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"
164 . ////////////////////////////////////////////////////////////////////////////
167 . ////////////////////////////////////////////////////////////////////////////
168 . The <bookinfo> element is removed from the XML before processing for ASCII
170 . ////////////////////////////////////////////////////////////////////////////
174 <title>Specification of the Exim Mail Transfer Agent</title>
175 <titleabbrev>The Exim MTA</titleabbrev>
179 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
180 <authorinitials>EM</authorinitials>
181 <revhistory><revision>
183 <authorinitials>EM</authorinitials>
184 </revision></revhistory>
187 </year><holder>University of Cambridge</holder></copyright>
192 . /////////////////////////////////////////////////////////////////////////////
193 . This chunk of literal XML implements index entries of the form "x, see y" and
194 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
195 . at the top level, so we have to put the .chapter directive first.
196 . /////////////////////////////////////////////////////////////////////////////
198 .chapter "Introduction" "CHID1"
201 <indexterm role="variable">
202 <primary>$1, $2, etc.</primary>
203 <see><emphasis>numerical variables</emphasis></see>
205 <indexterm role="concept">
206 <primary>address</primary>
207 <secondary>rewriting</secondary>
208 <see><emphasis>rewriting</emphasis></see>
210 <indexterm role="concept">
211 <primary>Bounce Address Tag Validation</primary>
212 <see><emphasis>BATV</emphasis></see>
214 <indexterm role="concept">
215 <primary>Client SMTP Authorization</primary>
216 <see><emphasis>CSA</emphasis></see>
218 <indexterm role="concept">
219 <primary>CR character</primary>
220 <see><emphasis>carriage return</emphasis></see>
222 <indexterm role="concept">
223 <primary>CRL</primary>
224 <see><emphasis>certificate revocation list</emphasis></see>
226 <indexterm role="concept">
227 <primary>delivery</primary>
228 <secondary>failure report</secondary>
229 <see><emphasis>bounce message</emphasis></see>
231 <indexterm role="concept">
232 <primary>dialup</primary>
233 <see><emphasis>intermittently connected hosts</emphasis></see>
235 <indexterm role="concept">
236 <primary>exiscan</primary>
237 <see><emphasis>content scanning</emphasis></see>
239 <indexterm role="concept">
240 <primary>failover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>fallover</primary>
245 <see><emphasis>fallback</emphasis></see>
247 <indexterm role="concept">
248 <primary>filter</primary>
249 <secondary>Sieve</secondary>
250 <see><emphasis>Sieve filter</emphasis></see>
252 <indexterm role="concept">
253 <primary>ident</primary>
254 <see><emphasis>RFC 1413</emphasis></see>
256 <indexterm role="concept">
257 <primary>LF character</primary>
258 <see><emphasis>linefeed</emphasis></see>
260 <indexterm role="concept">
261 <primary>maximum</primary>
262 <seealso><emphasis>limit</emphasis></seealso>
264 <indexterm role="concept">
265 <primary>monitor</primary>
266 <see><emphasis>Exim monitor</emphasis></see>
268 <indexterm role="concept">
269 <primary>no_<emphasis>xxx</emphasis></primary>
270 <see>entry for xxx</see>
272 <indexterm role="concept">
273 <primary>NUL</primary>
274 <see><emphasis>binary zero</emphasis></see>
276 <indexterm role="concept">
277 <primary>passwd file</primary>
278 <see><emphasis>/etc/passwd</emphasis></see>
280 <indexterm role="concept">
281 <primary>process id</primary>
282 <see><emphasis>pid</emphasis></see>
284 <indexterm role="concept">
285 <primary>RBL</primary>
286 <see><emphasis>DNS list</emphasis></see>
288 <indexterm role="concept">
289 <primary>redirection</primary>
290 <see><emphasis>address redirection</emphasis></see>
292 <indexterm role="concept">
293 <primary>return path</primary>
294 <seealso><emphasis>envelope sender</emphasis></seealso>
296 <indexterm role="concept">
297 <primary>scanning</primary>
298 <see><emphasis>content scanning</emphasis></see>
300 <indexterm role="concept">
301 <primary>SSL</primary>
302 <see><emphasis>TLS</emphasis></see>
304 <indexterm role="concept">
305 <primary>string</primary>
306 <secondary>expansion</secondary>
307 <see><emphasis>expansion</emphasis></see>
309 <indexterm role="concept">
310 <primary>top bit</primary>
311 <see><emphasis>8-bit characters</emphasis></see>
313 <indexterm role="concept">
314 <primary>variables</primary>
315 <see><emphasis>expansion, variables</emphasis></see>
317 <indexterm role="concept">
318 <primary>zero, binary</primary>
319 <see><emphasis>binary zero</emphasis></see>
325 . /////////////////////////////////////////////////////////////////////////////
326 . This is the real start of the first chapter. See the comment above as to why
327 . we can't have the .chapter line here.
328 . chapter "Introduction"
329 . /////////////////////////////////////////////////////////////////////////////
331 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
332 Unix-like operating systems. It was designed on the assumption that it would be
333 run on hosts that are permanently connected to the Internet. However, it can be
334 used on intermittently connected hosts with suitable configuration adjustments.
336 Configuration files currently exist for the following operating systems: AIX,
337 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
338 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
339 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
340 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
341 Some of these operating systems are no longer current and cannot easily be
342 tested, so the configuration files may no longer work in practice.
344 There are also configuration files for compiling Exim in the Cygwin environment
345 that can be installed on systems running Windows. However, this document does
346 not contain any information about running Exim in the Cygwin environment.
348 The terms and conditions for the use and distribution of Exim are contained in
349 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
350 Public Licence, a copy of which may be found in the file &_LICENCE_&.
352 The use, supply, or promotion of Exim for the purpose of sending bulk,
353 unsolicited electronic mail is incompatible with the basic aims of Exim,
354 which revolve around the free provision of a service that enhances the quality
355 of personal communications. The author of Exim regards indiscriminate
356 mass-mailing as an antisocial, irresponsible abuse of the Internet.
358 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
359 experience of running and working on the Smail 3 code, I could never have
360 contemplated starting to write a new MTA. Many of the ideas and user interfaces
361 were originally taken from Smail 3, though the actual code of Exim is entirely
362 new, and has developed far beyond the initial concept.
364 Many people, both in Cambridge and around the world, have contributed to the
365 development and the testing of Exim, and to porting it to various operating
366 systems. I am grateful to them all. The distribution now contains a file called
367 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
371 .section "Exim documentation" "SECID1"
372 . Keep this example change bar when updating the documentation!
375 .cindex "documentation"
376 This edition of the Exim specification applies to version &version() of Exim.
377 Substantive changes from the &previousversion; edition are marked in some
378 renditions of this document; this paragraph is so marked if the rendition is
379 capable of showing a change indicator.
382 This document is very much a reference manual; it is not a tutorial. The reader
383 is expected to have some familiarity with the SMTP mail transfer protocol and
384 with general Unix system administration. Although there are some discussions
385 and examples in places, the information is mostly organized in a way that makes
386 it easy to look up, rather than in a natural order for sequential reading.
387 Furthermore, this manual aims to cover every aspect of Exim in detail, including
388 a number of rarely-used, special-purpose features that are unlikely to be of
391 .cindex "books about Exim"
392 An &"easier"& discussion of Exim which provides more in-depth explanatory,
393 introductory, and tutorial material can be found in a book entitled &'The Exim
394 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
395 (&url(https://www.uit.co.uk/exim-book/)).
397 The book also contains a chapter that gives a general introduction to SMTP and
398 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
399 with the latest release of Exim. (Note that the earlier book about Exim,
400 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
402 .cindex "Debian" "information sources"
403 If you are using a Debian distribution of Exim, you will find information about
404 Debian-specific features in the file
405 &_/usr/share/doc/exim4-base/README.Debian_&.
406 The command &(man update-exim.conf)& is another source of Debian-specific
409 .cindex "&_doc/NewStuff_&"
410 .cindex "&_doc/ChangeLog_&"
412 As Exim develops, there may be features in newer versions that have not
413 yet made it into this document, which is updated only when the most significant
414 digit of the fractional part of the version number changes. Specifications of
415 new features that are not yet in this manual are placed in the file
416 &_doc/NewStuff_& in the Exim distribution.
418 Some features may be classified as &"experimental"&. These may change
419 incompatibly while they are developing, or even be withdrawn. For this reason,
420 they are not documented in this manual. Information about experimental features
421 can be found in the file &_doc/experimental.txt_&.
423 All changes to Exim (whether new features, bug fixes, or other kinds of
424 change) are noted briefly in the file called &_doc/ChangeLog_&.
426 .cindex "&_doc/spec.txt_&"
427 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
428 that it can easily be searched with a text editor. Other files in the &_doc_&
432 .row &_OptionLists.txt_& "list of all options in alphabetical order"
433 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
434 .row &_exim.8_& "a man page of Exim's command line options"
435 .row &_experimental.txt_& "documentation of experimental features"
436 .row &_filter.txt_& "specification of the filter language"
437 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
438 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
439 .row &_openssl.txt_& "installing a current OpenSSL release"
442 The main specification and the specification of the filtering language are also
443 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
444 &<<SECTavail>>& below tells you how to get hold of these.
448 .section "FTP site and websites" "SECID2"
451 The primary site for Exim source distributions is the &%exim.org%& FTP site,
452 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
453 website, are hosted at the University of Cambridge.
457 As well as Exim distribution tar files, the Exim website contains a number of
458 differently formatted versions of the documentation. A recent addition to the
459 online information is the Exim wiki (&url(https://wiki.exim.org)),
460 which contains what used to be a separate FAQ, as well as various other
461 examples, tips, and know-how that have been contributed by Exim users.
462 The wiki site should always redirect to the correct place, which is currently
463 provided by GitHub, and is open to editing by anyone with a GitHub account.
466 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
467 this to report bugs, and also to add items to the wish list. Please search
468 first to check that you are not duplicating a previous entry.
469 Please do not ask for configuration help in the bug-tracker.
472 .section "Mailing lists" "SECID3"
473 .cindex "mailing lists" "for Exim users"
474 The following Exim mailing lists exist:
477 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
478 .row &'exim-users@exim.org'& "General discussion list"
479 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
480 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
483 You can subscribe to these lists, change your existing subscriptions, and view
484 or search the archives via the mailing lists link on the Exim home page.
485 .cindex "Debian" "mailing list for"
486 If you are using a Debian distribution of Exim, you may wish to subscribe to
487 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
490 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on that list and not on the general Exim
495 .section "Bug reports" "SECID5"
496 .cindex "bug reports"
497 .cindex "reporting bugs"
498 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
499 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
500 whether some behaviour is a bug or not, the best thing to do is to post a
501 message to the &'exim-dev'& mailing list and have it discussed.
505 .section "Where to find the Exim distribution" "SECTavail"
507 .cindex "HTTPS download site"
508 .cindex "distribution" "FTP site"
509 .cindex "distribution" "https site"
510 The master distribution site for the Exim distribution is
512 &url(https://downloads.exim.org/)
514 The service is available over HTTPS, HTTP and FTP.
515 We encourage people to migrate to HTTPS.
517 The content served at &url(https://downloads.exim.org/) is identical to the
518 content served at &url(https://ftp.exim.org/pub/exim) and
519 &url(ftp://ftp.exim.org/pub/exim).
521 If accessing via a hostname containing &'ftp'&, then the file references that
522 follow are relative to the &_exim_& directories at these sites.
523 If accessing via the hostname &'downloads'& then the subdirectories described
524 here are top-level directories.
526 There are now quite a number of independent mirror sites around
527 the world. Those that I know about are listed in the file called &_Mirrors_&.
529 Within the top exim directory there are subdirectories called &_exim3_& (for
530 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
531 distributions), and &_Testing_& for testing versions. In the &_exim4_&
532 subdirectory, the current release can always be found in files called
536 &_exim-n.nn.tar.bz2_&
538 where &'n.nn'& is the highest such version number in the directory. The three
539 files contain identical data; the only difference is the type of compression.
540 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
541 most portable to old systems.
543 .cindex "distribution" "signing details"
544 .cindex "distribution" "public key"
545 .cindex "public key for signed distribution"
546 The distributions will be PGP signed by an individual key of the Release
547 Coordinator. This key will have a uid containing an email address in the
548 &'exim.org'& domain and will have signatures from other people, including
549 other Exim maintainers. We expect that the key will be in the "strong set" of
550 PGP keys. There should be a trust path to that key from the Exim Maintainer's
551 PGP keys, a version of which can be found in the release directory in the file
552 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
553 such as &'pool.sks-keyservers.net'&.
555 At the time of the last update, releases were being made by Jeremy Harris and signed
556 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
557 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
558 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.xz.asc_&
563 &_exim-n.nn.tar.gz.asc_&
564 &_exim-n.nn.tar.bz2.asc_&
566 For each released version, the log of changes is made available in a
567 separate file in the directory &_ChangeLogs_& so that it is possible to
568 find out what has changed without having to download the entire distribution.
570 .cindex "documentation" "available formats"
571 The main distribution contains ASCII versions of this specification and other
572 documentation; other formats of the documents are available in separate files
573 inside the &_exim4_& directory of the FTP site:
575 &_exim-html-n.nn.tar.gz_&
576 &_exim-pdf-n.nn.tar.gz_&
577 &_exim-postscript-n.nn.tar.gz_&
578 &_exim-texinfo-n.nn.tar.gz_&
580 These tar files contain only the &_doc_& directory, not the complete
581 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
584 .section "Limitations" "SECID6"
586 .cindex "limitations of Exim"
587 .cindex "bang paths" "not handled by Exim"
588 Exim is designed for use as an Internet MTA, and therefore handles addresses in
589 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
590 simple two-component bang paths can be converted by a straightforward rewriting
591 configuration. This restriction does not prevent Exim from being interfaced to
592 UUCP as a transport mechanism, provided that domain addresses are used.
594 .cindex "domainless addresses"
595 .cindex "address" "without domain"
596 Exim insists that every address it handles has a domain attached. For incoming
597 local messages, domainless addresses are automatically qualified with a
598 configured domain value. Configuration options specify from which remote
599 systems unqualified addresses are acceptable. These are then qualified on
602 .cindex "transport" "external"
603 .cindex "external transports"
604 The only external transport mechanisms that are currently implemented are SMTP
605 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
606 transport is available, and there are facilities for writing messages to files
607 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
608 to send messages to other transport mechanisms such as UUCP, provided they can
609 handle domain-style addresses. Batched SMTP input is also catered for.
611 Exim is not designed for storing mail for dial-in hosts. When the volumes of
612 such mail are large, it is better to get the messages &"delivered"& into files
613 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
616 Although Exim does have basic facilities for scanning incoming messages, these
617 are not comprehensive enough to do full virus or spam scanning. Such operations
618 are best carried out using additional specialized software packages. If you
619 compile Exim with the content-scanning extension, straightforward interfaces to
620 a number of common scanners are provided.
624 .section "Runtime configuration" "SECID7"
625 Exim's runtime configuration is held in a single text file that is divided
626 into a number of sections. The entries in this file consist of keywords and
627 values, in the style of Smail 3 configuration files. A default configuration
628 file which is suitable for simple online installations is provided in the
629 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
632 .section "Calling interface" "SECID8"
633 .cindex "Sendmail compatibility" "command line interface"
634 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
635 can be a straight replacement for &_/usr/lib/sendmail_& or
636 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
637 about Sendmail in order to run Exim. For actions other than sending messages,
638 Sendmail-compatible options also exist, but those that produce output (for
639 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
640 format. There are also some additional options that are compatible with Smail
641 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
642 documents all Exim's command line options. This information is automatically
643 made into the man page that forms part of the Exim distribution.
645 Control of messages in the queue can be done via certain privileged command
646 line options. There is also an optional monitor program called &'eximon'&,
647 which displays current information in an X window, and which contains a menu
648 interface to Exim's command line administration options.
652 .section "Terminology" "SECID9"
653 .cindex "terminology definitions"
654 .cindex "body of message" "definition of"
655 The &'body'& of a message is the actual data that the sender wants to transmit.
656 It is the last part of a message and is separated from the &'header'& (see
657 below) by a blank line.
659 .cindex "bounce message" "definition of"
660 When a message cannot be delivered, it is normally returned to the sender in a
661 delivery failure message or a &"non-delivery report"& (NDR). The term
662 &'bounce'& is commonly used for this action, and the error reports are often
663 called &'bounce messages'&. This is a convenient shorthand for &"delivery
664 failure error report"&. Such messages have an empty sender address in the
665 message's &'envelope'& (see below) to ensure that they cannot themselves give
666 rise to further bounce messages.
668 The term &'default'& appears frequently in this manual. It is used to qualify a
669 value which is used in the absence of any setting in the configuration. It may
670 also qualify an action which is taken unless a configuration setting specifies
673 The term &'defer'& is used when the delivery of a message to a specific
674 destination cannot immediately take place for some reason (a remote host may be
675 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
678 The word &'domain'& is sometimes used to mean all but the first component of a
679 host's name. It is &'not'& used in that sense here, where it normally refers to
680 the part of an email address following the @ sign.
682 .cindex "envelope, definition of"
683 .cindex "sender" "definition of"
684 A message in transit has an associated &'envelope'&, as well as a header and a
685 body. The envelope contains a sender address (to which bounce messages should
686 be delivered), and any number of recipient addresses. References to the
687 sender or the recipients of a message usually mean the addresses in the
688 envelope. An MTA uses these addresses for delivery, and for returning bounce
689 messages, not the addresses that appear in the header lines.
691 .cindex "message" "header, definition of"
692 .cindex "header section" "definition of"
693 The &'header'& of a message is the first part of a message's text, consisting
694 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
695 &'Subject:'&, etc. Long header lines can be split over several text lines by
696 indenting the continuations. The header is separated from the body by a blank
699 .cindex "local part" "definition of"
700 .cindex "domain" "definition of"
701 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
702 part of an email address that precedes the @ sign. The part that follows the
703 @ sign is called the &'domain'& or &'mail domain'&.
705 .cindex "local delivery" "definition of"
706 .cindex "remote delivery, definition of"
707 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
708 delivery to a file or a pipe on the local host from delivery by SMTP over
709 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
710 host it is running on are &'remote'&.
712 .cindex "return path" "definition of"
713 &'Return path'& is another name that is used for the sender address in a
716 .cindex "queue" "definition of"
717 The term &'queue'& is used to refer to the set of messages awaiting delivery
718 because this term is in widespread use in the context of MTAs. However, in
719 Exim's case, the reality is more like a pool than a queue, because there is
720 normally no ordering of waiting messages.
722 .cindex "queue runner" "definition of"
723 The term &'queue runner'& is used to describe a process that scans the queue
724 and attempts to deliver those messages whose retry times have come. This term
725 is used by other MTAs and also relates to the command &%runq%&, but in Exim
726 the waiting messages are normally processed in an unpredictable order.
728 .cindex "spool directory" "definition of"
729 The term &'spool directory'& is used for a directory in which Exim keeps the
730 messages in its queue &-- that is, those that it is in the process of
731 delivering. This should not be confused with the directory in which local
732 mailboxes are stored, which is called a &"spool directory"& by some people. In
733 the Exim documentation, &"spool"& is always used in the first sense.
740 . ////////////////////////////////////////////////////////////////////////////
741 . ////////////////////////////////////////////////////////////////////////////
743 .chapter "Incorporated code" "CHID2"
744 .cindex "incorporated code"
745 .cindex "regular expressions" "library"
748 A number of pieces of external code are included in the Exim distribution.
751 Regular expressions are supported in the main Exim program and in the
752 Exim monitor using the freely-distributable PCRE library, copyright
753 © University of Cambridge. The source to PCRE is no longer shipped with
754 Exim, so you will need to use the version of PCRE shipped with your system,
755 or obtain and install the full version of the library from
756 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
758 .cindex "cdb" "acknowledgment"
759 Support for the cdb (Constant DataBase) lookup method is provided by code
760 contributed by Nigel Metheringham of (at the time he contributed it) Planet
761 Online Ltd. The implementation is completely contained within the code of Exim.
762 It does not link against an external cdb library. The code contains the
763 following statements:
766 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
768 This program is free software; you can redistribute it and/or modify it under
769 the terms of the GNU General Public License as published by the Free Software
770 Foundation; either version 2 of the License, or (at your option) any later
772 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
773 the spec and sample code for cdb can be obtained from
774 &url(https://cr.yp.to/cdb.html). This implementation borrows
775 some code from Dan Bernstein's implementation (which has no license
776 restrictions applied to it).
779 .cindex "SPA authentication"
780 .cindex "Samba project"
781 .cindex "Microsoft Secure Password Authentication"
782 Client support for Microsoft's &'Secure Password Authentication'& is provided
783 by code contributed by Marc Prud'hommeaux. Server support was contributed by
784 Tom Kistner. This includes code taken from the Samba project, which is released
788 .cindex "&'pwcheck'& daemon"
789 .cindex "&'pwauthd'& daemon"
790 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
791 by code taken from the Cyrus-SASL library and adapted by Alexander S.
792 Sabourenkov. The permission notice appears below, in accordance with the
793 conditions expressed therein.
796 Copyright © 2001 Carnegie Mellon University. All rights reserved.
798 Redistribution and use in source and binary forms, with or without
799 modification, are permitted provided that the following conditions
803 Redistributions of source code must retain the above copyright
804 notice, this list of conditions and the following disclaimer.
806 Redistributions in binary form must reproduce the above copyright
807 notice, this list of conditions and the following disclaimer in
808 the documentation and/or other materials provided with the
811 The name &"Carnegie Mellon University"& must not be used to
812 endorse or promote products derived from this software without
813 prior written permission. For permission or any other legal
814 details, please contact
816 Office of Technology Transfer
817 Carnegie Mellon University
819 Pittsburgh, PA 15213-3890
820 (412) 268-4387, fax: (412) 268-7395
821 tech-transfer@andrew.cmu.edu
824 Redistributions of any form whatsoever must retain the following
827 &"This product includes software developed by Computing Services
828 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
830 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
831 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
832 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
833 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
834 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
835 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
836 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
841 .cindex "Exim monitor" "acknowledgment"
844 The Exim Monitor program, which is an X-Window application, includes
845 modified versions of the Athena StripChart and TextPop widgets.
846 This code is copyright by DEC and MIT, and their permission notice appears
847 below, in accordance with the conditions expressed therein.
850 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
851 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
855 Permission to use, copy, modify, and distribute this software and its
856 documentation for any purpose and without fee is hereby granted,
857 provided that the above copyright notice appear in all copies and that
858 both that copyright notice and this permission notice appear in
859 supporting documentation, and that the names of Digital or MIT not be
860 used in advertising or publicity pertaining to distribution of the
861 software without specific, written prior permission.
863 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
864 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
865 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
866 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
867 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
868 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
873 .cindex "opendmarc" "acknowledgment"
874 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
875 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
876 derived code are indicated in the respective source files. The full OpenDMARC
877 license is provided in the LICENSE.opendmarc file contained in the distributed
881 Many people have contributed code fragments, some large, some small, that were
882 not covered by any specific license requirements. It is assumed that the
883 contributors are happy to see their code incorporated into Exim under the GPL.
890 . ////////////////////////////////////////////////////////////////////////////
891 . ////////////////////////////////////////////////////////////////////////////
893 .chapter "How Exim receives and delivers mail" "CHID11" &&&
894 "Receiving and delivering mail"
897 .section "Overall philosophy" "SECID10"
898 .cindex "design philosophy"
899 Exim is designed to work efficiently on systems that are permanently connected
900 to the Internet and are handling a general mix of mail. In such circumstances,
901 most messages can be delivered immediately. Consequently, Exim does not
902 maintain independent queues of messages for specific domains or hosts, though
903 it does try to send several messages in a single SMTP connection after a host
904 has been down, and it also maintains per-host retry information.
907 .section "Policy control" "SECID11"
908 .cindex "policy control" "overview"
909 Policy controls are now an important feature of MTAs that are connected to the
910 Internet. Perhaps their most important job is to stop MTAs from being abused as
911 &"open relays"& by misguided individuals who send out vast amounts of
912 unsolicited junk and want to disguise its source. Exim provides flexible
913 facilities for specifying policy controls on incoming mail:
916 .cindex "&ACL;" "introduction"
917 Exim 4 (unlike previous versions of Exim) implements policy controls on
918 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
919 series of statements that may either grant or deny access. ACLs can be used at
920 several places in the SMTP dialogue while receiving a message from a remote
921 host. However, the most common places are after each RCPT command, and at the
922 very end of the message. The sysadmin can specify conditions for accepting or
923 rejecting individual recipients or the entire message, respectively, at these
924 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
927 An ACL is also available for locally generated, non-SMTP messages. In this
928 case, the only available actions are to accept or deny the entire message.
930 When Exim is compiled with the content-scanning extension, facilities are
931 provided in the ACL mechanism for passing the message to external virus and/or
932 spam scanning software. The result of such a scan is passed back to the ACL,
933 which can then use it to decide what to do with the message.
935 When a message has been received, either from a remote host or from the local
936 host, but before the final acknowledgment has been sent, a locally supplied C
937 function called &[local_scan()]& can be run to inspect the message and decide
938 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
939 is accepted, the list of recipients can be modified by the function.
941 Using the &[local_scan()]& mechanism is another way of calling external scanner
942 software. The &%SA-Exim%& add-on package works this way. It does not require
943 Exim to be compiled with the content-scanning extension.
945 After a message has been accepted, a further checking mechanism is available in
946 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
947 runs at the start of every delivery process.
952 .section "User filters" "SECID12"
953 .cindex "filter" "introduction"
954 .cindex "Sieve filter"
955 In a conventional Exim configuration, users are able to run private filters by
956 setting up appropriate &_.forward_& files in their home directories. See
957 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
958 configuration needed to support this, and the separate document entitled
959 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
960 of filtering are available:
963 Sieve filters are written in the standard filtering language that is defined
966 Exim filters are written in a syntax that is unique to Exim, but which is more
967 powerful than Sieve, which it pre-dates.
970 User filters are run as part of the routing process, described below.
974 .section "Message identification" "SECTmessiden"
975 .cindex "message ids" "details of format"
976 .cindex "format" "of message id"
977 .cindex "id of message"
982 Every message handled by Exim is given a &'message id'& which is sixteen
983 characters long. It is divided into three parts, separated by hyphens, for
984 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
985 normally encoding numbers in base 62. However, in the Darwin operating
986 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
987 (avoiding the use of lower case letters) is used instead, because the message
988 id is used to construct filenames, and the names of files in those systems are
989 not always case-sensitive.
991 .cindex "pid (process id)" "re-use of"
992 The detail of the contents of the message id have changed as Exim has evolved.
993 Earlier versions relied on the operating system not re-using a process id (pid)
994 within one second. On modern operating systems, this assumption can no longer
995 be made, so the algorithm had to be changed. To retain backward compatibility,
996 the format of the message id was retained, which is why the following rules are
1000 The first six characters of the message id are the time at which the message
1001 started to be received, to a granularity of one second. That is, this field
1002 contains the number of seconds since the start of the epoch (the normal Unix
1003 way of representing the date and time of day).
1005 After the first hyphen, the next six characters are the id of the process that
1006 received the message.
1008 There are two different possibilities for the final two characters:
1010 .oindex "&%localhost_number%&"
1011 If &%localhost_number%& is not set, this value is the fractional part of the
1012 time of reception, normally in units of 1/2000 of a second, but for systems
1013 that must use base 36 instead of base 62 (because of case-insensitive file
1014 systems), the units are 1/1000 of a second.
1016 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1017 the fractional part of the time, which in this case is in units of 1/200
1018 (1/100) of a second.
1022 After a message has been received, Exim waits for the clock to tick at the
1023 appropriate resolution before proceeding, so that if another message is
1024 received by the same process, or by another process with the same (re-used)
1025 pid, it is guaranteed that the time will be different. In most cases, the clock
1026 will already have ticked while the message was being received.
1029 .section "Receiving mail" "SECID13"
1030 .cindex "receiving mail"
1031 .cindex "message" "reception"
1032 The only way Exim can receive mail from another host is using SMTP over
1033 TCP/IP, in which case the sender and recipient addresses are transferred using
1034 SMTP commands. However, from a locally running process (such as a user's MUA),
1035 there are several possibilities:
1038 If the process runs Exim with the &%-bm%& option, the message is read
1039 non-interactively (usually via a pipe), with the recipients taken from the
1040 command line, or from the body of the message if &%-t%& is also used.
1042 If the process runs Exim with the &%-bS%& option, the message is also read
1043 non-interactively, but in this case the recipients are listed at the start of
1044 the message in a series of SMTP RCPT commands, terminated by a DATA
1045 command. This is called &"batch SMTP"& format,
1046 but it isn't really SMTP. The SMTP commands are just another way of passing
1047 envelope addresses in a non-interactive submission.
1049 If the process runs Exim with the &%-bs%& option, the message is read
1050 interactively, using the SMTP protocol. A two-way pipe is normally used for
1051 passing data between the local process and the Exim process.
1052 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1053 example, the ACLs for SMTP commands are used for this form of submission.
1055 A local process may also make a TCP/IP call to the host's loopback address
1056 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1057 does not treat the loopback address specially. It treats all such connections
1058 in the same way as connections from other hosts.
1062 .cindex "message sender, constructed by Exim"
1063 .cindex "sender" "constructed by Exim"
1064 In the three cases that do not involve TCP/IP, the sender address is
1065 constructed from the login name of the user that called Exim and a default
1066 qualification domain (which can be set by the &%qualify_domain%& configuration
1067 option). For local or batch SMTP, a sender address that is passed using the
1068 SMTP MAIL command is ignored. However, the system administrator may allow
1069 certain users (&"trusted users"&) to specify a different sender addresses
1070 unconditionally, or all users to specify certain forms of different sender
1071 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1072 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1073 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1074 users to change sender addresses.
1076 Messages received by either of the non-interactive mechanisms are subject to
1077 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1078 (either over TCP/IP or interacting with a local process) can be checked by a
1079 number of ACLs that operate at different times during the SMTP session. Either
1080 individual recipients or the entire message can be rejected if local policy
1081 requirements are not met. The &[local_scan()]& function (see chapter
1082 &<<CHAPlocalscan>>&) is run for all incoming messages.
1084 Exim can be configured not to start a delivery process when a message is
1085 received; this can be unconditional, or depend on the number of incoming SMTP
1086 connections or the system load. In these situations, new messages wait on the
1087 queue until a queue runner process picks them up. However, in standard
1088 configurations under normal conditions, delivery is started as soon as a
1089 message is received.
1095 .section "Handling an incoming message" "SECID14"
1096 .cindex "spool directory" "files that hold a message"
1097 .cindex "file" "how a message is held"
1098 When Exim accepts a message, it writes two files in its spool directory. The
1099 first contains the envelope information, the current status of the message, and
1100 the header lines, and the second contains the body of the message. The names of
1101 the two spool files consist of the message id, followed by &`-H`& for the
1102 file containing the envelope and header, and &`-D`& for the data file.
1104 .cindex "spool directory" "&_input_& sub-directory"
1105 By default, all these message files are held in a single directory called
1106 &_input_& inside the general Exim spool directory. Some operating systems do
1107 not perform very well if the number of files in a directory gets large; to
1108 improve performance in such cases, the &%split_spool_directory%& option can be
1109 used. This causes Exim to split up the input files into 62 sub-directories
1110 whose names are single letters or digits. When this is done, the queue is
1111 processed one sub-directory at a time instead of all at once, which can improve
1112 overall performance even when there are not enough files in each directory to
1113 affect file system performance.
1115 The envelope information consists of the address of the message's sender and
1116 the addresses of the recipients. This information is entirely separate from
1117 any addresses contained in the header lines. The status of the message includes
1118 a list of recipients who have already received the message. The format of the
1119 first spool file is described in chapter &<<CHAPspool>>&.
1121 .cindex "rewriting" "addresses"
1122 Address rewriting that is specified in the rewrite section of the configuration
1123 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1124 both in the header lines and the envelope, at the time the message is accepted.
1125 If during the course of delivery additional addresses are generated (for
1126 example, via aliasing), these new addresses are rewritten as soon as they are
1127 generated. At the time a message is actually delivered (transported) further
1128 rewriting can take place; because this is a transport option, it can be
1129 different for different forms of delivery. It is also possible to specify the
1130 addition or removal of certain header lines at the time the message is
1131 delivered (see chapters &<<CHAProutergeneric>>& and
1132 &<<CHAPtransportgeneric>>&).
1136 .section "Life of a message" "SECID15"
1137 .cindex "message" "life of"
1138 .cindex "message" "frozen"
1139 A message remains in the spool directory until it is completely delivered to
1140 its recipients or to an error address, or until it is deleted by an
1141 administrator or by the user who originally created it. In cases when delivery
1142 cannot proceed &-- for example when a message can neither be delivered to its
1143 recipients nor returned to its sender, the message is marked &"frozen"& on the
1144 spool, and no more deliveries are attempted.
1146 .cindex "frozen messages" "thawing"
1147 .cindex "message" "thawing frozen"
1148 An administrator can &"thaw"& such messages when the problem has been
1149 corrected, and can also freeze individual messages by hand if necessary. In
1150 addition, an administrator can force a delivery error, causing a bounce message
1153 .oindex "&%timeout_frozen_after%&"
1154 .oindex "&%ignore_bounce_errors_after%&"
1155 There are options called &%ignore_bounce_errors_after%& and
1156 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1157 The first applies only to frozen bounces, the second to all frozen messages.
1159 .cindex "message" "log file for"
1160 .cindex "log" "file for each message"
1161 While Exim is working on a message, it writes information about each delivery
1162 attempt to its main log file. This includes successful, unsuccessful, and
1163 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1164 lines are also written to a separate &'message log'& file for each message.
1165 These logs are solely for the benefit of the administrator and are normally
1166 deleted along with the spool files when processing of a message is complete.
1167 The use of individual message logs can be disabled by setting
1168 &%no_message_logs%&; this might give an improvement in performance on very busy
1171 .cindex "journal file"
1172 .cindex "file" "journal"
1173 All the information Exim itself needs to set up a delivery is kept in the first
1174 spool file, along with the header lines. When a successful delivery occurs, the
1175 address is immediately written at the end of a journal file, whose name is the
1176 message id followed by &`-J`&. At the end of a delivery run, if there are some
1177 addresses left to be tried again later, the first spool file (the &`-H`& file)
1178 is updated to indicate which these are, and the journal file is then deleted.
1179 Updating the spool file is done by writing a new file and renaming it, to
1180 minimize the possibility of data loss.
1182 Should the system or Exim crash after a successful delivery but before
1183 the spool file has been updated, the journal is left lying around. The next
1184 time Exim attempts to deliver the message, it reads the journal file and
1185 updates the spool file before proceeding. This minimizes the chances of double
1186 deliveries caused by crashes.
1190 .section "Processing an address for delivery" "SECTprocaddress"
1191 .cindex "drivers" "definition of"
1192 .cindex "router" "definition of"
1193 .cindex "transport" "definition of"
1194 The main delivery processing elements of Exim are called &'routers'& and
1195 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1196 number of them is provided in the source distribution, and compile-time options
1197 specify which ones are included in the binary. Runtime options specify which
1198 ones are actually used for delivering messages.
1200 .cindex "drivers" "instance definition"
1201 Each driver that is specified in the runtime configuration is an &'instance'&
1202 of that particular driver type. Multiple instances are allowed; for example,
1203 you can set up several different &(smtp)& transports, each with different
1204 option values that might specify different ports or different timeouts. Each
1205 instance has its own identifying name. In what follows we will normally use the
1206 instance name when discussing one particular instance (that is, one specific
1207 configuration of the driver), and the generic driver name when discussing
1208 the driver's features in general.
1210 A &'router'& is a driver that operates on an address, either determining how
1211 its delivery should happen, by assigning it to a specific transport, or
1212 converting the address into one or more new addresses (for example, via an
1213 alias file). A router may also explicitly choose to fail an address, causing it
1216 A &'transport'& is a driver that transmits a copy of the message from Exim's
1217 spool to some destination. There are two kinds of transport: for a &'local'&
1218 transport, the destination is a file or a pipe on the local host, whereas for a
1219 &'remote'& transport the destination is some other host. A message is passed
1220 to a specific transport as a result of successful routing. If a message has
1221 several recipients, it may be passed to a number of different transports.
1223 .cindex "preconditions" "definition of"
1224 An address is processed by passing it to each configured router instance in
1225 turn, subject to certain preconditions, until a router accepts the address or
1226 specifies that it should be bounced. We will describe this process in more
1227 detail shortly. First, as a simple example, we consider how each recipient
1228 address in a message is processed in a small configuration of three routers.
1230 To make this a more concrete example, it is described in terms of some actual
1231 routers, but remember, this is only an example. You can configure Exim's
1232 routers in many different ways, and there may be any number of routers in a
1235 The first router that is specified in a configuration is often one that handles
1236 addresses in domains that are not recognized specifically by the local host.
1237 Typically these are addresses for arbitrary domains on the Internet. A precondition
1238 is set up which looks for the special domains known to the host (for example,
1239 its own domain name), and the router is run for addresses that do &'not'&
1240 match. Typically, this is a router that looks up domains in the DNS in order to
1241 find the hosts to which this address routes. If it succeeds, the address is
1242 assigned to a suitable SMTP transport; if it does not succeed, the router is
1243 configured to fail the address.
1245 The second router is reached only when the domain is recognized as one that
1246 &"belongs"& to the local host. This router does redirection &-- also known as
1247 aliasing and forwarding. When it generates one or more new addresses from the
1248 original, each of them is routed independently from the start. Otherwise, the
1249 router may cause an address to fail, or it may simply decline to handle the
1250 address, in which case the address is passed to the next router.
1252 The final router in many configurations is one that checks to see if the
1253 address belongs to a local mailbox. The precondition may involve a check to
1254 see if the local part is the name of a login account, or it may look up the
1255 local part in a file or a database. If its preconditions are not met, or if
1256 the router declines, we have reached the end of the routers. When this happens,
1257 the address is bounced.
1261 .section "Processing an address for verification" "SECID16"
1262 .cindex "router" "for verification"
1263 .cindex "verifying address" "overview"
1264 As well as being used to decide how to deliver to an address, Exim's routers
1265 are also used for &'address verification'&. Verification can be requested as
1266 one of the checks to be performed in an ACL for incoming messages, on both
1267 sender and recipient addresses, and it can be tested using the &%-bv%& and
1268 &%-bvs%& command line options.
1270 When an address is being verified, the routers are run in &"verify mode"&. This
1271 does not affect the way the routers work, but it is a state that can be
1272 detected. By this means, a router can be skipped or made to behave differently
1273 when verifying. A common example is a configuration in which the first router
1274 sends all messages to a message-scanning program unless they have been
1275 previously scanned. Thus, the first router accepts all addresses without any
1276 checking, making it useless for verifying. Normally, the &%no_verify%& option
1277 would be set for such a router, causing it to be skipped in verify mode.
1282 .section "Running an individual router" "SECTrunindrou"
1283 .cindex "router" "running details"
1284 .cindex "preconditions" "checking"
1285 .cindex "router" "result of running"
1286 As explained in the example above, a number of preconditions are checked before
1287 running a router. If any are not met, the router is skipped, and the address is
1288 passed to the next router. When all the preconditions on a router &'are'& met,
1289 the router is run. What happens next depends on the outcome, which is one of
1293 &'accept'&: The router accepts the address, and either assigns it to a
1294 transport or generates one or more &"child"& addresses. Processing the
1295 original address ceases
1296 .oindex "&%unseen%&"
1297 unless the &%unseen%& option is set on the router. This option
1298 can be used to set up multiple deliveries with different routing (for example,
1299 for keeping archive copies of messages). When &%unseen%& is set, the address is
1300 passed to the next router. Normally, however, an &'accept'& return marks the
1303 Any child addresses generated by the router are processed independently,
1304 starting with the first router by default. It is possible to change this by
1305 setting the &%redirect_router%& option to specify which router to start at for
1306 child addresses. Unlike &%pass_router%& (see below) the router specified by
1307 &%redirect_router%& may be anywhere in the router configuration.
1309 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1310 requests that the address be passed to another router. By default, the address
1311 is passed to the next router, but this can be changed by setting the
1312 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1313 must be below the current router (to avoid loops).
1315 &'decline'&: The router declines to accept the address because it does not
1316 recognize it at all. By default, the address is passed to the next router, but
1317 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1318 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1319 &'decline'& into &'fail'&.
1321 &'fail'&: The router determines that the address should fail, and queues it for
1322 the generation of a bounce message. There is no further processing of the
1323 original address unless &%unseen%& is set on the router.
1325 &'defer'&: The router cannot handle the address at the present time. (A
1326 database may be offline, or a DNS lookup may have timed out.) No further
1327 processing of the address happens in this delivery attempt. It is tried again
1328 next time the message is considered for delivery.
1330 &'error'&: There is some error in the router (for example, a syntax error in
1331 its configuration). The action is as for defer.
1334 If an address reaches the end of the routers without having been accepted by
1335 any of them, it is bounced as unrouteable. The default error message in this
1336 situation is &"unrouteable address"&, but you can set your own message by
1337 making use of the &%cannot_route_message%& option. This can be set for any
1338 router; the value from the last router that &"saw"& the address is used.
1340 Sometimes while routing you want to fail a delivery when some conditions are
1341 met but others are not, instead of passing the address on for further routing.
1342 You can do this by having a second router that explicitly fails the delivery
1343 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1344 facility for this purpose.
1347 .section "Duplicate addresses" "SECID17"
1348 .cindex "case of local parts"
1349 .cindex "address duplicate, discarding"
1350 .cindex "duplicate addresses"
1351 Once routing is complete, Exim scans the addresses that are assigned to local
1352 and remote transports and discards any duplicates that it finds. During this
1353 check, local parts are treated case-sensitively. This happens only when
1354 actually delivering a message; when testing routers with &%-bt%&, all the
1355 routed addresses are shown.
1359 .section "Router preconditions" "SECTrouprecon"
1360 .cindex "router" "preconditions, order of processing"
1361 .cindex "preconditions" "order of processing"
1362 The preconditions that are tested for each router are listed below, in the
1363 order in which they are tested. The individual configuration options are
1364 described in more detail in chapter &<<CHAProutergeneric>>&.
1367 .cindex affix "router precondition"
1368 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1369 the local parts handled by the router may or must have certain prefixes and/or
1370 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1371 skipped. These conditions are tested first. When an affix is present, it is
1372 removed from the local part before further processing, including the evaluation
1373 of any other conditions.
1375 Routers can be designated for use only when not verifying an address, that is,
1376 only when routing it for delivery (or testing its delivery routing). If the
1377 &%verify%& option is set false, the router is skipped when Exim is verifying an
1379 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1380 &%verify_recipient%&, which independently control the use of the router for
1381 sender and recipient verification. You can set these options directly if
1382 you want a router to be used for only one type of verification.
1383 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1385 If the &%address_test%& option is set false, the router is skipped when Exim is
1386 run with the &%-bt%& option to test an address routing. This can be helpful
1387 when the first router sends all new messages to a scanner of some sort; it
1388 makes it possible to use &%-bt%& to test subsequent delivery routing without
1389 having to simulate the effect of the scanner.
1391 Routers can be designated for use only when verifying an address, as
1392 opposed to routing it for delivery. The &%verify_only%& option controls this.
1393 Again, cutthrough delivery counts as a verification.
1395 Individual routers can be explicitly skipped when running the routers to
1396 check an address given in the SMTP EXPN command (see the &%expn%& option).
1398 If the &%domains%& option is set, the domain of the address must be in the set
1399 of domains that it defines.
1401 .vindex "&$local_part_prefix$&"
1402 .vindex "&$local_part_prefix_v$&"
1403 .vindex "&$local_part$&"
1404 .vindex "&$local_part_suffix$&"
1405 .vindex "&$local_part_suffix_v$&"
1406 .cindex affix "router precondition"
1407 If the &%local_parts%& option is set, the local part of the address must be in
1408 the set of local parts that it defines. If &%local_part_prefix%& or
1409 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1410 part before this check. If you want to do precondition tests on local parts
1411 that include affixes, you can do so by using a &%condition%& option (see below)
1412 that uses the variables &$local_part$&, &$local_part_prefix$&,
1413 &$local_part_prefix_v$&, &$local_part_suffix$&
1414 and &$local_part_suffix_v$& as necessary.
1416 .vindex "&$local_user_uid$&"
1417 .vindex "&$local_user_gid$&"
1419 If the &%check_local_user%& option is set, the local part must be the name of
1420 an account on the local host. If this check succeeds, the uid and gid of the
1421 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1422 user's home directory is placed in &$home$&; these values can be used in the
1423 remaining preconditions.
1425 If the &%router_home_directory%& option is set, it is expanded at this point,
1426 because it overrides the value of &$home$&. If this expansion were left till
1427 later, the value of &$home$& as set by &%check_local_user%& would be used in
1428 subsequent tests. Having two different values of &$home$& in the same router
1429 could lead to confusion.
1431 If the &%senders%& option is set, the envelope sender address must be in the
1432 set of addresses that it defines.
1434 If the &%require_files%& option is set, the existence or non-existence of
1435 specified files is tested.
1437 .cindex "customizing" "precondition"
1438 If the &%condition%& option is set, it is evaluated and tested. This option
1439 uses an expanded string to allow you to set up your own custom preconditions.
1440 Expanded strings are described in chapter &<<CHAPexpand>>&.
1444 Note that &%require_files%& comes near the end of the list, so you cannot use
1445 it to check for the existence of a file in which to lookup up a domain, local
1446 part, or sender. However, as these options are all expanded, you can use the
1447 &%exists%& expansion condition to make such tests within each condition. The
1448 &%require_files%& option is intended for checking files that the router may be
1449 going to use internally, or which are needed by a specific transport (for
1450 example, &_.procmailrc_&).
1454 .section "Delivery in detail" "SECID18"
1455 .cindex "delivery" "in detail"
1456 When a message is to be delivered, the sequence of events is as follows:
1459 If a system-wide filter file is specified, the message is passed to it. The
1460 filter may add recipients to the message, replace the recipients, discard the
1461 message, cause a new message to be generated, or cause the message delivery to
1462 fail. The format of the system filter file is the same as for Exim user filter
1463 files, described in the separate document entitled &'Exim's interfaces to mail
1465 .cindex "Sieve filter" "not available for system filter"
1466 (&*Note*&: Sieve cannot be used for system filter files.)
1468 Some additional features are available in system filters &-- see chapter
1469 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1470 filter only once per delivery attempt, however many recipients it has. However,
1471 if there are several delivery attempts because one or more addresses could not
1472 be immediately delivered, the system filter is run each time. The filter
1473 condition &%first_delivery%& can be used to detect the first run of the system
1476 Each recipient address is offered to each configured router, in turn, subject to
1477 its preconditions, until one is able to handle it. If no router can handle the
1478 address, that is, if they all decline, the address is failed. Because routers
1479 can be targeted at particular domains, several locally handled domains can be
1480 processed entirely independently of each other.
1482 .cindex "routing" "loops in"
1483 .cindex "loop" "while routing"
1484 A router that accepts an address may assign it to a local or a remote
1485 transport. However, the transport is not run at this time. Instead, the address
1486 is placed on a list for the particular transport, which will be run later.
1487 Alternatively, the router may generate one or more new addresses (typically
1488 from alias, forward, or filter files). New addresses are fed back into this
1489 process from the top, but in order to avoid loops, a router ignores any address
1490 which has an identically-named ancestor that was processed by itself.
1492 When all the routing has been done, addresses that have been successfully
1493 handled are passed to their assigned transports. When local transports are
1494 doing real local deliveries, they handle only one address at a time, but if a
1495 local transport is being used as a pseudo-remote transport (for example, to
1496 collect batched SMTP messages for transmission by some other means) multiple
1497 addresses can be handled. Remote transports can always handle more than one
1498 address at a time, but can be configured not to do so, or to restrict multiple
1499 addresses to the same domain.
1501 Each local delivery to a file or a pipe runs in a separate process under a
1502 non-privileged uid, and these deliveries are run one at a time. Remote
1503 deliveries also run in separate processes, normally under a uid that is private
1504 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1505 run in parallel. The maximum number of simultaneous remote deliveries for any
1506 one message is set by the &%remote_max_parallel%& option.
1507 The order in which deliveries are done is not defined, except that all local
1508 deliveries happen before any remote deliveries.
1510 .cindex "queue runner"
1511 When it encounters a local delivery during a queue run, Exim checks its retry
1512 database to see if there has been a previous temporary delivery failure for the
1513 address before running the local transport. If there was a previous failure,
1514 Exim does not attempt a new delivery until the retry time for the address is
1515 reached. However, this happens only for delivery attempts that are part of a
1516 queue run. Local deliveries are always attempted when delivery immediately
1517 follows message reception, even if retry times are set for them. This makes for
1518 better behaviour if one particular message is causing problems (for example,
1519 causing quota overflow, or provoking an error in a filter file).
1521 .cindex "delivery" "retry in remote transports"
1522 Remote transports do their own retry handling, since an address may be
1523 deliverable to one of a number of hosts, each of which may have a different
1524 retry time. If there have been previous temporary failures and no host has
1525 reached its retry time, no delivery is attempted, whether in a queue run or
1526 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1528 If there were any permanent errors, a bounce message is returned to an
1529 appropriate address (the sender in the common case), with details of the error
1530 for each failing address. Exim can be configured to send copies of bounce
1531 messages to other addresses.
1533 .cindex "delivery" "deferral"
1534 If one or more addresses suffered a temporary failure, the message is left on
1535 the queue, to be tried again later. Delivery of these addresses is said to be
1538 When all the recipient addresses have either been delivered or bounced,
1539 handling of the message is complete. The spool files and message log are
1540 deleted, though the message log can optionally be preserved if required.
1546 .section "Retry mechanism" "SECID19"
1547 .cindex "delivery" "retry mechanism"
1548 .cindex "retry" "description of mechanism"
1549 .cindex "queue runner"
1550 Exim's mechanism for retrying messages that fail to get delivered at the first
1551 attempt is the queue runner process. You must either run an Exim daemon that
1552 uses the &%-q%& option with a time interval to start queue runners at regular
1553 intervals or use some other means (such as &'cron'&) to start them. If you do
1554 not arrange for queue runners to be run, messages that fail temporarily at the
1555 first attempt will remain in your queue forever. A queue runner process works
1556 its way through the queue, one message at a time, trying each delivery that has
1557 passed its retry time.
1558 You can run several queue runners at once.
1560 Exim uses a set of configured rules to determine when next to retry the failing
1561 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1562 should give up trying to deliver to the address, at which point it generates a
1563 bounce message. If no retry rules are set for a particular host, address, and
1564 error combination, no retries are attempted, and temporary errors are treated
1569 .section "Temporary delivery failure" "SECID20"
1570 .cindex "delivery" "temporary failure"
1571 There are many reasons why a message may not be immediately deliverable to a
1572 particular address. Failure to connect to a remote machine (because it, or the
1573 connection to it, is down) is one of the most common. Temporary failures may be
1574 detected during routing as well as during the transport stage of delivery.
1575 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1576 is on a file system where the user is over quota. Exim can be configured to
1577 impose its own quotas on local mailboxes; where system quotas are set they will
1580 If a host is unreachable for a period of time, a number of messages may be
1581 waiting for it by the time it recovers, and sending them in a single SMTP
1582 connection is clearly beneficial. Whenever a delivery to a remote host is
1584 .cindex "hints database" "deferred deliveries"
1585 Exim makes a note in its hints database, and whenever a successful
1586 SMTP delivery has happened, it looks to see if any other messages are waiting
1587 for the same host. If any are found, they are sent over the same SMTP
1588 connection, subject to a configuration limit as to the maximum number in any
1593 .section "Permanent delivery failure" "SECID21"
1594 .cindex "delivery" "permanent failure"
1595 .cindex "bounce message" "when generated"
1596 When a message cannot be delivered to some or all of its intended recipients, a
1597 bounce message is generated. Temporary delivery failures turn into permanent
1598 errors when their timeout expires. All the addresses that fail in a given
1599 delivery attempt are listed in a single message. If the original message has
1600 many recipients, it is possible for some addresses to fail in one delivery
1601 attempt and others to fail subsequently, giving rise to more than one bounce
1602 message. The wording of bounce messages can be customized by the administrator.
1603 See chapter &<<CHAPemsgcust>>& for details.
1605 .cindex "&'X-Failed-Recipients:'& header line"
1606 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1607 failed addresses, for the benefit of programs that try to analyse such messages
1610 .cindex "bounce message" "recipient of"
1611 A bounce message is normally sent to the sender of the original message, as
1612 obtained from the message's envelope. For incoming SMTP messages, this is the
1613 address given in the MAIL command. However, when an address is expanded via a
1614 forward or alias file, an alternative address can be specified for delivery
1615 failures of the generated addresses. For a mailing list expansion (see section
1616 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1621 .section "Failures to deliver bounce messages" "SECID22"
1622 .cindex "bounce message" "failure to deliver"
1623 If a bounce message (either locally generated or received from a remote host)
1624 itself suffers a permanent delivery failure, the message is left in the queue,
1625 but it is frozen, awaiting the attention of an administrator. There are options
1626 that can be used to make Exim discard such failed messages, or to keep them
1627 for only a short time (see &%timeout_frozen_after%& and
1628 &%ignore_bounce_errors_after%&).
1634 . ////////////////////////////////////////////////////////////////////////////
1635 . ////////////////////////////////////////////////////////////////////////////
1637 .chapter "Building and installing Exim" "CHID3"
1638 .scindex IIDbuex "building Exim"
1640 .section "Unpacking" "SECID23"
1641 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1642 creates a directory with the name of the current release (for example,
1643 &_exim-&version()_&) into which the following files are placed:
1646 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1647 .irow &_CHANGES_& "contains a reference to where changes are &&&
1649 .irow &_LICENCE_& "the GNU General Public Licence"
1650 .irow &_Makefile_& "top-level make file"
1651 .irow &_NOTICE_& "conditions for the use of Exim"
1652 .irow &_README_& "list of files, directories and simple build &&&
1656 Other files whose names begin with &_README_& may also be present. The
1657 following subdirectories are created:
1660 .irow &_Local_& "an empty directory for local configuration files"
1661 .irow &_OS_& "OS-specific files"
1662 .irow &_doc_& "documentation files"
1663 .irow &_exim_monitor_& "source files for the Exim monitor"
1664 .irow &_scripts_& "scripts used in the build process"
1665 .irow &_src_& "remaining source files"
1666 .irow &_util_& "independent utilities"
1669 The main utility programs are contained in the &_src_& directory and are built
1670 with the Exim binary. The &_util_& directory contains a few optional scripts
1671 that may be useful to some sites.
1674 .section "Multiple machine architectures and operating systems" "SECID24"
1675 .cindex "building Exim" "multiple OS/architectures"
1676 The building process for Exim is arranged to make it easy to build binaries for
1677 a number of different architectures and operating systems from the same set of
1678 source files. Compilation does not take place in the &_src_& directory.
1679 Instead, a &'build directory'& is created for each architecture and operating
1681 .cindex "symbolic link" "to build directory"
1682 Symbolic links to the sources are installed in this directory, which is where
1683 the actual building takes place. In most cases, Exim can discover the machine
1684 architecture and operating system for itself, but the defaults can be
1685 overridden if necessary.
1686 .cindex compiler requirements
1687 .cindex compiler version
1688 A C99-capable compiler will be required for the build.
1691 .section "PCRE library" "SECTpcre"
1692 .cindex "PCRE library"
1693 Exim no longer has an embedded PCRE library as the vast majority of
1694 modern systems include PCRE as a system library, although you may need to
1695 install the PCRE package or the PCRE development package for your operating
1696 system. If your system has a normal PCRE installation the Exim build
1697 process will need no further configuration. If the library or the
1698 headers are in an unusual location you will need to either set the PCRE_LIBS
1699 and INCLUDE directives appropriately,
1700 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1701 If your operating system has no
1702 PCRE support then you will need to obtain and build the current PCRE
1703 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1704 More information on PCRE is available at &url(https://www.pcre.org/).
1706 .section "DBM libraries" "SECTdb"
1707 .cindex "DBM libraries" "discussion of"
1708 .cindex "hints database" "DBM files used for"
1709 Even if you do not use any DBM files in your configuration, Exim still needs a
1710 DBM library in order to operate, because it uses indexed files for its hints
1711 databases. Unfortunately, there are a number of DBM libraries in existence, and
1712 different operating systems often have different ones installed.
1714 .cindex "Solaris" "DBM library for"
1715 .cindex "IRIX, DBM library for"
1716 .cindex "BSD, DBM library for"
1717 .cindex "Linux, DBM library for"
1718 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1719 Linux distribution, the DBM configuration should happen automatically, and you
1720 may be able to ignore this section. Otherwise, you may have to learn more than
1721 you would like about DBM libraries from what follows.
1723 .cindex "&'ndbm'& DBM library"
1724 Licensed versions of Unix normally contain a library of DBM functions operating
1725 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1726 versions of Unix seem to vary in what they contain as standard. In particular,
1727 some early versions of Linux have no default DBM library, and different
1728 distributors have chosen to bundle different libraries with their packaged
1729 versions. However, the more recent releases seem to have standardized on the
1730 Berkeley DB library.
1732 Different DBM libraries have different conventions for naming the files they
1733 use. When a program opens a file called &_dbmfile_&, there are several
1737 A traditional &'ndbm'& implementation, such as that supplied as part of
1738 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1740 .cindex "&'gdbm'& DBM library"
1741 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1742 compatibility interface it makes two different hard links to it with names
1743 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1744 filename is used unmodified.
1746 .cindex "Berkeley DB library"
1747 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1748 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1749 programmer exactly the same as the traditional &'ndbm'& implementation.
1751 If the Berkeley package is used in its native mode, it operates on a single
1752 file called &_dbmfile_&; the programmer's interface is somewhat different to
1753 the traditional &'ndbm'& interface.
1755 To complicate things further, there are several very different versions of the
1756 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1757 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1758 Maintenance of some of the earlier releases has ceased. All versions of
1759 Berkeley DB could be obtained from
1760 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1761 page with far newer versions listed.
1762 It is probably wise to plan to move your storage configurations away from
1763 Berkeley DB format, as today there are smaller and simpler alternatives more
1764 suited to Exim's usage model.
1766 .cindex "&'tdb'& DBM library"
1767 Yet another DBM library, called &'tdb'&, is available from
1768 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1769 operates on a single file.
1773 .cindex "DBM libraries" "configuration for building"
1774 Exim and its utilities can be compiled to use any of these interfaces. In order
1775 to use any version of the Berkeley DB package in native mode, you must set
1776 USE_DB in an appropriate configuration file (typically
1777 &_Local/Makefile_&). For example:
1781 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1782 error is diagnosed if you set more than one of these.
1784 At the lowest level, the build-time configuration sets none of these options,
1785 thereby assuming an interface of type (1). However, some operating system
1786 configuration files (for example, those for the BSD operating systems and
1787 Linux) assume type (4) by setting USE_DB as their default, and the
1788 configuration files for Cygwin set USE_GDBM. Anything you set in
1789 &_Local/Makefile_&, however, overrides these system defaults.
1791 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1792 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1793 in one of these lines:
1798 Settings like that will work if the DBM library is installed in the standard
1799 place. Sometimes it is not, and the library's header file may also not be in
1800 the default path. You may need to set INCLUDE to specify where the header
1801 file is, and to specify the path to the library more fully in DBMLIB, as in
1804 INCLUDE=-I/usr/local/include/db-4.1
1805 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1807 There is further detailed discussion about the various DBM libraries in the
1808 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1812 .section "Pre-building configuration" "SECID25"
1813 .cindex "building Exim" "pre-building configuration"
1814 .cindex "configuration for building Exim"
1815 .cindex "&_Local/Makefile_&"
1816 .cindex "&_src/EDITME_&"
1817 Before building Exim, a local configuration file that specifies options
1818 independent of any operating system has to be created with the name
1819 &_Local/Makefile_&. A template for this file is supplied as the file
1820 &_src/EDITME_&, and it contains full descriptions of all the option settings
1821 therein. These descriptions are therefore not repeated here. If you are
1822 building Exim for the first time, the simplest thing to do is to copy
1823 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1825 There are three settings that you must supply, because Exim will not build
1826 without them. They are the location of the runtime configuration file
1827 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1828 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1829 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1830 a colon-separated list of filenames; Exim uses the first of them that exists.
1832 There are a few other parameters that can be specified either at build time or
1833 at runtime, to enable the same binary to be used on a number of different
1834 machines. However, if the locations of Exim's spool directory and log file
1835 directory (if not within the spool directory) are fixed, it is recommended that
1836 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1837 detected early in Exim's execution (such as a malformed configuration file) can
1840 .cindex "content scanning" "specifying at build time"
1841 Exim's interfaces for calling virus and spam scanning software directly from
1842 access control lists are not compiled by default. If you want to include these
1843 facilities, you need to set
1845 WITH_CONTENT_SCAN=yes
1847 in your &_Local/Makefile_&. For details of the facilities themselves, see
1848 chapter &<<CHAPexiscan>>&.
1851 .cindex "&_Local/eximon.conf_&"
1852 .cindex "&_exim_monitor/EDITME_&"
1853 If you are going to build the Exim monitor, a similar configuration process is
1854 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1855 your installation and saved under the name &_Local/eximon.conf_&. If you are
1856 happy with the default settings described in &_exim_monitor/EDITME_&,
1857 &_Local/eximon.conf_& can be empty, but it must exist.
1859 This is all the configuration that is needed in straightforward cases for known
1860 operating systems. However, the building process is set up so that it is easy
1861 to override options that are set by default or by operating-system-specific
1862 configuration files, for example, to change the C compiler, which
1863 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1868 .section "Support for iconv()" "SECID26"
1869 .cindex "&[iconv()]& support"
1871 The contents of header lines in messages may be encoded according to the rules
1872 described RFC 2047. This makes it possible to transmit characters that are not
1873 in the ASCII character set, and to label them as being in a particular
1874 character set. When Exim is inspecting header lines by means of the &%$h_%&
1875 mechanism, it decodes them, and translates them into a specified character set
1876 (default is set at build time). The translation is possible only if the operating system
1877 supports the &[iconv()]& function.
1879 However, some of the operating systems that supply &[iconv()]& do not support
1880 very many conversions. The GNU &%libiconv%& library (available from
1881 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1882 systems to remedy this deficiency, as well as on systems that do not supply
1883 &[iconv()]& at all. After installing &%libiconv%&, you should add
1887 to your &_Local/Makefile_& and rebuild Exim.
1891 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1892 .cindex "TLS" "including support for TLS"
1893 .cindex "encryption" "including support for"
1894 .cindex "OpenSSL" "building Exim with"
1895 .cindex "GnuTLS" "building Exim with"
1896 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1897 command as per RFC 2487. It can also support clients that expect to
1898 start a TLS session immediately on connection to a non-standard port (see the
1899 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1902 If you want to build Exim with TLS support, you must first install either the
1903 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1906 If you do not want TLS support you should set
1910 in &_Local/Makefile_&.
1912 If OpenSSL is installed, you should set
1915 TLS_LIBS=-lssl -lcrypto
1917 in &_Local/Makefile_&. You may also need to specify the locations of the
1918 OpenSSL library and include files. For example:
1921 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1922 TLS_INCLUDE=-I/usr/local/openssl/include/
1924 .cindex "pkg-config" "OpenSSL"
1925 If you have &'pkg-config'& available, then instead you can just use:
1928 USE_OPENSSL_PC=openssl
1930 .cindex "USE_GNUTLS"
1931 If GnuTLS is installed, you should set
1934 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1936 in &_Local/Makefile_&, and again you may need to specify the locations of the
1937 library and include files. For example:
1940 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1941 TLS_INCLUDE=-I/usr/gnu/include
1943 .cindex "pkg-config" "GnuTLS"
1944 If you have &'pkg-config'& available, then instead you can just use:
1947 USE_GNUTLS_PC=gnutls
1950 You do not need to set TLS_INCLUDE if the relevant directory is already
1951 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1952 given in chapter &<<CHAPTLS>>&.
1957 .section "Use of tcpwrappers" "SECID27"
1959 .cindex "tcpwrappers, building Exim to support"
1960 .cindex "USE_TCP_WRAPPERS"
1961 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1962 .cindex "tcp_wrappers_daemon_name"
1963 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1964 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1965 alternative to Exim's own checking facilities for installations that are
1966 already making use of &'tcpwrappers'& for other purposes. To do this, you
1967 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1968 &_tcpd.h_& to be available at compile time, and also ensure that the library
1969 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1970 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1973 USE_TCP_WRAPPERS=yes
1974 CFLAGS=-O -I/usr/local/include
1975 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1977 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1978 files is &"exim"&. For example, the line
1980 exim : LOCAL 192.168.1. .friendly.domain.example
1982 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1983 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1984 All other connections are denied. The daemon name used by &'tcpwrappers'&
1985 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1986 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1987 configure file. Consult the &'tcpwrappers'& documentation for
1991 .section "Including support for IPv6" "SECID28"
1992 .cindex "IPv6" "including support for"
1993 Exim contains code for use on systems that have IPv6 support. Setting
1994 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1995 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1996 where the IPv6 support is not fully integrated into the normal include and
1999 Two different types of DNS record for handling IPv6 addresses have been
2000 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2001 currently seen as the mainstream. Another record type called A6 was proposed
2002 as better than AAAA because it had more flexibility. However, it was felt to be
2003 over-complex, and its status was reduced to &"experimental"&.
2005 have a compile option for including A6 record support but this has now been
2010 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2011 .cindex "lookup modules"
2012 .cindex "dynamic modules"
2013 .cindex ".so building"
2014 On some platforms, Exim supports not compiling all lookup types directly into
2015 the main binary, instead putting some into external modules which can be loaded
2017 This permits packagers to build Exim with support for lookups with extensive
2018 library dependencies without requiring all users to install all of those
2020 Most, but not all, lookup types can be built this way.
2022 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2023 installed; Exim will only load modules from that directory, as a security
2024 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2025 for your OS; see &_OS/Makefile-Linux_& for an example.
2026 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2027 see &_src/EDITME_& for details.
2029 Then, for each module to be loaded dynamically, define the relevant
2030 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2031 For example, this will build in lsearch but load sqlite and mysql support
2040 .section "The building process" "SECID29"
2041 .cindex "build directory"
2042 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2043 created, run &'make'& at the top level. It determines the architecture and
2044 operating system types, and creates a build directory if one does not exist.
2045 For example, on a Sun system running Solaris 8, the directory
2046 &_build-SunOS5-5.8-sparc_& is created.
2047 .cindex "symbolic link" "to source files"
2048 Symbolic links to relevant source files are installed in the build directory.
2050 If this is the first time &'make'& has been run, it calls a script that builds
2051 a make file inside the build directory, using the configuration files from the
2052 &_Local_& directory. The new make file is then passed to another instance of
2053 &'make'&. This does the real work, building a number of utility scripts, and
2054 then compiling and linking the binaries for the Exim monitor (if configured), a
2055 number of utility programs, and finally Exim itself. The command &`make
2056 makefile`& can be used to force a rebuild of the make file in the build
2057 directory, should this ever be necessary.
2059 If you have problems building Exim, check for any comments there may be in the
2060 &_README_& file concerning your operating system, and also take a look at the
2061 FAQ, where some common problems are covered.
2065 .section 'Output from &"make"&' "SECID283"
2066 The output produced by the &'make'& process for compile lines is often very
2067 unreadable, because these lines can be very long. For this reason, the normal
2068 output is suppressed by default, and instead output similar to that which
2069 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2070 each module that is being compiled or linked. However, it is still possible to
2071 get the full output, by calling &'make'& like this:
2075 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2076 command reflection in &'make'&. When you ask for the full output, it is
2077 given in addition to the short output.
2081 .section "Overriding build-time options for Exim" "SECToverride"
2082 .cindex "build-time options, overriding"
2083 The main make file that is created at the beginning of the building process
2084 consists of the concatenation of a number of files which set configuration
2085 values, followed by a fixed set of &'make'& instructions. If a value is set
2086 more than once, the last setting overrides any previous ones. This provides a
2087 convenient way of overriding defaults. The files that are concatenated are, in
2090 &_OS/Makefile-Default_&
2091 &_OS/Makefile-_&<&'ostype'&>
2093 &_Local/Makefile-_&<&'ostype'&>
2094 &_Local/Makefile-_&<&'archtype'&>
2095 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2096 &_OS/Makefile-Base_&
2098 .cindex "&_Local/Makefile_&"
2099 .cindex "building Exim" "operating system type"
2100 .cindex "building Exim" "architecture type"
2101 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2102 architecture type. &_Local/Makefile_& is required to exist, and the building
2103 process fails if it is absent. The other three &_Local_& files are optional,
2104 and are often not needed.
2106 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2107 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2108 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2109 values are used, thereby providing a means of forcing particular settings.
2110 Otherwise, the scripts try to get values from the &%uname%& command. If this
2111 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2112 of &'ad hoc'& transformations are then applied, to produce the standard names
2113 that Exim expects. You can run these scripts directly from the shell in order
2114 to find out what values are being used on your system.
2117 &_OS/Makefile-Default_& contains comments about the variables that are set
2118 therein. Some (but not all) are mentioned below. If there is something that
2119 needs changing, review the contents of this file and the contents of the make
2120 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2124 .cindex "building Exim" "overriding default settings"
2125 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2126 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2127 need to change the original files. Instead, you should make the changes by
2128 putting the new values in an appropriate &_Local_& file. For example,
2129 .cindex "Tru64-Unix build-time settings"
2130 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2131 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2132 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2133 called with the option &%-std1%&, to make it recognize some of the features of
2134 Standard C that Exim uses. (Most other compilers recognize Standard C by
2135 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2136 containing the lines
2141 If you are compiling for just one operating system, it may be easier to put
2142 these lines directly into &_Local/Makefile_&.
2144 Keeping all your local configuration settings separate from the distributed
2145 files makes it easy to transfer them to new versions of Exim simply by copying
2146 the contents of the &_Local_& directory.
2149 .cindex "NIS lookup type" "including support for"
2150 .cindex "NIS+ lookup type" "including support for"
2151 .cindex "LDAP" "including support for"
2152 .cindex "lookup" "inclusion in binary"
2153 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2154 lookup, but not all systems have these components installed, so the default is
2155 not to include the relevant code in the binary. All the different kinds of file
2156 and database lookup that Exim supports are implemented as separate code modules
2157 which are included only if the relevant compile-time options are set. In the
2158 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2164 and similar settings apply to the other lookup types. They are all listed in
2165 &_src/EDITME_&. In many cases the relevant include files and interface
2166 libraries need to be installed before compiling Exim.
2167 .cindex "cdb" "including support for"
2168 However, there are some optional lookup types (such as cdb) for which
2169 the code is entirely contained within Exim, and no external include
2170 files or libraries are required. When a lookup type is not included in the
2171 binary, attempts to configure Exim to use it cause runtime configuration
2174 .cindex "pkg-config" "lookups"
2175 .cindex "pkg-config" "authenticators"
2176 Many systems now use a tool called &'pkg-config'& to encapsulate information
2177 about how to compile against a library; Exim has some initial support for
2178 being able to use pkg-config for lookups and authenticators. For any given
2179 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2180 variable with the &`_PC`& suffix in the name and assign as the value the
2181 name of the package to be queried. The results of querying via the
2182 &'pkg-config'& command will be added to the appropriate Makefile variables
2183 with &`+=`& directives, so your version of &'make'& will need to support that
2184 syntax. For instance:
2187 LOOKUP_SQLITE_PC=sqlite3
2189 AUTH_GSASL_PC=libgsasl
2190 AUTH_HEIMDAL_GSSAPI=yes
2191 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2194 .cindex "Perl" "including support for"
2195 Exim can be linked with an embedded Perl interpreter, allowing Perl
2196 subroutines to be called during string expansion. To enable this facility,
2200 must be defined in &_Local/Makefile_&. Details of this facility are given in
2201 chapter &<<CHAPperl>>&.
2203 .cindex "X11 libraries, location of"
2204 The location of the X11 libraries is something that varies a lot between
2205 operating systems, and there may be different versions of X11 to cope
2206 with. Exim itself makes no use of X11, but if you are compiling the Exim
2207 monitor, the X11 libraries must be available.
2208 The following three variables are set in &_OS/Makefile-Default_&:
2211 XINCLUDE=-I$(X11)/include
2212 XLFLAGS=-L$(X11)/lib
2214 These are overridden in some of the operating-system configuration files. For
2215 example, in &_OS/Makefile-SunOS5_& there is
2218 XINCLUDE=-I$(X11)/include
2219 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2221 If you need to override the default setting for your operating system, place a
2222 definition of all three of these variables into your
2223 &_Local/Makefile-<ostype>_& file.
2226 If you need to add any extra libraries to the link steps, these can be put in a
2227 variable called EXTRALIBS, which appears in all the link commands, but by
2228 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2229 command for linking the main Exim binary, and not for any associated utilities.
2231 .cindex "DBM libraries" "configuration for building"
2232 There is also DBMLIB, which appears in the link commands for binaries that
2233 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2234 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2235 binary, and which can be used, for example, to include additional X11
2238 .cindex "configuration file" "editing"
2239 The make file copes with rebuilding Exim correctly if any of the configuration
2240 files are edited. However, if an optional configuration file is deleted, it is
2241 necessary to touch the associated non-optional file (that is,
2242 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2245 .section "OS-specific header files" "SECID30"
2247 .cindex "building Exim" "OS-specific C header files"
2248 The &_OS_& directory contains a number of files with names of the form
2249 &_os.h-<ostype>_&. These are system-specific C header files that should not
2250 normally need to be changed. There is a list of macro settings that are
2251 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2252 are porting Exim to a new operating system.
2256 .section "Overriding build-time options for the monitor" "SECID31"
2257 .cindex "building Eximon"
2258 A similar process is used for overriding things when building the Exim monitor,
2259 where the files that are involved are
2261 &_OS/eximon.conf-Default_&
2262 &_OS/eximon.conf-_&<&'ostype'&>
2263 &_Local/eximon.conf_&
2264 &_Local/eximon.conf-_&<&'ostype'&>
2265 &_Local/eximon.conf-_&<&'archtype'&>
2266 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2268 .cindex "&_Local/eximon.conf_&"
2269 As with Exim itself, the final three files need not exist, and in this case the
2270 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2271 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2272 variables of the same name, preceded by EXIMON_. For example, setting
2273 EXIMON_LOG_DEPTH in the environment overrides the value of
2274 LOG_DEPTH at runtime.
2278 .section "Installing Exim binaries and scripts" "SECID32"
2279 .cindex "installing Exim"
2280 .cindex "BIN_DIRECTORY"
2281 The command &`make install`& runs the &(exim_install)& script with no
2282 arguments. The script copies binaries and utility scripts into the directory
2283 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2284 .cindex "setuid" "installing Exim with"
2285 The install script copies files only if they are newer than the files they are
2286 going to replace. The Exim binary is required to be owned by root and have the
2287 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2288 install`& as root so that it can set up the Exim binary in this way. However, in
2289 some special situations (for example, if a host is doing no local deliveries)
2290 it may be possible to run Exim without making the binary setuid root (see
2291 chapter &<<CHAPsecurity>>& for details).
2293 .cindex "CONFIGURE_FILE"
2294 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2295 in &_Local/Makefile_&. If this names a single file, and the file does not
2296 exist, the default configuration file &_src/configure.default_& is copied there
2297 by the installation script. If a runtime configuration file already exists, it
2298 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2299 alternative files, no default is installed.
2301 .cindex "system aliases file"
2302 .cindex "&_/etc/aliases_&"
2303 One change is made to the default configuration file when it is installed: the
2304 default configuration contains a router that references a system aliases file.
2305 The path to this file is set to the value specified by
2306 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2307 If the system aliases file does not exist, the installation script creates it,
2308 and outputs a comment to the user.
2310 The created file contains no aliases, but it does contain comments about the
2311 aliases a site should normally have. Mail aliases have traditionally been
2312 kept in &_/etc/aliases_&. However, some operating systems are now using
2313 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2314 Exim's configuration if necessary.
2316 The default configuration uses the local host's name as the only local domain,
2317 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2318 running as the local user. System aliases and &_.forward_& files in users' home
2319 directories are supported, but no NIS or NIS+ support is configured. Domains
2320 other than the name of the local host are routed using the DNS, with delivery
2323 It is possible to install Exim for special purposes (such as building a binary
2324 distribution) in a private part of the file system. You can do this by a
2327 make DESTDIR=/some/directory/ install
2329 This has the effect of pre-pending the specified directory to all the file
2330 paths, except the name of the system aliases file that appears in the default
2331 configuration. (If a default alias file is created, its name &'is'& modified.)
2332 For backwards compatibility, ROOT is used if DESTDIR is not set,
2333 but this usage is deprecated.
2335 .cindex "installing Exim" "what is not installed"
2336 Running &'make install'& does not copy the Exim 4 conversion script
2337 &'convert4r4'&. You will probably run this only once if you are
2338 upgrading from Exim 3. None of the documentation files in the &_doc_&
2339 directory are copied, except for the info files when you have set
2340 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2342 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2343 to their names. The Exim binary itself, however, is handled differently. It is
2344 installed under a name that includes the version number and the compile number,
2345 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2346 called &_exim_& to point to the binary. If you are updating a previous version
2347 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2348 from the directory (as seen by other processes).
2350 .cindex "installing Exim" "testing the script"
2351 If you want to see what the &'make install'& will do before running it for
2352 real, you can pass the &%-n%& option to the installation script by this
2355 make INSTALL_ARG=-n install
2357 The contents of the variable INSTALL_ARG are passed to the installation
2358 script. You do not need to be root to run this test. Alternatively, you can run
2359 the installation script directly, but this must be from within the build
2360 directory. For example, from the top-level Exim directory you could use this
2363 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2365 .cindex "installing Exim" "install script options"
2366 There are two other options that can be supplied to the installation script.
2369 &%-no_chown%& bypasses the call to change the owner of the installed binary
2370 to root, and the call to make it a setuid binary.
2372 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2376 INSTALL_ARG can be used to pass these options to the script. For example:
2378 make INSTALL_ARG=-no_symlink install
2380 The installation script can also be given arguments specifying which files are
2381 to be copied. For example, to install just the Exim binary, and nothing else,
2382 without creating the symbolic link, you could use:
2384 make INSTALL_ARG='-no_symlink exim' install
2389 .section "Installing info documentation" "SECTinsinfdoc"
2390 .cindex "installing Exim" "&'info'& documentation"
2391 Not all systems use the GNU &'info'& system for documentation, and for this
2392 reason, the Texinfo source of Exim's documentation is not included in the main
2393 distribution. Instead it is available separately from the FTP site (see section
2396 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2397 source of the documentation is found in the source tree, running &`make
2398 install`& automatically builds the info files and installs them.
2402 .section "Setting up the spool directory" "SECID33"
2403 .cindex "spool directory" "creating"
2404 When it starts up, Exim tries to create its spool directory if it does not
2405 exist. The Exim uid and gid are used for the owner and group of the spool
2406 directory. Sub-directories are automatically created in the spool directory as
2412 .section "Testing" "SECID34"
2413 .cindex "testing" "installation"
2414 Having installed Exim, you can check that the runtime configuration file is
2415 syntactically valid by running the following command, which assumes that the
2416 Exim binary directory is within your PATH environment variable:
2420 If there are any errors in the configuration file, Exim outputs error messages.
2421 Otherwise it outputs the version number and build date,
2422 the DBM library that is being used, and information about which drivers and
2423 other optional code modules are included in the binary.
2424 Some simple routing tests can be done by using the address testing option. For
2427 &`exim -bt`& <&'local username'&>
2429 should verify that it recognizes a local mailbox, and
2431 &`exim -bt`& <&'remote address'&>
2433 a remote one. Then try getting it to deliver mail, both locally and remotely.
2434 This can be done by passing messages directly to Exim, without going through a
2435 user agent. For example:
2437 exim -v postmaster@your.domain.example
2438 From: user@your.domain.example
2439 To: postmaster@your.domain.example
2440 Subject: Testing Exim
2442 This is a test message.
2445 The &%-v%& option causes Exim to output some verification of what it is doing.
2446 In this case you should see copies of three log lines, one for the message's
2447 arrival, one for its delivery, and one containing &"Completed"&.
2449 .cindex "delivery" "problems with"
2450 If you encounter problems, look at Exim's log files (&'mainlog'& and
2451 &'paniclog'&) to see if there is any relevant information there. Another source
2452 of information is running Exim with debugging turned on, by specifying the
2453 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2454 with debugging turned on by a command of the form
2456 &`exim -d -M`& <&'exim-message-id'&>
2458 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2459 produces rather a lot of output, but you can cut this down to specific areas.
2460 For example, if you use &%-d-all+route%& only the debugging information
2461 relevant to routing is included. (See the &%-d%& option in chapter
2462 &<<CHAPcommandline>>& for more details.)
2464 .cindex '&"sticky"& bit'
2465 .cindex "lock files"
2466 One specific problem that has shown up on some sites is the inability to do
2467 local deliveries into a shared mailbox directory, because it does not have the
2468 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2469 writing to a mailbox file, and if it cannot create the lock file, the delivery
2470 is deferred. You can get round this either by setting the &"sticky bit"& on the
2471 directory, or by setting a specific group for local deliveries and allowing
2472 that group to create files in the directory (see the comments above the
2473 &(local_delivery)& transport in the default configuration file). Another
2474 approach is to configure Exim not to use lock files, but just to rely on
2475 &[fcntl()]& locking instead. However, you should do this only if all user
2476 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2477 see chapter &<<CHAPappendfile>>&.
2479 One thing that cannot be tested on a system that is already running an MTA is
2480 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2481 &%-oX%& option can be used to run an Exim daemon that listens on some other
2482 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2483 &'exim_checkaccess'& utility can be used to check out policy controls on
2486 Testing a new version on a system that is already running Exim can most easily
2487 be done by building a binary with a different CONFIGURE_FILE setting. From
2488 within the runtime configuration, all other file and directory names
2489 that Exim uses can be altered, in order to keep it entirely clear of the
2493 .section "Replacing another MTA with Exim" "SECID35"
2494 .cindex "replacing another MTA"
2495 Building and installing Exim for the first time does not of itself put it in
2496 general use. The name by which the system's MTA is called by mail user agents
2497 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2498 operating system), and it is necessary to make this name point to the &'exim'&
2499 binary in order to get the user agents to pass messages to Exim. This is
2500 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2501 or &_/usr/lib/sendmail_&
2502 .cindex "symbolic link" "to &'exim'& binary"
2503 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2504 privilege and executable status from the old MTA. It is then necessary to stop
2505 and restart the mailer daemon, if one is running.
2507 .cindex "FreeBSD, MTA indirection"
2508 .cindex "&_/etc/mail/mailer.conf_&"
2509 Some operating systems have introduced alternative ways of switching MTAs. For
2510 example, if you are running FreeBSD, you need to edit the file
2511 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2512 described. A typical example of the contents of this file for running Exim is
2515 sendmail /usr/exim/bin/exim
2516 send-mail /usr/exim/bin/exim
2517 mailq /usr/exim/bin/exim -bp
2518 newaliases /usr/bin/true
2520 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2521 your Exim installation is &"live"&. Check it by sending a message from your
2522 favourite user agent.
2524 You should consider what to tell your users about the change of MTA. Exim may
2525 have different capabilities to what was previously running, and there are
2526 various operational differences such as the text of messages produced by
2527 command line options and in bounce messages. If you allow your users to make
2528 use of Exim's filtering capabilities, you should make the document entitled
2529 &'Exim's interface to mail filtering'& available to them.
2533 .section "Upgrading Exim" "SECID36"
2534 .cindex "upgrading Exim"
2535 If you are already running Exim on your host, building and installing a new
2536 version automatically makes it available to MUAs, or any other programs that
2537 call the MTA directly. However, if you are running an Exim daemon, you do need
2538 .cindex restart "on HUP signal"
2539 .cindex signal "HUP, to restart"
2540 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2541 new binary. You do not need to stop processing mail in order to install a new
2542 version of Exim. The install script does not modify an existing runtime
2548 .section "Stopping the Exim daemon on Solaris" "SECID37"
2549 .cindex "Solaris" "stopping Exim on"
2550 The standard command for stopping the mailer daemon on Solaris is
2552 /etc/init.d/sendmail stop
2554 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2555 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2556 for the text &"sendmail"&; this is not present because the actual program name
2557 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2558 solution is to replace the line that finds the process id with something like
2560 pid=`cat /var/spool/exim/exim-daemon.pid`
2562 to obtain the daemon's pid directly from the file that Exim saves it in.
2564 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2565 still be received from local processes, and if automatic delivery is configured
2566 (the normal case), deliveries will still occur.
2571 . ////////////////////////////////////////////////////////////////////////////
2572 . ////////////////////////////////////////////////////////////////////////////
2574 .chapter "The Exim command line" "CHAPcommandline"
2575 .scindex IIDclo1 "command line" "options"
2576 .scindex IIDclo2 "options" "command line"
2577 Exim's command line takes the standard Unix form of a sequence of options,
2578 each starting with a hyphen character, followed by a number of arguments. The
2579 options are compatible with the main options of Sendmail, and there are also
2580 some additional options, some of which are compatible with Smail 3. Certain
2581 combinations of options do not make sense, and provoke an error if used.
2582 The form of the arguments depends on which options are set.
2585 .section "Setting options by program name" "SECID38"
2587 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2588 were present before any other options.
2589 The &%-bp%& option requests a listing of the contents of the mail queue on the
2591 This feature is for compatibility with some systems that contain a command of
2592 that name in one of the standard libraries, symbolically linked to
2593 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2596 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2597 were present before any other options, for compatibility with Smail. The
2598 &%-bS%& option is used for reading in a number of messages in batched SMTP
2602 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2603 &%-oee%& options were present before any other options, for compatibility with
2604 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2607 .cindex "queue runner"
2608 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2609 were present before any other options, for compatibility with Smail. The &%-q%&
2610 option causes a single queue runner process to be started.
2612 .cindex "&'newaliases'&"
2613 .cindex "alias file" "building"
2614 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2615 If Exim is called under the name &'newaliases'& it behaves as if the option
2616 &%-bi%& were present before any other options, for compatibility with Sendmail.
2617 This option is used for rebuilding Sendmail's alias file. Exim does not have
2618 the concept of a single alias file, but can be configured to run a given
2619 command if called with the &%-bi%& option.
2622 .section "Trusted and admin users" "SECTtrustedadmin"
2623 Some Exim options are available only to &'trusted users'& and others are
2624 available only to &'admin users'&. In the description below, the phrases &"Exim
2625 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2626 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2627 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2630 .cindex "trusted users" "definition of"
2631 .cindex "user" "trusted definition of"
2632 The trusted users are root, the Exim user, any user listed in the
2633 &%trusted_users%& configuration option, and any user whose current group or any
2634 supplementary group is one of those listed in the &%trusted_groups%&
2635 configuration option. Note that the Exim group is not automatically trusted.
2637 .cindex '&"From"& line'
2638 .cindex "envelope from"
2639 .cindex "envelope sender"
2640 Trusted users are always permitted to use the &%-f%& option or a leading
2641 &"From&~"& line to specify the envelope sender of a message that is passed to
2642 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2643 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2644 users to set envelope senders.
2646 .cindex "&'From:'& header line"
2647 .cindex "&'Sender:'& header line"
2648 .cindex "header lines" "From:"
2649 .cindex "header lines" "Sender:"
2650 For a trusted user, there is never any check on the contents of the &'From:'&
2651 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2652 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2654 Trusted users may also specify a host name, host address, interface address,
2655 protocol name, ident value, and authentication data when submitting a message
2656 locally. Thus, they are able to insert messages into Exim's queue locally that
2657 have the characteristics of messages received from a remote host. Untrusted
2658 users may in some circumstances use &%-f%&, but can never set the other values
2659 that are available to trusted users.
2661 .cindex "user" "admin definition of"
2662 .cindex "admin user" "definition of"
2663 The admin users are root, the Exim user, and any user that is a member of the
2664 Exim group or of any group listed in the &%admin_groups%& configuration option.
2665 The current group does not have to be one of these groups.
2667 Admin users are permitted to list the queue, and to carry out certain
2668 operations on messages, for example, to force delivery failures. It is also
2669 necessary to be an admin user in order to see the full information provided by
2670 the Exim monitor, and full debugging output.
2672 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2673 Exim to attempt delivery of messages on its queue is restricted to admin users.
2674 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2675 option false (that is, specifying &%no_prod_requires_admin%&).
2677 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2678 is restricted to admin users unless &%queue_list_requires_admin%& is set
2683 &*Warning*&: If you configure your system so that admin users are able to
2684 edit Exim's configuration file, you are giving those users an easy way of
2685 getting root. There is further discussion of this issue at the start of chapter
2691 .section "Command line options" "SECID39"
2692 Exim's command line options are described in alphabetical order below. If none
2693 of the options that specifies a specific action (such as starting the daemon or
2694 a queue runner, or testing an address, or receiving a message in a specific
2695 format, or listing the queue) are present, and there is at least one argument
2696 on the command line, &%-bm%& (accept a local message on the standard input,
2697 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2698 outputs a brief message about itself and exits.
2700 . ////////////////////////////////////////////////////////////////////////////
2701 . Insert a stylized XML comment here, to identify the start of the command line
2702 . options. This is for the benefit of the Perl script that automatically
2703 . creates a man page for the options.
2704 . ////////////////////////////////////////////////////////////////////////////
2707 <!-- === Start of command line options === -->
2714 .cindex "options" "command line; terminating"
2715 This is a pseudo-option whose only purpose is to terminate the options and
2716 therefore to cause subsequent command line items to be treated as arguments
2717 rather than options, even if they begin with hyphens.
2720 .oindex "&%--help%&"
2721 This option causes Exim to output a few sentences stating what it is.
2722 The same output is generated if the Exim binary is called with no options and
2725 .vitem &%--version%&
2726 .oindex "&%--version%&"
2727 This option is an alias for &%-bV%& and causes version information to be
2734 These options are used by Sendmail for selecting configuration files and are
2737 .vitem &%-B%&<&'type'&>
2739 .cindex "8-bit characters"
2740 .cindex "Sendmail compatibility" "8-bit characters"
2741 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2742 clean; it ignores this option.
2747 .cindex "SMTP" "listener"
2748 .cindex "queue runner"
2749 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2750 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2751 that the daemon should also initiate periodic queue runs.
2753 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2754 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2755 disconnect from the controlling terminal. When running this way, it can be
2756 stopped by pressing ctrl-C.
2758 By default, Exim listens for incoming connections to the standard SMTP port on
2759 all the host's running interfaces. However, it is possible to listen on other
2760 ports, on multiple ports, and only on specific interfaces. Chapter
2761 &<<CHAPinterfaces>>& contains a description of the options that control this.
2763 When a listening daemon
2764 .cindex "daemon" "process id (pid)"
2765 .cindex "pid (process id)" "of daemon"
2766 is started without the use of &%-oX%& (that is, without overriding the normal
2767 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2768 in Exim's spool directory. This location can be overridden by setting
2769 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2772 When &%-oX%& is used on the command line to start a listening daemon, the
2773 process id is not written to the normal pid file path. However, &%-oP%& can be
2774 used to specify a path on the command line if a pid file is required.
2778 .cindex restart "on HUP signal"
2779 .cindex signal "HUP, to restart"
2780 .cindex "daemon" "restarting"
2781 .cindex signal "to reload configuration"
2782 .cindex daemon "reload configuration"
2783 .cindex reload configuration
2784 can be used to cause the daemon to re-execute itself. This should be done
2785 whenever Exim's configuration file, or any file that is incorporated into it by
2786 means of the &%.include%& facility, is changed, and also whenever a new version
2787 of Exim is installed. It is not necessary to do this when other files that are
2788 referenced from the configuration (for example, alias files) are changed,
2789 because these are reread each time they are used.
2793 This option has the same effect as &%-bd%& except that it never disconnects
2794 from the controlling terminal, even when no debugging is specified.
2798 .cindex "testing" "string expansion"
2799 .cindex "expansion" "testing"
2800 Run Exim in expansion testing mode. Exim discards its root privilege, to
2801 prevent ordinary users from using this mode to read otherwise inaccessible
2802 files. If no arguments are given, Exim runs interactively, prompting for lines
2803 of data. Otherwise, it processes each argument in turn.
2805 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2806 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2807 used without command line arguments. If successful, it uses the &[readline()]&
2808 function, which provides extensive line-editing facilities, for reading the
2809 test data. A line history is supported.
2811 Long expansion expressions can be split over several lines by using backslash
2812 continuations. As in Exim's runtime configuration, white space at the start of
2813 continuation lines is ignored. Each argument or data line is passed through the
2814 string expansion mechanism, and the result is output. Variable values from the
2815 configuration file (for example, &$qualify_domain$&) are available, but no
2816 message-specific values (such as &$message_exim_id$&) are set, because no message
2817 is being processed (but see &%-bem%& and &%-Mset%&).
2819 &*Note*&: If you use this mechanism to test lookups, and you change the data
2820 files or databases you are using, you must exit and restart Exim before trying
2821 the same lookup again. Otherwise, because each Exim process caches the results
2822 of lookups, you will just get the same result as before.
2824 Macro processing is done on lines before string-expansion: new macros can be
2825 defined and macros will be expanded.
2826 Because macros in the config file are often used for secrets, those are only
2827 available to admin users.
2829 .vitem &%-bem%&&~<&'filename'&>
2831 .cindex "testing" "string expansion"
2832 .cindex "expansion" "testing"
2833 This option operates like &%-be%& except that it must be followed by the name
2834 of a file. For example:
2836 exim -bem /tmp/testmessage
2838 The file is read as a message (as if receiving a locally-submitted non-SMTP
2839 message) before any of the test expansions are done. Thus, message-specific
2840 variables such as &$message_size$& and &$header_from:$& are available. However,
2841 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2842 recipients are read from the headers in the normal way, and are shown in the
2843 &$recipients$& variable. Note that recipients cannot be given on the command
2844 line, because further arguments are taken as strings to expand (just like
2847 .vitem &%-bF%&&~<&'filename'&>
2849 .cindex "system filter" "testing"
2850 .cindex "testing" "system filter"
2851 This option is the same as &%-bf%& except that it assumes that the filter being
2852 tested is a system filter. The additional commands that are available only in
2853 system filters are recognized.
2855 .vitem &%-bf%&&~<&'filename'&>
2857 .cindex "filter" "testing"
2858 .cindex "testing" "filter file"
2859 .cindex "forward file" "testing"
2860 .cindex "testing" "forward file"
2861 .cindex "Sieve filter" "testing"
2862 This option runs Exim in user filter testing mode; the file is the filter file
2863 to be tested, and a test message must be supplied on the standard input. If
2864 there are no message-dependent tests in the filter, an empty file can be
2867 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2868 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2869 filter and a user filter in the same run. For example:
2871 exim -bF /system/filter -bf /user/filter </test/message
2873 This is helpful when the system filter adds header lines or sets filter
2874 variables that are used by the user filter.
2876 If the test filter file does not begin with one of the special lines
2881 it is taken to be a normal &_.forward_& file, and is tested for validity under
2882 that interpretation. See sections &<<SECTitenonfilred>>& to
2883 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2886 The result of an Exim command that uses &%-bf%&, provided no errors are
2887 detected, is a list of the actions that Exim would try to take if presented
2888 with the message for real. More details of filter testing are given in the
2889 separate document entitled &'Exim's interfaces to mail filtering'&.
2891 When testing a filter file,
2892 .cindex "&""From""& line"
2893 .cindex "envelope from"
2894 .cindex "envelope sender"
2895 .oindex "&%-f%&" "for filter testing"
2896 the envelope sender can be set by the &%-f%& option,
2897 or by a &"From&~"& line at the start of the test message. Various parameters
2898 that would normally be taken from the envelope recipient address of the message
2899 can be set by means of additional command line options (see the next four
2902 .vitem &%-bfd%&&~<&'domain'&>
2904 .vindex "&$qualify_domain$&"
2905 This sets the domain of the recipient address when a filter file is being
2906 tested by means of the &%-bf%& option. The default is the value of
2909 .vitem &%-bfl%&&~<&'local&~part'&>
2911 This sets the local part of the recipient address when a filter file is being
2912 tested by means of the &%-bf%& option. The default is the username of the
2913 process that calls Exim. A local part should be specified with any prefix or
2914 suffix stripped, because that is how it appears to the filter when a message is
2915 actually being delivered.
2917 .vitem &%-bfp%&&~<&'prefix'&>
2919 .cindex affix "filter testing"
2920 This sets the prefix of the local part of the recipient address when a filter
2921 file is being tested by means of the &%-bf%& option. The default is an empty
2924 .vitem &%-bfs%&&~<&'suffix'&>
2926 .cindex affix "filter testing"
2927 This sets the suffix of the local part of the recipient address when a filter
2928 file is being tested by means of the &%-bf%& option. The default is an empty
2931 .vitem &%-bh%&&~<&'IP&~address'&>
2933 .cindex "testing" "incoming SMTP"
2934 .cindex "SMTP" "testing incoming"
2935 .cindex "testing" "relay control"
2936 .cindex "relaying" "testing configuration"
2937 .cindex "policy control" "testing"
2938 .cindex "debugging" "&%-bh%& option"
2939 This option runs a fake SMTP session as if from the given IP address, using the
2940 standard input and output. The IP address may include a port number at the end,
2941 after a full stop. For example:
2943 exim -bh 10.9.8.7.1234
2944 exim -bh fe80::a00:20ff:fe86:a061.5678
2946 When an IPv6 address is given, it is converted into canonical form. In the case
2947 of the second example above, the value of &$sender_host_address$& after
2948 conversion to the canonical form is
2949 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2951 Comments as to what is going on are written to the standard error file. These
2952 include lines beginning with &"LOG"& for anything that would have been logged.
2953 This facility is provided for testing configuration options for incoming
2954 messages, to make sure they implement the required policy. For example, you can
2955 test your relay controls using &%-bh%&.
2959 You can test features of the configuration that rely on ident (RFC 1413)
2960 information by using the &%-oMt%& option. However, Exim cannot actually perform
2961 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2964 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2965 are also skipped when testing using &%-bh%&. If you want these callouts to
2966 occur, use &%-bhc%& instead.
2968 Messages supplied during the testing session are discarded, and nothing is
2969 written to any of the real log files. There may be pauses when DNS (and other)
2970 lookups are taking place, and of course these may time out. The &%-oMi%& option
2971 can be used to specify a specific IP interface and port if this is important,
2972 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2973 session were authenticated.
2975 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2976 output just states whether a given recipient address from a given host is
2977 acceptable or not. See section &<<SECTcheckaccess>>&.
2979 Features such as authentication and encryption, where the client input is not
2980 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2981 specialized SMTP test program such as
2982 &url(https://www.jetmore.org/john/code/swaks/,swaks).
2984 .vitem &%-bhc%&&~<&'IP&~address'&>
2986 This option operates in the same way as &%-bh%&, except that address
2987 verification callouts are performed if required. This includes consulting and
2988 updating the callout cache database.
2992 .cindex "alias file" "building"
2993 .cindex "building alias file"
2994 .cindex "Sendmail compatibility" "&%-bi%& option"
2995 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2996 Exim does not have the concept of a single alias file, and so it cannot mimic
2997 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2998 tend to appear in various scripts such as NIS make files, so the option must be
3001 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3002 configuration option is run, under the uid and gid of the caller of Exim. If
3003 the &%-oA%& option is used, its value is passed to the command as an argument.
3004 The command set by &%bi_command%& may not contain arguments. The command can
3005 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3006 if this is required. If the &%bi_command%& option is not set, calling Exim with
3009 . // Keep :help first, then the rest in alphabetical order
3011 .oindex "&%-bI:help%&"
3012 .cindex "querying exim information"
3013 We shall provide various options starting &`-bI:`& for querying Exim for
3014 information. The output of many of these will be intended for machine
3015 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3016 synopsis of supported options beginning &`-bI:`&. Use of any of these
3017 options shall cause Exim to exit after producing the requested output.
3020 .oindex "&%-bI:dscp%&"
3021 .cindex "DSCP" "values"
3022 This option causes Exim to emit an alphabetically sorted list of all
3023 recognised DSCP names.
3025 .vitem &%-bI:sieve%&
3026 .oindex "&%-bI:sieve%&"
3027 .cindex "Sieve filter" "capabilities"
3028 This option causes Exim to emit an alphabetically sorted list of all supported
3029 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3030 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3031 &`SIEVE`& capability response line. As the precise list may depend upon
3032 compile-time build options, which this option will adapt to, this is the only
3033 way to guarantee a correct response.
3037 .cindex "local message reception"
3038 This option runs an Exim receiving process that accepts an incoming,
3039 locally-generated message on the standard input. The recipients are given as the
3040 command arguments (except when &%-t%& is also present &-- see below). Each
3041 argument can be a comma-separated list of RFC 2822 addresses. This is the
3042 default option for selecting the overall action of an Exim call; it is assumed
3043 if no other conflicting option is present.
3045 If any addresses in the message are unqualified (have no domain), they are
3046 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3047 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3048 suppressing this for special cases.
3050 Policy checks on the contents of local messages can be enforced by means of
3051 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3053 .cindex "return code" "for &%-bm%&"
3054 The return code is zero if the message is successfully accepted. Otherwise, the
3055 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3058 .cindex "message" "format"
3059 .cindex "format" "message"
3060 .cindex "&""From""& line"
3061 .cindex "UUCP" "&""From""& line"
3062 .cindex "Sendmail compatibility" "&""From""& line"
3063 of the message must be as defined in RFC 2822, except that, for
3064 compatibility with Sendmail and Smail, a line in one of the forms
3066 From sender Fri Jan 5 12:55 GMT 1997
3067 From sender Fri, 5 Jan 97 12:55:01
3069 (with the weekday optional, and possibly with additional text after the date)
3070 is permitted to appear at the start of the message. There appears to be no
3071 authoritative specification of the format of this line. Exim recognizes it by
3072 matching against the regular expression defined by the &%uucp_from_pattern%&
3073 option, which can be changed if necessary.
3075 .oindex "&%-f%&" "overriding &""From""& line"
3076 The specified sender is treated as if it were given as the argument to the
3077 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3078 preference to the address taken from the message. The caller of Exim must be a
3079 trusted user for the sender of a message to be set in this way.
3081 .vitem &%-bmalware%&&~<&'filename'&>
3082 .oindex "&%-bmalware%&"
3083 .cindex "testing", "malware"
3084 .cindex "malware scan test"
3085 This debugging option causes Exim to scan the given file or directory
3086 (depending on the used scanner interface),
3087 using the malware scanning framework. The option of &%av_scanner%& influences
3088 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3089 the expansion should have defaults which apply to this invocation. ACLs are
3090 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3091 will never be populated and &%-bmalware%& will fail.
3093 Exim will have changed working directory before resolving the filename, so
3094 using fully qualified pathnames is advisable. Exim will be running as the Exim
3095 user when it tries to open the file, rather than as the invoking user.
3096 This option requires admin privileges.
3098 The &%-bmalware%& option will not be extended to be more generally useful,
3099 there are better tools for file-scanning. This option exists to help
3100 administrators verify their Exim and AV scanner configuration.
3104 .cindex "address qualification, suppressing"
3105 By default, Exim automatically qualifies unqualified addresses (those
3106 without domains) that appear in messages that are submitted locally (that
3107 is, not over TCP/IP). This qualification applies both to addresses in
3108 envelopes, and addresses in header lines. Sender addresses are qualified using
3109 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3110 defaults to the value of &%qualify_domain%&).
3112 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3113 being used to re-submit messages that originally came from remote hosts after
3114 content scanning, you probably do not want to qualify unqualified addresses in
3115 header lines. (Such lines will be present only if you have not enabled a header
3116 syntax check in the appropriate ACL.)
3118 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3119 messages that originate on the local host. When this is used, unqualified
3120 addresses in the envelope provoke errors (causing message rejection) and
3121 unqualified addresses in header lines are left alone.
3126 .cindex "configuration options" "extracting"
3127 .cindex "options" "configuration &-- extracting"
3128 If this option is given with no arguments, it causes the values of all Exim's
3129 main configuration options to be written to the standard output. The values
3130 of one or more specific options can be requested by giving their names as
3131 arguments, for example:
3133 exim -bP qualify_domain hold_domains
3135 .cindex "hiding configuration option values"
3136 .cindex "configuration options" "hiding value of"
3137 .cindex "options" "hiding value of"
3138 However, any option setting that is preceded by the word &"hide"& in the
3139 configuration file is not shown in full, except to an admin user. For other
3140 users, the output is as in this example:
3142 mysql_servers = <value not displayable>
3144 If &%config%& is given as an argument, the config is
3145 output, as it was parsed, any include file resolved, any comment removed.
3147 If &%config_file%& is given as an argument, the name of the runtime
3148 configuration file is output. (&%configure_file%& works too, for
3149 backward compatibility.)
3150 If a list of configuration files was supplied, the value that is output here
3151 is the name of the file that was actually used.
3153 .cindex "options" "hiding name of"
3154 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3155 name will not be output.
3157 .cindex "daemon" "process id (pid)"
3158 .cindex "pid (process id)" "of daemon"
3159 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3160 directories where log files and daemon pid files are written are output,
3161 respectively. If these values are unset, log files are written in a
3162 sub-directory of the spool directory called &%log%&, and the pid file is
3163 written directly into the spool directory.
3165 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3167 exim -bP +local_domains
3169 it searches for a matching named list of any type (domain, host, address, or
3170 local part) and outputs what it finds.
3172 .cindex "options" "router &-- extracting"
3173 .cindex "options" "transport &-- extracting"
3174 .cindex "options" "authenticator &-- extracting"
3175 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3176 followed by the name of an appropriate driver instance, the option settings for
3177 that driver are output. For example:
3179 exim -bP transport local_delivery
3181 The generic driver options are output first, followed by the driver's private
3182 options. A list of the names of drivers of a particular type can be obtained by
3183 using one of the words &%router_list%&, &%transport_list%&, or
3184 &%authenticator_list%&, and a complete list of all drivers with their option
3185 settings can be obtained by using &%routers%&, &%transports%&, or
3188 .cindex "environment"
3189 If &%environment%& is given as an argument, the set of environment
3190 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3193 .cindex "options" "macro &-- extracting"
3194 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3195 are available, similarly to the drivers. Because macros are sometimes used
3196 for storing passwords, this option is restricted.
3197 The output format is one item per line.
3198 For the "-bP macro <name>" form, if no such macro is found
3199 the exit status will be nonzero.
3203 .cindex "queue" "listing messages in"
3204 .cindex "listing" "messages in the queue"
3205 This option requests a listing of the contents of the mail queue on the
3206 standard output. If the &%-bp%& option is followed by a list of message ids,
3207 just those messages are listed. By default, this option can be used only by an
3208 admin user. However, the &%queue_list_requires_admin%& option can be set false
3209 to allow any user to see the queue.
3211 Each message in the queue is displayed as in the following example:
3213 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3214 red.king@looking-glass.fict.example
3217 .cindex "message" "size in queue listing"
3218 .cindex "size" "of message"
3219 The first line contains the length of time the message has been in the queue
3220 (in this case 25 minutes), the size of the message (2.9K), the unique local
3221 identifier for the message, and the message sender, as contained in the
3222 envelope. For bounce messages, the sender address is empty, and appears as
3223 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3224 the default sender address, the user's login name is shown in parentheses
3225 before the sender address.
3227 .cindex "frozen messages" "in queue listing"
3228 If the message is frozen (attempts to deliver it are suspended) then the text
3229 &"*** frozen ***"& is displayed at the end of this line.
3231 The recipients of the message (taken from the envelope, not the headers) are
3232 displayed on subsequent lines. Those addresses to which the message has already
3233 been delivered are marked with the letter D. If an original address gets
3234 expanded into several addresses via an alias or forward file, the original is
3235 displayed with a D only when deliveries for all of its child addresses are
3241 This option operates like &%-bp%&, but in addition it shows delivered addresses
3242 that were generated from the original top level address(es) in each message by
3243 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3249 .cindex "queue" "count of messages on"
3250 This option counts the number of messages in the queue, and writes the total
3251 to the standard output. It is restricted to admin users, unless
3252 &%queue_list_requires_admin%& is set false.
3257 This option operates like &%-bp%&, but the output is not sorted into
3258 chronological order of message arrival. This can speed it up when there are
3259 lots of messages in the queue, and is particularly useful if the output is
3260 going to be post-processed in a way that doesn't need the sorting.
3264 This option is a combination of &%-bpr%& and &%-bpa%&.
3268 This option is a combination of &%-bpr%& and &%-bpu%&.
3273 This option operates like &%-bp%& but shows only undelivered top-level
3274 addresses for each message displayed. Addresses generated by aliasing or
3275 forwarding are not shown, unless the message was deferred after processing by a
3276 router with the &%one_time%& option set.
3281 .cindex "testing" "retry configuration"
3282 .cindex "retry" "configuration testing"
3283 This option is for testing retry rules, and it must be followed by up to three
3284 arguments. It causes Exim to look for a retry rule that matches the values
3285 and to write it to the standard output. For example:
3287 exim -brt bach.comp.mus.example
3288 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3290 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3291 argument, which is required, can be a complete address in the form
3292 &'local_part@domain'&, or it can be just a domain name. If the second argument
3293 contains a dot, it is interpreted as an optional second domain name; if no
3294 retry rule is found for the first argument, the second is tried. This ties in
3295 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3296 rule is found that matches the host, one that matches the mail domain is
3297 sought. Finally, an argument that is the name of a specific delivery error, as
3298 used in setting up retry rules, can be given. For example:
3300 exim -brt haydn.comp.mus.example quota_3d
3301 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3306 .cindex "testing" "rewriting"
3307 .cindex "rewriting" "testing"
3308 This option is for testing address rewriting rules, and it must be followed by
3309 a single argument, consisting of either a local part without a domain, or a
3310 complete address with a fully qualified domain. Exim outputs how this address
3311 would be rewritten for each possible place it might appear. See chapter
3312 &<<CHAPrewrite>>& for further details.
3316 .cindex "SMTP" "batched incoming"
3317 .cindex "batched SMTP input"
3318 This option is used for batched SMTP input, which is an alternative interface
3319 for non-interactive local message submission. A number of messages can be
3320 submitted in a single run. However, despite its name, this is not really SMTP
3321 input. Exim reads each message's envelope from SMTP commands on the standard
3322 input, but generates no responses. If the caller is trusted, or
3323 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3324 believed; otherwise the sender is always the caller of Exim.
3326 The message itself is read from the standard input, in SMTP format (leading
3327 dots doubled), terminated by a line containing just a single dot. An error is
3328 provoked if the terminating dot is missing. A further message may then follow.
3330 As for other local message submissions, the contents of incoming batch SMTP
3331 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3332 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3333 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3335 Some other SMTP commands are recognized in the input. HELO and EHLO act
3336 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3337 QUIT quits, ignoring the rest of the standard input.
3339 .cindex "return code" "for &%-bS%&"
3340 If any error is encountered, reports are written to the standard output and
3341 error streams, and Exim gives up immediately. The return code is 0 if no error
3342 was detected; it is 1 if one or more messages were accepted before the error
3343 was detected; otherwise it is 2.
3345 More details of input using batched SMTP are given in section
3346 &<<SECTincomingbatchedSMTP>>&.
3350 .cindex "SMTP" "local input"
3351 .cindex "local SMTP input"
3352 This option causes Exim to accept one or more messages by reading SMTP commands
3353 on the standard input, and producing SMTP replies on the standard output. SMTP
3354 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3355 Some user agents use this interface as a way of passing locally-generated
3356 messages to the MTA.
3359 .cindex "sender" "source of"
3360 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3361 set, the senders of messages are taken from the SMTP MAIL commands.
3362 Otherwise the content of these commands is ignored and the sender is set up as
3363 the calling user. Unqualified addresses are automatically qualified using
3364 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3365 &%-bnq%& option is used.
3369 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3370 using a listening daemon. Exim can distinguish the two cases by checking
3371 whether the standard input is a TCP/IP socket. When Exim is called from
3372 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3373 above concerning senders and qualification do not apply. In this situation,
3374 Exim behaves in exactly the same way as it does when receiving a message via
3375 the listening daemon.
3379 .cindex "testing" "addresses"
3380 .cindex "address" "testing"
3381 This option runs Exim in address testing mode, in which each argument is taken
3382 as a recipient address to be tested for deliverability. The results are
3383 written to the standard output. If a test fails, and the caller is not an admin
3384 user, no details of the failure are output, because these might contain
3385 sensitive information such as usernames and passwords for database lookups.
3387 If no arguments are given, Exim runs in an interactive manner, prompting with a
3388 right angle bracket for addresses to be tested.
3390 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3391 &[readline()]& function, because it is running as &'root'& and there are
3394 Each address is handled as if it were the recipient address of a message
3395 (compare the &%-bv%& option). It is passed to the routers and the result is
3396 written to the standard output. However, any router that has
3397 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3398 genuine routing tests if your first router passes everything to a scanner
3401 .cindex "return code" "for &%-bt%&"
3402 The return code is 2 if any address failed outright; it is 1 if no address
3403 failed outright but at least one could not be resolved for some reason. Return
3404 code 0 is given only when all addresses succeed.
3406 .cindex "duplicate addresses"
3407 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3408 addresses after routing is complete, so that only one delivery takes place.
3409 This does not happen when testing with &%-bt%&; the full results of routing are
3412 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3413 routers in the configuration makes any tests on the sender address of a
3415 .oindex "&%-f%&" "for address testing"
3416 you can use the &%-f%& option to set an appropriate sender when running
3417 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3418 default qualifying domain. However, if you have set up (for example) routers
3419 whose behaviour depends on the contents of an incoming message, you cannot test
3420 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3425 .cindex "version number of Exim"
3426 This option causes Exim to write the current version number, compilation
3427 number, and compilation date of the &'exim'& binary to the standard output.
3428 It also lists the DBM library that is being used, the optional modules (such as
3429 specific lookup types), the drivers that are included in the binary, and the
3430 name of the runtime configuration file that is in use.
3432 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3433 configuration file. However, this is a static check only. It cannot check
3434 values that are to be expanded. For example, although a misspelt ACL verb is
3435 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3436 alone to discover (for example) all the typos in the configuration; some
3437 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3438 dynamic testing facilities.
3442 .cindex "verifying address" "using &%-bv%&"
3443 .cindex "address" "verification"
3444 This option runs Exim in address verification mode, in which each argument is
3445 taken as a recipient address to be verified by the routers. (This does
3446 not involve any verification callouts). During normal operation, verification
3447 happens mostly as a consequence processing a &%verify%& condition in an ACL
3448 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3449 including callouts, see the &%-bh%& and &%-bhc%& options.
3451 If verification fails, and the caller is not an admin user, no details of the
3452 failure are output, because these might contain sensitive information such as
3453 usernames and passwords for database lookups.
3455 If no arguments are given, Exim runs in an interactive manner, prompting with a
3456 right angle bracket for addresses to be verified.
3458 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3459 &[readline()]& function, because it is running as &'exim'& and there are
3462 Verification differs from address testing (the &%-bt%& option) in that routers
3463 that have &%no_verify%& set are skipped, and if the address is accepted by a
3464 router that has &%fail_verify%& set, verification fails. The address is
3465 verified as a recipient if &%-bv%& is used; to test verification for a sender
3466 address, &%-bvs%& should be used.
3468 If the &%-v%& option is not set, the output consists of a single line for each
3469 address, stating whether it was verified or not, and giving a reason in the
3470 latter case. Without &%-v%&, generating more than one address by redirection
3471 causes verification to end successfully, without considering the generated
3472 addresses. However, if just one address is generated, processing continues,
3473 and the generated address must verify successfully for the overall verification
3476 When &%-v%& is set, more details are given of how the address has been handled,
3477 and in the case of address redirection, all the generated addresses are also
3478 considered. Verification may succeed for some and fail for others.
3481 .cindex "return code" "for &%-bv%&"
3482 return code is 2 if any address failed outright; it is 1 if no address
3483 failed outright but at least one could not be resolved for some reason. Return
3484 code 0 is given only when all addresses succeed.
3486 If any of the routers in the configuration makes any tests on the sender
3487 address of a message, you should use the &%-f%& option to set an appropriate
3488 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3489 calling user at the default qualifying domain.
3493 This option acts like &%-bv%&, but verifies the address as a sender rather
3494 than a recipient address. This affects any rewriting and qualification that
3501 .cindex "inetd" "wait mode"
3502 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3503 similarly to the &%-bd%& option. All port specifications on the command-line
3504 and in the configuration file are ignored. Queue-running may not be specified.
3506 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3507 listening for connections. This permits the system to start up and have
3508 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3509 each port only when the first connection is received.
3511 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3512 which the daemon will exit, which should cause inetd to listen once more.
3514 .vitem &%-C%&&~<&'filelist'&>
3516 .cindex "configuration file" "alternate"
3517 .cindex "CONFIGURE_FILE"
3518 .cindex "alternate configuration file"
3519 This option causes Exim to find the runtime configuration file from the given
3520 list instead of from the list specified by the CONFIGURE_FILE
3521 compile-time setting. Usually, the list will consist of just a single filename,
3522 but it can be a colon-separated list of names. In this case, the first
3523 file that exists is used. Failure to open an existing file stops Exim from
3524 proceeding any further along the list, and an error is generated.
3526 When this option is used by a caller other than root, and the list is different
3527 from the compiled-in list, Exim gives up its root privilege immediately, and
3528 runs with the real and effective uid and gid set to those of the caller.
3529 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3530 file contains a list of full pathnames, one per line, for configuration files
3531 which are trusted. Root privilege is retained for any configuration file so
3532 listed, as long as the caller is the Exim user (or the user specified in the
3533 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3534 not writeable by inappropriate users or groups.
3536 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3537 configuration using &%-C%& right through message reception and delivery,
3538 even if the caller is root. The reception works, but by that time, Exim is
3539 running as the Exim user, so when it re-executes to regain privilege for the
3540 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3541 test reception and delivery using two separate commands (one to put a message
3542 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3544 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3545 prefix string with which any file named in a &%-C%& command line option
3546 must start. In addition, the filename must not contain the sequence &`/../`&.
3547 However, if the value of the &%-C%& option is identical to the value of
3548 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3549 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3550 unset, any filename can be used with &%-C%&.
3552 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3553 to a directory to which only root has access. This prevents someone who has
3554 broken into the Exim account from running a privileged Exim with an arbitrary
3557 The &%-C%& facility is useful for ensuring that configuration files are
3558 syntactically correct, but cannot be used for test deliveries, unless the
3559 caller is privileged, or unless it is an exotic configuration that does not
3560 require privilege. No check is made on the owner or group of the files
3561 specified by this option.
3564 .vitem &%-D%&<&'macro'&>=<&'value'&>
3566 .cindex "macro" "setting on command line"
3567 This option can be used to override macro definitions in the configuration file
3568 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3569 unprivileged caller, it causes Exim to give up its root privilege.
3570 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3571 completely disabled, and its use causes an immediate error exit.
3573 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3574 colon-separated list of macros which are considered safe and, if &%-D%& only
3575 supplies macros from this list, and the values are acceptable, then Exim will
3576 not give up root privilege if the caller is root, the Exim run-time user, or
3577 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3578 to be removed in the future. Acceptable values for the macros satisfy the
3579 regexp: &`^[A-Za-z0-9_/.-]*$`&
3581 The entire option (including equals sign if present) must all be within one
3582 command line item. &%-D%& can be used to set the value of a macro to the empty
3583 string, in which case the equals sign is optional. These two commands are
3589 To include spaces in a macro definition item, quotes must be used. If you use
3590 quotes, spaces are permitted around the macro name and the equals sign. For
3593 exim '-D ABC = something' ...
3595 &%-D%& may be repeated up to 10 times on a command line.
3596 Only macro names up to 22 letters long can be set.
3599 .vitem &%-d%&<&'debug&~options'&>
3601 .cindex "debugging" "list of selectors"
3602 .cindex "debugging" "&%-d%& option"
3603 This option causes debugging information to be written to the standard
3604 error stream. It is restricted to admin users because debugging output may show
3605 database queries that contain password information. Also, the details of users'
3606 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3607 writes an error message to the standard error stream and exits with a non-zero
3610 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3611 standard debugging data is output. This can be reduced, or increased to include
3612 some more rarely needed information, by directly following &%-d%& with a string
3613 made up of names preceded by plus or minus characters. These add or remove sets
3614 of debugging data, respectively. For example, &%-d+filter%& adds filter
3615 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3616 no spaces are allowed in the debug setting. The available debugging categories
3619 &`acl `& ACL interpretation
3620 &`auth `& authenticators
3621 &`deliver `& general delivery logic
3622 &`dns `& DNS lookups (see also resolver)
3623 &`dnsbl `& DNS black list (aka RBL) code
3624 &`exec `& arguments for &[execv()]& calls
3625 &`expand `& detailed debugging for string expansions
3626 &`filter `& filter handling
3627 &`hints_lookup `& hints data lookups
3628 &`host_lookup `& all types of name-to-IP address handling
3629 &`ident `& ident lookup
3630 &`interface `& lists of local interfaces
3631 &`lists `& matching things in lists
3632 &`load `& system load checks
3633 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3634 &<<CHAPlocalscan>>&)
3635 &`lookup `& general lookup code and all lookups
3636 &`memory `& memory handling
3637 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3638 &`pid `& modifier: add pid to debug output lines
3639 &`process_info `& setting info for the process log
3640 &`queue_run `& queue runs
3641 &`receive `& general message reception logic
3642 &`resolver `& turn on the DNS resolver's debugging output
3643 &`retry `& retry handling
3644 &`rewrite `& address rewriting
3645 &`route `& address routing
3646 &`timestamp `& modifier: add timestamp to debug output lines
3648 &`transport `& transports
3649 &`uid `& changes of uid/gid and looking up uid/gid
3650 &`verify `& address verification logic
3651 &`all `& almost all of the above (see below), and also &%-v%&
3653 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3654 for &`-all`&. The reason for this is that &`+all`& is something that people
3655 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3656 is included, an awful lot of output that is very rarely of interest is
3657 generated, so it now has to be explicitly requested. However, &`-all`& does
3658 turn everything off.
3660 .cindex "resolver, debugging output"
3661 .cindex "DNS resolver, debugging output"
3662 The &`resolver`& option produces output only if the DNS resolver was compiled
3663 with DEBUG enabled. This is not the case in some operating systems. Also,
3664 unfortunately, debugging output from the DNS resolver is written to stdout
3667 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3668 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3669 However, the &`pid`& selector is forced when debugging is turned on for a
3670 daemon, which then passes it on to any re-executed Exims. Exim also
3671 automatically adds the pid to debug lines when several remote deliveries are
3674 The &`timestamp`& selector causes the current time to be inserted at the start
3675 of all debug output lines. This can be useful when trying to track down delays
3678 .cindex debugging "UTF-8 in"
3679 .cindex UTF-8 "in debug output"
3680 The &`noutf8`& selector disables the use of
3681 UTF-8 line-drawing characters to group related information.
3682 When disabled. ascii-art is used instead.
3683 Using the &`+all`& option does not set this modifier,
3685 If the &%debug_print%& option is set in any driver, it produces output whenever
3686 any debugging is selected, or if &%-v%& is used.
3688 .vitem &%-dd%&<&'debug&~options'&>
3690 This option behaves exactly like &%-d%& except when used on a command that
3691 starts a daemon process. In that case, debugging is turned off for the
3692 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3693 behaviour of the daemon without creating as much output as full debugging does.
3696 .oindex "&%-dropcr%&"
3697 This is an obsolete option that is now a no-op. It used to affect the way Exim
3698 handled CR and LF characters in incoming messages. What happens now is
3699 described in section &<<SECTlineendings>>&.
3703 .cindex "bounce message" "generating"
3704 This option specifies that an incoming message is a locally-generated delivery
3705 failure report. It is used internally by Exim when handling delivery failures
3706 and is not intended for external use. Its only effect is to stop Exim
3707 generating certain messages to the postmaster, as otherwise message cascades
3708 could occur in some situations. As part of the same option, a message id may
3709 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3710 new message contains the id, following &"R="&, as a cross-reference.
3713 .oindex "&%-e%&&'x'&"
3714 There are a number of Sendmail options starting with &%-oe%& which seem to be
3715 called by various programs without the leading &%o%& in the option. For
3716 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3717 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3719 .vitem &%-F%&&~<&'string'&>
3721 .cindex "sender" "name"
3722 .cindex "name" "of sender"
3723 This option sets the sender's full name for use when a locally-generated
3724 message is being accepted. In the absence of this option, the user's &'gecos'&
3725 entry from the password data is used. As users are generally permitted to alter
3726 their &'gecos'& entries, no security considerations are involved. White space
3727 between &%-F%& and the <&'string'&> is optional.
3729 .vitem &%-f%&&~<&'address'&>
3731 .cindex "sender" "address"
3732 .cindex "address" "sender"
3733 .cindex "trusted users"
3734 .cindex "envelope from"
3735 .cindex "envelope sender"
3736 .cindex "user" "trusted"
3737 This option sets the address of the envelope sender of a locally-generated
3738 message (also known as the return path). The option can normally be used only
3739 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3742 Processes running as root or the Exim user are always trusted. Other
3743 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3744 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3745 of a local message is set to the caller's login name at the default qualify
3748 There is one exception to the restriction on the use of &%-f%&: an empty sender
3749 can be specified by any user, trusted or not, to create a message that can
3750 never provoke a bounce. An empty sender can be specified either as an empty
3751 string, or as a pair of angle brackets with nothing between them, as in these
3752 examples of shell commands:
3754 exim -f '<>' user@domain
3755 exim -f "" user@domain
3757 In addition, the use of &%-f%& is not restricted when testing a filter file
3758 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3761 Allowing untrusted users to change the sender address does not of itself make
3762 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3763 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3764 though this can be overridden by setting &%no_local_from_check%&.
3767 .cindex "&""From""& line"
3768 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3769 given as two arguments or one combined argument). The sender of a
3770 locally-generated message can also be set (when permitted) by an initial
3771 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3772 if &%-f%& is also present, it overrides &"From&~"&.
3776 .cindex "submission fixups, suppressing (command-line)"
3777 This option is equivalent to an ACL applying:
3779 control = suppress_local_fixups
3781 for every message received. Note that Sendmail will complain about such
3782 bad formatting, where Exim silently just does not fix it up. This may change
3785 As this affects audit information, the caller must be a trusted user to use
3788 .vitem &%-h%&&~<&'number'&>
3790 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3791 This option is accepted for compatibility with Sendmail, but has no effect. (In
3792 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3797 .cindex "Solaris" "&'mail'& command"
3798 .cindex "dot" "in incoming non-SMTP message"
3799 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3800 line by itself should not terminate an incoming, non-SMTP message. I can find
3801 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3802 command in Solaris 2.4 uses it. See also &%-ti%&.
3804 .vitem &%-L%&&~<&'tag'&>
3806 .cindex "syslog" "process name; set with flag"
3807 This option is equivalent to setting &%syslog_processname%& in the config
3808 file and setting &%log_file_path%& to &`syslog`&.
3809 Its use is restricted to administrators. The configuration file has to be
3810 read and parsed, to determine access rights, before this is set and takes
3811 effect, so early configuration file errors will not honour this flag.
3813 The tag should not be longer than 32 characters.
3815 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3817 .cindex "forcing delivery"
3818 .cindex "delivery" "forcing attempt"
3819 .cindex "frozen messages" "forcing delivery"
3820 This option requests Exim to run a delivery attempt on each message in turn. If
3821 any of the messages are frozen, they are automatically thawed before the
3822 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3823 and &%hold_domains%& are ignored.
3826 .cindex "hints database" "overriding retry hints"
3827 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3828 the normal retry time has not yet been reached. This option requires the caller
3829 to be an admin user. However, there is an option called &%prod_requires_admin%&
3830 which can be set false to relax this restriction (and also the same requirement
3831 for the &%-q%&, &%-R%&, and &%-S%& options).
3833 The deliveries happen synchronously, that is, the original Exim process does
3834 not terminate until all the delivery attempts have finished. No output is
3835 produced unless there is a serious error. If you want to see what is happening,
3836 use the &%-v%& option as well, or inspect Exim's main log.
3838 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3840 .cindex "message" "adding recipients"
3841 .cindex "recipient" "adding"
3842 This option requests Exim to add the addresses to the list of recipients of the
3843 message (&"ar"& for &"add recipients"&). The first argument must be a message
3844 id, and the remaining ones must be email addresses. However, if the message is
3845 active (in the middle of a delivery attempt), it is not altered. This option
3846 can be used only by an admin user.
3848 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3849 &~<&'message&~id'&>"
3851 .cindex "SMTP" "passed connection"
3852 .cindex "SMTP" "multiple deliveries"
3853 .cindex "multiple SMTP deliveries"
3854 This option is not intended for use by external callers. It is used internally
3855 by Exim to invoke another instance of itself to deliver a waiting message using
3856 an existing SMTP connection, which is passed as the standard input. Details are
3857 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3858 must be root or the Exim user in order to use it.
3862 This option is not intended for use by external callers. It is used internally
3863 by Exim in conjunction with the &%-MC%& option. It signifies that the
3864 connection to the remote host has been authenticated.
3868 This option is not intended for use by external callers. It is used internally
3869 by Exim in conjunction with the &%-MC%& option. It signifies that the
3870 remote host supports the ESMTP &_DSN_& extension.
3874 This option is not intended for use by external callers. It is used internally
3875 by Exim in conjunction with the &%-d%& option
3876 to pass on an information string on the purpose of the process.
3878 .vitem &%-MCG%&&~<&'queue&~name'&>
3880 This option is not intended for use by external callers. It is used internally
3881 by Exim in conjunction with the &%-MC%& option. It signifies that an
3882 alternate queue is used, named by the following argument.
3886 This option is not intended for use by external callers. It is used internally
3887 by Exim in conjunction with the &%-MC%& option. It signifies that a
3888 remote host supports the ESMTP &_CHUNKING_& extension.
3892 This option is not intended for use by external callers. It is used internally
3893 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3894 which Exim is connected supports pipelining.
3896 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3898 This option is not intended for use by external callers. It is used internally
3899 by Exim in conjunction with the &%-MC%& option when the original delivery was
3900 started by a queue runner. It passes on the process id of the queue runner,
3901 together with the file descriptor number of an open pipe. Closure of the pipe
3902 signals the final completion of the sequence of processes that are passing
3903 messages through the same SMTP connection.
3906 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3908 This option is not intended for use by external callers. It is used internally
3909 by Exim to implement quota checking for local users.
3914 This option is not intended for use by external callers. It is used internally
3915 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3916 ESMTP SIZE option should be used on messages delivered down the existing
3921 This option is not intended for use by external callers. It is used internally
3922 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3923 host to which Exim is connected supports TLS encryption.
3925 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3927 This option is not intended for use by external callers. It is used internally
3928 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3929 connection is being proxied by a parent process for handling TLS encryption.
3930 The arguments give the local address and port being proxied, and the TLS cipher.
3932 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3934 .cindex "hints database" "not overridden by &%-Mc%&"
3935 .cindex "delivery" "manually started &-- not forced"
3936 This option requests Exim to run a delivery attempt on each message, in turn,
3937 but unlike the &%-M%& option, it does check for retry hints, and respects any
3938 that are found. This option is not very useful to external callers. It is
3939 provided mainly for internal use by Exim when it needs to re-invoke itself in
3940 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3941 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3942 respects retry times and other options such as &%hold_domains%& that are
3943 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3944 If you want to run a specific delivery as if in a queue run, you should use
3945 &%-q%& with a message id argument. A distinction between queue run deliveries
3946 and other deliveries is made in one or two places.
3948 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3950 .cindex "message" "changing sender"
3951 .cindex "sender" "changing"
3952 This option requests Exim to change the sender address in the message to the
3953 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3954 &"edit sender"&). There must be exactly two arguments. The first argument must
3955 be a message id, and the second one an email address. However, if the message
3956 is active (in the middle of a delivery attempt), its status is not altered.
3957 This option can be used only by an admin user.
3959 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3961 .cindex "freezing messages"
3962 .cindex "message" "manually freezing"
3963 This option requests Exim to mark each listed message as &"frozen"&. This
3964 prevents any delivery attempts taking place until the message is &"thawed"&,
3965 either manually or as a result of the &%auto_thaw%& configuration option.
3966 However, if any of the messages are active (in the middle of a delivery
3967 attempt), their status is not altered. This option can be used only by an admin
3970 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3972 .cindex "giving up on messages"
3973 .cindex "message" "abandoning delivery attempts"
3974 .cindex "delivery" "abandoning further attempts"
3975 This option requests Exim to give up trying to deliver the listed messages,
3976 including any that are frozen. However, if any of the messages are active,
3977 their status is not altered. For non-bounce messages, a delivery error message
3978 is sent to the sender, containing the text &"cancelled by administrator"&.
3979 Bounce messages are just discarded. This option can be used only by an admin
3982 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
3985 .cindex "named queues" "moving messages"
3986 .cindex "queue" "moving messages"
3987 This option requests that each listed message be moved from its current
3988 queue to the given named queue.
3989 The destination queue name argument is required, but can be an empty
3990 string to define the default queue.
3991 If the messages are not currently located in the default queue,
3992 a &%-qG<name>%& option will be required to define the source queue.
3994 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3996 .cindex "delivery" "cancelling all"
3997 This option requests Exim to mark all the recipient addresses in the messages
3998 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3999 message is active (in the middle of a delivery attempt), its status is not
4000 altered. This option can be used only by an admin user.
4002 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4004 .cindex "delivery" "cancelling by address"
4005 .cindex "recipient" "removing"
4006 .cindex "removing recipients"
4007 This option requests Exim to mark the given addresses as already delivered
4008 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4009 the remaining ones must be email addresses. These are matched to recipient
4010 addresses in the message in a case-sensitive manner. If the message is active
4011 (in the middle of a delivery attempt), its status is not altered. This option
4012 can be used only by an admin user.
4014 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4016 .cindex "removing messages"
4017 .cindex "abandoning mail"
4018 .cindex "message" "manually discarding"
4019 This option requests Exim to remove the given messages from the queue. No
4020 bounce messages are sent; each message is simply forgotten. However, if any of
4021 the messages are active, their status is not altered. This option can be used
4022 only by an admin user or by the user who originally caused the message to be
4023 placed in the queue.
4028 . .cindex REQUIRETLS
4029 . This option is used to request REQUIRETLS processing on the message.
4030 . It is used internally by Exim in conjunction with -E when generating
4034 .vitem &%-Mset%&&~<&'message&~id'&>
4036 .cindex "testing" "string expansion"
4037 .cindex "expansion" "testing"
4038 This option is useful only in conjunction with &%-be%& (that is, when testing
4039 string expansions). Exim loads the given message from its spool before doing
4040 the test expansions, thus setting message-specific variables such as
4041 &$message_size$& and the header variables. The &$recipients$& variable is made
4042 available. This feature is provided to make it easier to test expansions that
4043 make use of these variables. However, this option can be used only by an admin
4044 user. See also &%-bem%&.
4046 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4048 .cindex "thawing messages"
4049 .cindex "unfreezing messages"
4050 .cindex "frozen messages" "thawing"
4051 .cindex "message" "thawing frozen"
4052 This option requests Exim to &"thaw"& any of the listed messages that are
4053 &"frozen"&, so that delivery attempts can resume. However, if any of the
4054 messages are active, their status is not altered. This option can be used only
4057 .vitem &%-Mvb%&&~<&'message&~id'&>
4059 .cindex "listing" "message body"
4060 .cindex "message" "listing body of"
4061 This option causes the contents of the message body (-D) spool file to be
4062 written to the standard output. This option can be used only by an admin user.
4064 .vitem &%-Mvc%&&~<&'message&~id'&>
4066 .cindex "message" "listing in RFC 2822 format"
4067 .cindex "listing" "message in RFC 2822 format"
4068 This option causes a copy of the complete message (header lines plus body) to
4069 be written to the standard output in RFC 2822 format. This option can be used
4070 only by an admin user.
4072 .vitem &%-Mvh%&&~<&'message&~id'&>
4074 .cindex "listing" "message headers"
4075 .cindex "header lines" "listing"
4076 .cindex "message" "listing header lines"
4077 This option causes the contents of the message headers (-H) spool file to be
4078 written to the standard output. This option can be used only by an admin user.
4080 .vitem &%-Mvl%&&~<&'message&~id'&>
4082 .cindex "listing" "message log"
4083 .cindex "message" "listing message log"
4084 This option causes the contents of the message log spool file to be written to
4085 the standard output. This option can be used only by an admin user.
4089 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4090 treats it that way too.
4094 .cindex "debugging" "&%-N%& option"
4095 .cindex "debugging" "suppressing delivery"
4096 This is a debugging option that inhibits delivery of a message at the transport
4097 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4098 it just doesn't actually transport the message, but instead behaves as if it
4099 had successfully done so. However, it does not make any updates to the retry
4100 database, and the log entries for deliveries are flagged with &"*>"& rather
4103 Because &%-N%& discards any message to which it applies, only root or the Exim
4104 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4105 words, an ordinary user can use it only when supplying an incoming message to
4106 which it will apply. Although transportation never fails when &%-N%& is set, an
4107 address may be deferred because of a configuration problem on a transport, or a
4108 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4109 the message, and applies to any subsequent delivery attempts that may happen
4114 This option is interpreted by Sendmail to mean &"no aliasing"&.
4115 For normal modes of operation, it is ignored by Exim.
4116 When combined with &%-bP%& it makes the output more terse (suppresses
4117 option names, environment values and config pretty printing).
4119 .vitem &%-O%&&~<&'data'&>
4121 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4124 .vitem &%-oA%&&~<&'file&~name'&>
4126 .cindex "Sendmail compatibility" "&%-oA%& option"
4127 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4128 alternative alias filename. Exim handles &%-bi%& differently; see the
4131 .vitem &%-oB%&&~<&'n'&>
4133 .cindex "SMTP" "passed connection"
4134 .cindex "SMTP" "multiple deliveries"
4135 .cindex "multiple SMTP deliveries"
4136 This is a debugging option which limits the maximum number of messages that can
4137 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4138 transport. If <&'n'&> is omitted, the limit is set to 1.
4142 .cindex "background delivery"
4143 .cindex "delivery" "in the background"
4144 This option applies to all modes in which Exim accepts incoming messages,
4145 including the listening daemon. It requests &"background"& delivery of such
4146 messages, which means that the accepting process automatically starts a
4147 delivery process for each message received, but does not wait for the delivery
4148 processes to finish.
4150 When all the messages have been received, the reception process exits,
4151 leaving the delivery processes to finish in their own time. The standard output
4152 and error streams are closed at the start of each delivery process.
4153 This is the default action if none of the &%-od%& options are present.
4155 If one of the queueing options in the configuration file
4156 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4157 overrides it if &%queue_only_override%& is set true, which is the default
4158 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4162 .cindex "foreground delivery"
4163 .cindex "delivery" "in the foreground"
4164 This option requests &"foreground"& (synchronous) delivery when Exim has
4165 accepted a locally-generated message. (For the daemon it is exactly the same as
4166 &%-odb%&.) A delivery process is automatically started to deliver the message,
4167 and Exim waits for it to complete before proceeding.
4169 The original Exim reception process does not finish until the delivery
4170 process for the final message has ended. The standard error stream is left open
4173 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4174 false and one of the queueing options in the configuration file is in effect.
4176 If there is a temporary delivery error during foreground delivery, the
4177 message is left in the queue for later delivery, and the original reception
4178 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4179 restricted configuration that never queues messages.
4184 This option is synonymous with &%-odf%&. It is provided for compatibility with
4189 .cindex "non-immediate delivery"
4190 .cindex "delivery" "suppressing immediate"
4191 .cindex "queueing incoming messages"
4192 This option applies to all modes in which Exim accepts incoming messages,
4193 including the listening daemon. It specifies that the accepting process should
4194 not automatically start a delivery process for each message received. Messages
4195 are placed in the queue, and remain there until a subsequent queue runner
4196 process encounters them. There are several configuration options (such as
4197 &%queue_only%&) that can be used to queue incoming messages under certain
4198 conditions. This option overrides all of them and also &%-odqs%&. It always
4203 .cindex "SMTP" "delaying delivery"
4204 .cindex "first pass routing"
4205 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4206 However, like &%-odb%& and &%-odi%&, this option has no effect if
4207 &%queue_only_override%& is false and one of the queueing options in the
4208 configuration file is in effect.
4210 When &%-odqs%& does operate, a delivery process is started for each incoming
4211 message, in the background by default, but in the foreground if &%-odi%& is
4212 also present. The recipient addresses are routed, and local deliveries are done
4213 in the normal way. However, if any SMTP deliveries are required, they are not
4214 done at this time, so the message remains in the queue until a subsequent queue
4215 runner process encounters it. Because routing was done, Exim knows which
4216 messages are waiting for which hosts, and so a number of messages for the same
4217 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4218 configuration option has the same effect for specific domains. See also the
4223 .cindex "error" "reporting"
4224 If an error is detected while a non-SMTP message is being received (for
4225 example, a malformed address), the error is reported to the sender in a mail
4228 .cindex "return code" "for &%-oee%&"
4230 this error message is successfully sent, the Exim receiving process
4231 exits with a return code of zero. If not, the return code is 2 if the problem
4232 is that the original message has no recipients, or 1 for any other error.
4233 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4237 .cindex "error" "reporting"
4238 .cindex "return code" "for &%-oem%&"
4239 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4240 return code, whether or not the error message was successfully sent.
4241 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4245 .cindex "error" "reporting"
4246 If an error is detected while a non-SMTP message is being received, the
4247 error is reported by writing a message to the standard error file (stderr).
4248 .cindex "return code" "for &%-oep%&"
4249 The return code is 1 for all errors.
4253 .cindex "error" "reporting"
4254 This option is supported for compatibility with Sendmail, but has the same
4259 .cindex "error" "reporting"
4260 This option is supported for compatibility with Sendmail, but has the same
4265 .cindex "dot" "in incoming non-SMTP message"
4266 This option, which has the same effect as &%-i%&, specifies that a dot on a
4267 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4268 single dot does terminate, though Exim does no special processing for other
4269 lines that start with a dot. This option is set by default if Exim is called as
4270 &'rmail'&. See also &%-ti%&.
4273 .oindex "&%-oitrue%&"
4274 This option is treated as synonymous with &%-oi%&.
4276 .vitem &%-oMa%&&~<&'host&~address'&>
4278 .cindex "sender" "host address, specifying for local message"
4279 A number of options starting with &%-oM%& can be used to set values associated
4280 with remote hosts on locally-submitted messages (that is, messages not received
4281 over TCP/IP). These options can be used by any caller in conjunction with the
4282 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4283 other circumstances, they are ignored unless the caller is trusted.
4285 The &%-oMa%& option sets the sender host address. This may include a port
4286 number at the end, after a full stop (period). For example:
4288 exim -bs -oMa 10.9.8.7.1234
4290 An alternative syntax is to enclose the IP address in square brackets,
4291 followed by a colon and the port number:
4293 exim -bs -oMa [10.9.8.7]:1234
4295 The IP address is placed in the &$sender_host_address$& variable, and the
4296 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4297 are present on the command line, the sender host IP address is taken from
4298 whichever one is last.
4300 .vitem &%-oMaa%&&~<&'name'&>
4302 .cindex "authentication" "name, specifying for local message"
4303 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4304 option sets the value of &$sender_host_authenticated$& (the authenticator
4305 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4306 This option can be used with &%-bh%& and &%-bs%& to set up an
4307 authenticated SMTP session without actually using the SMTP AUTH command.
4309 .vitem &%-oMai%&&~<&'string'&>
4311 .cindex "authentication" "id, specifying for local message"
4312 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4313 option sets the value of &$authenticated_id$& (the id that was authenticated).
4314 This overrides the default value (the caller's login id, except with &%-bh%&,
4315 where there is no default) for messages from local sources. See chapter
4316 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4318 .vitem &%-oMas%&&~<&'address'&>
4320 .cindex "authentication" "sender, specifying for local message"
4321 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4322 option sets the authenticated sender value in &$authenticated_sender$&. It
4323 overrides the sender address that is created from the caller's login id for
4324 messages from local sources, except when &%-bh%& is used, when there is no
4325 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4326 specified on a MAIL command overrides this value. See chapter
4327 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4329 .vitem &%-oMi%&&~<&'interface&~address'&>
4331 .cindex "interface" "address, specifying for local message"
4332 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4333 option sets the IP interface address value. A port number may be included,
4334 using the same syntax as for &%-oMa%&. The interface address is placed in
4335 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4337 .vitem &%-oMm%&&~<&'message&~reference'&>
4339 .cindex "message reference" "message reference, specifying for local message"
4340 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4341 option sets the message reference, e.g. message-id, and is logged during
4342 delivery. This is useful when some kind of audit trail is required to tie
4343 messages together. The format of the message reference is checked and will
4344 abort if the format is invalid. The option will only be accepted if exim is
4345 running in trusted mode, not as any regular user.
4347 The best example of a message reference is when Exim sends a bounce message.
4348 The message reference is the message-id of the original message for which Exim
4349 is sending the bounce.
4351 .vitem &%-oMr%&&~<&'protocol&~name'&>
4353 .cindex "protocol, specifying for local message"
4354 .vindex "&$received_protocol$&"
4355 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4356 option sets the received protocol value that is stored in
4357 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4358 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4359 SMTP protocol names (see the description of &$received_protocol$& in section
4360 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4361 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4362 be set by &%-oMr%&. Repeated use of this option is not supported.
4364 .vitem &%-oMs%&&~<&'host&~name'&>
4366 .cindex "sender" "host name, specifying for local message"
4367 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4368 option sets the sender host name in &$sender_host_name$&. When this option is
4369 present, Exim does not attempt to look up a host name from an IP address; it
4370 uses the name it is given.
4372 .vitem &%-oMt%&&~<&'ident&~string'&>
4374 .cindex "sender" "ident string, specifying for local message"
4375 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4376 option sets the sender ident value in &$sender_ident$&. The default setting for
4377 local callers is the login id of the calling process, except when &%-bh%& is
4378 used, when there is no default.
4382 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4383 In Sendmail, this option means &"me too"&, indicating that the sender of a
4384 message should receive a copy of the message if the sender appears in an alias
4385 expansion. Exim always does this, so the option does nothing.
4389 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4390 This option is ignored. In Sendmail it specifies &"old style headers"&,
4391 whatever that means.
4393 .vitem &%-oP%&&~<&'path'&>
4395 .cindex "pid (process id)" "of daemon"
4396 .cindex "daemon" "process id (pid)"
4397 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4398 value. The option specifies the file to which the process id of the daemon is
4399 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4400 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4401 because in those cases, the normal pid file is not used.
4405 .cindex "pid (process id)" "of daemon"
4406 .cindex "daemon" "process id (pid)"
4407 This option is not intended for general use.
4408 The daemon uses it when terminating due to a SIGTEM, possibly in
4409 combination with &%-oP%&&~<&'path'&>.
4410 It causes the pid file to be removed.
4412 .vitem &%-or%&&~<&'time'&>
4414 .cindex "timeout" "for non-SMTP input"
4415 This option sets a timeout value for incoming non-SMTP messages. If it is not
4416 set, Exim will wait forever for the standard input. The value can also be set
4417 by the &%receive_timeout%& option. The format used for specifying times is
4418 described in section &<<SECTtimeformat>>&.
4420 .vitem &%-os%&&~<&'time'&>
4422 .cindex "timeout" "for SMTP input"
4423 .cindex "SMTP" "input timeout"
4424 This option sets a timeout value for incoming SMTP messages. The timeout
4425 applies to each SMTP command and block of data. The value can also be set by
4426 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4427 for specifying times is described in section &<<SECTtimeformat>>&.
4431 This option has exactly the same effect as &%-v%&.
4433 .vitem &%-oX%&&~<&'number&~or&~string'&>
4435 .cindex "TCP/IP" "setting listening ports"
4436 .cindex "TCP/IP" "setting listening interfaces"
4437 .cindex "port" "receiving TCP/IP"
4438 This option is relevant only when the &%-bd%& (start listening daemon) option
4439 is also given. It controls which ports and interfaces the daemon uses. Details
4440 of the syntax, and how it interacts with configuration file options, are given
4441 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4442 file is written unless &%-oP%& is also present to specify a pid filename.
4446 .cindex "Perl" "starting the interpreter"
4447 This option applies when an embedded Perl interpreter is linked with Exim (see
4448 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4449 option, forcing the starting of the interpreter to be delayed until it is
4454 .cindex "Perl" "starting the interpreter"
4455 This option applies when an embedded Perl interpreter is linked with Exim (see
4456 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4457 option, forcing the starting of the interpreter to occur as soon as Exim is
4460 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4462 For compatibility with Sendmail, this option is equivalent to
4464 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4466 It sets the incoming protocol and host name (for trusted callers). The
4467 host name and its colon can be omitted when only the protocol is to be set.
4468 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4469 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4470 or &`s`& using this option (but that does not seem a real limitation).
4471 Repeated use of this option is not supported.
4475 .cindex "queue runner" "starting manually"
4476 This option is normally restricted to admin users. However, there is a
4477 configuration option called &%prod_requires_admin%& which can be set false to
4478 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4479 and &%-S%& options).
4481 .cindex "queue runner" "description of operation"
4482 If other commandline options do not specify an action,
4483 the &%-q%& option starts one queue runner process. This scans the queue of
4484 waiting messages, and runs a delivery process for each one in turn. It waits
4485 for each delivery process to finish before starting the next one. A delivery
4486 process may not actually do any deliveries if the retry times for the addresses
4487 have not been reached. Use &%-qf%& (see below) if you want to override this.
4490 .cindex "SMTP" "passed connection"
4491 .cindex "SMTP" "multiple deliveries"
4492 .cindex "multiple SMTP deliveries"
4493 the delivery process spawns other processes to deliver other messages down
4494 passed SMTP connections, the queue runner waits for these to finish before
4497 When all the queued messages have been considered, the original queue runner
4498 process terminates. In other words, a single pass is made over the waiting
4499 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4500 this to be repeated periodically.
4502 Exim processes the waiting messages in an unpredictable order. It isn't very
4503 random, but it is likely to be different each time, which is all that matters.
4504 If one particular message screws up a remote MTA, other messages to the same
4505 MTA have a chance of getting through if they get tried first.
4507 It is possible to cause the messages to be processed in lexical message id
4508 order, which is essentially the order in which they arrived, by setting the
4509 &%queue_run_in_order%& option, but this is not recommended for normal use.
4511 .vitem &%-q%&<&'qflags'&>
4512 The &%-q%& option may be followed by one or more flag letters that change its
4513 behaviour. They are all optional, but if more than one is present, they must
4514 appear in the correct order. Each flag is described in a separate item below.
4518 .cindex "queue" "double scanning"
4519 .cindex "queue" "routing"
4520 .cindex "routing" "whole queue before delivery"
4521 .cindex "first pass routing"
4522 .cindex "queue runner" "two phase"
4523 An option starting with &%-qq%& requests a two-stage queue run. In the first
4524 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4525 every domain. Addresses are routed, local deliveries happen, but no remote
4528 Performance will be best if the &%queue_run_in_order%& option is false.
4529 If that is so and the &%queue_fast_ramp%& option is true then
4530 in the first phase of the run,
4531 once a threshold number of messages are routed for a given host,
4532 a delivery process is forked in parallel with the rest of the scan.
4534 .cindex "hints database" "remembering routing"
4535 The hints database that remembers which messages are waiting for specific hosts
4536 is updated, as if delivery to those hosts had been deferred. After this is
4537 complete, a second, normal queue scan happens, with routing and delivery taking
4538 place as normal. Messages that are routed to the same host should mostly be
4539 delivered down a single SMTP
4540 .cindex "SMTP" "passed connection"
4541 .cindex "SMTP" "multiple deliveries"
4542 .cindex "multiple SMTP deliveries"
4543 connection because of the hints that were set up during the first queue scan.
4544 This option may be useful for hosts that are connected to the Internet
4547 .vitem &%-q[q]i...%&
4549 .cindex "queue" "initial delivery"
4550 If the &'i'& flag is present, the queue runner runs delivery processes only for
4551 those messages that haven't previously been tried. (&'i'& stands for &"initial
4552 delivery"&.) This can be helpful if you are putting messages in the queue using
4553 &%-odq%& and want a queue runner just to process the new messages.
4555 .vitem &%-q[q][i]f...%&
4557 .cindex "queue" "forcing delivery"
4558 .cindex "delivery" "forcing in queue run"
4559 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4560 message, whereas without &'f'& only those non-frozen addresses that have passed
4561 their retry times are tried.
4563 .vitem &%-q[q][i]ff...%&
4565 .cindex "frozen messages" "forcing delivery"
4566 If &'ff'& is present, a delivery attempt is forced for every message, whether
4569 .vitem &%-q[q][i][f[f]]l%&
4571 .cindex "queue" "local deliveries only"
4572 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4573 be done. If a message requires any remote deliveries, it remains in the queue
4576 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4579 .cindex "named queues" "deliver from"
4580 .cindex "queue" "delivering specific messages"
4581 If the &'G'& flag and a name is present, the queue runner operates on the
4582 queue with the given name rather than the default queue.
4583 The name should not contain a &'/'& character.
4584 For a periodic queue run (see below)
4585 append to the name a slash and a time value.
4587 If other commandline options specify an action, a &'-qG<name>'& option
4588 will specify a queue to operate on.
4591 exim -bp -qGquarantine
4593 exim -qGoffpeak -Rf @special.domain.example
4596 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4597 When scanning the queue, Exim can be made to skip over messages whose ids are
4598 lexically less than a given value by following the &%-q%& option with a
4599 starting message id. For example:
4601 exim -q 0t5C6f-0000c8-00
4603 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4604 second message id is given, messages whose ids are lexically greater than it
4605 are also skipped. If the same id is given twice, for example,
4607 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4609 just one delivery process is started, for that message. This differs from
4610 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4611 that it counts as a delivery from a queue run. Note that the selection
4612 mechanism does not affect the order in which the messages are scanned. There
4613 are also other ways of selecting specific sets of messages for delivery in a
4614 queue run &-- see &%-R%& and &%-S%&.
4616 .vitem &%-q%&<&'qflags'&><&'time'&>
4617 .cindex "queue runner" "starting periodically"
4618 .cindex "periodic queue running"
4619 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4620 starting a queue runner process at intervals specified by the given time value
4621 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4622 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4623 single daemon process handles both functions. A common way of starting up a
4624 combined daemon at system boot time is to use a command such as
4626 /usr/exim/bin/exim -bd -q30m
4628 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4629 process every 30 minutes.
4631 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4632 pid file is written unless one is explicitly requested by the &%-oP%& option.
4634 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4636 This option is synonymous with &%-R%&. It is provided for Sendmail
4639 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4641 This option is synonymous with &%-S%&.
4643 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4645 .cindex "queue runner" "for specific recipients"
4646 .cindex "delivery" "to given domain"
4647 .cindex "domain" "delivery to"
4648 The <&'rsflags'&> may be empty, in which case the white space before the string
4649 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4650 which are the possible values for <&'rsflags'&>. White space is required if
4651 <&'rsflags'&> is not empty.
4653 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4654 perform a single queue run, except that, when scanning the messages on the
4655 queue, Exim processes only those that have at least one undelivered recipient
4656 address containing the given string, which is checked in a case-independent
4657 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4658 regular expression; otherwise it is a literal string.
4660 If you want to do periodic queue runs for messages with specific recipients,
4661 you can combine &%-R%& with &%-q%& and a time value. For example:
4663 exim -q25m -R @special.domain.example
4665 This example does a queue run for messages with recipients in the given domain
4666 every 25 minutes. Any additional flags that are specified with &%-q%& are
4667 applied to each queue run.
4669 Once a message is selected for delivery by this mechanism, all its addresses
4670 are processed. For the first selected message, Exim overrides any retry
4671 information and forces a delivery attempt for each undelivered address. This
4672 means that if delivery of any address in the first message is successful, any
4673 existing retry information is deleted, and so delivery attempts for that
4674 address in subsequently selected messages (which are processed without forcing)
4675 will run. However, if delivery of any address does not succeed, the retry
4676 information is updated, and in subsequently selected messages, the failing
4677 address will be skipped.
4679 .cindex "frozen messages" "forcing delivery"
4680 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4681 all selected messages, not just the first; frozen messages are included when
4684 The &%-R%& option makes it straightforward to initiate delivery of all messages
4685 to a given domain after a host has been down for some time. When the SMTP
4686 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4687 effect is to run Exim with the &%-R%& option, but it can be configured to run
4688 an arbitrary command instead.
4692 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4694 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4696 .cindex "delivery" "from given sender"
4697 .cindex "queue runner" "for specific senders"
4698 This option acts like &%-R%& except that it checks the string against each
4699 message's sender instead of against the recipients. If &%-R%& is also set, both
4700 conditions must be met for a message to be selected. If either of the options
4701 has &'f'& or &'ff'& in its flags, the associated action is taken.
4703 .vitem &%-Tqt%&&~<&'times'&>
4705 This is an option that is exclusively for use by the Exim testing suite. It is not
4706 recognized when Exim is run normally. It allows for the setting up of explicit
4707 &"queue times"& so that various warning/retry features can be tested.
4711 .cindex "recipient" "extracting from header lines"
4712 .cindex "&'Bcc:'& header line"
4713 .cindex "&'Cc:'& header line"
4714 .cindex "&'To:'& header line"
4715 When Exim is receiving a locally-generated, non-SMTP message on its standard
4716 input, the &%-t%& option causes the recipients of the message to be obtained
4717 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4718 from the command arguments. The addresses are extracted before any rewriting
4719 takes place and the &'Bcc:'& header line, if present, is then removed.
4721 .cindex "Sendmail compatibility" "&%-t%& option"
4722 If the command has any arguments, they specify addresses to which the message
4723 is &'not'& to be delivered. That is, the argument addresses are removed from
4724 the recipients list obtained from the headers. This is compatible with Smail 3
4725 and in accordance with the documented behaviour of several versions of
4726 Sendmail, as described in man pages on a number of operating systems (e.g.
4727 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4728 argument addresses to those obtained from the headers, and the O'Reilly
4729 Sendmail book documents it that way. Exim can be made to add argument addresses
4730 instead of subtracting them by setting the option
4731 &%extract_addresses_remove_arguments%& false.
4733 .cindex "&%Resent-%& header lines" "with &%-t%&"
4734 If there are any &%Resent-%& header lines in the message, Exim extracts
4735 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4736 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4737 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4738 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4740 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4741 message is resent several times). The RFC also specifies that they should be
4742 added at the front of the message, and separated by &'Received:'& lines. It is
4743 not at all clear how &%-t%& should operate in the present of multiple sets,
4744 nor indeed exactly what constitutes a &"set"&.
4745 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4746 are often added at the end of the header, and if a message is resent more than
4747 once, it is common for the original set of &%Resent-%& headers to be renamed as
4748 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4752 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4753 compatibility with Sendmail.
4755 .vitem &%-tls-on-connect%&
4756 .oindex "&%-tls-on-connect%&"
4757 .cindex "TLS" "use without STARTTLS"
4758 .cindex "TLS" "automatic start"
4759 This option is available when Exim is compiled with TLS support. It forces all
4760 incoming SMTP connections to behave as if the incoming port is listed in the
4761 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4762 &<<CHAPTLS>>& for further details.
4767 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4768 Sendmail uses this option for &"initial message submission"&, and its
4769 documentation states that in future releases, it may complain about
4770 syntactically invalid messages rather than fixing them when this flag is not
4771 set. Exim ignores this option.
4775 This option causes Exim to write information to the standard error stream,
4776 describing what it is doing. In particular, it shows the log lines for
4777 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4778 dialogue is shown. Some of the log lines shown may not actually be written to
4779 the log if the setting of &%log_selector%& discards them. Any relevant
4780 selectors are shown with each log line. If none are shown, the logging is
4785 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4786 National Language Support extended characters in the body of the mail item"&).
4787 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4790 .vitem &%-X%&&~<&'logfile'&>
4792 This option is interpreted by Sendmail to cause debug information to be sent
4793 to the named file. It is ignored by Exim.
4795 .vitem &%-z%&&~<&'log-line'&>
4797 This option writes its argument to Exim's logfile.
4798 Use is restricted to administrators; the intent is for operational notes.
4799 Quotes should be used to maintain a multi-word item as a single argument,
4807 . ////////////////////////////////////////////////////////////////////////////
4808 . Insert a stylized DocBook comment here, to identify the end of the command
4809 . line options. This is for the benefit of the Perl script that automatically
4810 . creates a man page for the options.
4811 . ////////////////////////////////////////////////////////////////////////////
4814 <!-- === End of command line options === -->
4821 . ////////////////////////////////////////////////////////////////////////////
4822 . ////////////////////////////////////////////////////////////////////////////
4825 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4826 "The runtime configuration file"
4828 .cindex "runtime configuration"
4829 .cindex "configuration file" "general description"
4830 .cindex "CONFIGURE_FILE"
4831 .cindex "configuration file" "errors in"
4832 .cindex "error" "in configuration file"
4833 .cindex "return code" "for bad configuration"
4834 Exim uses a single runtime configuration file that is read whenever an Exim
4835 binary is executed. Note that in normal operation, this happens frequently,
4836 because Exim is designed to operate in a distributed manner, without central
4839 If a syntax error is detected while reading the configuration file, Exim
4840 writes a message on the standard error, and exits with a non-zero return code.
4841 The message is also written to the panic log. &*Note*&: Only simple syntax
4842 errors can be detected at this time. The values of any expanded options are
4843 not checked until the expansion happens, even when the expansion does not
4844 actually alter the string.
4846 The name of the configuration file is compiled into the binary for security
4847 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4848 most configurations, this specifies a single file. However, it is permitted to
4849 give a colon-separated list of filenames, in which case Exim uses the first
4850 existing file in the list.
4853 .cindex "EXIM_GROUP"
4854 .cindex "CONFIGURE_OWNER"
4855 .cindex "CONFIGURE_GROUP"
4856 .cindex "configuration file" "ownership"
4857 .cindex "ownership" "configuration file"
4858 The runtime configuration file must be owned by root or by the user that is
4859 specified at compile time by the CONFIGURE_OWNER option (if set). The
4860 configuration file must not be world-writeable, or group-writeable unless its
4861 group is the root group or the one specified at compile time by the
4862 CONFIGURE_GROUP option.
4864 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4865 to root, anybody who is able to edit the runtime configuration file has an
4866 easy way to run commands as root. If you specify a user or group in the
4867 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4868 who are members of that group will trivially be able to obtain root privileges.
4870 Up to Exim version 4.72, the runtime configuration file was also permitted to
4871 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4872 since it offered a simple privilege escalation for any attacker who managed to
4873 compromise the Exim user account.
4875 A default configuration file, which will work correctly in simple situations,
4876 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4877 defines just one filename, the installation process copies the default
4878 configuration to a new file of that name if it did not previously exist. If
4879 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4880 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4885 .section "Using a different configuration file" "SECID40"
4886 .cindex "configuration file" "alternate"
4887 A one-off alternate configuration can be specified by the &%-C%& command line
4888 option, which may specify a single file or a list of files. However, when
4889 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4890 unless the argument for &%-C%& is identical to the built-in value from
4891 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4892 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4893 is useful mainly for checking the syntax of configuration files before
4894 installing them. No owner or group checks are done on a configuration file
4895 specified by &%-C%&, if root privilege has been dropped.
4897 Even the Exim user is not trusted to specify an arbitrary configuration file
4898 with the &%-C%& option to be used with root privileges, unless that file is
4899 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4900 testing a configuration using &%-C%& right through message reception and
4901 delivery, even if the caller is root. The reception works, but by that time,
4902 Exim is running as the Exim user, so when it re-execs to regain privilege for
4903 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4904 can test reception and delivery using two separate commands (one to put a
4905 message in the queue, using &%-odq%&, and another to do the delivery, using
4908 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4909 prefix string with which any file named in a &%-C%& command line option must
4910 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4911 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4912 filename can be used with &%-C%&.
4914 One-off changes to a configuration can be specified by the &%-D%& command line
4915 option, which defines and overrides values for macros used inside the
4916 configuration file. However, like &%-C%&, the use of this option by a
4917 non-privileged user causes Exim to discard its root privilege.
4918 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4919 completely disabled, and its use causes an immediate error exit.
4921 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4922 to declare certain macro names trusted, such that root privilege will not
4923 necessarily be discarded.
4924 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4925 considered safe and, if &%-D%& only supplies macros from this list, and the
4926 values are acceptable, then Exim will not give up root privilege if the caller
4927 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4928 transition mechanism and is expected to be removed in the future. Acceptable
4929 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4931 Some sites may wish to use the same Exim binary on different machines that
4932 share a file system, but to use different configuration files on each machine.
4933 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4934 looks for a file whose name is the configuration filename followed by a dot
4935 and the machine's node name, as obtained from the &[uname()]& function. If this
4936 file does not exist, the standard name is tried. This processing occurs for
4937 each filename in the list given by CONFIGURE_FILE or &%-C%&.
4939 In some esoteric situations different versions of Exim may be run under
4940 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4941 help with this. See the comments in &_src/EDITME_& for details.
4945 .section "Configuration file format" "SECTconffilfor"
4946 .cindex "configuration file" "format of"
4947 .cindex "format" "configuration file"
4948 Exim's configuration file is divided into a number of different parts. General
4949 option settings must always appear at the start of the file. The other parts
4950 are all optional, and may appear in any order. Each part other than the first
4951 is introduced by the word &"begin"& followed by at least one literal
4952 space, and the name of the part. The optional parts are:
4955 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4958 .cindex "AUTH" "configuration"
4959 &'authenticators'&: Configuration settings for the authenticator drivers. These
4960 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4962 &'routers'&: Configuration settings for the router drivers. Routers process
4963 addresses and determine how the message is to be delivered (see chapters
4964 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4966 &'transports'&: Configuration settings for the transport drivers. Transports
4967 define mechanisms for copying messages to destinations (see chapters
4968 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4970 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4971 If there is no retry section, or if it is empty (that is, no retry rules are
4972 defined), Exim will not retry deliveries. In this situation, temporary errors
4973 are treated the same as permanent errors. Retry rules are discussed in chapter
4976 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4977 when new addresses are generated during delivery. Rewriting is discussed in
4978 chapter &<<CHAPrewrite>>&.
4980 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4981 want to use this feature, you must set
4983 LOCAL_SCAN_HAS_OPTIONS=yes
4985 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4986 facility are given in chapter &<<CHAPlocalscan>>&.
4989 .cindex "configuration file" "leading white space in"
4990 .cindex "configuration file" "trailing white space in"
4991 .cindex "white space" "in configuration file"
4992 Leading and trailing white space in configuration lines is always ignored.
4994 Blank lines in the file, and lines starting with a # character (ignoring
4995 leading white space) are treated as comments and are ignored. &*Note*&: A
4996 # character other than at the beginning of a line is not treated specially,
4997 and does not introduce a comment.
4999 Any non-comment line can be continued by ending it with a backslash. Note that
5000 the general rule for white space means that trailing white space after the
5001 backslash and leading white space at the start of continuation
5002 lines is ignored. Comment lines beginning with # (but not empty lines) may
5003 appear in the middle of a sequence of continuation lines.
5005 A convenient way to create a configuration file is to start from the
5006 default, which is supplied in &_src/configure.default_&, and add, delete, or
5007 change settings as required.
5009 The ACLs, retry rules, and rewriting rules have their own syntax which is
5010 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5011 respectively. The other parts of the configuration file have some syntactic
5012 items in common, and these are described below, from section &<<SECTcos>>&
5013 onwards. Before that, the inclusion, macro, and conditional facilities are
5018 .section "File inclusions in the configuration file" "SECID41"
5019 .cindex "inclusions in configuration file"
5020 .cindex "configuration file" "including other files"
5021 .cindex "&`.include`& in configuration file"
5022 .cindex "&`.include_if_exists`& in configuration file"
5023 You can include other files inside Exim's runtime configuration file by
5026 &`.include`& <&'filename'&>
5027 &`.include_if_exists`& <&'filename'&>
5029 on a line by itself. Double quotes round the filename are optional. If you use
5030 the first form, a configuration error occurs if the file does not exist; the
5031 second form does nothing for non-existent files.
5032 The first form allows a relative name. It is resolved relative to
5033 the directory of the including file. For the second form an absolute filename
5036 Includes may be nested to any depth, but remember that Exim reads its
5037 configuration file often, so it is a good idea to keep them to a minimum.
5038 If you change the contents of an included file, you must HUP the daemon,
5039 because an included file is read only when the configuration itself is read.
5041 The processing of inclusions happens early, at a physical line level, so, like
5042 comment lines, an inclusion can be used in the middle of an option setting,
5045 hosts_lookup = a.b.c \
5048 Include processing happens after macro processing (see below). Its effect is to
5049 process the lines of the included file as if they occurred inline where the
5054 .section "Macros in the configuration file" "SECTmacrodefs"
5055 .cindex "macro" "description of"
5056 .cindex "configuration file" "macros"
5057 If a line in the main part of the configuration (that is, before the first
5058 &"begin"& line) begins with an upper case letter, it is taken as a macro
5059 definition, and must be of the form
5061 <&'name'&> = <&'rest of line'&>
5063 The name must consist of letters, digits, and underscores, and need not all be
5064 in upper case, though that is recommended. The rest of the line, including any
5065 continuations, is the replacement text, and has leading and trailing white
5066 space removed. Quotes are not removed. The replacement text can never end with
5067 a backslash character, but this doesn't seem to be a serious limitation.
5069 Macros may also be defined between router, transport, authenticator, or ACL
5070 definitions. They may not, however, be defined within an individual driver or
5071 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5073 .section "Macro substitution" "SECID42"
5074 Once a macro is defined, all subsequent lines in the file (and any included
5075 files) are scanned for the macro name; if there are several macros, the line is
5076 scanned for each, in turn, in the order in which the macros are defined. The
5077 replacement text is not re-scanned for the current macro, though it is scanned
5078 for subsequently defined macros. For this reason, a macro name may not contain
5079 the name of a previously defined macro as a substring. You could, for example,
5082 &`ABCD_XYZ = `&<&'something'&>
5083 &`ABCD = `&<&'something else'&>
5085 but putting the definitions in the opposite order would provoke a configuration
5086 error. Macro expansion is applied to individual physical lines from the file,
5087 before checking for line continuation or file inclusion (see above). If a line
5088 consists solely of a macro name, and the expansion of the macro is empty, the
5089 line is ignored. A macro at the start of a line may turn the line into a
5090 comment line or a &`.include`& line.
5093 .section "Redefining macros" "SECID43"
5094 Once defined, the value of a macro can be redefined later in the configuration
5095 (or in an included file). Redefinition is specified by using &'=='& instead of
5100 MAC == updated value
5102 Redefinition does not alter the order in which the macros are applied to the
5103 subsequent lines of the configuration file. It is still the same order in which
5104 the macros were originally defined. All that changes is the macro's value.
5105 Redefinition makes it possible to accumulate values. For example:
5109 MAC == MAC and something added
5111 This can be helpful in situations where the configuration file is built
5112 from a number of other files.
5114 .section "Overriding macro values" "SECID44"
5115 The values set for macros in the configuration file can be overridden by the
5116 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5117 used, unless called by root or the Exim user. A definition on the command line
5118 using the &%-D%& option causes all definitions and redefinitions within the
5123 .section "Example of macro usage" "SECID45"
5124 As an example of macro usage, consider a configuration where aliases are looked
5125 up in a MySQL database. It helps to keep the file less cluttered if long
5126 strings such as SQL statements are defined separately as macros, for example:
5128 ALIAS_QUERY = select mailbox from user where \
5129 login='${quote_mysql:$local_part}';
5131 This can then be used in a &(redirect)& router setting like this:
5133 data = ${lookup mysql{ALIAS_QUERY}}
5135 In earlier versions of Exim macros were sometimes used for domain, host, or
5136 address lists. In Exim 4 these are handled better by named lists &-- see
5137 section &<<SECTnamedlists>>&.
5140 .section "Builtin macros" "SECTbuiltinmacros"
5141 Exim defines some macros depending on facilities available, which may
5142 differ due to build-time definitions and from one release to another.
5143 All of these macros start with an underscore.
5144 They can be used to conditionally include parts of a configuration
5147 The following classes of macros are defined:
5149 &` _HAVE_* `& build-time defines
5150 &` _DRIVER_ROUTER_* `& router drivers
5151 &` _DRIVER_TRANSPORT_* `& transport drivers
5152 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5153 &` _LOG_* `& log_selector values
5154 &` _OPT_MAIN_* `& main config options
5155 &` _OPT_ROUTERS_* `& generic router options
5156 &` _OPT_TRANSPORTS_* `& generic transport options
5157 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5158 &` _OPT_ROUTER_*_* `& private router options
5159 &` _OPT_TRANSPORT_*_* `& private transport options
5160 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5163 Use an &"exim -bP macros"& command to get the list of macros.
5166 .section "Conditional skips in the configuration file" "SECID46"
5167 .cindex "configuration file" "conditional skips"
5168 .cindex "&`.ifdef`&"
5169 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5170 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5171 portions of the configuration file. The processing happens whenever the file is
5172 read (that is, when an Exim binary starts to run).
5174 The implementation is very simple. Instances of the first four directives must
5175 be followed by text that includes the names of one or macros. The condition
5176 that is tested is whether or not any macro substitution has taken place in the
5180 message_size_limit = 50M
5182 message_size_limit = 100M
5185 sets a message size limit of 50M if the macro &`AAA`& is defined
5186 (or &`A`& or &`AA`&), and 100M
5187 otherwise. If there is more than one macro named on the line, the condition
5188 is true if any of them are defined. That is, it is an &"or"& condition. To
5189 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5191 Although you can use a macro expansion to generate one of these directives,
5192 it is not very useful, because the condition &"there was a macro substitution
5193 in this line"& will always be true.
5195 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5196 to clarify complicated nestings.
5200 .section "Common option syntax" "SECTcos"
5201 .cindex "common option syntax"
5202 .cindex "syntax of common options"
5203 .cindex "configuration file" "common option syntax"
5204 For the main set of options, driver options, and &[local_scan()]& options,
5205 each setting is on a line by itself, and starts with a name consisting of
5206 lower-case letters and underscores. Many options require a data value, and in
5207 these cases the name must be followed by an equals sign (with optional white
5208 space) and then the value. For example:
5210 qualify_domain = mydomain.example.com
5212 .cindex "hiding configuration option values"
5213 .cindex "configuration options" "hiding value of"
5214 .cindex "options" "hiding value of"
5215 Some option settings may contain sensitive data, for example, passwords for
5216 accessing databases. To stop non-admin users from using the &%-bP%& command
5217 line option to read these values, you can precede the option settings with the
5218 word &"hide"&. For example:
5220 hide mysql_servers = localhost/users/admin/secret-password
5222 For non-admin users, such options are displayed like this:
5224 mysql_servers = <value not displayable>
5226 If &"hide"& is used on a driver option, it hides the value of that option on
5227 all instances of the same driver.
5229 The following sections describe the syntax used for the different data types
5230 that are found in option settings.
5233 .section "Boolean options" "SECID47"
5234 .cindex "format" "boolean"
5235 .cindex "boolean configuration values"
5236 .oindex "&%no_%&&'xxx'&"
5237 .oindex "&%not_%&&'xxx'&"
5238 Options whose type is given as boolean are on/off switches. There are two
5239 different ways of specifying such options: with and without a data value. If
5240 the option name is specified on its own without data, the switch is turned on;
5241 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5242 boolean options may be followed by an equals sign and one of the words
5243 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5244 the following two settings have exactly the same effect:
5249 The following two lines also have the same (opposite) effect:
5254 You can use whichever syntax you prefer.
5259 .section "Integer values" "SECID48"
5260 .cindex "integer configuration values"
5261 .cindex "format" "integer"
5262 If an option's type is given as &"integer"&, the value can be given in decimal,
5263 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5264 number is assumed. Otherwise, it is treated as an octal number unless it starts
5265 with the characters &"0x"&, in which case the remainder is interpreted as a
5268 If an integer value is followed by the letter K, it is multiplied by 1024; if
5269 it is followed by the letter M, it is multiplied by 1024x1024;
5270 if by the letter G, 1024x1024x1024.
5272 of integer option settings are output, values which are an exact multiple of
5273 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5274 and M. The printing style is independent of the actual input format that was
5278 .section "Octal integer values" "SECID49"
5279 .cindex "integer format"
5280 .cindex "format" "octal integer"
5281 If an option's type is given as &"octal integer"&, its value is always
5282 interpreted as an octal number, whether or not it starts with the digit zero.
5283 Such options are always output in octal.
5286 .section "Fixed point numbers" "SECID50"
5287 .cindex "fixed point configuration values"
5288 .cindex "format" "fixed point"
5289 If an option's type is given as &"fixed-point"&, its value must be a decimal
5290 integer, optionally followed by a decimal point and up to three further digits.
5294 .section "Time intervals" "SECTtimeformat"
5295 .cindex "time interval" "specifying in configuration"
5296 .cindex "format" "time interval"
5297 A time interval is specified as a sequence of numbers, each followed by one of
5298 the following letters, with no intervening white space:
5308 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5309 intervals are output in the same format. Exim does not restrict the values; it
5310 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5314 .section "String values" "SECTstrings"
5315 .cindex "string" "format of configuration values"
5316 .cindex "format" "string"
5317 If an option's type is specified as &"string"&, the value can be specified with
5318 or without double-quotes. If it does not start with a double-quote, the value
5319 consists of the remainder of the line plus any continuation lines, starting at
5320 the first character after any leading white space, with trailing white space
5321 removed, and with no interpretation of the characters in the string. Because
5322 Exim removes comment lines (those beginning with #) at an early stage, they can
5323 appear in the middle of a multi-line string. The following two settings are
5324 therefore equivalent:
5326 trusted_users = uucp:mail
5327 trusted_users = uucp:\
5328 # This comment line is ignored
5331 .cindex "string" "quoted"
5332 .cindex "escape characters in quoted strings"
5333 If a string does start with a double-quote, it must end with a closing
5334 double-quote, and any backslash characters other than those used for line
5335 continuation are interpreted as escape characters, as follows:
5338 .irow &`\\`& "single backslash"
5339 .irow &`\n`& "newline"
5340 .irow &`\r`& "carriage return"
5342 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5343 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5347 If a backslash is followed by some other character, including a double-quote
5348 character, that character replaces the pair.
5350 Quoting is necessary only if you want to make use of the backslash escapes to
5351 insert special characters, or if you need to specify a value with leading or
5352 trailing spaces. These cases are rare, so quoting is almost never needed in
5353 current versions of Exim. In versions of Exim before 3.14, quoting was required
5354 in order to continue lines, so you may come across older configuration files
5355 and examples that apparently quote unnecessarily.
5358 .section "Expanded strings" "SECID51"
5359 .cindex "expansion" "definition of"
5360 Some strings in the configuration file are subjected to &'string expansion'&,
5361 by which means various parts of the string may be changed according to the
5362 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5363 is as just described; in particular, the handling of backslashes in quoted
5364 strings is done as part of the input process, before expansion takes place.
5365 However, backslash is also an escape character for the expander, so any
5366 backslashes that are required for that reason must be doubled if they are
5367 within a quoted configuration string.
5370 .section "User and group names" "SECID52"
5371 .cindex "user name" "format of"
5372 .cindex "format" "user name"
5373 .cindex "groups" "name format"
5374 .cindex "format" "group name"
5375 User and group names are specified as strings, using the syntax described
5376 above, but the strings are interpreted specially. A user or group name must
5377 either consist entirely of digits, or be a name that can be looked up using the
5378 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5381 .section "List construction" "SECTlistconstruct"
5382 .cindex "list" "syntax of in configuration"
5383 .cindex "format" "list item in configuration"
5384 .cindex "string" "list, definition of"
5385 The data for some configuration options is a list of items, with colon as the
5386 default separator. Many of these options are shown with type &"string list"& in
5387 the descriptions later in this document. Others are listed as &"domain list"&,
5388 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5389 are all the same; however, those other than &"string list"& are subject to
5390 particular kinds of interpretation, as described in chapter
5391 &<<CHAPdomhosaddlists>>&.
5393 In all these cases, the entire list is treated as a single string as far as the
5394 input syntax is concerned. The &%trusted_users%& setting in section
5395 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5396 in a list, it must be entered as two colons. Leading and trailing white space
5397 on each item in a list is ignored. This makes it possible to include items that
5398 start with a colon, and in particular, certain forms of IPv6 address. For
5401 local_interfaces = 127.0.0.1 : ::::1
5403 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5405 &*Note*&: Although leading and trailing white space is ignored in individual
5406 list items, it is not ignored when parsing the list. The space after the first
5407 colon in the example above is necessary. If it were not there, the list would
5408 be interpreted as the two items 127.0.0.1:: and 1.
5410 .section "Changing list separators" "SECTlistsepchange"
5411 .cindex "list separator" "changing"
5412 .cindex "IPv6" "addresses in lists"
5413 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5414 introduced to allow the separator character to be changed. If a list begins
5415 with a left angle bracket, followed by any punctuation character, that
5416 character is used instead of colon as the list separator. For example, the list
5417 above can be rewritten to use a semicolon separator like this:
5419 local_interfaces = <; 127.0.0.1 ; ::1
5421 This facility applies to all lists, with the exception of the list in
5422 &%log_file_path%&. It is recommended that the use of non-colon separators be
5423 confined to circumstances where they really are needed.
5425 .cindex "list separator" "newline as"
5426 .cindex "newline" "as list separator"
5427 It is also possible to use newline and other control characters (those with
5428 code values less than 32, plus DEL) as separators in lists. Such separators
5429 must be provided literally at the time the list is processed. For options that
5430 are string-expanded, you can write the separator using a normal escape
5431 sequence. This will be processed by the expander before the string is
5432 interpreted as a list. For example, if a newline-separated list of domains is
5433 generated by a lookup, you can process it directly by a line such as this:
5435 domains = <\n ${lookup mysql{.....}}
5437 This avoids having to change the list separator in such data. You are unlikely
5438 to want to use a control character as a separator in an option that is not
5439 expanded, because the value is literal text. However, it can be done by giving
5440 the value in quotes. For example:
5442 local_interfaces = "<\n 127.0.0.1 \n ::1"
5444 Unlike printing character separators, which can be included in list items by
5445 doubling, it is not possible to include a control character as data when it is
5446 set as the separator. Two such characters in succession are interpreted as
5447 enclosing an empty list item.
5451 .section "Empty items in lists" "SECTempitelis"
5452 .cindex "list" "empty item in"
5453 An empty item at the end of a list is always ignored. In other words, trailing
5454 separator characters are ignored. Thus, the list in
5456 senders = user@domain :
5458 contains only a single item. If you want to include an empty string as one item
5459 in a list, it must not be the last item. For example, this list contains three
5460 items, the second of which is empty:
5462 senders = user1@domain : : user2@domain
5464 &*Note*&: There must be white space between the two colons, as otherwise they
5465 are interpreted as representing a single colon data character (and the list
5466 would then contain just one item). If you want to specify a list that contains
5467 just one, empty item, you can do it as in this example:
5471 In this case, the first item is empty, and the second is discarded because it
5472 is at the end of the list.
5477 .section "Format of driver configurations" "SECTfordricon"
5478 .cindex "drivers" "configuration format"
5479 There are separate parts in the configuration for defining routers, transports,
5480 and authenticators. In each part, you are defining a number of driver
5481 instances, each with its own set of options. Each driver instance is defined by
5482 a sequence of lines like this:
5484 <&'instance name'&>:
5489 In the following example, the instance name is &(localuser)&, and it is
5490 followed by three options settings:
5495 transport = local_delivery
5497 For each driver instance, you specify which Exim code module it uses &-- by the
5498 setting of the &%driver%& option &-- and (optionally) some configuration
5499 settings. For example, in the case of transports, if you want a transport to
5500 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5501 a local file you would use the &(appendfile)& driver. Each of the drivers is
5502 described in detail in its own separate chapter later in this manual.
5504 You can have several routers, transports, or authenticators that are based on
5505 the same underlying driver (each must have a different instance name).
5507 The order in which routers are defined is important, because addresses are
5508 passed to individual routers one by one, in order. The order in which
5509 transports are defined does not matter at all. The order in which
5510 authenticators are defined is used only when Exim, as a client, is searching
5511 them to find one that matches an authentication mechanism offered by the
5514 .cindex "generic options"
5515 .cindex "options" "generic &-- definition of"
5516 Within a driver instance definition, there are two kinds of option: &'generic'&
5517 and &'private'&. The generic options are those that apply to all drivers of the
5518 same type (that is, all routers, all transports or all authenticators). The
5519 &%driver%& option is a generic option that must appear in every definition.
5520 .cindex "private options"
5521 The private options are special for each driver, and none need appear, because
5522 they all have default values.
5524 The options may appear in any order, except that the &%driver%& option must
5525 precede any private options, since these depend on the particular driver. For
5526 this reason, it is recommended that &%driver%& always be the first option.
5528 Driver instance names, which are used for reference in log entries and
5529 elsewhere, can be any sequence of letters, digits, and underscores (starting
5530 with a letter) and must be unique among drivers of the same type. A router and
5531 a transport (for example) can each have the same name, but no two router
5532 instances can have the same name. The name of a driver instance should not be
5533 confused with the name of the underlying driver module. For example, the
5534 configuration lines:
5539 create an instance of the &(smtp)& transport driver whose name is
5540 &(remote_smtp)&. The same driver code can be used more than once, with
5541 different instance names and different option settings each time. A second
5542 instance of the &(smtp)& transport, with different options, might be defined
5548 command_timeout = 10s
5550 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5551 these transport instances from routers, and these names would appear in log
5554 Comment lines may be present in the middle of driver specifications. The full
5555 list of option settings for any particular driver instance, including all the
5556 defaulted values, can be extracted by making use of the &%-bP%& command line
5564 . ////////////////////////////////////////////////////////////////////////////
5565 . ////////////////////////////////////////////////////////////////////////////
5567 .chapter "The default configuration file" "CHAPdefconfil"
5568 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5569 .cindex "default" "configuration file &""walk through""&"
5570 The default configuration file supplied with Exim as &_src/configure.default_&
5571 is sufficient for a host with simple mail requirements. As an introduction to
5572 the way Exim is configured, this chapter &"walks through"& the default
5573 configuration, giving brief explanations of the settings. Detailed descriptions
5574 of the options are given in subsequent chapters. The default configuration file
5575 itself contains extensive comments about ways you might want to modify the
5576 initial settings. However, note that there are many options that are not
5577 mentioned at all in the default configuration.
5581 .section "Macros" "SECTdefconfmacros"
5582 All macros should be defined before any options.
5584 One macro is specified, but commented out, in the default configuration:
5586 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5588 If all off-site mail is expected to be delivered to a "smarthost", then set the
5589 hostname here and uncomment the macro. This will affect which router is used
5590 later on. If this is left commented out, then Exim will perform direct-to-MX
5591 deliveries using a &(dnslookup)& router.
5593 In addition to macros defined here, Exim includes a number of built-in macros
5594 to enable configuration to be guarded by a binary built with support for a
5595 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5598 .section "Main configuration settings" "SECTdefconfmain"
5599 The main (global) configuration option settings section must always come first
5600 in the file, after the macros.
5601 The first thing you'll see in the file, after some initial comments, is the line
5603 # primary_hostname =
5605 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5606 to know the official, fully qualified name of your host, and this is where you
5607 can specify it. However, in most cases you do not need to set this option. When
5608 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5610 The first three non-comment configuration lines are as follows:
5612 domainlist local_domains = @
5613 domainlist relay_to_domains =
5614 hostlist relay_from_hosts = 127.0.0.1
5616 These are not, in fact, option settings. They are definitions of two named
5617 domain lists and one named host list. Exim allows you to give names to lists of
5618 domains, hosts, and email addresses, in order to make it easier to manage the
5619 configuration file (see section &<<SECTnamedlists>>&).
5621 The first line defines a domain list called &'local_domains'&; this is used
5622 later in the configuration to identify domains that are to be delivered
5625 .cindex "@ in a domain list"
5626 There is just one item in this list, the string &"@"&. This is a special form
5627 of entry which means &"the name of the local host"&. Thus, if the local host is
5628 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5629 be delivered locally. Because the local host's name is referenced indirectly,
5630 the same configuration file can be used on different hosts.
5632 The second line defines a domain list called &'relay_to_domains'&, but the
5633 list itself is empty. Later in the configuration we will come to the part that
5634 controls mail relaying through the local host; it allows relaying to any
5635 domains in this list. By default, therefore, no relaying on the basis of a mail
5636 domain is permitted.
5638 The third line defines a host list called &'relay_from_hosts'&. This list is
5639 used later in the configuration to permit relaying from any host or IP address
5640 that matches the list. The default contains just the IP address of the IPv4
5641 loopback interface, which means that processes on the local host are able to
5642 submit mail for relaying by sending it over TCP/IP to that interface. No other
5643 hosts are permitted to submit messages for relaying.
5645 Just to be sure there's no misunderstanding: at this point in the configuration
5646 we aren't actually setting up any controls. We are just defining some domains
5647 and hosts that will be used in the controls that are specified later.
5649 The next two configuration lines are genuine option settings:
5651 acl_smtp_rcpt = acl_check_rcpt
5652 acl_smtp_data = acl_check_data
5654 These options specify &'Access Control Lists'& (ACLs) that are to be used
5655 during an incoming SMTP session for every recipient of a message (every RCPT
5656 command), and after the contents of the message have been received,
5657 respectively. The names of the lists are &'acl_check_rcpt'& and
5658 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5659 section of the configuration. The RCPT ACL controls which recipients are
5660 accepted for an incoming message &-- if a configuration does not provide an ACL
5661 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5662 contents of a message to be checked.
5664 Two commented-out option settings are next:
5666 # av_scanner = clamd:/tmp/clamd
5667 # spamd_address = 127.0.0.1 783
5669 These are example settings that can be used when Exim is compiled with the
5670 content-scanning extension. The first specifies the interface to the virus
5671 scanner, and the second specifies the interface to SpamAssassin. Further
5672 details are given in chapter &<<CHAPexiscan>>&.
5674 Three more commented-out option settings follow:
5676 # tls_advertise_hosts = *
5677 # tls_certificate = /etc/ssl/exim.crt
5678 # tls_privatekey = /etc/ssl/exim.pem
5680 These are example settings that can be used when Exim is compiled with
5681 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5682 first one specifies the list of clients that are allowed to use TLS when
5683 connecting to this server; in this case, the wildcard means all clients. The
5684 other options specify where Exim should find its TLS certificate and private
5685 key, which together prove the server's identity to any clients that connect.
5686 More details are given in chapter &<<CHAPTLS>>&.
5688 Another two commented-out option settings follow:
5690 # daemon_smtp_ports = 25 : 465 : 587
5691 # tls_on_connect_ports = 465
5693 .cindex "port" "465 and 587"
5694 .cindex "port" "for message submission"
5695 .cindex "message" "submission, ports for"
5696 .cindex "submissions protocol"
5697 .cindex "smtps protocol"
5698 .cindex "ssmtp protocol"
5699 .cindex "SMTP" "submissions protocol"
5700 .cindex "SMTP" "ssmtp protocol"
5701 .cindex "SMTP" "smtps protocol"
5702 These options provide better support for roaming users who wish to use this
5703 server for message submission. They are not much use unless you have turned on
5704 TLS (as described in the previous paragraph) and authentication (about which
5705 more in section &<<SECTdefconfauth>>&).
5706 Mail submission from mail clients (MUAs) should be separate from inbound mail
5707 to your domain (MX delivery) for various good reasons (eg, ability to impose
5708 much saner TLS protocol and ciphersuite requirements without unintended
5710 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5711 which uses STARTTLS, so this is the &"submission"& port.
5712 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5713 which should be used in preference to 587.
5714 You should also consider deploying SRV records to help clients find
5716 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5718 Two more commented-out options settings follow:
5721 # qualify_recipient =
5723 The first of these specifies a domain that Exim uses when it constructs a
5724 complete email address from a local login name. This is often needed when Exim
5725 receives a message from a local process. If you do not set &%qualify_domain%&,
5726 the value of &%primary_hostname%& is used. If you set both of these options,
5727 you can have different qualification domains for sender and recipient
5728 addresses. If you set only the first one, its value is used in both cases.
5730 .cindex "domain literal" "recognizing format"
5731 The following line must be uncommented if you want Exim to recognize
5732 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5733 (an IP address within square brackets) instead of a named domain.
5735 # allow_domain_literals
5737 The RFCs still require this form, but many people think that in the modern
5738 Internet it makes little sense to permit mail to be sent to specific hosts by
5739 quoting their IP addresses. This ancient format has been used by people who
5740 try to abuse hosts by using them for unwanted relaying. However, some
5741 people believe there are circumstances (for example, messages addressed to
5742 &'postmaster'&) where domain literals are still useful.
5744 The next configuration line is a kind of trigger guard:
5748 It specifies that no delivery must ever be run as the root user. The normal
5749 convention is to set up &'root'& as an alias for the system administrator. This
5750 setting is a guard against slips in the configuration.
5751 The list of users specified by &%never_users%& is not, however, the complete
5752 list; the build-time configuration in &_Local/Makefile_& has an option called
5753 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5754 contents of &%never_users%& are added to this list. By default
5755 FIXED_NEVER_USERS also specifies root.
5757 When a remote host connects to Exim in order to send mail, the only information
5758 Exim has about the host's identity is its IP address. The next configuration
5763 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5764 in order to get a host name. This improves the quality of the logging
5765 information, but if you feel it is too expensive, you can remove it entirely,
5766 or restrict the lookup to hosts on &"nearby"& networks.
5767 Note that it is not always possible to find a host name from an IP address,
5768 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5771 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5772 1413 (hence their names):
5775 rfc1413_query_timeout = 0s
5777 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5778 Few hosts offer RFC1413 service these days; calls have to be
5779 terminated by a timeout and this needlessly delays the startup
5780 of an incoming SMTP connection.
5781 If you have hosts for which you trust RFC1413 and need this
5782 information, you can change this.
5784 This line enables an efficiency SMTP option. It is negotiated by clients
5785 and not expected to cause problems but can be disabled if needed.
5790 When Exim receives messages over SMTP connections, it expects all addresses to
5791 be fully qualified with a domain, as required by the SMTP definition. However,
5792 if you are running a server to which simple clients submit messages, you may
5793 find that they send unqualified addresses. The two commented-out options:
5795 # sender_unqualified_hosts =
5796 # recipient_unqualified_hosts =
5798 show how you can specify hosts that are permitted to send unqualified sender
5799 and recipient addresses, respectively.
5801 The &%log_selector%& option is used to increase the detail of logging
5804 log_selector = +smtp_protocol_error +smtp_syntax_error \
5805 +tls_certificate_verified
5808 The &%percent_hack_domains%& option is also commented out:
5810 # percent_hack_domains =
5812 It provides a list of domains for which the &"percent hack"& is to operate.
5813 This is an almost obsolete form of explicit email routing. If you do not know
5814 anything about it, you can safely ignore this topic.
5816 The next two settings in the main part of the default configuration are
5817 concerned with messages that have been &"frozen"& on Exim's queue. When a
5818 message is frozen, Exim no longer continues to try to deliver it. Freezing
5819 occurs when a bounce message encounters a permanent failure because the sender
5820 address of the original message that caused the bounce is invalid, so the
5821 bounce cannot be delivered. This is probably the most common case, but there
5822 are also other conditions that cause freezing, and frozen messages are not
5823 always bounce messages.
5825 ignore_bounce_errors_after = 2d
5826 timeout_frozen_after = 7d
5828 The first of these options specifies that failing bounce messages are to be
5829 discarded after 2 days in the queue. The second specifies that any frozen
5830 message (whether a bounce message or not) is to be timed out (and discarded)
5831 after a week. In this configuration, the first setting ensures that no failing
5832 bounce message ever lasts a week.
5834 Exim queues it's messages in a spool directory. If you expect to have
5835 large queues, you may consider using this option. It splits the spool
5836 directory into subdirectories to avoid file system degradation from
5837 many files in a single directory, resulting in better performance.
5838 Manual manipulation of queued messages becomes more complex (though fortunately
5841 # split_spool_directory = true
5844 In an ideal world everybody follows the standards. For non-ASCII
5845 messages RFC 2047 is a standard, allowing a maximum line length of 76
5846 characters. Exim adheres that standard and won't process messages which
5847 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5848 In particular, the Exim maintainers have had multiple reports of
5849 problems from Russian administrators of issues until they disable this
5850 check, because of some popular, yet buggy, mail composition software.
5852 # check_rfc2047_length = false
5855 If you need to be strictly RFC compliant you may wish to disable the
5856 8BITMIME advertisement. Use this, if you exchange mails with systems
5857 that are not 8-bit clean.
5859 # accept_8bitmime = false
5862 Libraries you use may depend on specific environment settings. This
5863 imposes a security risk (e.g. PATH). There are two lists:
5864 &%keep_environment%& for the variables to import as they are, and
5865 &%add_environment%& for variables we want to set to a fixed value.
5866 Note that TZ is handled separately, by the $%timezone%$ runtime
5867 option and by the TIMEZONE_DEFAULT buildtime option.
5869 # keep_environment = ^LDAP
5870 # add_environment = PATH=/usr/bin::/bin
5874 .section "ACL configuration" "SECID54"
5875 .cindex "default" "ACLs"
5876 .cindex "&ACL;" "default configuration"
5877 In the default configuration, the ACL section follows the main configuration.
5878 It starts with the line
5882 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5883 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5884 and &%acl_smtp_data%& above.
5886 .cindex "RCPT" "ACL for"
5887 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5888 RCPT command specifies one of the message's recipients. The ACL statements
5889 are considered in order, until the recipient address is either accepted or
5890 rejected. The RCPT command is then accepted or rejected, according to the
5891 result of the ACL processing.
5895 This line, consisting of a name terminated by a colon, marks the start of the
5900 This ACL statement accepts the recipient if the sending host matches the list.
5901 But what does that strange list mean? It doesn't actually contain any host
5902 names or IP addresses. The presence of the colon puts an empty item in the
5903 list; Exim matches this only if the incoming message did not come from a remote
5904 host, because in that case, the remote hostname is empty. The colon is
5905 important. Without it, the list itself is empty, and can never match anything.
5907 What this statement is doing is to accept unconditionally all recipients in
5908 messages that are submitted by SMTP from local processes using the standard
5909 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5912 deny domains = +local_domains
5913 local_parts = ^[.] : ^.*[@%!/|]
5914 message = Restricted characters in address
5916 deny domains = !+local_domains
5917 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5918 message = Restricted characters in address
5920 These statements are concerned with local parts that contain any of the
5921 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5922 Although these characters are entirely legal in local parts (in the case of
5923 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5924 in Internet mail addresses.
5926 The first three have in the past been associated with explicitly routed
5927 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5928 option). Addresses containing these characters are regularly tried by spammers
5929 in an attempt to bypass relaying restrictions, and also by open relay testing
5930 programs. Unless you really need them it is safest to reject these characters
5931 at this early stage. This configuration is heavy-handed in rejecting these
5932 characters for all messages it accepts from remote hosts. This is a deliberate
5933 policy of being as safe as possible.
5935 The first rule above is stricter, and is applied to messages that are addressed
5936 to one of the local domains handled by this host. This is implemented by the
5937 first condition, which restricts it to domains that are listed in the
5938 &'local_domains'& domain list. The &"+"& character is used to indicate a
5939 reference to a named list. In this configuration, there is just one domain in
5940 &'local_domains'&, but in general there may be many.
5942 The second condition on the first statement uses two regular expressions to
5943 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5944 or &"|"&. If you have local accounts that include these characters, you will
5945 have to modify this rule.
5947 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5948 allows them because they have been encountered in practice. (Consider the
5949 common convention of local parts constructed as
5950 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5951 the author of Exim, who has no second initial.) However, a local part starting
5952 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5953 filename (for example, for a mailing list). This is also true for local parts
5954 that contain slashes. A pipe symbol can also be troublesome if the local part
5955 is incorporated unthinkingly into a shell command line.
5957 The second rule above applies to all other domains, and is less strict. This
5958 allows your own users to send outgoing messages to sites that use slashes
5959 and vertical bars in their local parts. It blocks local parts that begin
5960 with a dot, slash, or vertical bar, but allows these characters within the
5961 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5962 and &"!"& is blocked, as before. The motivation here is to prevent your users
5963 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5965 accept local_parts = postmaster
5966 domains = +local_domains
5968 This statement, which has two conditions, accepts an incoming address if the
5969 local part is &'postmaster'& and the domain is one of those listed in the
5970 &'local_domains'& domain list. The &"+"& character is used to indicate a
5971 reference to a named list. In this configuration, there is just one domain in
5972 &'local_domains'&, but in general there may be many.
5974 The presence of this statement means that mail to postmaster is never blocked
5975 by any of the subsequent tests. This can be helpful while sorting out problems
5976 in cases where the subsequent tests are incorrectly denying access.
5978 require verify = sender
5980 This statement requires the sender address to be verified before any subsequent
5981 ACL statement can be used. If verification fails, the incoming recipient
5982 address is refused. Verification consists of trying to route the address, to
5983 see if a bounce message could be delivered to it. In the case of remote
5984 addresses, basic verification checks only the domain, but &'callouts'& can be
5985 used for more verification if required. Section &<<SECTaddressverification>>&
5986 discusses the details of address verification.
5988 accept hosts = +relay_from_hosts
5989 control = submission
5991 This statement accepts the address if the message is coming from one of the
5992 hosts that are defined as being allowed to relay through this host. Recipient
5993 verification is omitted here, because in many cases the clients are dumb MUAs
5994 that do not cope well with SMTP error responses. For the same reason, the
5995 second line specifies &"submission mode"& for messages that are accepted. This
5996 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5997 messages that are deficient in some way, for example, because they lack a
5998 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5999 probably add recipient verification here, and disable submission mode.
6001 accept authenticated = *
6002 control = submission
6004 This statement accepts the address if the client host has authenticated itself.
6005 Submission mode is again specified, on the grounds that such messages are most
6006 likely to come from MUAs. The default configuration does not define any
6007 authenticators, though it does include some nearly complete commented-out
6008 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6009 fact authenticate until you complete the authenticator definitions.
6011 require message = relay not permitted
6012 domains = +local_domains : +relay_to_domains
6014 This statement rejects the address if its domain is neither a local domain nor
6015 one of the domains for which this host is a relay.
6017 require verify = recipient
6019 This statement requires the recipient address to be verified; if verification
6020 fails, the address is rejected.
6022 # deny dnslists = black.list.example
6023 # message = rejected because $sender_host_address \
6024 # is in a black list at $dnslist_domain\n\
6027 # warn dnslists = black.list.example
6028 # add_header = X-Warning: $sender_host_address is in \
6029 # a black list at $dnslist_domain
6030 # log_message = found in $dnslist_domain
6032 These commented-out lines are examples of how you could configure Exim to check
6033 sending hosts against a DNS black list. The first statement rejects messages
6034 from blacklisted hosts, whereas the second just inserts a warning header
6037 # require verify = csa
6039 This commented-out line is an example of how you could turn on client SMTP
6040 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6045 The final statement in the first ACL unconditionally accepts any recipient
6046 address that has successfully passed all the previous tests.
6050 This line marks the start of the second ACL, and names it. Most of the contents
6051 of this ACL are commented out:
6054 # message = This message contains a virus \
6057 These lines are examples of how to arrange for messages to be scanned for
6058 viruses when Exim has been compiled with the content-scanning extension, and a
6059 suitable virus scanner is installed. If the message is found to contain a
6060 virus, it is rejected with the given custom error message.
6062 # warn spam = nobody
6063 # message = X-Spam_score: $spam_score\n\
6064 # X-Spam_score_int: $spam_score_int\n\
6065 # X-Spam_bar: $spam_bar\n\
6066 # X-Spam_report: $spam_report
6068 These lines are an example of how to arrange for messages to be scanned by
6069 SpamAssassin when Exim has been compiled with the content-scanning extension,
6070 and SpamAssassin has been installed. The SpamAssassin check is run with
6071 &`nobody`& as its user parameter, and the results are added to the message as a
6072 series of extra header line. In this case, the message is not rejected,
6073 whatever the spam score.
6077 This final line in the DATA ACL accepts the message unconditionally.
6080 .section "Router configuration" "SECID55"
6081 .cindex "default" "routers"
6082 .cindex "routers" "default"
6083 The router configuration comes next in the default configuration, introduced
6088 Routers are the modules in Exim that make decisions about where to send
6089 messages. An address is passed to each router, in turn, until it is either
6090 accepted, or failed. This means that the order in which you define the routers
6091 matters. Each router is fully described in its own chapter later in this
6092 manual. Here we give only brief overviews.
6095 # driver = ipliteral
6096 # domains = !+local_domains
6097 # transport = remote_smtp
6099 .cindex "domain literal" "default router"
6100 This router is commented out because the majority of sites do not want to
6101 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6102 you uncomment this router, you also need to uncomment the setting of
6103 &%allow_domain_literals%& in the main part of the configuration.
6105 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6106 macro has been defined, per
6108 .ifdef ROUTER_SMARTHOST
6117 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6118 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6119 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6120 skip these routers because of the &%domains%& option.
6124 driver = manualroute
6125 domains = ! +local_domains
6126 transport = smarthost_smtp
6127 route_data = ROUTER_SMARTHOST
6128 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6131 This router only handles mail which is not to any local domains; this is
6132 specified by the line
6134 domains = ! +local_domains
6136 The &%domains%& option lists the domains to which this router applies, but the
6137 exclamation mark is a negation sign, so the router is used only for domains
6138 that are not in the domain list called &'local_domains'& (which was defined at
6139 the start of the configuration). The plus sign before &'local_domains'&
6140 indicates that it is referring to a named list. Addresses in other domains are
6141 passed on to the following routers.
6143 The name of the router driver is &(manualroute)& because we are manually
6144 specifying how mail should be routed onwards, instead of using DNS MX.
6145 While the name of this router instance is arbitrary, the &%driver%& option must
6146 be one of the driver modules that is in the Exim binary.
6148 With no pre-conditions other than &%domains%&, all mail for non-local domains
6149 will be handled by this router, and the &%no_more%& setting will ensure that no
6150 other routers will be used for messages matching the pre-conditions. See
6151 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6152 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6153 and the macro supplies the value; the address is then queued for the
6154 &(smarthost_smtp)& transport.
6159 domains = ! +local_domains
6160 transport = remote_smtp
6161 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6164 The &%domains%& option behaves as per smarthost, above.
6166 The name of the router driver is &(dnslookup)&,
6167 and is specified by the &%driver%& option. Do not be confused by the fact that
6168 the name of this router instance is the same as the name of the driver. The
6169 instance name is arbitrary, but the name set in the &%driver%& option must be
6170 one of the driver modules that is in the Exim binary.
6172 The &(dnslookup)& router routes addresses by looking up their domains in the
6173 DNS in order to obtain a list of hosts to which the address is routed. If the
6174 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6175 specified by the &%transport%& option. If the router does not find the domain
6176 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6177 the address fails and is bounced.
6179 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6180 be entirely ignored. This option is present because a number of cases have been
6181 encountered where MX records in the DNS point to host names
6182 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6183 Completely ignoring these IP addresses causes Exim to fail to route the
6184 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6185 continue to try to deliver the message periodically until the address timed
6192 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6194 file_transport = address_file
6195 pipe_transport = address_pipe
6197 Control reaches this and subsequent routers only for addresses in the local
6198 domains. This router checks to see whether the local part is defined as an
6199 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6200 data that it looks up from that file. If no data is found for the local part,
6201 the value of the &%data%& option is empty, causing the address to be passed to
6204 &_/etc/aliases_& is a conventional name for the system aliases file that is
6205 often used. That is why it is referenced by from the default configuration
6206 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6207 &_Local/Makefile_& before building Exim.
6212 # local_part_suffix = +* : -*
6213 # local_part_suffix_optional
6214 file = $home/.forward
6219 file_transport = address_file
6220 pipe_transport = address_pipe
6221 reply_transport = address_reply
6223 This is the most complicated router in the default configuration. It is another
6224 redirection router, but this time it is looking for forwarding data set up by
6225 individual users. The &%check_local_user%& setting specifies a check that the
6226 local part of the address is the login name of a local user. If it is not, the
6227 router is skipped. The two commented options that follow &%check_local_user%&,
6230 # local_part_suffix = +* : -*
6231 # local_part_suffix_optional
6233 .vindex "&$local_part_suffix$&"
6234 show how you can specify the recognition of local part suffixes. If the first
6235 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6236 by any sequence of characters, is removed from the local part and placed in the
6237 variable &$local_part_suffix$&. The second suffix option specifies that the
6238 presence of a suffix in the local part is optional. When a suffix is present,
6239 the check for a local login uses the local part with the suffix removed.
6241 When a local user account is found, the file called &_.forward_& in the user's
6242 home directory is consulted. If it does not exist, or is empty, the router
6243 declines. Otherwise, the contents of &_.forward_& are interpreted as
6244 redirection data (see chapter &<<CHAPredirect>>& for more details).
6246 .cindex "Sieve filter" "enabling in default router"
6247 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6248 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6249 is commented out by default), the contents of the file are interpreted as a set
6250 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6251 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6252 separate document entitled &'Exim's interfaces to mail filtering'&.
6254 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6255 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6256 There are two reasons for doing this:
6259 Whether or not a local user has a &_.forward_& file is not really relevant when
6260 checking an address for validity; it makes sense not to waste resources doing
6263 More importantly, when Exim is verifying addresses or handling an EXPN
6264 command during an SMTP session, it is running as the Exim user, not as root.
6265 The group is the Exim group, and no additional groups are set up.
6266 It may therefore not be possible for Exim to read users' &_.forward_& files at
6270 The setting of &%check_ancestor%& prevents the router from generating a new
6271 address that is the same as any previous address that was redirected. (This
6272 works round a problem concerning a bad interaction between aliasing and
6273 forwarding &-- see section &<<SECTredlocmai>>&).
6275 The final three option settings specify the transports that are to be used when
6276 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6277 auto-reply, respectively. For example, if a &_.forward_& file contains
6279 a.nother@elsewhere.example, /home/spqr/archive
6281 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6287 # local_part_suffix = +* : -*
6288 # local_part_suffix_optional
6289 transport = local_delivery
6291 The final router sets up delivery into local mailboxes, provided that the local
6292 part is the name of a local login, by accepting the address and assigning it to
6293 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6294 routers, so the address is bounced. The commented suffix settings fulfil the
6295 same purpose as they do for the &(userforward)& router.
6298 .section "Transport configuration" "SECID56"
6299 .cindex "default" "transports"
6300 .cindex "transports" "default"
6301 Transports define mechanisms for actually delivering messages. They operate
6302 only when referenced from routers, so the order in which they are defined does
6303 not matter. The transports section of the configuration starts with
6307 Two remote transports and four local transports are defined.
6311 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6316 This transport is used for delivering messages over SMTP connections.
6317 The list of remote hosts comes from the router.
6318 The &%message_size_limit%& usage is a hack to avoid sending on messages
6319 with over-long lines.
6321 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6322 negotiated between client and server and not expected to cause problems
6323 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6324 use of the &%hosts_try_prdr%& configuration option.
6326 The other remote transport is used when delivering to a specific smarthost
6327 with whom there must be some kind of existing relationship, instead of the
6328 usual federated system.
6333 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6337 # Comment out any of these which you have to, then file a Support
6338 # request with your smarthost provider to get things fixed:
6339 hosts_require_tls = *
6340 tls_verify_hosts = *
6341 # As long as tls_verify_hosts is enabled, this won't matter, but if you
6342 # have to comment it out then this will at least log whether you succeed
6344 tls_try_verify_hosts = *
6346 # The SNI name should match the name which we'll expect to verify;
6347 # many mail systems don't use SNI and this doesn't matter, but if it does,
6348 # we need to send a name which the remote site will recognize.
6349 # This _should_ be the name which the smarthost operators specified as
6350 # the hostname for sending your mail to.
6351 tls_sni = ROUTER_SMARTHOST
6353 .ifdef _HAVE_OPENSSL
6354 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6357 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6364 After the same &%message_size_limit%& hack, we then specify that this Transport
6365 can handle messages to multiple domains in one run. The assumption here is
6366 that you're routing all non-local mail to the same place and that place is
6367 happy to take all messages from you as quickly as possible.
6368 All other options depend upon built-in macros; if Exim was built without TLS support
6369 then no other options are defined.
6370 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6371 and versions using the &%tls_require_ciphers%& option, where the value to be
6372 used depends upon the library providing TLS.
6373 Beyond that, the options adopt the stance that you should have TLS support available
6374 from your smarthost on today's Internet, so we turn on requiring TLS for the
6375 mail to be delivered, and requiring that the certificate be valid, and match
6376 the expected hostname. The &%tls_sni%& option can be used by service providers
6377 to select an appropriate certificate to present to you and here we re-use the
6378 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6379 You want to specify the hostname which you'll expect to validate for, and that
6380 should not be subject to insecure tampering via DNS results.
6382 For the &%hosts_try_prdr%& option see the previous transport.
6384 All other options are defaulted.
6388 file = /var/mail/$local_part_data
6395 This &(appendfile)& transport is used for local delivery to user mailboxes in
6396 traditional BSD mailbox format.
6398 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6399 as it is provided by a potential bad actor.
6400 Instead we use &$local_part_data$&,
6401 the result of looking up &$local_part$& in the user database
6402 (done by using &%check_local_user%& in the the router).
6404 By default &(appendfile)& runs under the uid and gid of the
6405 local user, which requires the sticky bit to be set on the &_/var/mail_&
6406 directory. Some systems use the alternative approach of running mail deliveries
6407 under a particular group instead of using the sticky bit. The commented options
6408 show how this can be done.
6410 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6411 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6412 similarly-named options above.
6418 This transport is used for handling deliveries to pipes that are generated by
6419 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6420 option specifies that any output on stdout or stderr generated by the pipe is to
6421 be returned to the sender.
6429 This transport is used for handling deliveries to files that are generated by
6430 redirection. The name of the file is not specified in this instance of
6431 &(appendfile)&, because it comes from the &(redirect)& router.
6436 This transport is used for handling automatic replies generated by users'
6441 .section "Default retry rule" "SECID57"
6442 .cindex "retry" "default rule"
6443 .cindex "default" "retry rule"
6444 The retry section of the configuration file contains rules which affect the way
6445 Exim retries deliveries that cannot be completed at the first attempt. It is
6446 introduced by the line
6450 In the default configuration, there is just one rule, which applies to all
6453 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6455 This causes any temporarily failing address to be retried every 15 minutes for
6456 2 hours, then at intervals starting at one hour and increasing by a factor of
6457 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6458 is not delivered after 4 days of temporary failure, it is bounced. The time is
6459 measured from first failure, not from the time the message was received.
6461 If the retry section is removed from the configuration, or is empty (that is,
6462 if no retry rules are defined), Exim will not retry deliveries. This turns
6463 temporary errors into permanent errors.
6466 .section "Rewriting configuration" "SECID58"
6467 The rewriting section of the configuration, introduced by
6471 contains rules for rewriting addresses in messages as they arrive. There are no
6472 rewriting rules in the default configuration file.
6476 .section "Authenticators configuration" "SECTdefconfauth"
6477 .cindex "AUTH" "configuration"
6478 The authenticators section of the configuration, introduced by
6480 begin authenticators
6482 defines mechanisms for the use of the SMTP AUTH command. The default
6483 configuration file contains two commented-out example authenticators
6484 which support plaintext username/password authentication using the
6485 standard PLAIN mechanism and the traditional but non-standard LOGIN
6486 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6487 to support most MUA software.
6489 The example PLAIN authenticator looks like this:
6492 # driver = plaintext
6493 # server_set_id = $auth2
6494 # server_prompts = :
6495 # server_condition = Authentication is not yet configured
6496 # server_advertise_condition = ${if def:tls_in_cipher }
6498 And the example LOGIN authenticator looks like this:
6501 # driver = plaintext
6502 # server_set_id = $auth1
6503 # server_prompts = <| Username: | Password:
6504 # server_condition = Authentication is not yet configured
6505 # server_advertise_condition = ${if def:tls_in_cipher }
6508 The &%server_set_id%& option makes Exim remember the authenticated username
6509 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6510 &%server_prompts%& option configures the &(plaintext)& authenticator so
6511 that it implements the details of the specific authentication mechanism,
6512 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6513 when Exim offers authentication to clients; in the examples, this is only
6514 when TLS or SSL has been started, so to enable the authenticators you also
6515 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6517 The &%server_condition%& setting defines how to verify that the username and
6518 password are correct. In the examples it just produces an error message.
6519 To make the authenticators work, you can use a string expansion
6520 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6522 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6523 usercode and password are in different positions.
6524 Chapter &<<CHAPplaintext>>& covers both.
6526 .ecindex IIDconfiwal
6530 . ////////////////////////////////////////////////////////////////////////////
6531 . ////////////////////////////////////////////////////////////////////////////
6533 .chapter "Regular expressions" "CHAPregexp"
6535 .cindex "regular expressions" "library"
6537 Exim supports the use of regular expressions in many of its options. It
6538 uses the PCRE regular expression library; this provides regular expression
6539 matching that is compatible with Perl 5. The syntax and semantics of
6540 regular expressions is discussed in
6541 online Perl manpages, in
6542 many Perl reference books, and also in
6543 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6544 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6545 . --- the http: URL here redirects to another page with the ISBN in the URL
6546 . --- where trying to use https: just redirects back to http:, so sticking
6547 . --- to the old URL for now. 2018-09-07.
6549 The documentation for the syntax and semantics of the regular expressions that
6550 are supported by PCRE is included in the PCRE distribution, and no further
6551 description is included here. The PCRE functions are called from Exim using
6552 the default option settings (that is, with no PCRE options set), except that
6553 the PCRE_CASELESS option is set when the matching is required to be
6556 In most cases, when a regular expression is required in an Exim configuration,
6557 it has to start with a circumflex, in order to distinguish it from plain text
6558 or an &"ends with"& wildcard. In this example of a configuration setting, the
6559 second item in the colon-separated list is a regular expression.
6561 domains = a.b.c : ^\\d{3} : *.y.z : ...
6563 The doubling of the backslash is required because of string expansion that
6564 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6565 of this issue, and a way of avoiding the need for doubling backslashes. The
6566 regular expression that is eventually used in this example contains just one
6567 backslash. The circumflex is included in the regular expression, and has the
6568 normal effect of &"anchoring"& it to the start of the string that is being
6571 There are, however, two cases where a circumflex is not required for the
6572 recognition of a regular expression: these are the &%match%& condition in a
6573 string expansion, and the &%matches%& condition in an Exim filter file. In
6574 these cases, the relevant string is always treated as a regular expression; if
6575 it does not start with a circumflex, the expression is not anchored, and can
6576 match anywhere in the subject string.
6578 In all cases, if you want a regular expression to match at the end of a string,
6579 you must code the $ metacharacter to indicate this. For example:
6581 domains = ^\\d{3}\\.example
6583 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6586 domains = ^\\d{3}\\.example\$
6588 if you want &'example'& to be the top-level domain. The backslash before the
6589 $ is needed because string expansion also interprets dollar characters.
6593 . ////////////////////////////////////////////////////////////////////////////
6594 . ////////////////////////////////////////////////////////////////////////////
6596 .chapter "File and database lookups" "CHAPfdlookup"
6597 .scindex IIDfidalo1 "file" "lookups"
6598 .scindex IIDfidalo2 "database" "lookups"
6599 .cindex "lookup" "description of"
6600 Exim can be configured to look up data in files or databases as it processes
6601 messages. Two different kinds of syntax are used:
6604 A string that is to be expanded may contain explicit lookup requests. These
6605 cause parts of the string to be replaced by data that is obtained from the
6606 lookup. Lookups of this type are conditional expansion items. Different results
6607 can be defined for the cases of lookup success and failure. See chapter
6608 &<<CHAPexpand>>&, where string expansions are described in detail.
6609 The key for the lookup is &*specified*& as part of the string expansion.
6611 Lists of domains, hosts, and email addresses can contain lookup requests as a
6612 way of avoiding excessively long linear lists. In this case, the data that is
6613 returned by the lookup is often (but not always) discarded; whether the lookup
6614 succeeds or fails is what really counts. These kinds of list are described in
6615 chapter &<<CHAPdomhosaddlists>>&.
6616 The key for the lookup is &*implicit*&,
6617 given by the context in which the list is expanded.
6620 String expansions, lists, and lookups interact with each other in such a way
6621 that there is no order in which to describe any one of them that does not
6622 involve references to the others. Each of these three chapters makes more sense
6623 if you have read the other two first. If you are reading this for the first
6624 time, be aware that some of it will make a lot more sense after you have read
6625 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6627 .section "Examples of different lookup syntax" "SECID60"
6628 It is easy to confuse the two different kinds of lookup, especially as the
6629 lists that may contain the second kind are always expanded before being
6630 processed as lists. Therefore, they may also contain lookups of the first kind.
6631 Be careful to distinguish between the following two examples:
6633 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6634 domains = lsearch;/some/file
6636 The first uses a string expansion, the result of which must be a domain list.
6637 No strings have been specified for a successful or a failing lookup; the
6638 defaults in this case are the looked-up data and an empty string, respectively.
6639 The expansion takes place before the string is processed as a list, and the
6640 file that is searched could contain lines like this:
6642 192.168.3.4: domain1:domain2:...
6643 192.168.1.9: domain3:domain4:...
6645 When the lookup succeeds, the result of the expansion is a list of domains (and
6646 possibly other types of item that are allowed in domain lists).
6647 .cindex "tainted data" "de-tainting"
6648 The result of the expansion is not tainted.
6650 In the second example, the lookup is a single item in a domain list. It causes
6651 Exim to use a lookup to see if the domain that is being processed can be found
6653 The file could contains lines like this:
6658 Any data that follows the keys is not relevant when checking that the domain
6659 matches the list item.
6661 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6662 Consider a file containing lines like this:
6664 192.168.5.6: lsearch;/another/file
6666 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6667 first &%domains%& setting above generates the second setting, which therefore
6668 causes a second lookup to occur.
6671 The lookup type may optionally be followed by a comma
6672 and a comma-separated list of options.
6673 Each option is a &"name=value"& pair.
6674 Whether an option is meaningful depands on the lookup type.
6676 All lookups support the option &"cache=no_rd"&.
6677 If this is given then the cache that Exim manages for lookup results
6678 is not checked before diong the lookup.
6679 The result of the lookup is still written to the cache.
6682 The rest of this chapter describes the different lookup types that are
6683 available. Any of them can be used in any part of the configuration where a
6684 lookup is permitted.
6687 .section "Lookup types" "SECID61"
6688 .cindex "lookup" "types of"
6689 .cindex "single-key lookup" "definition of"
6690 Two different types of data lookup are implemented:
6693 The &'single-key'& type requires the specification of a file in which to look,
6694 and a single key to search for. The key must be a non-empty string for the
6695 lookup to succeed. The lookup type determines how the file is searched.
6696 .cindex "tainted data" "single-key lookups"
6697 The file string may not be tainted
6699 .cindex "tainted data" "de-tainting"
6700 All single-key lookups support the option &"ret=key"&.
6701 If this is given and the lookup
6702 (either underlying implementation or cached value)
6703 returns data, the result is replaced with a non-tainted
6704 version of the lookup key.
6705 .cindex "tainted data" "de-tainting"
6707 .cindex "query-style lookup" "definition of"
6708 The &'query-style'& type accepts a generalized database query. No particular
6709 key value is assumed by Exim for query-style lookups. You can use whichever
6710 Exim variables you need to construct the database query.
6713 The code for each lookup type is in a separate source file that is included in
6714 the binary of Exim only if the corresponding compile-time option is set. The
6715 default settings in &_src/EDITME_& are:
6720 which means that only linear searching and DBM lookups are included by default.
6721 For some types of lookup (e.g. SQL databases), you need to install appropriate
6722 libraries and header files before building Exim.
6727 .section "Single-key lookup types" "SECTsinglekeylookups"
6728 .cindex "lookup" "single-key types"
6729 .cindex "single-key lookup" "list of types"
6730 The following single-key lookup types are implemented:
6733 .cindex "cdb" "description of"
6734 .cindex "lookup" "cdb"
6735 .cindex "binary zero" "in lookup key"
6736 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6737 string without a terminating binary zero. The cdb format is designed for
6738 indexed files that are read frequently and never updated, except by total
6739 re-creation. As such, it is particularly suitable for large files containing
6740 aliases or other indexed data referenced by an MTA. Information about cdb and
6741 tools for building the files can be found in several places:
6743 &url(https://cr.yp.to/cdb.html)
6744 &url(https://www.corpit.ru/mjt/tinycdb.html)
6745 &url(https://packages.debian.org/stable/utils/freecdb)
6746 &url(https://github.com/philpennock/cdbtools) (in Go)
6748 A cdb distribution is not needed in order to build Exim with cdb support,
6749 because the code for reading cdb files is included directly in Exim itself.
6750 However, no means of building or testing cdb files is provided with Exim, so
6751 you need to obtain a cdb distribution in order to do this.
6753 .cindex "DBM" "lookup type"
6754 .cindex "lookup" "dbm"
6755 .cindex "binary zero" "in lookup key"
6756 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6757 DBM file by looking up the record with the given key. A terminating binary
6758 zero is included in the key that is passed to the DBM library. See section
6759 &<<SECTdb>>& for a discussion of DBM libraries.
6761 .cindex "Berkeley DB library" "file format"
6762 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6763 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6764 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6765 the DB_UNKNOWN option. This enables it to handle any of the types of database
6766 that the library supports, and can be useful for accessing DBM files created by
6767 other applications. (For earlier DB versions, DB_HASH is always used.)
6769 .cindex "lookup" "dbmjz"
6770 .cindex "lookup" "dbm &-- embedded NULs"
6772 .cindex "dbmjz lookup type"
6773 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6774 interpreted as an Exim list; the elements of the list are joined together with
6775 ASCII NUL characters to form the lookup key. An example usage would be to
6776 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6777 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6778 &(cram_md5)& authenticator.
6780 .cindex "lookup" "dbmnz"
6781 .cindex "lookup" "dbm &-- terminating zero"
6782 .cindex "binary zero" "in lookup key"
6784 .cindex "&_/etc/userdbshadow.dat_&"
6785 .cindex "dbmnz lookup type"
6786 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6787 is not included in the key that is passed to the DBM library. You may need this
6788 if you want to look up data in files that are created by or shared with some
6789 other application that does not use terminating zeros. For example, you need to
6790 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6791 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6792 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6793 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6795 .cindex "lookup" "dsearch"
6796 .cindex "dsearch lookup type"
6797 &(dsearch)&: The given file must be an
6799 directory path; this is searched for an entry
6800 whose name is the key by calling the &[lstat()]& function.
6802 contain any forward slash characters.
6803 If &[lstat()]& succeeds then so does the lookup.
6804 .cindex "tainted data" "dsearch result"
6805 The result is regarded as untainted.
6807 Options for the lookup can be given by appending them after the word "dsearch",
6808 separated by a comma. Options, if present, are a comma-separated list having
6809 each element starting with a tag name and an equals.
6811 Two options are supported, for the return value and for filtering match
6813 The "ret" option requests an alternate result value of
6814 the entire path for the entry. Example:
6816 ${lookup {passwd} dsearch,ret=full {/etc}}
6818 The default result is just the requested entry.
6819 The "filter" option requests that only directory entries of a given type
6820 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6821 not matching "." or ".."). Example:
6823 ${lookup {passwd} dsearch,filter=file {/etc}}
6825 The default matching is for any entry type, including directories
6828 An example of how this
6829 lookup can be used to support virtual domains is given in section
6830 &<<SECTvirtualdomains>>&.
6832 .cindex "lookup" "iplsearch"
6833 .cindex "iplsearch lookup type"
6834 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6835 terminated by a colon or white space or the end of the line. The keys in the
6836 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6837 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6838 being interpreted as a key terminator. For example:
6840 1.2.3.4: data for 1.2.3.4
6841 192.168.0.0/16: data for 192.168.0.0/16
6842 "abcd::cdab": data for abcd::cdab
6843 "abcd:abcd::/32" data for abcd:abcd::/32
6845 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6846 file is searched linearly, using the CIDR masks where present, until a matching
6847 key is found. The first key that matches is used; there is no attempt to find a
6848 &"best"& match. Apart from the way the keys are matched, the processing for
6849 &(iplsearch)& is the same as for &(lsearch)&.
6851 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6852 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6853 lookup types support only literal keys.
6855 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6856 the implicit key is the host's IP address rather than its name (see section
6857 &<<SECThoslispatsikey>>&).
6859 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6860 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6861 notation before executing the lookup.)
6864 .cindex json "lookup type"
6865 .cindex JSON expansions
6866 &(json)&: The given file is a text file with a JSON structure.
6867 An element of the structure is extracted, defined by the search key.
6868 The key is a list of subelement selectors
6869 (colon-separated by default but changeable in the usual way)
6870 which are applied in turn to select smaller and smaller portions
6871 of the JSON structure.
6872 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6873 nunbered array element is selected.
6874 Otherwise it must apply to a JSON object; the named element is selected.
6875 The final resulting element can be a simple JSON type or a JSON object
6876 or array; for the latter two a string-representation of the JSON
6878 For elements of type string, the returned value is de-quoted.
6885 .cindex database lmdb
6886 &(lmdb)&: The given file is an LMDB database.
6887 LMDB is a memory-mapped key-value store,
6888 with API modeled loosely on that of BerkeleyDB.
6889 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6890 for the feature set and operation modes.
6892 Exim provides read-only access via the LMDB C library.
6893 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6894 or your operating system package repository.
6895 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6897 You will need to separately create the LMDB database file,
6898 possibly using the &"mdb_load"& utility.
6903 .cindex "linear search"
6904 .cindex "lookup" "lsearch"
6905 .cindex "lsearch lookup type"
6906 .cindex "case sensitivity" "in lsearch lookup"
6907 &(lsearch)&: The given file is a text file that is searched linearly for a
6908 line beginning with the search key, terminated by a colon or white space or the
6909 end of the line. The search is case-insensitive; that is, upper and lower case
6910 letters are treated as the same. The first occurrence of the key that is found
6911 in the file is used.
6913 White space between the key and the colon is permitted. The remainder of the
6914 line, with leading and trailing white space removed, is the data. This can be
6915 continued onto subsequent lines by starting them with any amount of white
6916 space, but only a single space character is included in the data at such a
6917 junction. If the data begins with a colon, the key must be terminated by a
6922 Empty lines and lines beginning with # are ignored, even if they occur in the
6923 middle of an item. This is the traditional textual format of alias files. Note
6924 that the keys in an &(lsearch)& file are literal strings. There is no
6925 wildcarding of any kind.
6927 .cindex "lookup" "lsearch &-- colons in keys"
6928 .cindex "white space" "in lsearch key"
6929 In most &(lsearch)& files, keys are not required to contain colons or #
6930 characters, or white space. However, if you need this feature, it is available.
6931 If a key begins with a doublequote character, it is terminated only by a
6932 matching quote (or end of line), and the normal escaping rules apply to its
6933 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6934 quoted keys (exactly as for unquoted keys). There is no special handling of
6935 quotes for the data part of an &(lsearch)& line.
6938 .cindex "NIS lookup type"
6939 .cindex "lookup" "NIS"
6940 .cindex "binary zero" "in lookup key"
6941 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6942 the given key, without a terminating binary zero. There is a variant called
6943 &(nis0)& which does include the terminating binary zero in the key. This is
6944 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6945 aliases; the full map names must be used.
6948 .cindex "wildlsearch lookup type"
6949 .cindex "lookup" "wildlsearch"
6950 .cindex "nwildlsearch lookup type"
6951 .cindex "lookup" "nwildlsearch"
6952 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6953 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6954 the file may be wildcarded. The difference between these two lookup types is
6955 that for &(wildlsearch)&, each key in the file is string-expanded before being
6956 used, whereas for &(nwildlsearch)&, no expansion takes place.
6958 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6959 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6960 file that are regular expressions can be made case-sensitive by the use of
6961 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6963 . ==== As this is a nested list, any displays it contains must be indented
6964 . ==== as otherwise they are too far to the left.
6967 The string may begin with an asterisk to mean &"ends with"&. For example:
6969 *.a.b.c data for anything.a.b.c
6970 *fish data for anythingfish
6973 The string may begin with a circumflex to indicate a regular expression. For
6974 example, for &(wildlsearch)&:
6976 ^\N\d+\.a\.b\N data for <digits>.a.b
6978 Note the use of &`\N`& to disable expansion of the contents of the regular
6979 expression. If you are using &(nwildlsearch)&, where the keys are not
6980 string-expanded, the equivalent entry is:
6982 ^\d+\.a\.b data for <digits>.a.b
6984 The case-insensitive flag is set at the start of compiling the regular
6985 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6986 For example, to make the entire pattern case-sensitive:
6988 ^(?-i)\d+\.a\.b data for <digits>.a.b
6991 If the regular expression contains white space or colon characters, you must
6992 either quote it (see &(lsearch)& above), or represent these characters in other
6993 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6994 colon. This may be easier than quoting, because if you quote, you have to
6995 escape all the backslashes inside the quotes.
6997 &*Note*&: It is not possible to capture substrings in a regular expression
6998 match for later use, because the results of all lookups are cached. If a lookup
6999 is repeated, the result is taken from the cache, and no actual pattern matching
7000 takes place. The values of all the numeric variables are unset after a
7001 &((n)wildlsearch)& match.
7004 Although I cannot see it being of much use, the general matching function that
7005 is used to implement &((n)wildlsearch)& means that the string may begin with a
7006 lookup name terminated by a semicolon, and followed by lookup data. For
7009 cdb;/some/file data for keys that match the file
7011 The data that is obtained from the nested lookup is discarded.
7014 Keys that do not match any of these patterns are interpreted literally. The
7015 continuation rules for the data are the same as for &(lsearch)&, and keys may
7016 be followed by optional colons.
7018 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7019 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7020 lookup types support only literal keys.
7023 .cindex "spf lookup type"
7024 .cindex "lookup" "spf"
7025 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7026 (as opposed to the standard ACL condition method).
7027 For details see section &<<SECSPF>>&.
7031 .section "Query-style lookup types" "SECTquerystylelookups"
7032 .cindex "lookup" "query-style types"
7033 .cindex "query-style lookup" "list of types"
7034 The supported query-style lookup types are listed below. Further details about
7035 many of them are given in later sections.
7038 .cindex "DNS" "as a lookup type"
7039 .cindex "lookup" "DNS"
7040 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7041 are given in the supplied query. The resulting data is the contents of the
7042 records. See section &<<SECTdnsdb>>&.
7044 .cindex "InterBase lookup type"
7045 .cindex "lookup" "InterBase"
7046 &(ibase)&: This does a lookup in an InterBase database.
7048 .cindex "LDAP" "lookup type"
7049 .cindex "lookup" "LDAP"
7050 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7051 returns attributes from a single entry. There is a variant called &(ldapm)&
7052 that permits values from multiple entries to be returned. A third variant
7053 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7054 any attribute values. See section &<<SECTldap>>&.
7056 .cindex "MySQL" "lookup type"
7057 .cindex "lookup" "MySQL"
7058 &(mysql)&: The format of the query is an SQL statement that is passed to a
7059 MySQL database. See section &<<SECTsql>>&.
7061 .cindex "NIS+ lookup type"
7062 .cindex "lookup" "NIS+"
7063 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7064 the field to be returned. See section &<<SECTnisplus>>&.
7066 .cindex "Oracle" "lookup type"
7067 .cindex "lookup" "Oracle"
7068 &(oracle)&: The format of the query is an SQL statement that is passed to an
7069 Oracle database. See section &<<SECTsql>>&.
7071 .cindex "lookup" "passwd"
7072 .cindex "passwd lookup type"
7073 .cindex "&_/etc/passwd_&"
7074 &(passwd)& is a query-style lookup with queries that are just user names. The
7075 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7076 success, the result string is the same as you would get from an &(lsearch)&
7077 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7078 password value. For example:
7080 *:42:42:King Rat:/home/kr:/bin/bash
7083 .cindex "PostgreSQL lookup type"
7084 .cindex "lookup" "PostgreSQL"
7085 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7086 PostgreSQL database. See section &<<SECTsql>>&.
7089 .cindex "Redis lookup type"
7090 .cindex lookup Redis
7091 &(redis)&: The format of the query is either a simple get or simple set,
7092 passed to a Redis database. See section &<<SECTsql>>&.
7095 .cindex "sqlite lookup type"
7096 .cindex "lookup" "sqlite"
7097 &(sqlite)&: The format of the query is
7098 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7101 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7102 not likely to be useful in normal operation.
7104 .cindex "whoson lookup type"
7105 .cindex "lookup" "whoson"
7106 . --- still http:-only, 2018-09-07
7107 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7108 allows a server to check whether a particular (dynamically allocated) IP
7109 address is currently allocated to a known (trusted) user and, optionally, to
7110 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7111 at one time for &"POP before SMTP"& authentication, but that approach has been
7112 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7113 &"POP before SMTP"& checking using ACL statements such as
7115 require condition = \
7116 ${lookup whoson {$sender_host_address}{yes}{no}}
7118 The query consists of a single IP address. The value returned is the name of
7119 the authenticated user, which is stored in the variable &$value$&. However, in
7120 this example, the data in &$value$& is not used; the result of the lookup is
7121 one of the fixed strings &"yes"& or &"no"&.
7126 .section "Temporary errors in lookups" "SECID63"
7127 .cindex "lookup" "temporary error in"
7128 Lookup functions can return temporary error codes if the lookup cannot be
7129 completed. For example, an SQL or LDAP database might be unavailable. For this
7130 reason, it is not advisable to use a lookup that might do this for critical
7131 options such as a list of local domains.
7133 When a lookup cannot be completed in a router or transport, delivery
7134 of the message (to the relevant address) is deferred, as for any other
7135 temporary error. In other circumstances Exim may assume the lookup has failed,
7136 or may give up altogether.
7140 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7141 .cindex "wildcard lookups"
7142 .cindex "lookup" "default values"
7143 .cindex "lookup" "wildcard"
7144 .cindex "lookup" "* added to type"
7145 .cindex "default" "in single-key lookups"
7146 In this context, a &"default value"& is a value specified by the administrator
7147 that is to be used if a lookup fails.
7149 &*Note:*& This section applies only to single-key lookups. For query-style
7150 lookups, the facilities of the query language must be used. An attempt to
7151 specify a default for a query-style lookup provokes an error.
7153 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7154 and the initial lookup fails, the key &"*"& is looked up in the file to
7155 provide a default value. See also the section on partial matching below.
7157 .cindex "*@ with single-key lookup"
7158 .cindex "lookup" "*@ added to type"
7159 .cindex "alias file" "per-domain default"
7160 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7161 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7162 character, a second lookup is done with everything before the last @ replaced
7163 by *. This makes it possible to provide per-domain defaults in alias files
7164 that include the domains in the keys. If the second lookup fails (or doesn't
7165 take place because there is no @ in the key), &"*"& is looked up.
7166 For example, a &(redirect)& router might contain:
7168 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7170 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7171 looks up these keys, in this order:
7177 The data is taken from whichever key it finds first. &*Note*&: In an
7178 &(lsearch)& file, this does not mean the first of these keys in the file. A
7179 complete scan is done for each key, and only if it is not found at all does
7180 Exim move on to try the next key.
7184 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7185 .cindex "partial matching"
7186 .cindex "wildcard lookups"
7187 .cindex "lookup" "partial matching"
7188 .cindex "lookup" "wildcard"
7189 .cindex "asterisk" "in search type"
7190 The normal operation of a single-key lookup is to search the file for an exact
7191 match with the given key. However, in a number of situations where domains are
7192 being looked up, it is useful to be able to do partial matching. In this case,
7193 information in the file that has a key starting with &"*."& is matched by any
7194 domain that ends with the components that follow the full stop. For example, if
7195 a key in a DBM file is
7197 *.dates.fict.example
7199 then when partial matching is enabled this is matched by (amongst others)
7200 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7201 by &'dates.fict.example'&, if that does not appear as a separate key in the
7204 &*Note*&: Partial matching is not available for query-style lookups. It is
7205 also not available for any lookup items in address lists (see section
7206 &<<SECTaddresslist>>&).
7208 Partial matching is implemented by doing a series of separate lookups using
7209 keys constructed by modifying the original subject key. This means that it can
7210 be used with any of the single-key lookup types, provided that
7211 partial matching keys
7212 beginning with a special prefix (default &"*."&) are included in the data file.
7213 Keys in the file that do not begin with the prefix are matched only by
7214 unmodified subject keys when partial matching is in use.
7216 Partial matching is requested by adding the string &"partial-"& to the front of
7217 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7218 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7219 is added at the start of the subject key, and it is looked up again. If that
7220 fails, further lookups are tried with dot-separated components removed from the
7221 start of the subject key, one-by-one, and &"*."& added on the front of what
7224 A minimum number of two non-* components are required. This can be adjusted
7225 by including a number before the hyphen in the search type. For example,
7226 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7227 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7228 subject key is &'2250.dates.fict.example'& then the following keys are looked
7229 up when the minimum number of non-* components is two:
7231 2250.dates.fict.example
7232 *.2250.dates.fict.example
7233 *.dates.fict.example
7236 As soon as one key in the sequence is successfully looked up, the lookup
7239 .cindex "lookup" "partial matching &-- changing prefix"
7240 .cindex "prefix" "for partial matching"
7241 The use of &"*."& as the partial matching prefix is a default that can be
7242 changed. The motivation for this feature is to allow Exim to operate with file
7243 formats that are used by other MTAs. A different prefix can be supplied in
7244 parentheses instead of the hyphen after &"partial"&. For example:
7246 domains = partial(.)lsearch;/some/file
7248 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7249 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7250 components is unchanged). The prefix may consist of any punctuation characters
7251 other than a closing parenthesis. It may be empty, for example:
7253 domains = partial1()cdb;/some/file
7255 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7256 &`a.b.c`&, &`b.c`&, and &`c`&.
7258 If &"partial0"& is specified, what happens at the end (when the lookup with
7259 just one non-wild component has failed, and the original key is shortened right
7260 down to the null string) depends on the prefix:
7263 If the prefix has zero length, the whole lookup fails.
7265 If the prefix has length 1, a lookup for just the prefix is done. For
7266 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7268 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7269 remainder is looked up. With the default prefix, therefore, the final lookup is
7270 for &"*"& on its own.
7272 Otherwise, the whole prefix is looked up.
7276 If the search type ends in &"*"& or &"*@"& (see section
7277 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7278 this implies happens after all partial lookups have failed. If &"partial0"& is
7279 specified, adding &"*"& to the search type has no effect with the default
7280 prefix, because the &"*"& key is already included in the sequence of partial
7281 lookups. However, there might be a use for lookup types such as
7282 &"partial0(.)lsearch*"&.
7284 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7285 in domain lists and the like. Partial matching works only in terms of
7286 dot-separated components; a key such as &`*fict.example`&
7287 in a database file is useless, because the asterisk in a partial matching
7288 subject key is always followed by a dot.
7293 .section "Lookup caching" "SECID64"
7294 .cindex "lookup" "caching"
7295 .cindex "caching" "lookup data"
7296 Exim caches all lookup results in order to avoid needless repetition of
7297 lookups. However, because (apart from the daemon) Exim operates as a collection
7298 of independent, short-lived processes, this caching applies only within a
7299 single Exim process. There is no inter-process lookup caching facility.
7301 For single-key lookups, Exim keeps the relevant files open in case there is
7302 another lookup that needs them. In some types of configuration this can lead to
7303 many files being kept open for messages with many recipients. To avoid hitting
7304 the operating system limit on the number of simultaneously open files, Exim
7305 closes the least recently used file when it needs to open more files than its
7306 own internal limit, which can be changed via the &%lookup_open_max%& option.
7308 The single-key lookup files are closed and the lookup caches are flushed at
7309 strategic points during delivery &-- for example, after all routing is
7315 .section "Quoting lookup data" "SECID65"
7316 .cindex "lookup" "quoting"
7317 .cindex "quoting" "in lookups"
7318 When data from an incoming message is included in a query-style lookup, there
7319 is the possibility of special characters in the data messing up the syntax of
7320 the query. For example, a NIS+ query that contains
7324 will be broken if the local part happens to contain a closing square bracket.
7325 For NIS+, data can be enclosed in double quotes like this:
7327 [name="$local_part"]
7329 but this still leaves the problem of a double quote in the data. The rule for
7330 NIS+ is that double quotes must be doubled. Other lookup types have different
7331 rules, and to cope with the differing requirements, an expansion operator
7332 of the following form is provided:
7334 ${quote_<lookup-type>:<string>}
7336 For example, the safest way to write the NIS+ query is
7338 [name="${quote_nisplus:$local_part}"]
7340 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7341 operator can be used for all lookup types, but has no effect for single-key
7342 lookups, since no quoting is ever needed in their key strings.
7347 .section "More about dnsdb" "SECTdnsdb"
7348 .cindex "dnsdb lookup"
7349 .cindex "lookup" "dnsdb"
7350 .cindex "DNS" "as a lookup type"
7351 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7352 of a record type and a domain name, separated by an equals sign. For example,
7353 an expansion string could contain:
7355 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7357 If the lookup succeeds, the result is placed in &$value$&, which in this case
7358 is used on its own as the result. If the lookup does not succeed, the
7359 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7360 &<<SECTforexpfai>>& for an explanation of what this means.
7362 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7363 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7364 If no type is given, TXT is assumed.
7366 For any record type, if multiple records are found, the data is returned as a
7367 concatenation, with newline as the default separator. The order, of course,
7368 depends on the DNS resolver. You can specify a different separator character
7369 between multiple records by putting a right angle-bracket followed immediately
7370 by the new separator at the start of the query. For example:
7372 ${lookup dnsdb{>: a=host1.example}}
7374 It is permitted to specify a space as the separator character. Further
7375 white space is ignored.
7376 For lookup types that return multiple fields per record,
7377 an alternate field separator can be specified using a comma after the main
7378 separator character, followed immediately by the field separator.
7380 .cindex "PTR record" "in &(dnsdb)& lookup"
7381 When the type is PTR,
7382 the data can be an IP address, written as normal; inversion and the addition of
7383 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7385 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7387 If the data for a PTR record is not a syntactically valid IP address, it is not
7388 altered and nothing is added.
7390 .cindex "MX record" "in &(dnsdb)& lookup"
7391 .cindex "SRV record" "in &(dnsdb)& lookup"
7392 For an MX lookup, both the preference value and the host name are returned for
7393 each record, separated by a space. For an SRV lookup, the priority, weight,
7394 port, and host name are returned for each record, separated by spaces.
7395 The field separator can be modified as above.
7397 .cindex "TXT record" "in &(dnsdb)& lookup"
7398 .cindex "SPF record" "in &(dnsdb)& lookup"
7399 For TXT records with multiple items of data, only the first item is returned,
7400 unless a field separator is specified.
7401 To concatenate items without a separator, use a semicolon instead.
7403 default behaviour is to concatenate multiple items without using a separator.
7405 ${lookup dnsdb{>\n,: txt=a.b.example}}
7406 ${lookup dnsdb{>\n; txt=a.b.example}}
7407 ${lookup dnsdb{spf=example.org}}
7409 It is permitted to specify a space as the separator character. Further
7410 white space is ignored.
7412 .cindex "SOA record" "in &(dnsdb)& lookup"
7413 For an SOA lookup, while no result is obtained the lookup is redone with
7414 successively more leading components dropped from the given domain.
7415 Only the primary-nameserver field is returned unless a field separator is
7418 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7421 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7422 .cindex "dnsdb modifiers"
7423 .cindex "modifiers" "dnsdb"
7424 .cindex "options" "dnsdb"
7425 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7426 each followed by a comma,
7427 that may appear before the record type.
7429 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7430 temporary DNS error for any of them, the behaviour is controlled by
7431 a defer-option modifier.
7432 The possible keywords are
7433 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7434 With &"strict"& behaviour, any temporary DNS error causes the
7435 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7436 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7437 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7438 error causes the whole lookup to defer only if none of the other lookups
7439 succeed. The default is &"lax"&, so the following lookups are equivalent:
7441 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7442 ${lookup dnsdb{a=one.host.com:two.host.com}}
7444 Thus, in the default case, as long as at least one of the DNS lookups
7445 yields some data, the lookup succeeds.
7447 .cindex "DNSSEC" "dns lookup"
7448 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7449 The possible keywords are
7450 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7451 With &"strict"& or &"lax"& DNSSEC information is requested
7453 With &"strict"& a response from the DNS resolver that
7454 is not labelled as authenticated data
7455 is treated as equivalent to a temporary DNS error.
7456 The default is &"lax"&.
7458 See also the &$lookup_dnssec_authenticated$& variable.
7460 .cindex timeout "dns lookup"
7461 .cindex "DNS" timeout
7462 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7463 The form is &"retrans_VAL"& where VAL is an Exim time specification
7465 The default value is set by the main configuration option &%dns_retrans%&.
7467 Retries for the dnsdb lookup can be controlled by a retry modifier.
7468 The form if &"retry_VAL"& where VAL is an integer.
7469 The default count is set by the main configuration option &%dns_retry%&.
7471 .cindex caching "of dns lookup"
7472 .cindex TTL "of dns lookup"
7474 Dnsdb lookup results are cached within a single process (and its children).
7475 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7476 value of the set of returned DNS records.
7479 .section "Pseudo dnsdb record types" "SECID66"
7480 .cindex "MX record" "in &(dnsdb)& lookup"
7481 By default, both the preference value and the host name are returned for
7482 each MX record, separated by a space. If you want only host names, you can use
7483 the pseudo-type MXH:
7485 ${lookup dnsdb{mxh=a.b.example}}
7487 In this case, the preference values are omitted, and just the host names are
7490 .cindex "name server for enclosing domain"
7491 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7492 records on the given domain, but if none are found, it removes the first
7493 component of the domain name, and tries again. This process continues until NS
7494 records are found or there are no more components left (or there is a DNS
7495 error). In other words, it may return the name servers for a top-level domain,
7496 but it never returns the root name servers. If there are no NS records for the
7497 top-level domain, the lookup fails. Consider these examples:
7499 ${lookup dnsdb{zns=xxx.quercite.com}}
7500 ${lookup dnsdb{zns=xxx.edu}}
7502 Assuming that in each case there are no NS records for the full domain name,
7503 the first returns the name servers for &%quercite.com%&, and the second returns
7504 the name servers for &%edu%&.
7506 You should be careful about how you use this lookup because, unless the
7507 top-level domain does not exist, the lookup always returns some host names. The
7508 sort of use to which this might be put is for seeing if the name servers for a
7509 given domain are on a blacklist. You can probably assume that the name servers
7510 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7513 .cindex "CSA" "in &(dnsdb)& lookup"
7514 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7515 records according to the CSA rules, which are described in section
7516 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7517 not sufficient because of the extra parent domain search behaviour of CSA. The
7518 result of a successful lookup such as:
7520 ${lookup dnsdb {csa=$sender_helo_name}}
7522 has two space-separated fields: an authorization code and a target host name.
7523 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7524 authorization required but absent, or &"?"& for unknown.
7526 .cindex "A+" "in &(dnsdb)& lookup"
7527 The pseudo-type A+ performs an AAAA
7528 and then an A lookup. All results are returned; defer processing
7529 (see below) is handled separately for each lookup. Example:
7531 ${lookup dnsdb {>; a+=$sender_helo_name}}
7535 .section "Multiple dnsdb lookups" "SECID67"
7536 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7537 However, you can specify a list of domains or IP addresses in a single
7538 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7539 the default separator, but with the ability to change this. For example:
7541 ${lookup dnsdb{one.domain.com:two.domain.com}}
7542 ${lookup dnsdb{a=one.host.com:two.host.com}}
7543 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7545 In order to retain backwards compatibility, there is one special case: if
7546 the lookup type is PTR and no change of separator is specified, Exim looks
7547 to see if the rest of the string is precisely one IPv6 address. In this
7548 case, it does not treat it as a list.
7550 The data from each lookup is concatenated, with newline separators by default,
7551 in the same way that multiple DNS records for a single item are handled. A
7552 different separator can be specified, as described above.
7557 .section "More about LDAP" "SECTldap"
7558 .cindex "LDAP" "lookup, more about"
7559 .cindex "lookup" "LDAP"
7560 .cindex "Solaris" "LDAP"
7561 The original LDAP implementation came from the University of Michigan; this has
7562 become &"Open LDAP"&, and there are now two different releases. Another
7563 implementation comes from Netscape, and Solaris 7 and subsequent releases
7564 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7565 the lookup function level, their error handling is different. For this reason
7566 it is necessary to set a compile-time variable when building Exim with LDAP, to
7567 indicate which LDAP library is in use. One of the following should appear in
7568 your &_Local/Makefile_&:
7570 LDAP_LIB_TYPE=UMICHIGAN
7571 LDAP_LIB_TYPE=OPENLDAP1
7572 LDAP_LIB_TYPE=OPENLDAP2
7573 LDAP_LIB_TYPE=NETSCAPE
7574 LDAP_LIB_TYPE=SOLARIS
7576 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7577 same interface as the University of Michigan version.
7579 There are three LDAP lookup types in Exim. These behave slightly differently in
7580 the way they handle the results of a query:
7583 &(ldap)& requires the result to contain just one entry; if there are more, it
7586 &(ldapdn)& also requires the result to contain just one entry, but it is the
7587 Distinguished Name that is returned rather than any attribute values.
7589 &(ldapm)& permits the result to contain more than one entry; the attributes
7590 from all of them are returned.
7594 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7595 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7596 the data returned by a successful lookup is described in the next section.
7597 First we explain how LDAP queries are coded.
7600 .section "Format of LDAP queries" "SECTforldaque"
7601 .cindex "LDAP" "query format"
7602 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7603 the configuration of a &(redirect)& router one might have this setting:
7605 data = ${lookup ldap \
7606 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7607 c=UK?mailbox?base?}}
7609 .cindex "LDAP" "with TLS"
7610 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7611 secure (encrypted) LDAP connections. The second of these ensures that an
7612 encrypted TLS connection is used.
7614 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7615 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7616 See the &%ldap_start_tls%& option.
7618 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7619 controlled. Every part of the TLS configuration can be configured by settings in
7620 &_exim.conf_&. Depending on the version of the client libraries installed on
7621 your system, some of the initialization may have required setting options in
7622 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7623 certificates. This revealed a nuance where the current UID that exim was
7624 running as could affect which config files it read. With Exim 4.83, these
7625 methods become optional, only taking effect if not specifically set in
7629 .section "LDAP quoting" "SECID68"
7630 .cindex "LDAP" "quoting"
7631 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7632 and the second because the LDAP query is represented as a URL. Furthermore,
7633 within an LDAP query, two different kinds of quoting are required. For this
7634 reason, there are two different LDAP-specific quoting operators.
7636 The &%quote_ldap%& operator is designed for use on strings that are part of
7637 filter specifications. Conceptually, it first does the following conversions on
7645 in accordance with RFC 2254. The resulting string is then quoted according
7646 to the rules for URLs, that is, all non-alphanumeric characters except
7650 are converted to their hex values, preceded by a percent sign. For example:
7652 ${quote_ldap: a(bc)*, a<yz>; }
7656 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7658 Removing the URL quoting, this is (with a leading and a trailing space):
7660 a\28bc\29\2A, a<yz>;
7662 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7663 base DN specifications in queries. Conceptually, it first converts the string
7664 by inserting a backslash in front of any of the following characters:
7668 It also inserts a backslash before any leading spaces or # characters, and
7669 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7670 is then quoted according to the rules for URLs. For example:
7672 ${quote_ldap_dn: a(bc)*, a<yz>; }
7676 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7678 Removing the URL quoting, this is (with a trailing space):
7680 \ a(bc)*\, a\<yz\>\;\
7682 There are some further comments about quoting in the section on LDAP
7683 authentication below.
7686 .section "LDAP connections" "SECID69"
7687 .cindex "LDAP" "connections"
7688 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7689 is in use, via a Unix domain socket. The example given above does not specify
7690 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7693 ldap://<hostname>:<port>/...
7695 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7696 used. When no server is specified in a query, a list of default servers is
7697 taken from the &%ldap_default_servers%& configuration option. This supplies a
7698 colon-separated list of servers which are tried in turn until one successfully
7699 handles a query, or there is a serious error. Successful handling either
7700 returns the requested data, or indicates that it does not exist. Serious errors
7701 are syntactical, or multiple values when only a single value is expected.
7702 Errors which cause the next server to be tried are connection failures, bind
7703 failures, and timeouts.
7705 For each server name in the list, a port number can be given. The standard way
7706 of specifying a host and port is to use a colon separator (RFC 1738). Because
7707 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7708 doubled. For example
7710 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7712 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7713 to the LDAP library with no server name, and the library's default (normally
7714 the local host) is used.
7716 If you are using the OpenLDAP library, you can connect to an LDAP server using
7717 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7718 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7719 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7722 For this type of connection, instead of a host name for the server, a pathname
7723 for the socket is required, and the port number is not relevant. The pathname
7724 can be specified either as an item in &%ldap_default_servers%&, or inline in
7725 the query. In the former case, you can have settings such as
7727 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7729 When the pathname is given in the query, you have to escape the slashes as
7730 &`%2F`& to fit in with the LDAP URL syntax. For example:
7732 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7734 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7735 a pathname, it uses the Unix domain socket code, even if the query actually
7736 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7737 socket connection. This behaviour means that you can use a setting of
7738 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7739 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7740 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7743 If an explicit &`ldapi`& type is given in a query when a host name is
7744 specified, an error is diagnosed. However, if there are more items in
7745 &%ldap_default_servers%&, they are tried. In other words:
7748 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7751 Using &`ldapi`& with a host name causes an error.
7755 Using &`ldapi`& with no host or path in the query, and no setting of
7756 &%ldap_default_servers%&, does whatever the library does by default.
7760 .section "LDAP authentication and control information" "SECID70"
7761 .cindex "LDAP" "authentication"
7762 The LDAP URL syntax provides no way of passing authentication and other control
7763 information to the server. To make this possible, the URL in an LDAP query may
7764 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7765 spaces. If a value contains spaces it must be enclosed in double quotes, and
7766 when double quotes are used, backslash is interpreted in the usual way inside
7767 them. The following names are recognized:
7769 &`DEREFERENCE`& set the dereferencing parameter
7770 &`NETTIME `& set a timeout for a network operation
7771 &`USER `& set the DN, for authenticating the LDAP bind
7772 &`PASS `& set the password, likewise
7773 &`REFERRALS `& set the referrals parameter
7774 &`SERVERS `& set alternate server list for this query only
7775 &`SIZE `& set the limit for the number of entries returned
7776 &`TIME `& set the maximum waiting time for a query
7778 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7779 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7780 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7781 library from trying to follow referrals issued by the LDAP server.
7783 .cindex LDAP timeout
7784 .cindex timeout "LDAP lookup"
7785 The name CONNECT is an obsolete name for NETTIME, retained for
7786 backwards compatibility. This timeout (specified as a number of seconds) is
7787 enforced from the client end for operations that can be carried out over a
7788 network. Specifically, it applies to network connections and calls to the
7789 &'ldap_result()'& function. If the value is greater than zero, it is used if
7790 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7791 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7792 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7793 Netscape SDK; for OpenLDAP no action is taken.
7795 The TIME parameter (also a number of seconds) is passed to the server to
7796 set a server-side limit on the time taken to complete a search.
7798 The SERVERS parameter allows you to specify an alternate list of ldap servers
7799 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7800 default list of ldap servers, and a single lookup can specify a single ldap
7801 server to use. But when you need to do a lookup with a list of servers that is
7802 different than the default list (maybe different order, maybe a completely
7803 different set of servers), the SERVERS parameter allows you to specify this
7804 alternate list (colon-separated).
7806 Here is an example of an LDAP query in an Exim lookup that uses some of these
7807 values. This is a single line, folded to fit on the page:
7810 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7811 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7814 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7815 any of the auxiliary data. Exim configuration settings that include lookups
7816 which contain password information should be preceded by &"hide"& to prevent
7817 non-admin users from using the &%-bP%& option to see their values.
7819 The auxiliary data items may be given in any order. The default is no
7820 connection timeout (the system timeout is used), no user or password, no limit
7821 on the number of entries returned, and no time limit on queries.
7823 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7824 removes any URL quoting that it may contain before passing it LDAP. Apparently
7825 some libraries do this for themselves, but some do not. Removing the URL
7826 quoting has two advantages:
7829 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7830 DNs as with DNs inside actual queries.
7832 It permits spaces inside USER= DNs.
7835 For example, a setting such as
7837 USER=cn=${quote_ldap_dn:$1}
7839 should work even if &$1$& contains spaces.
7841 Expanded data for the PASS= value should be quoted using the &%quote%&
7842 expansion operator, rather than the LDAP quote operators. The only reason this
7843 field needs quoting is to ensure that it conforms to the Exim syntax, which
7844 does not allow unquoted spaces. For example:
7848 The LDAP authentication mechanism can be used to check passwords as part of
7849 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7854 .section "Format of data returned by LDAP" "SECID71"
7855 .cindex "LDAP" "returned data formats"
7856 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7857 as a sequence of values, for example
7859 cn=manager,o=University of Cambridge,c=UK
7861 The &(ldap)& lookup type generates an error if more than one entry matches the
7862 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7863 the result between the data from different entries. It is possible for multiple
7864 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7865 you know that whatever values are returned all came from a single entry in the
7868 In the common case where you specify a single attribute in your LDAP query, the
7869 result is not quoted, and does not contain the attribute name. If the attribute
7870 has multiple values, they are separated by commas. Any comma that is
7871 part of an attribute's value is doubled.
7873 If you specify multiple attributes, the result contains space-separated, quoted
7874 strings, each preceded by the attribute name and an equals sign. Within the
7875 quotes, the quote character, backslash, and newline are escaped with
7876 backslashes, and commas are used to separate multiple values for the attribute.
7877 Any commas in attribute values are doubled
7878 (permitting treatment of the values as a comma-separated list).
7879 Apart from the escaping, the string within quotes takes the same form as the
7880 output when a single attribute is requested. Specifying no attributes is the
7881 same as specifying all of an entry's attributes.
7883 Here are some examples of the output format. The first line of each pair is an
7884 LDAP query, and the second is the data that is returned. The attribute called
7885 &%attr1%& has two values, one of them with an embedded comma, whereas
7886 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7887 (they have SUP &%attr%& in their schema definitions).
7890 ldap:///o=base?attr1?sub?(uid=fred)
7893 ldap:///o=base?attr2?sub?(uid=fred)
7896 ldap:///o=base?attr?sub?(uid=fred)
7897 value1.1,value1,,2,value two
7899 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7900 attr1="value1.1,value1,,2" attr2="value two"
7902 ldap:///o=base??sub?(uid=fred)
7903 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7906 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7907 results of LDAP lookups.
7908 The &%extract%& operator in string expansions can be used to pick out
7909 individual fields from data that consists of &'key'&=&'value'& pairs.
7910 The &%listextract%& operator should be used to pick out individual values
7911 of attributes, even when only a single value is expected.
7912 The doubling of embedded commas allows you to use the returned data as a
7913 comma separated list (using the "<," syntax for changing the input list separator).
7918 .section "More about NIS+" "SECTnisplus"
7919 .cindex "NIS+ lookup type"
7920 .cindex "lookup" "NIS+"
7921 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7922 and field name. If this is given, the result of a successful query is the
7923 contents of the named field; otherwise the result consists of a concatenation
7924 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7925 values containing spaces are quoted. For example, the query
7927 [name=mg1456],passwd.org_dir
7929 might return the string
7931 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7932 home=/home/mg1456 shell=/bin/bash shadow=""
7934 (split over two lines here to fit on the page), whereas
7936 [name=mg1456],passwd.org_dir:gcos
7942 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7943 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7944 operator is to double any quote characters within the text.
7948 .section "SQL lookups" "SECTsql"
7949 .cindex "SQL lookup types"
7950 .cindex "MySQL" "lookup type"
7951 .cindex "PostgreSQL lookup type"
7952 .cindex "lookup" "MySQL"
7953 .cindex "lookup" "PostgreSQL"
7954 .cindex "Oracle" "lookup type"
7955 .cindex "lookup" "Oracle"
7956 .cindex "InterBase lookup type"
7957 .cindex "lookup" "InterBase"
7958 .cindex "Redis lookup type"
7959 .cindex lookup Redis
7960 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7962 databases. Queries for these databases contain SQL statements, so an example
7965 ${lookup mysql{select mailbox from users where id='userx'}\
7968 If the result of the query contains more than one field, the data for each
7969 field in the row is returned, preceded by its name, so the result of
7971 ${lookup pgsql{select home,name from users where id='userx'}\
7976 home=/home/userx name="Mister X"
7978 Empty values and values containing spaces are double quoted, with embedded
7979 quotes escaped by a backslash. If the result of the query contains just one
7980 field, the value is passed back verbatim, without a field name, for example:
7984 If the result of the query yields more than one row, it is all concatenated,
7985 with a newline between the data for each row.
7988 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7989 .cindex "MySQL" "lookup type"
7990 .cindex "PostgreSQL lookup type"
7991 .cindex "lookup" "MySQL"
7992 .cindex "lookup" "PostgreSQL"
7993 .cindex "Oracle" "lookup type"
7994 .cindex "lookup" "Oracle"
7995 .cindex "InterBase lookup type"
7996 .cindex "lookup" "InterBase"
7997 .cindex "Redis lookup type"
7998 .cindex lookup Redis
7999 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8000 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8001 or &%redis_servers%&
8002 option (as appropriate) must be set to a colon-separated list of server
8004 .oindex &%mysql_servers%&
8005 .oindex &%pgsql_servers%&
8006 .oindex &%oracle_servers%&
8007 .oindex &%ibase_servers%&
8008 .oindex &%redis_servers%&
8009 (For MySQL and PostgreSQL, the global option need not be set if all
8010 queries contain their own server information &-- see section
8011 &<<SECTspeserque>>&.)
8013 each item in the list is a slash-separated list of four
8014 items: host name, database name, user name, and password. In the case of
8015 Oracle, the host name field is used for the &"service name"&, and the database
8016 name field is not used and should be empty. For example:
8018 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8020 Because password data is sensitive, you should always precede the setting with
8021 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8022 option. Here is an example where two MySQL servers are listed:
8024 hide mysql_servers = localhost/users/root/secret:\
8025 otherhost/users/root/othersecret
8027 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8028 because this is a colon-separated list, the colon has to be doubled. For each
8029 query, these parameter groups are tried in order until a connection is made and
8030 a query is successfully processed. The result of a query may be that no data is
8031 found, but that is still a successful query. In other words, the list of
8032 servers provides a backup facility, not a list of different places to look.
8034 For Redis the global option need not be specified if all queries contain their
8035 own server information &-- see section &<<SECTspeserque>>&.
8036 If specified, the option must be set to a colon-separated list of server
8038 Each item in the list is a slash-separated list of three items:
8039 host, database number, and password.
8041 The host is required and may be either an IPv4 address and optional
8042 port number (separated by a colon, which needs doubling due to the
8043 higher-level list), or a Unix socket pathname enclosed in parentheses
8045 The database number is optional; if present that number is selected in the backend
8047 The password is optional; if present it is used to authenticate to the backend
8050 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8051 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8052 respectively, and the characters single-quote, double-quote, and backslash
8053 itself are escaped with backslashes.
8055 The &%quote_redis%& expansion operator
8056 escapes whitespace and backslash characters with a backslash.
8058 .section "Specifying the server in the query" "SECTspeserque"
8059 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8060 it is possible to specify a list of servers with an individual query. This is
8061 done by appending a comma-separated option to the query type:
8063 &`,servers=`&&'server1:server2:server3:...'&
8065 Each item in the list may take one of two forms:
8067 If it contains no slashes it is assumed to be just a host name. The appropriate
8068 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8069 of the same name, and the remaining parameters (database, user, password) are
8072 If it contains any slashes, it is taken as a complete parameter set.
8074 The list of servers is used in exactly the same way as the global list.
8075 Once a connection to a server has happened and a query has been
8076 successfully executed, processing of the lookup ceases.
8078 This feature is intended for use in master/slave situations where updates
8079 are occurring and you want to update the master rather than a slave. If the
8080 master is in the list as a backup for reading, you might have a global setting
8083 mysql_servers = slave1/db/name/pw:\
8087 In an updating lookup, you could then write:
8089 ${lookup mysql,servers=master {UPDATE ...} }
8091 That query would then be sent only to the master server. If, on the other hand,
8092 the master is not to be used for reading, and so is not present in the global
8093 option, you can still update it by a query of this form:
8095 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8098 An older syntax places the servers specification before the query,
8099 semicolon separated:
8101 ${lookup mysql{servers=master; UPDATE ...} }
8103 The new version avoids potential issues with tainted
8104 arguments in the query, for explicit expansion.
8105 &*Note*&: server specifications in list-style lookups are still problematic.
8108 .section "Special MySQL features" "SECID73"
8109 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8110 causes a connection to the server on the local host by means of a Unix domain
8111 socket. An alternate socket can be specified in parentheses.
8112 An option group name for MySQL option files can be specified in square brackets;
8113 the default value is &"exim"&.
8114 The full syntax of each item in &%mysql_servers%& is:
8116 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8117 <&'database'&>/<&'user'&>/<&'password'&>
8119 Any of the four sub-parts of the first field can be omitted. For normal use on
8120 the local host it can be left blank or set to just &"localhost"&.
8122 No database need be supplied &-- but if it is absent here, it must be given in
8125 If a MySQL query is issued that does not request any data (an insert, update,
8126 or delete command), the result of the lookup is the number of rows affected.
8128 &*Warning*&: This can be misleading. If an update does not actually change
8129 anything (for example, setting a field to the value it already has), the result
8130 is zero because no rows are affected.
8133 .section "Special PostgreSQL features" "SECID74"
8134 PostgreSQL lookups can also use Unix domain socket connections to the database.
8135 This is usually faster and costs less CPU time than a TCP/IP connection.
8136 However it can be used only if the mail server runs on the same machine as the
8137 database server. A configuration line for PostgreSQL via Unix domain sockets
8140 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8142 In other words, instead of supplying a host name, a path to the socket is
8143 given. The path name is enclosed in parentheses so that its slashes aren't
8144 visually confused with the delimiters for the other server parameters.
8146 If a PostgreSQL query is issued that does not request any data (an insert,
8147 update, or delete command), the result of the lookup is the number of rows
8150 .section "More about SQLite" "SECTsqlite"
8151 .cindex "lookup" "SQLite"
8152 .cindex "sqlite lookup type"
8153 SQLite is different to the other SQL lookups because a filename is required in
8154 addition to the SQL query. An SQLite database is a single file, and there is no
8155 daemon as in the other SQL databases.
8158 .oindex &%sqlite_dbfile%&
8159 There are two ways of
8160 specifying the file.
8161 The first is is by using the &%sqlite_dbfile%& main option.
8162 The second, which allows separate files for each query,
8163 is to use an option appended, comma-separated, to the &"sqlite"&
8164 lookup type word. The option is the word &"file"&, then an equals,
8166 The filename in this case cannot contain whitespace or open-brace charachters.
8169 A deprecated method is available, prefixing the query with the filename
8170 separated by white space.
8172 .cindex "tainted data" "sqlite file"
8173 the query cannot use any tainted values, as that taints
8174 the entire query including the filename - resulting in a refusal to open
8177 In all the above cases the filename must be an absolute path.
8179 Here is a lookup expansion example:
8181 sqlite_dbfile = /some/thing/sqlitedb
8183 ${lookup sqlite {select name from aliases where id='userx';}}
8185 In a list, the syntax is similar. For example:
8187 domainlist relay_to_domains = sqlite;\
8188 select * from relays where ip='$sender_host_address';
8190 The only character affected by the &%quote_sqlite%& operator is a single
8191 quote, which it doubles.
8193 .cindex timeout SQLite
8194 .cindex sqlite "lookup timeout"
8195 The SQLite library handles multiple simultaneous accesses to the database
8196 internally. Multiple readers are permitted, but only one process can
8197 update at once. Attempts to access the database while it is being updated
8198 are rejected after a timeout period, during which the SQLite library
8199 waits for the lock to be released. In Exim, the default timeout is set
8200 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8203 .section "More about Redis" "SECTredis"
8204 .cindex "lookup" "Redis"
8205 .cindex "redis lookup type"
8206 Redis is a non-SQL database. Commands are simple get and set.
8209 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8210 ${lookup redis{get keyname}}
8213 As of release 4.91, "lightweight" support for Redis Cluster is available.
8214 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8215 of which must be reachable from the running exim instance. If the cluster has
8216 master/slave replication, the list must contain all the master and slave
8219 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8220 immediately follow the redirection but treats the response as a DEFER, moving on
8221 to the next server in the &%redis_servers%& list until the correct server is
8228 . ////////////////////////////////////////////////////////////////////////////
8229 . ////////////////////////////////////////////////////////////////////////////
8231 .chapter "Domain, host, address, and local part lists" &&&
8232 "CHAPdomhosaddlists" &&&
8233 "Domain, host, and address lists"
8234 .scindex IIDdohoadli "lists of domains; hosts; etc."
8235 A number of Exim configuration options contain lists of domains, hosts,
8236 email addresses, or local parts. For example, the &%hold_domains%& option
8237 contains a list of domains whose delivery is currently suspended. These lists
8238 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8239 arguments to expansion conditions such as &%match_domain%&.
8241 Each item in one of these lists is a pattern to be matched against a domain,
8242 host, email address, or local part, respectively. In the sections below, the
8243 different types of pattern for each case are described, but first we cover some
8244 general facilities that apply to all four kinds of list.
8246 Note that other parts of Exim use a &'string list'& which does not
8247 support all the complexity available in
8248 domain, host, address and local part lists.
8252 .section "Expansion of lists" "SECTlistexpand"
8253 .cindex "expansion" "of lists"
8254 Each list is expanded as a single string before it is used.
8256 &'Exception: the router headers_remove option, where list-item
8257 splitting is done before string-expansion.'&
8260 expansion must be a list, possibly containing empty items, which is split up
8261 into separate items for matching. By default, colon is the separator character,
8262 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8263 &<<SECTempitelis>>& for details of the list syntax; the second of these
8264 discusses the way to specify empty list items.
8267 If the string expansion is forced to fail, Exim behaves as if the item it is
8268 testing (domain, host, address, or local part) is not in the list. Other
8269 expansion failures cause temporary errors.
8271 If an item in a list is a regular expression, backslashes, dollars and possibly
8272 other special characters in the expression must be protected against
8273 misinterpretation by the string expander. The easiest way to do this is to use
8274 the &`\N`& expansion feature to indicate that the contents of the regular
8275 expression should not be expanded. For example, in an ACL you might have:
8277 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8278 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8280 The first item is a regular expression that is protected from expansion by
8281 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8282 senders based on the receiving domain.
8287 .section "Negated items in lists" "SECID76"
8288 .cindex "list" "negation"
8289 .cindex "negation" "in lists"
8290 Items in a list may be positive or negative. Negative items are indicated by a
8291 leading exclamation mark, which may be followed by optional white space. A list
8292 defines a set of items (domains, etc). When Exim processes one of these lists,
8293 it is trying to find out whether a domain, host, address, or local part
8294 (respectively) is in the set that is defined by the list. It works like this:
8296 The list is scanned from left to right. If a positive item is matched, the
8297 subject that is being checked is in the set; if a negative item is matched, the
8298 subject is not in the set. If the end of the list is reached without the
8299 subject having matched any of the patterns, it is in the set if the last item
8300 was a negative one, but not if it was a positive one. For example, the list in
8302 domainlist relay_to_domains = !a.b.c : *.b.c
8304 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8305 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8306 list is positive. However, if the setting were
8308 domainlist relay_to_domains = !a.b.c
8310 then all domains other than &'a.b.c'& would match because the last item in the
8311 list is negative. In other words, a list that ends with a negative item behaves
8312 as if it had an extra item &`:*`& on the end.
8314 Another way of thinking about positive and negative items in lists is to read
8315 the connector as &"or"& after a positive item and as &"and"& after a negative
8320 .section "File names in lists" "SECTfilnamlis"
8321 .cindex "list" "filename in"
8322 If an item in a domain, host, address, or local part list is an absolute
8323 filename (beginning with a slash character), each line of the file is read and
8324 processed as if it were an independent item in the list, except that further
8325 filenames are not allowed,
8326 and no expansion of the data from the file takes place.
8327 Empty lines in the file are ignored, and the file may also contain comment
8331 For domain and host lists, if a # character appears anywhere in a line of the
8332 file, it and all following characters are ignored.
8334 Because local parts may legitimately contain # characters, a comment in an
8335 address list or local part list file is recognized only if # is preceded by
8336 white space or the start of the line. For example:
8338 not#comment@x.y.z # but this is a comment
8342 Putting a filename in a list has the same effect as inserting each line of the
8343 file as an item in the list (blank lines and comments excepted). However, there
8344 is one important difference: the file is read each time the list is processed,
8345 so if its contents vary over time, Exim's behaviour changes.
8347 If a filename is preceded by an exclamation mark, the sense of any match
8348 within the file is inverted. For example, if
8350 hold_domains = !/etc/nohold-domains
8352 and the file contains the lines
8357 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8358 any domain matching &`*.b.c`& is not.
8362 .section "An lsearch file is not an out-of-line list" "SECID77"
8363 As will be described in the sections that follow, lookups can be used in lists
8364 to provide indexed methods of checking list membership. There has been some
8365 confusion about the way &(lsearch)& lookups work in lists. Because
8366 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8367 sometimes thought that it is allowed to contain wild cards and other kinds of
8368 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8369 always fixed strings, just as for any other single-key lookup type.
8371 If you want to use a file to contain wild-card patterns that form part of a
8372 list, just give the filename on its own, without a search type, as described
8373 in the previous section. You could also use the &(wildlsearch)& or
8374 &(nwildlsearch)&, but there is no advantage in doing this.
8379 .section "Results of list checking" SECTlistresults
8380 The primary result of doing a list check is a truth value.
8381 In some contexts additional information is stored
8382 about the list element that matched:
8385 A &%hosts%& ACL condition
8386 will store a result in the &$host_data$& variable.
8388 A &%local_parts%& router option or &%local_parts%& ACL condition
8389 will store a result in the &$local_part_data$& variable.
8391 A &%domains%& router option or &%domains%& ACL condition
8393 A &%senders%& router option or &%senders%& ACL condition
8394 will store a result in the &$sender_data$& variable.
8396 A &%recipients%& ACL condition
8397 will store a result in the &$recipient_data$& variable.
8400 The detail of the additional information depends on the
8401 type of match and is given below as the &*value*& information.
8406 .section "Named lists" "SECTnamedlists"
8407 .cindex "named lists"
8408 .cindex "list" "named"
8409 A list of domains, hosts, email addresses, or local parts can be given a name
8410 which is then used to refer to the list elsewhere in the configuration. This is
8411 particularly convenient if the same list is required in several different
8412 places. It also allows lists to be given meaningful names, which can improve
8413 the readability of the configuration. For example, it is conventional to define
8414 a domain list called &'local_domains'& for all the domains that are handled
8415 locally on a host, using a configuration line such as
8417 domainlist local_domains = localhost:my.dom.example
8419 Named lists are referenced by giving their name preceded by a plus sign, so,
8420 for example, a router that is intended to handle local domains would be
8421 configured with the line
8423 domains = +local_domains
8425 The first router in a configuration is often one that handles all domains
8426 except the local ones, using a configuration with a negated item like this:
8430 domains = ! +local_domains
8431 transport = remote_smtp
8434 The four kinds of named list are created by configuration lines starting with
8435 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8436 respectively. Then there follows the name that you are defining, followed by an
8437 equals sign and the list itself. For example:
8439 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8440 addresslist bad_senders = cdb;/etc/badsenders
8442 A named list may refer to other named lists:
8444 domainlist dom1 = first.example : second.example
8445 domainlist dom2 = +dom1 : third.example
8446 domainlist dom3 = fourth.example : +dom2 : fifth.example
8448 &*Warning*&: If the last item in a referenced list is a negative one, the
8449 effect may not be what you intended, because the negation does not propagate
8450 out to the higher level. For example, consider:
8452 domainlist dom1 = !a.b
8453 domainlist dom2 = +dom1 : *.b
8455 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8456 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8457 means it matches the second list as well. The effect is not the same as
8459 domainlist dom2 = !a.b : *.b
8461 where &'x.y'& does not match. It's best to avoid negation altogether in
8462 referenced lists if you can.
8464 .cindex "hiding named list values"
8465 .cindex "named lists" "hiding value of"
8466 Some named list definitions may contain sensitive data, for example, passwords for
8467 accessing databases. To stop non-admin users from using the &%-bP%& command
8468 line option to read these values, you can precede the definition with the
8469 word &"hide"&. For example:
8471 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8475 Named lists may have a performance advantage. When Exim is routing an
8476 address or checking an incoming message, it caches the result of tests on named
8477 lists. So, if you have a setting such as
8479 domains = +local_domains
8481 on several of your routers
8482 or in several ACL statements,
8483 the actual test is done only for the first one. However, the caching works only
8484 if there are no expansions within the list itself or any sublists that it
8485 references. In other words, caching happens only for lists that are known to be
8486 the same each time they are referenced.
8488 By default, there may be up to 16 named lists of each type. This limit can be
8489 extended by changing a compile-time variable. The use of domain and host lists
8490 is recommended for concepts such as local domains, relay domains, and relay
8491 hosts. The default configuration is set up like this.
8495 .section "Named lists compared with macros" "SECID78"
8496 .cindex "list" "named compared with macro"
8497 .cindex "macro" "compared with named list"
8498 At first sight, named lists might seem to be no different from macros in the
8499 configuration file. However, macros are just textual substitutions. If you
8502 ALIST = host1 : host2
8503 auth_advertise_hosts = !ALIST
8505 it probably won't do what you want, because that is exactly the same as
8507 auth_advertise_hosts = !host1 : host2
8509 Notice that the second host name is not negated. However, if you use a host
8512 hostlist alist = host1 : host2
8513 auth_advertise_hosts = ! +alist
8515 the negation applies to the whole list, and so that is equivalent to
8517 auth_advertise_hosts = !host1 : !host2
8521 .section "Named list caching" "SECID79"
8522 .cindex "list" "caching of named"
8523 .cindex "caching" "named lists"
8524 While processing a message, Exim caches the result of checking a named list if
8525 it is sure that the list is the same each time. In practice, this means that
8526 the cache operates only if the list contains no $ characters, which guarantees
8527 that it will not change when it is expanded. Sometimes, however, you may have
8528 an expanded list that you know will be the same each time within a given
8529 message. For example:
8531 domainlist special_domains = \
8532 ${lookup{$sender_host_address}cdb{/some/file}}
8534 This provides a list of domains that depends only on the sending host's IP
8535 address. If this domain list is referenced a number of times (for example,
8536 in several ACL lines, or in several routers) the result of the check is not
8537 cached by default, because Exim does not know that it is going to be the
8538 same list each time.
8540 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8541 cache the result anyway. For example:
8543 domainlist_cache special_domains = ${lookup{...
8545 If you do this, you should be absolutely sure that caching is going to do
8546 the right thing in all cases. When in doubt, leave it out.
8550 .section "Domain lists" "SECTdomainlist"
8551 .cindex "domain list" "patterns for"
8552 .cindex "list" "domain list"
8553 Domain lists contain patterns that are to be matched against a mail domain.
8554 The following types of item may appear in domain lists:
8557 .cindex "primary host name"
8558 .cindex "host name" "matched in domain list"
8559 .oindex "&%primary_hostname%&"
8560 .cindex "domain list" "matching primary host name"
8561 .cindex "@ in a domain list"
8562 If a pattern consists of a single @ character, it matches the local host name,
8563 as set by the &%primary_hostname%& option (or defaulted). This makes it
8564 possible to use the same configuration file on several different hosts that
8565 differ only in their names.
8567 The value for a match will be the primary host name.
8571 .cindex "@[] in a domain list"
8572 .cindex "domain list" "matching local IP interfaces"
8573 .cindex "domain literal"
8574 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8575 in square brackets (as in an email address that contains a domain literal), but
8576 only if that IP address is recognized as local for email routing purposes. The
8577 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8578 control which of a host's several IP addresses are treated as local.
8579 In today's Internet, the use of domain literals is controversial;
8580 see the &%allow_domain_literals%& main option.
8582 The value for a match will be the string &`@[]`&.
8587 .cindex "@mx_primary"
8588 .cindex "@mx_secondary"
8589 .cindex "domain list" "matching MX pointers to local host"
8590 If a pattern consists of the string &`@mx_any`& it matches any domain that
8591 has an MX record pointing to the local host or to any host that is listed in
8592 .oindex "&%hosts_treat_as_local%&"
8593 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8594 are similar, except that the first matches only when a primary MX target is the
8595 local host, and the second only when no primary MX target is the local host,
8596 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8597 preference value &-- there may of course be more than one of them.
8599 The MX lookup that takes place when matching a pattern of this type is
8600 performed with the resolver options for widening names turned off. Thus, for
8601 example, a single-component domain will &'not'& be expanded by adding the
8602 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8603 options of the &(dnslookup)& router for a discussion of domain widening.
8605 Sometimes you may want to ignore certain IP addresses when using one of these
8606 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8607 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8608 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8609 on a router). For example:
8611 domains = @mx_any/ignore=127.0.0.1
8613 This example matches any domain that has an MX record pointing to one of
8614 the local host's IP addresses other than 127.0.0.1.
8616 The list of IP addresses is in fact processed by the same code that processes
8617 host lists, so it may contain CIDR-coded network specifications and it may also
8618 contain negative items.
8620 Because the list of IP addresses is a sublist within a domain list, you have to
8621 be careful about delimiters if there is more than one address. Like any other
8622 list, the default delimiter can be changed. Thus, you might have:
8624 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8625 an.other.domain : ...
8627 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8628 involved, it is easiest to change the delimiter for the main list as well:
8630 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8631 an.other.domain ? ...
8633 The value for a match will be the list element string (starting &`@mx_`&).
8637 .cindex "asterisk" "in domain list"
8638 .cindex "domain list" "asterisk in"
8639 .cindex "domain list" "matching &""ends with""&"
8640 If a pattern starts with an asterisk, the remaining characters of the pattern
8641 are compared with the terminating characters of the domain. The use of &"*"& in
8642 domain lists differs from its use in partial matching lookups. In a domain
8643 list, the character following the asterisk need not be a dot, whereas partial
8644 matching works only in terms of dot-separated components. For example, a domain
8645 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8648 The value for a match will be the list element string (starting with the asterisk).
8649 Additionally, &$0$& will be set to the matched string
8650 and &$1$& to the variable portion which the asterisk matched.
8653 .cindex "regular expressions" "in domain list"
8654 .cindex "domain list" "matching regular expression"
8655 If a pattern starts with a circumflex character, it is treated as a regular
8656 expression, and matched against the domain using a regular expression matching
8657 function. The circumflex is treated as part of the regular expression.
8658 Email domains are case-independent, so this regular expression match is by
8659 default case-independent, but you can make it case-dependent by starting it
8660 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8661 are given in chapter &<<CHAPregexp>>&.
8663 &*Warning*&: Because domain lists are expanded before being processed, you
8664 must escape any backslash and dollar characters in the regular expression, or
8665 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8666 it is not to be expanded (unless you really do want to build a regular
8667 expression by expansion, of course).
8669 The value for a match will be the list element string (starting with the circumflex).
8670 Additionally, &$0$& will be set to the string matching the regular expression,
8671 and &$1$& (onwards) to any submatches identified by parentheses.
8676 .cindex "lookup" "in domain list"
8677 .cindex "domain list" "matching by lookup"
8678 If a pattern starts with the name of a single-key lookup type followed by a
8679 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8680 must be a filename in a suitable format for the lookup type. For example, for
8681 &"cdb;"& it must be an absolute path:
8683 domains = cdb;/etc/mail/local_domains.cdb
8685 The appropriate type of lookup is done on the file using the domain name as the
8686 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8687 only in whether or not the key is present in the file. However, when a lookup
8688 is used for the &%domains%& option on a router
8689 or a &%domains%& condition in an ACL statement, the value is preserved in the
8690 &$domain_data$& variable and can be referred to in other router options or
8691 other statements in the same ACL.
8692 .cindex "tainted data" "de-tainting"
8693 The value will be untainted.
8697 Any of the single-key lookup type names may be preceded by
8698 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8700 domains = partial-dbm;/partial/domains
8702 This causes partial matching logic to be invoked; a description of how this
8703 works is given in section &<<SECTpartiallookup>>&.
8706 .cindex "asterisk" "in lookup type"
8707 Any of the single-key lookup types may be followed by an asterisk. This causes
8708 a default lookup for a key consisting of a single asterisk to be done if the
8709 original lookup fails. This is not a useful feature when using a domain list to
8710 select particular domains (because any domain would match), but it might have
8711 value if the result of the lookup is being used via the &$domain_data$&
8715 If the pattern starts with the name of a query-style lookup type followed by a
8716 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8717 pattern must be an appropriate query for the lookup type, as described in
8718 chapter &<<CHAPfdlookup>>&. For example:
8720 hold_domains = mysql;select domain from holdlist \
8721 where domain = '${quote_mysql:$domain}';
8723 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8724 example, it doesn't matter what field you select). Exim is interested only in
8725 whether or not the query succeeds. However, when a lookup is used for the
8726 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8727 variable and can be referred to in other options.
8728 .cindex "tainted data" "de-tainting"
8729 The value will be untainted.
8732 If the pattern starts with the name of a lookup type
8733 of either kind (single-key or query-style) it may be
8734 followed by a comma and options,
8735 The options are lookup-type specific and consist of a comma-separated list.
8736 Each item starts with a tag and and equals "=".
8739 .cindex "domain list" "matching literal domain name"
8740 If none of the above cases apply, a caseless textual comparison is made
8741 between the pattern and the domain.
8743 The value for a match will be the list element string.
8744 .cindex "tainted data" "de-tainting"
8745 Note that this is commonly untainted
8746 (depending on the way the list was created).
8747 Specifically, explicit text in the configuration file in not tainted.
8748 This is a useful way of obtaining an untainted equivalent to
8749 the domain, for later operations.
8751 However if the list (including one-element lists)
8752 is created by expanding a variable containing tainted data,
8753 it is tainted and so will the match value be.
8757 Here is an example that uses several different kinds of pattern:
8759 domainlist funny_domains = \
8762 *.foundation.fict.example : \
8763 \N^[1-2]\d{3}\.fict\.example$\N : \
8764 partial-dbm;/opt/data/penguin/book : \
8765 nis;domains.byname : \
8766 nisplus;[name=$domain,status=local],domains.org_dir
8768 There are obvious processing trade-offs among the various matching modes. Using
8769 an asterisk is faster than a regular expression, and listing a few names
8770 explicitly probably is too. The use of a file or database lookup is expensive,
8771 but may be the only option if hundreds of names are required. Because the
8772 patterns are tested in order, it makes sense to put the most commonly matched
8777 .section "Host lists" "SECThostlist"
8778 .cindex "host list" "patterns in"
8779 .cindex "list" "host list"
8780 Host lists are used to control what remote hosts are allowed to do. For
8781 example, some hosts may be allowed to use the local host as a relay, and some
8782 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8783 two different ways, by name or by IP address. In a host list, some types of
8784 pattern are matched to a host name, and some are matched to an IP address.
8785 You need to be particularly careful with this when single-key lookups are
8786 involved, to ensure that the right value is being used as the key.
8789 .section "Special host list patterns" "SECID80"
8790 .cindex "empty item in hosts list"
8791 .cindex "host list" "empty string in"
8792 If a host list item is the empty string, it matches only when no remote host is
8793 involved. This is the case when a message is being received from a local
8794 process using SMTP on the standard input, that is, when a TCP/IP connection is
8797 .cindex "asterisk" "in host list"
8798 The special pattern &"*"& in a host list matches any host or no host. Neither
8799 the IP address nor the name is actually inspected.
8803 .section "Host list patterns that match by IP address" "SECThoslispatip"
8804 .cindex "host list" "matching IP addresses"
8805 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8806 the incoming address actually appears in the IPv6 host as
8807 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8808 list, it is converted into a traditional IPv4 address first. (Not all operating
8809 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8812 The following types of pattern in a host list check the remote host by
8813 inspecting its IP address:
8816 If the pattern is a plain domain name (not a regular expression, not starting
8817 with *, not a lookup of any kind), Exim calls the operating system function
8818 to find the associated IP address(es). Exim uses the newer
8819 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8820 This typically causes a forward DNS lookup of the name. The result is compared
8821 with the IP address of the subject host.
8823 If there is a temporary problem (such as a DNS timeout) with the host name
8824 lookup, a temporary error occurs. For example, if the list is being used in an
8825 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8826 temporary SMTP error code. If no IP address can be found for the host name,
8827 what happens is described in section &<<SECTbehipnot>>& below.
8830 .cindex "@ in a host list"
8831 If the pattern is &"@"&, the primary host name is substituted and used as a
8832 domain name, as just described.
8835 If the pattern is an IP address, it is matched against the IP address of the
8836 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8837 IPv6 addresses can be given in colon-separated format, but the colons have to
8838 be doubled so as not to be taken as item separators when the default list
8839 separator is used. IPv6 addresses are recognized even when Exim is compiled
8840 without IPv6 support. This means that if they appear in a host list on an
8841 IPv4-only host, Exim will not treat them as host names. They are just addresses
8842 that can never match a client host.
8845 .cindex "@[] in a host list"
8846 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8847 the local host. For example, if the local host is an IPv4 host with one
8848 interface address 10.45.23.56, these two ACL statements have the same effect:
8850 accept hosts = 127.0.0.1 : 10.45.23.56
8854 .cindex "CIDR notation"
8855 If the pattern is an IP address followed by a slash and a mask length (for
8856 example 10.11.42.0/24), it is matched against the IP address of the subject
8857 host under the given mask. This allows, an entire network of hosts to be
8858 included (or excluded) by a single item. The mask uses CIDR notation; it
8859 specifies the number of address bits that must match, starting from the most
8860 significant end of the address.
8862 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8863 of a range of addresses. It is the number of bits in the network portion of the
8864 address. The above example specifies a 24-bit netmask, so it matches all 256
8865 addresses in the 10.11.42.0 network. An item such as
8869 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8870 32 for an IPv4 address is the same as no mask at all; just a single address
8873 Here is another example which shows an IPv4 and an IPv6 network:
8875 recipient_unqualified_hosts = 192.168.0.0/16: \
8876 3ffe::ffff::836f::::/48
8878 The doubling of list separator characters applies only when these items
8879 appear inline in a host list. It is not required when indirecting via a file.
8882 recipient_unqualified_hosts = /opt/exim/unqualnets
8884 could make use of a file containing
8889 to have exactly the same effect as the previous example. When listing IPv6
8890 addresses inline, it is usually more convenient to use the facility for
8891 changing separator characters. This list contains the same two networks:
8893 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8896 The separator is changed to semicolon by the leading &"<;"& at the start of the
8902 .section "Host list patterns for single-key lookups by host address" &&&
8903 "SECThoslispatsikey"
8904 .cindex "host list" "lookup of IP address"
8905 When a host is to be identified by a single-key lookup of its complete IP
8906 address, the pattern takes this form:
8908 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8912 hosts_lookup = net-cdb;/hosts-by-ip.db
8914 The text form of the IP address of the subject host is used as the lookup key.
8915 IPv6 addresses are converted to an unabbreviated form, using lower case
8916 letters, with dots as separators because colon is the key terminator in
8917 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8918 quoting the keys, but this is a facility that was added later.] The data
8919 returned by the lookup is not used.
8921 .cindex "IP address" "masking"
8922 .cindex "host list" "masked IP address"
8923 Single-key lookups can also be performed using masked IP addresses, using
8924 patterns of this form:
8926 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8930 net24-dbm;/networks.db
8932 The IP address of the subject host is masked using <&'number'&> as the mask
8933 length. A textual string is constructed from the masked value, followed by the
8934 mask, and this is used as the lookup key. For example, if the host's IP address
8935 is 192.168.34.6, the key that is looked up for the above example is
8936 &"192.168.34.0/24"&.
8938 When an IPv6 address is converted to a string, dots are normally used instead
8939 of colons, so that keys in &(lsearch)& files need not contain colons (which
8940 terminate &(lsearch)& keys). This was implemented some time before the ability
8941 to quote keys was made available in &(lsearch)& files. However, the more
8942 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8943 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8944 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8945 converted using colons and not dots.
8946 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
8947 addresses are always used.
8948 The latter are converted to IPv4 addresses, in dotted-quad form.
8950 Ideally, it would be nice to tidy up this anomalous situation by changing to
8951 colons in all cases, given that quoting is now available for &(lsearch)&.
8952 However, this would be an incompatible change that might break some existing
8955 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8956 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8957 the former case the key strings include the mask value, whereas in the latter
8958 case the IP address is used on its own.
8962 .section "Host list patterns that match by host name" "SECThoslispatnam"
8963 .cindex "host" "lookup failures"
8964 .cindex "unknown host name"
8965 .cindex "host list" "matching host name"
8966 There are several types of pattern that require Exim to know the name of the
8967 remote host. These are either wildcard patterns or lookups by name. (If a
8968 complete hostname is given without any wildcarding, it is used to find an IP
8969 address to match against, as described in section &<<SECThoslispatip>>&
8972 If the remote host name is not already known when Exim encounters one of these
8973 patterns, it has to be found from the IP address.
8974 Although many sites on the Internet are conscientious about maintaining reverse
8975 DNS data for their hosts, there are also many that do not do this.
8976 Consequently, a name cannot always be found, and this may lead to unwanted
8977 effects. Take care when configuring host lists with wildcarded name patterns.
8978 Consider what will happen if a name cannot be found.
8980 Because of the problems of determining host names from IP addresses, matching
8981 against host names is not as common as matching against IP addresses.
8983 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8984 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8985 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8986 are done can be changed by setting the &%host_lookup_order%& option. For
8987 security, once Exim has found one or more names, it looks up the IP addresses
8988 for these names and compares them with the IP address that it started with.
8989 Only those names whose IP addresses match are accepted. Any other names are
8990 discarded. If no names are left, Exim behaves as if the host name cannot be
8991 found. In the most common case there is only one name and one IP address.
8993 There are some options that control what happens if a host name cannot be
8994 found. These are described in section &<<SECTbehipnot>>& below.
8996 .cindex "host" "alias for"
8997 .cindex "alias for host"
8998 As a result of aliasing, hosts may have more than one name. When processing any
8999 of the following types of pattern, all the host's names are checked:
9002 .cindex "asterisk" "in host list"
9003 If a pattern starts with &"*"& the remainder of the item must match the end of
9004 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9005 &'.b.c'&. This special simple form is provided because this is a very common
9006 requirement. Other kinds of wildcarding require the use of a regular
9009 .cindex "regular expressions" "in host list"
9010 .cindex "host list" "regular expression in"
9011 If the item starts with &"^"& it is taken to be a regular expression which is
9012 matched against the host name. Host names are case-independent, so this regular
9013 expression match is by default case-independent, but you can make it
9014 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9015 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9020 is a regular expression that matches either of the two hosts &'a.c.d'& or
9021 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9022 that backslash and dollar characters are not misinterpreted as part of the
9023 string expansion. The simplest way to do this is to use &`\N`& to mark that
9024 part of the string as non-expandable. For example:
9026 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9028 &*Warning*&: If you want to match a complete host name, you must include the
9029 &`$`& terminating metacharacter in the regular expression, as in the above
9030 example. Without it, a match at the start of the host name is all that is
9037 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9038 .cindex "host" "lookup failures, permanent"
9039 While processing a host list, Exim may need to look up an IP address from a
9040 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9041 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9042 behaviour when it fails to find the information it is seeking is the same.
9044 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9045 apply to temporary DNS errors, whose handling is described in the next section.
9047 .cindex "&`+include_unknown`&"
9048 .cindex "&`+ignore_unknown`&"
9049 Exim parses a host list from left to right. If it encounters a permanent
9050 lookup failure in any item in the host list before it has found a match,
9051 Exim treats it as a failure and the default behavior is as if the host
9052 does not match the list. This may not always be what you want to happen.
9053 To change Exim's behaviour, the special items &`+include_unknown`& or
9054 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9055 not recognized in an indirected file).
9058 If any item that follows &`+include_unknown`& requires information that
9059 cannot found, Exim behaves as if the host does match the list. For example,
9061 host_reject_connection = +include_unknown:*.enemy.ex
9063 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9064 any hosts whose name it cannot find.
9067 If any item that follows &`+ignore_unknown`& requires information that cannot
9068 be found, Exim ignores that item and proceeds to the rest of the list. For
9071 accept hosts = +ignore_unknown : friend.example : \
9074 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9075 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9076 name can be found for 192.168.4.5, it is rejected.
9079 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9080 list. The effect of each one lasts until the next, or until the end of the
9083 .section "Mixing wildcarded host names and addresses in host lists" &&&
9085 .cindex "host list" "mixing names and addresses in"
9087 This section explains the host/ip processing logic with the same concepts
9088 as the previous section, but specifically addresses what happens when a
9089 wildcarded hostname is one of the items in the hostlist.
9092 If you have name lookups or wildcarded host names and
9093 IP addresses in the same host list, you should normally put the IP
9094 addresses first. For example, in an ACL you could have:
9096 accept hosts = 10.9.8.7 : *.friend.example
9098 The reason you normally would order it this way lies in the
9099 left-to-right way that Exim processes lists. It can test IP addresses
9100 without doing any DNS lookups, but when it reaches an item that requires
9101 a host name, it fails if it cannot find a host name to compare with the
9102 pattern. If the above list is given in the opposite order, the
9103 &%accept%& statement fails for a host whose name cannot be found, even
9104 if its IP address is 10.9.8.7.
9107 If you really do want to do the name check first, and still recognize the IP
9108 address, you can rewrite the ACL like this:
9110 accept hosts = *.friend.example
9111 accept hosts = 10.9.8.7
9113 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9114 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9115 &`+ignore_unknown`&, which was discussed in depth in the first example in
9120 .section "Temporary DNS errors when looking up host information" &&&
9122 .cindex "host" "lookup failures, temporary"
9123 .cindex "&`+include_defer`&"
9124 .cindex "&`+ignore_defer`&"
9125 A temporary DNS lookup failure normally causes a defer action (except when
9126 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9127 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9128 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9129 section. These options should be used with care, probably only in non-critical
9130 host lists such as whitelists.
9134 .section "Host list patterns for single-key lookups by host name" &&&
9135 "SECThoslispatnamsk"
9136 .cindex "unknown host name"
9137 .cindex "host list" "matching host name"
9138 If a pattern is of the form
9140 <&'single-key-search-type'&>;<&'search-data'&>
9144 dbm;/host/accept/list
9146 a single-key lookup is performed, using the host name as its key. If the
9147 lookup succeeds, the host matches the item. The actual data that is looked up
9150 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9151 keys in the file, not IP addresses. If you want to do lookups based on IP
9152 addresses, you must precede the search type with &"net-"& (see section
9153 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9154 two items in the same list, one doing an address lookup and one doing a name
9155 lookup, both using the same file.
9159 .section "Host list patterns for query-style lookups" "SECID81"
9160 If a pattern is of the form
9162 <&'query-style-search-type'&>;<&'query'&>
9164 the query is obeyed, and if it succeeds, the host matches the item. The actual
9165 data that is looked up is not used. The variables &$sender_host_address$& and
9166 &$sender_host_name$& can be used in the query. For example:
9168 hosts_lookup = pgsql;\
9169 select ip from hostlist where ip='$sender_host_address'
9171 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9172 can use the &%sg%& expansion item to change this if you need to. If you want to
9173 use masked IP addresses in database queries, you can use the &%mask%& expansion
9176 If the query contains a reference to &$sender_host_name$&, Exim automatically
9177 looks up the host name if it has not already done so. (See section
9178 &<<SECThoslispatnam>>& for comments on finding host names.)
9180 Historical note: prior to release 4.30, Exim would always attempt to find a
9181 host name before running the query, unless the search type was preceded by
9182 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9183 still recognized for query-style lookups, but its presence or absence has no
9184 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9185 See section &<<SECThoslispatsikey>>&.)
9191 .section "Address lists" "SECTaddresslist"
9192 .cindex "list" "address list"
9193 .cindex "address list" "empty item"
9194 .cindex "address list" "patterns"
9195 Address lists contain patterns that are matched against mail addresses. There
9196 is one special case to be considered: the sender address of a bounce message is
9197 always empty. You can test for this by providing an empty item in an address
9198 list. For example, you can set up a router to process bounce messages by
9199 using this option setting:
9203 The presence of the colon creates an empty item. If you do not provide any
9204 data, the list is empty and matches nothing. The empty sender can also be
9205 detected by a regular expression that matches an empty string,
9206 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9208 Non-empty items in an address list can be straightforward email addresses. For
9211 senders = jbc@askone.example : hs@anacreon.example
9213 A certain amount of wildcarding is permitted. If a pattern contains an @
9214 character, but is not a regular expression and does not begin with a
9215 semicolon-terminated lookup type (described below), the local part of the
9216 subject address is compared with the local part of the pattern, which may start
9217 with an asterisk. If the local parts match, the domain is checked in exactly
9218 the same way as for a pattern in a domain list. For example, the domain can be
9219 wildcarded, refer to a named list, or be a lookup:
9221 deny senders = *@*.spamming.site:\
9222 *@+hostile_domains:\
9223 bozo@partial-lsearch;/list/of/dodgy/sites:\
9224 *@dbm;/bad/domains.db
9226 .cindex "local part" "starting with !"
9227 .cindex "address list" "local part starting with !"
9228 If a local part that begins with an exclamation mark is required, it has to be
9229 specified using a regular expression, because otherwise the exclamation mark is
9230 treated as a sign of negation, as is standard in lists.
9232 If a non-empty pattern that is not a regular expression or a lookup does not
9233 contain an @ character, it is matched against the domain part of the subject
9234 address. The only two formats that are recognized this way are a literal
9235 domain, or a domain pattern that starts with *. In both these cases, the effect
9236 is the same as if &`*@`& preceded the pattern. For example:
9238 deny senders = enemy.domain : *.enemy.domain
9241 The following kinds of more complicated address list pattern can match any
9242 address, including the empty address that is characteristic of bounce message
9246 .cindex "regular expressions" "in address list"
9247 .cindex "address list" "regular expression in"
9248 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9249 done against the complete address, with the pattern as the regular expression.
9250 You must take care that backslash and dollar characters are not misinterpreted
9251 as part of the string expansion. The simplest way to do this is to use &`\N`&
9252 to mark that part of the string as non-expandable. For example:
9254 deny senders = \N^.*this.*@example\.com$\N : \
9255 \N^\d{8}.+@spamhaus.example$\N : ...
9257 The &`\N`& sequences are removed by the expansion, so these items do indeed
9258 start with &"^"& by the time they are being interpreted as address patterns.
9261 .cindex "address list" "lookup for complete address"
9262 Complete addresses can be looked up by using a pattern that starts with a
9263 lookup type terminated by a semicolon, followed by the data for the lookup. For
9266 deny senders = cdb;/etc/blocked.senders : \
9267 mysql;select address from blocked where \
9268 address='${quote_mysql:$sender_address}'
9270 Both query-style and single-key lookup types can be used. For a single-key
9271 lookup type, Exim uses the complete address as the key. However, empty keys are
9272 not supported for single-key lookups, so a match against the empty address
9273 always fails. This restriction does not apply to query-style lookups.
9275 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9276 cannot be used, and is ignored if specified, with an entry being written to the
9278 .cindex "*@ with single-key lookup"
9279 However, you can configure lookup defaults, as described in section
9280 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9281 default. For example, with this lookup:
9283 accept senders = lsearch*@;/some/file
9285 the file could contains lines like this:
9287 user1@domain1.example
9290 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9293 nimrod@jaeger.example
9297 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9298 would mean that every address matches, thus rendering the test useless.
9300 &*Warning 2*&: Do not confuse these two kinds of item:
9302 deny recipients = dbm*@;/some/file
9303 deny recipients = *@dbm;/some/file
9305 The first does a whole address lookup, with defaulting, as just described,
9306 because it starts with a lookup type. The second matches the local part and
9307 domain independently, as described in a bullet point below.
9311 The following kinds of address list pattern can match only non-empty addresses.
9312 If the subject address is empty, a match against any of these pattern types
9317 .cindex "@@ with single-key lookup"
9318 .cindex "address list" "@@ lookup type"
9319 .cindex "address list" "split local part and domain"
9320 If a pattern starts with &"@@"& followed by a single-key lookup item
9321 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9322 split into a local part and a domain. The domain is looked up in the file. If
9323 it is not found, there is no match. If it is found, the data that is looked up
9324 from the file is treated as a colon-separated list of local part patterns, each
9325 of which is matched against the subject local part in turn.
9327 .cindex "asterisk" "in address list"
9328 The lookup may be a partial one, and/or one involving a search for a default
9329 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9330 patterns that are looked up can be regular expressions or begin with &"*"&, or
9331 even be further lookups. They may also be independently negated. For example,
9334 deny senders = @@dbm;/etc/reject-by-domain
9336 the data from which the DBM file is built could contain lines like
9338 baddomain.com: !postmaster : *
9340 to reject all senders except &%postmaster%& from that domain.
9342 .cindex "local part" "starting with !"
9343 If a local part that actually begins with an exclamation mark is required, it
9344 has to be specified using a regular expression. In &(lsearch)& files, an entry
9345 may be split over several lines by indenting the second and subsequent lines,
9346 but the separating colon must still be included at line breaks. White space
9347 surrounding the colons is ignored. For example:
9349 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9352 As in all colon-separated lists in Exim, a colon can be included in an item by
9355 If the last item in the list starts with a right angle-bracket, the remainder
9356 of the item is taken as a new key to look up in order to obtain a continuation
9357 list of local parts. The new key can be any sequence of characters. Thus one
9358 might have entries like
9360 aol.com: spammer1 : spammer 2 : >*
9361 xyz.com: spammer3 : >*
9364 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9365 local parts for all domains, in addition to the specific local parts listed for
9366 each domain. Of course, using this feature costs another lookup each time a
9367 chain is followed, but the effort needed to maintain the data is reduced.
9369 .cindex "loop" "in lookups"
9370 It is possible to construct loops using this facility, and in order to catch
9371 them, the chains may be no more than fifty items long.
9374 The @@<&'lookup'&> style of item can also be used with a query-style
9375 lookup, but in this case, the chaining facility is not available. The lookup
9376 can only return a single list of local parts.
9379 &*Warning*&: There is an important difference between the address list items
9380 in these two examples:
9383 senders = *@+my_list
9385 In the first one, &`my_list`& is a named address list, whereas in the second
9386 example it is a named domain list.
9391 .section "Case of letters in address lists" "SECTcasletadd"
9392 .cindex "case of local parts"
9393 .cindex "address list" "case forcing"
9394 .cindex "case forcing in address lists"
9395 Domains in email addresses are always handled caselessly, but for local parts
9396 case may be significant on some systems (see &%caseful_local_part%& for how
9397 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9398 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9399 blocking lists should be done in a case-independent manner. Since most address
9400 lists in Exim are used for this kind of control, Exim attempts to do this by
9403 The domain portion of an address is always lowercased before matching it to an
9404 address list. The local part is lowercased by default, and any string
9405 comparisons that take place are done caselessly. This means that the data in
9406 the address list itself, in files included as plain filenames, and in any file
9407 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9408 keys in files that are looked up by a search type other than &(lsearch)& (which
9409 works caselessly) must be in lower case, because these lookups are not
9412 .cindex "&`+caseful`&"
9413 To allow for the possibility of caseful address list matching, if an item in
9414 an address list is the string &"+caseful"&, the original case of the local
9415 part is restored for any comparisons that follow, and string comparisons are no
9416 longer case-independent. This does not affect the domain, which remains in
9417 lower case. However, although independent matches on the domain alone are still
9418 performed caselessly, regular expressions that match against an entire address
9419 become case-sensitive after &"+caseful"& has been seen.
9423 .section "Local part lists" "SECTlocparlis"
9424 .cindex "list" "local part list"
9425 .cindex "local part" "list"
9426 Case-sensitivity in local part lists is handled in the same way as for address
9427 lists, as just described. The &"+caseful"& item can be used if required. In a
9428 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9429 set false, the subject is lowercased and the matching is initially
9430 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9431 matching in the local part list, but not elsewhere in the router. If
9432 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9433 option is case-sensitive from the start.
9435 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9436 comments are handled in the same way as address lists &-- they are recognized
9437 only if the # is preceded by white space or the start of the line.
9438 Otherwise, local part lists are matched in the same way as domain lists, except
9439 that the special items that refer to the local host (&`@`&, &`@[]`&,
9440 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9441 Refer to section &<<SECTdomainlist>>& for details of the other available item
9443 .ecindex IIDdohoadli
9448 . ////////////////////////////////////////////////////////////////////////////
9449 . ////////////////////////////////////////////////////////////////////////////
9451 .chapter "String expansions" "CHAPexpand"
9452 .scindex IIDstrexp "expansion" "of strings"
9453 Many strings in Exim's runtime configuration are expanded before use. Some of
9454 them are expanded every time they are used; others are expanded only once.
9456 When a string is being expanded it is copied verbatim from left to right except
9457 .cindex expansion "string concatenation"
9458 when a dollar or backslash character is encountered. A dollar specifies the
9459 start of a portion of the string that is interpreted and replaced as described
9460 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9461 escape character, as described in the following section.
9463 Whether a string is expanded depends upon the context. Usually this is solely
9464 dependent upon the option for which a value is sought; in this documentation,
9465 options for which string expansion is performed are marked with † after
9466 the data type. ACL rules always expand strings. A couple of expansion
9467 conditions do not expand some of the brace-delimited branches, for security
9469 .cindex "tainted data" expansion
9470 .cindex "tainted data" definition
9471 .cindex expansion "tainted data"
9472 and expansion of data deriving from the sender (&"tainted data"&)
9476 Common ways of obtaining untainted equivalents of variables with
9478 .cindex "tainted data" "de-tainting"
9479 come down to using the tainted value as a lookup key in a trusted database.
9480 This database could be the filesystem structure,
9481 or the password file,
9482 or accessed via a DBMS.
9483 Specific methods are indexed under &"de-tainting"&.
9488 .section "Literal text in expanded strings" "SECTlittext"
9489 .cindex "expansion" "including literal text"
9490 An uninterpreted dollar can be included in an expanded string by putting a
9491 backslash in front of it. A backslash can be used to prevent any special
9492 character being treated specially in an expansion, including backslash itself.
9493 If the string appears in quotes in the configuration file, two backslashes are
9494 required because the quotes themselves cause interpretation of backslashes when
9495 the string is read in (see section &<<SECTstrings>>&).
9497 .cindex "expansion" "non-expandable substrings"
9498 A portion of the string can specified as non-expandable by placing it between
9499 two occurrences of &`\N`&. This is particularly useful for protecting regular
9500 expressions, which often contain backslashes and dollar signs. For example:
9502 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9504 On encountering the first &`\N`&, the expander copies subsequent characters
9505 without interpretation until it reaches the next &`\N`& or the end of the
9510 .section "Character escape sequences in expanded strings" "SECID82"
9511 .cindex "expansion" "escape sequences"
9512 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9513 expanded string is recognized as an escape sequence for the character newline,
9514 carriage return, or tab, respectively. A backslash followed by up to three
9515 octal digits is recognized as an octal encoding for a single character, and a
9516 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9519 These escape sequences are also recognized in quoted strings when they are read
9520 in. Their interpretation in expansions as well is useful for unquoted strings,
9521 and for other cases such as looked-up strings that are then expanded.
9524 .section "Testing string expansions" "SECID83"
9525 .cindex "expansion" "testing"
9526 .cindex "testing" "string expansion"
9528 Many expansions can be tested by calling Exim with the &%-be%& option. This
9529 takes the command arguments, or lines from the standard input if there are no
9530 arguments, runs them through the string expansion code, and writes the results
9531 to the standard output. Variables based on configuration values are set up, but
9532 since no message is being processed, variables such as &$local_part$& have no
9533 value. Nevertheless the &%-be%& option can be useful for checking out file and
9534 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9537 Exim gives up its root privilege when it is called with the &%-be%& option, and
9538 instead runs under the uid and gid it was called with, to prevent users from
9539 using &%-be%& for reading files to which they do not have access.
9542 If you want to test expansions that include variables whose values are taken
9543 from a message, there are two other options that can be used. The &%-bem%&
9544 option is like &%-be%& except that it is followed by a filename. The file is
9545 read as a message before doing the test expansions. For example:
9547 exim -bem /tmp/test.message '$h_subject:'
9549 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9550 Exim message identifier. For example:
9552 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9554 This loads the message from Exim's spool before doing the test expansions, and
9555 is therefore restricted to admin users.
9558 .section "Forced expansion failure" "SECTforexpfai"
9559 .cindex "expansion" "forced failure"
9560 A number of expansions that are described in the following section have
9561 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9562 (which are sometimes called &"curly brackets"&). Which of the two strings is
9563 used depends on some condition that is evaluated as part of the expansion. If,
9564 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9565 the entire string expansion fails in a way that can be detected by the code
9566 that requested the expansion. This is called &"forced expansion failure"&, and
9567 its consequences depend on the circumstances. In some cases it is no different
9568 from any other expansion failure, but in others a different action may be
9569 taken. Such variations are mentioned in the documentation of the option that is
9575 .section "Expansion items" "SECTexpansionitems"
9576 The following items are recognized in expanded strings. White space may be used
9577 between sub-items that are keywords or substrings enclosed in braces inside an
9578 outer set of braces, to improve readability. &*Warning*&: Within braces,
9579 white space is significant.
9582 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9583 .cindex "expansion" "variables"
9584 Substitute the contents of the named variable, for example:
9589 The second form can be used to separate the name from subsequent alphanumeric
9590 characters. This form (using braces) is available only for variables; it does
9591 &'not'& apply to message headers. The names of the variables are given in
9592 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9593 given, the expansion fails.
9595 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9596 .cindex "expansion" "operators"
9597 The string is first itself expanded, and then the operation specified by
9598 <&'op'&> is applied to it. For example:
9602 The string starts with the first character after the colon, which may be
9603 leading white space. A list of operators is given in section &<<SECTexpop>>&
9604 below. The operator notation is used for simple expansion items that have just
9605 one argument, because it reduces the number of braces and therefore makes the
9606 string easier to understand.
9608 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9609 This item inserts &"basic"& header lines. It is described with the &%header%&
9610 expansion item below.
9613 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9614 .cindex "expansion" "calling an acl"
9615 .cindex "&%acl%&" "call from expansion"
9616 The name and zero to nine argument strings are first expanded separately. The expanded
9617 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9618 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9619 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9620 and may use the variables; if another acl expansion is used the values
9621 are restored after it returns. If the ACL sets
9622 a value using a "message =" modifier and returns accept or deny, the value becomes
9623 the result of the expansion.
9624 If no message is set and the ACL returns accept or deny
9625 the expansion result is an empty string.
9626 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9629 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9630 .cindex authentication "results header"
9631 .cindex headers "authentication-results:"
9632 .cindex authentication "expansion item"
9633 This item returns a string suitable for insertion as an
9634 &'Authentication-Results:'&
9636 The given <&'authserv-id'&> is included in the result; typically this
9637 will be a domain name identifying the system performing the authentications.
9638 Methods that might be present in the result include:
9647 Example use (as an ACL modifier):
9649 add_header = :at_start:${authresults {$primary_hostname}}
9651 This is safe even if no authentication results are available.
9654 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9655 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9656 .cindex "expansion" "extracting certificate fields"
9657 .cindex "&%certextract%&" "certificate fields"
9658 .cindex "certificate" "extracting fields"
9659 The <&'certificate'&> must be a variable of type certificate.
9660 The field name is expanded and used to retrieve the relevant field from
9661 the certificate. Supported fields are:
9665 &`subject `& RFC4514 DN
9666 &`issuer `& RFC4514 DN
9671 &`subj_altname `& tagged list
9675 If the field is found,
9676 <&'string2'&> is expanded, and replaces the whole item;
9677 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9678 variable &$value$& contains the value that has been extracted. Afterwards, it
9679 is restored to any previous value it might have had.
9681 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9682 key is not found. If {<&'string2'&>} is also omitted, the value that was
9685 Some field names take optional modifiers, appended and separated by commas.
9687 The field selectors marked as "RFC4514" above
9688 output a Distinguished Name string which is
9690 parseable by Exim as a comma-separated tagged list
9691 (the exceptions being elements containing commas).
9692 RDN elements of a single type may be selected by
9693 a modifier of the type label; if so the expansion
9694 result is a list (newline-separated by default).
9695 The separator may be changed by another modifier of
9696 a right angle-bracket followed immediately by the new separator.
9697 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9699 The field selectors marked as "time" above
9700 take an optional modifier of "int"
9701 for which the result is the number of seconds since epoch.
9702 Otherwise the result is a human-readable string
9703 in the timezone selected by the main "timezone" option.
9705 The field selectors marked as "list" above return a list,
9706 newline-separated by default,
9707 (embedded separator characters in elements are doubled).
9708 The separator may be changed by a modifier of
9709 a right angle-bracket followed immediately by the new separator.
9711 The field selectors marked as "tagged" above
9712 prefix each list element with a type string and an equals sign.
9713 Elements of only one type may be selected by a modifier
9714 which is one of "dns", "uri" or "mail";
9715 if so the element tags are omitted.
9717 If not otherwise noted field values are presented in human-readable form.
9719 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9720 {*&<&'arg'&>&*}...}*&"
9722 This expansion dynamically loads and then calls a locally-written C function.
9723 This functionality is available only if Exim is compiled with
9727 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9728 object so that it doesn't reload the same object file in the same Exim process
9729 (but of course Exim does start new processes frequently).
9731 There may be from zero to eight arguments to the function.
9734 a local function that is to be called in this way,
9735 first &_DLFUNC_IMPL_& should be defined,
9736 and second &_local_scan.h_& should be included.
9737 The Exim variables and functions that are defined by that API
9738 are also available for dynamically loaded functions. The function itself
9739 must have the following type:
9741 int dlfunction(uschar **yield, int argc, uschar *argv[])
9743 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9744 function should return one of the following values:
9746 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9747 into the expanded string that is being built.
9749 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9750 from &'yield'&, if it is set.
9752 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9753 taken from &'yield'& if it is set.
9755 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9757 When compiling a function that is to be used in this way with gcc,
9758 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9759 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9762 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9763 .cindex "expansion" "extracting value from environment"
9764 .cindex "environment" "values from"
9765 The key is first expanded separately, and leading and trailing white space
9767 This is then searched for as a name in the environment.
9768 If a variable is found then its value is placed in &$value$&
9769 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9771 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9772 appear, for example:
9774 ${env{USER}{$value} fail }
9776 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9777 {<&'string1'&>} must be present for &"fail"& to be recognized.
9779 If {<&'string2'&>} is omitted an empty string is substituted on
9781 If {<&'string1'&>} is omitted the search result is substituted on
9784 The environment is adjusted by the &%keep_environment%& and
9785 &%add_environment%& main section options.
9788 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9789 {*&<&'string3'&>&*}}*&"
9790 .cindex "expansion" "extracting substrings by key"
9791 .cindex "&%extract%&" "substrings by key"
9792 The key and <&'string1'&> are first expanded separately. Leading and trailing
9793 white space is removed from the key (but not from any of the strings). The key
9794 must not be empty and must not consist entirely of digits.
9795 The expanded <&'string1'&> must be of the form:
9797 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9800 where the equals signs and spaces (but not both) are optional. If any of the
9801 values contain white space, they must be enclosed in double quotes, and any
9802 values that are enclosed in double quotes are subject to escape processing as
9803 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9804 for the value that corresponds to the key. The search is case-insensitive. If
9805 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9806 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9807 variable &$value$& contains the value that has been extracted. Afterwards, it
9808 is restored to any previous value it might have had.
9810 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9811 key is not found. If {<&'string2'&>} is also omitted, the value that was
9812 extracted is used. Thus, for example, these two expansions are identical, and
9815 ${extract{gid}{uid=1984 gid=2001}}
9816 ${extract{gid}{uid=1984 gid=2001}{$value}}
9818 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9819 appear, for example:
9821 ${extract{Z}{A=... B=...}{$value} fail }
9823 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9824 {<&'string2'&>} must be present for &"fail"& to be recognized.
9826 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9827 {*&<&'string3'&>&*}}*&" &&&
9828 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9829 {*&<&'string3'&>&*}}*&"
9830 .cindex "expansion" "extracting from JSON object"
9831 .cindex JSON expansions
9832 The key and <&'string1'&> are first expanded separately. Leading and trailing
9833 white space is removed from the key (but not from any of the strings). The key
9834 must not be empty and must not consist entirely of digits.
9835 The expanded <&'string1'&> must be of the form:
9837 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9840 The braces, commas and colons, and the quoting of the member name are required;
9841 the spaces are optional.
9842 Matching of the key against the member names is done case-sensitively.
9843 For the &"json"& variant,
9844 if a returned value is a JSON string, it retains its leading and
9846 For the &"jsons"& variant, which is intended for use with JSON strings, the
9847 leading and trailing quotes are removed from the returned value.
9848 . XXX should be a UTF-8 compare
9850 The results of matching are handled as above.
9853 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9854 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9855 .cindex "expansion" "extracting substrings by number"
9856 .cindex "&%extract%&" "substrings by number"
9857 The <&'number'&> argument must consist entirely of decimal digits,
9858 apart from leading and trailing white space, which is ignored.
9859 This is what distinguishes this form of &%extract%& from the previous kind. It
9860 behaves in the same way, except that, instead of extracting a named field, it
9861 extracts from <&'string1'&> the field whose number is given as the first
9862 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9863 <&'string3'&> as before.
9865 The fields in the string are separated by any one of the characters in the
9866 separator string. These may include space or tab characters.
9867 The first field is numbered one. If the number is negative, the fields are
9868 counted from the end of the string, with the rightmost one numbered -1. If the
9869 number given is zero, the entire string is returned. If the modulus of the
9870 number is greater than the number of fields in the string, the result is the
9871 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9872 provided. For example:
9874 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9878 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9880 yields &"99"&. Two successive separators mean that the field between them is
9881 empty (for example, the fifth field above).
9884 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
9885 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
9886 "&*${extract jsons{*&<&'number'&>&*}}&&&
9887 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9888 .cindex "expansion" "extracting from JSON array"
9889 .cindex JSON expansions
9890 The <&'number'&> argument must consist entirely of decimal digits,
9891 apart from leading and trailing white space, which is ignored.
9893 Field selection and result handling is as above;
9894 there is no choice of field separator.
9895 For the &"json"& variant,
9896 if a returned value is a JSON string, it retains its leading and
9898 For the &"jsons"& variant, which is intended for use with JSON strings, the
9899 leading and trailing quotes are removed from the returned value.
9902 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9903 .cindex "list" "selecting by condition"
9904 .cindex "expansion" "selecting from list by condition"
9906 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9907 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9909 in this list, its value is place in &$item$&, and then the condition is
9910 evaluated. If the condition is true, &$item$& is added to the output as an
9911 item in a new list; if the condition is false, the item is discarded. The
9912 separator used for the output list is the same as the one used for the
9913 input, but a separator setting is not included in the output. For example:
9915 ${filter{a:b:c}{!eq{$item}{b}}}
9917 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9918 to what it was before. See also the &%map%& and &%reduce%& expansion items.
9921 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9922 .cindex "hash function" "textual"
9923 .cindex "expansion" "textual hash"
9924 This is a textual hashing function, and was the first to be implemented in
9925 early versions of Exim. In current releases, there are other hashing functions
9926 (numeric, MD5, and SHA-1), which are described below.
9928 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9929 <&'n'&>. If you are using fixed values for these numbers, that is, if
9930 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9931 use the simpler operator notation that avoids some of the braces:
9933 ${hash_<n>_<m>:<string>}
9935 The second number is optional (in both notations). If <&'n'&> is greater than
9936 or equal to the length of the string, the expansion item returns the string.
9937 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9938 function to the string. The new string consists of characters taken from the
9939 first <&'m'&> characters of the string
9941 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9943 If <&'m'&> is not present the value 26 is used, so that only lower case
9944 letters appear. For example:
9946 &`$hash{3}{monty}} `& yields &`jmg`&
9947 &`$hash{5}{monty}} `& yields &`monty`&
9948 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9951 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9952 &*$h_*&<&'header&~name'&>&*:*&" &&&
9953 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9954 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9955 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9956 &*$lh_*&<&'header&~name'&>&*:*&" &&&
9957 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9958 &*$rh_*&<&'header&~name'&>&*:*&"
9959 .cindex "expansion" "header insertion"
9960 .vindex "&$header_$&"
9961 .vindex "&$bheader_$&"
9962 .vindex "&$lheader_$&"
9963 .vindex "&$rheader_$&"
9964 .cindex "header lines" "in expansion strings"
9965 .cindex "header lines" "character sets"
9966 .cindex "header lines" "decoding"
9967 Substitute the contents of the named message header line, for example
9971 The newline that terminates a header line is not included in the expansion, but
9972 internal newlines (caused by splitting the header line over several physical
9973 lines) may be present.
9975 The difference between the four pairs of expansions is in the way
9976 the data in the header line is interpreted.
9979 .cindex "white space" "in header lines"
9980 &%rheader%& gives the original &"raw"& content of the header line, with no
9981 processing at all, and without the removal of leading and trailing white space.
9984 .cindex "list" "of header lines"
9985 &%lheader%& gives a colon-separated list, one element per header when there
9986 are multiple headers with a given name.
9987 Any embedded colon characters within an element are doubled, so normal Exim
9988 list-processing facilities can be used.
9989 The terminating newline of each element is removed; in other respects
9990 the content is &"raw"&.
9993 .cindex "base64 encoding" "in header lines"
9994 &%bheader%& removes leading and trailing white space, and then decodes base64
9995 or quoted-printable MIME &"words"& within the header text, but does no
9996 character set translation. If decoding of what looks superficially like a MIME
9997 &"word"& fails, the raw string is returned. If decoding
9998 .cindex "binary zero" "in header line"
9999 produces a binary zero character, it is replaced by a question mark &-- this is
10000 what Exim does for binary zeros that are actually received in header lines.
10003 &%header%& tries to translate the string as decoded by &%bheader%& to a
10004 standard character set. This is an attempt to produce the same string as would
10005 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10006 returned. Translation is attempted only on operating systems that support the
10007 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10008 a system Makefile or in &_Local/Makefile_&.
10011 In a filter file, the target character set for &%header%& can be specified by a
10012 command of the following form:
10014 headers charset "UTF-8"
10016 This command affects all references to &$h_$& (or &$header_$&) expansions in
10017 subsequently obeyed filter commands. In the absence of this command, the target
10018 character set in a filter is taken from the setting of the &%headers_charset%&
10019 option in the runtime configuration. The value of this option defaults to the
10020 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10023 Header names follow the syntax of RFC 2822, which states that they may contain
10024 any printing characters except space and colon. Consequently, curly brackets
10025 &'do not'& terminate header names, and should not be used to enclose them as
10026 if they were variables. Attempting to do so causes a syntax error.
10028 Only header lines that are common to all copies of a message are visible to
10029 this mechanism. These are the original header lines that are received with the
10030 message, and any that are added by an ACL statement or by a system
10031 filter. Header lines that are added to a particular copy of a message by a
10032 router or transport are not accessible.
10034 For incoming SMTP messages, no header lines are visible in
10035 ACLs that are obeyed before the data phase completes,
10036 because the header structure is not set up until the message is received.
10037 They are visible in DKIM, PRDR and DATA ACLs.
10038 Header lines that are added in a RCPT ACL (for example)
10039 are saved until the message's incoming header lines are available, at which
10040 point they are added.
10041 When any of the above ACLs ar
10042 running, however, header lines added by earlier ACLs are visible.
10044 Upper case and lower case letters are synonymous in header names. If the
10045 following character is white space, the terminating colon may be omitted, but
10046 this is not recommended, because you may then forget it when it is needed. When
10047 white space terminates the header name, this white space is included in the
10048 expanded string. If the message does not contain the given header, the
10049 expansion item is replaced by an empty string. (See the &%def%& condition in
10050 section &<<SECTexpcond>>& for a means of testing for the existence of a
10053 If there is more than one header with the same name, they are all concatenated
10054 to form the substitution string, up to a maximum length of 64K. Unless
10055 &%rheader%& is being used, leading and trailing white space is removed from
10056 each header before concatenation, and a completely empty header is ignored. A
10057 newline character is then inserted between non-empty headers, but there is no
10058 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10059 those headers that contain lists of addresses, a comma is also inserted at the
10060 junctions between headers. This does not happen for the &%rheader%& expansion.
10062 .cindex "tainted data"
10063 When the headers are from an incoming message,
10064 the result of expanding any of these variables is tainted.
10067 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10068 .cindex "expansion" "hmac hashing"
10070 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10071 shared secret and some text into a message authentication code, as specified in
10072 RFC 2104. This differs from &`${md5:secret_text...}`& or
10073 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10074 cryptographic hash, allowing for authentication that is not possible with MD5
10075 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10076 present. For example:
10078 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10080 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10083 dd97e3ba5d1a61b5006108f8c8252953
10085 As an example of how this might be used, you might put in the main part of
10086 an Exim configuration:
10088 SPAMSCAN_SECRET=cohgheeLei2thahw
10090 In a router or a transport you could then have:
10093 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10094 ${hmac{md5}{SPAMSCAN_SECRET}\
10095 {${primary_hostname},${message_exim_id},$h_message-id:}}
10097 Then given a message, you can check where it was scanned by looking at the
10098 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10099 this header line is authentic by recomputing the authentication code from the
10100 host name, message ID and the &'Message-id:'& header line. This can be done
10101 using Exim's &%-be%& option, or by other means, for example, by using the
10102 &'hmac_md5_hex()'& function in Perl.
10105 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10106 .cindex "expansion" "conditional"
10107 .cindex "&%if%&, expansion item"
10108 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10109 item; otherwise <&'string2'&> is used. The available conditions are described
10110 in section &<<SECTexpcond>>& below. For example:
10112 ${if eq {$local_part}{postmaster} {yes}{no} }
10114 The second string need not be present; if it is not and the condition is not
10115 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10116 be present instead of the second string (without any curly brackets). In this
10117 case, the expansion is forced to fail if the condition is not true (see section
10118 &<<SECTforexpfai>>&).
10120 If both strings are omitted, the result is the string &`true`& if the condition
10121 is true, and the empty string if the condition is false. This makes it less
10122 cumbersome to write custom ACL and router conditions. For example, instead of
10124 condition = ${if >{$acl_m4}{3}{true}{false}}
10128 condition = ${if >{$acl_m4}{3}}
10133 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10134 .cindex expansion "imap folder"
10135 .cindex "&%imapfolder%& expansion item"
10136 This item converts a (possibly multilevel, or with non-ASCII characters)
10137 folder specification to a Maildir name for filesystem use.
10138 For information on internationalisation support see &<<SECTi18nMDA>>&.
10142 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10143 .cindex "expansion" "string truncation"
10144 .cindex "&%length%& expansion item"
10145 The &%length%& item is used to extract the initial portion of a string. Both
10146 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10147 you are using a fixed value for the number, that is, if <&'string1'&> does not
10148 change when expanded, you can use the simpler operator notation that avoids
10149 some of the braces:
10151 ${length_<n>:<string>}
10153 The result of this item is either the first <&'n'&> bytes or the whole
10154 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10155 &%strlen%&, which gives the length of a string.
10156 All measurement is done in bytes and is not UTF-8 aware.
10159 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10160 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10161 .cindex "expansion" "extracting list elements by number"
10162 .cindex "&%listextract%&" "extract list elements by number"
10163 .cindex "list" "extracting elements by number"
10164 The <&'number'&> argument must consist entirely of decimal digits,
10165 apart from an optional leading minus,
10166 and leading and trailing white space (which is ignored).
10168 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10169 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10171 The first field of the list is numbered one.
10172 If the number is negative, the fields are
10173 counted from the end of the list, with the rightmost one numbered -1.
10174 The numbered element of the list is extracted and placed in &$value$&,
10175 then <&'string2'&> is expanded as the result.
10177 If the modulus of the
10178 number is zero or greater than the number of fields in the string,
10179 the result is the expansion of <&'string3'&>.
10183 ${listextract{2}{x:42:99}}
10187 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10189 yields &"result: 42"&.
10191 If {<&'string3'&>} is omitted, an empty string is used for string3.
10192 If {<&'string2'&>} is also omitted, the value that was
10194 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10198 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10199 .cindex quoting "for list"
10200 .cindex list quoting
10201 This item doubles any occurrence of the separator character
10202 in the given string.
10203 An empty string is replaced with a single space.
10204 This converts the string into a safe form for use as a list element,
10205 in a list using the given separator.
10209 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10210 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10211 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10212 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10213 .cindex "expansion" "lookup in"
10214 .cindex "file" "lookups"
10215 .cindex "lookup" "in expanded string"
10216 The two forms of lookup item specify data lookups in files and databases, as
10217 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10218 lookups, and the second is used for query-style lookups. The <&'key'&>,
10219 <&'file'&>, and <&'query'&> strings are expanded before use.
10221 If there is any white space in a lookup item which is part of a filter command,
10222 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10223 other place where white space is significant, the lookup item must be enclosed
10224 in double quotes. The use of data lookups in users' filter files may be locked
10225 out by the system administrator.
10227 .vindex "&$value$&"
10228 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10229 During its expansion, the variable &$value$& contains the data returned by the
10230 lookup. Afterwards it reverts to the value it had previously (at the outer
10231 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10232 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10233 string on failure. If <&'string2'&> is provided, it can itself be a nested
10234 lookup, thus providing a mechanism for looking up a default value when the
10235 original lookup fails.
10237 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10238 data for the outer lookup while the parameters of the second lookup are
10239 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10240 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10241 appear, and in this case, if the lookup fails, the entire expansion is forced
10242 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10243 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10244 successful lookup, and nothing in the case of failure.
10246 For single-key lookups, the string &"partial"& is permitted to precede the
10247 search type in order to do partial matching, and * or *@ may follow a search
10248 type to request default lookups if the key does not match (see sections
10249 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10251 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10252 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10253 and non-wild parts of the key during the expansion of the replacement text.
10254 They return to their previous values at the end of the lookup item.
10256 This example looks up the postmaster alias in the conventional alias file:
10258 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10260 This example uses NIS+ to look up the full name of the user corresponding to
10261 the local part of an address, forcing the expansion to fail if it is not found:
10263 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10268 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10269 .cindex "expansion" "list creation"
10271 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10272 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10274 in this list, its value is place in &$item$&, and then <&'string2'&> is
10275 expanded and added to the output as an item in a new list. The separator used
10276 for the output list is the same as the one used for the input, but a separator
10277 setting is not included in the output. For example:
10279 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10281 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10282 value of &$item$& is restored to what it was before. See also the &%filter%&
10283 and &%reduce%& expansion items.
10285 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10286 .cindex "expansion" "numeric hash"
10287 .cindex "hash function" "numeric"
10288 The three strings are expanded; the first two must yield numbers. Call them
10289 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10290 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10291 can use the simpler operator notation that avoids some of the braces:
10293 ${nhash_<n>_<m>:<string>}
10295 The second number is optional (in both notations). If there is only one number,
10296 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10297 processed by a div/mod hash function that returns two numbers, separated by a
10298 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10301 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10303 returns the string &"6/33"&.
10307 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10308 .cindex "Perl" "use in expanded string"
10309 .cindex "expansion" "calling Perl from"
10310 This item is available only if Exim has been built to include an embedded Perl
10311 interpreter. The subroutine name and the arguments are first separately
10312 expanded, and then the Perl subroutine is called with those arguments. No
10313 additional arguments need be given; the maximum number permitted, including the
10314 name of the subroutine, is nine.
10316 The return value of the subroutine is inserted into the expanded string, unless
10317 the return value is &%undef%&. In that case, the expansion fails in the same
10318 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
10319 Whatever you return is evaluated in a scalar context. For example, if you
10320 return the name of a Perl vector, the return value is the size of the vector,
10323 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10324 with the error message that was passed to &%die%&. More details of the embedded
10325 Perl facility are given in chapter &<<CHAPperl>>&.
10327 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10328 out the use of this expansion item in filter files.
10331 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10332 .cindex "&%prvs%& expansion item"
10333 The first argument is a complete email address and the second is secret
10334 keystring. The third argument, specifying a key number, is optional. If absent,
10335 it defaults to 0. The result of the expansion is a prvs-signed email address,
10336 to be typically used with the &%return_path%& option on an &(smtp)& transport
10337 as part of a bounce address tag validation (BATV) scheme. For more discussion
10338 and an example, see section &<<SECTverifyPRVS>>&.
10340 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10341 {*&<&'string'&>&*}}*&"
10342 .cindex "&%prvscheck%& expansion item"
10343 This expansion item is the complement of the &%prvs%& item. It is used for
10344 checking prvs-signed addresses. If the expansion of the first argument does not
10345 yield a syntactically valid prvs-signed address, the whole item expands to the
10346 empty string. When the first argument does expand to a syntactically valid
10347 prvs-signed address, the second argument is expanded, with the prvs-decoded
10348 version of the address and the key number extracted from the address in the
10349 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10351 These two variables can be used in the expansion of the second argument to
10352 retrieve the secret. The validity of the prvs-signed address is then checked
10353 against the secret. The result is stored in the variable &$prvscheck_result$&,
10354 which is empty for failure or &"1"& for success.
10356 The third argument is optional; if it is missing, it defaults to an empty
10357 string. This argument is now expanded. If the result is an empty string, the
10358 result of the expansion is the decoded version of the address. This is the case
10359 whether or not the signature was valid. Otherwise, the result of the expansion
10360 is the expansion of the third argument.
10362 All three variables can be used in the expansion of the third argument.
10363 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10364 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10366 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10367 .cindex "expansion" "inserting an entire file"
10368 .cindex "file" "inserting into expansion"
10369 .cindex "&%readfile%& expansion item"
10370 The filename and end-of-line string are first expanded separately. The file is
10371 then read, and its contents replace the entire item. All newline characters in
10372 the file are replaced by the end-of-line string if it is present. Otherwise,
10373 newlines are left in the string.
10374 String expansion is not applied to the contents of the file. If you want this,
10375 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10376 the string expansion fails.
10378 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10379 locks out the use of this expansion item in filter files.
10383 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10384 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10385 .cindex "expansion" "inserting from a socket"
10386 .cindex "socket, use of in expansion"
10387 .cindex "&%readsocket%& expansion item"
10388 This item inserts data from a Unix domain or TCP socket into the expanded
10389 string. The minimal way of using it uses just two arguments, as in these
10392 ${readsocket{/socket/name}{request string}}
10393 ${readsocket{inet:some.host:1234}{request string}}
10395 For a Unix domain socket, the first substring must be the path to the socket.
10396 For an Internet socket, the first substring must contain &`inet:`& followed by
10397 a host name or IP address, followed by a colon and a port, which can be a
10398 number or the name of a TCP port in &_/etc/services_&. An IP address may
10399 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10402 ${readsocket{inet:[::1]:1234}{request string}}
10404 Only a single host name may be given, but if looking it up yields more than
10405 one IP address, they are each tried in turn until a connection is made. For
10406 both kinds of socket, Exim makes a connection, writes the request string
10407 unless it is an empty string; and no terminating NUL is ever sent)
10408 and reads from the socket until an end-of-file
10409 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10410 extend what can be done. Firstly, you can vary the timeout. For example:
10412 ${readsocket{/socket/name}{request string}{3s}}
10415 The third argument is a list of options, of which the first element is the timeout
10416 and must be present if any options are given.
10417 Further elements are options of form &'name=value'&.
10420 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10423 The following option names are recognised:
10426 Defines if the result data can be cached for use by a later identical
10427 request in the same process.
10428 Values are &"yes"& or &"no"& (the default).
10429 If not, all cached results for this connection specification
10430 will be invalidated.
10434 Defines whether or not a write-shutdown is done on the connection after
10435 sending the request. Values are &"yes"& (the default) or &"no"&
10436 (preferred, eg. by some webservers).
10440 Controls the use of TLS on the connection.
10441 Values are &"yes"& or &"no"& (the default).
10442 If it is enabled, a shutdown as descripbed above is never done.
10446 A fourth argument allows you to change any newlines that are in the data
10447 that is read, in the same way as for &%readfile%& (see above). This example
10448 turns them into spaces:
10450 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10452 As with all expansions, the substrings are expanded before the processing
10453 happens. Errors in these sub-expansions cause the expansion to fail. In
10454 addition, the following errors can occur:
10457 Failure to create a socket file descriptor;
10459 Failure to connect the socket;
10461 Failure to write the request string;
10463 Timeout on reading from the socket.
10466 By default, any of these errors causes the expansion to fail. However, if
10467 you supply a fifth substring, it is expanded and used when any of the above
10468 errors occurs. For example:
10470 ${readsocket{/socket/name}{request string}{3s}{\n}\
10473 You can test for the existence of a Unix domain socket by wrapping this
10474 expansion in &`${if exists`&, but there is a race condition between that test
10475 and the actual opening of the socket, so it is safer to use the fifth argument
10476 if you want to be absolutely sure of avoiding an expansion error for a
10477 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10479 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10480 locks out the use of this expansion item in filter files.
10483 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10484 .cindex "expansion" "reducing a list to a scalar"
10485 .cindex "list" "reducing to a scalar"
10486 .vindex "&$value$&"
10488 This operation reduces a list to a single, scalar string. After expansion,
10489 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10490 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10491 Then <&'string2'&> is expanded and
10492 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10493 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10494 them. The result of that expansion is assigned to &$value$& before the next
10495 iteration. When the end of the list is reached, the final value of &$value$& is
10496 added to the expansion output. The &%reduce%& expansion item can be used in a
10497 number of ways. For example, to add up a list of numbers:
10499 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10501 The result of that expansion would be &`6`&. The maximum of a list of numbers
10504 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10506 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10507 restored to what they were before. See also the &%filter%& and &%map%&
10510 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10511 This item inserts &"raw"& header lines. It is described with the &%header%&
10512 expansion item in section &<<SECTexpansionitems>>& above.
10514 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10515 {*&<&'string2'&>&*}}*&"
10516 .cindex "expansion" "running a command"
10517 .cindex "&%run%& expansion item"
10518 The command and its arguments are first expanded as one string. The string is
10519 split apart into individual arguments by spaces, and then the command is run
10520 in a separate process, but under the same uid and gid. As in other command
10521 executions from Exim, a shell is not used by default. If the command requires
10522 a shell, you must explicitly code it.
10524 Since the arguments are split by spaces, when there is a variable expansion
10525 which has an empty result, it will cause the situation that the argument will
10526 simply be omitted when the program is actually executed by Exim. If the
10527 script/program requires a specific number of arguments and the expanded
10528 variable could possibly result in this empty expansion, the variable must be
10529 quoted. This is more difficult if the expanded variable itself could result
10530 in a string containing quotes, because it would interfere with the quotes
10531 around the command arguments. A possible guard against this is to wrap the
10532 variable in the &%sg%& operator to change any quote marks to some other
10535 The standard input for the command exists, but is empty. The standard output
10536 and standard error are set to the same file descriptor.
10537 .cindex "return code" "from &%run%& expansion"
10538 .vindex "&$value$&"
10539 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10540 and replaces the entire item; during this expansion, the standard output/error
10541 from the command is in the variable &$value$&. If the command fails,
10542 <&'string2'&>, if present, is expanded and used. Once again, during the
10543 expansion, the standard output/error from the command is in the variable
10546 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10547 can be the word &"fail"& (not in braces) to force expansion failure if the
10548 command does not succeed. If both strings are omitted, the result is contents
10549 of the standard output/error on success, and nothing on failure.
10551 .vindex "&$run_in_acl$&"
10552 The standard output/error of the command is put in the variable &$value$&.
10553 In this ACL example, the output of a command is logged for the admin to
10556 warn condition = ${run{/usr/bin/id}{yes}{no}}
10557 log_message = Output of id: $value
10559 If the command requires shell idioms, such as the > redirect operator, the
10560 shell must be invoked directly, such as with:
10562 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10565 .vindex "&$runrc$&"
10566 The return code from the command is put in the variable &$runrc$&, and this
10567 remains set afterwards, so in a filter file you can do things like this:
10569 if "${run{x y z}{}}$runrc" is 1 then ...
10570 elif $runrc is 2 then ...
10574 If execution of the command fails (for example, the command does not exist),
10575 the return code is 127 &-- the same code that shells use for non-existent
10578 &*Warning*&: In a router or transport, you cannot assume the order in which
10579 option values are expanded, except for those preconditions whose order of
10580 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10581 by the expansion of one option, and use it in another.
10583 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10584 out the use of this expansion item in filter files.
10587 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10588 .cindex "expansion" "string substitution"
10589 .cindex "&%sg%& expansion item"
10590 This item works like Perl's substitution operator (s) with the global (/g)
10591 option; hence its name. However, unlike the Perl equivalent, Exim does not
10592 modify the subject string; instead it returns the modified string for insertion
10593 into the overall expansion. The item takes three arguments: the subject string,
10594 a regular expression, and a substitution string. For example:
10596 ${sg{abcdefabcdef}{abc}{xyz}}
10598 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10599 if any $, } or \ characters are required in the regular expression or in the
10600 substitution string, they have to be escaped. For example:
10602 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10604 yields &"defabc"&, and
10606 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10608 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10609 the regular expression from string expansion.
10611 The regular expression is compiled in 8-bit mode, working against bytes
10612 rather than any Unicode-aware character handling.
10615 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10616 .cindex sorting "a list"
10617 .cindex list sorting
10618 .cindex expansion "list sorting"
10619 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10620 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10621 The <&'comparator'&> argument is interpreted as the operator
10622 of a two-argument expansion condition.
10623 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10624 The comparison should return true when applied to two values
10625 if the first value should sort before the second value.
10626 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10627 the element being placed in &$item$&,
10628 to give values for comparison.
10630 The item result is a sorted list,
10631 with the original list separator,
10632 of the list elements (in full) of the original.
10636 ${sort{3:2:1:4}{<}{$item}}
10638 sorts a list of numbers, and
10640 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10642 will sort an MX lookup into priority order.
10647 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10648 SRS encoding. See SECT &<<SECTSRS>>& for details.
10653 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10654 .cindex "&%substr%& expansion item"
10655 .cindex "substring extraction"
10656 .cindex "expansion" "substring extraction"
10657 The three strings are expanded; the first two must yield numbers. Call them
10658 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10659 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10660 can use the simpler operator notation that avoids some of the braces:
10662 ${substr_<n>_<m>:<string>}
10664 The second number is optional (in both notations).
10665 If it is absent in the simpler format, the preceding underscore must also be
10668 The &%substr%& item can be used to extract more general substrings than
10669 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10670 length required. For example
10672 ${substr{3}{2}{$local_part}}
10674 If the starting offset is greater than the string length the result is the
10675 null string; if the length plus starting offset is greater than the string
10676 length, the result is the right-hand part of the string, starting from the
10677 given offset. The first byte (character) in the string has offset zero.
10679 The &%substr%& expansion item can take negative offset values to count
10680 from the right-hand end of its operand. The last byte (character) is offset -1,
10681 the second-last is offset -2, and so on. Thus, for example,
10683 ${substr{-5}{2}{1234567}}
10685 yields &"34"&. If the absolute value of a negative offset is greater than the
10686 length of the string, the substring starts at the beginning of the string, and
10687 the length is reduced by the amount of overshoot. Thus, for example,
10689 ${substr{-5}{2}{12}}
10691 yields an empty string, but
10693 ${substr{-3}{2}{12}}
10697 When the second number is omitted from &%substr%&, the remainder of the string
10698 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10699 string preceding the offset point are taken. For example, an offset of -1 and
10700 no length, as in these semantically identical examples:
10703 ${substr{-1}{abcde}}
10705 yields all but the last character of the string, that is, &"abcd"&.
10707 All measurement is done in bytes and is not UTF-8 aware.
10711 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10712 {*&<&'replacements'&>&*}}*&"
10713 .cindex "expansion" "character translation"
10714 .cindex "&%tr%& expansion item"
10715 This item does single-character (in bytes) translation on its subject string. The second
10716 argument is a list of characters to be translated in the subject string. Each
10717 matching character is replaced by the corresponding character from the
10718 replacement list. For example
10720 ${tr{abcdea}{ac}{13}}
10722 yields &`1b3de1`&. If there are duplicates in the second character string, the
10723 last occurrence is used. If the third string is shorter than the second, its
10724 last character is replicated. However, if it is empty, no translation takes
10727 All character handling is done in bytes and is not UTF-8 aware.
10733 .section "Expansion operators" "SECTexpop"
10734 .cindex "expansion" "operators"
10735 For expansion items that perform transformations on a single argument string,
10736 the &"operator"& notation is used because it is simpler and uses fewer braces.
10737 The substring is first expanded before the operation is applied to it. The
10738 following operations can be performed:
10741 .vitem &*${address:*&<&'string'&>&*}*&
10742 .cindex "expansion" "RFC 2822 address handling"
10743 .cindex "&%address%& expansion item"
10744 The string is interpreted as an RFC 2822 address, as it might appear in a
10745 header line, and the effective address is extracted from it. If the string does
10746 not parse successfully, the result is empty.
10748 The parsing correctly handles SMTPUTF8 Unicode in the string.
10751 .vitem &*${addresses:*&<&'string'&>&*}*&
10752 .cindex "expansion" "RFC 2822 address handling"
10753 .cindex "&%addresses%& expansion item"
10754 The string (after expansion) is interpreted as a list of addresses in RFC
10755 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10756 operative address (&'local-part@domain'&) is extracted from each item, and the
10757 result of the expansion is a colon-separated list, with appropriate
10758 doubling of colons should any happen to be present in the email addresses.
10759 Syntactically invalid RFC2822 address items are omitted from the output.
10761 It is possible to specify a character other than colon for the output
10762 separator by starting the string with > followed by the new separator
10763 character. For example:
10765 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10767 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10768 first, so if the expanded string starts with >, it may change the output
10769 separator unintentionally. This can be avoided by setting the output
10770 separator explicitly:
10772 ${addresses:>:$h_from:}
10775 Compare the &%address%& (singular)
10776 expansion item, which extracts the working address from a single RFC2822
10777 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10780 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10781 a strict interpretation of header line formatting. Exim parses the bare,
10782 unquoted portion of an email address and if it finds a comma, treats it as an
10783 email address separator. For the example header line:
10785 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10787 The first example below demonstrates that Q-encoded email addresses are parsed
10788 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10789 It does not see the comma because it's still encoded as "=2C". The second
10790 example below is passed the contents of &`$header_from:`&, meaning it gets
10791 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10792 The third example shows that the presence of a comma is skipped when it is
10793 quoted. The fourth example shows SMTPUTF8 handling.
10795 # exim -be '${addresses:From: \
10796 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10798 # exim -be '${addresses:From: Last, First <user@example.com>}'
10799 Last:user@example.com
10800 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10802 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10806 .vitem &*${base32:*&<&'digits'&>&*}*&
10807 .cindex "&%base32%& expansion item"
10808 .cindex "expansion" "conversion to base 32"
10809 The string must consist entirely of decimal digits. The number is converted to
10810 base 32 and output as a (empty, for zero) string of characters.
10811 Only lowercase letters are used.
10813 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10814 .cindex "&%base32d%& expansion item"
10815 .cindex "expansion" "conversion to base 32"
10816 The string must consist entirely of base-32 digits.
10817 The number is converted to decimal and output as a string.
10819 .vitem &*${base62:*&<&'digits'&>&*}*&
10820 .cindex "&%base62%& expansion item"
10821 .cindex "expansion" "conversion to base 62"
10822 The string must consist entirely of decimal digits. The number is converted to
10823 base 62 and output as a string of six characters, including leading zeros. In
10824 the few operating environments where Exim uses base 36 instead of base 62 for
10825 its message identifiers (because those systems do not have case-sensitive
10826 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10827 to be absolutely clear: this is &'not'& base64 encoding.
10829 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10830 .cindex "&%base62d%& expansion item"
10831 .cindex "expansion" "conversion to base 62"
10832 The string must consist entirely of base-62 digits, or, in operating
10833 environments where Exim uses base 36 instead of base 62 for its message
10834 identifiers, base-36 digits. The number is converted to decimal and output as a
10837 .vitem &*${base64:*&<&'string'&>&*}*&
10838 .cindex "expansion" "base64 encoding"
10839 .cindex "base64 encoding" "in string expansion"
10840 .cindex "&%base64%& expansion item"
10841 .cindex certificate "base64 of DER"
10842 This operator converts a string into one that is base64 encoded.
10844 If the string is a single variable of type certificate,
10845 returns the base64 encoding of the DER form of the certificate.
10848 .vitem &*${base64d:*&<&'string'&>&*}*&
10849 .cindex "expansion" "base64 decoding"
10850 .cindex "base64 decoding" "in string expansion"
10851 .cindex "&%base64d%& expansion item"
10852 This operator converts a base64-encoded string into the un-coded form.
10855 .vitem &*${domain:*&<&'string'&>&*}*&
10856 .cindex "domain" "extraction"
10857 .cindex "expansion" "domain extraction"
10858 The string is interpreted as an RFC 2822 address and the domain is extracted
10859 from it. If the string does not parse successfully, the result is empty.
10862 .vitem &*${escape:*&<&'string'&>&*}*&
10863 .cindex "expansion" "escaping non-printing characters"
10864 .cindex "&%escape%& expansion item"
10865 If the string contains any non-printing characters, they are converted to
10866 escape sequences starting with a backslash. Whether characters with the most
10867 significant bit set (so-called &"8-bit characters"&) count as printing or not
10868 is controlled by the &%print_topbitchars%& option.
10870 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10871 .cindex "expansion" "escaping 8-bit characters"
10872 .cindex "&%escape8bit%& expansion item"
10873 If the string contains and characters with the most significant bit set,
10874 they are converted to escape sequences starting with a backslash.
10875 Backslashes and DEL characters are also converted.
10878 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10879 .cindex "expansion" "expression evaluation"
10880 .cindex "expansion" "arithmetic expression"
10881 .cindex "&%eval%& expansion item"
10882 These items supports simple arithmetic and bitwise logical operations in
10883 expansion strings. The string (after expansion) must be a conventional
10884 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10885 logical operators, and parentheses. All operations are carried out using
10886 integer arithmetic. The operator priorities are as follows (the same as in the
10887 C programming language):
10889 .irow &'highest:'& "not (~), negate (-)"
10890 .irow "" "multiply (*), divide (/), remainder (%)"
10891 .irow "" "plus (+), minus (-)"
10892 .irow "" "shift-left (<<), shift-right (>>)"
10893 .irow "" "and (&&)"
10895 .irow &'lowest:'& "or (|)"
10897 Binary operators with the same priority are evaluated from left to right. White
10898 space is permitted before or after operators.
10900 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10901 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10902 decimal, even if they start with a leading zero; hexadecimal numbers are not
10903 permitted. This can be useful when processing numbers extracted from dates or
10904 times, which often do have leading zeros.
10906 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10908 respectively. Negative numbers are supported. The result of the computation is
10909 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10912 &`${eval:1+1} `& yields 2
10913 &`${eval:1+2*3} `& yields 7
10914 &`${eval:(1+2)*3} `& yields 9
10915 &`${eval:2+42%5} `& yields 4
10916 &`${eval:0xc&5} `& yields 4
10917 &`${eval:0xc|5} `& yields 13
10918 &`${eval:0xc^5} `& yields 9
10919 &`${eval:0xc>>1} `& yields 6
10920 &`${eval:0xc<<1} `& yields 24
10921 &`${eval:~255&0x1234} `& yields 4608
10922 &`${eval:-(~255&0x1234)} `& yields -4608
10925 As a more realistic example, in an ACL you might have
10929 {>{$rcpt_count}{10}} \
10932 {$recipients_count} \
10933 {${eval:$rcpt_count/2}} \
10936 message = Too many bad recipients
10938 The condition is true if there have been more than 10 RCPT commands and
10939 fewer than half of them have resulted in a valid recipient.
10942 .vitem &*${expand:*&<&'string'&>&*}*&
10943 .cindex "expansion" "re-expansion of substring"
10944 The &%expand%& operator causes a string to be expanded for a second time. For
10947 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10949 first looks up a string in a file while expanding the operand for &%expand%&,
10950 and then re-expands what it has found.
10953 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10955 .cindex "UTF-8" "conversion from"
10956 .cindex "expansion" "UTF-8 conversion"
10957 .cindex "&%from_utf8%& expansion item"
10958 The world is slowly moving towards Unicode, although there are no standards for
10959 email yet. However, other applications (including some databases) are starting
10960 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10961 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10962 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10963 the result is an undefined sequence of bytes.
10965 Unicode code points with values less than 256 are compatible with ASCII and
10966 ISO-8859-1 (also known as Latin-1).
10967 For example, character 169 is the copyright symbol in both cases, though the
10968 way it is encoded is different. In UTF-8, more than one byte is needed for
10969 characters with code values greater than 127, whereas ISO-8859-1 is a
10970 single-byte encoding (but thereby limited to 256 characters). This makes
10971 translation from UTF-8 to ISO-8859-1 straightforward.
10974 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10975 .cindex "hash function" "textual"
10976 .cindex "expansion" "textual hash"
10977 The &%hash%& operator is a simpler interface to the hashing function that can
10978 be used when the two parameters are fixed numbers (as opposed to strings that
10979 change when expanded). The effect is the same as
10981 ${hash{<n>}{<m>}{<string>}}
10983 See the description of the general &%hash%& item above for details. The
10984 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10988 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10989 .cindex "base64 encoding" "conversion from hex"
10990 .cindex "expansion" "hex to base64"
10991 .cindex "&%hex2b64%& expansion item"
10992 This operator converts a hex string into one that is base64 encoded. This can
10993 be useful for processing the output of the various hashing functions.
10997 .vitem &*${hexquote:*&<&'string'&>&*}*&
10998 .cindex "quoting" "hex-encoded unprintable characters"
10999 .cindex "&%hexquote%& expansion item"
11000 This operator converts non-printable characters in a string into a hex
11001 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11002 as is, and other byte values are converted to &`\xNN`&, for example, a
11003 byte value 127 is converted to &`\x7f`&.
11006 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11007 .cindex "&%ipv6denorm%& expansion item"
11008 .cindex "IP address" normalisation
11009 This expands an IPv6 address to a full eight-element colon-separated set
11010 of hex digits including leading zeroes.
11011 A trailing ipv4-style dotted-decimal set is converted to hex.
11012 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11014 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11015 .cindex "&%ipv6norm%& expansion item"
11016 .cindex "IP address" normalisation
11017 .cindex "IP address" "canonical form"
11018 This converts an IPv6 address to canonical form.
11019 Leading zeroes of groups are omitted, and the longest
11020 set of zero-valued groups is replaced with a double colon.
11021 A trailing ipv4-style dotted-decimal set is converted to hex.
11022 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11025 .vitem &*${lc:*&<&'string'&>&*}*&
11026 .cindex "case forcing in strings"
11027 .cindex "string" "case forcing"
11028 .cindex "lower casing"
11029 .cindex "expansion" "case forcing"
11030 .cindex "&%lc%& expansion item"
11031 This forces the letters in the string into lower-case, for example:
11035 Case is defined per the system C locale.
11037 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11038 .cindex "expansion" "string truncation"
11039 .cindex "&%length%& expansion item"
11040 The &%length%& operator is a simpler interface to the &%length%& function that
11041 can be used when the parameter is a fixed number (as opposed to a string that
11042 changes when expanded). The effect is the same as
11044 ${length{<number>}{<string>}}
11046 See the description of the general &%length%& item above for details. Note that
11047 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11048 when &%length%& is used as an operator.
11049 All measurement is done in bytes and is not UTF-8 aware.
11052 .vitem &*${listcount:*&<&'string'&>&*}*&
11053 .cindex "expansion" "list item count"
11054 .cindex "list" "item count"
11055 .cindex "list" "count of items"
11056 .cindex "&%listcount%& expansion item"
11057 The string is interpreted as a list and the number of items is returned.
11060 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11061 .cindex "expansion" "named list"
11062 .cindex "&%listnamed%& expansion item"
11063 The name is interpreted as a named list and the content of the list is returned,
11064 expanding any referenced lists, re-quoting as needed for colon-separation.
11065 If the optional type is given it must be one of "a", "d", "h" or "l"
11066 and selects address-, domain-, host- or localpart- lists to search among respectively.
11067 Otherwise all types are searched in an undefined order and the first
11068 matching list is returned.
11071 .vitem &*${local_part:*&<&'string'&>&*}*&
11072 .cindex "expansion" "local part extraction"
11073 .cindex "&%local_part%& expansion item"
11074 The string is interpreted as an RFC 2822 address and the local part is
11075 extracted from it. If the string does not parse successfully, the result is
11077 The parsing correctly handles SMTPUTF8 Unicode in the string.
11080 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11081 .cindex "masked IP address"
11082 .cindex "IP address" "masking"
11083 .cindex "CIDR notation"
11084 .cindex "expansion" "IP address masking"
11085 .cindex "&%mask%& expansion item"
11086 If the form of the string to be operated on is not an IP address followed by a
11087 slash and an integer (that is, a network address in CIDR notation), the
11088 expansion fails. Otherwise, this operator converts the IP address to binary,
11089 masks off the least significant bits according to the bit count, and converts
11090 the result back to text, with mask appended. For example,
11092 ${mask:10.111.131.206/28}
11094 returns the string &"10.111.131.192/28"&. Since this operation is expected to
11095 be mostly used for looking up masked addresses in files, the result for an IPv6
11096 address uses dots to separate components instead of colons, because colon
11097 terminates a key string in lsearch files. So, for example,
11099 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11103 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11105 Letters in IPv6 addresses are always output in lower case.
11108 .vitem &*${md5:*&<&'string'&>&*}*&
11110 .cindex "expansion" "MD5 hash"
11111 .cindex certificate fingerprint
11112 .cindex "&%md5%& expansion item"
11113 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11114 as a 32-digit hexadecimal number, in which any letters are in lower case.
11116 If the string is a single variable of type certificate,
11117 returns the MD5 hash fingerprint of the certificate.
11120 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11121 .cindex "expansion" "numeric hash"
11122 .cindex "hash function" "numeric"
11123 The &%nhash%& operator is a simpler interface to the numeric hashing function
11124 that can be used when the two parameters are fixed numbers (as opposed to
11125 strings that change when expanded). The effect is the same as
11127 ${nhash{<n>}{<m>}{<string>}}
11129 See the description of the general &%nhash%& item above for details.
11132 .vitem &*${quote:*&<&'string'&>&*}*&
11133 .cindex "quoting" "in string expansions"
11134 .cindex "expansion" "quoting"
11135 .cindex "&%quote%& expansion item"
11136 The &%quote%& operator puts its argument into double quotes if it
11137 is an empty string or
11138 contains anything other than letters, digits, underscores, dots, and hyphens.
11139 Any occurrences of double quotes and backslashes are escaped with a backslash.
11140 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11141 respectively For example,
11149 The place where this is useful is when the argument is a substitution from a
11150 variable or a message header.
11152 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11153 .cindex "&%quote_local_part%& expansion item"
11154 This operator is like &%quote%&, except that it quotes the string only if
11155 required to do so by the rules of RFC 2822 for quoting local parts. For
11156 example, a plus sign would not cause quoting (but it would for &%quote%&).
11157 If you are creating a new email address from the contents of &$local_part$&
11158 (or any other unknown data), you should always use this operator.
11160 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11161 will likely use the quoting form.
11162 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11165 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11166 .cindex "quoting" "lookup-specific"
11167 This operator applies lookup-specific quoting rules to the string. Each
11168 query-style lookup type has its own quoting rules which are described with
11169 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11171 ${quote_ldap:two * two}
11177 For single-key lookup types, no quoting is ever necessary and this operator
11178 yields an unchanged string.
11181 .vitem &*${randint:*&<&'n'&>&*}*&
11182 .cindex "random number"
11183 This operator returns a somewhat random number which is less than the
11184 supplied number and is at least 0. The quality of this randomness depends
11185 on how Exim was built; the values are not suitable for keying material.
11186 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11187 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11188 for versions of GnuTLS with that function.
11189 Otherwise, the implementation may be arc4random(), random() seeded by
11190 srandomdev() or srandom(), or a custom implementation even weaker than
11194 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11195 .cindex "expansion" "IP address"
11196 This operator reverses an IP address; for IPv4 addresses, the result is in
11197 dotted-quad decimal form, while for IPv6 addresses the result is in
11198 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11199 for DNS. For example,
11201 ${reverse_ip:192.0.2.4}
11202 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11207 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11211 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11212 .cindex "expansion" "RFC 2047"
11213 .cindex "RFC 2047" "expansion operator"
11214 .cindex "&%rfc2047%& expansion item"
11215 This operator encodes text according to the rules of RFC 2047. This is an
11216 encoding that is used in header lines to encode non-ASCII characters. It is
11217 assumed that the input string is in the encoding specified by the
11218 &%headers_charset%& option, which gets its default at build time. If the string
11219 contains only characters in the range 33&--126, and no instances of the
11222 ? = ( ) < > @ , ; : \ " . [ ] _
11224 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11225 string, using as many &"encoded words"& as necessary to encode all the
11229 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11230 .cindex "expansion" "RFC 2047"
11231 .cindex "RFC 2047" "decoding"
11232 .cindex "&%rfc2047d%& expansion item"
11233 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11234 bytes are replaced by question marks. Characters are converted into the
11235 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11236 not recognized unless &%check_rfc2047_length%& is set false.
11238 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11239 access a header line, RFC 2047 decoding is done automatically. You do not need
11240 to use this operator as well.
11244 .vitem &*${rxquote:*&<&'string'&>&*}*&
11245 .cindex "quoting" "in regular expressions"
11246 .cindex "regular expressions" "quoting"
11247 .cindex "&%rxquote%& expansion item"
11248 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11249 characters in its argument. This is useful when substituting the values of
11250 variables or headers inside regular expressions.
11253 .vitem &*${sha1:*&<&'string'&>&*}*&
11254 .cindex "SHA-1 hash"
11255 .cindex "expansion" "SHA-1 hashing"
11256 .cindex certificate fingerprint
11257 .cindex "&%sha1%& expansion item"
11258 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11259 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11261 If the string is a single variable of type certificate,
11262 returns the SHA-1 hash fingerprint of the certificate.
11265 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11266 &*${sha2:*&<&'string'&>&*}*& &&&
11267 &*${sha2_<n>:*&<&'string'&>&*}*&
11268 .cindex "SHA-256 hash"
11269 .cindex "SHA-2 hash"
11270 .cindex certificate fingerprint
11271 .cindex "expansion" "SHA-256 hashing"
11272 .cindex "&%sha256%& expansion item"
11273 .cindex "&%sha2%& expansion item"
11274 The &%sha256%& operator computes the SHA-256 hash value of the string
11276 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11278 If the string is a single variable of type certificate,
11279 returns the SHA-256 hash fingerprint of the certificate.
11281 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11282 (except for certificates, which are not supported).
11283 Finally, if an underbar
11284 and a number is appended it specifies the output length, selecting a
11285 member of the SHA-2 family of hash functions.
11286 Values of 256, 384 and 512 are accepted, with 256 being the default.
11289 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11290 &*${sha3_<n>:*&<&'string'&>&*}*&
11291 .cindex "SHA3 hash"
11292 .cindex "expansion" "SHA3 hashing"
11293 .cindex "&%sha3%& expansion item"
11294 The &%sha3%& operator computes the SHA3-256 hash value of the string
11296 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11298 If a number is appended, separated by an underbar, it specifies
11299 the output length. Values of 224, 256, 384 and 512 are accepted;
11300 with 256 being the default.
11302 The &%sha3%& expansion item is only supported if Exim has been
11303 compiled with GnuTLS 3.5.0 or later,
11304 or OpenSSL 1.1.1 or later.
11305 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11308 .vitem &*${stat:*&<&'string'&>&*}*&
11309 .cindex "expansion" "statting a file"
11310 .cindex "file" "extracting characteristics"
11311 .cindex "&%stat%& expansion item"
11312 The string, after expansion, must be a file path. A call to the &[stat()]&
11313 function is made for this path. If &[stat()]& fails, an error occurs and the
11314 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11315 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11316 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11317 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11318 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11319 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11320 can extract individual fields using the &%extract%& expansion item.
11322 The use of the &%stat%& expansion in users' filter files can be locked out by
11323 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11324 systems for files larger than 2GB.
11326 .vitem &*${str2b64:*&<&'string'&>&*}*&
11327 .cindex "&%str2b64%& expansion item"
11328 Now deprecated, a synonym for the &%base64%& expansion operator.
11332 .vitem &*${strlen:*&<&'string'&>&*}*&
11333 .cindex "expansion" "string length"
11334 .cindex "string" "length in expansion"
11335 .cindex "&%strlen%& expansion item"
11336 The item is replace by the length of the expanded string, expressed as a
11337 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11338 All measurement is done in bytes and is not UTF-8 aware.
11341 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11342 .cindex "&%substr%& expansion item"
11343 .cindex "substring extraction"
11344 .cindex "expansion" "substring expansion"
11345 The &%substr%& operator is a simpler interface to the &%substr%& function that
11346 can be used when the two parameters are fixed numbers (as opposed to strings
11347 that change when expanded). The effect is the same as
11349 ${substr{<start>}{<length>}{<string>}}
11351 See the description of the general &%substr%& item above for details. The
11352 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11353 All measurement is done in bytes and is not UTF-8 aware.
11355 .vitem &*${time_eval:*&<&'string'&>&*}*&
11356 .cindex "&%time_eval%& expansion item"
11357 .cindex "time interval" "decoding"
11358 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11361 .vitem &*${time_interval:*&<&'string'&>&*}*&
11362 .cindex "&%time_interval%& expansion item"
11363 .cindex "time interval" "formatting"
11364 The argument (after sub-expansion) must be a sequence of decimal digits that
11365 represents an interval of time as a number of seconds. It is converted into a
11366 number of larger units and output in Exim's normal time format, for example,
11369 .vitem &*${uc:*&<&'string'&>&*}*&
11370 .cindex "case forcing in strings"
11371 .cindex "string" "case forcing"
11372 .cindex "upper casing"
11373 .cindex "expansion" "case forcing"
11374 .cindex "&%uc%& expansion item"
11375 This forces the letters in the string into upper-case.
11376 Case is defined per the system C locale.
11378 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11379 .cindex "correction of invalid utf-8 sequences in strings"
11380 .cindex "utf-8" "utf-8 sequences"
11381 .cindex "incorrect utf-8"
11382 .cindex "expansion" "utf-8 forcing"
11383 .cindex "&%utf8clean%& expansion item"
11384 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11385 In versions of Exim before 4.92, this did not correctly do so for a truncated
11386 final codepoint's encoding, and the character would be silently dropped.
11387 If you must handle detection of this scenario across both sets of Exim behavior,
11388 the complexity will depend upon the task.
11389 For instance, to detect if the first character is multibyte and a 1-byte
11390 extraction can be successfully used as a path component (as is common for
11391 dividing up delivery folders), you might use:
11393 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11395 (which will false-positive if the first character of the local part is a
11396 literal question mark).
11398 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11399 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11400 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11401 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11402 .cindex expansion UTF-8
11403 .cindex UTF-8 expansion
11405 .cindex internationalisation
11406 .cindex "&%utf8_domain_to_alabel%& expansion item"
11407 .cindex "&%utf8_domain_from_alabel%& expansion item"
11408 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11409 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11410 These convert EAI mail name components between UTF-8 and a-label forms.
11411 For information on internationalisation support see &<<SECTi18nMTA>>&.
11419 .section "Expansion conditions" "SECTexpcond"
11420 .scindex IIDexpcond "expansion" "conditions"
11421 The following conditions are available for testing by the &%${if%& construct
11422 while expanding strings:
11425 .vitem &*!*&<&'condition'&>
11426 .cindex "expansion" "negating a condition"
11427 .cindex "negation" "in expansion condition"
11428 Preceding any condition with an exclamation mark negates the result of the
11431 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11432 .cindex "numeric comparison"
11433 .cindex "expansion" "numeric comparison"
11434 There are a number of symbolic operators for doing numeric comparisons. They
11440 &`>= `& greater or equal
11442 &`<= `& less or equal
11446 ${if >{$message_size}{10M} ...
11448 Note that the general negation operator provides for inequality testing. The
11449 two strings must take the form of optionally signed decimal integers,
11450 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11451 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11452 As a special case, the numerical value of an empty string is taken as
11455 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11456 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11457 10M, not if 10M is larger than &$message_size$&.
11460 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11461 {*&<&'arg2'&>&*}...}*&
11462 .cindex "expansion" "calling an acl"
11463 .cindex "&%acl%&" "expansion condition"
11464 The name and zero to nine argument strings are first expanded separately. The expanded
11465 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11466 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11467 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11468 and may use the variables; if another acl expansion is used the values
11469 are restored after it returns. If the ACL sets
11470 a value using a "message =" modifier the variable $value becomes
11471 the result of the expansion, otherwise it is empty.
11472 If the ACL returns accept the condition is true; if deny, false.
11473 If the ACL returns defer the result is a forced-fail.
11475 .vitem &*bool&~{*&<&'string'&>&*}*&
11476 .cindex "expansion" "boolean parsing"
11477 .cindex "&%bool%& expansion condition"
11478 This condition turns a string holding a true or false representation into
11479 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11480 (case-insensitively); also integer numbers map to true if non-zero,
11482 An empty string is treated as false.
11483 Leading and trailing whitespace is ignored;
11484 thus a string consisting only of whitespace is false.
11485 All other string values will result in expansion failure.
11487 When combined with ACL variables, this expansion condition will let you
11488 make decisions in one place and act on those decisions in another place.
11491 ${if bool{$acl_m_privileged_sender} ...
11495 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11496 .cindex "expansion" "boolean parsing"
11497 .cindex "&%bool_lax%& expansion condition"
11498 Like &%bool%&, this condition turns a string into a boolean state. But
11499 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11500 loose definition that the Router &%condition%& option uses. The empty string
11501 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11502 true. Leading and trailing whitespace is ignored.
11504 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11506 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11507 .cindex "expansion" "encrypted comparison"
11508 .cindex "encrypted strings, comparing"
11509 .cindex "&%crypteq%& expansion condition"
11510 This condition is included in the Exim binary if it is built to support any
11511 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11512 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11513 included in the binary.
11515 The &%crypteq%& condition has two arguments. The first is encrypted and
11516 compared against the second, which is already encrypted. The second string may
11517 be in the LDAP form for storing encrypted strings, which starts with the
11518 encryption type in curly brackets, followed by the data. If the second string
11519 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11520 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11521 Typically this will be a field from a password file. An example of an encrypted
11522 string in LDAP form is:
11524 {md5}CY9rzUYh03PK3k6DJie09g==
11526 If such a string appears directly in an expansion, the curly brackets have to
11527 be quoted, because they are part of the expansion syntax. For example:
11529 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11531 The following encryption types (whose names are matched case-independently) are
11536 .cindex "base64 encoding" "in encrypted password"
11537 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11538 printable characters to compare with the remainder of the second string. If the
11539 length of the comparison string is 24, Exim assumes that it is base64 encoded
11540 (as in the above example). If the length is 32, Exim assumes that it is a
11541 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11545 .cindex "SHA-1 hash"
11546 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11547 printable characters to compare with the remainder of the second string. If the
11548 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11549 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11550 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11553 .cindex "&[crypt()]&"
11554 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11555 only the first eight characters of the password. However, in modern operating
11556 systems this is no longer true, and in many cases the entire password is used,
11557 whatever its length.
11560 .cindex "&[crypt16()]&"
11561 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11562 use up to 16 characters of the password in some operating systems. Again, in
11563 modern operating systems, more characters may be used.
11565 Exim has its own version of &[crypt16()]&, which is just a double call to
11566 &[crypt()]&. For operating systems that have their own version, setting
11567 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11568 operating system version instead of its own. This option is set by default in
11569 the OS-dependent &_Makefile_& for those operating systems that are known to
11570 support &[crypt16()]&.
11572 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11573 it was not using the same algorithm as some operating systems' versions. It
11574 turns out that as well as &[crypt16()]& there is a function called
11575 &[bigcrypt()]& in some operating systems. This may or may not use the same
11576 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11578 However, since there is now a move away from the traditional &[crypt()]&
11579 functions towards using SHA1 and other algorithms, tidying up this area of
11580 Exim is seen as very low priority.
11582 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11583 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11584 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11585 default is &`{crypt}`&. Whatever the default, you can always use either
11586 function by specifying it explicitly in curly brackets.
11588 .vitem &*def:*&<&'variable&~name'&>
11589 .cindex "expansion" "checking for empty variable"
11590 .cindex "&%def%& expansion condition"
11591 The &%def%& condition must be followed by the name of one of the expansion
11592 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11593 variable does not contain the empty string. For example:
11595 ${if def:sender_ident {from $sender_ident}}
11597 Note that the variable name is given without a leading &%$%& character. If the
11598 variable does not exist, the expansion fails.
11600 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11601 &~&*def:h_*&<&'header&~name'&>&*:*&"
11602 .cindex "expansion" "checking header line existence"
11603 This condition is true if a message is being processed and the named header
11604 exists in the message. For example,
11606 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11608 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11609 the header name must be terminated by a colon if white space does not follow.
11611 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11612 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11613 .cindex "string" "comparison"
11614 .cindex "expansion" "string comparison"
11615 .cindex "&%eq%& expansion condition"
11616 .cindex "&%eqi%& expansion condition"
11617 The two substrings are first expanded. The condition is true if the two
11618 resulting strings are identical. For &%eq%& the comparison includes the case of
11619 letters, whereas for &%eqi%& the comparison is case-independent, where
11620 case is defined per the system C locale.
11622 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11623 .cindex "expansion" "file existence test"
11624 .cindex "file" "existence test"
11625 .cindex "&%exists%&, expansion condition"
11626 The substring is first expanded and then interpreted as an absolute path. The
11627 condition is true if the named file (or directory) exists. The existence test
11628 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11629 users' filter files may be locked out by the system administrator.
11631 .vitem &*first_delivery*&
11632 .cindex "delivery" "first"
11633 .cindex "first delivery"
11634 .cindex "expansion" "first delivery test"
11635 .cindex "&%first_delivery%& expansion condition"
11636 This condition, which has no data, is true during a message's first delivery
11637 attempt. It is false during any subsequent delivery attempts.
11640 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11641 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11642 .cindex "list" "iterative conditions"
11643 .cindex "expansion" "&*forall*& condition"
11644 .cindex "expansion" "&*forany*& condition"
11646 These conditions iterate over a list. The first argument is expanded to form
11647 the list. By default, the list separator is a colon, but it can be changed by
11648 the normal method (&<<SECTlistsepchange>>&).
11649 The second argument is interpreted as a condition that is to
11650 be applied to each item in the list in turn. During the interpretation of the
11651 condition, the current list item is placed in a variable called &$item$&.
11653 For &*forany*&, interpretation stops if the condition is true for any item, and
11654 the result of the whole condition is true. If the condition is false for all
11655 items in the list, the overall condition is false.
11657 For &*forall*&, interpretation stops if the condition is false for any item,
11658 and the result of the whole condition is false. If the condition is true for
11659 all items in the list, the overall condition is true.
11661 Note that negation of &*forany*& means that the condition must be false for all
11662 items for the overall condition to succeed, and negation of &*forall*& means
11663 that the condition must be false for at least one item. In this example, the
11664 list separator is changed to a comma:
11666 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11668 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11669 being processed, to enable these expansion items to be nested.
11671 To scan a named list, expand it with the &*listnamed*& operator.
11673 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11674 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11675 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11676 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11677 .cindex JSON "iterative conditions"
11678 .cindex JSON expansions
11679 .cindex expansion "&*forall_json*& condition"
11680 .cindex expansion "&*forany_json*& condition"
11681 .cindex expansion "&*forall_jsons*& condition"
11682 .cindex expansion "&*forany_jsons*& condition"
11683 As for the above, except that the first argument must, after expansion,
11685 The array separator is not changeable.
11686 For the &"jsons"& variants the elements are expected to be JSON strings
11687 and have their quotes removed before the evaluation of the condition.
11691 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11692 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11693 .cindex "string" "comparison"
11694 .cindex "expansion" "string comparison"
11695 .cindex "&%ge%& expansion condition"
11696 .cindex "&%gei%& expansion condition"
11697 The two substrings are first expanded. The condition is true if the first
11698 string is lexically greater than or equal to the second string. For &%ge%& the
11699 comparison includes the case of letters, whereas for &%gei%& the comparison is
11701 Case and collation order are defined per the system C locale.
11703 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11704 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11705 .cindex "string" "comparison"
11706 .cindex "expansion" "string comparison"
11707 .cindex "&%gt%& expansion condition"
11708 .cindex "&%gti%& expansion condition"
11709 The two substrings are first expanded. The condition is true if the first
11710 string is lexically greater than the second string. For &%gt%& the comparison
11711 includes the case of letters, whereas for &%gti%& the comparison is
11713 Case and collation order are defined per the system C locale.
11717 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11718 SRS decode. See SECT &<<SECTSRS>>& for details.
11722 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11723 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11724 .cindex "string" "comparison"
11725 .cindex "list" "iterative conditions"
11726 Both strings are expanded; the second string is treated as a list of simple
11727 strings; if the first string is a member of the second, then the condition
11729 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11731 These are simpler to use versions of the more powerful &*forany*& condition.
11732 Examples, and the &*forany*& equivalents:
11734 ${if inlist{needle}{foo:needle:bar}}
11735 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11736 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11737 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11740 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11741 &*isip4&~{*&<&'string'&>&*}*& &&&
11742 &*isip6&~{*&<&'string'&>&*}*&
11743 .cindex "IP address" "testing string format"
11744 .cindex "string" "testing for IP address"
11745 .cindex "&%isip%& expansion condition"
11746 .cindex "&%isip4%& expansion condition"
11747 .cindex "&%isip6%& expansion condition"
11748 The substring is first expanded, and then tested to see if it has the form of
11749 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11750 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11752 For an IPv4 address, the test is for four dot-separated components, each of
11753 which consists of from one to three digits. For an IPv6 address, up to eight
11754 colon-separated components are permitted, each containing from one to four
11755 hexadecimal digits. There may be fewer than eight components if an empty
11756 component (adjacent colons) is present. Only one empty component is permitted.
11758 &*Note*&: The checks used to be just on the form of the address; actual numerical
11759 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11761 This is no longer the case.
11763 The main use of these tests is to distinguish between IP addresses and
11764 host names, or between IPv4 and IPv6 addresses. For example, you could use
11766 ${if isip4{$sender_host_address}...
11768 to test which IP version an incoming SMTP connection is using.
11770 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11771 .cindex "LDAP" "use for authentication"
11772 .cindex "expansion" "LDAP authentication test"
11773 .cindex "&%ldapauth%& expansion condition"
11774 This condition supports user authentication using LDAP. See section
11775 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11776 queries. For this use, the query must contain a user name and password. The
11777 query itself is not used, and can be empty. The condition is true if the
11778 password is not empty, and the user name and password are accepted by the LDAP
11779 server. An empty password is rejected without calling LDAP because LDAP binds
11780 with an empty password are considered anonymous regardless of the username, and
11781 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11782 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11786 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11787 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11788 .cindex "string" "comparison"
11789 .cindex "expansion" "string comparison"
11790 .cindex "&%le%& expansion condition"
11791 .cindex "&%lei%& expansion condition"
11792 The two substrings are first expanded. The condition is true if the first
11793 string is lexically less than or equal to the second string. For &%le%& the
11794 comparison includes the case of letters, whereas for &%lei%& the comparison is
11796 Case and collation order are defined per the system C locale.
11798 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11799 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11800 .cindex "string" "comparison"
11801 .cindex "expansion" "string comparison"
11802 .cindex "&%lt%& expansion condition"
11803 .cindex "&%lti%& expansion condition"
11804 The two substrings are first expanded. The condition is true if the first
11805 string is lexically less than the second string. For &%lt%& the comparison
11806 includes the case of letters, whereas for &%lti%& the comparison is
11808 Case and collation order are defined per the system C locale.
11811 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11812 .cindex "expansion" "regular expression comparison"
11813 .cindex "regular expressions" "match in expanded string"
11814 .cindex "&%match%& expansion condition"
11815 The two substrings are first expanded. The second is then treated as a regular
11816 expression and applied to the first. Because of the pre-expansion, if the
11817 regular expression contains dollar, or backslash characters, they must be
11818 escaped. Care must also be taken if the regular expression contains braces
11819 (curly brackets). A closing brace must be escaped so that it is not taken as a
11820 premature termination of <&'string2'&>. The easiest approach is to use the
11821 &`\N`& feature to disable expansion of the regular expression.
11824 ${if match {$local_part}{\N^\d{3}\N} ...
11826 If the whole expansion string is in double quotes, further escaping of
11827 backslashes is also required.
11829 The condition is true if the regular expression match succeeds.
11830 The regular expression is not required to begin with a circumflex
11831 metacharacter, but if there is no circumflex, the expression is not anchored,
11832 and it may match anywhere in the subject, not just at the start. If you want
11833 the pattern to match at the end of the subject, you must include the &`$`&
11834 metacharacter at an appropriate point.
11835 All character handling is done in bytes and is not UTF-8 aware,
11836 but we might change this in a future Exim release.
11838 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11839 At the start of an &%if%& expansion the values of the numeric variable
11840 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11841 succeeds causes them to be reset to the substrings of that condition and they
11842 will have these values during the expansion of the success string. At the end
11843 of the &%if%& expansion, the previous values are restored. After testing a
11844 combination of conditions using &%or%&, the subsequent values of the numeric
11845 variables are those of the condition that succeeded.
11847 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11848 .cindex "&%match_address%& expansion condition"
11849 See &*match_local_part*&.
11851 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11852 .cindex "&%match_domain%& expansion condition"
11853 See &*match_local_part*&.
11855 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11856 .cindex "&%match_ip%& expansion condition"
11857 This condition matches an IP address to a list of IP address patterns. It must
11858 be followed by two argument strings. The first (after expansion) must be an IP
11859 address or an empty string. The second (not expanded) is a restricted host
11860 list that can match only an IP address, not a host name. For example:
11862 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11864 The specific types of host list item that are permitted in the list are:
11867 An IP address, optionally with a CIDR mask.
11869 A single asterisk, which matches any IP address.
11871 An empty item, which matches only if the IP address is empty. This could be
11872 useful for testing for a locally submitted message or one from specific hosts
11873 in a single test such as
11874 . ==== As this is a nested list, any displays it contains must be indented
11875 . ==== as otherwise they are too far to the left. This comment applies to
11876 . ==== the use of xmlto plus fop. There's no problem when formatting with
11877 . ==== sdop, with or without the extra indent.
11879 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11881 where the first item in the list is the empty string.
11883 The item @[] matches any of the local host's interface addresses.
11885 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11886 even if &`net-`& is not specified. There is never any attempt to turn the IP
11887 address into a host name. The most common type of linear search for
11888 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11889 masks. For example:
11891 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11893 It is of course possible to use other kinds of lookup, and in such a case, you
11894 do need to specify the &`net-`& prefix if you want to specify a specific
11895 address mask, for example:
11897 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11899 However, unless you are combining a &%match_ip%& condition with others, it is
11900 just as easy to use the fact that a lookup is itself a condition, and write:
11902 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11906 Note that <&'string2'&> is not itself subject to string expansion, unless
11907 Exim was built with the EXPAND_LISTMATCH_RHS option.
11909 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11911 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11912 .cindex "domain list" "in expansion condition"
11913 .cindex "address list" "in expansion condition"
11914 .cindex "local part" "list, in expansion condition"
11915 .cindex "&%match_local_part%& expansion condition"
11916 This condition, together with &%match_address%& and &%match_domain%&, make it
11917 possible to test domain, address, and local part lists within expansions. Each
11918 condition requires two arguments: an item and a list to match. A trivial
11921 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11923 In each case, the second argument may contain any of the allowable items for a
11924 list of the appropriate type. Also, because the second argument
11925 is a standard form of list, it is possible to refer to a named list.
11926 Thus, you can use conditions like this:
11928 ${if match_domain{$domain}{+local_domains}{...
11930 .cindex "&`+caseful`&"
11931 For address lists, the matching starts off caselessly, but the &`+caseful`&
11932 item can be used, as in all address lists, to cause subsequent items to
11933 have their local parts matched casefully. Domains are always matched
11936 Note that <&'string2'&> is not itself subject to string expansion, unless
11937 Exim was built with the EXPAND_LISTMATCH_RHS option.
11939 &*Note*&: Host lists are &'not'& supported in this way. This is because
11940 hosts have two identities: a name and an IP address, and it is not clear
11941 how to specify cleanly how such a test would work. However, IP addresses can be
11942 matched using &%match_ip%&.
11944 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11945 .cindex "PAM authentication"
11946 .cindex "AUTH" "with PAM"
11947 .cindex "Solaris" "PAM support"
11948 .cindex "expansion" "PAM authentication test"
11949 .cindex "&%pam%& expansion condition"
11950 &'Pluggable Authentication Modules'&
11951 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
11952 available in the latest releases of Solaris and in some GNU/Linux
11953 distributions. The Exim support, which is intended for use in conjunction with
11954 the SMTP AUTH command, is available only if Exim is compiled with
11958 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11959 in some releases of GNU/Linux &%-ldl%& is also needed.
11961 The argument string is first expanded, and the result must be a
11962 colon-separated list of strings. Leading and trailing white space is ignored.
11963 The PAM module is initialized with the service name &"exim"& and the user name
11964 taken from the first item in the colon-separated data string (<&'string1'&>).
11965 The remaining items in the data string are passed over in response to requests
11966 from the authentication function. In the simple case there will only be one
11967 request, for a password, so the data consists of just two strings.
11969 There can be problems if any of the strings are permitted to contain colon
11970 characters. In the usual way, these have to be doubled to avoid being taken as
11972 The &%listquote%& expansion item can be used for this.
11973 For example, the configuration
11974 of a LOGIN authenticator might contain this setting:
11976 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
11978 In some operating systems, PAM authentication can be done only from a process
11979 running as root. Since Exim is running as the Exim user when receiving
11980 messages, this means that PAM cannot be used directly in those systems.
11981 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
11984 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11985 .cindex "&'pwcheck'& daemon"
11987 .cindex "expansion" "&'pwcheck'& authentication test"
11988 .cindex "&%pwcheck%& expansion condition"
11989 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11990 This is one way of making it possible for passwords to be checked by a process
11991 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11992 deprecated. Its replacement is &'saslauthd'& (see below).
11994 The pwcheck support is not included in Exim by default. You need to specify
11995 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11996 building Exim. For example:
11998 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12000 You do not need to install the full Cyrus software suite in order to use
12001 the pwcheck daemon. You can compile and install just the daemon alone
12002 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12003 access to the &_/var/pwcheck_& directory.
12005 The &%pwcheck%& condition takes one argument, which must be the user name and
12006 password, separated by a colon. For example, in a LOGIN authenticator
12007 configuration, you might have this:
12009 server_condition = ${if pwcheck{$auth1:$auth2}}
12011 Again, for a PLAIN authenticator configuration, this would be:
12013 server_condition = ${if pwcheck{$auth2:$auth3}}
12015 .vitem &*queue_running*&
12016 .cindex "queue runner" "detecting when delivering from"
12017 .cindex "expansion" "queue runner test"
12018 .cindex "&%queue_running%& expansion condition"
12019 This condition, which has no data, is true during delivery attempts that are
12020 initiated by queue runner processes, and false otherwise.
12023 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12025 .cindex "expansion" "Radius authentication"
12026 .cindex "&%radius%& expansion condition"
12027 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12028 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12029 the Radius client configuration file in order to build Exim with Radius
12032 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12033 library, using the original API. If you are using release 0.4.0 or later of
12034 this library, you need to set
12036 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12038 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12039 &%libradius%& library that comes with FreeBSD. To do this, set
12041 RADIUS_LIB_TYPE=RADLIB
12043 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12044 You may also have to supply a suitable setting in EXTRALIBS so that the
12045 Radius library can be found when Exim is linked.
12047 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12048 Radius client library, which calls the Radius server. The condition is true if
12049 the authentication is successful. For example:
12051 server_condition = ${if radius{<arguments>}}
12055 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12056 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12057 .cindex "&'saslauthd'& daemon"
12059 .cindex "expansion" "&'saslauthd'& authentication test"
12060 .cindex "&%saslauthd%& expansion condition"
12061 This condition supports user authentication using the Cyrus &'saslauthd'&
12062 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12063 Using this daemon is one way of making it possible for passwords to be checked
12064 by a process that is not running as root.
12066 The saslauthd support is not included in Exim by default. You need to specify
12067 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12068 building Exim. For example:
12070 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12072 You do not need to install the full Cyrus software suite in order to use
12073 the saslauthd daemon. You can compile and install just the daemon alone
12074 from the Cyrus SASL library.
12076 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12077 two are mandatory. For example:
12079 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12081 The service and the realm are optional (which is why the arguments are enclosed
12082 in their own set of braces). For details of the meaning of the service and
12083 realm, and how to run the daemon, consult the Cyrus documentation.
12088 .section "Combining expansion conditions" "SECID84"
12089 .cindex "expansion" "combining conditions"
12090 Several conditions can be tested at once by combining them using the &%and%&
12091 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12092 conditions on their own, and precede their lists of sub-conditions. Each
12093 sub-condition must be enclosed in braces within the overall braces that contain
12094 the list. No repetition of &%if%& is used.
12098 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12099 .cindex "&""or""& expansion condition"
12100 .cindex "expansion" "&""or""& of conditions"
12101 The sub-conditions are evaluated from left to right. The condition is true if
12102 any one of the sub-conditions is true.
12105 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12107 When a true sub-condition is found, the following ones are parsed but not
12108 evaluated. If there are several &"match"& sub-conditions the values of the
12109 numeric variables afterwards are taken from the first one that succeeds.
12111 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12112 .cindex "&""and""& expansion condition"
12113 .cindex "expansion" "&""and""& of conditions"
12114 The sub-conditions are evaluated from left to right. The condition is true if
12115 all of the sub-conditions are true. If there are several &"match"&
12116 sub-conditions, the values of the numeric variables afterwards are taken from
12117 the last one. When a false sub-condition is found, the following ones are
12118 parsed but not evaluated.
12120 .ecindex IIDexpcond
12125 .section "Expansion variables" "SECTexpvar"
12126 .cindex "expansion" "variables, list of"
12127 This section contains an alphabetical list of all the expansion variables. Some
12128 of them are available only when Exim is compiled with specific options such as
12129 support for TLS or the content scanning extension.
12132 .vitem "&$0$&, &$1$&, etc"
12133 .cindex "numerical variables (&$1$& &$2$& etc)"
12134 When a &%match%& expansion condition succeeds, these variables contain the
12135 captured substrings identified by the regular expression during subsequent
12136 processing of the success string of the containing &%if%& expansion item.
12137 In the expansion condition case
12138 they do not retain their values afterwards; in fact, their previous
12139 values are restored at the end of processing an &%if%& item. The numerical
12140 variables may also be set externally by some other matching process which
12141 precedes the expansion of the string. For example, the commands available in
12142 Exim filter files include an &%if%& command with its own regular expression
12143 matching condition.
12145 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12146 Within an acl condition, expansion condition or expansion item
12147 any arguments are copied to these variables,
12148 any unused variables being made empty.
12150 .vitem "&$acl_c...$&"
12151 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12152 can be given any name that starts with &$acl_c$& and is at least six characters
12153 long, but the sixth character must be either a digit or an underscore. For
12154 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12155 variables persist throughout the lifetime of an SMTP connection. They can be
12156 used to pass information between ACLs and between different invocations of the
12157 same ACL. When a message is received, the values of these variables are saved
12158 with the message, and can be accessed by filters, routers, and transports
12159 during subsequent delivery.
12161 .vitem "&$acl_m...$&"
12162 These variables are like the &$acl_c...$& variables, except that their values
12163 are reset after a message has been received. Thus, if several messages are
12164 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12165 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12166 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12167 message is received, the values of these variables are saved with the message,
12168 and can be accessed by filters, routers, and transports during subsequent
12171 .vitem &$acl_narg$&
12172 Within an acl condition, expansion condition or expansion item
12173 this variable has the number of arguments.
12175 .vitem &$acl_verify_message$&
12176 .vindex "&$acl_verify_message$&"
12177 After an address verification has failed, this variable contains the failure
12178 message. It retains its value for use in subsequent modifiers. The message can
12179 be preserved by coding like this:
12181 warn !verify = sender
12182 set acl_m0 = $acl_verify_message
12184 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12185 &%log_message%& modifiers, to include information about the verification
12188 .vitem &$address_data$&
12189 .vindex "&$address_data$&"
12190 This variable is set by means of the &%address_data%& option in routers. The
12191 value then remains with the address while it is processed by subsequent routers
12192 and eventually a transport. If the transport is handling multiple addresses,
12193 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12194 for more details. &*Note*&: The contents of &$address_data$& are visible in
12197 If &$address_data$& is set when the routers are called from an ACL to verify
12198 a recipient address, the final value is still in the variable for subsequent
12199 conditions and modifiers of the ACL statement. If routing the address caused it
12200 to be redirected to just one address, the child address is also routed as part
12201 of the verification, and in this case the final value of &$address_data$& is
12202 from the child's routing.
12204 If &$address_data$& is set when the routers are called from an ACL to verify a
12205 sender address, the final value is also preserved, but this time in
12206 &$sender_address_data$&, to distinguish it from data from a recipient
12209 In both cases (recipient and sender verification), the value does not persist
12210 after the end of the current ACL statement. If you want to preserve
12211 these values for longer, you can save them in ACL variables.
12213 .vitem &$address_file$&
12214 .vindex "&$address_file$&"
12215 When, as a result of aliasing, forwarding, or filtering, a message is directed
12216 to a specific file, this variable holds the name of the file when the transport
12217 is running. At other times, the variable is empty. For example, using the
12218 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12220 /home/r2d2/savemail
12222 then when the &(address_file)& transport is running, &$address_file$&
12223 contains the text string &`/home/r2d2/savemail`&.
12224 .cindex "Sieve filter" "value of &$address_file$&"
12225 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12226 then up to the transport configuration to generate an appropriate absolute path
12227 to the relevant file.
12229 .vitem &$address_pipe$&
12230 .vindex "&$address_pipe$&"
12231 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12232 this variable holds the pipe command when the transport is running.
12234 .vitem "&$auth1$& &-- &$auth3$&"
12235 .vindex "&$auth1$&, &$auth2$&, etc"
12236 These variables are used in SMTP authenticators (see chapters
12237 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12239 .vitem &$authenticated_id$&
12240 .cindex "authentication" "id"
12241 .vindex "&$authenticated_id$&"
12242 When a server successfully authenticates a client it may be configured to
12243 preserve some of the authentication information in the variable
12244 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12245 user/password authenticator configuration might preserve the user name for use
12246 in the routers. Note that this is not the same information that is saved in
12247 &$sender_host_authenticated$&.
12249 When a message is submitted locally (that is, not over a TCP connection)
12250 the value of &$authenticated_id$& is normally the login name of the calling
12251 process. However, a trusted user can override this by means of the &%-oMai%&
12252 command line option.
12253 This second case also sets up information used by the
12254 &$authresults$& expansion item.
12256 .vitem &$authenticated_fail_id$&
12257 .cindex "authentication" "fail" "id"
12258 .vindex "&$authenticated_fail_id$&"
12259 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12260 will contain the failed authentication id. If more than one authentication
12261 id is attempted, it will contain only the last one. The variable is
12262 available for processing in the ACL's, generally the quit or notquit ACL.
12263 A message to a local recipient could still be accepted without requiring
12264 authentication, which means this variable could also be visible in all of
12268 .vitem &$authenticated_sender$&
12269 .cindex "sender" "authenticated"
12270 .cindex "authentication" "sender"
12271 .cindex "AUTH" "on MAIL command"
12272 .vindex "&$authenticated_sender$&"
12273 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12274 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12275 described in section &<<SECTauthparamail>>&. Unless the data is the string
12276 &"<>"&, it is set as the authenticated sender of the message, and the value is
12277 available during delivery in the &$authenticated_sender$& variable. If the
12278 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12280 .vindex "&$qualify_domain$&"
12281 When a message is submitted locally (that is, not over a TCP connection), the
12282 value of &$authenticated_sender$& is an address constructed from the login
12283 name of the calling process and &$qualify_domain$&, except that a trusted user
12284 can override this by means of the &%-oMas%& command line option.
12287 .vitem &$authentication_failed$&
12288 .cindex "authentication" "failure"
12289 .vindex "&$authentication_failed$&"
12290 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12291 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12292 possible to distinguish between &"did not try to authenticate"&
12293 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12294 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12295 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12296 negative response to an AUTH command, including (for example) an attempt to use
12297 an undefined mechanism.
12299 .vitem &$av_failed$&
12300 .cindex "content scanning" "AV scanner failure"
12301 This variable is available when Exim is compiled with the content-scanning
12302 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12303 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12304 the ACL malware condition.
12306 .vitem &$body_linecount$&
12307 .cindex "message body" "line count"
12308 .cindex "body of message" "line count"
12309 .vindex "&$body_linecount$&"
12310 When a message is being received or delivered, this variable contains the
12311 number of lines in the message's body. See also &$message_linecount$&.
12313 .vitem &$body_zerocount$&
12314 .cindex "message body" "binary zero count"
12315 .cindex "body of message" "binary zero count"
12316 .cindex "binary zero" "in message body"
12317 .vindex "&$body_zerocount$&"
12318 When a message is being received or delivered, this variable contains the
12319 number of binary zero bytes (ASCII NULs) in the message's body.
12321 .vitem &$bounce_recipient$&
12322 .vindex "&$bounce_recipient$&"
12323 This is set to the recipient address of a bounce message while Exim is creating
12324 it. It is useful if a customized bounce message text file is in use (see
12325 chapter &<<CHAPemsgcust>>&).
12327 .vitem &$bounce_return_size_limit$&
12328 .vindex "&$bounce_return_size_limit$&"
12329 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12330 up to a multiple of 1000. It is useful when a customized error message text
12331 file is in use (see chapter &<<CHAPemsgcust>>&).
12333 .vitem &$caller_gid$&
12334 .cindex "gid (group id)" "caller"
12335 .vindex "&$caller_gid$&"
12336 The real group id under which the process that called Exim was running. This is
12337 not the same as the group id of the originator of a message (see
12338 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12339 incarnation normally contains the Exim gid.
12341 .vitem &$caller_uid$&
12342 .cindex "uid (user id)" "caller"
12343 .vindex "&$caller_uid$&"
12344 The real user id under which the process that called Exim was running. This is
12345 not the same as the user id of the originator of a message (see
12346 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12347 incarnation normally contains the Exim uid.
12349 .vitem &$callout_address$&
12350 .vindex "&$callout_address$&"
12351 After a callout for verification, spamd or malware daemon service, the
12352 address that was connected to.
12354 .vitem &$compile_number$&
12355 .vindex "&$compile_number$&"
12356 The building process for Exim keeps a count of the number
12357 of times it has been compiled. This serves to distinguish different
12358 compilations of the same version of Exim.
12360 .vitem &$config_dir$&
12361 .vindex "&$config_dir$&"
12362 The directory name of the main configuration file. That is, the content of
12363 &$config_file$& with the last component stripped. The value does not
12364 contain the trailing slash. If &$config_file$& does not contain a slash,
12365 &$config_dir$& is ".".
12367 .vitem &$config_file$&
12368 .vindex "&$config_file$&"
12369 The name of the main configuration file Exim is using.
12371 .vitem &$dkim_verify_status$&
12372 Results of DKIM verification.
12373 For details see section &<<SECDKIMVFY>>&.
12375 .vitem &$dkim_cur_signer$& &&&
12376 &$dkim_verify_reason$& &&&
12377 &$dkim_domain$& &&&
12378 &$dkim_identity$& &&&
12379 &$dkim_selector$& &&&
12381 &$dkim_canon_body$& &&&
12382 &$dkim_canon_headers$& &&&
12383 &$dkim_copiedheaders$& &&&
12384 &$dkim_bodylength$& &&&
12385 &$dkim_created$& &&&
12386 &$dkim_expires$& &&&
12387 &$dkim_headernames$& &&&
12388 &$dkim_key_testing$& &&&
12389 &$dkim_key_nosubdomains$& &&&
12390 &$dkim_key_srvtype$& &&&
12391 &$dkim_key_granularity$& &&&
12392 &$dkim_key_notes$& &&&
12393 &$dkim_key_length$&
12394 These variables are only available within the DKIM ACL.
12395 For details see section &<<SECDKIMVFY>>&.
12397 .vitem &$dkim_signers$&
12398 .vindex &$dkim_signers$&
12399 When a message has been received this variable contains
12400 a colon-separated list of signer domains and identities for the message.
12401 For details see section &<<SECDKIMVFY>>&.
12403 .vitem &$dmarc_domain_policy$& &&&
12404 &$dmarc_status$& &&&
12405 &$dmarc_status_text$& &&&
12406 &$dmarc_used_domains$&
12407 Results of DMARC verification.
12408 For details see section &<<SECDMARC>>&.
12410 .vitem &$dnslist_domain$& &&&
12411 &$dnslist_matched$& &&&
12412 &$dnslist_text$& &&&
12414 .vindex "&$dnslist_domain$&"
12415 .vindex "&$dnslist_matched$&"
12416 .vindex "&$dnslist_text$&"
12417 .vindex "&$dnslist_value$&"
12418 .cindex "black list (DNS)"
12419 When a DNS (black) list lookup succeeds, these variables are set to contain
12420 the following data from the lookup: the list's domain name, the key that was
12421 looked up, the contents of any associated TXT record, and the value from the
12422 main A record. See section &<<SECID204>>& for more details.
12425 .vindex "&$domain$&"
12426 When an address is being routed, or delivered on its own, this variable
12427 contains the domain. Uppercase letters in the domain are converted into lower
12428 case for &$domain$&.
12430 Global address rewriting happens when a message is received, so the value of
12431 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12432 is set during user filtering, but not during system filtering, because a
12433 message may have many recipients and the system filter is called just once.
12435 When more than one address is being delivered at once (for example, several
12436 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12437 have the same domain. Transports can be restricted to handling only one domain
12438 at a time if the value of &$domain$& is required at transport time &-- this is
12439 the default for local transports. For further details of the environment in
12440 which local transports are run, see chapter &<<CHAPenvironment>>&.
12442 .oindex "&%delay_warning_condition%&"
12443 At the end of a delivery, if all deferred addresses have the same domain, it is
12444 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12446 The &$domain$& variable is also used in some other circumstances:
12449 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12450 the recipient address. The domain of the &'sender'& address is in
12451 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12452 normally set during the running of the MAIL ACL. However, if the sender address
12453 is verified with a callout during the MAIL ACL, the sender domain is placed in
12454 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12455 the &(smtp)& transport.
12458 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12459 &$domain$& contains the domain portion of the address that is being rewritten;
12460 it can be used in the expansion of the replacement address, for example, to
12461 rewrite domains by file lookup.
12464 With one important exception, whenever a domain list is being scanned,
12465 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12466 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12467 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12468 that, in a RCPT ACL, the sender domain list can be dependent on the
12469 recipient domain (which is what is in &$domain$& at this time).
12472 .cindex "ETRN" "value of &$domain$&"
12473 .oindex "&%smtp_etrn_command%&"
12474 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12475 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12478 .cindex "tainted data"
12479 If the origin of the data is an incoming message,
12480 the result of expanding this variable is tainted and may not
12481 be further expanded or used as a filename.
12482 When an untainted version is needed, one should be obtained from
12483 looking up the value in a local (therefore trusted) database.
12484 Often &$domain_data$& is usable in this role.
12487 .vitem &$domain_data$&
12488 .vindex "&$domain_data$&"
12489 When the &%domains%& condition on a router
12493 against a list, the match value is copied to &$domain_data$&.
12494 This is an enhancement over previous versions of Exim, when it only
12495 applied to the data read by a lookup.
12496 For details on match values see section &<<SECTlistresults>>& et. al.
12499 If the router routes the
12500 address to a transport, the value is available in that transport. If the
12501 transport is handling multiple addresses, the value from the first address is
12504 &$domain_data$& set in an ACL is available during
12505 the rest of the ACL statement.
12507 .vitem &$exim_gid$&
12508 .vindex "&$exim_gid$&"
12509 This variable contains the numerical value of the Exim group id.
12511 .vitem &$exim_path$&
12512 .vindex "&$exim_path$&"
12513 This variable contains the path to the Exim binary.
12515 .vitem &$exim_uid$&
12516 .vindex "&$exim_uid$&"
12517 This variable contains the numerical value of the Exim user id.
12519 .vitem &$exim_version$&
12520 .vindex "&$exim_version$&"
12521 This variable contains the version string of the Exim build.
12522 The first character is a major version number, currently 4.
12523 Then after a dot, the next group of digits is a minor version number.
12524 There may be other characters following the minor version.
12525 This value may be overridden by the &%exim_version%& main config option.
12527 .vitem &$header_$&<&'name'&>
12528 This is not strictly an expansion variable. It is expansion syntax for
12529 inserting the message header line with the given name. Note that the name must
12530 be terminated by colon or white space, because it may contain a wide variety of
12531 characters. Note also that braces must &'not'& be used.
12532 See the full description in section &<<SECTexpansionitems>>& above.
12534 .vitem &$headers_added$&
12535 .vindex "&$headers_added$&"
12536 Within an ACL this variable contains the headers added so far by
12537 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12538 The headers are a newline-separated list.
12542 When the &%check_local_user%& option is set for a router, the user's home
12543 directory is placed in &$home$& when the check succeeds. In particular, this
12544 means it is set during the running of users' filter files. A router may also
12545 explicitly set a home directory for use by a transport; this can be overridden
12546 by a setting on the transport itself.
12548 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12549 of the environment variable HOME, which is subject to the
12550 &%keep_environment%& and &%add_environment%& main config options.
12554 If a router assigns an address to a transport (any transport), and passes a
12555 list of hosts with the address, the value of &$host$& when the transport starts
12556 to run is the name of the first host on the list. Note that this applies both
12557 to local and remote transports.
12559 .cindex "transport" "filter"
12560 .cindex "filter" "transport filter"
12561 For the &(smtp)& transport, if there is more than one host, the value of
12562 &$host$& changes as the transport works its way through the list. In
12563 particular, when the &(smtp)& transport is expanding its options for encryption
12564 using TLS, or for specifying a transport filter (see chapter
12565 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12568 When used in the client part of an authenticator configuration (see chapter
12569 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12570 client is connected.
12573 .vitem &$host_address$&
12574 .vindex "&$host_address$&"
12575 This variable is set to the remote host's IP address whenever &$host$& is set
12576 for a remote connection. It is also set to the IP address that is being checked
12577 when the &%ignore_target_hosts%& option is being processed.
12579 .vitem &$host_data$&
12580 .vindex "&$host_data$&"
12581 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12582 result of the lookup is made available in the &$host_data$& variable. This
12583 allows you, for example, to do things like this:
12585 deny hosts = net-lsearch;/some/file
12586 message = $host_data
12588 .vitem &$host_lookup_deferred$&
12589 .cindex "host name" "lookup, failure of"
12590 .vindex "&$host_lookup_deferred$&"
12591 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12592 message comes from a remote host and there is an attempt to look up the host's
12593 name from its IP address, and the attempt is not successful, one of these
12594 variables is set to &"1"&.
12597 If the lookup receives a definite negative response (for example, a DNS lookup
12598 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12601 If there is any kind of problem during the lookup, such that Exim cannot
12602 tell whether or not the host name is defined (for example, a timeout for a DNS
12603 lookup), &$host_lookup_deferred$& is set to &"1"&.
12606 Looking up a host's name from its IP address consists of more than just a
12607 single reverse lookup. Exim checks that a forward lookup of at least one of the
12608 names it receives from a reverse lookup yields the original IP address. If this
12609 is not the case, Exim does not accept the looked up name(s), and
12610 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12611 IP address (for example, the existence of a PTR record in the DNS) is not
12612 sufficient on its own for the success of a host name lookup. If the reverse
12613 lookup succeeds, but there is a lookup problem such as a timeout when checking
12614 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12615 &"1"&. See also &$sender_host_name$&.
12617 .cindex authentication "expansion item"
12618 Performing these checks sets up information used by the
12619 &%authresults%& expansion item.
12622 .vitem &$host_lookup_failed$&
12623 .vindex "&$host_lookup_failed$&"
12624 See &$host_lookup_deferred$&.
12626 .vitem &$host_port$&
12627 .vindex "&$host_port$&"
12628 This variable is set to the remote host's TCP port whenever &$host$& is set
12629 for an outbound connection.
12631 .vitem &$initial_cwd$&
12632 .vindex "&$initial_cwd$&
12633 This variable contains the full path name of the initial working
12634 directory of the current Exim process. This may differ from the current
12635 working directory, as Exim changes this to "/" during early startup, and
12636 to &$spool_directory$& later.
12639 .vindex "&$inode$&"
12640 The only time this variable is set is while expanding the &%directory_file%&
12641 option in the &(appendfile)& transport. The variable contains the inode number
12642 of the temporary file which is about to be renamed. It can be used to construct
12643 a unique name for the file.
12645 .vitem &$interface_address$&
12646 .vindex "&$interface_address$&"
12647 This is an obsolete name for &$received_ip_address$&.
12649 .vitem &$interface_port$&
12650 .vindex "&$interface_port$&"
12651 This is an obsolete name for &$received_port$&.
12655 This variable is used during the expansion of &*forall*& and &*forany*&
12656 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12657 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12661 .vindex "&$ldap_dn$&"
12662 This variable, which is available only when Exim is compiled with LDAP support,
12663 contains the DN from the last entry in the most recently successful LDAP
12666 .vitem &$load_average$&
12667 .vindex "&$load_average$&"
12668 This variable contains the system load average, multiplied by 1000 so that it
12669 is an integer. For example, if the load average is 0.21, the value of the
12670 variable is 210. The value is recomputed every time the variable is referenced.
12672 .vitem &$local_part$&
12673 .vindex "&$local_part$&"
12674 When an address is being routed, or delivered on its own, this
12675 variable contains the local part. When a number of addresses are being
12676 delivered together (for example, multiple RCPT commands in an SMTP
12677 session), &$local_part$& is not set.
12679 Global address rewriting happens when a message is received, so the value of
12680 &$local_part$& during routing and delivery is the value after rewriting.
12681 &$local_part$& is set during user filtering, but not during system filtering,
12682 because a message may have many recipients and the system filter is called just
12685 .cindex "tainted data"
12686 If the origin of the data is an incoming message,
12687 the result of expanding this variable is tainted and
12688 may not be further expanded or used as a filename.
12690 &*Warning*&: the content of this variable is usually provided by a potential
12692 Consider carefully the implications of using it unvalidated as a name
12694 This presents issues for users' &_.forward_& and filter files.
12695 For traditional full user accounts, use &%check_local_users%& and the
12696 &$local_part_data$& variable rather than this one.
12697 For virtual users, store a suitable pathname component in the database
12698 which is used for account name validation, and use that retrieved value
12699 rather than this variable.
12700 Often &$local_part_data$& is usable in this role.
12701 If needed, use a router &%address_data%& or &%set%& option for
12702 the retrieved data.
12704 When a message is being delivered to a file, pipe, or autoreply transport as a
12705 result of aliasing or forwarding, &$local_part$& is set to the local part of
12706 the parent address, not to the filename or command (see &$address_file$& and
12709 When an ACL is running for a RCPT command, &$local_part$& contains the
12710 local part of the recipient address.
12712 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12713 &$local_part$& contains the local part of the address that is being rewritten;
12714 it can be used in the expansion of the replacement address, for example.
12716 In all cases, all quoting is removed from the local part. For example, for both
12719 "abc:xyz"@test.example
12720 abc\:xyz@test.example
12722 the value of &$local_part$& is
12726 If you use &$local_part$& to create another address, you should always wrap it
12727 inside a quoting operator. For example, in a &(redirect)& router you could
12730 data = ${quote_local_part:$local_part}@new.domain.example
12732 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12733 to process local parts in a case-dependent manner in a router, you can set the
12734 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12736 .vitem &$local_part_data$&
12737 .vindex "&$local_part_data$&"
12738 When the &%local_parts%& condition on a router or ACL
12739 matches a local part list
12741 the match value is copied to &$local_part_data$&.
12742 This is an enhancement over previous versions of Exim, when it only
12743 applied to the data read by a lookup.
12744 For details on match values see section &<<SECTlistresults>>& et. al.
12747 The &%check_local_user%& router option also sets this variable.
12749 .vindex &$local_part_prefix$& &&&
12750 &$local_part_prefix_v$& &&&
12751 &$local_part_suffix$& &&&
12752 &$local_part_suffix_v$&
12753 .cindex affix variables
12754 If a local part prefix or suffix has been recognized, it is not included in the
12755 value of &$local_part$& during routing and subsequent delivery. The values of
12756 any prefix or suffix are in &$local_part_prefix$& and
12757 &$local_part_suffix$&, respectively.
12758 .cindex "tainted data"
12759 If the specification did not include a wildcard then
12760 the affix variable value is not tainted.
12762 If the affix specification included a wildcard then the portion of
12763 the affix matched by the wildcard is in
12764 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12765 and both the whole and varying values are tainted.
12767 .vitem &$local_scan_data$&
12768 .vindex "&$local_scan_data$&"
12769 This variable contains the text returned by the &[local_scan()]& function when
12770 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12772 .vitem &$local_user_gid$&
12773 .vindex "&$local_user_gid$&"
12774 See &$local_user_uid$&.
12776 .vitem &$local_user_uid$&
12777 .vindex "&$local_user_uid$&"
12778 This variable and &$local_user_gid$& are set to the uid and gid after the
12779 &%check_local_user%& router precondition succeeds. This means that their values
12780 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12781 and &%condition%&), for the &%address_data%& expansion, and for any
12782 router-specific expansions. At all other times, the values in these variables
12783 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12785 .vitem &$localhost_number$&
12786 .vindex "&$localhost_number$&"
12787 This contains the expanded value of the
12788 &%localhost_number%& option. The expansion happens after the main options have
12791 .vitem &$log_inodes$&
12792 .vindex "&$log_inodes$&"
12793 The number of free inodes in the disk partition where Exim's
12794 log files are being written. The value is recalculated whenever the variable is
12795 referenced. If the relevant file system does not have the concept of inodes,
12796 the value of is -1. See also the &%check_log_inodes%& option.
12798 .vitem &$log_space$&
12799 .vindex "&$log_space$&"
12800 The amount of free space (as a number of kilobytes) in the disk
12801 partition where Exim's log files are being written. The value is recalculated
12802 whenever the variable is referenced. If the operating system does not have the
12803 ability to find the amount of free space (only true for experimental systems),
12804 the space value is -1. See also the &%check_log_space%& option.
12807 .vitem &$lookup_dnssec_authenticated$&
12808 .vindex "&$lookup_dnssec_authenticated$&"
12809 This variable is set after a DNS lookup done by
12810 a dnsdb lookup expansion, dnslookup router or smtp transport.
12811 .cindex "DNS" "DNSSEC"
12812 It will be empty if &(DNSSEC)& was not requested,
12813 &"no"& if the result was not labelled as authenticated data
12814 and &"yes"& if it was.
12815 Results that are labelled as authoritative answer that match
12816 the &%dns_trust_aa%& configuration variable count also
12817 as authenticated data.
12819 .vitem &$mailstore_basename$&
12820 .vindex "&$mailstore_basename$&"
12821 This variable is set only when doing deliveries in &"mailstore"& format in the
12822 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12823 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12824 contains the basename of the files that are being written, that is, the name
12825 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12828 .vitem &$malware_name$&
12829 .vindex "&$malware_name$&"
12830 This variable is available when Exim is compiled with the
12831 content-scanning extension. It is set to the name of the virus that was found
12832 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12834 .vitem &$max_received_linelength$&
12835 .vindex "&$max_received_linelength$&"
12836 .cindex "maximum" "line length"
12837 .cindex "line length" "maximum"
12838 This variable contains the number of bytes in the longest line that was
12839 received as part of the message, not counting the line termination
12841 It is not valid if the &%spool_files_wireformat%& option is used.
12843 .vitem &$message_age$&
12844 .cindex "message" "age of"
12845 .vindex "&$message_age$&"
12846 This variable is set at the start of a delivery attempt to contain the number
12847 of seconds since the message was received. It does not change during a single
12850 .vitem &$message_body$&
12851 .cindex "body of message" "expansion variable"
12852 .cindex "message body" "in expansion"
12853 .cindex "binary zero" "in message body"
12854 .vindex "&$message_body$&"
12855 .oindex "&%message_body_visible%&"
12856 This variable contains the initial portion of a message's body while it is
12857 being delivered, and is intended mainly for use in filter files. The maximum
12858 number of characters of the body that are put into the variable is set by the
12859 &%message_body_visible%& configuration option; the default is 500.
12861 .oindex "&%message_body_newlines%&"
12862 By default, newlines are converted into spaces in &$message_body$&, to make it
12863 easier to search for phrases that might be split over a line break. However,
12864 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12865 zeros are always converted into spaces.
12867 .vitem &$message_body_end$&
12868 .cindex "body of message" "expansion variable"
12869 .cindex "message body" "in expansion"
12870 .vindex "&$message_body_end$&"
12871 This variable contains the final portion of a message's
12872 body while it is being delivered. The format and maximum size are as for
12875 .vitem &$message_body_size$&
12876 .cindex "body of message" "size"
12877 .cindex "message body" "size"
12878 .vindex "&$message_body_size$&"
12879 When a message is being delivered, this variable contains the size of the body
12880 in bytes. The count starts from the character after the blank line that
12881 separates the body from the header. Newlines are included in the count. See
12882 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12884 If the spool file is wireformat
12885 (see the &%spool_files_wireformat%& main option)
12886 the CRLF line-terminators are included in the count.
12888 .vitem &$message_exim_id$&
12889 .vindex "&$message_exim_id$&"
12890 When a message is being received or delivered, this variable contains the
12891 unique message id that is generated and used by Exim to identify the message.
12892 An id is not created for a message until after its header has been successfully
12893 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12894 line; it is the local id that Exim assigns to the message, for example:
12895 &`1BXTIK-0001yO-VA`&.
12897 .vitem &$message_headers$&
12898 .vindex &$message_headers$&
12899 This variable contains a concatenation of all the header lines when a message
12900 is being processed, except for lines added by routers or transports. The header
12901 lines are separated by newline characters. Their contents are decoded in the
12902 same way as a header line that is inserted by &%bheader%&.
12904 .vitem &$message_headers_raw$&
12905 .vindex &$message_headers_raw$&
12906 This variable is like &$message_headers$& except that no processing of the
12907 contents of header lines is done.
12909 .vitem &$message_id$&
12910 This is an old name for &$message_exim_id$&. It is now deprecated.
12912 .vitem &$message_linecount$&
12913 .vindex "&$message_linecount$&"
12914 This variable contains the total number of lines in the header and body of the
12915 message. Compare &$body_linecount$&, which is the count for the body only.
12916 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12917 number of lines received. Before delivery happens (that is, before filters,
12918 routers, and transports run) the count is increased to include the
12919 &'Received:'& header line that Exim standardly adds, and also any other header
12920 lines that are added by ACLs. The blank line that separates the message header
12921 from the body is not counted.
12923 As with the special case of &$message_size$&, during the expansion of the
12924 appendfile transport's maildir_tag option in maildir format, the value of
12925 &$message_linecount$& is the precise size of the number of newlines in the
12926 file that has been written (minus one for the blank line between the
12927 header and the body).
12929 Here is an example of the use of this variable in a DATA ACL:
12932 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12933 message = Too many lines in message header
12935 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12936 message has not yet been received.
12938 This variable is not valid if the &%spool_files_wireformat%& option is used.
12940 .vitem &$message_size$&
12941 .cindex "size" "of message"
12942 .cindex "message" "size"
12943 .vindex "&$message_size$&"
12944 When a message is being processed, this variable contains its size in bytes. In
12945 most cases, the size includes those headers that were received with the
12946 message, but not those (such as &'Envelope-to:'&) that are added to individual
12947 deliveries as they are written. However, there is one special case: during the
12948 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12949 doing a delivery in maildir format, the value of &$message_size$& is the
12950 precise size of the file that has been written. See also
12951 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12953 .cindex "RCPT" "value of &$message_size$&"
12954 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12955 contains the size supplied on the MAIL command, or -1 if no size was given. The
12956 value may not, of course, be truthful.
12958 .vitem &$mime_$&&'xxx'&
12959 A number of variables whose names start with &$mime$& are
12960 available when Exim is compiled with the content-scanning extension. For
12961 details, see section &<<SECTscanmimepart>>&.
12963 .vitem "&$n0$& &-- &$n9$&"
12964 These variables are counters that can be incremented by means
12965 of the &%add%& command in filter files.
12967 .vitem &$original_domain$&
12968 .vindex "&$domain$&"
12969 .vindex "&$original_domain$&"
12970 When a top-level address is being processed for delivery, this contains the
12971 same value as &$domain$&. However, if a &"child"& address (for example,
12972 generated by an alias, forward, or filter file) is being processed, this
12973 variable contains the domain of the original address (lower cased). This
12974 differs from &$parent_domain$& only when there is more than one level of
12975 aliasing or forwarding. When more than one address is being delivered in a
12976 single transport run, &$original_domain$& is not set.
12978 If a new address is created by means of a &%deliver%& command in a system
12979 filter, it is set up with an artificial &"parent"& address. This has the local
12980 part &'system-filter'& and the default qualify domain.
12982 .vitem &$original_local_part$&
12983 .vindex "&$local_part$&"
12984 .vindex "&$original_local_part$&"
12985 When a top-level address is being processed for delivery, this contains the
12986 same value as &$local_part$&, unless a prefix or suffix was removed from the
12987 local part, because &$original_local_part$& always contains the full local
12988 part. When a &"child"& address (for example, generated by an alias, forward, or
12989 filter file) is being processed, this variable contains the full local part of
12990 the original address.
12992 If the router that did the redirection processed the local part
12993 case-insensitively, the value in &$original_local_part$& is in lower case.
12994 This variable differs from &$parent_local_part$& only when there is more than
12995 one level of aliasing or forwarding. When more than one address is being
12996 delivered in a single transport run, &$original_local_part$& is not set.
12998 If a new address is created by means of a &%deliver%& command in a system
12999 filter, it is set up with an artificial &"parent"& address. This has the local
13000 part &'system-filter'& and the default qualify domain.
13002 .vitem &$originator_gid$&
13003 .cindex "gid (group id)" "of originating user"
13004 .cindex "sender" "gid"
13005 .vindex "&$caller_gid$&"
13006 .vindex "&$originator_gid$&"
13007 This variable contains the value of &$caller_gid$& that was set when the
13008 message was received. For messages received via the command line, this is the
13009 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13010 normally the gid of the Exim user.
13012 .vitem &$originator_uid$&
13013 .cindex "uid (user id)" "of originating user"
13014 .cindex "sender" "uid"
13015 .vindex "&$caller_uid$&"
13016 .vindex "&$originator_uid$&"
13017 The value of &$caller_uid$& that was set when the message was received. For
13018 messages received via the command line, this is the uid of the sending user.
13019 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13022 .vitem &$parent_domain$&
13023 .vindex "&$parent_domain$&"
13024 This variable is similar to &$original_domain$& (see
13025 above), except that it refers to the immediately preceding parent address.
13027 .vitem &$parent_local_part$&
13028 .vindex "&$parent_local_part$&"
13029 This variable is similar to &$original_local_part$&
13030 (see above), except that it refers to the immediately preceding parent address.
13033 .cindex "pid (process id)" "of current process"
13035 This variable contains the current process id.
13037 .vitem &$pipe_addresses$&
13038 .cindex "filter" "transport filter"
13039 .cindex "transport" "filter"
13040 .vindex "&$pipe_addresses$&"
13041 This is not an expansion variable, but is mentioned here because the string
13042 &`$pipe_addresses`& is handled specially in the command specification for the
13043 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13044 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13045 It cannot be used in general expansion strings, and provokes an &"unknown
13046 variable"& error if encountered.
13048 .vitem &$primary_hostname$&
13049 .vindex "&$primary_hostname$&"
13050 This variable contains the value set by &%primary_hostname%& in the
13051 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13052 a single-component name, Exim calls &[gethostbyname()]& (or
13053 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13054 qualified host name. See also &$smtp_active_hostname$&.
13057 .vitem &$proxy_external_address$& &&&
13058 &$proxy_external_port$& &&&
13059 &$proxy_local_address$& &&&
13060 &$proxy_local_port$& &&&
13062 These variables are only available when built with Proxy Protocol
13064 For details see chapter &<<SECTproxyInbound>>&.
13066 .vitem &$prdr_requested$&
13067 .cindex "PRDR" "variable for"
13068 This variable is set to &"yes"& if PRDR was requested by the client for the
13069 current message, otherwise &"no"&.
13071 .vitem &$prvscheck_address$&
13072 This variable is used in conjunction with the &%prvscheck%& expansion item,
13073 which is described in sections &<<SECTexpansionitems>>& and
13074 &<<SECTverifyPRVS>>&.
13076 .vitem &$prvscheck_keynum$&
13077 This variable is used in conjunction with the &%prvscheck%& expansion item,
13078 which is described in sections &<<SECTexpansionitems>>& and
13079 &<<SECTverifyPRVS>>&.
13081 .vitem &$prvscheck_result$&
13082 This variable is used in conjunction with the &%prvscheck%& expansion item,
13083 which is described in sections &<<SECTexpansionitems>>& and
13084 &<<SECTverifyPRVS>>&.
13086 .vitem &$qualify_domain$&
13087 .vindex "&$qualify_domain$&"
13088 The value set for the &%qualify_domain%& option in the configuration file.
13090 .vitem &$qualify_recipient$&
13091 .vindex "&$qualify_recipient$&"
13092 The value set for the &%qualify_recipient%& option in the configuration file,
13093 or if not set, the value of &$qualify_domain$&.
13095 .vitem &$queue_name$&
13096 .vindex &$queue_name$&
13097 .cindex "named queues" variable
13098 .cindex queues named
13099 The name of the spool queue in use; empty for the default queue.
13101 .vitem &$queue_size$&
13102 .vindex "&$queue_size$&"
13103 .cindex "queue" "size of"
13104 .cindex "spool" "number of messages"
13105 This variable contains the number of messages queued.
13106 It is evaluated on demand, but no more often than once every minute.
13110 .cindex router variables
13111 Values can be placed in these variables by the &%set%& option of a router.
13112 They can be given any name that starts with &$r_$&.
13113 The values persist for the address being handled through subsequent routers
13114 and the eventual transport.
13116 .vitem &$rcpt_count$&
13117 .vindex "&$rcpt_count$&"
13118 When a message is being received by SMTP, this variable contains the number of
13119 RCPT commands received for the current message. If this variable is used in a
13120 RCPT ACL, its value includes the current command.
13122 .vitem &$rcpt_defer_count$&
13123 .vindex "&$rcpt_defer_count$&"
13124 .cindex "4&'xx'& responses" "count of"
13125 When a message is being received by SMTP, this variable contains the number of
13126 RCPT commands in the current message that have previously been rejected with a
13127 temporary (4&'xx'&) response.
13129 .vitem &$rcpt_fail_count$&
13130 .vindex "&$rcpt_fail_count$&"
13131 When a message is being received by SMTP, this variable contains the number of
13132 RCPT commands in the current message that have previously been rejected with a
13133 permanent (5&'xx'&) response.
13135 .vitem &$received_count$&
13136 .vindex "&$received_count$&"
13137 This variable contains the number of &'Received:'& header lines in the message,
13138 including the one added by Exim (so its value is always greater than zero). It
13139 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13142 .vitem &$received_for$&
13143 .vindex "&$received_for$&"
13144 If there is only a single recipient address in an incoming message, this
13145 variable contains that address when the &'Received:'& header line is being
13146 built. The value is copied after recipient rewriting has happened, but before
13147 the &[local_scan()]& function is run.
13149 .vitem &$received_ip_address$&
13150 .vindex "&$received_ip_address$&"
13151 As soon as an Exim server starts processing an incoming TCP/IP connection, this
13152 variable is set to the address of the local IP interface, and &$received_port$&
13153 is set to the local port number. (The remote IP address and port are in
13154 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13155 the port value is -1 unless it has been set using the &%-oMi%& command line
13158 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13159 could be used, for example, to make the filename for a TLS certificate depend
13160 on which interface and/or port is being used for the incoming connection. The
13161 values of &$received_ip_address$& and &$received_port$& are saved with any
13162 messages that are received, thus making these variables available at delivery
13164 For outbound connections see &$sending_ip_address$&.
13166 .vitem &$received_port$&
13167 .vindex "&$received_port$&"
13168 See &$received_ip_address$&.
13170 .vitem &$received_protocol$&
13171 .vindex "&$received_protocol$&"
13172 When a message is being processed, this variable contains the name of the
13173 protocol by which it was received. Most of the names used by Exim are defined
13174 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13175 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13176 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13177 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13178 connection and the client was successfully authenticated.
13180 Exim uses the protocol name &"smtps"& for the case when encryption is
13181 automatically set up on connection without the use of STARTTLS (see
13182 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13183 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13184 where the client initially uses EHLO, sets up an encrypted connection using
13185 STARTTLS, and then uses HELO afterwards.
13187 The &%-oMr%& option provides a way of specifying a custom protocol name for
13188 messages that are injected locally by trusted callers. This is commonly used to
13189 identify messages that are being re-injected after some kind of scanning.
13191 .vitem &$received_time$&
13192 .vindex "&$received_time$&"
13193 This variable contains the date and time when the current message was received,
13194 as a number of seconds since the start of the Unix epoch.
13196 .vitem &$recipient_data$&
13197 .vindex "&$recipient_data$&"
13198 This variable is set after an indexing lookup success in an ACL &%recipients%&
13199 condition. It contains the data from the lookup, and the value remains set
13200 until the next &%recipients%& test. Thus, you can do things like this:
13202 &`require recipients = cdb*@;/some/file`&
13203 &`deny `&&'some further test involving'& &`$recipient_data`&
13205 &*Warning*&: This variable is set only when a lookup is used as an indexing
13206 method in the address list, using the semicolon syntax as in the example above.
13207 The variable is not set for a lookup that is used as part of the string
13208 expansion that all such lists undergo before being interpreted.
13210 .vitem &$recipient_verify_failure$&
13211 .vindex "&$recipient_verify_failure$&"
13212 In an ACL, when a recipient verification fails, this variable contains
13213 information about the failure. It is set to one of the following words:
13216 &"qualify"&: The address was unqualified (no domain), and the message
13217 was neither local nor came from an exempted host.
13220 &"route"&: Routing failed.
13223 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13224 or before the MAIL command (that is, on initial connection, HELO, or
13228 &"recipient"&: The RCPT command in a callout was rejected.
13231 &"postmaster"&: The postmaster check in a callout was rejected.
13234 The main use of this variable is expected to be to distinguish between
13235 rejections of MAIL and rejections of RCPT.
13237 .vitem &$recipients$&
13238 .vindex "&$recipients$&"
13239 This variable contains a list of envelope recipients for a message. A comma and
13240 a space separate the addresses in the replacement text. However, the variable
13241 is not generally available, to prevent exposure of Bcc recipients in
13242 unprivileged users' filter files. You can use &$recipients$& only in these
13246 In a system filter file.
13248 In the ACLs associated with the DATA command and with non-SMTP messages, that
13249 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13250 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13251 &%acl_not_smtp_mime%&.
13253 From within a &[local_scan()]& function.
13257 .vitem &$recipients_count$&
13258 .vindex "&$recipients_count$&"
13259 When a message is being processed, this variable contains the number of
13260 envelope recipients that came with the message. Duplicates are not excluded
13261 from the count. While a message is being received over SMTP, the number
13262 increases for each accepted recipient. It can be referenced in an ACL.
13265 .vitem &$regex_match_string$&
13266 .vindex "&$regex_match_string$&"
13267 This variable is set to contain the matching regular expression after a
13268 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13270 .vitem "&$regex1$&, &$regex2$&, etc"
13271 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13272 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13273 these variables contain the
13274 captured substrings identified by the regular expression.
13277 .vitem &$reply_address$&
13278 .vindex "&$reply_address$&"
13279 When a message is being processed, this variable contains the contents of the
13280 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13281 contents of the &'From:'& header line. Apart from the removal of leading
13282 white space, the value is not processed in any way. In particular, no RFC 2047
13283 decoding or character code translation takes place.
13285 .vitem &$return_path$&
13286 .vindex "&$return_path$&"
13287 When a message is being delivered, this variable contains the return path &--
13288 the sender field that will be sent as part of the envelope. It is not enclosed
13289 in <> characters. At the start of routing an address, &$return_path$& has the
13290 same value as &$sender_address$&, but if, for example, an incoming message to a
13291 mailing list has been expanded by a router which specifies a different address
13292 for bounce messages, &$return_path$& subsequently contains the new bounce
13293 address, whereas &$sender_address$& always contains the original sender address
13294 that was received with the message. In other words, &$sender_address$& contains
13295 the incoming envelope sender, and &$return_path$& contains the outgoing
13298 .vitem &$return_size_limit$&
13299 .vindex "&$return_size_limit$&"
13300 This is an obsolete name for &$bounce_return_size_limit$&.
13302 .vitem &$router_name$&
13303 .cindex "router" "name"
13304 .cindex "name" "of router"
13305 .vindex "&$router_name$&"
13306 During the running of a router this variable contains its name.
13309 .cindex "return code" "from &%run%& expansion"
13310 .vindex "&$runrc$&"
13311 This variable contains the return code from a command that is run by the
13312 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13313 assume the order in which option values are expanded, except for those
13314 preconditions whose order of testing is documented. Therefore, you cannot
13315 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13318 .vitem &$self_hostname$&
13319 .oindex "&%self%&" "value of host name"
13320 .vindex "&$self_hostname$&"
13321 When an address is routed to a supposedly remote host that turns out to be the
13322 local host, what happens is controlled by the &%self%& generic router option.
13323 One of its values causes the address to be passed to another router. When this
13324 happens, &$self_hostname$& is set to the name of the local host that the
13325 original router encountered. In other circumstances its contents are null.
13327 .vitem &$sender_address$&
13328 .vindex "&$sender_address$&"
13329 When a message is being processed, this variable contains the sender's address
13330 that was received in the message's envelope. The case of letters in the address
13331 is retained, in both the local part and the domain. For bounce messages, the
13332 value of this variable is the empty string. See also &$return_path$&.
13334 .vitem &$sender_address_data$&
13335 .vindex "&$address_data$&"
13336 .vindex "&$sender_address_data$&"
13337 If &$address_data$& is set when the routers are called from an ACL to verify a
13338 sender address, the final value is preserved in &$sender_address_data$&, to
13339 distinguish it from data from a recipient address. The value does not persist
13340 after the end of the current ACL statement. If you want to preserve it for
13341 longer, you can save it in an ACL variable.
13343 .vitem &$sender_address_domain$&
13344 .vindex "&$sender_address_domain$&"
13345 The domain portion of &$sender_address$&.
13347 .vitem &$sender_address_local_part$&
13348 .vindex "&$sender_address_local_part$&"
13349 The local part portion of &$sender_address$&.
13351 .vitem &$sender_data$&
13352 .vindex "&$sender_data$&"
13353 This variable is set after a lookup success in an ACL &%senders%& condition or
13354 in a router &%senders%& option. It contains the data from the lookup, and the
13355 value remains set until the next &%senders%& test. Thus, you can do things like
13358 &`require senders = cdb*@;/some/file`&
13359 &`deny `&&'some further test involving'& &`$sender_data`&
13361 &*Warning*&: This variable is set only when a lookup is used as an indexing
13362 method in the address list, using the semicolon syntax as in the example above.
13363 The variable is not set for a lookup that is used as part of the string
13364 expansion that all such lists undergo before being interpreted.
13366 .vitem &$sender_fullhost$&
13367 .vindex "&$sender_fullhost$&"
13368 When a message is received from a remote host, this variable contains the host
13369 name and IP address in a single string. It ends with the IP address in square
13370 brackets, followed by a colon and a port number if the logging of ports is
13371 enabled. The format of the rest of the string depends on whether the host
13372 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13373 looking up its IP address. (Looking up the IP address can be forced by the
13374 &%host_lookup%& option, independent of verification.) A plain host name at the
13375 start of the string is a verified host name; if this is not present,
13376 verification either failed or was not requested. A host name in parentheses is
13377 the argument of a HELO or EHLO command. This is omitted if it is identical to
13378 the verified host name or to the host's IP address in square brackets.
13380 .vitem &$sender_helo_dnssec$&
13381 .vindex "&$sender_helo_dnssec$&"
13382 This boolean variable is true if a successful HELO verification was
13383 .cindex "DNS" "DNSSEC"
13384 done using DNS information the resolver library stated was authenticated data.
13386 .vitem &$sender_helo_name$&
13387 .vindex "&$sender_helo_name$&"
13388 When a message is received from a remote host that has issued a HELO or EHLO
13389 command, the argument of that command is placed in this variable. It is also
13390 set if HELO or EHLO is used when a message is received using SMTP locally via
13391 the &%-bs%& or &%-bS%& options.
13393 .vitem &$sender_host_address$&
13394 .vindex "&$sender_host_address$&"
13395 When a message is received from a remote host using SMTP,
13396 this variable contains that
13397 host's IP address. For locally non-SMTP submitted messages, it is empty.
13399 .vitem &$sender_host_authenticated$&
13400 .vindex "&$sender_host_authenticated$&"
13401 This variable contains the name (not the public name) of the authenticator
13402 driver that successfully authenticated the client from which the message was
13403 received. It is empty if there was no successful authentication. See also
13404 &$authenticated_id$&.
13406 .vitem &$sender_host_dnssec$&
13407 .vindex "&$sender_host_dnssec$&"
13408 If an attempt to populate &$sender_host_name$& has been made
13409 (by reference, &%hosts_lookup%& or
13410 otherwise) then this boolean will have been set true if, and only if, the
13411 resolver library states that both
13412 the reverse and forward DNS were authenticated data. At all
13413 other times, this variable is false.
13415 .cindex "DNS" "DNSSEC"
13416 It is likely that you will need to coerce DNSSEC support on in the resolver
13417 library, by setting:
13422 In addition, on Linux with glibc 2.31 or newer the resolver library will
13423 default to stripping out a successful validation status.
13424 This will break a previously working Exim installation.
13425 Provided that you do trust the resolver (ie, is on localhost) you can tell
13426 glibc to pass through any successful validation with a new option in
13427 &_/etc/resolv.conf_&:
13432 Exim does not perform DNSSEC validation itself, instead leaving that to a
13433 validating resolver (e.g. unbound, or bind with suitable configuration).
13435 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13436 mechanism in the list, then this variable will be false.
13438 This requires that your system resolver library support EDNS0 (and that
13439 DNSSEC flags exist in the system headers). If the resolver silently drops
13440 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13441 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13444 .vitem &$sender_host_name$&
13445 .vindex "&$sender_host_name$&"
13446 When a message is received from a remote host, this variable contains the
13447 host's name as obtained by looking up its IP address. For messages received by
13448 other means, this variable is empty.
13450 .vindex "&$host_lookup_failed$&"
13451 If the host name has not previously been looked up, a reference to
13452 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13453 A looked up name is accepted only if it leads back to the original IP address
13454 via a forward lookup. If either the reverse or the forward lookup fails to find
13455 any data, or if the forward lookup does not yield the original IP address,
13456 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13458 .vindex "&$host_lookup_deferred$&"
13459 However, if either of the lookups cannot be completed (for example, there is a
13460 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13461 &$host_lookup_failed$& remains set to &"0"&.
13463 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13464 host name again if there is a subsequent reference to &$sender_host_name$&
13465 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13468 Exim does not automatically look up every calling host's name. If you want
13469 maximum efficiency, you should arrange your configuration so that it avoids
13470 these lookups altogether. The lookup happens only if one or more of the
13471 following are true:
13474 A string containing &$sender_host_name$& is expanded.
13476 The calling host matches the list in &%host_lookup%&. In the default
13477 configuration, this option is set to *, so it must be changed if lookups are
13478 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13480 Exim needs the host name in order to test an item in a host list. The items
13481 that require this are described in sections &<<SECThoslispatnam>>& and
13482 &<<SECThoslispatnamsk>>&.
13484 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13485 In this case, the host name is required to compare with the name quoted in any
13486 EHLO or HELO commands that the client issues.
13488 The remote host issues a EHLO or HELO command that quotes one of the
13489 domains in &%helo_lookup_domains%&. The default value of this option is
13490 . ==== As this is a nested list, any displays it contains must be indented
13491 . ==== as otherwise they are too far to the left.
13493 helo_lookup_domains = @ : @[]
13495 which causes a lookup if a remote host (incorrectly) gives the server's name or
13496 IP address in an EHLO or HELO command.
13500 .vitem &$sender_host_port$&
13501 .vindex "&$sender_host_port$&"
13502 When a message is received from a remote host, this variable contains the port
13503 number that was used on the remote host.
13505 .vitem &$sender_ident$&
13506 .vindex "&$sender_ident$&"
13507 When a message is received from a remote host, this variable contains the
13508 identification received in response to an RFC 1413 request. When a message has
13509 been received locally, this variable contains the login name of the user that
13512 .vitem &$sender_rate_$&&'xxx'&
13513 A number of variables whose names begin &$sender_rate_$& are set as part of the
13514 &%ratelimit%& ACL condition. Details are given in section
13515 &<<SECTratelimiting>>&.
13517 .vitem &$sender_rcvhost$&
13518 .cindex "DNS" "reverse lookup"
13519 .cindex "reverse DNS lookup"
13520 .vindex "&$sender_rcvhost$&"
13521 This is provided specifically for use in &'Received:'& headers. It starts with
13522 either the verified host name (as obtained from a reverse DNS lookup) or, if
13523 there is no verified host name, the IP address in square brackets. After that
13524 there may be text in parentheses. When the first item is a verified host name,
13525 the first thing in the parentheses is the IP address in square brackets,
13526 followed by a colon and a port number if port logging is enabled. When the
13527 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13530 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13531 was used and its argument was not identical to the real host name or IP
13532 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13533 all three items are present in the parentheses, a newline and tab are inserted
13534 into the string, to improve the formatting of the &'Received:'& header.
13536 .vitem &$sender_verify_failure$&
13537 .vindex "&$sender_verify_failure$&"
13538 In an ACL, when a sender verification fails, this variable contains information
13539 about the failure. The details are the same as for
13540 &$recipient_verify_failure$&.
13542 .vitem &$sending_ip_address$&
13543 .vindex "&$sending_ip_address$&"
13544 This variable is set whenever an outgoing SMTP connection to another host has
13545 been set up. It contains the IP address of the local interface that is being
13546 used. This is useful if a host that has more than one IP address wants to take
13547 on different personalities depending on which one is being used. For incoming
13548 connections, see &$received_ip_address$&.
13550 .vitem &$sending_port$&
13551 .vindex "&$sending_port$&"
13552 This variable is set whenever an outgoing SMTP connection to another host has
13553 been set up. It contains the local port that is being used. For incoming
13554 connections, see &$received_port$&.
13556 .vitem &$smtp_active_hostname$&
13557 .vindex "&$smtp_active_hostname$&"
13558 During an incoming SMTP session, this variable contains the value of the active
13559 host name, as specified by the &%smtp_active_hostname%& option. The value of
13560 &$smtp_active_hostname$& is saved with any message that is received, so its
13561 value can be consulted during routing and delivery.
13563 .vitem &$smtp_command$&
13564 .vindex "&$smtp_command$&"
13565 During the processing of an incoming SMTP command, this variable contains the
13566 entire command. This makes it possible to distinguish between HELO and EHLO in
13567 the HELO ACL, and also to distinguish between commands such as these:
13572 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13573 command, the address in &$smtp_command$& is the original address before any
13574 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13575 the address after SMTP-time rewriting.
13577 .vitem &$smtp_command_argument$&
13578 .cindex "SMTP" "command, argument for"
13579 .vindex "&$smtp_command_argument$&"
13580 While an ACL is running to check an SMTP command, this variable contains the
13581 argument, that is, the text that follows the command name, with leading white
13582 space removed. Following the introduction of &$smtp_command$&, this variable is
13583 somewhat redundant, but is retained for backwards compatibility.
13585 .vitem &$smtp_command_history$&
13586 .cindex SMTP "command history"
13587 .vindex "&$smtp_command_history$&"
13588 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13589 received, in time-order left to right. Only a limited number of commands
13592 .vitem &$smtp_count_at_connection_start$&
13593 .vindex "&$smtp_count_at_connection_start$&"
13594 This variable is set greater than zero only in processes spawned by the Exim
13595 daemon for handling incoming SMTP connections. The name is deliberately long,
13596 in order to emphasize what the contents are. When the daemon accepts a new
13597 connection, it increments this variable. A copy of the variable is passed to
13598 the child process that handles the connection, but its value is fixed, and
13599 never changes. It is only an approximation of how many incoming connections
13600 there actually are, because many other connections may come and go while a
13601 single connection is being processed. When a child process terminates, the
13602 daemon decrements its copy of the variable.
13604 .vitem "&$sn0$& &-- &$sn9$&"
13605 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13606 that were current at the end of the system filter file. This allows a system
13607 filter file to set values that can be tested in users' filter files. For
13608 example, a system filter could set a value indicating how likely it is that a
13609 message is junk mail.
13611 .vitem &$spam_$&&'xxx'&
13612 A number of variables whose names start with &$spam$& are available when Exim
13613 is compiled with the content-scanning extension. For details, see section
13614 &<<SECTscanspamass>>&.
13616 .vitem &$spf_header_comment$& &&&
13617 &$spf_received$& &&&
13619 &$spf_result_guessed$& &&&
13620 &$spf_smtp_comment$&
13621 These variables are only available if Exim is built with SPF support.
13622 For details see section &<<SECSPF>>&.
13624 .vitem &$spool_directory$&
13625 .vindex "&$spool_directory$&"
13626 The name of Exim's spool directory.
13628 .vitem &$spool_inodes$&
13629 .vindex "&$spool_inodes$&"
13630 The number of free inodes in the disk partition where Exim's spool files are
13631 being written. The value is recalculated whenever the variable is referenced.
13632 If the relevant file system does not have the concept of inodes, the value of
13633 is -1. See also the &%check_spool_inodes%& option.
13635 .vitem &$spool_space$&
13636 .vindex "&$spool_space$&"
13637 The amount of free space (as a number of kilobytes) in the disk partition where
13638 Exim's spool files are being written. The value is recalculated whenever the
13639 variable is referenced. If the operating system does not have the ability to
13640 find the amount of free space (only true for experimental systems), the space
13641 value is -1. For example, to check in an ACL that there is at least 50
13642 megabytes free on the spool, you could write:
13644 condition = ${if > {$spool_space}{50000}}
13646 See also the &%check_spool_space%& option.
13649 .vitem &$thisaddress$&
13650 .vindex "&$thisaddress$&"
13651 This variable is set only during the processing of the &%foranyaddress%&
13652 command in a filter file. Its use is explained in the description of that
13653 command, which can be found in the separate document entitled &'Exim's
13654 interfaces to mail filtering'&.
13656 .vitem &$tls_in_bits$&
13657 .vindex "&$tls_in_bits$&"
13658 Contains an approximation of the TLS cipher's bit-strength
13659 on the inbound connection; the meaning of
13660 this depends upon the TLS implementation used.
13661 If TLS has not been negotiated, the value will be 0.
13662 The value of this is automatically fed into the Cyrus SASL authenticator
13663 when acting as a server, to specify the "external SSF" (a SASL term).
13665 The deprecated &$tls_bits$& variable refers to the inbound side
13666 except when used in the context of an outbound SMTP delivery, when it refers to
13669 .vitem &$tls_out_bits$&
13670 .vindex "&$tls_out_bits$&"
13671 Contains an approximation of the TLS cipher's bit-strength
13672 on an outbound SMTP connection; the meaning of
13673 this depends upon the TLS implementation used.
13674 If TLS has not been negotiated, the value will be 0.
13676 .vitem &$tls_in_ourcert$&
13677 .vindex "&$tls_in_ourcert$&"
13678 .cindex certificate variables
13679 This variable refers to the certificate presented to the peer of an
13680 inbound connection when the message was received.
13681 It is only useful as the argument of a
13682 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13683 or a &%def%& condition.
13685 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13686 when a list of more than one
13687 file is used for &%tls_certificate%&, this variable is not reliable.
13688 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13690 .vitem &$tls_in_peercert$&
13691 .vindex "&$tls_in_peercert$&"
13692 This variable refers to the certificate presented by the peer of an
13693 inbound connection when the message was received.
13694 It is only useful as the argument of a
13695 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13696 or a &%def%& condition.
13697 If certificate verification fails it may refer to a failing chain element
13698 which is not the leaf.
13700 .vitem &$tls_out_ourcert$&
13701 .vindex "&$tls_out_ourcert$&"
13702 This variable refers to the certificate presented to the peer of an
13703 outbound connection. It is only useful as the argument of a
13704 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13705 or a &%def%& condition.
13707 .vitem &$tls_out_peercert$&
13708 .vindex "&$tls_out_peercert$&"
13709 This variable refers to the certificate presented by the peer of an
13710 outbound connection. It is only useful as the argument of a
13711 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13712 or a &%def%& condition.
13713 If certificate verification fails it may refer to a failing chain element
13714 which is not the leaf.
13716 .vitem &$tls_in_certificate_verified$&
13717 .vindex "&$tls_in_certificate_verified$&"
13718 This variable is set to &"1"& if a TLS certificate was verified when the
13719 message was received, and &"0"& otherwise.
13721 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13722 except when used in the context of an outbound SMTP delivery, when it refers to
13725 .vitem &$tls_out_certificate_verified$&
13726 .vindex "&$tls_out_certificate_verified$&"
13727 This variable is set to &"1"& if a TLS certificate was verified when an
13728 outbound SMTP connection was made,
13729 and &"0"& otherwise.
13731 .vitem &$tls_in_cipher$&
13732 .vindex "&$tls_in_cipher$&"
13733 .vindex "&$tls_cipher$&"
13734 When a message is received from a remote host over an encrypted SMTP
13735 connection, this variable is set to the cipher suite that was negotiated, for
13736 example DES-CBC3-SHA. In other circumstances, in particular, for message
13737 received over unencrypted connections, the variable is empty. Testing
13738 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13739 non-encrypted connections during ACL processing.
13741 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13742 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13743 becomes the same as &$tls_out_cipher$&.
13745 .vitem &$tls_in_cipher_std$&
13746 .vindex "&$tls_in_cipher_std$&"
13747 As above, but returning the RFC standard name for the cipher suite.
13749 .vitem &$tls_out_cipher$&
13750 .vindex "&$tls_out_cipher$&"
13752 cleared before any outgoing SMTP connection is made,
13753 and then set to the outgoing cipher suite if one is negotiated. See chapter
13754 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13755 details of the &(smtp)& transport.
13757 .vitem &$tls_out_cipher_std$&
13758 .vindex "&$tls_out_cipher_std$&"
13759 As above, but returning the RFC standard name for the cipher suite.
13761 .vitem &$tls_out_dane$&
13762 .vindex &$tls_out_dane$&
13763 DANE active status. See section &<<SECDANE>>&.
13765 .vitem &$tls_in_ocsp$&
13766 .vindex "&$tls_in_ocsp$&"
13767 When a message is received from a remote client connection
13768 the result of any OCSP request from the client is encoded in this variable:
13770 0 OCSP proof was not requested (default value)
13771 1 No response to request
13772 2 Response not verified
13773 3 Verification failed
13774 4 Verification succeeded
13777 .vitem &$tls_out_ocsp$&
13778 .vindex "&$tls_out_ocsp$&"
13779 When a message is sent to a remote host connection
13780 the result of any OCSP request made is encoded in this variable.
13781 See &$tls_in_ocsp$& for values.
13783 .vitem &$tls_in_peerdn$&
13784 .vindex "&$tls_in_peerdn$&"
13785 .vindex "&$tls_peerdn$&"
13786 .cindex certificate "extracting fields"
13787 When a message is received from a remote host over an encrypted SMTP
13788 connection, and Exim is configured to request a certificate from the client,
13789 the value of the Distinguished Name of the certificate is made available in the
13790 &$tls_in_peerdn$& during subsequent processing.
13791 If certificate verification fails it may refer to a failing chain element
13792 which is not the leaf.
13794 The deprecated &$tls_peerdn$& variable refers to the inbound side
13795 except when used in the context of an outbound SMTP delivery, when it refers to
13798 .vitem &$tls_out_peerdn$&
13799 .vindex "&$tls_out_peerdn$&"
13800 When a message is being delivered to a remote host over an encrypted SMTP
13801 connection, and Exim is configured to request a certificate from the server,
13802 the value of the Distinguished Name of the certificate is made available in the
13803 &$tls_out_peerdn$& during subsequent processing.
13804 If certificate verification fails it may refer to a failing chain element
13805 which is not the leaf.
13809 .vitem &$tls_in_resumption$& &&&
13810 &$tls_out_resumption$&
13811 .vindex &$tls_in_resumption$&
13812 .vindex &$tls_out_resumption$&
13813 .cindex TLS resumption
13814 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13818 .vitem &$tls_in_sni$&
13819 .vindex "&$tls_in_sni$&"
13820 .vindex "&$tls_sni$&"
13821 .cindex "TLS" "Server Name Indication"
13823 .cindex SNI "observability on server"
13824 When a TLS session is being established, if the client sends the Server
13825 Name Indication extension, the value will be placed in this variable.
13826 If the variable appears in &%tls_certificate%& then this option and
13827 some others, described in &<<SECTtlssni>>&,
13828 will be re-expanded early in the TLS session, to permit
13829 a different certificate to be presented (and optionally a different key to be
13830 used) to the client, based upon the value of the SNI extension.
13832 The deprecated &$tls_sni$& variable refers to the inbound side
13833 except when used in the context of an outbound SMTP delivery, when it refers to
13836 .vitem &$tls_out_sni$&
13837 .vindex "&$tls_out_sni$&"
13838 .cindex "TLS" "Server Name Indication"
13840 .cindex SNI "observability in client"
13842 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13845 .vitem &$tls_out_tlsa_usage$&
13846 .vindex &$tls_out_tlsa_usage$&
13847 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13849 .vitem &$tls_in_ver$&
13850 .vindex "&$tls_in_ver$&"
13851 When a message is received from a remote host over an encrypted SMTP connection
13852 this variable is set to the protocol version, eg &'TLS1.2'&.
13854 .vitem &$tls_out_ver$&
13855 .vindex "&$tls_out_ver$&"
13856 When a message is being delivered to a remote host over an encrypted SMTP connection
13857 this variable is set to the protocol version.
13860 .vitem &$tod_bsdinbox$&
13861 .vindex "&$tod_bsdinbox$&"
13862 The time of day and the date, in the format required for BSD-style mailbox
13863 files, for example: Thu Oct 17 17:14:09 1995.
13865 .vitem &$tod_epoch$&
13866 .vindex "&$tod_epoch$&"
13867 The time and date as a number of seconds since the start of the Unix epoch.
13869 .vitem &$tod_epoch_l$&
13870 .vindex "&$tod_epoch_l$&"
13871 The time and date as a number of microseconds since the start of the Unix epoch.
13873 .vitem &$tod_full$&
13874 .vindex "&$tod_full$&"
13875 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13876 +0100. The timezone is always given as a numerical offset from UTC, with
13877 positive values used for timezones that are ahead (east) of UTC, and negative
13878 values for those that are behind (west).
13881 .vindex "&$tod_log$&"
13882 The time and date in the format used for writing Exim's log files, for example:
13883 1995-10-12 15:32:29, but without a timezone.
13885 .vitem &$tod_logfile$&
13886 .vindex "&$tod_logfile$&"
13887 This variable contains the date in the format yyyymmdd. This is the format that
13888 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13891 .vitem &$tod_zone$&
13892 .vindex "&$tod_zone$&"
13893 This variable contains the numerical value of the local timezone, for example:
13896 .vitem &$tod_zulu$&
13897 .vindex "&$tod_zulu$&"
13898 This variable contains the UTC date and time in &"Zulu"& format, as specified
13899 by ISO 8601, for example: 20030221154023Z.
13901 .vitem &$transport_name$&
13902 .cindex "transport" "name"
13903 .cindex "name" "of transport"
13904 .vindex "&$transport_name$&"
13905 During the running of a transport, this variable contains its name.
13908 .vindex "&$value$&"
13909 This variable contains the result of an expansion lookup, extraction operation,
13910 or external command, as described above. It is also used during a
13911 &*reduce*& expansion.
13913 .vitem &$verify_mode$&
13914 .vindex "&$verify_mode$&"
13915 While a router or transport is being run in verify mode or for cutthrough delivery,
13916 contains "S" for sender-verification or "R" for recipient-verification.
13919 .vitem &$version_number$&
13920 .vindex "&$version_number$&"
13921 The version number of Exim. Same as &$exim_version$&, may be overridden
13922 by the &%exim_version%& main config option.
13924 .vitem &$warn_message_delay$&
13925 .vindex "&$warn_message_delay$&"
13926 This variable is set only during the creation of a message warning about a
13927 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13929 .vitem &$warn_message_recipients$&
13930 .vindex "&$warn_message_recipients$&"
13931 This variable is set only during the creation of a message warning about a
13932 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13938 . ////////////////////////////////////////////////////////////////////////////
13939 . ////////////////////////////////////////////////////////////////////////////
13941 .chapter "Embedded Perl" "CHAPperl"
13942 .scindex IIDperl "Perl" "calling from Exim"
13943 Exim can be built to include an embedded Perl interpreter. When this is done,
13944 Perl subroutines can be called as part of the string expansion process. To make
13945 use of the Perl support, you need version 5.004 or later of Perl installed on
13946 your system. To include the embedded interpreter in the Exim binary, include
13951 in your &_Local/Makefile_& and then build Exim in the normal way.
13954 .section "Setting up so Perl can be used" "SECID85"
13955 .oindex "&%perl_startup%&"
13956 Access to Perl subroutines is via a global configuration option called
13957 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13958 no &%perl_startup%& option in the Exim configuration file then no Perl
13959 interpreter is started and there is almost no overhead for Exim (since none of
13960 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13961 option then the associated value is taken to be Perl code which is executed in
13962 a newly created Perl interpreter.
13964 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13965 need backslashes before any characters to escape special meanings. The option
13966 should usually be something like
13968 perl_startup = do '/etc/exim.pl'
13970 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13971 use from Exim. Exim can be configured either to start up a Perl interpreter as
13972 soon as it is entered, or to wait until the first time it is needed. Starting
13973 the interpreter at the beginning ensures that it is done while Exim still has
13974 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13975 fact used in a particular run. Also, note that this does not mean that Exim is
13976 necessarily running as root when Perl is called at a later time. By default,
13977 the interpreter is started only when it is needed, but this can be changed in
13981 .oindex "&%perl_at_start%&"
13982 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13983 a startup when Exim is entered.
13985 The command line option &%-ps%& also requests a startup when Exim is entered,
13986 overriding the setting of &%perl_at_start%&.
13989 There is also a command line option &%-pd%& (for delay) which suppresses the
13990 initial startup, even if &%perl_at_start%& is set.
13993 .oindex "&%perl_taintmode%&"
13994 .cindex "Perl" "taintmode"
13995 To provide more security executing Perl code via the embedded Perl
13996 interpreter, the &%perl_taintmode%& option can be set. This enables the
13997 taint mode of the Perl interpreter. You are encouraged to set this
13998 option to a true value. To avoid breaking existing installations, it
14002 .section "Calling Perl subroutines" "SECID86"
14003 When the configuration file includes a &%perl_startup%& option you can make use
14004 of the string expansion item to call the Perl subroutines that are defined
14005 by the &%perl_startup%& code. The operator is used in any of the following
14009 ${perl{foo}{argument}}
14010 ${perl{foo}{argument1}{argument2} ... }
14012 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14013 arguments may be passed. Passing more than this results in an expansion failure
14014 with an error message of the form
14016 Too many arguments passed to Perl subroutine "foo" (max is 8)
14018 The return value of the Perl subroutine is evaluated in a scalar context before
14019 it is passed back to Exim to be inserted into the expanded string. If the
14020 return value is &'undef'&, the expansion is forced to fail in the same way as
14021 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14022 by obeying Perl's &%die%& function, the expansion fails with the error message
14023 that was passed to &%die%&.
14026 .section "Calling Exim functions from Perl" "SECID87"
14027 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14028 is available to call back into Exim's string expansion function. For example,
14031 my $lp = Exim::expand_string('$local_part');
14033 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14034 Note those are single quotes and not double quotes to protect against
14035 &$local_part$& being interpolated as a Perl variable.
14037 If the string expansion is forced to fail by a &"fail"& item, the result of
14038 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14039 expansion string, the Perl call from the original expansion string fails with
14040 an appropriate error message, in the same way as if &%die%& were used.
14042 .cindex "debugging" "from embedded Perl"
14043 .cindex "log" "writing from embedded Perl"
14044 Two other Exim functions are available for use from within Perl code.
14045 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14046 debugging is enabled. If you want a newline at the end, you must supply it.
14047 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14048 timestamp. In this case, you should not supply a terminating newline.
14051 .section "Use of standard output and error by Perl" "SECID88"
14052 .cindex "Perl" "standard output and error"
14053 You should not write to the standard error or output streams from within your
14054 Perl code, as it is not defined how these are set up. In versions of Exim
14055 before 4.50, it is possible for the standard output or error to refer to the
14056 SMTP connection during message reception via the daemon. Writing to this stream
14057 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14058 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14059 avoided, but the output is lost.
14061 .cindex "Perl" "use of &%warn%&"
14062 The Perl &%warn%& statement writes to the standard error stream by default.
14063 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14064 you have no control. When Exim starts up the Perl interpreter, it arranges for
14065 output from the &%warn%& statement to be written to the Exim main log. You can
14066 change this by including appropriate Perl magic somewhere in your Perl code.
14067 For example, to discard &%warn%& output completely, you need this:
14069 $SIG{__WARN__} = sub { };
14071 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14072 example, the code for the subroutine is empty, so it does nothing, but you can
14073 include any Perl code that you like. The text of the &%warn%& message is passed
14074 as the first subroutine argument.
14078 . ////////////////////////////////////////////////////////////////////////////
14079 . ////////////////////////////////////////////////////////////////////////////
14081 .chapter "Starting the daemon and the use of network interfaces" &&&
14082 "CHAPinterfaces" &&&
14083 "Starting the daemon"
14084 .cindex "daemon" "starting"
14085 .cindex "interface" "listening"
14086 .cindex "network interface"
14087 .cindex "interface" "network"
14088 .cindex "IP address" "for listening"
14089 .cindex "daemon" "listening IP addresses"
14090 .cindex "TCP/IP" "setting listening interfaces"
14091 .cindex "TCP/IP" "setting listening ports"
14092 A host that is connected to a TCP/IP network may have one or more physical
14093 hardware network interfaces. Each of these interfaces may be configured as one
14094 or more &"logical"& interfaces, which are the entities that a program actually
14095 works with. Each of these logical interfaces is associated with an IP address.
14096 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14097 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14098 knowledge about the host's interfaces for use in three different circumstances:
14101 When a listening daemon is started, Exim needs to know which interfaces
14102 and ports to listen on.
14104 When Exim is routing an address, it needs to know which IP addresses
14105 are associated with local interfaces. This is required for the correct
14106 processing of MX lists by removing the local host and others with the
14107 same or higher priority values. Also, Exim needs to detect cases
14108 when an address is routed to an IP address that in fact belongs to the
14109 local host. Unless the &%self%& router option or the &%allow_localhost%&
14110 option of the smtp transport is set (as appropriate), this is treated
14111 as an error situation.
14113 When Exim connects to a remote host, it may need to know which interface to use
14114 for the outgoing connection.
14118 Exim's default behaviour is likely to be appropriate in the vast majority
14119 of cases. If your host has only one interface, and you want all its IP
14120 addresses to be treated in the same way, and you are using only the
14121 standard SMTP port, you should not need to take any special action. The
14122 rest of this chapter does not apply to you.
14124 In a more complicated situation you may want to listen only on certain
14125 interfaces, or on different ports, and for this reason there are a number of
14126 options that can be used to influence Exim's behaviour. The rest of this
14127 chapter describes how they operate.
14129 When a message is received over TCP/IP, the interface and port that were
14130 actually used are set in &$received_ip_address$& and &$received_port$&.
14134 .section "Starting a listening daemon" "SECID89"
14135 When a listening daemon is started (by means of the &%-bd%& command line
14136 option), the interfaces and ports on which it listens are controlled by the
14140 &%daemon_smtp_ports%& contains a list of default ports
14142 (For backward compatibility, this option can also be specified in the singular.)
14144 &%local_interfaces%& contains list of interface IP addresses on which to
14145 listen. Each item may optionally also specify a port.
14148 The default list separator in both cases is a colon, but this can be changed as
14149 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14150 it is usually best to change the separator to avoid having to double all the
14151 colons. For example:
14153 local_interfaces = <; 127.0.0.1 ; \
14156 3ffe:ffff:836f::fe86:a061
14158 There are two different formats for specifying a port along with an IP address
14159 in &%local_interfaces%&:
14162 The port is added onto the address with a dot separator. For example, to listen
14163 on port 1234 on two different IP addresses:
14165 local_interfaces = <; 192.168.23.65.1234 ; \
14166 3ffe:ffff:836f::fe86:a061.1234
14169 The IP address is enclosed in square brackets, and the port is added
14170 with a colon separator, for example:
14172 local_interfaces = <; [192.168.23.65]:1234 ; \
14173 [3ffe:ffff:836f::fe86:a061]:1234
14177 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14178 default setting contains just one port:
14180 daemon_smtp_ports = smtp
14182 If more than one port is listed, each interface that does not have its own port
14183 specified listens on all of them. Ports that are listed in
14184 &%daemon_smtp_ports%& can be identified either by name (defined in
14185 &_/etc/services_&) or by number. However, when ports are given with individual
14186 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14190 .section "Special IP listening addresses" "SECID90"
14191 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14192 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14193 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14194 instead of setting up separate listening sockets for each interface. The
14195 default value of &%local_interfaces%& is
14197 local_interfaces = 0.0.0.0
14199 when Exim is built without IPv6 support; otherwise it is:
14201 local_interfaces = <; ::0 ; 0.0.0.0
14203 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14207 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14208 The &%-oX%& command line option can be used to override the values of
14209 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14210 instance. Another way of doing this would be to use macros and the &%-D%&
14211 option. However, &%-oX%& can be used by any admin user, whereas modification of
14212 the runtime configuration by &%-D%& is allowed only when the caller is root or
14215 The value of &%-oX%& is a list of items. The default colon separator can be
14216 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14217 If there are any items that do not
14218 contain dots or colons (that is, are not IP addresses), the value of
14219 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14220 items that do contain dots or colons, the value of &%local_interfaces%& is
14221 replaced by those items. Thus, for example,
14225 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14228 -oX 192.168.34.5.1125
14230 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14231 (However, since &%local_interfaces%& now contains no items without ports, the
14232 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14236 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14237 .cindex "submissions protocol"
14238 .cindex "ssmtp protocol"
14239 .cindex "smtps protocol"
14240 .cindex "SMTP" "ssmtp protocol"
14241 .cindex "SMTP" "smtps protocol"
14242 Exim supports the use of TLS-on-connect, used by mail clients in the
14243 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14244 For some years, IETF Standards Track documents only blessed the
14245 STARTTLS-based Submission service (port 587) while common practice was to support
14246 the same feature set on port 465, but using TLS-on-connect.
14247 If your installation needs to provide service to mail clients
14248 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14251 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14252 service names, connections to those ports must first establish TLS, before
14253 proceeding to the application layer use of the SMTP protocol.
14255 The common use of this option is expected to be
14257 tls_on_connect_ports = 465
14260 There is also a command line option &%-tls-on-connect%&, which forces all ports
14261 to behave in this way when a daemon is started.
14263 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14264 daemon to listen on those ports. You must still specify them in
14265 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14266 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14267 connections via the daemon.)
14272 .section "IPv6 address scopes" "SECID92"
14273 .cindex "IPv6" "address scopes"
14274 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14275 can, in principle, have the same link-local IPv6 address on different
14276 interfaces. Thus, additional information is needed, over and above the IP
14277 address, to distinguish individual interfaces. A convention of using a
14278 percent sign followed by something (often the interface name) has been
14279 adopted in some cases, leading to addresses like this:
14281 fe80::202:b3ff:fe03:45c1%eth0
14283 To accommodate this usage, a percent sign followed by an arbitrary string is
14284 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14285 to convert a textual IPv6 address for actual use. This function recognizes the
14286 percent convention in operating systems that support it, and it processes the
14287 address appropriately. Unfortunately, some older libraries have problems with
14288 &[getaddrinfo()]&. If
14290 IPV6_USE_INET_PTON=yes
14292 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14293 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14294 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14295 function.) Of course, this means that the additional functionality of
14296 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14298 .section "Disabling IPv6" "SECID93"
14299 .cindex "IPv6" "disabling"
14300 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14301 run on a host whose kernel does not support IPv6. The binary will fall back to
14302 using IPv4, but it may waste resources looking up AAAA records, and trying to
14303 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14304 .oindex "&%disable_ipv6%&"
14305 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14306 activities take place. AAAA records are never looked up, and any IPv6 addresses
14307 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14308 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14309 to handle IPv6 literal addresses.
14311 On the other hand, when IPv6 is in use, there may be times when you want to
14312 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14313 option to globally suppress the lookup of AAAA records for specified domains,
14314 and you can use the &%ignore_target_hosts%& generic router option to ignore
14315 IPv6 addresses in an individual router.
14319 .section "Examples of starting a listening daemon" "SECID94"
14320 The default case in an IPv6 environment is
14322 daemon_smtp_ports = smtp
14323 local_interfaces = <; ::0 ; 0.0.0.0
14325 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14326 Either one or two sockets may be used, depending on the characteristics of
14327 the TCP/IP stack. (This is complicated and messy; for more information,
14328 read the comments in the &_daemon.c_& source file.)
14330 To specify listening on ports 25 and 26 on all interfaces:
14332 daemon_smtp_ports = 25 : 26
14334 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14336 local_interfaces = <; ::0.25 ; ::0.26 \
14337 0.0.0.0.25 ; 0.0.0.0.26
14339 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14340 IPv4 loopback address only:
14342 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14344 To specify listening on the default port on specific interfaces only:
14346 local_interfaces = 10.0.0.67 : 192.168.34.67
14348 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14352 .section "Recognizing the local host" "SECTreclocipadd"
14353 The &%local_interfaces%& option is also used when Exim needs to determine
14354 whether or not an IP address refers to the local host. That is, the IP
14355 addresses of all the interfaces on which a daemon is listening are always
14358 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14359 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14360 available interfaces from the operating system, and extracts the relevant
14361 (that is, IPv4 or IPv6) addresses to use for checking.
14363 Some systems set up large numbers of virtual interfaces in order to provide
14364 many virtual web servers. In this situation, you may want to listen for
14365 email on only a few of the available interfaces, but nevertheless treat all
14366 interfaces as local when routing. You can do this by setting
14367 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14368 &"all"& wildcard values. These addresses are recognized as local, but are not
14369 used for listening. Consider this example:
14371 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14373 3ffe:2101:12:1:a00:20ff:fe86:a061
14375 extra_local_interfaces = <; ::0 ; 0.0.0.0
14377 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14378 address, but all available interface addresses are treated as local when
14381 In some environments the local host name may be in an MX list, but with an IP
14382 address that is not assigned to any local interface. In other cases it may be
14383 desirable to treat other host names as if they referred to the local host. Both
14384 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14385 This contains host names rather than IP addresses. When a host is referenced
14386 during routing, either via an MX record or directly, it is treated as the local
14387 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14388 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14392 .section "Delivering to a remote host" "SECID95"
14393 Delivery to a remote host is handled by the smtp transport. By default, it
14394 allows the system's TCP/IP functions to choose which interface to use (if
14395 there is more than one) when connecting to a remote host. However, the
14396 &%interface%& option can be set to specify which interface is used. See the
14397 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14403 . ////////////////////////////////////////////////////////////////////////////
14404 . ////////////////////////////////////////////////////////////////////////////
14406 .chapter "Main configuration" "CHAPmainconfig"
14407 .scindex IIDconfima "configuration file" "main section"
14408 .scindex IIDmaiconf "main configuration"
14409 The first part of the runtime configuration file contains three types of item:
14412 Macro definitions: These lines start with an upper case letter. See section
14413 &<<SECTmacrodefs>>& for details of macro processing.
14415 Named list definitions: These lines start with one of the words &"domainlist"&,
14416 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14417 section &<<SECTnamedlists>>&.
14419 Main configuration settings: Each setting occupies one line of the file
14420 (with possible continuations). If any setting is preceded by the word
14421 &"hide"&, the &%-bP%& command line option displays its value to admin users
14422 only. See section &<<SECTcos>>& for a description of the syntax of these option
14426 This chapter specifies all the main configuration options, along with their
14427 types and default values. For ease of finding a particular option, they appear
14428 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14429 are now so many options, they are first listed briefly in functional groups, as
14430 an aid to finding the name of the option you are looking for. Some options are
14431 listed in more than one group.
14433 .section "Miscellaneous" "SECID96"
14435 .row &%bi_command%& "to run for &%-bi%& command line option"
14436 .row &%debug_store%& "do extra internal checks"
14437 .row &%disable_ipv6%& "do no IPv6 processing"
14438 .row &%keep_malformed%& "for broken files &-- should not happen"
14439 .row &%localhost_number%& "for unique message ids in clusters"
14440 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14441 .row &%message_body_visible%& "how much to show in &$message_body$&"
14442 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14443 .row &%print_topbitchars%& "top-bit characters are printing"
14444 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14445 .row &%timezone%& "force time zone"
14449 .section "Exim parameters" "SECID97"
14451 .row &%exim_group%& "override compiled-in value"
14452 .row &%exim_path%& "override compiled-in value"
14453 .row &%exim_user%& "override compiled-in value"
14454 .row &%primary_hostname%& "default from &[uname()]&"
14455 .row &%split_spool_directory%& "use multiple directories"
14456 .row &%spool_directory%& "override compiled-in value"
14461 .section "Privilege controls" "SECID98"
14463 .row &%admin_groups%& "groups that are Exim admin users"
14464 .row &%commandline_checks_require_admin%& "require admin for various checks"
14465 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14466 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14467 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14468 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14469 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14470 .row &%never_users%& "do not run deliveries as these"
14471 .row &%prod_requires_admin%& "forced delivery requires admin user"
14472 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14473 .row &%trusted_groups%& "groups that are trusted"
14474 .row &%trusted_users%& "users that are trusted"
14479 .section "Logging" "SECID99"
14481 .row &%event_action%& "custom logging"
14482 .row &%hosts_connection_nolog%& "exemption from connect logging"
14483 .row &%log_file_path%& "override compiled-in value"
14484 .row &%log_selector%& "set/unset optional logging"
14485 .row &%log_timezone%& "add timezone to log lines"
14486 .row &%message_logs%& "create per-message logs"
14487 .row &%preserve_message_logs%& "after message completion"
14488 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14489 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14490 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14491 .row &%syslog_facility%& "set syslog &""facility""& field"
14492 .row &%syslog_pid%& "pid in syslog lines"
14493 .row &%syslog_processname%& "set syslog &""ident""& field"
14494 .row &%syslog_timestamp%& "timestamp syslog lines"
14495 .row &%write_rejectlog%& "control use of message log"
14500 .section "Frozen messages" "SECID100"
14502 .row &%auto_thaw%& "sets time for retrying frozen messages"
14503 .row &%freeze_tell%& "send message when freezing"
14504 .row &%move_frozen_messages%& "to another directory"
14505 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14510 .section "Data lookups" "SECID101"
14512 .row &%ibase_servers%& "InterBase servers"
14513 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14514 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14515 .row &%ldap_cert_file%& "client cert file for LDAP"
14516 .row &%ldap_cert_key%& "client key file for LDAP"
14517 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14518 .row &%ldap_default_servers%& "used if no server in query"
14519 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14520 .row &%ldap_start_tls%& "require TLS within LDAP"
14521 .row &%ldap_version%& "set protocol version"
14522 .row &%lookup_open_max%& "lookup files held open"
14523 .row &%mysql_servers%& "default MySQL servers"
14524 .row &%oracle_servers%& "Oracle servers"
14525 .row &%pgsql_servers%& "default PostgreSQL servers"
14526 .row &%sqlite_lock_timeout%& "as it says"
14531 .section "Message ids" "SECID102"
14533 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14534 .row &%message_id_header_text%& "ditto"
14539 .section "Embedded Perl Startup" "SECID103"
14541 .row &%perl_at_start%& "always start the interpreter"
14542 .row &%perl_startup%& "code to obey when starting Perl"
14543 .row &%perl_taintmode%& "enable taint mode in Perl"
14548 .section "Daemon" "SECID104"
14550 .row &%daemon_smtp_ports%& "default ports"
14551 .row &%daemon_startup_retries%& "number of times to retry"
14552 .row &%daemon_startup_sleep%& "time to sleep between tries"
14553 .row &%extra_local_interfaces%& "not necessarily listened on"
14554 .row &%local_interfaces%& "on which to listen, with optional ports"
14555 .row &%notifier_socket%& "override compiled-in value"
14556 .row &%pid_file_path%& "override compiled-in value"
14557 .row &%queue_run_max%& "maximum simultaneous queue runners"
14562 .section "Resource control" "SECID105"
14564 .row &%check_log_inodes%& "before accepting a message"
14565 .row &%check_log_space%& "before accepting a message"
14566 .row &%check_spool_inodes%& "before accepting a message"
14567 .row &%check_spool_space%& "before accepting a message"
14568 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14569 .row &%queue_only_load%& "queue incoming if load high"
14570 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14571 .row &%queue_run_max%& "maximum simultaneous queue runners"
14572 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14573 .row &%smtp_accept_max%& "simultaneous incoming connections"
14574 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14575 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14576 .row &%smtp_accept_max_per_connection%& "messages per connection"
14577 .row &%smtp_accept_max_per_host%& "connections from one host"
14578 .row &%smtp_accept_queue%& "queue mail if more connections"
14579 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14581 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14582 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14583 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14584 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14585 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14590 .section "Policy controls" "SECID106"
14592 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14593 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14594 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14595 .row &%acl_smtp_auth%& "ACL for AUTH"
14596 .row &%acl_smtp_connect%& "ACL for connection"
14597 .row &%acl_smtp_data%& "ACL for DATA"
14598 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14599 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14600 .row &%acl_smtp_etrn%& "ACL for ETRN"
14601 .row &%acl_smtp_expn%& "ACL for EXPN"
14602 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14603 .row &%acl_smtp_mail%& "ACL for MAIL"
14604 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14605 .row &%acl_smtp_mime%& "ACL for MIME parts"
14606 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14607 .row &%acl_smtp_predata%& "ACL for start of data"
14608 .row &%acl_smtp_quit%& "ACL for QUIT"
14609 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14610 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14611 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14612 .row &%av_scanner%& "specify virus scanner"
14613 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14615 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14616 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14617 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14618 .row &%header_maxsize%& "total size of message header"
14619 .row &%header_line_maxsize%& "individual header line limit"
14620 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14621 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14622 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14623 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14624 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14625 .row &%host_lookup%& "host name looked up for these hosts"
14626 .row &%host_lookup_order%& "order of DNS and local name lookups"
14627 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14628 .row &%host_reject_connection%& "reject connection from these hosts"
14629 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14630 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14631 .row &%message_size_limit%& "for all messages"
14632 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14633 .row &%spamd_address%& "set interface to SpamAssassin"
14634 .row &%strict_acl_vars%& "object to unset ACL variables"
14635 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14640 .section "Callout cache" "SECID107"
14642 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14644 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14646 .row &%callout_negative_expire%& "timeout for negative address cache item"
14647 .row &%callout_positive_expire%& "timeout for positive address cache item"
14648 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14653 .section "TLS" "SECID108"
14655 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14656 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14657 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14658 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14659 .row &%tls_certificate%& "location of server certificate"
14660 .row &%tls_crl%& "certificate revocation list"
14661 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14662 .row &%tls_dhparam%& "DH parameters for server"
14663 .row &%tls_eccurve%& "EC curve selection for server"
14664 .row &%tls_ocsp_file%& "location of server certificate status proof"
14665 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14666 .row &%tls_privatekey%& "location of server private key"
14667 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14668 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14669 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14670 .row &%tls_verify_certificates%& "expected client certificates"
14671 .row &%tls_verify_hosts%& "insist on client certificate verify"
14676 .section "Local user handling" "SECID109"
14678 .row &%finduser_retries%& "useful in NIS environments"
14679 .row &%gecos_name%& "used when creating &'Sender:'&"
14680 .row &%gecos_pattern%& "ditto"
14681 .row &%max_username_length%& "for systems that truncate"
14682 .row &%unknown_login%& "used when no login name found"
14683 .row &%unknown_username%& "ditto"
14684 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14685 .row &%uucp_from_sender%& "ditto"
14690 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14692 .row &%header_maxsize%& "total size of message header"
14693 .row &%header_line_maxsize%& "individual header line limit"
14694 .row &%message_size_limit%& "applies to all messages"
14695 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14696 .row &%received_header_text%& "expanded to make &'Received:'&"
14697 .row &%received_headers_max%& "for mail loop detection"
14698 .row &%recipients_max%& "limit per message"
14699 .row &%recipients_max_reject%& "permanently reject excess recipients"
14705 .section "Non-SMTP incoming messages" "SECID111"
14707 .row &%receive_timeout%& "for non-SMTP messages"
14714 .section "Incoming SMTP messages" "SECID112"
14715 See also the &'Policy controls'& section above.
14718 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14719 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14720 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14721 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14722 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14723 .row &%dmarc_history_file%& "DMARC results log"
14724 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14725 .row &%host_lookup%& "host name looked up for these hosts"
14726 .row &%host_lookup_order%& "order of DNS and local name lookups"
14727 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14728 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14729 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14730 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14731 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14732 .row &%smtp_accept_max%& "simultaneous incoming connections"
14733 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14734 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14735 .row &%smtp_accept_max_per_connection%& "messages per connection"
14736 .row &%smtp_accept_max_per_host%& "connections from one host"
14737 .row &%smtp_accept_queue%& "queue mail if more connections"
14738 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14740 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14741 .row &%smtp_active_hostname%& "host name to use in messages"
14742 .row &%smtp_banner%& "text for welcome banner"
14743 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14744 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14745 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14746 .row &%smtp_etrn_command%& "what to run for ETRN"
14747 .row &%smtp_etrn_serialize%& "only one at once"
14748 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14749 .row &%smtp_max_unknown_commands%& "before dropping connection"
14750 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14751 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14752 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14753 .row &%smtp_receive_timeout%& "per command or data line"
14754 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14755 .row &%smtp_return_error_details%& "give detail on rejections"
14760 .section "SMTP extensions" "SECID113"
14762 .row &%accept_8bitmime%& "advertise 8BITMIME"
14763 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14764 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14765 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14766 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14767 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14768 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14769 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14770 .row &%prdr_enable%& "advertise PRDR to all hosts"
14771 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14772 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14777 .section "Processing messages" "SECID114"
14779 .row &%allow_domain_literals%& "recognize domain literal syntax"
14780 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14781 .row &%allow_utf8_domains%& "in addresses"
14782 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14784 .row &%delivery_date_remove%& "from incoming messages"
14785 .row &%envelope_to_remove%& "from incoming messages"
14786 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14787 .row &%headers_charset%& "default for translations"
14788 .row &%qualify_domain%& "default for senders"
14789 .row &%qualify_recipient%& "default for recipients"
14790 .row &%return_path_remove%& "from incoming messages"
14791 .row &%strip_excess_angle_brackets%& "in addresses"
14792 .row &%strip_trailing_dot%& "at end of addresses"
14793 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14798 .section "System filter" "SECID115"
14800 .row &%system_filter%& "locate system filter"
14801 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14803 .row &%system_filter_file_transport%& "transport for delivery to a file"
14804 .row &%system_filter_group%& "group for filter running"
14805 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14806 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14807 .row &%system_filter_user%& "user for filter running"
14812 .section "Routing and delivery" "SECID116"
14814 .row &%disable_ipv6%& "do no IPv6 processing"
14815 .row &%dns_again_means_nonexist%& "for broken domains"
14816 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14817 .row &%dns_dnssec_ok%& "parameter for resolver"
14818 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14819 .row &%dns_retrans%& "parameter for resolver"
14820 .row &%dns_retry%& "parameter for resolver"
14821 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14822 .row &%dns_use_edns0%& "parameter for resolver"
14823 .row &%hold_domains%& "hold delivery for these domains"
14824 .row &%local_interfaces%& "for routing checks"
14825 .row &%queue_domains%& "no immediate delivery for these"
14826 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14827 .row &%queue_only%& "no immediate delivery at all"
14828 .row &%queue_only_file%& "no immediate delivery if file exists"
14829 .row &%queue_only_load%& "no immediate delivery if load is high"
14830 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14831 .row &%queue_only_override%& "allow command line to override"
14832 .row &%queue_run_in_order%& "order of arrival"
14833 .row &%queue_run_max%& "of simultaneous queue runners"
14834 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14835 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14836 .row &%remote_sort_domains%& "order of remote deliveries"
14837 .row &%retry_data_expire%& "timeout for retry data"
14838 .row &%retry_interval_max%& "safety net for retry rules"
14843 .section "Bounce and warning messages" "SECID117"
14845 .row &%bounce_message_file%& "content of bounce"
14846 .row &%bounce_message_text%& "content of bounce"
14847 .row &%bounce_return_body%& "include body if returning message"
14848 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14849 .row &%bounce_return_message%& "include original message in bounce"
14850 .row &%bounce_return_size_limit%& "limit on returned message"
14851 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14852 .row &%dsn_from%& "set &'From:'& contents in bounces"
14853 .row &%errors_copy%& "copy bounce messages"
14854 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14855 .row &%delay_warning%& "time schedule"
14856 .row &%delay_warning_condition%& "condition for warning messages"
14857 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14858 .row &%smtp_return_error_details%& "give detail on rejections"
14859 .row &%warn_message_file%& "content of warning message"
14864 .section "Alphabetical list of main options" "SECTalomo"
14865 Those options that undergo string expansion before use are marked with
14868 .option accept_8bitmime main boolean true
14870 .cindex "8-bit characters"
14871 .cindex "log" "selectors"
14872 .cindex "log" "8BITMIME"
14873 .cindex "ESMTP extensions" 8BITMIME
14874 This option causes Exim to send 8BITMIME in its response to an SMTP
14875 EHLO command, and to accept the BODY= parameter on MAIL commands.
14876 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14877 takes no steps to do anything special with messages received by this route.
14879 Historically Exim kept this option off by default, but the maintainers
14880 feel that in today's Internet, this causes more problems than it solves.
14881 It now defaults to true.
14882 A more detailed analysis of the issues is provided by Dan Bernstein:
14884 &url(https://cr.yp.to/smtp/8bitmime.html)
14887 To log received 8BITMIME status use
14889 log_selector = +8bitmime
14892 .option acl_not_smtp main string&!! unset
14893 .cindex "&ACL;" "for non-SMTP messages"
14894 .cindex "non-SMTP messages" "ACLs for"
14895 This option defines the ACL that is run when a non-SMTP message has been
14896 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14899 .option acl_not_smtp_mime main string&!! unset
14900 This option defines the ACL that is run for individual MIME parts of non-SMTP
14901 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14904 .option acl_not_smtp_start main string&!! unset
14905 .cindex "&ACL;" "at start of non-SMTP message"
14906 .cindex "non-SMTP messages" "ACLs for"
14907 This option defines the ACL that is run before Exim starts reading a
14908 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14910 .option acl_smtp_auth main string&!! unset
14911 .cindex "&ACL;" "setting up for SMTP commands"
14912 .cindex "AUTH" "ACL for"
14913 This option defines the ACL that is run when an SMTP AUTH command is
14914 received. See chapter &<<CHAPACL>>& for further details.
14916 .option acl_smtp_connect main string&!! unset
14917 .cindex "&ACL;" "on SMTP connection"
14918 This option defines the ACL that is run when an SMTP connection is received.
14919 See chapter &<<CHAPACL>>& for further details.
14921 .option acl_smtp_data main string&!! unset
14922 .cindex "DATA" "ACL for"
14923 This option defines the ACL that is run after an SMTP DATA command has been
14924 processed and the message itself has been received, but before the final
14925 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14927 .option acl_smtp_data_prdr main string&!! accept
14928 .cindex "PRDR" "ACL for"
14929 .cindex "DATA" "PRDR ACL for"
14930 .cindex "&ACL;" "PRDR-related"
14931 .cindex "&ACL;" "per-user data processing"
14932 This option defines the ACL that,
14933 if the PRDR feature has been negotiated,
14934 is run for each recipient after an SMTP DATA command has been
14935 processed and the message itself has been received, but before the
14936 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14938 .option acl_smtp_dkim main string&!! unset
14939 .cindex DKIM "ACL for"
14940 This option defines the ACL that is run for each DKIM signature
14941 (by default, or as specified in the dkim_verify_signers option)
14942 of a received message.
14943 See section &<<SECDKIMVFY>>& for further details.
14945 .option acl_smtp_etrn main string&!! unset
14946 .cindex "ETRN" "ACL for"
14947 This option defines the ACL that is run when an SMTP ETRN command is
14948 received. See chapter &<<CHAPACL>>& for further details.
14950 .option acl_smtp_expn main string&!! unset
14951 .cindex "EXPN" "ACL for"
14952 This option defines the ACL that is run when an SMTP EXPN command is
14953 received. See chapter &<<CHAPACL>>& for further details.
14955 .option acl_smtp_helo main string&!! unset
14956 .cindex "EHLO" "ACL for"
14957 .cindex "HELO" "ACL for"
14958 This option defines the ACL that is run when an SMTP EHLO or HELO
14959 command is received. See chapter &<<CHAPACL>>& for further details.
14962 .option acl_smtp_mail main string&!! unset
14963 .cindex "MAIL" "ACL for"
14964 This option defines the ACL that is run when an SMTP MAIL command is
14965 received. See chapter &<<CHAPACL>>& for further details.
14967 .option acl_smtp_mailauth main string&!! unset
14968 .cindex "AUTH" "on MAIL command"
14969 This option defines the ACL that is run when there is an AUTH parameter on
14970 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14971 &<<CHAPSMTPAUTH>>& for details of authentication.
14973 .option acl_smtp_mime main string&!! unset
14974 .cindex "MIME content scanning" "ACL for"
14975 This option is available when Exim is built with the content-scanning
14976 extension. It defines the ACL that is run for each MIME part in a message. See
14977 section &<<SECTscanmimepart>>& for details.
14979 .option acl_smtp_notquit main string&!! unset
14980 .cindex "not-QUIT, ACL for"
14981 This option defines the ACL that is run when an SMTP session
14982 ends without a QUIT command being received.
14983 See chapter &<<CHAPACL>>& for further details.
14985 .option acl_smtp_predata main string&!! unset
14986 This option defines the ACL that is run when an SMTP DATA command is
14987 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14990 .option acl_smtp_quit main string&!! unset
14991 .cindex "QUIT, ACL for"
14992 This option defines the ACL that is run when an SMTP QUIT command is
14993 received. See chapter &<<CHAPACL>>& for further details.
14995 .option acl_smtp_rcpt main string&!! unset
14996 .cindex "RCPT" "ACL for"
14997 This option defines the ACL that is run when an SMTP RCPT command is
14998 received. See chapter &<<CHAPACL>>& for further details.
15000 .option acl_smtp_starttls main string&!! unset
15001 .cindex "STARTTLS, ACL for"
15002 This option defines the ACL that is run when an SMTP STARTTLS command is
15003 received. See chapter &<<CHAPACL>>& for further details.
15005 .option acl_smtp_vrfy main string&!! unset
15006 .cindex "VRFY" "ACL for"
15007 This option defines the ACL that is run when an SMTP VRFY command is
15008 received. See chapter &<<CHAPACL>>& for further details.
15010 .option add_environment main "string list" empty
15011 .cindex "environment" "set values"
15012 This option adds individual environment variables that the
15013 currently linked libraries and programs in child processes may use.
15014 Each list element should be of the form &"name=value"&.
15016 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15018 .option admin_groups main "string list&!!" unset
15019 .cindex "admin user"
15020 This option is expanded just once, at the start of Exim's processing. If the
15021 current group or any of the supplementary groups of an Exim caller is in this
15022 colon-separated list, the caller has admin privileges. If all your system
15023 programmers are in a specific group, for example, you can give them all Exim
15024 admin privileges by putting that group in &%admin_groups%&. However, this does
15025 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15026 To permit this, you have to add individuals to the Exim group.
15028 .option allow_domain_literals main boolean false
15029 .cindex "domain literal"
15030 If this option is set, the RFC 2822 domain literal format is permitted in
15031 email addresses. The option is not set by default, because the domain literal
15032 format is not normally required these days, and few people know about it. It
15033 has, however, been exploited by mail abusers.
15035 Unfortunately, it seems that some DNS black list maintainers are using this
15036 format to report black listing to postmasters. If you want to accept messages
15037 addressed to your hosts by IP address, you need to set
15038 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15039 domains (defined in the named domain list &%local_domains%& in the default
15040 configuration). This &"magic string"& matches the domain literal form of all
15041 the local host's IP addresses.
15044 .option allow_mx_to_ip main boolean false
15045 .cindex "MX record" "pointing to IP address"
15046 It appears that more and more DNS zone administrators are breaking the rules
15047 and putting domain names that look like IP addresses on the right hand side of
15048 MX records. Exim follows the rules and rejects this, giving an error message
15049 that explains the misconfiguration. However, some other MTAs support this
15050 practice, so to avoid &"Why can't Exim do this?"& complaints,
15051 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15052 recommended, except when you have no other choice.
15054 .option allow_utf8_domains main boolean false
15055 .cindex "domain" "UTF-8 characters in"
15056 .cindex "UTF-8" "in domain name"
15057 Lots of discussion is going on about internationalized domain names. One
15058 camp is strongly in favour of just using UTF-8 characters, and it seems
15059 that at least two other MTAs permit this.
15060 This option allows Exim users to experiment if they wish.
15062 If it is set true, Exim's domain parsing function allows valid
15063 UTF-8 multicharacters to appear in domain name components, in addition to
15064 letters, digits, and hyphens.
15066 If Exim is built with internationalization support
15067 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15068 this option can be left as default.
15070 if you want to look up such domain names in the DNS, you must also
15071 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15072 suitable setting is:
15074 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15075 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15077 Alternatively, you can just disable this feature by setting
15079 dns_check_names_pattern =
15081 That is, set the option to an empty string so that no check is done.
15084 .option auth_advertise_hosts main "host list&!!" *
15085 .cindex "authentication" "advertising"
15086 .cindex "AUTH" "advertising"
15087 .cindex "ESMTP extensions" AUTH
15088 If any server authentication mechanisms are configured, Exim advertises them in
15089 response to an EHLO command only if the calling host matches this list.
15090 Otherwise, Exim does not advertise AUTH.
15091 Exim does not accept AUTH commands from clients to which it has not
15092 advertised the availability of AUTH. The advertising of individual
15093 authentication mechanisms can be controlled by the use of the
15094 &%server_advertise_condition%& generic authenticator option on the individual
15095 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15097 Certain mail clients (for example, Netscape) require the user to provide a name
15098 and password for authentication if AUTH is advertised, even though it may
15099 not be needed (the host may accept messages from hosts on its local LAN without
15100 authentication, for example). The &%auth_advertise_hosts%& option can be used
15101 to make these clients more friendly by excluding them from the set of hosts to
15102 which Exim advertises AUTH.
15104 .cindex "AUTH" "advertising when encrypted"
15105 If you want to advertise the availability of AUTH only when the connection
15106 is encrypted using TLS, you can make use of the fact that the value of this
15107 option is expanded, with a setting like this:
15109 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15111 .vindex "&$tls_in_cipher$&"
15112 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15113 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15114 expansion is *, which matches all hosts.
15117 .option auto_thaw main time 0s
15118 .cindex "thawing messages"
15119 .cindex "unfreezing messages"
15120 If this option is set to a time greater than zero, a queue runner will try a
15121 new delivery attempt on any frozen message, other than a bounce message, if
15122 this much time has passed since it was frozen. This may result in the message
15123 being re-frozen if nothing has changed since the last attempt. It is a way of
15124 saying &"keep on trying, even though there are big problems"&.
15126 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15127 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15128 thought to be very useful any more, and its use should probably be avoided.
15131 .option av_scanner main string "see below"
15132 This option is available if Exim is built with the content-scanning extension.
15133 It specifies which anti-virus scanner to use. The default value is:
15135 sophie:/var/run/sophie
15137 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15138 before use. See section &<<SECTscanvirus>>& for further details.
15141 .option bi_command main string unset
15143 This option supplies the name of a command that is run when Exim is called with
15144 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15145 just the command name, it is not a complete command line. If an argument is
15146 required, it must come from the &%-oA%& command line option.
15149 .option bounce_message_file main string&!! unset
15150 .cindex "bounce message" "customizing"
15151 .cindex "customizing" "bounce message"
15152 This option defines a template file containing paragraphs of text to be used
15153 for constructing bounce messages. Details of the file's contents are given in
15154 chapter &<<CHAPemsgcust>>&.
15155 .cindex bounce_message_file "tainted data"
15156 The option is expanded to give the file path, which must be
15157 absolute and untainted.
15158 See also &%warn_message_file%&.
15161 .option bounce_message_text main string unset
15162 When this option is set, its contents are included in the default bounce
15163 message immediately after &"This message was created automatically by mail
15164 delivery software."& It is not used if &%bounce_message_file%& is set.
15166 .option bounce_return_body main boolean true
15167 .cindex "bounce message" "including body"
15168 This option controls whether the body of an incoming message is included in a
15169 bounce message when &%bounce_return_message%& is true. The default setting
15170 causes the entire message, both header and body, to be returned (subject to the
15171 value of &%bounce_return_size_limit%&). If this option is false, only the
15172 message header is included. In the case of a non-SMTP message containing an
15173 error that is detected during reception, only those header lines preceding the
15174 point at which the error was detected are returned.
15175 .cindex "bounce message" "including original"
15177 .option bounce_return_linesize_limit main integer 998
15178 .cindex "size" "of bounce lines, limit"
15179 .cindex "bounce message" "line length limit"
15180 .cindex "limit" "bounce message line length"
15181 This option sets a limit in bytes on the line length of messages
15182 that are returned to senders due to delivery problems,
15183 when &%bounce_return_message%& is true.
15184 The default value corresponds to RFC limits.
15185 If the message being returned has lines longer than this value it is
15186 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15188 The option also applies to bounces returned when an error is detected
15189 during reception of a message.
15190 In this case lines from the original are truncated.
15192 The option does not apply to messages generated by an &(autoreply)& transport.
15195 .option bounce_return_message main boolean true
15196 If this option is set false, none of the original message is included in
15197 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15198 &%bounce_return_body%&.
15201 .option bounce_return_size_limit main integer 100K
15202 .cindex "size" "of bounce, limit"
15203 .cindex "bounce message" "size limit"
15204 .cindex "limit" "bounce message size"
15205 This option sets a limit in bytes on the size of messages that are returned to
15206 senders as part of bounce messages when &%bounce_return_message%& is true. The
15207 limit should be less than the value of the global &%message_size_limit%& and of
15208 any &%message_size_limit%& settings on transports, to allow for the bounce text
15209 that Exim generates. If this option is set to zero there is no limit.
15211 When the body of any message that is to be included in a bounce message is
15212 greater than the limit, it is truncated, and a comment pointing this out is
15213 added at the top. The actual cutoff may be greater than the value given, owing
15214 to the use of buffering for transferring the message in chunks (typically 8K in
15215 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15218 .option bounce_sender_authentication main string unset
15219 .cindex "bounce message" "sender authentication"
15220 .cindex "authentication" "bounce message"
15221 .cindex "AUTH" "on bounce message"
15222 This option provides an authenticated sender address that is sent with any
15223 bounce messages generated by Exim that are sent over an authenticated SMTP
15224 connection. A typical setting might be:
15226 bounce_sender_authentication = mailer-daemon@my.domain.example
15228 which would cause bounce messages to be sent using the SMTP command:
15230 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15232 The value of &%bounce_sender_authentication%& must always be a complete email
15235 .option callout_domain_negative_expire main time 3h
15236 .cindex "caching" "callout timeouts"
15237 .cindex "callout" "caching timeouts"
15238 This option specifies the expiry time for negative callout cache data for a
15239 domain. See section &<<SECTcallver>>& for details of callout verification, and
15240 section &<<SECTcallvercache>>& for details of the caching.
15243 .option callout_domain_positive_expire main time 7d
15244 This option specifies the expiry time for positive callout cache data for a
15245 domain. See section &<<SECTcallver>>& for details of callout verification, and
15246 section &<<SECTcallvercache>>& for details of the caching.
15249 .option callout_negative_expire main time 2h
15250 This option specifies the expiry time for negative callout cache data for an
15251 address. See section &<<SECTcallver>>& for details of callout verification, and
15252 section &<<SECTcallvercache>>& for details of the caching.
15255 .option callout_positive_expire main time 24h
15256 This option specifies the expiry time for positive callout cache data for an
15257 address. See section &<<SECTcallver>>& for details of callout verification, and
15258 section &<<SECTcallvercache>>& for details of the caching.
15261 .option callout_random_local_part main string&!! "see below"
15262 This option defines the &"random"& local part that can be used as part of
15263 callout verification. The default value is
15265 $primary_hostname-$tod_epoch-testing
15267 See section &<<CALLaddparcall>>& for details of how this value is used.
15270 .option check_log_inodes main integer 100
15271 See &%check_spool_space%& below.
15274 .option check_log_space main integer 10M
15275 See &%check_spool_space%& below.
15277 .oindex "&%check_rfc2047_length%&"
15278 .cindex "RFC 2047" "disabling length check"
15279 .option check_rfc2047_length main boolean true
15280 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15281 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15282 word; strings to be encoded that exceed this length are supposed to use
15283 multiple encoded words. By default, Exim does not recognize encoded words that
15284 exceed the maximum length. However, it seems that some software, in violation
15285 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15286 set false, Exim recognizes encoded words of any length.
15289 .option check_spool_inodes main integer 100
15290 See &%check_spool_space%& below.
15293 .option check_spool_space main integer 10M
15294 .cindex "checking disk space"
15295 .cindex "disk space, checking"
15296 .cindex "spool directory" "checking space"
15297 The four &%check_...%& options allow for checking of disk resources before a
15298 message is accepted.
15300 .vindex "&$log_inodes$&"
15301 .vindex "&$log_space$&"
15302 .vindex "&$spool_inodes$&"
15303 .vindex "&$spool_space$&"
15304 When any of these options are nonzero, they apply to all incoming messages. If you
15305 want to apply different checks to different kinds of message, you can do so by
15306 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15307 &$spool_space$& in an ACL with appropriate additional conditions.
15310 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15311 either value is greater than zero, for example:
15313 check_spool_space = 100M
15314 check_spool_inodes = 100
15316 The spool partition is the one that contains the directory defined by
15317 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15320 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15321 files are written if either is greater than zero. These should be set only if
15322 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15324 If there is less space or fewer inodes than requested, Exim refuses to accept
15325 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15326 error response to the MAIL command. If ESMTP is in use and there was a
15327 SIZE parameter on the MAIL command, its value is added to the
15328 &%check_spool_space%& value, and the check is performed even if
15329 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15331 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15332 number of kilobytes (though specified in bytes).
15333 If a non-multiple of 1024 is specified, it is rounded up.
15335 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15336 failure a message is written to stderr and Exim exits with a non-zero code, as
15337 it obviously cannot send an error message of any kind.
15339 There is a slight performance penalty for these checks.
15340 Versions of Exim preceding 4.88 had these disabled by default;
15341 high-rate installations confident they will never run out of resources
15342 may wish to deliberately disable them.
15344 .option chunking_advertise_hosts main "host list&!!" *
15345 .cindex CHUNKING advertisement
15346 .cindex "RFC 3030" "CHUNKING"
15347 .cindex "ESMTP extensions" CHUNKING
15348 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15350 Hosts may use the BDAT command as an alternate to DATA.
15352 .option commandline_checks_require_admin main boolean &`false`&
15353 .cindex "restricting access to features"
15354 This option restricts various basic checking features to require an
15355 administrative user.
15356 This affects most of the &%-b*%& options, such as &%-be%&.
15358 .option debug_store main boolean &`false`&
15359 .cindex debugging "memory corruption"
15360 .cindex memory debugging
15361 This option, when true, enables extra checking in Exim's internal memory
15362 management. For use when a memory corruption issue is being investigated,
15363 it should normally be left as default.
15365 .option daemon_smtp_ports main string &`smtp`&
15366 .cindex "port" "for daemon"
15367 .cindex "TCP/IP" "setting listening ports"
15368 This option specifies one or more default SMTP ports on which the Exim daemon
15369 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15370 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15372 .option daemon_startup_retries main integer 9
15373 .cindex "daemon startup, retrying"
15374 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15375 the daemon at startup when it cannot immediately bind a listening socket
15376 (typically because the socket is already in use): &%daemon_startup_retries%&
15377 defines the number of retries after the first failure, and
15378 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15380 .option daemon_startup_sleep main time 30s
15381 See &%daemon_startup_retries%&.
15383 .option delay_warning main "time list" 24h
15384 .cindex "warning of delay"
15385 .cindex "delay warning, specifying"
15386 .cindex "queue" "delay warning"
15387 When a message is delayed, Exim sends a warning message to the sender at
15388 intervals specified by this option. The data is a colon-separated list of times
15389 after which to send warning messages. If the value of the option is an empty
15390 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15391 message has been in the queue for longer than the last time, the last interval
15392 between the times is used to compute subsequent warning times. For example,
15395 delay_warning = 4h:8h:24h
15397 the first message is sent after 4 hours, the second after 8 hours, and
15398 the third one after 24 hours. After that, messages are sent every 16 hours,
15399 because that is the interval between the last two times on the list. If you set
15400 just one time, it specifies the repeat interval. For example, with:
15404 messages are repeated every six hours. To stop warnings after a given time, set
15405 a very large time at the end of the list. For example:
15407 delay_warning = 2h:12h:99d
15409 Note that the option is only evaluated at the time a delivery attempt fails,
15410 which depends on retry and queue-runner configuration.
15411 Typically retries will be configured more frequently than warning messages.
15413 .option delay_warning_condition main string&!! "see below"
15414 .vindex "&$domain$&"
15415 The string is expanded at the time a warning message might be sent. If all the
15416 deferred addresses have the same domain, it is set in &$domain$& during the
15417 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15418 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15419 &"false"& (the comparison being done caselessly) then the warning message is
15420 not sent. The default is:
15422 delay_warning_condition = ${if or {\
15423 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15424 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15425 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15428 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15429 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15430 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15431 &"auto-replied"& in an &'Auto-Submitted:'& header.
15433 .option deliver_drop_privilege main boolean false
15434 .cindex "unprivileged delivery"
15435 .cindex "delivery" "unprivileged"
15436 If this option is set true, Exim drops its root privilege at the start of a
15437 delivery process, and runs as the Exim user throughout. This severely restricts
15438 the kinds of local delivery that are possible, but is viable in certain types
15439 of configuration. There is a discussion about the use of root privilege in
15440 chapter &<<CHAPsecurity>>&.
15442 .option deliver_queue_load_max main fixed-point unset
15443 .cindex "load average"
15444 .cindex "queue runner" "abandoning"
15445 When this option is set, a queue run is abandoned if the system load average
15446 becomes greater than the value of the option. The option has no effect on
15447 ancient operating systems on which Exim cannot determine the load average.
15448 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15451 .option delivery_date_remove main boolean true
15452 .cindex "&'Delivery-date:'& header line"
15453 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15454 message when it is delivered, in exactly the same way as &'Return-path:'& is
15455 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15456 should not be present in incoming messages, and this option causes them to be
15457 removed at the time the message is received, to avoid any problems that might
15458 occur when a delivered message is subsequently sent on to some other recipient.
15460 .option disable_fsync main boolean false
15461 .cindex "&[fsync()]&, disabling"
15462 This option is available only if Exim was built with the compile-time option
15463 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15464 a runtime configuration generates an &"unknown option"& error. You should not
15465 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15466 really, really, really understand what you are doing. &'No pre-compiled
15467 distributions of Exim should ever make this option available.'&
15469 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15470 updated files' data to be written to disc before continuing. Unexpected events
15471 such as crashes and power outages may cause data to be lost or scrambled.
15472 Here be Dragons. &*Beware.*&
15475 .option disable_ipv6 main boolean false
15476 .cindex "IPv6" "disabling"
15477 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15478 activities take place. AAAA records are never looked up, and any IPv6 addresses
15479 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15480 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15481 to handle IPv6 literal addresses.
15484 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15485 .cindex DKIM "selecting signature algorithms"
15486 This option gives a list of hash types which are acceptable in signatures,
15487 and an order of processing.
15488 Signatures with algorithms not in the list will be ignored.
15490 Acceptable values include:
15497 Note that the acceptance of sha1 violates RFC 8301.
15499 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15500 This option gives a list of key types which are acceptable in signatures,
15501 and an order of processing.
15502 Signatures with algorithms not in the list will be ignored.
15505 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15506 This option gives a list of key sizes which are acceptable in signatures.
15507 The list is keyed by the algorithm type for the key; the values are in bits.
15508 Signatures with keys smaller than given by this option will fail verification.
15510 The default enforces the RFC 8301 minimum key size for RSA signatures.
15512 .option dkim_verify_minimal main boolean false
15513 If set to true, verification of signatures will terminate after the
15516 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15517 .cindex DKIM "controlling calls to the ACL"
15518 This option gives a list of DKIM domains for which the DKIM ACL is run.
15519 It is expanded after the message is received; by default it runs
15520 the ACL once for each signature in the message.
15521 See section &<<SECDKIMVFY>>&.
15524 .option dmarc_forensic_sender main string&!! unset
15525 .option dmarc_history_file main string unset
15526 .option dmarc_tld_file main string unset
15527 .cindex DMARC "main section options"
15528 These options control DMARC processing.
15529 See section &<<SECDMARC>>& for details.
15532 .option dns_again_means_nonexist main "domain list&!!" unset
15533 .cindex "DNS" "&""try again""& response; overriding"
15534 DNS lookups give a &"try again"& response for the DNS errors
15535 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15536 keep trying to deliver a message, or to give repeated temporary errors to
15537 incoming mail. Sometimes the effect is caused by a badly set up name server and
15538 may persist for a long time. If a domain which exhibits this problem matches
15539 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15540 This option should be used with care. You can make it apply to reverse lookups
15541 by a setting such as this:
15543 dns_again_means_nonexist = *.in-addr.arpa
15545 This option applies to all DNS lookups that Exim does. It also applies when the
15546 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15547 since these are most likely to be caused by DNS lookup problems. The
15548 &(dnslookup)& router has some options of its own for controlling what happens
15549 when lookups for MX or SRV records give temporary errors. These more specific
15550 options are applied after this global option.
15552 .option dns_check_names_pattern main string "see below"
15553 .cindex "DNS" "pre-check of name syntax"
15554 When this option is set to a non-empty string, it causes Exim to check domain
15555 names for characters that are not allowed in host names before handing them to
15556 the DNS resolver, because some resolvers give temporary errors for names that
15557 contain unusual characters. If a domain name contains any unwanted characters,
15558 a &"not found"& result is forced, and the resolver is not called. The check is
15559 done by matching the domain name against a regular expression, which is the
15560 value of this option. The default pattern is
15562 dns_check_names_pattern = \
15563 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15565 which permits only letters, digits, slashes, and hyphens in components, but
15566 they must start and end with a letter or digit. Slashes are not, in fact,
15567 permitted in host names, but they are found in certain NS records (which can be
15568 accessed in Exim by using a &%dnsdb%& lookup). If you set
15569 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15572 .option dns_csa_search_limit main integer 5
15573 This option controls the depth of parental searching for CSA SRV records in the
15574 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15576 .option dns_csa_use_reverse main boolean true
15577 This option controls whether or not an IP address, given as a CSA domain, is
15578 reversed and looked up in the reverse DNS, as described in more detail in
15579 section &<<SECTverifyCSA>>&.
15581 .option dns_cname_loops main integer 1
15582 .cindex DNS "CNAME following"
15583 This option controls the following of CNAME chains, needed if the resolver does
15584 not do it internally.
15585 As of 2018 most should, and the default can be left.
15586 If you have an ancient one, a value of 10 is likely needed.
15588 The default value of one CNAME-follow is needed
15589 thanks to the observed return for an MX request,
15590 given no MX presence but a CNAME to an A, of the CNAME.
15593 .option dns_dnssec_ok main integer -1
15594 .cindex "DNS" "resolver options"
15595 .cindex "DNS" "DNSSEC"
15596 If this option is set to a non-negative number then Exim will initialise the
15597 DNS resolver library to either use or not use DNSSEC, overriding the system
15598 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15600 If the resolver library does not support DNSSEC then this option has no effect.
15602 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15603 will default to stripping out a successful validation status.
15604 This will break a previously working Exim installation.
15605 Provided that you do trust the resolver (ie, is on localhost) you can tell
15606 glibc to pass through any successful validation with a new option in
15607 &_/etc/resolv.conf_&:
15613 .option dns_ipv4_lookup main "domain list&!!" unset
15614 .cindex "IPv6" "DNS lookup for AAAA records"
15615 .cindex "DNS" "IPv6 lookup for AAAA records"
15616 .cindex DNS "IPv6 disabling"
15617 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15618 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15619 (A records) when trying to find IP addresses for hosts, unless the host's
15620 domain matches this list.
15622 This is a fudge to help with name servers that give big delays or otherwise do
15623 not work for the AAAA record type. In due course, when the world's name
15624 servers have all been upgraded, there should be no need for this option.
15625 Note that all lookups, including those done for verification, are affected;
15626 this will result in verify failure for IPv6 connections or ones using names
15627 only valid for IPv6 addresses.
15630 .option dns_retrans main time 0s
15631 .cindex "DNS" "resolver options"
15632 .cindex timeout "dns lookup"
15633 .cindex "DNS" timeout
15634 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15635 retransmission and retry parameters for DNS lookups. Values of zero (the
15636 defaults) leave the system default settings unchanged. The first value is the
15637 time between retries, and the second is the number of retries. It isn't
15638 totally clear exactly how these settings affect the total time a DNS lookup may
15639 take. I haven't found any documentation about timeouts on DNS lookups; these
15640 parameter values are available in the external resolver interface structure,
15641 but nowhere does it seem to describe how they are used or what you might want
15643 See also the &%slow_lookup_log%& option.
15646 .option dns_retry main integer 0
15647 See &%dns_retrans%& above.
15650 .option dns_trust_aa main "domain list&!!" unset
15651 .cindex "DNS" "resolver options"
15652 .cindex "DNS" "DNSSEC"
15653 If this option is set then lookup results marked with the AA bit
15654 (Authoritative Answer) are trusted the same way as if they were
15655 DNSSEC-verified. The authority section's name of the answer must
15656 match with this expanded domain list.
15658 Use this option only if you talk directly to a resolver that is
15659 authoritative for some zones and does not set the AD (Authentic Data)
15660 bit in the answer. Some DNS servers may have an configuration option to
15661 mark the answers from their own zones as verified (they set the AD bit).
15662 Others do not have this option. It is considered as poor practice using
15663 a resolver that is an authoritative server for some zones.
15665 Use this option only if you really have to (e.g. if you want
15666 to use DANE for remote delivery to a server that is listed in the DNS
15667 zones that your resolver is authoritative for).
15669 If the DNS answer packet has the AA bit set and contains resource record
15670 in the answer section, the name of the first NS record appearing in the
15671 authority section is compared against the list. If the answer packet is
15672 authoritative but the answer section is empty, the name of the first SOA
15673 record in the authoritative section is used instead.
15675 .cindex "DNS" "resolver options"
15676 .option dns_use_edns0 main integer -1
15677 .cindex "DNS" "resolver options"
15678 .cindex "DNS" "EDNS0"
15679 .cindex "DNS" "OpenBSD
15680 If this option is set to a non-negative number then Exim will initialise the
15681 DNS resolver library to either use or not use EDNS0 extensions, overriding
15682 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15685 If the resolver library does not support EDNS0 then this option has no effect.
15687 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15688 means that DNSSEC will not work with Exim on that platform either, unless Exim
15689 is linked against an alternative DNS client library.
15692 .option drop_cr main boolean false
15693 This is an obsolete option that is now a no-op. It used to affect the way Exim
15694 handled CR and LF characters in incoming messages. What happens now is
15695 described in section &<<SECTlineendings>>&.
15697 .option dsn_advertise_hosts main "host list&!!" unset
15698 .cindex "bounce messages" "success"
15699 .cindex "DSN" "success"
15700 .cindex "Delivery Status Notification" "success"
15701 .cindex "ESMTP extensions" DSN
15702 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15703 and accepted from, these hosts.
15704 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15705 and RET and ORCPT options on MAIL FROM commands.
15706 A NOTIFY=SUCCESS option requests success-DSN messages.
15707 A NOTIFY= option with no argument requests that no delay or failure DSNs
15709 &*Note*&: Supplying success-DSN messages has been criticised
15710 on privacy grounds; it can leak details of internal forwarding.
15712 .option dsn_from main "string&!!" "see below"
15713 .cindex "&'From:'& header line" "in bounces"
15714 .cindex "bounce messages" "&'From:'& line, specifying"
15715 This option can be used to vary the contents of &'From:'& header lines in
15716 bounces and other automatically generated messages (&"Delivery Status
15717 Notifications"& &-- hence the name of the option). The default setting is:
15719 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15721 The value is expanded every time it is needed. If the expansion fails, a
15722 panic is logged, and the default value is used.
15724 .option envelope_to_remove main boolean true
15725 .cindex "&'Envelope-to:'& header line"
15726 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15727 message when it is delivered, in exactly the same way as &'Return-path:'& is
15728 handled. &'Envelope-to:'& records the original recipient address from the
15729 message's envelope that caused the delivery to happen. Such headers should not
15730 be present in incoming messages, and this option causes them to be removed at
15731 the time the message is received, to avoid any problems that might occur when a
15732 delivered message is subsequently sent on to some other recipient.
15735 .option errors_copy main "string list&!!" unset
15736 .cindex "bounce message" "copy to other address"
15737 .cindex "copy of bounce message"
15738 Setting this option causes Exim to send bcc copies of bounce messages that it
15739 generates to other addresses. &*Note*&: This does not apply to bounce messages
15740 coming from elsewhere. The value of the option is a colon-separated list of
15741 items. Each item consists of a pattern, terminated by white space, followed by
15742 a comma-separated list of email addresses. If a pattern contains spaces, it
15743 must be enclosed in double quotes.
15745 Each pattern is processed in the same way as a single item in an address list
15746 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15747 the bounce message, the message is copied to the addresses on the list. The
15748 items are scanned in order, and once a matching one is found, no further items
15749 are examined. For example:
15751 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15752 rqps@mydomain hostmaster@mydomain.example,\
15753 postmaster@mydomain.example
15755 .vindex "&$domain$&"
15756 .vindex "&$local_part$&"
15757 The address list is expanded before use. The expansion variables &$local_part$&
15758 and &$domain$& are set from the original recipient of the error message, and if
15759 there was any wildcard matching in the pattern, the expansion
15760 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15761 variables &$0$&, &$1$&, etc. are set in the normal way.
15764 .option errors_reply_to main string unset
15765 .cindex "bounce message" "&'Reply-to:'& in"
15766 By default, Exim's bounce and delivery warning messages contain the header line
15768 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15770 .oindex &%quota_warn_message%&
15771 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15772 A warning message that is generated by the &%quota_warn_message%& option in an
15773 &(appendfile)& transport may contain its own &'From:'& header line that
15774 overrides the default.
15776 Experience shows that people reply to bounce messages. If the
15777 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15778 and warning messages. For example:
15780 errors_reply_to = postmaster@my.domain.example
15782 The value of the option is not expanded. It must specify a valid RFC 2822
15783 address. However, if a warning message that is generated by the
15784 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15785 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15789 .option event_action main string&!! unset
15791 This option declares a string to be expanded for Exim's events mechanism.
15792 For details see chapter &<<CHAPevents>>&.
15795 .option exim_group main string "compile-time configured"
15796 .cindex "gid (group id)" "Exim's own"
15797 .cindex "Exim group"
15798 This option changes the gid under which Exim runs when it gives up root
15799 privilege. The default value is compiled into the binary. The value of this
15800 option is used only when &%exim_user%& is also set. Unless it consists entirely
15801 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15802 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15806 .option exim_path main string "see below"
15807 .cindex "Exim binary, path name"
15808 This option specifies the path name of the Exim binary, which is used when Exim
15809 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15810 the directory configured at compile time by the BIN_DIRECTORY setting. It
15811 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15813 &*Warning*&: Do not use a macro to define the value of this option, because
15814 you will break those Exim utilities that scan the configuration file to find
15815 where the binary is. (They then use the &%-bP%& option to extract option
15816 settings such as the value of &%spool_directory%&.)
15819 .option exim_user main string "compile-time configured"
15820 .cindex "uid (user id)" "Exim's own"
15821 .cindex "Exim user"
15822 This option changes the uid under which Exim runs when it gives up root
15823 privilege. The default value is compiled into the binary. Ownership of the run
15824 time configuration file and the use of the &%-C%& and &%-D%& command line
15825 options is checked against the values in the binary, not what is set here.
15827 Unless it consists entirely of digits, the string is looked up using
15828 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15829 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15830 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15833 .option exim_version main string "current version"
15834 .cindex "Exim version"
15835 .cindex customizing "version number"
15836 .cindex "version number of Exim" override
15837 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15838 various places. Use with care; this may fool stupid security scanners.
15841 .option extra_local_interfaces main "string list" unset
15842 This option defines network interfaces that are to be considered local when
15843 routing, but which are not used for listening by the daemon. See section
15844 &<<SECTreclocipadd>>& for details.
15847 . Allow this long option name to split; give it unsplit as a fifth argument
15848 . for the automatic .oindex that is generated by .option.
15850 .option "extract_addresses_remove_arguments" main boolean true &&&
15851 extract_addresses_remove_arguments
15853 .cindex "command line" "addresses with &%-t%&"
15854 .cindex "Sendmail compatibility" "&%-t%& option"
15855 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15856 are present on the command line when the &%-t%& option is used to build an
15857 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15858 line addresses are removed from the recipients list. This is also how Smail
15859 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15860 command line addresses are added to those obtained from the header lines. When
15861 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15862 argument headers. If it is set false, Exim adds rather than removes argument
15866 .option finduser_retries main integer 0
15867 .cindex "NIS, retrying user lookups"
15868 On systems running NIS or other schemes in which user and group information is
15869 distributed from a remote system, there can be times when &[getpwnam()]& and
15870 related functions fail, even when given valid data, because things time out.
15871 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15872 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15873 many extra times to find a user or a group, waiting for one second between
15876 .cindex "&_/etc/passwd_&" "multiple reading of"
15877 You should not set this option greater than zero if your user information is in
15878 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15879 search the file multiple times for non-existent users, and also cause delay.
15883 .option freeze_tell main "string list, comma separated" unset
15884 .cindex "freezing messages" "sending a message when freezing"
15885 On encountering certain errors, or when configured to do so in a system filter,
15886 ACL, or special router, Exim freezes a message. This means that no further
15887 delivery attempts take place until an administrator thaws the message, or the
15888 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15889 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15890 warning message whenever it freezes something, unless the message it is
15891 freezing is a locally-generated bounce message. (Without this exception there
15892 is the possibility of looping.) The warning message is sent to the addresses
15893 supplied as the comma-separated value of this option. If several of the
15894 message's addresses cause freezing, only a single message is sent. If the
15895 freezing was automatic, the reason(s) for freezing can be found in the message
15896 log. If you configure freezing in a filter or ACL, you must arrange for any
15897 logging that you require.
15900 .option gecos_name main string&!! unset
15902 .cindex "&""gecos""& field, parsing"
15903 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
15904 password file to hold other information in addition to users' real names. Exim
15905 looks up this field for use when it is creating &'Sender:'& or &'From:'&
15906 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
15907 of the field are used unchanged, except that, if an ampersand is encountered,
15908 it is replaced by the user's login name with the first character forced to
15909 upper case, since this is a convention that is observed on many systems.
15911 When these options are set, &%gecos_pattern%& is treated as a regular
15912 expression that is to be applied to the field (again with && replaced by the
15913 login name), and if it matches, &%gecos_name%& is expanded and used as the
15916 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
15917 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
15918 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
15919 name terminates at the first comma, the following can be used:
15921 gecos_pattern = ([^,]*)
15925 .option gecos_pattern main string unset
15926 See &%gecos_name%& above.
15929 .option gnutls_compat_mode main boolean unset
15930 This option controls whether GnuTLS is used in compatibility mode in an Exim
15931 server. This reduces security slightly, but improves interworking with older
15932 implementations of TLS.
15935 .option gnutls_allow_auto_pkcs11 main boolean unset
15936 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
15937 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
15940 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
15945 .option headers_charset main string "see below"
15946 This option sets a default character set for translating from encoded MIME
15947 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
15948 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
15949 ultimate default is ISO-8859-1. For more details see the description of header
15950 insertions in section &<<SECTexpansionitems>>&.
15954 .option header_maxsize main integer "see below"
15955 .cindex "header section" "maximum size of"
15956 .cindex "limit" "size of message header section"
15957 This option controls the overall maximum size of a message's header
15958 section. The default is the value of HEADER_MAXSIZE in
15959 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
15960 sections are rejected.
15963 .option header_line_maxsize main integer 0
15964 .cindex "header lines" "maximum size of"
15965 .cindex "limit" "size of one header line"
15966 This option limits the length of any individual header line in a message, after
15967 all the continuations have been joined together. Messages with individual
15968 header lines that are longer than the limit are rejected. The default value of
15969 zero means &"no limit"&.
15974 .option helo_accept_junk_hosts main "host list&!!" unset
15975 .cindex "HELO" "accepting junk data"
15976 .cindex "EHLO" "accepting junk data"
15977 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
15978 mail, and gives an error response for invalid data. Unfortunately, there are
15979 some SMTP clients that send syntactic junk. They can be accommodated by setting
15980 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
15981 if you want to do semantic checking.
15982 See also &%helo_allow_chars%& for a way of extending the permitted character
15986 .option helo_allow_chars main string unset
15987 .cindex "HELO" "underscores in"
15988 .cindex "EHLO" "underscores in"
15989 .cindex "underscore in EHLO/HELO"
15990 This option can be set to a string of rogue characters that are permitted in
15991 all EHLO and HELO names in addition to the standard letters, digits,
15992 hyphens, and dots. If you really must allow underscores, you can set
15994 helo_allow_chars = _
15996 Note that the value is one string, not a list.
15999 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16000 .cindex "HELO" "forcing reverse lookup"
16001 .cindex "EHLO" "forcing reverse lookup"
16002 If the domain given by a client in a HELO or EHLO command matches this
16003 list, a reverse lookup is done in order to establish the host's true name. The
16004 default forces a lookup if the client host gives the server's name or any of
16005 its IP addresses (in brackets), something that broken clients have been seen to
16009 .option helo_try_verify_hosts main "host list&!!" unset
16010 .cindex "HELO verifying" "optional"
16011 .cindex "EHLO" "verifying, optional"
16012 By default, Exim just checks the syntax of HELO and EHLO commands (see
16013 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16014 to do more extensive checking of the data supplied by these commands. The ACL
16015 condition &`verify = helo`& is provided to make this possible.
16016 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16017 to force the check to occur. From release 4.53 onwards, this is no longer
16018 necessary. If the check has not been done before &`verify = helo`& is
16019 encountered, it is done at that time. Consequently, this option is obsolete.
16020 Its specification is retained here for backwards compatibility.
16022 When an EHLO or HELO command is received, if the calling host matches
16023 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16024 EHLO command either:
16027 is an IP literal matching the calling address of the host, or
16029 .cindex "DNS" "reverse lookup"
16030 .cindex "reverse DNS lookup"
16031 matches the host name that Exim obtains by doing a reverse lookup of the
16032 calling host address, or
16034 when looked up in DNS yields the calling host address.
16037 However, the EHLO or HELO command is not rejected if any of the checks
16038 fail. Processing continues, but the result of the check is remembered, and can
16039 be detected later in an ACL by the &`verify = helo`& condition.
16041 If DNS was used for successful verification, the variable
16042 .cindex "DNS" "DNSSEC"
16043 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16045 .option helo_verify_hosts main "host list&!!" unset
16046 .cindex "HELO verifying" "mandatory"
16047 .cindex "EHLO" "verifying, mandatory"
16048 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16049 backwards compatibility. For hosts that match this option, Exim checks the host
16050 name given in the HELO or EHLO in the same way as for
16051 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16052 rejected with a 550 error, and entries are written to the main and reject logs.
16053 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16056 .option hold_domains main "domain list&!!" unset
16057 .cindex "domain" "delaying delivery"
16058 .cindex "delivery" "delaying certain domains"
16059 This option allows mail for particular domains to be held in the queue
16060 manually. The option is overridden if a message delivery is forced with the
16061 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16062 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16063 item in &%hold_domains%&, no routing or delivery for that address is done, and
16064 it is deferred every time the message is looked at.
16066 This option is intended as a temporary operational measure for delaying the
16067 delivery of mail while some problem is being sorted out, or some new
16068 configuration tested. If you just want to delay the processing of some
16069 domains until a queue run occurs, you should use &%queue_domains%& or
16070 &%queue_smtp_domains%&, not &%hold_domains%&.
16072 A setting of &%hold_domains%& does not override Exim's code for removing
16073 messages from the queue if they have been there longer than the longest retry
16074 time in any retry rule. If you want to hold messages for longer than the normal
16075 retry times, insert a dummy retry rule with a long retry time.
16078 .option host_lookup main "host list&!!" unset
16079 .cindex "host name" "lookup, forcing"
16080 Exim does not look up the name of a calling host from its IP address unless it
16081 is required to compare against some host list, or the host matches
16082 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16083 option (which normally contains IP addresses rather than host names). The
16084 default configuration file contains
16088 which causes a lookup to happen for all hosts. If the expense of these lookups
16089 is felt to be too great, the setting can be changed or removed.
16091 After a successful reverse lookup, Exim does a forward lookup on the name it
16092 has obtained, to verify that it yields the IP address that it started with. If
16093 this check fails, Exim behaves as if the name lookup failed.
16095 .vindex "&$host_lookup_failed$&"
16096 .vindex "&$sender_host_name$&"
16097 After any kind of failure, the host name (in &$sender_host_name$&) remains
16098 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16099 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16100 &`verify = reverse_host_lookup`& in ACLs.
16103 .option host_lookup_order main "string list" &`bydns:byaddr`&
16104 This option specifies the order of different lookup methods when Exim is trying
16105 to find a host name from an IP address. The default is to do a DNS lookup
16106 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16107 if that fails. You can change the order of these lookups, or omit one entirely,
16110 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16111 multiple PTR records in the DNS and the IP address is not listed in
16112 &_/etc/hosts_&. Different operating systems give different results in this
16113 case. That is why the default tries a DNS lookup first.
16117 .option host_reject_connection main "host list&!!" unset
16118 .cindex "host" "rejecting connections from"
16119 If this option is set, incoming SMTP calls from the hosts listed are rejected
16120 as soon as the connection is made.
16121 This option is obsolete, and retained only for backward compatibility, because
16122 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16123 connections immediately.
16125 The ability to give an immediate rejection (either by this option or using an
16126 ACL) is provided for use in unusual cases. Many hosts will just try again,
16127 sometimes without much delay. Normally, it is better to use an ACL to reject
16128 incoming messages at a later stage, such as after RCPT commands. See
16129 chapter &<<CHAPACL>>&.
16132 .option hosts_connection_nolog main "host list&!!" unset
16133 .cindex "host" "not logging connections from"
16134 This option defines a list of hosts for which connection logging does not
16135 happen, even though the &%smtp_connection%& log selector is set. For example,
16136 you might want not to log SMTP connections from local processes, or from
16137 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16138 the daemon; you should therefore strive to restrict its value to a short inline
16139 list of IP addresses and networks. To disable logging SMTP connections from
16140 local processes, you must create a host list with an empty item. For example:
16142 hosts_connection_nolog = :
16144 If the &%smtp_connection%& log selector is not set, this option has no effect.
16148 .option hosts_proxy main "host list&!!" unset
16149 .cindex proxy "proxy protocol"
16150 This option enables use of Proxy Protocol proxies for incoming
16151 connections. For details see section &<<SECTproxyInbound>>&.
16154 .option hosts_treat_as_local main "domain list&!!" unset
16155 .cindex "local host" "domains treated as"
16156 .cindex "host" "treated as local"
16157 If this option is set, any host names that match the domain list are treated as
16158 if they were the local host when Exim is scanning host lists obtained from MX
16160 or other sources. Note that the value of this option is a domain list, not a
16161 host list, because it is always used to check host names, not IP addresses.
16163 This option also applies when Exim is matching the special items
16164 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16165 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16166 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16167 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16168 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16169 interfaces and recognizing the local host.
16172 .option ibase_servers main "string list" unset
16173 .cindex "InterBase" "server list"
16174 This option provides a list of InterBase servers and associated connection data,
16175 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16176 The option is available only if Exim has been built with InterBase support.
16180 .option ignore_bounce_errors_after main time 10w
16181 .cindex "bounce message" "discarding"
16182 .cindex "discarding bounce message"
16183 This option affects the processing of bounce messages that cannot be delivered,
16184 that is, those that suffer a permanent delivery failure. (Bounce messages that
16185 suffer temporary delivery failures are of course retried in the usual way.)
16187 After a permanent delivery failure, bounce messages are frozen,
16188 because there is no sender to whom they can be returned. When a frozen bounce
16189 message has been in the queue for more than the given time, it is unfrozen at
16190 the next queue run, and a further delivery is attempted. If delivery fails
16191 again, the bounce message is discarded. This makes it possible to keep failed
16192 bounce messages around for a shorter time than the normal maximum retry time
16193 for frozen messages. For example,
16195 ignore_bounce_errors_after = 12h
16197 retries failed bounce message deliveries after 12 hours, discarding any further
16198 failures. If the value of this option is set to a zero time period, bounce
16199 failures are discarded immediately. Setting a very long time (as in the default
16200 value) has the effect of disabling this option. For ways of automatically
16201 dealing with other kinds of frozen message, see &%auto_thaw%& and
16202 &%timeout_frozen_after%&.
16205 .option ignore_fromline_hosts main "host list&!!" unset
16206 .cindex "&""From""& line"
16207 .cindex "UUCP" "&""From""& line"
16208 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16209 the headers of a message. By default this is treated as the start of the
16210 message's body, which means that any following headers are not recognized as
16211 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16212 match those hosts that insist on sending it. If the sender is actually a local
16213 process rather than a remote host, and is using &%-bs%& to inject the messages,
16214 &%ignore_fromline_local%& must be set to achieve this effect.
16217 .option ignore_fromline_local main boolean false
16218 See &%ignore_fromline_hosts%& above.
16220 .option keep_environment main "string list" unset
16221 .cindex "environment" "values from"
16222 This option contains a string list of environment variables to keep.
16223 You have to trust these variables or you have to be sure that
16224 these variables do not impose any security risk. Keep in mind that
16225 during the startup phase Exim is running with an effective UID 0 in most
16226 installations. As the default value is an empty list, the default
16227 environment for using libraries, running embedded Perl code, or running
16228 external binaries is empty, and does not not even contain PATH or HOME.
16230 Actually the list is interpreted as a list of patterns
16231 (&<<SECTlistexpand>>&), except that it is not expanded first.
16233 WARNING: Macro substitution is still done first, so having a macro
16234 FOO and having FOO_HOME in your &%keep_environment%& option may have
16235 unexpected results. You may work around this using a regular expression
16236 that does not match the macro name: ^[F]OO_HOME$.
16238 Current versions of Exim issue a warning during startup if you do not mention
16239 &%keep_environment%& in your runtime configuration file and if your
16240 current environment is not empty. Future versions may not issue that warning
16243 See the &%add_environment%& main config option for a way to set
16244 environment variables to a fixed value. The environment for &(pipe)&
16245 transports is handled separately, see section &<<SECTpipeenv>>& for
16249 .option keep_malformed main time 4d
16250 This option specifies the length of time to keep messages whose spool files
16251 have been corrupted in some way. This should, of course, never happen. At the
16252 next attempt to deliver such a message, it gets removed. The incident is
16256 .option ldap_ca_cert_dir main string unset
16257 .cindex "LDAP", "TLS CA certificate directory"
16258 .cindex certificate "directory for LDAP"
16259 This option indicates which directory contains CA certificates for verifying
16260 a TLS certificate presented by an LDAP server.
16261 While Exim does not provide a default value, your SSL library may.
16262 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16263 and constrained to be a directory.
16266 .option ldap_ca_cert_file main string unset
16267 .cindex "LDAP", "TLS CA certificate file"
16268 .cindex certificate "file for LDAP"
16269 This option indicates which file contains CA certificates for verifying
16270 a TLS certificate presented by an LDAP server.
16271 While Exim does not provide a default value, your SSL library may.
16272 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16273 and constrained to be a file.
16276 .option ldap_cert_file main string unset
16277 .cindex "LDAP" "TLS client certificate file"
16278 .cindex certificate "file for LDAP"
16279 This option indicates which file contains an TLS client certificate which
16280 Exim should present to the LDAP server during TLS negotiation.
16281 Should be used together with &%ldap_cert_key%&.
16284 .option ldap_cert_key main string unset
16285 .cindex "LDAP" "TLS client key file"
16286 .cindex certificate "key for LDAP"
16287 This option indicates which file contains the secret/private key to use
16288 to prove identity to the LDAP server during TLS negotiation.
16289 Should be used together with &%ldap_cert_file%&, which contains the
16290 identity to be proven.
16293 .option ldap_cipher_suite main string unset
16294 .cindex "LDAP" "TLS cipher suite"
16295 This controls the TLS cipher-suite negotiation during TLS negotiation with
16296 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16297 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16300 .option ldap_default_servers main "string list" unset
16301 .cindex "LDAP" "default servers"
16302 This option provides a list of LDAP servers which are tried in turn when an
16303 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16304 details of LDAP queries. This option is available only when Exim has been built
16308 .option ldap_require_cert main string unset.
16309 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16310 This should be one of the values "hard", "demand", "allow", "try" or "never".
16311 A value other than one of these is interpreted as "never".
16312 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16313 Although Exim does not set a default, the LDAP library probably defaults
16317 .option ldap_start_tls main boolean false
16318 .cindex "LDAP" "whether or not to negotiate TLS"
16319 If set, Exim will attempt to negotiate TLS with the LDAP server when
16320 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16321 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16323 In the event of failure to negotiate TLS, the action taken is controlled
16324 by &%ldap_require_cert%&.
16325 This option is ignored for &`ldapi`& connections.
16328 .option ldap_version main integer unset
16329 .cindex "LDAP" "protocol version, forcing"
16330 This option can be used to force Exim to set a specific protocol version for
16331 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16332 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16333 the LDAP headers; otherwise it is 2. This option is available only when Exim
16334 has been built with LDAP support.
16338 .option local_from_check main boolean true
16339 .cindex "&'Sender:'& header line" "disabling addition of"
16340 .cindex "&'From:'& header line" "disabling checking of"
16341 When a message is submitted locally (that is, not over a TCP/IP connection) by
16342 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16343 checks that the &'From:'& header line matches the login of the calling user and
16344 the domain specified by &%qualify_domain%&.
16346 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16347 locally submitted message is automatically qualified by Exim, unless the
16348 &%-bnq%& command line option is used.
16350 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16351 on the local part. If the &'From:'& header line does not match, Exim adds a
16352 &'Sender:'& header with an address constructed from the calling user's login
16353 and the default qualify domain.
16355 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16356 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16357 &'Sender:'& header lines supplied by untrusted users, you must also set
16358 &%local_sender_retain%& to be true.
16360 .cindex "envelope from"
16361 .cindex "envelope sender"
16362 These options affect only the header lines in the message. The envelope sender
16363 is still forced to be the login id at the qualify domain unless
16364 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16366 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16367 request similar header line checking. See section &<<SECTthesenhea>>&, which
16368 has more details about &'Sender:'& processing.
16373 .option local_from_prefix main string unset
16374 When Exim checks the &'From:'& header line of locally submitted messages for
16375 matching the login id (see &%local_from_check%& above), it can be configured to
16376 ignore certain prefixes and suffixes in the local part of the address. This is
16377 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16378 appropriate lists, in the same form as the &%local_part_prefix%& and
16379 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16382 local_from_prefix = *-
16384 is set, a &'From:'& line containing
16386 From: anything-user@your.domain.example
16388 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16389 matches the actual sender address that is constructed from the login name and
16393 .option local_from_suffix main string unset
16394 See &%local_from_prefix%& above.
16397 .option local_interfaces main "string list" "see below"
16398 This option controls which network interfaces are used by the daemon for
16399 listening; they are also used to identify the local host when routing. Chapter
16400 &<<CHAPinterfaces>>& contains a full description of this option and the related
16401 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16402 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16403 &%local_interfaces%& is
16405 local_interfaces = 0.0.0.0
16407 when Exim is built without IPv6 support; otherwise it is
16409 local_interfaces = <; ::0 ; 0.0.0.0
16412 .option local_scan_timeout main time 5m
16413 .cindex "timeout" "for &[local_scan()]& function"
16414 .cindex "&[local_scan()]& function" "timeout"
16415 This timeout applies to the &[local_scan()]& function (see chapter
16416 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16417 the incoming message is rejected with a temporary error if it is an SMTP
16418 message. For a non-SMTP message, the message is dropped and Exim ends with a
16419 non-zero code. The incident is logged on the main and reject logs.
16423 .option local_sender_retain main boolean false
16424 .cindex "&'Sender:'& header line" "retaining from local submission"
16425 When a message is submitted locally (that is, not over a TCP/IP connection) by
16426 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16427 do not want this to happen, you must set &%local_sender_retain%&, and you must
16428 also set &%local_from_check%& to be false (Exim will complain if you do not).
16429 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16430 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16435 .option localhost_number main string&!! unset
16436 .cindex "host" "locally unique number for"
16437 .cindex "message ids" "with multiple hosts"
16438 .vindex "&$localhost_number$&"
16439 Exim's message ids are normally unique only within the local host. If
16440 uniqueness among a set of hosts is required, each host must set a different
16441 value for the &%localhost_number%& option. The string is expanded immediately
16442 after reading the configuration file (so that a number can be computed from the
16443 host name, for example) and the result of the expansion must be a number in the
16444 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16445 systems). This is available in subsequent string expansions via the variable
16446 &$localhost_number$&. When &%localhost_number is set%&, the final two
16447 characters of the message id, instead of just being a fractional part of the
16448 time, are computed from the time and the local host number as described in
16449 section &<<SECTmessiden>>&.
16453 .option log_file_path main "string list&!!" "set at compile time"
16454 .cindex "log" "file path for"
16455 This option sets the path which is used to determine the names of Exim's log
16456 files, or indicates that logging is to be to syslog, or both. It is expanded
16457 when Exim is entered, so it can, for example, contain a reference to the host
16458 name. If no specific path is set for the log files at compile or runtime,
16459 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16460 they are written in a sub-directory called &_log_& in Exim's spool directory.
16461 A path must start with a slash.
16462 To send to syslog, use the word &"syslog"&.
16463 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16464 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16465 used. If this string is fixed at your installation (contains no expansion
16466 variables) it is recommended that you do not set this option in the
16467 configuration file, but instead supply the path using LOG_FILE_PATH in
16468 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16469 early on &-- in particular, failure to read the configuration file.
16472 .option log_selector main string unset
16473 .cindex "log" "selectors"
16474 This option can be used to reduce or increase the number of things that Exim
16475 writes to its log files. Its argument is made up of names preceded by plus or
16476 minus characters. For example:
16478 log_selector = +arguments -retry_defer
16480 A list of possible names and what they control is given in the chapter on
16481 logging, in section &<<SECTlogselector>>&.
16484 .option log_timezone main boolean false
16485 .cindex "log" "timezone for entries"
16486 .vindex "&$tod_log$&"
16487 .vindex "&$tod_zone$&"
16488 By default, the timestamps on log lines are in local time without the
16489 timezone. This means that if your timezone changes twice a year, the timestamps
16490 in log lines are ambiguous for an hour when the clocks go back. One way of
16491 avoiding this problem is to set the timezone to UTC. An alternative is to set
16492 &%log_timezone%& true. This turns on the addition of the timezone offset to
16493 timestamps in log lines. Turning on this option can add quite a lot to the size
16494 of log files because each line is extended by 6 characters. Note that the
16495 &$tod_log$& variable contains the log timestamp without the zone, but there is
16496 another variable called &$tod_zone$& that contains just the timezone offset.
16499 .option lookup_open_max main integer 25
16500 .cindex "too many open files"
16501 .cindex "open files, too many"
16502 .cindex "file" "too many open"
16503 .cindex "lookup" "maximum open files"
16504 .cindex "limit" "open files for lookups"
16505 This option limits the number of simultaneously open files for single-key
16506 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16507 Exim normally keeps these files open during routing, because often the same
16508 file is required several times. If the limit is reached, Exim closes the least
16509 recently used file. Note that if you are using the &'ndbm'& library, it
16510 actually opens two files for each logical DBM database, though it still counts
16511 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16512 open files"& errors with NDBM, you need to reduce the value of
16513 &%lookup_open_max%&.
16516 .option max_username_length main integer 0
16517 .cindex "length of login name"
16518 .cindex "user name" "maximum length"
16519 .cindex "limit" "user name length"
16520 Some operating systems are broken in that they truncate long arguments to
16521 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16522 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16523 an argument that is longer behaves as if &[getpwnam()]& failed.
16526 .option message_body_newlines main bool false
16527 .cindex "message body" "newlines in variables"
16528 .cindex "newline" "in message body variables"
16529 .vindex "&$message_body$&"
16530 .vindex "&$message_body_end$&"
16531 By default, newlines in the message body are replaced by spaces when setting
16532 the &$message_body$& and &$message_body_end$& expansion variables. If this
16533 option is set true, this no longer happens.
16536 .option message_body_visible main integer 500
16537 .cindex "body of message" "visible size"
16538 .cindex "message body" "visible size"
16539 .vindex "&$message_body$&"
16540 .vindex "&$message_body_end$&"
16541 This option specifies how much of a message's body is to be included in the
16542 &$message_body$& and &$message_body_end$& expansion variables.
16545 .option message_id_header_domain main string&!! unset
16546 .cindex "&'Message-ID:'& header line"
16547 If this option is set, the string is expanded and used as the right hand side
16548 (domain) of the &'Message-ID:'& header that Exim creates if a
16549 locally-originated incoming message does not have one. &"Locally-originated"&
16550 means &"not received over TCP/IP."&
16551 Otherwise, the primary host name is used.
16552 Only letters, digits, dot and hyphen are accepted; any other characters are
16553 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16554 empty string, the option is ignored.
16557 .option message_id_header_text main string&!! unset
16558 If this variable is set, the string is expanded and used to augment the text of
16559 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16560 message does not have one. The text of this header is required by RFC 2822 to
16561 take the form of an address. By default, Exim uses its internal message id as
16562 the local part, and the primary host name as the domain. If this option is set,
16563 it is expanded, and provided the expansion is not forced to fail, and does not
16564 yield an empty string, the result is inserted into the header immediately
16565 before the @, separated from the internal message id by a dot. Any characters
16566 that are illegal in an address are automatically converted into hyphens. This
16567 means that variables such as &$tod_log$& can be used, because the spaces and
16568 colons will become hyphens.
16571 .option message_logs main boolean true
16572 .cindex "message logs" "disabling"
16573 .cindex "log" "message log; disabling"
16574 If this option is turned off, per-message log files are not created in the
16575 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16576 Exim, by reducing the number of files involved in handling a message from a
16577 minimum of four (header spool file, body spool file, delivery journal, and
16578 per-message log) to three. The other major I/O activity is Exim's main log,
16579 which is not affected by this option.
16582 .option message_size_limit main string&!! 50M
16583 .cindex "message" "size limit"
16584 .cindex "limit" "message size"
16585 .cindex "size" "of message, limit"
16586 This option limits the maximum size of message that Exim will process. The
16587 value is expanded for each incoming connection so, for example, it can be made
16588 to depend on the IP address of the remote host for messages arriving via
16589 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16590 optionally followed by K or M.
16592 .cindex "SIZE" "ESMTP extension, advertising"
16593 .cindex "ESMTP extensions" SIZE
16594 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16595 service extension keyword.
16597 &*Note*&: This limit cannot be made to depend on a message's sender or any
16598 other properties of an individual message, because it has to be advertised in
16599 the server's response to EHLO. String expansion failure causes a temporary
16600 error. A value of zero means no limit, but its use is not recommended. See also
16601 &%bounce_return_size_limit%&.
16603 Incoming SMTP messages are failed with a 552 error if the limit is
16604 exceeded; locally-generated messages either get a stderr message or a delivery
16605 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16606 an oversized message is logged in both the main and the reject logs. See also
16607 the generic transport option &%message_size_limit%&, which limits the size of
16608 message that an individual transport can process.
16610 If you use a virus-scanner and set this option to to a value larger than the
16611 maximum size that your virus-scanner is configured to support, you may get
16612 failures triggered by large mails. The right size to configure for the
16613 virus-scanner depends upon what data is passed and the options in use but it's
16614 probably safest to just set it to a little larger than this value. E.g., with a
16615 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16616 some problems may result.
16618 A value of 0 will disable size limit checking; Exim will still advertise the
16619 SIZE extension in an EHLO response, but without a limit, so as to permit
16620 SMTP clients to still indicate the message size along with the MAIL verb.
16623 .option move_frozen_messages main boolean false
16624 .cindex "frozen messages" "moving"
16625 This option, which is available only if Exim has been built with the setting
16627 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16629 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16630 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16631 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16632 standard utilities for handling such moved messages, and they do not show up in
16633 lists generated by &%-bp%& or by the Exim monitor.
16636 .option mua_wrapper main boolean false
16637 Setting this option true causes Exim to run in a very restrictive mode in which
16638 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16639 contains a full description of this facility.
16643 .option mysql_servers main "string list" unset
16644 .cindex "MySQL" "server list"
16645 This option provides a list of MySQL servers and associated connection data, to
16646 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16647 option is available only if Exim has been built with MySQL support.
16650 .option never_users main "string list&!!" unset
16651 This option is expanded just once, at the start of Exim's processing. Local
16652 message deliveries are normally run in processes that are setuid to the
16653 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16654 It is usually desirable to prevent any deliveries from running as root, as a
16657 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16658 list of users that must not be used for local deliveries. This list is fixed in
16659 the binary and cannot be overridden by the configuration file. By default, it
16660 contains just the single user name &"root"&. The &%never_users%& runtime option
16661 can be used to add more users to the fixed list.
16663 If a message is to be delivered as one of the users on the fixed list or the
16664 &%never_users%& list, an error occurs, and delivery is deferred. A common
16667 never_users = root:daemon:bin
16669 Including root is redundant if it is also on the fixed list, but it does no
16670 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16674 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16675 This option gives the name for a unix-domain socket on which the daemon
16676 listens for work and information-requests.
16677 Only installations running multiple daemons sharing a spool directory
16678 should need to modify the default.
16680 The option is expanded before use.
16681 If the platform supports Linux-style abstract socket names, the result
16682 is used with a nul byte prefixed.
16683 Otherwise, it should be a full path name and use a directory accessible
16686 If the Exim command line uses a &%-oX%& option and does not use &%-oP%&
16687 then a notifier socket is not created.
16690 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16691 .cindex "OpenSSL "compatibility options"
16692 This option allows an administrator to adjust the SSL options applied
16693 by OpenSSL to connections. It is given as a space-separated list of items,
16694 each one to be +added or -subtracted from the current value.
16696 This option is only available if Exim is built against OpenSSL. The values
16697 available for this option vary according to the age of your OpenSSL install.
16698 The &"all"& value controls a subset of flags which are available, typically
16699 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16700 list the values known on your system and Exim should support all the
16701 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16702 names lose the leading &"SSL_OP_"& and are lower-cased.
16704 Note that adjusting the options can have severe impact upon the security of
16705 SSL as used by Exim. It is possible to disable safety checks and shoot
16706 yourself in the foot in various unpleasant ways. This option should not be
16707 adjusted lightly. An unrecognised item will be detected at startup, by
16708 invoking Exim with the &%-bV%& flag.
16710 The option affects Exim operating both as a server and as a client.
16712 Historical note: prior to release 4.80, Exim defaulted this value to
16713 "+dont_insert_empty_fragments", which may still be needed for compatibility
16714 with some clients, but which lowers security by increasing exposure to
16715 some now infamous attacks.
16719 # Make both old MS and old Eudora happy:
16720 openssl_options = -all +microsoft_big_sslv3_buffer \
16721 +dont_insert_empty_fragments
16723 # Disable older protocol versions:
16724 openssl_options = +no_sslv2 +no_sslv3
16727 Possible options may include:
16731 &`allow_unsafe_legacy_renegotiation`&
16733 &`cipher_server_preference`&
16735 &`dont_insert_empty_fragments`&
16739 &`legacy_server_connect`&
16741 &`microsoft_big_sslv3_buffer`&
16743 &`microsoft_sess_id_bug`&
16745 &`msie_sslv2_rsa_padding`&
16747 &`netscape_challenge_bug`&
16749 &`netscape_reuse_cipher_change_bug`&
16753 &`no_session_resumption_on_renegotiation`&
16767 &`safari_ecdhe_ecdsa_bug`&
16771 &`single_ecdh_use`&
16773 &`ssleay_080_client_dh_bug`&
16775 &`sslref2_reuse_cert_type_bug`&
16777 &`tls_block_padding_bug`&
16781 &`tls_rollback_bug`&
16784 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16785 all clients connecting using the MacOS SecureTransport TLS facility prior
16786 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16787 to negotiate TLS then this option value might help, provided that your OpenSSL
16788 release is new enough to contain this work-around. This may be a situation
16789 where you have to upgrade OpenSSL to get buggy clients working.
16792 .option oracle_servers main "string list" unset
16793 .cindex "Oracle" "server list"
16794 This option provides a list of Oracle servers and associated connection data,
16795 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16796 The option is available only if Exim has been built with Oracle support.
16799 .option percent_hack_domains main "domain list&!!" unset
16800 .cindex "&""percent hack""&"
16801 .cindex "source routing" "in email address"
16802 .cindex "address" "source-routed"
16803 The &"percent hack"& is the convention whereby a local part containing a
16804 percent sign is re-interpreted as a new email address, with the percent
16805 replaced by @. This is sometimes called &"source routing"&, though that term is
16806 also applied to RFC 2822 addresses that begin with an @ character. If this
16807 option is set, Exim implements the percent facility for those domains listed,
16808 but no others. This happens before an incoming SMTP address is tested against
16811 &*Warning*&: The &"percent hack"& has often been abused by people who are
16812 trying to get round relaying restrictions. For this reason, it is best avoided
16813 if at all possible. Unfortunately, a number of less security-conscious MTAs
16814 implement it unconditionally. If you are running Exim on a gateway host, and
16815 routing mail through to internal MTAs without processing the local parts, it is
16816 a good idea to reject recipient addresses with percent characters in their
16817 local parts. Exim's default configuration does this.
16820 .option perl_at_start main boolean false
16822 This option is available only when Exim is built with an embedded Perl
16823 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16826 .option perl_startup main string unset
16828 This option is available only when Exim is built with an embedded Perl
16829 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16831 .option perl_taintmode main boolean false
16833 This option enables the taint mode of the embedded Perl interpreter.
16836 .option pgsql_servers main "string list" unset
16837 .cindex "PostgreSQL lookup type" "server list"
16838 This option provides a list of PostgreSQL servers and associated connection
16839 data, to be used in conjunction with &(pgsql)& lookups (see section
16840 &<<SECID72>>&). The option is available only if Exim has been built with
16841 PostgreSQL support.
16844 .option pid_file_path main string&!! "set at compile time"
16845 .cindex "daemon" "pid file path"
16846 .cindex "pid file, path for"
16847 This option sets the name of the file to which the Exim daemon writes its
16848 process id. The string is expanded, so it can contain, for example, references
16851 pid_file_path = /var/log/$primary_hostname/exim.pid
16853 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16855 The value set by the option can be overridden by the &%-oP%& command line
16856 option. A pid file is not written if a &"non-standard"& daemon is run by means
16857 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16860 .option pipelining_advertise_hosts main "host list&!!" *
16861 .cindex "PIPELINING" "suppressing advertising"
16862 .cindex "ESMTP extensions" PIPELINING
16863 This option can be used to suppress the advertisement of the SMTP
16864 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16865 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16866 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16867 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16868 that clients will use it; &"out of order"& commands that are &"expected"& do
16869 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16871 .option pipelining_connect_advertise_hosts main "host list&!!" *
16872 .cindex "pipelining" "early connection"
16873 .cindex "pipelining" PIPE_CONNECT
16874 .cindex "ESMTP extensions" X_PIPE_CONNECT
16875 If Exim is built with the SUPPORT_PIPE_CONNECT build option
16876 this option controls which hosts the facility is advertised to
16877 and from which pipeline early-connection (before MAIL) SMTP
16878 commands are acceptable.
16879 When used, the pipelining saves on roundtrip times.
16881 See also the &%hosts_pipe_connect%& smtp transport option.
16883 Currently the option name &"X_PIPE_CONNECT"& is used.
16886 .option prdr_enable main boolean false
16887 .cindex "PRDR" "enabling on server"
16888 .cindex "ESMTP extensions" PRDR
16889 This option can be used to enable the Per-Recipient Data Response extension
16890 to SMTP, defined by Eric Hall.
16891 If the option is set, PRDR is advertised by Exim when operating as a server.
16892 If the client requests PRDR, and more than one recipient, for a message
16893 an additional ACL is called for each recipient after the message content
16894 is received. See section &<<SECTPRDRACL>>&.
16896 .option preserve_message_logs main boolean false
16897 .cindex "message logs" "preserving"
16898 If this option is set, message log files are not deleted when messages are
16899 completed. Instead, they are moved to a sub-directory of the spool directory
16900 called &_msglog.OLD_&, where they remain available for statistical or debugging
16901 purposes. This is a dangerous option to set on systems with any appreciable
16902 volume of mail. Use with care!
16905 .option primary_hostname main string "see below"
16906 .cindex "name" "of local host"
16907 .cindex "host" "name of local"
16908 .cindex "local host" "name of"
16909 .vindex "&$primary_hostname$&"
16910 This specifies the name of the current host. It is used in the default EHLO or
16911 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
16912 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
16913 The value is also used by default in some SMTP response messages from an Exim
16914 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
16916 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
16917 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
16918 contains only one component, Exim passes it to &[gethostbyname()]& (or
16919 &[getipnodebyname()]& when available) in order to obtain the fully qualified
16920 version. The variable &$primary_hostname$& contains the host name, whether set
16921 explicitly by this option, or defaulted.
16924 .option print_topbitchars main boolean false
16925 .cindex "printing characters"
16926 .cindex "8-bit characters"
16927 By default, Exim considers only those characters whose codes lie in the range
16928 32&--126 to be printing characters. In a number of circumstances (for example,
16929 when writing log entries) non-printing characters are converted into escape
16930 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
16931 is set, code values of 128 and above are also considered to be printing
16934 This option also affects the header syntax checks performed by the
16935 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
16936 the user's full name when constructing From: and Sender: addresses (as
16937 described in section &<<SECTconstr>>&). Setting this option can cause
16938 Exim to generate eight bit message headers that do not conform to the
16942 .option process_log_path main string unset
16943 .cindex "process log path"
16944 .cindex "log" "process log"
16945 .cindex "&'exiwhat'&"
16946 This option sets the name of the file to which an Exim process writes its
16947 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
16948 utility script. If this option is unset, the file called &_exim-process.info_&
16949 in Exim's spool directory is used. The ability to specify the name explicitly
16950 can be useful in environments where two different Exims are running, using
16951 different spool directories.
16954 .option prod_requires_admin main boolean true
16955 .cindex "restricting access to features"
16959 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
16960 admin user unless &%prod_requires_admin%& is set false. See also
16961 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
16964 .option qualify_domain main string "see below"
16965 .cindex "domain" "for qualifying addresses"
16966 .cindex "address" "qualification"
16967 This option specifies the domain name that is added to any envelope sender
16968 addresses that do not have a domain qualification. It also applies to
16969 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
16970 are accepted by default only for locally-generated messages. Qualification is
16971 also applied to addresses in header lines such as &'From:'& and &'To:'& for
16972 locally-generated messages, unless the &%-bnq%& command line option is used.
16974 Messages from external sources must always contain fully qualified addresses,
16975 unless the sending host matches &%sender_unqualified_hosts%& or
16976 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
16977 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
16978 necessary. Internally, Exim always works with fully qualified envelope
16979 addresses. If &%qualify_domain%& is not set, it defaults to the
16980 &%primary_hostname%& value.
16983 .option qualify_recipient main string "see below"
16984 This option allows you to specify a different domain for qualifying recipient
16985 addresses to the one that is used for senders. See &%qualify_domain%& above.
16989 .option queue_domains main "domain list&!!" unset
16990 .cindex "domain" "specifying non-immediate delivery"
16991 .cindex "queueing incoming messages"
16992 .cindex "message" "queueing certain domains"
16993 This option lists domains for which immediate delivery is not required.
16994 A delivery process is started whenever a message is received, but only those
16995 domains that do not match are processed. All other deliveries wait until the
16996 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17000 .option queue_fast_ramp main boolean false
17001 .cindex "queue runner" "two phase"
17002 .cindex "queue" "double scanning"
17003 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17004 command line, may start parallel delivery processes during their first
17005 phase. This will be done when a threshold number of messages have been
17006 routed for a single host.
17010 .option queue_list_requires_admin main boolean true
17011 .cindex "restricting access to features"
17013 The &%-bp%& command-line option, which lists the messages that are on the
17014 queue, requires the caller to be an admin user unless
17015 &%queue_list_requires_admin%& is set false.
17016 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17019 .option queue_only main boolean false
17020 .cindex "queueing incoming messages"
17021 .cindex "message" "queueing unconditionally"
17022 If &%queue_only%& is set, a delivery process is not automatically started
17023 whenever a message is received. Instead, the message waits in the queue for the
17024 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17025 delivered immediately when certain conditions (such as heavy load) occur.
17027 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17028 and &%-odi%& command line options override &%queue_only%& unless
17029 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17030 &%queue_only_load%&, and &%smtp_accept_queue%&.
17033 .option queue_only_file main string unset
17034 .cindex "queueing incoming messages"
17035 .cindex "message" "queueing by file existence"
17036 This option can be set to a colon-separated list of absolute path names, each
17037 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17038 it tests for the existence of each listed path using a call to &[stat()]&. For
17039 each path that exists, the corresponding queueing option is set.
17040 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17041 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17043 queue_only_file = smtp/some/file
17045 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17046 &_/some/file_& exists.
17049 .option queue_only_load main fixed-point unset
17050 .cindex "load average"
17051 .cindex "queueing incoming messages"
17052 .cindex "message" "queueing by load"
17053 If the system load average is higher than this value, incoming messages from
17054 all sources are queued, and no automatic deliveries are started. If this
17055 happens during local or remote SMTP input, all subsequent messages received on
17056 the same SMTP connection are queued by default, whatever happens to the load in
17057 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17060 Deliveries will subsequently be performed by queue runner processes. This
17061 option has no effect on ancient operating systems on which Exim cannot
17062 determine the load average. See also &%deliver_queue_load_max%& and
17063 &%smtp_load_reserve%&.
17066 .option queue_only_load_latch main boolean true
17067 .cindex "load average" "re-evaluating per message"
17068 When this option is true (the default), once one message has been queued
17069 because the load average is higher than the value set by &%queue_only_load%&,
17070 all subsequent messages received on the same SMTP connection are also queued.
17071 This is a deliberate choice; even though the load average may fall below the
17072 threshold, it doesn't seem right to deliver later messages on the same
17073 connection when not delivering earlier ones. However, there are special
17074 circumstances such as very long-lived connections from scanning appliances
17075 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17076 should be set false. This causes the value of the load average to be
17077 re-evaluated for each message.
17080 .option queue_only_override main boolean true
17081 .cindex "queueing incoming messages"
17082 When this option is true, the &%-od%&&'x'& command line options override the
17083 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17084 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17085 to override; they are accepted, but ignored.
17088 .option queue_run_in_order main boolean false
17089 .cindex "queue runner" "processing messages in order"
17090 If this option is set, queue runs happen in order of message arrival instead of
17091 in an arbitrary order. For this to happen, a complete list of the entire queue
17092 must be set up before the deliveries start. When the queue is all held in a
17093 single directory (the default), a single list is created for both the ordered
17094 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17095 single list is not created when &%queue_run_in_order%& is false. In this case,
17096 the sub-directories are processed one at a time (in a random order), and this
17097 avoids setting up one huge list for the whole queue. Thus, setting
17098 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17099 when the queue is large, because of the extra work in setting up the single,
17100 large list. In most situations, &%queue_run_in_order%& should not be set.
17104 .option queue_run_max main integer&!! 5
17105 .cindex "queue runner" "maximum number of"
17106 This controls the maximum number of queue runner processes that an Exim daemon
17107 can run simultaneously. This does not mean that it starts them all at once,
17108 but rather that if the maximum number are still running when the time comes to
17109 start another one, it refrains from starting another one. This can happen with
17110 very large queues and/or very sluggish deliveries. This option does not,
17111 however, interlock with other processes, so additional queue runners can be
17112 started by other means, or by killing and restarting the daemon.
17114 Setting this option to zero does not suppress queue runs; rather, it disables
17115 the limit, allowing any number of simultaneous queue runner processes to be
17116 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17117 the daemon's command line.
17119 .cindex queues named
17120 .cindex "named queues" "resource limit"
17121 To set limits for different named queues use
17122 an expansion depending on the &$queue_name$& variable.
17124 .option queue_smtp_domains main "domain list&!!" unset
17125 .cindex "queueing incoming messages"
17126 .cindex "message" "queueing remote deliveries"
17127 .cindex "first pass routing"
17128 When this option is set, a delivery process is started whenever a message is
17129 received, routing is performed, and local deliveries take place.
17130 However, if any SMTP deliveries are required for domains that match
17131 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17132 message waits in the queue for the next queue run. Since routing of the message
17133 has taken place, Exim knows to which remote hosts it must be delivered, and so
17134 when the queue run happens, multiple messages for the same host are delivered
17135 over a single SMTP connection. The &%-odqs%& command line option causes all
17136 SMTP deliveries to be queued in this way, and is equivalent to setting
17137 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17141 .option receive_timeout main time 0s
17142 .cindex "timeout" "for non-SMTP input"
17143 This option sets the timeout for accepting a non-SMTP message, that is, the
17144 maximum time that Exim waits when reading a message on the standard input. If
17145 the value is zero, it will wait forever. This setting is overridden by the
17146 &%-or%& command line option. The timeout for incoming SMTP messages is
17147 controlled by &%smtp_receive_timeout%&.
17149 .option received_header_text main string&!! "see below"
17150 .cindex "customizing" "&'Received:'& header"
17151 .cindex "&'Received:'& header line" "customizing"
17152 This string defines the contents of the &'Received:'& message header that is
17153 added to each message, except for the timestamp, which is automatically added
17154 on at the end (preceded by a semicolon). The string is expanded each time it is
17155 used. If the expansion yields an empty string, no &'Received:'& header line is
17156 added to the message. Otherwise, the string should start with the text
17157 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17159 The default setting is:
17162 received_header_text = Received: \
17163 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17164 {${if def:sender_ident \
17165 {from ${quote_local_part:$sender_ident} }}\
17166 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17167 by $primary_hostname \
17168 ${if def:received_protocol {with $received_protocol }}\
17169 ${if def:tls_in_ver { ($tls_in_ver)}}\
17170 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17171 (Exim $version_number)\n\t\
17172 ${if def:sender_address \
17173 {(envelope-from <$sender_address>)\n\t}}\
17174 id $message_exim_id\
17175 ${if def:received_for {\n\tfor $received_for}}
17178 The references to the TLS version and cipher are
17179 omitted when Exim is built without TLS
17180 support. The use of conditional expansions ensures that this works for both
17181 locally generated messages and messages received from remote hosts, giving
17182 header lines such as the following:
17184 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17185 by marley.carol.example with esmtp (Exim 4.00)
17186 (envelope-from <bob@carol.example>)
17187 id 16IOWa-00019l-00
17188 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17189 Received: by scrooge.carol.example with local (Exim 4.00)
17190 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17192 Until the body of the message has been received, the timestamp is the time when
17193 the message started to be received. Once the body has arrived, and all policy
17194 checks have taken place, the timestamp is updated to the time at which the
17195 message was accepted.
17198 .option received_headers_max main integer 30
17199 .cindex "loop" "prevention"
17200 .cindex "mail loop prevention"
17201 .cindex "&'Received:'& header line" "counting"
17202 When a message is to be delivered, the number of &'Received:'& headers is
17203 counted, and if it is greater than this parameter, a mail loop is assumed to
17204 have occurred, the delivery is abandoned, and an error message is generated.
17205 This applies to both local and remote deliveries.
17208 .option recipient_unqualified_hosts main "host list&!!" unset
17209 .cindex "unqualified addresses"
17210 .cindex "host" "unqualified addresses from"
17211 This option lists those hosts from which Exim is prepared to accept unqualified
17212 recipient addresses in message envelopes. The addresses are made fully
17213 qualified by the addition of the &%qualify_recipient%& value. This option also
17214 affects message header lines. Exim does not reject unqualified recipient
17215 addresses in headers, but it qualifies them only if the message came from a
17216 host that matches &%recipient_unqualified_hosts%&,
17217 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17218 option was not set.
17221 .option recipients_max main integer 0
17222 .cindex "limit" "number of recipients"
17223 .cindex "recipient" "maximum number"
17224 If this option is set greater than zero, it specifies the maximum number of
17225 original recipients for any message. Additional recipients that are generated
17226 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17227 all recipients over the limit; earlier recipients are delivered as normal.
17228 Non-SMTP messages with too many recipients are failed, and no deliveries are
17231 .cindex "RCPT" "maximum number of incoming"
17232 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17233 RCPT commands in a single message.
17236 .option recipients_max_reject main boolean false
17237 If this option is set true, Exim rejects SMTP messages containing too many
17238 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17239 error to the eventual DATA command. Otherwise (the default) it gives a 452
17240 error to the surplus RCPT commands and accepts the message on behalf of the
17241 initial set of recipients. The remote server should then re-send the message
17242 for the remaining recipients at a later time.
17245 .option remote_max_parallel main integer 2
17246 .cindex "delivery" "parallelism for remote"
17247 This option controls parallel delivery of one message to a number of remote
17248 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17249 does all the remote deliveries for a message one by one. Otherwise, if a single
17250 message has to be delivered to more than one remote host, or if several copies
17251 have to be sent to the same remote host, up to &%remote_max_parallel%&
17252 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17253 deliveries are required, the maximum number of processes are started, and as
17254 each one finishes, another is begun. The order of starting processes is the
17255 same as if sequential delivery were being done, and can be controlled by the
17256 &%remote_sort_domains%& option. If parallel delivery takes place while running
17257 with debugging turned on, the debugging output from each delivery process is
17258 tagged with its process id.
17260 This option controls only the maximum number of parallel deliveries for one
17261 message in one Exim delivery process. Because Exim has no central queue
17262 manager, there is no way of controlling the total number of simultaneous
17263 deliveries if the configuration allows a delivery attempt as soon as a message
17266 .cindex "number of deliveries"
17267 .cindex "delivery" "maximum number of"
17268 If you want to control the total number of deliveries on the system, you
17269 need to set the &%queue_only%& option. This ensures that all incoming messages
17270 are added to the queue without starting a delivery process. Then set up an Exim
17271 daemon to start queue runner processes at appropriate intervals (probably
17272 fairly often, for example, every minute), and limit the total number of queue
17273 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17274 delivers only one message at a time, the maximum number of deliveries that can
17275 then take place at once is &%queue_run_max%& multiplied by
17276 &%remote_max_parallel%&.
17278 If it is purely remote deliveries you want to control, use
17279 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17280 doing the SMTP routing before queueing, so that several messages for the same
17281 host will eventually get delivered down the same connection.
17284 .option remote_sort_domains main "domain list&!!" unset
17285 .cindex "sorting remote deliveries"
17286 .cindex "delivery" "sorting remote"
17287 When there are a number of remote deliveries for a message, they are sorted by
17288 domain into the order given by this list. For example,
17290 remote_sort_domains = *.cam.ac.uk:*.uk
17292 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17293 then to those in the &%uk%& domain, then to any others.
17296 .option retry_data_expire main time 7d
17297 .cindex "hints database" "data expiry"
17298 This option sets a &"use before"& time on retry information in Exim's hints
17299 database. Any older retry data is ignored. This means that, for example, once a
17300 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17304 .option retry_interval_max main time 24h
17305 .cindex "retry" "limit on interval"
17306 .cindex "limit" "on retry interval"
17307 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17308 intervals between delivery attempts for messages that cannot be delivered
17309 straight away. This option sets an overall limit to the length of time between
17310 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17314 .option return_path_remove main boolean true
17315 .cindex "&'Return-path:'& header line" "removing"
17316 RFC 2821, section 4.4, states that an SMTP server must insert a
17317 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17318 The &'Return-path:'& header preserves the sender address as received in the
17319 MAIL command. This description implies that this header should not be present
17320 in an incoming message. If &%return_path_remove%& is true, any existing
17321 &'Return-path:'& headers are removed from messages at the time they are
17322 received. Exim's transports have options for adding &'Return-path:'& headers at
17323 the time of delivery. They are normally used only for final local deliveries.
17326 .option return_size_limit main integer 100K
17327 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17330 .option rfc1413_hosts main "host list&!!" @[]
17332 .cindex "host" "for RFC 1413 calls"
17333 RFC 1413 identification calls are made to any client host which matches
17334 an item in the list.
17335 The default value specifies just this host, being any local interface
17338 .option rfc1413_query_timeout main time 0s
17339 .cindex "RFC 1413" "query timeout"
17340 .cindex "timeout" "for RFC 1413 call"
17341 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17342 no RFC 1413 calls are ever made.
17345 .option sender_unqualified_hosts main "host list&!!" unset
17346 .cindex "unqualified addresses"
17347 .cindex "host" "unqualified addresses from"
17348 This option lists those hosts from which Exim is prepared to accept unqualified
17349 sender addresses. The addresses are made fully qualified by the addition of
17350 &%qualify_domain%&. This option also affects message header lines. Exim does
17351 not reject unqualified addresses in headers that contain sender addresses, but
17352 it qualifies them only if the message came from a host that matches
17353 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17354 using TCP/IP), and the &%-bnq%& option was not set.
17357 .option slow_lookup_log main integer 0
17358 .cindex "logging" "slow lookups"
17359 .cindex "dns" "logging slow lookups"
17360 This option controls logging of slow lookups.
17361 If the value is nonzero it is taken as a number of milliseconds
17362 and lookups taking longer than this are logged.
17363 Currently this applies only to DNS lookups.
17367 .option smtp_accept_keepalive main boolean true
17368 .cindex "keepalive" "on incoming connection"
17369 This option controls the setting of the SO_KEEPALIVE option on incoming
17370 TCP/IP socket connections. When set, it causes the kernel to probe idle
17371 connections periodically, by sending packets with &"old"& sequence numbers. The
17372 other end of the connection should send an acknowledgment if the connection is
17373 still okay or a reset if the connection has been aborted. The reason for doing
17374 this is that it has the beneficial effect of freeing up certain types of
17375 connection that can get stuck when the remote host is disconnected without
17376 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17377 hours to detect unreachable hosts.
17381 .option smtp_accept_max main integer 20
17382 .cindex "limit" "incoming SMTP connections"
17383 .cindex "SMTP" "incoming connection count"
17385 This option specifies the maximum number of simultaneous incoming SMTP calls
17386 that Exim will accept. It applies only to the listening daemon; there is no
17387 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17388 value is set to zero, no limit is applied. However, it is required to be
17389 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17390 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17392 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17393 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17394 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17395 and &%smtp_load_reserve%& are then checked before accepting the connection.
17398 .option smtp_accept_max_nonmail main integer 10
17399 .cindex "limit" "non-mail SMTP commands"
17400 .cindex "SMTP" "limiting non-mail commands"
17401 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17402 the connection if there are too many. This option defines &"too many"&. The
17403 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17404 client looping sending EHLO, for example. The check is applied only if the
17405 client host matches &%smtp_accept_max_nonmail_hosts%&.
17407 When a new message is expected, one occurrence of RSET is not counted. This
17408 allows a client to send one RSET between messages (this is not necessary,
17409 but some clients do it). Exim also allows one uncounted occurrence of HELO
17410 or EHLO, and one occurrence of STARTTLS between messages. After
17411 starting up a TLS session, another EHLO is expected, and so it too is not
17412 counted. The first occurrence of AUTH in a connection, or immediately
17413 following STARTTLS is not counted. Otherwise, all commands other than
17414 MAIL, RCPT, DATA, and QUIT are counted.
17417 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17418 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17419 check by setting this option. The default value makes it apply to all hosts. By
17420 changing the value, you can exclude any badly-behaved hosts that you have to
17424 . Allow this long option name to split; give it unsplit as a fifth argument
17425 . for the automatic .oindex that is generated by .option.
17426 . We insert " &~&~" which is both pretty nasty visually and results in
17427 . non-searchable text. HowItWorks.txt mentions an option for inserting
17428 . zero-width-space, which would be nicer visually and results in (at least)
17429 . html that Firefox will split on when it's forced to reflow (rather than
17430 . inserting a horizontal scrollbar). However, the text is still not
17431 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17432 . the option name to split.
17434 .option "smtp_accept_max_per_connection" main integer 1000 &&&
17435 smtp_accept_max_per_connection
17436 .cindex "SMTP" "limiting incoming message count"
17437 .cindex "limit" "messages per SMTP connection"
17438 The value of this option limits the number of MAIL commands that Exim is
17439 prepared to accept over a single SMTP connection, whether or not each command
17440 results in the transfer of a message. After the limit is reached, a 421
17441 response is given to subsequent MAIL commands. This limit is a safety
17442 precaution against a client that goes mad (incidents of this type have been
17446 .option smtp_accept_max_per_host main string&!! unset
17447 .cindex "limit" "SMTP connections from one host"
17448 .cindex "host" "limiting SMTP connections from"
17449 This option restricts the number of simultaneous IP connections from a single
17450 host (strictly, from a single IP address) to the Exim daemon. The option is
17451 expanded, to enable different limits to be applied to different hosts by
17452 reference to &$sender_host_address$&. Once the limit is reached, additional
17453 connection attempts from the same host are rejected with error code 421. This
17454 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17455 of zero imposes no limit. If this option is set greater than zero, it is
17456 required that &%smtp_accept_max%& be non-zero.
17458 &*Warning*&: When setting this option you should not use any expansion
17459 constructions that take an appreciable amount of time. The expansion and test
17460 happen in the main daemon loop, in order to reject additional connections
17461 without forking additional processes (otherwise a denial-of-service attack
17462 could cause a vast number or processes to be created). While the daemon is
17463 doing this processing, it cannot accept any other incoming connections.
17467 .option smtp_accept_queue main integer 0
17468 .cindex "SMTP" "incoming connection count"
17469 .cindex "queueing incoming messages"
17470 .cindex "message" "queueing by SMTP connection count"
17471 If the number of simultaneous incoming SMTP connections being handled via the
17472 listening daemon exceeds this value, messages received by SMTP are just placed
17473 in the queue; no delivery processes are started automatically. The count is
17474 fixed at the start of an SMTP connection. It cannot be updated in the
17475 subprocess that receives messages, and so the queueing or not queueing applies
17476 to all messages received in the same connection.
17478 A value of zero implies no limit, and clearly any non-zero value is useful only
17479 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17480 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17481 various &%-od%&&'x'& command line options.
17484 . See the comment on smtp_accept_max_per_connection
17486 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17487 smtp_accept_queue_per_connection
17488 .cindex "queueing incoming messages"
17489 .cindex "message" "queueing by message count"
17490 This option limits the number of delivery processes that Exim starts
17491 automatically when receiving messages via SMTP, whether via the daemon or by
17492 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17493 and the number of messages received in a single SMTP session exceeds this
17494 number, subsequent messages are placed in the queue, but no delivery processes
17495 are started. This helps to limit the number of Exim processes when a server
17496 restarts after downtime and there is a lot of mail waiting for it on other
17497 systems. On large systems, the default should probably be increased, and on
17498 dial-in client systems it should probably be set to zero (that is, disabled).
17501 .option smtp_accept_reserve main integer 0
17502 .cindex "SMTP" "incoming call count"
17503 .cindex "host" "reserved"
17504 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17505 number of SMTP connections that are reserved for connections from the hosts
17506 that are specified in &%smtp_reserve_hosts%&. The value set in
17507 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17508 restricted to this number of connections; the option specifies a minimum number
17509 of connection slots for them, not a maximum. It is a guarantee that this group
17510 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17511 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17514 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17515 set to 5, once there are 45 active connections (from any hosts), new
17516 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17517 provided the other criteria for acceptance are met.
17520 .option smtp_active_hostname main string&!! unset
17521 .cindex "host" "name in SMTP responses"
17522 .cindex "SMTP" "host name in responses"
17523 .vindex "&$primary_hostname$&"
17524 This option is provided for multi-homed servers that want to masquerade as
17525 several different hosts. At the start of an incoming SMTP connection, its value
17526 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17527 responses. For example, it is used as domain name in the response to an
17528 incoming HELO or EHLO command.
17530 .vindex "&$smtp_active_hostname$&"
17531 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17532 is saved with any messages that are received. It is therefore available for use
17533 in routers and transports when the message is later delivered.
17535 If this option is unset, or if its expansion is forced to fail, or if the
17536 expansion results in an empty string, the value of &$primary_hostname$& is
17537 used. Other expansion failures cause a message to be written to the main and
17538 panic logs, and the SMTP command receives a temporary error. Typically, the
17539 value of &%smtp_active_hostname%& depends on the incoming interface address.
17542 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17543 {cox.mydomain}{box.mydomain}}
17546 Although &$smtp_active_hostname$& is primarily concerned with incoming
17547 messages, it is also used as the default for HELO commands in callout
17548 verification if there is no remote transport from which to obtain a
17549 &%helo_data%& value.
17551 .option smtp_banner main string&!! "see below"
17552 .cindex "SMTP" "welcome banner"
17553 .cindex "banner for SMTP"
17554 .cindex "welcome banner for SMTP"
17555 .cindex "customizing" "SMTP banner"
17556 This string, which is expanded every time it is used, is output as the initial
17557 positive response to an SMTP connection. The default setting is:
17559 smtp_banner = $smtp_active_hostname ESMTP Exim \
17560 $version_number $tod_full
17562 Failure to expand the string causes a panic error. If you want to create a
17563 multiline response to the initial SMTP connection, use &"\n"& in the string at
17564 appropriate points, but not at the end. Note that the 220 code is not included
17565 in this string. Exim adds it automatically (several times in the case of a
17566 multiline response).
17569 .option smtp_check_spool_space main boolean true
17570 .cindex "checking disk space"
17571 .cindex "disk space, checking"
17572 .cindex "spool directory" "checking space"
17573 When this option is set, if an incoming SMTP session encounters the SIZE
17574 option on a MAIL command, it checks that there is enough space in the
17575 spool directory's partition to accept a message of that size, while still
17576 leaving free the amount specified by &%check_spool_space%& (even if that value
17577 is zero). If there isn't enough space, a temporary error code is returned.
17580 .option smtp_connect_backlog main integer 20
17581 .cindex "connection backlog"
17582 .cindex "SMTP" "connection backlog"
17583 .cindex "backlog of connections"
17584 This option specifies a maximum number of waiting SMTP connections. Exim passes
17585 this value to the TCP/IP system when it sets up its listener. Once this number
17586 of connections are waiting for the daemon's attention, subsequent connection
17587 attempts are refused at the TCP/IP level. At least, that is what the manuals
17588 say; in some circumstances such connection attempts have been observed to time
17589 out instead. For large systems it is probably a good idea to increase the
17590 value (to 50, say). It also gives some protection against denial-of-service
17591 attacks by SYN flooding.
17594 .option smtp_enforce_sync main boolean true
17595 .cindex "SMTP" "synchronization checking"
17596 .cindex "synchronization checking in SMTP"
17597 The SMTP protocol specification requires the client to wait for a response from
17598 the server at certain points in the dialogue. Without PIPELINING these
17599 synchronization points are after every command; with PIPELINING they are
17600 fewer, but they still exist.
17602 Some spamming sites send out a complete set of SMTP commands without waiting
17603 for any response. Exim protects against this by rejecting a message if the
17604 client has sent further input when it should not have. The error response &"554
17605 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17606 for this error cannot be perfect because of transmission delays (unexpected
17607 input may be on its way but not yet received when Exim checks). However, it
17608 does detect many instances.
17610 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17611 If you want to disable the check selectively (for example, only for certain
17612 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17613 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17617 .option smtp_etrn_command main string&!! unset
17618 .cindex "ETRN" "command to be run"
17619 .cindex "ESMTP extensions" ETRN
17620 .vindex "&$domain$&"
17621 If this option is set, the given command is run whenever an SMTP ETRN
17622 command is received from a host that is permitted to issue such commands (see
17623 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17624 are independently expanded. The expansion variable &$domain$& is set to the
17625 argument of the ETRN command, and no syntax checking is done on it. For
17628 smtp_etrn_command = /etc/etrn_command $domain \
17629 $sender_host_address
17631 If the option is not set, the argument for the ETRN command must
17632 be a &'#'& followed by an address string.
17633 In this case an &'exim -R <string>'& command is used;
17634 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17636 A new process is created to run the command, but Exim does not wait for it to
17637 complete. Consequently, its status cannot be checked. If the command cannot be
17638 run, a line is written to the panic log, but the ETRN caller still receives
17639 a 250 success response. Exim is normally running under its own uid when
17640 receiving SMTP, so it is not possible for it to change the uid before running
17644 .option smtp_etrn_serialize main boolean true
17645 .cindex "ETRN" "serializing"
17646 When this option is set, it prevents the simultaneous execution of more than
17647 one identical command as a result of ETRN in an SMTP connection. See
17648 section &<<SECTETRN>>& for details.
17651 .option smtp_load_reserve main fixed-point unset
17652 .cindex "load average"
17653 If the system load average ever gets higher than this, incoming SMTP calls are
17654 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17655 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17656 the load is over the limit. The option has no effect on ancient operating
17657 systems on which Exim cannot determine the load average. See also
17658 &%deliver_queue_load_max%& and &%queue_only_load%&.
17662 .option smtp_max_synprot_errors main integer 3
17663 .cindex "SMTP" "limiting syntax and protocol errors"
17664 .cindex "limit" "SMTP syntax and protocol errors"
17665 Exim rejects SMTP commands that contain syntax or protocol errors. In
17666 particular, a syntactically invalid email address, as in this command:
17668 RCPT TO:<abc xyz@a.b.c>
17670 causes immediate rejection of the command, before any other tests are done.
17671 (The ACL cannot be run if there is no valid address to set up for it.) An
17672 example of a protocol error is receiving RCPT before MAIL. If there are
17673 too many syntax or protocol errors in one SMTP session, the connection is
17674 dropped. The limit is set by this option.
17676 .cindex "PIPELINING" "expected errors"
17677 When the PIPELINING extension to SMTP is in use, some protocol errors are
17678 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17679 Exim assumes that PIPELINING will be used if it advertises it (see
17680 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17681 not count towards the limit.
17685 .option smtp_max_unknown_commands main integer 3
17686 .cindex "SMTP" "limiting unknown commands"
17687 .cindex "limit" "unknown SMTP commands"
17688 If there are too many unrecognized commands in an incoming SMTP session, an
17689 Exim server drops the connection. This is a defence against some kinds of abuse
17692 into making connections to SMTP ports; in these circumstances, a number of
17693 non-SMTP command lines are sent first.
17697 .option smtp_ratelimit_hosts main "host list&!!" unset
17698 .cindex "SMTP" "rate limiting"
17699 .cindex "limit" "rate of message arrival"
17700 .cindex "RCPT" "rate limiting"
17701 Some sites find it helpful to be able to limit the rate at which certain hosts
17702 can send them messages, and the rate at which an individual message can specify
17705 Exim has two rate-limiting facilities. This section describes the older
17706 facility, which can limit rates within a single connection. The newer
17707 &%ratelimit%& ACL condition can limit rates across all connections. See section
17708 &<<SECTratelimiting>>& for details of the newer facility.
17710 When a host matches &%smtp_ratelimit_hosts%&, the values of
17711 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17712 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17713 respectively. Each option, if set, must contain a set of four comma-separated
17717 A threshold, before which there is no rate limiting.
17719 An initial time delay. Unlike other times in Exim, numbers with decimal
17720 fractional parts are allowed here.
17722 A factor by which to increase the delay each time.
17724 A maximum value for the delay. This should normally be less than 5 minutes,
17725 because after that time, the client is liable to timeout the SMTP command.
17728 For example, these settings have been used successfully at the site which
17729 first suggested this feature, for controlling mail from their customers:
17731 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17732 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17734 The first setting specifies delays that are applied to MAIL commands after
17735 two have been received over a single connection. The initial delay is 0.5
17736 seconds, increasing by a factor of 1.05 each time. The second setting applies
17737 delays to RCPT commands when more than four occur in a single message.
17740 .option smtp_ratelimit_mail main string unset
17741 See &%smtp_ratelimit_hosts%& above.
17744 .option smtp_ratelimit_rcpt main string unset
17745 See &%smtp_ratelimit_hosts%& above.
17748 .option smtp_receive_timeout main time&!! 5m
17749 .cindex "timeout" "for SMTP input"
17750 .cindex "SMTP" "input timeout"
17751 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17752 input, including batch SMTP. If a line of input (either an SMTP command or a
17753 data line) is not received within this time, the SMTP connection is dropped and
17754 the message is abandoned.
17755 A line is written to the log containing one of the following messages:
17757 SMTP command timeout on connection from...
17758 SMTP data timeout on connection from...
17760 The former means that Exim was expecting to read an SMTP command; the latter
17761 means that it was in the DATA phase, reading the contents of a message.
17763 If the first character of the option is a &"$"& the option is
17764 expanded before use and may depend on
17765 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17769 The value set by this option can be overridden by the
17770 &%-os%& command-line option. A setting of zero time disables the timeout, but
17771 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17772 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17773 timeout is controlled by &%receive_timeout%& and &%-or%&.
17776 .option smtp_reserve_hosts main "host list&!!" unset
17777 This option defines hosts for which SMTP connections are reserved; see
17778 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17781 .option smtp_return_error_details main boolean false
17782 .cindex "SMTP" "details policy failures"
17783 .cindex "policy control" "rejection, returning details"
17784 In the default state, Exim uses bland messages such as
17785 &"Administrative prohibition"& when it rejects SMTP commands for policy
17786 reasons. Many sysadmins like this because it gives away little information
17787 to spammers. However, some other sysadmins who are applying strict checking
17788 policies want to give out much fuller information about failures. Setting
17789 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17790 example, instead of &"Administrative prohibition"&, it might give:
17792 550-Rejected after DATA: '>' missing at end of address:
17793 550 failing address in "From" header is: <user@dom.ain
17797 .option smtputf8_advertise_hosts main "host list&!!" *
17798 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17799 .cindex "ESMTP extensions" SMTPUTF8
17800 When Exim is built with support for internationalised mail names,
17801 the availability thereof is advertised in
17802 response to EHLO only to those client hosts that match this option. See
17803 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17806 .option spamd_address main string "127.0.0.1 783"
17807 This option is available when Exim is compiled with the content-scanning
17808 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17809 See section &<<SECTscanspamass>>& for more details.
17813 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17814 This option is available when Exim is compiled with SPF support.
17815 See section &<<SECSPF>>& for more details.
17817 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
17818 This option is available when Exim is compiled with SPF support. It
17819 allows the customisation of the SMTP comment that the SPF library
17820 generates. You are strongly encouraged to link to your own explanative
17821 site. The template must not contain spaces. If you need spaces in the
17822 output, use the proper placeholder. If libspf2 can not parse the
17823 template, it uses a built-in default broken link. The following placeholders
17824 (along with Exim variables (but see below)) are allowed in the template:
17828 &*%{L}*&: Envelope sender's local part.
17830 &*%{S}*&: Envelope sender.
17832 &*%{O}*&: Envelope sender's domain.
17834 &*%{D}*&: Current(?) domain.
17836 &*%{I}*&: SMTP client Ip.
17838 &*%{C}*&: SMTP client pretty IP.
17840 &*%{T}*&: Epoch time (UTC).
17842 &*%{P}*&: SMTP client domain name.
17844 &*%{V}*&: IP version.
17846 &*%{H}*&: EHLO/HELO domain.
17848 &*%{R}*&: Receiving domain.
17850 The capitalized placeholders do proper URL encoding, if you use them
17851 lowercased, no encoding takes place. This list was compiled from the
17854 A note on using Exim variables: As
17855 currently the SPF library is initialized before the SMTP EHLO phase,
17856 the variables useful for expansion are quite limited.
17859 .option split_spool_directory main boolean false
17860 .cindex "multiple spool directories"
17861 .cindex "spool directory" "split"
17862 .cindex "directories, multiple"
17863 If this option is set, it causes Exim to split its input directory into 62
17864 subdirectories, each with a single alphanumeric character as its name. The
17865 sixth character of the message id is used to allocate messages to
17866 subdirectories; this is the least significant base-62 digit of the time of
17867 arrival of the message.
17869 Splitting up the spool in this way may provide better performance on systems
17870 where there are long mail queues, by reducing the number of files in any one
17871 directory. The msglog directory is also split up in a similar way to the input
17872 directory; however, if &%preserve_message_logs%& is set, all old msglog files
17873 are still placed in the single directory &_msglog.OLD_&.
17875 It is not necessary to take any special action for existing messages when
17876 changing &%split_spool_directory%&. Exim notices messages that are in the
17877 &"wrong"& place, and continues to process them. If the option is turned off
17878 after a period of being on, the subdirectories will eventually empty and be
17879 automatically deleted.
17881 When &%split_spool_directory%& is set, the behaviour of queue runner processes
17882 changes. Instead of creating a list of all messages in the queue, and then
17883 trying to deliver each one, in turn, it constructs a list of those in one
17884 sub-directory and tries to deliver them, before moving on to the next
17885 sub-directory. The sub-directories are processed in a random order. This
17886 spreads out the scanning of the input directories, and uses less memory. It is
17887 particularly beneficial when there are lots of messages in the queue. However,
17888 if &%queue_run_in_order%& is set, none of this new processing happens. The
17889 entire queue has to be scanned and sorted before any deliveries can start.
17892 .option spool_directory main string&!! "set at compile time"
17893 .cindex "spool directory" "path to"
17894 This defines the directory in which Exim keeps its spool, that is, the messages
17895 it is waiting to deliver. The default value is taken from the compile-time
17896 configuration setting, if there is one. If not, this option must be set. The
17897 string is expanded, so it can contain, for example, a reference to
17898 &$primary_hostname$&.
17900 If the spool directory name is fixed on your installation, it is recommended
17901 that you set it at build time rather than from this option, particularly if the
17902 log files are being written to the spool directory (see &%log_file_path%&).
17903 Otherwise log files cannot be used for errors that are detected early on, such
17904 as failures in the configuration file.
17906 By using this option to override the compiled-in path, it is possible to run
17907 tests of Exim without using the standard spool.
17909 .option spool_wireformat main boolean false
17910 .cindex "spool directory" "file formats"
17911 If this option is set, Exim may for some messages use an alternative format
17912 for data-files in the spool which matches the wire format.
17913 Doing this permits more efficient message reception and transmission.
17914 Currently it is only done for messages received using the ESMTP CHUNKING
17917 The following variables will not have useful values:
17919 $max_received_linelength
17924 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
17925 and any external programs which are passed a reference to a message data file
17926 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
17927 will need to be aware of the different formats potentially available.
17929 Using any of the ACL conditions noted will negate the reception benefit
17930 (as a Unix-mbox-format file is constructed for them).
17931 The transmission benefit is maintained.
17933 .option sqlite_lock_timeout main time 5s
17934 .cindex "sqlite lookup type" "lock timeout"
17935 This option controls the timeout that the &(sqlite)& lookup uses when trying to
17936 access an SQLite database. See section &<<SECTsqlite>>& for more details.
17938 .option strict_acl_vars main boolean false
17939 .cindex "&ACL;" "variables, handling unset"
17940 This option controls what happens if a syntactically valid but undefined ACL
17941 variable is referenced. If it is false (the default), an empty string
17942 is substituted; if it is true, an error is generated. See section
17943 &<<SECTaclvariables>>& for details of ACL variables.
17945 .option strip_excess_angle_brackets main boolean false
17946 .cindex "angle brackets, excess"
17947 If this option is set, redundant pairs of angle brackets round &"route-addr"&
17948 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
17949 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
17950 passed on to another MTA, the excess angle brackets are not passed on. If this
17951 option is not set, multiple pairs of angle brackets cause a syntax error.
17954 .option strip_trailing_dot main boolean false
17955 .cindex "trailing dot on domain"
17956 .cindex "dot" "trailing on domain"
17957 If this option is set, a trailing dot at the end of a domain in an address is
17958 ignored. If this is in the envelope and the message is passed on to another
17959 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
17960 domain causes a syntax error.
17961 However, addresses in header lines are checked only when an ACL requests header
17965 .option syslog_duplication main boolean true
17966 .cindex "syslog" "duplicate log lines; suppressing"
17967 When Exim is logging to syslog, it writes the log lines for its three
17968 separate logs at different syslog priorities so that they can in principle
17969 be separated on the logging hosts. Some installations do not require this
17970 separation, and in those cases, the duplication of certain log lines is a
17971 nuisance. If &%syslog_duplication%& is set false, only one copy of any
17972 particular log line is written to syslog. For lines that normally go to
17973 both the main log and the reject log, the reject log version (possibly
17974 containing message header lines) is written, at LOG_NOTICE priority.
17975 Lines that normally go to both the main and the panic log are written at
17976 the LOG_ALERT priority.
17979 .option syslog_facility main string unset
17980 .cindex "syslog" "facility; setting"
17981 This option sets the syslog &"facility"& name, used when Exim is logging to
17982 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
17983 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
17984 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
17985 details of Exim's logging.
17988 .option syslog_pid main boolean true
17989 .cindex "syslog" "pid"
17990 If &%syslog_pid%& is set false, the PID on Exim's log lines are
17991 omitted when these lines are sent to syslog. (Syslog normally prefixes
17992 the log lines with the PID of the logging process automatically.) You need
17993 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
17994 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
17998 .option syslog_processname main string &`exim`&
17999 .cindex "syslog" "process name; setting"
18000 This option sets the syslog &"ident"& name, used when Exim is logging to
18001 syslog. The value must be no longer than 32 characters. See chapter
18002 &<<CHAPlog>>& for details of Exim's logging.
18006 .option syslog_timestamp main boolean true
18007 .cindex "syslog" "timestamps"
18008 .cindex timestamps syslog
18009 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18010 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18011 details of Exim's logging.
18014 .option system_filter main string&!! unset
18015 .cindex "filter" "system filter"
18016 .cindex "system filter" "specifying"
18017 .cindex "Sieve filter" "not available for system filter"
18018 This option specifies an Exim filter file that is applied to all messages at
18019 the start of each delivery attempt, before any routing is done. System filters
18020 must be Exim filters; they cannot be Sieve filters. If the system filter
18021 generates any deliveries to files or pipes, or any new mail messages, the
18022 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18023 which transports are to be used. Details of this facility are given in chapter
18024 &<<CHAPsystemfilter>>&.
18025 A forced expansion failure results in no filter operation.
18028 .option system_filter_directory_transport main string&!! unset
18029 .vindex "&$address_file$&"
18030 This sets the name of the transport driver that is to be used when the
18031 &%save%& command in a system message filter specifies a path ending in &"/"&,
18032 implying delivery of each message into a separate file in some directory.
18033 During the delivery, the variable &$address_file$& contains the path name.
18036 .option system_filter_file_transport main string&!! unset
18037 .cindex "file" "transport for system filter"
18038 This sets the name of the transport driver that is to be used when the &%save%&
18039 command in a system message filter specifies a path not ending in &"/"&. During
18040 the delivery, the variable &$address_file$& contains the path name.
18042 .option system_filter_group main string unset
18043 .cindex "gid (group id)" "system filter"
18044 This option is used only when &%system_filter_user%& is also set. It sets the
18045 gid under which the system filter is run, overriding any gid that is associated
18046 with the user. The value may be numerical or symbolic.
18048 .option system_filter_pipe_transport main string&!! unset
18049 .cindex "&(pipe)& transport" "for system filter"
18050 .vindex "&$address_pipe$&"
18051 This specifies the transport driver that is to be used when a &%pipe%& command
18052 is used in a system filter. During the delivery, the variable &$address_pipe$&
18053 contains the pipe command.
18056 .option system_filter_reply_transport main string&!! unset
18057 .cindex "&(autoreply)& transport" "for system filter"
18058 This specifies the transport driver that is to be used when a &%mail%& command
18059 is used in a system filter.
18062 .option system_filter_user main string unset
18063 .cindex "uid (user id)" "system filter"
18064 If this option is set to root, the system filter is run in the main Exim
18065 delivery process, as root. Otherwise, the system filter runs in a separate
18066 process, as the given user, defaulting to the Exim run-time user.
18067 Unless the string consists entirely of digits, it
18068 is looked up in the password data. Failure to find the named user causes a
18069 configuration error. The gid is either taken from the password data, or
18070 specified by &%system_filter_group%&. When the uid is specified numerically,
18071 &%system_filter_group%& is required to be set.
18073 If the system filter generates any pipe, file, or reply deliveries, the uid
18074 under which the filter is run is used when transporting them, unless a
18075 transport option overrides.
18078 .option tcp_nodelay main boolean true
18079 .cindex "daemon" "TCP_NODELAY on sockets"
18080 .cindex "Nagle algorithm"
18081 .cindex "TCP_NODELAY on listening sockets"
18082 If this option is set false, it stops the Exim daemon setting the
18083 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18084 turns off the &"Nagle algorithm"&, which is a way of improving network
18085 performance in interactive (character-by-character) situations. Turning it off
18086 should improve Exim's performance a bit, so that is what happens by default.
18087 However, it appears that some broken clients cannot cope, and time out. Hence
18088 this option. It affects only those sockets that are set up for listening by the
18089 daemon. Sockets created by the smtp transport for delivering mail always set
18093 .option timeout_frozen_after main time 0s
18094 .cindex "frozen messages" "timing out"
18095 .cindex "timeout" "frozen messages"
18096 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18097 message of any kind that has been in the queue for longer than the given time
18098 is automatically cancelled at the next queue run. If the frozen message is a
18099 bounce message, it is just discarded; otherwise, a bounce is sent to the
18100 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18101 If you want to timeout frozen bounce messages earlier than other kinds of
18102 frozen message, see &%ignore_bounce_errors_after%&.
18104 &*Note:*& the default value of zero means no timeouts; with this setting,
18105 frozen messages remain in the queue forever (except for any frozen bounce
18106 messages that are released by &%ignore_bounce_errors_after%&).
18109 .option timezone main string unset
18110 .cindex "timezone, setting"
18111 .cindex "environment" "values from"
18112 The value of &%timezone%& is used to set the environment variable TZ while
18113 running Exim (if it is different on entry). This ensures that all timestamps
18114 created by Exim are in the required timezone. If you want all your timestamps
18115 to be in UTC (aka GMT) you should set
18119 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18120 or, if that is not set, from the value of the TZ environment variable when Exim
18121 is built. If &%timezone%& is set to the empty string, either at build or run
18122 time, any existing TZ variable is removed from the environment when Exim
18123 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18124 unfortunately not all, operating systems.
18127 .option tls_advertise_hosts main "host list&!!" *
18128 .cindex "TLS" "advertising"
18129 .cindex "encryption" "on SMTP connection"
18130 .cindex "SMTP" "encrypted connection"
18131 .cindex "ESMTP extensions" STARTTLS
18132 When Exim is built with support for TLS encrypted connections, the availability
18133 of the STARTTLS command to set up an encrypted session is advertised in
18134 response to EHLO only to those client hosts that match this option. See
18135 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18136 Note that the default value requires that a certificate be supplied
18137 using the &%tls_certificate%& option. If TLS support for incoming connections
18138 is not required the &%tls_advertise_hosts%& option should be set empty.
18141 .option tls_certificate main string list&!! unset
18142 .cindex "TLS" "server certificate; location of"
18143 .cindex "certificate" "server, location of"
18144 The value of this option is expanded, and must then be a list of absolute paths to
18145 files which contain the server's certificates (in PEM format).
18146 Commonly only one file is needed.
18147 The server's private key is also
18148 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18149 &<<CHAPTLS>>& for further details.
18151 &*Note*&: The certificates defined by this option are used only when Exim is
18152 receiving incoming messages as a server. If you want to supply certificates for
18153 use when sending messages as a client, you must set the &%tls_certificate%&
18154 option in the relevant &(smtp)& transport.
18156 &*Note*&: If you use filenames based on IP addresses, change the list
18157 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18159 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18160 when a list of more than one
18161 file is used, the &$tls_in_ourcert$& variable is unreliable.
18162 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18164 .cindex SNI "selecting server certificate based on"
18165 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18166 if the OpenSSL build supports TLS extensions and the TLS client sends the
18167 Server Name Indication extension, then this option and others documented in
18168 &<<SECTtlssni>>& will be re-expanded.
18170 If this option is unset or empty a fresh self-signed certificate will be
18171 generated for every connection.
18173 .option tls_crl main string&!! unset
18174 .cindex "TLS" "server certificate revocation list"
18175 .cindex "certificate" "revocation list for server"
18176 This option specifies a certificate revocation list. The expanded value must
18177 be the name of a file that contains CRLs in PEM format.
18179 Under OpenSSL the option can specify a directory with CRL files.
18181 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18182 for each signing element of the certificate chain (i.e. all but the leaf).
18183 For the file variant this can be multiple PEM blocks in the one file.
18185 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18188 .option tls_dh_max_bits main integer 2236
18189 .cindex "TLS" "D-H bit count"
18190 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18191 the chosen TLS library. That value might prove to be too high for
18192 interoperability. This option provides a maximum clamp on the value
18193 suggested, trading off security for interoperability.
18195 The value must be at least 1024.
18197 The value 2236 was chosen because, at time of adding the option, it was the
18198 hard-coded maximum value supported by the NSS cryptographic library, as used
18199 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18201 If you prefer more security and are willing to break some clients, raise this
18204 Note that the value passed to GnuTLS for *generating* a new prime may be a
18205 little less than this figure, because GnuTLS is inexact and may produce a
18206 larger prime than requested.
18209 .option tls_dhparam main string&!! unset
18210 .cindex "TLS" "D-H parameters for server"
18211 The value of this option is expanded and indicates the source of DH parameters
18212 to be used by Exim.
18214 This option is ignored for GnuTLS version 3.6.0 and later.
18215 The library manages parameter negotiation internally.
18217 &*Note: The Exim Maintainers strongly recommend,
18218 for other TLS library versions,
18219 using a filename with site-generated
18220 local DH parameters*&, which has been supported across all versions of Exim. The
18221 other specific constants available are a fallback so that even when
18222 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18224 If &%tls_dhparam%& is a filename starting with a &`/`&,
18225 then it names a file from which DH
18226 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18227 PKCS#3 representation of the DH prime. If the file does not exist, for
18228 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18229 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18230 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18231 and treated as though the &%tls_dhparam%& were set to "none".
18233 If this option expands to the string "none", then no DH parameters will be
18236 If this option expands to the string "historic" and Exim is using GnuTLS, then
18237 Exim will attempt to load a file from inside the spool directory. If the file
18238 does not exist, Exim will attempt to create it.
18239 See section &<<SECTgnutlsparam>>& for further details.
18241 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18242 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18244 In older versions of Exim the default was the 2048 bit prime described in section
18245 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18246 in IKE is assigned number 23.
18248 Otherwise, the option must expand to the name used by Exim for any of a number
18249 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18250 sources. As names, Exim uses a standard specified name, else "ike" followed by
18251 the number used by IKE, or "default" which corresponds to
18252 &`exim.dev.20160529.3`&.
18254 The available standard primes are:
18255 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18256 &`ike1`&, &`ike2`&, &`ike5`&,
18257 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18258 &`ike22`&, &`ike23`& and &`ike24`&.
18260 The available additional primes are:
18261 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18263 Some of these will be too small to be accepted by clients.
18264 Some may be too large to be accepted by clients.
18265 The open cryptographic community has suspicions about the integrity of some
18266 of the later IKE values, which led into RFC7919 providing new fixed constants
18267 (the "ffdhe" identifiers).
18269 At this point, all of the "ike" values should be considered obsolete;
18270 they're still in Exim to avoid breaking unusual configurations, but are
18271 candidates for removal the next time we have backwards-incompatible changes.
18273 The TLS protocol does not negotiate an acceptable size for this; clients tend
18274 to hard-drop connections if what is offered by the server is unacceptable,
18275 whether too large or too small, and there's no provision for the client to
18276 tell the server what these constraints are. Thus, as a server operator, you
18277 need to make an educated guess as to what is most likely to work for your
18280 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18281 is most likely to maximise interoperability. The upper bound comes from
18282 applications using the Mozilla Network Security Services (NSS) library, which
18283 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18284 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18285 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18286 acceptable bound from 1024 to 2048.
18289 .option tls_eccurve main string&!! &`auto`&
18290 .cindex TLS "EC cryptography"
18291 This option selects a EC curve for use by Exim when used with OpenSSL.
18292 It has no effect when Exim is used with GnuTLS.
18294 After expansion it must contain a valid EC curve parameter, such as
18295 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18296 for valid selections.
18298 For OpenSSL versions before (and not including) 1.0.2, the string
18299 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18300 &`auto`& tells the library to choose.
18302 If the option expands to an empty string, no EC curves will be enabled.
18305 .option tls_ocsp_file main string&!! unset
18306 .cindex TLS "certificate status"
18307 .cindex TLS "OCSP proof file"
18309 must if set expand to the absolute path to a file which contains a current
18310 status proof for the server's certificate, as obtained from the
18311 Certificate Authority.
18313 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18314 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18316 For OpenSSL 1.1.0 or later, and
18317 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18318 of files, to match a list given for the &%tls_certificate%& option.
18319 The ordering of the two lists must match.
18320 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18322 The file(s) should be in DER format,
18323 except for GnuTLS 3.6.3 or later
18325 when an optional filetype prefix can be used.
18326 The prefix must be one of "DER" or "PEM", followed by
18327 a single space. If one is used it sets the format for subsequent
18328 files in the list; the initial format is DER.
18329 If multiple proofs are wanted, for multiple chain elements
18330 (this only works under TLS1.3)
18331 they must be coded as a combined OCSP response.
18333 Although GnuTLS will accept PEM files with multiple separate
18334 PEM blobs (ie. separate OCSP responses), it sends them in the
18335 TLS Certificate record interleaved with the certificates of the chain;
18336 although a GnuTLS client is happy with that, an OpenSSL client is not.
18338 .option tls_on_connect_ports main "string list" unset
18341 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18342 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18343 set up without waiting for the client to issue a STARTTLS command. For
18344 further details, see section &<<SECTsupobssmt>>&.
18348 .option tls_privatekey main string list&!! unset
18349 .cindex "TLS" "server private key; location of"
18350 The value of this option is expanded, and must then be a list of absolute paths to
18351 files which contains the server's private keys.
18352 If this option is unset, or if
18353 the expansion is forced to fail, or the result is an empty string, the private
18354 key is assumed to be in the same file as the server's certificates. See chapter
18355 &<<CHAPTLS>>& for further details.
18357 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18360 .option tls_remember_esmtp main boolean false
18361 .cindex "TLS" "esmtp state; remembering"
18362 .cindex "TLS" "broken clients"
18363 If this option is set true, Exim violates the RFCs by remembering that it is in
18364 &"esmtp"& state after successfully negotiating a TLS session. This provides
18365 support for broken clients that fail to send a new EHLO after starting a
18369 .option tls_require_ciphers main string&!! unset
18370 .cindex "TLS" "requiring specific ciphers"
18371 .cindex "cipher" "requiring specific"
18372 This option controls which ciphers can be used for incoming TLS connections.
18373 The &(smtp)& transport has an option of the same name for controlling outgoing
18374 connections. This option is expanded for each connection, so can be varied for
18375 different clients if required. The value of this option must be a list of
18376 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18377 in somewhat different ways. If GnuTLS is being used, the client controls the
18378 preference order of the available ciphers. Details are given in sections
18379 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18383 .option tls_resumption_hosts main "host list&!!" unset
18384 .cindex TLS resumption
18385 This option controls which connections to offer the TLS resumption feature.
18386 See &<<SECTresumption>>& for details.
18390 .option tls_try_verify_hosts main "host list&!!" unset
18391 .cindex "TLS" "client certificate verification"
18392 .cindex "certificate" "verification of client"
18393 See &%tls_verify_hosts%& below.
18396 .option tls_verify_certificates main string&!! system
18397 .cindex "TLS" "client certificate verification"
18398 .cindex "certificate" "verification of client"
18399 The value of this option is expanded, and must then be either the
18401 or the absolute path to
18402 a file or directory containing permitted certificates for clients that
18403 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18405 The "system" value for the option will use a
18406 system default location compiled into the SSL library.
18407 This is not available for GnuTLS versions preceding 3.0.20,
18408 and will be taken as empty; an explicit location
18411 The use of a directory for the option value is not available for GnuTLS versions
18412 preceding 3.3.6 and a single file must be used.
18414 With OpenSSL the certificates specified
18416 either by file or directory
18417 are added to those given by the system default location.
18419 These certificates should be for the certificate authorities trusted, rather
18420 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18421 the value is a file then the certificates are sent by Exim as a server to
18422 connecting clients, defining the list of accepted certificate authorities.
18423 Thus the values defined should be considered public data. To avoid this,
18424 use the explicit directory version.
18426 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18428 A forced expansion failure or setting to an empty string is equivalent to
18432 .option tls_verify_hosts main "host list&!!" unset
18433 .cindex "TLS" "client certificate verification"
18434 .cindex "certificate" "verification of client"
18435 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18436 certificates from clients. The expected certificates are defined by
18437 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18438 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18439 &%tls_verify_certificates%& is not set.
18441 Any client that matches &%tls_verify_hosts%& is constrained by
18442 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18443 present one of the listed certificates. If it does not, the connection is
18444 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18445 the host to use TLS. It can still send SMTP commands through unencrypted
18446 connections. Forcing a client to use TLS has to be done separately using an
18447 ACL to reject inappropriate commands when the connection is not encrypted.
18449 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18450 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18451 certificate and checks it against &%tls_verify_certificates%&, but does not
18452 abort the connection if there is no certificate or if it does not match. This
18453 state can be detected in an ACL, which makes it possible to implement policies
18454 such as &"accept for relay only if a verified certificate has been received,
18455 but accept for local delivery if encrypted, even without a verified
18458 Client hosts that match neither of these lists are not asked to present
18462 .option trusted_groups main "string list&!!" unset
18463 .cindex "trusted groups"
18464 .cindex "groups" "trusted"
18465 This option is expanded just once, at the start of Exim's processing. If this
18466 option is set, any process that is running in one of the listed groups, or
18467 which has one of them as a supplementary group, is trusted. The groups can be
18468 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18469 details of what trusted callers are permitted to do. If neither
18470 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18473 .option trusted_users main "string list&!!" unset
18474 .cindex "trusted users"
18475 .cindex "user" "trusted"
18476 This option is expanded just once, at the start of Exim's processing. If this
18477 option is set, any process that is running as one of the listed users is
18478 trusted. The users can be specified numerically or by name. See section
18479 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18480 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18481 Exim user are trusted.
18483 .option unknown_login main string&!! unset
18484 .cindex "uid (user id)" "unknown caller"
18485 .vindex "&$caller_uid$&"
18486 This is a specialized feature for use in unusual configurations. By default, if
18487 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18488 gives up. The &%unknown_login%& option can be used to set a login name to be
18489 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18490 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18491 is used for the user's real name (gecos field), unless this has been set by the
18494 .option unknown_username main string unset
18495 See &%unknown_login%&.
18497 .option untrusted_set_sender main "address list&!!" unset
18498 .cindex "trusted users"
18499 .cindex "sender" "setting by untrusted user"
18500 .cindex "untrusted user setting sender"
18501 .cindex "user" "untrusted setting sender"
18502 .cindex "envelope from"
18503 .cindex "envelope sender"
18504 When an untrusted user submits a message to Exim using the standard input, Exim
18505 normally creates an envelope sender address from the user's login and the
18506 default qualification domain. Data from the &%-f%& option (for setting envelope
18507 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18508 is used) is ignored.
18510 However, untrusted users are permitted to set an empty envelope sender address,
18511 to declare that a message should never generate any bounces. For example:
18513 exim -f '<>' user@domain.example
18515 .vindex "&$sender_ident$&"
18516 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18517 other envelope sender addresses in a controlled way. When it is set, untrusted
18518 users are allowed to set envelope sender addresses that match any of the
18519 patterns in the list. Like all address lists, the string is expanded. The
18520 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18521 users to setting senders that start with their login ids
18522 followed by a hyphen
18523 by a setting like this:
18525 untrusted_set_sender = ^$sender_ident-
18527 If you want to allow untrusted users to set envelope sender addresses without
18528 restriction, you can use
18530 untrusted_set_sender = *
18532 The &%untrusted_set_sender%& option applies to all forms of local input, but
18533 only to the setting of the envelope sender. It does not permit untrusted users
18534 to use the other options which trusted user can use to override message
18535 parameters. Furthermore, it does not stop Exim from removing an existing
18536 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18537 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18538 overriding these actions. The handling of the &'Sender:'& header is also
18539 described in section &<<SECTthesenhea>>&.
18541 The log line for a message's arrival shows the envelope sender following
18542 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18543 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18544 envelope sender address, the user's login is shown in parentheses after the
18548 .option uucp_from_pattern main string "see below"
18549 .cindex "&""From""& line"
18550 .cindex "UUCP" "&""From""& line"
18551 Some applications that pass messages to an MTA via a command line interface use
18552 an initial line starting with &"From&~"& to pass the envelope sender. In
18553 particular, this is used by UUCP software. Exim recognizes such a line by means
18554 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18555 matches, the sender address is constructed by expanding the contents of
18556 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18557 default pattern recognizes lines in the following two forms:
18559 From ph10 Fri Jan 5 12:35 GMT 1996
18560 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18562 The pattern can be seen by running
18564 exim -bP uucp_from_pattern
18566 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18567 year in the second case. The first word after &"From&~"& is matched in the
18568 regular expression by a parenthesized subpattern. The default value for
18569 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18570 (&"ph10"& in the example above) as the message's sender. See also
18571 &%ignore_fromline_hosts%&.
18574 .option uucp_from_sender main string&!! &`$1`&
18575 See &%uucp_from_pattern%& above.
18578 .option warn_message_file main string&!! unset
18579 .cindex "warning of delay" "customizing the message"
18580 .cindex "customizing" "warning message"
18581 This option defines a template file containing paragraphs of text to be used
18582 for constructing the warning message which is sent by Exim when a message has
18583 been in the queue for a specified amount of time, as specified by
18584 &%delay_warning%&. Details of the file's contents are given in chapter
18585 &<<CHAPemsgcust>>&.
18586 .cindex warn_message_file "tainted data"
18587 The option is expanded to give the file path, which must be
18588 absolute and untainted.
18589 See also &%bounce_message_file%&.
18592 .option write_rejectlog main boolean true
18593 .cindex "reject log" "disabling"
18594 If this option is set false, Exim no longer writes anything to the reject log.
18595 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18596 .ecindex IIDconfima
18597 .ecindex IIDmaiconf
18602 . ////////////////////////////////////////////////////////////////////////////
18603 . ////////////////////////////////////////////////////////////////////////////
18605 .chapter "Generic options for routers" "CHAProutergeneric"
18606 .scindex IIDgenoprou1 "options" "generic; for routers"
18607 .scindex IIDgenoprou2 "generic options" "router"
18608 This chapter describes the generic options that apply to all routers.
18609 Those that are preconditions are marked with ‡ in the &"use"& field.
18611 For a general description of how a router operates, see sections
18612 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18613 which the preconditions are tested. The order of expansion of the options that
18614 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18615 &%headers_remove%&, &%transport%&.
18619 .option address_data routers string&!! unset
18620 .cindex "router" "data attached to address"
18621 The string is expanded just before the router is run, that is, after all the
18622 precondition tests have succeeded. If the expansion is forced to fail, the
18623 router declines, the value of &%address_data%& remains unchanged, and the
18624 &%more%& option controls what happens next. Other expansion failures cause
18625 delivery of the address to be deferred.
18627 .vindex "&$address_data$&"
18628 When the expansion succeeds, the value is retained with the address, and can be
18629 accessed using the variable &$address_data$& in the current router, subsequent
18630 routers, and the eventual transport.
18632 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18633 that runs a user's filter file, the contents of &$address_data$& are accessible
18634 in the filter. This is not normally a problem, because such data is usually
18635 either not confidential or it &"belongs"& to the current user, but if you do
18636 put confidential data into &$address_data$& you need to remember this point.
18638 Even if the router declines or passes, the value of &$address_data$& remains
18639 with the address, though it can be changed by another &%address_data%& setting
18640 on a subsequent router. If a router generates child addresses, the value of
18641 &$address_data$& propagates to them. This also applies to the special kind of
18642 &"child"& that is generated by a router with the &%unseen%& option.
18644 The idea of &%address_data%& is that you can use it to look up a lot of data
18645 for the address once, and then pick out parts of the data later. For example,
18646 you could use a single LDAP lookup to return a string of the form
18648 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18650 In the transport you could pick out the mailbox by a setting such as
18652 file = ${extract{mailbox}{$address_data}}
18654 This makes the configuration file less messy, and also reduces the number of
18655 lookups (though Exim does cache lookups).
18657 See also the &%set%& option below.
18659 .vindex "&$sender_address_data$&"
18660 .vindex "&$address_data$&"
18661 The &%address_data%& facility is also useful as a means of passing information
18662 from one router to another, and from a router to a transport. In addition, if
18663 &$address_data$& is set by a router when verifying a recipient address from an
18664 ACL, it remains available for use in the rest of the ACL statement. After
18665 verifying a sender, the value is transferred to &$sender_address_data$&.
18669 .option address_test routers&!? boolean true
18671 .cindex "router" "skipping when address testing"
18672 If this option is set false, the router is skipped when routing is being tested
18673 by means of the &%-bt%& command line option. This can be a convenience when
18674 your first router sends messages to an external scanner, because it saves you
18675 having to set the &"already scanned"& indicator when testing real address
18680 .option cannot_route_message routers string&!! unset
18681 .cindex "router" "customizing &""cannot route""& message"
18682 .cindex "customizing" "&""cannot route""& message"
18683 This option specifies a text message that is used when an address cannot be
18684 routed because Exim has run out of routers. The default message is
18685 &"Unrouteable address"&. This option is useful only on routers that have
18686 &%more%& set false, or on the very last router in a configuration, because the
18687 value that is used is taken from the last router that is considered. This
18688 includes a router that is skipped because its preconditions are not met, as
18689 well as a router that declines. For example, using the default configuration,
18692 cannot_route_message = Remote domain not found in DNS
18694 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18697 cannot_route_message = Unknown local user
18699 on the final router that checks for local users. If string expansion fails for
18700 this option, the default message is used. Unless the expansion failure was
18701 explicitly forced, a message about the failure is written to the main and panic
18702 logs, in addition to the normal message about the routing failure.
18705 .option caseful_local_part routers boolean false
18706 .cindex "case of local parts"
18707 .cindex "router" "case of local parts"
18708 By default, routers handle the local parts of addresses in a case-insensitive
18709 manner, though the actual case is preserved for transmission with the message.
18710 If you want the case of letters to be significant in a router, you must set
18711 this option true. For individual router options that contain address or local
18712 part lists (for example, &%local_parts%&), case-sensitive matching can be
18713 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18716 .vindex "&$local_part$&"
18717 .vindex "&$original_local_part$&"
18718 .vindex "&$parent_local_part$&"
18719 The value of the &$local_part$& variable is forced to lower case while a
18720 router is running unless &%caseful_local_part%& is set. When a router assigns
18721 an address to a transport, the value of &$local_part$& when the transport runs
18722 is the same as it was in the router. Similarly, when a router generates child
18723 addresses by aliasing or forwarding, the values of &$original_local_part$&
18724 and &$parent_local_part$& are those that were used by the redirecting router.
18726 This option applies to the processing of an address by a router. When a
18727 recipient address is being processed in an ACL, there is a separate &%control%&
18728 modifier that can be used to specify case-sensitive processing within the ACL
18729 (see section &<<SECTcontrols>>&).
18733 .option check_local_user routers&!? boolean false
18734 .cindex "local user, checking in router"
18735 .cindex "router" "checking for local user"
18736 .cindex "&_/etc/passwd_&"
18738 When this option is true, Exim checks that the local part of the recipient
18739 address (with affixes removed if relevant) is the name of an account on the
18740 local system. The check is done by calling the &[getpwnam()]& function rather
18741 than trying to read &_/etc/passwd_& directly. This means that other methods of
18742 holding password data (such as NIS) are supported. If the local part is a local
18743 user, &$home$& is set from the password data, and can be tested in other
18744 preconditions that are evaluated after this one (the order of evaluation is
18745 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18746 overridden by &%router_home_directory%&. If the local part is not a local user,
18747 the router is skipped.
18749 If you want to check that the local part is either the name of a local user
18750 or matches something else, you cannot combine &%check_local_user%& with a
18751 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18752 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18753 setting to achieve this. For example:
18755 local_parts = passwd;$local_part : lsearch;/etc/other/users
18757 Note, however, that the side effects of &%check_local_user%& (such as setting
18758 up a home directory) do not occur when a &(passwd)& lookup is used in a
18759 &%local_parts%& (or any other) precondition.
18763 .option condition routers&!? string&!! unset
18764 .cindex "router" "customized precondition"
18765 This option specifies a general precondition test that has to succeed for the
18766 router to be called. The &%condition%& option is the last precondition to be
18767 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18768 result is a forced failure, or an empty string, or one of the strings &"0"& or
18769 &"no"& or &"false"& (checked without regard to the case of the letters), the
18770 router is skipped, and the address is offered to the next one.
18772 If the result is any other value, the router is run (as this is the last
18773 precondition to be evaluated, all the other preconditions must be true).
18775 This option is unusual in that multiple &%condition%& options may be present.
18776 All &%condition%& options must succeed.
18778 The &%condition%& option provides a means of applying custom conditions to the
18779 running of routers. Note that in the case of a simple conditional expansion,
18780 the default expansion values are exactly what is wanted. For example:
18782 condition = ${if >{$message_age}{600}}
18784 Because of the default behaviour of the string expansion, this is equivalent to
18786 condition = ${if >{$message_age}{600}{true}{}}
18789 A multiple condition example, which succeeds:
18791 condition = ${if >{$message_age}{600}}
18792 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18796 If the expansion fails (other than forced failure) delivery is deferred. Some
18797 of the other precondition options are common special cases that could in fact
18798 be specified using &%condition%&.
18800 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18801 are far older, and use one set of semantics. ACLs are newer and when
18802 they were created, the ACL &%condition%& process was given far stricter
18803 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18804 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18805 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18806 Router rules processing behavior.
18808 This is best illustrated in an example:
18810 # If used in an ACL condition will fail with a syntax error, but
18811 # in a router condition any extra characters are treated as a string
18813 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18816 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18819 In each example above, the &%if%& statement actually ends after
18820 &"{google.com}}"&. Since no true or false braces were defined, the
18821 default &%if%& behavior is to return a boolean true or a null answer
18822 (which evaluates to false). The rest of the line is then treated as a
18823 string. So the first example resulted in the boolean answer &"true"&
18824 with the string &" {yes} {no}}"& appended to it. The second example
18825 resulted in the null output (indicating false) with the string
18826 &" {yes} {no}}"& appended to it.
18828 In fact you can put excess forward braces in too. In the router
18829 &%condition%&, Exim's parser only looks for &"{"& symbols when they
18830 mean something, like after a &"$"& or when required as part of a
18831 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
18834 Thus, in a Router, the above expansion strings will both always evaluate
18835 true, as the result of expansion is a non-empty string which doesn't
18836 match an explicit false value. This can be tricky to debug. By
18837 contrast, in an ACL either of those strings will always result in an
18838 expansion error because the result doesn't look sufficiently boolean.
18841 .option debug_print routers string&!! unset
18842 .cindex "testing" "variables in drivers"
18843 If this option is set and debugging is enabled (see the &%-d%& command line
18844 option) or in address-testing mode (see the &%-bt%& command line option),
18845 the string is expanded and included in the debugging output.
18846 If expansion of the string fails, the error message is written to the debugging
18847 output, and Exim carries on processing.
18848 This option is provided to help with checking out the values of variables and
18849 so on when debugging router configurations. For example, if a &%condition%&
18850 option appears not to be working, &%debug_print%& can be used to output the
18851 variables it references. The output happens after checks for &%domains%&,
18852 &%local_parts%&, and &%check_local_user%& but before any other preconditions
18853 are tested. A newline is added to the text if it does not end with one.
18854 The variable &$router_name$& contains the name of the router.
18858 .option disable_logging routers boolean false
18859 If this option is set true, nothing is logged for any routing errors
18860 or for any deliveries caused by this router. You should not set this option
18861 unless you really, really know what you are doing. See also the generic
18862 transport option of the same name.
18864 .option dnssec_request_domains routers "domain list&!!" *
18865 .cindex "MX record" "security"
18866 .cindex "DNSSEC" "MX lookup"
18867 .cindex "security" "MX lookup"
18868 .cindex "DNS" "DNSSEC"
18869 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
18870 the dnssec request bit set.
18871 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18873 .option dnssec_require_domains routers "domain list&!!" unset
18874 .cindex "MX record" "security"
18875 .cindex "DNSSEC" "MX lookup"
18876 .cindex "security" "MX lookup"
18877 .cindex "DNS" "DNSSEC"
18878 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
18879 the dnssec request bit set. Any returns not having the Authenticated Data bit
18880 (AD bit) set will be ignored and logged as a host-lookup failure.
18881 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18884 .option domains routers&!? "domain list&!!" unset
18885 .cindex "router" "restricting to specific domains"
18886 .vindex "&$domain_data$&"
18887 If this option is set, the router is skipped unless the current domain matches
18888 the list. If the match is achieved by means of a file lookup, the data that the
18889 lookup returned for the domain is placed in &$domain_data$& for use in string
18890 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
18891 a list of the order in which preconditions are evaluated.
18895 .option driver routers string unset
18896 This option must always be set. It specifies which of the available routers is
18900 .option dsn_lasthop routers boolean false
18901 .cindex "DSN" "success"
18902 .cindex "Delivery Status Notification" "success"
18903 If this option is set true, and extended DSN (RFC3461) processing is in effect,
18904 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
18905 instead send a success DSN as if the next hop does not support DSN.
18906 Not effective on redirect routers.
18910 .option errors_to routers string&!! unset
18911 .cindex "envelope from"
18912 .cindex "envelope sender"
18913 .cindex "router" "changing address for errors"
18914 If a router successfully handles an address, it may assign the address to a
18915 transport for delivery or it may generate child addresses. In both cases, if
18916 there is a delivery problem during later processing, the resulting bounce
18917 message is sent to the address that results from expanding this string,
18918 provided that the address verifies successfully. The &%errors_to%& option is
18919 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
18921 The &%errors_to%& setting associated with an address can be overridden if it
18922 subsequently passes through other routers that have their own &%errors_to%&
18923 settings, or if the message is delivered by a transport with a &%return_path%&
18926 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
18927 the expansion fails to verify, the errors address associated with the incoming
18928 address is used. At top level, this is the envelope sender. A non-forced
18929 expansion failure causes delivery to be deferred.
18931 If an address for which &%errors_to%& has been set ends up being delivered over
18932 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
18933 any bounces that are generated by other MTAs on the delivery route are also
18934 sent there. You can set &%errors_to%& to the empty string by either of these
18940 An expansion item that yields an empty string has the same effect. If you do
18941 this, a locally detected delivery error for addresses processed by this router
18942 no longer gives rise to a bounce message; the error is discarded. If the
18943 address is delivered to a remote host, the return path is set to &`<>`&, unless
18944 overridden by the &%return_path%& option on the transport.
18946 .vindex "&$address_data$&"
18947 If for some reason you want to discard local errors, but use a non-empty
18948 MAIL command for remote delivery, you can preserve the original return
18949 path in &$address_data$& in the router, and reinstate it in the transport by
18950 setting &%return_path%&.
18952 The most common use of &%errors_to%& is to direct mailing list bounces to the
18953 manager of the list, as described in section &<<SECTmailinglists>>&, or to
18954 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
18958 .option expn routers&!? boolean true
18959 .cindex "address" "testing"
18960 .cindex "testing" "addresses"
18961 .cindex "EXPN" "router skipping"
18962 .cindex "router" "skipping for EXPN"
18963 If this option is turned off, the router is skipped when testing an address
18964 as a result of processing an SMTP EXPN command. You might, for example,
18965 want to turn it off on a router for users' &_.forward_& files, while leaving it
18966 on for the system alias file.
18967 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18970 The use of the SMTP EXPN command is controlled by an ACL (see chapter
18971 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
18972 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
18976 .option fail_verify routers boolean false
18977 .cindex "router" "forcing verification failure"
18978 Setting this option has the effect of setting both &%fail_verify_sender%& and
18979 &%fail_verify_recipient%& to the same value.
18983 .option fail_verify_recipient routers boolean false
18984 If this option is true and an address is accepted by this router when
18985 verifying a recipient, verification fails.
18989 .option fail_verify_sender routers boolean false
18990 If this option is true and an address is accepted by this router when
18991 verifying a sender, verification fails.
18995 .option fallback_hosts routers "string list" unset
18996 .cindex "router" "fallback hosts"
18997 .cindex "fallback" "hosts specified on router"
18998 String expansion is not applied to this option. The argument must be a
18999 colon-separated list of host names or IP addresses. The list separator can be
19000 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19001 each name or address. In fact, the format of each item is exactly the same as
19002 defined for the list of hosts in a &(manualroute)& router (see section
19003 &<<SECTformatonehostitem>>&).
19005 If a router queues an address for a remote transport, this host list is
19006 associated with the address, and used instead of the transport's fallback host
19007 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19008 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19009 transport for further details.
19012 .option group routers string&!! "see below"
19013 .cindex "gid (group id)" "local delivery"
19014 .cindex "local transports" "uid and gid"
19015 .cindex "transport" "local"
19016 .cindex "router" "setting group"
19017 When a router queues an address for a transport, and the transport does not
19018 specify a group, the group given here is used when running the delivery
19020 The group may be specified numerically or by name. If expansion fails, the
19021 error is logged and delivery is deferred.
19022 The default is unset, unless &%check_local_user%& is set, when the default
19023 is taken from the password information. See also &%initgroups%& and &%user%&
19024 and the discussion in chapter &<<CHAPenvironment>>&.
19028 .option headers_add routers list&!! unset
19029 .cindex "header lines" "adding"
19030 .cindex "router" "adding header lines"
19031 This option specifies a list of text headers,
19032 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19033 that is associated with any addresses that are accepted by the router.
19034 Each item is separately expanded, at routing time. However, this
19035 option has no effect when an address is just being verified. The way in which
19036 the text is used to add header lines at transport time is described in section
19037 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19038 message is in the process of being transported. This means that references to
19039 header lines in string expansions in the transport's configuration do not
19040 &"see"& the added header lines.
19042 The &%headers_add%& option is expanded after &%errors_to%&, but before
19043 &%headers_remove%& and &%transport%&. If an item is empty, or if
19044 an item expansion is forced to fail, the item has no effect. Other expansion
19045 failures are treated as configuration errors.
19047 Unlike most options, &%headers_add%& can be specified multiple times
19048 for a router; all listed headers are added.
19050 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19051 router that has the &%one_time%& option set.
19053 .cindex "duplicate addresses"
19054 .oindex "&%unseen%&"
19055 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19056 additions are deleted when the address is passed on to subsequent routers.
19057 For a &%redirect%& router, if a generated address is the same as the incoming
19058 address, this can lead to duplicate addresses with different header
19059 modifications. Exim does not do duplicate deliveries (except, in certain
19060 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19061 which of the duplicates is discarded, so this ambiguous situation should be
19062 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19066 .option headers_remove routers list&!! unset
19067 .cindex "header lines" "removing"
19068 .cindex "router" "removing header lines"
19069 This option specifies a list of text headers,
19070 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19071 that is associated with any addresses that are accepted by the router.
19072 However, the option has no effect when an address is just being verified.
19073 Each list item is separately expanded, at transport time.
19074 If an item ends in *, it will match any header with the given prefix.
19076 the text is used to remove header lines at transport time is described in
19077 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19078 the message is in the process of being transported. This means that references
19079 to header lines in string expansions in the transport's configuration still
19080 &"see"& the original header lines.
19082 The &%headers_remove%& option is handled after &%errors_to%& and
19083 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19084 the item has no effect. Other expansion failures are treated as configuration
19087 Unlike most options, &%headers_remove%& can be specified multiple times
19088 for a router; all listed headers are removed.
19090 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19091 router that has the &%one_time%& option set.
19093 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19094 removal requests are deleted when the address is passed on to subsequent
19095 routers, and this can lead to problems with duplicates -- see the similar
19096 warning for &%headers_add%& above.
19098 &*Warning 3*&: Because of the separate expansion of the list items,
19099 items that contain a list separator must have it doubled.
19100 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19104 .option ignore_target_hosts routers "host list&!!" unset
19105 .cindex "IP address" "discarding"
19106 .cindex "router" "discarding IP addresses"
19107 Although this option is a host list, it should normally contain IP address
19108 entries rather than names. If any host that is looked up by the router has an
19109 IP address that matches an item in this list, Exim behaves as if that IP
19110 address did not exist. This option allows you to cope with rogue DNS entries
19113 remote.domain.example. A 127.0.0.1
19117 ignore_target_hosts = 127.0.0.1
19119 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19120 discarded in this way, the router declines. In a conventional configuration, an
19121 attempt to mail to such a domain would normally provoke the &"unrouteable
19122 domain"& error, and an attempt to verify an address in the domain would fail.
19123 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19124 router declines if presented with one of the listed addresses.
19126 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19127 means of the first or the second of the following settings, respectively:
19129 ignore_target_hosts = 0.0.0.0/0
19130 ignore_target_hosts = <; 0::0/0
19132 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19133 in the second line matches all IPv6 addresses.
19135 This option may also be useful for ignoring link-local and site-local IPv6
19136 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19137 is expanded before use as a list, it is possible to make it dependent on the
19138 domain that is being routed.
19140 .vindex "&$host_address$&"
19141 During its expansion, &$host_address$& is set to the IP address that is being
19144 .option initgroups routers boolean false
19145 .cindex "additional groups"
19146 .cindex "groups" "additional"
19147 .cindex "local transports" "uid and gid"
19148 .cindex "transport" "local"
19149 If the router queues an address for a transport, and this option is true, and
19150 the uid supplied by the router is not overridden by the transport, the
19151 &[initgroups()]& function is called when running the transport to ensure that
19152 any additional groups associated with the uid are set up. See also &%group%&
19153 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19157 .option local_part_prefix routers&!? "string list" unset
19158 .cindex affix "router precondition"
19159 .cindex "router" "prefix for local part"
19160 .cindex "prefix" "for local part, used in router"
19161 If this option is set, the router is skipped unless the local part starts with
19162 one of the given strings, or &%local_part_prefix_optional%& is true. See
19163 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19166 The list is scanned from left to right, and the first prefix that matches is
19167 used. A limited form of wildcard is available; if the prefix begins with an
19168 asterisk, it matches the longest possible sequence of arbitrary characters at
19169 the start of the local part. An asterisk should therefore always be followed by
19170 some character that does not occur in normal local parts.
19171 .cindex "multiple mailboxes"
19172 .cindex "mailbox" "multiple"
19173 Wildcarding can be used to set up multiple user mailboxes, as described in
19174 section &<<SECTmulbox>>&.
19176 .vindex "&$local_part$&"
19177 .vindex "&$local_part_prefix$&"
19178 During the testing of the &%local_parts%& option, and while the router is
19179 running, the prefix is removed from the local part, and is available in the
19180 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19181 the router accepts the address, this remains true during subsequent delivery by
19182 a transport. In particular, the local part that is transmitted in the RCPT
19183 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19184 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19185 the relevant transport.
19187 .vindex &$local_part_prefix_v$&
19188 If wildcarding (above) was used then the part of the prefix matching the
19189 wildcard is available in &$local_part_prefix_v$&.
19191 When an address is being verified, &%local_part_prefix%& affects only the
19192 behaviour of the router. If the callout feature of verification is in use, this
19193 means that the full address, including the prefix, will be used during the
19196 The prefix facility is commonly used to handle local parts of the form
19197 &%owner-something%&. Another common use is to support local parts of the form
19198 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19199 to tell a user their forwarding is broken &-- by placing a router like this one
19200 immediately before the router that handles &_.forward_& files:
19204 local_part_prefix = real-
19206 transport = local_delivery
19208 For security, it would probably be a good idea to restrict the use of this
19209 router to locally-generated messages, using a condition such as this:
19211 condition = ${if match {$sender_host_address}\
19212 {\N^(|127\.0\.0\.1)$\N}}
19215 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19216 both conditions must be met if not optional. Care must be taken if wildcards
19217 are used in both a prefix and a suffix on the same router. Different
19218 separator characters must be used to avoid ambiguity.
19221 .option local_part_prefix_optional routers boolean false
19222 See &%local_part_prefix%& above.
19226 .option local_part_suffix routers&!? "string list" unset
19227 .cindex "router" "suffix for local part"
19228 .cindex "suffix for local part" "used in router"
19229 This option operates in the same way as &%local_part_prefix%&, except that the
19230 local part must end (rather than start) with the given string, the
19231 &%local_part_suffix_optional%& option determines whether the suffix is
19232 mandatory, and the wildcard * character, if present, must be the last
19233 character of the suffix. This option facility is commonly used to handle local
19234 parts of the form &%something-request%& and multiple user mailboxes of the form
19238 .option local_part_suffix_optional routers boolean false
19239 See &%local_part_suffix%& above.
19243 .option local_parts routers&!? "local part list&!!" unset
19244 .cindex "router" "restricting to specific local parts"
19245 .cindex "local part" "checking in router"
19246 The router is run only if the local part of the address matches the list.
19247 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19249 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19250 string is expanded, it is possible to make it depend on the domain, for
19253 local_parts = dbm;/usr/local/specials/$domain
19255 .vindex "&$local_part_data$&"
19256 If the match is achieved by a lookup, the data that the lookup returned
19257 for the local part is placed in the variable &$local_part_data$& for use in
19258 expansions of the router's private options. You might use this option, for
19259 example, if you have a large number of local virtual domains, and you want to
19260 send all postmaster mail to the same place without having to set up an alias in
19261 each virtual domain:
19265 local_parts = postmaster
19266 data = postmaster@real.domain.example
19270 .option log_as_local routers boolean "see below"
19271 .cindex "log" "delivery line"
19272 .cindex "delivery" "log line format"
19273 Exim has two logging styles for delivery, the idea being to make local
19274 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19275 recipient address is given just as the local part, without a domain. The use of
19276 this style is controlled by this option. It defaults to true for the &(accept)&
19277 router, and false for all the others. This option applies only when a
19278 router assigns an address to a transport. It has no effect on routers that
19279 redirect addresses.
19283 .option more routers boolean&!! true
19284 The result of string expansion for this option must be a valid boolean value,
19285 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19286 result causes an error, and delivery is deferred. If the expansion is forced to
19287 fail, the default value for the option (true) is used. Other failures cause
19288 delivery to be deferred.
19290 If this option is set false, and the router declines to handle the address, no
19291 further routers are tried, routing fails, and the address is bounced.
19293 However, if the router explicitly passes an address to the following router by
19294 means of the setting
19298 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19299 does not affect the behaviour if one of the precondition tests fails. In that
19300 case, the address is always passed to the next router.
19302 Note that &%address_data%& is not considered to be a precondition. If its
19303 expansion is forced to fail, the router declines, and the value of &%more%&
19304 controls what happens next.
19307 .option pass_on_timeout routers boolean false
19308 .cindex "timeout" "of router"
19309 .cindex "router" "timeout"
19310 If a router times out during a host lookup, it normally causes deferral of the
19311 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19312 router, overriding &%no_more%&. This may be helpful for systems that are
19313 intermittently connected to the Internet, or those that want to pass to a smart
19314 host any messages that cannot immediately be delivered.
19316 There are occasional other temporary errors that can occur while doing DNS
19317 lookups. They are treated in the same way as a timeout, and this option
19318 applies to all of them.
19322 .option pass_router routers string unset
19323 .cindex "router" "go to after &""pass""&"
19324 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19325 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19326 routing to continue, and overriding a false setting of &%more%&. When one of
19327 these routers returns &"pass"&, the address is normally handed on to the next
19328 router in sequence. This can be changed by setting &%pass_router%& to the name
19329 of another router. However (unlike &%redirect_router%&) the named router must
19330 be below the current router, to avoid loops. Note that this option applies only
19331 to the special case of &"pass"&. It does not apply when a router returns
19332 &"decline"& because it cannot handle an address.
19336 .option redirect_router routers string unset
19337 .cindex "router" "start at after redirection"
19338 Sometimes an administrator knows that it is pointless to reprocess addresses
19339 generated from alias or forward files with the same router again. For
19340 example, if an alias file translates real names into login ids there is no
19341 point searching the alias file a second time, especially if it is a large file.
19343 The &%redirect_router%& option can be set to the name of any router instance.
19344 It causes the routing of any generated addresses to start at the named router
19345 instead of at the first router. This option has no effect if the router in
19346 which it is set does not generate new addresses.
19350 .option require_files routers&!? "string list&!!" unset
19351 .cindex "file" "requiring for router"
19352 .cindex "router" "requiring file existence"
19353 This option provides a general mechanism for predicating the running of a
19354 router on the existence or non-existence of certain files or directories.
19355 Before running a router, as one of its precondition tests, Exim works its way
19356 through the &%require_files%& list, expanding each item separately.
19358 Because the list is split before expansion, any colons in expansion items must
19359 be doubled, or the facility for using a different list separator must be used
19360 (&<<SECTlistsepchange>>&).
19361 If any expansion is forced to fail, the item is ignored. Other expansion
19362 failures cause routing of the address to be deferred.
19364 If any expanded string is empty, it is ignored. Otherwise, except as described
19365 below, each string must be a fully qualified file path, optionally preceded by
19366 &"!"&. The paths are passed to the &[stat()]& function to test for the
19367 existence of the files or directories. The router is skipped if any paths not
19368 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19371 If &[stat()]& cannot determine whether a file exists or not, delivery of
19372 the message is deferred. This can happen when NFS-mounted filesystems are
19375 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19376 options, so you cannot use it to check for the existence of a file in which to
19377 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19378 full list of the order in which preconditions are evaluated.) However, as
19379 these options are all expanded, you can use the &%exists%& expansion condition
19380 to make such tests. The &%require_files%& option is intended for checking files
19381 that the router may be going to use internally, or which are needed by a
19382 transport (e.g., &_.procmailrc_&).
19384 During delivery, the &[stat()]& function is run as root, but there is a
19385 facility for some checking of the accessibility of a file by another user.
19386 This is not a proper permissions check, but just a &"rough"& check that
19387 operates as follows:
19389 If an item in a &%require_files%& list does not contain any forward slash
19390 characters, it is taken to be the user (and optional group, separated by a
19391 comma) to be checked for subsequent files in the list. If no group is specified
19392 but the user is specified symbolically, the gid associated with the uid is
19395 require_files = mail:/some/file
19396 require_files = $local_part_data:$home/.procmailrc
19398 If a user or group name in a &%require_files%& list does not exist, the
19399 &%require_files%& condition fails.
19401 Exim performs the check by scanning along the components of the file path, and
19402 checking the access for the given uid and gid. It checks for &"x"& access on
19403 directories, and &"r"& access on the final file. Note that this means that file
19404 access control lists, if the operating system has them, are ignored.
19406 &*Warning 1*&: When the router is being run to verify addresses for an
19407 incoming SMTP message, Exim is not running as root, but under its own uid. This
19408 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19409 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19410 user is not permitted to read one of the directories on the file's path.
19412 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19413 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19414 without root access. In this case, if a check for access by a particular user
19415 is requested, Exim creates a subprocess that runs as that user, and tries the
19416 check again in that process.
19418 The default action for handling an unresolved EACCES is to consider it to
19419 be caused by a configuration error, and routing is deferred because the
19420 existence or non-existence of the file cannot be determined. However, in some
19421 circumstances it may be desirable to treat this condition as if the file did
19422 not exist. If the filename (or the exclamation mark that precedes the filename
19423 for non-existence) is preceded by a plus sign, the EACCES error is treated
19424 as if the file did not exist. For example:
19426 require_files = +/some/file
19428 If the router is not an essential part of verification (for example, it
19429 handles users' &_.forward_& files), another solution is to set the &%verify%&
19430 option false so that the router is skipped when verifying.
19434 .option retry_use_local_part routers boolean "see below"
19435 .cindex "hints database" "retry keys"
19436 .cindex "local part" "in retry keys"
19437 When a delivery suffers a temporary routing failure, a retry record is created
19438 in Exim's hints database. For addresses whose routing depends only on the
19439 domain, the key for the retry record should not involve the local part, but for
19440 other addresses, both the domain and the local part should be included.
19441 Usually, remote routing is of the former kind, and local routing is of the
19444 This option controls whether the local part is used to form the key for retry
19445 hints for addresses that suffer temporary errors while being handled by this
19446 router. The default value is true for any router that has any of
19447 &%check_local_user%&,
19450 &%local_part_prefix%&,
19451 &%local_part_suffix%&,
19454 set, and false otherwise. Note that this option does not apply to hints keys
19455 for transport delays; they are controlled by a generic transport option of the
19458 Failing to set this option when it is needed
19459 (because a remote router handles only some of the local-parts for a domain)
19460 can result in incorrect error messages being generated.
19462 The setting of &%retry_use_local_part%& applies only to the router on which it
19463 appears. If the router generates child addresses, they are routed
19464 independently; this setting does not become attached to them.
19468 .option router_home_directory routers string&!! unset
19469 .cindex "router" "home directory for"
19470 .cindex "home directory" "for router"
19472 This option sets a home directory for use while the router is running. (Compare
19473 &%transport_home_directory%&, which sets a home directory for later
19474 transporting.) In particular, if used on a &(redirect)& router, this option
19475 sets a value for &$home$& while a filter is running. The value is expanded;
19476 forced expansion failure causes the option to be ignored &-- other failures
19477 cause the router to defer.
19479 Expansion of &%router_home_directory%& happens immediately after the
19480 &%check_local_user%& test (if configured), before any further expansions take
19482 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19484 While the router is running, &%router_home_directory%& overrides the value of
19485 &$home$& that came from &%check_local_user%&.
19487 When a router accepts an address and assigns it to a local transport (including
19488 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19489 delivery), the home directory setting for the transport is taken from the first
19490 of these values that is set:
19493 The &%home_directory%& option on the transport;
19495 The &%transport_home_directory%& option on the router;
19497 The password data if &%check_local_user%& is set on the router;
19499 The &%router_home_directory%& option on the router.
19502 In other words, &%router_home_directory%& overrides the password data for the
19503 router, but not for the transport.
19507 .option self routers string freeze
19508 .cindex "MX record" "pointing to local host"
19509 .cindex "local host" "MX pointing to"
19510 This option applies to those routers that use a recipient address to find a
19511 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19512 and &(manualroute)& routers.
19513 Certain configurations of the &(queryprogram)& router can also specify a list
19515 Usually such routers are configured to send the message to a remote host via an
19516 &(smtp)& transport. The &%self%& option specifies what happens when the first
19517 host on the list turns out to be the local host.
19518 The way in which Exim checks for the local host is described in section
19519 &<<SECTreclocipadd>>&.
19521 Normally this situation indicates either an error in Exim's configuration (for
19522 example, the router should be configured not to process this domain), or an
19523 error in the DNS (for example, the MX should not point to this host). For this
19524 reason, the default action is to log the incident, defer the address, and
19525 freeze the message. The following alternatives are provided for use in special
19530 Delivery of the message is tried again later, but the message is not frozen.
19532 .vitem "&%reroute%&: <&'domain'&>"
19533 The domain is changed to the given domain, and the address is passed back to
19534 be reprocessed by the routers. No rewriting of headers takes place. This
19535 behaviour is essentially a redirection.
19537 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19538 The domain is changed to the given domain, and the address is passed back to be
19539 reprocessed by the routers. Any headers that contain the original domain are
19544 .vindex "&$self_hostname$&"
19545 The router passes the address to the next router, or to the router named in the
19546 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19547 subsequent routing and delivery, the variable &$self_hostname$& contains the
19548 name of the local host that the router encountered. This can be used to
19549 distinguish between different cases for hosts with multiple names. The
19555 ensures that only those addresses that routed to the local host are passed on.
19556 Without &%no_more%&, addresses that were declined for other reasons would also
19557 be passed to the next router.
19560 Delivery fails and an error report is generated.
19563 .cindex "local host" "sending to"
19564 The anomaly is ignored and the address is queued for the transport. This
19565 setting should be used with extreme caution. For an &(smtp)& transport, it
19566 makes sense only in cases where the program that is listening on the SMTP port
19567 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19568 different configuration file that handles the domain in another way.
19573 .option senders routers&!? "address list&!!" unset
19574 .cindex "router" "checking senders"
19575 If this option is set, the router is skipped unless the message's sender
19576 address matches something on the list.
19577 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19580 There are issues concerning verification when the running of routers is
19581 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19582 setting, it sets the sender to the null string. When using the &%-bt%& option
19583 to check a configuration file, it is necessary also to use the &%-f%& option to
19584 set an appropriate sender. For incoming mail, the sender is unset when
19585 verifying the sender, but is available when verifying any recipients. If the
19586 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19590 .option set routers "string list" unset
19591 .cindex router variables
19592 This option may be used multiple times on a router;
19593 because of this the list aspect is mostly irrelevant.
19594 The list separator is a semicolon but can be changed in the
19597 Each list-element given must be of the form &"name = value"&
19598 and the names used must start with the string &"r_"&.
19599 Values containing a list-separator should have them doubled.
19600 When a router runs, the strings are evaluated in order,
19601 to create variables which are added to the set associated with
19603 The variable is set with the expansion of the value.
19604 The variables can be used by the router options
19605 (not including any preconditions)
19606 and by the transport.
19607 Later definitions of a given named variable will override former ones.
19608 Variable use is via the usual &$r_...$& syntax.
19610 This is similar to the &%address_data%& option, except that
19611 many independent variables can be used, with choice of naming.
19614 .option translate_ip_address routers string&!! unset
19615 .cindex "IP address" "translating"
19616 .cindex "packet radio"
19617 .cindex "router" "IP address translation"
19618 There exist some rare networking situations (for example, packet radio) where
19619 it is helpful to be able to translate IP addresses generated by normal routing
19620 mechanisms into other IP addresses, thus performing a kind of manual IP
19621 routing. This should be done only if the normal IP routing of the TCP/IP stack
19622 is inadequate or broken. Because this is an extremely uncommon requirement, the
19623 code to support this option is not included in the Exim binary unless
19624 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19626 .vindex "&$host_address$&"
19627 The &%translate_ip_address%& string is expanded for every IP address generated
19628 by the router, with the generated address set in &$host_address$&. If the
19629 expansion is forced to fail, no action is taken.
19630 For any other expansion error, delivery of the message is deferred.
19631 If the result of the expansion is an IP address, that replaces the original
19632 address; otherwise the result is assumed to be a host name &-- this is looked
19633 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19634 produce one or more replacement IP addresses. For example, to subvert all IP
19635 addresses in some specific networks, this could be added to a router:
19637 translate_ip_address = \
19638 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19641 The file would contain lines like
19643 10.2.3.128/26 some.host
19644 10.8.4.34/26 10.44.8.15
19646 You should not make use of this facility unless you really understand what you
19651 .option transport routers string&!! unset
19652 This option specifies the transport to be used when a router accepts an address
19653 and sets it up for delivery. A transport is never needed if a router is used
19654 only for verification. The value of the option is expanded at routing time,
19655 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19656 and result must be the name of one of the configured transports. If it is not,
19657 delivery is deferred.
19659 The &%transport%& option is not used by the &(redirect)& router, but it does
19660 have some private options that set up transports for pipe and file deliveries
19661 (see chapter &<<CHAPredirect>>&).
19665 .option transport_current_directory routers string&!! unset
19666 .cindex "current directory for local transport"
19667 This option associates a current directory with any address that is routed
19668 to a local transport. This can happen either because a transport is
19669 explicitly configured for the router, or because it generates a delivery to a
19670 file or a pipe. During the delivery process (that is, at transport time), this
19671 option string is expanded and is set as the current directory, unless
19672 overridden by a setting on the transport.
19673 If the expansion fails for any reason, including forced failure, an error is
19674 logged, and delivery is deferred.
19675 See chapter &<<CHAPenvironment>>& for details of the local delivery
19681 .option transport_home_directory routers string&!! "see below"
19682 .cindex "home directory" "for local transport"
19683 This option associates a home directory with any address that is routed to a
19684 local transport. This can happen either because a transport is explicitly
19685 configured for the router, or because it generates a delivery to a file or a
19686 pipe. During the delivery process (that is, at transport time), the option
19687 string is expanded and is set as the home directory, unless overridden by a
19688 setting of &%home_directory%& on the transport.
19689 If the expansion fails for any reason, including forced failure, an error is
19690 logged, and delivery is deferred.
19692 If the transport does not specify a home directory, and
19693 &%transport_home_directory%& is not set for the router, the home directory for
19694 the transport is taken from the password data if &%check_local_user%& is set for
19695 the router. Otherwise it is taken from &%router_home_directory%& if that option
19696 is set; if not, no home directory is set for the transport.
19698 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19704 .option unseen routers boolean&!! false
19705 .cindex "router" "carrying on after success"
19706 The result of string expansion for this option must be a valid boolean value,
19707 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19708 result causes an error, and delivery is deferred. If the expansion is forced to
19709 fail, the default value for the option (false) is used. Other failures cause
19710 delivery to be deferred.
19712 When this option is set true, routing does not cease if the router accepts the
19713 address. Instead, a copy of the incoming address is passed to the next router,
19714 overriding a false setting of &%more%&. There is little point in setting
19715 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19716 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19717 sometimes true and sometimes false).
19719 .cindex "copy of message (&%unseen%& option)"
19720 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19721 qualifier in filter files. It can be used to cause copies of messages to be
19722 delivered to some other destination, while also carrying out a normal delivery.
19723 In effect, the current address is made into a &"parent"& that has two children
19724 &-- one that is delivered as specified by this router, and a clone that goes on
19725 to be routed further. For this reason, &%unseen%& may not be combined with the
19726 &%one_time%& option in a &(redirect)& router.
19728 &*Warning*&: Header lines added to the address (or specified for removal) by
19729 this router or by previous routers affect the &"unseen"& copy of the message
19730 only. The clone that continues to be processed by further routers starts with
19731 no added headers and none specified for removal. For a &%redirect%& router, if
19732 a generated address is the same as the incoming address, this can lead to
19733 duplicate addresses with different header modifications. Exim does not do
19734 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19735 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19736 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19737 &%redirect%& router may be of help.
19739 Unlike the handling of header modifications, any data that was set by the
19740 &%address_data%& option in the current or previous routers &'is'& passed on to
19741 subsequent routers.
19744 .option user routers string&!! "see below"
19745 .cindex "uid (user id)" "local delivery"
19746 .cindex "local transports" "uid and gid"
19747 .cindex "transport" "local"
19748 .cindex "router" "user for filter processing"
19749 .cindex "filter" "user for processing"
19750 When a router queues an address for a transport, and the transport does not
19751 specify a user, the user given here is used when running the delivery process.
19752 The user may be specified numerically or by name. If expansion fails, the
19753 error is logged and delivery is deferred.
19754 This user is also used by the &(redirect)& router when running a filter file.
19755 The default is unset, except when &%check_local_user%& is set. In this case,
19756 the default is taken from the password information. If the user is specified as
19757 a name, and &%group%& is not set, the group associated with the user is used.
19758 See also &%initgroups%& and &%group%& and the discussion in chapter
19759 &<<CHAPenvironment>>&.
19763 .option verify routers&!? boolean true
19764 Setting this option has the effect of setting &%verify_sender%& and
19765 &%verify_recipient%& to the same value.
19768 .option verify_only routers&!? boolean false
19769 .cindex "EXPN" "with &%verify_only%&"
19771 .cindex "router" "used only when verifying"
19772 If this option is set, the router is used only when verifying an address,
19773 delivering in cutthrough mode or
19774 testing with the &%-bv%& option, not when actually doing a delivery, testing
19775 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19776 restricted to verifying only senders or recipients by means of
19777 &%verify_sender%& and &%verify_recipient%&.
19779 &*Warning*&: When the router is being run to verify addresses for an incoming
19780 SMTP message, Exim is not running as root, but under its own uid. If the router
19781 accesses any files, you need to make sure that they are accessible to the Exim
19785 .option verify_recipient routers&!? boolean true
19786 If this option is false, the router is skipped when verifying recipient
19788 delivering in cutthrough mode
19789 or testing recipient verification using &%-bv%&.
19790 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19792 See also the &$verify_mode$& variable.
19795 .option verify_sender routers&!? boolean true
19796 If this option is false, the router is skipped when verifying sender addresses
19797 or testing sender verification using &%-bvs%&.
19798 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19800 See also the &$verify_mode$& variable.
19801 .ecindex IIDgenoprou1
19802 .ecindex IIDgenoprou2
19809 . ////////////////////////////////////////////////////////////////////////////
19810 . ////////////////////////////////////////////////////////////////////////////
19812 .chapter "The accept router" "CHID4"
19813 .cindex "&(accept)& router"
19814 .cindex "routers" "&(accept)&"
19815 The &(accept)& router has no private options of its own. Unless it is being
19816 used purely for verification (see &%verify_only%&) a transport is required to
19817 be defined by the generic &%transport%& option. If the preconditions that are
19818 specified by generic options are met, the router accepts the address and queues
19819 it for the given transport. The most common use of this router is for setting
19820 up deliveries to local mailboxes. For example:
19824 domains = mydomain.example
19826 transport = local_delivery
19828 The &%domains%& condition in this example checks the domain of the address, and
19829 &%check_local_user%& checks that the local part is the login of a local user.
19830 When both preconditions are met, the &(accept)& router runs, and queues the
19831 address for the &(local_delivery)& transport.
19838 . ////////////////////////////////////////////////////////////////////////////
19839 . ////////////////////////////////////////////////////////////////////////////
19841 .chapter "The dnslookup router" "CHAPdnslookup"
19842 .scindex IIDdnsrou1 "&(dnslookup)& router"
19843 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
19844 The &(dnslookup)& router looks up the hosts that handle mail for the
19845 recipient's domain in the DNS. A transport must always be set for this router,
19846 unless &%verify_only%& is set.
19848 If SRV support is configured (see &%check_srv%& below), Exim first searches for
19849 SRV records. If none are found, or if SRV support is not configured,
19850 MX records are looked up. If no MX records exist, address records are sought.
19851 However, &%mx_domains%& can be set to disable the direct use of address
19854 MX records of equal priority are sorted by Exim into a random order. Exim then
19855 looks for address records for the host names obtained from MX or SRV records.
19856 When a host has more than one IP address, they are sorted into a random order,
19857 except that IPv6 addresses are sorted before IPv4 addresses. If all the
19858 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
19859 generic option, the router declines.
19861 Unless they have the highest priority (lowest MX value), MX records that point
19862 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
19863 are discarded, together with any other MX records of equal or lower priority.
19865 .cindex "MX record" "pointing to local host"
19866 .cindex "local host" "MX pointing to"
19867 .oindex "&%self%&" "in &(dnslookup)& router"
19868 If the host pointed to by the highest priority MX record, or looked up as an
19869 address record, is the local host, or matches &%hosts_treat_as_local%&, what
19870 happens is controlled by the generic &%self%& option.
19873 .section "Problems with DNS lookups" "SECTprowitdnsloo"
19874 There have been problems with DNS servers when SRV records are looked up.
19875 Some misbehaving servers return a DNS error or timeout when a non-existent
19876 SRV record is sought. Similar problems have in the past been reported for
19877 MX records. The global &%dns_again_means_nonexist%& option can help with this
19878 problem, but it is heavy-handed because it is a global option.
19880 For this reason, there are two options, &%srv_fail_domains%& and
19881 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
19882 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
19883 an attempt to look up an SRV or MX record causes one of these results, and the
19884 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
19885 such record"&. In the case of an SRV lookup, this means that the router
19886 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
19887 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
19888 case routing fails.
19891 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
19892 .cindex "&(dnslookup)& router" "declines"
19893 There are a few cases where a &(dnslookup)& router will decline to accept
19894 an address; if such a router is expected to handle "all remaining non-local
19895 domains", then it is important to set &%no_more%&.
19897 The router will defer rather than decline if the domain
19898 is found in the &%fail_defer_domains%& router option.
19900 Reasons for a &(dnslookup)& router to decline currently include:
19902 The domain does not exist in DNS
19904 The domain exists but the MX record's host part is just "."; this is a common
19905 convention (borrowed from SRV) used to indicate that there is no such service
19906 for this domain and to not fall back to trying A/AAAA records.
19908 Ditto, but for SRV records, when &%check_srv%& is set on this router.
19910 MX record points to a non-existent host.
19912 MX record points to an IP address and the main section option
19913 &%allow_mx_to_ip%& is not set.
19915 MX records exist and point to valid hosts, but all hosts resolve only to
19916 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
19918 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
19919 &%dns_check_names_pattern%& for handling one variant of this)
19921 &%check_secondary_mx%& is set on this router but the local host can
19922 not be found in the MX records (see below)
19928 .section "Private options for dnslookup" "SECID118"
19929 .cindex "options" "&(dnslookup)& router"
19930 The private options for the &(dnslookup)& router are as follows:
19932 .option check_secondary_mx dnslookup boolean false
19933 .cindex "MX record" "checking for secondary"
19934 If this option is set, the router declines unless the local host is found in
19935 (and removed from) the list of hosts obtained by MX lookup. This can be used to
19936 process domains for which the local host is a secondary mail exchanger
19937 differently to other domains. The way in which Exim decides whether a host is
19938 the local host is described in section &<<SECTreclocipadd>>&.
19941 .option check_srv dnslookup string&!! unset
19942 .cindex "SRV record" "enabling use of"
19943 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
19944 addition to MX and address records. The support is disabled by default. To
19945 enable SRV support, set the &%check_srv%& option to the name of the service
19946 required. For example,
19950 looks for SRV records that refer to the normal smtp service. The option is
19951 expanded, so the service name can vary from message to message or address
19952 to address. This might be helpful if SRV records are being used for a
19953 submission service. If the expansion is forced to fail, the &%check_srv%&
19954 option is ignored, and the router proceeds to look for MX records in the
19957 When the expansion succeeds, the router searches first for SRV records for
19958 the given service (it assumes TCP protocol). A single SRV record with a
19959 host name that consists of just a single dot indicates &"no such service for
19960 this domain"&; if this is encountered, the router declines. If other kinds of
19961 SRV record are found, they are used to construct a host list for delivery
19962 according to the rules of RFC 2782. MX records are not sought in this case.
19964 When no SRV records are found, MX records (and address records) are sought in
19965 the traditional way. In other words, SRV records take precedence over MX
19966 records, just as MX records take precedence over address records. Note that
19967 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
19968 defined it. It is apparently believed that MX records are sufficient for email
19969 and that SRV records should not be used for this purpose. However, SRV records
19970 have an additional &"weight"& feature which some people might find useful when
19971 trying to split an SMTP load between hosts of different power.
19973 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
19974 when there is a DNS lookup error.
19979 .option fail_defer_domains dnslookup "domain list&!!" unset
19980 .cindex "MX record" "not found"
19981 DNS lookups for domains matching &%fail_defer_domains%&
19982 which find no matching record will cause the router to defer
19983 rather than the default behaviour of decline.
19984 This maybe be useful for queueing messages for a newly created
19985 domain while the DNS configuration is not ready.
19986 However, it will result in any message with mistyped domains
19990 .option ipv4_only "string&!!" unset
19991 .cindex IPv6 disabling
19992 .cindex DNS "IPv6 disabling"
19993 The string is expanded, and if the result is anything but a forced failure,
19994 or an empty string, or one of the strings “0” or “no” or “false”
19995 (checked without regard to the case of the letters),
19996 only A records are used.
19998 .option ipv4_prefer "string&!!" unset
19999 .cindex IPv4 preference
20000 .cindex DNS "IPv4 preference"
20001 The string is expanded, and if the result is anything but a forced failure,
20002 or an empty string, or one of the strings “0” or “no” or “false”
20003 (checked without regard to the case of the letters),
20004 A records are sorted before AAAA records (inverting the default).
20006 .option mx_domains dnslookup "domain list&!!" unset
20007 .cindex "MX record" "required to exist"
20008 .cindex "SRV record" "required to exist"
20009 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20010 record in order to be recognized. (The name of this option could be improved.)
20011 For example, if all the mail hosts in &'fict.example'& are known to have MX
20012 records, except for those in &'discworld.fict.example'&, you could use this
20015 mx_domains = ! *.discworld.fict.example : *.fict.example
20017 This specifies that messages addressed to a domain that matches the list but
20018 has no MX record should be bounced immediately instead of being routed using
20019 the address record.
20022 .option mx_fail_domains dnslookup "domain list&!!" unset
20023 If the DNS lookup for MX records for one of the domains in this list causes a
20024 DNS lookup error, Exim behaves as if no MX records were found. See section
20025 &<<SECTprowitdnsloo>>& for more discussion.
20030 .option qualify_single dnslookup boolean true
20031 .cindex "DNS" "resolver options"
20032 .cindex "DNS" "qualifying single-component names"
20033 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20034 lookups. Typically, but not standardly, this causes the resolver to qualify
20035 single-component names with the default domain. For example, on a machine
20036 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20037 &'thesaurus.ref.example'& inside the resolver. For details of what your
20038 resolver actually does, consult your man pages for &'resolver'& and
20043 .option rewrite_headers dnslookup boolean true
20044 .cindex "rewriting" "header lines"
20045 .cindex "header lines" "rewriting"
20046 If the domain name in the address that is being processed is not fully
20047 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20048 an address is specified as &'dormouse@teaparty'&, the domain might be
20049 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20050 occur as a result of setting the &%widen_domains%& option. If
20051 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20052 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20053 header lines of the message are rewritten with the full domain name.
20055 This option should be turned off only when it is known that no message is
20056 ever going to be sent outside an environment where the abbreviation makes
20059 When an MX record is looked up in the DNS and matches a wildcard record, name
20060 servers normally return a record containing the name that has been looked up,
20061 making it impossible to detect whether a wildcard was present or not. However,
20062 some name servers have recently been seen to return the wildcard entry. If the
20063 name returned by a DNS lookup begins with an asterisk, it is not used for
20067 .option same_domain_copy_routing dnslookup boolean false
20068 .cindex "address" "copying routing"
20069 Addresses with the same domain are normally routed by the &(dnslookup)& router
20070 to the same list of hosts. However, this cannot be presumed, because the router
20071 options and preconditions may refer to the local part of the address. By
20072 default, therefore, Exim routes each address in a message independently. DNS
20073 servers run caches, so repeated DNS lookups are not normally expensive, and in
20074 any case, personal messages rarely have more than a few recipients.
20076 If you are running mailing lists with large numbers of subscribers at the same
20077 domain, and you are using a &(dnslookup)& router which is independent of the
20078 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20079 lookups for identical domains in one message. In this case, when &(dnslookup)&
20080 routes an address to a remote transport, any other unrouted addresses in the
20081 message that have the same domain are automatically given the same routing
20082 without processing them independently,
20083 provided the following conditions are met:
20086 No router that processed the address specified &%headers_add%& or
20087 &%headers_remove%&.
20089 The router did not change the address in any way, for example, by &"widening"&
20096 .option search_parents dnslookup boolean false
20097 .cindex "DNS" "resolver options"
20098 When this option is true, the resolver option RES_DNSRCH is set for DNS
20099 lookups. This is different from the &%qualify_single%& option in that it
20100 applies to domains containing dots. Typically, but not standardly, it causes
20101 the resolver to search for the name in the current domain and in parent
20102 domains. For example, on a machine in the &'fict.example'& domain, if looking
20103 up &'teaparty.wonderland'& failed, the resolver would try
20104 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20105 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20107 Setting this option true can cause problems in domains that have a wildcard MX
20108 record, because any domain that does not have its own MX record matches the
20113 .option srv_fail_domains dnslookup "domain list&!!" unset
20114 If the DNS lookup for SRV records for one of the domains in this list causes a
20115 DNS lookup error, Exim behaves as if no SRV records were found. See section
20116 &<<SECTprowitdnsloo>>& for more discussion.
20121 .option widen_domains dnslookup "string list" unset
20122 .cindex "domain" "partial; widening"
20123 If a DNS lookup fails and this option is set, each of its strings in turn is
20124 added onto the end of the domain, and the lookup is tried again. For example,
20127 widen_domains = fict.example:ref.example
20129 is set and a lookup of &'klingon.dictionary'& fails,
20130 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20131 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20132 and &%search_parents%& options can cause some widening to be undertaken inside
20133 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20134 when verifying, unless &%rewrite_headers%& is false (not the default).
20137 .section "Effect of qualify_single and search_parents" "SECID119"
20138 When a domain from an envelope recipient is changed by the resolver as a result
20139 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20140 corresponding address in the message's header lines unless &%rewrite_headers%&
20141 is set false. Exim then re-routes the address, using the full domain.
20143 These two options affect only the DNS lookup that takes place inside the router
20144 for the domain of the address that is being routed. They do not affect lookups
20145 such as that implied by
20149 that may happen while processing a router precondition before the router is
20150 entered. No widening ever takes place for these lookups.
20151 .ecindex IIDdnsrou1
20152 .ecindex IIDdnsrou2
20162 . ////////////////////////////////////////////////////////////////////////////
20163 . ////////////////////////////////////////////////////////////////////////////
20165 .chapter "The ipliteral router" "CHID5"
20166 .cindex "&(ipliteral)& router"
20167 .cindex "domain literal" "routing"
20168 .cindex "routers" "&(ipliteral)&"
20169 This router has no private options. Unless it is being used purely for
20170 verification (see &%verify_only%&) a transport is required to be defined by the
20171 generic &%transport%& option. The router accepts the address if its domain part
20172 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20173 router handles the address
20177 by setting up delivery to the host with that IP address. IPv4 domain literals
20178 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20179 are similar, but the address is preceded by &`ipv6:`&. For example:
20181 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20183 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20184 grounds that sooner or later somebody will try it.
20186 .oindex "&%self%&" "in &(ipliteral)& router"
20187 If the IP address matches something in &%ignore_target_hosts%&, the router
20188 declines. If an IP literal turns out to refer to the local host, the generic
20189 &%self%& option determines what happens.
20191 The RFCs require support for domain literals; however, their use is
20192 controversial in today's Internet. If you want to use this router, you must
20193 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20194 Exim will not recognize the domain literal syntax in addresses.
20198 . ////////////////////////////////////////////////////////////////////////////
20199 . ////////////////////////////////////////////////////////////////////////////
20201 .chapter "The iplookup router" "CHID6"
20202 .cindex "&(iplookup)& router"
20203 .cindex "routers" "&(iplookup)&"
20204 The &(iplookup)& router was written to fulfil a specific requirement in
20205 Cambridge University (which in fact no longer exists). For this reason, it is
20206 not included in the binary of Exim by default. If you want to include it, you
20209 ROUTER_IPLOOKUP=yes
20211 in your &_Local/Makefile_& configuration file.
20213 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20214 connection to one or more specific hosts. The host can then return the same or
20215 a different address &-- in effect rewriting the recipient address in the
20216 message's envelope. The new address is then passed on to subsequent routers. If
20217 this process fails, the address can be passed on to other routers, or delivery
20218 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20219 must not be specified for it.
20221 .cindex "options" "&(iplookup)& router"
20222 .option hosts iplookup string unset
20223 This option must be supplied. Its value is a colon-separated list of host
20224 names. The hosts are looked up using &[gethostbyname()]&
20225 (or &[getipnodebyname()]& when available)
20226 and are tried in order until one responds to the query. If none respond, what
20227 happens is controlled by &%optional%&.
20230 .option optional iplookup boolean false
20231 If &%optional%& is true, if no response is obtained from any host, the address
20232 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20233 delivery to the address is deferred.
20236 .option port iplookup integer 0
20237 .cindex "port" "&(iplookup)& router"
20238 This option must be supplied. It specifies the port number for the TCP or UDP
20242 .option protocol iplookup string udp
20243 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20244 protocols is to be used.
20247 .option query iplookup string&!! "see below"
20248 This defines the content of the query that is sent to the remote hosts. The
20251 $local_part@$domain $local_part@$domain
20253 The repetition serves as a way of checking that a response is to the correct
20254 query in the default case (see &%response_pattern%& below).
20257 .option reroute iplookup string&!! unset
20258 If this option is not set, the rerouted address is precisely the byte string
20259 returned by the remote host, up to the first white space, if any. If set, the
20260 string is expanded to form the rerouted address. It can include parts matched
20261 in the response by &%response_pattern%& by means of numeric variables such as
20262 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20263 whether or not a pattern is in use. In all cases, the rerouted address must end
20264 up in the form &'local_part@domain'&.
20267 .option response_pattern iplookup string unset
20268 This option can be set to a regular expression that is applied to the string
20269 returned from the remote host. If the pattern does not match the response, the
20270 router declines. If &%response_pattern%& is not set, no checking of the
20271 response is done, unless the query was defaulted, in which case there is a
20272 check that the text returned after the first white space is the original
20273 address. This checks that the answer that has been received is in response to
20274 the correct question. For example, if the response is just a new domain, the
20275 following could be used:
20277 response_pattern = ^([^@]+)$
20278 reroute = $local_part@$1
20281 .option timeout iplookup time 5s
20282 This specifies the amount of time to wait for a response from the remote
20283 machine. The same timeout is used for the &[connect()]& function for a TCP
20284 call. It does not apply to UDP.
20289 . ////////////////////////////////////////////////////////////////////////////
20290 . ////////////////////////////////////////////////////////////////////////////
20292 .chapter "The manualroute router" "CHID7"
20293 .scindex IIDmanrou1 "&(manualroute)& router"
20294 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20295 .cindex "domain" "manually routing"
20296 The &(manualroute)& router is so-called because it provides a way of manually
20297 routing an address according to its domain. It is mainly used when you want to
20298 route addresses to remote hosts according to your own rules, bypassing the
20299 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20300 route to local transports, a facility that may be useful if you want to save
20301 messages for dial-in hosts in local files.
20303 The &(manualroute)& router compares a list of domain patterns with the domain
20304 it is trying to route. If there is no match, the router declines. Each pattern
20305 has associated with it a list of hosts and some other optional data, which may
20306 include a transport. The combination of a pattern and its data is called a
20307 &"routing rule"&. For patterns that do not have an associated transport, the
20308 generic &%transport%& option must specify a transport, unless the router is
20309 being used purely for verification (see &%verify_only%&).
20312 In the case of verification, matching the domain pattern is sufficient for the
20313 router to accept the address. When actually routing an address for delivery,
20314 an address that matches a domain pattern is queued for the associated
20315 transport. If the transport is not a local one, a host list must be associated
20316 with the pattern; IP addresses are looked up for the hosts, and these are
20317 passed to the transport along with the mail address. For local transports, a
20318 host list is optional. If it is present, it is passed in &$host$& as a single
20321 The list of routing rules can be provided as an inline string in
20322 &%route_list%&, or the data can be obtained by looking up the domain in a file
20323 or database by setting &%route_data%&. Only one of these settings may appear in
20324 any one instance of &(manualroute)&. The format of routing rules is described
20325 below, following the list of private options.
20328 .section "Private options for manualroute" "SECTprioptman"
20330 .cindex "options" "&(manualroute)& router"
20331 The private options for the &(manualroute)& router are as follows:
20333 .option host_all_ignored manualroute string defer
20334 See &%host_find_failed%&.
20336 .option host_find_failed manualroute string freeze
20337 This option controls what happens when &(manualroute)& tries to find an IP
20338 address for a host, and the host does not exist. The option can be set to one
20339 of the following values:
20348 The default (&"freeze"&) assumes that this state is a serious configuration
20349 error. The difference between &"pass"& and &"decline"& is that the former
20350 forces the address to be passed to the next router (or the router defined by
20353 overriding &%no_more%&, whereas the latter passes the address to the next
20354 router only if &%more%& is true.
20356 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20357 cannot be found. If all the hosts in the list are ignored, the behaviour is
20358 controlled by the &%host_all_ignored%& option. This takes the same values
20359 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20361 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20362 state; if a host lookup gets a temporary error, delivery is deferred unless the
20363 generic &%pass_on_timeout%& option is set.
20366 .option hosts_randomize manualroute boolean false
20367 .cindex "randomized host list"
20368 .cindex "host" "list of; randomized"
20369 If this option is set, the order of the items in a host list in a routing rule
20370 is randomized each time the list is used, unless an option in the routing rule
20371 overrides (see below). Randomizing the order of a host list can be used to do
20372 crude load sharing. However, if more than one mail address is routed by the
20373 same router to the same host list, the host lists are considered to be the same
20374 (even though they may be randomized into different orders) for the purpose of
20375 deciding whether to batch the deliveries into a single SMTP transaction.
20377 When &%hosts_randomize%& is true, a host list may be split
20378 into groups whose order is separately randomized. This makes it possible to
20379 set up MX-like behaviour. The boundaries between groups are indicated by an
20380 item that is just &`+`& in the host list. For example:
20382 route_list = * host1:host2:host3:+:host4:host5
20384 The order of the first three hosts and the order of the last two hosts is
20385 randomized for each use, but the first three always end up before the last two.
20386 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20387 randomized host list is passed to an &(smtp)& transport that also has
20388 &%hosts_randomize set%&, the list is not re-randomized.
20391 .option route_data manualroute string&!! unset
20392 If this option is set, it must expand to yield the data part of a routing rule.
20393 Typically, the expansion string includes a lookup based on the domain. For
20396 route_data = ${lookup{$domain}dbm{/etc/routes}}
20398 If the expansion is forced to fail, or the result is an empty string, the
20399 router declines. Other kinds of expansion failure cause delivery to be
20403 .option route_list manualroute "string list" unset
20404 This string is a list of routing rules, in the form defined below. Note that,
20405 unlike most string lists, the items are separated by semicolons. This is so
20406 that they may contain colon-separated host lists.
20409 .option same_domain_copy_routing manualroute boolean false
20410 .cindex "address" "copying routing"
20411 Addresses with the same domain are normally routed by the &(manualroute)&
20412 router to the same list of hosts. However, this cannot be presumed, because the
20413 router options and preconditions may refer to the local part of the address. By
20414 default, therefore, Exim routes each address in a message independently. DNS
20415 servers run caches, so repeated DNS lookups are not normally expensive, and in
20416 any case, personal messages rarely have more than a few recipients.
20418 If you are running mailing lists with large numbers of subscribers at the same
20419 domain, and you are using a &(manualroute)& router which is independent of the
20420 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20421 lookups for identical domains in one message. In this case, when
20422 &(manualroute)& routes an address to a remote transport, any other unrouted
20423 addresses in the message that have the same domain are automatically given the
20424 same routing without processing them independently. However, this is only done
20425 if &%headers_add%& and &%headers_remove%& are unset.
20430 .section "Routing rules in route_list" "SECID120"
20431 The value of &%route_list%& is a string consisting of a sequence of routing
20432 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20433 entered as two semicolons. Alternatively, the list separator can be changed as
20434 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20435 Empty rules are ignored. The format of each rule is
20437 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20439 The following example contains two rules, each with a simple domain pattern and
20443 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20444 thes.ref.example mail-3.ref.example:mail-4.ref.example
20446 The three parts of a rule are separated by white space. The pattern and the
20447 list of hosts can be enclosed in quotes if necessary, and if they are, the
20448 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20449 single domain pattern, which is the only mandatory item in the rule. The
20450 pattern is in the same format as one item in a domain list (see section
20451 &<<SECTdomainlist>>&),
20452 except that it may not be the name of an interpolated file.
20453 That is, it may be wildcarded, or a regular expression, or a file or database
20454 lookup (with semicolons doubled, because of the use of semicolon as a separator
20455 in a &%route_list%&).
20457 The rules in &%route_list%& are searched in order until one of the patterns
20458 matches the domain that is being routed. The list of hosts and then options are
20459 then used as described below. If there is no match, the router declines. When
20460 &%route_list%& is set, &%route_data%& must not be set.
20464 .section "Routing rules in route_data" "SECID121"
20465 The use of &%route_list%& is convenient when there are only a small number of
20466 routing rules. For larger numbers, it is easier to use a file or database to
20467 hold the routing information, and use the &%route_data%& option instead.
20468 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20469 Most commonly, &%route_data%& is set as a string that contains an
20470 expansion lookup. For example, suppose we place two routing rules in a file
20473 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20474 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20476 This data can be accessed by setting
20478 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20480 Failure of the lookup results in an empty string, causing the router to
20481 decline. However, you do not have to use a lookup in &%route_data%&. The only
20482 requirement is that the result of expanding the string is a list of hosts,
20483 possibly followed by options, separated by white space. The list of hosts must
20484 be enclosed in quotes if it contains white space.
20489 .section "Format of the list of hosts" "SECID122"
20490 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20491 always separately expanded before use. If the expansion fails, the router
20492 declines. The result of the expansion must be a colon-separated list of names
20493 and/or IP addresses, optionally also including ports.
20494 If the list is written with spaces, it must be protected with quotes.
20495 The format of each item
20496 in the list is described in the next section. The list separator can be changed
20497 as described in section &<<SECTlistsepchange>>&.
20499 If the list of hosts was obtained from a &%route_list%& item, the following
20500 variables are set during its expansion:
20503 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20504 If the domain was matched against a regular expression, the numeric variables
20505 &$1$&, &$2$&, etc. may be set. For example:
20507 route_list = ^domain(\d+) host-$1.text.example
20510 &$0$& is always set to the entire domain.
20512 &$1$& is also set when partial matching is done in a file lookup.
20515 .vindex "&$value$&"
20516 If the pattern that matched the domain was a lookup item, the data that was
20517 looked up is available in the expansion variable &$value$&. For example:
20519 route_list = lsearch;;/some/file.routes $value
20523 Note the doubling of the semicolon in the pattern that is necessary because
20524 semicolon is the default route list separator.
20528 .section "Format of one host item" "SECTformatonehostitem"
20529 Each item in the list of hosts can be either a host name or an IP address,
20530 optionally with an attached port number, or it can be a single "+"
20531 (see &%hosts_randomize%&).
20532 When no port is given, an IP address
20533 is not enclosed in brackets. When a port is specified, it overrides the port
20534 specification on the transport. The port is separated from the name or address
20535 by a colon. This leads to some complications:
20538 Because colon is the default separator for the list of hosts, either
20539 the colon that specifies a port must be doubled, or the list separator must
20540 be changed. The following two examples have the same effect:
20542 route_list = * "host1.tld::1225 : host2.tld::1226"
20543 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20546 When IPv6 addresses are involved, it gets worse, because they contain
20547 colons of their own. To make this case easier, it is permitted to
20548 enclose an IP address (either v4 or v6) in square brackets if a port
20549 number follows. For example:
20551 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20555 .section "How the list of hosts is used" "SECThostshowused"
20556 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20557 the hosts is tried, in the order specified, when carrying out the SMTP
20558 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20559 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20562 Hosts may be listed by name or by IP address. An unadorned name in the list of
20563 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20564 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20565 records in the DNS. For example:
20567 route_list = * x.y.z:p.q.r/MX:e.f.g
20569 If this feature is used with a port specifier, the port must come last. For
20572 route_list = * dom1.tld/mx::1225
20574 If the &%hosts_randomize%& option is set, the order of the items in the list is
20575 randomized before any lookups are done. Exim then scans the list; for any name
20576 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20577 be an interface on the local host and the item is not the first in the list,
20578 Exim discards it and any subsequent items. If it is the first item, what
20579 happens is controlled by the
20580 .oindex "&%self%&" "in &(manualroute)& router"
20581 &%self%& option of the router.
20583 A name on the list that is followed by &`/MX`& is replaced with the list of
20584 hosts obtained by looking up MX records for the name. This is always a DNS
20585 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20586 below) are not relevant here. The order of these hosts is determined by the
20587 preference values in the MX records, according to the usual rules. Because
20588 randomizing happens before the MX lookup, it does not affect the order that is
20589 defined by MX preferences.
20591 If the local host is present in the sublist obtained from MX records, but is
20592 not the most preferred host in that list, it and any equally or less
20593 preferred hosts are removed before the sublist is inserted into the main list.
20595 If the local host is the most preferred host in the MX list, what happens
20596 depends on where in the original list of hosts the &`/MX`& item appears. If it
20597 is not the first item (that is, there are previous hosts in the main list),
20598 Exim discards this name and any subsequent items in the main list.
20600 If the MX item is first in the list of hosts, and the local host is the
20601 most preferred host, what happens is controlled by the &%self%& option of the
20604 DNS failures when lookup up the MX records are treated in the same way as DNS
20605 failures when looking up IP addresses: &%pass_on_timeout%& and
20606 &%host_find_failed%& are used when relevant.
20608 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20609 whether obtained from an MX lookup or not.
20613 .section "How the options are used" "SECThowoptused"
20614 The options are a sequence of words, space-separated.
20615 One of the words can be the name of a transport; this overrides the
20616 &%transport%& option on the router for this particular routing rule only. The
20617 other words (if present) control randomization of the list of hosts on a
20618 per-rule basis, and how the IP addresses of the hosts are to be found when
20619 routing to a remote transport. These options are as follows:
20622 &%randomize%&: randomize the order of the hosts in this list, overriding the
20623 setting of &%hosts_randomize%& for this routing rule only.
20625 &%no_randomize%&: do not randomize the order of the hosts in this list,
20626 overriding the setting of &%hosts_randomize%& for this routing rule only.
20628 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20629 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20630 also look in &_/etc/hosts_& or other sources of information.
20632 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20633 no address records are found. If there is a temporary DNS error (such as a
20634 timeout), delivery is deferred.
20636 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20638 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20643 route_list = domain1 host1:host2:host3 randomize bydns;\
20644 domain2 host4:host5
20646 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20647 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20648 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20649 or &[gethostbyname()]&, and the result of the lookup is the result of that
20652 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20653 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20654 instead of TRY_AGAIN. That is why the default action is to try a DNS
20655 lookup first. Only if that gives a definite &"no such host"& is the local
20658 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20659 inadvertent constraint that a transport name as an option had to be the last
20664 If no IP address for a host can be found, what happens is controlled by the
20665 &%host_find_failed%& option.
20668 When an address is routed to a local transport, IP addresses are not looked up.
20669 The host list is passed to the transport in the &$host$& variable.
20673 .section "Manualroute examples" "SECID123"
20674 In some of the examples that follow, the presence of the &%remote_smtp%&
20675 transport, as defined in the default configuration file, is assumed:
20678 .cindex "smart host" "example router"
20679 The &(manualroute)& router can be used to forward all external mail to a
20680 &'smart host'&. If you have set up, in the main part of the configuration, a
20681 named domain list that contains your local domains, for example:
20683 domainlist local_domains = my.domain.example
20685 You can arrange for all other domains to be routed to a smart host by making
20686 your first router something like this:
20689 driver = manualroute
20690 domains = !+local_domains
20691 transport = remote_smtp
20692 route_list = * smarthost.ref.example
20694 This causes all non-local addresses to be sent to the single host
20695 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20696 they are tried in order
20697 (but you can use &%hosts_randomize%& to vary the order each time).
20698 Another way of configuring the same thing is this:
20701 driver = manualroute
20702 transport = remote_smtp
20703 route_list = !+local_domains smarthost.ref.example
20705 There is no difference in behaviour between these two routers as they stand.
20706 However, they behave differently if &%no_more%& is added to them. In the first
20707 example, the router is skipped if the domain does not match the &%domains%&
20708 precondition; the following router is always tried. If the router runs, it
20709 always matches the domain and so can never decline. Therefore, &%no_more%&
20710 would have no effect. In the second case, the router is never skipped; it
20711 always runs. However, if it doesn't match the domain, it declines. In this case
20712 &%no_more%& would prevent subsequent routers from running.
20715 .cindex "mail hub example"
20716 A &'mail hub'& is a host which receives mail for a number of domains via MX
20717 records in the DNS and delivers it via its own private routing mechanism. Often
20718 the final destinations are behind a firewall, with the mail hub being the one
20719 machine that can connect to machines both inside and outside the firewall. The
20720 &(manualroute)& router is usually used on a mail hub to route incoming messages
20721 to the correct hosts. For a small number of domains, the routing can be inline,
20722 using the &%route_list%& option, but for a larger number a file or database
20723 lookup is easier to manage.
20725 If the domain names are in fact the names of the machines to which the mail is
20726 to be sent by the mail hub, the configuration can be quite simple. For
20730 driver = manualroute
20731 transport = remote_smtp
20732 route_list = *.rhodes.tvs.example $domain
20734 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20735 whose names are the same as the mail domains. A similar approach can be taken
20736 if the host name can be obtained from the domain name by a string manipulation
20737 that the expansion facilities can handle. Otherwise, a lookup based on the
20738 domain can be used to find the host:
20741 driver = manualroute
20742 transport = remote_smtp
20743 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20745 The result of the lookup must be the name or IP address of the host (or
20746 hosts) to which the address is to be routed. If the lookup fails, the route
20747 data is empty, causing the router to decline. The address then passes to the
20751 .cindex "batched SMTP output example"
20752 .cindex "SMTP" "batched outgoing; example"
20753 You can use &(manualroute)& to deliver messages to pipes or files in batched
20754 SMTP format for onward transportation by some other means. This is one way of
20755 storing mail for a dial-up host when it is not connected. The route list entry
20756 can be as simple as a single domain name in a configuration like this:
20759 driver = manualroute
20760 transport = batchsmtp_appendfile
20761 route_list = saved.domain.example
20763 though often a pattern is used to pick up more than one domain. If there are
20764 several domains or groups of domains with different transport requirements,
20765 different transports can be listed in the routing information:
20768 driver = manualroute
20770 *.saved.domain1.example $domain batch_appendfile; \
20771 *.saved.domain2.example \
20772 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20775 .vindex "&$domain$&"
20777 The first of these just passes the domain in the &$host$& variable, which
20778 doesn't achieve much (since it is also in &$domain$&), but the second does a
20779 file lookup to find a value to pass, causing the router to decline to handle
20780 the address if the lookup fails.
20783 .cindex "UUCP" "example of router for"
20784 Routing mail directly to UUCP software is a specific case of the use of
20785 &(manualroute)& in a gateway to another mail environment. This is an example of
20786 one way it can be done:
20792 command = /usr/local/bin/uux -r - \
20793 ${substr_-5:$host}!rmail ${local_part}
20794 return_fail_output = true
20799 driver = manualroute
20801 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20803 The file &_/usr/local/exim/uucphosts_& contains entries like
20805 darksite.ethereal.example: darksite.UUCP
20807 It can be set up more simply without adding and removing &".UUCP"& but this way
20808 makes clear the distinction between the domain name
20809 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20811 .ecindex IIDmanrou1
20812 .ecindex IIDmanrou2
20821 . ////////////////////////////////////////////////////////////////////////////
20822 . ////////////////////////////////////////////////////////////////////////////
20824 .chapter "The queryprogram router" "CHAPdriverlast"
20825 .scindex IIDquerou1 "&(queryprogram)& router"
20826 .scindex IIDquerou2 "routers" "&(queryprogram)&"
20827 .cindex "routing" "by external program"
20828 The &(queryprogram)& router routes an address by running an external command
20829 and acting on its output. This is an expensive way to route, and is intended
20830 mainly for use in lightly-loaded systems, or for performing experiments.
20831 However, if it is possible to use the precondition options (&%domains%&,
20832 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
20833 be used in special cases, even on a busy host. There are the following private
20835 .cindex "options" "&(queryprogram)& router"
20837 .option command queryprogram string&!! unset
20838 This option must be set. It specifies the command that is to be run. The
20839 command is split up into a command name and arguments, and then each is
20840 expanded separately (exactly as for a &(pipe)& transport, described in chapter
20841 &<<CHAPpipetransport>>&).
20844 .option command_group queryprogram string unset
20845 .cindex "gid (group id)" "in &(queryprogram)& router"
20846 This option specifies a gid to be set when running the command while routing an
20847 address for deliver. It must be set if &%command_user%& specifies a numerical
20848 uid. If it begins with a digit, it is interpreted as the numerical value of the
20849 gid. Otherwise it is looked up using &[getgrnam()]&.
20852 .option command_user queryprogram string unset
20853 .cindex "uid (user id)" "for &(queryprogram)&"
20854 This option must be set. It specifies the uid which is set when running the
20855 command while routing an address for delivery. If the value begins with a digit,
20856 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
20857 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
20858 not set, a value for the gid also.
20860 &*Warning:*& Changing uid and gid is possible only when Exim is running as
20861 root, which it does during a normal delivery in a conventional configuration.
20862 However, when an address is being verified during message reception, Exim is
20863 usually running as the Exim user, not as root. If the &(queryprogram)& router
20864 is called from a non-root process, Exim cannot change uid or gid before running
20865 the command. In this circumstance the command runs under the current uid and
20869 .option current_directory queryprogram string /
20870 This option specifies an absolute path which is made the current directory
20871 before running the command.
20874 .option timeout queryprogram time 1h
20875 If the command does not complete within the timeout period, its process group
20876 is killed and the message is frozen. A value of zero time specifies no
20880 The standard output of the command is connected to a pipe, which is read when
20881 the command terminates. It should consist of a single line of output,
20882 containing up to five fields, separated by white space. The maximum length of
20883 the line is 1023 characters. Longer lines are silently truncated. The first
20884 field is one of the following words (case-insensitive):
20887 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
20890 &'Decline'&: the router declines; pass the address to the next router, unless
20891 &%no_more%& is set.
20893 &'Fail'&: routing failed; do not pass the address to any more routers. Any
20894 subsequent text on the line is an error message. If the router is run as part
20895 of address verification during an incoming SMTP message, the message is
20896 included in the SMTP response.
20898 &'Defer'&: routing could not be completed at this time; try again later. Any
20899 subsequent text on the line is an error message which is logged. It is not
20900 included in any SMTP response.
20902 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
20904 &'Pass'&: pass the address to the next router (or the router specified by
20905 &%pass_router%&), overriding &%no_more%&.
20907 &'Redirect'&: the message is redirected. The remainder of the line is a list of
20908 new addresses, which are routed independently, starting with the first router,
20909 or the router specified by &%redirect_router%&, if set.
20912 When the first word is &'accept'&, the remainder of the line consists of a
20913 number of keyed data values, as follows (split into two lines here, to fit on
20916 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
20917 LOOKUP=byname|bydns DATA=<text>
20919 The data items can be given in any order, and all are optional. If no transport
20920 is included, the transport specified by the generic &%transport%& option is
20921 used. The list of hosts and the lookup type are needed only if the transport is
20922 an &(smtp)& transport that does not itself supply a list of hosts.
20924 The format of the list of hosts is the same as for the &(manualroute)& router.
20925 As well as host names and IP addresses with optional port numbers, as described
20926 in section &<<SECTformatonehostitem>>&, it may contain names followed by
20927 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
20928 (see section &<<SECThostshowused>>&).
20930 If the lookup type is not specified, Exim behaves as follows when trying to
20931 find an IP address for each host: First, a DNS lookup is done. If this yields
20932 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
20933 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
20934 result of the lookup is the result of that call.
20936 .vindex "&$address_data$&"
20937 If the DATA field is set, its value is placed in the &$address_data$&
20938 variable. For example, this return line
20940 accept hosts=x1.y.example:x2.y.example data="rule1"
20942 routes the address to the default transport, passing a list of two hosts. When
20943 the transport runs, the string &"rule1"& is in &$address_data$&.
20944 .ecindex IIDquerou1
20945 .ecindex IIDquerou2
20950 . ////////////////////////////////////////////////////////////////////////////
20951 . ////////////////////////////////////////////////////////////////////////////
20953 .chapter "The redirect router" "CHAPredirect"
20954 .scindex IIDredrou1 "&(redirect)& router"
20955 .scindex IIDredrou2 "routers" "&(redirect)&"
20956 .cindex "alias file" "in a &(redirect)& router"
20957 .cindex "address redirection" "&(redirect)& router"
20958 The &(redirect)& router handles several kinds of address redirection. Its most
20959 common uses are for resolving local part aliases from a central alias file
20960 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
20961 files, but it has many other potential uses. The incoming address can be
20962 redirected in several different ways:
20965 It can be replaced by one or more new addresses which are themselves routed
20968 It can be routed to be delivered to a given file or directory.
20970 It can be routed to be delivered to a specified pipe command.
20972 It can cause an automatic reply to be generated.
20974 It can be forced to fail, optionally with a custom error message.
20976 It can be temporarily deferred, optionally with a custom message.
20978 It can be discarded.
20981 The generic &%transport%& option must not be set for &(redirect)& routers.
20982 However, there are some private options which define transports for delivery to
20983 files and pipes, and for generating autoreplies. See the &%file_transport%&,
20984 &%pipe_transport%& and &%reply_transport%& descriptions below.
20986 If success DSNs have been requested
20987 .cindex "DSN" "success"
20988 .cindex "Delivery Status Notification" "success"
20989 redirection triggers one and the DSN options are not passed any further.
20993 .section "Redirection data" "SECID124"
20994 The router operates by interpreting a text string which it obtains either by
20995 expanding the contents of the &%data%& option, or by reading the entire
20996 contents of a file whose name is given in the &%file%& option. These two
20997 options are mutually exclusive. The first is commonly used for handling system
20998 aliases, in a configuration like this:
21002 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21004 If the lookup fails, the expanded string in this example is empty. When the
21005 expansion of &%data%& results in an empty string, the router declines. A forced
21006 expansion failure also causes the router to decline; other expansion failures
21007 cause delivery to be deferred.
21009 A configuration using &%file%& is commonly used for handling users'
21010 &_.forward_& files, like this:
21015 file = $home/.forward
21018 If the file does not exist, or causes no action to be taken (for example, it is
21019 empty or consists only of comments), the router declines. &*Warning*&: This
21020 is not the case when the file contains syntactically valid items that happen to
21021 yield empty addresses, for example, items containing only RFC 2822 address
21024 .cindex "tainted data" "in filenames"
21025 .cindex redirect "tainted data"
21026 Tainted data may not be used for a filename.
21028 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21029 directly for redirection,
21030 as they are provided by a potential attacker.
21031 In the examples above, &$local_part$& is used for looking up data held locally
21032 on the system, and not used directly (the second example derives &$home$& via
21033 the passsword file or database, using &$local_part$&).
21037 .section "Forward files and address verification" "SECID125"
21038 .cindex "address redirection" "while verifying"
21039 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21040 &_.forward_& files, as in the example above. There are two reasons for this:
21043 When Exim is receiving an incoming SMTP message from a remote host, it is
21044 running under the Exim uid, not as root. Exim is unable to change uid to read
21045 the file as the user, and it may not be able to read it as the Exim user. So in
21046 practice the router may not be able to operate.
21048 However, even when the router can operate, the existence of a &_.forward_& file
21049 is unimportant when verifying an address. What should be checked is whether the
21050 local part is a valid user name or not. Cutting out the redirection processing
21051 saves some resources.
21059 .section "Interpreting redirection data" "SECID126"
21060 .cindex "Sieve filter" "specifying in redirection data"
21061 .cindex "filter" "specifying in redirection data"
21062 The contents of the data string, whether obtained from &%data%& or &%file%&,
21063 can be interpreted in two different ways:
21066 If the &%allow_filter%& option is set true, and the data begins with the text
21067 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21068 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21069 respectively. Details of the syntax and semantics of filter files are described
21070 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21071 document is intended for use by end users.
21073 Otherwise, the data must be a comma-separated list of redirection items, as
21074 described in the next section.
21077 When a message is redirected to a file (a &"mail folder"&), the filename given
21078 in a non-filter redirection list must always be an absolute path. A filter may
21079 generate a relative path &-- how this is handled depends on the transport's
21080 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21081 for the &(appendfile)& transport.
21085 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21086 .cindex "address redirection" "non-filter list items"
21087 When the redirection data is not an Exim or Sieve filter, for example, if it
21088 comes from a conventional alias or forward file, it consists of a list of
21089 addresses, filenames, pipe commands, or certain special items (see section
21090 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21091 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21092 depending on their default values. The items in the list are separated by
21093 commas or newlines.
21094 If a comma is required in an item, the entire item must be enclosed in double
21097 Lines starting with a # character are comments, and are ignored, and # may
21098 also appear following a comma, in which case everything between the # and the
21099 next newline character is ignored.
21101 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21102 double quotes are retained because some forms of mail address require their use
21103 (but never to enclose the entire address). In the following description,
21104 &"item"& refers to what remains after any surrounding double quotes have been
21107 .vindex "&$local_part$&"
21108 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21109 and the expansion contains a reference to &$local_part$&, you should make use
21110 of the &%quote_local_part%& expansion operator, in case the local part contains
21111 special characters. For example, to redirect all mail for the domain
21112 &'obsolete.example'&, retaining the existing local part, you could use this
21115 data = ${quote_local_part:$local_part}@newdomain.example
21119 .section "Redirecting to a local mailbox" "SECTredlocmai"
21120 .cindex "routing" "loops in"
21121 .cindex "loop" "while routing, avoidance of"
21122 .cindex "address redirection" "to local mailbox"
21123 A redirection item may safely be the same as the address currently under
21124 consideration. This does not cause a routing loop, because a router is
21125 automatically skipped if any ancestor of the address that is being processed
21126 is the same as the current address and was processed by the current router.
21127 Such an address is therefore passed to the following routers, so it is handled
21128 as if there were no redirection. When making this loop-avoidance test, the
21129 complete local part, including any prefix or suffix, is used.
21131 .cindex "address redirection" "local part without domain"
21132 Specifying the same local part without a domain is a common usage in personal
21133 filter files when the user wants to have messages delivered to the local
21134 mailbox and also forwarded elsewhere. For example, the user whose login is
21135 &'cleo'& might have a &_.forward_& file containing this:
21137 cleo, cleopatra@egypt.example
21139 .cindex "backslash in alias file"
21140 .cindex "alias file" "backslash in"
21141 For compatibility with other MTAs, such unqualified local parts may be
21142 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21143 it does make a difference if more than one domain is being handled
21146 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21147 2822 address that does not include a domain, the item is qualified using the
21148 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21149 addresses are qualified using the value in &%qualify_recipient%&, but you can
21150 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21152 Care must be taken if there are alias names for local users.
21153 Consider an MTA handling a single local domain where the system alias file
21158 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21159 messages in the local mailbox, and also forward copies elsewhere. He creates
21162 Sam.Reman, spqr@reme.elsewhere.example
21164 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21165 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21166 second time round, because it has previously routed it,
21167 and the following routers presumably cannot handle the alias. The forward file
21168 should really contain
21170 spqr, spqr@reme.elsewhere.example
21172 but because this is such a common error, the &%check_ancestor%& option (see
21173 below) exists to provide a way to get round it. This is normally set on a
21174 &(redirect)& router that is handling users' &_.forward_& files.
21178 .section "Special items in redirection lists" "SECTspecitredli"
21179 In addition to addresses, the following types of item may appear in redirection
21180 lists (that is, in non-filter redirection data):
21183 .cindex "pipe" "in redirection list"
21184 .cindex "address redirection" "to pipe"
21185 An item is treated as a pipe command if it begins with &"|"& and does not parse
21186 as a valid RFC 2822 address that includes a domain. A transport for running the
21187 command must be specified by the &%pipe_transport%& option.
21188 Normally, either the router or the transport specifies a user and a group under
21189 which to run the delivery. The default is to use the Exim user and group.
21191 Single or double quotes can be used for enclosing the individual arguments of
21192 the pipe command; no interpretation of escapes is done for single quotes. If
21193 the command contains a comma character, it is necessary to put the whole item
21194 in double quotes, for example:
21196 "|/some/command ready,steady,go"
21198 since items in redirection lists are terminated by commas. Do not, however,
21199 quote just the command. An item such as
21201 |"/some/command ready,steady,go"
21203 is interpreted as a pipe with a rather strange command name, and no arguments.
21205 Note that the above example assumes that the text comes from a lookup source
21206 of some sort, so that the quotes are part of the data. If composing a
21207 redirect router with a &%data%& option directly specifying this command, the
21208 quotes will be used by the configuration parser to define the extent of one
21209 string, but will not be passed down into the redirect router itself. There
21210 are two main approaches to get around this: escape quotes to be part of the
21211 data itself, or avoid using this mechanism and instead create a custom
21212 transport with the &%command%& option set and reference that transport from
21213 an &%accept%& router.
21216 .cindex "file" "in redirection list"
21217 .cindex "address redirection" "to file"
21218 An item is interpreted as a path name if it begins with &"/"& and does not
21219 parse as a valid RFC 2822 address that includes a domain. For example,
21221 /home/world/minbari
21223 is treated as a filename, but
21225 /s=molari/o=babylon/@x400gate.way
21227 is treated as an address. For a filename, a transport must be specified using
21228 the &%file_transport%& option. However, if the generated path name ends with a
21229 forward slash character, it is interpreted as a directory name rather than a
21230 filename, and &%directory_transport%& is used instead.
21232 Normally, either the router or the transport specifies a user and a group under
21233 which to run the delivery. The default is to use the Exim user and group.
21235 .cindex "&_/dev/null_&"
21236 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21237 bypassed at a high level, and the log entry shows &"**bypassed**"&
21238 instead of a transport name. In this case the user and group are not used.
21241 .cindex "included address list"
21242 .cindex "address redirection" "included external list"
21243 If an item is of the form
21245 :include:<path name>
21247 a list of further items is taken from the given file and included at that
21248 point. &*Note*&: Such a file can not be a filter file; it is just an
21249 out-of-line addition to the list. The items in the included list are separated
21250 by commas or newlines and are not subject to expansion. If this is the first
21251 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21252 the alias name. This example is incorrect:
21254 list1 :include:/opt/lists/list1
21256 It must be given as
21258 list1: :include:/opt/lists/list1
21260 .cindex "tainted data" "in filenames"
21261 .cindex redirect "tainted data"
21262 Tainted data may not be used for a filename.
21264 .cindex "address redirection" "to black hole"
21265 .cindex "delivery" "discard"
21266 .cindex "delivery" "blackhole"
21267 .cindex "black hole"
21268 .cindex "abandoning mail"
21269 Sometimes you want to throw away mail to a particular local part. Making the
21270 &%data%& option expand to an empty string does not work, because that causes
21271 the router to decline. Instead, the alias item
21275 can be used. It does what its name implies. No delivery is
21276 done, and no error message is generated. This has the same effect as specifying
21277 &_/dev/null_& as a destination, but it can be independently disabled.
21279 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21280 delivery is done for the original local part, even if other redirection items
21281 are present. If you are generating a multi-item list (for example, by reading a
21282 database) and need the ability to provide a no-op item, you must use
21286 .cindex "delivery" "forcing failure"
21287 .cindex "delivery" "forcing deferral"
21288 .cindex "failing delivery" "forcing"
21289 .cindex "deferred delivery, forcing"
21290 .cindex "customizing" "failure message"
21291 An attempt to deliver a particular address can be deferred or forced to fail by
21292 redirection items of the form
21297 respectively. When a redirection list contains such an item, it applies
21298 to the entire redirection; any other items in the list are ignored. Any
21299 text following &':fail:'& or &':defer:'& is placed in the error text
21300 associated with the failure. For example, an alias file might contain:
21302 X.Employee: :fail: Gone away, no forwarding address
21304 In the case of an address that is being verified from an ACL or as the subject
21306 .cindex "VRFY" "error text, display of"
21307 VRFY command, the text is included in the SMTP error response by
21309 .cindex "EXPN" "error text, display of"
21310 The text is not included in the response to an EXPN command. In non-SMTP cases
21311 the text is included in the error message that Exim generates.
21313 .cindex "SMTP" "error codes"
21314 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21315 &':fail:'&. However, if the message starts with three digits followed by a
21316 space, optionally followed by an extended code of the form &'n.n.n'&, also
21317 followed by a space, and the very first digit is the same as the default error
21318 code, the code from the message is used instead. If the very first digit is
21319 incorrect, a panic error is logged, and the default code is used. You can
21320 suppress the use of the supplied code in a redirect router by setting the
21321 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21324 .vindex "&$acl_verify_message$&"
21325 In an ACL, an explicitly provided message overrides the default, but the
21326 default message is available in the variable &$acl_verify_message$& and can
21327 therefore be included in a custom message if this is desired.
21329 Normally the error text is the rest of the redirection list &-- a comma does
21330 not terminate it &-- but a newline does act as a terminator. Newlines are not
21331 normally present in alias expansions. In &(lsearch)& lookups they are removed
21332 as part of the continuation process, but they may exist in other kinds of
21333 lookup and in &':include:'& files.
21335 During routing for message delivery (as opposed to verification), a redirection
21336 containing &':fail:'& causes an immediate failure of the incoming address,
21337 whereas &':defer:'& causes the message to remain in the queue so that a
21338 subsequent delivery attempt can happen at a later time. If an address is
21339 deferred for too long, it will ultimately fail, because the normal retry
21343 .cindex "alias file" "exception to default"
21344 Sometimes it is useful to use a single-key search type with a default (see
21345 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21346 for exceptions to the default. These can be handled by aliasing them to
21347 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21348 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21349 results in an empty redirection list has the same effect.
21353 .section "Duplicate addresses" "SECTdupaddr"
21354 .cindex "duplicate addresses"
21355 .cindex "address duplicate, discarding"
21356 .cindex "pipe" "duplicated"
21357 Exim removes duplicate addresses from the list to which it is delivering, so as
21358 to deliver just one copy to each address. This does not apply to deliveries
21359 routed to pipes by different immediate parent addresses, but an indirect
21360 aliasing scheme of the type
21362 pipe: |/some/command $local_part
21366 does not work with a message that is addressed to both local parts, because
21367 when the second is aliased to the intermediate local part &"pipe"& it gets
21368 discarded as being the same as a previously handled address. However, a scheme
21371 localpart1: |/some/command $local_part
21372 localpart2: |/some/command $local_part
21374 does result in two different pipe deliveries, because the immediate parents of
21375 the pipes are distinct.
21379 .section "Repeated redirection expansion" "SECID128"
21380 .cindex "repeated redirection expansion"
21381 .cindex "address redirection" "repeated for each delivery attempt"
21382 When a message cannot be delivered to all of its recipients immediately,
21383 leading to two or more delivery attempts, redirection expansion is carried out
21384 afresh each time for those addresses whose children were not all previously
21385 delivered. If redirection is being used as a mailing list, this can lead to new
21386 members of the list receiving copies of old messages. The &%one_time%& option
21387 can be used to avoid this.
21390 .section "Errors in redirection lists" "SECID129"
21391 .cindex "address redirection" "errors"
21392 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21393 error is skipped, and an entry is written to the main log. This may be useful
21394 for mailing lists that are automatically managed. Otherwise, if an error is
21395 detected while generating the list of new addresses, the original address is
21396 deferred. See also &%syntax_errors_to%&.
21400 .section "Private options for the redirect router" "SECID130"
21402 .cindex "options" "&(redirect)& router"
21403 The private options for the &(redirect)& router are as follows:
21406 .option allow_defer redirect boolean false
21407 Setting this option allows the use of &':defer:'& in non-filter redirection
21408 data, or the &%defer%& command in an Exim filter file.
21411 .option allow_fail redirect boolean false
21412 .cindex "failing delivery" "from filter"
21413 If this option is true, the &':fail:'& item can be used in a redirection list,
21414 and the &%fail%& command may be used in an Exim filter file.
21417 .option allow_filter redirect boolean false
21418 .cindex "filter" "enabling use of"
21419 .cindex "Sieve filter" "enabling use of"
21420 Setting this option allows Exim to interpret redirection data that starts with
21421 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21422 are some features of Exim filter files that some administrators may wish to
21423 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21425 It is also possible to lock out Exim filters or Sieve filters while allowing
21426 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21429 The filter is run using the uid and gid set by the generic &%user%& and
21430 &%group%& options. These take their defaults from the password data if
21431 &%check_local_user%& is set, so in the normal case of users' personal filter
21432 files, the filter is run as the relevant user. When &%allow_filter%& is set
21433 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21437 .option allow_freeze redirect boolean false
21438 .cindex "freezing messages" "allowing in filter"
21439 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21440 This command is more normally encountered in system filters, and is disabled by
21441 default for redirection filters because it isn't something you usually want to
21442 let ordinary users do.
21446 .option check_ancestor redirect boolean false
21447 This option is concerned with handling generated addresses that are the same
21448 as some address in the list of redirection ancestors of the current address.
21449 Although it is turned off by default in the code, it is set in the default
21450 configuration file for handling users' &_.forward_& files. It is recommended
21451 for this use of the &(redirect)& router.
21453 When &%check_ancestor%& is set, if a generated address (including the domain)
21454 is the same as any ancestor of the current address, it is replaced by a copy of
21455 the current address. This helps in the case where local part A is aliased to B,
21456 and B has a &_.forward_& file pointing back to A. For example, within a single
21457 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21458 &_&~jb/.forward_& contains:
21460 \Joe.Bloggs, <other item(s)>
21462 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21463 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21464 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21465 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21466 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21467 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21468 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21469 original address. See also the &%repeat_use%& option below.
21472 .option check_group redirect boolean "see below"
21473 When the &%file%& option is used, the group owner of the file is checked only
21474 when this option is set. The permitted groups are those listed in the
21475 &%owngroups%& option, together with the user's default group if
21476 &%check_local_user%& is set. If the file has the wrong group, routing is
21477 deferred. The default setting for this option is true if &%check_local_user%&
21478 is set and the &%modemask%& option permits the group write bit, or if the
21479 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21483 .option check_owner redirect boolean "see below"
21484 When the &%file%& option is used, the owner of the file is checked only when
21485 this option is set. If &%check_local_user%& is set, the local user is
21486 permitted; otherwise the owner must be one of those listed in the &%owners%&
21487 option. The default value for this option is true if &%check_local_user%& or
21488 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21491 .option data redirect string&!! unset
21492 This option is mutually exclusive with &%file%&. One or other of them must be
21493 set, but not both. The contents of &%data%& are expanded, and then used as the
21494 list of forwarding items, or as a set of filtering instructions. If the
21495 expansion is forced to fail, or the result is an empty string or a string that
21496 has no effect (consists entirely of comments), the router declines.
21498 When filtering instructions are used, the string must begin with &"#Exim
21499 filter"&, and all comments in the string, including this initial one, must be
21500 terminated with newline characters. For example:
21502 data = #Exim filter\n\
21503 if $h_to: contains Exim then save $home/mail/exim endif
21505 If you are reading the data from a database where newlines cannot be included,
21506 you can use the &${sg}$& expansion item to turn the escape string of your
21507 choice into a newline.
21510 .option directory_transport redirect string&!! unset
21511 A &(redirect)& router sets up a direct delivery to a directory when a path name
21512 ending with a slash is specified as a new &"address"&. The transport used is
21513 specified by this option, which, after expansion, must be the name of a
21514 configured transport. This should normally be an &(appendfile)& transport.
21517 .option file redirect string&!! unset
21518 This option specifies the name of a file that contains the redirection data. It
21519 is mutually exclusive with the &%data%& option. The string is expanded before
21520 use; if the expansion is forced to fail, the router declines. Other expansion
21521 failures cause delivery to be deferred. The result of a successful expansion
21522 must be an absolute path. The entire file is read and used as the redirection
21523 data. If the data is an empty string or a string that has no effect (consists
21524 entirely of comments), the router declines.
21526 .cindex "NFS" "checking for file existence"
21527 If the attempt to open the file fails with a &"does not exist"& error, Exim
21528 runs a check on the containing directory,
21529 unless &%ignore_enotdir%& is true (see below).
21530 If the directory does not appear to exist, delivery is deferred. This can
21531 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21532 is a mount problem. If the containing directory does exist, but the file does
21533 not, the router declines.
21536 .option file_transport redirect string&!! unset
21537 .vindex "&$address_file$&"
21538 A &(redirect)& router sets up a direct delivery to a file when a path name not
21539 ending in a slash is specified as a new &"address"&. The transport used is
21540 specified by this option, which, after expansion, must be the name of a
21541 configured transport. This should normally be an &(appendfile)& transport. When
21542 it is running, the filename is in &$address_file$&.
21545 .option filter_prepend_home redirect boolean true
21546 When this option is true, if a &(save)& command in an Exim filter specifies a
21547 relative path, and &$home$& is defined, it is automatically prepended to the
21548 relative path. If this option is set false, this action does not happen. The
21549 relative path is then passed to the transport unmodified.
21552 .option forbid_blackhole redirect boolean false
21553 .cindex "restricting access to features"
21554 .cindex "filter" "locking out certain features"
21555 If this option is true, the &':blackhole:'& item may not appear in a
21559 .option forbid_exim_filter redirect boolean false
21560 .cindex "restricting access to features"
21561 .cindex "filter" "locking out certain features"
21562 If this option is set true, only Sieve filters are permitted when
21563 &%allow_filter%& is true.
21568 .option forbid_file redirect boolean false
21569 .cindex "restricting access to features"
21570 .cindex "delivery" "to file; forbidding"
21571 .cindex "filter" "locking out certain features"
21572 .cindex "Sieve filter" "forbidding delivery to a file"
21573 .cindex "Sieve filter" "&""keep""& facility; disabling"
21574 If this option is true, this router may not generate a new address that
21575 specifies delivery to a local file or directory, either from a filter or from a
21576 conventional forward file. This option is forced to be true if &%one_time%& is
21577 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21578 locks out the Sieve's &"keep"& facility.
21581 .option forbid_filter_dlfunc redirect boolean false
21582 .cindex "restricting access to features"
21583 .cindex "filter" "locking out certain features"
21584 If this option is true, string expansions in Exim filters are not allowed to
21585 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21588 .option forbid_filter_existstest redirect boolean false
21589 .cindex "restricting access to features"
21590 .cindex "filter" "locking out certain features"
21591 .cindex "expansion" "statting a file"
21592 If this option is true, string expansions in Exim filters are not allowed to
21593 make use of the &%exists%& condition or the &%stat%& expansion item.
21595 .option forbid_filter_logwrite redirect boolean false
21596 .cindex "restricting access to features"
21597 .cindex "filter" "locking out certain features"
21598 If this option is true, use of the logging facility in Exim filters is not
21599 permitted. Logging is in any case available only if the filter is being run
21600 under some unprivileged uid (which is normally the case for ordinary users'
21601 &_.forward_& files).
21604 .option forbid_filter_lookup redirect boolean false
21605 .cindex "restricting access to features"
21606 .cindex "filter" "locking out certain features"
21607 If this option is true, string expansions in Exim filter files are not allowed
21608 to make use of &%lookup%& items.
21611 .option forbid_filter_perl redirect boolean false
21612 .cindex "restricting access to features"
21613 .cindex "filter" "locking out certain features"
21614 This option has an effect only if Exim is built with embedded Perl support. If
21615 it is true, string expansions in Exim filter files are not allowed to make use
21616 of the embedded Perl support.
21619 .option forbid_filter_readfile redirect boolean false
21620 .cindex "restricting access to features"
21621 .cindex "filter" "locking out certain features"
21622 If this option is true, string expansions in Exim filter files are not allowed
21623 to make use of &%readfile%& items.
21626 .option forbid_filter_readsocket redirect boolean false
21627 .cindex "restricting access to features"
21628 .cindex "filter" "locking out certain features"
21629 If this option is true, string expansions in Exim filter files are not allowed
21630 to make use of &%readsocket%& items.
21633 .option forbid_filter_reply redirect boolean false
21634 .cindex "restricting access to features"
21635 .cindex "filter" "locking out certain features"
21636 If this option is true, this router may not generate an automatic reply
21637 message. Automatic replies can be generated only from Exim or Sieve filter
21638 files, not from traditional forward files. This option is forced to be true if
21639 &%one_time%& is set.
21642 .option forbid_filter_run redirect boolean false
21643 .cindex "restricting access to features"
21644 .cindex "filter" "locking out certain features"
21645 If this option is true, string expansions in Exim filter files are not allowed
21646 to make use of &%run%& items.
21649 .option forbid_include redirect boolean false
21650 .cindex "restricting access to features"
21651 .cindex "filter" "locking out certain features"
21652 If this option is true, items of the form
21654 :include:<path name>
21656 are not permitted in non-filter redirection lists.
21659 .option forbid_pipe redirect boolean false
21660 .cindex "restricting access to features"
21661 .cindex "filter" "locking out certain features"
21662 .cindex "delivery" "to pipe; forbidding"
21663 If this option is true, this router may not generate a new address which
21664 specifies delivery to a pipe, either from an Exim filter or from a conventional
21665 forward file. This option is forced to be true if &%one_time%& is set.
21668 .option forbid_sieve_filter redirect boolean false
21669 .cindex "restricting access to features"
21670 .cindex "filter" "locking out certain features"
21671 If this option is set true, only Exim filters are permitted when
21672 &%allow_filter%& is true.
21675 .cindex "SMTP" "error codes"
21676 .option forbid_smtp_code redirect boolean false
21677 If this option is set true, any SMTP error codes that are present at the start
21678 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21679 the default codes (451 and 550, respectively) are always used.
21684 .option hide_child_in_errmsg redirect boolean false
21685 .cindex "bounce message" "redirection details; suppressing"
21686 If this option is true, it prevents Exim from quoting a child address if it
21687 generates a bounce or delay message for it. Instead it says &"an address
21688 generated from <&'the top level address'&>"&. Of course, this applies only to
21689 bounces generated locally. If a message is forwarded to another host, &'its'&
21690 bounce may well quote the generated address.
21693 .option ignore_eacces redirect boolean false
21695 If this option is set and an attempt to open a redirection file yields the
21696 EACCES error (permission denied), the &(redirect)& router behaves as if the
21697 file did not exist.
21700 .option ignore_enotdir redirect boolean false
21702 If this option is set and an attempt to open a redirection file yields the
21703 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21704 router behaves as if the file did not exist.
21706 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21707 router that has the &%file%& option set discovers that the file does not exist
21708 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21709 against unmounted NFS directories. If the parent can not be statted, delivery
21710 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21711 is set, because that option tells Exim to ignore &"something on the path is not
21712 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21713 that some operating systems give ENOENT where others give ENOTDIR.
21717 .option include_directory redirect string unset
21718 If this option is set, the path names of any &':include:'& items in a
21719 redirection list must start with this directory.
21722 .option modemask redirect "octal integer" 022
21723 This specifies mode bits which must not be set for a file specified by the
21724 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21727 .option one_time redirect boolean false
21728 .cindex "one-time aliasing/forwarding expansion"
21729 .cindex "alias file" "one-time expansion"
21730 .cindex "forward file" "one-time expansion"
21731 .cindex "mailing lists" "one-time expansion"
21732 .cindex "address redirection" "one-time expansion"
21733 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21734 files each time it tries to deliver a message causes a problem when one or more
21735 of the generated addresses fails be delivered at the first attempt. The problem
21736 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21737 but of what happens when the redirection list changes during the time that the
21738 message is on Exim's queue. This is particularly true in the case of mailing
21739 lists, where new subscribers might receive copies of messages that were posted
21740 before they subscribed.
21742 If &%one_time%& is set and any addresses generated by the router fail to
21743 deliver at the first attempt, the failing addresses are added to the message as
21744 &"top level"& addresses, and the parent address that generated them is marked
21745 &"delivered"&. Thus, redirection does not happen again at the next delivery
21748 &*Warning 1*&: Any header line addition or removal that is specified by this
21749 router would be lost if delivery did not succeed at the first attempt. For this
21750 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21751 permitted when &%one_time%& is set.
21753 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21754 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21755 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21757 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21760 The original top-level address is remembered with each of the generated
21761 addresses, and is output in any log messages. However, any intermediate parent
21762 addresses are not recorded. This makes a difference to the log only if
21763 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21764 typically be used for mailing lists, where there is normally just one level of
21768 .option owners redirect "string list" unset
21769 .cindex "ownership" "alias file"
21770 .cindex "ownership" "forward file"
21771 .cindex "alias file" "ownership"
21772 .cindex "forward file" "ownership"
21773 This specifies a list of permitted owners for the file specified by &%file%&.
21774 This list is in addition to the local user when &%check_local_user%& is set.
21775 See &%check_owner%& above.
21778 .option owngroups redirect "string list" unset
21779 This specifies a list of permitted groups for the file specified by &%file%&.
21780 The list is in addition to the local user's primary group when
21781 &%check_local_user%& is set. See &%check_group%& above.
21784 .option pipe_transport redirect string&!! unset
21785 .vindex "&$address_pipe$&"
21786 A &(redirect)& router sets up a direct delivery to a pipe when a string
21787 starting with a vertical bar character is specified as a new &"address"&. The
21788 transport used is specified by this option, which, after expansion, must be the
21789 name of a configured transport. This should normally be a &(pipe)& transport.
21790 When the transport is run, the pipe command is in &$address_pipe$&.
21793 .option qualify_domain redirect string&!! unset
21794 .vindex "&$qualify_recipient$&"
21795 If this option is set, and an unqualified address (one without a domain) is
21796 generated, and that address would normally be qualified by the global setting
21797 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21798 expanding this string. If the expansion fails, the router declines. If you want
21799 to revert to the default, you can have the expansion generate
21800 &$qualify_recipient$&.
21802 This option applies to all unqualified addresses generated by Exim filters,
21803 but for traditional &_.forward_& files, it applies only to addresses that are
21804 not preceded by a backslash. Sieve filters cannot generate unqualified
21807 .option qualify_preserve_domain redirect boolean false
21808 .cindex "domain" "in redirection; preserving"
21809 .cindex "preserving domain in redirection"
21810 .cindex "address redirection" "domain; preserving"
21811 If this option is set, the router's local &%qualify_domain%& option must not be
21812 set (a configuration error occurs if it is). If an unqualified address (one
21813 without a domain) is generated, it is qualified with the domain of the parent
21814 address (the immediately preceding ancestor) instead of the global
21815 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
21816 this applies whether or not the address is preceded by a backslash.
21819 .option repeat_use redirect boolean true
21820 If this option is set false, the router is skipped for a child address that has
21821 any ancestor that was routed by this router. This test happens before any of
21822 the other preconditions are tested. Exim's default anti-looping rules skip
21823 only when the ancestor is the same as the current address. See also
21824 &%check_ancestor%& above and the generic &%redirect_router%& option.
21827 .option reply_transport redirect string&!! unset
21828 A &(redirect)& router sets up an automatic reply when a &%mail%& or
21829 &%vacation%& command is used in a filter file. The transport used is specified
21830 by this option, which, after expansion, must be the name of a configured
21831 transport. This should normally be an &(autoreply)& transport. Other transports
21832 are unlikely to do anything sensible or useful.
21835 .option rewrite redirect boolean true
21836 .cindex "address redirection" "disabling rewriting"
21837 If this option is set false, addresses generated by the router are not
21838 subject to address rewriting. Otherwise, they are treated like new addresses
21839 and are rewritten according to the global rewriting rules.
21842 .option sieve_subaddress redirect string&!! unset
21843 The value of this option is passed to a Sieve filter to specify the
21844 :subaddress part of an address.
21846 .option sieve_useraddress redirect string&!! unset
21847 The value of this option is passed to a Sieve filter to specify the :user part
21848 of an address. However, if it is unset, the entire original local part
21849 (including any prefix or suffix) is used for :user.
21852 .option sieve_vacation_directory redirect string&!! unset
21853 .cindex "Sieve filter" "vacation directory"
21854 To enable the &"vacation"& extension for Sieve filters, you must set
21855 &%sieve_vacation_directory%& to the directory where vacation databases are held
21856 (do not put anything else in that directory), and ensure that the
21857 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
21858 needs their own directory; Exim will create it if necessary.
21862 .option skip_syntax_errors redirect boolean false
21863 .cindex "forward file" "broken"
21864 .cindex "address redirection" "broken files"
21865 .cindex "alias file" "broken"
21866 .cindex "broken alias or forward files"
21867 .cindex "ignoring faulty addresses"
21868 .cindex "skipping faulty addresses"
21869 .cindex "error" "skipping bad syntax"
21870 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
21871 non-filter redirection data are skipped, and each failing address is logged. If
21872 &%syntax_errors_to%& is set, a message is sent to the address it defines,
21873 giving details of the failures. If &%syntax_errors_text%& is set, its contents
21874 are expanded and placed at the head of the error message generated by
21875 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
21876 be the same address as the generic &%errors_to%& option. The
21877 &%skip_syntax_errors%& option is often used when handling mailing lists.
21879 If all the addresses in a redirection list are skipped because of syntax
21880 errors, the router declines to handle the original address, and it is passed to
21881 the following routers.
21883 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
21884 error in the filter causes filtering to be abandoned without any action being
21885 taken. The incident is logged, and the router declines to handle the address,
21886 so it is passed to the following routers.
21888 .cindex "Sieve filter" "syntax errors in"
21889 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
21890 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
21891 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
21893 &%skip_syntax_errors%& can be used to specify that errors in users' forward
21894 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
21895 option, used with an address that does not get redirected, can be used to
21896 notify users of these errors, by means of a router like this:
21902 file = $home/.forward
21903 file_transport = address_file
21904 pipe_transport = address_pipe
21905 reply_transport = address_reply
21908 syntax_errors_to = real-$local_part@$domain
21909 syntax_errors_text = \
21910 This is an automatically generated message. An error has\n\
21911 been found in your .forward file. Details of the error are\n\
21912 reported below. While this error persists, you will receive\n\
21913 a copy of this message for every message that is addressed\n\
21914 to you. If your .forward file is a filter file, or if it is\n\
21915 a non-filter file containing no valid forwarding addresses,\n\
21916 a copy of each incoming message will be put in your normal\n\
21917 mailbox. If a non-filter file contains at least one valid\n\
21918 forwarding address, forwarding to the valid addresses will\n\
21919 happen, and those will be the only deliveries that occur.
21921 You also need a router to ensure that local addresses that are prefixed by
21922 &`real-`& are recognized, but not forwarded or filtered. For example, you could
21923 put this immediately before the &(userforward)& router:
21928 local_part_prefix = real-
21929 transport = local_delivery
21931 For security, it would probably be a good idea to restrict the use of this
21932 router to locally-generated messages, using a condition such as this:
21934 condition = ${if match {$sender_host_address}\
21935 {\N^(|127\.0\.0\.1)$\N}}
21939 .option syntax_errors_text redirect string&!! unset
21940 See &%skip_syntax_errors%& above.
21943 .option syntax_errors_to redirect string unset
21944 See &%skip_syntax_errors%& above.
21945 .ecindex IIDredrou1
21946 .ecindex IIDredrou2
21953 . ////////////////////////////////////////////////////////////////////////////
21954 . ////////////////////////////////////////////////////////////////////////////
21956 .chapter "Environment for running local transports" "CHAPenvironment" &&&
21957 "Environment for local transports"
21958 .scindex IIDenvlotra1 "local transports" "environment for"
21959 .scindex IIDenvlotra2 "environment" "local transports"
21960 .scindex IIDenvlotra3 "transport" "local; environment for"
21961 Local transports handle deliveries to files and pipes. (The &(autoreply)&
21962 transport can be thought of as similar to a pipe.) Exim always runs transports
21963 in subprocesses, under specified uids and gids. Typical deliveries to local
21964 mailboxes run under the uid and gid of the local user.
21966 Exim also sets a specific current directory while running the transport; for
21967 some transports a home directory setting is also relevant. The &(pipe)&
21968 transport is the only one that sets up environment variables; see section
21969 &<<SECTpipeenv>>& for details.
21971 The values used for the uid, gid, and the directories may come from several
21972 different places. In many cases, the router that handles the address associates
21973 settings with that address as a result of its &%check_local_user%&, &%group%&,
21974 or &%user%& options. However, values may also be given in the transport's own
21975 configuration, and these override anything that comes from the router.
21979 .section "Concurrent deliveries" "SECID131"
21980 .cindex "concurrent deliveries"
21981 .cindex "simultaneous deliveries"
21982 If two different messages for the same local recipient arrive more or less
21983 simultaneously, the two delivery processes are likely to run concurrently. When
21984 the &(appendfile)& transport is used to write to a file, Exim applies locking
21985 rules to stop concurrent processes from writing to the same file at the same
21988 However, when you use a &(pipe)& transport, it is up to you to arrange any
21989 locking that is needed. Here is a silly example:
21993 command = /bin/sh -c 'cat >>/some/file'
21995 This is supposed to write the message at the end of the file. However, if two
21996 messages arrive at the same time, the file will be scrambled. You can use the
21997 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
21998 file using the same algorithm that Exim itself uses.
22003 .section "Uids and gids" "SECTenvuidgid"
22004 .cindex "local transports" "uid and gid"
22005 .cindex "transport" "local; uid and gid"
22006 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22007 overrides any group that the router set in the address, even if &%user%& is not
22008 set for the transport. This makes it possible, for example, to run local mail
22009 delivery under the uid of the recipient (set by the router), but in a special
22010 group (set by the transport). For example:
22013 # User/group are set by check_local_user in this router
22017 transport = group_delivery
22020 # This transport overrides the group
22022 driver = appendfile
22023 file = /var/spool/mail/$local_part_data
22026 If &%user%& is set for a transport, its value overrides what is set in the
22027 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22028 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22031 .oindex "&%initgroups%&"
22032 When the uid is taken from the transport's configuration, the &[initgroups()]&
22033 function is called for the groups associated with that uid if the
22034 &%initgroups%& option is set for the transport. When the uid is not specified
22035 by the transport, but is associated with the address by a router, the option
22036 for calling &[initgroups()]& is taken from the router configuration.
22038 .cindex "&(pipe)& transport" "uid for"
22039 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22040 is set and &%user%& is not set, the uid of the process that called Exim to
22041 receive the message is used, and if &%group%& is not set, the corresponding
22042 original gid is also used.
22044 This is the detailed preference order for obtaining a gid; the first of the
22045 following that is set is used:
22048 A &%group%& setting of the transport;
22050 A &%group%& setting of the router;
22052 A gid associated with a user setting of the router, either as a result of
22053 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22055 The group associated with a non-numeric &%user%& setting of the transport;
22057 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22058 the uid is the creator's uid;
22060 The Exim gid if the Exim uid is being used as a default.
22063 If, for example, the user is specified numerically on the router and there are
22064 no group settings, no gid is available. In this situation, an error occurs.
22065 This is different for the uid, for which there always is an ultimate default.
22066 The first of the following that is set is used:
22069 A &%user%& setting of the transport;
22071 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22073 A &%user%& setting of the router;
22075 A &%check_local_user%& setting of the router;
22080 Of course, an error will still occur if the uid that is chosen is on the
22081 &%never_users%& list.
22087 .section "Current and home directories" "SECID132"
22088 .cindex "current directory for local transport"
22089 .cindex "home directory" "for local transport"
22090 .cindex "transport" "local; home directory for"
22091 .cindex "transport" "local; current directory for"
22092 Routers may set current and home directories for local transports by means of
22093 the &%transport_current_directory%& and &%transport_home_directory%& options.
22094 However, if the transport's &%current_directory%& or &%home_directory%& options
22095 are set, they override the router's values. In detail, the home directory
22096 for a local transport is taken from the first of these values that is set:
22099 The &%home_directory%& option on the transport;
22101 The &%transport_home_directory%& option on the router;
22103 The password data if &%check_local_user%& is set on the router;
22105 The &%router_home_directory%& option on the router.
22108 The current directory is taken from the first of these values that is set:
22111 The &%current_directory%& option on the transport;
22113 The &%transport_current_directory%& option on the router.
22117 If neither the router nor the transport sets a current directory, Exim uses the
22118 value of the home directory, if it is set. Otherwise it sets the current
22119 directory to &_/_& before running a local transport.
22123 .section "Expansion variables derived from the address" "SECID133"
22124 .vindex "&$domain$&"
22125 .vindex "&$local_part$&"
22126 .vindex "&$original_domain$&"
22127 Normally a local delivery is handling a single address, and in that case the
22128 variables such as &$domain$& and &$local_part$& are set during local
22129 deliveries. However, in some circumstances more than one address may be handled
22130 at once (for example, while writing batch SMTP for onward transmission by some
22131 other means). In this case, the variables associated with the local part are
22132 never set, &$domain$& is set only if all the addresses have the same domain,
22133 and &$original_domain$& is never set.
22134 .ecindex IIDenvlotra1
22135 .ecindex IIDenvlotra2
22136 .ecindex IIDenvlotra3
22144 . ////////////////////////////////////////////////////////////////////////////
22145 . ////////////////////////////////////////////////////////////////////////////
22147 .chapter "Generic options for transports" "CHAPtransportgeneric"
22148 .scindex IIDgenoptra1 "generic options" "transport"
22149 .scindex IIDgenoptra2 "options" "generic; for transports"
22150 .scindex IIDgenoptra3 "transport" "generic options for"
22151 The following generic options apply to all transports:
22154 .option body_only transports boolean false
22155 .cindex "transport" "body only"
22156 .cindex "message" "transporting body only"
22157 .cindex "body of message" "transporting"
22158 If this option is set, the message's headers are not transported. It is
22159 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22160 or &(pipe)& transports, the settings of &%message_prefix%& and
22161 &%message_suffix%& should be checked, because this option does not
22162 automatically suppress them.
22165 .option current_directory transports string&!! unset
22166 .cindex "transport" "current directory for"
22167 This specifies the current directory that is to be set while running the
22168 transport, overriding any value that may have been set by the router.
22169 If the expansion fails for any reason, including forced failure, an error is
22170 logged, and delivery is deferred.
22173 .option disable_logging transports boolean false
22174 If this option is set true, nothing is logged for any
22175 deliveries by the transport or for any
22176 transport errors. You should not set this option unless you really, really know
22177 what you are doing.
22180 .option debug_print transports string&!! unset
22181 .cindex "testing" "variables in drivers"
22182 If this option is set and debugging is enabled (see the &%-d%& command line
22183 option), the string is expanded and included in the debugging output when the
22185 If expansion of the string fails, the error message is written to the debugging
22186 output, and Exim carries on processing.
22187 This facility is provided to help with checking out the values of variables and
22188 so on when debugging driver configurations. For example, if a &%headers_add%&
22189 option is not working properly, &%debug_print%& could be used to output the
22190 variables it references. A newline is added to the text if it does not end with
22192 The variables &$transport_name$& and &$router_name$& contain the name of the
22193 transport and the router that called it.
22195 .option delivery_date_add transports boolean false
22196 .cindex "&'Delivery-date:'& header line"
22197 If this option is true, a &'Delivery-date:'& header is added to the message.
22198 This gives the actual time the delivery was made. As this is not a standard
22199 header, Exim has a configuration option (&%delivery_date_remove%&) which
22200 requests its removal from incoming messages, so that delivered messages can
22201 safely be resent to other recipients.
22204 .option driver transports string unset
22205 This specifies which of the available transport drivers is to be used.
22206 There is no default, and this option must be set for every transport.
22209 .option envelope_to_add transports boolean false
22210 .cindex "&'Envelope-to:'& header line"
22211 If this option is true, an &'Envelope-to:'& header is added to the message.
22212 This gives the original address(es) in the incoming envelope that caused this
22213 delivery to happen. More than one address may be present if the transport is
22214 configured to handle several addresses at once, or if more than one original
22215 address was redirected to the same final address. As this is not a standard
22216 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22217 its removal from incoming messages, so that delivered messages can safely be
22218 resent to other recipients.
22221 .option event_action transports string&!! unset
22223 This option declares a string to be expanded for Exim's events mechanism.
22224 For details see chapter &<<CHAPevents>>&.
22227 .option group transports string&!! "Exim group"
22228 .cindex "transport" "group; specifying"
22229 This option specifies a gid for running the transport process, overriding any
22230 value that the router supplies, and also overriding any value associated with
22231 &%user%& (see below).
22234 .option headers_add transports list&!! unset
22235 .cindex "header lines" "adding in transport"
22236 .cindex "transport" "header lines; adding"
22237 This option specifies a list of text headers,
22238 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22239 which are (separately) expanded and added to the header
22240 portion of a message as it is transported, as described in section
22241 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22242 routers. If the result of the expansion is an empty string, or if the expansion
22243 is forced to fail, no action is taken. Other expansion failures are treated as
22244 errors and cause the delivery to be deferred.
22246 Unlike most options, &%headers_add%& can be specified multiple times
22247 for a transport; all listed headers are added.
22250 .option headers_only transports boolean false
22251 .cindex "transport" "header lines only"
22252 .cindex "message" "transporting headers only"
22253 .cindex "header lines" "transporting"
22254 If this option is set, the message's body is not transported. It is mutually
22255 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22256 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22257 checked, since this option does not automatically suppress them.
22260 .option headers_remove transports list&!! unset
22261 .cindex "header lines" "removing"
22262 .cindex "transport" "header lines; removing"
22263 This option specifies a list of text headers,
22264 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22265 to be removed from the message.
22266 However, the option has no effect when an address is just being verified.
22267 Each list item is separately expanded.
22268 If the result of the expansion is an empty string, or if the expansion
22269 is forced to fail, no action is taken. Other expansion failures are treated as
22270 errors and cause the delivery to be deferred.
22271 If an item ends in *, it will match any header with the given prefix.
22273 Matching headers are omitted from the message as it is transported, as described
22274 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22277 Unlike most options, &%headers_remove%& can be specified multiple times
22278 for a transport; all listed headers are removed.
22280 &*Warning*&: Because of the separate expansion of the list items,
22281 items that contain a list separator must have it doubled.
22282 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22286 .option headers_rewrite transports string unset
22287 .cindex "transport" "header lines; rewriting"
22288 .cindex "rewriting" "at transport time"
22289 This option allows addresses in header lines to be rewritten at transport time,
22290 that is, as the message is being copied to its destination. The contents of the
22291 option are a colon-separated list of rewriting rules. Each rule is in exactly
22292 the same form as one of the general rewriting rules that are applied when a
22293 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22296 headers_rewrite = a@b c@d f : \
22299 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22300 &'w@z'& in all address-bearing header lines. The rules are applied to the
22301 header lines just before they are written out at transport time, so they affect
22302 only those copies of the message that pass through the transport. However, only
22303 the message's original header lines, and any that were added by a system
22304 filter, are rewritten. If a router or transport adds header lines, they are not
22305 affected by this option. These rewriting rules are &'not'& applied to the
22306 envelope. You can change the return path using &%return_path%&, but you cannot
22307 change envelope recipients at this time.
22310 .option home_directory transports string&!! unset
22311 .cindex "transport" "home directory for"
22313 This option specifies a home directory setting for a local transport,
22314 overriding any value that may be set by the router. The home directory is
22315 placed in &$home$& while expanding the transport's private options. It is also
22316 used as the current directory if no current directory is set by the
22317 &%current_directory%& option on the transport or the
22318 &%transport_current_directory%& option on the router. If the expansion fails
22319 for any reason, including forced failure, an error is logged, and delivery is
22323 .option initgroups transports boolean false
22324 .cindex "additional groups"
22325 .cindex "groups" "additional"
22326 .cindex "transport" "group; additional"
22327 If this option is true and the uid for the delivery process is provided by the
22328 transport, the &[initgroups()]& function is called when running the transport
22329 to ensure that any additional groups associated with the uid are set up.
22332 .option max_parallel transports integer&!! unset
22333 .cindex limit "transport parallelism"
22334 .cindex transport "parallel processes"
22335 .cindex transport "concurrency limit"
22336 .cindex "delivery" "parallelism for transport"
22337 If this option is set and expands to an integer greater than zero
22338 it limits the number of concurrent runs of the transport.
22339 The control does not apply to shadow transports.
22341 .cindex "hints database" "transport concurrency control"
22342 Exim implements this control by means of a hints database in which a record is
22343 incremented whenever a transport process is being created. The record
22344 is decremented and possibly removed when the process terminates.
22345 Obviously there is scope for
22346 records to get left lying around if there is a system or program crash. To
22347 guard against this, Exim ignores any records that are more than six hours old.
22349 If you use this option, you should also arrange to delete the
22350 relevant hints database whenever your system reboots. The names of the files
22351 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22352 may be one or two files, depending on the type of DBM in use. The same files
22353 are used for ETRN and smtp transport serialization.
22356 .option message_size_limit transports string&!! 0
22357 .cindex "limit" "message size per transport"
22358 .cindex "size" "of message, limit"
22359 .cindex "transport" "message size; limiting"
22360 This option controls the size of messages passed through the transport. It is
22361 expanded before use; the result of the expansion must be a sequence of decimal
22362 digits, optionally followed by K or M. If the expansion fails for any reason,
22363 including forced failure, or if the result is not of the required form,
22364 delivery is deferred. If the value is greater than zero and the size of a
22365 message exceeds this limit, the address is failed. If there is any chance that
22366 the resulting bounce message could be routed to the same transport, you should
22367 ensure that &%return_size_limit%& is less than the transport's
22368 &%message_size_limit%&, as otherwise the bounce message will fail to get
22373 .option rcpt_include_affixes transports boolean false
22374 .cindex "prefix" "for local part, including in envelope"
22375 .cindex "suffix for local part" "including in envelope"
22376 .cindex "local part" "prefix"
22377 .cindex "local part" "suffix"
22378 When this option is false (the default), and an address that has had any
22379 affixes (prefixes or suffixes) removed from the local part is delivered by any
22380 form of SMTP or LMTP, the affixes are not included. For example, if a router
22383 local_part_prefix = *-
22385 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22388 RCPT TO:<xyz@some.domain>
22390 This is also the case when an ACL-time callout is being used to verify a
22391 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22392 whole local part is included in the RCPT command. This option applies to BSMTP
22393 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22394 &(lmtp)& and &(smtp)& transports.
22397 .option retry_use_local_part transports boolean "see below"
22398 .cindex "hints database" "retry keys"
22399 When a delivery suffers a temporary failure, a retry record is created
22400 in Exim's hints database. For remote deliveries, the key for the retry record
22401 is based on the name and/or IP address of the failing remote host. For local
22402 deliveries, the key is normally the entire address, including both the local
22403 part and the domain. This is suitable for most common cases of local delivery
22404 temporary failure &-- for example, exceeding a mailbox quota should delay only
22405 deliveries to that mailbox, not to the whole domain.
22407 However, in some special cases you may want to treat a temporary local delivery
22408 as a failure associated with the domain, and not with a particular local part.
22409 (For example, if you are storing all mail for some domain in files.) You can do
22410 this by setting &%retry_use_local_part%& false.
22412 For all the local transports, its default value is true. For remote transports,
22413 the default value is false for tidiness, but changing the value has no effect
22414 on a remote transport in the current implementation.
22417 .option return_path transports string&!! unset
22418 .cindex "envelope sender"
22419 .cindex "envelope from"
22420 .cindex "transport" "return path; changing"
22421 .cindex "return path" "changing in transport"
22422 If this option is set, the string is expanded at transport time and replaces
22423 the existing return path (envelope sender) value in the copy of the message
22424 that is being delivered. An empty return path is permitted. This feature is
22425 designed for remote deliveries, where the value of this option is used in the
22426 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22427 only effect is to change the address that is placed in the &'Return-path:'&
22428 header line, if one is added to the message (see the next option).
22430 &*Note:*& A changed return path is not logged unless you add
22431 &%return_path_on_delivery%& to the log selector.
22433 .vindex "&$return_path$&"
22434 The expansion can refer to the existing value via &$return_path$&. This is
22435 either the message's envelope sender, or an address set by the
22436 &%errors_to%& option on a router. If the expansion is forced to fail, no
22437 replacement occurs; if it fails for another reason, delivery is deferred. This
22438 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22439 section &<<SECTverp>>&.
22441 &*Note*&: If a delivery error is detected locally, including the case when a
22442 remote server rejects a message at SMTP time, the bounce message is not sent to
22443 the value of this option. It is sent to the previously set errors address.
22444 This defaults to the incoming sender address, but can be changed by setting
22445 &%errors_to%& in a router.
22449 .option return_path_add transports boolean false
22450 .cindex "&'Return-path:'& header line"
22451 If this option is true, a &'Return-path:'& header is added to the message.
22452 Although the return path is normally available in the prefix line of BSD
22453 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22454 have easy access to it.
22456 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22457 the delivery SMTP server makes the final delivery"&. This implies that this
22458 header should not be present in incoming messages. Exim has a configuration
22459 option, &%return_path_remove%&, which requests removal of this header from
22460 incoming messages, so that delivered messages can safely be resent to other
22464 .option shadow_condition transports string&!! unset
22465 See &%shadow_transport%& below.
22468 .option shadow_transport transports string unset
22469 .cindex "shadow transport"
22470 .cindex "transport" "shadow"
22471 A local transport may set the &%shadow_transport%& option to the name of
22472 another local transport. Shadow remote transports are not supported.
22474 Whenever a delivery to the main transport succeeds, and either
22475 &%shadow_condition%& is unset, or its expansion does not result in the empty
22476 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22477 passed to the shadow transport, with the same delivery address or addresses. If
22478 expansion fails, no action is taken except that non-forced expansion failures
22479 cause a log line to be written.
22481 The result of the shadow transport is discarded and does not affect the
22482 subsequent processing of the message. Only a single level of shadowing is
22483 provided; the &%shadow_transport%& option is ignored on any transport when it
22484 is running as a shadow. Options concerned with output from pipes are also
22485 ignored. The log line for the successful delivery has an item added on the end,
22488 ST=<shadow transport name>
22490 If the shadow transport did not succeed, the error message is put in
22491 parentheses afterwards. Shadow transports can be used for a number of different
22492 purposes, including keeping more detailed log information than Exim normally
22493 provides, and implementing automatic acknowledgment policies based on message
22494 headers that some sites insist on.
22497 .option transport_filter transports string&!! unset
22498 .cindex "transport" "filter"
22499 .cindex "filter" "transport filter"
22500 This option sets up a filtering (in the Unix shell sense) process for messages
22501 at transport time. It should not be confused with mail filtering as set up by
22502 individual users or via a system filter.
22503 If unset, or expanding to an empty string, no filtering is done.
22505 When the message is about to be written out, the command specified by
22506 &%transport_filter%& is started up in a separate, parallel process, and
22507 the entire message, including the header lines, is passed to it on its standard
22508 input (this in fact is done from a third process, to avoid deadlock). The
22509 command must be specified as an absolute path.
22511 The lines of the message that are written to the transport filter are
22512 terminated by newline (&"\n"&). The message is passed to the filter before any
22513 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22514 lines beginning with a dot, and also before any processing implied by the
22515 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22516 &(pipe)& transports.
22518 The standard error for the filter process is set to the same destination as its
22519 standard output; this is read and written to the message's ultimate
22520 destination. The process that writes the message to the filter, the
22521 filter itself, and the original process that reads the result and delivers it
22522 are all run in parallel, like a shell pipeline.
22524 The filter can perform any transformations it likes, but of course should take
22525 care not to break RFC 2822 syntax. Exim does not check the result, except to
22526 test for a final newline when SMTP is in use. All messages transmitted over
22527 SMTP must end with a newline, so Exim supplies one if it is missing.
22529 .cindex "content scanning" "per user"
22530 A transport filter can be used to provide content-scanning on a per-user basis
22531 at delivery time if the only required effect of the scan is to modify the
22532 message. For example, a content scan could insert a new header line containing
22533 a spam score. This could be interpreted by a filter in the user's MUA. It is
22534 not possible to discard a message at this stage.
22536 .cindex "SIZE" "ESMTP extension"
22537 A problem might arise if the filter increases the size of a message that is
22538 being sent down an SMTP connection. If the receiving SMTP server has indicated
22539 support for the SIZE parameter, Exim will have sent the size of the message
22540 at the start of the SMTP session. If what is actually sent is substantially
22541 more, the server might reject the message. This can be worked round by setting
22542 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22543 additions to the message, or to disable the use of SIZE altogether.
22545 .vindex "&$pipe_addresses$&"
22546 The value of the &%transport_filter%& option is the command string for starting
22547 the filter, which is run directly from Exim, not under a shell. The string is
22548 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22549 Exim breaks it up into arguments and then expands each argument separately (see
22550 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22551 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22552 of arguments, one for each address that applies to this delivery. (This isn't
22553 an ideal name for this feature here, but as it was already implemented for the
22554 &(pipe)& transport, it seemed sensible not to change it.)
22557 .vindex "&$host_address$&"
22558 The expansion variables &$host$& and &$host_address$& are available when the
22559 transport is a remote one. They contain the name and IP address of the host to
22560 which the message is being sent. For example:
22562 transport_filter = /some/directory/transport-filter.pl \
22563 $host $host_address $sender_address $pipe_addresses
22566 Two problems arise if you want to use more complicated expansion items to
22567 generate transport filter commands, both of which due to the fact that the
22568 command is split up &'before'& expansion.
22570 If an expansion item contains white space, you must quote it, so that it is all
22571 part of the same command item. If the entire option setting is one such
22572 expansion item, you have to take care what kind of quoting you use. For
22575 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22577 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22578 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22579 stripped by Exim when it read the option's value. When the value is used, if
22580 the single quotes were missing, the line would be split into two items,
22581 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22582 Exim tried to expand the first one.
22584 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22585 expansion cannot generate multiple arguments, or a command name followed by
22586 arguments. Consider this example:
22588 transport_filter = ${lookup{$host}lsearch{/a/file}\
22589 {$value}{/bin/cat}}
22591 The result of the lookup is interpreted as the name of the command, even
22592 if it contains white space. The simplest way round this is to use a shell:
22594 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22595 {$value}{/bin/cat}}
22599 The filter process is run under the same uid and gid as the normal delivery.
22600 For remote deliveries this is the Exim uid/gid by default. The command should
22601 normally yield a zero return code. Transport filters are not supposed to fail.
22602 A non-zero code is taken to mean that the transport filter encountered some
22603 serious problem. Delivery of the message is deferred; the message remains on
22604 the queue and is tried again later. It is not possible to cause a message to be
22605 bounced from a transport filter.
22607 If a transport filter is set on an autoreply transport, the original message is
22608 passed through the filter as it is being copied into the newly generated
22609 message, which happens if the &%return_message%& option is set.
22612 .option transport_filter_timeout transports time 5m
22613 .cindex "transport" "filter, timeout"
22614 When Exim is reading the output of a transport filter, it applies a timeout
22615 that can be set by this option. Exceeding the timeout is normally treated as a
22616 temporary delivery failure. However, if a transport filter is used with a
22617 &(pipe)& transport, a timeout in the transport filter is treated in the same
22618 way as a timeout in the pipe command itself. By default, a timeout is a hard
22619 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22620 becomes a temporary error.
22623 .option user transports string&!! "Exim user"
22624 .cindex "uid (user id)" "local delivery"
22625 .cindex "transport" "user, specifying"
22626 This option specifies the user under whose uid the delivery process is to be
22627 run, overriding any uid that may have been set by the router. If the user is
22628 given as a name, the uid is looked up from the password data, and the
22629 associated group is taken as the value of the gid to be used if the &%group%&
22632 For deliveries that use local transports, a user and group are normally
22633 specified explicitly or implicitly (for example, as a result of
22634 &%check_local_user%&) by the router or transport.
22636 .cindex "hints database" "access by remote transport"
22637 For remote transports, you should leave this option unset unless you really are
22638 sure you know what you are doing. When a remote transport is running, it needs
22639 to be able to access Exim's hints databases, because each host may have its own
22641 .ecindex IIDgenoptra1
22642 .ecindex IIDgenoptra2
22643 .ecindex IIDgenoptra3
22650 . ////////////////////////////////////////////////////////////////////////////
22651 . ////////////////////////////////////////////////////////////////////////////
22653 .chapter "Address batching in local transports" "CHAPbatching" &&&
22655 .cindex "transport" "local; address batching in"
22656 The only remote transport (&(smtp)&) is normally configured to handle more than
22657 one address at a time, so that when several addresses are routed to the same
22658 remote host, just one copy of the message is sent. Local transports, however,
22659 normally handle one address at a time. That is, a separate instance of the
22660 transport is run for each address that is routed to the transport. A separate
22661 copy of the message is delivered each time.
22663 .cindex "batched local delivery"
22664 .oindex "&%batch_max%&"
22665 .oindex "&%batch_id%&"
22666 In special cases, it may be desirable to handle several addresses at once in a
22667 local transport, for example:
22670 In an &(appendfile)& transport, when storing messages in files for later
22671 delivery by some other means, a single copy of the message with multiple
22672 recipients saves space.
22674 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22675 a single copy saves time, and is the normal way LMTP is expected to work.
22677 In a &(pipe)& transport, when passing the message
22678 to a scanner program or
22679 to some other delivery mechanism such as UUCP, multiple recipients may be
22683 These three local transports all have the same options for controlling multiple
22684 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22685 repeating the information for each transport, these options are described here.
22687 The &%batch_max%& option specifies the maximum number of addresses that can be
22688 delivered together in a single run of the transport. Its default value is one
22689 (no batching). When more than one address is routed to a transport that has a
22690 &%batch_max%& value greater than one, the addresses are delivered in a batch
22691 (that is, in a single run of the transport with multiple recipients), subject
22692 to certain conditions:
22695 .vindex "&$local_part$&"
22696 If any of the transport's options contain a reference to &$local_part$&, no
22697 batching is possible.
22699 .vindex "&$domain$&"
22700 If any of the transport's options contain a reference to &$domain$&, only
22701 addresses with the same domain are batched.
22703 .cindex "customizing" "batching condition"
22704 If &%batch_id%& is set, it is expanded for each address, and only those
22705 addresses with the same expanded value are batched. This allows you to specify
22706 customized batching conditions. Failure of the expansion for any reason,
22707 including forced failure, disables batching, but it does not stop the delivery
22710 Batched addresses must also have the same errors address (where to send
22711 delivery errors), the same header additions and removals, the same user and
22712 group for the transport, and if a host list is present, the first host must
22716 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22717 both when the file or pipe command is specified in the transport, and when it
22718 is specified by a &(redirect)& router, but all the batched addresses must of
22719 course be routed to the same file or pipe command. These two transports have an
22720 option called &%use_bsmtp%&, which causes them to deliver the message in
22721 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22722 &%check_string%& and &%escape_string%& options are forced to the values
22725 escape_string = ".."
22727 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22728 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22729 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22731 .cindex "&'Envelope-to:'& header line"
22732 If the generic &%envelope_to_add%& option is set for a batching transport, the
22733 &'Envelope-to:'& header that is added to the message contains all the addresses
22734 that are being processed together. If you are using a batching &(appendfile)&
22735 transport without &%use_bsmtp%&, the only way to preserve the recipient
22736 addresses is to set the &%envelope_to_add%& option.
22738 .cindex "&(pipe)& transport" "with multiple addresses"
22739 .vindex "&$pipe_addresses$&"
22740 If you are using a &(pipe)& transport without BSMTP, and setting the
22741 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22742 the command. This is not a true variable; it is a bit of magic that causes each
22743 of the recipient addresses to be inserted into the command as a separate
22744 argument. This provides a way of accessing all the addresses that are being
22745 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22746 are specified by a &(redirect)& router.
22751 . ////////////////////////////////////////////////////////////////////////////
22752 . ////////////////////////////////////////////////////////////////////////////
22754 .chapter "The appendfile transport" "CHAPappendfile"
22755 .scindex IIDapptra1 "&(appendfile)& transport"
22756 .scindex IIDapptra2 "transports" "&(appendfile)&"
22757 .cindex "directory creation"
22758 .cindex "creating directories"
22759 The &(appendfile)& transport delivers a message by appending it to an existing
22760 file, or by creating an entirely new file in a specified directory. Single
22761 files to which messages are appended can be in the traditional Unix mailbox
22762 format, or optionally in the MBX format supported by the Pine MUA and
22763 University of Washington IMAP daemon, &'inter alia'&. When each message is
22764 being delivered as a separate file, &"maildir"& format can optionally be used
22765 to give added protection against failures that happen part-way through the
22766 delivery. A third form of separate-file delivery known as &"mailstore"& is also
22767 supported. For all file formats, Exim attempts to create as many levels of
22768 directory as necessary, provided that &%create_directory%& is set.
22770 The code for the optional formats is not included in the Exim binary by
22771 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22772 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22775 .cindex "quota" "system"
22776 Exim recognizes system quota errors, and generates an appropriate message. Exim
22777 also supports its own quota control within the transport, for use when the
22778 system facility is unavailable or cannot be used for some reason.
22780 If there is an error while appending to a file (for example, quota exceeded or
22781 partition filled), Exim attempts to reset the file's length and last
22782 modification time back to what they were before. If there is an error while
22783 creating an entirely new file, the new file is removed.
22785 Before appending to a file, a number of security checks are made, and the
22786 file is locked. A detailed description is given below, after the list of
22789 The &(appendfile)& transport is most commonly used for local deliveries to
22790 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22791 putting messages into files for remote delivery by some means other than Exim.
22792 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22797 .section "The file and directory options" "SECTfildiropt"
22798 The &%file%& option specifies a single file, to which the message is appended;
22799 the &%directory%& option specifies a directory, in which a new file containing
22800 the message is created. Only one of these two options can be set, and for
22801 normal deliveries to mailboxes, one of them &'must'& be set.
22803 .vindex "&$address_file$&"
22804 .vindex "&$local_part$&"
22805 However, &(appendfile)& is also used for delivering messages to files or
22806 directories whose names (or parts of names) are obtained from alias,
22807 forwarding, or filtering operations (for example, a &%save%& command in a
22808 user's Exim filter). When such a transport is running, &$local_part$& contains
22809 the local part that was aliased or forwarded, and &$address_file$& contains the
22810 name (or partial name) of the file or directory generated by the redirection
22811 operation. There are two cases:
22814 If neither &%file%& nor &%directory%& is set, the redirection operation
22815 must specify an absolute path (one that begins with &`/`&). This is the most
22816 common case when users with local accounts use filtering to sort mail into
22817 different folders. See for example, the &(address_file)& transport in the
22818 default configuration. If the path ends with a slash, it is assumed to be the
22819 name of a directory. A delivery to a directory can also be forced by setting
22820 &%maildir_format%& or &%mailstore_format%&.
22822 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
22823 used to determine the file or directory name for the delivery. Normally, the
22824 contents of &$address_file$& are used in some way in the string expansion.
22826 .cindex "tainted data" "in filenames"
22827 .cindex appendfile "tainted data"
22828 Tainted data may not be used for a file or directory name.
22829 This means that, for instance, &$local_part$& cannot be used directly
22830 as a component of a path. It can however be used as the key for a lookup
22831 which returns a path (or component).
22834 .cindex "Sieve filter" "configuring &(appendfile)&"
22835 .cindex "Sieve filter" "relative mailbox path handling"
22836 As an example of the second case, consider an environment where users do not
22837 have home directories. They may be permitted to use Exim filter commands of the
22842 or Sieve filter commands of the form:
22844 require "fileinto";
22845 fileinto "folder23";
22847 In this situation, the expansion of &%file%& or &%directory%& in the transport
22848 must transform the relative path into an appropriate absolute filename. In the
22849 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
22850 is used as a result of a &"keep"& action in the filter. This example shows one
22851 way of handling this requirement:
22853 file = ${if eq{$address_file}{inbox} \
22854 {/var/mail/$local_part_data} \
22855 {${if eq{${substr_0_1:$address_file}}{/} \
22857 {$home/mail/$address_file} \
22861 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
22862 location, absolute paths are used without change, and other folders are in the
22863 &_mail_& directory within the home directory.
22865 &*Note 1*&: While processing an Exim filter, a relative path such as
22866 &_folder23_& is turned into an absolute path if a home directory is known to
22867 the router. In particular, this is the case if &%check_local_user%& is set. If
22868 you want to prevent this happening at routing time, you can set
22869 &%router_home_directory%& empty. This forces the router to pass the relative
22870 path to the transport.
22872 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
22873 the &%file%& or &%directory%& option is still used if it is set.
22878 .section "Private options for appendfile" "SECID134"
22879 .cindex "options" "&(appendfile)& transport"
22883 .option allow_fifo appendfile boolean false
22884 .cindex "fifo (named pipe)"
22885 .cindex "named pipe (fifo)"
22886 .cindex "pipe" "named (fifo)"
22887 Setting this option permits delivery to named pipes (FIFOs) as well as to
22888 regular files. If no process is reading the named pipe at delivery time, the
22889 delivery is deferred.
22892 .option allow_symlink appendfile boolean false
22893 .cindex "symbolic link" "to mailbox"
22894 .cindex "mailbox" "symbolic link"
22895 By default, &(appendfile)& will not deliver if the path name for the file is
22896 that of a symbolic link. Setting this option relaxes that constraint, but there
22897 are security issues involved in the use of symbolic links. Be sure you know
22898 what you are doing if you set this. Details of exactly what this option affects
22899 are included in the discussion which follows this list of options.
22902 .option batch_id appendfile string&!! unset
22903 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22904 However, batching is automatically disabled for &(appendfile)& deliveries that
22905 happen as a result of forwarding or aliasing or other redirection directly to a
22909 .option batch_max appendfile integer 1
22910 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22913 .option check_group appendfile boolean false
22914 When this option is set, the group owner of the file defined by the &%file%&
22915 option is checked to see that it is the same as the group under which the
22916 delivery process is running. The default setting is false because the default
22917 file mode is 0600, which means that the group is irrelevant.
22920 .option check_owner appendfile boolean true
22921 When this option is set, the owner of the file defined by the &%file%& option
22922 is checked to ensure that it is the same as the user under which the delivery
22923 process is running.
22926 .option check_string appendfile string "see below"
22927 .cindex "&""From""& line"
22928 As &(appendfile)& writes the message, the start of each line is tested for
22929 matching &%check_string%&, and if it does, the initial matching characters are
22930 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
22931 a literal string, not a regular expression, and the case of any letters it
22932 contains is significant.
22934 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
22935 are forced to &"."& and &".."& respectively, and any settings in the
22936 configuration are ignored. Otherwise, they default to &"From&~"& and
22937 &">From&~"& when the &%file%& option is set, and unset when any of the
22938 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
22940 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
22941 suitable for traditional &"BSD"& mailboxes, where a line beginning with
22942 &"From&~"& indicates the start of a new message. All four options need changing
22943 if another format is used. For example, to deliver to mailboxes in MMDF format:
22944 .cindex "MMDF format mailbox"
22945 .cindex "mailbox" "MMDF format"
22947 check_string = "\1\1\1\1\n"
22948 escape_string = "\1\1\1\1 \n"
22949 message_prefix = "\1\1\1\1\n"
22950 message_suffix = "\1\1\1\1\n"
22952 .option create_directory appendfile boolean true
22953 .cindex "directory creation"
22954 When this option is true, Exim attempts to create any missing superior
22955 directories for the file that it is about to write. A created directory's mode
22956 is given by the &%directory_mode%& option.
22958 The group ownership of a newly created directory is highly dependent on the
22959 operating system (and possibly the file system) that is being used. For
22960 example, in Solaris, if the parent directory has the setgid bit set, its group
22961 is propagated to the child; if not, the currently set group is used. However,
22962 in FreeBSD, the parent's group is always used.
22966 .option create_file appendfile string anywhere
22967 This option constrains the location of files and directories that are created
22968 by this transport. It applies to files defined by the &%file%& option and
22969 directories defined by the &%directory%& option. In the case of maildir
22970 delivery, it applies to the top level directory, not the maildir directories
22973 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
22974 &"belowhome"&. In the second and third cases, a home directory must have been
22975 set for the transport. This option is not useful when an explicit filename is
22976 given for normal mailbox deliveries. It is intended for the case when filenames
22977 are generated from users' &_.forward_& files. These are usually handled
22978 by an &(appendfile)& transport called &%address_file%&. See also
22979 &%file_must_exist%&.
22982 .option directory appendfile string&!! unset
22983 This option is mutually exclusive with the &%file%& option, but one of &%file%&
22984 or &%directory%& must be set, unless the delivery is the direct result of a
22985 redirection (see section &<<SECTfildiropt>>&).
22987 When &%directory%& is set, the string is expanded, and the message is delivered
22988 into a new file or files in or below the given directory, instead of being
22989 appended to a single mailbox file. A number of different formats are provided
22990 (see &%maildir_format%& and &%mailstore_format%&), and see section
22991 &<<SECTopdir>>& for further details of this form of delivery.
22994 .option directory_file appendfile string&!! "see below"
22996 .vindex "&$inode$&"
22997 When &%directory%& is set, but neither &%maildir_format%& nor
22998 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
22999 whose name is obtained by expanding this string. The default value is:
23001 q${base62:$tod_epoch}-$inode
23003 This generates a unique name from the current time, in base 62 form, and the
23004 inode of the file. The variable &$inode$& is available only when expanding this
23008 .option directory_mode appendfile "octal integer" 0700
23009 If &(appendfile)& creates any directories as a result of the
23010 &%create_directory%& option, their mode is specified by this option.
23013 .option escape_string appendfile string "see description"
23014 See &%check_string%& above.
23017 .option file appendfile string&!! unset
23018 This option is mutually exclusive with the &%directory%& option, but one of
23019 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23020 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23021 specifies a single file, to which the message is appended. One or more of
23022 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23025 .cindex "NFS" "lock file"
23026 .cindex "locking files"
23027 .cindex "lock files"
23028 If you are using more than one host to deliver over NFS into the same
23029 mailboxes, you should always use lock files.
23031 The string value is expanded for each delivery, and must yield an absolute
23032 path. The most common settings of this option are variations on one of these
23035 file = /var/spool/mail/$local_part_data
23036 file = /home/$local_part_data/inbox
23039 .cindex "&""sticky""& bit"
23040 In the first example, all deliveries are done into the same directory. If Exim
23041 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23042 create a file in the directory, so the &"sticky"& bit must be turned on for
23043 deliveries to be possible, or alternatively the &%group%& option can be used to
23044 run the delivery under a group id which has write access to the directory.
23048 .option file_format appendfile string unset
23049 .cindex "file" "mailbox; checking existing format"
23050 This option requests the transport to check the format of an existing file
23051 before adding to it. The check consists of matching a specific string at the
23052 start of the file. The value of the option consists of an even number of
23053 colon-separated strings. The first of each pair is the test string, and the
23054 second is the name of a transport. If the transport associated with a matched
23055 string is not the current transport, control is passed over to the other
23056 transport. For example, suppose the standard &(local_delivery)& transport has
23059 file_format = "From : local_delivery :\
23060 \1\1\1\1\n : local_mmdf_delivery"
23062 Mailboxes that begin with &"From"& are still handled by this transport, but if
23063 a mailbox begins with four binary ones followed by a newline, control is passed
23064 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23065 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23066 is assumed to match the current transport. If the start of a mailbox doesn't
23067 match any string, or if the transport named for a given string is not defined,
23068 delivery is deferred.
23071 .option file_must_exist appendfile boolean false
23072 If this option is true, the file specified by the &%file%& option must exist.
23073 A temporary error occurs if it does not, causing delivery to be deferred.
23074 If this option is false, the file is created if it does not exist.
23077 .option lock_fcntl_timeout appendfile time 0s
23078 .cindex "timeout" "mailbox locking"
23079 .cindex "mailbox" "locking, blocking and non-blocking"
23080 .cindex "locking files"
23081 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23082 when locking an open mailbox file. If the call fails, the delivery process
23083 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23084 Non-blocking calls are used so that the file is not kept open during the wait
23085 for the lock; the reason for this is to make it as safe as possible for
23086 deliveries over NFS in the case when processes might be accessing an NFS
23087 mailbox without using a lock file. This should not be done, but
23088 misunderstandings and hence misconfigurations are not unknown.
23090 On a busy system, however, the performance of a non-blocking lock approach is
23091 not as good as using a blocking lock with a timeout. In this case, the waiting
23092 is done inside the system call, and Exim's delivery process acquires the lock
23093 and can proceed as soon as the previous lock holder releases it.
23095 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23096 timeout, are used. There may still be some retrying: the maximum number of
23099 (lock_retries * lock_interval) / lock_fcntl_timeout
23101 rounded up to the next whole number. In other words, the total time during
23102 which &(appendfile)& is trying to get a lock is roughly the same, unless
23103 &%lock_fcntl_timeout%& is set very large.
23105 You should consider setting this option if you are getting a lot of delayed
23106 local deliveries because of errors of the form
23108 failed to lock mailbox /some/file (fcntl)
23111 .option lock_flock_timeout appendfile time 0s
23112 This timeout applies to file locking when using &[flock()]& (see
23113 &%use_flock%&); the timeout operates in a similar manner to
23114 &%lock_fcntl_timeout%&.
23117 .option lock_interval appendfile time 3s
23118 This specifies the time to wait between attempts to lock the file. See below
23119 for details of locking.
23122 .option lock_retries appendfile integer 10
23123 This specifies the maximum number of attempts to lock the file. A value of zero
23124 is treated as 1. See below for details of locking.
23127 .option lockfile_mode appendfile "octal integer" 0600
23128 This specifies the mode of the created lock file, when a lock file is being
23129 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23132 .option lockfile_timeout appendfile time 30m
23133 .cindex "timeout" "mailbox locking"
23134 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23135 exists and is older than this value, it is assumed to have been left behind by
23136 accident, and Exim attempts to remove it.
23139 .option mailbox_filecount appendfile string&!! unset
23140 .cindex "mailbox" "specifying size of"
23141 .cindex "size" "of mailbox"
23142 If this option is set, it is expanded, and the result is taken as the current
23143 number of files in the mailbox. It must be a decimal number, optionally
23144 followed by K or M. This provides a way of obtaining this information from an
23145 external source that maintains the data.
23148 .option mailbox_size appendfile string&!! unset
23149 .cindex "mailbox" "specifying size of"
23150 .cindex "size" "of mailbox"
23151 If this option is set, it is expanded, and the result is taken as the current
23152 size the mailbox. It must be a decimal number, optionally followed by K or M.
23153 This provides a way of obtaining this information from an external source that
23154 maintains the data. This is likely to be helpful for maildir deliveries where
23155 it is computationally expensive to compute the size of a mailbox.
23159 .option maildir_format appendfile boolean false
23160 .cindex "maildir format" "specifying"
23161 If this option is set with the &%directory%& option, the delivery is into a new
23162 file, in the &"maildir"& format that is used by other mail software. When the
23163 transport is activated directly from a &(redirect)& router (for example, the
23164 &(address_file)& transport in the default configuration), setting
23165 &%maildir_format%& causes the path received from the router to be treated as a
23166 directory, whether or not it ends with &`/`&. This option is available only if
23167 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23168 &<<SECTmaildirdelivery>>& below for further details.
23171 .option maildir_quota_directory_regex appendfile string "See below"
23172 .cindex "maildir format" "quota; directories included in"
23173 .cindex "quota" "maildir; directories included in"
23174 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23175 a regular expression for specifying directories, relative to the quota
23176 directory (see &%quota_directory%&), that should be included in the quota
23177 calculation. The default value is:
23179 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23181 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23182 (directories whose names begin with a dot). If you want to exclude the
23184 folder from the count (as some sites do), you need to change this setting to
23186 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23188 This uses a negative lookahead in the regular expression to exclude the
23189 directory whose name is &_.Trash_&. When a directory is excluded from quota
23190 calculations, quota processing is bypassed for any messages that are delivered
23191 directly into that directory.
23194 .option maildir_retries appendfile integer 10
23195 This option specifies the number of times to retry when writing a file in
23196 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23199 .option maildir_tag appendfile string&!! unset
23200 This option applies only to deliveries in maildir format, and is described in
23201 section &<<SECTmaildirdelivery>>& below.
23204 .option maildir_use_size_file appendfile&!! boolean false
23205 .cindex "maildir format" "&_maildirsize_& file"
23206 The result of string expansion for this option must be a valid boolean value.
23207 If it is true, it enables support for &_maildirsize_& files. Exim
23208 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23209 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23210 value is zero. See &%maildir_quota_directory_regex%& above and section
23211 &<<SECTmaildirdelivery>>& below for further details.
23213 .option maildirfolder_create_regex appendfile string unset
23214 .cindex "maildir format" "&_maildirfolder_& file"
23215 .cindex "&_maildirfolder_&, creating"
23216 The value of this option is a regular expression. If it is unset, it has no
23217 effect. Otherwise, before a maildir delivery takes place, the pattern is
23218 matched against the name of the maildir directory, that is, the directory
23219 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23220 delivery. If there is a match, Exim checks for the existence of a file called
23221 &_maildirfolder_& in the directory, and creates it if it does not exist.
23222 See section &<<SECTmaildirdelivery>>& for more details.
23225 .option mailstore_format appendfile boolean false
23226 .cindex "mailstore format" "specifying"
23227 If this option is set with the &%directory%& option, the delivery is into two
23228 new files in &"mailstore"& format. The option is available only if
23229 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23230 below for further details.
23233 .option mailstore_prefix appendfile string&!! unset
23234 This option applies only to deliveries in mailstore format, and is described in
23235 section &<<SECTopdir>>& below.
23238 .option mailstore_suffix appendfile string&!! unset
23239 This option applies only to deliveries in mailstore format, and is described in
23240 section &<<SECTopdir>>& below.
23243 .option mbx_format appendfile boolean false
23244 .cindex "locking files"
23245 .cindex "file" "locking"
23246 .cindex "file" "MBX format"
23247 .cindex "MBX format, specifying"
23248 This option is available only if Exim has been compiled with SUPPORT_MBX
23249 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23250 the message is appended to the mailbox file in MBX format instead of
23251 traditional Unix format. This format is supported by Pine4 and its associated
23252 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23254 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23255 automatically changed by the use of &%mbx_format%&. They should normally be set
23256 empty when using MBX format, so this option almost always appears in this
23263 If none of the locking options are mentioned in the configuration,
23264 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23265 is possible to specify the other kinds of locking with &%mbx_format%&, but
23266 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23267 interworks with &'c-client'&, providing for shared access to the mailbox. It
23268 should not be used if any program that does not use this form of locking is
23269 going to access the mailbox, nor should it be used if the mailbox file is NFS
23270 mounted, because it works only when the mailbox is accessed from a single host.
23272 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23273 the standard version of &'c-client'&, because as long as it has a mailbox open
23274 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23275 append messages to it.
23278 .option message_prefix appendfile string&!! "see below"
23279 .cindex "&""From""& line"
23280 The string specified here is expanded and output at the start of every message.
23281 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23282 in which case it is:
23284 message_prefix = "From ${if def:return_path{$return_path}\
23285 {MAILER-DAEMON}} $tod_bsdinbox\n"
23287 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23288 &`\n`& to &`\r\n`& in &%message_prefix%&.
23290 .option message_suffix appendfile string&!! "see below"
23291 The string specified here is expanded and output at the end of every message.
23292 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23293 in which case it is a single newline character. The suffix can be suppressed by
23298 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23299 &`\n`& to &`\r\n`& in &%message_suffix%&.
23301 .option mode appendfile "octal integer" 0600
23302 If the output file is created, it is given this mode. If it already exists and
23303 has wider permissions, they are reduced to this mode. If it has narrower
23304 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23305 if the delivery is the result of a &%save%& command in a filter file specifying
23306 a particular mode, the mode of the output file is always forced to take that
23307 value, and this option is ignored.
23310 .option mode_fail_narrower appendfile boolean true
23311 This option applies in the case when an existing mailbox file has a narrower
23312 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23313 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23314 continues with the delivery attempt, using the existing mode of the file.
23317 .option notify_comsat appendfile boolean false
23318 If this option is true, the &'comsat'& daemon is notified after every
23319 successful delivery to a user mailbox. This is the daemon that notifies logged
23320 on users about incoming mail.
23323 .option quota appendfile string&!! unset
23324 .cindex "quota" "imposed by Exim"
23325 This option imposes a limit on the size of the file to which Exim is appending,
23326 or to the total space used in the directory tree when the &%directory%& option
23327 is set. In the latter case, computation of the space used is expensive, because
23328 all the files in the directory (and any sub-directories) have to be
23329 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23330 &%maildir_use_size_file%& for ways to avoid this in environments where users
23331 have no shell access to their mailboxes).
23333 As there is no interlock against two simultaneous deliveries into a
23334 multi-file mailbox, it is possible for the quota to be overrun in this case.
23335 For single-file mailboxes, of course, an interlock is a necessity.
23337 A file's size is taken as its &'used'& value. Because of blocking effects, this
23338 may be a lot less than the actual amount of disk space allocated to the file.
23339 If the sizes of a number of files are being added up, the rounding effect can
23340 become quite noticeable, especially on systems that have large block sizes.
23341 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23342 the obvious value which users understand most easily.
23344 The value of the option is expanded, and must then be a numerical value
23345 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23346 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23347 and further option modifiers. If Exim is running on a system with
23348 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23351 The option modifier &%no_check%& can be used to force delivery even if the over
23352 quota condition is met. The quota gets updated as usual.
23354 &*Note*&: A value of zero is interpreted as &"no quota"&.
23356 The expansion happens while Exim is running as root, before it changes uid for
23357 the delivery. This means that files that are inaccessible to the end user can
23358 be used to hold quota values that are looked up in the expansion. When delivery
23359 fails because this quota is exceeded, the handling of the error is as for
23360 system quota failures.
23362 By default, Exim's quota checking mimics system quotas, and restricts the
23363 mailbox to the specified maximum size, though the value is not accurate to the
23364 last byte, owing to separator lines and additional headers that may get added
23365 during message delivery. When a mailbox is nearly full, large messages may get
23366 refused even though small ones are accepted, because the size of the current
23367 message is added to the quota when the check is made. This behaviour can be
23368 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23369 for exceeding the quota does not include the current message. Thus, deliveries
23370 continue until the quota has been exceeded; thereafter, no further messages are
23371 delivered. See also &%quota_warn_threshold%&.
23374 .option quota_directory appendfile string&!! unset
23375 This option defines the directory to check for quota purposes when delivering
23376 into individual files. The default is the delivery directory, or, if a file
23377 called &_maildirfolder_& exists in a maildir directory, the parent of the
23378 delivery directory.
23381 .option quota_filecount appendfile string&!! 0
23382 This option applies when the &%directory%& option is set. It limits the total
23383 number of files in the directory (compare the inode limit in system quotas). It
23384 can only be used if &%quota%& is also set. The value is expanded; an expansion
23385 failure causes delivery to be deferred. A value of zero is interpreted as
23388 The option modifier &%no_check%& can be used to force delivery even if the over
23389 quota condition is met. The quota gets updated as usual.
23391 .option quota_is_inclusive appendfile boolean true
23392 See &%quota%& above.
23395 .option quota_size_regex appendfile string unset
23396 This option applies when one of the delivery modes that writes a separate file
23397 for each message is being used. When Exim wants to find the size of one of
23398 these files in order to test the quota, it first checks &%quota_size_regex%&.
23399 If this is set to a regular expression that matches the filename, and it
23400 captures one string, that string is interpreted as a representation of the
23401 file's size. The value of &%quota_size_regex%& is not expanded.
23403 This feature is useful only when users have no shell access to their mailboxes
23404 &-- otherwise they could defeat the quota simply by renaming the files. This
23405 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23406 the file length to the filename. For example:
23408 maildir_tag = ,S=$message_size
23409 quota_size_regex = ,S=(\d+)
23411 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23412 number of lines in the message.
23414 The regular expression should not assume that the length is at the end of the
23415 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23416 sometimes add other information onto the ends of message filenames.
23418 Section &<<SECID136>>& contains further information.
23420 This option should not be used when other message-handling software
23421 may duplicate messages by making hardlinks to the files. When that is done Exim
23422 will count the message size once for each filename, in contrast with the actual
23423 disk usage. When the option is not set, calculating total usage requires
23424 a system-call per file to get the size; the number of links is then available also
23425 as is used to adjust the effective size.
23428 .option quota_warn_message appendfile string&!! "see below"
23429 See below for the use of this option. If it is not set when
23430 &%quota_warn_threshold%& is set, it defaults to
23432 quota_warn_message = "\
23433 To: $local_part@$domain\n\
23434 Subject: Your mailbox\n\n\
23435 This message is automatically created \
23436 by mail delivery software.\n\n\
23437 The size of your mailbox has exceeded \
23438 a warning threshold that is\n\
23439 set by the system administrator.\n"
23443 .option quota_warn_threshold appendfile string&!! 0
23444 .cindex "quota" "warning threshold"
23445 .cindex "mailbox" "size warning"
23446 .cindex "size" "of mailbox"
23447 This option is expanded in the same way as &%quota%& (see above). If the
23448 resulting value is greater than zero, and delivery of the message causes the
23449 size of the file or total space in the directory tree to cross the given
23450 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23451 may be specified as a percentage of it by following the value with a percent
23455 quota_warn_threshold = 75%
23457 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23458 percent sign is ignored.
23460 The warning message itself is specified by the &%quota_warn_message%& option,
23461 and it must start with a &'To:'& header line containing the recipient(s) of the
23462 warning message. These do not necessarily have to include the recipient(s) of
23463 the original message. A &'Subject:'& line should also normally be supplied. You
23464 can include any other header lines that you want. If you do not include a
23465 &'From:'& line, the default is:
23467 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23469 .oindex &%errors_reply_to%&
23470 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23473 The &%quota%& option does not have to be set in order to use this option; they
23474 are independent of one another except when the threshold is specified as a
23478 .option use_bsmtp appendfile boolean false
23479 .cindex "envelope from"
23480 .cindex "envelope sender"
23481 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23482 format, with the envelope sender and recipient(s) included as SMTP commands. If
23483 you want to include a leading HELO command with such messages, you can do
23484 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23485 for details of batch SMTP.
23488 .option use_crlf appendfile boolean false
23489 .cindex "carriage return"
23491 This option causes lines to be terminated with the two-character CRLF sequence
23492 (carriage return, linefeed) instead of just a linefeed character. In the case
23493 of batched SMTP, the byte sequence written to the file is then an exact image
23494 of what would be sent down a real SMTP connection.
23496 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23497 (which are used to supply the traditional &"From&~"& and blank line separators
23498 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23499 carriage return characters if these are needed. In cases where these options
23500 have non-empty defaults, the values end with a single linefeed, so they must be
23501 changed to end with &`\r\n`& if &%use_crlf%& is set.
23504 .option use_fcntl_lock appendfile boolean "see below"
23505 This option controls the use of the &[fcntl()]& function to lock a file for
23506 exclusive use when a message is being appended. It is set by default unless
23507 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23508 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23509 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23512 .option use_flock_lock appendfile boolean false
23513 This option is provided to support the use of &[flock()]& for file locking, for
23514 the few situations where it is needed. Most modern operating systems support
23515 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23516 each other. Exim uses &[fcntl()]& locking by default.
23518 This option is required only if you are using an operating system where
23519 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23520 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23521 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23523 .cindex "Solaris" "&[flock()]& support"
23524 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23525 have it (and some, I think, provide a not quite right version built on top of
23526 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23527 the ability to use it, and any attempt to do so will cause a configuration
23530 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23531 is just being mapped onto &[fcntl()]& by the OS).
23534 .option use_lockfile appendfile boolean "see below"
23535 If this option is turned off, Exim does not attempt to create a lock file when
23536 appending to a mailbox file. In this situation, the only locking is by
23537 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23538 sure that every MUA that is ever going to look at your users' mailboxes uses
23539 &[fcntl()]& rather than a lock file, and even then only when you are not
23540 delivering over NFS from more than one host.
23542 .cindex "NFS" "lock file"
23543 In order to append to an NFS file safely from more than one host, it is
23544 necessary to take out a lock &'before'& opening the file, and the lock file
23545 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23548 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23549 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23550 except when &%mbx_format%& is set.
23553 .option use_mbx_lock appendfile boolean "see below"
23554 This option is available only if Exim has been compiled with SUPPORT_MBX
23555 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23556 locking rules be used. It is set by default if &%mbx_format%& is set and none
23557 of the locking options are mentioned in the configuration. The locking rules
23558 are the same as are used by the &'c-client'& library that underlies Pine and
23559 the IMAP4 and POP daemons that come with it (see the discussion below). The
23560 rules allow for shared access to the mailbox. However, this kind of locking
23561 does not work when the mailbox is NFS mounted.
23563 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23564 &%use_flock_lock%& to control what kind of locking is used in implementing the
23565 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23566 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23571 .section "Operational details for appending" "SECTopappend"
23572 .cindex "appending to a file"
23573 .cindex "file" "appending"
23574 Before appending to a file, the following preparations are made:
23577 If the name of the file is &_/dev/null_&, no action is taken, and a success
23581 .cindex "directory creation"
23582 If any directories on the file's path are missing, Exim creates them if the
23583 &%create_directory%& option is set. A created directory's mode is given by the
23584 &%directory_mode%& option.
23587 If &%file_format%& is set, the format of an existing file is checked. If this
23588 indicates that a different transport should be used, control is passed to that
23592 .cindex "file" "locking"
23593 .cindex "locking files"
23594 .cindex "NFS" "lock file"
23595 If &%use_lockfile%& is set, a lock file is built in a way that will work
23596 reliably over NFS, as follows:
23599 Create a &"hitching post"& file whose name is that of the lock file with the
23600 current time, primary host name, and process id added, by opening for writing
23601 as a new file. If this fails with an access error, delivery is deferred.
23603 Close the hitching post file, and hard link it to the lock filename.
23605 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23606 Unlink the hitching post name.
23608 Otherwise, use &[stat()]& to get information about the hitching post file, and
23609 then unlink hitching post name. If the number of links is exactly two, creation
23610 of the lock file succeeded but something (for example, an NFS server crash and
23611 restart) caused this fact not to be communicated to the &[link()]& call.
23613 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23614 up to &%lock_retries%& times. However, since any program that writes to a
23615 mailbox should complete its task very quickly, it is reasonable to time out old
23616 lock files that are normally the result of user agent and system crashes. If an
23617 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23618 it before trying again.
23622 A call is made to &[lstat()]& to discover whether the main file exists, and if
23623 so, what its characteristics are. If &[lstat()]& fails for any reason other
23624 than non-existence, delivery is deferred.
23627 .cindex "symbolic link" "to mailbox"
23628 .cindex "mailbox" "symbolic link"
23629 If the file does exist and is a symbolic link, delivery is deferred, unless the
23630 &%allow_symlink%& option is set, in which case the ownership of the link is
23631 checked, and then &[stat()]& is called to find out about the real file, which
23632 is then subjected to the checks below. The check on the top-level link
23633 ownership prevents one user creating a link for another's mailbox in a sticky
23634 directory, though allowing symbolic links in this case is definitely not a good
23635 idea. If there is a chain of symbolic links, the intermediate ones are not
23639 If the file already exists but is not a regular file, or if the file's owner
23640 and group (if the group is being checked &-- see &%check_group%& above) are
23641 different from the user and group under which the delivery is running,
23642 delivery is deferred.
23645 If the file's permissions are more generous than specified, they are reduced.
23646 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23647 is set false, in which case the delivery is tried using the existing
23651 The file's inode number is saved, and the file is then opened for appending.
23652 If this fails because the file has vanished, &(appendfile)& behaves as if it
23653 hadn't existed (see below). For any other failures, delivery is deferred.
23656 If the file is opened successfully, check that the inode number hasn't
23657 changed, that it is still a regular file, and that the owner and permissions
23658 have not changed. If anything is wrong, defer delivery and freeze the message.
23661 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23662 option is set. Otherwise, check that the file is being created in a permitted
23663 directory if the &%create_file%& option is set (deferring on failure), and then
23664 open for writing as a new file, with the O_EXCL and O_CREAT options,
23665 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23666 set). In this case, which can happen if the link points to a non-existent file,
23667 the file is opened for writing using O_CREAT but not O_EXCL, because
23668 that prevents link following.
23671 .cindex "loop" "while file testing"
23672 If opening fails because the file exists, obey the tests given above for
23673 existing files. However, to avoid looping in a situation where the file is
23674 being continuously created and destroyed, the exists/not-exists loop is broken
23675 after 10 repetitions, and the message is then frozen.
23678 If opening fails with any other error, defer delivery.
23681 .cindex "file" "locking"
23682 .cindex "locking files"
23683 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23684 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23685 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23686 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23687 file, and an exclusive lock on the file whose name is
23689 /tmp/.<device-number>.<inode-number>
23691 using the device and inode numbers of the open mailbox file, in accordance with
23692 the MBX locking rules. This file is created with a mode that is specified by
23693 the &%lockfile_mode%& option.
23695 If Exim fails to lock the file, there are two possible courses of action,
23696 depending on the value of the locking timeout. This is obtained from
23697 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23699 If the timeout value is zero, the file is closed, Exim waits for
23700 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23701 to lock it again. This happens up to &%lock_retries%& times, after which the
23702 delivery is deferred.
23704 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23705 &[flock()]& are used (with the given timeout), so there has already been some
23706 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23707 immediately. It retries up to
23709 (lock_retries * lock_interval) / <timeout>
23711 times (rounded up).
23714 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23715 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23718 .section "Operational details for delivery to a new file" "SECTopdir"
23719 .cindex "delivery" "to single file"
23720 .cindex "&""From""& line"
23721 When the &%directory%& option is set instead of &%file%&, each message is
23722 delivered into a newly-created file or set of files. When &(appendfile)& is
23723 activated directly from a &(redirect)& router, neither &%file%& nor
23724 &%directory%& is normally set, because the path for delivery is supplied by the
23725 router. (See for example, the &(address_file)& transport in the default
23726 configuration.) In this case, delivery is to a new file if either the path name
23727 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23729 No locking is required while writing the message to a new file, so the various
23730 locking options of the transport are ignored. The &"From"& line that by default
23731 separates messages in a single file is not normally needed, nor is the escaping
23732 of message lines that start with &"From"&, and there is no need to ensure a
23733 newline at the end of each message. Consequently, the default values for
23734 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
23735 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
23737 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
23738 the files in the delivery directory by default. However, you can specify a
23739 different directory by setting &%quota_directory%&. Also, for maildir
23740 deliveries (see below) the &_maildirfolder_& convention is honoured.
23743 .cindex "maildir format"
23744 .cindex "mailstore format"
23745 There are three different ways in which delivery to individual files can be
23746 done, controlled by the settings of the &%maildir_format%& and
23747 &%mailstore_format%& options. Note that code to support maildir or mailstore
23748 formats is not included in the binary unless SUPPORT_MAILDIR or
23749 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
23751 .cindex "directory creation"
23752 In all three cases an attempt is made to create the directory and any necessary
23753 sub-directories if they do not exist, provided that the &%create_directory%&
23754 option is set (the default). The location of a created directory can be
23755 constrained by setting &%create_file%&. A created directory's mode is given by
23756 the &%directory_mode%& option. If creation fails, or if the
23757 &%create_directory%& option is not set when creation is required, delivery is
23762 .section "Maildir delivery" "SECTmaildirdelivery"
23763 .cindex "maildir format" "description of"
23764 If the &%maildir_format%& option is true, Exim delivers each message by writing
23765 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
23766 directory that is defined by the &%directory%& option (the &"delivery
23767 directory"&). If the delivery is successful, the file is renamed into the
23768 &_new_& subdirectory.
23770 In the filename, <&'stime'&> is the current time of day in seconds, and
23771 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
23772 Exim checks that the time-of-day clock has moved on by at least one microsecond
23773 before terminating the delivery process. This guarantees uniqueness for the
23774 filename. However, as a precaution, Exim calls &[stat()]& for the file before
23775 opening it. If any response other than ENOENT (does not exist) is given,
23776 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
23778 Before Exim carries out a maildir delivery, it ensures that subdirectories
23779 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
23780 do not exist, Exim tries to create them and any superior directories in their
23781 path, subject to the &%create_directory%& and &%create_file%& options. If the
23782 &%maildirfolder_create_regex%& option is set, and the regular expression it
23783 contains matches the delivery directory, Exim also ensures that a file called
23784 &_maildirfolder_& exists in the delivery directory. If a missing directory or
23785 &_maildirfolder_& file cannot be created, delivery is deferred.
23787 These features make it possible to use Exim to create all the necessary files
23788 and directories in a maildir mailbox, including subdirectories for maildir++
23789 folders. Consider this example:
23791 maildir_format = true
23792 directory = /var/mail/$local_part_data\
23793 ${if eq{$local_part_suffix}{}{}\
23794 {/.${substr_1:$local_part_suffix}}}
23795 maildirfolder_create_regex = /\.[^/]+$
23797 If &$local_part_suffix$& is empty (there was no suffix for the local part),
23798 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
23799 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
23800 not match this name, so Exim will not look for or create the file
23801 &_/var/mail/pimbo/maildirfolder_&, though it will create
23802 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
23804 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
23805 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
23806 does match &%maildirfolder_create_regex%&. In this case, Exim will create
23807 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
23808 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
23810 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
23811 not inadvertently match the toplevel maildir directory, because a
23812 &_maildirfolder_& file at top level would completely break quota calculations.
23814 .cindex "quota" "in maildir delivery"
23815 .cindex "maildir++"
23816 If Exim is required to check a &%quota%& setting before a maildir delivery, and
23817 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
23818 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
23819 Exim assumes the directory is a maildir++ folder directory, which is one level
23820 down from the user's top level mailbox directory. This causes it to start at
23821 the parent directory instead of the current directory when calculating the
23822 amount of space used.
23824 One problem with delivering into a multi-file mailbox is that it is
23825 computationally expensive to compute the size of the mailbox for quota
23826 checking. Various approaches have been taken to reduce the amount of work
23827 needed. The next two sections describe two of them. A third alternative is to
23828 use some external process for maintaining the size data, and use the expansion
23829 of the &%mailbox_size%& option as a way of importing it into Exim.
23834 .section "Using tags to record message sizes" "SECID135"
23835 If &%maildir_tag%& is set, the string is expanded for each delivery.
23836 When the maildir file is renamed into the &_new_& sub-directory, the
23837 tag is added to its name. However, if adding the tag takes the length of the
23838 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
23839 the tag is dropped and the maildir file is created with no tag.
23842 .vindex "&$message_size$&"
23843 Tags can be used to encode the size of files in their names; see
23844 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
23845 happens after the message has been written. The value of the &$message_size$&
23846 variable is set to the number of bytes actually written. If the expansion is
23847 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
23848 be deferred. The expanded tag may contain any printing characters except &"/"&.
23849 Non-printing characters in the string are ignored; if the resulting string is
23850 empty, it is ignored. If it starts with an alphanumeric character, a leading
23851 colon is inserted; this default has not proven to be the path that popular
23852 maildir implementations have chosen (but changing it in Exim would break
23853 backwards compatibility).
23855 For one common implementation, you might set:
23857 maildir_tag = ,S=${message_size}
23859 but you should check the documentation of the other software to be sure.
23861 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
23862 as this allows Exim to extract the size from your tag, instead of having to
23863 &[stat()]& each message file.
23866 .section "Using a maildirsize file" "SECID136"
23867 .cindex "quota" "in maildir delivery"
23868 .cindex "maildir format" "&_maildirsize_& file"
23869 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
23870 storing quota and message size information in a file called &_maildirsize_&
23871 within the toplevel maildir directory. If this file does not exist, Exim
23872 creates it, setting the quota from the &%quota%& option of the transport. If
23873 the maildir directory itself does not exist, it is created before any attempt
23874 to write a &_maildirsize_& file.
23876 The &_maildirsize_& file is used to hold information about the sizes of
23877 messages in the maildir, thus speeding up quota calculations. The quota value
23878 in the file is just a cache; if the quota is changed in the transport, the new
23879 value overrides the cached value when the next message is delivered. The cache
23880 is maintained for the benefit of other programs that access the maildir and
23881 need to know the quota.
23883 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
23884 file is maintained (with a zero quota setting), but no quota is imposed.
23886 A regular expression is available for controlling which directories in the
23887 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
23888 See the description of the &%maildir_quota_directory_regex%& option above for
23892 .section "Mailstore delivery" "SECID137"
23893 .cindex "mailstore format" "description of"
23894 If the &%mailstore_format%& option is true, each message is written as two
23895 files in the given directory. A unique base name is constructed from the
23896 message id and the current delivery process, and the files that are written use
23897 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
23898 contains the message's envelope, and the &_.msg_& file contains the message
23899 itself. The base name is placed in the variable &$mailstore_basename$&.
23901 During delivery, the envelope is first written to a file with the suffix
23902 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
23903 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
23904 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
23905 file before accessing either of them. An alternative approach is to wait for
23906 the absence of a &_.tmp_& file.
23908 The envelope file starts with any text defined by the &%mailstore_prefix%&
23909 option, expanded and terminated by a newline if there isn't one. Then follows
23910 the sender address on one line, then all the recipient addresses, one per line.
23911 There can be more than one recipient only if the &%batch_max%& option is set
23912 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
23913 appended to the file, followed by a newline if it does not end with one.
23915 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
23916 failure, it is ignored. Other expansion errors are treated as serious
23917 configuration errors, and delivery is deferred. The variable
23918 &$mailstore_basename$& is available for use during these expansions.
23921 .section "Non-special new file delivery" "SECID138"
23922 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
23923 file is created directly in the named directory. For example, when delivering
23924 messages into files in batched SMTP format for later delivery to some host (see
23925 section &<<SECTbatchSMTP>>&), a setting such as
23927 directory = /var/bsmtp/$host
23929 might be used. A message is written to a file with a temporary name, which is
23930 then renamed when the delivery is complete. The final name is obtained by
23931 expanding the contents of the &%directory_file%& option.
23932 .ecindex IIDapptra1
23933 .ecindex IIDapptra2
23940 . ////////////////////////////////////////////////////////////////////////////
23941 . ////////////////////////////////////////////////////////////////////////////
23943 .chapter "The autoreply transport" "CHID8"
23944 .scindex IIDauttra1 "transports" "&(autoreply)&"
23945 .scindex IIDauttra2 "&(autoreply)& transport"
23946 The &(autoreply)& transport is not a true transport in that it does not cause
23947 the message to be transmitted. Instead, it generates a new mail message as an
23948 automatic reply to the incoming message. &'References:'& and
23949 &'Auto-Submitted:'& header lines are included. These are constructed according
23950 to the rules in RFCs 2822 and 3834, respectively.
23952 If the router that passes the message to this transport does not have the
23953 &%unseen%& option set, the original message (for the current recipient) is not
23954 delivered anywhere. However, when the &%unseen%& option is set on the router
23955 that passes the message to this transport, routing of the address continues, so
23956 another router can set up a normal message delivery.
23959 The &(autoreply)& transport is usually run as the result of mail filtering, a
23960 &"vacation"& message being the standard example. However, it can also be run
23961 directly from a router like any other transport. To reduce the possibility of
23962 message cascades, messages created by the &(autoreply)& transport always have
23963 empty envelope sender addresses, like bounce messages.
23965 The parameters of the message to be sent can be specified in the configuration
23966 by options described below. However, these are used only when the address
23967 passed to the transport does not contain its own reply information. When the
23968 transport is run as a consequence of a
23970 or &%vacation%& command in a filter file, the parameters of the message are
23971 supplied by the filter, and passed with the address. The transport's options
23972 that define the message are then ignored (so they are not usually set in this
23973 case). The message is specified entirely by the filter or by the transport; it
23974 is never built from a mixture of options. However, the &%file_optional%&,
23975 &%mode%&, and &%return_message%& options apply in all cases.
23977 &(Autoreply)& is implemented as a local transport. When used as a result of a
23978 command in a user's filter file, &(autoreply)& normally runs under the uid and
23979 gid of the user, and with appropriate current and home directories (see chapter
23980 &<<CHAPenvironment>>&).
23982 There is a subtle difference between routing a message to a &(pipe)& transport
23983 that generates some text to be returned to the sender, and routing it to an
23984 &(autoreply)& transport. This difference is noticeable only if more than one
23985 address from the same message is so handled. In the case of a pipe, the
23986 separate outputs from the different addresses are gathered up and returned to
23987 the sender in a single message, whereas if &(autoreply)& is used, a separate
23988 message is generated for each address that is passed to it.
23990 Non-printing characters are not permitted in the header lines generated for the
23991 message that &(autoreply)& creates, with the exception of newlines that are
23992 immediately followed by white space. If any non-printing characters are found,
23993 the transport defers.
23994 Whether characters with the top bit set count as printing characters or not is
23995 controlled by the &%print_topbitchars%& global option.
23997 If any of the generic options for manipulating headers (for example,
23998 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
23999 of the original message that is included in the generated message when
24000 &%return_message%& is set. They do not apply to the generated message itself.
24002 .vindex "&$sender_address$&"
24003 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24004 the message, indicating that there were no recipients, it does not treat this
24005 as an error. This means that autoreplies sent to &$sender_address$& when this
24006 is empty (because the incoming message is a bounce message) do not cause
24007 problems. They are just discarded.
24011 .section "Private options for autoreply" "SECID139"
24012 .cindex "options" "&(autoreply)& transport"
24014 .option bcc autoreply string&!! unset
24015 This specifies the addresses that are to receive &"blind carbon copies"& of the
24016 message when the message is specified by the transport.
24019 .option cc autoreply string&!! unset
24020 This specifies recipients of the message and the contents of the &'Cc:'& header
24021 when the message is specified by the transport.
24024 .option file autoreply string&!! unset
24025 The contents of the file are sent as the body of the message when the message
24026 is specified by the transport. If both &%file%& and &%text%& are set, the text
24027 string comes first.
24030 .option file_expand autoreply boolean false
24031 If this is set, the contents of the file named by the &%file%& option are
24032 subjected to string expansion as they are added to the message.
24035 .option file_optional autoreply boolean false
24036 If this option is true, no error is generated if the file named by the &%file%&
24037 option or passed with the address does not exist or cannot be read.
24040 .option from autoreply string&!! unset
24041 This specifies the contents of the &'From:'& header when the message is
24042 specified by the transport.
24045 .option headers autoreply string&!! unset
24046 This specifies additional RFC 2822 headers that are to be added to the message
24047 when the message is specified by the transport. Several can be given by using
24048 &"\n"& to separate them. There is no check on the format.
24051 .option log autoreply string&!! unset
24052 This option names a file in which a record of every message sent is logged when
24053 the message is specified by the transport.
24056 .option mode autoreply "octal integer" 0600
24057 If either the log file or the &"once"& file has to be created, this mode is
24061 .option never_mail autoreply "address list&!!" unset
24062 If any run of the transport creates a message with a recipient that matches any
24063 item in the list, that recipient is quietly discarded. If all recipients are
24064 discarded, no message is created. This applies both when the recipients are
24065 generated by a filter and when they are specified in the transport.
24069 .option once autoreply string&!! unset
24070 This option names a file or DBM database in which a record of each &'To:'&
24071 recipient is kept when the message is specified by the transport. &*Note*&:
24072 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24074 If &%once%& is unset, or is set to an empty string, the message is always sent.
24075 By default, if &%once%& is set to a non-empty filename, the message
24076 is not sent if a potential recipient is already listed in the database.
24077 However, if the &%once_repeat%& option specifies a time greater than zero, the
24078 message is sent if that much time has elapsed since a message was last sent to
24079 this recipient. A setting of zero time for &%once_repeat%& (the default)
24080 prevents a message from being sent a second time &-- in this case, zero means
24083 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24084 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24085 greater than zero, it changes the way Exim implements the &%once%& option.
24086 Instead of using a DBM file to record every recipient it sends to, it uses a
24087 regular file, whose size will never get larger than the given value.
24089 In the file, Exim keeps a linear list of recipient addresses and the times at
24090 which they were sent messages. If the file is full when a new address needs to
24091 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24092 means that a given recipient may receive multiple messages, but at
24093 unpredictable intervals that depend on the rate of turnover of addresses in the
24094 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24097 .option once_file_size autoreply integer 0
24098 See &%once%& above.
24101 .option once_repeat autoreply time&!! 0s
24102 See &%once%& above.
24103 After expansion, the value of this option must be a valid time value.
24106 .option reply_to autoreply string&!! unset
24107 This specifies the contents of the &'Reply-To:'& header when the message is
24108 specified by the transport.
24111 .option return_message autoreply boolean false
24112 If this is set, a copy of the original message is returned with the new
24113 message, subject to the maximum size set in the &%return_size_limit%& global
24114 configuration option.
24117 .option subject autoreply string&!! unset
24118 This specifies the contents of the &'Subject:'& header when the message is
24119 specified by the transport. It is tempting to quote the original subject in
24120 automatic responses. For example:
24122 subject = Re: $h_subject:
24124 There is a danger in doing this, however. It may allow a third party to
24125 subscribe your users to an opt-in mailing list, provided that the list accepts
24126 bounce messages as subscription confirmations. Well-managed lists require a
24127 non-bounce message to confirm a subscription, so the danger is relatively
24132 .option text autoreply string&!! unset
24133 This specifies a single string to be used as the body of the message when the
24134 message is specified by the transport. If both &%text%& and &%file%& are set,
24135 the text comes first.
24138 .option to autoreply string&!! unset
24139 This specifies recipients of the message and the contents of the &'To:'& header
24140 when the message is specified by the transport.
24141 .ecindex IIDauttra1
24142 .ecindex IIDauttra2
24147 . ////////////////////////////////////////////////////////////////////////////
24148 . ////////////////////////////////////////////////////////////////////////////
24150 .chapter "The lmtp transport" "CHAPLMTP"
24151 .cindex "transports" "&(lmtp)&"
24152 .cindex "&(lmtp)& transport"
24153 .cindex "LMTP" "over a pipe"
24154 .cindex "LMTP" "over a socket"
24155 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24157 or by interacting with a Unix domain socket.
24158 This transport is something of a cross between the &(pipe)& and &(smtp)&
24159 transports. Exim also has support for using LMTP over TCP/IP; this is
24160 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24161 to be of minority interest, the default build-time configure in &_src/EDITME_&
24162 has it commented out. You need to ensure that
24166 .cindex "options" "&(lmtp)& transport"
24167 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24168 included in the Exim binary. The private options of the &(lmtp)& transport are
24171 .option batch_id lmtp string&!! unset
24172 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24175 .option batch_max lmtp integer 1
24176 This limits the number of addresses that can be handled in a single delivery.
24177 Most LMTP servers can handle several addresses at once, so it is normally a
24178 good idea to increase this value. See the description of local delivery
24179 batching in chapter &<<CHAPbatching>>&.
24182 .option command lmtp string&!! unset
24183 This option must be set if &%socket%& is not set. The string is a command which
24184 is run in a separate process. It is split up into a command name and list of
24185 arguments, each of which is separately expanded (so expansion cannot change the
24186 number of arguments). The command is run directly, not via a shell. The message
24187 is passed to the new process using the standard input and output to operate the
24190 .option ignore_quota lmtp boolean false
24191 .cindex "LMTP" "ignoring quota errors"
24192 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24193 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24194 in its response to the LHLO command.
24196 .option socket lmtp string&!! unset
24197 This option must be set if &%command%& is not set. The result of expansion must
24198 be the name of a Unix domain socket. The transport connects to the socket and
24199 delivers the message to it using the LMTP protocol.
24202 .option timeout lmtp time 5m
24203 The transport is aborted if the created process or Unix domain socket does not
24204 respond to LMTP commands or message input within this timeout. Delivery
24205 is deferred, and will be tried again later. Here is an example of a typical
24210 command = /some/local/lmtp/delivery/program
24214 This delivers up to 20 addresses at a time, in a mixture of domains if
24215 necessary, running as the user &'exim'&.
24219 . ////////////////////////////////////////////////////////////////////////////
24220 . ////////////////////////////////////////////////////////////////////////////
24222 .chapter "The pipe transport" "CHAPpipetransport"
24223 .scindex IIDpiptra1 "transports" "&(pipe)&"
24224 .scindex IIDpiptra2 "&(pipe)& transport"
24225 The &(pipe)& transport is used to deliver messages via a pipe to a command
24226 running in another process. One example is the use of &(pipe)& as a
24227 pseudo-remote transport for passing messages to some other delivery mechanism
24228 (such as UUCP). Another is the use by individual users to automatically process
24229 their incoming messages. The &(pipe)& transport can be used in one of the
24233 .vindex "&$local_part$&"
24234 A router routes one address to a transport in the normal way, and the
24235 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24236 contains the local part of the address (as usual), and the command that is run
24237 is specified by the &%command%& option on the transport.
24239 .vindex "&$pipe_addresses$&"
24240 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24241 transport can handle more than one address in a single run. In this case, when
24242 more than one address is routed to the transport, &$local_part$& is not set
24243 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24244 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24245 that are routed to the transport.
24247 .vindex "&$address_pipe$&"
24248 A router redirects an address directly to a pipe command (for example, from an
24249 alias or forward file). In this case, &$address_pipe$& contains the text of the
24250 pipe command, and the &%command%& option on the transport is ignored unless
24251 &%force_command%& is set. If only one address is being transported
24252 (&%batch_max%& is not greater than one, or only one address was redirected to
24253 this pipe command), &$local_part$& contains the local part that was redirected.
24257 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24258 deliver messages over pipes using the LMTP interactive protocol. This is
24259 implemented by the &(lmtp)& transport.
24261 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24262 &_.forward_& file, the command runs under the uid and gid of that user. In
24263 other cases, the uid and gid have to be specified explicitly, either on the
24264 transport or on the router that handles the address. Current and &"home"&
24265 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24266 details of the local delivery environment and chapter &<<CHAPbatching>>&
24267 for a discussion of local delivery batching.
24269 .cindex "tainted data" "in pipe command"
24270 .cindex pipe "tainted data"
24271 Tainted data may not be used for the command name.
24274 .section "Concurrent delivery" "SECID140"
24275 If two messages arrive at almost the same time, and both are routed to a pipe
24276 delivery, the two pipe transports may be run concurrently. You must ensure that
24277 any pipe commands you set up are robust against this happening. If the commands
24278 write to a file, the &%exim_lock%& utility might be of use.
24279 Alternatively the &%max_parallel%& option could be used with a value
24280 of "1" to enforce serialization.
24285 .section "Returned status and data" "SECID141"
24286 .cindex "&(pipe)& transport" "returned data"
24287 If the command exits with a non-zero return code, the delivery is deemed to
24288 have failed, unless either the &%ignore_status%& option is set (in which case
24289 the return code is treated as zero), or the return code is one of those listed
24290 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24291 later"&. In this case, delivery is deferred. Details of a permanent failure are
24292 logged, but are not included in the bounce message, which merely contains
24293 &"local delivery failed"&.
24295 If the command exits on a signal and the &%freeze_signal%& option is set then
24296 the message will be frozen in the queue. If that option is not set, a bounce
24297 will be sent as normal.
24299 If the return code is greater than 128 and the command being run is a shell
24300 script, it normally means that the script was terminated by a signal whose
24301 value is the return code minus 128. The &%freeze_signal%& option does not
24302 apply in this case.
24304 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24305 return code is set to 127. This is the value that a shell returns if it is
24306 asked to run a non-existent command. The wording for the log line suggests that
24307 a non-existent command may be the problem.
24309 The &%return_output%& option can affect the result of a pipe delivery. If it is
24310 set and the command produces any output on its standard output or standard
24311 error streams, the command is considered to have failed, even if it gave a zero
24312 return code or if &%ignore_status%& is set. The output from the command is
24313 included as part of the bounce message. The &%return_fail_output%& option is
24314 similar, except that output is returned only when the command exits with a
24315 failure return code, that is, a value other than zero or a code that matches
24320 .section "How the command is run" "SECThowcommandrun"
24321 .cindex "&(pipe)& transport" "path for command"
24322 The command line is (by default) broken down into a command name and arguments
24323 by the &(pipe)& transport itself. The &%allow_commands%& and
24324 &%restrict_to_path%& options can be used to restrict the commands that may be
24327 .cindex "quoting" "in pipe command"
24328 Unquoted arguments are delimited by white space. If an argument appears in
24329 double quotes, backslash is interpreted as an escape character in the usual
24330 way. If an argument appears in single quotes, no escaping is done.
24332 String expansion is applied to the command line except when it comes from a
24333 traditional &_.forward_& file (commands from a filter file are expanded). The
24334 expansion is applied to each argument in turn rather than to the whole line.
24335 For this reason, any string expansion item that contains white space must be
24336 quoted so as to be contained within a single argument. A setting such as
24338 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24340 will not work, because the expansion item gets split between several
24341 arguments. You have to write
24343 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24345 to ensure that it is all in one argument. The expansion is done in this way,
24346 argument by argument, so that the number of arguments cannot be changed as a
24347 result of expansion, and quotes or backslashes in inserted variables do not
24348 interact with external quoting. However, this leads to problems if you want to
24349 generate multiple arguments (or the command name plus arguments) from a single
24350 expansion. In this situation, the simplest solution is to use a shell. For
24353 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24356 .cindex "transport" "filter"
24357 .cindex "filter" "transport filter"
24358 .vindex "&$pipe_addresses$&"
24359 Special handling takes place when an argument consists of precisely the text
24360 &`$pipe_addresses`& (no quotes).
24361 This is not a general expansion variable; the only
24362 place this string is recognized is when it appears as an argument for a pipe or
24363 transport filter command. It causes each address that is being handled to be
24364 inserted in the argument list at that point &'as a separate argument'&. This
24365 avoids any problems with spaces or shell metacharacters, and is of use when a
24366 &(pipe)& transport is handling groups of addresses in a batch.
24368 If &%force_command%& is enabled on the transport, special handling takes place
24369 for an argument that consists of precisely the text &`$address_pipe`&. It
24370 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24371 argument is inserted in the argument list at that point
24372 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24373 the only item in the argument; in fact, if it were then &%force_command%&
24374 should behave as a no-op. Rather, it should be used to adjust the command
24375 run while preserving the argument vector separation.
24377 After splitting up into arguments and expansion, the resulting command is run
24378 in a subprocess directly from the transport, &'not'& under a shell. The
24379 message that is being delivered is supplied on the standard input, and the
24380 standard output and standard error are both connected to a single pipe that is
24381 read by Exim. The &%max_output%& option controls how much output the command
24382 may produce, and the &%return_output%& and &%return_fail_output%& options
24383 control what is done with it.
24385 Not running the command under a shell (by default) lessens the security risks
24386 in cases when a command from a user's filter file is built out of data that was
24387 taken from an incoming message. If a shell is required, it can of course be
24388 explicitly specified as the command to be run. However, there are circumstances
24389 where existing commands (for example, in &_.forward_& files) expect to be run
24390 under a shell and cannot easily be modified. To allow for these cases, there is
24391 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24392 works. Instead of breaking up the command line as just described, it expands it
24393 as a single string and passes the result to &_/bin/sh_&. The
24394 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24395 with &%use_shell%&, and the whole mechanism is inherently less secure.
24399 .section "Environment variables" "SECTpipeenv"
24400 .cindex "&(pipe)& transport" "environment for command"
24401 .cindex "environment" "&(pipe)& transport"
24402 The environment variables listed below are set up when the command is invoked.
24403 This list is a compromise for maximum compatibility with other MTAs. Note that
24404 the &%environment%& option can be used to add additional variables to this
24405 environment. The environment for the &(pipe)& transport is not subject
24406 to the &%add_environment%& and &%keep_environment%& main config options.
24408 &`DOMAIN `& the domain of the address
24409 &`HOME `& the home directory, if set
24410 &`HOST `& the host name when called from a router (see below)
24411 &`LOCAL_PART `& see below
24412 &`LOCAL_PART_PREFIX `& see below
24413 &`LOCAL_PART_SUFFIX `& see below
24414 &`LOGNAME `& see below
24415 &`MESSAGE_ID `& Exim's local ID for the message
24416 &`PATH `& as specified by the &%path%& option below
24417 &`QUALIFY_DOMAIN `& the sender qualification domain
24418 &`RECIPIENT `& the complete recipient address
24419 &`SENDER `& the sender of the message (empty if a bounce)
24420 &`SHELL `& &`/bin/sh`&
24421 &`TZ `& the value of the &%timezone%& option, if set
24422 &`USER `& see below
24424 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24425 router, LOCAL_PART is set to the local part of the address. When it is
24426 called as a result of a forward or alias expansion, LOCAL_PART is set to
24427 the local part of the address that was expanded. In both cases, any affixes are
24428 removed from the local part, and made available in LOCAL_PART_PREFIX and
24429 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24430 same value as LOCAL_PART for compatibility with other MTAs.
24433 HOST is set only when a &(pipe)& transport is called from a router that
24434 associates hosts with an address, typically when using &(pipe)& as a
24435 pseudo-remote transport. HOST is set to the first host name specified by
24439 If the transport's generic &%home_directory%& option is set, its value is used
24440 for the HOME environment variable. Otherwise, a home directory may be set
24441 by the router's &%transport_home_directory%& option, which defaults to the
24442 user's home directory if &%check_local_user%& is set.
24445 .section "Private options for pipe" "SECID142"
24446 .cindex "options" "&(pipe)& transport"
24450 .option allow_commands pipe "string list&!!" unset
24451 .cindex "&(pipe)& transport" "permitted commands"
24452 The string is expanded, and is then interpreted as a colon-separated list of
24453 permitted commands. If &%restrict_to_path%& is not set, the only commands
24454 permitted are those in the &%allow_commands%& list. They need not be absolute
24455 paths; the &%path%& option is still used for relative paths. If
24456 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24457 in the &%allow_commands%& list, or a name without any slashes that is found on
24458 the path. In other words, if neither &%allow_commands%& nor
24459 &%restrict_to_path%& is set, there is no restriction on the command, but
24460 otherwise only commands that are permitted by one or the other are allowed. For
24463 allow_commands = /usr/bin/vacation
24465 and &%restrict_to_path%& is not set, the only permitted command is
24466 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24467 &%use_shell%& is set.
24470 .option batch_id pipe string&!! unset
24471 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24474 .option batch_max pipe integer 1
24475 This limits the number of addresses that can be handled in a single delivery.
24476 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24479 .option check_string pipe string unset
24480 As &(pipe)& writes the message, the start of each line is tested for matching
24481 &%check_string%&, and if it does, the initial matching characters are replaced
24482 by the contents of &%escape_string%&, provided both are set. The value of
24483 &%check_string%& is a literal string, not a regular expression, and the case of
24484 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24485 of &%check_string%& and &%escape_string%& are forced to values that implement
24486 the SMTP escaping protocol. Any settings made in the configuration file are
24490 .option command pipe string&!! unset
24491 This option need not be set when &(pipe)& is being used to deliver to pipes
24492 obtained directly from address redirections. In other cases, the option must be
24493 set, to provide a command to be run. It need not yield an absolute path (see
24494 the &%path%& option below). The command is split up into separate arguments by
24495 Exim, and each argument is separately expanded, as described in section
24496 &<<SECThowcommandrun>>& above.
24499 .option environment pipe string&!! unset
24500 .cindex "&(pipe)& transport" "environment for command"
24501 .cindex "environment" "&(pipe)& transport"
24502 This option is used to add additional variables to the environment in which the
24503 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24504 a string which is expanded, and then interpreted as a colon-separated list of
24505 environment settings of the form <&'name'&>=<&'value'&>.
24508 .option escape_string pipe string unset
24509 See &%check_string%& above.
24512 .option freeze_exec_fail pipe boolean false
24513 .cindex "exec failure"
24514 .cindex "failure of exec"
24515 .cindex "&(pipe)& transport" "failure of exec"
24516 Failure to exec the command in a pipe transport is by default treated like
24517 any other failure while running the command. However, if &%freeze_exec_fail%&
24518 is set, failure to exec is treated specially, and causes the message to be
24519 frozen, whatever the setting of &%ignore_status%&.
24522 .option freeze_signal pipe boolean false
24523 .cindex "signal exit"
24524 .cindex "&(pipe)& transport", "signal exit"
24525 Normally if the process run by a command in a pipe transport exits on a signal,
24526 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24527 frozen in Exim's queue instead.
24530 .option force_command pipe boolean false
24531 .cindex "force command"
24532 .cindex "&(pipe)& transport", "force command"
24533 Normally when a router redirects an address directly to a pipe command
24534 the &%command%& option on the transport is ignored. If &%force_command%&
24535 is set, the &%command%& option will used. This is especially
24536 useful for forcing a wrapper or additional argument to be added to the
24537 command. For example:
24539 command = /usr/bin/remote_exec myhost -- $address_pipe
24543 Note that &$address_pipe$& is handled specially in &%command%& when
24544 &%force_command%& is set, expanding out to the original argument vector as
24545 separate items, similarly to a Unix shell &`"$@"`& construct.
24548 .option ignore_status pipe boolean false
24549 If this option is true, the status returned by the subprocess that is set up to
24550 run the command is ignored, and Exim behaves as if zero had been returned.
24551 Otherwise, a non-zero status or termination by signal causes an error return
24552 from the transport unless the status value is one of those listed in
24553 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24555 &*Note*&: This option does not apply to timeouts, which do not return a status.
24556 See the &%timeout_defer%& option for how timeouts are handled.
24559 .option log_defer_output pipe boolean false
24560 .cindex "&(pipe)& transport" "logging output"
24561 If this option is set, and the status returned by the command is
24562 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24563 and any output was produced on stdout or stderr, the first line of it is
24564 written to the main log.
24567 .option log_fail_output pipe boolean false
24568 If this option is set, and the command returns any output on stdout or
24569 stderr, and also ends with a return code that is neither zero nor one of
24570 the return codes listed in &%temp_errors%& (that is, the delivery
24571 failed), the first line of output is written to the main log. This
24572 option and &%log_output%& are mutually exclusive. Only one of them may
24576 .option log_output pipe boolean false
24577 If this option is set and the command returns any output on stdout or
24578 stderr, the first line of output is written to the main log, whatever
24579 the return code. This option and &%log_fail_output%& are mutually
24580 exclusive. Only one of them may be set.
24583 .option max_output pipe integer 20K
24584 This specifies the maximum amount of output that the command may produce on its
24585 standard output and standard error file combined. If the limit is exceeded, the
24586 process running the command is killed. This is intended as a safety measure to
24587 catch runaway processes. The limit is applied independently of the settings of
24588 the options that control what is done with such output (for example,
24589 &%return_output%&). Because of buffering effects, the amount of output may
24590 exceed the limit by a small amount before Exim notices.
24593 .option message_prefix pipe string&!! "see below"
24594 The string specified here is expanded and output at the start of every message.
24595 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24598 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24602 .cindex "&%tmail%&"
24603 .cindex "&""From""& line"
24604 This is required by the commonly used &_/usr/bin/vacation_& program.
24605 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24606 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24611 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24612 &`\n`& to &`\r\n`& in &%message_prefix%&.
24615 .option message_suffix pipe string&!! "see below"
24616 The string specified here is expanded and output at the end of every message.
24617 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24618 The suffix can be suppressed by setting
24622 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24623 &`\n`& to &`\r\n`& in &%message_suffix%&.
24626 .option path pipe string&!! "/bin:/usr/bin"
24627 This option is expanded and
24628 specifies the string that is set up in the PATH environment
24629 variable of the subprocess.
24630 If the &%command%& option does not yield an absolute path name, the command is
24631 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24632 apply to a command specified as a transport filter.
24635 .option permit_coredump pipe boolean false
24636 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24637 a core-dump of a pipe command, enable this command. This enables core-dumps
24638 during delivery and affects both the Exim binary and the pipe command run.
24639 It is recommended that this option remain off unless and until you have a need
24640 for it and that this only be enabled when needed, as the risk of excessive
24641 resource consumption can be quite high. Note also that Exim is typically
24642 installed as a setuid binary and most operating systems will inhibit coredumps
24643 of these by default, so further OS-specific action may be required.
24646 .option pipe_as_creator pipe boolean false
24647 .cindex "uid (user id)" "local delivery"
24648 If the generic &%user%& option is not set and this option is true, the delivery
24649 process is run under the uid that was in force when Exim was originally called
24650 to accept the message. If the group id is not otherwise set (via the generic
24651 &%group%& option), the gid that was in force when Exim was originally called to
24652 accept the message is used.
24655 .option restrict_to_path pipe boolean false
24656 When this option is set, any command name not listed in &%allow_commands%& must
24657 contain no slashes. The command is searched for only in the directories listed
24658 in the &%path%& option. This option is intended for use in the case when a pipe
24659 command has been generated from a user's &_.forward_& file. This is usually
24660 handled by a &(pipe)& transport called &%address_pipe%&.
24663 .option return_fail_output pipe boolean false
24664 If this option is true, and the command produced any output and ended with a
24665 return code other than zero or one of the codes listed in &%temp_errors%& (that
24666 is, the delivery failed), the output is returned in the bounce message.
24667 However, if the message has a null sender (that is, it is itself a bounce
24668 message), output from the command is discarded. This option and
24669 &%return_output%& are mutually exclusive. Only one of them may be set.
24673 .option return_output pipe boolean false
24674 If this option is true, and the command produced any output, the delivery is
24675 deemed to have failed whatever the return code from the command, and the output
24676 is returned in the bounce message. Otherwise, the output is just discarded.
24677 However, if the message has a null sender (that is, it is a bounce message),
24678 output from the command is always discarded, whatever the setting of this
24679 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24680 of them may be set.
24684 .option temp_errors pipe "string list" "see below"
24685 .cindex "&(pipe)& transport" "temporary failure"
24686 This option contains either a colon-separated list of numbers, or a single
24687 asterisk. If &%ignore_status%& is false
24688 and &%return_output%& is not set,
24689 and the command exits with a non-zero return code, the failure is treated as
24690 temporary and the delivery is deferred if the return code matches one of the
24691 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24692 codes are treated as permanent errors. The default setting contains the codes
24693 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24694 compiled on a system that does not define these macros, it assumes values of 75
24695 and 73, respectively.
24698 .option timeout pipe time 1h
24699 If the command fails to complete within this time, it is killed. This normally
24700 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24701 specifies no timeout. In order to ensure that any subprocesses created by the
24702 command are also killed, Exim makes the initial process a process group leader,
24703 and kills the whole process group on a timeout. However, this can be defeated
24704 if one of the processes starts a new process group.
24706 .option timeout_defer pipe boolean false
24707 A timeout in a &(pipe)& transport, either in the command that the transport
24708 runs, or in a transport filter that is associated with it, is by default
24709 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24710 is set true, both kinds of timeout become temporary errors, causing the
24711 delivery to be deferred.
24713 .option umask pipe "octal integer" 022
24714 This specifies the umask setting for the subprocess that runs the command.
24717 .option use_bsmtp pipe boolean false
24718 .cindex "envelope sender"
24719 If this option is set true, the &(pipe)& transport writes messages in &"batch
24720 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24721 commands. If you want to include a leading HELO command with such messages,
24722 you can do so by setting the &%message_prefix%& option. See section
24723 &<<SECTbatchSMTP>>& for details of batch SMTP.
24725 .option use_classresources pipe boolean false
24726 .cindex "class resources (BSD)"
24727 This option is available only when Exim is running on FreeBSD, NetBSD, or
24728 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
24729 resource limits when a &(pipe)& transport is run to perform a delivery. The
24730 limits for the uid under which the pipe is to run are obtained from the login
24734 .option use_crlf pipe boolean false
24735 .cindex "carriage return"
24737 This option causes lines to be terminated with the two-character CRLF sequence
24738 (carriage return, linefeed) instead of just a linefeed character. In the case
24739 of batched SMTP, the byte sequence written to the pipe is then an exact image
24740 of what would be sent down a real SMTP connection.
24742 The contents of the &%message_prefix%& and &%message_suffix%& options are
24743 written verbatim, so must contain their own carriage return characters if these
24744 are needed. When &%use_bsmtp%& is not set, the default values for both
24745 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
24746 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
24749 .option use_shell pipe boolean false
24750 .vindex "&$pipe_addresses$&"
24751 If this option is set, it causes the command to be passed to &_/bin/sh_&
24752 instead of being run directly from the transport, as described in section
24753 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
24754 where the command is expected to be run under a shell and cannot easily be
24755 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
24756 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
24757 command is expanded as a single string, and handed to &_/bin/sh_& as data for
24762 .section "Using an external local delivery agent" "SECID143"
24763 .cindex "local delivery" "using an external agent"
24764 .cindex "&'procmail'&"
24765 .cindex "external local delivery"
24766 .cindex "delivery" "&'procmail'&"
24767 .cindex "delivery" "by external agent"
24768 The &(pipe)& transport can be used to pass all messages that require local
24769 delivery to a separate local delivery agent such as &%procmail%&. When doing
24770 this, care must be taken to ensure that the pipe is run under an appropriate
24771 uid and gid. In some configurations one wants this to be a uid that is trusted
24772 by the delivery agent to supply the correct sender of the message. It may be
24773 necessary to recompile or reconfigure the delivery agent so that it trusts an
24774 appropriate user. The following is an example transport and router
24775 configuration for &%procmail%&:
24780 command = /usr/local/bin/procmail -d $local_part_data
24784 check_string = "From "
24785 escape_string = ">From "
24787 user = $local_part_data
24794 transport = procmail_pipe
24796 In this example, the pipe is run as the local user, but with the group set to
24797 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
24798 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
24799 user to supply a correct sender address. If you do not specify either a
24800 &%group%& or a &%user%& option, the pipe command is run as the local user. The
24801 home directory is the user's home directory by default.
24803 &*Note*&: The command that the pipe transport runs does &'not'& begin with
24807 as shown in some &%procmail%& documentation, because Exim does not by default
24808 use a shell to run pipe commands.
24811 The next example shows a transport and a router for a system where local
24812 deliveries are handled by the Cyrus IMAP server.
24815 local_delivery_cyrus:
24817 command = /usr/cyrus/bin/deliver \
24818 -m ${substr_1:$local_part_suffix} -- $local_part
24830 local_part_suffix = .*
24831 transport = local_delivery_cyrus
24833 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
24834 &%return_output%& to cause any text written by Cyrus to be returned to the
24836 .ecindex IIDpiptra1
24837 .ecindex IIDpiptra2
24840 . ////////////////////////////////////////////////////////////////////////////
24841 . ////////////////////////////////////////////////////////////////////////////
24843 .chapter "The smtp transport" "CHAPsmtptrans"
24844 .scindex IIDsmttra1 "transports" "&(smtp)&"
24845 .scindex IIDsmttra2 "&(smtp)& transport"
24846 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
24847 or LMTP protocol. The list of hosts to try can either be taken from the address
24848 that is being processed (having been set up by the router), or specified
24849 explicitly for the transport. Timeout and retry processing (see chapter
24850 &<<CHAPretry>>&) is applied to each IP address independently.
24853 .section "Multiple messages on a single connection" "SECID144"
24854 The sending of multiple messages over a single TCP/IP connection can arise in
24858 If a message contains more than &%max_rcpt%& (see below) addresses that are
24859 routed to the same host, more than one copy of the message has to be sent to
24860 that host. In this situation, multiple copies may be sent in a single run of
24861 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
24862 does when it has too many addresses to send in one message also depends on the
24863 value of the global &%remote_max_parallel%& option. Details are given in
24864 section &<<SECToutSMTPTCP>>&.)
24866 .cindex "hints database" "remembering routing"
24867 When a message has been successfully delivered over a TCP/IP connection, Exim
24868 looks in its hints database to see if there are any other messages awaiting a
24869 connection to the same host. If there are, a new delivery process is started
24870 for one of them, and the current TCP/IP connection is passed on to it. The new
24871 process may in turn send multiple copies and possibly create yet another
24876 For each copy sent over the same TCP/IP connection, a sequence counter is
24877 incremented, and if it ever gets to the value of &%connection_max_messages%&,
24878 no further messages are sent over that connection.
24882 .section "Use of the $host and $host_address variables" "SECID145"
24884 .vindex "&$host_address$&"
24885 At the start of a run of the &(smtp)& transport, the values of &$host$& and
24886 &$host_address$& are the name and IP address of the first host on the host list
24887 passed by the router. However, when the transport is about to connect to a
24888 specific host, and while it is connected to that host, &$host$& and
24889 &$host_address$& are set to the values for that host. These are the values
24890 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
24891 &%serialize_hosts%&, and the various TLS options are expanded.
24894 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
24895 .vindex &$tls_bits$&
24896 .vindex &$tls_cipher$&
24897 .vindex &$tls_peerdn$&
24898 .vindex &$tls_sni$&
24899 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
24900 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
24901 are the values that were set when the message was received.
24902 These are the values that are used for options that are expanded before any
24903 SMTP connections are made. Just before each connection is made, these four
24904 variables are emptied. If TLS is subsequently started, they are set to the
24905 appropriate values for the outgoing connection, and these are the values that
24906 are in force when any authenticators are run and when the
24907 &%authenticated_sender%& option is expanded.
24909 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
24910 and will be removed in a future release.
24913 .section "Private options for smtp" "SECID146"
24914 .cindex "options" "&(smtp)& transport"
24915 The private options of the &(smtp)& transport are as follows:
24918 .option address_retry_include_sender smtp boolean true
24919 .cindex "4&'xx'& responses" "retrying after"
24920 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
24921 is the combination of sender and recipient that is delayed in subsequent queue
24922 runs until the retry time is reached. You can delay the recipient without
24923 reference to the sender (which is what earlier versions of Exim did), by
24924 setting &%address_retry_include_sender%& false. However, this can lead to
24925 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
24927 .option allow_localhost smtp boolean false
24928 .cindex "local host" "sending to"
24929 .cindex "fallback" "hosts specified on transport"
24930 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
24931 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
24932 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
24933 the delivery anyway. This should be used only in special cases when the
24934 configuration ensures that no looping will result (for example, a differently
24935 configured Exim is listening on the port to which the message is sent).
24938 .option authenticated_sender smtp string&!! unset
24940 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
24941 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
24942 overriding any existing authenticated sender value. If the string expansion is
24943 forced to fail, the option is ignored. Other expansion failures cause delivery
24944 to be deferred. If the result of expansion is an empty string, that is also
24947 The expansion happens after the outgoing connection has been made and TLS
24948 started, if required. This means that the &$host$&, &$host_address$&,
24949 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
24950 particular connection.
24952 If the SMTP session is not authenticated, the expansion of
24953 &%authenticated_sender%& still happens (and can cause the delivery to be
24954 deferred if it fails), but no AUTH= item is added to MAIL commands
24955 unless &%authenticated_sender_force%& is true.
24957 This option allows you to use the &(smtp)& transport in LMTP mode to
24958 deliver mail to Cyrus IMAP and provide the proper local part as the
24959 &"authenticated sender"&, via a setting such as:
24961 authenticated_sender = $local_part
24963 This removes the need for IMAP subfolders to be assigned special ACLs to
24964 allow direct delivery to those subfolders.
24966 Because of expected uses such as that just described for Cyrus (when no
24967 domain is involved), there is no checking on the syntax of the provided
24971 .option authenticated_sender_force smtp boolean false
24972 If this option is set true, the &%authenticated_sender%& option's value
24973 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
24974 authenticated as a client.
24977 .option command_timeout smtp time 5m
24978 This sets a timeout for receiving a response to an SMTP command that has been
24979 sent out. It is also used when waiting for the initial banner line from the
24980 remote host. Its value must not be zero.
24983 .option connect_timeout smtp time 5m
24984 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
24985 to a remote host. A setting of zero allows the system timeout (typically
24986 several minutes) to act. To have any effect, the value of this option must be
24987 less than the system timeout. However, it has been observed that on some
24988 systems there is no system timeout, which is why the default value for this
24989 option is 5 minutes, a value recommended by RFC 1123.
24992 .option connection_max_messages smtp integer 500
24993 .cindex "SMTP" "passed connection"
24994 .cindex "SMTP" "multiple deliveries"
24995 .cindex "multiple SMTP deliveries"
24996 This controls the maximum number of separate message deliveries that are sent
24997 over a single TCP/IP connection. If the value is zero, there is no limit.
24998 For testing purposes, this value can be overridden by the &%-oB%& command line
25002 .option dane_require_tls_ciphers smtp string&!! unset
25003 .cindex "TLS" "requiring specific ciphers for DANE"
25004 .cindex "cipher" "requiring specific"
25005 .cindex DANE "TLS ciphers"
25006 This option may be used to override &%tls_require_ciphers%& for connections
25007 where DANE has been determined to be in effect.
25008 If not set, then &%tls_require_ciphers%& will be used.
25009 Normal SMTP delivery is not able to make strong demands of TLS cipher
25010 configuration, because delivery will fall back to plaintext. Once DANE has
25011 been determined to be in effect, there is no plaintext fallback and making the
25012 TLS cipherlist configuration stronger will increase security, rather than
25013 counter-intuitively decreasing it.
25014 If the option expands to be empty or is forced to fail, then it will
25015 be treated as unset and &%tls_require_ciphers%& will be used instead.
25018 .option data_timeout smtp time 5m
25019 This sets a timeout for the transmission of each block in the data portion of
25020 the message. As a result, the overall timeout for a message depends on the size
25021 of the message. Its value must not be zero. See also &%final_timeout%&.
25024 .option dkim_canon smtp string&!! unset
25025 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25026 .option dkim_domain smtp string list&!! unset
25027 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25028 .option dkim_hash smtp string&!! sha256
25029 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25030 .option dkim_identity smtp string&!! unset
25031 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25032 .option dkim_private_key smtp string&!! unset
25033 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25034 .option dkim_selector smtp string&!! unset
25035 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25036 .option dkim_strict smtp string&!! unset
25037 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25038 .option dkim_sign_headers smtp string&!! "per RFC"
25039 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25040 .option dkim_timestamps smtp string&!! unset
25041 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25044 .option delay_after_cutoff smtp boolean true
25045 .cindex "final cutoff" "retries, controlling"
25046 .cindex retry "final cutoff"
25047 This option controls what happens when all remote IP addresses for a given
25048 domain have been inaccessible for so long that they have passed their retry
25051 In the default state, if the next retry time has not been reached for any of
25052 them, the address is bounced without trying any deliveries. In other words,
25053 Exim delays retrying an IP address after the final cutoff time until a new
25054 retry time is reached, and can therefore bounce an address without ever trying
25055 a delivery, when machines have been down for a long time. Some people are
25056 unhappy at this prospect, so...
25058 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25059 addresses are past their final cutoff time, Exim tries to deliver to those
25060 IP addresses that have not been tried since the message arrived. If there are
25061 none, of if they all fail, the address is bounced. In other words, it does not
25062 delay when a new message arrives, but immediately tries those expired IP
25063 addresses that haven't been tried since the message arrived. If there is a
25064 continuous stream of messages for the dead hosts, unsetting
25065 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25069 .option dns_qualify_single smtp boolean true
25070 If the &%hosts%& or &%fallback_hosts%& option is being used,
25071 and the &%gethostbyname%& option is false,
25072 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25073 in chapter &<<CHAPdnslookup>>& for more details.
25076 .option dns_search_parents smtp boolean false
25077 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25078 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25079 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25083 .option dnssec_request_domains smtp "domain list&!!" *
25084 .cindex "MX record" "security"
25085 .cindex "DNSSEC" "MX lookup"
25086 .cindex "security" "MX lookup"
25087 .cindex "DNS" "DNSSEC"
25088 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25089 the dnssec request bit set. Setting this transport option is only useful if the
25090 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25095 .option dnssec_require_domains smtp "domain list&!!" unset
25096 .cindex "MX record" "security"
25097 .cindex "DNSSEC" "MX lookup"
25098 .cindex "security" "MX lookup"
25099 .cindex "DNS" "DNSSEC"
25100 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25101 the dnssec request bit set. Setting this transport option is only
25102 useful if the transport overrides or sets the host names. See the
25103 &%dnssec_require_domains%& router option.
25107 .option dscp smtp string&!! unset
25108 .cindex "DCSP" "outbound"
25109 This option causes the DSCP value associated with a socket to be set to one
25110 of a number of fixed strings or to numeric value.
25111 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25112 Common values include &`throughput`&, &`mincost`&, and on newer systems
25113 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25115 The outbound packets from Exim will be marked with this value in the header
25116 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25117 that these values will have any effect, not be stripped by networking
25118 equipment, or do much of anything without cooperation with your Network
25119 Engineer and those of all network operators between the source and destination.
25122 .option fallback_hosts smtp "string list" unset
25123 .cindex "fallback" "hosts specified on transport"
25124 String expansion is not applied to this option. The argument must be a
25125 colon-separated list of host names or IP addresses, optionally also including
25126 port numbers, though the separator can be changed, as described in section
25127 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25128 item in a &%route_list%& setting for the &(manualroute)& router, as described
25129 in section &<<SECTformatonehostitem>>&.
25131 Fallback hosts can also be specified on routers, which associate them with the
25132 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25133 &%fallback_hosts%& specified on the transport is used only if the address does
25134 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25135 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25136 However, &%hosts_randomize%& does apply to fallback host lists.
25138 If Exim is unable to deliver to any of the hosts for a particular address, and
25139 the errors are not permanent rejections, the address is put on a separate
25140 transport queue with its host list replaced by the fallback hosts, unless the
25141 address was routed via MX records and the current host was in the original MX
25142 list. In that situation, the fallback host list is not used.
25144 Once normal deliveries are complete, the fallback queue is delivered by
25145 re-running the same transports with the new host lists. If several failing
25146 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25147 copy of the message is sent.
25149 The resolution of the host names on the fallback list is controlled by the
25150 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25151 both to cases when the host list comes with the address and when it is taken
25152 from &%hosts%&. This option provides a &"use a smart host only if delivery
25156 .option final_timeout smtp time 10m
25157 This is the timeout that applies while waiting for the response to the final
25158 line containing just &"."& that terminates a message. Its value must not be
25161 .option gethostbyname smtp boolean false
25162 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25163 being used, names are looked up using &[gethostbyname()]&
25164 (or &[getipnodebyname()]& when available)
25165 instead of using the DNS. Of course, that function may in fact use the DNS, but
25166 it may also consult other sources of information such as &_/etc/hosts_&.
25168 .option gnutls_compat_mode smtp boolean unset
25169 This option controls whether GnuTLS is used in compatibility mode in an Exim
25170 server. This reduces security slightly, but improves interworking with older
25171 implementations of TLS.
25173 .option helo_data smtp string&!! "see below"
25174 .cindex "HELO" "argument, setting"
25175 .cindex "EHLO" "argument, setting"
25176 .cindex "LHLO argument setting"
25177 The value of this option is expanded after a connection to a another host has
25178 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25179 command that starts the outgoing SMTP or LMTP session. The default value of the
25184 During the expansion, the variables &$host$& and &$host_address$& are set to
25185 the identity of the remote host, and the variables &$sending_ip_address$& and
25186 &$sending_port$& are set to the local IP address and port number that are being
25187 used. These variables can be used to generate different values for different
25188 servers or different local IP addresses. For example, if you want the string
25189 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25190 interface address, you could use this:
25192 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25193 {$primary_hostname}}
25195 The use of &%helo_data%& applies both to sending messages and when doing
25198 .option hosts smtp "string list&!!" unset
25199 Hosts are associated with an address by a router such as &(dnslookup)&, which
25200 finds the hosts by looking up the address domain in the DNS, or by
25201 &(manualroute)&, which has lists of hosts in its configuration. However,
25202 email addresses can be passed to the &(smtp)& transport by any router, and not
25203 all of them can provide an associated list of hosts.
25205 The &%hosts%& option specifies a list of hosts to be used if the address being
25206 processed does not have any hosts associated with it. The hosts specified by
25207 &%hosts%& are also used, whether or not the address has its own hosts, if
25208 &%hosts_override%& is set.
25210 The string is first expanded, before being interpreted as a colon-separated
25211 list of host names or IP addresses, possibly including port numbers. The
25212 separator may be changed to something other than colon, as described in section
25213 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25214 item in a &%route_list%& setting for the &(manualroute)& router, as described
25215 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25216 of the &(manualroute)& router is not available here.
25218 If the expansion fails, delivery is deferred. Unless the failure was caused by
25219 the inability to complete a lookup, the error is logged to the panic log as
25220 well as the main log. Host names are looked up either by searching directly for
25221 address records in the DNS or by calling &[gethostbyname()]& (or
25222 &[getipnodebyname()]& when available), depending on the setting of the
25223 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25224 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25227 During delivery, the hosts are tried in order, subject to their retry status,
25228 unless &%hosts_randomize%& is set.
25231 .option hosts_avoid_esmtp smtp "host list&!!" unset
25232 .cindex "ESMTP, avoiding use of"
25233 .cindex "HELO" "forcing use of"
25234 .cindex "EHLO" "avoiding use of"
25235 .cindex "PIPELINING" "avoiding the use of"
25236 This option is for use with broken hosts that announce ESMTP facilities (for
25237 example, PIPELINING) and then fail to implement them properly. When a host
25238 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25239 start of the SMTP session. This means that it cannot use any of the ESMTP
25240 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25243 .option hosts_avoid_pipelining smtp "host list&!!" unset
25244 .cindex "PIPELINING" "avoiding the use of"
25245 .cindex "ESMTP extensions" PIPELINING
25246 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25247 that matches this list, even if the server host advertises PIPELINING support.
25249 .option hosts_pipe_connect smtp "host list&!!" unset
25250 .cindex "pipelining" "early connection"
25251 .cindex "pipelining" PIPE_CONNECT
25252 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25253 this option controls which to hosts the facility watched for
25254 and recorded, and used for subsequent connections.
25256 The retry hints database is used for the record,
25257 and records are subject to the &%retry_data_expire%& option.
25258 When used, the pipelining saves on roundtrip times.
25259 It also turns SMTP into a client-first protocol
25260 so combines well with TCP Fast Open.
25262 See also the &%pipelining_connect_advertise_hosts%& main option.
25265 When the facility is used, the transport &%helo_data%& option
25266 will be expanded before the &$sending_ip_address$& variable
25268 A check is made for the use of that variable, without the
25269 presence of a &"def:"& test on it, but suitably complex coding
25270 can avoid the check and produce unexpected results.
25271 You have been warned.
25274 .option hosts_avoid_tls smtp "host list&!!" unset
25275 .cindex "TLS" "avoiding for certain hosts"
25276 Exim will not try to start a TLS session when delivering to any host that
25277 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25279 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25280 .cindex "TLS" "avoiding for certain hosts"
25281 Exim will not try to start a TLS session for a verify callout,
25282 or when delivering in cutthrough mode,
25283 to any host that matches this list.
25286 .option hosts_max_try smtp integer 5
25287 .cindex "host" "maximum number to try"
25288 .cindex "limit" "number of hosts tried"
25289 .cindex "limit" "number of MX tried"
25290 .cindex "MX record" "maximum tried"
25291 This option limits the number of IP addresses that are tried for any one
25292 delivery in cases where there are temporary delivery errors. Section
25293 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25296 .option hosts_max_try_hardlimit smtp integer 50
25297 This is an additional check on the maximum number of IP addresses that Exim
25298 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25303 .option hosts_nopass_tls smtp "host list&!!" unset
25304 .cindex "TLS" "passing connection"
25305 .cindex "multiple SMTP deliveries"
25306 .cindex "TLS" "multiple message deliveries"
25307 For any host that matches this list, a connection on which a TLS session has
25308 been started will not be passed to a new delivery process for sending another
25309 message on the same connection. See section &<<SECTmulmessam>>& for an
25310 explanation of when this might be needed.
25312 .option hosts_noproxy_tls smtp "host list&!!" unset
25313 .cindex "TLS" "passing connection"
25314 .cindex "multiple SMTP deliveries"
25315 .cindex "TLS" "multiple message deliveries"
25316 For any host that matches this list, a TLS session which has
25317 been started will not be passed to a new delivery process for sending another
25318 message on the same session.
25320 The traditional implementation closes down TLS and re-starts it in the new
25321 process, on the same open TCP connection, for each successive message
25322 sent. If permitted by this option a pipe to to the new process is set up
25323 instead, and the original process maintains the TLS connection and proxies
25324 the SMTP connection from and to the new process and any subsequents.
25325 The new process has no access to TLS information, so cannot include it in
25330 .option hosts_override smtp boolean false
25331 If this option is set and the &%hosts%& option is also set, any hosts that are
25332 attached to the address are ignored, and instead the hosts specified by the
25333 &%hosts%& option are always used. This option does not apply to
25334 &%fallback_hosts%&.
25337 .option hosts_randomize smtp boolean false
25338 .cindex "randomized host list"
25339 .cindex "host" "list of; randomized"
25340 .cindex "fallback" "randomized hosts"
25341 If this option is set, and either the list of hosts is taken from the
25342 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25343 were not obtained from MX records (this includes fallback hosts from the
25344 router), and were not randomized by the router, the order of trying the hosts
25345 is randomized each time the transport runs. Randomizing the order of a host
25346 list can be used to do crude load sharing.
25348 When &%hosts_randomize%& is true, a host list may be split into groups whose
25349 order is separately randomized. This makes it possible to set up MX-like
25350 behaviour. The boundaries between groups are indicated by an item that is just
25351 &`+`& in the host list. For example:
25353 hosts = host1:host2:host3:+:host4:host5
25355 The order of the first three hosts and the order of the last two hosts is
25356 randomized for each use, but the first three always end up before the last two.
25357 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25359 .option hosts_require_auth smtp "host list&!!" unset
25360 .cindex "authentication" "required by client"
25361 This option provides a list of servers for which authentication must succeed
25362 before Exim will try to transfer a message. If authentication fails for
25363 servers which are not in this list, Exim tries to send unauthenticated. If
25364 authentication fails for one of these servers, delivery is deferred. This
25365 temporary error is detectable in the retry rules, so it can be turned into a
25366 hard failure if required. See also &%hosts_try_auth%&, and chapter
25367 &<<CHAPSMTPAUTH>>& for details of authentication.
25370 .option hosts_request_ocsp smtp "host list&!!" *
25371 .cindex "TLS" "requiring for certain servers"
25372 Exim will request a Certificate Status on a
25373 TLS session for any host that matches this list.
25374 &%tls_verify_certificates%& should also be set for the transport.
25376 .option hosts_require_dane smtp "host list&!!" unset
25377 .cindex DANE "transport options"
25378 .cindex DANE "requiring for certain servers"
25379 If built with DANE support, Exim will require that a DNSSEC-validated
25380 TLSA record is present for any host matching the list,
25381 and that a DANE-verified TLS connection is made. See
25382 the &%dnssec_request_domains%& router and transport options.
25383 There will be no fallback to in-clear communication.
25384 See section &<<SECDANE>>&.
25386 .option hosts_require_ocsp smtp "host list&!!" unset
25387 .cindex "TLS" "requiring for certain servers"
25388 Exim will request, and check for a valid Certificate Status being given, on a
25389 TLS session for any host that matches this list.
25390 &%tls_verify_certificates%& should also be set for the transport.
25392 .option hosts_require_tls smtp "host list&!!" unset
25393 .cindex "TLS" "requiring for certain servers"
25394 Exim will insist on using a TLS session when delivering to any host that
25395 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25396 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25397 incoming messages, use an appropriate ACL.
25399 .option hosts_try_auth smtp "host list&!!" unset
25400 .cindex "authentication" "optional in client"
25401 This option provides a list of servers to which, provided they announce
25402 authentication support, Exim will attempt to authenticate as a client when it
25403 connects. If authentication fails, Exim will try to transfer the message
25404 unauthenticated. See also &%hosts_require_auth%&, and chapter
25405 &<<CHAPSMTPAUTH>>& for details of authentication.
25407 .option hosts_try_chunking smtp "host list&!!" *
25408 .cindex CHUNKING "enabling, in client"
25409 .cindex BDAT "SMTP command"
25410 .cindex "RFC 3030" "CHUNKING"
25411 This option provides a list of servers to which, provided they announce
25412 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25413 Unless DKIM signing is being done,
25414 BDAT will not be used in conjunction with a transport filter.
25416 .option hosts_try_dane smtp "host list&!!" *
25417 .cindex DANE "transport options"
25418 .cindex DANE "attempting for certain servers"
25419 If built with DANE support, Exim will require that a DNSSEC-validated
25420 TLSA record is present for any host matching the list,
25421 and that a DANE-verified TLS connection is made. See
25422 the &%dnssec_request_domains%& router and transport options.
25423 There will be no fallback to in-clear communication.
25424 See section &<<SECDANE>>&.
25426 .option hosts_try_fastopen smtp "host list&!!" *
25427 .cindex "fast open, TCP" "enabling, in client"
25428 .cindex "TCP Fast Open" "enabling, in client"
25429 .cindex "RFC 7413" "TCP Fast Open"
25430 This option provides a list of servers to which, provided
25431 the facility is supported by this system, Exim will attempt to
25432 perform a TCP Fast Open.
25433 No data is sent on the SYN segment but, if the remote server also
25434 supports the facility, it can send its SMTP banner immediately after
25435 the SYN,ACK segment. This can save up to one round-trip time.
25437 The facility is only active for previously-contacted servers,
25438 as the initiator must present a cookie in the SYN segment.
25440 On (at least some) current Linux distributions the facility must be enabled
25441 in the kernel by the sysadmin before the support is usable.
25442 There is no option for control of the server side; if the system supports
25443 it it is always enabled. Note that lengthy operations in the connect ACL,
25444 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25446 .option hosts_try_prdr smtp "host list&!!" *
25447 .cindex "PRDR" "enabling, optional in client"
25448 .cindex "ESMTP extensions" PRDR
25449 This option provides a list of servers to which, provided they announce
25450 PRDR support, Exim will attempt to negotiate PRDR
25451 for multi-recipient messages.
25452 The option can usually be left as default.
25454 .option interface smtp "string list&!!" unset
25455 .cindex "bind IP address"
25456 .cindex "IP address" "binding"
25458 .vindex "&$host_address$&"
25459 This option specifies which interface to bind to when making an outgoing SMTP
25460 call. The value is an IP address, not an interface name such as
25461 &`eth0`&. Do not confuse this with the interface address that was used when a
25462 message was received, which is in &$received_ip_address$&, formerly known as
25463 &$interface_address$&. The name was changed to minimize confusion with the
25464 outgoing interface address. There is no variable that contains an outgoing
25465 interface address because, unless it is set by this option, its value is
25468 During the expansion of the &%interface%& option the variables &$host$& and
25469 &$host_address$& refer to the host to which a connection is about to be made
25470 during the expansion of the string. Forced expansion failure, or an empty
25471 string result causes the option to be ignored. Otherwise, after expansion, the
25472 string must be a list of IP addresses, colon-separated by default, but the
25473 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25476 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25478 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25479 connection. If none of them are the correct type, the option is ignored. If
25480 &%interface%& is not set, or is ignored, the system's IP functions choose which
25481 interface to use if the host has more than one.
25484 .option keepalive smtp boolean true
25485 .cindex "keepalive" "on outgoing connection"
25486 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25487 connections. When set, it causes the kernel to probe idle connections
25488 periodically, by sending packets with &"old"& sequence numbers. The other end
25489 of the connection should send a acknowledgment if the connection is still okay
25490 or a reset if the connection has been aborted. The reason for doing this is
25491 that it has the beneficial effect of freeing up certain types of connection
25492 that can get stuck when the remote host is disconnected without tidying up the
25493 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25497 .option lmtp_ignore_quota smtp boolean false
25498 .cindex "LMTP" "ignoring quota errors"
25499 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25500 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25501 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25503 .option max_rcpt smtp integer 100
25504 .cindex "RCPT" "maximum number of outgoing"
25505 This option limits the number of RCPT commands that are sent in a single
25506 SMTP message transaction. Each set of addresses is treated independently, and
25507 so can cause parallel connections to the same host if &%remote_max_parallel%&
25512 .option message_linelength_limit smtp integer 998
25513 .cindex "line length" limit
25514 This option sets the maximum line length, in bytes, that the transport
25515 will send. Any messages with lines exceeding the given value
25516 will fail and a failure-DSN ("bounce") message will if possible be returned
25518 The default value is that defined by the SMTP standards.
25520 It is generally wise to also check in the data ACL so that messages
25521 received via SMTP can be refused without producing a bounce.
25525 .option multi_domain smtp boolean&!! true
25526 .vindex "&$domain$&"
25527 When this option is set, the &(smtp)& transport can handle a number of
25528 addresses containing a mixture of different domains provided they all resolve
25529 to the same list of hosts. Turning the option off restricts the transport to
25530 handling only one domain at a time. This is useful if you want to use
25531 &$domain$& in an expansion for the transport, because it is set only when there
25532 is a single domain involved in a remote delivery.
25534 It is expanded per-address and can depend on any of
25535 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25536 &$host$&, &$host_address$& and &$host_port$&.
25538 .option port smtp string&!! "see below"
25539 .cindex "port" "sending TCP/IP"
25540 .cindex "TCP/IP" "setting outgoing port"
25541 This option specifies the TCP/IP port on the server to which Exim connects.
25542 &*Note:*& Do not confuse this with the port that was used when a message was
25543 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25544 The name was changed to minimize confusion with the outgoing port. There is no
25545 variable that contains an outgoing port.
25547 If the value of this option begins with a digit it is taken as a port number;
25548 otherwise it is looked up using &[getservbyname()]&. The default value is
25550 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25551 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25552 If the expansion fails, or if a port number cannot be found, delivery
25555 Note that at least one Linux distribution has been seen failing
25556 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25560 .option protocol smtp string smtp
25561 .cindex "LMTP" "over TCP/IP"
25562 .cindex "ssmtp protocol" "outbound"
25563 .cindex "TLS" "SSL-on-connect outbound"
25565 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25566 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25567 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25568 deliveries into closed message stores. Exim also has support for running LMTP
25569 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25571 If this option is set to &"smtps"&, the default value for the &%port%& option
25572 changes to &"smtps"&, and the transport initiates TLS immediately after
25573 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25574 The Internet standards bodies used to strongly discourage use of this mode,
25575 but as of RFC 8314 it is perferred over STARTTLS for message submission
25576 (as distinct from MTA-MTA communication).
25579 .option retry_include_ip_address smtp boolean&!! true
25580 Exim normally includes both the host name and the IP address in the key it
25581 constructs for indexing retry data after a temporary delivery failure. This
25582 means that when one of several IP addresses for a host is failing, it gets
25583 tried periodically (controlled by the retry rules), but use of the other IP
25584 addresses is not affected.
25586 However, in some dialup environments hosts are assigned a different IP address
25587 each time they connect. In this situation the use of the IP address as part of
25588 the retry key leads to undesirable behaviour. Setting this option false causes
25589 Exim to use only the host name.
25590 Since it is expanded it can be made to depend on the host or domain.
25593 .option serialize_hosts smtp "host list&!!" unset
25594 .cindex "serializing connections"
25595 .cindex "host" "serializing connections"
25596 Because Exim operates in a distributed manner, if several messages for the same
25597 host arrive at around the same time, more than one simultaneous connection to
25598 the remote host can occur. This is not usually a problem except when there is a
25599 slow link between the hosts. In that situation it may be helpful to restrict
25600 Exim to one connection at a time. This can be done by setting
25601 &%serialize_hosts%& to match the relevant hosts.
25603 .cindex "hints database" "serializing deliveries to a host"
25604 Exim implements serialization by means of a hints database in which a record is
25605 written whenever a process connects to one of the restricted hosts. The record
25606 is deleted when the connection is completed. Obviously there is scope for
25607 records to get left lying around if there is a system or program crash. To
25608 guard against this, Exim ignores any records that are more than six hours old.
25610 If you set up this kind of serialization, you should also arrange to delete the
25611 relevant hints database whenever your system reboots. The names of the files
25612 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25613 may be one or two files, depending on the type of DBM in use. The same files
25614 are used for ETRN serialization.
25616 See also the &%max_parallel%& generic transport option.
25619 .option size_addition smtp integer 1024
25620 .cindex "SIZE" "ESMTP extension"
25621 .cindex "message" "size issue for transport filter"
25622 .cindex "size" "of message"
25623 .cindex "transport" "filter"
25624 .cindex "filter" "transport filter"
25625 If a remote SMTP server indicates that it supports the SIZE option of the
25626 MAIL command, Exim uses this to pass over the message size at the start of
25627 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25628 sends, to allow for headers and other text that may be added during delivery by
25629 configuration options or in a transport filter. It may be necessary to increase
25630 this if a lot of text is added to messages.
25632 Alternatively, if the value of &%size_addition%& is set negative, it disables
25633 the use of the SIZE option altogether.
25636 .option socks_proxy smtp string&!! unset
25637 .cindex proxy SOCKS
25638 This option enables use of SOCKS proxies for connections made by the
25639 transport. For details see section &<<SECTproxySOCKS>>&.
25642 .option tls_certificate smtp string&!! unset
25643 .cindex "TLS" "client certificate, location of"
25644 .cindex "certificate" "client, location of"
25646 .vindex "&$host_address$&"
25647 The value of this option must be the absolute path to a file which contains the
25648 client's certificate, for possible use when sending a message over an encrypted
25649 connection. The values of &$host$& and &$host_address$& are set to the name and
25650 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25653 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25654 certificate when sending messages as a client. The global option of the same
25655 name specifies the certificate for Exim as a server; it is not automatically
25656 assumed that the same certificate should be used when Exim is operating as a
25660 .option tls_crl smtp string&!! unset
25661 .cindex "TLS" "client certificate revocation list"
25662 .cindex "certificate" "revocation list for client"
25663 This option specifies a certificate revocation list. The expanded value must
25664 be the name of a file that contains a CRL in PEM format.
25667 .option tls_dh_min_bits smtp integer 1024
25668 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
25669 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
25670 key agreement is negotiated, the server will provide a large prime number
25671 for use. This option establishes the minimum acceptable size of that number.
25672 If the parameter offered by the server is too small, then the TLS handshake
25675 Only supported when using GnuTLS.
25678 .option tls_privatekey smtp string&!! unset
25679 .cindex "TLS" "client private key, location of"
25681 .vindex "&$host_address$&"
25682 The value of this option must be the absolute path to a file which contains the
25683 client's private key. This is used when sending a message over an encrypted
25684 connection using a client certificate. The values of &$host$& and
25685 &$host_address$& are set to the name and address of the server during the
25686 expansion. If this option is unset, or the expansion is forced to fail, or the
25687 result is an empty string, the private key is assumed to be in the same file as
25688 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
25691 .option tls_require_ciphers smtp string&!! unset
25692 .cindex "TLS" "requiring specific ciphers"
25693 .cindex "cipher" "requiring specific"
25695 .vindex "&$host_address$&"
25696 The value of this option must be a list of permitted cipher suites, for use
25697 when setting up an outgoing encrypted connection. (There is a global option of
25698 the same name for controlling incoming connections.) The values of &$host$& and
25699 &$host_address$& are set to the name and address of the server during the
25700 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
25701 is used in different ways by OpenSSL and GnuTLS (see sections
25702 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
25703 ciphers is a preference order.
25707 .option tls_resumption_hosts smtp "host list&!!" unset
25708 .cindex TLS resumption
25709 This option controls which connections to use the TLS resumption feature.
25710 See &<<SECTresumption>>& for details.
25715 .option tls_sni smtp string&!! unset
25716 .cindex "TLS" "Server Name Indication"
25718 .cindex SNI "setting in client"
25719 .vindex "&$tls_sni$&"
25720 If this option is set then it sets the $tls_out_sni variable and causes any
25721 TLS session to pass this value as the Server Name Indication extension to
25722 the remote side, which can be used by the remote side to select an appropriate
25723 certificate and private key for the session.
25725 See &<<SECTtlssni>>& for more information.
25727 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
25733 .option tls_tempfail_tryclear smtp boolean true
25734 .cindex "4&'xx'& responses" "to STARTTLS"
25735 When the server host is not in &%hosts_require_tls%&, and there is a problem in
25736 setting up a TLS session, this option determines whether or not Exim should try
25737 to deliver the message unencrypted. If it is set false, delivery to the
25738 current host is deferred; if there are other hosts, they are tried. If this
25739 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
25740 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
25741 TLS negotiation fails, Exim closes the current connection (because it is in an
25742 unknown state), opens a new one to the same host, and then tries the delivery
25746 .option tls_try_verify_hosts smtp "host list&!!" *
25747 .cindex "TLS" "server certificate verification"
25748 .cindex "certificate" "verification of server"
25749 This option gives a list of hosts for which, on encrypted connections,
25750 certificate verification will be tried but need not succeed.
25751 The &%tls_verify_certificates%& option must also be set.
25752 Note that unless the host is in this list
25753 TLS connections will be denied to hosts using self-signed certificates
25754 when &%tls_verify_certificates%& is matched.
25755 The &$tls_out_certificate_verified$& variable is set when
25756 certificate verification succeeds.
25759 .option tls_verify_cert_hostnames smtp "host list&!!" *
25760 .cindex "TLS" "server certificate hostname verification"
25761 .cindex "certificate" "verification of server"
25762 This option give a list of hosts for which,
25763 while verifying the server certificate,
25764 checks will be included on the host name
25765 (note that this will generally be the result of a DNS MX lookup)
25766 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
25767 limited to being the initial component of a 3-or-more component FQDN.
25769 There is no equivalent checking on client certificates.
25772 .option tls_verify_certificates smtp string&!! system
25773 .cindex "TLS" "server certificate verification"
25774 .cindex "certificate" "verification of server"
25776 .vindex "&$host_address$&"
25777 The value of this option must be either the
25779 or the absolute path to
25780 a file or directory containing permitted certificates for servers,
25781 for use when setting up an encrypted connection.
25783 The "system" value for the option will use a location compiled into the SSL library.
25784 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
25785 is taken as empty and an explicit location
25788 The use of a directory for the option value is not available for GnuTLS versions
25789 preceding 3.3.6 and a single file must be used.
25791 With OpenSSL the certificates specified
25793 either by file or directory
25794 are added to those given by the system default location.
25796 The values of &$host$& and
25797 &$host_address$& are set to the name and address of the server during the
25798 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
25800 For back-compatibility,
25801 if neither tls_verify_hosts nor tls_try_verify_hosts are set
25802 (a single-colon empty list counts as being set)
25803 and certificate verification fails the TLS connection is closed.
25806 .option tls_verify_hosts smtp "host list&!!" unset
25807 .cindex "TLS" "server certificate verification"
25808 .cindex "certificate" "verification of server"
25809 This option gives a list of hosts for which, on encrypted connections,
25810 certificate verification must succeed.
25811 The &%tls_verify_certificates%& option must also be set.
25812 If both this option and &%tls_try_verify_hosts%& are unset
25813 operation is as if this option selected all hosts.
25815 .option utf8_downconvert smtp integer&!! -1
25816 .cindex utf8 "address downconversion"
25817 .cindex i18n "utf8 address downconversion"
25818 If built with internationalization support,
25819 this option controls conversion of UTF-8 in message envelope addresses
25821 If, after expansion, the value is 1, 0, or -1 then this value overrides
25822 any value previously set for the message. Otherwise, any previously
25823 set value is used. To permit use of a previous value,
25824 set this option to an empty string.
25825 For details on the values see section &<<SECTi18nMTA>>&.
25830 .section "How the limits for the number of hosts to try are used" &&&
25832 .cindex "host" "maximum number to try"
25833 .cindex "limit" "hosts; maximum number tried"
25834 There are two options that are concerned with the number of hosts that are
25835 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
25836 &%hosts_max_try_hardlimit%&.
25839 The &%hosts_max_try%& option limits the number of hosts that are tried
25840 for a single delivery. However, despite the term &"host"& in its name, the
25841 option actually applies to each IP address independently. In other words, a
25842 multihomed host is treated as several independent hosts, just as it is for
25845 Many of the larger ISPs have multiple MX records which often point to
25846 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
25847 created as a result of routing one of these domains.
25849 Trying every single IP address on such a long list does not seem sensible; if
25850 several at the top of the list fail, it is reasonable to assume there is some
25851 problem that is likely to affect all of them. Roughly speaking, the value of
25852 &%hosts_max_try%& is the maximum number that are tried before deferring the
25853 delivery. However, the logic cannot be quite that simple.
25855 Firstly, IP addresses that are skipped because their retry times have not
25856 arrived do not count, and in addition, addresses that are past their retry
25857 limits are also not counted, even when they are tried. This means that when
25858 some IP addresses are past their retry limits, more than the value of
25859 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
25860 that all IP addresses are considered before timing out an email address (but
25861 see below for an exception).
25863 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
25864 list to see if there is a subsequent host with a different (higher valued) MX.
25865 If there is, that host is considered next, and the current IP address is used
25866 but not counted. This behaviour helps in the case of a domain with a retry rule
25867 that hardly ever delays any hosts, as is now explained:
25869 Consider the case of a long list of hosts with one MX value, and a few with a
25870 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
25871 hosts at the top of the list are tried at first. With the default retry rule,
25872 which specifies increasing retry times, the higher MX hosts are eventually
25873 tried when those at the top of the list are skipped because they have not
25874 reached their retry times.
25876 However, it is common practice to put a fixed short retry time on domains for
25877 large ISPs, on the grounds that their servers are rarely down for very long.
25878 Unfortunately, these are exactly the domains that tend to resolve to long lists
25879 of hosts. The short retry time means that the lowest MX hosts are tried every
25880 time. The attempts may be in a different order because of random sorting, but
25881 without the special MX check, the higher MX hosts would never be tried until
25882 all the lower MX hosts had timed out (which might be several days), because
25883 there are always some lower MX hosts that have reached their retry times. With
25884 the special check, Exim considers at least one IP address from each MX value at
25885 every delivery attempt, even if the &%hosts_max_try%& limit has already been
25888 The above logic means that &%hosts_max_try%& is not a hard limit, and in
25889 particular, Exim normally eventually tries all the IP addresses before timing
25890 out an email address. When &%hosts_max_try%& was implemented, this seemed a
25891 reasonable thing to do. Recently, however, some lunatic DNS configurations have
25892 been set up with hundreds of IP addresses for some domains. It can
25893 take a very long time indeed for an address to time out in these cases.
25895 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
25896 Exim never tries more than this number of IP addresses; if it hits this limit
25897 and they are all timed out, the email address is bounced, even though not all
25898 possible IP addresses have been tried.
25899 .ecindex IIDsmttra1
25900 .ecindex IIDsmttra2
25906 . ////////////////////////////////////////////////////////////////////////////
25907 . ////////////////////////////////////////////////////////////////////////////
25909 .chapter "Address rewriting" "CHAPrewrite"
25910 .scindex IIDaddrew "rewriting" "addresses"
25911 There are some circumstances in which Exim automatically rewrites domains in
25912 addresses. The two most common are when an address is given without a domain
25913 (referred to as an &"unqualified address"&) or when an address contains an
25914 abbreviated domain that is expanded by DNS lookup.
25916 Unqualified envelope addresses are accepted only for locally submitted
25917 messages, or for messages that are received from hosts matching
25918 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
25919 appropriate. Unqualified addresses in header lines are qualified if they are in
25920 locally submitted messages, or messages from hosts that are permitted to send
25921 unqualified envelope addresses. Otherwise, unqualified addresses in header
25922 lines are neither qualified nor rewritten.
25924 One situation in which Exim does &'not'& automatically rewrite a domain is
25925 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
25926 such a domain should be rewritten using the &"canonical"& name, and some MTAs
25927 do this. The new RFCs do not contain this suggestion.
25930 .section "Explicitly configured address rewriting" "SECID147"
25931 This chapter describes the rewriting rules that can be used in the
25932 main rewrite section of the configuration file, and also in the generic
25933 &%headers_rewrite%& option that can be set on any transport.
25935 Some people believe that configured address rewriting is a Mortal Sin.
25936 Others believe that life is not possible without it. Exim provides the
25937 facility; you do not have to use it.
25939 The main rewriting rules that appear in the &"rewrite"& section of the
25940 configuration file are applied to addresses in incoming messages, both envelope
25941 addresses and addresses in header lines. Each rule specifies the types of
25942 address to which it applies.
25944 Whether or not addresses in header lines are rewritten depends on the origin of
25945 the headers and the type of rewriting. Global rewriting, that is, rewriting
25946 rules from the rewrite section of the configuration file, is applied only to
25947 those headers that were received with the message. Header lines that are added
25948 by ACLs or by a system filter or by individual routers or transports (which
25949 are specific to individual recipient addresses) are not rewritten by the global
25952 Rewriting at transport time, by means of the &%headers_rewrite%& option,
25953 applies all headers except those added by routers and transports. That is, as
25954 well as the headers that were received with the message, it also applies to
25955 headers that were added by an ACL or a system filter.
25958 In general, rewriting addresses from your own system or domain has some
25959 legitimacy. Rewriting other addresses should be done only with great care and
25960 in special circumstances. The author of Exim believes that rewriting should be
25961 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
25962 Although it can sometimes be used as a routing tool, this is very strongly
25965 There are two commonly encountered circumstances where rewriting is used, as
25966 illustrated by these examples:
25969 The company whose domain is &'hitch.fict.example'& has a number of hosts that
25970 exchange mail with each other behind a firewall, but there is only a single
25971 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
25972 &'hitch.fict.example'& when sending mail off-site.
25974 A host rewrites the local parts of its own users so that, for example,
25975 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
25980 .section "When does rewriting happen?" "SECID148"
25981 .cindex "rewriting" "timing of"
25982 .cindex "&ACL;" "rewriting addresses in"
25983 Configured address rewriting can take place at several different stages of a
25984 message's processing.
25986 .vindex "&$sender_address$&"
25987 At the start of an ACL for MAIL, the sender address may have been rewritten
25988 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
25989 ordinary rewrite rules have yet been applied. If, however, the sender address
25990 is verified in the ACL, it is rewritten before verification, and remains
25991 rewritten thereafter. The subsequent value of &$sender_address$& is the
25992 rewritten address. This also applies if sender verification happens in a
25993 RCPT ACL. Otherwise, when the sender address is not verified, it is
25994 rewritten as soon as a message's header lines have been received.
25996 .vindex "&$domain$&"
25997 .vindex "&$local_part$&"
25998 Similarly, at the start of an ACL for RCPT, the current recipient's address
25999 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26000 rewrite rules have yet been applied to it. However, the behaviour is different
26001 from the sender address when a recipient is verified. The address is rewritten
26002 for the verification, but the rewriting is not remembered at this stage. The
26003 value of &$local_part$& and &$domain$& after verification are always the same
26004 as they were before (that is, they contain the unrewritten &-- except for
26005 SMTP-time rewriting &-- address).
26007 As soon as a message's header lines have been received, all the envelope
26008 recipient addresses are permanently rewritten, and rewriting is also applied to
26009 the addresses in the header lines (if configured). This happens before adding
26010 any header lines that were specified in MAIL or RCPT ACLs, and
26011 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26012 before the DATA ACL and &[local_scan()]& functions are run.
26014 When an address is being routed, either for delivery or for verification,
26015 rewriting is applied immediately to child addresses that are generated by
26016 redirection, unless &%no_rewrite%& is set on the router.
26018 .cindex "envelope from"
26019 .cindex "envelope sender" "rewriting at transport time"
26020 .cindex "rewriting" "at transport time"
26021 .cindex "header lines" "rewriting at transport time"
26022 At transport time, additional rewriting of addresses in header lines can be
26023 specified by setting the generic &%headers_rewrite%& option on a transport.
26024 This option contains rules that are identical in form to those in the rewrite
26025 section of the configuration file. They are applied to the original message
26026 header lines and any that were added by ACLs or a system filter. They are not
26027 applied to header lines that are added by routers or the transport.
26029 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26030 transport option. However, it is not possible to rewrite envelope recipients at
26036 .section "Testing the rewriting rules that apply on input" "SECID149"
26037 .cindex "rewriting" "testing"
26038 .cindex "testing" "rewriting"
26039 Exim's input rewriting configuration appears in a part of the runtime
26040 configuration file headed by &"begin rewrite"&. It can be tested by the
26041 &%-brw%& command line option. This takes an address (which can be a full RFC
26042 2822 address) as its argument. The output is a list of how the address would be
26043 transformed by the rewriting rules for each of the different places it might
26044 appear in an incoming message, that is, for each different header and for the
26045 envelope sender and recipient fields. For example,
26047 exim -brw ph10@exim.workshop.example
26049 might produce the output
26051 sender: Philip.Hazel@exim.workshop.example
26052 from: Philip.Hazel@exim.workshop.example
26053 to: ph10@exim.workshop.example
26054 cc: ph10@exim.workshop.example
26055 bcc: ph10@exim.workshop.example
26056 reply-to: Philip.Hazel@exim.workshop.example
26057 env-from: Philip.Hazel@exim.workshop.example
26058 env-to: ph10@exim.workshop.example
26060 which shows that rewriting has been set up for that address when used in any of
26061 the source fields, but not when it appears as a recipient address. At the
26062 present time, there is no equivalent way of testing rewriting rules that are
26063 set for a particular transport.
26066 .section "Rewriting rules" "SECID150"
26067 .cindex "rewriting" "rules"
26068 The rewrite section of the configuration file consists of lines of rewriting
26071 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26073 Rewriting rules that are specified for the &%headers_rewrite%& generic
26074 transport option are given as a colon-separated list. Each item in the list
26075 takes the same form as a line in the main rewriting configuration (except that
26076 any colons must be doubled, of course).
26078 The formats of source patterns and replacement strings are described below.
26079 Each is terminated by white space, unless enclosed in double quotes, in which
26080 case normal quoting conventions apply inside the quotes. The flags are single
26081 characters which may appear in any order. Spaces and tabs between them are
26084 For each address that could potentially be rewritten, the rules are scanned in
26085 order, and replacements for the address from earlier rules can themselves be
26086 replaced by later rules (but see the &"q"& and &"R"& flags).
26088 The order in which addresses are rewritten is undefined, may change between
26089 releases, and must not be relied on, with one exception: when a message is
26090 received, the envelope sender is always rewritten first, before any header
26091 lines are rewritten. For example, the replacement string for a rewrite of an
26092 address in &'To:'& must not assume that the message's address in &'From:'& has
26093 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26094 that the envelope sender has already been rewritten.
26096 .vindex "&$domain$&"
26097 .vindex "&$local_part$&"
26098 The variables &$local_part$& and &$domain$& can be used in the replacement
26099 string to refer to the address that is being rewritten. Note that lookup-driven
26100 rewriting can be done by a rule of the form
26104 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26105 refer to the address that is being rewritten.
26108 .section "Rewriting patterns" "SECID151"
26109 .cindex "rewriting" "patterns"
26110 .cindex "address list" "in a rewriting pattern"
26111 The source pattern in a rewriting rule is any item which may appear in an
26112 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26113 single-item address list, which means that it is expanded before being tested
26114 against the address. As always, if you use a regular expression as a pattern,
26115 you must take care to escape dollar and backslash characters, or use the &`\N`&
26116 facility to suppress string expansion within the regular expression.
26118 Domains in patterns should be given in lower case. Local parts in patterns are
26119 case-sensitive. If you want to do case-insensitive matching of local parts, you
26120 can use a regular expression that starts with &`^(?i)`&.
26122 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26123 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26124 depending on the type of match which occurred. These can be used in the
26125 replacement string to insert portions of the incoming address. &$0$& always
26126 refers to the complete incoming address. When a regular expression is used, the
26127 numerical variables are set from its capturing subexpressions. For other types
26128 of pattern they are set as follows:
26131 If a local part or domain starts with an asterisk, the numerical variables
26132 refer to the character strings matched by asterisks, with &$1$& associated with
26133 the first asterisk, and &$2$& with the second, if present. For example, if the
26136 *queen@*.fict.example
26138 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26140 $0 = hearts-queen@wonderland.fict.example
26144 Note that if the local part does not start with an asterisk, but the domain
26145 does, it is &$1$& that contains the wild part of the domain.
26148 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26149 of the domain are placed in the next available numerical variables. Suppose,
26150 for example, that the address &'foo@bar.baz.example'& is processed by a
26151 rewriting rule of the form
26153 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26155 and the key in the file that matches the domain is &`*.baz.example`&. Then
26161 If the address &'foo@baz.example'& is looked up, this matches the same
26162 wildcard file entry, and in this case &$2$& is set to the empty string, but
26163 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26164 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26165 whole domain. For non-partial domain lookups, no numerical variables are set.
26169 .section "Rewriting replacements" "SECID152"
26170 .cindex "rewriting" "replacements"
26171 If the replacement string for a rule is a single asterisk, addresses that
26172 match the pattern and the flags are &'not'& rewritten, and no subsequent
26173 rewriting rules are scanned. For example,
26175 hatta@lookingglass.fict.example * f
26177 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26180 .vindex "&$domain$&"
26181 .vindex "&$local_part$&"
26182 If the replacement string is not a single asterisk, it is expanded, and must
26183 yield a fully qualified address. Within the expansion, the variables
26184 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26185 Any letters they contain retain their original case &-- they are not lower
26186 cased. The numerical variables are set up according to the type of pattern that
26187 matched the address, as described above. If the expansion is forced to fail by
26188 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26189 current rule is abandoned, but subsequent rules may take effect. Any other
26190 expansion failure causes the entire rewriting operation to be abandoned, and an
26191 entry written to the panic log.
26195 .section "Rewriting flags" "SECID153"
26196 There are three different kinds of flag that may appear on rewriting rules:
26199 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26202 A flag that specifies rewriting at SMTP time: S.
26204 Flags that control the rewriting process: Q, q, R, w.
26207 For rules that are part of the &%headers_rewrite%& generic transport option,
26208 E, F, T, and S are not permitted.
26212 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26214 .cindex "rewriting" "flags"
26215 If none of the following flag letters, nor the &"S"& flag (see section
26216 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26217 and to both the sender and recipient fields of the envelope, whereas a
26218 transport-time rewriting rule just applies to all headers. Otherwise, the
26219 rewriting rule is skipped unless the relevant addresses are being processed.
26221 &`E`& rewrite all envelope fields
26222 &`F`& rewrite the envelope From field
26223 &`T`& rewrite the envelope To field
26224 &`b`& rewrite the &'Bcc:'& header
26225 &`c`& rewrite the &'Cc:'& header
26226 &`f`& rewrite the &'From:'& header
26227 &`h`& rewrite all headers
26228 &`r`& rewrite the &'Reply-To:'& header
26229 &`s`& rewrite the &'Sender:'& header
26230 &`t`& rewrite the &'To:'& header
26232 "All headers" means all of the headers listed above that can be selected
26233 individually, plus their &'Resent-'& versions. It does not include
26234 other headers such as &'Subject:'& etc.
26236 You should be particularly careful about rewriting &'Sender:'& headers, and
26237 restrict this to special known cases in your own domains.
26240 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26241 .cindex "SMTP" "rewriting malformed addresses"
26242 .cindex "RCPT" "rewriting argument of"
26243 .cindex "MAIL" "rewriting argument of"
26244 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26245 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26246 before any other processing; even before syntax checking. The pattern is
26247 required to be a regular expression, and it is matched against the whole of the
26248 data for the command, including any surrounding angle brackets.
26250 .vindex "&$domain$&"
26251 .vindex "&$local_part$&"
26252 This form of rewrite rule allows for the handling of addresses that are not
26253 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26254 input). Because the input is not required to be a syntactically valid address,
26255 the variables &$local_part$& and &$domain$& are not available during the
26256 expansion of the replacement string. The result of rewriting replaces the
26257 original address in the MAIL or RCPT command.
26260 .section "Flags controlling the rewriting process" "SECID155"
26261 There are four flags which control the way the rewriting process works. These
26262 take effect only when a rule is invoked, that is, when the address is of the
26263 correct type (matches the flags) and matches the pattern:
26266 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26267 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26268 absence of &"Q"& the rewritten address must always include a domain.
26270 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26271 even if no rewriting actually takes place because of a &"fail"& in the
26272 expansion. The &"q"& flag is not effective if the address is of the wrong type
26273 (does not match the flags) or does not match the pattern.
26275 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26276 address, up to ten times. It can be combined with the &"q"& flag, to stop
26277 rewriting once it fails to match (after at least one successful rewrite).
26279 .cindex "rewriting" "whole addresses"
26280 When an address in a header is rewritten, the rewriting normally applies only
26281 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26282 left unchanged. For example, rewriting might change
26284 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26288 From: Ford Prefect <prefectf@hitch.fict.example>
26291 Sometimes there is a need to replace the whole address item, and this can be
26292 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26293 causes an address in a header line to be rewritten, the entire address is
26294 replaced, not just the working part. The replacement must be a complete RFC
26295 2822 address, including the angle brackets if necessary. If text outside angle
26296 brackets contains a character whose value is greater than 126 or less than 32
26297 (except for tab), the text is encoded according to RFC 2047. The character set
26298 is taken from &%headers_charset%&, which gets its default at build time.
26300 When the &"w"& flag is set on a rule that causes an envelope address to be
26301 rewritten, all but the working part of the replacement address is discarded.
26305 .section "Rewriting examples" "SECID156"
26306 Here is an example of the two common rewriting paradigms:
26308 *@*.hitch.fict.example $1@hitch.fict.example
26309 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26310 {$value}fail}@hitch.fict.example bctfrF
26312 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26313 the string expansion to fail if the lookup does not succeed. In this context it
26314 has the effect of leaving the original address unchanged, but Exim goes on to
26315 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26316 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26317 explicitly, which would cause the rewritten address to be the same as before,
26318 at the cost of a small bit of processing. Not supplying either of these is an
26319 error, since the rewritten address would then contain no local part.
26321 The first example above replaces the domain with a superior, more general
26322 domain. This may not be desirable for certain local parts. If the rule
26324 root@*.hitch.fict.example *
26326 were inserted before the first rule, rewriting would be suppressed for the
26327 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26329 Rewriting can be made conditional on a number of tests, by making use of
26330 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26331 messages that originate outside the local host:
26333 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26334 {$1@hitch.fict.example}fail}"
26336 The replacement string is quoted in this example because it contains white
26339 .cindex "rewriting" "bang paths"
26340 .cindex "bang paths" "rewriting"
26341 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26342 an address it treats it as an unqualified local part which it qualifies with
26343 the local qualification domain (if the source of the message is local or if the
26344 remote host is permitted to send unqualified addresses). Rewriting can
26345 sometimes be used to handle simple bang paths with a fixed number of
26346 components. For example, the rule
26348 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26350 rewrites a two-component bang path &'host.name!user'& as the domain address
26351 &'user@host.name'&. However, there is a security implication in using this as
26352 a global rewriting rule for envelope addresses. It can provide a backdoor
26353 method for using your system as a relay, because the incoming addresses appear
26354 to be local. If the bang path addresses are received via SMTP, it is safer to
26355 use the &"S"& flag to rewrite them as they are received, so that relay checking
26356 can be done on the rewritten addresses.
26363 . ////////////////////////////////////////////////////////////////////////////
26364 . ////////////////////////////////////////////////////////////////////////////
26366 .chapter "Retry configuration" "CHAPretry"
26367 .scindex IIDretconf1 "retry" "configuration, description of"
26368 .scindex IIDregconf2 "configuration file" "retry section"
26369 The &"retry"& section of the runtime configuration file contains a list of
26370 retry rules that control how often Exim tries to deliver messages that cannot
26371 be delivered at the first attempt. If there are no retry rules (the section is
26372 empty or not present), there are no retries. In this situation, temporary
26373 errors are treated as permanent. The default configuration contains a single,
26374 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26375 line option can be used to test which retry rule will be used for a given
26376 address, domain and error.
26378 The most common cause of retries is temporary failure to deliver to a remote
26379 host because the host is down, or inaccessible because of a network problem.
26380 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26381 address) basis, not on a per-message basis. Thus, if one message has recently
26382 been delayed, delivery of a new message to the same host is not immediately
26383 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26384 log selector is set, the message
26385 .cindex "retry" "time not reached"
26386 &"retry time not reached"& is written to the main log whenever a delivery is
26387 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26388 the handling of errors during remote deliveries.
26390 Retry processing applies to routing as well as to delivering, except as covered
26391 in the next paragraph. The retry rules do not distinguish between these
26392 actions. It is not possible, for example, to specify different behaviour for
26393 failures to route the domain &'snark.fict.example'& and failures to deliver to
26394 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26395 added complication, so did not implement it. However, although they share the
26396 same retry rule, the actual retry times for routing and transporting a given
26397 domain are maintained independently.
26399 When a delivery is not part of a queue run (typically an immediate delivery on
26400 receipt of a message), the routers are always run, and local deliveries are
26401 always attempted, even if retry times are set for them. This makes for better
26402 behaviour if one particular message is causing problems (for example, causing
26403 quota overflow, or provoking an error in a filter file). If such a delivery
26404 suffers a temporary failure, the retry data is updated as normal, and
26405 subsequent delivery attempts from queue runs occur only when the retry time for
26406 the local address is reached.
26408 .section "Changing retry rules" "SECID157"
26409 If you change the retry rules in your configuration, you should consider
26410 whether or not to delete the retry data that is stored in Exim's spool area in
26411 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26412 always safe; that is why they are called &"hints"&.
26414 The hints retry data contains suggested retry times based on the previous
26415 rules. In the case of a long-running problem with a remote host, it might
26416 record the fact that the host has timed out. If your new rules increase the
26417 timeout time for such a host, you should definitely remove the old retry data
26418 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26419 messages that it should now be retaining.
26423 .section "Format of retry rules" "SECID158"
26424 .cindex "retry" "rules"
26425 Each retry rule occupies one line and consists of three or four parts,
26426 separated by white space: a pattern, an error name, an optional list of sender
26427 addresses, and a list of retry parameters. The pattern and sender lists must be
26428 enclosed in double quotes if they contain white space. The rules are searched
26429 in order until one is found where the pattern, error name, and sender list (if
26430 present) match the failing host or address, the error that occurred, and the
26431 message's sender, respectively.
26434 The pattern is any single item that may appear in an address list (see section
26435 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26436 which means that it is expanded before being tested against the address that
26437 has been delayed. A negated address list item is permitted. Address
26438 list processing treats a plain domain name as if it were preceded by &"*@"&,
26439 which makes it possible for many retry rules to start with just a domain. For
26442 lookingglass.fict.example * F,24h,30m;
26444 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26447 alice@lookingglass.fict.example * F,24h,30m;
26449 applies only to temporary failures involving the local part &%alice%&.
26450 In practice, almost all rules start with a domain name pattern without a local
26453 .cindex "regular expressions" "in retry rules"
26454 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26455 must match a complete address, not just a domain, because that is how regular
26456 expressions work in address lists.
26458 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26459 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26463 .section "Choosing which retry rule to use for address errors" "SECID159"
26464 When Exim is looking for a retry rule after a routing attempt has failed (for
26465 example, after a DNS timeout), each line in the retry configuration is tested
26466 against the complete address only if &%retry_use_local_part%& is set for the
26467 router. Otherwise, only the domain is used, except when matching against a
26468 regular expression, when the local part of the address is replaced with &"*"&.
26469 A domain on its own can match a domain pattern, or a pattern that starts with
26470 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26471 &%check_local_user%& is true, and false for other routers.
26473 Similarly, when Exim is looking for a retry rule after a local delivery has
26474 failed (for example, after a mailbox full error), each line in the retry
26475 configuration is tested against the complete address only if
26476 &%retry_use_local_part%& is set for the transport (it defaults true for all
26479 .cindex "4&'xx'& responses" "retry rules for"
26480 However, when Exim is looking for a retry rule after a remote delivery attempt
26481 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26482 whole address is always used as the key when searching the retry rules. The
26483 rule that is found is used to create a retry time for the combination of the
26484 failing address and the message's sender. It is the combination of sender and
26485 recipient that is delayed in subsequent queue runs until its retry time is
26486 reached. You can delay the recipient without regard to the sender by setting
26487 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26488 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26493 .section "Choosing which retry rule to use for host and message errors" &&&
26495 For a temporary error that is not related to an individual address (for
26496 example, a connection timeout), each line in the retry configuration is checked
26497 twice. First, the name of the remote host is used as a domain name (preceded by
26498 &"*@"& when matching a regular expression). If this does not match the line,
26499 the domain from the email address is tried in a similar fashion. For example,
26500 suppose the MX records for &'a.b.c.example'& are
26502 a.b.c.example MX 5 x.y.z.example
26506 and the retry rules are
26508 p.q.r.example * F,24h,30m;
26509 a.b.c.example * F,4d,45m;
26511 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26512 first rule matches neither the host nor the domain, so Exim looks at the second
26513 rule. This does not match the host, but it does match the domain, so it is used
26514 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26515 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26516 first retry rule is used, because it matches the host.
26518 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26519 first rule to determine retry times, but for all the other hosts for the domain
26520 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26521 routing to &'a.b.c.example'& suffers a temporary failure.
26523 &*Note*&: The host name is used when matching the patterns, not its IP address.
26524 However, if a message is routed directly to an IP address without the use of a
26525 host name, for example, if a &(manualroute)& router contains a setting such as:
26527 route_list = *.a.example 192.168.34.23
26529 then the &"host name"& that is used when searching for a retry rule is the
26530 textual form of the IP address.
26532 .section "Retry rules for specific errors" "SECID161"
26533 .cindex "retry" "specific errors; specifying"
26534 The second field in a retry rule is the name of a particular error, or an
26535 asterisk, which matches any error. The errors that can be tested for are:
26538 .vitem &%auth_failed%&
26539 Authentication failed when trying to send to a host in the
26540 &%hosts_require_auth%& list in an &(smtp)& transport.
26542 .vitem &%data_4xx%&
26543 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26544 after the command, or after sending the message's data.
26546 .vitem &%mail_4xx%&
26547 A 4&'xx'& error was received for an outgoing MAIL command.
26549 .vitem &%rcpt_4xx%&
26550 A 4&'xx'& error was received for an outgoing RCPT command.
26553 For the three 4&'xx'& errors, either the first or both of the x's can be given
26554 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26555 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26556 and have retries every ten minutes with a one-hour timeout, you could set up a
26557 retry rule of this form:
26559 the.domain.name rcpt_452 F,1h,10m
26561 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26562 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26565 .vitem &%lost_connection%&
26566 A server unexpectedly closed the SMTP connection. There may, of course,
26567 legitimate reasons for this (host died, network died), but if it repeats a lot
26568 for the same host, it indicates something odd.
26571 A DNS lookup for a host failed.
26572 Note that a &%dnslookup%& router will need to have matched
26573 its &%fail_defer_domains%& option for this retry type to be usable.
26574 Also note that a &%manualroute%& router will probably need
26575 its &%host_find_failed%& option set to &%defer%&.
26577 .vitem &%refused_MX%&
26578 A connection to a host obtained from an MX record was refused.
26580 .vitem &%refused_A%&
26581 A connection to a host not obtained from an MX record was refused.
26584 A connection was refused.
26586 .vitem &%timeout_connect_MX%&
26587 A connection attempt to a host obtained from an MX record timed out.
26589 .vitem &%timeout_connect_A%&
26590 A connection attempt to a host not obtained from an MX record timed out.
26592 .vitem &%timeout_connect%&
26593 A connection attempt timed out.
26595 .vitem &%timeout_MX%&
26596 There was a timeout while connecting or during an SMTP session with a host
26597 obtained from an MX record.
26599 .vitem &%timeout_A%&
26600 There was a timeout while connecting or during an SMTP session with a host not
26601 obtained from an MX record.
26604 There was a timeout while connecting or during an SMTP session.
26606 .vitem &%tls_required%&
26607 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26608 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26609 to STARTTLS, or there was a problem setting up the TLS connection.
26612 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26615 .vitem &%quota_%&<&'time'&>
26616 .cindex "quota" "error testing in retry rule"
26617 .cindex "retry" "quota error testing"
26618 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26619 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26620 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26624 .cindex "mailbox" "time of last read"
26625 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26626 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26627 it should be based on the last time that the user accessed the mailbox.
26628 However, it is not always possible to determine this. Exim uses the following
26632 If the mailbox is a single file, the time of last access (the &"atime"&) is
26633 used. As no new messages are being delivered (because the mailbox is over
26634 quota), Exim does not access the file, so this is the time of last user access.
26636 .cindex "maildir format" "time of last read"
26637 For a maildir delivery, the time of last modification of the &_new_&
26638 subdirectory is used. As the mailbox is over quota, no new files are created in
26639 the &_new_& subdirectory, because no new messages are being delivered. Any
26640 change to the &_new_& subdirectory is therefore assumed to be the result of an
26641 MUA moving a new message to the &_cur_& directory when it is first read. The
26642 time that is used is therefore the last time that the user read a new message.
26644 For other kinds of multi-file mailbox, the time of last access cannot be
26645 obtained, so a retry rule that uses this type of error field is never matched.
26648 The quota errors apply both to system-enforced quotas and to Exim's own quota
26649 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26650 when a local delivery is deferred because a partition is full (the ENOSPC
26655 .section "Retry rules for specified senders" "SECID162"
26656 .cindex "retry" "rules; sender-specific"
26657 You can specify retry rules that apply only when the failing message has a
26658 specific sender. In particular, this can be used to define retry rules that
26659 apply only to bounce messages. The third item in a retry rule can be of this
26662 &`senders=`&<&'address list'&>
26664 The retry timings themselves are then the fourth item. For example:
26666 * rcpt_4xx senders=: F,1h,30m
26668 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
26669 host. If the address list contains white space, it must be enclosed in quotes.
26672 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
26674 &*Warning*&: This facility can be unhelpful if it is used for host errors
26675 (which do not depend on the recipient). The reason is that the sender is used
26676 only to match the retry rule. Once the rule has been found for a host error,
26677 its contents are used to set a retry time for the host, and this will apply to
26678 all messages, not just those with specific senders.
26680 When testing retry rules using &%-brt%&, you can supply a sender using the
26681 &%-f%& command line option, like this:
26683 exim -f "" -brt user@dom.ain
26685 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
26686 list is never matched.
26692 .section "Retry parameters" "SECID163"
26693 .cindex "retry" "parameters in rules"
26694 The third (or fourth, if a senders list is present) field in a retry rule is a
26695 sequence of retry parameter sets, separated by semicolons. Each set consists of
26697 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
26699 The letter identifies the algorithm for computing a new retry time; the cutoff
26700 time is the time beyond which this algorithm no longer applies, and the
26701 arguments vary the algorithm's action. The cutoff time is measured from the
26702 time that the first failure for the domain (combined with the local part if
26703 relevant) was detected, not from the time the message was received.
26705 .cindex "retry" "algorithms"
26706 .cindex "retry" "fixed intervals"
26707 .cindex "retry" "increasing intervals"
26708 .cindex "retry" "random intervals"
26709 The available algorithms are:
26712 &'F'&: retry at fixed intervals. There is a single time parameter specifying
26715 &'G'&: retry at geometrically increasing intervals. The first argument
26716 specifies a starting value for the interval, and the second a multiplier, which
26717 is used to increase the size of the interval at each retry.
26719 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
26720 retry, the previous interval is multiplied by the factor in order to get a
26721 maximum for the next interval. The minimum interval is the first argument of
26722 the parameter, and an actual interval is chosen randomly between them. Such a
26723 rule has been found to be helpful in cluster configurations when all the
26724 members of the cluster restart at once, and may therefore synchronize their
26725 queue processing times.
26728 When computing the next retry time, the algorithm definitions are scanned in
26729 order until one whose cutoff time has not yet passed is reached. This is then
26730 used to compute a new retry time that is later than the current time. In the
26731 case of fixed interval retries, this simply means adding the interval to the
26732 current time. For geometrically increasing intervals, retry intervals are
26733 computed from the rule's parameters until one that is greater than the previous
26734 interval is found. The main configuration variable
26735 .cindex "limit" "retry interval"
26736 .cindex "retry" "interval, maximum"
26737 .oindex "&%retry_interval_max%&"
26738 &%retry_interval_max%& limits the maximum interval between retries. It
26739 cannot be set greater than &`24h`&, which is its default value.
26741 A single remote domain may have a number of hosts associated with it, and each
26742 host may have more than one IP address. Retry algorithms are selected on the
26743 basis of the domain name, but are applied to each IP address independently. If,
26744 for example, a host has two IP addresses and one is unusable, Exim will
26745 generate retry times for it and will not try to use it until its next retry
26746 time comes. Thus the good IP address is likely to be tried first most of the
26749 .cindex "hints database" "use for retrying"
26750 Retry times are hints rather than promises. Exim does not make any attempt to
26751 run deliveries exactly at the computed times. Instead, a queue runner process
26752 starts delivery processes for delayed messages periodically, and these attempt
26753 new deliveries only for those addresses that have passed their next retry time.
26754 If a new message arrives for a deferred address, an immediate delivery attempt
26755 occurs only if the address has passed its retry time. In the absence of new
26756 messages, the minimum time between retries is the interval between queue runner
26757 processes. There is not much point in setting retry times of five minutes if
26758 your queue runners happen only once an hour, unless there are a significant
26759 number of incoming messages (which might be the case on a system that is
26760 sending everything to a smart host, for example).
26762 The data in the retry hints database can be inspected by using the
26763 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
26764 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
26765 &'exinext'& utility script can be used to find out what the next retry times
26766 are for the hosts associated with a particular mail domain, and also for local
26767 deliveries that have been deferred.
26770 .section "Retry rule examples" "SECID164"
26771 Here are some example retry rules:
26773 alice@wonderland.fict.example quota_5d F,7d,3h
26774 wonderland.fict.example quota_5d
26775 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
26776 lookingglass.fict.example * F,24h,30m;
26777 * refused_A F,2h,20m;
26778 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
26780 The first rule sets up special handling for mail to
26781 &'alice@wonderland.fict.example'& when there is an over-quota error and the
26782 mailbox has not been read for at least 5 days. Retries continue every three
26783 hours for 7 days. The second rule handles over-quota errors for all other local
26784 parts at &'wonderland.fict.example'&; the absence of a local part has the same
26785 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
26786 fail are bounced immediately if the mailbox has not been read for at least 5
26789 The third rule handles all other errors at &'wonderland.fict.example'&; retries
26790 happen every 15 minutes for an hour, then with geometrically increasing
26791 intervals until two days have passed since a delivery first failed. After the
26792 first hour there is a delay of one hour, then two hours, then four hours, and
26793 so on (this is a rather extreme example).
26795 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
26796 They happen every 30 minutes for 24 hours only. The remaining two rules handle
26797 all other domains, with special action for connection refusal from hosts that
26798 were not obtained from an MX record.
26800 The final rule in a retry configuration should always have asterisks in the
26801 first two fields so as to provide a general catch-all for any addresses that do
26802 not have their own special handling. This example tries every 15 minutes for 2
26803 hours, then with intervals starting at one hour and increasing by a factor of
26804 1.5 up to 16 hours, then every 8 hours up to 5 days.
26808 .section "Timeout of retry data" "SECID165"
26809 .cindex "timeout" "of retry data"
26810 .oindex "&%retry_data_expire%&"
26811 .cindex "hints database" "data expiry"
26812 .cindex "retry" "timeout of data"
26813 Exim timestamps the data that it writes to its retry hints database. When it
26814 consults the data during a delivery it ignores any that is older than the value
26815 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
26816 been tried for 7 days, Exim will try to deliver to it immediately a message
26817 arrives, and if that fails, it will calculate a retry time as if it were
26818 failing for the first time.
26820 This improves the behaviour for messages routed to rarely-used hosts such as MX
26821 backups. If such a host was down at one time, and happens to be down again when
26822 Exim tries a month later, using the old retry data would imply that it had been
26823 down all the time, which is not a justified assumption.
26825 If a host really is permanently dead, this behaviour causes a burst of retries
26826 every now and again, but only if messages routed to it are rare. If there is a
26827 message at least once every 7 days the retry data never expires.
26832 .section "Long-term failures" "SECID166"
26833 .cindex "delivery failure, long-term"
26834 .cindex "retry" "after long-term failure"
26835 Special processing happens when an email address has been failing for so long
26836 that the cutoff time for the last algorithm is reached. For example, using the
26837 default retry rule:
26839 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
26841 the cutoff time is four days. Reaching the retry cutoff is independent of how
26842 long any specific message has been failing; it is the length of continuous
26843 failure for the recipient address that counts.
26845 When the cutoff time is reached for a local delivery, or for all the IP
26846 addresses associated with a remote delivery, a subsequent delivery failure
26847 causes Exim to give up on the address, and a bounce message is generated.
26848 In order to cater for new messages that use the failing address, a next retry
26849 time is still computed from the final algorithm, and is used as follows:
26851 For local deliveries, one delivery attempt is always made for any subsequent
26852 messages. If this delivery fails, the address fails immediately. The
26853 post-cutoff retry time is not used.
26855 .cindex "final cutoff" "retries, controlling"
26856 .cindex retry "final cutoff"
26857 If the delivery is remote, there are two possibilities, controlled by the
26858 .oindex "&%delay_after_cutoff%&"
26859 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
26860 default. Until the post-cutoff retry time for one of the IP addresses,
26861 as set by the &%retry_data_expire%& option, is
26862 reached, the failing email address is bounced immediately, without a delivery
26863 attempt taking place. After that time, one new delivery attempt is made to
26864 those IP addresses that are past their retry times, and if that still fails,
26865 the address is bounced and new retry times are computed.
26867 In other words, when all the hosts for a given email address have been failing
26868 for a long time, Exim bounces rather then defers until one of the hosts' retry
26869 times is reached. Then it tries once, and bounces if that attempt fails. This
26870 behaviour ensures that few resources are wasted in repeatedly trying to deliver
26871 to a broken destination, but if the host does recover, Exim will eventually
26874 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
26875 addresses are past their final cutoff time, Exim tries to deliver to those IP
26876 addresses that have not been tried since the message arrived. If there are
26877 no suitable IP addresses, or if they all fail, the address is bounced. In other
26878 words, it does not delay when a new message arrives, but tries the expired
26879 addresses immediately, unless they have been tried since the message arrived.
26880 If there is a continuous stream of messages for the failing domains, setting
26881 &%delay_after_cutoff%& false means that there will be many more attempts to
26882 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
26885 .section "Deliveries that work intermittently" "SECID167"
26886 .cindex "retry" "intermittently working deliveries"
26887 Some additional logic is needed to cope with cases where a host is
26888 intermittently available, or when a message has some attribute that prevents
26889 its delivery when others to the same address get through. In this situation,
26890 because some messages are successfully delivered, the &"retry clock"& for the
26891 host or address keeps getting reset by the successful deliveries, and so
26892 failing messages remain in the queue for ever because the cutoff time is never
26895 Two exceptional actions are applied to prevent this happening. The first
26896 applies to errors that are related to a message rather than a remote host.
26897 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
26898 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
26899 commands, and quota failures. For this type of error, if a message's arrival
26900 time is earlier than the &"first failed"& time for the error, the earlier time
26901 is used when scanning the retry rules to decide when to try next and when to
26902 time out the address.
26904 The exceptional second action applies in all cases. If a message has been on
26905 the queue for longer than the cutoff time of any applicable retry rule for a
26906 given address, a delivery is attempted for that address, even if it is not yet
26907 time, and if this delivery fails, the address is timed out. A new retry time is
26908 not computed in this case, so that other messages for the same address are
26909 considered immediately.
26910 .ecindex IIDretconf1
26911 .ecindex IIDregconf2
26918 . ////////////////////////////////////////////////////////////////////////////
26919 . ////////////////////////////////////////////////////////////////////////////
26921 .chapter "SMTP authentication" "CHAPSMTPAUTH"
26922 .scindex IIDauthconf1 "SMTP" "authentication configuration"
26923 .scindex IIDauthconf2 "authentication"
26924 The &"authenticators"& section of Exim's runtime configuration is concerned
26925 with SMTP authentication. This facility is an extension to the SMTP protocol,
26926 described in RFC 2554, which allows a client SMTP host to authenticate itself
26927 to a server. This is a common way for a server to recognize clients that are
26928 permitted to use it as a relay. SMTP authentication is not of relevance to the
26929 transfer of mail between servers that have no managerial connection with each
26932 .cindex "AUTH" "description of"
26933 .cindex "ESMTP extensions" AUTH
26934 Very briefly, the way SMTP authentication works is as follows:
26937 The server advertises a number of authentication &'mechanisms'& in response to
26938 the client's EHLO command.
26940 The client issues an AUTH command, naming a specific mechanism. The command
26941 may, optionally, contain some authentication data.
26943 The server may issue one or more &'challenges'&, to which the client must send
26944 appropriate responses. In simple authentication mechanisms, the challenges are
26945 just prompts for user names and passwords. The server does not have to issue
26946 any challenges &-- in some mechanisms the relevant data may all be transmitted
26947 with the AUTH command.
26949 The server either accepts or denies authentication.
26951 If authentication succeeds, the client may optionally make use of the AUTH
26952 option on the MAIL command to pass an authenticated sender in subsequent
26953 mail transactions. Authentication lasts for the remainder of the SMTP
26956 If authentication fails, the client may give up, or it may try a different
26957 authentication mechanism, or it may try transferring mail over the
26958 unauthenticated connection.
26961 If you are setting up a client, and want to know which authentication
26962 mechanisms the server supports, you can use Telnet to connect to port 25 (the
26963 SMTP port) on the server, and issue an EHLO command. The response to this
26964 includes the list of supported mechanisms. For example:
26966 &`$ `&&*&`telnet server.example 25`&*&
26967 &`Trying 192.168.34.25...`&
26968 &`Connected to server.example.`&
26969 &`Escape character is '^]'.`&
26970 &`220 server.example ESMTP Exim 4.20 ...`&
26971 &*&`ehlo client.example`&*&
26972 &`250-server.example Hello client.example [10.8.4.5]`&
26973 &`250-SIZE 52428800`&
26978 The second-last line of this example output shows that the server supports
26979 authentication using the PLAIN mechanism. In Exim, the different authentication
26980 mechanisms are configured by specifying &'authenticator'& drivers. Like the
26981 routers and transports, which authenticators are included in the binary is
26982 controlled by build-time definitions. The following are currently available,
26983 included by setting
26986 AUTH_CYRUS_SASL=yes
26990 AUTH_HEIMDAL_GSSAPI=yes
26995 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
26996 authentication mechanism (RFC 2195), and the second provides an interface to
26997 the Cyrus SASL authentication library.
26998 The third is an interface to Dovecot's authentication system, delegating the
26999 work via a socket interface.
27000 The fourth provides for negotiation of authentication done via non-SMTP means,
27001 as defined by RFC 4422 Appendix A.
27002 The fifth provides an interface to the GNU SASL authentication library, which
27003 provides mechanisms but typically not data sources.
27004 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27005 supporting setting a server keytab.
27006 The seventh can be configured to support
27007 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27008 not formally documented, but used by several MUAs.
27009 The eighth authenticator
27010 supports Microsoft's &'Secure Password Authentication'& mechanism.
27011 The last is an Exim authenticator but not an SMTP one;
27012 instead it can use information from a TLS negotiation.
27014 The authenticators are configured using the same syntax as other drivers (see
27015 section &<<SECTfordricon>>&). If no authenticators are required, no
27016 authentication section need be present in the configuration file. Each
27017 authenticator can in principle have both server and client functions. When Exim
27018 is receiving SMTP mail, it is acting as a server; when it is sending out
27019 messages over SMTP, it is acting as a client. Authenticator configuration
27020 options are provided for use in both these circumstances.
27022 To make it clear which options apply to which situation, the prefixes
27023 &%server_%& and &%client_%& are used on option names that are specific to
27024 either the server or the client function, respectively. Server and client
27025 functions are disabled if none of their options are set. If an authenticator is
27026 to be used for both server and client functions, a single definition, using
27027 both sets of options, is required. For example:
27031 public_name = CRAM-MD5
27032 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27034 client_secret = secret2
27036 The &%server_%& option is used when Exim is acting as a server, and the
27037 &%client_%& options when it is acting as a client.
27039 Descriptions of the individual authenticators are given in subsequent chapters.
27040 The remainder of this chapter covers the generic options for the
27041 authenticators, followed by general discussion of the way authentication works
27044 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27045 per-mechanism basis. Please read carefully to determine which variables hold
27046 account labels such as usercodes and which hold passwords or other
27047 authenticating data.
27049 Note that some mechanisms support two different identifiers for accounts: the
27050 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27051 and &'authz'& are commonly encountered. The American spelling is standard here.
27052 Conceptually, authentication data such as passwords are tied to the identifier
27053 used to authenticate; servers may have rules to permit one user to act as a
27054 second user, so that after login the session is treated as though that second
27055 user had logged in. That second user is the &'authorization id'&. A robust
27056 configuration might confirm that the &'authz'& field is empty or matches the
27057 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27058 as verified data, the &'authz'& as an unverified request which the server might
27061 A &'realm'& is a text string, typically a domain name, presented by a server
27062 to a client to help it select an account and credentials to use. In some
27063 mechanisms, the client and server provably agree on the realm, but clients
27064 typically can not treat the realm as secure data to be blindly trusted.
27068 .section "Generic options for authenticators" "SECID168"
27069 .cindex "authentication" "generic options"
27070 .cindex "options" "generic; for authenticators"
27072 .option client_condition authenticators string&!! unset
27073 When Exim is authenticating as a client, it skips any authenticator whose
27074 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27075 used, for example, to skip plain text authenticators when the connection is not
27076 encrypted by a setting such as:
27078 client_condition = ${if !eq{$tls_out_cipher}{}}
27082 .option client_set_id authenticators string&!! unset
27083 When client authentication succeeds, this condition is expanded; the
27084 result is used in the log lines for outbound messages.
27085 Typically it will be the user name used for authentication.
27088 .option driver authenticators string unset
27089 This option must always be set. It specifies which of the available
27090 authenticators is to be used.
27093 .option public_name authenticators string unset
27094 This option specifies the name of the authentication mechanism that the driver
27095 implements, and by which it is known to the outside world. These names should
27096 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27097 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27098 defaults to the driver's instance name.
27101 .option server_advertise_condition authenticators string&!! unset
27102 When a server is about to advertise an authentication mechanism, the condition
27103 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27104 mechanism is not advertised.
27105 If the expansion fails, the mechanism is not advertised. If the failure was not
27106 forced, and was not caused by a lookup defer, the incident is logged.
27107 See section &<<SECTauthexiser>>& below for further discussion.
27110 .option server_condition authenticators string&!! unset
27111 This option must be set for a &%plaintext%& server authenticator, where it
27112 is used directly to control authentication. See section &<<SECTplainserver>>&
27115 For the &(gsasl)& authenticator, this option is required for various
27116 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27118 For the other authenticators, &%server_condition%& can be used as an additional
27119 authentication or authorization mechanism that is applied after the other
27120 authenticator conditions succeed. If it is set, it is expanded when the
27121 authenticator would otherwise return a success code. If the expansion is forced
27122 to fail, authentication fails. Any other expansion failure causes a temporary
27123 error code to be returned. If the result of a successful expansion is an empty
27124 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27125 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27126 other result, a temporary error code is returned, with the expanded string as
27130 .option server_debug_print authenticators string&!! unset
27131 If this option is set and authentication debugging is enabled (see the &%-d%&
27132 command line option), the string is expanded and included in the debugging
27133 output when the authenticator is run as a server. This can help with checking
27134 out the values of variables.
27135 If expansion of the string fails, the error message is written to the debugging
27136 output, and Exim carries on processing.
27139 .option server_set_id authenticators string&!! unset
27140 .vindex "&$authenticated_id$&"
27141 .vindex "&$authenticated_fail_id$&"
27142 When an Exim server successfully authenticates a client, this string is
27143 expanded using data from the authentication, and preserved for any incoming
27144 messages in the variable &$authenticated_id$&. It is also included in the log
27145 lines for incoming messages. For example, a user/password authenticator
27146 configuration might preserve the user name that was used to authenticate, and
27147 refer to it subsequently during delivery of the message.
27148 On a failing authentication the expansion result is instead saved in
27149 the &$authenticated_fail_id$& variable.
27150 If expansion fails, the option is ignored.
27153 .option server_mail_auth_condition authenticators string&!! unset
27154 This option allows a server to discard authenticated sender addresses supplied
27155 as part of MAIL commands in SMTP connections that are authenticated by the
27156 driver on which &%server_mail_auth_condition%& is set. The option is not used
27157 as part of the authentication process; instead its (unexpanded) value is
27158 remembered for later use.
27159 How it is used is described in the following section.
27165 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27166 .cindex "authentication" "sender; authenticated"
27167 .cindex "AUTH" "on MAIL command"
27168 When a client supplied an AUTH= item on a MAIL command, Exim applies
27169 the following checks before accepting it as the authenticated sender of the
27173 If the connection is not using extended SMTP (that is, HELO was used rather
27174 than EHLO), the use of AUTH= is a syntax error.
27176 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27178 .vindex "&$authenticated_sender$&"
27179 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27180 running, the value of &$authenticated_sender$& is set to the value obtained
27181 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27182 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27183 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27184 given for the MAIL command.
27186 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27187 is accepted and placed in &$authenticated_sender$& only if the client has
27190 If the AUTH= value was accepted by either of the two previous rules, and
27191 the client has authenticated, and the authenticator has a setting for the
27192 &%server_mail_auth_condition%&, the condition is checked at this point. The
27193 valued that was saved from the authenticator is expanded. If the expansion
27194 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27195 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27196 the value of &$authenticated_sender$& is retained and passed on with the
27201 When &$authenticated_sender$& is set for a message, it is passed on to other
27202 hosts to which Exim authenticates as a client. Do not confuse this value with
27203 &$authenticated_id$&, which is a string obtained from the authentication
27204 process, and which is not usually a complete email address.
27206 .vindex "&$sender_address$&"
27207 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27208 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27209 therefore make use of &$authenticated_sender$&. The converse is not true: the
27210 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27215 .section "Authentication on an Exim server" "SECTauthexiser"
27216 .cindex "authentication" "on an Exim server"
27217 When Exim receives an EHLO command, it advertises the public names of those
27218 authenticators that are configured as servers, subject to the following
27222 The client host must match &%auth_advertise_hosts%& (default *).
27224 It the &%server_advertise_condition%& option is set, its expansion must not
27225 yield the empty string, &"0"&, &"no"&, or &"false"&.
27228 The order in which the authenticators are defined controls the order in which
27229 the mechanisms are advertised.
27231 Some mail clients (for example, some versions of Netscape) require the user to
27232 provide a name and password for authentication whenever AUTH is advertised,
27233 even though authentication may not in fact be needed (for example, Exim may be
27234 set up to allow unconditional relaying from the client by an IP address check).
27235 You can make such clients more friendly by not advertising AUTH to them.
27236 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27237 that runs for RCPT) to relay without authentication, you should set
27239 auth_advertise_hosts = ! 10.9.8.0/24
27241 so that no authentication mechanisms are advertised to them.
27243 The &%server_advertise_condition%& controls the advertisement of individual
27244 authentication mechanisms. For example, it can be used to restrict the
27245 advertisement of a particular mechanism to encrypted connections, by a setting
27248 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27250 .vindex "&$tls_in_cipher$&"
27251 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27252 yields &"yes"&, which allows the advertisement to happen.
27254 When an Exim server receives an AUTH command from a client, it rejects it
27255 immediately if AUTH was not advertised in response to an earlier EHLO
27256 command. This is the case if
27259 The client host does not match &%auth_advertise_hosts%&; or
27261 No authenticators are configured with server options; or
27263 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27264 server authenticators.
27268 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27269 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27270 AUTH is accepted from any client host.
27272 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27273 server authentication mechanism that was advertised in response to EHLO and
27274 that matches the one named in the AUTH command. If it finds one, it runs
27275 the appropriate authentication protocol, and authentication either succeeds or
27276 fails. If there is no matching advertised mechanism, the AUTH command is
27277 rejected with a 504 error.
27279 .vindex "&$received_protocol$&"
27280 .vindex "&$sender_host_authenticated$&"
27281 When a message is received from an authenticated host, the value of
27282 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27283 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27284 public name) of the authenticator driver that successfully authenticated the
27285 client from which the message was received. This variable is empty if there was
27286 no successful authentication.
27288 .cindex authentication "expansion item"
27289 Successful authentication sets up information used by the
27290 &%authresults%& expansion item.
27295 .section "Testing server authentication" "SECID169"
27296 .cindex "authentication" "testing a server"
27297 .cindex "AUTH" "testing a server"
27298 .cindex "base64 encoding" "creating authentication test data"
27299 Exim's &%-bh%& option can be useful for testing server authentication
27300 configurations. The data for the AUTH command has to be sent using base64
27301 encoding. A quick way to produce such data for testing is the following Perl
27305 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27307 .cindex "binary zero" "in authentication data"
27308 This interprets its argument as a Perl string, and then encodes it. The
27309 interpretation as a Perl string allows binary zeros, which are required for
27310 some kinds of authentication, to be included in the data. For example, a
27311 command line to run this script on such data might be
27313 encode '\0user\0password'
27315 Note the use of single quotes to prevent the shell interpreting the
27316 backslashes, so that they can be interpreted by Perl to specify characters
27317 whose code value is zero.
27319 &*Warning 1*&: If either of the user or password strings starts with an octal
27320 digit, you must use three zeros instead of one after the leading backslash. If
27321 you do not, the octal digit that starts your string will be incorrectly
27322 interpreted as part of the code for the first character.
27324 &*Warning 2*&: If there are characters in the strings that Perl interprets
27325 specially, you must use a Perl escape to prevent them being misinterpreted. For
27326 example, a command such as
27328 encode '\0user@domain.com\0pas$$word'
27330 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27332 If you have the &%mimencode%& command installed, another way to do produce
27333 base64-encoded strings is to run the command
27335 echo -e -n `\0user\0password' | mimencode
27337 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27338 in the argument, and the &%-n%& option specifies no newline at the end of its
27339 output. However, not all versions of &%echo%& recognize these options, so you
27340 should check your version before relying on this suggestion.
27344 .section "Authentication by an Exim client" "SECID170"
27345 .cindex "authentication" "on an Exim client"
27346 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27347 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27348 announces support for authentication, and the host matches an entry in either
27349 of these options, Exim (as a client) tries to authenticate as follows:
27352 For each authenticator that is configured as a client, in the order in which
27353 they are defined in the configuration, it searches the authentication
27354 mechanisms announced by the server for one whose name matches the public name
27355 of the authenticator.
27358 .vindex "&$host_address$&"
27359 When it finds one that matches, it runs the authenticator's client code. The
27360 variables &$host$& and &$host_address$& are available for any string expansions
27361 that the client might do. They are set to the server's name and IP address. If
27362 any expansion is forced to fail, the authentication attempt is abandoned, and
27363 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27364 delivery to be deferred.
27366 If the result of the authentication attempt is a temporary error or a timeout,
27367 Exim abandons trying to send the message to the host for the moment. It will
27368 try again later. If there are any backup hosts available, they are tried in the
27371 If the response to authentication is a permanent error (5&'xx'& code), Exim
27372 carries on searching the list of authenticators and tries another one if
27373 possible. If all authentication attempts give permanent errors, or if there are
27374 no attempts because no mechanisms match (or option expansions force failure),
27375 what happens depends on whether the host matches &%hosts_require_auth%& or
27376 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27377 delivery is deferred. The error can be detected in the retry rules, and thereby
27378 turned into a permanent error if you wish. In the second case, Exim tries to
27379 deliver the message unauthenticated.
27382 Note that the hostlist test for whether to do authentication can be
27383 confused if name-IP lookups change between the time the peer is decided
27384 upon and the time that the transport runs. For example, with a manualroute
27385 router given a host name, and with DNS "round-robin" used by that name: if
27386 the local resolver cache times out between the router and the transport
27387 running, the transport may get an IP for the name for its authentication
27388 check which does not match the connection peer IP.
27389 No authentication will then be done, despite the names being identical.
27391 For such cases use a separate transport which always authenticates.
27393 .cindex "AUTH" "on MAIL command"
27394 When Exim has authenticated itself to a remote server, it adds the AUTH
27395 parameter to the MAIL commands it sends, if it has an authenticated sender for
27396 the message. If the message came from a remote host, the authenticated sender
27397 is the one that was receiving on an incoming MAIL command, provided that the
27398 incoming connection was authenticated and the &%server_mail_auth%& condition
27399 allowed the authenticated sender to be retained. If a local process calls Exim
27400 to send a message, the sender address that is built from the login name and
27401 &%qualify_domain%& is treated as authenticated. However, if the
27402 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27403 the authenticated sender that was received with the message.
27404 .ecindex IIDauthconf1
27405 .ecindex IIDauthconf2
27412 . ////////////////////////////////////////////////////////////////////////////
27413 . ////////////////////////////////////////////////////////////////////////////
27415 .chapter "The plaintext authenticator" "CHAPplaintext"
27416 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27417 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27418 The &(plaintext)& authenticator can be configured to support the PLAIN and
27419 LOGIN authentication mechanisms, both of which transfer authentication data as
27420 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27421 security risk; you are strongly advised to insist on the use of SMTP encryption
27422 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27423 use unencrypted plain text, you should not use the same passwords for SMTP
27424 connections as you do for login accounts.
27426 .section "Avoiding cleartext use" "SECTplain_TLS"
27427 The following generic option settings will disable &(plaintext)& authenticators when
27428 TLS is not being used:
27430 server_advertise_condition = ${if def:tls_in_cipher }
27431 client_condition = ${if def:tls_out_cipher}
27434 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27435 but is still vulnerable to a Man In The Middle attack unless certificates
27436 (including their names) have been properly verified.
27438 .section "Plaintext server options" "SECID171"
27439 .cindex "options" "&(plaintext)& authenticator (server)"
27440 When configured as a server, &(plaintext)& uses the following options:
27442 .option server_condition authenticators string&!! unset
27443 This is actually a global authentication option, but it must be set in order to
27444 configure the &(plaintext)& driver as a server. Its use is described below.
27446 .option server_prompts plaintext "string list&!!" unset
27447 The contents of this option, after expansion, must be a colon-separated list of
27448 prompt strings. If expansion fails, a temporary authentication rejection is
27451 .section "Using plaintext in a server" "SECTplainserver"
27452 .cindex "AUTH" "in &(plaintext)& authenticator"
27453 .cindex "binary zero" "in &(plaintext)& authenticator"
27454 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27455 "in &(plaintext)& authenticator"
27456 .vindex "&$auth1$&, &$auth2$&, etc"
27457 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27459 When running as a server, &(plaintext)& performs the authentication test by
27460 expanding a string. The data sent by the client with the AUTH command, or in
27461 response to subsequent prompts, is base64 encoded, and so may contain any byte
27462 values when decoded. If any data is supplied with the command, it is treated as
27463 a list of strings, separated by NULs (binary zeros), the first three of which
27464 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27465 (neither LOGIN nor PLAIN uses more than three strings).
27467 For compatibility with previous releases of Exim, the values are also placed in
27468 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27469 variables for this purpose is now deprecated, as it can lead to confusion in
27470 string expansions that also use them for other things.
27472 If there are more strings in &%server_prompts%& than the number of strings
27473 supplied with the AUTH command, the remaining prompts are used to obtain more
27474 data. Each response from the client may be a list of NUL-separated strings.
27476 .vindex "&$authenticated_id$&"
27477 Once a sufficient number of data strings have been received,
27478 &%server_condition%& is expanded. If the expansion is forced to fail,
27479 authentication fails. Any other expansion failure causes a temporary error code
27480 to be returned. If the result of a successful expansion is an empty string,
27481 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27482 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27483 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27484 For any other result, a temporary error code is returned, with the expanded
27485 string as the error text.
27487 &*Warning*&: If you use a lookup in the expansion to find the user's
27488 password, be sure to make the authentication fail if the user is unknown.
27489 There are good and bad examples at the end of the next section.
27493 .section "The PLAIN authentication mechanism" "SECID172"
27494 .cindex "PLAIN authentication mechanism"
27495 .cindex authentication PLAIN
27496 .cindex "binary zero" "in &(plaintext)& authenticator"
27497 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27498 sent as one item of data (that is, one combined string containing two NUL
27499 separators). The data is sent either as part of the AUTH command, or
27500 subsequently in response to an empty prompt from the server.
27502 The second and third strings are a user name and a corresponding password.
27503 Using a single fixed user name and password as an example, this could be
27504 configured as follows:
27508 public_name = PLAIN
27510 server_condition = \
27511 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27512 server_set_id = $auth2
27514 Note that the default result strings from &%if%& (&"true"& or an empty string)
27515 are exactly what we want here, so they need not be specified. Obviously, if the
27516 password contains expansion-significant characters such as dollar, backslash,
27517 or closing brace, they have to be escaped.
27519 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27520 the end of a string list are ignored). If all the data comes as part of the
27521 AUTH command, as is commonly the case, the prompt is not used. This
27522 authenticator is advertised in the response to EHLO as
27526 and a client host can authenticate itself by sending the command
27528 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27530 As this contains three strings (more than the number of prompts), no further
27531 data is required from the client. Alternatively, the client may just send
27535 to initiate authentication, in which case the server replies with an empty
27536 prompt. The client must respond with the combined data string.
27538 The data string is base64 encoded, as required by the RFC. This example,
27539 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27540 represents a zero byte. This is split up into three strings, the first of which
27541 is empty. The &%server_condition%& option in the authenticator checks that the
27542 second two are &`username`& and &`mysecret`& respectively.
27544 Having just one fixed user name and password, as in this example, is not very
27545 realistic, though for a small organization with only a handful of
27546 authenticating clients it could make sense.
27548 A more sophisticated instance of this authenticator could use the user name in
27549 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27550 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27551 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27552 This is an incorrect example:
27554 server_condition = \
27555 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27557 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27558 which it then compares to the supplied password (&$auth3$&). Why is this example
27559 incorrect? It works fine for existing users, but consider what happens if a
27560 non-existent user name is given. The lookup fails, but as no success/failure
27561 strings are given for the lookup, it yields an empty string. Thus, to defeat
27562 the authentication, all a client has to do is to supply a non-existent user
27563 name and an empty password. The correct way of writing this test is:
27565 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27566 {${if eq{$value}{$auth3}}} {false}}
27568 In this case, if the lookup succeeds, the result is checked; if the lookup
27569 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27570 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27571 always fails if its second argument is empty. However, the second way of
27572 writing the test makes the logic clearer.
27575 .section "The LOGIN authentication mechanism" "SECID173"
27576 .cindex "LOGIN authentication mechanism"
27577 .cindex authentication LOGIN
27578 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27579 in a number of programs. No data is sent with the AUTH command. Instead, a
27580 user name and password are supplied separately, in response to prompts. The
27581 plaintext authenticator can be configured to support this as in this example:
27585 public_name = LOGIN
27586 server_prompts = User Name : Password
27587 server_condition = \
27588 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27589 server_set_id = $auth1
27591 Because of the way plaintext operates, this authenticator accepts data supplied
27592 with the AUTH command (in contravention of the specification of LOGIN), but
27593 if the client does not supply it (as is the case for LOGIN clients), the prompt
27594 strings are used to obtain two data items.
27596 Some clients are very particular about the precise text of the prompts. For
27597 example, Outlook Express is reported to recognize only &"Username:"& and
27598 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27599 strings. It uses the &%ldapauth%& expansion condition to check the user
27600 name and password by binding to an LDAP server:
27604 public_name = LOGIN
27605 server_prompts = Username:: : Password::
27606 server_condition = ${if and{{ \
27609 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27610 pass=${quote:$auth2} \
27611 ldap://ldap.example.org/} }} }
27612 server_set_id = uid=$auth1,ou=people,o=example.org
27614 We have to check that the username is not empty before using it, because LDAP
27615 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27616 operator to correctly quote the DN for authentication. However, the basic
27617 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27618 correct one to use for the password, because quoting is needed only to make
27619 the password conform to the Exim syntax. At the LDAP level, the password is an
27620 uninterpreted string.
27623 .section "Support for different kinds of authentication" "SECID174"
27624 A number of string expansion features are provided for the purpose of
27625 interfacing to different ways of user authentication. These include checking
27626 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27627 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27633 .section "Using plaintext in a client" "SECID175"
27634 .cindex "options" "&(plaintext)& authenticator (client)"
27635 The &(plaintext)& authenticator has two client options:
27637 .option client_ignore_invalid_base64 plaintext boolean false
27638 If the client receives a server prompt that is not a valid base64 string,
27639 authentication is abandoned by default. However, if this option is set true,
27640 the error in the challenge is ignored and the client sends the response as
27643 .option client_send plaintext string&!! unset
27644 The string is a colon-separated list of authentication data strings. Each
27645 string is independently expanded before being sent to the server. The first
27646 string is sent with the AUTH command; any more strings are sent in response
27647 to prompts from the server. Before each string is expanded, the value of the
27648 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27649 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27650 way. Thus, the prompt that is received in response to sending the first string
27651 (with the AUTH command) can be used in the expansion of the second string, and
27652 so on. If an invalid base64 string is received when
27653 &%client_ignore_invalid_base64%& is set, an empty string is put in the
27654 &$auth$&<&'n'&> variable.
27656 &*Note*&: You cannot use expansion to create multiple strings, because
27657 splitting takes priority and happens first.
27659 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
27660 the data, further processing is applied to each string before it is sent. If
27661 there are any single circumflex characters in the string, they are converted to
27662 NULs. Should an actual circumflex be required as data, it must be doubled in
27665 This is an example of a client configuration that implements the PLAIN
27666 authentication mechanism with a fixed user name and password:
27670 public_name = PLAIN
27671 client_send = ^username^mysecret
27673 The lack of colons means that the entire text is sent with the AUTH
27674 command, with the circumflex characters converted to NULs. A similar example
27675 that uses the LOGIN mechanism is:
27679 public_name = LOGIN
27680 client_send = : username : mysecret
27682 The initial colon means that the first string is empty, so no data is sent with
27683 the AUTH command itself. The remaining strings are sent in response to
27685 .ecindex IIDplaiauth1
27686 .ecindex IIDplaiauth2
27691 . ////////////////////////////////////////////////////////////////////////////
27692 . ////////////////////////////////////////////////////////////////////////////
27694 .chapter "The cram_md5 authenticator" "CHID9"
27695 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
27696 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
27697 .cindex "CRAM-MD5 authentication mechanism"
27698 .cindex authentication CRAM-MD5
27699 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
27700 sends a challenge string to the client, and the response consists of a user
27701 name and the CRAM-MD5 digest of the challenge string combined with a secret
27702 string (password) which is known to both server and client. Thus, the secret
27703 is not sent over the network as plain text, which makes this authenticator more
27704 secure than &(plaintext)&. However, the downside is that the secret has to be
27705 available in plain text at either end.
27708 .section "Using cram_md5 as a server" "SECID176"
27709 .cindex "options" "&(cram_md5)& authenticator (server)"
27710 This authenticator has one server option, which must be set to configure the
27711 authenticator as a server:
27713 .option server_secret cram_md5 string&!! unset
27714 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
27715 When the server receives the client's response, the user name is placed in
27716 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
27717 obtain the password for that user. The server then computes the CRAM-MD5 digest
27718 that the client should have sent, and checks that it received the correct
27719 string. If the expansion of &%server_secret%& is forced to fail, authentication
27720 fails. If the expansion fails for some other reason, a temporary error code is
27721 returned to the client.
27723 For compatibility with previous releases of Exim, the user name is also placed
27724 in &$1$&. However, the use of this variables for this purpose is now
27725 deprecated, as it can lead to confusion in string expansions that also use
27726 numeric variables for other things.
27728 For example, the following authenticator checks that the user name given by the
27729 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
27730 user name, authentication fails.
27734 public_name = CRAM-MD5
27735 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
27736 server_set_id = $auth1
27738 .vindex "&$authenticated_id$&"
27739 If authentication succeeds, the setting of &%server_set_id%& preserves the user
27740 name in &$authenticated_id$&. A more typical configuration might look up the
27741 secret string in a file, using the user name as the key. For example:
27745 public_name = CRAM-MD5
27746 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
27748 server_set_id = $auth1
27750 Note that this expansion explicitly forces failure if the lookup fails
27751 because &$auth1$& contains an unknown user name.
27753 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
27754 using the relevant libraries, you need to know the realm to specify in the
27755 lookup and then ask for the &"userPassword"& attribute for that user in that
27760 public_name = CRAM-MD5
27761 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
27762 dbmjz{/etc/sasldb2}{$value}fail}
27763 server_set_id = $auth1
27766 .section "Using cram_md5 as a client" "SECID177"
27767 .cindex "options" "&(cram_md5)& authenticator (client)"
27768 When used as a client, the &(cram_md5)& authenticator has two options:
27772 .option client_name cram_md5 string&!! "the primary host name"
27773 This string is expanded, and the result used as the user name data when
27774 computing the response to the server's challenge.
27777 .option client_secret cram_md5 string&!! unset
27778 This option must be set for the authenticator to work as a client. Its value is
27779 expanded and the result used as the secret string when computing the response.
27783 .vindex "&$host_address$&"
27784 Different user names and secrets can be used for different servers by referring
27785 to &$host$& or &$host_address$& in the options. Forced failure of either
27786 expansion string is treated as an indication that this authenticator is not
27787 prepared to handle this case. Exim moves on to the next configured client
27788 authenticator. Any other expansion failure causes Exim to give up trying to
27789 send the message to the current server.
27791 A simple example configuration of a &(cram_md5)& authenticator, using fixed
27796 public_name = CRAM-MD5
27798 client_secret = secret
27800 .ecindex IIDcramauth1
27801 .ecindex IIDcramauth2
27805 . ////////////////////////////////////////////////////////////////////////////
27806 . ////////////////////////////////////////////////////////////////////////////
27808 .chapter "The cyrus_sasl authenticator" "CHID10"
27809 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
27810 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
27811 .cindex "Cyrus" "SASL library"
27813 The code for this authenticator was provided by Matthew Byng-Maddick while
27814 at A L Digital Ltd.
27816 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
27817 library implementation of the RFC 2222 (&"Simple Authentication and Security
27818 Layer"&). This library supports a number of authentication mechanisms,
27819 including PLAIN and LOGIN, but also several others that Exim does not support
27820 directly. In particular, there is support for Kerberos authentication.
27822 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
27823 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
27824 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
27825 name of the driver to determine which mechanism to support.
27827 Where access to some kind of secret file is required, for example, in GSSAPI
27828 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
27829 user, and that the Cyrus SASL library has no way of escalating privileges
27830 by default. You may also find you need to set environment variables,
27831 depending on the driver you are using.
27833 The application name provided by Exim is &"exim"&, so various SASL options may
27834 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
27835 Kerberos, note that because of limitations in the GSSAPI interface,
27836 changing the server keytab might need to be communicated down to the Kerberos
27837 layer independently. The mechanism for doing so is dependent upon the Kerberos
27840 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
27841 may be set to point to an alternative keytab file. Exim will pass this
27842 variable through from its own inherited environment when started as root or the
27843 Exim user. The keytab file needs to be readable by the Exim user.
27844 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
27845 environment variable. In practice, for those releases, the Cyrus authenticator
27846 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
27847 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
27850 .section "Using cyrus_sasl as a server" "SECID178"
27851 The &(cyrus_sasl)& authenticator has four private options. It puts the username
27852 (on a successful authentication) into &$auth1$&. For compatibility with
27853 previous releases of Exim, the username is also placed in &$1$&. However, the
27854 use of this variable for this purpose is now deprecated, as it can lead to
27855 confusion in string expansions that also use numeric variables for other
27859 .option server_hostname cyrus_sasl string&!! "see below"
27860 This option selects the hostname that is used when communicating with the
27861 library. The default value is &`$primary_hostname`&. It is up to the underlying
27862 SASL plug-in what it does with this data.
27865 .option server_mech cyrus_sasl string "see below"
27866 This option selects the authentication mechanism this driver should use. The
27867 default is the value of the generic &%public_name%& option. This option allows
27868 you to use a different underlying mechanism from the advertised name. For
27872 driver = cyrus_sasl
27873 public_name = X-ANYTHING
27874 server_mech = CRAM-MD5
27875 server_set_id = $auth1
27878 .option server_realm cyrus_sasl string&!! unset
27879 This specifies the SASL realm that the server claims to be in.
27882 .option server_service cyrus_sasl string &`smtp`&
27883 This is the SASL service that the server claims to implement.
27886 For straightforward cases, you do not need to set any of the authenticator's
27887 private options. All you need to do is to specify an appropriate mechanism as
27888 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
27889 PLAIN, you could have two authenticators as follows:
27892 driver = cyrus_sasl
27893 public_name = CRAM-MD5
27894 server_set_id = $auth1
27897 driver = cyrus_sasl
27898 public_name = PLAIN
27899 server_set_id = $auth2
27901 Cyrus SASL does implement the LOGIN authentication method, even though it is
27902 not a standard method. It is disabled by default in the source distribution,
27903 but it is present in many binary distributions.
27904 .ecindex IIDcyrauth1
27905 .ecindex IIDcyrauth2
27910 . ////////////////////////////////////////////////////////////////////////////
27911 . ////////////////////////////////////////////////////////////////////////////
27912 .chapter "The dovecot authenticator" "CHAPdovecot"
27913 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
27914 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
27915 This authenticator is an interface to the authentication facility of the
27916 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
27917 Note that Dovecot must be configured to use auth-client not auth-userdb.
27918 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
27919 to use the same mechanisms for SMTP authentication. This is a server
27920 authenticator only. There is only one option:
27922 .option server_socket dovecot string unset
27924 This option must specify the UNIX socket that is the interface to Dovecot
27925 authentication. The &%public_name%& option must specify an authentication
27926 mechanism that Dovecot is configured to support. You can have several
27927 authenticators for different mechanisms. For example:
27931 public_name = PLAIN
27932 server_socket = /var/run/dovecot/auth-client
27933 server_set_id = $auth1
27938 server_socket = /var/run/dovecot/auth-client
27939 server_set_id = $auth1
27941 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
27942 &$received_ip_address$& (that is, the connection is local), the &"secured"&
27943 option is passed in the Dovecot authentication command. If, for a TLS
27944 connection, a client certificate has been verified, the &"valid-client-cert"&
27945 option is passed. When authentication succeeds, the identity of the user
27946 who authenticated is placed in &$auth1$&.
27948 The Dovecot configuration to match the above wil look
27951 conf.d/10-master.conf :-
27956 unix_listener auth-client {
27963 conf.d/10-auth.conf :-
27965 auth_mechanisms = plain login ntlm
27968 .ecindex IIDdcotauth1
27969 .ecindex IIDdcotauth2
27972 . ////////////////////////////////////////////////////////////////////////////
27973 . ////////////////////////////////////////////////////////////////////////////
27974 .chapter "The gsasl authenticator" "CHAPgsasl"
27975 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
27976 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
27977 .cindex "authentication" "GNU SASL"
27978 .cindex "authentication" "SASL"
27979 .cindex "authentication" "EXTERNAL"
27980 .cindex "authentication" "ANONYMOUS"
27981 .cindex "authentication" "PLAIN"
27982 .cindex "authentication" "LOGIN"
27983 .cindex "authentication" "DIGEST-MD5"
27984 .cindex "authentication" "CRAM-MD5"
27985 .cindex "authentication" "SCRAM family"
27986 The &(gsasl)& authenticator provides integration for the GNU SASL
27987 library and the mechanisms it provides. This is new as of the 4.80 release
27988 and there are a few areas where the library does not let Exim smoothly
27989 scale to handle future authentication mechanisms, so no guarantee can be
27990 made that any particular new authentication mechanism will be supported
27991 without code changes in Exim.
27993 The library is expected to add support in an upcoming
27994 realease for the SCRAM-SHA-256 method.
27995 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
27999 .option client_authz gsasl string&!! unset
28000 This option can be used to supply an &'authorization id'&
28001 which is different to the &'authentication_id'& provided
28002 by &%client_username%& option.
28003 If unset or (after expansion) empty it is not used,
28004 which is the common case.
28006 .option client_channelbinding gsasl boolean false
28007 See &%server_channelbinding%& below.
28009 .option client_password gsasl string&!! unset
28010 This option is exapanded before use, and should result in
28011 the password to be used, in clear.
28013 .option client_username gsasl string&!! unset
28014 This option is exapanded before use, and should result in
28015 the account name to be used.
28017 .option client_spassword gsasl string&!! unset
28018 If a SCRAM mechanism is being used and this option is set
28019 it is used in preference to &%client_password%&.
28020 The value after expansion should be
28021 a 40 (for SHA-1) or 64 (for SHA-256) character string
28022 with the PBKDF2-prepared password, hex-encoded.
28023 Note that this value will depend on the salt and iteration-count
28024 supplied by the server.
28028 .option server_channelbinding gsasl boolean false
28029 Do not set this true and rely on the properties
28030 without consulting a cryptographic engineer.
28032 Some authentication mechanisms are able to use external context at both ends
28033 of the session to bind the authentication to that context, and fail the
28034 authentication process if that context differs. Specifically, some TLS
28035 ciphersuites can provide identifying information about the cryptographic
28038 This should have meant that certificate identity and verification becomes a
28039 non-issue, as a man-in-the-middle attack will cause the correct client and
28040 server to see different identifiers and authentication will fail.
28043 only usable by mechanisms which support "channel binding"; at time of
28044 writing, that's the SCRAM family.
28045 When using this feature the "-PLUS" variants of the method names need to be used.
28047 This defaults off to ensure smooth upgrade across Exim releases, in case
28048 this option causes some clients to start failing. Some future release
28049 of Exim might have switched the default to be true.
28051 However, Channel Binding in TLS has proven to be vulnerable in current versions.
28052 Do not plan to rely upon this feature for security, ever, without consulting
28053 with a subject matter expert (a cryptographic engineer).
28056 .option server_hostname gsasl string&!! "see below"
28057 This option selects the hostname that is used when communicating with the
28058 library. The default value is &`$primary_hostname`&.
28059 Some mechanisms will use this data.
28062 .option server_mech gsasl string "see below"
28063 This option selects the authentication mechanism this driver should use. The
28064 default is the value of the generic &%public_name%& option. This option allows
28065 you to use a different underlying mechanism from the advertised name. For
28070 public_name = X-ANYTHING
28071 server_mech = CRAM-MD5
28072 server_set_id = $auth1
28076 .option server_password gsasl string&!! unset
28077 Various mechanisms need access to the cleartext password on the server, so
28078 that proof-of-possession can be demonstrated on the wire, without sending
28079 the password itself.
28081 The data available for lookup varies per mechanism.
28082 In all cases, &$auth1$& is set to the &'authentication id'&.
28083 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28084 if available, else the empty string.
28085 The &$auth3$& variable will always be the &'realm'& if available,
28086 else the empty string.
28088 A forced failure will cause authentication to defer.
28090 If using this option, it may make sense to set the &%server_condition%&
28091 option to be simply "true".
28094 .option server_realm gsasl string&!! unset
28095 This specifies the SASL realm that the server claims to be in.
28096 Some mechanisms will use this data.
28099 .option server_scram_iter gsasl string&!! 4096
28100 This option provides data for the SCRAM family of mechanisms.
28101 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28102 when this option is expanded.
28104 The result of expansion should be a decimal number,
28105 and represents both a lower-bound on the security, and
28106 a compute cost factor imposed on the client
28107 (if it does not cache results, or the server changes
28108 either the iteration count or the salt).
28109 A minimum value of 4096 is required by the standards
28110 for all current SCRAM mechanism variants.
28112 .option server_scram_salt gsasl string&!! unset
28113 This option provides data for the SCRAM family of mechanisms.
28114 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28115 when this option is expanded.
28116 The value should be a base64-encoded string,
28117 of random data typically 4-to-16 bytes long.
28118 If unset or empty after expansion the library will provides a value for the
28119 protocol conversation.
28122 .option server_key gsasl string&!! unset
28123 .option server_skey gsasl string&!! unset
28124 These options can be used for the SCRAM family of mechanisms
28125 to provide stored information related to a password,
28126 the storage of which is preferable to plaintext.
28128 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28129 &%server_skey%& is StoredKey.
28131 They are only available for version 1.9.0 (or later) of the gsasl library.
28132 When this is so, the macros
28133 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28134 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28137 The &$authN$& variables are available when these options are expanded.
28139 If set, the results of expansion should for each
28140 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28141 of base64-coded data, and will be used in preference to the
28142 &%server_password%& option.
28143 If unset or not of the right length, &%server_password%& will be used.
28145 The libgsasl library release includes a utility &'gsasl'& which can be used
28146 to generate these values.
28149 .option server_service gsasl string &`smtp`&
28150 This is the SASL service that the server claims to implement.
28151 Some mechanisms will use this data.
28154 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28155 .vindex "&$auth1$&, &$auth2$&, etc"
28156 These may be set when evaluating specific options, as detailed above.
28157 They will also be set when evaluating &%server_condition%&.
28159 Unless otherwise stated below, the &(gsasl)& integration will use the following
28160 meanings for these variables:
28163 .vindex "&$auth1$&"
28164 &$auth1$&: the &'authentication id'&
28166 .vindex "&$auth2$&"
28167 &$auth2$&: the &'authorization id'&
28169 .vindex "&$auth3$&"
28170 &$auth3$&: the &'realm'&
28173 On a per-mechanism basis:
28176 .cindex "authentication" "EXTERNAL"
28177 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28178 the &%server_condition%& option must be present.
28180 .cindex "authentication" "ANONYMOUS"
28181 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28182 the &%server_condition%& option must be present.
28184 .cindex "authentication" "GSSAPI"
28185 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28186 &$auth2$& will be set to the &'authorization id'&,
28187 the &%server_condition%& option must be present.
28190 An &'anonymous token'& is something passed along as an unauthenticated
28191 identifier; this is analogous to FTP anonymous authentication passing an
28192 email address, or software-identifier@, as the "password".
28195 An example showing the password having the realm specified in the callback
28196 and demonstrating a Cyrus SASL to GSASL migration approach is:
28198 gsasl_cyrusless_crammd5:
28200 public_name = CRAM-MD5
28201 server_realm = imap.example.org
28202 server_password = ${lookup{$auth1:$auth3:userPassword}\
28203 dbmjz{/etc/sasldb2}{$value}fail}
28204 server_set_id = ${quote:$auth1}
28205 server_condition = yes
28209 . ////////////////////////////////////////////////////////////////////////////
28210 . ////////////////////////////////////////////////////////////////////////////
28212 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28213 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28214 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28215 .cindex "authentication" "GSSAPI"
28216 .cindex "authentication" "Kerberos"
28217 The &(heimdal_gssapi)& authenticator provides server integration for the
28218 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28221 .option server_hostname heimdal_gssapi string&!! "see below"
28222 This option selects the hostname that is used, with &%server_service%&,
28223 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28224 identifier. The default value is &`$primary_hostname`&.
28226 .option server_keytab heimdal_gssapi string&!! unset
28227 If set, then Heimdal will not use the system default keytab (typically
28228 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28229 The value should be a pathname, with no &"file:"& prefix.
28231 .option server_service heimdal_gssapi string&!! "smtp"
28232 This option specifies the service identifier used, in conjunction with
28233 &%server_hostname%&, for building the identifier for finding credentials
28237 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28238 Beware that these variables will typically include a realm, thus will appear
28239 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28240 not verified, so a malicious client can set it to anything.
28242 The &$auth1$& field should be safely trustable as a value from the Key
28243 Distribution Center. Note that these are not quite email addresses.
28244 Each identifier is for a role, and so the left-hand-side may include a
28245 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28247 .vindex "&$auth1$&, &$auth2$&, etc"
28249 .vindex "&$auth1$&"
28250 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28252 .vindex "&$auth2$&"
28253 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28254 authentication. If that was empty, this will also be set to the
28259 . ////////////////////////////////////////////////////////////////////////////
28260 . ////////////////////////////////////////////////////////////////////////////
28262 .chapter "The spa authenticator" "CHAPspa"
28263 .scindex IIDspaauth1 "&(spa)& authenticator"
28264 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28265 .cindex "authentication" "Microsoft Secure Password"
28266 .cindex "authentication" "NTLM"
28267 .cindex "Microsoft Secure Password Authentication"
28268 .cindex "NTLM authentication"
28269 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28270 Password Authentication'& mechanism,
28271 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28272 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28273 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28274 server side was subsequently contributed by Tom Kistner. The mechanism works as
28278 After the AUTH command has been accepted, the client sends an SPA
28279 authentication request based on the user name and optional domain.
28281 The server sends back a challenge.
28283 The client builds a challenge response which makes use of the user's password
28284 and sends it to the server, which then accepts or rejects it.
28287 Encryption is used to protect the password in transit.
28291 .section "Using spa as a server" "SECID179"
28292 .cindex "options" "&(spa)& authenticator (server)"
28293 The &(spa)& authenticator has just one server option:
28295 .option server_password spa string&!! unset
28296 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28297 This option is expanded, and the result must be the cleartext password for the
28298 authenticating user, whose name is at this point in &$auth1$&. For
28299 compatibility with previous releases of Exim, the user name is also placed in
28300 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28301 it can lead to confusion in string expansions that also use numeric variables
28302 for other things. For example:
28307 server_password = \
28308 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28310 If the expansion is forced to fail, authentication fails. Any other expansion
28311 failure causes a temporary error code to be returned.
28317 .section "Using spa as a client" "SECID180"
28318 .cindex "options" "&(spa)& authenticator (client)"
28319 The &(spa)& authenticator has the following client options:
28323 .option client_domain spa string&!! unset
28324 This option specifies an optional domain for the authentication.
28327 .option client_password spa string&!! unset
28328 This option specifies the user's password, and must be set.
28331 .option client_username spa string&!! unset
28332 This option specifies the user name, and must be set. Here is an example of a
28333 configuration of this authenticator for use with the mail servers at
28339 client_username = msn/msn_username
28340 client_password = msn_plaintext_password
28341 client_domain = DOMAIN_OR_UNSET
28343 .ecindex IIDspaauth1
28344 .ecindex IIDspaauth2
28350 . ////////////////////////////////////////////////////////////////////////////
28351 . ////////////////////////////////////////////////////////////////////////////
28353 .chapter "The external authenticator" "CHAPexternauth"
28354 .scindex IIDexternauth1 "&(external)& authenticator"
28355 .scindex IIDexternauth2 "authenticators" "&(external)&"
28356 .cindex "authentication" "Client Certificate"
28357 .cindex "authentication" "X509"
28358 .cindex "Certificate-based authentication"
28359 The &(external)& authenticator provides support for
28360 authentication based on non-SMTP information.
28361 The specification is in RFC 4422 Appendix A
28362 (&url(https://tools.ietf.org/html/rfc4422)).
28363 It is only a transport and negotiation mechanism;
28364 the process of authentication is entirely controlled
28365 by the server configuration.
28367 The client presents an identity in-clear.
28368 It is probably wise for a server to only advertise,
28369 and for clients to only attempt,
28370 this authentication method on a secure (eg. under TLS) connection.
28372 One possible use, compatible with the
28373 K-9 Mail Andoid client (&url(https://k9mail.github.io/)),
28374 is for using X509 client certificates.
28376 It thus overlaps in function with the TLS authenticator
28377 (see &<<CHAPtlsauth>>&)
28378 but is a full SMTP SASL authenticator
28379 rather than being implicit for TLS-connection carried
28380 client certificates only.
28382 The examples and discussion in this chapter assume that
28383 client-certificate authentication is being done.
28385 The client must present a certificate,
28386 for which it must have been requested via the
28387 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28388 (see &<<CHAPTLS>>&).
28389 For authentication to be effective the certificate should be
28390 verifiable against a trust-anchor certificate known to the server.
28392 .section "External options" "SECTexternsoptions"
28393 .cindex "options" "&(external)& authenticator (server)"
28394 The &(external)& authenticator has two server options:
28396 .option server_param2 external string&!! unset
28397 .option server_param3 external string&!! unset
28398 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28399 These options are expanded before the &%server_condition%& option
28400 and the result are placed in &$auth2$& and &$auth3$& resectively.
28401 If the expansion is forced to fail, authentication fails. Any other expansion
28402 failure causes a temporary error code to be returned.
28404 They can be used to clarify the coding of a complex &%server_condition%&.
28406 .section "Using external in a server" "SECTexternserver"
28407 .cindex "AUTH" "in &(external)& authenticator"
28408 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28409 "in &(external)& authenticator"
28410 .vindex "&$auth1$&, &$auth2$&, etc"
28411 .cindex "base64 encoding" "in &(external)& authenticator"
28413 When running as a server, &(external)& performs the authentication test by
28414 expanding a string. The data sent by the client with the AUTH command, or in
28415 response to subsequent prompts, is base64 encoded, and so may contain any byte
28416 values when decoded. The decoded value is treated as
28417 an identity for authentication and
28418 placed in the expansion variable &$auth1$&.
28420 For compatibility with previous releases of Exim, the value is also placed in
28421 the expansion variable &$1$&. However, the use of this
28422 variable for this purpose is now deprecated, as it can lead to confusion in
28423 string expansions that also use them for other things.
28425 .vindex "&$authenticated_id$&"
28426 Once an identity has been received,
28427 &%server_condition%& is expanded. If the expansion is forced to fail,
28428 authentication fails. Any other expansion failure causes a temporary error code
28429 to be returned. If the result of a successful expansion is an empty string,
28430 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28431 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28432 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28433 For any other result, a temporary error code is returned, with the expanded
28434 string as the error text.
28438 ext_ccert_san_mail:
28440 public_name = EXTERNAL
28442 server_advertise_condition = $tls_in_certificate_verified
28443 server_param2 = ${certextract {subj_altname,mail,>:} \
28444 {$tls_in_peercert}}
28445 server_condition = ${if forany {$auth2} \
28446 {eq {$item}{$auth1}}}
28447 server_set_id = $auth1
28449 This accepts a client certificate that is verifiable against any
28450 of your configured trust-anchors
28451 (which usually means the full set of public CAs)
28452 and which has a mail-SAN matching the claimed identity sent by the client.
28454 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28455 The account name is therefore guessable by an opponent.
28456 TLS 1.3 protects both server and client certificates, and is not vulnerable
28460 .section "Using external in a client" "SECTexternclient"
28461 .cindex "options" "&(external)& authenticator (client)"
28462 The &(external)& authenticator has one client option:
28464 .option client_send external string&!! unset
28465 This option is expanded and sent with the AUTH command as the
28466 identity being asserted.
28472 public_name = EXTERNAL
28474 client_condition = ${if !eq{$tls_out_cipher}{}}
28475 client_send = myaccount@smarthost.example.net
28479 .ecindex IIDexternauth1
28480 .ecindex IIDexternauth2
28486 . ////////////////////////////////////////////////////////////////////////////
28487 . ////////////////////////////////////////////////////////////////////////////
28489 .chapter "The tls authenticator" "CHAPtlsauth"
28490 .scindex IIDtlsauth1 "&(tls)& authenticator"
28491 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28492 .cindex "authentication" "Client Certificate"
28493 .cindex "authentication" "X509"
28494 .cindex "Certificate-based authentication"
28495 The &(tls)& authenticator provides server support for
28496 authentication based on client certificates.
28498 It is not an SMTP authentication mechanism and is not
28499 advertised by the server as part of the SMTP EHLO response.
28500 It is an Exim authenticator in the sense that it affects
28501 the protocol element of the log line, can be tested for
28502 by the &%authenticated%& ACL condition, and can set
28503 the &$authenticated_id$& variable.
28505 The client must present a verifiable certificate,
28506 for which it must have been requested via the
28507 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28508 (see &<<CHAPTLS>>&).
28510 If an authenticator of this type is configured it is
28511 run before any SMTP-level communication is done,
28512 and can authenticate the connection.
28513 If it does, SMTP authentication is not offered.
28515 A maximum of one authenticator of this type may be present.
28518 .cindex "options" "&(tls)& authenticator (server)"
28519 The &(tls)& authenticator has three server options:
28521 .option server_param1 tls string&!! unset
28522 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28523 This option is expanded after the TLS negotiation and
28524 the result is placed in &$auth1$&.
28525 If the expansion is forced to fail, authentication fails. Any other expansion
28526 failure causes a temporary error code to be returned.
28528 .option server_param2 tls string&!! unset
28529 .option server_param3 tls string&!! unset
28530 As above, for &$auth2$& and &$auth3$&.
28532 &%server_param1%& may also be spelled &%server_param%&.
28539 server_param1 = ${certextract {subj_altname,mail,>:} \
28540 {$tls_in_peercert}}
28541 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28544 {${lookup ldap{ldap:///\
28545 mailname=${quote_ldap_dn:${lc:$item}},\
28546 ou=users,LDAP_DC?mailid} {$value}{0} \
28548 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28550 This accepts a client certificate that is verifiable against any
28551 of your configured trust-anchors
28552 (which usually means the full set of public CAs)
28553 and which has a SAN with a good account name.
28555 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28556 The account name is therefore guessable by an opponent.
28557 TLS 1.3 protects both server and client certificates, and is not vulnerable
28559 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28561 . An alternative might use
28563 . server_param1 = ${sha256:$tls_in_peercert}
28565 . to require one of a set of specific certs that define a given account
28566 . (the verification is still required, but mostly irrelevant).
28567 . This would help for per-device use.
28569 . However, for the future we really need support for checking a
28570 . user cert in LDAP - which probably wants a base-64 DER.
28572 .ecindex IIDtlsauth1
28573 .ecindex IIDtlsauth2
28576 Note that because authentication is traditionally an SMTP operation,
28577 the &%authenticated%& ACL condition cannot be used in
28578 a connect- or helo-ACL.
28582 . ////////////////////////////////////////////////////////////////////////////
28583 . ////////////////////////////////////////////////////////////////////////////
28585 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28586 "Encrypted SMTP connections"
28587 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28588 .scindex IIDencsmtp2 "SMTP" "encryption"
28589 .cindex "TLS" "on SMTP connection"
28592 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28593 Sockets Layer), is implemented by making use of the OpenSSL library or the
28594 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28595 cryptographic code in the Exim distribution itself for implementing TLS. In
28596 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28597 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28598 You also need to understand the basic concepts of encryption at a managerial
28599 level, and in particular, the way that public keys, private keys, and
28600 certificates are used.
28602 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28603 connection is established, the client issues a STARTTLS command. If the
28604 server accepts this, the client and the server negotiate an encryption
28605 mechanism. If the negotiation succeeds, the data that subsequently passes
28606 between them is encrypted.
28608 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28609 and if so, what cipher suite is in use, whether the client supplied a
28610 certificate, and whether or not that certificate was verified. This makes it
28611 possible for an Exim server to deny or accept certain commands based on the
28614 &*Warning*&: Certain types of firewall and certain anti-virus products can
28615 disrupt TLS connections. You need to turn off SMTP scanning for these products
28616 in order to get TLS to work.
28620 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
28622 .cindex "submissions protocol"
28623 .cindex "ssmtp protocol"
28624 .cindex "smtps protocol"
28625 .cindex "SMTP" "submissions protocol"
28626 .cindex "SMTP" "ssmtp protocol"
28627 .cindex "SMTP" "smtps protocol"
28628 The history of port numbers for TLS in SMTP is a little messy and has been
28629 contentious. As of RFC 8314, the common practice of using the historically
28630 allocated port 465 for "email submission but with TLS immediately upon connect
28631 instead of using STARTTLS" is officially blessed by the IETF, and recommended
28632 by them in preference to STARTTLS.
28634 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
28635 clarity emerged over the dual roles of SMTP, for MX delivery and Email
28636 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
28638 This approach was, for a while, officially abandoned when encrypted SMTP was
28639 standardized, but many clients kept using it, even as the TCP port number was
28640 reassigned for other use.
28641 Thus you may encounter guidance claiming that you shouldn't enable use of
28643 In practice, a number of mail-clients have only ever supported submissions,
28644 not submission with STARTTLS upgrade.
28645 Ideally, offer both submission (587) and submissions (465) service.
28647 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
28648 global option. Its value must be a list of port numbers;
28649 the most common use is expected to be:
28651 tls_on_connect_ports = 465
28653 The port numbers specified by this option apply to all SMTP connections, both
28654 via the daemon and via &'inetd'&. You still need to specify all the ports that
28655 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
28656 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
28657 an extra port &-- rather, it specifies different behaviour on a port that is
28660 There is also a &%-tls-on-connect%& command line option. This overrides
28661 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
28668 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
28669 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
28670 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
28671 To build Exim to use OpenSSL you need to set
28677 To build Exim to use GnuTLS, you need to set
28683 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
28684 include files and libraries for GnuTLS can be found.
28686 There are some differences in usage when using GnuTLS instead of OpenSSL:
28689 The &%tls_verify_certificates%& option
28690 cannot be the path of a directory
28691 for GnuTLS versions before 3.3.6
28692 (for later versions, or OpenSSL, it can be either).
28694 The default value for &%tls_dhparam%& differs for historical reasons.
28696 .vindex "&$tls_in_peerdn$&"
28697 .vindex "&$tls_out_peerdn$&"
28698 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
28699 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
28700 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
28702 OpenSSL identifies cipher suites using hyphens as separators, for example:
28703 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
28704 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
28705 in a cipher list. To make life simpler, Exim changes underscores to hyphens
28706 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
28707 to handle its own older variants) when processing lists of cipher suites in the
28708 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
28711 The &%tls_require_ciphers%& options operate differently, as described in the
28712 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
28714 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
28715 When using OpenSSL, this option is ignored.
28716 (If an API is found to let OpenSSL be configured in this way,
28717 let the Exim Maintainers know and we'll likely use it).
28719 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
28720 main option, it must be ordered to match the &%tls_certificate%& list.
28722 Some other recently added features may only be available in one or the other.
28723 This should be documented with the feature. If the documentation does not
28724 explicitly state that the feature is infeasible in the other TLS
28725 implementation, then patches are welcome.
28729 .section "GnuTLS parameter computation" "SECTgnutlsparam"
28730 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
28731 an explicit path; if the latter, then the text about generation still applies,
28732 but not the chosen filename.
28733 By default, as of Exim 4.80 a hard-coded D-H prime is used.
28734 See the documentation of &%tls_dhparam%& for more information.
28736 GnuTLS uses D-H parameters that may take a substantial amount of time
28737 to compute. It is unreasonable to re-compute them for every TLS session.
28738 Therefore, Exim keeps this data in a file in its spool directory, called
28739 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
28741 The file is owned by the Exim user and is readable only by
28742 its owner. Every Exim process that start up GnuTLS reads the D-H
28743 parameters from this file. If the file does not exist, the first Exim process
28744 that needs it computes the data and writes it to a temporary file which is
28745 renamed once it is complete. It does not matter if several Exim processes do
28746 this simultaneously (apart from wasting a few resources). Once a file is in
28747 place, new Exim processes immediately start using it.
28749 For maximum security, the parameters that are stored in this file should be
28750 recalculated periodically, the frequency depending on your paranoia level.
28751 If you are avoiding using the fixed D-H primes published in RFCs, then you
28752 are concerned about some advanced attacks and will wish to do this; if you do
28753 not regenerate then you might as well stick to the standard primes.
28755 Arranging this is easy in principle; just delete the file when you want new
28756 values to be computed. However, there may be a problem. The calculation of new
28757 parameters needs random numbers, and these are obtained from &_/dev/random_&.
28758 If the system is not very active, &_/dev/random_& may delay returning data
28759 until enough randomness (entropy) is available. This may cause Exim to hang for
28760 a substantial amount of time, causing timeouts on incoming connections.
28762 The solution is to generate the parameters externally to Exim. They are stored
28763 in &_gnutls-params-N_& in PEM format, which means that they can be
28764 generated externally using the &(certtool)& command that is part of GnuTLS.
28766 To replace the parameters with new ones, instead of deleting the file
28767 and letting Exim re-create it, you can generate new parameters using
28768 &(certtool)& and, when this has been done, replace Exim's cache file by
28769 renaming. The relevant commands are something like this:
28772 [ look for file; assume gnutls-params-2236 is the most recent ]
28775 # chown exim:exim new-params
28776 # chmod 0600 new-params
28777 # certtool --generate-dh-params --bits 2236 >>new-params
28778 # openssl dhparam -noout -text -in new-params | head
28779 [ check the first line, make sure it's not more than 2236;
28780 if it is, then go back to the start ("rm") and repeat
28781 until the size generated is at most the size requested ]
28782 # chmod 0400 new-params
28783 # mv new-params gnutls-params-2236
28785 If Exim never has to generate the parameters itself, the possibility of
28786 stalling is removed.
28788 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
28789 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
28790 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
28791 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
28792 and Exim does so. This attempt to remove Exim from TLS policy decisions
28793 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
28794 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
28795 which applies to all D-H usage, client or server. If the value returned by
28796 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
28797 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
28798 limit, which is still much higher than Exim historically used.
28800 The filename and bits used will change as the GnuTLS maintainers change the
28801 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
28802 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
28803 2432 bits, while NSS is limited to 2236 bits.
28805 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
28806 increase the chance of the generated prime actually being within acceptable
28807 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
28808 procedure above. There is no sane procedure available to Exim to double-check
28809 the size of the generated prime, so it might still be too large.
28812 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
28813 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
28814 .oindex "&%tls_require_ciphers%&" "OpenSSL"
28815 There is a function in the OpenSSL library that can be passed a list of cipher
28816 suites before the cipher negotiation takes place. This specifies which ciphers
28817 are acceptable for TLS versions prior to 1.3.
28818 The list is colon separated and may contain names like
28819 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
28820 directly to this function call.
28821 Many systems will install the OpenSSL manual-pages, so you may have
28822 &'ciphers(1)'& available to you.
28823 The following quotation from the OpenSSL
28824 documentation specifies what forms of item are allowed in the cipher string:
28827 It can consist of a single cipher suite such as RC4-SHA.
28829 It can represent a list of cipher suites containing a certain algorithm,
28830 or cipher suites of a certain type. For example SHA1 represents all
28831 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
28834 Lists of cipher suites can be combined in a single cipher string using
28835 the + character. This is used as a logical and operation. For example
28836 SHA1+DES represents all cipher suites containing the SHA1 and the DES
28840 Each cipher string can be optionally preceded by one of the characters &`!`&,
28843 If &`!`& is used, the ciphers are permanently deleted from the list. The
28844 ciphers deleted can never reappear in the list even if they are explicitly
28847 If &`-`& is used, the ciphers are deleted from the list, but some or all
28848 of the ciphers can be added again by later options.
28850 If &`+`& is used, the ciphers are moved to the end of the list. This
28851 option does not add any new ciphers; it just moves matching existing ones.
28854 If none of these characters is present, the string is interpreted as
28855 a list of ciphers to be appended to the current preference list. If the list
28856 includes any ciphers already present they will be ignored: that is, they will
28857 not be moved to the end of the list.
28860 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
28863 # note single-quotes to get ! past any shell history expansion
28864 $ openssl ciphers 'HIGH:!MD5:!SHA1'
28867 This example will let the library defaults be permitted on the MX port, where
28868 there's probably no identity verification anyway, but ups the ante on the
28869 submission ports where the administrator might have some influence on the
28870 choice of clients used:
28872 # OpenSSL variant; see man ciphers(1)
28873 tls_require_ciphers = ${if =={$received_port}{25}\
28878 This example will prefer ECDSA-authenticated ciphers over RSA ones:
28880 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
28883 For TLS version 1.3 the control available is less fine-grained
28884 and Exim does not provide access to it at present.
28885 The value of the &%tls_require_ciphers%& option is ignored when
28886 TLS version 1.3 is negotiated.
28888 As of writing the library default cipher suite list for TLSv1.3 is
28890 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
28894 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
28896 .cindex "GnuTLS" "specifying parameters for"
28897 .cindex "TLS" "specifying ciphers (GnuTLS)"
28898 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
28899 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
28900 .cindex "TLS" "specifying protocols (GnuTLS)"
28901 .cindex "TLS" "specifying priority string (GnuTLS)"
28902 .oindex "&%tls_require_ciphers%&" "GnuTLS"
28903 The GnuTLS library allows the caller to provide a "priority string", documented
28904 as part of the &[gnutls_priority_init]& function. This is very similar to the
28905 ciphersuite specification in OpenSSL.
28907 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
28908 and controls both protocols and ciphers.
28910 The &%tls_require_ciphers%& option is available both as an global option,
28911 controlling how Exim behaves as a server, and also as an option of the
28912 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
28913 the value is string expanded. The resulting string is not an Exim list and
28914 the string is given to the GnuTLS library, so that Exim does not need to be
28915 aware of future feature enhancements of GnuTLS.
28917 Documentation of the strings accepted may be found in the GnuTLS manual, under
28918 "Priority strings". This is online as
28919 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
28920 but beware that this relates to GnuTLS 3, which may be newer than the version
28921 installed on your system. If you are using GnuTLS 3,
28922 then the example code
28923 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
28924 on that site can be used to test a given string.
28928 # Disable older versions of protocols
28929 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
28932 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
28933 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
28934 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
28936 This example will let the library defaults be permitted on the MX port, where
28937 there's probably no identity verification anyway, and lowers security further
28938 by increasing compatibility; but this ups the ante on the submission ports
28939 where the administrator might have some influence on the choice of clients
28943 tls_require_ciphers = ${if =={$received_port}{25}\
28949 .section "Configuring an Exim server to use TLS" "SECID182"
28950 .cindex "TLS" "configuring an Exim server"
28951 .cindex "ESMTP extensions" STARTTLS
28952 When Exim has been built with TLS support, it advertises the availability of
28953 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
28954 but not to any others. The default value of this option is *, which means
28955 that STARTTLS is always advertised. Set it to blank to never advertise;
28956 this is reasonable for systems that want to use TLS only as a client.
28958 If STARTTLS is to be used you
28959 need to set some other options in order to make TLS available.
28961 If a client issues a STARTTLS command and there is some configuration
28962 problem in the server, the command is rejected with a 454 error. If the client
28963 persists in trying to issue SMTP commands, all except QUIT are rejected
28966 554 Security failure
28968 If a STARTTLS command is issued within an existing TLS session, it is
28969 rejected with a 554 error code.
28971 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
28972 must be set to match some hosts. The default is * which matches all hosts.
28974 If this is all you do, TLS encryption will be enabled but not authentication -
28975 meaning that the peer has no assurance it is actually you he is talking to.
28976 You gain protection from a passive sniffer listening on the wire but not
28977 from someone able to intercept the communication.
28979 Further protection requires some further configuration at the server end.
28981 To make TLS work you need to set, in the server,
28983 tls_certificate = /some/file/name
28984 tls_privatekey = /some/file/name
28986 These options are, in fact, expanded strings, so you can make them depend on
28987 the identity of the client that is connected if you wish. The first file
28988 contains the server's X509 certificate, and the second contains the private key
28989 that goes with it. These files need to be
28990 PEM format and readable by the Exim user, and must
28991 always be given as full path names.
28992 The key must not be password-protected.
28993 They can be the same file if both the
28994 certificate and the key are contained within it. If &%tls_privatekey%& is not
28995 set, or if its expansion is forced to fail or results in an empty string, this
28996 is assumed to be the case. The certificate file may also contain intermediate
28997 certificates that need to be sent to the client to enable it to authenticate
28998 the server's certificate.
29000 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29001 colon-separated lists of file paths. Ciphers using given authentication
29002 algorithms require the presence of a suitable certificate to supply the
29003 public-key. The server selects among the certificates to present to the
29004 client depending on the selected cipher, hence the priority ordering for
29005 ciphers will affect which certificate is used.
29007 If you do not understand about certificates and keys, please try to find a
29008 source of this background information, which is not Exim-specific. (There are a
29009 few comments below in section &<<SECTcerandall>>&.)
29011 &*Note*&: These options do not apply when Exim is operating as a client &--
29012 they apply only in the case of a server. If you need to use a certificate in an
29013 Exim client, you must set the options of the same names in an &(smtp)&
29016 With just these options, an Exim server will be able to use TLS. It does not
29017 require the client to have a certificate (but see below for how to insist on
29018 this). There is one other option that may be needed in other situations. If
29020 tls_dhparam = /some/file/name
29022 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29023 with the parameters contained in the file.
29024 Set this to &`none`& to disable use of DH entirely, by making no prime
29029 This may also be set to a string identifying a standard prime to be used for
29030 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29031 used is &`ike23`&. There are a few standard primes available, see the
29032 documentation for &%tls_dhparam%& for the complete list.
29038 for a way of generating file data.
29040 The strings supplied for these three options are expanded every time a client
29041 host connects. It is therefore possible to use different certificates and keys
29042 for different hosts, if you so wish, by making use of the client's IP address
29043 in &$sender_host_address$& to control the expansion. If a string expansion is
29044 forced to fail, Exim behaves as if the option is not set.
29046 .cindex "cipher" "logging"
29047 .cindex "log" "TLS cipher"
29048 .vindex "&$tls_in_cipher$&"
29049 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29050 an incoming TLS connection. It is included in the &'Received:'& header of an
29051 incoming message (by default &-- you can, of course, change this), and it is
29052 also included in the log line that records a message's arrival, keyed by
29053 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29054 condition can be used to test for specific cipher suites in ACLs.
29056 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29057 can check the name of the cipher suite and vary their actions accordingly. The
29058 cipher suite names vary, depending on which TLS library is being used. For
29059 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29060 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29061 documentation for more details.
29063 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29064 (again depending on the &%tls_cipher%& log selector).
29067 .section "Requesting and verifying client certificates" "SECID183"
29068 .cindex "certificate" "verification of client"
29069 .cindex "TLS" "client certificate verification"
29070 If you want an Exim server to request a certificate when negotiating a TLS
29071 session with a client, you must set either &%tls_verify_hosts%& or
29072 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29073 apply to all TLS connections. For any host that matches one of these options,
29074 Exim requests a certificate as part of the setup of the TLS session. The
29075 contents of the certificate are verified by comparing it with a list of
29076 expected trust-anchors or certificates.
29077 These may be the system default set (depending on library version),
29078 an explicit file or,
29079 depending on library version, a directory, identified by
29080 &%tls_verify_certificates%&.
29082 A file can contain multiple certificates, concatenated end to end. If a
29085 each certificate must be in a separate file, with a name (or a symbolic link)
29086 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29087 certificate. You can compute the relevant hash by running the command
29089 openssl x509 -hash -noout -in /cert/file
29091 where &_/cert/file_& contains a single certificate.
29093 There is no checking of names of the client against the certificate
29094 Subject Name or Subject Alternate Names.
29096 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29097 what happens if the client does not supply a certificate, or if the certificate
29098 does not match any of the certificates in the collection named by
29099 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29100 attempt to set up a TLS session is aborted, and the incoming connection is
29101 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29102 session continues. ACLs that run for subsequent SMTP commands can detect the
29103 fact that no certificate was verified, and vary their actions accordingly. For
29104 example, you can insist on a certificate before accepting a message for
29105 relaying, but not when the message is destined for local delivery.
29107 .vindex "&$tls_in_peerdn$&"
29108 When a client supplies a certificate (whether it verifies or not), the value of
29109 the Distinguished Name of the certificate is made available in the variable
29110 &$tls_in_peerdn$& during subsequent processing of the message.
29112 .cindex "log" "distinguished name"
29113 Because it is often a long text string, it is not included in the log line or
29114 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29115 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29116 &%received_header_text%& to change the &'Received:'& header. When no
29117 certificate is supplied, &$tls_in_peerdn$& is empty.
29120 .section "Revoked certificates" "SECID184"
29121 .cindex "TLS" "revoked certificates"
29122 .cindex "revocation list"
29123 .cindex "certificate" "revocation list"
29124 .cindex "OCSP" "stapling"
29125 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29126 certificates are revoked. If you have such a list, you can pass it to an Exim
29127 server using the global option called &%tls_crl%& and to an Exim client using
29128 an identically named option for the &(smtp)& transport. In each case, the value
29129 of the option is expanded and must then be the name of a file that contains a
29131 The downside is that clients have to periodically re-download a potentially huge
29132 file from every certificate authority they know of.
29134 The way with most moving parts at query time is Online Certificate
29135 Status Protocol (OCSP), where the client verifies the certificate
29136 against an OCSP server run by the CA. This lets the CA track all
29137 usage of the certs. It requires running software with access to the
29138 private key of the CA, to sign the responses to the OCSP queries. OCSP
29139 is based on HTTP and can be proxied accordingly.
29141 The only widespread OCSP server implementation (known to this writer)
29142 comes as part of OpenSSL and aborts on an invalid request, such as
29143 connecting to the port and then disconnecting. This requires
29144 re-entering the passphrase each time some random client does this.
29146 The third way is OCSP Stapling; in this, the server using a certificate
29147 issued by the CA periodically requests an OCSP proof of validity from
29148 the OCSP server, then serves it up inline as part of the TLS
29149 negotiation. This approach adds no extra round trips, does not let the
29150 CA track users, scales well with number of certs issued by the CA and is
29151 resilient to temporary OCSP server failures, as long as the server
29152 starts retrying to fetch an OCSP proof some time before its current
29153 proof expires. The downside is that it requires server support.
29155 Unless Exim is built with the support disabled,
29156 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29157 support for OCSP stapling is included.
29159 There is a global option called &%tls_ocsp_file%&.
29160 The file specified therein is expected to be in DER format, and contain
29161 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29162 option will be re-expanded for SNI, if the &%tls_certificate%& option
29163 contains &`tls_in_sni`&, as per other TLS options.
29165 Exim does not at this time implement any support for fetching a new OCSP
29166 proof. The burden is on the administrator to handle this, outside of
29167 Exim. The file specified should be replaced atomically, so that the
29168 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29169 on each connection, so a new file will be handled transparently on the
29172 When built with OpenSSL Exim will check for a valid next update timestamp
29173 in the OCSP proof; if not present, or if the proof has expired, it will be
29176 For the client to be able to verify the stapled OCSP the server must
29177 also supply, in its stapled information, any intermediate
29178 certificates for the chain leading to the OCSP proof from the signer
29179 of the server certificate. There may be zero or one such. These
29180 intermediate certificates should be added to the server OCSP stapling
29181 file named by &%tls_ocsp_file%&.
29183 Note that the proof only covers the terminal server certificate,
29184 not any of the chain from CA to it.
29186 There is no current way to staple a proof for a client certificate.
29189 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29190 OCSP server is supplied. The server URL may be included in the
29191 server certificate, if the CA is helpful.
29193 One failure mode seen was the OCSP Signer cert expiring before the end
29194 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29195 noted this as invalid overall, but the re-fetch script did not.
29201 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29202 .cindex "cipher" "logging"
29203 .cindex "log" "TLS cipher"
29204 .cindex "log" "distinguished name"
29205 .cindex "TLS" "configuring an Exim client"
29206 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29207 deliveries as well as to incoming, the latter one causing logging of the
29208 server certificate's DN. The remaining client configuration for TLS is all
29209 within the &(smtp)& transport.
29211 .cindex "ESMTP extensions" STARTTLS
29212 It is not necessary to set any options to have TLS work in the &(smtp)&
29213 transport. If Exim is built with TLS support, and TLS is advertised by a
29214 server, the &(smtp)& transport always tries to start a TLS session. However,
29215 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29216 transport) to a list of server hosts for which TLS should not be used.
29218 If you do not want Exim to attempt to send messages unencrypted when an attempt
29219 to set up an encrypted connection fails in any way, you can set
29220 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29221 those hosts, delivery is always deferred if an encrypted connection cannot be
29222 set up. If there are any other hosts for the address, they are tried in the
29225 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29226 the message unencrypted. It always does this if the response to STARTTLS is
29227 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29228 session after a success response code, what happens is controlled by the
29229 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29230 delivery to this host is deferred, and other hosts (if available) are tried. If
29231 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29232 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29233 negotiation fails, Exim closes the current connection (because it is in an
29234 unknown state), opens a new one to the same host, and then tries the delivery
29237 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29238 transport provide the client with a certificate, which is passed to the server
29239 if it requests it. If the server is Exim, it will request a certificate only if
29240 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29242 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29243 for client use (they are usable for server use).
29244 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29245 in failed connections.
29247 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29248 specifies a collection of expected server certificates.
29250 the system default set (depending on library version),
29252 or (depending on library version) a directory.
29253 The client verifies the server's certificate
29254 against this collection, taking into account any revoked certificates that are
29255 in the list defined by &%tls_crl%&.
29256 Failure to verify fails the TLS connection unless either of the
29257 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29259 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29260 certificate verification to the listed servers. Verification either must
29261 or need not succeed respectively.
29263 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29264 name checks are made on the server certificate.
29266 The match against this list is, as per other Exim usage, the
29267 IP for the host. That is most closely associated with the
29268 name on the DNS A (or AAAA) record for the host.
29269 However, the name that needs to be in the certificate
29270 is the one at the head of any CNAME chain leading to the A record.
29272 The option defaults to always checking.
29274 The &(smtp)& transport has two OCSP-related options:
29275 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29276 is requested and required for the connection to proceed. The default
29278 &%hosts_request_ocsp%&; a host-list for which (additionally)
29279 a Certificate Status is requested (but not necessarily verified). The default
29280 value is "*" meaning that requests are made unless configured
29283 The host(s) should also be in &%hosts_require_tls%&, and
29284 &%tls_verify_certificates%& configured for the transport,
29285 for OCSP to be relevant.
29288 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29289 list of permitted cipher suites. If either of these checks fails, delivery to
29290 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29291 alternative hosts, if any.
29294 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29295 is operating as a client. Exim does not assume that a server certificate (set
29296 by the global options of the same name) should also be used when operating as a
29300 .vindex "&$host_address$&"
29301 All the TLS options in the &(smtp)& transport are expanded before use, with
29302 &$host$& and &$host_address$& containing the name and address of the server to
29303 which the client is connected. Forced failure of an expansion causes Exim to
29304 behave as if the relevant option were unset.
29306 .vindex &$tls_out_bits$&
29307 .vindex &$tls_out_cipher$&
29308 .vindex &$tls_out_peerdn$&
29309 .vindex &$tls_out_sni$&
29310 Before an SMTP connection is established, the
29311 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29312 variables are emptied. (Until the first connection, they contain the values
29313 that were set when the message was received.) If STARTTLS is subsequently
29314 successfully obeyed, these variables are set to the relevant values for the
29315 outgoing connection.
29319 .section "Use of TLS Server Name Indication" "SECTtlssni"
29320 .cindex "TLS" "Server Name Indication"
29323 .vindex "&$tls_in_sni$&"
29324 .oindex "&%tls_in_sni%&"
29325 With TLS1.0 or above, there is an extension mechanism by which extra
29326 information can be included at various points in the protocol. One of these
29327 extensions, documented in RFC 6066 (and before that RFC 4366) is
29328 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29329 client in the initial handshake, so that the server can examine the servername
29330 within and possibly choose to use different certificates and keys (and more)
29333 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29334 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29337 With SMTP to MX, there are the same problems here as in choosing the identity
29338 against which to validate a certificate: you can't rely on insecure DNS to
29339 provide the identity which you then cryptographically verify. So this will
29340 be of limited use in that environment.
29342 With SMTP to Submission, there is a well-defined hostname which clients are
29343 connecting to and can validate certificates against. Thus clients &*can*&
29344 choose to include this information in the TLS negotiation. If this becomes
29345 wide-spread, then hosters can choose to present different certificates to
29346 different clients. Or even negotiate different cipher suites.
29348 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29349 if not empty, will be sent on a TLS session as part of the handshake. There's
29350 nothing more to it. Choosing a sensible value not derived insecurely is the
29351 only point of caution. The &$tls_out_sni$& variable will be set to this string
29352 for the lifetime of the client connection (including during authentication).
29354 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29355 received from a client.
29356 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29358 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29359 option (prior to expansion) then the following options will be re-expanded
29360 during TLS session handshake, to permit alternative values to be chosen:
29363 &%tls_certificate%&
29369 &%tls_verify_certificates%&
29374 Great care should be taken to deal with matters of case, various injection
29375 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29376 can always be referenced; it is important to remember that &$tls_in_sni$& is
29377 arbitrary unverified data provided prior to authentication.
29378 Further, the initial certificate is loaded before SNI has arrived, so
29379 an expansion for &%tls_certificate%& must have a default which is used
29380 when &$tls_in_sni$& is empty.
29382 The Exim developers are proceeding cautiously and so far no other TLS options
29385 When Exim is built against OpenSSL, OpenSSL must have been built with support
29386 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29387 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29388 see &`-servername`& in the output, then OpenSSL has support.
29390 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29391 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29392 built, then you have SNI support).
29396 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29398 .cindex "multiple SMTP deliveries with TLS"
29399 .cindex "TLS" "multiple message deliveries"
29400 Exim sends multiple messages down the same TCP/IP connection by starting up
29401 an entirely new delivery process for each message, passing the socket from
29402 one process to the next. This implementation does not fit well with the use
29403 of TLS, because there is quite a lot of state information associated with a TLS
29404 connection, not just a socket identification. Passing all the state information
29405 to a new process is not feasible. Consequently, for sending using TLS Exim
29406 starts an additional proxy process for handling the encryption, piping the
29407 unencrypted data stream from and to the delivery processes.
29409 An older mode of operation can be enabled on a per-host basis by the
29410 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29411 this list the proxy process described above is not used; instead Exim
29412 shuts down an existing TLS session being run by the delivery process
29413 before passing the socket to a new process. The new process may then
29414 try to start a new TLS session, and if successful, may try to re-authenticate
29415 if AUTH is in use, before sending the next message.
29417 The RFC is not clear as to whether or not an SMTP session continues in clear
29418 after TLS has been shut down, or whether TLS may be restarted again later, as
29419 just described. However, if the server is Exim, this shutdown and
29420 reinitialization works. It is not known which (if any) other servers operate
29421 successfully if the client closes a TLS session and continues with unencrypted
29422 SMTP, but there are certainly some that do not work. For such servers, Exim
29423 should not pass the socket to another process, because the failure of the
29424 subsequent attempt to use it would cause Exim to record a temporary host error,
29425 and delay other deliveries to that host.
29427 To test for this case, Exim sends an EHLO command to the server after
29428 closing down the TLS session. If this fails in any way, the connection is
29429 closed instead of being passed to a new delivery process, but no retry
29430 information is recorded.
29432 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29433 &(smtp)& transport to match those hosts for which Exim should not pass
29434 connections to new processes if TLS has been used.
29439 .section "Certificates and all that" "SECTcerandall"
29440 .cindex "certificate" "references to discussion"
29441 In order to understand fully how TLS works, you need to know about
29442 certificates, certificate signing, and certificate authorities.
29443 This is a large topic and an introductory guide is unsuitable for the Exim
29444 reference manual, so instead we provide pointers to existing documentation.
29446 The Apache web-server was for a long time the canonical guide, so their
29447 documentation is a good place to start; their SSL module's Introduction
29448 document is currently at
29450 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29452 and their FAQ is at
29454 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29457 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29458 0-201-61598-3) in 2001, contains both introductory and more in-depth
29460 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29461 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29462 Ivan is the author of the popular TLS testing tools at
29463 &url(https://www.ssllabs.com/).
29466 .section "Certificate chains" "SECID186"
29467 The file named by &%tls_certificate%& may contain more than one
29468 certificate. This is useful in the case where the certificate that is being
29469 sent is validated by an intermediate certificate which the other end does
29470 not have. Multiple certificates must be in the correct order in the file.
29471 First the host's certificate itself, then the first intermediate
29472 certificate to validate the issuer of the host certificate, then the next
29473 intermediate certificate to validate the issuer of the first intermediate
29474 certificate, and so on, until finally (optionally) the root certificate.
29475 The root certificate must already be trusted by the recipient for
29476 validation to succeed, of course, but if it's not preinstalled, sending the
29477 root certificate along with the rest makes it available for the user to
29478 install if the receiving end is a client MUA that can interact with a user.
29480 Note that certificates using MD5 are unlikely to work on today's Internet;
29481 even if your libraries allow loading them for use in Exim when acting as a
29482 server, increasingly clients will not accept such certificates. The error
29483 diagnostics in such a case can be frustratingly vague.
29487 .section "Self-signed certificates" "SECID187"
29488 .cindex "certificate" "self-signed"
29489 You can create a self-signed certificate using the &'req'& command provided
29490 with OpenSSL, like this:
29491 . ==== Do not shorten the duration here without reading and considering
29492 . ==== the text below. Please leave it at 9999 days.
29494 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29497 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29498 delimited and so can be identified independently. The &%-days%& option
29499 specifies a period for which the certificate is valid. The &%-nodes%& option is
29500 important: if you do not set it, the key is encrypted with a passphrase
29501 that you are prompted for, and any use that is made of the key causes more
29502 prompting for the passphrase. This is not helpful if you are going to use
29503 this certificate and key in an MTA, where prompting is not possible.
29505 . ==== I expect to still be working 26 years from now. The less technical
29506 . ==== debt I create, in terms of storing up trouble for my later years, the
29507 . ==== happier I will be then. We really have reached the point where we
29508 . ==== should start, at the very least, provoking thought and making folks
29509 . ==== pause before proceeding, instead of leaving all the fixes until two
29510 . ==== years before 2^31 seconds after the 1970 Unix epoch.
29512 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
29513 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
29514 the above command might produce a date in the past. Think carefully about
29515 the lifetime of the systems you're deploying, and either reduce the duration
29516 of the certificate or reconsider your platform deployment. (At time of
29517 writing, reducing the duration is the most likely choice, but the inexorable
29518 progression of time takes us steadily towards an era where this will not
29519 be a sensible resolution).
29521 A self-signed certificate made in this way is sufficient for testing, and
29522 may be adequate for all your requirements if you are mainly interested in
29523 encrypting transfers, and not in secure identification.
29525 However, many clients require that the certificate presented by the server be a
29526 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
29527 certificate. In this situation, the self-signed certificate described above
29528 must be installed on the client host as a trusted root &'certification
29529 authority'& (CA), and the certificate used by Exim must be a user certificate
29530 signed with that self-signed certificate.
29532 For information on creating self-signed CA certificates and using them to sign
29533 user certificates, see the &'General implementation overview'& chapter of the
29534 Open-source PKI book, available online at
29535 &url(https://sourceforge.net/projects/ospkibook/).
29536 .ecindex IIDencsmtp1
29537 .ecindex IIDencsmtp2
29541 .section "TLS Resumption" "SECTresumption"
29542 .cindex TLS resumption
29543 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
29544 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
29547 Session resumption (this is the "stateless" variant) involves the server sending
29548 a "session ticket" to the client on one connection, which can be stored by the
29549 client and used for a later session. The ticket contains sufficient state for
29550 the server to reconstruct the TLS session, avoiding some expensive crypto
29551 calculation and (on TLS1.2) one full packet roundtrip time.
29554 Operational cost/benefit:
29556 The extra data being transmitted costs a minor amount, and the client has
29557 extra costs in storing and retrieving the data.
29559 In the Exim/Gnutls implementation the extra cost on an initial connection
29560 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
29561 The saved cost on a subsequent connection is about 4ms; three or more
29562 connections become a net win. On longer network paths, two or more
29563 connections will have an average lower startup time thanks to the one
29564 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
29567 .cindex "hints database" tls
29568 Since a new hints DB is used on the TLS client,
29569 the hints DB maintenance should be updated to additionally handle "tls".
29574 The session ticket is encrypted, but is obviously an additional security
29575 vulnarability surface. An attacker able to decrypt it would have access
29576 all connections using the resumed session.
29577 The session ticket encryption key is not committed to storage by the server
29578 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
29579 overlap; GnuTLS 6hr but does not specify any overlap).
29580 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
29581 OpenSSL. GnuTLS 2hr, appears to not do overlap).
29583 There is a question-mark over the security of the Diffie-Helman parameters
29584 used for session negotiation.
29589 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
29592 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
29593 have bits 0-4 indicating respectively
29594 support built, client requested ticket, client offered session,
29595 server issued ticket, resume used. A suitable decode list is provided
29596 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
29601 The &%tls_resumption_hosts%& main option specifies a hostlist for which
29602 exim, operating as a server, will offer resumption to clients.
29603 Current best practice is to not offer the feature to MUA connection.
29604 Commonly this can be done like this:
29606 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
29608 If the peer host matches the list after expansion then resumption
29609 is offered and/or accepted.
29611 The &%tls_resumption_hosts%& smtp transport option performs the
29612 equivalent function for operation as a client.
29613 If the peer host matches the list after expansion then resumption
29614 is attempted (if a stored session is available) or the information
29615 stored (if supplied by the peer).
29621 In a resumed session:
29623 The variables &$tls_{in,out}_cipher$& will have values different
29624 to the original (under GnuTLS).
29626 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
29627 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
29628 . XXX need to do something with that hosts_require_ocsp
29635 .section DANE "SECDANE"
29637 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
29638 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
29639 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
29640 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
29641 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
29642 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
29644 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
29645 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
29646 by (a) is thought to be smaller than that of the set of root CAs.
29648 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
29649 fail to pass on a server's STARTTLS.
29651 DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
29652 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
29653 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
29655 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
29656 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
29657 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
29659 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
29660 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
29662 There are no changes to Exim specific to server-side operation of DANE.
29663 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
29664 in &_Local/Makefile_&.
29665 If it has been included, the macro "_HAVE_DANE" will be defined.
29667 A TLSA record consist of 4 fields, the "Certificate Usage", the
29668 "Selector", the "Matching type", and the "Certificate Association Data".
29669 For a detailed description of the TLSA record see
29670 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
29672 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
29673 These are the "Trust Anchor" and "End Entity" variants.
29674 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
29675 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
29676 this is appropriate for a single system, using a self-signed certificate.
29677 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
29679 A private CA at simplest is just a self-signed certificate (with certain
29680 attributes) which is used to sign server certificates, but running one securely
29681 does require careful arrangement.
29682 With DANE-TA, as implemented in Exim and commonly in other MTAs,
29683 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
29684 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
29685 all of which point to a single TLSA record.
29686 DANE-TA and DANE-EE can both be used together.
29688 Our recommendation is to use DANE with a certificate from a public CA,
29689 because this enables a variety of strategies for remote clients to verify
29691 You can then publish information both via DANE and another technology,
29692 "MTA-STS", described below.
29694 When you use DANE-TA to publish trust anchor information, you ask entities
29695 outside your administrative control to trust the Certificate Authority for
29696 connections to you.
29697 If using a private CA then you should expect others to still apply the
29698 technical criteria they'd use for a public CA to your certificates.
29699 In particular, you should probably try to follow current best practices for CA
29700 operation around hash algorithms and key sizes.
29701 Do not expect other organizations to lower their security expectations just
29702 because a particular profile might be reasonable for your own internal use.
29704 When this text was last updated, this in practice means to avoid use of SHA-1
29705 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
29706 than 4096, for interoperability); to use keyUsage fields correctly; to use
29707 random serial numbers.
29708 The list of requirements is subject to change as best practices evolve.
29709 If you're not already using a private CA, or it doesn't meet these
29710 requirements, then we encourage you to avoid all these issues and use a public
29711 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
29713 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
29714 a "Matching Type" (3rd) field of SHA2-512(2).
29716 For the "Certificate Authority Data" (4th) field, commands like
29719 openssl x509 -pubkey -noout <certificate.pem \
29720 | openssl rsa -outform der -pubin 2>/dev/null \
29725 are workable to create a hash of the certificate's public key.
29727 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
29730 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
29733 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
29734 is useful for quickly generating TLSA records.
29737 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
29739 The Certificate issued by the CA published in the DANE-TA model should be
29740 issued using a strong hash algorithm.
29741 Exim, and importantly various other MTAs sending to you, will not
29742 re-enable hash algorithms which have been disabled by default in TLS
29744 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
29745 interoperability (and probably the maximum too, in 2018).
29747 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
29748 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
29749 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
29752 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
29753 {= {4}{$tls_out_tlsa_usage}} } \
29757 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
29758 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
29759 found. If the definition of &%hosts_request_ocsp%& includes the
29760 string "tls_out_tlsa_usage", they are re-expanded in time to
29761 control the OCSP request.
29763 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
29764 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
29767 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
29768 and &%dane_require_tls_ciphers%&.
29769 The &"require"& variant will result in failure if the target host is not
29770 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
29771 the &%dnssec_request_domains%& router or transport option.
29773 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
29775 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
29776 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
29777 will be required for the host. If it does not, the host will not
29778 be used; there is no fallback to non-DANE or non-TLS.
29780 If DANE is requested and usable, then the TLS cipher list configuration
29781 prefers to use the option &%dane_require_tls_ciphers%& and falls
29782 back to &%tls_require_ciphers%& only if that is unset.
29783 This lets you configure "decent crypto" for DANE and "better than nothing
29784 crypto" as the default. Note though that while GnuTLS lets the string control
29785 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
29786 limited to ciphersuite constraints.
29788 If DANE is requested and useable (see above) the following transport options are ignored:
29792 tls_try_verify_hosts
29793 tls_verify_certificates
29795 tls_verify_cert_hostnames
29798 If DANE is not usable, whether requested or not, and CA-anchored
29799 verification evaluation is wanted, the above variables should be set appropriately.
29801 The router and transport option &%dnssec_request_domains%& must not be
29802 set to &"never"&, and &%dnssec_require_domains%& is ignored.
29804 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
29806 There is a new variable &$tls_out_dane$& which will have "yes" if
29807 verification succeeded using DANE and "no" otherwise (only useful
29808 in combination with events; see &<<CHAPevents>>&),
29809 and a new variable &$tls_out_tlsa_usage$& (detailed above).
29811 .cindex DANE reporting
29812 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
29813 to achieve DANE-verified connection, if one was either requested and offered, or
29814 required. This is intended to support TLS-reporting as defined in
29815 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
29816 The &$event_data$& will be one of the Result Types defined in
29817 Section 4.3 of that document.
29819 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
29821 DANE is specified in published RFCs and decouples certificate authority trust
29822 selection from a "race to the bottom" of "you must trust everything for mail
29823 to get through". There is an alternative technology called MTA-STS, which
29824 instead publishes MX trust anchor information on an HTTPS website. At the
29825 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
29826 Exim has no support for MTA-STS as a client, but Exim mail server operators
29827 can choose to publish information describing their TLS configuration using
29828 MTA-STS to let those clients who do use that protocol derive trust
29831 The MTA-STS design requires a certificate from a public Certificate Authority
29832 which is recognized by clients sending to you.
29833 That selection of which CAs are trusted by others is outside your control.
29835 The most interoperable course of action is probably to use
29836 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
29837 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
29838 records for DANE clients (such as Exim and Postfix) and to publish anchor
29839 information for MTA-STS as well. This is what is done for the &'exim.org'&
29840 domain itself (with caveats around occasionally broken MTA-STS because of
29841 incompatible specification changes prior to reaching RFC status).
29845 . ////////////////////////////////////////////////////////////////////////////
29846 . ////////////////////////////////////////////////////////////////////////////
29848 .chapter "Access control lists" "CHAPACL"
29849 .scindex IIDacl "&ACL;" "description"
29850 .cindex "control of incoming mail"
29851 .cindex "message" "controlling incoming"
29852 .cindex "policy control" "access control lists"
29853 Access Control Lists (ACLs) are defined in a separate section of the runtime
29854 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
29855 name, terminated by a colon. Here is a complete ACL section that contains just
29856 one very small ACL:
29860 accept hosts = one.host.only
29862 You can have as many lists as you like in the ACL section, and the order in
29863 which they appear does not matter. The lists are self-terminating.
29865 The majority of ACLs are used to control Exim's behaviour when it receives
29866 certain SMTP commands. This applies both to incoming TCP/IP connections, and
29867 when a local process submits a message using SMTP by specifying the &%-bs%&
29868 option. The most common use is for controlling which recipients are accepted
29869 in incoming messages. In addition, you can define an ACL that is used to check
29870 local non-SMTP messages. The default configuration file contains an example of
29871 a realistic ACL for checking RCPT commands. This is discussed in chapter
29872 &<<CHAPdefconfil>>&.
29875 .section "Testing ACLs" "SECID188"
29876 The &%-bh%& command line option provides a way of testing your ACL
29877 configuration locally by running a fake SMTP session with which you interact.
29880 .section "Specifying when ACLs are used" "SECID189"
29881 .cindex "&ACL;" "options for specifying"
29882 In order to cause an ACL to be used, you have to name it in one of the relevant
29883 options in the main part of the configuration. These options are:
29884 .cindex "AUTH" "ACL for"
29885 .cindex "DATA" "ACLs for"
29886 .cindex "ETRN" "ACL for"
29887 .cindex "EXPN" "ACL for"
29888 .cindex "HELO" "ACL for"
29889 .cindex "EHLO" "ACL for"
29890 .cindex "DKIM" "ACL for"
29891 .cindex "MAIL" "ACL for"
29892 .cindex "QUIT, ACL for"
29893 .cindex "RCPT" "ACL for"
29894 .cindex "STARTTLS, ACL for"
29895 .cindex "VRFY" "ACL for"
29896 .cindex "SMTP" "connection, ACL for"
29897 .cindex "non-SMTP messages" "ACLs for"
29898 .cindex "MIME content scanning" "ACL for"
29899 .cindex "PRDR" "ACL for"
29902 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
29903 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
29904 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
29905 .irow &%acl_smtp_auth%& "ACL for AUTH"
29906 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
29907 .irow &%acl_smtp_data%& "ACL after DATA is complete"
29908 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
29909 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
29910 .irow &%acl_smtp_etrn%& "ACL for ETRN"
29911 .irow &%acl_smtp_expn%& "ACL for EXPN"
29912 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
29913 .irow &%acl_smtp_mail%& "ACL for MAIL"
29914 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
29915 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
29916 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
29917 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
29918 .irow &%acl_smtp_quit%& "ACL for QUIT"
29919 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
29920 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
29921 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
29924 For example, if you set
29926 acl_smtp_rcpt = small_acl
29928 the little ACL defined above is used whenever Exim receives a RCPT command
29929 in an SMTP dialogue. The majority of policy tests on incoming messages can be
29930 done when RCPT commands arrive. A rejection of RCPT should cause the
29931 sending MTA to give up on the recipient address contained in the RCPT
29932 command, whereas rejection at other times may cause the client MTA to keep on
29933 trying to deliver the message. It is therefore recommended that you do as much
29934 testing as possible at RCPT time.
29937 .section "The non-SMTP ACLs" "SECID190"
29938 .cindex "non-SMTP messages" "ACLs for"
29939 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
29940 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
29941 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
29942 the state of the SMTP connection such as encryption and authentication) are not
29943 relevant and are forbidden in these ACLs. However, the sender and recipients
29944 are known, so the &%senders%& and &%sender_domains%& conditions and the
29945 &$sender_address$& and &$recipients$& variables can be used. Variables such as
29946 &$authenticated_sender$& are also available. You can specify added header lines
29947 in any of these ACLs.
29949 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
29950 non-SMTP message, before any of the message has been read. (This is the
29951 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
29952 batched SMTP input, it runs after the DATA command has been reached. The
29953 result of this ACL is ignored; it cannot be used to reject a message. If you
29954 really need to, you could set a value in an ACL variable here and reject based
29955 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
29956 controls, and in particular, it can be used to set
29958 control = suppress_local_fixups
29960 This cannot be used in the other non-SMTP ACLs because by the time they are
29961 run, it is too late.
29963 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
29964 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
29966 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
29967 kind of rejection is treated as permanent, because there is no way of sending a
29968 temporary error for these kinds of message.
29971 .section "The SMTP connect ACL" "SECID191"
29972 .cindex "SMTP" "connection, ACL for"
29973 .oindex &%smtp_banner%&
29974 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
29975 session, after the test specified by &%host_reject_connection%& (which is now
29976 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
29977 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
29978 the message override the banner message that is otherwise specified by the
29979 &%smtp_banner%& option.
29982 .section "The EHLO/HELO ACL" "SECID192"
29983 .cindex "EHLO" "ACL for"
29984 .cindex "HELO" "ACL for"
29985 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
29986 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
29987 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
29988 Note that a client may issue more than one EHLO or HELO command in an SMTP
29989 session, and indeed is required to issue a new EHLO or HELO after successfully
29990 setting up encryption following a STARTTLS command.
29992 Note also that a deny neither forces the client to go away nor means that
29993 mail will be refused on the connection. Consider checking for
29994 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
29996 If the command is accepted by an &%accept%& verb that has a &%message%&
29997 modifier, the message may not contain more than one line (it will be truncated
29998 at the first newline and a panic logged if it does). Such a message cannot
29999 affect the EHLO options that are listed on the second and subsequent lines of
30003 .section "The DATA ACLs" "SECID193"
30004 .cindex "DATA" "ACLs for"
30005 Two ACLs are associated with the DATA command, because it is two-stage
30006 command, with two responses being sent to the client.
30007 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30008 is obeyed. This gives you control after all the RCPT commands, but before
30009 the message itself is received. It offers the opportunity to give a negative
30010 response to the DATA command before the data is transmitted. Header lines
30011 added by MAIL or RCPT ACLs are not visible at this time, but any that
30012 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30014 You cannot test the contents of the message, for example, to verify addresses
30015 in the headers, at RCPT time or when the DATA command is received. Such
30016 tests have to appear in the ACL that is run after the message itself has been
30017 received, before the final response to the DATA command is sent. This is
30018 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30019 associated with the DATA command.
30021 .cindex CHUNKING "BDAT command"
30022 .cindex BDAT "SMTP command"
30023 .cindex "RFC 3030" CHUNKING
30024 If CHUNKING was advertised and a BDAT command sequence is received,
30025 the &%acl_smtp_predata%& ACL is not run.
30026 . XXX why not? It should be possible, for the first BDAT.
30027 The &%acl_smtp_data%& is run after the last BDAT command and all of
30028 the data specified is received.
30030 For both of these ACLs, it is not possible to reject individual recipients. An
30031 error response rejects the entire message. Unfortunately, it is known that some
30032 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30033 before or after the data) correctly &-- they keep the message on their queues
30034 and try again later, but that is their problem, though it does waste some of
30037 The &%acl_smtp_data%& ACL is run after
30038 the &%acl_smtp_data_prdr%&,
30039 the &%acl_smtp_dkim%&
30040 and the &%acl_smtp_mime%& ACLs.
30042 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30043 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30044 enabled (which is the default).
30046 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30047 received, and is executed for each DKIM signature found in a message. If not
30048 otherwise specified, the default action is to accept.
30050 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30052 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30055 .section "The SMTP MIME ACL" "SECID194"
30056 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30057 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30059 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30062 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30063 .cindex "PRDR" "ACL for"
30064 .oindex "&%prdr_enable%&"
30065 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30066 with PRDR support enabled (which is the default).
30067 It becomes active only when the PRDR feature is negotiated between
30068 client and server for a message, and more than one recipient
30071 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30072 has been received, and is executed once for each recipient of the message
30073 with &$local_part$& and &$domain$& valid.
30074 The test may accept, defer or deny for individual recipients.
30075 The &%acl_smtp_data%& will still be called after this ACL and
30076 can reject the message overall, even if this ACL has accepted it
30077 for some or all recipients.
30079 PRDR may be used to support per-user content filtering. Without it
30080 one must defer any recipient after the first that has a different
30081 content-filter configuration. With PRDR, the RCPT-time check
30082 .cindex "PRDR" "variable for"
30083 for this can be disabled when the variable &$prdr_requested$&
30085 Any required difference in behaviour of the main DATA-time
30086 ACL should however depend on the PRDR-time ACL having run, as Exim
30087 will avoid doing so in some situations (e.g. single-recipient mails).
30089 See also the &%prdr_enable%& global option
30090 and the &%hosts_try_prdr%& smtp transport option.
30092 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30093 If the ACL is not defined, processing completes as if
30094 the feature was not requested by the client.
30096 .section "The QUIT ACL" "SECTQUITACL"
30097 .cindex "QUIT, ACL for"
30098 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30099 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30100 does not in fact control any access.
30101 For this reason, it may only accept
30102 or warn as its final result.
30104 This ACL can be used for tasks such as custom logging at the end of an SMTP
30105 session. For example, you can use ACL variables in other ACLs to count
30106 messages, recipients, etc., and log the totals at QUIT time using one or
30107 more &%logwrite%& modifiers on a &%warn%& verb.
30109 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30110 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30112 You do not need to have a final &%accept%&, but if you do, you can use a
30113 &%message%& modifier to specify custom text that is sent as part of the 221
30116 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30117 failure (for example, failure to open a log file, or when Exim is bombing out
30118 because it has detected an unrecoverable error), all SMTP commands from the
30119 client are given temporary error responses until QUIT is received or the
30120 connection is closed. In these special cases, the QUIT ACL does not run.
30123 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30124 .vindex &$acl_smtp_notquit$&
30125 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30126 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30127 trouble, such as being unable to write to its log files, this ACL is not run,
30128 because it might try to do things (such as write to log files) that make the
30129 situation even worse.
30131 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30132 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30133 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30136 .vindex &$smtp_notquit_reason$&
30137 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30138 to a string that indicates the reason for the termination of the SMTP
30139 connection. The possible values are:
30141 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30142 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30143 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30144 .irow &`connection-lost`& "The SMTP connection has been lost"
30145 .irow &`data-timeout`& "Timeout while reading message data"
30146 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30147 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30148 .irow &`signal-exit`& "SIGTERM or SIGINT"
30149 .irow &`synchronization-error`& "SMTP synchronization error"
30150 .irow &`tls-failed`& "TLS failed to start"
30152 In most cases when an SMTP connection is closed without having received QUIT,
30153 Exim sends an SMTP response message before actually closing the connection.
30154 With the exception of the &`acl-drop`& case, the default message can be
30155 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30156 &%drop%& verb in another ACL, it is the message from the other ACL that is
30160 .section "Finding an ACL to use" "SECID195"
30161 .cindex "&ACL;" "finding which to use"
30162 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30163 you can use different ACLs in different circumstances. For example,
30165 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30166 {acl_check_rcpt} {acl_check_rcpt_submit} }
30168 In the default configuration file there are some example settings for
30169 providing an RFC 4409 message &"submission"& service on port 587 and
30170 an RFC 8314 &"submissions"& service on port 465. You can use a string
30171 expansion like this to choose an ACL for MUAs on these ports which is
30172 more appropriate for this purpose than the default ACL on port 25.
30174 The expanded string does not have to be the name of an ACL in the
30175 configuration file; there are other possibilities. Having expanded the
30176 string, Exim searches for an ACL as follows:
30179 If the string begins with a slash, Exim uses it as a filename, and reads its
30180 contents as an ACL. The lines are processed in the same way as lines in the
30181 Exim configuration file. In particular, continuation lines are supported, blank
30182 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30183 If the file does not exist or cannot be read, an error occurs (typically
30184 causing a temporary failure of whatever caused the ACL to be run). For example:
30186 acl_smtp_data = /etc/acls/\
30187 ${lookup{$sender_host_address}lsearch\
30188 {/etc/acllist}{$value}{default}}
30190 This looks up an ACL file to use on the basis of the host's IP address, falling
30191 back to a default if the lookup fails. If an ACL is successfully read from a
30192 file, it is retained in memory for the duration of the Exim process, so that it
30193 can be re-used without having to re-read the file.
30195 If the string does not start with a slash, and does not contain any spaces,
30196 Exim searches the ACL section of the configuration for an ACL whose name
30197 matches the string.
30199 If no named ACL is found, or if the string contains spaces, Exim parses
30200 the string as an inline ACL. This can save typing in cases where you just
30201 want to have something like
30203 acl_smtp_vrfy = accept
30205 in order to allow free use of the VRFY command. Such a string may contain
30206 newlines; it is processed in the same way as an ACL that is read from a file.
30212 .section "ACL return codes" "SECID196"
30213 .cindex "&ACL;" "return codes"
30214 Except for the QUIT ACL, which does not affect the SMTP return code (see
30215 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30216 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30217 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30218 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30219 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30220 This also causes a 4&'xx'& return code.
30222 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30223 &"deny"&, because there is no mechanism for passing temporary errors to the
30224 submitters of non-SMTP messages.
30227 ACLs that are relevant to message reception may also return &"discard"&. This
30228 has the effect of &"accept"&, but causes either the entire message or an
30229 individual recipient address to be discarded. In other words, it is a
30230 blackholing facility. Use it with care.
30232 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30233 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30234 RCPT ACL is to discard just the one recipient address. If there are no
30235 recipients left when the message's data is received, the DATA ACL is not
30236 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30237 remaining recipients. The &"discard"& return is not permitted for the
30238 &%acl_smtp_predata%& ACL.
30240 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30241 is done on the address and the result determines the SMTP response.
30244 .cindex "&[local_scan()]& function" "when all recipients discarded"
30245 The &[local_scan()]& function is always run, even if there are no remaining
30246 recipients; it may create new recipients.
30250 .section "Unset ACL options" "SECID197"
30251 .cindex "&ACL;" "unset options"
30252 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30253 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30254 not defined at all. For any defined ACL, the default action when control
30255 reaches the end of the ACL statements is &"deny"&.
30257 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30258 these two are ACLs that are used only for their side effects. They cannot be
30259 used to accept or reject anything.
30261 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30262 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30263 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30264 when the ACL is not defined is &"accept"&.
30266 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30267 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30268 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30269 messages over an SMTP connection. For an example, see the ACL in the default
30270 configuration file.
30275 .section "Data for message ACLs" "SECID198"
30276 .cindex "&ACL;" "data for message ACL"
30278 .vindex &$local_part$&
30279 .vindex &$sender_address$&
30280 .vindex &$sender_host_address$&
30281 .vindex &$smtp_command$&
30282 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30283 that contain information about the host and the message's sender (for example,
30284 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30285 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30286 &$local_part$& are set from the argument address. The entire SMTP command
30287 is available in &$smtp_command$&.
30289 When an ACL for the AUTH parameter of MAIL is running, the variables that
30290 contain information about the host are set, but &$sender_address$& is not yet
30291 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30294 .vindex "&$message_size$&"
30295 The &$message_size$& variable is set to the value of the SIZE parameter on
30296 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30297 that parameter is not given. The value is updated to the true message size by
30298 the time the final DATA ACL is run (after the message data has been
30301 .vindex "&$rcpt_count$&"
30302 .vindex "&$recipients_count$&"
30303 The &$rcpt_count$& variable increases by one for each RCPT command received.
30304 The &$recipients_count$& variable increases by one each time a RCPT command is
30305 accepted, so while an ACL for RCPT is being processed, it contains the number
30306 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30307 &$rcpt_count$& contains the total number of RCPT commands, and
30308 &$recipients_count$& contains the total number of accepted recipients.
30314 .section "Data for non-message ACLs" "SECTdatfornon"
30315 .cindex "&ACL;" "data for non-message ACL"
30316 .vindex &$smtp_command_argument$&
30317 .vindex &$smtp_command$&
30318 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30319 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30320 and the entire SMTP command is available in &$smtp_command$&.
30321 These variables can be tested using a &%condition%& condition. For example,
30322 here is an ACL for use with AUTH, which insists that either the session is
30323 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30324 does not permit authentication methods that use cleartext passwords on
30325 unencrypted connections.
30328 accept encrypted = *
30329 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30331 deny message = TLS encryption or CRAM-MD5 required
30333 (Another way of applying this restriction is to arrange for the authenticators
30334 that use cleartext passwords not to be advertised when the connection is not
30335 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30336 option to do this.)
30340 .section "Format of an ACL" "SECID199"
30341 .cindex "&ACL;" "format of"
30342 .cindex "&ACL;" "verbs, definition of"
30343 An individual ACL consists of a number of statements. Each statement starts
30344 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30345 Modifiers can change the way the verb operates, define error and log messages,
30346 set variables, insert delays, and vary the processing of accepted messages.
30348 If all the conditions are met, the verb is obeyed. The same condition may be
30349 used (with different arguments) more than once in the same statement. This
30350 provides a means of specifying an &"and"& conjunction between conditions. For
30353 deny dnslists = list1.example
30354 dnslists = list2.example
30356 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30357 the conditions and modifiers when it reaches a condition that fails. What
30358 happens then depends on the verb (and in one case, on a special modifier). Not
30359 all the conditions make sense at every testing point. For example, you cannot
30360 test a sender address in the ACL that is run for a VRFY command.
30363 .section "ACL verbs" "SECID200"
30364 The ACL verbs are as follows:
30367 .cindex "&%accept%& ACL verb"
30368 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30369 of the conditions are not met, what happens depends on whether &%endpass%&
30370 appears among the conditions (for syntax see below). If the failing condition
30371 is before &%endpass%&, control is passed to the next ACL statement; if it is
30372 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30373 check a RCPT command:
30375 accept domains = +local_domains
30379 If the recipient domain does not match the &%domains%& condition, control
30380 passes to the next statement. If it does match, the recipient is verified, and
30381 the command is accepted if verification succeeds. However, if verification
30382 fails, the ACL yields &"deny"&, because the failing condition is after
30385 The &%endpass%& feature has turned out to be confusing to many people, so its
30386 use is not recommended nowadays. It is always possible to rewrite an ACL so
30387 that &%endpass%& is not needed, and it is no longer used in the default
30390 .cindex "&%message%& ACL modifier" "with &%accept%&"
30391 If a &%message%& modifier appears on an &%accept%& statement, its action
30392 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30393 (when an &%accept%& verb either accepts or passes control to the next
30394 statement), &%message%& can be used to vary the message that is sent when an
30395 SMTP command is accepted. For example, in a RCPT ACL you could have:
30397 &`accept `&<&'some conditions'&>
30398 &` message = OK, I will allow you through today`&
30400 You can specify an SMTP response code, optionally followed by an &"extended
30401 response code"& at the start of the message, but the first digit must be the
30402 same as would be sent by default, which is 2 for an &%accept%& verb.
30404 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30405 an error message that is used when access is denied. This behaviour is retained
30406 for backward compatibility, but current &"best practice"& is to avoid the use
30411 .cindex "&%defer%& ACL verb"
30412 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30413 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30414 &%defer%& is the same as &%deny%&, because there is no way of sending a
30415 temporary error. For a RCPT command, &%defer%& is much the same as using a
30416 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30417 be used in any ACL, and even for a recipient it might be a simpler approach.
30421 .cindex "&%deny%& ACL verb"
30422 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30423 the conditions are not met, control is passed to the next ACL statement. For
30426 deny dnslists = blackholes.mail-abuse.org
30428 rejects commands from hosts that are on a DNS black list.
30432 .cindex "&%discard%& ACL verb"
30433 &%discard%&: This verb behaves like &%accept%&, except that it returns
30434 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30435 that are concerned with receiving messages. When all the conditions are true,
30436 the sending entity receives a &"success"& response. However, &%discard%& causes
30437 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30438 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30439 message's recipients are discarded. Recipients that are discarded before DATA
30440 do not appear in the log line when the &%received_recipients%& log selector is set.
30442 If the &%log_message%& modifier is set when &%discard%& operates,
30443 its contents are added to the line that is automatically written to the log.
30444 The &%message%& modifier operates exactly as it does for &%accept%&.
30448 .cindex "&%drop%& ACL verb"
30449 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30450 forcibly closed after the 5&'xx'& error message has been sent. For example:
30452 drop condition = ${if > {$rcpt_count}{20}}
30453 message = I don't take more than 20 RCPTs
30455 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30456 The connection is always dropped after sending a 550 response.
30459 .cindex "&%require%& ACL verb"
30460 &%require%&: If all the conditions are met, control is passed to the next ACL
30461 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30462 example, when checking a RCPT command,
30464 require message = Sender did not verify
30467 passes control to subsequent statements only if the message's sender can be
30468 verified. Otherwise, it rejects the command. Note the positioning of the
30469 &%message%& modifier, before the &%verify%& condition. The reason for this is
30470 discussed in section &<<SECTcondmodproc>>&.
30473 .cindex "&%warn%& ACL verb"
30474 &%warn%&: If all the conditions are true, a line specified by the
30475 &%log_message%& modifier is written to Exim's main log. Control always passes
30476 to the next ACL statement. If any condition is false, the log line is not
30477 written. If an identical log line is requested several times in the same
30478 message, only one copy is actually written to the log. If you want to force
30479 duplicates to be written, use the &%logwrite%& modifier instead.
30481 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
30482 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
30483 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
30484 first failing condition. There is more about adding header lines in section
30485 &<<SECTaddheadacl>>&.
30487 If any condition on a &%warn%& statement cannot be completed (that is, there is
30488 some sort of defer), the log line specified by &%log_message%& is not written.
30489 This does not include the case of a forced failure from a lookup, which
30490 is considered to be a successful completion. After a defer, no further
30491 conditions or modifiers in the &%warn%& statement are processed. The incident
30492 is logged, and the ACL continues to be processed, from the next statement
30496 .vindex "&$acl_verify_message$&"
30497 When one of the &%warn%& conditions is an address verification that fails, the
30498 text of the verification failure message is in &$acl_verify_message$&. If you
30499 want this logged, you must set it up explicitly. For example:
30501 warn !verify = sender
30502 log_message = sender verify failed: $acl_verify_message
30506 At the end of each ACL there is an implicit unconditional &%deny%&.
30508 As you can see from the examples above, the conditions and modifiers are
30509 written one to a line, with the first one on the same line as the verb, and
30510 subsequent ones on following lines. If you have a very long condition, you can
30511 continue it onto several physical lines by the usual backslash continuation
30512 mechanism. It is conventional to align the conditions vertically.
30516 .section "ACL variables" "SECTaclvariables"
30517 .cindex "&ACL;" "variables"
30518 There are some special variables that can be set during ACL processing. They
30519 can be used to pass information between different ACLs, different invocations
30520 of the same ACL in the same SMTP connection, and between ACLs and the routers,
30521 transports, and filters that are used to deliver a message. The names of these
30522 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
30523 an underscore, but the remainder of the name can be any sequence of
30524 alphanumeric characters and underscores that you choose. There is no limit on
30525 the number of ACL variables. The two sets act as follows:
30527 The values of those variables whose names begin with &$acl_c$& persist
30528 throughout an SMTP connection. They are never reset. Thus, a value that is set
30529 while receiving one message is still available when receiving the next message
30530 on the same SMTP connection.
30532 The values of those variables whose names begin with &$acl_m$& persist only
30533 while a message is being received. They are reset afterwards. They are also
30534 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
30537 When a message is accepted, the current values of all the ACL variables are
30538 preserved with the message and are subsequently made available at delivery
30539 time. The ACL variables are set by a modifier called &%set%&. For example:
30541 accept hosts = whatever
30542 set acl_m4 = some value
30543 accept authenticated = *
30544 set acl_c_auth = yes
30546 &*Note*&: A leading dollar sign is not used when naming a variable that is to
30547 be set. If you want to set a variable without taking any action, you can use a
30548 &%warn%& verb without any other modifiers or conditions.
30550 .oindex &%strict_acl_vars%&
30551 What happens if a syntactically valid but undefined ACL variable is
30552 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
30553 false (the default), an empty string is substituted; if it is true, an
30554 error is generated.
30556 Versions of Exim before 4.64 have a limited set of numbered variables, but
30557 their names are compatible, so there is no problem with upgrading.
30560 .section "Condition and modifier processing" "SECTcondmodproc"
30561 .cindex "&ACL;" "conditions; processing"
30562 .cindex "&ACL;" "modifiers; processing"
30563 An exclamation mark preceding a condition negates its result. For example:
30565 deny domains = *.dom.example
30566 !verify = recipient
30568 causes the ACL to return &"deny"& if the recipient domain ends in
30569 &'dom.example'& and the recipient address cannot be verified. Sometimes
30570 negation can be used on the right-hand side of a condition. For example, these
30571 two statements are equivalent:
30573 deny hosts = !192.168.3.4
30574 deny !hosts = 192.168.3.4
30576 However, for many conditions (&%verify%& being a good example), only left-hand
30577 side negation of the whole condition is possible.
30579 The arguments of conditions and modifiers are expanded. A forced failure
30580 of an expansion causes a condition to be ignored, that is, it behaves as if the
30581 condition is true. Consider these two statements:
30583 accept senders = ${lookup{$host_name}lsearch\
30584 {/some/file}{$value}fail}
30585 accept senders = ${lookup{$host_name}lsearch\
30586 {/some/file}{$value}{}}
30588 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
30589 the returned list is searched, but if the lookup fails the behaviour is
30590 different in the two cases. The &%fail%& in the first statement causes the
30591 condition to be ignored, leaving no further conditions. The &%accept%& verb
30592 therefore succeeds. The second statement, however, generates an empty list when
30593 the lookup fails. No sender can match an empty list, so the condition fails,
30594 and therefore the &%accept%& also fails.
30596 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
30597 specify actions that are taken as the conditions for a statement are checked;
30598 others specify text for messages that are used when access is denied or a
30599 warning is generated. The &%control%& modifier affects the way an incoming
30600 message is handled.
30602 The positioning of the modifiers in an ACL statement is important, because the
30603 processing of a verb ceases as soon as its outcome is known. Only those
30604 modifiers that have already been encountered will take effect. For example,
30605 consider this use of the &%message%& modifier:
30607 require message = Can't verify sender
30609 message = Can't verify recipient
30611 message = This message cannot be used
30613 If sender verification fails, Exim knows that the result of the statement is
30614 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
30615 so its text is used as the error message. If sender verification succeeds, but
30616 recipient verification fails, the second message is used. If recipient
30617 verification succeeds, the third message becomes &"current"&, but is never used
30618 because there are no more conditions to cause failure.
30620 For the &%deny%& verb, on the other hand, it is always the last &%message%&
30621 modifier that is used, because all the conditions must be true for rejection to
30622 happen. Specifying more than one &%message%& modifier does not make sense, and
30623 the message can even be specified after all the conditions. For example:
30626 !senders = *@my.domain.example
30627 message = Invalid sender from client host
30629 The &"deny"& result does not happen until the end of the statement is reached,
30630 by which time Exim has set up the message.
30634 .section "ACL modifiers" "SECTACLmodi"
30635 .cindex "&ACL;" "modifiers; list of"
30636 The ACL modifiers are as follows:
30639 .vitem &*add_header*&&~=&~<&'text'&>
30640 This modifier specifies one or more header lines that are to be added to an
30641 incoming message, assuming, of course, that the message is ultimately
30642 accepted. For details, see section &<<SECTaddheadacl>>&.
30644 .vitem &*continue*&&~=&~<&'text'&>
30645 .cindex "&%continue%& ACL modifier"
30646 .cindex "database" "updating in ACL"
30647 This modifier does nothing of itself, and processing of the ACL always
30648 continues with the next condition or modifier. The value of &%continue%& is in
30649 the side effects of expanding its argument. Typically this could be used to
30650 update a database. It is really just a syntactic tidiness, to avoid having to
30651 write rather ugly lines like this:
30653 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
30655 Instead, all you need is
30657 &`continue = `&<&'some expansion'&>
30660 .vitem &*control*&&~=&~<&'text'&>
30661 .cindex "&%control%& ACL modifier"
30662 This modifier affects the subsequent processing of the SMTP connection or of an
30663 incoming message that is accepted. The effect of the first type of control
30664 lasts for the duration of the connection, whereas the effect of the second type
30665 lasts only until the current message has been received. The message-specific
30666 controls always apply to the whole message, not to individual recipients,
30667 even if the &%control%& modifier appears in a RCPT ACL.
30669 As there are now quite a few controls that can be applied, they are described
30670 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
30671 in several different ways. For example:
30673 . ==== As this is a nested list, any displays it contains must be indented
30674 . ==== as otherwise they are too far to the left. That comment applies only
30675 . ==== when xmlto and fop are used; formatting with sdop gets it right either
30679 It can be at the end of an &%accept%& statement:
30681 accept ...some conditions
30684 In this case, the control is applied when this statement yields &"accept"&, in
30685 other words, when the conditions are all true.
30688 It can be in the middle of an &%accept%& statement:
30690 accept ...some conditions...
30692 ...some more conditions...
30694 If the first set of conditions are true, the control is applied, even if the
30695 statement does not accept because one of the second set of conditions is false.
30696 In this case, some subsequent statement must yield &"accept"& for the control
30700 It can be used with &%warn%& to apply the control, leaving the
30701 decision about accepting or denying to a subsequent verb. For
30704 warn ...some conditions...
30708 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
30709 &%logwrite%&, so it does not add anything to the message and does not write a
30713 If you want to apply a control unconditionally, you can use it with a
30714 &%require%& verb. For example:
30716 require control = no_multiline_responses
30720 .vitem &*delay*&&~=&~<&'time'&>
30721 .cindex "&%delay%& ACL modifier"
30723 This modifier may appear in any ACL except notquit. It causes Exim to wait for
30724 the time interval before proceeding. However, when testing Exim using the
30725 &%-bh%& option, the delay is not actually imposed (an appropriate message is
30726 output instead). The time is given in the usual Exim notation, and the delay
30727 happens as soon as the modifier is processed. In an SMTP session, pending
30728 output is flushed before the delay is imposed.
30730 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
30733 deny ...some conditions...
30736 The delay happens if all the conditions are true, before the statement returns
30737 &"deny"&. Compare this with:
30740 ...some conditions...
30742 which waits for 30s before processing the conditions. The &%delay%& modifier
30743 can also be used with &%warn%& and together with &%control%&:
30745 warn ...some conditions...
30751 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
30752 responses to several commands are no longer buffered and sent in one packet (as
30753 they would normally be) because all output is flushed before imposing the
30754 delay. This optimization is disabled so that a number of small delays do not
30755 appear to the client as one large aggregated delay that might provoke an
30756 unwanted timeout. You can, however, disable output flushing for &%delay%& by
30757 using a &%control%& modifier to set &%no_delay_flush%&.
30761 .cindex "&%endpass%& ACL modifier"
30762 This modifier, which has no argument, is recognized only in &%accept%& and
30763 &%discard%& statements. It marks the boundary between the conditions whose
30764 failure causes control to pass to the next statement, and the conditions whose
30765 failure causes the ACL to return &"deny"&. This concept has proved to be
30766 confusing to some people, so the use of &%endpass%& is no longer recommended as
30767 &"best practice"&. See the description of &%accept%& above for more details.
30770 .vitem &*log_message*&&~=&~<&'text'&>
30771 .cindex "&%log_message%& ACL modifier"
30772 This modifier sets up a message that is used as part of the log message if the
30773 ACL denies access or a &%warn%& statement's conditions are true. For example:
30775 require log_message = wrong cipher suite $tls_in_cipher
30776 encrypted = DES-CBC3-SHA
30778 &%log_message%& is also used when recipients are discarded by &%discard%&. For
30781 &`discard `&<&'some conditions'&>
30782 &` log_message = Discarded $local_part@$domain because...`&
30784 When access is denied, &%log_message%& adds to any underlying error message
30785 that may exist because of a condition failure. For example, while verifying a
30786 recipient address, a &':fail:'& redirection might have already set up a
30789 The message may be defined before the conditions to which it applies, because
30790 the string expansion does not happen until Exim decides that access is to be
30791 denied. This means that any variables that are set by the condition are
30792 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
30793 variables are set after a DNS black list lookup succeeds. If the expansion of
30794 &%log_message%& fails, or if the result is an empty string, the modifier is
30797 .vindex "&$acl_verify_message$&"
30798 If you want to use a &%warn%& statement to log the result of an address
30799 verification, you can use &$acl_verify_message$& to include the verification
30802 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
30803 the start of the logged message. If the same warning log message is requested
30804 more than once while receiving a single email message, only one copy is
30805 actually logged. If you want to log multiple copies, use &%logwrite%& instead
30806 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
30807 is logged for a successful &%warn%& statement.
30809 If &%log_message%& is not present and there is no underlying error message (for
30810 example, from the failure of address verification), but &%message%& is present,
30811 the &%message%& text is used for logging rejections. However, if any text for
30812 logging contains newlines, only the first line is logged. In the absence of
30813 both &%log_message%& and &%message%&, a default built-in message is used for
30814 logging rejections.
30817 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
30818 .cindex "&%log_reject_target%& ACL modifier"
30819 .cindex "logging in ACL" "specifying which log"
30820 This modifier makes it possible to specify which logs are used for messages
30821 about ACL rejections. Its argument is a colon-separated list of words that can
30822 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
30823 may be empty, in which case a rejection is not logged at all. For example, this
30824 ACL fragment writes no logging information when access is denied:
30826 &`deny `&<&'some conditions'&>
30827 &` log_reject_target =`&
30829 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
30830 permanent and temporary rejections. Its effect lasts for the rest of the
30834 .vitem &*logwrite*&&~=&~<&'text'&>
30835 .cindex "&%logwrite%& ACL modifier"
30836 .cindex "logging in ACL" "immediate"
30837 This modifier writes a message to a log file as soon as it is encountered when
30838 processing an ACL. (Compare &%log_message%&, which, except in the case of
30839 &%warn%& and &%discard%&, is used only if the ACL statement denies
30840 access.) The &%logwrite%& modifier can be used to log special incidents in
30843 &`accept `&<&'some special conditions'&>
30844 &` control = freeze`&
30845 &` logwrite = froze message because ...`&
30847 By default, the message is written to the main log. However, it may begin
30848 with a colon, followed by a comma-separated list of log names, and then
30849 another colon, to specify exactly which logs are to be written. For
30852 logwrite = :main,reject: text for main and reject logs
30853 logwrite = :panic: text for panic log only
30857 .vitem &*message*&&~=&~<&'text'&>
30858 .cindex "&%message%& ACL modifier"
30859 This modifier sets up a text string that is expanded and used as a response
30860 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
30861 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
30862 there is some complication if &%endpass%& is involved; see the description of
30863 &%accept%& for details.)
30865 The expansion of the message happens at the time Exim decides that the ACL is
30866 to end, not at the time it processes &%message%&. If the expansion fails, or
30867 generates an empty string, the modifier is ignored. Here is an example where
30868 &%message%& must be specified first, because the ACL ends with a rejection if
30869 the &%hosts%& condition fails:
30871 require message = Host not recognized
30874 (Once a condition has failed, no further conditions or modifiers are
30877 .cindex "SMTP" "error codes"
30878 .oindex "&%smtp_banner%&
30879 For ACLs that are triggered by SMTP commands, the message is returned as part
30880 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
30881 is meaningful only for SMTP, as no message is returned when a non-SMTP message
30882 is accepted. In the case of the connect ACL, accepting with a message modifier
30883 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
30884 accept message may not contain more than one line (otherwise it will be
30885 truncated at the first newline and a panic logged), and it cannot affect the
30888 When SMTP is involved, the message may begin with an overriding response code,
30889 consisting of three digits optionally followed by an &"extended response code"&
30890 of the form &'n.n.n'&, each code being followed by a space. For example:
30892 deny message = 599 1.2.3 Host not welcome
30893 hosts = 192.168.34.0/24
30895 The first digit of the supplied response code must be the same as would be sent
30896 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
30897 access, but for the predata ACL, note that the default success code is 354, not
30900 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
30901 the message modifier cannot override the 221 response code.
30903 The text in a &%message%& modifier is literal; any quotes are taken as
30904 literals, but because the string is expanded, backslash escapes are processed
30905 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
30908 .vindex "&$acl_verify_message$&"
30909 For ACLs that are called by an &%acl =%& ACL condition, the message is
30910 stored in &$acl_verify_message$&, from which the calling ACL may use it.
30912 If &%message%& is used on a statement that verifies an address, the message
30913 specified overrides any message that is generated by the verification process.
30914 However, the original message is available in the variable
30915 &$acl_verify_message$&, so you can incorporate it into your message if you
30916 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
30917 routers to be passed back as part of the SMTP response, you should either not
30918 use a &%message%& modifier, or make use of &$acl_verify_message$&.
30920 For compatibility with previous releases of Exim, a &%message%& modifier that
30921 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
30922 modifier, but this usage is now deprecated. However, &%message%& acts only when
30923 all the conditions are true, wherever it appears in an ACL command, whereas
30924 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
30925 &%warn%& in an ACL that is not concerned with receiving a message, it has no
30929 .vitem &*queue*&&~=&~<&'text'&>
30930 .cindex "&%queue%& ACL modifier"
30931 .cindex "named queues" "selecting in ACL"
30932 This modifier specifies the use of a named queue for spool files
30934 It can only be used before the message is received (i.e. not in
30936 This could be used, for example, for known high-volume burst sources
30937 of traffic, or for quarantine of messages.
30938 Separate queue-runner processes will be needed for named queues.
30939 If the text after expansion is empty, the default queue is used.
30942 .vitem &*remove_header*&&~=&~<&'text'&>
30943 This modifier specifies one or more header names in a colon-separated list
30944 that are to be removed from an incoming message, assuming, of course, that
30945 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
30948 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
30949 .cindex "&%set%& ACL modifier"
30950 This modifier puts a value into one of the ACL variables (see section
30951 &<<SECTaclvariables>>&).
30954 .vitem &*udpsend*&&~=&~<&'parameters'&>
30955 .cindex "UDP communications"
30956 This modifier sends a UDP packet, for purposes such as statistics
30957 collection or behaviour monitoring. The parameters are expanded, and
30958 the result of the expansion must be a colon-separated list consisting
30959 of a destination server, port number, and the packet contents. The
30960 server can be specified as a host name or IPv4 or IPv6 address. The
30961 separator can be changed with the usual angle bracket syntax. For
30962 example, you might want to collect information on which hosts connect
30965 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
30966 $tod_zulu $sender_host_address
30973 .section "Use of the control modifier" "SECTcontrols"
30974 .cindex "&%control%& ACL modifier"
30975 The &%control%& modifier supports the following settings:
30978 .vitem &*control&~=&~allow_auth_unadvertised*&
30979 This modifier allows a client host to use the SMTP AUTH command even when it
30980 has not been advertised in response to EHLO. Furthermore, because there are
30981 apparently some really broken clients that do this, Exim will accept AUTH after
30982 HELO (rather than EHLO) when this control is set. It should be used only if you
30983 really need it, and you should limit its use to those broken clients that do
30984 not work without it. For example:
30986 warn hosts = 192.168.34.25
30987 control = allow_auth_unadvertised
30989 Normally, when an Exim server receives an AUTH command, it checks the name of
30990 the authentication mechanism that is given in the command to ensure that it
30991 matches an advertised mechanism. When this control is set, the check that a
30992 mechanism has been advertised is bypassed. Any configured mechanism can be used
30993 by the client. This control is permitted only in the connection and HELO ACLs.
30996 .vitem &*control&~=&~caseful_local_part*& &&&
30997 &*control&~=&~caselower_local_part*&
30998 .cindex "&ACL;" "case of local part in"
30999 .cindex "case of local parts"
31000 .vindex "&$local_part$&"
31001 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31002 (that is, during RCPT processing). By default, the contents of &$local_part$&
31003 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31004 any uppercase letters in the original local part are restored in &$local_part$&
31005 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31008 These controls affect only the current recipient. Moreover, they apply only to
31009 local part handling that takes place directly in the ACL (for example, as a key
31010 in lookups). If a test to verify the recipient is obeyed, the case-related
31011 handling of the local part during the verification is controlled by the router
31012 configuration (see the &%caseful_local_part%& generic router option).
31014 This facility could be used, for example, to add a spam score to local parts
31015 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31018 warn control = caseful_local_part
31019 set acl_m4 = ${eval:\
31021 ${if match{$local_part}{[A-Z]}{1}{0}}\
31023 control = caselower_local_part
31025 Notice that we put back the lower cased version afterwards, assuming that
31026 is what is wanted for subsequent tests.
31029 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31030 .cindex "&ACL;" "cutthrough routing"
31031 .cindex "cutthrough" "requesting"
31032 This option requests delivery be attempted while the item is being received.
31034 The option is usable in the RCPT ACL.
31035 If enabled for a message received via smtp and routed to an smtp transport,
31036 and only one transport, interface, destination host and port combination
31037 is used for all recipients of the message,
31038 then the delivery connection is made while the receiving connection is open
31039 and data is copied from one to the other.
31041 An attempt to set this option for any recipient but the first
31042 for a mail will be quietly ignored.
31043 If a recipient-verify callout
31045 connection is subsequently
31046 requested in the same ACL it is held open and used for
31047 any subsequent recipients and the data,
31048 otherwise one is made after the initial RCPT ACL completes.
31050 Note that routers are used in verify mode,
31051 and cannot depend on content of received headers.
31052 Note also that headers cannot be
31053 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31054 Headers may be modified by routers (subject to the above) and transports.
31055 The &'Received-By:'& header is generated as soon as the body reception starts,
31056 rather than the traditional time after the full message is received;
31057 this will affect the timestamp.
31059 All the usual ACLs are called; if one results in the message being
31060 rejected, all effort spent in delivery (including the costs on
31061 the ultimate destination) will be wasted.
31062 Note that in the case of data-time ACLs this includes the entire
31065 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31066 of outgoing messages is done, because it sends data to the ultimate destination
31067 before the entire message has been received from the source.
31068 It is not supported for messages received with the SMTP PRDR
31072 Should the ultimate destination system positively accept or reject the mail,
31073 a corresponding indication is given to the source system and nothing is queued.
31074 If the item is successfully delivered in cutthrough mode
31075 the delivery log lines are tagged with ">>" rather than "=>" and appear
31076 before the acceptance "<=" line.
31078 If there is a temporary error the item is queued for later delivery in the
31080 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31081 to the control; the default value is &"spool"& and the alternate value
31082 &"pass"& copies an SMTP defer response from the target back to the initiator
31083 and does not queue the message.
31084 Note that this is independent of any recipient verify conditions in the ACL.
31086 Delivery in this mode avoids the generation of a bounce mail to a
31088 sender when the destination system is doing content-scan based rejection.
31091 .vitem &*control&~=&~debug/*&<&'options'&>
31092 .cindex "&ACL;" "enabling debug logging"
31093 .cindex "debugging" "enabling from an ACL"
31094 This control turns on debug logging, almost as though Exim had been invoked
31095 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31096 by default called &'debuglog'&.
31097 The filename can be adjusted with the &'tag'& option, which
31098 may access any variables already defined. The logging may be adjusted with
31099 the &'opts'& option, which takes the same values as the &`-d`& command-line
31101 Logging started this way may be stopped, and the file removed,
31102 with the &'kill'& option.
31103 Some examples (which depend on variables that don't exist in all
31107 control = debug/tag=.$sender_host_address
31108 control = debug/opts=+expand+acl
31109 control = debug/tag=.$message_exim_id/opts=+expand
31110 control = debug/kill
31114 .vitem &*control&~=&~dkim_disable_verify*&
31115 .cindex "disable DKIM verify"
31116 .cindex "DKIM" "disable verify"
31117 This control turns off DKIM verification processing entirely. For details on
31118 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31121 .vitem &*control&~=&~dmarc_disable_verify*&
31122 .cindex "disable DMARC verify"
31123 .cindex "DMARC" "disable verify"
31124 This control turns off DMARC verification processing entirely. For details on
31125 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31128 .vitem &*control&~=&~dscp/*&<&'value'&>
31129 .cindex "&ACL;" "setting DSCP value"
31130 .cindex "DSCP" "inbound"
31131 This option causes the DSCP value associated with the socket for the inbound
31132 connection to be adjusted to a given value, given as one of a number of fixed
31133 strings or to numeric value.
31134 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31135 Common values include &`throughput`&, &`mincost`&, and on newer systems
31136 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31138 The outbound packets from Exim will be marked with this value in the header
31139 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31140 that these values will have any effect, not be stripped by networking
31141 equipment, or do much of anything without cooperation with your Network
31142 Engineer and those of all network operators between the source and destination.
31145 .vitem &*control&~=&~enforce_sync*& &&&
31146 &*control&~=&~no_enforce_sync*&
31147 .cindex "SMTP" "synchronization checking"
31148 .cindex "synchronization checking in SMTP"
31149 These controls make it possible to be selective about when SMTP synchronization
31150 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31151 state of the switch (it is true by default). See the description of this option
31152 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31154 The effect of these two controls lasts for the remainder of the SMTP
31155 connection. They can appear in any ACL except the one for the non-SMTP
31156 messages. The most straightforward place to put them is in the ACL defined by
31157 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31158 before the first synchronization check. The expected use is to turn off the
31159 synchronization checks for badly-behaved hosts that you nevertheless need to
31163 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31164 .cindex "fake defer"
31165 .cindex "defer, fake"
31166 This control works in exactly the same way as &%fakereject%& (described below)
31167 except that it causes an SMTP 450 response after the message data instead of a
31168 550 response. You must take care when using &%fakedefer%& because it causes the
31169 messages to be duplicated when the sender retries. Therefore, you should not
31170 use &%fakedefer%& if the message is to be delivered normally.
31172 .vitem &*control&~=&~fakereject/*&<&'message'&>
31173 .cindex "fake rejection"
31174 .cindex "rejection, fake"
31175 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31176 words, only when an SMTP message is being received. If Exim accepts the
31177 message, instead the final 250 response, a 550 rejection message is sent.
31178 However, Exim proceeds to deliver the message as normal. The control applies
31179 only to the current message, not to any subsequent ones that may be received in
31180 the same SMTP connection.
31182 The text for the 550 response is taken from the &%control%& modifier. If no
31183 message is supplied, the following is used:
31185 550-Your message has been rejected but is being
31186 550-kept for evaluation.
31187 550-If it was a legitimate message, it may still be
31188 550 delivered to the target recipient(s).
31190 This facility should be used with extreme caution.
31192 .vitem &*control&~=&~freeze*&
31193 .cindex "frozen messages" "forcing in ACL"
31194 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31195 other words, only when a message is being received. If the message is accepted,
31196 it is placed on Exim's queue and frozen. The control applies only to the
31197 current message, not to any subsequent ones that may be received in the same
31200 This modifier can optionally be followed by &`/no_tell`&. If the global option
31201 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31202 is told about the freezing), provided all the &*control=freeze*& modifiers that
31203 are obeyed for the current message have the &`/no_tell`& option.
31205 .vitem &*control&~=&~no_delay_flush*&
31206 .cindex "SMTP" "output flushing, disabling for delay"
31207 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31208 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31209 use. This control, as long as it is encountered before the &%delay%& modifier,
31210 disables such output flushing.
31212 .vitem &*control&~=&~no_callout_flush*&
31213 .cindex "SMTP" "output flushing, disabling for callout"
31214 Exim normally flushes SMTP output before performing a callout in an ACL, to
31215 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31216 use. This control, as long as it is encountered before the &%verify%& condition
31217 that causes the callout, disables such output flushing.
31219 .vitem &*control&~=&~no_mbox_unspool*&
31220 This control is available when Exim is compiled with the content scanning
31221 extension. Content scanning may require a copy of the current message, or parts
31222 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31223 or spam scanner. Normally, such copies are deleted when they are no longer
31224 needed. If this control is set, the copies are not deleted. The control applies
31225 only to the current message, not to any subsequent ones that may be received in
31226 the same SMTP connection. It is provided for debugging purposes and is unlikely
31227 to be useful in production.
31229 .vitem &*control&~=&~no_multiline_responses*&
31230 .cindex "multiline responses, suppressing"
31231 This control is permitted for any ACL except the one for non-SMTP messages.
31232 It seems that there are broken clients in use that cannot handle multiline
31233 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31235 If this control is set, multiline SMTP responses from ACL rejections are
31236 suppressed. One way of doing this would have been to put out these responses as
31237 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31238 (&"use multiline responses for more"& it says &-- ha!), and some of the
31239 responses might get close to that. So this facility, which is after all only a
31240 sop to broken clients, is implemented by doing two very easy things:
31243 Extra information that is normally output as part of a rejection caused by
31244 sender verification failure is omitted. Only the final line (typically &"sender
31245 verification failed"&) is sent.
31247 If a &%message%& modifier supplies a multiline response, only the first
31251 The setting of the switch can, of course, be made conditional on the
31252 calling host. Its effect lasts until the end of the SMTP connection.
31254 .vitem &*control&~=&~no_pipelining*&
31255 .cindex "PIPELINING" "suppressing advertising"
31256 .cindex "ESMTP extensions" PIPELINING
31257 This control turns off the advertising of the PIPELINING extension to SMTP in
31258 the current session. To be useful, it must be obeyed before Exim sends its
31259 response to an EHLO command. Therefore, it should normally appear in an ACL
31260 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31261 &%pipelining_advertise_hosts%&.
31263 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31264 &*control&~=&~queue_only*&
31265 .oindex "&%queue%&"
31266 .oindex "&%queue_only%&"
31267 .cindex "queueing incoming messages"
31268 .cindex queueing "forcing in ACL"
31269 .cindex "first pass routing"
31270 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31271 other words, only when a message is being received. If the message is accepted,
31272 it is placed on Exim's queue and left there for delivery by a subsequent queue
31274 If used with no options set,
31275 no immediate delivery process is started. In other words, it has the
31276 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31278 If the &'first_pass_route'& option is given then
31279 the behaviour is like the command-line &'-oqds'& option;
31280 a delivery process is started which stops short of making
31281 any SMTP delivery. The benefit is that the hints database will be updated for
31282 the message being waiting for a specific host, and a later queue run will be
31283 able to send all such messages on a single connection.
31285 The control only applies to the current message, not to any subsequent ones that
31286 may be received in the same SMTP connection.
31288 .vitem &*control&~=&~submission/*&<&'options'&>
31289 .cindex "message" "submission"
31290 .cindex "submission mode"
31291 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31292 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31293 the current message is a submission from a local MUA. In this case, Exim
31294 operates in &"submission mode"&, and applies certain fixups to the message if
31295 necessary. For example, it adds a &'Date:'& header line if one is not present.
31296 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31297 late (the message has already been created).
31299 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31300 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31301 submission mode; the available options for this control are described there.
31302 The control applies only to the current message, not to any subsequent ones
31303 that may be received in the same SMTP connection.
31305 .vitem &*control&~=&~suppress_local_fixups*&
31306 .cindex "submission fixups, suppressing"
31307 This control applies to locally submitted (non TCP/IP) messages, and is the
31308 complement of &`control = submission`&. It disables the fixups that are
31309 normally applied to locally-submitted messages. Specifically:
31312 Any &'Sender:'& header line is left alone (in this respect, it is a
31313 dynamic version of &%local_sender_retain%&).
31315 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31317 There is no check that &'From:'& corresponds to the actual sender.
31320 This control may be useful when a remotely-originated message is accepted,
31321 passed to some scanning program, and then re-submitted for delivery. It can be
31322 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31323 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31326 &*Note:*& This control applies only to the current message, not to any others
31327 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31329 .vitem &*control&~=&~utf8_downconvert*&
31330 This control enables conversion of UTF-8 in message envelope addresses
31332 For details see section &<<SECTi18nMTA>>&.
31336 .section "Summary of message fixup control" "SECTsummesfix"
31337 All four possibilities for message fixups can be specified:
31340 Locally submitted, fixups applied: the default.
31342 Locally submitted, no fixups applied: use
31343 &`control = suppress_local_fixups`&.
31345 Remotely submitted, no fixups applied: the default.
31347 Remotely submitted, fixups applied: use &`control = submission`&.
31352 .section "Adding header lines in ACLs" "SECTaddheadacl"
31353 .cindex "header lines" "adding in an ACL"
31354 .cindex "header lines" "position of added lines"
31355 .cindex "&%add_header%& ACL modifier"
31356 The &%add_header%& modifier can be used to add one or more extra header lines
31357 to an incoming message, as in this example:
31359 warn dnslists = sbl.spamhaus.org : \
31360 dialup.mail-abuse.org
31361 add_header = X-blacklisted-at: $dnslist_domain
31363 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31364 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31365 receiving a message). The message must ultimately be accepted for
31366 &%add_header%& to have any significant effect. You can use &%add_header%& with
31367 any ACL verb, including &%deny%& (though this is potentially useful only in a
31370 Headers will not be added to the message if the modifier is used in
31371 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31373 Leading and trailing newlines are removed from
31374 the data for the &%add_header%& modifier; if it then
31375 contains one or more newlines that
31376 are not followed by a space or a tab, it is assumed to contain multiple header
31377 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31378 front of any line that is not a valid header line.
31380 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31381 They are added to the message before processing the DATA and MIME ACLs.
31382 However, if an identical header line is requested more than once, only one copy
31383 is actually added to the message. Further header lines may be accumulated
31384 during the DATA and MIME ACLs, after which they are added to the message, again
31385 with duplicates suppressed. Thus, it is possible to add two identical header
31386 lines to an SMTP message, but only if one is added before DATA and one after.
31387 In the case of non-SMTP messages, new headers are accumulated during the
31388 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31389 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31390 are included in the entry that is written to the reject log.
31392 .cindex "header lines" "added; visibility of"
31393 Header lines are not visible in string expansions
31395 until they are added to the
31396 message. It follows that header lines defined in the MAIL, RCPT, and predata
31397 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31398 header lines that are added by the DATA or MIME ACLs are not visible in those
31399 ACLs. Because of this restriction, you cannot use header lines as a way of
31400 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31401 this, you can use ACL variables, as described in section
31402 &<<SECTaclvariables>>&.
31404 The list of headers yet to be added is given by the &%$headers_added%& variable.
31406 The &%add_header%& modifier acts immediately as it is encountered during the
31407 processing of an ACL. Notice the difference between these two cases:
31409 &`accept add_header = ADDED: some text`&
31410 &` `&<&'some condition'&>
31412 &`accept `&<&'some condition'&>
31413 &` add_header = ADDED: some text`&
31415 In the first case, the header line is always added, whether or not the
31416 condition is true. In the second case, the header line is added only if the
31417 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31418 ACL statement. All those that are encountered before a condition fails are
31421 .cindex "&%warn%& ACL verb"
31422 For compatibility with previous versions of Exim, a &%message%& modifier for a
31423 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31424 effect only if all the conditions are true, even if it appears before some of
31425 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31426 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31427 are present on a &%warn%& verb, both are processed according to their
31430 By default, new header lines are added to a message at the end of the existing
31431 header lines. However, you can specify that any particular header line should
31432 be added right at the start (before all the &'Received:'& lines), immediately
31433 after the first block of &'Received:'& lines, or immediately before any line
31434 that is not a &'Received:'& or &'Resent-something:'& header.
31436 This is done by specifying &":at_start:"&, &":after_received:"&, or
31437 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31438 header line, respectively. (Header text cannot start with a colon, as there has
31439 to be a header name first.) For example:
31441 warn add_header = \
31442 :after_received:X-My-Header: something or other...
31444 If more than one header line is supplied in a single &%add_header%& modifier,
31445 each one is treated independently and can therefore be placed differently. If
31446 you add more than one line at the start, or after the Received: block, they end
31447 up in reverse order.
31449 &*Warning*&: This facility currently applies only to header lines that are
31450 added in an ACL. It does NOT work for header lines that are added in a
31451 system filter or in a router or transport.
31455 .section "Removing header lines in ACLs" "SECTremoveheadacl"
31456 .cindex "header lines" "removing in an ACL"
31457 .cindex "header lines" "position of removed lines"
31458 .cindex "&%remove_header%& ACL modifier"
31459 The &%remove_header%& modifier can be used to remove one or more header lines
31460 from an incoming message, as in this example:
31462 warn message = Remove internal headers
31463 remove_header = x-route-mail1 : x-route-mail2
31465 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31466 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31467 receiving a message). The message must ultimately be accepted for
31468 &%remove_header%& to have any significant effect. You can use &%remove_header%&
31469 with any ACL verb, including &%deny%&, though this is really not useful for
31470 any verb that doesn't result in a delivered message.
31472 Headers will not be removed from the message if the modifier is used in
31473 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31475 More than one header can be removed at the same time by using a colon separated
31476 list of header names. The header matching is case insensitive. Wildcards are
31477 not permitted, nor is list expansion performed, so you cannot use hostlists to
31478 create a list of headers, however both connection and message variable expansion
31479 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
31481 warn hosts = +internal_hosts
31482 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
31483 warn message = Remove internal headers
31484 remove_header = $acl_c_ihdrs
31486 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
31487 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
31488 If multiple header lines match, all are removed.
31489 There is no harm in attempting to remove the same header twice nor in removing
31490 a non-existent header. Further header lines to be removed may be accumulated
31491 during the DATA and MIME ACLs, after which they are removed from the message,
31492 if present. In the case of non-SMTP messages, headers to be removed are
31493 accumulated during the non-SMTP ACLs, and are removed from the message after
31494 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
31495 ACL, there really is no effect because there is no logging of what headers
31496 would have been removed.
31498 .cindex "header lines" "removed; visibility of"
31499 Header lines are not visible in string expansions until the DATA phase when it
31500 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
31501 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
31502 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
31503 this restriction, you cannot use header lines as a way of controlling data
31504 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
31505 you should instead use ACL variables, as described in section
31506 &<<SECTaclvariables>>&.
31508 The &%remove_header%& modifier acts immediately as it is encountered during the
31509 processing of an ACL. Notice the difference between these two cases:
31511 &`accept remove_header = X-Internal`&
31512 &` `&<&'some condition'&>
31514 &`accept `&<&'some condition'&>
31515 &` remove_header = X-Internal`&
31517 In the first case, the header line is always removed, whether or not the
31518 condition is true. In the second case, the header line is removed only if the
31519 condition is true. Multiple occurrences of &%remove_header%& may occur in the
31520 same ACL statement. All those that are encountered before a condition fails
31523 &*Warning*&: This facility currently applies only to header lines that are
31524 present during ACL processing. It does NOT remove header lines that are added
31525 in a system filter or in a router or transport.
31530 .section "ACL conditions" "SECTaclconditions"
31531 .cindex "&ACL;" "conditions; list of"
31532 Some of the conditions listed in this section are available only when Exim is
31533 compiled with the content-scanning extension. They are included here briefly
31534 for completeness. More detailed descriptions can be found in the discussion on
31535 content scanning in chapter &<<CHAPexiscan>>&.
31537 Not all conditions are relevant in all circumstances. For example, testing
31538 senders and recipients does not make sense in an ACL that is being run as the
31539 result of the arrival of an ETRN command, and checks on message headers can be
31540 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
31541 can use the same condition (with different parameters) more than once in the
31542 same ACL statement. This provides a way of specifying an &"and"& conjunction.
31543 The conditions are as follows:
31547 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
31548 .cindex "&ACL;" "nested"
31549 .cindex "&ACL;" "indirect"
31550 .cindex "&ACL;" "arguments"
31551 .cindex "&%acl%& ACL condition"
31552 The possible values of the argument are the same as for the
31553 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
31554 &"accept"& the condition is true; if it returns &"deny"& the condition is
31555 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
31556 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
31557 condition false. This means that further processing of the &%warn%& verb
31558 ceases, but processing of the ACL continues.
31560 If the argument is a named ACL, up to nine space-separated optional values
31561 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
31562 and $acl_narg is set to the count of values.
31563 Previous values of these variables are restored after the call returns.
31564 The name and values are expanded separately.
31565 Note that spaces in complex expansions which are used as arguments
31566 will act as argument separators.
31568 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
31569 the connection is dropped. If it returns &"discard"&, the verb must be
31570 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
31571 conditions are tested.
31573 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
31574 loops. This condition allows you to use different ACLs in different
31575 circumstances. For example, different ACLs can be used to handle RCPT commands
31576 for different local users or different local domains.
31578 .vitem &*authenticated&~=&~*&<&'string&~list'&>
31579 .cindex "&%authenticated%& ACL condition"
31580 .cindex "authentication" "ACL checking"
31581 .cindex "&ACL;" "testing for authentication"
31582 If the SMTP connection is not authenticated, the condition is false. Otherwise,
31583 the name of the authenticator is tested against the list. To test for
31584 authentication by any authenticator, you can set
31589 .vitem &*condition&~=&~*&<&'string'&>
31590 .cindex "&%condition%& ACL condition"
31591 .cindex "customizing" "ACL condition"
31592 .cindex "&ACL;" "customized test"
31593 .cindex "&ACL;" "testing, customized"
31594 This feature allows you to make up custom conditions. If the result of
31595 expanding the string is an empty string, the number zero, or one of the strings
31596 &"no"& or &"false"&, the condition is false. If the result is any non-zero
31597 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
31598 any other value, some error is assumed to have occurred, and the ACL returns
31599 &"defer"&. However, if the expansion is forced to fail, the condition is
31600 ignored. The effect is to treat it as true, whether it is positive or
31603 .vitem &*decode&~=&~*&<&'location'&>
31604 .cindex "&%decode%& ACL condition"
31605 This condition is available only when Exim is compiled with the
31606 content-scanning extension, and it is allowed only in the ACL defined by
31607 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
31608 If all goes well, the condition is true. It is false only if there are
31609 problems such as a syntax error or a memory shortage. For more details, see
31610 chapter &<<CHAPexiscan>>&.
31612 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
31613 .cindex "&%dnslists%& ACL condition"
31614 .cindex "DNS list" "in ACL"
31615 .cindex "black list (DNS)"
31616 .cindex "&ACL;" "testing a DNS list"
31617 This condition checks for entries in DNS black lists. These are also known as
31618 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
31619 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
31620 different variants of this condition to describe briefly here. See sections
31621 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
31623 .vitem &*domains&~=&~*&<&'domain&~list'&>
31624 .cindex "&%domains%& ACL condition"
31625 .cindex "domain" "ACL checking"
31626 .cindex "&ACL;" "testing a recipient domain"
31627 .vindex "&$domain_data$&"
31628 This condition is relevant only after a RCPT command. It checks that the domain
31629 of the recipient address is in the domain list. If percent-hack processing is
31630 enabled, it is done before this test is done. If the check succeeds with a
31631 lookup, the result of the lookup is placed in &$domain_data$& until the next
31634 &*Note carefully*& (because many people seem to fall foul of this): you cannot
31635 use &%domains%& in a DATA ACL.
31638 .vitem &*encrypted&~=&~*&<&'string&~list'&>
31639 .cindex "&%encrypted%& ACL condition"
31640 .cindex "encryption" "checking in an ACL"
31641 .cindex "&ACL;" "testing for encryption"
31642 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
31643 name of the cipher suite in use is tested against the list. To test for
31644 encryption without testing for any specific cipher suite(s), set
31650 .vitem &*hosts&~=&~*&<&'host&~list'&>
31651 .cindex "&%hosts%& ACL condition"
31652 .cindex "host" "ACL checking"
31653 .cindex "&ACL;" "testing the client host"
31654 This condition tests that the calling host matches the host list. If you have
31655 name lookups or wildcarded host names and IP addresses in the same host list,
31656 you should normally put the IP addresses first. For example, you could have:
31658 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
31660 The lookup in this example uses the host name for its key. This is implied by
31661 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
31662 and it wouldn't matter which way round you had these two items.)
31664 The reason for the problem with host names lies in the left-to-right way that
31665 Exim processes lists. It can test IP addresses without doing any DNS lookups,
31666 but when it reaches an item that requires a host name, it fails if it cannot
31667 find a host name to compare with the pattern. If the above list is given in the
31668 opposite order, the &%accept%& statement fails for a host whose name cannot be
31669 found, even if its IP address is 10.9.8.7.
31671 If you really do want to do the name check first, and still recognize the IP
31672 address even if the name lookup fails, you can rewrite the ACL like this:
31674 accept hosts = dbm;/etc/friendly/hosts
31675 accept hosts = 10.9.8.7
31677 The default action on failing to find the host name is to assume that the host
31678 is not in the list, so the first &%accept%& statement fails. The second
31679 statement can then check the IP address.
31681 .vindex "&$host_data$&"
31682 If a &%hosts%& condition is satisfied by means of a lookup, the result
31683 of the lookup is made available in the &$host_data$& variable. This
31684 allows you, for example, to set up a statement like this:
31686 deny hosts = net-lsearch;/some/file
31687 message = $host_data
31689 which gives a custom error message for each denied host.
31691 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
31692 .cindex "&%local_parts%& ACL condition"
31693 .cindex "local part" "ACL checking"
31694 .cindex "&ACL;" "testing a local part"
31695 .vindex "&$local_part_data$&"
31696 This condition is relevant only after a RCPT command. It checks that the local
31697 part of the recipient address is in the list. If percent-hack processing is
31698 enabled, it is done before this test. If the check succeeds with a lookup, the
31699 result of the lookup is placed in &$local_part_data$&, which remains set until
31700 the next &%local_parts%& test.
31702 .vitem &*malware&~=&~*&<&'option'&>
31703 .cindex "&%malware%& ACL condition"
31704 .cindex "&ACL;" "virus scanning"
31705 .cindex "&ACL;" "scanning for viruses"
31706 This condition is available only when Exim is compiled with the
31707 content-scanning extension
31708 and only after a DATA command.
31709 It causes the incoming message to be scanned for
31710 viruses. For details, see chapter &<<CHAPexiscan>>&.
31712 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
31713 .cindex "&%mime_regex%& ACL condition"
31714 .cindex "&ACL;" "testing by regex matching"
31715 This condition is available only when Exim is compiled with the
31716 content-scanning extension, and it is allowed only in the ACL defined by
31717 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
31718 with any of the regular expressions. For details, see chapter
31721 .vitem &*ratelimit&~=&~*&<&'parameters'&>
31722 .cindex "rate limiting"
31723 This condition can be used to limit the rate at which a user or host submits
31724 messages. Details are given in section &<<SECTratelimiting>>&.
31726 .vitem &*recipients&~=&~*&<&'address&~list'&>
31727 .cindex "&%recipients%& ACL condition"
31728 .cindex "recipient" "ACL checking"
31729 .cindex "&ACL;" "testing a recipient"
31730 This condition is relevant only after a RCPT command. It checks the entire
31731 recipient address against a list of recipients.
31733 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
31734 .cindex "&%regex%& ACL condition"
31735 .cindex "&ACL;" "testing by regex matching"
31736 This condition is available only when Exim is compiled with the
31737 content-scanning extension, and is available only in the DATA, MIME, and
31738 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
31739 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
31741 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
31742 .cindex "&%sender_domains%& ACL condition"
31743 .cindex "sender" "ACL checking"
31744 .cindex "&ACL;" "testing a sender domain"
31745 .vindex "&$domain$&"
31746 .vindex "&$sender_address_domain$&"
31747 This condition tests the domain of the sender of the message against the given
31748 domain list. &*Note*&: The domain of the sender address is in
31749 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
31750 of this condition. This is an exception to the general rule for testing domain
31751 lists. It is done this way so that, if this condition is used in an ACL for a
31752 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
31753 influence the sender checking.
31755 &*Warning*&: It is a bad idea to use this condition on its own as a control on
31756 relaying, because sender addresses are easily, and commonly, forged.
31758 .vitem &*senders&~=&~*&<&'address&~list'&>
31759 .cindex "&%senders%& ACL condition"
31760 .cindex "sender" "ACL checking"
31761 .cindex "&ACL;" "testing a sender"
31762 This condition tests the sender of the message against the given list. To test
31763 for a bounce message, which has an empty sender, set
31767 &*Warning*&: It is a bad idea to use this condition on its own as a control on
31768 relaying, because sender addresses are easily, and commonly, forged.
31770 .vitem &*spam&~=&~*&<&'username'&>
31771 .cindex "&%spam%& ACL condition"
31772 .cindex "&ACL;" "scanning for spam"
31773 This condition is available only when Exim is compiled with the
31774 content-scanning extension. It causes the incoming message to be scanned by
31775 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
31777 .vitem &*verify&~=&~certificate*&
31778 .cindex "&%verify%& ACL condition"
31779 .cindex "TLS" "client certificate verification"
31780 .cindex "certificate" "verification of client"
31781 .cindex "&ACL;" "certificate verification"
31782 .cindex "&ACL;" "testing a TLS certificate"
31783 This condition is true in an SMTP session if the session is encrypted, and a
31784 certificate was received from the client, and the certificate was verified. The
31785 server requests a certificate only if the client matches &%tls_verify_hosts%&
31786 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
31788 .vitem &*verify&~=&~csa*&
31789 .cindex "CSA verification"
31790 This condition checks whether the sending host (the client) is authorized to
31791 send email. Details of how this works are given in section
31792 &<<SECTverifyCSA>>&.
31794 .vitem &*verify&~=&~header_names_ascii*&
31795 .cindex "&%verify%& ACL condition"
31796 .cindex "&ACL;" "verifying header names only ASCII"
31797 .cindex "header lines" "verifying header names only ASCII"
31798 .cindex "verifying" "header names only ASCII"
31799 This condition is relevant only in an ACL that is run after a message has been
31801 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
31802 It checks all header names (not the content) to make sure
31803 there are no non-ASCII characters, also excluding control characters. The
31804 allowable characters are decimal ASCII values 33 through 126.
31806 Exim itself will handle headers with non-ASCII characters, but it can cause
31807 problems for downstream applications, so this option will allow their
31808 detection and rejection in the DATA ACL's.
31810 .vitem &*verify&~=&~header_sender/*&<&'options'&>
31811 .cindex "&%verify%& ACL condition"
31812 .cindex "&ACL;" "verifying sender in the header"
31813 .cindex "header lines" "verifying the sender in"
31814 .cindex "sender" "verifying in header"
31815 .cindex "verifying" "sender in header"
31816 This condition is relevant only in an ACL that is run after a message has been
31817 received, that is, in an ACL specified by &%acl_smtp_data%& or
31818 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
31819 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
31820 is loosely thought of as a &"sender"& address (hence the name of the test).
31821 However, an address that appears in one of these headers need not be an address
31822 that accepts bounce messages; only sender addresses in envelopes are required
31823 to accept bounces. Therefore, if you use the callout option on this check, you
31824 might want to arrange for a non-empty address in the MAIL command.
31826 Details of address verification and the options are given later, starting at
31827 section &<<SECTaddressverification>>& (callouts are described in section
31828 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
31829 condition to restrict it to bounce messages only:
31832 !verify = header_sender
31833 message = A valid sender header is required for bounces
31836 .vitem &*verify&~=&~header_syntax*&
31837 .cindex "&%verify%& ACL condition"
31838 .cindex "&ACL;" "verifying header syntax"
31839 .cindex "header lines" "verifying syntax"
31840 .cindex "verifying" "header syntax"
31841 This condition is relevant only in an ACL that is run after a message has been
31842 received, that is, in an ACL specified by &%acl_smtp_data%& or
31843 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
31844 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
31845 and &'Bcc:'&), returning true if there are no problems.
31846 Unqualified addresses (local parts without domains) are
31847 permitted only in locally generated messages and from hosts that match
31848 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
31851 Note that this condition is a syntax check only. However, a common spamming
31852 ploy used to be to send syntactically invalid headers such as
31856 and this condition can be used to reject such messages, though they are not as
31857 common as they used to be.
31859 .vitem &*verify&~=&~helo*&
31860 .cindex "&%verify%& ACL condition"
31861 .cindex "&ACL;" "verifying HELO/EHLO"
31862 .cindex "HELO" "verifying"
31863 .cindex "EHLO" "verifying"
31864 .cindex "verifying" "EHLO"
31865 .cindex "verifying" "HELO"
31866 This condition is true if a HELO or EHLO command has been received from the
31867 client host, and its contents have been verified. If there has been no previous
31868 attempt to verify the HELO/EHLO contents, it is carried out when this
31869 condition is encountered. See the description of the &%helo_verify_hosts%& and
31870 &%helo_try_verify_hosts%& options for details of how to request verification
31871 independently of this condition, and for detail of the verification.
31873 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
31874 option), this condition is always true.
31877 .vitem &*verify&~=&~not_blind/*&<&'options'&>
31878 .cindex "verifying" "not blind"
31879 .cindex "bcc recipients, verifying none"
31880 This condition checks that there are no blind (bcc) recipients in the message.
31881 Every envelope recipient must appear either in a &'To:'& header line or in a
31882 &'Cc:'& header line for this condition to be true. Local parts are checked
31883 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
31884 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
31885 used only in a DATA or non-SMTP ACL.
31887 There is one possible option, &`case_insensitive`&. If this is present then
31888 local parts are checked case-insensitively.
31890 There are, of course, many legitimate messages that make use of blind (bcc)
31891 recipients. This check should not be used on its own for blocking messages.
31894 .vitem &*verify&~=&~recipient/*&<&'options'&>
31895 .cindex "&%verify%& ACL condition"
31896 .cindex "&ACL;" "verifying recipient"
31897 .cindex "recipient" "verifying"
31898 .cindex "verifying" "recipient"
31899 .vindex "&$address_data$&"
31900 This condition is relevant only after a RCPT command. It verifies the current
31901 recipient. Details of address verification are given later, starting at section
31902 &<<SECTaddressverification>>&. After a recipient has been verified, the value
31903 of &$address_data$& is the last value that was set while routing the address.
31904 This applies even if the verification fails. When an address that is being
31905 verified is redirected to a single address, verification continues with the new
31906 address, and in that case, the subsequent value of &$address_data$& is the
31907 value for the child address.
31909 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
31910 .cindex "&%verify%& ACL condition"
31911 .cindex "&ACL;" "verifying host reverse lookup"
31912 .cindex "host" "verifying reverse lookup"
31913 This condition ensures that a verified host name has been looked up from the IP
31914 address of the client host. (This may have happened already if the host name
31915 was needed for checking a host list, or if the host matched &%host_lookup%&.)
31916 Verification ensures that the host name obtained from a reverse DNS lookup, or
31917 one of its aliases, does, when it is itself looked up in the DNS, yield the
31918 original IP address.
31920 There is one possible option, &`defer_ok`&. If this is present and a
31921 DNS operation returns a temporary error, the verify condition succeeds.
31923 If this condition is used for a locally generated message (that is, when there
31924 is no client host involved), it always succeeds.
31926 .vitem &*verify&~=&~sender/*&<&'options'&>
31927 .cindex "&%verify%& ACL condition"
31928 .cindex "&ACL;" "verifying sender"
31929 .cindex "sender" "verifying"
31930 .cindex "verifying" "sender"
31931 This condition is relevant only after a MAIL or RCPT command, or after a
31932 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
31933 the message's sender is empty (that is, this is a bounce message), the
31934 condition is true. Otherwise, the sender address is verified.
31936 .vindex "&$address_data$&"
31937 .vindex "&$sender_address_data$&"
31938 If there is data in the &$address_data$& variable at the end of routing, its
31939 value is placed in &$sender_address_data$& at the end of verification. This
31940 value can be used in subsequent conditions and modifiers in the same ACL
31941 statement. It does not persist after the end of the current statement. If you
31942 want to preserve the value for longer, you can save it in an ACL variable.
31944 Details of verification are given later, starting at section
31945 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
31946 to avoid doing it more than once per message.
31948 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
31949 .cindex "&%verify%& ACL condition"
31950 This is a variation of the previous option, in which a modified address is
31951 verified as a sender.
31953 Note that '/' is legal in local-parts; if the address may have such
31954 (eg. is generated from the received message)
31955 they must be protected from the options parsing by doubling:
31957 verify = sender=${listquote{/}{${address:$h_sender:}}}
31963 .section "Using DNS lists" "SECTmorednslists"
31964 .cindex "DNS list" "in ACL"
31965 .cindex "black list (DNS)"
31966 .cindex "&ACL;" "testing a DNS list"
31967 In its simplest form, the &%dnslists%& condition tests whether the calling host
31968 is on at least one of a number of DNS lists by looking up the inverted IP
31969 address in one or more DNS domains. (Note that DNS list domains are not mail
31970 domains, so the &`+`& syntax for named lists doesn't work - it is used for
31971 special options instead.) For example, if the calling host's IP
31972 address is 192.168.62.43, and the ACL statement is
31974 deny dnslists = blackholes.mail-abuse.org : \
31975 dialups.mail-abuse.org
31977 the following records are looked up:
31979 43.62.168.192.blackholes.mail-abuse.org
31980 43.62.168.192.dialups.mail-abuse.org
31982 As soon as Exim finds an existing DNS record, processing of the list stops.
31983 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
31984 to test that a host is on more than one list (an &"and"& conjunction), you can
31985 use two separate conditions:
31987 deny dnslists = blackholes.mail-abuse.org
31988 dnslists = dialups.mail-abuse.org
31990 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
31991 behaves as if the host does not match the list item, that is, as if the DNS
31992 record does not exist. If there are further items in the DNS list, they are
31995 This is usually the required action when &%dnslists%& is used with &%deny%&
31996 (which is the most common usage), because it prevents a DNS failure from
31997 blocking mail. However, you can change this behaviour by putting one of the
31998 following special items in the list:
32000 &`+include_unknown `& behave as if the item is on the list
32001 &`+exclude_unknown `& behave as if the item is not on the list (default)
32002 &`+defer_unknown `& give a temporary error
32004 .cindex "&`+include_unknown`&"
32005 .cindex "&`+exclude_unknown`&"
32006 .cindex "&`+defer_unknown`&"
32007 Each of these applies to any subsequent items on the list. For example:
32009 deny dnslists = +defer_unknown : foo.bar.example
32011 Testing the list of domains stops as soon as a match is found. If you want to
32012 warn for one list and block for another, you can use two different statements:
32014 deny dnslists = blackholes.mail-abuse.org
32015 warn dnslists = dialups.mail-abuse.org
32016 message = X-Warn: sending host is on dialups list
32018 .cindex caching "of dns lookup"
32020 DNS list lookups are cached by Exim for the duration of the SMTP session
32021 (but limited by the DNS return TTL value),
32022 so a lookup based on the IP address is done at most once for any incoming
32023 connection (assuming long-enough TTL).
32024 Exim does not share information between multiple incoming
32025 connections (but your local name server cache should be active).
32027 There are a number of DNS lists to choose from, some commercial, some free,
32028 or free for small deployments. An overview can be found at
32029 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32033 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32034 .cindex "DNS list" "keyed by explicit IP address"
32035 By default, the IP address that is used in a DNS list lookup is the IP address
32036 of the calling host. However, you can specify another IP address by listing it
32037 after the domain name, introduced by a slash. For example:
32039 deny dnslists = black.list.tld/192.168.1.2
32041 This feature is not very helpful with explicit IP addresses; it is intended for
32042 use with IP addresses that are looked up, for example, the IP addresses of the
32043 MX hosts or nameservers of an email sender address. For an example, see section
32044 &<<SECTmulkeyfor>>& below.
32049 .section "DNS lists keyed on domain names" "SECID202"
32050 .cindex "DNS list" "keyed by domain name"
32051 There are some lists that are keyed on domain names rather than inverted IP
32052 addresses (see, e.g., the &'domain based zones'& link at
32053 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32054 with these lists. You can change the name that is looked up in a DNS list by
32055 listing it after the domain name, introduced by a slash. For example,
32057 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32058 message = Sender's domain is listed at $dnslist_domain
32060 This particular example is useful only in ACLs that are obeyed after the
32061 RCPT or DATA commands, when a sender address is available. If (for
32062 example) the message's sender is &'user@tld.example'& the name that is looked
32063 up by this example is
32065 tld.example.dsn.rfc-ignorant.org
32067 A single &%dnslists%& condition can contain entries for both names and IP
32068 addresses. For example:
32070 deny dnslists = sbl.spamhaus.org : \
32071 dsn.rfc-ignorant.org/$sender_address_domain
32073 The first item checks the sending host's IP address; the second checks a domain
32074 name. The whole condition is true if either of the DNS lookups succeeds.
32079 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32080 .cindex "DNS list" "multiple keys for"
32081 The syntax described above for looking up explicitly-defined values (either
32082 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32083 name for the DNS list, what follows the slash can in fact be a list of items.
32084 As with all lists in Exim, the default separator is a colon. However, because
32085 this is a sublist within the list of DNS blacklist domains, it is necessary
32086 either to double the separators like this:
32088 dnslists = black.list.tld/name.1::name.2
32090 or to change the separator character, like this:
32092 dnslists = black.list.tld/<;name.1;name.2
32094 If an item in the list is an IP address, it is inverted before the DNS
32095 blacklist domain is appended. If it is not an IP address, no inversion
32096 occurs. Consider this condition:
32098 dnslists = black.list.tld/<;192.168.1.2;a.domain
32100 The DNS lookups that occur are:
32102 2.1.168.192.black.list.tld
32103 a.domain.black.list.tld
32105 Once a DNS record has been found (that matches a specific IP return
32106 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32107 are done. If there is a temporary DNS error, the rest of the sublist of domains
32108 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32109 only if no other DNS lookup in this sublist succeeds. In other words, a
32110 successful lookup for any of the items in the sublist overrides a temporary
32111 error for a previous item.
32113 The ability to supply a list of items after the slash is in some sense just a
32114 syntactic convenience. These two examples have the same effect:
32116 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32117 dnslists = black.list.tld/a.domain::b.domain
32119 However, when the data for the list is obtained from a lookup, the second form
32120 is usually much more convenient. Consider this example:
32122 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32123 ${lookup dnsdb {>|mxh=\
32124 $sender_address_domain} }} }
32125 message = The mail servers for the domain \
32126 $sender_address_domain \
32127 are listed at $dnslist_domain ($dnslist_value); \
32130 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32131 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32132 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32133 of expanding the condition might be something like this:
32135 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32137 Thus, this example checks whether or not the IP addresses of the sender
32138 domain's mail servers are on the Spamhaus black list.
32140 The key that was used for a successful DNS list lookup is put into the variable
32141 &$dnslist_matched$& (see section &<<SECID204>>&).
32146 .section "Data returned by DNS lists" "SECID203"
32147 .cindex "DNS list" "data returned from"
32148 DNS lists are constructed using address records in the DNS. The original RBL
32149 just used the address 127.0.0.1 on the right hand side of each record, but the
32150 RBL+ list and some other lists use a number of values with different meanings.
32151 The values used on the RBL+ list are:
32155 127.1.0.3 DUL and RBL
32157 127.1.0.5 RSS and RBL
32158 127.1.0.6 RSS and DUL
32159 127.1.0.7 RSS and DUL and RBL
32161 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32162 different values. Some DNS lists may return more than one address record;
32163 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32166 .section "Variables set from DNS lists" "SECID204"
32167 .cindex "expansion" "variables, set from DNS list"
32168 .cindex "DNS list" "variables set from"
32169 .vindex "&$dnslist_domain$&"
32170 .vindex "&$dnslist_matched$&"
32171 .vindex "&$dnslist_text$&"
32172 .vindex "&$dnslist_value$&"
32173 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32174 the name of the overall domain that matched (for example,
32175 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32176 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32177 the DNS record. When the key is an IP address, it is not reversed in
32178 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32179 cases, for example:
32181 deny dnslists = spamhaus.example
32183 the key is also available in another variable (in this case,
32184 &$sender_host_address$&). In more complicated cases, however, this is not true.
32185 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32186 might generate a dnslists lookup like this:
32188 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32190 If this condition succeeds, the value in &$dnslist_matched$& might be
32191 &`192.168.6.7`& (for example).
32193 If more than one address record is returned by the DNS lookup, all the IP
32194 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32195 The variable &$dnslist_text$& contains the contents of any associated TXT
32196 record. For lists such as RBL+ the TXT record for a merged entry is often not
32197 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32200 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32201 &-- even if these appear before the condition in the ACL, they are not
32202 expanded until after it has failed. For example:
32204 deny hosts = !+local_networks
32205 message = $sender_host_address is listed \
32207 dnslists = rbl-plus.mail-abuse.example
32212 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32213 .cindex "DNS list" "matching specific returned data"
32214 You can add an equals sign and an IP address after a &%dnslists%& domain name
32215 in order to restrict its action to DNS records with a matching right hand side.
32218 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32220 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32221 any address record is considered to be a match. For the moment, we assume
32222 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32223 describes how multiple records are handled.
32225 More than one IP address may be given for checking, using a comma as a
32226 separator. These are alternatives &-- if any one of them matches, the
32227 &%dnslists%& condition is true. For example:
32229 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32231 If you want to specify a constraining address list and also specify names or IP
32232 addresses to be looked up, the constraining address list must be specified
32233 first. For example:
32235 deny dnslists = dsn.rfc-ignorant.org\
32236 =127.0.0.2/$sender_address_domain
32239 If the character &`&&`& is used instead of &`=`&, the comparison for each
32240 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32241 In other words, the listed addresses are used as bit masks. The comparison is
32242 true if all the bits in the mask are present in the address that is being
32243 tested. For example:
32245 dnslists = a.b.c&0.0.0.3
32247 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32248 want to test whether one bit or another bit is present (as opposed to both
32249 being present), you must use multiple values. For example:
32251 dnslists = a.b.c&0.0.0.1,0.0.0.2
32253 matches if the final component of the address is an odd number or two times
32258 .section "Negated DNS matching conditions" "SECID205"
32259 You can supply a negative list of IP addresses as part of a &%dnslists%&
32262 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32264 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32265 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32267 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32269 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32270 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32271 words, the result of the test is inverted if an exclamation mark appears before
32272 the &`=`& (or the &`&&`&) sign.
32274 &*Note*&: This kind of negation is not the same as negation in a domain,
32275 host, or address list (which is why the syntax is different).
32277 If you are using just one list, the negation syntax does not gain you much. The
32278 previous example is precisely equivalent to
32280 deny dnslists = a.b.c
32281 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32283 However, if you are using multiple lists, the negation syntax is clearer.
32284 Consider this example:
32286 deny dnslists = sbl.spamhaus.org : \
32288 dnsbl.njabl.org!=127.0.0.3 : \
32291 Using only positive lists, this would have to be:
32293 deny dnslists = sbl.spamhaus.org : \
32295 deny dnslists = dnsbl.njabl.org
32296 !dnslists = dnsbl.njabl.org=127.0.0.3
32297 deny dnslists = relays.ordb.org
32299 which is less clear, and harder to maintain.
32304 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32305 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32306 thereby providing more than one IP address. When an item in a &%dnslists%& list
32307 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32308 the match to specific results from the DNS lookup, there are two ways in which
32309 the checking can be handled. For example, consider the condition:
32311 dnslists = a.b.c=127.0.0.1
32313 What happens if the DNS lookup for the incoming IP address yields both
32314 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32315 condition true because at least one given value was found, or is it false
32316 because at least one of the found values was not listed? And how does this
32317 affect negated conditions? Both possibilities are provided for with the help of
32318 additional separators &`==`& and &`=&&`&.
32321 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32322 IP addresses matches one of the listed addresses. For the example above, the
32323 condition is true because 127.0.0.1 matches.
32325 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32326 looked up IP addresses matches one of the listed addresses. If the condition is
32329 dnslists = a.b.c==127.0.0.1
32331 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32332 false because 127.0.0.2 is not listed. You would need to have:
32334 dnslists = a.b.c==127.0.0.1,127.0.0.2
32336 for the condition to be true.
32339 When &`!`& is used to negate IP address matching, it inverts the result, giving
32340 the precise opposite of the behaviour above. Thus:
32342 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32343 addresses matches one of the listed addresses. Consider:
32345 dnslists = a.b.c!&0.0.0.1
32347 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32348 false because 127.0.0.1 matches.
32350 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32351 looked up IP address that does not match. Consider:
32353 dnslists = a.b.c!=&0.0.0.1
32355 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32356 true, because 127.0.0.2 does not match. You would need to have:
32358 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32360 for the condition to be false.
32362 When the DNS lookup yields only a single IP address, there is no difference
32363 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32368 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32369 .cindex "DNS list" "information from merged"
32370 When the facility for restricting the matching IP values in a DNS list is used,
32371 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32372 the true reason for rejection. This happens when lists are merged and the IP
32373 address in the A record is used to distinguish them; unfortunately there is
32374 only one TXT record. One way round this is not to use merged lists, but that
32375 can be inefficient because it requires multiple DNS lookups where one would do
32376 in the vast majority of cases when the host of interest is not on any of the
32379 A less inefficient way of solving this problem is available. If
32380 two domain names, comma-separated, are given, the second is used first to
32381 do an initial check, making use of any IP value restrictions that are set.
32382 If there is a match, the first domain is used, without any IP value
32383 restrictions, to get the TXT record. As a byproduct of this, there is also
32384 a check that the IP being tested is indeed on the first list. The first
32385 domain is the one that is put in &$dnslist_domain$&. For example:
32388 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32389 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32391 rejected because $sender_host_address is blacklisted \
32392 at $dnslist_domain\n$dnslist_text
32394 For the first blacklist item, this starts by doing a lookup in
32395 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32396 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32397 value, and as long as something is found, it looks for the corresponding TXT
32398 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32399 The second blacklist item is processed similarly.
32401 If you are interested in more than one merged list, the same list must be
32402 given several times, but because the results of the DNS lookups are cached,
32403 the DNS calls themselves are not repeated. For example:
32406 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32407 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32408 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32409 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32411 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32412 values matches (or if no record is found), this is the only lookup that is
32413 done. Only if there is a match is one of the more specific lists consulted.
32417 .section "DNS lists and IPv6" "SECTmorednslistslast"
32418 .cindex "IPv6" "DNS black lists"
32419 .cindex "DNS list" "IPv6 usage"
32420 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32421 nibble by nibble. For example, if the calling host's IP address is
32422 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
32424 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
32425 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
32427 (split over two lines here to fit on the page). Unfortunately, some of the DNS
32428 lists contain wildcard records, intended for IPv4, that interact badly with
32429 IPv6. For example, the DNS entry
32431 *.3.some.list.example. A 127.0.0.1
32433 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
32434 Unfortunately, it also matches the entire 3::/4 IPv6 network.
32436 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
32437 &%condition%& condition, as in this example:
32439 deny condition = ${if isip4{$sender_host_address}}
32440 dnslists = some.list.example
32443 If an explicit key is being used for a DNS lookup and it may be an IPv6
32444 address you should specify alternate list separators for both the outer
32445 (DNS list name) list and inner (lookup keys) list:
32447 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
32450 .section "Rate limiting incoming messages" "SECTratelimiting"
32451 .cindex "rate limiting" "client sending"
32452 .cindex "limiting client sending rates"
32453 .oindex "&%smtp_ratelimit_*%&"
32454 The &%ratelimit%& ACL condition can be used to measure and control the rate at
32455 which clients can send email. This is more powerful than the
32456 &%smtp_ratelimit_*%& options, because those options control the rate of
32457 commands in a single SMTP session only, whereas the &%ratelimit%& condition
32458 works across all connections (concurrent and sequential) from the same client
32459 host. The syntax of the &%ratelimit%& condition is:
32461 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
32463 If the average client sending rate is less than &'m'& messages per time
32464 period &'p'& then the condition is false; otherwise it is true.
32466 As a side-effect, the &%ratelimit%& condition sets the expansion variable
32467 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
32468 configured value of &'m'&, and &$sender_rate_period$& to the configured value
32471 The parameter &'p'& is the smoothing time constant, in the form of an Exim
32472 time interval, for example, &`8h`& for eight hours. A larger time constant
32473 means that it takes Exim longer to forget a client's past behaviour. The
32474 parameter &'m'& is the maximum number of messages that a client is permitted to
32475 send in each time interval. It also specifies the number of messages permitted
32476 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
32477 constant, you can allow a client to send more messages in a burst without
32478 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
32479 both small, messages must be sent at an even rate.
32481 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
32482 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
32483 when deploying the &%ratelimit%& ACL condition. The script prints usage
32484 instructions when it is run with no arguments.
32486 The key is used to look up the data for calculating the client's average
32487 sending rate. This data is stored in Exim's spool directory, alongside the
32488 retry and other hints databases. The default key is &$sender_host_address$&,
32489 which means Exim computes the sending rate of each client host IP address.
32490 By changing the key you can change how Exim identifies clients for the purpose
32491 of ratelimiting. For example, to limit the sending rate of each authenticated
32492 user, independent of the computer they are sending from, set the key to
32493 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
32494 example, &$authenticated_id$& is only meaningful if the client has
32495 authenticated (which you can check with the &%authenticated%& ACL condition).
32497 The lookup key does not have to identify clients: If you want to limit the
32498 rate at which a recipient receives messages, you can use the key
32499 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
32502 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
32503 specifies what Exim measures the rate of, for example, messages or recipients
32504 or bytes. You can adjust the measurement using the &%unique=%& and/or
32505 &%count=%& options. You can also control when Exim updates the recorded rate
32506 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
32507 separated by a slash, like the other parameters. They may appear in any order.
32509 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
32510 any options that alter the meaning of the stored data. The limit &'m'& is not
32511 stored, so you can alter the configured maximum rate and Exim will still
32512 remember clients' past behaviour. If you change the &%per_*%& mode or add or
32513 remove the &%unique=%& option, the lookup key changes so Exim will forget past
32514 behaviour. The lookup key is not affected by changes to the update mode and
32515 the &%count=%& option.
32518 .section "Ratelimit options for what is being measured" "ratoptmea"
32519 .cindex "rate limiting" "per_* options"
32520 The &%per_conn%& option limits the client's connection rate. It is not
32521 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
32522 &%acl_not_smtp_start%& ACLs.
32524 The &%per_mail%& option limits the client's rate of sending messages. This is
32525 the default if none of the &%per_*%& options is specified. It can be used in
32526 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
32527 &%acl_smtp_data%&, or &%acl_not_smtp%&.
32529 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
32530 the same ACLs as the &%per_mail%& option, though it is best to use this option
32531 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
32532 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
32533 in its MAIL command, which may be inaccurate or completely missing. You can
32534 follow the limit &'m'& in the configuration with K, M, or G to specify limits
32535 in kilobytes, megabytes, or gigabytes, respectively.
32537 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
32538 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
32539 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
32540 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
32541 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
32542 in either case the rate limiting engine will see a message with many
32543 recipients as a large high-speed burst.
32545 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
32546 number of different recipients that the client has sent messages to in the
32547 last time period. That is, if the client repeatedly sends messages to the same
32548 recipient, its measured rate is not increased. This option can only be used in
32551 The &%per_cmd%& option causes Exim to recompute the rate every time the
32552 condition is processed. This can be used to limit the rate of any SMTP
32553 command. If it is used in multiple ACLs it can limit the aggregate rate of
32554 multiple different commands.
32556 The &%count=%& option can be used to alter how much Exim adds to the client's
32557 measured rate. For example, the &%per_byte%& option is equivalent to
32558 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
32559 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
32560 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
32562 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
32565 .section "Ratelimit update modes" "ratoptupd"
32566 .cindex "rate limiting" "reading data without updating"
32567 You can specify one of three options with the &%ratelimit%& condition to
32568 control when its database is updated. This section describes the &%readonly%&
32569 mode, and the next section describes the &%strict%& and &%leaky%& modes.
32571 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
32572 previously-computed rate to check against the limit.
32574 For example, you can test the client's sending rate and deny it access (when
32575 it is too fast) in the connect ACL. If the client passes this check then it
32576 can go on to send a message, in which case its recorded rate will be updated
32577 in the MAIL ACL. Subsequent connections from the same client will check this
32581 deny ratelimit = 100 / 5m / readonly
32582 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
32583 (max $sender_rate_limit)
32586 warn ratelimit = 100 / 5m / strict
32587 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
32588 (max $sender_rate_limit)
32591 If Exim encounters multiple &%ratelimit%& conditions with the same key when
32592 processing a message then it may increase the client's measured rate more than
32593 it should. For example, this will happen if you check the &%per_rcpt%& option
32594 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
32595 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
32596 multiple update problems by using the &%readonly%& option on later ratelimit
32599 The &%per_*%& options described above do not make sense in some ACLs. If you
32600 use a &%per_*%& option in an ACL where it is not normally permitted then the
32601 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
32602 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
32603 next section) so you must specify the &%readonly%& option explicitly.
32606 .section "Ratelimit options for handling fast clients" "ratoptfast"
32607 .cindex "rate limiting" "strict and leaky modes"
32608 If a client's average rate is greater than the maximum, the rate limiting
32609 engine can react in two possible ways, depending on the presence of the
32610 &%strict%& or &%leaky%& update modes. This is independent of the other
32611 counter-measures (such as rejecting the message) that may be specified by the
32614 The &%leaky%& (default) option means that the client's recorded rate is not
32615 updated if it is above the limit. The effect of this is that Exim measures the
32616 client's average rate of successfully sent email,
32617 up to the given limit.
32618 This is appropriate if the countermeasure when the condition is true
32619 consists of refusing the message, and
32620 is generally the better choice if you have clients that retry automatically.
32621 If the action when true is anything more complex then this option is
32622 likely not what is wanted.
32624 The &%strict%& option means that the client's recorded rate is always
32625 updated. The effect of this is that Exim measures the client's average rate
32626 of attempts to send email, which can be much higher than the maximum it is
32627 actually allowed. If the client is over the limit it may be subjected to
32628 counter-measures by the ACL. It must slow down and allow sufficient time to
32629 pass that its computed rate falls below the maximum before it can send email
32630 again. The time (the number of smoothing periods) it must wait and not
32631 attempt to send mail can be calculated with this formula:
32633 ln(peakrate/maxrate)
32637 .section "Limiting the rate of different events" "ratoptuniq"
32638 .cindex "rate limiting" "counting unique events"
32639 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
32640 rate of different events. For example, the &%per_addr%& option uses this
32641 mechanism to count the number of different recipients that the client has
32642 sent messages to in the last time period; it is equivalent to
32643 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
32644 measure the rate that a client uses different sender addresses with the
32645 options &`per_mail/unique=$sender_address`&.
32647 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
32648 has seen for that key. The whole set is thrown away when it is older than the
32649 rate smoothing period &'p'&, so each different event is counted at most once
32650 per period. In the &%leaky%& update mode, an event that causes the client to
32651 go over the limit is not added to the set, in the same way that the client's
32652 recorded rate is not updated in the same situation.
32654 When you combine the &%unique=%& and &%readonly%& options, the specific
32655 &%unique=%& value is ignored, and Exim just retrieves the client's stored
32658 The &%unique=%& mechanism needs more space in the ratelimit database than the
32659 other &%ratelimit%& options in order to store the event set. The number of
32660 unique values is potentially as large as the rate limit, so the extra space
32661 required increases with larger limits.
32663 The uniqueification is not perfect: there is a small probability that Exim
32664 will think a new event has happened before. If the sender's rate is less than
32665 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
32666 the measured rate can go above the limit, in which case Exim may under-count
32667 events by a significant margin. Fortunately, if the rate is high enough (2.7
32668 times the limit) that the false positive rate goes above 9%, then Exim will
32669 throw away the over-full event set before the measured rate falls below the
32670 limit. Therefore the only harm should be that exceptionally high sending rates
32671 are logged incorrectly; any countermeasures you configure will be as effective
32675 .section "Using rate limiting" "useratlim"
32676 Exim's other ACL facilities are used to define what counter-measures are taken
32677 when the rate limit is exceeded. This might be anything from logging a warning
32678 (for example, while measuring existing sending rates in order to define
32679 policy), through time delays to slow down fast senders, up to rejecting the
32680 message. For example:
32682 # Log all senders' rates
32683 warn ratelimit = 0 / 1h / strict
32684 log_message = Sender rate $sender_rate / $sender_rate_period
32686 # Slow down fast senders; note the need to truncate $sender_rate
32687 # at the decimal point.
32688 warn ratelimit = 100 / 1h / per_rcpt / strict
32689 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
32690 $sender_rate_limit }s
32692 # Keep authenticated users under control
32693 deny authenticated = *
32694 ratelimit = 100 / 1d / strict / $authenticated_id
32696 # System-wide rate limit
32697 defer ratelimit = 10 / 1s / $primary_hostname
32698 message = Sorry, too busy. Try again later.
32700 # Restrict incoming rate from each host, with a default
32701 # set using a macro and special cases looked up in a table.
32702 defer ratelimit = ${lookup {$sender_host_address} \
32703 cdb {DB/ratelimits.cdb} \
32704 {$value} {RATELIMIT} }
32705 message = Sender rate exceeds $sender_rate_limit \
32706 messages per $sender_rate_period
32708 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
32709 especially with the &%per_rcpt%& option, you may suffer from a performance
32710 bottleneck caused by locking on the ratelimit hints database. Apart from
32711 making your ACLs less complicated, you can reduce the problem by using a
32712 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
32713 this means that Exim will lose its hints data after a reboot (including retry
32714 hints, the callout cache, and ratelimit data).
32718 .section "Address verification" "SECTaddressverification"
32719 .cindex "verifying address" "options for"
32720 .cindex "policy control" "address verification"
32721 Several of the &%verify%& conditions described in section
32722 &<<SECTaclconditions>>& cause addresses to be verified. Section
32723 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
32724 The verification conditions can be followed by options that modify the
32725 verification process. The options are separated from the keyword and from each
32726 other by slashes, and some of them contain parameters. For example:
32728 verify = sender/callout
32729 verify = recipient/defer_ok/callout=10s,defer_ok
32731 The first stage of address verification, which always happens, is to run the
32732 address through the routers, in &"verify mode"&. Routers can detect the
32733 difference between verification and routing for delivery, and their actions can
32734 be varied by a number of generic options such as &%verify%& and &%verify_only%&
32735 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
32736 The available options are as follows:
32739 If the &%callout%& option is specified, successful routing to one or more
32740 remote hosts is followed by a &"callout"& to those hosts as an additional
32741 check. Callouts and their sub-options are discussed in the next section.
32743 If there is a defer error while doing verification routing, the ACL
32744 normally returns &"defer"&. However, if you include &%defer_ok%& in the
32745 options, the condition is forced to be true instead. Note that this is a main
32746 verification option as well as a suboption for callouts.
32748 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
32749 discusses the reporting of sender address verification failures.
32751 The &%success_on_redirect%& option causes verification always to succeed
32752 immediately after a successful redirection. By default, if a redirection
32753 generates just one address, that address is also verified. See further
32754 discussion in section &<<SECTredirwhilveri>>&.
32757 If the &%quota%& option is specified for recipient verify,
32758 successful routing to an appendfile transport is followed by a call into
32759 the transport to evaluate the quota status for the recipient.
32760 No actual delivery is done, but verification will succeed if the quota
32761 is sufficient for the message (if the sender gave a message size) or
32762 not already exceeded (otherwise).
32766 .cindex "verifying address" "differentiating failures"
32767 .vindex "&$recipient_verify_failure$&"
32768 .vindex "&$sender_verify_failure$&"
32769 .vindex "&$acl_verify_message$&"
32770 After an address verification failure, &$acl_verify_message$& contains the
32771 error message that is associated with the failure. It can be preserved by
32774 warn !verify = sender
32775 set acl_m0 = $acl_verify_message
32777 If you are writing your own custom rejection message or log message when
32778 denying access, you can use this variable to include information about the
32779 verification failure.
32781 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
32782 appropriate) contains one of the following words:
32785 &%qualify%&: The address was unqualified (no domain), and the message
32786 was neither local nor came from an exempted host.
32788 &%route%&: Routing failed.
32790 &%mail%&: Routing succeeded, and a callout was attempted; rejection
32791 occurred at or before the MAIL command (that is, on initial
32792 connection, HELO, or MAIL).
32794 &%recipient%&: The RCPT command in a callout was rejected.
32796 &%postmaster%&: The postmaster check in a callout was rejected.
32799 &%quota%&: The quota check for a local recipient did non pass.
32802 The main use of these variables is expected to be to distinguish between
32803 rejections of MAIL and rejections of RCPT in callouts.
32805 The above variables may also be set after a &*successful*&
32806 address verification to:
32809 &%random%&: A random local-part callout succeeded
32815 .section "Callout verification" "SECTcallver"
32816 .cindex "verifying address" "by callout"
32817 .cindex "callout" "verification"
32818 .cindex "SMTP" "callout verification"
32819 For non-local addresses, routing verifies the domain, but is unable to do any
32820 checking of the local part. There are situations where some means of verifying
32821 the local part is desirable. One way this can be done is to make an SMTP
32822 &'callback'& to a delivery host for the sender address or a &'callforward'& to
32823 a subsequent host for a recipient address, to see if the host accepts the
32824 address. We use the term &'callout'& to cover both cases. Note that for a
32825 sender address, the callback is not to the client host that is trying to
32826 deliver the message, but to one of the hosts that accepts incoming mail for the
32829 Exim does not do callouts by default. If you want them to happen, you must
32830 request them by setting appropriate options on the &%verify%& condition, as
32831 described below. This facility should be used with care, because it can add a
32832 lot of resource usage to the cost of verifying an address. However, Exim does
32833 cache the results of callouts, which helps to reduce the cost. Details of
32834 caching are in section &<<SECTcallvercache>>&.
32836 Recipient callouts are usually used only between hosts that are controlled by
32837 the same administration. For example, a corporate gateway host could use
32838 callouts to check for valid recipients on an internal mailserver. A successful
32839 callout does not guarantee that a real delivery to the address would succeed;
32840 on the other hand, a failing callout does guarantee that a delivery would fail.
32842 If the &%callout%& option is present on a condition that verifies an address, a
32843 second stage of verification occurs if the address is successfully routed to
32844 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
32845 &(manualroute)& router, where the router specifies the hosts. However, if a
32846 router that does not set up hosts routes to an &(smtp)& transport with a
32847 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
32848 &%hosts_override%& set, its hosts are always used, whether or not the router
32849 supplies a host list.
32850 Callouts are only supported on &(smtp)& transports.
32852 The port that is used is taken from the transport, if it is specified and is a
32853 remote transport. (For routers that do verification only, no transport need be
32854 specified.) Otherwise, the default SMTP port is used. If a remote transport
32855 specifies an outgoing interface, this is used; otherwise the interface is not
32856 specified. Likewise, the text that is used for the HELO command is taken from
32857 the transport's &%helo_data%& option; if there is no transport, the value of
32858 &$smtp_active_hostname$& is used.
32860 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
32861 test whether a bounce message could be delivered to the sender address. The
32862 following SMTP commands are sent:
32864 &`HELO `&<&'local host name'&>
32866 &`RCPT TO:`&<&'the address to be tested'&>
32869 LHLO is used instead of HELO if the transport's &%protocol%& option is
32872 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
32875 A recipient callout check is similar. By default, it also uses an empty address
32876 for the sender. This default is chosen because most hosts do not make use of
32877 the sender address when verifying a recipient. Using the same address means
32878 that a single cache entry can be used for each recipient. Some sites, however,
32879 do make use of the sender address when verifying. These are catered for by the
32880 &%use_sender%& and &%use_postmaster%& options, described in the next section.
32882 If the response to the RCPT command is a 2&'xx'& code, the verification
32883 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
32884 Exim tries the next host, if any. If there is a problem with all the remote
32885 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
32886 &%callout%& option is given, in which case the condition is forced to succeed.
32888 .cindex "SMTP" "output flushing, disabling for callout"
32889 A callout may take a little time. For this reason, Exim normally flushes SMTP
32890 output before performing a callout in an ACL, to avoid unexpected timeouts in
32891 clients when the SMTP PIPELINING extension is in use. The flushing can be
32892 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
32897 .section "Additional parameters for callouts" "CALLaddparcall"
32898 .cindex "callout" "additional parameters for"
32899 The &%callout%& option can be followed by an equals sign and a number of
32900 optional parameters, separated by commas. For example:
32902 verify = recipient/callout=10s,defer_ok
32904 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
32905 separate verify options, is retained for backwards compatibility, but is now
32906 deprecated. The additional parameters for &%callout%& are as follows:
32910 .vitem <&'a&~time&~interval'&>
32911 .cindex "callout" "timeout, specifying"
32912 This specifies the timeout that applies for the callout attempt to each host.
32915 verify = sender/callout=5s
32917 The default is 30 seconds. The timeout is used for each response from the
32918 remote host. It is also used for the initial connection, unless overridden by
32919 the &%connect%& parameter.
32922 .vitem &*connect&~=&~*&<&'time&~interval'&>
32923 .cindex "callout" "connection timeout, specifying"
32924 This parameter makes it possible to set a different (usually smaller) timeout
32925 for making the SMTP connection. For example:
32927 verify = sender/callout=5s,connect=1s
32929 If not specified, this timeout defaults to the general timeout value.
32931 .vitem &*defer_ok*&
32932 .cindex "callout" "defer, action on"
32933 When this parameter is present, failure to contact any host, or any other kind
32934 of temporary error, is treated as success by the ACL. However, the cache is not
32935 updated in this circumstance.
32937 .vitem &*fullpostmaster*&
32938 .cindex "callout" "full postmaster check"
32939 This operates like the &%postmaster%& option (see below), but if the check for
32940 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
32941 accordance with the specification in RFC 2821. The RFC states that the
32942 unqualified address &'postmaster'& should be accepted.
32945 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
32946 .cindex "callout" "sender when verifying header"
32947 When verifying addresses in header lines using the &%header_sender%&
32948 verification option, Exim behaves by default as if the addresses are envelope
32949 sender addresses from a message. Callout verification therefore tests to see
32950 whether a bounce message could be delivered, by using an empty address in the
32951 MAIL command. However, it is arguable that these addresses might never be used
32952 as envelope senders, and could therefore justifiably reject bounce messages
32953 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
32954 address to use in the MAIL command. For example:
32956 require verify = header_sender/callout=mailfrom=abcd@x.y.z
32958 This parameter is available only for the &%header_sender%& verification option.
32961 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
32962 .cindex "callout" "overall timeout, specifying"
32963 This parameter sets an overall timeout for performing a callout verification.
32966 verify = sender/callout=5s,maxwait=30s
32968 This timeout defaults to four times the callout timeout for individual SMTP
32969 commands. The overall timeout applies when there is more than one host that can
32970 be tried. The timeout is checked before trying the next host. This prevents
32971 very long delays if there are a large number of hosts and all are timing out
32972 (for example, when network connections are timing out).
32975 .vitem &*no_cache*&
32976 .cindex "callout" "cache, suppressing"
32977 .cindex "caching callout, suppressing"
32978 When this parameter is given, the callout cache is neither read nor updated.
32980 .vitem &*postmaster*&
32981 .cindex "callout" "postmaster; checking"
32982 When this parameter is set, a successful callout check is followed by a similar
32983 check for the local part &'postmaster'& at the same domain. If this address is
32984 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
32985 the postmaster check is recorded in a cache record; if it is a failure, this is
32986 used to fail subsequent callouts for the domain without a connection being
32987 made, until the cache record expires.
32989 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
32990 The postmaster check uses an empty sender in the MAIL command by default.
32991 You can use this parameter to do a postmaster check using a different address.
32994 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
32996 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
32997 one overrides. The &%postmaster%& parameter is equivalent to this example:
32999 require verify = sender/callout=postmaster_mailfrom=
33001 &*Warning*&: The caching arrangements for postmaster checking do not take
33002 account of the sender address. It is assumed that either the empty address or
33003 a fixed non-empty address will be used. All that Exim remembers is that the
33004 postmaster check for the domain succeeded or failed.
33008 .cindex "callout" "&""random""& check"
33009 When this parameter is set, before doing the normal callout check, Exim does a
33010 check for a &"random"& local part at the same domain. The local part is not
33011 really random &-- it is defined by the expansion of the option
33012 &%callout_random_local_part%&, which defaults to
33014 $primary_hostname-$tod_epoch-testing
33016 The idea here is to try to determine whether the remote host accepts all local
33017 parts without checking. If it does, there is no point in doing callouts for
33018 specific local parts. If the &"random"& check succeeds, the result is saved in
33019 a cache record, and used to force the current and subsequent callout checks to
33020 succeed without a connection being made, until the cache record expires.
33022 .vitem &*use_postmaster*&
33023 .cindex "callout" "sender for recipient check"
33024 This parameter applies to recipient callouts only. For example:
33026 deny !verify = recipient/callout=use_postmaster
33028 .vindex "&$qualify_domain$&"
33029 It causes a non-empty postmaster address to be used in the MAIL command when
33030 performing the callout for the recipient, and also for a &"random"& check if
33031 that is configured. The local part of the address is &`postmaster`& and the
33032 domain is the contents of &$qualify_domain$&.
33034 .vitem &*use_sender*&
33035 This option applies to recipient callouts only. For example:
33037 require verify = recipient/callout=use_sender
33039 It causes the message's actual sender address to be used in the MAIL
33040 command when performing the callout, instead of an empty address. There is no
33041 need to use this option unless you know that the called hosts make use of the
33042 sender when checking recipients. If used indiscriminately, it reduces the
33043 usefulness of callout caching.
33046 This option applies to recipient callouts only. For example:
33048 require verify = recipient/callout=use_sender,hold
33050 It causes the connection to be held open and used for any further recipients
33051 and for eventual delivery (should that be done quickly).
33052 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33053 when that is used for the connections.
33054 The advantage is only gained if there are no callout cache hits
33055 (which could be enforced by the no_cache option),
33056 if the use_sender option is used,
33057 if neither the random nor the use_postmaster option is used,
33058 and if no other callouts intervene.
33061 If you use any of the parameters that set a non-empty sender for the MAIL
33062 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33063 &%use_sender%&), you should think about possible loops. Recipient checking is
33064 usually done between two hosts that are under the same management, and the host
33065 that receives the callouts is not normally configured to do callouts itself.
33066 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33067 these circumstances.
33069 However, if you use a non-empty sender address for a callout to an arbitrary
33070 host, there is the likelihood that the remote host will itself initiate a
33071 callout check back to your host. As it is checking what appears to be a message
33072 sender, it is likely to use an empty address in MAIL, thus avoiding a
33073 callout loop. However, to be on the safe side it would be best to set up your
33074 own ACLs so that they do not do sender verification checks when the recipient
33075 is the address you use for header sender or postmaster callout checking.
33077 Another issue to think about when using non-empty senders for callouts is
33078 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33079 by the sender/recipient combination; thus, for any given recipient, many more
33080 actual callouts are performed than when an empty sender or postmaster is used.
33085 .section "Callout caching" "SECTcallvercache"
33086 .cindex "hints database" "callout cache"
33087 .cindex "callout" "cache, description of"
33088 .cindex "caching" "callout"
33089 Exim caches the results of callouts in order to reduce the amount of resources
33090 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33091 option. A hints database called &"callout"& is used for the cache. Two
33092 different record types are used: one records the result of a callout check for
33093 a specific address, and the other records information that applies to the
33094 entire domain (for example, that it accepts the local part &'postmaster'&).
33096 When an original callout fails, a detailed SMTP error message is given about
33097 the failure. However, for subsequent failures use the cache data, this message
33100 The expiry times for negative and positive address cache records are
33101 independent, and can be set by the global options &%callout_negative_expire%&
33102 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33104 If a host gives a negative response to an SMTP connection, or rejects any
33105 commands up to and including
33109 (but not including the MAIL command with a non-empty address),
33110 any callout attempt is bound to fail. Exim remembers such failures in a
33111 domain cache record, which it uses to fail callouts for the domain without
33112 making new connections, until the domain record times out. There are two
33113 separate expiry times for domain cache records:
33114 &%callout_domain_negative_expire%& (default 3h) and
33115 &%callout_domain_positive_expire%& (default 7d).
33117 Domain records expire when the negative expiry time is reached if callouts
33118 cannot be made for the domain, or if the postmaster check failed.
33119 Otherwise, they expire when the positive expiry time is reached. This
33120 ensures that, for example, a host that stops accepting &"random"& local parts
33121 will eventually be noticed.
33123 The callout caching mechanism is based on the domain of the address that is
33124 being tested. If the domain routes to several hosts, it is assumed that their
33125 behaviour will be the same.
33130 .section "Quota caching" "SECTquotacache"
33131 .cindex "hints database" "quota cache"
33132 .cindex "quota" "cache, description of"
33133 .cindex "caching" "quota"
33134 Exim caches the results of quota verification
33135 in order to reduce the amount of resources used.
33136 The &"callout"& hints database is used.
33138 The default cache periods are five minutes for a positive (good) result
33139 and one hour for a negative result.
33140 To change the periods the &%quota%& option can be followed by an equals sign
33141 and a number of optional paramemters, separated by commas.
33144 verify = recipient/quota=cachepos=1h,cacheneg=1d
33146 Possible parameters are:
33148 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33149 .cindex "quota cache" "positive entry expiry, specifying"
33150 Set the lifetime for a positive cache entry.
33151 A value of zero seconds is legitimate.
33153 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33154 .cindex "quota cache" "negative entry expiry, specifying"
33155 As above, for a negative entry.
33157 .vitem &*no_cache*&
33158 Set both positive and negative lifetimes to zero.
33161 .section "Sender address verification reporting" "SECTsenaddver"
33162 .cindex "verifying" "suppressing error details"
33163 See section &<<SECTaddressverification>>& for a general discussion of
33164 verification. When sender verification fails in an ACL, the details of the
33165 failure are given as additional output lines before the 550 response to the
33166 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33169 MAIL FROM:<xyz@abc.example>
33171 RCPT TO:<pqr@def.example>
33172 550-Verification failed for <xyz@abc.example>
33173 550-Called: 192.168.34.43
33174 550-Sent: RCPT TO:<xyz@abc.example>
33175 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33176 550 Sender verification failed
33178 If more than one RCPT command fails in the same way, the details are given
33179 only for the first of them. However, some administrators do not want to send
33180 out this much information. You can suppress the details by adding
33181 &`/no_details`& to the ACL statement that requests sender verification. For
33184 verify = sender/no_details
33187 .section "Redirection while verifying" "SECTredirwhilveri"
33188 .cindex "verifying" "redirection while"
33189 .cindex "address redirection" "while verifying"
33190 A dilemma arises when a local address is redirected by aliasing or forwarding
33191 during verification: should the generated addresses themselves be verified,
33192 or should the successful expansion of the original address be enough to verify
33193 it? By default, Exim takes the following pragmatic approach:
33196 When an incoming address is redirected to just one child address, verification
33197 continues with the child address, and if that fails to verify, the original
33198 verification also fails.
33200 When an incoming address is redirected to more than one child address,
33201 verification does not continue. A success result is returned.
33204 This seems the most reasonable behaviour for the common use of aliasing as a
33205 way of redirecting different local parts to the same mailbox. It means, for
33206 example, that a pair of alias entries of the form
33209 aw123: :fail: Gone away, no forwarding address
33211 work as expected, with both local parts causing verification failure. When a
33212 redirection generates more than one address, the behaviour is more like a
33213 mailing list, where the existence of the alias itself is sufficient for
33214 verification to succeed.
33216 It is possible, however, to change the default behaviour so that all successful
33217 redirections count as successful verifications, however many new addresses are
33218 generated. This is specified by the &%success_on_redirect%& verification
33219 option. For example:
33221 require verify = recipient/success_on_redirect/callout=10s
33223 In this example, verification succeeds if a router generates a new address, and
33224 the callout does not occur, because no address was routed to a remote host.
33226 When verification is being tested via the &%-bv%& option, the treatment of
33227 redirections is as just described, unless the &%-v%& or any debugging option is
33228 also specified. In that case, full verification is done for every generated
33229 address and a report is output for each of them.
33233 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33234 .cindex "CSA" "verifying"
33235 Client SMTP Authorization is a system that allows a site to advertise
33236 which machines are and are not permitted to send email. This is done by placing
33237 special SRV records in the DNS; these are looked up using the client's HELO
33238 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33239 Authorization checks in Exim are performed by the ACL condition:
33243 This fails if the client is not authorized. If there is a DNS problem, or if no
33244 valid CSA SRV record is found, or if the client is authorized, the condition
33245 succeeds. These three cases can be distinguished using the expansion variable
33246 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33247 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33248 be likely to cause problems for legitimate email.
33250 The error messages produced by the CSA code include slightly more
33251 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33252 looking up the CSA SRV record, or problems looking up the CSA target
33253 address record. There are four reasons for &$csa_status$& being &"fail"&:
33256 The client's host name is explicitly not authorized.
33258 The client's IP address does not match any of the CSA target IP addresses.
33260 The client's host name is authorized but it has no valid target IP addresses
33261 (for example, the target's addresses are IPv6 and the client is using IPv4).
33263 The client's host name has no CSA SRV record but a parent domain has asserted
33264 that all subdomains must be explicitly authorized.
33267 The &%csa%& verification condition can take an argument which is the domain to
33268 use for the DNS query. The default is:
33270 verify = csa/$sender_helo_name
33272 This implementation includes an extension to CSA. If the query domain
33273 is an address literal such as [192.0.2.95], or if it is a bare IP
33274 address, Exim searches for CSA SRV records in the reverse DNS as if
33275 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33278 verify = csa/$sender_host_address
33280 In fact, this is the check that Exim performs if the client does not say HELO.
33281 This extension can be turned off by setting the main configuration option
33282 &%dns_csa_use_reverse%& to be false.
33284 If a CSA SRV record is not found for the domain itself, a search
33285 is performed through its parent domains for a record which might be
33286 making assertions about subdomains. The maximum depth of this search is limited
33287 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33288 default. Exim does not look for CSA SRV records in a top level domain, so the
33289 default settings handle HELO domains as long as seven
33290 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33291 of legitimate HELO domains.
33293 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33294 direct SRV lookups, this is not sufficient because of the extra parent domain
33295 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33296 addresses into lookups in the reverse DNS space. The result of a successful
33299 ${lookup dnsdb {csa=$sender_helo_name}}
33301 has two space-separated fields: an authorization code and a target host name.
33302 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33303 authorization required but absent, or &"?"& for unknown.
33308 .section "Bounce address tag validation" "SECTverifyPRVS"
33309 .cindex "BATV, verifying"
33310 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33311 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33312 Genuine incoming bounce messages should therefore always be addressed to
33313 recipients that have a valid tag. This scheme is a way of detecting unwanted
33314 bounce messages caused by sender address forgeries (often called &"collateral
33315 spam"&), because the recipients of such messages do not include valid tags.
33317 There are two expansion items to help with the implementation of the BATV
33318 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33319 the original envelope sender address by using a simple key to add a hash of the
33320 address and some time-based randomizing information. The &%prvs%& expansion
33321 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33322 The syntax of these expansion items is described in section
33323 &<<SECTexpansionitems>>&.
33324 The validity period on signed addresses is seven days.
33326 As an example, suppose the secret per-address keys are stored in an MySQL
33327 database. A query to look up the key for an address could be defined as a macro
33330 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33331 WHERE sender='${quote_mysql:$prvscheck_address}'\
33334 Suppose also that the senders who make use of BATV are defined by an address
33335 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33338 # Bounces: drop unsigned addresses for BATV senders
33340 recipients = +batv_senders
33341 message = This address does not send an unsigned reverse path
33343 # Bounces: In case of prvs-signed address, check signature.
33345 condition = ${prvscheck {$local_part@$domain}\
33346 {PRVSCHECK_SQL}{1}}
33347 !condition = $prvscheck_result
33348 message = Invalid reverse path signature.
33350 The first statement rejects recipients for bounce messages that are addressed
33351 to plain BATV sender addresses, because it is known that BATV senders do not
33352 send out messages with plain sender addresses. The second statement rejects
33353 recipients that are prvs-signed, but with invalid signatures (either because
33354 the key is wrong, or the signature has timed out).
33356 A non-prvs-signed address is not rejected by the second statement, because the
33357 &%prvscheck%& expansion yields an empty string if its first argument is not a
33358 prvs-signed address, thus causing the &%condition%& condition to be false. If
33359 the first argument is a syntactically valid prvs-signed address, the yield is
33360 the third string (in this case &"1"&), whether or not the cryptographic and
33361 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33362 of the checks (empty for failure, &"1"& for success).
33364 There is one more issue you must consider when implementing prvs-signing:
33365 you have to ensure that the routers accept prvs-signed addresses and
33366 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33367 router to remove the signature with a configuration along these lines:
33371 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33373 This works because, if the third argument of &%prvscheck%& is empty, the result
33374 of the expansion of a prvs-signed address is the decoded value of the original
33375 address. This router should probably be the first of your routers that handles
33378 To create BATV-signed addresses in the first place, a transport of this form
33381 external_smtp_batv:
33383 return_path = ${prvs {$return_path} \
33384 {${lookup mysql{SELECT \
33385 secret FROM batv_prvs WHERE \
33386 sender='${quote_mysql:$sender_address}'} \
33389 If no key can be found for the existing return path, no signing takes place.
33393 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33394 .cindex "&ACL;" "relay control"
33395 .cindex "relaying" "control by ACL"
33396 .cindex "policy control" "relay control"
33397 An MTA is said to &'relay'& a message if it receives it from some host and
33398 delivers it directly to another host as a result of a remote address contained
33399 within it. Redirecting a local address via an alias or forward file and then
33400 passing the message on to another host is not relaying,
33401 .cindex "&""percent hack""&"
33402 but a redirection as a result of the &"percent hack"& is.
33404 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33405 A host which is acting as a gateway or an MX backup is concerned with incoming
33406 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33407 a host which is acting as a smart host for a number of clients is concerned
33408 with outgoing relaying from those clients to the Internet at large. Often the
33409 same host is fulfilling both functions,
33411 . as illustrated in the diagram below,
33413 but in principle these two kinds of relaying are entirely independent. What is
33414 not wanted is the transmission of mail from arbitrary remote hosts through your
33415 system to arbitrary domains.
33418 You can implement relay control by means of suitable statements in the ACL that
33419 runs for each RCPT command. For convenience, it is often easiest to use
33420 Exim's named list facility to define the domains and hosts involved. For
33421 example, suppose you want to do the following:
33424 Deliver a number of domains to mailboxes on the local host (or process them
33425 locally in some other way). Let's say these are &'my.dom1.example'& and
33426 &'my.dom2.example'&.
33428 Relay mail for a number of other domains for which you are the secondary MX.
33429 These might be &'friend1.example'& and &'friend2.example'&.
33431 Relay mail from the hosts on your local LAN, to whatever domains are involved.
33432 Suppose your LAN is 192.168.45.0/24.
33436 In the main part of the configuration, you put the following definitions:
33438 domainlist local_domains = my.dom1.example : my.dom2.example
33439 domainlist relay_to_domains = friend1.example : friend2.example
33440 hostlist relay_from_hosts = 192.168.45.0/24
33442 Now you can use these definitions in the ACL that is run for every RCPT
33446 accept domains = +local_domains : +relay_to_domains
33447 accept hosts = +relay_from_hosts
33449 The first statement accepts any RCPT command that contains an address in
33450 the local or relay domains. For any other domain, control passes to the second
33451 statement, which accepts the command only if it comes from one of the relay
33452 hosts. In practice, you will probably want to make your ACL more sophisticated
33453 than this, for example, by including sender and recipient verification. The
33454 default configuration includes a more comprehensive example, which is described
33455 in chapter &<<CHAPdefconfil>>&.
33459 .section "Checking a relay configuration" "SECTcheralcon"
33460 .cindex "relaying" "checking control of"
33461 You can check the relay characteristics of your configuration in the same way
33462 that you can test any ACL behaviour for an incoming SMTP connection, by using
33463 the &%-bh%& option to run a fake SMTP session with which you interact.
33468 . ////////////////////////////////////////////////////////////////////////////
33469 . ////////////////////////////////////////////////////////////////////////////
33471 .chapter "Content scanning at ACL time" "CHAPexiscan"
33472 .scindex IIDcosca "content scanning" "at ACL time"
33473 The extension of Exim to include content scanning at ACL time, formerly known
33474 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
33475 was integrated into the main source for Exim release 4.50, and Tom continues to
33476 maintain it. Most of the wording of this chapter is taken from Tom's
33479 It is also possible to scan the content of messages at other times. The
33480 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
33481 scanning after all the ACLs have run. A transport filter can be used to scan
33482 messages at delivery time (see the &%transport_filter%& option, described in
33483 chapter &<<CHAPtransportgeneric>>&).
33485 If you want to include the ACL-time content-scanning features when you compile
33486 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
33487 &_Local/Makefile_&. When you do that, the Exim binary is built with:
33490 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
33491 for all MIME parts for SMTP and non-SMTP messages, respectively.
33493 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
33494 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
33495 run at the end of message reception (the &%acl_smtp_data%& ACL).
33497 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
33498 of messages, or parts of messages, for debugging purposes.
33500 Additional expansion variables that are set in the new ACL and by the new
33503 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
33506 Content-scanning is continually evolving, and new features are still being
33507 added. While such features are still unstable and liable to incompatible
33508 changes, they are made available in Exim by setting options whose names begin
33509 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
33510 this manual. You can find out about them by reading the file called
33511 &_doc/experimental.txt_&.
33513 All the content-scanning facilities work on a MBOX copy of the message that is
33514 temporarily created in a file called:
33516 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
33518 The &_.eml_& extension is a friendly hint to virus scanners that they can
33519 expect an MBOX-like structure inside that file. The file is created when the
33520 first content scanning facility is called. Subsequent calls to content
33521 scanning conditions open the same file again. The directory is recursively
33522 removed when the &%acl_smtp_data%& ACL has finished running, unless
33524 control = no_mbox_unspool
33526 has been encountered. When the MIME ACL decodes files, they are put into the
33527 same directory by default.
33531 .section "Scanning for viruses" "SECTscanvirus"
33532 .cindex "virus scanning"
33533 .cindex "content scanning" "for viruses"
33534 .cindex "content scanning" "the &%malware%& condition"
33535 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
33536 It supports a &"generic"& interface to scanners called via the shell, and
33537 specialized interfaces for &"daemon"& type virus scanners, which are resident
33538 in memory and thus are much faster.
33540 Since message data needs to have arrived,
33541 the condition may be only called in ACL defined by
33543 &%acl_smtp_data_prdr%&,
33544 &%acl_smtp_mime%& or
33547 A timeout of 2 minutes is applied to a scanner call (by default);
33548 if it expires then a defer action is taken.
33550 .oindex "&%av_scanner%&"
33551 You can set the &%av_scanner%& option in the main part of the configuration
33552 to specify which scanner to use, together with any additional options that
33553 are needed. The basic syntax is as follows:
33555 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
33557 If you do not set &%av_scanner%&, it defaults to
33559 av_scanner = sophie:/var/run/sophie
33561 If the value of &%av_scanner%& starts with a dollar character, it is expanded
33563 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
33564 The following scanner types are supported in this release,
33565 though individual ones can be included or not at build time:
33569 .cindex "virus scanners" "avast"
33570 This is the scanner daemon of Avast. It has been tested with Avast Core
33571 Security (currently at version 2.2.0).
33572 You can get a trial version at &url(https://www.avast.com) or for Linux
33573 at &url(https://www.avast.com/linux-server-antivirus).
33574 This scanner type takes one option,
33575 which can be either a full path to a UNIX socket,
33576 or host and port specifiers separated by white space.
33577 The host may be a name or an IP address; the port is either a
33578 single number or a pair of numbers with a dash between.
33579 A list of options may follow. These options are interpreted on the
33580 Exim's side of the malware scanner, or are given on separate lines to
33581 the daemon as options before the main scan command.
33583 .cindex &`pass_unscanned`& "avast"
33584 If &`pass_unscanned`&
33585 is set, any files the Avast scanner can't scan (e.g.
33586 decompression bombs, or invalid archives) are considered clean. Use with
33591 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
33592 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
33593 av_scanner = avast:192.168.2.22 5036
33595 If you omit the argument, the default path
33596 &_/var/run/avast/scan.sock_&
33598 If you use a remote host,
33599 you need to make Exim's spool directory available to it,
33600 as the scanner is passed a file path, not file contents.
33601 For information about available commands and their options you may use
33603 $ socat UNIX:/var/run/avast/scan.sock STDIO:
33609 If the scanner returns a temporary failure (e.g. license issues, or
33610 permission problems), the message is deferred and a paniclog entry is
33611 written. The usual &`defer_ok`& option is available.
33613 .vitem &%aveserver%&
33614 .cindex "virus scanners" "Kaspersky"
33615 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
33616 at &url(https://www.kaspersky.com/). This scanner type takes one option,
33617 which is the path to the daemon's UNIX socket. The default is shown in this
33620 av_scanner = aveserver:/var/run/aveserver
33625 .cindex "virus scanners" "clamd"
33626 This daemon-type scanner is GPL and free. You can get it at
33627 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
33628 unpack MIME containers, so it used to be recommended to unpack MIME attachments
33629 in the MIME ACL. This is no longer believed to be necessary.
33631 The options are a list of server specifiers, which may be
33632 a UNIX socket specification,
33633 a TCP socket specification,
33634 or a (global) option.
33636 A socket specification consists of a space-separated list.
33637 For a Unix socket the first element is a full path for the socket,
33638 for a TCP socket the first element is the IP address
33639 and the second a port number,
33640 Any further elements are per-server (non-global) options.
33641 These per-server options are supported:
33643 retry=<timespec> Retry on connect fail
33646 The &`retry`& option specifies a time after which a single retry for
33647 a failed connect is made. The default is to not retry.
33649 If a Unix socket file is specified, only one server is supported.
33653 av_scanner = clamd:/opt/clamd/socket
33654 av_scanner = clamd:192.0.2.3 1234
33655 av_scanner = clamd:192.0.2.3 1234:local
33656 av_scanner = clamd:192.0.2.3 1234 retry=10s
33657 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
33659 If the value of av_scanner points to a UNIX socket file or contains the
33661 option, then the ClamAV interface will pass a filename containing the data
33662 to be scanned, which should normally result in less I/O happening and be
33663 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
33664 Exim does not assume that there is a common filesystem with the remote host.
33666 The final example shows that multiple TCP targets can be specified. Exim will
33667 randomly use one for each incoming email (i.e. it load balances them). Note
33668 that only TCP targets may be used if specifying a list of scanners; a UNIX
33669 socket cannot be mixed in with TCP targets. If one of the servers becomes
33670 unavailable, Exim will try the remaining one(s) until it finds one that works.
33671 When a clamd server becomes unreachable, Exim will log a message. Exim does
33672 not keep track of scanner state between multiple messages, and the scanner
33673 selection is random, so the message will get logged in the mainlog for each
33674 email that the down scanner gets chosen first (message wrapped to be readable):
33676 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
33677 clamd: connection to localhost, port 3310 failed
33678 (Connection refused)
33681 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
33682 contributing the code for this scanner.
33685 .cindex "virus scanners" "command line interface"
33686 This is the keyword for the generic command line scanner interface. It can be
33687 used to attach virus scanners that are invoked from the shell. This scanner
33688 type takes 3 mandatory options:
33691 The full path and name of the scanner binary, with all command line options,
33692 and a placeholder (&`%s`&) for the directory to scan.
33695 A regular expression to match against the STDOUT and STDERR output of the
33696 virus scanner. If the expression matches, a virus was found. You must make
33697 absolutely sure that this expression matches on &"virus found"&. This is called
33698 the &"trigger"& expression.
33701 Another regular expression, containing exactly one pair of parentheses, to
33702 match the name of the virus found in the scanners output. This is called the
33703 &"name"& expression.
33706 For example, Sophos Sweep reports a virus on a line like this:
33708 Virus 'W32/Magistr-B' found in file ./those.bat
33710 For the trigger expression, we can match the phrase &"found in file"&. For the
33711 name expression, we want to extract the W32/Magistr-B string, so we can match
33712 for the single quotes left and right of it. Altogether, this makes the
33713 configuration setting:
33715 av_scanner = cmdline:\
33716 /path/to/sweep -ss -all -rec -archive %s:\
33717 found in file:'(.+)'
33720 .cindex "virus scanners" "DrWeb"
33721 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
33723 either a full path to a UNIX socket,
33724 or host and port specifiers separated by white space.
33725 The host may be a name or an IP address; the port is either a
33726 single number or a pair of numbers with a dash between.
33729 av_scanner = drweb:/var/run/drwebd.sock
33730 av_scanner = drweb:192.168.2.20 31337
33732 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
33733 is used. Thanks to Alex Miller for contributing the code for this scanner.
33736 .cindex "virus scanners" "f-protd"
33737 The f-protd scanner is accessed via HTTP over TCP.
33738 One argument is taken, being a space-separated hostname and port number
33742 av_scanner = f-protd:localhost 10200-10204
33744 If you omit the argument, the default values shown above are used.
33746 .vitem &%f-prot6d%&
33747 .cindex "virus scanners" "f-prot6d"
33748 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
33749 One argument is taken, being a space-separated hostname and port number.
33752 av_scanner = f-prot6d:localhost 10200
33754 If you omit the argument, the default values show above are used.
33757 .cindex "virus scanners" "F-Secure"
33758 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
33759 argument which is the path to a UNIX socket. For example:
33761 av_scanner = fsecure:/path/to/.fsav
33763 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
33764 Thelmen for contributing the code for this scanner.
33766 .vitem &%kavdaemon%&
33767 .cindex "virus scanners" "Kaspersky"
33768 This is the scanner daemon of Kaspersky Version 4. This version of the
33769 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
33770 scanner type takes one option, which is the path to the daemon's UNIX socket.
33773 av_scanner = kavdaemon:/opt/AVP/AvpCtl
33775 The default path is &_/var/run/AvpCtl_&.
33778 .cindex "virus scanners" "mksd"
33779 This was a daemon type scanner that is aimed mainly at Polish users,
33780 though some documentation was available in English.
33781 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
33782 and this appears to be a candidate for removal from Exim, unless
33783 we are informed of other virus scanners which use the same protocol
33785 The only option for this scanner type is
33786 the maximum number of processes used simultaneously to scan the attachments,
33787 provided that mksd has
33788 been run with at least the same number of child processes. For example:
33790 av_scanner = mksd:2
33792 You can safely omit this option (the default value is 1).
33795 .cindex "virus scanners" "simple socket-connected"
33796 This is a general-purpose way of talking to simple scanner daemons
33797 running on the local machine.
33798 There are four options:
33799 an address (which may be an IP address and port, or the path of a Unix socket),
33800 a commandline to send (may include a single %s which will be replaced with
33801 the path to the mail file to be scanned),
33802 an RE to trigger on from the returned data,
33803 and an RE to extract malware_name from the returned data.
33806 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
33808 Note that surrounding whitespace is stripped from each option, meaning
33809 there is no way to specify a trailing newline.
33810 The socket specifier and both regular-expressions are required.
33811 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
33812 specify an empty element to get this.
33815 .cindex "virus scanners" "Sophos and Sophie"
33816 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
33817 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
33818 for this scanner type is the path to the UNIX socket that Sophie uses for
33819 client communication. For example:
33821 av_scanner = sophie:/tmp/sophie
33823 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
33827 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
33828 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
33831 The &%av_scanner%& option is expanded each time &%malware%& is called. This
33832 makes it possible to use different scanners. See further below for an example.
33833 The &%malware%& condition caches its results, so when you use it multiple times
33834 for the same message, the actual scanning process is only carried out once.
33835 However, using expandable items in &%av_scanner%& disables this caching, in
33836 which case each use of the &%malware%& condition causes a new scan of the
33839 The &%malware%& condition takes a right-hand argument that is expanded before
33840 use and taken as a list, slash-separated by default.
33841 The first element can then be one of
33844 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
33845 The condition succeeds if a virus was found, and fail otherwise. This is the
33848 &"false"& or &"0"& or an empty string, in which case no scanning is done and
33849 the condition fails immediately.
33851 A regular expression, in which case the message is scanned for viruses. The
33852 condition succeeds if a virus is found and its name matches the regular
33853 expression. This allows you to take special actions on certain types of virus.
33854 Note that &"/"& characters in the RE must be doubled due to the list-processing,
33855 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
33858 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
33859 messages even if there is a problem with the virus scanner.
33860 Otherwise, such a problem causes the ACL to defer.
33862 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
33863 specify a non-default timeout. The default is two minutes.
33866 malware = * / defer_ok / tmo=10s
33868 A timeout causes the ACL to defer.
33870 .vindex "&$callout_address$&"
33871 When a connection is made to the scanner the expansion variable &$callout_address$&
33872 is set to record the actual address used.
33874 .vindex "&$malware_name$&"
33875 When a virus is found, the condition sets up an expansion variable called
33876 &$malware_name$& that contains the name of the virus. You can use it in a
33877 &%message%& modifier that specifies the error returned to the sender, and/or in
33880 Beware the interaction of Exim's &%message_size_limit%& with any size limits
33881 imposed by your anti-virus scanner.
33883 Here is a very simple scanning example:
33886 message = This message contains malware ($malware_name)
33888 The next example accepts messages when there is a problem with the scanner:
33890 deny malware = */defer_ok
33891 message = This message contains malware ($malware_name)
33893 The next example shows how to use an ACL variable to scan with both sophie and
33894 aveserver. It assumes you have set:
33896 av_scanner = $acl_m0
33898 in the main Exim configuration.
33900 deny set acl_m0 = sophie
33902 message = This message contains malware ($malware_name)
33904 deny set acl_m0 = aveserver
33906 message = This message contains malware ($malware_name)
33910 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
33911 .cindex "content scanning" "for spam"
33912 .cindex "spam scanning"
33913 .cindex "SpamAssassin"
33915 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
33916 score and a report for the message.
33917 Support is also provided for Rspamd.
33919 For more information about installation and configuration of SpamAssassin or
33920 Rspamd refer to their respective websites at
33921 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
33923 SpamAssassin can be installed with CPAN by running:
33925 perl -MCPAN -e 'install Mail::SpamAssassin'
33927 SpamAssassin has its own set of configuration files. Please review its
33928 documentation to see how you can tweak it. The default installation should work
33931 .oindex "&%spamd_address%&"
33932 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
33933 intend to use an instance running on the local host you do not need to set
33934 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
33935 you must set the &%spamd_address%& option in the global part of the Exim
33936 configuration as follows (example):
33938 spamd_address = 192.168.99.45 783
33940 The SpamAssassin protocol relies on a TCP half-close from the client.
33941 If your SpamAssassin client side is running a Linux system with an
33942 iptables firewall, consider setting
33943 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
33944 timeout, Exim uses when waiting for a response from the SpamAssassin
33945 server (currently defaulting to 120s). With a lower value the Linux
33946 connection tracking may consider your half-closed connection as dead too
33950 To use Rspamd (which by default listens on all local addresses
33952 you should add &%variant=rspamd%& after the address/port pair, for example:
33954 spamd_address = 127.0.0.1 11333 variant=rspamd
33957 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
33958 sockets. If you want to us these, supply &%spamd_address%& with an absolute
33959 filename instead of an address/port pair:
33961 spamd_address = /var/run/spamd_socket
33963 You can have multiple &%spamd%& servers to improve scalability. These can
33964 reside on other hardware reachable over the network. To specify multiple
33965 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
33966 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
33968 spamd_address = 192.168.2.10 783 : \
33969 192.168.2.11 783 : \
33972 Up to 32 &%spamd%& servers are supported.
33973 When a server fails to respond to the connection attempt, all other
33974 servers are tried until one succeeds. If no server responds, the &%spam%&
33977 Unix and TCP socket specifications may be mixed in any order.
33978 Each element of the list is a list itself, space-separated by default
33979 and changeable in the usual way (&<<SECTlistsepchange>>&);
33980 take care to not double the separator.
33982 For TCP socket specifications a host name or IP (v4 or v6, but
33983 subject to list-separator quoting rules) address can be used,
33984 and the port can be one or a dash-separated pair.
33985 In the latter case, the range is tried in strict order.
33987 Elements after the first for Unix sockets, or second for TCP socket,
33989 The supported options are:
33991 pri=<priority> Selection priority
33992 weight=<value> Selection bias
33993 time=<start>-<end> Use only between these times of day
33994 retry=<timespec> Retry on connect fail
33995 tmo=<timespec> Connection time limit
33996 variant=rspamd Use Rspamd rather than SpamAssassin protocol
33999 The &`pri`& option specifies a priority for the server within the list,
34000 higher values being tried first.
34001 The default priority is 1.
34003 The &`weight`& option specifies a selection bias.
34004 Within a priority set
34005 servers are queried in a random fashion, weighted by this value.
34006 The default value for selection bias is 1.
34008 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34009 in the local time zone; each element being one or more digits.
34010 Either the seconds or both minutes and seconds, plus the leading &`.`&
34011 characters, may be omitted and will be taken as zero.
34013 Timeout specifications for the &`retry`& and &`tmo`& options
34014 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34016 The &`tmo`& option specifies an overall timeout for communication.
34017 The default value is two minutes.
34019 The &`retry`& option specifies a time after which a single retry for
34020 a failed connect is made.
34021 The default is to not retry.
34023 The &%spamd_address%& variable is expanded before use if it starts with
34024 a dollar sign. In this case, the expansion may return a string that is
34025 used as the list so that multiple spamd servers can be the result of an
34028 .vindex "&$callout_address$&"
34029 When a connection is made to the server the expansion variable &$callout_address$&
34030 is set to record the actual address used.
34032 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34033 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34036 message = This message was classified as SPAM
34038 The right-hand side of the &%spam%& condition specifies a name. This is
34039 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34040 to scan using a specific profile, but rather use the SpamAssassin system-wide
34041 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34042 Rspamd does not use this setting. However, you must put something on the
34045 The name allows you to use per-domain or per-user antispam profiles in
34046 principle, but this is not straightforward in practice, because a message may
34047 have multiple recipients, not necessarily all in the same domain. Because the
34048 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34049 read the contents of the message, the variables &$local_part$& and &$domain$&
34051 Careful enforcement of single-recipient messages
34052 (e.g. by responding with defer in the recipient ACL for all recipients
34054 or the use of PRDR,
34055 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34056 are needed to use this feature.
34058 The right-hand side of the &%spam%& condition is expanded before being used, so
34059 you can put lookups or conditions there. When the right-hand side evaluates to
34060 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34063 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34064 large ones may cause significant performance degradation. As most spam messages
34065 are quite small, it is recommended that you do not scan the big ones. For
34068 deny condition = ${if < {$message_size}{10K}}
34070 message = This message was classified as SPAM
34073 The &%spam%& condition returns true if the threshold specified in the user's
34074 SpamAssassin profile has been matched or exceeded. If you want to use the
34075 &%spam%& condition for its side effects (see the variables below), you can make
34076 it always return &"true"& by appending &`:true`& to the username.
34078 .cindex "spam scanning" "returned variables"
34079 When the &%spam%& condition is run, it sets up a number of expansion
34081 Except for &$spam_report$&,
34082 these variables are saved with the received message so are
34083 available for use at delivery time.
34086 .vitem &$spam_score$&
34087 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34088 for inclusion in log or reject messages.
34090 .vitem &$spam_score_int$&
34091 The spam score of the message, multiplied by ten, as an integer value. For
34092 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34093 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34094 The integer value is useful for numeric comparisons in conditions.
34096 .vitem &$spam_bar$&
34097 A string consisting of a number of &"+"& or &"-"& characters, representing the
34098 integer part of the spam score value. A spam score of 4.4 would have a
34099 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34100 headers, since MUAs can match on such strings. The maximum length of the
34101 spam bar is 50 characters.
34103 .vitem &$spam_report$&
34104 A multiline text table, containing the full SpamAssassin report for the
34105 message. Useful for inclusion in headers or reject messages.
34106 This variable is only usable in a DATA-time ACL.
34107 Beware that SpamAssassin may return non-ASCII characters, especially
34108 when running in country-specific locales, which are not legal
34109 unencoded in headers.
34111 .vitem &$spam_action$&
34112 For SpamAssassin either 'reject' or 'no action' depending on the
34113 spam score versus threshold.
34114 For Rspamd, the recommended action.
34118 The &%spam%& condition caches its results unless expansion in
34119 spamd_address was used. If you call it again with the same user name, it
34120 does not scan again, but rather returns the same values as before.
34122 The &%spam%& condition returns DEFER if there is any error while running
34123 the message through SpamAssassin or if the expansion of spamd_address
34124 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34125 statement block), append &`/defer_ok`& to the right-hand side of the
34126 spam condition, like this:
34128 deny spam = joe/defer_ok
34129 message = This message was classified as SPAM
34131 This causes messages to be accepted even if there is a problem with &%spamd%&.
34133 Here is a longer, commented example of the use of the &%spam%&
34136 # put headers in all messages (no matter if spam or not)
34137 warn spam = nobody:true
34138 add_header = X-Spam-Score: $spam_score ($spam_bar)
34139 add_header = X-Spam-Report: $spam_report
34141 # add second subject line with *SPAM* marker when message
34142 # is over threshold
34144 add_header = Subject: *SPAM* $h_Subject:
34146 # reject spam at high scores (> 12)
34147 deny spam = nobody:true
34148 condition = ${if >{$spam_score_int}{120}{1}{0}}
34149 message = This message scored $spam_score spam points.
34154 .section "Scanning MIME parts" "SECTscanmimepart"
34155 .cindex "content scanning" "MIME parts"
34156 .cindex "MIME content scanning"
34157 .oindex "&%acl_smtp_mime%&"
34158 .oindex "&%acl_not_smtp_mime%&"
34159 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34160 each MIME part of an SMTP message, including multipart types, in the sequence
34161 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34162 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34163 options may both refer to the same ACL if you want the same processing in both
34166 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34167 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34168 the case of a non-SMTP message. However, a MIME ACL is called only if the
34169 message contains a &'Content-Type:'& header line. When a call to a MIME
34170 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34171 result code is sent to the client. In the case of an SMTP message, the
34172 &%acl_smtp_data%& ACL is not called when this happens.
34174 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34175 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34176 condition to match against the raw MIME part. You can also use the
34177 &%mime_regex%& condition to match against the decoded MIME part (see section
34178 &<<SECTscanregex>>&).
34180 At the start of a MIME ACL, a number of variables are set from the header
34181 information for the relevant MIME part. These are described below. The contents
34182 of the MIME part are not by default decoded into a disk file except for MIME
34183 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34184 part into a disk file, you can use the &%decode%& condition. The general
34187 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34189 The right hand side is expanded before use. After expansion,
34193 &"0"& or &"false"&, in which case no decoding is done.
34195 The string &"default"&. In that case, the file is put in the temporary
34196 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34197 a sequential filename consisting of the message id and a sequence number. The
34198 full path and name is available in &$mime_decoded_filename$& after decoding.
34200 A full path name starting with a slash. If the full name is an existing
34201 directory, it is used as a replacement for the default directory. The filename
34202 is then sequentially assigned. If the path does not exist, it is used as
34203 the full path and filename.
34205 If the string does not start with a slash, it is used as the
34206 filename, and the default path is then used.
34208 The &%decode%& condition normally succeeds. It is only false for syntax
34209 errors or unusual circumstances such as memory shortages. You can easily decode
34210 a file with its original, proposed filename using
34212 decode = $mime_filename
34214 However, you should keep in mind that &$mime_filename$& might contain
34215 anything. If you place files outside of the default path, they are not
34216 automatically unlinked.
34218 For RFC822 attachments (these are messages attached to messages, with a
34219 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34220 as for the primary message, only that the &$mime_is_rfc822$& expansion
34221 variable is set (see below). Attached messages are always decoded to disk
34222 before being checked, and the files are unlinked once the check is done.
34224 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34225 used to match regular expressions against raw and decoded MIME parts,
34226 respectively. They are described in section &<<SECTscanregex>>&.
34228 .cindex "MIME content scanning" "returned variables"
34229 The following list describes all expansion variables that are
34230 available in the MIME ACL:
34233 .vitem &$mime_anomaly_level$& &&&
34234 &$mime_anomaly_text$&
34235 .vindex &$mime_anomaly_level$&
34236 .vindex &$mime_anomaly_text$&
34237 If there are problems decoding, these variables contain information on
34238 the detected issue.
34240 .vitem &$mime_boundary$&
34241 .vindex &$mime_boundary$&
34242 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34243 have a boundary string, which is stored in this variable. If the current part
34244 has no boundary parameter in the &'Content-Type:'& header, this variable
34245 contains the empty string.
34247 .vitem &$mime_charset$&
34248 .vindex &$mime_charset$&
34249 This variable contains the character set identifier, if one was found in the
34250 &'Content-Type:'& header. Examples for charset identifiers are:
34256 Please note that this value is not normalized, so you should do matches
34257 case-insensitively.
34259 .vitem &$mime_content_description$&
34260 .vindex &$mime_content_description$&
34261 This variable contains the normalized content of the &'Content-Description:'&
34262 header. It can contain a human-readable description of the parts content. Some
34263 implementations repeat the filename for attachments here, but they are usually
34264 only used for display purposes.
34266 .vitem &$mime_content_disposition$&
34267 .vindex &$mime_content_disposition$&
34268 This variable contains the normalized content of the &'Content-Disposition:'&
34269 header. You can expect strings like &"attachment"& or &"inline"& here.
34271 .vitem &$mime_content_id$&
34272 .vindex &$mime_content_id$&
34273 This variable contains the normalized content of the &'Content-ID:'& header.
34274 This is a unique ID that can be used to reference a part from another part.
34276 .vitem &$mime_content_size$&
34277 .vindex &$mime_content_size$&
34278 This variable is set only after the &%decode%& modifier (see above) has been
34279 successfully run. It contains the size of the decoded part in kilobytes. The
34280 size is always rounded up to full kilobytes, so only a completely empty part
34281 has a &$mime_content_size$& of zero.
34283 .vitem &$mime_content_transfer_encoding$&
34284 .vindex &$mime_content_transfer_encoding$&
34285 This variable contains the normalized content of the
34286 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34287 type. Typical values are &"base64"& and &"quoted-printable"&.
34289 .vitem &$mime_content_type$&
34290 .vindex &$mime_content_type$&
34291 If the MIME part has a &'Content-Type:'& header, this variable contains its
34292 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34293 are some examples of popular MIME types, as they may appear in this variable:
34297 application/octet-stream
34301 If the MIME part has no &'Content-Type:'& header, this variable contains the
34304 .vitem &$mime_decoded_filename$&
34305 .vindex &$mime_decoded_filename$&
34306 This variable is set only after the &%decode%& modifier (see above) has been
34307 successfully run. It contains the full path and filename of the file
34308 containing the decoded data.
34313 .vitem &$mime_filename$&
34314 .vindex &$mime_filename$&
34315 This is perhaps the most important of the MIME variables. It contains a
34316 proposed filename for an attachment, if one was found in either the
34317 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34320 decoded, but no additional sanity checks are done.
34322 found, this variable contains the empty string.
34324 .vitem &$mime_is_coverletter$&
34325 .vindex &$mime_is_coverletter$&
34326 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34327 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34328 content in the cover letter, while not restricting attachments at all.
34330 The variable contains 1 (true) for a MIME part believed to be part of the
34331 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34335 The outermost MIME part of a message is always a cover letter.
34338 If a multipart/alternative or multipart/related MIME part is a cover letter,
34339 so are all MIME subparts within that multipart.
34342 If any other multipart is a cover letter, the first subpart is a cover letter,
34343 and the rest are attachments.
34346 All parts contained within an attachment multipart are attachments.
34349 As an example, the following will ban &"HTML mail"& (including that sent with
34350 alternative plain text), while allowing HTML files to be attached. HTML
34351 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34353 deny !condition = $mime_is_rfc822
34354 condition = $mime_is_coverletter
34355 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34356 message = HTML mail is not accepted here
34359 .vitem &$mime_is_multipart$&
34360 .vindex &$mime_is_multipart$&
34361 This variable has the value 1 (true) when the current part has the main type
34362 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34363 Since multipart entities only serve as containers for other parts, you may not
34364 want to carry out specific actions on them.
34366 .vitem &$mime_is_rfc822$&
34367 .vindex &$mime_is_rfc822$&
34368 This variable has the value 1 (true) if the current part is not a part of the
34369 checked message itself, but part of an attached message. Attached message
34370 decoding is fully recursive.
34372 .vitem &$mime_part_count$&
34373 .vindex &$mime_part_count$&
34374 This variable is a counter that is raised for each processed MIME part. It
34375 starts at zero for the very first part (which is usually a multipart). The
34376 counter is per-message, so it is reset when processing RFC822 attachments (see
34377 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34378 complete, so you can use it in the DATA ACL to determine the number of MIME
34379 parts of a message. For non-MIME messages, this variable contains the value -1.
34384 .section "Scanning with regular expressions" "SECTscanregex"
34385 .cindex "content scanning" "with regular expressions"
34386 .cindex "regular expressions" "content scanning with"
34387 You can specify your own custom regular expression matches on the full body of
34388 the message, or on individual MIME parts.
34390 The &%regex%& condition takes one or more regular expressions as arguments and
34391 matches them against the full message (when called in the DATA ACL) or a raw
34392 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34393 linewise, with a maximum line length of 32K characters. That means you cannot
34394 have multiline matches with the &%regex%& condition.
34396 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34397 to 32K of decoded content (the whole content at once, not linewise). If the
34398 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34399 is decoded automatically when &%mime_regex%& is executed (using default path
34400 and filename values). If the decoded data is larger than 32K, only the first
34401 32K characters are checked.
34403 The regular expressions are passed as a colon-separated list. To include a
34404 literal colon, you must double it. Since the whole right-hand side string is
34405 expanded before being used, you must also escape dollar signs and backslashes
34406 with more backslashes, or use the &`\N`& facility to disable expansion.
34407 Here is a simple example that contains two regular expressions:
34409 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34410 message = contains blacklisted regex ($regex_match_string)
34412 The conditions returns true if any one of the regular expressions matches. The
34413 &$regex_match_string$& expansion variable is then set up and contains the
34414 matching regular expression.
34415 The expansion variables &$regex1$& &$regex2$& etc
34416 are set to any substrings captured by the regular expression.
34418 &*Warning*&: With large messages, these conditions can be fairly
34426 . ////////////////////////////////////////////////////////////////////////////
34427 . ////////////////////////////////////////////////////////////////////////////
34429 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
34430 "Local scan function"
34431 .scindex IIDlosca "&[local_scan()]& function" "description of"
34432 .cindex "customizing" "input scan using C function"
34433 .cindex "policy control" "by local scan function"
34434 In these days of email worms, viruses, and ever-increasing spam, some sites
34435 want to apply a lot of checking to messages before accepting them.
34437 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
34438 passing messages to external virus and spam scanning software. You can also do
34439 a certain amount in Exim itself through string expansions and the &%condition%&
34440 condition in the ACL that runs after the SMTP DATA command or the ACL for
34441 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
34443 To allow for further customization to a site's own requirements, there is the
34444 possibility of linking Exim with a private message scanning function, written
34445 in C. If you want to run code that is written in something other than C, you
34446 can of course use a little C stub to call it.
34448 The local scan function is run once for every incoming message, at the point
34449 when Exim is just about to accept the message.
34450 It can therefore be used to control non-SMTP messages from local processes as
34451 well as messages arriving via SMTP.
34453 Exim applies a timeout to calls of the local scan function, and there is an
34454 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
34455 Zero means &"no timeout"&.
34456 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
34457 before calling the local scan function, so that the most common types of crash
34458 are caught. If the timeout is exceeded or one of those signals is caught, the
34459 incoming message is rejected with a temporary error if it is an SMTP message.
34460 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
34461 code. The incident is logged on the main and reject logs.
34465 .section "Building Exim to use a local scan function" "SECID207"
34466 .cindex "&[local_scan()]& function" "building Exim to use"
34467 To make use of the local scan function feature, you must tell Exim where your
34468 function is before building Exim, by setting
34469 both HAVE_LOCAL_SCAN and
34470 LOCAL_SCAN_SOURCE in your
34471 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
34472 directory, so you might set
34474 HAVE_LOCAL_SCAN=yes
34475 LOCAL_SCAN_SOURCE=Local/local_scan.c
34477 for example. The function must be called &[local_scan()]&;
34478 the source file(s) for it should first #define LOCAL_SCAN
34479 and then #include "local_scan.h".
34481 Exim after it has received a message, when the success return code is about to
34482 be sent. This is after all the ACLs have been run. The return code from your
34483 function controls whether the message is actually accepted or not. There is a
34484 commented template function (that just accepts the message) in the file
34485 _src/local_scan.c_.
34487 If you want to make use of Exim's runtime configuration file to set options
34488 for your &[local_scan()]& function, you must also set
34490 LOCAL_SCAN_HAS_OPTIONS=yes
34492 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
34497 .section "API for local_scan()" "SECTapiforloc"
34498 .cindex "&[local_scan()]& function" "API description"
34499 .cindex &%dlfunc%& "API description"
34500 You must include this line near the start of your code:
34503 #include "local_scan.h"
34505 This header file defines a number of variables and other values, and the
34506 prototype for the function itself. Exim is coded to use unsigned char values
34507 almost exclusively, and one of the things this header defines is a shorthand
34508 for &`unsigned char`& called &`uschar`&.
34509 It also makes available the following macro definitions, to simplify casting character
34510 strings and pointers to character strings:
34512 #define CS (char *)
34513 #define CCS (const char *)
34514 #define CSS (char **)
34515 #define US (unsigned char *)
34516 #define CUS (const unsigned char *)
34517 #define USS (unsigned char **)
34519 The function prototype for &[local_scan()]& is:
34521 extern int local_scan(int fd, uschar **return_text);
34523 The arguments are as follows:
34526 &%fd%& is a file descriptor for the file that contains the body of the message
34527 (the -D file). The file is open for reading and writing, but updating it is not
34528 recommended. &*Warning*&: You must &'not'& close this file descriptor.
34530 The descriptor is positioned at character 19 of the file, which is the first
34531 character of the body itself, because the first 19 characters are the message
34532 id followed by &`-D`& and a newline. If you rewind the file, you should use the
34533 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
34534 case this changes in some future version.
34536 &%return_text%& is an address which you can use to return a pointer to a text
34537 string at the end of the function. The value it points to on entry is NULL.
34540 The function must return an &%int%& value which is one of the following macros:
34543 .vitem &`LOCAL_SCAN_ACCEPT`&
34544 .vindex "&$local_scan_data$&"
34545 The message is accepted. If you pass back a string of text, it is saved with
34546 the message, and made available in the variable &$local_scan_data$&. No
34547 newlines are permitted (if there are any, they are turned into spaces) and the
34548 maximum length of text is 1000 characters.
34550 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
34551 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34552 queued without immediate delivery, and is frozen.
34554 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
34555 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34556 queued without immediate delivery.
34558 .vitem &`LOCAL_SCAN_REJECT`&
34559 The message is rejected; the returned text is used as an error message which is
34560 passed back to the sender and which is also logged. Newlines are permitted &--
34561 they cause a multiline response for SMTP rejections, but are converted to
34562 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
34565 .vitem &`LOCAL_SCAN_TEMPREJECT`&
34566 The message is temporarily rejected; the returned text is used as an error
34567 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
34570 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
34571 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
34572 message is not written to the reject log. It has the effect of unsetting the
34573 &%rejected_header%& log selector for just this rejection. If
34574 &%rejected_header%& is already unset (see the discussion of the
34575 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
34576 same as LOCAL_SCAN_REJECT.
34578 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
34579 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
34580 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
34583 If the message is not being received by interactive SMTP, rejections are
34584 reported by writing to &%stderr%& or by sending an email, as configured by the
34585 &%-oe%& command line options.
34589 .section "Configuration options for local_scan()" "SECTconoptloc"
34590 .cindex "&[local_scan()]& function" "configuration options"
34591 It is possible to have option settings in the main configuration file
34592 that set values in static variables in the &[local_scan()]& module. If you
34593 want to do this, you must have the line
34595 LOCAL_SCAN_HAS_OPTIONS=yes
34597 in your &_Local/Makefile_& when you build Exim. (This line is in
34598 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
34599 file, you must define static variables to hold the option values, and a table
34602 The table must be a vector called &%local_scan_options%&, of type
34603 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
34604 and a pointer to the variable that holds the value. The entries must appear in
34605 alphabetical order. Following &%local_scan_options%& you must also define a
34606 variable called &%local_scan_options_count%& that contains the number of
34607 entries in the table. Here is a short example, showing two kinds of option:
34609 static int my_integer_option = 42;
34610 static uschar *my_string_option = US"a default string";
34612 optionlist local_scan_options[] = {
34613 { "my_integer", opt_int, &my_integer_option },
34614 { "my_string", opt_stringptr, &my_string_option }
34617 int local_scan_options_count =
34618 sizeof(local_scan_options)/sizeof(optionlist);
34620 The values of the variables can now be changed from Exim's runtime
34621 configuration file by including a local scan section as in this example:
34625 my_string = some string of text...
34627 The available types of option data are as follows:
34630 .vitem &*opt_bool*&
34631 This specifies a boolean (true/false) option. The address should point to a
34632 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
34633 that are defined as &"1"& and &"0"&, respectively. If you want to detect
34634 whether such a variable has been set at all, you can initialize it to
34635 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
34638 .vitem &*opt_fixed*&
34639 This specifies a fixed point number, such as is used for load averages.
34640 The address should point to a variable of type &`int`&. The value is stored
34641 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
34644 This specifies an integer; the address should point to a variable of type
34645 &`int`&. The value may be specified in any of the integer formats accepted by
34648 .vitem &*opt_mkint*&
34649 This is the same as &%opt_int%&, except that when such a value is output in a
34650 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
34651 printed with the suffix K or M.
34653 .vitem &*opt_octint*&
34654 This also specifies an integer, but the value is always interpreted as an
34655 octal integer, whether or not it starts with the digit zero, and it is
34656 always output in octal.
34658 .vitem &*opt_stringptr*&
34659 This specifies a string value; the address must be a pointer to a
34660 variable that points to a string (for example, of type &`uschar *`&).
34662 .vitem &*opt_time*&
34663 This specifies a time interval value. The address must point to a variable of
34664 type &`int`&. The value that is placed there is a number of seconds.
34667 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
34668 out the values of all the &[local_scan()]& options.
34672 .section "Available Exim variables" "SECID208"
34673 .cindex "&[local_scan()]& function" "available Exim variables"
34674 The header &_local_scan.h_& gives you access to a number of C variables. These
34675 are the only ones that are guaranteed to be maintained from release to release.
34676 Note, however, that you can obtain the value of any Exim expansion variable,
34677 including &$recipients$&, by calling &'expand_string()'&. The exported
34678 C variables are as follows:
34681 .vitem &*int&~body_linecount*&
34682 This variable contains the number of lines in the message's body.
34683 It is not valid if the &%spool_files_wireformat%& option is used.
34685 .vitem &*int&~body_zerocount*&
34686 This variable contains the number of binary zero bytes in the message's body.
34687 It is not valid if the &%spool_files_wireformat%& option is used.
34689 .vitem &*unsigned&~int&~debug_selector*&
34690 This variable is set to zero when no debugging is taking place. Otherwise, it
34691 is a bitmap of debugging selectors. Two bits are identified for use in
34692 &[local_scan()]&; they are defined as macros:
34695 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
34696 testing option that is not privileged &-- any caller may set it. All the
34697 other selector bits can be set only by admin users.
34700 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
34701 by the &`+local_scan`& debug selector. It is not included in the default set
34705 Thus, to write to the debugging output only when &`+local_scan`& has been
34706 selected, you should use code like this:
34708 if ((debug_selector & D_local_scan) != 0)
34709 debug_printf("xxx", ...);
34711 .vitem &*uschar&~*expand_string_message*&
34712 After a failing call to &'expand_string()'& (returned value NULL), the
34713 variable &%expand_string_message%& contains the error message, zero-terminated.
34715 .vitem &*header_line&~*header_list*&
34716 A pointer to a chain of header lines. The &%header_line%& structure is
34719 .vitem &*header_line&~*header_last*&
34720 A pointer to the last of the header lines.
34722 .vitem &*uschar&~*headers_charset*&
34723 The value of the &%headers_charset%& configuration option.
34725 .vitem &*BOOL&~host_checking*&
34726 This variable is TRUE during a host checking session that is initiated by the
34727 &%-bh%& command line option.
34729 .vitem &*uschar&~*interface_address*&
34730 The IP address of the interface that received the message, as a string. This
34731 is NULL for locally submitted messages.
34733 .vitem &*int&~interface_port*&
34734 The port on which this message was received. When testing with the &%-bh%&
34735 command line option, the value of this variable is -1 unless a port has been
34736 specified via the &%-oMi%& option.
34738 .vitem &*uschar&~*message_id*&
34739 This variable contains Exim's message id for the incoming message (the value of
34740 &$message_exim_id$&) as a zero-terminated string.
34742 .vitem &*uschar&~*received_protocol*&
34743 The name of the protocol by which the message was received.
34745 .vitem &*int&~recipients_count*&
34746 The number of accepted recipients.
34748 .vitem &*recipient_item&~*recipients_list*&
34749 .cindex "recipient" "adding in local scan"
34750 .cindex "recipient" "removing in local scan"
34751 The list of accepted recipients, held in a vector of length
34752 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
34753 can add additional recipients by calling &'receive_add_recipient()'& (see
34754 below). You can delete recipients by removing them from the vector and
34755 adjusting the value in &%recipients_count%&. In particular, by setting
34756 &%recipients_count%& to zero you remove all recipients. If you then return the
34757 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
34758 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
34759 and then call &'receive_add_recipient()'& as often as needed.
34761 .vitem &*uschar&~*sender_address*&
34762 The envelope sender address. For bounce messages this is the empty string.
34764 .vitem &*uschar&~*sender_host_address*&
34765 The IP address of the sending host, as a string. This is NULL for
34766 locally-submitted messages.
34768 .vitem &*uschar&~*sender_host_authenticated*&
34769 The name of the authentication mechanism that was used, or NULL if the message
34770 was not received over an authenticated SMTP connection.
34772 .vitem &*uschar&~*sender_host_name*&
34773 The name of the sending host, if known.
34775 .vitem &*int&~sender_host_port*&
34776 The port on the sending host.
34778 .vitem &*BOOL&~smtp_input*&
34779 This variable is TRUE for all SMTP input, including BSMTP.
34781 .vitem &*BOOL&~smtp_batched_input*&
34782 This variable is TRUE for BSMTP input.
34784 .vitem &*int&~store_pool*&
34785 The contents of this variable control which pool of memory is used for new
34786 requests. See section &<<SECTmemhanloc>>& for details.
34790 .section "Structure of header lines" "SECID209"
34791 The &%header_line%& structure contains the members listed below.
34792 You can add additional header lines by calling the &'header_add()'& function
34793 (see below). You can cause header lines to be ignored (deleted) by setting
34798 .vitem &*struct&~header_line&~*next*&
34799 A pointer to the next header line, or NULL for the last line.
34801 .vitem &*int&~type*&
34802 A code identifying certain headers that Exim recognizes. The codes are printing
34803 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
34804 Notice in particular that any header line whose type is * is not transmitted
34805 with the message. This flagging is used for header lines that have been
34806 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
34807 lines.) Effectively, * means &"deleted"&.
34809 .vitem &*int&~slen*&
34810 The number of characters in the header line, including the terminating and any
34813 .vitem &*uschar&~*text*&
34814 A pointer to the text of the header. It always ends with a newline, followed by
34815 a zero byte. Internal newlines are preserved.
34820 .section "Structure of recipient items" "SECID210"
34821 The &%recipient_item%& structure contains these members:
34824 .vitem &*uschar&~*address*&
34825 This is a pointer to the recipient address as it was received.
34827 .vitem &*int&~pno*&
34828 This is used in later Exim processing when top level addresses are created by
34829 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
34830 and must always contain -1 at this stage.
34832 .vitem &*uschar&~*errors_to*&
34833 If this value is not NULL, bounce messages caused by failing to deliver to the
34834 recipient are sent to the address it contains. In other words, it overrides the
34835 envelope sender for this one recipient. (Compare the &%errors_to%& generic
34836 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
34837 an unqualified address, Exim qualifies it using the domain from
34838 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
34839 is NULL for all recipients.
34844 .section "Available Exim functions" "SECID211"
34845 .cindex "&[local_scan()]& function" "available Exim functions"
34846 The header &_local_scan.h_& gives you access to a number of Exim functions.
34847 These are the only ones that are guaranteed to be maintained from release to
34851 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
34852 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
34854 This function creates a child process that runs the command specified by
34855 &%argv%&. The environment for the process is specified by &%envp%&, which can
34856 be NULL if no environment variables are to be passed. A new umask is supplied
34857 for the process in &%newumask%&.
34859 Pipes to the standard input and output of the new process are set up
34860 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
34861 standard error is cloned to the standard output. If there are any file
34862 descriptors &"in the way"& in the new process, they are closed. If the final
34863 argument is TRUE, the new process is made into a process group leader.
34865 The function returns the pid of the new process, or -1 if things go wrong.
34867 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
34868 This function waits for a child process to terminate, or for a timeout (in
34869 seconds) to expire. A timeout value of zero means wait as long as it takes. The
34870 return value is as follows:
34875 The process terminated by a normal exit and the value is the process
34881 The process was terminated by a signal and the value is the negation of the
34887 The process timed out.
34891 The was some other error in wait(); &%errno%& is still set.
34894 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
34895 This function provide you with a means of submitting a new message to
34896 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
34897 want, but this packages it all up for you.) The function creates a pipe,
34898 forks a subprocess that is running
34900 exim -t -oem -oi -f <>
34902 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
34903 that is connected to the standard input. The yield of the function is the PID
34904 of the subprocess. You can then write a message to the file descriptor, with
34905 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
34907 When you have finished, call &'child_close()'& to wait for the process to
34908 finish and to collect its ending status. A timeout value of zero is usually
34909 fine in this circumstance. Unless you have made a mistake with the recipient
34910 addresses, you should get a return code of zero.
34913 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
34914 *sender_authentication)*&
34915 This function is a more sophisticated version of &'child_open()'&. The command
34918 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
34920 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
34923 .vitem &*void&~debug_printf(char&~*,&~...)*&
34924 This is Exim's debugging function, with arguments as for &'(printf()'&. The
34925 output is written to the standard error stream. If no debugging is selected,
34926 calls to &'debug_printf()'& have no effect. Normally, you should make calls
34927 conditional on the &`local_scan`& debug selector by coding like this:
34929 if ((debug_selector & D_local_scan) != 0)
34930 debug_printf("xxx", ...);
34933 .vitem &*uschar&~*expand_string(uschar&~*string)*&
34934 This is an interface to Exim's string expansion code. The return value is the
34935 expanded string, or NULL if there was an expansion failure.
34936 The C variable &%expand_string_message%& contains an error message after an
34937 expansion failure. If expansion does not change the string, the return value is
34938 the pointer to the input string. Otherwise, the return value points to a new
34939 block of memory that was obtained by a call to &'store_get()'&. See section
34940 &<<SECTmemhanloc>>& below for a discussion of memory handling.
34942 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
34943 This function allows you to an add additional header line at the end of the
34944 existing ones. The first argument is the type, and should normally be a space
34945 character. The second argument is a format string and any number of
34946 substitution arguments as for &[sprintf()]&. You may include internal newlines
34947 if you want, and you must ensure that the string ends with a newline.
34949 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
34950 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
34951 This function adds a new header line at a specified point in the header
34952 chain. The header itself is specified as for &'header_add()'&.
34954 If &%name%& is NULL, the new header is added at the end of the chain if
34955 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
34956 NULL, the header lines are searched for the first non-deleted header that
34957 matches the name. If one is found, the new header is added before it if
34958 &%after%& is false. If &%after%& is true, the new header is added after the
34959 found header and any adjacent subsequent ones with the same name (even if
34960 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
34961 option controls where the header is added. If it is true, addition is at the
34962 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
34963 headers, or at the top if there are no &'Received:'& headers, you could use
34965 header_add_at_position(TRUE, US"Received", TRUE,
34966 ' ', "X-xxx: ...");
34968 Normally, there is always at least one non-deleted &'Received:'& header, but
34969 there may not be if &%received_header_text%& expands to an empty string.
34972 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
34973 This function removes header lines. If &%occurrence%& is zero or negative, all
34974 occurrences of the header are removed. If occurrence is greater than zero, that
34975 particular instance of the header is removed. If no header(s) can be found that
34976 match the specification, the function does nothing.
34979 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
34980 int&~length,&~BOOL&~notdel)*&"
34981 This function tests whether the given header has the given name. It is not just
34982 a string comparison, because white space is permitted between the name and the
34983 colon. If the &%notdel%& argument is true, a false return is forced for all
34984 &"deleted"& headers; otherwise they are not treated specially. For example:
34986 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
34988 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
34989 .cindex "base64 encoding" "functions for &[local_scan()]& use"
34990 This function base64-encodes a string, which is passed by address and length.
34991 The text may contain bytes of any value, including zero. The result is passed
34992 back in dynamic memory that is obtained by calling &'store_get()'&. It is
34995 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
34996 This function decodes a base64-encoded string. Its arguments are a
34997 zero-terminated base64-encoded string and the address of a variable that is set
34998 to point to the result, which is in dynamic memory. The length of the decoded
34999 string is the yield of the function. If the input is invalid base64 data, the
35000 yield is -1. A zero byte is added to the end of the output string to make it
35001 easy to interpret as a C string (assuming it contains no zeros of its own). The
35002 added zero byte is not included in the returned count.
35004 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35005 This function checks for a match in a domain list. Domains are always
35006 matched caselessly. The return value is one of the following:
35008 &`OK `& match succeeded
35009 &`FAIL `& match failed
35010 &`DEFER `& match deferred
35012 DEFER is usually caused by some kind of lookup defer, such as the
35013 inability to contact a database.
35015 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35017 This function checks for a match in a local part list. The third argument
35018 controls case-sensitivity. The return values are as for
35019 &'lss_match_domain()'&.
35021 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35023 This function checks for a match in an address list. The third argument
35024 controls the case-sensitivity of the local part match. The domain is always
35025 matched caselessly. The return values are as for &'lss_match_domain()'&.
35027 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35029 This function checks for a match in a host list. The most common usage is
35032 lss_match_host(sender_host_name, sender_host_address, ...)
35034 .vindex "&$sender_host_address$&"
35035 An empty address field matches an empty item in the host list. If the host name
35036 is NULL, the name corresponding to &$sender_host_address$& is automatically
35037 looked up if a host name is required to match an item in the list. The return
35038 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35039 returns ERROR in the case when it had to look up a host name, but the lookup
35042 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35044 This function writes to Exim's log files. The first argument should be zero (it
35045 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35046 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35047 them. It specifies to which log or logs the message is written. The remaining
35048 arguments are a format and relevant insertion arguments. The string should not
35049 contain any newlines, not even at the end.
35052 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35053 This function adds an additional recipient to the message. The first argument
35054 is the recipient address. If it is unqualified (has no domain), it is qualified
35055 with the &%qualify_recipient%& domain. The second argument must always be -1.
35057 This function does not allow you to specify a private &%errors_to%& address (as
35058 described with the structure of &%recipient_item%& above), because it pre-dates
35059 the addition of that field to the structure. However, it is easy to add such a
35060 value afterwards. For example:
35062 receive_add_recipient(US"monitor@mydom.example", -1);
35063 recipients_list[recipients_count-1].errors_to =
35064 US"postmaster@mydom.example";
35067 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35068 This is a convenience function to remove a named recipient from the list of
35069 recipients. It returns true if a recipient was removed, and false if no
35070 matching recipient could be found. The argument must be a complete email
35077 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35078 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35079 This function decodes strings that are encoded according to RFC 2047. Typically
35080 these are the contents of header lines. First, each &"encoded word"& is decoded
35081 from the Q or B encoding into a byte-string. Then, if provided with the name of
35082 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35083 made to translate the result to the named character set. If this fails, the
35084 binary string is returned with an error message.
35086 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35087 maximum MIME word length is enforced. The third argument is the target
35088 encoding, or NULL if no translation is wanted.
35090 .cindex "binary zero" "in RFC 2047 decoding"
35091 .cindex "RFC 2047" "binary zero in"
35092 If a binary zero is encountered in the decoded string, it is replaced by the
35093 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35094 not be 0 because header lines are handled as zero-terminated strings.
35096 The function returns the result of processing the string, zero-terminated; if
35097 &%lenptr%& is not NULL, the length of the result is set in the variable to
35098 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35100 If an error is encountered, the function returns NULL and uses the &%error%&
35101 argument to return an error message. The variable pointed to by &%error%& is
35102 set to NULL if there is no error; it may be set non-NULL even when the function
35103 returns a non-NULL value if decoding was successful, but there was a problem
35107 .vitem &*int&~smtp_fflush(void)*&
35108 This function is used in conjunction with &'smtp_printf()'&, as described
35111 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35112 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35113 output stream. You should use this function only when there is an SMTP output
35114 stream, that is, when the incoming message is being received via interactive
35115 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35116 is FALSE. If you want to test for an incoming message from another host (as
35117 opposed to a local process that used the &%-bs%& command line option), you can
35118 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35121 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35122 output function, so it can be used for all forms of SMTP connection.
35124 The second argument is used to request that the data be buffered
35125 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35126 This is advisory only, but likely to save on system-calls and packets
35127 sent when a sequence of calls to the function are made.
35129 The argument was added in Exim version 4.90 - changing the API/ABI.
35130 Nobody noticed until 4.93 was imminent, at which point the
35131 ABI version number was incremented.
35133 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35134 must start with an appropriate response code: 550 if you are going to return
35135 LOCAL_SCAN_REJECT, 451 if you are going to return
35136 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35137 initial lines of a multi-line response, the code must be followed by a hyphen
35138 to indicate that the line is not the final response line. You must also ensure
35139 that the lines you write terminate with CRLF. For example:
35141 smtp_printf("550-this is some extra info\r\n");
35142 return LOCAL_SCAN_REJECT;
35144 Note that you can also create multi-line responses by including newlines in
35145 the data returned via the &%return_text%& argument. The added value of using
35146 &'smtp_printf()'& is that, for instance, you could introduce delays between
35147 multiple output lines.
35149 The &'smtp_printf()'& function does not return any error indication, because it
35151 guarantee a flush of
35152 pending output, and therefore does not test
35153 the state of the stream. (In the main code of Exim, flushing and error
35154 detection is done when Exim is ready for the next SMTP input command.) If
35155 you want to flush the output and check for an error (for example, the
35156 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35157 arguments. It flushes the output stream, and returns a non-zero value if there
35160 .vitem &*void&~*store_get(int,BOOL)*&
35161 This function accesses Exim's internal store (memory) manager. It gets a new
35162 chunk of memory whose size is given by the first argument.
35163 The second argument should be given as TRUE if the memory will be used for
35164 data possibly coming from an attacker (eg. the message content),
35165 FALSE if it is locally-sourced.
35166 Exim bombs out if it ever
35167 runs out of memory. See the next section for a discussion of memory handling.
35169 .vitem &*void&~*store_get_perm(int,BOOL)*&
35170 This function is like &'store_get()'&, but it always gets memory from the
35171 permanent pool. See the next section for a discussion of memory handling.
35173 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35176 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35179 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35180 These three functions create strings using Exim's dynamic memory facilities.
35181 The first makes a copy of an entire string. The second copies up to a maximum
35182 number of characters, indicated by the second argument. The third uses a format
35183 and insertion arguments to create a new string. In each case, the result is a
35184 pointer to a new string in the current memory pool. See the next section for
35190 .section "More about Exim's memory handling" "SECTmemhanloc"
35191 .cindex "&[local_scan()]& function" "memory handling"
35192 No function is provided for freeing memory, because that is never needed.
35193 The dynamic memory that Exim uses when receiving a message is automatically
35194 recycled if another message is received by the same process (this applies only
35195 to incoming SMTP connections &-- other input methods can supply only one
35196 message at a time). After receiving the last message, a reception process
35199 Because it is recycled, the normal dynamic memory cannot be used for holding
35200 data that must be preserved over a number of incoming messages on the same SMTP
35201 connection. However, Exim in fact uses two pools of dynamic memory; the second
35202 one is not recycled, and can be used for this purpose.
35204 If you want to allocate memory that remains available for subsequent messages
35205 in the same SMTP connection, you should set
35207 store_pool = POOL_PERM
35209 before calling the function that does the allocation. There is no need to
35210 restore the value if you do not need to; however, if you do want to revert to
35211 the normal pool, you can either restore the previous value of &%store_pool%& or
35212 set it explicitly to POOL_MAIN.
35214 The pool setting applies to all functions that get dynamic memory, including
35215 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35216 There is also a convenience function called &'store_get_perm()'& that gets a
35217 block of memory from the permanent pool while preserving the value of
35224 . ////////////////////////////////////////////////////////////////////////////
35225 . ////////////////////////////////////////////////////////////////////////////
35227 .chapter "System-wide message filtering" "CHAPsystemfilter"
35228 .scindex IIDsysfil1 "filter" "system filter"
35229 .scindex IIDsysfil2 "filtering all mail"
35230 .scindex IIDsysfil3 "system filter"
35231 The previous chapters (on ACLs and the local scan function) describe checks
35232 that can be applied to messages before they are accepted by a host. There is
35233 also a mechanism for checking messages once they have been received, but before
35234 they are delivered. This is called the &'system filter'&.
35236 The system filter operates in a similar manner to users' filter files, but it
35237 is run just once per message (however many recipients the message has).
35238 It should not normally be used as a substitute for routing, because &%deliver%&
35239 commands in a system router provide new envelope recipient addresses.
35240 The system filter must be an Exim filter. It cannot be a Sieve filter.
35242 The system filter is run at the start of a delivery attempt, before any routing
35243 is done. If a message fails to be completely delivered at the first attempt,
35244 the system filter is run again at the start of every retry.
35245 If you want your filter to do something only once per message, you can make use
35246 of the &%first_delivery%& condition in an &%if%& command in the filter to
35247 prevent it happening on retries.
35249 .vindex "&$domain$&"
35250 .vindex "&$local_part$&"
35251 &*Warning*&: Because the system filter runs just once, variables that are
35252 specific to individual recipient addresses, such as &$local_part$& and
35253 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35254 you want to run a centrally-specified filter for each recipient address
35255 independently, you can do so by setting up a suitable &(redirect)& router, as
35256 described in section &<<SECTperaddfil>>& below.
35259 .section "Specifying a system filter" "SECID212"
35260 .cindex "uid (user id)" "system filter"
35261 .cindex "gid (group id)" "system filter"
35262 The name of the file that contains the system filter must be specified by
35263 setting &%system_filter%&. If you want the filter to run under a uid and gid
35264 other than root, you must also set &%system_filter_user%& and
35265 &%system_filter_group%& as appropriate. For example:
35267 system_filter = /etc/mail/exim.filter
35268 system_filter_user = exim
35270 If a system filter generates any deliveries directly to files or pipes (via the
35271 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35272 specified by setting &%system_filter_file_transport%& and
35273 &%system_filter_pipe_transport%&, respectively. Similarly,
35274 &%system_filter_reply_transport%& must be set to handle any messages generated
35275 by the &%reply%& command.
35278 .section "Testing a system filter" "SECID213"
35279 You can run simple tests of a system filter in the same way as for a user
35280 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35281 are permitted only in system filters are recognized.
35283 If you want to test the combined effect of a system filter and a user filter,
35284 you can use both &%-bF%& and &%-bf%& on the same command line.
35288 .section "Contents of a system filter" "SECID214"
35289 The language used to specify system filters is the same as for users' filter
35290 files. It is described in the separate end-user document &'Exim's interface to
35291 mail filtering'&. However, there are some additional features that are
35292 available only in system filters; these are described in subsequent sections.
35293 If they are encountered in a user's filter file or when testing with &%-bf%&,
35296 .cindex "frozen messages" "manual thaw; testing in filter"
35297 There are two special conditions which, though available in users' filter
35298 files, are designed for use in system filters. The condition &%first_delivery%&
35299 is true only for the first attempt at delivering a message, and
35300 &%manually_thawed%& is true only if the message has been frozen, and
35301 subsequently thawed by an admin user. An explicit forced delivery counts as a
35302 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35304 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35305 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35306 succeed, it will not be tried again.
35307 If you want Exim to retry an unseen delivery until it succeeds, you should
35308 arrange to set it up every time the filter runs.
35310 When a system filter finishes running, the values of the variables &$n0$& &--
35311 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35312 users' filter files. Thus a system filter can, for example, set up &"scores"&
35313 to which users' filter files can refer.
35317 .section "Additional variable for system filters" "SECID215"
35318 .vindex "&$recipients$&"
35319 The expansion variable &$recipients$&, containing a list of all the recipients
35320 of the message (separated by commas and white space), is available in system
35321 filters. It is not available in users' filters for privacy reasons.
35325 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35326 .cindex "freezing messages"
35327 .cindex "message" "freezing"
35328 .cindex "message" "forced failure"
35329 .cindex "&%fail%&" "in system filter"
35330 .cindex "&%freeze%& in system filter"
35331 .cindex "&%defer%& in system filter"
35332 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35333 always available in system filters, but are not normally enabled in users'
35334 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35335 for the &(redirect)& router.) These commands can optionally be followed by the
35336 word &%text%& and a string containing an error message, for example:
35338 fail text "this message looks like spam to me"
35340 The keyword &%text%& is optional if the next character is a double quote.
35342 The &%defer%& command defers delivery of the original recipients of the
35343 message. The &%fail%& command causes all the original recipients to be failed,
35344 and a bounce message to be created. The &%freeze%& command suspends all
35345 delivery attempts for the original recipients. In all cases, any new deliveries
35346 that are specified by the filter are attempted as normal after the filter has
35349 The &%freeze%& command is ignored if the message has been manually unfrozen and
35350 not manually frozen since. This means that automatic freezing by a system
35351 filter can be used as a way of checking out suspicious messages. If a message
35352 is found to be all right, manually unfreezing it allows it to be delivered.
35354 .cindex "log" "&%fail%& command log line"
35355 .cindex "&%fail%&" "log line; reducing"
35356 The text given with a fail command is used as part of the bounce message as
35357 well as being written to the log. If the message is quite long, this can fill
35358 up a lot of log space when such failures are common. To reduce the size of the
35359 log message, Exim interprets the text in a special way if it starts with the
35360 two characters &`<<`& and contains &`>>`& later. The text between these two
35361 strings is written to the log, and the rest of the text is used in the bounce
35362 message. For example:
35364 fail "<<filter test 1>>Your message is rejected \
35365 because it contains attachments that we are \
35366 not prepared to receive."
35369 .cindex "loop" "caused by &%fail%&"
35370 Take great care with the &%fail%& command when basing the decision to fail on
35371 the contents of the message, because the bounce message will of course include
35372 the contents of the original message and will therefore trigger the &%fail%&
35373 command again (causing a mail loop) unless steps are taken to prevent this.
35374 Testing the &%error_message%& condition is one way to prevent this. You could
35377 if $message_body contains "this is spam" and not error_message
35378 then fail text "spam is not wanted here" endif
35380 though of course that might let through unwanted bounce messages. The
35381 alternative is clever checking of the body and/or headers to detect bounces
35382 generated by the filter.
35384 The interpretation of a system filter file ceases after a
35386 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35387 set up earlier in the filter file are honoured, so you can use a sequence such
35393 to send a specified message when the system filter is freezing (or deferring or
35394 failing) a message. The normal deliveries for the message do not, of course,
35399 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35400 .cindex "header lines" "adding; in system filter"
35401 .cindex "header lines" "removing; in system filter"
35402 .cindex "filter" "header lines; adding/removing"
35403 Two filter commands that are available only in system filters are:
35405 headers add <string>
35406 headers remove <string>
35408 The argument for the &%headers add%& is a string that is expanded and then
35409 added to the end of the message's headers. It is the responsibility of the
35410 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35411 space is ignored, and if the string is otherwise empty, or if the expansion is
35412 forced to fail, the command has no effect.
35414 You can use &"\n"& within the string, followed by white space, to specify
35415 continued header lines. More than one header may be added in one command by
35416 including &"\n"& within the string without any following white space. For
35419 headers add "X-header-1: ....\n \
35420 continuation of X-header-1 ...\n\
35423 Note that the header line continuation white space after the first newline must
35424 be placed before the backslash that continues the input string, because white
35425 space after input continuations is ignored.
35427 The argument for &%headers remove%& is a colon-separated list of header names.
35428 This command applies only to those headers that are stored with the message;
35429 those that are added at delivery time (such as &'Envelope-To:'& and
35430 &'Return-Path:'&) cannot be removed by this means. If there is more than one
35431 header with the same name, they are all removed.
35433 The &%headers%& command in a system filter makes an immediate change to the set
35434 of header lines that was received with the message (with possible additions
35435 from ACL processing). Subsequent commands in the system filter operate on the
35436 modified set, which also forms the basis for subsequent message delivery.
35437 Unless further modified during routing or transporting, this set of headers is
35438 used for all recipients of the message.
35440 During routing and transporting, the variables that refer to the contents of
35441 header lines refer only to those lines that are in this set. Thus, header lines
35442 that are added by a system filter are visible to users' filter files and to all
35443 routers and transports. This contrasts with the manipulation of header lines by
35444 routers and transports, which is not immediate, but which instead is saved up
35445 until the message is actually being written (see section
35446 &<<SECTheadersaddrem>>&).
35448 If the message is not delivered at the first attempt, header lines that were
35449 added by the system filter are stored with the message, and so are still
35450 present at the next delivery attempt. Header lines that were removed are still
35451 present, but marked &"deleted"& so that they are not transported with the
35452 message. For this reason, it is usual to make the &%headers%& command
35453 conditional on &%first_delivery%& so that the set of header lines is not
35454 modified more than once.
35456 Because header modification in a system filter acts immediately, you have to
35457 use an indirect approach if you want to modify the contents of a header line.
35460 headers add "Old-Subject: $h_subject:"
35461 headers remove "Subject"
35462 headers add "Subject: new subject (was: $h_old-subject:)"
35463 headers remove "Old-Subject"
35468 .section "Setting an errors address in a system filter" "SECID217"
35469 .cindex "envelope from"
35470 .cindex "envelope sender"
35471 In a system filter, if a &%deliver%& command is followed by
35473 errors_to <some address>
35475 in order to change the envelope sender (and hence the error reporting) for that
35476 delivery, any address may be specified. (In a user filter, only the current
35477 user's address can be set.) For example, if some mail is being monitored, you
35480 unseen deliver monitor@spying.example errors_to root@local.example
35482 to take a copy which would not be sent back to the normal error reporting
35483 address if its delivery failed.
35487 .section "Per-address filtering" "SECTperaddfil"
35488 .vindex "&$domain_data$&"
35489 .vindex "&$local_part_data$&"
35490 In contrast to the system filter, which is run just once per message for each
35491 delivery attempt, it is also possible to set up a system-wide filtering
35492 operation that runs once for each recipient address. In this case, variables
35493 such as &$local_part_data$& and &$domain_data$& can be used,
35494 and indeed, the choice of filter file could be made dependent on them.
35495 This is an example of a router which implements such a filter:
35500 domains = +local_domains
35501 file = /central/filters/$local_part_data
35506 The filter is run in a separate process under its own uid. Therefore, either
35507 &%check_local_user%& must be set (as above), in which case the filter is run as
35508 the local user, or the &%user%& option must be used to specify which user to
35509 use. If both are set, &%user%& overrides.
35511 Care should be taken to ensure that none of the commands in the filter file
35512 specify a significant delivery if the message is to go on to be delivered to
35513 its intended recipient. The router will not then claim to have dealt with the
35514 address, so it will be passed on to subsequent routers to be delivered in the
35516 .ecindex IIDsysfil1
35517 .ecindex IIDsysfil2
35518 .ecindex IIDsysfil3
35525 . ////////////////////////////////////////////////////////////////////////////
35526 . ////////////////////////////////////////////////////////////////////////////
35528 .chapter "Message processing" "CHAPmsgproc"
35529 .scindex IIDmesproc "message" "general processing"
35530 Exim performs various transformations on the sender and recipient addresses of
35531 all messages that it handles, and also on the messages' header lines. Some of
35532 these are optional and configurable, while others always take place. All of
35533 this processing, except rewriting as a result of routing, and the addition or
35534 removal of header lines while delivering, happens when a message is received,
35535 before it is placed on Exim's queue.
35537 Some of the automatic processing takes place by default only for
35538 &"locally-originated"& messages. This adjective is used to describe messages
35539 that are not received over TCP/IP, but instead are passed to an Exim process on
35540 its standard input. This includes the interactive &"local SMTP"& case that is
35541 set up by the &%-bs%& command line option.
35543 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
35544 or ::1) are not considered to be locally-originated. Exim does not treat the
35545 loopback interface specially in any way.
35547 If you want the loopback interface to be treated specially, you must ensure
35548 that there are appropriate entries in your ACLs.
35553 .section "Submission mode for non-local messages" "SECTsubmodnon"
35554 .cindex "message" "submission"
35555 .cindex "submission mode"
35556 Processing that happens automatically for locally-originated messages (unless
35557 &%suppress_local_fixups%& is set) can also be requested for messages that are
35558 received over TCP/IP. The term &"submission mode"& is used to describe this
35559 state. Submission mode is set by the modifier
35561 control = submission
35563 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
35564 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
35565 a local submission, and is normally used when the source of the message is
35566 known to be an MUA running on a client host (as opposed to an MTA). For
35567 example, to set submission mode for messages originating on the IPv4 loopback
35568 interface, you could include the following in the MAIL ACL:
35570 warn hosts = 127.0.0.1
35571 control = submission
35573 .cindex "&%sender_retain%& submission option"
35574 There are some options that can be used when setting submission mode. A slash
35575 is used to separate options. For example:
35577 control = submission/sender_retain
35579 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
35580 true and &%local_from_check%& false for the current incoming message. The first
35581 of these allows an existing &'Sender:'& header in the message to remain, and
35582 the second suppresses the check to ensure that &'From:'& matches the
35583 authenticated sender. With this setting, Exim still fixes up messages by adding
35584 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
35585 attempt to check sender authenticity in header lines.
35587 When &%sender_retain%& is not set, a submission mode setting may specify a
35588 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
35591 control = submission/domain=some.domain
35593 The domain may be empty. How this value is used is described in sections
35594 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
35595 that allows you to specify the user's full name for inclusion in a created
35596 &'Sender:'& or &'From:'& header line. For example:
35598 accept authenticated = *
35599 control = submission/domain=wonderland.example/\
35600 name=${lookup {$authenticated_id} \
35601 lsearch {/etc/exim/namelist}}
35603 Because the name may contain any characters, including slashes, the &%name%&
35604 option must be given last. The remainder of the string is used as the name. For
35605 the example above, if &_/etc/exim/namelist_& contains:
35607 bigegg: Humpty Dumpty
35609 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
35612 Sender: Humpty Dumpty <bigegg@wonderland.example>
35614 .cindex "return path" "in submission mode"
35615 By default, submission mode forces the return path to the same address as is
35616 used to create the &'Sender:'& header. However, if &%sender_retain%& is
35617 specified, the return path is also left unchanged.
35619 &*Note*&: The changes caused by submission mode take effect after the predata
35620 ACL. This means that any sender checks performed before the fix-ups use the
35621 untrusted sender address specified by the user, not the trusted sender address
35622 specified by submission mode. Although this might be slightly unexpected, it
35623 does mean that you can configure ACL checks to spot that a user is trying to
35624 spoof another's address.
35626 .section "Line endings" "SECTlineendings"
35627 .cindex "line endings"
35628 .cindex "carriage return"
35630 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
35631 linefeed) is the line ending for messages transmitted over the Internet using
35632 SMTP over TCP/IP. However, within individual operating systems, different
35633 conventions are used. For example, Unix-like systems use just LF, but others
35634 use CRLF or just CR.
35636 Exim was designed for Unix-like systems, and internally, it stores messages
35637 using the system's convention of a single LF as a line terminator. When
35638 receiving a message, all line endings are translated to this standard format.
35639 Originally, it was thought that programs that passed messages directly to an
35640 MTA within an operating system would use that system's convention. Experience
35641 has shown that this is not the case; for example, there are Unix applications
35642 that use CRLF in this circumstance. For this reason, and for compatibility with
35643 other MTAs, the way Exim handles line endings for all messages is now as
35647 LF not preceded by CR is treated as a line ending.
35649 CR is treated as a line ending; if it is immediately followed by LF, the LF
35652 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
35653 nor a local message in the state where a line containing only a dot is a
35656 If a bare CR is encountered within a header line, an extra space is added after
35657 the line terminator so as not to end the header line. The reasoning behind this
35658 is that bare CRs in header lines are most likely either to be mistakes, or
35659 people trying to play silly games.
35661 If the first header line received in a message ends with CRLF, a subsequent
35662 bare LF in a header line is treated in the same way as a bare CR in a header
35670 .section "Unqualified addresses" "SECID218"
35671 .cindex "unqualified addresses"
35672 .cindex "address" "qualification"
35673 By default, Exim expects every envelope address it receives from an external
35674 host to be fully qualified. Unqualified addresses cause negative responses to
35675 SMTP commands. However, because SMTP is used as a means of transporting
35676 messages from MUAs running on personal workstations, there is sometimes a
35677 requirement to accept unqualified addresses from specific hosts or IP networks.
35679 Exim has two options that separately control which hosts may send unqualified
35680 sender or recipient addresses in SMTP commands, namely
35681 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
35682 cases, if an unqualified address is accepted, it is qualified by adding the
35683 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
35685 .oindex "&%qualify_domain%&"
35686 .oindex "&%qualify_recipient%&"
35687 Unqualified addresses in header lines are automatically qualified for messages
35688 that are locally originated, unless the &%-bnq%& option is given on the command
35689 line. For messages received over SMTP, unqualified addresses in header lines
35690 are qualified only if unqualified addresses are permitted in SMTP commands. In
35691 other words, such qualification is also controlled by
35692 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
35697 .section "The UUCP From line" "SECID219"
35698 .cindex "&""From""& line"
35699 .cindex "UUCP" "&""From""& line"
35700 .cindex "sender" "address"
35701 .oindex "&%uucp_from_pattern%&"
35702 .oindex "&%uucp_from_sender%&"
35703 .cindex "envelope from"
35704 .cindex "envelope sender"
35705 .cindex "Sendmail compatibility" "&""From""& line"
35706 Messages that have come from UUCP (and some other applications) often begin
35707 with a line containing the envelope sender and a timestamp, following the word
35708 &"From"&. Examples of two common formats are:
35710 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
35711 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
35713 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
35714 Exim recognizes such lines at the start of messages that are submitted to it
35715 via the command line (that is, on the standard input). It does not recognize
35716 such lines in incoming SMTP messages, unless the sending host matches
35717 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
35718 and &%ignore_fromline_local%& is set. The recognition is controlled by a
35719 regular expression that is defined by the &%uucp_from_pattern%& option, whose
35720 default value matches the two common cases shown above and puts the address
35721 that follows &"From"& into &$1$&.
35723 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
35724 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
35725 a trusted user, the message's sender address is constructed by expanding the
35726 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
35727 then parsed as an RFC 2822 address. If there is no domain, the local part is
35728 qualified with &%qualify_domain%& unless it is the empty string. However, if
35729 the command line &%-f%& option is used, it overrides the &"From"& line.
35731 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
35732 sender address is not changed. This is also the case for incoming SMTP messages
35733 that are permitted to contain &"From"& lines.
35735 Only one &"From"& line is recognized. If there is more than one, the second is
35736 treated as a data line that starts the body of the message, as it is not valid
35737 as a header line. This also happens if a &"From"& line is present in an
35738 incoming SMTP message from a source that is not permitted to send them.
35742 .section "Resent- header lines" "SECID220"
35743 .cindex "&%Resent-%& header lines"
35744 .cindex "header lines" "Resent-"
35745 RFC 2822 makes provision for sets of header lines starting with the string
35746 &`Resent-`& to be added to a message when it is resent by the original
35747 recipient to somebody else. These headers are &'Resent-Date:'&,
35748 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
35749 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
35752 &'Resent fields are strictly informational. They MUST NOT be used in the normal
35753 processing of replies or other such automatic actions on messages.'&
35756 This leaves things a bit vague as far as other processing actions such as
35757 address rewriting are concerned. Exim treats &%Resent-%& header lines as
35761 A &'Resent-From:'& line that just contains the login id of the submitting user
35762 is automatically rewritten in the same way as &'From:'& (see below).
35764 If there's a rewriting rule for a particular header line, it is also applied to
35765 &%Resent-%& header lines of the same type. For example, a rule that rewrites
35766 &'From:'& also rewrites &'Resent-From:'&.
35768 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
35771 For a locally-submitted message,
35772 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
35773 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
35774 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
35775 included in log lines in this case.
35777 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
35778 &%Resent-%& header lines are present.
35784 .section "The Auto-Submitted: header line" "SECID221"
35785 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
35786 includes the header line:
35788 Auto-Submitted: auto-replied
35791 .section "The Bcc: header line" "SECID222"
35792 .cindex "&'Bcc:'& header line"
35793 If Exim is called with the &%-t%& option, to take recipient addresses from a
35794 message's header, it removes any &'Bcc:'& header line that may exist (after
35795 extracting its addresses). If &%-t%& is not present on the command line, any
35796 existing &'Bcc:'& is not removed.
35799 .section "The Date: header line" "SECID223"
35800 .cindex "&'Date:'& header line"
35801 .cindex "header lines" "Date:"
35802 If a locally-generated or submission-mode message has no &'Date:'& header line,
35803 Exim adds one, using the current date and time, unless the
35804 &%suppress_local_fixups%& control has been specified.
35806 .section "The Delivery-date: header line" "SECID224"
35807 .cindex "&'Delivery-date:'& header line"
35808 .oindex "&%delivery_date_remove%&"
35809 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
35810 set. Exim can be configured to add them to the final delivery of messages. (See
35811 the generic &%delivery_date_add%& transport option.) They should not be present
35812 in messages in transit. If the &%delivery_date_remove%& configuration option is
35813 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
35817 .section "The Envelope-to: header line" "SECID225"
35818 .cindex "&'Envelope-to:'& header line"
35819 .cindex "header lines" "Envelope-to:"
35820 .oindex "&%envelope_to_remove%&"
35821 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
35822 Exim can be configured to add them to the final delivery of messages. (See the
35823 generic &%envelope_to_add%& transport option.) They should not be present in
35824 messages in transit. If the &%envelope_to_remove%& configuration option is set
35825 (the default), Exim removes &'Envelope-to:'& header lines from incoming
35829 .section "The From: header line" "SECTthefrohea"
35830 .cindex "&'From:'& header line"
35831 .cindex "header lines" "From:"
35832 .cindex "Sendmail compatibility" "&""From""& line"
35833 .cindex "message" "submission"
35834 .cindex "submission mode"
35835 If a submission-mode message does not contain a &'From:'& header line, Exim
35836 adds one if either of the following conditions is true:
35839 The envelope sender address is not empty (that is, this is not a bounce
35840 message). The added header line copies the envelope sender address.
35842 .vindex "&$authenticated_id$&"
35843 The SMTP session is authenticated and &$authenticated_id$& is not empty.
35845 .vindex "&$qualify_domain$&"
35846 If no domain is specified by the submission control, the local part is
35847 &$authenticated_id$& and the domain is &$qualify_domain$&.
35849 If a non-empty domain is specified by the submission control, the local
35850 part is &$authenticated_id$&, and the domain is the specified domain.
35852 If an empty domain is specified by the submission control,
35853 &$authenticated_id$& is assumed to be the complete address.
35857 A non-empty envelope sender takes precedence.
35859 If a locally-generated incoming message does not contain a &'From:'& header
35860 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
35861 containing the sender's address. The calling user's login name and full name
35862 are used to construct the address, as described in section &<<SECTconstr>>&.
35863 They are obtained from the password data by calling &[getpwuid()]& (but see the
35864 &%unknown_login%& configuration option). The address is qualified with
35865 &%qualify_domain%&.
35867 For compatibility with Sendmail, if an incoming, non-SMTP message has a
35868 &'From:'& header line containing just the unqualified login name of the calling
35869 user, this is replaced by an address containing the user's login name and full
35870 name as described in section &<<SECTconstr>>&.
35873 .section "The Message-ID: header line" "SECID226"
35874 .cindex "&'Message-ID:'& header line"
35875 .cindex "header lines" "Message-ID:"
35876 .cindex "message" "submission"
35877 .oindex "&%message_id_header_text%&"
35878 If a locally-generated or submission-mode incoming message does not contain a
35879 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
35880 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
35881 to the message. If there are any &'Resent-:'& headers in the message, it
35882 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
35883 message id, preceded by the letter E to ensure it starts with a letter, and
35884 followed by @ and the primary host name. Additional information can be included
35885 in this header line by setting the &%message_id_header_text%& and/or
35886 &%message_id_header_domain%& options.
35889 .section "The Received: header line" "SECID227"
35890 .cindex "&'Received:'& header line"
35891 .cindex "header lines" "Received:"
35892 A &'Received:'& header line is added at the start of every message. The
35893 contents are defined by the &%received_header_text%& configuration option, and
35894 Exim automatically adds a semicolon and a timestamp to the configured string.
35896 The &'Received:'& header is generated as soon as the message's header lines
35897 have been received. At this stage, the timestamp in the &'Received:'& header
35898 line is the time that the message started to be received. This is the value
35899 that is seen by the DATA ACL and by the &[local_scan()]& function.
35901 Once a message is accepted, the timestamp in the &'Received:'& header line is
35902 changed to the time of acceptance, which is (apart from a small delay while the
35903 -H spool file is written) the earliest time at which delivery could start.
35906 .section "The References: header line" "SECID228"
35907 .cindex "&'References:'& header line"
35908 .cindex "header lines" "References:"
35909 Messages created by the &(autoreply)& transport include a &'References:'&
35910 header line. This is constructed according to the rules that are described in
35911 section 3.64 of RFC 2822 (which states that replies should contain such a
35912 header line), and section 3.14 of RFC 3834 (which states that automatic
35913 responses are not different in this respect). However, because some mail
35914 processing software does not cope well with very long header lines, no more
35915 than 12 message IDs are copied from the &'References:'& header line in the
35916 incoming message. If there are more than 12, the first one and then the final
35917 11 are copied, before adding the message ID of the incoming message.
35921 .section "The Return-path: header line" "SECID229"
35922 .cindex "&'Return-path:'& header line"
35923 .cindex "header lines" "Return-path:"
35924 .oindex "&%return_path_remove%&"
35925 &'Return-path:'& header lines are defined as something an MTA may insert when
35926 it does the final delivery of messages. (See the generic &%return_path_add%&
35927 transport option.) Therefore, they should not be present in messages in
35928 transit. If the &%return_path_remove%& configuration option is set (the
35929 default), Exim removes &'Return-path:'& header lines from incoming messages.
35933 .section "The Sender: header line" "SECTthesenhea"
35934 .cindex "&'Sender:'& header line"
35935 .cindex "message" "submission"
35936 .cindex "header lines" "Sender:"
35937 For a locally-originated message from an untrusted user, Exim may remove an
35938 existing &'Sender:'& header line, and it may add a new one. You can modify
35939 these actions by setting the &%local_sender_retain%& option true, the
35940 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
35943 When a local message is received from an untrusted user and
35944 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
35945 control has not been set, a check is made to see if the address given in the
35946 &'From:'& header line is the correct (local) sender of the message. The address
35947 that is expected has the login name as the local part and the value of
35948 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
35949 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
35950 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
35951 line is added to the message.
35953 If you set &%local_from_check%& false, this checking does not occur. However,
35954 the removal of an existing &'Sender:'& line still happens, unless you also set
35955 &%local_sender_retain%& to be true. It is not possible to set both of these
35956 options true at the same time.
35958 .cindex "submission mode"
35959 By default, no processing of &'Sender:'& header lines is done for messages
35960 received over TCP/IP or for messages submitted by trusted users. However, when
35961 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
35962 not specified on the submission control, the following processing takes place:
35964 .vindex "&$authenticated_id$&"
35965 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
35966 authenticated, and &$authenticated_id$& is not empty, a sender address is
35967 created as follows:
35970 .vindex "&$qualify_domain$&"
35971 If no domain is specified by the submission control, the local part is
35972 &$authenticated_id$& and the domain is &$qualify_domain$&.
35974 If a non-empty domain is specified by the submission control, the local part
35975 is &$authenticated_id$&, and the domain is the specified domain.
35977 If an empty domain is specified by the submission control,
35978 &$authenticated_id$& is assumed to be the complete address.
35981 This address is compared with the address in the &'From:'& header line. If they
35982 are different, a &'Sender:'& header line containing the created address is
35983 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
35984 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
35986 .cindex "return path" "created from &'Sender:'&"
35987 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
35988 the message (the envelope sender address) is changed to be the same address,
35989 except in the case of submission mode when &%sender_retain%& is specified.
35993 .section "Adding and removing header lines in routers and transports" &&&
35994 "SECTheadersaddrem"
35995 .cindex "header lines" "adding; in router or transport"
35996 .cindex "header lines" "removing; in router or transport"
35997 When a message is delivered, the addition and removal of header lines can be
35998 specified in a system filter, or on any of the routers and transports that
35999 process the message. Section &<<SECTaddremheasys>>& contains details about
36000 modifying headers in a system filter. Header lines can also be added in an ACL
36001 as a message is received (see section &<<SECTaddheadacl>>&).
36003 In contrast to what happens in a system filter, header modifications that are
36004 specified on routers and transports apply only to the particular recipient
36005 addresses that are being processed by those routers and transports. These
36006 changes do not actually take place until a copy of the message is being
36007 transported. Therefore, they do not affect the basic set of header lines, and
36008 they do not affect the values of the variables that refer to header lines.
36010 &*Note*&: In particular, this means that any expansions in the configuration of
36011 the transport cannot refer to the modified header lines, because such
36012 expansions all occur before the message is actually transported.
36014 For both routers and transports, the argument of a &%headers_add%&
36015 option must be in the form of one or more RFC 2822 header lines, separated by
36016 newlines (coded as &"\n"&). For example:
36018 headers_add = X-added-header: added by $primary_hostname\n\
36019 X-added-second: another added header line
36021 Exim does not check the syntax of these added header lines.
36023 Multiple &%headers_add%& options for a single router or transport can be
36024 specified; the values will append to a single list of header lines.
36025 Each header-line is separately expanded.
36027 The argument of a &%headers_remove%& option must consist of a colon-separated
36028 list of header names. This is confusing, because header names themselves are
36029 often terminated by colons. In this case, the colons are the list separators,
36030 not part of the names. For example:
36032 headers_remove = return-receipt-to:acknowledge-to
36035 Multiple &%headers_remove%& options for a single router or transport can be
36036 specified; the arguments will append to a single header-names list.
36037 Each item is separately expanded.
36038 Note that colons in complex expansions which are used to
36039 form all or part of a &%headers_remove%& list
36040 will act as list separators.
36042 When &%headers_add%& or &%headers_remove%& is specified on a router,
36043 items are expanded at routing time,
36044 and then associated with all addresses that are
36045 accepted by that router, and also with any new addresses that it generates. If
36046 an address passes through several routers as a result of aliasing or
36047 forwarding, the changes are cumulative.
36049 .oindex "&%unseen%&"
36050 However, this does not apply to multiple routers that result from the use of
36051 the &%unseen%& option. Any header modifications that were specified by the
36052 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36054 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36055 settings cannot be delivered together in a batch, so a transport is always
36056 dealing with a set of addresses that have the same header-processing
36059 The transport starts by writing the original set of header lines that arrived
36060 with the message, possibly modified by the system filter. As it writes out
36061 these lines, it consults the list of header names that were attached to the
36062 recipient address(es) by &%headers_remove%& options in routers, and it also
36063 consults the transport's own &%headers_remove%& option. Header lines whose
36064 names are on either of these lists are not written out. If there are multiple
36065 instances of any listed header, they are all skipped.
36067 After the remaining original header lines have been written, new header
36068 lines that were specified by routers' &%headers_add%& options are written, in
36069 the order in which they were attached to the address. These are followed by any
36070 header lines specified by the transport's &%headers_add%& option.
36072 This way of handling header line modifications in routers and transports has
36073 the following consequences:
36076 The original set of header lines, possibly modified by the system filter,
36077 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36078 to it, at all times.
36080 Header lines that are added by a router's
36081 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36082 expansion syntax in subsequent routers or the transport.
36084 Conversely, header lines that are specified for removal by &%headers_remove%&
36085 in a router remain visible to subsequent routers and the transport.
36087 Headers added to an address by &%headers_add%& in a router cannot be removed by
36088 a later router or by a transport.
36090 An added header can refer to the contents of an original header that is to be
36091 removed, even it has the same name as the added header. For example:
36093 headers_remove = subject
36094 headers_add = Subject: new subject (was: $h_subject:)
36098 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36099 for a &(redirect)& router that has the &%one_time%& option set.
36105 .section "Constructed addresses" "SECTconstr"
36106 .cindex "address" "constructed"
36107 .cindex "constructed address"
36108 When Exim constructs a sender address for a locally-generated message, it uses
36111 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36115 Zaphod Beeblebrox <zaphod@end.univ.example>
36117 The user name is obtained from the &%-F%& command line option if set, or
36118 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36119 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36120 ampersand character, this is replaced by the login name with the first letter
36121 upper cased, as is conventional in a number of operating systems. See the
36122 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36123 The &%unknown_username%& option can be used to specify user names in cases when
36124 there is no password file entry.
36127 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36128 parts of it if necessary. In addition, if it contains any non-printing
36129 characters, it is encoded as described in RFC 2047, which defines a way of
36130 including non-ASCII characters in header lines. The value of the
36131 &%headers_charset%& option specifies the name of the encoding that is used (the
36132 characters are assumed to be in this encoding). The setting of
36133 &%print_topbitchars%& controls whether characters with the top bit set (that
36134 is, with codes greater than 127) count as printing characters or not.
36138 .section "Case of local parts" "SECID230"
36139 .cindex "case of local parts"
36140 .cindex "local part" "case of"
36141 RFC 2822 states that the case of letters in the local parts of addresses cannot
36142 be assumed to be non-significant. Exim preserves the case of local parts of
36143 addresses, but by default it uses a lower-cased form when it is routing,
36144 because on most Unix systems, usernames are in lower case and case-insensitive
36145 routing is required. However, any particular router can be made to use the
36146 original case for local parts by setting the &%caseful_local_part%& generic
36149 .cindex "mixed-case login names"
36150 If you must have mixed-case user names on your system, the best way to proceed,
36151 assuming you want case-independent handling of incoming email, is to set up
36152 your first router to convert incoming local parts in your domains to the
36153 correct case by means of a file lookup. For example:
36157 domains = +local_domains
36158 data = ${lookup{$local_part}cdb\
36159 {/etc/usercased.cdb}{$value}fail}\
36162 For this router, the local part is forced to lower case by the default action
36163 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36164 up a new local part in the correct case. If you then set &%caseful_local_part%&
36165 on any subsequent routers which process your domains, they will operate on
36166 local parts with the correct case in a case-sensitive manner.
36170 .section "Dots in local parts" "SECID231"
36171 .cindex "dot" "in local part"
36172 .cindex "local part" "dots in"
36173 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36174 part may not begin or end with a dot, nor have two consecutive dots in the
36175 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36176 empty components for compatibility.
36180 .section "Rewriting addresses" "SECID232"
36181 .cindex "rewriting" "addresses"
36182 Rewriting of sender and recipient addresses, and addresses in headers, can
36183 happen automatically, or as the result of configuration options, as described
36184 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36185 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36187 Automatic rewriting includes qualification, as mentioned above. The other case
36188 in which it can happen is when an incomplete non-local domain is given. The
36189 routing process may cause this to be expanded into the full domain name. For
36190 example, a header such as
36194 might get rewritten as
36196 To: hare@teaparty.wonderland.fict.example
36198 Rewriting as a result of routing is the one kind of message processing that
36199 does not happen at input time, as it cannot be done until the address has
36202 Strictly, one should not do &'any'& deliveries of a message until all its
36203 addresses have been routed, in case any of the headers get changed as a
36204 result of routing. However, doing this in practice would hold up many
36205 deliveries for unreasonable amounts of time, just because one address could not
36206 immediately be routed. Exim therefore does not delay other deliveries when
36207 routing of one or more addresses is deferred.
36208 .ecindex IIDmesproc
36212 . ////////////////////////////////////////////////////////////////////////////
36213 . ////////////////////////////////////////////////////////////////////////////
36215 .chapter "SMTP processing" "CHAPSMTP"
36216 .scindex IIDsmtpproc1 "SMTP" "processing details"
36217 .scindex IIDsmtpproc2 "LMTP" "processing details"
36218 Exim supports a number of different ways of using the SMTP protocol, and its
36219 LMTP variant, which is an interactive protocol for transferring messages into a
36220 closed mail store application. This chapter contains details of how SMTP is
36221 processed. For incoming mail, the following are available:
36224 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36226 SMTP over the standard input and output (the &%-bs%& option);
36228 Batched SMTP on the standard input (the &%-bS%& option).
36231 For mail delivery, the following are available:
36234 SMTP over TCP/IP (the &(smtp)& transport);
36236 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36239 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36242 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36243 the &%use_bsmtp%& option set).
36246 &'Batched SMTP'& is the name for a process in which batches of messages are
36247 stored in or read from files (or pipes), in a format in which SMTP commands are
36248 used to contain the envelope information.
36252 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36253 .cindex "SMTP" "outgoing over TCP/IP"
36254 .cindex "outgoing SMTP over TCP/IP"
36255 .cindex "LMTP" "over TCP/IP"
36256 .cindex "outgoing LMTP over TCP/IP"
36259 .cindex "SIZE" "option on MAIL command"
36260 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36261 The &%protocol%& option selects which protocol is to be used, but the actual
36262 processing is the same in both cases.
36264 .cindex "ESMTP extensions" SIZE
36265 If, in response to its EHLO command, Exim is told that the SIZE
36266 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36267 command. The value of <&'n'&> is the message size plus the value of the
36268 &%size_addition%& option (default 1024) to allow for additions to the message
36269 such as per-transport header lines, or changes made in a
36270 .cindex "transport" "filter"
36271 .cindex "filter" "transport filter"
36272 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36275 If the remote server advertises support for PIPELINING, Exim uses the
36276 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36277 required for the transaction.
36279 If the remote server advertises support for the STARTTLS command, and Exim
36280 was built to support TLS encryption, it tries to start a TLS session unless the
36281 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36282 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36283 is called for verification.
36285 If the remote server advertises support for the AUTH command, Exim scans
36286 the authenticators configuration for any suitable client settings, as described
36287 in chapter &<<CHAPSMTPAUTH>>&.
36289 .cindex "carriage return"
36291 Responses from the remote host are supposed to be terminated by CR followed by
36292 LF. However, there are known to be hosts that do not send CR characters, so in
36293 order to be able to interwork with such hosts, Exim treats LF on its own as a
36296 If a message contains a number of different addresses, all those with the same
36297 characteristics (for example, the same envelope sender) that resolve to the
36298 same set of hosts, in the same order, are sent in a single SMTP transaction,
36299 even if they are for different domains, unless there are more than the setting
36300 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36301 they are split into groups containing no more than &%max_rcpt%&s addresses
36302 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36303 in parallel sessions. The order of hosts with identical MX values is not
36304 significant when checking whether addresses can be batched in this way.
36306 When the &(smtp)& transport suffers a temporary failure that is not
36307 message-related, Exim updates its transport-specific database, which contains
36308 records indexed by host name that remember which messages are waiting for each
36309 particular host. It also updates the retry database with new retry times.
36311 .cindex "hints database" "retry keys"
36312 Exim's retry hints are based on host name plus IP address, so if one address of
36313 a multi-homed host is broken, it will soon be skipped most of the time.
36314 See the next section for more detail about error handling.
36316 .cindex "SMTP" "passed connection"
36317 .cindex "SMTP" "batching over TCP/IP"
36318 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36319 looks in the hints database for the transport to see if there are any queued
36320 messages waiting for the host to which it is connected. If it finds one, it
36321 creates a new Exim process using the &%-MC%& option (which can only be used by
36322 a process running as root or the Exim user) and passes the TCP/IP socket to it
36323 so that it can deliver another message using the same socket. The new process
36324 does only those deliveries that are routed to the connected host, and may in
36325 turn pass the socket on to a third process, and so on.
36327 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36328 limit the number of messages sent down a single TCP/IP connection.
36330 .cindex "asterisk" "after IP address"
36331 The second and subsequent messages delivered down an existing connection are
36332 identified in the main log by the addition of an asterisk after the closing
36333 square bracket of the IP address.
36338 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36339 .cindex "error" "in outgoing SMTP"
36340 .cindex "SMTP" "errors in outgoing"
36341 .cindex "host" "error"
36342 Three different kinds of error are recognized for outgoing SMTP: host errors,
36343 message errors, and recipient errors.
36346 .vitem "&*Host errors*&"
36347 A host error is not associated with a particular message or with a
36348 particular recipient of a message. The host errors are:
36351 Connection refused or timed out,
36353 Any error response code on connection,
36355 Any error response code to EHLO or HELO,
36357 Loss of connection at any time, except after &"."&,
36359 I/O errors at any time,
36361 Timeouts during the session, other than in response to MAIL, RCPT or
36362 the &"."& at the end of the data.
36365 For a host error, a permanent error response on connection, or in response to
36366 EHLO, causes all addresses routed to the host to be failed. Any other host
36367 error causes all addresses to be deferred, and retry data to be created for the
36368 host. It is not tried again, for any message, until its retry time arrives. If
36369 the current set of addresses are not all delivered in this run (to some
36370 alternative host), the message is added to the list of those waiting for this
36371 host, so if it is still undelivered when a subsequent successful delivery is
36372 made to the host, it will be sent down the same SMTP connection.
36374 .vitem "&*Message errors*&"
36375 .cindex "message" "error"
36376 A message error is associated with a particular message when sent to a
36377 particular host, but not with a particular recipient of the message. The
36378 message errors are:
36381 Any error response code to MAIL, DATA, or the &"."& that terminates
36384 Timeout after MAIL,
36386 Timeout or loss of connection after the &"."& that terminates the data. A
36387 timeout after the DATA command itself is treated as a host error, as is loss of
36388 connection at any other time.
36391 For a message error, a permanent error response (5&'xx'&) causes all addresses
36392 to be failed, and a delivery error report to be returned to the sender. A
36393 temporary error response (4&'xx'&), or one of the timeouts, causes all
36394 addresses to be deferred. Retry data is not created for the host, but instead,
36395 a retry record for the combination of host plus message id is created. The
36396 message is not added to the list of those waiting for this host. This ensures
36397 that the failing message will not be sent to this host again until the retry
36398 time arrives. However, other messages that are routed to the host are not
36399 affected, so if it is some property of the message that is causing the error,
36400 it will not stop the delivery of other mail.
36402 If the remote host specified support for the SIZE parameter in its response
36403 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36404 over-large message will cause a message error because the error arrives as a
36407 .vitem "&*Recipient errors*&"
36408 .cindex "recipient" "error"
36409 A recipient error is associated with a particular recipient of a message. The
36410 recipient errors are:
36413 Any error response to RCPT,
36415 Timeout after RCPT.
36418 For a recipient error, a permanent error response (5&'xx'&) causes the
36419 recipient address to be failed, and a bounce message to be returned to the
36420 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36421 address to be deferred, and routing retry data to be created for it. This is
36422 used to delay processing of the address in subsequent queue runs, until its
36423 routing retry time arrives. This applies to all messages, but because it
36424 operates only in queue runs, one attempt will be made to deliver a new message
36425 to the failing address before the delay starts to operate. This ensures that,
36426 if the failure is really related to the message rather than the recipient
36427 (&"message too big for this recipient"& is a possible example), other messages
36428 have a chance of getting delivered. If a delivery to the address does succeed,
36429 the retry information gets cleared, so all stuck messages get tried again, and
36430 the retry clock is reset.
36432 The message is not added to the list of those waiting for this host. Use of the
36433 host for other messages is unaffected, and except in the case of a timeout,
36434 other recipients are processed independently, and may be successfully delivered
36435 in the current SMTP session. After a timeout it is of course impossible to
36436 proceed with the session, so all addresses get deferred. However, those other
36437 than the one that failed do not suffer any subsequent retry delays. Therefore,
36438 if one recipient is causing trouble, the others have a chance of getting
36439 through when a subsequent delivery attempt occurs before the failing
36440 recipient's retry time.
36443 In all cases, if there are other hosts (or IP addresses) available for the
36444 current set of addresses (for example, from multiple MX records), they are
36445 tried in this run for any undelivered addresses, subject of course to their
36446 own retry data. In other words, recipient error retry data does not take effect
36447 until the next delivery attempt.
36449 Some hosts have been observed to give temporary error responses to every
36450 MAIL command at certain times (&"insufficient space"& has been seen). It
36451 would be nice if such circumstances could be recognized, and defer data for the
36452 host itself created, but this is not possible within the current Exim design.
36453 What actually happens is that retry data for every (host, message) combination
36456 The reason that timeouts after MAIL and RCPT are treated specially is that
36457 these can sometimes arise as a result of the remote host's verification
36458 procedures. Exim makes this assumption, and treats them as if a temporary error
36459 response had been received. A timeout after &"."& is treated specially because
36460 it is known that some broken implementations fail to recognize the end of the
36461 message if the last character of the last line is a binary zero. Thus, it is
36462 helpful to treat this case as a message error.
36464 Timeouts at other times are treated as host errors, assuming a problem with the
36465 host, or the connection to it. If a timeout after MAIL, RCPT,
36466 or &"."& is really a connection problem, the assumption is that at the next try
36467 the timeout is likely to occur at some other point in the dialogue, causing it
36468 then to be treated as a host error.
36470 There is experimental evidence that some MTAs drop the connection after the
36471 terminating &"."& if they do not like the contents of the message for some
36472 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
36473 should be given. That is why Exim treats this case as a message rather than a
36474 host error, in order not to delay other messages to the same host.
36479 .section "Incoming SMTP messages over TCP/IP" "SECID233"
36480 .cindex "SMTP" "incoming over TCP/IP"
36481 .cindex "incoming SMTP over TCP/IP"
36484 Incoming SMTP messages can be accepted in one of two ways: by running a
36485 listening daemon, or by using &'inetd'&. In the latter case, the entry in
36486 &_/etc/inetd.conf_& should be like this:
36488 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
36490 Exim distinguishes between this case and the case of a locally running user
36491 agent using the &%-bs%& option by checking whether or not the standard input is
36492 a socket. When it is, either the port must be privileged (less than 1024), or
36493 the caller must be root or the Exim user. If any other user passes a socket
36494 with an unprivileged port number, Exim prints a message on the standard error
36495 stream and exits with an error code.
36497 By default, Exim does not make a log entry when a remote host connects or
36498 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
36499 unexpected. It can be made to write such log entries by setting the
36500 &%smtp_connection%& log selector.
36502 .cindex "carriage return"
36504 Commands from the remote host are supposed to be terminated by CR followed by
36505 LF. However, there are known to be hosts that do not send CR characters. In
36506 order to be able to interwork with such hosts, Exim treats LF on its own as a
36508 Furthermore, because common code is used for receiving messages from all
36509 sources, a CR on its own is also interpreted as a line terminator. However, the
36510 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
36512 .cindex "EHLO" "invalid data"
36513 .cindex "HELO" "invalid data"
36514 One area that sometimes gives rise to problems concerns the EHLO or
36515 HELO commands. Some clients send syntactically invalid versions of these
36516 commands, which Exim rejects by default. (This is nothing to do with verifying
36517 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
36518 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
36519 match the broken hosts that send invalid commands.
36521 .cindex "SIZE option on MAIL command"
36522 .cindex "MAIL" "SIZE option"
36523 The amount of disk space available is checked whenever SIZE is received on
36524 a MAIL command, independently of whether &%message_size_limit%& or
36525 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
36526 false. A temporary error is given if there is not enough space. If
36527 &%check_spool_space%& is set, the check is for that amount of space plus the
36528 value given with SIZE, that is, it checks that the addition of the incoming
36529 message will not reduce the space below the threshold.
36531 When a message is successfully received, Exim includes the local message id in
36532 its response to the final &"."& that terminates the data. If the remote host
36533 logs this text it can help with tracing what has happened to a message.
36535 The Exim daemon can limit the number of simultaneous incoming connections it is
36536 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
36537 number of simultaneous incoming connections from a single remote host (see the
36538 &%smtp_accept_max_per_host%& option). Additional connection attempts are
36539 rejected using the SMTP temporary error code 421.
36541 The Exim daemon does not rely on the SIGCHLD signal to detect when a
36542 subprocess has finished, as this can get lost at busy times. Instead, it looks
36543 for completed subprocesses every time it wakes up. Provided there are other
36544 things happening (new incoming calls, starts of queue runs), completed
36545 processes will be noticed and tidied away. On very quiet systems you may
36546 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
36547 it will be noticed when the daemon next wakes up.
36549 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
36550 and can also be set up to reject SMTP calls from non-reserved hosts at times of
36551 high system load &-- for details see the &%smtp_accept_reserve%&,
36552 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
36553 applies in both the daemon and &'inetd'& cases.
36555 Exim normally starts a delivery process for each message received, though this
36556 can be varied by means of the &%-odq%& command line option and the
36557 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
36558 number of simultaneously running delivery processes started in this way from
36559 SMTP input can be limited by the &%smtp_accept_queue%& and
36560 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
36561 subsequently received messages are just put on the input queue without starting
36562 a delivery process.
36564 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
36565 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
36566 started up from the &'inetd'& daemon, because in that case each connection is
36567 handled by an entirely independent Exim process. Control by load average is,
36568 however, available with &'inetd'&.
36570 Exim can be configured to verify addresses in incoming SMTP commands as they
36571 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
36572 to rewrite addresses at this time &-- before any syntax checking is done. See
36573 section &<<SECTrewriteS>>&.
36575 Exim can also be configured to limit the rate at which a client host submits
36576 MAIL and RCPT commands in a single SMTP session. See the
36577 &%smtp_ratelimit_hosts%& option.
36581 .section "Unrecognized SMTP commands" "SECID234"
36582 .cindex "SMTP" "unrecognized commands"
36583 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
36584 commands during a single SMTP connection, it drops the connection after sending
36585 the error response to the last command. The default value for
36586 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
36587 abuse that subvert web servers into making connections to SMTP ports; in these
36588 circumstances, a number of non-SMTP lines are sent first.
36591 .section "Syntax and protocol errors in SMTP commands" "SECID235"
36592 .cindex "SMTP" "syntax errors"
36593 .cindex "SMTP" "protocol errors"
36594 A syntax error is detected if an SMTP command is recognized, but there is
36595 something syntactically wrong with its data, for example, a malformed email
36596 address in a RCPT command. Protocol errors include invalid command
36597 sequencing such as RCPT before MAIL. If Exim receives more than
36598 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
36599 drops the connection after sending the error response to the last command. The
36600 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
36601 broken clients that loop sending bad commands (yes, it has been seen).
36605 .section "Use of non-mail SMTP commands" "SECID236"
36606 .cindex "SMTP" "non-mail commands"
36607 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
36608 DATA. Exim counts such commands, and drops the connection if there are too
36609 many of them in a single SMTP session. This action catches some
36610 denial-of-service attempts and things like repeated failing AUTHs, or a mad
36611 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
36612 defines what &"too many"& means. Its default value is 10.
36614 When a new message is expected, one occurrence of RSET is not counted. This
36615 allows a client to send one RSET between messages (this is not necessary,
36616 but some clients do it). Exim also allows one uncounted occurrence of HELO
36617 or EHLO, and one occurrence of STARTTLS between messages. After
36618 starting up a TLS session, another EHLO is expected, and so it too is not
36621 The first occurrence of AUTH in a connection, or immediately following
36622 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
36623 RCPT, DATA, and QUIT are counted.
36625 You can control which hosts are subject to the limit set by
36626 &%smtp_accept_max_nonmail%& by setting
36627 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
36628 the limit apply to all hosts. This option means that you can exclude any
36629 specific badly-behaved hosts that you have to live with.
36634 .section "The VRFY and EXPN commands" "SECID237"
36635 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
36636 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
36637 appropriate) in order to decide whether the command should be accepted or not.
36639 .cindex "VRFY" "processing"
36640 When no ACL is defined for VRFY, or if it rejects without
36641 setting an explicit response code, the command is accepted
36642 (with a 252 SMTP response code)
36643 in order to support awkward clients that do a VRFY before every RCPT.
36644 When VRFY is accepted, it runs exactly the same code as when Exim is
36645 called with the &%-bv%& option, and returns 250/451/550
36646 SMTP response codes.
36648 .cindex "EXPN" "processing"
36649 If no ACL for EXPN is defined, the command is rejected.
36650 When EXPN is accepted, a single-level expansion of the address is done.
36651 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
36652 than a verification (the &%-bv%& option). If an unqualified local part is given
36653 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
36654 of VRFY and EXPN commands are logged on the main and reject logs, and
36655 VRFY verification failures are logged on the main log for consistency with
36660 .section "The ETRN command" "SECTETRN"
36661 .cindex "ETRN" "processing"
36662 .cindex "ESMTP extensions" ETRN
36663 RFC 1985 describes an ESMTP command called ETRN that is designed to
36664 overcome the security problems of the TURN command (which has fallen into
36665 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
36666 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
36667 should be accepted or not. If no ACL is defined, the command is rejected.
36669 The ETRN command is concerned with &"releasing"& messages that are awaiting
36670 delivery to certain hosts. As Exim does not organize its message queue by host,
36671 the only form of ETRN that is supported by default is the one where the
36672 text starts with the &"#"& prefix, in which case the remainder of the text is
36673 specific to the SMTP server. A valid ETRN command causes a run of Exim with
36674 the &%-R%& option to happen, with the remainder of the ETRN text as its
36675 argument. For example,
36683 which causes a delivery attempt on all messages with undelivered addresses
36684 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
36685 default), Exim prevents the simultaneous execution of more than one queue run
36686 for the same argument string as a result of an ETRN command. This stops
36687 a misbehaving client from starting more than one queue runner at once.
36689 .cindex "hints database" "ETRN serialization"
36690 Exim implements the serialization by means of a hints database in which a
36691 record is written whenever a process is started by ETRN, and deleted when
36692 the process completes. However, Exim does not keep the SMTP session waiting for
36693 the ETRN process to complete. Once ETRN is accepted, the client is sent
36694 a &"success"& return code. Obviously there is scope for hints records to get
36695 left lying around if there is a system or program crash. To guard against this,
36696 Exim ignores any records that are more than six hours old.
36698 .oindex "&%smtp_etrn_command%&"
36699 For more control over what ETRN does, the &%smtp_etrn_command%& option can
36700 used. This specifies a command that is run whenever ETRN is received,
36701 whatever the form of its argument. For
36704 smtp_etrn_command = /etc/etrn_command $domain \
36705 $sender_host_address
36707 .vindex "&$domain$&"
36708 The string is split up into arguments which are independently expanded. The
36709 expansion variable &$domain$& is set to the argument of the ETRN command,
36710 and no syntax checking is done on the contents of this argument. Exim does not
36711 wait for the command to complete, so its status code is not checked. Exim runs
36712 under its own uid and gid when receiving incoming SMTP, so it is not possible
36713 for it to change them before running the command.
36717 .section "Incoming local SMTP" "SECID238"
36718 .cindex "SMTP" "local incoming"
36719 Some user agents use SMTP to pass messages to their local MTA using the
36720 standard input and output, as opposed to passing the envelope on the command
36721 line and writing the message to the standard input. This is supported by the
36722 &%-bs%& option. This form of SMTP is handled in the same way as incoming
36723 messages over TCP/IP (including the use of ACLs), except that the envelope
36724 sender given in a MAIL command is ignored unless the caller is trusted. In
36725 an ACL you can detect this form of SMTP input by testing for an empty host
36726 identification. It is common to have this as the first line in the ACL that
36727 runs for RCPT commands:
36731 This accepts SMTP messages from local processes without doing any other tests.
36735 .section "Outgoing batched SMTP" "SECTbatchSMTP"
36736 .cindex "SMTP" "batched outgoing"
36737 .cindex "batched SMTP output"
36738 Both the &(appendfile)& and &(pipe)& transports can be used for handling
36739 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
36740 be output in BSMTP format. No SMTP responses are possible for this form of
36741 delivery. All it is doing is using SMTP commands as a way of transmitting the
36742 envelope along with the message.
36744 The message is written to the file or pipe preceded by the SMTP commands
36745 MAIL and RCPT, and followed by a line containing a single dot. Lines in
36746 the message that start with a dot have an extra dot added. The SMTP command
36747 HELO is not normally used. If it is required, the &%message_prefix%& option
36748 can be used to specify it.
36750 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
36751 one recipient address at a time by default. However, you can arrange for them
36752 to handle several addresses at once by setting the &%batch_max%& option. When
36753 this is done for BSMTP, messages may contain multiple RCPT commands. See
36754 chapter &<<CHAPbatching>>& for more details.
36757 When one or more addresses are routed to a BSMTP transport by a router that
36758 sets up a host list, the name of the first host on the list is available to the
36759 transport in the variable &$host$&. Here is an example of such a transport and
36764 driver = manualroute
36765 transport = smtp_appendfile
36766 route_list = domain.example batch.host.example
36770 driver = appendfile
36771 directory = /var/bsmtp/$host
36776 This causes messages addressed to &'domain.example'& to be written in BSMTP
36777 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
36778 message (unless there are more than 1000 recipients).
36782 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
36783 .cindex "SMTP" "batched incoming"
36784 .cindex "batched SMTP input"
36785 The &%-bS%& command line option causes Exim to accept one or more messages by
36786 reading SMTP on the standard input, but to generate no responses. If the caller
36787 is trusted, the senders in the MAIL commands are believed; otherwise the
36788 sender is always the caller of Exim. Unqualified senders and receivers are not
36789 rejected (there seems little point) but instead just get qualified. HELO
36790 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
36791 as NOOP; QUIT quits.
36793 Minimal policy checking is done for BSMTP input. Only the non-SMTP
36794 ACL is run in the same way as for non-SMTP local input.
36796 If an error is detected while reading a message, including a missing &"."& at
36797 the end, Exim gives up immediately. It writes details of the error to the
36798 standard output in a stylized way that the calling program should be able to
36799 make some use of automatically, for example:
36801 554 Unexpected end of file
36802 Transaction started in line 10
36803 Error detected in line 14
36805 It writes a more verbose version, for human consumption, to the standard error
36808 An error was detected while processing a file of BSMTP input.
36809 The error message was:
36811 501 '>' missing at end of address
36813 The SMTP transaction started in line 10.
36814 The error was detected in line 12.
36815 The SMTP command at fault was:
36817 rcpt to:<malformed@in.com.plete
36819 1 previous message was successfully processed.
36820 The rest of the batch was abandoned.
36822 The return code from Exim is zero only if there were no errors. It is 1 if some
36823 messages were accepted before an error was detected, and 2 if no messages were
36825 .ecindex IIDsmtpproc1
36826 .ecindex IIDsmtpproc2
36830 . ////////////////////////////////////////////////////////////////////////////
36831 . ////////////////////////////////////////////////////////////////////////////
36833 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
36834 "Customizing messages"
36835 When a message fails to be delivered, or remains in the queue for more than a
36836 configured amount of time, Exim sends a message to the original sender, or
36837 to an alternative configured address. The text of these messages is built into
36838 the code of Exim, but it is possible to change it, either by adding a single
36839 string, or by replacing each of the paragraphs by text supplied in a file.
36841 The &'From:'& and &'To:'& header lines are automatically generated; you can
36842 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
36843 option. Exim also adds the line
36845 Auto-Submitted: auto-generated
36847 to all warning and bounce messages,
36850 .section "Customizing bounce messages" "SECID239"
36851 .cindex "customizing" "bounce message"
36852 .cindex "bounce message" "customizing"
36853 If &%bounce_message_text%& is set, its contents are included in the default
36854 message immediately after &"This message was created automatically by mail
36855 delivery software."& The string is not expanded. It is not used if
36856 &%bounce_message_file%& is set.
36858 When &%bounce_message_file%& is set, it must point to a template file for
36859 constructing error messages. The file consists of a series of text items,
36860 separated by lines consisting of exactly four asterisks. If the file cannot be
36861 opened, default text is used and a message is written to the main and panic
36862 logs. If any text item in the file is empty, default text is used for that
36865 .vindex "&$bounce_recipient$&"
36866 .vindex "&$bounce_return_size_limit$&"
36867 Each item of text that is read from the file is expanded, and there are two
36868 expansion variables which can be of use here: &$bounce_recipient$& is set to
36869 the recipient of an error message while it is being created, and
36870 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
36871 option, rounded to a whole number.
36873 The items must appear in the file in the following order:
36876 The first item is included in the headers, and should include at least a
36877 &'Subject:'& header. Exim does not check the syntax of these headers.
36879 The second item forms the start of the error message. After it, Exim lists the
36880 failing addresses with their error messages.
36882 The third item is used to introduce any text from pipe transports that is to be
36883 returned to the sender. It is omitted if there is no such text.
36885 The fourth, fifth and sixth items will be ignored and may be empty.
36886 The fields exist for back-compatibility
36889 The default state (&%bounce_message_file%& unset) is equivalent to the
36890 following file, in which the sixth item is empty. The &'Subject:'& and some
36891 other lines have been split in order to fit them on the page:
36893 Subject: Mail delivery failed
36894 ${if eq{$sender_address}{$bounce_recipient}
36895 {: returning message to sender}}
36897 This message was created automatically by mail delivery software.
36899 A message ${if eq{$sender_address}{$bounce_recipient}
36900 {that you sent }{sent by
36904 }}could not be delivered to all of its recipients.
36905 This is a permanent error. The following address(es) failed:
36907 The following text was generated during the delivery attempt(s):
36909 ------ This is a copy of the message, including all the headers.
36912 ------ The body of the message is $message_size characters long;
36914 ------ $bounce_return_size_limit or so are included here.
36917 .section "Customizing warning messages" "SECTcustwarn"
36918 .cindex "customizing" "warning message"
36919 .cindex "warning of delay" "customizing the message"
36920 The option &%warn_message_file%& can be pointed at a template file for use when
36921 warnings about message delays are created. In this case there are only three
36925 The first item is included in the headers, and should include at least a
36926 &'Subject:'& header. Exim does not check the syntax of these headers.
36928 The second item forms the start of the warning message. After it, Exim lists
36929 the delayed addresses.
36931 The third item then ends the message.
36934 The default state is equivalent to the following file, except that some lines
36935 have been split here, in order to fit them on the page:
36937 Subject: Warning: message $message_exim_id delayed
36938 $warn_message_delay
36940 This message was created automatically by mail delivery software.
36942 A message ${if eq{$sender_address}{$warn_message_recipients}
36943 {that you sent }{sent by
36947 }}has not been delivered to all of its recipients after
36948 more than $warn_message_delay in the queue on $primary_hostname.
36950 The message identifier is: $message_exim_id
36951 The subject of the message is: $h_subject
36952 The date of the message is: $h_date
36954 The following address(es) have not yet been delivered:
36956 No action is required on your part. Delivery attempts will
36957 continue for some time, and this warning may be repeated at
36958 intervals if the message remains undelivered. Eventually the
36959 mail delivery software will give up, and when that happens,
36960 the message will be returned to you.
36962 .vindex "&$warn_message_delay$&"
36963 .vindex "&$warn_message_recipients$&"
36964 However, in the default state the subject and date lines are omitted if no
36965 appropriate headers exist. During the expansion of this file,
36966 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
36967 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
36968 of recipients for the warning message. There may be more than one if there are
36969 multiple addresses with different &%errors_to%& settings on the routers that
36975 . ////////////////////////////////////////////////////////////////////////////
36976 . ////////////////////////////////////////////////////////////////////////////
36978 .chapter "Some common configuration settings" "CHAPcomconreq"
36979 This chapter discusses some configuration settings that seem to be fairly
36980 common. More examples and discussion can be found in the Exim book.
36984 .section "Sending mail to a smart host" "SECID240"
36985 .cindex "smart host" "example router"
36986 If you want to send all mail for non-local domains to a &"smart host"&, you
36987 should replace the default &(dnslookup)& router with a router which does the
36988 routing explicitly:
36990 send_to_smart_host:
36991 driver = manualroute
36992 route_list = !+local_domains smart.host.name
36993 transport = remote_smtp
36995 You can use the smart host's IP address instead of the name if you wish.
36996 If you are using Exim only to submit messages to a smart host, and not for
36997 receiving incoming messages, you can arrange for it to do the submission
36998 synchronously by setting the &%mua_wrapper%& option (see chapter
36999 &<<CHAPnonqueueing>>&).
37004 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37005 .cindex "mailing lists"
37006 Exim can be used to run simple mailing lists, but for large and/or complicated
37007 requirements, the use of additional specialized mailing list software such as
37008 Majordomo or Mailman is recommended.
37010 The &(redirect)& router can be used to handle mailing lists where each list
37011 is maintained in a separate file, which can therefore be managed by an
37012 independent manager. The &%domains%& router option can be used to run these
37013 lists in a separate domain from normal mail. For example:
37017 domains = lists.example
37018 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37021 errors_to = ${quote_local_part:$local_part-request}@lists.example
37024 This router is skipped for domains other than &'lists.example'&. For addresses
37025 in that domain, it looks for a file that matches the local part. If there is no
37026 such file, the router declines, but because &%no_more%& is set, no subsequent
37027 routers are tried, and so the whole delivery fails.
37029 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37030 expanded into a filename or a pipe delivery, which is usually inappropriate in
37033 .oindex "&%errors_to%&"
37034 The &%errors_to%& option specifies that any delivery errors caused by addresses
37035 taken from a mailing list are to be sent to the given address rather than the
37036 original sender of the message. However, before acting on this, Exim verifies
37037 the error address, and ignores it if verification fails.
37039 For example, using the configuration above, mail sent to
37040 &'dicts@lists.example'& is passed on to those addresses contained in
37041 &_/usr/lists/dicts_&, with error reports directed to
37042 &'dicts-request@lists.example'&, provided that this address can be verified.
37043 There could be a file called &_/usr/lists/dicts-request_& containing
37044 the address(es) of this particular list's manager(s), but other approaches,
37045 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37046 or &%local_part_suffix%& options) to handle addresses of the form
37047 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37051 .section "Syntax errors in mailing lists" "SECID241"
37052 .cindex "mailing lists" "syntax errors in"
37053 If an entry in redirection data contains a syntax error, Exim normally defers
37054 delivery of the original address. That means that a syntax error in a mailing
37055 list holds up all deliveries to the list. This may not be appropriate when a
37056 list is being maintained automatically from data supplied by users, and the
37057 addresses are not rigorously checked.
37059 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37060 entries that fail to parse, noting the incident in the log. If in addition
37061 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37062 whenever a broken address is skipped. It is usually appropriate to set
37063 &%syntax_errors_to%& to the same address as &%errors_to%&.
37067 .section "Re-expansion of mailing lists" "SECID242"
37068 .cindex "mailing lists" "re-expansion of"
37069 Exim remembers every individual address to which a message has been delivered,
37070 in order to avoid duplication, but it normally stores only the original
37071 recipient addresses with a message. If all the deliveries to a mailing list
37072 cannot be done at the first attempt, the mailing list is re-expanded when the
37073 delivery is next tried. This means that alterations to the list are taken into
37074 account at each delivery attempt, so addresses that have been added to
37075 the list since the message arrived will therefore receive a copy of the
37076 message, even though it pre-dates their subscription.
37078 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37079 on the &(redirect)& router. If this is done, any addresses generated by the
37080 router that fail to deliver at the first attempt are added to the message as
37081 &"top level"& addresses, and the parent address that generated them is marked
37082 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37083 subsequent delivery attempts. The disadvantage of this is that if any of the
37084 failing addresses are incorrect, correcting them in the file has no effect on
37085 pre-existing messages.
37087 The original top-level address is remembered with each of the generated
37088 addresses, and is output in any log messages. However, any intermediate parent
37089 addresses are not recorded. This makes a difference to the log only if the
37090 &%all_parents%& selector is set, but for mailing lists there is normally only
37091 one level of expansion anyway.
37095 .section "Closed mailing lists" "SECID243"
37096 .cindex "mailing lists" "closed"
37097 The examples so far have assumed open mailing lists, to which anybody may
37098 send mail. It is also possible to set up closed lists, where mail is accepted
37099 from specified senders only. This is done by making use of the generic
37100 &%senders%& option to restrict the router that handles the list.
37102 The following example uses the same file as a list of recipients and as a list
37103 of permitted senders. It requires three routers:
37107 domains = lists.example
37108 local_part_suffix = -request
37109 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37110 file = /usr/lists/${local_part_data}-request
37115 domains = lists.example
37116 senders = ${if exists {/usr/lists/$local_part}\
37117 {lsearch;/usr/lists/$local_part}{*}}
37118 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37121 errors_to = ${quote_local_part:$local_part-request}@lists.example
37126 domains = lists.example
37128 data = :fail: $local_part@lists.example is a closed mailing list
37130 All three routers have the same &%domains%& setting, so for any other domains,
37131 they are all skipped. The first router runs only if the local part ends in
37132 &%-request%&. It handles messages to the list manager(s) by means of an open
37135 The second router runs only if the &%senders%& precondition is satisfied. It
37136 checks for the existence of a list that corresponds to the local part, and then
37137 checks that the sender is on the list by means of a linear search. It is
37138 necessary to check for the existence of the file before trying to search it,
37139 because otherwise Exim thinks there is a configuration error. If the file does
37140 not exist, the expansion of &%senders%& is *, which matches all senders. This
37141 means that the router runs, but because there is no list, declines, and
37142 &%no_more%& ensures that no further routers are run. The address fails with an
37143 &"unrouteable address"& error.
37145 The third router runs only if the second router is skipped, which happens when
37146 a mailing list exists, but the sender is not on it. This router forcibly fails
37147 the address, giving a suitable error message.
37152 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37154 .cindex "Variable Envelope Return Paths"
37155 .cindex "envelope from"
37156 .cindex "envelope sender"
37157 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37158 are a way of helping mailing list administrators discover which subscription
37159 address is the cause of a particular delivery failure. The idea is to encode
37160 the original recipient address in the outgoing envelope sender address, so that
37161 if the message is forwarded by another host and then subsequently bounces, the
37162 original recipient can be extracted from the recipient address of the bounce.
37164 .oindex &%errors_to%&
37165 .oindex &%return_path%&
37166 Envelope sender addresses can be modified by Exim using two different
37167 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37168 list examples), or the &%return_path%& option on a transport. The second of
37169 these is effective only if the message is successfully delivered to another
37170 host; it is not used for errors detected on the local host (see the description
37171 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37172 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37178 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37179 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37181 This has the effect of rewriting the return path (envelope sender) on outgoing
37182 SMTP messages, if the local part of the original return path ends in
37183 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37184 local part and domain of the recipient into the return path. Suppose, for
37185 example, that a message whose return path has been set to
37186 &'somelist-request@your.dom.example'& is sent to
37187 &'subscriber@other.dom.example'&. In the transport, the return path is
37190 somelist-request+subscriber=other.dom.example@your.dom.example
37192 .vindex "&$local_part$&"
37193 For this to work, you must tell Exim to send multiple copies of messages that
37194 have more than one recipient, so that each copy has just one recipient. This is
37195 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37196 might be sent to several different recipients in the same domain, in which case
37197 &$local_part$& is not available in the transport, because it is not unique.
37199 Unless your host is doing nothing but mailing list deliveries, you should
37200 probably use a separate transport for the VERP deliveries, so as not to use
37201 extra resources in making one-per-recipient copies for other deliveries. This
37202 can easily be done by expanding the &%transport%& option in the router:
37206 domains = ! +local_domains
37208 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37209 {verp_smtp}{remote_smtp}}
37212 If you want to change the return path using &%errors_to%& in a router instead
37213 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37214 routers that handle mailing list addresses. This will ensure that all delivery
37215 errors, including those detected on the local host, are sent to the VERP
37218 On a host that does no local deliveries and has no manual routing, only the
37219 &(dnslookup)& router needs to be changed. A special transport is not needed for
37220 SMTP deliveries. Every mailing list recipient has its own return path value,
37221 and so Exim must hand them to the transport one at a time. Here is an example
37222 of a &(dnslookup)& router that implements VERP:
37226 domains = ! +local_domains
37227 transport = remote_smtp
37229 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37230 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37233 Before you start sending out messages with VERPed return paths, you must also
37234 configure Exim to accept the bounce messages that come back to those paths.
37235 Typically this is done by setting a &%local_part_suffix%& option for a
37236 router, and using this to route the messages to wherever you want to handle
37239 The overhead incurred in using VERP depends very much on the size of the
37240 message, the number of recipient addresses that resolve to the same remote
37241 host, and the speed of the connection over which the message is being sent. If
37242 a lot of addresses resolve to the same host and the connection is slow, sending
37243 a separate copy of the message for each address may take substantially longer
37244 than sending a single copy with many recipients (for which VERP cannot be
37252 .section "Virtual domains" "SECTvirtualdomains"
37253 .cindex "virtual domains"
37254 .cindex "domain" "virtual"
37255 The phrase &'virtual domain'& is unfortunately used with two rather different
37259 A domain for which there are no real mailboxes; all valid local parts are
37260 aliases for other email addresses. Common examples are organizational
37261 top-level domains and &"vanity"& domains.
37263 One of a number of independent domains that are all handled by the same host,
37264 with mailboxes on that host, but where the mailbox owners do not necessarily
37265 have login accounts on that host.
37268 The first usage is probably more common, and does seem more &"virtual"& than
37269 the second. This kind of domain can be handled in Exim with a straightforward
37270 aliasing router. One approach is to create a separate alias file for each
37271 virtual domain. Exim can test for the existence of the alias file to determine
37272 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37273 to a router of this form:
37277 domains = dsearch;/etc/mail/virtual
37278 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37281 The &%domains%& option specifies that the router is to be skipped, unless there
37282 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37283 domain that is being processed.
37284 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37285 being placed into the &$domain_data$& variable.
37287 When the router runs, it looks up the local
37288 part in the file to find a new address (or list of addresses). The &%no_more%&
37289 setting ensures that if the lookup fails (leading to &%data%& being an empty
37290 string), Exim gives up on the address without trying any subsequent routers.
37292 This one router can handle all the virtual domains because the alias filenames
37293 follow a fixed pattern. Permissions can be arranged so that appropriate people
37294 can edit the different alias files. A successful aliasing operation results in
37295 a new envelope recipient address, which is then routed from scratch.
37297 The other kind of &"virtual"& domain can also be handled in a straightforward
37298 way. One approach is to create a file for each domain containing a list of
37299 valid local parts, and use it in a router like this:
37303 domains = dsearch;/etc/mail/domains
37304 local_parts = lsearch;/etc/mail/domains/$domain
37305 transport = my_mailboxes
37307 The address is accepted if there is a file for the domain, and the local part
37308 can be found in the file. The &%domains%& option is used to check for the
37309 file's existence because &%domains%& is tested before the &%local_parts%&
37310 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37311 because that option is tested after &%local_parts%&. The transport is as
37315 driver = appendfile
37316 file = /var/mail/$domain_data/$local_part_data
37319 This uses a directory of mailboxes for each domain. The &%user%& setting is
37320 required, to specify which uid is to be used for writing to the mailboxes.
37322 The configuration shown here is just one example of how you might support this
37323 requirement. There are many other ways this kind of configuration can be set
37324 up, for example, by using a database instead of separate files to hold all the
37325 information about the domains.
37329 .section "Multiple user mailboxes" "SECTmulbox"
37330 .cindex "multiple mailboxes"
37331 .cindex "mailbox" "multiple"
37332 .cindex "local part" "prefix"
37333 .cindex "local part" "suffix"
37334 Heavy email users often want to operate with multiple mailboxes, into which
37335 incoming mail is automatically sorted. A popular way of handling this is to
37336 allow users to use multiple sender addresses, so that replies can easily be
37337 identified. Users are permitted to add prefixes or suffixes to their local
37338 parts for this purpose. The wildcard facility of the generic router options
37339 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37340 example, consider this router:
37345 file = $home/.forward
37346 local_part_suffix = -*
37347 local_part_suffix_optional
37350 .vindex "&$local_part_suffix$&"
37351 It runs a user's &_.forward_& file for all local parts of the form
37352 &'username-*'&. Within the filter file the user can distinguish different
37353 cases by testing the variable &$local_part_suffix$&. For example:
37355 if $local_part_suffix contains -special then
37356 save /home/$local_part_data/Mail/special
37359 If the filter file does not exist, or does not deal with such addresses, they
37360 fall through to subsequent routers, and, assuming no subsequent use of the
37361 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37362 control over which suffixes are valid.
37364 Alternatively, a suffix can be used to trigger the use of a different
37365 &_.forward_& file &-- which is the way a similar facility is implemented in
37371 local_part_suffix = -*
37372 local_part_suffix_optional
37373 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37376 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37377 example, &_.forward-special_& is used. Once again, if the appropriate file
37378 does not exist, or does not deal with the address, it is passed on to
37379 subsequent routers, which could, if required, look for an unqualified
37380 &_.forward_& file to use as a default.
37384 .section "Simplified vacation processing" "SECID244"
37385 .cindex "vacation processing"
37386 The traditional way of running the &'vacation'& program is for a user to set up
37387 a pipe command in a &_.forward_& file
37388 (see section &<<SECTspecitredli>>& for syntax details).
37389 This is prone to error by inexperienced users. There are two features of Exim
37390 that can be used to make this process simpler for users:
37393 A local part prefix such as &"vacation-"& can be specified on a router which
37394 can cause the message to be delivered directly to the &'vacation'& program, or
37395 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37396 &_.forward_& file are then much simpler. For example:
37398 spqr, vacation-spqr
37401 The &%require_files%& generic router option can be used to trigger a
37402 vacation delivery by checking for the existence of a certain file in the
37403 user's home directory. The &%unseen%& generic option should also be used, to
37404 ensure that the original delivery also proceeds. In this case, all the user has
37405 to do is to create a file called, say, &_.vacation_&, containing a vacation
37409 Another advantage of both these methods is that they both work even when the
37410 use of arbitrary pipes by users is locked out.
37414 .section "Taking copies of mail" "SECID245"
37415 .cindex "message" "copying every"
37416 Some installations have policies that require archive copies of all messages to
37417 be made. A single copy of each message can easily be taken by an appropriate
37418 command in a system filter, which could, for example, use a different file for
37419 each day's messages.
37421 There is also a shadow transport mechanism that can be used to take copies of
37422 messages that are successfully delivered by local transports, one copy per
37423 delivery. This could be used, &'inter alia'&, to implement automatic
37424 notification of delivery by sites that insist on doing such things.
37428 .section "Intermittently connected hosts" "SECID246"
37429 .cindex "intermittently connected hosts"
37430 It has become quite common (because it is cheaper) for hosts to connect to the
37431 Internet periodically rather than remain connected all the time. The normal
37432 arrangement is that mail for such hosts accumulates on a system that is
37433 permanently connected.
37435 Exim was designed for use on permanently connected hosts, and so it is not
37436 particularly well-suited to use in an intermittently connected environment.
37437 Nevertheless there are some features that can be used.
37440 .section "Exim on the upstream server host" "SECID247"
37441 It is tempting to arrange for incoming mail for the intermittently connected
37442 host to remain in Exim's queue until the client connects. However, this
37443 approach does not scale very well. Two different kinds of waiting message are
37444 being mixed up in the same queue &-- those that cannot be delivered because of
37445 some temporary problem, and those that are waiting for their destination host
37446 to connect. This makes it hard to manage the queue, as well as wasting
37447 resources, because each queue runner scans the entire queue.
37449 A better approach is to separate off those messages that are waiting for an
37450 intermittently connected host. This can be done by delivering these messages
37451 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
37452 format, from where they are transmitted by other software when their
37453 destination connects. This makes it easy to collect all the mail for one host
37454 in a single directory, and to apply local timeout rules on a per-message basis
37457 On a very small scale, leaving the mail on Exim's queue can be made to work. If
37458 you are doing this, you should configure Exim with a long retry period for the
37459 intermittent host. For example:
37461 cheshire.wonderland.fict.example * F,5d,24h
37463 This stops a lot of failed delivery attempts from occurring, but Exim remembers
37464 which messages it has queued up for that host. Once the intermittent host comes
37465 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
37466 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
37467 causes all the queued up messages to be delivered, often down a single SMTP
37468 connection. While the host remains connected, any new messages get delivered
37471 If the connecting hosts do not have fixed IP addresses, that is, if a host is
37472 issued with a different IP address each time it connects, Exim's retry
37473 mechanisms on the holding host get confused, because the IP address is normally
37474 used as part of the key string for holding retry information. This can be
37475 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
37476 Since this has disadvantages for permanently connected hosts, it is best to
37477 arrange a separate transport for the intermittently connected ones.
37481 .section "Exim on the intermittently connected client host" "SECID248"
37482 The value of &%smtp_accept_queue_per_connection%& should probably be
37483 increased, or even set to zero (that is, disabled) on the intermittently
37484 connected host, so that all incoming messages down a single connection get
37485 delivered immediately.
37487 .cindex "SMTP" "passed connection"
37488 .cindex "SMTP" "multiple deliveries"
37489 .cindex "multiple SMTP deliveries"
37490 .cindex "first pass routing"
37491 Mail waiting to be sent from an intermittently connected host will probably
37492 not have been routed, because without a connection DNS lookups are not
37493 possible. This means that if a normal queue run is done at connection time,
37494 each message is likely to be sent in a separate SMTP session. This can be
37495 avoided by starting the queue run with a command line option beginning with
37496 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
37497 first pass, routing is done but no deliveries take place. The second pass is a
37498 normal queue run; since all the messages have been previously routed, those
37499 destined for the same host are likely to get sent as multiple deliveries in a
37500 single SMTP connection.
37504 . ////////////////////////////////////////////////////////////////////////////
37505 . ////////////////////////////////////////////////////////////////////////////
37507 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
37508 "Exim as a non-queueing client"
37509 .cindex "client, non-queueing"
37510 .cindex "smart host" "suppressing queueing"
37511 On a personal computer, it is a common requirement for all
37512 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
37513 configured to operate that way, for all the popular operating systems.
37514 However, there are some MUAs for Unix-like systems that cannot be so
37515 configured: they submit messages using the command line interface of
37516 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
37519 If the personal computer runs continuously, there is no problem, because it can
37520 run a conventional MTA that handles delivery to the smart host, and deal with
37521 any delays via its queueing mechanism. However, if the computer does not run
37522 continuously or runs different operating systems at different times, queueing
37523 email is not desirable.
37525 There is therefore a requirement for something that can provide the
37526 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
37527 any queueing or retrying facilities. Furthermore, the delivery to the smart
37528 host should be synchronous, so that if it fails, the sending MUA is immediately
37529 informed. In other words, we want something that extends an MUA that submits
37530 to a local MTA via the command line so that it behaves like one that submits
37531 to a remote smart host using TCP/SMTP.
37533 There are a number of applications (for example, there is one called &'ssmtp'&)
37534 that do this job. However, people have found them to be lacking in various
37535 ways. For instance, you might want to allow aliasing and forwarding to be done
37536 before sending a message to the smart host.
37538 Exim already had the necessary infrastructure for doing this job. Just a few
37539 tweaks were needed to make it behave as required, though it is somewhat of an
37540 overkill to use a fully-featured MTA for this purpose.
37542 .oindex "&%mua_wrapper%&"
37543 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
37544 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
37545 assumes that it is being used to &"wrap"& a command-line MUA in the manner
37546 just described. As well as setting &%mua_wrapper%&, you also need to provide a
37547 compatible router and transport configuration. Typically there will be just one
37548 router and one transport, sending everything to a smart host.
37550 When run in MUA wrapping mode, the behaviour of Exim changes in the
37554 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
37555 In other words, the only way to submit messages is via the command line.
37557 Each message is synchronously delivered as soon as it is received (&%-odi%& is
37558 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
37559 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
37560 does not finish until the delivery attempt is complete. If the delivery is
37561 successful, a zero return code is given.
37563 Address redirection is permitted, but the final routing for all addresses must
37564 be to the same remote transport, and to the same list of hosts. Furthermore,
37565 the return address (envelope sender) must be the same for all recipients, as
37566 must any added or deleted header lines. In other words, it must be possible to
37567 deliver the message in a single SMTP transaction, however many recipients there
37570 If these conditions are not met, or if routing any address results in a
37571 failure or defer status, or if Exim is unable to deliver all the recipients
37572 successfully to one of the smart hosts, delivery of the entire message fails.
37574 Because no queueing is allowed, all failures are treated as permanent; there
37575 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
37576 smart host. Furthermore, because only a single yes/no response can be given to
37577 the caller, it is not possible to deliver to some recipients and not others. If
37578 there is an error (temporary or permanent) for any recipient, all are failed.
37580 If more than one smart host is listed, Exim will try another host after a
37581 connection failure or a timeout, in the normal way. However, if this kind of
37582 failure happens for all the hosts, the delivery fails.
37584 When delivery fails, an error message is written to the standard error stream
37585 (as well as to Exim's log), and Exim exits to the caller with a return code
37586 value 1. The message is expunged from Exim's spool files. No bounce messages
37587 are ever generated.
37589 No retry data is maintained, and any retry rules are ignored.
37591 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
37592 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
37593 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
37596 The overall effect is that Exim makes a single synchronous attempt to deliver
37597 the message, failing if there is any kind of problem. Because no local
37598 deliveries are done and no daemon can be run, Exim does not need root
37599 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
37600 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
37601 the advantages and disadvantages of running without root privilege.
37606 . ////////////////////////////////////////////////////////////////////////////
37607 . ////////////////////////////////////////////////////////////////////////////
37609 .chapter "Log files" "CHAPlog"
37610 .scindex IIDloggen "log" "general description"
37611 .cindex "log" "types of"
37612 Exim writes three different logs, referred to as the main log, the reject log,
37617 The main log records the arrival of each message and each delivery in a single
37618 line in each case. The format is as compact as possible, in an attempt to keep
37619 down the size of log files. Two-character flag sequences make it easy to pick
37620 out these lines. A number of other events are recorded in the main log. Some of
37621 them are optional, in which case the &%log_selector%& option controls whether
37622 they are included or not. A Perl script called &'eximstats'&, which does simple
37623 analysis of main log files, is provided in the Exim distribution (see section
37624 &<<SECTmailstat>>&).
37626 .cindex "reject log"
37627 The reject log records information from messages that are rejected as a result
37628 of a configuration option (that is, for policy reasons).
37629 The first line of each rejection is a copy of the line that is also written to
37630 the main log. Then, if the message's header has been read at the time the log
37631 is written, its contents are written to this log. Only the original header
37632 lines are available; header lines added by ACLs are not logged. You can use the
37633 reject log to check that your policy controls are working correctly; on a busy
37634 host this may be easier than scanning the main log for rejection messages. You
37635 can suppress the writing of the reject log by setting &%write_rejectlog%&
37638 .cindex "panic log"
37639 .cindex "system log"
37640 When certain serious errors occur, Exim writes entries to its panic log. If the
37641 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
37642 are usually written to the main log as well, but can get lost amid the mass of
37643 other entries. The panic log should be empty under normal circumstances. It is
37644 therefore a good idea to check it (or to have a &'cron'& script check it)
37645 regularly, in order to become aware of any problems. When Exim cannot open its
37646 panic log, it tries as a last resort to write to the system log (syslog). This
37647 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
37648 message itself is written at priority LOG_CRIT.
37651 Every log line starts with a timestamp, in the format shown in the following
37652 example. Note that many of the examples shown in this chapter are line-wrapped.
37653 In the log file, this would be all on one line:
37655 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
37658 By default, the timestamps are in the local timezone. There are two
37659 ways of changing this:
37662 You can set the &%timezone%& option to a different time zone; in particular, if
37667 the timestamps will be in UTC (aka GMT).
37669 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
37672 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
37676 .cindex "log" "process ids in"
37677 .cindex "pid (process id)" "in log lines"
37678 Exim does not include its process id in log lines by default, but you can
37679 request that it does so by specifying the &`pid`& log selector (see section
37680 &<<SECTlogselector>>&). When this is set, the process id is output, in square
37681 brackets, immediately after the time and date.
37686 .section "Where the logs are written" "SECTwhelogwri"
37687 .cindex "log" "destination"
37688 .cindex "log" "to file"
37689 .cindex "log" "to syslog"
37691 The logs may be written to local files, or to syslog, or both. However, it
37692 should be noted that many syslog implementations use UDP as a transport, and
37693 are therefore unreliable in the sense that messages are not guaranteed to
37694 arrive at the loghost, nor is the ordering of messages necessarily maintained.
37695 It has also been reported that on large log files (tens of megabytes) you may
37696 need to tweak syslog to prevent it syncing the file with each write &-- on
37697 Linux this has been seen to make syslog take 90% plus of CPU time.
37699 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
37700 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
37701 configuration. This latter string is expanded, so it can contain, for example,
37702 references to the host name:
37704 log_file_path = /var/log/$primary_hostname/exim_%slog
37706 It is generally advisable, however, to set the string in &_Local/Makefile_&
37707 rather than at runtime, because then the setting is available right from the
37708 start of Exim's execution. Otherwise, if there's something it wants to log
37709 before it has read the configuration file (for example, an error in the
37710 configuration file) it will not use the path you want, and may not be able to
37713 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
37714 list, currently limited to at most two items. This is one option where the
37715 facility for changing a list separator may not be used. The list must always be
37716 colon-separated. If an item in the list is &"syslog"& then syslog is used;
37717 otherwise the item must either be an absolute path, containing &`%s`& at the
37718 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
37719 implying the use of a default path.
37721 When Exim encounters an empty item in the list, it searches the list defined by
37722 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
37723 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
37724 mean &"use the path specified at build time"&. It no such item exists, log
37725 files are written in the &_log_& subdirectory of the spool directory. This is
37726 equivalent to the setting:
37728 log_file_path = $spool_directory/log/%slog
37730 If you do not specify anything at build time or runtime,
37731 or if you unset the option at runtime (i.e. &`log_file_path = `&),
37732 that is where the logs are written.
37734 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
37735 are in use &-- see section &<<SECTdatlogfil>>& below.
37737 Here are some examples of possible settings:
37739 &`LOG_FILE_PATH=syslog `& syslog only
37740 &`LOG_FILE_PATH=:syslog `& syslog and default path
37741 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
37742 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
37744 If there are more than two paths in the list, the first is used and a panic
37749 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
37750 .cindex "log" "cycling local files"
37751 .cindex "cycling logs"
37752 .cindex "&'exicyclog'&"
37753 .cindex "log" "local files; writing to"
37754 Some operating systems provide centralized and standardized methods for cycling
37755 log files. For those that do not, a utility script called &'exicyclog'& is
37756 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
37757 main and reject logs each time it is called. The maximum number of old logs to
37758 keep can be set. It is suggested this script is run as a daily &'cron'& job.
37760 An Exim delivery process opens the main log when it first needs to write to it,
37761 and it keeps the file open in case subsequent entries are required &-- for
37762 example, if a number of different deliveries are being done for the same
37763 message. However, remote SMTP deliveries can take a long time, and this means
37764 that the file may be kept open long after it is renamed if &'exicyclog'& or
37765 something similar is being used to rename log files on a regular basis. To
37766 ensure that a switch of log files is noticed as soon as possible, Exim calls
37767 &[stat()]& on the main log's name before reusing an open file, and if the file
37768 does not exist, or its inode has changed, the old file is closed and Exim
37769 tries to open the main log from scratch. Thus, an old log file may remain open
37770 for quite some time, but no Exim processes should write to it once it has been
37775 .section "Datestamped log files" "SECTdatlogfil"
37776 .cindex "log" "datestamped files"
37777 Instead of cycling the main and reject log files by renaming them
37778 periodically, some sites like to use files whose names contain a datestamp,
37779 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
37780 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
37781 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
37782 point where the datestamp is required. For example:
37784 log_file_path = /var/spool/exim/log/%slog-%D
37785 log_file_path = /var/log/exim-%s-%D.log
37786 log_file_path = /var/spool/exim/log/%D-%slog
37787 log_file_path = /var/log/exim/%s.%M
37789 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
37790 examples of names generated by the above examples:
37792 /var/spool/exim/log/mainlog-20021225
37793 /var/log/exim-reject-20021225.log
37794 /var/spool/exim/log/20021225-mainlog
37795 /var/log/exim/main.200212
37797 When this form of log file is specified, Exim automatically switches to new
37798 files at midnight. It does not make any attempt to compress old logs; you
37799 will need to write your own script if you require this. You should not
37800 run &'exicyclog'& with this form of logging.
37802 The location of the panic log is also determined by &%log_file_path%&, but it
37803 is not datestamped, because rotation of the panic log does not make sense.
37804 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
37805 the string. In addition, if it immediately follows a slash, a following
37806 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
37807 character is removed. Thus, the four examples above would give these panic
37810 /var/spool/exim/log/paniclog
37811 /var/log/exim-panic.log
37812 /var/spool/exim/log/paniclog
37813 /var/log/exim/panic
37817 .section "Logging to syslog" "SECID249"
37818 .cindex "log" "syslog; writing to"
37819 The use of syslog does not change what Exim logs or the format of its messages,
37820 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
37821 Exim's log lines are omitted when these lines are sent to syslog. Apart from
37822 that, the same strings are written to syslog as to log files. The syslog
37823 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
37824 by default, but you can change these by setting the &%syslog_facility%& and
37825 &%syslog_processname%& options, respectively. If Exim was compiled with
37826 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
37827 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
37828 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
37829 the time and host name to each line.
37830 The three log streams are mapped onto syslog priorities as follows:
37833 &'mainlog'& is mapped to LOG_INFO
37835 &'rejectlog'& is mapped to LOG_NOTICE
37837 &'paniclog'& is mapped to LOG_ALERT
37840 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
37841 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
37842 these are routed by syslog to the same place. You can suppress this duplication
37843 by setting &%syslog_duplication%& false.
37845 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
37846 entries contain multiple lines when headers are included. To cope with both
37847 these cases, entries written to syslog are split into separate &[syslog()]&
37848 calls at each internal newline, and also after a maximum of
37849 870 data characters. (This allows for a total syslog line length of 1024, when
37850 additions such as timestamps are added.) If you are running a syslog
37851 replacement that can handle lines longer than the 1024 characters allowed by
37852 RFC 3164, you should set
37854 SYSLOG_LONG_LINES=yes
37856 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
37857 lines, but it still splits at internal newlines in &'reject'& log entries.
37859 To make it easy to re-assemble split lines later, each component of a split
37860 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
37861 where <&'n'&> is the component number and <&'m'&> is the total number of
37862 components in the entry. The / delimiter is used when the line was split
37863 because it was too long; if it was split because of an internal newline, the \
37864 delimiter is used. For example, supposing the length limit to be 50 instead of
37865 870, the following would be the result of a typical rejection message to
37866 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
37867 name, and pid as added by syslog:
37869 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
37870 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
37871 [3/5] when scanning for sender: missing or malformed lo
37872 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
37875 The same error might cause the following lines to be written to &"rejectlog"&
37878 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
37879 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
37880 [3/18] er when scanning for sender: missing or malformed
37881 [4/18] local part in "<>" (envelope sender is <ph10@cam
37883 [6\18] Recipients: ph10@some.domain.cam.example
37884 [7\18] P Received: from [127.0.0.1] (ident=ph10)
37885 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
37886 [9\18] id 16RdAL-0006pc-00
37887 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
37888 [11\18] 09:43 +0100
37890 [13\18] Subject: this is a test header
37891 [18\18] X-something: this is another header
37892 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
37895 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
37897 Log lines that are neither too long nor contain newlines are written to syslog
37898 without modification.
37900 If only syslog is being used, the Exim monitor is unable to provide a log tail
37901 display, unless syslog is routing &'mainlog'& to a file on the local host and
37902 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
37907 .section "Log line flags" "SECID250"
37908 One line is written to the main log for each message received, and for each
37909 successful, unsuccessful, and delayed delivery. These lines can readily be
37910 picked out by the distinctive two-character flags that immediately follow the
37911 timestamp. The flags are:
37913 &`<=`& message arrival
37914 &`(=`& message fakereject
37915 &`=>`& normal message delivery
37916 &`->`& additional address in same delivery
37917 &`>>`& cutthrough message delivery
37918 &`*>`& delivery suppressed by &%-N%&
37919 &`**`& delivery failed; address bounced
37920 &`==`& delivery deferred; temporary problem
37924 .section "Logging message reception" "SECID251"
37925 .cindex "log" "reception line"
37926 The format of the single-line entry in the main log that is written for every
37927 message received is shown in the basic example below, which is split over
37928 several lines in order to fit it on the page:
37930 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
37931 H=mailer.fict.example [192.168.123.123] U=exim
37932 P=smtp S=5678 id=<incoming message id>
37934 The address immediately following &"<="& is the envelope sender address. A
37935 bounce message is shown with the sender address &"<>"&, and if it is locally
37936 generated, this is followed by an item of the form
37940 which is a reference to the message that caused the bounce to be sent.
37944 For messages from other hosts, the H and U fields identify the remote host and
37945 record the RFC 1413 identity of the user that sent the message, if one was
37946 received. The number given in square brackets is the IP address of the sending
37947 host. If there is a single, unparenthesized host name in the H field, as
37948 above, it has been verified to correspond to the IP address (see the
37949 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
37950 by the remote host in the SMTP HELO or EHLO command, and has not been
37951 verified. If verification yields a different name to that given for HELO or
37952 EHLO, the verified name appears first, followed by the HELO or EHLO
37953 name in parentheses.
37955 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
37956 without brackets, in the HELO or EHLO command, leading to entries in
37957 the log containing text like these examples:
37959 H=(10.21.32.43) [192.168.8.34]
37960 H=([10.21.32.43]) [192.168.8.34]
37962 This can be confusing. Only the final address in square brackets can be relied
37965 For locally generated messages (that is, messages not received over TCP/IP),
37966 the H field is omitted, and the U field contains the login name of the caller
37969 .cindex "authentication" "logging"
37970 .cindex "AUTH" "logging"
37971 For all messages, the P field specifies the protocol used to receive the
37972 message. This is the value that is stored in &$received_protocol$&. In the case
37973 of incoming SMTP messages, the value indicates whether or not any SMTP
37974 extensions (ESMTP), encryption, or authentication were used. If the SMTP
37975 session was encrypted, there is an additional X field that records the cipher
37976 suite that was used.
37978 .cindex log protocol
37979 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
37980 hosts that have authenticated themselves using the SMTP AUTH command. The first
37981 value is used when the SMTP connection was encrypted (&"secure"&). In this case
37982 there is an additional item A= followed by the name of the authenticator that
37983 was used. If an authenticated identification was set up by the authenticator's
37984 &%server_set_id%& option, this is logged too, separated by a colon from the
37985 authenticator name.
37987 .cindex "size" "of message"
37988 The id field records the existing message id, if present. The size of the
37989 received message is given by the S field. When the message is delivered,
37990 headers may be removed or added, so that the size of delivered copies of the
37991 message may not correspond with this value (and indeed may be different to each
37994 The &%log_selector%& option can be used to request the logging of additional
37995 data when a message is received. See section &<<SECTlogselector>>& below.
37999 .section "Logging deliveries" "SECID252"
38000 .cindex "log" "delivery line"
38001 The format of the single-line entry in the main log that is written for every
38002 delivery is shown in one of the examples below, for local and remote
38003 deliveries, respectively. Each example has been split into multiple lines in order
38004 to fit it on the page:
38006 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38007 <marv@hitch.fict.example> R=localuser T=local_delivery
38008 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38009 monk@holistic.fict.example R=dnslookup T=remote_smtp
38010 H=holistic.fict.example [192.168.234.234]
38012 For ordinary local deliveries, the original address is given in angle brackets
38013 after the final delivery address, which might be a pipe or a file. If
38014 intermediate address(es) exist between the original and the final address, the
38015 last of these is given in parentheses after the final address. The R and T
38016 fields record the router and transport that were used to process the address.
38018 If SMTP AUTH was used for the delivery there is an additional item A=
38019 followed by the name of the authenticator that was used.
38020 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38021 option, this is logged too, separated by a colon from the authenticator name.
38023 If a shadow transport was run after a successful local delivery, the log line
38024 for the successful delivery has an item added on the end, of the form
38026 &`ST=<`&&'shadow transport name'&&`>`&
38028 If the shadow transport did not succeed, the error message is put in
38029 parentheses afterwards.
38031 .cindex "asterisk" "after IP address"
38032 When more than one address is included in a single delivery (for example, two
38033 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38034 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38035 down a single SMTP connection, an asterisk follows the IP address in the log
38036 lines for the second and subsequent messages.
38037 When two or more messages are delivered down a single TLS connection, the
38038 DNS and some TLS-related information logged for the first message delivered
38039 will not be present in the log lines for the second and subsequent messages.
38040 TLS cipher information is still available.
38042 .cindex "delivery" "cutthrough; logging"
38043 .cindex "cutthrough" "logging"
38044 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38045 line precedes the reception line, since cutthrough waits for a possible
38046 rejection from the destination in case it can reject the sourced item.
38048 The generation of a reply message by a filter file gets logged as a
38049 &"delivery"& to the addressee, preceded by &">"&.
38051 The &%log_selector%& option can be used to request the logging of additional
38052 data when a message is delivered. See section &<<SECTlogselector>>& below.
38055 .section "Discarded deliveries" "SECID253"
38056 .cindex "discarded messages"
38057 .cindex "message" "discarded"
38058 .cindex "delivery" "discarded; logging"
38059 When a message is discarded as a result of the command &"seen finish"& being
38060 obeyed in a filter file which generates no deliveries, a log entry of the form
38062 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38063 <low.club@bridge.example> R=userforward
38065 is written, to record why no deliveries are logged. When a message is discarded
38066 because it is aliased to &":blackhole:"& the log line is like this:
38068 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38069 <hole@nowhere.example> R=blackhole_router
38073 .section "Deferred deliveries" "SECID254"
38074 When a delivery is deferred, a line of the following form is logged:
38076 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38077 R=dnslookup T=smtp defer (146): Connection refused
38079 In the case of remote deliveries, the error is the one that was given for the
38080 last IP address that was tried. Details of individual SMTP failures are also
38081 written to the log, so the above line would be preceded by something like
38083 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38084 mail1.endrest.example [192.168.239.239]: Connection refused
38086 When a deferred address is skipped because its retry time has not been reached,
38087 a message is written to the log, but this can be suppressed by setting an
38088 appropriate value in &%log_selector%&.
38092 .section "Delivery failures" "SECID255"
38093 .cindex "delivery" "failure; logging"
38094 If a delivery fails because an address cannot be routed, a line of the
38095 following form is logged:
38097 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38098 <jim@trek99.example>: unknown mail domain
38100 If a delivery fails at transport time, the router and transport are shown, and
38101 the response from the remote host is included, as in this example:
38103 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38104 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38105 after pipelined RCPT TO:<ace400@pb.example>: host
38106 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38107 <ace400@pb.example>...Addressee unknown
38109 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38110 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38111 disabling PIPELINING. The log lines for all forms of delivery failure are
38112 flagged with &`**`&.
38116 .section "Fake deliveries" "SECID256"
38117 .cindex "delivery" "fake; logging"
38118 If a delivery does not actually take place because the &%-N%& option has been
38119 used to suppress it, a normal delivery line is written to the log, except that
38120 &"=>"& is replaced by &"*>"&.
38124 .section "Completion" "SECID257"
38127 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38129 is written to the main log when a message is about to be removed from the spool
38130 at the end of its processing.
38135 .section "Summary of Fields in Log Lines" "SECID258"
38136 .cindex "log" "summary of fields"
38137 A summary of the field identifiers that are used in log lines is shown in
38138 the following table:
38140 &`A `& authenticator name (and optional id and sender)
38141 &`C `& SMTP confirmation on delivery
38142 &` `& command list for &"no mail in SMTP session"&
38143 &`CV `& certificate verification status
38144 &`D `& duration of &"no mail in SMTP session"&
38145 &`DKIM`& domain verified in incoming message
38146 &`DN `& distinguished name from peer certificate
38147 &`DS `& DNSSEC secured lookups
38148 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38149 &`F `& sender address (on delivery lines)
38150 &`H `& host name and IP address
38151 &`I `& local interface used
38152 &`id `& message id (from header) for incoming message
38153 &`K `& CHUNKING extension used
38154 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38155 &`M8S `& 8BITMIME status for incoming message
38156 &`P `& on &`<=`& lines: protocol used
38157 &` `& on &`=>`& and &`**`& lines: return path
38158 &`PRDR`& PRDR extension used
38159 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38160 &`Q `& alternate queue name
38161 &`QT `& on &`=>`& lines: time spent on queue so far
38162 &` `& on &"Completed"& lines: time spent on queue
38163 &`R `& on &`<=`& lines: reference for local bounce
38164 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38165 &`RT `& on &`<=`& lines: time taken for reception
38166 &`S `& size of message in bytes
38167 &`SNI `& server name indication from TLS client hello
38168 &`ST `& shadow transport name
38169 &`T `& on &`<=`& lines: message subject (topic)
38170 &`TFO `& connection took advantage of TCP Fast Open
38171 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38172 &`U `& local user or RFC 1413 identity
38173 &`X `& TLS cipher suite
38177 .section "Other log entries" "SECID259"
38178 Various other types of log entry are written from time to time. Most should be
38179 self-explanatory. Among the more common are:
38182 .cindex "retry" "time not reached"
38183 &'retry time not reached'&&~&~An address previously suffered a temporary error
38184 during routing or local delivery, and the time to retry has not yet arrived.
38185 This message is not written to an individual message log file unless it happens
38186 during the first delivery attempt.
38188 &'retry time not reached for any host'&&~&~An address previously suffered
38189 temporary errors during remote delivery, and the retry time has not yet arrived
38190 for any of the hosts to which it is routed.
38192 .cindex "spool directory" "file locked"
38193 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38194 some other Exim process is already working on the message. This can be quite
38195 common if queue running processes are started at frequent intervals. The
38196 &'exiwhat'& utility script can be used to find out what Exim processes are
38199 .cindex "error" "ignored"
38200 &'error ignored'&&~&~There are several circumstances that give rise to this
38203 Exim failed to deliver a bounce message whose age was greater than
38204 &%ignore_bounce_errors_after%&. The bounce was discarded.
38206 A filter file set up a delivery using the &"noerror"& option, and the delivery
38207 failed. The delivery was discarded.
38209 A delivery set up by a router configured with
38210 . ==== As this is a nested list, any displays it contains must be indented
38211 . ==== as otherwise they are too far to the left.
38215 failed. The delivery was discarded.
38218 .cindex DKIM "log line"
38219 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38220 logging and the message has a DKIM signature header.
38227 .section "Reducing or increasing what is logged" "SECTlogselector"
38228 .cindex "log" "selectors"
38229 By setting the &%log_selector%& global option, you can disable some of Exim's
38230 default logging, or you can request additional logging. The value of
38231 &%log_selector%& is made up of names preceded by plus or minus characters. For
38234 log_selector = +arguments -retry_defer
38236 The list of optional log items is in the following table, with the default
38237 selection marked by asterisks:
38239 &` 8bitmime `& received 8BITMIME status
38240 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38241 &` address_rewrite `& address rewriting
38242 &` all_parents `& all parents in => lines
38243 &` arguments `& command line arguments
38244 &`*connection_reject `& connection rejections
38245 &`*delay_delivery `& immediate delivery delayed
38246 &` deliver_time `& time taken to attempt delivery
38247 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38248 &`*dkim `& DKIM verified domain on <= lines
38249 &` dkim_verbose `& separate full DKIM verification result line, per signature
38250 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38251 &` dnssec `& DNSSEC secured lookups
38252 &`*etrn `& ETRN commands
38253 &`*host_lookup_failed `& as it says
38254 &` ident_timeout `& timeout for ident connection
38255 &` incoming_interface `& local interface on <= and => lines
38256 &` incoming_port `& remote port on <= lines
38257 &`*lost_incoming_connection `& as it says (includes timeouts)
38258 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38259 &`*msg_id `& on <= lines, Message-ID: header value
38260 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38261 &` outgoing_interface `& local interface on => lines
38262 &` outgoing_port `& add remote port to => lines
38263 &`*queue_run `& start and end queue runs
38264 &` queue_time `& time on queue for one recipient
38265 &` queue_time_overall `& time on queue for whole message
38266 &` pid `& Exim process id
38267 &` pipelining `& PIPELINING use, on <= and => lines
38268 &` proxy `& proxy address on <= and => lines
38269 &` receive_time `& time taken to receive message
38270 &` received_recipients `& recipients on <= lines
38271 &` received_sender `& sender on <= lines
38272 &`*rejected_header `& header contents on reject log
38273 &`*retry_defer `& &"retry time not reached"&
38274 &` return_path_on_delivery `& put return path on => and ** lines
38275 &` sender_on_delivery `& add sender to => lines
38276 &`*sender_verify_fail `& sender verification failures
38277 &`*size_reject `& rejection because too big
38278 &`*skip_delivery `& delivery skipped in a queue run
38279 &`*smtp_confirmation `& SMTP confirmation on => lines
38280 &` smtp_connection `& incoming SMTP connections
38281 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38282 &` smtp_mailauth `& AUTH argument to MAIL commands
38283 &` smtp_no_mail `& session with no MAIL commands
38284 &` smtp_protocol_error `& SMTP protocol errors
38285 &` smtp_syntax_error `& SMTP syntax errors
38286 &` subject `& contents of &'Subject:'& on <= lines
38287 &`*tls_certificate_verified `& certificate verification status
38288 &`*tls_cipher `& TLS cipher suite on <= and => lines
38289 &` tls_peerdn `& TLS peer DN on <= and => lines
38290 &` tls_resumption `& append * to cipher field
38291 &` tls_sni `& TLS SNI on <= lines
38292 &` unknown_in_list `& DNS lookup failed in list match
38294 &` all `& all of the above
38296 See also the &%slow_lookup_log%& main configuration option,
38297 section &<<SECID99>>&
38299 More details on each of these items follows:
38303 .cindex "log" "8BITMIME"
38304 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38305 which may help in tracking down interoperability issues with ancient MTAs
38306 that are not 8bit clean. This is added to the &"<="& line, tagged with
38307 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38308 &`7BIT`& and &`8BITMIME`& respectively.
38310 .cindex "&%warn%& ACL verb" "log when skipping"
38311 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38312 its conditions cannot be evaluated, a log line to this effect is written if
38313 this log selector is set.
38315 .cindex "log" "rewriting"
38316 .cindex "rewriting" "logging"
38317 &%address_rewrite%&: This applies both to global rewrites and per-transport
38318 rewrites, but not to rewrites in filters run as an unprivileged user (because
38319 such users cannot access the log).
38321 .cindex "log" "full parentage"
38322 &%all_parents%&: Normally only the original and final addresses are logged on
38323 delivery lines; with this selector, intermediate parents are given in
38324 parentheses between them.
38326 .cindex "log" "Exim arguments"
38327 .cindex "Exim arguments, logging"
38328 &%arguments%&: This causes Exim to write the arguments with which it was called
38329 to the main log, preceded by the current working directory. This is a debugging
38330 feature, added to make it easier to find out how certain MUAs call
38331 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38332 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38333 that are empty or that contain white space are quoted. Non-printing characters
38334 are shown as escape sequences. This facility cannot log unrecognized arguments,
38335 because the arguments are checked before the configuration file is read. The
38336 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38337 between the caller and Exim.
38339 .cindex "log" "connection rejections"
38340 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38341 connection is rejected, for whatever reason.
38343 .cindex "log" "delayed delivery"
38344 .cindex "delayed delivery, logging"
38345 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38346 started for an incoming message because the load is too high or too many
38347 messages were received on one connection. Logging does not occur if no delivery
38348 process is started because &%queue_only%& is set or &%-odq%& was used.
38350 .cindex "log" "delivery duration"
38351 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38352 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38353 If millisecond logging is enabled, short times will be shown with greater
38354 precision, eg. &`DT=0.304s`&.
38356 .cindex "log" "message size on delivery"
38357 .cindex "size" "of message"
38358 &%delivery_size%&: For each delivery, the size of message delivered is added to
38359 the &"=>"& line, tagged with S=.
38361 .cindex log "DKIM verification"
38362 .cindex DKIM "verification logging"
38363 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38364 verifies successfully a tag of DKIM is added, with one of the verified domains.
38366 .cindex log "DKIM verification"
38367 .cindex DKIM "verification logging"
38368 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38370 .cindex "log" "dnslist defer"
38371 .cindex "DNS list" "logging defer"
38372 .cindex "black list (DNS)"
38373 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38374 DNS black list suffers a temporary error.
38377 .cindex dnssec logging
38378 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38379 dns lookups gave secure results a tag of DS is added.
38380 For acceptance this covers the reverse and forward lookups for host name verification.
38381 It does not cover helo-name verification.
38382 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38384 .cindex "log" "ETRN commands"
38385 .cindex "ETRN" "logging"
38386 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38387 is run to determine whether or not it is actually accepted. An invalid ETRN
38388 command, or one received within a message transaction is not logged by this
38389 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38391 .cindex "log" "host lookup failure"
38392 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38393 any addresses, or when a lookup of an IP address fails to find a host name, a
38394 log line is written. This logging does not apply to direct DNS lookups when
38395 routing email addresses, but it does apply to &"byname"& lookups.
38397 .cindex "log" "ident timeout"
38398 .cindex "RFC 1413" "logging timeout"
38399 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38400 client's ident port times out.
38402 .cindex "log" "incoming interface"
38403 .cindex "log" "local interface"
38404 .cindex "log" "local address and port"
38405 .cindex "TCP/IP" "logging local address and port"
38406 .cindex "interface" "logging"
38407 &%incoming_interface%&: The interface on which a message was received is added
38408 to the &"<="& line as an IP address in square brackets, tagged by I= and
38409 followed by a colon and the port number. The local interface and port are also
38410 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38411 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
38412 The latter can be disabled by turning off the &%outgoing_interface%& option.
38414 .cindex log "incoming proxy address"
38415 .cindex proxy "logging proxy address"
38416 .cindex "TCP/IP" "logging proxy address"
38417 &%proxy%&: The internal (closest to the system running Exim) IP address
38418 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
38419 on a proxied connection
38420 or the &"=>"& line for a message delivered on a proxied connection.
38421 See &<<SECTproxyInbound>>& for more information.
38423 .cindex "log" "incoming remote port"
38424 .cindex "port" "logging remote"
38425 .cindex "TCP/IP" "logging incoming remote port"
38426 .vindex "&$sender_fullhost$&"
38427 .vindex "&$sender_rcvhost$&"
38428 &%incoming_port%&: The remote port number from which a message was received is
38429 added to log entries and &'Received:'& header lines, following the IP address
38430 in square brackets, and separated from it by a colon. This is implemented by
38431 changing the value that is put in the &$sender_fullhost$& and
38432 &$sender_rcvhost$& variables. Recording the remote port number has become more
38433 important with the widening use of NAT (see RFC 2505).
38435 .cindex "log" "dropped connection"
38436 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
38437 connection is unexpectedly dropped.
38439 .cindex "log" "millisecond timestamps"
38440 .cindex millisecond logging
38441 .cindex timestamps "millisecond, in logs"
38442 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
38443 appended to the seconds value.
38445 .cindex "log" "message id"
38446 &%msg_id%&: The value of the Message-ID: header.
38448 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
38449 This will be either because the message is a bounce, or was submitted locally
38450 (submission mode) without one.
38451 The field identifier will have an asterix appended: &"id*="&.
38453 .cindex "log" "outgoing interface"
38454 .cindex "log" "local interface"
38455 .cindex "log" "local address and port"
38456 .cindex "TCP/IP" "logging local address and port"
38457 .cindex "interface" "logging"
38458 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
38459 interface on which a message was sent is added to delivery lines as an I= tag
38460 followed by IP address in square brackets. You can disable this by turning
38461 off the &%outgoing_interface%& option.
38463 .cindex "log" "outgoing remote port"
38464 .cindex "port" "logging outgoing remote"
38465 .cindex "TCP/IP" "logging outgoing remote port"
38466 &%outgoing_port%&: The remote port number is added to delivery log lines (those
38467 containing => tags) following the IP address.
38468 The local port is also added if &%incoming_interface%& and
38469 &%outgoing_interface%& are both enabled.
38470 This option is not included in the default setting, because for most ordinary
38471 configurations, the remote port number is always 25 (the SMTP port), and the
38472 local port is a random ephemeral port.
38474 .cindex "log" "process ids in"
38475 .cindex "pid (process id)" "in log lines"
38476 &%pid%&: The current process id is added to every log line, in square brackets,
38477 immediately after the time and date.
38479 .cindex log pipelining
38480 .cindex pipelining "logging outgoing"
38481 &%pipelining%&: A field is added to delivery and accept
38482 log lines when the ESMTP PIPELINING extension was used.
38483 The field is a single "L".
38485 On accept lines, where PIPELINING was offered but not used by the client,
38486 the field has a minus appended.
38488 .cindex "pipelining" "early connection"
38489 If Exim is built with the SUPPORT_PIPE_CONNECT build option
38490 accept "L" fields have a period appended if the feature was
38491 offered but not used, or an asterisk appended if used.
38492 Delivery "L" fields have an asterisk appended if used.
38495 .cindex "log" "queue run"
38496 .cindex "queue runner" "logging"
38497 &%queue_run%&: The start and end of every queue run are logged.
38499 .cindex "log" "queue time"
38500 &%queue_time%&: The amount of time the message has been in the queue on the
38501 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
38502 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
38503 includes reception time as well as the delivery time for the current address.
38504 This means that it may be longer than the difference between the arrival and
38505 delivery log line times, because the arrival log line is not written until the
38506 message has been successfully received.
38507 If millisecond logging is enabled, short times will be shown with greater
38508 precision, eg. &`QT=1.578s`&.
38510 &%queue_time_overall%&: The amount of time the message has been in the queue on
38511 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
38512 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
38513 message, so it includes reception time as well as the total delivery time.
38515 .cindex "log" "receive duration"
38516 &%receive_time%&: For each message, the amount of real time it has taken to
38517 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
38518 If millisecond logging is enabled, short times will be shown with greater
38519 precision, eg. &`RT=0.204s`&.
38521 .cindex "log" "recipients"
38522 &%received_recipients%&: The recipients of a message are listed in the main log
38523 as soon as the message is received. The list appears at the end of the log line
38524 that is written when a message is received, preceded by the word &"for"&. The
38525 addresses are listed after they have been qualified, but before any rewriting
38527 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
38530 .cindex "log" "sender reception"
38531 &%received_sender%&: The unrewritten original sender of a message is added to
38532 the end of the log line that records the message's arrival, after the word
38533 &"from"& (before the recipients if &%received_recipients%& is also set).
38535 .cindex "log" "header lines for rejection"
38536 &%rejected_header%&: If a message's header has been received at the time a
38537 rejection is written to the reject log, the complete header is added to the
38538 log. Header logging can be turned off individually for messages that are
38539 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
38541 .cindex "log" "retry defer"
38542 &%retry_defer%&: A log line is written if a delivery is deferred because a
38543 retry time has not yet been reached. However, this &"retry time not reached"&
38544 message is always omitted from individual message logs after the first delivery
38547 .cindex "log" "return path"
38548 &%return_path_on_delivery%&: The return path that is being transmitted with
38549 the message is included in delivery and bounce lines, using the tag P=.
38550 This is omitted if no delivery actually happens, for example, if routing fails,
38551 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
38553 .cindex "log" "sender on delivery"
38554 &%sender_on_delivery%&: The message's sender address is added to every delivery
38555 and bounce line, tagged by F= (for &"from"&).
38556 This is the original sender that was received with the message; it is not
38557 necessarily the same as the outgoing return path.
38559 .cindex "log" "sender verify failure"
38560 &%sender_verify_fail%&: If this selector is unset, the separate log line that
38561 gives details of a sender verification failure is not written. Log lines for
38562 the rejection of SMTP commands contain just &"sender verify failed"&, so some
38565 .cindex "log" "size rejection"
38566 &%size_reject%&: A log line is written whenever a message is rejected because
38569 .cindex "log" "frozen messages; skipped"
38570 .cindex "frozen messages" "logging skipping"
38571 &%skip_delivery%&: A log line is written whenever a message is skipped during a
38572 queue run because it is frozen or because another process is already delivering
38574 .cindex "&""spool file is locked""&"
38575 The message that is written is &"spool file is locked"&.
38577 .cindex "log" "smtp confirmation"
38578 .cindex "SMTP" "logging confirmation"
38579 .cindex "LMTP" "logging confirmation"
38580 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
38581 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
38582 A number of MTAs (including Exim) return an identifying string in this
38585 .cindex "log" "SMTP connections"
38586 .cindex "SMTP" "logging connections"
38587 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
38588 established or closed, unless the connection is from a host that matches
38589 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
38590 only when the closure is unexpected.) This applies to connections from local
38591 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
38592 dropped in the middle of a message, a log line is always written, whether or
38593 not this selector is set, but otherwise nothing is written at the start and end
38594 of connections unless this selector is enabled.
38596 For TCP/IP connections to an Exim daemon, the current number of connections is
38597 included in the log message for each new connection, but note that the count is
38598 reset if the daemon is restarted.
38599 Also, because connections are closed (and the closure is logged) in
38600 subprocesses, the count may not include connections that have been closed but
38601 whose termination the daemon has not yet noticed. Thus, while it is possible to
38602 match up the opening and closing of connections in the log, the value of the
38603 logged counts may not be entirely accurate.
38605 .cindex "log" "SMTP transaction; incomplete"
38606 .cindex "SMTP" "logging incomplete transactions"
38607 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
38608 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
38609 and the message sender plus any accepted recipients are included in the log
38610 line. This can provide evidence of dictionary attacks.
38612 .cindex "log" "non-MAIL SMTP sessions"
38613 .cindex "MAIL" "logging session without"
38614 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
38615 connection terminates without having issued a MAIL command. This includes both
38616 the case when the connection is dropped, and the case when QUIT is used. It
38617 does not include cases where the connection is rejected right at the start (by
38618 an ACL, or because there are too many connections, or whatever). These cases
38619 already have their own log lines.
38621 The log line that is written contains the identity of the client in the usual
38622 way, followed by D= and a time, which records the duration of the connection.
38623 If the connection was authenticated, this fact is logged exactly as it is for
38624 an incoming message, with an A= item. If the connection was encrypted, CV=,
38625 DN=, and X= items may appear as they do for an incoming message, controlled by
38626 the same logging options.
38628 Finally, if any SMTP commands were issued during the connection, a C= item
38629 is added to the line, listing the commands that were used. For example,
38633 shows that the client issued QUIT straight after EHLO. If there were fewer
38634 than 20 commands, they are all listed. If there were more than 20 commands,
38635 the last 20 are listed, preceded by &"..."&. However, with the default
38636 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
38637 have been aborted before 20 non-mail commands are processed.
38639 &%smtp_mailauth%&: A third subfield with the authenticated sender,
38640 colon-separated, is appended to the A= item for a message arrival or delivery
38641 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
38642 was accepted or used.
38644 .cindex "log" "SMTP protocol error"
38645 .cindex "SMTP" "logging protocol error"
38646 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
38647 encountered. Exim does not have perfect detection of all protocol errors
38648 because of transmission delays and the use of pipelining. If PIPELINING has
38649 been advertised to a client, an Exim server assumes that the client will use
38650 it, and therefore it does not count &"expected"& errors (for example, RCPT
38651 received after rejecting MAIL) as protocol errors.
38653 .cindex "SMTP" "logging syntax errors"
38654 .cindex "SMTP" "syntax errors; logging"
38655 .cindex "SMTP" "unknown command; logging"
38656 .cindex "log" "unknown SMTP command"
38657 .cindex "log" "SMTP syntax error"
38658 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
38659 encountered. An unrecognized command is treated as a syntax error. For an
38660 external connection, the host identity is given; for an internal connection
38661 using &%-bs%& the sender identification (normally the calling user) is given.
38663 .cindex "log" "subject"
38664 .cindex "subject, logging"
38665 &%subject%&: The subject of the message is added to the arrival log line,
38666 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
38667 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
38668 specifies whether characters with values greater than 127 should be logged
38669 unchanged, or whether they should be rendered as escape sequences.
38671 .cindex "log" "certificate verification"
38673 .cindex DANE logging
38674 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
38675 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
38677 using a CA trust anchor,
38678 &`CA=dane`& if using a DNS trust anchor,
38679 and &`CV=no`& if not.
38681 .cindex "log" "TLS cipher"
38682 .cindex "TLS" "logging cipher"
38683 &%tls_cipher%&: When a message is sent or received over an encrypted
38684 connection, the cipher suite used is added to the log line, preceded by X=.
38686 .cindex "log" "TLS peer DN"
38687 .cindex "TLS" "logging peer DN"
38688 &%tls_peerdn%&: When a message is sent or received over an encrypted
38689 connection, and a certificate is supplied by the remote host, the peer DN is
38690 added to the log line, preceded by DN=.
38692 .cindex "log" "TLS resumption"
38693 .cindex "TLS" "logging session resumption"
38695 &%tls_resumption%&: When a message is sent or received over an encrypted
38696 connection and the TLS session resumed one used on a previous TCP connection,
38697 an asterisk is appended to the X= cipher field in the log line.
38700 .cindex "log" "TLS SNI"
38701 .cindex "TLS" "logging SNI"
38702 .cindex SNI logging
38703 &%tls_sni%&: When a message is received over an encrypted connection, and
38704 the remote host provided the Server Name Indication extension, the SNI is
38705 added to the log line, preceded by SNI=.
38707 .cindex "log" "DNS failure in list"
38708 &%unknown_in_list%&: This setting causes a log entry to be written when the
38709 result of a list match is failure because a DNS lookup failed.
38713 .section "Message log" "SECID260"
38714 .cindex "message" "log file for"
38715 .cindex "log" "message log; description of"
38716 .cindex "&_msglog_& directory"
38717 .oindex "&%preserve_message_logs%&"
38718 In addition to the general log files, Exim writes a log file for each message
38719 that it handles. The names of these per-message logs are the message ids, and
38720 they are kept in the &_msglog_& sub-directory of the spool directory. Each
38721 message log contains copies of the log lines that apply to the message. This
38722 makes it easier to inspect the status of an individual message without having
38723 to search the main log. A message log is deleted when processing of the message
38724 is complete, unless &%preserve_message_logs%& is set, but this should be used
38725 only with great care because they can fill up your disk very quickly.
38727 On a heavily loaded system, it may be desirable to disable the use of
38728 per-message logs, in order to reduce disk I/O. This can be done by setting the
38729 &%message_logs%& option false.
38735 . ////////////////////////////////////////////////////////////////////////////
38736 . ////////////////////////////////////////////////////////////////////////////
38738 .chapter "Exim utilities" "CHAPutils"
38739 .scindex IIDutils "utilities"
38740 A number of utility scripts and programs are supplied with Exim and are
38741 described in this chapter. There is also the Exim Monitor, which is covered in
38742 the next chapter. The utilities described here are:
38744 .itable none 0 0 3 7* left 15* left 40* left
38745 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
38746 "list what Exim processes are doing"
38747 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
38748 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
38749 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
38750 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
38752 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
38753 .irow &<<SECTmailstat>>& &'eximstats'& &&&
38754 "extract statistics from the log"
38755 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
38756 "check address acceptance from given IP"
38757 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
38758 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
38759 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
38760 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
38761 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
38762 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
38765 Another utility that might be of use to sites with many MTAs is Tom Kistner's
38766 &'exilog'&. It provides log visualizations across multiple Exim servers. See
38767 &url(https://duncanthrax.net/exilog/) for details.
38772 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
38773 .cindex "&'exiwhat'&"
38774 .cindex "process, querying"
38776 On operating systems that can restart a system call after receiving a signal
38777 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
38778 a line describing what it is doing to the file &_exim-process.info_& in the
38779 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
38780 processes it can find, having first emptied the file. It then waits for one
38781 second to allow the Exim processes to react before displaying the results. In
38782 order to run &'exiwhat'& successfully you have to have sufficient privilege to
38783 send the signal to the Exim processes, so it is normally run as root.
38785 &*Warning*&: This is not an efficient process. It is intended for occasional
38786 use by system administrators. It is not sensible, for example, to set up a
38787 script that sends SIGUSR1 signals to Exim processes at short intervals.
38790 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
38791 varies in different operating systems. Not only are different options used,
38792 but the format of the output is different. For this reason, there are some
38793 system configuration options that configure exactly how &'exiwhat'& works. If
38794 it doesn't seem to be working for you, check the following compile-time
38797 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
38798 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
38799 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
38800 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
38802 An example of typical output from &'exiwhat'& is
38804 164 daemon: -q1h, listening on port 25
38805 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
38806 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
38807 [10.19.42.42] (editor@ref.example)
38808 10592 handling incoming call from [192.168.243.242]
38809 10628 accepting a local non-SMTP message
38811 The first number in the output line is the process number. The third line has
38812 been split here, in order to fit it on the page.
38816 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
38817 .cindex "&'exiqgrep'&"
38818 .cindex "queue" "grepping"
38819 This utility is a Perl script contributed by Matt Hubbard. It runs
38823 or (in case &*-a*& switch is specified)
38827 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
38828 contain alternate exim configuration the queue management might be using.
38830 to obtain a queue listing, and then greps the output to select messages
38831 that match given criteria. The following selection options are available:
38834 .vitem &*-f*&&~<&'regex'&>
38835 Match the sender address using a case-insensitive search. The field that is
38836 tested is enclosed in angle brackets, so you can test for bounce messages with
38840 .vitem &*-r*&&~<&'regex'&>
38841 Match a recipient address using a case-insensitive search. The field that is
38842 tested is not enclosed in angle brackets.
38844 .vitem &*-s*&&~<&'regex'&>
38845 Match against the size field.
38847 .vitem &*-y*&&~<&'seconds'&>
38848 Match messages that are younger than the given time.
38850 .vitem &*-o*&&~<&'seconds'&>
38851 Match messages that are older than the given time.
38854 Match only frozen messages.
38857 Match only non-frozen messages.
38859 .vitem &*-G*&&~<&'queuename'&>
38860 Match only messages in the given queue. Without this, the default queue is searched.
38863 The following options control the format of the output:
38867 Display only the count of matching messages.
38870 Long format &-- display the full message information as output by Exim. This is
38874 Display message ids only.
38877 Brief format &-- one line per message.
38880 Display messages in reverse order.
38883 Include delivered recipients in queue listing.
38886 There is one more option, &%-h%&, which outputs a list of options.
38890 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
38891 .cindex "&'exiqsumm'&"
38892 .cindex "queue" "summary"
38893 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
38894 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
38895 running a command such as
38897 exim -bp | exiqsumm
38899 The output consists of one line for each domain that has messages waiting for
38900 it, as in the following example:
38902 3 2322 74m 66m msn.com.example
38904 Each line lists the number of pending deliveries for a domain, their total
38905 volume, and the length of time that the oldest and the newest messages have
38906 been waiting. Note that the number of pending deliveries is greater than the
38907 number of messages when messages have more than one recipient.
38909 A summary line is output at the end. By default the output is sorted on the
38910 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
38911 the output to be sorted by oldest message and by count of messages,
38912 respectively. There are also three options that split the messages for each
38913 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
38914 separates frozen messages, and &%-s%& separates messages according to their
38917 The output of &'exim -bp'& contains the original addresses in the message, so
38918 this also applies to the output from &'exiqsumm'&. No domains from addresses
38919 generated by aliasing or forwarding are included (unless the &%one_time%&
38920 option of the &(redirect)& router has been used to convert them into &"top
38921 level"& addresses).
38926 .section "Extracting specific information from the log (exigrep)" &&&
38928 .cindex "&'exigrep'&"
38929 .cindex "log" "extracts; grepping for"
38930 The &'exigrep'& utility is a Perl script that searches one or more main log
38931 files for entries that match a given pattern. When it finds a match, it
38932 extracts all the log entries for the relevant message, not just those that
38933 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
38934 given message, or all mail for a given user, or for a given host, for example.
38935 The input files can be in Exim log format or syslog format.
38936 If a matching log line is not associated with a specific message, it is
38937 included in &'exigrep'&'s output without any additional lines. The usage is:
38939 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
38941 If no log filenames are given on the command line, the standard input is read.
38943 The &%-t%& argument specifies a number of seconds. It adds an additional
38944 condition for message selection. Messages that are complete are shown only if
38945 they spent more than <&'n'&> seconds in the queue.
38947 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
38948 makes it case-sensitive. This may give a performance improvement when searching
38949 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
38950 option; with &%-I%& they do not. In both cases it is possible to change the
38951 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
38953 The &%-l%& option means &"literal"&, that is, treat all characters in the
38954 pattern as standing for themselves. Otherwise the pattern must be a Perl
38955 regular expression.
38957 The &%-v%& option inverts the matching condition. That is, a line is selected
38958 if it does &'not'& match the pattern.
38960 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
38961 that are generated as a result/response to a message that &'exigrep'& matched
38965 user_a sends a message to user_b, which generates a bounce back to user_b. If
38966 &'exigrep'& is used to search for &"user_a"&, only the first message will be
38967 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
38968 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
38969 when searching for &"user_a"& will show both messages since the bounce is
38970 &"related"& to or a &"result"& of the first message that was found by the
38973 If the location of a &'zcat'& command is known from the definition of
38974 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
38975 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
38976 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
38977 autodetection of some well known compression extensions.
38980 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
38981 .cindex "&'exipick'&"
38982 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
38983 lists messages from the queue according to a variety of criteria. For details
38984 of &'exipick'&'s facilities, run &'exipick'& with
38985 the &%--help%& option.
38988 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
38989 .cindex "log" "cycling local files"
38990 .cindex "cycling logs"
38991 .cindex "&'exicyclog'&"
38992 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
38993 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
38994 you are using log files with datestamps in their names (see section
38995 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
38996 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
38997 There are two command line options for &'exicyclog'&:
38999 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39000 default that is set when Exim is built. The default default is 10.
39002 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39003 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39004 overriding the script's default, which is to find the setting from Exim's
39008 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39009 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39010 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39011 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39012 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39013 logs are handled similarly.
39015 If the limit is greater than 99, the script uses 3-digit numbers such as
39016 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39017 to one that is greater, or &'vice versa'&, you will have to fix the names of
39018 any existing log files.
39020 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39021 the end are deleted. All files with numbers greater than 01 are compressed,
39022 using a compression command which is configured by the COMPRESS_COMMAND
39023 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39024 root &%crontab%& entry of the form
39026 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39028 assuming you have used the name &"exim"& for the Exim user. You can run
39029 &'exicyclog'& as root if you wish, but there is no need.
39033 .section "Mail statistics (eximstats)" "SECTmailstat"
39034 .cindex "statistics"
39035 .cindex "&'eximstats'&"
39036 A Perl script called &'eximstats'& is provided for extracting statistical
39037 information from log files. The output is either plain text, or HTML.
39038 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39039 . --- 404 error and everything else points to that.
39041 The &'eximstats'& script has been hacked about quite a bit over time. The
39042 latest version is the result of some extensive revision by Steve Campbell. A
39043 lot of information is given by default, but there are options for suppressing
39044 various parts of it. Following any options, the arguments to the script are a
39045 list of files, which should be main log files. For example:
39047 eximstats -nr /var/spool/exim/log/mainlog.01
39049 By default, &'eximstats'& extracts information about the number and volume of
39050 messages received from or delivered to various hosts. The information is sorted
39051 both by message count and by volume, and the top fifty hosts in each category
39052 are listed on the standard output. Similar information, based on email
39053 addresses or domains instead of hosts can be requested by means of various
39054 options. For messages delivered and received locally, similar statistics are
39055 also produced per user.
39057 The output also includes total counts and statistics about delivery errors, and
39058 histograms showing the number of messages received and deliveries made in each
39059 hour of the day. A delivery with more than one address in its envelope (for
39060 example, an SMTP transaction with more than one RCPT command) is counted
39061 as a single delivery by &'eximstats'&.
39063 Though normally more deliveries than receipts are reported (as messages may
39064 have multiple recipients), it is possible for &'eximstats'& to report more
39065 messages received than delivered, even though the queue is empty at the start
39066 and end of the period in question. If an incoming message contains no valid
39067 recipients, no deliveries are recorded for it. A bounce message is handled as
39068 an entirely separate message.
39070 &'eximstats'& always outputs a grand total summary giving the volume and number
39071 of messages received and deliveries made, and the number of hosts involved in
39072 each case. It also outputs the number of messages that were delayed (that is,
39073 not completely delivered at the first attempt), and the number that had at
39074 least one address that failed.
39076 The remainder of the output is in sections that can be independently disabled
39077 or modified by various options. It consists of a summary of deliveries by
39078 transport, histograms of messages received and delivered per time interval
39079 (default per hour), information about the time messages spent in the queue,
39080 a list of relayed messages, lists of the top fifty sending hosts, local
39081 senders, destination hosts, and destination local users by count and by volume,
39082 and a list of delivery errors that occurred.
39084 The relay information lists messages that were actually relayed, that is, they
39085 came from a remote host and were directly delivered to some other remote host,
39086 without being processed (for example, for aliasing or forwarding) locally.
39088 There are quite a few options for &'eximstats'& to control exactly what it
39089 outputs. These are documented in the Perl script itself, and can be extracted
39090 by running the command &(perldoc)& on the script. For example:
39092 perldoc /usr/exim/bin/eximstats
39095 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39096 .cindex "&'exim_checkaccess'&"
39097 .cindex "policy control" "checking access"
39098 .cindex "checking access"
39099 The &%-bh%& command line argument allows you to run a fake SMTP session with
39100 debugging output, in order to check what Exim is doing when it is applying
39101 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39102 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39103 sometimes you just want to answer the question &"Does this address have
39104 access?"& without bothering with any further details.
39106 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39107 two arguments, an IP address and an email address:
39109 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39111 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39112 given email address would be accepted in a RCPT command in a TCP/IP
39113 connection from the host with the given IP address. The output of the utility
39114 is either the word &"accepted"&, or the SMTP error response, for example:
39117 550 Relay not permitted
39119 When running this test, the utility uses &`<>`& as the envelope sender address
39120 for the MAIL command, but you can change this by providing additional
39121 options. These are passed directly to the Exim command. For example, to specify
39122 that the test is to be run with the sender address &'himself@there.example'&
39125 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39126 -f himself@there.example
39128 Note that these additional Exim command line items must be given after the two
39129 mandatory arguments.
39131 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39132 while running its checks. You can run checks that include callouts by using
39133 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39137 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39138 .cindex "DBM" "building dbm files"
39139 .cindex "building DBM files"
39140 .cindex "&'exim_dbmbuild'&"
39141 .cindex "lower casing"
39142 .cindex "binary zero" "in lookup key"
39143 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39144 the format used by the &(lsearch)& lookup (see section
39145 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39146 names as keys and the remainder of the information as data. The lower-casing
39147 can be prevented by calling the program with the &%-nolc%& option.
39149 A terminating zero is included as part of the key string. This is expected by
39150 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39151 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39152 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39155 The program requires two arguments: the name of the input file (which can be a
39156 single hyphen to indicate the standard input), and the name of the output file.
39157 It creates the output under a temporary name, and then renames it if all went
39161 If the native DB interface is in use (USE_DB is set in a compile-time
39162 configuration file &-- this is common in free versions of Unix) the two
39163 filenames must be different, because in this mode the Berkeley DB functions
39164 create a single output file using exactly the name given. For example,
39166 exim_dbmbuild /etc/aliases /etc/aliases.db
39168 reads the system alias file and creates a DBM version of it in
39169 &_/etc/aliases.db_&.
39171 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39172 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39173 environment, the suffixes are added to the second argument of
39174 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39175 when the Berkeley functions are used in compatibility mode (though this is not
39176 recommended), because in that case it adds a &_.db_& suffix to the filename.
39178 If a duplicate key is encountered, the program outputs a warning, and when it
39179 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39180 option is used. By default, only the first of a set of duplicates is used &--
39181 this makes it compatible with &(lsearch)& lookups. There is an option
39182 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39183 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39184 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39190 .section "Finding individual retry times (exinext)" "SECTfinindret"
39191 .cindex "retry" "times"
39192 .cindex "&'exinext'&"
39193 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39194 fish specific information out of the retry database. Given a mail domain (or a
39195 complete address), it looks up the hosts for that domain, and outputs any retry
39196 information for the hosts or for the domain. At present, the retry information
39197 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39198 output. For example:
39200 $ exinext piglet@milne.fict.example
39201 kanga.milne.example:192.168.8.1 error 146: Connection refused
39202 first failed: 21-Feb-1996 14:57:34
39203 last tried: 21-Feb-1996 14:57:34
39204 next try at: 21-Feb-1996 15:02:34
39205 roo.milne.example:192.168.8.3 error 146: Connection refused
39206 first failed: 20-Jan-1996 13:12:08
39207 last tried: 21-Feb-1996 11:42:03
39208 next try at: 21-Feb-1996 19:42:03
39209 past final cutoff time
39211 You can also give &'exinext'& a local part, without a domain, and it
39212 will give any retry information for that local part in your default domain.
39213 A message id can be used to obtain retry information pertaining to a specific
39214 message. This exists only when an attempt to deliver a message to a remote host
39215 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39216 &'exinext'& is not particularly efficient, but then it is not expected to be
39219 The &'exinext'& utility calls Exim to find out information such as the location
39220 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39221 passed on to the &'exim'& commands. The first specifies an alternate Exim
39222 configuration file, and the second sets macros for use within the configuration
39223 file. These features are mainly to help in testing, but might also be useful in
39224 environments where more than one configuration file is in use.
39228 .section "Hints database maintenance" "SECThindatmai"
39229 .cindex "hints database" "maintenance"
39230 .cindex "maintaining Exim's hints database"
39231 Three utility programs are provided for maintaining the DBM files that Exim
39232 uses to contain its delivery hint information. Each program requires two
39233 arguments. The first specifies the name of Exim's spool directory, and the
39234 second is the name of the database it is to operate on. These are as follows:
39237 &'retry'&: the database of retry information
39239 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39242 &'callout'&: the callout cache
39244 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39247 &'tls'&: TLS session resumption data
39250 &'misc'&: other hints data
39253 The &'misc'& database is used for
39256 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39258 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39259 &(smtp)& transport)
39261 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39267 .section "exim_dumpdb" "SECID261"
39268 .cindex "&'exim_dumpdb'&"
39269 The entire contents of a database are written to the standard output by the
39270 &'exim_dumpdb'& program, which has no options or arguments other than the
39271 spool and database names. For example, to dump the retry database:
39273 exim_dumpdb /var/spool/exim retry
39275 Two lines of output are produced for each entry:
39277 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39278 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39280 The first item on the first line is the key of the record. It starts with one
39281 of the letters R, or T, depending on whether it refers to a routing or
39282 transport retry. For a local delivery, the next part is the local address; for
39283 a remote delivery it is the name of the remote host, followed by its failing IP
39284 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39285 transport). If the remote port is not the standard one (port 25), it is added
39286 to the IP address. Then there follows an error code, an additional error code,
39287 and a textual description of the error.
39289 The three times on the second line are the time of first failure, the time of
39290 the last delivery attempt, and the computed time for the next attempt. The line
39291 ends with an asterisk if the cutoff time for the last retry rule has been
39294 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39295 consists of a host name followed by a list of ids for messages that are or were
39296 waiting to be delivered to that host. If there are a very large number for any
39297 one host, continuation records, with a sequence number added to the host name,
39298 may be seen. The data in these records is often out of date, because a message
39299 may be routed to several alternative hosts, and Exim makes no effort to keep
39304 .section "exim_tidydb" "SECID262"
39305 .cindex "&'exim_tidydb'&"
39306 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39307 database. If run with no options, it removes all records that are more than 30
39308 days old. The age is calculated from the date and time that the record was last
39309 updated. Note that, in the case of the retry database, it is &'not'& the time
39310 since the first delivery failure. Information about a host that has been down
39311 for more than 30 days will remain in the database, provided that the record is
39312 updated sufficiently often.
39314 The cutoff date can be altered by means of the &%-t%& option, which must be
39315 followed by a time. For example, to remove all records older than a week from
39316 the retry database:
39318 exim_tidydb -t 7d /var/spool/exim retry
39320 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39321 message ids. In the former these appear as data in records keyed by host &--
39322 they were messages that were waiting for that host &-- and in the latter they
39323 are the keys for retry information for messages that have suffered certain
39324 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39325 message ids in database records are those of messages that are still on the
39326 queue. Message ids for messages that no longer exist are removed from
39327 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39328 For the &'retry'& database, records whose keys are non-existent message ids are
39329 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39330 whenever it removes information from the database.
39332 Certain records are automatically removed by Exim when they are no longer
39333 needed, but others are not. For example, if all the MX hosts for a domain are
39334 down, a retry record is created for each one. If the primary MX host comes back
39335 first, its record is removed when Exim successfully delivers to it, but the
39336 records for the others remain because Exim has not tried to use those hosts.
39338 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39339 hints databases. You should do this at a quiet time of day, because it requires
39340 a database to be locked (and therefore inaccessible to Exim) while it does its
39341 work. Removing records from a DBM file does not normally make the file smaller,
39342 but all the common DBM libraries are able to re-use the space that is released.
39343 After an initial phase of increasing in size, the databases normally reach a
39344 point at which they no longer get any bigger, as long as they are regularly
39347 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39348 databases is likely to keep on increasing.
39353 .section "exim_fixdb" "SECID263"
39354 .cindex "&'exim_fixdb'&"
39355 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39356 Its main use is for testing Exim, but it might also be occasionally useful for
39357 getting round problems in a live system. It has no options, and its interface
39358 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39359 key of a database record can then be entered, and the data for that record is
39362 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39363 except the &'retry'& database, that is the only operation that can be carried
39364 out. For the &'retry'& database, each field is output preceded by a number, and
39365 data for individual fields can be changed by typing the field number followed
39366 by new data, for example:
39370 resets the time of the next delivery attempt. Time values are given as a
39371 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39372 used as optional separators.
39377 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39378 .cindex "mailbox" "maintenance"
39379 .cindex "&'exim_lock'&"
39380 .cindex "locking mailboxes"
39381 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39382 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39383 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39384 a user agent while investigating a problem. The utility requires the name of
39385 the file as its first argument. If the locking is successful, the second
39386 argument is run as a command (using C's &[system()]& function); if there is no
39387 second argument, the value of the SHELL environment variable is used; if this
39388 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39389 is unlocked and the utility ends. The following options are available:
39393 Use &[fcntl()]& locking on the open mailbox.
39396 Use &[flock()]& locking on the open mailbox, provided the operating system
39399 .vitem &%-interval%&
39400 This must be followed by a number, which is a number of seconds; it sets the
39401 interval to sleep between retries (default 3).
39403 .vitem &%-lockfile%&
39404 Create a lock file before opening the mailbox.
39407 Lock the mailbox using MBX rules.
39410 Suppress verification output.
39412 .vitem &%-retries%&
39413 This must be followed by a number; it sets the number of times to try to get
39414 the lock (default 10).
39416 .vitem &%-restore_time%&
39417 This option causes &%exim_lock%& to restore the modified and read times to the
39418 locked file before exiting. This allows you to access a locked mailbox (for
39419 example, to take a backup copy) without disturbing the times that the user
39422 .vitem &%-timeout%&
39423 This must be followed by a number, which is a number of seconds; it sets a
39424 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
39425 default), a non-blocking call is used.
39428 Generate verbose output.
39431 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
39432 default is to create a lock file and also to use &[fcntl()]& locking on the
39433 mailbox, which is the same as Exim's default. The use of &%-flock%& or
39434 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
39435 requires that the directory containing the file be writeable. Locking by lock
39436 file does not last forever; Exim assumes that a lock file is expired if it is
39437 more than 30 minutes old.
39439 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
39440 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
39441 to be taken out on the open mailbox, and an exclusive lock on the file
39442 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
39443 number of the mailbox file. When the locking is released, if an exclusive lock
39444 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
39446 The default output contains verification of the locking that takes place. The
39447 &%-v%& option causes some additional information to be given. The &%-q%& option
39448 suppresses all output except error messages.
39452 exim_lock /var/spool/mail/spqr
39454 runs an interactive shell while the file is locked, whereas
39456 &`exim_lock -q /var/spool/mail/spqr <<End`&
39457 <&'some commands'&>
39460 runs a specific non-interactive sequence of commands while the file is locked,
39461 suppressing all verification output. A single command can be run by a command
39464 exim_lock -q /var/spool/mail/spqr \
39465 "cp /var/spool/mail/spqr /some/where"
39467 Note that if a command is supplied, it must be entirely contained within the
39468 second argument &-- hence the quotes.
39472 . ////////////////////////////////////////////////////////////////////////////
39473 . ////////////////////////////////////////////////////////////////////////////
39475 .chapter "The Exim monitor" "CHAPeximon"
39476 .scindex IIDeximon "Exim monitor" "description"
39477 .cindex "X-windows"
39478 .cindex "&'eximon'&"
39479 .cindex "Local/eximon.conf"
39480 .cindex "&_exim_monitor/EDITME_&"
39481 The Exim monitor is an application which displays in an X window information
39482 about the state of Exim's queue and what Exim is doing. An admin user can
39483 perform certain operations on messages from this GUI interface; however all
39484 such facilities are also available from the command line, and indeed, the
39485 monitor itself makes use of the command line to perform any actions requested.
39489 .section "Running the monitor" "SECID264"
39490 The monitor is started by running the script called &'eximon'&. This is a shell
39491 script that sets up a number of environment variables, and then runs the
39492 binary called &_eximon.bin_&. The default appearance of the monitor window can
39493 be changed by editing the &_Local/eximon.conf_& file created by editing
39494 &_exim_monitor/EDITME_&. Comments in that file describe what the various
39495 parameters are for.
39497 The parameters that get built into the &'eximon'& script can be overridden for
39498 a particular invocation by setting up environment variables of the same names,
39499 preceded by &`EXIMON_`&. For example, a shell command such as
39501 EXIMON_LOG_DEPTH=400 eximon
39503 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
39504 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
39505 overrides the Exim log file configuration. This makes it possible to have
39506 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
39507 syslog messages are routed to a file on the local host.
39509 X resources can be used to change the appearance of the window in the normal
39510 way. For example, a resource setting of the form
39512 Eximon*background: gray94
39514 changes the colour of the background to light grey rather than white. The
39515 stripcharts are drawn with both the data lines and the reference lines in
39516 black. This means that the reference lines are not visible when on top of the
39517 data. However, their colour can be changed by setting a resource called
39518 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
39519 For example, if your X server is running Unix, you could set up lighter
39520 reference lines in the stripcharts by obeying
39523 Eximon*highlight: gray
39526 .cindex "admin user"
39527 In order to see the contents of messages in the queue, and to operate on them,
39528 &'eximon'& must either be run as root or by an admin user.
39530 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
39531 contain X11 resource parameters interpreted by the X11 library. In addition,
39532 if the first parameter starts with the string "gdb" then it is removed and the
39533 binary is invoked under gdb (the parameter is used as the gdb command-name, so
39534 versioned variants of gdb can be invoked).
39536 The monitor's window is divided into three parts. The first contains one or
39537 more stripcharts and two action buttons, the second contains a &"tail"& of the
39538 main log file, and the third is a display of the queue of messages awaiting
39539 delivery, with two more action buttons. The following sections describe these
39540 different parts of the display.
39545 .section "The stripcharts" "SECID265"
39546 .cindex "stripchart"
39547 The first stripchart is always a count of messages in the queue. Its name can
39548 be configured by setting QUEUE_STRIPCHART_NAME in the
39549 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
39550 configuration script by regular expression matches on log file entries, making
39551 it possible to display, for example, counts of messages delivered to certain
39552 hosts or using certain transports. The supplied defaults display counts of
39553 received and delivered messages, and of local and SMTP deliveries. The default
39554 period between stripchart updates is one minute; this can be adjusted by a
39555 parameter in the &_Local/eximon.conf_& file.
39557 The stripchart displays rescale themselves automatically as the value they are
39558 displaying changes. There are always 10 horizontal lines in each chart; the
39559 title string indicates the value of each division when it is greater than one.
39560 For example, &"x2"& means that each division represents a value of 2.
39562 It is also possible to have a stripchart which shows the percentage fullness of
39563 a particular disk partition, which is useful when local deliveries are confined
39564 to a single partition.
39566 .cindex "&%statvfs%& function"
39567 This relies on the availability of the &[statvfs()]& function or equivalent in
39568 the operating system. Most, but not all versions of Unix that support Exim have
39569 this. For this particular stripchart, the top of the chart always represents
39570 100%, and the scale is given as &"x10%"&. This chart is configured by setting
39571 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
39572 &_Local/eximon.conf_& file.
39577 .section "Main action buttons" "SECID266"
39578 .cindex "size" "of monitor window"
39579 .cindex "Exim monitor" "window size"
39580 .cindex "window size"
39581 Below the stripcharts there is an action button for quitting the monitor. Next
39582 to this is another button marked &"Size"&. They are placed here so that
39583 shrinking the window to its default minimum size leaves just the queue count
39584 stripchart and these two buttons visible. Pressing the &"Size"& button causes
39585 the window to expand to its maximum size, unless it is already at the maximum,
39586 in which case it is reduced to its minimum.
39588 When expanding to the maximum, if the window cannot be fully seen where it
39589 currently is, it is moved back to where it was the last time it was at full
39590 size. When it is expanding from its minimum size, the old position is
39591 remembered, and next time it is reduced to the minimum it is moved back there.
39593 The idea is that you can keep a reduced window just showing one or two
39594 stripcharts at a convenient place on your screen, easily expand it to show
39595 the full window when required, and just as easily put it back to what it was.
39596 The idea is copied from what the &'twm'& window manager does for its
39597 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
39598 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
39600 Normally, the monitor starts up with the window at its full size, but it can be
39601 built so that it starts up with the window at its smallest size, by setting
39602 START_SMALL=yes in &_Local/eximon.conf_&.
39606 .section "The log display" "SECID267"
39607 .cindex "log" "tail of; in monitor"
39608 The second section of the window is an area in which a display of the tail of
39609 the main log is maintained.
39610 To save space on the screen, the timestamp on each log line is shortened by
39611 removing the date and, if &%log_timezone%& is set, the timezone.
39612 The log tail is not available when the only destination for logging data is
39613 syslog, unless the syslog lines are routed to a local file whose name is passed
39614 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
39616 The log sub-window has a scroll bar at its lefthand side which can be used to
39617 move back to look at earlier text, and the up and down arrow keys also have a
39618 scrolling effect. The amount of log that is kept depends on the setting of
39619 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
39620 to use. When this is full, the earlier 50% of data is discarded &-- this is
39621 much more efficient than throwing it away line by line. The sub-window also has
39622 a horizontal scroll bar for accessing the ends of long log lines. This is the
39623 only means of horizontal scrolling; the right and left arrow keys are not
39624 available. Text can be cut from this part of the window using the mouse in the
39625 normal way. The size of this subwindow is controlled by parameters in the
39626 configuration file &_Local/eximon.conf_&.
39628 Searches of the text in the log window can be carried out by means of the ^R
39629 and ^S keystrokes, which default to a reverse and a forward search,
39630 respectively. The search covers only the text that is displayed in the window.
39631 It cannot go further back up the log.
39633 The point from which the search starts is indicated by a caret marker. This is
39634 normally at the end of the text in the window, but can be positioned explicitly
39635 by pointing and clicking with the left mouse button, and is moved automatically
39636 by a successful search. If new text arrives in the window when it is scrolled
39637 back, the caret remains where it is, but if the window is not scrolled back,
39638 the caret is moved to the end of the new text.
39640 Pressing ^R or ^S pops up a window into which the search text can be typed.
39641 There are buttons for selecting forward or reverse searching, for carrying out
39642 the search, and for cancelling. If the &"Search"& button is pressed, the search
39643 happens and the window remains so that further searches can be done. If the
39644 &"Return"& key is pressed, a single search is done and the window is closed. If
39645 ^C is typed the search is cancelled.
39647 The searching facility is implemented using the facilities of the Athena text
39648 widget. By default this pops up a window containing both &"search"& and
39649 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
39650 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
39651 However, the linkers in BSDI and HP-UX seem unable to handle an externally
39652 provided version of &%TextPop%& when the remaining parts of the text widget
39653 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
39654 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
39655 on these systems, at the expense of having unwanted items in the search popup
39660 .section "The queue display" "SECID268"
39661 .cindex "queue" "display in monitor"
39662 The bottom section of the monitor window contains a list of all messages that
39663 are in the queue, which includes those currently being received or delivered,
39664 as well as those awaiting delivery. The size of this subwindow is controlled by
39665 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
39666 at which it is updated is controlled by another parameter in the same file &--
39667 the default is 5 minutes, since queue scans can be quite expensive. However,
39668 there is an &"Update"& action button just above the display which can be used
39669 to force an update of the queue display at any time.
39671 When a host is down for some time, a lot of pending mail can build up for it,
39672 and this can make it hard to deal with other messages in the queue. To help
39673 with this situation there is a button next to &"Update"& called &"Hide"&. If
39674 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
39675 type anything in here and press &"Return"&, the text is added to a chain of
39676 such texts, and if every undelivered address in a message matches at least one
39677 of the texts, the message is not displayed.
39679 If there is an address that does not match any of the texts, all the addresses
39680 are displayed as normal. The matching happens on the ends of addresses so, for
39681 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
39682 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
39683 has been set up, a button called &"Unhide"& is displayed. If pressed, it
39684 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
39685 a hide request is automatically cancelled after one hour.
39687 While the dialogue box is displayed, you can't press any buttons or do anything
39688 else to the monitor window. For this reason, if you want to cut text from the
39689 queue display to use in the dialogue box, you have to do the cutting before
39690 pressing the &"Hide"& button.
39692 The queue display contains, for each unhidden queued message, the length of
39693 time it has been in the queue, the size of the message, the message id, the
39694 message sender, and the first undelivered recipient, all on one line. If it is
39695 a bounce message, the sender is shown as &"<>"&. If there is more than one
39696 recipient to which the message has not yet been delivered, subsequent ones are
39697 listed on additional lines, up to a maximum configured number, following which
39698 an ellipsis is displayed. Recipients that have already received the message are
39701 .cindex "frozen messages" "display"
39702 If a message is frozen, an asterisk is displayed at the left-hand side.
39704 The queue display has a vertical scroll bar, and can also be scrolled by means
39705 of the arrow keys. Text can be cut from it using the mouse in the normal way.
39706 The text searching facilities, as described above for the log window, are also
39707 available, but the caret is always moved to the end of the text when the queue
39708 display is updated.
39712 .section "The queue menu" "SECID269"
39713 .cindex "queue" "menu in monitor"
39714 If the &%shift%& key is held down and the left button is clicked when the mouse
39715 pointer is over the text for any message, an action menu pops up, and the first
39716 line of the queue display for the message is highlighted. This does not affect
39719 If you want to use some other event for popping up the menu, you can set the
39720 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
39721 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
39722 value set in this parameter is a standard X event description. For example, to
39723 run eximon using &%ctrl%& rather than &%shift%& you could use
39725 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
39727 The title of the menu is the message id, and it contains entries which act as
39731 &'message log'&: The contents of the message log for the message are displayed
39732 in a new text window.
39734 &'headers'&: Information from the spool file that contains the envelope
39735 information and headers is displayed in a new text window. See chapter
39736 &<<CHAPspool>>& for a description of the format of spool files.
39738 &'body'&: The contents of the spool file containing the body of the message are
39739 displayed in a new text window. There is a default limit of 20,000 bytes to the
39740 amount of data displayed. This can be changed by setting the BODY_MAX
39741 option at compile time, or the EXIMON_BODY_MAX option at runtime.
39743 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
39744 delivery of the message. This causes an automatic thaw if the message is
39745 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
39746 a new text window. The delivery is run in a separate process, to avoid holding
39747 up the monitor while the delivery proceeds.
39749 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
39750 that the message be frozen.
39752 .cindex "thawing messages"
39753 .cindex "unfreezing messages"
39754 .cindex "frozen messages" "thawing"
39755 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
39756 that the message be thawed.
39758 .cindex "delivery" "forcing failure"
39759 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
39760 that Exim gives up trying to deliver the message. A bounce message is generated
39761 for any remaining undelivered addresses.
39763 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
39764 that the message be deleted from the system without generating a bounce
39767 &'add recipient'&: A dialog box is displayed into which a recipient address can
39768 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
39769 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
39770 Otherwise it must be entered as a fully qualified address. Pressing RETURN
39771 causes a call to Exim to be made using the &%-Mar%& option to request that an
39772 additional recipient be added to the message, unless the entry box is empty, in
39773 which case no action is taken.
39775 &'mark delivered'&: A dialog box is displayed into which a recipient address
39776 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
39777 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
39778 Otherwise it must be entered as a fully qualified address. Pressing RETURN
39779 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
39780 recipient address as already delivered, unless the entry box is empty, in which
39781 case no action is taken.
39783 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
39784 mark all recipient addresses as already delivered.
39786 &'edit sender'&: A dialog box is displayed initialized with the current
39787 sender's address. Pressing RETURN causes a call to Exim to be made using the
39788 &%-Mes%& option to replace the sender address, unless the entry box is empty,
39789 in which case no action is taken. If you want to set an empty sender (as in
39790 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
39791 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
39792 the address is qualified with that domain.
39795 When a delivery is forced, a window showing the &%-v%& output is displayed. In
39796 other cases when a call to Exim is made, if there is any output from Exim (in
39797 particular, if the command fails) a window containing the command and the
39798 output is displayed. Otherwise, the results of the action are normally apparent
39799 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
39800 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
39801 if no output is generated.
39803 The queue display is automatically updated for actions such as freezing and
39804 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
39805 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
39806 force an update of the display after one of these actions.
39808 In any text window that is displayed as result of a menu action, the normal
39809 cut-and-paste facility is available, and searching can be carried out using ^R
39810 and ^S, as described above for the log tail window.
39817 . ////////////////////////////////////////////////////////////////////////////
39818 . ////////////////////////////////////////////////////////////////////////////
39820 .chapter "Security considerations" "CHAPsecurity"
39821 .scindex IIDsecurcon "security" "discussion of"
39822 This chapter discusses a number of issues concerned with security, some of
39823 which are also covered in other parts of this manual.
39825 For reasons that this author does not understand, some people have promoted
39826 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
39827 existence of this chapter in the documentation. However, the intent of the
39828 chapter is simply to describe the way Exim works in relation to certain
39829 security concerns, not to make any specific claims about the effectiveness of
39830 its security as compared with other MTAs.
39832 What follows is a description of the way Exim is supposed to be. Best efforts
39833 have been made to try to ensure that the code agrees with the theory, but an
39834 absence of bugs can never be guaranteed. Any that are reported will get fixed
39835 as soon as possible.
39838 .section "Building a more &""hardened""& Exim" "SECID286"
39839 .cindex "security" "build-time features"
39840 There are a number of build-time options that can be set in &_Local/Makefile_&
39841 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
39842 Exim administrator who does not have the root password, or by someone who has
39843 penetrated the Exim (but not the root) account. These options are as follows:
39846 ALT_CONFIG_PREFIX can be set to a string that is required to match the
39847 start of any filenames used with the &%-C%& option. When it is set, these
39848 filenames are also not allowed to contain the sequence &"/../"&. (However, if
39849 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
39850 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
39851 default setting for &%ALT_CONFIG_PREFIX%&.
39853 If the permitted configuration files are confined to a directory to
39854 which only root has access, this guards against someone who has broken
39855 into the Exim account from running a privileged Exim with an arbitrary
39856 configuration file, and using it to break into other accounts.
39859 If a non-trusted configuration file (i.e. not the default configuration file
39860 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
39861 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
39862 the next item), then root privilege is retained only if the caller of Exim is
39863 root. This locks out the possibility of testing a configuration using &%-C%&
39864 right through message reception and delivery, even if the caller is root. The
39865 reception works, but by that time, Exim is running as the Exim user, so when
39866 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
39867 privilege to be lost. However, root can test reception and delivery using two
39871 The WHITELIST_D_MACROS build option declares some macros to be safe to override
39872 with &%-D%& if the real uid is one of root, the Exim run-time user or the
39873 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
39874 requiring the run-time value supplied to &%-D%& to match a regex that errs on
39875 the restrictive side. Requiring build-time selection of safe macros is onerous
39876 but this option is intended solely as a transition mechanism to permit
39877 previously-working configurations to continue to work after release 4.73.
39879 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
39882 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
39883 never to be used for any deliveries. This is like the &%never_users%& runtime
39884 option, but it cannot be overridden; the runtime option adds additional users
39885 to the list. The default setting is &"root"&; this prevents a non-root user who
39886 is permitted to modify the runtime file from using Exim as a way to get root.
39891 .section "Root privilege" "SECID270"
39893 .cindex "root privilege"
39894 The Exim binary is normally setuid to root, which means that it gains root
39895 privilege (runs as root) when it starts execution. In some special cases (for
39896 example, when the daemon is not in use and there are no local deliveries), it
39897 may be possible to run Exim setuid to some user other than root. This is
39898 discussed in the next section. However, in most installations, root privilege
39899 is required for two things:
39902 To set up a socket connected to the standard SMTP port (25) when initialising
39903 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
39906 To be able to change uid and gid in order to read users' &_.forward_& files and
39907 perform local deliveries as the receiving user or as specified in the
39911 It is not necessary to be root to do any of the other things Exim does, such as
39912 receiving messages and delivering them externally over SMTP, and it is
39913 obviously more secure if Exim does not run as root except when necessary.
39914 For this reason, a user and group for Exim to use must be defined in
39915 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
39916 group"&. Their values can be changed by the runtime configuration, though this
39917 is not recommended. Often a user called &'exim'& is used, but some sites use
39918 &'mail'& or another user name altogether.
39920 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
39921 abdication; the process cannot regain root afterwards. Prior to release 4.00,
39922 &[seteuid()]& was used in some circumstances, but this is no longer the case.
39924 After a new Exim process has interpreted its command line options, it changes
39925 uid and gid in the following cases:
39930 If the &%-C%& option is used to specify an alternate configuration file, or if
39931 the &%-D%& option is used to define macro values for the configuration, and the
39932 calling process is not running as root, the uid and gid are changed to those of
39933 the calling process.
39934 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
39935 option may not be used at all.
39936 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
39937 can be supplied if the calling process is running as root, the Exim run-time
39938 user or CONFIGURE_OWNER, if defined.
39943 If the expansion test option (&%-be%&) or one of the filter testing options
39944 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
39947 If the process is not a daemon process or a queue runner process or a delivery
39948 process or a process for testing address routing (started with &%-bt%&), the
39949 uid and gid are changed to the Exim user and group. This means that Exim always
39950 runs under its own uid and gid when receiving messages. This also applies when
39951 testing address verification
39954 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
39957 For a daemon, queue runner, delivery, or address testing process, the uid
39958 remains as root at this stage, but the gid is changed to the Exim group.
39961 The processes that initially retain root privilege behave as follows:
39964 A daemon process changes the gid to the Exim group and the uid to the Exim
39965 user after setting up one or more listening sockets. The &[initgroups()]&
39966 function is called, so that if the Exim user is in any additional groups, they
39967 will be used during message reception.
39969 A queue runner process retains root privilege throughout its execution. Its
39970 job is to fork a controlled sequence of delivery processes.
39972 A delivery process retains root privilege throughout most of its execution,
39973 but any actual deliveries (that is, the transports themselves) are run in
39974 subprocesses which always change to a non-root uid and gid. For local
39975 deliveries this is typically the uid and gid of the owner of the mailbox; for
39976 remote deliveries, the Exim uid and gid are used. Once all the delivery
39977 subprocesses have been run, a delivery process changes to the Exim uid and gid
39978 while doing post-delivery tidying up such as updating the retry database and
39979 generating bounce and warning messages.
39981 While the recipient addresses in a message are being routed, the delivery
39982 process runs as root. However, if a user's filter file has to be processed,
39983 this is done in a subprocess that runs under the individual user's uid and
39984 gid. A system filter is run as root unless &%system_filter_user%& is set.
39986 A process that is testing addresses (the &%-bt%& option) runs as root so that
39987 the routing is done in the same environment as a message delivery.
39993 .section "Running Exim without privilege" "SECTrunexiwitpri"
39994 .cindex "privilege, running without"
39995 .cindex "unprivileged running"
39996 .cindex "root privilege" "running without"
39997 Some installations like to run Exim in an unprivileged state for more of its
39998 operation, for added security. Support for this mode of operation is provided
39999 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40000 gid are changed to the Exim user and group at the start of a delivery process
40001 (and also queue runner and address testing processes). This means that address
40002 routing is no longer run as root, and the deliveries themselves cannot change
40006 .cindex "daemon" "restarting"
40007 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40008 that the daemon can still be started in the usual way, and it can respond
40009 correctly to SIGHUP because the re-invocation regains root privilege.
40011 An alternative approach is to make Exim setuid to the Exim user and also setgid
40012 to the Exim group. If you do this, the daemon must be started from a root
40013 process. (Calling Exim from a root process makes it behave in the way it does
40014 when it is setuid root.) However, the daemon cannot restart itself after a
40015 SIGHUP signal because it cannot regain privilege.
40017 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40018 stops Exim from trying to re-invoke itself to do a delivery after a message has
40019 been received. Such a re-invocation is a waste of resources because it has no
40022 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40023 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40024 to the Exim user seems a clean approach, but there is one complication:
40026 In this style of operation, Exim is running with the real uid and gid set to
40027 those of the calling process, and the effective uid/gid set to Exim's values.
40028 Ideally, any association with the calling process' uid/gid should be dropped,
40029 that is, the real uid/gid should be reset to the effective values so as to
40030 discard any privileges that the caller may have. While some operating systems
40031 have a function that permits this action for a non-root effective uid, quite a
40032 number of them do not. Because of this lack of standardization, Exim does not
40033 address this problem at this time.
40035 For this reason, the recommended approach for &"mostly unprivileged"& running
40036 is to keep the Exim binary setuid to root, and to set
40037 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40038 be used in the most straightforward way.
40040 If you configure Exim not to run delivery processes as root, there are a
40041 number of restrictions on what you can do:
40044 You can deliver only as the Exim user/group. You should explicitly use the
40045 &%user%& and &%group%& options to override routers or local transports that
40046 normally deliver as the recipient. This makes sure that configurations that
40047 work in this mode function the same way in normal mode. Any implicit or
40048 explicit specification of another user causes an error.
40050 Use of &_.forward_& files is severely restricted, such that it is usually
40051 not worthwhile to include them in the configuration.
40053 Users who wish to use &_.forward_& would have to make their home directory and
40054 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40055 and their equivalents in Exim filters, cannot be used. While they could be
40056 enabled in the Exim user's name, that would be insecure and not very useful.
40058 Unless the local user mailboxes are all owned by the Exim user (possible in
40059 some POP3 or IMAP-only environments):
40062 They must be owned by the Exim group and be writeable by that group. This
40063 implies you must set &%mode%& in the appendfile configuration, as well as the
40064 mode of the mailbox files themselves.
40066 You must set &%no_check_owner%&, since most or all of the files will not be
40067 owned by the Exim user.
40069 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40070 on a newly created mailbox when unprivileged. This also implies that new
40071 mailboxes need to be created manually.
40076 These restrictions severely restrict what can be done in local deliveries.
40077 However, there are no restrictions on remote deliveries. If you are running a
40078 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40079 gives more security at essentially no cost.
40081 If you are using the &%mua_wrapper%& facility (see chapter
40082 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40087 .section "Delivering to local files" "SECID271"
40088 Full details of the checks applied by &(appendfile)& before it writes to a file
40089 are given in chapter &<<CHAPappendfile>>&.
40093 .section "Running local commands" "SECTsecconslocalcmds"
40094 .cindex "security" "local commands"
40095 .cindex "security" "command injection attacks"
40096 There are a number of ways in which an administrator can configure Exim to run
40097 commands based upon received, untrustworthy, data. Further, in some
40098 configurations a user who can control a &_.forward_& file can also arrange to
40099 run commands. Configuration to check includes, but is not limited to:
40102 Use of &%use_shell%& in the pipe transport: various forms of shell command
40103 injection may be possible with this option present. It is dangerous and should
40104 be used only with considerable caution. Consider constraints which whitelist
40105 allowed characters in a variable which is to be used in a pipe transport that
40106 has &%use_shell%& enabled.
40108 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40109 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40110 &_.forward_& files in a redirect router. If Exim is running on a central mail
40111 hub to which ordinary users do not have shell access, but home directories are
40112 NFS mounted (for instance) then administrators should review the list of these
40113 forbid options available, and should bear in mind that the options that may
40114 need forbidding can change as new features are added between releases.
40116 The &%${run...}%& expansion item does not use a shell by default, but
40117 administrators can configure use of &_/bin/sh_& as part of the command.
40118 Such invocations should be viewed with prejudicial suspicion.
40120 Administrators who use embedded Perl are advised to explore how Perl's
40121 taint checking might apply to their usage.
40123 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40124 administrators are well advised to view its use with suspicion, in case (for
40125 instance) it allows a local-part to contain embedded Exim directives.
40127 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40128 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40129 each can reference arbitrary lists and files, rather than just being a list
40131 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40132 real-world security vulnerabilities caused by its use with untrustworthy data
40133 injected in, for SQL injection attacks.
40134 Consider the use of the &%inlisti%& expansion condition instead.
40140 .section "Trust in configuration data" "SECTsecconfdata"
40141 .cindex "security" "data sources"
40142 .cindex "security" "regular expressions"
40143 .cindex "regular expressions" "security"
40144 .cindex "PCRE" "security"
40145 If configuration data for Exim can come from untrustworthy sources, there
40146 are some issues to be aware of:
40149 Use of &%${expand...}%& may provide a path for shell injection attacks.
40151 Letting untrusted data provide a regular expression is unwise.
40153 Using &%${match...}%& to apply a fixed regular expression against untrusted
40154 data may result in pathological behaviour within PCRE. Be aware of what
40155 "backtracking" means and consider options for being more strict with a regular
40156 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40157 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40158 possessive quantifiers or just not using regular expressions against untrusted
40161 It can be important to correctly use &%${quote:...}%&,
40162 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40163 items to ensure that data is correctly constructed.
40165 Some lookups might return multiple results, even though normal usage is only
40166 expected to yield one result.
40172 .section "IPv4 source routing" "SECID272"
40173 .cindex "source routing" "in IP packets"
40174 .cindex "IP source routing"
40175 Many operating systems suppress IP source-routed packets in the kernel, but
40176 some cannot be made to do this, so Exim does its own check. It logs incoming
40177 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40178 IPv6. No special checking is currently done.
40182 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40183 Support for these SMTP commands is disabled by default. If required, they can
40184 be enabled by defining suitable ACLs.
40189 .section "Privileged users" "SECID274"
40190 .cindex "trusted users"
40191 .cindex "admin user"
40192 .cindex "privileged user"
40193 .cindex "user" "trusted"
40194 .cindex "user" "admin"
40195 Exim recognizes two sets of users with special privileges. Trusted users are
40196 able to submit new messages to Exim locally, but supply their own sender
40197 addresses and information about a sending host. For other users submitting
40198 local messages, Exim sets up the sender address from the uid, and doesn't
40199 permit a remote host to be specified.
40202 However, an untrusted user is permitted to use the &%-f%& command line option
40203 in the special form &%-f <>%& to indicate that a delivery failure for the
40204 message should not cause an error report. This affects the message's envelope,
40205 but it does not affect the &'Sender:'& header. Untrusted users may also be
40206 permitted to use specific forms of address with the &%-f%& option by setting
40207 the &%untrusted_set_sender%& option.
40209 Trusted users are used to run processes that receive mail messages from some
40210 other mail domain and pass them on to Exim for delivery either locally, or over
40211 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40212 as any user listed in the &%trusted_users%& configuration option, or under any
40213 group listed in the &%trusted_groups%& option.
40215 Admin users are permitted to do things to the messages on Exim's queue. They
40216 can freeze or thaw messages, cause them to be returned to their senders, remove
40217 them entirely, or modify them in various ways. In addition, admin users can run
40218 the Exim monitor and see all the information it is capable of providing, which
40219 includes the contents of files on the spool.
40223 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40224 delivery of messages on its queue is restricted to admin users. This
40225 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40226 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40227 queue is also restricted to admin users. This restriction can be relaxed by
40228 setting &%no_queue_list_requires_admin%&.
40230 Exim recognizes an admin user if the calling process is running as root or as
40231 the Exim user or if any of the groups associated with the calling process is
40232 the Exim group. It is not necessary actually to be running under the Exim
40233 group. However, if admin users who are not root or the Exim user are to access
40234 the contents of files on the spool via the Exim monitor (which runs
40235 unprivileged), Exim must be built to allow group read access to its spool
40238 By default, regular users are trusted to perform basic testing and
40239 introspection commands, as themselves. This setting can be tightened by
40240 setting the &%commandline_checks_require_admin%& option.
40241 This affects most of the checking options,
40242 such as &%-be%& and anything else &%-b*%&.
40245 .section "Spool files" "SECID275"
40246 .cindex "spool directory" "files"
40247 Exim's spool directory and everything it contains is owned by the Exim user and
40248 set to the Exim group. The mode for spool files is defined in the
40249 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40250 any user who is a member of the Exim group can access these files.
40254 .section "Use of argv[0]" "SECID276"
40255 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40256 of specific strings, Exim assumes certain options. For example, calling Exim
40257 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40258 to calling it with the option &%-bS%&. There are no security implications in
40263 .section "Use of %f formatting" "SECID277"
40264 The only use made of &"%f"& by Exim is in formatting load average values. These
40265 are actually stored in integer variables as 1000 times the load average.
40266 Consequently, their range is limited and so therefore is the length of the
40271 .section "Embedded Exim path" "SECID278"
40272 Exim uses its own path name, which is embedded in the code, only when it needs
40273 to re-exec in order to regain root privilege. Therefore, it is not root when it
40274 does so. If some bug allowed the path to get overwritten, it would lead to an
40275 arbitrary program's being run as exim, not as root.
40279 .section "Dynamic module directory" "SECTdynmoddir"
40280 Any dynamically loadable modules must be installed into the directory
40281 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40285 .section "Use of sprintf()" "SECID279"
40286 .cindex "&[sprintf()]&"
40287 A large number of occurrences of &"sprintf"& in the code are actually calls to
40288 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40289 The intermediate formatting is done into a large fixed buffer by a function
40290 that runs through the format string itself, and checks the length of each
40291 conversion before performing it, thus preventing buffer overruns.
40293 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40294 the output buffer is known to be sufficiently long to contain the converted
40299 .section "Use of debug_printf() and log_write()" "SECID280"
40300 Arbitrary strings are passed to both these functions, but they do their
40301 formatting by calling the function &'string_vformat()'&, which runs through
40302 the format string itself, and checks the length of each conversion.
40306 .section "Use of strcat() and strcpy()" "SECID281"
40307 These are used only in cases where the output buffer is known to be large
40308 enough to hold the result.
40309 .ecindex IIDsecurcon
40314 . ////////////////////////////////////////////////////////////////////////////
40315 . ////////////////////////////////////////////////////////////////////////////
40317 .chapter "Format of spool files" "CHAPspool"
40318 .scindex IIDforspo1 "format" "spool files"
40319 .scindex IIDforspo2 "spool directory" "format of files"
40320 .scindex IIDforspo3 "spool files" "format of"
40321 .cindex "spool files" "editing"
40322 A message on Exim's queue consists of two files, whose names are the message id
40323 followed by -D and -H, respectively. The data portion of the message is kept in
40324 the -D file on its own. The message's envelope, status, and headers are all
40325 kept in the -H file, whose format is described in this chapter. Each of these
40326 two files contains the final component of its own name as its first line. This
40327 is insurance against disk crashes where the directory is lost but the files
40328 themselves are recoverable.
40330 The file formats may be changed, or new formats added, at any release.
40331 Spool files are not intended as an interface to other programs
40332 and should not be used as such.
40334 Some people are tempted into editing -D files in order to modify messages. You
40335 need to be extremely careful if you do this; it is not recommended and you are
40336 on your own if you do it. Here are some of the pitfalls:
40339 You must ensure that Exim does not try to deliver the message while you are
40340 fiddling with it. The safest way is to take out a write lock on the -D file,
40341 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40342 place, the lock will be retained. If you write a new file and rename it, the
40343 lock will be lost at the instant of rename.
40345 .vindex "&$body_linecount$&"
40346 If you change the number of lines in the file, the value of
40347 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40348 cause incomplete transmission of messages or undeliverable messages.
40350 If the message is in MIME format, you must take care not to break it.
40352 If the message is cryptographically signed, any change will invalidate the
40355 All in all, modifying -D files is fraught with danger.
40357 Files whose names end with -J may also be seen in the &_input_& directory (or
40358 its subdirectories when &%split_spool_directory%& is set). These are journal
40359 files, used to record addresses to which the message has been delivered during
40360 the course of a delivery attempt. If there are still undelivered recipients at
40361 the end, the -H file is updated, and the -J file is deleted. If, however, there
40362 is some kind of crash (for example, a power outage) before this happens, the -J
40363 file remains in existence. When Exim next processes the message, it notices the
40364 -J file and uses it to update the -H file before starting the next delivery
40367 Files whose names end with -K or .eml may also be seen in the spool.
40368 These are temporaries used for DKIM or malware processing, when that is used.
40369 They should be tidied up by normal operations; any old ones are probably
40370 relics of crashes and can be removed.
40372 .section "Format of the -H file" "SECID282"
40373 .cindex "uid (user id)" "in spool file"
40374 .cindex "gid (group id)" "in spool file"
40375 The second line of the -H file contains the login name for the uid of the
40376 process that called Exim to read the message, followed by the numerical uid and
40377 gid. For a locally generated message, this is normally the user who sent the
40378 message. For a message received over TCP/IP via the daemon, it is
40379 normally the Exim user.
40381 The third line of the file contains the address of the message's sender as
40382 transmitted in the envelope, contained in angle brackets. The sender address is
40383 empty for bounce messages. For incoming SMTP mail, the sender address is given
40384 in the MAIL command. For locally generated mail, the sender address is
40385 created by Exim from the login name of the current user and the configured
40386 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40387 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40388 &"<>"& or an address that matches &%untrusted_set_senders%&.
40390 The fourth line contains two numbers. The first is the time that the message
40391 was received, in the conventional Unix form &-- the number of seconds since the
40392 start of the epoch. The second number is a count of the number of messages
40393 warning of delayed delivery that have been sent to the sender.
40395 There follow a number of lines starting with a hyphen. These can appear in any
40396 order, and are omitted when not relevant:
40399 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40400 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40401 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40402 recognized, to provide backward compatibility. In the old format, a line of
40403 this form is present for every ACL variable that is not empty. The number
40404 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40405 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40406 the data string for the variable. The string itself starts at the beginning of
40407 the next line, and is followed by a newline character. It may contain internal
40410 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
40411 A line of this form is present for every ACL connection variable that is
40412 defined. Note that there is a space between &%-aclc%& and the rest of the name.
40413 The length is the length of the data string for the variable. The string itself
40414 starts at the beginning of the next line, and is followed by a newline
40415 character. It may contain internal newlines.
40417 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
40418 A line of this form is present for every ACL message variable that is defined.
40419 Note that there is a space between &%-aclm%& and the rest of the name. The
40420 length is the length of the data string for the variable. The string itself
40421 starts at the beginning of the next line, and is followed by a newline
40422 character. It may contain internal newlines.
40424 .vitem "&%-active_hostname%&&~<&'hostname'&>"
40425 This is present if, when the message was received over SMTP, the value of
40426 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
40428 .vitem &%-allow_unqualified_recipient%&
40429 This is present if unqualified recipient addresses are permitted in header
40430 lines (to stop such addresses from being qualified if rewriting occurs at
40431 transport time). Local messages that were input using &%-bnq%& and remote
40432 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
40434 .vitem &%-allow_unqualified_sender%&
40435 This is present if unqualified sender addresses are permitted in header lines
40436 (to stop such addresses from being qualified if rewriting occurs at transport
40437 time). Local messages that were input using &%-bnq%& and remote messages from
40438 hosts that match &%sender_unqualified_hosts%& set this flag.
40440 .vitem "&%-auth_id%&&~<&'text'&>"
40441 The id information for a message received on an authenticated SMTP connection
40442 &-- the value of the &$authenticated_id$& variable.
40444 .vitem "&%-auth_sender%&&~<&'address'&>"
40445 The address of an authenticated sender &-- the value of the
40446 &$authenticated_sender$& variable.
40448 .vitem "&%-body_linecount%&&~<&'number'&>"
40449 This records the number of lines in the body of the message, and is
40450 present unless &%-spool_file_wireformat%& is.
40452 .vitem "&%-body_zerocount%&&~<&'number'&>"
40453 This records the number of binary zero bytes in the body of the message, and is
40454 present if the number is greater than zero.
40456 .vitem &%-deliver_firsttime%&
40457 This is written when a new message is first added to the spool. When the spool
40458 file is updated after a deferral, it is omitted.
40460 .vitem "&%-frozen%&&~<&'time'&>"
40461 .cindex "frozen messages" "spool data"
40462 The message is frozen, and the freezing happened at <&'time'&>.
40464 .vitem "&%-helo_name%&&~<&'text'&>"
40465 This records the host name as specified by a remote host in a HELO or EHLO
40468 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
40469 This records the IP address of the host from which the message was received and
40470 the remote port number that was used. It is omitted for locally generated
40473 .vitem "&%-host_auth%&&~<&'text'&>"
40474 If the message was received on an authenticated SMTP connection, this records
40475 the name of the authenticator &-- the value of the
40476 &$sender_host_authenticated$& variable.
40478 .vitem &%-host_lookup_failed%&
40479 This is present if an attempt to look up the sending host's name from its IP
40480 address failed. It corresponds to the &$host_lookup_failed$& variable.
40482 .vitem "&%-host_name%&&~<&'text'&>"
40483 .cindex "reverse DNS lookup"
40484 .cindex "DNS" "reverse lookup"
40485 This records the name of the remote host from which the message was received,
40486 if the host name was looked up from the IP address when the message was being
40487 received. It is not present if no reverse lookup was done.
40489 .vitem "&%-ident%&&~<&'text'&>"
40490 For locally submitted messages, this records the login of the originating user,
40491 unless it was a trusted user and the &%-oMt%& option was used to specify an
40492 ident value. For messages received over TCP/IP, this records the ident string
40493 supplied by the remote host, if any.
40495 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
40496 This records the IP address of the local interface and the port number through
40497 which a message was received from a remote host. It is omitted for locally
40498 generated messages.
40501 The message is from a local sender.
40503 .vitem &%-localerror%&
40504 The message is a locally-generated bounce message.
40506 .vitem "&%-local_scan%&&~<&'string'&>"
40507 This records the data string that was returned by the &[local_scan()]& function
40508 when the message was received &-- the value of the &$local_scan_data$&
40509 variable. It is omitted if no data was returned.
40511 .vitem &%-manual_thaw%&
40512 The message was frozen but has been thawed manually, that is, by an explicit
40513 Exim command rather than via the auto-thaw process.
40516 A testing delivery process was started using the &%-N%& option to suppress any
40517 actual deliveries, but delivery was deferred. At any further delivery attempts,
40520 .vitem &%-received_protocol%&
40521 This records the value of the &$received_protocol$& variable, which contains
40522 the name of the protocol by which the message was received.
40524 .vitem &%-sender_set_untrusted%&
40525 The envelope sender of this message was set by an untrusted local caller (used
40526 to ensure that the caller is displayed in queue listings).
40528 .vitem "&%-spam_score_int%&&~<&'number'&>"
40529 If a message was scanned by SpamAssassin, this is present. It records the value
40530 of &$spam_score_int$&.
40532 .vitem &%-spool_file_wireformat%&
40533 The -D file for this message is in wire-format (for ESMTP CHUNKING)
40534 rather than Unix-format.
40535 The line-ending is CRLF rather than newline.
40536 There is still, however, no leading-dot-stuffing.
40538 .vitem &%-tls_certificate_verified%&
40539 A TLS certificate was received from the client that sent this message, and the
40540 certificate was verified by the server.
40542 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
40543 When the message was received over an encrypted connection, this records the
40544 name of the cipher suite that was used.
40546 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
40547 When the message was received over an encrypted connection, and a certificate
40548 was received from the client, this records the Distinguished Name from that
40552 Any of the above may have an extra hyphen prepended, to indicate the the
40553 corresponding data is untrusted.
40555 Following the options there is a list of those addresses to which the message
40556 is not to be delivered. This set of addresses is initialized from the command
40557 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
40558 is set; otherwise it starts out empty. Whenever a successful delivery is made,
40559 the address is added to this set. The addresses are kept internally as a
40560 balanced binary tree, and it is a representation of that tree which is written
40561 to the spool file. If an address is expanded via an alias or forward file, the
40562 original address is added to the tree when deliveries to all its child
40563 addresses are complete.
40565 If the tree is empty, there is a single line in the spool file containing just
40566 the text &"XX"&. Otherwise, each line consists of two letters, which are either
40567 Y or N, followed by an address. The address is the value for the node of the
40568 tree, and the letters indicate whether the node has a left branch and/or a
40569 right branch attached to it, respectively. If branches exist, they immediately
40570 follow. Here is an example of a three-node tree:
40572 YY darcy@austen.fict.example
40573 NN alice@wonderland.fict.example
40574 NN editor@thesaurus.ref.example
40576 After the non-recipients tree, there is a list of the message's recipients.
40577 This is a simple list, preceded by a count. It includes all the original
40578 recipients of the message, including those to whom the message has already been
40579 delivered. In the simplest case, the list contains one address per line. For
40583 editor@thesaurus.ref.example
40584 darcy@austen.fict.example
40586 alice@wonderland.fict.example
40588 However, when a child address has been added to the top-level addresses as a
40589 result of the use of the &%one_time%& option on a &(redirect)& router, each
40590 line is of the following form:
40592 <&'top-level address'&> <&'errors_to address'&> &&&
40593 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
40595 The 01 flag bit indicates the presence of the three other fields that follow
40596 the top-level address. Other bits may be used in future to support additional
40597 fields. The <&'parent number'&> is the offset in the recipients list of the
40598 original parent of the &"one time"& address. The first two fields are the
40599 envelope sender that is associated with this address and its length. If the
40600 length is zero, there is no special envelope sender (there are then two space
40601 characters in the line). A non-empty field can arise from a &(redirect)& router
40602 that has an &%errors_to%& setting.
40605 A blank line separates the envelope and status information from the headers
40606 which follow. A header may occupy several lines of the file, and to save effort
40607 when reading it in, each header is preceded by a number and an identifying
40608 character. The number is the number of characters in the header, including any
40609 embedded newlines and the terminating newline. The character is one of the
40613 .row <&'blank'&> "header in which Exim has no special interest"
40614 .row &`B`& "&'Bcc:'& header"
40615 .row &`C`& "&'Cc:'& header"
40616 .row &`F`& "&'From:'& header"
40617 .row &`I`& "&'Message-id:'& header"
40618 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
40619 .row &`R`& "&'Reply-To:'& header"
40620 .row &`S`& "&'Sender:'& header"
40621 .row &`T`& "&'To:'& header"
40622 .row &`*`& "replaced or deleted header"
40625 Deleted or replaced (rewritten) headers remain in the spool file for debugging
40626 purposes. They are not transmitted when the message is delivered. Here is a
40627 typical set of headers:
40629 111P Received: by hobbit.fict.example with local (Exim 4.00)
40630 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
40631 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
40632 038* X-rewrote-sender: bb@hobbit.fict.example
40633 042* From: Bilbo Baggins <bb@hobbit.fict.example>
40634 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
40635 099* To: alice@wonderland.fict.example, rdo@foundation,
40636 darcy@austen.fict.example, editor@thesaurus.ref.example
40637 104T To: alice@wonderland.fict.example, rdo@foundation.example,
40638 darcy@austen.fict.example, editor@thesaurus.ref.example
40639 038 Date: Fri, 11 May 2001 10:28:59 +0100
40641 The asterisked headers indicate that the envelope sender, &'From:'& header, and
40642 &'To:'& header have been rewritten, the last one because routing expanded the
40643 unqualified domain &'foundation'&.
40644 .ecindex IIDforspo1
40645 .ecindex IIDforspo2
40646 .ecindex IIDforspo3
40648 .section "Format of the -D file" "SECID282a"
40649 The data file is traditionally in Unix-standard format: lines are ended with
40650 an ASCII newline character.
40651 However, when the &%spool_wireformat%& main option is used some -D files
40652 can have an alternate format.
40653 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
40654 The -D file lines (not including the first name-component line) are
40655 suitable for direct copying to the wire when transmitting using the
40656 ESMTP CHUNKING option, meaning lower processing overhead.
40657 Lines are terminated with an ASCII CRLF pair.
40658 There is no dot-stuffing (and no dot-termination).
40660 . ////////////////////////////////////////////////////////////////////////////
40661 . ////////////////////////////////////////////////////////////////////////////
40663 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
40664 "DKIM, SPF, SRS and DMARC Support"
40666 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
40669 DKIM is a mechanism by which messages sent by some entity can be provably
40670 linked to a domain which that entity controls. It permits reputation to
40671 be tracked on a per-domain basis, rather than merely upon source IP address.
40672 DKIM is documented in RFC 6376.
40674 As DKIM relies on the message being unchanged in transit, messages handled
40675 by a mailing-list (which traditionally adds to the message) will not match
40676 any original DKIM signature.
40678 DKIM support is compiled into Exim by default if TLS support is present.
40679 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
40681 Exim's DKIM implementation allows for
40683 Signing outgoing messages: This function is implemented in the SMTP transport.
40684 It can co-exist with all other Exim features
40685 (including transport filters)
40686 except cutthrough delivery.
40688 Verifying signatures in incoming messages: This is implemented by an additional
40689 ACL (acl_smtp_dkim), which can be called several times per message, with
40690 different signature contexts.
40693 In typical Exim style, the verification implementation does not include any
40694 default "policy". Instead it enables you to build your own policy using
40695 Exim's standard controls.
40697 Please note that verification of DKIM signatures in incoming mail is turned
40698 on by default for logging (in the <= line) purposes.
40700 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
40701 When set, for each signature in incoming email,
40702 exim will log a line displaying the most important signature details, and the
40703 signature status. Here is an example (with line-breaks added for clarity):
40705 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
40706 d=facebookmail.com s=q1-2009b
40707 c=relaxed/relaxed a=rsa-sha1
40708 i=@facebookmail.com t=1252484542 [verification succeeded]
40711 You might want to turn off DKIM verification processing entirely for internal
40712 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
40713 control modifier. This should typically be done in the RCPT ACL, at points
40714 where you accept mail from relay sources (internal hosts or authenticated
40718 .section "Signing outgoing messages" "SECDKIMSIGN"
40719 .cindex "DKIM" "signing"
40721 For signing to be usable you must have published a DKIM record in DNS.
40722 Note that RFC 8301 (which does not cover EC keys) says:
40724 rsa-sha1 MUST NOT be used for signing or verifying.
40726 Signers MUST use RSA keys of at least 1024 bits for all keys.
40727 Signers SHOULD use RSA keys of at least 2048 bits.
40730 Note also that the key content (the 'p=' field)
40731 in the DNS record is different between RSA and EC keys;
40732 for the former it is the base64 of the ASN.1 for the RSA public key
40733 (equivalent to the private-key .pem with the header/trailer stripped)
40734 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
40736 Signing is enabled by setting private options on the SMTP transport.
40737 These options take (expandable) strings as arguments.
40739 .option dkim_domain smtp string list&!! unset
40740 The domain(s) you want to sign with.
40741 After expansion, this can be a list.
40742 Each element in turn,
40744 is put into the &%$dkim_domain%& expansion variable
40745 while expanding the remaining signing options.
40746 If it is empty after expansion, DKIM signing is not done,
40747 and no error will result even if &%dkim_strict%& is set.
40749 .option dkim_selector smtp string list&!! unset
40750 This sets the key selector string.
40751 After expansion, which can use &$dkim_domain$&, this can be a list.
40752 Each element in turn is put in the expansion
40753 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
40754 option along with &%$dkim_domain%&.
40755 If the option is empty after expansion, DKIM signing is not done for this domain,
40756 and no error will result even if &%dkim_strict%& is set.
40758 .option dkim_private_key smtp string&!! unset
40759 This sets the private key to use.
40760 You can use the &%$dkim_domain%& and
40761 &%$dkim_selector%& expansion variables to determine the private key to use.
40762 The result can either
40764 be a valid RSA private key in ASCII armor (.pem file), including line breaks
40766 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
40767 be a valid Ed25519 private key (same format as above)
40769 start with a slash, in which case it is treated as a file that contains
40772 be "0", "false" or the empty string, in which case the message will not
40773 be signed. This case will not result in an error, even if &%dkim_strict%&
40777 To generate keys under OpenSSL:
40779 openssl genrsa -out dkim_rsa.private 2048
40780 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
40782 The result file from the first command should be retained, and
40783 this option set to use it.
40784 Take the base-64 lines from the output of the second command, concatenated,
40785 for the DNS TXT record.
40786 See section 3.6 of RFC6376 for the record specification.
40790 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
40791 certtool --load-privkey=dkim_rsa.private --pubkey-info
40794 Note that RFC 8301 says:
40796 Signers MUST use RSA keys of at least 1024 bits for all keys.
40797 Signers SHOULD use RSA keys of at least 2048 bits.
40800 EC keys for DKIM are defined by RFC 8463.
40801 They are considerably smaller than RSA keys for equivalent protection.
40802 As they are a recent development, users should consider dual-signing
40803 (by setting a list of selectors, and an expansion for this option)
40804 for some transition period.
40805 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
40808 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
40810 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
40811 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
40814 To produce the required public key value for a DNS record:
40816 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
40817 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
40820 Exim also supports an alternate format
40821 of Ed25519 keys in DNS which was a candidate during development
40822 of the standard, but not adopted.
40823 A future release will probably drop that support.
40825 .option dkim_hash smtp string&!! sha256
40826 Can be set to any one of the supported hash methods, which are:
40828 &`sha1`& &-- should not be used, is old and insecure
40830 &`sha256`& &-- the default
40832 &`sha512`& &-- possibly more secure but less well supported
40835 Note that RFC 8301 says:
40837 rsa-sha1 MUST NOT be used for signing or verifying.
40840 .option dkim_identity smtp string&!! unset
40841 If set after expansion, the value is used to set an "i=" tag in
40842 the signing header. The DKIM standards restrict the permissible
40843 syntax of this optional tag to a mail address, with possibly-empty
40844 local part, an @, and a domain identical to or subdomain of the "d="
40845 tag value. Note that Exim does not check the value.
40847 .option dkim_canon smtp string&!! unset
40848 This option sets the canonicalization method used when signing a message.
40849 The DKIM RFC currently supports two methods: "simple" and "relaxed".
40850 The option defaults to "relaxed" when unset. Note: the current implementation
40851 only supports signing with the same canonicalization method for both headers and body.
40853 .option dkim_strict smtp string&!! unset
40854 This option defines how Exim behaves when signing a message that
40855 should be signed fails for some reason. When the expansion evaluates to
40856 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
40857 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
40860 .option dkim_sign_headers smtp string&!! "see below"
40861 If set, this option must expand to a colon-separated
40862 list of header names.
40863 Headers with these names, or the absence or such a header, will be included
40864 in the message signature.
40865 When unspecified, the header names listed in RFC4871 will be used,
40866 whether or not each header is present in the message.
40867 The default list is available for the expansion in the macro
40868 &"_DKIM_SIGN_HEADERS"&
40869 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
40871 If a name is repeated, multiple headers by that name (or the absence thereof)
40872 will be signed. The textually later headers in the headers part of the
40873 message are signed first, if there are multiples.
40875 A name can be prefixed with either an &"="& or a &"+"& character.
40876 If an &"="& prefix is used, all headers that are present with this name
40878 If a &"+"& prefix if used, all headers that are present with this name
40879 will be signed, and one signature added for a missing header with the
40880 name will be appended.
40882 .option dkim_timestamps smtp integer&!! unset
40883 This option controls the inclusion of timestamp information in the signature.
40884 If not set, no such information will be included.
40885 Otherwise, must be an unsigned number giving an offset in seconds from the current time
40887 (eg. 1209600 for two weeks);
40888 both creation (t=) and expiry (x=) tags will be included.
40890 RFC 6376 lists these tags as RECOMMENDED.
40893 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
40894 .cindex "DKIM" "verification"
40896 Verification of DKIM signatures in SMTP incoming email is done for all
40897 messages for which an ACL control &%dkim_disable_verify%& has not been set.
40898 .cindex DKIM "selecting signature algorithms"
40899 Individual classes of signature algorithm can be ignored by changing
40900 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
40901 The &%dkim_verify_minimal%& option can be set to cease verification
40902 processing for a message once the first passing signature is found.
40904 .cindex authentication "expansion item"
40905 Performing verification sets up information used by the
40906 &%authresults%& expansion item.
40908 For most purposes the default option settings suffice and the remainder
40909 of this section can be ignored.
40911 The results of verification are made available to the
40912 &%acl_smtp_dkim%& ACL, which can examine and modify them.
40913 A missing ACL definition defaults to accept.
40914 By default, the ACL is called once for each
40915 syntactically(!) correct signature in the incoming message.
40916 If any ACL call does not accept, the message is not accepted.
40917 If a cutthrough delivery was in progress for the message, that is
40918 summarily dropped (having wasted the transmission effort).
40920 To evaluate the verification result in the ACL
40921 a large number of expansion variables
40922 containing the signature status and its details are set up during the
40923 runtime of the ACL.
40925 Calling the ACL only for existing signatures is not sufficient to build
40926 more advanced policies. For that reason, the main option
40927 &%dkim_verify_signers%&, and an expansion variable
40928 &%$dkim_signers%& exist.
40930 The main option &%dkim_verify_signers%& can be set to a colon-separated
40931 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
40932 called. It is expanded when the message has been received. At this point,
40933 the expansion variable &%$dkim_signers%& already contains a colon-separated
40934 list of signer domains and identities for the message. When
40935 &%dkim_verify_signers%& is not specified in the main configuration,
40938 dkim_verify_signers = $dkim_signers
40940 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
40941 DKIM signature in the message. Current DKIM verifiers may want to explicitly
40942 call the ACL for known domains or identities. This would be achieved as follows:
40944 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
40946 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
40947 and "ebay.com", plus all domains and identities that have signatures in the message.
40948 You can also be more creative in constructing your policy. For example:
40950 dkim_verify_signers = $sender_address_domain:$dkim_signers
40953 If a domain or identity is listed several times in the (expanded) value of
40954 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
40956 Note that if the option is set using untrustworthy data
40957 (such as the From: header)
40958 care should be taken to force lowercase for domains
40959 and for the domain part if identities.
40960 The default setting can be regarded as trustworthy in this respect.
40962 If multiple signatures match a domain (or identity), the ACL is called once
40963 for each matching signature.
40966 Inside the DKIM ACL, the following expansion variables are
40967 available (from most to least important):
40971 .vitem &%$dkim_cur_signer%&
40972 The signer that is being evaluated in this ACL run. This can be a domain or
40973 an identity. This is one of the list items from the expanded main option
40974 &%dkim_verify_signers%& (see above).
40976 .vitem &%$dkim_verify_status%&
40977 Within the DKIM ACL,
40978 a string describing the general status of the signature. One of
40980 &%none%&: There is no signature in the message for the current domain or
40981 identity (as reflected by &%$dkim_cur_signer%&).
40983 &%invalid%&: The signature could not be verified due to a processing error.
40984 More detail is available in &%$dkim_verify_reason%&.
40986 &%fail%&: Verification of the signature failed. More detail is
40987 available in &%$dkim_verify_reason%&.
40989 &%pass%&: The signature passed verification. It is valid.
40992 This variable can be overwritten using an ACL 'set' modifier.
40993 This might, for instance, be done to enforce a policy restriction on
40994 hash-method or key-size:
40996 warn condition = ${if eq {$dkim_verify_status}{pass}}
40997 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
40998 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
40999 {< {$dkim_key_length}{1024}}}}
41000 logwrite = NOTE: forcing DKIM verify fail (was pass)
41001 set dkim_verify_status = fail
41002 set dkim_verify_reason = hash too weak or key too short
41005 So long as a DKIM ACL is defined (it need do no more than accept),
41006 after all the DKIM ACL runs have completed, the value becomes a
41007 colon-separated list of the values after each run.
41008 This is maintained for the mime, prdr and data ACLs.
41010 .vitem &%$dkim_verify_reason%&
41011 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41012 "fail" or "invalid". One of
41014 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41015 key for the domain could not be retrieved. This may be a temporary problem.
41017 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41018 record for the domain is syntactically invalid.
41020 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41021 body hash does not match the one specified in the signature header. This
41022 means that the message body was modified in transit.
41024 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41025 could not be verified. This may mean that headers were modified,
41026 re-written or otherwise changed in a way which is incompatible with
41027 DKIM verification. It may of course also mean that the signature is forged.
41030 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41032 .vitem &%$dkim_domain%&
41033 The signing domain. IMPORTANT: This variable is only populated if there is
41034 an actual signature in the message for the current domain or identity (as
41035 reflected by &%$dkim_cur_signer%&).
41037 .vitem &%$dkim_identity%&
41038 The signing identity, if present. IMPORTANT: This variable is only populated
41039 if there is an actual signature in the message for the current domain or
41040 identity (as reflected by &%$dkim_cur_signer%&).
41042 .vitem &%$dkim_selector%&
41043 The key record selector string.
41045 .vitem &%$dkim_algo%&
41046 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41047 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41048 may also be 'ed25519-sha256'.
41049 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41052 Note that RFC 8301 says:
41054 rsa-sha1 MUST NOT be used for signing or verifying.
41056 DKIM signatures identified as having been signed with historic
41057 algorithms (currently, rsa-sha1) have permanently failed evaluation
41060 To enforce this you must either have a DKIM ACL which checks this variable
41061 and overwrites the &$dkim_verify_status$& variable as discussed above,
41062 or have set the main option &%dkim_verify_hashes%& to exclude
41063 processing of such signatures.
41065 .vitem &%$dkim_canon_body%&
41066 The body canonicalization method. One of 'relaxed' or 'simple'.
41068 .vitem &%$dkim_canon_headers%&
41069 The header canonicalization method. One of 'relaxed' or 'simple'.
41071 .vitem &%$dkim_copiedheaders%&
41072 A transcript of headers and their values which are included in the signature
41073 (copied from the 'z=' tag of the signature).
41074 Note that RFC6376 requires that verification fail if the From: header is
41075 not included in the signature. Exim does not enforce this; sites wishing
41076 strict enforcement should code the check explicitly.
41078 .vitem &%$dkim_bodylength%&
41079 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41080 limit was set by the signer, "9999999999999" is returned. This makes sure
41081 that this variable always expands to an integer value.
41082 &*Note:*& The presence of the signature tag specifying a signing body length
41083 is one possible route to spoofing of valid DKIM signatures.
41084 A paranoid implementation might wish to regard signature where this variable
41085 shows less than the "no limit" return as being invalid.
41087 .vitem &%$dkim_created%&
41088 UNIX timestamp reflecting the date and time when the signature was created.
41089 When this was not specified by the signer, "0" is returned.
41091 .vitem &%$dkim_expires%&
41092 UNIX timestamp reflecting the date and time when the signer wants the
41093 signature to be treated as "expired". When this was not specified by the
41094 signer, "9999999999999" is returned. This makes it possible to do useful
41095 integer size comparisons against this value.
41096 Note that Exim does not check this value.
41098 .vitem &%$dkim_headernames%&
41099 A colon-separated list of names of headers included in the signature.
41101 .vitem &%$dkim_key_testing%&
41102 "1" if the key record has the "testing" flag set, "0" if not.
41104 .vitem &%$dkim_key_nosubdomains%&
41105 "1" if the key record forbids subdomaining, "0" otherwise.
41107 .vitem &%$dkim_key_srvtype%&
41108 Service type (tag s=) from the key record. Defaults to "*" if not specified
41111 .vitem &%$dkim_key_granularity%&
41112 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41115 .vitem &%$dkim_key_notes%&
41116 Notes from the key record (tag n=).
41118 .vitem &%$dkim_key_length%&
41119 Number of bits in the key.
41120 Valid only once the key is loaded, which is at the time the header signature
41121 is verified, which is after the body hash is.
41123 Note that RFC 8301 says:
41125 Verifiers MUST NOT consider signatures using RSA keys of
41126 less than 1024 bits as valid signatures.
41129 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41134 In addition, two ACL conditions are provided:
41137 .vitem &%dkim_signers%&
41138 ACL condition that checks a colon-separated list of domains or identities
41139 for a match against the domain or identity that the ACL is currently verifying
41140 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41141 verb to a group of domains or identities. For example:
41144 # Warn when Mail purportedly from GMail has no gmail signature
41145 warn sender_domains = gmail.com
41146 dkim_signers = gmail.com
41148 log_message = GMail sender without gmail.com DKIM signature
41151 Note that the above does not check for a total lack of DKIM signing;
41152 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41154 .vitem &%dkim_status%&
41155 ACL condition that checks a colon-separated list of possible DKIM verification
41156 results against the actual result of verification. This is typically used
41157 to restrict an ACL verb to a list of verification outcomes, for example:
41160 deny sender_domains = paypal.com:paypal.de
41161 dkim_signers = paypal.com:paypal.de
41162 dkim_status = none:invalid:fail
41163 message = Mail from Paypal with invalid/missing signature
41166 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41167 see the documentation of the &%$dkim_verify_status%& expansion variable above
41168 for more information of what they mean.
41174 .section "SPF (Sender Policy Framework)" SECSPF
41175 .cindex SPF verification
41177 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41178 messages with its domain in the envelope from, documented by RFC 7208.
41179 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41180 the &url(http://openspf.org).
41181 . --- 2019-10-28: still not https, open-spf.org is told to be a
41182 . --- web-archive copy of the now dead openspf.org site
41183 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41186 Messages sent by a system not authorised will fail checking of such assertions.
41187 This includes retransmissions done by traditional forwarders.
41189 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41190 &_Local/Makefile_&. The support uses the &_libspf2_& library
41191 &url(https://www.libspf2.org/).
41192 There is no Exim involvement in the transmission of messages;
41193 publishing certain DNS records is all that is required.
41195 For verification, an ACL condition and an expansion lookup are provided.
41196 .cindex authentication "expansion item"
41197 Performing verification sets up information used by the
41198 &%authresults%& expansion item.
41201 .cindex SPF "ACL condition"
41202 .cindex ACL "spf condition"
41203 The ACL condition "spf" can be used at or after the MAIL ACL.
41204 It takes as an argument a list of strings giving the outcome of the SPF check,
41205 and will succeed for any matching outcome.
41209 The SPF check passed, the sending host is positively verified by SPF.
41212 The SPF check failed, the sending host is NOT allowed to send mail for the
41213 domain in the envelope-from address.
41215 .vitem &%softfail%&
41216 The SPF check failed, but the queried domain can't absolutely confirm that this
41220 The queried domain does not publish SPF records.
41223 The SPF check returned a "neutral" state. This means the queried domain has
41224 published a SPF record, but wants to allow outside servers to send mail under
41225 its domain as well. This should be treated like "none".
41227 .vitem &%permerror%&
41228 This indicates a syntax error in the SPF record of the queried domain.
41229 You may deny messages when this occurs.
41231 .vitem &%temperror%&
41232 This indicates a temporary error during all processing, including Exim's
41233 SPF processing. You may defer messages when this occurs.
41236 You can prefix each string with an exclamation mark to invert
41237 its meaning, for example "!fail" will match all results but
41238 "fail". The string list is evaluated left-to-right, in a
41239 short-circuit fashion.
41244 message = $sender_host_address is not allowed to send mail from \
41245 ${if def:sender_address_domain \
41246 {$sender_address_domain}{$sender_helo_name}}. \
41247 Please see http://www.open-spf.org/Why;\
41248 identity=${if def:sender_address_domain \
41249 {$sender_address}{$sender_helo_name}};\
41250 ip=$sender_host_address
41253 Note: The above mentioned URL may not be as helpful as expected. You are
41254 encouraged to replace the link with a link to a site with more
41257 When the spf condition has run, it sets up several expansion
41260 .cindex SPF "verification variables"
41262 .vitem &$spf_header_comment$&
41263 .vindex &$spf_header_comment$&
41264 This contains a human-readable string describing the outcome
41265 of the SPF check. You can add it to a custom header or use
41266 it for logging purposes.
41268 .vitem &$spf_received$&
41269 .vindex &$spf_received$&
41270 This contains a complete Received-SPF: header that can be
41271 added to the message. Please note that according to the SPF
41272 draft, this header must be added at the top of the header
41273 list. Please see section 10 on how you can do this.
41275 Note: in case of "Best-guess" (see below), the convention is
41276 to put this string in a header called X-SPF-Guess: instead.
41278 .vitem &$spf_result$&
41279 .vindex &$spf_result$&
41280 This contains the outcome of the SPF check in string form,
41281 one of pass, fail, softfail, none, neutral, permerror or
41284 .vitem &$spf_result_guessed$&
41285 .vindex &$spf_result_guessed$&
41286 This boolean is true only if a best-guess operation was used
41287 and required in order to obtain a result.
41289 .vitem &$spf_smtp_comment$&
41290 .vindex &$spf_smtp_comment$&
41291 .vindex &%spf_smtp_comment_template%&
41292 This contains a string that can be used in a SMTP response
41293 to the calling party. Useful for "fail".
41294 The string is generated by the SPF library from the template configured in the main config
41295 option &%spf_smtp_comment_template%&.
41299 .cindex SPF "ACL condition"
41300 .cindex ACL "spf_guess condition"
41301 .cindex SPF "best guess"
41302 In addition to SPF, you can also perform checks for so-called
41303 "Best-guess". Strictly speaking, "Best-guess" is not standard
41304 SPF, but it is supported by the same framework that enables SPF
41306 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41307 for a description of what it means.
41308 . --- 2019-10-28: still not https:
41310 To access this feature, simply use the spf_guess condition in place
41311 of the spf one. For example:
41314 deny spf_guess = fail
41315 message = $sender_host_address doesn't look trustworthy to me
41318 In case you decide to reject messages based on this check, you
41319 should note that although it uses the same framework, "Best-guess"
41320 is not SPF, and therefore you should not mention SPF at all in your
41323 When the spf_guess condition has run, it sets up the same expansion
41324 variables as when spf condition is run, described above.
41326 Additionally, since Best-guess is not standardized, you may redefine
41327 what "Best-guess" means to you by redefining the main configuration
41328 &%spf_guess%& option.
41329 For example, the following:
41332 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41335 would relax host matching rules to a broader network range.
41338 .cindex SPF "lookup expansion"
41340 A lookup expansion is also available. It takes an email
41341 address as the key and an IP address
41346 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41349 The lookup will return the same result strings as can appear in
41350 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41356 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41357 .cindex SRS "sender rewriting scheme"
41360 SRS can be used to modify sender addresses when forwarding so that
41361 SPF verification does not object to them.
41362 It operates by encoding the original envelope sender in a new
41363 sender local part and using a domain run by the forwarding site
41364 as the new domain for the sender. Any DSN message should be returned
41365 to this new sender at the forwarding site, which can extract the
41366 original sender from the coded local part and forward the DSN to
41369 This is a way of avoiding the breakage that SPF does to forwarding.
41370 The constructed local-part will be longer than the original,
41371 leading to possible problems with very long addresses.
41372 The changing of the sender address also hinders the tracing of mail
41375 Exim can be built to include native SRS support. To do this
41376 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41377 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41379 The support is limited to SRS0-encoding; SRS1 is not supported.
41381 .cindex SRS excoding
41382 To encode an address use this expansion item:
41384 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41385 .cindex "&%srs_encode%& expansion item"
41386 .cindex SRS "expansion item"
41387 The first argument should be a secret known and used by all systems
41388 handling the recipient domain for the original message.
41389 There is no need to periodically change this key; a timestamp is also
41391 The second argument should be given as the envelope sender address before this
41392 encoding operation.
41393 The third argument should be the recipient domain of the message when
41394 it arrived at this system.
41397 .cindex SRS decoding
41398 To decode an address use this expansion condition:
41400 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
41401 The first argument should be the recipient local prt as is was received.
41402 The second argument is the site secret.
41404 If the messages is not for an SRS-encoded recipient the condition will
41405 return false. If it is, the condition will return true and the variable
41406 &$srs_recipient$& will be set to the decoded (original) value.
41412 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
41418 # if outbound, and forwarding has been done, use an alternate transport
41419 domains = ! +my_domains
41420 transport = ${if eq {$local_part@$domain} \
41421 {$original_local_part@$original_domain} \
41422 {remote_smtp} {remote_forwarded_smtp}}
41427 domains = +my_domains
41428 # detect inbound bounces which are SRS'd, and decode them
41429 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
41430 data = $srs_recipient
41432 inbound_srs_failure:
41435 domains = +my_domains
41436 # detect inbound bounces which look SRS'd but are invalid
41437 condition = ${if inbound_srs {$local_part} {}}
41439 data = :fail: Invalid SRS recipient address
41441 #... further routers here
41444 # transport; should look like the non-forward outbound
41445 # one, plus the max_rcpt and return_path options
41446 remote_forwarded_smtp:
41448 # modify the envelope from, for mails that we forward
41450 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
41458 .section DMARC SECDMARC
41459 .cindex DMARC verification
41461 DMARC combines feedback from SPF, DKIM, and header From: in order
41462 to attempt to provide better indicators of the authenticity of an
41463 email. This document does not explain the fundamentals; you
41464 should read and understand how it works by visiting the website at
41465 &url(http://www.dmarc.org/).
41467 If Exim is built with DMARC support,
41468 the libopendmarc library is used.
41470 For building Exim yourself, obtain the library from
41471 &url(http://sourceforge.net/projects/opendmarc/)
41472 to obtain a copy, or find it in your favorite package
41473 repository. You will need to attend to the local/Makefile feature
41474 SUPPORT_DMARC and the associated LDFLAGS addition.
41475 This description assumes
41476 that headers will be in /usr/local/include, and that the libraries
41477 are in /usr/local/lib.
41481 There are three main-configuration options:
41482 .cindex DMARC "configuration options"
41484 The &%dmarc_tld_file%& option
41485 .oindex &%dmarc_tld_file%&
41486 defines the location of a text file of valid
41487 top level domains the opendmarc library uses
41488 during domain parsing. Maintained by Mozilla,
41489 the most current version can be downloaded
41490 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
41491 See also the util/renew-opendmarc-tlds.sh script.
41492 The default for the option is unset.
41493 If not set, DMARC processing is disabled.
41496 The &%dmarc_history_file%& option, if set
41497 .oindex &%dmarc_history_file%&
41498 defines the location of a file to log results
41499 of dmarc verification on inbound emails. The
41500 contents are importable by the opendmarc tools
41501 which will manage the data, send out DMARC
41502 reports, and expire the data. Make sure the
41503 directory of this file is writable by the user
41505 The default is unset.
41507 The &%dmarc_forensic_sender%& option
41508 .oindex &%dmarc_forensic_sender%&
41509 defines an alternate email address to use when sending a
41510 forensic report detailing alignment failures
41511 if a sender domain's dmarc record specifies it
41512 and you have configured Exim to send them.
41513 If set, this is expanded and used for the
41514 From: header line; the address is extracted
41515 from it and used for the envelope from.
41516 If not set (the default), the From: header is expanded from
41517 the dsn_from option, and <> is used for the
41520 . I wish we had subsections...
41522 .cindex DMARC controls
41523 By default, the DMARC processing will run for any remote,
41524 non-authenticated user. It makes sense to only verify DMARC
41525 status of messages coming from remote, untrusted sources. You can
41526 use standard conditions such as hosts, senders, etc, to decide that
41527 DMARC verification should *not* be performed for them and disable
41528 DMARC with an ACL control modifier:
41530 control = dmarc_disable_verify
41532 A DMARC record can also specify a "forensic address", which gives
41533 exim an email address to submit reports about failed alignment.
41534 Exim does not do this by default because in certain conditions it
41535 results in unintended information leakage (what lists a user might
41536 be subscribed to, etc). You must configure exim to submit forensic
41537 reports to the owner of the domain. If the DMARC record contains a
41538 forensic address and you specify the control statement below, then
41539 exim will send these forensic emails. It is also advised that you
41540 configure a &%dmarc_forensic_sender%& because the default sender address
41541 construction might be inadequate.
41543 control = dmarc_enable_forensic
41545 (AGAIN: You can choose not to send these forensic reports by simply
41546 not putting the dmarc_enable_forensic control line at any point in
41547 your exim config. If you don't tell exim to send them, it will not
41550 There are no options to either control. Both must appear before
41555 DMARC checks cam be run on incoming SMTP messages by using the
41556 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
41557 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
41558 condition. Putting this condition in the ACLs is required in order
41559 for a DMARC check to actually occur. All of the variables are set
41560 up before the DATA ACL, but there is no actual DMARC check that
41561 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
41563 The &"dmarc_status"& condition takes a list of strings on its
41564 right-hand side. These strings describe recommended action based
41565 on the DMARC check. To understand what the policy recommendations
41566 mean, refer to the DMARC website above. Valid strings are:
41568 &'accept '& The DMARC check passed and the library recommends accepting the email.
41569 &'reject '& The DMARC check failed and the library recommends rejecting the email.
41570 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
41571 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
41572 &'norecord '& No policy section in the DMARC record for this sender domain.
41573 &'nofrom '& Unable to determine the domain of the sender.
41574 &'temperror '& Library error or dns error.
41575 &'off '& The DMARC check was disabled for this email.
41577 You can prefix each string with an exclamation mark to invert its
41578 meaning, for example "!accept" will match all results but
41579 "accept". The string list is evaluated left-to-right in a
41580 short-circuit fashion. When a string matches the outcome of the
41581 DMARC check, the condition succeeds. If none of the listed
41582 strings matches the outcome of the DMARC check, the condition
41585 Of course, you can also use any other lookup method that Exim
41586 supports, including LDAP, Postgres, MySQL, etc, as long as the
41587 result is a list of colon-separated strings.
41589 Performing the check sets up information used by the
41590 &%authresults%& expansion item.
41592 Several expansion variables are set before the DATA ACL is
41593 processed, and you can use them in this ACL. The following
41594 expansion variables are available:
41597 .vitem &$dmarc_status$&
41598 .vindex &$dmarc_status$&
41599 .cindex DMARC result
41600 A one word status indicating what the DMARC library
41601 thinks of the email. It is a combination of the results of
41602 DMARC record lookup and the SPF/DKIM/DMARC processing results
41603 (if a DMARC record was found). The actual policy declared
41604 in the DMARC record is in a separate expansion variable.
41606 .vitem &$dmarc_status_text$&
41607 .vindex &$dmarc_status_text$&
41608 Slightly longer, human readable status.
41610 .vitem &$dmarc_used_domain$&
41611 .vindex &$dmarc_used_domain$&
41612 The domain which DMARC used to look up the DMARC policy record.
41614 .vitem &$dmarc_domain_policy$&
41615 .vindex &$dmarc_domain_policy$&
41616 The policy declared in the DMARC record. Valid values
41617 are "none", "reject" and "quarantine". It is blank when there
41618 is any error, including no DMARC record.
41623 By default, Exim's DMARC configuration is intended to be
41624 non-intrusive and conservative. To facilitate this, Exim will not
41625 create any type of logging files without explicit configuration by
41626 you, the admin. Nor will Exim send out any emails/reports about
41627 DMARC issues without explicit configuration by you, the admin (other
41628 than typical bounce messages that may come about due to ACL
41629 processing or failure delivery issues).
41631 In order to log statistics suitable to be imported by the opendmarc
41632 tools, you need to:
41634 Configure the global option &%dmarc_history_file%&
41636 Configure cron jobs to call the appropriate opendmarc history
41637 import scripts and truncating the dmarc_history_file
41640 In order to send forensic reports, you need to:
41642 Configure the global option &%dmarc_forensic_sender%&
41644 Configure, somewhere before the DATA ACL, the control option to
41645 enable sending DMARC forensic reports
41653 warn domains = +local_domains
41654 hosts = +local_hosts
41655 control = dmarc_disable_verify
41657 warn !domains = +screwed_up_dmarc_records
41658 control = dmarc_enable_forensic
41660 warn condition = (lookup if destined to mailing list)
41661 set acl_m_mailing_list = 1
41664 warn dmarc_status = accept : none : off
41666 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
41668 warn dmarc_status = !accept
41670 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
41672 warn dmarc_status = quarantine
41674 set $acl_m_quarantine = 1
41675 # Do something in a transport with this flag variable
41677 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
41678 condition = ${if eq{$acl_m_mailing_list}{1}}
41679 message = Messages from $dmarc_used_domain break mailing lists
41681 deny dmarc_status = reject
41683 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
41685 warn add_header = :at_start:${authresults {$primary_hostname}}
41692 . ////////////////////////////////////////////////////////////////////////////
41693 . ////////////////////////////////////////////////////////////////////////////
41695 .chapter "Proxies" "CHAPproxies" &&&
41697 .cindex "proxy support"
41698 .cindex "proxy" "access via"
41700 A proxy is an intermediate system through which communication is passed.
41701 Proxies may provide a security, availability or load-distribution function.
41704 .section "Inbound proxies" SECTproxyInbound
41705 .cindex proxy inbound
41706 .cindex proxy "server side"
41707 .cindex proxy "Proxy protocol"
41708 .cindex "Proxy protocol" proxy
41710 Exim has support for receiving inbound SMTP connections via a proxy
41711 that uses &"Proxy Protocol"& to speak to it.
41712 To include this support, include &"SUPPORT_PROXY=yes"&
41715 It was built on the HAProxy specification, found at
41716 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
41718 The purpose of this facility is so that an application load balancer,
41719 such as HAProxy, can sit in front of several Exim servers
41720 to distribute load.
41721 Exim uses the local protocol communication with the proxy to obtain
41722 the remote SMTP system IP address and port information.
41723 There is no logging if a host passes or
41724 fails Proxy Protocol negotiation, but it can easily be determined and
41725 recorded in an ACL (example is below).
41727 Use of a proxy is enabled by setting the &%hosts_proxy%&
41728 main configuration option to a hostlist; connections from these
41729 hosts will use Proxy Protocol.
41730 Exim supports both version 1 and version 2 of the Proxy Protocol and
41731 automatically determines which version is in use.
41733 The Proxy Protocol header is the first data received on a TCP connection
41734 and is inserted before any TLS-on-connect handshake from the client; Exim
41735 negotiates TLS between Exim-as-server and the remote client, not between
41736 Exim and the proxy server.
41738 The following expansion variables are usable
41739 (&"internal"& and &"external"& here refer to the interfaces
41742 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
41743 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
41744 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
41745 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
41746 &'proxy_session '& boolean: SMTP connection via proxy
41748 If &$proxy_session$& is set but &$proxy_external_address$& is empty
41749 there was a protocol error.
41750 The variables &$sender_host_address$& and &$sender_host_port$&
41751 will have values for the actual client system, not the proxy.
41753 Since the real connections are all coming from the proxy, and the
41754 per host connection tracking is done before Proxy Protocol is
41755 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
41756 handle all of the parallel volume you expect per inbound proxy.
41757 With the option set so high, you lose the ability
41758 to protect your server from many connections from one IP.
41759 In order to prevent your server from overload, you
41760 need to add a per connection ratelimit to your connect ACL.
41761 A possible solution is:
41763 # Set max number of connections per host
41765 # Or do some kind of IP lookup in a flat file or database
41766 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
41768 defer ratelimit = LIMIT / 5s / per_conn / strict
41769 message = Too many connections from this IP right now
41774 .section "Outbound proxies" SECTproxySOCKS
41775 .cindex proxy outbound
41776 .cindex proxy "client side"
41777 .cindex proxy SOCKS
41778 .cindex SOCKS proxy
41779 Exim has support for sending outbound SMTP via a proxy
41780 using a protocol called SOCKS5 (defined by RFC1928).
41781 The support can be optionally included by defining SUPPORT_SOCKS=yes in
41784 Use of a proxy is enabled by setting the &%socks_proxy%& option
41785 on an smtp transport.
41786 The option value is expanded and should then be a list
41787 (colon-separated by default) of proxy specifiers.
41788 Each proxy specifier is a list
41789 (space-separated by default) where the initial element
41790 is an IP address and any subsequent elements are options.
41792 Options are a string <name>=<value>.
41793 The list of options is in the following table:
41795 &'auth '& authentication method
41796 &'name '& authentication username
41797 &'pass '& authentication password
41799 &'tmo '& connection timeout
41801 &'weight '& selection bias
41804 More details on each of these options follows:
41807 .cindex authentication "to proxy"
41808 .cindex proxy authentication
41809 &%auth%&: Either &"none"& (default) or &"name"&.
41810 Using &"name"& selects username/password authentication per RFC 1929
41811 for access to the proxy.
41812 Default is &"none"&.
41814 &%name%&: sets the username for the &"name"& authentication method.
41817 &%pass%&: sets the password for the &"name"& authentication method.
41820 &%port%&: the TCP port number to use for the connection to the proxy.
41823 &%tmo%&: sets a connection timeout in seconds for this proxy.
41826 &%pri%&: specifies a priority for the proxy within the list,
41827 higher values being tried first.
41828 The default priority is 1.
41830 &%weight%&: specifies a selection bias.
41831 Within a priority set servers are queried in a random fashion,
41832 weighted by this value.
41833 The default value for selection bias is 1.
41836 Proxies from the list are tried according to their priority
41837 and weight settings until one responds. The timeout for the
41838 overall connection applies to the set of proxied attempts.
41840 .section Logging SECTproxyLog
41841 To log the (local) IP of a proxy in the incoming or delivery logline,
41842 add &"+proxy"& to the &%log_selector%& option.
41843 This will add a component tagged with &"PRX="& to the line.
41845 . ////////////////////////////////////////////////////////////////////////////
41846 . ////////////////////////////////////////////////////////////////////////////
41848 .chapter "Internationalisation" "CHAPi18n" &&&
41849 "Internationalisation""
41850 .cindex internationalisation "email address"
41853 .cindex utf8 "mail name handling"
41855 Exim has support for Internationalised mail names.
41856 To include this it must be built with SUPPORT_I18N and the libidn library.
41857 Standards supported are RFCs 2060, 5890, 6530 and 6533.
41859 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
41860 instead of it) then IDNA2008 is supported; this adds an extra library
41861 requirement, upon libidn2.
41863 .section "MTA operations" SECTi18nMTA
41864 .cindex SMTPUTF8 "ESMTP option"
41865 .cindex "ESMTP extensions" SMTPUTF8
41866 The main configuration option &%smtputf8_advertise_hosts%& specifies
41867 a host list. If this matches the sending host and
41868 accept_8bitmime is true (the default) then the ESMTP option
41869 SMTPUTF8 will be advertised.
41871 If the sender specifies the SMTPUTF8 option on a MAIL command
41872 international handling for the message is enabled and
41873 the expansion variable &$message_smtputf8$& will have value TRUE.
41875 The option &%allow_utf8_domains%& is set to true for this
41876 message. All DNS lookups are converted to a-label form
41877 whatever the setting of &%allow_utf8_domains%&
41878 when Exim is built with SUPPORT_I18N.
41880 Both localparts and domain are maintained as the original
41881 UTF-8 form internally; any comparison or regular-expression use will
41882 require appropriate care. Filenames created, eg. by
41883 the appendfile transport, will have UTF-8 names.
41885 HELO names sent by the smtp transport will have any UTF-8
41886 components expanded to a-label form,
41887 and any certificate name checks will be done using the a-label
41890 .cindex log protocol
41891 .cindex SMTPUTF8 logging
41892 .cindex i18n logging
41893 Log lines and Received-by: header lines will acquire a "utf8"
41894 prefix on the protocol element, eg. utf8esmtp.
41896 The following expansion operators can be used:
41898 ${utf8_domain_to_alabel:str}
41899 ${utf8_domain_from_alabel:str}
41900 ${utf8_localpart_to_alabel:str}
41901 ${utf8_localpart_from_alabel:str}
41904 .cindex utf8 "address downconversion"
41905 .cindex i18n "utf8 address downconversion"
41907 may use the following modifier:
41909 control = utf8_downconvert
41910 control = utf8_downconvert/<value>
41912 This sets a flag requiring that envelope addresses are converted to
41913 a-label form before smtp delivery.
41914 This is usually for use in a Message Submission Agent context,
41915 but could be used for any message.
41917 If a value is appended it may be:
41919 &`1 `& mandatory downconversion
41920 &`0 `& no downconversion
41921 &`-1 `& if SMTPUTF8 not supported by destination host
41923 If no value is given, 1 is used.
41925 If mua_wrapper is set, the utf8_downconvert control
41926 is initially set to -1.
41928 The smtp transport has an option &%utf8_downconvert%&.
41929 If set it must expand to one of the three values described above,
41930 or an empty string.
41931 If non-empty it overrides value previously set
41932 (due to mua_wrapper or by an ACL control).
41935 There is no explicit support for VRFY and EXPN.
41936 Configurations supporting these should inspect
41937 &$smtp_command_argument$& for an SMTPUTF8 argument.
41939 There is no support for LMTP on Unix sockets.
41940 Using the "lmtp" protocol option on an smtp transport,
41941 for LMTP over TCP, should work as expected.
41943 There is no support for DSN unitext handling,
41944 and no provision for converting logging from or to UTF-8.
41948 .section "MDA operations" SECTi18nMDA
41949 To aid in constructing names suitable for IMAP folders
41950 the following expansion operator can be used:
41952 ${imapfolder {<string>} {<sep>} {<specials>}}
41955 The string is converted from the charset specified by
41956 the "headers charset" command (in a filter file)
41957 or &%headers_charset%& main configuration option (otherwise),
41959 modified UTF-7 encoding specified by RFC 2060,
41960 with the following exception: All occurrences of <sep>
41961 (which has to be a single character)
41962 are replaced with periods ("."), and all periods and slashes that are not
41963 <sep> and are not in the <specials> string are BASE64 encoded.
41965 The third argument can be omitted, defaulting to an empty string.
41966 The second argument can be omitted, defaulting to "/".
41968 This is the encoding used by Courier for Maildir names on disk, and followed
41969 by many other IMAP servers.
41973 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
41974 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
41975 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
41978 Note that the source charset setting is vital, and also that characters
41979 must be representable in UTF-16.
41982 . ////////////////////////////////////////////////////////////////////////////
41983 . ////////////////////////////////////////////////////////////////////////////
41985 .chapter "Events" "CHAPevents" &&&
41989 The events mechanism in Exim can be used to intercept processing at a number
41990 of points. It was originally invented to give a way to do customised logging
41991 actions (for example, to a database) but can also be used to modify some
41992 processing actions.
41994 Most installations will never need to use Events.
41995 The support can be left out of a build by defining DISABLE_EVENT=yes
41996 in &_Local/Makefile_&.
41998 There are two major classes of events: main and transport.
41999 The main configuration option &%event_action%& controls reception events;
42000 a transport option &%event_action%& controls delivery events.
42002 Both options are a string which is expanded when the event fires.
42003 An example might look like:
42004 .cindex logging custom
42006 event_action = ${if eq {msg:delivery}{$event_name} \
42007 {${lookup pgsql {SELECT * FROM record_Delivery( \
42008 '${quote_pgsql:$sender_address_domain}',\
42009 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42010 '${quote_pgsql:$domain}', \
42011 '${quote_pgsql:${lc:$local_part}}', \
42012 '${quote_pgsql:$host_address}', \
42013 '${quote_pgsql:${lc:$host}}', \
42014 '${quote_pgsql:$message_exim_id}')}} \
42018 Events have names which correspond to the point in process at which they fire.
42019 The name is placed in the variable &$event_name$& and the event action
42020 expansion must check this, as it will be called for every possible event type.
42022 The current list of events is:
42024 &`dane:fail after transport `& per connection
42025 &`msg:complete after main `& per message
42026 &`msg:defer after transport `& per message per delivery try
42027 &`msg:delivery after transport `& per recipient
42028 &`msg:rcpt:host:defer after transport `& per recipient per host
42029 &`msg:rcpt:defer after transport `& per recipient
42030 &`msg:host:defer after transport `& per host per delivery try; host errors
42031 &`msg:fail:delivery after transport `& per recipient
42032 &`msg:fail:internal after main `& per recipient
42033 &`tcp:connect before transport `& per connection
42034 &`tcp:close after transport `& per connection
42035 &`tls:cert before both `& per certificate in verification chain
42036 &`smtp:connect after transport `& per connection
42037 &`smtp:ehlo after transport `& per connection
42039 New event types may be added in future.
42041 The event name is a colon-separated list, defining the type of
42042 event in a tree of possibilities. It may be used as a list
42043 or just matched on as a whole. There will be no spaces in the name.
42045 The second column in the table above describes whether the event fires
42046 before or after the action is associates with. Those which fire before
42047 can be used to affect that action (more on this below).
42049 The third column in the table above says what section of the configuration
42050 should define the event action.
42052 An additional variable, &$event_data$&, is filled with information varying
42053 with the event type:
42055 &`dane:fail `& failure reason
42056 &`msg:defer `& error string
42057 &`msg:delivery `& smtp confirmation message
42058 &`msg:fail:internal `& failure reason
42059 &`msg:fail:delivery `& smtp error message
42060 &`msg:host:defer `& error string
42061 &`msg:rcpt:host:defer `& error string
42062 &`msg:rcpt:defer `& error string
42063 &`tls:cert `& verification chain depth
42064 &`smtp:connect `& smtp banner
42065 &`smtp:ehlo `& smtp ehlo response
42068 The :defer events populate one extra variable: &$event_defer_errno$&.
42070 For complex operations an ACL expansion can be used in &%event_action%&
42071 however due to the multiple contexts that Exim operates in during
42072 the course of its processing:
42074 variables set in transport events will not be visible outside that
42077 acl_m variables in a server context are lost on a new connection,
42078 and after smtp helo/ehlo/mail/starttls/rset commands
42080 Using an ACL expansion with the logwrite modifier can be
42081 a useful way of writing to the main log.
42083 The expansion of the event_action option should normally
42084 return an empty string. Should it return anything else the
42085 following will be forced:
42087 &`tcp:connect `& do not connect
42088 &`tls:cert `& refuse verification
42089 &`smtp:connect `& close connection
42091 All other message types ignore the result string, and
42092 no other use is made of it.
42094 For a tcp:connect event, if the connection is being made to a proxy
42095 then the address and port variables will be that of the proxy and not
42098 For tls:cert events, if GnuTLS is in use this will trigger only per
42099 chain element received on the connection.
42100 For OpenSSL it will trigger for every chain element including those
42103 . ////////////////////////////////////////////////////////////////////////////
42104 . ////////////////////////////////////////////////////////////////////////////
42106 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42107 "Adding drivers or lookups"
42108 .cindex "adding drivers"
42109 .cindex "new drivers, adding"
42110 .cindex "drivers" "adding new"
42111 The following actions have to be taken in order to add a new router, transport,
42112 authenticator, or lookup type to Exim:
42115 Choose a name for the driver or lookup type that does not conflict with any
42116 existing name; I will use &"newdriver"& in what follows.
42118 Add to &_src/EDITME_& the line:
42120 <&'type'&>&`_NEWDRIVER=yes`&
42122 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42123 code is not to be included in the binary by default, comment this line out. You
42124 should also add any relevant comments about the driver or lookup type.
42126 Add to &_src/config.h.defaults_& the line:
42128 #define <type>_NEWDRIVER
42131 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42132 and create a table entry as is done for all the other drivers and lookup types.
42134 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42135 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42136 Add your &`NEWDRIVER`& to that list.
42137 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42138 simple form that most lookups have.
42140 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42141 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42142 driver or lookup type and add it to the definition of OBJ.
42144 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42145 definition of OBJ_MACRO. Add a set of line to do the compile also.
42147 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42150 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42151 as for other drivers and lookups.
42154 Then all you need to do is write the code! A good way to start is to make a
42155 proforma by copying an existing module of the same type, globally changing all
42156 occurrences of the name, and cutting out most of the code. Note that any
42157 options you create must be listed in alphabetical order, because the tables are
42158 searched using a binary chop procedure.
42160 There is a &_README_& file in each of the sub-directories of &_src_& describing
42161 the interface that is expected.
42166 . ////////////////////////////////////////////////////////////////////////////
42167 . ////////////////////////////////////////////////////////////////////////////
42169 . /////////////////////////////////////////////////////////////////////////////
42170 . These lines are processing instructions for the Simple DocBook Processor that
42171 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42172 . PDFs than using xmlto and fop. They will be ignored by all other XML
42174 . /////////////////////////////////////////////////////////////////////////////
42179 foot_right_recto="&chaptertitle;"
42180 foot_right_verso="&chaptertitle;"
42184 .makeindex "Options index" "option"
42185 .makeindex "Variables index" "variable"
42186 .makeindex "Concept index" "concept"
42189 . /////////////////////////////////////////////////////////////////////////////
42190 . /////////////////////////////////////////////////////////////////////////////