the binary. Runtime options specify which
1211 ones are actually used for delivering messages.
1213 .cindex "drivers" "instance definition"
1214 Each driver that is specified in the runtime configuration is an &'instance'&
1215 of that particular driver type. Multiple instances are allowed; for example,
1216 you can set up several different &(smtp)& transports, each with different
1217 option values that might specify different ports or different timeouts. Each
1218 instance has its own identifying name. In what follows we will normally use the
1219 instance name when discussing one particular instance (that is, one specific
1220 configuration of the driver), and the generic driver name when discussing
1221 the driver's features in general.
1223 A &'router'& is a driver that operates on an address, either determining how
1224 its delivery should happen, by assigning it to a specific transport, or
1225 converting the address into one or more new addresses (for example, via an
1226 alias file). A router may also explicitly choose to fail an address, causing it
1229 A &'transport'& is a driver that transmits a copy of the message from Exim's
1230 spool to some destination. There are two kinds of transport: for a &'local'&
1231 transport, the destination is a file or a pipe on the local host, whereas for a
1232 &'remote'& transport the destination is some other host. A message is passed
1233 to a specific transport as a result of successful routing. If a message has
1234 several recipients, it may be passed to a number of different transports.
1236 .cindex "preconditions" "definition of"
1237 An address is processed by passing it to each configured router instance in
1238 turn, subject to certain preconditions, until a router accepts the address or
1239 specifies that it should be bounced. We will describe this process in more
1240 detail shortly. First, as a simple example, we consider how each recipient
1241 address in a message is processed in a small configuration of three routers.
1243 To make this a more concrete example, it is described in terms of some actual
1244 routers, but remember, this is only an example. You can configure Exim's
1245 routers in many different ways, and there may be any number of routers in a
1248 The first router that is specified in a configuration is often one that handles
1249 addresses in domains that are not recognized specifically by the local host.
1250 Typically these are addresses for arbitrary domains on the Internet. A precondition
1251 is set up which looks for the special domains known to the host (for example,
1252 its own domain name), and the router is run for addresses that do &'not'&
1253 match. Typically, this is a router that looks up domains in the DNS in order to
1254 find the hosts to which this address routes. If it succeeds, the address is
1255 assigned to a suitable SMTP transport; if it does not succeed, the router is
1256 configured to fail the address.
1258 The second router is reached only when the domain is recognized as one that
1259 &"belongs"& to the local host. This router does redirection &-- also known as
1260 aliasing and forwarding. When it generates one or more new addresses from the
1261 original, each of them is routed independently from the start. Otherwise, the
1262 router may cause an address to fail, or it may simply decline to handle the
1263 address, in which case the address is passed to the next router.
1265 The final router in many configurations is one that checks to see if the
1266 address belongs to a local mailbox. The precondition may involve a check to
1267 see if the local part is the name of a login account, or it may look up the
1268 local part in a file or a database. If its preconditions are not met, or if
1269 the router declines, we have reached the end of the routers. When this happens,
1270 the address is bounced.
1274 .section "Processing an address for verification" "SECID16"
1275 .cindex "router" "for verification"
1276 .cindex "verifying address" "overview"
1277 As well as being used to decide how to deliver to an address, Exim's routers
1278 are also used for &'address verification'&. Verification can be requested as
1279 one of the checks to be performed in an ACL for incoming messages, on both
1280 sender and recipient addresses, and it can be tested using the &%-bv%& and
1281 &%-bvs%& command line options.
1283 When an address is being verified, the routers are run in &"verify mode"&. This
1284 does not affect the way the routers work, but it is a state that can be
1285 detected. By this means, a router can be skipped or made to behave differently
1286 when verifying. A common example is a configuration in which the first router
1287 sends all messages to a message-scanning program unless they have been
1288 previously scanned. Thus, the first router accepts all addresses without any
1289 checking, making it useless for verifying. Normally, the &%no_verify%& option
1290 would be set for such a router, causing it to be skipped in verify mode.
1295 .section "Running an individual router" "SECTrunindrou"
1296 .cindex "router" "running details"
1297 .cindex "preconditions" "checking"
1298 .cindex "router" "result of running"
1299 As explained in the example above, a number of preconditions are checked before
1300 running a router. If any are not met, the router is skipped, and the address is
1301 passed to the next router. When all the preconditions on a router &'are'& met,
1302 the router is run. What happens next depends on the outcome, which is one of
1306 &'accept'&: The router accepts the address, and either assigns it to a
1307 transport or generates one or more &"child"& addresses. Processing the
1308 original address ceases
1309 .oindex "&%unseen%&"
1310 unless the &%unseen%& option is set on the router. This option
1311 can be used to set up multiple deliveries with different routing (for example,
1312 for keeping archive copies of messages). When &%unseen%& is set, the address is
1313 passed to the next router. Normally, however, an &'accept'& return marks the
1316 Any child addresses generated by the router are processed independently,
1317 starting with the first router by default. It is possible to change this by
1318 setting the &%redirect_router%& option to specify which router to start at for
1319 child addresses. Unlike &%pass_router%& (see below) the router specified by
1320 &%redirect_router%& may be anywhere in the router configuration.
1322 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1323 requests that the address be passed to another router. By default, the address
1324 is passed to the next router, but this can be changed by setting the
1325 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1326 must be below the current router (to avoid loops).
1328 &'decline'&: The router declines to accept the address because it does not
1329 recognize it at all. By default, the address is passed to the next router, but
1330 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1331 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1332 &'decline'& into &'fail'&.
1334 &'fail'&: The router determines that the address should fail, and queues it for
1335 the generation of a bounce message. There is no further processing of the
1336 original address unless &%unseen%& is set on the router.
1338 &'defer'&: The router cannot handle the address at the present time. (A
1339 database may be offline, or a DNS lookup may have timed out.) No further
1340 processing of the address happens in this delivery attempt. It is tried again
1341 next time the message is considered for delivery.
1343 &'error'&: There is some error in the router (for example, a syntax error in
1344 its configuration). The action is as for defer.
1347 If an address reaches the end of the routers without having been accepted by
1348 any of them, it is bounced as unrouteable. The default error message in this
1349 situation is &"unrouteable address"&, but you can set your own message by
1350 making use of the &%cannot_route_message%& option. This can be set for any
1351 router; the value from the last router that &"saw"& the address is used.
1353 Sometimes while routing you want to fail a delivery when some conditions are
1354 met but others are not, instead of passing the address on for further routing.
1355 You can do this by having a second router that explicitly fails the delivery
1356 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1357 facility for this purpose.
1360 .section "Duplicate addresses" "SECID17"
1361 .cindex "case of local parts"
1362 .cindex "address duplicate, discarding"
1363 .cindex "duplicate addresses"
1364 Once routing is complete, Exim scans the addresses that are assigned to local
1365 and remote transports and discards any duplicates that it finds. During this
1366 check, local parts are treated case-sensitively. This happens only when
1367 actually delivering a message; when testing routers with &%-bt%&, all the
1368 routed addresses are shown.
1372 .section "Router preconditions" "SECTrouprecon"
1373 .cindex "router" "preconditions, order of processing"
1374 .cindex "preconditions" "order of processing"
1375 The preconditions that are tested for each router are listed below, in the
1376 order in which they are tested. The individual configuration options are
1377 described in more detail in chapter &<<CHAProutergeneric>>&.
1380 .cindex affix "router precondition"
1381 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1382 the local parts handled by the router may or must have certain prefixes and/or
1383 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1384 skipped. These conditions are tested first. When an affix is present, it is
1385 removed from the local part before further processing, including the evaluation
1386 of any other conditions.
1388 Routers can be designated for use only when not verifying an address, that is,
1389 only when routing it for delivery (or testing its delivery routing). If the
1390 &%verify%& option is set false, the router is skipped when Exim is verifying an
1392 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1393 &%verify_recipient%&, which independently control the use of the router for
1394 sender and recipient verification. You can set these options directly if
1395 you want a router to be used for only one type of verification.
1396 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1398 If the &%address_test%& option is set false, the router is skipped when Exim is
1399 run with the &%-bt%& option to test an address routing. This can be helpful
1400 when the first router sends all new messages to a scanner of some sort; it
1401 makes it possible to use &%-bt%& to test subsequent delivery routing without
1402 having to simulate the effect of the scanner.
1404 Routers can be designated for use only when verifying an address, as
1405 opposed to routing it for delivery. The &%verify_only%& option controls this.
1406 Again, cutthrough delivery counts as a verification.
1408 Individual routers can be explicitly skipped when running the routers to
1409 check an address given in the SMTP EXPN command (see the &%expn%& option).
1412 If the &%domains%& option is set, the domain of the address must be in the set
1413 of domains that it defines.
1415 .cindex "tainted data" "de-tainting"
1416 A match verifies the variable &$domain$& (which carries tainted data)
1417 and assigns an untainted value to the &$domain_data$& variable.
1418 Such an untainted value is often needed in the transport.
1419 For specifics of the matching operation and the resulting untainted value,
1420 refer to section &<<SECTdomainlist>>&.
1422 When an untainted value is wanted, use this option
1423 rather than the generic &%condition%& option.
1427 .vindex "&$local_part_prefix$&"
1428 .vindex "&$local_part_prefix_v$&"
1429 .vindex "&$local_part$&"
1430 .vindex "&$local_part_suffix$&"
1431 .vindex "&$local_part_suffix_v$&"
1432 .cindex affix "router precondition"
1433 If the &%local_parts%& option is set, the local part of the address must be in
1434 the set of local parts that it defines.
1436 A match verifies the variable &$local_part$& (which carries tainted data)
1437 and assigns an untainted value to the &$local_part_data$& variable.
1438 Such an untainted value is often needed in the transport.
1439 For specifics of the matching operation and the resulting untainted value,
1440 refer to section &<<SECTlocparlis>>&.
1442 When an untainted value is wanted, use this option
1443 rather than the generic &%condition%& option.
1446 If &%local_part_prefix%& or
1447 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1448 part before this check. If you want to do precondition tests on local parts
1449 that include affixes, you can do so by using a &%condition%& option (see below)
1450 that uses the variables &$local_part$&, &$local_part_prefix$&,
1451 &$local_part_prefix_v$&, &$local_part_suffix$&
1452 and &$local_part_suffix_v$& as necessary.
1455 .vindex "&$local_user_uid$&"
1456 .vindex "&$local_user_gid$&"
1458 If the &%check_local_user%& option is set, the local part must be the name of
1459 an account on the local host. If this check succeeds, the uid and gid of the
1460 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1461 user's home directory is placed in &$home$&; these values can be used in the
1462 remaining preconditions.
1465 If the &%router_home_directory%& option is set, it is expanded at this point,
1466 because it overrides the value of &$home$&. If this expansion were left till
1467 later, the value of &$home$& as set by &%check_local_user%& would be used in
1468 subsequent tests. Having two different values of &$home$& in the same router
1469 could lead to confusion.
1472 If the &%senders%& option is set, the envelope sender address must be in the
1473 set of addresses that it defines.
1476 If the &%require_files%& option is set, the existence or non-existence of
1477 specified files is tested.
1480 .cindex "customizing" "precondition"
1481 If the &%condition%& option is set, it is evaluated and tested. This option
1482 uses an expanded string to allow you to set up your own custom preconditions.
1483 Expanded strings are described in chapter &<<CHAPexpand>>&.
1486 Note that while using
1487 this option for address matching technically works,
1488 it does not set any de-tainted values.
1489 Such values are often needed, either for router-specific options or
1490 for transport options.
1491 Using the &%domains%& and &%local_parts%& options is usually the most
1492 convenient way to obtain them.
1497 Note that &%require_files%& comes near the end of the list, so you cannot use
1498 it to check for the existence of a file in which to lookup up a domain, local
1499 part, or sender. However, as these options are all expanded, you can use the
1500 &%exists%& expansion condition to make such tests within each condition. The
1501 &%require_files%& option is intended for checking files that the router may be
1502 going to use internally, or which are needed by a specific transport (for
1503 example, &_.procmailrc_&).
1507 .section "Delivery in detail" "SECID18"
1508 .cindex "delivery" "in detail"
1509 When a message is to be delivered, the sequence of events is as follows:
1512 If a system-wide filter file is specified, the message is passed to it. The
1513 filter may add recipients to the message, replace the recipients, discard the
1514 message, cause a new message to be generated, or cause the message delivery to
1515 fail. The format of the system filter file is the same as for Exim user filter
1516 files, described in the separate document entitled &'Exim's interfaces to mail
1518 .cindex "Sieve filter" "not available for system filter"
1519 (&*Note*&: Sieve cannot be used for system filter files.)
1521 Some additional features are available in system filters &-- see chapter
1522 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1523 filter only once per delivery attempt, however many recipients it has. However,
1524 if there are several delivery attempts because one or more addresses could not
1525 be immediately delivered, the system filter is run each time. The filter
1526 condition &%first_delivery%& can be used to detect the first run of the system
1529 Each recipient address is offered to each configured router, in turn, subject to
1530 its preconditions, until one is able to handle it. If no router can handle the
1531 address, that is, if they all decline, the address is failed. Because routers
1532 can be targeted at particular domains, several locally handled domains can be
1533 processed entirely independently of each other.
1535 .cindex "routing" "loops in"
1536 .cindex "loop" "while routing"
1537 A router that accepts an address may assign it to a local or a remote
1538 transport. However, the transport is not run at this time. Instead, the address
1539 is placed on a list for the particular transport, which will be run later.
1540 Alternatively, the router may generate one or more new addresses (typically
1541 from alias, forward, or filter files). New addresses are fed back into this
1542 process from the top, but in order to avoid loops, a router ignores any address
1543 which has an identically-named ancestor that was processed by itself.
1545 When all the routing has been done, addresses that have been successfully
1546 handled are passed to their assigned transports. When local transports are
1547 doing real local deliveries, they handle only one address at a time, but if a
1548 local transport is being used as a pseudo-remote transport (for example, to
1549 collect batched SMTP messages for transmission by some other means) multiple
1550 addresses can be handled. Remote transports can always handle more than one
1551 address at a time, but can be configured not to do so, or to restrict multiple
1552 addresses to the same domain.
1554 Each local delivery to a file or a pipe runs in a separate process under a
1555 non-privileged uid, and these deliveries are run one at a time. Remote
1556 deliveries also run in separate processes, normally under a uid that is private
1557 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1558 run in parallel. The maximum number of simultaneous remote deliveries for any
1559 one message is set by the &%remote_max_parallel%& option.
1560 The order in which deliveries are done is not defined, except that all local
1561 deliveries happen before any remote deliveries.
1563 .cindex "queue runner"
1564 When it encounters a local delivery during a queue run, Exim checks its retry
1565 database to see if there has been a previous temporary delivery failure for the
1566 address before running the local transport. If there was a previous failure,
1567 Exim does not attempt a new delivery until the retry time for the address is
1568 reached. However, this happens only for delivery attempts that are part of a
1569 queue run. Local deliveries are always attempted when delivery immediately
1570 follows message reception, even if retry times are set for them. This makes for
1571 better behaviour if one particular message is causing problems (for example,
1572 causing quota overflow, or provoking an error in a filter file).
1574 .cindex "delivery" "retry in remote transports"
1575 Remote transports do their own retry handling, since an address may be
1576 deliverable to one of a number of hosts, each of which may have a different
1577 retry time. If there have been previous temporary failures and no host has
1578 reached its retry time, no delivery is attempted, whether in a queue run or
1579 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1581 If there were any permanent errors, a bounce message is returned to an
1582 appropriate address (the sender in the common case), with details of the error
1583 for each failing address. Exim can be configured to send copies of bounce
1584 messages to other addresses.
1586 .cindex "delivery" "deferral"
1587 If one or more addresses suffered a temporary failure, the message is left on
1588 the queue, to be tried again later. Delivery of these addresses is said to be
1591 When all the recipient addresses have either been delivered or bounced,
1592 handling of the message is complete. The spool files and message log are
1593 deleted, though the message log can optionally be preserved if required.
1599 .section "Retry mechanism" "SECID19"
1600 .cindex "delivery" "retry mechanism"
1601 .cindex "retry" "description of mechanism"
1602 .cindex "queue runner"
1603 Exim's mechanism for retrying messages that fail to get delivered at the first
1604 attempt is the queue runner process. You must either run an Exim daemon that
1605 uses the &%-q%& option with a time interval to start queue runners at regular
1606 intervals or use some other means (such as &'cron'&) to start them. If you do
1607 not arrange for queue runners to be run, messages that fail temporarily at the
1608 first attempt will remain in your queue forever. A queue runner process works
1609 its way through the queue, one message at a time, trying each delivery that has
1610 passed its retry time.
1611 You can run several queue runners at once.
1613 Exim uses a set of configured rules to determine when next to retry the failing
1614 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1615 should give up trying to deliver to the address, at which point it generates a
1616 bounce message. If no retry rules are set for a particular host, address, and
1617 error combination, no retries are attempted, and temporary errors are treated
1622 .section "Temporary delivery failure" "SECID20"
1623 .cindex "delivery" "temporary failure"
1624 There are many reasons why a message may not be immediately deliverable to a
1625 particular address. Failure to connect to a remote machine (because it, or the
1626 connection to it, is down) is one of the most common. Temporary failures may be
1627 detected during routing as well as during the transport stage of delivery.
1628 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1629 is on a file system where the user is over quota. Exim can be configured to
1630 impose its own quotas on local mailboxes; where system quotas are set they will
1633 If a host is unreachable for a period of time, a number of messages may be
1634 waiting for it by the time it recovers, and sending them in a single SMTP
1635 connection is clearly beneficial. Whenever a delivery to a remote host is
1637 .cindex "hints database" "deferred deliveries"
1638 Exim makes a note in its hints database, and whenever a successful
1639 SMTP delivery has happened, it looks to see if any other messages are waiting
1640 for the same host. If any are found, they are sent over the same SMTP
1641 connection, subject to a configuration limit as to the maximum number in any
1646 .section "Permanent delivery failure" "SECID21"
1647 .cindex "delivery" "permanent failure"
1648 .cindex "bounce message" "when generated"
1649 When a message cannot be delivered to some or all of its intended recipients, a
1650 bounce message is generated. Temporary delivery failures turn into permanent
1651 errors when their timeout expires. All the addresses that fail in a given
1652 delivery attempt are listed in a single message. If the original message has
1653 many recipients, it is possible for some addresses to fail in one delivery
1654 attempt and others to fail subsequently, giving rise to more than one bounce
1655 message. The wording of bounce messages can be customized by the administrator.
1656 See chapter &<<CHAPemsgcust>>& for details.
1658 .cindex "&'X-Failed-Recipients:'& header line"
1659 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1660 failed addresses, for the benefit of programs that try to analyse such messages
1663 .cindex "bounce message" "recipient of"
1664 A bounce message is normally sent to the sender of the original message, as
1665 obtained from the message's envelope. For incoming SMTP messages, this is the
1666 address given in the MAIL command. However, when an address is expanded via a
1667 forward or alias file, an alternative address can be specified for delivery
1668 failures of the generated addresses. For a mailing list expansion (see section
1669 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1674 .section "Failures to deliver bounce messages" "SECID22"
1675 .cindex "bounce message" "failure to deliver"
1676 If a bounce message (either locally generated or received from a remote host)
1677 itself suffers a permanent delivery failure, the message is left in the queue,
1678 but it is frozen, awaiting the attention of an administrator. There are options
1679 that can be used to make Exim discard such failed messages, or to keep them
1680 for only a short time (see &%timeout_frozen_after%& and
1681 &%ignore_bounce_errors_after%&).
1687 . ////////////////////////////////////////////////////////////////////////////
1688 . ////////////////////////////////////////////////////////////////////////////
1690 .chapter "Building and installing Exim" "CHID3"
1691 .scindex IIDbuex "building Exim"
1693 .section "Unpacking" "SECID23"
1694 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1695 creates a directory with the name of the current release (for example,
1696 &_exim-&version()_&) into which the following files are placed:
1699 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1700 .irow &_CHANGES_& "contains a reference to where changes are &&&
1702 .irow &_LICENCE_& "the GNU General Public Licence"
1703 .irow &_Makefile_& "top-level make file"
1704 .irow &_NOTICE_& "conditions for the use of Exim"
1705 .irow &_README_& "list of files, directories and simple build &&&
1709 Other files whose names begin with &_README_& may also be present. The
1710 following subdirectories are created:
1713 .irow &_Local_& "an empty directory for local configuration files"
1714 .irow &_OS_& "OS-specific files"
1715 .irow &_doc_& "documentation files"
1716 .irow &_exim_monitor_& "source files for the Exim monitor"
1717 .irow &_scripts_& "scripts used in the build process"
1718 .irow &_src_& "remaining source files"
1719 .irow &_util_& "independent utilities"
1722 The main utility programs are contained in the &_src_& directory and are built
1723 with the Exim binary. The &_util_& directory contains a few optional scripts
1724 that may be useful to some sites.
1727 .section "Multiple machine architectures and operating systems" "SECID24"
1728 .cindex "building Exim" "multiple OS/architectures"
1729 The building process for Exim is arranged to make it easy to build binaries for
1730 a number of different architectures and operating systems from the same set of
1731 source files. Compilation does not take place in the &_src_& directory.
1732 Instead, a &'build directory'& is created for each architecture and operating
1734 .cindex "symbolic link" "to build directory"
1735 Symbolic links to the sources are installed in this directory, which is where
1736 the actual building takes place. In most cases, Exim can discover the machine
1737 architecture and operating system for itself, but the defaults can be
1738 overridden if necessary.
1739 .cindex compiler requirements
1740 .cindex compiler version
1741 A C99-capable compiler will be required for the build.
1744 .section "PCRE library" "SECTpcre"
1745 .cindex "PCRE library"
1746 Exim no longer has an embedded PCRE library as the vast majority of
1747 modern systems include PCRE as a system library, although you may need to
1748 install the PCRE package or the PCRE development package for your operating
1749 system. If your system has a normal PCRE installation the Exim build
1750 process will need no further configuration. If the library or the
1751 headers are in an unusual location you will need to either set the PCRE_LIBS
1752 and INCLUDE directives appropriately,
1753 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1754 If your operating system has no
1755 PCRE support then you will need to obtain and build the current PCRE
1756 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1757 More information on PCRE is available at &url(https://www.pcre.org/).
1759 .section "DBM libraries" "SECTdb"
1760 .cindex "DBM libraries" "discussion of"
1761 .cindex "hints database" "DBM files used for"
1762 Even if you do not use any DBM files in your configuration, Exim still needs a
1763 DBM library in order to operate, because it uses indexed files for its hints
1764 databases. Unfortunately, there are a number of DBM libraries in existence, and
1765 different operating systems often have different ones installed.
1767 .cindex "Solaris" "DBM library for"
1768 .cindex "IRIX, DBM library for"
1769 .cindex "BSD, DBM library for"
1770 .cindex "Linux, DBM library for"
1771 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1772 Linux distribution, the DBM configuration should happen automatically, and you
1773 may be able to ignore this section. Otherwise, you may have to learn more than
1774 you would like about DBM libraries from what follows.
1776 .cindex "&'ndbm'& DBM library"
1777 Licensed versions of Unix normally contain a library of DBM functions operating
1778 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1779 versions of Unix seem to vary in what they contain as standard. In particular,
1780 some early versions of Linux have no default DBM library, and different
1781 distributors have chosen to bundle different libraries with their packaged
1782 versions. However, the more recent releases seem to have standardized on the
1783 Berkeley DB library.
1785 Different DBM libraries have different conventions for naming the files they
1786 use. When a program opens a file called &_dbmfile_&, there are several
1790 A traditional &'ndbm'& implementation, such as that supplied as part of
1791 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1793 .cindex "&'gdbm'& DBM library"
1794 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1795 compatibility interface it makes two different hard links to it with names
1796 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1797 filename is used unmodified.
1799 .cindex "Berkeley DB library"
1800 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1801 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1802 programmer exactly the same as the traditional &'ndbm'& implementation.
1804 If the Berkeley package is used in its native mode, it operates on a single
1805 file called &_dbmfile_&; the programmer's interface is somewhat different to
1806 the traditional &'ndbm'& interface.
1808 To complicate things further, there are several very different versions of the
1809 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1810 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1811 Maintenance of some of the earlier releases has ceased. All versions of
1812 Berkeley DB could be obtained from
1813 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1814 page with far newer versions listed.
1815 It is probably wise to plan to move your storage configurations away from
1816 Berkeley DB format, as today there are smaller and simpler alternatives more
1817 suited to Exim's usage model.
1819 .cindex "&'tdb'& DBM library"
1820 Yet another DBM library, called &'tdb'&, is available from
1821 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1822 operates on a single file.
1826 .cindex "DBM libraries" "configuration for building"
1827 Exim and its utilities can be compiled to use any of these interfaces. In order
1828 to use any version of the Berkeley DB package in native mode, you must set
1829 USE_DB in an appropriate configuration file (typically
1830 &_Local/Makefile_&). For example:
1834 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1835 error is diagnosed if you set more than one of these.
1837 At the lowest level, the build-time configuration sets none of these options,
1838 thereby assuming an interface of type (1). However, some operating system
1839 configuration files (for example, those for the BSD operating systems and
1840 Linux) assume type (4) by setting USE_DB as their default, and the
1841 configuration files for Cygwin set USE_GDBM. Anything you set in
1842 &_Local/Makefile_&, however, overrides these system defaults.
1844 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1845 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1846 in one of these lines:
1851 Settings like that will work if the DBM library is installed in the standard
1852 place. Sometimes it is not, and the library's header file may also not be in
1853 the default path. You may need to set INCLUDE to specify where the header
1854 file is, and to specify the path to the library more fully in DBMLIB, as in
1857 INCLUDE=-I/usr/local/include/db-4.1
1858 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1860 There is further detailed discussion about the various DBM libraries in the
1861 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1865 .section "Pre-building configuration" "SECID25"
1866 .cindex "building Exim" "pre-building configuration"
1867 .cindex "configuration for building Exim"
1868 .cindex "&_Local/Makefile_&"
1869 .cindex "&_src/EDITME_&"
1870 Before building Exim, a local configuration file that specifies options
1871 independent of any operating system has to be created with the name
1872 &_Local/Makefile_&. A template for this file is supplied as the file
1873 &_src/EDITME_&, and it contains full descriptions of all the option settings
1874 therein. These descriptions are therefore not repeated here. If you are
1875 building Exim for the first time, the simplest thing to do is to copy
1876 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1878 There are three settings that you must supply, because Exim will not build
1879 without them. They are the location of the runtime configuration file
1880 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1881 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1882 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1883 a colon-separated list of filenames; Exim uses the first of them that exists.
1885 There are a few other parameters that can be specified either at build time or
1886 at runtime, to enable the same binary to be used on a number of different
1887 machines. However, if the locations of Exim's spool directory and log file
1888 directory (if not within the spool directory) are fixed, it is recommended that
1889 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1890 detected early in Exim's execution (such as a malformed configuration file) can
1893 .cindex "content scanning" "specifying at build time"
1894 Exim's interfaces for calling virus and spam scanning software directly from
1895 access control lists are not compiled by default. If you want to include these
1896 facilities, you need to set
1898 WITH_CONTENT_SCAN=yes
1900 in your &_Local/Makefile_&. For details of the facilities themselves, see
1901 chapter &<<CHAPexiscan>>&.
1904 .cindex "&_Local/eximon.conf_&"
1905 .cindex "&_exim_monitor/EDITME_&"
1906 If you are going to build the Exim monitor, a similar configuration process is
1907 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1908 your installation and saved under the name &_Local/eximon.conf_&. If you are
1909 happy with the default settings described in &_exim_monitor/EDITME_&,
1910 &_Local/eximon.conf_& can be empty, but it must exist.
1912 This is all the configuration that is needed in straightforward cases for known
1913 operating systems. However, the building process is set up so that it is easy
1914 to override options that are set by default or by operating-system-specific
1915 configuration files, for example, to change the C compiler, which
1916 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1921 .section "Support for iconv()" "SECID26"
1922 .cindex "&[iconv()]& support"
1924 The contents of header lines in messages may be encoded according to the rules
1925 described RFC 2047. This makes it possible to transmit characters that are not
1926 in the ASCII character set, and to label them as being in a particular
1927 character set. When Exim is inspecting header lines by means of the &%$h_%&
1928 mechanism, it decodes them, and translates them into a specified character set
1929 (default is set at build time). The translation is possible only if the operating system
1930 supports the &[iconv()]& function.
1932 However, some of the operating systems that supply &[iconv()]& do not support
1933 very many conversions. The GNU &%libiconv%& library (available from
1934 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1935 systems to remedy this deficiency, as well as on systems that do not supply
1936 &[iconv()]& at all. After installing &%libiconv%&, you should add
1940 to your &_Local/Makefile_& and rebuild Exim.
1944 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1945 .cindex "TLS" "including support for TLS"
1946 .cindex "encryption" "including support for"
1947 .cindex "OpenSSL" "building Exim with"
1948 .cindex "GnuTLS" "building Exim with"
1949 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1950 command as per RFC 2487. It can also support clients that expect to
1951 start a TLS session immediately on connection to a non-standard port (see the
1952 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1955 If you want to build Exim with TLS support, you must first install either the
1956 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1959 If you do not want TLS support you should set
1963 in &_Local/Makefile_&.
1965 If OpenSSL is installed, you should set
1968 TLS_LIBS=-lssl -lcrypto
1970 in &_Local/Makefile_&. You may also need to specify the locations of the
1971 OpenSSL library and include files. For example:
1974 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1975 TLS_INCLUDE=-I/usr/local/openssl/include/
1977 .cindex "pkg-config" "OpenSSL"
1978 If you have &'pkg-config'& available, then instead you can just use:
1981 USE_OPENSSL_PC=openssl
1983 .cindex "USE_GNUTLS"
1984 If GnuTLS is installed, you should set
1987 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1989 in &_Local/Makefile_&, and again you may need to specify the locations of the
1990 library and include files. For example:
1993 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1994 TLS_INCLUDE=-I/usr/gnu/include
1996 .cindex "pkg-config" "GnuTLS"
1997 If you have &'pkg-config'& available, then instead you can just use:
2000 USE_GNUTLS_PC=gnutls
2003 You do not need to set TLS_INCLUDE if the relevant directory is already
2004 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
2005 given in chapter &<<CHAPTLS>>&.
2010 .section "Use of tcpwrappers" "SECID27"
2012 .cindex "tcpwrappers, building Exim to support"
2013 .cindex "USE_TCP_WRAPPERS"
2014 .cindex "TCP_WRAPPERS_DAEMON_NAME"
2015 .cindex "tcp_wrappers_daemon_name"
2016 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
2017 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
2018 alternative to Exim's own checking facilities for installations that are
2019 already making use of &'tcpwrappers'& for other purposes. To do this, you
2020 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
2021 &_tcpd.h_& to be available at compile time, and also ensure that the library
2022 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
2023 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
2026 USE_TCP_WRAPPERS=yes
2027 CFLAGS=-O -I/usr/local/include
2028 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
2030 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
2031 files is &"exim"&. For example, the line
2033 exim : LOCAL 192.168.1. .friendly.domain.example
2035 in your &_/etc/hosts.allow_& file allows connections from the local host, from
2036 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
2037 All other connections are denied. The daemon name used by &'tcpwrappers'&
2038 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
2039 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
2040 configure file. Consult the &'tcpwrappers'& documentation for
2044 .section "Including support for IPv6" "SECID28"
2045 .cindex "IPv6" "including support for"
2046 Exim contains code for use on systems that have IPv6 support. Setting
2047 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2048 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2049 where the IPv6 support is not fully integrated into the normal include and
2052 Two different types of DNS record for handling IPv6 addresses have been
2053 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2054 currently seen as the mainstream. Another record type called A6 was proposed
2055 as better than AAAA because it had more flexibility. However, it was felt to be
2056 over-complex, and its status was reduced to &"experimental"&.
2058 have a compile option for including A6 record support but this has now been
2063 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2064 .cindex "lookup modules"
2065 .cindex "dynamic modules"
2066 .cindex ".so building"
2067 On some platforms, Exim supports not compiling all lookup types directly into
2068 the main binary, instead putting some into external modules which can be loaded
2070 This permits packagers to build Exim with support for lookups with extensive
2071 library dependencies without requiring all users to install all of those
2073 Most, but not all, lookup types can be built this way.
2075 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2076 installed; Exim will only load modules from that directory, as a security
2077 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2078 for your OS; see &_OS/Makefile-Linux_& for an example.
2079 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2080 see &_src/EDITME_& for details.
2082 Then, for each module to be loaded dynamically, define the relevant
2083 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2084 For example, this will build in lsearch but load sqlite and mysql support
2093 .section "The building process" "SECID29"
2094 .cindex "build directory"
2095 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2096 created, run &'make'& at the top level. It determines the architecture and
2097 operating system types, and creates a build directory if one does not exist.
2098 For example, on a Sun system running Solaris 8, the directory
2099 &_build-SunOS5-5.8-sparc_& is created.
2100 .cindex "symbolic link" "to source files"
2101 Symbolic links to relevant source files are installed in the build directory.
2103 If this is the first time &'make'& has been run, it calls a script that builds
2104 a make file inside the build directory, using the configuration files from the
2105 &_Local_& directory. The new make file is then passed to another instance of
2106 &'make'&. This does the real work, building a number of utility scripts, and
2107 then compiling and linking the binaries for the Exim monitor (if configured), a
2108 number of utility programs, and finally Exim itself. The command &`make
2109 makefile`& can be used to force a rebuild of the make file in the build
2110 directory, should this ever be necessary.
2112 If you have problems building Exim, check for any comments there may be in the
2113 &_README_& file concerning your operating system, and also take a look at the
2114 FAQ, where some common problems are covered.
2118 .section 'Output from &"make"&' "SECID283"
2119 The output produced by the &'make'& process for compile lines is often very
2120 unreadable, because these lines can be very long. For this reason, the normal
2121 output is suppressed by default, and instead output similar to that which
2122 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2123 each module that is being compiled or linked. However, it is still possible to
2124 get the full output, by calling &'make'& like this:
2128 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2129 command reflection in &'make'&. When you ask for the full output, it is
2130 given in addition to the short output.
2134 .section "Overriding build-time options for Exim" "SECToverride"
2135 .cindex "build-time options, overriding"
2136 The main make file that is created at the beginning of the building process
2137 consists of the concatenation of a number of files which set configuration
2138 values, followed by a fixed set of &'make'& instructions. If a value is set
2139 more than once, the last setting overrides any previous ones. This provides a
2140 convenient way of overriding defaults. The files that are concatenated are, in
2143 &_OS/Makefile-Default_&
2144 &_OS/Makefile-_&<&'ostype'&>
2146 &_Local/Makefile-_&<&'ostype'&>
2147 &_Local/Makefile-_&<&'archtype'&>
2148 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2149 &_OS/Makefile-Base_&
2151 .cindex "&_Local/Makefile_&"
2152 .cindex "building Exim" "operating system type"
2153 .cindex "building Exim" "architecture type"
2154 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2155 architecture type. &_Local/Makefile_& is required to exist, and the building
2156 process fails if it is absent. The other three &_Local_& files are optional,
2157 and are often not needed.
2159 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2160 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2161 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2162 values are used, thereby providing a means of forcing particular settings.
2163 Otherwise, the scripts try to get values from the &%uname%& command. If this
2164 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2165 of &'ad hoc'& transformations are then applied, to produce the standard names
2166 that Exim expects. You can run these scripts directly from the shell in order
2167 to find out what values are being used on your system.
2170 &_OS/Makefile-Default_& contains comments about the variables that are set
2171 therein. Some (but not all) are mentioned below. If there is something that
2172 needs changing, review the contents of this file and the contents of the make
2173 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2177 .cindex "building Exim" "overriding default settings"
2178 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2179 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2180 need to change the original files. Instead, you should make the changes by
2181 putting the new values in an appropriate &_Local_& file. For example,
2182 .cindex "Tru64-Unix build-time settings"
2183 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2184 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2185 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2186 called with the option &%-std1%&, to make it recognize some of the features of
2187 Standard C that Exim uses. (Most other compilers recognize Standard C by
2188 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2189 containing the lines
2194 If you are compiling for just one operating system, it may be easier to put
2195 these lines directly into &_Local/Makefile_&.
2197 Keeping all your local configuration settings separate from the distributed
2198 files makes it easy to transfer them to new versions of Exim simply by copying
2199 the contents of the &_Local_& directory.
2202 .cindex "NIS lookup type" "including support for"
2203 .cindex "NIS+ lookup type" "including support for"
2204 .cindex "LDAP" "including support for"
2205 .cindex "lookup" "inclusion in binary"
2206 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2207 lookup, but not all systems have these components installed, so the default is
2208 not to include the relevant code in the binary. All the different kinds of file
2209 and database lookup that Exim supports are implemented as separate code modules
2210 which are included only if the relevant compile-time options are set. In the
2211 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2217 and similar settings apply to the other lookup types. They are all listed in
2218 &_src/EDITME_&. In many cases the relevant include files and interface
2219 libraries need to be installed before compiling Exim.
2220 .cindex "cdb" "including support for"
2221 However, there are some optional lookup types (such as cdb) for which
2222 the code is entirely contained within Exim, and no external include
2223 files or libraries are required. When a lookup type is not included in the
2224 binary, attempts to configure Exim to use it cause runtime configuration
2227 .cindex "pkg-config" "lookups"
2228 .cindex "pkg-config" "authenticators"
2229 Many systems now use a tool called &'pkg-config'& to encapsulate information
2230 about how to compile against a library; Exim has some initial support for
2231 being able to use pkg-config for lookups and authenticators. For any given
2232 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2233 variable with the &`_PC`& suffix in the name and assign as the value the
2234 name of the package to be queried. The results of querying via the
2235 &'pkg-config'& command will be added to the appropriate Makefile variables
2236 with &`+=`& directives, so your version of &'make'& will need to support that
2237 syntax. For instance:
2240 LOOKUP_SQLITE_PC=sqlite3
2242 AUTH_GSASL_PC=libgsasl
2243 AUTH_HEIMDAL_GSSAPI=yes
2244 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2247 .cindex "Perl" "including support for"
2248 Exim can be linked with an embedded Perl interpreter, allowing Perl
2249 subroutines to be called during string expansion. To enable this facility,
2253 must be defined in &_Local/Makefile_&. Details of this facility are given in
2254 chapter &<<CHAPperl>>&.
2256 .cindex "X11 libraries, location of"
2257 The location of the X11 libraries is something that varies a lot between
2258 operating systems, and there may be different versions of X11 to cope
2259 with. Exim itself makes no use of X11, but if you are compiling the Exim
2260 monitor, the X11 libraries must be available.
2261 The following three variables are set in &_OS/Makefile-Default_&:
2264 XINCLUDE=-I$(X11)/include
2265 XLFLAGS=-L$(X11)/lib
2267 These are overridden in some of the operating-system configuration files. For
2268 example, in &_OS/Makefile-SunOS5_& there is
2271 XINCLUDE=-I$(X11)/include
2272 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2274 If you need to override the default setting for your operating system, place a
2275 definition of all three of these variables into your
2276 &_Local/Makefile-<ostype>_& file.
2279 If you need to add any extra libraries to the link steps, these can be put in a
2280 variable called EXTRALIBS, which appears in all the link commands, but by
2281 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2282 command for linking the main Exim binary, and not for any associated utilities.
2284 .cindex "DBM libraries" "configuration for building"
2285 There is also DBMLIB, which appears in the link commands for binaries that
2286 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2287 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2288 binary, and which can be used, for example, to include additional X11
2291 .cindex "configuration file" "editing"
2292 The make file copes with rebuilding Exim correctly if any of the configuration
2293 files are edited. However, if an optional configuration file is deleted, it is
2294 necessary to touch the associated non-optional file (that is,
2295 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2298 .section "OS-specific header files" "SECID30"
2300 .cindex "building Exim" "OS-specific C header files"
2301 The &_OS_& directory contains a number of files with names of the form
2302 &_os.h-<ostype>_&. These are system-specific C header files that should not
2303 normally need to be changed. There is a list of macro settings that are
2304 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2305 are porting Exim to a new operating system.
2309 .section "Overriding build-time options for the monitor" "SECID31"
2310 .cindex "building Eximon"
2311 A similar process is used for overriding things when building the Exim monitor,
2312 where the files that are involved are
2314 &_OS/eximon.conf-Default_&
2315 &_OS/eximon.conf-_&<&'ostype'&>
2316 &_Local/eximon.conf_&
2317 &_Local/eximon.conf-_&<&'ostype'&>
2318 &_Local/eximon.conf-_&<&'archtype'&>
2319 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2321 .cindex "&_Local/eximon.conf_&"
2322 As with Exim itself, the final three files need not exist, and in this case the
2323 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2324 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2325 variables of the same name, preceded by EXIMON_. For example, setting
2326 EXIMON_LOG_DEPTH in the environment overrides the value of
2327 LOG_DEPTH at runtime.
2331 .section "Installing Exim binaries and scripts" "SECID32"
2332 .cindex "installing Exim"
2333 .cindex "BIN_DIRECTORY"
2334 The command &`make install`& runs the &(exim_install)& script with no
2335 arguments. The script copies binaries and utility scripts into the directory
2336 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2337 .cindex "setuid" "installing Exim with"
2338 The install script copies files only if they are newer than the files they are
2339 going to replace. The Exim binary is required to be owned by root and have the
2340 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2341 install`& as root so that it can set up the Exim binary in this way. However, in
2342 some special situations (for example, if a host is doing no local deliveries)
2343 it may be possible to run Exim without making the binary setuid root (see
2344 chapter &<<CHAPsecurity>>& for details).
2346 .cindex "CONFIGURE_FILE"
2347 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2348 in &_Local/Makefile_&. If this names a single file, and the file does not
2349 exist, the default configuration file &_src/configure.default_& is copied there
2350 by the installation script. If a runtime configuration file already exists, it
2351 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2352 alternative files, no default is installed.
2354 .cindex "system aliases file"
2355 .cindex "&_/etc/aliases_&"
2356 One change is made to the default configuration file when it is installed: the
2357 default configuration contains a router that references a system aliases file.
2358 The path to this file is set to the value specified by
2359 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2360 If the system aliases file does not exist, the installation script creates it,
2361 and outputs a comment to the user.
2363 The created file contains no aliases, but it does contain comments about the
2364 aliases a site should normally have. Mail aliases have traditionally been
2365 kept in &_/etc/aliases_&. However, some operating systems are now using
2366 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2367 Exim's configuration if necessary.
2369 The default configuration uses the local host's name as the only local domain,
2370 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2371 running as the local user. System aliases and &_.forward_& files in users' home
2372 directories are supported, but no NIS or NIS+ support is configured. Domains
2373 other than the name of the local host are routed using the DNS, with delivery
2376 It is possible to install Exim for special purposes (such as building a binary
2377 distribution) in a private part of the file system. You can do this by a
2380 make DESTDIR=/some/directory/ install
2382 This has the effect of pre-pending the specified directory to all the file
2383 paths, except the name of the system aliases file that appears in the default
2384 configuration. (If a default alias file is created, its name &'is'& modified.)
2385 For backwards compatibility, ROOT is used if DESTDIR is not set,
2386 but this usage is deprecated.
2388 .cindex "installing Exim" "what is not installed"
2389 Running &'make install'& does not copy the Exim 4 conversion script
2390 &'convert4r4'&. You will probably run this only once if you are
2391 upgrading from Exim 3. None of the documentation files in the &_doc_&
2392 directory are copied, except for the info files when you have set
2393 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2395 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2396 to their names. The Exim binary itself, however, is handled differently. It is
2397 installed under a name that includes the version number and the compile number,
2398 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2399 called &_exim_& to point to the binary. If you are updating a previous version
2400 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2401 from the directory (as seen by other processes).
2403 .cindex "installing Exim" "testing the script"
2404 If you want to see what the &'make install'& will do before running it for
2405 real, you can pass the &%-n%& option to the installation script by this
2408 make INSTALL_ARG=-n install
2410 The contents of the variable INSTALL_ARG are passed to the installation
2411 script. You do not need to be root to run this test. Alternatively, you can run
2412 the installation script directly, but this must be from within the build
2413 directory. For example, from the top-level Exim directory you could use this
2416 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2418 .cindex "installing Exim" "install script options"
2419 There are two other options that can be supplied to the installation script.
2422 &%-no_chown%& bypasses the call to change the owner of the installed binary
2423 to root, and the call to make it a setuid binary.
2425 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2429 INSTALL_ARG can be used to pass these options to the script. For example:
2431 make INSTALL_ARG=-no_symlink install
2433 The installation script can also be given arguments specifying which files are
2434 to be copied. For example, to install just the Exim binary, and nothing else,
2435 without creating the symbolic link, you could use:
2437 make INSTALL_ARG='-no_symlink exim' install
2442 .section "Installing info documentation" "SECTinsinfdoc"
2443 .cindex "installing Exim" "&'info'& documentation"
2444 Not all systems use the GNU &'info'& system for documentation, and for this
2445 reason, the Texinfo source of Exim's documentation is not included in the main
2446 distribution. Instead it is available separately from the FTP site (see section
2449 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2450 source of the documentation is found in the source tree, running &`make
2451 install`& automatically builds the info files and installs them.
2455 .section "Setting up the spool directory" "SECID33"
2456 .cindex "spool directory" "creating"
2457 When it starts up, Exim tries to create its spool directory if it does not
2458 exist. The Exim uid and gid are used for the owner and group of the spool
2459 directory. Sub-directories are automatically created in the spool directory as
2465 .section "Testing" "SECID34"
2466 .cindex "testing" "installation"
2467 Having installed Exim, you can check that the runtime configuration file is
2468 syntactically valid by running the following command, which assumes that the
2469 Exim binary directory is within your PATH environment variable:
2473 If there are any errors in the configuration file, Exim outputs error messages.
2474 Otherwise it outputs the version number and build date,
2475 the DBM library that is being used, and information about which drivers and
2476 other optional code modules are included in the binary.
2477 Some simple routing tests can be done by using the address testing option. For
2480 &`exim -bt`& <&'local username'&>
2482 should verify that it recognizes a local mailbox, and
2484 &`exim -bt`& <&'remote address'&>
2486 a remote one. Then try getting it to deliver mail, both locally and remotely.
2487 This can be done by passing messages directly to Exim, without going through a
2488 user agent. For example:
2490 exim -v postmaster@your.domain.example
2491 From: user@your.domain.example
2492 To: postmaster@your.domain.example
2493 Subject: Testing Exim
2495 This is a test message.
2498 The &%-v%& option causes Exim to output some verification of what it is doing.
2499 In this case you should see copies of three log lines, one for the message's
2500 arrival, one for its delivery, and one containing &"Completed"&.
2502 .cindex "delivery" "problems with"
2503 If you encounter problems, look at Exim's log files (&'mainlog'& and
2504 &'paniclog'&) to see if there is any relevant information there. Another source
2505 of information is running Exim with debugging turned on, by specifying the
2506 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2507 with debugging turned on by a command of the form
2509 &`exim -d -M`& <&'exim-message-id'&>
2511 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2512 produces rather a lot of output, but you can cut this down to specific areas.
2513 For example, if you use &%-d-all+route%& only the debugging information
2514 relevant to routing is included. (See the &%-d%& option in chapter
2515 &<<CHAPcommandline>>& for more details.)
2517 .cindex '&"sticky"& bit'
2518 .cindex "lock files"
2519 One specific problem that has shown up on some sites is the inability to do
2520 local deliveries into a shared mailbox directory, because it does not have the
2521 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2522 writing to a mailbox file, and if it cannot create the lock file, the delivery
2523 is deferred. You can get round this either by setting the &"sticky bit"& on the
2524 directory, or by setting a specific group for local deliveries and allowing
2525 that group to create files in the directory (see the comments above the
2526 &(local_delivery)& transport in the default configuration file). Another
2527 approach is to configure Exim not to use lock files, but just to rely on
2528 &[fcntl()]& locking instead. However, you should do this only if all user
2529 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2530 see chapter &<<CHAPappendfile>>&.
2532 One thing that cannot be tested on a system that is already running an MTA is
2533 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2534 &%-oX%& option can be used to run an Exim daemon that listens on some other
2535 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2536 &'exim_checkaccess'& utility can be used to check out policy controls on
2539 Testing a new version on a system that is already running Exim can most easily
2540 be done by building a binary with a different CONFIGURE_FILE setting. From
2541 within the runtime configuration, all other file and directory names
2542 that Exim uses can be altered, in order to keep it entirely clear of the
2546 .section "Replacing another MTA with Exim" "SECID35"
2547 .cindex "replacing another MTA"
2548 Building and installing Exim for the first time does not of itself put it in
2549 general use. The name by which the system's MTA is called by mail user agents
2550 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2551 operating system), and it is necessary to make this name point to the &'exim'&
2552 binary in order to get the user agents to pass messages to Exim. This is
2553 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2554 or &_/usr/lib/sendmail_&
2555 .cindex "symbolic link" "to &'exim'& binary"
2556 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2557 privilege and executable status from the old MTA. It is then necessary to stop
2558 and restart the mailer daemon, if one is running.
2560 .cindex "FreeBSD, MTA indirection"
2561 .cindex "&_/etc/mail/mailer.conf_&"
2562 Some operating systems have introduced alternative ways of switching MTAs. For
2563 example, if you are running FreeBSD, you need to edit the file
2564 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2565 described. A typical example of the contents of this file for running Exim is
2568 sendmail /usr/exim/bin/exim
2569 send-mail /usr/exim/bin/exim
2570 mailq /usr/exim/bin/exim -bp
2571 newaliases /usr/bin/true
2573 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2574 your Exim installation is &"live"&. Check it by sending a message from your
2575 favourite user agent.
2577 You should consider what to tell your users about the change of MTA. Exim may
2578 have different capabilities to what was previously running, and there are
2579 various operational differences such as the text of messages produced by
2580 command line options and in bounce messages. If you allow your users to make
2581 use of Exim's filtering capabilities, you should make the document entitled
2582 &'Exim's interface to mail filtering'& available to them.
2586 .section "Upgrading Exim" "SECID36"
2587 .cindex "upgrading Exim"
2588 If you are already running Exim on your host, building and installing a new
2589 version automatically makes it available to MUAs, or any other programs that
2590 call the MTA directly. However, if you are running an Exim daemon, you do need
2591 .cindex restart "on HUP signal"
2592 .cindex signal "HUP, to restart"
2593 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2594 new binary. You do not need to stop processing mail in order to install a new
2595 version of Exim. The install script does not modify an existing runtime
2601 .section "Stopping the Exim daemon on Solaris" "SECID37"
2602 .cindex "Solaris" "stopping Exim on"
2603 The standard command for stopping the mailer daemon on Solaris is
2605 /etc/init.d/sendmail stop
2607 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2608 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2609 for the text &"sendmail"&; this is not present because the actual program name
2610 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2611 solution is to replace the line that finds the process id with something like
2613 pid=`cat /var/spool/exim/exim-daemon.pid`
2615 to obtain the daemon's pid directly from the file that Exim saves it in.
2617 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2618 still be received from local processes, and if automatic delivery is configured
2619 (the normal case), deliveries will still occur.
2624 . ////////////////////////////////////////////////////////////////////////////
2625 . ////////////////////////////////////////////////////////////////////////////
2627 .chapter "The Exim command line" "CHAPcommandline"
2628 .scindex IIDclo1 "command line" "options"
2629 .scindex IIDclo2 "options" "command line"
2630 Exim's command line takes the standard Unix form of a sequence of options,
2631 each starting with a hyphen character, followed by a number of arguments. The
2632 options are compatible with the main options of Sendmail, and there are also
2633 some additional options, some of which are compatible with Smail 3. Certain
2634 combinations of options do not make sense, and provoke an error if used.
2635 The form of the arguments depends on which options are set.
2638 .section "Setting options by program name" "SECID38"
2640 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2641 were present before any other options.
2642 The &%-bp%& option requests a listing of the contents of the mail queue on the
2644 This feature is for compatibility with some systems that contain a command of
2645 that name in one of the standard libraries, symbolically linked to
2646 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2649 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2650 were present before any other options, for compatibility with Smail. The
2651 &%-bS%& option is used for reading in a number of messages in batched SMTP
2655 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2656 &%-oee%& options were present before any other options, for compatibility with
2657 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2660 .cindex "queue runner"
2661 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2662 were present before any other options, for compatibility with Smail. The &%-q%&
2663 option causes a single queue runner process to be started.
2665 .cindex "&'newaliases'&"
2666 .cindex "alias file" "building"
2667 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2668 If Exim is called under the name &'newaliases'& it behaves as if the option
2669 &%-bi%& were present before any other options, for compatibility with Sendmail.
2670 This option is used for rebuilding Sendmail's alias file. Exim does not have
2671 the concept of a single alias file, but can be configured to run a given
2672 command if called with the &%-bi%& option.
2675 .section "Trusted and admin users" "SECTtrustedadmin"
2676 Some Exim options are available only to &'trusted users'& and others are
2677 available only to &'admin users'&. In the description below, the phrases &"Exim
2678 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2679 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2680 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2683 .cindex "trusted users" "definition of"
2684 .cindex "user" "trusted definition of"
2685 The trusted users are root, the Exim user, any user listed in the
2686 &%trusted_users%& configuration option, and any user whose current group or any
2687 supplementary group is one of those listed in the &%trusted_groups%&
2688 configuration option. Note that the Exim group is not automatically trusted.
2690 .cindex '&"From"& line'
2691 .cindex "envelope from"
2692 .cindex "envelope sender"
2693 Trusted users are always permitted to use the &%-f%& option or a leading
2694 &"From&~"& line to specify the envelope sender of a message that is passed to
2695 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2696 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2697 users to set envelope senders.
2701 For a trusted user, there is never any check on the contents of the &'From:'&
2702 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2703 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2705 Trusted users may also specify a host name, host address, interface address,
2706 protocol name, ident value, and authentication data when submitting a message
2707 locally. Thus, they are able to insert messages into Exim's queue locally that
2708 have the characteristics of messages received from a remote host. Untrusted
2709 users may in some circumstances use &%-f%&, but can never set the other values
2710 that are available to trusted users.
2712 .cindex "user" "admin definition of"
2713 .cindex "admin user" "definition of"
2714 The admin users are root, the Exim user, and any user that is a member of the
2715 Exim group or of any group listed in the &%admin_groups%& configuration option.
2716 The current group does not have to be one of these groups.
2718 Admin users are permitted to list the queue, and to carry out certain
2719 operations on messages, for example, to force delivery failures. It is also
2720 necessary to be an admin user in order to see the full information provided by
2721 the Exim monitor, and full debugging output.
2723 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2724 Exim to attempt delivery of messages on its queue is restricted to admin users.
2725 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2726 option false (that is, specifying &%no_prod_requires_admin%&).
2728 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2729 is restricted to admin users unless &%queue_list_requires_admin%& is set
2734 &*Warning*&: If you configure your system so that admin users are able to
2735 edit Exim's configuration file, you are giving those users an easy way of
2736 getting root. There is further discussion of this issue at the start of chapter
2742 .section "Command line options" "SECID39"
2743 Exim's command line options are described in alphabetical order below. If none
2744 of the options that specifies a specific action (such as starting the daemon or
2745 a queue runner, or testing an address, or receiving a message in a specific
2746 format, or listing the queue) are present, and there is at least one argument
2747 on the command line, &%-bm%& (accept a local message on the standard input,
2748 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2749 outputs a brief message about itself and exits.
2751 . ////////////////////////////////////////////////////////////////////////////
2752 . Insert a stylized XML comment here, to identify the start of the command line
2753 . options. This is for the benefit of the Perl script that automatically
2754 . creates a man page for the options.
2755 . ////////////////////////////////////////////////////////////////////////////
2758 <!-- === Start of command line options === -->
2765 .cindex "options" "command line; terminating"
2766 This is a pseudo-option whose only purpose is to terminate the options and
2767 therefore to cause subsequent command line items to be treated as arguments
2768 rather than options, even if they begin with hyphens.
2771 .oindex "&%--help%&"
2772 This option causes Exim to output a few sentences stating what it is.
2773 The same output is generated if the Exim binary is called with no options and
2776 .vitem &%--version%&
2777 .oindex "&%--version%&"
2778 This option is an alias for &%-bV%& and causes version information to be
2785 These options are used by Sendmail for selecting configuration files and are
2788 .vitem &%-B%&<&'type'&>
2790 .cindex "8-bit characters"
2791 .cindex "Sendmail compatibility" "8-bit characters"
2792 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2793 clean; it ignores this option.
2798 .cindex "SMTP" "listener"
2799 .cindex "queue runner"
2800 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2801 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2802 that the daemon should also initiate periodic queue runs.
2804 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2805 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2806 disconnect from the controlling terminal. When running this way, it can be
2807 stopped by pressing ctrl-C.
2809 By default, Exim listens for incoming connections to the standard SMTP port on
2810 all the host's running interfaces. However, it is possible to listen on other
2811 ports, on multiple ports, and only on specific interfaces. Chapter
2812 &<<CHAPinterfaces>>& contains a description of the options that control this.
2814 When a listening daemon
2815 .cindex "daemon" "process id (pid)"
2816 .cindex "pid (process id)" "of daemon"
2817 is started without the use of &%-oX%& (that is, without overriding the normal
2818 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2819 in Exim's spool directory. This location can be overridden by setting
2820 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2823 When &%-oX%& is used on the command line to start a listening daemon, the
2824 process id is not written to the normal pid file path. However, &%-oP%& can be
2825 used to specify a path on the command line if a pid file is required.
2829 .cindex restart "on HUP signal"
2830 .cindex signal "HUP, to restart"
2831 .cindex "daemon" "restarting"
2832 .cindex signal "to reload configuration"
2833 .cindex daemon "reload configuration"
2834 .cindex reload configuration
2835 can be used to cause the daemon to re-execute itself. This should be done
2836 whenever Exim's configuration file, or any file that is incorporated into it by
2837 means of the &%.include%& facility, is changed, and also whenever a new version
2838 of Exim is installed. It is not necessary to do this when other files that are
2839 referenced from the configuration (for example, alias files) are changed,
2840 because these are reread each time they are used.
2844 This option has the same effect as &%-bd%& except that it never disconnects
2845 from the controlling terminal, even when no debugging is specified.
2849 .cindex "testing" "string expansion"
2850 .cindex "expansion" "testing"
2851 Run Exim in expansion testing mode. Exim discards its root privilege, to
2852 prevent ordinary users from using this mode to read otherwise inaccessible
2853 files. If no arguments are given, Exim runs interactively, prompting for lines
2854 of data. Otherwise, it processes each argument in turn.
2856 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2857 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2858 used without command line arguments. If successful, it uses the &[readline()]&
2859 function, which provides extensive line-editing facilities, for reading the
2860 test data. A line history is supported.
2862 Long expansion expressions can be split over several lines by using backslash
2863 continuations. As in Exim's runtime configuration, white space at the start of
2864 continuation lines is ignored. Each argument or data line is passed through the
2865 string expansion mechanism, and the result is output. Variable values from the
2866 configuration file (for example, &$qualify_domain$&) are available, but no
2867 message-specific values (such as &$message_exim_id$&) are set, because no message
2868 is being processed (but see &%-bem%& and &%-Mset%&).
2870 &*Note*&: If you use this mechanism to test lookups, and you change the data
2871 files or databases you are using, you must exit and restart Exim before trying
2872 the same lookup again. Otherwise, because each Exim process caches the results
2873 of lookups, you will just get the same result as before.
2875 Macro processing is done on lines before string-expansion: new macros can be
2876 defined and macros will be expanded.
2877 Because macros in the config file are often used for secrets, those are only
2878 available to admin users.
2880 .vitem &%-bem%&&~<&'filename'&>
2882 .cindex "testing" "string expansion"
2883 .cindex "expansion" "testing"
2884 This option operates like &%-be%& except that it must be followed by the name
2885 of a file. For example:
2887 exim -bem /tmp/testmessage
2889 The file is read as a message (as if receiving a locally-submitted non-SMTP
2890 message) before any of the test expansions are done. Thus, message-specific
2891 variables such as &$message_size$& and &$header_from:$& are available. However,
2892 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2893 recipients are read from the headers in the normal way, and are shown in the
2894 &$recipients$& variable. Note that recipients cannot be given on the command
2895 line, because further arguments are taken as strings to expand (just like
2898 .vitem &%-bF%&&~<&'filename'&>
2900 .cindex "system filter" "testing"
2901 .cindex "testing" "system filter"
2902 This option is the same as &%-bf%& except that it assumes that the filter being
2903 tested is a system filter. The additional commands that are available only in
2904 system filters are recognized.
2906 .vitem &%-bf%&&~<&'filename'&>
2908 .cindex "filter" "testing"
2909 .cindex "testing" "filter file"
2910 .cindex "forward file" "testing"
2911 .cindex "testing" "forward file"
2912 .cindex "Sieve filter" "testing"
2913 This option runs Exim in user filter testing mode; the file is the filter file
2914 to be tested, and a test message must be supplied on the standard input. If
2915 there are no message-dependent tests in the filter, an empty file can be
2918 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2919 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2920 filter and a user filter in the same run. For example:
2922 exim -bF /system/filter -bf /user/filter </test/message
2924 This is helpful when the system filter adds header lines or sets filter
2925 variables that are used by the user filter.
2927 If the test filter file does not begin with one of the special lines
2932 it is taken to be a normal &_.forward_& file, and is tested for validity under
2933 that interpretation. See sections &<<SECTitenonfilred>>& to
2934 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2937 The result of an Exim command that uses &%-bf%&, provided no errors are
2938 detected, is a list of the actions that Exim would try to take if presented
2939 with the message for real. More details of filter testing are given in the
2940 separate document entitled &'Exim's interfaces to mail filtering'&.
2942 When testing a filter file,
2943 .cindex "&""From""& line"
2944 .cindex "envelope from"
2945 .cindex "envelope sender"
2946 .oindex "&%-f%&" "for filter testing"
2947 the envelope sender can be set by the &%-f%& option,
2948 or by a &"From&~"& line at the start of the test message. Various parameters
2949 that would normally be taken from the envelope recipient address of the message
2950 can be set by means of additional command line options (see the next four
2953 .vitem &%-bfd%&&~<&'domain'&>
2955 .vindex "&$qualify_domain$&"
2956 This sets the domain of the recipient address when a filter file is being
2957 tested by means of the &%-bf%& option. The default is the value of
2960 .vitem &%-bfl%&&~<&'local&~part'&>
2962 This sets the local part of the recipient address when a filter file is being
2963 tested by means of the &%-bf%& option. The default is the username of the
2964 process that calls Exim. A local part should be specified with any prefix or
2965 suffix stripped, because that is how it appears to the filter when a message is
2966 actually being delivered.
2968 .vitem &%-bfp%&&~<&'prefix'&>
2970 .cindex affix "filter testing"
2971 This sets the prefix of the local part of the recipient address when a filter
2972 file is being tested by means of the &%-bf%& option. The default is an empty
2975 .vitem &%-bfs%&&~<&'suffix'&>
2977 .cindex affix "filter testing"
2978 This sets the suffix of the local part of the recipient address when a filter
2979 file is being tested by means of the &%-bf%& option. The default is an empty
2982 .vitem &%-bh%&&~<&'IP&~address'&>
2984 .cindex "testing" "incoming SMTP"
2985 .cindex "SMTP" "testing incoming"
2986 .cindex "testing" "relay control"
2987 .cindex "relaying" "testing configuration"
2988 .cindex "policy control" "testing"
2989 .cindex "debugging" "&%-bh%& option"
2990 This option runs a fake SMTP session as if from the given IP address, using the
2991 standard input and output. The IP address may include a port number at the end,
2992 after a full stop. For example:
2994 exim -bh 10.9.8.7.1234
2995 exim -bh fe80::a00:20ff:fe86:a061.5678
2997 When an IPv6 address is given, it is converted into canonical form. In the case
2998 of the second example above, the value of &$sender_host_address$& after
2999 conversion to the canonical form is
3000 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
3002 Comments as to what is going on are written to the standard error file. These
3003 include lines beginning with &"LOG"& for anything that would have been logged.
3004 This facility is provided for testing configuration options for incoming
3005 messages, to make sure they implement the required policy. For example, you can
3006 test your relay controls using &%-bh%&.
3010 You can test features of the configuration that rely on ident (RFC 1413)
3011 information by using the &%-oMt%& option. However, Exim cannot actually perform
3012 an ident callout when testing using &%-bh%& because there is no incoming SMTP
3015 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
3016 are also skipped when testing using &%-bh%&. If you want these callouts to
3017 occur, use &%-bhc%& instead.
3019 Messages supplied during the testing session are discarded, and nothing is
3020 written to any of the real log files. There may be pauses when DNS (and other)
3021 lookups are taking place, and of course these may time out. The &%-oMi%& option
3022 can be used to specify a specific IP interface and port if this is important,
3023 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
3024 session were authenticated.
3026 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
3027 output just states whether a given recipient address from a given host is
3028 acceptable or not. See section &<<SECTcheckaccess>>&.
3030 Features such as authentication and encryption, where the client input is not
3031 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
3032 specialized SMTP test program such as
3033 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3035 .vitem &%-bhc%&&~<&'IP&~address'&>
3037 This option operates in the same way as &%-bh%&, except that address
3038 verification callouts are performed if required. This includes consulting and
3039 updating the callout cache database.
3043 .cindex "alias file" "building"
3044 .cindex "building alias file"
3045 .cindex "Sendmail compatibility" "&%-bi%& option"
3046 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3047 Exim does not have the concept of a single alias file, and so it cannot mimic
3048 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3049 tend to appear in various scripts such as NIS make files, so the option must be
3052 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3053 configuration option is run, under the uid and gid of the caller of Exim. If
3054 the &%-oA%& option is used, its value is passed to the command as an argument.
3055 The command set by &%bi_command%& may not contain arguments. The command can
3056 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3057 if this is required. If the &%bi_command%& option is not set, calling Exim with
3060 . // Keep :help first, then the rest in alphabetical order
3062 .oindex "&%-bI:help%&"
3063 .cindex "querying exim information"
3064 We shall provide various options starting &`-bI:`& for querying Exim for
3065 information. The output of many of these will be intended for machine
3066 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3067 synopsis of supported options beginning &`-bI:`&. Use of any of these
3068 options shall cause Exim to exit after producing the requested output.
3071 .oindex "&%-bI:dscp%&"
3072 .cindex "DSCP" "values"
3073 This option causes Exim to emit an alphabetically sorted list of all
3074 recognised DSCP names.
3076 .vitem &%-bI:sieve%&
3077 .oindex "&%-bI:sieve%&"
3078 .cindex "Sieve filter" "capabilities"
3079 This option causes Exim to emit an alphabetically sorted list of all supported
3080 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3081 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3082 &`SIEVE`& capability response line. As the precise list may depend upon
3083 compile-time build options, which this option will adapt to, this is the only
3084 way to guarantee a correct response.
3088 .cindex "local message reception"
3089 This option runs an Exim receiving process that accepts an incoming,
3090 locally-generated message on the standard input. The recipients are given as the
3091 command arguments (except when &%-t%& is also present &-- see below). Each
3092 argument can be a comma-separated list of RFC 2822 addresses. This is the
3093 default option for selecting the overall action of an Exim call; it is assumed
3094 if no other conflicting option is present.
3096 If any addresses in the message are unqualified (have no domain), they are
3097 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3098 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3099 suppressing this for special cases.
3101 Policy checks on the contents of local messages can be enforced by means of
3102 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3104 .cindex "return code" "for &%-bm%&"
3105 The return code is zero if the message is successfully accepted. Otherwise, the
3106 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3109 .cindex "message" "format"
3110 .cindex "format" "message"
3111 .cindex "&""From""& line"
3112 .cindex "UUCP" "&""From""& line"
3113 .cindex "Sendmail compatibility" "&""From""& line"
3114 of the message must be as defined in RFC 2822, except that, for
3115 compatibility with Sendmail and Smail, a line in one of the forms
3117 From sender Fri Jan 5 12:55 GMT 1997
3118 From sender Fri, 5 Jan 97 12:55:01
3120 (with the weekday optional, and possibly with additional text after the date)
3121 is permitted to appear at the start of the message. There appears to be no
3122 authoritative specification of the format of this line. Exim recognizes it by
3123 matching against the regular expression defined by the &%uucp_from_pattern%&
3124 option, which can be changed if necessary.
3126 .oindex "&%-f%&" "overriding &""From""& line"
3127 The specified sender is treated as if it were given as the argument to the
3128 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3129 preference to the address taken from the message. The caller of Exim must be a
3130 trusted user for the sender of a message to be set in this way.
3132 .vitem &%-bmalware%&&~<&'filename'&>
3133 .oindex "&%-bmalware%&"
3134 .cindex "testing", "malware"
3135 .cindex "malware scan test"
3136 This debugging option causes Exim to scan the given file or directory
3137 (depending on the used scanner interface),
3138 using the malware scanning framework. The option of &%av_scanner%& influences
3139 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3140 the expansion should have defaults which apply to this invocation. ACLs are
3141 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3142 will never be populated and &%-bmalware%& will fail.
3144 Exim will have changed working directory before resolving the filename, so
3145 using fully qualified pathnames is advisable. Exim will be running as the Exim
3146 user when it tries to open the file, rather than as the invoking user.
3147 This option requires admin privileges.
3149 The &%-bmalware%& option will not be extended to be more generally useful,
3150 there are better tools for file-scanning. This option exists to help
3151 administrators verify their Exim and AV scanner configuration.
3155 .cindex "address qualification, suppressing"
3156 By default, Exim automatically qualifies unqualified addresses (those
3157 without domains) that appear in messages that are submitted locally (that
3158 is, not over TCP/IP). This qualification applies both to addresses in
3159 envelopes, and addresses in header lines. Sender addresses are qualified using
3160 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3161 defaults to the value of &%qualify_domain%&).
3163 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3164 being used to re-submit messages that originally came from remote hosts after
3165 content scanning, you probably do not want to qualify unqualified addresses in
3166 header lines. (Such lines will be present only if you have not enabled a header
3167 syntax check in the appropriate ACL.)
3169 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3170 messages that originate on the local host. When this is used, unqualified
3171 addresses in the envelope provoke errors (causing message rejection) and
3172 unqualified addresses in header lines are left alone.
3177 .cindex "configuration options" "extracting"
3178 .cindex "options" "configuration &-- extracting"
3179 If this option is given with no arguments, it causes the values of all Exim's
3180 main configuration options to be written to the standard output. The values
3181 of one or more specific options can be requested by giving their names as
3182 arguments, for example:
3184 exim -bP qualify_domain hold_domains
3186 .cindex "hiding configuration option values"
3187 .cindex "configuration options" "hiding value of"
3188 .cindex "options" "hiding value of"
3189 However, any option setting that is preceded by the word &"hide"& in the
3190 configuration file is not shown in full, except to an admin user. For other
3191 users, the output is as in this example:
3193 mysql_servers = <value not displayable>
3195 If &%config%& is given as an argument, the config is
3196 output, as it was parsed, any include file resolved, any comment removed.
3198 If &%config_file%& is given as an argument, the name of the runtime
3199 configuration file is output. (&%configure_file%& works too, for
3200 backward compatibility.)
3201 If a list of configuration files was supplied, the value that is output here
3202 is the name of the file that was actually used.
3204 .cindex "options" "hiding name of"
3205 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3206 name will not be output.
3208 .cindex "daemon" "process id (pid)"
3209 .cindex "pid (process id)" "of daemon"
3210 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3211 directories where log files and daemon pid files are written are output,
3212 respectively. If these values are unset, log files are written in a
3213 sub-directory of the spool directory called &%log%&, and the pid file is
3214 written directly into the spool directory.
3216 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3218 exim -bP +local_domains
3220 it searches for a matching named list of any type (domain, host, address, or
3221 local part) and outputs what it finds.
3223 .cindex "options" "router &-- extracting"
3224 .cindex "options" "transport &-- extracting"
3225 .cindex "options" "authenticator &-- extracting"
3226 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3227 followed by the name of an appropriate driver instance, the option settings for
3228 that driver are output. For example:
3230 exim -bP transport local_delivery
3232 The generic driver options are output first, followed by the driver's private
3233 options. A list of the names of drivers of a particular type can be obtained by
3234 using one of the words &%router_list%&, &%transport_list%&, or
3235 &%authenticator_list%&, and a complete list of all drivers with their option
3236 settings can be obtained by using &%routers%&, &%transports%&, or
3239 .cindex "environment"
3240 If &%environment%& is given as an argument, the set of environment
3241 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3244 .cindex "options" "macro &-- extracting"
3245 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3246 are available, similarly to the drivers. Because macros are sometimes used
3247 for storing passwords, this option is restricted.
3248 The output format is one item per line.
3249 For the "-bP macro <name>" form, if no such macro is found
3250 the exit status will be nonzero.
3254 .cindex "queue" "listing messages in"
3255 .cindex "listing" "messages in the queue"
3256 This option requests a listing of the contents of the mail queue on the
3257 standard output. If the &%-bp%& option is followed by a list of message ids,
3258 just those messages are listed. By default, this option can be used only by an
3259 admin user. However, the &%queue_list_requires_admin%& option can be set false
3260 to allow any user to see the queue.
3262 Each message in the queue is displayed as in the following example:
3264 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3265 red.king@looking-glass.fict.example
3268 .cindex "message" "size in queue listing"
3269 .cindex "size" "of message"
3270 The first line contains the length of time the message has been in the queue
3271 (in this case 25 minutes), the size of the message (2.9K), the unique local
3272 identifier for the message, and the message sender, as contained in the
3273 envelope. For bounce messages, the sender address is empty, and appears as
3274 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3275 the default sender address, the user's login name is shown in parentheses
3276 before the sender address.
3278 .cindex "frozen messages" "in queue listing"
3279 If the message is frozen (attempts to deliver it are suspended) then the text
3280 &"*** frozen ***"& is displayed at the end of this line.
3282 The recipients of the message (taken from the envelope, not the headers) are
3283 displayed on subsequent lines. Those addresses to which the message has already
3284 been delivered are marked with the letter D. If an original address gets
3285 expanded into several addresses via an alias or forward file, the original is
3286 displayed with a D only when deliveries for all of its child addresses are
3292 This option operates like &%-bp%&, but in addition it shows delivered addresses
3293 that were generated from the original top level address(es) in each message by
3294 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3300 .cindex "queue" "count of messages on"
3301 This option counts the number of messages in the queue, and writes the total
3302 to the standard output. It is restricted to admin users, unless
3303 &%queue_list_requires_admin%& is set false.
3308 This option operates like &%-bp%&, but the output is not sorted into
3309 chronological order of message arrival. This can speed it up when there are
3310 lots of messages in the queue, and is particularly useful if the output is
3311 going to be post-processed in a way that doesn't need the sorting.
3315 This option is a combination of &%-bpr%& and &%-bpa%&.
3319 This option is a combination of &%-bpr%& and &%-bpu%&.
3324 This option operates like &%-bp%& but shows only undelivered top-level
3325 addresses for each message displayed. Addresses generated by aliasing or
3326 forwarding are not shown, unless the message was deferred after processing by a
3327 router with the &%one_time%& option set.
3332 .cindex "testing" "retry configuration"
3333 .cindex "retry" "configuration testing"
3334 This option is for testing retry rules, and it must be followed by up to three
3335 arguments. It causes Exim to look for a retry rule that matches the values
3336 and to write it to the standard output. For example:
3338 exim -brt bach.comp.mus.example
3339 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3341 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3342 argument, which is required, can be a complete address in the form
3343 &'local_part@domain'&, or it can be just a domain name. If the second argument
3344 contains a dot, it is interpreted as an optional second domain name; if no
3345 retry rule is found for the first argument, the second is tried. This ties in
3346 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3347 rule is found that matches the host, one that matches the mail domain is
3348 sought. Finally, an argument that is the name of a specific delivery error, as
3349 used in setting up retry rules, can be given. For example:
3351 exim -brt haydn.comp.mus.example quota_3d
3352 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3357 .cindex "testing" "rewriting"
3358 .cindex "rewriting" "testing"
3359 This option is for testing address rewriting rules, and it must be followed by
3360 a single argument, consisting of either a local part without a domain, or a
3361 complete address with a fully qualified domain. Exim outputs how this address
3362 would be rewritten for each possible place it might appear. See chapter
3363 &<<CHAPrewrite>>& for further details.
3367 .cindex "SMTP" "batched incoming"
3368 .cindex "batched SMTP input"
3369 This option is used for batched SMTP input, which is an alternative interface
3370 for non-interactive local message submission. A number of messages can be
3371 submitted in a single run. However, despite its name, this is not really SMTP
3372 input. Exim reads each message's envelope from SMTP commands on the standard
3373 input, but generates no responses. If the caller is trusted, or
3374 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3375 believed; otherwise the sender is always the caller of Exim.
3377 The message itself is read from the standard input, in SMTP format (leading
3378 dots doubled), terminated by a line containing just a single dot. An error is
3379 provoked if the terminating dot is missing. A further message may then follow.
3381 As for other local message submissions, the contents of incoming batch SMTP
3382 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3383 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3384 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3386 Some other SMTP commands are recognized in the input. HELO and EHLO act
3387 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3388 QUIT quits, ignoring the rest of the standard input.
3390 .cindex "return code" "for &%-bS%&"
3391 If any error is encountered, reports are written to the standard output and
3392 error streams, and Exim gives up immediately. The return code is 0 if no error
3393 was detected; it is 1 if one or more messages were accepted before the error
3394 was detected; otherwise it is 2.
3396 More details of input using batched SMTP are given in section
3397 &<<SECTincomingbatchedSMTP>>&.
3401 .cindex "SMTP" "local input"
3402 .cindex "local SMTP input"
3403 This option causes Exim to accept one or more messages by reading SMTP commands
3404 on the standard input, and producing SMTP replies on the standard output. SMTP
3405 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3406 Some user agents use this interface as a way of passing locally-generated
3407 messages to the MTA.
3410 .cindex "sender" "source of"
3411 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3412 set, the senders of messages are taken from the SMTP MAIL commands.
3413 Otherwise the content of these commands is ignored and the sender is set up as
3414 the calling user. Unqualified addresses are automatically qualified using
3415 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3416 &%-bnq%& option is used.
3420 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3421 using a listening daemon. Exim can distinguish the two cases by checking
3422 whether the standard input is a TCP/IP socket. When Exim is called from
3423 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3424 above concerning senders and qualification do not apply. In this situation,
3425 Exim behaves in exactly the same way as it does when receiving a message via
3426 the listening daemon.
3430 .cindex "testing" "addresses"
3431 .cindex "address" "testing"
3432 This option runs Exim in address testing mode, in which each argument is taken
3433 as a recipient address to be tested for deliverability. The results are
3434 written to the standard output. If a test fails, and the caller is not an admin
3435 user, no details of the failure are output, because these might contain
3436 sensitive information such as usernames and passwords for database lookups.
3438 If no arguments are given, Exim runs in an interactive manner, prompting with a
3439 right angle bracket for addresses to be tested.
3441 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3442 &[readline()]& function, because it is running as &'root'& and there are
3445 Each address is handled as if it were the recipient address of a message
3446 (compare the &%-bv%& option). It is passed to the routers and the result is
3447 written to the standard output. However, any router that has
3448 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3449 genuine routing tests if your first router passes everything to a scanner
3452 .cindex "return code" "for &%-bt%&"
3453 The return code is 2 if any address failed outright; it is 1 if no address
3454 failed outright but at least one could not be resolved for some reason. Return
3455 code 0 is given only when all addresses succeed.
3457 .cindex "duplicate addresses"
3458 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3459 addresses after routing is complete, so that only one delivery takes place.
3460 This does not happen when testing with &%-bt%&; the full results of routing are
3463 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3464 routers in the configuration makes any tests on the sender address of a
3466 .oindex "&%-f%&" "for address testing"
3467 you can use the &%-f%& option to set an appropriate sender when running
3468 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3469 default qualifying domain. However, if you have set up (for example) routers
3470 whose behaviour depends on the contents of an incoming message, you cannot test
3471 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3476 .cindex "version number of Exim"
3477 This option causes Exim to write the current version number, compilation
3478 number, and compilation date of the &'exim'& binary to the standard output.
3479 It also lists the DBM library that is being used, the optional modules (such as
3480 specific lookup types), the drivers that are included in the binary, and the
3481 name of the runtime configuration file that is in use.
3483 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3484 configuration file. However, this is a static check only. It cannot check
3485 values that are to be expanded. For example, although a misspelt ACL verb is
3486 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3487 alone to discover (for example) all the typos in the configuration; some
3488 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3489 dynamic testing facilities.
3493 .cindex "verifying address" "using &%-bv%&"
3494 .cindex "address" "verification"
3495 This option runs Exim in address verification mode, in which each argument is
3496 taken as a recipient address to be verified by the routers. (This does
3497 not involve any verification callouts). During normal operation, verification
3498 happens mostly as a consequence processing a &%verify%& condition in an ACL
3499 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3500 including callouts, see the &%-bh%& and &%-bhc%& options.
3502 If verification fails, and the caller is not an admin user, no details of the
3503 failure are output, because these might contain sensitive information such as
3504 usernames and passwords for database lookups.
3506 If no arguments are given, Exim runs in an interactive manner, prompting with a
3507 right angle bracket for addresses to be verified.
3509 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3510 &[readline()]& function, because it is running as &'exim'& and there are
3513 Verification differs from address testing (the &%-bt%& option) in that routers
3514 that have &%no_verify%& set are skipped, and if the address is accepted by a
3515 router that has &%fail_verify%& set, verification fails. The address is
3516 verified as a recipient if &%-bv%& is used; to test verification for a sender
3517 address, &%-bvs%& should be used.
3519 If the &%-v%& option is not set, the output consists of a single line for each
3520 address, stating whether it was verified or not, and giving a reason in the
3521 latter case. Without &%-v%&, generating more than one address by redirection
3522 causes verification to end successfully, without considering the generated
3523 addresses. However, if just one address is generated, processing continues,
3524 and the generated address must verify successfully for the overall verification
3527 When &%-v%& is set, more details are given of how the address has been handled,
3528 and in the case of address redirection, all the generated addresses are also
3529 considered. Verification may succeed for some and fail for others.
3532 .cindex "return code" "for &%-bv%&"
3533 return code is 2 if any address failed outright; it is 1 if no address
3534 failed outright but at least one could not be resolved for some reason. Return
3535 code 0 is given only when all addresses succeed.
3537 If any of the routers in the configuration makes any tests on the sender
3538 address of a message, you should use the &%-f%& option to set an appropriate
3539 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3540 calling user at the default qualifying domain.
3544 This option acts like &%-bv%&, but verifies the address as a sender rather
3545 than a recipient address. This affects any rewriting and qualification that
3552 .cindex "inetd" "wait mode"
3553 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3554 similarly to the &%-bd%& option. All port specifications on the command-line
3555 and in the configuration file are ignored. Queue-running may not be specified.
3557 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3558 listening for connections. This permits the system to start up and have
3559 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3560 each port only when the first connection is received.
3562 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3563 which the daemon will exit, which should cause inetd to listen once more.
3565 .vitem &%-C%&&~<&'filelist'&>
3567 .cindex "configuration file" "alternate"
3568 .cindex "CONFIGURE_FILE"
3569 .cindex "alternate configuration file"
3570 This option causes Exim to find the runtime configuration file from the given
3571 list instead of from the list specified by the CONFIGURE_FILE
3572 compile-time setting. Usually, the list will consist of just a single filename,
3573 but it can be a colon-separated list of names. In this case, the first
3574 file that exists is used. Failure to open an existing file stops Exim from
3575 proceeding any further along the list, and an error is generated.
3577 When this option is used by a caller other than root, and the list is different
3578 from the compiled-in list, Exim gives up its root privilege immediately, and
3579 runs with the real and effective uid and gid set to those of the caller.
3580 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3581 file contains a list of full pathnames, one per line, for configuration files
3582 which are trusted. Root privilege is retained for any configuration file so
3583 listed, as long as the caller is the Exim user (or the user specified in the
3584 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3585 not writeable by inappropriate users or groups.
3587 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3588 configuration using &%-C%& right through message reception and delivery,
3589 even if the caller is root. The reception works, but by that time, Exim is
3590 running as the Exim user, so when it re-executes to regain privilege for the
3591 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3592 test reception and delivery using two separate commands (one to put a message
3593 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3595 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3596 prefix string with which any file named in a &%-C%& command line option
3597 must start. In addition, the filename must not contain the sequence &`/../`&.
3598 However, if the value of the &%-C%& option is identical to the value of
3599 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3600 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3601 unset, any filename can be used with &%-C%&.
3603 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3604 to a directory to which only root has access. This prevents someone who has
3605 broken into the Exim account from running a privileged Exim with an arbitrary
3608 The &%-C%& facility is useful for ensuring that configuration files are
3609 syntactically correct, but cannot be used for test deliveries, unless the
3610 caller is privileged, or unless it is an exotic configuration that does not
3611 require privilege. No check is made on the owner or group of the files
3612 specified by this option.
3615 .vitem &%-D%&<&'macro'&>=<&'value'&>
3617 .cindex "macro" "setting on command line"
3618 This option can be used to override macro definitions in the configuration file
3619 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3620 unprivileged caller, it causes Exim to give up its root privilege.
3621 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3622 completely disabled, and its use causes an immediate error exit.
3624 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3625 colon-separated list of macros which are considered safe and, if &%-D%& only
3626 supplies macros from this list, and the values are acceptable, then Exim will
3627 not give up root privilege if the caller is root, the Exim run-time user, or
3628 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3629 to be removed in the future. Acceptable values for the macros satisfy the
3630 regexp: &`^[A-Za-z0-9_/.-]*$`&
3632 The entire option (including equals sign if present) must all be within one
3633 command line item. &%-D%& can be used to set the value of a macro to the empty
3634 string, in which case the equals sign is optional. These two commands are
3640 To include spaces in a macro definition item, quotes must be used. If you use
3641 quotes, spaces are permitted around the macro name and the equals sign. For
3644 exim '-D ABC = something' ...
3646 &%-D%& may be repeated up to 10 times on a command line.
3647 Only macro names up to 22 letters long can be set.
3650 .vitem &%-d%&<&'debug&~options'&>
3652 .cindex "debugging" "list of selectors"
3653 .cindex "debugging" "&%-d%& option"
3654 This option causes debugging information to be written to the standard
3655 error stream. It is restricted to admin users because debugging output may show
3656 database queries that contain password information. Also, the details of users'
3657 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3658 writes an error message to the standard error stream and exits with a non-zero
3661 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3662 standard debugging data is output. This can be reduced, or increased to include
3663 some more rarely needed information, by directly following &%-d%& with a string
3664 made up of names preceded by plus or minus characters. These add or remove sets
3665 of debugging data, respectively. For example, &%-d+filter%& adds filter
3666 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3667 no spaces are allowed in the debug setting. The available debugging categories
3670 &`acl `& ACL interpretation
3671 &`auth `& authenticators
3672 &`deliver `& general delivery logic
3673 &`dns `& DNS lookups (see also resolver)
3674 &`dnsbl `& DNS black list (aka RBL) code
3675 &`exec `& arguments for &[execv()]& calls
3676 &`expand `& detailed debugging for string expansions
3677 &`filter `& filter handling
3678 &`hints_lookup `& hints data lookups
3679 &`host_lookup `& all types of name-to-IP address handling
3680 &`ident `& ident lookup
3681 &`interface `& lists of local interfaces
3682 &`lists `& matching things in lists
3683 &`load `& system load checks
3684 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3685 &<<CHAPlocalscan>>&)
3686 &`lookup `& general lookup code and all lookups
3687 &`memory `& memory handling
3688 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3689 &`pid `& modifier: add pid to debug output lines
3690 &`process_info `& setting info for the process log
3691 &`queue_run `& queue runs
3692 &`receive `& general message reception logic
3693 &`resolver `& turn on the DNS resolver's debugging output
3694 &`retry `& retry handling
3695 &`rewrite `& address rewriting
3696 &`route `& address routing
3697 &`timestamp `& modifier: add timestamp to debug output lines
3699 &`transport `& transports
3700 &`uid `& changes of uid/gid and looking up uid/gid
3701 &`verify `& address verification logic
3702 &`all `& almost all of the above (see below), and also &%-v%&
3704 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3705 for &`-all`&. The reason for this is that &`+all`& is something that people
3706 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3707 is included, an awful lot of output that is very rarely of interest is
3708 generated, so it now has to be explicitly requested. However, &`-all`& does
3709 turn everything off.
3711 .cindex "resolver, debugging output"
3712 .cindex "DNS resolver, debugging output"
3713 The &`resolver`& option produces output only if the DNS resolver was compiled
3714 with DEBUG enabled. This is not the case in some operating systems. Also,
3715 unfortunately, debugging output from the DNS resolver is written to stdout
3718 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3719 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3720 However, the &`pid`& selector is forced when debugging is turned on for a
3721 daemon, which then passes it on to any re-executed Exims. Exim also
3722 automatically adds the pid to debug lines when several remote deliveries are
3725 The &`timestamp`& selector causes the current time to be inserted at the start
3726 of all debug output lines. This can be useful when trying to track down delays
3729 .cindex debugging "UTF-8 in"
3730 .cindex UTF-8 "in debug output"
3731 The &`noutf8`& selector disables the use of
3732 UTF-8 line-drawing characters to group related information.
3733 When disabled. ascii-art is used instead.
3734 Using the &`+all`& option does not set this modifier,
3736 If the &%debug_print%& option is set in any driver, it produces output whenever
3737 any debugging is selected, or if &%-v%& is used.
3739 .vitem &%-dd%&<&'debug&~options'&>
3741 This option behaves exactly like &%-d%& except when used on a command that
3742 starts a daemon process. In that case, debugging is turned off for the
3743 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3744 behaviour of the daemon without creating as much output as full debugging does.
3747 .oindex "&%-dropcr%&"
3748 This is an obsolete option that is now a no-op. It used to affect the way Exim
3749 handled CR and LF characters in incoming messages. What happens now is
3750 described in section &<<SECTlineendings>>&.
3754 .cindex "bounce message" "generating"
3755 This option specifies that an incoming message is a locally-generated delivery
3756 failure report. It is used internally by Exim when handling delivery failures
3757 and is not intended for external use. Its only effect is to stop Exim
3758 generating certain messages to the postmaster, as otherwise message cascades
3759 could occur in some situations. As part of the same option, a message id may
3760 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3761 new message contains the id, following &"R="&, as a cross-reference.
3764 .oindex "&%-e%&&'x'&"
3765 There are a number of Sendmail options starting with &%-oe%& which seem to be
3766 called by various programs without the leading &%o%& in the option. For
3767 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3768 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3770 .vitem &%-F%&&~<&'string'&>
3772 .cindex "sender" "name"
3773 .cindex "name" "of sender"
3774 This option sets the sender's full name for use when a locally-generated
3775 message is being accepted. In the absence of this option, the user's &'gecos'&
3776 entry from the password data is used. As users are generally permitted to alter
3777 their &'gecos'& entries, no security considerations are involved. White space
3778 between &%-F%& and the <&'string'&> is optional.
3780 .vitem &%-f%&&~<&'address'&>
3782 .cindex "sender" "address"
3783 .cindex "address" "sender"
3784 .cindex "trusted users"
3785 .cindex "envelope from"
3786 .cindex "envelope sender"
3787 .cindex "user" "trusted"
3788 This option sets the address of the envelope sender of a locally-generated
3789 message (also known as the return path). The option can normally be used only
3790 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3793 Processes running as root or the Exim user are always trusted. Other
3794 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3795 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3796 of a local message is set to the caller's login name at the default qualify
3799 There is one exception to the restriction on the use of &%-f%&: an empty sender
3800 can be specified by any user, trusted or not, to create a message that can
3801 never provoke a bounce. An empty sender can be specified either as an empty
3802 string, or as a pair of angle brackets with nothing between them, as in these
3803 examples of shell commands:
3805 exim -f '<>' user@domain
3806 exim -f "" user@domain
3808 In addition, the use of &%-f%& is not restricted when testing a filter file
3809 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3812 Allowing untrusted users to change the sender address does not of itself make
3813 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3814 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3815 though this can be overridden by setting &%no_local_from_check%&.
3818 .cindex "&""From""& line"
3819 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3820 given as two arguments or one combined argument). The sender of a
3821 locally-generated message can also be set (when permitted) by an initial
3822 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3823 if &%-f%& is also present, it overrides &"From&~"&.
3827 .cindex "submission fixups, suppressing (command-line)"
3828 This option is equivalent to an ACL applying:
3830 control = suppress_local_fixups
3832 for every message received. Note that Sendmail will complain about such
3833 bad formatting, where Exim silently just does not fix it up. This may change
3836 As this affects audit information, the caller must be a trusted user to use
3839 .vitem &%-h%&&~<&'number'&>
3841 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3842 This option is accepted for compatibility with Sendmail, but has no effect. (In
3843 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3848 .cindex "Solaris" "&'mail'& command"
3849 .cindex "dot" "in incoming non-SMTP message"
3850 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3851 line by itself should not terminate an incoming, non-SMTP message. I can find
3852 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3853 command in Solaris 2.4 uses it. See also &%-ti%&.
3855 .vitem &%-L%&&~<&'tag'&>
3857 .cindex "syslog" "process name; set with flag"
3858 This option is equivalent to setting &%syslog_processname%& in the config
3859 file and setting &%log_file_path%& to &`syslog`&.
3860 Its use is restricted to administrators. The configuration file has to be
3861 read and parsed, to determine access rights, before this is set and takes
3862 effect, so early configuration file errors will not honour this flag.
3864 The tag should not be longer than 32 characters.
3866 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3868 .cindex "forcing delivery"
3869 .cindex "delivery" "forcing attempt"
3870 .cindex "frozen messages" "forcing delivery"
3871 This option requests Exim to run a delivery attempt on each message in turn. If
3872 any of the messages are frozen, they are automatically thawed before the
3873 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3874 and &%hold_domains%& are ignored.
3877 .cindex "hints database" "overriding retry hints"
3878 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3879 the normal retry time has not yet been reached. This option requires the caller
3880 to be an admin user. However, there is an option called &%prod_requires_admin%&
3881 which can be set false to relax this restriction (and also the same requirement
3882 for the &%-q%&, &%-R%&, and &%-S%& options).
3884 The deliveries happen synchronously, that is, the original Exim process does
3885 not terminate until all the delivery attempts have finished. No output is
3886 produced unless there is a serious error. If you want to see what is happening,
3887 use the &%-v%& option as well, or inspect Exim's main log.
3889 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3891 .cindex "message" "adding recipients"
3892 .cindex "recipient" "adding"
3893 This option requests Exim to add the addresses to the list of recipients of the
3894 message (&"ar"& for &"add recipients"&). The first argument must be a message
3895 id, and the remaining ones must be email addresses. However, if the message is
3896 active (in the middle of a delivery attempt), it is not altered. This option
3897 can be used only by an admin user.
3899 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3901 &~<&'sequence&~number'&>&&&
3902 &~<&'message&~id'&>"
3904 .cindex "SMTP" "passed connection"
3905 .cindex "SMTP" "multiple deliveries"
3906 .cindex "multiple SMTP deliveries"
3907 This option is not intended for use by external callers. It is used internally
3908 by Exim to invoke another instance of itself to deliver a waiting message using
3909 an existing SMTP connection, which is passed as the standard input. Details are
3910 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3911 must be root or the Exim user in order to use it.
3915 This option is not intended for use by external callers. It is used internally
3916 by Exim in conjunction with the &%-MC%& option. It signifies that the
3917 connection to the remote host has been authenticated.
3921 This option is not intended for use by external callers. It is used internally
3922 by Exim in conjunction with the &%-MC%& option. It signifies that the
3923 remote host supports the ESMTP &_DSN_& extension.
3927 This option is not intended for use by external callers. It is used internally
3928 by Exim in conjunction with the &%-d%& option
3929 to pass on an information string on the purpose of the process.
3931 .vitem &%-MCG%&&~<&'queue&~name'&>
3933 This option is not intended for use by external callers. It is used internally
3934 by Exim in conjunction with the &%-MC%& option. It signifies that an
3935 alternate queue is used, named by the following argument.
3939 This option is not intended for use by external callers. It is used internally
3940 by Exim in conjunction with the &%-MC%& option. It signifies that a
3941 remote host supports the ESMTP &_CHUNKING_& extension.
3945 This option is not intended for use by external callers. It is used internally
3946 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3947 which Exim is connected supports pipelining.
3952 This option is not intended for use by external callers. It is used internally
3953 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3954 t a remote server is via a SOCKS proxy, using addresses and ports given by
3955 the following four arguments.
3958 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3960 This option is not intended for use by external callers. It is used internally
3961 by Exim in conjunction with the &%-MC%& option when the original delivery was
3962 started by a queue runner. It passes on the process id of the queue runner,
3963 together with the file descriptor number of an open pipe. Closure of the pipe
3964 signals the final completion of the sequence of processes that are passing
3965 messages through the same SMTP connection.
3968 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3970 This option is not intended for use by external callers. It is used internally
3971 by Exim to implement quota checking for local users.
3976 This option is not intended for use by external callers. It is used internally
3977 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3978 ESMTP SIZE option should be used on messages delivered down the existing
3983 This option is not intended for use by external callers. It is used internally
3984 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3985 host to which Exim is connected supports TLS encryption.
3988 .vitem &%-MCr%&&~<&'SNI'&> &&&
3992 These options are not intended for use by external callers. It is used internally
3993 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
3994 a TLS Server Name Indication was sent as part of the channel establishment.
3995 The argument gives the SNI string.
3996 The "r" variant indicates a DANE-verified connection.
3999 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
4001 This option is not intended for use by external callers. It is used internally
4002 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4003 connection is being proxied by a parent process for handling TLS encryption.
4004 The arguments give the local address and port being proxied, and the TLS cipher.
4006 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4008 .cindex "hints database" "not overridden by &%-Mc%&"
4009 .cindex "delivery" "manually started &-- not forced"
4010 This option requests Exim to run a delivery attempt on each message, in turn,
4011 but unlike the &%-M%& option, it does check for retry hints, and respects any
4012 that are found. This option is not very useful to external callers. It is
4013 provided mainly for internal use by Exim when it needs to re-invoke itself in
4014 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
4015 However, &%-Mc%& can be useful when testing, in order to run a delivery that
4016 respects retry times and other options such as &%hold_domains%& that are
4017 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
4018 If you want to run a specific delivery as if in a queue run, you should use
4019 &%-q%& with a message id argument. A distinction between queue run deliveries
4020 and other deliveries is made in one or two places.
4022 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
4024 .cindex "message" "changing sender"
4025 .cindex "sender" "changing"
4026 This option requests Exim to change the sender address in the message to the
4027 given address, which must be a fully qualified address or &"<>"& (&"es"& for
4028 &"edit sender"&). There must be exactly two arguments. The first argument must
4029 be a message id, and the second one an email address. However, if the message
4030 is active (in the middle of a delivery attempt), its status is not altered.
4031 This option can be used only by an admin user.
4033 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4035 .cindex "freezing messages"
4036 .cindex "message" "manually freezing"
4037 This option requests Exim to mark each listed message as &"frozen"&. This
4038 prevents any delivery attempts taking place until the message is &"thawed"&,
4039 either manually or as a result of the &%auto_thaw%& configuration option.
4040 However, if any of the messages are active (in the middle of a delivery
4041 attempt), their status is not altered. This option can be used only by an admin
4044 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4046 .cindex "giving up on messages"
4047 .cindex "message" "abandoning delivery attempts"
4048 .cindex "delivery" "abandoning further attempts"
4049 This option requests Exim to give up trying to deliver the listed messages,
4050 including any that are frozen. However, if any of the messages are active,
4051 their status is not altered. For non-bounce messages, a delivery error message
4052 is sent to the sender, containing the text &"cancelled by administrator"&.
4053 Bounce messages are just discarded. This option can be used only by an admin
4056 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4059 .cindex "named queues" "moving messages"
4060 .cindex "queue" "moving messages"
4061 This option requests that each listed message be moved from its current
4062 queue to the given named queue.
4063 The destination queue name argument is required, but can be an empty
4064 string to define the default queue.
4065 If the messages are not currently located in the default queue,
4066 a &%-qG<name>%& option will be required to define the source queue.
4068 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4070 .cindex "delivery" "cancelling all"
4071 This option requests Exim to mark all the recipient addresses in the messages
4072 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4073 message is active (in the middle of a delivery attempt), its status is not
4074 altered. This option can be used only by an admin user.
4076 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4078 .cindex "delivery" "cancelling by address"
4079 .cindex "recipient" "removing"
4080 .cindex "removing recipients"
4081 This option requests Exim to mark the given addresses as already delivered
4082 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4083 the remaining ones must be email addresses. These are matched to recipient
4084 addresses in the message in a case-sensitive manner. If the message is active
4085 (in the middle of a delivery attempt), its status is not altered. This option
4086 can be used only by an admin user.
4088 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4090 .cindex "removing messages"
4091 .cindex "abandoning mail"
4092 .cindex "message" "manually discarding"
4093 This option requests Exim to remove the given messages from the queue. No
4094 bounce messages are sent; each message is simply forgotten. However, if any of
4095 the messages are active, their status is not altered. This option can be used
4096 only by an admin user or by the user who originally caused the message to be
4097 placed in the queue.
4102 . .cindex REQUIRETLS
4103 . This option is used to request REQUIRETLS processing on the message.
4104 . It is used internally by Exim in conjunction with -E when generating
4108 .vitem &%-Mset%&&~<&'message&~id'&>
4110 .cindex "testing" "string expansion"
4111 .cindex "expansion" "testing"
4112 This option is useful only in conjunction with &%-be%& (that is, when testing
4113 string expansions). Exim loads the given message from its spool before doing
4114 the test expansions, thus setting message-specific variables such as
4115 &$message_size$& and the header variables. The &$recipients$& variable is made
4116 available. This feature is provided to make it easier to test expansions that
4117 make use of these variables. However, this option can be used only by an admin
4118 user. See also &%-bem%&.
4120 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4122 .cindex "thawing messages"
4123 .cindex "unfreezing messages"
4124 .cindex "frozen messages" "thawing"
4125 .cindex "message" "thawing frozen"
4126 This option requests Exim to &"thaw"& any of the listed messages that are
4127 &"frozen"&, so that delivery attempts can resume. However, if any of the
4128 messages are active, their status is not altered. This option can be used only
4131 .vitem &%-Mvb%&&~<&'message&~id'&>
4133 .cindex "listing" "message body"
4134 .cindex "message" "listing body of"
4135 This option causes the contents of the message body (-D) spool file to be
4136 written to the standard output. This option can be used only by an admin user.
4138 .vitem &%-Mvc%&&~<&'message&~id'&>
4140 .cindex "message" "listing in RFC 2822 format"
4141 .cindex "listing" "message in RFC 2822 format"
4142 This option causes a copy of the complete message (header lines plus body) to
4143 be written to the standard output in RFC 2822 format. This option can be used
4144 only by an admin user.
4146 .vitem &%-Mvh%&&~<&'message&~id'&>
4148 .cindex "listing" "message headers"
4149 .cindex "header lines" "listing"
4150 .cindex "message" "listing header lines"
4151 This option causes the contents of the message headers (-H) spool file to be
4152 written to the standard output. This option can be used only by an admin user.
4154 .vitem &%-Mvl%&&~<&'message&~id'&>
4156 .cindex "listing" "message log"
4157 .cindex "message" "listing message log"
4158 This option causes the contents of the message log spool file to be written to
4159 the standard output. This option can be used only by an admin user.
4163 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4164 treats it that way too.
4168 .cindex "debugging" "&%-N%& option"
4169 .cindex "debugging" "suppressing delivery"
4170 This is a debugging option that inhibits delivery of a message at the transport
4171 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4172 it just doesn't actually transport the message, but instead behaves as if it
4173 had successfully done so. However, it does not make any updates to the retry
4174 database, and the log entries for deliveries are flagged with &"*>"& rather
4177 Because &%-N%& discards any message to which it applies, only root or the Exim
4178 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4179 words, an ordinary user can use it only when supplying an incoming message to
4180 which it will apply. Although transportation never fails when &%-N%& is set, an
4181 address may be deferred because of a configuration problem on a transport, or a
4182 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4183 the message, and applies to any subsequent delivery attempts that may happen
4188 This option is interpreted by Sendmail to mean &"no aliasing"&.
4189 For normal modes of operation, it is ignored by Exim.
4190 When combined with &%-bP%& it makes the output more terse (suppresses
4191 option names, environment values and config pretty printing).
4193 .vitem &%-O%&&~<&'data'&>
4195 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4198 .vitem &%-oA%&&~<&'file&~name'&>
4200 .cindex "Sendmail compatibility" "&%-oA%& option"
4201 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4202 alternative alias filename. Exim handles &%-bi%& differently; see the
4205 .vitem &%-oB%&&~<&'n'&>
4207 .cindex "SMTP" "passed connection"
4208 .cindex "SMTP" "multiple deliveries"
4209 .cindex "multiple SMTP deliveries"
4210 This is a debugging option which limits the maximum number of messages that can
4211 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4212 transport. If <&'n'&> is omitted, the limit is set to 1.
4216 .cindex "background delivery"
4217 .cindex "delivery" "in the background"
4218 This option applies to all modes in which Exim accepts incoming messages,
4219 including the listening daemon. It requests &"background"& delivery of such
4220 messages, which means that the accepting process automatically starts a
4221 delivery process for each message received, but does not wait for the delivery
4222 processes to finish.
4224 When all the messages have been received, the reception process exits,
4225 leaving the delivery processes to finish in their own time. The standard output
4226 and error streams are closed at the start of each delivery process.
4227 This is the default action if none of the &%-od%& options are present.
4229 If one of the queueing options in the configuration file
4230 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4231 overrides it if &%queue_only_override%& is set true, which is the default
4232 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4236 .cindex "foreground delivery"
4237 .cindex "delivery" "in the foreground"
4238 This option requests &"foreground"& (synchronous) delivery when Exim has
4239 accepted a locally-generated message. (For the daemon it is exactly the same as
4240 &%-odb%&.) A delivery process is automatically started to deliver the message,
4241 and Exim waits for it to complete before proceeding.
4243 The original Exim reception process does not finish until the delivery
4244 process for the final message has ended. The standard error stream is left open
4247 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4248 false and one of the queueing options in the configuration file is in effect.
4250 If there is a temporary delivery error during foreground delivery, the
4251 message is left in the queue for later delivery, and the original reception
4252 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4253 restricted configuration that never queues messages.
4258 This option is synonymous with &%-odf%&. It is provided for compatibility with
4263 .cindex "non-immediate delivery"
4264 .cindex "delivery" "suppressing immediate"
4265 .cindex "queueing incoming messages"
4266 This option applies to all modes in which Exim accepts incoming messages,
4267 including the listening daemon. It specifies that the accepting process should
4268 not automatically start a delivery process for each message received. Messages
4269 are placed in the queue, and remain there until a subsequent queue runner
4270 process encounters them. There are several configuration options (such as
4271 &%queue_only%&) that can be used to queue incoming messages under certain
4272 conditions. This option overrides all of them and also &%-odqs%&. It always
4277 .cindex "SMTP" "delaying delivery"
4278 .cindex "first pass routing"
4279 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4280 However, like &%-odb%& and &%-odi%&, this option has no effect if
4281 &%queue_only_override%& is false and one of the queueing options in the
4282 configuration file is in effect.
4284 When &%-odqs%& does operate, a delivery process is started for each incoming
4285 message, in the background by default, but in the foreground if &%-odi%& is
4286 also present. The recipient addresses are routed, and local deliveries are done
4287 in the normal way. However, if any SMTP deliveries are required, they are not
4288 done at this time, so the message remains in the queue until a subsequent queue
4289 runner process encounters it. Because routing was done, Exim knows which
4290 messages are waiting for which hosts, and so a number of messages for the same
4291 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4292 configuration option has the same effect for specific domains. See also the
4297 .cindex "error" "reporting"
4298 If an error is detected while a non-SMTP message is being received (for
4299 example, a malformed address), the error is reported to the sender in a mail
4302 .cindex "return code" "for &%-oee%&"
4304 this error message is successfully sent, the Exim receiving process
4305 exits with a return code of zero. If not, the return code is 2 if the problem
4306 is that the original message has no recipients, or 1 for any other error.
4307 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4311 .cindex "error" "reporting"
4312 .cindex "return code" "for &%-oem%&"
4313 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4314 return code, whether or not the error message was successfully sent.
4315 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4319 .cindex "error" "reporting"
4320 If an error is detected while a non-SMTP message is being received, the
4321 error is reported by writing a message to the standard error file (stderr).
4322 .cindex "return code" "for &%-oep%&"
4323 The return code is 1 for all errors.
4327 .cindex "error" "reporting"
4328 This option is supported for compatibility with Sendmail, but has the same
4333 .cindex "error" "reporting"
4334 This option is supported for compatibility with Sendmail, but has the same
4339 .cindex "dot" "in incoming non-SMTP message"
4340 This option, which has the same effect as &%-i%&, specifies that a dot on a
4341 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4342 single dot does terminate, though Exim does no special processing for other
4343 lines that start with a dot. This option is set by default if Exim is called as
4344 &'rmail'&. See also &%-ti%&.
4347 .oindex "&%-oitrue%&"
4348 This option is treated as synonymous with &%-oi%&.
4350 .vitem &%-oMa%&&~<&'host&~address'&>
4352 .cindex "sender" "host address, specifying for local message"
4353 A number of options starting with &%-oM%& can be used to set values associated
4354 with remote hosts on locally-submitted messages (that is, messages not received
4355 over TCP/IP). These options can be used by any caller in conjunction with the
4356 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4357 other circumstances, they are ignored unless the caller is trusted.
4359 The &%-oMa%& option sets the sender host address. This may include a port
4360 number at the end, after a full stop (period). For example:
4362 exim -bs -oMa 10.9.8.7.1234
4364 An alternative syntax is to enclose the IP address in square brackets,
4365 followed by a colon and the port number:
4367 exim -bs -oMa [10.9.8.7]:1234
4369 The IP address is placed in the &$sender_host_address$& variable, and the
4370 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4371 are present on the command line, the sender host IP address is taken from
4372 whichever one is last.
4374 .vitem &%-oMaa%&&~<&'name'&>
4376 .cindex "authentication" "name, specifying for local message"
4377 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4378 option sets the value of &$sender_host_authenticated$& (the authenticator
4379 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4380 This option can be used with &%-bh%& and &%-bs%& to set up an
4381 authenticated SMTP session without actually using the SMTP AUTH command.
4383 .vitem &%-oMai%&&~<&'string'&>
4385 .cindex "authentication" "id, specifying for local message"
4386 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4387 option sets the value of &$authenticated_id$& (the id that was authenticated).
4388 This overrides the default value (the caller's login id, except with &%-bh%&,
4389 where there is no default) for messages from local sources. See chapter
4390 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4392 .vitem &%-oMas%&&~<&'address'&>
4394 .cindex "authentication" "sender, specifying for local message"
4395 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4396 option sets the authenticated sender value in &$authenticated_sender$&. It
4397 overrides the sender address that is created from the caller's login id for
4398 messages from local sources, except when &%-bh%& is used, when there is no
4399 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4400 specified on a MAIL command overrides this value. See chapter
4401 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4403 .vitem &%-oMi%&&~<&'interface&~address'&>
4405 .cindex "interface" "address, specifying for local message"
4406 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4407 option sets the IP interface address value. A port number may be included,
4408 using the same syntax as for &%-oMa%&. The interface address is placed in
4409 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4411 .vitem &%-oMm%&&~<&'message&~reference'&>
4413 .cindex "message reference" "message reference, specifying for local message"
4414 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4415 option sets the message reference, e.g. message-id, and is logged during
4416 delivery. This is useful when some kind of audit trail is required to tie
4417 messages together. The format of the message reference is checked and will
4418 abort if the format is invalid. The option will only be accepted if exim is
4419 running in trusted mode, not as any regular user.
4421 The best example of a message reference is when Exim sends a bounce message.
4422 The message reference is the message-id of the original message for which Exim
4423 is sending the bounce.
4425 .vitem &%-oMr%&&~<&'protocol&~name'&>
4427 .cindex "protocol, specifying for local message"
4428 .vindex "&$received_protocol$&"
4429 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4430 option sets the received protocol value that is stored in
4431 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4432 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4433 SMTP protocol names (see the description of &$received_protocol$& in section
4434 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4435 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4436 be set by &%-oMr%&. Repeated use of this option is not supported.
4438 .vitem &%-oMs%&&~<&'host&~name'&>
4440 .cindex "sender" "host name, specifying for local message"
4441 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4442 option sets the sender host name in &$sender_host_name$&. When this option is
4443 present, Exim does not attempt to look up a host name from an IP address; it
4444 uses the name it is given.
4446 .vitem &%-oMt%&&~<&'ident&~string'&>
4448 .cindex "sender" "ident string, specifying for local message"
4449 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4450 option sets the sender ident value in &$sender_ident$&. The default setting for
4451 local callers is the login id of the calling process, except when &%-bh%& is
4452 used, when there is no default.
4456 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4457 In Sendmail, this option means &"me too"&, indicating that the sender of a
4458 message should receive a copy of the message if the sender appears in an alias
4459 expansion. Exim always does this, so the option does nothing.
4463 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4464 This option is ignored. In Sendmail it specifies &"old style headers"&,
4465 whatever that means.
4467 .vitem &%-oP%&&~<&'path'&>
4469 .cindex "pid (process id)" "of daemon"
4470 .cindex "daemon" "process id (pid)"
4471 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4472 value. The option specifies the file to which the process id of the daemon is
4473 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4474 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4475 because in those cases, the normal pid file is not used.
4479 .cindex "pid (process id)" "of daemon"
4480 .cindex "daemon" "process id (pid)"
4481 This option is not intended for general use.
4482 The daemon uses it when terminating due to a SIGTEM, possibly in
4483 combination with &%-oP%&&~<&'path'&>.
4484 It causes the pid file to be removed.
4486 .vitem &%-or%&&~<&'time'&>
4488 .cindex "timeout" "for non-SMTP input"
4489 This option sets a timeout value for incoming non-SMTP messages. If it is not
4490 set, Exim will wait forever for the standard input. The value can also be set
4491 by the &%receive_timeout%& option. The format used for specifying times is
4492 described in section &<<SECTtimeformat>>&.
4494 .vitem &%-os%&&~<&'time'&>
4496 .cindex "timeout" "for SMTP input"
4497 .cindex "SMTP" "input timeout"
4498 This option sets a timeout value for incoming SMTP messages. The timeout
4499 applies to each SMTP command and block of data. The value can also be set by
4500 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4501 for specifying times is described in section &<<SECTtimeformat>>&.
4505 This option has exactly the same effect as &%-v%&.
4507 .vitem &%-oX%&&~<&'number&~or&~string'&>
4509 .cindex "TCP/IP" "setting listening ports"
4510 .cindex "TCP/IP" "setting listening interfaces"
4511 .cindex "port" "receiving TCP/IP"
4512 This option is relevant only when the &%-bd%& (start listening daemon) option
4513 is also given. It controls which ports and interfaces the daemon uses. Details
4514 of the syntax, and how it interacts with configuration file options, are given
4515 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4516 file is written unless &%-oP%& is also present to specify a pid filename.
4521 .cindex "daemon notifier socket"
4522 This option controls the creation of an inter-process communications endpoint
4524 It is only relevant when the &%-bd%& (start listening daemon) option is also
4526 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4527 option is also present.
4528 If this option is given then the socket will not be created. This could be
4529 required if the system is running multiple daemons.
4531 The socket is currently used for
4533 fast ramp-up of queue runner processes
4535 obtaining a current queue size
4541 .cindex "Perl" "starting the interpreter"
4542 This option applies when an embedded Perl interpreter is linked with Exim (see
4543 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4544 option, forcing the starting of the interpreter to be delayed until it is
4549 .cindex "Perl" "starting the interpreter"
4550 This option applies when an embedded Perl interpreter is linked with Exim (see
4551 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4552 option, forcing the starting of the interpreter to occur as soon as Exim is
4555 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4557 For compatibility with Sendmail, this option is equivalent to
4559 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4561 It sets the incoming protocol and host name (for trusted callers). The
4562 host name and its colon can be omitted when only the protocol is to be set.
4563 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4564 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4565 or &`s`& using this option (but that does not seem a real limitation).
4566 Repeated use of this option is not supported.
4570 .cindex "queue runner" "starting manually"
4571 This option is normally restricted to admin users. However, there is a
4572 configuration option called &%prod_requires_admin%& which can be set false to
4573 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4574 and &%-S%& options).
4576 .cindex "queue runner" "description of operation"
4577 If other commandline options do not specify an action,
4578 the &%-q%& option starts one queue runner process. This scans the queue of
4579 waiting messages, and runs a delivery process for each one in turn. It waits
4580 for each delivery process to finish before starting the next one. A delivery
4581 process may not actually do any deliveries if the retry times for the addresses
4582 have not been reached. Use &%-qf%& (see below) if you want to override this.
4585 .cindex "SMTP" "passed connection"
4586 .cindex "SMTP" "multiple deliveries"
4587 .cindex "multiple SMTP deliveries"
4588 the delivery process spawns other processes to deliver other messages down
4589 passed SMTP connections, the queue runner waits for these to finish before
4592 When all the queued messages have been considered, the original queue runner
4593 process terminates. In other words, a single pass is made over the waiting
4594 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4595 this to be repeated periodically.
4597 Exim processes the waiting messages in an unpredictable order. It isn't very
4598 random, but it is likely to be different each time, which is all that matters.
4599 If one particular message screws up a remote MTA, other messages to the same
4600 MTA have a chance of getting through if they get tried first.
4602 It is possible to cause the messages to be processed in lexical message id
4603 order, which is essentially the order in which they arrived, by setting the
4604 &%queue_run_in_order%& option, but this is not recommended for normal use.
4606 .vitem &%-q%&<&'qflags'&>
4607 The &%-q%& option may be followed by one or more flag letters that change its
4608 behaviour. They are all optional, but if more than one is present, they must
4609 appear in the correct order. Each flag is described in a separate item below.
4613 .cindex "queue" "double scanning"
4614 .cindex "queue" "routing"
4615 .cindex "routing" "whole queue before delivery"
4616 .cindex "first pass routing"
4617 .cindex "queue runner" "two phase"
4618 An option starting with &%-qq%& requests a two-stage queue run. In the first
4619 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4620 every domain. Addresses are routed, local deliveries happen, but no remote
4623 Performance will be best if the &%queue_run_in_order%& option is false.
4624 If that is so and the &%queue_fast_ramp%& option is true then
4625 in the first phase of the run,
4626 once a threshold number of messages are routed for a given host,
4627 a delivery process is forked in parallel with the rest of the scan.
4629 .cindex "hints database" "remembering routing"
4630 The hints database that remembers which messages are waiting for specific hosts
4631 is updated, as if delivery to those hosts had been deferred. After this is
4632 complete, a second, normal queue scan happens, with routing and delivery taking
4633 place as normal. Messages that are routed to the same host should mostly be
4634 delivered down a single SMTP
4635 .cindex "SMTP" "passed connection"
4636 .cindex "SMTP" "multiple deliveries"
4637 .cindex "multiple SMTP deliveries"
4638 connection because of the hints that were set up during the first queue scan.
4639 This option may be useful for hosts that are connected to the Internet
4642 .vitem &%-q[q]i...%&
4644 .cindex "queue" "initial delivery"
4645 If the &'i'& flag is present, the queue runner runs delivery processes only for
4646 those messages that haven't previously been tried. (&'i'& stands for &"initial
4647 delivery"&.) This can be helpful if you are putting messages in the queue using
4648 &%-odq%& and want a queue runner just to process the new messages.
4650 .vitem &%-q[q][i]f...%&
4652 .cindex "queue" "forcing delivery"
4653 .cindex "delivery" "forcing in queue run"
4654 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4655 message, whereas without &'f'& only those non-frozen addresses that have passed
4656 their retry times are tried.
4658 .vitem &%-q[q][i]ff...%&
4660 .cindex "frozen messages" "forcing delivery"
4661 If &'ff'& is present, a delivery attempt is forced for every message, whether
4664 .vitem &%-q[q][i][f[f]]l%&
4666 .cindex "queue" "local deliveries only"
4667 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4668 be done. If a message requires any remote deliveries, it remains in the queue
4671 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4674 .cindex "named queues" "deliver from"
4675 .cindex "queue" "delivering specific messages"
4676 If the &'G'& flag and a name is present, the queue runner operates on the
4677 queue with the given name rather than the default queue.
4678 The name should not contain a &'/'& character.
4679 For a periodic queue run (see below)
4680 append to the name a slash and a time value.
4682 If other commandline options specify an action, a &'-qG<name>'& option
4683 will specify a queue to operate on.
4686 exim -bp -qGquarantine
4688 exim -qGoffpeak -Rf @special.domain.example
4691 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4692 When scanning the queue, Exim can be made to skip over messages whose ids are
4693 lexically less than a given value by following the &%-q%& option with a
4694 starting message id. For example:
4696 exim -q 0t5C6f-0000c8-00
4698 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4699 second message id is given, messages whose ids are lexically greater than it
4700 are also skipped. If the same id is given twice, for example,
4702 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4704 just one delivery process is started, for that message. This differs from
4705 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4706 that it counts as a delivery from a queue run. Note that the selection
4707 mechanism does not affect the order in which the messages are scanned. There
4708 are also other ways of selecting specific sets of messages for delivery in a
4709 queue run &-- see &%-R%& and &%-S%&.
4711 .vitem &%-q%&<&'qflags'&><&'time'&>
4712 .cindex "queue runner" "starting periodically"
4713 .cindex "periodic queue running"
4714 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4715 starting a queue runner process at intervals specified by the given time value
4716 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4717 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4718 single daemon process handles both functions. A common way of starting up a
4719 combined daemon at system boot time is to use a command such as
4721 /usr/exim/bin/exim -bd -q30m
4723 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4724 process every 30 minutes.
4726 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4727 pid file is written unless one is explicitly requested by the &%-oP%& option.
4729 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4731 This option is synonymous with &%-R%&. It is provided for Sendmail
4734 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4736 This option is synonymous with &%-S%&.
4738 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4740 .cindex "queue runner" "for specific recipients"
4741 .cindex "delivery" "to given domain"
4742 .cindex "domain" "delivery to"
4743 The <&'rsflags'&> may be empty, in which case the white space before the string
4744 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4745 which are the possible values for <&'rsflags'&>. White space is required if
4746 <&'rsflags'&> is not empty.
4748 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4749 perform a single queue run, except that, when scanning the messages on the
4750 queue, Exim processes only those that have at least one undelivered recipient
4751 address containing the given string, which is checked in a case-independent
4752 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4753 regular expression; otherwise it is a literal string.
4755 If you want to do periodic queue runs for messages with specific recipients,
4756 you can combine &%-R%& with &%-q%& and a time value. For example:
4758 exim -q25m -R @special.domain.example
4760 This example does a queue run for messages with recipients in the given domain
4761 every 25 minutes. Any additional flags that are specified with &%-q%& are
4762 applied to each queue run.
4764 Once a message is selected for delivery by this mechanism, all its addresses
4765 are processed. For the first selected message, Exim overrides any retry
4766 information and forces a delivery attempt for each undelivered address. This
4767 means that if delivery of any address in the first message is successful, any
4768 existing retry information is deleted, and so delivery attempts for that
4769 address in subsequently selected messages (which are processed without forcing)
4770 will run. However, if delivery of any address does not succeed, the retry
4771 information is updated, and in subsequently selected messages, the failing
4772 address will be skipped.
4774 .cindex "frozen messages" "forcing delivery"
4775 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4776 all selected messages, not just the first; frozen messages are included when
4779 The &%-R%& option makes it straightforward to initiate delivery of all messages
4780 to a given domain after a host has been down for some time. When the SMTP
4781 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4782 effect is to run Exim with the &%-R%& option, but it can be configured to run
4783 an arbitrary command instead.
4787 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4789 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4791 .cindex "delivery" "from given sender"
4792 .cindex "queue runner" "for specific senders"
4793 This option acts like &%-R%& except that it checks the string against each
4794 message's sender instead of against the recipients. If &%-R%& is also set, both
4795 conditions must be met for a message to be selected. If either of the options
4796 has &'f'& or &'ff'& in its flags, the associated action is taken.
4798 .vitem &%-Tqt%&&~<&'times'&>
4800 This is an option that is exclusively for use by the Exim testing suite. It is not
4801 recognized when Exim is run normally. It allows for the setting up of explicit
4802 &"queue times"& so that various warning/retry features can be tested.
4806 .cindex "recipient" "extracting from header lines"
4810 When Exim is receiving a locally-generated, non-SMTP message on its standard
4811 input, the &%-t%& option causes the recipients of the message to be obtained
4812 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4813 from the command arguments. The addresses are extracted before any rewriting
4814 takes place and the &'Bcc:'& header line, if present, is then removed.
4816 .cindex "Sendmail compatibility" "&%-t%& option"
4817 If the command has any arguments, they specify addresses to which the message
4818 is &'not'& to be delivered. That is, the argument addresses are removed from
4819 the recipients list obtained from the headers. This is compatible with Smail 3
4820 and in accordance with the documented behaviour of several versions of
4821 Sendmail, as described in man pages on a number of operating systems (e.g.
4822 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4823 argument addresses to those obtained from the headers, and the O'Reilly
4824 Sendmail book documents it that way. Exim can be made to add argument addresses
4825 instead of subtracting them by setting the option
4826 &%extract_addresses_remove_arguments%& false.
4828 .cindex "&%Resent-%& header lines" "with &%-t%&"
4829 If there are any &%Resent-%& header lines in the message, Exim extracts
4830 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4831 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4832 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4833 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4835 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4836 message is resent several times). The RFC also specifies that they should be
4837 added at the front of the message, and separated by &'Received:'& lines. It is
4838 not at all clear how &%-t%& should operate in the present of multiple sets,
4839 nor indeed exactly what constitutes a &"set"&.
4840 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4841 are often added at the end of the header, and if a message is resent more than
4842 once, it is common for the original set of &%Resent-%& headers to be renamed as
4843 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4847 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4848 compatibility with Sendmail.
4850 .vitem &%-tls-on-connect%&
4851 .oindex "&%-tls-on-connect%&"
4852 .cindex "TLS" "use without STARTTLS"
4853 .cindex "TLS" "automatic start"
4854 This option is available when Exim is compiled with TLS support. It forces all
4855 incoming SMTP connections to behave as if the incoming port is listed in the
4856 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4857 &<<CHAPTLS>>& for further details.
4862 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4863 Sendmail uses this option for &"initial message submission"&, and its
4864 documentation states that in future releases, it may complain about
4865 syntactically invalid messages rather than fixing them when this flag is not
4866 set. Exim ignores this option.
4870 This option causes Exim to write information to the standard error stream,
4871 describing what it is doing. In particular, it shows the log lines for
4872 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4873 dialogue is shown. Some of the log lines shown may not actually be written to
4874 the log if the setting of &%log_selector%& discards them. Any relevant
4875 selectors are shown with each log line. If none are shown, the logging is
4880 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4881 National Language Support extended characters in the body of the mail item"&).
4882 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4885 .vitem &%-X%&&~<&'logfile'&>
4887 This option is interpreted by Sendmail to cause debug information to be sent
4888 to the named file. It is ignored by Exim.
4890 .vitem &%-z%&&~<&'log-line'&>
4892 This option writes its argument to Exim's logfile.
4893 Use is restricted to administrators; the intent is for operational notes.
4894 Quotes should be used to maintain a multi-word item as a single argument,
4902 . ////////////////////////////////////////////////////////////////////////////
4903 . Insert a stylized DocBook comment here, to identify the end of the command
4904 . line options. This is for the benefit of the Perl script that automatically
4905 . creates a man page for the options.
4906 . ////////////////////////////////////////////////////////////////////////////
4909 <!-- === End of command line options === -->
4916 . ////////////////////////////////////////////////////////////////////////////
4917 . ////////////////////////////////////////////////////////////////////////////
4920 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4921 "The runtime configuration file"
4923 .cindex "runtime configuration"
4924 .cindex "configuration file" "general description"
4925 .cindex "CONFIGURE_FILE"
4926 .cindex "configuration file" "errors in"
4927 .cindex "error" "in configuration file"
4928 .cindex "return code" "for bad configuration"
4929 Exim uses a single runtime configuration file that is read whenever an Exim
4930 binary is executed. Note that in normal operation, this happens frequently,
4931 because Exim is designed to operate in a distributed manner, without central
4934 If a syntax error is detected while reading the configuration file, Exim
4935 writes a message on the standard error, and exits with a non-zero return code.
4936 The message is also written to the panic log. &*Note*&: Only simple syntax
4937 errors can be detected at this time. The values of any expanded options are
4938 not checked until the expansion happens, even when the expansion does not
4939 actually alter the string.
4941 The name of the configuration file is compiled into the binary for security
4942 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4943 most configurations, this specifies a single file. However, it is permitted to
4944 give a colon-separated list of filenames, in which case Exim uses the first
4945 existing file in the list.
4948 .cindex "EXIM_GROUP"
4949 .cindex "CONFIGURE_OWNER"
4950 .cindex "CONFIGURE_GROUP"
4951 .cindex "configuration file" "ownership"
4952 .cindex "ownership" "configuration file"
4953 The runtime configuration file must be owned by root or by the user that is
4954 specified at compile time by the CONFIGURE_OWNER option (if set). The
4955 configuration file must not be world-writeable, or group-writeable unless its
4956 group is the root group or the one specified at compile time by the
4957 CONFIGURE_GROUP option.
4959 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4960 to root, anybody who is able to edit the runtime configuration file has an
4961 easy way to run commands as root. If you specify a user or group in the
4962 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4963 who are members of that group will trivially be able to obtain root privileges.
4965 Up to Exim version 4.72, the runtime configuration file was also permitted to
4966 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4967 since it offered a simple privilege escalation for any attacker who managed to
4968 compromise the Exim user account.
4970 A default configuration file, which will work correctly in simple situations,
4971 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4972 defines just one filename, the installation process copies the default
4973 configuration to a new file of that name if it did not previously exist. If
4974 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4975 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4980 .section "Using a different configuration file" "SECID40"
4981 .cindex "configuration file" "alternate"
4982 A one-off alternate configuration can be specified by the &%-C%& command line
4983 option, which may specify a single file or a list of files. However, when
4984 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4985 unless the argument for &%-C%& is identical to the built-in value from
4986 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4987 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4988 is useful mainly for checking the syntax of configuration files before
4989 installing them. No owner or group checks are done on a configuration file
4990 specified by &%-C%&, if root privilege has been dropped.
4992 Even the Exim user is not trusted to specify an arbitrary configuration file
4993 with the &%-C%& option to be used with root privileges, unless that file is
4994 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4995 testing a configuration using &%-C%& right through message reception and
4996 delivery, even if the caller is root. The reception works, but by that time,
4997 Exim is running as the Exim user, so when it re-execs to regain privilege for
4998 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4999 can test reception and delivery using two separate commands (one to put a
5000 message in the queue, using &%-odq%&, and another to do the delivery, using
5003 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
5004 prefix string with which any file named in a &%-C%& command line option must
5005 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
5006 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
5007 filename can be used with &%-C%&.
5009 One-off changes to a configuration can be specified by the &%-D%& command line
5010 option, which defines and overrides values for macros used inside the
5011 configuration file. However, like &%-C%&, the use of this option by a
5012 non-privileged user causes Exim to discard its root privilege.
5013 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
5014 completely disabled, and its use causes an immediate error exit.
5016 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
5017 to declare certain macro names trusted, such that root privilege will not
5018 necessarily be discarded.
5019 WHITELIST_D_MACROS defines a colon-separated list of macros which are
5020 considered safe and, if &%-D%& only supplies macros from this list, and the
5021 values are acceptable, then Exim will not give up root privilege if the caller
5022 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
5023 transition mechanism and is expected to be removed in the future. Acceptable
5024 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
5026 Some sites may wish to use the same Exim binary on different machines that
5027 share a file system, but to use different configuration files on each machine.
5028 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
5029 looks for a file whose name is the configuration filename followed by a dot
5030 and the machine's node name, as obtained from the &[uname()]& function. If this
5031 file does not exist, the standard name is tried. This processing occurs for
5032 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5034 In some esoteric situations different versions of Exim may be run under
5035 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5036 help with this. See the comments in &_src/EDITME_& for details.
5040 .section "Configuration file format" "SECTconffilfor"
5041 .cindex "configuration file" "format of"
5042 .cindex "format" "configuration file"
5043 Exim's configuration file is divided into a number of different parts. General
5044 option settings must always appear at the start of the file. The other parts
5045 are all optional, and may appear in any order. Each part other than the first
5046 is introduced by the word &"begin"& followed by at least one literal
5047 space, and the name of the part. The optional parts are:
5050 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5053 .cindex "AUTH" "configuration"
5054 &'authenticators'&: Configuration settings for the authenticator drivers. These
5055 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5057 &'routers'&: Configuration settings for the router drivers. Routers process
5058 addresses and determine how the message is to be delivered (see chapters
5059 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5061 &'transports'&: Configuration settings for the transport drivers. Transports
5062 define mechanisms for copying messages to destinations (see chapters
5063 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5065 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5066 If there is no retry section, or if it is empty (that is, no retry rules are
5067 defined), Exim will not retry deliveries. In this situation, temporary errors
5068 are treated the same as permanent errors. Retry rules are discussed in chapter
5071 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5072 when new addresses are generated during delivery. Rewriting is discussed in
5073 chapter &<<CHAPrewrite>>&.
5075 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5076 want to use this feature, you must set
5078 LOCAL_SCAN_HAS_OPTIONS=yes
5080 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5081 facility are given in chapter &<<CHAPlocalscan>>&.
5084 .cindex "configuration file" "leading white space in"
5085 .cindex "configuration file" "trailing white space in"
5086 .cindex "white space" "in configuration file"
5087 Leading and trailing white space in configuration lines is always ignored.
5089 Blank lines in the file, and lines starting with a # character (ignoring
5090 leading white space) are treated as comments and are ignored. &*Note*&: A
5091 # character other than at the beginning of a line is not treated specially,
5092 and does not introduce a comment.
5094 Any non-comment line can be continued by ending it with a backslash. Note that
5095 the general rule for white space means that trailing white space after the
5096 backslash and leading white space at the start of continuation
5097 lines is ignored. Comment lines beginning with # (but not empty lines) may
5098 appear in the middle of a sequence of continuation lines.
5100 A convenient way to create a configuration file is to start from the
5101 default, which is supplied in &_src/configure.default_&, and add, delete, or
5102 change settings as required.
5104 The ACLs, retry rules, and rewriting rules have their own syntax which is
5105 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5106 respectively. The other parts of the configuration file have some syntactic
5107 items in common, and these are described below, from section &<<SECTcos>>&
5108 onwards. Before that, the inclusion, macro, and conditional facilities are
5113 .section "File inclusions in the configuration file" "SECID41"
5114 .cindex "inclusions in configuration file"
5115 .cindex "configuration file" "including other files"
5116 .cindex "&`.include`& in configuration file"
5117 .cindex "&`.include_if_exists`& in configuration file"
5118 You can include other files inside Exim's runtime configuration file by
5121 &`.include`& <&'filename'&>
5122 &`.include_if_exists`& <&'filename'&>
5124 on a line by itself. Double quotes round the filename are optional. If you use
5125 the first form, a configuration error occurs if the file does not exist; the
5126 second form does nothing for non-existent files.
5127 The first form allows a relative name. It is resolved relative to
5128 the directory of the including file. For the second form an absolute filename
5131 Includes may be nested to any depth, but remember that Exim reads its
5132 configuration file often, so it is a good idea to keep them to a minimum.
5133 If you change the contents of an included file, you must HUP the daemon,
5134 because an included file is read only when the configuration itself is read.
5136 The processing of inclusions happens early, at a physical line level, so, like
5137 comment lines, an inclusion can be used in the middle of an option setting,
5140 hosts_lookup = a.b.c \
5143 Include processing happens after macro processing (see below). Its effect is to
5144 process the lines of the included file as if they occurred inline where the
5149 .section "Macros in the configuration file" "SECTmacrodefs"
5150 .cindex "macro" "description of"
5151 .cindex "configuration file" "macros"
5152 If a line in the main part of the configuration (that is, before the first
5153 &"begin"& line) begins with an upper case letter, it is taken as a macro
5154 definition, and must be of the form
5156 <&'name'&> = <&'rest of line'&>
5158 The name must consist of letters, digits, and underscores, and need not all be
5159 in upper case, though that is recommended. The rest of the line, including any
5160 continuations, is the replacement text, and has leading and trailing white
5161 space removed. Quotes are not removed. The replacement text can never end with
5162 a backslash character, but this doesn't seem to be a serious limitation.
5164 Macros may also be defined between router, transport, authenticator, or ACL
5165 definitions. They may not, however, be defined within an individual driver or
5166 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5168 .section "Macro substitution" "SECID42"
5169 Once a macro is defined, all subsequent lines in the file (and any included
5170 files) are scanned for the macro name; if there are several macros, the line is
5171 scanned for each, in turn, in the order in which the macros are defined. The
5172 replacement text is not re-scanned for the current macro, though it is scanned
5173 for subsequently defined macros. For this reason, a macro name may not contain
5174 the name of a previously defined macro as a substring. You could, for example,
5177 &`ABCD_XYZ = `&<&'something'&>
5178 &`ABCD = `&<&'something else'&>
5180 but putting the definitions in the opposite order would provoke a configuration
5181 error. Macro expansion is applied to individual physical lines from the file,
5182 before checking for line continuation or file inclusion (see above). If a line
5183 consists solely of a macro name, and the expansion of the macro is empty, the
5184 line is ignored. A macro at the start of a line may turn the line into a
5185 comment line or a &`.include`& line.
5188 .section "Redefining macros" "SECID43"
5189 Once defined, the value of a macro can be redefined later in the configuration
5190 (or in an included file). Redefinition is specified by using &'=='& instead of
5195 MAC == updated value
5197 Redefinition does not alter the order in which the macros are applied to the
5198 subsequent lines of the configuration file. It is still the same order in which
5199 the macros were originally defined. All that changes is the macro's value.
5200 Redefinition makes it possible to accumulate values. For example:
5204 MAC == MAC and something added
5206 This can be helpful in situations where the configuration file is built
5207 from a number of other files.
5209 .section "Overriding macro values" "SECID44"
5210 The values set for macros in the configuration file can be overridden by the
5211 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5212 used, unless called by root or the Exim user. A definition on the command line
5213 using the &%-D%& option causes all definitions and redefinitions within the
5218 .section "Example of macro usage" "SECID45"
5219 As an example of macro usage, consider a configuration where aliases are looked
5220 up in a MySQL database. It helps to keep the file less cluttered if long
5221 strings such as SQL statements are defined separately as macros, for example:
5223 ALIAS_QUERY = select mailbox from user where \
5224 login='${quote_mysql:$local_part}';
5226 This can then be used in a &(redirect)& router setting like this:
5228 data = ${lookup mysql{ALIAS_QUERY}}
5230 In earlier versions of Exim macros were sometimes used for domain, host, or
5231 address lists. In Exim 4 these are handled better by named lists &-- see
5232 section &<<SECTnamedlists>>&.
5235 .section "Builtin macros" "SECTbuiltinmacros"
5236 Exim defines some macros depending on facilities available, which may
5237 differ due to build-time definitions and from one release to another.
5238 All of these macros start with an underscore.
5239 They can be used to conditionally include parts of a configuration
5242 The following classes of macros are defined:
5244 &` _HAVE_* `& build-time defines
5245 &` _DRIVER_ROUTER_* `& router drivers
5246 &` _DRIVER_TRANSPORT_* `& transport drivers
5247 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5248 &` _LOG_* `& log_selector values
5249 &` _OPT_MAIN_* `& main config options
5250 &` _OPT_ROUTERS_* `& generic router options
5251 &` _OPT_TRANSPORTS_* `& generic transport options
5252 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5253 &` _OPT_ROUTER_*_* `& private router options
5254 &` _OPT_TRANSPORT_*_* `& private transport options
5255 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5258 Use an &"exim -bP macros"& command to get the list of macros.
5261 .section "Conditional skips in the configuration file" "SECID46"
5262 .cindex "configuration file" "conditional skips"
5263 .cindex "&`.ifdef`&"
5264 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5265 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5266 portions of the configuration file. The processing happens whenever the file is
5267 read (that is, when an Exim binary starts to run).
5269 The implementation is very simple. Instances of the first four directives must
5270 be followed by text that includes the names of one or macros. The condition
5271 that is tested is whether or not any macro substitution has taken place in the
5275 message_size_limit = 50M
5277 message_size_limit = 100M
5280 sets a message size limit of 50M if the macro &`AAA`& is defined
5281 (or &`A`& or &`AA`&), and 100M
5282 otherwise. If there is more than one macro named on the line, the condition
5283 is true if any of them are defined. That is, it is an &"or"& condition. To
5284 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5286 Although you can use a macro expansion to generate one of these directives,
5287 it is not very useful, because the condition &"there was a macro substitution
5288 in this line"& will always be true.
5290 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5291 to clarify complicated nestings.
5295 .section "Common option syntax" "SECTcos"
5296 .cindex "common option syntax"
5297 .cindex "syntax of common options"
5298 .cindex "configuration file" "common option syntax"
5299 For the main set of options, driver options, and &[local_scan()]& options,
5300 each setting is on a line by itself, and starts with a name consisting of
5301 lower-case letters and underscores. Many options require a data value, and in
5302 these cases the name must be followed by an equals sign (with optional white
5303 space) and then the value. For example:
5305 qualify_domain = mydomain.example.com
5307 .cindex "hiding configuration option values"
5308 .cindex "configuration options" "hiding value of"
5309 .cindex "options" "hiding value of"
5310 Some option settings may contain sensitive data, for example, passwords for
5311 accessing databases. To stop non-admin users from using the &%-bP%& command
5312 line option to read these values, you can precede the option settings with the
5313 word &"hide"&. For example:
5315 hide mysql_servers = localhost/users/admin/secret-password
5317 For non-admin users, such options are displayed like this:
5319 mysql_servers = <value not displayable>
5321 If &"hide"& is used on a driver option, it hides the value of that option on
5322 all instances of the same driver.
5324 The following sections describe the syntax used for the different data types
5325 that are found in option settings.
5328 .section "Boolean options" "SECID47"
5329 .cindex "format" "boolean"
5330 .cindex "boolean configuration values"
5331 .oindex "&%no_%&&'xxx'&"
5332 .oindex "&%not_%&&'xxx'&"
5333 Options whose type is given as boolean are on/off switches. There are two
5334 different ways of specifying such options: with and without a data value. If
5335 the option name is specified on its own without data, the switch is turned on;
5336 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5337 boolean options may be followed by an equals sign and one of the words
5338 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5339 the following two settings have exactly the same effect:
5344 The following two lines also have the same (opposite) effect:
5349 You can use whichever syntax you prefer.
5354 .section "Integer values" "SECID48"
5355 .cindex "integer configuration values"
5356 .cindex "format" "integer"
5357 If an option's type is given as &"integer"&, the value can be given in decimal,
5358 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5359 number is assumed. Otherwise, it is treated as an octal number unless it starts
5360 with the characters &"0x"&, in which case the remainder is interpreted as a
5363 If an integer value is followed by the letter K, it is multiplied by 1024; if
5364 it is followed by the letter M, it is multiplied by 1024x1024;
5365 if by the letter G, 1024x1024x1024.
5367 of integer option settings are output, values which are an exact multiple of
5368 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5369 and M. The printing style is independent of the actual input format that was
5373 .section "Octal integer values" "SECID49"
5374 .cindex "integer format"
5375 .cindex "format" "octal integer"
5376 If an option's type is given as &"octal integer"&, its value is always
5377 interpreted as an octal number, whether or not it starts with the digit zero.
5378 Such options are always output in octal.
5381 .section "Fixed point numbers" "SECID50"
5382 .cindex "fixed point configuration values"
5383 .cindex "format" "fixed point"
5384 If an option's type is given as &"fixed-point"&, its value must be a decimal
5385 integer, optionally followed by a decimal point and up to three further digits.
5389 .section "Time intervals" "SECTtimeformat"
5390 .cindex "time interval" "specifying in configuration"
5391 .cindex "format" "time interval"
5392 A time interval is specified as a sequence of numbers, each followed by one of
5393 the following letters, with no intervening white space:
5403 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5404 intervals are output in the same format. Exim does not restrict the values; it
5405 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5409 .section "String values" "SECTstrings"
5410 .cindex "string" "format of configuration values"
5411 .cindex "format" "string"
5412 If an option's type is specified as &"string"&, the value can be specified with
5413 or without double-quotes. If it does not start with a double-quote, the value
5414 consists of the remainder of the line plus any continuation lines, starting at
5415 the first character after any leading white space, with trailing white space
5416 removed, and with no interpretation of the characters in the string. Because
5417 Exim removes comment lines (those beginning with #) at an early stage, they can
5418 appear in the middle of a multi-line string. The following two settings are
5419 therefore equivalent:
5421 trusted_users = uucp:mail
5422 trusted_users = uucp:\
5423 # This comment line is ignored
5426 .cindex "string" "quoted"
5427 .cindex "escape characters in quoted strings"
5428 If a string does start with a double-quote, it must end with a closing
5429 double-quote, and any backslash characters other than those used for line
5430 continuation are interpreted as escape characters, as follows:
5433 .irow &`\\`& "single backslash"
5434 .irow &`\n`& "newline"
5435 .irow &`\r`& "carriage return"
5437 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5438 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5442 If a backslash is followed by some other character, including a double-quote
5443 character, that character replaces the pair.
5445 Quoting is necessary only if you want to make use of the backslash escapes to
5446 insert special characters, or if you need to specify a value with leading or
5447 trailing spaces. These cases are rare, so quoting is almost never needed in
5448 current versions of Exim. In versions of Exim before 3.14, quoting was required
5449 in order to continue lines, so you may come across older configuration files
5450 and examples that apparently quote unnecessarily.
5453 .section "Expanded strings" "SECID51"
5454 .cindex "expansion" "definition of"
5455 Some strings in the configuration file are subjected to &'string expansion'&,
5456 by which means various parts of the string may be changed according to the
5457 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5458 is as just described; in particular, the handling of backslashes in quoted
5459 strings is done as part of the input process, before expansion takes place.
5460 However, backslash is also an escape character for the expander, so any
5461 backslashes that are required for that reason must be doubled if they are
5462 within a quoted configuration string.
5465 .section "User and group names" "SECID52"
5466 .cindex "user name" "format of"
5467 .cindex "format" "user name"
5468 .cindex "groups" "name format"
5469 .cindex "format" "group name"
5470 User and group names are specified as strings, using the syntax described
5471 above, but the strings are interpreted specially. A user or group name must
5472 either consist entirely of digits, or be a name that can be looked up using the
5473 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5476 .section "List construction" "SECTlistconstruct"
5477 .cindex "list" "syntax of in configuration"
5478 .cindex "format" "list item in configuration"
5479 .cindex "string" "list, definition of"
5480 The data for some configuration options is a list of items, with colon as the
5481 default separator. Many of these options are shown with type &"string list"& in
5482 the descriptions later in this document. Others are listed as &"domain list"&,
5483 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5484 are all the same; however, those other than &"string list"& are subject to
5485 particular kinds of interpretation, as described in chapter
5486 &<<CHAPdomhosaddlists>>&.
5488 In all these cases, the entire list is treated as a single string as far as the
5489 input syntax is concerned. The &%trusted_users%& setting in section
5490 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5491 in a list, it must be entered as two colons. Leading and trailing white space
5492 on each item in a list is ignored. This makes it possible to include items that
5493 start with a colon, and in particular, certain forms of IPv6 address. For
5496 local_interfaces = 127.0.0.1 : ::::1
5498 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5500 &*Note*&: Although leading and trailing white space is ignored in individual
5501 list items, it is not ignored when parsing the list. The spaces around the first
5502 colon in the example above are necessary. If they were not there, the list would
5503 be interpreted as the two items 127.0.0.1:: and 1.
5505 .section "Changing list separators" "SECTlistsepchange"
5506 .cindex "list separator" "changing"
5507 .cindex "IPv6" "addresses in lists"
5508 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5509 introduced to allow the separator character to be changed. If a list begins
5510 with a left angle bracket, followed by any punctuation character, that
5511 character is used instead of colon as the list separator. For example, the list
5512 above can be rewritten to use a semicolon separator like this:
5514 local_interfaces = <; 127.0.0.1 ; ::1
5516 This facility applies to all lists, with the exception of the list in
5517 &%log_file_path%&. It is recommended that the use of non-colon separators be
5518 confined to circumstances where they really are needed.
5520 .cindex "list separator" "newline as"
5521 .cindex "newline" "as list separator"
5522 It is also possible to use newline and other control characters (those with
5523 code values less than 32, plus DEL) as separators in lists. Such separators
5524 must be provided literally at the time the list is processed. For options that
5525 are string-expanded, you can write the separator using a normal escape
5526 sequence. This will be processed by the expander before the string is
5527 interpreted as a list. For example, if a newline-separated list of domains is
5528 generated by a lookup, you can process it directly by a line such as this:
5530 domains = <\n ${lookup mysql{.....}}
5532 This avoids having to change the list separator in such data. You are unlikely
5533 to want to use a control character as a separator in an option that is not
5534 expanded, because the value is literal text. However, it can be done by giving
5535 the value in quotes. For example:
5537 local_interfaces = "<\n 127.0.0.1 \n ::1"
5539 Unlike printing character separators, which can be included in list items by
5540 doubling, it is not possible to include a control character as data when it is
5541 set as the separator. Two such characters in succession are interpreted as
5542 enclosing an empty list item.
5546 .section "Empty items in lists" "SECTempitelis"
5547 .cindex "list" "empty item in"
5548 An empty item at the end of a list is always ignored. In other words, trailing
5549 separator characters are ignored. Thus, the list in
5551 senders = user@domain :
5553 contains only a single item. If you want to include an empty string as one item
5554 in a list, it must not be the last item. For example, this list contains three
5555 items, the second of which is empty:
5557 senders = user1@domain : : user2@domain
5559 &*Note*&: There must be white space between the two colons, as otherwise they
5560 are interpreted as representing a single colon data character (and the list
5561 would then contain just one item). If you want to specify a list that contains
5562 just one, empty item, you can do it as in this example:
5566 In this case, the first item is empty, and the second is discarded because it
5567 is at the end of the list.
5572 .section "Format of driver configurations" "SECTfordricon"
5573 .cindex "drivers" "configuration format"
5574 There are separate parts in the configuration for defining routers, transports,
5575 and authenticators. In each part, you are defining a number of driver
5576 instances, each with its own set of options. Each driver instance is defined by
5577 a sequence of lines like this:
5579 <&'instance name'&>:
5584 In the following example, the instance name is &(localuser)&, and it is
5585 followed by three options settings:
5590 transport = local_delivery
5592 For each driver instance, you specify which Exim code module it uses &-- by the
5593 setting of the &%driver%& option &-- and (optionally) some configuration
5594 settings. For example, in the case of transports, if you want a transport to
5595 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5596 a local file you would use the &(appendfile)& driver. Each of the drivers is
5597 described in detail in its own separate chapter later in this manual.
5599 You can have several routers, transports, or authenticators that are based on
5600 the same underlying driver (each must have a different instance name).
5602 The order in which routers are defined is important, because addresses are
5603 passed to individual routers one by one, in order. The order in which
5604 transports are defined does not matter at all. The order in which
5605 authenticators are defined is used only when Exim, as a client, is searching
5606 them to find one that matches an authentication mechanism offered by the
5609 .cindex "generic options"
5610 .cindex "options" "generic &-- definition of"
5611 Within a driver instance definition, there are two kinds of option: &'generic'&
5612 and &'private'&. The generic options are those that apply to all drivers of the
5613 same type (that is, all routers, all transports or all authenticators). The
5614 &%driver%& option is a generic option that must appear in every definition.
5615 .cindex "private options"
5616 The private options are special for each driver, and none need appear, because
5617 they all have default values.
5619 The options may appear in any order, except that the &%driver%& option must
5620 precede any private options, since these depend on the particular driver. For
5621 this reason, it is recommended that &%driver%& always be the first option.
5623 Driver instance names, which are used for reference in log entries and
5624 elsewhere, can be any sequence of letters, digits, and underscores (starting
5625 with a letter) and must be unique among drivers of the same type. A router and
5626 a transport (for example) can each have the same name, but no two router
5627 instances can have the same name. The name of a driver instance should not be
5628 confused with the name of the underlying driver module. For example, the
5629 configuration lines:
5634 create an instance of the &(smtp)& transport driver whose name is
5635 &(remote_smtp)&. The same driver code can be used more than once, with
5636 different instance names and different option settings each time. A second
5637 instance of the &(smtp)& transport, with different options, might be defined
5643 command_timeout = 10s
5645 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5646 these transport instances from routers, and these names would appear in log
5649 Comment lines may be present in the middle of driver specifications. The full
5650 list of option settings for any particular driver instance, including all the
5651 defaulted values, can be extracted by making use of the &%-bP%& command line
5659 . ////////////////////////////////////////////////////////////////////////////
5660 . ////////////////////////////////////////////////////////////////////////////
5662 .chapter "The default configuration file" "CHAPdefconfil"
5663 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5664 .cindex "default" "configuration file &""walk through""&"
5665 The default configuration file supplied with Exim as &_src/configure.default_&
5666 is sufficient for a host with simple mail requirements. As an introduction to
5667 the way Exim is configured, this chapter &"walks through"& the default
5668 configuration, giving brief explanations of the settings. Detailed descriptions
5669 of the options are given in subsequent chapters. The default configuration file
5670 itself contains extensive comments about ways you might want to modify the
5671 initial settings. However, note that there are many options that are not
5672 mentioned at all in the default configuration.
5676 .section "Macros" "SECTdefconfmacros"
5677 All macros should be defined before any options.
5679 One macro is specified, but commented out, in the default configuration:
5681 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5683 If all off-site mail is expected to be delivered to a "smarthost", then set the
5684 hostname here and uncomment the macro. This will affect which router is used
5685 later on. If this is left commented out, then Exim will perform direct-to-MX
5686 deliveries using a &(dnslookup)& router.
5688 In addition to macros defined here, Exim includes a number of built-in macros
5689 to enable configuration to be guarded by a binary built with support for a
5690 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5693 .section "Main configuration settings" "SECTdefconfmain"
5694 The main (global) configuration option settings section must always come first
5695 in the file, after the macros.
5696 The first thing you'll see in the file, after some initial comments, is the line
5698 # primary_hostname =
5700 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5701 to know the official, fully qualified name of your host, and this is where you
5702 can specify it. However, in most cases you do not need to set this option. When
5703 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5705 The first three non-comment configuration lines are as follows:
5707 domainlist local_domains = @
5708 domainlist relay_to_domains =
5709 hostlist relay_from_hosts = 127.0.0.1
5711 These are not, in fact, option settings. They are definitions of two named
5712 domain lists and one named host list. Exim allows you to give names to lists of
5713 domains, hosts, and email addresses, in order to make it easier to manage the
5714 configuration file (see section &<<SECTnamedlists>>&).
5716 The first line defines a domain list called &'local_domains'&; this is used
5717 later in the configuration to identify domains that are to be delivered
5720 .cindex "@ in a domain list"
5721 There is just one item in this list, the string &"@"&. This is a special form
5722 of entry which means &"the name of the local host"&. Thus, if the local host is
5723 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5724 be delivered locally. Because the local host's name is referenced indirectly,
5725 the same configuration file can be used on different hosts.
5727 The second line defines a domain list called &'relay_to_domains'&, but the
5728 list itself is empty. Later in the configuration we will come to the part that
5729 controls mail relaying through the local host; it allows relaying to any
5730 domains in this list. By default, therefore, no relaying on the basis of a mail
5731 domain is permitted.
5733 The third line defines a host list called &'relay_from_hosts'&. This list is
5734 used later in the configuration to permit relaying from any host or IP address
5735 that matches the list. The default contains just the IP address of the IPv4
5736 loopback interface, which means that processes on the local host are able to
5737 submit mail for relaying by sending it over TCP/IP to that interface. No other
5738 hosts are permitted to submit messages for relaying.
5740 Just to be sure there's no misunderstanding: at this point in the configuration
5741 we aren't actually setting up any controls. We are just defining some domains
5742 and hosts that will be used in the controls that are specified later.
5744 The next two configuration lines are genuine option settings:
5746 acl_smtp_rcpt = acl_check_rcpt
5747 acl_smtp_data = acl_check_data
5749 These options specify &'Access Control Lists'& (ACLs) that are to be used
5750 during an incoming SMTP session for every recipient of a message (every RCPT
5751 command), and after the contents of the message have been received,
5752 respectively. The names of the lists are &'acl_check_rcpt'& and
5753 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5754 section of the configuration. The RCPT ACL controls which recipients are
5755 accepted for an incoming message &-- if a configuration does not provide an ACL
5756 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5757 contents of a message to be checked.
5759 Two commented-out option settings are next:
5761 # av_scanner = clamd:/tmp/clamd
5762 # spamd_address = 127.0.0.1 783
5764 These are example settings that can be used when Exim is compiled with the
5765 content-scanning extension. The first specifies the interface to the virus
5766 scanner, and the second specifies the interface to SpamAssassin. Further
5767 details are given in chapter &<<CHAPexiscan>>&.
5769 Three more commented-out option settings follow:
5771 # tls_advertise_hosts = *
5772 # tls_certificate = /etc/ssl/exim.crt
5773 # tls_privatekey = /etc/ssl/exim.pem
5775 These are example settings that can be used when Exim is compiled with
5776 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5777 first one specifies the list of clients that are allowed to use TLS when
5778 connecting to this server; in this case, the wildcard means all clients. The
5779 other options specify where Exim should find its TLS certificate and private
5780 key, which together prove the server's identity to any clients that connect.
5781 More details are given in chapter &<<CHAPTLS>>&.
5783 Another two commented-out option settings follow:
5785 # daemon_smtp_ports = 25 : 465 : 587
5786 # tls_on_connect_ports = 465
5788 .cindex "port" "465 and 587"
5789 .cindex "port" "for message submission"
5790 .cindex "message" "submission, ports for"
5791 .cindex "submissions protocol"
5792 .cindex "smtps protocol"
5793 .cindex "ssmtp protocol"
5794 .cindex "SMTP" "submissions protocol"
5795 .cindex "SMTP" "ssmtp protocol"
5796 .cindex "SMTP" "smtps protocol"
5797 These options provide better support for roaming users who wish to use this
5798 server for message submission. They are not much use unless you have turned on
5799 TLS (as described in the previous paragraph) and authentication (about which
5800 more in section &<<SECTdefconfauth>>&).
5801 Mail submission from mail clients (MUAs) should be separate from inbound mail
5802 to your domain (MX delivery) for various good reasons (eg, ability to impose
5803 much saner TLS protocol and ciphersuite requirements without unintended
5805 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5806 which uses STARTTLS, so this is the &"submission"& port.
5807 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5808 which should be used in preference to 587.
5809 You should also consider deploying SRV records to help clients find
5811 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5813 Two more commented-out options settings follow:
5816 # qualify_recipient =
5818 The first of these specifies a domain that Exim uses when it constructs a
5819 complete email address from a local login name. This is often needed when Exim
5820 receives a message from a local process. If you do not set &%qualify_domain%&,
5821 the value of &%primary_hostname%& is used. If you set both of these options,
5822 you can have different qualification domains for sender and recipient
5823 addresses. If you set only the first one, its value is used in both cases.
5825 .cindex "domain literal" "recognizing format"
5826 The following line must be uncommented if you want Exim to recognize
5827 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5828 (an IP address within square brackets) instead of a named domain.
5830 # allow_domain_literals
5832 The RFCs still require this form, but many people think that in the modern
5833 Internet it makes little sense to permit mail to be sent to specific hosts by
5834 quoting their IP addresses. This ancient format has been used by people who
5835 try to abuse hosts by using them for unwanted relaying. However, some
5836 people believe there are circumstances (for example, messages addressed to
5837 &'postmaster'&) where domain literals are still useful.
5839 The next configuration line is a kind of trigger guard:
5843 It specifies that no delivery must ever be run as the root user. The normal
5844 convention is to set up &'root'& as an alias for the system administrator. This
5845 setting is a guard against slips in the configuration.
5846 The list of users specified by &%never_users%& is not, however, the complete
5847 list; the build-time configuration in &_Local/Makefile_& has an option called
5848 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5849 contents of &%never_users%& are added to this list. By default
5850 FIXED_NEVER_USERS also specifies root.
5852 When a remote host connects to Exim in order to send mail, the only information
5853 Exim has about the host's identity is its IP address. The next configuration
5858 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5859 in order to get a host name. This improves the quality of the logging
5860 information, but if you feel it is too expensive, you can remove it entirely,
5861 or restrict the lookup to hosts on &"nearby"& networks.
5862 Note that it is not always possible to find a host name from an IP address,
5863 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5866 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5867 1413 (hence their names):
5870 rfc1413_query_timeout = 0s
5872 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5873 Few hosts offer RFC1413 service these days; calls have to be
5874 terminated by a timeout and this needlessly delays the startup
5875 of an incoming SMTP connection.
5876 If you have hosts for which you trust RFC1413 and need this
5877 information, you can change this.
5879 This line enables an efficiency SMTP option. It is negotiated by clients
5880 and not expected to cause problems but can be disabled if needed.
5885 When Exim receives messages over SMTP connections, it expects all addresses to
5886 be fully qualified with a domain, as required by the SMTP definition. However,
5887 if you are running a server to which simple clients submit messages, you may
5888 find that they send unqualified addresses. The two commented-out options:
5890 # sender_unqualified_hosts =
5891 # recipient_unqualified_hosts =
5893 show how you can specify hosts that are permitted to send unqualified sender
5894 and recipient addresses, respectively.
5896 The &%log_selector%& option is used to increase the detail of logging
5899 log_selector = +smtp_protocol_error +smtp_syntax_error \
5900 +tls_certificate_verified
5903 The &%percent_hack_domains%& option is also commented out:
5905 # percent_hack_domains =
5907 It provides a list of domains for which the &"percent hack"& is to operate.
5908 This is an almost obsolete form of explicit email routing. If you do not know
5909 anything about it, you can safely ignore this topic.
5911 The next two settings in the main part of the default configuration are
5912 concerned with messages that have been &"frozen"& on Exim's queue. When a
5913 message is frozen, Exim no longer continues to try to deliver it. Freezing
5914 occurs when a bounce message encounters a permanent failure because the sender
5915 address of the original message that caused the bounce is invalid, so the
5916 bounce cannot be delivered. This is probably the most common case, but there
5917 are also other conditions that cause freezing, and frozen messages are not
5918 always bounce messages.
5920 ignore_bounce_errors_after = 2d
5921 timeout_frozen_after = 7d
5923 The first of these options specifies that failing bounce messages are to be
5924 discarded after 2 days in the queue. The second specifies that any frozen
5925 message (whether a bounce message or not) is to be timed out (and discarded)
5926 after a week. In this configuration, the first setting ensures that no failing
5927 bounce message ever lasts a week.
5929 Exim queues it's messages in a spool directory. If you expect to have
5930 large queues, you may consider using this option. It splits the spool
5931 directory into subdirectories to avoid file system degradation from
5932 many files in a single directory, resulting in better performance.
5933 Manual manipulation of queued messages becomes more complex (though fortunately
5936 # split_spool_directory = true
5939 In an ideal world everybody follows the standards. For non-ASCII
5940 messages RFC 2047 is a standard, allowing a maximum line length of 76
5941 characters. Exim adheres that standard and won't process messages which
5942 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5943 In particular, the Exim maintainers have had multiple reports of
5944 problems from Russian administrators of issues until they disable this
5945 check, because of some popular, yet buggy, mail composition software.
5947 # check_rfc2047_length = false
5950 If you need to be strictly RFC compliant you may wish to disable the
5951 8BITMIME advertisement. Use this, if you exchange mails with systems
5952 that are not 8-bit clean.
5954 # accept_8bitmime = false
5957 Libraries you use may depend on specific environment settings. This
5958 imposes a security risk (e.g. PATH). There are two lists:
5959 &%keep_environment%& for the variables to import as they are, and
5960 &%add_environment%& for variables we want to set to a fixed value.
5961 Note that TZ is handled separately, by the $%timezone%$ runtime
5962 option and by the TIMEZONE_DEFAULT buildtime option.
5964 # keep_environment = ^LDAP
5965 # add_environment = PATH=/usr/bin::/bin
5969 .section "ACL configuration" "SECID54"
5970 .cindex "default" "ACLs"
5971 .cindex "&ACL;" "default configuration"
5972 In the default configuration, the ACL section follows the main configuration.
5973 It starts with the line
5977 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5978 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5979 and &%acl_smtp_data%& above.
5981 .cindex "RCPT" "ACL for"
5982 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5983 RCPT command specifies one of the message's recipients. The ACL statements
5984 are considered in order, until the recipient address is either accepted or
5985 rejected. The RCPT command is then accepted or rejected, according to the
5986 result of the ACL processing.
5990 This line, consisting of a name terminated by a colon, marks the start of the
5995 This ACL statement accepts the recipient if the sending host matches the list.
5996 But what does that strange list mean? It doesn't actually contain any host
5997 names or IP addresses. The presence of the colon puts an empty item in the
5998 list; Exim matches this only if the incoming message did not come from a remote
5999 host, because in that case, the remote hostname is empty. The colon is
6000 important. Without it, the list itself is empty, and can never match anything.
6002 What this statement is doing is to accept unconditionally all recipients in
6003 messages that are submitted by SMTP from local processes using the standard
6004 input and output (that is, not using TCP/IP). A number of MUAs operate in this
6007 deny domains = +local_domains
6008 local_parts = ^[.] : ^.*[@%!/|]
6009 message = Restricted characters in address
6011 deny domains = !+local_domains
6012 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
6013 message = Restricted characters in address
6015 These statements are concerned with local parts that contain any of the
6016 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
6017 Although these characters are entirely legal in local parts (in the case of
6018 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
6019 in Internet mail addresses.
6021 The first three have in the past been associated with explicitly routed
6022 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
6023 option). Addresses containing these characters are regularly tried by spammers
6024 in an attempt to bypass relaying restrictions, and also by open relay testing
6025 programs. Unless you really need them it is safest to reject these characters
6026 at this early stage. This configuration is heavy-handed in rejecting these
6027 characters for all messages it accepts from remote hosts. This is a deliberate
6028 policy of being as safe as possible.
6030 The first rule above is stricter, and is applied to messages that are addressed
6031 to one of the local domains handled by this host. This is implemented by the
6032 first condition, which restricts it to domains that are listed in the
6033 &'local_domains'& domain list. The &"+"& character is used to indicate a
6034 reference to a named list. In this configuration, there is just one domain in
6035 &'local_domains'&, but in general there may be many.
6037 The second condition on the first statement uses two regular expressions to
6038 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6039 or &"|"&. If you have local accounts that include these characters, you will
6040 have to modify this rule.
6042 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6043 allows them because they have been encountered in practice. (Consider the
6044 common convention of local parts constructed as
6045 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6046 the author of Exim, who has no second initial.) However, a local part starting
6047 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6048 filename (for example, for a mailing list). This is also true for local parts
6049 that contain slashes. A pipe symbol can also be troublesome if the local part
6050 is incorporated unthinkingly into a shell command line.
6052 The second rule above applies to all other domains, and is less strict. This
6053 allows your own users to send outgoing messages to sites that use slashes
6054 and vertical bars in their local parts. It blocks local parts that begin
6055 with a dot, slash, or vertical bar, but allows these characters within the
6056 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6057 and &"!"& is blocked, as before. The motivation here is to prevent your users
6058 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6060 accept local_parts = postmaster
6061 domains = +local_domains
6063 This statement, which has two conditions, accepts an incoming address if the
6064 local part is &'postmaster'& and the domain is one of those listed in the
6065 &'local_domains'& domain list. The &"+"& character is used to indicate a
6066 reference to a named list. In this configuration, there is just one domain in
6067 &'local_domains'&, but in general there may be many.
6069 The presence of this statement means that mail to postmaster is never blocked
6070 by any of the subsequent tests. This can be helpful while sorting out problems
6071 in cases where the subsequent tests are incorrectly denying access.
6073 require verify = sender
6075 This statement requires the sender address to be verified before any subsequent
6076 ACL statement can be used. If verification fails, the incoming recipient
6077 address is refused. Verification consists of trying to route the address, to
6078 see if a bounce message could be delivered to it. In the case of remote
6079 addresses, basic verification checks only the domain, but &'callouts'& can be
6080 used for more verification if required. Section &<<SECTaddressverification>>&
6081 discusses the details of address verification.
6083 accept hosts = +relay_from_hosts
6084 control = submission
6086 This statement accepts the address if the message is coming from one of the
6087 hosts that are defined as being allowed to relay through this host. Recipient
6088 verification is omitted here, because in many cases the clients are dumb MUAs
6089 that do not cope well with SMTP error responses. For the same reason, the
6090 second line specifies &"submission mode"& for messages that are accepted. This
6091 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6092 messages that are deficient in some way, for example, because they lack a
6093 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6094 probably add recipient verification here, and disable submission mode.
6096 accept authenticated = *
6097 control = submission
6099 This statement accepts the address if the client host has authenticated itself.
6100 Submission mode is again specified, on the grounds that such messages are most
6101 likely to come from MUAs. The default configuration does not define any
6102 authenticators, though it does include some nearly complete commented-out
6103 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6104 fact authenticate until you complete the authenticator definitions.
6106 require message = relay not permitted
6107 domains = +local_domains : +relay_to_domains
6109 This statement rejects the address if its domain is neither a local domain nor
6110 one of the domains for which this host is a relay.
6112 require verify = recipient
6114 This statement requires the recipient address to be verified; if verification
6115 fails, the address is rejected.
6117 # deny dnslists = black.list.example
6118 # message = rejected because $sender_host_address \
6119 # is in a black list at $dnslist_domain\n\
6122 # warn dnslists = black.list.example
6123 # add_header = X-Warning: $sender_host_address is in \
6124 # a black list at $dnslist_domain
6125 # log_message = found in $dnslist_domain
6127 These commented-out lines are examples of how you could configure Exim to check
6128 sending hosts against a DNS black list. The first statement rejects messages
6129 from blacklisted hosts, whereas the second just inserts a warning header
6132 # require verify = csa
6134 This commented-out line is an example of how you could turn on client SMTP
6135 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6140 The final statement in the first ACL unconditionally accepts any recipient
6141 address that has successfully passed all the previous tests.
6145 This line marks the start of the second ACL, and names it. Most of the contents
6146 of this ACL are commented out:
6149 # message = This message contains a virus \
6152 These lines are examples of how to arrange for messages to be scanned for
6153 viruses when Exim has been compiled with the content-scanning extension, and a
6154 suitable virus scanner is installed. If the message is found to contain a
6155 virus, it is rejected with the given custom error message.
6157 # warn spam = nobody
6158 # message = X-Spam_score: $spam_score\n\
6159 # X-Spam_score_int: $spam_score_int\n\
6160 # X-Spam_bar: $spam_bar\n\
6161 # X-Spam_report: $spam_report
6163 These lines are an example of how to arrange for messages to be scanned by
6164 SpamAssassin when Exim has been compiled with the content-scanning extension,
6165 and SpamAssassin has been installed. The SpamAssassin check is run with
6166 &`nobody`& as its user parameter, and the results are added to the message as a
6167 series of extra header line. In this case, the message is not rejected,
6168 whatever the spam score.
6172 This final line in the DATA ACL accepts the message unconditionally.
6175 .section "Router configuration" "SECID55"
6176 .cindex "default" "routers"
6177 .cindex "routers" "default"
6178 The router configuration comes next in the default configuration, introduced
6183 Routers are the modules in Exim that make decisions about where to send
6184 messages. An address is passed to each router, in turn, until it is either
6185 accepted, or failed. This means that the order in which you define the routers
6186 matters. Each router is fully described in its own chapter later in this
6187 manual. Here we give only brief overviews.
6190 # driver = ipliteral
6191 # domains = !+local_domains
6192 # transport = remote_smtp
6194 .cindex "domain literal" "default router"
6195 This router is commented out because the majority of sites do not want to
6196 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6197 you uncomment this router, you also need to uncomment the setting of
6198 &%allow_domain_literals%& in the main part of the configuration.
6200 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6201 macro has been defined, per
6203 .ifdef ROUTER_SMARTHOST
6212 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6213 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6214 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6215 skip these routers because of the &%domains%& option.
6219 driver = manualroute
6220 domains = ! +local_domains
6221 transport = smarthost_smtp
6222 route_data = ROUTER_SMARTHOST
6223 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6226 This router only handles mail which is not to any local domains; this is
6227 specified by the line
6229 domains = ! +local_domains
6231 The &%domains%& option lists the domains to which this router applies, but the
6232 exclamation mark is a negation sign, so the router is used only for domains
6233 that are not in the domain list called &'local_domains'& (which was defined at
6234 the start of the configuration). The plus sign before &'local_domains'&
6235 indicates that it is referring to a named list. Addresses in other domains are
6236 passed on to the following routers.
6238 The name of the router driver is &(manualroute)& because we are manually
6239 specifying how mail should be routed onwards, instead of using DNS MX.
6240 While the name of this router instance is arbitrary, the &%driver%& option must
6241 be one of the driver modules that is in the Exim binary.
6243 With no pre-conditions other than &%domains%&, all mail for non-local domains
6244 will be handled by this router, and the &%no_more%& setting will ensure that no
6245 other routers will be used for messages matching the pre-conditions. See
6246 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6247 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6248 and the macro supplies the value; the address is then queued for the
6249 &(smarthost_smtp)& transport.
6254 domains = ! +local_domains
6255 transport = remote_smtp
6256 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6259 The &%domains%& option behaves as per smarthost, above.
6261 The name of the router driver is &(dnslookup)&,
6262 and is specified by the &%driver%& option. Do not be confused by the fact that
6263 the name of this router instance is the same as the name of the driver. The
6264 instance name is arbitrary, but the name set in the &%driver%& option must be
6265 one of the driver modules that is in the Exim binary.
6267 The &(dnslookup)& router routes addresses by looking up their domains in the
6268 DNS in order to obtain a list of hosts to which the address is routed. If the
6269 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6270 specified by the &%transport%& option. If the router does not find the domain
6271 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6272 the address fails and is bounced.
6274 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6275 be entirely ignored. This option is present because a number of cases have been
6276 encountered where MX records in the DNS point to host names
6277 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6278 Completely ignoring these IP addresses causes Exim to fail to route the
6279 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6280 continue to try to deliver the message periodically until the address timed
6287 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6289 file_transport = address_file
6290 pipe_transport = address_pipe
6292 Control reaches this and subsequent routers only for addresses in the local
6293 domains. This router checks to see whether the local part is defined as an
6294 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6295 data that it looks up from that file. If no data is found for the local part,
6296 the value of the &%data%& option is empty, causing the address to be passed to
6299 &_/etc/aliases_& is a conventional name for the system aliases file that is
6300 often used. That is why it is referenced by from the default configuration
6301 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6302 &_Local/Makefile_& before building Exim.
6307 # local_part_suffix = +* : -*
6308 # local_part_suffix_optional
6309 file = $home/.forward
6314 file_transport = address_file
6315 pipe_transport = address_pipe
6316 reply_transport = address_reply
6318 This is the most complicated router in the default configuration. It is another
6319 redirection router, but this time it is looking for forwarding data set up by
6320 individual users. The &%check_local_user%& setting specifies a check that the
6321 local part of the address is the login name of a local user. If it is not, the
6322 router is skipped. The two commented options that follow &%check_local_user%&,
6325 # local_part_suffix = +* : -*
6326 # local_part_suffix_optional
6328 .vindex "&$local_part_suffix$&"
6329 show how you can specify the recognition of local part suffixes. If the first
6330 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6331 by any sequence of characters, is removed from the local part and placed in the
6332 variable &$local_part_suffix$&. The second suffix option specifies that the
6333 presence of a suffix in the local part is optional. When a suffix is present,
6334 the check for a local login uses the local part with the suffix removed.
6336 When a local user account is found, the file called &_.forward_& in the user's
6337 home directory is consulted. If it does not exist, or is empty, the router
6338 declines. Otherwise, the contents of &_.forward_& are interpreted as
6339 redirection data (see chapter &<<CHAPredirect>>& for more details).
6341 .cindex "Sieve filter" "enabling in default router"
6342 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6343 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6344 is commented out by default), the contents of the file are interpreted as a set
6345 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6346 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6347 separate document entitled &'Exim's interfaces to mail filtering'&.
6349 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6350 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6351 There are two reasons for doing this:
6354 Whether or not a local user has a &_.forward_& file is not really relevant when
6355 checking an address for validity; it makes sense not to waste resources doing
6358 More importantly, when Exim is verifying addresses or handling an EXPN
6359 command during an SMTP session, it is running as the Exim user, not as root.
6360 The group is the Exim group, and no additional groups are set up.
6361 It may therefore not be possible for Exim to read users' &_.forward_& files at
6365 The setting of &%check_ancestor%& prevents the router from generating a new
6366 address that is the same as any previous address that was redirected. (This
6367 works round a problem concerning a bad interaction between aliasing and
6368 forwarding &-- see section &<<SECTredlocmai>>&).
6370 The final three option settings specify the transports that are to be used when
6371 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6372 auto-reply, respectively. For example, if a &_.forward_& file contains
6374 a.nother@elsewhere.example, /home/spqr/archive
6376 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6382 # local_part_suffix = +* : -*
6383 # local_part_suffix_optional
6384 transport = local_delivery
6386 The final router sets up delivery into local mailboxes, provided that the local
6387 part is the name of a local login, by accepting the address and assigning it to
6388 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6389 routers, so the address is bounced. The commented suffix settings fulfil the
6390 same purpose as they do for the &(userforward)& router.
6393 .section "Transport configuration" "SECID56"
6394 .cindex "default" "transports"
6395 .cindex "transports" "default"
6396 Transports define mechanisms for actually delivering messages. They operate
6397 only when referenced from routers, so the order in which they are defined does
6398 not matter. The transports section of the configuration starts with
6402 Two remote transports and four local transports are defined.
6406 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6411 This transport is used for delivering messages over SMTP connections.
6412 The list of remote hosts comes from the router.
6413 The &%message_size_limit%& usage is a hack to avoid sending on messages
6414 with over-long lines.
6416 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6417 negotiated between client and server and not expected to cause problems
6418 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6419 use of the &%hosts_try_prdr%& configuration option.
6421 The other remote transport is used when delivering to a specific smarthost
6422 with whom there must be some kind of existing relationship, instead of the
6423 usual federated system.
6428 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6432 # Comment out any of these which you have to, then file a Support
6433 # request with your smarthost provider to get things fixed:
6434 hosts_require_tls = *
6435 tls_verify_hosts = *
6436 # As long as tls_verify_hosts is enabled, this this will have no effect,
6437 # but if you have to comment it out then this will at least log whether
6438 # you succeed or not:
6439 tls_try_verify_hosts = *
6441 # The SNI name should match the name which we'll expect to verify;
6442 # many mail systems don't use SNI and this doesn't matter, but if it does,
6443 # we need to send a name which the remote site will recognize.
6444 # This _should_ be the name which the smarthost operators specified as
6445 # the hostname for sending your mail to.
6446 tls_sni = ROUTER_SMARTHOST
6448 .ifdef _HAVE_OPENSSL
6449 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6452 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6459 After the same &%message_size_limit%& hack, we then specify that this Transport
6460 can handle messages to multiple domains in one run. The assumption here is
6461 that you're routing all non-local mail to the same place and that place is
6462 happy to take all messages from you as quickly as possible.
6463 All other options depend upon built-in macros; if Exim was built without TLS support
6464 then no other options are defined.
6465 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6466 and versions using the &%tls_require_ciphers%& option, where the value to be
6467 used depends upon the library providing TLS.
6468 Beyond that, the options adopt the stance that you should have TLS support available
6469 from your smarthost on today's Internet, so we turn on requiring TLS for the
6470 mail to be delivered, and requiring that the certificate be valid, and match
6471 the expected hostname. The &%tls_sni%& option can be used by service providers
6472 to select an appropriate certificate to present to you and here we re-use the
6473 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6474 You want to specify the hostname which you'll expect to validate for, and that
6475 should not be subject to insecure tampering via DNS results.
6477 For the &%hosts_try_prdr%& option see the previous transport.
6479 All other options are defaulted.
6483 file = /var/mail/$local_part_data
6490 This &(appendfile)& transport is used for local delivery to user mailboxes in
6491 traditional BSD mailbox format.
6493 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6494 as it is provided by a potential bad actor.
6495 Instead we use &$local_part_data$&,
6496 the result of looking up &$local_part$& in the user database
6497 (done by using &%check_local_user%& in the the router).
6499 By default &(appendfile)& runs under the uid and gid of the
6500 local user, which requires the sticky bit to be set on the &_/var/mail_&
6501 directory. Some systems use the alternative approach of running mail deliveries
6502 under a particular group instead of using the sticky bit. The commented options
6503 show how this can be done.
6505 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6506 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6507 similarly-named options above.
6513 This transport is used for handling deliveries to pipes that are generated by
6514 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6515 option specifies that any output on stdout or stderr generated by the pipe is to
6516 be returned to the sender.
6524 This transport is used for handling deliveries to files that are generated by
6525 redirection. The name of the file is not specified in this instance of
6526 &(appendfile)&, because it comes from the &(redirect)& router.
6531 This transport is used for handling automatic replies generated by users'
6536 .section "Default retry rule" "SECID57"
6537 .cindex "retry" "default rule"
6538 .cindex "default" "retry rule"
6539 The retry section of the configuration file contains rules which affect the way
6540 Exim retries deliveries that cannot be completed at the first attempt. It is
6541 introduced by the line
6545 In the default configuration, there is just one rule, which applies to all
6548 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6550 This causes any temporarily failing address to be retried every 15 minutes for
6551 2 hours, then at intervals starting at one hour and increasing by a factor of
6552 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6553 is not delivered after 4 days of temporary failure, it is bounced. The time is
6554 measured from first failure, not from the time the message was received.
6556 If the retry section is removed from the configuration, or is empty (that is,
6557 if no retry rules are defined), Exim will not retry deliveries. This turns
6558 temporary errors into permanent errors.
6561 .section "Rewriting configuration" "SECID58"
6562 The rewriting section of the configuration, introduced by
6566 contains rules for rewriting addresses in messages as they arrive. There are no
6567 rewriting rules in the default configuration file.
6571 .section "Authenticators configuration" "SECTdefconfauth"
6572 .cindex "AUTH" "configuration"
6573 The authenticators section of the configuration, introduced by
6575 begin authenticators
6577 defines mechanisms for the use of the SMTP AUTH command. The default
6578 configuration file contains two commented-out example authenticators
6579 which support plaintext username/password authentication using the
6580 standard PLAIN mechanism and the traditional but non-standard LOGIN
6581 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6582 to support most MUA software.
6584 The example PLAIN authenticator looks like this:
6587 # driver = plaintext
6588 # server_set_id = $auth2
6589 # server_prompts = :
6590 # server_condition = Authentication is not yet configured
6591 # server_advertise_condition = ${if def:tls_in_cipher }
6593 And the example LOGIN authenticator looks like this:
6596 # driver = plaintext
6597 # server_set_id = $auth1
6598 # server_prompts = <| Username: | Password:
6599 # server_condition = Authentication is not yet configured
6600 # server_advertise_condition = ${if def:tls_in_cipher }
6603 The &%server_set_id%& option makes Exim remember the authenticated username
6604 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6605 &%server_prompts%& option configures the &(plaintext)& authenticator so
6606 that it implements the details of the specific authentication mechanism,
6607 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6608 when Exim offers authentication to clients; in the examples, this is only
6609 when TLS or SSL has been started, so to enable the authenticators you also
6610 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6612 The &%server_condition%& setting defines how to verify that the username and
6613 password are correct. In the examples it just produces an error message.
6614 To make the authenticators work, you can use a string expansion
6615 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6617 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6618 usercode and password are in different positions.
6619 Chapter &<<CHAPplaintext>>& covers both.
6621 .ecindex IIDconfiwal
6625 . ////////////////////////////////////////////////////////////////////////////
6626 . ////////////////////////////////////////////////////////////////////////////
6628 .chapter "Regular expressions" "CHAPregexp"
6630 .cindex "regular expressions" "library"
6632 Exim supports the use of regular expressions in many of its options. It
6633 uses the PCRE regular expression library; this provides regular expression
6634 matching that is compatible with Perl 5. The syntax and semantics of
6635 regular expressions is discussed in
6636 online Perl manpages, in
6637 many Perl reference books, and also in
6638 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6639 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6640 . --- the http: URL here redirects to another page with the ISBN in the URL
6641 . --- where trying to use https: just redirects back to http:, so sticking
6642 . --- to the old URL for now. 2018-09-07.
6644 The documentation for the syntax and semantics of the regular expressions that
6645 are supported by PCRE is included in the PCRE distribution, and no further
6646 description is included here. The PCRE functions are called from Exim using
6647 the default option settings (that is, with no PCRE options set), except that
6648 the PCRE_CASELESS option is set when the matching is required to be
6651 In most cases, when a regular expression is required in an Exim configuration,
6652 it has to start with a circumflex, in order to distinguish it from plain text
6653 or an &"ends with"& wildcard. In this example of a configuration setting, the
6654 second item in the colon-separated list is a regular expression.
6656 domains = a.b.c : ^\\d{3} : *.y.z : ...
6658 The doubling of the backslash is required because of string expansion that
6659 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6660 of this issue, and a way of avoiding the need for doubling backslashes. The
6661 regular expression that is eventually used in this example contains just one
6662 backslash. The circumflex is included in the regular expression, and has the
6663 normal effect of &"anchoring"& it to the start of the string that is being
6666 There are, however, two cases where a circumflex is not required for the
6667 recognition of a regular expression: these are the &%match%& condition in a
6668 string expansion, and the &%matches%& condition in an Exim filter file. In
6669 these cases, the relevant string is always treated as a regular expression; if
6670 it does not start with a circumflex, the expression is not anchored, and can
6671 match anywhere in the subject string.
6673 In all cases, if you want a regular expression to match at the end of a string,
6674 you must code the $ metacharacter to indicate this. For example:
6676 domains = ^\\d{3}\\.example
6678 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6681 domains = ^\\d{3}\\.example\$
6683 if you want &'example'& to be the top-level domain. The backslash before the
6684 $ is needed because string expansion also interprets dollar characters.
6688 . ////////////////////////////////////////////////////////////////////////////
6689 . ////////////////////////////////////////////////////////////////////////////
6691 .chapter "File and database lookups" "CHAPfdlookup"
6692 .scindex IIDfidalo1 "file" "lookups"
6693 .scindex IIDfidalo2 "database" "lookups"
6694 .cindex "lookup" "description of"
6695 Exim can be configured to look up data in files or databases as it processes
6696 messages. Two different kinds of syntax are used:
6699 A string that is to be expanded may contain explicit lookup requests. These
6700 cause parts of the string to be replaced by data that is obtained from the
6701 lookup. Lookups of this type are conditional expansion items. Different results
6702 can be defined for the cases of lookup success and failure. See chapter
6703 &<<CHAPexpand>>&, where string expansions are described in detail.
6704 The key for the lookup is &*specified*& as part of the string expansion.
6706 Lists of domains, hosts, and email addresses can contain lookup requests as a
6707 way of avoiding excessively long linear lists. In this case, the data that is
6708 returned by the lookup is often (but not always) discarded; whether the lookup
6709 succeeds or fails is what really counts. These kinds of list are described in
6710 chapter &<<CHAPdomhosaddlists>>&.
6711 The key for the lookup is &*implicit*&,
6712 given by the context in which the list is expanded.
6715 String expansions, lists, and lookups interact with each other in such a way
6716 that there is no order in which to describe any one of them that does not
6717 involve references to the others. Each of these three chapters makes more sense
6718 if you have read the other two first. If you are reading this for the first
6719 time, be aware that some of it will make a lot more sense after you have read
6720 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6722 .section "Examples of different lookup syntax" "SECID60"
6723 It is easy to confuse the two different kinds of lookup, especially as the
6724 lists that may contain the second kind are always expanded before being
6725 processed as lists. Therefore, they may also contain lookups of the first kind.
6726 Be careful to distinguish between the following two examples:
6728 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6729 domains = lsearch;/some/file
6731 The first uses a string expansion, the result of which must be a domain list.
6732 No strings have been specified for a successful or a failing lookup; the
6733 defaults in this case are the looked-up data and an empty string, respectively.
6734 The expansion takes place before the string is processed as a list, and the
6735 file that is searched could contain lines like this:
6737 192.168.3.4: domain1:domain2:...
6738 192.168.1.9: domain3:domain4:...
6740 When the lookup succeeds, the result of the expansion is a list of domains (and
6741 possibly other types of item that are allowed in domain lists).
6742 .cindex "tainted data" "de-tainting"
6743 The result of the expansion is not tainted.
6745 In the second example, the lookup is a single item in a domain list. It causes
6746 Exim to use a lookup to see if the domain that is being processed can be found
6748 The file could contains lines like this:
6753 Any data that follows the keys is not relevant when checking that the domain
6754 matches the list item.
6756 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6757 Consider a file containing lines like this:
6759 192.168.5.6: lsearch;/another/file
6761 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6762 first &%domains%& setting above generates the second setting, which therefore
6763 causes a second lookup to occur.
6766 The lookup type may optionally be followed by a comma
6767 and a comma-separated list of options.
6768 Each option is a &"name=value"& pair.
6769 Whether an option is meaningful depends on the lookup type.
6771 All lookups support the option &"cache=no_rd"&.
6772 If this is given then the cache that Exim manages for lookup results
6773 is not checked before doing the lookup.
6774 The result of the lookup is still written to the cache.
6777 The rest of this chapter describes the different lookup types that are
6778 available. Any of them can be used in any part of the configuration where a
6779 lookup is permitted.
6782 .section "Lookup types" "SECID61"
6783 .cindex "lookup" "types of"
6784 .cindex "single-key lookup" "definition of"
6785 Two different types of data lookup are implemented:
6788 The &'single-key'& type requires the specification of a file in which to look,
6789 and a single key to search for. The key must be a non-empty string for the
6790 lookup to succeed. The lookup type determines how the file is searched.
6791 .cindex "tainted data" "single-key lookups"
6792 The file string may not be tainted
6794 .cindex "tainted data" "de-tainting"
6795 All single-key lookups support the option &"ret=key"&.
6796 If this is given and the lookup
6797 (either underlying implementation or cached value)
6798 returns data, the result is replaced with a non-tainted
6799 version of the lookup key.
6800 .cindex "tainted data" "de-tainting"
6802 .cindex "query-style lookup" "definition of"
6803 The &'query-style'& type accepts a generalized database query. No particular
6804 key value is assumed by Exim for query-style lookups. You can use whichever
6805 Exim variables you need to construct the database query.
6808 The code for each lookup type is in a separate source file that is included in
6809 the binary of Exim only if the corresponding compile-time option is set. The
6810 default settings in &_src/EDITME_& are:
6815 which means that only linear searching and DBM lookups are included by default.
6816 For some types of lookup (e.g. SQL databases), you need to install appropriate
6817 libraries and header files before building Exim.
6822 .section "Single-key lookup types" "SECTsinglekeylookups"
6823 .cindex "lookup" "single-key types"
6824 .cindex "single-key lookup" "list of types"
6825 The following single-key lookup types are implemented:
6828 .cindex "cdb" "description of"
6829 .cindex "lookup" "cdb"
6830 .cindex "binary zero" "in lookup key"
6831 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6832 string without a terminating binary zero. The cdb format is designed for
6833 indexed files that are read frequently and never updated, except by total
6834 re-creation. As such, it is particularly suitable for large files containing
6835 aliases or other indexed data referenced by an MTA. Information about cdb and
6836 tools for building the files can be found in several places:
6838 &url(https://cr.yp.to/cdb.html)
6839 &url(https://www.corpit.ru/mjt/tinycdb.html)
6840 &url(https://packages.debian.org/stable/utils/freecdb)
6841 &url(https://github.com/philpennock/cdbtools) (in Go)
6843 A cdb distribution is not needed in order to build Exim with cdb support,
6844 because the code for reading cdb files is included directly in Exim itself.
6845 However, no means of building or testing cdb files is provided with Exim, so
6846 you need to obtain a cdb distribution in order to do this.
6848 .cindex "DBM" "lookup type"
6849 .cindex "lookup" "dbm"
6850 .cindex "binary zero" "in lookup key"
6851 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6852 DBM file by looking up the record with the given key. A terminating binary
6853 zero is included in the key that is passed to the DBM library. See section
6854 &<<SECTdb>>& for a discussion of DBM libraries.
6856 .cindex "Berkeley DB library" "file format"
6857 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6858 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6859 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6860 the DB_UNKNOWN option. This enables it to handle any of the types of database
6861 that the library supports, and can be useful for accessing DBM files created by
6862 other applications. (For earlier DB versions, DB_HASH is always used.)
6864 .cindex "lookup" "dbmjz"
6865 .cindex "lookup" "dbm &-- embedded NULs"
6867 .cindex "dbmjz lookup type"
6868 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6869 interpreted as an Exim list; the elements of the list are joined together with
6870 ASCII NUL characters to form the lookup key. An example usage would be to
6871 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6872 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6873 &(cram_md5)& authenticator.
6875 .cindex "lookup" "dbmnz"
6876 .cindex "lookup" "dbm &-- terminating zero"
6877 .cindex "binary zero" "in lookup key"
6879 .cindex "&_/etc/userdbshadow.dat_&"
6880 .cindex "dbmnz lookup type"
6881 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6882 is not included in the key that is passed to the DBM library. You may need this
6883 if you want to look up data in files that are created by or shared with some
6884 other application that does not use terminating zeros. For example, you need to
6885 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6886 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6887 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6888 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6890 .cindex "lookup" "dsearch"
6891 .cindex "dsearch lookup type"
6892 &(dsearch)&: The given file must be an
6894 directory path; this is searched for an entry
6895 whose name is the key by calling the &[lstat()]& function.
6897 contain any forward slash characters.
6898 If &[lstat()]& succeeds then so does the lookup.
6899 .cindex "tainted data" "dsearch result"
6900 The result is regarded as untainted.
6902 Options for the lookup can be given by appending them after the word "dsearch",
6903 separated by a comma. Options, if present, are a comma-separated list having
6904 each element starting with a tag name and an equals.
6906 Two options are supported, for the return value and for filtering match
6908 The "ret" option requests an alternate result value of
6909 the entire path for the entry. Example:
6911 ${lookup {passwd} dsearch,ret=full {/etc}}
6913 The default result is just the requested entry.
6914 The "filter" option requests that only directory entries of a given type
6915 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6916 not matching "." or ".."). Example:
6918 ${lookup {passwd} dsearch,filter=file {/etc}}
6920 The default matching is for any entry type, including directories
6923 An example of how this
6924 lookup can be used to support virtual domains is given in section
6925 &<<SECTvirtualdomains>>&.
6927 .cindex "lookup" "iplsearch"
6928 .cindex "iplsearch lookup type"
6929 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6930 terminated by a colon or white space or the end of the line. The keys in the
6931 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6932 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6933 being interpreted as a key terminator. For example:
6935 1.2.3.4: data for 1.2.3.4
6936 192.168.0.0/16: data for 192.168.0.0/16
6937 "abcd::cdab": data for abcd::cdab
6938 "abcd:abcd::/32" data for abcd:abcd::/32
6940 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6941 file is searched linearly, using the CIDR masks where present, until a matching
6942 key is found. The first key that matches is used; there is no attempt to find a
6943 &"best"& match. Apart from the way the keys are matched, the processing for
6944 &(iplsearch)& is the same as for &(lsearch)&.
6946 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6947 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6948 lookup types support only literal keys.
6950 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6951 the implicit key is the host's IP address rather than its name (see section
6952 &<<SECThoslispatsikey>>&).
6954 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6955 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6956 notation before executing the lookup.)
6959 One option is supported, "ret=full", to request the return of the entire line
6960 rather than omitting the key porttion.
6961 Note however that the key portion will have been de-quoted.
6966 .cindex json "lookup type"
6967 .cindex JSON expansions
6968 &(json)&: The given file is a text file with a JSON structure.
6969 An element of the structure is extracted, defined by the search key.
6970 The key is a list of subelement selectors
6971 (colon-separated by default but changeable in the usual way)
6972 which are applied in turn to select smaller and smaller portions
6973 of the JSON structure.
6974 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6975 nunbered array element is selected.
6976 Otherwise it must apply to a JSON object; the named element is selected.
6977 The final resulting element can be a simple JSON type or a JSON object
6978 or array; for the latter two a string-representation of the JSON
6980 For elements of type string, the returned value is de-quoted.
6987 .cindex database lmdb
6988 &(lmdb)&: The given file is an LMDB database.
6989 LMDB is a memory-mapped key-value store,
6990 with API modeled loosely on that of BerkeleyDB.
6991 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6992 for the feature set and operation modes.
6994 Exim provides read-only access via the LMDB C library.
6995 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6996 or your operating system package repository.
6997 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6999 You will need to separately create the LMDB database file,
7000 possibly using the &"mdb_load"& utility.
7005 .cindex "linear search"
7006 .cindex "lookup" "lsearch"
7007 .cindex "lsearch lookup type"
7008 .cindex "case sensitivity" "in lsearch lookup"
7009 &(lsearch)&: The given file is a text file that is searched linearly for a
7010 line beginning with the search key, terminated by a colon or white space or the
7011 end of the line. The search is case-insensitive; that is, upper and lower case
7012 letters are treated as the same. The first occurrence of the key that is found
7013 in the file is used.
7015 White space between the key and the colon is permitted. The remainder of the
7016 line, with leading and trailing white space removed, is the data. This can be
7017 continued onto subsequent lines by starting them with any amount of white
7018 space, but only a single space character is included in the data at such a
7019 junction. If the data begins with a colon, the key must be terminated by a
7024 Empty lines and lines beginning with # are ignored, even if they occur in the
7025 middle of an item. This is the traditional textual format of alias files. Note
7026 that the keys in an &(lsearch)& file are literal strings. There is no
7027 wildcarding of any kind.
7029 .cindex "lookup" "lsearch &-- colons in keys"
7030 .cindex "white space" "in lsearch key"
7031 In most &(lsearch)& files, keys are not required to contain colons or #
7032 characters, or white space. However, if you need this feature, it is available.
7033 If a key begins with a doublequote character, it is terminated only by a
7034 matching quote (or end of line), and the normal escaping rules apply to its
7035 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7036 quoted keys (exactly as for unquoted keys). There is no special handling of
7037 quotes for the data part of an &(lsearch)& line.
7040 .cindex "NIS lookup type"
7041 .cindex "lookup" "NIS"
7042 .cindex "binary zero" "in lookup key"
7043 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7044 the given key, without a terminating binary zero. There is a variant called
7045 &(nis0)& which does include the terminating binary zero in the key. This is
7046 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7047 aliases; the full map names must be used.
7050 .cindex "wildlsearch lookup type"
7051 .cindex "lookup" "wildlsearch"
7052 .cindex "nwildlsearch lookup type"
7053 .cindex "lookup" "nwildlsearch"
7054 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7055 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7056 the file may be wildcarded. The difference between these two lookup types is
7057 that for &(wildlsearch)&, each key in the file is string-expanded before being
7058 used, whereas for &(nwildlsearch)&, no expansion takes place.
7060 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7061 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7062 file that are regular expressions can be made case-sensitive by the use of
7063 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7065 . ==== As this is a nested list, any displays it contains must be indented
7066 . ==== as otherwise they are too far to the left.
7069 The string may begin with an asterisk to mean &"ends with"&. For example:
7071 *.a.b.c data for anything.a.b.c
7072 *fish data for anythingfish
7075 The string may begin with a circumflex to indicate a regular expression. For
7076 example, for &(wildlsearch)&:
7078 ^\N\d+\.a\.b\N data for <digits>.a.b
7080 Note the use of &`\N`& to disable expansion of the contents of the regular
7081 expression. If you are using &(nwildlsearch)&, where the keys are not
7082 string-expanded, the equivalent entry is:
7084 ^\d+\.a\.b data for <digits>.a.b
7086 The case-insensitive flag is set at the start of compiling the regular
7087 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7088 For example, to make the entire pattern case-sensitive:
7090 ^(?-i)\d+\.a\.b data for <digits>.a.b
7093 If the regular expression contains white space or colon characters, you must
7094 either quote it (see &(lsearch)& above), or represent these characters in other
7095 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7096 colon. This may be easier than quoting, because if you quote, you have to
7097 escape all the backslashes inside the quotes.
7099 &*Note*&: It is not possible to capture substrings in a regular expression
7100 match for later use, because the results of all lookups are cached. If a lookup
7101 is repeated, the result is taken from the cache, and no actual pattern matching
7102 takes place. The values of all the numeric variables are unset after a
7103 &((n)wildlsearch)& match.
7106 Although I cannot see it being of much use, the general matching function that
7107 is used to implement &((n)wildlsearch)& means that the string may begin with a
7108 lookup name terminated by a semicolon, and followed by lookup data. For
7111 cdb;/some/file data for keys that match the file
7113 The data that is obtained from the nested lookup is discarded.
7116 Keys that do not match any of these patterns are interpreted literally. The
7117 continuation rules for the data are the same as for &(lsearch)&, and keys may
7118 be followed by optional colons.
7120 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7121 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7122 lookup types support only literal keys.
7125 .cindex "spf lookup type"
7126 .cindex "lookup" "spf"
7127 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7128 (as opposed to the standard ACL condition method).
7129 For details see section &<<SECSPF>>&.
7133 .section "Query-style lookup types" "SECTquerystylelookups"
7134 .cindex "lookup" "query-style types"
7135 .cindex "query-style lookup" "list of types"
7136 The supported query-style lookup types are listed below. Further details about
7137 many of them are given in later sections.
7140 .cindex "DNS" "as a lookup type"
7141 .cindex "lookup" "DNS"
7142 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7143 are given in the supplied query. The resulting data is the contents of the
7144 records. See section &<<SECTdnsdb>>&.
7146 .cindex "InterBase lookup type"
7147 .cindex "lookup" "InterBase"
7148 &(ibase)&: This does a lookup in an InterBase database.
7150 .cindex "LDAP" "lookup type"
7151 .cindex "lookup" "LDAP"
7152 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7153 returns attributes from a single entry. There is a variant called &(ldapm)&
7154 that permits values from multiple entries to be returned. A third variant
7155 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7156 any attribute values. See section &<<SECTldap>>&.
7158 .cindex "MySQL" "lookup type"
7159 .cindex "lookup" "MySQL"
7160 &(mysql)&: The format of the query is an SQL statement that is passed to a
7161 MySQL database. See section &<<SECTsql>>&.
7163 .cindex "NIS+ lookup type"
7164 .cindex "lookup" "NIS+"
7165 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7166 the field to be returned. See section &<<SECTnisplus>>&.
7168 .cindex "Oracle" "lookup type"
7169 .cindex "lookup" "Oracle"
7170 &(oracle)&: The format of the query is an SQL statement that is passed to an
7171 Oracle database. See section &<<SECTsql>>&.
7173 .cindex "lookup" "passwd"
7174 .cindex "passwd lookup type"
7175 .cindex "&_/etc/passwd_&"
7176 &(passwd)& is a query-style lookup with queries that are just user names. The
7177 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7178 success, the result string is the same as you would get from an &(lsearch)&
7179 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7180 password value. For example:
7182 *:42:42:King Rat:/home/kr:/bin/bash
7185 .cindex "PostgreSQL lookup type"
7186 .cindex "lookup" "PostgreSQL"
7187 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7188 PostgreSQL database. See section &<<SECTsql>>&.
7191 .cindex "Redis lookup type"
7192 .cindex lookup Redis
7193 &(redis)&: The format of the query is either a simple get or simple set,
7194 passed to a Redis database. See section &<<SECTsql>>&.
7197 .cindex "sqlite lookup type"
7198 .cindex "lookup" "sqlite"
7199 &(sqlite)&: The format of the query is
7200 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7203 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7204 not likely to be useful in normal operation.
7206 .cindex "whoson lookup type"
7207 .cindex "lookup" "whoson"
7208 . --- still http:-only, 2018-09-07
7209 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7210 allows a server to check whether a particular (dynamically allocated) IP
7211 address is currently allocated to a known (trusted) user and, optionally, to
7212 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7213 at one time for &"POP before SMTP"& authentication, but that approach has been
7214 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7215 &"POP before SMTP"& checking using ACL statements such as
7217 require condition = \
7218 ${lookup whoson {$sender_host_address}{yes}{no}}
7220 The query consists of a single IP address. The value returned is the name of
7221 the authenticated user, which is stored in the variable &$value$&. However, in
7222 this example, the data in &$value$& is not used; the result of the lookup is
7223 one of the fixed strings &"yes"& or &"no"&.
7228 .section "Temporary errors in lookups" "SECID63"
7229 .cindex "lookup" "temporary error in"
7230 Lookup functions can return temporary error codes if the lookup cannot be
7231 completed. For example, an SQL or LDAP database might be unavailable. For this
7232 reason, it is not advisable to use a lookup that might do this for critical
7233 options such as a list of local domains.
7235 When a lookup cannot be completed in a router or transport, delivery
7236 of the message (to the relevant address) is deferred, as for any other
7237 temporary error. In other circumstances Exim may assume the lookup has failed,
7238 or may give up altogether.
7242 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7243 .cindex "wildcard lookups"
7244 .cindex "lookup" "default values"
7245 .cindex "lookup" "wildcard"
7246 .cindex "lookup" "* added to type"
7247 .cindex "default" "in single-key lookups"
7248 In this context, a &"default value"& is a value specified by the administrator
7249 that is to be used if a lookup fails.
7251 &*Note:*& This section applies only to single-key lookups. For query-style
7252 lookups, the facilities of the query language must be used. An attempt to
7253 specify a default for a query-style lookup provokes an error.
7255 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7256 and the initial lookup fails, the key &"*"& is looked up in the file to
7257 provide a default value. See also the section on partial matching below.
7259 .cindex "*@ with single-key lookup"
7260 .cindex "lookup" "*@ added to type"
7261 .cindex "alias file" "per-domain default"
7262 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7263 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7264 character, a second lookup is done with everything before the last @ replaced
7265 by *. This makes it possible to provide per-domain defaults in alias files
7266 that include the domains in the keys. If the second lookup fails (or doesn't
7267 take place because there is no @ in the key), &"*"& is looked up.
7268 For example, a &(redirect)& router might contain:
7270 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7272 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7273 looks up these keys, in this order:
7279 The data is taken from whichever key it finds first. &*Note*&: In an
7280 &(lsearch)& file, this does not mean the first of these keys in the file. A
7281 complete scan is done for each key, and only if it is not found at all does
7282 Exim move on to try the next key.
7286 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7287 .cindex "partial matching"
7288 .cindex "wildcard lookups"
7289 .cindex "lookup" "partial matching"
7290 .cindex "lookup" "wildcard"
7291 .cindex "asterisk" "in search type"
7292 The normal operation of a single-key lookup is to search the file for an exact
7293 match with the given key. However, in a number of situations where domains are
7294 being looked up, it is useful to be able to do partial matching. In this case,
7295 information in the file that has a key starting with &"*."& is matched by any
7296 domain that ends with the components that follow the full stop. For example, if
7297 a key in a DBM file is
7299 *.dates.fict.example
7301 then when partial matching is enabled this is matched by (amongst others)
7302 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7303 by &'dates.fict.example'&, if that does not appear as a separate key in the
7306 &*Note*&: Partial matching is not available for query-style lookups. It is
7307 also not available for any lookup items in address lists (see section
7308 &<<SECTaddresslist>>&).
7310 Partial matching is implemented by doing a series of separate lookups using
7311 keys constructed by modifying the original subject key. This means that it can
7312 be used with any of the single-key lookup types, provided that
7313 partial matching keys
7314 beginning with a special prefix (default &"*."&) are included in the data file.
7315 Keys in the file that do not begin with the prefix are matched only by
7316 unmodified subject keys when partial matching is in use.
7318 Partial matching is requested by adding the string &"partial-"& to the front of
7319 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7320 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7321 is added at the start of the subject key, and it is looked up again. If that
7322 fails, further lookups are tried with dot-separated components removed from the
7323 start of the subject key, one-by-one, and &"*."& added on the front of what
7326 A minimum number of two non-* components are required. This can be adjusted
7327 by including a number before the hyphen in the search type. For example,
7328 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7329 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7330 subject key is &'2250.dates.fict.example'& then the following keys are looked
7331 up when the minimum number of non-* components is two:
7333 2250.dates.fict.example
7334 *.2250.dates.fict.example
7335 *.dates.fict.example
7338 As soon as one key in the sequence is successfully looked up, the lookup
7341 .cindex "lookup" "partial matching &-- changing prefix"
7342 .cindex "prefix" "for partial matching"
7343 The use of &"*."& as the partial matching prefix is a default that can be
7344 changed. The motivation for this feature is to allow Exim to operate with file
7345 formats that are used by other MTAs. A different prefix can be supplied in
7346 parentheses instead of the hyphen after &"partial"&. For example:
7348 domains = partial(.)lsearch;/some/file
7350 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7351 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7352 components is unchanged). The prefix may consist of any punctuation characters
7353 other than a closing parenthesis. It may be empty, for example:
7355 domains = partial1()cdb;/some/file
7357 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7358 &`a.b.c`&, &`b.c`&, and &`c`&.
7360 If &"partial0"& is specified, what happens at the end (when the lookup with
7361 just one non-wild component has failed, and the original key is shortened right
7362 down to the null string) depends on the prefix:
7365 If the prefix has zero length, the whole lookup fails.
7367 If the prefix has length 1, a lookup for just the prefix is done. For
7368 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7370 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7371 remainder is looked up. With the default prefix, therefore, the final lookup is
7372 for &"*"& on its own.
7374 Otherwise, the whole prefix is looked up.
7378 If the search type ends in &"*"& or &"*@"& (see section
7379 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7380 this implies happens after all partial lookups have failed. If &"partial0"& is
7381 specified, adding &"*"& to the search type has no effect with the default
7382 prefix, because the &"*"& key is already included in the sequence of partial
7383 lookups. However, there might be a use for lookup types such as
7384 &"partial0(.)lsearch*"&.
7386 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7387 in domain lists and the like. Partial matching works only in terms of
7388 dot-separated components; a key such as &`*fict.example`&
7389 in a database file is useless, because the asterisk in a partial matching
7390 subject key is always followed by a dot.
7395 .section "Lookup caching" "SECID64"
7396 .cindex "lookup" "caching"
7397 .cindex "caching" "lookup data"
7398 Exim caches all lookup results in order to avoid needless repetition of
7399 lookups. However, because (apart from the daemon) Exim operates as a collection
7400 of independent, short-lived processes, this caching applies only within a
7401 single Exim process. There is no inter-process lookup caching facility.
7403 For single-key lookups, Exim keeps the relevant files open in case there is
7404 another lookup that needs them. In some types of configuration this can lead to
7405 many files being kept open for messages with many recipients. To avoid hitting
7406 the operating system limit on the number of simultaneously open files, Exim
7407 closes the least recently used file when it needs to open more files than its
7408 own internal limit, which can be changed via the &%lookup_open_max%& option.
7410 The single-key lookup files are closed and the lookup caches are flushed at
7411 strategic points during delivery &-- for example, after all routing is
7417 .section "Quoting lookup data" "SECID65"
7418 .cindex "lookup" "quoting"
7419 .cindex "quoting" "in lookups"
7420 When data from an incoming message is included in a query-style lookup, there
7421 is the possibility of special characters in the data messing up the syntax of
7422 the query. For example, a NIS+ query that contains
7426 will be broken if the local part happens to contain a closing square bracket.
7427 For NIS+, data can be enclosed in double quotes like this:
7429 [name="$local_part"]
7431 but this still leaves the problem of a double quote in the data. The rule for
7432 NIS+ is that double quotes must be doubled. Other lookup types have different
7433 rules, and to cope with the differing requirements, an expansion operator
7434 of the following form is provided:
7436 ${quote_<lookup-type>:<string>}
7438 For example, the safest way to write the NIS+ query is
7440 [name="${quote_nisplus:$local_part}"]
7442 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7443 operator can be used for all lookup types, but has no effect for single-key
7444 lookups, since no quoting is ever needed in their key strings.
7449 .section "More about dnsdb" "SECTdnsdb"
7450 .cindex "dnsdb lookup"
7451 .cindex "lookup" "dnsdb"
7452 .cindex "DNS" "as a lookup type"
7453 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7454 of a record type and a domain name, separated by an equals sign. For example,
7455 an expansion string could contain:
7457 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7459 If the lookup succeeds, the result is placed in &$value$&, which in this case
7460 is used on its own as the result. If the lookup does not succeed, the
7461 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7462 &<<SECTforexpfai>>& for an explanation of what this means.
7464 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7465 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7466 If no type is given, TXT is assumed.
7468 For any record type, if multiple records are found, the data is returned as a
7469 concatenation, with newline as the default separator. The order, of course,
7470 depends on the DNS resolver. You can specify a different separator character
7471 between multiple records by putting a right angle-bracket followed immediately
7472 by the new separator at the start of the query. For example:
7474 ${lookup dnsdb{>: a=host1.example}}
7476 It is permitted to specify a space as the separator character. Further
7477 white space is ignored.
7478 For lookup types that return multiple fields per record,
7479 an alternate field separator can be specified using a comma after the main
7480 separator character, followed immediately by the field separator.
7482 .cindex "PTR record" "in &(dnsdb)& lookup"
7483 When the type is PTR,
7484 the data can be an IP address, written as normal; inversion and the addition of
7485 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7487 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7489 If the data for a PTR record is not a syntactically valid IP address, it is not
7490 altered and nothing is added.
7492 .cindex "MX record" "in &(dnsdb)& lookup"
7493 .cindex "SRV record" "in &(dnsdb)& lookup"
7494 For an MX lookup, both the preference value and the host name are returned for
7495 each record, separated by a space. For an SRV lookup, the priority, weight,
7496 port, and host name are returned for each record, separated by spaces.
7497 The field separator can be modified as above.
7499 .cindex "TXT record" "in &(dnsdb)& lookup"
7500 .cindex "SPF record" "in &(dnsdb)& lookup"
7501 For TXT records with multiple items of data, only the first item is returned,
7502 unless a field separator is specified.
7503 To concatenate items without a separator, use a semicolon instead.
7505 default behaviour is to concatenate multiple items without using a separator.
7507 ${lookup dnsdb{>\n,: txt=a.b.example}}
7508 ${lookup dnsdb{>\n; txt=a.b.example}}
7509 ${lookup dnsdb{spf=example.org}}
7511 It is permitted to specify a space as the separator character. Further
7512 white space is ignored.
7514 .cindex "SOA record" "in &(dnsdb)& lookup"
7515 For an SOA lookup, while no result is obtained the lookup is redone with
7516 successively more leading components dropped from the given domain.
7517 Only the primary-nameserver field is returned unless a field separator is
7520 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7523 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7524 .cindex "dnsdb modifiers"
7525 .cindex "modifiers" "dnsdb"
7526 .cindex "options" "dnsdb"
7527 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7528 each followed by a comma,
7529 that may appear before the record type.
7531 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7532 temporary DNS error for any of them, the behaviour is controlled by
7533 a defer-option modifier.
7534 The possible keywords are
7535 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7536 With &"strict"& behaviour, any temporary DNS error causes the
7537 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7538 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7539 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7540 error causes the whole lookup to defer only if none of the other lookups
7541 succeed. The default is &"lax"&, so the following lookups are equivalent:
7543 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7544 ${lookup dnsdb{a=one.host.com:two.host.com}}
7546 Thus, in the default case, as long as at least one of the DNS lookups
7547 yields some data, the lookup succeeds.
7549 .cindex "DNSSEC" "dns lookup"
7550 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7551 The possible keywords are
7552 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7553 With &"strict"& or &"lax"& DNSSEC information is requested
7555 With &"strict"& a response from the DNS resolver that
7556 is not labelled as authenticated data
7557 is treated as equivalent to a temporary DNS error.
7558 The default is &"lax"&.
7560 See also the &$lookup_dnssec_authenticated$& variable.
7562 .cindex timeout "dns lookup"
7563 .cindex "DNS" timeout
7564 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7565 The form is &"retrans_VAL"& where VAL is an Exim time specification
7567 The default value is set by the main configuration option &%dns_retrans%&.
7569 Retries for the dnsdb lookup can be controlled by a retry modifier.
7570 The form if &"retry_VAL"& where VAL is an integer.
7571 The default count is set by the main configuration option &%dns_retry%&.
7573 .cindex caching "of dns lookup"
7574 .cindex TTL "of dns lookup"
7576 Dnsdb lookup results are cached within a single process (and its children).
7577 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7578 value of the set of returned DNS records.
7581 .section "Pseudo dnsdb record types" "SECID66"
7582 .cindex "MX record" "in &(dnsdb)& lookup"
7583 By default, both the preference value and the host name are returned for
7584 each MX record, separated by a space. If you want only host names, you can use
7585 the pseudo-type MXH:
7587 ${lookup dnsdb{mxh=a.b.example}}
7589 In this case, the preference values are omitted, and just the host names are
7592 .cindex "name server for enclosing domain"
7593 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7594 records on the given domain, but if none are found, it removes the first
7595 component of the domain name, and tries again. This process continues until NS
7596 records are found or there are no more components left (or there is a DNS
7597 error). In other words, it may return the name servers for a top-level domain,
7598 but it never returns the root name servers. If there are no NS records for the
7599 top-level domain, the lookup fails. Consider these examples:
7601 ${lookup dnsdb{zns=xxx.quercite.com}}
7602 ${lookup dnsdb{zns=xxx.edu}}
7604 Assuming that in each case there are no NS records for the full domain name,
7605 the first returns the name servers for &%quercite.com%&, and the second returns
7606 the name servers for &%edu%&.
7608 You should be careful about how you use this lookup because, unless the
7609 top-level domain does not exist, the lookup always returns some host names. The
7610 sort of use to which this might be put is for seeing if the name servers for a
7611 given domain are on a blacklist. You can probably assume that the name servers
7612 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7615 .cindex "CSA" "in &(dnsdb)& lookup"
7616 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7617 records according to the CSA rules, which are described in section
7618 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7619 not sufficient because of the extra parent domain search behaviour of CSA. The
7620 result of a successful lookup such as:
7622 ${lookup dnsdb {csa=$sender_helo_name}}
7624 has two space-separated fields: an authorization code and a target host name.
7625 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7626 authorization required but absent, or &"?"& for unknown.
7628 .cindex "A+" "in &(dnsdb)& lookup"
7629 The pseudo-type A+ performs an AAAA
7630 and then an A lookup. All results are returned; defer processing
7631 (see below) is handled separately for each lookup. Example:
7633 ${lookup dnsdb {>; a+=$sender_helo_name}}
7637 .section "Multiple dnsdb lookups" "SECID67"
7638 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7639 However, you can specify a list of domains or IP addresses in a single
7640 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7641 the default separator, but with the ability to change this. For example:
7643 ${lookup dnsdb{one.domain.com:two.domain.com}}
7644 ${lookup dnsdb{a=one.host.com:two.host.com}}
7645 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7647 In order to retain backwards compatibility, there is one special case: if
7648 the lookup type is PTR and no change of separator is specified, Exim looks
7649 to see if the rest of the string is precisely one IPv6 address. In this
7650 case, it does not treat it as a list.
7652 The data from each lookup is concatenated, with newline separators by default,
7653 in the same way that multiple DNS records for a single item are handled. A
7654 different separator can be specified, as described above.
7659 .section "More about LDAP" "SECTldap"
7660 .cindex "LDAP" "lookup, more about"
7661 .cindex "lookup" "LDAP"
7662 .cindex "Solaris" "LDAP"
7663 The original LDAP implementation came from the University of Michigan; this has
7664 become &"Open LDAP"&, and there are now two different releases. Another
7665 implementation comes from Netscape, and Solaris 7 and subsequent releases
7666 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7667 the lookup function level, their error handling is different. For this reason
7668 it is necessary to set a compile-time variable when building Exim with LDAP, to
7669 indicate which LDAP library is in use. One of the following should appear in
7670 your &_Local/Makefile_&:
7672 LDAP_LIB_TYPE=UMICHIGAN
7673 LDAP_LIB_TYPE=OPENLDAP1
7674 LDAP_LIB_TYPE=OPENLDAP2
7675 LDAP_LIB_TYPE=NETSCAPE
7676 LDAP_LIB_TYPE=SOLARIS
7678 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7679 same interface as the University of Michigan version.
7681 There are three LDAP lookup types in Exim. These behave slightly differently in
7682 the way they handle the results of a query:
7685 &(ldap)& requires the result to contain just one entry; if there are more, it
7688 &(ldapdn)& also requires the result to contain just one entry, but it is the
7689 Distinguished Name that is returned rather than any attribute values.
7691 &(ldapm)& permits the result to contain more than one entry; the attributes
7692 from all of them are returned.
7696 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7697 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7698 the data returned by a successful lookup is described in the next section.
7699 First we explain how LDAP queries are coded.
7702 .section "Format of LDAP queries" "SECTforldaque"
7703 .cindex "LDAP" "query format"
7704 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7705 the configuration of a &(redirect)& router one might have this setting:
7707 data = ${lookup ldap \
7708 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7709 c=UK?mailbox?base?}}
7711 .cindex "LDAP" "with TLS"
7712 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7713 secure (encrypted) LDAP connections. The second of these ensures that an
7714 encrypted TLS connection is used.
7716 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7717 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7718 See the &%ldap_start_tls%& option.
7720 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7721 controlled. Every part of the TLS configuration can be configured by settings in
7722 &_exim.conf_&. Depending on the version of the client libraries installed on
7723 your system, some of the initialization may have required setting options in
7724 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7725 certificates. This revealed a nuance where the current UID that exim was
7726 running as could affect which config files it read. With Exim 4.83, these
7727 methods become optional, only taking effect if not specifically set in
7731 .section "LDAP quoting" "SECID68"
7732 .cindex "LDAP" "quoting"
7733 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7734 and the second because the LDAP query is represented as a URL. Furthermore,
7735 within an LDAP query, two different kinds of quoting are required. For this
7736 reason, there are two different LDAP-specific quoting operators.
7738 The &%quote_ldap%& operator is designed for use on strings that are part of
7739 filter specifications. Conceptually, it first does the following conversions on
7747 in accordance with RFC 2254. The resulting string is then quoted according
7748 to the rules for URLs, that is, all non-alphanumeric characters except
7752 are converted to their hex values, preceded by a percent sign. For example:
7754 ${quote_ldap: a(bc)*, a<yz>; }
7758 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7760 Removing the URL quoting, this is (with a leading and a trailing space):
7762 a\28bc\29\2A, a<yz>;
7764 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7765 base DN specifications in queries. Conceptually, it first converts the string
7766 by inserting a backslash in front of any of the following characters:
7770 It also inserts a backslash before any leading spaces or # characters, and
7771 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7772 is then quoted according to the rules for URLs. For example:
7774 ${quote_ldap_dn: a(bc)*, a<yz>; }
7778 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7780 Removing the URL quoting, this is (with a trailing space):
7782 \ a(bc)*\, a\<yz\>\;\
7784 There are some further comments about quoting in the section on LDAP
7785 authentication below.
7788 .section "LDAP connections" "SECID69"
7789 .cindex "LDAP" "connections"
7790 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7791 is in use, via a Unix domain socket. The example given above does not specify
7792 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7795 ldap://<hostname>:<port>/...
7797 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7798 used. When no server is specified in a query, a list of default servers is
7799 taken from the &%ldap_default_servers%& configuration option. This supplies a
7800 colon-separated list of servers which are tried in turn until one successfully
7801 handles a query, or there is a serious error. Successful handling either
7802 returns the requested data, or indicates that it does not exist. Serious errors
7803 are syntactical, or multiple values when only a single value is expected.
7804 Errors which cause the next server to be tried are connection failures, bind
7805 failures, and timeouts.
7807 For each server name in the list, a port number can be given. The standard way
7808 of specifying a host and port is to use a colon separator (RFC 1738). Because
7809 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7810 doubled. For example
7812 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7814 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7815 to the LDAP library with no server name, and the library's default (normally
7816 the local host) is used.
7818 If you are using the OpenLDAP library, you can connect to an LDAP server using
7819 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7820 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7821 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7824 For this type of connection, instead of a host name for the server, a pathname
7825 for the socket is required, and the port number is not relevant. The pathname
7826 can be specified either as an item in &%ldap_default_servers%&, or inline in
7827 the query. In the former case, you can have settings such as
7829 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7831 When the pathname is given in the query, you have to escape the slashes as
7832 &`%2F`& to fit in with the LDAP URL syntax. For example:
7834 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7836 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7837 a pathname, it uses the Unix domain socket code, even if the query actually
7838 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7839 socket connection. This behaviour means that you can use a setting of
7840 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7841 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7842 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7845 If an explicit &`ldapi`& type is given in a query when a host name is
7846 specified, an error is diagnosed. However, if there are more items in
7847 &%ldap_default_servers%&, they are tried. In other words:
7850 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7853 Using &`ldapi`& with a host name causes an error.
7857 Using &`ldapi`& with no host or path in the query, and no setting of
7858 &%ldap_default_servers%&, does whatever the library does by default.
7862 .section "LDAP authentication and control information" "SECID70"
7863 .cindex "LDAP" "authentication"
7864 The LDAP URL syntax provides no way of passing authentication and other control
7865 information to the server. To make this possible, the URL in an LDAP query may
7866 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7867 spaces. If a value contains spaces it must be enclosed in double quotes, and
7868 when double quotes are used, backslash is interpreted in the usual way inside
7869 them. The following names are recognized:
7871 &`DEREFERENCE`& set the dereferencing parameter
7872 &`NETTIME `& set a timeout for a network operation
7873 &`USER `& set the DN, for authenticating the LDAP bind
7874 &`PASS `& set the password, likewise
7875 &`REFERRALS `& set the referrals parameter
7876 &`SERVERS `& set alternate server list for this query only
7877 &`SIZE `& set the limit for the number of entries returned
7878 &`TIME `& set the maximum waiting time for a query
7880 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7881 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7882 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7883 library from trying to follow referrals issued by the LDAP server.
7885 .cindex LDAP timeout
7886 .cindex timeout "LDAP lookup"
7887 The name CONNECT is an obsolete name for NETTIME, retained for
7888 backwards compatibility. This timeout (specified as a number of seconds) is
7889 enforced from the client end for operations that can be carried out over a
7890 network. Specifically, it applies to network connections and calls to the
7891 &'ldap_result()'& function. If the value is greater than zero, it is used if
7892 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7893 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7894 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7895 Netscape SDK; for OpenLDAP no action is taken.
7897 The TIME parameter (also a number of seconds) is passed to the server to
7898 set a server-side limit on the time taken to complete a search.
7900 The SERVERS parameter allows you to specify an alternate list of ldap servers
7901 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7902 default list of ldap servers, and a single lookup can specify a single ldap
7903 server to use. But when you need to do a lookup with a list of servers that is
7904 different than the default list (maybe different order, maybe a completely
7905 different set of servers), the SERVERS parameter allows you to specify this
7906 alternate list (colon-separated).
7908 Here is an example of an LDAP query in an Exim lookup that uses some of these
7909 values. This is a single line, folded to fit on the page:
7912 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7913 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7916 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7917 any of the auxiliary data. Exim configuration settings that include lookups
7918 which contain password information should be preceded by &"hide"& to prevent
7919 non-admin users from using the &%-bP%& option to see their values.
7921 The auxiliary data items may be given in any order. The default is no
7922 connection timeout (the system timeout is used), no user or password, no limit
7923 on the number of entries returned, and no time limit on queries.
7925 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7926 removes any URL quoting that it may contain before passing it LDAP. Apparently
7927 some libraries do this for themselves, but some do not. Removing the URL
7928 quoting has two advantages:
7931 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7932 DNs as with DNs inside actual queries.
7934 It permits spaces inside USER= DNs.
7937 For example, a setting such as
7939 USER=cn=${quote_ldap_dn:$1}
7941 should work even if &$1$& contains spaces.
7943 Expanded data for the PASS= value should be quoted using the &%quote%&
7944 expansion operator, rather than the LDAP quote operators. The only reason this
7945 field needs quoting is to ensure that it conforms to the Exim syntax, which
7946 does not allow unquoted spaces. For example:
7950 The LDAP authentication mechanism can be used to check passwords as part of
7951 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7956 .section "Format of data returned by LDAP" "SECID71"
7957 .cindex "LDAP" "returned data formats"
7958 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7959 as a sequence of values, for example
7961 cn=manager,o=University of Cambridge,c=UK
7963 The &(ldap)& lookup type generates an error if more than one entry matches the
7964 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7965 the result between the data from different entries. It is possible for multiple
7966 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7967 you know that whatever values are returned all came from a single entry in the
7970 In the common case where you specify a single attribute in your LDAP query, the
7971 result is not quoted, and does not contain the attribute name. If the attribute
7972 has multiple values, they are separated by commas. Any comma that is
7973 part of an attribute's value is doubled.
7975 If you specify multiple attributes, the result contains space-separated, quoted
7976 strings, each preceded by the attribute name and an equals sign. Within the
7977 quotes, the quote character, backslash, and newline are escaped with
7978 backslashes, and commas are used to separate multiple values for the attribute.
7979 Any commas in attribute values are doubled
7980 (permitting treatment of the values as a comma-separated list).
7981 Apart from the escaping, the string within quotes takes the same form as the
7982 output when a single attribute is requested. Specifying no attributes is the
7983 same as specifying all of an entry's attributes.
7985 Here are some examples of the output format. The first line of each pair is an
7986 LDAP query, and the second is the data that is returned. The attribute called
7987 &%attr1%& has two values, one of them with an embedded comma, whereas
7988 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7989 (they have SUP &%attr%& in their schema definitions).
7992 ldap:///o=base?attr1?sub?(uid=fred)
7995 ldap:///o=base?attr2?sub?(uid=fred)
7998 ldap:///o=base?attr?sub?(uid=fred)
7999 value1.1,value1,,2,value two
8001 ldap:///o=base?attr1,attr2?sub?(uid=fred)
8002 attr1="value1.1,value1,,2" attr2="value two"
8004 ldap:///o=base??sub?(uid=fred)
8005 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
8008 make use of Exim's &%-be%& option to run expansion tests and thereby check the
8009 results of LDAP lookups.
8010 The &%extract%& operator in string expansions can be used to pick out
8011 individual fields from data that consists of &'key'&=&'value'& pairs.
8012 The &%listextract%& operator should be used to pick out individual values
8013 of attributes, even when only a single value is expected.
8014 The doubling of embedded commas allows you to use the returned data as a
8015 comma separated list (using the "<," syntax for changing the input list separator).
8020 .section "More about NIS+" "SECTnisplus"
8021 .cindex "NIS+ lookup type"
8022 .cindex "lookup" "NIS+"
8023 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
8024 and field name. If this is given, the result of a successful query is the
8025 contents of the named field; otherwise the result consists of a concatenation
8026 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8027 values containing spaces are quoted. For example, the query
8029 [name=mg1456],passwd.org_dir
8031 might return the string
8033 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8034 home=/home/mg1456 shell=/bin/bash shadow=""
8036 (split over two lines here to fit on the page), whereas
8038 [name=mg1456],passwd.org_dir:gcos
8044 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8045 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8046 operator is to double any quote characters within the text.
8050 .section "SQL lookups" "SECTsql"
8051 .cindex "SQL lookup types"
8052 .cindex "MySQL" "lookup type"
8053 .cindex "PostgreSQL lookup type"
8054 .cindex "lookup" "MySQL"
8055 .cindex "lookup" "PostgreSQL"
8056 .cindex "Oracle" "lookup type"
8057 .cindex "lookup" "Oracle"
8058 .cindex "InterBase lookup type"
8059 .cindex "lookup" "InterBase"
8060 .cindex "Redis lookup type"
8061 .cindex lookup Redis
8062 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8064 databases. Queries for these databases contain SQL statements, so an example
8067 ${lookup mysql{select mailbox from users where id='userx'}\
8070 If the result of the query contains more than one field, the data for each
8071 field in the row is returned, preceded by its name, so the result of
8073 ${lookup pgsql{select home,name from users where id='userx'}\
8078 home=/home/userx name="Mister X"
8080 Empty values and values containing spaces are double quoted, with embedded
8081 quotes escaped by a backslash. If the result of the query contains just one
8082 field, the value is passed back verbatim, without a field name, for example:
8086 If the result of the query yields more than one row, it is all concatenated,
8087 with a newline between the data for each row.
8090 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8091 .cindex "MySQL" "lookup type"
8092 .cindex "PostgreSQL lookup type"
8093 .cindex "lookup" "MySQL"
8094 .cindex "lookup" "PostgreSQL"
8095 .cindex "Oracle" "lookup type"
8096 .cindex "lookup" "Oracle"
8097 .cindex "InterBase lookup type"
8098 .cindex "lookup" "InterBase"
8099 .cindex "Redis lookup type"
8100 .cindex lookup Redis
8101 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8102 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8103 or &%redis_servers%&
8104 option (as appropriate) must be set to a colon-separated list of server
8106 .oindex &%mysql_servers%&
8107 .oindex &%pgsql_servers%&
8108 .oindex &%oracle_servers%&
8109 .oindex &%ibase_servers%&
8110 .oindex &%redis_servers%&
8111 (For MySQL and PostgreSQL, the global option need not be set if all
8112 queries contain their own server information &-- see section
8113 &<<SECTspeserque>>&.)
8115 each item in the list is a slash-separated list of four
8116 items: host name, database name, user name, and password. In the case of
8117 Oracle, the host name field is used for the &"service name"&, and the database
8118 name field is not used and should be empty. For example:
8120 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8122 Because password data is sensitive, you should always precede the setting with
8123 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8124 option. Here is an example where two MySQL servers are listed:
8126 hide mysql_servers = localhost/users/root/secret:\
8127 otherhost/users/root/othersecret
8129 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8130 because this is a colon-separated list, the colon has to be doubled. For each
8131 query, these parameter groups are tried in order until a connection is made and
8132 a query is successfully processed. The result of a query may be that no data is
8133 found, but that is still a successful query. In other words, the list of
8134 servers provides a backup facility, not a list of different places to look.
8136 For Redis the global option need not be specified if all queries contain their
8137 own server information &-- see section &<<SECTspeserque>>&.
8138 If specified, the option must be set to a colon-separated list of server
8140 Each item in the list is a slash-separated list of three items:
8141 host, database number, and password.
8143 The host is required and may be either an IPv4 address and optional
8144 port number (separated by a colon, which needs doubling due to the
8145 higher-level list), or a Unix socket pathname enclosed in parentheses
8147 The database number is optional; if present that number is selected in the backend
8149 The password is optional; if present it is used to authenticate to the backend
8152 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8153 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8154 respectively, and the characters single-quote, double-quote, and backslash
8155 itself are escaped with backslashes.
8157 The &%quote_redis%& expansion operator
8158 escapes whitespace and backslash characters with a backslash.
8160 .section "Specifying the server in the query" "SECTspeserque"
8161 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8162 it is possible to specify a list of servers with an individual query. This is
8163 done by appending a comma-separated option to the query type:
8165 &`,servers=`&&'server1:server2:server3:...'&
8167 Each item in the list may take one of two forms:
8169 If it contains no slashes it is assumed to be just a host name. The appropriate
8170 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8171 of the same name, and the remaining parameters (database, user, password) are
8174 If it contains any slashes, it is taken as a complete parameter set.
8176 The list of servers is used in exactly the same way as the global list.
8177 Once a connection to a server has happened and a query has been
8178 successfully executed, processing of the lookup ceases.
8180 This feature is intended for use in master/slave situations where updates
8181 are occurring and you want to update the master rather than a slave. If the
8182 master is in the list as a backup for reading, you might have a global setting
8185 mysql_servers = slave1/db/name/pw:\
8189 In an updating lookup, you could then write:
8191 ${lookup mysql,servers=master {UPDATE ...} }
8193 That query would then be sent only to the master server. If, on the other hand,
8194 the master is not to be used for reading, and so is not present in the global
8195 option, you can still update it by a query of this form:
8197 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8200 An older syntax places the servers specification before the query,
8201 semicolon separated:
8203 ${lookup mysql{servers=master; UPDATE ...} }
8205 The new version avoids potential issues with tainted
8206 arguments in the query, for explicit expansion.
8207 &*Note*&: server specifications in list-style lookups are still problematic.
8210 .section "Special MySQL features" "SECID73"
8211 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8212 causes a connection to the server on the local host by means of a Unix domain
8213 socket. An alternate socket can be specified in parentheses.
8214 An option group name for MySQL option files can be specified in square brackets;
8215 the default value is &"exim"&.
8216 The full syntax of each item in &%mysql_servers%& is:
8218 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8219 <&'database'&>/<&'user'&>/<&'password'&>
8221 Any of the four sub-parts of the first field can be omitted. For normal use on
8222 the local host it can be left blank or set to just &"localhost"&.
8224 No database need be supplied &-- but if it is absent here, it must be given in
8227 If a MySQL query is issued that does not request any data (an insert, update,
8228 or delete command), the result of the lookup is the number of rows affected.
8230 &*Warning*&: This can be misleading. If an update does not actually change
8231 anything (for example, setting a field to the value it already has), the result
8232 is zero because no rows are affected.
8235 .section "Special PostgreSQL features" "SECID74"
8236 PostgreSQL lookups can also use Unix domain socket connections to the database.
8237 This is usually faster and costs less CPU time than a TCP/IP connection.
8238 However it can be used only if the mail server runs on the same machine as the
8239 database server. A configuration line for PostgreSQL via Unix domain sockets
8242 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8244 In other words, instead of supplying a host name, a path to the socket is
8245 given. The path name is enclosed in parentheses so that its slashes aren't
8246 visually confused with the delimiters for the other server parameters.
8248 If a PostgreSQL query is issued that does not request any data (an insert,
8249 update, or delete command), the result of the lookup is the number of rows
8252 .section "More about SQLite" "SECTsqlite"
8253 .cindex "lookup" "SQLite"
8254 .cindex "sqlite lookup type"
8255 SQLite is different to the other SQL lookups because a filename is required in
8256 addition to the SQL query. An SQLite database is a single file, and there is no
8257 daemon as in the other SQL databases.
8260 .oindex &%sqlite_dbfile%&
8261 There are two ways of
8262 specifying the file.
8263 The first is is by using the &%sqlite_dbfile%& main option.
8264 The second, which allows separate files for each query,
8265 is to use an option appended, comma-separated, to the &"sqlite"&
8266 lookup type word. The option is the word &"file"&, then an equals,
8268 The filename in this case cannot contain whitespace or open-brace charachters.
8271 A deprecated method is available, prefixing the query with the filename
8272 separated by white space.
8274 .cindex "tainted data" "sqlite file"
8275 the query cannot use any tainted values, as that taints
8276 the entire query including the filename - resulting in a refusal to open
8279 In all the above cases the filename must be an absolute path.
8281 Here is a lookup expansion example:
8283 sqlite_dbfile = /some/thing/sqlitedb
8285 ${lookup sqlite {select name from aliases where id='userx';}}
8287 In a list, the syntax is similar. For example:
8289 domainlist relay_to_domains = sqlite;\
8290 select * from relays where ip='$sender_host_address';
8292 The only character affected by the &%quote_sqlite%& operator is a single
8293 quote, which it doubles.
8295 .cindex timeout SQLite
8296 .cindex sqlite "lookup timeout"
8297 The SQLite library handles multiple simultaneous accesses to the database
8298 internally. Multiple readers are permitted, but only one process can
8299 update at once. Attempts to access the database while it is being updated
8300 are rejected after a timeout period, during which the SQLite library
8301 waits for the lock to be released. In Exim, the default timeout is set
8302 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8305 .section "More about Redis" "SECTredis"
8306 .cindex "lookup" "Redis"
8307 .cindex "redis lookup type"
8308 Redis is a non-SQL database. Commands are simple get and set.
8311 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8312 ${lookup redis{get keyname}}
8315 As of release 4.91, "lightweight" support for Redis Cluster is available.
8316 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8317 of which must be reachable from the running exim instance. If the cluster has
8318 master/slave replication, the list must contain all the master and slave
8321 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8322 immediately follow the redirection but treats the response as a DEFER, moving on
8323 to the next server in the &%redis_servers%& list until the correct server is
8330 . ////////////////////////////////////////////////////////////////////////////
8331 . ////////////////////////////////////////////////////////////////////////////
8333 .chapter "Domain, host, address, and local part lists" &&&
8334 "CHAPdomhosaddlists" &&&
8335 "Domain, host, and address lists"
8336 .scindex IIDdohoadli "lists of domains; hosts; etc."
8337 A number of Exim configuration options contain lists of domains, hosts,
8338 email addresses, or local parts. For example, the &%hold_domains%& option
8339 contains a list of domains whose delivery is currently suspended. These lists
8340 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8341 arguments to expansion conditions such as &%match_domain%&.
8343 Each item in one of these lists is a pattern to be matched against a domain,
8344 host, email address, or local part, respectively. In the sections below, the
8345 different types of pattern for each case are described, but first we cover some
8346 general facilities that apply to all four kinds of list.
8348 Note that other parts of Exim use a &'string list'& which does not
8349 support all the complexity available in
8350 domain, host, address and local part lists.
8354 .section "Expansion of lists" "SECTlistexpand"
8355 .cindex "expansion" "of lists"
8356 Each list is expanded as a single string before it is used.
8358 &'Exception: the router headers_remove option, where list-item
8359 splitting is done before string-expansion.'&
8362 expansion must be a list, possibly containing empty items, which is split up
8363 into separate items for matching. By default, colon is the separator character,
8364 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8365 &<<SECTempitelis>>& for details of the list syntax; the second of these
8366 discusses the way to specify empty list items.
8369 If the string expansion is forced to fail, Exim behaves as if the item it is
8370 testing (domain, host, address, or local part) is not in the list. Other
8371 expansion failures cause temporary errors.
8373 If an item in a list is a regular expression, backslashes, dollars and possibly
8374 other special characters in the expression must be protected against
8375 misinterpretation by the string expander. The easiest way to do this is to use
8376 the &`\N`& expansion feature to indicate that the contents of the regular
8377 expression should not be expanded. For example, in an ACL you might have:
8379 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8380 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8382 The first item is a regular expression that is protected from expansion by
8383 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8384 senders based on the receiving domain.
8389 .section "Negated items in lists" "SECID76"
8390 .cindex "list" "negation"
8391 .cindex "negation" "in lists"
8392 Items in a list may be positive or negative. Negative items are indicated by a
8393 leading exclamation mark, which may be followed by optional white space. A list
8394 defines a set of items (domains, etc). When Exim processes one of these lists,
8395 it is trying to find out whether a domain, host, address, or local part
8396 (respectively) is in the set that is defined by the list. It works like this:
8398 The list is scanned from left to right. If a positive item is matched, the
8399 subject that is being checked is in the set; if a negative item is matched, the
8400 subject is not in the set. If the end of the list is reached without the
8401 subject having matched any of the patterns, it is in the set if the last item
8402 was a negative one, but not if it was a positive one. For example, the list in
8404 domainlist relay_to_domains = !a.b.c : *.b.c
8406 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8407 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8408 list is positive. However, if the setting were
8410 domainlist relay_to_domains = !a.b.c
8412 then all domains other than &'a.b.c'& would match because the last item in the
8413 list is negative. In other words, a list that ends with a negative item behaves
8414 as if it had an extra item &`:*`& on the end.
8416 Another way of thinking about positive and negative items in lists is to read
8417 the connector as &"or"& after a positive item and as &"and"& after a negative
8422 .section "File names in lists" "SECTfilnamlis"
8423 .cindex "list" "filename in"
8424 If an item in a domain, host, address, or local part list is an absolute
8425 filename (beginning with a slash character), each line of the file is read and
8426 processed as if it were an independent item in the list, except that further
8427 filenames are not allowed,
8428 and no expansion of the data from the file takes place.
8429 Empty lines in the file are ignored, and the file may also contain comment
8433 For domain and host lists, if a # character appears anywhere in a line of the
8434 file, it and all following characters are ignored.
8436 Because local parts may legitimately contain # characters, a comment in an
8437 address list or local part list file is recognized only if # is preceded by
8438 white space or the start of the line. For example:
8440 not#comment@x.y.z # but this is a comment
8444 Putting a filename in a list has the same effect as inserting each line of the
8445 file as an item in the list (blank lines and comments excepted). However, there
8446 is one important difference: the file is read each time the list is processed,
8447 so if its contents vary over time, Exim's behaviour changes.
8449 If a filename is preceded by an exclamation mark, the sense of any match
8450 within the file is inverted. For example, if
8452 hold_domains = !/etc/nohold-domains
8454 and the file contains the lines
8459 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8460 any domain matching &`*.b.c`& is not.
8464 .section "An lsearch file is not an out-of-line list" "SECID77"
8465 As will be described in the sections that follow, lookups can be used in lists
8466 to provide indexed methods of checking list membership. There has been some
8467 confusion about the way &(lsearch)& lookups work in lists. Because
8468 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8469 sometimes thought that it is allowed to contain wild cards and other kinds of
8470 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8471 always fixed strings, just as for any other single-key lookup type.
8473 If you want to use a file to contain wild-card patterns that form part of a
8474 list, just give the filename on its own, without a search type, as described
8475 in the previous section. You could also use the &(wildlsearch)& or
8476 &(nwildlsearch)&, but there is no advantage in doing this.
8481 .section "Results of list checking" SECTlistresults
8482 The primary result of doing a list check is a truth value.
8483 In some contexts additional information is stored
8484 about the list element that matched:
8487 A &%hosts%& ACL condition
8488 will store a result in the &$host_data$& variable.
8490 A &%local_parts%& router option or &%local_parts%& ACL condition
8491 will store a result in the &$local_part_data$& variable.
8494 A &%domains%& router option or &%domains%& ACL condition
8495 will store a result in the &$domain_data$& variable
8498 A &%senders%& router option or &%senders%& ACL condition
8499 will store a result in the &$sender_data$& variable.
8501 A &%recipients%& ACL condition
8502 will store a result in the &$recipient_data$& variable.
8505 The detail of the additional information depends on the
8506 type of match and is given below as the &*value*& information.
8511 .section "Named lists" "SECTnamedlists"
8512 .cindex "named lists"
8513 .cindex "list" "named"
8514 A list of domains, hosts, email addresses, or local parts can be given a name
8515 which is then used to refer to the list elsewhere in the configuration. This is
8516 particularly convenient if the same list is required in several different
8517 places. It also allows lists to be given meaningful names, which can improve
8518 the readability of the configuration. For example, it is conventional to define
8519 a domain list called &'local_domains'& for all the domains that are handled
8520 locally on a host, using a configuration line such as
8522 domainlist local_domains = localhost:my.dom.example
8524 Named lists are referenced by giving their name preceded by a plus sign, so,
8525 for example, a router that is intended to handle local domains would be
8526 configured with the line
8528 domains = +local_domains
8530 The first router in a configuration is often one that handles all domains
8531 except the local ones, using a configuration with a negated item like this:
8535 domains = ! +local_domains
8536 transport = remote_smtp
8539 The four kinds of named list are created by configuration lines starting with
8540 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8541 respectively. Then there follows the name that you are defining, followed by an
8542 equals sign and the list itself. For example:
8544 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8545 addresslist bad_senders = cdb;/etc/badsenders
8547 A named list may refer to other named lists:
8549 domainlist dom1 = first.example : second.example
8550 domainlist dom2 = +dom1 : third.example
8551 domainlist dom3 = fourth.example : +dom2 : fifth.example
8553 &*Warning*&: If the last item in a referenced list is a negative one, the
8554 effect may not be what you intended, because the negation does not propagate
8555 out to the higher level. For example, consider:
8557 domainlist dom1 = !a.b
8558 domainlist dom2 = +dom1 : *.b
8560 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8561 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8562 means it matches the second list as well. The effect is not the same as
8564 domainlist dom2 = !a.b : *.b
8566 where &'x.y'& does not match. It's best to avoid negation altogether in
8567 referenced lists if you can.
8569 .cindex "hiding named list values"
8570 .cindex "named lists" "hiding value of"
8571 Some named list definitions may contain sensitive data, for example, passwords for
8572 accessing databases. To stop non-admin users from using the &%-bP%& command
8573 line option to read these values, you can precede the definition with the
8574 word &"hide"&. For example:
8576 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8580 Named lists may have a performance advantage. When Exim is routing an
8581 address or checking an incoming message, it caches the result of tests on named
8582 lists. So, if you have a setting such as
8584 domains = +local_domains
8586 on several of your routers
8587 or in several ACL statements,
8588 the actual test is done only for the first one. However, the caching works only
8589 if there are no expansions within the list itself or any sublists that it
8590 references. In other words, caching happens only for lists that are known to be
8591 the same each time they are referenced.
8593 By default, there may be up to 16 named lists of each type. This limit can be
8594 extended by changing a compile-time variable. The use of domain and host lists
8595 is recommended for concepts such as local domains, relay domains, and relay
8596 hosts. The default configuration is set up like this.
8600 .section "Named lists compared with macros" "SECID78"
8601 .cindex "list" "named compared with macro"
8602 .cindex "macro" "compared with named list"
8603 At first sight, named lists might seem to be no different from macros in the
8604 configuration file. However, macros are just textual substitutions. If you
8607 ALIST = host1 : host2
8608 auth_advertise_hosts = !ALIST
8610 it probably won't do what you want, because that is exactly the same as
8612 auth_advertise_hosts = !host1 : host2
8614 Notice that the second host name is not negated. However, if you use a host
8617 hostlist alist = host1 : host2
8618 auth_advertise_hosts = ! +alist
8620 the negation applies to the whole list, and so that is equivalent to
8622 auth_advertise_hosts = !host1 : !host2
8626 .section "Named list caching" "SECID79"
8627 .cindex "list" "caching of named"
8628 .cindex "caching" "named lists"
8629 While processing a message, Exim caches the result of checking a named list if
8630 it is sure that the list is the same each time. In practice, this means that
8631 the cache operates only if the list contains no $ characters, which guarantees
8632 that it will not change when it is expanded. Sometimes, however, you may have
8633 an expanded list that you know will be the same each time within a given
8634 message. For example:
8636 domainlist special_domains = \
8637 ${lookup{$sender_host_address}cdb{/some/file}}
8639 This provides a list of domains that depends only on the sending host's IP
8640 address. If this domain list is referenced a number of times (for example,
8641 in several ACL lines, or in several routers) the result of the check is not
8642 cached by default, because Exim does not know that it is going to be the
8643 same list each time.
8645 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8646 cache the result anyway. For example:
8648 domainlist_cache special_domains = ${lookup{...
8650 If you do this, you should be absolutely sure that caching is going to do
8651 the right thing in all cases. When in doubt, leave it out.
8655 .section "Domain lists" "SECTdomainlist"
8656 .cindex "domain list" "patterns for"
8657 .cindex "list" "domain list"
8658 Domain lists contain patterns that are to be matched against a mail domain.
8659 The following types of item may appear in domain lists:
8662 .cindex "primary host name"
8663 .cindex "host name" "matched in domain list"
8664 .oindex "&%primary_hostname%&"
8665 .cindex "domain list" "matching primary host name"
8666 .cindex "@ in a domain list"
8667 If a pattern consists of a single @ character, it matches the local host name,
8668 as set by the &%primary_hostname%& option (or defaulted). This makes it
8669 possible to use the same configuration file on several different hosts that
8670 differ only in their names.
8672 The value for a match will be the primary host name.
8676 .cindex "@[] in a domain list"
8677 .cindex "domain list" "matching local IP interfaces"
8678 .cindex "domain literal"
8679 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8680 in square brackets (as in an email address that contains a domain literal), but
8681 only if that IP address is recognized as local for email routing purposes. The
8682 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8683 control which of a host's several IP addresses are treated as local.
8684 In today's Internet, the use of domain literals is controversial;
8685 see the &%allow_domain_literals%& main option.
8687 The value for a match will be the string &`@[]`&.
8692 .cindex "@mx_primary"
8693 .cindex "@mx_secondary"
8694 .cindex "domain list" "matching MX pointers to local host"
8695 If a pattern consists of the string &`@mx_any`& it matches any domain that
8696 has an MX record pointing to the local host or to any host that is listed in
8697 .oindex "&%hosts_treat_as_local%&"
8698 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8699 are similar, except that the first matches only when a primary MX target is the
8700 local host, and the second only when no primary MX target is the local host,
8701 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8702 preference value &-- there may of course be more than one of them.
8704 The MX lookup that takes place when matching a pattern of this type is
8705 performed with the resolver options for widening names turned off. Thus, for
8706 example, a single-component domain will &'not'& be expanded by adding the
8707 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8708 options of the &(dnslookup)& router for a discussion of domain widening.
8710 Sometimes you may want to ignore certain IP addresses when using one of these
8711 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8712 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8713 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8714 on a router). For example:
8716 domains = @mx_any/ignore=127.0.0.1
8718 This example matches any domain that has an MX record pointing to one of
8719 the local host's IP addresses other than 127.0.0.1.
8721 The list of IP addresses is in fact processed by the same code that processes
8722 host lists, so it may contain CIDR-coded network specifications and it may also
8723 contain negative items.
8725 Because the list of IP addresses is a sublist within a domain list, you have to
8726 be careful about delimiters if there is more than one address. Like any other
8727 list, the default delimiter can be changed. Thus, you might have:
8729 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8730 an.other.domain : ...
8732 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8733 involved, it is easiest to change the delimiter for the main list as well:
8735 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8736 an.other.domain ? ...
8738 The value for a match will be the list element string (starting &`@mx_`&).
8742 .cindex "asterisk" "in domain list"
8743 .cindex "domain list" "asterisk in"
8744 .cindex "domain list" "matching &""ends with""&"
8745 If a pattern starts with an asterisk, the remaining characters of the pattern
8746 are compared with the terminating characters of the domain. The use of &"*"& in
8747 domain lists differs from its use in partial matching lookups. In a domain
8748 list, the character following the asterisk need not be a dot, whereas partial
8749 matching works only in terms of dot-separated components. For example, a domain
8750 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8753 The value for a match will be the list element string (starting with the asterisk).
8754 Additionally, &$0$& will be set to the matched string
8755 and &$1$& to the variable portion which the asterisk matched.
8758 .cindex "regular expressions" "in domain list"
8759 .cindex "domain list" "matching regular expression"
8760 If a pattern starts with a circumflex character, it is treated as a regular
8761 expression, and matched against the domain using a regular expression matching
8762 function. The circumflex is treated as part of the regular expression.
8763 Email domains are case-independent, so this regular expression match is by
8764 default case-independent, but you can make it case-dependent by starting it
8765 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8766 are given in chapter &<<CHAPregexp>>&.
8768 &*Warning*&: Because domain lists are expanded before being processed, you
8769 must escape any backslash and dollar characters in the regular expression, or
8770 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8771 it is not to be expanded (unless you really do want to build a regular
8772 expression by expansion, of course).
8774 The value for a match will be the list element string (starting with the circumflex).
8775 Additionally, &$0$& will be set to the string matching the regular expression,
8776 and &$1$& (onwards) to any submatches identified by parentheses.
8781 .cindex "lookup" "in domain list"
8782 .cindex "domain list" "matching by lookup"
8783 If a pattern starts with the name of a single-key lookup type followed by a
8784 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8785 must be a filename in a suitable format for the lookup type. For example, for
8786 &"cdb;"& it must be an absolute path:
8788 domains = cdb;/etc/mail/local_domains.cdb
8790 The appropriate type of lookup is done on the file using the domain name as the
8791 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8792 only in whether or not the key is present in the file. However, when a lookup
8793 is used for the &%domains%& option on a router
8794 or a &%domains%& condition in an ACL statement, the value is preserved in the
8795 &$domain_data$& variable and can be referred to in other router options or
8796 other statements in the same ACL.
8797 .cindex "tainted data" "de-tainting"
8798 The value will be untainted.
8801 &*Note*&: If the data result of the lookup (as opposed to the key)
8802 is empty, then this empty value is stored in &$domain_data$&.
8803 The option to return the key for the lookup, as the value,
8804 may be what is wanted.
8809 Any of the single-key lookup type names may be preceded by
8810 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8812 domains = partial-dbm;/partial/domains
8814 This causes partial matching logic to be invoked; a description of how this
8815 works is given in section &<<SECTpartiallookup>>&.
8818 .cindex "asterisk" "in lookup type"
8819 Any of the single-key lookup types may be followed by an asterisk. This causes
8820 a default lookup for a key consisting of a single asterisk to be done if the
8821 original lookup fails. This is not a useful feature when using a domain list to
8822 select particular domains (because any domain would match), but it might have
8823 value if the result of the lookup is being used via the &$domain_data$&
8827 If the pattern starts with the name of a query-style lookup type followed by a
8828 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8829 pattern must be an appropriate query for the lookup type, as described in
8830 chapter &<<CHAPfdlookup>>&. For example:
8832 hold_domains = mysql;select domain from holdlist \
8833 where domain = '${quote_mysql:$domain}';
8835 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8836 example, it doesn't matter what field you select). Exim is interested only in
8837 whether or not the query succeeds. However, when a lookup is used for the
8838 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8839 variable and can be referred to in other options.
8840 .cindex "tainted data" "de-tainting"
8841 The value will be untainted.
8844 If the pattern starts with the name of a lookup type
8845 of either kind (single-key or query-style) it may be
8846 followed by a comma and options,
8847 The options are lookup-type specific and consist of a comma-separated list.
8848 Each item starts with a tag and and equals "=".
8851 .cindex "domain list" "matching literal domain name"
8852 If none of the above cases apply, a caseless textual comparison is made
8853 between the pattern and the domain.
8855 The value for a match will be the list element string.
8856 .cindex "tainted data" "de-tainting"
8857 Note that this is commonly untainted
8858 (depending on the way the list was created).
8859 Specifically, explicit text in the configuration file in not tainted.
8860 This is a useful way of obtaining an untainted equivalent to
8861 the domain, for later operations.
8863 However if the list (including one-element lists)
8864 is created by expanding a variable containing tainted data,
8865 it is tainted and so will the match value be.
8869 Here is an example that uses several different kinds of pattern:
8871 domainlist funny_domains = \
8874 *.foundation.fict.example : \
8875 \N^[1-2]\d{3}\.fict\.example$\N : \
8876 partial-dbm;/opt/data/penguin/book : \
8877 nis;domains.byname : \
8878 nisplus;[name=$domain,status=local],domains.org_dir
8880 There are obvious processing trade-offs among the various matching modes. Using
8881 an asterisk is faster than a regular expression, and listing a few names
8882 explicitly probably is too. The use of a file or database lookup is expensive,
8883 but may be the only option if hundreds of names are required. Because the
8884 patterns are tested in order, it makes sense to put the most commonly matched
8889 .section "Host lists" "SECThostlist"
8890 .cindex "host list" "patterns in"
8891 .cindex "list" "host list"
8892 Host lists are used to control what remote hosts are allowed to do. For
8893 example, some hosts may be allowed to use the local host as a relay, and some
8894 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8895 two different ways, by name or by IP address. In a host list, some types of
8896 pattern are matched to a host name, and some are matched to an IP address.
8897 You need to be particularly careful with this when single-key lookups are
8898 involved, to ensure that the right value is being used as the key.
8901 .section "Special host list patterns" "SECID80"
8902 .cindex "empty item in hosts list"
8903 .cindex "host list" "empty string in"
8904 If a host list item is the empty string, it matches only when no remote host is
8905 involved. This is the case when a message is being received from a local
8906 process using SMTP on the standard input, that is, when a TCP/IP connection is
8909 .cindex "asterisk" "in host list"
8910 The special pattern &"*"& in a host list matches any host or no host. Neither
8911 the IP address nor the name is actually inspected.
8915 .section "Host list patterns that match by IP address" "SECThoslispatip"
8916 .cindex "host list" "matching IP addresses"
8917 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8918 the incoming address actually appears in the IPv6 host as
8919 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8920 list, it is converted into a traditional IPv4 address first. (Not all operating
8921 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8924 The following types of pattern in a host list check the remote host by
8925 inspecting its IP address:
8928 If the pattern is a plain domain name (not a regular expression, not starting
8929 with *, not a lookup of any kind), Exim calls the operating system function
8930 to find the associated IP address(es). Exim uses the newer
8931 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8932 This typically causes a forward DNS lookup of the name. The result is compared
8933 with the IP address of the subject host.
8935 If there is a temporary problem (such as a DNS timeout) with the host name
8936 lookup, a temporary error occurs. For example, if the list is being used in an
8937 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8938 temporary SMTP error code. If no IP address can be found for the host name,
8939 what happens is described in section &<<SECTbehipnot>>& below.
8942 .cindex "@ in a host list"
8943 If the pattern is &"@"&, the primary host name is substituted and used as a
8944 domain name, as just described.
8947 If the pattern is an IP address, it is matched against the IP address of the
8948 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8949 IPv6 addresses can be given in colon-separated format, but the colons have to
8950 be doubled so as not to be taken as item separators when the default list
8951 separator is used. IPv6 addresses are recognized even when Exim is compiled
8952 without IPv6 support. This means that if they appear in a host list on an
8953 IPv4-only host, Exim will not treat them as host names. They are just addresses
8954 that can never match a client host.
8957 .cindex "@[] in a host list"
8958 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8959 the local host. For example, if the local host is an IPv4 host with one
8960 interface address 10.45.23.56, these two ACL statements have the same effect:
8962 accept hosts = 127.0.0.1 : 10.45.23.56
8966 .cindex "CIDR notation"
8967 If the pattern is an IP address followed by a slash and a mask length (for
8968 example 10.11.42.0/24), it is matched against the IP address of the subject
8969 host under the given mask. This allows, an entire network of hosts to be
8970 included (or excluded) by a single item. The mask uses CIDR notation; it
8971 specifies the number of address bits that must match, starting from the most
8972 significant end of the address.
8974 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8975 of a range of addresses. It is the number of bits in the network portion of the
8976 address. The above example specifies a 24-bit netmask, so it matches all 256
8977 addresses in the 10.11.42.0 network. An item such as
8981 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8982 32 for an IPv4 address is the same as no mask at all; just a single address
8985 Here is another example which shows an IPv4 and an IPv6 network:
8987 recipient_unqualified_hosts = 192.168.0.0/16: \
8988 3ffe::ffff::836f::::/48
8990 The doubling of list separator characters applies only when these items
8991 appear inline in a host list. It is not required when indirecting via a file.
8994 recipient_unqualified_hosts = /opt/exim/unqualnets
8996 could make use of a file containing
9001 to have exactly the same effect as the previous example. When listing IPv6
9002 addresses inline, it is usually more convenient to use the facility for
9003 changing separator characters. This list contains the same two networks:
9005 recipient_unqualified_hosts = <; 172.16.0.0/12; \
9008 The separator is changed to semicolon by the leading &"<;"& at the start of the
9014 .section "Host list patterns for single-key lookups by host address" &&&
9015 "SECThoslispatsikey"
9016 .cindex "host list" "lookup of IP address"
9017 When a host is to be identified by a single-key lookup of its complete IP
9018 address, the pattern takes this form:
9020 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9024 hosts_lookup = net-cdb;/hosts-by-ip.db
9026 The text form of the IP address of the subject host is used as the lookup key.
9027 IPv6 addresses are converted to an unabbreviated form, using lower case
9028 letters, with dots as separators because colon is the key terminator in
9029 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9030 quoting the keys, but this is a facility that was added later.] The data
9031 returned by the lookup is not used.
9033 .cindex "IP address" "masking"
9034 .cindex "host list" "masked IP address"
9035 Single-key lookups can also be performed using masked IP addresses, using
9036 patterns of this form:
9038 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9042 net24-dbm;/networks.db
9044 The IP address of the subject host is masked using <&'number'&> as the mask
9045 length. A textual string is constructed from the masked value, followed by the
9046 mask, and this is used as the lookup key. For example, if the host's IP address
9047 is 192.168.34.6, the key that is looked up for the above example is
9048 &"192.168.34.0/24"&.
9050 When an IPv6 address is converted to a string, dots are normally used instead
9051 of colons, so that keys in &(lsearch)& files need not contain colons (which
9052 terminate &(lsearch)& keys). This was implemented some time before the ability
9053 to quote keys was made available in &(lsearch)& files. However, the more
9054 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9055 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9056 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9057 converted using colons and not dots.
9058 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9059 addresses are always used.
9060 The latter are converted to IPv4 addresses, in dotted-quad form.
9062 Ideally, it would be nice to tidy up this anomalous situation by changing to
9063 colons in all cases, given that quoting is now available for &(lsearch)&.
9064 However, this would be an incompatible change that might break some existing
9067 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9068 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9069 the former case the key strings include the mask value, whereas in the latter
9070 case the IP address is used on its own.
9074 .section "Host list patterns that match by host name" "SECThoslispatnam"
9075 .cindex "host" "lookup failures"
9076 .cindex "unknown host name"
9077 .cindex "host list" "matching host name"
9078 There are several types of pattern that require Exim to know the name of the
9079 remote host. These are either wildcard patterns or lookups by name. (If a
9080 complete hostname is given without any wildcarding, it is used to find an IP
9081 address to match against, as described in section &<<SECThoslispatip>>&
9084 If the remote host name is not already known when Exim encounters one of these
9085 patterns, it has to be found from the IP address.
9086 Although many sites on the Internet are conscientious about maintaining reverse
9087 DNS data for their hosts, there are also many that do not do this.
9088 Consequently, a name cannot always be found, and this may lead to unwanted
9089 effects. Take care when configuring host lists with wildcarded name patterns.
9090 Consider what will happen if a name cannot be found.
9092 Because of the problems of determining host names from IP addresses, matching
9093 against host names is not as common as matching against IP addresses.
9095 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9096 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9097 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9098 are done can be changed by setting the &%host_lookup_order%& option. For
9099 security, once Exim has found one or more names, it looks up the IP addresses
9100 for these names and compares them with the IP address that it started with.
9101 Only those names whose IP addresses match are accepted. Any other names are
9102 discarded. If no names are left, Exim behaves as if the host name cannot be
9103 found. In the most common case there is only one name and one IP address.
9105 There are some options that control what happens if a host name cannot be
9106 found. These are described in section &<<SECTbehipnot>>& below.
9108 .cindex "host" "alias for"
9109 .cindex "alias for host"
9110 As a result of aliasing, hosts may have more than one name. When processing any
9111 of the following types of pattern, all the host's names are checked:
9114 .cindex "asterisk" "in host list"
9115 If a pattern starts with &"*"& the remainder of the item must match the end of
9116 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9117 &'.b.c'&. This special simple form is provided because this is a very common
9118 requirement. Other kinds of wildcarding require the use of a regular
9121 .cindex "regular expressions" "in host list"
9122 .cindex "host list" "regular expression in"
9123 If the item starts with &"^"& it is taken to be a regular expression which is
9124 matched against the host name. Host names are case-independent, so this regular
9125 expression match is by default case-independent, but you can make it
9126 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9127 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9132 is a regular expression that matches either of the two hosts &'a.c.d'& or
9133 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9134 that backslash and dollar characters are not misinterpreted as part of the
9135 string expansion. The simplest way to do this is to use &`\N`& to mark that
9136 part of the string as non-expandable. For example:
9138 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9140 &*Warning*&: If you want to match a complete host name, you must include the
9141 &`$`& terminating metacharacter in the regular expression, as in the above
9142 example. Without it, a match at the start of the host name is all that is
9149 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9150 .cindex "host" "lookup failures, permanent"
9151 While processing a host list, Exim may need to look up an IP address from a
9152 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9153 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9154 behaviour when it fails to find the information it is seeking is the same.
9156 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9157 apply to temporary DNS errors, whose handling is described in the next section.
9159 .cindex "&`+include_unknown`&"
9160 .cindex "&`+ignore_unknown`&"
9161 Exim parses a host list from left to right. If it encounters a permanent
9162 lookup failure in any item in the host list before it has found a match,
9163 Exim treats it as a failure and the default behavior is as if the host
9164 does not match the list. This may not always be what you want to happen.
9165 To change Exim's behaviour, the special items &`+include_unknown`& or
9166 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9167 not recognized in an indirected file).
9170 If any item that follows &`+include_unknown`& requires information that
9171 cannot found, Exim behaves as if the host does match the list. For example,
9173 host_reject_connection = +include_unknown:*.enemy.ex
9175 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9176 any hosts whose name it cannot find.
9179 If any item that follows &`+ignore_unknown`& requires information that cannot
9180 be found, Exim ignores that item and proceeds to the rest of the list. For
9183 accept hosts = +ignore_unknown : friend.example : \
9186 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9187 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9188 name can be found for 192.168.4.5, it is rejected.
9191 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9192 list. The effect of each one lasts until the next, or until the end of the
9195 .section "Mixing wildcarded host names and addresses in host lists" &&&
9197 .cindex "host list" "mixing names and addresses in"
9199 This section explains the host/ip processing logic with the same concepts
9200 as the previous section, but specifically addresses what happens when a
9201 wildcarded hostname is one of the items in the hostlist.
9204 If you have name lookups or wildcarded host names and
9205 IP addresses in the same host list, you should normally put the IP
9206 addresses first. For example, in an ACL you could have:
9208 accept hosts = 10.9.8.7 : *.friend.example
9210 The reason you normally would order it this way lies in the
9211 left-to-right way that Exim processes lists. It can test IP addresses
9212 without doing any DNS lookups, but when it reaches an item that requires
9213 a host name, it fails if it cannot find a host name to compare with the
9214 pattern. If the above list is given in the opposite order, the
9215 &%accept%& statement fails for a host whose name cannot be found, even
9216 if its IP address is 10.9.8.7.
9219 If you really do want to do the name check first, and still recognize the IP
9220 address, you can rewrite the ACL like this:
9222 accept hosts = *.friend.example
9223 accept hosts = 10.9.8.7
9225 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9226 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9227 &`+ignore_unknown`&, which was discussed in depth in the first example in
9232 .section "Temporary DNS errors when looking up host information" &&&
9234 .cindex "host" "lookup failures, temporary"
9235 .cindex "&`+include_defer`&"
9236 .cindex "&`+ignore_defer`&"
9237 A temporary DNS lookup failure normally causes a defer action (except when
9238 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9239 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9240 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9241 section. These options should be used with care, probably only in non-critical
9242 host lists such as whitelists.
9246 .section "Host list patterns for single-key lookups by host name" &&&
9247 "SECThoslispatnamsk"
9248 .cindex "unknown host name"
9249 .cindex "host list" "matching host name"
9250 If a pattern is of the form
9252 <&'single-key-search-type'&>;<&'search-data'&>
9256 dbm;/host/accept/list
9258 a single-key lookup is performed, using the host name as its key. If the
9259 lookup succeeds, the host matches the item. The actual data that is looked up
9262 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9263 keys in the file, not IP addresses. If you want to do lookups based on IP
9264 addresses, you must precede the search type with &"net-"& (see section
9265 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9266 two items in the same list, one doing an address lookup and one doing a name
9267 lookup, both using the same file.
9271 .section "Host list patterns for query-style lookups" "SECID81"
9272 If a pattern is of the form
9274 <&'query-style-search-type'&>;<&'query'&>
9276 the query is obeyed, and if it succeeds, the host matches the item. The actual
9277 data that is looked up is not used. The variables &$sender_host_address$& and
9278 &$sender_host_name$& can be used in the query. For example:
9280 hosts_lookup = pgsql;\
9281 select ip from hostlist where ip='$sender_host_address'
9283 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9284 can use the &%sg%& expansion item to change this if you need to. If you want to
9285 use masked IP addresses in database queries, you can use the &%mask%& expansion
9288 If the query contains a reference to &$sender_host_name$&, Exim automatically
9289 looks up the host name if it has not already done so. (See section
9290 &<<SECThoslispatnam>>& for comments on finding host names.)
9292 Historical note: prior to release 4.30, Exim would always attempt to find a
9293 host name before running the query, unless the search type was preceded by
9294 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9295 still recognized for query-style lookups, but its presence or absence has no
9296 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9297 See section &<<SECThoslispatsikey>>&.)
9303 .section "Address lists" "SECTaddresslist"
9304 .cindex "list" "address list"
9305 .cindex "address list" "empty item"
9306 .cindex "address list" "patterns"
9307 Address lists contain patterns that are matched against mail addresses. There
9308 is one special case to be considered: the sender address of a bounce message is
9309 always empty. You can test for this by providing an empty item in an address
9310 list. For example, you can set up a router to process bounce messages by
9311 using this option setting:
9315 The presence of the colon creates an empty item. If you do not provide any
9316 data, the list is empty and matches nothing. The empty sender can also be
9317 detected by a regular expression that matches an empty string,
9318 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9320 Non-empty items in an address list can be straightforward email addresses. For
9323 senders = jbc@askone.example : hs@anacreon.example
9325 A certain amount of wildcarding is permitted. If a pattern contains an @
9326 character, but is not a regular expression and does not begin with a
9327 semicolon-terminated lookup type (described below), the local part of the
9328 subject address is compared with the local part of the pattern, which may start
9329 with an asterisk. If the local parts match, the domain is checked in exactly
9330 the same way as for a pattern in a domain list. For example, the domain can be
9331 wildcarded, refer to a named list, or be a lookup:
9333 deny senders = *@*.spamming.site:\
9334 *@+hostile_domains:\
9335 bozo@partial-lsearch;/list/of/dodgy/sites:\
9336 *@dbm;/bad/domains.db
9338 .cindex "local part" "starting with !"
9339 .cindex "address list" "local part starting with !"
9340 If a local part that begins with an exclamation mark is required, it has to be
9341 specified using a regular expression, because otherwise the exclamation mark is
9342 treated as a sign of negation, as is standard in lists.
9344 If a non-empty pattern that is not a regular expression or a lookup does not
9345 contain an @ character, it is matched against the domain part of the subject
9346 address. The only two formats that are recognized this way are a literal
9347 domain, or a domain pattern that starts with *. In both these cases, the effect
9348 is the same as if &`*@`& preceded the pattern. For example:
9350 deny senders = enemy.domain : *.enemy.domain
9353 The following kinds of more complicated address list pattern can match any
9354 address, including the empty address that is characteristic of bounce message
9358 .cindex "regular expressions" "in address list"
9359 .cindex "address list" "regular expression in"
9360 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9361 done against the complete address, with the pattern as the regular expression.
9362 You must take care that backslash and dollar characters are not misinterpreted
9363 as part of the string expansion. The simplest way to do this is to use &`\N`&
9364 to mark that part of the string as non-expandable. For example:
9366 deny senders = \N^.*this.*@example\.com$\N : \
9367 \N^\d{8}.+@spamhaus.example$\N : ...
9369 The &`\N`& sequences are removed by the expansion, so these items do indeed
9370 start with &"^"& by the time they are being interpreted as address patterns.
9373 .cindex "address list" "lookup for complete address"
9374 Complete addresses can be looked up by using a pattern that starts with a
9375 lookup type terminated by a semicolon, followed by the data for the lookup. For
9378 deny senders = cdb;/etc/blocked.senders : \
9379 mysql;select address from blocked where \
9380 address='${quote_mysql:$sender_address}'
9382 Both query-style and single-key lookup types can be used. For a single-key
9383 lookup type, Exim uses the complete address as the key. However, empty keys are
9384 not supported for single-key lookups, so a match against the empty address
9385 always fails. This restriction does not apply to query-style lookups.
9387 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9388 cannot be used, and is ignored if specified, with an entry being written to the
9390 .cindex "*@ with single-key lookup"
9391 However, you can configure lookup defaults, as described in section
9392 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9393 default. For example, with this lookup:
9395 accept senders = lsearch*@;/some/file
9397 the file could contains lines like this:
9399 user1@domain1.example
9402 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9405 nimrod@jaeger.example
9409 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9410 would mean that every address matches, thus rendering the test useless.
9412 &*Warning 2*&: Do not confuse these two kinds of item:
9414 deny recipients = dbm*@;/some/file
9415 deny recipients = *@dbm;/some/file
9417 The first does a whole address lookup, with defaulting, as just described,
9418 because it starts with a lookup type. The second matches the local part and
9419 domain independently, as described in a bullet point below.
9423 The following kinds of address list pattern can match only non-empty addresses.
9424 If the subject address is empty, a match against any of these pattern types
9429 .cindex "@@ with single-key lookup"
9430 .cindex "address list" "@@ lookup type"
9431 .cindex "address list" "split local part and domain"
9432 If a pattern starts with &"@@"& followed by a single-key lookup item
9433 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9434 split into a local part and a domain. The domain is looked up in the file. If
9435 it is not found, there is no match. If it is found, the data that is looked up
9436 from the file is treated as a colon-separated list of local part patterns, each
9437 of which is matched against the subject local part in turn.
9439 .cindex "asterisk" "in address list"
9440 The lookup may be a partial one, and/or one involving a search for a default
9441 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9442 patterns that are looked up can be regular expressions or begin with &"*"&, or
9443 even be further lookups. They may also be independently negated. For example,
9446 deny senders = @@dbm;/etc/reject-by-domain
9448 the data from which the DBM file is built could contain lines like
9450 baddomain.com: !postmaster : *
9452 to reject all senders except &%postmaster%& from that domain.
9454 .cindex "local part" "starting with !"
9455 If a local part that actually begins with an exclamation mark is required, it
9456 has to be specified using a regular expression. In &(lsearch)& files, an entry
9457 may be split over several lines by indenting the second and subsequent lines,
9458 but the separating colon must still be included at line breaks. White space
9459 surrounding the colons is ignored. For example:
9461 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9464 As in all colon-separated lists in Exim, a colon can be included in an item by
9467 If the last item in the list starts with a right angle-bracket, the remainder
9468 of the item is taken as a new key to look up in order to obtain a continuation
9469 list of local parts. The new key can be any sequence of characters. Thus one
9470 might have entries like
9472 aol.com: spammer1 : spammer 2 : >*
9473 xyz.com: spammer3 : >*
9476 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9477 local parts for all domains, in addition to the specific local parts listed for
9478 each domain. Of course, using this feature costs another lookup each time a
9479 chain is followed, but the effort needed to maintain the data is reduced.
9481 .cindex "loop" "in lookups"
9482 It is possible to construct loops using this facility, and in order to catch
9483 them, the chains may be no more than fifty items long.
9486 The @@<&'lookup'&> style of item can also be used with a query-style
9487 lookup, but in this case, the chaining facility is not available. The lookup
9488 can only return a single list of local parts.
9491 &*Warning*&: There is an important difference between the address list items
9492 in these two examples:
9495 senders = *@+my_list
9497 In the first one, &`my_list`& is a named address list, whereas in the second
9498 example it is a named domain list.
9503 .section "Case of letters in address lists" "SECTcasletadd"
9504 .cindex "case of local parts"
9505 .cindex "address list" "case forcing"
9506 .cindex "case forcing in address lists"
9507 Domains in email addresses are always handled caselessly, but for local parts
9508 case may be significant on some systems (see &%caseful_local_part%& for how
9509 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9510 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9511 blocking lists should be done in a case-independent manner. Since most address
9512 lists in Exim are used for this kind of control, Exim attempts to do this by
9515 The domain portion of an address is always lowercased before matching it to an
9516 address list. The local part is lowercased by default, and any string
9517 comparisons that take place are done caselessly. This means that the data in
9518 the address list itself, in files included as plain filenames, and in any file
9519 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9520 keys in files that are looked up by a search type other than &(lsearch)& (which
9521 works caselessly) must be in lower case, because these lookups are not
9524 .cindex "&`+caseful`&"
9525 To allow for the possibility of caseful address list matching, if an item in
9526 an address list is the string &"+caseful"&, the original case of the local
9527 part is restored for any comparisons that follow, and string comparisons are no
9528 longer case-independent. This does not affect the domain, which remains in
9529 lower case. However, although independent matches on the domain alone are still
9530 performed caselessly, regular expressions that match against an entire address
9531 become case-sensitive after &"+caseful"& has been seen.
9535 .section "Local part lists" "SECTlocparlis"
9536 .cindex "list" "local part list"
9537 .cindex "local part" "list"
9538 These behave in the same way as domain and host lists, with the following
9541 Case-sensitivity in local part lists is handled in the same way as for address
9542 lists, as just described. The &"+caseful"& item can be used if required. In a
9543 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9544 set false, the subject is lowercased and the matching is initially
9545 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9546 matching in the local part list, but not elsewhere in the router. If
9547 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9548 option is case-sensitive from the start.
9550 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9551 comments are handled in the same way as address lists &-- they are recognized
9552 only if the # is preceded by white space or the start of the line.
9553 Otherwise, local part lists are matched in the same way as domain lists, except
9554 that the special items that refer to the local host (&`@`&, &`@[]`&,
9555 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9556 Refer to section &<<SECTdomainlist>>& for details of the other available item
9558 .ecindex IIDdohoadli
9563 . ////////////////////////////////////////////////////////////////////////////
9564 . ////////////////////////////////////////////////////////////////////////////
9566 .chapter "String expansions" "CHAPexpand"
9567 .scindex IIDstrexp "expansion" "of strings"
9568 Many strings in Exim's runtime configuration are expanded before use. Some of
9569 them are expanded every time they are used; others are expanded only once.
9571 When a string is being expanded it is copied verbatim from left to right except
9572 .cindex expansion "string concatenation"
9573 when a dollar or backslash character is encountered. A dollar specifies the
9574 start of a portion of the string that is interpreted and replaced as described
9575 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9576 escape character, as described in the following section.
9578 Whether a string is expanded depends upon the context. Usually this is solely
9579 dependent upon the option for which a value is sought; in this documentation,
9580 options for which string expansion is performed are marked with † after
9581 the data type. ACL rules always expand strings. A couple of expansion
9582 conditions do not expand some of the brace-delimited branches, for security
9584 .cindex "tainted data" expansion
9585 .cindex "tainted data" definition
9586 .cindex expansion "tainted data"
9587 and expansion of data deriving from the sender (&"tainted data"&)
9589 is not permitted (including acessing a file using a tainted name).
9593 Common ways of obtaining untainted equivalents of variables with
9595 .cindex "tainted data" "de-tainting"
9596 come down to using the tainted value as a lookup key in a trusted database.
9597 This database could be the filesystem structure,
9598 or the password file,
9599 or accessed via a DBMS.
9600 Specific methods are indexed under &"de-tainting"&.
9605 .section "Literal text in expanded strings" "SECTlittext"
9606 .cindex "expansion" "including literal text"
9607 An uninterpreted dollar can be included in an expanded string by putting a
9608 backslash in front of it. A backslash can be used to prevent any special
9609 character being treated specially in an expansion, including backslash itself.
9610 If the string appears in quotes in the configuration file, two backslashes are
9611 required because the quotes themselves cause interpretation of backslashes when
9612 the string is read in (see section &<<SECTstrings>>&).
9614 .cindex "expansion" "non-expandable substrings"
9615 A portion of the string can specified as non-expandable by placing it between
9616 two occurrences of &`\N`&. This is particularly useful for protecting regular
9617 expressions, which often contain backslashes and dollar signs. For example:
9619 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9621 On encountering the first &`\N`&, the expander copies subsequent characters
9622 without interpretation until it reaches the next &`\N`& or the end of the
9627 .section "Character escape sequences in expanded strings" "SECID82"
9628 .cindex "expansion" "escape sequences"
9629 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9630 expanded string is recognized as an escape sequence for the character newline,
9631 carriage return, or tab, respectively. A backslash followed by up to three
9632 octal digits is recognized as an octal encoding for a single character, and a
9633 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9636 These escape sequences are also recognized in quoted strings when they are read
9637 in. Their interpretation in expansions as well is useful for unquoted strings,
9638 and for other cases such as looked-up strings that are then expanded.
9641 .section "Testing string expansions" "SECID83"
9642 .cindex "expansion" "testing"
9643 .cindex "testing" "string expansion"
9645 Many expansions can be tested by calling Exim with the &%-be%& option. This
9646 takes the command arguments, or lines from the standard input if there are no
9647 arguments, runs them through the string expansion code, and writes the results
9648 to the standard output. Variables based on configuration values are set up, but
9649 since no message is being processed, variables such as &$local_part$& have no
9650 value. Nevertheless the &%-be%& option can be useful for checking out file and
9651 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9654 Exim gives up its root privilege when it is called with the &%-be%& option, and
9655 instead runs under the uid and gid it was called with, to prevent users from
9656 using &%-be%& for reading files to which they do not have access.
9659 If you want to test expansions that include variables whose values are taken
9660 from a message, there are two other options that can be used. The &%-bem%&
9661 option is like &%-be%& except that it is followed by a filename. The file is
9662 read as a message before doing the test expansions. For example:
9664 exim -bem /tmp/test.message '$h_subject:'
9666 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9667 Exim message identifier. For example:
9669 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9671 This loads the message from Exim's spool before doing the test expansions, and
9672 is therefore restricted to admin users.
9675 .section "Forced expansion failure" "SECTforexpfai"
9676 .cindex "expansion" "forced failure"
9677 A number of expansions that are described in the following section have
9678 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9679 (which are sometimes called &"curly brackets"&). Which of the two strings is
9680 used depends on some condition that is evaluated as part of the expansion. If,
9681 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9682 the entire string expansion fails in a way that can be detected by the code
9683 that requested the expansion. This is called &"forced expansion failure"&, and
9684 its consequences depend on the circumstances. In some cases it is no different
9685 from any other expansion failure, but in others a different action may be
9686 taken. Such variations are mentioned in the documentation of the option that is
9692 .section "Expansion items" "SECTexpansionitems"
9693 The following items are recognized in expanded strings. White space may be used
9694 between sub-items that are keywords or substrings enclosed in braces inside an
9695 outer set of braces, to improve readability. &*Warning*&: Within braces,
9696 white space is significant.
9699 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9700 .cindex "expansion" "variables"
9701 Substitute the contents of the named variable, for example:
9706 The second form can be used to separate the name from subsequent alphanumeric
9707 characters. This form (using braces) is available only for variables; it does
9708 &'not'& apply to message headers. The names of the variables are given in
9709 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9710 given, the expansion fails.
9712 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9713 .cindex "expansion" "operators"
9714 The string is first itself expanded, and then the operation specified by
9715 <&'op'&> is applied to it. For example:
9719 The string starts with the first character after the colon, which may be
9720 leading white space. A list of operators is given in section &<<SECTexpop>>&
9721 below. The operator notation is used for simple expansion items that have just
9722 one argument, because it reduces the number of braces and therefore makes the
9723 string easier to understand.
9725 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9726 This item inserts &"basic"& header lines. It is described with the &%header%&
9727 expansion item below.
9730 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9731 .cindex "expansion" "calling an acl"
9732 .cindex "&%acl%&" "call from expansion"
9733 The name and zero to nine argument strings are first expanded separately. The expanded
9734 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9735 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9736 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9737 and may use the variables; if another acl expansion is used the values
9738 are restored after it returns. If the ACL sets
9739 a value using a "message =" modifier and returns accept or deny, the value becomes
9740 the result of the expansion.
9741 If no message is set and the ACL returns accept or deny
9742 the expansion result is an empty string.
9743 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9746 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9747 .cindex authentication "results header"
9748 .chindex Authentication-Results:
9749 .cindex authentication "expansion item"
9750 This item returns a string suitable for insertion as an
9751 &'Authentication-Results:'&
9753 The given <&'authserv-id'&> is included in the result; typically this
9754 will be a domain name identifying the system performing the authentications.
9755 Methods that might be present in the result include:
9764 Example use (as an ACL modifier):
9766 add_header = :at_start:${authresults {$primary_hostname}}
9768 This is safe even if no authentication results are available.
9771 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9772 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9773 .cindex "expansion" "extracting certificate fields"
9774 .cindex "&%certextract%&" "certificate fields"
9775 .cindex "certificate" "extracting fields"
9776 The <&'certificate'&> must be a variable of type certificate.
9777 The field name is expanded and used to retrieve the relevant field from
9778 the certificate. Supported fields are:
9782 &`subject `& RFC4514 DN
9783 &`issuer `& RFC4514 DN
9788 &`subj_altname `& tagged list
9792 If the field is found,
9793 <&'string2'&> is expanded, and replaces the whole item;
9794 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9795 variable &$value$& contains the value that has been extracted. Afterwards, it
9796 is restored to any previous value it might have had.
9798 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9799 key is not found. If {<&'string2'&>} is also omitted, the value that was
9802 Some field names take optional modifiers, appended and separated by commas.
9804 The field selectors marked as "RFC4514" above
9805 output a Distinguished Name string which is
9807 parseable by Exim as a comma-separated tagged list
9808 (the exceptions being elements containing commas).
9809 RDN elements of a single type may be selected by
9810 a modifier of the type label; if so the expansion
9811 result is a list (newline-separated by default).
9812 The separator may be changed by another modifier of
9813 a right angle-bracket followed immediately by the new separator.
9814 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9816 The field selectors marked as "time" above
9817 take an optional modifier of "int"
9818 for which the result is the number of seconds since epoch.
9819 Otherwise the result is a human-readable string
9820 in the timezone selected by the main "timezone" option.
9822 The field selectors marked as "list" above return a list,
9823 newline-separated by default,
9824 (embedded separator characters in elements are doubled).
9825 The separator may be changed by a modifier of
9826 a right angle-bracket followed immediately by the new separator.
9828 The field selectors marked as "tagged" above
9829 prefix each list element with a type string and an equals sign.
9830 Elements of only one type may be selected by a modifier
9831 which is one of "dns", "uri" or "mail";
9832 if so the element tags are omitted.
9834 If not otherwise noted field values are presented in human-readable form.
9836 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9837 {*&<&'arg'&>&*}...}*&"
9839 This expansion dynamically loads and then calls a locally-written C function.
9840 This functionality is available only if Exim is compiled with
9844 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9845 object so that it doesn't reload the same object file in the same Exim process
9846 (but of course Exim does start new processes frequently).
9848 There may be from zero to eight arguments to the function.
9851 a local function that is to be called in this way,
9852 first &_DLFUNC_IMPL_& should be defined,
9853 and second &_local_scan.h_& should be included.
9854 The Exim variables and functions that are defined by that API
9855 are also available for dynamically loaded functions. The function itself
9856 must have the following type:
9858 int dlfunction(uschar **yield, int argc, uschar *argv[])
9860 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9861 function should return one of the following values:
9863 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9864 into the expanded string that is being built.
9866 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9867 from &'yield'&, if it is set.
9869 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9870 taken from &'yield'& if it is set.
9872 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9874 When compiling a function that is to be used in this way with gcc,
9875 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9876 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9879 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9880 .cindex "expansion" "extracting value from environment"
9881 .cindex "environment" "values from"
9882 The key is first expanded separately, and leading and trailing white space
9884 This is then searched for as a name in the environment.
9885 If a variable is found then its value is placed in &$value$&
9886 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9888 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9889 appear, for example:
9891 ${env{USER}{$value} fail }
9893 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9894 {<&'string1'&>} must be present for &"fail"& to be recognized.
9896 If {<&'string2'&>} is omitted an empty string is substituted on
9898 If {<&'string1'&>} is omitted the search result is substituted on
9901 The environment is adjusted by the &%keep_environment%& and
9902 &%add_environment%& main section options.
9905 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9906 {*&<&'string3'&>&*}}*&"
9907 .cindex "expansion" "extracting substrings by key"
9908 .cindex "&%extract%&" "substrings by key"
9909 The key and <&'string1'&> are first expanded separately. Leading and trailing
9910 white space is removed from the key (but not from any of the strings). The key
9911 must not be empty and must not consist entirely of digits.
9912 The expanded <&'string1'&> must be of the form:
9914 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9917 where the equals signs and spaces (but not both) are optional. If any of the
9918 values contain white space, they must be enclosed in double quotes, and any
9919 values that are enclosed in double quotes are subject to escape processing as
9920 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9921 for the value that corresponds to the key. The search is case-insensitive. If
9922 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9923 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9924 variable &$value$& contains the value that has been extracted. Afterwards, it
9925 is restored to any previous value it might have had.
9927 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9928 key is not found. If {<&'string2'&>} is also omitted, the value that was
9929 extracted is used. Thus, for example, these two expansions are identical, and
9932 ${extract{gid}{uid=1984 gid=2001}}
9933 ${extract{gid}{uid=1984 gid=2001}{$value}}
9935 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9936 appear, for example:
9938 ${extract{Z}{A=... B=...}{$value} fail }
9940 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9941 {<&'string2'&>} must be present for &"fail"& to be recognized.
9943 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9944 {*&<&'string3'&>&*}}*&" &&&
9945 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9946 {*&<&'string3'&>&*}}*&"
9947 .cindex "expansion" "extracting from JSON object"
9948 .cindex JSON expansions
9949 The key and <&'string1'&> are first expanded separately. Leading and trailing
9950 white space is removed from the key (but not from any of the strings). The key
9951 must not be empty and must not consist entirely of digits.
9952 The expanded <&'string1'&> must be of the form:
9954 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9957 The braces, commas and colons, and the quoting of the member name are required;
9958 the spaces are optional.
9959 Matching of the key against the member names is done case-sensitively.
9960 For the &"json"& variant,
9961 if a returned value is a JSON string, it retains its leading and
9963 For the &"jsons"& variant, which is intended for use with JSON strings, the
9964 leading and trailing quotes are removed from the returned value.
9965 . XXX should be a UTF-8 compare
9967 The results of matching are handled as above.
9970 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9971 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9972 .cindex "expansion" "extracting substrings by number"
9973 .cindex "&%extract%&" "substrings by number"
9974 The <&'number'&> argument must consist entirely of decimal digits,
9975 apart from leading and trailing white space, which is ignored.
9976 This is what distinguishes this form of &%extract%& from the previous kind. It
9977 behaves in the same way, except that, instead of extracting a named field, it
9978 extracts from <&'string1'&> the field whose number is given as the first
9979 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9980 <&'string3'&> as before.
9982 The fields in the string are separated by any one of the characters in the
9983 separator string. These may include space or tab characters.
9984 The first field is numbered one. If the number is negative, the fields are
9985 counted from the end of the string, with the rightmost one numbered -1. If the
9986 number given is zero, the entire string is returned. If the modulus of the
9987 number is greater than the number of fields in the string, the result is the
9988 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9989 provided. For example:
9991 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9995 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9997 yields &"99"&. Two successive separators mean that the field between them is
9998 empty (for example, the fifth field above).
10001 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
10002 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
10003 "&*${extract jsons{*&<&'number'&>&*}}&&&
10004 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10005 .cindex "expansion" "extracting from JSON array"
10006 .cindex JSON expansions
10007 The <&'number'&> argument must consist entirely of decimal digits,
10008 apart from leading and trailing white space, which is ignored.
10010 Field selection and result handling is as above;
10011 there is no choice of field separator.
10012 For the &"json"& variant,
10013 if a returned value is a JSON string, it retains its leading and
10015 For the &"jsons"& variant, which is intended for use with JSON strings, the
10016 leading and trailing quotes are removed from the returned value.
10019 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
10020 .cindex "list" "selecting by condition"
10021 .cindex "expansion" "selecting from list by condition"
10023 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10024 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10026 in this list, its value is place in &$item$&, and then the condition is
10027 evaluated. If the condition is true, &$item$& is added to the output as an
10028 item in a new list; if the condition is false, the item is discarded. The
10029 separator used for the output list is the same as the one used for the
10030 input, but a separator setting is not included in the output. For example:
10032 ${filter{a:b:c}{!eq{$item}{b}}}
10034 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10035 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10038 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10039 .cindex "hash function" "textual"
10040 .cindex "expansion" "textual hash"
10041 This is a textual hashing function, and was the first to be implemented in
10042 early versions of Exim. In current releases, there are other hashing functions
10043 (numeric, MD5, and SHA-1), which are described below.
10045 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10046 <&'n'&>. If you are using fixed values for these numbers, that is, if
10047 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10048 use the simpler operator notation that avoids some of the braces:
10050 ${hash_<n>_<m>:<string>}
10052 The second number is optional (in both notations). If <&'n'&> is greater than
10053 or equal to the length of the string, the expansion item returns the string.
10054 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10055 function to the string. The new string consists of characters taken from the
10056 first <&'m'&> characters of the string
10058 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10060 If <&'m'&> is not present the value 26 is used, so that only lower case
10061 letters appear. For example:
10063 &`$hash{3}{monty}} `& yields &`jmg`&
10064 &`$hash{5}{monty}} `& yields &`monty`&
10065 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10068 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10069 &*$h_*&<&'header&~name'&>&*:*&" &&&
10070 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10071 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10072 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10073 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10074 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10075 &*$rh_*&<&'header&~name'&>&*:*&"
10076 .cindex "expansion" "header insertion"
10077 .vindex "&$header_$&"
10078 .vindex "&$bheader_$&"
10079 .vindex "&$lheader_$&"
10080 .vindex "&$rheader_$&"
10081 .cindex "header lines" "in expansion strings"
10082 .cindex "header lines" "character sets"
10083 .cindex "header lines" "decoding"
10084 Substitute the contents of the named message header line, for example
10088 The newline that terminates a header line is not included in the expansion, but
10089 internal newlines (caused by splitting the header line over several physical
10090 lines) may be present.
10092 The difference between the four pairs of expansions is in the way
10093 the data in the header line is interpreted.
10096 .cindex "white space" "in header lines"
10097 &%rheader%& gives the original &"raw"& content of the header line, with no
10098 processing at all, and without the removal of leading and trailing white space.
10101 .cindex "list" "of header lines"
10102 &%lheader%& gives a colon-separated list, one element per header when there
10103 are multiple headers with a given name.
10104 Any embedded colon characters within an element are doubled, so normal Exim
10105 list-processing facilities can be used.
10106 The terminating newline of each element is removed; in other respects
10107 the content is &"raw"&.
10110 .cindex "base64 encoding" "in header lines"
10111 &%bheader%& removes leading and trailing white space, and then decodes base64
10112 or quoted-printable MIME &"words"& within the header text, but does no
10113 character set translation. If decoding of what looks superficially like a MIME
10114 &"word"& fails, the raw string is returned. If decoding
10115 .cindex "binary zero" "in header line"
10116 produces a binary zero character, it is replaced by a question mark &-- this is
10117 what Exim does for binary zeros that are actually received in header lines.
10120 &%header%& tries to translate the string as decoded by &%bheader%& to a
10121 standard character set. This is an attempt to produce the same string as would
10122 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10123 returned. Translation is attempted only on operating systems that support the
10124 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10125 a system Makefile or in &_Local/Makefile_&.
10128 In a filter file, the target character set for &%header%& can be specified by a
10129 command of the following form:
10131 headers charset "UTF-8"
10133 This command affects all references to &$h_$& (or &$header_$&) expansions in
10134 subsequently obeyed filter commands. In the absence of this command, the target
10135 character set in a filter is taken from the setting of the &%headers_charset%&
10136 option in the runtime configuration. The value of this option defaults to the
10137 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10140 Header names follow the syntax of RFC 2822, which states that they may contain
10141 any printing characters except space and colon. Consequently, curly brackets
10142 &'do not'& terminate header names, and should not be used to enclose them as
10143 if they were variables. Attempting to do so causes a syntax error.
10145 Only header lines that are common to all copies of a message are visible to
10146 this mechanism. These are the original header lines that are received with the
10147 message, and any that are added by an ACL statement or by a system
10148 filter. Header lines that are added to a particular copy of a message by a
10149 router or transport are not accessible.
10151 For incoming SMTP messages, no header lines are visible in
10152 ACLs that are obeyed before the data phase completes,
10153 because the header structure is not set up until the message is received.
10154 They are visible in DKIM, PRDR and DATA ACLs.
10155 Header lines that are added in a RCPT ACL (for example)
10156 are saved until the message's incoming header lines are available, at which
10157 point they are added.
10158 When any of the above ACLs ar
10159 running, however, header lines added by earlier ACLs are visible.
10161 Upper case and lower case letters are synonymous in header names. If the
10162 following character is white space, the terminating colon may be omitted, but
10163 this is not recommended, because you may then forget it when it is needed. When
10164 white space terminates the header name, this white space is included in the
10165 expanded string. If the message does not contain the given header, the
10166 expansion item is replaced by an empty string. (See the &%def%& condition in
10167 section &<<SECTexpcond>>& for a means of testing for the existence of a
10170 If there is more than one header with the same name, they are all concatenated
10171 to form the substitution string, up to a maximum length of 64K. Unless
10172 &%rheader%& is being used, leading and trailing white space is removed from
10173 each header before concatenation, and a completely empty header is ignored. A
10174 newline character is then inserted between non-empty headers, but there is no
10175 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10176 those headers that contain lists of addresses, a comma is also inserted at the
10177 junctions between headers. This does not happen for the &%rheader%& expansion.
10179 .cindex "tainted data" "message headers"
10180 When the headers are from an incoming message,
10181 the result of expanding any of these variables is tainted.
10184 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10185 .cindex "expansion" "hmac hashing"
10187 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10188 shared secret and some text into a message authentication code, as specified in
10189 RFC 2104. This differs from &`${md5:secret_text...}`& or
10190 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10191 cryptographic hash, allowing for authentication that is not possible with MD5
10192 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10193 present. For example:
10195 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10197 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10200 dd97e3ba5d1a61b5006108f8c8252953
10202 As an example of how this might be used, you might put in the main part of
10203 an Exim configuration:
10205 SPAMSCAN_SECRET=cohgheeLei2thahw
10207 In a router or a transport you could then have:
10210 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10211 ${hmac{md5}{SPAMSCAN_SECRET}\
10212 {${primary_hostname},${message_exim_id},$h_message-id:}}
10214 Then given a message, you can check where it was scanned by looking at the
10215 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10216 this header line is authentic by recomputing the authentication code from the
10217 host name, message ID and the &'Message-id:'& header line. This can be done
10218 using Exim's &%-be%& option, or by other means, for example, by using the
10219 &'hmac_md5_hex()'& function in Perl.
10222 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10223 .cindex "expansion" "conditional"
10224 .cindex "&%if%&, expansion item"
10225 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10226 item; otherwise <&'string2'&> is used. The available conditions are described
10227 in section &<<SECTexpcond>>& below. For example:
10229 ${if eq {$local_part}{postmaster} {yes}{no} }
10231 The second string need not be present; if it is not and the condition is not
10232 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10233 be present instead of the second string (without any curly brackets). In this
10234 case, the expansion is forced to fail if the condition is not true (see section
10235 &<<SECTforexpfai>>&).
10237 If both strings are omitted, the result is the string &`true`& if the condition
10238 is true, and the empty string if the condition is false. This makes it less
10239 cumbersome to write custom ACL and router conditions. For example, instead of
10241 condition = ${if >{$acl_m4}{3}{true}{false}}
10245 condition = ${if >{$acl_m4}{3}}
10250 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10251 .cindex expansion "imap folder"
10252 .cindex "&%imapfolder%& expansion item"
10253 This item converts a (possibly multilevel, or with non-ASCII characters)
10254 folder specification to a Maildir name for filesystem use.
10255 For information on internationalisation support see &<<SECTi18nMDA>>&.
10259 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10260 .cindex "expansion" "string truncation"
10261 .cindex "&%length%& expansion item"
10262 The &%length%& item is used to extract the initial portion of a string. Both
10263 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10264 you are using a fixed value for the number, that is, if <&'string1'&> does not
10265 change when expanded, you can use the simpler operator notation that avoids
10266 some of the braces:
10268 ${length_<n>:<string>}
10270 The result of this item is either the first <&'n'&> bytes or the whole
10271 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10272 &%strlen%&, which gives the length of a string.
10273 All measurement is done in bytes and is not UTF-8 aware.
10276 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10277 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10278 .cindex "expansion" "extracting list elements by number"
10279 .cindex "&%listextract%&" "extract list elements by number"
10280 .cindex "list" "extracting elements by number"
10281 The <&'number'&> argument must consist entirely of decimal digits,
10282 apart from an optional leading minus,
10283 and leading and trailing white space (which is ignored).
10285 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10286 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10288 The first field of the list is numbered one.
10289 If the number is negative, the fields are
10290 counted from the end of the list, with the rightmost one numbered -1.
10291 The numbered element of the list is extracted and placed in &$value$&,
10292 then <&'string2'&> is expanded as the result.
10294 If the modulus of the
10295 number is zero or greater than the number of fields in the string,
10296 the result is the expansion of <&'string3'&>.
10300 ${listextract{2}{x:42:99}}
10304 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10306 yields &"result: 42"&.
10308 If {<&'string3'&>} is omitted, an empty string is used for string3.
10309 If {<&'string2'&>} is also omitted, the value that was
10311 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10315 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10316 .cindex quoting "for list"
10317 .cindex list quoting
10318 This item doubles any occurrence of the separator character
10319 in the given string.
10320 An empty string is replaced with a single space.
10321 This converts the string into a safe form for use as a list element,
10322 in a list using the given separator.
10326 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10327 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10328 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10329 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10330 .cindex "expansion" "lookup in"
10331 .cindex "file" "lookups"
10332 .cindex "lookup" "in expanded string"
10333 The two forms of lookup item specify data lookups in files and databases, as
10334 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10335 lookups, and the second is used for query-style lookups. The <&'key'&>,
10336 <&'file'&>, and <&'query'&> strings are expanded before use.
10338 If there is any white space in a lookup item which is part of a filter command,
10339 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10340 other place where white space is significant, the lookup item must be enclosed
10341 in double quotes. The use of data lookups in users' filter files may be locked
10342 out by the system administrator.
10344 .vindex "&$value$&"
10345 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10346 During its expansion, the variable &$value$& contains the data returned by the
10347 lookup. Afterwards it reverts to the value it had previously (at the outer
10348 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10349 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10350 string on failure. If <&'string2'&> is provided, it can itself be a nested
10351 lookup, thus providing a mechanism for looking up a default value when the
10352 original lookup fails.
10354 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10355 data for the outer lookup while the parameters of the second lookup are
10356 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10357 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10358 appear, and in this case, if the lookup fails, the entire expansion is forced
10359 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10360 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10361 successful lookup, and nothing in the case of failure.
10363 For single-key lookups, the string &"partial"& is permitted to precede the
10364 search type in order to do partial matching, and * or *@ may follow a search
10365 type to request default lookups if the key does not match (see sections
10366 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10368 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10369 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10370 and non-wild parts of the key during the expansion of the replacement text.
10371 They return to their previous values at the end of the lookup item.
10373 This example looks up the postmaster alias in the conventional alias file:
10375 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10377 This example uses NIS+ to look up the full name of the user corresponding to
10378 the local part of an address, forcing the expansion to fail if it is not found:
10380 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10385 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10386 .cindex "expansion" "list creation"
10388 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10389 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10391 in this list, its value is place in &$item$&, and then <&'string2'&> is
10392 expanded and added to the output as an item in a new list. The separator used
10393 for the output list is the same as the one used for the input, but a separator
10394 setting is not included in the output. For example:
10396 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10398 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10399 value of &$item$& is restored to what it was before. See also the &%filter%&
10400 and &%reduce%& expansion items.
10402 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10403 .cindex "expansion" "numeric hash"
10404 .cindex "hash function" "numeric"
10405 The three strings are expanded; the first two must yield numbers. Call them
10406 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10407 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10408 can use the simpler operator notation that avoids some of the braces:
10410 ${nhash_<n>_<m>:<string>}
10412 The second number is optional (in both notations). If there is only one number,
10413 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10414 processed by a div/mod hash function that returns two numbers, separated by a
10415 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10418 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10420 returns the string &"6/33"&.
10424 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10425 .cindex "Perl" "use in expanded string"
10426 .cindex "expansion" "calling Perl from"
10427 This item is available only if Exim has been built to include an embedded Perl
10428 interpreter. The subroutine name and the arguments are first separately
10429 expanded, and then the Perl subroutine is called with those arguments. No
10430 additional arguments need be given; the maximum number permitted, including the
10431 name of the subroutine, is nine.
10433 The return value of the subroutine is inserted into the expanded string, unless
10434 the return value is &%undef%&. In that case, the expansion fails in the same
10435 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
10436 Whatever you return is evaluated in a scalar context. For example, if you
10437 return the name of a Perl vector, the return value is the size of the vector,
10440 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10441 with the error message that was passed to &%die%&. More details of the embedded
10442 Perl facility are given in chapter &<<CHAPperl>>&.
10444 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10445 out the use of this expansion item in filter files.
10448 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10449 .cindex "&%prvs%& expansion item"
10450 The first argument is a complete email address and the second is secret
10451 keystring. The third argument, specifying a key number, is optional. If absent,
10452 it defaults to 0. The result of the expansion is a prvs-signed email address,
10453 to be typically used with the &%return_path%& option on an &(smtp)& transport
10454 as part of a bounce address tag validation (BATV) scheme. For more discussion
10455 and an example, see section &<<SECTverifyPRVS>>&.
10457 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10458 {*&<&'string'&>&*}}*&"
10459 .cindex "&%prvscheck%& expansion item"
10460 This expansion item is the complement of the &%prvs%& item. It is used for
10461 checking prvs-signed addresses. If the expansion of the first argument does not
10462 yield a syntactically valid prvs-signed address, the whole item expands to the
10463 empty string. When the first argument does expand to a syntactically valid
10464 prvs-signed address, the second argument is expanded, with the prvs-decoded
10465 version of the address and the key number extracted from the address in the
10466 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10468 These two variables can be used in the expansion of the second argument to
10469 retrieve the secret. The validity of the prvs-signed address is then checked
10470 against the secret. The result is stored in the variable &$prvscheck_result$&,
10471 which is empty for failure or &"1"& for success.
10473 The third argument is optional; if it is missing, it defaults to an empty
10474 string. This argument is now expanded. If the result is an empty string, the
10475 result of the expansion is the decoded version of the address. This is the case
10476 whether or not the signature was valid. Otherwise, the result of the expansion
10477 is the expansion of the third argument.
10479 All three variables can be used in the expansion of the third argument.
10480 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10481 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10483 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10484 .cindex "expansion" "inserting an entire file"
10485 .cindex "file" "inserting into expansion"
10486 .cindex "&%readfile%& expansion item"
10487 The filename and end-of-line string are first expanded separately. The file is
10488 then read, and its contents replace the entire item. All newline characters in
10489 the file are replaced by the end-of-line string if it is present. Otherwise,
10490 newlines are left in the string.
10491 String expansion is not applied to the contents of the file. If you want this,
10492 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10493 the string expansion fails.
10495 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10496 locks out the use of this expansion item in filter files.
10500 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10501 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10502 .cindex "expansion" "inserting from a socket"
10503 .cindex "socket, use of in expansion"
10504 .cindex "&%readsocket%& expansion item"
10505 This item inserts data from a Unix domain or TCP socket into the expanded
10506 string. The minimal way of using it uses just two arguments, as in these
10509 ${readsocket{/socket/name}{request string}}
10510 ${readsocket{inet:some.host:1234}{request string}}
10512 For a Unix domain socket, the first substring must be the path to the socket.
10513 For an Internet socket, the first substring must contain &`inet:`& followed by
10514 a host name or IP address, followed by a colon and a port, which can be a
10515 number or the name of a TCP port in &_/etc/services_&. An IP address may
10516 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10519 ${readsocket{inet:[::1]:1234}{request string}}
10521 Only a single host name may be given, but if looking it up yields more than
10522 one IP address, they are each tried in turn until a connection is made. For
10523 both kinds of socket, Exim makes a connection, writes the request string
10524 unless it is an empty string; and no terminating NUL is ever sent)
10525 and reads from the socket until an end-of-file
10526 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10527 extend what can be done. Firstly, you can vary the timeout. For example:
10529 ${readsocket{/socket/name}{request string}{3s}}
10532 The third argument is a list of options, of which the first element is the timeout
10533 and must be present if any options are given.
10534 Further elements are options of form &'name=value'&.
10537 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10540 The following option names are recognised:
10543 Defines if the result data can be cached for use by a later identical
10544 request in the same process.
10545 Values are &"yes"& or &"no"& (the default).
10546 If not, all cached results for this connection specification
10547 will be invalidated.
10551 Defines whether or not a write-shutdown is done on the connection after
10552 sending the request. Values are &"yes"& (the default) or &"no"&
10553 (preferred, eg. by some webservers).
10557 Controls the use of TLS on the connection.
10558 Values are &"yes"& or &"no"& (the default).
10559 If it is enabled, a shutdown as descripbed above is never done.
10563 A fourth argument allows you to change any newlines that are in the data
10564 that is read, in the same way as for &%readfile%& (see above). This example
10565 turns them into spaces:
10567 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10569 As with all expansions, the substrings are expanded before the processing
10570 happens. Errors in these sub-expansions cause the expansion to fail. In
10571 addition, the following errors can occur:
10574 Failure to create a socket file descriptor;
10576 Failure to connect the socket;
10578 Failure to write the request string;
10580 Timeout on reading from the socket.
10583 By default, any of these errors causes the expansion to fail. However, if
10584 you supply a fifth substring, it is expanded and used when any of the above
10585 errors occurs. For example:
10587 ${readsocket{/socket/name}{request string}{3s}{\n}\
10590 You can test for the existence of a Unix domain socket by wrapping this
10591 expansion in &`${if exists`&, but there is a race condition between that test
10592 and the actual opening of the socket, so it is safer to use the fifth argument
10593 if you want to be absolutely sure of avoiding an expansion error for a
10594 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10596 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10597 locks out the use of this expansion item in filter files.
10600 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10601 .cindex "expansion" "reducing a list to a scalar"
10602 .cindex "list" "reducing to a scalar"
10603 .vindex "&$value$&"
10605 This operation reduces a list to a single, scalar string. After expansion,
10606 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10607 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10608 Then <&'string2'&> is expanded and
10609 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10610 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10611 them. The result of that expansion is assigned to &$value$& before the next
10612 iteration. When the end of the list is reached, the final value of &$value$& is
10613 added to the expansion output. The &%reduce%& expansion item can be used in a
10614 number of ways. For example, to add up a list of numbers:
10616 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10618 The result of that expansion would be &`6`&. The maximum of a list of numbers
10621 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10623 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10624 restored to what they were before. See also the &%filter%& and &%map%&
10627 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10628 This item inserts &"raw"& header lines. It is described with the &%header%&
10629 expansion item in section &<<SECTexpansionitems>>& above.
10631 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10632 {*&<&'string2'&>&*}}*&"
10633 .cindex "expansion" "running a command"
10634 .cindex "&%run%& expansion item"
10635 The command and its arguments are first expanded as one string. The string is
10636 split apart into individual arguments by spaces, and then the command is run
10637 in a separate process, but under the same uid and gid. As in other command
10638 executions from Exim, a shell is not used by default. If the command requires
10639 a shell, you must explicitly code it.
10641 Since the arguments are split by spaces, when there is a variable expansion
10642 which has an empty result, it will cause the situation that the argument will
10643 simply be omitted when the program is actually executed by Exim. If the
10644 script/program requires a specific number of arguments and the expanded
10645 variable could possibly result in this empty expansion, the variable must be
10646 quoted. This is more difficult if the expanded variable itself could result
10647 in a string containing quotes, because it would interfere with the quotes
10648 around the command arguments. A possible guard against this is to wrap the
10649 variable in the &%sg%& operator to change any quote marks to some other
10652 The standard input for the command exists, but is empty. The standard output
10653 and standard error are set to the same file descriptor.
10654 .cindex "return code" "from &%run%& expansion"
10655 .vindex "&$value$&"
10656 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10657 and replaces the entire item; during this expansion, the standard output/error
10658 from the command is in the variable &$value$&. If the command fails,
10659 <&'string2'&>, if present, is expanded and used. Once again, during the
10660 expansion, the standard output/error from the command is in the variable
10663 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10664 can be the word &"fail"& (not in braces) to force expansion failure if the
10665 command does not succeed. If both strings are omitted, the result is contents
10666 of the standard output/error on success, and nothing on failure.
10668 .vindex "&$run_in_acl$&"
10669 The standard output/error of the command is put in the variable &$value$&.
10670 In this ACL example, the output of a command is logged for the admin to
10673 warn condition = ${run{/usr/bin/id}{yes}{no}}
10674 log_message = Output of id: $value
10676 If the command requires shell idioms, such as the > redirect operator, the
10677 shell must be invoked directly, such as with:
10679 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10682 .vindex "&$runrc$&"
10683 The return code from the command is put in the variable &$runrc$&, and this
10684 remains set afterwards, so in a filter file you can do things like this:
10686 if "${run{x y z}{}}$runrc" is 1 then ...
10687 elif $runrc is 2 then ...
10691 If execution of the command fails (for example, the command does not exist),
10692 the return code is 127 &-- the same code that shells use for non-existent
10695 &*Warning*&: In a router or transport, you cannot assume the order in which
10696 option values are expanded, except for those preconditions whose order of
10697 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10698 by the expansion of one option, and use it in another.
10700 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10701 out the use of this expansion item in filter files.
10704 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10705 .cindex "expansion" "string substitution"
10706 .cindex "&%sg%& expansion item"
10707 This item works like Perl's substitution operator (s) with the global (/g)
10708 option; hence its name. However, unlike the Perl equivalent, Exim does not
10709 modify the subject string; instead it returns the modified string for insertion
10710 into the overall expansion. The item takes three arguments: the subject string,
10711 a regular expression, and a substitution string. For example:
10713 ${sg{abcdefabcdef}{abc}{xyz}}
10715 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10716 if any $, } or \ characters are required in the regular expression or in the
10717 substitution string, they have to be escaped. For example:
10719 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10721 yields &"defabc"&, and
10723 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10725 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10726 the regular expression from string expansion.
10728 The regular expression is compiled in 8-bit mode, working against bytes
10729 rather than any Unicode-aware character handling.
10732 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10733 .cindex sorting "a list"
10734 .cindex list sorting
10735 .cindex expansion "list sorting"
10736 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10737 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10738 The <&'comparator'&> argument is interpreted as the operator
10739 of a two-argument expansion condition.
10740 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10741 The comparison should return true when applied to two values
10742 if the first value should sort before the second value.
10743 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10744 the element being placed in &$item$&,
10745 to give values for comparison.
10747 The item result is a sorted list,
10748 with the original list separator,
10749 of the list elements (in full) of the original.
10753 ${sort{3:2:1:4}{<}{$item}}
10755 sorts a list of numbers, and
10757 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10759 will sort an MX lookup into priority order.
10764 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10765 SRS encoding. See SECT &<<SECTSRS>>& for details.
10770 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10771 .cindex "&%substr%& expansion item"
10772 .cindex "substring extraction"
10773 .cindex "expansion" "substring extraction"
10774 The three strings are expanded; the first two must yield numbers. Call them
10775 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10776 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10777 can use the simpler operator notation that avoids some of the braces:
10779 ${substr_<n>_<m>:<string>}
10781 The second number is optional (in both notations).
10782 If it is absent in the simpler format, the preceding underscore must also be
10785 The &%substr%& item can be used to extract more general substrings than
10786 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10787 length required. For example
10789 ${substr{3}{2}{$local_part}}
10791 If the starting offset is greater than the string length the result is the
10792 null string; if the length plus starting offset is greater than the string
10793 length, the result is the right-hand part of the string, starting from the
10794 given offset. The first byte (character) in the string has offset zero.
10796 The &%substr%& expansion item can take negative offset values to count
10797 from the right-hand end of its operand. The last byte (character) is offset -1,
10798 the second-last is offset -2, and so on. Thus, for example,
10800 ${substr{-5}{2}{1234567}}
10802 yields &"34"&. If the absolute value of a negative offset is greater than the
10803 length of the string, the substring starts at the beginning of the string, and
10804 the length is reduced by the amount of overshoot. Thus, for example,
10806 ${substr{-5}{2}{12}}
10808 yields an empty string, but
10810 ${substr{-3}{2}{12}}
10814 When the second number is omitted from &%substr%&, the remainder of the string
10815 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10816 string preceding the offset point are taken. For example, an offset of -1 and
10817 no length, as in these semantically identical examples:
10820 ${substr{-1}{abcde}}
10822 yields all but the last character of the string, that is, &"abcd"&.
10824 All measurement is done in bytes and is not UTF-8 aware.
10828 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10829 {*&<&'replacements'&>&*}}*&"
10830 .cindex "expansion" "character translation"
10831 .cindex "&%tr%& expansion item"
10832 This item does single-character (in bytes) translation on its subject string. The second
10833 argument is a list of characters to be translated in the subject string. Each
10834 matching character is replaced by the corresponding character from the
10835 replacement list. For example
10837 ${tr{abcdea}{ac}{13}}
10839 yields &`1b3de1`&. If there are duplicates in the second character string, the
10840 last occurrence is used. If the third string is shorter than the second, its
10841 last character is replicated. However, if it is empty, no translation takes
10844 All character handling is done in bytes and is not UTF-8 aware.
10850 .section "Expansion operators" "SECTexpop"
10851 .cindex "expansion" "operators"
10852 For expansion items that perform transformations on a single argument string,
10853 the &"operator"& notation is used because it is simpler and uses fewer braces.
10854 The substring is first expanded before the operation is applied to it. The
10855 following operations can be performed:
10858 .vitem &*${address:*&<&'string'&>&*}*&
10859 .cindex "expansion" "RFC 2822 address handling"
10860 .cindex "&%address%& expansion item"
10861 The string is interpreted as an RFC 2822 address, as it might appear in a
10862 header line, and the effective address is extracted from it. If the string does
10863 not parse successfully, the result is empty.
10865 The parsing correctly handles SMTPUTF8 Unicode in the string.
10868 .vitem &*${addresses:*&<&'string'&>&*}*&
10869 .cindex "expansion" "RFC 2822 address handling"
10870 .cindex "&%addresses%& expansion item"
10871 The string (after expansion) is interpreted as a list of addresses in RFC
10872 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10873 operative address (&'local-part@domain'&) is extracted from each item, and the
10874 result of the expansion is a colon-separated list, with appropriate
10875 doubling of colons should any happen to be present in the email addresses.
10876 Syntactically invalid RFC2822 address items are omitted from the output.
10878 It is possible to specify a character other than colon for the output
10879 separator by starting the string with > followed by the new separator
10880 character. For example:
10882 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10884 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10885 first, so if the expanded string starts with >, it may change the output
10886 separator unintentionally. This can be avoided by setting the output
10887 separator explicitly:
10889 ${addresses:>:$h_from:}
10892 Compare the &%address%& (singular)
10893 expansion item, which extracts the working address from a single RFC2822
10894 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10897 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10898 a strict interpretation of header line formatting. Exim parses the bare,
10899 unquoted portion of an email address and if it finds a comma, treats it as an
10900 email address separator. For the example header line:
10902 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10904 The first example below demonstrates that Q-encoded email addresses are parsed
10905 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10906 It does not see the comma because it's still encoded as "=2C". The second
10907 example below is passed the contents of &`$header_from:`&, meaning it gets
10908 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10909 The third example shows that the presence of a comma is skipped when it is
10910 quoted. The fourth example shows SMTPUTF8 handling.
10912 # exim -be '${addresses:From: \
10913 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10915 # exim -be '${addresses:From: Last, First <user@example.com>}'
10916 Last:user@example.com
10917 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10919 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10923 .vitem &*${base32:*&<&'digits'&>&*}*&
10924 .cindex "&%base32%& expansion item"
10925 .cindex "expansion" "conversion to base 32"
10926 The string must consist entirely of decimal digits. The number is converted to
10927 base 32 and output as a (empty, for zero) string of characters.
10928 Only lowercase letters are used.
10930 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10931 .cindex "&%base32d%& expansion item"
10932 .cindex "expansion" "conversion to base 32"
10933 The string must consist entirely of base-32 digits.
10934 The number is converted to decimal and output as a string.
10936 .vitem &*${base62:*&<&'digits'&>&*}*&
10937 .cindex "&%base62%& expansion item"
10938 .cindex "expansion" "conversion to base 62"
10939 The string must consist entirely of decimal digits. The number is converted to
10940 base 62 and output as a string of six characters, including leading zeros. In
10941 the few operating environments where Exim uses base 36 instead of base 62 for
10942 its message identifiers (because those systems do not have case-sensitive
10943 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10944 to be absolutely clear: this is &'not'& base64 encoding.
10946 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10947 .cindex "&%base62d%& expansion item"
10948 .cindex "expansion" "conversion to base 62"
10949 The string must consist entirely of base-62 digits, or, in operating
10950 environments where Exim uses base 36 instead of base 62 for its message
10951 identifiers, base-36 digits. The number is converted to decimal and output as a
10954 .vitem &*${base64:*&<&'string'&>&*}*&
10955 .cindex "expansion" "base64 encoding"
10956 .cindex "base64 encoding" "in string expansion"
10957 .cindex "&%base64%& expansion item"
10958 .cindex certificate "base64 of DER"
10959 This operator converts a string into one that is base64 encoded.
10961 If the string is a single variable of type certificate,
10962 returns the base64 encoding of the DER form of the certificate.
10965 .vitem &*${base64d:*&<&'string'&>&*}*&
10966 .cindex "expansion" "base64 decoding"
10967 .cindex "base64 decoding" "in string expansion"
10968 .cindex "&%base64d%& expansion item"
10969 This operator converts a base64-encoded string into the un-coded form.
10972 .vitem &*${domain:*&<&'string'&>&*}*&
10973 .cindex "domain" "extraction"
10974 .cindex "expansion" "domain extraction"
10975 The string is interpreted as an RFC 2822 address and the domain is extracted
10976 from it. If the string does not parse successfully, the result is empty.
10979 .vitem &*${escape:*&<&'string'&>&*}*&
10980 .cindex "expansion" "escaping non-printing characters"
10981 .cindex "&%escape%& expansion item"
10982 If the string contains any non-printing characters, they are converted to
10983 escape sequences starting with a backslash. Whether characters with the most
10984 significant bit set (so-called &"8-bit characters"&) count as printing or not
10985 is controlled by the &%print_topbitchars%& option.
10987 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10988 .cindex "expansion" "escaping 8-bit characters"
10989 .cindex "&%escape8bit%& expansion item"
10990 If the string contains and characters with the most significant bit set,
10991 they are converted to escape sequences starting with a backslash.
10992 Backslashes and DEL characters are also converted.
10995 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10996 .cindex "expansion" "expression evaluation"
10997 .cindex "expansion" "arithmetic expression"
10998 .cindex "&%eval%& expansion item"
10999 These items supports simple arithmetic and bitwise logical operations in
11000 expansion strings. The string (after expansion) must be a conventional
11001 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
11002 logical operators, and parentheses. All operations are carried out using
11003 integer arithmetic. The operator priorities are as follows (the same as in the
11004 C programming language):
11006 .irow &'highest:'& "not (~), negate (-)"
11007 .irow "" "multiply (*), divide (/), remainder (%)"
11008 .irow "" "plus (+), minus (-)"
11009 .irow "" "shift-left (<<), shift-right (>>)"
11010 .irow "" "and (&&)"
11012 .irow &'lowest:'& "or (|)"
11014 Binary operators with the same priority are evaluated from left to right. White
11015 space is permitted before or after operators.
11017 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
11018 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
11019 decimal, even if they start with a leading zero; hexadecimal numbers are not
11020 permitted. This can be useful when processing numbers extracted from dates or
11021 times, which often do have leading zeros.
11023 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
11025 respectively. Negative numbers are supported. The result of the computation is
11026 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11029 &`${eval:1+1} `& yields 2
11030 &`${eval:1+2*3} `& yields 7
11031 &`${eval:(1+2)*3} `& yields 9
11032 &`${eval:2+42%5} `& yields 4
11033 &`${eval:0xc&5} `& yields 4
11034 &`${eval:0xc|5} `& yields 13
11035 &`${eval:0xc^5} `& yields 9
11036 &`${eval:0xc>>1} `& yields 6
11037 &`${eval:0xc<<1} `& yields 24
11038 &`${eval:~255&0x1234} `& yields 4608
11039 &`${eval:-(~255&0x1234)} `& yields -4608
11042 As a more realistic example, in an ACL you might have
11046 {>{$rcpt_count}{10}} \
11049 {$recipients_count} \
11050 {${eval:$rcpt_count/2}} \
11053 message = Too many bad recipients
11055 The condition is true if there have been more than 10 RCPT commands and
11056 fewer than half of them have resulted in a valid recipient.
11059 .vitem &*${expand:*&<&'string'&>&*}*&
11060 .cindex "expansion" "re-expansion of substring"
11061 The &%expand%& operator causes a string to be expanded for a second time. For
11064 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11066 first looks up a string in a file while expanding the operand for &%expand%&,
11067 and then re-expands what it has found.
11070 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11072 .cindex "UTF-8" "conversion from"
11073 .cindex "expansion" "UTF-8 conversion"
11074 .cindex "&%from_utf8%& expansion item"
11075 The world is slowly moving towards Unicode, although there are no standards for
11076 email yet. However, other applications (including some databases) are starting
11077 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11078 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11079 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11080 the result is an undefined sequence of bytes.
11082 Unicode code points with values less than 256 are compatible with ASCII and
11083 ISO-8859-1 (also known as Latin-1).
11084 For example, character 169 is the copyright symbol in both cases, though the
11085 way it is encoded is different. In UTF-8, more than one byte is needed for
11086 characters with code values greater than 127, whereas ISO-8859-1 is a
11087 single-byte encoding (but thereby limited to 256 characters). This makes
11088 translation from UTF-8 to ISO-8859-1 straightforward.
11091 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11092 .cindex "hash function" "textual"
11093 .cindex "expansion" "textual hash"
11094 The &%hash%& operator is a simpler interface to the hashing function that can
11095 be used when the two parameters are fixed numbers (as opposed to strings that
11096 change when expanded). The effect is the same as
11098 ${hash{<n>}{<m>}{<string>}}
11100 See the description of the general &%hash%& item above for details. The
11101 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11105 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11106 .cindex "base64 encoding" "conversion from hex"
11107 .cindex "expansion" "hex to base64"
11108 .cindex "&%hex2b64%& expansion item"
11109 This operator converts a hex string into one that is base64 encoded. This can
11110 be useful for processing the output of the various hashing functions.
11114 .vitem &*${hexquote:*&<&'string'&>&*}*&
11115 .cindex "quoting" "hex-encoded unprintable characters"
11116 .cindex "&%hexquote%& expansion item"
11117 This operator converts non-printable characters in a string into a hex
11118 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11119 as is, and other byte values are converted to &`\xNN`&, for example, a
11120 byte value 127 is converted to &`\x7f`&.
11123 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11124 .cindex "&%ipv6denorm%& expansion item"
11125 .cindex "IP address" normalisation
11126 This expands an IPv6 address to a full eight-element colon-separated set
11127 of hex digits including leading zeroes.
11128 A trailing ipv4-style dotted-decimal set is converted to hex.
11129 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11131 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11132 .cindex "&%ipv6norm%& expansion item"
11133 .cindex "IP address" normalisation
11134 .cindex "IP address" "canonical form"
11135 This converts an IPv6 address to canonical form.
11136 Leading zeroes of groups are omitted, and the longest
11137 set of zero-valued groups is replaced with a double colon.
11138 A trailing ipv4-style dotted-decimal set is converted to hex.
11139 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11142 .vitem &*${lc:*&<&'string'&>&*}*&
11143 .cindex "case forcing in strings"
11144 .cindex "string" "case forcing"
11145 .cindex "lower casing"
11146 .cindex "expansion" "case forcing"
11147 .cindex "&%lc%& expansion item"
11148 This forces the letters in the string into lower-case, for example:
11152 Case is defined per the system C locale.
11154 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11155 .cindex "expansion" "string truncation"
11156 .cindex "&%length%& expansion item"
11157 The &%length%& operator is a simpler interface to the &%length%& function that
11158 can be used when the parameter is a fixed number (as opposed to a string that
11159 changes when expanded). The effect is the same as
11161 ${length{<number>}{<string>}}
11163 See the description of the general &%length%& item above for details. Note that
11164 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11165 when &%length%& is used as an operator.
11166 All measurement is done in bytes and is not UTF-8 aware.
11169 .vitem &*${listcount:*&<&'string'&>&*}*&
11170 .cindex "expansion" "list item count"
11171 .cindex "list" "item count"
11172 .cindex "list" "count of items"
11173 .cindex "&%listcount%& expansion item"
11174 The string is interpreted as a list and the number of items is returned.
11177 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11178 .cindex "expansion" "named list"
11179 .cindex "&%listnamed%& expansion item"
11180 The name is interpreted as a named list and the content of the list is returned,
11181 expanding any referenced lists, re-quoting as needed for colon-separation.
11182 If the optional type is given it must be one of "a", "d", "h" or "l"
11183 and selects address-, domain-, host- or localpart- lists to search among respectively.
11184 Otherwise all types are searched in an undefined order and the first
11185 matching list is returned.
11187 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11188 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11192 .vitem &*${local_part:*&<&'string'&>&*}*&
11193 .cindex "expansion" "local part extraction"
11194 .cindex "&%local_part%& expansion item"
11195 The string is interpreted as an RFC 2822 address and the local part is
11196 extracted from it. If the string does not parse successfully, the result is
11198 The parsing correctly handles SMTPUTF8 Unicode in the string.
11201 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11202 .cindex "masked IP address"
11203 .cindex "IP address" "masking"
11204 .cindex "CIDR notation"
11205 .cindex "expansion" "IP address masking"
11206 .cindex "&%mask%& expansion item"
11207 If the form of the string to be operated on is not an IP address followed by a
11208 slash and an integer (that is, a network address in CIDR notation), the
11209 expansion fails. Otherwise, this operator converts the IP address to binary,
11210 masks off the least significant bits according to the bit count, and converts
11211 the result back to text, with mask appended. For example,
11213 ${mask:10.111.131.206/28}
11215 returns the string &"10.111.131.192/28"&. Since this operation is expected to
11216 be mostly used for looking up masked addresses in files, the result for an IPv6
11217 address uses dots to separate components instead of colons, because colon
11218 terminates a key string in lsearch files. So, for example,
11220 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11224 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11226 Letters in IPv6 addresses are always output in lower case.
11229 .vitem &*${md5:*&<&'string'&>&*}*&
11231 .cindex "expansion" "MD5 hash"
11232 .cindex certificate fingerprint
11233 .cindex "&%md5%& expansion item"
11234 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11235 as a 32-digit hexadecimal number, in which any letters are in lower case.
11237 If the string is a single variable of type certificate,
11238 returns the MD5 hash fingerprint of the certificate.
11241 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11242 .cindex "expansion" "numeric hash"
11243 .cindex "hash function" "numeric"
11244 The &%nhash%& operator is a simpler interface to the numeric hashing function
11245 that can be used when the two parameters are fixed numbers (as opposed to
11246 strings that change when expanded). The effect is the same as
11248 ${nhash{<n>}{<m>}{<string>}}
11250 See the description of the general &%nhash%& item above for details.
11253 .vitem &*${quote:*&<&'string'&>&*}*&
11254 .cindex "quoting" "in string expansions"
11255 .cindex "expansion" "quoting"
11256 .cindex "&%quote%& expansion item"
11257 The &%quote%& operator puts its argument into double quotes if it
11258 is an empty string or
11259 contains anything other than letters, digits, underscores, dots, and hyphens.
11260 Any occurrences of double quotes and backslashes are escaped with a backslash.
11261 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11262 respectively For example,
11270 The place where this is useful is when the argument is a substitution from a
11271 variable or a message header.
11273 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11274 .cindex "&%quote_local_part%& expansion item"
11275 This operator is like &%quote%&, except that it quotes the string only if
11276 required to do so by the rules of RFC 2822 for quoting local parts. For
11277 example, a plus sign would not cause quoting (but it would for &%quote%&).
11278 If you are creating a new email address from the contents of &$local_part$&
11279 (or any other unknown data), you should always use this operator.
11281 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11282 will likely use the quoting form.
11283 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11286 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11287 .cindex "quoting" "lookup-specific"
11288 This operator applies lookup-specific quoting rules to the string. Each
11289 query-style lookup type has its own quoting rules which are described with
11290 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11292 ${quote_ldap:two * two}
11298 For single-key lookup types, no quoting is ever necessary and this operator
11299 yields an unchanged string.
11302 .vitem &*${randint:*&<&'n'&>&*}*&
11303 .cindex "random number"
11304 This operator returns a somewhat random number which is less than the
11305 supplied number and is at least 0. The quality of this randomness depends
11306 on how Exim was built; the values are not suitable for keying material.
11307 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11308 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11309 for versions of GnuTLS with that function.
11310 Otherwise, the implementation may be arc4random(), random() seeded by
11311 srandomdev() or srandom(), or a custom implementation even weaker than
11315 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11316 .cindex "expansion" "IP address"
11317 This operator reverses an IP address; for IPv4 addresses, the result is in
11318 dotted-quad decimal form, while for IPv6 addresses the result is in
11319 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11320 for DNS. For example,
11322 ${reverse_ip:192.0.2.4}
11323 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11328 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11332 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11333 .cindex "expansion" "RFC 2047"
11334 .cindex "RFC 2047" "expansion operator"
11335 .cindex "&%rfc2047%& expansion item"
11336 This operator encodes text according to the rules of RFC 2047. This is an
11337 encoding that is used in header lines to encode non-ASCII characters. It is
11338 assumed that the input string is in the encoding specified by the
11339 &%headers_charset%& option, which gets its default at build time. If the string
11340 contains only characters in the range 33&--126, and no instances of the
11343 ? = ( ) < > @ , ; : \ " . [ ] _
11345 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11346 string, using as many &"encoded words"& as necessary to encode all the
11350 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11351 .cindex "expansion" "RFC 2047"
11352 .cindex "RFC 2047" "decoding"
11353 .cindex "&%rfc2047d%& expansion item"
11354 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11355 bytes are replaced by question marks. Characters are converted into the
11356 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11357 not recognized unless &%check_rfc2047_length%& is set false.
11359 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11360 access a header line, RFC 2047 decoding is done automatically. You do not need
11361 to use this operator as well.
11365 .vitem &*${rxquote:*&<&'string'&>&*}*&
11366 .cindex "quoting" "in regular expressions"
11367 .cindex "regular expressions" "quoting"
11368 .cindex "&%rxquote%& expansion item"
11369 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11370 characters in its argument. This is useful when substituting the values of
11371 variables or headers inside regular expressions.
11374 .vitem &*${sha1:*&<&'string'&>&*}*&
11375 .cindex "SHA-1 hash"
11376 .cindex "expansion" "SHA-1 hashing"
11377 .cindex certificate fingerprint
11378 .cindex "&%sha1%& expansion item"
11379 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11380 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11382 If the string is a single variable of type certificate,
11383 returns the SHA-1 hash fingerprint of the certificate.
11386 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11387 &*${sha2:*&<&'string'&>&*}*& &&&
11388 &*${sha2_<n>:*&<&'string'&>&*}*&
11389 .cindex "SHA-256 hash"
11390 .cindex "SHA-2 hash"
11391 .cindex certificate fingerprint
11392 .cindex "expansion" "SHA-256 hashing"
11393 .cindex "&%sha256%& expansion item"
11394 .cindex "&%sha2%& expansion item"
11395 The &%sha256%& operator computes the SHA-256 hash value of the string
11397 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11399 If the string is a single variable of type certificate,
11400 returns the SHA-256 hash fingerprint of the certificate.
11402 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11403 (except for certificates, which are not supported).
11404 Finally, if an underbar
11405 and a number is appended it specifies the output length, selecting a
11406 member of the SHA-2 family of hash functions.
11407 Values of 256, 384 and 512 are accepted, with 256 being the default.
11410 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11411 &*${sha3_<n>:*&<&'string'&>&*}*&
11412 .cindex "SHA3 hash"
11413 .cindex "expansion" "SHA3 hashing"
11414 .cindex "&%sha3%& expansion item"
11415 The &%sha3%& operator computes the SHA3-256 hash value of the string
11417 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11419 If a number is appended, separated by an underbar, it specifies
11420 the output length. Values of 224, 256, 384 and 512 are accepted;
11421 with 256 being the default.
11423 The &%sha3%& expansion item is only supported if Exim has been
11424 compiled with GnuTLS 3.5.0 or later,
11425 or OpenSSL 1.1.1 or later.
11426 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11429 .vitem &*${stat:*&<&'string'&>&*}*&
11430 .cindex "expansion" "statting a file"
11431 .cindex "file" "extracting characteristics"
11432 .cindex "&%stat%& expansion item"
11433 The string, after expansion, must be a file path. A call to the &[stat()]&
11434 function is made for this path. If &[stat()]& fails, an error occurs and the
11435 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11436 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11437 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11438 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11439 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11440 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11441 can extract individual fields using the &%extract%& expansion item.
11443 The use of the &%stat%& expansion in users' filter files can be locked out by
11444 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11445 systems for files larger than 2GB.
11447 .vitem &*${str2b64:*&<&'string'&>&*}*&
11448 .cindex "&%str2b64%& expansion item"
11449 Now deprecated, a synonym for the &%base64%& expansion operator.
11453 .vitem &*${strlen:*&<&'string'&>&*}*&
11454 .cindex "expansion" "string length"
11455 .cindex "string" "length in expansion"
11456 .cindex "&%strlen%& expansion item"
11457 The item is replace by the length of the expanded string, expressed as a
11458 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11459 All measurement is done in bytes and is not UTF-8 aware.
11462 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11463 .cindex "&%substr%& expansion item"
11464 .cindex "substring extraction"
11465 .cindex "expansion" "substring expansion"
11466 The &%substr%& operator is a simpler interface to the &%substr%& function that
11467 can be used when the two parameters are fixed numbers (as opposed to strings
11468 that change when expanded). The effect is the same as
11470 ${substr{<start>}{<length>}{<string>}}
11472 See the description of the general &%substr%& item above for details. The
11473 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11474 All measurement is done in bytes and is not UTF-8 aware.
11476 .vitem &*${time_eval:*&<&'string'&>&*}*&
11477 .cindex "&%time_eval%& expansion item"
11478 .cindex "time interval" "decoding"
11479 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11482 .vitem &*${time_interval:*&<&'string'&>&*}*&
11483 .cindex "&%time_interval%& expansion item"
11484 .cindex "time interval" "formatting"
11485 The argument (after sub-expansion) must be a sequence of decimal digits that
11486 represents an interval of time as a number of seconds. It is converted into a
11487 number of larger units and output in Exim's normal time format, for example,
11490 .vitem &*${uc:*&<&'string'&>&*}*&
11491 .cindex "case forcing in strings"
11492 .cindex "string" "case forcing"
11493 .cindex "upper casing"
11494 .cindex "expansion" "case forcing"
11495 .cindex "&%uc%& expansion item"
11496 This forces the letters in the string into upper-case.
11497 Case is defined per the system C locale.
11499 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11500 .cindex "correction of invalid utf-8 sequences in strings"
11501 .cindex "utf-8" "utf-8 sequences"
11502 .cindex "incorrect utf-8"
11503 .cindex "expansion" "utf-8 forcing"
11504 .cindex "&%utf8clean%& expansion item"
11505 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11506 In versions of Exim before 4.92, this did not correctly do so for a truncated
11507 final codepoint's encoding, and the character would be silently dropped.
11508 If you must handle detection of this scenario across both sets of Exim behavior,
11509 the complexity will depend upon the task.
11510 For instance, to detect if the first character is multibyte and a 1-byte
11511 extraction can be successfully used as a path component (as is common for
11512 dividing up delivery folders), you might use:
11514 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11516 (which will false-positive if the first character of the local part is a
11517 literal question mark).
11519 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11520 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11521 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11522 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11523 .cindex expansion UTF-8
11524 .cindex UTF-8 expansion
11526 .cindex internationalisation
11527 .cindex "&%utf8_domain_to_alabel%& expansion item"
11528 .cindex "&%utf8_domain_from_alabel%& expansion item"
11529 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11530 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11531 These convert EAI mail name components between UTF-8 and a-label forms.
11532 For information on internationalisation support see &<<SECTi18nMTA>>&.
11540 .section "Expansion conditions" "SECTexpcond"
11541 .scindex IIDexpcond "expansion" "conditions"
11542 The following conditions are available for testing by the &%${if%& construct
11543 while expanding strings:
11546 .vitem &*!*&<&'condition'&>
11547 .cindex "expansion" "negating a condition"
11548 .cindex "negation" "in expansion condition"
11549 Preceding any condition with an exclamation mark negates the result of the
11552 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11553 .cindex "numeric comparison"
11554 .cindex "expansion" "numeric comparison"
11555 There are a number of symbolic operators for doing numeric comparisons. They
11561 &`>= `& greater or equal
11563 &`<= `& less or equal
11567 ${if >{$message_size}{10M} ...
11569 Note that the general negation operator provides for inequality testing. The
11570 two strings must take the form of optionally signed decimal integers,
11571 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11572 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11573 As a special case, the numerical value of an empty string is taken as
11576 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11577 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11578 10M, not if 10M is larger than &$message_size$&.
11581 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11582 {*&<&'arg2'&>&*}...}*&
11583 .cindex "expansion" "calling an acl"
11584 .cindex "&%acl%&" "expansion condition"
11585 The name and zero to nine argument strings are first expanded separately. The expanded
11586 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11587 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11588 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11589 and may use the variables; if another acl expansion is used the values
11590 are restored after it returns. If the ACL sets
11591 a value using a "message =" modifier the variable $value becomes
11592 the result of the expansion, otherwise it is empty.
11593 If the ACL returns accept the condition is true; if deny, false.
11594 If the ACL returns defer the result is a forced-fail.
11596 .vitem &*bool&~{*&<&'string'&>&*}*&
11597 .cindex "expansion" "boolean parsing"
11598 .cindex "&%bool%& expansion condition"
11599 This condition turns a string holding a true or false representation into
11600 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11601 (case-insensitively); also integer numbers map to true if non-zero,
11603 An empty string is treated as false.
11604 Leading and trailing whitespace is ignored;
11605 thus a string consisting only of whitespace is false.
11606 All other string values will result in expansion failure.
11608 When combined with ACL variables, this expansion condition will let you
11609 make decisions in one place and act on those decisions in another place.
11612 ${if bool{$acl_m_privileged_sender} ...
11616 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11617 .cindex "expansion" "boolean parsing"
11618 .cindex "&%bool_lax%& expansion condition"
11619 Like &%bool%&, this condition turns a string into a boolean state. But
11620 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11621 loose definition that the Router &%condition%& option uses. The empty string
11622 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11623 true. Leading and trailing whitespace is ignored.
11625 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11627 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11628 .cindex "expansion" "encrypted comparison"
11629 .cindex "encrypted strings, comparing"
11630 .cindex "&%crypteq%& expansion condition"
11631 This condition is included in the Exim binary if it is built to support any
11632 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11633 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11634 included in the binary.
11636 The &%crypteq%& condition has two arguments. The first is encrypted and
11637 compared against the second, which is already encrypted. The second string may
11638 be in the LDAP form for storing encrypted strings, which starts with the
11639 encryption type in curly brackets, followed by the data. If the second string
11640 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11641 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11642 Typically this will be a field from a password file. An example of an encrypted
11643 string in LDAP form is:
11645 {md5}CY9rzUYh03PK3k6DJie09g==
11647 If such a string appears directly in an expansion, the curly brackets have to
11648 be quoted, because they are part of the expansion syntax. For example:
11650 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11652 The following encryption types (whose names are matched case-independently) are
11657 .cindex "base64 encoding" "in encrypted password"
11658 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11659 printable characters to compare with the remainder of the second string. If the
11660 length of the comparison string is 24, Exim assumes that it is base64 encoded
11661 (as in the above example). If the length is 32, Exim assumes that it is a
11662 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11666 .cindex "SHA-1 hash"
11667 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11668 printable characters to compare with the remainder of the second string. If the
11669 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11670 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11671 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11674 .cindex "&[crypt()]&"
11675 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11676 only the first eight characters of the password. However, in modern operating
11677 systems this is no longer true, and in many cases the entire password is used,
11678 whatever its length.
11681 .cindex "&[crypt16()]&"
11682 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11683 use up to 16 characters of the password in some operating systems. Again, in
11684 modern operating systems, more characters may be used.
11686 Exim has its own version of &[crypt16()]&, which is just a double call to
11687 &[crypt()]&. For operating systems that have their own version, setting
11688 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11689 operating system version instead of its own. This option is set by default in
11690 the OS-dependent &_Makefile_& for those operating systems that are known to
11691 support &[crypt16()]&.
11693 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11694 it was not using the same algorithm as some operating systems' versions. It
11695 turns out that as well as &[crypt16()]& there is a function called
11696 &[bigcrypt()]& in some operating systems. This may or may not use the same
11697 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11699 However, since there is now a move away from the traditional &[crypt()]&
11700 functions towards using SHA1 and other algorithms, tidying up this area of
11701 Exim is seen as very low priority.
11703 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11704 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11705 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11706 default is &`{crypt}`&. Whatever the default, you can always use either
11707 function by specifying it explicitly in curly brackets.
11709 .vitem &*def:*&<&'variable&~name'&>
11710 .cindex "expansion" "checking for empty variable"
11711 .cindex "&%def%& expansion condition"
11712 The &%def%& condition must be followed by the name of one of the expansion
11713 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11714 variable does not contain the empty string. For example:
11716 ${if def:sender_ident {from $sender_ident}}
11718 Note that the variable name is given without a leading &%$%& character. If the
11719 variable does not exist, the expansion fails.
11721 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11722 &~&*def:h_*&<&'header&~name'&>&*:*&"
11723 .cindex "expansion" "checking header line existence"
11724 This condition is true if a message is being processed and the named header
11725 exists in the message. For example,
11727 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11729 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11730 the header name must be terminated by a colon if white space does not follow.
11732 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11733 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11734 .cindex "string" "comparison"
11735 .cindex "expansion" "string comparison"
11736 .cindex "&%eq%& expansion condition"
11737 .cindex "&%eqi%& expansion condition"
11738 The two substrings are first expanded. The condition is true if the two
11739 resulting strings are identical. For &%eq%& the comparison includes the case of
11740 letters, whereas for &%eqi%& the comparison is case-independent, where
11741 case is defined per the system C locale.
11743 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11744 .cindex "expansion" "file existence test"
11745 .cindex "file" "existence test"
11746 .cindex "&%exists%&, expansion condition"
11747 The substring is first expanded and then interpreted as an absolute path. The
11748 condition is true if the named file (or directory) exists. The existence test
11749 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11750 users' filter files may be locked out by the system administrator.
11753 &*Note:*& Testing a path using this condition is not a sufficient way of
11755 Consider using a dsearch lookup.
11758 .vitem &*first_delivery*&
11759 .cindex "delivery" "first"
11760 .cindex "first delivery"
11761 .cindex "expansion" "first delivery test"
11762 .cindex "&%first_delivery%& expansion condition"
11763 This condition, which has no data, is true during a message's first delivery
11764 attempt. It is false during any subsequent delivery attempts.
11767 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11768 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11769 .cindex "list" "iterative conditions"
11770 .cindex "expansion" "&*forall*& condition"
11771 .cindex "expansion" "&*forany*& condition"
11773 These conditions iterate over a list. The first argument is expanded to form
11774 the list. By default, the list separator is a colon, but it can be changed by
11775 the normal method (&<<SECTlistsepchange>>&).
11776 The second argument is interpreted as a condition that is to
11777 be applied to each item in the list in turn. During the interpretation of the
11778 condition, the current list item is placed in a variable called &$item$&.
11780 For &*forany*&, interpretation stops if the condition is true for any item, and
11781 the result of the whole condition is true. If the condition is false for all
11782 items in the list, the overall condition is false.
11784 For &*forall*&, interpretation stops if the condition is false for any item,
11785 and the result of the whole condition is false. If the condition is true for
11786 all items in the list, the overall condition is true.
11788 Note that negation of &*forany*& means that the condition must be false for all
11789 items for the overall condition to succeed, and negation of &*forall*& means
11790 that the condition must be false for at least one item. In this example, the
11791 list separator is changed to a comma:
11793 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11795 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11796 being processed, to enable these expansion items to be nested.
11798 To scan a named list, expand it with the &*listnamed*& operator.
11800 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11801 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11802 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11803 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11804 .cindex JSON "iterative conditions"
11805 .cindex JSON expansions
11806 .cindex expansion "&*forall_json*& condition"
11807 .cindex expansion "&*forany_json*& condition"
11808 .cindex expansion "&*forall_jsons*& condition"
11809 .cindex expansion "&*forany_jsons*& condition"
11810 As for the above, except that the first argument must, after expansion,
11812 The array separator is not changeable.
11813 For the &"jsons"& variants the elements are expected to be JSON strings
11814 and have their quotes removed before the evaluation of the condition.
11818 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11819 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11820 .cindex "string" "comparison"
11821 .cindex "expansion" "string comparison"
11822 .cindex "&%ge%& expansion condition"
11823 .cindex "&%gei%& expansion condition"
11824 The two substrings are first expanded. The condition is true if the first
11825 string is lexically greater than or equal to the second string. For &%ge%& the
11826 comparison includes the case of letters, whereas for &%gei%& the comparison is
11828 Case and collation order are defined per the system C locale.
11830 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11831 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11832 .cindex "string" "comparison"
11833 .cindex "expansion" "string comparison"
11834 .cindex "&%gt%& expansion condition"
11835 .cindex "&%gti%& expansion condition"
11836 The two substrings are first expanded. The condition is true if the first
11837 string is lexically greater than the second string. For &%gt%& the comparison
11838 includes the case of letters, whereas for &%gti%& the comparison is
11840 Case and collation order are defined per the system C locale.
11844 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11845 SRS decode. See SECT &<<SECTSRS>>& for details.
11849 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11850 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11851 .cindex "string" "comparison"
11852 .cindex "list" "iterative conditions"
11853 Both strings are expanded; the second string is treated as a list of simple
11854 strings; if the first string is a member of the second, then the condition
11856 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11858 These are simpler to use versions of the more powerful &*forany*& condition.
11859 Examples, and the &*forany*& equivalents:
11861 ${if inlist{needle}{foo:needle:bar}}
11862 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11863 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11864 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11867 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11868 &*isip4&~{*&<&'string'&>&*}*& &&&
11869 &*isip6&~{*&<&'string'&>&*}*&
11870 .cindex "IP address" "testing string format"
11871 .cindex "string" "testing for IP address"
11872 .cindex "&%isip%& expansion condition"
11873 .cindex "&%isip4%& expansion condition"
11874 .cindex "&%isip6%& expansion condition"
11875 The substring is first expanded, and then tested to see if it has the form of
11876 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11877 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11879 For an IPv4 address, the test is for four dot-separated components, each of
11880 which consists of from one to three digits. For an IPv6 address, up to eight
11881 colon-separated components are permitted, each containing from one to four
11882 hexadecimal digits. There may be fewer than eight components if an empty
11883 component (adjacent colons) is present. Only one empty component is permitted.
11885 &*Note*&: The checks used to be just on the form of the address; actual numerical
11886 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11888 This is no longer the case.
11890 The main use of these tests is to distinguish between IP addresses and
11891 host names, or between IPv4 and IPv6 addresses. For example, you could use
11893 ${if isip4{$sender_host_address}...
11895 to test which IP version an incoming SMTP connection is using.
11897 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11898 .cindex "LDAP" "use for authentication"
11899 .cindex "expansion" "LDAP authentication test"
11900 .cindex "&%ldapauth%& expansion condition"
11901 This condition supports user authentication using LDAP. See section
11902 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11903 queries. For this use, the query must contain a user name and password. The
11904 query itself is not used, and can be empty. The condition is true if the
11905 password is not empty, and the user name and password are accepted by the LDAP
11906 server. An empty password is rejected without calling LDAP because LDAP binds
11907 with an empty password are considered anonymous regardless of the username, and
11908 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11909 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11913 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11914 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11915 .cindex "string" "comparison"
11916 .cindex "expansion" "string comparison"
11917 .cindex "&%le%& expansion condition"
11918 .cindex "&%lei%& expansion condition"
11919 The two substrings are first expanded. The condition is true if the first
11920 string is lexically less than or equal to the second string. For &%le%& the
11921 comparison includes the case of letters, whereas for &%lei%& the comparison is
11923 Case and collation order are defined per the system C locale.
11925 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11926 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11927 .cindex "string" "comparison"
11928 .cindex "expansion" "string comparison"
11929 .cindex "&%lt%& expansion condition"
11930 .cindex "&%lti%& expansion condition"
11931 The two substrings are first expanded. The condition is true if the first
11932 string is lexically less than the second string. For &%lt%& the comparison
11933 includes the case of letters, whereas for &%lti%& the comparison is
11935 Case and collation order are defined per the system C locale.
11938 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11939 .cindex "expansion" "regular expression comparison"
11940 .cindex "regular expressions" "match in expanded string"
11941 .cindex "&%match%& expansion condition"
11942 The two substrings are first expanded. The second is then treated as a regular
11943 expression and applied to the first. Because of the pre-expansion, if the
11944 regular expression contains dollar, or backslash characters, they must be
11945 escaped. Care must also be taken if the regular expression contains braces
11946 (curly brackets). A closing brace must be escaped so that it is not taken as a
11947 premature termination of <&'string2'&>. The easiest approach is to use the
11948 &`\N`& feature to disable expansion of the regular expression.
11951 ${if match {$local_part}{\N^\d{3}\N} ...
11953 If the whole expansion string is in double quotes, further escaping of
11954 backslashes is also required.
11956 The condition is true if the regular expression match succeeds.
11957 The regular expression is not required to begin with a circumflex
11958 metacharacter, but if there is no circumflex, the expression is not anchored,
11959 and it may match anywhere in the subject, not just at the start. If you want
11960 the pattern to match at the end of the subject, you must include the &`$`&
11961 metacharacter at an appropriate point.
11962 All character handling is done in bytes and is not UTF-8 aware,
11963 but we might change this in a future Exim release.
11965 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11966 At the start of an &%if%& expansion the values of the numeric variable
11967 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11968 succeeds causes them to be reset to the substrings of that condition and they
11969 will have these values during the expansion of the success string. At the end
11970 of the &%if%& expansion, the previous values are restored. After testing a
11971 combination of conditions using &%or%&, the subsequent values of the numeric
11972 variables are those of the condition that succeeded.
11974 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11975 .cindex "&%match_address%& expansion condition"
11976 See &*match_local_part*&.
11978 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11979 .cindex "&%match_domain%& expansion condition"
11980 See &*match_local_part*&.
11982 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11983 .cindex "&%match_ip%& expansion condition"
11984 This condition matches an IP address to a list of IP address patterns. It must
11985 be followed by two argument strings. The first (after expansion) must be an IP
11986 address or an empty string. The second (not expanded) is a restricted host
11987 list that can match only an IP address, not a host name. For example:
11989 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11991 The specific types of host list item that are permitted in the list are:
11994 An IP address, optionally with a CIDR mask.
11996 A single asterisk, which matches any IP address.
11998 An empty item, which matches only if the IP address is empty. This could be
11999 useful for testing for a locally submitted message or one from specific hosts
12000 in a single test such as
12001 . ==== As this is a nested list, any displays it contains must be indented
12002 . ==== as otherwise they are too far to the left. This comment applies to
12003 . ==== the use of xmlto plus fop. There's no problem when formatting with
12004 . ==== sdop, with or without the extra indent.
12006 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
12008 where the first item in the list is the empty string.
12010 The item @[] matches any of the local host's interface addresses.
12012 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
12013 even if &`net-`& is not specified. There is never any attempt to turn the IP
12014 address into a host name. The most common type of linear search for
12015 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
12016 masks. For example:
12018 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
12020 It is of course possible to use other kinds of lookup, and in such a case, you
12021 do need to specify the &`net-`& prefix if you want to specify a specific
12022 address mask, for example:
12024 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
12026 However, unless you are combining a &%match_ip%& condition with others, it is
12027 just as easy to use the fact that a lookup is itself a condition, and write:
12029 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12033 Note that <&'string2'&> is not itself subject to string expansion, unless
12034 Exim was built with the EXPAND_LISTMATCH_RHS option.
12036 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12038 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12039 .cindex "domain list" "in expansion condition"
12040 .cindex "address list" "in expansion condition"
12041 .cindex "local part" "list, in expansion condition"
12042 .cindex "&%match_local_part%& expansion condition"
12043 This condition, together with &%match_address%& and &%match_domain%&, make it
12044 possible to test domain, address, and local part lists within expansions. Each
12045 condition requires two arguments: an item and a list to match. A trivial
12048 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12050 In each case, the second argument may contain any of the allowable items for a
12051 list of the appropriate type. Also, because the second argument
12052 is a standard form of list, it is possible to refer to a named list.
12053 Thus, you can use conditions like this:
12055 ${if match_domain{$domain}{+local_domains}{...
12057 .cindex "&`+caseful`&"
12058 For address lists, the matching starts off caselessly, but the &`+caseful`&
12059 item can be used, as in all address lists, to cause subsequent items to
12060 have their local parts matched casefully. Domains are always matched
12063 Note that <&'string2'&> is not itself subject to string expansion, unless
12064 Exim was built with the EXPAND_LISTMATCH_RHS option.
12066 &*Note*&: Host lists are &'not'& supported in this way. This is because
12067 hosts have two identities: a name and an IP address, and it is not clear
12068 how to specify cleanly how such a test would work. However, IP addresses can be
12069 matched using &%match_ip%&.
12071 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12072 .cindex "PAM authentication"
12073 .cindex "AUTH" "with PAM"
12074 .cindex "Solaris" "PAM support"
12075 .cindex "expansion" "PAM authentication test"
12076 .cindex "&%pam%& expansion condition"
12077 &'Pluggable Authentication Modules'&
12078 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12079 available in the latest releases of Solaris and in some GNU/Linux
12080 distributions. The Exim support, which is intended for use in conjunction with
12081 the SMTP AUTH command, is available only if Exim is compiled with
12085 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12086 in some releases of GNU/Linux &%-ldl%& is also needed.
12088 The argument string is first expanded, and the result must be a
12089 colon-separated list of strings. Leading and trailing white space is ignored.
12090 The PAM module is initialized with the service name &"exim"& and the user name
12091 taken from the first item in the colon-separated data string (<&'string1'&>).
12092 The remaining items in the data string are passed over in response to requests
12093 from the authentication function. In the simple case there will only be one
12094 request, for a password, so the data consists of just two strings.
12096 There can be problems if any of the strings are permitted to contain colon
12097 characters. In the usual way, these have to be doubled to avoid being taken as
12099 The &%listquote%& expansion item can be used for this.
12100 For example, the configuration
12101 of a LOGIN authenticator might contain this setting:
12103 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12105 In some operating systems, PAM authentication can be done only from a process
12106 running as root. Since Exim is running as the Exim user when receiving
12107 messages, this means that PAM cannot be used directly in those systems.
12108 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12111 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12112 .cindex "&'pwcheck'& daemon"
12114 .cindex "expansion" "&'pwcheck'& authentication test"
12115 .cindex "&%pwcheck%& expansion condition"
12116 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12117 This is one way of making it possible for passwords to be checked by a process
12118 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12119 deprecated. Its replacement is &'saslauthd'& (see below).
12121 The pwcheck support is not included in Exim by default. You need to specify
12122 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12123 building Exim. For example:
12125 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12127 You do not need to install the full Cyrus software suite in order to use
12128 the pwcheck daemon. You can compile and install just the daemon alone
12129 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12130 access to the &_/var/pwcheck_& directory.
12132 The &%pwcheck%& condition takes one argument, which must be the user name and
12133 password, separated by a colon. For example, in a LOGIN authenticator
12134 configuration, you might have this:
12136 server_condition = ${if pwcheck{$auth1:$auth2}}
12138 Again, for a PLAIN authenticator configuration, this would be:
12140 server_condition = ${if pwcheck{$auth2:$auth3}}
12142 .vitem &*queue_running*&
12143 .cindex "queue runner" "detecting when delivering from"
12144 .cindex "expansion" "queue runner test"
12145 .cindex "&%queue_running%& expansion condition"
12146 This condition, which has no data, is true during delivery attempts that are
12147 initiated by queue runner processes, and false otherwise.
12150 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12152 .cindex "expansion" "Radius authentication"
12153 .cindex "&%radius%& expansion condition"
12154 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12155 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12156 the Radius client configuration file in order to build Exim with Radius
12159 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12160 library, using the original API. If you are using release 0.4.0 or later of
12161 this library, you need to set
12163 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12165 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12166 &%libradius%& library that comes with FreeBSD. To do this, set
12168 RADIUS_LIB_TYPE=RADLIB
12170 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12171 You may also have to supply a suitable setting in EXTRALIBS so that the
12172 Radius library can be found when Exim is linked.
12174 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12175 Radius client library, which calls the Radius server. The condition is true if
12176 the authentication is successful. For example:
12178 server_condition = ${if radius{<arguments>}}
12182 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12183 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12184 .cindex "&'saslauthd'& daemon"
12186 .cindex "expansion" "&'saslauthd'& authentication test"
12187 .cindex "&%saslauthd%& expansion condition"
12188 This condition supports user authentication using the Cyrus &'saslauthd'&
12189 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12190 Using this daemon is one way of making it possible for passwords to be checked
12191 by a process that is not running as root.
12193 The saslauthd support is not included in Exim by default. You need to specify
12194 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12195 building Exim. For example:
12197 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12199 You do not need to install the full Cyrus software suite in order to use
12200 the saslauthd daemon. You can compile and install just the daemon alone
12201 from the Cyrus SASL library.
12203 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12204 two are mandatory. For example:
12206 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12208 The service and the realm are optional (which is why the arguments are enclosed
12209 in their own set of braces). For details of the meaning of the service and
12210 realm, and how to run the daemon, consult the Cyrus documentation.
12215 .section "Combining expansion conditions" "SECID84"
12216 .cindex "expansion" "combining conditions"
12217 Several conditions can be tested at once by combining them using the &%and%&
12218 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12219 conditions on their own, and precede their lists of sub-conditions. Each
12220 sub-condition must be enclosed in braces within the overall braces that contain
12221 the list. No repetition of &%if%& is used.
12225 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12226 .cindex "&""or""& expansion condition"
12227 .cindex "expansion" "&""or""& of conditions"
12228 The sub-conditions are evaluated from left to right. The condition is true if
12229 any one of the sub-conditions is true.
12232 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12234 When a true sub-condition is found, the following ones are parsed but not
12235 evaluated. If there are several &"match"& sub-conditions the values of the
12236 numeric variables afterwards are taken from the first one that succeeds.
12238 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12239 .cindex "&""and""& expansion condition"
12240 .cindex "expansion" "&""and""& of conditions"
12241 The sub-conditions are evaluated from left to right. The condition is true if
12242 all of the sub-conditions are true. If there are several &"match"&
12243 sub-conditions, the values of the numeric variables afterwards are taken from
12244 the last one. When a false sub-condition is found, the following ones are
12245 parsed but not evaluated.
12247 .ecindex IIDexpcond
12252 .section "Expansion variables" "SECTexpvar"
12253 .cindex "expansion" "variables, list of"
12254 This section contains an alphabetical list of all the expansion variables. Some
12255 of them are available only when Exim is compiled with specific options such as
12256 support for TLS or the content scanning extension.
12259 .vitem "&$0$&, &$1$&, etc"
12260 .cindex "numerical variables (&$1$& &$2$& etc)"
12261 When a &%match%& expansion condition succeeds, these variables contain the
12262 captured substrings identified by the regular expression during subsequent
12263 processing of the success string of the containing &%if%& expansion item.
12264 In the expansion condition case
12265 they do not retain their values afterwards; in fact, their previous
12266 values are restored at the end of processing an &%if%& item. The numerical
12267 variables may also be set externally by some other matching process which
12268 precedes the expansion of the string. For example, the commands available in
12269 Exim filter files include an &%if%& command with its own regular expression
12270 matching condition.
12272 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12273 Within an acl condition, expansion condition or expansion item
12274 any arguments are copied to these variables,
12275 any unused variables being made empty.
12277 .vitem "&$acl_c...$&"
12278 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12279 can be given any name that starts with &$acl_c$& and is at least six characters
12280 long, but the sixth character must be either a digit or an underscore. For
12281 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12282 variables persist throughout the lifetime of an SMTP connection. They can be
12283 used to pass information between ACLs and between different invocations of the
12284 same ACL. When a message is received, the values of these variables are saved
12285 with the message, and can be accessed by filters, routers, and transports
12286 during subsequent delivery.
12288 .vitem "&$acl_m...$&"
12289 These variables are like the &$acl_c...$& variables, except that their values
12290 are reset after a message has been received. Thus, if several messages are
12291 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12292 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12293 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12294 message is received, the values of these variables are saved with the message,
12295 and can be accessed by filters, routers, and transports during subsequent
12298 .vitem &$acl_narg$&
12299 Within an acl condition, expansion condition or expansion item
12300 this variable has the number of arguments.
12302 .vitem &$acl_verify_message$&
12303 .vindex "&$acl_verify_message$&"
12304 After an address verification has failed, this variable contains the failure
12305 message. It retains its value for use in subsequent modifiers. The message can
12306 be preserved by coding like this:
12308 warn !verify = sender
12309 set acl_m0 = $acl_verify_message
12311 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12312 &%log_message%& modifiers, to include information about the verification
12315 .vitem &$address_data$&
12316 .vindex "&$address_data$&"
12317 This variable is set by means of the &%address_data%& option in routers. The
12318 value then remains with the address while it is processed by subsequent routers
12319 and eventually a transport. If the transport is handling multiple addresses,
12320 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12321 for more details. &*Note*&: The contents of &$address_data$& are visible in
12324 If &$address_data$& is set when the routers are called from an ACL to verify
12325 a recipient address, the final value is still in the variable for subsequent
12326 conditions and modifiers of the ACL statement. If routing the address caused it
12327 to be redirected to just one address, the child address is also routed as part
12328 of the verification, and in this case the final value of &$address_data$& is
12329 from the child's routing.
12331 If &$address_data$& is set when the routers are called from an ACL to verify a
12332 sender address, the final value is also preserved, but this time in
12333 &$sender_address_data$&, to distinguish it from data from a recipient
12336 In both cases (recipient and sender verification), the value does not persist
12337 after the end of the current ACL statement. If you want to preserve
12338 these values for longer, you can save them in ACL variables.
12340 .vitem &$address_file$&
12341 .vindex "&$address_file$&"
12342 When, as a result of aliasing, forwarding, or filtering, a message is directed
12343 to a specific file, this variable holds the name of the file when the transport
12344 is running. At other times, the variable is empty. For example, using the
12345 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12347 /home/r2d2/savemail
12349 then when the &(address_file)& transport is running, &$address_file$&
12350 contains the text string &`/home/r2d2/savemail`&.
12351 .cindex "Sieve filter" "value of &$address_file$&"
12352 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12353 then up to the transport configuration to generate an appropriate absolute path
12354 to the relevant file.
12356 .vitem &$address_pipe$&
12357 .vindex "&$address_pipe$&"
12358 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12359 this variable holds the pipe command when the transport is running.
12361 .vitem "&$auth1$& &-- &$auth4$&"
12362 .vindex "&$auth1$&, &$auth2$&, etc"
12363 These variables are used in SMTP authenticators (see chapters
12364 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12366 .vitem &$authenticated_id$&
12367 .cindex "authentication" "id"
12368 .vindex "&$authenticated_id$&"
12369 When a server successfully authenticates a client it may be configured to
12370 preserve some of the authentication information in the variable
12371 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12372 user/password authenticator configuration might preserve the user name for use
12373 in the routers. Note that this is not the same information that is saved in
12374 &$sender_host_authenticated$&.
12376 When a message is submitted locally (that is, not over a TCP connection)
12377 the value of &$authenticated_id$& is normally the login name of the calling
12378 process. However, a trusted user can override this by means of the &%-oMai%&
12379 command line option.
12380 This second case also sets up information used by the
12381 &$authresults$& expansion item.
12383 .vitem &$authenticated_fail_id$&
12384 .cindex "authentication" "fail" "id"
12385 .vindex "&$authenticated_fail_id$&"
12386 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12387 will contain the failed authentication id. If more than one authentication
12388 id is attempted, it will contain only the last one. The variable is
12389 available for processing in the ACL's, generally the quit or notquit ACL.
12390 A message to a local recipient could still be accepted without requiring
12391 authentication, which means this variable could also be visible in all of
12395 .vitem &$authenticated_sender$&
12396 .cindex "sender" "authenticated"
12397 .cindex "authentication" "sender"
12398 .cindex "AUTH" "on MAIL command"
12399 .vindex "&$authenticated_sender$&"
12400 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12401 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12402 described in section &<<SECTauthparamail>>&. Unless the data is the string
12403 &"<>"&, it is set as the authenticated sender of the message, and the value is
12404 available during delivery in the &$authenticated_sender$& variable. If the
12405 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12407 .vindex "&$qualify_domain$&"
12408 When a message is submitted locally (that is, not over a TCP connection), the
12409 value of &$authenticated_sender$& is an address constructed from the login
12410 name of the calling process and &$qualify_domain$&, except that a trusted user
12411 can override this by means of the &%-oMas%& command line option.
12414 .vitem &$authentication_failed$&
12415 .cindex "authentication" "failure"
12416 .vindex "&$authentication_failed$&"
12417 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12418 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12419 possible to distinguish between &"did not try to authenticate"&
12420 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12421 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12422 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12423 negative response to an AUTH command, including (for example) an attempt to use
12424 an undefined mechanism.
12426 .vitem &$av_failed$&
12427 .cindex "content scanning" "AV scanner failure"
12428 This variable is available when Exim is compiled with the content-scanning
12429 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12430 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12431 the ACL malware condition.
12433 .vitem &$body_linecount$&
12434 .cindex "message body" "line count"
12435 .cindex "body of message" "line count"
12436 .vindex "&$body_linecount$&"
12437 When a message is being received or delivered, this variable contains the
12438 number of lines in the message's body. See also &$message_linecount$&.
12440 .vitem &$body_zerocount$&
12441 .cindex "message body" "binary zero count"
12442 .cindex "body of message" "binary zero count"
12443 .cindex "binary zero" "in message body"
12444 .vindex "&$body_zerocount$&"
12445 When a message is being received or delivered, this variable contains the
12446 number of binary zero bytes (ASCII NULs) in the message's body.
12448 .vitem &$bounce_recipient$&
12449 .vindex "&$bounce_recipient$&"
12450 This is set to the recipient address of a bounce message while Exim is creating
12451 it. It is useful if a customized bounce message text file is in use (see
12452 chapter &<<CHAPemsgcust>>&).
12454 .vitem &$bounce_return_size_limit$&
12455 .vindex "&$bounce_return_size_limit$&"
12456 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12457 up to a multiple of 1000. It is useful when a customized error message text
12458 file is in use (see chapter &<<CHAPemsgcust>>&).
12460 .vitem &$caller_gid$&
12461 .cindex "gid (group id)" "caller"
12462 .vindex "&$caller_gid$&"
12463 The real group id under which the process that called Exim was running. This is
12464 not the same as the group id of the originator of a message (see
12465 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12466 incarnation normally contains the Exim gid.
12468 .vitem &$caller_uid$&
12469 .cindex "uid (user id)" "caller"
12470 .vindex "&$caller_uid$&"
12471 The real user id under which the process that called Exim was running. This is
12472 not the same as the user id of the originator of a message (see
12473 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12474 incarnation normally contains the Exim uid.
12476 .vitem &$callout_address$&
12477 .vindex "&$callout_address$&"
12478 After a callout for verification, spamd or malware daemon service, the
12479 address that was connected to.
12481 .vitem &$compile_number$&
12482 .vindex "&$compile_number$&"
12483 The building process for Exim keeps a count of the number
12484 of times it has been compiled. This serves to distinguish different
12485 compilations of the same version of Exim.
12487 .vitem &$config_dir$&
12488 .vindex "&$config_dir$&"
12489 The directory name of the main configuration file. That is, the content of
12490 &$config_file$& with the last component stripped. The value does not
12491 contain the trailing slash. If &$config_file$& does not contain a slash,
12492 &$config_dir$& is ".".
12494 .vitem &$config_file$&
12495 .vindex "&$config_file$&"
12496 The name of the main configuration file Exim is using.
12498 .vitem &$dkim_verify_status$&
12499 Results of DKIM verification.
12500 For details see section &<<SECDKIMVFY>>&.
12502 .vitem &$dkim_cur_signer$& &&&
12503 &$dkim_verify_reason$& &&&
12504 &$dkim_domain$& &&&
12505 &$dkim_identity$& &&&
12506 &$dkim_selector$& &&&
12508 &$dkim_canon_body$& &&&
12509 &$dkim_canon_headers$& &&&
12510 &$dkim_copiedheaders$& &&&
12511 &$dkim_bodylength$& &&&
12512 &$dkim_created$& &&&
12513 &$dkim_expires$& &&&
12514 &$dkim_headernames$& &&&
12515 &$dkim_key_testing$& &&&
12516 &$dkim_key_nosubdomains$& &&&
12517 &$dkim_key_srvtype$& &&&
12518 &$dkim_key_granularity$& &&&
12519 &$dkim_key_notes$& &&&
12520 &$dkim_key_length$&
12521 These variables are only available within the DKIM ACL.
12522 For details see section &<<SECDKIMVFY>>&.
12524 .vitem &$dkim_signers$&
12525 .vindex &$dkim_signers$&
12526 When a message has been received this variable contains
12527 a colon-separated list of signer domains and identities for the message.
12528 For details see section &<<SECDKIMVFY>>&.
12530 .vitem &$dmarc_domain_policy$& &&&
12531 &$dmarc_status$& &&&
12532 &$dmarc_status_text$& &&&
12533 &$dmarc_used_domains$&
12534 Results of DMARC verification.
12535 For details see section &<<SECDMARC>>&.
12537 .vitem &$dnslist_domain$& &&&
12538 &$dnslist_matched$& &&&
12539 &$dnslist_text$& &&&
12541 .vindex "&$dnslist_domain$&"
12542 .vindex "&$dnslist_matched$&"
12543 .vindex "&$dnslist_text$&"
12544 .vindex "&$dnslist_value$&"
12545 .cindex "black list (DNS)"
12546 When a DNS (black) list lookup succeeds, these variables are set to contain
12547 the following data from the lookup: the list's domain name, the key that was
12548 looked up, the contents of any associated TXT record, and the value from the
12549 main A record. See section &<<SECID204>>& for more details.
12552 .vindex "&$domain$&"
12553 When an address is being routed, or delivered on its own, this variable
12554 contains the domain. Uppercase letters in the domain are converted into lower
12555 case for &$domain$&.
12557 Global address rewriting happens when a message is received, so the value of
12558 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12559 is set during user filtering, but not during system filtering, because a
12560 message may have many recipients and the system filter is called just once.
12562 When more than one address is being delivered at once (for example, several
12563 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12564 have the same domain. Transports can be restricted to handling only one domain
12565 at a time if the value of &$domain$& is required at transport time &-- this is
12566 the default for local transports. For further details of the environment in
12567 which local transports are run, see chapter &<<CHAPenvironment>>&.
12569 .oindex "&%delay_warning_condition%&"
12570 At the end of a delivery, if all deferred addresses have the same domain, it is
12571 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12573 The &$domain$& variable is also used in some other circumstances:
12576 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12577 the recipient address. The domain of the &'sender'& address is in
12578 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12579 normally set during the running of the MAIL ACL. However, if the sender address
12580 is verified with a callout during the MAIL ACL, the sender domain is placed in
12581 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12582 the &(smtp)& transport.
12585 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12586 &$domain$& contains the domain portion of the address that is being rewritten;
12587 it can be used in the expansion of the replacement address, for example, to
12588 rewrite domains by file lookup.
12591 With one important exception, whenever a domain list is being scanned,
12592 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12593 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12594 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12595 that, in a RCPT ACL, the sender domain list can be dependent on the
12596 recipient domain (which is what is in &$domain$& at this time).
12599 .cindex "ETRN" "value of &$domain$&"
12600 .oindex "&%smtp_etrn_command%&"
12601 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12602 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12605 .cindex "tainted data"
12606 If the origin of the data is an incoming message,
12607 the result of expanding this variable is tainted and may not
12608 be further expanded or used as a filename.
12609 When an untainted version is needed, one should be obtained from
12610 looking up the value in a local (therefore trusted) database.
12611 Often &$domain_data$& is usable in this role.
12614 .vitem &$domain_data$&
12615 .vindex "&$domain_data$&"
12616 When the &%domains%& condition on a router
12620 against a list, the match value is copied to &$domain_data$&.
12621 This is an enhancement over previous versions of Exim, when it only
12622 applied to the data read by a lookup.
12623 For details on match values see section &<<SECTlistresults>>& et. al.
12626 If the router routes the
12627 address to a transport, the value is available in that transport. If the
12628 transport is handling multiple addresses, the value from the first address is
12631 &$domain_data$& set in an ACL is available during
12632 the rest of the ACL statement.
12634 .vitem &$exim_gid$&
12635 .vindex "&$exim_gid$&"
12636 This variable contains the numerical value of the Exim group id.
12638 .vitem &$exim_path$&
12639 .vindex "&$exim_path$&"
12640 This variable contains the path to the Exim binary.
12642 .vitem &$exim_uid$&
12643 .vindex "&$exim_uid$&"
12644 This variable contains the numerical value of the Exim user id.
12646 .vitem &$exim_version$&
12647 .vindex "&$exim_version$&"
12648 This variable contains the version string of the Exim build.
12649 The first character is a major version number, currently 4.
12650 Then after a dot, the next group of digits is a minor version number.
12651 There may be other characters following the minor version.
12652 This value may be overridden by the &%exim_version%& main config option.
12654 .vitem &$header_$&<&'name'&>
12655 This is not strictly an expansion variable. It is expansion syntax for
12656 inserting the message header line with the given name. Note that the name must
12657 be terminated by colon or white space, because it may contain a wide variety of
12658 characters. Note also that braces must &'not'& be used.
12659 See the full description in section &<<SECTexpansionitems>>& above.
12661 .vitem &$headers_added$&
12662 .vindex "&$headers_added$&"
12663 Within an ACL this variable contains the headers added so far by
12664 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12665 The headers are a newline-separated list.
12669 When the &%check_local_user%& option is set for a router, the user's home
12670 directory is placed in &$home$& when the check succeeds. In particular, this
12671 means it is set during the running of users' filter files. A router may also
12672 explicitly set a home directory for use by a transport; this can be overridden
12673 by a setting on the transport itself.
12675 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12676 of the environment variable HOME, which is subject to the
12677 &%keep_environment%& and &%add_environment%& main config options.
12681 If a router assigns an address to a transport (any transport), and passes a
12682 list of hosts with the address, the value of &$host$& when the transport starts
12683 to run is the name of the first host on the list. Note that this applies both
12684 to local and remote transports.
12686 .cindex "transport" "filter"
12687 .cindex "filter" "transport filter"
12688 For the &(smtp)& transport, if there is more than one host, the value of
12689 &$host$& changes as the transport works its way through the list. In
12690 particular, when the &(smtp)& transport is expanding its options for encryption
12691 using TLS, or for specifying a transport filter (see chapter
12692 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12695 When used in the client part of an authenticator configuration (see chapter
12696 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12697 client is connected.
12700 .vitem &$host_address$&
12701 .vindex "&$host_address$&"
12702 This variable is set to the remote host's IP address whenever &$host$& is set
12703 for a remote connection. It is also set to the IP address that is being checked
12704 when the &%ignore_target_hosts%& option is being processed.
12706 .vitem &$host_data$&
12707 .vindex "&$host_data$&"
12708 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12709 result of the lookup is made available in the &$host_data$& variable. This
12710 allows you, for example, to do things like this:
12712 deny hosts = net-lsearch;/some/file
12713 message = $host_data
12715 .vitem &$host_lookup_deferred$&
12716 .cindex "host name" "lookup, failure of"
12717 .vindex "&$host_lookup_deferred$&"
12718 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12719 message comes from a remote host and there is an attempt to look up the host's
12720 name from its IP address, and the attempt is not successful, one of these
12721 variables is set to &"1"&.
12724 If the lookup receives a definite negative response (for example, a DNS lookup
12725 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12728 If there is any kind of problem during the lookup, such that Exim cannot
12729 tell whether or not the host name is defined (for example, a timeout for a DNS
12730 lookup), &$host_lookup_deferred$& is set to &"1"&.
12733 Looking up a host's name from its IP address consists of more than just a
12734 single reverse lookup. Exim checks that a forward lookup of at least one of the
12735 names it receives from a reverse lookup yields the original IP address. If this
12736 is not the case, Exim does not accept the looked up name(s), and
12737 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12738 IP address (for example, the existence of a PTR record in the DNS) is not
12739 sufficient on its own for the success of a host name lookup. If the reverse
12740 lookup succeeds, but there is a lookup problem such as a timeout when checking
12741 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12742 &"1"&. See also &$sender_host_name$&.
12744 .cindex authentication "expansion item"
12745 Performing these checks sets up information used by the
12746 &%authresults%& expansion item.
12749 .vitem &$host_lookup_failed$&
12750 .vindex "&$host_lookup_failed$&"
12751 See &$host_lookup_deferred$&.
12753 .vitem &$host_port$&
12754 .vindex "&$host_port$&"
12755 This variable is set to the remote host's TCP port whenever &$host$& is set
12756 for an outbound connection.
12758 .vitem &$initial_cwd$&
12759 .vindex "&$initial_cwd$&
12760 This variable contains the full path name of the initial working
12761 directory of the current Exim process. This may differ from the current
12762 working directory, as Exim changes this to "/" during early startup, and
12763 to &$spool_directory$& later.
12766 .vindex "&$inode$&"
12767 The only time this variable is set is while expanding the &%directory_file%&
12768 option in the &(appendfile)& transport. The variable contains the inode number
12769 of the temporary file which is about to be renamed. It can be used to construct
12770 a unique name for the file.
12772 .vitem &$interface_address$&
12773 .vindex "&$interface_address$&"
12774 This is an obsolete name for &$received_ip_address$&.
12776 .vitem &$interface_port$&
12777 .vindex "&$interface_port$&"
12778 This is an obsolete name for &$received_port$&.
12782 This variable is used during the expansion of &*forall*& and &*forany*&
12783 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12784 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12788 .vindex "&$ldap_dn$&"
12789 This variable, which is available only when Exim is compiled with LDAP support,
12790 contains the DN from the last entry in the most recently successful LDAP
12793 .vitem &$load_average$&
12794 .vindex "&$load_average$&"
12795 This variable contains the system load average, multiplied by 1000 so that it
12796 is an integer. For example, if the load average is 0.21, the value of the
12797 variable is 210. The value is recomputed every time the variable is referenced.
12799 .vitem &$local_part$&
12800 .vindex "&$local_part$&"
12801 When an address is being routed, or delivered on its own, this
12802 variable contains the local part. When a number of addresses are being
12803 delivered together (for example, multiple RCPT commands in an SMTP
12804 session), &$local_part$& is not set.
12806 Global address rewriting happens when a message is received, so the value of
12807 &$local_part$& during routing and delivery is the value after rewriting.
12808 &$local_part$& is set during user filtering, but not during system filtering,
12809 because a message may have many recipients and the system filter is called just
12812 .cindex "tainted data"
12813 If the origin of the data is an incoming message,
12814 the result of expanding this variable is tainted and
12815 may not be further expanded or used as a filename.
12817 &*Warning*&: the content of this variable is usually provided by a potential
12819 Consider carefully the implications of using it unvalidated as a name
12821 This presents issues for users' &_.forward_& and filter files.
12822 For traditional full user accounts, use &%check_local_users%& and the
12823 &$local_part_data$& variable rather than this one.
12824 For virtual users, store a suitable pathname component in the database
12825 which is used for account name validation, and use that retrieved value
12826 rather than this variable.
12827 Often &$local_part_data$& is usable in this role.
12828 If needed, use a router &%address_data%& or &%set%& option for
12829 the retrieved data.
12831 When a message is being delivered to a file, pipe, or autoreply transport as a
12832 result of aliasing or forwarding, &$local_part$& is set to the local part of
12833 the parent address, not to the filename or command (see &$address_file$& and
12836 When an ACL is running for a RCPT command, &$local_part$& contains the
12837 local part of the recipient address.
12839 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12840 &$local_part$& contains the local part of the address that is being rewritten;
12841 it can be used in the expansion of the replacement address, for example.
12843 In all cases, all quoting is removed from the local part. For example, for both
12846 "abc:xyz"@test.example
12847 abc\:xyz@test.example
12849 the value of &$local_part$& is
12853 If you use &$local_part$& to create another address, you should always wrap it
12854 inside a quoting operator. For example, in a &(redirect)& router you could
12857 data = ${quote_local_part:$local_part}@new.domain.example
12859 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12860 to process local parts in a case-dependent manner in a router, you can set the
12861 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12863 .vitem &$local_part_data$&
12864 .vindex "&$local_part_data$&"
12865 When the &%local_parts%& condition on a router or ACL
12866 matches a local part list
12868 the match value is copied to &$local_part_data$&.
12869 This is an enhancement over previous versions of Exim, when it only
12870 applied to the data read by a lookup.
12871 For details on match values see section &<<SECTlistresults>>& et. al.
12874 The &%check_local_user%& router option also sets this variable.
12876 .vindex &$local_part_prefix$& &&&
12877 &$local_part_prefix_v$& &&&
12878 &$local_part_suffix$& &&&
12879 &$local_part_suffix_v$&
12880 .cindex affix variables
12881 If a local part prefix or suffix has been recognized, it is not included in the
12882 value of &$local_part$& during routing and subsequent delivery. The values of
12883 any prefix or suffix are in &$local_part_prefix$& and
12884 &$local_part_suffix$&, respectively.
12885 .cindex "tainted data"
12886 If the specification did not include a wildcard then
12887 the affix variable value is not tainted.
12889 If the affix specification included a wildcard then the portion of
12890 the affix matched by the wildcard is in
12891 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12892 and both the whole and varying values are tainted.
12894 .vitem &$local_scan_data$&
12895 .vindex "&$local_scan_data$&"
12896 This variable contains the text returned by the &[local_scan()]& function when
12897 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12899 .vitem &$local_user_gid$&
12900 .vindex "&$local_user_gid$&"
12901 See &$local_user_uid$&.
12903 .vitem &$local_user_uid$&
12904 .vindex "&$local_user_uid$&"
12905 This variable and &$local_user_gid$& are set to the uid and gid after the
12906 &%check_local_user%& router precondition succeeds. This means that their values
12907 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12908 and &%condition%&), for the &%address_data%& expansion, and for any
12909 router-specific expansions. At all other times, the values in these variables
12910 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12912 .vitem &$localhost_number$&
12913 .vindex "&$localhost_number$&"
12914 This contains the expanded value of the
12915 &%localhost_number%& option. The expansion happens after the main options have
12918 .vitem &$log_inodes$&
12919 .vindex "&$log_inodes$&"
12920 The number of free inodes in the disk partition where Exim's
12921 log files are being written. The value is recalculated whenever the variable is
12922 referenced. If the relevant file system does not have the concept of inodes,
12923 the value of is -1. See also the &%check_log_inodes%& option.
12925 .vitem &$log_space$&
12926 .vindex "&$log_space$&"
12927 The amount of free space (as a number of kilobytes) in the disk
12928 partition where Exim's log files are being written. The value is recalculated
12929 whenever the variable is referenced. If the operating system does not have the
12930 ability to find the amount of free space (only true for experimental systems),
12931 the space value is -1. See also the &%check_log_space%& option.
12934 .vitem &$lookup_dnssec_authenticated$&
12935 .vindex "&$lookup_dnssec_authenticated$&"
12936 This variable is set after a DNS lookup done by
12937 a dnsdb lookup expansion, dnslookup router or smtp transport.
12938 .cindex "DNS" "DNSSEC"
12939 It will be empty if &(DNSSEC)& was not requested,
12940 &"no"& if the result was not labelled as authenticated data
12941 and &"yes"& if it was.
12942 Results that are labelled as authoritative answer that match
12943 the &%dns_trust_aa%& configuration variable count also
12944 as authenticated data.
12946 .vitem &$mailstore_basename$&
12947 .vindex "&$mailstore_basename$&"
12948 This variable is set only when doing deliveries in &"mailstore"& format in the
12949 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12950 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12951 contains the basename of the files that are being written, that is, the name
12952 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12955 .vitem &$malware_name$&
12956 .vindex "&$malware_name$&"
12957 This variable is available when Exim is compiled with the
12958 content-scanning extension. It is set to the name of the virus that was found
12959 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12961 .vitem &$max_received_linelength$&
12962 .vindex "&$max_received_linelength$&"
12963 .cindex "maximum" "line length"
12964 .cindex "line length" "maximum"
12965 This variable contains the number of bytes in the longest line that was
12966 received as part of the message, not counting the line termination
12968 It is not valid if the &%spool_files_wireformat%& option is used.
12970 .vitem &$message_age$&
12971 .cindex "message" "age of"
12972 .vindex "&$message_age$&"
12973 This variable is set at the start of a delivery attempt to contain the number
12974 of seconds since the message was received. It does not change during a single
12977 .vitem &$message_body$&
12978 .cindex "body of message" "expansion variable"
12979 .cindex "message body" "in expansion"
12980 .cindex "binary zero" "in message body"
12981 .vindex "&$message_body$&"
12982 .oindex "&%message_body_visible%&"
12983 This variable contains the initial portion of a message's body while it is
12984 being delivered, and is intended mainly for use in filter files. The maximum
12985 number of characters of the body that are put into the variable is set by the
12986 &%message_body_visible%& configuration option; the default is 500.
12988 .oindex "&%message_body_newlines%&"
12989 By default, newlines are converted into spaces in &$message_body$&, to make it
12990 easier to search for phrases that might be split over a line break. However,
12991 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12992 zeros are always converted into spaces.
12994 .vitem &$message_body_end$&
12995 .cindex "body of message" "expansion variable"
12996 .cindex "message body" "in expansion"
12997 .vindex "&$message_body_end$&"
12998 This variable contains the final portion of a message's
12999 body while it is being delivered. The format and maximum size are as for
13002 .vitem &$message_body_size$&
13003 .cindex "body of message" "size"
13004 .cindex "message body" "size"
13005 .vindex "&$message_body_size$&"
13006 When a message is being delivered, this variable contains the size of the body
13007 in bytes. The count starts from the character after the blank line that
13008 separates the body from the header. Newlines are included in the count. See
13009 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
13011 If the spool file is wireformat
13012 (see the &%spool_files_wireformat%& main option)
13013 the CRLF line-terminators are included in the count.
13015 .vitem &$message_exim_id$&
13016 .vindex "&$message_exim_id$&"
13017 When a message is being received or delivered, this variable contains the
13018 unique message id that is generated and used by Exim to identify the message.
13019 An id is not created for a message until after its header has been successfully
13020 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13021 line; it is the local id that Exim assigns to the message, for example:
13022 &`1BXTIK-0001yO-VA`&.
13024 .vitem &$message_headers$&
13025 .vindex &$message_headers$&
13026 This variable contains a concatenation of all the header lines when a message
13027 is being processed, except for lines added by routers or transports. The header
13028 lines are separated by newline characters. Their contents are decoded in the
13029 same way as a header line that is inserted by &%bheader%&.
13031 .vitem &$message_headers_raw$&
13032 .vindex &$message_headers_raw$&
13033 This variable is like &$message_headers$& except that no processing of the
13034 contents of header lines is done.
13036 .vitem &$message_id$&
13037 This is an old name for &$message_exim_id$&. It is now deprecated.
13039 .vitem &$message_linecount$&
13040 .vindex "&$message_linecount$&"
13041 This variable contains the total number of lines in the header and body of the
13042 message. Compare &$body_linecount$&, which is the count for the body only.
13043 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13044 number of lines received. Before delivery happens (that is, before filters,
13045 routers, and transports run) the count is increased to include the
13046 &'Received:'& header line that Exim standardly adds, and also any other header
13047 lines that are added by ACLs. The blank line that separates the message header
13048 from the body is not counted.
13050 As with the special case of &$message_size$&, during the expansion of the
13051 appendfile transport's maildir_tag option in maildir format, the value of
13052 &$message_linecount$& is the precise size of the number of newlines in the
13053 file that has been written (minus one for the blank line between the
13054 header and the body).
13056 Here is an example of the use of this variable in a DATA ACL:
13059 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13060 message = Too many lines in message header
13062 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13063 message has not yet been received.
13065 This variable is not valid if the &%spool_files_wireformat%& option is used.
13067 .vitem &$message_size$&
13068 .cindex "size" "of message"
13069 .cindex "message" "size"
13070 .vindex "&$message_size$&"
13071 When a message is being processed, this variable contains its size in bytes. In
13072 most cases, the size includes those headers that were received with the
13073 message, but not those (such as &'Envelope-to:'&) that are added to individual
13074 deliveries as they are written. However, there is one special case: during the
13075 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13076 doing a delivery in maildir format, the value of &$message_size$& is the
13077 precise size of the file that has been written. See also
13078 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13080 .cindex "RCPT" "value of &$message_size$&"
13081 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13082 contains the size supplied on the MAIL command, or -1 if no size was given. The
13083 value may not, of course, be truthful.
13085 .vitem &$mime_$&&'xxx'&
13086 A number of variables whose names start with &$mime$& are
13087 available when Exim is compiled with the content-scanning extension. For
13088 details, see section &<<SECTscanmimepart>>&.
13090 .vitem "&$n0$& &-- &$n9$&"
13091 These variables are counters that can be incremented by means
13092 of the &%add%& command in filter files.
13094 .vitem &$original_domain$&
13095 .vindex "&$domain$&"
13096 .vindex "&$original_domain$&"
13097 When a top-level address is being processed for delivery, this contains the
13098 same value as &$domain$&. However, if a &"child"& address (for example,
13099 generated by an alias, forward, or filter file) is being processed, this
13100 variable contains the domain of the original address (lower cased). This
13101 differs from &$parent_domain$& only when there is more than one level of
13102 aliasing or forwarding. When more than one address is being delivered in a
13103 single transport run, &$original_domain$& is not set.
13105 If a new address is created by means of a &%deliver%& command in a system
13106 filter, it is set up with an artificial &"parent"& address. This has the local
13107 part &'system-filter'& and the default qualify domain.
13109 .vitem &$original_local_part$&
13110 .vindex "&$local_part$&"
13111 .vindex "&$original_local_part$&"
13112 When a top-level address is being processed for delivery, this contains the
13113 same value as &$local_part$&, unless a prefix or suffix was removed from the
13114 local part, because &$original_local_part$& always contains the full local
13115 part. When a &"child"& address (for example, generated by an alias, forward, or
13116 filter file) is being processed, this variable contains the full local part of
13117 the original address.
13119 If the router that did the redirection processed the local part
13120 case-insensitively, the value in &$original_local_part$& is in lower case.
13121 This variable differs from &$parent_local_part$& only when there is more than
13122 one level of aliasing or forwarding. When more than one address is being
13123 delivered in a single transport run, &$original_local_part$& is not set.
13125 If a new address is created by means of a &%deliver%& command in a system
13126 filter, it is set up with an artificial &"parent"& address. This has the local
13127 part &'system-filter'& and the default qualify domain.
13129 .vitem &$originator_gid$&
13130 .cindex "gid (group id)" "of originating user"
13131 .cindex "sender" "gid"
13132 .vindex "&$caller_gid$&"
13133 .vindex "&$originator_gid$&"
13134 This variable contains the value of &$caller_gid$& that was set when the
13135 message was received. For messages received via the command line, this is the
13136 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13137 normally the gid of the Exim user.
13139 .vitem &$originator_uid$&
13140 .cindex "uid (user id)" "of originating user"
13141 .cindex "sender" "uid"
13142 .vindex "&$caller_uid$&"
13143 .vindex "&$originator_uid$&"
13144 The value of &$caller_uid$& that was set when the message was received. For
13145 messages received via the command line, this is the uid of the sending user.
13146 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13149 .vitem &$parent_domain$&
13150 .vindex "&$parent_domain$&"
13151 This variable is similar to &$original_domain$& (see
13152 above), except that it refers to the immediately preceding parent address.
13154 .vitem &$parent_local_part$&
13155 .vindex "&$parent_local_part$&"
13156 This variable is similar to &$original_local_part$&
13157 (see above), except that it refers to the immediately preceding parent address.
13160 .cindex "pid (process id)" "of current process"
13162 This variable contains the current process id.
13164 .vitem &$pipe_addresses$&
13165 .cindex "filter" "transport filter"
13166 .cindex "transport" "filter"
13167 .vindex "&$pipe_addresses$&"
13168 This is not an expansion variable, but is mentioned here because the string
13169 &`$pipe_addresses`& is handled specially in the command specification for the
13170 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13171 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13172 It cannot be used in general expansion strings, and provokes an &"unknown
13173 variable"& error if encountered.
13175 .vitem &$primary_hostname$&
13176 .vindex "&$primary_hostname$&"
13177 This variable contains the value set by &%primary_hostname%& in the
13178 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13179 a single-component name, Exim calls &[gethostbyname()]& (or
13180 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13181 qualified host name. See also &$smtp_active_hostname$&.
13184 .vitem &$proxy_external_address$& &&&
13185 &$proxy_external_port$& &&&
13186 &$proxy_local_address$& &&&
13187 &$proxy_local_port$& &&&
13189 These variables are only available when built with Proxy Protocol
13191 For details see chapter &<<SECTproxyInbound>>&.
13193 .vitem &$prdr_requested$&
13194 .cindex "PRDR" "variable for"
13195 This variable is set to &"yes"& if PRDR was requested by the client for the
13196 current message, otherwise &"no"&.
13198 .vitem &$prvscheck_address$&
13199 This variable is used in conjunction with the &%prvscheck%& expansion item,
13200 which is described in sections &<<SECTexpansionitems>>& and
13201 &<<SECTverifyPRVS>>&.
13203 .vitem &$prvscheck_keynum$&
13204 This variable is used in conjunction with the &%prvscheck%& expansion item,
13205 which is described in sections &<<SECTexpansionitems>>& and
13206 &<<SECTverifyPRVS>>&.
13208 .vitem &$prvscheck_result$&
13209 This variable is used in conjunction with the &%prvscheck%& expansion item,
13210 which is described in sections &<<SECTexpansionitems>>& and
13211 &<<SECTverifyPRVS>>&.
13213 .vitem &$qualify_domain$&
13214 .vindex "&$qualify_domain$&"
13215 The value set for the &%qualify_domain%& option in the configuration file.
13217 .vitem &$qualify_recipient$&
13218 .vindex "&$qualify_recipient$&"
13219 The value set for the &%qualify_recipient%& option in the configuration file,
13220 or if not set, the value of &$qualify_domain$&.
13222 .vitem &$queue_name$&
13223 .vindex &$queue_name$&
13224 .cindex "named queues" variable
13225 .cindex queues named
13226 The name of the spool queue in use; empty for the default queue.
13228 .vitem &$queue_size$&
13229 .vindex "&$queue_size$&"
13230 .cindex "queue" "size of"
13231 .cindex "spool" "number of messages"
13232 This variable contains the number of messages queued.
13233 It is evaluated on demand, but no more often than once every minute.
13234 If there is no daemon notifier socket open, the value will be
13239 .cindex router variables
13240 Values can be placed in these variables by the &%set%& option of a router.
13241 They can be given any name that starts with &$r_$&.
13242 The values persist for the address being handled through subsequent routers
13243 and the eventual transport.
13245 .vitem &$rcpt_count$&
13246 .vindex "&$rcpt_count$&"
13247 When a message is being received by SMTP, this variable contains the number of
13248 RCPT commands received for the current message. If this variable is used in a
13249 RCPT ACL, its value includes the current command.
13251 .vitem &$rcpt_defer_count$&
13252 .vindex "&$rcpt_defer_count$&"
13253 .cindex "4&'xx'& responses" "count of"
13254 When a message is being received by SMTP, this variable contains the number of
13255 RCPT commands in the current message that have previously been rejected with a
13256 temporary (4&'xx'&) response.
13258 .vitem &$rcpt_fail_count$&
13259 .vindex "&$rcpt_fail_count$&"
13260 When a message is being received by SMTP, this variable contains the number of
13261 RCPT commands in the current message that have previously been rejected with a
13262 permanent (5&'xx'&) response.
13264 .vitem &$received_count$&
13265 .vindex "&$received_count$&"
13266 This variable contains the number of &'Received:'& header lines in the message,
13267 including the one added by Exim (so its value is always greater than zero). It
13268 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13271 .vitem &$received_for$&
13272 .vindex "&$received_for$&"
13273 If there is only a single recipient address in an incoming message, this
13274 variable contains that address when the &'Received:'& header line is being
13275 built. The value is copied after recipient rewriting has happened, but before
13276 the &[local_scan()]& function is run.
13278 .vitem &$received_ip_address$&
13279 .vindex "&$received_ip_address$&"
13280 As soon as an Exim server starts processing an incoming TCP/IP connection, this
13281 variable is set to the address of the local IP interface, and &$received_port$&
13282 is set to the local port number. (The remote IP address and port are in
13283 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13284 the port value is -1 unless it has been set using the &%-oMi%& command line
13287 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13288 could be used, for example, to make the filename for a TLS certificate depend
13289 on which interface and/or port is being used for the incoming connection. The
13290 values of &$received_ip_address$& and &$received_port$& are saved with any
13291 messages that are received, thus making these variables available at delivery
13293 For outbound connections see &$sending_ip_address$&.
13295 .vitem &$received_port$&
13296 .vindex "&$received_port$&"
13297 See &$received_ip_address$&.
13299 .vitem &$received_protocol$&
13300 .vindex "&$received_protocol$&"
13301 When a message is being processed, this variable contains the name of the
13302 protocol by which it was received. Most of the names used by Exim are defined
13303 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13304 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13305 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13306 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13307 connection and the client was successfully authenticated.
13309 Exim uses the protocol name &"smtps"& for the case when encryption is
13310 automatically set up on connection without the use of STARTTLS (see
13311 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13312 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13313 where the client initially uses EHLO, sets up an encrypted connection using
13314 STARTTLS, and then uses HELO afterwards.
13316 The &%-oMr%& option provides a way of specifying a custom protocol name for
13317 messages that are injected locally by trusted callers. This is commonly used to
13318 identify messages that are being re-injected after some kind of scanning.
13320 .vitem &$received_time$&
13321 .vindex "&$received_time$&"
13322 This variable contains the date and time when the current message was received,
13323 as a number of seconds since the start of the Unix epoch.
13325 .vitem &$recipient_data$&
13326 .vindex "&$recipient_data$&"
13327 This variable is set after an indexing lookup success in an ACL &%recipients%&
13328 condition. It contains the data from the lookup, and the value remains set
13329 until the next &%recipients%& test. Thus, you can do things like this:
13331 &`require recipients = cdb*@;/some/file`&
13332 &`deny `&&'some further test involving'& &`$recipient_data`&
13334 &*Warning*&: This variable is set only when a lookup is used as an indexing
13335 method in the address list, using the semicolon syntax as in the example above.
13336 The variable is not set for a lookup that is used as part of the string
13337 expansion that all such lists undergo before being interpreted.
13339 .vitem &$recipient_verify_failure$&
13340 .vindex "&$recipient_verify_failure$&"
13341 In an ACL, when a recipient verification fails, this variable contains
13342 information about the failure. It is set to one of the following words:
13345 &"qualify"&: The address was unqualified (no domain), and the message
13346 was neither local nor came from an exempted host.
13349 &"route"&: Routing failed.
13352 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13353 or before the MAIL command (that is, on initial connection, HELO, or
13357 &"recipient"&: The RCPT command in a callout was rejected.
13360 &"postmaster"&: The postmaster check in a callout was rejected.
13363 The main use of this variable is expected to be to distinguish between
13364 rejections of MAIL and rejections of RCPT.
13366 .vitem &$recipients$&
13367 .vindex "&$recipients$&"
13368 This variable contains a list of envelope recipients for a message. A comma and
13369 a space separate the addresses in the replacement text. However, the variable
13370 is not generally available, to prevent exposure of Bcc recipients in
13371 unprivileged users' filter files. You can use &$recipients$& only in these
13375 In a system filter file.
13377 In the ACLs associated with the DATA command and with non-SMTP messages, that
13378 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13379 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13380 &%acl_not_smtp_mime%&.
13382 From within a &[local_scan()]& function.
13386 .vitem &$recipients_count$&
13387 .vindex "&$recipients_count$&"
13388 When a message is being processed, this variable contains the number of
13389 envelope recipients that came with the message. Duplicates are not excluded
13390 from the count. While a message is being received over SMTP, the number
13391 increases for each accepted recipient. It can be referenced in an ACL.
13394 .vitem &$regex_match_string$&
13395 .vindex "&$regex_match_string$&"
13396 This variable is set to contain the matching regular expression after a
13397 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13399 .vitem "&$regex1$&, &$regex2$&, etc"
13400 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13401 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13402 these variables contain the
13403 captured substrings identified by the regular expression.
13406 .vitem &$reply_address$&
13407 .vindex "&$reply_address$&"
13408 When a message is being processed, this variable contains the contents of the
13409 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13410 contents of the &'From:'& header line. Apart from the removal of leading
13411 white space, the value is not processed in any way. In particular, no RFC 2047
13412 decoding or character code translation takes place.
13414 .vitem &$return_path$&
13415 .vindex "&$return_path$&"
13416 When a message is being delivered, this variable contains the return path &--
13417 the sender field that will be sent as part of the envelope. It is not enclosed
13418 in <> characters. At the start of routing an address, &$return_path$& has the
13419 same value as &$sender_address$&, but if, for example, an incoming message to a
13420 mailing list has been expanded by a router which specifies a different address
13421 for bounce messages, &$return_path$& subsequently contains the new bounce
13422 address, whereas &$sender_address$& always contains the original sender address
13423 that was received with the message. In other words, &$sender_address$& contains
13424 the incoming envelope sender, and &$return_path$& contains the outgoing
13427 .vitem &$return_size_limit$&
13428 .vindex "&$return_size_limit$&"
13429 This is an obsolete name for &$bounce_return_size_limit$&.
13431 .vitem &$router_name$&
13432 .cindex "router" "name"
13433 .cindex "name" "of router"
13434 .vindex "&$router_name$&"
13435 During the running of a router this variable contains its name.
13438 .cindex "return code" "from &%run%& expansion"
13439 .vindex "&$runrc$&"
13440 This variable contains the return code from a command that is run by the
13441 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13442 assume the order in which option values are expanded, except for those
13443 preconditions whose order of testing is documented. Therefore, you cannot
13444 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13447 .vitem &$self_hostname$&
13448 .oindex "&%self%&" "value of host name"
13449 .vindex "&$self_hostname$&"
13450 When an address is routed to a supposedly remote host that turns out to be the
13451 local host, what happens is controlled by the &%self%& generic router option.
13452 One of its values causes the address to be passed to another router. When this
13453 happens, &$self_hostname$& is set to the name of the local host that the
13454 original router encountered. In other circumstances its contents are null.
13456 .vitem &$sender_address$&
13457 .vindex "&$sender_address$&"
13458 When a message is being processed, this variable contains the sender's address
13459 that was received in the message's envelope. The case of letters in the address
13460 is retained, in both the local part and the domain. For bounce messages, the
13461 value of this variable is the empty string. See also &$return_path$&.
13463 .vitem &$sender_address_data$&
13464 .vindex "&$address_data$&"
13465 .vindex "&$sender_address_data$&"
13466 If &$address_data$& is set when the routers are called from an ACL to verify a
13467 sender address, the final value is preserved in &$sender_address_data$&, to
13468 distinguish it from data from a recipient address. The value does not persist
13469 after the end of the current ACL statement. If you want to preserve it for
13470 longer, you can save it in an ACL variable.
13472 .vitem &$sender_address_domain$&
13473 .vindex "&$sender_address_domain$&"
13474 The domain portion of &$sender_address$&.
13476 .vitem &$sender_address_local_part$&
13477 .vindex "&$sender_address_local_part$&"
13478 The local part portion of &$sender_address$&.
13480 .vitem &$sender_data$&
13481 .vindex "&$sender_data$&"
13482 This variable is set after a lookup success in an ACL &%senders%& condition or
13483 in a router &%senders%& option. It contains the data from the lookup, and the
13484 value remains set until the next &%senders%& test. Thus, you can do things like
13487 &`require senders = cdb*@;/some/file`&
13488 &`deny `&&'some further test involving'& &`$sender_data`&
13490 &*Warning*&: This variable is set only when a lookup is used as an indexing
13491 method in the address list, using the semicolon syntax as in the example above.
13492 The variable is not set for a lookup that is used as part of the string
13493 expansion that all such lists undergo before being interpreted.
13495 .vitem &$sender_fullhost$&
13496 .vindex "&$sender_fullhost$&"
13497 When a message is received from a remote host, this variable contains the host
13498 name and IP address in a single string. It ends with the IP address in square
13499 brackets, followed by a colon and a port number if the logging of ports is
13500 enabled. The format of the rest of the string depends on whether the host
13501 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13502 looking up its IP address. (Looking up the IP address can be forced by the
13503 &%host_lookup%& option, independent of verification.) A plain host name at the
13504 start of the string is a verified host name; if this is not present,
13505 verification either failed or was not requested. A host name in parentheses is
13506 the argument of a HELO or EHLO command. This is omitted if it is identical to
13507 the verified host name or to the host's IP address in square brackets.
13509 .vitem &$sender_helo_dnssec$&
13510 .vindex "&$sender_helo_dnssec$&"
13511 This boolean variable is true if a successful HELO verification was
13512 .cindex "DNS" "DNSSEC"
13513 done using DNS information the resolver library stated was authenticated data.
13515 .vitem &$sender_helo_name$&
13516 .vindex "&$sender_helo_name$&"
13517 When a message is received from a remote host that has issued a HELO or EHLO
13518 command, the argument of that command is placed in this variable. It is also
13519 set if HELO or EHLO is used when a message is received using SMTP locally via
13520 the &%-bs%& or &%-bS%& options.
13522 .vitem &$sender_host_address$&
13523 .vindex "&$sender_host_address$&"
13524 When a message is received from a remote host using SMTP,
13525 this variable contains that
13526 host's IP address. For locally non-SMTP submitted messages, it is empty.
13528 .vitem &$sender_host_authenticated$&
13529 .vindex "&$sender_host_authenticated$&"
13530 This variable contains the name (not the public name) of the authenticator
13531 driver that successfully authenticated the client from which the message was
13532 received. It is empty if there was no successful authentication. See also
13533 &$authenticated_id$&.
13535 .vitem &$sender_host_dnssec$&
13536 .vindex "&$sender_host_dnssec$&"
13537 If an attempt to populate &$sender_host_name$& has been made
13538 (by reference, &%hosts_lookup%& or
13539 otherwise) then this boolean will have been set true if, and only if, the
13540 resolver library states that both
13541 the reverse and forward DNS were authenticated data. At all
13542 other times, this variable is false.
13544 .cindex "DNS" "DNSSEC"
13545 It is likely that you will need to coerce DNSSEC support on in the resolver
13546 library, by setting:
13551 In addition, on Linux with glibc 2.31 or newer the resolver library will
13552 default to stripping out a successful validation status.
13553 This will break a previously working Exim installation.
13554 Provided that you do trust the resolver (ie, is on localhost) you can tell
13555 glibc to pass through any successful validation with a new option in
13556 &_/etc/resolv.conf_&:
13561 Exim does not perform DNSSEC validation itself, instead leaving that to a
13562 validating resolver (e.g. unbound, or bind with suitable configuration).
13564 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13565 mechanism in the list, then this variable will be false.
13567 This requires that your system resolver library support EDNS0 (and that
13568 DNSSEC flags exist in the system headers). If the resolver silently drops
13569 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13570 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13573 .vitem &$sender_host_name$&
13574 .vindex "&$sender_host_name$&"
13575 When a message is received from a remote host, this variable contains the
13576 host's name as obtained by looking up its IP address. For messages received by
13577 other means, this variable is empty.
13579 .vindex "&$host_lookup_failed$&"
13580 If the host name has not previously been looked up, a reference to
13581 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13582 A looked up name is accepted only if it leads back to the original IP address
13583 via a forward lookup. If either the reverse or the forward lookup fails to find
13584 any data, or if the forward lookup does not yield the original IP address,
13585 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13587 .vindex "&$host_lookup_deferred$&"
13588 However, if either of the lookups cannot be completed (for example, there is a
13589 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13590 &$host_lookup_failed$& remains set to &"0"&.
13592 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13593 host name again if there is a subsequent reference to &$sender_host_name$&
13594 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13597 Exim does not automatically look up every calling host's name. If you want
13598 maximum efficiency, you should arrange your configuration so that it avoids
13599 these lookups altogether. The lookup happens only if one or more of the
13600 following are true:
13603 A string containing &$sender_host_name$& is expanded.
13605 The calling host matches the list in &%host_lookup%&. In the default
13606 configuration, this option is set to *, so it must be changed if lookups are
13607 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13609 Exim needs the host name in order to test an item in a host list. The items
13610 that require this are described in sections &<<SECThoslispatnam>>& and
13611 &<<SECThoslispatnamsk>>&.
13613 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13614 In this case, the host name is required to compare with the name quoted in any
13615 EHLO or HELO commands that the client issues.
13617 The remote host issues a EHLO or HELO command that quotes one of the
13618 domains in &%helo_lookup_domains%&. The default value of this option is
13619 . ==== As this is a nested list, any displays it contains must be indented
13620 . ==== as otherwise they are too far to the left.
13622 helo_lookup_domains = @ : @[]
13624 which causes a lookup if a remote host (incorrectly) gives the server's name or
13625 IP address in an EHLO or HELO command.
13629 .vitem &$sender_host_port$&
13630 .vindex "&$sender_host_port$&"
13631 When a message is received from a remote host, this variable contains the port
13632 number that was used on the remote host.
13634 .vitem &$sender_ident$&
13635 .vindex "&$sender_ident$&"
13636 When a message is received from a remote host, this variable contains the
13637 identification received in response to an RFC 1413 request. When a message has
13638 been received locally, this variable contains the login name of the user that
13641 .vitem &$sender_rate_$&&'xxx'&
13642 A number of variables whose names begin &$sender_rate_$& are set as part of the
13643 &%ratelimit%& ACL condition. Details are given in section
13644 &<<SECTratelimiting>>&.
13646 .vitem &$sender_rcvhost$&
13647 .cindex "DNS" "reverse lookup"
13648 .cindex "reverse DNS lookup"
13649 .vindex "&$sender_rcvhost$&"
13650 This is provided specifically for use in &'Received:'& headers. It starts with
13651 either the verified host name (as obtained from a reverse DNS lookup) or, if
13652 there is no verified host name, the IP address in square brackets. After that
13653 there may be text in parentheses. When the first item is a verified host name,
13654 the first thing in the parentheses is the IP address in square brackets,
13655 followed by a colon and a port number if port logging is enabled. When the
13656 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13659 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13660 was used and its argument was not identical to the real host name or IP
13661 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13662 all three items are present in the parentheses, a newline and tab are inserted
13663 into the string, to improve the formatting of the &'Received:'& header.
13665 .vitem &$sender_verify_failure$&
13666 .vindex "&$sender_verify_failure$&"
13667 In an ACL, when a sender verification fails, this variable contains information
13668 about the failure. The details are the same as for
13669 &$recipient_verify_failure$&.
13671 .vitem &$sending_ip_address$&
13672 .vindex "&$sending_ip_address$&"
13673 This variable is set whenever an outgoing SMTP connection to another host has
13674 been set up. It contains the IP address of the local interface that is being
13675 used. This is useful if a host that has more than one IP address wants to take
13676 on different personalities depending on which one is being used. For incoming
13677 connections, see &$received_ip_address$&.
13679 .vitem &$sending_port$&
13680 .vindex "&$sending_port$&"
13681 This variable is set whenever an outgoing SMTP connection to another host has
13682 been set up. It contains the local port that is being used. For incoming
13683 connections, see &$received_port$&.
13685 .vitem &$smtp_active_hostname$&
13686 .vindex "&$smtp_active_hostname$&"
13687 During an incoming SMTP session, this variable contains the value of the active
13688 host name, as specified by the &%smtp_active_hostname%& option. The value of
13689 &$smtp_active_hostname$& is saved with any message that is received, so its
13690 value can be consulted during routing and delivery.
13692 .vitem &$smtp_command$&
13693 .vindex "&$smtp_command$&"
13694 During the processing of an incoming SMTP command, this variable contains the
13695 entire command. This makes it possible to distinguish between HELO and EHLO in
13696 the HELO ACL, and also to distinguish between commands such as these:
13701 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13702 command, the address in &$smtp_command$& is the original address before any
13703 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13704 the address after SMTP-time rewriting.
13706 .vitem &$smtp_command_argument$&
13707 .cindex "SMTP" "command, argument for"
13708 .vindex "&$smtp_command_argument$&"
13709 While an ACL is running to check an SMTP command, this variable contains the
13710 argument, that is, the text that follows the command name, with leading white
13711 space removed. Following the introduction of &$smtp_command$&, this variable is
13712 somewhat redundant, but is retained for backwards compatibility.
13714 .vitem &$smtp_command_history$&
13715 .cindex SMTP "command history"
13716 .vindex "&$smtp_command_history$&"
13717 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13718 received, in time-order left to right. Only a limited number of commands
13721 .vitem &$smtp_count_at_connection_start$&
13722 .vindex "&$smtp_count_at_connection_start$&"
13723 This variable is set greater than zero only in processes spawned by the Exim
13724 daemon for handling incoming SMTP connections. The name is deliberately long,
13725 in order to emphasize what the contents are. When the daemon accepts a new
13726 connection, it increments this variable. A copy of the variable is passed to
13727 the child process that handles the connection, but its value is fixed, and
13728 never changes. It is only an approximation of how many incoming connections
13729 there actually are, because many other connections may come and go while a
13730 single connection is being processed. When a child process terminates, the
13731 daemon decrements its copy of the variable.
13733 .vitem "&$sn0$& &-- &$sn9$&"
13734 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13735 that were current at the end of the system filter file. This allows a system
13736 filter file to set values that can be tested in users' filter files. For
13737 example, a system filter could set a value indicating how likely it is that a
13738 message is junk mail.
13740 .vitem &$spam_score$& &&&
13741 &$spam_score_int$& &&&
13743 &$spam_report$& &&&
13745 A number of variables whose names start with &$spam$& are available when Exim
13746 is compiled with the content-scanning extension. For details, see section
13747 &<<SECTscanspamass>>&.
13749 .vitem &$spf_header_comment$& &&&
13750 &$spf_received$& &&&
13752 &$spf_result_guessed$& &&&
13753 &$spf_smtp_comment$&
13754 These variables are only available if Exim is built with SPF support.
13755 For details see section &<<SECSPF>>&.
13757 .vitem &$spool_directory$&
13758 .vindex "&$spool_directory$&"
13759 The name of Exim's spool directory.
13761 .vitem &$spool_inodes$&
13762 .vindex "&$spool_inodes$&"
13763 The number of free inodes in the disk partition where Exim's spool files are
13764 being written. The value is recalculated whenever the variable is referenced.
13765 If the relevant file system does not have the concept of inodes, the value of
13766 is -1. See also the &%check_spool_inodes%& option.
13768 .vitem &$spool_space$&
13769 .vindex "&$spool_space$&"
13770 The amount of free space (as a number of kilobytes) in the disk partition where
13771 Exim's spool files are being written. The value is recalculated whenever the
13772 variable is referenced. If the operating system does not have the ability to
13773 find the amount of free space (only true for experimental systems), the space
13774 value is -1. For example, to check in an ACL that there is at least 50
13775 megabytes free on the spool, you could write:
13777 condition = ${if > {$spool_space}{50000}}
13779 See also the &%check_spool_space%& option.
13782 .vitem &$thisaddress$&
13783 .vindex "&$thisaddress$&"
13784 This variable is set only during the processing of the &%foranyaddress%&
13785 command in a filter file. Its use is explained in the description of that
13786 command, which can be found in the separate document entitled &'Exim's
13787 interfaces to mail filtering'&.
13789 .vitem &$tls_in_bits$&
13790 .vindex "&$tls_in_bits$&"
13791 Contains an approximation of the TLS cipher's bit-strength
13792 on the inbound connection; the meaning of
13793 this depends upon the TLS implementation used.
13794 If TLS has not been negotiated, the value will be 0.
13795 The value of this is automatically fed into the Cyrus SASL authenticator
13796 when acting as a server, to specify the "external SSF" (a SASL term).
13798 The deprecated &$tls_bits$& variable refers to the inbound side
13799 except when used in the context of an outbound SMTP delivery, when it refers to
13802 .vitem &$tls_out_bits$&
13803 .vindex "&$tls_out_bits$&"
13804 Contains an approximation of the TLS cipher's bit-strength
13805 on an outbound SMTP connection; the meaning of
13806 this depends upon the TLS implementation used.
13807 If TLS has not been negotiated, the value will be 0.
13809 .vitem &$tls_in_ourcert$&
13810 .vindex "&$tls_in_ourcert$&"
13811 .cindex certificate variables
13812 This variable refers to the certificate presented to the peer of an
13813 inbound connection when the message was received.
13814 It is only useful as the argument of a
13815 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13816 or a &%def%& condition.
13818 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13819 when a list of more than one
13820 file is used for &%tls_certificate%&, this variable is not reliable.
13821 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13823 .vitem &$tls_in_peercert$&
13824 .vindex "&$tls_in_peercert$&"
13825 This variable refers to the certificate presented by the peer of an
13826 inbound connection when the message was received.
13827 It is only useful as the argument of a
13828 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13829 or a &%def%& condition.
13830 If certificate verification fails it may refer to a failing chain element
13831 which is not the leaf.
13833 .vitem &$tls_out_ourcert$&
13834 .vindex "&$tls_out_ourcert$&"
13835 This variable refers to the certificate presented to the peer of an
13836 outbound connection. It is only useful as the argument of a
13837 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13838 or a &%def%& condition.
13840 .vitem &$tls_out_peercert$&
13841 .vindex "&$tls_out_peercert$&"
13842 This variable refers to the certificate presented by the peer of an
13843 outbound connection. It is only useful as the argument of a
13844 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13845 or a &%def%& condition.
13846 If certificate verification fails it may refer to a failing chain element
13847 which is not the leaf.
13849 .vitem &$tls_in_certificate_verified$&
13850 .vindex "&$tls_in_certificate_verified$&"
13851 This variable is set to &"1"& if a TLS certificate was verified when the
13852 message was received, and &"0"& otherwise.
13854 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13855 except when used in the context of an outbound SMTP delivery, when it refers to
13858 .vitem &$tls_out_certificate_verified$&
13859 .vindex "&$tls_out_certificate_verified$&"
13860 This variable is set to &"1"& if a TLS certificate was verified when an
13861 outbound SMTP connection was made,
13862 and &"0"& otherwise.
13864 .vitem &$tls_in_cipher$&
13865 .vindex "&$tls_in_cipher$&"
13866 .vindex "&$tls_cipher$&"
13867 When a message is received from a remote host over an encrypted SMTP
13868 connection, this variable is set to the cipher suite that was negotiated, for
13869 example DES-CBC3-SHA. In other circumstances, in particular, for message
13870 received over unencrypted connections, the variable is empty. Testing
13871 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13872 non-encrypted connections during ACL processing.
13874 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13875 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13876 becomes the same as &$tls_out_cipher$&.
13878 .vitem &$tls_in_cipher_std$&
13879 .vindex "&$tls_in_cipher_std$&"
13880 As above, but returning the RFC standard name for the cipher suite.
13882 .vitem &$tls_out_cipher$&
13883 .vindex "&$tls_out_cipher$&"
13885 cleared before any outgoing SMTP connection is made,
13886 and then set to the outgoing cipher suite if one is negotiated. See chapter
13887 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13888 details of the &(smtp)& transport.
13890 .vitem &$tls_out_cipher_std$&
13891 .vindex "&$tls_out_cipher_std$&"
13892 As above, but returning the RFC standard name for the cipher suite.
13894 .vitem &$tls_out_dane$&
13895 .vindex &$tls_out_dane$&
13896 DANE active status. See section &<<SECDANE>>&.
13898 .vitem &$tls_in_ocsp$&
13899 .vindex "&$tls_in_ocsp$&"
13900 When a message is received from a remote client connection
13901 the result of any OCSP request from the client is encoded in this variable:
13903 0 OCSP proof was not requested (default value)
13904 1 No response to request
13905 2 Response not verified
13906 3 Verification failed
13907 4 Verification succeeded
13910 .vitem &$tls_out_ocsp$&
13911 .vindex "&$tls_out_ocsp$&"
13912 When a message is sent to a remote host connection
13913 the result of any OCSP request made is encoded in this variable.
13914 See &$tls_in_ocsp$& for values.
13916 .vitem &$tls_in_peerdn$&
13917 .vindex "&$tls_in_peerdn$&"
13918 .vindex "&$tls_peerdn$&"
13919 .cindex certificate "extracting fields"
13920 When a message is received from a remote host over an encrypted SMTP
13921 connection, and Exim is configured to request a certificate from the client,
13922 the value of the Distinguished Name of the certificate is made available in the
13923 &$tls_in_peerdn$& during subsequent processing.
13924 If certificate verification fails it may refer to a failing chain element
13925 which is not the leaf.
13927 The deprecated &$tls_peerdn$& variable refers to the inbound side
13928 except when used in the context of an outbound SMTP delivery, when it refers to
13931 .vitem &$tls_out_peerdn$&
13932 .vindex "&$tls_out_peerdn$&"
13933 When a message is being delivered to a remote host over an encrypted SMTP
13934 connection, and Exim is configured to request a certificate from the server,
13935 the value of the Distinguished Name of the certificate is made available in the
13936 &$tls_out_peerdn$& during subsequent processing.
13937 If certificate verification fails it may refer to a failing chain element
13938 which is not the leaf.
13942 .vitem &$tls_in_resumption$& &&&
13943 &$tls_out_resumption$&
13944 .vindex &$tls_in_resumption$&
13945 .vindex &$tls_out_resumption$&
13946 .cindex TLS resumption
13947 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13951 .vitem &$tls_in_sni$&
13952 .vindex "&$tls_in_sni$&"
13953 .vindex "&$tls_sni$&"
13954 .cindex "TLS" "Server Name Indication"
13956 .cindex SNI "observability on server"
13957 When a TLS session is being established, if the client sends the Server
13958 Name Indication extension, the value will be placed in this variable.
13959 If the variable appears in &%tls_certificate%& then this option and
13960 some others, described in &<<SECTtlssni>>&,
13961 will be re-expanded early in the TLS session, to permit
13962 a different certificate to be presented (and optionally a different key to be
13963 used) to the client, based upon the value of the SNI extension.
13965 The deprecated &$tls_sni$& variable refers to the inbound side
13966 except when used in the context of an outbound SMTP delivery, when it refers to
13969 .vitem &$tls_out_sni$&
13970 .vindex "&$tls_out_sni$&"
13971 .cindex "TLS" "Server Name Indication"
13973 .cindex SNI "observability in client"
13975 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13978 .vitem &$tls_out_tlsa_usage$&
13979 .vindex &$tls_out_tlsa_usage$&
13980 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13982 .vitem &$tls_in_ver$&
13983 .vindex "&$tls_in_ver$&"
13984 When a message is received from a remote host over an encrypted SMTP connection
13985 this variable is set to the protocol version, eg &'TLS1.2'&.
13987 .vitem &$tls_out_ver$&
13988 .vindex "&$tls_out_ver$&"
13989 When a message is being delivered to a remote host over an encrypted SMTP connection
13990 this variable is set to the protocol version.
13993 .vitem &$tod_bsdinbox$&
13994 .vindex "&$tod_bsdinbox$&"
13995 The time of day and the date, in the format required for BSD-style mailbox
13996 files, for example: Thu Oct 17 17:14:09 1995.
13998 .vitem &$tod_epoch$&
13999 .vindex "&$tod_epoch$&"
14000 The time and date as a number of seconds since the start of the Unix epoch.
14002 .vitem &$tod_epoch_l$&
14003 .vindex "&$tod_epoch_l$&"
14004 The time and date as a number of microseconds since the start of the Unix epoch.
14006 .vitem &$tod_full$&
14007 .vindex "&$tod_full$&"
14008 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
14009 +0100. The timezone is always given as a numerical offset from UTC, with
14010 positive values used for timezones that are ahead (east) of UTC, and negative
14011 values for those that are behind (west).
14014 .vindex "&$tod_log$&"
14015 The time and date in the format used for writing Exim's log files, for example:
14016 1995-10-12 15:32:29, but without a timezone.
14018 .vitem &$tod_logfile$&
14019 .vindex "&$tod_logfile$&"
14020 This variable contains the date in the format yyyymmdd. This is the format that
14021 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14024 .vitem &$tod_zone$&
14025 .vindex "&$tod_zone$&"
14026 This variable contains the numerical value of the local timezone, for example:
14029 .vitem &$tod_zulu$&
14030 .vindex "&$tod_zulu$&"
14031 This variable contains the UTC date and time in &"Zulu"& format, as specified
14032 by ISO 8601, for example: 20030221154023Z.
14034 .vitem &$transport_name$&
14035 .cindex "transport" "name"
14036 .cindex "name" "of transport"
14037 .vindex "&$transport_name$&"
14038 During the running of a transport, this variable contains its name.
14041 .vindex "&$value$&"
14042 This variable contains the result of an expansion lookup, extraction operation,
14043 or external command, as described above. It is also used during a
14044 &*reduce*& expansion.
14046 .vitem &$verify_mode$&
14047 .vindex "&$verify_mode$&"
14048 While a router or transport is being run in verify mode or for cutthrough delivery,
14049 contains "S" for sender-verification or "R" for recipient-verification.
14052 .vitem &$version_number$&
14053 .vindex "&$version_number$&"
14054 The version number of Exim. Same as &$exim_version$&, may be overridden
14055 by the &%exim_version%& main config option.
14057 .vitem &$warn_message_delay$&
14058 .vindex "&$warn_message_delay$&"
14059 This variable is set only during the creation of a message warning about a
14060 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14062 .vitem &$warn_message_recipients$&
14063 .vindex "&$warn_message_recipients$&"
14064 This variable is set only during the creation of a message warning about a
14065 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14071 . ////////////////////////////////////////////////////////////////////////////
14072 . ////////////////////////////////////////////////////////////////////////////
14074 .chapter "Embedded Perl" "CHAPperl"
14075 .scindex IIDperl "Perl" "calling from Exim"
14076 Exim can be built to include an embedded Perl interpreter. When this is done,
14077 Perl subroutines can be called as part of the string expansion process. To make
14078 use of the Perl support, you need version 5.004 or later of Perl installed on
14079 your system. To include the embedded interpreter in the Exim binary, include
14084 in your &_Local/Makefile_& and then build Exim in the normal way.
14087 .section "Setting up so Perl can be used" "SECID85"
14088 .oindex "&%perl_startup%&"
14089 Access to Perl subroutines is via a global configuration option called
14090 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14091 no &%perl_startup%& option in the Exim configuration file then no Perl
14092 interpreter is started and there is almost no overhead for Exim (since none of
14093 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14094 option then the associated value is taken to be Perl code which is executed in
14095 a newly created Perl interpreter.
14097 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14098 need backslashes before any characters to escape special meanings. The option
14099 should usually be something like
14101 perl_startup = do '/etc/exim.pl'
14103 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14104 use from Exim. Exim can be configured either to start up a Perl interpreter as
14105 soon as it is entered, or to wait until the first time it is needed. Starting
14106 the interpreter at the beginning ensures that it is done while Exim still has
14107 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14108 fact used in a particular run. Also, note that this does not mean that Exim is
14109 necessarily running as root when Perl is called at a later time. By default,
14110 the interpreter is started only when it is needed, but this can be changed in
14114 .oindex "&%perl_at_start%&"
14115 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14116 a startup when Exim is entered.
14118 The command line option &%-ps%& also requests a startup when Exim is entered,
14119 overriding the setting of &%perl_at_start%&.
14122 There is also a command line option &%-pd%& (for delay) which suppresses the
14123 initial startup, even if &%perl_at_start%& is set.
14126 .oindex "&%perl_taintmode%&"
14127 .cindex "Perl" "taintmode"
14128 To provide more security executing Perl code via the embedded Perl
14129 interpreter, the &%perl_taintmode%& option can be set. This enables the
14130 taint mode of the Perl interpreter. You are encouraged to set this
14131 option to a true value. To avoid breaking existing installations, it
14135 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14139 .section "Calling Perl subroutines" "SECID86"
14140 When the configuration file includes a &%perl_startup%& option you can make use
14141 of the string expansion item to call the Perl subroutines that are defined
14142 by the &%perl_startup%& code. The operator is used in any of the following
14146 ${perl{foo}{argument}}
14147 ${perl{foo}{argument1}{argument2} ... }
14149 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14150 arguments may be passed. Passing more than this results in an expansion failure
14151 with an error message of the form
14153 Too many arguments passed to Perl subroutine "foo" (max is 8)
14155 The return value of the Perl subroutine is evaluated in a scalar context before
14156 it is passed back to Exim to be inserted into the expanded string. If the
14157 return value is &'undef'&, the expansion is forced to fail in the same way as
14158 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14159 by obeying Perl's &%die%& function, the expansion fails with the error message
14160 that was passed to &%die%&.
14163 .section "Calling Exim functions from Perl" "SECID87"
14164 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14165 is available to call back into Exim's string expansion function. For example,
14168 my $lp = Exim::expand_string('$local_part');
14170 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14171 Note those are single quotes and not double quotes to protect against
14172 &$local_part$& being interpolated as a Perl variable.
14174 If the string expansion is forced to fail by a &"fail"& item, the result of
14175 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14176 expansion string, the Perl call from the original expansion string fails with
14177 an appropriate error message, in the same way as if &%die%& were used.
14179 .cindex "debugging" "from embedded Perl"
14180 .cindex "log" "writing from embedded Perl"
14181 Two other Exim functions are available for use from within Perl code.
14182 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14183 debugging is enabled. If you want a newline at the end, you must supply it.
14184 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14185 timestamp. In this case, you should not supply a terminating newline.
14188 .section "Use of standard output and error by Perl" "SECID88"
14189 .cindex "Perl" "standard output and error"
14190 You should not write to the standard error or output streams from within your
14191 Perl code, as it is not defined how these are set up. In versions of Exim
14192 before 4.50, it is possible for the standard output or error to refer to the
14193 SMTP connection during message reception via the daemon. Writing to this stream
14194 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14195 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14196 avoided, but the output is lost.
14198 .cindex "Perl" "use of &%warn%&"
14199 The Perl &%warn%& statement writes to the standard error stream by default.
14200 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14201 you have no control. When Exim starts up the Perl interpreter, it arranges for
14202 output from the &%warn%& statement to be written to the Exim main log. You can
14203 change this by including appropriate Perl magic somewhere in your Perl code.
14204 For example, to discard &%warn%& output completely, you need this:
14206 $SIG{__WARN__} = sub { };
14208 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14209 example, the code for the subroutine is empty, so it does nothing, but you can
14210 include any Perl code that you like. The text of the &%warn%& message is passed
14211 as the first subroutine argument.
14215 . ////////////////////////////////////////////////////////////////////////////
14216 . ////////////////////////////////////////////////////////////////////////////
14218 .chapter "Starting the daemon and the use of network interfaces" &&&
14219 "CHAPinterfaces" &&&
14220 "Starting the daemon"
14221 .cindex "daemon" "starting"
14222 .cindex "interface" "listening"
14223 .cindex "network interface"
14224 .cindex "interface" "network"
14225 .cindex "IP address" "for listening"
14226 .cindex "daemon" "listening IP addresses"
14227 .cindex "TCP/IP" "setting listening interfaces"
14228 .cindex "TCP/IP" "setting listening ports"
14229 A host that is connected to a TCP/IP network may have one or more physical
14230 hardware network interfaces. Each of these interfaces may be configured as one
14231 or more &"logical"& interfaces, which are the entities that a program actually
14232 works with. Each of these logical interfaces is associated with an IP address.
14233 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14234 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14235 knowledge about the host's interfaces for use in three different circumstances:
14238 When a listening daemon is started, Exim needs to know which interfaces
14239 and ports to listen on.
14241 When Exim is routing an address, it needs to know which IP addresses
14242 are associated with local interfaces. This is required for the correct
14243 processing of MX lists by removing the local host and others with the
14244 same or higher priority values. Also, Exim needs to detect cases
14245 when an address is routed to an IP address that in fact belongs to the
14246 local host. Unless the &%self%& router option or the &%allow_localhost%&
14247 option of the smtp transport is set (as appropriate), this is treated
14248 as an error situation.
14250 When Exim connects to a remote host, it may need to know which interface to use
14251 for the outgoing connection.
14255 Exim's default behaviour is likely to be appropriate in the vast majority
14256 of cases. If your host has only one interface, and you want all its IP
14257 addresses to be treated in the same way, and you are using only the
14258 standard SMTP port, you should not need to take any special action. The
14259 rest of this chapter does not apply to you.
14261 In a more complicated situation you may want to listen only on certain
14262 interfaces, or on different ports, and for this reason there are a number of
14263 options that can be used to influence Exim's behaviour. The rest of this
14264 chapter describes how they operate.
14266 When a message is received over TCP/IP, the interface and port that were
14267 actually used are set in &$received_ip_address$& and &$received_port$&.
14271 .section "Starting a listening daemon" "SECID89"
14272 When a listening daemon is started (by means of the &%-bd%& command line
14273 option), the interfaces and ports on which it listens are controlled by the
14277 &%daemon_smtp_ports%& contains a list of default ports
14279 (For backward compatibility, this option can also be specified in the singular.)
14281 &%local_interfaces%& contains list of interface IP addresses on which to
14282 listen. Each item may optionally also specify a port.
14285 The default list separator in both cases is a colon, but this can be changed as
14286 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14287 it is usually best to change the separator to avoid having to double all the
14288 colons. For example:
14290 local_interfaces = <; 127.0.0.1 ; \
14293 3ffe:ffff:836f::fe86:a061
14295 There are two different formats for specifying a port along with an IP address
14296 in &%local_interfaces%&:
14299 The port is added onto the address with a dot separator. For example, to listen
14300 on port 1234 on two different IP addresses:
14302 local_interfaces = <; 192.168.23.65.1234 ; \
14303 3ffe:ffff:836f::fe86:a061.1234
14306 The IP address is enclosed in square brackets, and the port is added
14307 with a colon separator, for example:
14309 local_interfaces = <; [192.168.23.65]:1234 ; \
14310 [3ffe:ffff:836f::fe86:a061]:1234
14314 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14315 default setting contains just one port:
14317 daemon_smtp_ports = smtp
14319 If more than one port is listed, each interface that does not have its own port
14320 specified listens on all of them. Ports that are listed in
14321 &%daemon_smtp_ports%& can be identified either by name (defined in
14322 &_/etc/services_&) or by number. However, when ports are given with individual
14323 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14327 .section "Special IP listening addresses" "SECID90"
14328 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14329 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14330 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14331 instead of setting up separate listening sockets for each interface. The
14332 default value of &%local_interfaces%& is
14334 local_interfaces = 0.0.0.0
14336 when Exim is built without IPv6 support; otherwise it is:
14338 local_interfaces = <; ::0 ; 0.0.0.0
14340 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14344 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14345 The &%-oX%& command line option can be used to override the values of
14346 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14347 instance. Another way of doing this would be to use macros and the &%-D%&
14348 option. However, &%-oX%& can be used by any admin user, whereas modification of
14349 the runtime configuration by &%-D%& is allowed only when the caller is root or
14352 The value of &%-oX%& is a list of items. The default colon separator can be
14353 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14354 If there are any items that do not
14355 contain dots or colons (that is, are not IP addresses), the value of
14356 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14357 items that do contain dots or colons, the value of &%local_interfaces%& is
14358 replaced by those items. Thus, for example,
14362 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14365 -oX 192.168.34.5.1125
14367 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14368 (However, since &%local_interfaces%& now contains no items without ports, the
14369 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14373 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14374 .cindex "submissions protocol"
14375 .cindex "ssmtp protocol"
14376 .cindex "smtps protocol"
14377 .cindex "SMTP" "ssmtp protocol"
14378 .cindex "SMTP" "smtps protocol"
14379 Exim supports the use of TLS-on-connect, used by mail clients in the
14380 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14381 For some years, IETF Standards Track documents only blessed the
14382 STARTTLS-based Submission service (port 587) while common practice was to support
14383 the same feature set on port 465, but using TLS-on-connect.
14384 If your installation needs to provide service to mail clients
14385 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14388 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14389 service names, connections to those ports must first establish TLS, before
14390 proceeding to the application layer use of the SMTP protocol.
14392 The common use of this option is expected to be
14394 tls_on_connect_ports = 465
14397 There is also a command line option &%-tls-on-connect%&, which forces all ports
14398 to behave in this way when a daemon is started.
14400 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14401 daemon to listen on those ports. You must still specify them in
14402 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14403 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14404 connections via the daemon.)
14409 .section "IPv6 address scopes" "SECID92"
14410 .cindex "IPv6" "address scopes"
14411 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14412 can, in principle, have the same link-local IPv6 address on different
14413 interfaces. Thus, additional information is needed, over and above the IP
14414 address, to distinguish individual interfaces. A convention of using a
14415 percent sign followed by something (often the interface name) has been
14416 adopted in some cases, leading to addresses like this:
14418 fe80::202:b3ff:fe03:45c1%eth0
14420 To accommodate this usage, a percent sign followed by an arbitrary string is
14421 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14422 to convert a textual IPv6 address for actual use. This function recognizes the
14423 percent convention in operating systems that support it, and it processes the
14424 address appropriately. Unfortunately, some older libraries have problems with
14425 &[getaddrinfo()]&. If
14427 IPV6_USE_INET_PTON=yes
14429 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14430 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14431 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14432 function.) Of course, this means that the additional functionality of
14433 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14435 .section "Disabling IPv6" "SECID93"
14436 .cindex "IPv6" "disabling"
14437 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14438 run on a host whose kernel does not support IPv6. The binary will fall back to
14439 using IPv4, but it may waste resources looking up AAAA records, and trying to
14440 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14441 .oindex "&%disable_ipv6%&"
14442 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14443 activities take place. AAAA records are never looked up, and any IPv6 addresses
14444 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14445 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14446 to handle IPv6 literal addresses.
14448 On the other hand, when IPv6 is in use, there may be times when you want to
14449 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14450 option to globally suppress the lookup of AAAA records for specified domains,
14451 and you can use the &%ignore_target_hosts%& generic router option to ignore
14452 IPv6 addresses in an individual router.
14456 .section "Examples of starting a listening daemon" "SECID94"
14457 The default case in an IPv6 environment is
14459 daemon_smtp_ports = smtp
14460 local_interfaces = <; ::0 ; 0.0.0.0
14462 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14463 Either one or two sockets may be used, depending on the characteristics of
14464 the TCP/IP stack. (This is complicated and messy; for more information,
14465 read the comments in the &_daemon.c_& source file.)
14467 To specify listening on ports 25 and 26 on all interfaces:
14469 daemon_smtp_ports = 25 : 26
14471 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14473 local_interfaces = <; ::0.25 ; ::0.26 \
14474 0.0.0.0.25 ; 0.0.0.0.26
14476 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14477 IPv4 loopback address only:
14479 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14481 To specify listening on the default port on specific interfaces only:
14483 local_interfaces = 10.0.0.67 : 192.168.34.67
14485 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14489 .section "Recognizing the local host" "SECTreclocipadd"
14490 The &%local_interfaces%& option is also used when Exim needs to determine
14491 whether or not an IP address refers to the local host. That is, the IP
14492 addresses of all the interfaces on which a daemon is listening are always
14495 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14496 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14497 available interfaces from the operating system, and extracts the relevant
14498 (that is, IPv4 or IPv6) addresses to use for checking.
14500 Some systems set up large numbers of virtual interfaces in order to provide
14501 many virtual web servers. In this situation, you may want to listen for
14502 email on only a few of the available interfaces, but nevertheless treat all
14503 interfaces as local when routing. You can do this by setting
14504 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14505 &"all"& wildcard values. These addresses are recognized as local, but are not
14506 used for listening. Consider this example:
14508 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14510 3ffe:2101:12:1:a00:20ff:fe86:a061
14512 extra_local_interfaces = <; ::0 ; 0.0.0.0
14514 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14515 address, but all available interface addresses are treated as local when
14518 In some environments the local host name may be in an MX list, but with an IP
14519 address that is not assigned to any local interface. In other cases it may be
14520 desirable to treat other host names as if they referred to the local host. Both
14521 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14522 This contains host names rather than IP addresses. When a host is referenced
14523 during routing, either via an MX record or directly, it is treated as the local
14524 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14525 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14529 .section "Delivering to a remote host" "SECID95"
14530 Delivery to a remote host is handled by the smtp transport. By default, it
14531 allows the system's TCP/IP functions to choose which interface to use (if
14532 there is more than one) when connecting to a remote host. However, the
14533 &%interface%& option can be set to specify which interface is used. See the
14534 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14540 . ////////////////////////////////////////////////////////////////////////////
14541 . ////////////////////////////////////////////////////////////////////////////
14543 .chapter "Main configuration" "CHAPmainconfig"
14544 .scindex IIDconfima "configuration file" "main section"
14545 .scindex IIDmaiconf "main configuration"
14546 The first part of the runtime configuration file contains three types of item:
14549 Macro definitions: These lines start with an upper case letter. See section
14550 &<<SECTmacrodefs>>& for details of macro processing.
14552 Named list definitions: These lines start with one of the words &"domainlist"&,
14553 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14554 section &<<SECTnamedlists>>&.
14556 Main configuration settings: Each setting occupies one line of the file
14557 (with possible continuations). If any setting is preceded by the word
14558 &"hide"&, the &%-bP%& command line option displays its value to admin users
14559 only. See section &<<SECTcos>>& for a description of the syntax of these option
14563 This chapter specifies all the main configuration options, along with their
14564 types and default values. For ease of finding a particular option, they appear
14565 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14566 are now so many options, they are first listed briefly in functional groups, as
14567 an aid to finding the name of the option you are looking for. Some options are
14568 listed in more than one group.
14570 .section "Miscellaneous" "SECID96"
14572 .row &%add_environment%& "environment variables"
14573 .row &%bi_command%& "to run for &%-bi%& command line option"
14574 .row &%debug_store%& "do extra internal checks"
14575 .row &%disable_ipv6%& "do no IPv6 processing"
14576 .row &%keep_environment%& "environment variables"
14577 .row &%keep_malformed%& "for broken files &-- should not happen"
14578 .row &%localhost_number%& "for unique message ids in clusters"
14579 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14580 .row &%message_body_visible%& "how much to show in &$message_body$&"
14581 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14582 .row &%print_topbitchars%& "top-bit characters are printing"
14583 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14584 .row &%timezone%& "force time zone"
14588 .section "Exim parameters" "SECID97"
14590 .row &%exim_group%& "override compiled-in value"
14591 .row &%exim_path%& "override compiled-in value"
14592 .row &%exim_user%& "override compiled-in value"
14593 .row &%primary_hostname%& "default from &[uname()]&"
14594 .row &%split_spool_directory%& "use multiple directories"
14595 .row &%spool_directory%& "override compiled-in value"
14600 .section "Privilege controls" "SECID98"
14602 .row &%admin_groups%& "groups that are Exim admin users"
14603 .row &%commandline_checks_require_admin%& "require admin for various checks"
14604 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14605 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14606 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14607 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14608 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14609 .row &%never_users%& "do not run deliveries as these"
14610 .row &%prod_requires_admin%& "forced delivery requires admin user"
14611 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14612 .row &%trusted_groups%& "groups that are trusted"
14613 .row &%trusted_users%& "users that are trusted"
14618 .section "Logging" "SECID99"
14620 .row &%event_action%& "custom logging"
14621 .row &%hosts_connection_nolog%& "exemption from connect logging"
14622 .row &%log_file_path%& "override compiled-in value"
14623 .row &%log_selector%& "set/unset optional logging"
14624 .row &%log_timezone%& "add timezone to log lines"
14625 .row &%message_logs%& "create per-message logs"
14626 .row &%preserve_message_logs%& "after message completion"
14627 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14628 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14629 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14630 .row &%syslog_facility%& "set syslog &""facility""& field"
14631 .row &%syslog_pid%& "pid in syslog lines"
14632 .row &%syslog_processname%& "set syslog &""ident""& field"
14633 .row &%syslog_timestamp%& "timestamp syslog lines"
14634 .row &%write_rejectlog%& "control use of message log"
14639 .section "Frozen messages" "SECID100"
14641 .row &%auto_thaw%& "sets time for retrying frozen messages"
14642 .row &%freeze_tell%& "send message when freezing"
14643 .row &%move_frozen_messages%& "to another directory"
14644 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14649 .section "Data lookups" "SECID101"
14651 .row &%ibase_servers%& "InterBase servers"
14652 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14653 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14654 .row &%ldap_cert_file%& "client cert file for LDAP"
14655 .row &%ldap_cert_key%& "client key file for LDAP"
14656 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14657 .row &%ldap_default_servers%& "used if no server in query"
14658 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14659 .row &%ldap_start_tls%& "require TLS within LDAP"
14660 .row &%ldap_version%& "set protocol version"
14661 .row &%lookup_open_max%& "lookup files held open"
14662 .row &%mysql_servers%& "default MySQL servers"
14663 .row &%oracle_servers%& "Oracle servers"
14664 .row &%pgsql_servers%& "default PostgreSQL servers"
14665 .row &%sqlite_lock_timeout%& "as it says"
14670 .section "Message ids" "SECID102"
14672 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14673 .row &%message_id_header_text%& "ditto"
14678 .section "Embedded Perl Startup" "SECID103"
14680 .row &%perl_at_start%& "always start the interpreter"
14681 .row &%perl_startup%& "code to obey when starting Perl"
14682 .row &%perl_taintmode%& "enable taint mode in Perl"
14687 .section "Daemon" "SECID104"
14689 .row &%daemon_smtp_ports%& "default ports"
14690 .row &%daemon_startup_retries%& "number of times to retry"
14691 .row &%daemon_startup_sleep%& "time to sleep between tries"
14692 .row &%extra_local_interfaces%& "not necessarily listened on"
14693 .row &%local_interfaces%& "on which to listen, with optional ports"
14694 .row &%notifier_socket%& "override compiled-in value"
14695 .row &%pid_file_path%& "override compiled-in value"
14696 .row &%queue_run_max%& "maximum simultaneous queue runners"
14701 .section "Resource control" "SECID105"
14703 .row &%check_log_inodes%& "before accepting a message"
14704 .row &%check_log_space%& "before accepting a message"
14705 .row &%check_spool_inodes%& "before accepting a message"
14706 .row &%check_spool_space%& "before accepting a message"
14707 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14708 .row &%queue_only_load%& "queue incoming if load high"
14709 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14710 .row &%queue_run_max%& "maximum simultaneous queue runners"
14711 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14712 .row &%smtp_accept_max%& "simultaneous incoming connections"
14713 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14714 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14715 .row &%smtp_accept_max_per_connection%& "messages per connection"
14716 .row &%smtp_accept_max_per_host%& "connections from one host"
14717 .row &%smtp_accept_queue%& "queue mail if more connections"
14718 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14720 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14721 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14722 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14723 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14724 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14729 .section "Policy controls" "SECID106"
14731 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14732 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14733 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14734 .row &%acl_smtp_auth%& "ACL for AUTH"
14735 .row &%acl_smtp_connect%& "ACL for connection"
14736 .row &%acl_smtp_data%& "ACL for DATA"
14737 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14738 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14739 .row &%acl_smtp_etrn%& "ACL for ETRN"
14740 .row &%acl_smtp_expn%& "ACL for EXPN"
14741 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14742 .row &%acl_smtp_mail%& "ACL for MAIL"
14743 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14744 .row &%acl_smtp_mime%& "ACL for MIME parts"
14745 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14746 .row &%acl_smtp_predata%& "ACL for start of data"
14747 .row &%acl_smtp_quit%& "ACL for QUIT"
14748 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14749 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14750 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14751 .row &%av_scanner%& "specify virus scanner"
14752 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14754 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14755 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14756 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14757 .row &%header_maxsize%& "total size of message header"
14758 .row &%header_line_maxsize%& "individual header line limit"
14759 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14760 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14761 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14762 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14763 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14764 .row &%host_lookup%& "host name looked up for these hosts"
14765 .row &%host_lookup_order%& "order of DNS and local name lookups"
14766 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14767 .row &%host_reject_connection%& "reject connection from these hosts"
14768 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14769 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14770 .row &%message_size_limit%& "for all messages"
14771 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14772 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14773 .row &%spamd_address%& "set interface to SpamAssassin"
14774 .row &%strict_acl_vars%& "object to unset ACL variables"
14775 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14780 .section "Callout cache" "SECID107"
14782 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14784 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14786 .row &%callout_negative_expire%& "timeout for negative address cache item"
14787 .row &%callout_positive_expire%& "timeout for positive address cache item"
14788 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14793 .section "TLS" "SECID108"
14795 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14796 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14797 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14798 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14799 .row &%tls_certificate%& "location of server certificate"
14800 .row &%tls_crl%& "certificate revocation list"
14801 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14802 .row &%tls_dhparam%& "DH parameters for server"
14803 .row &%tls_eccurve%& "EC curve selection for server"
14804 .row &%tls_ocsp_file%& "location of server certificate status proof"
14805 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14806 .row &%tls_privatekey%& "location of server private key"
14807 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14808 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14809 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14810 .row &%tls_verify_certificates%& "expected client certificates"
14811 .row &%tls_verify_hosts%& "insist on client certificate verify"
14816 .section "Local user handling" "SECID109"
14818 .row &%finduser_retries%& "useful in NIS environments"
14819 .row &%gecos_name%& "used when creating &'Sender:'&"
14820 .row &%gecos_pattern%& "ditto"
14821 .row &%max_username_length%& "for systems that truncate"
14822 .row &%unknown_login%& "used when no login name found"
14823 .row &%unknown_username%& "ditto"
14824 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14825 .row &%uucp_from_sender%& "ditto"
14830 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14832 .row &%header_maxsize%& "total size of message header"
14833 .row &%header_line_maxsize%& "individual header line limit"
14834 .row &%message_size_limit%& "applies to all messages"
14835 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14836 .row &%received_header_text%& "expanded to make &'Received:'&"
14837 .row &%received_headers_max%& "for mail loop detection"
14838 .row &%recipients_max%& "limit per message"
14839 .row &%recipients_max_reject%& "permanently reject excess recipients"
14845 .section "Non-SMTP incoming messages" "SECID111"
14847 .row &%receive_timeout%& "for non-SMTP messages"
14854 .section "Incoming SMTP messages" "SECID112"
14855 See also the &'Policy controls'& section above.
14858 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14859 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14860 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14861 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14862 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14863 .row &%dmarc_history_file%& "DMARC results log"
14864 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14865 .row &%host_lookup%& "host name looked up for these hosts"
14866 .row &%host_lookup_order%& "order of DNS and local name lookups"
14867 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14868 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14869 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14870 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14871 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14872 .row &%smtp_accept_max%& "simultaneous incoming connections"
14873 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14874 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14875 .row &%smtp_accept_max_per_connection%& "messages per connection"
14876 .row &%smtp_accept_max_per_host%& "connections from one host"
14877 .row &%smtp_accept_queue%& "queue mail if more connections"
14878 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14880 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14881 .row &%smtp_active_hostname%& "host name to use in messages"
14882 .row &%smtp_banner%& "text for welcome banner"
14883 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14884 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14885 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14886 .row &%smtp_etrn_command%& "what to run for ETRN"
14887 .row &%smtp_etrn_serialize%& "only one at once"
14888 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14889 .row &%smtp_max_unknown_commands%& "before dropping connection"
14890 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14891 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14892 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14893 .row &%smtp_receive_timeout%& "per command or data line"
14894 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14895 .row &%smtp_return_error_details%& "give detail on rejections"
14900 .section "SMTP extensions" "SECID113"
14902 .row &%accept_8bitmime%& "advertise 8BITMIME"
14903 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14904 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14905 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14906 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14907 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14908 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14909 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14910 .row &%prdr_enable%& "advertise PRDR to all hosts"
14911 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14912 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14917 .section "Processing messages" "SECID114"
14919 .row &%allow_domain_literals%& "recognize domain literal syntax"
14920 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14921 .row &%allow_utf8_domains%& "in addresses"
14922 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14924 .row &%delivery_date_remove%& "from incoming messages"
14925 .row &%envelope_to_remove%& "from incoming messages"
14926 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14927 .row &%headers_charset%& "default for translations"
14928 .row &%qualify_domain%& "default for senders"
14929 .row &%qualify_recipient%& "default for recipients"
14930 .row &%return_path_remove%& "from incoming messages"
14931 .row &%strip_excess_angle_brackets%& "in addresses"
14932 .row &%strip_trailing_dot%& "at end of addresses"
14933 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14938 .section "System filter" "SECID115"
14940 .row &%system_filter%& "locate system filter"
14941 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14943 .row &%system_filter_file_transport%& "transport for delivery to a file"
14944 .row &%system_filter_group%& "group for filter running"
14945 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14946 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14947 .row &%system_filter_user%& "user for filter running"
14952 .section "Routing and delivery" "SECID116"
14954 .row &%disable_ipv6%& "do no IPv6 processing"
14955 .row &%dns_again_means_nonexist%& "for broken domains"
14956 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14957 .row &%dns_dnssec_ok%& "parameter for resolver"
14958 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14959 .row &%dns_retrans%& "parameter for resolver"
14960 .row &%dns_retry%& "parameter for resolver"
14961 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14962 .row &%dns_use_edns0%& "parameter for resolver"
14963 .row &%hold_domains%& "hold delivery for these domains"
14964 .row &%local_interfaces%& "for routing checks"
14965 .row &%queue_domains%& "no immediate delivery for these"
14966 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14967 .row &%queue_only%& "no immediate delivery at all"
14968 .row &%queue_only_file%& "no immediate delivery if file exists"
14969 .row &%queue_only_load%& "no immediate delivery if load is high"
14970 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14971 .row &%queue_only_override%& "allow command line to override"
14972 .row &%queue_run_in_order%& "order of arrival"
14973 .row &%queue_run_max%& "of simultaneous queue runners"
14974 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14975 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14976 .row &%remote_sort_domains%& "order of remote deliveries"
14977 .row &%retry_data_expire%& "timeout for retry data"
14978 .row &%retry_interval_max%& "safety net for retry rules"
14983 .section "Bounce and warning messages" "SECID117"
14985 .row &%bounce_message_file%& "content of bounce"
14986 .row &%bounce_message_text%& "content of bounce"
14987 .row &%bounce_return_body%& "include body if returning message"
14988 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14989 .row &%bounce_return_message%& "include original message in bounce"
14990 .row &%bounce_return_size_limit%& "limit on returned message"
14991 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14992 .row &%dsn_from%& "set &'From:'& contents in bounces"
14993 .row &%errors_copy%& "copy bounce messages"
14994 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14995 .row &%delay_warning%& "time schedule"
14996 .row &%delay_warning_condition%& "condition for warning messages"
14997 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14998 .row &%smtp_return_error_details%& "give detail on rejections"
14999 .row &%warn_message_file%& "content of warning message"
15004 .section "Alphabetical list of main options" "SECTalomo"
15005 Those options that undergo string expansion before use are marked with
15008 .option accept_8bitmime main boolean true
15010 .cindex "8-bit characters"
15011 .cindex "log" "selectors"
15012 .cindex "log" "8BITMIME"
15013 .cindex "ESMTP extensions" 8BITMIME
15014 This option causes Exim to send 8BITMIME in its response to an SMTP
15015 EHLO command, and to accept the BODY= parameter on MAIL commands.
15016 However, though Exim is 8-bit clean, it is not a protocol converter, and it
15017 takes no steps to do anything special with messages received by this route.
15019 Historically Exim kept this option off by default, but the maintainers
15020 feel that in today's Internet, this causes more problems than it solves.
15021 It now defaults to true.
15022 A more detailed analysis of the issues is provided by Dan Bernstein:
15024 &url(https://cr.yp.to/smtp/8bitmime.html)
15027 To log received 8BITMIME status use
15029 log_selector = +8bitmime
15032 .option acl_not_smtp main string&!! unset
15033 .cindex "&ACL;" "for non-SMTP messages"
15034 .cindex "non-SMTP messages" "ACLs for"
15035 This option defines the ACL that is run when a non-SMTP message has been
15036 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15039 .option acl_not_smtp_mime main string&!! unset
15040 This option defines the ACL that is run for individual MIME parts of non-SMTP
15041 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15044 .option acl_not_smtp_start main string&!! unset
15045 .cindex "&ACL;" "at start of non-SMTP message"
15046 .cindex "non-SMTP messages" "ACLs for"
15047 This option defines the ACL that is run before Exim starts reading a
15048 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15050 .option acl_smtp_auth main string&!! unset
15051 .cindex "&ACL;" "setting up for SMTP commands"
15052 .cindex "AUTH" "ACL for"
15053 This option defines the ACL that is run when an SMTP AUTH command is
15054 received. See chapter &<<CHAPACL>>& for further details.
15056 .option acl_smtp_connect main string&!! unset
15057 .cindex "&ACL;" "on SMTP connection"
15058 This option defines the ACL that is run when an SMTP connection is received.
15059 See chapter &<<CHAPACL>>& for further details.
15061 .option acl_smtp_data main string&!! unset
15062 .cindex "DATA" "ACL for"
15063 This option defines the ACL that is run after an SMTP DATA command has been
15064 processed and the message itself has been received, but before the final
15065 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15067 .option acl_smtp_data_prdr main string&!! accept
15068 .cindex "PRDR" "ACL for"
15069 .cindex "DATA" "PRDR ACL for"
15070 .cindex "&ACL;" "PRDR-related"
15071 .cindex "&ACL;" "per-user data processing"
15072 This option defines the ACL that,
15073 if the PRDR feature has been negotiated,
15074 is run for each recipient after an SMTP DATA command has been
15075 processed and the message itself has been received, but before the
15076 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15078 .option acl_smtp_dkim main string&!! unset
15079 .cindex DKIM "ACL for"
15080 This option defines the ACL that is run for each DKIM signature
15081 (by default, or as specified in the dkim_verify_signers option)
15082 of a received message.
15083 See section &<<SECDKIMVFY>>& for further details.
15085 .option acl_smtp_etrn main string&!! unset
15086 .cindex "ETRN" "ACL for"
15087 This option defines the ACL that is run when an SMTP ETRN command is
15088 received. See chapter &<<CHAPACL>>& for further details.
15090 .option acl_smtp_expn main string&!! unset
15091 .cindex "EXPN" "ACL for"
15092 This option defines the ACL that is run when an SMTP EXPN command is
15093 received. See chapter &<<CHAPACL>>& for further details.
15095 .option acl_smtp_helo main string&!! unset
15096 .cindex "EHLO" "ACL for"
15097 .cindex "HELO" "ACL for"
15098 This option defines the ACL that is run when an SMTP EHLO or HELO
15099 command is received. See chapter &<<CHAPACL>>& for further details.
15102 .option acl_smtp_mail main string&!! unset
15103 .cindex "MAIL" "ACL for"
15104 This option defines the ACL that is run when an SMTP MAIL command is
15105 received. See chapter &<<CHAPACL>>& for further details.
15107 .option acl_smtp_mailauth main string&!! unset
15108 .cindex "AUTH" "on MAIL command"
15109 This option defines the ACL that is run when there is an AUTH parameter on
15110 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15111 &<<CHAPSMTPAUTH>>& for details of authentication.
15113 .option acl_smtp_mime main string&!! unset
15114 .cindex "MIME content scanning" "ACL for"
15115 This option is available when Exim is built with the content-scanning
15116 extension. It defines the ACL that is run for each MIME part in a message. See
15117 section &<<SECTscanmimepart>>& for details.
15119 .option acl_smtp_notquit main string&!! unset
15120 .cindex "not-QUIT, ACL for"
15121 This option defines the ACL that is run when an SMTP session
15122 ends without a QUIT command being received.
15123 See chapter &<<CHAPACL>>& for further details.
15125 .option acl_smtp_predata main string&!! unset
15126 This option defines the ACL that is run when an SMTP DATA command is
15127 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15130 .option acl_smtp_quit main string&!! unset
15131 .cindex "QUIT, ACL for"
15132 This option defines the ACL that is run when an SMTP QUIT command is
15133 received. See chapter &<<CHAPACL>>& for further details.
15135 .option acl_smtp_rcpt main string&!! unset
15136 .cindex "RCPT" "ACL for"
15137 This option defines the ACL that is run when an SMTP RCPT command is
15138 received. See chapter &<<CHAPACL>>& for further details.
15140 .option acl_smtp_starttls main string&!! unset
15141 .cindex "STARTTLS, ACL for"
15142 This option defines the ACL that is run when an SMTP STARTTLS command is
15143 received. See chapter &<<CHAPACL>>& for further details.
15145 .option acl_smtp_vrfy main string&!! unset
15146 .cindex "VRFY" "ACL for"
15147 This option defines the ACL that is run when an SMTP VRFY command is
15148 received. See chapter &<<CHAPACL>>& for further details.
15150 .option add_environment main "string list" empty
15151 .cindex "environment" "set values"
15152 This option adds individual environment variables that the
15153 currently linked libraries and programs in child processes may use.
15154 Each list element should be of the form &"name=value"&.
15156 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15158 .option admin_groups main "string list&!!" unset
15159 .cindex "admin user"
15160 This option is expanded just once, at the start of Exim's processing. If the
15161 current group or any of the supplementary groups of an Exim caller is in this
15162 colon-separated list, the caller has admin privileges. If all your system
15163 programmers are in a specific group, for example, you can give them all Exim
15164 admin privileges by putting that group in &%admin_groups%&. However, this does
15165 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15166 To permit this, you have to add individuals to the Exim group.
15168 .option allow_domain_literals main boolean false
15169 .cindex "domain literal"
15170 If this option is set, the RFC 2822 domain literal format is permitted in
15171 email addresses. The option is not set by default, because the domain literal
15172 format is not normally required these days, and few people know about it. It
15173 has, however, been exploited by mail abusers.
15175 Unfortunately, it seems that some DNS black list maintainers are using this
15176 format to report black listing to postmasters. If you want to accept messages
15177 addressed to your hosts by IP address, you need to set
15178 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15179 domains (defined in the named domain list &%local_domains%& in the default
15180 configuration). This &"magic string"& matches the domain literal form of all
15181 the local host's IP addresses.
15184 .option allow_mx_to_ip main boolean false
15185 .cindex "MX record" "pointing to IP address"
15186 It appears that more and more DNS zone administrators are breaking the rules
15187 and putting domain names that look like IP addresses on the right hand side of
15188 MX records. Exim follows the rules and rejects this, giving an error message
15189 that explains the misconfiguration. However, some other MTAs support this
15190 practice, so to avoid &"Why can't Exim do this?"& complaints,
15191 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15192 recommended, except when you have no other choice.
15194 .option allow_utf8_domains main boolean false
15195 .cindex "domain" "UTF-8 characters in"
15196 .cindex "UTF-8" "in domain name"
15197 Lots of discussion is going on about internationalized domain names. One
15198 camp is strongly in favour of just using UTF-8 characters, and it seems
15199 that at least two other MTAs permit this.
15200 This option allows Exim users to experiment if they wish.
15202 If it is set true, Exim's domain parsing function allows valid
15203 UTF-8 multicharacters to appear in domain name components, in addition to
15204 letters, digits, and hyphens.
15206 If Exim is built with internationalization support
15207 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15208 this option can be left as default.
15210 if you want to look up such domain names in the DNS, you must also
15211 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15212 suitable setting is:
15214 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15215 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15217 Alternatively, you can just disable this feature by setting
15219 dns_check_names_pattern =
15221 That is, set the option to an empty string so that no check is done.
15224 .option auth_advertise_hosts main "host list&!!" *
15225 .cindex "authentication" "advertising"
15226 .cindex "AUTH" "advertising"
15227 .cindex "ESMTP extensions" AUTH
15228 If any server authentication mechanisms are configured, Exim advertises them in
15229 response to an EHLO command only if the calling host matches this list.
15230 Otherwise, Exim does not advertise AUTH.
15231 Exim does not accept AUTH commands from clients to which it has not
15232 advertised the availability of AUTH. The advertising of individual
15233 authentication mechanisms can be controlled by the use of the
15234 &%server_advertise_condition%& generic authenticator option on the individual
15235 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15237 Certain mail clients (for example, Netscape) require the user to provide a name
15238 and password for authentication if AUTH is advertised, even though it may
15239 not be needed (the host may accept messages from hosts on its local LAN without
15240 authentication, for example). The &%auth_advertise_hosts%& option can be used
15241 to make these clients more friendly by excluding them from the set of hosts to
15242 which Exim advertises AUTH.
15244 .cindex "AUTH" "advertising when encrypted"
15245 If you want to advertise the availability of AUTH only when the connection
15246 is encrypted using TLS, you can make use of the fact that the value of this
15247 option is expanded, with a setting like this:
15249 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15251 .vindex "&$tls_in_cipher$&"
15252 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15253 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15254 expansion is *, which matches all hosts.
15257 .option auto_thaw main time 0s
15258 .cindex "thawing messages"
15259 .cindex "unfreezing messages"
15260 If this option is set to a time greater than zero, a queue runner will try a
15261 new delivery attempt on any frozen message, other than a bounce message, if
15262 this much time has passed since it was frozen. This may result in the message
15263 being re-frozen if nothing has changed since the last attempt. It is a way of
15264 saying &"keep on trying, even though there are big problems"&.
15266 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15267 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15268 thought to be very useful any more, and its use should probably be avoided.
15271 .option av_scanner main string "see below"
15272 This option is available if Exim is built with the content-scanning extension.
15273 It specifies which anti-virus scanner to use. The default value is:
15275 sophie:/var/run/sophie
15277 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15278 before use. See section &<<SECTscanvirus>>& for further details.
15281 .option bi_command main string unset
15283 This option supplies the name of a command that is run when Exim is called with
15284 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15285 just the command name, it is not a complete command line. If an argument is
15286 required, it must come from the &%-oA%& command line option.
15289 .option bounce_message_file main string&!! unset
15290 .cindex "bounce message" "customizing"
15291 .cindex "customizing" "bounce message"
15292 This option defines a template file containing paragraphs of text to be used
15293 for constructing bounce messages. Details of the file's contents are given in
15294 chapter &<<CHAPemsgcust>>&.
15295 .cindex bounce_message_file "tainted data"
15296 The option is expanded to give the file path, which must be
15297 absolute and untainted.
15298 See also &%warn_message_file%&.
15301 .option bounce_message_text main string unset
15302 When this option is set, its contents are included in the default bounce
15303 message immediately after &"This message was created automatically by mail
15304 delivery software."& It is not used if &%bounce_message_file%& is set.
15306 .option bounce_return_body main boolean true
15307 .cindex "bounce message" "including body"
15308 This option controls whether the body of an incoming message is included in a
15309 bounce message when &%bounce_return_message%& is true. The default setting
15310 causes the entire message, both header and body, to be returned (subject to the
15311 value of &%bounce_return_size_limit%&). If this option is false, only the
15312 message header is included. In the case of a non-SMTP message containing an
15313 error that is detected during reception, only those header lines preceding the
15314 point at which the error was detected are returned.
15315 .cindex "bounce message" "including original"
15317 .option bounce_return_linesize_limit main integer 998
15318 .cindex "size" "of bounce lines, limit"
15319 .cindex "bounce message" "line length limit"
15320 .cindex "limit" "bounce message line length"
15321 This option sets a limit in bytes on the line length of messages
15322 that are returned to senders due to delivery problems,
15323 when &%bounce_return_message%& is true.
15324 The default value corresponds to RFC limits.
15325 If the message being returned has lines longer than this value it is
15326 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15328 The option also applies to bounces returned when an error is detected
15329 during reception of a message.
15330 In this case lines from the original are truncated.
15332 The option does not apply to messages generated by an &(autoreply)& transport.
15335 .option bounce_return_message main boolean true
15336 If this option is set false, none of the original message is included in
15337 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15338 &%bounce_return_body%&.
15341 .option bounce_return_size_limit main integer 100K
15342 .cindex "size" "of bounce, limit"
15343 .cindex "bounce message" "size limit"
15344 .cindex "limit" "bounce message size"
15345 This option sets a limit in bytes on the size of messages that are returned to
15346 senders as part of bounce messages when &%bounce_return_message%& is true. The
15347 limit should be less than the value of the global &%message_size_limit%& and of
15348 any &%message_size_limit%& settings on transports, to allow for the bounce text
15349 that Exim generates. If this option is set to zero there is no limit.
15351 When the body of any message that is to be included in a bounce message is
15352 greater than the limit, it is truncated, and a comment pointing this out is
15353 added at the top. The actual cutoff may be greater than the value given, owing
15354 to the use of buffering for transferring the message in chunks (typically 8K in
15355 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15358 .option bounce_sender_authentication main string unset
15359 .cindex "bounce message" "sender authentication"
15360 .cindex "authentication" "bounce message"
15361 .cindex "AUTH" "on bounce message"
15362 This option provides an authenticated sender address that is sent with any
15363 bounce messages generated by Exim that are sent over an authenticated SMTP
15364 connection. A typical setting might be:
15366 bounce_sender_authentication = mailer-daemon@my.domain.example
15368 which would cause bounce messages to be sent using the SMTP command:
15370 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15372 The value of &%bounce_sender_authentication%& must always be a complete email
15375 .option callout_domain_negative_expire main time 3h
15376 .cindex "caching" "callout timeouts"
15377 .cindex "callout" "caching timeouts"
15378 This option specifies the expiry time for negative callout cache data for a
15379 domain. See section &<<SECTcallver>>& for details of callout verification, and
15380 section &<<SECTcallvercache>>& for details of the caching.
15383 .option callout_domain_positive_expire main time 7d
15384 This option specifies the expiry time for positive callout cache data for a
15385 domain. See section &<<SECTcallver>>& for details of callout verification, and
15386 section &<<SECTcallvercache>>& for details of the caching.
15389 .option callout_negative_expire main time 2h
15390 This option specifies the expiry time for negative callout cache data for an
15391 address. See section &<<SECTcallver>>& for details of callout verification, and
15392 section &<<SECTcallvercache>>& for details of the caching.
15395 .option callout_positive_expire main time 24h
15396 This option specifies the expiry time for positive callout cache data for an
15397 address. See section &<<SECTcallver>>& for details of callout verification, and
15398 section &<<SECTcallvercache>>& for details of the caching.
15401 .option callout_random_local_part main string&!! "see below"
15402 This option defines the &"random"& local part that can be used as part of
15403 callout verification. The default value is
15405 $primary_hostname-$tod_epoch-testing
15407 See section &<<CALLaddparcall>>& for details of how this value is used.
15410 .option check_log_inodes main integer 100
15411 See &%check_spool_space%& below.
15414 .option check_log_space main integer 10M
15415 See &%check_spool_space%& below.
15417 .oindex "&%check_rfc2047_length%&"
15418 .cindex "RFC 2047" "disabling length check"
15419 .option check_rfc2047_length main boolean true
15420 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15421 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15422 word; strings to be encoded that exceed this length are supposed to use
15423 multiple encoded words. By default, Exim does not recognize encoded words that
15424 exceed the maximum length. However, it seems that some software, in violation
15425 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15426 set false, Exim recognizes encoded words of any length.
15429 .option check_spool_inodes main integer 100
15430 See &%check_spool_space%& below.
15433 .option check_spool_space main integer 10M
15434 .cindex "checking disk space"
15435 .cindex "disk space, checking"
15436 .cindex "spool directory" "checking space"
15437 The four &%check_...%& options allow for checking of disk resources before a
15438 message is accepted.
15440 .vindex "&$log_inodes$&"
15441 .vindex "&$log_space$&"
15442 .vindex "&$spool_inodes$&"
15443 .vindex "&$spool_space$&"
15444 When any of these options are nonzero, they apply to all incoming messages. If you
15445 want to apply different checks to different kinds of message, you can do so by
15446 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15447 &$spool_space$& in an ACL with appropriate additional conditions.
15450 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15451 either value is greater than zero, for example:
15453 check_spool_space = 100M
15454 check_spool_inodes = 100
15456 The spool partition is the one that contains the directory defined by
15457 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15460 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15461 files are written if either is greater than zero. These should be set only if
15462 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15464 If there is less space or fewer inodes than requested, Exim refuses to accept
15465 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15466 error response to the MAIL command. If ESMTP is in use and there was a
15467 SIZE parameter on the MAIL command, its value is added to the
15468 &%check_spool_space%& value, and the check is performed even if
15469 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15471 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15472 number of kilobytes (though specified in bytes).
15473 If a non-multiple of 1024 is specified, it is rounded up.
15475 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15476 failure a message is written to stderr and Exim exits with a non-zero code, as
15477 it obviously cannot send an error message of any kind.
15479 There is a slight performance penalty for these checks.
15480 Versions of Exim preceding 4.88 had these disabled by default;
15481 high-rate installations confident they will never run out of resources
15482 may wish to deliberately disable them.
15484 .option chunking_advertise_hosts main "host list&!!" *
15485 .cindex CHUNKING advertisement
15486 .cindex "RFC 3030" "CHUNKING"
15487 .cindex "ESMTP extensions" CHUNKING
15488 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15490 Hosts may use the BDAT command as an alternate to DATA.
15492 .option commandline_checks_require_admin main boolean &`false`&
15493 .cindex "restricting access to features"
15494 This option restricts various basic checking features to require an
15495 administrative user.
15496 This affects most of the &%-b*%& options, such as &%-be%&.
15498 .option debug_store main boolean &`false`&
15499 .cindex debugging "memory corruption"
15500 .cindex memory debugging
15501 This option, when true, enables extra checking in Exim's internal memory
15502 management. For use when a memory corruption issue is being investigated,
15503 it should normally be left as default.
15505 .option daemon_smtp_ports main string &`smtp`&
15506 .cindex "port" "for daemon"
15507 .cindex "TCP/IP" "setting listening ports"
15508 This option specifies one or more default SMTP ports on which the Exim daemon
15509 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15510 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15512 .option daemon_startup_retries main integer 9
15513 .cindex "daemon startup, retrying"
15514 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15515 the daemon at startup when it cannot immediately bind a listening socket
15516 (typically because the socket is already in use): &%daemon_startup_retries%&
15517 defines the number of retries after the first failure, and
15518 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15520 .option daemon_startup_sleep main time 30s
15521 See &%daemon_startup_retries%&.
15523 .option delay_warning main "time list" 24h
15524 .cindex "warning of delay"
15525 .cindex "delay warning, specifying"
15526 .cindex "queue" "delay warning"
15527 When a message is delayed, Exim sends a warning message to the sender at
15528 intervals specified by this option. The data is a colon-separated list of times
15529 after which to send warning messages. If the value of the option is an empty
15530 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15531 message has been in the queue for longer than the last time, the last interval
15532 between the times is used to compute subsequent warning times. For example,
15535 delay_warning = 4h:8h:24h
15537 the first message is sent after 4 hours, the second after 8 hours, and
15538 the third one after 24 hours. After that, messages are sent every 16 hours,
15539 because that is the interval between the last two times on the list. If you set
15540 just one time, it specifies the repeat interval. For example, with:
15544 messages are repeated every six hours. To stop warnings after a given time, set
15545 a very large time at the end of the list. For example:
15547 delay_warning = 2h:12h:99d
15549 Note that the option is only evaluated at the time a delivery attempt fails,
15550 which depends on retry and queue-runner configuration.
15551 Typically retries will be configured more frequently than warning messages.
15553 .option delay_warning_condition main string&!! "see below"
15554 .vindex "&$domain$&"
15555 The string is expanded at the time a warning message might be sent. If all the
15556 deferred addresses have the same domain, it is set in &$domain$& during the
15557 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15558 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15559 &"false"& (the comparison being done caselessly) then the warning message is
15560 not sent. The default is:
15562 delay_warning_condition = ${if or {\
15563 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15564 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15565 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15568 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15569 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15570 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15571 &"auto-replied"& in an &'Auto-Submitted:'& header.
15573 .option deliver_drop_privilege main boolean false
15574 .cindex "unprivileged delivery"
15575 .cindex "delivery" "unprivileged"
15576 If this option is set true, Exim drops its root privilege at the start of a
15577 delivery process, and runs as the Exim user throughout. This severely restricts
15578 the kinds of local delivery that are possible, but is viable in certain types
15579 of configuration. There is a discussion about the use of root privilege in
15580 chapter &<<CHAPsecurity>>&.
15582 .option deliver_queue_load_max main fixed-point unset
15583 .cindex "load average"
15584 .cindex "queue runner" "abandoning"
15585 When this option is set, a queue run is abandoned if the system load average
15586 becomes greater than the value of the option. The option has no effect on
15587 ancient operating systems on which Exim cannot determine the load average.
15588 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15591 .option delivery_date_remove main boolean true
15592 .cindex "&'Delivery-date:'& header line"
15593 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15594 message when it is delivered, in exactly the same way as &'Return-path:'& is
15595 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15596 should not be present in incoming messages, and this option causes them to be
15597 removed at the time the message is received, to avoid any problems that might
15598 occur when a delivered message is subsequently sent on to some other recipient.
15600 .option disable_fsync main boolean false
15601 .cindex "&[fsync()]&, disabling"
15602 This option is available only if Exim was built with the compile-time option
15603 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15604 a runtime configuration generates an &"unknown option"& error. You should not
15605 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15606 really, really, really understand what you are doing. &'No pre-compiled
15607 distributions of Exim should ever make this option available.'&
15609 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15610 updated files' data to be written to disc before continuing. Unexpected events
15611 such as crashes and power outages may cause data to be lost or scrambled.
15612 Here be Dragons. &*Beware.*&
15615 .option disable_ipv6 main boolean false
15616 .cindex "IPv6" "disabling"
15617 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15618 activities take place. AAAA records are never looked up, and any IPv6 addresses
15619 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15620 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15621 to handle IPv6 literal addresses.
15624 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15625 .cindex DKIM "selecting signature algorithms"
15626 This option gives a list of hash types which are acceptable in signatures,
15627 and an order of processing.
15628 Signatures with algorithms not in the list will be ignored.
15630 Acceptable values include:
15637 Note that the acceptance of sha1 violates RFC 8301.
15639 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15640 This option gives a list of key types which are acceptable in signatures,
15641 and an order of processing.
15642 Signatures with algorithms not in the list will be ignored.
15645 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15646 This option gives a list of key sizes which are acceptable in signatures.
15647 The list is keyed by the algorithm type for the key; the values are in bits.
15648 Signatures with keys smaller than given by this option will fail verification.
15650 The default enforces the RFC 8301 minimum key size for RSA signatures.
15652 .option dkim_verify_minimal main boolean false
15653 If set to true, verification of signatures will terminate after the
15656 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15657 .cindex DKIM "controlling calls to the ACL"
15658 This option gives a list of DKIM domains for which the DKIM ACL is run.
15659 It is expanded after the message is received; by default it runs
15660 the ACL once for each signature in the message.
15661 See section &<<SECDKIMVFY>>&.
15664 .option dmarc_forensic_sender main string&!! unset
15665 .option dmarc_history_file main string unset
15666 .option dmarc_tld_file main string unset
15667 .cindex DMARC "main section options"
15668 These options control DMARC processing.
15669 See section &<<SECDMARC>>& for details.
15672 .option dns_again_means_nonexist main "domain list&!!" unset
15673 .cindex "DNS" "&""try again""& response; overriding"
15674 DNS lookups give a &"try again"& response for the DNS errors
15675 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15676 keep trying to deliver a message, or to give repeated temporary errors to
15677 incoming mail. Sometimes the effect is caused by a badly set up name server and
15678 may persist for a long time. If a domain which exhibits this problem matches
15679 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15680 This option should be used with care. You can make it apply to reverse lookups
15681 by a setting such as this:
15683 dns_again_means_nonexist = *.in-addr.arpa
15685 This option applies to all DNS lookups that Exim does. It also applies when the
15686 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15687 since these are most likely to be caused by DNS lookup problems. The
15688 &(dnslookup)& router has some options of its own for controlling what happens
15689 when lookups for MX or SRV records give temporary errors. These more specific
15690 options are applied after this global option.
15692 .option dns_check_names_pattern main string "see below"
15693 .cindex "DNS" "pre-check of name syntax"
15694 When this option is set to a non-empty string, it causes Exim to check domain
15695 names for characters that are not allowed in host names before handing them to
15696 the DNS resolver, because some resolvers give temporary errors for names that
15697 contain unusual characters. If a domain name contains any unwanted characters,
15698 a &"not found"& result is forced, and the resolver is not called. The check is
15699 done by matching the domain name against a regular expression, which is the
15700 value of this option. The default pattern is
15702 dns_check_names_pattern = \
15703 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15705 which permits only letters, digits, slashes, and hyphens in components, but
15706 they must start and end with a letter or digit. Slashes are not, in fact,
15707 permitted in host names, but they are found in certain NS records (which can be
15708 accessed in Exim by using a &%dnsdb%& lookup). If you set
15709 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15712 .option dns_csa_search_limit main integer 5
15713 This option controls the depth of parental searching for CSA SRV records in the
15714 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15716 .option dns_csa_use_reverse main boolean true
15717 This option controls whether or not an IP address, given as a CSA domain, is
15718 reversed and looked up in the reverse DNS, as described in more detail in
15719 section &<<SECTverifyCSA>>&.
15721 .option dns_cname_loops main integer 1
15722 .cindex DNS "CNAME following"
15723 This option controls the following of CNAME chains, needed if the resolver does
15724 not do it internally.
15725 As of 2018 most should, and the default can be left.
15726 If you have an ancient one, a value of 10 is likely needed.
15728 The default value of one CNAME-follow is needed
15729 thanks to the observed return for an MX request,
15730 given no MX presence but a CNAME to an A, of the CNAME.
15733 .option dns_dnssec_ok main integer -1
15734 .cindex "DNS" "resolver options"
15735 .cindex "DNS" "DNSSEC"
15736 If this option is set to a non-negative number then Exim will initialise the
15737 DNS resolver library to either use or not use DNSSEC, overriding the system
15738 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15740 If the resolver library does not support DNSSEC then this option has no effect.
15742 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15743 will default to stripping out a successful validation status.
15744 This will break a previously working Exim installation.
15745 Provided that you do trust the resolver (ie, is on localhost) you can tell
15746 glibc to pass through any successful validation with a new option in
15747 &_/etc/resolv.conf_&:
15753 .option dns_ipv4_lookup main "domain list&!!" unset
15754 .cindex "IPv6" "DNS lookup for AAAA records"
15755 .cindex "DNS" "IPv6 lookup for AAAA records"
15756 .cindex DNS "IPv6 disabling"
15757 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15758 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15759 (A records) when trying to find IP addresses for hosts, unless the host's
15760 domain matches this list.
15762 This is a fudge to help with name servers that give big delays or otherwise do
15763 not work for the AAAA record type. In due course, when the world's name
15764 servers have all been upgraded, there should be no need for this option.
15765 Note that all lookups, including those done for verification, are affected;
15766 this will result in verify failure for IPv6 connections or ones using names
15767 only valid for IPv6 addresses.
15770 .option dns_retrans main time 0s
15771 .cindex "DNS" "resolver options"
15772 .cindex timeout "dns lookup"
15773 .cindex "DNS" timeout
15774 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15775 retransmission and retry parameters for DNS lookups. Values of zero (the
15776 defaults) leave the system default settings unchanged. The first value is the
15777 time between retries, and the second is the number of retries. It isn't
15778 totally clear exactly how these settings affect the total time a DNS lookup may
15779 take. I haven't found any documentation about timeouts on DNS lookups; these
15780 parameter values are available in the external resolver interface structure,
15781 but nowhere does it seem to describe how they are used or what you might want
15783 See also the &%slow_lookup_log%& option.
15786 .option dns_retry main integer 0
15787 See &%dns_retrans%& above.
15790 .option dns_trust_aa main "domain list&!!" unset
15791 .cindex "DNS" "resolver options"
15792 .cindex "DNS" "DNSSEC"
15793 If this option is set then lookup results marked with the AA bit
15794 (Authoritative Answer) are trusted the same way as if they were
15795 DNSSEC-verified. The authority section's name of the answer must
15796 match with this expanded domain list.
15798 Use this option only if you talk directly to a resolver that is
15799 authoritative for some zones and does not set the AD (Authentic Data)
15800 bit in the answer. Some DNS servers may have an configuration option to
15801 mark the answers from their own zones as verified (they set the AD bit).
15802 Others do not have this option. It is considered as poor practice using
15803 a resolver that is an authoritative server for some zones.
15805 Use this option only if you really have to (e.g. if you want
15806 to use DANE for remote delivery to a server that is listed in the DNS
15807 zones that your resolver is authoritative for).
15809 If the DNS answer packet has the AA bit set and contains resource record
15810 in the answer section, the name of the first NS record appearing in the
15811 authority section is compared against the list. If the answer packet is
15812 authoritative but the answer section is empty, the name of the first SOA
15813 record in the authoritative section is used instead.
15815 .cindex "DNS" "resolver options"
15816 .option dns_use_edns0 main integer -1
15817 .cindex "DNS" "resolver options"
15818 .cindex "DNS" "EDNS0"
15819 .cindex "DNS" "OpenBSD
15820 If this option is set to a non-negative number then Exim will initialise the
15821 DNS resolver library to either use or not use EDNS0 extensions, overriding
15822 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15825 If the resolver library does not support EDNS0 then this option has no effect.
15827 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15828 means that DNSSEC will not work with Exim on that platform either, unless Exim
15829 is linked against an alternative DNS client library.
15832 .option drop_cr main boolean false
15833 This is an obsolete option that is now a no-op. It used to affect the way Exim
15834 handled CR and LF characters in incoming messages. What happens now is
15835 described in section &<<SECTlineendings>>&.
15837 .option dsn_advertise_hosts main "host list&!!" unset
15838 .cindex "bounce messages" "success"
15839 .cindex "DSN" "success"
15840 .cindex "Delivery Status Notification" "success"
15841 .cindex "ESMTP extensions" DSN
15842 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15843 and accepted from, these hosts.
15844 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15845 and RET and ORCPT options on MAIL FROM commands.
15846 A NOTIFY=SUCCESS option requests success-DSN messages.
15847 A NOTIFY= option with no argument requests that no delay or failure DSNs
15849 &*Note*&: Supplying success-DSN messages has been criticised
15850 on privacy grounds; it can leak details of internal forwarding.
15852 .option dsn_from main "string&!!" "see below"
15853 .cindex "&'From:'& header line" "in bounces"
15854 .cindex "bounce messages" "&'From:'& line, specifying"
15855 This option can be used to vary the contents of &'From:'& header lines in
15856 bounces and other automatically generated messages (&"Delivery Status
15857 Notifications"& &-- hence the name of the option). The default setting is:
15859 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15861 The value is expanded every time it is needed. If the expansion fails, a
15862 panic is logged, and the default value is used.
15864 .option envelope_to_remove main boolean true
15865 .cindex "&'Envelope-to:'& header line"
15866 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15867 message when it is delivered, in exactly the same way as &'Return-path:'& is
15868 handled. &'Envelope-to:'& records the original recipient address from the
15869 message's envelope that caused the delivery to happen. Such headers should not
15870 be present in incoming messages, and this option causes them to be removed at
15871 the time the message is received, to avoid any problems that might occur when a
15872 delivered message is subsequently sent on to some other recipient.
15875 .option errors_copy main "string list&!!" unset
15876 .cindex "bounce message" "copy to other address"
15877 .cindex "copy of bounce message"
15878 Setting this option causes Exim to send bcc copies of bounce messages that it
15879 generates to other addresses. &*Note*&: This does not apply to bounce messages
15880 coming from elsewhere. The value of the option is a colon-separated list of
15881 items. Each item consists of a pattern, terminated by white space, followed by
15882 a comma-separated list of email addresses. If a pattern contains spaces, it
15883 must be enclosed in double quotes.
15885 Each pattern is processed in the same way as a single item in an address list
15886 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15887 the bounce message, the message is copied to the addresses on the list. The
15888 items are scanned in order, and once a matching one is found, no further items
15889 are examined. For example:
15891 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15892 rqps@mydomain hostmaster@mydomain.example,\
15893 postmaster@mydomain.example
15895 .vindex "&$domain$&"
15896 .vindex "&$local_part$&"
15897 The address list is expanded before use. The expansion variables &$local_part$&
15898 and &$domain$& are set from the original recipient of the error message, and if
15899 there was any wildcard matching in the pattern, the expansion
15900 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15901 variables &$0$&, &$1$&, etc. are set in the normal way.
15904 .option errors_reply_to main string unset
15905 .cindex "bounce message" "&'Reply-to:'& in"
15906 By default, Exim's bounce and delivery warning messages contain the header line
15908 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15910 .oindex &%quota_warn_message%&
15911 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15912 A warning message that is generated by the &%quota_warn_message%& option in an
15913 &(appendfile)& transport may contain its own &'From:'& header line that
15914 overrides the default.
15916 Experience shows that people reply to bounce messages. If the
15917 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15918 and warning messages. For example:
15920 errors_reply_to = postmaster@my.domain.example
15922 The value of the option is not expanded. It must specify a valid RFC 2822
15923 address. However, if a warning message that is generated by the
15924 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15925 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15929 .option event_action main string&!! unset
15931 This option declares a string to be expanded for Exim's events mechanism.
15932 For details see chapter &<<CHAPevents>>&.
15935 .option exim_group main string "compile-time configured"
15936 .cindex "gid (group id)" "Exim's own"
15937 .cindex "Exim group"
15938 This option changes the gid under which Exim runs when it gives up root
15939 privilege. The default value is compiled into the binary. The value of this
15940 option is used only when &%exim_user%& is also set. Unless it consists entirely
15941 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15942 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15946 .option exim_path main string "see below"
15947 .cindex "Exim binary, path name"
15948 This option specifies the path name of the Exim binary, which is used when Exim
15949 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15950 the directory configured at compile time by the BIN_DIRECTORY setting. It
15951 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15953 &*Warning*&: Do not use a macro to define the value of this option, because
15954 you will break those Exim utilities that scan the configuration file to find
15955 where the binary is. (They then use the &%-bP%& option to extract option
15956 settings such as the value of &%spool_directory%&.)
15959 .option exim_user main string "compile-time configured"
15960 .cindex "uid (user id)" "Exim's own"
15961 .cindex "Exim user"
15962 This option changes the uid under which Exim runs when it gives up root
15963 privilege. The default value is compiled into the binary. Ownership of the run
15964 time configuration file and the use of the &%-C%& and &%-D%& command line
15965 options is checked against the values in the binary, not what is set here.
15967 Unless it consists entirely of digits, the string is looked up using
15968 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15969 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15970 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15973 .option exim_version main string "current version"
15974 .cindex "Exim version"
15975 .cindex customizing "version number"
15976 .cindex "version number of Exim" override
15977 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15978 various places. Use with care; this may fool stupid security scanners.
15981 .option extra_local_interfaces main "string list" unset
15982 This option defines network interfaces that are to be considered local when
15983 routing, but which are not used for listening by the daemon. See section
15984 &<<SECTreclocipadd>>& for details.
15987 . Allow this long option name to split; give it unsplit as a fifth argument
15988 . for the automatic .oindex that is generated by .option.
15990 .option "extract_addresses_remove_arguments" main boolean true &&&
15991 extract_addresses_remove_arguments
15993 .cindex "command line" "addresses with &%-t%&"
15994 .cindex "Sendmail compatibility" "&%-t%& option"
15995 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15996 are present on the command line when the &%-t%& option is used to build an
15997 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15998 line addresses are removed from the recipients list. This is also how Smail
15999 behaves. However, other Sendmail documentation (the O'Reilly book) states that
16000 command line addresses are added to those obtained from the header lines. When
16001 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
16002 argument headers. If it is set false, Exim adds rather than removes argument
16006 .option finduser_retries main integer 0
16007 .cindex "NIS, retrying user lookups"
16008 On systems running NIS or other schemes in which user and group information is
16009 distributed from a remote system, there can be times when &[getpwnam()]& and
16010 related functions fail, even when given valid data, because things time out.
16011 Unfortunately these failures cannot be distinguished from genuine &"not found"&
16012 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
16013 many extra times to find a user or a group, waiting for one second between
16016 .cindex "&_/etc/passwd_&" "multiple reading of"
16017 You should not set this option greater than zero if your user information is in
16018 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16019 search the file multiple times for non-existent users, and also cause delay.
16023 .option freeze_tell main "string list, comma separated" unset
16024 .cindex "freezing messages" "sending a message when freezing"
16025 On encountering certain errors, or when configured to do so in a system filter,
16026 ACL, or special router, Exim freezes a message. This means that no further
16027 delivery attempts take place until an administrator thaws the message, or the
16028 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16029 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16030 warning message whenever it freezes something, unless the message it is
16031 freezing is a locally-generated bounce message. (Without this exception there
16032 is the possibility of looping.) The warning message is sent to the addresses
16033 supplied as the comma-separated value of this option. If several of the
16034 message's addresses cause freezing, only a single message is sent. If the
16035 freezing was automatic, the reason(s) for freezing can be found in the message
16036 log. If you configure freezing in a filter or ACL, you must arrange for any
16037 logging that you require.
16040 .option gecos_name main string&!! unset
16042 .cindex "&""gecos""& field, parsing"
16043 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16044 password file to hold other information in addition to users' real names. Exim
16045 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16046 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16047 of the field are used unchanged, except that, if an ampersand is encountered,
16048 it is replaced by the user's login name with the first character forced to
16049 upper case, since this is a convention that is observed on many systems.
16051 When these options are set, &%gecos_pattern%& is treated as a regular
16052 expression that is to be applied to the field (again with && replaced by the
16053 login name), and if it matches, &%gecos_name%& is expanded and used as the
16056 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16057 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16058 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16059 name terminates at the first comma, the following can be used:
16061 gecos_pattern = ([^,]*)
16065 .option gecos_pattern main string unset
16066 See &%gecos_name%& above.
16069 .option gnutls_compat_mode main boolean unset
16070 This option controls whether GnuTLS is used in compatibility mode in an Exim
16071 server. This reduces security slightly, but improves interworking with older
16072 implementations of TLS.
16075 .option gnutls_allow_auto_pkcs11 main boolean unset
16076 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16077 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16080 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16085 .option headers_charset main string "see below"
16086 This option sets a default character set for translating from encoded MIME
16087 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16088 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16089 ultimate default is ISO-8859-1. For more details see the description of header
16090 insertions in section &<<SECTexpansionitems>>&.
16094 .option header_maxsize main integer "see below"
16095 .cindex "header section" "maximum size of"
16096 .cindex "limit" "size of message header section"
16097 This option controls the overall maximum size of a message's header
16098 section. The default is the value of HEADER_MAXSIZE in
16099 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16100 sections are rejected.
16103 .option header_line_maxsize main integer 0
16104 .cindex "header lines" "maximum size of"
16105 .cindex "limit" "size of one header line"
16106 This option limits the length of any individual header line in a message, after
16107 all the continuations have been joined together. Messages with individual
16108 header lines that are longer than the limit are rejected. The default value of
16109 zero means &"no limit"&.
16114 .option helo_accept_junk_hosts main "host list&!!" unset
16115 .cindex "HELO" "accepting junk data"
16116 .cindex "EHLO" "accepting junk data"
16117 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16118 mail, and gives an error response for invalid data. Unfortunately, there are
16119 some SMTP clients that send syntactic junk. They can be accommodated by setting
16120 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16121 if you want to do semantic checking.
16122 See also &%helo_allow_chars%& for a way of extending the permitted character
16126 .option helo_allow_chars main string unset
16127 .cindex "HELO" "underscores in"
16128 .cindex "EHLO" "underscores in"
16129 .cindex "underscore in EHLO/HELO"
16130 This option can be set to a string of rogue characters that are permitted in
16131 all EHLO and HELO names in addition to the standard letters, digits,
16132 hyphens, and dots. If you really must allow underscores, you can set
16134 helo_allow_chars = _
16136 Note that the value is one string, not a list.
16139 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16140 .cindex "HELO" "forcing reverse lookup"
16141 .cindex "EHLO" "forcing reverse lookup"
16142 If the domain given by a client in a HELO or EHLO command matches this
16143 list, a reverse lookup is done in order to establish the host's true name. The
16144 default forces a lookup if the client host gives the server's name or any of
16145 its IP addresses (in brackets), something that broken clients have been seen to
16149 .option helo_try_verify_hosts main "host list&!!" unset
16150 .cindex "HELO verifying" "optional"
16151 .cindex "EHLO" "verifying, optional"
16152 By default, Exim just checks the syntax of HELO and EHLO commands (see
16153 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16154 to do more extensive checking of the data supplied by these commands. The ACL
16155 condition &`verify = helo`& is provided to make this possible.
16156 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16157 to force the check to occur. From release 4.53 onwards, this is no longer
16158 necessary. If the check has not been done before &`verify = helo`& is
16159 encountered, it is done at that time. Consequently, this option is obsolete.
16160 Its specification is retained here for backwards compatibility.
16162 When an EHLO or HELO command is received, if the calling host matches
16163 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16164 EHLO command either:
16167 is an IP literal matching the calling address of the host, or
16169 .cindex "DNS" "reverse lookup"
16170 .cindex "reverse DNS lookup"
16171 matches the host name that Exim obtains by doing a reverse lookup of the
16172 calling host address, or
16174 when looked up in DNS yields the calling host address.
16177 However, the EHLO or HELO command is not rejected if any of the checks
16178 fail. Processing continues, but the result of the check is remembered, and can
16179 be detected later in an ACL by the &`verify = helo`& condition.
16181 If DNS was used for successful verification, the variable
16182 .cindex "DNS" "DNSSEC"
16183 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16185 .option helo_verify_hosts main "host list&!!" unset
16186 .cindex "HELO verifying" "mandatory"
16187 .cindex "EHLO" "verifying, mandatory"
16188 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16189 backwards compatibility. For hosts that match this option, Exim checks the host
16190 name given in the HELO or EHLO in the same way as for
16191 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16192 rejected with a 550 error, and entries are written to the main and reject logs.
16193 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16196 .option hold_domains main "domain list&!!" unset
16197 .cindex "domain" "delaying delivery"
16198 .cindex "delivery" "delaying certain domains"
16199 This option allows mail for particular domains to be held in the queue
16200 manually. The option is overridden if a message delivery is forced with the
16201 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16202 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16203 item in &%hold_domains%&, no routing or delivery for that address is done, and
16204 it is deferred every time the message is looked at.
16206 This option is intended as a temporary operational measure for delaying the
16207 delivery of mail while some problem is being sorted out, or some new
16208 configuration tested. If you just want to delay the processing of some
16209 domains until a queue run occurs, you should use &%queue_domains%& or
16210 &%queue_smtp_domains%&, not &%hold_domains%&.
16212 A setting of &%hold_domains%& does not override Exim's code for removing
16213 messages from the queue if they have been there longer than the longest retry
16214 time in any retry rule. If you want to hold messages for longer than the normal
16215 retry times, insert a dummy retry rule with a long retry time.
16218 .option host_lookup main "host list&!!" unset
16219 .cindex "host name" "lookup, forcing"
16220 Exim does not look up the name of a calling host from its IP address unless it
16221 is required to compare against some host list, or the host matches
16222 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16223 option (which normally contains IP addresses rather than host names). The
16224 default configuration file contains
16228 which causes a lookup to happen for all hosts. If the expense of these lookups
16229 is felt to be too great, the setting can be changed or removed.
16231 After a successful reverse lookup, Exim does a forward lookup on the name it
16232 has obtained, to verify that it yields the IP address that it started with. If
16233 this check fails, Exim behaves as if the name lookup failed.
16235 .vindex "&$host_lookup_failed$&"
16236 .vindex "&$sender_host_name$&"
16237 After any kind of failure, the host name (in &$sender_host_name$&) remains
16238 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16239 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16240 &`verify = reverse_host_lookup`& in ACLs.
16243 .option host_lookup_order main "string list" &`bydns:byaddr`&
16244 This option specifies the order of different lookup methods when Exim is trying
16245 to find a host name from an IP address. The default is to do a DNS lookup
16246 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16247 if that fails. You can change the order of these lookups, or omit one entirely,
16250 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16251 multiple PTR records in the DNS and the IP address is not listed in
16252 &_/etc/hosts_&. Different operating systems give different results in this
16253 case. That is why the default tries a DNS lookup first.
16257 .option host_reject_connection main "host list&!!" unset
16258 .cindex "host" "rejecting connections from"
16259 If this option is set, incoming SMTP calls from the hosts listed are rejected
16260 as soon as the connection is made.
16261 This option is obsolete, and retained only for backward compatibility, because
16262 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16263 connections immediately.
16265 The ability to give an immediate rejection (either by this option or using an
16266 ACL) is provided for use in unusual cases. Many hosts will just try again,
16267 sometimes without much delay. Normally, it is better to use an ACL to reject
16268 incoming messages at a later stage, such as after RCPT commands. See
16269 chapter &<<CHAPACL>>&.
16272 .option hosts_connection_nolog main "host list&!!" unset
16273 .cindex "host" "not logging connections from"
16274 This option defines a list of hosts for which connection logging does not
16275 happen, even though the &%smtp_connection%& log selector is set. For example,
16276 you might want not to log SMTP connections from local processes, or from
16277 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16278 the daemon; you should therefore strive to restrict its value to a short inline
16279 list of IP addresses and networks. To disable logging SMTP connections from
16280 local processes, you must create a host list with an empty item. For example:
16282 hosts_connection_nolog = :
16284 If the &%smtp_connection%& log selector is not set, this option has no effect.
16288 .option hosts_proxy main "host list&!!" unset
16289 .cindex proxy "proxy protocol"
16290 This option enables use of Proxy Protocol proxies for incoming
16291 connections. For details see section &<<SECTproxyInbound>>&.
16294 .option hosts_treat_as_local main "domain list&!!" unset
16295 .cindex "local host" "domains treated as"
16296 .cindex "host" "treated as local"
16297 If this option is set, any host names that match the domain list are treated as
16298 if they were the local host when Exim is scanning host lists obtained from MX
16300 or other sources. Note that the value of this option is a domain list, not a
16301 host list, because it is always used to check host names, not IP addresses.
16303 This option also applies when Exim is matching the special items
16304 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16305 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16306 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16307 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16308 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16309 interfaces and recognizing the local host.
16312 .option ibase_servers main "string list" unset
16313 .cindex "InterBase" "server list"
16314 This option provides a list of InterBase servers and associated connection data,
16315 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16316 The option is available only if Exim has been built with InterBase support.
16320 .option ignore_bounce_errors_after main time 10w
16321 .cindex "bounce message" "discarding"
16322 .cindex "discarding bounce message"
16323 This option affects the processing of bounce messages that cannot be delivered,
16324 that is, those that suffer a permanent delivery failure. (Bounce messages that
16325 suffer temporary delivery failures are of course retried in the usual way.)
16327 After a permanent delivery failure, bounce messages are frozen,
16328 because there is no sender to whom they can be returned. When a frozen bounce
16329 message has been in the queue for more than the given time, it is unfrozen at
16330 the next queue run, and a further delivery is attempted. If delivery fails
16331 again, the bounce message is discarded. This makes it possible to keep failed
16332 bounce messages around for a shorter time than the normal maximum retry time
16333 for frozen messages. For example,
16335 ignore_bounce_errors_after = 12h
16337 retries failed bounce message deliveries after 12 hours, discarding any further
16338 failures. If the value of this option is set to a zero time period, bounce
16339 failures are discarded immediately. Setting a very long time (as in the default
16340 value) has the effect of disabling this option. For ways of automatically
16341 dealing with other kinds of frozen message, see &%auto_thaw%& and
16342 &%timeout_frozen_after%&.
16345 .option ignore_fromline_hosts main "host list&!!" unset
16346 .cindex "&""From""& line"
16347 .cindex "UUCP" "&""From""& line"
16348 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16349 the headers of a message. By default this is treated as the start of the
16350 message's body, which means that any following headers are not recognized as
16351 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16352 match those hosts that insist on sending it. If the sender is actually a local
16353 process rather than a remote host, and is using &%-bs%& to inject the messages,
16354 &%ignore_fromline_local%& must be set to achieve this effect.
16357 .option ignore_fromline_local main boolean false
16358 See &%ignore_fromline_hosts%& above.
16360 .option keep_environment main "string list" unset
16361 .cindex "environment" "values from"
16362 This option contains a string list of environment variables to keep.
16363 You have to trust these variables or you have to be sure that
16364 these variables do not impose any security risk. Keep in mind that
16365 during the startup phase Exim is running with an effective UID 0 in most
16366 installations. As the default value is an empty list, the default
16367 environment for using libraries, running embedded Perl code, or running
16368 external binaries is empty, and does not not even contain PATH or HOME.
16370 Actually the list is interpreted as a list of patterns
16371 (&<<SECTlistexpand>>&), except that it is not expanded first.
16373 WARNING: Macro substitution is still done first, so having a macro
16374 FOO and having FOO_HOME in your &%keep_environment%& option may have
16375 unexpected results. You may work around this using a regular expression
16376 that does not match the macro name: ^[F]OO_HOME$.
16378 Current versions of Exim issue a warning during startup if you do not mention
16379 &%keep_environment%& in your runtime configuration file and if your
16380 current environment is not empty. Future versions may not issue that warning
16383 See the &%add_environment%& main config option for a way to set
16384 environment variables to a fixed value. The environment for &(pipe)&
16385 transports is handled separately, see section &<<SECTpipeenv>>& for
16389 .option keep_malformed main time 4d
16390 This option specifies the length of time to keep messages whose spool files
16391 have been corrupted in some way. This should, of course, never happen. At the
16392 next attempt to deliver such a message, it gets removed. The incident is
16396 .option ldap_ca_cert_dir main string unset
16397 .cindex "LDAP", "TLS CA certificate directory"
16398 .cindex certificate "directory for LDAP"
16399 This option indicates which directory contains CA certificates for verifying
16400 a TLS certificate presented by an LDAP server.
16401 While Exim does not provide a default value, your SSL library may.
16402 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16403 and constrained to be a directory.
16406 .option ldap_ca_cert_file main string unset
16407 .cindex "LDAP", "TLS CA certificate file"
16408 .cindex certificate "file for LDAP"
16409 This option indicates which file contains CA certificates for verifying
16410 a TLS certificate presented by an LDAP server.
16411 While Exim does not provide a default value, your SSL library may.
16412 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16413 and constrained to be a file.
16416 .option ldap_cert_file main string unset
16417 .cindex "LDAP" "TLS client certificate file"
16418 .cindex certificate "file for LDAP"
16419 This option indicates which file contains an TLS client certificate which
16420 Exim should present to the LDAP server during TLS negotiation.
16421 Should be used together with &%ldap_cert_key%&.
16424 .option ldap_cert_key main string unset
16425 .cindex "LDAP" "TLS client key file"
16426 .cindex certificate "key for LDAP"
16427 This option indicates which file contains the secret/private key to use
16428 to prove identity to the LDAP server during TLS negotiation.
16429 Should be used together with &%ldap_cert_file%&, which contains the
16430 identity to be proven.
16433 .option ldap_cipher_suite main string unset
16434 .cindex "LDAP" "TLS cipher suite"
16435 This controls the TLS cipher-suite negotiation during TLS negotiation with
16436 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16437 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16440 .option ldap_default_servers main "string list" unset
16441 .cindex "LDAP" "default servers"
16442 This option provides a list of LDAP servers which are tried in turn when an
16443 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16444 details of LDAP queries. This option is available only when Exim has been built
16448 .option ldap_require_cert main string unset.
16449 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16450 This should be one of the values "hard", "demand", "allow", "try" or "never".
16451 A value other than one of these is interpreted as "never".
16452 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16453 Although Exim does not set a default, the LDAP library probably defaults
16457 .option ldap_start_tls main boolean false
16458 .cindex "LDAP" "whether or not to negotiate TLS"
16459 If set, Exim will attempt to negotiate TLS with the LDAP server when
16460 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16461 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16463 In the event of failure to negotiate TLS, the action taken is controlled
16464 by &%ldap_require_cert%&.
16465 This option is ignored for &`ldapi`& connections.
16468 .option ldap_version main integer unset
16469 .cindex "LDAP" "protocol version, forcing"
16470 This option can be used to force Exim to set a specific protocol version for
16471 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16472 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16473 the LDAP headers; otherwise it is 2. This option is available only when Exim
16474 has been built with LDAP support.
16478 .option local_from_check main boolean true
16479 .cindex "&'Sender:'& header line" "disabling addition of"
16480 .cindex "&'From:'& header line" "disabling checking of"
16481 When a message is submitted locally (that is, not over a TCP/IP connection) by
16482 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16483 checks that the &'From:'& header line matches the login of the calling user and
16484 the domain specified by &%qualify_domain%&.
16486 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16487 locally submitted message is automatically qualified by Exim, unless the
16488 &%-bnq%& command line option is used.
16490 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16491 on the local part. If the &'From:'& header line does not match, Exim adds a
16492 &'Sender:'& header with an address constructed from the calling user's login
16493 and the default qualify domain.
16495 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16496 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16497 &'Sender:'& header lines supplied by untrusted users, you must also set
16498 &%local_sender_retain%& to be true.
16500 .cindex "envelope from"
16501 .cindex "envelope sender"
16502 These options affect only the header lines in the message. The envelope sender
16503 is still forced to be the login id at the qualify domain unless
16504 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16506 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16507 request similar header line checking. See section &<<SECTthesenhea>>&, which
16508 has more details about &'Sender:'& processing.
16513 .option local_from_prefix main string unset
16514 When Exim checks the &'From:'& header line of locally submitted messages for
16515 matching the login id (see &%local_from_check%& above), it can be configured to
16516 ignore certain prefixes and suffixes in the local part of the address. This is
16517 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16518 appropriate lists, in the same form as the &%local_part_prefix%& and
16519 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16522 local_from_prefix = *-
16524 is set, a &'From:'& line containing
16526 From: anything-user@your.domain.example
16528 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16529 matches the actual sender address that is constructed from the login name and
16533 .option local_from_suffix main string unset
16534 See &%local_from_prefix%& above.
16537 .option local_interfaces main "string list" "see below"
16538 This option controls which network interfaces are used by the daemon for
16539 listening; they are also used to identify the local host when routing. Chapter
16540 &<<CHAPinterfaces>>& contains a full description of this option and the related
16541 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16542 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16543 &%local_interfaces%& is
16545 local_interfaces = 0.0.0.0
16547 when Exim is built without IPv6 support; otherwise it is
16549 local_interfaces = <; ::0 ; 0.0.0.0
16552 .option local_scan_timeout main time 5m
16553 .cindex "timeout" "for &[local_scan()]& function"
16554 .cindex "&[local_scan()]& function" "timeout"
16555 This timeout applies to the &[local_scan()]& function (see chapter
16556 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16557 the incoming message is rejected with a temporary error if it is an SMTP
16558 message. For a non-SMTP message, the message is dropped and Exim ends with a
16559 non-zero code. The incident is logged on the main and reject logs.
16563 .option local_sender_retain main boolean false
16564 .cindex "&'Sender:'& header line" "retaining from local submission"
16565 When a message is submitted locally (that is, not over a TCP/IP connection) by
16566 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16567 do not want this to happen, you must set &%local_sender_retain%&, and you must
16568 also set &%local_from_check%& to be false (Exim will complain if you do not).
16569 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16570 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16575 .option localhost_number main string&!! unset
16576 .cindex "host" "locally unique number for"
16577 .cindex "message ids" "with multiple hosts"
16578 .vindex "&$localhost_number$&"
16579 Exim's message ids are normally unique only within the local host. If
16580 uniqueness among a set of hosts is required, each host must set a different
16581 value for the &%localhost_number%& option. The string is expanded immediately
16582 after reading the configuration file (so that a number can be computed from the
16583 host name, for example) and the result of the expansion must be a number in the
16584 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16585 systems). This is available in subsequent string expansions via the variable
16586 &$localhost_number$&. When &%localhost_number is set%&, the final two
16587 characters of the message id, instead of just being a fractional part of the
16588 time, are computed from the time and the local host number as described in
16589 section &<<SECTmessiden>>&.
16593 .option log_file_path main "string list&!!" "set at compile time"
16594 .cindex "log" "file path for"
16595 This option sets the path which is used to determine the names of Exim's log
16596 files, or indicates that logging is to be to syslog, or both. It is expanded
16597 when Exim is entered, so it can, for example, contain a reference to the host
16598 name. If no specific path is set for the log files at compile or runtime,
16599 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16600 they are written in a sub-directory called &_log_& in Exim's spool directory.
16601 A path must start with a slash.
16602 To send to syslog, use the word &"syslog"&.
16603 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16604 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16605 used. If this string is fixed at your installation (contains no expansion
16606 variables) it is recommended that you do not set this option in the
16607 configuration file, but instead supply the path using LOG_FILE_PATH in
16608 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16609 early on &-- in particular, failure to read the configuration file.
16612 .option log_selector main string unset
16613 .cindex "log" "selectors"
16614 This option can be used to reduce or increase the number of things that Exim
16615 writes to its log files. Its argument is made up of names preceded by plus or
16616 minus characters. For example:
16618 log_selector = +arguments -retry_defer
16620 A list of possible names and what they control is given in the chapter on
16621 logging, in section &<<SECTlogselector>>&.
16624 .option log_timezone main boolean false
16625 .cindex "log" "timezone for entries"
16626 .vindex "&$tod_log$&"
16627 .vindex "&$tod_zone$&"
16628 By default, the timestamps on log lines are in local time without the
16629 timezone. This means that if your timezone changes twice a year, the timestamps
16630 in log lines are ambiguous for an hour when the clocks go back. One way of
16631 avoiding this problem is to set the timezone to UTC. An alternative is to set
16632 &%log_timezone%& true. This turns on the addition of the timezone offset to
16633 timestamps in log lines. Turning on this option can add quite a lot to the size
16634 of log files because each line is extended by 6 characters. Note that the
16635 &$tod_log$& variable contains the log timestamp without the zone, but there is
16636 another variable called &$tod_zone$& that contains just the timezone offset.
16639 .option lookup_open_max main integer 25
16640 .cindex "too many open files"
16641 .cindex "open files, too many"
16642 .cindex "file" "too many open"
16643 .cindex "lookup" "maximum open files"
16644 .cindex "limit" "open files for lookups"
16645 This option limits the number of simultaneously open files for single-key
16646 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16647 Exim normally keeps these files open during routing, because often the same
16648 file is required several times. If the limit is reached, Exim closes the least
16649 recently used file. Note that if you are using the &'ndbm'& library, it
16650 actually opens two files for each logical DBM database, though it still counts
16651 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16652 open files"& errors with NDBM, you need to reduce the value of
16653 &%lookup_open_max%&.
16656 .option max_username_length main integer 0
16657 .cindex "length of login name"
16658 .cindex "user name" "maximum length"
16659 .cindex "limit" "user name length"
16660 Some operating systems are broken in that they truncate long arguments to
16661 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16662 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16663 an argument that is longer behaves as if &[getpwnam()]& failed.
16666 .option message_body_newlines main bool false
16667 .cindex "message body" "newlines in variables"
16668 .cindex "newline" "in message body variables"
16669 .vindex "&$message_body$&"
16670 .vindex "&$message_body_end$&"
16671 By default, newlines in the message body are replaced by spaces when setting
16672 the &$message_body$& and &$message_body_end$& expansion variables. If this
16673 option is set true, this no longer happens.
16676 .option message_body_visible main integer 500
16677 .cindex "body of message" "visible size"
16678 .cindex "message body" "visible size"
16679 .vindex "&$message_body$&"
16680 .vindex "&$message_body_end$&"
16681 This option specifies how much of a message's body is to be included in the
16682 &$message_body$& and &$message_body_end$& expansion variables.
16685 .option message_id_header_domain main string&!! unset
16686 .cindex "&'Message-ID:'& header line"
16687 If this option is set, the string is expanded and used as the right hand side
16688 (domain) of the &'Message-ID:'& header that Exim creates if a
16689 locally-originated incoming message does not have one. &"Locally-originated"&
16690 means &"not received over TCP/IP."&
16691 Otherwise, the primary host name is used.
16692 Only letters, digits, dot and hyphen are accepted; any other characters are
16693 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16694 empty string, the option is ignored.
16697 .option message_id_header_text main string&!! unset
16698 If this variable is set, the string is expanded and used to augment the text of
16699 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16700 message does not have one. The text of this header is required by RFC 2822 to
16701 take the form of an address. By default, Exim uses its internal message id as
16702 the local part, and the primary host name as the domain. If this option is set,
16703 it is expanded, and provided the expansion is not forced to fail, and does not
16704 yield an empty string, the result is inserted into the header immediately
16705 before the @, separated from the internal message id by a dot. Any characters
16706 that are illegal in an address are automatically converted into hyphens. This
16707 means that variables such as &$tod_log$& can be used, because the spaces and
16708 colons will become hyphens.
16711 .option message_logs main boolean true
16712 .cindex "message logs" "disabling"
16713 .cindex "log" "message log; disabling"
16714 If this option is turned off, per-message log files are not created in the
16715 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16716 Exim, by reducing the number of files involved in handling a message from a
16717 minimum of four (header spool file, body spool file, delivery journal, and
16718 per-message log) to three. The other major I/O activity is Exim's main log,
16719 which is not affected by this option.
16722 .option message_size_limit main string&!! 50M
16723 .cindex "message" "size limit"
16724 .cindex "limit" "message size"
16725 .cindex "size" "of message, limit"
16726 This option limits the maximum size of message that Exim will process. The
16727 value is expanded for each incoming connection so, for example, it can be made
16728 to depend on the IP address of the remote host for messages arriving via
16729 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16730 optionally followed by K or M.
16732 .cindex "SIZE" "ESMTP extension, advertising"
16733 .cindex "ESMTP extensions" SIZE
16734 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16735 service extension keyword.
16737 &*Note*&: This limit cannot be made to depend on a message's sender or any
16738 other properties of an individual message, because it has to be advertised in
16739 the server's response to EHLO. String expansion failure causes a temporary
16740 error. A value of zero means no limit, but its use is not recommended. See also
16741 &%bounce_return_size_limit%&.
16743 Incoming SMTP messages are failed with a 552 error if the limit is
16744 exceeded; locally-generated messages either get a stderr message or a delivery
16745 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16746 an oversized message is logged in both the main and the reject logs. See also
16747 the generic transport option &%message_size_limit%&, which limits the size of
16748 message that an individual transport can process.
16750 If you use a virus-scanner and set this option to to a value larger than the
16751 maximum size that your virus-scanner is configured to support, you may get
16752 failures triggered by large mails. The right size to configure for the
16753 virus-scanner depends upon what data is passed and the options in use but it's
16754 probably safest to just set it to a little larger than this value. E.g., with a
16755 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16756 some problems may result.
16758 A value of 0 will disable size limit checking; Exim will still advertise the
16759 SIZE extension in an EHLO response, but without a limit, so as to permit
16760 SMTP clients to still indicate the message size along with the MAIL verb.
16763 .option move_frozen_messages main boolean false
16764 .cindex "frozen messages" "moving"
16765 This option, which is available only if Exim has been built with the setting
16767 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16769 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16770 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16771 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16772 standard utilities for handling such moved messages, and they do not show up in
16773 lists generated by &%-bp%& or by the Exim monitor.
16776 .option mua_wrapper main boolean false
16777 Setting this option true causes Exim to run in a very restrictive mode in which
16778 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16779 contains a full description of this facility.
16783 .option mysql_servers main "string list" unset
16784 .cindex "MySQL" "server list"
16785 This option provides a list of MySQL servers and associated connection data, to
16786 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16787 option is available only if Exim has been built with MySQL support.
16790 .option never_users main "string list&!!" unset
16791 This option is expanded just once, at the start of Exim's processing. Local
16792 message deliveries are normally run in processes that are setuid to the
16793 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16794 It is usually desirable to prevent any deliveries from running as root, as a
16797 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16798 list of users that must not be used for local deliveries. This list is fixed in
16799 the binary and cannot be overridden by the configuration file. By default, it
16800 contains just the single user name &"root"&. The &%never_users%& runtime option
16801 can be used to add more users to the fixed list.
16803 If a message is to be delivered as one of the users on the fixed list or the
16804 &%never_users%& list, an error occurs, and delivery is deferred. A common
16807 never_users = root:daemon:bin
16809 Including root is redundant if it is also on the fixed list, but it does no
16810 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16814 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16815 This option gives the name for a unix-domain socket on which the daemon
16816 listens for work and information-requests.
16817 Only installations running multiple daemons sharing a spool directory
16818 should need to modify the default.
16820 The option is expanded before use.
16821 If the platform supports Linux-style abstract socket names, the result
16822 is used with a nul byte prefixed.
16824 .new "if nonempty,"
16825 it should be a full path name and use a directory accessible
16829 If this option is set as empty,
16830 or the command line &%-oY%& option is used, or
16832 the command line uses a &%-oX%& option and does not use &%-oP%&,
16833 then a notifier socket is not created.
16836 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16837 .cindex "OpenSSL "compatibility options"
16838 This option allows an administrator to adjust the SSL options applied
16839 by OpenSSL to connections. It is given as a space-separated list of items,
16840 each one to be +added or -subtracted from the current value.
16842 This option is only available if Exim is built against OpenSSL. The values
16843 available for this option vary according to the age of your OpenSSL install.
16844 The &"all"& value controls a subset of flags which are available, typically
16845 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16846 list the values known on your system and Exim should support all the
16847 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16848 names lose the leading &"SSL_OP_"& and are lower-cased.
16850 Note that adjusting the options can have severe impact upon the security of
16851 SSL as used by Exim. It is possible to disable safety checks and shoot
16852 yourself in the foot in various unpleasant ways. This option should not be
16853 adjusted lightly. An unrecognised item will be detected at startup, by
16854 invoking Exim with the &%-bV%& flag.
16856 The option affects Exim operating both as a server and as a client.
16858 Historical note: prior to release 4.80, Exim defaulted this value to
16859 "+dont_insert_empty_fragments", which may still be needed for compatibility
16860 with some clients, but which lowers security by increasing exposure to
16861 some now infamous attacks.
16865 # Make both old MS and old Eudora happy:
16866 openssl_options = -all +microsoft_big_sslv3_buffer \
16867 +dont_insert_empty_fragments
16869 # Disable older protocol versions:
16870 openssl_options = +no_sslv2 +no_sslv3
16873 Possible options may include:
16877 &`allow_unsafe_legacy_renegotiation`&
16879 &`cipher_server_preference`&
16881 &`dont_insert_empty_fragments`&
16885 &`legacy_server_connect`&
16887 &`microsoft_big_sslv3_buffer`&
16889 &`microsoft_sess_id_bug`&
16891 &`msie_sslv2_rsa_padding`&
16893 &`netscape_challenge_bug`&
16895 &`netscape_reuse_cipher_change_bug`&
16899 &`no_session_resumption_on_renegotiation`&
16913 &`safari_ecdhe_ecdsa_bug`&
16917 &`single_ecdh_use`&
16919 &`ssleay_080_client_dh_bug`&
16921 &`sslref2_reuse_cert_type_bug`&
16923 &`tls_block_padding_bug`&
16927 &`tls_rollback_bug`&
16930 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16931 all clients connecting using the MacOS SecureTransport TLS facility prior
16932 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16933 to negotiate TLS then this option value might help, provided that your OpenSSL
16934 release is new enough to contain this work-around. This may be a situation
16935 where you have to upgrade OpenSSL to get buggy clients working.
16938 .option oracle_servers main "string list" unset
16939 .cindex "Oracle" "server list"
16940 This option provides a list of Oracle servers and associated connection data,
16941 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16942 The option is available only if Exim has been built with Oracle support.
16945 .option percent_hack_domains main "domain list&!!" unset
16946 .cindex "&""percent hack""&"
16947 .cindex "source routing" "in email address"
16948 .cindex "address" "source-routed"
16949 The &"percent hack"& is the convention whereby a local part containing a
16950 percent sign is re-interpreted as a new email address, with the percent
16951 replaced by @. This is sometimes called &"source routing"&, though that term is
16952 also applied to RFC 2822 addresses that begin with an @ character. If this
16953 option is set, Exim implements the percent facility for those domains listed,
16954 but no others. This happens before an incoming SMTP address is tested against
16957 &*Warning*&: The &"percent hack"& has often been abused by people who are
16958 trying to get round relaying restrictions. For this reason, it is best avoided
16959 if at all possible. Unfortunately, a number of less security-conscious MTAs
16960 implement it unconditionally. If you are running Exim on a gateway host, and
16961 routing mail through to internal MTAs without processing the local parts, it is
16962 a good idea to reject recipient addresses with percent characters in their
16963 local parts. Exim's default configuration does this.
16966 .option perl_at_start main boolean false
16968 This option is available only when Exim is built with an embedded Perl
16969 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16972 .option perl_startup main string unset
16974 This option is available only when Exim is built with an embedded Perl
16975 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16977 .option perl_taintmode main boolean false
16979 This option enables the taint mode of the embedded Perl interpreter.
16982 .option pgsql_servers main "string list" unset
16983 .cindex "PostgreSQL lookup type" "server list"
16984 This option provides a list of PostgreSQL servers and associated connection
16985 data, to be used in conjunction with &(pgsql)& lookups (see section
16986 &<<SECID72>>&). The option is available only if Exim has been built with
16987 PostgreSQL support.
16990 .option pid_file_path main string&!! "set at compile time"
16991 .cindex "daemon" "pid file path"
16992 .cindex "pid file, path for"
16993 This option sets the name of the file to which the Exim daemon writes its
16994 process id. The string is expanded, so it can contain, for example, references
16997 pid_file_path = /var/log/$primary_hostname/exim.pid
16999 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17001 The value set by the option can be overridden by the &%-oP%& command line
17002 option. A pid file is not written if a &"non-standard"& daemon is run by means
17003 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17006 .option pipelining_advertise_hosts main "host list&!!" *
17007 .cindex "PIPELINING" "suppressing advertising"
17008 .cindex "ESMTP extensions" PIPELINING
17009 This option can be used to suppress the advertisement of the SMTP
17010 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17011 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17012 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17013 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17014 that clients will use it; &"out of order"& commands that are &"expected"& do
17015 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17017 .option pipelining_connect_advertise_hosts main "host list&!!" *
17018 .cindex "pipelining" "early connection"
17019 .cindex "pipelining" PIPE_CONNECT
17020 .cindex "ESMTP extensions" PIPE_CONNECT
17021 If Exim is built with the SUPPORT_PIPE_CONNECT build option
17022 this option controls which hosts the facility is advertised to
17023 and from which pipeline early-connection (before MAIL) SMTP
17024 commands are acceptable.
17025 When used, the pipelining saves on roundtrip times.
17027 See also the &%hosts_pipe_connect%& smtp transport option.
17030 The SMTP service extension keyword advertised is &"PIPE_CONNECT"&.
17034 .option prdr_enable main boolean false
17035 .cindex "PRDR" "enabling on server"
17036 .cindex "ESMTP extensions" PRDR
17037 This option can be used to enable the Per-Recipient Data Response extension
17038 to SMTP, defined by Eric Hall.
17039 If the option is set, PRDR is advertised by Exim when operating as a server.
17040 If the client requests PRDR, and more than one recipient, for a message
17041 an additional ACL is called for each recipient after the message content
17042 is received. See section &<<SECTPRDRACL>>&.
17044 .option preserve_message_logs main boolean false
17045 .cindex "message logs" "preserving"
17046 If this option is set, message log files are not deleted when messages are
17047 completed. Instead, they are moved to a sub-directory of the spool directory
17048 called &_msglog.OLD_&, where they remain available for statistical or debugging
17049 purposes. This is a dangerous option to set on systems with any appreciable
17050 volume of mail. Use with care!
17053 .option primary_hostname main string "see below"
17054 .cindex "name" "of local host"
17055 .cindex "host" "name of local"
17056 .cindex "local host" "name of"
17057 .vindex "&$primary_hostname$&"
17058 This specifies the name of the current host. It is used in the default EHLO or
17059 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17060 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17061 The value is also used by default in some SMTP response messages from an Exim
17062 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17064 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17065 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17066 contains only one component, Exim passes it to &[gethostbyname()]& (or
17067 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17068 version. The variable &$primary_hostname$& contains the host name, whether set
17069 explicitly by this option, or defaulted.
17072 .option print_topbitchars main boolean false
17073 .cindex "printing characters"
17074 .cindex "8-bit characters"
17075 By default, Exim considers only those characters whose codes lie in the range
17076 32&--126 to be printing characters. In a number of circumstances (for example,
17077 when writing log entries) non-printing characters are converted into escape
17078 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17079 is set, code values of 128 and above are also considered to be printing
17082 This option also affects the header syntax checks performed by the
17083 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17084 the user's full name when constructing From: and Sender: addresses (as
17085 described in section &<<SECTconstr>>&). Setting this option can cause
17086 Exim to generate eight bit message headers that do not conform to the
17090 .option process_log_path main string unset
17091 .cindex "process log path"
17092 .cindex "log" "process log"
17093 .cindex "&'exiwhat'&"
17094 This option sets the name of the file to which an Exim process writes its
17095 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17096 utility script. If this option is unset, the file called &_exim-process.info_&
17097 in Exim's spool directory is used. The ability to specify the name explicitly
17098 can be useful in environments where two different Exims are running, using
17099 different spool directories.
17102 .option prod_requires_admin main boolean true
17103 .cindex "restricting access to features"
17107 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17108 admin user unless &%prod_requires_admin%& is set false. See also
17109 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17113 .option proxy_protocol_timeout main time 3s
17114 .cindex proxy "proxy protocol"
17115 This option sets the timeout for proxy protocol negotiation.
17116 For details see section &<<SECTproxyInbound>>&.
17120 .option qualify_domain main string "see below"
17121 .cindex "domain" "for qualifying addresses"
17122 .cindex "address" "qualification"
17123 This option specifies the domain name that is added to any envelope sender
17124 addresses that do not have a domain qualification. It also applies to
17125 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17126 are accepted by default only for locally-generated messages. Qualification is
17127 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17128 locally-generated messages, unless the &%-bnq%& command line option is used.
17130 Messages from external sources must always contain fully qualified addresses,
17131 unless the sending host matches &%sender_unqualified_hosts%& or
17132 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17133 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17134 necessary. Internally, Exim always works with fully qualified envelope
17135 addresses. If &%qualify_domain%& is not set, it defaults to the
17136 &%primary_hostname%& value.
17139 .option qualify_recipient main string "see below"
17140 This option allows you to specify a different domain for qualifying recipient
17141 addresses to the one that is used for senders. See &%qualify_domain%& above.
17145 .option queue_domains main "domain list&!!" unset
17146 .cindex "domain" "specifying non-immediate delivery"
17147 .cindex "queueing incoming messages"
17148 .cindex "message" "queueing certain domains"
17149 This option lists domains for which immediate delivery is not required.
17150 A delivery process is started whenever a message is received, but only those
17151 domains that do not match are processed. All other deliveries wait until the
17152 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17156 .option queue_fast_ramp main boolean false
17157 .cindex "queue runner" "two phase"
17158 .cindex "queue" "double scanning"
17159 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17160 command line, may start parallel delivery processes during their first
17161 phase. This will be done when a threshold number of messages have been
17162 routed for a single host.
17166 .option queue_list_requires_admin main boolean true
17167 .cindex "restricting access to features"
17169 The &%-bp%& command-line option, which lists the messages that are on the
17170 queue, requires the caller to be an admin user unless
17171 &%queue_list_requires_admin%& is set false.
17172 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17175 .option queue_only main boolean false
17176 .cindex "queueing incoming messages"
17177 .cindex "message" "queueing unconditionally"
17178 If &%queue_only%& is set, a delivery process is not automatically started
17179 whenever a message is received. Instead, the message waits in the queue for the
17180 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17181 delivered immediately when certain conditions (such as heavy load) occur.
17183 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17184 and &%-odi%& command line options override &%queue_only%& unless
17185 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17186 &%queue_only_load%&, and &%smtp_accept_queue%&.
17189 .option queue_only_file main string unset
17190 .cindex "queueing incoming messages"
17191 .cindex "message" "queueing by file existence"
17192 This option can be set to a colon-separated list of absolute path names, each
17193 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17194 it tests for the existence of each listed path using a call to &[stat()]&. For
17195 each path that exists, the corresponding queueing option is set.
17196 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17197 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17199 queue_only_file = smtp/some/file
17201 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17202 &_/some/file_& exists.
17205 .option queue_only_load main fixed-point unset
17206 .cindex "load average"
17207 .cindex "queueing incoming messages"
17208 .cindex "message" "queueing by load"
17209 If the system load average is higher than this value, incoming messages from
17210 all sources are queued, and no automatic deliveries are started. If this
17211 happens during local or remote SMTP input, all subsequent messages received on
17212 the same SMTP connection are queued by default, whatever happens to the load in
17213 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17216 Deliveries will subsequently be performed by queue runner processes. This
17217 option has no effect on ancient operating systems on which Exim cannot
17218 determine the load average. See also &%deliver_queue_load_max%& and
17219 &%smtp_load_reserve%&.
17222 .option queue_only_load_latch main boolean true
17223 .cindex "load average" "re-evaluating per message"
17224 When this option is true (the default), once one message has been queued
17225 because the load average is higher than the value set by &%queue_only_load%&,
17226 all subsequent messages received on the same SMTP connection are also queued.
17227 This is a deliberate choice; even though the load average may fall below the
17228 threshold, it doesn't seem right to deliver later messages on the same
17229 connection when not delivering earlier ones. However, there are special
17230 circumstances such as very long-lived connections from scanning appliances
17231 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17232 should be set false. This causes the value of the load average to be
17233 re-evaluated for each message.
17236 .option queue_only_override main boolean true
17237 .cindex "queueing incoming messages"
17238 When this option is true, the &%-od%&&'x'& command line options override the
17239 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17240 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17241 to override; they are accepted, but ignored.
17244 .option queue_run_in_order main boolean false
17245 .cindex "queue runner" "processing messages in order"
17246 If this option is set, queue runs happen in order of message arrival instead of
17247 in an arbitrary order. For this to happen, a complete list of the entire queue
17248 must be set up before the deliveries start. When the queue is all held in a
17249 single directory (the default), a single list is created for both the ordered
17250 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17251 single list is not created when &%queue_run_in_order%& is false. In this case,
17252 the sub-directories are processed one at a time (in a random order), and this
17253 avoids setting up one huge list for the whole queue. Thus, setting
17254 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17255 when the queue is large, because of the extra work in setting up the single,
17256 large list. In most situations, &%queue_run_in_order%& should not be set.
17260 .option queue_run_max main integer&!! 5
17261 .cindex "queue runner" "maximum number of"
17262 This controls the maximum number of queue runner processes that an Exim daemon
17263 can run simultaneously. This does not mean that it starts them all at once,
17264 but rather that if the maximum number are still running when the time comes to
17265 start another one, it refrains from starting another one. This can happen with
17266 very large queues and/or very sluggish deliveries. This option does not,
17267 however, interlock with other processes, so additional queue runners can be
17268 started by other means, or by killing and restarting the daemon.
17270 Setting this option to zero does not suppress queue runs; rather, it disables
17271 the limit, allowing any number of simultaneous queue runner processes to be
17272 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17273 the daemon's command line.
17275 .cindex queues named
17276 .cindex "named queues" "resource limit"
17277 To set limits for different named queues use
17278 an expansion depending on the &$queue_name$& variable.
17280 .option queue_smtp_domains main "domain list&!!" unset
17281 .cindex "queueing incoming messages"
17282 .cindex "message" "queueing remote deliveries"
17283 .cindex "first pass routing"
17284 When this option is set, a delivery process is started whenever a message is
17285 received, routing is performed, and local deliveries take place.
17286 However, if any SMTP deliveries are required for domains that match
17287 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17288 message waits in the queue for the next queue run. Since routing of the message
17289 has taken place, Exim knows to which remote hosts it must be delivered, and so
17290 when the queue run happens, multiple messages for the same host are delivered
17291 over a single SMTP connection. The &%-odqs%& command line option causes all
17292 SMTP deliveries to be queued in this way, and is equivalent to setting
17293 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17297 .option receive_timeout main time 0s
17298 .cindex "timeout" "for non-SMTP input"
17299 This option sets the timeout for accepting a non-SMTP message, that is, the
17300 maximum time that Exim waits when reading a message on the standard input. If
17301 the value is zero, it will wait forever. This setting is overridden by the
17302 &%-or%& command line option. The timeout for incoming SMTP messages is
17303 controlled by &%smtp_receive_timeout%&.
17305 .option received_header_text main string&!! "see below"
17306 .cindex "customizing" "&'Received:'& header"
17307 .cindex "&'Received:'& header line" "customizing"
17308 This string defines the contents of the &'Received:'& message header that is
17309 added to each message, except for the timestamp, which is automatically added
17310 on at the end (preceded by a semicolon). The string is expanded each time it is
17311 used. If the expansion yields an empty string, no &'Received:'& header line is
17312 added to the message. Otherwise, the string should start with the text
17313 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17315 The default setting is:
17318 received_header_text = Received: \
17319 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17320 {${if def:sender_ident \
17321 {from ${quote_local_part:$sender_ident} }}\
17322 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17323 by $primary_hostname \
17324 ${if def:received_protocol {with $received_protocol }}\
17325 ${if def:tls_in_ver { ($tls_in_ver)}}\
17326 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17327 (Exim $version_number)\n\t\
17328 ${if def:sender_address \
17329 {(envelope-from <$sender_address>)\n\t}}\
17330 id $message_exim_id\
17331 ${if def:received_for {\n\tfor $received_for}}
17334 The references to the TLS version and cipher are
17335 omitted when Exim is built without TLS
17336 support. The use of conditional expansions ensures that this works for both
17337 locally generated messages and messages received from remote hosts, giving
17338 header lines such as the following:
17340 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17341 by marley.carol.example with esmtp (Exim 4.00)
17342 (envelope-from <bob@carol.example>)
17343 id 16IOWa-00019l-00
17344 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17345 Received: by scrooge.carol.example with local (Exim 4.00)
17346 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17348 Until the body of the message has been received, the timestamp is the time when
17349 the message started to be received. Once the body has arrived, and all policy
17350 checks have taken place, the timestamp is updated to the time at which the
17351 message was accepted.
17354 .option received_headers_max main integer 30
17355 .cindex "loop" "prevention"
17356 .cindex "mail loop prevention"
17357 .cindex "&'Received:'& header line" "counting"
17358 When a message is to be delivered, the number of &'Received:'& headers is
17359 counted, and if it is greater than this parameter, a mail loop is assumed to
17360 have occurred, the delivery is abandoned, and an error message is generated.
17361 This applies to both local and remote deliveries.
17364 .option recipient_unqualified_hosts main "host list&!!" unset
17365 .cindex "unqualified addresses"
17366 .cindex "host" "unqualified addresses from"
17367 This option lists those hosts from which Exim is prepared to accept unqualified
17368 recipient addresses in message envelopes. The addresses are made fully
17369 qualified by the addition of the &%qualify_recipient%& value. This option also
17370 affects message header lines. Exim does not reject unqualified recipient
17371 addresses in headers, but it qualifies them only if the message came from a
17372 host that matches &%recipient_unqualified_hosts%&,
17373 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17374 option was not set.
17377 .option recipients_max main integer 0
17378 .cindex "limit" "number of recipients"
17379 .cindex "recipient" "maximum number"
17380 If this option is set greater than zero, it specifies the maximum number of
17381 original recipients for any message. Additional recipients that are generated
17382 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17383 all recipients over the limit; earlier recipients are delivered as normal.
17384 Non-SMTP messages with too many recipients are failed, and no deliveries are
17387 .cindex "RCPT" "maximum number of incoming"
17388 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17389 RCPT commands in a single message.
17392 .option recipients_max_reject main boolean false
17393 If this option is set true, Exim rejects SMTP messages containing too many
17394 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17395 error to the eventual DATA command. Otherwise (the default) it gives a 452
17396 error to the surplus RCPT commands and accepts the message on behalf of the
17397 initial set of recipients. The remote server should then re-send the message
17398 for the remaining recipients at a later time.
17401 .option remote_max_parallel main integer 2
17402 .cindex "delivery" "parallelism for remote"
17403 This option controls parallel delivery of one message to a number of remote
17404 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17405 does all the remote deliveries for a message one by one. Otherwise, if a single
17406 message has to be delivered to more than one remote host, or if several copies
17407 have to be sent to the same remote host, up to &%remote_max_parallel%&
17408 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17409 deliveries are required, the maximum number of processes are started, and as
17410 each one finishes, another is begun. The order of starting processes is the
17411 same as if sequential delivery were being done, and can be controlled by the
17412 &%remote_sort_domains%& option. If parallel delivery takes place while running
17413 with debugging turned on, the debugging output from each delivery process is
17414 tagged with its process id.
17416 This option controls only the maximum number of parallel deliveries for one
17417 message in one Exim delivery process. Because Exim has no central queue
17418 manager, there is no way of controlling the total number of simultaneous
17419 deliveries if the configuration allows a delivery attempt as soon as a message
17422 See also the &%max_parallel%& generic transport option,
17423 and the &%serialize_hosts%& smtp transport option.
17425 .cindex "number of deliveries"
17426 .cindex "delivery" "maximum number of"
17427 If you want to control the total number of deliveries on the system, you
17428 need to set the &%queue_only%& option. This ensures that all incoming messages
17429 are added to the queue without starting a delivery process. Then set up an Exim
17430 daemon to start queue runner processes at appropriate intervals (probably
17431 fairly often, for example, every minute), and limit the total number of queue
17432 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17433 delivers only one message at a time, the maximum number of deliveries that can
17434 then take place at once is &%queue_run_max%& multiplied by
17435 &%remote_max_parallel%&.
17437 If it is purely remote deliveries you want to control, use
17438 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17439 doing the SMTP routing before queueing, so that several messages for the same
17440 host will eventually get delivered down the same connection.
17443 .option remote_sort_domains main "domain list&!!" unset
17444 .cindex "sorting remote deliveries"
17445 .cindex "delivery" "sorting remote"
17446 When there are a number of remote deliveries for a message, they are sorted by
17447 domain into the order given by this list. For example,
17449 remote_sort_domains = *.cam.ac.uk:*.uk
17451 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17452 then to those in the &%uk%& domain, then to any others.
17455 .option retry_data_expire main time 7d
17456 .cindex "hints database" "data expiry"
17457 This option sets a &"use before"& time on retry information in Exim's hints
17458 database. Any older retry data is ignored. This means that, for example, once a
17459 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17463 .option retry_interval_max main time 24h
17464 .cindex "retry" "limit on interval"
17465 .cindex "limit" "on retry interval"
17466 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17467 intervals between delivery attempts for messages that cannot be delivered
17468 straight away. This option sets an overall limit to the length of time between
17469 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17473 .option return_path_remove main boolean true
17474 .cindex "&'Return-path:'& header line" "removing"
17475 RFC 2821, section 4.4, states that an SMTP server must insert a
17476 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17477 The &'Return-path:'& header preserves the sender address as received in the
17478 MAIL command. This description implies that this header should not be present
17479 in an incoming message. If &%return_path_remove%& is true, any existing
17480 &'Return-path:'& headers are removed from messages at the time they are
17481 received. Exim's transports have options for adding &'Return-path:'& headers at
17482 the time of delivery. They are normally used only for final local deliveries.
17485 .option return_size_limit main integer 100K
17486 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17489 .option rfc1413_hosts main "host list&!!" @[]
17491 .cindex "host" "for RFC 1413 calls"
17492 RFC 1413 identification calls are made to any client host which matches
17493 an item in the list.
17494 The default value specifies just this host, being any local interface
17497 .option rfc1413_query_timeout main time 0s
17498 .cindex "RFC 1413" "query timeout"
17499 .cindex "timeout" "for RFC 1413 call"
17500 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17501 no RFC 1413 calls are ever made.
17504 .option sender_unqualified_hosts main "host list&!!" unset
17505 .cindex "unqualified addresses"
17506 .cindex "host" "unqualified addresses from"
17507 This option lists those hosts from which Exim is prepared to accept unqualified
17508 sender addresses. The addresses are made fully qualified by the addition of
17509 &%qualify_domain%&. This option also affects message header lines. Exim does
17510 not reject unqualified addresses in headers that contain sender addresses, but
17511 it qualifies them only if the message came from a host that matches
17512 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17513 using TCP/IP), and the &%-bnq%& option was not set.
17516 .option slow_lookup_log main integer 0
17517 .cindex "logging" "slow lookups"
17518 .cindex "dns" "logging slow lookups"
17519 This option controls logging of slow lookups.
17520 If the value is nonzero it is taken as a number of milliseconds
17521 and lookups taking longer than this are logged.
17522 Currently this applies only to DNS lookups.
17526 .option smtp_accept_keepalive main boolean true
17527 .cindex "keepalive" "on incoming connection"
17528 This option controls the setting of the SO_KEEPALIVE option on incoming
17529 TCP/IP socket connections. When set, it causes the kernel to probe idle
17530 connections periodically, by sending packets with &"old"& sequence numbers. The
17531 other end of the connection should send an acknowledgment if the connection is
17532 still okay or a reset if the connection has been aborted. The reason for doing
17533 this is that it has the beneficial effect of freeing up certain types of
17534 connection that can get stuck when the remote host is disconnected without
17535 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17536 hours to detect unreachable hosts.
17540 .option smtp_accept_max main integer 20
17541 .cindex "limit" "incoming SMTP connections"
17542 .cindex "SMTP" "incoming connection count"
17544 This option specifies the maximum number of simultaneous incoming SMTP calls
17545 that Exim will accept. It applies only to the listening daemon; there is no
17546 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17547 value is set to zero, no limit is applied. However, it is required to be
17548 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17549 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17551 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17552 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17553 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17554 and &%smtp_load_reserve%& are then checked before accepting the connection.
17557 .option smtp_accept_max_nonmail main integer 10
17558 .cindex "limit" "non-mail SMTP commands"
17559 .cindex "SMTP" "limiting non-mail commands"
17560 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17561 the connection if there are too many. This option defines &"too many"&. The
17562 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17563 client looping sending EHLO, for example. The check is applied only if the
17564 client host matches &%smtp_accept_max_nonmail_hosts%&.
17566 When a new message is expected, one occurrence of RSET is not counted. This
17567 allows a client to send one RSET between messages (this is not necessary,
17568 but some clients do it). Exim also allows one uncounted occurrence of HELO
17569 or EHLO, and one occurrence of STARTTLS between messages. After
17570 starting up a TLS session, another EHLO is expected, and so it too is not
17571 counted. The first occurrence of AUTH in a connection, or immediately
17572 following STARTTLS is not counted. Otherwise, all commands other than
17573 MAIL, RCPT, DATA, and QUIT are counted.
17576 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17577 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17578 check by setting this option. The default value makes it apply to all hosts. By
17579 changing the value, you can exclude any badly-behaved hosts that you have to
17583 . Allow this long option name to split; give it unsplit as a fifth argument
17584 . for the automatic .oindex that is generated by .option.
17585 . We insert " &~&~" which is both pretty nasty visually and results in
17586 . non-searchable text. HowItWorks.txt mentions an option for inserting
17587 . zero-width-space, which would be nicer visually and results in (at least)
17588 . html that Firefox will split on when it's forced to reflow (rather than
17589 . inserting a horizontal scrollbar). However, the text is still not
17590 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17591 . the option name to split.
17593 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17594 smtp_accept_max_per_connection
17595 .cindex "SMTP" "limiting incoming message count"
17596 .cindex "limit" "messages per SMTP connection"
17597 The value of this option limits the number of MAIL commands that Exim is
17598 prepared to accept over a single SMTP connection, whether or not each command
17599 results in the transfer of a message. After the limit is reached, a 421
17600 response is given to subsequent MAIL commands. This limit is a safety
17601 precaution against a client that goes mad (incidents of this type have been
17604 The option is expanded after the HELO or EHLO is received
17605 and may depend on values available at that time.
17606 An empty or zero value after expansion removes the limit.
17610 .option smtp_accept_max_per_host main string&!! unset
17611 .cindex "limit" "SMTP connections from one host"
17612 .cindex "host" "limiting SMTP connections from"
17613 This option restricts the number of simultaneous IP connections from a single
17614 host (strictly, from a single IP address) to the Exim daemon. The option is
17615 expanded, to enable different limits to be applied to different hosts by
17616 reference to &$sender_host_address$&. Once the limit is reached, additional
17617 connection attempts from the same host are rejected with error code 421. This
17618 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17619 of zero imposes no limit. If this option is set greater than zero, it is
17620 required that &%smtp_accept_max%& be non-zero.
17622 &*Warning*&: When setting this option you should not use any expansion
17623 constructions that take an appreciable amount of time. The expansion and test
17624 happen in the main daemon loop, in order to reject additional connections
17625 without forking additional processes (otherwise a denial-of-service attack
17626 could cause a vast number or processes to be created). While the daemon is
17627 doing this processing, it cannot accept any other incoming connections.
17631 .option smtp_accept_queue main integer 0
17632 .cindex "SMTP" "incoming connection count"
17633 .cindex "queueing incoming messages"
17634 .cindex "message" "queueing by SMTP connection count"
17635 If the number of simultaneous incoming SMTP connections being handled via the
17636 listening daemon exceeds this value, messages received by SMTP are just placed
17637 in the queue; no delivery processes are started automatically. The count is
17638 fixed at the start of an SMTP connection. It cannot be updated in the
17639 subprocess that receives messages, and so the queueing or not queueing applies
17640 to all messages received in the same connection.
17642 A value of zero implies no limit, and clearly any non-zero value is useful only
17643 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17644 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17645 various &%-od%&&'x'& command line options.
17648 . See the comment on smtp_accept_max_per_connection
17650 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17651 smtp_accept_queue_per_connection
17652 .cindex "queueing incoming messages"
17653 .cindex "message" "queueing by message count"
17654 This option limits the number of delivery processes that Exim starts
17655 automatically when receiving messages via SMTP, whether via the daemon or by
17656 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17657 and the number of messages received in a single SMTP session exceeds this
17658 number, subsequent messages are placed in the queue, but no delivery processes
17659 are started. This helps to limit the number of Exim processes when a server
17660 restarts after downtime and there is a lot of mail waiting for it on other
17661 systems. On large systems, the default should probably be increased, and on
17662 dial-in client systems it should probably be set to zero (that is, disabled).
17665 .option smtp_accept_reserve main integer 0
17666 .cindex "SMTP" "incoming call count"
17667 .cindex "host" "reserved"
17668 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17669 number of SMTP connections that are reserved for connections from the hosts
17670 that are specified in &%smtp_reserve_hosts%&. The value set in
17671 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17672 restricted to this number of connections; the option specifies a minimum number
17673 of connection slots for them, not a maximum. It is a guarantee that this group
17674 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17675 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17678 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17679 set to 5, once there are 45 active connections (from any hosts), new
17680 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17681 provided the other criteria for acceptance are met.
17684 .option smtp_active_hostname main string&!! unset
17685 .cindex "host" "name in SMTP responses"
17686 .cindex "SMTP" "host name in responses"
17687 .vindex "&$primary_hostname$&"
17688 This option is provided for multi-homed servers that want to masquerade as
17689 several different hosts. At the start of an incoming SMTP connection, its value
17690 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17691 responses. For example, it is used as domain name in the response to an
17692 incoming HELO or EHLO command.
17694 .vindex "&$smtp_active_hostname$&"
17695 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17696 is saved with any messages that are received. It is therefore available for use
17697 in routers and transports when the message is later delivered.
17699 If this option is unset, or if its expansion is forced to fail, or if the
17700 expansion results in an empty string, the value of &$primary_hostname$& is
17701 used. Other expansion failures cause a message to be written to the main and
17702 panic logs, and the SMTP command receives a temporary error. Typically, the
17703 value of &%smtp_active_hostname%& depends on the incoming interface address.
17706 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17707 {cox.mydomain}{box.mydomain}}
17710 Although &$smtp_active_hostname$& is primarily concerned with incoming
17711 messages, it is also used as the default for HELO commands in callout
17712 verification if there is no remote transport from which to obtain a
17713 &%helo_data%& value.
17715 .option smtp_banner main string&!! "see below"
17716 .cindex "SMTP" "welcome banner"
17717 .cindex "banner for SMTP"
17718 .cindex "welcome banner for SMTP"
17719 .cindex "customizing" "SMTP banner"
17720 This string, which is expanded every time it is used, is output as the initial
17721 positive response to an SMTP connection. The default setting is:
17723 smtp_banner = $smtp_active_hostname ESMTP Exim \
17724 $version_number $tod_full
17726 Failure to expand the string causes a panic error. If you want to create a
17727 multiline response to the initial SMTP connection, use &"\n"& in the string at
17728 appropriate points, but not at the end. Note that the 220 code is not included
17729 in this string. Exim adds it automatically (several times in the case of a
17730 multiline response).
17733 .option smtp_check_spool_space main boolean true
17734 .cindex "checking disk space"
17735 .cindex "disk space, checking"
17736 .cindex "spool directory" "checking space"
17737 When this option is set, if an incoming SMTP session encounters the SIZE
17738 option on a MAIL command, it checks that there is enough space in the
17739 spool directory's partition to accept a message of that size, while still
17740 leaving free the amount specified by &%check_spool_space%& (even if that value
17741 is zero). If there isn't enough space, a temporary error code is returned.
17744 .option smtp_connect_backlog main integer 20
17745 .cindex "connection backlog"
17746 .cindex "SMTP" "connection backlog"
17747 .cindex "backlog of connections"
17748 This option specifies a maximum number of waiting SMTP connections. Exim passes
17749 this value to the TCP/IP system when it sets up its listener. Once this number
17750 of connections are waiting for the daemon's attention, subsequent connection
17751 attempts are refused at the TCP/IP level. At least, that is what the manuals
17752 say; in some circumstances such connection attempts have been observed to time
17753 out instead. For large systems it is probably a good idea to increase the
17754 value (to 50, say). It also gives some protection against denial-of-service
17755 attacks by SYN flooding.
17758 .option smtp_enforce_sync main boolean true
17759 .cindex "SMTP" "synchronization checking"
17760 .cindex "synchronization checking in SMTP"
17761 The SMTP protocol specification requires the client to wait for a response from
17762 the server at certain points in the dialogue. Without PIPELINING these
17763 synchronization points are after every command; with PIPELINING they are
17764 fewer, but they still exist.
17766 Some spamming sites send out a complete set of SMTP commands without waiting
17767 for any response. Exim protects against this by rejecting a message if the
17768 client has sent further input when it should not have. The error response &"554
17769 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17770 for this error cannot be perfect because of transmission delays (unexpected
17771 input may be on its way but not yet received when Exim checks). However, it
17772 does detect many instances.
17774 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17775 If you want to disable the check selectively (for example, only for certain
17776 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17777 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17781 .option smtp_etrn_command main string&!! unset
17782 .cindex "ETRN" "command to be run"
17783 .cindex "ESMTP extensions" ETRN
17784 .vindex "&$domain$&"
17785 If this option is set, the given command is run whenever an SMTP ETRN
17786 command is received from a host that is permitted to issue such commands (see
17787 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17788 are independently expanded. The expansion variable &$domain$& is set to the
17789 argument of the ETRN command, and no syntax checking is done on it. For
17792 smtp_etrn_command = /etc/etrn_command $domain \
17793 $sender_host_address
17795 If the option is not set, the argument for the ETRN command must
17796 be a &'#'& followed by an address string.
17797 In this case an &'exim -R <string>'& command is used;
17798 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17800 A new process is created to run the command, but Exim does not wait for it to
17801 complete. Consequently, its status cannot be checked. If the command cannot be
17802 run, a line is written to the panic log, but the ETRN caller still receives
17803 a 250 success response. Exim is normally running under its own uid when
17804 receiving SMTP, so it is not possible for it to change the uid before running
17808 .option smtp_etrn_serialize main boolean true
17809 .cindex "ETRN" "serializing"
17810 When this option is set, it prevents the simultaneous execution of more than
17811 one identical command as a result of ETRN in an SMTP connection. See
17812 section &<<SECTETRN>>& for details.
17815 .option smtp_load_reserve main fixed-point unset
17816 .cindex "load average"
17817 If the system load average ever gets higher than this, incoming SMTP calls are
17818 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17819 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17820 the load is over the limit. The option has no effect on ancient operating
17821 systems on which Exim cannot determine the load average. See also
17822 &%deliver_queue_load_max%& and &%queue_only_load%&.
17826 .option smtp_max_synprot_errors main integer 3
17827 .cindex "SMTP" "limiting syntax and protocol errors"
17828 .cindex "limit" "SMTP syntax and protocol errors"
17829 Exim rejects SMTP commands that contain syntax or protocol errors. In
17830 particular, a syntactically invalid email address, as in this command:
17832 RCPT TO:<abc xyz@a.b.c>
17834 causes immediate rejection of the command, before any other tests are done.
17835 (The ACL cannot be run if there is no valid address to set up for it.) An
17836 example of a protocol error is receiving RCPT before MAIL. If there are
17837 too many syntax or protocol errors in one SMTP session, the connection is
17838 dropped. The limit is set by this option.
17840 .cindex "PIPELINING" "expected errors"
17841 When the PIPELINING extension to SMTP is in use, some protocol errors are
17842 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17843 Exim assumes that PIPELINING will be used if it advertises it (see
17844 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17845 not count towards the limit.
17849 .option smtp_max_unknown_commands main integer 3
17850 .cindex "SMTP" "limiting unknown commands"
17851 .cindex "limit" "unknown SMTP commands"
17852 If there are too many unrecognized commands in an incoming SMTP session, an
17853 Exim server drops the connection. This is a defence against some kinds of abuse
17856 into making connections to SMTP ports; in these circumstances, a number of
17857 non-SMTP command lines are sent first.
17861 .option smtp_ratelimit_hosts main "host list&!!" unset
17862 .cindex "SMTP" "rate limiting"
17863 .cindex "limit" "rate of message arrival"
17864 .cindex "RCPT" "rate limiting"
17865 Some sites find it helpful to be able to limit the rate at which certain hosts
17866 can send them messages, and the rate at which an individual message can specify
17869 Exim has two rate-limiting facilities. This section describes the older
17870 facility, which can limit rates within a single connection. The newer
17871 &%ratelimit%& ACL condition can limit rates across all connections. See section
17872 &<<SECTratelimiting>>& for details of the newer facility.
17874 When a host matches &%smtp_ratelimit_hosts%&, the values of
17875 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17876 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17877 respectively. Each option, if set, must contain a set of four comma-separated
17881 A threshold, before which there is no rate limiting.
17883 An initial time delay. Unlike other times in Exim, numbers with decimal
17884 fractional parts are allowed here.
17886 A factor by which to increase the delay each time.
17888 A maximum value for the delay. This should normally be less than 5 minutes,
17889 because after that time, the client is liable to timeout the SMTP command.
17892 For example, these settings have been used successfully at the site which
17893 first suggested this feature, for controlling mail from their customers:
17895 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17896 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17898 The first setting specifies delays that are applied to MAIL commands after
17899 two have been received over a single connection. The initial delay is 0.5
17900 seconds, increasing by a factor of 1.05 each time. The second setting applies
17901 delays to RCPT commands when more than four occur in a single message.
17904 .option smtp_ratelimit_mail main string unset
17905 See &%smtp_ratelimit_hosts%& above.
17908 .option smtp_ratelimit_rcpt main string unset
17909 See &%smtp_ratelimit_hosts%& above.
17912 .option smtp_receive_timeout main time&!! 5m
17913 .cindex "timeout" "for SMTP input"
17914 .cindex "SMTP" "input timeout"
17915 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17916 input, including batch SMTP. If a line of input (either an SMTP command or a
17917 data line) is not received within this time, the SMTP connection is dropped and
17918 the message is abandoned.
17919 A line is written to the log containing one of the following messages:
17921 SMTP command timeout on connection from...
17922 SMTP data timeout on connection from...
17924 The former means that Exim was expecting to read an SMTP command; the latter
17925 means that it was in the DATA phase, reading the contents of a message.
17927 If the first character of the option is a &"$"& the option is
17928 expanded before use and may depend on
17929 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17933 The value set by this option can be overridden by the
17934 &%-os%& command-line option. A setting of zero time disables the timeout, but
17935 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17936 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17937 timeout is controlled by &%receive_timeout%& and &%-or%&.
17940 .option smtp_reserve_hosts main "host list&!!" unset
17941 This option defines hosts for which SMTP connections are reserved; see
17942 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17945 .option smtp_return_error_details main boolean false
17946 .cindex "SMTP" "details policy failures"
17947 .cindex "policy control" "rejection, returning details"
17948 In the default state, Exim uses bland messages such as
17949 &"Administrative prohibition"& when it rejects SMTP commands for policy
17950 reasons. Many sysadmins like this because it gives away little information
17951 to spammers. However, some other sysadmins who are applying strict checking
17952 policies want to give out much fuller information about failures. Setting
17953 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17954 example, instead of &"Administrative prohibition"&, it might give:
17956 550-Rejected after DATA: '>' missing at end of address:
17957 550 failing address in "From" header is: <user@dom.ain
17961 .option smtputf8_advertise_hosts main "host list&!!" *
17962 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17963 .cindex "ESMTP extensions" SMTPUTF8
17964 When Exim is built with support for internationalised mail names,
17965 the availability thereof is advertised in
17966 response to EHLO only to those client hosts that match this option. See
17967 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17970 .option spamd_address main string "127.0.0.1 783"
17971 This option is available when Exim is compiled with the content-scanning
17972 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17973 See section &<<SECTscanspamass>>& for more details.
17977 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17978 This option is available when Exim is compiled with SPF support.
17979 See section &<<SECSPF>>& for more details.
17981 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
17982 This option is available when Exim is compiled with SPF support. It
17983 allows the customisation of the SMTP comment that the SPF library
17984 generates. You are strongly encouraged to link to your own explanative
17985 site. The template must not contain spaces. If you need spaces in the
17986 output, use the proper placeholder. If libspf2 can not parse the
17987 template, it uses a built-in default broken link. The following placeholders
17988 (along with Exim variables (but see below)) are allowed in the template:
17992 &*%{L}*&: Envelope sender's local part.
17994 &*%{S}*&: Envelope sender.
17996 &*%{O}*&: Envelope sender's domain.
17998 &*%{D}*&: Current(?) domain.
18000 &*%{I}*&: SMTP client Ip.
18002 &*%{C}*&: SMTP client pretty IP.
18004 &*%{T}*&: Epoch time (UTC).
18006 &*%{P}*&: SMTP client domain name.
18008 &*%{V}*&: IP version.
18010 &*%{H}*&: EHLO/HELO domain.
18012 &*%{R}*&: Receiving domain.
18014 The capitalized placeholders do proper URL encoding, if you use them
18015 lowercased, no encoding takes place. This list was compiled from the
18018 A note on using Exim variables: As
18019 currently the SPF library is initialized before the SMTP EHLO phase,
18020 the variables useful for expansion are quite limited.
18023 .option split_spool_directory main boolean false
18024 .cindex "multiple spool directories"
18025 .cindex "spool directory" "split"
18026 .cindex "directories, multiple"
18027 If this option is set, it causes Exim to split its input directory into 62
18028 subdirectories, each with a single alphanumeric character as its name. The
18029 sixth character of the message id is used to allocate messages to
18030 subdirectories; this is the least significant base-62 digit of the time of
18031 arrival of the message.
18033 Splitting up the spool in this way may provide better performance on systems
18034 where there are long mail queues, by reducing the number of files in any one
18035 directory. The msglog directory is also split up in a similar way to the input
18036 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18037 are still placed in the single directory &_msglog.OLD_&.
18039 It is not necessary to take any special action for existing messages when
18040 changing &%split_spool_directory%&. Exim notices messages that are in the
18041 &"wrong"& place, and continues to process them. If the option is turned off
18042 after a period of being on, the subdirectories will eventually empty and be
18043 automatically deleted.
18045 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18046 changes. Instead of creating a list of all messages in the queue, and then
18047 trying to deliver each one, in turn, it constructs a list of those in one
18048 sub-directory and tries to deliver them, before moving on to the next
18049 sub-directory. The sub-directories are processed in a random order. This
18050 spreads out the scanning of the input directories, and uses less memory. It is
18051 particularly beneficial when there are lots of messages in the queue. However,
18052 if &%queue_run_in_order%& is set, none of this new processing happens. The
18053 entire queue has to be scanned and sorted before any deliveries can start.
18056 .option spool_directory main string&!! "set at compile time"
18057 .cindex "spool directory" "path to"
18058 This defines the directory in which Exim keeps its spool, that is, the messages
18059 it is waiting to deliver. The default value is taken from the compile-time
18060 configuration setting, if there is one. If not, this option must be set. The
18061 string is expanded, so it can contain, for example, a reference to
18062 &$primary_hostname$&.
18064 If the spool directory name is fixed on your installation, it is recommended
18065 that you set it at build time rather than from this option, particularly if the
18066 log files are being written to the spool directory (see &%log_file_path%&).
18067 Otherwise log files cannot be used for errors that are detected early on, such
18068 as failures in the configuration file.
18070 By using this option to override the compiled-in path, it is possible to run
18071 tests of Exim without using the standard spool.
18073 .option spool_wireformat main boolean false
18074 .cindex "spool directory" "file formats"
18075 If this option is set, Exim may for some messages use an alternative format
18076 for data-files in the spool which matches the wire format.
18077 Doing this permits more efficient message reception and transmission.
18078 Currently it is only done for messages received using the ESMTP CHUNKING
18081 The following variables will not have useful values:
18083 $max_received_linelength
18088 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18089 and any external programs which are passed a reference to a message data file
18090 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18091 will need to be aware of the different formats potentially available.
18093 Using any of the ACL conditions noted will negate the reception benefit
18094 (as a Unix-mbox-format file is constructed for them).
18095 The transmission benefit is maintained.
18097 .option sqlite_lock_timeout main time 5s
18098 .cindex "sqlite lookup type" "lock timeout"
18099 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18100 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18102 .option strict_acl_vars main boolean false
18103 .cindex "&ACL;" "variables, handling unset"
18104 This option controls what happens if a syntactically valid but undefined ACL
18105 variable is referenced. If it is false (the default), an empty string
18106 is substituted; if it is true, an error is generated. See section
18107 &<<SECTaclvariables>>& for details of ACL variables.
18109 .option strip_excess_angle_brackets main boolean false
18110 .cindex "angle brackets, excess"
18111 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18112 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18113 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18114 passed on to another MTA, the excess angle brackets are not passed on. If this
18115 option is not set, multiple pairs of angle brackets cause a syntax error.
18118 .option strip_trailing_dot main boolean false
18119 .cindex "trailing dot on domain"
18120 .cindex "dot" "trailing on domain"
18121 If this option is set, a trailing dot at the end of a domain in an address is
18122 ignored. If this is in the envelope and the message is passed on to another
18123 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18124 domain causes a syntax error.
18125 However, addresses in header lines are checked only when an ACL requests header
18129 .option syslog_duplication main boolean true
18130 .cindex "syslog" "duplicate log lines; suppressing"
18131 When Exim is logging to syslog, it writes the log lines for its three
18132 separate logs at different syslog priorities so that they can in principle
18133 be separated on the logging hosts. Some installations do not require this
18134 separation, and in those cases, the duplication of certain log lines is a
18135 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18136 particular log line is written to syslog. For lines that normally go to
18137 both the main log and the reject log, the reject log version (possibly
18138 containing message header lines) is written, at LOG_NOTICE priority.
18139 Lines that normally go to both the main and the panic log are written at
18140 the LOG_ALERT priority.
18143 .option syslog_facility main string unset
18144 .cindex "syslog" "facility; setting"
18145 This option sets the syslog &"facility"& name, used when Exim is logging to
18146 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18147 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18148 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18149 details of Exim's logging.
18152 .option syslog_pid main boolean true
18153 .cindex "syslog" "pid"
18154 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18155 omitted when these lines are sent to syslog. (Syslog normally prefixes
18156 the log lines with the PID of the logging process automatically.) You need
18157 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18158 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18162 .option syslog_processname main string &`exim`&
18163 .cindex "syslog" "process name; setting"
18164 This option sets the syslog &"ident"& name, used when Exim is logging to
18165 syslog. The value must be no longer than 32 characters. See chapter
18166 &<<CHAPlog>>& for details of Exim's logging.
18170 .option syslog_timestamp main boolean true
18171 .cindex "syslog" "timestamps"
18172 .cindex timestamps syslog
18173 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18174 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18175 details of Exim's logging.
18178 .option system_filter main string&!! unset
18179 .cindex "filter" "system filter"
18180 .cindex "system filter" "specifying"
18181 .cindex "Sieve filter" "not available for system filter"
18182 This option specifies an Exim filter file that is applied to all messages at
18183 the start of each delivery attempt, before any routing is done. System filters
18184 must be Exim filters; they cannot be Sieve filters. If the system filter
18185 generates any deliveries to files or pipes, or any new mail messages, the
18186 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18187 which transports are to be used. Details of this facility are given in chapter
18188 &<<CHAPsystemfilter>>&.
18189 A forced expansion failure results in no filter operation.
18192 .option system_filter_directory_transport main string&!! unset
18193 .vindex "&$address_file$&"
18194 This sets the name of the transport driver that is to be used when the
18195 &%save%& command in a system message filter specifies a path ending in &"/"&,
18196 implying delivery of each message into a separate file in some directory.
18197 During the delivery, the variable &$address_file$& contains the path name.
18200 .option system_filter_file_transport main string&!! unset
18201 .cindex "file" "transport for system filter"
18202 This sets the name of the transport driver that is to be used when the &%save%&
18203 command in a system message filter specifies a path not ending in &"/"&. During
18204 the delivery, the variable &$address_file$& contains the path name.
18206 .option system_filter_group main string unset
18207 .cindex "gid (group id)" "system filter"
18208 This option is used only when &%system_filter_user%& is also set. It sets the
18209 gid under which the system filter is run, overriding any gid that is associated
18210 with the user. The value may be numerical or symbolic.
18212 .option system_filter_pipe_transport main string&!! unset
18213 .cindex "&(pipe)& transport" "for system filter"
18214 .vindex "&$address_pipe$&"
18215 This specifies the transport driver that is to be used when a &%pipe%& command
18216 is used in a system filter. During the delivery, the variable &$address_pipe$&
18217 contains the pipe command.
18220 .option system_filter_reply_transport main string&!! unset
18221 .cindex "&(autoreply)& transport" "for system filter"
18222 This specifies the transport driver that is to be used when a &%mail%& command
18223 is used in a system filter.
18226 .option system_filter_user main string unset
18227 .cindex "uid (user id)" "system filter"
18228 If this option is set to root, the system filter is run in the main Exim
18229 delivery process, as root. Otherwise, the system filter runs in a separate
18230 process, as the given user, defaulting to the Exim run-time user.
18231 Unless the string consists entirely of digits, it
18232 is looked up in the password data. Failure to find the named user causes a
18233 configuration error. The gid is either taken from the password data, or
18234 specified by &%system_filter_group%&. When the uid is specified numerically,
18235 &%system_filter_group%& is required to be set.
18237 If the system filter generates any pipe, file, or reply deliveries, the uid
18238 under which the filter is run is used when transporting them, unless a
18239 transport option overrides.
18242 .option tcp_nodelay main boolean true
18243 .cindex "daemon" "TCP_NODELAY on sockets"
18244 .cindex "Nagle algorithm"
18245 .cindex "TCP_NODELAY on listening sockets"
18246 If this option is set false, it stops the Exim daemon setting the
18247 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18248 turns off the &"Nagle algorithm"&, which is a way of improving network
18249 performance in interactive (character-by-character) situations. Turning it off
18250 should improve Exim's performance a bit, so that is what happens by default.
18251 However, it appears that some broken clients cannot cope, and time out. Hence
18252 this option. It affects only those sockets that are set up for listening by the
18253 daemon. Sockets created by the smtp transport for delivering mail always set
18257 .option timeout_frozen_after main time 0s
18258 .cindex "frozen messages" "timing out"
18259 .cindex "timeout" "frozen messages"
18260 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18261 message of any kind that has been in the queue for longer than the given time
18262 is automatically cancelled at the next queue run. If the frozen message is a
18263 bounce message, it is just discarded; otherwise, a bounce is sent to the
18264 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18265 If you want to timeout frozen bounce messages earlier than other kinds of
18266 frozen message, see &%ignore_bounce_errors_after%&.
18268 &*Note:*& the default value of zero means no timeouts; with this setting,
18269 frozen messages remain in the queue forever (except for any frozen bounce
18270 messages that are released by &%ignore_bounce_errors_after%&).
18273 .option timezone main string unset
18274 .cindex "timezone, setting"
18275 .cindex "environment" "values from"
18276 The value of &%timezone%& is used to set the environment variable TZ while
18277 running Exim (if it is different on entry). This ensures that all timestamps
18278 created by Exim are in the required timezone. If you want all your timestamps
18279 to be in UTC (aka GMT) you should set
18283 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18284 or, if that is not set, from the value of the TZ environment variable when Exim
18285 is built. If &%timezone%& is set to the empty string, either at build or run
18286 time, any existing TZ variable is removed from the environment when Exim
18287 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18288 unfortunately not all, operating systems.
18291 .option tls_advertise_hosts main "host list&!!" *
18292 .cindex "TLS" "advertising"
18293 .cindex "encryption" "on SMTP connection"
18294 .cindex "SMTP" "encrypted connection"
18295 .cindex "ESMTP extensions" STARTTLS
18296 When Exim is built with support for TLS encrypted connections, the availability
18297 of the STARTTLS command to set up an encrypted session is advertised in
18298 response to EHLO only to those client hosts that match this option. See
18299 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18300 Note that the default value requires that a certificate be supplied
18301 using the &%tls_certificate%& option. If TLS support for incoming connections
18302 is not required the &%tls_advertise_hosts%& option should be set empty.
18305 .option tls_certificate main string list&!! unset
18306 .cindex "TLS" "server certificate; location of"
18307 .cindex "certificate" "server, location of"
18308 The value of this option is expanded, and must then be a list of absolute paths to
18309 files which contain the server's certificates (in PEM format).
18310 Commonly only one file is needed.
18311 The server's private key is also
18312 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18313 &<<CHAPTLS>>& for further details.
18315 &*Note*&: The certificates defined by this option are used only when Exim is
18316 receiving incoming messages as a server. If you want to supply certificates for
18317 use when sending messages as a client, you must set the &%tls_certificate%&
18318 option in the relevant &(smtp)& transport.
18320 &*Note*&: If you use filenames based on IP addresses, change the list
18321 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18323 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18324 when a list of more than one
18325 file is used, the &$tls_in_ourcert$& variable is unreliable.
18326 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18328 .cindex SNI "selecting server certificate based on"
18329 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18330 if the OpenSSL build supports TLS extensions and the TLS client sends the
18331 Server Name Indication extension, then this option and others documented in
18332 &<<SECTtlssni>>& will be re-expanded.
18334 If this option is unset or empty a fresh self-signed certificate will be
18335 generated for every connection.
18337 .option tls_crl main string&!! unset
18338 .cindex "TLS" "server certificate revocation list"
18339 .cindex "certificate" "revocation list for server"
18340 This option specifies a certificate revocation list. The expanded value must
18341 be the name of a file that contains CRLs in PEM format.
18343 Under OpenSSL the option can specify a directory with CRL files.
18345 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18346 for each signing element of the certificate chain (i.e. all but the leaf).
18347 For the file variant this can be multiple PEM blocks in the one file.
18349 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18352 .option tls_dh_max_bits main integer 2236
18353 .cindex "TLS" "D-H bit count"
18354 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18355 the chosen TLS library. That value might prove to be too high for
18356 interoperability. This option provides a maximum clamp on the value
18357 suggested, trading off security for interoperability.
18359 The value must be at least 1024.
18361 The value 2236 was chosen because, at time of adding the option, it was the
18362 hard-coded maximum value supported by the NSS cryptographic library, as used
18363 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18365 If you prefer more security and are willing to break some clients, raise this
18368 Note that the value passed to GnuTLS for *generating* a new prime may be a
18369 little less than this figure, because GnuTLS is inexact and may produce a
18370 larger prime than requested.
18373 .option tls_dhparam main string&!! unset
18374 .cindex "TLS" "D-H parameters for server"
18375 The value of this option is expanded and indicates the source of DH parameters
18376 to be used by Exim.
18378 This option is ignored for GnuTLS version 3.6.0 and later.
18379 The library manages parameter negotiation internally.
18381 &*Note: The Exim Maintainers strongly recommend,
18382 for other TLS library versions,
18383 using a filename with site-generated
18384 local DH parameters*&, which has been supported across all versions of Exim. The
18385 other specific constants available are a fallback so that even when
18386 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18388 If &%tls_dhparam%& is a filename starting with a &`/`&,
18389 then it names a file from which DH
18390 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18391 PKCS#3 representation of the DH prime. If the file does not exist, for
18392 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18393 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18394 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18395 and treated as though the &%tls_dhparam%& were set to "none".
18397 If this option expands to the string "none", then no DH parameters will be
18400 If this option expands to the string "historic" and Exim is using GnuTLS, then
18401 Exim will attempt to load a file from inside the spool directory. If the file
18402 does not exist, Exim will attempt to create it.
18403 See section &<<SECTgnutlsparam>>& for further details.
18405 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18406 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18408 In older versions of Exim the default was the 2048 bit prime described in section
18409 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18410 in IKE is assigned number 23.
18412 Otherwise, the option must expand to the name used by Exim for any of a number
18413 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18414 sources. As names, Exim uses a standard specified name, else "ike" followed by
18415 the number used by IKE, or "default" which corresponds to
18416 &`exim.dev.20160529.3`&.
18418 The available standard primes are:
18419 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18420 &`ike1`&, &`ike2`&, &`ike5`&,
18421 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18422 &`ike22`&, &`ike23`& and &`ike24`&.
18424 The available additional primes are:
18425 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18427 Some of these will be too small to be accepted by clients.
18428 Some may be too large to be accepted by clients.
18429 The open cryptographic community has suspicions about the integrity of some
18430 of the later IKE values, which led into RFC7919 providing new fixed constants
18431 (the "ffdhe" identifiers).
18433 At this point, all of the "ike" values should be considered obsolete;
18434 they're still in Exim to avoid breaking unusual configurations, but are
18435 candidates for removal the next time we have backwards-incompatible changes.
18437 The TLS protocol does not negotiate an acceptable size for this; clients tend
18438 to hard-drop connections if what is offered by the server is unacceptable,
18439 whether too large or too small, and there's no provision for the client to
18440 tell the server what these constraints are. Thus, as a server operator, you
18441 need to make an educated guess as to what is most likely to work for your
18444 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18445 is most likely to maximise interoperability. The upper bound comes from
18446 applications using the Mozilla Network Security Services (NSS) library, which
18447 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18448 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18449 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18450 acceptable bound from 1024 to 2048.
18453 .option tls_eccurve main string&!! &`auto`&
18454 .cindex TLS "EC cryptography"
18455 This option selects a EC curve for use by Exim when used with OpenSSL.
18456 It has no effect when Exim is used with GnuTLS.
18458 After expansion it must contain a valid EC curve parameter, such as
18459 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18460 for valid selections.
18462 For OpenSSL versions before (and not including) 1.0.2, the string
18463 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18464 &`auto`& tells the library to choose.
18466 If the option expands to an empty string, no EC curves will be enabled.
18469 .option tls_ocsp_file main string&!! unset
18470 .cindex TLS "certificate status"
18471 .cindex TLS "OCSP proof file"
18473 must if set expand to the absolute path to a file which contains a current
18474 status proof for the server's certificate, as obtained from the
18475 Certificate Authority.
18477 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18478 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18480 For OpenSSL 1.1.0 or later, and
18481 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18482 of files, to match a list given for the &%tls_certificate%& option.
18483 The ordering of the two lists must match.
18484 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18486 The file(s) should be in DER format,
18487 except for GnuTLS 3.6.3 or later
18489 when an optional filetype prefix can be used.
18490 The prefix must be one of "DER" or "PEM", followed by
18491 a single space. If one is used it sets the format for subsequent
18492 files in the list; the initial format is DER.
18493 If multiple proofs are wanted, for multiple chain elements
18494 (this only works under TLS1.3)
18495 they must be coded as a combined OCSP response.
18497 Although GnuTLS will accept PEM files with multiple separate
18498 PEM blobs (ie. separate OCSP responses), it sends them in the
18499 TLS Certificate record interleaved with the certificates of the chain;
18500 although a GnuTLS client is happy with that, an OpenSSL client is not.
18502 .option tls_on_connect_ports main "string list" unset
18505 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18506 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18507 set up without waiting for the client to issue a STARTTLS command. For
18508 further details, see section &<<SECTsupobssmt>>&.
18512 .option tls_privatekey main string list&!! unset
18513 .cindex "TLS" "server private key; location of"
18514 The value of this option is expanded, and must then be a list of absolute paths to
18515 files which contains the server's private keys.
18516 If this option is unset, or if
18517 the expansion is forced to fail, or the result is an empty string, the private
18518 key is assumed to be in the same file as the server's certificates. See chapter
18519 &<<CHAPTLS>>& for further details.
18521 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18524 .option tls_remember_esmtp main boolean false
18525 .cindex "TLS" "esmtp state; remembering"
18526 .cindex "TLS" "broken clients"
18527 If this option is set true, Exim violates the RFCs by remembering that it is in
18528 &"esmtp"& state after successfully negotiating a TLS session. This provides
18529 support for broken clients that fail to send a new EHLO after starting a
18533 .option tls_require_ciphers main string&!! unset
18534 .cindex "TLS" "requiring specific ciphers"
18535 .cindex "cipher" "requiring specific"
18536 This option controls which ciphers can be used for incoming TLS connections.
18537 The &(smtp)& transport has an option of the same name for controlling outgoing
18538 connections. This option is expanded for each connection, so can be varied for
18539 different clients if required. The value of this option must be a list of
18540 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18541 in somewhat different ways. If GnuTLS is being used, the client controls the
18542 preference order of the available ciphers. Details are given in sections
18543 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18547 .option tls_resumption_hosts main "host list&!!" unset
18548 .cindex TLS resumption
18549 This option controls which connections to offer the TLS resumption feature.
18550 See &<<SECTresumption>>& for details.
18554 .option tls_try_verify_hosts main "host list&!!" unset
18555 .cindex "TLS" "client certificate verification"
18556 .cindex "certificate" "verification of client"
18557 See &%tls_verify_hosts%& below.
18560 .option tls_verify_certificates main string&!! system
18561 .cindex "TLS" "client certificate verification"
18562 .cindex "certificate" "verification of client"
18563 The value of this option is expanded, and must then be either the
18565 or the absolute path to
18566 a file or directory containing permitted certificates for clients that
18567 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18569 The "system" value for the option will use a
18570 system default location compiled into the SSL library.
18571 This is not available for GnuTLS versions preceding 3.0.20,
18572 and will be taken as empty; an explicit location
18575 The use of a directory for the option value is not available for GnuTLS versions
18576 preceding 3.3.6 and a single file must be used.
18578 With OpenSSL the certificates specified
18580 either by file or directory
18581 are added to those given by the system default location.
18583 These certificates should be for the certificate authorities trusted, rather
18584 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18585 the value is a file then the certificates are sent by Exim as a server to
18586 connecting clients, defining the list of accepted certificate authorities.
18587 Thus the values defined should be considered public data. To avoid this,
18588 use the explicit directory version. (If your peer is Exim up to 4.85,
18589 using GnuTLS, you may need to send the CAs (thus using the file
18590 variant). Otherwise the peer doesn't send its certificate.)
18592 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18594 A forced expansion failure or setting to an empty string is equivalent to
18598 .option tls_verify_hosts main "host list&!!" unset
18599 .cindex "TLS" "client certificate verification"
18600 .cindex "certificate" "verification of client"
18601 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18602 certificates from clients. The expected certificates are defined by
18603 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18604 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18605 &%tls_verify_certificates%& is not set.
18607 Any client that matches &%tls_verify_hosts%& is constrained by
18608 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18609 present one of the listed certificates. If it does not, the connection is
18610 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18611 the host to use TLS. It can still send SMTP commands through unencrypted
18612 connections. Forcing a client to use TLS has to be done separately using an
18613 ACL to reject inappropriate commands when the connection is not encrypted.
18615 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18616 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18617 certificate and checks it against &%tls_verify_certificates%&, but does not
18618 abort the connection if there is no certificate or if it does not match. This
18619 state can be detected in an ACL, which makes it possible to implement policies
18620 such as &"accept for relay only if a verified certificate has been received,
18621 but accept for local delivery if encrypted, even without a verified
18624 Client hosts that match neither of these lists are not asked to present
18628 .option trusted_groups main "string list&!!" unset
18629 .cindex "trusted groups"
18630 .cindex "groups" "trusted"
18631 This option is expanded just once, at the start of Exim's processing. If this
18632 option is set, any process that is running in one of the listed groups, or
18633 which has one of them as a supplementary group, is trusted. The groups can be
18634 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18635 details of what trusted callers are permitted to do. If neither
18636 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18639 .option trusted_users main "string list&!!" unset
18640 .cindex "trusted users"
18641 .cindex "user" "trusted"
18642 This option is expanded just once, at the start of Exim's processing. If this
18643 option is set, any process that is running as one of the listed users is
18644 trusted. The users can be specified numerically or by name. See section
18645 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18646 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18647 Exim user are trusted.
18649 .option unknown_login main string&!! unset
18650 .cindex "uid (user id)" "unknown caller"
18651 .vindex "&$caller_uid$&"
18652 This is a specialized feature for use in unusual configurations. By default, if
18653 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18654 gives up. The &%unknown_login%& option can be used to set a login name to be
18655 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18656 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18657 is used for the user's real name (gecos field), unless this has been set by the
18660 .option unknown_username main string unset
18661 See &%unknown_login%&.
18663 .option untrusted_set_sender main "address list&!!" unset
18664 .cindex "trusted users"
18665 .cindex "sender" "setting by untrusted user"
18666 .cindex "untrusted user setting sender"
18667 .cindex "user" "untrusted setting sender"
18668 .cindex "envelope from"
18669 .cindex "envelope sender"
18670 When an untrusted user submits a message to Exim using the standard input, Exim
18671 normally creates an envelope sender address from the user's login and the
18672 default qualification domain. Data from the &%-f%& option (for setting envelope
18673 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18674 is used) is ignored.
18676 However, untrusted users are permitted to set an empty envelope sender address,
18677 to declare that a message should never generate any bounces. For example:
18679 exim -f '<>' user@domain.example
18681 .vindex "&$sender_ident$&"
18682 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18683 other envelope sender addresses in a controlled way. When it is set, untrusted
18684 users are allowed to set envelope sender addresses that match any of the
18685 patterns in the list. Like all address lists, the string is expanded. The
18686 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18687 users to setting senders that start with their login ids
18688 followed by a hyphen
18689 by a setting like this:
18691 untrusted_set_sender = ^$sender_ident-
18693 If you want to allow untrusted users to set envelope sender addresses without
18694 restriction, you can use
18696 untrusted_set_sender = *
18698 The &%untrusted_set_sender%& option applies to all forms of local input, but
18699 only to the setting of the envelope sender. It does not permit untrusted users
18700 to use the other options which trusted user can use to override message
18701 parameters. Furthermore, it does not stop Exim from removing an existing
18702 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18703 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18704 overriding these actions. The handling of the &'Sender:'& header is also
18705 described in section &<<SECTthesenhea>>&.
18707 The log line for a message's arrival shows the envelope sender following
18708 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18709 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18710 envelope sender address, the user's login is shown in parentheses after the
18714 .option uucp_from_pattern main string "see below"
18715 .cindex "&""From""& line"
18716 .cindex "UUCP" "&""From""& line"
18717 Some applications that pass messages to an MTA via a command line interface use
18718 an initial line starting with &"From&~"& to pass the envelope sender. In
18719 particular, this is used by UUCP software. Exim recognizes such a line by means
18720 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18721 matches, the sender address is constructed by expanding the contents of
18722 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18723 default pattern recognizes lines in the following two forms:
18725 From ph10 Fri Jan 5 12:35 GMT 1996
18726 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18728 The pattern can be seen by running
18730 exim -bP uucp_from_pattern
18732 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18733 year in the second case. The first word after &"From&~"& is matched in the
18734 regular expression by a parenthesized subpattern. The default value for
18735 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18736 (&"ph10"& in the example above) as the message's sender. See also
18737 &%ignore_fromline_hosts%&.
18740 .option uucp_from_sender main string&!! &`$1`&
18741 See &%uucp_from_pattern%& above.
18744 .option warn_message_file main string&!! unset
18745 .cindex "warning of delay" "customizing the message"
18746 .cindex "customizing" "warning message"
18747 This option defines a template file containing paragraphs of text to be used
18748 for constructing the warning message which is sent by Exim when a message has
18749 been in the queue for a specified amount of time, as specified by
18750 &%delay_warning%&. Details of the file's contents are given in chapter
18751 &<<CHAPemsgcust>>&.
18752 .cindex warn_message_file "tainted data"
18753 The option is expanded to give the file path, which must be
18754 absolute and untainted.
18755 See also &%bounce_message_file%&.
18758 .option write_rejectlog main boolean true
18759 .cindex "reject log" "disabling"
18760 If this option is set false, Exim no longer writes anything to the reject log.
18761 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18762 .ecindex IIDconfima
18763 .ecindex IIDmaiconf
18768 . ////////////////////////////////////////////////////////////////////////////
18769 . ////////////////////////////////////////////////////////////////////////////
18771 .chapter "Generic options for routers" "CHAProutergeneric"
18772 .scindex IIDgenoprou1 "options" "generic; for routers"
18773 .scindex IIDgenoprou2 "generic options" "router"
18774 This chapter describes the generic options that apply to all routers.
18775 Those that are preconditions are marked with ‡ in the &"use"& field.
18777 For a general description of how a router operates, see sections
18778 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18779 which the preconditions are tested. The order of expansion of the options that
18780 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18781 &%headers_remove%&, &%transport%&.
18785 .option address_data routers string&!! unset
18786 .cindex "router" "data attached to address"
18787 The string is expanded just before the router is run, that is, after all the
18788 precondition tests have succeeded. If the expansion is forced to fail, the
18789 router declines, the value of &%address_data%& remains unchanged, and the
18790 &%more%& option controls what happens next. Other expansion failures cause
18791 delivery of the address to be deferred.
18793 .vindex "&$address_data$&"
18794 When the expansion succeeds, the value is retained with the address, and can be
18795 accessed using the variable &$address_data$& in the current router, subsequent
18796 routers, and the eventual transport.
18798 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18799 that runs a user's filter file, the contents of &$address_data$& are accessible
18800 in the filter. This is not normally a problem, because such data is usually
18801 either not confidential or it &"belongs"& to the current user, but if you do
18802 put confidential data into &$address_data$& you need to remember this point.
18804 Even if the router declines or passes, the value of &$address_data$& remains
18805 with the address, though it can be changed by another &%address_data%& setting
18806 on a subsequent router. If a router generates child addresses, the value of
18807 &$address_data$& propagates to them. This also applies to the special kind of
18808 &"child"& that is generated by a router with the &%unseen%& option.
18810 The idea of &%address_data%& is that you can use it to look up a lot of data
18811 for the address once, and then pick out parts of the data later. For example,
18812 you could use a single LDAP lookup to return a string of the form
18814 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18816 In the transport you could pick out the mailbox by a setting such as
18818 file = ${extract{mailbox}{$address_data}}
18820 This makes the configuration file less messy, and also reduces the number of
18821 lookups (though Exim does cache lookups).
18823 See also the &%set%& option below.
18825 .vindex "&$sender_address_data$&"
18826 .vindex "&$address_data$&"
18827 The &%address_data%& facility is also useful as a means of passing information
18828 from one router to another, and from a router to a transport. In addition, if
18829 &$address_data$& is set by a router when verifying a recipient address from an
18830 ACL, it remains available for use in the rest of the ACL statement. After
18831 verifying a sender, the value is transferred to &$sender_address_data$&.
18835 .option address_test routers&!? boolean true
18837 .cindex "router" "skipping when address testing"
18838 If this option is set false, the router is skipped when routing is being tested
18839 by means of the &%-bt%& command line option. This can be a convenience when
18840 your first router sends messages to an external scanner, because it saves you
18841 having to set the &"already scanned"& indicator when testing real address
18846 .option cannot_route_message routers string&!! unset
18847 .cindex "router" "customizing &""cannot route""& message"
18848 .cindex "customizing" "&""cannot route""& message"
18849 This option specifies a text message that is used when an address cannot be
18850 routed because Exim has run out of routers. The default message is
18851 &"Unrouteable address"&. This option is useful only on routers that have
18852 &%more%& set false, or on the very last router in a configuration, because the
18853 value that is used is taken from the last router that is considered. This
18854 includes a router that is skipped because its preconditions are not met, as
18855 well as a router that declines. For example, using the default configuration,
18858 cannot_route_message = Remote domain not found in DNS
18860 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18863 cannot_route_message = Unknown local user
18865 on the final router that checks for local users. If string expansion fails for
18866 this option, the default message is used. Unless the expansion failure was
18867 explicitly forced, a message about the failure is written to the main and panic
18868 logs, in addition to the normal message about the routing failure.
18871 .option caseful_local_part routers boolean false
18872 .cindex "case of local parts"
18873 .cindex "router" "case of local parts"
18874 By default, routers handle the local parts of addresses in a case-insensitive
18875 manner, though the actual case is preserved for transmission with the message.
18876 If you want the case of letters to be significant in a router, you must set
18877 this option true. For individual router options that contain address or local
18878 part lists (for example, &%local_parts%&), case-sensitive matching can be
18879 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18882 .vindex "&$local_part$&"
18883 .vindex "&$original_local_part$&"
18884 .vindex "&$parent_local_part$&"
18885 The value of the &$local_part$& variable is forced to lower case while a
18886 router is running unless &%caseful_local_part%& is set. When a router assigns
18887 an address to a transport, the value of &$local_part$& when the transport runs
18888 is the same as it was in the router. Similarly, when a router generates child
18889 addresses by aliasing or forwarding, the values of &$original_local_part$&
18890 and &$parent_local_part$& are those that were used by the redirecting router.
18892 This option applies to the processing of an address by a router. When a
18893 recipient address is being processed in an ACL, there is a separate &%control%&
18894 modifier that can be used to specify case-sensitive processing within the ACL
18895 (see section &<<SECTcontrols>>&).
18899 .option check_local_user routers&!? boolean false
18900 .cindex "local user, checking in router"
18901 .cindex "router" "checking for local user"
18902 .cindex "&_/etc/passwd_&"
18904 When this option is true, Exim checks that the local part of the recipient
18905 address (with affixes removed if relevant) is the name of an account on the
18906 local system. The check is done by calling the &[getpwnam()]& function rather
18907 than trying to read &_/etc/passwd_& directly. This means that other methods of
18908 holding password data (such as NIS) are supported. If the local part is a local
18910 .cindex "tainted data" "de-tainting"
18911 &$local_part_data$& is set to an untainted version of the local part and
18912 &$home$& is set from the password data. The latter can be tested in other
18913 preconditions that are evaluated after this one (the order of evaluation is
18914 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18915 overridden by &%router_home_directory%&. If the local part is not a local user,
18916 the router is skipped.
18918 If you want to check that the local part is either the name of a local user
18919 or matches something else, you cannot combine &%check_local_user%& with a
18920 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18921 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18922 setting to achieve this. For example:
18924 local_parts = passwd;$local_part : lsearch;/etc/other/users
18926 Note, however, that the side effects of &%check_local_user%& (such as setting
18927 up a home directory) do not occur when a &(passwd)& lookup is used in a
18928 &%local_parts%& (or any other) precondition.
18932 .option condition routers&!? string&!! unset
18933 .cindex "router" "customized precondition"
18934 This option specifies a general precondition test that has to succeed for the
18935 router to be called. The &%condition%& option is the last precondition to be
18936 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18937 result is a forced failure, or an empty string, or one of the strings &"0"& or
18938 &"no"& or &"false"& (checked without regard to the case of the letters), the
18939 router is skipped, and the address is offered to the next one.
18941 If the result is any other value, the router is run (as this is the last
18942 precondition to be evaluated, all the other preconditions must be true).
18944 This option is unusual in that multiple &%condition%& options may be present.
18945 All &%condition%& options must succeed.
18947 The &%condition%& option provides a means of applying custom conditions to the
18948 running of routers. Note that in the case of a simple conditional expansion,
18949 the default expansion values are exactly what is wanted. For example:
18951 condition = ${if >{$message_age}{600}}
18953 Because of the default behaviour of the string expansion, this is equivalent to
18955 condition = ${if >{$message_age}{600}{true}{}}
18958 A multiple condition example, which succeeds:
18960 condition = ${if >{$message_age}{600}}
18961 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18965 If the expansion fails (other than forced failure) delivery is deferred. Some
18966 of the other precondition options are common special cases that could in fact
18967 be specified using &%condition%&.
18969 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18970 are far older, and use one set of semantics. ACLs are newer and when
18971 they were created, the ACL &%condition%& process was given far stricter
18972 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18973 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18974 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18975 Router rules processing behavior.
18977 This is best illustrated in an example:
18979 # If used in an ACL condition will fail with a syntax error, but
18980 # in a router condition any extra characters are treated as a string
18982 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18985 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18988 In each example above, the &%if%& statement actually ends after
18989 &"{google.com}}"&. Since no true or false braces were defined, the
18990 default &%if%& behavior is to return a boolean true or a null answer
18991 (which evaluates to false). The rest of the line is then treated as a
18992 string. So the first example resulted in the boolean answer &"true"&
18993 with the string &" {yes} {no}}"& appended to it. The second example
18994 resulted in the null output (indicating false) with the string
18995 &" {yes} {no}}"& appended to it.
18997 In fact you can put excess forward braces in too. In the router
18998 &%condition%&, Exim's parser only looks for &"{"& symbols when they
18999 mean something, like after a &"$"& or when required as part of a
19000 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19003 Thus, in a Router, the above expansion strings will both always evaluate
19004 true, as the result of expansion is a non-empty string which doesn't
19005 match an explicit false value. This can be tricky to debug. By
19006 contrast, in an ACL either of those strings will always result in an
19007 expansion error because the result doesn't look sufficiently boolean.
19010 .option debug_print routers string&!! unset
19011 .cindex "testing" "variables in drivers"
19012 If this option is set and debugging is enabled (see the &%-d%& command line
19013 option) or in address-testing mode (see the &%-bt%& command line option),
19014 the string is expanded and included in the debugging output.
19015 If expansion of the string fails, the error message is written to the debugging
19016 output, and Exim carries on processing.
19017 This option is provided to help with checking out the values of variables and
19018 so on when debugging router configurations. For example, if a &%condition%&
19019 option appears not to be working, &%debug_print%& can be used to output the
19020 variables it references. The output happens after checks for &%domains%&,
19021 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19022 are tested. A newline is added to the text if it does not end with one.
19023 The variable &$router_name$& contains the name of the router.
19027 .option disable_logging routers boolean false
19028 If this option is set true, nothing is logged for any routing errors
19029 or for any deliveries caused by this router. You should not set this option
19030 unless you really, really know what you are doing. See also the generic
19031 transport option of the same name.
19033 .option dnssec_request_domains routers "domain list&!!" *
19034 .cindex "MX record" "security"
19035 .cindex "DNSSEC" "MX lookup"
19036 .cindex "security" "MX lookup"
19037 .cindex "DNS" "DNSSEC"
19038 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19039 the DNSSEC request bit set.
19040 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19042 .option dnssec_require_domains routers "domain list&!!" unset
19043 .cindex "MX record" "security"
19044 .cindex "DNSSEC" "MX lookup"
19045 .cindex "security" "MX lookup"
19046 .cindex "DNS" "DNSSEC"
19047 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19048 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19049 (AD bit) set will be ignored and logged as a host-lookup failure.
19050 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19053 .option domains routers&!? "domain list&!!" unset
19054 .cindex "router" "restricting to specific domains"
19055 .vindex "&$domain_data$&"
19056 If this option is set, the router is skipped unless the current domain matches
19057 the list. If the match is achieved by means of a file lookup, the data that the
19058 lookup returned for the domain is placed in &$domain_data$& for use in string
19059 expansions of the driver's private options and in the transport.
19060 See section &<<SECTrouprecon>>& for
19061 a list of the order in which preconditions are evaluated.
19065 .option driver routers string unset
19066 This option must always be set. It specifies which of the available routers is
19070 .option dsn_lasthop routers boolean false
19071 .cindex "DSN" "success"
19072 .cindex "Delivery Status Notification" "success"
19073 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19074 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19075 instead send a success DSN as if the next hop does not support DSN.
19076 Not effective on redirect routers.
19080 .option errors_to routers string&!! unset
19081 .cindex "envelope from"
19082 .cindex "envelope sender"
19083 .cindex "router" "changing address for errors"
19084 If a router successfully handles an address, it may assign the address to a
19085 transport for delivery or it may generate child addresses. In both cases, if
19086 there is a delivery problem during later processing, the resulting bounce
19087 message is sent to the address that results from expanding this string,
19088 provided that the address verifies successfully. The &%errors_to%& option is
19089 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19091 The &%errors_to%& setting associated with an address can be overridden if it
19092 subsequently passes through other routers that have their own &%errors_to%&
19093 settings, or if the message is delivered by a transport with a &%return_path%&
19096 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19097 the expansion fails to verify, the errors address associated with the incoming
19098 address is used. At top level, this is the envelope sender. A non-forced
19099 expansion failure causes delivery to be deferred.
19101 If an address for which &%errors_to%& has been set ends up being delivered over
19102 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19103 any bounces that are generated by other MTAs on the delivery route are also
19104 sent there. You can set &%errors_to%& to the empty string by either of these
19110 An expansion item that yields an empty string has the same effect. If you do
19111 this, a locally detected delivery error for addresses processed by this router
19112 no longer gives rise to a bounce message; the error is discarded. If the
19113 address is delivered to a remote host, the return path is set to &`<>`&, unless
19114 overridden by the &%return_path%& option on the transport.
19116 .vindex "&$address_data$&"
19117 If for some reason you want to discard local errors, but use a non-empty
19118 MAIL command for remote delivery, you can preserve the original return
19119 path in &$address_data$& in the router, and reinstate it in the transport by
19120 setting &%return_path%&.
19122 The most common use of &%errors_to%& is to direct mailing list bounces to the
19123 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19124 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19128 .option expn routers&!? boolean true
19129 .cindex "address" "testing"
19130 .cindex "testing" "addresses"
19131 .cindex "EXPN" "router skipping"
19132 .cindex "router" "skipping for EXPN"
19133 If this option is turned off, the router is skipped when testing an address
19134 as a result of processing an SMTP EXPN command. You might, for example,
19135 want to turn it off on a router for users' &_.forward_& files, while leaving it
19136 on for the system alias file.
19137 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19140 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19141 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19142 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19146 .option fail_verify routers boolean false
19147 .cindex "router" "forcing verification failure"
19148 Setting this option has the effect of setting both &%fail_verify_sender%& and
19149 &%fail_verify_recipient%& to the same value.
19153 .option fail_verify_recipient routers boolean false
19154 If this option is true and an address is accepted by this router when
19155 verifying a recipient, verification fails.
19159 .option fail_verify_sender routers boolean false
19160 If this option is true and an address is accepted by this router when
19161 verifying a sender, verification fails.
19165 .option fallback_hosts routers "string list" unset
19166 .cindex "router" "fallback hosts"
19167 .cindex "fallback" "hosts specified on router"
19168 String expansion is not applied to this option. The argument must be a
19169 colon-separated list of host names or IP addresses. The list separator can be
19170 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19171 each name or address. In fact, the format of each item is exactly the same as
19172 defined for the list of hosts in a &(manualroute)& router (see section
19173 &<<SECTformatonehostitem>>&).
19175 If a router queues an address for a remote transport, this host list is
19176 associated with the address, and used instead of the transport's fallback host
19177 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19178 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19179 transport for further details.
19182 .option group routers string&!! "see below"
19183 .cindex "gid (group id)" "local delivery"
19184 .cindex "local transports" "uid and gid"
19185 .cindex "transport" "local"
19186 .cindex "router" "setting group"
19187 When a router queues an address for a transport, and the transport does not
19188 specify a group, the group given here is used when running the delivery
19190 The group may be specified numerically or by name. If expansion fails, the
19191 error is logged and delivery is deferred.
19192 The default is unset, unless &%check_local_user%& is set, when the default
19193 is taken from the password information. See also &%initgroups%& and &%user%&
19194 and the discussion in chapter &<<CHAPenvironment>>&.
19198 .option headers_add routers list&!! unset
19199 .cindex "header lines" "adding"
19200 .cindex "router" "adding header lines"
19201 This option specifies a list of text headers,
19202 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19203 that is associated with any addresses that are accepted by the router.
19204 Each item is separately expanded, at routing time. However, this
19205 option has no effect when an address is just being verified. The way in which
19206 the text is used to add header lines at transport time is described in section
19207 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19208 message is in the process of being transported. This means that references to
19209 header lines in string expansions in the transport's configuration do not
19210 &"see"& the added header lines.
19212 The &%headers_add%& option is expanded after &%errors_to%&, but before
19213 &%headers_remove%& and &%transport%&. If an item is empty, or if
19214 an item expansion is forced to fail, the item has no effect. Other expansion
19215 failures are treated as configuration errors.
19217 Unlike most options, &%headers_add%& can be specified multiple times
19218 for a router; all listed headers are added.
19220 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19221 router that has the &%one_time%& option set.
19223 .cindex "duplicate addresses"
19224 .oindex "&%unseen%&"
19225 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19226 additions are deleted when the address is passed on to subsequent routers.
19227 For a &%redirect%& router, if a generated address is the same as the incoming
19228 address, this can lead to duplicate addresses with different header
19229 modifications. Exim does not do duplicate deliveries (except, in certain
19230 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19231 which of the duplicates is discarded, so this ambiguous situation should be
19232 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19236 .option headers_remove routers list&!! unset
19237 .cindex "header lines" "removing"
19238 .cindex "router" "removing header lines"
19239 This option specifies a list of text headers,
19240 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19241 that is associated with any addresses that are accepted by the router.
19242 However, the option has no effect when an address is just being verified.
19243 Each list item is separately expanded, at transport time.
19244 If an item ends in *, it will match any header with the given prefix.
19246 the text is used to remove header lines at transport time is described in
19247 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19248 the message is in the process of being transported. This means that references
19249 to header lines in string expansions in the transport's configuration still
19250 &"see"& the original header lines.
19252 The &%headers_remove%& option is handled after &%errors_to%& and
19253 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19254 the item has no effect. Other expansion failures are treated as configuration
19257 Unlike most options, &%headers_remove%& can be specified multiple times
19258 for a router; all listed headers are removed.
19260 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19261 router that has the &%one_time%& option set.
19263 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19264 removal requests are deleted when the address is passed on to subsequent
19265 routers, and this can lead to problems with duplicates -- see the similar
19266 warning for &%headers_add%& above.
19268 &*Warning 3*&: Because of the separate expansion of the list items,
19269 items that contain a list separator must have it doubled.
19270 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19274 .option ignore_target_hosts routers "host list&!!" unset
19275 .cindex "IP address" "discarding"
19276 .cindex "router" "discarding IP addresses"
19277 Although this option is a host list, it should normally contain IP address
19278 entries rather than names. If any host that is looked up by the router has an
19279 IP address that matches an item in this list, Exim behaves as if that IP
19280 address did not exist. This option allows you to cope with rogue DNS entries
19283 remote.domain.example. A 127.0.0.1
19287 ignore_target_hosts = 127.0.0.1
19289 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19290 discarded in this way, the router declines. In a conventional configuration, an
19291 attempt to mail to such a domain would normally provoke the &"unrouteable
19292 domain"& error, and an attempt to verify an address in the domain would fail.
19293 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19294 router declines if presented with one of the listed addresses.
19296 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19297 means of the first or the second of the following settings, respectively:
19299 ignore_target_hosts = 0.0.0.0/0
19300 ignore_target_hosts = <; 0::0/0
19302 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19303 in the second line matches all IPv6 addresses.
19305 This option may also be useful for ignoring link-local and site-local IPv6
19306 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19307 is expanded before use as a list, it is possible to make it dependent on the
19308 domain that is being routed.
19310 .vindex "&$host_address$&"
19311 During its expansion, &$host_address$& is set to the IP address that is being
19314 .option initgroups routers boolean false
19315 .cindex "additional groups"
19316 .cindex "groups" "additional"
19317 .cindex "local transports" "uid and gid"
19318 .cindex "transport" "local"
19319 If the router queues an address for a transport, and this option is true, and
19320 the uid supplied by the router is not overridden by the transport, the
19321 &[initgroups()]& function is called when running the transport to ensure that
19322 any additional groups associated with the uid are set up. See also &%group%&
19323 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19327 .option local_part_prefix routers&!? "string list" unset
19328 .cindex affix "router precondition"
19329 .cindex "router" "prefix for local part"
19330 .cindex "prefix" "for local part, used in router"
19331 If this option is set, the router is skipped unless the local part starts with
19332 one of the given strings, or &%local_part_prefix_optional%& is true. See
19333 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19336 The list is scanned from left to right, and the first prefix that matches is
19337 used. A limited form of wildcard is available; if the prefix begins with an
19338 asterisk, it matches the longest possible sequence of arbitrary characters at
19339 the start of the local part. An asterisk should therefore always be followed by
19340 some character that does not occur in normal local parts.
19341 .cindex "multiple mailboxes"
19342 .cindex "mailbox" "multiple"
19343 Wildcarding can be used to set up multiple user mailboxes, as described in
19344 section &<<SECTmulbox>>&.
19346 .vindex "&$local_part$&"
19347 .vindex "&$local_part_prefix$&"
19348 During the testing of the &%local_parts%& option, and while the router is
19349 running, the prefix is removed from the local part, and is available in the
19350 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19351 the router accepts the address, this remains true during subsequent delivery by
19352 a transport. In particular, the local part that is transmitted in the RCPT
19353 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19354 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19355 the relevant transport.
19357 .vindex &$local_part_prefix_v$&
19358 If wildcarding (above) was used then the part of the prefix matching the
19359 wildcard is available in &$local_part_prefix_v$&.
19361 When an address is being verified, &%local_part_prefix%& affects only the
19362 behaviour of the router. If the callout feature of verification is in use, this
19363 means that the full address, including the prefix, will be used during the
19366 The prefix facility is commonly used to handle local parts of the form
19367 &%owner-something%&. Another common use is to support local parts of the form
19368 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19369 to tell a user their forwarding is broken &-- by placing a router like this one
19370 immediately before the router that handles &_.forward_& files:
19374 local_part_prefix = real-
19376 transport = local_delivery
19378 For security, it would probably be a good idea to restrict the use of this
19379 router to locally-generated messages, using a condition such as this:
19381 condition = ${if match {$sender_host_address}\
19382 {\N^(|127\.0\.0\.1)$\N}}
19385 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19386 both conditions must be met if not optional. Care must be taken if wildcards
19387 are used in both a prefix and a suffix on the same router. Different
19388 separator characters must be used to avoid ambiguity.
19391 .option local_part_prefix_optional routers boolean false
19392 See &%local_part_prefix%& above.
19396 .option local_part_suffix routers&!? "string list" unset
19397 .cindex "router" "suffix for local part"
19398 .cindex "suffix for local part" "used in router"
19399 This option operates in the same way as &%local_part_prefix%&, except that the
19400 local part must end (rather than start) with the given string, the
19401 &%local_part_suffix_optional%& option determines whether the suffix is
19402 mandatory, and the wildcard * character, if present, must be the last
19403 character of the suffix. This option facility is commonly used to handle local
19404 parts of the form &%something-request%& and multiple user mailboxes of the form
19408 .option local_part_suffix_optional routers boolean false
19409 See &%local_part_suffix%& above.
19413 .option local_parts routers&!? "local part list&!!" unset
19414 .cindex "router" "restricting to specific local parts"
19415 .cindex "local part" "checking in router"
19416 The router is run only if the local part of the address matches the list.
19417 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19419 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19420 string is expanded, it is possible to make it depend on the domain, for
19423 local_parts = dbm;/usr/local/specials/$domain_data
19425 .vindex "&$local_part_data$&"
19426 If the match is achieved by a lookup, the data that the lookup returned
19427 for the local part is placed in the variable &$local_part_data$& for use in
19428 expansions of the router's private options or in the transport.
19429 You might use this option, for
19430 example, if you have a large number of local virtual domains, and you want to
19431 send all postmaster mail to the same place without having to set up an alias in
19432 each virtual domain:
19436 local_parts = postmaster
19437 data = postmaster@real.domain.example
19441 .option log_as_local routers boolean "see below"
19442 .cindex "log" "delivery line"
19443 .cindex "delivery" "log line format"
19444 Exim has two logging styles for delivery, the idea being to make local
19445 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19446 recipient address is given just as the local part, without a domain. The use of
19447 this style is controlled by this option. It defaults to true for the &(accept)&
19448 router, and false for all the others. This option applies only when a
19449 router assigns an address to a transport. It has no effect on routers that
19450 redirect addresses.
19454 .option more routers boolean&!! true
19455 The result of string expansion for this option must be a valid boolean value,
19456 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19457 result causes an error, and delivery is deferred. If the expansion is forced to
19458 fail, the default value for the option (true) is used. Other failures cause
19459 delivery to be deferred.
19461 If this option is set false, and the router declines to handle the address, no
19462 further routers are tried, routing fails, and the address is bounced.
19464 However, if the router explicitly passes an address to the following router by
19465 means of the setting
19469 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19470 does not affect the behaviour if one of the precondition tests fails. In that
19471 case, the address is always passed to the next router.
19473 Note that &%address_data%& is not considered to be a precondition. If its
19474 expansion is forced to fail, the router declines, and the value of &%more%&
19475 controls what happens next.
19478 .option pass_on_timeout routers boolean false
19479 .cindex "timeout" "of router"
19480 .cindex "router" "timeout"
19481 If a router times out during a host lookup, it normally causes deferral of the
19482 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19483 router, overriding &%no_more%&. This may be helpful for systems that are
19484 intermittently connected to the Internet, or those that want to pass to a smart
19485 host any messages that cannot immediately be delivered.
19487 There are occasional other temporary errors that can occur while doing DNS
19488 lookups. They are treated in the same way as a timeout, and this option
19489 applies to all of them.
19493 .option pass_router routers string unset
19494 .cindex "router" "go to after &""pass""&"
19495 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19496 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19497 routing to continue, and overriding a false setting of &%more%&. When one of
19498 these routers returns &"pass"&, the address is normally handed on to the next
19499 router in sequence. This can be changed by setting &%pass_router%& to the name
19500 of another router. However (unlike &%redirect_router%&) the named router must
19501 be below the current router, to avoid loops. Note that this option applies only
19502 to the special case of &"pass"&. It does not apply when a router returns
19503 &"decline"& because it cannot handle an address.
19507 .option redirect_router routers string unset
19508 .cindex "router" "start at after redirection"
19509 Sometimes an administrator knows that it is pointless to reprocess addresses
19510 generated from alias or forward files with the same router again. For
19511 example, if an alias file translates real names into login ids there is no
19512 point searching the alias file a second time, especially if it is a large file.
19514 The &%redirect_router%& option can be set to the name of any router instance.
19515 It causes the routing of any generated addresses to start at the named router
19516 instead of at the first router. This option has no effect if the router in
19517 which it is set does not generate new addresses.
19521 .option require_files routers&!? "string list&!!" unset
19522 .cindex "file" "requiring for router"
19523 .cindex "router" "requiring file existence"
19524 This option provides a general mechanism for predicating the running of a
19525 router on the existence or non-existence of certain files or directories.
19526 Before running a router, as one of its precondition tests, Exim works its way
19527 through the &%require_files%& list, expanding each item separately.
19529 Because the list is split before expansion, any colons in expansion items must
19530 be doubled, or the facility for using a different list separator must be used
19531 (&<<SECTlistsepchange>>&).
19532 If any expansion is forced to fail, the item is ignored. Other expansion
19533 failures cause routing of the address to be deferred.
19535 If any expanded string is empty, it is ignored. Otherwise, except as described
19536 below, each string must be a fully qualified file path, optionally preceded by
19537 &"!"&. The paths are passed to the &[stat()]& function to test for the
19538 existence of the files or directories. The router is skipped if any paths not
19539 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19542 If &[stat()]& cannot determine whether a file exists or not, delivery of
19543 the message is deferred. This can happen when NFS-mounted filesystems are
19546 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19547 options, so you cannot use it to check for the existence of a file in which to
19548 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19549 full list of the order in which preconditions are evaluated.) However, as
19550 these options are all expanded, you can use the &%exists%& expansion condition
19551 to make such tests. The &%require_files%& option is intended for checking files
19552 that the router may be going to use internally, or which are needed by a
19553 transport (e.g., &_.procmailrc_&).
19555 During delivery, the &[stat()]& function is run as root, but there is a
19556 facility for some checking of the accessibility of a file by another user.
19557 This is not a proper permissions check, but just a &"rough"& check that
19558 operates as follows:
19560 If an item in a &%require_files%& list does not contain any forward slash
19561 characters, it is taken to be the user (and optional group, separated by a
19562 comma) to be checked for subsequent files in the list. If no group is specified
19563 but the user is specified symbolically, the gid associated with the uid is
19566 require_files = mail:/some/file
19567 require_files = $local_part_data:$home/.procmailrc
19569 If a user or group name in a &%require_files%& list does not exist, the
19570 &%require_files%& condition fails.
19572 Exim performs the check by scanning along the components of the file path, and
19573 checking the access for the given uid and gid. It checks for &"x"& access on
19574 directories, and &"r"& access on the final file. Note that this means that file
19575 access control lists, if the operating system has them, are ignored.
19577 &*Warning 1*&: When the router is being run to verify addresses for an
19578 incoming SMTP message, Exim is not running as root, but under its own uid. This
19579 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19580 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19581 user is not permitted to read one of the directories on the file's path.
19583 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19584 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19585 without root access. In this case, if a check for access by a particular user
19586 is requested, Exim creates a subprocess that runs as that user, and tries the
19587 check again in that process.
19589 The default action for handling an unresolved EACCES is to consider it to
19590 be caused by a configuration error, and routing is deferred because the
19591 existence or non-existence of the file cannot be determined. However, in some
19592 circumstances it may be desirable to treat this condition as if the file did
19593 not exist. If the filename (or the exclamation mark that precedes the filename
19594 for non-existence) is preceded by a plus sign, the EACCES error is treated
19595 as if the file did not exist. For example:
19597 require_files = +/some/file
19599 If the router is not an essential part of verification (for example, it
19600 handles users' &_.forward_& files), another solution is to set the &%verify%&
19601 option false so that the router is skipped when verifying.
19605 .option retry_use_local_part routers boolean "see below"
19606 .cindex "hints database" "retry keys"
19607 .cindex "local part" "in retry keys"
19608 When a delivery suffers a temporary routing failure, a retry record is created
19609 in Exim's hints database. For addresses whose routing depends only on the
19610 domain, the key for the retry record should not involve the local part, but for
19611 other addresses, both the domain and the local part should be included.
19612 Usually, remote routing is of the former kind, and local routing is of the
19615 This option controls whether the local part is used to form the key for retry
19616 hints for addresses that suffer temporary errors while being handled by this
19617 router. The default value is true for any router that has any of
19618 &%check_local_user%&,
19621 &%local_part_prefix%&,
19622 &%local_part_suffix%&,
19625 set, and false otherwise. Note that this option does not apply to hints keys
19626 for transport delays; they are controlled by a generic transport option of the
19629 Failing to set this option when it is needed
19630 (because a remote router handles only some of the local-parts for a domain)
19631 can result in incorrect error messages being generated.
19633 The setting of &%retry_use_local_part%& applies only to the router on which it
19634 appears. If the router generates child addresses, they are routed
19635 independently; this setting does not become attached to them.
19639 .option router_home_directory routers string&!! unset
19640 .cindex "router" "home directory for"
19641 .cindex "home directory" "for router"
19643 This option sets a home directory for use while the router is running. (Compare
19644 &%transport_home_directory%&, which sets a home directory for later
19645 transporting.) In particular, if used on a &(redirect)& router, this option
19646 sets a value for &$home$& while a filter is running. The value is expanded;
19647 forced expansion failure causes the option to be ignored &-- other failures
19648 cause the router to defer.
19650 Expansion of &%router_home_directory%& happens immediately after the
19651 &%check_local_user%& test (if configured), before any further expansions take
19653 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19655 While the router is running, &%router_home_directory%& overrides the value of
19656 &$home$& that came from &%check_local_user%&.
19658 When a router accepts an address and assigns it to a local transport (including
19659 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19660 delivery), the home directory setting for the transport is taken from the first
19661 of these values that is set:
19664 The &%home_directory%& option on the transport;
19666 The &%transport_home_directory%& option on the router;
19668 The password data if &%check_local_user%& is set on the router;
19670 The &%router_home_directory%& option on the router.
19673 In other words, &%router_home_directory%& overrides the password data for the
19674 router, but not for the transport.
19678 .option self routers string freeze
19679 .cindex "MX record" "pointing to local host"
19680 .cindex "local host" "MX pointing to"
19681 This option applies to those routers that use a recipient address to find a
19682 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19683 and &(manualroute)& routers.
19684 Certain configurations of the &(queryprogram)& router can also specify a list
19686 Usually such routers are configured to send the message to a remote host via an
19687 &(smtp)& transport. The &%self%& option specifies what happens when the first
19688 host on the list turns out to be the local host.
19689 The way in which Exim checks for the local host is described in section
19690 &<<SECTreclocipadd>>&.
19692 Normally this situation indicates either an error in Exim's configuration (for
19693 example, the router should be configured not to process this domain), or an
19694 error in the DNS (for example, the MX should not point to this host). For this
19695 reason, the default action is to log the incident, defer the address, and
19696 freeze the message. The following alternatives are provided for use in special
19701 Delivery of the message is tried again later, but the message is not frozen.
19703 .vitem "&%reroute%&: <&'domain'&>"
19704 The domain is changed to the given domain, and the address is passed back to
19705 be reprocessed by the routers. No rewriting of headers takes place. This
19706 behaviour is essentially a redirection.
19708 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19709 The domain is changed to the given domain, and the address is passed back to be
19710 reprocessed by the routers. Any headers that contain the original domain are
19715 .vindex "&$self_hostname$&"
19716 The router passes the address to the next router, or to the router named in the
19717 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19718 subsequent routing and delivery, the variable &$self_hostname$& contains the
19719 name of the local host that the router encountered. This can be used to
19720 distinguish between different cases for hosts with multiple names. The
19726 ensures that only those addresses that routed to the local host are passed on.
19727 Without &%no_more%&, addresses that were declined for other reasons would also
19728 be passed to the next router.
19731 Delivery fails and an error report is generated.
19734 .cindex "local host" "sending to"
19735 The anomaly is ignored and the address is queued for the transport. This
19736 setting should be used with extreme caution. For an &(smtp)& transport, it
19737 makes sense only in cases where the program that is listening on the SMTP port
19738 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19739 different configuration file that handles the domain in another way.
19744 .option senders routers&!? "address list&!!" unset
19745 .cindex "router" "checking senders"
19746 If this option is set, the router is skipped unless the message's sender
19747 address matches something on the list.
19748 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19751 There are issues concerning verification when the running of routers is
19752 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19753 setting, it sets the sender to the null string. When using the &%-bt%& option
19754 to check a configuration file, it is necessary also to use the &%-f%& option to
19755 set an appropriate sender. For incoming mail, the sender is unset when
19756 verifying the sender, but is available when verifying any recipients. If the
19757 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19761 .option set routers "string list" unset
19762 .cindex router variables
19763 This option may be used multiple times on a router;
19764 because of this the list aspect is mostly irrelevant.
19765 The list separator is a semicolon but can be changed in the
19768 Each list-element given must be of the form &"name = value"&
19769 and the names used must start with the string &"r_"&.
19770 Values containing a list-separator should have them doubled.
19771 When a router runs, the strings are evaluated in order,
19772 to create variables which are added to the set associated with
19775 This is done immediately after all the preconditions, before the
19776 evaluation of the &%address_data%& option.
19778 The variable is set with the expansion of the value.
19779 The variables can be used by the router options
19780 (not including any preconditions)
19781 and by the transport.
19782 Later definitions of a given named variable will override former ones.
19783 Variable use is via the usual &$r_...$& syntax.
19785 This is similar to the &%address_data%& option, except that
19786 many independent variables can be used, with choice of naming.
19789 .option translate_ip_address routers string&!! unset
19790 .cindex "IP address" "translating"
19791 .cindex "packet radio"
19792 .cindex "router" "IP address translation"
19793 There exist some rare networking situations (for example, packet radio) where
19794 it is helpful to be able to translate IP addresses generated by normal routing
19795 mechanisms into other IP addresses, thus performing a kind of manual IP
19796 routing. This should be done only if the normal IP routing of the TCP/IP stack
19797 is inadequate or broken. Because this is an extremely uncommon requirement, the
19798 code to support this option is not included in the Exim binary unless
19799 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19801 .vindex "&$host_address$&"
19802 The &%translate_ip_address%& string is expanded for every IP address generated
19803 by the router, with the generated address set in &$host_address$&. If the
19804 expansion is forced to fail, no action is taken.
19805 For any other expansion error, delivery of the message is deferred.
19806 If the result of the expansion is an IP address, that replaces the original
19807 address; otherwise the result is assumed to be a host name &-- this is looked
19808 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19809 produce one or more replacement IP addresses. For example, to subvert all IP
19810 addresses in some specific networks, this could be added to a router:
19812 translate_ip_address = \
19813 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19816 The file would contain lines like
19818 10.2.3.128/26 some.host
19819 10.8.4.34/26 10.44.8.15
19821 You should not make use of this facility unless you really understand what you
19826 .option transport routers string&!! unset
19827 This option specifies the transport to be used when a router accepts an address
19828 and sets it up for delivery. A transport is never needed if a router is used
19829 only for verification. The value of the option is expanded at routing time,
19830 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19831 and result must be the name of one of the configured transports. If it is not,
19832 delivery is deferred.
19834 The &%transport%& option is not used by the &(redirect)& router, but it does
19835 have some private options that set up transports for pipe and file deliveries
19836 (see chapter &<<CHAPredirect>>&).
19840 .option transport_current_directory routers string&!! unset
19841 .cindex "current directory for local transport"
19842 This option associates a current directory with any address that is routed
19843 to a local transport. This can happen either because a transport is
19844 explicitly configured for the router, or because it generates a delivery to a
19845 file or a pipe. During the delivery process (that is, at transport time), this
19846 option string is expanded and is set as the current directory, unless
19847 overridden by a setting on the transport.
19848 If the expansion fails for any reason, including forced failure, an error is
19849 logged, and delivery is deferred.
19850 See chapter &<<CHAPenvironment>>& for details of the local delivery
19856 .option transport_home_directory routers string&!! "see below"
19857 .cindex "home directory" "for local transport"
19858 This option associates a home directory with any address that is routed to a
19859 local transport. This can happen either because a transport is explicitly
19860 configured for the router, or because it generates a delivery to a file or a
19861 pipe. During the delivery process (that is, at transport time), the option
19862 string is expanded and is set as the home directory, unless overridden by a
19863 setting of &%home_directory%& on the transport.
19864 If the expansion fails for any reason, including forced failure, an error is
19865 logged, and delivery is deferred.
19867 If the transport does not specify a home directory, and
19868 &%transport_home_directory%& is not set for the router, the home directory for
19869 the transport is taken from the password data if &%check_local_user%& is set for
19870 the router. Otherwise it is taken from &%router_home_directory%& if that option
19871 is set; if not, no home directory is set for the transport.
19873 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19879 .option unseen routers boolean&!! false
19880 .cindex "router" "carrying on after success"
19881 The result of string expansion for this option must be a valid boolean value,
19882 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19883 result causes an error, and delivery is deferred. If the expansion is forced to
19884 fail, the default value for the option (false) is used. Other failures cause
19885 delivery to be deferred.
19887 When this option is set true, routing does not cease if the router accepts the
19888 address. Instead, a copy of the incoming address is passed to the next router,
19889 overriding a false setting of &%more%&. There is little point in setting
19890 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19891 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19892 sometimes true and sometimes false).
19894 .cindex "copy of message (&%unseen%& option)"
19895 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19896 qualifier in filter files. It can be used to cause copies of messages to be
19897 delivered to some other destination, while also carrying out a normal delivery.
19898 In effect, the current address is made into a &"parent"& that has two children
19899 &-- one that is delivered as specified by this router, and a clone that goes on
19900 to be routed further. For this reason, &%unseen%& may not be combined with the
19901 &%one_time%& option in a &(redirect)& router.
19903 &*Warning*&: Header lines added to the address (or specified for removal) by
19904 this router or by previous routers affect the &"unseen"& copy of the message
19905 only. The clone that continues to be processed by further routers starts with
19906 no added headers and none specified for removal. For a &%redirect%& router, if
19907 a generated address is the same as the incoming address, this can lead to
19908 duplicate addresses with different header modifications. Exim does not do
19909 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19910 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19911 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19912 &%redirect%& router may be of help.
19914 Unlike the handling of header modifications, any data that was set by the
19915 &%address_data%& option in the current or previous routers &'is'& passed on to
19916 subsequent routers.
19919 .option user routers string&!! "see below"
19920 .cindex "uid (user id)" "local delivery"
19921 .cindex "local transports" "uid and gid"
19922 .cindex "transport" "local"
19923 .cindex "router" "user for filter processing"
19924 .cindex "filter" "user for processing"
19925 When a router queues an address for a transport, and the transport does not
19926 specify a user, the user given here is used when running the delivery process.
19927 The user may be specified numerically or by name. If expansion fails, the
19928 error is logged and delivery is deferred.
19929 This user is also used by the &(redirect)& router when running a filter file.
19930 The default is unset, except when &%check_local_user%& is set. In this case,
19931 the default is taken from the password information. If the user is specified as
19932 a name, and &%group%& is not set, the group associated with the user is used.
19933 See also &%initgroups%& and &%group%& and the discussion in chapter
19934 &<<CHAPenvironment>>&.
19938 .option verify routers&!? boolean true
19939 Setting this option has the effect of setting &%verify_sender%& and
19940 &%verify_recipient%& to the same value.
19943 .option verify_only routers&!? boolean false
19944 .cindex "EXPN" "with &%verify_only%&"
19946 .cindex "router" "used only when verifying"
19947 If this option is set, the router is used only when verifying an address,
19948 delivering in cutthrough mode or
19949 testing with the &%-bv%& option, not when actually doing a delivery, testing
19950 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19951 restricted to verifying only senders or recipients by means of
19952 &%verify_sender%& and &%verify_recipient%&.
19954 &*Warning*&: When the router is being run to verify addresses for an incoming
19955 SMTP message, Exim is not running as root, but under its own uid. If the router
19956 accesses any files, you need to make sure that they are accessible to the Exim
19960 .option verify_recipient routers&!? boolean true
19961 If this option is false, the router is skipped when verifying recipient
19963 delivering in cutthrough mode
19964 or testing recipient verification using &%-bv%&.
19965 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19967 See also the &$verify_mode$& variable.
19970 .option verify_sender routers&!? boolean true
19971 If this option is false, the router is skipped when verifying sender addresses
19972 or testing sender verification using &%-bvs%&.
19973 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19975 See also the &$verify_mode$& variable.
19976 .ecindex IIDgenoprou1
19977 .ecindex IIDgenoprou2
19984 . ////////////////////////////////////////////////////////////////////////////
19985 . ////////////////////////////////////////////////////////////////////////////
19987 .chapter "The accept router" "CHID4"
19988 .cindex "&(accept)& router"
19989 .cindex "routers" "&(accept)&"
19990 The &(accept)& router has no private options of its own. Unless it is being
19991 used purely for verification (see &%verify_only%&) a transport is required to
19992 be defined by the generic &%transport%& option. If the preconditions that are
19993 specified by generic options are met, the router accepts the address and queues
19994 it for the given transport. The most common use of this router is for setting
19995 up deliveries to local mailboxes. For example:
19999 domains = mydomain.example
20001 transport = local_delivery
20003 The &%domains%& condition in this example checks the domain of the address, and
20004 &%check_local_user%& checks that the local part is the login of a local user.
20005 When both preconditions are met, the &(accept)& router runs, and queues the
20006 address for the &(local_delivery)& transport.
20013 . ////////////////////////////////////////////////////////////////////////////
20014 . ////////////////////////////////////////////////////////////////////////////
20016 .chapter "The dnslookup router" "CHAPdnslookup"
20017 .scindex IIDdnsrou1 "&(dnslookup)& router"
20018 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20019 The &(dnslookup)& router looks up the hosts that handle mail for the
20020 recipient's domain in the DNS. A transport must always be set for this router,
20021 unless &%verify_only%& is set.
20023 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20024 SRV records. If none are found, or if SRV support is not configured,
20025 MX records are looked up. If no MX records exist, address records are sought.
20026 However, &%mx_domains%& can be set to disable the direct use of address
20029 MX records of equal priority are sorted by Exim into a random order. Exim then
20030 looks for address records for the host names obtained from MX or SRV records.
20031 When a host has more than one IP address, they are sorted into a random order,
20032 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20033 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20034 generic option, the router declines.
20036 Unless they have the highest priority (lowest MX value), MX records that point
20037 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20038 are discarded, together with any other MX records of equal or lower priority.
20040 .cindex "MX record" "pointing to local host"
20041 .cindex "local host" "MX pointing to"
20042 .oindex "&%self%&" "in &(dnslookup)& router"
20043 If the host pointed to by the highest priority MX record, or looked up as an
20044 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20045 happens is controlled by the generic &%self%& option.
20048 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20049 There have been problems with DNS servers when SRV records are looked up.
20050 Some misbehaving servers return a DNS error or timeout when a non-existent
20051 SRV record is sought. Similar problems have in the past been reported for
20052 MX records. The global &%dns_again_means_nonexist%& option can help with this
20053 problem, but it is heavy-handed because it is a global option.
20055 For this reason, there are two options, &%srv_fail_domains%& and
20056 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20057 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20058 an attempt to look up an SRV or MX record causes one of these results, and the
20059 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20060 such record"&. In the case of an SRV lookup, this means that the router
20061 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20062 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20063 case routing fails.
20066 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20067 .cindex "&(dnslookup)& router" "declines"
20068 There are a few cases where a &(dnslookup)& router will decline to accept
20069 an address; if such a router is expected to handle "all remaining non-local
20070 domains", then it is important to set &%no_more%&.
20072 The router will defer rather than decline if the domain
20073 is found in the &%fail_defer_domains%& router option.
20075 Reasons for a &(dnslookup)& router to decline currently include:
20077 The domain does not exist in DNS
20079 The domain exists but the MX record's host part is just "."; this is a common
20080 convention (borrowed from SRV) used to indicate that there is no such service
20081 for this domain and to not fall back to trying A/AAAA records.
20083 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20085 MX record points to a non-existent host.
20087 MX record points to an IP address and the main section option
20088 &%allow_mx_to_ip%& is not set.
20090 MX records exist and point to valid hosts, but all hosts resolve only to
20091 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20093 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20094 &%dns_check_names_pattern%& for handling one variant of this)
20096 &%check_secondary_mx%& is set on this router but the local host can
20097 not be found in the MX records (see below)
20103 .section "Private options for dnslookup" "SECID118"
20104 .cindex "options" "&(dnslookup)& router"
20105 The private options for the &(dnslookup)& router are as follows:
20107 .option check_secondary_mx dnslookup boolean false
20108 .cindex "MX record" "checking for secondary"
20109 If this option is set, the router declines unless the local host is found in
20110 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20111 process domains for which the local host is a secondary mail exchanger
20112 differently to other domains. The way in which Exim decides whether a host is
20113 the local host is described in section &<<SECTreclocipadd>>&.
20116 .option check_srv dnslookup string&!! unset
20117 .cindex "SRV record" "enabling use of"
20118 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20119 addition to MX and address records. The support is disabled by default. To
20120 enable SRV support, set the &%check_srv%& option to the name of the service
20121 required. For example,
20125 looks for SRV records that refer to the normal smtp service. The option is
20126 expanded, so the service name can vary from message to message or address
20127 to address. This might be helpful if SRV records are being used for a
20128 submission service. If the expansion is forced to fail, the &%check_srv%&
20129 option is ignored, and the router proceeds to look for MX records in the
20132 When the expansion succeeds, the router searches first for SRV records for
20133 the given service (it assumes TCP protocol). A single SRV record with a
20134 host name that consists of just a single dot indicates &"no such service for
20135 this domain"&; if this is encountered, the router declines. If other kinds of
20136 SRV record are found, they are used to construct a host list for delivery
20137 according to the rules of RFC 2782. MX records are not sought in this case.
20139 When no SRV records are found, MX records (and address records) are sought in
20140 the traditional way. In other words, SRV records take precedence over MX
20141 records, just as MX records take precedence over address records. Note that
20142 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20143 defined it. It is apparently believed that MX records are sufficient for email
20144 and that SRV records should not be used for this purpose. However, SRV records
20145 have an additional &"weight"& feature which some people might find useful when
20146 trying to split an SMTP load between hosts of different power.
20148 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20149 when there is a DNS lookup error.
20154 .option fail_defer_domains dnslookup "domain list&!!" unset
20155 .cindex "MX record" "not found"
20156 DNS lookups for domains matching &%fail_defer_domains%&
20157 which find no matching record will cause the router to defer
20158 rather than the default behaviour of decline.
20159 This maybe be useful for queueing messages for a newly created
20160 domain while the DNS configuration is not ready.
20161 However, it will result in any message with mistyped domains
20165 .option ipv4_only "string&!!" unset
20166 .cindex IPv6 disabling
20167 .cindex DNS "IPv6 disabling"
20168 The string is expanded, and if the result is anything but a forced failure,
20169 or an empty string, or one of the strings “0” or “no” or “false”
20170 (checked without regard to the case of the letters),
20171 only A records are used.
20173 .option ipv4_prefer "string&!!" unset
20174 .cindex IPv4 preference
20175 .cindex DNS "IPv4 preference"
20176 The string is expanded, and if the result is anything but a forced failure,
20177 or an empty string, or one of the strings “0” or “no” or “false”
20178 (checked without regard to the case of the letters),
20179 A records are sorted before AAAA records (inverting the default).
20181 .option mx_domains dnslookup "domain list&!!" unset
20182 .cindex "MX record" "required to exist"
20183 .cindex "SRV record" "required to exist"
20184 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20185 record in order to be recognized. (The name of this option could be improved.)
20186 For example, if all the mail hosts in &'fict.example'& are known to have MX
20187 records, except for those in &'discworld.fict.example'&, you could use this
20190 mx_domains = ! *.discworld.fict.example : *.fict.example
20192 This specifies that messages addressed to a domain that matches the list but
20193 has no MX record should be bounced immediately instead of being routed using
20194 the address record.
20197 .option mx_fail_domains dnslookup "domain list&!!" unset
20198 If the DNS lookup for MX records for one of the domains in this list causes a
20199 DNS lookup error, Exim behaves as if no MX records were found. See section
20200 &<<SECTprowitdnsloo>>& for more discussion.
20205 .option qualify_single dnslookup boolean true
20206 .cindex "DNS" "resolver options"
20207 .cindex "DNS" "qualifying single-component names"
20208 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20209 lookups. Typically, but not standardly, this causes the resolver to qualify
20210 single-component names with the default domain. For example, on a machine
20211 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20212 &'thesaurus.ref.example'& inside the resolver. For details of what your
20213 resolver actually does, consult your man pages for &'resolver'& and
20218 .option rewrite_headers dnslookup boolean true
20219 .cindex "rewriting" "header lines"
20220 .cindex "header lines" "rewriting"
20221 If the domain name in the address that is being processed is not fully
20222 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20223 an address is specified as &'dormouse@teaparty'&, the domain might be
20224 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20225 occur as a result of setting the &%widen_domains%& option. If
20226 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20227 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20228 header lines of the message are rewritten with the full domain name.
20230 This option should be turned off only when it is known that no message is
20231 ever going to be sent outside an environment where the abbreviation makes
20234 When an MX record is looked up in the DNS and matches a wildcard record, name
20235 servers normally return a record containing the name that has been looked up,
20236 making it impossible to detect whether a wildcard was present or not. However,
20237 some name servers have recently been seen to return the wildcard entry. If the
20238 name returned by a DNS lookup begins with an asterisk, it is not used for
20242 .option same_domain_copy_routing dnslookup boolean false
20243 .cindex "address" "copying routing"
20244 Addresses with the same domain are normally routed by the &(dnslookup)& router
20245 to the same list of hosts. However, this cannot be presumed, because the router
20246 options and preconditions may refer to the local part of the address. By
20247 default, therefore, Exim routes each address in a message independently. DNS
20248 servers run caches, so repeated DNS lookups are not normally expensive, and in
20249 any case, personal messages rarely have more than a few recipients.
20251 If you are running mailing lists with large numbers of subscribers at the same
20252 domain, and you are using a &(dnslookup)& router which is independent of the
20253 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20254 lookups for identical domains in one message. In this case, when &(dnslookup)&
20255 routes an address to a remote transport, any other unrouted addresses in the
20256 message that have the same domain are automatically given the same routing
20257 without processing them independently,
20258 provided the following conditions are met:
20261 No router that processed the address specified &%headers_add%& or
20262 &%headers_remove%&.
20264 The router did not change the address in any way, for example, by &"widening"&
20271 .option search_parents dnslookup boolean false
20272 .cindex "DNS" "resolver options"
20273 When this option is true, the resolver option RES_DNSRCH is set for DNS
20274 lookups. This is different from the &%qualify_single%& option in that it
20275 applies to domains containing dots. Typically, but not standardly, it causes
20276 the resolver to search for the name in the current domain and in parent
20277 domains. For example, on a machine in the &'fict.example'& domain, if looking
20278 up &'teaparty.wonderland'& failed, the resolver would try
20279 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20280 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20282 Setting this option true can cause problems in domains that have a wildcard MX
20283 record, because any domain that does not have its own MX record matches the
20288 .option srv_fail_domains dnslookup "domain list&!!" unset
20289 If the DNS lookup for SRV records for one of the domains in this list causes a
20290 DNS lookup error, Exim behaves as if no SRV records were found. See section
20291 &<<SECTprowitdnsloo>>& for more discussion.
20296 .option widen_domains dnslookup "string list" unset
20297 .cindex "domain" "partial; widening"
20298 If a DNS lookup fails and this option is set, each of its strings in turn is
20299 added onto the end of the domain, and the lookup is tried again. For example,
20302 widen_domains = fict.example:ref.example
20304 is set and a lookup of &'klingon.dictionary'& fails,
20305 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20306 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20307 and &%search_parents%& options can cause some widening to be undertaken inside
20308 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20309 when verifying, unless &%rewrite_headers%& is false (not the default).
20312 .section "Effect of qualify_single and search_parents" "SECID119"
20313 When a domain from an envelope recipient is changed by the resolver as a result
20314 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20315 corresponding address in the message's header lines unless &%rewrite_headers%&
20316 is set false. Exim then re-routes the address, using the full domain.
20318 These two options affect only the DNS lookup that takes place inside the router
20319 for the domain of the address that is being routed. They do not affect lookups
20320 such as that implied by
20324 that may happen while processing a router precondition before the router is
20325 entered. No widening ever takes place for these lookups.
20326 .ecindex IIDdnsrou1
20327 .ecindex IIDdnsrou2
20337 . ////////////////////////////////////////////////////////////////////////////
20338 . ////////////////////////////////////////////////////////////////////////////
20340 .chapter "The ipliteral router" "CHID5"
20341 .cindex "&(ipliteral)& router"
20342 .cindex "domain literal" "routing"
20343 .cindex "routers" "&(ipliteral)&"
20344 This router has no private options. Unless it is being used purely for
20345 verification (see &%verify_only%&) a transport is required to be defined by the
20346 generic &%transport%& option. The router accepts the address if its domain part
20347 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20348 router handles the address
20352 by setting up delivery to the host with that IP address. IPv4 domain literals
20353 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20354 are similar, but the address is preceded by &`ipv6:`&. For example:
20356 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20358 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20359 grounds that sooner or later somebody will try it.
20361 .oindex "&%self%&" "in &(ipliteral)& router"
20362 If the IP address matches something in &%ignore_target_hosts%&, the router
20363 declines. If an IP literal turns out to refer to the local host, the generic
20364 &%self%& option determines what happens.
20366 The RFCs require support for domain literals; however, their use is
20367 controversial in today's Internet. If you want to use this router, you must
20368 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20369 Exim will not recognize the domain literal syntax in addresses.
20373 . ////////////////////////////////////////////////////////////////////////////
20374 . ////////////////////////////////////////////////////////////////////////////
20376 .chapter "The iplookup router" "CHID6"
20377 .cindex "&(iplookup)& router"
20378 .cindex "routers" "&(iplookup)&"
20379 The &(iplookup)& router was written to fulfil a specific requirement in
20380 Cambridge University (which in fact no longer exists). For this reason, it is
20381 not included in the binary of Exim by default. If you want to include it, you
20384 ROUTER_IPLOOKUP=yes
20386 in your &_Local/Makefile_& configuration file.
20388 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20389 connection to one or more specific hosts. The host can then return the same or
20390 a different address &-- in effect rewriting the recipient address in the
20391 message's envelope. The new address is then passed on to subsequent routers. If
20392 this process fails, the address can be passed on to other routers, or delivery
20393 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20394 must not be specified for it.
20396 .cindex "options" "&(iplookup)& router"
20397 .option hosts iplookup string unset
20398 This option must be supplied. Its value is a colon-separated list of host
20399 names. The hosts are looked up using &[gethostbyname()]&
20400 (or &[getipnodebyname()]& when available)
20401 and are tried in order until one responds to the query. If none respond, what
20402 happens is controlled by &%optional%&.
20405 .option optional iplookup boolean false
20406 If &%optional%& is true, if no response is obtained from any host, the address
20407 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20408 delivery to the address is deferred.
20411 .option port iplookup integer 0
20412 .cindex "port" "&(iplookup)& router"
20413 This option must be supplied. It specifies the port number for the TCP or UDP
20417 .option protocol iplookup string udp
20418 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20419 protocols is to be used.
20422 .option query iplookup string&!! "see below"
20423 This defines the content of the query that is sent to the remote hosts. The
20426 $local_part@$domain $local_part@$domain
20428 The repetition serves as a way of checking that a response is to the correct
20429 query in the default case (see &%response_pattern%& below).
20432 .option reroute iplookup string&!! unset
20433 If this option is not set, the rerouted address is precisely the byte string
20434 returned by the remote host, up to the first white space, if any. If set, the
20435 string is expanded to form the rerouted address. It can include parts matched
20436 in the response by &%response_pattern%& by means of numeric variables such as
20437 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20438 whether or not a pattern is in use. In all cases, the rerouted address must end
20439 up in the form &'local_part@domain'&.
20442 .option response_pattern iplookup string unset
20443 This option can be set to a regular expression that is applied to the string
20444 returned from the remote host. If the pattern does not match the response, the
20445 router declines. If &%response_pattern%& is not set, no checking of the
20446 response is done, unless the query was defaulted, in which case there is a
20447 check that the text returned after the first white space is the original
20448 address. This checks that the answer that has been received is in response to
20449 the correct question. For example, if the response is just a new domain, the
20450 following could be used:
20452 response_pattern = ^([^@]+)$
20453 reroute = $local_part@$1
20456 .option timeout iplookup time 5s
20457 This specifies the amount of time to wait for a response from the remote
20458 machine. The same timeout is used for the &[connect()]& function for a TCP
20459 call. It does not apply to UDP.
20464 . ////////////////////////////////////////////////////////////////////////////
20465 . ////////////////////////////////////////////////////////////////////////////
20467 .chapter "The manualroute router" "CHID7"
20468 .scindex IIDmanrou1 "&(manualroute)& router"
20469 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20470 .cindex "domain" "manually routing"
20471 The &(manualroute)& router is so-called because it provides a way of manually
20472 routing an address according to its domain. It is mainly used when you want to
20473 route addresses to remote hosts according to your own rules, bypassing the
20474 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20475 route to local transports, a facility that may be useful if you want to save
20476 messages for dial-in hosts in local files.
20478 The &(manualroute)& router compares a list of domain patterns with the domain
20479 it is trying to route. If there is no match, the router declines. Each pattern
20480 has associated with it a list of hosts and some other optional data, which may
20481 include a transport. The combination of a pattern and its data is called a
20482 &"routing rule"&. For patterns that do not have an associated transport, the
20483 generic &%transport%& option must specify a transport, unless the router is
20484 being used purely for verification (see &%verify_only%&).
20487 In the case of verification, matching the domain pattern is sufficient for the
20488 router to accept the address. When actually routing an address for delivery,
20489 an address that matches a domain pattern is queued for the associated
20490 transport. If the transport is not a local one, a host list must be associated
20491 with the pattern; IP addresses are looked up for the hosts, and these are
20492 passed to the transport along with the mail address. For local transports, a
20493 host list is optional. If it is present, it is passed in &$host$& as a single
20496 The list of routing rules can be provided as an inline string in
20497 &%route_list%&, or the data can be obtained by looking up the domain in a file
20498 or database by setting &%route_data%&. Only one of these settings may appear in
20499 any one instance of &(manualroute)&. The format of routing rules is described
20500 below, following the list of private options.
20503 .section "Private options for manualroute" "SECTprioptman"
20505 .cindex "options" "&(manualroute)& router"
20506 The private options for the &(manualroute)& router are as follows:
20508 .option host_all_ignored manualroute string defer
20509 See &%host_find_failed%&.
20511 .option host_find_failed manualroute string freeze
20512 This option controls what happens when &(manualroute)& tries to find an IP
20513 address for a host, and the host does not exist. The option can be set to one
20514 of the following values:
20523 The default (&"freeze"&) assumes that this state is a serious configuration
20524 error. The difference between &"pass"& and &"decline"& is that the former
20525 forces the address to be passed to the next router (or the router defined by
20528 overriding &%no_more%&, whereas the latter passes the address to the next
20529 router only if &%more%& is true.
20531 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20532 cannot be found. If all the hosts in the list are ignored, the behaviour is
20533 controlled by the &%host_all_ignored%& option. This takes the same values
20534 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20536 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20537 state; if a host lookup gets a temporary error, delivery is deferred unless the
20538 generic &%pass_on_timeout%& option is set.
20541 .option hosts_randomize manualroute boolean false
20542 .cindex "randomized host list"
20543 .cindex "host" "list of; randomized"
20544 If this option is set, the order of the items in a host list in a routing rule
20545 is randomized each time the list is used, unless an option in the routing rule
20546 overrides (see below). Randomizing the order of a host list can be used to do
20547 crude load sharing. However, if more than one mail address is routed by the
20548 same router to the same host list, the host lists are considered to be the same
20549 (even though they may be randomized into different orders) for the purpose of
20550 deciding whether to batch the deliveries into a single SMTP transaction.
20552 When &%hosts_randomize%& is true, a host list may be split
20553 into groups whose order is separately randomized. This makes it possible to
20554 set up MX-like behaviour. The boundaries between groups are indicated by an
20555 item that is just &`+`& in the host list. For example:
20557 route_list = * host1:host2:host3:+:host4:host5
20559 The order of the first three hosts and the order of the last two hosts is
20560 randomized for each use, but the first three always end up before the last two.
20561 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20562 randomized host list is passed to an &(smtp)& transport that also has
20563 &%hosts_randomize set%&, the list is not re-randomized.
20566 .option route_data manualroute string&!! unset
20567 If this option is set, it must expand to yield the data part of a routing rule.
20568 Typically, the expansion string includes a lookup based on the domain. For
20571 route_data = ${lookup{$domain}dbm{/etc/routes}}
20573 If the expansion is forced to fail, or the result is an empty string, the
20574 router declines. Other kinds of expansion failure cause delivery to be
20578 .option route_list manualroute "string list" unset
20579 This string is a list of routing rules, in the form defined below. Note that,
20580 unlike most string lists, the items are separated by semicolons. This is so
20581 that they may contain colon-separated host lists.
20584 .option same_domain_copy_routing manualroute boolean false
20585 .cindex "address" "copying routing"
20586 Addresses with the same domain are normally routed by the &(manualroute)&
20587 router to the same list of hosts. However, this cannot be presumed, because the
20588 router options and preconditions may refer to the local part of the address. By
20589 default, therefore, Exim routes each address in a message independently. DNS
20590 servers run caches, so repeated DNS lookups are not normally expensive, and in
20591 any case, personal messages rarely have more than a few recipients.
20593 If you are running mailing lists with large numbers of subscribers at the same
20594 domain, and you are using a &(manualroute)& router which is independent of the
20595 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20596 lookups for identical domains in one message. In this case, when
20597 &(manualroute)& routes an address to a remote transport, any other unrouted
20598 addresses in the message that have the same domain are automatically given the
20599 same routing without processing them independently. However, this is only done
20600 if &%headers_add%& and &%headers_remove%& are unset.
20605 .section "Routing rules in route_list" "SECID120"
20606 The value of &%route_list%& is a string consisting of a sequence of routing
20607 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20608 entered as two semicolons. Alternatively, the list separator can be changed as
20609 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20610 Empty rules are ignored. The format of each rule is
20612 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20614 The following example contains two rules, each with a simple domain pattern and
20618 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20619 thes.ref.example mail-3.ref.example:mail-4.ref.example
20621 The three parts of a rule are separated by white space. The pattern and the
20622 list of hosts can be enclosed in quotes if necessary, and if they are, the
20623 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20624 single domain pattern, which is the only mandatory item in the rule. The
20625 pattern is in the same format as one item in a domain list (see section
20626 &<<SECTdomainlist>>&),
20627 except that it may not be the name of an interpolated file.
20628 That is, it may be wildcarded, or a regular expression, or a file or database
20629 lookup (with semicolons doubled, because of the use of semicolon as a separator
20630 in a &%route_list%&).
20632 The rules in &%route_list%& are searched in order until one of the patterns
20633 matches the domain that is being routed. The list of hosts and then options are
20634 then used as described below. If there is no match, the router declines. When
20635 &%route_list%& is set, &%route_data%& must not be set.
20639 .section "Routing rules in route_data" "SECID121"
20640 The use of &%route_list%& is convenient when there are only a small number of
20641 routing rules. For larger numbers, it is easier to use a file or database to
20642 hold the routing information, and use the &%route_data%& option instead.
20643 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20644 Most commonly, &%route_data%& is set as a string that contains an
20645 expansion lookup. For example, suppose we place two routing rules in a file
20648 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20649 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20651 This data can be accessed by setting
20653 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20655 Failure of the lookup results in an empty string, causing the router to
20656 decline. However, you do not have to use a lookup in &%route_data%&. The only
20657 requirement is that the result of expanding the string is a list of hosts,
20658 possibly followed by options, separated by white space. The list of hosts must
20659 be enclosed in quotes if it contains white space.
20664 .section "Format of the list of hosts" "SECID122"
20665 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20666 always separately expanded before use. If the expansion fails, the router
20667 declines. The result of the expansion must be a colon-separated list of names
20668 and/or IP addresses, optionally also including ports.
20669 If the list is written with spaces, it must be protected with quotes.
20670 The format of each item
20671 in the list is described in the next section. The list separator can be changed
20672 as described in section &<<SECTlistsepchange>>&.
20674 If the list of hosts was obtained from a &%route_list%& item, the following
20675 variables are set during its expansion:
20678 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20679 If the domain was matched against a regular expression, the numeric variables
20680 &$1$&, &$2$&, etc. may be set. For example:
20682 route_list = ^domain(\d+) host-$1.text.example
20685 &$0$& is always set to the entire domain.
20687 &$1$& is also set when partial matching is done in a file lookup.
20690 .vindex "&$value$&"
20691 If the pattern that matched the domain was a lookup item, the data that was
20692 looked up is available in the expansion variable &$value$&. For example:
20694 route_list = lsearch;;/some/file.routes $value
20698 Note the doubling of the semicolon in the pattern that is necessary because
20699 semicolon is the default route list separator.
20703 .section "Format of one host item" "SECTformatonehostitem"
20704 Each item in the list of hosts can be either a host name or an IP address,
20705 optionally with an attached port number, or it can be a single "+"
20706 (see &%hosts_randomize%&).
20707 When no port is given, an IP address
20708 is not enclosed in brackets. When a port is specified, it overrides the port
20709 specification on the transport. The port is separated from the name or address
20710 by a colon. This leads to some complications:
20713 Because colon is the default separator for the list of hosts, either
20714 the colon that specifies a port must be doubled, or the list separator must
20715 be changed. The following two examples have the same effect:
20717 route_list = * "host1.tld::1225 : host2.tld::1226"
20718 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20721 When IPv6 addresses are involved, it gets worse, because they contain
20722 colons of their own. To make this case easier, it is permitted to
20723 enclose an IP address (either v4 or v6) in square brackets if a port
20724 number follows. For example:
20726 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20730 .section "How the list of hosts is used" "SECThostshowused"
20731 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20732 the hosts is tried, in the order specified, when carrying out the SMTP
20733 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20734 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20737 Hosts may be listed by name or by IP address. An unadorned name in the list of
20738 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20739 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20740 records in the DNS. For example:
20742 route_list = * x.y.z:p.q.r/MX:e.f.g
20744 If this feature is used with a port specifier, the port must come last. For
20747 route_list = * dom1.tld/mx::1225
20749 If the &%hosts_randomize%& option is set, the order of the items in the list is
20750 randomized before any lookups are done. Exim then scans the list; for any name
20751 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20752 be an interface on the local host and the item is not the first in the list,
20753 Exim discards it and any subsequent items. If it is the first item, what
20754 happens is controlled by the
20755 .oindex "&%self%&" "in &(manualroute)& router"
20756 &%self%& option of the router.
20758 A name on the list that is followed by &`/MX`& is replaced with the list of
20759 hosts obtained by looking up MX records for the name. This is always a DNS
20760 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20761 below) are not relevant here. The order of these hosts is determined by the
20762 preference values in the MX records, according to the usual rules. Because
20763 randomizing happens before the MX lookup, it does not affect the order that is
20764 defined by MX preferences.
20766 If the local host is present in the sublist obtained from MX records, but is
20767 not the most preferred host in that list, it and any equally or less
20768 preferred hosts are removed before the sublist is inserted into the main list.
20770 If the local host is the most preferred host in the MX list, what happens
20771 depends on where in the original list of hosts the &`/MX`& item appears. If it
20772 is not the first item (that is, there are previous hosts in the main list),
20773 Exim discards this name and any subsequent items in the main list.
20775 If the MX item is first in the list of hosts, and the local host is the
20776 most preferred host, what happens is controlled by the &%self%& option of the
20779 DNS failures when lookup up the MX records are treated in the same way as DNS
20780 failures when looking up IP addresses: &%pass_on_timeout%& and
20781 &%host_find_failed%& are used when relevant.
20783 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20784 whether obtained from an MX lookup or not.
20788 .section "How the options are used" "SECThowoptused"
20789 The options are a sequence of words, space-separated.
20790 One of the words can be the name of a transport; this overrides the
20791 &%transport%& option on the router for this particular routing rule only. The
20792 other words (if present) control randomization of the list of hosts on a
20793 per-rule basis, and how the IP addresses of the hosts are to be found when
20794 routing to a remote transport. These options are as follows:
20797 &%randomize%&: randomize the order of the hosts in this list, overriding the
20798 setting of &%hosts_randomize%& for this routing rule only.
20800 &%no_randomize%&: do not randomize the order of the hosts in this list,
20801 overriding the setting of &%hosts_randomize%& for this routing rule only.
20803 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20804 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20805 also look in &_/etc/hosts_& or other sources of information.
20807 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20808 no address records are found. If there is a temporary DNS error (such as a
20809 timeout), delivery is deferred.
20811 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20813 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20818 route_list = domain1 host1:host2:host3 randomize bydns;\
20819 domain2 host4:host5
20821 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20822 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20823 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20824 or &[gethostbyname()]&, and the result of the lookup is the result of that
20827 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20828 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20829 instead of TRY_AGAIN. That is why the default action is to try a DNS
20830 lookup first. Only if that gives a definite &"no such host"& is the local
20833 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20834 inadvertent constraint that a transport name as an option had to be the last
20839 If no IP address for a host can be found, what happens is controlled by the
20840 &%host_find_failed%& option.
20843 When an address is routed to a local transport, IP addresses are not looked up.
20844 The host list is passed to the transport in the &$host$& variable.
20848 .section "Manualroute examples" "SECID123"
20849 In some of the examples that follow, the presence of the &%remote_smtp%&
20850 transport, as defined in the default configuration file, is assumed:
20853 .cindex "smart host" "example router"
20854 The &(manualroute)& router can be used to forward all external mail to a
20855 &'smart host'&. If you have set up, in the main part of the configuration, a
20856 named domain list that contains your local domains, for example:
20858 domainlist local_domains = my.domain.example
20860 You can arrange for all other domains to be routed to a smart host by making
20861 your first router something like this:
20864 driver = manualroute
20865 domains = !+local_domains
20866 transport = remote_smtp
20867 route_list = * smarthost.ref.example
20869 This causes all non-local addresses to be sent to the single host
20870 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20871 they are tried in order
20872 (but you can use &%hosts_randomize%& to vary the order each time).
20873 Another way of configuring the same thing is this:
20876 driver = manualroute
20877 transport = remote_smtp
20878 route_list = !+local_domains smarthost.ref.example
20880 There is no difference in behaviour between these two routers as they stand.
20881 However, they behave differently if &%no_more%& is added to them. In the first
20882 example, the router is skipped if the domain does not match the &%domains%&
20883 precondition; the following router is always tried. If the router runs, it
20884 always matches the domain and so can never decline. Therefore, &%no_more%&
20885 would have no effect. In the second case, the router is never skipped; it
20886 always runs. However, if it doesn't match the domain, it declines. In this case
20887 &%no_more%& would prevent subsequent routers from running.
20890 .cindex "mail hub example"
20891 A &'mail hub'& is a host which receives mail for a number of domains via MX
20892 records in the DNS and delivers it via its own private routing mechanism. Often
20893 the final destinations are behind a firewall, with the mail hub being the one
20894 machine that can connect to machines both inside and outside the firewall. The
20895 &(manualroute)& router is usually used on a mail hub to route incoming messages
20896 to the correct hosts. For a small number of domains, the routing can be inline,
20897 using the &%route_list%& option, but for a larger number a file or database
20898 lookup is easier to manage.
20900 If the domain names are in fact the names of the machines to which the mail is
20901 to be sent by the mail hub, the configuration can be quite simple. For
20905 driver = manualroute
20906 transport = remote_smtp
20907 route_list = *.rhodes.tvs.example $domain
20909 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20910 whose names are the same as the mail domains. A similar approach can be taken
20911 if the host name can be obtained from the domain name by a string manipulation
20912 that the expansion facilities can handle. Otherwise, a lookup based on the
20913 domain can be used to find the host:
20916 driver = manualroute
20917 transport = remote_smtp
20918 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20920 The result of the lookup must be the name or IP address of the host (or
20921 hosts) to which the address is to be routed. If the lookup fails, the route
20922 data is empty, causing the router to decline. The address then passes to the
20926 .cindex "batched SMTP output example"
20927 .cindex "SMTP" "batched outgoing; example"
20928 You can use &(manualroute)& to deliver messages to pipes or files in batched
20929 SMTP format for onward transportation by some other means. This is one way of
20930 storing mail for a dial-up host when it is not connected. The route list entry
20931 can be as simple as a single domain name in a configuration like this:
20934 driver = manualroute
20935 transport = batchsmtp_appendfile
20936 route_list = saved.domain.example
20938 though often a pattern is used to pick up more than one domain. If there are
20939 several domains or groups of domains with different transport requirements,
20940 different transports can be listed in the routing information:
20943 driver = manualroute
20945 *.saved.domain1.example $domain batch_appendfile; \
20946 *.saved.domain2.example \
20947 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20950 .vindex "&$domain$&"
20952 The first of these just passes the domain in the &$host$& variable, which
20953 doesn't achieve much (since it is also in &$domain$&), but the second does a
20954 file lookup to find a value to pass, causing the router to decline to handle
20955 the address if the lookup fails.
20958 .cindex "UUCP" "example of router for"
20959 Routing mail directly to UUCP software is a specific case of the use of
20960 &(manualroute)& in a gateway to another mail environment. This is an example of
20961 one way it can be done:
20967 command = /usr/local/bin/uux -r - \
20968 ${substr_-5:$host}!rmail ${local_part}
20969 return_fail_output = true
20974 driver = manualroute
20976 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20978 The file &_/usr/local/exim/uucphosts_& contains entries like
20980 darksite.ethereal.example: darksite.UUCP
20982 It can be set up more simply without adding and removing &".UUCP"& but this way
20983 makes clear the distinction between the domain name
20984 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20986 .ecindex IIDmanrou1
20987 .ecindex IIDmanrou2
20996 . ////////////////////////////////////////////////////////////////////////////
20997 . ////////////////////////////////////////////////////////////////////////////
20999 .chapter "The queryprogram router" "CHAPdriverlast"
21000 .scindex IIDquerou1 "&(queryprogram)& router"
21001 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21002 .cindex "routing" "by external program"
21003 The &(queryprogram)& router routes an address by running an external command
21004 and acting on its output. This is an expensive way to route, and is intended
21005 mainly for use in lightly-loaded systems, or for performing experiments.
21006 However, if it is possible to use the precondition options (&%domains%&,
21007 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21008 be used in special cases, even on a busy host. There are the following private
21010 .cindex "options" "&(queryprogram)& router"
21012 .option command queryprogram string&!! unset
21013 This option must be set. It specifies the command that is to be run. The
21014 command is split up into a command name and arguments, and then each is
21015 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21016 &<<CHAPpipetransport>>&).
21019 .option command_group queryprogram string unset
21020 .cindex "gid (group id)" "in &(queryprogram)& router"
21021 This option specifies a gid to be set when running the command while routing an
21022 address for deliver. It must be set if &%command_user%& specifies a numerical
21023 uid. If it begins with a digit, it is interpreted as the numerical value of the
21024 gid. Otherwise it is looked up using &[getgrnam()]&.
21027 .option command_user queryprogram string unset
21028 .cindex "uid (user id)" "for &(queryprogram)&"
21029 This option must be set. It specifies the uid which is set when running the
21030 command while routing an address for delivery. If the value begins with a digit,
21031 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21032 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21033 not set, a value for the gid also.
21035 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21036 root, which it does during a normal delivery in a conventional configuration.
21037 However, when an address is being verified during message reception, Exim is
21038 usually running as the Exim user, not as root. If the &(queryprogram)& router
21039 is called from a non-root process, Exim cannot change uid or gid before running
21040 the command. In this circumstance the command runs under the current uid and
21044 .option current_directory queryprogram string /
21045 This option specifies an absolute path which is made the current directory
21046 before running the command.
21049 .option timeout queryprogram time 1h
21050 If the command does not complete within the timeout period, its process group
21051 is killed and the message is frozen. A value of zero time specifies no
21055 The standard output of the command is connected to a pipe, which is read when
21056 the command terminates. It should consist of a single line of output,
21057 containing up to five fields, separated by white space. The maximum length of
21058 the line is 1023 characters. Longer lines are silently truncated. The first
21059 field is one of the following words (case-insensitive):
21062 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21065 &'Decline'&: the router declines; pass the address to the next router, unless
21066 &%no_more%& is set.
21068 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21069 subsequent text on the line is an error message. If the router is run as part
21070 of address verification during an incoming SMTP message, the message is
21071 included in the SMTP response.
21073 &'Defer'&: routing could not be completed at this time; try again later. Any
21074 subsequent text on the line is an error message which is logged. It is not
21075 included in any SMTP response.
21077 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21079 &'Pass'&: pass the address to the next router (or the router specified by
21080 &%pass_router%&), overriding &%no_more%&.
21082 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21083 new addresses, which are routed independently, starting with the first router,
21084 or the router specified by &%redirect_router%&, if set.
21087 When the first word is &'accept'&, the remainder of the line consists of a
21088 number of keyed data values, as follows (split into two lines here, to fit on
21091 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21092 LOOKUP=byname|bydns DATA=<text>
21094 The data items can be given in any order, and all are optional. If no transport
21095 is included, the transport specified by the generic &%transport%& option is
21096 used. The list of hosts and the lookup type are needed only if the transport is
21097 an &(smtp)& transport that does not itself supply a list of hosts.
21099 The format of the list of hosts is the same as for the &(manualroute)& router.
21100 As well as host names and IP addresses with optional port numbers, as described
21101 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21102 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21103 (see section &<<SECThostshowused>>&).
21105 If the lookup type is not specified, Exim behaves as follows when trying to
21106 find an IP address for each host: First, a DNS lookup is done. If this yields
21107 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21108 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21109 result of the lookup is the result of that call.
21111 .vindex "&$address_data$&"
21112 If the DATA field is set, its value is placed in the &$address_data$&
21113 variable. For example, this return line
21115 accept hosts=x1.y.example:x2.y.example data="rule1"
21117 routes the address to the default transport, passing a list of two hosts. When
21118 the transport runs, the string &"rule1"& is in &$address_data$&.
21119 .ecindex IIDquerou1
21120 .ecindex IIDquerou2
21125 . ////////////////////////////////////////////////////////////////////////////
21126 . ////////////////////////////////////////////////////////////////////////////
21128 .chapter "The redirect router" "CHAPredirect"
21129 .scindex IIDredrou1 "&(redirect)& router"
21130 .scindex IIDredrou2 "routers" "&(redirect)&"
21131 .cindex "alias file" "in a &(redirect)& router"
21132 .cindex "address redirection" "&(redirect)& router"
21133 The &(redirect)& router handles several kinds of address redirection. Its most
21134 common uses are for resolving local part aliases from a central alias file
21135 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21136 files, but it has many other potential uses. The incoming address can be
21137 redirected in several different ways:
21140 It can be replaced by one or more new addresses which are themselves routed
21143 It can be routed to be delivered to a given file or directory.
21145 It can be routed to be delivered to a specified pipe command.
21147 It can cause an automatic reply to be generated.
21149 It can be forced to fail, optionally with a custom error message.
21151 It can be temporarily deferred, optionally with a custom message.
21153 It can be discarded.
21156 The generic &%transport%& option must not be set for &(redirect)& routers.
21157 However, there are some private options which define transports for delivery to
21158 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21159 &%pipe_transport%& and &%reply_transport%& descriptions below.
21161 If success DSNs have been requested
21162 .cindex "DSN" "success"
21163 .cindex "Delivery Status Notification" "success"
21164 redirection triggers one and the DSN options are not passed any further.
21168 .section "Redirection data" "SECID124"
21169 The router operates by interpreting a text string which it obtains either by
21170 expanding the contents of the &%data%& option, or by reading the entire
21171 contents of a file whose name is given in the &%file%& option. These two
21172 options are mutually exclusive. The first is commonly used for handling system
21173 aliases, in a configuration like this:
21177 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21179 If the lookup fails, the expanded string in this example is empty. When the
21180 expansion of &%data%& results in an empty string, the router declines. A forced
21181 expansion failure also causes the router to decline; other expansion failures
21182 cause delivery to be deferred.
21184 A configuration using &%file%& is commonly used for handling users'
21185 &_.forward_& files, like this:
21190 file = $home/.forward
21193 If the file does not exist, or causes no action to be taken (for example, it is
21194 empty or consists only of comments), the router declines. &*Warning*&: This
21195 is not the case when the file contains syntactically valid items that happen to
21196 yield empty addresses, for example, items containing only RFC 2822 address
21199 .cindex "tainted data" "in filenames"
21200 .cindex redirect "tainted data"
21201 Tainted data may not be used for a filename.
21203 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21204 directly for redirection,
21205 as they are provided by a potential attacker.
21206 In the examples above, &$local_part$& is used for looking up data held locally
21207 on the system, and not used directly (the second example derives &$home$& via
21208 the passsword file or database, using &$local_part$&).
21212 .section "Forward files and address verification" "SECID125"
21213 .cindex "address redirection" "while verifying"
21214 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21215 &_.forward_& files, as in the example above. There are two reasons for this:
21218 When Exim is receiving an incoming SMTP message from a remote host, it is
21219 running under the Exim uid, not as root. Exim is unable to change uid to read
21220 the file as the user, and it may not be able to read it as the Exim user. So in
21221 practice the router may not be able to operate.
21223 However, even when the router can operate, the existence of a &_.forward_& file
21224 is unimportant when verifying an address. What should be checked is whether the
21225 local part is a valid user name or not. Cutting out the redirection processing
21226 saves some resources.
21234 .section "Interpreting redirection data" "SECID126"
21235 .cindex "Sieve filter" "specifying in redirection data"
21236 .cindex "filter" "specifying in redirection data"
21237 The contents of the data string, whether obtained from &%data%& or &%file%&,
21238 can be interpreted in two different ways:
21241 If the &%allow_filter%& option is set true, and the data begins with the text
21242 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21243 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21244 respectively. Details of the syntax and semantics of filter files are described
21245 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21246 document is intended for use by end users.
21248 Otherwise, the data must be a comma-separated list of redirection items, as
21249 described in the next section.
21252 When a message is redirected to a file (a &"mail folder"&), the filename given
21253 in a non-filter redirection list must always be an absolute path. A filter may
21254 generate a relative path &-- how this is handled depends on the transport's
21255 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21256 for the &(appendfile)& transport.
21260 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21261 .cindex "address redirection" "non-filter list items"
21262 When the redirection data is not an Exim or Sieve filter, for example, if it
21263 comes from a conventional alias or forward file, it consists of a list of
21264 addresses, filenames, pipe commands, or certain special items (see section
21265 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21266 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21267 depending on their default values. The items in the list are separated by
21268 commas or newlines.
21269 If a comma is required in an item, the entire item must be enclosed in double
21272 Lines starting with a # character are comments, and are ignored, and # may
21273 also appear following a comma, in which case everything between the # and the
21274 next newline character is ignored.
21276 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21277 double quotes are retained because some forms of mail address require their use
21278 (but never to enclose the entire address). In the following description,
21279 &"item"& refers to what remains after any surrounding double quotes have been
21282 .vindex "&$local_part$&"
21283 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21284 and the expansion contains a reference to &$local_part$&, you should make use
21285 of the &%quote_local_part%& expansion operator, in case the local part contains
21286 special characters. For example, to redirect all mail for the domain
21287 &'obsolete.example'&, retaining the existing local part, you could use this
21290 data = ${quote_local_part:$local_part}@newdomain.example
21294 .section "Redirecting to a local mailbox" "SECTredlocmai"
21295 .cindex "routing" "loops in"
21296 .cindex "loop" "while routing, avoidance of"
21297 .cindex "address redirection" "to local mailbox"
21298 A redirection item may safely be the same as the address currently under
21299 consideration. This does not cause a routing loop, because a router is
21300 automatically skipped if any ancestor of the address that is being processed
21301 is the same as the current address and was processed by the current router.
21302 Such an address is therefore passed to the following routers, so it is handled
21303 as if there were no redirection. When making this loop-avoidance test, the
21304 complete local part, including any prefix or suffix, is used.
21306 .cindex "address redirection" "local part without domain"
21307 Specifying the same local part without a domain is a common usage in personal
21308 filter files when the user wants to have messages delivered to the local
21309 mailbox and also forwarded elsewhere. For example, the user whose login is
21310 &'cleo'& might have a &_.forward_& file containing this:
21312 cleo, cleopatra@egypt.example
21314 .cindex "backslash in alias file"
21315 .cindex "alias file" "backslash in"
21316 For compatibility with other MTAs, such unqualified local parts may be
21317 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21318 it does make a difference if more than one domain is being handled
21321 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21322 2822 address that does not include a domain, the item is qualified using the
21323 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21324 addresses are qualified using the value in &%qualify_recipient%&, but you can
21325 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21327 Care must be taken if there are alias names for local users.
21328 Consider an MTA handling a single local domain where the system alias file
21333 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21334 messages in the local mailbox, and also forward copies elsewhere. He creates
21337 Sam.Reman, spqr@reme.elsewhere.example
21339 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21340 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21341 second time round, because it has previously routed it,
21342 and the following routers presumably cannot handle the alias. The forward file
21343 should really contain
21345 spqr, spqr@reme.elsewhere.example
21347 but because this is such a common error, the &%check_ancestor%& option (see
21348 below) exists to provide a way to get round it. This is normally set on a
21349 &(redirect)& router that is handling users' &_.forward_& files.
21353 .section "Special items in redirection lists" "SECTspecitredli"
21354 In addition to addresses, the following types of item may appear in redirection
21355 lists (that is, in non-filter redirection data):
21358 .cindex "pipe" "in redirection list"
21359 .cindex "address redirection" "to pipe"
21360 An item is treated as a pipe command if it begins with &"|"& and does not parse
21361 as a valid RFC 2822 address that includes a domain. A transport for running the
21362 command must be specified by the &%pipe_transport%& option.
21363 Normally, either the router or the transport specifies a user and a group under
21364 which to run the delivery. The default is to use the Exim user and group.
21366 Single or double quotes can be used for enclosing the individual arguments of
21367 the pipe command; no interpretation of escapes is done for single quotes. If
21368 the command contains a comma character, it is necessary to put the whole item
21369 in double quotes, for example:
21371 "|/some/command ready,steady,go"
21373 since items in redirection lists are terminated by commas. Do not, however,
21374 quote just the command. An item such as
21376 |"/some/command ready,steady,go"
21378 is interpreted as a pipe with a rather strange command name, and no arguments.
21380 Note that the above example assumes that the text comes from a lookup source
21381 of some sort, so that the quotes are part of the data. If composing a
21382 redirect router with a &%data%& option directly specifying this command, the
21383 quotes will be used by the configuration parser to define the extent of one
21384 string, but will not be passed down into the redirect router itself. There
21385 are two main approaches to get around this: escape quotes to be part of the
21386 data itself, or avoid using this mechanism and instead create a custom
21387 transport with the &%command%& option set and reference that transport from
21388 an &%accept%& router.
21391 .cindex "file" "in redirection list"
21392 .cindex "address redirection" "to file"
21393 An item is interpreted as a path name if it begins with &"/"& and does not
21394 parse as a valid RFC 2822 address that includes a domain. For example,
21396 /home/world/minbari
21398 is treated as a filename, but
21400 /s=molari/o=babylon/@x400gate.way
21402 is treated as an address. For a filename, a transport must be specified using
21403 the &%file_transport%& option. However, if the generated path name ends with a
21404 forward slash character, it is interpreted as a directory name rather than a
21405 filename, and &%directory_transport%& is used instead.
21407 Normally, either the router or the transport specifies a user and a group under
21408 which to run the delivery. The default is to use the Exim user and group.
21410 .cindex "&_/dev/null_&"
21411 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21412 bypassed at a high level, and the log entry shows &"**bypassed**"&
21413 instead of a transport name. In this case the user and group are not used.
21416 .cindex "included address list"
21417 .cindex "address redirection" "included external list"
21418 If an item is of the form
21420 :include:<path name>
21422 a list of further items is taken from the given file and included at that
21423 point. &*Note*&: Such a file can not be a filter file; it is just an
21424 out-of-line addition to the list. The items in the included list are separated
21425 by commas or newlines and are not subject to expansion. If this is the first
21426 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21427 the alias name. This example is incorrect:
21429 list1 :include:/opt/lists/list1
21431 It must be given as
21433 list1: :include:/opt/lists/list1
21435 .cindex "tainted data" "in filenames"
21436 .cindex redirect "tainted data"
21437 Tainted data may not be used for a filename.
21439 .cindex "address redirection" "to black hole"
21440 .cindex "delivery" "discard"
21441 .cindex "delivery" "blackhole"
21442 .cindex "black hole"
21443 .cindex "abandoning mail"
21444 Sometimes you want to throw away mail to a particular local part. Making the
21445 &%data%& option expand to an empty string does not work, because that causes
21446 the router to decline. Instead, the alias item
21450 can be used. It does what its name implies. No delivery is
21451 done, and no error message is generated. This has the same effect as specifying
21452 &_/dev/null_& as a destination, but it can be independently disabled.
21454 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21455 delivery is done for the original local part, even if other redirection items
21456 are present. If you are generating a multi-item list (for example, by reading a
21457 database) and need the ability to provide a no-op item, you must use
21461 .cindex "delivery" "forcing failure"
21462 .cindex "delivery" "forcing deferral"
21463 .cindex "failing delivery" "forcing"
21464 .cindex "deferred delivery, forcing"
21465 .cindex "customizing" "failure message"
21466 An attempt to deliver a particular address can be deferred or forced to fail by
21467 redirection items of the form
21472 respectively. When a redirection list contains such an item, it applies
21473 to the entire redirection; any other items in the list are ignored. Any
21474 text following &':fail:'& or &':defer:'& is placed in the error text
21475 associated with the failure. For example, an alias file might contain:
21477 X.Employee: :fail: Gone away, no forwarding address
21479 In the case of an address that is being verified from an ACL or as the subject
21481 .cindex "VRFY" "error text, display of"
21482 VRFY command, the text is included in the SMTP error response by
21484 .cindex "EXPN" "error text, display of"
21485 The text is not included in the response to an EXPN command. In non-SMTP cases
21486 the text is included in the error message that Exim generates.
21488 .cindex "SMTP" "error codes"
21489 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21490 &':fail:'&. However, if the message starts with three digits followed by a
21491 space, optionally followed by an extended code of the form &'n.n.n'&, also
21492 followed by a space, and the very first digit is the same as the default error
21493 code, the code from the message is used instead. If the very first digit is
21494 incorrect, a panic error is logged, and the default code is used. You can
21495 suppress the use of the supplied code in a redirect router by setting the
21496 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21499 .vindex "&$acl_verify_message$&"
21500 In an ACL, an explicitly provided message overrides the default, but the
21501 default message is available in the variable &$acl_verify_message$& and can
21502 therefore be included in a custom message if this is desired.
21504 Normally the error text is the rest of the redirection list &-- a comma does
21505 not terminate it &-- but a newline does act as a terminator. Newlines are not
21506 normally present in alias expansions. In &(lsearch)& lookups they are removed
21507 as part of the continuation process, but they may exist in other kinds of
21508 lookup and in &':include:'& files.
21510 During routing for message delivery (as opposed to verification), a redirection
21511 containing &':fail:'& causes an immediate failure of the incoming address,
21512 whereas &':defer:'& causes the message to remain in the queue so that a
21513 subsequent delivery attempt can happen at a later time. If an address is
21514 deferred for too long, it will ultimately fail, because the normal retry
21518 .cindex "alias file" "exception to default"
21519 Sometimes it is useful to use a single-key search type with a default (see
21520 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21521 for exceptions to the default. These can be handled by aliasing them to
21522 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21523 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21524 results in an empty redirection list has the same effect.
21528 .section "Duplicate addresses" "SECTdupaddr"
21529 .cindex "duplicate addresses"
21530 .cindex "address duplicate, discarding"
21531 .cindex "pipe" "duplicated"
21532 Exim removes duplicate addresses from the list to which it is delivering, so as
21533 to deliver just one copy to each address. This does not apply to deliveries
21534 routed to pipes by different immediate parent addresses, but an indirect
21535 aliasing scheme of the type
21537 pipe: |/some/command $local_part
21541 does not work with a message that is addressed to both local parts, because
21542 when the second is aliased to the intermediate local part &"pipe"& it gets
21543 discarded as being the same as a previously handled address. However, a scheme
21546 localpart1: |/some/command $local_part
21547 localpart2: |/some/command $local_part
21549 does result in two different pipe deliveries, because the immediate parents of
21550 the pipes are distinct.
21554 .section "Repeated redirection expansion" "SECID128"
21555 .cindex "repeated redirection expansion"
21556 .cindex "address redirection" "repeated for each delivery attempt"
21557 When a message cannot be delivered to all of its recipients immediately,
21558 leading to two or more delivery attempts, redirection expansion is carried out
21559 afresh each time for those addresses whose children were not all previously
21560 delivered. If redirection is being used as a mailing list, this can lead to new
21561 members of the list receiving copies of old messages. The &%one_time%& option
21562 can be used to avoid this.
21565 .section "Errors in redirection lists" "SECID129"
21566 .cindex "address redirection" "errors"
21567 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21568 error is skipped, and an entry is written to the main log. This may be useful
21569 for mailing lists that are automatically managed. Otherwise, if an error is
21570 detected while generating the list of new addresses, the original address is
21571 deferred. See also &%syntax_errors_to%&.
21575 .section "Private options for the redirect router" "SECID130"
21577 .cindex "options" "&(redirect)& router"
21578 The private options for the &(redirect)& router are as follows:
21581 .option allow_defer redirect boolean false
21582 Setting this option allows the use of &':defer:'& in non-filter redirection
21583 data, or the &%defer%& command in an Exim filter file.
21586 .option allow_fail redirect boolean false
21587 .cindex "failing delivery" "from filter"
21588 If this option is true, the &':fail:'& item can be used in a redirection list,
21589 and the &%fail%& command may be used in an Exim filter file.
21592 .option allow_filter redirect boolean false
21593 .cindex "filter" "enabling use of"
21594 .cindex "Sieve filter" "enabling use of"
21595 Setting this option allows Exim to interpret redirection data that starts with
21596 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21597 are some features of Exim filter files that some administrators may wish to
21598 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21600 It is also possible to lock out Exim filters or Sieve filters while allowing
21601 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21604 The filter is run using the uid and gid set by the generic &%user%& and
21605 &%group%& options. These take their defaults from the password data if
21606 &%check_local_user%& is set, so in the normal case of users' personal filter
21607 files, the filter is run as the relevant user. When &%allow_filter%& is set
21608 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21612 .option allow_freeze redirect boolean false
21613 .cindex "freezing messages" "allowing in filter"
21614 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21615 This command is more normally encountered in system filters, and is disabled by
21616 default for redirection filters because it isn't something you usually want to
21617 let ordinary users do.
21621 .option check_ancestor redirect boolean false
21622 This option is concerned with handling generated addresses that are the same
21623 as some address in the list of redirection ancestors of the current address.
21624 Although it is turned off by default in the code, it is set in the default
21625 configuration file for handling users' &_.forward_& files. It is recommended
21626 for this use of the &(redirect)& router.
21628 When &%check_ancestor%& is set, if a generated address (including the domain)
21629 is the same as any ancestor of the current address, it is replaced by a copy of
21630 the current address. This helps in the case where local part A is aliased to B,
21631 and B has a &_.forward_& file pointing back to A. For example, within a single
21632 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21633 &_&~jb/.forward_& contains:
21635 \Joe.Bloggs, <other item(s)>
21637 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21638 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21639 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21640 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21641 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21642 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21643 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21644 original address. See also the &%repeat_use%& option below.
21647 .option check_group redirect boolean "see below"
21648 When the &%file%& option is used, the group owner of the file is checked only
21649 when this option is set. The permitted groups are those listed in the
21650 &%owngroups%& option, together with the user's default group if
21651 &%check_local_user%& is set. If the file has the wrong group, routing is
21652 deferred. The default setting for this option is true if &%check_local_user%&
21653 is set and the &%modemask%& option permits the group write bit, or if the
21654 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21658 .option check_owner redirect boolean "see below"
21659 When the &%file%& option is used, the owner of the file is checked only when
21660 this option is set. If &%check_local_user%& is set, the local user is
21661 permitted; otherwise the owner must be one of those listed in the &%owners%&
21662 option. The default value for this option is true if &%check_local_user%& or
21663 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21666 .option data redirect string&!! unset
21667 This option is mutually exclusive with &%file%&. One or other of them must be
21668 set, but not both. The contents of &%data%& are expanded, and then used as the
21669 list of forwarding items, or as a set of filtering instructions. If the
21670 expansion is forced to fail, or the result is an empty string or a string that
21671 has no effect (consists entirely of comments), the router declines.
21673 When filtering instructions are used, the string must begin with &"#Exim
21674 filter"&, and all comments in the string, including this initial one, must be
21675 terminated with newline characters. For example:
21677 data = #Exim filter\n\
21678 if $h_to: contains Exim then save $home/mail/exim endif
21680 If you are reading the data from a database where newlines cannot be included,
21681 you can use the &${sg}$& expansion item to turn the escape string of your
21682 choice into a newline.
21685 .option directory_transport redirect string&!! unset
21686 A &(redirect)& router sets up a direct delivery to a directory when a path name
21687 ending with a slash is specified as a new &"address"&. The transport used is
21688 specified by this option, which, after expansion, must be the name of a
21689 configured transport. This should normally be an &(appendfile)& transport.
21692 .option file redirect string&!! unset
21693 This option specifies the name of a file that contains the redirection data. It
21694 is mutually exclusive with the &%data%& option. The string is expanded before
21695 use; if the expansion is forced to fail, the router declines. Other expansion
21696 failures cause delivery to be deferred. The result of a successful expansion
21697 must be an absolute path. The entire file is read and used as the redirection
21698 data. If the data is an empty string or a string that has no effect (consists
21699 entirely of comments), the router declines.
21701 .cindex "NFS" "checking for file existence"
21702 If the attempt to open the file fails with a &"does not exist"& error, Exim
21703 runs a check on the containing directory,
21704 unless &%ignore_enotdir%& is true (see below).
21705 If the directory does not appear to exist, delivery is deferred. This can
21706 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21707 is a mount problem. If the containing directory does exist, but the file does
21708 not, the router declines.
21711 .option file_transport redirect string&!! unset
21712 .vindex "&$address_file$&"
21713 A &(redirect)& router sets up a direct delivery to a file when a path name not
21714 ending in a slash is specified as a new &"address"&. The transport used is
21715 specified by this option, which, after expansion, must be the name of a
21716 configured transport. This should normally be an &(appendfile)& transport. When
21717 it is running, the filename is in &$address_file$&.
21720 .option filter_prepend_home redirect boolean true
21721 When this option is true, if a &(save)& command in an Exim filter specifies a
21722 relative path, and &$home$& is defined, it is automatically prepended to the
21723 relative path. If this option is set false, this action does not happen. The
21724 relative path is then passed to the transport unmodified.
21727 .option forbid_blackhole redirect boolean false
21728 .cindex "restricting access to features"
21729 .cindex "filter" "locking out certain features"
21730 If this option is true, the &':blackhole:'& item may not appear in a
21734 .option forbid_exim_filter redirect boolean false
21735 .cindex "restricting access to features"
21736 .cindex "filter" "locking out certain features"
21737 If this option is set true, only Sieve filters are permitted when
21738 &%allow_filter%& is true.
21743 .option forbid_file redirect boolean false
21744 .cindex "restricting access to features"
21745 .cindex "delivery" "to file; forbidding"
21746 .cindex "filter" "locking out certain features"
21747 .cindex "Sieve filter" "forbidding delivery to a file"
21748 .cindex "Sieve filter" "&""keep""& facility; disabling"
21749 If this option is true, this router may not generate a new address that
21750 specifies delivery to a local file or directory, either from a filter or from a
21751 conventional forward file. This option is forced to be true if &%one_time%& is
21752 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21753 locks out the Sieve's &"keep"& facility.
21756 .option forbid_filter_dlfunc redirect boolean false
21757 .cindex "restricting access to features"
21758 .cindex "filter" "locking out certain features"
21759 If this option is true, string expansions in Exim filters are not allowed to
21760 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21763 .option forbid_filter_existstest redirect boolean false
21764 .cindex "restricting access to features"
21765 .cindex "filter" "locking out certain features"
21766 .cindex "expansion" "statting a file"
21767 If this option is true, string expansions in Exim filters are not allowed to
21768 make use of the &%exists%& condition or the &%stat%& expansion item.
21770 .option forbid_filter_logwrite redirect boolean false
21771 .cindex "restricting access to features"
21772 .cindex "filter" "locking out certain features"
21773 If this option is true, use of the logging facility in Exim filters is not
21774 permitted. Logging is in any case available only if the filter is being run
21775 under some unprivileged uid (which is normally the case for ordinary users'
21776 &_.forward_& files).
21779 .option forbid_filter_lookup redirect boolean false
21780 .cindex "restricting access to features"
21781 .cindex "filter" "locking out certain features"
21782 If this option is true, string expansions in Exim filter files are not allowed
21783 to make use of &%lookup%& items.
21786 .option forbid_filter_perl redirect boolean false
21787 .cindex "restricting access to features"
21788 .cindex "filter" "locking out certain features"
21789 This option has an effect only if Exim is built with embedded Perl support. If
21790 it is true, string expansions in Exim filter files are not allowed to make use
21791 of the embedded Perl support.
21794 .option forbid_filter_readfile redirect boolean false
21795 .cindex "restricting access to features"
21796 .cindex "filter" "locking out certain features"
21797 If this option is true, string expansions in Exim filter files are not allowed
21798 to make use of &%readfile%& items.
21801 .option forbid_filter_readsocket redirect boolean false
21802 .cindex "restricting access to features"
21803 .cindex "filter" "locking out certain features"
21804 If this option is true, string expansions in Exim filter files are not allowed
21805 to make use of &%readsocket%& items.
21808 .option forbid_filter_reply redirect boolean false
21809 .cindex "restricting access to features"
21810 .cindex "filter" "locking out certain features"
21811 If this option is true, this router may not generate an automatic reply
21812 message. Automatic replies can be generated only from Exim or Sieve filter
21813 files, not from traditional forward files. This option is forced to be true if
21814 &%one_time%& is set.
21817 .option forbid_filter_run redirect boolean false
21818 .cindex "restricting access to features"
21819 .cindex "filter" "locking out certain features"
21820 If this option is true, string expansions in Exim filter files are not allowed
21821 to make use of &%run%& items.
21824 .option forbid_include redirect boolean false
21825 .cindex "restricting access to features"
21826 .cindex "filter" "locking out certain features"
21827 If this option is true, items of the form
21829 :include:<path name>
21831 are not permitted in non-filter redirection lists.
21834 .option forbid_pipe redirect boolean false
21835 .cindex "restricting access to features"
21836 .cindex "filter" "locking out certain features"
21837 .cindex "delivery" "to pipe; forbidding"
21838 If this option is true, this router may not generate a new address which
21839 specifies delivery to a pipe, either from an Exim filter or from a conventional
21840 forward file. This option is forced to be true if &%one_time%& is set.
21843 .option forbid_sieve_filter redirect boolean false
21844 .cindex "restricting access to features"
21845 .cindex "filter" "locking out certain features"
21846 If this option is set true, only Exim filters are permitted when
21847 &%allow_filter%& is true.
21850 .cindex "SMTP" "error codes"
21851 .option forbid_smtp_code redirect boolean false
21852 If this option is set true, any SMTP error codes that are present at the start
21853 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21854 the default codes (451 and 550, respectively) are always used.
21859 .option hide_child_in_errmsg redirect boolean false
21860 .cindex "bounce message" "redirection details; suppressing"
21861 If this option is true, it prevents Exim from quoting a child address if it
21862 generates a bounce or delay message for it. Instead it says &"an address
21863 generated from <&'the top level address'&>"&. Of course, this applies only to
21864 bounces generated locally. If a message is forwarded to another host, &'its'&
21865 bounce may well quote the generated address.
21868 .option ignore_eacces redirect boolean false
21870 If this option is set and an attempt to open a redirection file yields the
21871 EACCES error (permission denied), the &(redirect)& router behaves as if the
21872 file did not exist.
21875 .option ignore_enotdir redirect boolean false
21877 If this option is set and an attempt to open a redirection file yields the
21878 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21879 router behaves as if the file did not exist.
21881 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21882 router that has the &%file%& option set discovers that the file does not exist
21883 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21884 against unmounted NFS directories. If the parent can not be statted, delivery
21885 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21886 is set, because that option tells Exim to ignore &"something on the path is not
21887 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21888 that some operating systems give ENOENT where others give ENOTDIR.
21892 .option include_directory redirect string unset
21893 If this option is set, the path names of any &':include:'& items in a
21894 redirection list must start with this directory.
21897 .option modemask redirect "octal integer" 022
21898 This specifies mode bits which must not be set for a file specified by the
21899 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21902 .option one_time redirect boolean false
21903 .cindex "one-time aliasing/forwarding expansion"
21904 .cindex "alias file" "one-time expansion"
21905 .cindex "forward file" "one-time expansion"
21906 .cindex "mailing lists" "one-time expansion"
21907 .cindex "address redirection" "one-time expansion"
21908 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21909 files each time it tries to deliver a message causes a problem when one or more
21910 of the generated addresses fails be delivered at the first attempt. The problem
21911 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21912 but of what happens when the redirection list changes during the time that the
21913 message is on Exim's queue. This is particularly true in the case of mailing
21914 lists, where new subscribers might receive copies of messages that were posted
21915 before they subscribed.
21917 If &%one_time%& is set and any addresses generated by the router fail to
21918 deliver at the first attempt, the failing addresses are added to the message as
21919 &"top level"& addresses, and the parent address that generated them is marked
21920 &"delivered"&. Thus, redirection does not happen again at the next delivery
21923 &*Warning 1*&: Any header line addition or removal that is specified by this
21924 router would be lost if delivery did not succeed at the first attempt. For this
21925 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21926 permitted when &%one_time%& is set.
21928 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21929 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21930 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21932 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21935 The original top-level address is remembered with each of the generated
21936 addresses, and is output in any log messages. However, any intermediate parent
21937 addresses are not recorded. This makes a difference to the log only if
21938 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21939 typically be used for mailing lists, where there is normally just one level of
21943 .option owners redirect "string list" unset
21944 .cindex "ownership" "alias file"
21945 .cindex "ownership" "forward file"
21946 .cindex "alias file" "ownership"
21947 .cindex "forward file" "ownership"
21948 This specifies a list of permitted owners for the file specified by &%file%&.
21949 This list is in addition to the local user when &%check_local_user%& is set.
21950 See &%check_owner%& above.
21953 .option owngroups redirect "string list" unset
21954 This specifies a list of permitted groups for the file specified by &%file%&.
21955 The list is in addition to the local user's primary group when
21956 &%check_local_user%& is set. See &%check_group%& above.
21959 .option pipe_transport redirect string&!! unset
21960 .vindex "&$address_pipe$&"
21961 A &(redirect)& router sets up a direct delivery to a pipe when a string
21962 starting with a vertical bar character is specified as a new &"address"&. The
21963 transport used is specified by this option, which, after expansion, must be the
21964 name of a configured transport. This should normally be a &(pipe)& transport.
21965 When the transport is run, the pipe command is in &$address_pipe$&.
21968 .option qualify_domain redirect string&!! unset
21969 .vindex "&$qualify_recipient$&"
21970 If this option is set, and an unqualified address (one without a domain) is
21971 generated, and that address would normally be qualified by the global setting
21972 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21973 expanding this string. If the expansion fails, the router declines. If you want
21974 to revert to the default, you can have the expansion generate
21975 &$qualify_recipient$&.
21977 This option applies to all unqualified addresses generated by Exim filters,
21978 but for traditional &_.forward_& files, it applies only to addresses that are
21979 not preceded by a backslash. Sieve filters cannot generate unqualified
21982 .option qualify_preserve_domain redirect boolean false
21983 .cindex "domain" "in redirection; preserving"
21984 .cindex "preserving domain in redirection"
21985 .cindex "address redirection" "domain; preserving"
21986 If this option is set, the router's local &%qualify_domain%& option must not be
21987 set (a configuration error occurs if it is). If an unqualified address (one
21988 without a domain) is generated, it is qualified with the domain of the parent
21989 address (the immediately preceding ancestor) instead of the global
21990 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
21991 this applies whether or not the address is preceded by a backslash.
21994 .option repeat_use redirect boolean true
21995 If this option is set false, the router is skipped for a child address that has
21996 any ancestor that was routed by this router. This test happens before any of
21997 the other preconditions are tested. Exim's default anti-looping rules skip
21998 only when the ancestor is the same as the current address. See also
21999 &%check_ancestor%& above and the generic &%redirect_router%& option.
22002 .option reply_transport redirect string&!! unset
22003 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22004 &%vacation%& command is used in a filter file. The transport used is specified
22005 by this option, which, after expansion, must be the name of a configured
22006 transport. This should normally be an &(autoreply)& transport. Other transports
22007 are unlikely to do anything sensible or useful.
22010 .option rewrite redirect boolean true
22011 .cindex "address redirection" "disabling rewriting"
22012 If this option is set false, addresses generated by the router are not
22013 subject to address rewriting. Otherwise, they are treated like new addresses
22014 and are rewritten according to the global rewriting rules.
22017 .option sieve_subaddress redirect string&!! unset
22018 The value of this option is passed to a Sieve filter to specify the
22019 :subaddress part of an address.
22021 .option sieve_useraddress redirect string&!! unset
22022 The value of this option is passed to a Sieve filter to specify the :user part
22023 of an address. However, if it is unset, the entire original local part
22024 (including any prefix or suffix) is used for :user.
22027 .option sieve_vacation_directory redirect string&!! unset
22028 .cindex "Sieve filter" "vacation directory"
22029 To enable the &"vacation"& extension for Sieve filters, you must set
22030 &%sieve_vacation_directory%& to the directory where vacation databases are held
22031 (do not put anything else in that directory), and ensure that the
22032 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22033 needs their own directory; Exim will create it if necessary.
22037 .option skip_syntax_errors redirect boolean false
22038 .cindex "forward file" "broken"
22039 .cindex "address redirection" "broken files"
22040 .cindex "alias file" "broken"
22041 .cindex "broken alias or forward files"
22042 .cindex "ignoring faulty addresses"
22043 .cindex "skipping faulty addresses"
22044 .cindex "error" "skipping bad syntax"
22045 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22046 non-filter redirection data are skipped, and each failing address is logged. If
22047 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22048 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22049 are expanded and placed at the head of the error message generated by
22050 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22051 be the same address as the generic &%errors_to%& option. The
22052 &%skip_syntax_errors%& option is often used when handling mailing lists.
22054 If all the addresses in a redirection list are skipped because of syntax
22055 errors, the router declines to handle the original address, and it is passed to
22056 the following routers.
22058 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22059 error in the filter causes filtering to be abandoned without any action being
22060 taken. The incident is logged, and the router declines to handle the address,
22061 so it is passed to the following routers.
22063 .cindex "Sieve filter" "syntax errors in"
22064 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22065 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22066 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22068 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22069 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22070 option, used with an address that does not get redirected, can be used to
22071 notify users of these errors, by means of a router like this:
22077 file = $home/.forward
22078 file_transport = address_file
22079 pipe_transport = address_pipe
22080 reply_transport = address_reply
22083 syntax_errors_to = real-$local_part@$domain
22084 syntax_errors_text = \
22085 This is an automatically generated message. An error has\n\
22086 been found in your .forward file. Details of the error are\n\
22087 reported below. While this error persists, you will receive\n\
22088 a copy of this message for every message that is addressed\n\
22089 to you. If your .forward file is a filter file, or if it is\n\
22090 a non-filter file containing no valid forwarding addresses,\n\
22091 a copy of each incoming message will be put in your normal\n\
22092 mailbox. If a non-filter file contains at least one valid\n\
22093 forwarding address, forwarding to the valid addresses will\n\
22094 happen, and those will be the only deliveries that occur.
22096 You also need a router to ensure that local addresses that are prefixed by
22097 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22098 put this immediately before the &(userforward)& router:
22103 local_part_prefix = real-
22104 transport = local_delivery
22106 For security, it would probably be a good idea to restrict the use of this
22107 router to locally-generated messages, using a condition such as this:
22109 condition = ${if match {$sender_host_address}\
22110 {\N^(|127\.0\.0\.1)$\N}}
22114 .option syntax_errors_text redirect string&!! unset
22115 See &%skip_syntax_errors%& above.
22118 .option syntax_errors_to redirect string unset
22119 See &%skip_syntax_errors%& above.
22120 .ecindex IIDredrou1
22121 .ecindex IIDredrou2
22128 . ////////////////////////////////////////////////////////////////////////////
22129 . ////////////////////////////////////////////////////////////////////////////
22131 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22132 "Environment for local transports"
22133 .scindex IIDenvlotra1 "local transports" "environment for"
22134 .scindex IIDenvlotra2 "environment" "local transports"
22135 .scindex IIDenvlotra3 "transport" "local; environment for"
22136 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22137 transport can be thought of as similar to a pipe.) Exim always runs transports
22138 in subprocesses, under specified uids and gids. Typical deliveries to local
22139 mailboxes run under the uid and gid of the local user.
22141 Exim also sets a specific current directory while running the transport; for
22142 some transports a home directory setting is also relevant. The &(pipe)&
22143 transport is the only one that sets up environment variables; see section
22144 &<<SECTpipeenv>>& for details.
22146 The values used for the uid, gid, and the directories may come from several
22147 different places. In many cases, the router that handles the address associates
22148 settings with that address as a result of its &%check_local_user%&, &%group%&,
22149 or &%user%& options. However, values may also be given in the transport's own
22150 configuration, and these override anything that comes from the router.
22154 .section "Concurrent deliveries" "SECID131"
22155 .cindex "concurrent deliveries"
22156 .cindex "simultaneous deliveries"
22157 If two different messages for the same local recipient arrive more or less
22158 simultaneously, the two delivery processes are likely to run concurrently. When
22159 the &(appendfile)& transport is used to write to a file, Exim applies locking
22160 rules to stop concurrent processes from writing to the same file at the same
22163 However, when you use a &(pipe)& transport, it is up to you to arrange any
22164 locking that is needed. Here is a silly example:
22168 command = /bin/sh -c 'cat >>/some/file'
22170 This is supposed to write the message at the end of the file. However, if two
22171 messages arrive at the same time, the file will be scrambled. You can use the
22172 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22173 file using the same algorithm that Exim itself uses.
22178 .section "Uids and gids" "SECTenvuidgid"
22179 .cindex "local transports" "uid and gid"
22180 .cindex "transport" "local; uid and gid"
22181 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22182 overrides any group that the router set in the address, even if &%user%& is not
22183 set for the transport. This makes it possible, for example, to run local mail
22184 delivery under the uid of the recipient (set by the router), but in a special
22185 group (set by the transport). For example:
22188 # User/group are set by check_local_user in this router
22192 transport = group_delivery
22195 # This transport overrides the group
22197 driver = appendfile
22198 file = /var/spool/mail/$local_part_data
22201 If &%user%& is set for a transport, its value overrides what is set in the
22202 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22203 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22206 .oindex "&%initgroups%&"
22207 When the uid is taken from the transport's configuration, the &[initgroups()]&
22208 function is called for the groups associated with that uid if the
22209 &%initgroups%& option is set for the transport. When the uid is not specified
22210 by the transport, but is associated with the address by a router, the option
22211 for calling &[initgroups()]& is taken from the router configuration.
22213 .cindex "&(pipe)& transport" "uid for"
22214 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22215 is set and &%user%& is not set, the uid of the process that called Exim to
22216 receive the message is used, and if &%group%& is not set, the corresponding
22217 original gid is also used.
22219 This is the detailed preference order for obtaining a gid; the first of the
22220 following that is set is used:
22223 A &%group%& setting of the transport;
22225 A &%group%& setting of the router;
22227 A gid associated with a user setting of the router, either as a result of
22228 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22230 The group associated with a non-numeric &%user%& setting of the transport;
22232 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22233 the uid is the creator's uid;
22235 The Exim gid if the Exim uid is being used as a default.
22238 If, for example, the user is specified numerically on the router and there are
22239 no group settings, no gid is available. In this situation, an error occurs.
22240 This is different for the uid, for which there always is an ultimate default.
22241 The first of the following that is set is used:
22244 A &%user%& setting of the transport;
22246 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22248 A &%user%& setting of the router;
22250 A &%check_local_user%& setting of the router;
22255 Of course, an error will still occur if the uid that is chosen is on the
22256 &%never_users%& list.
22262 .section "Current and home directories" "SECID132"
22263 .cindex "current directory for local transport"
22264 .cindex "home directory" "for local transport"
22265 .cindex "transport" "local; home directory for"
22266 .cindex "transport" "local; current directory for"
22267 Routers may set current and home directories for local transports by means of
22268 the &%transport_current_directory%& and &%transport_home_directory%& options.
22269 However, if the transport's &%current_directory%& or &%home_directory%& options
22270 are set, they override the router's values. In detail, the home directory
22271 for a local transport is taken from the first of these values that is set:
22274 The &%home_directory%& option on the transport;
22276 The &%transport_home_directory%& option on the router;
22278 The password data if &%check_local_user%& is set on the router;
22280 The &%router_home_directory%& option on the router.
22283 The current directory is taken from the first of these values that is set:
22286 The &%current_directory%& option on the transport;
22288 The &%transport_current_directory%& option on the router.
22292 If neither the router nor the transport sets a current directory, Exim uses the
22293 value of the home directory, if it is set. Otherwise it sets the current
22294 directory to &_/_& before running a local transport.
22298 .section "Expansion variables derived from the address" "SECID133"
22299 .vindex "&$domain$&"
22300 .vindex "&$local_part$&"
22301 .vindex "&$original_domain$&"
22302 Normally a local delivery is handling a single address, and in that case the
22303 variables such as &$domain$& and &$local_part$& are set during local
22304 deliveries. However, in some circumstances more than one address may be handled
22305 at once (for example, while writing batch SMTP for onward transmission by some
22306 other means). In this case, the variables associated with the local part are
22307 never set, &$domain$& is set only if all the addresses have the same domain,
22308 and &$original_domain$& is never set.
22309 .ecindex IIDenvlotra1
22310 .ecindex IIDenvlotra2
22311 .ecindex IIDenvlotra3
22319 . ////////////////////////////////////////////////////////////////////////////
22320 . ////////////////////////////////////////////////////////////////////////////
22322 .chapter "Generic options for transports" "CHAPtransportgeneric"
22323 .scindex IIDgenoptra1 "generic options" "transport"
22324 .scindex IIDgenoptra2 "options" "generic; for transports"
22325 .scindex IIDgenoptra3 "transport" "generic options for"
22326 The following generic options apply to all transports:
22329 .option body_only transports boolean false
22330 .cindex "transport" "body only"
22331 .cindex "message" "transporting body only"
22332 .cindex "body of message" "transporting"
22333 If this option is set, the message's headers are not transported. It is
22334 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22335 or &(pipe)& transports, the settings of &%message_prefix%& and
22336 &%message_suffix%& should be checked, because this option does not
22337 automatically suppress them.
22340 .option current_directory transports string&!! unset
22341 .cindex "transport" "current directory for"
22342 This specifies the current directory that is to be set while running the
22343 transport, overriding any value that may have been set by the router.
22344 If the expansion fails for any reason, including forced failure, an error is
22345 logged, and delivery is deferred.
22348 .option disable_logging transports boolean false
22349 If this option is set true, nothing is logged for any
22350 deliveries by the transport or for any
22351 transport errors. You should not set this option unless you really, really know
22352 what you are doing.
22355 .option debug_print transports string&!! unset
22356 .cindex "testing" "variables in drivers"
22357 If this option is set and debugging is enabled (see the &%-d%& command line
22358 option), the string is expanded and included in the debugging output when the
22360 If expansion of the string fails, the error message is written to the debugging
22361 output, and Exim carries on processing.
22362 This facility is provided to help with checking out the values of variables and
22363 so on when debugging driver configurations. For example, if a &%headers_add%&
22364 option is not working properly, &%debug_print%& could be used to output the
22365 variables it references. A newline is added to the text if it does not end with
22367 The variables &$transport_name$& and &$router_name$& contain the name of the
22368 transport and the router that called it.
22370 .option delivery_date_add transports boolean false
22371 .cindex "&'Delivery-date:'& header line"
22372 If this option is true, a &'Delivery-date:'& header is added to the message.
22373 This gives the actual time the delivery was made. As this is not a standard
22374 header, Exim has a configuration option (&%delivery_date_remove%&) which
22375 requests its removal from incoming messages, so that delivered messages can
22376 safely be resent to other recipients.
22379 .option driver transports string unset
22380 This specifies which of the available transport drivers is to be used.
22381 There is no default, and this option must be set for every transport.
22384 .option envelope_to_add transports boolean false
22385 .cindex "&'Envelope-to:'& header line"
22386 If this option is true, an &'Envelope-to:'& header is added to the message.
22387 This gives the original address(es) in the incoming envelope that caused this
22388 delivery to happen. More than one address may be present if the transport is
22389 configured to handle several addresses at once, or if more than one original
22390 address was redirected to the same final address. As this is not a standard
22391 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22392 its removal from incoming messages, so that delivered messages can safely be
22393 resent to other recipients.
22396 .option event_action transports string&!! unset
22398 This option declares a string to be expanded for Exim's events mechanism.
22399 For details see chapter &<<CHAPevents>>&.
22402 .option group transports string&!! "Exim group"
22403 .cindex "transport" "group; specifying"
22404 This option specifies a gid for running the transport process, overriding any
22405 value that the router supplies, and also overriding any value associated with
22406 &%user%& (see below).
22409 .option headers_add transports list&!! unset
22410 .cindex "header lines" "adding in transport"
22411 .cindex "transport" "header lines; adding"
22412 This option specifies a list of text headers,
22413 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22414 which are (separately) expanded and added to the header
22415 portion of a message as it is transported, as described in section
22416 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22417 routers. If the result of the expansion is an empty string, or if the expansion
22418 is forced to fail, no action is taken. Other expansion failures are treated as
22419 errors and cause the delivery to be deferred.
22421 Unlike most options, &%headers_add%& can be specified multiple times
22422 for a transport; all listed headers are added.
22425 .option headers_only transports boolean false
22426 .cindex "transport" "header lines only"
22427 .cindex "message" "transporting headers only"
22428 .cindex "header lines" "transporting"
22429 If this option is set, the message's body is not transported. It is mutually
22430 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22431 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22432 checked, since this option does not automatically suppress them.
22435 .option headers_remove transports list&!! unset
22436 .cindex "header lines" "removing"
22437 .cindex "transport" "header lines; removing"
22438 This option specifies a list of text headers,
22439 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22440 to be removed from the message.
22441 However, the option has no effect when an address is just being verified.
22442 Each list item is separately expanded.
22443 If the result of the expansion is an empty string, or if the expansion
22444 is forced to fail, no action is taken. Other expansion failures are treated as
22445 errors and cause the delivery to be deferred.
22446 If an item ends in *, it will match any header with the given prefix.
22448 Matching headers are omitted from the message as it is transported, as described
22449 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22452 Unlike most options, &%headers_remove%& can be specified multiple times
22453 for a transport; all listed headers are removed.
22455 &*Warning*&: Because of the separate expansion of the list items,
22456 items that contain a list separator must have it doubled.
22457 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22461 .option headers_rewrite transports string unset
22462 .cindex "transport" "header lines; rewriting"
22463 .cindex "rewriting" "at transport time"
22464 This option allows addresses in header lines to be rewritten at transport time,
22465 that is, as the message is being copied to its destination. The contents of the
22466 option are a colon-separated list of rewriting rules. Each rule is in exactly
22467 the same form as one of the general rewriting rules that are applied when a
22468 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22471 headers_rewrite = a@b c@d f : \
22474 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22475 &'w@z'& in all address-bearing header lines. The rules are applied to the
22476 header lines just before they are written out at transport time, so they affect
22477 only those copies of the message that pass through the transport. However, only
22478 the message's original header lines, and any that were added by a system
22479 filter, are rewritten. If a router or transport adds header lines, they are not
22480 affected by this option. These rewriting rules are &'not'& applied to the
22481 envelope. You can change the return path using &%return_path%&, but you cannot
22482 change envelope recipients at this time.
22485 .option home_directory transports string&!! unset
22486 .cindex "transport" "home directory for"
22488 This option specifies a home directory setting for a local transport,
22489 overriding any value that may be set by the router. The home directory is
22490 placed in &$home$& while expanding the transport's private options. It is also
22491 used as the current directory if no current directory is set by the
22492 &%current_directory%& option on the transport or the
22493 &%transport_current_directory%& option on the router. If the expansion fails
22494 for any reason, including forced failure, an error is logged, and delivery is
22498 .option initgroups transports boolean false
22499 .cindex "additional groups"
22500 .cindex "groups" "additional"
22501 .cindex "transport" "group; additional"
22502 If this option is true and the uid for the delivery process is provided by the
22503 transport, the &[initgroups()]& function is called when running the transport
22504 to ensure that any additional groups associated with the uid are set up.
22507 .option max_parallel transports integer&!! unset
22508 .cindex limit "transport parallelism"
22509 .cindex transport "parallel processes"
22510 .cindex transport "concurrency limit"
22511 .cindex "delivery" "parallelism for transport"
22512 If this option is set and expands to an integer greater than zero
22513 it limits the number of concurrent runs of the transport.
22514 The control does not apply to shadow transports.
22516 .cindex "hints database" "transport concurrency control"
22517 Exim implements this control by means of a hints database in which a record is
22518 incremented whenever a transport process is being created. The record
22519 is decremented and possibly removed when the process terminates.
22520 Obviously there is scope for
22521 records to get left lying around if there is a system or program crash. To
22522 guard against this, Exim ignores any records that are more than six hours old.
22524 If you use this option, you should also arrange to delete the
22525 relevant hints database whenever your system reboots. The names of the files
22526 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22527 may be one or two files, depending on the type of DBM in use. The same files
22528 are used for ETRN and smtp transport serialization.
22531 .option message_size_limit transports string&!! 0
22532 .cindex "limit" "message size per transport"
22533 .cindex "size" "of message, limit"
22534 .cindex "transport" "message size; limiting"
22535 This option controls the size of messages passed through the transport. It is
22536 expanded before use; the result of the expansion must be a sequence of decimal
22537 digits, optionally followed by K or M. If the expansion fails for any reason,
22538 including forced failure, or if the result is not of the required form,
22539 delivery is deferred. If the value is greater than zero and the size of a
22540 message exceeds this limit, the address is failed. If there is any chance that
22541 the resulting bounce message could be routed to the same transport, you should
22542 ensure that &%return_size_limit%& is less than the transport's
22543 &%message_size_limit%&, as otherwise the bounce message will fail to get
22548 .option rcpt_include_affixes transports boolean false
22549 .cindex "prefix" "for local part, including in envelope"
22550 .cindex "suffix for local part" "including in envelope"
22551 .cindex "local part" "prefix"
22552 .cindex "local part" "suffix"
22553 When this option is false (the default), and an address that has had any
22554 affixes (prefixes or suffixes) removed from the local part is delivered by any
22555 form of SMTP or LMTP, the affixes are not included. For example, if a router
22558 local_part_prefix = *-
22560 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22563 RCPT TO:<xyz@some.domain>
22565 This is also the case when an ACL-time callout is being used to verify a
22566 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22567 whole local part is included in the RCPT command. This option applies to BSMTP
22568 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22569 &(lmtp)& and &(smtp)& transports.
22572 .option retry_use_local_part transports boolean "see below"
22573 .cindex "hints database" "retry keys"
22574 When a delivery suffers a temporary failure, a retry record is created
22575 in Exim's hints database. For remote deliveries, the key for the retry record
22576 is based on the name and/or IP address of the failing remote host. For local
22577 deliveries, the key is normally the entire address, including both the local
22578 part and the domain. This is suitable for most common cases of local delivery
22579 temporary failure &-- for example, exceeding a mailbox quota should delay only
22580 deliveries to that mailbox, not to the whole domain.
22582 However, in some special cases you may want to treat a temporary local delivery
22583 as a failure associated with the domain, and not with a particular local part.
22584 (For example, if you are storing all mail for some domain in files.) You can do
22585 this by setting &%retry_use_local_part%& false.
22587 For all the local transports, its default value is true. For remote transports,
22588 the default value is false for tidiness, but changing the value has no effect
22589 on a remote transport in the current implementation.
22592 .option return_path transports string&!! unset
22593 .cindex "envelope sender"
22594 .cindex "envelope from"
22595 .cindex "transport" "return path; changing"
22596 .cindex "return path" "changing in transport"
22597 If this option is set, the string is expanded at transport time and replaces
22598 the existing return path (envelope sender) value in the copy of the message
22599 that is being delivered. An empty return path is permitted. This feature is
22600 designed for remote deliveries, where the value of this option is used in the
22601 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22602 only effect is to change the address that is placed in the &'Return-path:'&
22603 header line, if one is added to the message (see the next option).
22605 &*Note:*& A changed return path is not logged unless you add
22606 &%return_path_on_delivery%& to the log selector.
22608 .vindex "&$return_path$&"
22609 The expansion can refer to the existing value via &$return_path$&. This is
22610 either the message's envelope sender, or an address set by the
22611 &%errors_to%& option on a router. If the expansion is forced to fail, no
22612 replacement occurs; if it fails for another reason, delivery is deferred. This
22613 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22614 section &<<SECTverp>>&.
22616 &*Note*&: If a delivery error is detected locally, including the case when a
22617 remote server rejects a message at SMTP time, the bounce message is not sent to
22618 the value of this option. It is sent to the previously set errors address.
22619 This defaults to the incoming sender address, but can be changed by setting
22620 &%errors_to%& in a router.
22624 .option return_path_add transports boolean false
22625 .chindex Return-path:
22626 If this option is true, a &'Return-path:'& header is added to the message.
22627 Although the return path is normally available in the prefix line of BSD
22628 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22629 have easy access to it.
22631 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22632 the delivery SMTP server makes the final delivery"&. This implies that this
22633 header should not be present in incoming messages. Exim has a configuration
22634 option, &%return_path_remove%&, which requests removal of this header from
22635 incoming messages, so that delivered messages can safely be resent to other
22639 .option shadow_condition transports string&!! unset
22640 See &%shadow_transport%& below.
22643 .option shadow_transport transports string unset
22644 .cindex "shadow transport"
22645 .cindex "transport" "shadow"
22646 A local transport may set the &%shadow_transport%& option to the name of
22647 another local transport. Shadow remote transports are not supported.
22649 Whenever a delivery to the main transport succeeds, and either
22650 &%shadow_condition%& is unset, or its expansion does not result in the empty
22651 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22652 passed to the shadow transport, with the same delivery address or addresses. If
22653 expansion fails, no action is taken except that non-forced expansion failures
22654 cause a log line to be written.
22656 The result of the shadow transport is discarded and does not affect the
22657 subsequent processing of the message. Only a single level of shadowing is
22658 provided; the &%shadow_transport%& option is ignored on any transport when it
22659 is running as a shadow. Options concerned with output from pipes are also
22660 ignored. The log line for the successful delivery has an item added on the end,
22663 ST=<shadow transport name>
22665 If the shadow transport did not succeed, the error message is put in
22666 parentheses afterwards. Shadow transports can be used for a number of different
22667 purposes, including keeping more detailed log information than Exim normally
22668 provides, and implementing automatic acknowledgment policies based on message
22669 headers that some sites insist on.
22672 .option transport_filter transports string&!! unset
22673 .cindex "transport" "filter"
22674 .cindex "filter" "transport filter"
22675 This option sets up a filtering (in the Unix shell sense) process for messages
22676 at transport time. It should not be confused with mail filtering as set up by
22677 individual users or via a system filter.
22678 If unset, or expanding to an empty string, no filtering is done.
22680 When the message is about to be written out, the command specified by
22681 &%transport_filter%& is started up in a separate, parallel process, and
22682 the entire message, including the header lines, is passed to it on its standard
22683 input (this in fact is done from a third process, to avoid deadlock). The
22684 command must be specified as an absolute path.
22686 The lines of the message that are written to the transport filter are
22687 terminated by newline (&"\n"&). The message is passed to the filter before any
22688 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22689 lines beginning with a dot, and also before any processing implied by the
22690 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22691 &(pipe)& transports.
22693 The standard error for the filter process is set to the same destination as its
22694 standard output; this is read and written to the message's ultimate
22695 destination. The process that writes the message to the filter, the
22696 filter itself, and the original process that reads the result and delivers it
22697 are all run in parallel, like a shell pipeline.
22699 The filter can perform any transformations it likes, but of course should take
22700 care not to break RFC 2822 syntax. Exim does not check the result, except to
22701 test for a final newline when SMTP is in use. All messages transmitted over
22702 SMTP must end with a newline, so Exim supplies one if it is missing.
22704 .cindex "content scanning" "per user"
22705 A transport filter can be used to provide content-scanning on a per-user basis
22706 at delivery time if the only required effect of the scan is to modify the
22707 message. For example, a content scan could insert a new header line containing
22708 a spam score. This could be interpreted by a filter in the user's MUA. It is
22709 not possible to discard a message at this stage.
22711 .cindex "SIZE" "ESMTP extension"
22712 A problem might arise if the filter increases the size of a message that is
22713 being sent down an SMTP connection. If the receiving SMTP server has indicated
22714 support for the SIZE parameter, Exim will have sent the size of the message
22715 at the start of the SMTP session. If what is actually sent is substantially
22716 more, the server might reject the message. This can be worked round by setting
22717 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22718 additions to the message, or to disable the use of SIZE altogether.
22720 .vindex "&$pipe_addresses$&"
22721 The value of the &%transport_filter%& option is the command string for starting
22722 the filter, which is run directly from Exim, not under a shell. The string is
22723 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22724 Exim breaks it up into arguments and then expands each argument separately (see
22725 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22726 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22727 of arguments, one for each address that applies to this delivery. (This isn't
22728 an ideal name for this feature here, but as it was already implemented for the
22729 &(pipe)& transport, it seemed sensible not to change it.)
22732 .vindex "&$host_address$&"
22733 The expansion variables &$host$& and &$host_address$& are available when the
22734 transport is a remote one. They contain the name and IP address of the host to
22735 which the message is being sent. For example:
22737 transport_filter = /some/directory/transport-filter.pl \
22738 $host $host_address $sender_address $pipe_addresses
22741 Two problems arise if you want to use more complicated expansion items to
22742 generate transport filter commands, both of which due to the fact that the
22743 command is split up &'before'& expansion.
22745 If an expansion item contains white space, you must quote it, so that it is all
22746 part of the same command item. If the entire option setting is one such
22747 expansion item, you have to take care what kind of quoting you use. For
22750 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22752 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22753 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22754 stripped by Exim when it read the option's value. When the value is used, if
22755 the single quotes were missing, the line would be split into two items,
22756 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22757 Exim tried to expand the first one.
22759 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22760 expansion cannot generate multiple arguments, or a command name followed by
22761 arguments. Consider this example:
22763 transport_filter = ${lookup{$host}lsearch{/a/file}\
22764 {$value}{/bin/cat}}
22766 The result of the lookup is interpreted as the name of the command, even
22767 if it contains white space. The simplest way round this is to use a shell:
22769 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22770 {$value}{/bin/cat}}
22774 The filter process is run under the same uid and gid as the normal delivery.
22775 For remote deliveries this is the Exim uid/gid by default. The command should
22776 normally yield a zero return code. Transport filters are not supposed to fail.
22777 A non-zero code is taken to mean that the transport filter encountered some
22778 serious problem. Delivery of the message is deferred; the message remains on
22779 the queue and is tried again later. It is not possible to cause a message to be
22780 bounced from a transport filter.
22782 If a transport filter is set on an autoreply transport, the original message is
22783 passed through the filter as it is being copied into the newly generated
22784 message, which happens if the &%return_message%& option is set.
22787 .option transport_filter_timeout transports time 5m
22788 .cindex "transport" "filter, timeout"
22789 When Exim is reading the output of a transport filter, it applies a timeout
22790 that can be set by this option. Exceeding the timeout is normally treated as a
22791 temporary delivery failure. However, if a transport filter is used with a
22792 &(pipe)& transport, a timeout in the transport filter is treated in the same
22793 way as a timeout in the pipe command itself. By default, a timeout is a hard
22794 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22795 becomes a temporary error.
22798 .option user transports string&!! "Exim user"
22799 .cindex "uid (user id)" "local delivery"
22800 .cindex "transport" "user, specifying"
22801 This option specifies the user under whose uid the delivery process is to be
22802 run, overriding any uid that may have been set by the router. If the user is
22803 given as a name, the uid is looked up from the password data, and the
22804 associated group is taken as the value of the gid to be used if the &%group%&
22807 For deliveries that use local transports, a user and group are normally
22808 specified explicitly or implicitly (for example, as a result of
22809 &%check_local_user%&) by the router or transport.
22811 .cindex "hints database" "access by remote transport"
22812 For remote transports, you should leave this option unset unless you really are
22813 sure you know what you are doing. When a remote transport is running, it needs
22814 to be able to access Exim's hints databases, because each host may have its own
22816 .ecindex IIDgenoptra1
22817 .ecindex IIDgenoptra2
22818 .ecindex IIDgenoptra3
22825 . ////////////////////////////////////////////////////////////////////////////
22826 . ////////////////////////////////////////////////////////////////////////////
22828 .chapter "Address batching in local transports" "CHAPbatching" &&&
22830 .cindex "transport" "local; address batching in"
22831 The only remote transport (&(smtp)&) is normally configured to handle more than
22832 one address at a time, so that when several addresses are routed to the same
22833 remote host, just one copy of the message is sent. Local transports, however,
22834 normally handle one address at a time. That is, a separate instance of the
22835 transport is run for each address that is routed to the transport. A separate
22836 copy of the message is delivered each time.
22838 .cindex "batched local delivery"
22839 .oindex "&%batch_max%&"
22840 .oindex "&%batch_id%&"
22841 In special cases, it may be desirable to handle several addresses at once in a
22842 local transport, for example:
22845 In an &(appendfile)& transport, when storing messages in files for later
22846 delivery by some other means, a single copy of the message with multiple
22847 recipients saves space.
22849 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22850 a single copy saves time, and is the normal way LMTP is expected to work.
22852 In a &(pipe)& transport, when passing the message
22853 to a scanner program or
22854 to some other delivery mechanism such as UUCP, multiple recipients may be
22858 These three local transports all have the same options for controlling multiple
22859 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22860 repeating the information for each transport, these options are described here.
22862 The &%batch_max%& option specifies the maximum number of addresses that can be
22863 delivered together in a single run of the transport. Its default value is one
22864 (no batching). When more than one address is routed to a transport that has a
22865 &%batch_max%& value greater than one, the addresses are delivered in a batch
22866 (that is, in a single run of the transport with multiple recipients), subject
22867 to certain conditions:
22870 .vindex "&$local_part$&"
22871 If any of the transport's options contain a reference to &$local_part$&, no
22872 batching is possible.
22874 .vindex "&$domain$&"
22875 If any of the transport's options contain a reference to &$domain$&, only
22876 addresses with the same domain are batched.
22878 .cindex "customizing" "batching condition"
22879 If &%batch_id%& is set, it is expanded for each address, and only those
22880 addresses with the same expanded value are batched. This allows you to specify
22881 customized batching conditions. Failure of the expansion for any reason,
22882 including forced failure, disables batching, but it does not stop the delivery
22885 Batched addresses must also have the same errors address (where to send
22886 delivery errors), the same header additions and removals, the same user and
22887 group for the transport, and if a host list is present, the first host must
22891 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22892 both when the file or pipe command is specified in the transport, and when it
22893 is specified by a &(redirect)& router, but all the batched addresses must of
22894 course be routed to the same file or pipe command. These two transports have an
22895 option called &%use_bsmtp%&, which causes them to deliver the message in
22896 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22897 &%check_string%& and &%escape_string%& options are forced to the values
22900 escape_string = ".."
22902 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22903 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22904 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22906 .cindex "&'Envelope-to:'& header line"
22907 If the generic &%envelope_to_add%& option is set for a batching transport, the
22908 &'Envelope-to:'& header that is added to the message contains all the addresses
22909 that are being processed together. If you are using a batching &(appendfile)&
22910 transport without &%use_bsmtp%&, the only way to preserve the recipient
22911 addresses is to set the &%envelope_to_add%& option.
22913 .cindex "&(pipe)& transport" "with multiple addresses"
22914 .vindex "&$pipe_addresses$&"
22915 If you are using a &(pipe)& transport without BSMTP, and setting the
22916 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22917 the command. This is not a true variable; it is a bit of magic that causes each
22918 of the recipient addresses to be inserted into the command as a separate
22919 argument. This provides a way of accessing all the addresses that are being
22920 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22921 are specified by a &(redirect)& router.
22926 . ////////////////////////////////////////////////////////////////////////////
22927 . ////////////////////////////////////////////////////////////////////////////
22929 .chapter "The appendfile transport" "CHAPappendfile"
22930 .scindex IIDapptra1 "&(appendfile)& transport"
22931 .scindex IIDapptra2 "transports" "&(appendfile)&"
22932 .cindex "directory creation"
22933 .cindex "creating directories"
22934 The &(appendfile)& transport delivers a message by appending it to an existing
22935 file, or by creating an entirely new file in a specified directory. Single
22936 files to which messages are appended can be in the traditional Unix mailbox
22937 format, or optionally in the MBX format supported by the Pine MUA and
22938 University of Washington IMAP daemon, &'inter alia'&. When each message is
22939 being delivered as a separate file, &"maildir"& format can optionally be used
22940 to give added protection against failures that happen part-way through the
22941 delivery. A third form of separate-file delivery known as &"mailstore"& is also
22942 supported. For all file formats, Exim attempts to create as many levels of
22943 directory as necessary, provided that &%create_directory%& is set.
22945 The code for the optional formats is not included in the Exim binary by
22946 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22947 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22950 .cindex "quota" "system"
22951 Exim recognizes system quota errors, and generates an appropriate message. Exim
22952 also supports its own quota control within the transport, for use when the
22953 system facility is unavailable or cannot be used for some reason.
22955 If there is an error while appending to a file (for example, quota exceeded or
22956 partition filled), Exim attempts to reset the file's length and last
22957 modification time back to what they were before. If there is an error while
22958 creating an entirely new file, the new file is removed.
22960 Before appending to a file, a number of security checks are made, and the
22961 file is locked. A detailed description is given below, after the list of
22964 The &(appendfile)& transport is most commonly used for local deliveries to
22965 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22966 putting messages into files for remote delivery by some means other than Exim.
22967 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22972 .section "The file and directory options" "SECTfildiropt"
22973 The &%file%& option specifies a single file, to which the message is appended;
22974 the &%directory%& option specifies a directory, in which a new file containing
22975 the message is created. Only one of these two options can be set, and for
22976 normal deliveries to mailboxes, one of them &'must'& be set.
22978 .vindex "&$address_file$&"
22979 .vindex "&$local_part$&"
22980 However, &(appendfile)& is also used for delivering messages to files or
22981 directories whose names (or parts of names) are obtained from alias,
22982 forwarding, or filtering operations (for example, a &%save%& command in a
22983 user's Exim filter). When such a transport is running, &$local_part$& contains
22984 the local part that was aliased or forwarded, and &$address_file$& contains the
22985 name (or partial name) of the file or directory generated by the redirection
22986 operation. There are two cases:
22989 If neither &%file%& nor &%directory%& is set, the redirection operation
22990 must specify an absolute path (one that begins with &`/`&). This is the most
22991 common case when users with local accounts use filtering to sort mail into
22992 different folders. See for example, the &(address_file)& transport in the
22993 default configuration. If the path ends with a slash, it is assumed to be the
22994 name of a directory. A delivery to a directory can also be forced by setting
22995 &%maildir_format%& or &%mailstore_format%&.
22997 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
22998 used to determine the file or directory name for the delivery. Normally, the
22999 contents of &$address_file$& are used in some way in the string expansion.
23001 .cindex "tainted data" "in filenames"
23002 .cindex appendfile "tainted data"
23003 Tainted data may not be used for a file or directory name.
23004 This means that, for instance, &$local_part$& cannot be used directly
23005 as a component of a path. It can however be used as the key for a lookup
23006 which returns a path (or component).
23009 .cindex "Sieve filter" "configuring &(appendfile)&"
23010 .cindex "Sieve filter" "relative mailbox path handling"
23011 As an example of the second case, consider an environment where users do not
23012 have home directories. They may be permitted to use Exim filter commands of the
23017 or Sieve filter commands of the form:
23019 require "fileinto";
23020 fileinto "folder23";
23022 In this situation, the expansion of &%file%& or &%directory%& in the transport
23023 must transform the relative path into an appropriate absolute filename. In the
23024 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23025 is used as a result of a &"keep"& action in the filter. This example shows one
23026 way of handling this requirement:
23028 file = ${if eq{$address_file}{inbox} \
23029 {/var/mail/$local_part_data} \
23030 {${if eq{${substr_0_1:$address_file}}{/} \
23032 {$home/mail/$address_file} \
23036 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23037 location, absolute paths are used without change, and other folders are in the
23038 &_mail_& directory within the home directory.
23040 &*Note 1*&: While processing an Exim filter, a relative path such as
23041 &_folder23_& is turned into an absolute path if a home directory is known to
23042 the router. In particular, this is the case if &%check_local_user%& is set. If
23043 you want to prevent this happening at routing time, you can set
23044 &%router_home_directory%& empty. This forces the router to pass the relative
23045 path to the transport.
23047 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23048 the &%file%& or &%directory%& option is still used if it is set.
23053 .section "Private options for appendfile" "SECID134"
23054 .cindex "options" "&(appendfile)& transport"
23058 .option allow_fifo appendfile boolean false
23059 .cindex "fifo (named pipe)"
23060 .cindex "named pipe (fifo)"
23061 .cindex "pipe" "named (fifo)"
23062 Setting this option permits delivery to named pipes (FIFOs) as well as to
23063 regular files. If no process is reading the named pipe at delivery time, the
23064 delivery is deferred.
23067 .option allow_symlink appendfile boolean false
23068 .cindex "symbolic link" "to mailbox"
23069 .cindex "mailbox" "symbolic link"
23070 By default, &(appendfile)& will not deliver if the path name for the file is
23071 that of a symbolic link. Setting this option relaxes that constraint, but there
23072 are security issues involved in the use of symbolic links. Be sure you know
23073 what you are doing if you set this. Details of exactly what this option affects
23074 are included in the discussion which follows this list of options.
23077 .option batch_id appendfile string&!! unset
23078 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23079 However, batching is automatically disabled for &(appendfile)& deliveries that
23080 happen as a result of forwarding or aliasing or other redirection directly to a
23084 .option batch_max appendfile integer 1
23085 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23088 .option check_group appendfile boolean false
23089 When this option is set, the group owner of the file defined by the &%file%&
23090 option is checked to see that it is the same as the group under which the
23091 delivery process is running. The default setting is false because the default
23092 file mode is 0600, which means that the group is irrelevant.
23095 .option check_owner appendfile boolean true
23096 When this option is set, the owner of the file defined by the &%file%& option
23097 is checked to ensure that it is the same as the user under which the delivery
23098 process is running.
23101 .option check_string appendfile string "see below"
23102 .cindex "&""From""& line"
23103 As &(appendfile)& writes the message, the start of each line is tested for
23104 matching &%check_string%&, and if it does, the initial matching characters are
23105 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23106 a literal string, not a regular expression, and the case of any letters it
23107 contains is significant.
23109 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23110 are forced to &"."& and &".."& respectively, and any settings in the
23111 configuration are ignored. Otherwise, they default to &"From&~"& and
23112 &">From&~"& when the &%file%& option is set, and unset when any of the
23113 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23115 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23116 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23117 &"From&~"& indicates the start of a new message. All four options need changing
23118 if another format is used. For example, to deliver to mailboxes in MMDF format:
23119 .cindex "MMDF format mailbox"
23120 .cindex "mailbox" "MMDF format"
23122 check_string = "\1\1\1\1\n"
23123 escape_string = "\1\1\1\1 \n"
23124 message_prefix = "\1\1\1\1\n"
23125 message_suffix = "\1\1\1\1\n"
23127 .option create_directory appendfile boolean true
23128 .cindex "directory creation"
23129 When this option is true, Exim attempts to create any missing superior
23130 directories for the file that it is about to write. A created directory's mode
23131 is given by the &%directory_mode%& option.
23133 The group ownership of a newly created directory is highly dependent on the
23134 operating system (and possibly the file system) that is being used. For
23135 example, in Solaris, if the parent directory has the setgid bit set, its group
23136 is propagated to the child; if not, the currently set group is used. However,
23137 in FreeBSD, the parent's group is always used.
23141 .option create_file appendfile string anywhere
23142 This option constrains the location of files and directories that are created
23143 by this transport. It applies to files defined by the &%file%& option and
23144 directories defined by the &%directory%& option. In the case of maildir
23145 delivery, it applies to the top level directory, not the maildir directories
23148 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23149 &"belowhome"&. In the second and third cases, a home directory must have been
23150 set for the transport. This option is not useful when an explicit filename is
23151 given for normal mailbox deliveries. It is intended for the case when filenames
23152 are generated from users' &_.forward_& files. These are usually handled
23153 by an &(appendfile)& transport called &%address_file%&. See also
23154 &%file_must_exist%&.
23157 .option directory appendfile string&!! unset
23158 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23159 or &%directory%& must be set, unless the delivery is the direct result of a
23160 redirection (see section &<<SECTfildiropt>>&).
23162 When &%directory%& is set, the string is expanded, and the message is delivered
23163 into a new file or files in or below the given directory, instead of being
23164 appended to a single mailbox file. A number of different formats are provided
23165 (see &%maildir_format%& and &%mailstore_format%&), and see section
23166 &<<SECTopdir>>& for further details of this form of delivery.
23169 .option directory_file appendfile string&!! "see below"
23171 .vindex "&$inode$&"
23172 When &%directory%& is set, but neither &%maildir_format%& nor
23173 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23174 whose name is obtained by expanding this string. The default value is:
23176 q${base62:$tod_epoch}-$inode
23178 This generates a unique name from the current time, in base 62 form, and the
23179 inode of the file. The variable &$inode$& is available only when expanding this
23183 .option directory_mode appendfile "octal integer" 0700
23184 If &(appendfile)& creates any directories as a result of the
23185 &%create_directory%& option, their mode is specified by this option.
23188 .option escape_string appendfile string "see description"
23189 See &%check_string%& above.
23192 .option file appendfile string&!! unset
23193 This option is mutually exclusive with the &%directory%& option, but one of
23194 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23195 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23196 specifies a single file, to which the message is appended. One or more of
23197 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23200 .cindex "NFS" "lock file"
23201 .cindex "locking files"
23202 .cindex "lock files"
23203 If you are using more than one host to deliver over NFS into the same
23204 mailboxes, you should always use lock files.
23206 The string value is expanded for each delivery, and must yield an absolute
23207 path. The most common settings of this option are variations on one of these
23210 file = /var/spool/mail/$local_part_data
23211 file = /home/$local_part_data/inbox
23214 .cindex "&""sticky""& bit"
23215 In the first example, all deliveries are done into the same directory. If Exim
23216 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23217 create a file in the directory, so the &"sticky"& bit must be turned on for
23218 deliveries to be possible, or alternatively the &%group%& option can be used to
23219 run the delivery under a group id which has write access to the directory.
23223 .option file_format appendfile string unset
23224 .cindex "file" "mailbox; checking existing format"
23225 This option requests the transport to check the format of an existing file
23226 before adding to it. The check consists of matching a specific string at the
23227 start of the file. The value of the option consists of an even number of
23228 colon-separated strings. The first of each pair is the test string, and the
23229 second is the name of a transport. If the transport associated with a matched
23230 string is not the current transport, control is passed over to the other
23231 transport. For example, suppose the standard &(local_delivery)& transport has
23234 file_format = "From : local_delivery :\
23235 \1\1\1\1\n : local_mmdf_delivery"
23237 Mailboxes that begin with &"From"& are still handled by this transport, but if
23238 a mailbox begins with four binary ones followed by a newline, control is passed
23239 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23240 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23241 is assumed to match the current transport. If the start of a mailbox doesn't
23242 match any string, or if the transport named for a given string is not defined,
23243 delivery is deferred.
23246 .option file_must_exist appendfile boolean false
23247 If this option is true, the file specified by the &%file%& option must exist.
23248 A temporary error occurs if it does not, causing delivery to be deferred.
23249 If this option is false, the file is created if it does not exist.
23252 .option lock_fcntl_timeout appendfile time 0s
23253 .cindex "timeout" "mailbox locking"
23254 .cindex "mailbox" "locking, blocking and non-blocking"
23255 .cindex "locking files"
23256 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23257 when locking an open mailbox file. If the call fails, the delivery process
23258 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23259 Non-blocking calls are used so that the file is not kept open during the wait
23260 for the lock; the reason for this is to make it as safe as possible for
23261 deliveries over NFS in the case when processes might be accessing an NFS
23262 mailbox without using a lock file. This should not be done, but
23263 misunderstandings and hence misconfigurations are not unknown.
23265 On a busy system, however, the performance of a non-blocking lock approach is
23266 not as good as using a blocking lock with a timeout. In this case, the waiting
23267 is done inside the system call, and Exim's delivery process acquires the lock
23268 and can proceed as soon as the previous lock holder releases it.
23270 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23271 timeout, are used. There may still be some retrying: the maximum number of
23274 (lock_retries * lock_interval) / lock_fcntl_timeout
23276 rounded up to the next whole number. In other words, the total time during
23277 which &(appendfile)& is trying to get a lock is roughly the same, unless
23278 &%lock_fcntl_timeout%& is set very large.
23280 You should consider setting this option if you are getting a lot of delayed
23281 local deliveries because of errors of the form
23283 failed to lock mailbox /some/file (fcntl)
23286 .option lock_flock_timeout appendfile time 0s
23287 This timeout applies to file locking when using &[flock()]& (see
23288 &%use_flock%&); the timeout operates in a similar manner to
23289 &%lock_fcntl_timeout%&.
23292 .option lock_interval appendfile time 3s
23293 This specifies the time to wait between attempts to lock the file. See below
23294 for details of locking.
23297 .option lock_retries appendfile integer 10
23298 This specifies the maximum number of attempts to lock the file. A value of zero
23299 is treated as 1. See below for details of locking.
23302 .option lockfile_mode appendfile "octal integer" 0600
23303 This specifies the mode of the created lock file, when a lock file is being
23304 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23307 .option lockfile_timeout appendfile time 30m
23308 .cindex "timeout" "mailbox locking"
23309 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23310 exists and is older than this value, it is assumed to have been left behind by
23311 accident, and Exim attempts to remove it.
23314 .option mailbox_filecount appendfile string&!! unset
23315 .cindex "mailbox" "specifying size of"
23316 .cindex "size" "of mailbox"
23317 If this option is set, it is expanded, and the result is taken as the current
23318 number of files in the mailbox. It must be a decimal number, optionally
23319 followed by K or M. This provides a way of obtaining this information from an
23320 external source that maintains the data.
23323 .option mailbox_size appendfile string&!! unset
23324 .cindex "mailbox" "specifying size of"
23325 .cindex "size" "of mailbox"
23326 If this option is set, it is expanded, and the result is taken as the current
23327 size the mailbox. It must be a decimal number, optionally followed by K or M.
23328 This provides a way of obtaining this information from an external source that
23329 maintains the data. This is likely to be helpful for maildir deliveries where
23330 it is computationally expensive to compute the size of a mailbox.
23334 .option maildir_format appendfile boolean false
23335 .cindex "maildir format" "specifying"
23336 If this option is set with the &%directory%& option, the delivery is into a new
23337 file, in the &"maildir"& format that is used by other mail software. When the
23338 transport is activated directly from a &(redirect)& router (for example, the
23339 &(address_file)& transport in the default configuration), setting
23340 &%maildir_format%& causes the path received from the router to be treated as a
23341 directory, whether or not it ends with &`/`&. This option is available only if
23342 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23343 &<<SECTmaildirdelivery>>& below for further details.
23346 .option maildir_quota_directory_regex appendfile string "See below"
23347 .cindex "maildir format" "quota; directories included in"
23348 .cindex "quota" "maildir; directories included in"
23349 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23350 a regular expression for specifying directories, relative to the quota
23351 directory (see &%quota_directory%&), that should be included in the quota
23352 calculation. The default value is:
23354 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23356 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23357 (directories whose names begin with a dot). If you want to exclude the
23359 folder from the count (as some sites do), you need to change this setting to
23361 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23363 This uses a negative lookahead in the regular expression to exclude the
23364 directory whose name is &_.Trash_&. When a directory is excluded from quota
23365 calculations, quota processing is bypassed for any messages that are delivered
23366 directly into that directory.
23369 .option maildir_retries appendfile integer 10
23370 This option specifies the number of times to retry when writing a file in
23371 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23374 .option maildir_tag appendfile string&!! unset
23375 This option applies only to deliveries in maildir format, and is described in
23376 section &<<SECTmaildirdelivery>>& below.
23379 .option maildir_use_size_file appendfile&!! boolean false
23380 .cindex "maildir format" "&_maildirsize_& file"
23381 The result of string expansion for this option must be a valid boolean value.
23382 If it is true, it enables support for &_maildirsize_& files. Exim
23383 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23384 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23385 value is zero. See &%maildir_quota_directory_regex%& above and section
23386 &<<SECTmaildirdelivery>>& below for further details.
23388 .option maildirfolder_create_regex appendfile string unset
23389 .cindex "maildir format" "&_maildirfolder_& file"
23390 .cindex "&_maildirfolder_&, creating"
23391 The value of this option is a regular expression. If it is unset, it has no
23392 effect. Otherwise, before a maildir delivery takes place, the pattern is
23393 matched against the name of the maildir directory, that is, the directory
23394 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23395 delivery. If there is a match, Exim checks for the existence of a file called
23396 &_maildirfolder_& in the directory, and creates it if it does not exist.
23397 See section &<<SECTmaildirdelivery>>& for more details.
23400 .option mailstore_format appendfile boolean false
23401 .cindex "mailstore format" "specifying"
23402 If this option is set with the &%directory%& option, the delivery is into two
23403 new files in &"mailstore"& format. The option is available only if
23404 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23405 below for further details.
23408 .option mailstore_prefix appendfile string&!! unset
23409 This option applies only to deliveries in mailstore format, and is described in
23410 section &<<SECTopdir>>& below.
23413 .option mailstore_suffix appendfile string&!! unset
23414 This option applies only to deliveries in mailstore format, and is described in
23415 section &<<SECTopdir>>& below.
23418 .option mbx_format appendfile boolean false
23419 .cindex "locking files"
23420 .cindex "file" "locking"
23421 .cindex "file" "MBX format"
23422 .cindex "MBX format, specifying"
23423 This option is available only if Exim has been compiled with SUPPORT_MBX
23424 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23425 the message is appended to the mailbox file in MBX format instead of
23426 traditional Unix format. This format is supported by Pine4 and its associated
23427 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23429 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23430 automatically changed by the use of &%mbx_format%&. They should normally be set
23431 empty when using MBX format, so this option almost always appears in this
23438 If none of the locking options are mentioned in the configuration,
23439 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23440 is possible to specify the other kinds of locking with &%mbx_format%&, but
23441 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23442 interworks with &'c-client'&, providing for shared access to the mailbox. It
23443 should not be used if any program that does not use this form of locking is
23444 going to access the mailbox, nor should it be used if the mailbox file is NFS
23445 mounted, because it works only when the mailbox is accessed from a single host.
23447 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23448 the standard version of &'c-client'&, because as long as it has a mailbox open
23449 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23450 append messages to it.
23453 .option message_prefix appendfile string&!! "see below"
23454 .cindex "&""From""& line"
23455 The string specified here is expanded and output at the start of every message.
23456 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23457 in which case it is:
23459 message_prefix = "From ${if def:return_path{$return_path}\
23460 {MAILER-DAEMON}} $tod_bsdinbox\n"
23462 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23463 &`\n`& to &`\r\n`& in &%message_prefix%&.
23465 .option message_suffix appendfile string&!! "see below"
23466 The string specified here is expanded and output at the end of every message.
23467 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23468 in which case it is a single newline character. The suffix can be suppressed by
23473 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23474 &`\n`& to &`\r\n`& in &%message_suffix%&.
23476 .option mode appendfile "octal integer" 0600
23477 If the output file is created, it is given this mode. If it already exists and
23478 has wider permissions, they are reduced to this mode. If it has narrower
23479 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23480 if the delivery is the result of a &%save%& command in a filter file specifying
23481 a particular mode, the mode of the output file is always forced to take that
23482 value, and this option is ignored.
23485 .option mode_fail_narrower appendfile boolean true
23486 This option applies in the case when an existing mailbox file has a narrower
23487 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23488 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23489 continues with the delivery attempt, using the existing mode of the file.
23492 .option notify_comsat appendfile boolean false
23493 If this option is true, the &'comsat'& daemon is notified after every
23494 successful delivery to a user mailbox. This is the daemon that notifies logged
23495 on users about incoming mail.
23498 .option quota appendfile string&!! unset
23499 .cindex "quota" "imposed by Exim"
23500 This option imposes a limit on the size of the file to which Exim is appending,
23501 or to the total space used in the directory tree when the &%directory%& option
23502 is set. In the latter case, computation of the space used is expensive, because
23503 all the files in the directory (and any sub-directories) have to be
23504 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23505 &%maildir_use_size_file%& for ways to avoid this in environments where users
23506 have no shell access to their mailboxes).
23508 As there is no interlock against two simultaneous deliveries into a
23509 multi-file mailbox, it is possible for the quota to be overrun in this case.
23510 For single-file mailboxes, of course, an interlock is a necessity.
23512 A file's size is taken as its &'used'& value. Because of blocking effects, this
23513 may be a lot less than the actual amount of disk space allocated to the file.
23514 If the sizes of a number of files are being added up, the rounding effect can
23515 become quite noticeable, especially on systems that have large block sizes.
23516 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23517 the obvious value which users understand most easily.
23519 The value of the option is expanded, and must then be a numerical value
23520 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23521 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23522 and further option modifiers. If Exim is running on a system with
23523 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23526 The option modifier &%no_check%& can be used to force delivery even if the over
23527 quota condition is met. The quota gets updated as usual.
23529 &*Note*&: A value of zero is interpreted as &"no quota"&.
23531 The expansion happens while Exim is running as root, before it changes uid for
23532 the delivery. This means that files that are inaccessible to the end user can
23533 be used to hold quota values that are looked up in the expansion. When delivery
23534 fails because this quota is exceeded, the handling of the error is as for
23535 system quota failures.
23537 By default, Exim's quota checking mimics system quotas, and restricts the
23538 mailbox to the specified maximum size, though the value is not accurate to the
23539 last byte, owing to separator lines and additional headers that may get added
23540 during message delivery. When a mailbox is nearly full, large messages may get
23541 refused even though small ones are accepted, because the size of the current
23542 message is added to the quota when the check is made. This behaviour can be
23543 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23544 for exceeding the quota does not include the current message. Thus, deliveries
23545 continue until the quota has been exceeded; thereafter, no further messages are
23546 delivered. See also &%quota_warn_threshold%&.
23549 .option quota_directory appendfile string&!! unset
23550 This option defines the directory to check for quota purposes when delivering
23551 into individual files. The default is the delivery directory, or, if a file
23552 called &_maildirfolder_& exists in a maildir directory, the parent of the
23553 delivery directory.
23556 .option quota_filecount appendfile string&!! 0
23557 This option applies when the &%directory%& option is set. It limits the total
23558 number of files in the directory (compare the inode limit in system quotas). It
23559 can only be used if &%quota%& is also set. The value is expanded; an expansion
23560 failure causes delivery to be deferred. A value of zero is interpreted as
23563 The option modifier &%no_check%& can be used to force delivery even if the over
23564 quota condition is met. The quota gets updated as usual.
23566 .option quota_is_inclusive appendfile boolean true
23567 See &%quota%& above.
23570 .option quota_size_regex appendfile string unset
23571 This option applies when one of the delivery modes that writes a separate file
23572 for each message is being used. When Exim wants to find the size of one of
23573 these files in order to test the quota, it first checks &%quota_size_regex%&.
23574 If this is set to a regular expression that matches the filename, and it
23575 captures one string, that string is interpreted as a representation of the
23576 file's size. The value of &%quota_size_regex%& is not expanded.
23578 This feature is useful only when users have no shell access to their mailboxes
23579 &-- otherwise they could defeat the quota simply by renaming the files. This
23580 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23581 the file length to the filename. For example:
23583 maildir_tag = ,S=$message_size
23584 quota_size_regex = ,S=(\d+)
23586 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23587 number of lines in the message.
23589 The regular expression should not assume that the length is at the end of the
23590 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23591 sometimes add other information onto the ends of message filenames.
23593 Section &<<SECID136>>& contains further information.
23595 This option should not be used when other message-handling software
23596 may duplicate messages by making hardlinks to the files. When that is done Exim
23597 will count the message size once for each filename, in contrast with the actual
23598 disk usage. When the option is not set, calculating total usage requires
23599 a system-call per file to get the size; the number of links is then available also
23600 as is used to adjust the effective size.
23603 .option quota_warn_message appendfile string&!! "see below"
23604 See below for the use of this option. If it is not set when
23605 &%quota_warn_threshold%& is set, it defaults to
23607 quota_warn_message = "\
23608 To: $local_part@$domain\n\
23609 Subject: Your mailbox\n\n\
23610 This message is automatically created \
23611 by mail delivery software.\n\n\
23612 The size of your mailbox has exceeded \
23613 a warning threshold that is\n\
23614 set by the system administrator.\n"
23618 .option quota_warn_threshold appendfile string&!! 0
23619 .cindex "quota" "warning threshold"
23620 .cindex "mailbox" "size warning"
23621 .cindex "size" "of mailbox"
23622 This option is expanded in the same way as &%quota%& (see above). If the
23623 resulting value is greater than zero, and delivery of the message causes the
23624 size of the file or total space in the directory tree to cross the given
23625 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23626 may be specified as a percentage of it by following the value with a percent
23630 quota_warn_threshold = 75%
23632 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23633 percent sign is ignored.
23635 The warning message itself is specified by the &%quota_warn_message%& option,
23636 and it must start with a &'To:'& header line containing the recipient(s) of the
23637 warning message. These do not necessarily have to include the recipient(s) of
23638 the original message. A &'Subject:'& line should also normally be supplied. You
23639 can include any other header lines that you want. If you do not include a
23640 &'From:'& line, the default is:
23642 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23644 .oindex &%errors_reply_to%&
23645 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23648 The &%quota%& option does not have to be set in order to use this option; they
23649 are independent of one another except when the threshold is specified as a
23653 .option use_bsmtp appendfile boolean false
23654 .cindex "envelope from"
23655 .cindex "envelope sender"
23656 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23657 format, with the envelope sender and recipient(s) included as SMTP commands. If
23658 you want to include a leading HELO command with such messages, you can do
23659 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23660 for details of batch SMTP.
23663 .option use_crlf appendfile boolean false
23664 .cindex "carriage return"
23666 This option causes lines to be terminated with the two-character CRLF sequence
23667 (carriage return, linefeed) instead of just a linefeed character. In the case
23668 of batched SMTP, the byte sequence written to the file is then an exact image
23669 of what would be sent down a real SMTP connection.
23671 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23672 (which are used to supply the traditional &"From&~"& and blank line separators
23673 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23674 carriage return characters if these are needed. In cases where these options
23675 have non-empty defaults, the values end with a single linefeed, so they must be
23676 changed to end with &`\r\n`& if &%use_crlf%& is set.
23679 .option use_fcntl_lock appendfile boolean "see below"
23680 This option controls the use of the &[fcntl()]& function to lock a file for
23681 exclusive use when a message is being appended. It is set by default unless
23682 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23683 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23684 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23687 .option use_flock_lock appendfile boolean false
23688 This option is provided to support the use of &[flock()]& for file locking, for
23689 the few situations where it is needed. Most modern operating systems support
23690 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23691 each other. Exim uses &[fcntl()]& locking by default.
23693 This option is required only if you are using an operating system where
23694 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23695 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23696 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23698 .cindex "Solaris" "&[flock()]& support"
23699 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23700 have it (and some, I think, provide a not quite right version built on top of
23701 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23702 the ability to use it, and any attempt to do so will cause a configuration
23705 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23706 is just being mapped onto &[fcntl()]& by the OS).
23709 .option use_lockfile appendfile boolean "see below"
23710 If this option is turned off, Exim does not attempt to create a lock file when
23711 appending to a mailbox file. In this situation, the only locking is by
23712 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23713 sure that every MUA that is ever going to look at your users' mailboxes uses
23714 &[fcntl()]& rather than a lock file, and even then only when you are not
23715 delivering over NFS from more than one host.
23717 .cindex "NFS" "lock file"
23718 In order to append to an NFS file safely from more than one host, it is
23719 necessary to take out a lock &'before'& opening the file, and the lock file
23720 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23723 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23724 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23725 except when &%mbx_format%& is set.
23728 .option use_mbx_lock appendfile boolean "see below"
23729 This option is available only if Exim has been compiled with SUPPORT_MBX
23730 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23731 locking rules be used. It is set by default if &%mbx_format%& is set and none
23732 of the locking options are mentioned in the configuration. The locking rules
23733 are the same as are used by the &'c-client'& library that underlies Pine and
23734 the IMAP4 and POP daemons that come with it (see the discussion below). The
23735 rules allow for shared access to the mailbox. However, this kind of locking
23736 does not work when the mailbox is NFS mounted.
23738 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23739 &%use_flock_lock%& to control what kind of locking is used in implementing the
23740 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23741 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23746 .section "Operational details for appending" "SECTopappend"
23747 .cindex "appending to a file"
23748 .cindex "file" "appending"
23749 Before appending to a file, the following preparations are made:
23752 If the name of the file is &_/dev/null_&, no action is taken, and a success
23756 .cindex "directory creation"
23757 If any directories on the file's path are missing, Exim creates them if the
23758 &%create_directory%& option is set. A created directory's mode is given by the
23759 &%directory_mode%& option.
23762 If &%file_format%& is set, the format of an existing file is checked. If this
23763 indicates that a different transport should be used, control is passed to that
23767 .cindex "file" "locking"
23768 .cindex "locking files"
23769 .cindex "NFS" "lock file"
23770 If &%use_lockfile%& is set, a lock file is built in a way that will work
23771 reliably over NFS, as follows:
23774 Create a &"hitching post"& file whose name is that of the lock file with the
23775 current time, primary host name, and process id added, by opening for writing
23776 as a new file. If this fails with an access error, delivery is deferred.
23778 Close the hitching post file, and hard link it to the lock filename.
23780 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23781 Unlink the hitching post name.
23783 Otherwise, use &[stat()]& to get information about the hitching post file, and
23784 then unlink hitching post name. If the number of links is exactly two, creation
23785 of the lock file succeeded but something (for example, an NFS server crash and
23786 restart) caused this fact not to be communicated to the &[link()]& call.
23788 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23789 up to &%lock_retries%& times. However, since any program that writes to a
23790 mailbox should complete its task very quickly, it is reasonable to time out old
23791 lock files that are normally the result of user agent and system crashes. If an
23792 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23793 it before trying again.
23797 A call is made to &[lstat()]& to discover whether the main file exists, and if
23798 so, what its characteristics are. If &[lstat()]& fails for any reason other
23799 than non-existence, delivery is deferred.
23802 .cindex "symbolic link" "to mailbox"
23803 .cindex "mailbox" "symbolic link"
23804 If the file does exist and is a symbolic link, delivery is deferred, unless the
23805 &%allow_symlink%& option is set, in which case the ownership of the link is
23806 checked, and then &[stat()]& is called to find out about the real file, which
23807 is then subjected to the checks below. The check on the top-level link
23808 ownership prevents one user creating a link for another's mailbox in a sticky
23809 directory, though allowing symbolic links in this case is definitely not a good
23810 idea. If there is a chain of symbolic links, the intermediate ones are not
23814 If the file already exists but is not a regular file, or if the file's owner
23815 and group (if the group is being checked &-- see &%check_group%& above) are
23816 different from the user and group under which the delivery is running,
23817 delivery is deferred.
23820 If the file's permissions are more generous than specified, they are reduced.
23821 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23822 is set false, in which case the delivery is tried using the existing
23826 The file's inode number is saved, and the file is then opened for appending.
23827 If this fails because the file has vanished, &(appendfile)& behaves as if it
23828 hadn't existed (see below). For any other failures, delivery is deferred.
23831 If the file is opened successfully, check that the inode number hasn't
23832 changed, that it is still a regular file, and that the owner and permissions
23833 have not changed. If anything is wrong, defer delivery and freeze the message.
23836 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23837 option is set. Otherwise, check that the file is being created in a permitted
23838 directory if the &%create_file%& option is set (deferring on failure), and then
23839 open for writing as a new file, with the O_EXCL and O_CREAT options,
23840 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23841 set). In this case, which can happen if the link points to a non-existent file,
23842 the file is opened for writing using O_CREAT but not O_EXCL, because
23843 that prevents link following.
23846 .cindex "loop" "while file testing"
23847 If opening fails because the file exists, obey the tests given above for
23848 existing files. However, to avoid looping in a situation where the file is
23849 being continuously created and destroyed, the exists/not-exists loop is broken
23850 after 10 repetitions, and the message is then frozen.
23853 If opening fails with any other error, defer delivery.
23856 .cindex "file" "locking"
23857 .cindex "locking files"
23858 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23859 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23860 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23861 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23862 file, and an exclusive lock on the file whose name is
23864 /tmp/.<device-number>.<inode-number>
23866 using the device and inode numbers of the open mailbox file, in accordance with
23867 the MBX locking rules. This file is created with a mode that is specified by
23868 the &%lockfile_mode%& option.
23870 If Exim fails to lock the file, there are two possible courses of action,
23871 depending on the value of the locking timeout. This is obtained from
23872 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23874 If the timeout value is zero, the file is closed, Exim waits for
23875 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23876 to lock it again. This happens up to &%lock_retries%& times, after which the
23877 delivery is deferred.
23879 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23880 &[flock()]& are used (with the given timeout), so there has already been some
23881 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23882 immediately. It retries up to
23884 (lock_retries * lock_interval) / <timeout>
23886 times (rounded up).
23889 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23890 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23893 .section "Operational details for delivery to a new file" "SECTopdir"
23894 .cindex "delivery" "to single file"
23895 .cindex "&""From""& line"
23896 When the &%directory%& option is set instead of &%file%&, each message is
23897 delivered into a newly-created file or set of files. When &(appendfile)& is
23898 activated directly from a &(redirect)& router, neither &%file%& nor
23899 &%directory%& is normally set, because the path for delivery is supplied by the
23900 router. (See for example, the &(address_file)& transport in the default
23901 configuration.) In this case, delivery is to a new file if either the path name
23902 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23904 No locking is required while writing the message to a new file, so the various
23905 locking options of the transport are ignored. The &"From"& line that by default
23906 separates messages in a single file is not normally needed, nor is the escaping
23907 of message lines that start with &"From"&, and there is no need to ensure a
23908 newline at the end of each message. Consequently, the default values for
23909 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
23910 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
23912 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
23913 the files in the delivery directory by default. However, you can specify a
23914 different directory by setting &%quota_directory%&. Also, for maildir
23915 deliveries (see below) the &_maildirfolder_& convention is honoured.
23918 .cindex "maildir format"
23919 .cindex "mailstore format"
23920 There are three different ways in which delivery to individual files can be
23921 done, controlled by the settings of the &%maildir_format%& and
23922 &%mailstore_format%& options. Note that code to support maildir or mailstore
23923 formats is not included in the binary unless SUPPORT_MAILDIR or
23924 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
23926 .cindex "directory creation"
23927 In all three cases an attempt is made to create the directory and any necessary
23928 sub-directories if they do not exist, provided that the &%create_directory%&
23929 option is set (the default). The location of a created directory can be
23930 constrained by setting &%create_file%&. A created directory's mode is given by
23931 the &%directory_mode%& option. If creation fails, or if the
23932 &%create_directory%& option is not set when creation is required, delivery is
23937 .section "Maildir delivery" "SECTmaildirdelivery"
23938 .cindex "maildir format" "description of"
23939 If the &%maildir_format%& option is true, Exim delivers each message by writing
23940 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
23941 directory that is defined by the &%directory%& option (the &"delivery
23942 directory"&). If the delivery is successful, the file is renamed into the
23943 &_new_& subdirectory.
23945 In the filename, <&'stime'&> is the current time of day in seconds, and
23946 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
23947 Exim checks that the time-of-day clock has moved on by at least one microsecond
23948 before terminating the delivery process. This guarantees uniqueness for the
23949 filename. However, as a precaution, Exim calls &[stat()]& for the file before
23950 opening it. If any response other than ENOENT (does not exist) is given,
23951 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
23953 Before Exim carries out a maildir delivery, it ensures that subdirectories
23954 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
23955 do not exist, Exim tries to create them and any superior directories in their
23956 path, subject to the &%create_directory%& and &%create_file%& options. If the
23957 &%maildirfolder_create_regex%& option is set, and the regular expression it
23958 contains matches the delivery directory, Exim also ensures that a file called
23959 &_maildirfolder_& exists in the delivery directory. If a missing directory or
23960 &_maildirfolder_& file cannot be created, delivery is deferred.
23962 These features make it possible to use Exim to create all the necessary files
23963 and directories in a maildir mailbox, including subdirectories for maildir++
23964 folders. Consider this example:
23966 maildir_format = true
23967 directory = /var/mail/$local_part_data\
23968 ${if eq{$local_part_suffix}{}{}\
23969 {/.${substr_1:$local_part_suffix}}}
23970 maildirfolder_create_regex = /\.[^/]+$
23972 If &$local_part_suffix$& is empty (there was no suffix for the local part),
23973 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
23974 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
23975 not match this name, so Exim will not look for or create the file
23976 &_/var/mail/pimbo/maildirfolder_&, though it will create
23977 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
23979 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
23980 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
23981 does match &%maildirfolder_create_regex%&. In this case, Exim will create
23982 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
23983 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
23985 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
23986 not inadvertently match the toplevel maildir directory, because a
23987 &_maildirfolder_& file at top level would completely break quota calculations.
23989 .cindex "quota" "in maildir delivery"
23990 .cindex "maildir++"
23991 If Exim is required to check a &%quota%& setting before a maildir delivery, and
23992 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
23993 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
23994 Exim assumes the directory is a maildir++ folder directory, which is one level
23995 down from the user's top level mailbox directory. This causes it to start at
23996 the parent directory instead of the current directory when calculating the
23997 amount of space used.
23999 One problem with delivering into a multi-file mailbox is that it is
24000 computationally expensive to compute the size of the mailbox for quota
24001 checking. Various approaches have been taken to reduce the amount of work
24002 needed. The next two sections describe two of them. A third alternative is to
24003 use some external process for maintaining the size data, and use the expansion
24004 of the &%mailbox_size%& option as a way of importing it into Exim.
24009 .section "Using tags to record message sizes" "SECID135"
24010 If &%maildir_tag%& is set, the string is expanded for each delivery.
24011 When the maildir file is renamed into the &_new_& sub-directory, the
24012 tag is added to its name. However, if adding the tag takes the length of the
24013 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24014 the tag is dropped and the maildir file is created with no tag.
24017 .vindex "&$message_size$&"
24018 Tags can be used to encode the size of files in their names; see
24019 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24020 happens after the message has been written. The value of the &$message_size$&
24021 variable is set to the number of bytes actually written. If the expansion is
24022 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24023 be deferred. The expanded tag may contain any printing characters except &"/"&.
24024 Non-printing characters in the string are ignored; if the resulting string is
24025 empty, it is ignored. If it starts with an alphanumeric character, a leading
24026 colon is inserted; this default has not proven to be the path that popular
24027 maildir implementations have chosen (but changing it in Exim would break
24028 backwards compatibility).
24030 For one common implementation, you might set:
24032 maildir_tag = ,S=${message_size}
24034 but you should check the documentation of the other software to be sure.
24036 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24037 as this allows Exim to extract the size from your tag, instead of having to
24038 &[stat()]& each message file.
24041 .section "Using a maildirsize file" "SECID136"
24042 .cindex "quota" "in maildir delivery"
24043 .cindex "maildir format" "&_maildirsize_& file"
24044 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24045 storing quota and message size information in a file called &_maildirsize_&
24046 within the toplevel maildir directory. If this file does not exist, Exim
24047 creates it, setting the quota from the &%quota%& option of the transport. If
24048 the maildir directory itself does not exist, it is created before any attempt
24049 to write a &_maildirsize_& file.
24051 The &_maildirsize_& file is used to hold information about the sizes of
24052 messages in the maildir, thus speeding up quota calculations. The quota value
24053 in the file is just a cache; if the quota is changed in the transport, the new
24054 value overrides the cached value when the next message is delivered. The cache
24055 is maintained for the benefit of other programs that access the maildir and
24056 need to know the quota.
24058 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24059 file is maintained (with a zero quota setting), but no quota is imposed.
24061 A regular expression is available for controlling which directories in the
24062 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24063 See the description of the &%maildir_quota_directory_regex%& option above for
24067 .section "Mailstore delivery" "SECID137"
24068 .cindex "mailstore format" "description of"
24069 If the &%mailstore_format%& option is true, each message is written as two
24070 files in the given directory. A unique base name is constructed from the
24071 message id and the current delivery process, and the files that are written use
24072 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24073 contains the message's envelope, and the &_.msg_& file contains the message
24074 itself. The base name is placed in the variable &$mailstore_basename$&.
24076 During delivery, the envelope is first written to a file with the suffix
24077 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24078 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24079 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24080 file before accessing either of them. An alternative approach is to wait for
24081 the absence of a &_.tmp_& file.
24083 The envelope file starts with any text defined by the &%mailstore_prefix%&
24084 option, expanded and terminated by a newline if there isn't one. Then follows
24085 the sender address on one line, then all the recipient addresses, one per line.
24086 There can be more than one recipient only if the &%batch_max%& option is set
24087 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24088 appended to the file, followed by a newline if it does not end with one.
24090 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24091 failure, it is ignored. Other expansion errors are treated as serious
24092 configuration errors, and delivery is deferred. The variable
24093 &$mailstore_basename$& is available for use during these expansions.
24096 .section "Non-special new file delivery" "SECID138"
24097 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24098 file is created directly in the named directory. For example, when delivering
24099 messages into files in batched SMTP format for later delivery to some host (see
24100 section &<<SECTbatchSMTP>>&), a setting such as
24102 directory = /var/bsmtp/$host
24104 might be used. A message is written to a file with a temporary name, which is
24105 then renamed when the delivery is complete. The final name is obtained by
24106 expanding the contents of the &%directory_file%& option.
24107 .ecindex IIDapptra1
24108 .ecindex IIDapptra2
24115 . ////////////////////////////////////////////////////////////////////////////
24116 . ////////////////////////////////////////////////////////////////////////////
24118 .chapter "The autoreply transport" "CHID8"
24119 .scindex IIDauttra1 "transports" "&(autoreply)&"
24120 .scindex IIDauttra2 "&(autoreply)& transport"
24121 The &(autoreply)& transport is not a true transport in that it does not cause
24122 the message to be transmitted. Instead, it generates a new mail message as an
24123 automatic reply to the incoming message. &'References:'& and
24124 &'Auto-Submitted:'& header lines are included. These are constructed according
24125 to the rules in RFCs 2822 and 3834, respectively.
24127 If the router that passes the message to this transport does not have the
24128 &%unseen%& option set, the original message (for the current recipient) is not
24129 delivered anywhere. However, when the &%unseen%& option is set on the router
24130 that passes the message to this transport, routing of the address continues, so
24131 another router can set up a normal message delivery.
24134 The &(autoreply)& transport is usually run as the result of mail filtering, a
24135 &"vacation"& message being the standard example. However, it can also be run
24136 directly from a router like any other transport. To reduce the possibility of
24137 message cascades, messages created by the &(autoreply)& transport always have
24138 empty envelope sender addresses, like bounce messages.
24140 The parameters of the message to be sent can be specified in the configuration
24141 by options described below. However, these are used only when the address
24142 passed to the transport does not contain its own reply information. When the
24143 transport is run as a consequence of a
24145 or &%vacation%& command in a filter file, the parameters of the message are
24146 supplied by the filter, and passed with the address. The transport's options
24147 that define the message are then ignored (so they are not usually set in this
24148 case). The message is specified entirely by the filter or by the transport; it
24149 is never built from a mixture of options. However, the &%file_optional%&,
24150 &%mode%&, and &%return_message%& options apply in all cases.
24152 &(Autoreply)& is implemented as a local transport. When used as a result of a
24153 command in a user's filter file, &(autoreply)& normally runs under the uid and
24154 gid of the user, and with appropriate current and home directories (see chapter
24155 &<<CHAPenvironment>>&).
24157 There is a subtle difference between routing a message to a &(pipe)& transport
24158 that generates some text to be returned to the sender, and routing it to an
24159 &(autoreply)& transport. This difference is noticeable only if more than one
24160 address from the same message is so handled. In the case of a pipe, the
24161 separate outputs from the different addresses are gathered up and returned to
24162 the sender in a single message, whereas if &(autoreply)& is used, a separate
24163 message is generated for each address that is passed to it.
24165 Non-printing characters are not permitted in the header lines generated for the
24166 message that &(autoreply)& creates, with the exception of newlines that are
24167 immediately followed by white space. If any non-printing characters are found,
24168 the transport defers.
24169 Whether characters with the top bit set count as printing characters or not is
24170 controlled by the &%print_topbitchars%& global option.
24172 If any of the generic options for manipulating headers (for example,
24173 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24174 of the original message that is included in the generated message when
24175 &%return_message%& is set. They do not apply to the generated message itself.
24177 .vindex "&$sender_address$&"
24178 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24179 the message, indicating that there were no recipients, it does not treat this
24180 as an error. This means that autoreplies sent to &$sender_address$& when this
24181 is empty (because the incoming message is a bounce message) do not cause
24182 problems. They are just discarded.
24186 .section "Private options for autoreply" "SECID139"
24187 .cindex "options" "&(autoreply)& transport"
24189 .option bcc autoreply string&!! unset
24190 This specifies the addresses that are to receive &"blind carbon copies"& of the
24191 message when the message is specified by the transport.
24194 .option cc autoreply string&!! unset
24195 This specifies recipients of the message and the contents of the &'Cc:'& header
24196 when the message is specified by the transport.
24199 .option file autoreply string&!! unset
24200 The contents of the file are sent as the body of the message when the message
24201 is specified by the transport. If both &%file%& and &%text%& are set, the text
24202 string comes first.
24205 .option file_expand autoreply boolean false
24206 If this is set, the contents of the file named by the &%file%& option are
24207 subjected to string expansion as they are added to the message.
24210 .option file_optional autoreply boolean false
24211 If this option is true, no error is generated if the file named by the &%file%&
24212 option or passed with the address does not exist or cannot be read.
24215 .option from autoreply string&!! unset
24216 This specifies the contents of the &'From:'& header when the message is
24217 specified by the transport.
24220 .option headers autoreply string&!! unset
24221 This specifies additional RFC 2822 headers that are to be added to the message
24222 when the message is specified by the transport. Several can be given by using
24223 &"\n"& to separate them. There is no check on the format.
24226 .option log autoreply string&!! unset
24227 This option names a file in which a record of every message sent is logged when
24228 the message is specified by the transport.
24231 .option mode autoreply "octal integer" 0600
24232 If either the log file or the &"once"& file has to be created, this mode is
24236 .option never_mail autoreply "address list&!!" unset
24237 If any run of the transport creates a message with a recipient that matches any
24238 item in the list, that recipient is quietly discarded. If all recipients are
24239 discarded, no message is created. This applies both when the recipients are
24240 generated by a filter and when they are specified in the transport.
24244 .option once autoreply string&!! unset
24245 This option names a file or DBM database in which a record of each &'To:'&
24246 recipient is kept when the message is specified by the transport. &*Note*&:
24247 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24249 If &%once%& is unset, or is set to an empty string, the message is always sent.
24250 By default, if &%once%& is set to a non-empty filename, the message
24251 is not sent if a potential recipient is already listed in the database.
24252 However, if the &%once_repeat%& option specifies a time greater than zero, the
24253 message is sent if that much time has elapsed since a message was last sent to
24254 this recipient. A setting of zero time for &%once_repeat%& (the default)
24255 prevents a message from being sent a second time &-- in this case, zero means
24258 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24259 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24260 greater than zero, it changes the way Exim implements the &%once%& option.
24261 Instead of using a DBM file to record every recipient it sends to, it uses a
24262 regular file, whose size will never get larger than the given value.
24264 In the file, Exim keeps a linear list of recipient addresses and the times at
24265 which they were sent messages. If the file is full when a new address needs to
24266 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24267 means that a given recipient may receive multiple messages, but at
24268 unpredictable intervals that depend on the rate of turnover of addresses in the
24269 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24272 .option once_file_size autoreply integer 0
24273 See &%once%& above.
24276 .option once_repeat autoreply time&!! 0s
24277 See &%once%& above.
24278 After expansion, the value of this option must be a valid time value.
24281 .option reply_to autoreply string&!! unset
24282 This specifies the contents of the &'Reply-To:'& header when the message is
24283 specified by the transport.
24286 .option return_message autoreply boolean false
24287 If this is set, a copy of the original message is returned with the new
24288 message, subject to the maximum size set in the &%return_size_limit%& global
24289 configuration option.
24292 .option subject autoreply string&!! unset
24293 This specifies the contents of the &'Subject:'& header when the message is
24294 specified by the transport. It is tempting to quote the original subject in
24295 automatic responses. For example:
24297 subject = Re: $h_subject:
24299 There is a danger in doing this, however. It may allow a third party to
24300 subscribe your users to an opt-in mailing list, provided that the list accepts
24301 bounce messages as subscription confirmations. Well-managed lists require a
24302 non-bounce message to confirm a subscription, so the danger is relatively
24307 .option text autoreply string&!! unset
24308 This specifies a single string to be used as the body of the message when the
24309 message is specified by the transport. If both &%text%& and &%file%& are set,
24310 the text comes first.
24313 .option to autoreply string&!! unset
24314 This specifies recipients of the message and the contents of the &'To:'& header
24315 when the message is specified by the transport.
24316 .ecindex IIDauttra1
24317 .ecindex IIDauttra2
24322 . ////////////////////////////////////////////////////////////////////////////
24323 . ////////////////////////////////////////////////////////////////////////////
24325 .chapter "The lmtp transport" "CHAPLMTP"
24326 .cindex "transports" "&(lmtp)&"
24327 .cindex "&(lmtp)& transport"
24328 .cindex "LMTP" "over a pipe"
24329 .cindex "LMTP" "over a socket"
24330 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24332 or by interacting with a Unix domain socket.
24333 This transport is something of a cross between the &(pipe)& and &(smtp)&
24334 transports. Exim also has support for using LMTP over TCP/IP; this is
24335 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24336 to be of minority interest, the default build-time configure in &_src/EDITME_&
24337 has it commented out. You need to ensure that
24341 .cindex "options" "&(lmtp)& transport"
24342 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24343 included in the Exim binary. The private options of the &(lmtp)& transport are
24346 .option batch_id lmtp string&!! unset
24347 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24350 .option batch_max lmtp integer 1
24351 This limits the number of addresses that can be handled in a single delivery.
24352 Most LMTP servers can handle several addresses at once, so it is normally a
24353 good idea to increase this value. See the description of local delivery
24354 batching in chapter &<<CHAPbatching>>&.
24357 .option command lmtp string&!! unset
24358 This option must be set if &%socket%& is not set. The string is a command which
24359 is run in a separate process. It is split up into a command name and list of
24360 arguments, each of which is separately expanded (so expansion cannot change the
24361 number of arguments). The command is run directly, not via a shell. The message
24362 is passed to the new process using the standard input and output to operate the
24365 .option ignore_quota lmtp boolean false
24366 .cindex "LMTP" "ignoring quota errors"
24367 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24368 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24369 in its response to the LHLO command.
24371 .option socket lmtp string&!! unset
24372 This option must be set if &%command%& is not set. The result of expansion must
24373 be the name of a Unix domain socket. The transport connects to the socket and
24374 delivers the message to it using the LMTP protocol.
24377 .option timeout lmtp time 5m
24378 The transport is aborted if the created process or Unix domain socket does not
24379 respond to LMTP commands or message input within this timeout. Delivery
24380 is deferred, and will be tried again later. Here is an example of a typical
24385 command = /some/local/lmtp/delivery/program
24389 This delivers up to 20 addresses at a time, in a mixture of domains if
24390 necessary, running as the user &'exim'&.
24394 . ////////////////////////////////////////////////////////////////////////////
24395 . ////////////////////////////////////////////////////////////////////////////
24397 .chapter "The pipe transport" "CHAPpipetransport"
24398 .scindex IIDpiptra1 "transports" "&(pipe)&"
24399 .scindex IIDpiptra2 "&(pipe)& transport"
24400 The &(pipe)& transport is used to deliver messages via a pipe to a command
24401 running in another process. One example is the use of &(pipe)& as a
24402 pseudo-remote transport for passing messages to some other delivery mechanism
24403 (such as UUCP). Another is the use by individual users to automatically process
24404 their incoming messages. The &(pipe)& transport can be used in one of the
24408 .vindex "&$local_part$&"
24409 A router routes one address to a transport in the normal way, and the
24410 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24411 contains the local part of the address (as usual), and the command that is run
24412 is specified by the &%command%& option on the transport.
24414 .vindex "&$pipe_addresses$&"
24415 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24416 transport can handle more than one address in a single run. In this case, when
24417 more than one address is routed to the transport, &$local_part$& is not set
24418 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24419 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24420 that are routed to the transport.
24422 .vindex "&$address_pipe$&"
24423 A router redirects an address directly to a pipe command (for example, from an
24424 alias or forward file). In this case, &$address_pipe$& contains the text of the
24425 pipe command, and the &%command%& option on the transport is ignored unless
24426 &%force_command%& is set. If only one address is being transported
24427 (&%batch_max%& is not greater than one, or only one address was redirected to
24428 this pipe command), &$local_part$& contains the local part that was redirected.
24432 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24433 deliver messages over pipes using the LMTP interactive protocol. This is
24434 implemented by the &(lmtp)& transport.
24436 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24437 &_.forward_& file, the command runs under the uid and gid of that user. In
24438 other cases, the uid and gid have to be specified explicitly, either on the
24439 transport or on the router that handles the address. Current and &"home"&
24440 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24441 details of the local delivery environment and chapter &<<CHAPbatching>>&
24442 for a discussion of local delivery batching.
24444 .cindex "tainted data" "in pipe command"
24445 .cindex pipe "tainted data"
24446 Tainted data may not be used for the command name.
24449 .section "Concurrent delivery" "SECID140"
24450 If two messages arrive at almost the same time, and both are routed to a pipe
24451 delivery, the two pipe transports may be run concurrently. You must ensure that
24452 any pipe commands you set up are robust against this happening. If the commands
24453 write to a file, the &%exim_lock%& utility might be of use.
24454 Alternatively the &%max_parallel%& option could be used with a value
24455 of "1" to enforce serialization.
24460 .section "Returned status and data" "SECID141"
24461 .cindex "&(pipe)& transport" "returned data"
24462 If the command exits with a non-zero return code, the delivery is deemed to
24463 have failed, unless either the &%ignore_status%& option is set (in which case
24464 the return code is treated as zero), or the return code is one of those listed
24465 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24466 later"&. In this case, delivery is deferred. Details of a permanent failure are
24467 logged, but are not included in the bounce message, which merely contains
24468 &"local delivery failed"&.
24470 If the command exits on a signal and the &%freeze_signal%& option is set then
24471 the message will be frozen in the queue. If that option is not set, a bounce
24472 will be sent as normal.
24474 If the return code is greater than 128 and the command being run is a shell
24475 script, it normally means that the script was terminated by a signal whose
24476 value is the return code minus 128. The &%freeze_signal%& option does not
24477 apply in this case.
24479 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24480 return code is set to 127. This is the value that a shell returns if it is
24481 asked to run a non-existent command. The wording for the log line suggests that
24482 a non-existent command may be the problem.
24484 The &%return_output%& option can affect the result of a pipe delivery. If it is
24485 set and the command produces any output on its standard output or standard
24486 error streams, the command is considered to have failed, even if it gave a zero
24487 return code or if &%ignore_status%& is set. The output from the command is
24488 included as part of the bounce message. The &%return_fail_output%& option is
24489 similar, except that output is returned only when the command exits with a
24490 failure return code, that is, a value other than zero or a code that matches
24495 .section "How the command is run" "SECThowcommandrun"
24496 .cindex "&(pipe)& transport" "path for command"
24497 The command line is (by default) broken down into a command name and arguments
24498 by the &(pipe)& transport itself. The &%allow_commands%& and
24499 &%restrict_to_path%& options can be used to restrict the commands that may be
24502 .cindex "quoting" "in pipe command"
24503 Unquoted arguments are delimited by white space. If an argument appears in
24504 double quotes, backslash is interpreted as an escape character in the usual
24505 way. If an argument appears in single quotes, no escaping is done.
24507 String expansion is applied to the command line except when it comes from a
24508 traditional &_.forward_& file (commands from a filter file are expanded). The
24509 expansion is applied to each argument in turn rather than to the whole line.
24510 For this reason, any string expansion item that contains white space must be
24511 quoted so as to be contained within a single argument. A setting such as
24513 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24515 will not work, because the expansion item gets split between several
24516 arguments. You have to write
24518 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24520 to ensure that it is all in one argument. The expansion is done in this way,
24521 argument by argument, so that the number of arguments cannot be changed as a
24522 result of expansion, and quotes or backslashes in inserted variables do not
24523 interact with external quoting. However, this leads to problems if you want to
24524 generate multiple arguments (or the command name plus arguments) from a single
24525 expansion. In this situation, the simplest solution is to use a shell. For
24528 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24531 .cindex "transport" "filter"
24532 .cindex "filter" "transport filter"
24533 .vindex "&$pipe_addresses$&"
24534 Special handling takes place when an argument consists of precisely the text
24535 &`$pipe_addresses`& (no quotes).
24536 This is not a general expansion variable; the only
24537 place this string is recognized is when it appears as an argument for a pipe or
24538 transport filter command. It causes each address that is being handled to be
24539 inserted in the argument list at that point &'as a separate argument'&. This
24540 avoids any problems with spaces or shell metacharacters, and is of use when a
24541 &(pipe)& transport is handling groups of addresses in a batch.
24543 If &%force_command%& is enabled on the transport, special handling takes place
24544 for an argument that consists of precisely the text &`$address_pipe`&. It
24545 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24546 argument is inserted in the argument list at that point
24547 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24548 the only item in the argument; in fact, if it were then &%force_command%&
24549 should behave as a no-op. Rather, it should be used to adjust the command
24550 run while preserving the argument vector separation.
24552 After splitting up into arguments and expansion, the resulting command is run
24553 in a subprocess directly from the transport, &'not'& under a shell. The
24554 message that is being delivered is supplied on the standard input, and the
24555 standard output and standard error are both connected to a single pipe that is
24556 read by Exim. The &%max_output%& option controls how much output the command
24557 may produce, and the &%return_output%& and &%return_fail_output%& options
24558 control what is done with it.
24560 Not running the command under a shell (by default) lessens the security risks
24561 in cases when a command from a user's filter file is built out of data that was
24562 taken from an incoming message. If a shell is required, it can of course be
24563 explicitly specified as the command to be run. However, there are circumstances
24564 where existing commands (for example, in &_.forward_& files) expect to be run
24565 under a shell and cannot easily be modified. To allow for these cases, there is
24566 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24567 works. Instead of breaking up the command line as just described, it expands it
24568 as a single string and passes the result to &_/bin/sh_&. The
24569 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24570 with &%use_shell%&, and the whole mechanism is inherently less secure.
24574 .section "Environment variables" "SECTpipeenv"
24575 .cindex "&(pipe)& transport" "environment for command"
24576 .cindex "environment" "&(pipe)& transport"
24577 The environment variables listed below are set up when the command is invoked.
24578 This list is a compromise for maximum compatibility with other MTAs. Note that
24579 the &%environment%& option can be used to add additional variables to this
24580 environment. The environment for the &(pipe)& transport is not subject
24581 to the &%add_environment%& and &%keep_environment%& main config options.
24583 &`DOMAIN `& the domain of the address
24584 &`HOME `& the home directory, if set
24585 &`HOST `& the host name when called from a router (see below)
24586 &`LOCAL_PART `& see below
24587 &`LOCAL_PART_PREFIX `& see below
24588 &`LOCAL_PART_SUFFIX `& see below
24589 &`LOGNAME `& see below
24590 &`MESSAGE_ID `& Exim's local ID for the message
24591 &`PATH `& as specified by the &%path%& option below
24592 &`QUALIFY_DOMAIN `& the sender qualification domain
24593 &`RECIPIENT `& the complete recipient address
24594 &`SENDER `& the sender of the message (empty if a bounce)
24595 &`SHELL `& &`/bin/sh`&
24596 &`TZ `& the value of the &%timezone%& option, if set
24597 &`USER `& see below
24599 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24600 router, LOCAL_PART is set to the local part of the address. When it is
24601 called as a result of a forward or alias expansion, LOCAL_PART is set to
24602 the local part of the address that was expanded. In both cases, any affixes are
24603 removed from the local part, and made available in LOCAL_PART_PREFIX and
24604 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24605 same value as LOCAL_PART for compatibility with other MTAs.
24608 HOST is set only when a &(pipe)& transport is called from a router that
24609 associates hosts with an address, typically when using &(pipe)& as a
24610 pseudo-remote transport. HOST is set to the first host name specified by
24614 If the transport's generic &%home_directory%& option is set, its value is used
24615 for the HOME environment variable. Otherwise, a home directory may be set
24616 by the router's &%transport_home_directory%& option, which defaults to the
24617 user's home directory if &%check_local_user%& is set.
24620 .section "Private options for pipe" "SECID142"
24621 .cindex "options" "&(pipe)& transport"
24625 .option allow_commands pipe "string list&!!" unset
24626 .cindex "&(pipe)& transport" "permitted commands"
24627 The string is expanded, and is then interpreted as a colon-separated list of
24628 permitted commands. If &%restrict_to_path%& is not set, the only commands
24629 permitted are those in the &%allow_commands%& list. They need not be absolute
24630 paths; the &%path%& option is still used for relative paths. If
24631 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24632 in the &%allow_commands%& list, or a name without any slashes that is found on
24633 the path. In other words, if neither &%allow_commands%& nor
24634 &%restrict_to_path%& is set, there is no restriction on the command, but
24635 otherwise only commands that are permitted by one or the other are allowed. For
24638 allow_commands = /usr/bin/vacation
24640 and &%restrict_to_path%& is not set, the only permitted command is
24641 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24642 &%use_shell%& is set.
24645 .option batch_id pipe string&!! unset
24646 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24649 .option batch_max pipe integer 1
24650 This limits the number of addresses that can be handled in a single delivery.
24651 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24654 .option check_string pipe string unset
24655 As &(pipe)& writes the message, the start of each line is tested for matching
24656 &%check_string%&, and if it does, the initial matching characters are replaced
24657 by the contents of &%escape_string%&, provided both are set. The value of
24658 &%check_string%& is a literal string, not a regular expression, and the case of
24659 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24660 of &%check_string%& and &%escape_string%& are forced to values that implement
24661 the SMTP escaping protocol. Any settings made in the configuration file are
24665 .option command pipe string&!! unset
24666 This option need not be set when &(pipe)& is being used to deliver to pipes
24667 obtained directly from address redirections. In other cases, the option must be
24668 set, to provide a command to be run. It need not yield an absolute path (see
24669 the &%path%& option below). The command is split up into separate arguments by
24670 Exim, and each argument is separately expanded, as described in section
24671 &<<SECThowcommandrun>>& above.
24674 .option environment pipe string&!! unset
24675 .cindex "&(pipe)& transport" "environment for command"
24676 .cindex "environment" "&(pipe)& transport"
24677 This option is used to add additional variables to the environment in which the
24678 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24679 a string which is expanded, and then interpreted as a colon-separated list of
24680 environment settings of the form <&'name'&>=<&'value'&>.
24683 .option escape_string pipe string unset
24684 See &%check_string%& above.
24687 .option freeze_exec_fail pipe boolean false
24688 .cindex "exec failure"
24689 .cindex "failure of exec"
24690 .cindex "&(pipe)& transport" "failure of exec"
24691 Failure to exec the command in a pipe transport is by default treated like
24692 any other failure while running the command. However, if &%freeze_exec_fail%&
24693 is set, failure to exec is treated specially, and causes the message to be
24694 frozen, whatever the setting of &%ignore_status%&.
24697 .option freeze_signal pipe boolean false
24698 .cindex "signal exit"
24699 .cindex "&(pipe)& transport", "signal exit"
24700 Normally if the process run by a command in a pipe transport exits on a signal,
24701 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24702 frozen in Exim's queue instead.
24705 .option force_command pipe boolean false
24706 .cindex "force command"
24707 .cindex "&(pipe)& transport", "force command"
24708 Normally when a router redirects an address directly to a pipe command
24709 the &%command%& option on the transport is ignored. If &%force_command%&
24710 is set, the &%command%& option will used. This is especially
24711 useful for forcing a wrapper or additional argument to be added to the
24712 command. For example:
24714 command = /usr/bin/remote_exec myhost -- $address_pipe
24718 Note that &$address_pipe$& is handled specially in &%command%& when
24719 &%force_command%& is set, expanding out to the original argument vector as
24720 separate items, similarly to a Unix shell &`"$@"`& construct.
24723 .option ignore_status pipe boolean false
24724 If this option is true, the status returned by the subprocess that is set up to
24725 run the command is ignored, and Exim behaves as if zero had been returned.
24726 Otherwise, a non-zero status or termination by signal causes an error return
24727 from the transport unless the status value is one of those listed in
24728 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24730 &*Note*&: This option does not apply to timeouts, which do not return a status.
24731 See the &%timeout_defer%& option for how timeouts are handled.
24734 .option log_defer_output pipe boolean false
24735 .cindex "&(pipe)& transport" "logging output"
24736 If this option is set, and the status returned by the command is
24737 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24738 and any output was produced on stdout or stderr, the first line of it is
24739 written to the main log.
24742 .option log_fail_output pipe boolean false
24743 If this option is set, and the command returns any output on stdout or
24744 stderr, and also ends with a return code that is neither zero nor one of
24745 the return codes listed in &%temp_errors%& (that is, the delivery
24746 failed), the first line of output is written to the main log. This
24747 option and &%log_output%& are mutually exclusive. Only one of them may
24751 .option log_output pipe boolean false
24752 If this option is set and the command returns any output on stdout or
24753 stderr, the first line of output is written to the main log, whatever
24754 the return code. This option and &%log_fail_output%& are mutually
24755 exclusive. Only one of them may be set.
24758 .option max_output pipe integer 20K
24759 This specifies the maximum amount of output that the command may produce on its
24760 standard output and standard error file combined. If the limit is exceeded, the
24761 process running the command is killed. This is intended as a safety measure to
24762 catch runaway processes. The limit is applied independently of the settings of
24763 the options that control what is done with such output (for example,
24764 &%return_output%&). Because of buffering effects, the amount of output may
24765 exceed the limit by a small amount before Exim notices.
24768 .option message_prefix pipe string&!! "see below"
24769 The string specified here is expanded and output at the start of every message.
24770 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24773 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24777 .cindex "&%tmail%&"
24778 .cindex "&""From""& line"
24779 This is required by the commonly used &_/usr/bin/vacation_& program.
24780 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24781 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24786 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24787 &`\n`& to &`\r\n`& in &%message_prefix%&.
24790 .option message_suffix pipe string&!! "see below"
24791 The string specified here is expanded and output at the end of every message.
24792 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24793 The suffix can be suppressed by setting
24797 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24798 &`\n`& to &`\r\n`& in &%message_suffix%&.
24801 .option path pipe string&!! "/bin:/usr/bin"
24802 This option is expanded and
24803 specifies the string that is set up in the PATH environment
24804 variable of the subprocess.
24805 If the &%command%& option does not yield an absolute path name, the command is
24806 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24807 apply to a command specified as a transport filter.
24810 .option permit_coredump pipe boolean false
24811 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24812 a core-dump of a pipe command, enable this command. This enables core-dumps
24813 during delivery and affects both the Exim binary and the pipe command run.
24814 It is recommended that this option remain off unless and until you have a need
24815 for it and that this only be enabled when needed, as the risk of excessive
24816 resource consumption can be quite high. Note also that Exim is typically
24817 installed as a setuid binary and most operating systems will inhibit coredumps
24818 of these by default, so further OS-specific action may be required.
24821 .option pipe_as_creator pipe boolean false
24822 .cindex "uid (user id)" "local delivery"
24823 If the generic &%user%& option is not set and this option is true, the delivery
24824 process is run under the uid that was in force when Exim was originally called
24825 to accept the message. If the group id is not otherwise set (via the generic
24826 &%group%& option), the gid that was in force when Exim was originally called to
24827 accept the message is used.
24830 .option restrict_to_path pipe boolean false
24831 When this option is set, any command name not listed in &%allow_commands%& must
24832 contain no slashes. The command is searched for only in the directories listed
24833 in the &%path%& option. This option is intended for use in the case when a pipe
24834 command has been generated from a user's &_.forward_& file. This is usually
24835 handled by a &(pipe)& transport called &%address_pipe%&.
24838 .option return_fail_output pipe boolean false
24839 If this option is true, and the command produced any output and ended with a
24840 return code other than zero or one of the codes listed in &%temp_errors%& (that
24841 is, the delivery failed), the output is returned in the bounce message.
24842 However, if the message has a null sender (that is, it is itself a bounce
24843 message), output from the command is discarded. This option and
24844 &%return_output%& are mutually exclusive. Only one of them may be set.
24848 .option return_output pipe boolean false
24849 If this option is true, and the command produced any output, the delivery is
24850 deemed to have failed whatever the return code from the command, and the output
24851 is returned in the bounce message. Otherwise, the output is just discarded.
24852 However, if the message has a null sender (that is, it is a bounce message),
24853 output from the command is always discarded, whatever the setting of this
24854 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24855 of them may be set.
24859 .option temp_errors pipe "string list" "see below"
24860 .cindex "&(pipe)& transport" "temporary failure"
24861 This option contains either a colon-separated list of numbers, or a single
24862 asterisk. If &%ignore_status%& is false
24863 and &%return_output%& is not set,
24864 and the command exits with a non-zero return code, the failure is treated as
24865 temporary and the delivery is deferred if the return code matches one of the
24866 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24867 codes are treated as permanent errors. The default setting contains the codes
24868 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24869 compiled on a system that does not define these macros, it assumes values of 75
24870 and 73, respectively.
24873 .option timeout pipe time 1h
24874 If the command fails to complete within this time, it is killed. This normally
24875 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24876 specifies no timeout. In order to ensure that any subprocesses created by the
24877 command are also killed, Exim makes the initial process a process group leader,
24878 and kills the whole process group on a timeout. However, this can be defeated
24879 if one of the processes starts a new process group.
24881 .option timeout_defer pipe boolean false
24882 A timeout in a &(pipe)& transport, either in the command that the transport
24883 runs, or in a transport filter that is associated with it, is by default
24884 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24885 is set true, both kinds of timeout become temporary errors, causing the
24886 delivery to be deferred.
24888 .option umask pipe "octal integer" 022
24889 This specifies the umask setting for the subprocess that runs the command.
24892 .option use_bsmtp pipe boolean false
24893 .cindex "envelope sender"
24894 If this option is set true, the &(pipe)& transport writes messages in &"batch
24895 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24896 commands. If you want to include a leading HELO command with such messages,
24897 you can do so by setting the &%message_prefix%& option. See section
24898 &<<SECTbatchSMTP>>& for details of batch SMTP.
24900 .option use_classresources pipe boolean false
24901 .cindex "class resources (BSD)"
24902 This option is available only when Exim is running on FreeBSD, NetBSD, or
24903 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
24904 resource limits when a &(pipe)& transport is run to perform a delivery. The
24905 limits for the uid under which the pipe is to run are obtained from the login
24909 .option use_crlf pipe boolean false
24910 .cindex "carriage return"
24912 This option causes lines to be terminated with the two-character CRLF sequence
24913 (carriage return, linefeed) instead of just a linefeed character. In the case
24914 of batched SMTP, the byte sequence written to the pipe is then an exact image
24915 of what would be sent down a real SMTP connection.
24917 The contents of the &%message_prefix%& and &%message_suffix%& options are
24918 written verbatim, so must contain their own carriage return characters if these
24919 are needed. When &%use_bsmtp%& is not set, the default values for both
24920 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
24921 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
24924 .option use_shell pipe boolean false
24925 .vindex "&$pipe_addresses$&"
24926 If this option is set, it causes the command to be passed to &_/bin/sh_&
24927 instead of being run directly from the transport, as described in section
24928 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
24929 where the command is expected to be run under a shell and cannot easily be
24930 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
24931 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
24932 command is expanded as a single string, and handed to &_/bin/sh_& as data for
24937 .section "Using an external local delivery agent" "SECID143"
24938 .cindex "local delivery" "using an external agent"
24939 .cindex "&'procmail'&"
24940 .cindex "external local delivery"
24941 .cindex "delivery" "&'procmail'&"
24942 .cindex "delivery" "by external agent"
24943 The &(pipe)& transport can be used to pass all messages that require local
24944 delivery to a separate local delivery agent such as &%procmail%&. When doing
24945 this, care must be taken to ensure that the pipe is run under an appropriate
24946 uid and gid. In some configurations one wants this to be a uid that is trusted
24947 by the delivery agent to supply the correct sender of the message. It may be
24948 necessary to recompile or reconfigure the delivery agent so that it trusts an
24949 appropriate user. The following is an example transport and router
24950 configuration for &%procmail%&:
24955 command = /usr/local/bin/procmail -d $local_part_data
24959 check_string = "From "
24960 escape_string = ">From "
24962 user = $local_part_data
24969 transport = procmail_pipe
24971 In this example, the pipe is run as the local user, but with the group set to
24972 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
24973 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
24974 user to supply a correct sender address. If you do not specify either a
24975 &%group%& or a &%user%& option, the pipe command is run as the local user. The
24976 home directory is the user's home directory by default.
24978 &*Note*&: The command that the pipe transport runs does &'not'& begin with
24982 as shown in some &%procmail%& documentation, because Exim does not by default
24983 use a shell to run pipe commands.
24986 The next example shows a transport and a router for a system where local
24987 deliveries are handled by the Cyrus IMAP server.
24990 local_delivery_cyrus:
24992 command = /usr/cyrus/bin/deliver \
24993 -m ${substr_1:$local_part_suffix} -- $local_part
25005 local_part_suffix = .*
25006 transport = local_delivery_cyrus
25008 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25009 &%return_output%& to cause any text written by Cyrus to be returned to the
25011 .ecindex IIDpiptra1
25012 .ecindex IIDpiptra2
25015 . ////////////////////////////////////////////////////////////////////////////
25016 . ////////////////////////////////////////////////////////////////////////////
25018 .chapter "The smtp transport" "CHAPsmtptrans"
25019 .scindex IIDsmttra1 "transports" "&(smtp)&"
25020 .scindex IIDsmttra2 "&(smtp)& transport"
25021 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25022 or LMTP protocol. The list of hosts to try can either be taken from the address
25023 that is being processed (having been set up by the router), or specified
25024 explicitly for the transport. Timeout and retry processing (see chapter
25025 &<<CHAPretry>>&) is applied to each IP address independently.
25028 .section "Multiple messages on a single connection" "SECID144"
25029 The sending of multiple messages over a single TCP/IP connection can arise in
25033 If a message contains more than &%max_rcpt%& (see below) addresses that are
25034 routed to the same host, more than one copy of the message has to be sent to
25035 that host. In this situation, multiple copies may be sent in a single run of
25036 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25037 does when it has too many addresses to send in one message also depends on the
25038 value of the global &%remote_max_parallel%& option. Details are given in
25039 section &<<SECToutSMTPTCP>>&.)
25041 .cindex "hints database" "remembering routing"
25042 When a message has been successfully delivered over a TCP/IP connection, Exim
25043 looks in its hints database to see if there are any other messages awaiting a
25044 connection to the same host. If there are, a new delivery process is started
25045 for one of them, and the current TCP/IP connection is passed on to it. The new
25046 process may in turn send multiple copies and possibly create yet another
25051 For each copy sent over the same TCP/IP connection, a sequence counter is
25052 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25053 no further messages are sent over that connection.
25057 .section "Use of the $host and $host_address variables" "SECID145"
25059 .vindex "&$host_address$&"
25060 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25061 &$host_address$& are the name and IP address of the first host on the host list
25062 passed by the router. However, when the transport is about to connect to a
25063 specific host, and while it is connected to that host, &$host$& and
25064 &$host_address$& are set to the values for that host. These are the values
25065 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25066 &%serialize_hosts%&, and the various TLS options are expanded.
25069 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25070 .vindex &$tls_bits$&
25071 .vindex &$tls_cipher$&
25072 .vindex &$tls_peerdn$&
25073 .vindex &$tls_sni$&
25074 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25075 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25076 are the values that were set when the message was received.
25077 These are the values that are used for options that are expanded before any
25078 SMTP connections are made. Just before each connection is made, these four
25079 variables are emptied. If TLS is subsequently started, they are set to the
25080 appropriate values for the outgoing connection, and these are the values that
25081 are in force when any authenticators are run and when the
25082 &%authenticated_sender%& option is expanded.
25084 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25085 and will be removed in a future release.
25088 .section "Private options for smtp" "SECID146"
25089 .cindex "options" "&(smtp)& transport"
25090 The private options of the &(smtp)& transport are as follows:
25093 .option address_retry_include_sender smtp boolean true
25094 .cindex "4&'xx'& responses" "retrying after"
25095 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25096 is the combination of sender and recipient that is delayed in subsequent queue
25097 runs until the retry time is reached. You can delay the recipient without
25098 reference to the sender (which is what earlier versions of Exim did), by
25099 setting &%address_retry_include_sender%& false. However, this can lead to
25100 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25102 .option allow_localhost smtp boolean false
25103 .cindex "local host" "sending to"
25104 .cindex "fallback" "hosts specified on transport"
25105 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25106 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25107 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25108 the delivery anyway. This should be used only in special cases when the
25109 configuration ensures that no looping will result (for example, a differently
25110 configured Exim is listening on the port to which the message is sent).
25113 .option authenticated_sender smtp string&!! unset
25115 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25116 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25117 overriding any existing authenticated sender value. If the string expansion is
25118 forced to fail, the option is ignored. Other expansion failures cause delivery
25119 to be deferred. If the result of expansion is an empty string, that is also
25122 The expansion happens after the outgoing connection has been made and TLS
25123 started, if required. This means that the &$host$&, &$host_address$&,
25124 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25125 particular connection.
25127 If the SMTP session is not authenticated, the expansion of
25128 &%authenticated_sender%& still happens (and can cause the delivery to be
25129 deferred if it fails), but no AUTH= item is added to MAIL commands
25130 unless &%authenticated_sender_force%& is true.
25132 This option allows you to use the &(smtp)& transport in LMTP mode to
25133 deliver mail to Cyrus IMAP and provide the proper local part as the
25134 &"authenticated sender"&, via a setting such as:
25136 authenticated_sender = $local_part
25138 This removes the need for IMAP subfolders to be assigned special ACLs to
25139 allow direct delivery to those subfolders.
25141 Because of expected uses such as that just described for Cyrus (when no
25142 domain is involved), there is no checking on the syntax of the provided
25146 .option authenticated_sender_force smtp boolean false
25147 If this option is set true, the &%authenticated_sender%& option's value
25148 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25149 authenticated as a client.
25152 .option command_timeout smtp time 5m
25153 .cindex timeout "smtp transport command"
25154 This sets a timeout for receiving a response to an SMTP command that has been
25155 sent out. It is also used when waiting for the initial banner line from the
25156 remote host. Its value must not be zero.
25159 .option connect_timeout smtp time 5m
25160 .cindex timeout "smtp transport connect"
25161 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25162 to a remote host. A setting of zero allows the system timeout (typically
25163 several minutes) to act. To have any effect, the value of this option must be
25164 less than the system timeout. However, it has been observed that on some
25165 systems there is no system timeout, which is why the default value for this
25166 option is 5 minutes, a value recommended by RFC 1123.
25169 .option connection_max_messages smtp integer 500
25170 .cindex "SMTP" "passed connection"
25171 .cindex "SMTP" "multiple deliveries"
25172 .cindex "multiple SMTP deliveries"
25173 This controls the maximum number of separate message deliveries that are sent
25174 over a single TCP/IP connection. If the value is zero, there is no limit.
25175 For testing purposes, this value can be overridden by the &%-oB%& command line
25179 .option dane_require_tls_ciphers smtp string&!! unset
25180 .cindex "TLS" "requiring specific ciphers for DANE"
25181 .cindex "cipher" "requiring specific"
25182 .cindex DANE "TLS ciphers"
25183 This option may be used to override &%tls_require_ciphers%& for connections
25184 where DANE has been determined to be in effect.
25185 If not set, then &%tls_require_ciphers%& will be used.
25186 Normal SMTP delivery is not able to make strong demands of TLS cipher
25187 configuration, because delivery will fall back to plaintext. Once DANE has
25188 been determined to be in effect, there is no plaintext fallback and making the
25189 TLS cipherlist configuration stronger will increase security, rather than
25190 counter-intuitively decreasing it.
25191 If the option expands to be empty or is forced to fail, then it will
25192 be treated as unset and &%tls_require_ciphers%& will be used instead.
25195 .option data_timeout smtp time 5m
25196 .cindex timeout "for transmitted SMTP data blocks"
25197 This sets a timeout for the transmission of each block in the data portion of
25198 the message. As a result, the overall timeout for a message depends on the size
25199 of the message. Its value must not be zero. See also &%final_timeout%&.
25202 .option dkim_canon smtp string&!! unset
25203 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25204 .option dkim_domain smtp string list&!! unset
25205 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25206 .option dkim_hash smtp string&!! sha256
25207 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25208 .option dkim_identity smtp string&!! unset
25209 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25210 .option dkim_private_key smtp string&!! unset
25211 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25212 .option dkim_selector smtp string&!! unset
25213 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25214 .option dkim_strict smtp string&!! unset
25215 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25216 .option dkim_sign_headers smtp string&!! "per RFC"
25217 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25218 .option dkim_timestamps smtp string&!! unset
25219 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25222 .option delay_after_cutoff smtp boolean true
25223 .cindex "final cutoff" "retries, controlling"
25224 .cindex retry "final cutoff"
25225 This option controls what happens when all remote IP addresses for a given
25226 domain have been inaccessible for so long that they have passed their retry
25229 In the default state, if the next retry time has not been reached for any of
25230 them, the address is bounced without trying any deliveries. In other words,
25231 Exim delays retrying an IP address after the final cutoff time until a new
25232 retry time is reached, and can therefore bounce an address without ever trying
25233 a delivery, when machines have been down for a long time. Some people are
25234 unhappy at this prospect, so...
25236 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25237 addresses are past their final cutoff time, Exim tries to deliver to those
25238 IP addresses that have not been tried since the message arrived. If there are
25239 none, of if they all fail, the address is bounced. In other words, it does not
25240 delay when a new message arrives, but immediately tries those expired IP
25241 addresses that haven't been tried since the message arrived. If there is a
25242 continuous stream of messages for the dead hosts, unsetting
25243 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25247 .option dns_qualify_single smtp boolean true
25248 If the &%hosts%& or &%fallback_hosts%& option is being used,
25249 and the &%gethostbyname%& option is false,
25250 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25251 in chapter &<<CHAPdnslookup>>& for more details.
25254 .option dns_search_parents smtp boolean false
25255 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25256 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25257 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25261 .option dnssec_request_domains smtp "domain list&!!" *
25262 .cindex "MX record" "security"
25263 .cindex "DNSSEC" "MX lookup"
25264 .cindex "security" "MX lookup"
25265 .cindex "DNS" "DNSSEC"
25266 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25267 the DNSSEC request bit set. Setting this transport option is only useful if the
25268 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25273 .option dnssec_require_domains smtp "domain list&!!" unset
25274 .cindex "MX record" "security"
25275 .cindex "DNSSEC" "MX lookup"
25276 .cindex "security" "MX lookup"
25277 .cindex "DNS" "DNSSEC"
25278 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25279 the DNSSEC request bit set. Setting this transport option is only
25280 useful if the transport overrides or sets the host names. See the
25281 &%dnssec_require_domains%& router option.
25285 .option dscp smtp string&!! unset
25286 .cindex "DCSP" "outbound"
25287 This option causes the DSCP value associated with a socket to be set to one
25288 of a number of fixed strings or to numeric value.
25289 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25290 Common values include &`throughput`&, &`mincost`&, and on newer systems
25291 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25293 The outbound packets from Exim will be marked with this value in the header
25294 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25295 that these values will have any effect, not be stripped by networking
25296 equipment, or do much of anything without cooperation with your Network
25297 Engineer and those of all network operators between the source and destination.
25300 .option fallback_hosts smtp "string list" unset
25301 .cindex "fallback" "hosts specified on transport"
25302 String expansion is not applied to this option. The argument must be a
25303 colon-separated list of host names or IP addresses, optionally also including
25304 port numbers, though the separator can be changed, as described in section
25305 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25306 item in a &%route_list%& setting for the &(manualroute)& router, as described
25307 in section &<<SECTformatonehostitem>>&.
25309 Fallback hosts can also be specified on routers, which associate them with the
25310 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25311 &%fallback_hosts%& specified on the transport is used only if the address does
25312 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25313 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25314 However, &%hosts_randomize%& does apply to fallback host lists.
25316 If Exim is unable to deliver to any of the hosts for a particular address, and
25317 the errors are not permanent rejections, the address is put on a separate
25318 transport queue with its host list replaced by the fallback hosts, unless the
25319 address was routed via MX records and the current host was in the original MX
25320 list. In that situation, the fallback host list is not used.
25322 Once normal deliveries are complete, the fallback queue is delivered by
25323 re-running the same transports with the new host lists. If several failing
25324 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25325 copy of the message is sent.
25327 The resolution of the host names on the fallback list is controlled by the
25328 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25329 both to cases when the host list comes with the address and when it is taken
25330 from &%hosts%&. This option provides a &"use a smart host only if delivery
25334 .option final_timeout smtp time 10m
25335 .cindex timeout "for transmitted SMTP data accept"
25336 This is the timeout that applies while waiting for the response to the final
25337 line containing just &"."& that terminates a message. Its value must not be
25340 .option gethostbyname smtp boolean false
25341 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25342 being used, names are looked up using &[gethostbyname()]&
25343 (or &[getipnodebyname()]& when available)
25344 instead of using the DNS. Of course, that function may in fact use the DNS, but
25345 it may also consult other sources of information such as &_/etc/hosts_&.
25347 .option gnutls_compat_mode smtp boolean unset
25348 This option controls whether GnuTLS is used in compatibility mode in an Exim
25349 server. This reduces security slightly, but improves interworking with older
25350 implementations of TLS.
25352 .option helo_data smtp string&!! "see below"
25353 .cindex "HELO" "argument, setting"
25354 .cindex "EHLO" "argument, setting"
25355 .cindex "LHLO argument setting"
25356 The value of this option is expanded after a connection to a another host has
25357 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25358 command that starts the outgoing SMTP or LMTP session. The default value of the
25363 During the expansion, the variables &$host$& and &$host_address$& are set to
25364 the identity of the remote host, and the variables &$sending_ip_address$& and
25365 &$sending_port$& are set to the local IP address and port number that are being
25366 used. These variables can be used to generate different values for different
25367 servers or different local IP addresses. For example, if you want the string
25368 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25369 interface address, you could use this:
25371 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25372 {$primary_hostname}}
25374 The use of &%helo_data%& applies both to sending messages and when doing
25377 .option hosts smtp "string list&!!" unset
25378 Hosts are associated with an address by a router such as &(dnslookup)&, which
25379 finds the hosts by looking up the address domain in the DNS, or by
25380 &(manualroute)&, which has lists of hosts in its configuration. However,
25381 email addresses can be passed to the &(smtp)& transport by any router, and not
25382 all of them can provide an associated list of hosts.
25384 The &%hosts%& option specifies a list of hosts to be used if the address being
25385 processed does not have any hosts associated with it. The hosts specified by
25386 &%hosts%& are also used, whether or not the address has its own hosts, if
25387 &%hosts_override%& is set.
25389 The string is first expanded, before being interpreted as a colon-separated
25390 list of host names or IP addresses, possibly including port numbers. The
25391 separator may be changed to something other than colon, as described in section
25392 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25393 item in a &%route_list%& setting for the &(manualroute)& router, as described
25394 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25395 of the &(manualroute)& router is not available here.
25397 If the expansion fails, delivery is deferred. Unless the failure was caused by
25398 the inability to complete a lookup, the error is logged to the panic log as
25399 well as the main log. Host names are looked up either by searching directly for
25400 address records in the DNS or by calling &[gethostbyname()]& (or
25401 &[getipnodebyname()]& when available), depending on the setting of the
25402 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25403 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25406 During delivery, the hosts are tried in order, subject to their retry status,
25407 unless &%hosts_randomize%& is set.
25410 .option hosts_avoid_esmtp smtp "host list&!!" unset
25411 .cindex "ESMTP, avoiding use of"
25412 .cindex "HELO" "forcing use of"
25413 .cindex "EHLO" "avoiding use of"
25414 .cindex "PIPELINING" "avoiding the use of"
25415 This option is for use with broken hosts that announce ESMTP facilities (for
25416 example, PIPELINING) and then fail to implement them properly. When a host
25417 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25418 start of the SMTP session. This means that it cannot use any of the ESMTP
25419 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25422 .option hosts_avoid_pipelining smtp "host list&!!" unset
25423 .cindex "PIPELINING" "avoiding the use of"
25424 .cindex "ESMTP extensions" PIPELINING
25425 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25426 that matches this list, even if the server host advertises PIPELINING support.
25428 .option hosts_pipe_connect smtp "host list&!!" unset
25429 .cindex "pipelining" "early connection"
25430 .cindex "pipelining" PIPE_CONNECT
25431 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25432 this option controls which to hosts the facility watched for
25433 and recorded, and used for subsequent connections.
25435 The retry hints database is used for the record,
25436 and records are subject to the &%retry_data_expire%& option.
25437 When used, the pipelining saves on roundtrip times.
25438 It also turns SMTP into a client-first protocol
25439 so combines well with TCP Fast Open.
25441 See also the &%pipelining_connect_advertise_hosts%& main option.
25444 When the facility is used, the transport &%helo_data%& option
25445 will be expanded before the &$sending_ip_address$& variable
25447 A check is made for the use of that variable, without the
25448 presence of a &"def:"& test on it, but suitably complex coding
25449 can avoid the check and produce unexpected results.
25450 You have been warned.
25453 .option hosts_avoid_tls smtp "host list&!!" unset
25454 .cindex "TLS" "avoiding for certain hosts"
25455 Exim will not try to start a TLS session when delivering to any host that
25456 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25458 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25459 .cindex "TLS" "avoiding for certain hosts"
25460 Exim will not try to start a TLS session for a verify callout,
25461 or when delivering in cutthrough mode,
25462 to any host that matches this list.
25465 .option hosts_max_try smtp integer 5
25466 .cindex "host" "maximum number to try"
25467 .cindex "limit" "number of hosts tried"
25468 .cindex "limit" "number of MX tried"
25469 .cindex "MX record" "maximum tried"
25470 This option limits the number of IP addresses that are tried for any one
25471 delivery in cases where there are temporary delivery errors. Section
25472 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25475 .option hosts_max_try_hardlimit smtp integer 50
25476 This is an additional check on the maximum number of IP addresses that Exim
25477 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25482 .option hosts_nopass_tls smtp "host list&!!" unset
25483 .cindex "TLS" "passing connection"
25484 .cindex "multiple SMTP deliveries"
25485 .cindex "TLS" "multiple message deliveries"
25486 For any host that matches this list, a connection on which a TLS session has
25487 been started will not be passed to a new delivery process for sending another
25488 message on the same connection. See section &<<SECTmulmessam>>& for an
25489 explanation of when this might be needed.
25491 .option hosts_noproxy_tls smtp "host list&!!" unset
25492 .cindex "TLS" "passing connection"
25493 .cindex "multiple SMTP deliveries"
25494 .cindex "TLS" "multiple message deliveries"
25495 For any host that matches this list, a TLS session which has
25496 been started will not be passed to a new delivery process for sending another
25497 message on the same session.
25499 The traditional implementation closes down TLS and re-starts it in the new
25500 process, on the same open TCP connection, for each successive message
25501 sent. If permitted by this option a pipe to to the new process is set up
25502 instead, and the original process maintains the TLS connection and proxies
25503 the SMTP connection from and to the new process and any subsequents.
25504 The new process has no access to TLS information, so cannot include it in
25509 .option hosts_override smtp boolean false
25510 If this option is set and the &%hosts%& option is also set, any hosts that are
25511 attached to the address are ignored, and instead the hosts specified by the
25512 &%hosts%& option are always used. This option does not apply to
25513 &%fallback_hosts%&.
25516 .option hosts_randomize smtp boolean false
25517 .cindex "randomized host list"
25518 .cindex "host" "list of; randomized"
25519 .cindex "fallback" "randomized hosts"
25520 If this option is set, and either the list of hosts is taken from the
25521 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25522 were not obtained from MX records (this includes fallback hosts from the
25523 router), and were not randomized by the router, the order of trying the hosts
25524 is randomized each time the transport runs. Randomizing the order of a host
25525 list can be used to do crude load sharing.
25527 When &%hosts_randomize%& is true, a host list may be split into groups whose
25528 order is separately randomized. This makes it possible to set up MX-like
25529 behaviour. The boundaries between groups are indicated by an item that is just
25530 &`+`& in the host list. For example:
25532 hosts = host1:host2:host3:+:host4:host5
25534 The order of the first three hosts and the order of the last two hosts is
25535 randomized for each use, but the first three always end up before the last two.
25536 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25538 .option hosts_require_auth smtp "host list&!!" unset
25539 .cindex "authentication" "required by client"
25540 This option provides a list of servers for which authentication must succeed
25541 before Exim will try to transfer a message. If authentication fails for
25542 servers which are not in this list, Exim tries to send unauthenticated. If
25543 authentication fails for one of these servers, delivery is deferred. This
25544 temporary error is detectable in the retry rules, so it can be turned into a
25545 hard failure if required. See also &%hosts_try_auth%&, and chapter
25546 &<<CHAPSMTPAUTH>>& for details of authentication.
25549 .option hosts_request_ocsp smtp "host list&!!" *
25550 .cindex "TLS" "requiring for certain servers"
25551 Exim will request a Certificate Status on a
25552 TLS session for any host that matches this list.
25553 &%tls_verify_certificates%& should also be set for the transport.
25555 .option hosts_require_dane smtp "host list&!!" unset
25556 .cindex DANE "transport options"
25557 .cindex DANE "requiring for certain servers"
25558 If built with DANE support, Exim will require that a DNSSEC-validated
25559 TLSA record is present for any host matching the list,
25560 and that a DANE-verified TLS connection is made.
25561 There will be no fallback to in-clear communication.
25562 See the &%dnssec_request_domains%& router and transport options.
25563 See section &<<SECDANE>>&.
25565 .option hosts_require_ocsp smtp "host list&!!" unset
25566 .cindex "TLS" "requiring for certain servers"
25567 Exim will request, and check for a valid Certificate Status being given, on a
25568 TLS session for any host that matches this list.
25569 &%tls_verify_certificates%& should also be set for the transport.
25571 .option hosts_require_tls smtp "host list&!!" unset
25572 .cindex "TLS" "requiring for certain servers"
25573 Exim will insist on using a TLS session when delivering to any host that
25574 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25575 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25576 incoming messages, use an appropriate ACL.
25578 .option hosts_try_auth smtp "host list&!!" unset
25579 .cindex "authentication" "optional in client"
25580 This option provides a list of servers to which, provided they announce
25581 authentication support, Exim will attempt to authenticate as a client when it
25582 connects. If authentication fails
25584 and &%hosts_require_auth%& permits,
25586 Exim will try to transfer the message unauthenticated.
25587 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25589 .option hosts_try_chunking smtp "host list&!!" *
25590 .cindex CHUNKING "enabling, in client"
25591 .cindex BDAT "SMTP command"
25592 .cindex "RFC 3030" "CHUNKING"
25593 This option provides a list of servers to which, provided they announce
25594 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25595 Unless DKIM signing is being done,
25596 BDAT will not be used in conjunction with a transport filter.
25598 .option hosts_try_dane smtp "host list&!!" *
25599 .cindex DANE "transport options"
25600 .cindex DANE "attempting for certain servers"
25602 If built with DANE support, Exim will look up a
25603 TLSA record for any host matching the list,
25604 If one is found and that lookup was DNSSEC-validated,
25605 then Exim requires that a DANE-verified TLS connection is made for that host;
25606 there will be no fallback to in-clear communication.
25608 See the &%dnssec_request_domains%& router and transport options.
25609 See section &<<SECDANE>>&.
25611 .option hosts_try_fastopen smtp "host list&!!" *
25612 .cindex "fast open, TCP" "enabling, in client"
25613 .cindex "TCP Fast Open" "enabling, in client"
25614 .cindex "RFC 7413" "TCP Fast Open"
25615 This option provides a list of servers to which, provided
25616 the facility is supported by this system, Exim will attempt to
25617 perform a TCP Fast Open.
25618 No data is sent on the SYN segment but, if the remote server also
25619 supports the facility, it can send its SMTP banner immediately after
25620 the SYN,ACK segment. This can save up to one round-trip time.
25622 The facility is only active for previously-contacted servers,
25623 as the initiator must present a cookie in the SYN segment.
25625 On (at least some) current Linux distributions the facility must be enabled
25626 in the kernel by the sysadmin before the support is usable.
25627 There is no option for control of the server side; if the system supports
25628 it it is always enabled. Note that lengthy operations in the connect ACL,
25629 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25631 .option hosts_try_prdr smtp "host list&!!" *
25632 .cindex "PRDR" "enabling, optional in client"
25633 .cindex "ESMTP extensions" PRDR
25634 This option provides a list of servers to which, provided they announce
25635 PRDR support, Exim will attempt to negotiate PRDR
25636 for multi-recipient messages.
25637 The option can usually be left as default.
25639 .option interface smtp "string list&!!" unset
25640 .cindex "bind IP address"
25641 .cindex "IP address" "binding"
25643 .vindex "&$host_address$&"
25644 This option specifies which interface to bind to when making an outgoing SMTP
25645 call. The value is an IP address, not an interface name such as
25646 &`eth0`&. Do not confuse this with the interface address that was used when a
25647 message was received, which is in &$received_ip_address$&, formerly known as
25648 &$interface_address$&. The name was changed to minimize confusion with the
25649 outgoing interface address. There is no variable that contains an outgoing
25650 interface address because, unless it is set by this option, its value is
25653 During the expansion of the &%interface%& option the variables &$host$& and
25654 &$host_address$& refer to the host to which a connection is about to be made
25655 during the expansion of the string. Forced expansion failure, or an empty
25656 string result causes the option to be ignored. Otherwise, after expansion, the
25657 string must be a list of IP addresses, colon-separated by default, but the
25658 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25661 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25663 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25664 connection. If none of them are the correct type, the option is ignored. If
25665 &%interface%& is not set, or is ignored, the system's IP functions choose which
25666 interface to use if the host has more than one.
25669 .option keepalive smtp boolean true
25670 .cindex "keepalive" "on outgoing connection"
25671 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25672 connections. When set, it causes the kernel to probe idle connections
25673 periodically, by sending packets with &"old"& sequence numbers. The other end
25674 of the connection should send a acknowledgment if the connection is still okay
25675 or a reset if the connection has been aborted. The reason for doing this is
25676 that it has the beneficial effect of freeing up certain types of connection
25677 that can get stuck when the remote host is disconnected without tidying up the
25678 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25682 .option lmtp_ignore_quota smtp boolean false
25683 .cindex "LMTP" "ignoring quota errors"
25684 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25685 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25686 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25688 .option max_rcpt smtp integer 100
25689 .cindex "RCPT" "maximum number of outgoing"
25690 This option limits the number of RCPT commands that are sent in a single
25691 SMTP message transaction. Each set of addresses is treated independently, and
25692 so can cause parallel connections to the same host if &%remote_max_parallel%&
25697 .option message_linelength_limit smtp integer 998
25698 .cindex "line length" limit
25699 This option sets the maximum line length, in bytes, that the transport
25700 will send. Any messages with lines exceeding the given value
25701 will fail and a failure-DSN ("bounce") message will if possible be returned
25703 The default value is that defined by the SMTP standards.
25705 It is generally wise to also check in the data ACL so that messages
25706 received via SMTP can be refused without producing a bounce.
25710 .option multi_domain smtp boolean&!! true
25711 .vindex "&$domain$&"
25712 When this option is set, the &(smtp)& transport can handle a number of
25713 addresses containing a mixture of different domains provided they all resolve
25714 to the same list of hosts. Turning the option off restricts the transport to
25715 handling only one domain at a time. This is useful if you want to use
25716 &$domain$& in an expansion for the transport, because it is set only when there
25717 is a single domain involved in a remote delivery.
25719 It is expanded per-address and can depend on any of
25720 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25721 &$host$&, &$host_address$& and &$host_port$&.
25724 If the connection is DANE-enabled then this option is ignored;
25725 only messages having the domain used for the DANE TLSA lookup are
25726 sent on the connection.
25729 .option port smtp string&!! "see below"
25730 .cindex "port" "sending TCP/IP"
25731 .cindex "TCP/IP" "setting outgoing port"
25732 This option specifies the TCP/IP port on the server to which Exim connects.
25733 &*Note:*& Do not confuse this with the port that was used when a message was
25734 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25735 The name was changed to minimize confusion with the outgoing port. There is no
25736 variable that contains an outgoing port.
25738 If the value of this option begins with a digit it is taken as a port number;
25739 otherwise it is looked up using &[getservbyname()]&. The default value is
25741 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25742 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25743 If the expansion fails, or if a port number cannot be found, delivery
25746 Note that at least one Linux distribution has been seen failing
25747 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25751 .option protocol smtp string smtp
25752 .cindex "LMTP" "over TCP/IP"
25753 .cindex "ssmtp protocol" "outbound"
25754 .cindex "TLS" "SSL-on-connect outbound"
25756 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25757 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25758 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25759 deliveries into closed message stores. Exim also has support for running LMTP
25760 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25762 If this option is set to &"smtps"&, the default value for the &%port%& option
25763 changes to &"smtps"&, and the transport initiates TLS immediately after
25764 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25765 The Internet standards bodies used to strongly discourage use of this mode,
25766 but as of RFC 8314 it is preferred over STARTTLS for message submission
25767 (as distinct from MTA-MTA communication).
25770 .option retry_include_ip_address smtp boolean&!! true
25771 Exim normally includes both the host name and the IP address in the key it
25772 constructs for indexing retry data after a temporary delivery failure. This
25773 means that when one of several IP addresses for a host is failing, it gets
25774 tried periodically (controlled by the retry rules), but use of the other IP
25775 addresses is not affected.
25777 However, in some dialup environments hosts are assigned a different IP address
25778 each time they connect. In this situation the use of the IP address as part of
25779 the retry key leads to undesirable behaviour. Setting this option false causes
25780 Exim to use only the host name.
25781 Since it is expanded it can be made to depend on the host or domain.
25784 .option serialize_hosts smtp "host list&!!" unset
25785 .cindex "serializing connections"
25786 .cindex "host" "serializing connections"
25787 Because Exim operates in a distributed manner, if several messages for the same
25788 host arrive at around the same time, more than one simultaneous connection to
25789 the remote host can occur. This is not usually a problem except when there is a
25790 slow link between the hosts. In that situation it may be helpful to restrict
25791 Exim to one connection at a time. This can be done by setting
25792 &%serialize_hosts%& to match the relevant hosts.
25794 .cindex "hints database" "serializing deliveries to a host"
25795 Exim implements serialization by means of a hints database in which a record is
25796 written whenever a process connects to one of the restricted hosts. The record
25797 is deleted when the connection is completed. Obviously there is scope for
25798 records to get left lying around if there is a system or program crash. To
25799 guard against this, Exim ignores any records that are more than six hours old.
25801 If you set up this kind of serialization, you should also arrange to delete the
25802 relevant hints database whenever your system reboots. The names of the files
25803 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25804 may be one or two files, depending on the type of DBM in use. The same files
25805 are used for ETRN serialization.
25807 See also the &%max_parallel%& generic transport option.
25810 .option size_addition smtp integer 1024
25811 .cindex "SIZE" "ESMTP extension"
25812 .cindex "message" "size issue for transport filter"
25813 .cindex "size" "of message"
25814 .cindex "transport" "filter"
25815 .cindex "filter" "transport filter"
25816 If a remote SMTP server indicates that it supports the SIZE option of the
25817 MAIL command, Exim uses this to pass over the message size at the start of
25818 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25819 sends, to allow for headers and other text that may be added during delivery by
25820 configuration options or in a transport filter. It may be necessary to increase
25821 this if a lot of text is added to messages.
25823 Alternatively, if the value of &%size_addition%& is set negative, it disables
25824 the use of the SIZE option altogether.
25827 .option socks_proxy smtp string&!! unset
25828 .cindex proxy SOCKS
25829 This option enables use of SOCKS proxies for connections made by the
25830 transport. For details see section &<<SECTproxySOCKS>>&.
25833 .option tls_certificate smtp string&!! unset
25834 .cindex "TLS" "client certificate, location of"
25835 .cindex "certificate" "client, location of"
25837 .vindex "&$host_address$&"
25838 The value of this option must be the absolute path to a file which contains the
25839 client's certificate, for possible use when sending a message over an encrypted
25840 connection. The values of &$host$& and &$host_address$& are set to the name and
25841 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25844 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25845 certificate when sending messages as a client. The global option of the same
25846 name specifies the certificate for Exim as a server; it is not automatically
25847 assumed that the same certificate should be used when Exim is operating as a
25851 .option tls_crl smtp string&!! unset
25852 .cindex "TLS" "client certificate revocation list"
25853 .cindex "certificate" "revocation list for client"
25854 This option specifies a certificate revocation list. The expanded value must
25855 be the name of a file that contains a CRL in PEM format.
25858 .option tls_dh_min_bits smtp integer 1024
25859 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
25860 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
25861 key agreement is negotiated, the server will provide a large prime number
25862 for use. This option establishes the minimum acceptable size of that number.
25863 If the parameter offered by the server is too small, then the TLS handshake
25866 Only supported when using GnuTLS.
25869 .option tls_privatekey smtp string&!! unset
25870 .cindex "TLS" "client private key, location of"
25872 .vindex "&$host_address$&"
25873 The value of this option must be the absolute path to a file which contains the
25874 client's private key. This is used when sending a message over an encrypted
25875 connection using a client certificate. The values of &$host$& and
25876 &$host_address$& are set to the name and address of the server during the
25877 expansion. If this option is unset, or the expansion is forced to fail, or the
25878 result is an empty string, the private key is assumed to be in the same file as
25879 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
25882 .option tls_require_ciphers smtp string&!! unset
25883 .cindex "TLS" "requiring specific ciphers"
25884 .cindex "cipher" "requiring specific"
25886 .vindex "&$host_address$&"
25887 The value of this option must be a list of permitted cipher suites, for use
25888 when setting up an outgoing encrypted connection. (There is a global option of
25889 the same name for controlling incoming connections.) The values of &$host$& and
25890 &$host_address$& are set to the name and address of the server during the
25891 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
25892 is used in different ways by OpenSSL and GnuTLS (see sections
25893 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
25894 ciphers is a preference order.
25898 .option tls_resumption_hosts smtp "host list&!!" unset
25899 .cindex TLS resumption
25900 This option controls which connections to use the TLS resumption feature.
25901 See &<<SECTresumption>>& for details.
25906 .option tls_sni smtp string&!! unset
25907 .cindex "TLS" "Server Name Indication"
25909 .cindex SNI "setting in client"
25910 .vindex "&$tls_sni$&"
25911 If this option is set
25913 and the connection is not DANE-validated
25915 then it sets the $tls_out_sni variable and causes any
25916 TLS session to pass this value as the Server Name Indication extension to
25917 the remote side, which can be used by the remote side to select an appropriate
25918 certificate and private key for the session.
25920 See &<<SECTtlssni>>& for more information.
25922 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
25928 .option tls_tempfail_tryclear smtp boolean true
25929 .cindex "4&'xx'& responses" "to STARTTLS"
25930 When the server host is not in &%hosts_require_tls%&, and there is a problem in
25931 setting up a TLS session, this option determines whether or not Exim should try
25932 to deliver the message unencrypted. If it is set false, delivery to the
25933 current host is deferred; if there are other hosts, they are tried. If this
25934 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
25935 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
25936 TLS negotiation fails, Exim closes the current connection (because it is in an
25937 unknown state), opens a new one to the same host, and then tries the delivery
25941 .option tls_try_verify_hosts smtp "host list&!!" *
25942 .cindex "TLS" "server certificate verification"
25943 .cindex "certificate" "verification of server"
25944 This option gives a list of hosts for which, on encrypted connections,
25945 certificate verification will be tried but need not succeed.
25946 The &%tls_verify_certificates%& option must also be set.
25947 Note that unless the host is in this list
25948 TLS connections will be denied to hosts using self-signed certificates
25949 when &%tls_verify_certificates%& is matched.
25950 The &$tls_out_certificate_verified$& variable is set when
25951 certificate verification succeeds.
25954 .option tls_verify_cert_hostnames smtp "host list&!!" *
25955 .cindex "TLS" "server certificate hostname verification"
25956 .cindex "certificate" "verification of server"
25957 This option give a list of hosts for which,
25958 while verifying the server certificate,
25959 checks will be included on the host name
25960 (note that this will generally be the result of a DNS MX lookup)
25961 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
25962 limited to being the initial component of a 3-or-more component FQDN.
25964 There is no equivalent checking on client certificates.
25967 .option tls_verify_certificates smtp string&!! system
25968 .cindex "TLS" "server certificate verification"
25969 .cindex "certificate" "verification of server"
25971 .vindex "&$host_address$&"
25972 The value of this option must be either the
25974 or the absolute path to
25975 a file or directory containing permitted certificates for servers,
25976 for use when setting up an encrypted connection.
25978 The "system" value for the option will use a location compiled into the SSL library.
25979 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
25980 is taken as empty and an explicit location
25983 The use of a directory for the option value is not available for GnuTLS versions
25984 preceding 3.3.6 and a single file must be used.
25986 With OpenSSL the certificates specified
25988 either by file or directory
25989 are added to those given by the system default location.
25991 The values of &$host$& and
25992 &$host_address$& are set to the name and address of the server during the
25993 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
25995 For back-compatibility,
25996 if neither tls_verify_hosts nor tls_try_verify_hosts are set
25997 (a single-colon empty list counts as being set)
25998 and certificate verification fails the TLS connection is closed.
26001 .option tls_verify_hosts smtp "host list&!!" unset
26002 .cindex "TLS" "server certificate verification"
26003 .cindex "certificate" "verification of server"
26004 This option gives a list of hosts for which, on encrypted connections,
26005 certificate verification must succeed.
26006 The &%tls_verify_certificates%& option must also be set.
26007 If both this option and &%tls_try_verify_hosts%& are unset
26008 operation is as if this option selected all hosts.
26010 .option utf8_downconvert smtp integer&!! -1
26011 .cindex utf8 "address downconversion"
26012 .cindex i18n "utf8 address downconversion"
26013 If built with internationalization support,
26014 this option controls conversion of UTF-8 in message envelope addresses
26016 If, after expansion, the value is 1, 0, or -1 then this value overrides
26017 any value previously set for the message. Otherwise, any previously
26018 set value is used. To permit use of a previous value,
26019 set this option to an empty string.
26020 For details on the values see section &<<SECTi18nMTA>>&.
26025 .section "How the limits for the number of hosts to try are used" &&&
26027 .cindex "host" "maximum number to try"
26028 .cindex "limit" "hosts; maximum number tried"
26029 There are two options that are concerned with the number of hosts that are
26030 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26031 &%hosts_max_try_hardlimit%&.
26034 The &%hosts_max_try%& option limits the number of hosts that are tried
26035 for a single delivery. However, despite the term &"host"& in its name, the
26036 option actually applies to each IP address independently. In other words, a
26037 multihomed host is treated as several independent hosts, just as it is for
26040 Many of the larger ISPs have multiple MX records which often point to
26041 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26042 created as a result of routing one of these domains.
26044 Trying every single IP address on such a long list does not seem sensible; if
26045 several at the top of the list fail, it is reasonable to assume there is some
26046 problem that is likely to affect all of them. Roughly speaking, the value of
26047 &%hosts_max_try%& is the maximum number that are tried before deferring the
26048 delivery. However, the logic cannot be quite that simple.
26050 Firstly, IP addresses that are skipped because their retry times have not
26051 arrived do not count, and in addition, addresses that are past their retry
26052 limits are also not counted, even when they are tried. This means that when
26053 some IP addresses are past their retry limits, more than the value of
26054 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26055 that all IP addresses are considered before timing out an email address (but
26056 see below for an exception).
26058 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26059 list to see if there is a subsequent host with a different (higher valued) MX.
26060 If there is, that host is considered next, and the current IP address is used
26061 but not counted. This behaviour helps in the case of a domain with a retry rule
26062 that hardly ever delays any hosts, as is now explained:
26064 Consider the case of a long list of hosts with one MX value, and a few with a
26065 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26066 hosts at the top of the list are tried at first. With the default retry rule,
26067 which specifies increasing retry times, the higher MX hosts are eventually
26068 tried when those at the top of the list are skipped because they have not
26069 reached their retry times.
26071 However, it is common practice to put a fixed short retry time on domains for
26072 large ISPs, on the grounds that their servers are rarely down for very long.
26073 Unfortunately, these are exactly the domains that tend to resolve to long lists
26074 of hosts. The short retry time means that the lowest MX hosts are tried every
26075 time. The attempts may be in a different order because of random sorting, but
26076 without the special MX check, the higher MX hosts would never be tried until
26077 all the lower MX hosts had timed out (which might be several days), because
26078 there are always some lower MX hosts that have reached their retry times. With
26079 the special check, Exim considers at least one IP address from each MX value at
26080 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26083 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26084 particular, Exim normally eventually tries all the IP addresses before timing
26085 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26086 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26087 been set up with hundreds of IP addresses for some domains. It can
26088 take a very long time indeed for an address to time out in these cases.
26090 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26091 Exim never tries more than this number of IP addresses; if it hits this limit
26092 and they are all timed out, the email address is bounced, even though not all
26093 possible IP addresses have been tried.
26094 .ecindex IIDsmttra1
26095 .ecindex IIDsmttra2
26101 . ////////////////////////////////////////////////////////////////////////////
26102 . ////////////////////////////////////////////////////////////////////////////
26104 .chapter "Address rewriting" "CHAPrewrite"
26105 .scindex IIDaddrew "rewriting" "addresses"
26106 There are some circumstances in which Exim automatically rewrites domains in
26107 addresses. The two most common are when an address is given without a domain
26108 (referred to as an &"unqualified address"&) or when an address contains an
26109 abbreviated domain that is expanded by DNS lookup.
26111 Unqualified envelope addresses are accepted only for locally submitted
26112 messages, or for messages that are received from hosts matching
26113 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26114 appropriate. Unqualified addresses in header lines are qualified if they are in
26115 locally submitted messages, or messages from hosts that are permitted to send
26116 unqualified envelope addresses. Otherwise, unqualified addresses in header
26117 lines are neither qualified nor rewritten.
26119 One situation in which Exim does &'not'& automatically rewrite a domain is
26120 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26121 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26122 do this. The new RFCs do not contain this suggestion.
26125 .section "Explicitly configured address rewriting" "SECID147"
26126 This chapter describes the rewriting rules that can be used in the
26127 main rewrite section of the configuration file, and also in the generic
26128 &%headers_rewrite%& option that can be set on any transport.
26130 Some people believe that configured address rewriting is a Mortal Sin.
26131 Others believe that life is not possible without it. Exim provides the
26132 facility; you do not have to use it.
26134 The main rewriting rules that appear in the &"rewrite"& section of the
26135 configuration file are applied to addresses in incoming messages, both envelope
26136 addresses and addresses in header lines. Each rule specifies the types of
26137 address to which it applies.
26139 Whether or not addresses in header lines are rewritten depends on the origin of
26140 the headers and the type of rewriting. Global rewriting, that is, rewriting
26141 rules from the rewrite section of the configuration file, is applied only to
26142 those headers that were received with the message. Header lines that are added
26143 by ACLs or by a system filter or by individual routers or transports (which
26144 are specific to individual recipient addresses) are not rewritten by the global
26147 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26148 applies all headers except those added by routers and transports. That is, as
26149 well as the headers that were received with the message, it also applies to
26150 headers that were added by an ACL or a system filter.
26153 In general, rewriting addresses from your own system or domain has some
26154 legitimacy. Rewriting other addresses should be done only with great care and
26155 in special circumstances. The author of Exim believes that rewriting should be
26156 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26157 Although it can sometimes be used as a routing tool, this is very strongly
26160 There are two commonly encountered circumstances where rewriting is used, as
26161 illustrated by these examples:
26164 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26165 exchange mail with each other behind a firewall, but there is only a single
26166 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26167 &'hitch.fict.example'& when sending mail off-site.
26169 A host rewrites the local parts of its own users so that, for example,
26170 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26175 .section "When does rewriting happen?" "SECID148"
26176 .cindex "rewriting" "timing of"
26177 .cindex "&ACL;" "rewriting addresses in"
26178 Configured address rewriting can take place at several different stages of a
26179 message's processing.
26181 .vindex "&$sender_address$&"
26182 At the start of an ACL for MAIL, the sender address may have been rewritten
26183 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26184 ordinary rewrite rules have yet been applied. If, however, the sender address
26185 is verified in the ACL, it is rewritten before verification, and remains
26186 rewritten thereafter. The subsequent value of &$sender_address$& is the
26187 rewritten address. This also applies if sender verification happens in a
26188 RCPT ACL. Otherwise, when the sender address is not verified, it is
26189 rewritten as soon as a message's header lines have been received.
26191 .vindex "&$domain$&"
26192 .vindex "&$local_part$&"
26193 Similarly, at the start of an ACL for RCPT, the current recipient's address
26194 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26195 rewrite rules have yet been applied to it. However, the behaviour is different
26196 from the sender address when a recipient is verified. The address is rewritten
26197 for the verification, but the rewriting is not remembered at this stage. The
26198 value of &$local_part$& and &$domain$& after verification are always the same
26199 as they were before (that is, they contain the unrewritten &-- except for
26200 SMTP-time rewriting &-- address).
26202 As soon as a message's header lines have been received, all the envelope
26203 recipient addresses are permanently rewritten, and rewriting is also applied to
26204 the addresses in the header lines (if configured). This happens before adding
26205 any header lines that were specified in MAIL or RCPT ACLs, and
26206 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26207 before the DATA ACL and &[local_scan()]& functions are run.
26209 When an address is being routed, either for delivery or for verification,
26210 rewriting is applied immediately to child addresses that are generated by
26211 redirection, unless &%no_rewrite%& is set on the router.
26213 .cindex "envelope from"
26214 .cindex "envelope sender" "rewriting at transport time"
26215 .cindex "rewriting" "at transport time"
26216 .cindex "header lines" "rewriting at transport time"
26217 At transport time, additional rewriting of addresses in header lines can be
26218 specified by setting the generic &%headers_rewrite%& option on a transport.
26219 This option contains rules that are identical in form to those in the rewrite
26220 section of the configuration file. They are applied to the original message
26221 header lines and any that were added by ACLs or a system filter. They are not
26222 applied to header lines that are added by routers or the transport.
26224 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26225 transport option. However, it is not possible to rewrite envelope recipients at
26231 .section "Testing the rewriting rules that apply on input" "SECID149"
26232 .cindex "rewriting" "testing"
26233 .cindex "testing" "rewriting"
26234 Exim's input rewriting configuration appears in a part of the runtime
26235 configuration file headed by &"begin rewrite"&. It can be tested by the
26236 &%-brw%& command line option. This takes an address (which can be a full RFC
26237 2822 address) as its argument. The output is a list of how the address would be
26238 transformed by the rewriting rules for each of the different places it might
26239 appear in an incoming message, that is, for each different header and for the
26240 envelope sender and recipient fields. For example,
26242 exim -brw ph10@exim.workshop.example
26244 might produce the output
26246 sender: Philip.Hazel@exim.workshop.example
26247 from: Philip.Hazel@exim.workshop.example
26248 to: ph10@exim.workshop.example
26249 cc: ph10@exim.workshop.example
26250 bcc: ph10@exim.workshop.example
26251 reply-to: Philip.Hazel@exim.workshop.example
26252 env-from: Philip.Hazel@exim.workshop.example
26253 env-to: ph10@exim.workshop.example
26255 which shows that rewriting has been set up for that address when used in any of
26256 the source fields, but not when it appears as a recipient address. At the
26257 present time, there is no equivalent way of testing rewriting rules that are
26258 set for a particular transport.
26261 .section "Rewriting rules" "SECID150"
26262 .cindex "rewriting" "rules"
26263 The rewrite section of the configuration file consists of lines of rewriting
26266 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26268 Rewriting rules that are specified for the &%headers_rewrite%& generic
26269 transport option are given as a colon-separated list. Each item in the list
26270 takes the same form as a line in the main rewriting configuration (except that
26271 any colons must be doubled, of course).
26273 The formats of source patterns and replacement strings are described below.
26274 Each is terminated by white space, unless enclosed in double quotes, in which
26275 case normal quoting conventions apply inside the quotes. The flags are single
26276 characters which may appear in any order. Spaces and tabs between them are
26279 For each address that could potentially be rewritten, the rules are scanned in
26280 order, and replacements for the address from earlier rules can themselves be
26281 replaced by later rules (but see the &"q"& and &"R"& flags).
26283 The order in which addresses are rewritten is undefined, may change between
26284 releases, and must not be relied on, with one exception: when a message is
26285 received, the envelope sender is always rewritten first, before any header
26286 lines are rewritten. For example, the replacement string for a rewrite of an
26287 address in &'To:'& must not assume that the message's address in &'From:'& has
26288 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26289 that the envelope sender has already been rewritten.
26291 .vindex "&$domain$&"
26292 .vindex "&$local_part$&"
26293 The variables &$local_part$& and &$domain$& can be used in the replacement
26294 string to refer to the address that is being rewritten. Note that lookup-driven
26295 rewriting can be done by a rule of the form
26299 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26300 refer to the address that is being rewritten.
26303 .section "Rewriting patterns" "SECID151"
26304 .cindex "rewriting" "patterns"
26305 .cindex "address list" "in a rewriting pattern"
26306 The source pattern in a rewriting rule is any item which may appear in an
26307 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26308 single-item address list, which means that it is expanded before being tested
26309 against the address. As always, if you use a regular expression as a pattern,
26310 you must take care to escape dollar and backslash characters, or use the &`\N`&
26311 facility to suppress string expansion within the regular expression.
26313 Domains in patterns should be given in lower case. Local parts in patterns are
26314 case-sensitive. If you want to do case-insensitive matching of local parts, you
26315 can use a regular expression that starts with &`^(?i)`&.
26317 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26318 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26319 depending on the type of match which occurred. These can be used in the
26320 replacement string to insert portions of the incoming address. &$0$& always
26321 refers to the complete incoming address. When a regular expression is used, the
26322 numerical variables are set from its capturing subexpressions. For other types
26323 of pattern they are set as follows:
26326 If a local part or domain starts with an asterisk, the numerical variables
26327 refer to the character strings matched by asterisks, with &$1$& associated with
26328 the first asterisk, and &$2$& with the second, if present. For example, if the
26331 *queen@*.fict.example
26333 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26335 $0 = hearts-queen@wonderland.fict.example
26339 Note that if the local part does not start with an asterisk, but the domain
26340 does, it is &$1$& that contains the wild part of the domain.
26343 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26344 of the domain are placed in the next available numerical variables. Suppose,
26345 for example, that the address &'foo@bar.baz.example'& is processed by a
26346 rewriting rule of the form
26348 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26350 and the key in the file that matches the domain is &`*.baz.example`&. Then
26356 If the address &'foo@baz.example'& is looked up, this matches the same
26357 wildcard file entry, and in this case &$2$& is set to the empty string, but
26358 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26359 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26360 whole domain. For non-partial domain lookups, no numerical variables are set.
26364 .section "Rewriting replacements" "SECID152"
26365 .cindex "rewriting" "replacements"
26366 If the replacement string for a rule is a single asterisk, addresses that
26367 match the pattern and the flags are &'not'& rewritten, and no subsequent
26368 rewriting rules are scanned. For example,
26370 hatta@lookingglass.fict.example * f
26372 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26375 .vindex "&$domain$&"
26376 .vindex "&$local_part$&"
26377 If the replacement string is not a single asterisk, it is expanded, and must
26378 yield a fully qualified address. Within the expansion, the variables
26379 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26380 Any letters they contain retain their original case &-- they are not lower
26381 cased. The numerical variables are set up according to the type of pattern that
26382 matched the address, as described above. If the expansion is forced to fail by
26383 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26384 current rule is abandoned, but subsequent rules may take effect. Any other
26385 expansion failure causes the entire rewriting operation to be abandoned, and an
26386 entry written to the panic log.
26390 .section "Rewriting flags" "SECID153"
26391 There are three different kinds of flag that may appear on rewriting rules:
26394 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26397 A flag that specifies rewriting at SMTP time: S.
26399 Flags that control the rewriting process: Q, q, R, w.
26402 For rules that are part of the &%headers_rewrite%& generic transport option,
26403 E, F, T, and S are not permitted.
26407 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26409 .cindex "rewriting" "flags"
26410 If none of the following flag letters, nor the &"S"& flag (see section
26411 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26412 and to both the sender and recipient fields of the envelope, whereas a
26413 transport-time rewriting rule just applies to all headers. Otherwise, the
26414 rewriting rule is skipped unless the relevant addresses are being processed.
26416 &`E`& rewrite all envelope fields
26417 &`F`& rewrite the envelope From field
26418 &`T`& rewrite the envelope To field
26419 &`b`& rewrite the &'Bcc:'& header
26420 &`c`& rewrite the &'Cc:'& header
26421 &`f`& rewrite the &'From:'& header
26422 &`h`& rewrite all headers
26423 &`r`& rewrite the &'Reply-To:'& header
26424 &`s`& rewrite the &'Sender:'& header
26425 &`t`& rewrite the &'To:'& header
26427 "All headers" means all of the headers listed above that can be selected
26428 individually, plus their &'Resent-'& versions. It does not include
26429 other headers such as &'Subject:'& etc.
26431 You should be particularly careful about rewriting &'Sender:'& headers, and
26432 restrict this to special known cases in your own domains.
26435 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26436 .cindex "SMTP" "rewriting malformed addresses"
26437 .cindex "RCPT" "rewriting argument of"
26438 .cindex "MAIL" "rewriting argument of"
26439 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26440 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26441 before any other processing; even before syntax checking. The pattern is
26442 required to be a regular expression, and it is matched against the whole of the
26443 data for the command, including any surrounding angle brackets.
26445 .vindex "&$domain$&"
26446 .vindex "&$local_part$&"
26447 This form of rewrite rule allows for the handling of addresses that are not
26448 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26449 input). Because the input is not required to be a syntactically valid address,
26450 the variables &$local_part$& and &$domain$& are not available during the
26451 expansion of the replacement string. The result of rewriting replaces the
26452 original address in the MAIL or RCPT command.
26455 .section "Flags controlling the rewriting process" "SECID155"
26456 There are four flags which control the way the rewriting process works. These
26457 take effect only when a rule is invoked, that is, when the address is of the
26458 correct type (matches the flags) and matches the pattern:
26461 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26462 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26463 absence of &"Q"& the rewritten address must always include a domain.
26465 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26466 even if no rewriting actually takes place because of a &"fail"& in the
26467 expansion. The &"q"& flag is not effective if the address is of the wrong type
26468 (does not match the flags) or does not match the pattern.
26470 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26471 address, up to ten times. It can be combined with the &"q"& flag, to stop
26472 rewriting once it fails to match (after at least one successful rewrite).
26474 .cindex "rewriting" "whole addresses"
26475 When an address in a header is rewritten, the rewriting normally applies only
26476 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26477 left unchanged. For example, rewriting might change
26479 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26483 From: Ford Prefect <prefectf@hitch.fict.example>
26486 Sometimes there is a need to replace the whole address item, and this can be
26487 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26488 causes an address in a header line to be rewritten, the entire address is
26489 replaced, not just the working part. The replacement must be a complete RFC
26490 2822 address, including the angle brackets if necessary. If text outside angle
26491 brackets contains a character whose value is greater than 126 or less than 32
26492 (except for tab), the text is encoded according to RFC 2047. The character set
26493 is taken from &%headers_charset%&, which gets its default at build time.
26495 When the &"w"& flag is set on a rule that causes an envelope address to be
26496 rewritten, all but the working part of the replacement address is discarded.
26500 .section "Rewriting examples" "SECID156"
26501 Here is an example of the two common rewriting paradigms:
26503 *@*.hitch.fict.example $1@hitch.fict.example
26504 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26505 {$value}fail}@hitch.fict.example bctfrF
26507 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26508 the string expansion to fail if the lookup does not succeed. In this context it
26509 has the effect of leaving the original address unchanged, but Exim goes on to
26510 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26511 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26512 explicitly, which would cause the rewritten address to be the same as before,
26513 at the cost of a small bit of processing. Not supplying either of these is an
26514 error, since the rewritten address would then contain no local part.
26516 The first example above replaces the domain with a superior, more general
26517 domain. This may not be desirable for certain local parts. If the rule
26519 root@*.hitch.fict.example *
26521 were inserted before the first rule, rewriting would be suppressed for the
26522 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26524 Rewriting can be made conditional on a number of tests, by making use of
26525 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26526 messages that originate outside the local host:
26528 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26529 {$1@hitch.fict.example}fail}"
26531 The replacement string is quoted in this example because it contains white
26534 .cindex "rewriting" "bang paths"
26535 .cindex "bang paths" "rewriting"
26536 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26537 an address it treats it as an unqualified local part which it qualifies with
26538 the local qualification domain (if the source of the message is local or if the
26539 remote host is permitted to send unqualified addresses). Rewriting can
26540 sometimes be used to handle simple bang paths with a fixed number of
26541 components. For example, the rule
26543 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26545 rewrites a two-component bang path &'host.name!user'& as the domain address
26546 &'user@host.name'&. However, there is a security implication in using this as
26547 a global rewriting rule for envelope addresses. It can provide a backdoor
26548 method for using your system as a relay, because the incoming addresses appear
26549 to be local. If the bang path addresses are received via SMTP, it is safer to
26550 use the &"S"& flag to rewrite them as they are received, so that relay checking
26551 can be done on the rewritten addresses.
26558 . ////////////////////////////////////////////////////////////////////////////
26559 . ////////////////////////////////////////////////////////////////////////////
26561 .chapter "Retry configuration" "CHAPretry"
26562 .scindex IIDretconf1 "retry" "configuration, description of"
26563 .scindex IIDregconf2 "configuration file" "retry section"
26564 The &"retry"& section of the runtime configuration file contains a list of
26565 retry rules that control how often Exim tries to deliver messages that cannot
26566 be delivered at the first attempt. If there are no retry rules (the section is
26567 empty or not present), there are no retries. In this situation, temporary
26568 errors are treated as permanent. The default configuration contains a single,
26569 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26570 line option can be used to test which retry rule will be used for a given
26571 address, domain and error.
26573 The most common cause of retries is temporary failure to deliver to a remote
26574 host because the host is down, or inaccessible because of a network problem.
26575 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26576 address) basis, not on a per-message basis. Thus, if one message has recently
26577 been delayed, delivery of a new message to the same host is not immediately
26578 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26579 log selector is set, the message
26580 .cindex "retry" "time not reached"
26581 &"retry time not reached"& is written to the main log whenever a delivery is
26582 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26583 the handling of errors during remote deliveries.
26585 Retry processing applies to routing as well as to delivering, except as covered
26586 in the next paragraph. The retry rules do not distinguish between these
26587 actions. It is not possible, for example, to specify different behaviour for
26588 failures to route the domain &'snark.fict.example'& and failures to deliver to
26589 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26590 added complication, so did not implement it. However, although they share the
26591 same retry rule, the actual retry times for routing and transporting a given
26592 domain are maintained independently.
26594 When a delivery is not part of a queue run (typically an immediate delivery on
26595 receipt of a message), the routers are always run, and local deliveries are
26596 always attempted, even if retry times are set for them. This makes for better
26597 behaviour if one particular message is causing problems (for example, causing
26598 quota overflow, or provoking an error in a filter file). If such a delivery
26599 suffers a temporary failure, the retry data is updated as normal, and
26600 subsequent delivery attempts from queue runs occur only when the retry time for
26601 the local address is reached.
26603 .section "Changing retry rules" "SECID157"
26604 If you change the retry rules in your configuration, you should consider
26605 whether or not to delete the retry data that is stored in Exim's spool area in
26606 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26607 always safe; that is why they are called &"hints"&.
26609 The hints retry data contains suggested retry times based on the previous
26610 rules. In the case of a long-running problem with a remote host, it might
26611 record the fact that the host has timed out. If your new rules increase the
26612 timeout time for such a host, you should definitely remove the old retry data
26613 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26614 messages that it should now be retaining.
26618 .section "Format of retry rules" "SECID158"
26619 .cindex "retry" "rules"
26620 Each retry rule occupies one line and consists of three or four parts,
26621 separated by white space: a pattern, an error name, an optional list of sender
26622 addresses, and a list of retry parameters. The pattern and sender lists must be
26623 enclosed in double quotes if they contain white space. The rules are searched
26624 in order until one is found where the pattern, error name, and sender list (if
26625 present) match the failing host or address, the error that occurred, and the
26626 message's sender, respectively.
26629 The pattern is any single item that may appear in an address list (see section
26630 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26631 which means that it is expanded before being tested against the address that
26632 has been delayed. A negated address list item is permitted. Address
26633 list processing treats a plain domain name as if it were preceded by &"*@"&,
26634 which makes it possible for many retry rules to start with just a domain. For
26637 lookingglass.fict.example * F,24h,30m;
26639 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26642 alice@lookingglass.fict.example * F,24h,30m;
26644 applies only to temporary failures involving the local part &%alice%&.
26645 In practice, almost all rules start with a domain name pattern without a local
26648 .cindex "regular expressions" "in retry rules"
26649 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26650 must match a complete address, not just a domain, because that is how regular
26651 expressions work in address lists.
26653 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26654 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26658 .section "Choosing which retry rule to use for address errors" "SECID159"
26659 When Exim is looking for a retry rule after a routing attempt has failed (for
26660 example, after a DNS timeout), each line in the retry configuration is tested
26661 against the complete address only if &%retry_use_local_part%& is set for the
26662 router. Otherwise, only the domain is used, except when matching against a
26663 regular expression, when the local part of the address is replaced with &"*"&.
26664 A domain on its own can match a domain pattern, or a pattern that starts with
26665 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26666 &%check_local_user%& is true, and false for other routers.
26668 Similarly, when Exim is looking for a retry rule after a local delivery has
26669 failed (for example, after a mailbox full error), each line in the retry
26670 configuration is tested against the complete address only if
26671 &%retry_use_local_part%& is set for the transport (it defaults true for all
26674 .cindex "4&'xx'& responses" "retry rules for"
26675 However, when Exim is looking for a retry rule after a remote delivery attempt
26676 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26677 whole address is always used as the key when searching the retry rules. The
26678 rule that is found is used to create a retry time for the combination of the
26679 failing address and the message's sender. It is the combination of sender and
26680 recipient that is delayed in subsequent queue runs until its retry time is
26681 reached. You can delay the recipient without regard to the sender by setting
26682 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26683 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26688 .section "Choosing which retry rule to use for host and message errors" &&&
26690 For a temporary error that is not related to an individual address (for
26691 example, a connection timeout), each line in the retry configuration is checked
26692 twice. First, the name of the remote host is used as a domain name (preceded by
26693 &"*@"& when matching a regular expression). If this does not match the line,
26694 the domain from the email address is tried in a similar fashion. For example,
26695 suppose the MX records for &'a.b.c.example'& are
26697 a.b.c.example MX 5 x.y.z.example
26701 and the retry rules are
26703 p.q.r.example * F,24h,30m;
26704 a.b.c.example * F,4d,45m;
26706 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26707 first rule matches neither the host nor the domain, so Exim looks at the second
26708 rule. This does not match the host, but it does match the domain, so it is used
26709 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26710 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26711 first retry rule is used, because it matches the host.
26713 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26714 first rule to determine retry times, but for all the other hosts for the domain
26715 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26716 routing to &'a.b.c.example'& suffers a temporary failure.
26718 &*Note*&: The host name is used when matching the patterns, not its IP address.
26719 However, if a message is routed directly to an IP address without the use of a
26720 host name, for example, if a &(manualroute)& router contains a setting such as:
26722 route_list = *.a.example 192.168.34.23
26724 then the &"host name"& that is used when searching for a retry rule is the
26725 textual form of the IP address.
26727 .section "Retry rules for specific errors" "SECID161"
26728 .cindex "retry" "specific errors; specifying"
26729 The second field in a retry rule is the name of a particular error, or an
26730 asterisk, which matches any error. The errors that can be tested for are:
26733 .vitem &%auth_failed%&
26734 Authentication failed when trying to send to a host in the
26735 &%hosts_require_auth%& list in an &(smtp)& transport.
26737 .vitem &%data_4xx%&
26738 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26739 after the command, or after sending the message's data.
26741 .vitem &%mail_4xx%&
26742 A 4&'xx'& error was received for an outgoing MAIL command.
26744 .vitem &%rcpt_4xx%&
26745 A 4&'xx'& error was received for an outgoing RCPT command.
26748 For the three 4&'xx'& errors, either the first or both of the x's can be given
26749 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26750 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26751 and have retries every ten minutes with a one-hour timeout, you could set up a
26752 retry rule of this form:
26754 the.domain.name rcpt_452 F,1h,10m
26756 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26757 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26760 .vitem &%lost_connection%&
26761 A server unexpectedly closed the SMTP connection. There may, of course,
26762 legitimate reasons for this (host died, network died), but if it repeats a lot
26763 for the same host, it indicates something odd.
26766 A DNS lookup for a host failed.
26767 Note that a &%dnslookup%& router will need to have matched
26768 its &%fail_defer_domains%& option for this retry type to be usable.
26769 Also note that a &%manualroute%& router will probably need
26770 its &%host_find_failed%& option set to &%defer%&.
26772 .vitem &%refused_MX%&
26773 A connection to a host obtained from an MX record was refused.
26775 .vitem &%refused_A%&
26776 A connection to a host not obtained from an MX record was refused.
26779 A connection was refused.
26781 .vitem &%timeout_connect_MX%&
26782 A connection attempt to a host obtained from an MX record timed out.
26784 .vitem &%timeout_connect_A%&
26785 A connection attempt to a host not obtained from an MX record timed out.
26787 .vitem &%timeout_connect%&
26788 A connection attempt timed out.
26790 .vitem &%timeout_MX%&
26791 There was a timeout while connecting or during an SMTP session with a host
26792 obtained from an MX record.
26794 .vitem &%timeout_A%&
26795 There was a timeout while connecting or during an SMTP session with a host not
26796 obtained from an MX record.
26799 There was a timeout while connecting or during an SMTP session.
26801 .vitem &%tls_required%&
26802 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26803 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26804 to STARTTLS, or there was a problem setting up the TLS connection.
26807 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26810 .vitem &%quota_%&<&'time'&>
26811 .cindex "quota" "error testing in retry rule"
26812 .cindex "retry" "quota error testing"
26813 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26814 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26815 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26819 .cindex "mailbox" "time of last read"
26820 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26821 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26822 it should be based on the last time that the user accessed the mailbox.
26823 However, it is not always possible to determine this. Exim uses the following
26827 If the mailbox is a single file, the time of last access (the &"atime"&) is
26828 used. As no new messages are being delivered (because the mailbox is over
26829 quota), Exim does not access the file, so this is the time of last user access.
26831 .cindex "maildir format" "time of last read"
26832 For a maildir delivery, the time of last modification of the &_new_&
26833 subdirectory is used. As the mailbox is over quota, no new files are created in
26834 the &_new_& subdirectory, because no new messages are being delivered. Any
26835 change to the &_new_& subdirectory is therefore assumed to be the result of an
26836 MUA moving a new message to the &_cur_& directory when it is first read. The
26837 time that is used is therefore the last time that the user read a new message.
26839 For other kinds of multi-file mailbox, the time of last access cannot be
26840 obtained, so a retry rule that uses this type of error field is never matched.
26843 The quota errors apply both to system-enforced quotas and to Exim's own quota
26844 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26845 when a local delivery is deferred because a partition is full (the ENOSPC
26850 .section "Retry rules for specified senders" "SECID162"
26851 .cindex "retry" "rules; sender-specific"
26852 You can specify retry rules that apply only when the failing message has a
26853 specific sender. In particular, this can be used to define retry rules that
26854 apply only to bounce messages. The third item in a retry rule can be of this
26857 &`senders=`&<&'address list'&>
26859 The retry timings themselves are then the fourth item. For example:
26861 * rcpt_4xx senders=: F,1h,30m
26863 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
26864 host. If the address list contains white space, it must be enclosed in quotes.
26867 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
26869 &*Warning*&: This facility can be unhelpful if it is used for host errors
26870 (which do not depend on the recipient). The reason is that the sender is used
26871 only to match the retry rule. Once the rule has been found for a host error,
26872 its contents are used to set a retry time for the host, and this will apply to
26873 all messages, not just those with specific senders.
26875 When testing retry rules using &%-brt%&, you can supply a sender using the
26876 &%-f%& command line option, like this:
26878 exim -f "" -brt user@dom.ain
26880 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
26881 list is never matched.
26887 .section "Retry parameters" "SECID163"
26888 .cindex "retry" "parameters in rules"
26889 The third (or fourth, if a senders list is present) field in a retry rule is a
26890 sequence of retry parameter sets, separated by semicolons. Each set consists of
26892 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
26894 The letter identifies the algorithm for computing a new retry time; the cutoff
26895 time is the time beyond which this algorithm no longer applies, and the
26896 arguments vary the algorithm's action. The cutoff time is measured from the
26897 time that the first failure for the domain (combined with the local part if
26898 relevant) was detected, not from the time the message was received.
26900 .cindex "retry" "algorithms"
26901 .cindex "retry" "fixed intervals"
26902 .cindex "retry" "increasing intervals"
26903 .cindex "retry" "random intervals"
26904 The available algorithms are:
26907 &'F'&: retry at fixed intervals. There is a single time parameter specifying
26910 &'G'&: retry at geometrically increasing intervals. The first argument
26911 specifies a starting value for the interval, and the second a multiplier, which
26912 is used to increase the size of the interval at each retry.
26914 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
26915 retry, the previous interval is multiplied by the factor in order to get a
26916 maximum for the next interval. The minimum interval is the first argument of
26917 the parameter, and an actual interval is chosen randomly between them. Such a
26918 rule has been found to be helpful in cluster configurations when all the
26919 members of the cluster restart at once, and may therefore synchronize their
26920 queue processing times.
26923 When computing the next retry time, the algorithm definitions are scanned in
26924 order until one whose cutoff time has not yet passed is reached. This is then
26925 used to compute a new retry time that is later than the current time. In the
26926 case of fixed interval retries, this simply means adding the interval to the
26927 current time. For geometrically increasing intervals, retry intervals are
26928 computed from the rule's parameters until one that is greater than the previous
26929 interval is found. The main configuration variable
26930 .cindex "limit" "retry interval"
26931 .cindex "retry" "interval, maximum"
26932 .oindex "&%retry_interval_max%&"
26933 &%retry_interval_max%& limits the maximum interval between retries. It
26934 cannot be set greater than &`24h`&, which is its default value.
26936 A single remote domain may have a number of hosts associated with it, and each
26937 host may have more than one IP address. Retry algorithms are selected on the
26938 basis of the domain name, but are applied to each IP address independently. If,
26939 for example, a host has two IP addresses and one is unusable, Exim will
26940 generate retry times for it and will not try to use it until its next retry
26941 time comes. Thus the good IP address is likely to be tried first most of the
26944 .cindex "hints database" "use for retrying"
26945 Retry times are hints rather than promises. Exim does not make any attempt to
26946 run deliveries exactly at the computed times. Instead, a queue runner process
26947 starts delivery processes for delayed messages periodically, and these attempt
26948 new deliveries only for those addresses that have passed their next retry time.
26949 If a new message arrives for a deferred address, an immediate delivery attempt
26950 occurs only if the address has passed its retry time. In the absence of new
26951 messages, the minimum time between retries is the interval between queue runner
26952 processes. There is not much point in setting retry times of five minutes if
26953 your queue runners happen only once an hour, unless there are a significant
26954 number of incoming messages (which might be the case on a system that is
26955 sending everything to a smart host, for example).
26957 The data in the retry hints database can be inspected by using the
26958 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
26959 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
26960 &'exinext'& utility script can be used to find out what the next retry times
26961 are for the hosts associated with a particular mail domain, and also for local
26962 deliveries that have been deferred.
26965 .section "Retry rule examples" "SECID164"
26966 Here are some example retry rules:
26968 alice@wonderland.fict.example quota_5d F,7d,3h
26969 wonderland.fict.example quota_5d
26970 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
26971 lookingglass.fict.example * F,24h,30m;
26972 * refused_A F,2h,20m;
26973 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
26975 The first rule sets up special handling for mail to
26976 &'alice@wonderland.fict.example'& when there is an over-quota error and the
26977 mailbox has not been read for at least 5 days. Retries continue every three
26978 hours for 7 days. The second rule handles over-quota errors for all other local
26979 parts at &'wonderland.fict.example'&; the absence of a local part has the same
26980 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
26981 fail are bounced immediately if the mailbox has not been read for at least 5
26984 The third rule handles all other errors at &'wonderland.fict.example'&; retries
26985 happen every 15 minutes for an hour, then with geometrically increasing
26986 intervals until two days have passed since a delivery first failed. After the
26987 first hour there is a delay of one hour, then two hours, then four hours, and
26988 so on (this is a rather extreme example).
26990 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
26991 They happen every 30 minutes for 24 hours only. The remaining two rules handle
26992 all other domains, with special action for connection refusal from hosts that
26993 were not obtained from an MX record.
26995 The final rule in a retry configuration should always have asterisks in the
26996 first two fields so as to provide a general catch-all for any addresses that do
26997 not have their own special handling. This example tries every 15 minutes for 2
26998 hours, then with intervals starting at one hour and increasing by a factor of
26999 1.5 up to 16 hours, then every 8 hours up to 5 days.
27003 .section "Timeout of retry data" "SECID165"
27004 .cindex "timeout" "of retry data"
27005 .oindex "&%retry_data_expire%&"
27006 .cindex "hints database" "data expiry"
27007 .cindex "retry" "timeout of data"
27008 Exim timestamps the data that it writes to its retry hints database. When it
27009 consults the data during a delivery it ignores any that is older than the value
27010 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27011 been tried for 7 days, Exim will try to deliver to it immediately a message
27012 arrives, and if that fails, it will calculate a retry time as if it were
27013 failing for the first time.
27015 This improves the behaviour for messages routed to rarely-used hosts such as MX
27016 backups. If such a host was down at one time, and happens to be down again when
27017 Exim tries a month later, using the old retry data would imply that it had been
27018 down all the time, which is not a justified assumption.
27020 If a host really is permanently dead, this behaviour causes a burst of retries
27021 every now and again, but only if messages routed to it are rare. If there is a
27022 message at least once every 7 days the retry data never expires.
27027 .section "Long-term failures" "SECID166"
27028 .cindex "delivery failure, long-term"
27029 .cindex "retry" "after long-term failure"
27030 Special processing happens when an email address has been failing for so long
27031 that the cutoff time for the last algorithm is reached. For example, using the
27032 default retry rule:
27034 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27036 the cutoff time is four days. Reaching the retry cutoff is independent of how
27037 long any specific message has been failing; it is the length of continuous
27038 failure for the recipient address that counts.
27040 When the cutoff time is reached for a local delivery, or for all the IP
27041 addresses associated with a remote delivery, a subsequent delivery failure
27042 causes Exim to give up on the address, and a bounce message is generated.
27043 In order to cater for new messages that use the failing address, a next retry
27044 time is still computed from the final algorithm, and is used as follows:
27046 For local deliveries, one delivery attempt is always made for any subsequent
27047 messages. If this delivery fails, the address fails immediately. The
27048 post-cutoff retry time is not used.
27050 .cindex "final cutoff" "retries, controlling"
27051 .cindex retry "final cutoff"
27052 If the delivery is remote, there are two possibilities, controlled by the
27053 .oindex "&%delay_after_cutoff%&"
27054 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27055 default. Until the post-cutoff retry time for one of the IP addresses,
27056 as set by the &%retry_data_expire%& option, is
27057 reached, the failing email address is bounced immediately, without a delivery
27058 attempt taking place. After that time, one new delivery attempt is made to
27059 those IP addresses that are past their retry times, and if that still fails,
27060 the address is bounced and new retry times are computed.
27062 In other words, when all the hosts for a given email address have been failing
27063 for a long time, Exim bounces rather then defers until one of the hosts' retry
27064 times is reached. Then it tries once, and bounces if that attempt fails. This
27065 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27066 to a broken destination, but if the host does recover, Exim will eventually
27069 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27070 addresses are past their final cutoff time, Exim tries to deliver to those IP
27071 addresses that have not been tried since the message arrived. If there are
27072 no suitable IP addresses, or if they all fail, the address is bounced. In other
27073 words, it does not delay when a new message arrives, but tries the expired
27074 addresses immediately, unless they have been tried since the message arrived.
27075 If there is a continuous stream of messages for the failing domains, setting
27076 &%delay_after_cutoff%& false means that there will be many more attempts to
27077 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27080 .section "Deliveries that work intermittently" "SECID167"
27081 .cindex "retry" "intermittently working deliveries"
27082 Some additional logic is needed to cope with cases where a host is
27083 intermittently available, or when a message has some attribute that prevents
27084 its delivery when others to the same address get through. In this situation,
27085 because some messages are successfully delivered, the &"retry clock"& for the
27086 host or address keeps getting reset by the successful deliveries, and so
27087 failing messages remain in the queue for ever because the cutoff time is never
27090 Two exceptional actions are applied to prevent this happening. The first
27091 applies to errors that are related to a message rather than a remote host.
27092 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27093 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27094 commands, and quota failures. For this type of error, if a message's arrival
27095 time is earlier than the &"first failed"& time for the error, the earlier time
27096 is used when scanning the retry rules to decide when to try next and when to
27097 time out the address.
27099 The exceptional second action applies in all cases. If a message has been on
27100 the queue for longer than the cutoff time of any applicable retry rule for a
27101 given address, a delivery is attempted for that address, even if it is not yet
27102 time, and if this delivery fails, the address is timed out. A new retry time is
27103 not computed in this case, so that other messages for the same address are
27104 considered immediately.
27105 .ecindex IIDretconf1
27106 .ecindex IIDregconf2
27113 . ////////////////////////////////////////////////////////////////////////////
27114 . ////////////////////////////////////////////////////////////////////////////
27116 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27117 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27118 .scindex IIDauthconf2 "authentication"
27119 The &"authenticators"& section of Exim's runtime configuration is concerned
27120 with SMTP authentication. This facility is an extension to the SMTP protocol,
27121 described in RFC 2554, which allows a client SMTP host to authenticate itself
27122 to a server. This is a common way for a server to recognize clients that are
27123 permitted to use it as a relay. SMTP authentication is not of relevance to the
27124 transfer of mail between servers that have no managerial connection with each
27127 .cindex "AUTH" "description of"
27128 .cindex "ESMTP extensions" AUTH
27129 Very briefly, the way SMTP authentication works is as follows:
27132 The server advertises a number of authentication &'mechanisms'& in response to
27133 the client's EHLO command.
27135 The client issues an AUTH command, naming a specific mechanism. The command
27136 may, optionally, contain some authentication data.
27138 The server may issue one or more &'challenges'&, to which the client must send
27139 appropriate responses. In simple authentication mechanisms, the challenges are
27140 just prompts for user names and passwords. The server does not have to issue
27141 any challenges &-- in some mechanisms the relevant data may all be transmitted
27142 with the AUTH command.
27144 The server either accepts or denies authentication.
27146 If authentication succeeds, the client may optionally make use of the AUTH
27147 option on the MAIL command to pass an authenticated sender in subsequent
27148 mail transactions. Authentication lasts for the remainder of the SMTP
27151 If authentication fails, the client may give up, or it may try a different
27152 authentication mechanism, or it may try transferring mail over the
27153 unauthenticated connection.
27156 If you are setting up a client, and want to know which authentication
27157 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27158 SMTP port) on the server, and issue an EHLO command. The response to this
27159 includes the list of supported mechanisms. For example:
27161 &`$ `&&*&`telnet server.example 25`&*&
27162 &`Trying 192.168.34.25...`&
27163 &`Connected to server.example.`&
27164 &`Escape character is '^]'.`&
27165 &`220 server.example ESMTP Exim 4.20 ...`&
27166 &*&`ehlo client.example`&*&
27167 &`250-server.example Hello client.example [10.8.4.5]`&
27168 &`250-SIZE 52428800`&
27173 The second-last line of this example output shows that the server supports
27174 authentication using the PLAIN mechanism. In Exim, the different authentication
27175 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27176 routers and transports, which authenticators are included in the binary is
27177 controlled by build-time definitions. The following are currently available,
27178 included by setting
27181 AUTH_CYRUS_SASL=yes
27185 AUTH_HEIMDAL_GSSAPI=yes
27190 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27191 authentication mechanism (RFC 2195), and the second provides an interface to
27192 the Cyrus SASL authentication library.
27193 The third is an interface to Dovecot's authentication system, delegating the
27194 work via a socket interface.
27195 The fourth provides for negotiation of authentication done via non-SMTP means,
27196 as defined by RFC 4422 Appendix A.
27197 The fifth provides an interface to the GNU SASL authentication library, which
27198 provides mechanisms but typically not data sources.
27199 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27200 supporting setting a server keytab.
27201 The seventh can be configured to support
27202 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27203 not formally documented, but used by several MUAs.
27204 The eighth authenticator
27205 supports Microsoft's &'Secure Password Authentication'& mechanism.
27206 The last is an Exim authenticator but not an SMTP one;
27207 instead it can use information from a TLS negotiation.
27209 The authenticators are configured using the same syntax as other drivers (see
27210 section &<<SECTfordricon>>&). If no authenticators are required, no
27211 authentication section need be present in the configuration file. Each
27212 authenticator can in principle have both server and client functions. When Exim
27213 is receiving SMTP mail, it is acting as a server; when it is sending out
27214 messages over SMTP, it is acting as a client. Authenticator configuration
27215 options are provided for use in both these circumstances.
27217 To make it clear which options apply to which situation, the prefixes
27218 &%server_%& and &%client_%& are used on option names that are specific to
27219 either the server or the client function, respectively. Server and client
27220 functions are disabled if none of their options are set. If an authenticator is
27221 to be used for both server and client functions, a single definition, using
27222 both sets of options, is required. For example:
27226 public_name = CRAM-MD5
27227 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27229 client_secret = secret2
27231 The &%server_%& option is used when Exim is acting as a server, and the
27232 &%client_%& options when it is acting as a client.
27234 Descriptions of the individual authenticators are given in subsequent chapters.
27235 The remainder of this chapter covers the generic options for the
27236 authenticators, followed by general discussion of the way authentication works
27239 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27240 per-mechanism basis. Please read carefully to determine which variables hold
27241 account labels such as usercodes and which hold passwords or other
27242 authenticating data.
27244 Note that some mechanisms support two different identifiers for accounts: the
27245 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27246 and &'authz'& are commonly encountered. The American spelling is standard here.
27247 Conceptually, authentication data such as passwords are tied to the identifier
27248 used to authenticate; servers may have rules to permit one user to act as a
27249 second user, so that after login the session is treated as though that second
27250 user had logged in. That second user is the &'authorization id'&. A robust
27251 configuration might confirm that the &'authz'& field is empty or matches the
27252 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27253 as verified data, the &'authz'& as an unverified request which the server might
27256 A &'realm'& is a text string, typically a domain name, presented by a server
27257 to a client to help it select an account and credentials to use. In some
27258 mechanisms, the client and server provably agree on the realm, but clients
27259 typically can not treat the realm as secure data to be blindly trusted.
27263 .section "Generic options for authenticators" "SECID168"
27264 .cindex "authentication" "generic options"
27265 .cindex "options" "generic; for authenticators"
27267 .option client_condition authenticators string&!! unset
27268 When Exim is authenticating as a client, it skips any authenticator whose
27269 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27270 used, for example, to skip plain text authenticators when the connection is not
27271 encrypted by a setting such as:
27273 client_condition = ${if !eq{$tls_out_cipher}{}}
27277 .option client_set_id authenticators string&!! unset
27278 When client authentication succeeds, this condition is expanded; the
27279 result is used in the log lines for outbound messages.
27280 Typically it will be the user name used for authentication.
27283 .option driver authenticators string unset
27284 This option must always be set. It specifies which of the available
27285 authenticators is to be used.
27288 .option public_name authenticators string unset
27289 This option specifies the name of the authentication mechanism that the driver
27290 implements, and by which it is known to the outside world. These names should
27291 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27292 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27293 defaults to the driver's instance name.
27296 .option server_advertise_condition authenticators string&!! unset
27297 When a server is about to advertise an authentication mechanism, the condition
27298 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27299 mechanism is not advertised.
27300 If the expansion fails, the mechanism is not advertised. If the failure was not
27301 forced, and was not caused by a lookup defer, the incident is logged.
27302 See section &<<SECTauthexiser>>& below for further discussion.
27305 .option server_condition authenticators string&!! unset
27306 This option must be set for a &%plaintext%& server authenticator, where it
27307 is used directly to control authentication. See section &<<SECTplainserver>>&
27310 For the &(gsasl)& authenticator, this option is required for various
27311 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27313 For the other authenticators, &%server_condition%& can be used as an additional
27314 authentication or authorization mechanism that is applied after the other
27315 authenticator conditions succeed. If it is set, it is expanded when the
27316 authenticator would otherwise return a success code. If the expansion is forced
27317 to fail, authentication fails. Any other expansion failure causes a temporary
27318 error code to be returned. If the result of a successful expansion is an empty
27319 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27320 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27321 other result, a temporary error code is returned, with the expanded string as
27325 .option server_debug_print authenticators string&!! unset
27326 If this option is set and authentication debugging is enabled (see the &%-d%&
27327 command line option), the string is expanded and included in the debugging
27328 output when the authenticator is run as a server. This can help with checking
27329 out the values of variables.
27330 If expansion of the string fails, the error message is written to the debugging
27331 output, and Exim carries on processing.
27334 .option server_set_id authenticators string&!! unset
27335 .vindex "&$authenticated_id$&"
27336 .vindex "&$authenticated_fail_id$&"
27337 When an Exim server successfully authenticates a client, this string is
27338 expanded using data from the authentication, and preserved for any incoming
27339 messages in the variable &$authenticated_id$&. It is also included in the log
27340 lines for incoming messages. For example, a user/password authenticator
27341 configuration might preserve the user name that was used to authenticate, and
27342 refer to it subsequently during delivery of the message.
27343 On a failing authentication the expansion result is instead saved in
27344 the &$authenticated_fail_id$& variable.
27345 If expansion fails, the option is ignored.
27348 .option server_mail_auth_condition authenticators string&!! unset
27349 This option allows a server to discard authenticated sender addresses supplied
27350 as part of MAIL commands in SMTP connections that are authenticated by the
27351 driver on which &%server_mail_auth_condition%& is set. The option is not used
27352 as part of the authentication process; instead its (unexpanded) value is
27353 remembered for later use.
27354 How it is used is described in the following section.
27360 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27361 .cindex "authentication" "sender; authenticated"
27362 .cindex "AUTH" "on MAIL command"
27363 When a client supplied an AUTH= item on a MAIL command, Exim applies
27364 the following checks before accepting it as the authenticated sender of the
27368 If the connection is not using extended SMTP (that is, HELO was used rather
27369 than EHLO), the use of AUTH= is a syntax error.
27371 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27373 .vindex "&$authenticated_sender$&"
27374 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27375 running, the value of &$authenticated_sender$& is set to the value obtained
27376 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27377 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27378 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27379 given for the MAIL command.
27381 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27382 is accepted and placed in &$authenticated_sender$& only if the client has
27385 If the AUTH= value was accepted by either of the two previous rules, and
27386 the client has authenticated, and the authenticator has a setting for the
27387 &%server_mail_auth_condition%&, the condition is checked at this point. The
27388 valued that was saved from the authenticator is expanded. If the expansion
27389 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27390 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27391 the value of &$authenticated_sender$& is retained and passed on with the
27396 When &$authenticated_sender$& is set for a message, it is passed on to other
27397 hosts to which Exim authenticates as a client. Do not confuse this value with
27398 &$authenticated_id$&, which is a string obtained from the authentication
27399 process, and which is not usually a complete email address.
27401 .vindex "&$sender_address$&"
27402 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27403 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27404 therefore make use of &$authenticated_sender$&. The converse is not true: the
27405 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27410 .section "Authentication on an Exim server" "SECTauthexiser"
27411 .cindex "authentication" "on an Exim server"
27412 When Exim receives an EHLO command, it advertises the public names of those
27413 authenticators that are configured as servers, subject to the following
27417 The client host must match &%auth_advertise_hosts%& (default *).
27419 If the &%server_advertise_condition%& option is set, its expansion must not
27420 yield the empty string, &"0"&, &"no"&, or &"false"&.
27423 The order in which the authenticators are defined controls the order in which
27424 the mechanisms are advertised.
27426 Some mail clients (for example, some versions of Netscape) require the user to
27427 provide a name and password for authentication whenever AUTH is advertised,
27428 even though authentication may not in fact be needed (for example, Exim may be
27429 set up to allow unconditional relaying from the client by an IP address check).
27430 You can make such clients more friendly by not advertising AUTH to them.
27431 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27432 that runs for RCPT) to relay without authentication, you should set
27434 auth_advertise_hosts = ! 10.9.8.0/24
27436 so that no authentication mechanisms are advertised to them.
27438 The &%server_advertise_condition%& controls the advertisement of individual
27439 authentication mechanisms. For example, it can be used to restrict the
27440 advertisement of a particular mechanism to encrypted connections, by a setting
27443 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27445 .vindex "&$tls_in_cipher$&"
27446 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27447 yields &"yes"&, which allows the advertisement to happen.
27449 When an Exim server receives an AUTH command from a client, it rejects it
27450 immediately if AUTH was not advertised in response to an earlier EHLO
27451 command. This is the case if
27454 The client host does not match &%auth_advertise_hosts%&; or
27456 No authenticators are configured with server options; or
27458 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27459 server authenticators.
27463 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27464 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27465 AUTH is accepted from any client host.
27467 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27468 server authentication mechanism that was advertised in response to EHLO and
27469 that matches the one named in the AUTH command. If it finds one, it runs
27470 the appropriate authentication protocol, and authentication either succeeds or
27471 fails. If there is no matching advertised mechanism, the AUTH command is
27472 rejected with a 504 error.
27474 .vindex "&$received_protocol$&"
27475 .vindex "&$sender_host_authenticated$&"
27476 When a message is received from an authenticated host, the value of
27477 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27478 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27479 public name) of the authenticator driver that successfully authenticated the
27480 client from which the message was received. This variable is empty if there was
27481 no successful authentication.
27483 .cindex authentication "expansion item"
27484 Successful authentication sets up information used by the
27485 &%authresults%& expansion item.
27490 .section "Testing server authentication" "SECID169"
27491 .cindex "authentication" "testing a server"
27492 .cindex "AUTH" "testing a server"
27493 .cindex "base64 encoding" "creating authentication test data"
27494 Exim's &%-bh%& option can be useful for testing server authentication
27495 configurations. The data for the AUTH command has to be sent using base64
27496 encoding. A quick way to produce such data for testing is the following Perl
27500 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27502 .cindex "binary zero" "in authentication data"
27503 This interprets its argument as a Perl string, and then encodes it. The
27504 interpretation as a Perl string allows binary zeros, which are required for
27505 some kinds of authentication, to be included in the data. For example, a
27506 command line to run this script on such data might be
27508 encode '\0user\0password'
27510 Note the use of single quotes to prevent the shell interpreting the
27511 backslashes, so that they can be interpreted by Perl to specify characters
27512 whose code value is zero.
27514 &*Warning 1*&: If either of the user or password strings starts with an octal
27515 digit, you must use three zeros instead of one after the leading backslash. If
27516 you do not, the octal digit that starts your string will be incorrectly
27517 interpreted as part of the code for the first character.
27519 &*Warning 2*&: If there are characters in the strings that Perl interprets
27520 specially, you must use a Perl escape to prevent them being misinterpreted. For
27521 example, a command such as
27523 encode '\0user@domain.com\0pas$$word'
27525 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27527 If you have the &%mimencode%& command installed, another way to produce
27528 base64-encoded strings is to run the command
27530 echo -e -n `\0user\0password' | mimencode
27532 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27533 in the argument, and the &%-n%& option specifies no newline at the end of its
27534 output. However, not all versions of &%echo%& recognize these options, so you
27535 should check your version before relying on this suggestion.
27539 .section "Authentication by an Exim client" "SECID170"
27540 .cindex "authentication" "on an Exim client"
27541 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27542 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27543 announces support for authentication, and the host matches an entry in either
27544 of these options, Exim (as a client) tries to authenticate as follows:
27547 For each authenticator that is configured as a client, in the order in which
27548 they are defined in the configuration, it searches the authentication
27549 mechanisms announced by the server for one whose name matches the public name
27550 of the authenticator.
27553 .vindex "&$host_address$&"
27554 When it finds one that matches, it runs the authenticator's client code. The
27555 variables &$host$& and &$host_address$& are available for any string expansions
27556 that the client might do. They are set to the server's name and IP address. If
27557 any expansion is forced to fail, the authentication attempt is abandoned, and
27558 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27559 delivery to be deferred.
27561 If the result of the authentication attempt is a temporary error or a timeout,
27562 Exim abandons trying to send the message to the host for the moment. It will
27563 try again later. If there are any backup hosts available, they are tried in the
27566 If the response to authentication is a permanent error (5&'xx'& code), Exim
27567 carries on searching the list of authenticators and tries another one if
27568 possible. If all authentication attempts give permanent errors, or if there are
27569 no attempts because no mechanisms match (or option expansions force failure),
27570 what happens depends on whether the host matches &%hosts_require_auth%& or
27571 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27572 delivery is deferred. The error can be detected in the retry rules, and thereby
27573 turned into a permanent error if you wish. In the second case, Exim tries to
27574 deliver the message unauthenticated.
27577 Note that the hostlist test for whether to do authentication can be
27578 confused if name-IP lookups change between the time the peer is decided
27579 upon and the time that the transport runs. For example, with a manualroute
27580 router given a host name, and with DNS "round-robin" used by that name: if
27581 the local resolver cache times out between the router and the transport
27582 running, the transport may get an IP for the name for its authentication
27583 check which does not match the connection peer IP.
27584 No authentication will then be done, despite the names being identical.
27586 For such cases use a separate transport which always authenticates.
27588 .cindex "AUTH" "on MAIL command"
27589 When Exim has authenticated itself to a remote server, it adds the AUTH
27590 parameter to the MAIL commands it sends, if it has an authenticated sender for
27591 the message. If the message came from a remote host, the authenticated sender
27592 is the one that was receiving on an incoming MAIL command, provided that the
27593 incoming connection was authenticated and the &%server_mail_auth%& condition
27594 allowed the authenticated sender to be retained. If a local process calls Exim
27595 to send a message, the sender address that is built from the login name and
27596 &%qualify_domain%& is treated as authenticated. However, if the
27597 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27598 the authenticated sender that was received with the message.
27599 .ecindex IIDauthconf1
27600 .ecindex IIDauthconf2
27607 . ////////////////////////////////////////////////////////////////////////////
27608 . ////////////////////////////////////////////////////////////////////////////
27610 .chapter "The plaintext authenticator" "CHAPplaintext"
27611 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27612 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27613 The &(plaintext)& authenticator can be configured to support the PLAIN and
27614 LOGIN authentication mechanisms, both of which transfer authentication data as
27615 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27616 security risk; you are strongly advised to insist on the use of SMTP encryption
27617 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27618 use unencrypted plain text, you should not use the same passwords for SMTP
27619 connections as you do for login accounts.
27621 .section "Avoiding cleartext use" "SECTplain_TLS"
27622 The following generic option settings will disable &(plaintext)& authenticators when
27623 TLS is not being used:
27625 server_advertise_condition = ${if def:tls_in_cipher }
27626 client_condition = ${if def:tls_out_cipher}
27629 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27630 but is still vulnerable to a Man In The Middle attack unless certificates
27631 (including their names) have been properly verified.
27633 .section "Plaintext server options" "SECID171"
27634 .cindex "options" "&(plaintext)& authenticator (server)"
27635 When configured as a server, &(plaintext)& uses the following options:
27637 .option server_condition authenticators string&!! unset
27638 This is actually a global authentication option, but it must be set in order to
27639 configure the &(plaintext)& driver as a server. Its use is described below.
27641 .option server_prompts plaintext "string list&!!" unset
27642 The contents of this option, after expansion, must be a colon-separated list of
27643 prompt strings. If expansion fails, a temporary authentication rejection is
27646 .section "Using plaintext in a server" "SECTplainserver"
27647 .cindex "AUTH" "in &(plaintext)& authenticator"
27648 .cindex "binary zero" "in &(plaintext)& authenticator"
27649 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27650 "in &(plaintext)& authenticator"
27651 .vindex "&$auth1$&, &$auth2$&, etc"
27652 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27654 When running as a server, &(plaintext)& performs the authentication test by
27655 expanding a string. The data sent by the client with the AUTH command, or in
27656 response to subsequent prompts, is base64 encoded, and so may contain any byte
27657 values when decoded. If any data is supplied with the command, it is treated as
27658 a list of strings, separated by NULs (binary zeros), the first three of which
27659 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27660 (neither LOGIN nor PLAIN uses more than three strings).
27662 For compatibility with previous releases of Exim, the values are also placed in
27663 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27664 variables for this purpose is now deprecated, as it can lead to confusion in
27665 string expansions that also use them for other things.
27667 If there are more strings in &%server_prompts%& than the number of strings
27668 supplied with the AUTH command, the remaining prompts are used to obtain more
27669 data. Each response from the client may be a list of NUL-separated strings.
27671 .vindex "&$authenticated_id$&"
27672 Once a sufficient number of data strings have been received,
27673 &%server_condition%& is expanded. If the expansion is forced to fail,
27674 authentication fails. Any other expansion failure causes a temporary error code
27675 to be returned. If the result of a successful expansion is an empty string,
27676 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27677 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27678 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27679 For any other result, a temporary error code is returned, with the expanded
27680 string as the error text.
27682 &*Warning*&: If you use a lookup in the expansion to find the user's
27683 password, be sure to make the authentication fail if the user is unknown.
27684 There are good and bad examples at the end of the next section.
27688 .section "The PLAIN authentication mechanism" "SECID172"
27689 .cindex "PLAIN authentication mechanism"
27690 .cindex authentication PLAIN
27691 .cindex "binary zero" "in &(plaintext)& authenticator"
27692 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27693 sent as one item of data (that is, one combined string containing two NUL
27694 separators). The data is sent either as part of the AUTH command, or
27695 subsequently in response to an empty prompt from the server.
27697 The second and third strings are a user name and a corresponding password.
27698 Using a single fixed user name and password as an example, this could be
27699 configured as follows:
27703 public_name = PLAIN
27705 server_condition = \
27706 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27707 server_set_id = $auth2
27709 Note that the default result strings from &%if%& (&"true"& or an empty string)
27710 are exactly what we want here, so they need not be specified. Obviously, if the
27711 password contains expansion-significant characters such as dollar, backslash,
27712 or closing brace, they have to be escaped.
27714 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27715 the end of a string list are ignored). If all the data comes as part of the
27716 AUTH command, as is commonly the case, the prompt is not used. This
27717 authenticator is advertised in the response to EHLO as
27721 and a client host can authenticate itself by sending the command
27723 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27725 As this contains three strings (more than the number of prompts), no further
27726 data is required from the client. Alternatively, the client may just send
27730 to initiate authentication, in which case the server replies with an empty
27731 prompt. The client must respond with the combined data string.
27733 The data string is base64 encoded, as required by the RFC. This example,
27734 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27735 represents a zero byte. This is split up into three strings, the first of which
27736 is empty. The &%server_condition%& option in the authenticator checks that the
27737 second two are &`username`& and &`mysecret`& respectively.
27739 Having just one fixed user name and password, as in this example, is not very
27740 realistic, though for a small organization with only a handful of
27741 authenticating clients it could make sense.
27743 A more sophisticated instance of this authenticator could use the user name in
27744 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27745 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27746 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27747 This is an incorrect example:
27749 server_condition = \
27750 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27752 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27753 which it then compares to the supplied password (&$auth3$&). Why is this example
27754 incorrect? It works fine for existing users, but consider what happens if a
27755 non-existent user name is given. The lookup fails, but as no success/failure
27756 strings are given for the lookup, it yields an empty string. Thus, to defeat
27757 the authentication, all a client has to do is to supply a non-existent user
27758 name and an empty password. The correct way of writing this test is:
27760 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27761 {${if eq{$value}{$auth3}}} {false}}
27763 In this case, if the lookup succeeds, the result is checked; if the lookup
27764 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27765 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27766 always fails if its second argument is empty. However, the second way of
27767 writing the test makes the logic clearer.
27770 .section "The LOGIN authentication mechanism" "SECID173"
27771 .cindex "LOGIN authentication mechanism"
27772 .cindex authentication LOGIN
27773 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27774 in a number of programs. No data is sent with the AUTH command. Instead, a
27775 user name and password are supplied separately, in response to prompts. The
27776 plaintext authenticator can be configured to support this as in this example:
27780 public_name = LOGIN
27781 server_prompts = User Name : Password
27782 server_condition = \
27783 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27784 server_set_id = $auth1
27786 Because of the way plaintext operates, this authenticator accepts data supplied
27787 with the AUTH command (in contravention of the specification of LOGIN), but
27788 if the client does not supply it (as is the case for LOGIN clients), the prompt
27789 strings are used to obtain two data items.
27791 Some clients are very particular about the precise text of the prompts. For
27792 example, Outlook Express is reported to recognize only &"Username:"& and
27793 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27794 strings. It uses the &%ldapauth%& expansion condition to check the user
27795 name and password by binding to an LDAP server:
27799 public_name = LOGIN
27800 server_prompts = Username:: : Password::
27801 server_condition = ${if and{{ \
27804 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27805 pass=${quote:$auth2} \
27806 ldap://ldap.example.org/} }} }
27807 server_set_id = uid=$auth1,ou=people,o=example.org
27809 We have to check that the username is not empty before using it, because LDAP
27810 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27811 operator to correctly quote the DN for authentication. However, the basic
27812 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27813 correct one to use for the password, because quoting is needed only to make
27814 the password conform to the Exim syntax. At the LDAP level, the password is an
27815 uninterpreted string.
27818 .section "Support for different kinds of authentication" "SECID174"
27819 A number of string expansion features are provided for the purpose of
27820 interfacing to different ways of user authentication. These include checking
27821 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27822 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27828 .section "Using plaintext in a client" "SECID175"
27829 .cindex "options" "&(plaintext)& authenticator (client)"
27830 The &(plaintext)& authenticator has two client options:
27832 .option client_ignore_invalid_base64 plaintext boolean false
27833 If the client receives a server prompt that is not a valid base64 string,
27834 authentication is abandoned by default. However, if this option is set true,
27835 the error in the challenge is ignored and the client sends the response as
27838 .option client_send plaintext string&!! unset
27839 The string is a colon-separated list of authentication data strings. Each
27840 string is independently expanded before being sent to the server. The first
27841 string is sent with the AUTH command; any more strings are sent in response
27842 to prompts from the server. Before each string is expanded, the value of the
27843 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27844 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27845 way. Thus, the prompt that is received in response to sending the first string
27846 (with the AUTH command) can be used in the expansion of the second string, and
27847 so on. If an invalid base64 string is received when
27848 &%client_ignore_invalid_base64%& is set, an empty string is put in the
27849 &$auth$&<&'n'&> variable.
27851 &*Note*&: You cannot use expansion to create multiple strings, because
27852 splitting takes priority and happens first.
27854 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
27855 the data, further processing is applied to each string before it is sent. If
27856 there are any single circumflex characters in the string, they are converted to
27857 NULs. Should an actual circumflex be required as data, it must be doubled in
27860 This is an example of a client configuration that implements the PLAIN
27861 authentication mechanism with a fixed user name and password:
27865 public_name = PLAIN
27866 client_send = ^username^mysecret
27868 The lack of colons means that the entire text is sent with the AUTH
27869 command, with the circumflex characters converted to NULs.
27871 Note that due to the ambiguity of parsing three consectutive circumflex characters
27872 there is no way to provide a password having a leading circumflex.
27877 that uses the LOGIN mechanism is:
27881 public_name = LOGIN
27882 client_send = : username : mysecret
27884 The initial colon means that the first string is empty, so no data is sent with
27885 the AUTH command itself. The remaining strings are sent in response to
27887 .ecindex IIDplaiauth1
27888 .ecindex IIDplaiauth2
27893 . ////////////////////////////////////////////////////////////////////////////
27894 . ////////////////////////////////////////////////////////////////////////////
27896 .chapter "The cram_md5 authenticator" "CHID9"
27897 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
27898 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
27899 .cindex "CRAM-MD5 authentication mechanism"
27900 .cindex authentication CRAM-MD5
27901 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
27902 sends a challenge string to the client, and the response consists of a user
27903 name and the CRAM-MD5 digest of the challenge string combined with a secret
27904 string (password) which is known to both server and client. Thus, the secret
27905 is not sent over the network as plain text, which makes this authenticator more
27906 secure than &(plaintext)&. However, the downside is that the secret has to be
27907 available in plain text at either end.
27910 .section "Using cram_md5 as a server" "SECID176"
27911 .cindex "options" "&(cram_md5)& authenticator (server)"
27912 This authenticator has one server option, which must be set to configure the
27913 authenticator as a server:
27915 .option server_secret cram_md5 string&!! unset
27916 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
27917 When the server receives the client's response, the user name is placed in
27918 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
27919 obtain the password for that user. The server then computes the CRAM-MD5 digest
27920 that the client should have sent, and checks that it received the correct
27921 string. If the expansion of &%server_secret%& is forced to fail, authentication
27922 fails. If the expansion fails for some other reason, a temporary error code is
27923 returned to the client.
27925 For compatibility with previous releases of Exim, the user name is also placed
27926 in &$1$&. However, the use of this variables for this purpose is now
27927 deprecated, as it can lead to confusion in string expansions that also use
27928 numeric variables for other things.
27930 For example, the following authenticator checks that the user name given by the
27931 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
27932 user name, authentication fails.
27936 public_name = CRAM-MD5
27937 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
27938 server_set_id = $auth1
27940 .vindex "&$authenticated_id$&"
27941 If authentication succeeds, the setting of &%server_set_id%& preserves the user
27942 name in &$authenticated_id$&. A more typical configuration might look up the
27943 secret string in a file, using the user name as the key. For example:
27947 public_name = CRAM-MD5
27948 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
27950 server_set_id = $auth1
27952 Note that this expansion explicitly forces failure if the lookup fails
27953 because &$auth1$& contains an unknown user name.
27955 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
27956 using the relevant libraries, you need to know the realm to specify in the
27957 lookup and then ask for the &"userPassword"& attribute for that user in that
27962 public_name = CRAM-MD5
27963 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
27964 dbmjz{/etc/sasldb2}{$value}fail}
27965 server_set_id = $auth1
27968 .section "Using cram_md5 as a client" "SECID177"
27969 .cindex "options" "&(cram_md5)& authenticator (client)"
27970 When used as a client, the &(cram_md5)& authenticator has two options:
27974 .option client_name cram_md5 string&!! "the primary host name"
27975 This string is expanded, and the result used as the user name data when
27976 computing the response to the server's challenge.
27979 .option client_secret cram_md5 string&!! unset
27980 This option must be set for the authenticator to work as a client. Its value is
27981 expanded and the result used as the secret string when computing the response.
27985 .vindex "&$host_address$&"
27986 Different user names and secrets can be used for different servers by referring
27987 to &$host$& or &$host_address$& in the options. Forced failure of either
27988 expansion string is treated as an indication that this authenticator is not
27989 prepared to handle this case. Exim moves on to the next configured client
27990 authenticator. Any other expansion failure causes Exim to give up trying to
27991 send the message to the current server.
27993 A simple example configuration of a &(cram_md5)& authenticator, using fixed
27998 public_name = CRAM-MD5
28000 client_secret = secret
28002 .ecindex IIDcramauth1
28003 .ecindex IIDcramauth2
28007 . ////////////////////////////////////////////////////////////////////////////
28008 . ////////////////////////////////////////////////////////////////////////////
28010 .chapter "The cyrus_sasl authenticator" "CHID10"
28011 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28012 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28013 .cindex "Cyrus" "SASL library"
28015 The code for this authenticator was provided by Matthew Byng-Maddick while
28016 at A L Digital Ltd.
28018 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28019 library implementation of the RFC 2222 (&"Simple Authentication and Security
28020 Layer"&). This library supports a number of authentication mechanisms,
28021 including PLAIN and LOGIN, but also several others that Exim does not support
28022 directly. In particular, there is support for Kerberos authentication.
28024 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28025 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28026 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28027 name of the driver to determine which mechanism to support.
28029 Where access to some kind of secret file is required, for example, in GSSAPI
28030 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28031 user, and that the Cyrus SASL library has no way of escalating privileges
28032 by default. You may also find you need to set environment variables,
28033 depending on the driver you are using.
28035 The application name provided by Exim is &"exim"&, so various SASL options may
28036 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28037 Kerberos, note that because of limitations in the GSSAPI interface,
28038 changing the server keytab might need to be communicated down to the Kerberos
28039 layer independently. The mechanism for doing so is dependent upon the Kerberos
28042 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28043 may be set to point to an alternative keytab file. Exim will pass this
28044 variable through from its own inherited environment when started as root or the
28045 Exim user. The keytab file needs to be readable by the Exim user.
28046 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28047 environment variable. In practice, for those releases, the Cyrus authenticator
28048 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28049 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28052 .section "Using cyrus_sasl as a server" "SECID178"
28053 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28054 (on a successful authentication) into &$auth1$&. For compatibility with
28055 previous releases of Exim, the username is also placed in &$1$&. However, the
28056 use of this variable for this purpose is now deprecated, as it can lead to
28057 confusion in string expansions that also use numeric variables for other
28061 .option server_hostname cyrus_sasl string&!! "see below"
28062 This option selects the hostname that is used when communicating with the
28063 library. The default value is &`$primary_hostname`&. It is up to the underlying
28064 SASL plug-in what it does with this data.
28067 .option server_mech cyrus_sasl string "see below"
28068 This option selects the authentication mechanism this driver should use. The
28069 default is the value of the generic &%public_name%& option. This option allows
28070 you to use a different underlying mechanism from the advertised name. For
28074 driver = cyrus_sasl
28075 public_name = X-ANYTHING
28076 server_mech = CRAM-MD5
28077 server_set_id = $auth1
28080 .option server_realm cyrus_sasl string&!! unset
28081 This specifies the SASL realm that the server claims to be in.
28084 .option server_service cyrus_sasl string &`smtp`&
28085 This is the SASL service that the server claims to implement.
28088 For straightforward cases, you do not need to set any of the authenticator's
28089 private options. All you need to do is to specify an appropriate mechanism as
28090 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28091 PLAIN, you could have two authenticators as follows:
28094 driver = cyrus_sasl
28095 public_name = CRAM-MD5
28096 server_set_id = $auth1
28099 driver = cyrus_sasl
28100 public_name = PLAIN
28101 server_set_id = $auth2
28103 Cyrus SASL does implement the LOGIN authentication method, even though it is
28104 not a standard method. It is disabled by default in the source distribution,
28105 but it is present in many binary distributions.
28106 .ecindex IIDcyrauth1
28107 .ecindex IIDcyrauth2
28112 . ////////////////////////////////////////////////////////////////////////////
28113 . ////////////////////////////////////////////////////////////////////////////
28114 .chapter "The dovecot authenticator" "CHAPdovecot"
28115 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28116 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28117 This authenticator is an interface to the authentication facility of the
28118 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28119 Note that Dovecot must be configured to use auth-client not auth-userdb.
28120 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28121 to use the same mechanisms for SMTP authentication. This is a server
28122 authenticator only. There is only one option:
28124 .option server_socket dovecot string unset
28126 This option must specify the UNIX socket that is the interface to Dovecot
28127 authentication. The &%public_name%& option must specify an authentication
28128 mechanism that Dovecot is configured to support. You can have several
28129 authenticators for different mechanisms. For example:
28133 public_name = PLAIN
28134 server_socket = /var/run/dovecot/auth-client
28135 server_set_id = $auth1
28140 server_socket = /var/run/dovecot/auth-client
28141 server_set_id = $auth1
28143 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28144 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28145 option is passed in the Dovecot authentication command. If, for a TLS
28146 connection, a client certificate has been verified, the &"valid-client-cert"&
28147 option is passed. When authentication succeeds, the identity of the user
28148 who authenticated is placed in &$auth1$&.
28150 The Dovecot configuration to match the above will look
28153 conf.d/10-master.conf :-
28158 unix_listener auth-client {
28165 conf.d/10-auth.conf :-
28167 auth_mechanisms = plain login ntlm
28170 .ecindex IIDdcotauth1
28171 .ecindex IIDdcotauth2
28174 . ////////////////////////////////////////////////////////////////////////////
28175 . ////////////////////////////////////////////////////////////////////////////
28176 .chapter "The gsasl authenticator" "CHAPgsasl"
28177 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28178 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28179 .cindex "authentication" "GNU SASL"
28180 .cindex "authentication" "SASL"
28181 .cindex "authentication" "EXTERNAL"
28182 .cindex "authentication" "ANONYMOUS"
28183 .cindex "authentication" "PLAIN"
28184 .cindex "authentication" "LOGIN"
28185 .cindex "authentication" "DIGEST-MD5"
28186 .cindex "authentication" "CRAM-MD5"
28187 .cindex "authentication" "SCRAM family"
28188 The &(gsasl)& authenticator provides integration for the GNU SASL
28189 library and the mechanisms it provides. This is new as of the 4.80 release
28190 and there are a few areas where the library does not let Exim smoothly
28191 scale to handle future authentication mechanisms, so no guarantee can be
28192 made that any particular new authentication mechanism will be supported
28193 without code changes in Exim.
28195 The library is expected to add support in an upcoming
28196 realease for the SCRAM-SHA-256 method.
28197 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28201 To see the list of mechanisms supported by the library run Exim with "auth" debug
28202 enabled and look for a line containing "GNU SASL supports".
28203 Note however that some may not have been tested from Exim.
28207 .option client_authz gsasl string&!! unset
28208 This option can be used to supply an &'authorization id'&
28209 which is different to the &'authentication_id'& provided
28210 by &%client_username%& option.
28211 If unset or (after expansion) empty it is not used,
28212 which is the common case.
28214 .option client_channelbinding gsasl boolean false
28215 See &%server_channelbinding%& below.
28217 .option client_password gsasl string&!! unset
28218 This option is exapanded before use, and should result in
28219 the password to be used, in clear.
28221 .option client_username gsasl string&!! unset
28222 This option is exapanded before use, and should result in
28223 the account name to be used.
28226 .option client_spassword gsasl string&!! unset
28228 This option is only supported for library versions 1.9.1 and greater.
28229 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28232 If a SCRAM mechanism is being used and this option is set
28233 and correctly sized
28234 it is used in preference to &%client_password%&.
28235 The value after expansion should be
28236 a 40 (for SHA-1) or 64 (for SHA-256) character string
28237 with the PBKDF2-prepared password, hex-encoded.
28239 Note that this value will depend on the salt and iteration-count
28240 supplied by the server.
28241 The option is expanded before use.
28243 During the expansion &$auth1$& is set with the client username,
28244 &$auth2$& with the iteration count, and
28245 &$auth3$& with the salt.
28247 The intent of this option
28248 is to support clients that can cache thes salted password
28249 to save on recalculation costs.
28250 The cache lookup should return an unusable value
28251 (eg. an empty string)
28252 if the salt or iteration count has changed
28254 If the authentication succeeds then the above variables are set,
28255 .vindex "&$auth4$&"
28256 plus the calculated salted password value value in &$auth4$&,
28257 during the expansion of the &%client_set_id%& option.
28258 A side-effect of this expansion can be used to prime the cache.
28262 .option server_channelbinding gsasl boolean false
28263 Some authentication mechanisms are able to use external context at both ends
28264 of the session to bind the authentication to that context, and fail the
28265 authentication process if that context differs. Specifically, some TLS
28266 ciphersuites can provide identifying information about the cryptographic
28269 This should have meant that certificate identity and verification becomes a
28270 non-issue, as a man-in-the-middle attack will cause the correct client and
28271 server to see different identifiers and authentication will fail.
28274 only usable by mechanisms which support "channel binding"; at time of
28275 writing, that's the SCRAM family.
28276 When using this feature the "-PLUS" variants of the method names need to be used.
28278 This defaults off to ensure smooth upgrade across Exim releases, in case
28279 this option causes some clients to start failing. Some future release
28280 of Exim might have switched the default to be true.
28282 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28283 . Do not plan to rely upon this feature for security, ever, without consulting
28284 . with a subject matter expert (a cryptographic engineer).
28287 This option was deprecated in previous releases due to doubts over
28288 the "Triple Handshake" vulnerability.
28289 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28290 Session Resumption was used) for safety.
28294 .option server_hostname gsasl string&!! "see below"
28295 This option selects the hostname that is used when communicating with the
28296 library. The default value is &`$primary_hostname`&.
28297 Some mechanisms will use this data.
28300 .option server_mech gsasl 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
28308 public_name = X-ANYTHING
28309 server_mech = CRAM-MD5
28310 server_set_id = $auth1
28314 .option server_password gsasl string&!! unset
28315 Various mechanisms need access to the cleartext password on the server, so
28316 that proof-of-possession can be demonstrated on the wire, without sending
28317 the password itself.
28319 The data available for lookup varies per mechanism.
28320 In all cases, &$auth1$& is set to the &'authentication id'&.
28321 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28322 if available, else the empty string.
28323 The &$auth3$& variable will always be the &'realm'& if available,
28324 else the empty string.
28326 A forced failure will cause authentication to defer.
28328 If using this option, it may make sense to set the &%server_condition%&
28329 option to be simply "true".
28332 .option server_realm gsasl string&!! unset
28333 This specifies the SASL realm that the server claims to be in.
28334 Some mechanisms will use this data.
28337 .option server_scram_iter gsasl string&!! 4096
28338 This option provides data for the SCRAM family of mechanisms.
28339 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28340 when this option is expanded.
28342 The result of expansion should be a decimal number,
28343 and represents both a lower-bound on the security, and
28344 a compute cost factor imposed on the client
28345 (if it does not cache results, or the server changes
28346 either the iteration count or the salt).
28347 A minimum value of 4096 is required by the standards
28348 for all current SCRAM mechanism variants.
28350 .option server_scram_salt gsasl string&!! unset
28351 This option provides data for the SCRAM family of mechanisms.
28352 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28353 when this option is expanded.
28354 The value should be a base64-encoded string,
28355 of random data typically 4-to-16 bytes long.
28356 If unset or empty after expansion the library will provides a value for the
28357 protocol conversation.
28360 .option server_key gsasl string&!! unset
28361 .option server_skey gsasl string&!! unset
28362 These options can be used for the SCRAM family of mechanisms
28363 to provide stored information related to a password,
28364 the storage of which is preferable to plaintext.
28366 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28367 &%server_skey%& is StoredKey.
28369 They are only available for version 1.9.0 (or later) of the gsasl library.
28370 When this is so, the macros
28371 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28372 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28375 The &$authN$& variables are available when these options are expanded.
28377 If set, the results of expansion should for each
28378 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28379 of base64-coded data, and will be used in preference to the
28380 &%server_password%& option.
28381 If unset or not of the right length, &%server_password%& will be used.
28383 The libgsasl library release includes a utility &'gsasl'& which can be used
28384 to generate these values.
28387 .option server_service gsasl string &`smtp`&
28388 This is the SASL service that the server claims to implement.
28389 Some mechanisms will use this data.
28392 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28393 .vindex "&$auth1$&, &$auth2$&, etc"
28394 These may be set when evaluating specific options, as detailed above.
28395 They will also be set when evaluating &%server_condition%&.
28397 Unless otherwise stated below, the &(gsasl)& integration will use the following
28398 meanings for these variables:
28401 .vindex "&$auth1$&"
28402 &$auth1$&: the &'authentication id'&
28404 .vindex "&$auth2$&"
28405 &$auth2$&: the &'authorization id'&
28407 .vindex "&$auth3$&"
28408 &$auth3$&: the &'realm'&
28411 On a per-mechanism basis:
28414 .cindex "authentication" "EXTERNAL"
28415 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28416 the &%server_condition%& option must be present.
28418 .cindex "authentication" "ANONYMOUS"
28419 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28420 the &%server_condition%& option must be present.
28422 .cindex "authentication" "GSSAPI"
28423 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28424 &$auth2$& will be set to the &'authorization id'&,
28425 the &%server_condition%& option must be present.
28428 An &'anonymous token'& is something passed along as an unauthenticated
28429 identifier; this is analogous to FTP anonymous authentication passing an
28430 email address, or software-identifier@, as the "password".
28433 An example showing the password having the realm specified in the callback
28434 and demonstrating a Cyrus SASL to GSASL migration approach is:
28436 gsasl_cyrusless_crammd5:
28438 public_name = CRAM-MD5
28439 server_realm = imap.example.org
28440 server_password = ${lookup{$auth1:$auth3:userPassword}\
28441 dbmjz{/etc/sasldb2}{$value}fail}
28442 server_set_id = ${quote:$auth1}
28443 server_condition = yes
28447 . ////////////////////////////////////////////////////////////////////////////
28448 . ////////////////////////////////////////////////////////////////////////////
28450 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28451 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28452 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28453 .cindex "authentication" "GSSAPI"
28454 .cindex "authentication" "Kerberos"
28455 The &(heimdal_gssapi)& authenticator provides server integration for the
28456 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28459 .option server_hostname heimdal_gssapi string&!! "see below"
28460 This option selects the hostname that is used, with &%server_service%&,
28461 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28462 identifier. The default value is &`$primary_hostname`&.
28464 .option server_keytab heimdal_gssapi string&!! unset
28465 If set, then Heimdal will not use the system default keytab (typically
28466 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28467 The value should be a pathname, with no &"file:"& prefix.
28469 .option server_service heimdal_gssapi string&!! "smtp"
28470 This option specifies the service identifier used, in conjunction with
28471 &%server_hostname%&, for building the identifier for finding credentials
28475 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28476 Beware that these variables will typically include a realm, thus will appear
28477 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28478 not verified, so a malicious client can set it to anything.
28480 The &$auth1$& field should be safely trustable as a value from the Key
28481 Distribution Center. Note that these are not quite email addresses.
28482 Each identifier is for a role, and so the left-hand-side may include a
28483 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28485 .vindex "&$auth1$&, &$auth2$&, etc"
28487 .vindex "&$auth1$&"
28488 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28490 .vindex "&$auth2$&"
28491 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28492 authentication. If that was empty, this will also be set to the
28497 . ////////////////////////////////////////////////////////////////////////////
28498 . ////////////////////////////////////////////////////////////////////////////
28500 .chapter "The spa authenticator" "CHAPspa"
28501 .scindex IIDspaauth1 "&(spa)& authenticator"
28502 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28503 .cindex "authentication" "Microsoft Secure Password"
28504 .cindex "authentication" "NTLM"
28505 .cindex "Microsoft Secure Password Authentication"
28506 .cindex "NTLM authentication"
28507 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28508 Password Authentication'& mechanism,
28509 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28510 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28511 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28512 server side was subsequently contributed by Tom Kistner. The mechanism works as
28516 After the AUTH command has been accepted, the client sends an SPA
28517 authentication request based on the user name and optional domain.
28519 The server sends back a challenge.
28521 The client builds a challenge response which makes use of the user's password
28522 and sends it to the server, which then accepts or rejects it.
28525 Encryption is used to protect the password in transit.
28529 .section "Using spa as a server" "SECID179"
28530 .cindex "options" "&(spa)& authenticator (server)"
28531 The &(spa)& authenticator has just one server option:
28533 .option server_password spa string&!! unset
28534 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28535 This option is expanded, and the result must be the cleartext password for the
28536 authenticating user, whose name is at this point in &$auth1$&. For
28537 compatibility with previous releases of Exim, the user name is also placed in
28538 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28539 it can lead to confusion in string expansions that also use numeric variables
28540 for other things. For example:
28545 server_password = \
28546 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28548 If the expansion is forced to fail, authentication fails. Any other expansion
28549 failure causes a temporary error code to be returned.
28555 .section "Using spa as a client" "SECID180"
28556 .cindex "options" "&(spa)& authenticator (client)"
28557 The &(spa)& authenticator has the following client options:
28561 .option client_domain spa string&!! unset
28562 This option specifies an optional domain for the authentication.
28565 .option client_password spa string&!! unset
28566 This option specifies the user's password, and must be set.
28569 .option client_username spa string&!! unset
28570 This option specifies the user name, and must be set. Here is an example of a
28571 configuration of this authenticator for use with the mail servers at
28577 client_username = msn/msn_username
28578 client_password = msn_plaintext_password
28579 client_domain = DOMAIN_OR_UNSET
28581 .ecindex IIDspaauth1
28582 .ecindex IIDspaauth2
28588 . ////////////////////////////////////////////////////////////////////////////
28589 . ////////////////////////////////////////////////////////////////////////////
28591 .chapter "The external authenticator" "CHAPexternauth"
28592 .scindex IIDexternauth1 "&(external)& authenticator"
28593 .scindex IIDexternauth2 "authenticators" "&(external)&"
28594 .cindex "authentication" "Client Certificate"
28595 .cindex "authentication" "X509"
28596 .cindex "Certificate-based authentication"
28597 The &(external)& authenticator provides support for
28598 authentication based on non-SMTP information.
28599 The specification is in RFC 4422 Appendix A
28600 (&url(https://tools.ietf.org/html/rfc4422)).
28601 It is only a transport and negotiation mechanism;
28602 the process of authentication is entirely controlled
28603 by the server configuration.
28605 The client presents an identity in-clear.
28606 It is probably wise for a server to only advertise,
28607 and for clients to only attempt,
28608 this authentication method on a secure (eg. under TLS) connection.
28610 One possible use, compatible with the
28611 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28612 is for using X509 client certificates.
28614 It thus overlaps in function with the TLS authenticator
28615 (see &<<CHAPtlsauth>>&)
28616 but is a full SMTP SASL authenticator
28617 rather than being implicit for TLS-connection carried
28618 client certificates only.
28620 The examples and discussion in this chapter assume that
28621 client-certificate authentication is being done.
28623 The client must present a certificate,
28624 for which it must have been requested via the
28625 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28626 (see &<<CHAPTLS>>&).
28627 For authentication to be effective the certificate should be
28628 verifiable against a trust-anchor certificate known to the server.
28630 .section "External options" "SECTexternsoptions"
28631 .cindex "options" "&(external)& authenticator (server)"
28632 The &(external)& authenticator has two server options:
28634 .option server_param2 external string&!! unset
28635 .option server_param3 external string&!! unset
28636 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28637 These options are expanded before the &%server_condition%& option
28638 and the result are placed in &$auth2$& and &$auth3$& resectively.
28639 If the expansion is forced to fail, authentication fails. Any other expansion
28640 failure causes a temporary error code to be returned.
28642 They can be used to clarify the coding of a complex &%server_condition%&.
28644 .section "Using external in a server" "SECTexternserver"
28645 .cindex "AUTH" "in &(external)& authenticator"
28646 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28647 "in &(external)& authenticator"
28648 .vindex "&$auth1$&, &$auth2$&, etc"
28649 .cindex "base64 encoding" "in &(external)& authenticator"
28651 When running as a server, &(external)& performs the authentication test by
28652 expanding a string. The data sent by the client with the AUTH command, or in
28653 response to subsequent prompts, is base64 encoded, and so may contain any byte
28654 values when decoded. The decoded value is treated as
28655 an identity for authentication and
28656 placed in the expansion variable &$auth1$&.
28658 For compatibility with previous releases of Exim, the value is also placed in
28659 the expansion variable &$1$&. However, the use of this
28660 variable for this purpose is now deprecated, as it can lead to confusion in
28661 string expansions that also use them for other things.
28663 .vindex "&$authenticated_id$&"
28664 Once an identity has been received,
28665 &%server_condition%& is expanded. If the expansion is forced to fail,
28666 authentication fails. Any other expansion failure causes a temporary error code
28667 to be returned. If the result of a successful expansion is an empty string,
28668 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28669 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28670 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28671 For any other result, a temporary error code is returned, with the expanded
28672 string as the error text.
28676 ext_ccert_san_mail:
28678 public_name = EXTERNAL
28680 server_advertise_condition = $tls_in_certificate_verified
28681 server_param2 = ${certextract {subj_altname,mail,>:} \
28682 {$tls_in_peercert}}
28683 server_condition = ${if forany {$auth2} \
28684 {eq {$item}{$auth1}}}
28685 server_set_id = $auth1
28687 This accepts a client certificate that is verifiable against any
28688 of your configured trust-anchors
28689 (which usually means the full set of public CAs)
28690 and which has a mail-SAN matching the claimed identity sent by the client.
28692 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28693 The account name is therefore guessable by an opponent.
28694 TLS 1.3 protects both server and client certificates, and is not vulnerable
28698 .section "Using external in a client" "SECTexternclient"
28699 .cindex "options" "&(external)& authenticator (client)"
28700 The &(external)& authenticator has one client option:
28702 .option client_send external string&!! unset
28703 This option is expanded and sent with the AUTH command as the
28704 identity being asserted.
28710 public_name = EXTERNAL
28712 client_condition = ${if !eq{$tls_out_cipher}{}}
28713 client_send = myaccount@smarthost.example.net
28717 .ecindex IIDexternauth1
28718 .ecindex IIDexternauth2
28724 . ////////////////////////////////////////////////////////////////////////////
28725 . ////////////////////////////////////////////////////////////////////////////
28727 .chapter "The tls authenticator" "CHAPtlsauth"
28728 .scindex IIDtlsauth1 "&(tls)& authenticator"
28729 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28730 .cindex "authentication" "Client Certificate"
28731 .cindex "authentication" "X509"
28732 .cindex "Certificate-based authentication"
28733 The &(tls)& authenticator provides server support for
28734 authentication based on client certificates.
28736 It is not an SMTP authentication mechanism and is not
28737 advertised by the server as part of the SMTP EHLO response.
28738 It is an Exim authenticator in the sense that it affects
28739 the protocol element of the log line, can be tested for
28740 by the &%authenticated%& ACL condition, and can set
28741 the &$authenticated_id$& variable.
28743 The client must present a verifiable certificate,
28744 for which it must have been requested via the
28745 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28746 (see &<<CHAPTLS>>&).
28748 If an authenticator of this type is configured it is
28749 run before any SMTP-level communication is done,
28750 and can authenticate the connection.
28751 If it does, SMTP authentication is not offered.
28753 A maximum of one authenticator of this type may be present.
28756 .cindex "options" "&(tls)& authenticator (server)"
28757 The &(tls)& authenticator has three server options:
28759 .option server_param1 tls string&!! unset
28760 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28761 This option is expanded after the TLS negotiation and
28762 the result is placed in &$auth1$&.
28763 If the expansion is forced to fail, authentication fails. Any other expansion
28764 failure causes a temporary error code to be returned.
28766 .option server_param2 tls string&!! unset
28767 .option server_param3 tls string&!! unset
28768 As above, for &$auth2$& and &$auth3$&.
28770 &%server_param1%& may also be spelled &%server_param%&.
28777 server_param1 = ${certextract {subj_altname,mail,>:} \
28778 {$tls_in_peercert}}
28779 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28782 {${lookup ldap{ldap:///\
28783 mailname=${quote_ldap_dn:${lc:$item}},\
28784 ou=users,LDAP_DC?mailid} {$value}{0} \
28786 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28788 This accepts a client certificate that is verifiable against any
28789 of your configured trust-anchors
28790 (which usually means the full set of public CAs)
28791 and which has a SAN with a good account name.
28793 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28794 The account name is therefore guessable by an opponent.
28795 TLS 1.3 protects both server and client certificates, and is not vulnerable
28797 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28799 . An alternative might use
28801 . server_param1 = ${sha256:$tls_in_peercert}
28803 . to require one of a set of specific certs that define a given account
28804 . (the verification is still required, but mostly irrelevant).
28805 . This would help for per-device use.
28807 . However, for the future we really need support for checking a
28808 . user cert in LDAP - which probably wants a base-64 DER.
28810 .ecindex IIDtlsauth1
28811 .ecindex IIDtlsauth2
28814 Note that because authentication is traditionally an SMTP operation,
28815 the &%authenticated%& ACL condition cannot be used in
28816 a connect- or helo-ACL.
28820 . ////////////////////////////////////////////////////////////////////////////
28821 . ////////////////////////////////////////////////////////////////////////////
28823 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28824 "Encrypted SMTP connections"
28825 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28826 .scindex IIDencsmtp2 "SMTP" "encryption"
28827 .cindex "TLS" "on SMTP connection"
28830 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28831 Sockets Layer), is implemented by making use of the OpenSSL library or the
28832 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28833 cryptographic code in the Exim distribution itself for implementing TLS. In
28834 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28835 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28836 You also need to understand the basic concepts of encryption at a managerial
28837 level, and in particular, the way that public keys, private keys, and
28838 certificates are used.
28840 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28841 connection is established, the client issues a STARTTLS command. If the
28842 server accepts this, the client and the server negotiate an encryption
28843 mechanism. If the negotiation succeeds, the data that subsequently passes
28844 between them is encrypted.
28846 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28847 and if so, what cipher suite is in use, whether the client supplied a
28848 certificate, and whether or not that certificate was verified. This makes it
28849 possible for an Exim server to deny or accept certain commands based on the
28852 &*Warning*&: Certain types of firewall and certain anti-virus products can
28853 disrupt TLS connections. You need to turn off SMTP scanning for these products
28854 in order to get TLS to work.
28858 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
28860 .cindex "submissions protocol"
28861 .cindex "ssmtp protocol"
28862 .cindex "smtps protocol"
28863 .cindex "SMTP" "submissions protocol"
28864 .cindex "SMTP" "ssmtp protocol"
28865 .cindex "SMTP" "smtps protocol"
28866 The history of port numbers for TLS in SMTP is a little messy and has been
28867 contentious. As of RFC 8314, the common practice of using the historically
28868 allocated port 465 for "email submission but with TLS immediately upon connect
28869 instead of using STARTTLS" is officially blessed by the IETF, and recommended
28870 by them in preference to STARTTLS.
28872 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
28873 clarity emerged over the dual roles of SMTP, for MX delivery and Email
28874 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
28876 This approach was, for a while, officially abandoned when encrypted SMTP was
28877 standardized, but many clients kept using it, even as the TCP port number was
28878 reassigned for other use.
28879 Thus you may encounter guidance claiming that you shouldn't enable use of
28881 In practice, a number of mail-clients have only ever supported submissions,
28882 not submission with STARTTLS upgrade.
28883 Ideally, offer both submission (587) and submissions (465) service.
28885 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
28886 global option. Its value must be a list of port numbers;
28887 the most common use is expected to be:
28889 tls_on_connect_ports = 465
28891 The port numbers specified by this option apply to all SMTP connections, both
28892 via the daemon and via &'inetd'&. You still need to specify all the ports that
28893 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
28894 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
28895 an extra port &-- rather, it specifies different behaviour on a port that is
28898 There is also a &%-tls-on-connect%& command line option. This overrides
28899 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
28906 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
28907 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
28908 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
28909 To build Exim to use OpenSSL you need to set
28915 To build Exim to use GnuTLS, you need to set
28921 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
28922 include files and libraries for GnuTLS can be found.
28924 There are some differences in usage when using GnuTLS instead of OpenSSL:
28927 The &%tls_verify_certificates%& option
28928 cannot be the path of a directory
28929 for GnuTLS versions before 3.3.6
28930 (for later versions, or OpenSSL, it can be either).
28932 The default value for &%tls_dhparam%& differs for historical reasons.
28934 .vindex "&$tls_in_peerdn$&"
28935 .vindex "&$tls_out_peerdn$&"
28936 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
28937 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
28938 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
28940 OpenSSL identifies cipher suites using hyphens as separators, for example:
28941 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
28942 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
28943 in a cipher list. To make life simpler, Exim changes underscores to hyphens
28944 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
28945 to handle its own older variants) when processing lists of cipher suites in the
28946 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
28949 The &%tls_require_ciphers%& options operate differently, as described in the
28950 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
28952 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
28953 When using OpenSSL, this option is ignored.
28954 (If an API is found to let OpenSSL be configured in this way,
28955 let the Exim Maintainers know and we'll likely use it).
28957 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
28958 main option, it must be ordered to match the &%tls_certificate%& list.
28960 Some other recently added features may only be available in one or the other.
28961 This should be documented with the feature. If the documentation does not
28962 explicitly state that the feature is infeasible in the other TLS
28963 implementation, then patches are welcome.
28966 The output from "exim -bV" will show which (if any) support was included
28968 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
28973 .section "GnuTLS parameter computation" "SECTgnutlsparam"
28974 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
28975 an explicit path; if the latter, then the text about generation still applies,
28976 but not the chosen filename.
28977 By default, as of Exim 4.80 a hard-coded D-H prime is used.
28978 See the documentation of &%tls_dhparam%& for more information.
28980 GnuTLS uses D-H parameters that may take a substantial amount of time
28981 to compute. It is unreasonable to re-compute them for every TLS session.
28982 Therefore, Exim keeps this data in a file in its spool directory, called
28983 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
28985 The file is owned by the Exim user and is readable only by
28986 its owner. Every Exim process that start up GnuTLS reads the D-H
28987 parameters from this file. If the file does not exist, the first Exim process
28988 that needs it computes the data and writes it to a temporary file which is
28989 renamed once it is complete. It does not matter if several Exim processes do
28990 this simultaneously (apart from wasting a few resources). Once a file is in
28991 place, new Exim processes immediately start using it.
28993 For maximum security, the parameters that are stored in this file should be
28994 recalculated periodically, the frequency depending on your paranoia level.
28995 If you are avoiding using the fixed D-H primes published in RFCs, then you
28996 are concerned about some advanced attacks and will wish to do this; if you do
28997 not regenerate then you might as well stick to the standard primes.
28999 Arranging this is easy in principle; just delete the file when you want new
29000 values to be computed. However, there may be a problem. The calculation of new
29001 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29002 If the system is not very active, &_/dev/random_& may delay returning data
29003 until enough randomness (entropy) is available. This may cause Exim to hang for
29004 a substantial amount of time, causing timeouts on incoming connections.
29006 The solution is to generate the parameters externally to Exim. They are stored
29007 in &_gnutls-params-N_& in PEM format, which means that they can be
29008 generated externally using the &(certtool)& command that is part of GnuTLS.
29010 To replace the parameters with new ones, instead of deleting the file
29011 and letting Exim re-create it, you can generate new parameters using
29012 &(certtool)& and, when this has been done, replace Exim's cache file by
29013 renaming. The relevant commands are something like this:
29016 [ look for file; assume gnutls-params-2236 is the most recent ]
29019 # chown exim:exim new-params
29020 # chmod 0600 new-params
29021 # certtool --generate-dh-params --bits 2236 >>new-params
29022 # openssl dhparam -noout -text -in new-params | head
29023 [ check the first line, make sure it's not more than 2236;
29024 if it is, then go back to the start ("rm") and repeat
29025 until the size generated is at most the size requested ]
29026 # chmod 0400 new-params
29027 # mv new-params gnutls-params-2236
29029 If Exim never has to generate the parameters itself, the possibility of
29030 stalling is removed.
29032 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29033 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29034 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29035 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29036 and Exim does so. This attempt to remove Exim from TLS policy decisions
29037 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29038 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29039 which applies to all D-H usage, client or server. If the value returned by
29040 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29041 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29042 limit, which is still much higher than Exim historically used.
29044 The filename and bits used will change as the GnuTLS maintainers change the
29045 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29046 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29047 2432 bits, while NSS is limited to 2236 bits.
29049 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29050 increase the chance of the generated prime actually being within acceptable
29051 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29052 procedure above. There is no sane procedure available to Exim to double-check
29053 the size of the generated prime, so it might still be too large.
29056 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29057 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29058 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29059 There is a function in the OpenSSL library that can be passed a list of cipher
29060 suites before the cipher negotiation takes place. This specifies which ciphers
29061 are acceptable for TLS versions prior to 1.3.
29062 The list is colon separated and may contain names like
29063 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29064 directly to this function call.
29065 Many systems will install the OpenSSL manual-pages, so you may have
29066 &'ciphers(1)'& available to you.
29067 The following quotation from the OpenSSL
29068 documentation specifies what forms of item are allowed in the cipher string:
29071 It can consist of a single cipher suite such as RC4-SHA.
29073 It can represent a list of cipher suites containing a certain algorithm,
29074 or cipher suites of a certain type. For example SHA1 represents all
29075 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29078 Lists of cipher suites can be combined in a single cipher string using
29079 the + character. This is used as a logical and operation. For example
29080 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29084 Each cipher string can be optionally preceded by one of the characters &`!`&,
29087 If &`!`& is used, the ciphers are permanently deleted from the list. The
29088 ciphers deleted can never reappear in the list even if they are explicitly
29091 If &`-`& is used, the ciphers are deleted from the list, but some or all
29092 of the ciphers can be added again by later options.
29094 If &`+`& is used, the ciphers are moved to the end of the list. This
29095 option does not add any new ciphers; it just moves matching existing ones.
29098 If none of these characters is present, the string is interpreted as
29099 a list of ciphers to be appended to the current preference list. If the list
29100 includes any ciphers already present they will be ignored: that is, they will
29101 not be moved to the end of the list.
29104 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29107 # note single-quotes to get ! past any shell history expansion
29108 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29111 This example will let the library defaults be permitted on the MX port, where
29112 there's probably no identity verification anyway, but ups the ante on the
29113 submission ports where the administrator might have some influence on the
29114 choice of clients used:
29116 # OpenSSL variant; see man ciphers(1)
29117 tls_require_ciphers = ${if =={$received_port}{25}\
29122 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29124 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29127 For TLS version 1.3 the control available is less fine-grained
29128 and Exim does not provide access to it at present.
29129 The value of the &%tls_require_ciphers%& option is ignored when
29130 TLS version 1.3 is negotiated.
29132 As of writing the library default cipher suite list for TLSv1.3 is
29134 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29138 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29140 .cindex "GnuTLS" "specifying parameters for"
29141 .cindex "TLS" "specifying ciphers (GnuTLS)"
29142 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29143 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29144 .cindex "TLS" "specifying protocols (GnuTLS)"
29145 .cindex "TLS" "specifying priority string (GnuTLS)"
29146 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29147 The GnuTLS library allows the caller to provide a "priority string", documented
29148 as part of the &[gnutls_priority_init]& function. This is very similar to the
29149 ciphersuite specification in OpenSSL.
29151 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29152 and controls both protocols and ciphers.
29154 The &%tls_require_ciphers%& option is available both as an global option,
29155 controlling how Exim behaves as a server, and also as an option of the
29156 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29157 the value is string expanded. The resulting string is not an Exim list and
29158 the string is given to the GnuTLS library, so that Exim does not need to be
29159 aware of future feature enhancements of GnuTLS.
29161 Documentation of the strings accepted may be found in the GnuTLS manual, under
29162 "Priority strings". This is online as
29163 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29164 but beware that this relates to GnuTLS 3, which may be newer than the version
29165 installed on your system. If you are using GnuTLS 3,
29166 then the example code
29167 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29168 on that site can be used to test a given string.
29172 # Disable older versions of protocols
29173 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29176 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29177 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29178 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29180 This example will let the library defaults be permitted on the MX port, where
29181 there's probably no identity verification anyway, and lowers security further
29182 by increasing compatibility; but this ups the ante on the submission ports
29183 where the administrator might have some influence on the choice of clients
29187 tls_require_ciphers = ${if =={$received_port}{25}\
29193 .section "Configuring an Exim server to use TLS" "SECID182"
29194 .cindex "TLS" "configuring an Exim server"
29195 .cindex "ESMTP extensions" STARTTLS
29196 When Exim has been built with TLS support, it advertises the availability of
29197 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29198 but not to any others. The default value of this option is *, which means
29199 that STARTTLS is always advertised. Set it to blank to never advertise;
29200 this is reasonable for systems that want to use TLS only as a client.
29202 If STARTTLS is to be used you
29203 need to set some other options in order to make TLS available.
29205 If a client issues a STARTTLS command and there is some configuration
29206 problem in the server, the command is rejected with a 454 error. If the client
29207 persists in trying to issue SMTP commands, all except QUIT are rejected
29210 554 Security failure
29212 If a STARTTLS command is issued within an existing TLS session, it is
29213 rejected with a 554 error code.
29215 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29216 must be set to match some hosts. The default is * which matches all hosts.
29218 If this is all you do, TLS encryption will be enabled but not authentication -
29219 meaning that the peer has no assurance it is actually you he is talking to.
29220 You gain protection from a passive sniffer listening on the wire but not
29221 from someone able to intercept the communication.
29223 Further protection requires some further configuration at the server end.
29225 To make TLS work you need to set, in the server,
29227 tls_certificate = /some/file/name
29228 tls_privatekey = /some/file/name
29230 These options are, in fact, expanded strings, so you can make them depend on
29231 the identity of the client that is connected if you wish. The first file
29232 contains the server's X509 certificate, and the second contains the private key
29233 that goes with it. These files need to be
29234 PEM format and readable by the Exim user, and must
29235 always be given as full path names.
29236 The key must not be password-protected.
29237 They can be the same file if both the
29238 certificate and the key are contained within it. If &%tls_privatekey%& is not
29239 set, or if its expansion is forced to fail or results in an empty string, this
29240 is assumed to be the case. The certificate file may also contain intermediate
29241 certificates that need to be sent to the client to enable it to authenticate
29242 the server's certificate.
29244 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29245 colon-separated lists of file paths. Ciphers using given authentication
29246 algorithms require the presence of a suitable certificate to supply the
29247 public-key. The server selects among the certificates to present to the
29248 client depending on the selected cipher, hence the priority ordering for
29249 ciphers will affect which certificate is used.
29251 If you do not understand about certificates and keys, please try to find a
29252 source of this background information, which is not Exim-specific. (There are a
29253 few comments below in section &<<SECTcerandall>>&.)
29255 &*Note*&: These options do not apply when Exim is operating as a client &--
29256 they apply only in the case of a server. If you need to use a certificate in an
29257 Exim client, you must set the options of the same names in an &(smtp)&
29260 With just these options, an Exim server will be able to use TLS. It does not
29261 require the client to have a certificate (but see below for how to insist on
29262 this). There is one other option that may be needed in other situations. If
29264 tls_dhparam = /some/file/name
29266 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29267 with the parameters contained in the file.
29268 Set this to &`none`& to disable use of DH entirely, by making no prime
29273 This may also be set to a string identifying a standard prime to be used for
29274 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29275 used is &`ike23`&. There are a few standard primes available, see the
29276 documentation for &%tls_dhparam%& for the complete list.
29282 for a way of generating file data.
29284 The strings supplied for these three options are expanded every time a client
29285 host connects. It is therefore possible to use different certificates and keys
29286 for different hosts, if you so wish, by making use of the client's IP address
29287 in &$sender_host_address$& to control the expansion. If a string expansion is
29288 forced to fail, Exim behaves as if the option is not set.
29290 .cindex "cipher" "logging"
29291 .cindex "log" "TLS cipher"
29292 .vindex "&$tls_in_cipher$&"
29293 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29294 an incoming TLS connection. It is included in the &'Received:'& header of an
29295 incoming message (by default &-- you can, of course, change this), and it is
29296 also included in the log line that records a message's arrival, keyed by
29297 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29298 condition can be used to test for specific cipher suites in ACLs.
29300 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29301 can check the name of the cipher suite and vary their actions accordingly. The
29302 cipher suite names vary, depending on which TLS library is being used. For
29303 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29304 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29305 documentation for more details.
29307 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29308 (again depending on the &%tls_cipher%& log selector).
29311 .section "Requesting and verifying client certificates" "SECID183"
29312 .cindex "certificate" "verification of client"
29313 .cindex "TLS" "client certificate verification"
29314 If you want an Exim server to request a certificate when negotiating a TLS
29315 session with a client, you must set either &%tls_verify_hosts%& or
29316 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29317 apply to all TLS connections. For any host that matches one of these options,
29318 Exim requests a certificate as part of the setup of the TLS session. The
29319 contents of the certificate are verified by comparing it with a list of
29320 expected trust-anchors or certificates.
29321 These may be the system default set (depending on library version),
29322 an explicit file or,
29323 depending on library version, a directory, identified by
29324 &%tls_verify_certificates%&.
29326 A file can contain multiple certificates, concatenated end to end. If a
29329 each certificate must be in a separate file, with a name (or a symbolic link)
29330 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29331 certificate. You can compute the relevant hash by running the command
29333 openssl x509 -hash -noout -in /cert/file
29335 where &_/cert/file_& contains a single certificate.
29337 There is no checking of names of the client against the certificate
29338 Subject Name or Subject Alternate Names.
29340 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29341 what happens if the client does not supply a certificate, or if the certificate
29342 does not match any of the certificates in the collection named by
29343 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29344 attempt to set up a TLS session is aborted, and the incoming connection is
29345 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29346 session continues. ACLs that run for subsequent SMTP commands can detect the
29347 fact that no certificate was verified, and vary their actions accordingly. For
29348 example, you can insist on a certificate before accepting a message for
29349 relaying, but not when the message is destined for local delivery.
29351 .vindex "&$tls_in_peerdn$&"
29352 When a client supplies a certificate (whether it verifies or not), the value of
29353 the Distinguished Name of the certificate is made available in the variable
29354 &$tls_in_peerdn$& during subsequent processing of the message.
29356 .cindex "log" "distinguished name"
29357 Because it is often a long text string, it is not included in the log line or
29358 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29359 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29360 &%received_header_text%& to change the &'Received:'& header. When no
29361 certificate is supplied, &$tls_in_peerdn$& is empty.
29364 .section "Revoked certificates" "SECID184"
29365 .cindex "TLS" "revoked certificates"
29366 .cindex "revocation list"
29367 .cindex "certificate" "revocation list"
29368 .cindex "OCSP" "stapling"
29369 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29370 certificates are revoked. If you have such a list, you can pass it to an Exim
29371 server using the global option called &%tls_crl%& and to an Exim client using
29372 an identically named option for the &(smtp)& transport. In each case, the value
29373 of the option is expanded and must then be the name of a file that contains a
29375 The downside is that clients have to periodically re-download a potentially huge
29376 file from every certificate authority they know of.
29378 The way with most moving parts at query time is Online Certificate
29379 Status Protocol (OCSP), where the client verifies the certificate
29380 against an OCSP server run by the CA. This lets the CA track all
29381 usage of the certs. It requires running software with access to the
29382 private key of the CA, to sign the responses to the OCSP queries. OCSP
29383 is based on HTTP and can be proxied accordingly.
29385 The only widespread OCSP server implementation (known to this writer)
29386 comes as part of OpenSSL and aborts on an invalid request, such as
29387 connecting to the port and then disconnecting. This requires
29388 re-entering the passphrase each time some random client does this.
29390 The third way is OCSP Stapling; in this, the server using a certificate
29391 issued by the CA periodically requests an OCSP proof of validity from
29392 the OCSP server, then serves it up inline as part of the TLS
29393 negotiation. This approach adds no extra round trips, does not let the
29394 CA track users, scales well with number of certs issued by the CA and is
29395 resilient to temporary OCSP server failures, as long as the server
29396 starts retrying to fetch an OCSP proof some time before its current
29397 proof expires. The downside is that it requires server support.
29399 Unless Exim is built with the support disabled,
29400 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29401 support for OCSP stapling is included.
29403 There is a global option called &%tls_ocsp_file%&.
29404 The file specified therein is expected to be in DER format, and contain
29405 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29406 option will be re-expanded for SNI, if the &%tls_certificate%& option
29407 contains &`tls_in_sni`&, as per other TLS options.
29409 Exim does not at this time implement any support for fetching a new OCSP
29410 proof. The burden is on the administrator to handle this, outside of
29411 Exim. The file specified should be replaced atomically, so that the
29412 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29413 on each connection, so a new file will be handled transparently on the
29416 When built with OpenSSL Exim will check for a valid next update timestamp
29417 in the OCSP proof; if not present, or if the proof has expired, it will be
29420 For the client to be able to verify the stapled OCSP the server must
29421 also supply, in its stapled information, any intermediate
29422 certificates for the chain leading to the OCSP proof from the signer
29423 of the server certificate. There may be zero or one such. These
29424 intermediate certificates should be added to the server OCSP stapling
29425 file named by &%tls_ocsp_file%&.
29427 Note that the proof only covers the terminal server certificate,
29428 not any of the chain from CA to it.
29430 There is no current way to staple a proof for a client certificate.
29433 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29434 OCSP server is supplied. The server URL may be included in the
29435 server certificate, if the CA is helpful.
29437 One failure mode seen was the OCSP Signer cert expiring before the end
29438 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29439 noted this as invalid overall, but the re-fetch script did not.
29444 .section "Caching of static server configuration items" "SECTserverTLScache"
29445 .cindex certificate caching
29446 .cindex privatekey caching
29447 .cindex crl caching
29448 .cindex ocsp caching
29449 .cindex ciphers caching
29450 .cindex "CA bundle" caching
29451 .cindex "certificate authorities" caching
29452 .cindex tls_certificate caching
29453 .cindex tls_privatekey caching
29454 .cindex tls_crl caching
29455 .cindex tls_ocsp_file caching
29456 .cindex tls_require_ciphers caching
29457 .cindex tls_verify_certificate caching
29458 .cindex caching certificate
29459 .cindex caching privatekey
29460 .cindex caching crl
29461 .cindex caching ocsp
29462 .cindex caching ciphers
29463 .cindex caching "certificate authorities
29464 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29465 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29466 expandable elements,
29467 then the associated information is loaded at daemon startup.
29468 It is made available
29469 to child processes forked for handling received SMTP connections.
29471 This caching is currently only supported under Linux and FreeBSD.
29473 If caching is not possible, for example if an item has to be dependent
29474 on the peer host so contains a &$sender_host_name$& expansion, the load
29475 of the associated information is done at the startup of the TLS connection.
29477 The cache is invalidated and reloaded after any changes to the directories
29478 containing files specified by these options.
29480 The information specified by the main option &%tls_verify_certificates%&
29481 is similarly cached so long as it specifies files explicitly
29482 or (under GnuTLS) is the string &"system,cache"&.
29483 The latter case is not automatically invalidated;
29484 it is the operator's responsibility to arrange for a daemon restart
29485 any time the system certificate authority bundle is updated.
29486 A HUP signal is sufficient for this.
29487 The value &"system"& results in no caching under GnuTLS.
29489 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29490 is acceptable in configurations for the Exim executavble.
29492 Caching of the system Certificate Authorities bundle can
29493 save siginificant time and processing on every TLS connection
29500 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29501 .cindex "cipher" "logging"
29502 .cindex "log" "TLS cipher"
29503 .cindex "log" "distinguished name"
29504 .cindex "TLS" "configuring an Exim client"
29505 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29506 deliveries as well as to incoming, the latter one causing logging of the
29507 server certificate's DN. The remaining client configuration for TLS is all
29508 within the &(smtp)& transport.
29510 .cindex "ESMTP extensions" STARTTLS
29511 It is not necessary to set any options to have TLS work in the &(smtp)&
29512 transport. If Exim is built with TLS support, and TLS is advertised by a
29513 server, the &(smtp)& transport always tries to start a TLS session. However,
29514 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29515 transport) to a list of server hosts for which TLS should not be used.
29517 If you do not want Exim to attempt to send messages unencrypted when an attempt
29518 to set up an encrypted connection fails in any way, you can set
29519 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29520 those hosts, delivery is always deferred if an encrypted connection cannot be
29521 set up. If there are any other hosts for the address, they are tried in the
29524 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29525 the message unencrypted. It always does this if the response to STARTTLS is
29526 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29527 session after a success response code, what happens is controlled by the
29528 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29529 delivery to this host is deferred, and other hosts (if available) are tried. If
29530 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29531 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29532 negotiation fails, Exim closes the current connection (because it is in an
29533 unknown state), opens a new one to the same host, and then tries the delivery
29536 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29537 transport provide the client with a certificate, which is passed to the server
29539 This is an optional thing for TLS connections, although either end
29541 If the server is Exim, it will request a certificate only if
29542 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29544 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29545 for client use (they are usable for server use).
29546 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29547 in failed connections.
29549 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29550 specifies a collection of expected server certificates.
29552 the system default set (depending on library version),
29554 or (depending on library version) a directory.
29555 The client verifies the server's certificate
29556 against this collection, taking into account any revoked certificates that are
29557 in the list defined by &%tls_crl%&.
29558 Failure to verify fails the TLS connection unless either of the
29559 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29561 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29562 certificate verification to the listed servers. Verification either must
29563 or need not succeed respectively.
29565 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29566 name checks are made on the server certificate.
29568 The match against this list is, as per other Exim usage, the
29569 IP for the host. That is most closely associated with the
29570 name on the DNS A (or AAAA) record for the host.
29571 However, the name that needs to be in the certificate
29572 is the one at the head of any CNAME chain leading to the A record.
29574 The option defaults to always checking.
29576 The &(smtp)& transport has two OCSP-related options:
29577 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29578 is requested and required for the connection to proceed. The default
29580 &%hosts_request_ocsp%&; a host-list for which (additionally)
29581 a Certificate Status is requested (but not necessarily verified). The default
29582 value is "*" meaning that requests are made unless configured
29585 The host(s) should also be in &%hosts_require_tls%&, and
29586 &%tls_verify_certificates%& configured for the transport,
29587 for OCSP to be relevant.
29590 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29591 list of permitted cipher suites. If either of these checks fails, delivery to
29592 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29593 alternative hosts, if any.
29596 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29597 is operating as a client. Exim does not assume that a server certificate (set
29598 by the global options of the same name) should also be used when operating as a
29602 .vindex "&$host_address$&"
29603 All the TLS options in the &(smtp)& transport are expanded before use, with
29604 &$host$& and &$host_address$& containing the name and address of the server to
29605 which the client is connected. Forced failure of an expansion causes Exim to
29606 behave as if the relevant option were unset.
29608 .vindex &$tls_out_bits$&
29609 .vindex &$tls_out_cipher$&
29610 .vindex &$tls_out_peerdn$&
29611 .vindex &$tls_out_sni$&
29612 Before an SMTP connection is established, the
29613 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29614 variables are emptied. (Until the first connection, they contain the values
29615 that were set when the message was received.) If STARTTLS is subsequently
29616 successfully obeyed, these variables are set to the relevant values for the
29617 outgoing connection.
29622 .section "Caching of static client configuration items" "SECTclientTLScache"
29623 .cindex certificate caching
29624 .cindex privatekey caching
29625 .cindex crl caching
29626 .cindex ciphers caching
29627 .cindex "CA bundle" caching
29628 .cindex "certificate authorities" caching
29629 .cindex tls_certificate caching
29630 .cindex tls_privatekey caching
29631 .cindex tls_crl caching
29632 .cindex tls_require_ciphers caching
29633 .cindex tls_verify_certificate caching
29634 .cindex caching certificate
29635 .cindex caching privatekey
29636 .cindex caching crl
29637 .cindex caching ciphers
29638 .cindex caching "certificate authorities
29639 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29640 and &%tls_crl%& have values with no
29641 expandable elements,
29642 then the associated information is loaded per smtp transport
29643 at daemon startup, at the start of a queue run, or on a
29644 command-line specified message delivery.
29645 It is made available
29646 to child processes forked for handling making SMTP connections.
29648 This caching is currently only supported under Linux.
29650 If caching is not possible, the load
29651 of the associated information is done at the startup of the TLS connection.
29653 The cache is invalidated in the daemon
29654 and reloaded after any changes to the directories
29655 containing files specified by these options.
29657 The information specified by the main option &%tls_verify_certificates%&
29658 is similarly cached so long as it specifies files explicitly
29659 or (under GnuTLS) is the string &"system,cache"&.
29660 The latter case is not automatically invaludated;
29661 it is the operator's responsibility to arrange for a daemon restart
29662 any time the system certificate authority bundle is updated.
29663 A HUP signal is sufficient for this.
29664 The value &"system"& results in no caching under GnuTLS.
29666 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29667 is acceptable in configurations for the Exim executavble.
29669 Caching of the system Certificate Authorities bundle can
29670 save siginificant time and processing on every TLS connection
29677 .section "Use of TLS Server Name Indication" "SECTtlssni"
29678 .cindex "TLS" "Server Name Indication"
29681 .vindex "&$tls_in_sni$&"
29682 .oindex "&%tls_in_sni%&"
29683 With TLS1.0 or above, there is an extension mechanism by which extra
29684 information can be included at various points in the protocol. One of these
29685 extensions, documented in RFC 6066 (and before that RFC 4366) is
29686 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29687 client in the initial handshake, so that the server can examine the servername
29688 within and possibly choose to use different certificates and keys (and more)
29691 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29692 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29695 With SMTP to MX, there are the same problems here as in choosing the identity
29696 against which to validate a certificate: you can't rely on insecure DNS to
29697 provide the identity which you then cryptographically verify. So this will
29698 be of limited use in that environment.
29700 With SMTP to Submission, there is a well-defined hostname which clients are
29701 connecting to and can validate certificates against. Thus clients &*can*&
29702 choose to include this information in the TLS negotiation. If this becomes
29703 wide-spread, then hosters can choose to present different certificates to
29704 different clients. Or even negotiate different cipher suites.
29706 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29707 if not empty, will be sent on a TLS session as part of the handshake. There's
29708 nothing more to it. Choosing a sensible value not derived insecurely is the
29709 only point of caution. The &$tls_out_sni$& variable will be set to this string
29710 for the lifetime of the client connection (including during authentication).
29713 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29714 is forced to the domain part of the recipient address.
29717 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29718 received from a client.
29719 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29721 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29722 option (prior to expansion) then the following options will be re-expanded
29723 during TLS session handshake, to permit alternative values to be chosen:
29726 &%tls_certificate%&
29732 &%tls_verify_certificates%&
29737 Great care should be taken to deal with matters of case, various injection
29738 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29739 can always be referenced; it is important to remember that &$tls_in_sni$& is
29740 arbitrary unverified data provided prior to authentication.
29741 Further, the initial certificate is loaded before SNI has arrived, so
29742 an expansion for &%tls_certificate%& must have a default which is used
29743 when &$tls_in_sni$& is empty.
29745 The Exim developers are proceeding cautiously and so far no other TLS options
29748 When Exim is built against OpenSSL, OpenSSL must have been built with support
29749 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29750 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29751 see &`-servername`& in the output, then OpenSSL has support.
29753 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29754 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29755 built, then you have SNI support).
29759 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29761 .cindex "multiple SMTP deliveries with TLS"
29762 .cindex "TLS" "multiple message deliveries"
29763 Exim sends multiple messages down the same TCP/IP connection by starting up
29764 an entirely new delivery process for each message, passing the socket from
29765 one process to the next. This implementation does not fit well with the use
29766 of TLS, because there is quite a lot of state information associated with a TLS
29767 connection, not just a socket identification. Passing all the state information
29768 to a new process is not feasible. Consequently, for sending using TLS Exim
29769 starts an additional proxy process for handling the encryption, piping the
29770 unencrypted data stream from and to the delivery processes.
29772 An older mode of operation can be enabled on a per-host basis by the
29773 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29774 this list the proxy process described above is not used; instead Exim
29775 shuts down an existing TLS session being run by the delivery process
29776 before passing the socket to a new process. The new process may then
29777 try to start a new TLS session, and if successful, may try to re-authenticate
29778 if AUTH is in use, before sending the next message.
29780 The RFC is not clear as to whether or not an SMTP session continues in clear
29781 after TLS has been shut down, or whether TLS may be restarted again later, as
29782 just described. However, if the server is Exim, this shutdown and
29783 reinitialization works. It is not known which (if any) other servers operate
29784 successfully if the client closes a TLS session and continues with unencrypted
29785 SMTP, but there are certainly some that do not work. For such servers, Exim
29786 should not pass the socket to another process, because the failure of the
29787 subsequent attempt to use it would cause Exim to record a temporary host error,
29788 and delay other deliveries to that host.
29790 To test for this case, Exim sends an EHLO command to the server after
29791 closing down the TLS session. If this fails in any way, the connection is
29792 closed instead of being passed to a new delivery process, but no retry
29793 information is recorded.
29795 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29796 &(smtp)& transport to match those hosts for which Exim should not pass
29797 connections to new processes if TLS has been used.
29802 .section "Certificates and all that" "SECTcerandall"
29803 .cindex "certificate" "references to discussion"
29804 In order to understand fully how TLS works, you need to know about
29805 certificates, certificate signing, and certificate authorities.
29806 This is a large topic and an introductory guide is unsuitable for the Exim
29807 reference manual, so instead we provide pointers to existing documentation.
29809 The Apache web-server was for a long time the canonical guide, so their
29810 documentation is a good place to start; their SSL module's Introduction
29811 document is currently at
29813 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29815 and their FAQ is at
29817 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29820 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29821 0-201-61598-3) in 2001, contains both introductory and more in-depth
29823 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29824 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29825 Ivan is the author of the popular TLS testing tools at
29826 &url(https://www.ssllabs.com/).
29829 .section "Certificate chains" "SECID186"
29830 A file named by &%tls_certificate%& may contain more than one
29831 certificate. This is useful in the case where the certificate that is being
29832 sent is validated by an intermediate certificate which the other end does
29833 not have. Multiple certificates must be in the correct order in the file.
29834 First the host's certificate itself, then the first intermediate
29835 certificate to validate the issuer of the host certificate, then the next
29836 intermediate certificate to validate the issuer of the first intermediate
29837 certificate, and so on, until finally (optionally) the root certificate.
29838 The root certificate must already be trusted by the recipient for
29839 validation to succeed, of course, but if it's not preinstalled, sending the
29840 root certificate along with the rest makes it available for the user to
29841 install if the receiving end is a client MUA that can interact with a user.
29843 Note that certificates using MD5 are unlikely to work on today's Internet;
29844 even if your libraries allow loading them for use in Exim when acting as a
29845 server, increasingly clients will not accept such certificates. The error
29846 diagnostics in such a case can be frustratingly vague.
29850 .section "Self-signed certificates" "SECID187"
29851 .cindex "certificate" "self-signed"
29852 You can create a self-signed certificate using the &'req'& command provided
29853 with OpenSSL, like this:
29854 . ==== Do not shorten the duration here without reading and considering
29855 . ==== the text below. Please leave it at 9999 days.
29857 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29860 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29861 delimited and so can be identified independently. The &%-days%& option
29862 specifies a period for which the certificate is valid. The &%-nodes%& option is
29863 important: if you do not set it, the key is encrypted with a passphrase
29864 that you are prompted for, and any use that is made of the key causes more
29865 prompting for the passphrase. This is not helpful if you are going to use
29866 this certificate and key in an MTA, where prompting is not possible.
29868 . ==== I expect to still be working 26 years from now. The less technical
29869 . ==== debt I create, in terms of storing up trouble for my later years, the
29870 . ==== happier I will be then. We really have reached the point where we
29871 . ==== should start, at the very least, provoking thought and making folks
29872 . ==== pause before proceeding, instead of leaving all the fixes until two
29873 . ==== years before 2^31 seconds after the 1970 Unix epoch.
29875 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
29876 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
29877 the above command might produce a date in the past. Think carefully about
29878 the lifetime of the systems you're deploying, and either reduce the duration
29879 of the certificate or reconsider your platform deployment. (At time of
29880 writing, reducing the duration is the most likely choice, but the inexorable
29881 progression of time takes us steadily towards an era where this will not
29882 be a sensible resolution).
29884 A self-signed certificate made in this way is sufficient for testing, and
29885 may be adequate for all your requirements if you are mainly interested in
29886 encrypting transfers, and not in secure identification.
29888 However, many clients require that the certificate presented by the server be a
29889 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
29890 certificate. In this situation, the self-signed certificate described above
29891 must be installed on the client host as a trusted root &'certification
29892 authority'& (CA), and the certificate used by Exim must be a user certificate
29893 signed with that self-signed certificate.
29895 For information on creating self-signed CA certificates and using them to sign
29896 user certificates, see the &'General implementation overview'& chapter of the
29897 Open-source PKI book, available online at
29898 &url(https://sourceforge.net/projects/ospkibook/).
29899 .ecindex IIDencsmtp1
29900 .ecindex IIDencsmtp2
29904 .section "TLS Resumption" "SECTresumption"
29905 .cindex TLS resumption
29906 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
29907 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
29910 Session resumption (this is the "stateless" variant) involves the server sending
29911 a "session ticket" to the client on one connection, which can be stored by the
29912 client and used for a later session. The ticket contains sufficient state for
29913 the server to reconstruct the TLS session, avoiding some expensive crypto
29914 calculation and (on TLS1.2) one full packet roundtrip time.
29917 Operational cost/benefit:
29919 The extra data being transmitted costs a minor amount, and the client has
29920 extra costs in storing and retrieving the data.
29922 In the Exim/Gnutls implementation the extra cost on an initial connection
29923 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
29924 The saved cost on a subsequent connection is about 4ms; three or more
29925 connections become a net win. On longer network paths, two or more
29926 connections will have an average lower startup time thanks to the one
29927 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
29930 .cindex "hints database" tls
29931 Since a new hints DB is used on the TLS client,
29932 the hints DB maintenance should be updated to additionally handle "tls".
29937 The session ticket is encrypted, but is obviously an additional security
29938 vulnarability surface. An attacker able to decrypt it would have access
29939 all connections using the resumed session.
29940 The session ticket encryption key is not committed to storage by the server
29941 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
29942 overlap; GnuTLS 6hr but does not specify any overlap).
29943 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
29944 OpenSSL. GnuTLS 2hr, appears to not do overlap).
29946 There is a question-mark over the security of the Diffie-Helman parameters
29947 used for session negotiation.
29952 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
29955 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
29956 have bits 0-4 indicating respectively
29957 support built, client requested ticket, client offered session,
29958 server issued ticket, resume used. A suitable decode list is provided
29959 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
29964 The &%tls_resumption_hosts%& main option specifies a hostlist for which
29965 exim, operating as a server, will offer resumption to clients.
29966 Current best practice is to not offer the feature to MUA connection.
29967 Commonly this can be done like this:
29969 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
29971 If the peer host matches the list after expansion then resumption
29972 is offered and/or accepted.
29974 The &%tls_resumption_hosts%& smtp transport option performs the
29975 equivalent function for operation as a client.
29976 If the peer host matches the list after expansion then resumption
29977 is attempted (if a stored session is available) or the information
29978 stored (if supplied by the peer).
29984 In a resumed session:
29986 The variables &$tls_{in,out}_cipher$& will have values different
29987 to the original (under GnuTLS).
29989 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
29990 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
29991 . XXX need to do something with that hosts_require_ocsp
29998 .section DANE "SECDANE"
30000 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30001 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30002 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30003 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30004 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30005 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30007 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30008 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30009 by (a) is thought to be smaller than that of the set of root CAs.
30011 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30012 fail to pass on a server's STARTTLS.
30014 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30015 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30016 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30018 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30019 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30020 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30022 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30023 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30025 There are no changes to Exim specific to server-side operation of DANE.
30026 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30027 in &_Local/Makefile_&.
30028 If it has been included, the macro "_HAVE_DANE" will be defined.
30030 A TLSA record consist of 4 fields, the "Certificate Usage", the
30031 "Selector", the "Matching type", and the "Certificate Association Data".
30032 For a detailed description of the TLSA record see
30033 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30035 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30036 These are the "Trust Anchor" and "End Entity" variants.
30037 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30038 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30039 this is appropriate for a single system, using a self-signed certificate.
30040 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30042 A private CA at simplest is just a self-signed certificate (with certain
30043 attributes) which is used to sign server certificates, but running one securely
30044 does require careful arrangement.
30045 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30046 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30047 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30048 all of which point to a single TLSA record.
30049 DANE-TA and DANE-EE can both be used together.
30051 Our recommendation is to use DANE with a certificate from a public CA,
30052 because this enables a variety of strategies for remote clients to verify
30054 You can then publish information both via DANE and another technology,
30055 "MTA-STS", described below.
30057 When you use DANE-TA to publish trust anchor information, you ask entities
30058 outside your administrative control to trust the Certificate Authority for
30059 connections to you.
30060 If using a private CA then you should expect others to still apply the
30061 technical criteria they'd use for a public CA to your certificates.
30062 In particular, you should probably try to follow current best practices for CA
30063 operation around hash algorithms and key sizes.
30064 Do not expect other organizations to lower their security expectations just
30065 because a particular profile might be reasonable for your own internal use.
30067 When this text was last updated, this in practice means to avoid use of SHA-1
30068 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30069 than 4096, for interoperability); to use keyUsage fields correctly; to use
30070 random serial numbers.
30071 The list of requirements is subject to change as best practices evolve.
30072 If you're not already using a private CA, or it doesn't meet these
30073 requirements, then we encourage you to avoid all these issues and use a public
30074 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30076 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30077 a "Matching Type" (3rd) field of SHA2-512(2).
30079 For the "Certificate Authority Data" (4th) field, commands like
30082 openssl x509 -pubkey -noout <certificate.pem \
30083 | openssl rsa -outform der -pubin 2>/dev/null \
30088 are workable to create a hash of the certificate's public key.
30090 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30093 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30096 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30097 is useful for quickly generating TLSA records.
30100 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30102 The Certificate issued by the CA published in the DANE-TA model should be
30103 issued using a strong hash algorithm.
30104 Exim, and importantly various other MTAs sending to you, will not
30105 re-enable hash algorithms which have been disabled by default in TLS
30107 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30108 interoperability (and probably the maximum too, in 2018).
30110 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30111 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30112 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30115 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30116 {= {4}{$tls_out_tlsa_usage}} } \
30120 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30121 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30122 found. If the definition of &%hosts_request_ocsp%& includes the
30123 string "tls_out_tlsa_usage", they are re-expanded in time to
30124 control the OCSP request.
30126 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30127 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30130 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30131 and &%dane_require_tls_ciphers%&.
30132 The &"require"& variant will result in failure if the target host is not
30133 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30134 the &%dnssec_request_domains%& router or transport option.
30136 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30138 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30139 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30140 will be required for the host. If it does not, the host will not
30141 be used; there is no fallback to non-DANE or non-TLS.
30143 If DANE is requested and usable, then the TLS cipher list configuration
30144 prefers to use the option &%dane_require_tls_ciphers%& and falls
30145 back to &%tls_require_ciphers%& only if that is unset.
30146 This lets you configure "decent crypto" for DANE and "better than nothing
30147 crypto" as the default. Note though that while GnuTLS lets the string control
30148 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30149 limited to ciphersuite constraints.
30151 If DANE is requested and useable (see above) the following transport options are ignored:
30155 tls_try_verify_hosts
30156 tls_verify_certificates
30158 tls_verify_cert_hostnames
30162 If DANE is not usable, whether requested or not, and CA-anchored
30163 verification evaluation is wanted, the above variables should be set appropriately.
30165 The router and transport option &%dnssec_request_domains%& must not be
30166 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30168 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30170 There is a new variable &$tls_out_dane$& which will have "yes" if
30171 verification succeeded using DANE and "no" otherwise (only useful
30172 in combination with events; see &<<CHAPevents>>&),
30173 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30175 .cindex DANE reporting
30176 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30177 to achieve DANE-verified connection, if one was either requested and offered, or
30178 required. This is intended to support TLS-reporting as defined in
30179 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30180 The &$event_data$& will be one of the Result Types defined in
30181 Section 4.3 of that document.
30183 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30185 DANE is specified in published RFCs and decouples certificate authority trust
30186 selection from a "race to the bottom" of "you must trust everything for mail
30187 to get through". There is an alternative technology called MTA-STS, which
30188 instead publishes MX trust anchor information on an HTTPS website. At the
30189 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30190 Exim has no support for MTA-STS as a client, but Exim mail server operators
30191 can choose to publish information describing their TLS configuration using
30192 MTA-STS to let those clients who do use that protocol derive trust
30195 The MTA-STS design requires a certificate from a public Certificate Authority
30196 which is recognized by clients sending to you.
30197 That selection of which CAs are trusted by others is outside your control.
30199 The most interoperable course of action is probably to use
30200 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30201 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30202 records for DANE clients (such as Exim and Postfix) and to publish anchor
30203 information for MTA-STS as well. This is what is done for the &'exim.org'&
30204 domain itself (with caveats around occasionally broken MTA-STS because of
30205 incompatible specification changes prior to reaching RFC status).
30209 . ////////////////////////////////////////////////////////////////////////////
30210 . ////////////////////////////////////////////////////////////////////////////
30212 .chapter "Access control lists" "CHAPACL"
30213 .scindex IIDacl "&ACL;" "description"
30214 .cindex "control of incoming mail"
30215 .cindex "message" "controlling incoming"
30216 .cindex "policy control" "access control lists"
30217 Access Control Lists (ACLs) are defined in a separate section of the runtime
30218 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30219 name, terminated by a colon. Here is a complete ACL section that contains just
30220 one very small ACL:
30224 accept hosts = one.host.only
30226 You can have as many lists as you like in the ACL section, and the order in
30227 which they appear does not matter. The lists are self-terminating.
30229 The majority of ACLs are used to control Exim's behaviour when it receives
30230 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30231 when a local process submits a message using SMTP by specifying the &%-bs%&
30232 option. The most common use is for controlling which recipients are accepted
30233 in incoming messages. In addition, you can define an ACL that is used to check
30234 local non-SMTP messages. The default configuration file contains an example of
30235 a realistic ACL for checking RCPT commands. This is discussed in chapter
30236 &<<CHAPdefconfil>>&.
30239 .section "Testing ACLs" "SECID188"
30240 The &%-bh%& command line option provides a way of testing your ACL
30241 configuration locally by running a fake SMTP session with which you interact.
30244 .section "Specifying when ACLs are used" "SECID189"
30245 .cindex "&ACL;" "options for specifying"
30246 In order to cause an ACL to be used, you have to name it in one of the relevant
30247 options in the main part of the configuration. These options are:
30248 .cindex "AUTH" "ACL for"
30249 .cindex "DATA" "ACLs for"
30250 .cindex "ETRN" "ACL for"
30251 .cindex "EXPN" "ACL for"
30252 .cindex "HELO" "ACL for"
30253 .cindex "EHLO" "ACL for"
30254 .cindex "DKIM" "ACL for"
30255 .cindex "MAIL" "ACL for"
30256 .cindex "QUIT, ACL for"
30257 .cindex "RCPT" "ACL for"
30258 .cindex "STARTTLS, ACL for"
30259 .cindex "VRFY" "ACL for"
30260 .cindex "SMTP" "connection, ACL for"
30261 .cindex "non-SMTP messages" "ACLs for"
30262 .cindex "MIME content scanning" "ACL for"
30263 .cindex "PRDR" "ACL for"
30266 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30267 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30268 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30269 .irow &%acl_smtp_auth%& "ACL for AUTH"
30270 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30271 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30272 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30273 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30274 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30275 .irow &%acl_smtp_expn%& "ACL for EXPN"
30276 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30277 .irow &%acl_smtp_mail%& "ACL for MAIL"
30278 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30279 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30280 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30281 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30282 .irow &%acl_smtp_quit%& "ACL for QUIT"
30283 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30284 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30285 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30288 For example, if you set
30290 acl_smtp_rcpt = small_acl
30292 the little ACL defined above is used whenever Exim receives a RCPT command
30293 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30294 done when RCPT commands arrive. A rejection of RCPT should cause the
30295 sending MTA to give up on the recipient address contained in the RCPT
30296 command, whereas rejection at other times may cause the client MTA to keep on
30297 trying to deliver the message. It is therefore recommended that you do as much
30298 testing as possible at RCPT time.
30301 .section "The non-SMTP ACLs" "SECID190"
30302 .cindex "non-SMTP messages" "ACLs for"
30303 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30304 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30305 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30306 the state of the SMTP connection such as encryption and authentication) are not
30307 relevant and are forbidden in these ACLs. However, the sender and recipients
30308 are known, so the &%senders%& and &%sender_domains%& conditions and the
30309 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30310 &$authenticated_sender$& are also available. You can specify added header lines
30311 in any of these ACLs.
30313 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30314 non-SMTP message, before any of the message has been read. (This is the
30315 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30316 batched SMTP input, it runs after the DATA command has been reached. The
30317 result of this ACL is ignored; it cannot be used to reject a message. If you
30318 really need to, you could set a value in an ACL variable here and reject based
30319 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30320 controls, and in particular, it can be used to set
30322 control = suppress_local_fixups
30324 This cannot be used in the other non-SMTP ACLs because by the time they are
30325 run, it is too late.
30327 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30328 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30330 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30331 kind of rejection is treated as permanent, because there is no way of sending a
30332 temporary error for these kinds of message.
30335 .section "The SMTP connect ACL" "SECID191"
30336 .cindex "SMTP" "connection, ACL for"
30337 .oindex &%smtp_banner%&
30338 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30339 session, after the test specified by &%host_reject_connection%& (which is now
30340 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30341 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30342 the message override the banner message that is otherwise specified by the
30343 &%smtp_banner%& option.
30346 .section "The EHLO/HELO ACL" "SECID192"
30347 .cindex "EHLO" "ACL for"
30348 .cindex "HELO" "ACL for"
30349 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30350 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30351 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30352 Note that a client may issue more than one EHLO or HELO command in an SMTP
30353 session, and indeed is required to issue a new EHLO or HELO after successfully
30354 setting up encryption following a STARTTLS command.
30356 Note also that a deny neither forces the client to go away nor means that
30357 mail will be refused on the connection. Consider checking for
30358 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30360 If the command is accepted by an &%accept%& verb that has a &%message%&
30361 modifier, the message may not contain more than one line (it will be truncated
30362 at the first newline and a panic logged if it does). Such a message cannot
30363 affect the EHLO options that are listed on the second and subsequent lines of
30367 .section "The DATA ACLs" "SECID193"
30368 .cindex "DATA" "ACLs for"
30369 Two ACLs are associated with the DATA command, because it is two-stage
30370 command, with two responses being sent to the client.
30371 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30372 is obeyed. This gives you control after all the RCPT commands, but before
30373 the message itself is received. It offers the opportunity to give a negative
30374 response to the DATA command before the data is transmitted. Header lines
30375 added by MAIL or RCPT ACLs are not visible at this time, but any that
30376 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30378 You cannot test the contents of the message, for example, to verify addresses
30379 in the headers, at RCPT time or when the DATA command is received. Such
30380 tests have to appear in the ACL that is run after the message itself has been
30381 received, before the final response to the DATA command is sent. This is
30382 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30383 associated with the DATA command.
30385 .cindex CHUNKING "BDAT command"
30386 .cindex BDAT "SMTP command"
30387 .cindex "RFC 3030" CHUNKING
30388 If CHUNKING was advertised and a BDAT command sequence is received,
30389 the &%acl_smtp_predata%& ACL is not run.
30390 . XXX why not? It should be possible, for the first BDAT.
30391 The &%acl_smtp_data%& is run after the last BDAT command and all of
30392 the data specified is received.
30394 For both of these ACLs, it is not possible to reject individual recipients. An
30395 error response rejects the entire message. Unfortunately, it is known that some
30396 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30397 before or after the data) correctly &-- they keep the message on their queues
30398 and try again later, but that is their problem, though it does waste some of
30401 The &%acl_smtp_data%& ACL is run after
30402 the &%acl_smtp_data_prdr%&,
30403 the &%acl_smtp_dkim%&
30404 and the &%acl_smtp_mime%& ACLs.
30406 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30407 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30408 enabled (which is the default).
30410 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30411 received, and is executed for each DKIM signature found in a message. If not
30412 otherwise specified, the default action is to accept.
30414 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30416 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30419 .section "The SMTP MIME ACL" "SECID194"
30420 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30421 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30423 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30426 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30427 .cindex "PRDR" "ACL for"
30428 .oindex "&%prdr_enable%&"
30429 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30430 with PRDR support enabled (which is the default).
30431 It becomes active only when the PRDR feature is negotiated between
30432 client and server for a message, and more than one recipient
30435 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30436 has been received, and is executed once for each recipient of the message
30437 with &$local_part$& and &$domain$& valid.
30438 The test may accept, defer or deny for individual recipients.
30439 The &%acl_smtp_data%& will still be called after this ACL and
30440 can reject the message overall, even if this ACL has accepted it
30441 for some or all recipients.
30443 PRDR may be used to support per-user content filtering. Without it
30444 one must defer any recipient after the first that has a different
30445 content-filter configuration. With PRDR, the RCPT-time check
30446 .cindex "PRDR" "variable for"
30447 for this can be disabled when the variable &$prdr_requested$&
30449 Any required difference in behaviour of the main DATA-time
30450 ACL should however depend on the PRDR-time ACL having run, as Exim
30451 will avoid doing so in some situations (e.g. single-recipient mails).
30453 See also the &%prdr_enable%& global option
30454 and the &%hosts_try_prdr%& smtp transport option.
30456 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30457 If the ACL is not defined, processing completes as if
30458 the feature was not requested by the client.
30460 .section "The QUIT ACL" "SECTQUITACL"
30461 .cindex "QUIT, ACL for"
30462 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30463 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30464 does not in fact control any access.
30465 For this reason, it may only accept
30466 or warn as its final result.
30468 This ACL can be used for tasks such as custom logging at the end of an SMTP
30469 session. For example, you can use ACL variables in other ACLs to count
30470 messages, recipients, etc., and log the totals at QUIT time using one or
30471 more &%logwrite%& modifiers on a &%warn%& verb.
30473 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30474 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30476 You do not need to have a final &%accept%&, but if you do, you can use a
30477 &%message%& modifier to specify custom text that is sent as part of the 221
30480 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30481 failure (for example, failure to open a log file, or when Exim is bombing out
30482 because it has detected an unrecoverable error), all SMTP commands from the
30483 client are given temporary error responses until QUIT is received or the
30484 connection is closed. In these special cases, the QUIT ACL does not run.
30487 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30488 .vindex &$acl_smtp_notquit$&
30489 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30490 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30491 trouble, such as being unable to write to its log files, this ACL is not run,
30492 because it might try to do things (such as write to log files) that make the
30493 situation even worse.
30495 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30496 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30497 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30500 .vindex &$smtp_notquit_reason$&
30501 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30502 to a string that indicates the reason for the termination of the SMTP
30503 connection. The possible values are:
30505 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30506 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30507 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30508 .irow &`connection-lost`& "The SMTP connection has been lost"
30509 .irow &`data-timeout`& "Timeout while reading message data"
30510 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30511 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30512 .irow &`signal-exit`& "SIGTERM or SIGINT"
30513 .irow &`synchronization-error`& "SMTP synchronization error"
30514 .irow &`tls-failed`& "TLS failed to start"
30516 In most cases when an SMTP connection is closed without having received QUIT,
30517 Exim sends an SMTP response message before actually closing the connection.
30518 With the exception of the &`acl-drop`& case, the default message can be
30519 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30520 &%drop%& verb in another ACL, it is the message from the other ACL that is
30524 .section "Finding an ACL to use" "SECID195"
30525 .cindex "&ACL;" "finding which to use"
30526 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30527 you can use different ACLs in different circumstances. For example,
30529 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30530 {acl_check_rcpt} {acl_check_rcpt_submit} }
30532 In the default configuration file there are some example settings for
30533 providing an RFC 4409 message &"submission"& service on port 587 and
30534 an RFC 8314 &"submissions"& service on port 465. You can use a string
30535 expansion like this to choose an ACL for MUAs on these ports which is
30536 more appropriate for this purpose than the default ACL on port 25.
30538 The expanded string does not have to be the name of an ACL in the
30539 configuration file; there are other possibilities. Having expanded the
30540 string, Exim searches for an ACL as follows:
30543 If the string begins with a slash, Exim uses it as a filename, and reads its
30544 contents as an ACL. The lines are processed in the same way as lines in the
30545 Exim configuration file. In particular, continuation lines are supported, blank
30546 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30547 If the file does not exist or cannot be read, an error occurs (typically
30548 causing a temporary failure of whatever caused the ACL to be run). For example:
30550 acl_smtp_data = /etc/acls/\
30551 ${lookup{$sender_host_address}lsearch\
30552 {/etc/acllist}{$value}{default}}
30554 This looks up an ACL file to use on the basis of the host's IP address, falling
30555 back to a default if the lookup fails. If an ACL is successfully read from a
30556 file, it is retained in memory for the duration of the Exim process, so that it
30557 can be re-used without having to re-read the file.
30559 If the string does not start with a slash, and does not contain any spaces,
30560 Exim searches the ACL section of the configuration for an ACL whose name
30561 matches the string.
30563 If no named ACL is found, or if the string contains spaces, Exim parses
30564 the string as an inline ACL. This can save typing in cases where you just
30565 want to have something like
30567 acl_smtp_vrfy = accept
30569 in order to allow free use of the VRFY command. Such a string may contain
30570 newlines; it is processed in the same way as an ACL that is read from a file.
30576 .section "ACL return codes" "SECID196"
30577 .cindex "&ACL;" "return codes"
30578 Except for the QUIT ACL, which does not affect the SMTP return code (see
30579 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30580 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30581 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30582 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30583 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30584 This also causes a 4&'xx'& return code.
30586 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30587 &"deny"&, because there is no mechanism for passing temporary errors to the
30588 submitters of non-SMTP messages.
30591 ACLs that are relevant to message reception may also return &"discard"&. This
30592 has the effect of &"accept"&, but causes either the entire message or an
30593 individual recipient address to be discarded. In other words, it is a
30594 blackholing facility. Use it with care.
30596 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30597 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30598 RCPT ACL is to discard just the one recipient address. If there are no
30599 recipients left when the message's data is received, the DATA ACL is not
30600 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30601 remaining recipients. The &"discard"& return is not permitted for the
30602 &%acl_smtp_predata%& ACL.
30604 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30605 is done on the address and the result determines the SMTP response.
30608 .cindex "&[local_scan()]& function" "when all recipients discarded"
30609 The &[local_scan()]& function is always run, even if there are no remaining
30610 recipients; it may create new recipients.
30614 .section "Unset ACL options" "SECID197"
30615 .cindex "&ACL;" "unset options"
30616 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30617 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30618 not defined at all. For any defined ACL, the default action when control
30619 reaches the end of the ACL statements is &"deny"&.
30621 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30622 these two are ACLs that are used only for their side effects. They cannot be
30623 used to accept or reject anything.
30625 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30626 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30627 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30628 when the ACL is not defined is &"accept"&.
30630 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30631 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30632 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30633 messages over an SMTP connection. For an example, see the ACL in the default
30634 configuration file.
30639 .section "Data for message ACLs" "SECID198"
30640 .cindex "&ACL;" "data for message ACL"
30642 .vindex &$local_part$&
30643 .vindex &$sender_address$&
30644 .vindex &$sender_host_address$&
30645 .vindex &$smtp_command$&
30646 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30647 that contain information about the host and the message's sender (for example,
30648 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30649 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30650 &$local_part$& are set from the argument address. The entire SMTP command
30651 is available in &$smtp_command$&.
30653 When an ACL for the AUTH parameter of MAIL is running, the variables that
30654 contain information about the host are set, but &$sender_address$& is not yet
30655 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30658 .vindex "&$message_size$&"
30659 The &$message_size$& variable is set to the value of the SIZE parameter on
30660 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30661 that parameter is not given. The value is updated to the true message size by
30662 the time the final DATA ACL is run (after the message data has been
30665 .vindex "&$rcpt_count$&"
30666 .vindex "&$recipients_count$&"
30667 The &$rcpt_count$& variable increases by one for each RCPT command received.
30668 The &$recipients_count$& variable increases by one each time a RCPT command is
30669 accepted, so while an ACL for RCPT is being processed, it contains the number
30670 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30671 &$rcpt_count$& contains the total number of RCPT commands, and
30672 &$recipients_count$& contains the total number of accepted recipients.
30678 .section "Data for non-message ACLs" "SECTdatfornon"
30679 .cindex "&ACL;" "data for non-message ACL"
30680 .vindex &$smtp_command_argument$&
30681 .vindex &$smtp_command$&
30682 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30683 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30684 and the entire SMTP command is available in &$smtp_command$&.
30685 These variables can be tested using a &%condition%& condition. For example,
30686 here is an ACL for use with AUTH, which insists that either the session is
30687 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30688 does not permit authentication methods that use cleartext passwords on
30689 unencrypted connections.
30692 accept encrypted = *
30693 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30695 deny message = TLS encryption or CRAM-MD5 required
30697 (Another way of applying this restriction is to arrange for the authenticators
30698 that use cleartext passwords not to be advertised when the connection is not
30699 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30700 option to do this.)
30704 .section "Format of an ACL" "SECID199"
30705 .cindex "&ACL;" "format of"
30706 .cindex "&ACL;" "verbs, definition of"
30707 An individual ACL consists of a number of statements. Each statement starts
30708 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30709 Modifiers can change the way the verb operates, define error and log messages,
30710 set variables, insert delays, and vary the processing of accepted messages.
30712 If all the conditions are met, the verb is obeyed. The same condition may be
30713 used (with different arguments) more than once in the same statement. This
30714 provides a means of specifying an &"and"& conjunction between conditions. For
30717 deny dnslists = list1.example
30718 dnslists = list2.example
30720 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30721 the conditions and modifiers when it reaches a condition that fails. What
30722 happens then depends on the verb (and in one case, on a special modifier). Not
30723 all the conditions make sense at every testing point. For example, you cannot
30724 test a sender address in the ACL that is run for a VRFY command.
30727 .section "ACL verbs" "SECID200"
30728 The ACL verbs are as follows:
30731 .cindex "&%accept%& ACL verb"
30732 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30733 of the conditions are not met, what happens depends on whether &%endpass%&
30734 appears among the conditions (for syntax see below). If the failing condition
30735 is before &%endpass%&, control is passed to the next ACL statement; if it is
30736 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30737 check a RCPT command:
30739 accept domains = +local_domains
30743 If the recipient domain does not match the &%domains%& condition, control
30744 passes to the next statement. If it does match, the recipient is verified, and
30745 the command is accepted if verification succeeds. However, if verification
30746 fails, the ACL yields &"deny"&, because the failing condition is after
30749 The &%endpass%& feature has turned out to be confusing to many people, so its
30750 use is not recommended nowadays. It is always possible to rewrite an ACL so
30751 that &%endpass%& is not needed, and it is no longer used in the default
30754 .cindex "&%message%& ACL modifier" "with &%accept%&"
30755 If a &%message%& modifier appears on an &%accept%& statement, its action
30756 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30757 (when an &%accept%& verb either accepts or passes control to the next
30758 statement), &%message%& can be used to vary the message that is sent when an
30759 SMTP command is accepted. For example, in a RCPT ACL you could have:
30761 &`accept `&<&'some conditions'&>
30762 &` message = OK, I will allow you through today`&
30764 You can specify an SMTP response code, optionally followed by an &"extended
30765 response code"& at the start of the message, but the first digit must be the
30766 same as would be sent by default, which is 2 for an &%accept%& verb.
30768 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30769 an error message that is used when access is denied. This behaviour is retained
30770 for backward compatibility, but current &"best practice"& is to avoid the use
30775 .cindex "&%defer%& ACL verb"
30776 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30777 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30778 &%defer%& is the same as &%deny%&, because there is no way of sending a
30779 temporary error. For a RCPT command, &%defer%& is much the same as using a
30780 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30781 be used in any ACL, and even for a recipient it might be a simpler approach.
30785 .cindex "&%deny%& ACL verb"
30786 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30787 the conditions are not met, control is passed to the next ACL statement. For
30790 deny dnslists = blackholes.mail-abuse.org
30792 rejects commands from hosts that are on a DNS black list.
30796 .cindex "&%discard%& ACL verb"
30797 &%discard%&: This verb behaves like &%accept%&, except that it returns
30798 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30799 that are concerned with receiving messages. When all the conditions are true,
30800 the sending entity receives a &"success"& response. However, &%discard%& causes
30801 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30802 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30803 message's recipients are discarded. Recipients that are discarded before DATA
30804 do not appear in the log line when the &%received_recipients%& log selector is set.
30806 If the &%log_message%& modifier is set when &%discard%& operates,
30807 its contents are added to the line that is automatically written to the log.
30808 The &%message%& modifier operates exactly as it does for &%accept%&.
30812 .cindex "&%drop%& ACL verb"
30813 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30814 forcibly closed after the 5&'xx'& error message has been sent. For example:
30816 drop condition = ${if > {$rcpt_count}{20}}
30817 message = I don't take more than 20 RCPTs
30819 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30820 The connection is always dropped after sending a 550 response.
30823 .cindex "&%require%& ACL verb"
30824 &%require%&: If all the conditions are met, control is passed to the next ACL
30825 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30826 example, when checking a RCPT command,
30828 require message = Sender did not verify
30831 passes control to subsequent statements only if the message's sender can be
30832 verified. Otherwise, it rejects the command. Note the positioning of the
30833 &%message%& modifier, before the &%verify%& condition. The reason for this is
30834 discussed in section &<<SECTcondmodproc>>&.
30837 .cindex "&%warn%& ACL verb"
30838 &%warn%&: If all the conditions are true, a line specified by the
30839 &%log_message%& modifier is written to Exim's main log. Control always passes
30840 to the next ACL statement. If any condition is false, the log line is not
30841 written. If an identical log line is requested several times in the same
30842 message, only one copy is actually written to the log. If you want to force
30843 duplicates to be written, use the &%logwrite%& modifier instead.
30845 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
30846 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
30847 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
30848 first failing condition. There is more about adding header lines in section
30849 &<<SECTaddheadacl>>&.
30851 If any condition on a &%warn%& statement cannot be completed (that is, there is
30852 some sort of defer), the log line specified by &%log_message%& is not written.
30853 This does not include the case of a forced failure from a lookup, which
30854 is considered to be a successful completion. After a defer, no further
30855 conditions or modifiers in the &%warn%& statement are processed. The incident
30856 is logged, and the ACL continues to be processed, from the next statement
30860 .vindex "&$acl_verify_message$&"
30861 When one of the &%warn%& conditions is an address verification that fails, the
30862 text of the verification failure message is in &$acl_verify_message$&. If you
30863 want this logged, you must set it up explicitly. For example:
30865 warn !verify = sender
30866 log_message = sender verify failed: $acl_verify_message
30870 At the end of each ACL there is an implicit unconditional &%deny%&.
30872 As you can see from the examples above, the conditions and modifiers are
30873 written one to a line, with the first one on the same line as the verb, and
30874 subsequent ones on following lines. If you have a very long condition, you can
30875 continue it onto several physical lines by the usual backslash continuation
30876 mechanism. It is conventional to align the conditions vertically.
30880 .section "ACL variables" "SECTaclvariables"
30881 .cindex "&ACL;" "variables"
30882 There are some special variables that can be set during ACL processing. They
30883 can be used to pass information between different ACLs, different invocations
30884 of the same ACL in the same SMTP connection, and between ACLs and the routers,
30885 transports, and filters that are used to deliver a message. The names of these
30886 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
30887 an underscore, but the remainder of the name can be any sequence of
30888 alphanumeric characters and underscores that you choose. There is no limit on
30889 the number of ACL variables. The two sets act as follows:
30891 The values of those variables whose names begin with &$acl_c$& persist
30892 throughout an SMTP connection. They are never reset. Thus, a value that is set
30893 while receiving one message is still available when receiving the next message
30894 on the same SMTP connection.
30896 The values of those variables whose names begin with &$acl_m$& persist only
30897 while a message is being received. They are reset afterwards. They are also
30898 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
30901 When a message is accepted, the current values of all the ACL variables are
30902 preserved with the message and are subsequently made available at delivery
30903 time. The ACL variables are set by a modifier called &%set%&. For example:
30905 accept hosts = whatever
30906 set acl_m4 = some value
30907 accept authenticated = *
30908 set acl_c_auth = yes
30910 &*Note*&: A leading dollar sign is not used when naming a variable that is to
30911 be set. If you want to set a variable without taking any action, you can use a
30912 &%warn%& verb without any other modifiers or conditions.
30914 .oindex &%strict_acl_vars%&
30915 What happens if a syntactically valid but undefined ACL variable is
30916 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
30917 false (the default), an empty string is substituted; if it is true, an
30918 error is generated.
30920 Versions of Exim before 4.64 have a limited set of numbered variables, but
30921 their names are compatible, so there is no problem with upgrading.
30924 .section "Condition and modifier processing" "SECTcondmodproc"
30925 .cindex "&ACL;" "conditions; processing"
30926 .cindex "&ACL;" "modifiers; processing"
30927 An exclamation mark preceding a condition negates its result. For example:
30929 deny domains = *.dom.example
30930 !verify = recipient
30932 causes the ACL to return &"deny"& if the recipient domain ends in
30933 &'dom.example'& and the recipient address cannot be verified. Sometimes
30934 negation can be used on the right-hand side of a condition. For example, these
30935 two statements are equivalent:
30937 deny hosts = !192.168.3.4
30938 deny !hosts = 192.168.3.4
30940 However, for many conditions (&%verify%& being a good example), only left-hand
30941 side negation of the whole condition is possible.
30943 The arguments of conditions and modifiers are expanded. A forced failure
30944 of an expansion causes a condition to be ignored, that is, it behaves as if the
30945 condition is true. Consider these two statements:
30947 accept senders = ${lookup{$host_name}lsearch\
30948 {/some/file}{$value}fail}
30949 accept senders = ${lookup{$host_name}lsearch\
30950 {/some/file}{$value}{}}
30952 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
30953 the returned list is searched, but if the lookup fails the behaviour is
30954 different in the two cases. The &%fail%& in the first statement causes the
30955 condition to be ignored, leaving no further conditions. The &%accept%& verb
30956 therefore succeeds. The second statement, however, generates an empty list when
30957 the lookup fails. No sender can match an empty list, so the condition fails,
30958 and therefore the &%accept%& also fails.
30960 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
30961 specify actions that are taken as the conditions for a statement are checked;
30962 others specify text for messages that are used when access is denied or a
30963 warning is generated. The &%control%& modifier affects the way an incoming
30964 message is handled.
30966 The positioning of the modifiers in an ACL statement is important, because the
30967 processing of a verb ceases as soon as its outcome is known. Only those
30968 modifiers that have already been encountered will take effect. For example,
30969 consider this use of the &%message%& modifier:
30971 require message = Can't verify sender
30973 message = Can't verify recipient
30975 message = This message cannot be used
30977 If sender verification fails, Exim knows that the result of the statement is
30978 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
30979 so its text is used as the error message. If sender verification succeeds, but
30980 recipient verification fails, the second message is used. If recipient
30981 verification succeeds, the third message becomes &"current"&, but is never used
30982 because there are no more conditions to cause failure.
30984 For the &%deny%& verb, on the other hand, it is always the last &%message%&
30985 modifier that is used, because all the conditions must be true for rejection to
30986 happen. Specifying more than one &%message%& modifier does not make sense, and
30987 the message can even be specified after all the conditions. For example:
30990 !senders = *@my.domain.example
30991 message = Invalid sender from client host
30993 The &"deny"& result does not happen until the end of the statement is reached,
30994 by which time Exim has set up the message.
30998 .section "ACL modifiers" "SECTACLmodi"
30999 .cindex "&ACL;" "modifiers; list of"
31000 The ACL modifiers are as follows:
31003 .vitem &*add_header*&&~=&~<&'text'&>
31004 This modifier specifies one or more header lines that are to be added to an
31005 incoming message, assuming, of course, that the message is ultimately
31006 accepted. For details, see section &<<SECTaddheadacl>>&.
31008 .vitem &*continue*&&~=&~<&'text'&>
31009 .cindex "&%continue%& ACL modifier"
31010 .cindex "database" "updating in ACL"
31011 This modifier does nothing of itself, and processing of the ACL always
31012 continues with the next condition or modifier. The value of &%continue%& is in
31013 the side effects of expanding its argument. Typically this could be used to
31014 update a database. It is really just a syntactic tidiness, to avoid having to
31015 write rather ugly lines like this:
31017 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31019 Instead, all you need is
31021 &`continue = `&<&'some expansion'&>
31024 .vitem &*control*&&~=&~<&'text'&>
31025 .cindex "&%control%& ACL modifier"
31026 This modifier affects the subsequent processing of the SMTP connection or of an
31027 incoming message that is accepted. The effect of the first type of control
31028 lasts for the duration of the connection, whereas the effect of the second type
31029 lasts only until the current message has been received. The message-specific
31030 controls always apply to the whole message, not to individual recipients,
31031 even if the &%control%& modifier appears in a RCPT ACL.
31033 As there are now quite a few controls that can be applied, they are described
31034 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31035 in several different ways. For example:
31037 . ==== As this is a nested list, any displays it contains must be indented
31038 . ==== as otherwise they are too far to the left. That comment applies only
31039 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31043 It can be at the end of an &%accept%& statement:
31045 accept ...some conditions
31048 In this case, the control is applied when this statement yields &"accept"&, in
31049 other words, when the conditions are all true.
31052 It can be in the middle of an &%accept%& statement:
31054 accept ...some conditions...
31056 ...some more conditions...
31058 If the first set of conditions are true, the control is applied, even if the
31059 statement does not accept because one of the second set of conditions is false.
31060 In this case, some subsequent statement must yield &"accept"& for the control
31064 It can be used with &%warn%& to apply the control, leaving the
31065 decision about accepting or denying to a subsequent verb. For
31068 warn ...some conditions...
31072 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31073 &%logwrite%&, so it does not add anything to the message and does not write a
31077 If you want to apply a control unconditionally, you can use it with a
31078 &%require%& verb. For example:
31080 require control = no_multiline_responses
31084 .vitem &*delay*&&~=&~<&'time'&>
31085 .cindex "&%delay%& ACL modifier"
31087 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31088 the time interval before proceeding. However, when testing Exim using the
31089 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31090 output instead). The time is given in the usual Exim notation, and the delay
31091 happens as soon as the modifier is processed. In an SMTP session, pending
31092 output is flushed before the delay is imposed.
31094 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31097 deny ...some conditions...
31100 The delay happens if all the conditions are true, before the statement returns
31101 &"deny"&. Compare this with:
31104 ...some conditions...
31106 which waits for 30s before processing the conditions. The &%delay%& modifier
31107 can also be used with &%warn%& and together with &%control%&:
31109 warn ...some conditions...
31115 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31116 responses to several commands are no longer buffered and sent in one packet (as
31117 they would normally be) because all output is flushed before imposing the
31118 delay. This optimization is disabled so that a number of small delays do not
31119 appear to the client as one large aggregated delay that might provoke an
31120 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31121 using a &%control%& modifier to set &%no_delay_flush%&.
31125 .cindex "&%endpass%& ACL modifier"
31126 This modifier, which has no argument, is recognized only in &%accept%& and
31127 &%discard%& statements. It marks the boundary between the conditions whose
31128 failure causes control to pass to the next statement, and the conditions whose
31129 failure causes the ACL to return &"deny"&. This concept has proved to be
31130 confusing to some people, so the use of &%endpass%& is no longer recommended as
31131 &"best practice"&. See the description of &%accept%& above for more details.
31134 .vitem &*log_message*&&~=&~<&'text'&>
31135 .cindex "&%log_message%& ACL modifier"
31136 This modifier sets up a message that is used as part of the log message if the
31137 ACL denies access or a &%warn%& statement's conditions are true. For example:
31139 require log_message = wrong cipher suite $tls_in_cipher
31140 encrypted = DES-CBC3-SHA
31142 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31145 &`discard `&<&'some conditions'&>
31146 &` log_message = Discarded $local_part@$domain because...`&
31148 When access is denied, &%log_message%& adds to any underlying error message
31149 that may exist because of a condition failure. For example, while verifying a
31150 recipient address, a &':fail:'& redirection might have already set up a
31153 The message may be defined before the conditions to which it applies, because
31154 the string expansion does not happen until Exim decides that access is to be
31155 denied. This means that any variables that are set by the condition are
31156 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31157 variables are set after a DNS black list lookup succeeds. If the expansion of
31158 &%log_message%& fails, or if the result is an empty string, the modifier is
31161 .vindex "&$acl_verify_message$&"
31162 If you want to use a &%warn%& statement to log the result of an address
31163 verification, you can use &$acl_verify_message$& to include the verification
31166 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31167 the start of the logged message. If the same warning log message is requested
31168 more than once while receiving a single email message, only one copy is
31169 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31170 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31171 is logged for a successful &%warn%& statement.
31173 If &%log_message%& is not present and there is no underlying error message (for
31174 example, from the failure of address verification), but &%message%& is present,
31175 the &%message%& text is used for logging rejections. However, if any text for
31176 logging contains newlines, only the first line is logged. In the absence of
31177 both &%log_message%& and &%message%&, a default built-in message is used for
31178 logging rejections.
31181 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31182 .cindex "&%log_reject_target%& ACL modifier"
31183 .cindex "logging in ACL" "specifying which log"
31184 This modifier makes it possible to specify which logs are used for messages
31185 about ACL rejections. Its argument is a colon-separated list of words that can
31186 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31187 may be empty, in which case a rejection is not logged at all. For example, this
31188 ACL fragment writes no logging information when access is denied:
31190 &`deny `&<&'some conditions'&>
31191 &` log_reject_target =`&
31193 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31194 permanent and temporary rejections. Its effect lasts for the rest of the
31198 .vitem &*logwrite*&&~=&~<&'text'&>
31199 .cindex "&%logwrite%& ACL modifier"
31200 .cindex "logging in ACL" "immediate"
31201 This modifier writes a message to a log file as soon as it is encountered when
31202 processing an ACL. (Compare &%log_message%&, which, except in the case of
31203 &%warn%& and &%discard%&, is used only if the ACL statement denies
31204 access.) The &%logwrite%& modifier can be used to log special incidents in
31207 &`accept `&<&'some special conditions'&>
31208 &` control = freeze`&
31209 &` logwrite = froze message because ...`&
31211 By default, the message is written to the main log. However, it may begin
31212 with a colon, followed by a comma-separated list of log names, and then
31213 another colon, to specify exactly which logs are to be written. For
31216 logwrite = :main,reject: text for main and reject logs
31217 logwrite = :panic: text for panic log only
31221 .vitem &*message*&&~=&~<&'text'&>
31222 .cindex "&%message%& ACL modifier"
31223 This modifier sets up a text string that is expanded and used as a response
31224 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31225 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31226 there is some complication if &%endpass%& is involved; see the description of
31227 &%accept%& for details.)
31229 The expansion of the message happens at the time Exim decides that the ACL is
31230 to end, not at the time it processes &%message%&. If the expansion fails, or
31231 generates an empty string, the modifier is ignored. Here is an example where
31232 &%message%& must be specified first, because the ACL ends with a rejection if
31233 the &%hosts%& condition fails:
31235 require message = Host not recognized
31238 (Once a condition has failed, no further conditions or modifiers are
31241 .cindex "SMTP" "error codes"
31242 .oindex "&%smtp_banner%&
31243 For ACLs that are triggered by SMTP commands, the message is returned as part
31244 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31245 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31246 is accepted. In the case of the connect ACL, accepting with a message modifier
31247 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31248 accept message may not contain more than one line (otherwise it will be
31249 truncated at the first newline and a panic logged), and it cannot affect the
31252 When SMTP is involved, the message may begin with an overriding response code,
31253 consisting of three digits optionally followed by an &"extended response code"&
31254 of the form &'n.n.n'&, each code being followed by a space. For example:
31256 deny message = 599 1.2.3 Host not welcome
31257 hosts = 192.168.34.0/24
31259 The first digit of the supplied response code must be the same as would be sent
31260 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31261 access, but for the predata ACL, note that the default success code is 354, not
31264 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31265 the message modifier cannot override the 221 response code.
31267 The text in a &%message%& modifier is literal; any quotes are taken as
31268 literals, but because the string is expanded, backslash escapes are processed
31269 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31272 .vindex "&$acl_verify_message$&"
31273 For ACLs that are called by an &%acl =%& ACL condition, the message is
31274 stored in &$acl_verify_message$&, from which the calling ACL may use it.
31276 If &%message%& is used on a statement that verifies an address, the message
31277 specified overrides any message that is generated by the verification process.
31278 However, the original message is available in the variable
31279 &$acl_verify_message$&, so you can incorporate it into your message if you
31280 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31281 routers to be passed back as part of the SMTP response, you should either not
31282 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31284 For compatibility with previous releases of Exim, a &%message%& modifier that
31285 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31286 modifier, but this usage is now deprecated. However, &%message%& acts only when
31287 all the conditions are true, wherever it appears in an ACL command, whereas
31288 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31289 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31293 .vitem &*queue*&&~=&~<&'text'&>
31294 .cindex "&%queue%& ACL modifier"
31295 .cindex "named queues" "selecting in ACL"
31296 This modifier specifies the use of a named queue for spool files
31298 It can only be used before the message is received (i.e. not in
31300 This could be used, for example, for known high-volume burst sources
31301 of traffic, or for quarantine of messages.
31302 Separate queue-runner processes will be needed for named queues.
31303 If the text after expansion is empty, the default queue is used.
31306 .vitem &*remove_header*&&~=&~<&'text'&>
31307 This modifier specifies one or more header names in a colon-separated list
31308 that are to be removed from an incoming message, assuming, of course, that
31309 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31312 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31313 .cindex "&%set%& ACL modifier"
31314 This modifier puts a value into one of the ACL variables (see section
31315 &<<SECTaclvariables>>&).
31318 .vitem &*udpsend*&&~=&~<&'parameters'&>
31319 .cindex "UDP communications"
31320 This modifier sends a UDP packet, for purposes such as statistics
31321 collection or behaviour monitoring. The parameters are expanded, and
31322 the result of the expansion must be a colon-separated list consisting
31323 of a destination server, port number, and the packet contents. The
31324 server can be specified as a host name or IPv4 or IPv6 address. The
31325 separator can be changed with the usual angle bracket syntax. For
31326 example, you might want to collect information on which hosts connect
31329 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31330 $tod_zulu $sender_host_address
31337 .section "Use of the control modifier" "SECTcontrols"
31338 .cindex "&%control%& ACL modifier"
31339 The &%control%& modifier supports the following settings:
31342 .vitem &*control&~=&~allow_auth_unadvertised*&
31343 This modifier allows a client host to use the SMTP AUTH command even when it
31344 has not been advertised in response to EHLO. Furthermore, because there are
31345 apparently some really broken clients that do this, Exim will accept AUTH after
31346 HELO (rather than EHLO) when this control is set. It should be used only if you
31347 really need it, and you should limit its use to those broken clients that do
31348 not work without it. For example:
31350 warn hosts = 192.168.34.25
31351 control = allow_auth_unadvertised
31353 Normally, when an Exim server receives an AUTH command, it checks the name of
31354 the authentication mechanism that is given in the command to ensure that it
31355 matches an advertised mechanism. When this control is set, the check that a
31356 mechanism has been advertised is bypassed. Any configured mechanism can be used
31357 by the client. This control is permitted only in the connection and HELO ACLs.
31360 .vitem &*control&~=&~caseful_local_part*& &&&
31361 &*control&~=&~caselower_local_part*&
31362 .cindex "&ACL;" "case of local part in"
31363 .cindex "case of local parts"
31364 .vindex "&$local_part$&"
31365 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31366 (that is, during RCPT processing). By default, the contents of &$local_part$&
31367 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31368 any uppercase letters in the original local part are restored in &$local_part$&
31369 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31372 These controls affect only the current recipient. Moreover, they apply only to
31373 local part handling that takes place directly in the ACL (for example, as a key
31374 in lookups). If a test to verify the recipient is obeyed, the case-related
31375 handling of the local part during the verification is controlled by the router
31376 configuration (see the &%caseful_local_part%& generic router option).
31378 This facility could be used, for example, to add a spam score to local parts
31379 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31382 warn control = caseful_local_part
31383 set acl_m4 = ${eval:\
31385 ${if match{$local_part}{[A-Z]}{1}{0}}\
31387 control = caselower_local_part
31389 Notice that we put back the lower cased version afterwards, assuming that
31390 is what is wanted for subsequent tests.
31393 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31394 .cindex "&ACL;" "cutthrough routing"
31395 .cindex "cutthrough" "requesting"
31396 This option requests delivery be attempted while the item is being received.
31398 The option is usable in the RCPT ACL.
31399 If enabled for a message received via smtp and routed to an smtp transport,
31400 and only one transport, interface, destination host and port combination
31401 is used for all recipients of the message,
31402 then the delivery connection is made while the receiving connection is open
31403 and data is copied from one to the other.
31405 An attempt to set this option for any recipient but the first
31406 for a mail will be quietly ignored.
31407 If a recipient-verify callout
31409 connection is subsequently
31410 requested in the same ACL it is held open and used for
31411 any subsequent recipients and the data,
31412 otherwise one is made after the initial RCPT ACL completes.
31414 Note that routers are used in verify mode,
31415 and cannot depend on content of received headers.
31416 Note also that headers cannot be
31417 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31418 Headers may be modified by routers (subject to the above) and transports.
31419 The &'Received-By:'& header is generated as soon as the body reception starts,
31420 rather than the traditional time after the full message is received;
31421 this will affect the timestamp.
31423 All the usual ACLs are called; if one results in the message being
31424 rejected, all effort spent in delivery (including the costs on
31425 the ultimate destination) will be wasted.
31426 Note that in the case of data-time ACLs this includes the entire
31429 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31430 of outgoing messages is done, because it sends data to the ultimate destination
31431 before the entire message has been received from the source.
31432 It is not supported for messages received with the SMTP PRDR
31436 Should the ultimate destination system positively accept or reject the mail,
31437 a corresponding indication is given to the source system and nothing is queued.
31438 If the item is successfully delivered in cutthrough mode
31439 the delivery log lines are tagged with ">>" rather than "=>" and appear
31440 before the acceptance "<=" line.
31442 If there is a temporary error the item is queued for later delivery in the
31444 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31445 to the control; the default value is &"spool"& and the alternate value
31446 &"pass"& copies an SMTP defer response from the target back to the initiator
31447 and does not queue the message.
31448 Note that this is independent of any recipient verify conditions in the ACL.
31450 Delivery in this mode avoids the generation of a bounce mail to a
31452 sender when the destination system is doing content-scan based rejection.
31455 .vitem &*control&~=&~debug/*&<&'options'&>
31456 .cindex "&ACL;" "enabling debug logging"
31457 .cindex "debugging" "enabling from an ACL"
31458 This control turns on debug logging, almost as though Exim had been invoked
31459 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31460 by default called &'debuglog'&.
31461 The filename can be adjusted with the &'tag'& option, which
31462 may access any variables already defined. The logging may be adjusted with
31463 the &'opts'& option, which takes the same values as the &`-d`& command-line
31465 Logging started this way may be stopped, and the file removed,
31466 with the &'kill'& option.
31467 Some examples (which depend on variables that don't exist in all
31471 control = debug/tag=.$sender_host_address
31472 control = debug/opts=+expand+acl
31473 control = debug/tag=.$message_exim_id/opts=+expand
31474 control = debug/kill
31478 .vitem &*control&~=&~dkim_disable_verify*&
31479 .cindex "disable DKIM verify"
31480 .cindex "DKIM" "disable verify"
31481 This control turns off DKIM verification processing entirely. For details on
31482 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31485 .vitem &*control&~=&~dmarc_disable_verify*&
31486 .cindex "disable DMARC verify"
31487 .cindex "DMARC" "disable verify"
31488 This control turns off DMARC verification processing entirely. For details on
31489 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31492 .vitem &*control&~=&~dscp/*&<&'value'&>
31493 .cindex "&ACL;" "setting DSCP value"
31494 .cindex "DSCP" "inbound"
31495 This option causes the DSCP value associated with the socket for the inbound
31496 connection to be adjusted to a given value, given as one of a number of fixed
31497 strings or to numeric value.
31498 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31499 Common values include &`throughput`&, &`mincost`&, and on newer systems
31500 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31502 The outbound packets from Exim will be marked with this value in the header
31503 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31504 that these values will have any effect, not be stripped by networking
31505 equipment, or do much of anything without cooperation with your Network
31506 Engineer and those of all network operators between the source and destination.
31509 .vitem &*control&~=&~enforce_sync*& &&&
31510 &*control&~=&~no_enforce_sync*&
31511 .cindex "SMTP" "synchronization checking"
31512 .cindex "synchronization checking in SMTP"
31513 These controls make it possible to be selective about when SMTP synchronization
31514 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31515 state of the switch (it is true by default). See the description of this option
31516 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31518 The effect of these two controls lasts for the remainder of the SMTP
31519 connection. They can appear in any ACL except the one for the non-SMTP
31520 messages. The most straightforward place to put them is in the ACL defined by
31521 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31522 before the first synchronization check. The expected use is to turn off the
31523 synchronization checks for badly-behaved hosts that you nevertheless need to
31527 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31528 .cindex "fake defer"
31529 .cindex "defer, fake"
31530 This control works in exactly the same way as &%fakereject%& (described below)
31531 except that it causes an SMTP 450 response after the message data instead of a
31532 550 response. You must take care when using &%fakedefer%& because it causes the
31533 messages to be duplicated when the sender retries. Therefore, you should not
31534 use &%fakedefer%& if the message is to be delivered normally.
31536 .vitem &*control&~=&~fakereject/*&<&'message'&>
31537 .cindex "fake rejection"
31538 .cindex "rejection, fake"
31539 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31540 words, only when an SMTP message is being received. If Exim accepts the
31541 message, instead the final 250 response, a 550 rejection message is sent.
31542 However, Exim proceeds to deliver the message as normal. The control applies
31543 only to the current message, not to any subsequent ones that may be received in
31544 the same SMTP connection.
31546 The text for the 550 response is taken from the &%control%& modifier. If no
31547 message is supplied, the following is used:
31549 550-Your message has been rejected but is being
31550 550-kept for evaluation.
31551 550-If it was a legitimate message, it may still be
31552 550 delivered to the target recipient(s).
31554 This facility should be used with extreme caution.
31556 .vitem &*control&~=&~freeze*&
31557 .cindex "frozen messages" "forcing in ACL"
31558 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31559 other words, only when a message is being received. If the message is accepted,
31560 it is placed on Exim's queue and frozen. The control applies only to the
31561 current message, not to any subsequent ones that may be received in the same
31564 This modifier can optionally be followed by &`/no_tell`&. If the global option
31565 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31566 is told about the freezing), provided all the &*control=freeze*& modifiers that
31567 are obeyed for the current message have the &`/no_tell`& option.
31569 .vitem &*control&~=&~no_delay_flush*&
31570 .cindex "SMTP" "output flushing, disabling for delay"
31571 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31572 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31573 use. This control, as long as it is encountered before the &%delay%& modifier,
31574 disables such output flushing.
31576 .vitem &*control&~=&~no_callout_flush*&
31577 .cindex "SMTP" "output flushing, disabling for callout"
31578 Exim normally flushes SMTP output before performing a callout in an ACL, to
31579 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31580 use. This control, as long as it is encountered before the &%verify%& condition
31581 that causes the callout, disables such output flushing.
31583 .vitem &*control&~=&~no_mbox_unspool*&
31584 This control is available when Exim is compiled with the content scanning
31585 extension. Content scanning may require a copy of the current message, or parts
31586 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31587 or spam scanner. Normally, such copies are deleted when they are no longer
31588 needed. If this control is set, the copies are not deleted. The control applies
31589 only to the current message, not to any subsequent ones that may be received in
31590 the same SMTP connection. It is provided for debugging purposes and is unlikely
31591 to be useful in production.
31593 .vitem &*control&~=&~no_multiline_responses*&
31594 .cindex "multiline responses, suppressing"
31595 This control is permitted for any ACL except the one for non-SMTP messages.
31596 It seems that there are broken clients in use that cannot handle multiline
31597 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31599 If this control is set, multiline SMTP responses from ACL rejections are
31600 suppressed. One way of doing this would have been to put out these responses as
31601 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31602 (&"use multiline responses for more"& it says &-- ha!), and some of the
31603 responses might get close to that. So this facility, which is after all only a
31604 sop to broken clients, is implemented by doing two very easy things:
31607 Extra information that is normally output as part of a rejection caused by
31608 sender verification failure is omitted. Only the final line (typically &"sender
31609 verification failed"&) is sent.
31611 If a &%message%& modifier supplies a multiline response, only the first
31615 The setting of the switch can, of course, be made conditional on the
31616 calling host. Its effect lasts until the end of the SMTP connection.
31618 .vitem &*control&~=&~no_pipelining*&
31619 .cindex "PIPELINING" "suppressing advertising"
31620 .cindex "ESMTP extensions" PIPELINING
31621 This control turns off the advertising of the PIPELINING extension to SMTP in
31622 the current session. To be useful, it must be obeyed before Exim sends its
31623 response to an EHLO command. Therefore, it should normally appear in an ACL
31624 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31625 &%pipelining_advertise_hosts%&.
31627 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31628 &*control&~=&~queue_only*&
31629 .oindex "&%queue%&"
31630 .oindex "&%queue_only%&"
31631 .cindex "queueing incoming messages"
31632 .cindex queueing "forcing in ACL"
31633 .cindex "first pass routing"
31634 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31635 other words, only when a message is being received. If the message is accepted,
31636 it is placed on Exim's queue and left there for delivery by a subsequent queue
31638 If used with no options set,
31639 no immediate delivery process is started. In other words, it has the
31640 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31642 If the &'first_pass_route'& option is given then
31643 the behaviour is like the command-line &'-oqds'& option;
31644 a delivery process is started which stops short of making
31645 any SMTP delivery. The benefit is that the hints database will be updated for
31646 the message being waiting for a specific host, and a later queue run will be
31647 able to send all such messages on a single connection.
31649 The control only applies to the current message, not to any subsequent ones that
31650 may be received in the same SMTP connection.
31652 .vitem &*control&~=&~submission/*&<&'options'&>
31653 .cindex "message" "submission"
31654 .cindex "submission mode"
31655 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31656 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31657 the current message is a submission from a local MUA. In this case, Exim
31658 operates in &"submission mode"&, and applies certain fixups to the message if
31659 necessary. For example, it adds a &'Date:'& header line if one is not present.
31660 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31661 late (the message has already been created).
31663 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31664 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31665 submission mode; the available options for this control are described there.
31666 The control applies only to the current message, not to any subsequent ones
31667 that may be received in the same SMTP connection.
31669 .vitem &*control&~=&~suppress_local_fixups*&
31670 .cindex "submission fixups, suppressing"
31671 This control applies to locally submitted (non TCP/IP) messages, and is the
31672 complement of &`control = submission`&. It disables the fixups that are
31673 normally applied to locally-submitted messages. Specifically:
31676 Any &'Sender:'& header line is left alone (in this respect, it is a
31677 dynamic version of &%local_sender_retain%&).
31679 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31681 There is no check that &'From:'& corresponds to the actual sender.
31684 This control may be useful when a remotely-originated message is accepted,
31685 passed to some scanning program, and then re-submitted for delivery. It can be
31686 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31687 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31690 &*Note:*& This control applies only to the current message, not to any others
31691 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31693 .vitem &*control&~=&~utf8_downconvert*&
31694 This control enables conversion of UTF-8 in message envelope addresses
31696 For details see section &<<SECTi18nMTA>>&.
31700 .section "Summary of message fixup control" "SECTsummesfix"
31701 All four possibilities for message fixups can be specified:
31704 Locally submitted, fixups applied: the default.
31706 Locally submitted, no fixups applied: use
31707 &`control = suppress_local_fixups`&.
31709 Remotely submitted, no fixups applied: the default.
31711 Remotely submitted, fixups applied: use &`control = submission`&.
31716 .section "Adding header lines in ACLs" "SECTaddheadacl"
31717 .cindex "header lines" "adding in an ACL"
31718 .cindex "header lines" "position of added lines"
31719 .cindex "&%add_header%& ACL modifier"
31720 The &%add_header%& modifier can be used to add one or more extra header lines
31721 to an incoming message, as in this example:
31723 warn dnslists = sbl.spamhaus.org : \
31724 dialup.mail-abuse.org
31725 add_header = X-blacklisted-at: $dnslist_domain
31727 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31728 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31729 receiving a message). The message must ultimately be accepted for
31730 &%add_header%& to have any significant effect. You can use &%add_header%& with
31731 any ACL verb, including &%deny%& (though this is potentially useful only in a
31734 Headers will not be added to the message if the modifier is used in
31735 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31737 Leading and trailing newlines are removed from
31738 the data for the &%add_header%& modifier; if it then
31739 contains one or more newlines that
31740 are not followed by a space or a tab, it is assumed to contain multiple header
31741 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31742 front of any line that is not a valid header line.
31744 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31745 They are added to the message before processing the DATA and MIME ACLs.
31746 However, if an identical header line is requested more than once, only one copy
31747 is actually added to the message. Further header lines may be accumulated
31748 during the DATA and MIME ACLs, after which they are added to the message, again
31749 with duplicates suppressed. Thus, it is possible to add two identical header
31750 lines to an SMTP message, but only if one is added before DATA and one after.
31751 In the case of non-SMTP messages, new headers are accumulated during the
31752 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31753 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31754 are included in the entry that is written to the reject log.
31756 .cindex "header lines" "added; visibility of"
31757 Header lines are not visible in string expansions
31759 until they are added to the
31760 message. It follows that header lines defined in the MAIL, RCPT, and predata
31761 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31762 header lines that are added by the DATA or MIME ACLs are not visible in those
31763 ACLs. Because of this restriction, you cannot use header lines as a way of
31764 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31765 this, you can use ACL variables, as described in section
31766 &<<SECTaclvariables>>&.
31768 The list of headers yet to be added is given by the &%$headers_added%& variable.
31770 The &%add_header%& modifier acts immediately as it is encountered during the
31771 processing of an ACL. Notice the difference between these two cases:
31773 &`accept add_header = ADDED: some text`&
31774 &` `&<&'some condition'&>
31776 &`accept `&<&'some condition'&>
31777 &` add_header = ADDED: some text`&
31779 In the first case, the header line is always added, whether or not the
31780 condition is true. In the second case, the header line is added only if the
31781 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31782 ACL statement. All those that are encountered before a condition fails are
31785 .cindex "&%warn%& ACL verb"
31786 For compatibility with previous versions of Exim, a &%message%& modifier for a
31787 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31788 effect only if all the conditions are true, even if it appears before some of
31789 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31790 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31791 are present on a &%warn%& verb, both are processed according to their
31794 By default, new header lines are added to a message at the end of the existing
31795 header lines. However, you can specify that any particular header line should
31796 be added right at the start (before all the &'Received:'& lines), immediately
31797 after the first block of &'Received:'& lines, or immediately before any line
31798 that is not a &'Received:'& or &'Resent-something:'& header.
31800 This is done by specifying &":at_start:"&, &":after_received:"&, or
31801 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31802 header line, respectively. (Header text cannot start with a colon, as there has
31803 to be a header name first.) For example:
31805 warn add_header = \
31806 :after_received:X-My-Header: something or other...
31808 If more than one header line is supplied in a single &%add_header%& modifier,
31809 each one is treated independently and can therefore be placed differently. If
31810 you add more than one line at the start, or after the Received: block, they end
31811 up in reverse order.
31813 &*Warning*&: This facility currently applies only to header lines that are
31814 added in an ACL. It does NOT work for header lines that are added in a
31815 system filter or in a router or transport.
31819 .section "Removing header lines in ACLs" "SECTremoveheadacl"
31820 .cindex "header lines" "removing in an ACL"
31821 .cindex "header lines" "position of removed lines"
31822 .cindex "&%remove_header%& ACL modifier"
31823 The &%remove_header%& modifier can be used to remove one or more header lines
31824 from an incoming message, as in this example:
31826 warn message = Remove internal headers
31827 remove_header = x-route-mail1 : x-route-mail2
31829 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31830 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31831 receiving a message). The message must ultimately be accepted for
31832 &%remove_header%& to have any significant effect. You can use &%remove_header%&
31833 with any ACL verb, including &%deny%&, though this is really not useful for
31834 any verb that doesn't result in a delivered message.
31836 Headers will not be removed from the message if the modifier is used in
31837 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31839 More than one header can be removed at the same time by using a colon separated
31840 list of header names. The header matching is case insensitive. Wildcards are
31841 not permitted, nor is list expansion performed, so you cannot use hostlists to
31842 create a list of headers, however both connection and message variable expansion
31843 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
31845 warn hosts = +internal_hosts
31846 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
31847 warn message = Remove internal headers
31848 remove_header = $acl_c_ihdrs
31850 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
31851 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
31852 If multiple header lines match, all are removed.
31853 There is no harm in attempting to remove the same header twice nor in removing
31854 a non-existent header. Further header lines to be removed may be accumulated
31855 during the DATA and MIME ACLs, after which they are removed from the message,
31856 if present. In the case of non-SMTP messages, headers to be removed are
31857 accumulated during the non-SMTP ACLs, and are removed from the message after
31858 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
31859 ACL, there really is no effect because there is no logging of what headers
31860 would have been removed.
31862 .cindex "header lines" "removed; visibility of"
31863 Header lines are not visible in string expansions until the DATA phase when it
31864 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
31865 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
31866 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
31867 this restriction, you cannot use header lines as a way of controlling data
31868 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
31869 you should instead use ACL variables, as described in section
31870 &<<SECTaclvariables>>&.
31872 The &%remove_header%& modifier acts immediately as it is encountered during the
31873 processing of an ACL. Notice the difference between these two cases:
31875 &`accept remove_header = X-Internal`&
31876 &` `&<&'some condition'&>
31878 &`accept `&<&'some condition'&>
31879 &` remove_header = X-Internal`&
31881 In the first case, the header line is always removed, whether or not the
31882 condition is true. In the second case, the header line is removed only if the
31883 condition is true. Multiple occurrences of &%remove_header%& may occur in the
31884 same ACL statement. All those that are encountered before a condition fails
31887 &*Warning*&: This facility currently applies only to header lines that are
31888 present during ACL processing. It does NOT remove header lines that are added
31889 in a system filter or in a router or transport.
31894 .section "ACL conditions" "SECTaclconditions"
31895 .cindex "&ACL;" "conditions; list of"
31896 Some of the conditions listed in this section are available only when Exim is
31897 compiled with the content-scanning extension. They are included here briefly
31898 for completeness. More detailed descriptions can be found in the discussion on
31899 content scanning in chapter &<<CHAPexiscan>>&.
31901 Not all conditions are relevant in all circumstances. For example, testing
31902 senders and recipients does not make sense in an ACL that is being run as the
31903 result of the arrival of an ETRN command, and checks on message headers can be
31904 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
31905 can use the same condition (with different parameters) more than once in the
31906 same ACL statement. This provides a way of specifying an &"and"& conjunction.
31907 The conditions are as follows:
31911 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
31912 .cindex "&ACL;" "nested"
31913 .cindex "&ACL;" "indirect"
31914 .cindex "&ACL;" "arguments"
31915 .cindex "&%acl%& ACL condition"
31916 The possible values of the argument are the same as for the
31917 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
31918 &"accept"& the condition is true; if it returns &"deny"& the condition is
31919 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
31920 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
31921 condition false. This means that further processing of the &%warn%& verb
31922 ceases, but processing of the ACL continues.
31924 If the argument is a named ACL, up to nine space-separated optional values
31925 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
31926 and $acl_narg is set to the count of values.
31927 Previous values of these variables are restored after the call returns.
31928 The name and values are expanded separately.
31929 Note that spaces in complex expansions which are used as arguments
31930 will act as argument separators.
31932 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
31933 the connection is dropped. If it returns &"discard"&, the verb must be
31934 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
31935 conditions are tested.
31937 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
31938 loops. This condition allows you to use different ACLs in different
31939 circumstances. For example, different ACLs can be used to handle RCPT commands
31940 for different local users or different local domains.
31942 .vitem &*authenticated&~=&~*&<&'string&~list'&>
31943 .cindex "&%authenticated%& ACL condition"
31944 .cindex "authentication" "ACL checking"
31945 .cindex "&ACL;" "testing for authentication"
31946 If the SMTP connection is not authenticated, the condition is false. Otherwise,
31947 the name of the authenticator is tested against the list. To test for
31948 authentication by any authenticator, you can set
31953 .vitem &*condition&~=&~*&<&'string'&>
31954 .cindex "&%condition%& ACL condition"
31955 .cindex "customizing" "ACL condition"
31956 .cindex "&ACL;" "customized test"
31957 .cindex "&ACL;" "testing, customized"
31958 This feature allows you to make up custom conditions. If the result of
31959 expanding the string is an empty string, the number zero, or one of the strings
31960 &"no"& or &"false"&, the condition is false. If the result is any non-zero
31961 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
31962 any other value, some error is assumed to have occurred, and the ACL returns
31963 &"defer"&. However, if the expansion is forced to fail, the condition is
31964 ignored. The effect is to treat it as true, whether it is positive or
31967 .vitem &*decode&~=&~*&<&'location'&>
31968 .cindex "&%decode%& ACL condition"
31969 This condition is available only when Exim is compiled with the
31970 content-scanning extension, and it is allowed only in the ACL defined by
31971 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
31972 If all goes well, the condition is true. It is false only if there are
31973 problems such as a syntax error or a memory shortage. For more details, see
31974 chapter &<<CHAPexiscan>>&.
31976 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
31977 .cindex "&%dnslists%& ACL condition"
31978 .cindex "DNS list" "in ACL"
31979 .cindex "black list (DNS)"
31980 .cindex "&ACL;" "testing a DNS list"
31981 This condition checks for entries in DNS black lists. These are also known as
31982 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
31983 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
31984 different variants of this condition to describe briefly here. See sections
31985 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
31987 .vitem &*domains&~=&~*&<&'domain&~list'&>
31988 .cindex "&%domains%& ACL condition"
31989 .cindex "domain" "ACL checking"
31990 .cindex "&ACL;" "testing a recipient domain"
31991 .vindex "&$domain_data$&"
31992 This condition is relevant only after a RCPT command. It checks that the domain
31993 of the recipient address is in the domain list. If percent-hack processing is
31994 enabled, it is done before this test is done. If the check succeeds with a
31995 lookup, the result of the lookup is placed in &$domain_data$& until the next
31998 &*Note carefully*& (because many people seem to fall foul of this): you cannot
31999 use &%domains%& in a DATA ACL.
32002 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32003 .cindex "&%encrypted%& ACL condition"
32004 .cindex "encryption" "checking in an ACL"
32005 .cindex "&ACL;" "testing for encryption"
32006 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32007 name of the cipher suite in use is tested against the list. To test for
32008 encryption without testing for any specific cipher suite(s), set
32014 .vitem &*hosts&~=&~*&<&'host&~list'&>
32015 .cindex "&%hosts%& ACL condition"
32016 .cindex "host" "ACL checking"
32017 .cindex "&ACL;" "testing the client host"
32018 This condition tests that the calling host matches the host list. If you have
32019 name lookups or wildcarded host names and IP addresses in the same host list,
32020 you should normally put the IP addresses first. For example, you could have:
32022 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32024 The lookup in this example uses the host name for its key. This is implied by
32025 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32026 and it wouldn't matter which way round you had these two items.)
32028 The reason for the problem with host names lies in the left-to-right way that
32029 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32030 but when it reaches an item that requires a host name, it fails if it cannot
32031 find a host name to compare with the pattern. If the above list is given in the
32032 opposite order, the &%accept%& statement fails for a host whose name cannot be
32033 found, even if its IP address is 10.9.8.7.
32035 If you really do want to do the name check first, and still recognize the IP
32036 address even if the name lookup fails, you can rewrite the ACL like this:
32038 accept hosts = dbm;/etc/friendly/hosts
32039 accept hosts = 10.9.8.7
32041 The default action on failing to find the host name is to assume that the host
32042 is not in the list, so the first &%accept%& statement fails. The second
32043 statement can then check the IP address.
32045 .vindex "&$host_data$&"
32046 If a &%hosts%& condition is satisfied by means of a lookup, the result
32047 of the lookup is made available in the &$host_data$& variable. This
32048 allows you, for example, to set up a statement like this:
32050 deny hosts = net-lsearch;/some/file
32051 message = $host_data
32053 which gives a custom error message for each denied host.
32055 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32056 .cindex "&%local_parts%& ACL condition"
32057 .cindex "local part" "ACL checking"
32058 .cindex "&ACL;" "testing a local part"
32059 .vindex "&$local_part_data$&"
32060 This condition is relevant only after a RCPT command. It checks that the local
32061 part of the recipient address is in the list. If percent-hack processing is
32062 enabled, it is done before this test. If the check succeeds with a lookup, the
32063 result of the lookup is placed in &$local_part_data$&, which remains set until
32064 the next &%local_parts%& test.
32066 .vitem &*malware&~=&~*&<&'option'&>
32067 .cindex "&%malware%& ACL condition"
32068 .cindex "&ACL;" "virus scanning"
32069 .cindex "&ACL;" "scanning for viruses"
32070 This condition is available only when Exim is compiled with the
32071 content-scanning extension
32072 and only after a DATA command.
32073 It causes the incoming message to be scanned for
32074 viruses. For details, see chapter &<<CHAPexiscan>>&.
32076 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32077 .cindex "&%mime_regex%& ACL condition"
32078 .cindex "&ACL;" "testing by regex matching"
32079 This condition is available only when Exim is compiled with the
32080 content-scanning extension, and it is allowed only in the ACL defined by
32081 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32082 with any of the regular expressions. For details, see chapter
32085 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32086 .cindex "rate limiting"
32087 This condition can be used to limit the rate at which a user or host submits
32088 messages. Details are given in section &<<SECTratelimiting>>&.
32090 .vitem &*recipients&~=&~*&<&'address&~list'&>
32091 .cindex "&%recipients%& ACL condition"
32092 .cindex "recipient" "ACL checking"
32093 .cindex "&ACL;" "testing a recipient"
32094 This condition is relevant only after a RCPT command. It checks the entire
32095 recipient address against a list of recipients.
32097 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32098 .cindex "&%regex%& ACL condition"
32099 .cindex "&ACL;" "testing by regex matching"
32100 This condition is available only when Exim is compiled with the
32101 content-scanning extension, and is available only in the DATA, MIME, and
32102 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32103 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32105 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32106 .cindex "&%sender_domains%& ACL condition"
32107 .cindex "sender" "ACL checking"
32108 .cindex "&ACL;" "testing a sender domain"
32109 .vindex "&$domain$&"
32110 .vindex "&$sender_address_domain$&"
32111 This condition tests the domain of the sender of the message against the given
32112 domain list. &*Note*&: The domain of the sender address is in
32113 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32114 of this condition. This is an exception to the general rule for testing domain
32115 lists. It is done this way so that, if this condition is used in an ACL for a
32116 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32117 influence the sender checking.
32119 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32120 relaying, because sender addresses are easily, and commonly, forged.
32122 .vitem &*senders&~=&~*&<&'address&~list'&>
32123 .cindex "&%senders%& ACL condition"
32124 .cindex "sender" "ACL checking"
32125 .cindex "&ACL;" "testing a sender"
32126 This condition tests the sender of the message against the given list. To test
32127 for a bounce message, which has an empty sender, set
32131 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32132 relaying, because sender addresses are easily, and commonly, forged.
32134 .vitem &*spam&~=&~*&<&'username'&>
32135 .cindex "&%spam%& ACL condition"
32136 .cindex "&ACL;" "scanning for spam"
32137 This condition is available only when Exim is compiled with the
32138 content-scanning extension. It causes the incoming message to be scanned by
32139 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32141 .vitem &*verify&~=&~certificate*&
32142 .cindex "&%verify%& ACL condition"
32143 .cindex "TLS" "client certificate verification"
32144 .cindex "certificate" "verification of client"
32145 .cindex "&ACL;" "certificate verification"
32146 .cindex "&ACL;" "testing a TLS certificate"
32147 This condition is true in an SMTP session if the session is encrypted, and a
32148 certificate was received from the client, and the certificate was verified. The
32149 server requests a certificate only if the client matches &%tls_verify_hosts%&
32150 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32152 .vitem &*verify&~=&~csa*&
32153 .cindex "CSA verification"
32154 This condition checks whether the sending host (the client) is authorized to
32155 send email. Details of how this works are given in section
32156 &<<SECTverifyCSA>>&.
32158 .vitem &*verify&~=&~header_names_ascii*&
32159 .cindex "&%verify%& ACL condition"
32160 .cindex "&ACL;" "verifying header names only ASCII"
32161 .cindex "header lines" "verifying header names only ASCII"
32162 .cindex "verifying" "header names only ASCII"
32163 This condition is relevant only in an ACL that is run after a message has been
32165 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32166 It checks all header names (not the content) to make sure
32167 there are no non-ASCII characters, also excluding control characters. The
32168 allowable characters are decimal ASCII values 33 through 126.
32170 Exim itself will handle headers with non-ASCII characters, but it can cause
32171 problems for downstream applications, so this option will allow their
32172 detection and rejection in the DATA ACL's.
32174 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32175 .cindex "&%verify%& ACL condition"
32176 .cindex "&ACL;" "verifying sender in the header"
32177 .cindex "header lines" "verifying the sender in"
32178 .cindex "sender" "verifying in header"
32179 .cindex "verifying" "sender in header"
32180 This condition is relevant only in an ACL that is run after a message has been
32181 received, that is, in an ACL specified by &%acl_smtp_data%& or
32182 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32183 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32184 is loosely thought of as a &"sender"& address (hence the name of the test).
32185 However, an address that appears in one of these headers need not be an address
32186 that accepts bounce messages; only sender addresses in envelopes are required
32187 to accept bounces. Therefore, if you use the callout option on this check, you
32188 might want to arrange for a non-empty address in the MAIL command.
32190 Details of address verification and the options are given later, starting at
32191 section &<<SECTaddressverification>>& (callouts are described in section
32192 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32193 condition to restrict it to bounce messages only:
32196 !verify = header_sender
32197 message = A valid sender header is required for bounces
32200 .vitem &*verify&~=&~header_syntax*&
32201 .cindex "&%verify%& ACL condition"
32202 .cindex "&ACL;" "verifying header syntax"
32203 .cindex "header lines" "verifying syntax"
32204 .cindex "verifying" "header syntax"
32205 This condition is relevant only in an ACL that is run after a message has been
32206 received, that is, in an ACL specified by &%acl_smtp_data%& or
32207 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32208 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32209 and &'Bcc:'&), returning true if there are no problems.
32210 Unqualified addresses (local parts without domains) are
32211 permitted only in locally generated messages and from hosts that match
32212 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32215 Note that this condition is a syntax check only. However, a common spamming
32216 ploy used to be to send syntactically invalid headers such as
32220 and this condition can be used to reject such messages, though they are not as
32221 common as they used to be.
32223 .vitem &*verify&~=&~helo*&
32224 .cindex "&%verify%& ACL condition"
32225 .cindex "&ACL;" "verifying HELO/EHLO"
32226 .cindex "HELO" "verifying"
32227 .cindex "EHLO" "verifying"
32228 .cindex "verifying" "EHLO"
32229 .cindex "verifying" "HELO"
32230 This condition is true if a HELO or EHLO command has been received from the
32231 client host, and its contents have been verified. If there has been no previous
32232 attempt to verify the HELO/EHLO contents, it is carried out when this
32233 condition is encountered. See the description of the &%helo_verify_hosts%& and
32234 &%helo_try_verify_hosts%& options for details of how to request verification
32235 independently of this condition, and for detail of the verification.
32237 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32238 option), this condition is always true.
32241 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32242 .cindex "verifying" "not blind"
32243 .cindex "bcc recipients, verifying none"
32244 This condition checks that there are no blind (bcc) recipients in the message.
32245 Every envelope recipient must appear either in a &'To:'& header line or in a
32246 &'Cc:'& header line for this condition to be true. Local parts are checked
32247 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32248 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32249 used only in a DATA or non-SMTP ACL.
32251 There is one possible option, &`case_insensitive`&. If this is present then
32252 local parts are checked case-insensitively.
32254 There are, of course, many legitimate messages that make use of blind (bcc)
32255 recipients. This check should not be used on its own for blocking messages.
32258 .vitem &*verify&~=&~recipient/*&<&'options'&>
32259 .cindex "&%verify%& ACL condition"
32260 .cindex "&ACL;" "verifying recipient"
32261 .cindex "recipient" "verifying"
32262 .cindex "verifying" "recipient"
32263 .vindex "&$address_data$&"
32264 This condition is relevant only after a RCPT command. It verifies the current
32265 recipient. Details of address verification are given later, starting at section
32266 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32267 of &$address_data$& is the last value that was set while routing the address.
32268 This applies even if the verification fails. When an address that is being
32269 verified is redirected to a single address, verification continues with the new
32270 address, and in that case, the subsequent value of &$address_data$& is the
32271 value for the child address.
32273 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32274 .cindex "&%verify%& ACL condition"
32275 .cindex "&ACL;" "verifying host reverse lookup"
32276 .cindex "host" "verifying reverse lookup"
32277 This condition ensures that a verified host name has been looked up from the IP
32278 address of the client host. (This may have happened already if the host name
32279 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32280 Verification ensures that the host name obtained from a reverse DNS lookup, or
32281 one of its aliases, does, when it is itself looked up in the DNS, yield the
32282 original IP address.
32284 There is one possible option, &`defer_ok`&. If this is present and a
32285 DNS operation returns a temporary error, the verify condition succeeds.
32287 If this condition is used for a locally generated message (that is, when there
32288 is no client host involved), it always succeeds.
32290 .vitem &*verify&~=&~sender/*&<&'options'&>
32291 .cindex "&%verify%& ACL condition"
32292 .cindex "&ACL;" "verifying sender"
32293 .cindex "sender" "verifying"
32294 .cindex "verifying" "sender"
32295 This condition is relevant only after a MAIL or RCPT command, or after a
32296 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32297 the message's sender is empty (that is, this is a bounce message), the
32298 condition is true. Otherwise, the sender address is verified.
32300 .vindex "&$address_data$&"
32301 .vindex "&$sender_address_data$&"
32302 If there is data in the &$address_data$& variable at the end of routing, its
32303 value is placed in &$sender_address_data$& at the end of verification. This
32304 value can be used in subsequent conditions and modifiers in the same ACL
32305 statement. It does not persist after the end of the current statement. If you
32306 want to preserve the value for longer, you can save it in an ACL variable.
32308 Details of verification are given later, starting at section
32309 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32310 to avoid doing it more than once per message.
32312 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32313 .cindex "&%verify%& ACL condition"
32314 This is a variation of the previous option, in which a modified address is
32315 verified as a sender.
32317 Note that '/' is legal in local-parts; if the address may have such
32318 (eg. is generated from the received message)
32319 they must be protected from the options parsing by doubling:
32321 verify = sender=${listquote{/}{${address:$h_sender:}}}
32327 .section "Using DNS lists" "SECTmorednslists"
32328 .cindex "DNS list" "in ACL"
32329 .cindex "black list (DNS)"
32330 .cindex "&ACL;" "testing a DNS list"
32331 In its simplest form, the &%dnslists%& condition tests whether the calling host
32332 is on at least one of a number of DNS lists by looking up the inverted IP
32333 address in one or more DNS domains. (Note that DNS list domains are not mail
32334 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32335 special options instead.) For example, if the calling host's IP
32336 address is 192.168.62.43, and the ACL statement is
32338 deny dnslists = blackholes.mail-abuse.org : \
32339 dialups.mail-abuse.org
32341 the following records are looked up:
32343 43.62.168.192.blackholes.mail-abuse.org
32344 43.62.168.192.dialups.mail-abuse.org
32346 As soon as Exim finds an existing DNS record, processing of the list stops.
32347 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32348 to test that a host is on more than one list (an &"and"& conjunction), you can
32349 use two separate conditions:
32351 deny dnslists = blackholes.mail-abuse.org
32352 dnslists = dialups.mail-abuse.org
32354 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32355 behaves as if the host does not match the list item, that is, as if the DNS
32356 record does not exist. If there are further items in the DNS list, they are
32359 This is usually the required action when &%dnslists%& is used with &%deny%&
32360 (which is the most common usage), because it prevents a DNS failure from
32361 blocking mail. However, you can change this behaviour by putting one of the
32362 following special items in the list:
32364 &`+include_unknown `& behave as if the item is on the list
32365 &`+exclude_unknown `& behave as if the item is not on the list (default)
32366 &`+defer_unknown `& give a temporary error
32368 .cindex "&`+include_unknown`&"
32369 .cindex "&`+exclude_unknown`&"
32370 .cindex "&`+defer_unknown`&"
32371 Each of these applies to any subsequent items on the list. For example:
32373 deny dnslists = +defer_unknown : foo.bar.example
32375 Testing the list of domains stops as soon as a match is found. If you want to
32376 warn for one list and block for another, you can use two different statements:
32378 deny dnslists = blackholes.mail-abuse.org
32379 warn dnslists = dialups.mail-abuse.org
32380 message = X-Warn: sending host is on dialups list
32382 .cindex caching "of dns lookup"
32384 DNS list lookups are cached by Exim for the duration of the SMTP session
32385 (but limited by the DNS return TTL value),
32386 so a lookup based on the IP address is done at most once for any incoming
32387 connection (assuming long-enough TTL).
32388 Exim does not share information between multiple incoming
32389 connections (but your local name server cache should be active).
32391 There are a number of DNS lists to choose from, some commercial, some free,
32392 or free for small deployments. An overview can be found at
32393 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32397 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32398 .cindex "DNS list" "keyed by explicit IP address"
32399 By default, the IP address that is used in a DNS list lookup is the IP address
32400 of the calling host. However, you can specify another IP address by listing it
32401 after the domain name, introduced by a slash. For example:
32403 deny dnslists = black.list.tld/192.168.1.2
32405 This feature is not very helpful with explicit IP addresses; it is intended for
32406 use with IP addresses that are looked up, for example, the IP addresses of the
32407 MX hosts or nameservers of an email sender address. For an example, see section
32408 &<<SECTmulkeyfor>>& below.
32413 .section "DNS lists keyed on domain names" "SECID202"
32414 .cindex "DNS list" "keyed by domain name"
32415 There are some lists that are keyed on domain names rather than inverted IP
32416 addresses (see, e.g., the &'domain based zones'& link at
32417 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32418 with these lists. You can change the name that is looked up in a DNS list by
32419 listing it after the domain name, introduced by a slash. For example,
32421 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32422 message = Sender's domain is listed at $dnslist_domain
32424 This particular example is useful only in ACLs that are obeyed after the
32425 RCPT or DATA commands, when a sender address is available. If (for
32426 example) the message's sender is &'user@tld.example'& the name that is looked
32427 up by this example is
32429 tld.example.dsn.rfc-ignorant.org
32431 A single &%dnslists%& condition can contain entries for both names and IP
32432 addresses. For example:
32434 deny dnslists = sbl.spamhaus.org : \
32435 dsn.rfc-ignorant.org/$sender_address_domain
32437 The first item checks the sending host's IP address; the second checks a domain
32438 name. The whole condition is true if either of the DNS lookups succeeds.
32443 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32444 .cindex "DNS list" "multiple keys for"
32445 The syntax described above for looking up explicitly-defined values (either
32446 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32447 name for the DNS list, what follows the slash can in fact be a list of items.
32448 As with all lists in Exim, the default separator is a colon. However, because
32449 this is a sublist within the list of DNS blacklist domains, it is necessary
32450 either to double the separators like this:
32452 dnslists = black.list.tld/name.1::name.2
32454 or to change the separator character, like this:
32456 dnslists = black.list.tld/<;name.1;name.2
32458 If an item in the list is an IP address, it is inverted before the DNS
32459 blacklist domain is appended. If it is not an IP address, no inversion
32460 occurs. Consider this condition:
32462 dnslists = black.list.tld/<;192.168.1.2;a.domain
32464 The DNS lookups that occur are:
32466 2.1.168.192.black.list.tld
32467 a.domain.black.list.tld
32469 Once a DNS record has been found (that matches a specific IP return
32470 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32471 are done. If there is a temporary DNS error, the rest of the sublist of domains
32472 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32473 only if no other DNS lookup in this sublist succeeds. In other words, a
32474 successful lookup for any of the items in the sublist overrides a temporary
32475 error for a previous item.
32477 The ability to supply a list of items after the slash is in some sense just a
32478 syntactic convenience. These two examples have the same effect:
32480 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32481 dnslists = black.list.tld/a.domain::b.domain
32483 However, when the data for the list is obtained from a lookup, the second form
32484 is usually much more convenient. Consider this example:
32486 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32487 ${lookup dnsdb {>|mxh=\
32488 $sender_address_domain} }} }
32489 message = The mail servers for the domain \
32490 $sender_address_domain \
32491 are listed at $dnslist_domain ($dnslist_value); \
32494 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32495 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32496 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32497 of expanding the condition might be something like this:
32499 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32501 Thus, this example checks whether or not the IP addresses of the sender
32502 domain's mail servers are on the Spamhaus black list.
32504 The key that was used for a successful DNS list lookup is put into the variable
32505 &$dnslist_matched$& (see section &<<SECID204>>&).
32510 .section "Data returned by DNS lists" "SECID203"
32511 .cindex "DNS list" "data returned from"
32512 DNS lists are constructed using address records in the DNS. The original RBL
32513 just used the address 127.0.0.1 on the right hand side of each record, but the
32514 RBL+ list and some other lists use a number of values with different meanings.
32515 The values used on the RBL+ list are:
32519 127.1.0.3 DUL and RBL
32521 127.1.0.5 RSS and RBL
32522 127.1.0.6 RSS and DUL
32523 127.1.0.7 RSS and DUL and RBL
32525 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32526 different values. Some DNS lists may return more than one address record;
32527 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32530 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32531 range. If a DNSBL operator loses control of the domain, lookups on it
32532 may start returning other addresses. Because of this, Exim now ignores
32533 returned values outside the 127/8 region.
32537 .section "Variables set from DNS lists" "SECID204"
32538 .cindex "expansion" "variables, set from DNS list"
32539 .cindex "DNS list" "variables set from"
32540 .vindex "&$dnslist_domain$&"
32541 .vindex "&$dnslist_matched$&"
32542 .vindex "&$dnslist_text$&"
32543 .vindex "&$dnslist_value$&"
32544 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32545 the name of the overall domain that matched (for example,
32546 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32547 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32548 the DNS record. When the key is an IP address, it is not reversed in
32549 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32550 cases, for example:
32552 deny dnslists = spamhaus.example
32554 the key is also available in another variable (in this case,
32555 &$sender_host_address$&). In more complicated cases, however, this is not true.
32556 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32557 might generate a dnslists lookup like this:
32559 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32561 If this condition succeeds, the value in &$dnslist_matched$& might be
32562 &`192.168.6.7`& (for example).
32564 If more than one address record is returned by the DNS lookup, all the IP
32565 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32566 The variable &$dnslist_text$& contains the contents of any associated TXT
32567 record. For lists such as RBL+ the TXT record for a merged entry is often not
32568 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32571 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32572 &-- even if these appear before the condition in the ACL, they are not
32573 expanded until after it has failed. For example:
32575 deny hosts = !+local_networks
32576 message = $sender_host_address is listed \
32578 dnslists = rbl-plus.mail-abuse.example
32583 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32584 .cindex "DNS list" "matching specific returned data"
32585 You can add an equals sign and an IP address after a &%dnslists%& domain name
32586 in order to restrict its action to DNS records with a matching right hand side.
32589 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32591 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32592 any address record is considered to be a match. For the moment, we assume
32593 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32594 describes how multiple records are handled.
32596 More than one IP address may be given for checking, using a comma as a
32597 separator. These are alternatives &-- if any one of them matches, the
32598 &%dnslists%& condition is true. For example:
32600 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32602 If you want to specify a constraining address list and also specify names or IP
32603 addresses to be looked up, the constraining address list must be specified
32604 first. For example:
32606 deny dnslists = dsn.rfc-ignorant.org\
32607 =127.0.0.2/$sender_address_domain
32610 If the character &`&&`& is used instead of &`=`&, the comparison for each
32611 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32612 In other words, the listed addresses are used as bit masks. The comparison is
32613 true if all the bits in the mask are present in the address that is being
32614 tested. For example:
32616 dnslists = a.b.c&0.0.0.3
32618 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32619 want to test whether one bit or another bit is present (as opposed to both
32620 being present), you must use multiple values. For example:
32622 dnslists = a.b.c&0.0.0.1,0.0.0.2
32624 matches if the final component of the address is an odd number or two times
32629 .section "Negated DNS matching conditions" "SECID205"
32630 You can supply a negative list of IP addresses as part of a &%dnslists%&
32633 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32635 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32636 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32638 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32640 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32641 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32642 words, the result of the test is inverted if an exclamation mark appears before
32643 the &`=`& (or the &`&&`&) sign.
32645 &*Note*&: This kind of negation is not the same as negation in a domain,
32646 host, or address list (which is why the syntax is different).
32648 If you are using just one list, the negation syntax does not gain you much. The
32649 previous example is precisely equivalent to
32651 deny dnslists = a.b.c
32652 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32654 However, if you are using multiple lists, the negation syntax is clearer.
32655 Consider this example:
32657 deny dnslists = sbl.spamhaus.org : \
32659 dnsbl.njabl.org!=127.0.0.3 : \
32662 Using only positive lists, this would have to be:
32664 deny dnslists = sbl.spamhaus.org : \
32666 deny dnslists = dnsbl.njabl.org
32667 !dnslists = dnsbl.njabl.org=127.0.0.3
32668 deny dnslists = relays.ordb.org
32670 which is less clear, and harder to maintain.
32672 Negation can also be used with a bitwise-and restriction.
32673 The dnslists condition with only be trus if a result is returned
32674 by the lookup which, anded with the restriction, is all zeroes.
32677 deny dnslists = zen.spamhaus.org!&0.255.255.0
32683 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32684 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32685 thereby providing more than one IP address. When an item in a &%dnslists%& list
32686 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32687 the match to specific results from the DNS lookup, there are two ways in which
32688 the checking can be handled. For example, consider the condition:
32690 dnslists = a.b.c=127.0.0.1
32692 What happens if the DNS lookup for the incoming IP address yields both
32693 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32694 condition true because at least one given value was found, or is it false
32695 because at least one of the found values was not listed? And how does this
32696 affect negated conditions? Both possibilities are provided for with the help of
32697 additional separators &`==`& and &`=&&`&.
32700 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32701 IP addresses matches one of the listed addresses. For the example above, the
32702 condition is true because 127.0.0.1 matches.
32704 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32705 looked up IP addresses matches one of the listed addresses. If the condition is
32708 dnslists = a.b.c==127.0.0.1
32710 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32711 false because 127.0.0.2 is not listed. You would need to have:
32713 dnslists = a.b.c==127.0.0.1,127.0.0.2
32715 for the condition to be true.
32718 When &`!`& is used to negate IP address matching, it inverts the result, giving
32719 the precise opposite of the behaviour above. Thus:
32721 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32722 addresses matches one of the listed addresses. Consider:
32724 dnslists = a.b.c!&0.0.0.1
32726 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32727 false because 127.0.0.1 matches.
32729 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32730 looked up IP address that does not match. Consider:
32732 dnslists = a.b.c!=&0.0.0.1
32734 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32735 true, because 127.0.0.2 does not match. You would need to have:
32737 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32739 for the condition to be false.
32741 When the DNS lookup yields only a single IP address, there is no difference
32742 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32747 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32748 .cindex "DNS list" "information from merged"
32749 When the facility for restricting the matching IP values in a DNS list is used,
32750 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32751 the true reason for rejection. This happens when lists are merged and the IP
32752 address in the A record is used to distinguish them; unfortunately there is
32753 only one TXT record. One way round this is not to use merged lists, but that
32754 can be inefficient because it requires multiple DNS lookups where one would do
32755 in the vast majority of cases when the host of interest is not on any of the
32758 A less inefficient way of solving this problem is available. If
32759 two domain names, comma-separated, are given, the second is used first to
32760 do an initial check, making use of any IP value restrictions that are set.
32761 If there is a match, the first domain is used, without any IP value
32762 restrictions, to get the TXT record. As a byproduct of this, there is also
32763 a check that the IP being tested is indeed on the first list. The first
32764 domain is the one that is put in &$dnslist_domain$&. For example:
32767 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32768 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32770 rejected because $sender_host_address is blacklisted \
32771 at $dnslist_domain\n$dnslist_text
32773 For the first blacklist item, this starts by doing a lookup in
32774 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32775 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32776 value, and as long as something is found, it looks for the corresponding TXT
32777 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32778 The second blacklist item is processed similarly.
32780 If you are interested in more than one merged list, the same list must be
32781 given several times, but because the results of the DNS lookups are cached,
32782 the DNS calls themselves are not repeated. For example:
32785 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32786 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32787 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32788 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32790 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32791 values matches (or if no record is found), this is the only lookup that is
32792 done. Only if there is a match is one of the more specific lists consulted.
32796 .section "DNS lists and IPv6" "SECTmorednslistslast"
32797 .cindex "IPv6" "DNS black lists"
32798 .cindex "DNS list" "IPv6 usage"
32799 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32800 nibble by nibble. For example, if the calling host's IP address is
32801 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
32803 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
32804 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
32806 (split over two lines here to fit on the page). Unfortunately, some of the DNS
32807 lists contain wildcard records, intended for IPv4, that interact badly with
32808 IPv6. For example, the DNS entry
32810 *.3.some.list.example. A 127.0.0.1
32812 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
32813 Unfortunately, it also matches the entire 3::/4 IPv6 network.
32815 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
32816 &%condition%& condition, as in this example:
32818 deny condition = ${if isip4{$sender_host_address}}
32819 dnslists = some.list.example
32822 If an explicit key is being used for a DNS lookup and it may be an IPv6
32823 address you should specify alternate list separators for both the outer
32824 (DNS list name) list and inner (lookup keys) list:
32826 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
32829 .section "Rate limiting incoming messages" "SECTratelimiting"
32830 .cindex "rate limiting" "client sending"
32831 .cindex "limiting client sending rates"
32832 .oindex "&%smtp_ratelimit_*%&"
32833 The &%ratelimit%& ACL condition can be used to measure and control the rate at
32834 which clients can send email. This is more powerful than the
32835 &%smtp_ratelimit_*%& options, because those options control the rate of
32836 commands in a single SMTP session only, whereas the &%ratelimit%& condition
32837 works across all connections (concurrent and sequential) from the same client
32838 host. The syntax of the &%ratelimit%& condition is:
32840 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
32842 If the average client sending rate is less than &'m'& messages per time
32843 period &'p'& then the condition is false; otherwise it is true.
32845 As a side-effect, the &%ratelimit%& condition sets the expansion variable
32846 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
32847 configured value of &'m'&, and &$sender_rate_period$& to the configured value
32850 The parameter &'p'& is the smoothing time constant, in the form of an Exim
32851 time interval, for example, &`8h`& for eight hours. A larger time constant
32852 means that it takes Exim longer to forget a client's past behaviour. The
32853 parameter &'m'& is the maximum number of messages that a client is permitted to
32854 send in each time interval. It also specifies the number of messages permitted
32855 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
32856 constant, you can allow a client to send more messages in a burst without
32857 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
32858 both small, messages must be sent at an even rate.
32860 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
32861 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
32862 when deploying the &%ratelimit%& ACL condition. The script prints usage
32863 instructions when it is run with no arguments.
32865 The key is used to look up the data for calculating the client's average
32866 sending rate. This data is stored in Exim's spool directory, alongside the
32867 retry and other hints databases. The default key is &$sender_host_address$&,
32868 which means Exim computes the sending rate of each client host IP address.
32869 By changing the key you can change how Exim identifies clients for the purpose
32870 of ratelimiting. For example, to limit the sending rate of each authenticated
32871 user, independent of the computer they are sending from, set the key to
32872 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
32873 example, &$authenticated_id$& is only meaningful if the client has
32874 authenticated (which you can check with the &%authenticated%& ACL condition).
32876 The lookup key does not have to identify clients: If you want to limit the
32877 rate at which a recipient receives messages, you can use the key
32878 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
32881 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
32882 specifies what Exim measures the rate of, for example, messages or recipients
32883 or bytes. You can adjust the measurement using the &%unique=%& and/or
32884 &%count=%& options. You can also control when Exim updates the recorded rate
32885 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
32886 separated by a slash, like the other parameters. They may appear in any order.
32888 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
32889 any options that alter the meaning of the stored data. The limit &'m'& is not
32890 stored, so you can alter the configured maximum rate and Exim will still
32891 remember clients' past behaviour. If you change the &%per_*%& mode or add or
32892 remove the &%unique=%& option, the lookup key changes so Exim will forget past
32893 behaviour. The lookup key is not affected by changes to the update mode and
32894 the &%count=%& option.
32897 .section "Ratelimit options for what is being measured" "ratoptmea"
32898 .cindex "rate limiting" "per_* options"
32899 The &%per_conn%& option limits the client's connection rate. It is not
32900 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
32901 &%acl_not_smtp_start%& ACLs.
32903 The &%per_mail%& option limits the client's rate of sending messages. This is
32904 the default if none of the &%per_*%& options is specified. It can be used in
32905 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
32906 &%acl_smtp_data%&, or &%acl_not_smtp%&.
32908 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
32909 the same ACLs as the &%per_mail%& option, though it is best to use this option
32910 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
32911 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
32912 in its MAIL command, which may be inaccurate or completely missing. You can
32913 follow the limit &'m'& in the configuration with K, M, or G to specify limits
32914 in kilobytes, megabytes, or gigabytes, respectively.
32916 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
32917 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
32918 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
32919 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
32920 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
32921 in either case the rate limiting engine will see a message with many
32922 recipients as a large high-speed burst.
32924 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
32925 number of different recipients that the client has sent messages to in the
32926 last time period. That is, if the client repeatedly sends messages to the same
32927 recipient, its measured rate is not increased. This option can only be used in
32930 The &%per_cmd%& option causes Exim to recompute the rate every time the
32931 condition is processed. This can be used to limit the rate of any SMTP
32932 command. If it is used in multiple ACLs it can limit the aggregate rate of
32933 multiple different commands.
32935 The &%count=%& option can be used to alter how much Exim adds to the client's
32936 measured rate. For example, the &%per_byte%& option is equivalent to
32937 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
32938 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
32939 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
32941 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
32944 .section "Ratelimit update modes" "ratoptupd"
32945 .cindex "rate limiting" "reading data without updating"
32946 You can specify one of three options with the &%ratelimit%& condition to
32947 control when its database is updated. This section describes the &%readonly%&
32948 mode, and the next section describes the &%strict%& and &%leaky%& modes.
32950 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
32951 previously-computed rate to check against the limit.
32953 For example, you can test the client's sending rate and deny it access (when
32954 it is too fast) in the connect ACL. If the client passes this check then it
32955 can go on to send a message, in which case its recorded rate will be updated
32956 in the MAIL ACL. Subsequent connections from the same client will check this
32960 deny ratelimit = 100 / 5m / readonly
32961 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
32962 (max $sender_rate_limit)
32965 warn ratelimit = 100 / 5m / strict
32966 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
32967 (max $sender_rate_limit)
32970 If Exim encounters multiple &%ratelimit%& conditions with the same key when
32971 processing a message then it may increase the client's measured rate more than
32972 it should. For example, this will happen if you check the &%per_rcpt%& option
32973 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
32974 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
32975 multiple update problems by using the &%readonly%& option on later ratelimit
32978 The &%per_*%& options described above do not make sense in some ACLs. If you
32979 use a &%per_*%& option in an ACL where it is not normally permitted then the
32980 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
32981 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
32982 next section) so you must specify the &%readonly%& option explicitly.
32985 .section "Ratelimit options for handling fast clients" "ratoptfast"
32986 .cindex "rate limiting" "strict and leaky modes"
32987 If a client's average rate is greater than the maximum, the rate limiting
32988 engine can react in two possible ways, depending on the presence of the
32989 &%strict%& or &%leaky%& update modes. This is independent of the other
32990 counter-measures (such as rejecting the message) that may be specified by the
32993 The &%leaky%& (default) option means that the client's recorded rate is not
32994 updated if it is above the limit. The effect of this is that Exim measures the
32995 client's average rate of successfully sent email,
32996 up to the given limit.
32997 This is appropriate if the countermeasure when the condition is true
32998 consists of refusing the message, and
32999 is generally the better choice if you have clients that retry automatically.
33000 If the action when true is anything more complex then this option is
33001 likely not what is wanted.
33003 The &%strict%& option means that the client's recorded rate is always
33004 updated. The effect of this is that Exim measures the client's average rate
33005 of attempts to send email, which can be much higher than the maximum it is
33006 actually allowed. If the client is over the limit it may be subjected to
33007 counter-measures by the ACL. It must slow down and allow sufficient time to
33008 pass that its computed rate falls below the maximum before it can send email
33009 again. The time (the number of smoothing periods) it must wait and not
33010 attempt to send mail can be calculated with this formula:
33012 ln(peakrate/maxrate)
33016 .section "Limiting the rate of different events" "ratoptuniq"
33017 .cindex "rate limiting" "counting unique events"
33018 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33019 rate of different events. For example, the &%per_addr%& option uses this
33020 mechanism to count the number of different recipients that the client has
33021 sent messages to in the last time period; it is equivalent to
33022 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33023 measure the rate that a client uses different sender addresses with the
33024 options &`per_mail/unique=$sender_address`&.
33026 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33027 has seen for that key. The whole set is thrown away when it is older than the
33028 rate smoothing period &'p'&, so each different event is counted at most once
33029 per period. In the &%leaky%& update mode, an event that causes the client to
33030 go over the limit is not added to the set, in the same way that the client's
33031 recorded rate is not updated in the same situation.
33033 When you combine the &%unique=%& and &%readonly%& options, the specific
33034 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33037 The &%unique=%& mechanism needs more space in the ratelimit database than the
33038 other &%ratelimit%& options in order to store the event set. The number of
33039 unique values is potentially as large as the rate limit, so the extra space
33040 required increases with larger limits.
33042 The uniqueification is not perfect: there is a small probability that Exim
33043 will think a new event has happened before. If the sender's rate is less than
33044 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33045 the measured rate can go above the limit, in which case Exim may under-count
33046 events by a significant margin. Fortunately, if the rate is high enough (2.7
33047 times the limit) that the false positive rate goes above 9%, then Exim will
33048 throw away the over-full event set before the measured rate falls below the
33049 limit. Therefore the only harm should be that exceptionally high sending rates
33050 are logged incorrectly; any countermeasures you configure will be as effective
33054 .section "Using rate limiting" "useratlim"
33055 Exim's other ACL facilities are used to define what counter-measures are taken
33056 when the rate limit is exceeded. This might be anything from logging a warning
33057 (for example, while measuring existing sending rates in order to define
33058 policy), through time delays to slow down fast senders, up to rejecting the
33059 message. For example:
33061 # Log all senders' rates
33062 warn ratelimit = 0 / 1h / strict
33063 log_message = Sender rate $sender_rate / $sender_rate_period
33065 # Slow down fast senders; note the need to truncate $sender_rate
33066 # at the decimal point.
33067 warn ratelimit = 100 / 1h / per_rcpt / strict
33068 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33069 $sender_rate_limit }s
33071 # Keep authenticated users under control
33072 deny authenticated = *
33073 ratelimit = 100 / 1d / strict / $authenticated_id
33075 # System-wide rate limit
33076 defer ratelimit = 10 / 1s / $primary_hostname
33077 message = Sorry, too busy. Try again later.
33079 # Restrict incoming rate from each host, with a default
33080 # set using a macro and special cases looked up in a table.
33081 defer ratelimit = ${lookup {$sender_host_address} \
33082 cdb {DB/ratelimits.cdb} \
33083 {$value} {RATELIMIT} }
33084 message = Sender rate exceeds $sender_rate_limit \
33085 messages per $sender_rate_period
33087 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33088 especially with the &%per_rcpt%& option, you may suffer from a performance
33089 bottleneck caused by locking on the ratelimit hints database. Apart from
33090 making your ACLs less complicated, you can reduce the problem by using a
33091 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33092 this means that Exim will lose its hints data after a reboot (including retry
33093 hints, the callout cache, and ratelimit data).
33097 .section "Address verification" "SECTaddressverification"
33098 .cindex "verifying address" "options for"
33099 .cindex "policy control" "address verification"
33100 Several of the &%verify%& conditions described in section
33101 &<<SECTaclconditions>>& cause addresses to be verified. Section
33102 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33103 The verification conditions can be followed by options that modify the
33104 verification process. The options are separated from the keyword and from each
33105 other by slashes, and some of them contain parameters. For example:
33107 verify = sender/callout
33108 verify = recipient/defer_ok/callout=10s,defer_ok
33110 The first stage of address verification, which always happens, is to run the
33111 address through the routers, in &"verify mode"&. Routers can detect the
33112 difference between verification and routing for delivery, and their actions can
33113 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33114 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33115 The available options are as follows:
33118 If the &%callout%& option is specified, successful routing to one or more
33119 remote hosts is followed by a &"callout"& to those hosts as an additional
33120 check. Callouts and their sub-options are discussed in the next section.
33122 If there is a defer error while doing verification routing, the ACL
33123 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33124 options, the condition is forced to be true instead. Note that this is a main
33125 verification option as well as a suboption for callouts.
33127 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33128 discusses the reporting of sender address verification failures.
33130 The &%success_on_redirect%& option causes verification always to succeed
33131 immediately after a successful redirection. By default, if a redirection
33132 generates just one address, that address is also verified. See further
33133 discussion in section &<<SECTredirwhilveri>>&.
33136 If the &%quota%& option is specified for recipient verify,
33137 successful routing to an appendfile transport is followed by a call into
33138 the transport to evaluate the quota status for the recipient.
33139 No actual delivery is done, but verification will succeed if the quota
33140 is sufficient for the message (if the sender gave a message size) or
33141 not already exceeded (otherwise).
33145 .cindex "verifying address" "differentiating failures"
33146 .vindex "&$recipient_verify_failure$&"
33147 .vindex "&$sender_verify_failure$&"
33148 .vindex "&$acl_verify_message$&"
33149 After an address verification failure, &$acl_verify_message$& contains the
33150 error message that is associated with the failure. It can be preserved by
33153 warn !verify = sender
33154 set acl_m0 = $acl_verify_message
33156 If you are writing your own custom rejection message or log message when
33157 denying access, you can use this variable to include information about the
33158 verification failure.
33160 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33161 appropriate) contains one of the following words:
33164 &%qualify%&: The address was unqualified (no domain), and the message
33165 was neither local nor came from an exempted host.
33167 &%route%&: Routing failed.
33169 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33170 occurred at or before the MAIL command (that is, on initial
33171 connection, HELO, or MAIL).
33173 &%recipient%&: The RCPT command in a callout was rejected.
33175 &%postmaster%&: The postmaster check in a callout was rejected.
33178 &%quota%&: The quota check for a local recipient did non pass.
33181 The main use of these variables is expected to be to distinguish between
33182 rejections of MAIL and rejections of RCPT in callouts.
33184 The above variables may also be set after a &*successful*&
33185 address verification to:
33188 &%random%&: A random local-part callout succeeded
33194 .section "Callout verification" "SECTcallver"
33195 .cindex "verifying address" "by callout"
33196 .cindex "callout" "verification"
33197 .cindex "SMTP" "callout verification"
33198 For non-local addresses, routing verifies the domain, but is unable to do any
33199 checking of the local part. There are situations where some means of verifying
33200 the local part is desirable. One way this can be done is to make an SMTP
33201 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33202 a subsequent host for a recipient address, to see if the host accepts the
33203 address. We use the term &'callout'& to cover both cases. Note that for a
33204 sender address, the callback is not to the client host that is trying to
33205 deliver the message, but to one of the hosts that accepts incoming mail for the
33208 Exim does not do callouts by default. If you want them to happen, you must
33209 request them by setting appropriate options on the &%verify%& condition, as
33210 described below. This facility should be used with care, because it can add a
33211 lot of resource usage to the cost of verifying an address. However, Exim does
33212 cache the results of callouts, which helps to reduce the cost. Details of
33213 caching are in section &<<SECTcallvercache>>&.
33215 Recipient callouts are usually used only between hosts that are controlled by
33216 the same administration. For example, a corporate gateway host could use
33217 callouts to check for valid recipients on an internal mailserver. A successful
33218 callout does not guarantee that a real delivery to the address would succeed;
33219 on the other hand, a failing callout does guarantee that a delivery would fail.
33221 If the &%callout%& option is present on a condition that verifies an address, a
33222 second stage of verification occurs if the address is successfully routed to
33223 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33224 &(manualroute)& router, where the router specifies the hosts. However, if a
33225 router that does not set up hosts routes to an &(smtp)& transport with a
33226 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33227 &%hosts_override%& set, its hosts are always used, whether or not the router
33228 supplies a host list.
33229 Callouts are only supported on &(smtp)& transports.
33231 The port that is used is taken from the transport, if it is specified and is a
33232 remote transport. (For routers that do verification only, no transport need be
33233 specified.) Otherwise, the default SMTP port is used. If a remote transport
33234 specifies an outgoing interface, this is used; otherwise the interface is not
33235 specified. Likewise, the text that is used for the HELO command is taken from
33236 the transport's &%helo_data%& option; if there is no transport, the value of
33237 &$smtp_active_hostname$& is used.
33239 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33240 test whether a bounce message could be delivered to the sender address. The
33241 following SMTP commands are sent:
33243 &`HELO `&<&'local host name'&>
33245 &`RCPT TO:`&<&'the address to be tested'&>
33248 LHLO is used instead of HELO if the transport's &%protocol%& option is
33251 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33254 A recipient callout check is similar. By default, it also uses an empty address
33255 for the sender. This default is chosen because most hosts do not make use of
33256 the sender address when verifying a recipient. Using the same address means
33257 that a single cache entry can be used for each recipient. Some sites, however,
33258 do make use of the sender address when verifying. These are catered for by the
33259 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33261 If the response to the RCPT command is a 2&'xx'& code, the verification
33262 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33263 Exim tries the next host, if any. If there is a problem with all the remote
33264 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33265 &%callout%& option is given, in which case the condition is forced to succeed.
33267 .cindex "SMTP" "output flushing, disabling for callout"
33268 A callout may take a little time. For this reason, Exim normally flushes SMTP
33269 output before performing a callout in an ACL, to avoid unexpected timeouts in
33270 clients when the SMTP PIPELINING extension is in use. The flushing can be
33271 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33276 .section "Additional parameters for callouts" "CALLaddparcall"
33277 .cindex "callout" "additional parameters for"
33278 The &%callout%& option can be followed by an equals sign and a number of
33279 optional parameters, separated by commas. For example:
33281 verify = recipient/callout=10s,defer_ok
33283 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33284 separate verify options, is retained for backwards compatibility, but is now
33285 deprecated. The additional parameters for &%callout%& are as follows:
33289 .vitem <&'a&~time&~interval'&>
33290 .cindex "callout" "timeout, specifying"
33291 This specifies the timeout that applies for the callout attempt to each host.
33294 verify = sender/callout=5s
33296 The default is 30 seconds. The timeout is used for each response from the
33297 remote host. It is also used for the initial connection, unless overridden by
33298 the &%connect%& parameter.
33301 .vitem &*connect&~=&~*&<&'time&~interval'&>
33302 .cindex "callout" "connection timeout, specifying"
33303 This parameter makes it possible to set a different (usually smaller) timeout
33304 for making the SMTP connection. For example:
33306 verify = sender/callout=5s,connect=1s
33308 If not specified, this timeout defaults to the general timeout value.
33310 .vitem &*defer_ok*&
33311 .cindex "callout" "defer, action on"
33312 When this parameter is present, failure to contact any host, or any other kind
33313 of temporary error, is treated as success by the ACL. However, the cache is not
33314 updated in this circumstance.
33316 .vitem &*fullpostmaster*&
33317 .cindex "callout" "full postmaster check"
33318 This operates like the &%postmaster%& option (see below), but if the check for
33319 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33320 accordance with the specification in RFC 2821. The RFC states that the
33321 unqualified address &'postmaster'& should be accepted.
33324 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33325 .cindex "callout" "sender when verifying header"
33326 When verifying addresses in header lines using the &%header_sender%&
33327 verification option, Exim behaves by default as if the addresses are envelope
33328 sender addresses from a message. Callout verification therefore tests to see
33329 whether a bounce message could be delivered, by using an empty address in the
33330 MAIL command. However, it is arguable that these addresses might never be used
33331 as envelope senders, and could therefore justifiably reject bounce messages
33332 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33333 address to use in the MAIL command. For example:
33335 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33337 This parameter is available only for the &%header_sender%& verification option.
33340 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33341 .cindex "callout" "overall timeout, specifying"
33342 This parameter sets an overall timeout for performing a callout verification.
33345 verify = sender/callout=5s,maxwait=30s
33347 This timeout defaults to four times the callout timeout for individual SMTP
33348 commands. The overall timeout applies when there is more than one host that can
33349 be tried. The timeout is checked before trying the next host. This prevents
33350 very long delays if there are a large number of hosts and all are timing out
33351 (for example, when network connections are timing out).
33354 .vitem &*no_cache*&
33355 .cindex "callout" "cache, suppressing"
33356 .cindex "caching callout, suppressing"
33357 When this parameter is given, the callout cache is neither read nor updated.
33359 .vitem &*postmaster*&
33360 .cindex "callout" "postmaster; checking"
33361 When this parameter is set, a successful callout check is followed by a similar
33362 check for the local part &'postmaster'& at the same domain. If this address is
33363 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33364 the postmaster check is recorded in a cache record; if it is a failure, this is
33365 used to fail subsequent callouts for the domain without a connection being
33366 made, until the cache record expires.
33368 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33369 The postmaster check uses an empty sender in the MAIL command by default.
33370 You can use this parameter to do a postmaster check using a different address.
33373 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33375 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33376 one overrides. The &%postmaster%& parameter is equivalent to this example:
33378 require verify = sender/callout=postmaster_mailfrom=
33380 &*Warning*&: The caching arrangements for postmaster checking do not take
33381 account of the sender address. It is assumed that either the empty address or
33382 a fixed non-empty address will be used. All that Exim remembers is that the
33383 postmaster check for the domain succeeded or failed.
33387 .cindex "callout" "&""random""& check"
33388 When this parameter is set, before doing the normal callout check, Exim does a
33389 check for a &"random"& local part at the same domain. The local part is not
33390 really random &-- it is defined by the expansion of the option
33391 &%callout_random_local_part%&, which defaults to
33393 $primary_hostname-$tod_epoch-testing
33395 The idea here is to try to determine whether the remote host accepts all local
33396 parts without checking. If it does, there is no point in doing callouts for
33397 specific local parts. If the &"random"& check succeeds, the result is saved in
33398 a cache record, and used to force the current and subsequent callout checks to
33399 succeed without a connection being made, until the cache record expires.
33401 .vitem &*use_postmaster*&
33402 .cindex "callout" "sender for recipient check"
33403 This parameter applies to recipient callouts only. For example:
33405 deny !verify = recipient/callout=use_postmaster
33407 .vindex "&$qualify_domain$&"
33408 It causes a non-empty postmaster address to be used in the MAIL command when
33409 performing the callout for the recipient, and also for a &"random"& check if
33410 that is configured. The local part of the address is &`postmaster`& and the
33411 domain is the contents of &$qualify_domain$&.
33413 .vitem &*use_sender*&
33414 This option applies to recipient callouts only. For example:
33416 require verify = recipient/callout=use_sender
33418 It causes the message's actual sender address to be used in the MAIL
33419 command when performing the callout, instead of an empty address. There is no
33420 need to use this option unless you know that the called hosts make use of the
33421 sender when checking recipients. If used indiscriminately, it reduces the
33422 usefulness of callout caching.
33425 This option applies to recipient callouts only. For example:
33427 require verify = recipient/callout=use_sender,hold
33429 It causes the connection to be held open and used for any further recipients
33430 and for eventual delivery (should that be done quickly).
33431 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33432 when that is used for the connections.
33433 The advantage is only gained if there are no callout cache hits
33434 (which could be enforced by the no_cache option),
33435 if the use_sender option is used,
33436 if neither the random nor the use_postmaster option is used,
33437 and if no other callouts intervene.
33440 If you use any of the parameters that set a non-empty sender for the MAIL
33441 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33442 &%use_sender%&), you should think about possible loops. Recipient checking is
33443 usually done between two hosts that are under the same management, and the host
33444 that receives the callouts is not normally configured to do callouts itself.
33445 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33446 these circumstances.
33448 However, if you use a non-empty sender address for a callout to an arbitrary
33449 host, there is the likelihood that the remote host will itself initiate a
33450 callout check back to your host. As it is checking what appears to be a message
33451 sender, it is likely to use an empty address in MAIL, thus avoiding a
33452 callout loop. However, to be on the safe side it would be best to set up your
33453 own ACLs so that they do not do sender verification checks when the recipient
33454 is the address you use for header sender or postmaster callout checking.
33456 Another issue to think about when using non-empty senders for callouts is
33457 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33458 by the sender/recipient combination; thus, for any given recipient, many more
33459 actual callouts are performed than when an empty sender or postmaster is used.
33464 .section "Callout caching" "SECTcallvercache"
33465 .cindex "hints database" "callout cache"
33466 .cindex "callout" "cache, description of"
33467 .cindex "caching" "callout"
33468 Exim caches the results of callouts in order to reduce the amount of resources
33469 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33470 option. A hints database called &"callout"& is used for the cache. Two
33471 different record types are used: one records the result of a callout check for
33472 a specific address, and the other records information that applies to the
33473 entire domain (for example, that it accepts the local part &'postmaster'&).
33475 When an original callout fails, a detailed SMTP error message is given about
33476 the failure. However, for subsequent failures use the cache data, this message
33479 The expiry times for negative and positive address cache records are
33480 independent, and can be set by the global options &%callout_negative_expire%&
33481 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33483 If a host gives a negative response to an SMTP connection, or rejects any
33484 commands up to and including
33488 (but not including the MAIL command with a non-empty address),
33489 any callout attempt is bound to fail. Exim remembers such failures in a
33490 domain cache record, which it uses to fail callouts for the domain without
33491 making new connections, until the domain record times out. There are two
33492 separate expiry times for domain cache records:
33493 &%callout_domain_negative_expire%& (default 3h) and
33494 &%callout_domain_positive_expire%& (default 7d).
33496 Domain records expire when the negative expiry time is reached if callouts
33497 cannot be made for the domain, or if the postmaster check failed.
33498 Otherwise, they expire when the positive expiry time is reached. This
33499 ensures that, for example, a host that stops accepting &"random"& local parts
33500 will eventually be noticed.
33502 The callout caching mechanism is based on the domain of the address that is
33503 being tested. If the domain routes to several hosts, it is assumed that their
33504 behaviour will be the same.
33509 .section "Quota caching" "SECTquotacache"
33510 .cindex "hints database" "quota cache"
33511 .cindex "quota" "cache, description of"
33512 .cindex "caching" "quota"
33513 Exim caches the results of quota verification
33514 in order to reduce the amount of resources used.
33515 The &"callout"& hints database is used.
33517 The default cache periods are five minutes for a positive (good) result
33518 and one hour for a negative result.
33519 To change the periods the &%quota%& option can be followed by an equals sign
33520 and a number of optional paramemters, separated by commas.
33523 verify = recipient/quota=cachepos=1h,cacheneg=1d
33525 Possible parameters are:
33527 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33528 .cindex "quota cache" "positive entry expiry, specifying"
33529 Set the lifetime for a positive cache entry.
33530 A value of zero seconds is legitimate.
33532 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33533 .cindex "quota cache" "negative entry expiry, specifying"
33534 As above, for a negative entry.
33536 .vitem &*no_cache*&
33537 Set both positive and negative lifetimes to zero.
33540 .section "Sender address verification reporting" "SECTsenaddver"
33541 .cindex "verifying" "suppressing error details"
33542 See section &<<SECTaddressverification>>& for a general discussion of
33543 verification. When sender verification fails in an ACL, the details of the
33544 failure are given as additional output lines before the 550 response to the
33545 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33548 MAIL FROM:<xyz@abc.example>
33550 RCPT TO:<pqr@def.example>
33551 550-Verification failed for <xyz@abc.example>
33552 550-Called: 192.168.34.43
33553 550-Sent: RCPT TO:<xyz@abc.example>
33554 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33555 550 Sender verification failed
33557 If more than one RCPT command fails in the same way, the details are given
33558 only for the first of them. However, some administrators do not want to send
33559 out this much information. You can suppress the details by adding
33560 &`/no_details`& to the ACL statement that requests sender verification. For
33563 verify = sender/no_details
33566 .section "Redirection while verifying" "SECTredirwhilveri"
33567 .cindex "verifying" "redirection while"
33568 .cindex "address redirection" "while verifying"
33569 A dilemma arises when a local address is redirected by aliasing or forwarding
33570 during verification: should the generated addresses themselves be verified,
33571 or should the successful expansion of the original address be enough to verify
33572 it? By default, Exim takes the following pragmatic approach:
33575 When an incoming address is redirected to just one child address, verification
33576 continues with the child address, and if that fails to verify, the original
33577 verification also fails.
33579 When an incoming address is redirected to more than one child address,
33580 verification does not continue. A success result is returned.
33583 This seems the most reasonable behaviour for the common use of aliasing as a
33584 way of redirecting different local parts to the same mailbox. It means, for
33585 example, that a pair of alias entries of the form
33588 aw123: :fail: Gone away, no forwarding address
33590 work as expected, with both local parts causing verification failure. When a
33591 redirection generates more than one address, the behaviour is more like a
33592 mailing list, where the existence of the alias itself is sufficient for
33593 verification to succeed.
33595 It is possible, however, to change the default behaviour so that all successful
33596 redirections count as successful verifications, however many new addresses are
33597 generated. This is specified by the &%success_on_redirect%& verification
33598 option. For example:
33600 require verify = recipient/success_on_redirect/callout=10s
33602 In this example, verification succeeds if a router generates a new address, and
33603 the callout does not occur, because no address was routed to a remote host.
33605 When verification is being tested via the &%-bv%& option, the treatment of
33606 redirections is as just described, unless the &%-v%& or any debugging option is
33607 also specified. In that case, full verification is done for every generated
33608 address and a report is output for each of them.
33612 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33613 .cindex "CSA" "verifying"
33614 Client SMTP Authorization is a system that allows a site to advertise
33615 which machines are and are not permitted to send email. This is done by placing
33616 special SRV records in the DNS; these are looked up using the client's HELO
33617 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33618 Authorization checks in Exim are performed by the ACL condition:
33622 This fails if the client is not authorized. If there is a DNS problem, or if no
33623 valid CSA SRV record is found, or if the client is authorized, the condition
33624 succeeds. These three cases can be distinguished using the expansion variable
33625 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33626 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33627 be likely to cause problems for legitimate email.
33629 The error messages produced by the CSA code include slightly more
33630 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33631 looking up the CSA SRV record, or problems looking up the CSA target
33632 address record. There are four reasons for &$csa_status$& being &"fail"&:
33635 The client's host name is explicitly not authorized.
33637 The client's IP address does not match any of the CSA target IP addresses.
33639 The client's host name is authorized but it has no valid target IP addresses
33640 (for example, the target's addresses are IPv6 and the client is using IPv4).
33642 The client's host name has no CSA SRV record but a parent domain has asserted
33643 that all subdomains must be explicitly authorized.
33646 The &%csa%& verification condition can take an argument which is the domain to
33647 use for the DNS query. The default is:
33649 verify = csa/$sender_helo_name
33651 This implementation includes an extension to CSA. If the query domain
33652 is an address literal such as [192.0.2.95], or if it is a bare IP
33653 address, Exim searches for CSA SRV records in the reverse DNS as if
33654 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33657 verify = csa/$sender_host_address
33659 In fact, this is the check that Exim performs if the client does not say HELO.
33660 This extension can be turned off by setting the main configuration option
33661 &%dns_csa_use_reverse%& to be false.
33663 If a CSA SRV record is not found for the domain itself, a search
33664 is performed through its parent domains for a record which might be
33665 making assertions about subdomains. The maximum depth of this search is limited
33666 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33667 default. Exim does not look for CSA SRV records in a top level domain, so the
33668 default settings handle HELO domains as long as seven
33669 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33670 of legitimate HELO domains.
33672 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33673 direct SRV lookups, this is not sufficient because of the extra parent domain
33674 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33675 addresses into lookups in the reverse DNS space. The result of a successful
33678 ${lookup dnsdb {csa=$sender_helo_name}}
33680 has two space-separated fields: an authorization code and a target host name.
33681 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33682 authorization required but absent, or &"?"& for unknown.
33687 .section "Bounce address tag validation" "SECTverifyPRVS"
33688 .cindex "BATV, verifying"
33689 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33690 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33691 Genuine incoming bounce messages should therefore always be addressed to
33692 recipients that have a valid tag. This scheme is a way of detecting unwanted
33693 bounce messages caused by sender address forgeries (often called &"collateral
33694 spam"&), because the recipients of such messages do not include valid tags.
33696 There are two expansion items to help with the implementation of the BATV
33697 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33698 the original envelope sender address by using a simple key to add a hash of the
33699 address and some time-based randomizing information. The &%prvs%& expansion
33700 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33701 The syntax of these expansion items is described in section
33702 &<<SECTexpansionitems>>&.
33703 The validity period on signed addresses is seven days.
33705 As an example, suppose the secret per-address keys are stored in an MySQL
33706 database. A query to look up the key for an address could be defined as a macro
33709 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33710 WHERE sender='${quote_mysql:$prvscheck_address}'\
33713 Suppose also that the senders who make use of BATV are defined by an address
33714 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33717 # Bounces: drop unsigned addresses for BATV senders
33719 recipients = +batv_senders
33720 message = This address does not send an unsigned reverse path
33722 # Bounces: In case of prvs-signed address, check signature.
33724 condition = ${prvscheck {$local_part@$domain}\
33725 {PRVSCHECK_SQL}{1}}
33726 !condition = $prvscheck_result
33727 message = Invalid reverse path signature.
33729 The first statement rejects recipients for bounce messages that are addressed
33730 to plain BATV sender addresses, because it is known that BATV senders do not
33731 send out messages with plain sender addresses. The second statement rejects
33732 recipients that are prvs-signed, but with invalid signatures (either because
33733 the key is wrong, or the signature has timed out).
33735 A non-prvs-signed address is not rejected by the second statement, because the
33736 &%prvscheck%& expansion yields an empty string if its first argument is not a
33737 prvs-signed address, thus causing the &%condition%& condition to be false. If
33738 the first argument is a syntactically valid prvs-signed address, the yield is
33739 the third string (in this case &"1"&), whether or not the cryptographic and
33740 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33741 of the checks (empty for failure, &"1"& for success).
33743 There is one more issue you must consider when implementing prvs-signing:
33744 you have to ensure that the routers accept prvs-signed addresses and
33745 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33746 router to remove the signature with a configuration along these lines:
33750 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33752 This works because, if the third argument of &%prvscheck%& is empty, the result
33753 of the expansion of a prvs-signed address is the decoded value of the original
33754 address. This router should probably be the first of your routers that handles
33757 To create BATV-signed addresses in the first place, a transport of this form
33760 external_smtp_batv:
33762 return_path = ${prvs {$return_path} \
33763 {${lookup mysql{SELECT \
33764 secret FROM batv_prvs WHERE \
33765 sender='${quote_mysql:$sender_address}'} \
33768 If no key can be found for the existing return path, no signing takes place.
33772 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33773 .cindex "&ACL;" "relay control"
33774 .cindex "relaying" "control by ACL"
33775 .cindex "policy control" "relay control"
33776 An MTA is said to &'relay'& a message if it receives it from some host and
33777 delivers it directly to another host as a result of a remote address contained
33778 within it. Redirecting a local address via an alias or forward file and then
33779 passing the message on to another host is not relaying,
33780 .cindex "&""percent hack""&"
33781 but a redirection as a result of the &"percent hack"& is.
33783 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33784 A host which is acting as a gateway or an MX backup is concerned with incoming
33785 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33786 a host which is acting as a smart host for a number of clients is concerned
33787 with outgoing relaying from those clients to the Internet at large. Often the
33788 same host is fulfilling both functions,
33790 . as illustrated in the diagram below,
33792 but in principle these two kinds of relaying are entirely independent. What is
33793 not wanted is the transmission of mail from arbitrary remote hosts through your
33794 system to arbitrary domains.
33797 You can implement relay control by means of suitable statements in the ACL that
33798 runs for each RCPT command. For convenience, it is often easiest to use
33799 Exim's named list facility to define the domains and hosts involved. For
33800 example, suppose you want to do the following:
33803 Deliver a number of domains to mailboxes on the local host (or process them
33804 locally in some other way). Let's say these are &'my.dom1.example'& and
33805 &'my.dom2.example'&.
33807 Relay mail for a number of other domains for which you are the secondary MX.
33808 These might be &'friend1.example'& and &'friend2.example'&.
33810 Relay mail from the hosts on your local LAN, to whatever domains are involved.
33811 Suppose your LAN is 192.168.45.0/24.
33815 In the main part of the configuration, you put the following definitions:
33817 domainlist local_domains = my.dom1.example : my.dom2.example
33818 domainlist relay_to_domains = friend1.example : friend2.example
33819 hostlist relay_from_hosts = 192.168.45.0/24
33821 Now you can use these definitions in the ACL that is run for every RCPT
33825 accept domains = +local_domains : +relay_to_domains
33826 accept hosts = +relay_from_hosts
33828 The first statement accepts any RCPT command that contains an address in
33829 the local or relay domains. For any other domain, control passes to the second
33830 statement, which accepts the command only if it comes from one of the relay
33831 hosts. In practice, you will probably want to make your ACL more sophisticated
33832 than this, for example, by including sender and recipient verification. The
33833 default configuration includes a more comprehensive example, which is described
33834 in chapter &<<CHAPdefconfil>>&.
33838 .section "Checking a relay configuration" "SECTcheralcon"
33839 .cindex "relaying" "checking control of"
33840 You can check the relay characteristics of your configuration in the same way
33841 that you can test any ACL behaviour for an incoming SMTP connection, by using
33842 the &%-bh%& option to run a fake SMTP session with which you interact.
33847 . ////////////////////////////////////////////////////////////////////////////
33848 . ////////////////////////////////////////////////////////////////////////////
33850 .chapter "Content scanning at ACL time" "CHAPexiscan"
33851 .scindex IIDcosca "content scanning" "at ACL time"
33852 The extension of Exim to include content scanning at ACL time, formerly known
33853 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
33854 was integrated into the main source for Exim release 4.50, and Tom continues to
33855 maintain it. Most of the wording of this chapter is taken from Tom's
33858 It is also possible to scan the content of messages at other times. The
33859 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
33860 scanning after all the ACLs have run. A transport filter can be used to scan
33861 messages at delivery time (see the &%transport_filter%& option, described in
33862 chapter &<<CHAPtransportgeneric>>&).
33864 If you want to include the ACL-time content-scanning features when you compile
33865 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
33866 &_Local/Makefile_&. When you do that, the Exim binary is built with:
33869 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
33870 for all MIME parts for SMTP and non-SMTP messages, respectively.
33872 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
33873 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
33874 run at the end of message reception (the &%acl_smtp_data%& ACL).
33876 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
33877 of messages, or parts of messages, for debugging purposes.
33879 Additional expansion variables that are set in the new ACL and by the new
33882 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
33885 Content-scanning is continually evolving, and new features are still being
33886 added. While such features are still unstable and liable to incompatible
33887 changes, they are made available in Exim by setting options whose names begin
33888 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
33889 this manual. You can find out about them by reading the file called
33890 &_doc/experimental.txt_&.
33892 All the content-scanning facilities work on a MBOX copy of the message that is
33893 temporarily created in a file called:
33895 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
33897 The &_.eml_& extension is a friendly hint to virus scanners that they can
33898 expect an MBOX-like structure inside that file. The file is created when the
33899 first content scanning facility is called. Subsequent calls to content
33900 scanning conditions open the same file again. The directory is recursively
33901 removed when the &%acl_smtp_data%& ACL has finished running, unless
33903 control = no_mbox_unspool
33905 has been encountered. When the MIME ACL decodes files, they are put into the
33906 same directory by default.
33910 .section "Scanning for viruses" "SECTscanvirus"
33911 .cindex "virus scanning"
33912 .cindex "content scanning" "for viruses"
33913 .cindex "content scanning" "the &%malware%& condition"
33914 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
33915 It supports a &"generic"& interface to scanners called via the shell, and
33916 specialized interfaces for &"daemon"& type virus scanners, which are resident
33917 in memory and thus are much faster.
33919 Since message data needs to have arrived,
33920 the condition may be only called in ACL defined by
33922 &%acl_smtp_data_prdr%&,
33923 &%acl_smtp_mime%& or
33926 A timeout of 2 minutes is applied to a scanner call (by default);
33927 if it expires then a defer action is taken.
33929 .oindex "&%av_scanner%&"
33930 You can set the &%av_scanner%& option in the main part of the configuration
33931 to specify which scanner to use, together with any additional options that
33932 are needed. The basic syntax is as follows:
33934 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
33936 If you do not set &%av_scanner%&, it defaults to
33938 av_scanner = sophie:/var/run/sophie
33940 If the value of &%av_scanner%& starts with a dollar character, it is expanded
33942 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
33943 The following scanner types are supported in this release,
33944 though individual ones can be included or not at build time:
33948 .cindex "virus scanners" "avast"
33949 This is the scanner daemon of Avast. It has been tested with Avast Core
33950 Security (currently at version 2.2.0).
33951 You can get a trial version at &url(https://www.avast.com) or for Linux
33952 at &url(https://www.avast.com/linux-server-antivirus).
33953 This scanner type takes one option,
33954 which can be either a full path to a UNIX socket,
33955 or host and port specifiers separated by white space.
33956 The host may be a name or an IP address; the port is either a
33957 single number or a pair of numbers with a dash between.
33958 A list of options may follow. These options are interpreted on the
33959 Exim's side of the malware scanner, or are given on separate lines to
33960 the daemon as options before the main scan command.
33962 .cindex &`pass_unscanned`& "avast"
33963 If &`pass_unscanned`&
33964 is set, any files the Avast scanner can't scan (e.g.
33965 decompression bombs, or invalid archives) are considered clean. Use with
33970 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
33971 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
33972 av_scanner = avast:192.168.2.22 5036
33974 If you omit the argument, the default path
33975 &_/var/run/avast/scan.sock_&
33977 If you use a remote host,
33978 you need to make Exim's spool directory available to it,
33979 as the scanner is passed a file path, not file contents.
33980 For information about available commands and their options you may use
33982 $ socat UNIX:/var/run/avast/scan.sock STDIO:
33988 If the scanner returns a temporary failure (e.g. license issues, or
33989 permission problems), the message is deferred and a paniclog entry is
33990 written. The usual &`defer_ok`& option is available.
33992 .vitem &%aveserver%&
33993 .cindex "virus scanners" "Kaspersky"
33994 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
33995 at &url(https://www.kaspersky.com/). This scanner type takes one option,
33996 which is the path to the daemon's UNIX socket. The default is shown in this
33999 av_scanner = aveserver:/var/run/aveserver
34004 .cindex "virus scanners" "clamd"
34005 This daemon-type scanner is GPL and free. You can get it at
34006 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34007 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34008 in the MIME ACL. This is no longer believed to be necessary.
34010 The options are a list of server specifiers, which may be
34011 a UNIX socket specification,
34012 a TCP socket specification,
34013 or a (global) option.
34015 A socket specification consists of a space-separated list.
34016 For a Unix socket the first element is a full path for the socket,
34017 for a TCP socket the first element is the IP address
34018 and the second a port number,
34019 Any further elements are per-server (non-global) options.
34020 These per-server options are supported:
34022 retry=<timespec> Retry on connect fail
34025 The &`retry`& option specifies a time after which a single retry for
34026 a failed connect is made. The default is to not retry.
34028 If a Unix socket file is specified, only one server is supported.
34032 av_scanner = clamd:/opt/clamd/socket
34033 av_scanner = clamd:192.0.2.3 1234
34034 av_scanner = clamd:192.0.2.3 1234:local
34035 av_scanner = clamd:192.0.2.3 1234 retry=10s
34036 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34038 If the value of av_scanner points to a UNIX socket file or contains the
34040 option, then the ClamAV interface will pass a filename containing the data
34041 to be scanned, which should normally result in less I/O happening and be
34042 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34043 Exim does not assume that there is a common filesystem with the remote host.
34045 The final example shows that multiple TCP targets can be specified. Exim will
34046 randomly use one for each incoming email (i.e. it load balances them). Note
34047 that only TCP targets may be used if specifying a list of scanners; a UNIX
34048 socket cannot be mixed in with TCP targets. If one of the servers becomes
34049 unavailable, Exim will try the remaining one(s) until it finds one that works.
34050 When a clamd server becomes unreachable, Exim will log a message. Exim does
34051 not keep track of scanner state between multiple messages, and the scanner
34052 selection is random, so the message will get logged in the mainlog for each
34053 email that the down scanner gets chosen first (message wrapped to be readable):
34055 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34056 clamd: connection to localhost, port 3310 failed
34057 (Connection refused)
34060 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34061 contributing the code for this scanner.
34064 .cindex "virus scanners" "command line interface"
34065 This is the keyword for the generic command line scanner interface. It can be
34066 used to attach virus scanners that are invoked from the shell. This scanner
34067 type takes 3 mandatory options:
34070 The full path and name of the scanner binary, with all command line options,
34071 and a placeholder (&`%s`&) for the directory to scan.
34074 A regular expression to match against the STDOUT and STDERR output of the
34075 virus scanner. If the expression matches, a virus was found. You must make
34076 absolutely sure that this expression matches on &"virus found"&. This is called
34077 the &"trigger"& expression.
34080 Another regular expression, containing exactly one pair of parentheses, to
34081 match the name of the virus found in the scanners output. This is called the
34082 &"name"& expression.
34085 For example, Sophos Sweep reports a virus on a line like this:
34087 Virus 'W32/Magistr-B' found in file ./those.bat
34089 For the trigger expression, we can match the phrase &"found in file"&. For the
34090 name expression, we want to extract the W32/Magistr-B string, so we can match
34091 for the single quotes left and right of it. Altogether, this makes the
34092 configuration setting:
34094 av_scanner = cmdline:\
34095 /path/to/sweep -ss -all -rec -archive %s:\
34096 found in file:'(.+)'
34099 .cindex "virus scanners" "DrWeb"
34100 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34102 either a full path to a UNIX socket,
34103 or host and port specifiers separated by white space.
34104 The host may be a name or an IP address; the port is either a
34105 single number or a pair of numbers with a dash between.
34108 av_scanner = drweb:/var/run/drwebd.sock
34109 av_scanner = drweb:192.168.2.20 31337
34111 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34112 is used. Thanks to Alex Miller for contributing the code for this scanner.
34115 .cindex "virus scanners" "f-protd"
34116 The f-protd scanner is accessed via HTTP over TCP.
34117 One argument is taken, being a space-separated hostname and port number
34121 av_scanner = f-protd:localhost 10200-10204
34123 If you omit the argument, the default values shown above are used.
34125 .vitem &%f-prot6d%&
34126 .cindex "virus scanners" "f-prot6d"
34127 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34128 One argument is taken, being a space-separated hostname and port number.
34131 av_scanner = f-prot6d:localhost 10200
34133 If you omit the argument, the default values show above are used.
34136 .cindex "virus scanners" "F-Secure"
34137 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34138 argument which is the path to a UNIX socket. For example:
34140 av_scanner = fsecure:/path/to/.fsav
34142 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34143 Thelmen for contributing the code for this scanner.
34145 .vitem &%kavdaemon%&
34146 .cindex "virus scanners" "Kaspersky"
34147 This is the scanner daemon of Kaspersky Version 4. This version of the
34148 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34149 scanner type takes one option, which is the path to the daemon's UNIX socket.
34152 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34154 The default path is &_/var/run/AvpCtl_&.
34157 .cindex "virus scanners" "mksd"
34158 This was a daemon type scanner that is aimed mainly at Polish users,
34159 though some documentation was available in English.
34160 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34161 and this appears to be a candidate for removal from Exim, unless
34162 we are informed of other virus scanners which use the same protocol
34164 The only option for this scanner type is
34165 the maximum number of processes used simultaneously to scan the attachments,
34166 provided that mksd has
34167 been run with at least the same number of child processes. For example:
34169 av_scanner = mksd:2
34171 You can safely omit this option (the default value is 1).
34174 .cindex "virus scanners" "simple socket-connected"
34175 This is a general-purpose way of talking to simple scanner daemons
34176 running on the local machine.
34177 There are four options:
34178 an address (which may be an IP address and port, or the path of a Unix socket),
34179 a commandline to send (may include a single %s which will be replaced with
34180 the path to the mail file to be scanned),
34181 an RE to trigger on from the returned data,
34182 and an RE to extract malware_name from the returned data.
34185 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34187 Note that surrounding whitespace is stripped from each option, meaning
34188 there is no way to specify a trailing newline.
34189 The socket specifier and both regular-expressions are required.
34190 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34191 specify an empty element to get this.
34194 .cindex "virus scanners" "Sophos and Sophie"
34195 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34196 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34197 for this scanner type is the path to the UNIX socket that Sophie uses for
34198 client communication. For example:
34200 av_scanner = sophie:/tmp/sophie
34202 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34206 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34207 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34210 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34211 makes it possible to use different scanners. See further below for an example.
34212 The &%malware%& condition caches its results, so when you use it multiple times
34213 for the same message, the actual scanning process is only carried out once.
34214 However, using expandable items in &%av_scanner%& disables this caching, in
34215 which case each use of the &%malware%& condition causes a new scan of the
34218 The &%malware%& condition takes a right-hand argument that is expanded before
34219 use and taken as a list, slash-separated by default.
34220 The first element can then be one of
34223 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34224 The condition succeeds if a virus was found, and fail otherwise. This is the
34227 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34228 the condition fails immediately.
34230 A regular expression, in which case the message is scanned for viruses. The
34231 condition succeeds if a virus is found and its name matches the regular
34232 expression. This allows you to take special actions on certain types of virus.
34233 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34234 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34237 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34238 messages even if there is a problem with the virus scanner.
34239 Otherwise, such a problem causes the ACL to defer.
34241 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34242 specify a non-default timeout. The default is two minutes.
34245 malware = * / defer_ok / tmo=10s
34247 A timeout causes the ACL to defer.
34249 .vindex "&$callout_address$&"
34250 When a connection is made to the scanner the expansion variable &$callout_address$&
34251 is set to record the actual address used.
34253 .vindex "&$malware_name$&"
34254 When a virus is found, the condition sets up an expansion variable called
34255 &$malware_name$& that contains the name of the virus. You can use it in a
34256 &%message%& modifier that specifies the error returned to the sender, and/or in
34259 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34260 imposed by your anti-virus scanner.
34262 Here is a very simple scanning example:
34265 message = This message contains malware ($malware_name)
34267 The next example accepts messages when there is a problem with the scanner:
34269 deny malware = */defer_ok
34270 message = This message contains malware ($malware_name)
34272 The next example shows how to use an ACL variable to scan with both sophie and
34273 aveserver. It assumes you have set:
34275 av_scanner = $acl_m0
34277 in the main Exim configuration.
34279 deny set acl_m0 = sophie
34281 message = This message contains malware ($malware_name)
34283 deny set acl_m0 = aveserver
34285 message = This message contains malware ($malware_name)
34289 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34290 .cindex "content scanning" "for spam"
34291 .cindex "spam scanning"
34292 .cindex "SpamAssassin"
34294 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34295 score and a report for the message.
34296 Support is also provided for Rspamd.
34298 For more information about installation and configuration of SpamAssassin or
34299 Rspamd refer to their respective websites at
34300 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34302 SpamAssassin can be installed with CPAN by running:
34304 perl -MCPAN -e 'install Mail::SpamAssassin'
34306 SpamAssassin has its own set of configuration files. Please review its
34307 documentation to see how you can tweak it. The default installation should work
34310 .oindex "&%spamd_address%&"
34311 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34312 intend to use an instance running on the local host you do not need to set
34313 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34314 you must set the &%spamd_address%& option in the global part of the Exim
34315 configuration as follows (example):
34317 spamd_address = 192.168.99.45 783
34319 The SpamAssassin protocol relies on a TCP half-close from the client.
34320 If your SpamAssassin client side is running a Linux system with an
34321 iptables firewall, consider setting
34322 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34323 timeout, Exim uses when waiting for a response from the SpamAssassin
34324 server (currently defaulting to 120s). With a lower value the Linux
34325 connection tracking may consider your half-closed connection as dead too
34329 To use Rspamd (which by default listens on all local addresses
34331 you should add &%variant=rspamd%& after the address/port pair, for example:
34333 spamd_address = 127.0.0.1 11333 variant=rspamd
34336 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34337 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34338 filename instead of an address/port pair:
34340 spamd_address = /var/run/spamd_socket
34342 You can have multiple &%spamd%& servers to improve scalability. These can
34343 reside on other hardware reachable over the network. To specify multiple
34344 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34345 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34347 spamd_address = 192.168.2.10 783 : \
34348 192.168.2.11 783 : \
34351 Up to 32 &%spamd%& servers are supported.
34352 When a server fails to respond to the connection attempt, all other
34353 servers are tried until one succeeds. If no server responds, the &%spam%&
34356 Unix and TCP socket specifications may be mixed in any order.
34357 Each element of the list is a list itself, space-separated by default
34358 and changeable in the usual way (&<<SECTlistsepchange>>&);
34359 take care to not double the separator.
34361 For TCP socket specifications a host name or IP (v4 or v6, but
34362 subject to list-separator quoting rules) address can be used,
34363 and the port can be one or a dash-separated pair.
34364 In the latter case, the range is tried in strict order.
34366 Elements after the first for Unix sockets, or second for TCP socket,
34368 The supported options are:
34370 pri=<priority> Selection priority
34371 weight=<value> Selection bias
34372 time=<start>-<end> Use only between these times of day
34373 retry=<timespec> Retry on connect fail
34374 tmo=<timespec> Connection time limit
34375 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34378 The &`pri`& option specifies a priority for the server within the list,
34379 higher values being tried first.
34380 The default priority is 1.
34382 The &`weight`& option specifies a selection bias.
34383 Within a priority set
34384 servers are queried in a random fashion, weighted by this value.
34385 The default value for selection bias is 1.
34387 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34388 in the local time zone; each element being one or more digits.
34389 Either the seconds or both minutes and seconds, plus the leading &`.`&
34390 characters, may be omitted and will be taken as zero.
34392 Timeout specifications for the &`retry`& and &`tmo`& options
34393 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34395 The &`tmo`& option specifies an overall timeout for communication.
34396 The default value is two minutes.
34398 The &`retry`& option specifies a time after which a single retry for
34399 a failed connect is made.
34400 The default is to not retry.
34402 The &%spamd_address%& variable is expanded before use if it starts with
34403 a dollar sign. In this case, the expansion may return a string that is
34404 used as the list so that multiple spamd servers can be the result of an
34407 .vindex "&$callout_address$&"
34408 When a connection is made to the server the expansion variable &$callout_address$&
34409 is set to record the actual address used.
34411 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34412 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34415 message = This message was classified as SPAM
34417 The right-hand side of the &%spam%& condition specifies a name. This is
34418 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34419 to scan using a specific profile, but rather use the SpamAssassin system-wide
34420 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34421 Rspamd does not use this setting. However, you must put something on the
34424 The name allows you to use per-domain or per-user antispam profiles in
34425 principle, but this is not straightforward in practice, because a message may
34426 have multiple recipients, not necessarily all in the same domain. Because the
34427 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34428 read the contents of the message, the variables &$local_part$& and &$domain$&
34430 Careful enforcement of single-recipient messages
34431 (e.g. by responding with defer in the recipient ACL for all recipients
34433 or the use of PRDR,
34434 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34435 are needed to use this feature.
34437 The right-hand side of the &%spam%& condition is expanded before being used, so
34438 you can put lookups or conditions there. When the right-hand side evaluates to
34439 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34442 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34443 large ones may cause significant performance degradation. As most spam messages
34444 are quite small, it is recommended that you do not scan the big ones. For
34447 deny condition = ${if < {$message_size}{10K}}
34449 message = This message was classified as SPAM
34452 The &%spam%& condition returns true if the threshold specified in the user's
34453 SpamAssassin profile has been matched or exceeded. If you want to use the
34454 &%spam%& condition for its side effects (see the variables below), you can make
34455 it always return &"true"& by appending &`:true`& to the username.
34457 .cindex "spam scanning" "returned variables"
34458 When the &%spam%& condition is run, it sets up a number of expansion
34460 Except for &$spam_report$&,
34461 these variables are saved with the received message so are
34462 available for use at delivery time.
34465 .vitem &$spam_score$&
34466 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34467 for inclusion in log or reject messages.
34469 .vitem &$spam_score_int$&
34470 The spam score of the message, multiplied by ten, as an integer value. For
34471 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34472 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34473 The integer value is useful for numeric comparisons in conditions.
34475 .vitem &$spam_bar$&
34476 A string consisting of a number of &"+"& or &"-"& characters, representing the
34477 integer part of the spam score value. A spam score of 4.4 would have a
34478 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34479 headers, since MUAs can match on such strings. The maximum length of the
34480 spam bar is 50 characters.
34482 .vitem &$spam_report$&
34483 A multiline text table, containing the full SpamAssassin report for the
34484 message. Useful for inclusion in headers or reject messages.
34485 This variable is only usable in a DATA-time ACL.
34486 Beware that SpamAssassin may return non-ASCII characters, especially
34487 when running in country-specific locales, which are not legal
34488 unencoded in headers.
34490 .vitem &$spam_action$&
34491 For SpamAssassin either 'reject' or 'no action' depending on the
34492 spam score versus threshold.
34493 For Rspamd, the recommended action.
34497 The &%spam%& condition caches its results unless expansion in
34498 spamd_address was used. If you call it again with the same user name, it
34499 does not scan again, but rather returns the same values as before.
34501 The &%spam%& condition returns DEFER if there is any error while running
34502 the message through SpamAssassin or if the expansion of spamd_address
34503 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34504 statement block), append &`/defer_ok`& to the right-hand side of the
34505 spam condition, like this:
34507 deny spam = joe/defer_ok
34508 message = This message was classified as SPAM
34510 This causes messages to be accepted even if there is a problem with &%spamd%&.
34512 Here is a longer, commented example of the use of the &%spam%&
34515 # put headers in all messages (no matter if spam or not)
34516 warn spam = nobody:true
34517 add_header = X-Spam-Score: $spam_score ($spam_bar)
34518 add_header = X-Spam-Report: $spam_report
34520 # add second subject line with *SPAM* marker when message
34521 # is over threshold
34523 add_header = Subject: *SPAM* $h_Subject:
34525 # reject spam at high scores (> 12)
34526 deny spam = nobody:true
34527 condition = ${if >{$spam_score_int}{120}{1}{0}}
34528 message = This message scored $spam_score spam points.
34533 .section "Scanning MIME parts" "SECTscanmimepart"
34534 .cindex "content scanning" "MIME parts"
34535 .cindex "MIME content scanning"
34536 .oindex "&%acl_smtp_mime%&"
34537 .oindex "&%acl_not_smtp_mime%&"
34538 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34539 each MIME part of an SMTP message, including multipart types, in the sequence
34540 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34541 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34542 options may both refer to the same ACL if you want the same processing in both
34545 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34546 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34547 the case of a non-SMTP message. However, a MIME ACL is called only if the
34548 message contains a &'Content-Type:'& header line. When a call to a MIME
34549 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34550 result code is sent to the client. In the case of an SMTP message, the
34551 &%acl_smtp_data%& ACL is not called when this happens.
34553 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34554 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34555 condition to match against the raw MIME part. You can also use the
34556 &%mime_regex%& condition to match against the decoded MIME part (see section
34557 &<<SECTscanregex>>&).
34559 At the start of a MIME ACL, a number of variables are set from the header
34560 information for the relevant MIME part. These are described below. The contents
34561 of the MIME part are not by default decoded into a disk file except for MIME
34562 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34563 part into a disk file, you can use the &%decode%& condition. The general
34566 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34568 The right hand side is expanded before use. After expansion,
34572 &"0"& or &"false"&, in which case no decoding is done.
34574 The string &"default"&. In that case, the file is put in the temporary
34575 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34576 a sequential filename consisting of the message id and a sequence number. The
34577 full path and name is available in &$mime_decoded_filename$& after decoding.
34579 A full path name starting with a slash. If the full name is an existing
34580 directory, it is used as a replacement for the default directory. The filename
34581 is then sequentially assigned. If the path does not exist, it is used as
34582 the full path and filename.
34584 If the string does not start with a slash, it is used as the
34585 filename, and the default path is then used.
34587 The &%decode%& condition normally succeeds. It is only false for syntax
34588 errors or unusual circumstances such as memory shortages. You can easily decode
34589 a file with its original, proposed filename using
34591 decode = $mime_filename
34593 However, you should keep in mind that &$mime_filename$& might contain
34594 anything. If you place files outside of the default path, they are not
34595 automatically unlinked.
34597 For RFC822 attachments (these are messages attached to messages, with a
34598 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34599 as for the primary message, only that the &$mime_is_rfc822$& expansion
34600 variable is set (see below). Attached messages are always decoded to disk
34601 before being checked, and the files are unlinked once the check is done.
34603 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34604 used to match regular expressions against raw and decoded MIME parts,
34605 respectively. They are described in section &<<SECTscanregex>>&.
34607 .cindex "MIME content scanning" "returned variables"
34608 The following list describes all expansion variables that are
34609 available in the MIME ACL:
34612 .vitem &$mime_anomaly_level$& &&&
34613 &$mime_anomaly_text$&
34614 .vindex &$mime_anomaly_level$&
34615 .vindex &$mime_anomaly_text$&
34616 If there are problems decoding, these variables contain information on
34617 the detected issue.
34619 .vitem &$mime_boundary$&
34620 .vindex &$mime_boundary$&
34621 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34622 have a boundary string, which is stored in this variable. If the current part
34623 has no boundary parameter in the &'Content-Type:'& header, this variable
34624 contains the empty string.
34626 .vitem &$mime_charset$&
34627 .vindex &$mime_charset$&
34628 This variable contains the character set identifier, if one was found in the
34629 &'Content-Type:'& header. Examples for charset identifiers are:
34635 Please note that this value is not normalized, so you should do matches
34636 case-insensitively.
34638 .vitem &$mime_content_description$&
34639 .vindex &$mime_content_description$&
34640 This variable contains the normalized content of the &'Content-Description:'&
34641 header. It can contain a human-readable description of the parts content. Some
34642 implementations repeat the filename for attachments here, but they are usually
34643 only used for display purposes.
34645 .vitem &$mime_content_disposition$&
34646 .vindex &$mime_content_disposition$&
34647 This variable contains the normalized content of the &'Content-Disposition:'&
34648 header. You can expect strings like &"attachment"& or &"inline"& here.
34650 .vitem &$mime_content_id$&
34651 .vindex &$mime_content_id$&
34652 This variable contains the normalized content of the &'Content-ID:'& header.
34653 This is a unique ID that can be used to reference a part from another part.
34655 .vitem &$mime_content_size$&
34656 .vindex &$mime_content_size$&
34657 This variable is set only after the &%decode%& modifier (see above) has been
34658 successfully run. It contains the size of the decoded part in kilobytes. The
34659 size is always rounded up to full kilobytes, so only a completely empty part
34660 has a &$mime_content_size$& of zero.
34662 .vitem &$mime_content_transfer_encoding$&
34663 .vindex &$mime_content_transfer_encoding$&
34664 This variable contains the normalized content of the
34665 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34666 type. Typical values are &"base64"& and &"quoted-printable"&.
34668 .vitem &$mime_content_type$&
34669 .vindex &$mime_content_type$&
34670 If the MIME part has a &'Content-Type:'& header, this variable contains its
34671 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34672 are some examples of popular MIME types, as they may appear in this variable:
34676 application/octet-stream
34680 If the MIME part has no &'Content-Type:'& header, this variable contains the
34683 .vitem &$mime_decoded_filename$&
34684 .vindex &$mime_decoded_filename$&
34685 This variable is set only after the &%decode%& modifier (see above) has been
34686 successfully run. It contains the full path and filename of the file
34687 containing the decoded data.
34692 .vitem &$mime_filename$&
34693 .vindex &$mime_filename$&
34694 This is perhaps the most important of the MIME variables. It contains a
34695 proposed filename for an attachment, if one was found in either the
34696 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34699 decoded, but no additional sanity checks are done.
34701 found, this variable contains the empty string.
34703 .vitem &$mime_is_coverletter$&
34704 .vindex &$mime_is_coverletter$&
34705 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34706 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34707 content in the cover letter, while not restricting attachments at all.
34709 The variable contains 1 (true) for a MIME part believed to be part of the
34710 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34714 The outermost MIME part of a message is always a cover letter.
34717 If a multipart/alternative or multipart/related MIME part is a cover letter,
34718 so are all MIME subparts within that multipart.
34721 If any other multipart is a cover letter, the first subpart is a cover letter,
34722 and the rest are attachments.
34725 All parts contained within an attachment multipart are attachments.
34728 As an example, the following will ban &"HTML mail"& (including that sent with
34729 alternative plain text), while allowing HTML files to be attached. HTML
34730 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34732 deny !condition = $mime_is_rfc822
34733 condition = $mime_is_coverletter
34734 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34735 message = HTML mail is not accepted here
34738 .vitem &$mime_is_multipart$&
34739 .vindex &$mime_is_multipart$&
34740 This variable has the value 1 (true) when the current part has the main type
34741 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34742 Since multipart entities only serve as containers for other parts, you may not
34743 want to carry out specific actions on them.
34745 .vitem &$mime_is_rfc822$&
34746 .vindex &$mime_is_rfc822$&
34747 This variable has the value 1 (true) if the current part is not a part of the
34748 checked message itself, but part of an attached message. Attached message
34749 decoding is fully recursive.
34751 .vitem &$mime_part_count$&
34752 .vindex &$mime_part_count$&
34753 This variable is a counter that is raised for each processed MIME part. It
34754 starts at zero for the very first part (which is usually a multipart). The
34755 counter is per-message, so it is reset when processing RFC822 attachments (see
34756 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34757 complete, so you can use it in the DATA ACL to determine the number of MIME
34758 parts of a message. For non-MIME messages, this variable contains the value -1.
34763 .section "Scanning with regular expressions" "SECTscanregex"
34764 .cindex "content scanning" "with regular expressions"
34765 .cindex "regular expressions" "content scanning with"
34766 You can specify your own custom regular expression matches on the full body of
34767 the message, or on individual MIME parts.
34769 The &%regex%& condition takes one or more regular expressions as arguments and
34770 matches them against the full message (when called in the DATA ACL) or a raw
34771 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34772 linewise, with a maximum line length of 32K characters. That means you cannot
34773 have multiline matches with the &%regex%& condition.
34775 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34776 to 32K of decoded content (the whole content at once, not linewise). If the
34777 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34778 is decoded automatically when &%mime_regex%& is executed (using default path
34779 and filename values). If the decoded data is larger than 32K, only the first
34780 32K characters are checked.
34782 The regular expressions are passed as a colon-separated list. To include a
34783 literal colon, you must double it. Since the whole right-hand side string is
34784 expanded before being used, you must also escape dollar signs and backslashes
34785 with more backslashes, or use the &`\N`& facility to disable expansion.
34786 Here is a simple example that contains two regular expressions:
34788 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34789 message = contains blacklisted regex ($regex_match_string)
34791 The conditions returns true if any one of the regular expressions matches. The
34792 &$regex_match_string$& expansion variable is then set up and contains the
34793 matching regular expression.
34794 The expansion variables &$regex1$& &$regex2$& etc
34795 are set to any substrings captured by the regular expression.
34797 &*Warning*&: With large messages, these conditions can be fairly
34805 . ////////////////////////////////////////////////////////////////////////////
34806 . ////////////////////////////////////////////////////////////////////////////
34808 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
34809 "Local scan function"
34810 .scindex IIDlosca "&[local_scan()]& function" "description of"
34811 .cindex "customizing" "input scan using C function"
34812 .cindex "policy control" "by local scan function"
34813 In these days of email worms, viruses, and ever-increasing spam, some sites
34814 want to apply a lot of checking to messages before accepting them.
34816 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
34817 passing messages to external virus and spam scanning software. You can also do
34818 a certain amount in Exim itself through string expansions and the &%condition%&
34819 condition in the ACL that runs after the SMTP DATA command or the ACL for
34820 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
34822 To allow for further customization to a site's own requirements, there is the
34823 possibility of linking Exim with a private message scanning function, written
34824 in C. If you want to run code that is written in something other than C, you
34825 can of course use a little C stub to call it.
34827 The local scan function is run once for every incoming message, at the point
34828 when Exim is just about to accept the message.
34829 It can therefore be used to control non-SMTP messages from local processes as
34830 well as messages arriving via SMTP.
34832 Exim applies a timeout to calls of the local scan function, and there is an
34833 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
34834 Zero means &"no timeout"&.
34835 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
34836 before calling the local scan function, so that the most common types of crash
34837 are caught. If the timeout is exceeded or one of those signals is caught, the
34838 incoming message is rejected with a temporary error if it is an SMTP message.
34839 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
34840 code. The incident is logged on the main and reject logs.
34844 .section "Building Exim to use a local scan function" "SECID207"
34845 .cindex "&[local_scan()]& function" "building Exim to use"
34846 To make use of the local scan function feature, you must tell Exim where your
34847 function is before building Exim, by setting
34848 both HAVE_LOCAL_SCAN and
34849 LOCAL_SCAN_SOURCE in your
34850 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
34851 directory, so you might set
34853 HAVE_LOCAL_SCAN=yes
34854 LOCAL_SCAN_SOURCE=Local/local_scan.c
34856 for example. The function must be called &[local_scan()]&;
34857 the source file(s) for it should first #define LOCAL_SCAN
34858 and then #include "local_scan.h".
34860 Exim after it has received a message, when the success return code is about to
34861 be sent. This is after all the ACLs have been run. The return code from your
34862 function controls whether the message is actually accepted or not. There is a
34863 commented template function (that just accepts the message) in the file
34864 _src/local_scan.c_.
34866 If you want to make use of Exim's runtime configuration file to set options
34867 for your &[local_scan()]& function, you must also set
34869 LOCAL_SCAN_HAS_OPTIONS=yes
34871 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
34876 .section "API for local_scan()" "SECTapiforloc"
34877 .cindex "&[local_scan()]& function" "API description"
34878 .cindex &%dlfunc%& "API description"
34879 You must include this line near the start of your code:
34882 #include "local_scan.h"
34884 This header file defines a number of variables and other values, and the
34885 prototype for the function itself. Exim is coded to use unsigned char values
34886 almost exclusively, and one of the things this header defines is a shorthand
34887 for &`unsigned char`& called &`uschar`&.
34888 It also makes available the following macro definitions, to simplify casting character
34889 strings and pointers to character strings:
34891 #define CS (char *)
34892 #define CCS (const char *)
34893 #define CSS (char **)
34894 #define US (unsigned char *)
34895 #define CUS (const unsigned char *)
34896 #define USS (unsigned char **)
34898 The function prototype for &[local_scan()]& is:
34900 extern int local_scan(int fd, uschar **return_text);
34902 The arguments are as follows:
34905 &%fd%& is a file descriptor for the file that contains the body of the message
34906 (the -D file). The file is open for reading and writing, but updating it is not
34907 recommended. &*Warning*&: You must &'not'& close this file descriptor.
34909 The descriptor is positioned at character 19 of the file, which is the first
34910 character of the body itself, because the first 19 characters are the message
34911 id followed by &`-D`& and a newline. If you rewind the file, you should use the
34912 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
34913 case this changes in some future version.
34915 &%return_text%& is an address which you can use to return a pointer to a text
34916 string at the end of the function. The value it points to on entry is NULL.
34919 The function must return an &%int%& value which is one of the following macros:
34922 .vitem &`LOCAL_SCAN_ACCEPT`&
34923 .vindex "&$local_scan_data$&"
34924 The message is accepted. If you pass back a string of text, it is saved with
34925 the message, and made available in the variable &$local_scan_data$&. No
34926 newlines are permitted (if there are any, they are turned into spaces) and the
34927 maximum length of text is 1000 characters.
34929 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
34930 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34931 queued without immediate delivery, and is frozen.
34933 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
34934 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34935 queued without immediate delivery.
34937 .vitem &`LOCAL_SCAN_REJECT`&
34938 The message is rejected; the returned text is used as an error message which is
34939 passed back to the sender and which is also logged. Newlines are permitted &--
34940 they cause a multiline response for SMTP rejections, but are converted to
34941 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
34944 .vitem &`LOCAL_SCAN_TEMPREJECT`&
34945 The message is temporarily rejected; the returned text is used as an error
34946 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
34949 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
34950 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
34951 message is not written to the reject log. It has the effect of unsetting the
34952 &%rejected_header%& log selector for just this rejection. If
34953 &%rejected_header%& is already unset (see the discussion of the
34954 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
34955 same as LOCAL_SCAN_REJECT.
34957 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
34958 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
34959 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
34962 If the message is not being received by interactive SMTP, rejections are
34963 reported by writing to &%stderr%& or by sending an email, as configured by the
34964 &%-oe%& command line options.
34968 .section "Configuration options for local_scan()" "SECTconoptloc"
34969 .cindex "&[local_scan()]& function" "configuration options"
34970 It is possible to have option settings in the main configuration file
34971 that set values in static variables in the &[local_scan()]& module. If you
34972 want to do this, you must have the line
34974 LOCAL_SCAN_HAS_OPTIONS=yes
34976 in your &_Local/Makefile_& when you build Exim. (This line is in
34977 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
34978 file, you must define static variables to hold the option values, and a table
34981 The table must be a vector called &%local_scan_options%&, of type
34982 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
34983 and a pointer to the variable that holds the value. The entries must appear in
34984 alphabetical order. Following &%local_scan_options%& you must also define a
34985 variable called &%local_scan_options_count%& that contains the number of
34986 entries in the table. Here is a short example, showing two kinds of option:
34988 static int my_integer_option = 42;
34989 static uschar *my_string_option = US"a default string";
34991 optionlist local_scan_options[] = {
34992 { "my_integer", opt_int, &my_integer_option },
34993 { "my_string", opt_stringptr, &my_string_option }
34996 int local_scan_options_count =
34997 sizeof(local_scan_options)/sizeof(optionlist);
34999 The values of the variables can now be changed from Exim's runtime
35000 configuration file by including a local scan section as in this example:
35004 my_string = some string of text...
35006 The available types of option data are as follows:
35009 .vitem &*opt_bool*&
35010 This specifies a boolean (true/false) option. The address should point to a
35011 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35012 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35013 whether such a variable has been set at all, you can initialize it to
35014 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35017 .vitem &*opt_fixed*&
35018 This specifies a fixed point number, such as is used for load averages.
35019 The address should point to a variable of type &`int`&. The value is stored
35020 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35023 This specifies an integer; the address should point to a variable of type
35024 &`int`&. The value may be specified in any of the integer formats accepted by
35027 .vitem &*opt_mkint*&
35028 This is the same as &%opt_int%&, except that when such a value is output in a
35029 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35030 printed with the suffix K or M.
35032 .vitem &*opt_octint*&
35033 This also specifies an integer, but the value is always interpreted as an
35034 octal integer, whether or not it starts with the digit zero, and it is
35035 always output in octal.
35037 .vitem &*opt_stringptr*&
35038 This specifies a string value; the address must be a pointer to a
35039 variable that points to a string (for example, of type &`uschar *`&).
35041 .vitem &*opt_time*&
35042 This specifies a time interval value. The address must point to a variable of
35043 type &`int`&. The value that is placed there is a number of seconds.
35046 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35047 out the values of all the &[local_scan()]& options.
35051 .section "Available Exim variables" "SECID208"
35052 .cindex "&[local_scan()]& function" "available Exim variables"
35053 The header &_local_scan.h_& gives you access to a number of C variables. These
35054 are the only ones that are guaranteed to be maintained from release to release.
35055 Note, however, that you can obtain the value of any Exim expansion variable,
35056 including &$recipients$&, by calling &'expand_string()'&. The exported
35057 C variables are as follows:
35060 .vitem &*int&~body_linecount*&
35061 This variable contains the number of lines in the message's body.
35062 It is not valid if the &%spool_files_wireformat%& option is used.
35064 .vitem &*int&~body_zerocount*&
35065 This variable contains the number of binary zero bytes in the message's body.
35066 It is not valid if the &%spool_files_wireformat%& option is used.
35068 .vitem &*unsigned&~int&~debug_selector*&
35069 This variable is set to zero when no debugging is taking place. Otherwise, it
35070 is a bitmap of debugging selectors. Two bits are identified for use in
35071 &[local_scan()]&; they are defined as macros:
35074 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35075 testing option that is not privileged &-- any caller may set it. All the
35076 other selector bits can be set only by admin users.
35079 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35080 by the &`+local_scan`& debug selector. It is not included in the default set
35084 Thus, to write to the debugging output only when &`+local_scan`& has been
35085 selected, you should use code like this:
35087 if ((debug_selector & D_local_scan) != 0)
35088 debug_printf("xxx", ...);
35090 .vitem &*uschar&~*expand_string_message*&
35091 After a failing call to &'expand_string()'& (returned value NULL), the
35092 variable &%expand_string_message%& contains the error message, zero-terminated.
35094 .vitem &*header_line&~*header_list*&
35095 A pointer to a chain of header lines. The &%header_line%& structure is
35098 .vitem &*header_line&~*header_last*&
35099 A pointer to the last of the header lines.
35101 .vitem &*uschar&~*headers_charset*&
35102 The value of the &%headers_charset%& configuration option.
35104 .vitem &*BOOL&~host_checking*&
35105 This variable is TRUE during a host checking session that is initiated by the
35106 &%-bh%& command line option.
35108 .vitem &*uschar&~*interface_address*&
35109 The IP address of the interface that received the message, as a string. This
35110 is NULL for locally submitted messages.
35112 .vitem &*int&~interface_port*&
35113 The port on which this message was received. When testing with the &%-bh%&
35114 command line option, the value of this variable is -1 unless a port has been
35115 specified via the &%-oMi%& option.
35117 .vitem &*uschar&~*message_id*&
35118 This variable contains Exim's message id for the incoming message (the value of
35119 &$message_exim_id$&) as a zero-terminated string.
35121 .vitem &*uschar&~*received_protocol*&
35122 The name of the protocol by which the message was received.
35124 .vitem &*int&~recipients_count*&
35125 The number of accepted recipients.
35127 .vitem &*recipient_item&~*recipients_list*&
35128 .cindex "recipient" "adding in local scan"
35129 .cindex "recipient" "removing in local scan"
35130 The list of accepted recipients, held in a vector of length
35131 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35132 can add additional recipients by calling &'receive_add_recipient()'& (see
35133 below). You can delete recipients by removing them from the vector and
35134 adjusting the value in &%recipients_count%&. In particular, by setting
35135 &%recipients_count%& to zero you remove all recipients. If you then return the
35136 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35137 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35138 and then call &'receive_add_recipient()'& as often as needed.
35140 .vitem &*uschar&~*sender_address*&
35141 The envelope sender address. For bounce messages this is the empty string.
35143 .vitem &*uschar&~*sender_host_address*&
35144 The IP address of the sending host, as a string. This is NULL for
35145 locally-submitted messages.
35147 .vitem &*uschar&~*sender_host_authenticated*&
35148 The name of the authentication mechanism that was used, or NULL if the message
35149 was not received over an authenticated SMTP connection.
35151 .vitem &*uschar&~*sender_host_name*&
35152 The name of the sending host, if known.
35154 .vitem &*int&~sender_host_port*&
35155 The port on the sending host.
35157 .vitem &*BOOL&~smtp_input*&
35158 This variable is TRUE for all SMTP input, including BSMTP.
35160 .vitem &*BOOL&~smtp_batched_input*&
35161 This variable is TRUE for BSMTP input.
35163 .vitem &*int&~store_pool*&
35164 The contents of this variable control which pool of memory is used for new
35165 requests. See section &<<SECTmemhanloc>>& for details.
35169 .section "Structure of header lines" "SECID209"
35170 The &%header_line%& structure contains the members listed below.
35171 You can add additional header lines by calling the &'header_add()'& function
35172 (see below). You can cause header lines to be ignored (deleted) by setting
35177 .vitem &*struct&~header_line&~*next*&
35178 A pointer to the next header line, or NULL for the last line.
35180 .vitem &*int&~type*&
35181 A code identifying certain headers that Exim recognizes. The codes are printing
35182 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35183 Notice in particular that any header line whose type is * is not transmitted
35184 with the message. This flagging is used for header lines that have been
35185 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35186 lines.) Effectively, * means &"deleted"&.
35188 .vitem &*int&~slen*&
35189 The number of characters in the header line, including the terminating and any
35192 .vitem &*uschar&~*text*&
35193 A pointer to the text of the header. It always ends with a newline, followed by
35194 a zero byte. Internal newlines are preserved.
35199 .section "Structure of recipient items" "SECID210"
35200 The &%recipient_item%& structure contains these members:
35203 .vitem &*uschar&~*address*&
35204 This is a pointer to the recipient address as it was received.
35206 .vitem &*int&~pno*&
35207 This is used in later Exim processing when top level addresses are created by
35208 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35209 and must always contain -1 at this stage.
35211 .vitem &*uschar&~*errors_to*&
35212 If this value is not NULL, bounce messages caused by failing to deliver to the
35213 recipient are sent to the address it contains. In other words, it overrides the
35214 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35215 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35216 an unqualified address, Exim qualifies it using the domain from
35217 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35218 is NULL for all recipients.
35223 .section "Available Exim functions" "SECID211"
35224 .cindex "&[local_scan()]& function" "available Exim functions"
35225 The header &_local_scan.h_& gives you access to a number of Exim functions.
35226 These are the only ones that are guaranteed to be maintained from release to
35230 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35231 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35233 This function creates a child process that runs the command specified by
35234 &%argv%&. The environment for the process is specified by &%envp%&, which can
35235 be NULL if no environment variables are to be passed. A new umask is supplied
35236 for the process in &%newumask%&.
35238 Pipes to the standard input and output of the new process are set up
35239 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35240 standard error is cloned to the standard output. If there are any file
35241 descriptors &"in the way"& in the new process, they are closed. If the final
35242 argument is TRUE, the new process is made into a process group leader.
35244 The function returns the pid of the new process, or -1 if things go wrong.
35246 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35247 This function waits for a child process to terminate, or for a timeout (in
35248 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35249 return value is as follows:
35254 The process terminated by a normal exit and the value is the process
35260 The process was terminated by a signal and the value is the negation of the
35266 The process timed out.
35270 The was some other error in wait(); &%errno%& is still set.
35273 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35274 This function provide you with a means of submitting a new message to
35275 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35276 want, but this packages it all up for you.) The function creates a pipe,
35277 forks a subprocess that is running
35279 exim -t -oem -oi -f <>
35281 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35282 that is connected to the standard input. The yield of the function is the PID
35283 of the subprocess. You can then write a message to the file descriptor, with
35284 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35286 When you have finished, call &'child_close()'& to wait for the process to
35287 finish and to collect its ending status. A timeout value of zero is usually
35288 fine in this circumstance. Unless you have made a mistake with the recipient
35289 addresses, you should get a return code of zero.
35292 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35293 *sender_authentication)*&
35294 This function is a more sophisticated version of &'child_open()'&. The command
35297 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35299 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35302 .vitem &*void&~debug_printf(char&~*,&~...)*&
35303 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35304 output is written to the standard error stream. If no debugging is selected,
35305 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35306 conditional on the &`local_scan`& debug selector by coding like this:
35308 if ((debug_selector & D_local_scan) != 0)
35309 debug_printf("xxx", ...);
35312 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35313 This is an interface to Exim's string expansion code. The return value is the
35314 expanded string, or NULL if there was an expansion failure.
35315 The C variable &%expand_string_message%& contains an error message after an
35316 expansion failure. If expansion does not change the string, the return value is
35317 the pointer to the input string. Otherwise, the return value points to a new
35318 block of memory that was obtained by a call to &'store_get()'&. See section
35319 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35321 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35322 This function allows you to an add additional header line at the end of the
35323 existing ones. The first argument is the type, and should normally be a space
35324 character. The second argument is a format string and any number of
35325 substitution arguments as for &[sprintf()]&. You may include internal newlines
35326 if you want, and you must ensure that the string ends with a newline.
35328 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35329 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35330 This function adds a new header line at a specified point in the header
35331 chain. The header itself is specified as for &'header_add()'&.
35333 If &%name%& is NULL, the new header is added at the end of the chain if
35334 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35335 NULL, the header lines are searched for the first non-deleted header that
35336 matches the name. If one is found, the new header is added before it if
35337 &%after%& is false. If &%after%& is true, the new header is added after the
35338 found header and any adjacent subsequent ones with the same name (even if
35339 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35340 option controls where the header is added. If it is true, addition is at the
35341 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35342 headers, or at the top if there are no &'Received:'& headers, you could use
35344 header_add_at_position(TRUE, US"Received", TRUE,
35345 ' ', "X-xxx: ...");
35347 Normally, there is always at least one non-deleted &'Received:'& header, but
35348 there may not be if &%received_header_text%& expands to an empty string.
35351 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35352 This function removes header lines. If &%occurrence%& is zero or negative, all
35353 occurrences of the header are removed. If occurrence is greater than zero, that
35354 particular instance of the header is removed. If no header(s) can be found that
35355 match the specification, the function does nothing.
35358 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35359 int&~length,&~BOOL&~notdel)*&"
35360 This function tests whether the given header has the given name. It is not just
35361 a string comparison, because white space is permitted between the name and the
35362 colon. If the &%notdel%& argument is true, a false return is forced for all
35363 &"deleted"& headers; otherwise they are not treated specially. For example:
35365 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35367 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35368 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35369 This function base64-encodes a string, which is passed by address and length.
35370 The text may contain bytes of any value, including zero. The result is passed
35371 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35374 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35375 This function decodes a base64-encoded string. Its arguments are a
35376 zero-terminated base64-encoded string and the address of a variable that is set
35377 to point to the result, which is in dynamic memory. The length of the decoded
35378 string is the yield of the function. If the input is invalid base64 data, the
35379 yield is -1. A zero byte is added to the end of the output string to make it
35380 easy to interpret as a C string (assuming it contains no zeros of its own). The
35381 added zero byte is not included in the returned count.
35383 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35384 This function checks for a match in a domain list. Domains are always
35385 matched caselessly. The return value is one of the following:
35387 &`OK `& match succeeded
35388 &`FAIL `& match failed
35389 &`DEFER `& match deferred
35391 DEFER is usually caused by some kind of lookup defer, such as the
35392 inability to contact a database.
35394 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35396 This function checks for a match in a local part list. The third argument
35397 controls case-sensitivity. The return values are as for
35398 &'lss_match_domain()'&.
35400 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35402 This function checks for a match in an address list. The third argument
35403 controls the case-sensitivity of the local part match. The domain is always
35404 matched caselessly. The return values are as for &'lss_match_domain()'&.
35406 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35408 This function checks for a match in a host list. The most common usage is
35411 lss_match_host(sender_host_name, sender_host_address, ...)
35413 .vindex "&$sender_host_address$&"
35414 An empty address field matches an empty item in the host list. If the host name
35415 is NULL, the name corresponding to &$sender_host_address$& is automatically
35416 looked up if a host name is required to match an item in the list. The return
35417 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35418 returns ERROR in the case when it had to look up a host name, but the lookup
35421 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35423 This function writes to Exim's log files. The first argument should be zero (it
35424 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35425 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35426 them. It specifies to which log or logs the message is written. The remaining
35427 arguments are a format and relevant insertion arguments. The string should not
35428 contain any newlines, not even at the end.
35431 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35432 This function adds an additional recipient to the message. The first argument
35433 is the recipient address. If it is unqualified (has no domain), it is qualified
35434 with the &%qualify_recipient%& domain. The second argument must always be -1.
35436 This function does not allow you to specify a private &%errors_to%& address (as
35437 described with the structure of &%recipient_item%& above), because it pre-dates
35438 the addition of that field to the structure. However, it is easy to add such a
35439 value afterwards. For example:
35441 receive_add_recipient(US"monitor@mydom.example", -1);
35442 recipients_list[recipients_count-1].errors_to =
35443 US"postmaster@mydom.example";
35446 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35447 This is a convenience function to remove a named recipient from the list of
35448 recipients. It returns true if a recipient was removed, and false if no
35449 matching recipient could be found. The argument must be a complete email
35456 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35457 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35458 This function decodes strings that are encoded according to RFC 2047. Typically
35459 these are the contents of header lines. First, each &"encoded word"& is decoded
35460 from the Q or B encoding into a byte-string. Then, if provided with the name of
35461 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35462 made to translate the result to the named character set. If this fails, the
35463 binary string is returned with an error message.
35465 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35466 maximum MIME word length is enforced. The third argument is the target
35467 encoding, or NULL if no translation is wanted.
35469 .cindex "binary zero" "in RFC 2047 decoding"
35470 .cindex "RFC 2047" "binary zero in"
35471 If a binary zero is encountered in the decoded string, it is replaced by the
35472 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35473 not be 0 because header lines are handled as zero-terminated strings.
35475 The function returns the result of processing the string, zero-terminated; if
35476 &%lenptr%& is not NULL, the length of the result is set in the variable to
35477 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35479 If an error is encountered, the function returns NULL and uses the &%error%&
35480 argument to return an error message. The variable pointed to by &%error%& is
35481 set to NULL if there is no error; it may be set non-NULL even when the function
35482 returns a non-NULL value if decoding was successful, but there was a problem
35486 .vitem &*int&~smtp_fflush(void)*&
35487 This function is used in conjunction with &'smtp_printf()'&, as described
35490 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35491 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35492 output stream. You should use this function only when there is an SMTP output
35493 stream, that is, when the incoming message is being received via interactive
35494 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35495 is FALSE. If you want to test for an incoming message from another host (as
35496 opposed to a local process that used the &%-bs%& command line option), you can
35497 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35500 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35501 output function, so it can be used for all forms of SMTP connection.
35503 The second argument is used to request that the data be buffered
35504 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35505 This is advisory only, but likely to save on system-calls and packets
35506 sent when a sequence of calls to the function are made.
35508 The argument was added in Exim version 4.90 - changing the API/ABI.
35509 Nobody noticed until 4.93 was imminent, at which point the
35510 ABI version number was incremented.
35512 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35513 must start with an appropriate response code: 550 if you are going to return
35514 LOCAL_SCAN_REJECT, 451 if you are going to return
35515 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35516 initial lines of a multi-line response, the code must be followed by a hyphen
35517 to indicate that the line is not the final response line. You must also ensure
35518 that the lines you write terminate with CRLF. For example:
35520 smtp_printf("550-this is some extra info\r\n");
35521 return LOCAL_SCAN_REJECT;
35523 Note that you can also create multi-line responses by including newlines in
35524 the data returned via the &%return_text%& argument. The added value of using
35525 &'smtp_printf()'& is that, for instance, you could introduce delays between
35526 multiple output lines.
35528 The &'smtp_printf()'& function does not return any error indication, because it
35530 guarantee a flush of
35531 pending output, and therefore does not test
35532 the state of the stream. (In the main code of Exim, flushing and error
35533 detection is done when Exim is ready for the next SMTP input command.) If
35534 you want to flush the output and check for an error (for example, the
35535 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35536 arguments. It flushes the output stream, and returns a non-zero value if there
35539 .vitem &*void&~*store_get(int,BOOL)*&
35540 This function accesses Exim's internal store (memory) manager. It gets a new
35541 chunk of memory whose size is given by the first argument.
35542 The second argument should be given as TRUE if the memory will be used for
35543 data possibly coming from an attacker (eg. the message content),
35544 FALSE if it is locally-sourced.
35545 Exim bombs out if it ever
35546 runs out of memory. See the next section for a discussion of memory handling.
35548 .vitem &*void&~*store_get_perm(int,BOOL)*&
35549 This function is like &'store_get()'&, but it always gets memory from the
35550 permanent pool. See the next section for a discussion of memory handling.
35552 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35555 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35558 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35559 These three functions create strings using Exim's dynamic memory facilities.
35560 The first makes a copy of an entire string. The second copies up to a maximum
35561 number of characters, indicated by the second argument. The third uses a format
35562 and insertion arguments to create a new string. In each case, the result is a
35563 pointer to a new string in the current memory pool. See the next section for
35569 .section "More about Exim's memory handling" "SECTmemhanloc"
35570 .cindex "&[local_scan()]& function" "memory handling"
35571 No function is provided for freeing memory, because that is never needed.
35572 The dynamic memory that Exim uses when receiving a message is automatically
35573 recycled if another message is received by the same process (this applies only
35574 to incoming SMTP connections &-- other input methods can supply only one
35575 message at a time). After receiving the last message, a reception process
35578 Because it is recycled, the normal dynamic memory cannot be used for holding
35579 data that must be preserved over a number of incoming messages on the same SMTP
35580 connection. However, Exim in fact uses two pools of dynamic memory; the second
35581 one is not recycled, and can be used for this purpose.
35583 If you want to allocate memory that remains available for subsequent messages
35584 in the same SMTP connection, you should set
35586 store_pool = POOL_PERM
35588 before calling the function that does the allocation. There is no need to
35589 restore the value if you do not need to; however, if you do want to revert to
35590 the normal pool, you can either restore the previous value of &%store_pool%& or
35591 set it explicitly to POOL_MAIN.
35593 The pool setting applies to all functions that get dynamic memory, including
35594 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35595 There is also a convenience function called &'store_get_perm()'& that gets a
35596 block of memory from the permanent pool while preserving the value of
35603 . ////////////////////////////////////////////////////////////////////////////
35604 . ////////////////////////////////////////////////////////////////////////////
35606 .chapter "System-wide message filtering" "CHAPsystemfilter"
35607 .scindex IIDsysfil1 "filter" "system filter"
35608 .scindex IIDsysfil2 "filtering all mail"
35609 .scindex IIDsysfil3 "system filter"
35610 The previous chapters (on ACLs and the local scan function) describe checks
35611 that can be applied to messages before they are accepted by a host. There is
35612 also a mechanism for checking messages once they have been received, but before
35613 they are delivered. This is called the &'system filter'&.
35615 The system filter operates in a similar manner to users' filter files, but it
35616 is run just once per message (however many recipients the message has).
35617 It should not normally be used as a substitute for routing, because &%deliver%&
35618 commands in a system router provide new envelope recipient addresses.
35619 The system filter must be an Exim filter. It cannot be a Sieve filter.
35621 The system filter is run at the start of a delivery attempt, before any routing
35622 is done. If a message fails to be completely delivered at the first attempt,
35623 the system filter is run again at the start of every retry.
35624 If you want your filter to do something only once per message, you can make use
35625 of the &%first_delivery%& condition in an &%if%& command in the filter to
35626 prevent it happening on retries.
35628 .vindex "&$domain$&"
35629 .vindex "&$local_part$&"
35630 &*Warning*&: Because the system filter runs just once, variables that are
35631 specific to individual recipient addresses, such as &$local_part$& and
35632 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35633 you want to run a centrally-specified filter for each recipient address
35634 independently, you can do so by setting up a suitable &(redirect)& router, as
35635 described in section &<<SECTperaddfil>>& below.
35638 .section "Specifying a system filter" "SECID212"
35639 .cindex "uid (user id)" "system filter"
35640 .cindex "gid (group id)" "system filter"
35641 The name of the file that contains the system filter must be specified by
35642 setting &%system_filter%&. If you want the filter to run under a uid and gid
35643 other than root, you must also set &%system_filter_user%& and
35644 &%system_filter_group%& as appropriate. For example:
35646 system_filter = /etc/mail/exim.filter
35647 system_filter_user = exim
35649 If a system filter generates any deliveries directly to files or pipes (via the
35650 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35651 specified by setting &%system_filter_file_transport%& and
35652 &%system_filter_pipe_transport%&, respectively. Similarly,
35653 &%system_filter_reply_transport%& must be set to handle any messages generated
35654 by the &%reply%& command.
35657 .section "Testing a system filter" "SECID213"
35658 You can run simple tests of a system filter in the same way as for a user
35659 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35660 are permitted only in system filters are recognized.
35662 If you want to test the combined effect of a system filter and a user filter,
35663 you can use both &%-bF%& and &%-bf%& on the same command line.
35667 .section "Contents of a system filter" "SECID214"
35668 The language used to specify system filters is the same as for users' filter
35669 files. It is described in the separate end-user document &'Exim's interface to
35670 mail filtering'&. However, there are some additional features that are
35671 available only in system filters; these are described in subsequent sections.
35672 If they are encountered in a user's filter file or when testing with &%-bf%&,
35675 .cindex "frozen messages" "manual thaw; testing in filter"
35676 There are two special conditions which, though available in users' filter
35677 files, are designed for use in system filters. The condition &%first_delivery%&
35678 is true only for the first attempt at delivering a message, and
35679 &%manually_thawed%& is true only if the message has been frozen, and
35680 subsequently thawed by an admin user. An explicit forced delivery counts as a
35681 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35683 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35684 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35685 succeed, it will not be tried again.
35686 If you want Exim to retry an unseen delivery until it succeeds, you should
35687 arrange to set it up every time the filter runs.
35689 When a system filter finishes running, the values of the variables &$n0$& &--
35690 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35691 users' filter files. Thus a system filter can, for example, set up &"scores"&
35692 to which users' filter files can refer.
35696 .section "Additional variable for system filters" "SECID215"
35697 .vindex "&$recipients$&"
35698 The expansion variable &$recipients$&, containing a list of all the recipients
35699 of the message (separated by commas and white space), is available in system
35700 filters. It is not available in users' filters for privacy reasons.
35704 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35705 .cindex "freezing messages"
35706 .cindex "message" "freezing"
35707 .cindex "message" "forced failure"
35708 .cindex "&%fail%&" "in system filter"
35709 .cindex "&%freeze%& in system filter"
35710 .cindex "&%defer%& in system filter"
35711 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35712 always available in system filters, but are not normally enabled in users'
35713 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35714 for the &(redirect)& router.) These commands can optionally be followed by the
35715 word &%text%& and a string containing an error message, for example:
35717 fail text "this message looks like spam to me"
35719 The keyword &%text%& is optional if the next character is a double quote.
35721 The &%defer%& command defers delivery of the original recipients of the
35722 message. The &%fail%& command causes all the original recipients to be failed,
35723 and a bounce message to be created. The &%freeze%& command suspends all
35724 delivery attempts for the original recipients. In all cases, any new deliveries
35725 that are specified by the filter are attempted as normal after the filter has
35728 The &%freeze%& command is ignored if the message has been manually unfrozen and
35729 not manually frozen since. This means that automatic freezing by a system
35730 filter can be used as a way of checking out suspicious messages. If a message
35731 is found to be all right, manually unfreezing it allows it to be delivered.
35733 .cindex "log" "&%fail%& command log line"
35734 .cindex "&%fail%&" "log line; reducing"
35735 The text given with a fail command is used as part of the bounce message as
35736 well as being written to the log. If the message is quite long, this can fill
35737 up a lot of log space when such failures are common. To reduce the size of the
35738 log message, Exim interprets the text in a special way if it starts with the
35739 two characters &`<<`& and contains &`>>`& later. The text between these two
35740 strings is written to the log, and the rest of the text is used in the bounce
35741 message. For example:
35743 fail "<<filter test 1>>Your message is rejected \
35744 because it contains attachments that we are \
35745 not prepared to receive."
35748 .cindex "loop" "caused by &%fail%&"
35749 Take great care with the &%fail%& command when basing the decision to fail on
35750 the contents of the message, because the bounce message will of course include
35751 the contents of the original message and will therefore trigger the &%fail%&
35752 command again (causing a mail loop) unless steps are taken to prevent this.
35753 Testing the &%error_message%& condition is one way to prevent this. You could
35756 if $message_body contains "this is spam" and not error_message
35757 then fail text "spam is not wanted here" endif
35759 though of course that might let through unwanted bounce messages. The
35760 alternative is clever checking of the body and/or headers to detect bounces
35761 generated by the filter.
35763 The interpretation of a system filter file ceases after a
35765 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35766 set up earlier in the filter file are honoured, so you can use a sequence such
35772 to send a specified message when the system filter is freezing (or deferring or
35773 failing) a message. The normal deliveries for the message do not, of course,
35778 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35779 .cindex "header lines" "adding; in system filter"
35780 .cindex "header lines" "removing; in system filter"
35781 .cindex "filter" "header lines; adding/removing"
35782 Two filter commands that are available only in system filters are:
35784 headers add <string>
35785 headers remove <string>
35787 The argument for the &%headers add%& is a string that is expanded and then
35788 added to the end of the message's headers. It is the responsibility of the
35789 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35790 space is ignored, and if the string is otherwise empty, or if the expansion is
35791 forced to fail, the command has no effect.
35793 You can use &"\n"& within the string, followed by white space, to specify
35794 continued header lines. More than one header may be added in one command by
35795 including &"\n"& within the string without any following white space. For
35798 headers add "X-header-1: ....\n \
35799 continuation of X-header-1 ...\n\
35802 Note that the header line continuation white space after the first newline must
35803 be placed before the backslash that continues the input string, because white
35804 space after input continuations is ignored.
35806 The argument for &%headers remove%& is a colon-separated list of header names.
35807 This command applies only to those headers that are stored with the message;
35808 those that are added at delivery time (such as &'Envelope-To:'& and
35809 &'Return-Path:'&) cannot be removed by this means. If there is more than one
35810 header with the same name, they are all removed.
35812 The &%headers%& command in a system filter makes an immediate change to the set
35813 of header lines that was received with the message (with possible additions
35814 from ACL processing). Subsequent commands in the system filter operate on the
35815 modified set, which also forms the basis for subsequent message delivery.
35816 Unless further modified during routing or transporting, this set of headers is
35817 used for all recipients of the message.
35819 During routing and transporting, the variables that refer to the contents of
35820 header lines refer only to those lines that are in this set. Thus, header lines
35821 that are added by a system filter are visible to users' filter files and to all
35822 routers and transports. This contrasts with the manipulation of header lines by
35823 routers and transports, which is not immediate, but which instead is saved up
35824 until the message is actually being written (see section
35825 &<<SECTheadersaddrem>>&).
35827 If the message is not delivered at the first attempt, header lines that were
35828 added by the system filter are stored with the message, and so are still
35829 present at the next delivery attempt. Header lines that were removed are still
35830 present, but marked &"deleted"& so that they are not transported with the
35831 message. For this reason, it is usual to make the &%headers%& command
35832 conditional on &%first_delivery%& so that the set of header lines is not
35833 modified more than once.
35835 Because header modification in a system filter acts immediately, you have to
35836 use an indirect approach if you want to modify the contents of a header line.
35839 headers add "Old-Subject: $h_subject:"
35840 headers remove "Subject"
35841 headers add "Subject: new subject (was: $h_old-subject:)"
35842 headers remove "Old-Subject"
35847 .section "Setting an errors address in a system filter" "SECID217"
35848 .cindex "envelope from"
35849 .cindex "envelope sender"
35850 In a system filter, if a &%deliver%& command is followed by
35852 errors_to <some address>
35854 in order to change the envelope sender (and hence the error reporting) for that
35855 delivery, any address may be specified. (In a user filter, only the current
35856 user's address can be set.) For example, if some mail is being monitored, you
35859 unseen deliver monitor@spying.example errors_to root@local.example
35861 to take a copy which would not be sent back to the normal error reporting
35862 address if its delivery failed.
35866 .section "Per-address filtering" "SECTperaddfil"
35867 .vindex "&$domain_data$&"
35868 .vindex "&$local_part_data$&"
35869 In contrast to the system filter, which is run just once per message for each
35870 delivery attempt, it is also possible to set up a system-wide filtering
35871 operation that runs once for each recipient address. In this case, variables
35872 such as &$local_part_data$& and &$domain_data$& can be used,
35873 and indeed, the choice of filter file could be made dependent on them.
35874 This is an example of a router which implements such a filter:
35879 domains = +local_domains
35880 file = /central/filters/$local_part_data
35885 The filter is run in a separate process under its own uid. Therefore, either
35886 &%check_local_user%& must be set (as above), in which case the filter is run as
35887 the local user, or the &%user%& option must be used to specify which user to
35888 use. If both are set, &%user%& overrides.
35890 Care should be taken to ensure that none of the commands in the filter file
35891 specify a significant delivery if the message is to go on to be delivered to
35892 its intended recipient. The router will not then claim to have dealt with the
35893 address, so it will be passed on to subsequent routers to be delivered in the
35895 .ecindex IIDsysfil1
35896 .ecindex IIDsysfil2
35897 .ecindex IIDsysfil3
35904 . ////////////////////////////////////////////////////////////////////////////
35905 . ////////////////////////////////////////////////////////////////////////////
35907 .chapter "Message processing" "CHAPmsgproc"
35908 .scindex IIDmesproc "message" "general processing"
35909 Exim performs various transformations on the sender and recipient addresses of
35910 all messages that it handles, and also on the messages' header lines. Some of
35911 these are optional and configurable, while others always take place. All of
35912 this processing, except rewriting as a result of routing, and the addition or
35913 removal of header lines while delivering, happens when a message is received,
35914 before it is placed on Exim's queue.
35916 Some of the automatic processing takes place by default only for
35917 &"locally-originated"& messages. This adjective is used to describe messages
35918 that are not received over TCP/IP, but instead are passed to an Exim process on
35919 its standard input. This includes the interactive &"local SMTP"& case that is
35920 set up by the &%-bs%& command line option.
35922 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
35923 or ::1) are not considered to be locally-originated. Exim does not treat the
35924 loopback interface specially in any way.
35926 If you want the loopback interface to be treated specially, you must ensure
35927 that there are appropriate entries in your ACLs.
35932 .section "Submission mode for non-local messages" "SECTsubmodnon"
35933 .cindex "message" "submission"
35934 .cindex "submission mode"
35935 Processing that happens automatically for locally-originated messages (unless
35936 &%suppress_local_fixups%& is set) can also be requested for messages that are
35937 received over TCP/IP. The term &"submission mode"& is used to describe this
35938 state. Submission mode is set by the modifier
35940 control = submission
35942 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
35943 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
35944 a local submission, and is normally used when the source of the message is
35945 known to be an MUA running on a client host (as opposed to an MTA). For
35946 example, to set submission mode for messages originating on the IPv4 loopback
35947 interface, you could include the following in the MAIL ACL:
35949 warn hosts = 127.0.0.1
35950 control = submission
35952 .cindex "&%sender_retain%& submission option"
35953 There are some options that can be used when setting submission mode. A slash
35954 is used to separate options. For example:
35956 control = submission/sender_retain
35958 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
35959 true and &%local_from_check%& false for the current incoming message. The first
35960 of these allows an existing &'Sender:'& header in the message to remain, and
35961 the second suppresses the check to ensure that &'From:'& matches the
35962 authenticated sender. With this setting, Exim still fixes up messages by adding
35963 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
35964 attempt to check sender authenticity in header lines.
35966 When &%sender_retain%& is not set, a submission mode setting may specify a
35967 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
35970 control = submission/domain=some.domain
35972 The domain may be empty. How this value is used is described in sections
35973 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
35974 that allows you to specify the user's full name for inclusion in a created
35975 &'Sender:'& or &'From:'& header line. For example:
35977 accept authenticated = *
35978 control = submission/domain=wonderland.example/\
35979 name=${lookup {$authenticated_id} \
35980 lsearch {/etc/exim/namelist}}
35982 Because the name may contain any characters, including slashes, the &%name%&
35983 option must be given last. The remainder of the string is used as the name. For
35984 the example above, if &_/etc/exim/namelist_& contains:
35986 bigegg: Humpty Dumpty
35988 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
35991 Sender: Humpty Dumpty <bigegg@wonderland.example>
35993 .cindex "return path" "in submission mode"
35994 By default, submission mode forces the return path to the same address as is
35995 used to create the &'Sender:'& header. However, if &%sender_retain%& is
35996 specified, the return path is also left unchanged.
35998 &*Note*&: The changes caused by submission mode take effect after the predata
35999 ACL. This means that any sender checks performed before the fix-ups use the
36000 untrusted sender address specified by the user, not the trusted sender address
36001 specified by submission mode. Although this might be slightly unexpected, it
36002 does mean that you can configure ACL checks to spot that a user is trying to
36003 spoof another's address.
36005 .section "Line endings" "SECTlineendings"
36006 .cindex "line endings"
36007 .cindex "carriage return"
36009 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36010 linefeed) is the line ending for messages transmitted over the Internet using
36011 SMTP over TCP/IP. However, within individual operating systems, different
36012 conventions are used. For example, Unix-like systems use just LF, but others
36013 use CRLF or just CR.
36015 Exim was designed for Unix-like systems, and internally, it stores messages
36016 using the system's convention of a single LF as a line terminator. When
36017 receiving a message, all line endings are translated to this standard format.
36018 Originally, it was thought that programs that passed messages directly to an
36019 MTA within an operating system would use that system's convention. Experience
36020 has shown that this is not the case; for example, there are Unix applications
36021 that use CRLF in this circumstance. For this reason, and for compatibility with
36022 other MTAs, the way Exim handles line endings for all messages is now as
36026 LF not preceded by CR is treated as a line ending.
36028 CR is treated as a line ending; if it is immediately followed by LF, the LF
36031 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36032 nor a local message in the state where a line containing only a dot is a
36035 If a bare CR is encountered within a header line, an extra space is added after
36036 the line terminator so as not to end the header line. The reasoning behind this
36037 is that bare CRs in header lines are most likely either to be mistakes, or
36038 people trying to play silly games.
36040 If the first header line received in a message ends with CRLF, a subsequent
36041 bare LF in a header line is treated in the same way as a bare CR in a header
36049 .section "Unqualified addresses" "SECID218"
36050 .cindex "unqualified addresses"
36051 .cindex "address" "qualification"
36052 By default, Exim expects every envelope address it receives from an external
36053 host to be fully qualified. Unqualified addresses cause negative responses to
36054 SMTP commands. However, because SMTP is used as a means of transporting
36055 messages from MUAs running on personal workstations, there is sometimes a
36056 requirement to accept unqualified addresses from specific hosts or IP networks.
36058 Exim has two options that separately control which hosts may send unqualified
36059 sender or recipient addresses in SMTP commands, namely
36060 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36061 cases, if an unqualified address is accepted, it is qualified by adding the
36062 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36064 .oindex "&%qualify_domain%&"
36065 .oindex "&%qualify_recipient%&"
36066 Unqualified addresses in header lines are automatically qualified for messages
36067 that are locally originated, unless the &%-bnq%& option is given on the command
36068 line. For messages received over SMTP, unqualified addresses in header lines
36069 are qualified only if unqualified addresses are permitted in SMTP commands. In
36070 other words, such qualification is also controlled by
36071 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36076 .section "The UUCP From line" "SECID219"
36077 .cindex "&""From""& line"
36078 .cindex "UUCP" "&""From""& line"
36079 .cindex "sender" "address"
36080 .oindex "&%uucp_from_pattern%&"
36081 .oindex "&%uucp_from_sender%&"
36082 .cindex "envelope from"
36083 .cindex "envelope sender"
36084 .cindex "Sendmail compatibility" "&""From""& line"
36085 Messages that have come from UUCP (and some other applications) often begin
36086 with a line containing the envelope sender and a timestamp, following the word
36087 &"From"&. Examples of two common formats are:
36089 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36090 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36092 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36093 Exim recognizes such lines at the start of messages that are submitted to it
36094 via the command line (that is, on the standard input). It does not recognize
36095 such lines in incoming SMTP messages, unless the sending host matches
36096 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36097 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36098 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36099 default value matches the two common cases shown above and puts the address
36100 that follows &"From"& into &$1$&.
36102 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36103 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36104 a trusted user, the message's sender address is constructed by expanding the
36105 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36106 then parsed as an RFC 2822 address. If there is no domain, the local part is
36107 qualified with &%qualify_domain%& unless it is the empty string. However, if
36108 the command line &%-f%& option is used, it overrides the &"From"& line.
36110 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36111 sender address is not changed. This is also the case for incoming SMTP messages
36112 that are permitted to contain &"From"& lines.
36114 Only one &"From"& line is recognized. If there is more than one, the second is
36115 treated as a data line that starts the body of the message, as it is not valid
36116 as a header line. This also happens if a &"From"& line is present in an
36117 incoming SMTP message from a source that is not permitted to send them.
36121 .section "Resent- header lines" "SECID220"
36123 RFC 2822 makes provision for sets of header lines starting with the string
36124 &`Resent-`& to be added to a message when it is resent by the original
36125 recipient to somebody else. These headers are &'Resent-Date:'&,
36126 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36127 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36130 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36131 processing of replies or other such automatic actions on messages.'&
36134 This leaves things a bit vague as far as other processing actions such as
36135 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36139 A &'Resent-From:'& line that just contains the login id of the submitting user
36140 is automatically rewritten in the same way as &'From:'& (see below).
36142 If there's a rewriting rule for a particular header line, it is also applied to
36143 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36144 &'From:'& also rewrites &'Resent-From:'&.
36146 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36149 For a locally-submitted message,
36150 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36151 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36152 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36153 included in log lines in this case.
36155 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36156 &%Resent-%& header lines are present.
36162 .section "The Auto-Submitted: header line" "SECID221"
36163 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36164 includes the header line:
36166 Auto-Submitted: auto-replied
36169 .section "The Bcc: header line" "SECID222"
36170 .cindex "&'Bcc:'& header line"
36171 If Exim is called with the &%-t%& option, to take recipient addresses from a
36172 message's header, it removes any &'Bcc:'& header line that may exist (after
36173 extracting its addresses). If &%-t%& is not present on the command line, any
36174 existing &'Bcc:'& is not removed.
36177 .section "The Date: header line" "SECID223"
36179 If a locally-generated or submission-mode message has no &'Date:'& header line,
36180 Exim adds one, using the current date and time, unless the
36181 &%suppress_local_fixups%& control has been specified.
36183 .section "The Delivery-date: header line" "SECID224"
36184 .cindex "&'Delivery-date:'& header line"
36185 .oindex "&%delivery_date_remove%&"
36186 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36187 set. Exim can be configured to add them to the final delivery of messages. (See
36188 the generic &%delivery_date_add%& transport option.) They should not be present
36189 in messages in transit. If the &%delivery_date_remove%& configuration option is
36190 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36194 .section "The Envelope-to: header line" "SECID225"
36195 .chindex Envelope-to:
36196 .oindex "&%envelope_to_remove%&"
36197 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36198 Exim can be configured to add them to the final delivery of messages. (See the
36199 generic &%envelope_to_add%& transport option.) They should not be present in
36200 messages in transit. If the &%envelope_to_remove%& configuration option is set
36201 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36205 .section "The From: header line" "SECTthefrohea"
36207 .cindex "Sendmail compatibility" "&""From""& line"
36208 .cindex "message" "submission"
36209 .cindex "submission mode"
36210 If a submission-mode message does not contain a &'From:'& header line, Exim
36211 adds one if either of the following conditions is true:
36214 The envelope sender address is not empty (that is, this is not a bounce
36215 message). The added header line copies the envelope sender address.
36217 .vindex "&$authenticated_id$&"
36218 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36220 .vindex "&$qualify_domain$&"
36221 If no domain is specified by the submission control, the local part is
36222 &$authenticated_id$& and the domain is &$qualify_domain$&.
36224 If a non-empty domain is specified by the submission control, the local
36225 part is &$authenticated_id$&, and the domain is the specified domain.
36227 If an empty domain is specified by the submission control,
36228 &$authenticated_id$& is assumed to be the complete address.
36232 A non-empty envelope sender takes precedence.
36234 If a locally-generated incoming message does not contain a &'From:'& header
36235 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36236 containing the sender's address. The calling user's login name and full name
36237 are used to construct the address, as described in section &<<SECTconstr>>&.
36238 They are obtained from the password data by calling &[getpwuid()]& (but see the
36239 &%unknown_login%& configuration option). The address is qualified with
36240 &%qualify_domain%&.
36242 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36243 &'From:'& header line containing just the unqualified login name of the calling
36244 user, this is replaced by an address containing the user's login name and full
36245 name as described in section &<<SECTconstr>>&.
36248 .section "The Message-ID: header line" "SECID226"
36249 .chindex Message-ID:
36250 .cindex "message" "submission"
36251 .oindex "&%message_id_header_text%&"
36252 If a locally-generated or submission-mode incoming message does not contain a
36253 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36254 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36255 to the message. If there are any &'Resent-:'& headers in the message, it
36256 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36257 message id, preceded by the letter E to ensure it starts with a letter, and
36258 followed by @ and the primary host name. Additional information can be included
36259 in this header line by setting the &%message_id_header_text%& and/or
36260 &%message_id_header_domain%& options.
36263 .section "The Received: header line" "SECID227"
36265 A &'Received:'& header line is added at the start of every message. The
36266 contents are defined by the &%received_header_text%& configuration option, and
36267 Exim automatically adds a semicolon and a timestamp to the configured string.
36269 The &'Received:'& header is generated as soon as the message's header lines
36270 have been received. At this stage, the timestamp in the &'Received:'& header
36271 line is the time that the message started to be received. This is the value
36272 that is seen by the DATA ACL and by the &[local_scan()]& function.
36274 Once a message is accepted, the timestamp in the &'Received:'& header line is
36275 changed to the time of acceptance, which is (apart from a small delay while the
36276 -H spool file is written) the earliest time at which delivery could start.
36279 .section "The References: header line" "SECID228"
36280 .chindex References:
36281 Messages created by the &(autoreply)& transport include a &'References:'&
36282 header line. This is constructed according to the rules that are described in
36283 section 3.64 of RFC 2822 (which states that replies should contain such a
36284 header line), and section 3.14 of RFC 3834 (which states that automatic
36285 responses are not different in this respect). However, because some mail
36286 processing software does not cope well with very long header lines, no more
36287 than 12 message IDs are copied from the &'References:'& header line in the
36288 incoming message. If there are more than 12, the first one and then the final
36289 11 are copied, before adding the message ID of the incoming message.
36293 .section "The Return-path: header line" "SECID229"
36294 .chindex Return-path:
36295 .oindex "&%return_path_remove%&"
36296 &'Return-path:'& header lines are defined as something an MTA may insert when
36297 it does the final delivery of messages. (See the generic &%return_path_add%&
36298 transport option.) Therefore, they should not be present in messages in
36299 transit. If the &%return_path_remove%& configuration option is set (the
36300 default), Exim removes &'Return-path:'& header lines from incoming messages.
36304 .section "The Sender: header line" "SECTthesenhea"
36305 .cindex "&'Sender:'& header line"
36306 .cindex "message" "submission"
36308 For a locally-originated message from an untrusted user, Exim may remove an
36309 existing &'Sender:'& header line, and it may add a new one. You can modify
36310 these actions by setting the &%local_sender_retain%& option true, the
36311 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36314 When a local message is received from an untrusted user and
36315 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36316 control has not been set, a check is made to see if the address given in the
36317 &'From:'& header line is the correct (local) sender of the message. The address
36318 that is expected has the login name as the local part and the value of
36319 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36320 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36321 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36322 line is added to the message.
36324 If you set &%local_from_check%& false, this checking does not occur. However,
36325 the removal of an existing &'Sender:'& line still happens, unless you also set
36326 &%local_sender_retain%& to be true. It is not possible to set both of these
36327 options true at the same time.
36329 .cindex "submission mode"
36330 By default, no processing of &'Sender:'& header lines is done for messages
36331 received over TCP/IP or for messages submitted by trusted users. However, when
36332 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36333 not specified on the submission control, the following processing takes place:
36335 .vindex "&$authenticated_id$&"
36336 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36337 authenticated, and &$authenticated_id$& is not empty, a sender address is
36338 created as follows:
36341 .vindex "&$qualify_domain$&"
36342 If no domain is specified by the submission control, the local part is
36343 &$authenticated_id$& and the domain is &$qualify_domain$&.
36345 If a non-empty domain is specified by the submission control, the local part
36346 is &$authenticated_id$&, and the domain is the specified domain.
36348 If an empty domain is specified by the submission control,
36349 &$authenticated_id$& is assumed to be the complete address.
36352 This address is compared with the address in the &'From:'& header line. If they
36353 are different, a &'Sender:'& header line containing the created address is
36354 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36355 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36357 .cindex "return path" "created from &'Sender:'&"
36358 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36359 the message (the envelope sender address) is changed to be the same address,
36360 except in the case of submission mode when &%sender_retain%& is specified.
36364 .section "Adding and removing header lines in routers and transports" &&&
36365 "SECTheadersaddrem"
36366 .cindex "header lines" "adding; in router or transport"
36367 .cindex "header lines" "removing; in router or transport"
36368 When a message is delivered, the addition and removal of header lines can be
36369 specified in a system filter, or on any of the routers and transports that
36370 process the message. Section &<<SECTaddremheasys>>& contains details about
36371 modifying headers in a system filter. Header lines can also be added in an ACL
36372 as a message is received (see section &<<SECTaddheadacl>>&).
36374 In contrast to what happens in a system filter, header modifications that are
36375 specified on routers and transports apply only to the particular recipient
36376 addresses that are being processed by those routers and transports. These
36377 changes do not actually take place until a copy of the message is being
36378 transported. Therefore, they do not affect the basic set of header lines, and
36379 they do not affect the values of the variables that refer to header lines.
36381 &*Note*&: In particular, this means that any expansions in the configuration of
36382 the transport cannot refer to the modified header lines, because such
36383 expansions all occur before the message is actually transported.
36385 For both routers and transports, the argument of a &%headers_add%&
36386 option must be in the form of one or more RFC 2822 header lines, separated by
36387 newlines (coded as &"\n"&). For example:
36389 headers_add = X-added-header: added by $primary_hostname\n\
36390 X-added-second: another added header line
36392 Exim does not check the syntax of these added header lines.
36394 Multiple &%headers_add%& options for a single router or transport can be
36395 specified; the values will append to a single list of header lines.
36396 Each header-line is separately expanded.
36398 The argument of a &%headers_remove%& option must consist of a colon-separated
36399 list of header names. This is confusing, because header names themselves are
36400 often terminated by colons. In this case, the colons are the list separators,
36401 not part of the names. For example:
36403 headers_remove = return-receipt-to:acknowledge-to
36406 Multiple &%headers_remove%& options for a single router or transport can be
36407 specified; the arguments will append to a single header-names list.
36408 Each item is separately expanded.
36409 Note that colons in complex expansions which are used to
36410 form all or part of a &%headers_remove%& list
36411 will act as list separators.
36413 When &%headers_add%& or &%headers_remove%& is specified on a router,
36414 items are expanded at routing time,
36415 and then associated with all addresses that are
36416 accepted by that router, and also with any new addresses that it generates. If
36417 an address passes through several routers as a result of aliasing or
36418 forwarding, the changes are cumulative.
36420 .oindex "&%unseen%&"
36421 However, this does not apply to multiple routers that result from the use of
36422 the &%unseen%& option. Any header modifications that were specified by the
36423 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36425 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36426 settings cannot be delivered together in a batch, so a transport is always
36427 dealing with a set of addresses that have the same header-processing
36430 The transport starts by writing the original set of header lines that arrived
36431 with the message, possibly modified by the system filter. As it writes out
36432 these lines, it consults the list of header names that were attached to the
36433 recipient address(es) by &%headers_remove%& options in routers, and it also
36434 consults the transport's own &%headers_remove%& option. Header lines whose
36435 names are on either of these lists are not written out. If there are multiple
36436 instances of any listed header, they are all skipped.
36438 After the remaining original header lines have been written, new header
36439 lines that were specified by routers' &%headers_add%& options are written, in
36440 the order in which they were attached to the address. These are followed by any
36441 header lines specified by the transport's &%headers_add%& option.
36443 This way of handling header line modifications in routers and transports has
36444 the following consequences:
36447 The original set of header lines, possibly modified by the system filter,
36448 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36449 to it, at all times.
36451 Header lines that are added by a router's
36452 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36453 expansion syntax in subsequent routers or the transport.
36455 Conversely, header lines that are specified for removal by &%headers_remove%&
36456 in a router remain visible to subsequent routers and the transport.
36458 Headers added to an address by &%headers_add%& in a router cannot be removed by
36459 a later router or by a transport.
36461 An added header can refer to the contents of an original header that is to be
36462 removed, even it has the same name as the added header. For example:
36464 headers_remove = subject
36465 headers_add = Subject: new subject (was: $h_subject:)
36469 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36470 for a &(redirect)& router that has the &%one_time%& option set.
36476 .section "Constructed addresses" "SECTconstr"
36477 .cindex "address" "constructed"
36478 .cindex "constructed address"
36479 When Exim constructs a sender address for a locally-generated message, it uses
36482 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36486 Zaphod Beeblebrox <zaphod@end.univ.example>
36488 The user name is obtained from the &%-F%& command line option if set, or
36489 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36490 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36491 ampersand character, this is replaced by the login name with the first letter
36492 upper cased, as is conventional in a number of operating systems. See the
36493 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36494 The &%unknown_username%& option can be used to specify user names in cases when
36495 there is no password file entry.
36498 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36499 parts of it if necessary. In addition, if it contains any non-printing
36500 characters, it is encoded as described in RFC 2047, which defines a way of
36501 including non-ASCII characters in header lines. The value of the
36502 &%headers_charset%& option specifies the name of the encoding that is used (the
36503 characters are assumed to be in this encoding). The setting of
36504 &%print_topbitchars%& controls whether characters with the top bit set (that
36505 is, with codes greater than 127) count as printing characters or not.
36509 .section "Case of local parts" "SECID230"
36510 .cindex "case of local parts"
36511 .cindex "local part" "case of"
36512 RFC 2822 states that the case of letters in the local parts of addresses cannot
36513 be assumed to be non-significant. Exim preserves the case of local parts of
36514 addresses, but by default it uses a lower-cased form when it is routing,
36515 because on most Unix systems, usernames are in lower case and case-insensitive
36516 routing is required. However, any particular router can be made to use the
36517 original case for local parts by setting the &%caseful_local_part%& generic
36520 .cindex "mixed-case login names"
36521 If you must have mixed-case user names on your system, the best way to proceed,
36522 assuming you want case-independent handling of incoming email, is to set up
36523 your first router to convert incoming local parts in your domains to the
36524 correct case by means of a file lookup. For example:
36528 domains = +local_domains
36529 data = ${lookup{$local_part}cdb\
36530 {/etc/usercased.cdb}{$value}fail}\
36533 For this router, the local part is forced to lower case by the default action
36534 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36535 up a new local part in the correct case. If you then set &%caseful_local_part%&
36536 on any subsequent routers which process your domains, they will operate on
36537 local parts with the correct case in a case-sensitive manner.
36541 .section "Dots in local parts" "SECID231"
36542 .cindex "dot" "in local part"
36543 .cindex "local part" "dots in"
36544 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36545 part may not begin or end with a dot, nor have two consecutive dots in the
36546 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36547 empty components for compatibility.
36551 .section "Rewriting addresses" "SECID232"
36552 .cindex "rewriting" "addresses"
36553 Rewriting of sender and recipient addresses, and addresses in headers, can
36554 happen automatically, or as the result of configuration options, as described
36555 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36556 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36558 Automatic rewriting includes qualification, as mentioned above. The other case
36559 in which it can happen is when an incomplete non-local domain is given. The
36560 routing process may cause this to be expanded into the full domain name. For
36561 example, a header such as
36565 might get rewritten as
36567 To: hare@teaparty.wonderland.fict.example
36569 Rewriting as a result of routing is the one kind of message processing that
36570 does not happen at input time, as it cannot be done until the address has
36573 Strictly, one should not do &'any'& deliveries of a message until all its
36574 addresses have been routed, in case any of the headers get changed as a
36575 result of routing. However, doing this in practice would hold up many
36576 deliveries for unreasonable amounts of time, just because one address could not
36577 immediately be routed. Exim therefore does not delay other deliveries when
36578 routing of one or more addresses is deferred.
36579 .ecindex IIDmesproc
36583 . ////////////////////////////////////////////////////////////////////////////
36584 . ////////////////////////////////////////////////////////////////////////////
36586 .chapter "SMTP processing" "CHAPSMTP"
36587 .scindex IIDsmtpproc1 "SMTP" "processing details"
36588 .scindex IIDsmtpproc2 "LMTP" "processing details"
36589 Exim supports a number of different ways of using the SMTP protocol, and its
36590 LMTP variant, which is an interactive protocol for transferring messages into a
36591 closed mail store application. This chapter contains details of how SMTP is
36592 processed. For incoming mail, the following are available:
36595 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36597 SMTP over the standard input and output (the &%-bs%& option);
36599 Batched SMTP on the standard input (the &%-bS%& option).
36602 For mail delivery, the following are available:
36605 SMTP over TCP/IP (the &(smtp)& transport);
36607 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36610 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36613 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36614 the &%use_bsmtp%& option set).
36617 &'Batched SMTP'& is the name for a process in which batches of messages are
36618 stored in or read from files (or pipes), in a format in which SMTP commands are
36619 used to contain the envelope information.
36623 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36624 .cindex "SMTP" "outgoing over TCP/IP"
36625 .cindex "outgoing SMTP over TCP/IP"
36626 .cindex "LMTP" "over TCP/IP"
36627 .cindex "outgoing LMTP over TCP/IP"
36630 .cindex "SIZE" "option on MAIL command"
36631 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36632 The &%protocol%& option selects which protocol is to be used, but the actual
36633 processing is the same in both cases.
36635 .cindex "ESMTP extensions" SIZE
36636 If, in response to its EHLO command, Exim is told that the SIZE
36637 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36638 command. The value of <&'n'&> is the message size plus the value of the
36639 &%size_addition%& option (default 1024) to allow for additions to the message
36640 such as per-transport header lines, or changes made in a
36641 .cindex "transport" "filter"
36642 .cindex "filter" "transport filter"
36643 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36646 If the remote server advertises support for PIPELINING, Exim uses the
36647 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36648 required for the transaction.
36650 If the remote server advertises support for the STARTTLS command, and Exim
36651 was built to support TLS encryption, it tries to start a TLS session unless the
36652 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36653 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36654 is called for verification.
36656 If the remote server advertises support for the AUTH command, Exim scans
36657 the authenticators configuration for any suitable client settings, as described
36658 in chapter &<<CHAPSMTPAUTH>>&.
36660 .cindex "carriage return"
36662 Responses from the remote host are supposed to be terminated by CR followed by
36663 LF. However, there are known to be hosts that do not send CR characters, so in
36664 order to be able to interwork with such hosts, Exim treats LF on its own as a
36667 If a message contains a number of different addresses, all those with the same
36668 characteristics (for example, the same envelope sender) that resolve to the
36669 same set of hosts, in the same order, are sent in a single SMTP transaction,
36670 even if they are for different domains, unless there are more than the setting
36671 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36672 they are split into groups containing no more than &%max_rcpt%&s addresses
36673 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36674 in parallel sessions. The order of hosts with identical MX values is not
36675 significant when checking whether addresses can be batched in this way.
36677 When the &(smtp)& transport suffers a temporary failure that is not
36678 message-related, Exim updates its transport-specific database, which contains
36679 records indexed by host name that remember which messages are waiting for each
36680 particular host. It also updates the retry database with new retry times.
36682 .cindex "hints database" "retry keys"
36683 Exim's retry hints are based on host name plus IP address, so if one address of
36684 a multi-homed host is broken, it will soon be skipped most of the time.
36685 See the next section for more detail about error handling.
36687 .cindex "SMTP" "passed connection"
36688 .cindex "SMTP" "batching over TCP/IP"
36689 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36690 looks in the hints database for the transport to see if there are any queued
36691 messages waiting for the host to which it is connected. If it finds one, it
36692 creates a new Exim process using the &%-MC%& option (which can only be used by
36693 a process running as root or the Exim user) and passes the TCP/IP socket to it
36694 so that it can deliver another message using the same socket. The new process
36695 does only those deliveries that are routed to the connected host, and may in
36696 turn pass the socket on to a third process, and so on.
36698 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36699 limit the number of messages sent down a single TCP/IP connection.
36701 .cindex "asterisk" "after IP address"
36702 The second and subsequent messages delivered down an existing connection are
36703 identified in the main log by the addition of an asterisk after the closing
36704 square bracket of the IP address.
36709 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36710 .cindex "error" "in outgoing SMTP"
36711 .cindex "SMTP" "errors in outgoing"
36712 .cindex "host" "error"
36713 Three different kinds of error are recognized for outgoing SMTP: host errors,
36714 message errors, and recipient errors.
36717 .vitem "&*Host errors*&"
36718 A host error is not associated with a particular message or with a
36719 particular recipient of a message. The host errors are:
36722 Connection refused or timed out,
36724 Any error response code on connection,
36726 Any error response code to EHLO or HELO,
36728 Loss of connection at any time, except after &"."&,
36730 I/O errors at any time,
36732 Timeouts during the session, other than in response to MAIL, RCPT or
36733 the &"."& at the end of the data.
36736 For a host error, a permanent error response on connection, or in response to
36737 EHLO, causes all addresses routed to the host to be failed. Any other host
36738 error causes all addresses to be deferred, and retry data to be created for the
36739 host. It is not tried again, for any message, until its retry time arrives. If
36740 the current set of addresses are not all delivered in this run (to some
36741 alternative host), the message is added to the list of those waiting for this
36742 host, so if it is still undelivered when a subsequent successful delivery is
36743 made to the host, it will be sent down the same SMTP connection.
36745 .vitem "&*Message errors*&"
36746 .cindex "message" "error"
36747 A message error is associated with a particular message when sent to a
36748 particular host, but not with a particular recipient of the message. The
36749 message errors are:
36752 Any error response code to MAIL, DATA, or the &"."& that terminates
36755 Timeout after MAIL,
36757 Timeout or loss of connection after the &"."& that terminates the data. A
36758 timeout after the DATA command itself is treated as a host error, as is loss of
36759 connection at any other time.
36762 For a message error, a permanent error response (5&'xx'&) causes all addresses
36763 to be failed, and a delivery error report to be returned to the sender. A
36764 temporary error response (4&'xx'&), or one of the timeouts, causes all
36765 addresses to be deferred. Retry data is not created for the host, but instead,
36766 a retry record for the combination of host plus message id is created. The
36767 message is not added to the list of those waiting for this host. This ensures
36768 that the failing message will not be sent to this host again until the retry
36769 time arrives. However, other messages that are routed to the host are not
36770 affected, so if it is some property of the message that is causing the error,
36771 it will not stop the delivery of other mail.
36773 If the remote host specified support for the SIZE parameter in its response
36774 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36775 over-large message will cause a message error because the error arrives as a
36778 .vitem "&*Recipient errors*&"
36779 .cindex "recipient" "error"
36780 A recipient error is associated with a particular recipient of a message. The
36781 recipient errors are:
36784 Any error response to RCPT,
36786 Timeout after RCPT.
36789 For a recipient error, a permanent error response (5&'xx'&) causes the
36790 recipient address to be failed, and a bounce message to be returned to the
36791 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36792 address to be deferred, and routing retry data to be created for it. This is
36793 used to delay processing of the address in subsequent queue runs, until its
36794 routing retry time arrives. This applies to all messages, but because it
36795 operates only in queue runs, one attempt will be made to deliver a new message
36796 to the failing address before the delay starts to operate. This ensures that,
36797 if the failure is really related to the message rather than the recipient
36798 (&"message too big for this recipient"& is a possible example), other messages
36799 have a chance of getting delivered. If a delivery to the address does succeed,
36800 the retry information gets cleared, so all stuck messages get tried again, and
36801 the retry clock is reset.
36803 The message is not added to the list of those waiting for this host. Use of the
36804 host for other messages is unaffected, and except in the case of a timeout,
36805 other recipients are processed independently, and may be successfully delivered
36806 in the current SMTP session. After a timeout it is of course impossible to
36807 proceed with the session, so all addresses get deferred. However, those other
36808 than the one that failed do not suffer any subsequent retry delays. Therefore,
36809 if one recipient is causing trouble, the others have a chance of getting
36810 through when a subsequent delivery attempt occurs before the failing
36811 recipient's retry time.
36814 In all cases, if there are other hosts (or IP addresses) available for the
36815 current set of addresses (for example, from multiple MX records), they are
36816 tried in this run for any undelivered addresses, subject of course to their
36817 own retry data. In other words, recipient error retry data does not take effect
36818 until the next delivery attempt.
36820 Some hosts have been observed to give temporary error responses to every
36821 MAIL command at certain times (&"insufficient space"& has been seen). It
36822 would be nice if such circumstances could be recognized, and defer data for the
36823 host itself created, but this is not possible within the current Exim design.
36824 What actually happens is that retry data for every (host, message) combination
36827 The reason that timeouts after MAIL and RCPT are treated specially is that
36828 these can sometimes arise as a result of the remote host's verification
36829 procedures. Exim makes this assumption, and treats them as if a temporary error
36830 response had been received. A timeout after &"."& is treated specially because
36831 it is known that some broken implementations fail to recognize the end of the
36832 message if the last character of the last line is a binary zero. Thus, it is
36833 helpful to treat this case as a message error.
36835 Timeouts at other times are treated as host errors, assuming a problem with the
36836 host, or the connection to it. If a timeout after MAIL, RCPT,
36837 or &"."& is really a connection problem, the assumption is that at the next try
36838 the timeout is likely to occur at some other point in the dialogue, causing it
36839 then to be treated as a host error.
36841 There is experimental evidence that some MTAs drop the connection after the
36842 terminating &"."& if they do not like the contents of the message for some
36843 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
36844 should be given. That is why Exim treats this case as a message rather than a
36845 host error, in order not to delay other messages to the same host.
36850 .section "Incoming SMTP messages over TCP/IP" "SECID233"
36851 .cindex "SMTP" "incoming over TCP/IP"
36852 .cindex "incoming SMTP over TCP/IP"
36855 Incoming SMTP messages can be accepted in one of two ways: by running a
36856 listening daemon, or by using &'inetd'&. In the latter case, the entry in
36857 &_/etc/inetd.conf_& should be like this:
36859 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
36861 Exim distinguishes between this case and the case of a locally running user
36862 agent using the &%-bs%& option by checking whether or not the standard input is
36863 a socket. When it is, either the port must be privileged (less than 1024), or
36864 the caller must be root or the Exim user. If any other user passes a socket
36865 with an unprivileged port number, Exim prints a message on the standard error
36866 stream and exits with an error code.
36868 By default, Exim does not make a log entry when a remote host connects or
36869 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
36870 unexpected. It can be made to write such log entries by setting the
36871 &%smtp_connection%& log selector.
36873 .cindex "carriage return"
36875 Commands from the remote host are supposed to be terminated by CR followed by
36876 LF. However, there are known to be hosts that do not send CR characters. In
36877 order to be able to interwork with such hosts, Exim treats LF on its own as a
36879 Furthermore, because common code is used for receiving messages from all
36880 sources, a CR on its own is also interpreted as a line terminator. However, the
36881 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
36883 .cindex "EHLO" "invalid data"
36884 .cindex "HELO" "invalid data"
36885 One area that sometimes gives rise to problems concerns the EHLO or
36886 HELO commands. Some clients send syntactically invalid versions of these
36887 commands, which Exim rejects by default. (This is nothing to do with verifying
36888 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
36889 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
36890 match the broken hosts that send invalid commands.
36892 .cindex "SIZE option on MAIL command"
36893 .cindex "MAIL" "SIZE option"
36894 The amount of disk space available is checked whenever SIZE is received on
36895 a MAIL command, independently of whether &%message_size_limit%& or
36896 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
36897 false. A temporary error is given if there is not enough space. If
36898 &%check_spool_space%& is set, the check is for that amount of space plus the
36899 value given with SIZE, that is, it checks that the addition of the incoming
36900 message will not reduce the space below the threshold.
36902 When a message is successfully received, Exim includes the local message id in
36903 its response to the final &"."& that terminates the data. If the remote host
36904 logs this text it can help with tracing what has happened to a message.
36906 The Exim daemon can limit the number of simultaneous incoming connections it is
36907 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
36908 number of simultaneous incoming connections from a single remote host (see the
36909 &%smtp_accept_max_per_host%& option). Additional connection attempts are
36910 rejected using the SMTP temporary error code 421.
36912 The Exim daemon does not rely on the SIGCHLD signal to detect when a
36913 subprocess has finished, as this can get lost at busy times. Instead, it looks
36914 for completed subprocesses every time it wakes up. Provided there are other
36915 things happening (new incoming calls, starts of queue runs), completed
36916 processes will be noticed and tidied away. On very quiet systems you may
36917 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
36918 it will be noticed when the daemon next wakes up.
36920 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
36921 and can also be set up to reject SMTP calls from non-reserved hosts at times of
36922 high system load &-- for details see the &%smtp_accept_reserve%&,
36923 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
36924 applies in both the daemon and &'inetd'& cases.
36926 Exim normally starts a delivery process for each message received, though this
36927 can be varied by means of the &%-odq%& command line option and the
36928 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
36929 number of simultaneously running delivery processes started in this way from
36930 SMTP input can be limited by the &%smtp_accept_queue%& and
36931 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
36932 subsequently received messages are just put on the input queue without starting
36933 a delivery process.
36935 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
36936 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
36937 started up from the &'inetd'& daemon, because in that case each connection is
36938 handled by an entirely independent Exim process. Control by load average is,
36939 however, available with &'inetd'&.
36941 Exim can be configured to verify addresses in incoming SMTP commands as they
36942 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
36943 to rewrite addresses at this time &-- before any syntax checking is done. See
36944 section &<<SECTrewriteS>>&.
36946 Exim can also be configured to limit the rate at which a client host submits
36947 MAIL and RCPT commands in a single SMTP session. See the
36948 &%smtp_ratelimit_hosts%& option.
36952 .section "Unrecognized SMTP commands" "SECID234"
36953 .cindex "SMTP" "unrecognized commands"
36954 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
36955 commands during a single SMTP connection, it drops the connection after sending
36956 the error response to the last command. The default value for
36957 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
36958 abuse that subvert web servers into making connections to SMTP ports; in these
36959 circumstances, a number of non-SMTP lines are sent first.
36962 .section "Syntax and protocol errors in SMTP commands" "SECID235"
36963 .cindex "SMTP" "syntax errors"
36964 .cindex "SMTP" "protocol errors"
36965 A syntax error is detected if an SMTP command is recognized, but there is
36966 something syntactically wrong with its data, for example, a malformed email
36967 address in a RCPT command. Protocol errors include invalid command
36968 sequencing such as RCPT before MAIL. If Exim receives more than
36969 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
36970 drops the connection after sending the error response to the last command. The
36971 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
36972 broken clients that loop sending bad commands (yes, it has been seen).
36976 .section "Use of non-mail SMTP commands" "SECID236"
36977 .cindex "SMTP" "non-mail commands"
36978 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
36979 DATA. Exim counts such commands, and drops the connection if there are too
36980 many of them in a single SMTP session. This action catches some
36981 denial-of-service attempts and things like repeated failing AUTHs, or a mad
36982 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
36983 defines what &"too many"& means. Its default value is 10.
36985 When a new message is expected, one occurrence of RSET is not counted. This
36986 allows a client to send one RSET between messages (this is not necessary,
36987 but some clients do it). Exim also allows one uncounted occurrence of HELO
36988 or EHLO, and one occurrence of STARTTLS between messages. After
36989 starting up a TLS session, another EHLO is expected, and so it too is not
36992 The first occurrence of AUTH in a connection, or immediately following
36993 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
36994 RCPT, DATA, and QUIT are counted.
36996 You can control which hosts are subject to the limit set by
36997 &%smtp_accept_max_nonmail%& by setting
36998 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
36999 the limit apply to all hosts. This option means that you can exclude any
37000 specific badly-behaved hosts that you have to live with.
37005 .section "The VRFY and EXPN commands" "SECID237"
37006 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37007 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37008 appropriate) in order to decide whether the command should be accepted or not.
37010 .cindex "VRFY" "processing"
37011 When no ACL is defined for VRFY, or if it rejects without
37012 setting an explicit response code, the command is accepted
37013 (with a 252 SMTP response code)
37014 in order to support awkward clients that do a VRFY before every RCPT.
37015 When VRFY is accepted, it runs exactly the same code as when Exim is
37016 called with the &%-bv%& option, and returns 250/451/550
37017 SMTP response codes.
37019 .cindex "EXPN" "processing"
37020 If no ACL for EXPN is defined, the command is rejected.
37021 When EXPN is accepted, a single-level expansion of the address is done.
37022 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37023 than a verification (the &%-bv%& option). If an unqualified local part is given
37024 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37025 of VRFY and EXPN commands are logged on the main and reject logs, and
37026 VRFY verification failures are logged on the main log for consistency with
37031 .section "The ETRN command" "SECTETRN"
37032 .cindex "ETRN" "processing"
37033 .cindex "ESMTP extensions" ETRN
37034 RFC 1985 describes an ESMTP command called ETRN that is designed to
37035 overcome the security problems of the TURN command (which has fallen into
37036 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37037 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37038 should be accepted or not. If no ACL is defined, the command is rejected.
37040 The ETRN command is concerned with &"releasing"& messages that are awaiting
37041 delivery to certain hosts. As Exim does not organize its message queue by host,
37042 the only form of ETRN that is supported by default is the one where the
37043 text starts with the &"#"& prefix, in which case the remainder of the text is
37044 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37045 the &%-R%& option to happen, with the remainder of the ETRN text as its
37046 argument. For example,
37054 which causes a delivery attempt on all messages with undelivered addresses
37055 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37056 default), Exim prevents the simultaneous execution of more than one queue run
37057 for the same argument string as a result of an ETRN command. This stops
37058 a misbehaving client from starting more than one queue runner at once.
37060 .cindex "hints database" "ETRN serialization"
37061 Exim implements the serialization by means of a hints database in which a
37062 record is written whenever a process is started by ETRN, and deleted when
37063 the process completes. However, Exim does not keep the SMTP session waiting for
37064 the ETRN process to complete. Once ETRN is accepted, the client is sent
37065 a &"success"& return code. Obviously there is scope for hints records to get
37066 left lying around if there is a system or program crash. To guard against this,
37067 Exim ignores any records that are more than six hours old.
37069 .oindex "&%smtp_etrn_command%&"
37070 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37071 used. This specifies a command that is run whenever ETRN is received,
37072 whatever the form of its argument. For
37075 smtp_etrn_command = /etc/etrn_command $domain \
37076 $sender_host_address
37078 .vindex "&$domain$&"
37079 The string is split up into arguments which are independently expanded. The
37080 expansion variable &$domain$& is set to the argument of the ETRN command,
37081 and no syntax checking is done on the contents of this argument. Exim does not
37082 wait for the command to complete, so its status code is not checked. Exim runs
37083 under its own uid and gid when receiving incoming SMTP, so it is not possible
37084 for it to change them before running the command.
37088 .section "Incoming local SMTP" "SECID238"
37089 .cindex "SMTP" "local incoming"
37090 Some user agents use SMTP to pass messages to their local MTA using the
37091 standard input and output, as opposed to passing the envelope on the command
37092 line and writing the message to the standard input. This is supported by the
37093 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37094 messages over TCP/IP (including the use of ACLs), except that the envelope
37095 sender given in a MAIL command is ignored unless the caller is trusted. In
37096 an ACL you can detect this form of SMTP input by testing for an empty host
37097 identification. It is common to have this as the first line in the ACL that
37098 runs for RCPT commands:
37102 This accepts SMTP messages from local processes without doing any other tests.
37106 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37107 .cindex "SMTP" "batched outgoing"
37108 .cindex "batched SMTP output"
37109 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37110 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37111 be output in BSMTP format. No SMTP responses are possible for this form of
37112 delivery. All it is doing is using SMTP commands as a way of transmitting the
37113 envelope along with the message.
37115 The message is written to the file or pipe preceded by the SMTP commands
37116 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37117 the message that start with a dot have an extra dot added. The SMTP command
37118 HELO is not normally used. If it is required, the &%message_prefix%& option
37119 can be used to specify it.
37121 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37122 one recipient address at a time by default. However, you can arrange for them
37123 to handle several addresses at once by setting the &%batch_max%& option. When
37124 this is done for BSMTP, messages may contain multiple RCPT commands. See
37125 chapter &<<CHAPbatching>>& for more details.
37128 When one or more addresses are routed to a BSMTP transport by a router that
37129 sets up a host list, the name of the first host on the list is available to the
37130 transport in the variable &$host$&. Here is an example of such a transport and
37135 driver = manualroute
37136 transport = smtp_appendfile
37137 route_list = domain.example batch.host.example
37141 driver = appendfile
37142 directory = /var/bsmtp/$host
37147 This causes messages addressed to &'domain.example'& to be written in BSMTP
37148 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37149 message (unless there are more than 1000 recipients).
37153 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37154 .cindex "SMTP" "batched incoming"
37155 .cindex "batched SMTP input"
37156 The &%-bS%& command line option causes Exim to accept one or more messages by
37157 reading SMTP on the standard input, but to generate no responses. If the caller
37158 is trusted, the senders in the MAIL commands are believed; otherwise the
37159 sender is always the caller of Exim. Unqualified senders and receivers are not
37160 rejected (there seems little point) but instead just get qualified. HELO
37161 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37162 as NOOP; QUIT quits.
37164 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37165 ACL is run in the same way as for non-SMTP local input.
37167 If an error is detected while reading a message, including a missing &"."& at
37168 the end, Exim gives up immediately. It writes details of the error to the
37169 standard output in a stylized way that the calling program should be able to
37170 make some use of automatically, for example:
37172 554 Unexpected end of file
37173 Transaction started in line 10
37174 Error detected in line 14
37176 It writes a more verbose version, for human consumption, to the standard error
37179 An error was detected while processing a file of BSMTP input.
37180 The error message was:
37182 501 '>' missing at end of address
37184 The SMTP transaction started in line 10.
37185 The error was detected in line 12.
37186 The SMTP command at fault was:
37188 rcpt to:<malformed@in.com.plete
37190 1 previous message was successfully processed.
37191 The rest of the batch was abandoned.
37193 The return code from Exim is zero only if there were no errors. It is 1 if some
37194 messages were accepted before an error was detected, and 2 if no messages were
37196 .ecindex IIDsmtpproc1
37197 .ecindex IIDsmtpproc2
37201 . ////////////////////////////////////////////////////////////////////////////
37202 . ////////////////////////////////////////////////////////////////////////////
37204 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37205 "Customizing messages"
37206 When a message fails to be delivered, or remains in the queue for more than a
37207 configured amount of time, Exim sends a message to the original sender, or
37208 to an alternative configured address. The text of these messages is built into
37209 the code of Exim, but it is possible to change it, either by adding a single
37210 string, or by replacing each of the paragraphs by text supplied in a file.
37212 The &'From:'& and &'To:'& header lines are automatically generated; you can
37213 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37214 option. Exim also adds the line
37216 Auto-Submitted: auto-generated
37218 to all warning and bounce messages,
37221 .section "Customizing bounce messages" "SECID239"
37222 .cindex "customizing" "bounce message"
37223 .cindex "bounce message" "customizing"
37224 If &%bounce_message_text%& is set, its contents are included in the default
37225 message immediately after &"This message was created automatically by mail
37226 delivery software."& The string is not expanded. It is not used if
37227 &%bounce_message_file%& is set.
37229 When &%bounce_message_file%& is set, it must point to a template file for
37230 constructing error messages. The file consists of a series of text items,
37231 separated by lines consisting of exactly four asterisks. If the file cannot be
37232 opened, default text is used and a message is written to the main and panic
37233 logs. If any text item in the file is empty, default text is used for that
37236 .vindex "&$bounce_recipient$&"
37237 .vindex "&$bounce_return_size_limit$&"
37238 Each item of text that is read from the file is expanded, and there are two
37239 expansion variables which can be of use here: &$bounce_recipient$& is set to
37240 the recipient of an error message while it is being created, and
37241 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37242 option, rounded to a whole number.
37244 The items must appear in the file in the following order:
37247 The first item is included in the headers, and should include at least a
37248 &'Subject:'& header. Exim does not check the syntax of these headers.
37250 The second item forms the start of the error message. After it, Exim lists the
37251 failing addresses with their error messages.
37253 The third item is used to introduce any text from pipe transports that is to be
37254 returned to the sender. It is omitted if there is no such text.
37256 The fourth, fifth and sixth items will be ignored and may be empty.
37257 The fields exist for back-compatibility
37260 The default state (&%bounce_message_file%& unset) is equivalent to the
37261 following file, in which the sixth item is empty. The &'Subject:'& and some
37262 other lines have been split in order to fit them on the page:
37264 Subject: Mail delivery failed
37265 ${if eq{$sender_address}{$bounce_recipient}
37266 {: returning message to sender}}
37268 This message was created automatically by mail delivery software.
37270 A message ${if eq{$sender_address}{$bounce_recipient}
37271 {that you sent }{sent by
37275 }}could not be delivered to all of its recipients.
37276 This is a permanent error. The following address(es) failed:
37278 The following text was generated during the delivery attempt(s):
37280 ------ This is a copy of the message, including all the headers.
37283 ------ The body of the message is $message_size characters long;
37285 ------ $bounce_return_size_limit or so are included here.
37288 .section "Customizing warning messages" "SECTcustwarn"
37289 .cindex "customizing" "warning message"
37290 .cindex "warning of delay" "customizing the message"
37291 The option &%warn_message_file%& can be pointed at a template file for use when
37292 warnings about message delays are created. In this case there are only three
37296 The first item is included in the headers, and should include at least a
37297 &'Subject:'& header. Exim does not check the syntax of these headers.
37299 The second item forms the start of the warning message. After it, Exim lists
37300 the delayed addresses.
37302 The third item then ends the message.
37305 The default state is equivalent to the following file, except that some lines
37306 have been split here, in order to fit them on the page:
37308 Subject: Warning: message $message_exim_id delayed
37309 $warn_message_delay
37311 This message was created automatically by mail delivery software.
37313 A message ${if eq{$sender_address}{$warn_message_recipients}
37314 {that you sent }{sent by
37318 }}has not been delivered to all of its recipients after
37319 more than $warn_message_delay in the queue on $primary_hostname.
37321 The message identifier is: $message_exim_id
37322 The subject of the message is: $h_subject
37323 The date of the message is: $h_date
37325 The following address(es) have not yet been delivered:
37327 No action is required on your part. Delivery attempts will
37328 continue for some time, and this warning may be repeated at
37329 intervals if the message remains undelivered. Eventually the
37330 mail delivery software will give up, and when that happens,
37331 the message will be returned to you.
37333 .vindex "&$warn_message_delay$&"
37334 .vindex "&$warn_message_recipients$&"
37335 However, in the default state the subject and date lines are omitted if no
37336 appropriate headers exist. During the expansion of this file,
37337 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37338 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37339 of recipients for the warning message. There may be more than one if there are
37340 multiple addresses with different &%errors_to%& settings on the routers that
37346 . ////////////////////////////////////////////////////////////////////////////
37347 . ////////////////////////////////////////////////////////////////////////////
37349 .chapter "Some common configuration settings" "CHAPcomconreq"
37350 This chapter discusses some configuration settings that seem to be fairly
37351 common. More examples and discussion can be found in the Exim book.
37355 .section "Sending mail to a smart host" "SECID240"
37356 .cindex "smart host" "example router"
37357 If you want to send all mail for non-local domains to a &"smart host"&, you
37358 should replace the default &(dnslookup)& router with a router which does the
37359 routing explicitly:
37361 send_to_smart_host:
37362 driver = manualroute
37363 route_list = !+local_domains smart.host.name
37364 transport = remote_smtp
37366 You can use the smart host's IP address instead of the name if you wish.
37367 If you are using Exim only to submit messages to a smart host, and not for
37368 receiving incoming messages, you can arrange for it to do the submission
37369 synchronously by setting the &%mua_wrapper%& option (see chapter
37370 &<<CHAPnonqueueing>>&).
37375 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37376 .cindex "mailing lists"
37377 Exim can be used to run simple mailing lists, but for large and/or complicated
37378 requirements, the use of additional specialized mailing list software such as
37379 Majordomo or Mailman is recommended.
37381 The &(redirect)& router can be used to handle mailing lists where each list
37382 is maintained in a separate file, which can therefore be managed by an
37383 independent manager. The &%domains%& router option can be used to run these
37384 lists in a separate domain from normal mail. For example:
37388 domains = lists.example
37389 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37392 errors_to = ${quote_local_part:$local_part-request}@lists.example
37395 This router is skipped for domains other than &'lists.example'&. For addresses
37396 in that domain, it looks for a file that matches the local part. If there is no
37397 such file, the router declines, but because &%no_more%& is set, no subsequent
37398 routers are tried, and so the whole delivery fails.
37400 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37401 expanded into a filename or a pipe delivery, which is usually inappropriate in
37404 .oindex "&%errors_to%&"
37405 The &%errors_to%& option specifies that any delivery errors caused by addresses
37406 taken from a mailing list are to be sent to the given address rather than the
37407 original sender of the message. However, before acting on this, Exim verifies
37408 the error address, and ignores it if verification fails.
37410 For example, using the configuration above, mail sent to
37411 &'dicts@lists.example'& is passed on to those addresses contained in
37412 &_/usr/lists/dicts_&, with error reports directed to
37413 &'dicts-request@lists.example'&, provided that this address can be verified.
37414 There could be a file called &_/usr/lists/dicts-request_& containing
37415 the address(es) of this particular list's manager(s), but other approaches,
37416 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37417 or &%local_part_suffix%& options) to handle addresses of the form
37418 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37422 .section "Syntax errors in mailing lists" "SECID241"
37423 .cindex "mailing lists" "syntax errors in"
37424 If an entry in redirection data contains a syntax error, Exim normally defers
37425 delivery of the original address. That means that a syntax error in a mailing
37426 list holds up all deliveries to the list. This may not be appropriate when a
37427 list is being maintained automatically from data supplied by users, and the
37428 addresses are not rigorously checked.
37430 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37431 entries that fail to parse, noting the incident in the log. If in addition
37432 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37433 whenever a broken address is skipped. It is usually appropriate to set
37434 &%syntax_errors_to%& to the same address as &%errors_to%&.
37438 .section "Re-expansion of mailing lists" "SECID242"
37439 .cindex "mailing lists" "re-expansion of"
37440 Exim remembers every individual address to which a message has been delivered,
37441 in order to avoid duplication, but it normally stores only the original
37442 recipient addresses with a message. If all the deliveries to a mailing list
37443 cannot be done at the first attempt, the mailing list is re-expanded when the
37444 delivery is next tried. This means that alterations to the list are taken into
37445 account at each delivery attempt, so addresses that have been added to
37446 the list since the message arrived will therefore receive a copy of the
37447 message, even though it pre-dates their subscription.
37449 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37450 on the &(redirect)& router. If this is done, any addresses generated by the
37451 router that fail to deliver at the first attempt are added to the message as
37452 &"top level"& addresses, and the parent address that generated them is marked
37453 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37454 subsequent delivery attempts. The disadvantage of this is that if any of the
37455 failing addresses are incorrect, correcting them in the file has no effect on
37456 pre-existing messages.
37458 The original top-level address is remembered with each of the generated
37459 addresses, and is output in any log messages. However, any intermediate parent
37460 addresses are not recorded. This makes a difference to the log only if the
37461 &%all_parents%& selector is set, but for mailing lists there is normally only
37462 one level of expansion anyway.
37466 .section "Closed mailing lists" "SECID243"
37467 .cindex "mailing lists" "closed"
37468 The examples so far have assumed open mailing lists, to which anybody may
37469 send mail. It is also possible to set up closed lists, where mail is accepted
37470 from specified senders only. This is done by making use of the generic
37471 &%senders%& option to restrict the router that handles the list.
37473 The following example uses the same file as a list of recipients and as a list
37474 of permitted senders. It requires three routers:
37478 domains = lists.example
37479 local_part_suffix = -request
37480 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37481 file = /usr/lists/${local_part_data}-request
37486 domains = lists.example
37487 senders = ${if exists {/usr/lists/$local_part}\
37488 {lsearch;/usr/lists/$local_part}{*}}
37489 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37492 errors_to = ${quote_local_part:$local_part-request}@lists.example
37497 domains = lists.example
37499 data = :fail: $local_part@lists.example is a closed mailing list
37501 All three routers have the same &%domains%& setting, so for any other domains,
37502 they are all skipped. The first router runs only if the local part ends in
37503 &%-request%&. It handles messages to the list manager(s) by means of an open
37506 The second router runs only if the &%senders%& precondition is satisfied. It
37507 checks for the existence of a list that corresponds to the local part, and then
37508 checks that the sender is on the list by means of a linear search. It is
37509 necessary to check for the existence of the file before trying to search it,
37510 because otherwise Exim thinks there is a configuration error. If the file does
37511 not exist, the expansion of &%senders%& is *, which matches all senders. This
37512 means that the router runs, but because there is no list, declines, and
37513 &%no_more%& ensures that no further routers are run. The address fails with an
37514 &"unrouteable address"& error.
37516 The third router runs only if the second router is skipped, which happens when
37517 a mailing list exists, but the sender is not on it. This router forcibly fails
37518 the address, giving a suitable error message.
37523 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37525 .cindex "Variable Envelope Return Paths"
37526 .cindex "envelope from"
37527 .cindex "envelope sender"
37528 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37529 are a way of helping mailing list administrators discover which subscription
37530 address is the cause of a particular delivery failure. The idea is to encode
37531 the original recipient address in the outgoing envelope sender address, so that
37532 if the message is forwarded by another host and then subsequently bounces, the
37533 original recipient can be extracted from the recipient address of the bounce.
37535 .oindex &%errors_to%&
37536 .oindex &%return_path%&
37537 Envelope sender addresses can be modified by Exim using two different
37538 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37539 list examples), or the &%return_path%& option on a transport. The second of
37540 these is effective only if the message is successfully delivered to another
37541 host; it is not used for errors detected on the local host (see the description
37542 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37543 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37549 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37550 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37552 This has the effect of rewriting the return path (envelope sender) on outgoing
37553 SMTP messages, if the local part of the original return path ends in
37554 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37555 local part and domain of the recipient into the return path. Suppose, for
37556 example, that a message whose return path has been set to
37557 &'somelist-request@your.dom.example'& is sent to
37558 &'subscriber@other.dom.example'&. In the transport, the return path is
37561 somelist-request+subscriber=other.dom.example@your.dom.example
37563 .vindex "&$local_part$&"
37564 For this to work, you must tell Exim to send multiple copies of messages that
37565 have more than one recipient, so that each copy has just one recipient. This is
37566 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37567 might be sent to several different recipients in the same domain, in which case
37568 &$local_part$& is not available in the transport, because it is not unique.
37570 Unless your host is doing nothing but mailing list deliveries, you should
37571 probably use a separate transport for the VERP deliveries, so as not to use
37572 extra resources in making one-per-recipient copies for other deliveries. This
37573 can easily be done by expanding the &%transport%& option in the router:
37577 domains = ! +local_domains
37579 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37580 {verp_smtp}{remote_smtp}}
37583 If you want to change the return path using &%errors_to%& in a router instead
37584 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37585 routers that handle mailing list addresses. This will ensure that all delivery
37586 errors, including those detected on the local host, are sent to the VERP
37589 On a host that does no local deliveries and has no manual routing, only the
37590 &(dnslookup)& router needs to be changed. A special transport is not needed for
37591 SMTP deliveries. Every mailing list recipient has its own return path value,
37592 and so Exim must hand them to the transport one at a time. Here is an example
37593 of a &(dnslookup)& router that implements VERP:
37597 domains = ! +local_domains
37598 transport = remote_smtp
37600 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37601 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37604 Before you start sending out messages with VERPed return paths, you must also
37605 configure Exim to accept the bounce messages that come back to those paths.
37606 Typically this is done by setting a &%local_part_suffix%& option for a
37607 router, and using this to route the messages to wherever you want to handle
37610 The overhead incurred in using VERP depends very much on the size of the
37611 message, the number of recipient addresses that resolve to the same remote
37612 host, and the speed of the connection over which the message is being sent. If
37613 a lot of addresses resolve to the same host and the connection is slow, sending
37614 a separate copy of the message for each address may take substantially longer
37615 than sending a single copy with many recipients (for which VERP cannot be
37623 .section "Virtual domains" "SECTvirtualdomains"
37624 .cindex "virtual domains"
37625 .cindex "domain" "virtual"
37626 The phrase &'virtual domain'& is unfortunately used with two rather different
37630 A domain for which there are no real mailboxes; all valid local parts are
37631 aliases for other email addresses. Common examples are organizational
37632 top-level domains and &"vanity"& domains.
37634 One of a number of independent domains that are all handled by the same host,
37635 with mailboxes on that host, but where the mailbox owners do not necessarily
37636 have login accounts on that host.
37639 The first usage is probably more common, and does seem more &"virtual"& than
37640 the second. This kind of domain can be handled in Exim with a straightforward
37641 aliasing router. One approach is to create a separate alias file for each
37642 virtual domain. Exim can test for the existence of the alias file to determine
37643 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37644 to a router of this form:
37648 domains = dsearch;/etc/mail/virtual
37649 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37652 The &%domains%& option specifies that the router is to be skipped, unless there
37653 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37654 domain that is being processed.
37655 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37656 being placed into the &$domain_data$& variable.
37658 When the router runs, it looks up the local
37659 part in the file to find a new address (or list of addresses). The &%no_more%&
37660 setting ensures that if the lookup fails (leading to &%data%& being an empty
37661 string), Exim gives up on the address without trying any subsequent routers.
37663 This one router can handle all the virtual domains because the alias filenames
37664 follow a fixed pattern. Permissions can be arranged so that appropriate people
37665 can edit the different alias files. A successful aliasing operation results in
37666 a new envelope recipient address, which is then routed from scratch.
37668 The other kind of &"virtual"& domain can also be handled in a straightforward
37669 way. One approach is to create a file for each domain containing a list of
37670 valid local parts, and use it in a router like this:
37674 domains = dsearch;/etc/mail/domains
37675 local_parts = lsearch;/etc/mail/domains/$domain
37676 transport = my_mailboxes
37678 The address is accepted if there is a file for the domain, and the local part
37679 can be found in the file. The &%domains%& option is used to check for the
37680 file's existence because &%domains%& is tested before the &%local_parts%&
37681 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37682 because that option is tested after &%local_parts%&. The transport is as
37686 driver = appendfile
37687 file = /var/mail/$domain_data/$local_part_data
37690 This uses a directory of mailboxes for each domain. The &%user%& setting is
37691 required, to specify which uid is to be used for writing to the mailboxes.
37693 The configuration shown here is just one example of how you might support this
37694 requirement. There are many other ways this kind of configuration can be set
37695 up, for example, by using a database instead of separate files to hold all the
37696 information about the domains.
37700 .section "Multiple user mailboxes" "SECTmulbox"
37701 .cindex "multiple mailboxes"
37702 .cindex "mailbox" "multiple"
37703 .cindex "local part" "prefix"
37704 .cindex "local part" "suffix"
37705 Heavy email users often want to operate with multiple mailboxes, into which
37706 incoming mail is automatically sorted. A popular way of handling this is to
37707 allow users to use multiple sender addresses, so that replies can easily be
37708 identified. Users are permitted to add prefixes or suffixes to their local
37709 parts for this purpose. The wildcard facility of the generic router options
37710 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37711 example, consider this router:
37716 file = $home/.forward
37717 local_part_suffix = -*
37718 local_part_suffix_optional
37721 .vindex "&$local_part_suffix$&"
37722 It runs a user's &_.forward_& file for all local parts of the form
37723 &'username-*'&. Within the filter file the user can distinguish different
37724 cases by testing the variable &$local_part_suffix$&. For example:
37726 if $local_part_suffix contains -special then
37727 save /home/$local_part_data/Mail/special
37730 If the filter file does not exist, or does not deal with such addresses, they
37731 fall through to subsequent routers, and, assuming no subsequent use of the
37732 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37733 control over which suffixes are valid.
37735 Alternatively, a suffix can be used to trigger the use of a different
37736 &_.forward_& file &-- which is the way a similar facility is implemented in
37742 local_part_suffix = -*
37743 local_part_suffix_optional
37744 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37747 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37748 example, &_.forward-special_& is used. Once again, if the appropriate file
37749 does not exist, or does not deal with the address, it is passed on to
37750 subsequent routers, which could, if required, look for an unqualified
37751 &_.forward_& file to use as a default.
37755 .section "Simplified vacation processing" "SECID244"
37756 .cindex "vacation processing"
37757 The traditional way of running the &'vacation'& program is for a user to set up
37758 a pipe command in a &_.forward_& file
37759 (see section &<<SECTspecitredli>>& for syntax details).
37760 This is prone to error by inexperienced users. There are two features of Exim
37761 that can be used to make this process simpler for users:
37764 A local part prefix such as &"vacation-"& can be specified on a router which
37765 can cause the message to be delivered directly to the &'vacation'& program, or
37766 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37767 &_.forward_& file are then much simpler. For example:
37769 spqr, vacation-spqr
37772 The &%require_files%& generic router option can be used to trigger a
37773 vacation delivery by checking for the existence of a certain file in the
37774 user's home directory. The &%unseen%& generic option should also be used, to
37775 ensure that the original delivery also proceeds. In this case, all the user has
37776 to do is to create a file called, say, &_.vacation_&, containing a vacation
37780 Another advantage of both these methods is that they both work even when the
37781 use of arbitrary pipes by users is locked out.
37785 .section "Taking copies of mail" "SECID245"
37786 .cindex "message" "copying every"
37787 Some installations have policies that require archive copies of all messages to
37788 be made. A single copy of each message can easily be taken by an appropriate
37789 command in a system filter, which could, for example, use a different file for
37790 each day's messages.
37792 There is also a shadow transport mechanism that can be used to take copies of
37793 messages that are successfully delivered by local transports, one copy per
37794 delivery. This could be used, &'inter alia'&, to implement automatic
37795 notification of delivery by sites that insist on doing such things.
37799 .section "Intermittently connected hosts" "SECID246"
37800 .cindex "intermittently connected hosts"
37801 It has become quite common (because it is cheaper) for hosts to connect to the
37802 Internet periodically rather than remain connected all the time. The normal
37803 arrangement is that mail for such hosts accumulates on a system that is
37804 permanently connected.
37806 Exim was designed for use on permanently connected hosts, and so it is not
37807 particularly well-suited to use in an intermittently connected environment.
37808 Nevertheless there are some features that can be used.
37811 .section "Exim on the upstream server host" "SECID247"
37812 It is tempting to arrange for incoming mail for the intermittently connected
37813 host to remain in Exim's queue until the client connects. However, this
37814 approach does not scale very well. Two different kinds of waiting message are
37815 being mixed up in the same queue &-- those that cannot be delivered because of
37816 some temporary problem, and those that are waiting for their destination host
37817 to connect. This makes it hard to manage the queue, as well as wasting
37818 resources, because each queue runner scans the entire queue.
37820 A better approach is to separate off those messages that are waiting for an
37821 intermittently connected host. This can be done by delivering these messages
37822 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
37823 format, from where they are transmitted by other software when their
37824 destination connects. This makes it easy to collect all the mail for one host
37825 in a single directory, and to apply local timeout rules on a per-message basis
37828 On a very small scale, leaving the mail on Exim's queue can be made to work. If
37829 you are doing this, you should configure Exim with a long retry period for the
37830 intermittent host. For example:
37832 cheshire.wonderland.fict.example * F,5d,24h
37834 This stops a lot of failed delivery attempts from occurring, but Exim remembers
37835 which messages it has queued up for that host. Once the intermittent host comes
37836 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
37837 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
37838 causes all the queued up messages to be delivered, often down a single SMTP
37839 connection. While the host remains connected, any new messages get delivered
37842 If the connecting hosts do not have fixed IP addresses, that is, if a host is
37843 issued with a different IP address each time it connects, Exim's retry
37844 mechanisms on the holding host get confused, because the IP address is normally
37845 used as part of the key string for holding retry information. This can be
37846 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
37847 Since this has disadvantages for permanently connected hosts, it is best to
37848 arrange a separate transport for the intermittently connected ones.
37852 .section "Exim on the intermittently connected client host" "SECID248"
37853 The value of &%smtp_accept_queue_per_connection%& should probably be
37854 increased, or even set to zero (that is, disabled) on the intermittently
37855 connected host, so that all incoming messages down a single connection get
37856 delivered immediately.
37858 .cindex "SMTP" "passed connection"
37859 .cindex "SMTP" "multiple deliveries"
37860 .cindex "multiple SMTP deliveries"
37861 .cindex "first pass routing"
37862 Mail waiting to be sent from an intermittently connected host will probably
37863 not have been routed, because without a connection DNS lookups are not
37864 possible. This means that if a normal queue run is done at connection time,
37865 each message is likely to be sent in a separate SMTP session. This can be
37866 avoided by starting the queue run with a command line option beginning with
37867 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
37868 first pass, routing is done but no deliveries take place. The second pass is a
37869 normal queue run; since all the messages have been previously routed, those
37870 destined for the same host are likely to get sent as multiple deliveries in a
37871 single SMTP connection.
37875 . ////////////////////////////////////////////////////////////////////////////
37876 . ////////////////////////////////////////////////////////////////////////////
37878 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
37879 "Exim as a non-queueing client"
37880 .cindex "client, non-queueing"
37881 .cindex "smart host" "suppressing queueing"
37882 On a personal computer, it is a common requirement for all
37883 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
37884 configured to operate that way, for all the popular operating systems.
37885 However, there are some MUAs for Unix-like systems that cannot be so
37886 configured: they submit messages using the command line interface of
37887 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
37890 If the personal computer runs continuously, there is no problem, because it can
37891 run a conventional MTA that handles delivery to the smart host, and deal with
37892 any delays via its queueing mechanism. However, if the computer does not run
37893 continuously or runs different operating systems at different times, queueing
37894 email is not desirable.
37896 There is therefore a requirement for something that can provide the
37897 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
37898 any queueing or retrying facilities. Furthermore, the delivery to the smart
37899 host should be synchronous, so that if it fails, the sending MUA is immediately
37900 informed. In other words, we want something that extends an MUA that submits
37901 to a local MTA via the command line so that it behaves like one that submits
37902 to a remote smart host using TCP/SMTP.
37904 There are a number of applications (for example, there is one called &'ssmtp'&)
37905 that do this job. However, people have found them to be lacking in various
37906 ways. For instance, you might want to allow aliasing and forwarding to be done
37907 before sending a message to the smart host.
37909 Exim already had the necessary infrastructure for doing this job. Just a few
37910 tweaks were needed to make it behave as required, though it is somewhat of an
37911 overkill to use a fully-featured MTA for this purpose.
37913 .oindex "&%mua_wrapper%&"
37914 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
37915 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
37916 assumes that it is being used to &"wrap"& a command-line MUA in the manner
37917 just described. As well as setting &%mua_wrapper%&, you also need to provide a
37918 compatible router and transport configuration. Typically there will be just one
37919 router and one transport, sending everything to a smart host.
37921 When run in MUA wrapping mode, the behaviour of Exim changes in the
37925 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
37926 In other words, the only way to submit messages is via the command line.
37928 Each message is synchronously delivered as soon as it is received (&%-odi%& is
37929 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
37930 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
37931 does not finish until the delivery attempt is complete. If the delivery is
37932 successful, a zero return code is given.
37934 Address redirection is permitted, but the final routing for all addresses must
37935 be to the same remote transport, and to the same list of hosts. Furthermore,
37936 the return address (envelope sender) must be the same for all recipients, as
37937 must any added or deleted header lines. In other words, it must be possible to
37938 deliver the message in a single SMTP transaction, however many recipients there
37941 If these conditions are not met, or if routing any address results in a
37942 failure or defer status, or if Exim is unable to deliver all the recipients
37943 successfully to one of the smart hosts, delivery of the entire message fails.
37945 Because no queueing is allowed, all failures are treated as permanent; there
37946 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
37947 smart host. Furthermore, because only a single yes/no response can be given to
37948 the caller, it is not possible to deliver to some recipients and not others. If
37949 there is an error (temporary or permanent) for any recipient, all are failed.
37951 If more than one smart host is listed, Exim will try another host after a
37952 connection failure or a timeout, in the normal way. However, if this kind of
37953 failure happens for all the hosts, the delivery fails.
37955 When delivery fails, an error message is written to the standard error stream
37956 (as well as to Exim's log), and Exim exits to the caller with a return code
37957 value 1. The message is expunged from Exim's spool files. No bounce messages
37958 are ever generated.
37960 No retry data is maintained, and any retry rules are ignored.
37962 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
37963 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
37964 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
37967 The overall effect is that Exim makes a single synchronous attempt to deliver
37968 the message, failing if there is any kind of problem. Because no local
37969 deliveries are done and no daemon can be run, Exim does not need root
37970 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
37971 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
37972 the advantages and disadvantages of running without root privilege.
37977 . ////////////////////////////////////////////////////////////////////////////
37978 . ////////////////////////////////////////////////////////////////////////////
37980 .chapter "Log files" "CHAPlog"
37981 .scindex IIDloggen "log" "general description"
37982 .cindex "log" "types of"
37983 Exim writes three different logs, referred to as the main log, the reject log,
37988 The main log records the arrival of each message and each delivery in a single
37989 line in each case. The format is as compact as possible, in an attempt to keep
37990 down the size of log files. Two-character flag sequences make it easy to pick
37991 out these lines. A number of other events are recorded in the main log. Some of
37992 them are optional, in which case the &%log_selector%& option controls whether
37993 they are included or not. A Perl script called &'eximstats'&, which does simple
37994 analysis of main log files, is provided in the Exim distribution (see section
37995 &<<SECTmailstat>>&).
37997 .cindex "reject log"
37998 The reject log records information from messages that are rejected as a result
37999 of a configuration option (that is, for policy reasons).
38000 The first line of each rejection is a copy of the line that is also written to
38001 the main log. Then, if the message's header has been read at the time the log
38002 is written, its contents are written to this log. Only the original header
38003 lines are available; header lines added by ACLs are not logged. You can use the
38004 reject log to check that your policy controls are working correctly; on a busy
38005 host this may be easier than scanning the main log for rejection messages. You
38006 can suppress the writing of the reject log by setting &%write_rejectlog%&
38009 .cindex "panic log"
38010 .cindex "system log"
38011 When certain serious errors occur, Exim writes entries to its panic log. If the
38012 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38013 are usually written to the main log as well, but can get lost amid the mass of
38014 other entries. The panic log should be empty under normal circumstances. It is
38015 therefore a good idea to check it (or to have a &'cron'& script check it)
38016 regularly, in order to become aware of any problems. When Exim cannot open its
38017 panic log, it tries as a last resort to write to the system log (syslog). This
38018 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38019 message itself is written at priority LOG_CRIT.
38022 Every log line starts with a timestamp, in the format shown in the following
38023 example. Note that many of the examples shown in this chapter are line-wrapped.
38024 In the log file, this would be all on one line:
38026 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38029 By default, the timestamps are in the local timezone. There are two
38030 ways of changing this:
38033 You can set the &%timezone%& option to a different time zone; in particular, if
38038 the timestamps will be in UTC (aka GMT).
38040 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38043 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38047 .cindex "log" "process ids in"
38048 .cindex "pid (process id)" "in log lines"
38049 Exim does not include its process id in log lines by default, but you can
38050 request that it does so by specifying the &`pid`& log selector (see section
38051 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38052 brackets, immediately after the time and date.
38057 .section "Where the logs are written" "SECTwhelogwri"
38058 .cindex "log" "destination"
38059 .cindex "log" "to file"
38060 .cindex "log" "to syslog"
38062 The logs may be written to local files, or to syslog, or both. However, it
38063 should be noted that many syslog implementations use UDP as a transport, and
38064 are therefore unreliable in the sense that messages are not guaranteed to
38065 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38066 It has also been reported that on large log files (tens of megabytes) you may
38067 need to tweak syslog to prevent it syncing the file with each write &-- on
38068 Linux this has been seen to make syslog take 90% plus of CPU time.
38070 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38071 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38072 configuration. This latter string is expanded, so it can contain, for example,
38073 references to the host name:
38075 log_file_path = /var/log/$primary_hostname/exim_%slog
38077 It is generally advisable, however, to set the string in &_Local/Makefile_&
38078 rather than at runtime, because then the setting is available right from the
38079 start of Exim's execution. Otherwise, if there's something it wants to log
38080 before it has read the configuration file (for example, an error in the
38081 configuration file) it will not use the path you want, and may not be able to
38084 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38085 list, currently limited to at most two items. This is one option where the
38086 facility for changing a list separator may not be used. The list must always be
38087 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38088 otherwise the item must either be an absolute path, containing &`%s`& at the
38089 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38090 implying the use of a default path.
38092 When Exim encounters an empty item in the list, it searches the list defined by
38093 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38094 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38095 mean &"use the path specified at build time"&. It no such item exists, log
38096 files are written in the &_log_& subdirectory of the spool directory. This is
38097 equivalent to the setting:
38099 log_file_path = $spool_directory/log/%slog
38101 If you do not specify anything at build time or runtime,
38102 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38103 that is where the logs are written.
38105 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38106 are in use &-- see section &<<SECTdatlogfil>>& below.
38108 Here are some examples of possible settings:
38110 &`LOG_FILE_PATH=syslog `& syslog only
38111 &`LOG_FILE_PATH=:syslog `& syslog and default path
38112 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38113 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38115 If there are more than two paths in the list, the first is used and a panic
38120 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38121 .cindex "log" "cycling local files"
38122 .cindex "cycling logs"
38123 .cindex "&'exicyclog'&"
38124 .cindex "log" "local files; writing to"
38125 Some operating systems provide centralized and standardized methods for cycling
38126 log files. For those that do not, a utility script called &'exicyclog'& is
38127 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38128 main and reject logs each time it is called. The maximum number of old logs to
38129 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38131 An Exim delivery process opens the main log when it first needs to write to it,
38132 and it keeps the file open in case subsequent entries are required &-- for
38133 example, if a number of different deliveries are being done for the same
38134 message. However, remote SMTP deliveries can take a long time, and this means
38135 that the file may be kept open long after it is renamed if &'exicyclog'& or
38136 something similar is being used to rename log files on a regular basis. To
38137 ensure that a switch of log files is noticed as soon as possible, Exim calls
38138 &[stat()]& on the main log's name before reusing an open file, and if the file
38139 does not exist, or its inode has changed, the old file is closed and Exim
38140 tries to open the main log from scratch. Thus, an old log file may remain open
38141 for quite some time, but no Exim processes should write to it once it has been
38146 .section "Datestamped log files" "SECTdatlogfil"
38147 .cindex "log" "datestamped files"
38148 Instead of cycling the main and reject log files by renaming them
38149 periodically, some sites like to use files whose names contain a datestamp,
38150 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38151 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38152 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38153 point where the datestamp is required. For example:
38155 log_file_path = /var/spool/exim/log/%slog-%D
38156 log_file_path = /var/log/exim-%s-%D.log
38157 log_file_path = /var/spool/exim/log/%D-%slog
38158 log_file_path = /var/log/exim/%s.%M
38160 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38161 examples of names generated by the above examples:
38163 /var/spool/exim/log/mainlog-20021225
38164 /var/log/exim-reject-20021225.log
38165 /var/spool/exim/log/20021225-mainlog
38166 /var/log/exim/main.200212
38168 When this form of log file is specified, Exim automatically switches to new
38169 files at midnight. It does not make any attempt to compress old logs; you
38170 will need to write your own script if you require this. You should not
38171 run &'exicyclog'& with this form of logging.
38173 The location of the panic log is also determined by &%log_file_path%&, but it
38174 is not datestamped, because rotation of the panic log does not make sense.
38175 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38176 the string. In addition, if it immediately follows a slash, a following
38177 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38178 character is removed. Thus, the four examples above would give these panic
38181 /var/spool/exim/log/paniclog
38182 /var/log/exim-panic.log
38183 /var/spool/exim/log/paniclog
38184 /var/log/exim/panic
38188 .section "Logging to syslog" "SECID249"
38189 .cindex "log" "syslog; writing to"
38190 The use of syslog does not change what Exim logs or the format of its messages,
38191 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38192 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38193 that, the same strings are written to syslog as to log files. The syslog
38194 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38195 by default, but you can change these by setting the &%syslog_facility%& and
38196 &%syslog_processname%& options, respectively. If Exim was compiled with
38197 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38198 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38199 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38200 the time and host name to each line.
38201 The three log streams are mapped onto syslog priorities as follows:
38204 &'mainlog'& is mapped to LOG_INFO
38206 &'rejectlog'& is mapped to LOG_NOTICE
38208 &'paniclog'& is mapped to LOG_ALERT
38211 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38212 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38213 these are routed by syslog to the same place. You can suppress this duplication
38214 by setting &%syslog_duplication%& false.
38216 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38217 entries contain multiple lines when headers are included. To cope with both
38218 these cases, entries written to syslog are split into separate &[syslog()]&
38219 calls at each internal newline, and also after a maximum of
38220 870 data characters. (This allows for a total syslog line length of 1024, when
38221 additions such as timestamps are added.) If you are running a syslog
38222 replacement that can handle lines longer than the 1024 characters allowed by
38223 RFC 3164, you should set
38225 SYSLOG_LONG_LINES=yes
38227 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38228 lines, but it still splits at internal newlines in &'reject'& log entries.
38230 To make it easy to re-assemble split lines later, each component of a split
38231 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38232 where <&'n'&> is the component number and <&'m'&> is the total number of
38233 components in the entry. The / delimiter is used when the line was split
38234 because it was too long; if it was split because of an internal newline, the \
38235 delimiter is used. For example, supposing the length limit to be 50 instead of
38236 870, the following would be the result of a typical rejection message to
38237 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38238 name, and pid as added by syslog:
38240 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38241 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38242 [3/5] when scanning for sender: missing or malformed lo
38243 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38246 The same error might cause the following lines to be written to &"rejectlog"&
38249 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38250 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38251 [3/18] er when scanning for sender: missing or malformed
38252 [4/18] local part in "<>" (envelope sender is <ph10@cam
38254 [6\18] Recipients: ph10@some.domain.cam.example
38255 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38256 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38257 [9\18] id 16RdAL-0006pc-00
38258 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38259 [11\18] 09:43 +0100
38261 [13\18] Subject: this is a test header
38262 [18\18] X-something: this is another header
38263 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38266 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38268 Log lines that are neither too long nor contain newlines are written to syslog
38269 without modification.
38271 If only syslog is being used, the Exim monitor is unable to provide a log tail
38272 display, unless syslog is routing &'mainlog'& to a file on the local host and
38273 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38278 .section "Log line flags" "SECID250"
38279 One line is written to the main log for each message received, and for each
38280 successful, unsuccessful, and delayed delivery. These lines can readily be
38281 picked out by the distinctive two-character flags that immediately follow the
38282 timestamp. The flags are:
38284 &`<=`& message arrival
38285 &`(=`& message fakereject
38286 &`=>`& normal message delivery
38287 &`->`& additional address in same delivery
38288 &`>>`& cutthrough message delivery
38289 &`*>`& delivery suppressed by &%-N%&
38290 &`**`& delivery failed; address bounced
38291 &`==`& delivery deferred; temporary problem
38295 .section "Logging message reception" "SECID251"
38296 .cindex "log" "reception line"
38297 The format of the single-line entry in the main log that is written for every
38298 message received is shown in the basic example below, which is split over
38299 several lines in order to fit it on the page:
38301 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38302 H=mailer.fict.example [192.168.123.123] U=exim
38303 P=smtp S=5678 id=<incoming message id>
38305 The address immediately following &"<="& is the envelope sender address. A
38306 bounce message is shown with the sender address &"<>"&, and if it is locally
38307 generated, this is followed by an item of the form
38311 which is a reference to the message that caused the bounce to be sent.
38315 For messages from other hosts, the H and U fields identify the remote host and
38316 record the RFC 1413 identity of the user that sent the message, if one was
38317 received. The number given in square brackets is the IP address of the sending
38318 host. If there is a single, unparenthesized host name in the H field, as
38319 above, it has been verified to correspond to the IP address (see the
38320 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38321 by the remote host in the SMTP HELO or EHLO command, and has not been
38322 verified. If verification yields a different name to that given for HELO or
38323 EHLO, the verified name appears first, followed by the HELO or EHLO
38324 name in parentheses.
38326 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38327 without brackets, in the HELO or EHLO command, leading to entries in
38328 the log containing text like these examples:
38330 H=(10.21.32.43) [192.168.8.34]
38331 H=([10.21.32.43]) [192.168.8.34]
38333 This can be confusing. Only the final address in square brackets can be relied
38336 For locally generated messages (that is, messages not received over TCP/IP),
38337 the H field is omitted, and the U field contains the login name of the caller
38340 .cindex "authentication" "logging"
38341 .cindex "AUTH" "logging"
38342 For all messages, the P field specifies the protocol used to receive the
38343 message. This is the value that is stored in &$received_protocol$&. In the case
38344 of incoming SMTP messages, the value indicates whether or not any SMTP
38345 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38346 session was encrypted, there is an additional X field that records the cipher
38347 suite that was used.
38349 .cindex log protocol
38350 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38351 hosts that have authenticated themselves using the SMTP AUTH command. The first
38352 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38353 there is an additional item A= followed by the name of the authenticator that
38354 was used. If an authenticated identification was set up by the authenticator's
38355 &%server_set_id%& option, this is logged too, separated by a colon from the
38356 authenticator name.
38358 .cindex "size" "of message"
38359 The id field records the existing message id, if present. The size of the
38360 received message is given by the S field. When the message is delivered,
38361 headers may be removed or added, so that the size of delivered copies of the
38362 message may not correspond with this value (and indeed may be different to each
38365 The &%log_selector%& option can be used to request the logging of additional
38366 data when a message is received. See section &<<SECTlogselector>>& below.
38370 .section "Logging deliveries" "SECID252"
38371 .cindex "log" "delivery line"
38372 The format of the single-line entry in the main log that is written for every
38373 delivery is shown in one of the examples below, for local and remote
38374 deliveries, respectively. Each example has been split into multiple lines in order
38375 to fit it on the page:
38377 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38378 <marv@hitch.fict.example> R=localuser T=local_delivery
38379 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38380 monk@holistic.fict.example R=dnslookup T=remote_smtp
38381 H=holistic.fict.example [192.168.234.234]
38383 For ordinary local deliveries, the original address is given in angle brackets
38384 after the final delivery address, which might be a pipe or a file. If
38385 intermediate address(es) exist between the original and the final address, the
38386 last of these is given in parentheses after the final address. The R and T
38387 fields record the router and transport that were used to process the address.
38389 If SMTP AUTH was used for the delivery there is an additional item A=
38390 followed by the name of the authenticator that was used.
38391 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38392 option, this is logged too, as a second colon-separated list item.
38393 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38395 If a shadow transport was run after a successful local delivery, the log line
38396 for the successful delivery has an item added on the end, of the form
38398 &`ST=<`&&'shadow transport name'&&`>`&
38400 If the shadow transport did not succeed, the error message is put in
38401 parentheses afterwards.
38403 .cindex "asterisk" "after IP address"
38404 When more than one address is included in a single delivery (for example, two
38405 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38406 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38407 down a single SMTP connection, an asterisk follows the
38409 remote IP address (and port if enabled)
38411 in the log lines for the second and subsequent messages.
38412 When two or more messages are delivered down a single TLS connection, the
38413 DNS and some TLS-related information logged for the first message delivered
38414 will not be present in the log lines for the second and subsequent messages.
38415 TLS cipher information is still available.
38417 .cindex "delivery" "cutthrough; logging"
38418 .cindex "cutthrough" "logging"
38419 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38420 line precedes the reception line, since cutthrough waits for a possible
38421 rejection from the destination in case it can reject the sourced item.
38423 The generation of a reply message by a filter file gets logged as a
38424 &"delivery"& to the addressee, preceded by &">"&.
38426 The &%log_selector%& option can be used to request the logging of additional
38427 data when a message is delivered. See section &<<SECTlogselector>>& below.
38430 .section "Discarded deliveries" "SECID253"
38431 .cindex "discarded messages"
38432 .cindex "message" "discarded"
38433 .cindex "delivery" "discarded; logging"
38434 When a message is discarded as a result of the command &"seen finish"& being
38435 obeyed in a filter file which generates no deliveries, a log entry of the form
38437 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38438 <low.club@bridge.example> R=userforward
38440 is written, to record why no deliveries are logged. When a message is discarded
38441 because it is aliased to &":blackhole:"& the log line is like this:
38443 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38444 <hole@nowhere.example> R=blackhole_router
38448 .section "Deferred deliveries" "SECID254"
38449 When a delivery is deferred, a line of the following form is logged:
38451 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38452 R=dnslookup T=smtp defer (146): Connection refused
38454 In the case of remote deliveries, the error is the one that was given for the
38455 last IP address that was tried. Details of individual SMTP failures are also
38456 written to the log, so the above line would be preceded by something like
38458 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38459 mail1.endrest.example [192.168.239.239]: Connection refused
38461 When a deferred address is skipped because its retry time has not been reached,
38462 a message is written to the log, but this can be suppressed by setting an
38463 appropriate value in &%log_selector%&.
38467 .section "Delivery failures" "SECID255"
38468 .cindex "delivery" "failure; logging"
38469 If a delivery fails because an address cannot be routed, a line of the
38470 following form is logged:
38472 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38473 <jim@trek99.example>: unknown mail domain
38475 If a delivery fails at transport time, the router and transport are shown, and
38476 the response from the remote host is included, as in this example:
38478 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38479 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38480 after pipelined RCPT TO:<ace400@pb.example>: host
38481 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38482 <ace400@pb.example>...Addressee unknown
38484 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38485 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38486 disabling PIPELINING. The log lines for all forms of delivery failure are
38487 flagged with &`**`&.
38491 .section "Fake deliveries" "SECID256"
38492 .cindex "delivery" "fake; logging"
38493 If a delivery does not actually take place because the &%-N%& option has been
38494 used to suppress it, a normal delivery line is written to the log, except that
38495 &"=>"& is replaced by &"*>"&.
38499 .section "Completion" "SECID257"
38502 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38504 is written to the main log when a message is about to be removed from the spool
38505 at the end of its processing.
38510 .section "Summary of Fields in Log Lines" "SECID258"
38511 .cindex "log" "summary of fields"
38512 A summary of the field identifiers that are used in log lines is shown in
38513 the following table:
38515 &`A `& authenticator name (and optional id and sender)
38516 &`C `& SMTP confirmation on delivery
38517 &` `& command list for &"no mail in SMTP session"&
38518 &`CV `& certificate verification status
38519 &`D `& duration of &"no mail in SMTP session"&
38520 &`DKIM`& domain verified in incoming message
38521 &`DN `& distinguished name from peer certificate
38522 &`DS `& DNSSEC secured lookups
38523 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38524 &`F `& sender address (on delivery lines)
38525 &`H `& host name and IP address
38526 &`I `& local interface used
38527 &`id `& message id (from header) for incoming message
38528 &`K `& CHUNKING extension used
38529 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38530 &`M8S `& 8BITMIME status for incoming message
38531 &`P `& on &`<=`& lines: protocol used
38532 &` `& on &`=>`& and &`**`& lines: return path
38533 &`PRDR`& PRDR extension used
38534 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38535 &`Q `& alternate queue name
38536 &`QT `& on &`=>`& lines: time spent on queue so far
38537 &` `& on &"Completed"& lines: time spent on queue
38538 &`R `& on &`<=`& lines: reference for local bounce
38539 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38540 &`RT `& on &`<=`& lines: time taken for reception
38541 &`S `& size of message in bytes
38542 &`SNI `& server name indication from TLS client hello
38543 &`ST `& shadow transport name
38544 &`T `& on &`<=`& lines: message subject (topic)
38545 &`TFO `& connection took advantage of TCP Fast Open
38546 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38547 &`U `& local user or RFC 1413 identity
38548 &`X `& TLS cipher suite
38552 .section "Other log entries" "SECID259"
38553 Various other types of log entry are written from time to time. Most should be
38554 self-explanatory. Among the more common are:
38557 .cindex "retry" "time not reached"
38558 &'retry time not reached'&&~&~An address previously suffered a temporary error
38559 during routing or local delivery, and the time to retry has not yet arrived.
38560 This message is not written to an individual message log file unless it happens
38561 during the first delivery attempt.
38563 &'retry time not reached for any host'&&~&~An address previously suffered
38564 temporary errors during remote delivery, and the retry time has not yet arrived
38565 for any of the hosts to which it is routed.
38567 .cindex "spool directory" "file locked"
38568 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38569 some other Exim process is already working on the message. This can be quite
38570 common if queue running processes are started at frequent intervals. The
38571 &'exiwhat'& utility script can be used to find out what Exim processes are
38574 .cindex "error" "ignored"
38575 &'error ignored'&&~&~There are several circumstances that give rise to this
38578 Exim failed to deliver a bounce message whose age was greater than
38579 &%ignore_bounce_errors_after%&. The bounce was discarded.
38581 A filter file set up a delivery using the &"noerror"& option, and the delivery
38582 failed. The delivery was discarded.
38584 A delivery set up by a router configured with
38585 . ==== As this is a nested list, any displays it contains must be indented
38586 . ==== as otherwise they are too far to the left.
38590 failed. The delivery was discarded.
38593 .cindex DKIM "log line"
38594 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38595 logging and the message has a DKIM signature header.
38602 .section "Reducing or increasing what is logged" "SECTlogselector"
38603 .cindex "log" "selectors"
38604 By setting the &%log_selector%& global option, you can disable some of Exim's
38605 default logging, or you can request additional logging. The value of
38606 &%log_selector%& is made up of names preceded by plus or minus characters. For
38609 log_selector = +arguments -retry_defer
38611 The list of optional log items is in the following table, with the default
38612 selection marked by asterisks:
38614 &` 8bitmime `& received 8BITMIME status
38615 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38616 &` address_rewrite `& address rewriting
38617 &` all_parents `& all parents in => lines
38618 &` arguments `& command line arguments
38619 &`*connection_reject `& connection rejections
38620 &`*delay_delivery `& immediate delivery delayed
38621 &` deliver_time `& time taken to attempt delivery
38622 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38623 &`*dkim `& DKIM verified domain on <= lines
38624 &` dkim_verbose `& separate full DKIM verification result line, per signature
38625 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38626 &` dnssec `& DNSSEC secured lookups
38627 &`*etrn `& ETRN commands
38628 &`*host_lookup_failed `& as it says
38629 &` ident_timeout `& timeout for ident connection
38630 &` incoming_interface `& local interface on <= and => lines
38631 &` incoming_port `& remote port on <= lines
38632 &`*lost_incoming_connection `& as it says (includes timeouts)
38633 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38634 &`*msg_id `& on <= lines, Message-ID: header value
38635 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38636 &` outgoing_interface `& local interface on => lines
38637 &` outgoing_port `& add remote port to => lines
38638 &`*queue_run `& start and end queue runs
38639 &` queue_time `& time on queue for one recipient
38640 &` queue_time_overall `& time on queue for whole message
38641 &` pid `& Exim process id
38642 &` pipelining `& PIPELINING use, on <= and => lines
38643 &` proxy `& proxy address on <= and => lines
38644 &` receive_time `& time taken to receive message
38645 &` received_recipients `& recipients on <= lines
38646 &` received_sender `& sender on <= lines
38647 &`*rejected_header `& header contents on reject log
38648 &`*retry_defer `& &"retry time not reached"&
38649 &` return_path_on_delivery `& put return path on => and ** lines
38650 &` sender_on_delivery `& add sender to => lines
38651 &`*sender_verify_fail `& sender verification failures
38652 &`*size_reject `& rejection because too big
38653 &`*skip_delivery `& delivery skipped in a queue run
38654 &`*smtp_confirmation `& SMTP confirmation on => lines
38655 &` smtp_connection `& incoming SMTP connections
38656 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38657 &` smtp_mailauth `& AUTH argument to MAIL commands
38658 &` smtp_no_mail `& session with no MAIL commands
38659 &` smtp_protocol_error `& SMTP protocol errors
38660 &` smtp_syntax_error `& SMTP syntax errors
38661 &` subject `& contents of &'Subject:'& on <= lines
38662 &`*tls_certificate_verified `& certificate verification status
38663 &`*tls_cipher `& TLS cipher suite on <= and => lines
38664 &` tls_peerdn `& TLS peer DN on <= and => lines
38665 &` tls_resumption `& append * to cipher field
38666 &` tls_sni `& TLS SNI on <= lines
38667 &` unknown_in_list `& DNS lookup failed in list match
38669 &` all `& all of the above
38671 See also the &%slow_lookup_log%& main configuration option,
38672 section &<<SECID99>>&
38674 More details on each of these items follows:
38678 .cindex "log" "8BITMIME"
38679 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38680 which may help in tracking down interoperability issues with ancient MTAs
38681 that are not 8bit clean. This is added to the &"<="& line, tagged with
38682 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38683 &`7BIT`& and &`8BITMIME`& respectively.
38685 .cindex "&%warn%& ACL verb" "log when skipping"
38686 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38687 its conditions cannot be evaluated, a log line to this effect is written if
38688 this log selector is set.
38690 .cindex "log" "rewriting"
38691 .cindex "rewriting" "logging"
38692 &%address_rewrite%&: This applies both to global rewrites and per-transport
38693 rewrites, but not to rewrites in filters run as an unprivileged user (because
38694 such users cannot access the log).
38696 .cindex "log" "full parentage"
38697 &%all_parents%&: Normally only the original and final addresses are logged on
38698 delivery lines; with this selector, intermediate parents are given in
38699 parentheses between them.
38701 .cindex "log" "Exim arguments"
38702 .cindex "Exim arguments, logging"
38703 &%arguments%&: This causes Exim to write the arguments with which it was called
38704 to the main log, preceded by the current working directory. This is a debugging
38705 feature, added to make it easier to find out how certain MUAs call
38706 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38707 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38708 that are empty or that contain white space are quoted. Non-printing characters
38709 are shown as escape sequences. This facility cannot log unrecognized arguments,
38710 because the arguments are checked before the configuration file is read. The
38711 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38712 between the caller and Exim.
38714 .cindex "log" "connection rejections"
38715 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38716 connection is rejected, for whatever reason.
38718 .cindex "log" "delayed delivery"
38719 .cindex "delayed delivery, logging"
38720 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38721 started for an incoming message because the load is too high or too many
38722 messages were received on one connection. Logging does not occur if no delivery
38723 process is started because &%queue_only%& is set or &%-odq%& was used.
38725 .cindex "log" "delivery duration"
38726 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38727 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38728 If millisecond logging is enabled, short times will be shown with greater
38729 precision, eg. &`DT=0.304s`&.
38731 .cindex "log" "message size on delivery"
38732 .cindex "size" "of message"
38733 &%delivery_size%&: For each delivery, the size of message delivered is added to
38734 the &"=>"& line, tagged with S=.
38736 .cindex log "DKIM verification"
38737 .cindex DKIM "verification logging"
38738 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38739 verifies successfully a tag of DKIM is added, with one of the verified domains.
38741 .cindex log "DKIM verification"
38742 .cindex DKIM "verification logging"
38743 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38745 .cindex "log" "dnslist defer"
38746 .cindex "DNS list" "logging defer"
38747 .cindex "black list (DNS)"
38748 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38749 DNS black list suffers a temporary error.
38752 .cindex dnssec logging
38753 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38754 dns lookups gave secure results a tag of DS is added.
38755 For acceptance this covers the reverse and forward lookups for host name verification.
38756 It does not cover helo-name verification.
38757 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38759 .cindex "log" "ETRN commands"
38760 .cindex "ETRN" "logging"
38761 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38762 is run to determine whether or not it is actually accepted. An invalid ETRN
38763 command, or one received within a message transaction is not logged by this
38764 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38766 .cindex "log" "host lookup failure"
38767 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38768 any addresses, or when a lookup of an IP address fails to find a host name, a
38769 log line is written. This logging does not apply to direct DNS lookups when
38770 routing email addresses, but it does apply to &"byname"& lookups.
38772 .cindex "log" "ident timeout"
38773 .cindex "RFC 1413" "logging timeout"
38774 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38775 client's ident port times out.
38777 .cindex "log" "incoming interface"
38778 .cindex "log" "outgoing interface"
38779 .cindex "log" "local interface"
38780 .cindex "log" "local address and port"
38781 .cindex "TCP/IP" "logging local address and port"
38782 .cindex "interface" "logging"
38783 &%incoming_interface%&: The interface on which a message was received is added
38784 to the &"<="& line as an IP address in square brackets, tagged by I= and
38785 followed by a colon and the port number. The local interface and port are also
38786 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38787 rejection lines, and (despite the name) to outgoing
38789 &"=>"&, &"->"&, &"=="& and &"**"& lines.
38791 The latter can be disabled by turning off the &%outgoing_interface%& option.
38793 .cindex log "incoming proxy address"
38794 .cindex proxy "logging proxy address"
38795 .cindex "TCP/IP" "logging proxy address"
38796 &%proxy%&: The internal (closest to the system running Exim) IP address
38797 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
38798 on a proxied connection
38799 or the &"=>"& line for a message delivered on a proxied connection.
38800 See &<<SECTproxyInbound>>& for more information.
38802 .cindex "log" "incoming remote port"
38803 .cindex "port" "logging remote"
38804 .cindex "TCP/IP" "logging incoming remote port"
38805 .vindex "&$sender_fullhost$&"
38806 .vindex "&$sender_rcvhost$&"
38807 &%incoming_port%&: The remote port number from which a message was received is
38808 added to log entries and &'Received:'& header lines, following the IP address
38809 in square brackets, and separated from it by a colon. This is implemented by
38810 changing the value that is put in the &$sender_fullhost$& and
38811 &$sender_rcvhost$& variables. Recording the remote port number has become more
38812 important with the widening use of NAT (see RFC 2505).
38814 .cindex "log" "dropped connection"
38815 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
38816 connection is unexpectedly dropped.
38818 .cindex "log" "millisecond timestamps"
38819 .cindex millisecond logging
38820 .cindex timestamps "millisecond, in logs"
38821 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
38822 appended to the seconds value.
38824 .cindex "log" "message id"
38825 &%msg_id%&: The value of the Message-ID: header.
38827 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
38828 This will be either because the message is a bounce, or was submitted locally
38829 (submission mode) without one.
38830 The field identifier will have an asterix appended: &"id*="&.
38832 .cindex "log" "outgoing interface"
38833 .cindex "log" "local interface"
38834 .cindex "log" "local address and port"
38835 .cindex "TCP/IP" "logging local address and port"
38836 .cindex "interface" "logging"
38837 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
38838 interface on which a message was sent is added to delivery lines as an I= tag
38839 followed by IP address in square brackets. You can disable this by turning
38840 off the &%outgoing_interface%& option.
38842 .cindex "log" "outgoing remote port"
38843 .cindex "port" "logging outgoing remote"
38844 .cindex "TCP/IP" "logging outgoing remote port"
38845 &%outgoing_port%&: The remote port number is added to delivery log lines (those
38846 containing => tags) following the IP address.
38847 The local port is also added if &%incoming_interface%& and
38848 &%outgoing_interface%& are both enabled.
38849 This option is not included in the default setting, because for most ordinary
38850 configurations, the remote port number is always 25 (the SMTP port), and the
38851 local port is a random ephemeral port.
38853 .cindex "log" "process ids in"
38854 .cindex "pid (process id)" "in log lines"
38855 &%pid%&: The current process id is added to every log line, in square brackets,
38856 immediately after the time and date.
38858 .cindex log pipelining
38859 .cindex pipelining "logging outgoing"
38860 &%pipelining%&: A field is added to delivery and accept
38861 log lines when the ESMTP PIPELINING extension was used.
38862 The field is a single "L".
38864 On accept lines, where PIPELINING was offered but not used by the client,
38865 the field has a minus appended.
38867 .cindex "pipelining" "early connection"
38868 If Exim is built with the SUPPORT_PIPE_CONNECT build option
38869 accept "L" fields have a period appended if the feature was
38870 offered but not used, or an asterisk appended if used.
38871 Delivery "L" fields have an asterisk appended if used.
38874 .cindex "log" "queue run"
38875 .cindex "queue runner" "logging"
38876 &%queue_run%&: The start and end of every queue run are logged.
38878 .cindex "log" "queue time"
38879 &%queue_time%&: The amount of time the message has been in the queue on the
38880 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
38881 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
38882 includes reception time as well as the delivery time for the current address.
38883 This means that it may be longer than the difference between the arrival and
38884 delivery log line times, because the arrival log line is not written until the
38885 message has been successfully received.
38886 If millisecond logging is enabled, short times will be shown with greater
38887 precision, eg. &`QT=1.578s`&.
38889 &%queue_time_overall%&: The amount of time the message has been in the queue on
38890 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
38891 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
38892 message, so it includes reception time as well as the total delivery time.
38894 .cindex "log" "receive duration"
38895 &%receive_time%&: For each message, the amount of real time it has taken to
38896 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
38897 If millisecond logging is enabled, short times will be shown with greater
38898 precision, eg. &`RT=0.204s`&.
38900 .cindex "log" "recipients"
38901 &%received_recipients%&: The recipients of a message are listed in the main log
38902 as soon as the message is received. The list appears at the end of the log line
38903 that is written when a message is received, preceded by the word &"for"&. The
38904 addresses are listed after they have been qualified, but before any rewriting
38906 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
38909 .cindex "log" "sender reception"
38910 &%received_sender%&: The unrewritten original sender of a message is added to
38911 the end of the log line that records the message's arrival, after the word
38912 &"from"& (before the recipients if &%received_recipients%& is also set).
38914 .cindex "log" "header lines for rejection"
38915 &%rejected_header%&: If a message's header has been received at the time a
38916 rejection is written to the reject log, the complete header is added to the
38917 log. Header logging can be turned off individually for messages that are
38918 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
38920 .cindex "log" "retry defer"
38921 &%retry_defer%&: A log line is written if a delivery is deferred because a
38922 retry time has not yet been reached. However, this &"retry time not reached"&
38923 message is always omitted from individual message logs after the first delivery
38926 .cindex "log" "return path"
38927 &%return_path_on_delivery%&: The return path that is being transmitted with
38928 the message is included in delivery and bounce lines, using the tag P=.
38929 This is omitted if no delivery actually happens, for example, if routing fails,
38930 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
38932 .cindex "log" "sender on delivery"
38933 &%sender_on_delivery%&: The message's sender address is added to every delivery
38934 and bounce line, tagged by F= (for &"from"&).
38935 This is the original sender that was received with the message; it is not
38936 necessarily the same as the outgoing return path.
38938 .cindex "log" "sender verify failure"
38939 &%sender_verify_fail%&: If this selector is unset, the separate log line that
38940 gives details of a sender verification failure is not written. Log lines for
38941 the rejection of SMTP commands contain just &"sender verify failed"&, so some
38944 .cindex "log" "size rejection"
38945 &%size_reject%&: A log line is written whenever a message is rejected because
38948 .cindex "log" "frozen messages; skipped"
38949 .cindex "frozen messages" "logging skipping"
38950 &%skip_delivery%&: A log line is written whenever a message is skipped during a
38951 queue run because it is frozen or because another process is already delivering
38953 .cindex "&""spool file is locked""&"
38954 The message that is written is &"spool file is locked"&.
38956 .cindex "log" "smtp confirmation"
38957 .cindex "SMTP" "logging confirmation"
38958 .cindex "LMTP" "logging confirmation"
38959 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
38960 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
38961 A number of MTAs (including Exim) return an identifying string in this
38964 .cindex "log" "SMTP connections"
38965 .cindex "SMTP" "logging connections"
38966 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
38967 established or closed, unless the connection is from a host that matches
38968 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
38969 only when the closure is unexpected.) This applies to connections from local
38970 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
38971 dropped in the middle of a message, a log line is always written, whether or
38972 not this selector is set, but otherwise nothing is written at the start and end
38973 of connections unless this selector is enabled.
38975 For TCP/IP connections to an Exim daemon, the current number of connections is
38976 included in the log message for each new connection, but note that the count is
38977 reset if the daemon is restarted.
38978 Also, because connections are closed (and the closure is logged) in
38979 subprocesses, the count may not include connections that have been closed but
38980 whose termination the daemon has not yet noticed. Thus, while it is possible to
38981 match up the opening and closing of connections in the log, the value of the
38982 logged counts may not be entirely accurate.
38984 .cindex "log" "SMTP transaction; incomplete"
38985 .cindex "SMTP" "logging incomplete transactions"
38986 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
38987 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
38988 and the message sender plus any accepted recipients are included in the log
38989 line. This can provide evidence of dictionary attacks.
38991 .cindex "log" "non-MAIL SMTP sessions"
38992 .cindex "MAIL" "logging session without"
38993 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
38994 connection terminates without having issued a MAIL command. This includes both
38995 the case when the connection is dropped, and the case when QUIT is used. It
38996 does not include cases where the connection is rejected right at the start (by
38997 an ACL, or because there are too many connections, or whatever). These cases
38998 already have their own log lines.
39000 The log line that is written contains the identity of the client in the usual
39001 way, followed by D= and a time, which records the duration of the connection.
39002 If the connection was authenticated, this fact is logged exactly as it is for
39003 an incoming message, with an A= item. If the connection was encrypted, CV=,
39004 DN=, and X= items may appear as they do for an incoming message, controlled by
39005 the same logging options.
39007 Finally, if any SMTP commands were issued during the connection, a C= item
39008 is added to the line, listing the commands that were used. For example,
39012 shows that the client issued QUIT straight after EHLO. If there were fewer
39013 than 20 commands, they are all listed. If there were more than 20 commands,
39014 the last 20 are listed, preceded by &"..."&. However, with the default
39015 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39016 have been aborted before 20 non-mail commands are processed.
39018 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39019 colon-separated, is appended to the A= item for a message arrival or delivery
39020 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39021 was accepted or used.
39023 .cindex "log" "SMTP protocol error"
39024 .cindex "SMTP" "logging protocol error"
39025 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39026 encountered. Exim does not have perfect detection of all protocol errors
39027 because of transmission delays and the use of pipelining. If PIPELINING has
39028 been advertised to a client, an Exim server assumes that the client will use
39029 it, and therefore it does not count &"expected"& errors (for example, RCPT
39030 received after rejecting MAIL) as protocol errors.
39032 .cindex "SMTP" "logging syntax errors"
39033 .cindex "SMTP" "syntax errors; logging"
39034 .cindex "SMTP" "unknown command; logging"
39035 .cindex "log" "unknown SMTP command"
39036 .cindex "log" "SMTP syntax error"
39037 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39038 encountered. An unrecognized command is treated as a syntax error. For an
39039 external connection, the host identity is given; for an internal connection
39040 using &%-bs%& the sender identification (normally the calling user) is given.
39042 .cindex "log" "subject"
39043 .cindex "subject, logging"
39044 &%subject%&: The subject of the message is added to the arrival log line,
39045 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39046 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39047 specifies whether characters with values greater than 127 should be logged
39048 unchanged, or whether they should be rendered as escape sequences.
39050 .cindex "log" "certificate verification"
39052 .cindex DANE logging
39053 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39054 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39056 using a CA trust anchor,
39057 &`CV=dane`& if using a DNS trust anchor,
39058 and &`CV=no`& if not.
39060 .cindex "log" "TLS cipher"
39061 .cindex "TLS" "logging cipher"
39062 &%tls_cipher%&: When a message is sent or received over an encrypted
39063 connection, the cipher suite used is added to the log line, preceded by X=.
39065 .cindex "log" "TLS peer DN"
39066 .cindex "TLS" "logging peer DN"
39067 &%tls_peerdn%&: When a message is sent or received over an encrypted
39068 connection, and a certificate is supplied by the remote host, the peer DN is
39069 added to the log line, preceded by DN=.
39071 .cindex "log" "TLS resumption"
39072 .cindex "TLS" "logging session resumption"
39074 &%tls_resumption%&: When a message is sent or received over an encrypted
39075 connection and the TLS session resumed one used on a previous TCP connection,
39076 an asterisk is appended to the X= cipher field in the log line.
39079 .cindex "log" "TLS SNI"
39080 .cindex "TLS" "logging SNI"
39081 .cindex SNI logging
39082 &%tls_sni%&: When a message is received over an encrypted connection, and
39083 the remote host provided the Server Name Indication extension, the SNI is
39084 added to the log line, preceded by SNI=.
39086 .cindex "log" "DNS failure in list"
39087 &%unknown_in_list%&: This setting causes a log entry to be written when the
39088 result of a list match is failure because a DNS lookup failed.
39092 .section "Message log" "SECID260"
39093 .cindex "message" "log file for"
39094 .cindex "log" "message log; description of"
39095 .cindex "&_msglog_& directory"
39096 .oindex "&%preserve_message_logs%&"
39097 In addition to the general log files, Exim writes a log file for each message
39098 that it handles. The names of these per-message logs are the message ids, and
39099 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39100 message log contains copies of the log lines that apply to the message. This
39101 makes it easier to inspect the status of an individual message without having
39102 to search the main log. A message log is deleted when processing of the message
39103 is complete, unless &%preserve_message_logs%& is set, but this should be used
39104 only with great care because they can fill up your disk very quickly.
39106 On a heavily loaded system, it may be desirable to disable the use of
39107 per-message logs, in order to reduce disk I/O. This can be done by setting the
39108 &%message_logs%& option false.
39114 . ////////////////////////////////////////////////////////////////////////////
39115 . ////////////////////////////////////////////////////////////////////////////
39117 .chapter "Exim utilities" "CHAPutils"
39118 .scindex IIDutils "utilities"
39119 A number of utility scripts and programs are supplied with Exim and are
39120 described in this chapter. There is also the Exim Monitor, which is covered in
39121 the next chapter. The utilities described here are:
39123 .itable none 0 0 3 7* left 15* left 40* left
39124 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39125 "list what Exim processes are doing"
39126 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39127 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39128 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39129 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39131 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39132 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39133 "extract statistics from the log"
39134 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39135 "check address acceptance from given IP"
39136 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39137 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39138 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39139 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39140 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39141 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39144 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39145 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39146 &url(https://duncanthrax.net/exilog/) for details.
39151 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39152 .cindex "&'exiwhat'&"
39153 .cindex "process, querying"
39155 On operating systems that can restart a system call after receiving a signal
39156 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39157 a line describing what it is doing to the file &_exim-process.info_& in the
39158 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39159 processes it can find, having first emptied the file. It then waits for one
39160 second to allow the Exim processes to react before displaying the results. In
39161 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39162 send the signal to the Exim processes, so it is normally run as root.
39164 &*Warning*&: This is not an efficient process. It is intended for occasional
39165 use by system administrators. It is not sensible, for example, to set up a
39166 script that sends SIGUSR1 signals to Exim processes at short intervals.
39169 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39170 varies in different operating systems. Not only are different options used,
39171 but the format of the output is different. For this reason, there are some
39172 system configuration options that configure exactly how &'exiwhat'& works. If
39173 it doesn't seem to be working for you, check the following compile-time
39176 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
39177 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
39178 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
39179 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
39181 An example of typical output from &'exiwhat'& is
39183 164 daemon: -q1h, listening on port 25
39184 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39185 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39186 [10.19.42.42] (editor@ref.example)
39187 10592 handling incoming call from [192.168.243.242]
39188 10628 accepting a local non-SMTP message
39190 The first number in the output line is the process number. The third line has
39191 been split here, in order to fit it on the page.
39195 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39196 .cindex "&'exiqgrep'&"
39197 .cindex "queue" "grepping"
39198 This utility is a Perl script contributed by Matt Hubbard. It runs
39202 or (in case &*-a*& switch is specified)
39206 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
39207 contain alternate exim configuration the queue management might be using.
39209 to obtain a queue listing, and then greps the output to select messages
39210 that match given criteria. The following selection options are available:
39213 .vitem &*-f*&&~<&'regex'&>
39214 Match the sender address using a case-insensitive search. The field that is
39215 tested is enclosed in angle brackets, so you can test for bounce messages with
39219 .vitem &*-r*&&~<&'regex'&>
39220 Match a recipient address using a case-insensitive search. The field that is
39221 tested is not enclosed in angle brackets.
39223 .vitem &*-s*&&~<&'regex'&>
39224 Match against the size field.
39226 .vitem &*-y*&&~<&'seconds'&>
39227 Match messages that are younger than the given time.
39229 .vitem &*-o*&&~<&'seconds'&>
39230 Match messages that are older than the given time.
39233 Match only frozen messages.
39236 Match only non-frozen messages.
39238 .vitem &*-G*&&~<&'queuename'&>
39239 Match only messages in the given queue. Without this, the default queue is searched.
39242 The following options control the format of the output:
39246 Display only the count of matching messages.
39249 Long format &-- display the full message information as output by Exim. This is
39253 Display message ids only.
39256 Brief format &-- one line per message.
39259 Display messages in reverse order.
39262 Include delivered recipients in queue listing.
39265 There is one more option, &%-h%&, which outputs a list of options.
39269 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39270 .cindex "&'exiqsumm'&"
39271 .cindex "queue" "summary"
39272 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39273 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39274 running a command such as
39276 exim -bp | exiqsumm
39278 The output consists of one line for each domain that has messages waiting for
39279 it, as in the following example:
39281 3 2322 74m 66m msn.com.example
39283 Each line lists the number of pending deliveries for a domain, their total
39284 volume, and the length of time that the oldest and the newest messages have
39285 been waiting. Note that the number of pending deliveries is greater than the
39286 number of messages when messages have more than one recipient.
39288 A summary line is output at the end. By default the output is sorted on the
39289 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39290 the output to be sorted by oldest message and by count of messages,
39291 respectively. There are also three options that split the messages for each
39292 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39293 separates frozen messages, and &%-s%& separates messages according to their
39296 The output of &'exim -bp'& contains the original addresses in the message, so
39297 this also applies to the output from &'exiqsumm'&. No domains from addresses
39298 generated by aliasing or forwarding are included (unless the &%one_time%&
39299 option of the &(redirect)& router has been used to convert them into &"top
39300 level"& addresses).
39305 .section "Extracting specific information from the log (exigrep)" &&&
39307 .cindex "&'exigrep'&"
39308 .cindex "log" "extracts; grepping for"
39309 The &'exigrep'& utility is a Perl script that searches one or more main log
39310 files for entries that match a given pattern. When it finds a match, it
39311 extracts all the log entries for the relevant message, not just those that
39312 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39313 given message, or all mail for a given user, or for a given host, for example.
39314 The input files can be in Exim log format or syslog format.
39315 If a matching log line is not associated with a specific message, it is
39316 included in &'exigrep'&'s output without any additional lines. The usage is:
39318 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39320 If no log filenames are given on the command line, the standard input is read.
39322 The &%-t%& argument specifies a number of seconds. It adds an additional
39323 condition for message selection. Messages that are complete are shown only if
39324 they spent more than <&'n'&> seconds in the queue.
39326 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39327 makes it case-sensitive. This may give a performance improvement when searching
39328 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39329 option; with &%-I%& they do not. In both cases it is possible to change the
39330 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39332 The &%-l%& option means &"literal"&, that is, treat all characters in the
39333 pattern as standing for themselves. Otherwise the pattern must be a Perl
39334 regular expression.
39336 The &%-v%& option inverts the matching condition. That is, a line is selected
39337 if it does &'not'& match the pattern.
39339 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39340 that are generated as a result/response to a message that &'exigrep'& matched
39344 user_a sends a message to user_b, which generates a bounce back to user_b. If
39345 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39346 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39347 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39348 when searching for &"user_a"& will show both messages since the bounce is
39349 &"related"& to or a &"result"& of the first message that was found by the
39352 If the location of a &'zcat'& command is known from the definition of
39353 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39354 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39355 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39356 autodetection of some well known compression extensions.
39359 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39360 .cindex "&'exipick'&"
39361 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39362 lists messages from the queue according to a variety of criteria. For details
39363 of &'exipick'&'s facilities, run &'exipick'& with
39364 the &%--help%& option.
39367 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39368 .cindex "log" "cycling local files"
39369 .cindex "cycling logs"
39370 .cindex "&'exicyclog'&"
39371 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39372 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39373 you are using log files with datestamps in their names (see section
39374 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39375 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39376 There are two command line options for &'exicyclog'&:
39378 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39379 default that is set when Exim is built. The default default is 10.
39381 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39382 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39383 overriding the script's default, which is to find the setting from Exim's
39387 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39388 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39389 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39390 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39391 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39392 logs are handled similarly.
39394 If the limit is greater than 99, the script uses 3-digit numbers such as
39395 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39396 to one that is greater, or &'vice versa'&, you will have to fix the names of
39397 any existing log files.
39399 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39400 the end are deleted. All files with numbers greater than 01 are compressed,
39401 using a compression command which is configured by the COMPRESS_COMMAND
39402 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39403 root &%crontab%& entry of the form
39405 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39407 assuming you have used the name &"exim"& for the Exim user. You can run
39408 &'exicyclog'& as root if you wish, but there is no need.
39412 .section "Mail statistics (eximstats)" "SECTmailstat"
39413 .cindex "statistics"
39414 .cindex "&'eximstats'&"
39415 A Perl script called &'eximstats'& is provided for extracting statistical
39416 information from log files. The output is either plain text, or HTML.
39417 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39418 . --- 404 error and everything else points to that.
39420 The &'eximstats'& script has been hacked about quite a bit over time. The
39421 latest version is the result of some extensive revision by Steve Campbell. A
39422 lot of information is given by default, but there are options for suppressing
39423 various parts of it. Following any options, the arguments to the script are a
39424 list of files, which should be main log files. For example:
39426 eximstats -nr /var/spool/exim/log/mainlog.01
39428 By default, &'eximstats'& extracts information about the number and volume of
39429 messages received from or delivered to various hosts. The information is sorted
39430 both by message count and by volume, and the top fifty hosts in each category
39431 are listed on the standard output. Similar information, based on email
39432 addresses or domains instead of hosts can be requested by means of various
39433 options. For messages delivered and received locally, similar statistics are
39434 also produced per user.
39436 The output also includes total counts and statistics about delivery errors, and
39437 histograms showing the number of messages received and deliveries made in each
39438 hour of the day. A delivery with more than one address in its envelope (for
39439 example, an SMTP transaction with more than one RCPT command) is counted
39440 as a single delivery by &'eximstats'&.
39442 Though normally more deliveries than receipts are reported (as messages may
39443 have multiple recipients), it is possible for &'eximstats'& to report more
39444 messages received than delivered, even though the queue is empty at the start
39445 and end of the period in question. If an incoming message contains no valid
39446 recipients, no deliveries are recorded for it. A bounce message is handled as
39447 an entirely separate message.
39449 &'eximstats'& always outputs a grand total summary giving the volume and number
39450 of messages received and deliveries made, and the number of hosts involved in
39451 each case. It also outputs the number of messages that were delayed (that is,
39452 not completely delivered at the first attempt), and the number that had at
39453 least one address that failed.
39455 The remainder of the output is in sections that can be independently disabled
39456 or modified by various options. It consists of a summary of deliveries by
39457 transport, histograms of messages received and delivered per time interval
39458 (default per hour), information about the time messages spent in the queue,
39459 a list of relayed messages, lists of the top fifty sending hosts, local
39460 senders, destination hosts, and destination local users by count and by volume,
39461 and a list of delivery errors that occurred.
39463 The relay information lists messages that were actually relayed, that is, they
39464 came from a remote host and were directly delivered to some other remote host,
39465 without being processed (for example, for aliasing or forwarding) locally.
39467 There are quite a few options for &'eximstats'& to control exactly what it
39468 outputs. These are documented in the Perl script itself, and can be extracted
39469 by running the command &(perldoc)& on the script. For example:
39471 perldoc /usr/exim/bin/eximstats
39474 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39475 .cindex "&'exim_checkaccess'&"
39476 .cindex "policy control" "checking access"
39477 .cindex "checking access"
39478 The &%-bh%& command line argument allows you to run a fake SMTP session with
39479 debugging output, in order to check what Exim is doing when it is applying
39480 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39481 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39482 sometimes you just want to answer the question &"Does this address have
39483 access?"& without bothering with any further details.
39485 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39486 two arguments, an IP address and an email address:
39488 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39490 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39491 given email address would be accepted in a RCPT command in a TCP/IP
39492 connection from the host with the given IP address. The output of the utility
39493 is either the word &"accepted"&, or the SMTP error response, for example:
39496 550 Relay not permitted
39498 When running this test, the utility uses &`<>`& as the envelope sender address
39499 for the MAIL command, but you can change this by providing additional
39500 options. These are passed directly to the Exim command. For example, to specify
39501 that the test is to be run with the sender address &'himself@there.example'&
39504 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39505 -f himself@there.example
39507 Note that these additional Exim command line items must be given after the two
39508 mandatory arguments.
39510 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39511 while running its checks. You can run checks that include callouts by using
39512 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39516 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39517 .cindex "DBM" "building dbm files"
39518 .cindex "building DBM files"
39519 .cindex "&'exim_dbmbuild'&"
39520 .cindex "lower casing"
39521 .cindex "binary zero" "in lookup key"
39522 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39523 the format used by the &(lsearch)& lookup (see section
39524 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39525 names as keys and the remainder of the information as data. The lower-casing
39526 can be prevented by calling the program with the &%-nolc%& option.
39528 A terminating zero is included as part of the key string. This is expected by
39529 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39530 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39531 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39534 The program requires two arguments: the name of the input file (which can be a
39535 single hyphen to indicate the standard input), and the name of the output file.
39536 It creates the output under a temporary name, and then renames it if all went
39540 If the native DB interface is in use (USE_DB is set in a compile-time
39541 configuration file &-- this is common in free versions of Unix) the two
39542 filenames must be different, because in this mode the Berkeley DB functions
39543 create a single output file using exactly the name given. For example,
39545 exim_dbmbuild /etc/aliases /etc/aliases.db
39547 reads the system alias file and creates a DBM version of it in
39548 &_/etc/aliases.db_&.
39550 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39551 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39552 environment, the suffixes are added to the second argument of
39553 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39554 when the Berkeley functions are used in compatibility mode (though this is not
39555 recommended), because in that case it adds a &_.db_& suffix to the filename.
39557 If a duplicate key is encountered, the program outputs a warning, and when it
39558 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39559 option is used. By default, only the first of a set of duplicates is used &--
39560 this makes it compatible with &(lsearch)& lookups. There is an option
39561 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39562 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39563 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39569 .section "Finding individual retry times (exinext)" "SECTfinindret"
39570 .cindex "retry" "times"
39571 .cindex "&'exinext'&"
39572 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39573 fish specific information out of the retry database. Given a mail domain (or a
39574 complete address), it looks up the hosts for that domain, and outputs any retry
39575 information for the hosts or for the domain. At present, the retry information
39576 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39577 output. For example:
39579 $ exinext piglet@milne.fict.example
39580 kanga.milne.example:192.168.8.1 error 146: Connection refused
39581 first failed: 21-Feb-1996 14:57:34
39582 last tried: 21-Feb-1996 14:57:34
39583 next try at: 21-Feb-1996 15:02:34
39584 roo.milne.example:192.168.8.3 error 146: Connection refused
39585 first failed: 20-Jan-1996 13:12:08
39586 last tried: 21-Feb-1996 11:42:03
39587 next try at: 21-Feb-1996 19:42:03
39588 past final cutoff time
39590 You can also give &'exinext'& a local part, without a domain, and it
39591 will give any retry information for that local part in your default domain.
39592 A message id can be used to obtain retry information pertaining to a specific
39593 message. This exists only when an attempt to deliver a message to a remote host
39594 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39595 &'exinext'& is not particularly efficient, but then it is not expected to be
39598 The &'exinext'& utility calls Exim to find out information such as the location
39599 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39600 passed on to the &'exim'& commands. The first specifies an alternate Exim
39601 configuration file, and the second sets macros for use within the configuration
39602 file. These features are mainly to help in testing, but might also be useful in
39603 environments where more than one configuration file is in use.
39607 .section "Hints database maintenance" "SECThindatmai"
39608 .cindex "hints database" "maintenance"
39609 .cindex "maintaining Exim's hints database"
39610 Three utility programs are provided for maintaining the DBM files that Exim
39611 uses to contain its delivery hint information. Each program requires two
39612 arguments. The first specifies the name of Exim's spool directory, and the
39613 second is the name of the database it is to operate on. These are as follows:
39616 &'retry'&: the database of retry information
39618 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39621 &'callout'&: the callout cache
39623 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39626 &'tls'&: TLS session resumption data
39629 &'misc'&: other hints data
39632 The &'misc'& database is used for
39635 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39637 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39638 &(smtp)& transport)
39640 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39646 .section "exim_dumpdb" "SECTdumpdb"
39647 .cindex "&'exim_dumpdb'&"
39648 The entire contents of a database are written to the standard output by the
39649 &'exim_dumpdb'& program, which has no options or arguments other than the
39650 spool and database names. For example, to dump the retry database:
39652 exim_dumpdb /var/spool/exim retry
39654 Two lines of output are produced for each entry:
39656 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39657 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39659 The first item on the first line is the key of the record. It starts with one
39660 of the letters R, or T, depending on whether it refers to a routing or
39661 transport retry. For a local delivery, the next part is the local address; for
39662 a remote delivery it is the name of the remote host, followed by its failing IP
39663 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39664 transport). If the remote port is not the standard one (port 25), it is added
39665 to the IP address. Then there follows an error code, an additional error code,
39666 and a textual description of the error.
39668 The three times on the second line are the time of first failure, the time of
39669 the last delivery attempt, and the computed time for the next attempt. The line
39670 ends with an asterisk if the cutoff time for the last retry rule has been
39673 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39674 consists of a host name followed by a list of ids for messages that are or were
39675 waiting to be delivered to that host. If there are a very large number for any
39676 one host, continuation records, with a sequence number added to the host name,
39677 may be seen. The data in these records is often out of date, because a message
39678 may be routed to several alternative hosts, and Exim makes no effort to keep
39683 .section "exim_tidydb" "SECTtidydb"
39684 .cindex "&'exim_tidydb'&"
39685 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39686 database. If run with no options, it removes all records that are more than 30
39687 days old. The age is calculated from the date and time that the record was last
39688 updated. Note that, in the case of the retry database, it is &'not'& the time
39689 since the first delivery failure. Information about a host that has been down
39690 for more than 30 days will remain in the database, provided that the record is
39691 updated sufficiently often.
39693 The cutoff date can be altered by means of the &%-t%& option, which must be
39694 followed by a time. For example, to remove all records older than a week from
39695 the retry database:
39697 exim_tidydb -t 7d /var/spool/exim retry
39699 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39700 message ids. In the former these appear as data in records keyed by host &--
39701 they were messages that were waiting for that host &-- and in the latter they
39702 are the keys for retry information for messages that have suffered certain
39703 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39704 message ids in database records are those of messages that are still on the
39705 queue. Message ids for messages that no longer exist are removed from
39706 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39707 For the &'retry'& database, records whose keys are non-existent message ids are
39708 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39709 whenever it removes information from the database.
39711 Certain records are automatically removed by Exim when they are no longer
39712 needed, but others are not. For example, if all the MX hosts for a domain are
39713 down, a retry record is created for each one. If the primary MX host comes back
39714 first, its record is removed when Exim successfully delivers to it, but the
39715 records for the others remain because Exim has not tried to use those hosts.
39717 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39718 hints databases. You should do this at a quiet time of day, because it requires
39719 a database to be locked (and therefore inaccessible to Exim) while it does its
39720 work. Removing records from a DBM file does not normally make the file smaller,
39721 but all the common DBM libraries are able to re-use the space that is released.
39722 After an initial phase of increasing in size, the databases normally reach a
39723 point at which they no longer get any bigger, as long as they are regularly
39726 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39727 databases is likely to keep on increasing.
39732 .section "exim_fixdb" "SECTfixdb"
39733 .cindex "&'exim_fixdb'&"
39734 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39735 Its main use is for testing Exim, but it might also be occasionally useful for
39736 getting round problems in a live system. It has no options, and its interface
39737 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39738 key of a database record can then be entered, and the data for that record is
39741 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39742 except the &'retry'& database, that is the only operation that can be carried
39743 out. For the &'retry'& database, each field is output preceded by a number, and
39744 data for individual fields can be changed by typing the field number followed
39745 by new data, for example:
39749 resets the time of the next delivery attempt. Time values are given as a
39750 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39751 used as optional separators.
39756 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39757 .cindex "mailbox" "maintenance"
39758 .cindex "&'exim_lock'&"
39759 .cindex "locking mailboxes"
39760 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39761 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39762 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39763 a user agent while investigating a problem. The utility requires the name of
39764 the file as its first argument. If the locking is successful, the second
39765 argument is run as a command (using C's &[system()]& function); if there is no
39766 second argument, the value of the SHELL environment variable is used; if this
39767 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39768 is unlocked and the utility ends. The following options are available:
39772 Use &[fcntl()]& locking on the open mailbox.
39775 Use &[flock()]& locking on the open mailbox, provided the operating system
39778 .vitem &%-interval%&
39779 This must be followed by a number, which is a number of seconds; it sets the
39780 interval to sleep between retries (default 3).
39782 .vitem &%-lockfile%&
39783 Create a lock file before opening the mailbox.
39786 Lock the mailbox using MBX rules.
39789 Suppress verification output.
39791 .vitem &%-retries%&
39792 This must be followed by a number; it sets the number of times to try to get
39793 the lock (default 10).
39795 .vitem &%-restore_time%&
39796 This option causes &%exim_lock%& to restore the modified and read times to the
39797 locked file before exiting. This allows you to access a locked mailbox (for
39798 example, to take a backup copy) without disturbing the times that the user
39801 .vitem &%-timeout%&
39802 This must be followed by a number, which is a number of seconds; it sets a
39803 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
39804 default), a non-blocking call is used.
39807 Generate verbose output.
39810 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
39811 default is to create a lock file and also to use &[fcntl()]& locking on the
39812 mailbox, which is the same as Exim's default. The use of &%-flock%& or
39813 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
39814 requires that the directory containing the file be writeable. Locking by lock
39815 file does not last forever; Exim assumes that a lock file is expired if it is
39816 more than 30 minutes old.
39818 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
39819 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
39820 to be taken out on the open mailbox, and an exclusive lock on the file
39821 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
39822 number of the mailbox file. When the locking is released, if an exclusive lock
39823 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
39825 The default output contains verification of the locking that takes place. The
39826 &%-v%& option causes some additional information to be given. The &%-q%& option
39827 suppresses all output except error messages.
39831 exim_lock /var/spool/mail/spqr
39833 runs an interactive shell while the file is locked, whereas
39835 &`exim_lock -q /var/spool/mail/spqr <<End`&
39836 <&'some commands'&>
39839 runs a specific non-interactive sequence of commands while the file is locked,
39840 suppressing all verification output. A single command can be run by a command
39843 exim_lock -q /var/spool/mail/spqr \
39844 "cp /var/spool/mail/spqr /some/where"
39846 Note that if a command is supplied, it must be entirely contained within the
39847 second argument &-- hence the quotes.
39851 . ////////////////////////////////////////////////////////////////////////////
39852 . ////////////////////////////////////////////////////////////////////////////
39854 .chapter "The Exim monitor" "CHAPeximon"
39855 .scindex IIDeximon "Exim monitor" "description"
39856 .cindex "X-windows"
39857 .cindex "&'eximon'&"
39858 .cindex "Local/eximon.conf"
39859 .cindex "&_exim_monitor/EDITME_&"
39860 The Exim monitor is an application which displays in an X window information
39861 about the state of Exim's queue and what Exim is doing. An admin user can
39862 perform certain operations on messages from this GUI interface; however all
39863 such facilities are also available from the command line, and indeed, the
39864 monitor itself makes use of the command line to perform any actions requested.
39868 .section "Running the monitor" "SECID264"
39869 The monitor is started by running the script called &'eximon'&. This is a shell
39870 script that sets up a number of environment variables, and then runs the
39871 binary called &_eximon.bin_&. The default appearance of the monitor window can
39872 be changed by editing the &_Local/eximon.conf_& file created by editing
39873 &_exim_monitor/EDITME_&. Comments in that file describe what the various
39874 parameters are for.
39876 The parameters that get built into the &'eximon'& script can be overridden for
39877 a particular invocation by setting up environment variables of the same names,
39878 preceded by &`EXIMON_`&. For example, a shell command such as
39880 EXIMON_LOG_DEPTH=400 eximon
39882 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
39883 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
39884 overrides the Exim log file configuration. This makes it possible to have
39885 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
39886 syslog messages are routed to a file on the local host.
39888 X resources can be used to change the appearance of the window in the normal
39889 way. For example, a resource setting of the form
39891 Eximon*background: gray94
39893 changes the colour of the background to light grey rather than white. The
39894 stripcharts are drawn with both the data lines and the reference lines in
39895 black. This means that the reference lines are not visible when on top of the
39896 data. However, their colour can be changed by setting a resource called
39897 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
39898 For example, if your X server is running Unix, you could set up lighter
39899 reference lines in the stripcharts by obeying
39902 Eximon*highlight: gray
39905 .cindex "admin user"
39906 In order to see the contents of messages in the queue, and to operate on them,
39907 &'eximon'& must either be run as root or by an admin user.
39909 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
39910 contain X11 resource parameters interpreted by the X11 library. In addition,
39911 if the first parameter starts with the string "gdb" then it is removed and the
39912 binary is invoked under gdb (the parameter is used as the gdb command-name, so
39913 versioned variants of gdb can be invoked).
39915 The monitor's window is divided into three parts. The first contains one or
39916 more stripcharts and two action buttons, the second contains a &"tail"& of the
39917 main log file, and the third is a display of the queue of messages awaiting
39918 delivery, with two more action buttons. The following sections describe these
39919 different parts of the display.
39924 .section "The stripcharts" "SECID265"
39925 .cindex "stripchart"
39926 The first stripchart is always a count of messages in the queue. Its name can
39927 be configured by setting QUEUE_STRIPCHART_NAME in the
39928 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
39929 configuration script by regular expression matches on log file entries, making
39930 it possible to display, for example, counts of messages delivered to certain
39931 hosts or using certain transports. The supplied defaults display counts of
39932 received and delivered messages, and of local and SMTP deliveries. The default
39933 period between stripchart updates is one minute; this can be adjusted by a
39934 parameter in the &_Local/eximon.conf_& file.
39936 The stripchart displays rescale themselves automatically as the value they are
39937 displaying changes. There are always 10 horizontal lines in each chart; the
39938 title string indicates the value of each division when it is greater than one.
39939 For example, &"x2"& means that each division represents a value of 2.
39941 It is also possible to have a stripchart which shows the percentage fullness of
39942 a particular disk partition, which is useful when local deliveries are confined
39943 to a single partition.
39945 .cindex "&%statvfs%& function"
39946 This relies on the availability of the &[statvfs()]& function or equivalent in
39947 the operating system. Most, but not all versions of Unix that support Exim have
39948 this. For this particular stripchart, the top of the chart always represents
39949 100%, and the scale is given as &"x10%"&. This chart is configured by setting
39950 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
39951 &_Local/eximon.conf_& file.
39956 .section "Main action buttons" "SECID266"
39957 .cindex "size" "of monitor window"
39958 .cindex "Exim monitor" "window size"
39959 .cindex "window size"
39960 Below the stripcharts there is an action button for quitting the monitor. Next
39961 to this is another button marked &"Size"&. They are placed here so that
39962 shrinking the window to its default minimum size leaves just the queue count
39963 stripchart and these two buttons visible. Pressing the &"Size"& button causes
39964 the window to expand to its maximum size, unless it is already at the maximum,
39965 in which case it is reduced to its minimum.
39967 When expanding to the maximum, if the window cannot be fully seen where it
39968 currently is, it is moved back to where it was the last time it was at full
39969 size. When it is expanding from its minimum size, the old position is
39970 remembered, and next time it is reduced to the minimum it is moved back there.
39972 The idea is that you can keep a reduced window just showing one or two
39973 stripcharts at a convenient place on your screen, easily expand it to show
39974 the full window when required, and just as easily put it back to what it was.
39975 The idea is copied from what the &'twm'& window manager does for its
39976 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
39977 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
39979 Normally, the monitor starts up with the window at its full size, but it can be
39980 built so that it starts up with the window at its smallest size, by setting
39981 START_SMALL=yes in &_Local/eximon.conf_&.
39985 .section "The log display" "SECID267"
39986 .cindex "log" "tail of; in monitor"
39987 The second section of the window is an area in which a display of the tail of
39988 the main log is maintained.
39989 To save space on the screen, the timestamp on each log line is shortened by
39990 removing the date and, if &%log_timezone%& is set, the timezone.
39991 The log tail is not available when the only destination for logging data is
39992 syslog, unless the syslog lines are routed to a local file whose name is passed
39993 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
39995 The log sub-window has a scroll bar at its lefthand side which can be used to
39996 move back to look at earlier text, and the up and down arrow keys also have a
39997 scrolling effect. The amount of log that is kept depends on the setting of
39998 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
39999 to use. When this is full, the earlier 50% of data is discarded &-- this is
40000 much more efficient than throwing it away line by line. The sub-window also has
40001 a horizontal scroll bar for accessing the ends of long log lines. This is the
40002 only means of horizontal scrolling; the right and left arrow keys are not
40003 available. Text can be cut from this part of the window using the mouse in the
40004 normal way. The size of this subwindow is controlled by parameters in the
40005 configuration file &_Local/eximon.conf_&.
40007 Searches of the text in the log window can be carried out by means of the ^R
40008 and ^S keystrokes, which default to a reverse and a forward search,
40009 respectively. The search covers only the text that is displayed in the window.
40010 It cannot go further back up the log.
40012 The point from which the search starts is indicated by a caret marker. This is
40013 normally at the end of the text in the window, but can be positioned explicitly
40014 by pointing and clicking with the left mouse button, and is moved automatically
40015 by a successful search. If new text arrives in the window when it is scrolled
40016 back, the caret remains where it is, but if the window is not scrolled back,
40017 the caret is moved to the end of the new text.
40019 Pressing ^R or ^S pops up a window into which the search text can be typed.
40020 There are buttons for selecting forward or reverse searching, for carrying out
40021 the search, and for cancelling. If the &"Search"& button is pressed, the search
40022 happens and the window remains so that further searches can be done. If the
40023 &"Return"& key is pressed, a single search is done and the window is closed. If
40024 ^C is typed the search is cancelled.
40026 The searching facility is implemented using the facilities of the Athena text
40027 widget. By default this pops up a window containing both &"search"& and
40028 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40029 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40030 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40031 provided version of &%TextPop%& when the remaining parts of the text widget
40032 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40033 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40034 on these systems, at the expense of having unwanted items in the search popup
40039 .section "The queue display" "SECID268"
40040 .cindex "queue" "display in monitor"
40041 The bottom section of the monitor window contains a list of all messages that
40042 are in the queue, which includes those currently being received or delivered,
40043 as well as those awaiting delivery. The size of this subwindow is controlled by
40044 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40045 at which it is updated is controlled by another parameter in the same file &--
40046 the default is 5 minutes, since queue scans can be quite expensive. However,
40047 there is an &"Update"& action button just above the display which can be used
40048 to force an update of the queue display at any time.
40050 When a host is down for some time, a lot of pending mail can build up for it,
40051 and this can make it hard to deal with other messages in the queue. To help
40052 with this situation there is a button next to &"Update"& called &"Hide"&. If
40053 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40054 type anything in here and press &"Return"&, the text is added to a chain of
40055 such texts, and if every undelivered address in a message matches at least one
40056 of the texts, the message is not displayed.
40058 If there is an address that does not match any of the texts, all the addresses
40059 are displayed as normal. The matching happens on the ends of addresses so, for
40060 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40061 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40062 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40063 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40064 a hide request is automatically cancelled after one hour.
40066 While the dialogue box is displayed, you can't press any buttons or do anything
40067 else to the monitor window. For this reason, if you want to cut text from the
40068 queue display to use in the dialogue box, you have to do the cutting before
40069 pressing the &"Hide"& button.
40071 The queue display contains, for each unhidden queued message, the length of
40072 time it has been in the queue, the size of the message, the message id, the
40073 message sender, and the first undelivered recipient, all on one line. If it is
40074 a bounce message, the sender is shown as &"<>"&. If there is more than one
40075 recipient to which the message has not yet been delivered, subsequent ones are
40076 listed on additional lines, up to a maximum configured number, following which
40077 an ellipsis is displayed. Recipients that have already received the message are
40080 .cindex "frozen messages" "display"
40081 If a message is frozen, an asterisk is displayed at the left-hand side.
40083 The queue display has a vertical scroll bar, and can also be scrolled by means
40084 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40085 The text searching facilities, as described above for the log window, are also
40086 available, but the caret is always moved to the end of the text when the queue
40087 display is updated.
40091 .section "The queue menu" "SECID269"
40092 .cindex "queue" "menu in monitor"
40093 If the &%shift%& key is held down and the left button is clicked when the mouse
40094 pointer is over the text for any message, an action menu pops up, and the first
40095 line of the queue display for the message is highlighted. This does not affect
40098 If you want to use some other event for popping up the menu, you can set the
40099 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40100 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40101 value set in this parameter is a standard X event description. For example, to
40102 run eximon using &%ctrl%& rather than &%shift%& you could use
40104 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40106 The title of the menu is the message id, and it contains entries which act as
40110 &'message log'&: The contents of the message log for the message are displayed
40111 in a new text window.
40113 &'headers'&: Information from the spool file that contains the envelope
40114 information and headers is displayed in a new text window. See chapter
40115 &<<CHAPspool>>& for a description of the format of spool files.
40117 &'body'&: The contents of the spool file containing the body of the message are
40118 displayed in a new text window. There is a default limit of 20,000 bytes to the
40119 amount of data displayed. This can be changed by setting the BODY_MAX
40120 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40122 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40123 delivery of the message. This causes an automatic thaw if the message is
40124 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40125 a new text window. The delivery is run in a separate process, to avoid holding
40126 up the monitor while the delivery proceeds.
40128 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40129 that the message be frozen.
40131 .cindex "thawing messages"
40132 .cindex "unfreezing messages"
40133 .cindex "frozen messages" "thawing"
40134 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40135 that the message be thawed.
40137 .cindex "delivery" "forcing failure"
40138 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40139 that Exim gives up trying to deliver the message. A bounce message is generated
40140 for any remaining undelivered addresses.
40142 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40143 that the message be deleted from the system without generating a bounce
40146 &'add recipient'&: A dialog box is displayed into which a recipient address can
40147 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40148 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40149 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40150 causes a call to Exim to be made using the &%-Mar%& option to request that an
40151 additional recipient be added to the message, unless the entry box is empty, in
40152 which case no action is taken.
40154 &'mark delivered'&: A dialog box is displayed into which a recipient address
40155 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40156 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40157 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40158 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40159 recipient address as already delivered, unless the entry box is empty, in which
40160 case no action is taken.
40162 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40163 mark all recipient addresses as already delivered.
40165 &'edit sender'&: A dialog box is displayed initialized with the current
40166 sender's address. Pressing RETURN causes a call to Exim to be made using the
40167 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40168 in which case no action is taken. If you want to set an empty sender (as in
40169 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40170 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40171 the address is qualified with that domain.
40174 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40175 other cases when a call to Exim is made, if there is any output from Exim (in
40176 particular, if the command fails) a window containing the command and the
40177 output is displayed. Otherwise, the results of the action are normally apparent
40178 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40179 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40180 if no output is generated.
40182 The queue display is automatically updated for actions such as freezing and
40183 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40184 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40185 force an update of the display after one of these actions.
40187 In any text window that is displayed as result of a menu action, the normal
40188 cut-and-paste facility is available, and searching can be carried out using ^R
40189 and ^S, as described above for the log tail window.
40196 . ////////////////////////////////////////////////////////////////////////////
40197 . ////////////////////////////////////////////////////////////////////////////
40199 .chapter "Security considerations" "CHAPsecurity"
40200 .scindex IIDsecurcon "security" "discussion of"
40201 This chapter discusses a number of issues concerned with security, some of
40202 which are also covered in other parts of this manual.
40204 For reasons that this author does not understand, some people have promoted
40205 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40206 existence of this chapter in the documentation. However, the intent of the
40207 chapter is simply to describe the way Exim works in relation to certain
40208 security concerns, not to make any specific claims about the effectiveness of
40209 its security as compared with other MTAs.
40211 What follows is a description of the way Exim is supposed to be. Best efforts
40212 have been made to try to ensure that the code agrees with the theory, but an
40213 absence of bugs can never be guaranteed. Any that are reported will get fixed
40214 as soon as possible.
40217 .section "Building a more &""hardened""& Exim" "SECID286"
40218 .cindex "security" "build-time features"
40219 There are a number of build-time options that can be set in &_Local/Makefile_&
40220 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40221 Exim administrator who does not have the root password, or by someone who has
40222 penetrated the Exim (but not the root) account. These options are as follows:
40225 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40226 start of any filenames used with the &%-C%& option. When it is set, these
40227 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40228 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40229 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40230 default setting for &%ALT_CONFIG_PREFIX%&.
40232 If the permitted configuration files are confined to a directory to
40233 which only root has access, this guards against someone who has broken
40234 into the Exim account from running a privileged Exim with an arbitrary
40235 configuration file, and using it to break into other accounts.
40238 If a non-trusted configuration file (i.e. not the default configuration file
40239 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40240 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40241 the next item), then root privilege is retained only if the caller of Exim is
40242 root. This locks out the possibility of testing a configuration using &%-C%&
40243 right through message reception and delivery, even if the caller is root. The
40244 reception works, but by that time, Exim is running as the Exim user, so when
40245 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40246 privilege to be lost. However, root can test reception and delivery using two
40250 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40251 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40252 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40253 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40254 the restrictive side. Requiring build-time selection of safe macros is onerous
40255 but this option is intended solely as a transition mechanism to permit
40256 previously-working configurations to continue to work after release 4.73.
40258 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40261 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40262 never to be used for any deliveries. This is like the &%never_users%& runtime
40263 option, but it cannot be overridden; the runtime option adds additional users
40264 to the list. The default setting is &"root"&; this prevents a non-root user who
40265 is permitted to modify the runtime file from using Exim as a way to get root.
40270 .section "Root privilege" "SECID270"
40272 .cindex "root privilege"
40273 The Exim binary is normally setuid to root, which means that it gains root
40274 privilege (runs as root) when it starts execution. In some special cases (for
40275 example, when the daemon is not in use and there are no local deliveries), it
40276 may be possible to run Exim setuid to some user other than root. This is
40277 discussed in the next section. However, in most installations, root privilege
40278 is required for two things:
40281 To set up a socket connected to the standard SMTP port (25) when initialising
40282 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40285 To be able to change uid and gid in order to read users' &_.forward_& files and
40286 perform local deliveries as the receiving user or as specified in the
40290 It is not necessary to be root to do any of the other things Exim does, such as
40291 receiving messages and delivering them externally over SMTP, and it is
40292 obviously more secure if Exim does not run as root except when necessary.
40293 For this reason, a user and group for Exim to use must be defined in
40294 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40295 group"&. Their values can be changed by the runtime configuration, though this
40296 is not recommended. Often a user called &'exim'& is used, but some sites use
40297 &'mail'& or another user name altogether.
40299 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40300 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40301 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40303 After a new Exim process has interpreted its command line options, it changes
40304 uid and gid in the following cases:
40309 If the &%-C%& option is used to specify an alternate configuration file, or if
40310 the &%-D%& option is used to define macro values for the configuration, and the
40311 calling process is not running as root, the uid and gid are changed to those of
40312 the calling process.
40313 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40314 option may not be used at all.
40315 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40316 can be supplied if the calling process is running as root, the Exim run-time
40317 user or CONFIGURE_OWNER, if defined.
40322 If the expansion test option (&%-be%&) or one of the filter testing options
40323 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40326 If the process is not a daemon process or a queue runner process or a delivery
40327 process or a process for testing address routing (started with &%-bt%&), the
40328 uid and gid are changed to the Exim user and group. This means that Exim always
40329 runs under its own uid and gid when receiving messages. This also applies when
40330 testing address verification
40333 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40336 For a daemon, queue runner, delivery, or address testing process, the uid
40337 remains as root at this stage, but the gid is changed to the Exim group.
40340 The processes that initially retain root privilege behave as follows:
40343 A daemon process changes the gid to the Exim group and the uid to the Exim
40344 user after setting up one or more listening sockets. The &[initgroups()]&
40345 function is called, so that if the Exim user is in any additional groups, they
40346 will be used during message reception.
40348 A queue runner process retains root privilege throughout its execution. Its
40349 job is to fork a controlled sequence of delivery processes.
40351 A delivery process retains root privilege throughout most of its execution,
40352 but any actual deliveries (that is, the transports themselves) are run in
40353 subprocesses which always change to a non-root uid and gid. For local
40354 deliveries this is typically the uid and gid of the owner of the mailbox; for
40355 remote deliveries, the Exim uid and gid are used. Once all the delivery
40356 subprocesses have been run, a delivery process changes to the Exim uid and gid
40357 while doing post-delivery tidying up such as updating the retry database and
40358 generating bounce and warning messages.
40360 While the recipient addresses in a message are being routed, the delivery
40361 process runs as root. However, if a user's filter file has to be processed,
40362 this is done in a subprocess that runs under the individual user's uid and
40363 gid. A system filter is run as root unless &%system_filter_user%& is set.
40365 A process that is testing addresses (the &%-bt%& option) runs as root so that
40366 the routing is done in the same environment as a message delivery.
40372 .section "Running Exim without privilege" "SECTrunexiwitpri"
40373 .cindex "privilege, running without"
40374 .cindex "unprivileged running"
40375 .cindex "root privilege" "running without"
40376 Some installations like to run Exim in an unprivileged state for more of its
40377 operation, for added security. Support for this mode of operation is provided
40378 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40379 gid are changed to the Exim user and group at the start of a delivery process
40380 (and also queue runner and address testing processes). This means that address
40381 routing is no longer run as root, and the deliveries themselves cannot change
40385 .cindex "daemon" "restarting"
40386 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40387 that the daemon can still be started in the usual way, and it can respond
40388 correctly to SIGHUP because the re-invocation regains root privilege.
40390 An alternative approach is to make Exim setuid to the Exim user and also setgid
40391 to the Exim group. If you do this, the daemon must be started from a root
40392 process. (Calling Exim from a root process makes it behave in the way it does
40393 when it is setuid root.) However, the daemon cannot restart itself after a
40394 SIGHUP signal because it cannot regain privilege.
40396 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40397 stops Exim from trying to re-invoke itself to do a delivery after a message has
40398 been received. Such a re-invocation is a waste of resources because it has no
40401 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40402 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40403 to the Exim user seems a clean approach, but there is one complication:
40405 In this style of operation, Exim is running with the real uid and gid set to
40406 those of the calling process, and the effective uid/gid set to Exim's values.
40407 Ideally, any association with the calling process' uid/gid should be dropped,
40408 that is, the real uid/gid should be reset to the effective values so as to
40409 discard any privileges that the caller may have. While some operating systems
40410 have a function that permits this action for a non-root effective uid, quite a
40411 number of them do not. Because of this lack of standardization, Exim does not
40412 address this problem at this time.
40414 For this reason, the recommended approach for &"mostly unprivileged"& running
40415 is to keep the Exim binary setuid to root, and to set
40416 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40417 be used in the most straightforward way.
40419 If you configure Exim not to run delivery processes as root, there are a
40420 number of restrictions on what you can do:
40423 You can deliver only as the Exim user/group. You should explicitly use the
40424 &%user%& and &%group%& options to override routers or local transports that
40425 normally deliver as the recipient. This makes sure that configurations that
40426 work in this mode function the same way in normal mode. Any implicit or
40427 explicit specification of another user causes an error.
40429 Use of &_.forward_& files is severely restricted, such that it is usually
40430 not worthwhile to include them in the configuration.
40432 Users who wish to use &_.forward_& would have to make their home directory and
40433 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40434 and their equivalents in Exim filters, cannot be used. While they could be
40435 enabled in the Exim user's name, that would be insecure and not very useful.
40437 Unless the local user mailboxes are all owned by the Exim user (possible in
40438 some POP3 or IMAP-only environments):
40441 They must be owned by the Exim group and be writeable by that group. This
40442 implies you must set &%mode%& in the appendfile configuration, as well as the
40443 mode of the mailbox files themselves.
40445 You must set &%no_check_owner%&, since most or all of the files will not be
40446 owned by the Exim user.
40448 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40449 on a newly created mailbox when unprivileged. This also implies that new
40450 mailboxes need to be created manually.
40455 These restrictions severely restrict what can be done in local deliveries.
40456 However, there are no restrictions on remote deliveries. If you are running a
40457 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40458 gives more security at essentially no cost.
40460 If you are using the &%mua_wrapper%& facility (see chapter
40461 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40466 .section "Delivering to local files" "SECID271"
40467 Full details of the checks applied by &(appendfile)& before it writes to a file
40468 are given in chapter &<<CHAPappendfile>>&.
40472 .section "Running local commands" "SECTsecconslocalcmds"
40473 .cindex "security" "local commands"
40474 .cindex "security" "command injection attacks"
40475 There are a number of ways in which an administrator can configure Exim to run
40476 commands based upon received, untrustworthy, data. Further, in some
40477 configurations a user who can control a &_.forward_& file can also arrange to
40478 run commands. Configuration to check includes, but is not limited to:
40481 Use of &%use_shell%& in the pipe transport: various forms of shell command
40482 injection may be possible with this option present. It is dangerous and should
40483 be used only with considerable caution. Consider constraints which whitelist
40484 allowed characters in a variable which is to be used in a pipe transport that
40485 has &%use_shell%& enabled.
40487 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40488 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40489 &_.forward_& files in a redirect router. If Exim is running on a central mail
40490 hub to which ordinary users do not have shell access, but home directories are
40491 NFS mounted (for instance) then administrators should review the list of these
40492 forbid options available, and should bear in mind that the options that may
40493 need forbidding can change as new features are added between releases.
40495 The &%${run...}%& expansion item does not use a shell by default, but
40496 administrators can configure use of &_/bin/sh_& as part of the command.
40497 Such invocations should be viewed with prejudicial suspicion.
40499 Administrators who use embedded Perl are advised to explore how Perl's
40500 taint checking might apply to their usage.
40502 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40503 administrators are well advised to view its use with suspicion, in case (for
40504 instance) it allows a local-part to contain embedded Exim directives.
40506 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40507 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40508 each can reference arbitrary lists and files, rather than just being a list
40510 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40511 real-world security vulnerabilities caused by its use with untrustworthy data
40512 injected in, for SQL injection attacks.
40513 Consider the use of the &%inlisti%& expansion condition instead.
40519 .section "Trust in configuration data" "SECTsecconfdata"
40520 .cindex "security" "data sources"
40521 .cindex "security" "regular expressions"
40522 .cindex "regular expressions" "security"
40523 .cindex "PCRE" "security"
40524 If configuration data for Exim can come from untrustworthy sources, there
40525 are some issues to be aware of:
40528 Use of &%${expand...}%& may provide a path for shell injection attacks.
40530 Letting untrusted data provide a regular expression is unwise.
40532 Using &%${match...}%& to apply a fixed regular expression against untrusted
40533 data may result in pathological behaviour within PCRE. Be aware of what
40534 "backtracking" means and consider options for being more strict with a regular
40535 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40536 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40537 possessive quantifiers or just not using regular expressions against untrusted
40540 It can be important to correctly use &%${quote:...}%&,
40541 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40542 items to ensure that data is correctly constructed.
40544 Some lookups might return multiple results, even though normal usage is only
40545 expected to yield one result.
40551 .section "IPv4 source routing" "SECID272"
40552 .cindex "source routing" "in IP packets"
40553 .cindex "IP source routing"
40554 Many operating systems suppress IP source-routed packets in the kernel, but
40555 some cannot be made to do this, so Exim does its own check. It logs incoming
40556 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40557 IPv6. No special checking is currently done.
40561 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40562 Support for these SMTP commands is disabled by default. If required, they can
40563 be enabled by defining suitable ACLs.
40568 .section "Privileged users" "SECID274"
40569 .cindex "trusted users"
40570 .cindex "admin user"
40571 .cindex "privileged user"
40572 .cindex "user" "trusted"
40573 .cindex "user" "admin"
40574 Exim recognizes two sets of users with special privileges. Trusted users are
40575 able to submit new messages to Exim locally, but supply their own sender
40576 addresses and information about a sending host. For other users submitting
40577 local messages, Exim sets up the sender address from the uid, and doesn't
40578 permit a remote host to be specified.
40581 However, an untrusted user is permitted to use the &%-f%& command line option
40582 in the special form &%-f <>%& to indicate that a delivery failure for the
40583 message should not cause an error report. This affects the message's envelope,
40584 but it does not affect the &'Sender:'& header. Untrusted users may also be
40585 permitted to use specific forms of address with the &%-f%& option by setting
40586 the &%untrusted_set_sender%& option.
40588 Trusted users are used to run processes that receive mail messages from some
40589 other mail domain and pass them on to Exim for delivery either locally, or over
40590 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40591 as any user listed in the &%trusted_users%& configuration option, or under any
40592 group listed in the &%trusted_groups%& option.
40594 Admin users are permitted to do things to the messages on Exim's queue. They
40595 can freeze or thaw messages, cause them to be returned to their senders, remove
40596 them entirely, or modify them in various ways. In addition, admin users can run
40597 the Exim monitor and see all the information it is capable of providing, which
40598 includes the contents of files on the spool.
40602 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40603 delivery of messages on its queue is restricted to admin users. This
40604 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40605 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40606 queue is also restricted to admin users. This restriction can be relaxed by
40607 setting &%no_queue_list_requires_admin%&.
40609 Exim recognizes an admin user if the calling process is running as root or as
40610 the Exim user or if any of the groups associated with the calling process is
40611 the Exim group. It is not necessary actually to be running under the Exim
40612 group. However, if admin users who are not root or the Exim user are to access
40613 the contents of files on the spool via the Exim monitor (which runs
40614 unprivileged), Exim must be built to allow group read access to its spool
40617 By default, regular users are trusted to perform basic testing and
40618 introspection commands, as themselves. This setting can be tightened by
40619 setting the &%commandline_checks_require_admin%& option.
40620 This affects most of the checking options,
40621 such as &%-be%& and anything else &%-b*%&.
40624 .section "Spool files" "SECID275"
40625 .cindex "spool directory" "files"
40626 Exim's spool directory and everything it contains is owned by the Exim user and
40627 set to the Exim group. The mode for spool files is defined in the
40628 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40629 any user who is a member of the Exim group can access these files.
40633 .section "Use of argv[0]" "SECID276"
40634 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40635 of specific strings, Exim assumes certain options. For example, calling Exim
40636 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40637 to calling it with the option &%-bS%&. There are no security implications in
40642 .section "Use of %f formatting" "SECID277"
40643 The only use made of &"%f"& by Exim is in formatting load average values. These
40644 are actually stored in integer variables as 1000 times the load average.
40645 Consequently, their range is limited and so therefore is the length of the
40650 .section "Embedded Exim path" "SECID278"
40651 Exim uses its own path name, which is embedded in the code, only when it needs
40652 to re-exec in order to regain root privilege. Therefore, it is not root when it
40653 does so. If some bug allowed the path to get overwritten, it would lead to an
40654 arbitrary program's being run as exim, not as root.
40658 .section "Dynamic module directory" "SECTdynmoddir"
40659 Any dynamically loadable modules must be installed into the directory
40660 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40664 .section "Use of sprintf()" "SECID279"
40665 .cindex "&[sprintf()]&"
40666 A large number of occurrences of &"sprintf"& in the code are actually calls to
40667 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40668 The intermediate formatting is done into a large fixed buffer by a function
40669 that runs through the format string itself, and checks the length of each
40670 conversion before performing it, thus preventing buffer overruns.
40672 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40673 the output buffer is known to be sufficiently long to contain the converted
40678 .section "Use of debug_printf() and log_write()" "SECID280"
40679 Arbitrary strings are passed to both these functions, but they do their
40680 formatting by calling the function &'string_vformat()'&, which runs through
40681 the format string itself, and checks the length of each conversion.
40685 .section "Use of strcat() and strcpy()" "SECID281"
40686 These are used only in cases where the output buffer is known to be large
40687 enough to hold the result.
40688 .ecindex IIDsecurcon
40693 . ////////////////////////////////////////////////////////////////////////////
40694 . ////////////////////////////////////////////////////////////////////////////
40696 .chapter "Format of spool files" "CHAPspool"
40697 .scindex IIDforspo1 "format" "spool files"
40698 .scindex IIDforspo2 "spool directory" "format of files"
40699 .scindex IIDforspo3 "spool files" "format of"
40700 .cindex "spool files" "editing"
40701 A message on Exim's queue consists of two files, whose names are the message id
40702 followed by -D and -H, respectively. The data portion of the message is kept in
40703 the -D file on its own. The message's envelope, status, and headers are all
40704 kept in the -H file, whose format is described in this chapter. Each of these
40705 two files contains the final component of its own name as its first line. This
40706 is insurance against disk crashes where the directory is lost but the files
40707 themselves are recoverable.
40709 The file formats may be changed, or new formats added, at any release.
40710 Spool files are not intended as an interface to other programs
40711 and should not be used as such.
40713 Some people are tempted into editing -D files in order to modify messages. You
40714 need to be extremely careful if you do this; it is not recommended and you are
40715 on your own if you do it. Here are some of the pitfalls:
40718 You must ensure that Exim does not try to deliver the message while you are
40719 fiddling with it. The safest way is to take out a write lock on the -D file,
40720 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40721 place, the lock will be retained. If you write a new file and rename it, the
40722 lock will be lost at the instant of rename.
40724 .vindex "&$body_linecount$&"
40725 If you change the number of lines in the file, the value of
40726 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40727 cause incomplete transmission of messages or undeliverable messages.
40729 If the message is in MIME format, you must take care not to break it.
40731 If the message is cryptographically signed, any change will invalidate the
40734 All in all, modifying -D files is fraught with danger.
40736 Files whose names end with -J may also be seen in the &_input_& directory (or
40737 its subdirectories when &%split_spool_directory%& is set). These are journal
40738 files, used to record addresses to which the message has been delivered during
40739 the course of a delivery attempt. If there are still undelivered recipients at
40740 the end, the -H file is updated, and the -J file is deleted. If, however, there
40741 is some kind of crash (for example, a power outage) before this happens, the -J
40742 file remains in existence. When Exim next processes the message, it notices the
40743 -J file and uses it to update the -H file before starting the next delivery
40746 Files whose names end with -K or .eml may also be seen in the spool.
40747 These are temporaries used for DKIM or malware processing, when that is used.
40748 They should be tidied up by normal operations; any old ones are probably
40749 relics of crashes and can be removed.
40751 .section "Format of the -H file" "SECID282"
40752 .cindex "uid (user id)" "in spool file"
40753 .cindex "gid (group id)" "in spool file"
40754 The second line of the -H file contains the login name for the uid of the
40755 process that called Exim to read the message, followed by the numerical uid and
40756 gid. For a locally generated message, this is normally the user who sent the
40757 message. For a message received over TCP/IP via the daemon, it is
40758 normally the Exim user.
40760 The third line of the file contains the address of the message's sender as
40761 transmitted in the envelope, contained in angle brackets. The sender address is
40762 empty for bounce messages. For incoming SMTP mail, the sender address is given
40763 in the MAIL command. For locally generated mail, the sender address is
40764 created by Exim from the login name of the current user and the configured
40765 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40766 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40767 &"<>"& or an address that matches &%untrusted_set_senders%&.
40769 The fourth line contains two numbers. The first is the time that the message
40770 was received, in the conventional Unix form &-- the number of seconds since the
40771 start of the epoch. The second number is a count of the number of messages
40772 warning of delayed delivery that have been sent to the sender.
40774 There follow a number of lines starting with a hyphen. These can appear in any
40775 order, and are omitted when not relevant:
40778 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40779 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40780 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40781 recognized, to provide backward compatibility. In the old format, a line of
40782 this form is present for every ACL variable that is not empty. The number
40783 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40784 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40785 the data string for the variable. The string itself starts at the beginning of
40786 the next line, and is followed by a newline character. It may contain internal
40789 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
40790 A line of this form is present for every ACL connection variable that is
40791 defined. Note that there is a space between &%-aclc%& and the rest of the name.
40792 The length is the length of the data string for the variable. The string itself
40793 starts at the beginning of the next line, and is followed by a newline
40794 character. It may contain internal newlines.
40796 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
40797 A line of this form is present for every ACL message variable that is defined.
40798 Note that there is a space between &%-aclm%& and the rest of the name. The
40799 length is the length of the data string for the variable. The string itself
40800 starts at the beginning of the next line, and is followed by a newline
40801 character. It may contain internal newlines.
40803 .vitem "&%-active_hostname%&&~<&'hostname'&>"
40804 This is present if, when the message was received over SMTP, the value of
40805 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
40807 .vitem &%-allow_unqualified_recipient%&
40808 This is present if unqualified recipient addresses are permitted in header
40809 lines (to stop such addresses from being qualified if rewriting occurs at
40810 transport time). Local messages that were input using &%-bnq%& and remote
40811 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
40813 .vitem &%-allow_unqualified_sender%&
40814 This is present if unqualified sender addresses are permitted in header lines
40815 (to stop such addresses from being qualified if rewriting occurs at transport
40816 time). Local messages that were input using &%-bnq%& and remote messages from
40817 hosts that match &%sender_unqualified_hosts%& set this flag.
40819 .vitem "&%-auth_id%&&~<&'text'&>"
40820 The id information for a message received on an authenticated SMTP connection
40821 &-- the value of the &$authenticated_id$& variable.
40823 .vitem "&%-auth_sender%&&~<&'address'&>"
40824 The address of an authenticated sender &-- the value of the
40825 &$authenticated_sender$& variable.
40827 .vitem "&%-body_linecount%&&~<&'number'&>"
40828 This records the number of lines in the body of the message, and is
40829 present unless &%-spool_file_wireformat%& is.
40831 .vitem "&%-body_zerocount%&&~<&'number'&>"
40832 This records the number of binary zero bytes in the body of the message, and is
40833 present if the number is greater than zero.
40835 .vitem &%-deliver_firsttime%&
40836 This is written when a new message is first added to the spool. When the spool
40837 file is updated after a deferral, it is omitted.
40839 .vitem "&%-frozen%&&~<&'time'&>"
40840 .cindex "frozen messages" "spool data"
40841 The message is frozen, and the freezing happened at <&'time'&>.
40843 .vitem "&%-helo_name%&&~<&'text'&>"
40844 This records the host name as specified by a remote host in a HELO or EHLO
40847 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
40848 This records the IP address of the host from which the message was received and
40849 the remote port number that was used. It is omitted for locally generated
40852 .vitem "&%-host_auth%&&~<&'text'&>"
40853 If the message was received on an authenticated SMTP connection, this records
40854 the name of the authenticator &-- the value of the
40855 &$sender_host_authenticated$& variable.
40857 .vitem &%-host_lookup_failed%&
40858 This is present if an attempt to look up the sending host's name from its IP
40859 address failed. It corresponds to the &$host_lookup_failed$& variable.
40861 .vitem "&%-host_name%&&~<&'text'&>"
40862 .cindex "reverse DNS lookup"
40863 .cindex "DNS" "reverse lookup"
40864 This records the name of the remote host from which the message was received,
40865 if the host name was looked up from the IP address when the message was being
40866 received. It is not present if no reverse lookup was done.
40868 .vitem "&%-ident%&&~<&'text'&>"
40869 For locally submitted messages, this records the login of the originating user,
40870 unless it was a trusted user and the &%-oMt%& option was used to specify an
40871 ident value. For messages received over TCP/IP, this records the ident string
40872 supplied by the remote host, if any.
40874 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
40875 This records the IP address of the local interface and the port number through
40876 which a message was received from a remote host. It is omitted for locally
40877 generated messages.
40880 The message is from a local sender.
40882 .vitem &%-localerror%&
40883 The message is a locally-generated bounce message.
40885 .vitem "&%-local_scan%&&~<&'string'&>"
40886 This records the data string that was returned by the &[local_scan()]& function
40887 when the message was received &-- the value of the &$local_scan_data$&
40888 variable. It is omitted if no data was returned.
40890 .vitem &%-manual_thaw%&
40891 The message was frozen but has been thawed manually, that is, by an explicit
40892 Exim command rather than via the auto-thaw process.
40895 A testing delivery process was started using the &%-N%& option to suppress any
40896 actual deliveries, but delivery was deferred. At any further delivery attempts,
40899 .vitem &%-received_protocol%&
40900 This records the value of the &$received_protocol$& variable, which contains
40901 the name of the protocol by which the message was received.
40903 .vitem &%-sender_set_untrusted%&
40904 The envelope sender of this message was set by an untrusted local caller (used
40905 to ensure that the caller is displayed in queue listings).
40907 .vitem "&%-spam_score_int%&&~<&'number'&>"
40908 If a message was scanned by SpamAssassin, this is present. It records the value
40909 of &$spam_score_int$&.
40911 .vitem &%-spool_file_wireformat%&
40912 The -D file for this message is in wire-format (for ESMTP CHUNKING)
40913 rather than Unix-format.
40914 The line-ending is CRLF rather than newline.
40915 There is still, however, no leading-dot-stuffing.
40917 .vitem &%-tls_certificate_verified%&
40918 A TLS certificate was received from the client that sent this message, and the
40919 certificate was verified by the server.
40921 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
40922 When the message was received over an encrypted connection, this records the
40923 name of the cipher suite that was used.
40925 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
40926 When the message was received over an encrypted connection, and a certificate
40927 was received from the client, this records the Distinguished Name from that
40931 Any of the above may have an extra hyphen prepended, to indicate the the
40932 corresponding data is untrusted.
40934 Following the options there is a list of those addresses to which the message
40935 is not to be delivered. This set of addresses is initialized from the command
40936 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
40937 is set; otherwise it starts out empty. Whenever a successful delivery is made,
40938 the address is added to this set. The addresses are kept internally as a
40939 balanced binary tree, and it is a representation of that tree which is written
40940 to the spool file. If an address is expanded via an alias or forward file, the
40941 original address is added to the tree when deliveries to all its child
40942 addresses are complete.
40944 If the tree is empty, there is a single line in the spool file containing just
40945 the text &"XX"&. Otherwise, each line consists of two letters, which are either
40946 Y or N, followed by an address. The address is the value for the node of the
40947 tree, and the letters indicate whether the node has a left branch and/or a
40948 right branch attached to it, respectively. If branches exist, they immediately
40949 follow. Here is an example of a three-node tree:
40951 YY darcy@austen.fict.example
40952 NN alice@wonderland.fict.example
40953 NN editor@thesaurus.ref.example
40955 After the non-recipients tree, there is a list of the message's recipients.
40956 This is a simple list, preceded by a count. It includes all the original
40957 recipients of the message, including those to whom the message has already been
40958 delivered. In the simplest case, the list contains one address per line. For
40962 editor@thesaurus.ref.example
40963 darcy@austen.fict.example
40965 alice@wonderland.fict.example
40967 However, when a child address has been added to the top-level addresses as a
40968 result of the use of the &%one_time%& option on a &(redirect)& router, each
40969 line is of the following form:
40971 <&'top-level address'&> <&'errors_to address'&> &&&
40972 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
40974 The 01 flag bit indicates the presence of the three other fields that follow
40975 the top-level address. Other bits may be used in future to support additional
40976 fields. The <&'parent number'&> is the offset in the recipients list of the
40977 original parent of the &"one time"& address. The first two fields are the
40978 envelope sender that is associated with this address and its length. If the
40979 length is zero, there is no special envelope sender (there are then two space
40980 characters in the line). A non-empty field can arise from a &(redirect)& router
40981 that has an &%errors_to%& setting.
40984 A blank line separates the envelope and status information from the headers
40985 which follow. A header may occupy several lines of the file, and to save effort
40986 when reading it in, each header is preceded by a number and an identifying
40987 character. The number is the number of characters in the header, including any
40988 embedded newlines and the terminating newline. The character is one of the
40992 .row <&'blank'&> "header in which Exim has no special interest"
40993 .row &`B`& "&'Bcc:'& header"
40994 .row &`C`& "&'Cc:'& header"
40995 .row &`F`& "&'From:'& header"
40996 .row &`I`& "&'Message-id:'& header"
40997 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
40998 .row &`R`& "&'Reply-To:'& header"
40999 .row &`S`& "&'Sender:'& header"
41000 .row &`T`& "&'To:'& header"
41001 .row &`*`& "replaced or deleted header"
41004 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41005 purposes. They are not transmitted when the message is delivered. Here is a
41006 typical set of headers:
41008 111P Received: by hobbit.fict.example with local (Exim 4.00)
41009 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41010 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41011 038* X-rewrote-sender: bb@hobbit.fict.example
41012 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41013 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41014 099* To: alice@wonderland.fict.example, rdo@foundation,
41015 darcy@austen.fict.example, editor@thesaurus.ref.example
41016 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41017 darcy@austen.fict.example, editor@thesaurus.ref.example
41018 038 Date: Fri, 11 May 2001 10:28:59 +0100
41020 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41021 &'To:'& header have been rewritten, the last one because routing expanded the
41022 unqualified domain &'foundation'&.
41023 .ecindex IIDforspo1
41024 .ecindex IIDforspo2
41025 .ecindex IIDforspo3
41027 .section "Format of the -D file" "SECID282a"
41028 The data file is traditionally in Unix-standard format: lines are ended with
41029 an ASCII newline character.
41030 However, when the &%spool_wireformat%& main option is used some -D files
41031 can have an alternate format.
41032 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41033 The -D file lines (not including the first name-component line) are
41034 suitable for direct copying to the wire when transmitting using the
41035 ESMTP CHUNKING option, meaning lower processing overhead.
41036 Lines are terminated with an ASCII CRLF pair.
41037 There is no dot-stuffing (and no dot-termination).
41039 . ////////////////////////////////////////////////////////////////////////////
41040 . ////////////////////////////////////////////////////////////////////////////
41042 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41043 "DKIM, SPF, SRS and DMARC Support"
41045 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41048 DKIM is a mechanism by which messages sent by some entity can be provably
41049 linked to a domain which that entity controls. It permits reputation to
41050 be tracked on a per-domain basis, rather than merely upon source IP address.
41051 DKIM is documented in RFC 6376.
41053 As DKIM relies on the message being unchanged in transit, messages handled
41054 by a mailing-list (which traditionally adds to the message) will not match
41055 any original DKIM signature.
41057 DKIM support is compiled into Exim by default if TLS support is present.
41058 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41060 Exim's DKIM implementation allows for
41062 Signing outgoing messages: This function is implemented in the SMTP transport.
41063 It can co-exist with all other Exim features
41064 (including transport filters)
41065 except cutthrough delivery.
41067 Verifying signatures in incoming messages: This is implemented by an additional
41068 ACL (acl_smtp_dkim), which can be called several times per message, with
41069 different signature contexts.
41072 In typical Exim style, the verification implementation does not include any
41073 default "policy". Instead it enables you to build your own policy using
41074 Exim's standard controls.
41076 Please note that verification of DKIM signatures in incoming mail is turned
41077 on by default for logging (in the <= line) purposes.
41079 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41080 When set, for each signature in incoming email,
41081 exim will log a line displaying the most important signature details, and the
41082 signature status. Here is an example (with line-breaks added for clarity):
41084 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41085 d=facebookmail.com s=q1-2009b
41086 c=relaxed/relaxed a=rsa-sha1
41087 i=@facebookmail.com t=1252484542 [verification succeeded]
41090 You might want to turn off DKIM verification processing entirely for internal
41091 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41092 control modifier. This should typically be done in the RCPT ACL, at points
41093 where you accept mail from relay sources (internal hosts or authenticated
41097 .section "Signing outgoing messages" "SECDKIMSIGN"
41098 .cindex "DKIM" "signing"
41100 For signing to be usable you must have published a DKIM record in DNS.
41101 Note that RFC 8301 (which does not cover EC keys) says:
41103 rsa-sha1 MUST NOT be used for signing or verifying.
41105 Signers MUST use RSA keys of at least 1024 bits for all keys.
41106 Signers SHOULD use RSA keys of at least 2048 bits.
41109 Note also that the key content (the 'p=' field)
41110 in the DNS record is different between RSA and EC keys;
41111 for the former it is the base64 of the ASN.1 for the RSA public key
41112 (equivalent to the private-key .pem with the header/trailer stripped)
41113 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41115 Signing is enabled by setting private options on the SMTP transport.
41116 These options take (expandable) strings as arguments.
41118 .option dkim_domain smtp "string list&!!" unset
41119 The domain(s) you want to sign with.
41120 After expansion, this can be a list.
41121 Each element in turn,
41123 is put into the &%$dkim_domain%& expansion variable
41124 while expanding the remaining signing options.
41125 If it is empty after expansion, DKIM signing is not done,
41126 and no error will result even if &%dkim_strict%& is set.
41128 .option dkim_selector smtp "string list&!!" unset
41129 This sets the key selector string.
41130 After expansion, which can use &$dkim_domain$&, this can be a list.
41131 Each element in turn is put in the expansion
41132 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41133 option along with &%$dkim_domain%&.
41134 If the option is empty after expansion, DKIM signing is not done for this domain,
41135 and no error will result even if &%dkim_strict%& is set.
41138 To do, for example, dual-signing with RSA and EC keys
41139 this could be be used:
41141 dkim_selector = ec_sel : rsa_sel
41142 dkim_private_key = KEYS_DIR/$dkim_selector
41146 .option dkim_private_key smtp string&!! unset
41147 This sets the private key to use.
41148 You can use the &%$dkim_domain%& and
41149 &%$dkim_selector%& expansion variables to determine the private key to use.
41150 The result can either
41152 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41154 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41155 be a valid Ed25519 private key (same format as above)
41157 start with a slash, in which case it is treated as a file that contains
41160 be "0", "false" or the empty string, in which case the message will not
41161 be signed. This case will not result in an error, even if &%dkim_strict%&
41165 To generate keys under OpenSSL:
41167 openssl genrsa -out dkim_rsa.private 2048
41168 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41170 The result file from the first command should be retained, and
41171 this option set to use it.
41172 Take the base-64 lines from the output of the second command, concatenated,
41173 for the DNS TXT record.
41174 See section 3.6 of RFC6376 for the record specification.
41178 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41179 certtool --load-privkey=dkim_rsa.private --pubkey-info
41182 Note that RFC 8301 says:
41184 Signers MUST use RSA keys of at least 1024 bits for all keys.
41185 Signers SHOULD use RSA keys of at least 2048 bits.
41188 EC keys for DKIM are defined by RFC 8463.
41189 They are considerably smaller than RSA keys for equivalent protection.
41190 As they are a recent development, users should consider dual-signing
41191 (by setting a list of selectors, and an expansion for this option)
41192 for some transition period.
41193 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41196 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41198 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41199 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41202 To produce the required public key value for a DNS record:
41204 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41205 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41208 Exim also supports an alternate format
41209 of Ed25519 keys in DNS which was a candidate during development
41210 of the standard, but not adopted.
41211 A future release will probably drop that support.
41213 .option dkim_hash smtp string&!! sha256
41214 Can be set to any one of the supported hash methods, which are:
41216 &`sha1`& &-- should not be used, is old and insecure
41218 &`sha256`& &-- the default
41220 &`sha512`& &-- possibly more secure but less well supported
41223 Note that RFC 8301 says:
41225 rsa-sha1 MUST NOT be used for signing or verifying.
41228 .option dkim_identity smtp string&!! unset
41229 If set after expansion, the value is used to set an "i=" tag in
41230 the signing header. The DKIM standards restrict the permissible
41231 syntax of this optional tag to a mail address, with possibly-empty
41232 local part, an @, and a domain identical to or subdomain of the "d="
41233 tag value. Note that Exim does not check the value.
41235 .option dkim_canon smtp string&!! unset
41236 This option sets the canonicalization method used when signing a message.
41237 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41238 The option defaults to "relaxed" when unset. Note: the current implementation
41239 only supports signing with the same canonicalization method for both headers and body.
41241 .option dkim_strict smtp string&!! unset
41242 This option defines how Exim behaves when signing a message that
41243 should be signed fails for some reason. When the expansion evaluates to
41244 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41245 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41248 .option dkim_sign_headers smtp string&!! "see below"
41249 If set, this option must expand to a colon-separated
41250 list of header names.
41251 Headers with these names, or the absence or such a header, will be included
41252 in the message signature.
41253 When unspecified, the header names listed in RFC4871 will be used,
41254 whether or not each header is present in the message.
41255 The default list is available for the expansion in the macro
41256 &"_DKIM_SIGN_HEADERS"&
41257 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41259 If a name is repeated, multiple headers by that name (or the absence thereof)
41260 will be signed. The textually later headers in the headers part of the
41261 message are signed first, if there are multiples.
41263 A name can be prefixed with either an &"="& or a &"+"& character.
41264 If an &"="& prefix is used, all headers that are present with this name
41266 If a &"+"& prefix if used, all headers that are present with this name
41267 will be signed, and one signature added for a missing header with the
41268 name will be appended.
41270 .option dkim_timestamps smtp integer&!! unset
41271 This option controls the inclusion of timestamp information in the signature.
41272 If not set, no such information will be included.
41273 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41275 (eg. 1209600 for two weeks);
41276 both creation (t=) and expiry (x=) tags will be included.
41278 RFC 6376 lists these tags as RECOMMENDED.
41281 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41282 .cindex "DKIM" "verification"
41284 Verification of DKIM signatures in SMTP incoming email is done for all
41285 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41286 .cindex DKIM "selecting signature algorithms"
41287 Individual classes of signature algorithm can be ignored by changing
41288 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41289 The &%dkim_verify_minimal%& option can be set to cease verification
41290 processing for a message once the first passing signature is found.
41292 .cindex authentication "expansion item"
41293 Performing verification sets up information used by the
41294 &%authresults%& expansion item.
41296 For most purposes the default option settings suffice and the remainder
41297 of this section can be ignored.
41299 The results of verification are made available to the
41300 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41301 A missing ACL definition defaults to accept.
41302 By default, the ACL is called once for each
41303 syntactically(!) correct signature in the incoming message.
41304 If any ACL call does not accept, the message is not accepted.
41305 If a cutthrough delivery was in progress for the message, that is
41306 summarily dropped (having wasted the transmission effort).
41308 To evaluate the verification result in the ACL
41309 a large number of expansion variables
41310 containing the signature status and its details are set up during the
41311 runtime of the ACL.
41313 Calling the ACL only for existing signatures is not sufficient to build
41314 more advanced policies. For that reason, the main option
41315 &%dkim_verify_signers%&, and an expansion variable
41316 &%$dkim_signers%& exist.
41318 The main option &%dkim_verify_signers%& can be set to a colon-separated
41319 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41320 called. It is expanded when the message has been received. At this point,
41321 the expansion variable &%$dkim_signers%& already contains a colon-separated
41322 list of signer domains and identities for the message. When
41323 &%dkim_verify_signers%& is not specified in the main configuration,
41326 dkim_verify_signers = $dkim_signers
41328 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41329 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41330 call the ACL for known domains or identities. This would be achieved as follows:
41332 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41334 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41335 and "ebay.com", plus all domains and identities that have signatures in the message.
41336 You can also be more creative in constructing your policy. For example:
41338 dkim_verify_signers = $sender_address_domain:$dkim_signers
41341 If a domain or identity is listed several times in the (expanded) value of
41342 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41344 Note that if the option is set using untrustworthy data
41345 (such as the From: header)
41346 care should be taken to force lowercase for domains
41347 and for the domain part if identities.
41348 The default setting can be regarded as trustworthy in this respect.
41350 If multiple signatures match a domain (or identity), the ACL is called once
41351 for each matching signature.
41354 Inside the DKIM ACL, the following expansion variables are
41355 available (from most to least important):
41359 .vitem &%$dkim_cur_signer%&
41360 The signer that is being evaluated in this ACL run. This can be a domain or
41361 an identity. This is one of the list items from the expanded main option
41362 &%dkim_verify_signers%& (see above).
41364 .vitem &%$dkim_verify_status%&
41365 Within the DKIM ACL,
41366 a string describing the general status of the signature. One of
41368 &%none%&: There is no signature in the message for the current domain or
41369 identity (as reflected by &%$dkim_cur_signer%&).
41371 &%invalid%&: The signature could not be verified due to a processing error.
41372 More detail is available in &%$dkim_verify_reason%&.
41374 &%fail%&: Verification of the signature failed. More detail is
41375 available in &%$dkim_verify_reason%&.
41377 &%pass%&: The signature passed verification. It is valid.
41380 This variable can be overwritten using an ACL 'set' modifier.
41381 This might, for instance, be done to enforce a policy restriction on
41382 hash-method or key-size:
41384 warn condition = ${if eq {$dkim_verify_status}{pass}}
41385 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41386 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41387 {< {$dkim_key_length}{1024}}}}
41388 logwrite = NOTE: forcing DKIM verify fail (was pass)
41389 set dkim_verify_status = fail
41390 set dkim_verify_reason = hash too weak or key too short
41393 So long as a DKIM ACL is defined (it need do no more than accept),
41394 after all the DKIM ACL runs have completed, the value becomes a
41395 colon-separated list of the values after each run.
41396 This is maintained for the mime, prdr and data ACLs.
41398 .vitem &%$dkim_verify_reason%&
41399 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41400 "fail" or "invalid". One of
41402 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41403 key for the domain could not be retrieved. This may be a temporary problem.
41405 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41406 record for the domain is syntactically invalid.
41408 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41409 body hash does not match the one specified in the signature header. This
41410 means that the message body was modified in transit.
41412 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41413 could not be verified. This may mean that headers were modified,
41414 re-written or otherwise changed in a way which is incompatible with
41415 DKIM verification. It may of course also mean that the signature is forged.
41418 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41420 .vitem &%$dkim_domain%&
41421 The signing domain. IMPORTANT: This variable is only populated if there is
41422 an actual signature in the message for the current domain or identity (as
41423 reflected by &%$dkim_cur_signer%&).
41425 .vitem &%$dkim_identity%&
41426 The signing identity, if present. IMPORTANT: This variable is only populated
41427 if there is an actual signature in the message for the current domain or
41428 identity (as reflected by &%$dkim_cur_signer%&).
41430 .vitem &%$dkim_selector%&
41431 The key record selector string.
41433 .vitem &%$dkim_algo%&
41434 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41435 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41436 may also be 'ed25519-sha256'.
41437 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41440 Note that RFC 8301 says:
41442 rsa-sha1 MUST NOT be used for signing or verifying.
41444 DKIM signatures identified as having been signed with historic
41445 algorithms (currently, rsa-sha1) have permanently failed evaluation
41448 To enforce this you must either have a DKIM ACL which checks this variable
41449 and overwrites the &$dkim_verify_status$& variable as discussed above,
41450 or have set the main option &%dkim_verify_hashes%& to exclude
41451 processing of such signatures.
41453 .vitem &%$dkim_canon_body%&
41454 The body canonicalization method. One of 'relaxed' or 'simple'.
41456 .vitem &%$dkim_canon_headers%&
41457 The header canonicalization method. One of 'relaxed' or 'simple'.
41459 .vitem &%$dkim_copiedheaders%&
41460 A transcript of headers and their values which are included in the signature
41461 (copied from the 'z=' tag of the signature).
41462 Note that RFC6376 requires that verification fail if the From: header is
41463 not included in the signature. Exim does not enforce this; sites wishing
41464 strict enforcement should code the check explicitly.
41466 .vitem &%$dkim_bodylength%&
41467 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41468 limit was set by the signer, "9999999999999" is returned. This makes sure
41469 that this variable always expands to an integer value.
41470 &*Note:*& The presence of the signature tag specifying a signing body length
41471 is one possible route to spoofing of valid DKIM signatures.
41472 A paranoid implementation might wish to regard signature where this variable
41473 shows less than the "no limit" return as being invalid.
41475 .vitem &%$dkim_created%&
41476 UNIX timestamp reflecting the date and time when the signature was created.
41477 When this was not specified by the signer, "0" is returned.
41479 .vitem &%$dkim_expires%&
41480 UNIX timestamp reflecting the date and time when the signer wants the
41481 signature to be treated as "expired". When this was not specified by the
41482 signer, "9999999999999" is returned. This makes it possible to do useful
41483 integer size comparisons against this value.
41484 Note that Exim does not check this value.
41486 .vitem &%$dkim_headernames%&
41487 A colon-separated list of names of headers included in the signature.
41489 .vitem &%$dkim_key_testing%&
41490 "1" if the key record has the "testing" flag set, "0" if not.
41492 .vitem &%$dkim_key_nosubdomains%&
41493 "1" if the key record forbids subdomaining, "0" otherwise.
41495 .vitem &%$dkim_key_srvtype%&
41496 Service type (tag s=) from the key record. Defaults to "*" if not specified
41499 .vitem &%$dkim_key_granularity%&
41500 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41503 .vitem &%$dkim_key_notes%&
41504 Notes from the key record (tag n=).
41506 .vitem &%$dkim_key_length%&
41507 Number of bits in the key.
41508 Valid only once the key is loaded, which is at the time the header signature
41509 is verified, which is after the body hash is.
41511 Note that RFC 8301 says:
41513 Verifiers MUST NOT consider signatures using RSA keys of
41514 less than 1024 bits as valid signatures.
41517 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41522 In addition, two ACL conditions are provided:
41525 .vitem &%dkim_signers%&
41526 ACL condition that checks a colon-separated list of domains or identities
41527 for a match against the domain or identity that the ACL is currently verifying
41528 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41529 verb to a group of domains or identities. For example:
41532 # Warn when Mail purportedly from GMail has no gmail signature
41533 warn sender_domains = gmail.com
41534 dkim_signers = gmail.com
41536 log_message = GMail sender without gmail.com DKIM signature
41539 Note that the above does not check for a total lack of DKIM signing;
41540 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41542 .vitem &%dkim_status%&
41543 ACL condition that checks a colon-separated list of possible DKIM verification
41544 results against the actual result of verification. This is typically used
41545 to restrict an ACL verb to a list of verification outcomes, for example:
41548 deny sender_domains = paypal.com:paypal.de
41549 dkim_signers = paypal.com:paypal.de
41550 dkim_status = none:invalid:fail
41551 message = Mail from Paypal with invalid/missing signature
41554 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41555 see the documentation of the &%$dkim_verify_status%& expansion variable above
41556 for more information of what they mean.
41562 .section "SPF (Sender Policy Framework)" SECSPF
41563 .cindex SPF verification
41565 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41566 messages with its domain in the envelope from, documented by RFC 7208.
41567 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41568 the &url(http://openspf.org).
41569 . --- 2019-10-28: still not https, open-spf.org is told to be a
41570 . --- web-archive copy of the now dead openspf.org site
41571 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41574 Messages sent by a system not authorised will fail checking of such assertions.
41575 This includes retransmissions done by traditional forwarders.
41577 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41578 &_Local/Makefile_&. The support uses the &_libspf2_& library
41579 &url(https://www.libspf2.org/).
41580 There is no Exim involvement in the transmission of messages;
41581 publishing certain DNS records is all that is required.
41583 For verification, an ACL condition and an expansion lookup are provided.
41584 .cindex authentication "expansion item"
41585 Performing verification sets up information used by the
41586 &%authresults%& expansion item.
41589 .cindex SPF "ACL condition"
41590 .cindex ACL "spf condition"
41591 The ACL condition "spf" can be used at or after the MAIL ACL.
41592 It takes as an argument a list of strings giving the outcome of the SPF check,
41593 and will succeed for any matching outcome.
41597 The SPF check passed, the sending host is positively verified by SPF.
41600 The SPF check failed, the sending host is NOT allowed to send mail for the
41601 domain in the envelope-from address.
41603 .vitem &%softfail%&
41604 The SPF check failed, but the queried domain can't absolutely confirm that this
41608 The queried domain does not publish SPF records.
41611 The SPF check returned a "neutral" state. This means the queried domain has
41612 published a SPF record, but wants to allow outside servers to send mail under
41613 its domain as well. This should be treated like "none".
41615 .vitem &%permerror%&
41616 This indicates a syntax error in the SPF record of the queried domain.
41617 You may deny messages when this occurs.
41619 .vitem &%temperror%&
41620 This indicates a temporary error during all processing, including Exim's
41621 SPF processing. You may defer messages when this occurs.
41624 You can prefix each string with an exclamation mark to invert
41625 its meaning, for example "!fail" will match all results but
41626 "fail". The string list is evaluated left-to-right, in a
41627 short-circuit fashion.
41632 message = $sender_host_address is not allowed to send mail from \
41633 ${if def:sender_address_domain \
41634 {$sender_address_domain}{$sender_helo_name}}. \
41635 Please see http://www.open-spf.org/Why;\
41636 identity=${if def:sender_address_domain \
41637 {$sender_address}{$sender_helo_name}};\
41638 ip=$sender_host_address
41641 Note: The above mentioned URL may not be as helpful as expected. You are
41642 encouraged to replace the link with a link to a site with more
41645 When the spf condition has run, it sets up several expansion
41648 .cindex SPF "verification variables"
41650 .vitem &$spf_header_comment$&
41651 .vindex &$spf_header_comment$&
41652 This contains a human-readable string describing the outcome
41653 of the SPF check. You can add it to a custom header or use
41654 it for logging purposes.
41656 .vitem &$spf_received$&
41657 .vindex &$spf_received$&
41658 This contains a complete Received-SPF: header that can be
41659 added to the message. Please note that according to the SPF
41660 draft, this header must be added at the top of the header
41661 list. Please see section 10 on how you can do this.
41663 Note: in case of "Best-guess" (see below), the convention is
41664 to put this string in a header called X-SPF-Guess: instead.
41666 .vitem &$spf_result$&
41667 .vindex &$spf_result$&
41668 This contains the outcome of the SPF check in string form,
41669 one of pass, fail, softfail, none, neutral, permerror or
41672 .vitem &$spf_result_guessed$&
41673 .vindex &$spf_result_guessed$&
41674 This boolean is true only if a best-guess operation was used
41675 and required in order to obtain a result.
41677 .vitem &$spf_smtp_comment$&
41678 .vindex &$spf_smtp_comment$&
41679 .vindex &%spf_smtp_comment_template%&
41680 This contains a string that can be used in a SMTP response
41681 to the calling party. Useful for "fail".
41682 The string is generated by the SPF library from the template configured in the main config
41683 option &%spf_smtp_comment_template%&.
41687 .cindex SPF "ACL condition"
41688 .cindex ACL "spf_guess condition"
41689 .cindex SPF "best guess"
41690 In addition to SPF, you can also perform checks for so-called
41691 "Best-guess". Strictly speaking, "Best-guess" is not standard
41692 SPF, but it is supported by the same framework that enables SPF
41694 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41695 for a description of what it means.
41696 . --- 2019-10-28: still not https:
41698 To access this feature, simply use the spf_guess condition in place
41699 of the spf one. For example:
41702 deny spf_guess = fail
41703 message = $sender_host_address doesn't look trustworthy to me
41706 In case you decide to reject messages based on this check, you
41707 should note that although it uses the same framework, "Best-guess"
41708 is not SPF, and therefore you should not mention SPF at all in your
41711 When the spf_guess condition has run, it sets up the same expansion
41712 variables as when spf condition is run, described above.
41714 Additionally, since Best-guess is not standardized, you may redefine
41715 what "Best-guess" means to you by redefining the main configuration
41716 &%spf_guess%& option.
41717 For example, the following:
41720 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41723 would relax host matching rules to a broader network range.
41726 .cindex SPF "lookup expansion"
41728 A lookup expansion is also available. It takes an email
41729 address as the key and an IP address
41734 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41737 The lookup will return the same result strings as can appear in
41738 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41744 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41745 .cindex SRS "sender rewriting scheme"
41748 SRS can be used to modify sender addresses when forwarding so that
41749 SPF verification does not object to them.
41750 It operates by encoding the original envelope sender in a new
41751 sender local part and using a domain run by the forwarding site
41752 as the new domain for the sender. Any DSN message should be returned
41753 to this new sender at the forwarding site, which can extract the
41754 original sender from the coded local part and forward the DSN to
41757 This is a way of avoiding the breakage that SPF does to forwarding.
41758 The constructed local-part will be longer than the original,
41759 leading to possible problems with very long addresses.
41760 The changing of the sender address also hinders the tracing of mail
41763 Exim can be built to include native SRS support. To do this
41764 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41765 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41767 The support is limited to SRS0-encoding; SRS1 is not supported.
41769 .cindex SRS excoding
41770 To encode an address use this expansion item:
41772 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41773 .cindex "&%srs_encode%& expansion item"
41774 .cindex SRS "expansion item"
41775 The first argument should be a secret known and used by all systems
41776 handling the recipient domain for the original message.
41777 There is no need to periodically change this key; a timestamp is also
41779 The second argument should be given as the envelope sender address before this
41780 encoding operation.
41781 The third argument should be the recipient domain of the message when
41782 it arrived at this system.
41785 .cindex SRS decoding
41786 To decode an address use this expansion condition:
41788 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
41789 The first argument should be the recipient local prt as is was received.
41790 The second argument is the site secret.
41792 If the messages is not for an SRS-encoded recipient the condition will
41793 return false. If it is, the condition will return true and the variable
41794 &$srs_recipient$& will be set to the decoded (original) value.
41800 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
41806 # if outbound, and forwarding has been done, use an alternate transport
41807 domains = ! +my_domains
41808 transport = ${if eq {$local_part@$domain} \
41809 {$original_local_part@$original_domain} \
41810 {remote_smtp} {remote_forwarded_smtp}}
41815 domains = +my_domains
41816 # detect inbound bounces which are SRS'd, and decode them
41817 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
41818 data = $srs_recipient
41820 inbound_srs_failure:
41823 domains = +my_domains
41824 # detect inbound bounces which look SRS'd but are invalid
41825 condition = ${if inbound_srs {$local_part} {}}
41827 data = :fail: Invalid SRS recipient address
41829 #... further routers here
41832 # transport; should look like the non-forward outbound
41833 # one, plus the max_rcpt and return_path options
41834 remote_forwarded_smtp:
41836 # modify the envelope from, for mails that we forward
41838 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
41846 .section DMARC SECDMARC
41847 .cindex DMARC verification
41849 DMARC combines feedback from SPF, DKIM, and header From: in order
41850 to attempt to provide better indicators of the authenticity of an
41851 email. This document does not explain the fundamentals; you
41852 should read and understand how it works by visiting the website at
41853 &url(http://www.dmarc.org/).
41855 If Exim is built with DMARC support,
41856 the libopendmarc library is used.
41858 For building Exim yourself, obtain the library from
41859 &url(http://sourceforge.net/projects/opendmarc/)
41860 to obtain a copy, or find it in your favorite package
41861 repository. You will need to attend to the local/Makefile feature
41862 SUPPORT_DMARC and the associated LDFLAGS addition.
41863 This description assumes
41864 that headers will be in /usr/local/include, and that the libraries
41865 are in /usr/local/lib.
41869 There are three main-configuration options:
41870 .cindex DMARC "configuration options"
41872 The &%dmarc_tld_file%& option
41873 .oindex &%dmarc_tld_file%&
41874 defines the location of a text file of valid
41875 top level domains the opendmarc library uses
41876 during domain parsing. Maintained by Mozilla,
41877 the most current version can be downloaded
41878 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
41879 See also the util/renew-opendmarc-tlds.sh script.
41880 The default for the option is unset.
41881 If not set, DMARC processing is disabled.
41884 The &%dmarc_history_file%& option, if set
41885 .oindex &%dmarc_history_file%&
41886 defines the location of a file to log results
41887 of dmarc verification on inbound emails. The
41888 contents are importable by the opendmarc tools
41889 which will manage the data, send out DMARC
41890 reports, and expire the data. Make sure the
41891 directory of this file is writable by the user
41893 The default is unset.
41895 The &%dmarc_forensic_sender%& option
41896 .oindex &%dmarc_forensic_sender%&
41897 defines an alternate email address to use when sending a
41898 forensic report detailing alignment failures
41899 if a sender domain's dmarc record specifies it
41900 and you have configured Exim to send them.
41901 If set, this is expanded and used for the
41902 From: header line; the address is extracted
41903 from it and used for the envelope from.
41904 If not set (the default), the From: header is expanded from
41905 the dsn_from option, and <> is used for the
41908 . I wish we had subsections...
41910 .cindex DMARC controls
41911 By default, the DMARC processing will run for any remote,
41912 non-authenticated user. It makes sense to only verify DMARC
41913 status of messages coming from remote, untrusted sources. You can
41914 use standard conditions such as hosts, senders, etc, to decide that
41915 DMARC verification should *not* be performed for them and disable
41916 DMARC with an ACL control modifier:
41918 control = dmarc_disable_verify
41920 A DMARC record can also specify a "forensic address", which gives
41921 exim an email address to submit reports about failed alignment.
41922 Exim does not do this by default because in certain conditions it
41923 results in unintended information leakage (what lists a user might
41924 be subscribed to, etc). You must configure exim to submit forensic
41925 reports to the owner of the domain. If the DMARC record contains a
41926 forensic address and you specify the control statement below, then
41927 exim will send these forensic emails. It is also advised that you
41928 configure a &%dmarc_forensic_sender%& because the default sender address
41929 construction might be inadequate.
41931 control = dmarc_enable_forensic
41933 (AGAIN: You can choose not to send these forensic reports by simply
41934 not putting the dmarc_enable_forensic control line at any point in
41935 your exim config. If you don't tell exim to send them, it will not
41938 There are no options to either control. Both must appear before
41943 DMARC checks cam be run on incoming SMTP messages by using the
41944 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
41945 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
41946 condition. Putting this condition in the ACLs is required in order
41947 for a DMARC check to actually occur. All of the variables are set
41948 up before the DATA ACL, but there is no actual DMARC check that
41949 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
41951 The &"dmarc_status"& condition takes a list of strings on its
41952 right-hand side. These strings describe recommended action based
41953 on the DMARC check. To understand what the policy recommendations
41954 mean, refer to the DMARC website above. Valid strings are:
41956 &'accept '& The DMARC check passed and the library recommends accepting the email.
41957 &'reject '& The DMARC check failed and the library recommends rejecting the email.
41958 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
41959 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
41960 &'norecord '& No policy section in the DMARC record for this RFC5322.From field
41961 &'nofrom '& Unable to determine the domain of the sender.
41962 &'temperror '& Library error or dns error.
41963 &'off '& The DMARC check was disabled for this email.
41965 You can prefix each string with an exclamation mark to invert its
41966 meaning, for example "!accept" will match all results but
41967 "accept". The string list is evaluated left-to-right in a
41968 short-circuit fashion. When a string matches the outcome of the
41969 DMARC check, the condition succeeds. If none of the listed
41970 strings matches the outcome of the DMARC check, the condition
41973 Of course, you can also use any other lookup method that Exim
41974 supports, including LDAP, Postgres, MySQL, etc, as long as the
41975 result is a list of colon-separated strings.
41977 Performing the check sets up information used by the
41978 &%authresults%& expansion item.
41980 Several expansion variables are set before the DATA ACL is
41981 processed, and you can use them in this ACL. The following
41982 expansion variables are available:
41985 .vitem &$dmarc_status$&
41986 .vindex &$dmarc_status$&
41987 .cindex DMARC result
41988 A one word status indicating what the DMARC library
41989 thinks of the email. It is a combination of the results of
41990 DMARC record lookup and the SPF/DKIM/DMARC processing results
41991 (if a DMARC record was found). The actual policy declared
41992 in the DMARC record is in a separate expansion variable.
41994 .vitem &$dmarc_status_text$&
41995 .vindex &$dmarc_status_text$&
41996 Slightly longer, human readable status.
41998 .vitem &$dmarc_used_domain$&
41999 .vindex &$dmarc_used_domain$&
42000 The domain which DMARC used to look up the DMARC policy record.
42002 .vitem &$dmarc_domain_policy$&
42003 .vindex &$dmarc_domain_policy$&
42004 The policy declared in the DMARC record. Valid values
42005 are "none", "reject" and "quarantine". It is blank when there
42006 is any error, including no DMARC record.
42011 By default, Exim's DMARC configuration is intended to be
42012 non-intrusive and conservative. To facilitate this, Exim will not
42013 create any type of logging files without explicit configuration by
42014 you, the admin. Nor will Exim send out any emails/reports about
42015 DMARC issues without explicit configuration by you, the admin (other
42016 than typical bounce messages that may come about due to ACL
42017 processing or failure delivery issues).
42019 In order to log statistics suitable to be imported by the opendmarc
42020 tools, you need to:
42022 Configure the global option &%dmarc_history_file%&
42024 Configure cron jobs to call the appropriate opendmarc history
42025 import scripts and truncating the dmarc_history_file
42028 In order to send forensic reports, you need to:
42030 Configure the global option &%dmarc_forensic_sender%&
42032 Configure, somewhere before the DATA ACL, the control option to
42033 enable sending DMARC forensic reports
42041 warn domains = +local_domains
42042 hosts = +local_hosts
42043 control = dmarc_disable_verify
42045 warn !domains = +screwed_up_dmarc_records
42046 control = dmarc_enable_forensic
42048 warn condition = (lookup if destined to mailing list)
42049 set acl_m_mailing_list = 1
42052 warn dmarc_status = accept : none : off
42054 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42056 warn dmarc_status = !accept
42058 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42060 warn dmarc_status = quarantine
42062 set $acl_m_quarantine = 1
42063 # Do something in a transport with this flag variable
42065 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42066 condition = ${if eq{$acl_m_mailing_list}{1}}
42067 message = Messages from $dmarc_used_domain break mailing lists
42069 deny dmarc_status = reject
42071 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42073 warn add_header = :at_start:${authresults {$primary_hostname}}
42080 . ////////////////////////////////////////////////////////////////////////////
42081 . ////////////////////////////////////////////////////////////////////////////
42083 .chapter "Proxies" "CHAPproxies" &&&
42085 .cindex "proxy support"
42086 .cindex "proxy" "access via"
42088 A proxy is an intermediate system through which communication is passed.
42089 Proxies may provide a security, availability or load-distribution function.
42092 .section "Inbound proxies" SECTproxyInbound
42093 .cindex proxy inbound
42094 .cindex proxy "server side"
42095 .cindex proxy "Proxy protocol"
42096 .cindex "Proxy protocol" proxy
42098 Exim has support for receiving inbound SMTP connections via a proxy
42099 that uses &"Proxy Protocol"& to speak to it.
42100 To include this support, include &"SUPPORT_PROXY=yes"&
42103 It was built on the HAProxy specification, found at
42104 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42106 The purpose of this facility is so that an application load balancer,
42107 such as HAProxy, can sit in front of several Exim servers
42108 to distribute load.
42109 Exim uses the local protocol communication with the proxy to obtain
42110 the remote SMTP system IP address and port information.
42111 There is no logging if a host passes or
42112 fails Proxy Protocol negotiation, but it can easily be determined and
42113 recorded in an ACL (example is below).
42115 Use of a proxy is enabled by setting the &%hosts_proxy%&
42116 main configuration option to a hostlist; connections from these
42117 hosts will use Proxy Protocol.
42118 Exim supports both version 1 and version 2 of the Proxy Protocol and
42119 automatically determines which version is in use.
42121 The Proxy Protocol header is the first data received on a TCP connection
42122 and is inserted before any TLS-on-connect handshake from the client; Exim
42123 negotiates TLS between Exim-as-server and the remote client, not between
42124 Exim and the proxy server. The Proxy Protocol header must be received
42125 within &%proxy_protocol_timeout%&, which defaults to 3s.
42127 The following expansion variables are usable
42128 (&"internal"& and &"external"& here refer to the interfaces
42131 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
42132 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
42133 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
42134 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
42135 &'proxy_session '& boolean: SMTP connection via proxy
42137 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42138 there was a protocol error.
42139 The variables &$sender_host_address$& and &$sender_host_port$&
42140 will have values for the actual client system, not the proxy.
42142 Since the real connections are all coming from the proxy, and the
42143 per host connection tracking is done before Proxy Protocol is
42144 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42145 handle all of the parallel volume you expect per inbound proxy.
42146 With the option set so high, you lose the ability
42147 to protect your server from many connections from one IP.
42148 In order to prevent your server from overload, you
42149 need to add a per connection ratelimit to your connect ACL.
42150 A possible solution is:
42152 # Set max number of connections per host
42154 # Or do some kind of IP lookup in a flat file or database
42155 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42157 defer ratelimit = LIMIT / 5s / per_conn / strict
42158 message = Too many connections from this IP right now
42163 .section "Outbound proxies" SECTproxySOCKS
42164 .cindex proxy outbound
42165 .cindex proxy "client side"
42166 .cindex proxy SOCKS
42167 .cindex SOCKS proxy
42168 Exim has support for sending outbound SMTP via a proxy
42169 using a protocol called SOCKS5 (defined by RFC1928).
42170 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42173 Use of a proxy is enabled by setting the &%socks_proxy%& option
42174 on an smtp transport.
42175 The option value is expanded and should then be a list
42176 (colon-separated by default) of proxy specifiers.
42177 Each proxy specifier is a list
42178 (space-separated by default) where the initial element
42179 is an IP address and any subsequent elements are options.
42181 Options are a string <name>=<value>.
42182 The list of options is in the following table:
42184 &'auth '& authentication method
42185 &'name '& authentication username
42186 &'pass '& authentication password
42188 &'tmo '& connection timeout
42190 &'weight '& selection bias
42193 More details on each of these options follows:
42196 .cindex authentication "to proxy"
42197 .cindex proxy authentication
42198 &%auth%&: Either &"none"& (default) or &"name"&.
42199 Using &"name"& selects username/password authentication per RFC 1929
42200 for access to the proxy.
42201 Default is &"none"&.
42203 &%name%&: sets the username for the &"name"& authentication method.
42206 &%pass%&: sets the password for the &"name"& authentication method.
42209 &%port%&: the TCP port number to use for the connection to the proxy.
42212 &%tmo%&: sets a connection timeout in seconds for this proxy.
42215 &%pri%&: specifies a priority for the proxy within the list,
42216 higher values being tried first.
42217 The default priority is 1.
42219 &%weight%&: specifies a selection bias.
42220 Within a priority set servers are queried in a random fashion,
42221 weighted by this value.
42222 The default value for selection bias is 1.
42225 Proxies from the list are tried according to their priority
42226 and weight settings until one responds. The timeout for the
42227 overall connection applies to the set of proxied attempts.
42229 .section Logging SECTproxyLog
42230 To log the (local) IP of a proxy in the incoming or delivery logline,
42231 add &"+proxy"& to the &%log_selector%& option.
42232 This will add a component tagged with &"PRX="& to the line.
42234 . ////////////////////////////////////////////////////////////////////////////
42235 . ////////////////////////////////////////////////////////////////////////////
42237 .chapter "Internationalisation" "CHAPi18n" &&&
42238 "Internationalisation""
42239 .cindex internationalisation "email address"
42242 .cindex utf8 "mail name handling"
42244 Exim has support for Internationalised mail names.
42245 To include this it must be built with SUPPORT_I18N and the libidn library.
42246 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42248 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42249 instead of it) then IDNA2008 is supported; this adds an extra library
42250 requirement, upon libidn2.
42252 .section "MTA operations" SECTi18nMTA
42253 .cindex SMTPUTF8 "ESMTP option"
42254 .cindex "ESMTP extensions" SMTPUTF8
42255 The main configuration option &%smtputf8_advertise_hosts%& specifies
42256 a host list. If this matches the sending host and
42257 accept_8bitmime is true (the default) then the ESMTP option
42258 SMTPUTF8 will be advertised.
42260 If the sender specifies the SMTPUTF8 option on a MAIL command
42261 international handling for the message is enabled and
42262 the expansion variable &$message_smtputf8$& will have value TRUE.
42264 The option &%allow_utf8_domains%& is set to true for this
42265 message. All DNS lookups are converted to a-label form
42266 whatever the setting of &%allow_utf8_domains%&
42267 when Exim is built with SUPPORT_I18N.
42269 Both localparts and domain are maintained as the original
42270 UTF-8 form internally; any comparison or regular-expression use will
42271 require appropriate care. Filenames created, eg. by
42272 the appendfile transport, will have UTF-8 names.
42274 HELO names sent by the smtp transport will have any UTF-8
42275 components expanded to a-label form,
42276 and any certificate name checks will be done using the a-label
42279 .cindex log protocol
42280 .cindex SMTPUTF8 logging
42281 .cindex i18n logging
42282 Log lines and Received-by: header lines will acquire a "utf8"
42283 prefix on the protocol element, eg. utf8esmtp.
42285 The following expansion operators can be used:
42287 ${utf8_domain_to_alabel:str}
42288 ${utf8_domain_from_alabel:str}
42289 ${utf8_localpart_to_alabel:str}
42290 ${utf8_localpart_from_alabel:str}
42293 .cindex utf8 "address downconversion"
42294 .cindex i18n "utf8 address downconversion"
42296 may use the following modifier:
42298 control = utf8_downconvert
42299 control = utf8_downconvert/<value>
42301 This sets a flag requiring that envelope addresses are converted to
42302 a-label form before smtp delivery.
42303 This is usually for use in a Message Submission Agent context,
42304 but could be used for any message.
42306 If a value is appended it may be:
42308 &`1 `& mandatory downconversion
42309 &`0 `& no downconversion
42310 &`-1 `& if SMTPUTF8 not supported by destination host
42312 If no value is given, 1 is used.
42314 If mua_wrapper is set, the utf8_downconvert control
42315 is initially set to -1.
42317 The smtp transport has an option &%utf8_downconvert%&.
42318 If set it must expand to one of the three values described above,
42319 or an empty string.
42320 If non-empty it overrides value previously set
42321 (due to mua_wrapper or by an ACL control).
42324 There is no explicit support for VRFY and EXPN.
42325 Configurations supporting these should inspect
42326 &$smtp_command_argument$& for an SMTPUTF8 argument.
42328 There is no support for LMTP on Unix sockets.
42329 Using the "lmtp" protocol option on an smtp transport,
42330 for LMTP over TCP, should work as expected.
42332 There is no support for DSN unitext handling,
42333 and no provision for converting logging from or to UTF-8.
42337 .section "MDA operations" SECTi18nMDA
42338 To aid in constructing names suitable for IMAP folders
42339 the following expansion operator can be used:
42341 ${imapfolder {<string>} {<sep>} {<specials>}}
42344 The string is converted from the charset specified by
42345 the "headers charset" command (in a filter file)
42346 or &%headers_charset%& main configuration option (otherwise),
42348 modified UTF-7 encoding specified by RFC 2060,
42349 with the following exception: All occurrences of <sep>
42350 (which has to be a single character)
42351 are replaced with periods ("."), and all periods and slashes that are not
42352 <sep> and are not in the <specials> string are BASE64 encoded.
42354 The third argument can be omitted, defaulting to an empty string.
42355 The second argument can be omitted, defaulting to "/".
42357 This is the encoding used by Courier for Maildir names on disk, and followed
42358 by many other IMAP servers.
42362 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42363 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42364 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42367 Note that the source charset setting is vital, and also that characters
42368 must be representable in UTF-16.
42371 . ////////////////////////////////////////////////////////////////////////////
42372 . ////////////////////////////////////////////////////////////////////////////
42374 .chapter "Events" "CHAPevents" &&&
42378 The events mechanism in Exim can be used to intercept processing at a number
42379 of points. It was originally invented to give a way to do customised logging
42380 actions (for example, to a database) but can also be used to modify some
42381 processing actions.
42383 Most installations will never need to use Events.
42384 The support can be left out of a build by defining DISABLE_EVENT=yes
42385 in &_Local/Makefile_&.
42387 There are two major classes of events: main and transport.
42388 The main configuration option &%event_action%& controls reception events;
42389 a transport option &%event_action%& controls delivery events.
42391 Both options are a string which is expanded when the event fires.
42392 An example might look like:
42393 .cindex logging custom
42395 event_action = ${if eq {msg:delivery}{$event_name} \
42396 {${lookup pgsql {SELECT * FROM record_Delivery( \
42397 '${quote_pgsql:$sender_address_domain}',\
42398 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42399 '${quote_pgsql:$domain}', \
42400 '${quote_pgsql:${lc:$local_part}}', \
42401 '${quote_pgsql:$host_address}', \
42402 '${quote_pgsql:${lc:$host}}', \
42403 '${quote_pgsql:$message_exim_id}')}} \
42407 Events have names which correspond to the point in process at which they fire.
42408 The name is placed in the variable &$event_name$& and the event action
42409 expansion must check this, as it will be called for every possible event type.
42411 The current list of events is:
42413 &`dane:fail after transport `& per connection
42414 &`msg:complete after main `& per message
42415 &`msg:defer after transport `& per message per delivery try
42416 &`msg:delivery after transport `& per recipient
42417 &`msg:rcpt:host:defer after transport `& per recipient per host
42418 &`msg:rcpt:defer after transport `& per recipient
42419 &`msg:host:defer after transport `& per host per delivery try; host errors
42420 &`msg:fail:delivery after transport `& per recipient
42421 &`msg:fail:internal after main `& per recipient
42422 &`tcp:connect before transport `& per connection
42423 &`tcp:close after transport `& per connection
42424 &`tls:cert before both `& per certificate in verification chain
42425 &`smtp:connect after transport `& per connection
42426 &`smtp:ehlo after transport `& per connection
42428 New event types may be added in future.
42430 The event name is a colon-separated list, defining the type of
42431 event in a tree of possibilities. It may be used as a list
42432 or just matched on as a whole. There will be no spaces in the name.
42434 The second column in the table above describes whether the event fires
42435 before or after the action is associates with. Those which fire before
42436 can be used to affect that action (more on this below).
42438 The third column in the table above says what section of the configuration
42439 should define the event action.
42441 An additional variable, &$event_data$&, is filled with information varying
42442 with the event type:
42444 &`dane:fail `& failure reason
42445 &`msg:defer `& error string
42446 &`msg:delivery `& smtp confirmation message
42447 &`msg:fail:internal `& failure reason
42448 &`msg:fail:delivery `& smtp error message
42449 &`msg:host:defer `& error string
42450 &`msg:rcpt:host:defer `& error string
42451 &`msg:rcpt:defer `& error string
42452 &`tls:cert `& verification chain depth
42453 &`smtp:connect `& smtp banner
42454 &`smtp:ehlo `& smtp ehlo response
42457 The :defer events populate one extra variable: &$event_defer_errno$&.
42459 For complex operations an ACL expansion can be used in &%event_action%&
42460 however due to the multiple contexts that Exim operates in during
42461 the course of its processing:
42463 variables set in transport events will not be visible outside that
42466 acl_m variables in a server context are lost on a new connection,
42467 and after smtp helo/ehlo/mail/starttls/rset commands
42469 Using an ACL expansion with the logwrite modifier can be
42470 a useful way of writing to the main log.
42472 The expansion of the event_action option should normally
42473 return an empty string. Should it return anything else the
42474 following will be forced:
42476 &`tcp:connect `& do not connect
42477 &`tls:cert `& refuse verification
42478 &`smtp:connect `& close connection
42480 All other message types ignore the result string, and
42481 no other use is made of it.
42483 For a tcp:connect event, if the connection is being made to a proxy
42484 then the address and port variables will be that of the proxy and not
42487 For tls:cert events, if GnuTLS is in use this will trigger only per
42488 chain element received on the connection.
42489 For OpenSSL it will trigger for every chain element including those
42492 . ////////////////////////////////////////////////////////////////////////////
42493 . ////////////////////////////////////////////////////////////////////////////
42495 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42496 "Adding drivers or lookups"
42497 .cindex "adding drivers"
42498 .cindex "new drivers, adding"
42499 .cindex "drivers" "adding new"
42500 The following actions have to be taken in order to add a new router, transport,
42501 authenticator, or lookup type to Exim:
42504 Choose a name for the driver or lookup type that does not conflict with any
42505 existing name; I will use &"newdriver"& in what follows.
42507 Add to &_src/EDITME_& the line:
42509 <&'type'&>&`_NEWDRIVER=yes`&
42511 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42512 code is not to be included in the binary by default, comment this line out. You
42513 should also add any relevant comments about the driver or lookup type.
42515 Add to &_src/config.h.defaults_& the line:
42517 #define <type>_NEWDRIVER
42520 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42521 and create a table entry as is done for all the other drivers and lookup types.
42523 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42524 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42525 Add your &`NEWDRIVER`& to that list.
42526 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42527 simple form that most lookups have.
42529 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42530 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42531 driver or lookup type and add it to the definition of OBJ.
42533 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42534 definition of OBJ_MACRO. Add a set of line to do the compile also.
42536 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42539 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42540 as for other drivers and lookups.
42543 Then all you need to do is write the code! A good way to start is to make a
42544 proforma by copying an existing module of the same type, globally changing all
42545 occurrences of the name, and cutting out most of the code. Note that any
42546 options you create must be listed in alphabetical order, because the tables are
42547 searched using a binary chop procedure.
42549 There is a &_README_& file in each of the sub-directories of &_src_& describing
42550 the interface that is expected.
42555 . ////////////////////////////////////////////////////////////////////////////
42556 . ////////////////////////////////////////////////////////////////////////////
42558 . /////////////////////////////////////////////////////////////////////////////
42559 . These lines are processing instructions for the Simple DocBook Processor that
42560 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42561 . PDFs than using xmlto and fop. They will be ignored by all other XML
42563 . /////////////////////////////////////////////////////////////////////////////
42568 foot_right_recto="&chaptertitle;"
42569 foot_right_verso="&chaptertitle;"
42573 .makeindex "Options index" "option"
42574 .makeindex "Variables index" "variable"
42575 .makeindex "Concept index" "concept"
42578 . /////////////////////////////////////////////////////////////////////////////
42579 . /////////////////////////////////////////////////////////////////////////////