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 printing 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 generate the outermost <book> element that wraps then 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 "4.86"
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 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 . --- the 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 the program,
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 the 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, the 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(http://www.uit.co.uk/exim-book/)).
397 This 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 the program 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 the program (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"
441 The main specification and the specification of the filtering language are also
442 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
443 &<<SECTavail>>& below tells you how to get hold of these.
447 .section "FTP and web sites" "SECID2"
450 The primary site for Exim source distributions is currently the University of
451 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
452 distribution'& below. In addition, there is a web site and an FTP site at
453 &%exim.org%&. These are now also hosted at the University of Cambridge. The
454 &%exim.org%& site was previously hosted for a number of years by Energis
455 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
459 As well as Exim distribution tar files, the Exim web site contains a number of
460 differently formatted versions of the documentation. A recent addition to the
461 online information is the Exim wiki (&url(http://wiki.exim.org)),
462 which contains what used to be a separate FAQ, as well as various other
463 examples, tips, and know-how that have been contributed by Exim users.
466 An Exim Bugzilla exists at &url(http://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.
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(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on this list and not on the general Exim
495 .section "Exim training" "SECID4"
496 .cindex "training courses"
497 Training courses in Cambridge (UK) used to be run annually by the author of
498 Exim, before he retired. At the time of writing, there are no plans to run
499 further Exim courses in Cambridge. However, if that changes, relevant
500 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
502 .section "Bug reports" "SECID5"
503 .cindex "bug reports"
504 .cindex "reporting bugs"
505 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
506 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
507 whether some behaviour is a bug or not, the best thing to do is to post a
508 message to the &'exim-dev'& mailing list and have it discussed.
512 .section "Where to find the Exim distribution" "SECTavail"
514 .cindex "distribution" "ftp site"
515 The master ftp site for the Exim distribution is
517 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
521 &*ftp://ftp.exim.org/pub/exim*&
523 The file references that follow are relative to the &_exim_& directories at
524 these sites. There are now quite a number of independent mirror sites around
525 the world. Those that I know about are listed in the file called &_Mirrors_&.
527 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
528 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
529 distributions), and &_Testing_& for testing versions. In the &_exim4_&
530 subdirectory, the current release can always be found in files called
533 &_exim-n.nn.tar.bz2_&
535 where &'n.nn'& is the highest such version number in the directory. The two
536 files contain identical data; the only difference is the type of compression.
537 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
539 .cindex "distribution" "signing details"
540 .cindex "distribution" "public key"
541 .cindex "public key for signed distribution"
542 The distributions will be PGP signed by an individual key of the Release
543 Coordinator. This key will have a uid containing an email address in the
544 &'exim.org'& domain and will have signatures from other people, including
545 other Exim maintainers. We expect that the key will be in the "strong set" of
546 PGP keys. There should be a trust path to that key from Nigel Metheringham's
547 PGP key, a version of which can be found in the release directory in the file
548 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
549 such as &'pool.sks-keyservers.net'&.
551 At time of last update, releases were being made by Phil Pennock and signed with
552 key &'0x403043153903637F'&, although that key is expected to be replaced in 2013.
553 A trust path from Nigel's key to Phil's can be observed at
554 &url(https://www.security.spodhuis.org/exim-trustpath).
556 Releases have also been authorized to be performed by Todd Lyons who signs with
557 key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil
558 Pennock and Todd Lyons through a common associate.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.gz.asc_&
563 &_exim-n.nn.tar.bz2.asc_&
565 For each released version, the log of changes is made separately available in a
566 separate file in the directory &_ChangeLogs_& so that it is possible to
567 find out what has changed without having to download the entire distribution.
569 .cindex "documentation" "available formats"
570 The main distribution contains ASCII versions of this specification and other
571 documentation; other formats of the documents are available in separate files
572 inside the &_exim4_& directory of the FTP site:
574 &_exim-html-n.nn.tar.gz_&
575 &_exim-pdf-n.nn.tar.gz_&
576 &_exim-postscript-n.nn.tar.gz_&
577 &_exim-texinfo-n.nn.tar.gz_&
579 These tar files contain only the &_doc_& directory, not the complete
580 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
583 .section "Limitations" "SECID6"
585 .cindex "limitations of Exim"
586 .cindex "bang paths" "not handled by Exim"
587 Exim is designed for use as an Internet MTA, and therefore handles addresses in
588 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
589 simple two-component bang paths can be converted by a straightforward rewriting
590 configuration. This restriction does not prevent Exim from being interfaced to
591 UUCP as a transport mechanism, provided that domain addresses are used.
593 .cindex "domainless addresses"
594 .cindex "address" "without domain"
595 Exim insists that every address it handles has a domain attached. For incoming
596 local messages, domainless addresses are automatically qualified with a
597 configured domain value. Configuration options specify from which remote
598 systems unqualified addresses are acceptable. These are then qualified on
601 .cindex "transport" "external"
602 .cindex "external transports"
603 The only external transport mechanisms that are currently implemented are SMTP
604 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
605 transport is available, and there are facilities for writing messages to files
606 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
607 to send messages to other transport mechanisms such as UUCP, provided they can
608 handle domain-style addresses. Batched SMTP input is also catered for.
610 Exim is not designed for storing mail for dial-in hosts. When the volumes of
611 such mail are large, it is better to get the messages &"delivered"& into files
612 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
615 Although Exim does have basic facilities for scanning incoming messages, these
616 are not comprehensive enough to do full virus or spam scanning. Such operations
617 are best carried out using additional specialized software packages. If you
618 compile Exim with the content-scanning extension, straightforward interfaces to
619 a number of common scanners are provided.
623 .section "Run time configuration" "SECID7"
624 Exim's run time configuration is held in a single text file that is divided
625 into a number of sections. The entries in this file consist of keywords and
626 values, in the style of Smail 3 configuration files. A default configuration
627 file which is suitable for simple online installations is provided in the
628 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
631 .section "Calling interface" "SECID8"
632 .cindex "Sendmail compatibility" "command line interface"
633 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
634 can be a straight replacement for &_/usr/lib/sendmail_& or
635 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
636 about Sendmail in order to run Exim. For actions other than sending messages,
637 Sendmail-compatible options also exist, but those that produce output (for
638 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
639 format. There are also some additional options that are compatible with Smail
640 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
641 documents all Exim's command line options. This information is automatically
642 made into the man page that forms part of the Exim distribution.
644 Control of messages on the queue can be done via certain privileged command
645 line options. There is also an optional monitor program called &'eximon'&,
646 which displays current information in an X window, and which contains a menu
647 interface to Exim's command line administration options.
651 .section "Terminology" "SECID9"
652 .cindex "terminology definitions"
653 .cindex "body of message" "definition of"
654 The &'body'& of a message is the actual data that the sender wants to transmit.
655 It is the last part of a message, and is separated from the &'header'& (see
656 below) by a blank line.
658 .cindex "bounce message" "definition of"
659 When a message cannot be delivered, it is normally returned to the sender in a
660 delivery failure message or a &"non-delivery report"& (NDR). The term
661 &'bounce'& is commonly used for this action, and the error reports are often
662 called &'bounce messages'&. This is a convenient shorthand for &"delivery
663 failure error report"&. Such messages have an empty sender address in the
664 message's &'envelope'& (see below) to ensure that they cannot themselves give
665 rise to further bounce messages.
667 The term &'default'& appears frequently in this manual. It is used to qualify a
668 value which is used in the absence of any setting in the configuration. It may
669 also qualify an action which is taken unless a configuration setting specifies
672 The term &'defer'& is used when the delivery of a message to a specific
673 destination cannot immediately take place for some reason (a remote host may be
674 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
677 The word &'domain'& is sometimes used to mean all but the first component of a
678 host's name. It is &'not'& used in that sense here, where it normally refers to
679 the part of an email address following the @ sign.
681 .cindex "envelope, definition of"
682 .cindex "sender" "definition of"
683 A message in transit has an associated &'envelope'&, as well as a header and a
684 body. The envelope contains a sender address (to which bounce messages should
685 be delivered), and any number of recipient addresses. References to the
686 sender or the recipients of a message usually mean the addresses in the
687 envelope. An MTA uses these addresses for delivery, and for returning bounce
688 messages, not the addresses that appear in the header lines.
690 .cindex "message" "header, definition of"
691 .cindex "header section" "definition of"
692 The &'header'& of a message is the first part of a message's text, consisting
693 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
694 &'Subject:'&, etc. Long header lines can be split over several text lines by
695 indenting the continuations. The header is separated from the body by a blank
698 .cindex "local part" "definition of"
699 .cindex "domain" "definition of"
700 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
701 part of an email address that precedes the @ sign. The part that follows the
702 @ sign is called the &'domain'& or &'mail domain'&.
704 .cindex "local delivery" "definition of"
705 .cindex "remote delivery, definition of"
706 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
707 delivery to a file or a pipe on the local host from delivery by SMTP over
708 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
709 host it is running on are &'remote'&.
711 .cindex "return path" "definition of"
712 &'Return path'& is another name that is used for the sender address in a
715 .cindex "queue" "definition of"
716 The term &'queue'& is used to refer to the set of messages awaiting delivery,
717 because this term is in widespread use in the context of MTAs. However, in
718 Exim's case the reality is more like a pool than a queue, because there is
719 normally no ordering of waiting messages.
721 .cindex "queue runner" "definition of"
722 The term &'queue runner'& is used to describe a process that scans the queue
723 and attempts to deliver those messages whose retry times have come. This term
724 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
725 the waiting messages are normally processed in an unpredictable order.
727 .cindex "spool directory" "definition of"
728 The term &'spool directory'& is used for a directory in which Exim keeps the
729 messages on its queue &-- that is, those that it is in the process of
730 delivering. This should not be confused with the directory in which local
731 mailboxes are stored, which is called a &"spool directory"& by some people. In
732 the Exim documentation, &"spool"& is always used in the first sense.
739 . ////////////////////////////////////////////////////////////////////////////
740 . ////////////////////////////////////////////////////////////////////////////
742 .chapter "Incorporated code" "CHID2"
743 .cindex "incorporated code"
744 .cindex "regular expressions" "library"
747 A number of pieces of external code are included in the Exim distribution.
750 Regular expressions are supported in the main Exim program and in the
751 Exim monitor using the freely-distributable PCRE library, copyright
752 © University of Cambridge. The source to PCRE is no longer shipped with
753 Exim, so you will need to use the version of PCRE shipped with your system,
754 or obtain and install the full version of the library from
755 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
757 .cindex "cdb" "acknowledgment"
758 Support for the cdb (Constant DataBase) lookup method is provided by code
759 contributed by Nigel Metheringham of (at the time he contributed it) Planet
760 Online Ltd. The implementation is completely contained within the code of Exim.
761 It does not link against an external cdb library. The code contains the
762 following statements:
765 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
767 This program is free software; you can redistribute it and/or modify it under
768 the terms of the GNU General Public License as published by the Free Software
769 Foundation; either version 2 of the License, or (at your option) any later
771 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
772 the spec and sample code for cdb can be obtained from
773 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
774 some code from Dan Bernstein's implementation (which has no license
775 restrictions applied to it).
778 .cindex "SPA authentication"
779 .cindex "Samba project"
780 .cindex "Microsoft Secure Password Authentication"
781 Client support for Microsoft's &'Secure Password Authentication'& is provided
782 by code contributed by Marc Prud'hommeaux. Server support was contributed by
783 Tom Kistner. This includes code taken from the Samba project, which is released
787 .cindex "&'pwcheck'& daemon"
788 .cindex "&'pwauthd'& daemon"
789 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
790 by code taken from the Cyrus-SASL library and adapted by Alexander S.
791 Sabourenkov. The permission notice appears below, in accordance with the
792 conditions expressed therein.
795 Copyright © 2001 Carnegie Mellon University. All rights reserved.
797 Redistribution and use in source and binary forms, with or without
798 modification, are permitted provided that the following conditions
802 Redistributions of source code must retain the above copyright
803 notice, this list of conditions and the following disclaimer.
805 Redistributions in binary form must reproduce the above copyright
806 notice, this list of conditions and the following disclaimer in
807 the documentation and/or other materials provided with the
810 The name &"Carnegie Mellon University"& must not be used to
811 endorse or promote products derived from this software without
812 prior written permission. For permission or any other legal
813 details, please contact
815 Office of Technology Transfer
816 Carnegie Mellon University
818 Pittsburgh, PA 15213-3890
819 (412) 268-4387, fax: (412) 268-7395
820 tech-transfer@andrew.cmu.edu
823 Redistributions of any form whatsoever must retain the following
826 &"This product includes software developed by Computing Services
827 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
829 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
830 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
831 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
832 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
833 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
834 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
835 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
840 .cindex "Exim monitor" "acknowledgment"
843 The Exim Monitor program, which is an X-Window application, includes
844 modified versions of the Athena StripChart and TextPop widgets.
845 This code is copyright by DEC and MIT, and their permission notice appears
846 below, in accordance with the conditions expressed therein.
849 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
850 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
854 Permission to use, copy, modify, and distribute this software and its
855 documentation for any purpose and without fee is hereby granted,
856 provided that the above copyright notice appear in all copies and that
857 both that copyright notice and this permission notice appear in
858 supporting documentation, and that the names of Digital or MIT not be
859 used in advertising or publicity pertaining to distribution of the
860 software without specific, written prior permission.
862 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
863 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
864 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
865 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
866 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
867 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
872 .cindex "opendmarc" "acknowledgment"
873 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
874 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
875 derived code are indicated in the respective source files. The full OpenDMARC
876 license is provided in the LICENSE.opendmarc file contained in the distributed
880 Many people have contributed code fragments, some large, some small, that were
881 not covered by any specific licence requirements. It is assumed that the
882 contributors are happy to see their code incorporated into Exim under the GPL.
889 . ////////////////////////////////////////////////////////////////////////////
890 . ////////////////////////////////////////////////////////////////////////////
892 .chapter "How Exim receives and delivers mail" "CHID11" &&&
893 "Receiving and delivering mail"
896 .section "Overall philosophy" "SECID10"
897 .cindex "design philosophy"
898 Exim is designed to work efficiently on systems that are permanently connected
899 to the Internet and are handling a general mix of mail. In such circumstances,
900 most messages can be delivered immediately. Consequently, Exim does not
901 maintain independent queues of messages for specific domains or hosts, though
902 it does try to send several messages in a single SMTP connection after a host
903 has been down, and it also maintains per-host retry information.
906 .section "Policy control" "SECID11"
907 .cindex "policy control" "overview"
908 Policy controls are now an important feature of MTAs that are connected to the
909 Internet. Perhaps their most important job is to stop MTAs being abused as
910 &"open relays"& by misguided individuals who send out vast amounts of
911 unsolicited junk, and want to disguise its source. Exim provides flexible
912 facilities for specifying policy controls on incoming mail:
915 .cindex "&ACL;" "introduction"
916 Exim 4 (unlike previous versions of Exim) implements policy controls on
917 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
918 series of statements that may either grant or deny access. ACLs can be used at
919 several places in the SMTP dialogue while receiving a message from a remote
920 host. However, the most common places are after each RCPT command, and at the
921 very end of the message. The sysadmin can specify conditions for accepting or
922 rejecting individual recipients or the entire message, respectively, at these
923 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
926 An ACL is also available for locally generated, non-SMTP messages. In this
927 case, the only available actions are to accept or deny the entire message.
929 When Exim is compiled with the content-scanning extension, facilities are
930 provided in the ACL mechanism for passing the message to external virus and/or
931 spam scanning software. The result of such a scan is passed back to the ACL,
932 which can then use it to decide what to do with the message.
934 When a message has been received, either from a remote host or from the local
935 host, but before the final acknowledgment has been sent, a locally supplied C
936 function called &[local_scan()]& can be run to inspect the message and decide
937 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
938 is accepted, the list of recipients can be modified by the function.
940 Using the &[local_scan()]& mechanism is another way of calling external scanner
941 software. The &%SA-Exim%& add-on package works this way. It does not require
942 Exim to be compiled with the content-scanning extension.
944 After a message has been accepted, a further checking mechanism is available in
945 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
946 runs at the start of every delivery process.
951 .section "User filters" "SECID12"
952 .cindex "filter" "introduction"
953 .cindex "Sieve filter"
954 In a conventional Exim configuration, users are able to run private filters by
955 setting up appropriate &_.forward_& files in their home directories. See
956 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
957 configuration needed to support this, and the separate document entitled
958 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
959 of filtering are available:
962 Sieve filters are written in the standard filtering language that is defined
965 Exim filters are written in a syntax that is unique to Exim, but which is more
966 powerful than Sieve, which it pre-dates.
969 User filters are run as part of the routing process, described below.
973 .section "Message identification" "SECTmessiden"
974 .cindex "message ids" "details of format"
975 .cindex "format" "of message id"
976 .cindex "id of message"
981 Every message handled by Exim is given a &'message id'& which is sixteen
982 characters long. It is divided into three parts, separated by hyphens, for
983 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
984 normally encoding numbers in base 62. However, in the Darwin operating
985 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
986 (avoiding the use of lower case letters) is used instead, because the message
987 id is used to construct file names, and the names of files in those systems are
988 not always case-sensitive.
990 .cindex "pid (process id)" "re-use of"
991 The detail of the contents of the message id have changed as Exim has evolved.
992 Earlier versions relied on the operating system not re-using a process id (pid)
993 within one second. On modern operating systems, this assumption can no longer
994 be made, so the algorithm had to be changed. To retain backward compatibility,
995 the format of the message id was retained, which is why the following rules are
999 The first six characters of the message id are the time at which the message
1000 started to be received, to a granularity of one second. That is, this field
1001 contains the number of seconds since the start of the epoch (the normal Unix
1002 way of representing the date and time of day).
1004 After the first hyphen, the next six characters are the id of the process that
1005 received the message.
1007 There are two different possibilities for the final two characters:
1009 .oindex "&%localhost_number%&"
1010 If &%localhost_number%& is not set, this value is the fractional part of the
1011 time of reception, normally in units of 1/2000 of a second, but for systems
1012 that must use base 36 instead of base 62 (because of case-insensitive file
1013 systems), the units are 1/1000 of a second.
1015 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1016 the fractional part of the time, which in this case is in units of 1/200
1017 (1/100) of a second.
1021 After a message has been received, Exim waits for the clock to tick at the
1022 appropriate resolution before proceeding, so that if another message is
1023 received by the same process, or by another process with the same (re-used)
1024 pid, it is guaranteed that the time will be different. In most cases, the clock
1025 will already have ticked while the message was being received.
1028 .section "Receiving mail" "SECID13"
1029 .cindex "receiving mail"
1030 .cindex "message" "reception"
1031 The only way Exim can receive mail from another host is using SMTP over
1032 TCP/IP, in which case the sender and recipient addresses are transferred using
1033 SMTP commands. However, from a locally running process (such as a user's MUA),
1034 there are several possibilities:
1037 If the process runs Exim with the &%-bm%& option, the message is read
1038 non-interactively (usually via a pipe), with the recipients taken from the
1039 command line, or from the body of the message if &%-t%& is also used.
1041 If the process runs Exim with the &%-bS%& option, the message is also read
1042 non-interactively, but in this case the recipients are listed at the start of
1043 the message in a series of SMTP RCPT commands, terminated by a DATA
1044 command. This is so-called &"batch SMTP"& format,
1045 but it isn't really SMTP. The SMTP commands are just another way of passing
1046 envelope addresses in a non-interactive submission.
1048 If the process runs Exim with the &%-bs%& option, the message is read
1049 interactively, using the SMTP protocol. A two-way pipe is normally used for
1050 passing data between the local process and the Exim process.
1051 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1052 example, the ACLs for SMTP commands are used for this form of submission.
1054 A local process may also make a TCP/IP call to the host's loopback address
1055 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1056 does not treat the loopback address specially. It treats all such connections
1057 in the same way as connections from other hosts.
1061 .cindex "message sender, constructed by Exim"
1062 .cindex "sender" "constructed by Exim"
1063 In the three cases that do not involve TCP/IP, the sender address is
1064 constructed from the login name of the user that called Exim and a default
1065 qualification domain (which can be set by the &%qualify_domain%& configuration
1066 option). For local or batch SMTP, a sender address that is passed using the
1067 SMTP MAIL command is ignored. However, the system administrator may allow
1068 certain users (&"trusted users"&) to specify a different sender address
1069 unconditionally, or all users to specify certain forms of different sender
1070 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1071 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1072 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1073 users to change sender addresses.
1075 Messages received by either of the non-interactive mechanisms are subject to
1076 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1077 (either over TCP/IP, or interacting with a local process) can be checked by a
1078 number of ACLs that operate at different times during the SMTP session. Either
1079 individual recipients, or the entire message, can be rejected if local policy
1080 requirements are not met. The &[local_scan()]& function (see chapter
1081 &<<CHAPlocalscan>>&) is run for all incoming messages.
1083 Exim can be configured not to start a delivery process when a message is
1084 received; this can be unconditional, or depend on the number of incoming SMTP
1085 connections or the system load. In these situations, new messages wait on the
1086 queue until a queue runner process picks them up. However, in standard
1087 configurations under normal conditions, delivery is started as soon as a
1088 message is received.
1094 .section "Handling an incoming message" "SECID14"
1095 .cindex "spool directory" "files that hold a message"
1096 .cindex "file" "how a message is held"
1097 When Exim accepts a message, it writes two files in its spool directory. The
1098 first contains the envelope information, the current status of the message, and
1099 the header lines, and the second contains the body of the message. The names of
1100 the two spool files consist of the message id, followed by &`-H`& for the
1101 file containing the envelope and header, and &`-D`& for the data file.
1103 .cindex "spool directory" "&_input_& sub-directory"
1104 By default all these message files are held in a single directory called
1105 &_input_& inside the general Exim spool directory. Some operating systems do
1106 not perform very well if the number of files in a directory gets large; to
1107 improve performance in such cases, the &%split_spool_directory%& option can be
1108 used. This causes Exim to split up the input files into 62 sub-directories
1109 whose names are single letters or digits. When this is done, the queue is
1110 processed one sub-directory at a time instead of all at once, which can improve
1111 overall performance even when there are not enough files in each directory to
1112 affect file system performance.
1114 The envelope information consists of the address of the message's sender and
1115 the addresses of the recipients. This information is entirely separate from
1116 any addresses contained in the header lines. The status of the message includes
1117 a list of recipients who have already received the message. The format of the
1118 first spool file is described in chapter &<<CHAPspool>>&.
1120 .cindex "rewriting" "addresses"
1121 Address rewriting that is specified in the rewrite section of the configuration
1122 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1123 both in the header lines and the envelope, at the time the message is accepted.
1124 If during the course of delivery additional addresses are generated (for
1125 example, via aliasing), these new addresses are rewritten as soon as they are
1126 generated. At the time a message is actually delivered (transported) further
1127 rewriting can take place; because this is a transport option, it can be
1128 different for different forms of delivery. It is also possible to specify the
1129 addition or removal of certain header lines at the time the message is
1130 delivered (see chapters &<<CHAProutergeneric>>& and
1131 &<<CHAPtransportgeneric>>&).
1135 .section "Life of a message" "SECID15"
1136 .cindex "message" "life of"
1137 .cindex "message" "frozen"
1138 A message remains in the spool directory until it is completely delivered to
1139 its recipients or to an error address, or until it is deleted by an
1140 administrator or by the user who originally created it. In cases when delivery
1141 cannot proceed &-- for example, when a message can neither be delivered to its
1142 recipients nor returned to its sender, the message is marked &"frozen"& on the
1143 spool, and no more deliveries are attempted.
1145 .cindex "frozen messages" "thawing"
1146 .cindex "message" "thawing frozen"
1147 An administrator can &"thaw"& such messages when the problem has been
1148 corrected, and can also freeze individual messages by hand if necessary. In
1149 addition, an administrator can force a delivery error, causing a bounce message
1152 .oindex "&%timeout_frozen_after%&"
1153 .oindex "&%ignore_bounce_errors_after%&"
1154 There are options called &%ignore_bounce_errors_after%& and
1155 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1156 The first applies only to frozen bounces, the second to any frozen messages.
1158 .cindex "message" "log file for"
1159 .cindex "log" "file for each message"
1160 While Exim is working on a message, it writes information about each delivery
1161 attempt to its main log file. This includes successful, unsuccessful, and
1162 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1163 lines are also written to a separate &'message log'& file for each message.
1164 These logs are solely for the benefit of the administrator, and are normally
1165 deleted along with the spool files when processing of a message is complete.
1166 The use of individual message logs can be disabled by setting
1167 &%no_message_logs%&; this might give an improvement in performance on very busy
1170 .cindex "journal file"
1171 .cindex "file" "journal"
1172 All the information Exim itself needs to set up a delivery is kept in the first
1173 spool file, along with the header lines. When a successful delivery occurs, the
1174 address is immediately written at the end of a journal file, whose name is the
1175 message id followed by &`-J`&. At the end of a delivery run, if there are some
1176 addresses left to be tried again later, the first spool file (the &`-H`& file)
1177 is updated to indicate which these are, and the journal file is then deleted.
1178 Updating the spool file is done by writing a new file and renaming it, to
1179 minimize the possibility of data loss.
1181 Should the system or the program crash after a successful delivery but before
1182 the spool file has been updated, the journal is left lying around. The next
1183 time Exim attempts to deliver the message, it reads the journal file and
1184 updates the spool file before proceeding. This minimizes the chances of double
1185 deliveries caused by crashes.
1189 .section "Processing an address for delivery" "SECTprocaddress"
1190 .cindex "drivers" "definition of"
1191 .cindex "router" "definition of"
1192 .cindex "transport" "definition of"
1193 The main delivery processing elements of Exim are called &'routers'& and
1194 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1195 number of them is provided in the source distribution, and compile-time options
1196 specify which ones are included in the binary. Run time options specify which
1197 ones are actually used for delivering messages.
1199 .cindex "drivers" "instance definition"
1200 Each driver that is specified in the run time configuration is an &'instance'&
1201 of that particular driver type. Multiple instances are allowed; for example,
1202 you can set up several different &(smtp)& transports, each with different
1203 option values that might specify different ports or different timeouts. Each
1204 instance has its own identifying name. In what follows we will normally use the
1205 instance name when discussing one particular instance (that is, one specific
1206 configuration of the driver), and the generic driver name when discussing
1207 the driver's features in general.
1209 A &'router'& is a driver that operates on an address, either determining how
1210 its delivery should happen, by assigning it to a specific transport, or
1211 converting the address into one or more new addresses (for example, via an
1212 alias file). A router may also explicitly choose to fail an address, causing it
1215 A &'transport'& is a driver that transmits a copy of the message from Exim's
1216 spool to some destination. There are two kinds of transport: for a &'local'&
1217 transport, the destination is a file or a pipe on the local host, whereas for a
1218 &'remote'& transport the destination is some other host. A message is passed
1219 to a specific transport as a result of successful routing. If a message has
1220 several recipients, it may be passed to a number of different transports.
1222 .cindex "preconditions" "definition of"
1223 An address is processed by passing it to each configured router instance in
1224 turn, subject to certain preconditions, until a router accepts the address or
1225 specifies that it should be bounced. We will describe this process in more
1226 detail shortly. First, as a simple example, we consider how each recipient
1227 address in a message is processed in a small configuration of three routers.
1229 To make this a more concrete example, it is described in terms of some actual
1230 routers, but remember, this is only an example. You can configure Exim's
1231 routers in many different ways, and there may be any number of routers in a
1234 The first router that is specified in a configuration is often one that handles
1235 addresses in domains that are not recognized specially by the local host. These
1236 are typically addresses for arbitrary domains on the Internet. A precondition
1237 is set up which looks for the special domains known to the host (for example,
1238 its own domain name), and the router is run for addresses that do &'not'&
1239 match. Typically, this is a router that looks up domains in the DNS in order to
1240 find the hosts to which this address routes. If it succeeds, the address is
1241 assigned to a suitable SMTP transport; if it does not succeed, the router is
1242 configured to fail the address.
1244 The second router is reached only when the domain is recognized as one that
1245 &"belongs"& to the local host. This router does redirection &-- also known as
1246 aliasing and forwarding. When it generates one or more new addresses from the
1247 original, each of them is routed independently from the start. Otherwise, the
1248 router may cause an address to fail, or it may simply decline to handle the
1249 address, in which case the address is passed to the next router.
1251 The final router in many configurations is one that checks to see if the
1252 address belongs to a local mailbox. The precondition may involve a check to
1253 see if the local part is the name of a login account, or it may look up the
1254 local part in a file or a database. If its preconditions are not met, or if
1255 the router declines, we have reached the end of the routers. When this happens,
1256 the address is bounced.
1260 .section "Processing an address for verification" "SECID16"
1261 .cindex "router" "for verification"
1262 .cindex "verifying address" "overview"
1263 As well as being used to decide how to deliver to an address, Exim's routers
1264 are also used for &'address verification'&. Verification can be requested as
1265 one of the checks to be performed in an ACL for incoming messages, on both
1266 sender and recipient addresses, and it can be tested using the &%-bv%& and
1267 &%-bvs%& command line options.
1269 When an address is being verified, the routers are run in &"verify mode"&. This
1270 does not affect the way the routers work, but it is a state that can be
1271 detected. By this means, a router can be skipped or made to behave differently
1272 when verifying. A common example is a configuration in which the first router
1273 sends all messages to a message-scanning program, unless they have been
1274 previously scanned. Thus, the first router accepts all addresses without any
1275 checking, making it useless for verifying. Normally, the &%no_verify%& option
1276 would be set for such a router, causing it to be skipped in verify mode.
1281 .section "Running an individual router" "SECTrunindrou"
1282 .cindex "router" "running details"
1283 .cindex "preconditions" "checking"
1284 .cindex "router" "result of running"
1285 As explained in the example above, a number of preconditions are checked before
1286 running a router. If any are not met, the router is skipped, and the address is
1287 passed to the next router. When all the preconditions on a router &'are'& met,
1288 the router is run. What happens next depends on the outcome, which is one of
1292 &'accept'&: The router accepts the address, and either assigns it to a
1293 transport, or generates one or more &"child"& addresses. Processing the
1294 original address ceases,
1295 .oindex "&%unseen%&"
1296 unless the &%unseen%& option is set on the router. This option
1297 can be used to set up multiple deliveries with different routing (for example,
1298 for keeping archive copies of messages). When &%unseen%& is set, the address is
1299 passed to the next router. Normally, however, an &'accept'& return marks the
1302 Any child addresses generated by the router are processed independently,
1303 starting with the first router by default. It is possible to change this by
1304 setting the &%redirect_router%& option to specify which router to start at for
1305 child addresses. Unlike &%pass_router%& (see below) the router specified by
1306 &%redirect_router%& may be anywhere in the router configuration.
1308 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1309 requests that the address be passed to another router. By default the address
1310 is passed to the next router, but this can be changed by setting the
1311 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1312 must be below the current router (to avoid loops).
1314 &'decline'&: The router declines to accept the address because it does not
1315 recognize it at all. By default, the address is passed to the next router, but
1316 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1317 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1318 &'decline'& into &'fail'&.
1320 &'fail'&: The router determines that the address should fail, and queues it for
1321 the generation of a bounce message. There is no further processing of the
1322 original address unless &%unseen%& is set on the router.
1324 &'defer'&: The router cannot handle the address at the present time. (A
1325 database may be offline, or a DNS lookup may have timed out.) No further
1326 processing of the address happens in this delivery attempt. It is tried again
1327 next time the message is considered for delivery.
1329 &'error'&: There is some error in the router (for example, a syntax error in
1330 its configuration). The action is as for defer.
1333 If an address reaches the end of the routers without having been accepted by
1334 any of them, it is bounced as unrouteable. The default error message in this
1335 situation is &"unrouteable address"&, but you can set your own message by
1336 making use of the &%cannot_route_message%& option. This can be set for any
1337 router; the value from the last router that &"saw"& the address is used.
1339 Sometimes while routing you want to fail a delivery when some conditions are
1340 met but others are not, instead of passing the address on for further routing.
1341 You can do this by having a second router that explicitly fails the delivery
1342 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1343 facility for this purpose.
1346 .section "Duplicate addresses" "SECID17"
1347 .cindex "case of local parts"
1348 .cindex "address duplicate, discarding"
1349 .cindex "duplicate addresses"
1350 Once routing is complete, Exim scans the addresses that are assigned to local
1351 and remote transports, and discards any duplicates that it finds. During this
1352 check, local parts are treated as case-sensitive. This happens only when
1353 actually delivering a message; when testing routers with &%-bt%&, all the
1354 routed addresses are shown.
1358 .section "Router preconditions" "SECTrouprecon"
1359 .cindex "router" "preconditions, order of processing"
1360 .cindex "preconditions" "order of processing"
1361 The preconditions that are tested for each router are listed below, in the
1362 order in which they are tested. The individual configuration options are
1363 described in more detail in chapter &<<CHAProutergeneric>>&.
1366 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1367 the local parts handled by the router may or must have certain prefixes and/or
1368 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1369 skipped. These conditions are tested first. When an affix is present, it is
1370 removed from the local part before further processing, including the evaluation
1371 of any other conditions.
1373 Routers can be designated for use only when not verifying an address, that is,
1374 only when routing it for delivery (or testing its delivery routing). If the
1375 &%verify%& option is set false, the router is skipped when Exim is verifying an
1377 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1378 &%verify_recipient%&, which independently control the use of the router for
1379 sender and recipient verification. You can set these options directly if
1380 you want a router to be used for only one type of verification.
1381 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1383 If the &%address_test%& option is set false, the router is skipped when Exim is
1384 run with the &%-bt%& option to test an address routing. This can be helpful
1385 when the first router sends all new messages to a scanner of some sort; it
1386 makes it possible to use &%-bt%& to test subsequent delivery routing without
1387 having to simulate the effect of the scanner.
1389 Routers can be designated for use only when verifying an address, as
1390 opposed to routing it for delivery. The &%verify_only%& option controls this.
1391 Again, cutthrough delivery counts as a verification.
1393 Individual routers can be explicitly skipped when running the routers to
1394 check an address given in the SMTP EXPN command (see the &%expn%& option).
1396 If the &%domains%& option is set, the domain of the address must be in the set
1397 of domains that it defines.
1399 .vindex "&$local_part_prefix$&"
1400 .vindex "&$local_part$&"
1401 .vindex "&$local_part_suffix$&"
1402 If the &%local_parts%& option is set, the local part of the address must be in
1403 the set of local parts that it defines. If &%local_part_prefix%& or
1404 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1405 part before this check. If you want to do precondition tests on local parts
1406 that include affixes, you can do so by using a &%condition%& option (see below)
1407 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1408 &$local_part_suffix$& as necessary.
1410 .vindex "&$local_user_uid$&"
1411 .vindex "&$local_user_gid$&"
1413 If the &%check_local_user%& option is set, the local part must be the name of
1414 an account on the local host. If this check succeeds, the uid and gid of the
1415 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1416 user's home directory is placed in &$home$&; these values can be used in the
1417 remaining preconditions.
1419 If the &%router_home_directory%& option is set, it is expanded at this point,
1420 because it overrides the value of &$home$&. If this expansion were left till
1421 later, the value of &$home$& as set by &%check_local_user%& would be used in
1422 subsequent tests. Having two different values of &$home$& in the same router
1423 could lead to confusion.
1425 If the &%senders%& option is set, the envelope sender address must be in the
1426 set of addresses that it defines.
1428 If the &%require_files%& option is set, the existence or non-existence of
1429 specified files is tested.
1431 .cindex "customizing" "precondition"
1432 If the &%condition%& option is set, it is evaluated and tested. This option
1433 uses an expanded string to allow you to set up your own custom preconditions.
1434 Expanded strings are described in chapter &<<CHAPexpand>>&.
1438 Note that &%require_files%& comes near the end of the list, so you cannot use
1439 it to check for the existence of a file in which to lookup up a domain, local
1440 part, or sender. However, as these options are all expanded, you can use the
1441 &%exists%& expansion condition to make such tests within each condition. The
1442 &%require_files%& option is intended for checking files that the router may be
1443 going to use internally, or which are needed by a specific transport (for
1444 example, &_.procmailrc_&).
1448 .section "Delivery in detail" "SECID18"
1449 .cindex "delivery" "in detail"
1450 When a message is to be delivered, the sequence of events is as follows:
1453 If a system-wide filter file is specified, the message is passed to it. The
1454 filter may add recipients to the message, replace the recipients, discard the
1455 message, cause a new message to be generated, or cause the message delivery to
1456 fail. The format of the system filter file is the same as for Exim user filter
1457 files, described in the separate document entitled &'Exim's interfaces to mail
1459 .cindex "Sieve filter" "not available for system filter"
1460 (&*Note*&: Sieve cannot be used for system filter files.)
1462 Some additional features are available in system filters &-- see chapter
1463 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1464 filter only once per delivery attempt, however many recipients it has. However,
1465 if there are several delivery attempts because one or more addresses could not
1466 be immediately delivered, the system filter is run each time. The filter
1467 condition &%first_delivery%& can be used to detect the first run of the system
1470 Each recipient address is offered to each configured router in turn, subject to
1471 its preconditions, until one is able to handle it. If no router can handle the
1472 address, that is, if they all decline, the address is failed. Because routers
1473 can be targeted at particular domains, several locally handled domains can be
1474 processed entirely independently of each other.
1476 .cindex "routing" "loops in"
1477 .cindex "loop" "while routing"
1478 A router that accepts an address may assign it to a local or a remote
1479 transport. However, the transport is not run at this time. Instead, the address
1480 is placed on a list for the particular transport, which will be run later.
1481 Alternatively, the router may generate one or more new addresses (typically
1482 from alias, forward, or filter files). New addresses are fed back into this
1483 process from the top, but in order to avoid loops, a router ignores any address
1484 which has an identically-named ancestor that was processed by itself.
1486 When all the routing has been done, addresses that have been successfully
1487 handled are passed to their assigned transports. When local transports are
1488 doing real local deliveries, they handle only one address at a time, but if a
1489 local transport is being used as a pseudo-remote transport (for example, to
1490 collect batched SMTP messages for transmission by some other means) multiple
1491 addresses can be handled. Remote transports can always handle more than one
1492 address at a time, but can be configured not to do so, or to restrict multiple
1493 addresses to the same domain.
1495 Each local delivery to a file or a pipe runs in a separate process under a
1496 non-privileged uid, and these deliveries are run one at a time. Remote
1497 deliveries also run in separate processes, normally under a uid that is private
1498 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1499 run in parallel. The maximum number of simultaneous remote deliveries for any
1500 one message is set by the &%remote_max_parallel%& option.
1501 The order in which deliveries are done is not defined, except that all local
1502 deliveries happen before any remote deliveries.
1504 .cindex "queue runner"
1505 When it encounters a local delivery during a queue run, Exim checks its retry
1506 database to see if there has been a previous temporary delivery failure for the
1507 address before running the local transport. If there was a previous failure,
1508 Exim does not attempt a new delivery until the retry time for the address is
1509 reached. However, this happens only for delivery attempts that are part of a
1510 queue run. Local deliveries are always attempted when delivery immediately
1511 follows message reception, even if retry times are set for them. This makes for
1512 better behaviour if one particular message is causing problems (for example,
1513 causing quota overflow, or provoking an error in a filter file).
1515 .cindex "delivery" "retry in remote transports"
1516 Remote transports do their own retry handling, since an address may be
1517 deliverable to one of a number of hosts, each of which may have a different
1518 retry time. If there have been previous temporary failures and no host has
1519 reached its retry time, no delivery is attempted, whether in a queue run or
1520 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1522 If there were any permanent errors, a bounce message is returned to an
1523 appropriate address (the sender in the common case), with details of the error
1524 for each failing address. Exim can be configured to send copies of bounce
1525 messages to other addresses.
1527 .cindex "delivery" "deferral"
1528 If one or more addresses suffered a temporary failure, the message is left on
1529 the queue, to be tried again later. Delivery of these addresses is said to be
1532 When all the recipient addresses have either been delivered or bounced,
1533 handling of the message is complete. The spool files and message log are
1534 deleted, though the message log can optionally be preserved if required.
1540 .section "Retry mechanism" "SECID19"
1541 .cindex "delivery" "retry mechanism"
1542 .cindex "retry" "description of mechanism"
1543 .cindex "queue runner"
1544 Exim's mechanism for retrying messages that fail to get delivered at the first
1545 attempt is the queue runner process. You must either run an Exim daemon that
1546 uses the &%-q%& option with a time interval to start queue runners at regular
1547 intervals, or use some other means (such as &'cron'&) to start them. If you do
1548 not arrange for queue runners to be run, messages that fail temporarily at the
1549 first attempt will remain on your queue for ever. A queue runner process works
1550 its way through the queue, one message at a time, trying each delivery that has
1551 passed its retry time.
1552 You can run several queue runners at once.
1554 Exim uses a set of configured rules to determine when next to retry the failing
1555 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1556 should give up trying to deliver to the address, at which point it generates a
1557 bounce message. If no retry rules are set for a particular host, address, and
1558 error combination, no retries are attempted, and temporary errors are treated
1563 .section "Temporary delivery failure" "SECID20"
1564 .cindex "delivery" "temporary failure"
1565 There are many reasons why a message may not be immediately deliverable to a
1566 particular address. Failure to connect to a remote machine (because it, or the
1567 connection to it, is down) is one of the most common. Temporary failures may be
1568 detected during routing as well as during the transport stage of delivery.
1569 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1570 is on a file system where the user is over quota. Exim can be configured to
1571 impose its own quotas on local mailboxes; where system quotas are set they will
1574 If a host is unreachable for a period of time, a number of messages may be
1575 waiting for it by the time it recovers, and sending them in a single SMTP
1576 connection is clearly beneficial. Whenever a delivery to a remote host is
1578 .cindex "hints database" "deferred deliveries"
1579 Exim makes a note in its hints database, and whenever a successful
1580 SMTP delivery has happened, it looks to see if any other messages are waiting
1581 for the same host. If any are found, they are sent over the same SMTP
1582 connection, subject to a configuration limit as to the maximum number in any
1587 .section "Permanent delivery failure" "SECID21"
1588 .cindex "delivery" "permanent failure"
1589 .cindex "bounce message" "when generated"
1590 When a message cannot be delivered to some or all of its intended recipients, a
1591 bounce message is generated. Temporary delivery failures turn into permanent
1592 errors when their timeout expires. All the addresses that fail in a given
1593 delivery attempt are listed in a single message. If the original message has
1594 many recipients, it is possible for some addresses to fail in one delivery
1595 attempt and others to fail subsequently, giving rise to more than one bounce
1596 message. The wording of bounce messages can be customized by the administrator.
1597 See chapter &<<CHAPemsgcust>>& for details.
1599 .cindex "&'X-Failed-Recipients:'& header line"
1600 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1601 failed addresses, for the benefit of programs that try to analyse such messages
1604 .cindex "bounce message" "recipient of"
1605 A bounce message is normally sent to the sender of the original message, as
1606 obtained from the message's envelope. For incoming SMTP messages, this is the
1607 address given in the MAIL command. However, when an address is expanded via a
1608 forward or alias file, an alternative address can be specified for delivery
1609 failures of the generated addresses. For a mailing list expansion (see section
1610 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1615 .section "Failures to deliver bounce messages" "SECID22"
1616 .cindex "bounce message" "failure to deliver"
1617 If a bounce message (either locally generated or received from a remote host)
1618 itself suffers a permanent delivery failure, the message is left on the queue,
1619 but it is frozen, awaiting the attention of an administrator. There are options
1620 that can be used to make Exim discard such failed messages, or to keep them
1621 for only a short time (see &%timeout_frozen_after%& and
1622 &%ignore_bounce_errors_after%&).
1628 . ////////////////////////////////////////////////////////////////////////////
1629 . ////////////////////////////////////////////////////////////////////////////
1631 .chapter "Building and installing Exim" "CHID3"
1632 .scindex IIDbuex "building Exim"
1634 .section "Unpacking" "SECID23"
1635 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1636 creates a directory with the name of the current release (for example,
1637 &_exim-&version()_&) into which the following files are placed:
1640 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1641 .irow &_CHANGES_& "contains a reference to where changes are &&&
1643 .irow &_LICENCE_& "the GNU General Public Licence"
1644 .irow &_Makefile_& "top-level make file"
1645 .irow &_NOTICE_& "conditions for the use of Exim"
1646 .irow &_README_& "list of files, directories and simple build &&&
1650 Other files whose names begin with &_README_& may also be present. The
1651 following subdirectories are created:
1654 .irow &_Local_& "an empty directory for local configuration files"
1655 .irow &_OS_& "OS-specific files"
1656 .irow &_doc_& "documentation files"
1657 .irow &_exim_monitor_& "source files for the Exim monitor"
1658 .irow &_scripts_& "scripts used in the build process"
1659 .irow &_src_& "remaining source files"
1660 .irow &_util_& "independent utilities"
1663 The main utility programs are contained in the &_src_& directory, and are built
1664 with the Exim binary. The &_util_& directory contains a few optional scripts
1665 that may be useful to some sites.
1668 .section "Multiple machine architectures and operating systems" "SECID24"
1669 .cindex "building Exim" "multiple OS/architectures"
1670 The building process for Exim is arranged to make it easy to build binaries for
1671 a number of different architectures and operating systems from the same set of
1672 source files. Compilation does not take place in the &_src_& directory.
1673 Instead, a &'build directory'& is created for each architecture and operating
1675 .cindex "symbolic link" "to build directory"
1676 Symbolic links to the sources are installed in this directory, which is where
1677 the actual building takes place. In most cases, Exim can discover the machine
1678 architecture and operating system for itself, but the defaults can be
1679 overridden if necessary.
1682 .section "PCRE library" "SECTpcre"
1683 .cindex "PCRE library"
1684 Exim no longer has an embedded PCRE library as the vast majority of
1685 modern systems include PCRE as a system library, although you may need
1686 to install the PCRE or PCRE development package for your operating
1687 system. If your system has a normal PCRE installation the Exim build
1688 process will need no further configuration. If the library or the
1689 headers are in an unusual location you will need to either set the PCRE_LIBS
1690 and INCLUDE directives appropriately,
1691 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1692 If your operating system has no
1693 PCRE support then you will need to obtain and build the current PCRE
1694 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1695 More information on PCRE is available at &url(http://www.pcre.org/).
1697 .section "DBM libraries" "SECTdb"
1698 .cindex "DBM libraries" "discussion of"
1699 .cindex "hints database" "DBM files used for"
1700 Even if you do not use any DBM files in your configuration, Exim still needs a
1701 DBM library in order to operate, because it uses indexed files for its hints
1702 databases. Unfortunately, there are a number of DBM libraries in existence, and
1703 different operating systems often have different ones installed.
1705 .cindex "Solaris" "DBM library for"
1706 .cindex "IRIX, DBM library for"
1707 .cindex "BSD, DBM library for"
1708 .cindex "Linux, DBM library for"
1709 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1710 Linux distribution, the DBM configuration should happen automatically, and you
1711 may be able to ignore this section. Otherwise, you may have to learn more than
1712 you would like about DBM libraries from what follows.
1714 .cindex "&'ndbm'& DBM library"
1715 Licensed versions of Unix normally contain a library of DBM functions operating
1716 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1717 versions of Unix seem to vary in what they contain as standard. In particular,
1718 some early versions of Linux have no default DBM library, and different
1719 distributors have chosen to bundle different libraries with their packaged
1720 versions. However, the more recent releases seem to have standardized on the
1721 Berkeley DB library.
1723 Different DBM libraries have different conventions for naming the files they
1724 use. When a program opens a file called &_dbmfile_&, there are several
1728 A traditional &'ndbm'& implementation, such as that supplied as part of
1729 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1731 .cindex "&'gdbm'& DBM library"
1732 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1733 compatibility interface it makes two different hard links to it with names
1734 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1735 file name is used unmodified.
1737 .cindex "Berkeley DB library"
1738 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1739 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1740 programmer exactly the same as the traditional &'ndbm'& implementation.
1742 If the Berkeley package is used in its native mode, it operates on a single
1743 file called &_dbmfile_&; the programmer's interface is somewhat different to
1744 the traditional &'ndbm'& interface.
1746 To complicate things further, there are several very different versions of the
1747 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1748 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1749 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1750 versions of Berkeley DB can be obtained from
1751 &url(http://www.sleepycat.com/).
1753 .cindex "&'tdb'& DBM library"
1754 Yet another DBM library, called &'tdb'&, is available from
1755 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1756 operates on a single file.
1760 .cindex "DBM libraries" "configuration for building"
1761 Exim and its utilities can be compiled to use any of these interfaces. In order
1762 to use any version of the Berkeley DB package in native mode, you must set
1763 USE_DB in an appropriate configuration file (typically
1764 &_Local/Makefile_&). For example:
1768 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1769 error is diagnosed if you set more than one of these.
1771 At the lowest level, the build-time configuration sets none of these options,
1772 thereby assuming an interface of type (1). However, some operating system
1773 configuration files (for example, those for the BSD operating systems and
1774 Linux) assume type (4) by setting USE_DB as their default, and the
1775 configuration files for Cygwin set USE_GDBM. Anything you set in
1776 &_Local/Makefile_&, however, overrides these system defaults.
1778 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1779 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1780 in one of these lines:
1785 Settings like that will work if the DBM library is installed in the standard
1786 place. Sometimes it is not, and the library's header file may also not be in
1787 the default path. You may need to set INCLUDE to specify where the header
1788 file is, and to specify the path to the library more fully in DBMLIB, as in
1791 INCLUDE=-I/usr/local/include/db-4.1
1792 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1794 There is further detailed discussion about the various DBM libraries in the
1795 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1799 .section "Pre-building configuration" "SECID25"
1800 .cindex "building Exim" "pre-building configuration"
1801 .cindex "configuration for building Exim"
1802 .cindex "&_Local/Makefile_&"
1803 .cindex "&_src/EDITME_&"
1804 Before building Exim, a local configuration file that specifies options
1805 independent of any operating system has to be created with the name
1806 &_Local/Makefile_&. A template for this file is supplied as the file
1807 &_src/EDITME_&, and it contains full descriptions of all the option settings
1808 therein. These descriptions are therefore not repeated here. If you are
1809 building Exim for the first time, the simplest thing to do is to copy
1810 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1812 There are three settings that you must supply, because Exim will not build
1813 without them. They are the location of the run time configuration file
1814 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1815 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1816 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1817 a colon-separated list of file names; Exim uses the first of them that exists.
1819 There are a few other parameters that can be specified either at build time or
1820 at run time, to enable the same binary to be used on a number of different
1821 machines. However, if the locations of Exim's spool directory and log file
1822 directory (if not within the spool directory) are fixed, it is recommended that
1823 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1824 detected early in Exim's execution (such as a malformed configuration file) can
1827 .cindex "content scanning" "specifying at build time"
1828 Exim's interfaces for calling virus and spam scanning software directly from
1829 access control lists are not compiled by default. If you want to include these
1830 facilities, you need to set
1832 WITH_CONTENT_SCAN=yes
1834 in your &_Local/Makefile_&. For details of the facilities themselves, see
1835 chapter &<<CHAPexiscan>>&.
1838 .cindex "&_Local/eximon.conf_&"
1839 .cindex "&_exim_monitor/EDITME_&"
1840 If you are going to build the Exim monitor, a similar configuration process is
1841 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1842 your installation and saved under the name &_Local/eximon.conf_&. If you are
1843 happy with the default settings described in &_exim_monitor/EDITME_&,
1844 &_Local/eximon.conf_& can be empty, but it must exist.
1846 This is all the configuration that is needed in straightforward cases for known
1847 operating systems. However, the building process is set up so that it is easy
1848 to override options that are set by default or by operating-system-specific
1849 configuration files, for example to change the name of the C compiler, which
1850 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1855 .section "Support for iconv()" "SECID26"
1856 .cindex "&[iconv()]& support"
1858 The contents of header lines in messages may be encoded according to the rules
1859 described RFC 2047. This makes it possible to transmit characters that are not
1860 in the ASCII character set, and to label them as being in a particular
1861 character set. When Exim is inspecting header lines by means of the &%$h_%&
1862 mechanism, it decodes them, and translates them into a specified character set
1863 (default is set at build time). The translation is possible only if the operating system
1864 supports the &[iconv()]& function.
1866 However, some of the operating systems that supply &[iconv()]& do not support
1867 very many conversions. The GNU &%libiconv%& library (available from
1868 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1869 systems to remedy this deficiency, as well as on systems that do not supply
1870 &[iconv()]& at all. After installing &%libiconv%&, you should add
1874 to your &_Local/Makefile_& and rebuild Exim.
1878 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1879 .cindex "TLS" "including support for TLS"
1880 .cindex "encryption" "including support for"
1881 .cindex "SUPPORT_TLS"
1882 .cindex "OpenSSL" "building Exim with"
1883 .cindex "GnuTLS" "building Exim with"
1884 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1885 command as per RFC 2487. It can also support legacy clients that expect to
1886 start a TLS session immediately on connection to a non-standard port (see the
1887 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1890 If you want to build Exim with TLS support, you must first install either the
1891 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1894 If OpenSSL is installed, you should set
1897 TLS_LIBS=-lssl -lcrypto
1899 in &_Local/Makefile_&. You may also need to specify the locations of the
1900 OpenSSL library and include files. For example:
1903 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1904 TLS_INCLUDE=-I/usr/local/openssl/include/
1906 .cindex "pkg-config" "OpenSSL"
1907 If you have &'pkg-config'& available, then instead you can just use:
1910 USE_OPENSSL_PC=openssl
1912 .cindex "USE_GNUTLS"
1913 If GnuTLS is installed, you should set
1917 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1919 in &_Local/Makefile_&, and again you may need to specify the locations of the
1920 library and include files. For example:
1924 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1925 TLS_INCLUDE=-I/usr/gnu/include
1927 .cindex "pkg-config" "GnuTLS"
1928 If you have &'pkg-config'& available, then instead you can just use:
1932 USE_GNUTLS_PC=gnutls
1935 You do not need to set TLS_INCLUDE if the relevant directory is already
1936 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1937 given in chapter &<<CHAPTLS>>&.
1942 .section "Use of tcpwrappers" "SECID27"
1944 .cindex "tcpwrappers, building Exim to support"
1945 .cindex "USE_TCP_WRAPPERS"
1946 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1947 .cindex "tcp_wrappers_daemon_name"
1948 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1949 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1950 alternative to Exim's own checking facilities for installations that are
1951 already making use of &'tcpwrappers'& for other purposes. To do this, you
1952 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1953 &_tcpd.h_& to be available at compile time, and also ensure that the library
1954 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1955 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1958 USE_TCP_WRAPPERS=yes
1959 CFLAGS=-O -I/usr/local/include
1960 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1962 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1963 files is &"exim"&. For example, the line
1965 exim : LOCAL 192.168.1. .friendly.domain.example
1967 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1968 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1969 All other connections are denied. The daemon name used by &'tcpwrappers'&
1970 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1971 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1972 configure file. Consult the &'tcpwrappers'& documentation for
1976 .section "Including support for IPv6" "SECID28"
1977 .cindex "IPv6" "including support for"
1978 Exim contains code for use on systems that have IPv6 support. Setting
1979 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1980 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1981 where the IPv6 support is not fully integrated into the normal include and
1984 Two different types of DNS record for handling IPv6 addresses have been
1985 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1986 currently seen as the mainstream. Another record type called A6 was proposed
1987 as better than AAAA because it had more flexibility. However, it was felt to be
1988 over-complex, and its status was reduced to &"experimental"&.
1990 have a compile option for including A6 record support but this has now been
1995 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1996 .cindex "lookup modules"
1997 .cindex "dynamic modules"
1998 .cindex ".so building"
1999 On some platforms, Exim supports not compiling all lookup types directly into
2000 the main binary, instead putting some into external modules which can be loaded
2002 This permits packagers to build Exim with support for lookups with extensive
2003 library dependencies without requiring all users to install all of those
2005 Most, but not all, lookup types can be built this way.
2007 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2008 installed; Exim will only load modules from that directory, as a security
2009 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2010 for your OS; see &_OS/Makefile-Linux_& for an example.
2011 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2012 see &_src/EDITME_& for details.
2014 Then, for each module to be loaded dynamically, define the relevant
2015 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2016 For example, this will build in lsearch but load sqlite and mysql support
2025 .section "The building process" "SECID29"
2026 .cindex "build directory"
2027 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2028 created, run &'make'& at the top level. It determines the architecture and
2029 operating system types, and creates a build directory if one does not exist.
2030 For example, on a Sun system running Solaris 8, the directory
2031 &_build-SunOS5-5.8-sparc_& is created.
2032 .cindex "symbolic link" "to source files"
2033 Symbolic links to relevant source files are installed in the build directory.
2035 If this is the first time &'make'& has been run, it calls a script that builds
2036 a make file inside the build directory, using the configuration files from the
2037 &_Local_& directory. The new make file is then passed to another instance of
2038 &'make'&. This does the real work, building a number of utility scripts, and
2039 then compiling and linking the binaries for the Exim monitor (if configured), a
2040 number of utility programs, and finally Exim itself. The command &`make
2041 makefile`& can be used to force a rebuild of the make file in the build
2042 directory, should this ever be necessary.
2044 If you have problems building Exim, check for any comments there may be in the
2045 &_README_& file concerning your operating system, and also take a look at the
2046 FAQ, where some common problems are covered.
2050 .section 'Output from &"make"&' "SECID283"
2051 The output produced by the &'make'& process for compile lines is often very
2052 unreadable, because these lines can be very long. For this reason, the normal
2053 output is suppressed by default, and instead output similar to that which
2054 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2055 each module that is being compiled or linked. However, it is still possible to
2056 get the full output, by calling &'make'& like this:
2060 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2061 command reflection in &'make'&. When you ask for the full output, it is
2062 given in addition to the short output.
2066 .section "Overriding build-time options for Exim" "SECToverride"
2067 .cindex "build-time options, overriding"
2068 The main make file that is created at the beginning of the building process
2069 consists of the concatenation of a number of files which set configuration
2070 values, followed by a fixed set of &'make'& instructions. If a value is set
2071 more than once, the last setting overrides any previous ones. This provides a
2072 convenient way of overriding defaults. The files that are concatenated are, in
2075 &_OS/Makefile-Default_&
2076 &_OS/Makefile-_&<&'ostype'&>
2078 &_Local/Makefile-_&<&'ostype'&>
2079 &_Local/Makefile-_&<&'archtype'&>
2080 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2081 &_OS/Makefile-Base_&
2083 .cindex "&_Local/Makefile_&"
2084 .cindex "building Exim" "operating system type"
2085 .cindex "building Exim" "architecture type"
2086 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2087 architecture type. &_Local/Makefile_& is required to exist, and the building
2088 process fails if it is absent. The other three &_Local_& files are optional,
2089 and are often not needed.
2091 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2092 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2093 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2094 values are used, thereby providing a means of forcing particular settings.
2095 Otherwise, the scripts try to get values from the &%uname%& command. If this
2096 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2097 of &'ad hoc'& transformations are then applied, to produce the standard names
2098 that Exim expects. You can run these scripts directly from the shell in order
2099 to find out what values are being used on your system.
2102 &_OS/Makefile-Default_& contains comments about the variables that are set
2103 therein. Some (but not all) are mentioned below. If there is something that
2104 needs changing, review the contents of this file and the contents of the make
2105 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2109 .cindex "building Exim" "overriding default settings"
2110 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2111 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2112 need to change the original files. Instead, you should make the changes by
2113 putting the new values in an appropriate &_Local_& file. For example,
2114 .cindex "Tru64-Unix build-time settings"
2115 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2116 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2117 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2118 called with the option &%-std1%&, to make it recognize some of the features of
2119 Standard C that Exim uses. (Most other compilers recognize Standard C by
2120 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2121 containing the lines
2126 If you are compiling for just one operating system, it may be easier to put
2127 these lines directly into &_Local/Makefile_&.
2129 Keeping all your local configuration settings separate from the distributed
2130 files makes it easy to transfer them to new versions of Exim simply by copying
2131 the contents of the &_Local_& directory.
2134 .cindex "NIS lookup type" "including support for"
2135 .cindex "NIS+ lookup type" "including support for"
2136 .cindex "LDAP" "including support for"
2137 .cindex "lookup" "inclusion in binary"
2138 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2139 lookup, but not all systems have these components installed, so the default is
2140 not to include the relevant code in the binary. All the different kinds of file
2141 and database lookup that Exim supports are implemented as separate code modules
2142 which are included only if the relevant compile-time options are set. In the
2143 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2149 and similar settings apply to the other lookup types. They are all listed in
2150 &_src/EDITME_&. In many cases the relevant include files and interface
2151 libraries need to be installed before compiling Exim.
2152 .cindex "cdb" "including support for"
2153 However, there are some optional lookup types (such as cdb) for which
2154 the code is entirely contained within Exim, and no external include
2155 files or libraries are required. When a lookup type is not included in the
2156 binary, attempts to configure Exim to use it cause run time configuration
2159 .cindex "pkg-config" "lookups"
2160 .cindex "pkg-config" "authenticators"
2161 Many systems now use a tool called &'pkg-config'& to encapsulate information
2162 about how to compile against a library; Exim has some initial support for
2163 being able to use pkg-config for lookups and authenticators. For any given
2164 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2165 variable with the &`_PC`& suffix in the name and assign as the value the
2166 name of the package to be queried. The results of querying via the
2167 &'pkg-config'& command will be added to the appropriate Makefile variables
2168 with &`+=`& directives, so your version of &'make'& will need to support that
2169 syntax. For instance:
2172 LOOKUP_SQLITE_PC=sqlite3
2174 AUTH_GSASL_PC=libgsasl
2175 AUTH_HEIMDAL_GSSAPI=yes
2176 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2179 .cindex "Perl" "including support for"
2180 Exim can be linked with an embedded Perl interpreter, allowing Perl
2181 subroutines to be called during string expansion. To enable this facility,
2185 must be defined in &_Local/Makefile_&. Details of this facility are given in
2186 chapter &<<CHAPperl>>&.
2188 .cindex "X11 libraries, location of"
2189 The location of the X11 libraries is something that varies a lot between
2190 operating systems, and there may be different versions of X11 to cope
2191 with. Exim itself makes no use of X11, but if you are compiling the Exim
2192 monitor, the X11 libraries must be available.
2193 The following three variables are set in &_OS/Makefile-Default_&:
2196 XINCLUDE=-I$(X11)/include
2197 XLFLAGS=-L$(X11)/lib
2199 These are overridden in some of the operating-system configuration files. For
2200 example, in &_OS/Makefile-SunOS5_& there is
2203 XINCLUDE=-I$(X11)/include
2204 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2206 If you need to override the default setting for your operating system, place a
2207 definition of all three of these variables into your
2208 &_Local/Makefile-<ostype>_& file.
2211 If you need to add any extra libraries to the link steps, these can be put in a
2212 variable called EXTRALIBS, which appears in all the link commands, but by
2213 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2214 command for linking the main Exim binary, and not for any associated utilities.
2216 .cindex "DBM libraries" "configuration for building"
2217 There is also DBMLIB, which appears in the link commands for binaries that
2218 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2219 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2220 binary, and which can be used, for example, to include additional X11
2223 .cindex "configuration file" "editing"
2224 The make file copes with rebuilding Exim correctly if any of the configuration
2225 files are edited. However, if an optional configuration file is deleted, it is
2226 necessary to touch the associated non-optional file (that is,
2227 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2230 .section "OS-specific header files" "SECID30"
2232 .cindex "building Exim" "OS-specific C header files"
2233 The &_OS_& directory contains a number of files with names of the form
2234 &_os.h-<ostype>_&. These are system-specific C header files that should not
2235 normally need to be changed. There is a list of macro settings that are
2236 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2237 are porting Exim to a new operating system.
2241 .section "Overriding build-time options for the monitor" "SECID31"
2242 .cindex "building Eximon"
2243 A similar process is used for overriding things when building the Exim monitor,
2244 where the files that are involved are
2246 &_OS/eximon.conf-Default_&
2247 &_OS/eximon.conf-_&<&'ostype'&>
2248 &_Local/eximon.conf_&
2249 &_Local/eximon.conf-_&<&'ostype'&>
2250 &_Local/eximon.conf-_&<&'archtype'&>
2251 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2253 .cindex "&_Local/eximon.conf_&"
2254 As with Exim itself, the final three files need not exist, and in this case the
2255 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2256 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2257 variables of the same name, preceded by EXIMON_. For example, setting
2258 EXIMON_LOG_DEPTH in the environment overrides the value of
2259 LOG_DEPTH at run time.
2263 .section "Installing Exim binaries and scripts" "SECID32"
2264 .cindex "installing Exim"
2265 .cindex "BIN_DIRECTORY"
2266 The command &`make install`& runs the &(exim_install)& script with no
2267 arguments. The script copies binaries and utility scripts into the directory
2268 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2269 .cindex "setuid" "installing Exim with"
2270 The install script copies files only if they are newer than the files they are
2271 going to replace. The Exim binary is required to be owned by root and have the
2272 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2273 install`& as root so that it can set up the Exim binary in this way. However, in
2274 some special situations (for example, if a host is doing no local deliveries)
2275 it may be possible to run Exim without making the binary setuid root (see
2276 chapter &<<CHAPsecurity>>& for details).
2278 .cindex "CONFIGURE_FILE"
2279 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2280 in &_Local/Makefile_&. If this names a single file, and the file does not
2281 exist, the default configuration file &_src/configure.default_& is copied there
2282 by the installation script. If a run time configuration file already exists, it
2283 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2284 alternative files, no default is installed.
2286 .cindex "system aliases file"
2287 .cindex "&_/etc/aliases_&"
2288 One change is made to the default configuration file when it is installed: the
2289 default configuration contains a router that references a system aliases file.
2290 The path to this file is set to the value specified by
2291 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2292 If the system aliases file does not exist, the installation script creates it,
2293 and outputs a comment to the user.
2295 The created file contains no aliases, but it does contain comments about the
2296 aliases a site should normally have. Mail aliases have traditionally been
2297 kept in &_/etc/aliases_&. However, some operating systems are now using
2298 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2299 Exim's configuration if necessary.
2301 The default configuration uses the local host's name as the only local domain,
2302 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2303 running as the local user. System aliases and &_.forward_& files in users' home
2304 directories are supported, but no NIS or NIS+ support is configured. Domains
2305 other than the name of the local host are routed using the DNS, with delivery
2308 It is possible to install Exim for special purposes (such as building a binary
2309 distribution) in a private part of the file system. You can do this by a
2312 make DESTDIR=/some/directory/ install
2314 This has the effect of pre-pending the specified directory to all the file
2315 paths, except the name of the system aliases file that appears in the default
2316 configuration. (If a default alias file is created, its name &'is'& modified.)
2317 For backwards compatibility, ROOT is used if DESTDIR is not set,
2318 but this usage is deprecated.
2320 .cindex "installing Exim" "what is not installed"
2321 Running &'make install'& does not copy the Exim 4 conversion script
2322 &'convert4r4'&. You will probably run this only once if you are
2323 upgrading from Exim 3. None of the documentation files in the &_doc_&
2324 directory are copied, except for the info files when you have set
2325 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2327 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2328 to their names. The Exim binary itself, however, is handled differently. It is
2329 installed under a name that includes the version number and the compile number,
2330 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2331 called &_exim_& to point to the binary. If you are updating a previous version
2332 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2333 from the directory (as seen by other processes).
2335 .cindex "installing Exim" "testing the script"
2336 If you want to see what the &'make install'& will do before running it for
2337 real, you can pass the &%-n%& option to the installation script by this
2340 make INSTALL_ARG=-n install
2342 The contents of the variable INSTALL_ARG are passed to the installation
2343 script. You do not need to be root to run this test. Alternatively, you can run
2344 the installation script directly, but this must be from within the build
2345 directory. For example, from the top-level Exim directory you could use this
2348 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2350 .cindex "installing Exim" "install script options"
2351 There are two other options that can be supplied to the installation script.
2354 &%-no_chown%& bypasses the call to change the owner of the installed binary
2355 to root, and the call to make it a setuid binary.
2357 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2361 INSTALL_ARG can be used to pass these options to the script. For example:
2363 make INSTALL_ARG=-no_symlink install
2365 The installation script can also be given arguments specifying which files are
2366 to be copied. For example, to install just the Exim binary, and nothing else,
2367 without creating the symbolic link, you could use:
2369 make INSTALL_ARG='-no_symlink exim' install
2374 .section "Installing info documentation" "SECTinsinfdoc"
2375 .cindex "installing Exim" "&'info'& documentation"
2376 Not all systems use the GNU &'info'& system for documentation, and for this
2377 reason, the Texinfo source of Exim's documentation is not included in the main
2378 distribution. Instead it is available separately from the ftp site (see section
2381 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2382 source of the documentation is found in the source tree, running &`make
2383 install`& automatically builds the info files and installs them.
2387 .section "Setting up the spool directory" "SECID33"
2388 .cindex "spool directory" "creating"
2389 When it starts up, Exim tries to create its spool directory if it does not
2390 exist. The Exim uid and gid are used for the owner and group of the spool
2391 directory. Sub-directories are automatically created in the spool directory as
2397 .section "Testing" "SECID34"
2398 .cindex "testing" "installation"
2399 Having installed Exim, you can check that the run time configuration file is
2400 syntactically valid by running the following command, which assumes that the
2401 Exim binary directory is within your PATH environment variable:
2405 If there are any errors in the configuration file, Exim outputs error messages.
2406 Otherwise it outputs the version number and build date,
2407 the DBM library that is being used, and information about which drivers and
2408 other optional code modules are included in the binary.
2409 Some simple routing tests can be done by using the address testing option. For
2412 &`exim -bt`& <&'local username'&>
2414 should verify that it recognizes a local mailbox, and
2416 &`exim -bt`& <&'remote address'&>
2418 a remote one. Then try getting it to deliver mail, both locally and remotely.
2419 This can be done by passing messages directly to Exim, without going through a
2420 user agent. For example:
2422 exim -v postmaster@your.domain.example
2423 From: user@your.domain.example
2424 To: postmaster@your.domain.example
2425 Subject: Testing Exim
2427 This is a test message.
2430 The &%-v%& option causes Exim to output some verification of what it is doing.
2431 In this case you should see copies of three log lines, one for the message's
2432 arrival, one for its delivery, and one containing &"Completed"&.
2434 .cindex "delivery" "problems with"
2435 If you encounter problems, look at Exim's log files (&'mainlog'& and
2436 &'paniclog'&) to see if there is any relevant information there. Another source
2437 of information is running Exim with debugging turned on, by specifying the
2438 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2439 with debugging turned on by a command of the form
2441 &`exim -d -M`& <&'exim-message-id'&>
2443 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2444 produces rather a lot of output, but you can cut this down to specific areas.
2445 For example, if you use &%-d-all+route%& only the debugging information
2446 relevant to routing is included. (See the &%-d%& option in chapter
2447 &<<CHAPcommandline>>& for more details.)
2449 .cindex '&"sticky"& bit'
2450 .cindex "lock files"
2451 One specific problem that has shown up on some sites is the inability to do
2452 local deliveries into a shared mailbox directory, because it does not have the
2453 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2454 writing to a mailbox file, and if it cannot create the lock file, the delivery
2455 is deferred. You can get round this either by setting the &"sticky bit"& on the
2456 directory, or by setting a specific group for local deliveries and allowing
2457 that group to create files in the directory (see the comments above the
2458 &(local_delivery)& transport in the default configuration file). Another
2459 approach is to configure Exim not to use lock files, but just to rely on
2460 &[fcntl()]& locking instead. However, you should do this only if all user
2461 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2462 see chapter &<<CHAPappendfile>>&.
2464 One thing that cannot be tested on a system that is already running an MTA is
2465 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2466 &%-oX%& option can be used to run an Exim daemon that listens on some other
2467 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2468 &'exim_checkaccess'& utility can be used to check out policy controls on
2471 Testing a new version on a system that is already running Exim can most easily
2472 be done by building a binary with a different CONFIGURE_FILE setting. From
2473 within the run time configuration, all other file and directory names
2474 that Exim uses can be altered, in order to keep it entirely clear of the
2478 .section "Replacing another MTA with Exim" "SECID35"
2479 .cindex "replacing another MTA"
2480 Building and installing Exim for the first time does not of itself put it in
2481 general use. The name by which the system's MTA is called by mail user agents
2482 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2483 operating system), and it is necessary to make this name point to the &'exim'&
2484 binary in order to get the user agents to pass messages to Exim. This is
2485 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2486 or &_/usr/lib/sendmail_&
2487 .cindex "symbolic link" "to &'exim'& binary"
2488 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2489 privilege and executable status from the old MTA. It is then necessary to stop
2490 and restart the mailer daemon, if one is running.
2492 .cindex "FreeBSD, MTA indirection"
2493 .cindex "&_/etc/mail/mailer.conf_&"
2494 Some operating systems have introduced alternative ways of switching MTAs. For
2495 example, if you are running FreeBSD, you need to edit the file
2496 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2497 described. A typical example of the contents of this file for running Exim is
2500 sendmail /usr/exim/bin/exim
2501 send-mail /usr/exim/bin/exim
2502 mailq /usr/exim/bin/exim -bp
2503 newaliases /usr/bin/true
2505 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2506 your Exim installation is &"live"&. Check it by sending a message from your
2507 favourite user agent.
2509 You should consider what to tell your users about the change of MTA. Exim may
2510 have different capabilities to what was previously running, and there are
2511 various operational differences such as the text of messages produced by
2512 command line options and in bounce messages. If you allow your users to make
2513 use of Exim's filtering capabilities, you should make the document entitled
2514 &'Exim's interface to mail filtering'& available to them.
2518 .section "Upgrading Exim" "SECID36"
2519 .cindex "upgrading Exim"
2520 If you are already running Exim on your host, building and installing a new
2521 version automatically makes it available to MUAs, or any other programs that
2522 call the MTA directly. However, if you are running an Exim daemon, you do need
2523 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2524 new binary. You do not need to stop processing mail in order to install a new
2525 version of Exim. The install script does not modify an existing runtime
2531 .section "Stopping the Exim daemon on Solaris" "SECID37"
2532 .cindex "Solaris" "stopping Exim on"
2533 The standard command for stopping the mailer daemon on Solaris is
2535 /etc/init.d/sendmail stop
2537 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2538 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2539 for the text &"sendmail"&; this is not present because the actual program name
2540 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2541 solution is to replace the line that finds the process id with something like
2543 pid=`cat /var/spool/exim/exim-daemon.pid`
2545 to obtain the daemon's pid directly from the file that Exim saves it in.
2547 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2548 still be received from local processes, and if automatic delivery is configured
2549 (the normal case), deliveries will still occur.
2554 . ////////////////////////////////////////////////////////////////////////////
2555 . ////////////////////////////////////////////////////////////////////////////
2557 .chapter "The Exim command line" "CHAPcommandline"
2558 .scindex IIDclo1 "command line" "options"
2559 .scindex IIDclo2 "options" "command line"
2560 Exim's command line takes the standard Unix form of a sequence of options,
2561 each starting with a hyphen character, followed by a number of arguments. The
2562 options are compatible with the main options of Sendmail, and there are also
2563 some additional options, some of which are compatible with Smail 3. Certain
2564 combinations of options do not make sense, and provoke an error if used.
2565 The form of the arguments depends on which options are set.
2568 .section "Setting options by program name" "SECID38"
2570 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2571 were present before any other options.
2572 The &%-bp%& option requests a listing of the contents of the mail queue on the
2574 This feature is for compatibility with some systems that contain a command of
2575 that name in one of the standard libraries, symbolically linked to
2576 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2579 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2580 were present before any other options, for compatibility with Smail. The
2581 &%-bS%& option is used for reading in a number of messages in batched SMTP
2585 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2586 &%-oee%& options were present before any other options, for compatibility with
2587 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2590 .cindex "queue runner"
2591 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2592 were present before any other options, for compatibility with Smail. The &%-q%&
2593 option causes a single queue runner process to be started.
2595 .cindex "&'newaliases'&"
2596 .cindex "alias file" "building"
2597 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2598 If Exim is called under the name &'newaliases'& it behaves as if the option
2599 &%-bi%& were present before any other options, for compatibility with Sendmail.
2600 This option is used for rebuilding Sendmail's alias file. Exim does not have
2601 the concept of a single alias file, but can be configured to run a given
2602 command if called with the &%-bi%& option.
2605 .section "Trusted and admin users" "SECTtrustedadmin"
2606 Some Exim options are available only to &'trusted users'& and others are
2607 available only to &'admin users'&. In the description below, the phrases &"Exim
2608 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2609 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2610 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2613 .cindex "trusted users" "definition of"
2614 .cindex "user" "trusted definition of"
2615 The trusted users are root, the Exim user, any user listed in the
2616 &%trusted_users%& configuration option, and any user whose current group or any
2617 supplementary group is one of those listed in the &%trusted_groups%&
2618 configuration option. Note that the Exim group is not automatically trusted.
2620 .cindex '&"From"& line'
2621 .cindex "envelope sender"
2622 Trusted users are always permitted to use the &%-f%& option or a leading
2623 &"From&~"& line to specify the envelope sender of a message that is passed to
2624 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2625 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2626 users to set envelope senders.
2628 .cindex "&'From:'& header line"
2629 .cindex "&'Sender:'& header line"
2630 For a trusted user, there is never any check on the contents of the &'From:'&
2631 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2632 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2634 Trusted users may also specify a host name, host address, interface address,
2635 protocol name, ident value, and authentication data when submitting a message
2636 locally. Thus, they are able to insert messages into Exim's queue locally that
2637 have the characteristics of messages received from a remote host. Untrusted
2638 users may in some circumstances use &%-f%&, but can never set the other values
2639 that are available to trusted users.
2641 .cindex "user" "admin definition of"
2642 .cindex "admin user" "definition of"
2643 The admin users are root, the Exim user, and any user that is a member of the
2644 Exim group or of any group listed in the &%admin_groups%& configuration option.
2645 The current group does not have to be one of these groups.
2647 Admin users are permitted to list the queue, and to carry out certain
2648 operations on messages, for example, to force delivery failures. It is also
2649 necessary to be an admin user in order to see the full information provided by
2650 the Exim monitor, and full debugging output.
2652 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2653 Exim to attempt delivery of messages on its queue is restricted to admin users.
2654 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2655 option false (that is, specifying &%no_prod_requires_admin%&).
2657 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2658 is restricted to admin users unless &%queue_list_requires_admin%& is set
2663 &*Warning*&: If you configure your system so that admin users are able to
2664 edit Exim's configuration file, you are giving those users an easy way of
2665 getting root. There is further discussion of this issue at the start of chapter
2671 .section "Command line options" "SECID39"
2672 Exim's command line options are described in alphabetical order below. If none
2673 of the options that specifies a specific action (such as starting the daemon or
2674 a queue runner, or testing an address, or receiving a message in a specific
2675 format, or listing the queue) are present, and there is at least one argument
2676 on the command line, &%-bm%& (accept a local message on the standard input,
2677 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2678 outputs a brief message about itself and exits.
2680 . ////////////////////////////////////////////////////////////////////////////
2681 . Insert a stylized XML comment here, to identify the start of the command line
2682 . options. This is for the benefit of the Perl script that automatically
2683 . creates a man page for the options.
2684 . ////////////////////////////////////////////////////////////////////////////
2687 <!-- === Start of command line options === -->
2694 .cindex "options" "command line; terminating"
2695 This is a pseudo-option whose only purpose is to terminate the options and
2696 therefore to cause subsequent command line items to be treated as arguments
2697 rather than options, even if they begin with hyphens.
2700 .oindex "&%--help%&"
2701 This option causes Exim to output a few sentences stating what it is.
2702 The same output is generated if the Exim binary is called with no options and
2705 .vitem &%--version%&
2706 .oindex "&%--version%&"
2707 This option is an alias for &%-bV%& and causes version information to be
2714 These options are used by Sendmail for selecting configuration files and are
2717 .vitem &%-B%&<&'type'&>
2719 .cindex "8-bit characters"
2720 .cindex "Sendmail compatibility" "8-bit characters"
2721 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2722 clean; it ignores this option.
2727 .cindex "SMTP" "listener"
2728 .cindex "queue runner"
2729 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2730 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2731 that the daemon should also initiate periodic queue runs.
2733 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2734 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2735 disconnect from the controlling terminal. When running this way, it can be
2736 stopped by pressing ctrl-C.
2738 By default, Exim listens for incoming connections to the standard SMTP port on
2739 all the host's running interfaces. However, it is possible to listen on other
2740 ports, on multiple ports, and only on specific interfaces. Chapter
2741 &<<CHAPinterfaces>>& contains a description of the options that control this.
2743 When a listening daemon
2744 .cindex "daemon" "process id (pid)"
2745 .cindex "pid (process id)" "of daemon"
2746 is started without the use of &%-oX%& (that is, without overriding the normal
2747 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2748 in Exim's spool directory. This location can be overridden by setting
2749 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2752 When &%-oX%& is used on the command line to start a listening daemon, the
2753 process id is not written to the normal pid file path. However, &%-oP%& can be
2754 used to specify a path on the command line if a pid file is required.
2758 .cindex "daemon" "restarting"
2759 can be used to cause the daemon to re-execute itself. This should be done
2760 whenever Exim's configuration file, or any file that is incorporated into it by
2761 means of the &%.include%& facility, is changed, and also whenever a new version
2762 of Exim is installed. It is not necessary to do this when other files that are
2763 referenced from the configuration (for example, alias files) are changed,
2764 because these are reread each time they are used.
2768 This option has the same effect as &%-bd%& except that it never disconnects
2769 from the controlling terminal, even when no debugging is specified.
2773 .cindex "testing" "string expansion"
2774 .cindex "expansion" "testing"
2775 Run Exim in expansion testing mode. Exim discards its root privilege, to
2776 prevent ordinary users from using this mode to read otherwise inaccessible
2777 files. If no arguments are given, Exim runs interactively, prompting for lines
2778 of data. Otherwise, it processes each argument in turn.
2780 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2781 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2782 used without command line arguments. If successful, it uses the &[readline()]&
2783 function, which provides extensive line-editing facilities, for reading the
2784 test data. A line history is supported.
2786 Long expansion expressions can be split over several lines by using backslash
2787 continuations. As in Exim's run time configuration, white space at the start of
2788 continuation lines is ignored. Each argument or data line is passed through the
2789 string expansion mechanism, and the result is output. Variable values from the
2790 configuration file (for example, &$qualify_domain$&) are available, but no
2791 message-specific values (such as &$sender_domain$&) are set, because no message
2792 is being processed (but see &%-bem%& and &%-Mset%&).
2794 &*Note*&: If you use this mechanism to test lookups, and you change the data
2795 files or databases you are using, you must exit and restart Exim before trying
2796 the same lookup again. Otherwise, because each Exim process caches the results
2797 of lookups, you will just get the same result as before.
2799 .vitem &%-bem%&&~<&'filename'&>
2801 .cindex "testing" "string expansion"
2802 .cindex "expansion" "testing"
2803 This option operates like &%-be%& except that it must be followed by the name
2804 of a file. For example:
2806 exim -bem /tmp/testmessage
2808 The file is read as a message (as if receiving a locally-submitted non-SMTP
2809 message) before any of the test expansions are done. Thus, message-specific
2810 variables such as &$message_size$& and &$header_from:$& are available. However,
2811 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2812 recipients are read from the headers in the normal way, and are shown in the
2813 &$recipients$& variable. Note that recipients cannot be given on the command
2814 line, because further arguments are taken as strings to expand (just like
2817 .vitem &%-bF%&&~<&'filename'&>
2819 .cindex "system filter" "testing"
2820 .cindex "testing" "system filter"
2821 This option is the same as &%-bf%& except that it assumes that the filter being
2822 tested is a system filter. The additional commands that are available only in
2823 system filters are recognized.
2825 .vitem &%-bf%&&~<&'filename'&>
2827 .cindex "filter" "testing"
2828 .cindex "testing" "filter file"
2829 .cindex "forward file" "testing"
2830 .cindex "testing" "forward file"
2831 .cindex "Sieve filter" "testing"
2832 This option runs Exim in user filter testing mode; the file is the filter file
2833 to be tested, and a test message must be supplied on the standard input. If
2834 there are no message-dependent tests in the filter, an empty file can be
2837 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2838 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2839 filter and a user filter in the same run. For example:
2841 exim -bF /system/filter -bf /user/filter </test/message
2843 This is helpful when the system filter adds header lines or sets filter
2844 variables that are used by the user filter.
2846 If the test filter file does not begin with one of the special lines
2851 it is taken to be a normal &_.forward_& file, and is tested for validity under
2852 that interpretation. See sections &<<SECTitenonfilred>>& to
2853 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2856 The result of an Exim command that uses &%-bf%&, provided no errors are
2857 detected, is a list of the actions that Exim would try to take if presented
2858 with the message for real. More details of filter testing are given in the
2859 separate document entitled &'Exim's interfaces to mail filtering'&.
2861 When testing a filter file,
2862 .cindex "&""From""& line"
2863 .cindex "envelope sender"
2864 .oindex "&%-f%&" "for filter testing"
2865 the envelope sender can be set by the &%-f%& option,
2866 or by a &"From&~"& line at the start of the test message. Various parameters
2867 that would normally be taken from the envelope recipient address of the message
2868 can be set by means of additional command line options (see the next four
2871 .vitem &%-bfd%&&~<&'domain'&>
2873 .vindex "&$qualify_domain$&"
2874 This sets the domain of the recipient address when a filter file is being
2875 tested by means of the &%-bf%& option. The default is the value of
2878 .vitem &%-bfl%&&~<&'local&~part'&>
2880 This sets the local part of the recipient address when a filter file is being
2881 tested by means of the &%-bf%& option. The default is the username of the
2882 process that calls Exim. A local part should be specified with any prefix or
2883 suffix stripped, because that is how it appears to the filter when a message is
2884 actually being delivered.
2886 .vitem &%-bfp%&&~<&'prefix'&>
2888 This sets the prefix of the local part of the recipient address when a filter
2889 file is being tested by means of the &%-bf%& option. The default is an empty
2892 .vitem &%-bfs%&&~<&'suffix'&>
2894 This sets the suffix of the local part of the recipient address when a filter
2895 file is being tested by means of the &%-bf%& option. The default is an empty
2898 .vitem &%-bh%&&~<&'IP&~address'&>
2900 .cindex "testing" "incoming SMTP"
2901 .cindex "SMTP" "testing incoming"
2902 .cindex "testing" "relay control"
2903 .cindex "relaying" "testing configuration"
2904 .cindex "policy control" "testing"
2905 .cindex "debugging" "&%-bh%& option"
2906 This option runs a fake SMTP session as if from the given IP address, using the
2907 standard input and output. The IP address may include a port number at the end,
2908 after a full stop. For example:
2910 exim -bh 10.9.8.7.1234
2911 exim -bh fe80::a00:20ff:fe86:a061.5678
2913 When an IPv6 address is given, it is converted into canonical form. In the case
2914 of the second example above, the value of &$sender_host_address$& after
2915 conversion to the canonical form is
2916 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2918 Comments as to what is going on are written to the standard error file. These
2919 include lines beginning with &"LOG"& for anything that would have been logged.
2920 This facility is provided for testing configuration options for incoming
2921 messages, to make sure they implement the required policy. For example, you can
2922 test your relay controls using &%-bh%&.
2926 You can test features of the configuration that rely on ident (RFC 1413)
2927 information by using the &%-oMt%& option. However, Exim cannot actually perform
2928 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2931 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2932 are also skipped when testing using &%-bh%&. If you want these callouts to
2933 occur, use &%-bhc%& instead.
2935 Messages supplied during the testing session are discarded, and nothing is
2936 written to any of the real log files. There may be pauses when DNS (and other)
2937 lookups are taking place, and of course these may time out. The &%-oMi%& option
2938 can be used to specify a specific IP interface and port if this is important,
2939 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2940 session were authenticated.
2942 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2943 output just states whether a given recipient address from a given host is
2944 acceptable or not. See section &<<SECTcheckaccess>>&.
2946 Features such as authentication and encryption, where the client input is not
2947 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2948 specialized SMTP test program such as
2949 &url(http://jetmore.org/john/code/#swaks,swaks).
2951 .vitem &%-bhc%&&~<&'IP&~address'&>
2953 This option operates in the same way as &%-bh%&, except that address
2954 verification callouts are performed if required. This includes consulting and
2955 updating the callout cache database.
2959 .cindex "alias file" "building"
2960 .cindex "building alias file"
2961 .cindex "Sendmail compatibility" "&%-bi%& option"
2962 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2963 Exim does not have the concept of a single alias file, and so it cannot mimic
2964 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2965 tend to appear in various scripts such as NIS make files, so the option must be
2968 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2969 configuration option is run, under the uid and gid of the caller of Exim. If
2970 the &%-oA%& option is used, its value is passed to the command as an argument.
2971 The command set by &%bi_command%& may not contain arguments. The command can
2972 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2973 if this is required. If the &%bi_command%& option is not set, calling Exim with
2976 . // Keep :help first, then the rest in alphabetical order
2978 .oindex "&%-bI:help%&"
2979 .cindex "querying exim information"
2980 We shall provide various options starting &`-bI:`& for querying Exim for
2981 information. The output of many of these will be intended for machine
2982 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2983 synopsis of supported options beginning &`-bI:`&. Use of any of these
2984 options shall cause Exim to exit after producing the requested output.
2987 .oindex "&%-bI:dscp%&"
2988 .cindex "DSCP" "values"
2989 This option causes Exim to emit an alphabetically sorted list of all
2990 recognised DSCP names.
2992 .vitem &%-bI:sieve%&
2993 .oindex "&%-bI:sieve%&"
2994 .cindex "Sieve filter" "capabilities"
2995 This option causes Exim to emit an alphabetically sorted list of all supported
2996 Sieve protocol extensions on stdout, one per line. This is anticipated to be
2997 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
2998 &`SIEVE`& capability response line. As the precise list may depend upon
2999 compile-time build options, which this option will adapt to, this is the only
3000 way to guarantee a correct response.
3004 .cindex "local message reception"
3005 This option runs an Exim receiving process that accepts an incoming,
3006 locally-generated message on the standard input. The recipients are given as the
3007 command arguments (except when &%-t%& is also present &-- see below). Each
3008 argument can be a comma-separated list of RFC 2822 addresses. This is the
3009 default option for selecting the overall action of an Exim call; it is assumed
3010 if no other conflicting option is present.
3012 If any addresses in the message are unqualified (have no domain), they are
3013 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3014 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3015 suppressing this for special cases.
3017 Policy checks on the contents of local messages can be enforced by means of
3018 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3020 .cindex "return code" "for &%-bm%&"
3021 The return code is zero if the message is successfully accepted. Otherwise, the
3022 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3025 .cindex "message" "format"
3026 .cindex "format" "message"
3027 .cindex "&""From""& line"
3028 .cindex "UUCP" "&""From""& line"
3029 .cindex "Sendmail compatibility" "&""From""& line"
3030 of the message must be as defined in RFC 2822, except that, for
3031 compatibility with Sendmail and Smail, a line in one of the forms
3033 From sender Fri Jan 5 12:55 GMT 1997
3034 From sender Fri, 5 Jan 97 12:55:01
3036 (with the weekday optional, and possibly with additional text after the date)
3037 is permitted to appear at the start of the message. There appears to be no
3038 authoritative specification of the format of this line. Exim recognizes it by
3039 matching against the regular expression defined by the &%uucp_from_pattern%&
3040 option, which can be changed if necessary.
3042 .oindex "&%-f%&" "overriding &""From""& line"
3043 The specified sender is treated as if it were given as the argument to the
3044 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3045 preference to the address taken from the message. The caller of Exim must be a
3046 trusted user for the sender of a message to be set in this way.
3048 .vitem &%-bmalware%&&~<&'filename'&>
3049 .oindex "&%-bmalware%&"
3050 .cindex "testing", "malware"
3051 .cindex "malware scan test"
3052 This debugging option causes Exim to scan the given file,
3053 using the malware scanning framework. The option of &%av_scanner%& influences
3054 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3055 the expansion should have defaults which apply to this invocation. ACLs are
3056 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3057 will never be populated and &%-bmalware%& will fail.
3059 Exim will have changed working directory before resolving the filename, so
3060 using fully qualified pathnames is advisable. Exim will be running as the Exim
3061 user when it tries to open the file, rather than as the invoking user.
3062 This option requires admin privileges.
3064 The &%-bmalware%& option will not be extended to be more generally useful,
3065 there are better tools for file-scanning. This option exists to help
3066 administrators verify their Exim and AV scanner configuration.
3070 .cindex "address qualification, suppressing"
3071 By default, Exim automatically qualifies unqualified addresses (those
3072 without domains) that appear in messages that are submitted locally (that
3073 is, not over TCP/IP). This qualification applies both to addresses in
3074 envelopes, and addresses in header lines. Sender addresses are qualified using
3075 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3076 defaults to the value of &%qualify_domain%&).
3078 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3079 being used to re-submit messages that originally came from remote hosts after
3080 content scanning, you probably do not want to qualify unqualified addresses in
3081 header lines. (Such lines will be present only if you have not enabled a header
3082 syntax check in the appropriate ACL.)
3084 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3085 messages that originate on the local host. When this is used, unqualified
3086 addresses in the envelope provoke errors (causing message rejection) and
3087 unqualified addresses in header lines are left alone.
3092 .cindex "configuration options" "extracting"
3093 .cindex "options" "configuration &-- extracting"
3094 If this option is given with no arguments, it causes the values of all Exim's
3095 main configuration options to be written to the standard output. The values
3096 of one or more specific options can be requested by giving their names as
3097 arguments, for example:
3099 exim -bP qualify_domain hold_domains
3101 .cindex "hiding configuration option values"
3102 .cindex "configuration options" "hiding value of"
3103 .cindex "options" "hiding value of"
3104 However, any option setting that is preceded by the word &"hide"& in the
3105 configuration file is not shown in full, except to an admin user. For other
3106 users, the output is as in this example:
3108 mysql_servers = <value not displayable>
3110 If &%config%& is given as an argument, the config is
3111 output, as it was parsed, any include file resolved, any comment removed.
3113 If &%config_file%& is given as an argument, the name of the run time
3114 configuration file is output. (&%configure_file%& works too, for
3115 backward compatibility.)
3116 If a list of configuration files was supplied, the value that is output here
3117 is the name of the file that was actually used.
3119 .cindex "options" "hiding name of"
3120 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3121 name will not be output.
3123 .cindex "daemon" "process id (pid)"
3124 .cindex "pid (process id)" "of daemon"
3125 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3126 directories where log files and daemon pid files are written are output,
3127 respectively. If these values are unset, log files are written in a
3128 sub-directory of the spool directory called &%log%&, and the pid file is
3129 written directly into the spool directory.
3131 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3133 exim -bP +local_domains
3135 it searches for a matching named list of any type (domain, host, address, or
3136 local part) and outputs what it finds.
3138 .cindex "options" "router &-- extracting"
3139 .cindex "options" "transport &-- extracting"
3140 .cindex "options" "authenticator &-- extracting"
3141 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3142 followed by the name of an appropriate driver instance, the option settings for
3143 that driver are output. For example:
3145 exim -bP transport local_delivery
3147 The generic driver options are output first, followed by the driver's private
3148 options. A list of the names of drivers of a particular type can be obtained by
3149 using one of the words &%router_list%&, &%transport_list%&, or
3150 &%authenticator_list%&, and a complete list of all drivers with their option
3151 settings can be obtained by using &%routers%&, &%transports%&, or
3154 .cindex "environment"
3155 If &%environment%& is given as an argument, the set of environment
3156 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3159 .cindex "options" "macro &-- extracting"
3160 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3161 are available, similarly to the drivers. Because macros are sometimes used
3162 for storing passwords, this option is restricted.
3163 The output format is one item per line.
3167 .cindex "queue" "listing messages on"
3168 .cindex "listing" "messages on the queue"
3169 This option requests a listing of the contents of the mail queue on the
3170 standard output. If the &%-bp%& option is followed by a list of message ids,
3171 just those messages are listed. By default, this option can be used only by an
3172 admin user. However, the &%queue_list_requires_admin%& option can be set false
3173 to allow any user to see the queue.
3175 Each message on the queue is displayed as in the following example:
3177 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3178 red.king@looking-glass.fict.example
3181 .cindex "message" "size in queue listing"
3182 .cindex "size" "of message"
3183 The first line contains the length of time the message has been on the queue
3184 (in this case 25 minutes), the size of the message (2.9K), the unique local
3185 identifier for the message, and the message sender, as contained in the
3186 envelope. For bounce messages, the sender address is empty, and appears as
3187 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3188 the default sender address, the user's login name is shown in parentheses
3189 before the sender address.
3191 .cindex "frozen messages" "in queue listing"
3192 If the message is frozen (attempts to deliver it are suspended) then the text
3193 &"*** frozen ***"& is displayed at the end of this line.
3195 The recipients of the message (taken from the envelope, not the headers) are
3196 displayed on subsequent lines. Those addresses to which the message has already
3197 been delivered are marked with the letter D. If an original address gets
3198 expanded into several addresses via an alias or forward file, the original is
3199 displayed with a D only when deliveries for all of its child addresses are
3205 This option operates like &%-bp%&, but in addition it shows delivered addresses
3206 that were generated from the original top level address(es) in each message by
3207 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3213 .cindex "queue" "count of messages on"
3214 This option counts the number of messages on the queue, and writes the total
3215 to the standard output. It is restricted to admin users, unless
3216 &%queue_list_requires_admin%& is set false.
3221 This option operates like &%-bp%&, but the output is not sorted into
3222 chronological order of message arrival. This can speed it up when there are
3223 lots of messages on the queue, and is particularly useful if the output is
3224 going to be post-processed in a way that doesn't need the sorting.
3228 This option is a combination of &%-bpr%& and &%-bpa%&.
3232 This option is a combination of &%-bpr%& and &%-bpu%&.
3237 This option operates like &%-bp%& but shows only undelivered top-level
3238 addresses for each message displayed. Addresses generated by aliasing or
3239 forwarding are not shown, unless the message was deferred after processing by a
3240 router with the &%one_time%& option set.
3245 .cindex "testing" "retry configuration"
3246 .cindex "retry" "configuration testing"
3247 This option is for testing retry rules, and it must be followed by up to three
3248 arguments. It causes Exim to look for a retry rule that matches the values
3249 and to write it to the standard output. For example:
3251 exim -brt bach.comp.mus.example
3252 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3254 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3255 argument, which is required, can be a complete address in the form
3256 &'local_part@domain'&, or it can be just a domain name. If the second argument
3257 contains a dot, it is interpreted as an optional second domain name; if no
3258 retry rule is found for the first argument, the second is tried. This ties in
3259 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3260 rule is found that matches the host, one that matches the mail domain is
3261 sought. Finally, an argument that is the name of a specific delivery error, as
3262 used in setting up retry rules, can be given. For example:
3264 exim -brt haydn.comp.mus.example quota_3d
3265 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3270 .cindex "testing" "rewriting"
3271 .cindex "rewriting" "testing"
3272 This option is for testing address rewriting rules, and it must be followed by
3273 a single argument, consisting of either a local part without a domain, or a
3274 complete address with a fully qualified domain. Exim outputs how this address
3275 would be rewritten for each possible place it might appear. See chapter
3276 &<<CHAPrewrite>>& for further details.
3280 .cindex "SMTP" "batched incoming"
3281 .cindex "batched SMTP input"
3282 This option is used for batched SMTP input, which is an alternative interface
3283 for non-interactive local message submission. A number of messages can be
3284 submitted in a single run. However, despite its name, this is not really SMTP
3285 input. Exim reads each message's envelope from SMTP commands on the standard
3286 input, but generates no responses. If the caller is trusted, or
3287 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3288 believed; otherwise the sender is always the caller of Exim.
3290 The message itself is read from the standard input, in SMTP format (leading
3291 dots doubled), terminated by a line containing just a single dot. An error is
3292 provoked if the terminating dot is missing. A further message may then follow.
3294 As for other local message submissions, the contents of incoming batch SMTP
3295 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3296 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3297 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3299 Some other SMTP commands are recognized in the input. HELO and EHLO act
3300 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3301 QUIT quits, ignoring the rest of the standard input.
3303 .cindex "return code" "for &%-bS%&"
3304 If any error is encountered, reports are written to the standard output and
3305 error streams, and Exim gives up immediately. The return code is 0 if no error
3306 was detected; it is 1 if one or more messages were accepted before the error
3307 was detected; otherwise it is 2.
3309 More details of input using batched SMTP are given in section
3310 &<<SECTincomingbatchedSMTP>>&.
3314 .cindex "SMTP" "local input"
3315 .cindex "local SMTP input"
3316 This option causes Exim to accept one or more messages by reading SMTP commands
3317 on the standard input, and producing SMTP replies on the standard output. SMTP
3318 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3319 Some user agents use this interface as a way of passing locally-generated
3320 messages to the MTA.
3323 .cindex "sender" "source of"
3324 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3325 set, the senders of messages are taken from the SMTP MAIL commands.
3326 Otherwise the content of these commands is ignored and the sender is set up as
3327 the calling user. Unqualified addresses are automatically qualified using
3328 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3329 &%-bnq%& option is used.
3333 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3334 using a listening daemon. Exim can distinguish the two cases by checking
3335 whether the standard input is a TCP/IP socket. When Exim is called from
3336 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3337 above concerning senders and qualification do not apply. In this situation,
3338 Exim behaves in exactly the same way as it does when receiving a message via
3339 the listening daemon.
3343 .cindex "testing" "addresses"
3344 .cindex "address" "testing"
3345 This option runs Exim in address testing mode, in which each argument is taken
3346 as a recipient address to be tested for deliverability. The results are
3347 written to the standard output. If a test fails, and the caller is not an admin
3348 user, no details of the failure are output, because these might contain
3349 sensitive information such as usernames and passwords for database lookups.
3351 If no arguments are given, Exim runs in an interactive manner, prompting with a
3352 right angle bracket for addresses to be tested.
3354 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3355 &[readline()]& function, because it is running as &'root'& and there are
3358 Each address is handled as if it were the recipient address of a message
3359 (compare the &%-bv%& option). It is passed to the routers and the result is
3360 written to the standard output. However, any router that has
3361 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3362 genuine routing tests if your first router passes everything to a scanner
3365 .cindex "return code" "for &%-bt%&"
3366 The return code is 2 if any address failed outright; it is 1 if no address
3367 failed outright but at least one could not be resolved for some reason. Return
3368 code 0 is given only when all addresses succeed.
3370 .cindex "duplicate addresses"
3371 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3372 addresses after routing is complete, so that only one delivery takes place.
3373 This does not happen when testing with &%-bt%&; the full results of routing are
3376 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3377 routers in the configuration makes any tests on the sender address of a
3379 .oindex "&%-f%&" "for address testing"
3380 you can use the &%-f%& option to set an appropriate sender when running
3381 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3382 default qualifying domain. However, if you have set up (for example) routers
3383 whose behaviour depends on the contents of an incoming message, you cannot test
3384 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3389 .cindex "version number of Exim"
3390 This option causes Exim to write the current version number, compilation
3391 number, and compilation date of the &'exim'& binary to the standard output.
3392 It also lists the DBM library that is being used, the optional modules (such as
3393 specific lookup types), the drivers that are included in the binary, and the
3394 name of the run time configuration file that is in use.
3396 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3397 configuration file. However, this is a static check only. It cannot check
3398 values that are to be expanded. For example, although a misspelt ACL verb is
3399 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3400 alone to discover (for example) all the typos in the configuration; some
3401 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3402 dynamic testing facilities.
3406 .cindex "verifying address" "using &%-bv%&"
3407 .cindex "address" "verification"
3408 This option runs Exim in address verification mode, in which each argument is
3409 taken as a recipient address to be verified by the routers. (This does
3410 not involve any verification callouts). During normal operation, verification
3411 happens mostly as a consequence processing a &%verify%& condition in an ACL
3412 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3413 including callouts, see the &%-bh%& and &%-bhc%& options.
3415 If verification fails, and the caller is not an admin user, no details of the
3416 failure are output, because these might contain sensitive information such as
3417 usernames and passwords for database lookups.
3419 If no arguments are given, Exim runs in an interactive manner, prompting with a
3420 right angle bracket for addresses to be verified.
3422 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3423 &[readline()]& function, because it is running as &'exim'& and there are
3426 Verification differs from address testing (the &%-bt%& option) in that routers
3427 that have &%no_verify%& set are skipped, and if the address is accepted by a
3428 router that has &%fail_verify%& set, verification fails. The address is
3429 verified as a recipient if &%-bv%& is used; to test verification for a sender
3430 address, &%-bvs%& should be used.
3432 If the &%-v%& option is not set, the output consists of a single line for each
3433 address, stating whether it was verified or not, and giving a reason in the
3434 latter case. Without &%-v%&, generating more than one address by redirection
3435 causes verification to end successfully, without considering the generated
3436 addresses. However, if just one address is generated, processing continues,
3437 and the generated address must verify successfully for the overall verification
3440 When &%-v%& is set, more details are given of how the address has been handled,
3441 and in the case of address redirection, all the generated addresses are also
3442 considered. Verification may succeed for some and fail for others.
3445 .cindex "return code" "for &%-bv%&"
3446 return code is 2 if any address failed outright; it is 1 if no address
3447 failed outright but at least one could not be resolved for some reason. Return
3448 code 0 is given only when all addresses succeed.
3450 If any of the routers in the configuration makes any tests on the sender
3451 address of a message, you should use the &%-f%& option to set an appropriate
3452 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3453 calling user at the default qualifying domain.
3457 This option acts like &%-bv%&, but verifies the address as a sender rather
3458 than a recipient address. This affects any rewriting and qualification that
3465 .cindex "inetd" "wait mode"
3466 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3467 similarly to the &%-bd%& option. All port specifications on the command-line
3468 and in the configuration file are ignored. Queue-running may not be specified.
3470 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3471 listening for connections. This permits the system to start up and have
3472 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3473 each port only when the first connection is received.
3475 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3476 which the daemon will exit, which should cause inetd to listen once more.
3478 .vitem &%-C%&&~<&'filelist'&>
3480 .cindex "configuration file" "alternate"
3481 .cindex "CONFIGURE_FILE"
3482 .cindex "alternate configuration file"
3483 This option causes Exim to find the run time configuration file from the given
3484 list instead of from the list specified by the CONFIGURE_FILE
3485 compile-time setting. Usually, the list will consist of just a single file
3486 name, but it can be a colon-separated list of names. In this case, the first
3487 file that exists is used. Failure to open an existing file stops Exim from
3488 proceeding any further along the list, and an error is generated.
3490 When this option is used by a caller other than root, and the list is different
3491 from the compiled-in list, Exim gives up its root privilege immediately, and
3492 runs with the real and effective uid and gid set to those of the caller.
3493 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3494 file contains a list of full pathnames, one per line, for configuration files
3495 which are trusted. Root privilege is retained for any configuration file so
3496 listed, as long as the caller is the Exim user (or the user specified in the
3497 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3498 not writeable by inappropriate users or groups.
3500 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3501 configuration using &%-C%& right through message reception and delivery,
3502 even if the caller is root. The reception works, but by that time, Exim is
3503 running as the Exim user, so when it re-executes to regain privilege for the
3504 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3505 test reception and delivery using two separate commands (one to put a message
3506 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3508 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3509 prefix string with which any file named in a &%-C%& command line option
3510 must start. In addition, the file name must not contain the sequence &`/../`&.
3511 However, if the value of the &%-C%& option is identical to the value of
3512 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3513 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3514 unset, any file name can be used with &%-C%&.
3516 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3517 to a directory to which only root has access. This prevents someone who has
3518 broken into the Exim account from running a privileged Exim with an arbitrary
3521 The &%-C%& facility is useful for ensuring that configuration files are
3522 syntactically correct, but cannot be used for test deliveries, unless the
3523 caller is privileged, or unless it is an exotic configuration that does not
3524 require privilege. No check is made on the owner or group of the files
3525 specified by this option.
3528 .vitem &%-D%&<&'macro'&>=<&'value'&>
3530 .cindex "macro" "setting on command line"
3531 This option can be used to override macro definitions in the configuration file
3532 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3533 unprivileged caller, it causes Exim to give up its root privilege.
3534 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3535 completely disabled, and its use causes an immediate error exit.
3537 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3538 colon-separated list of macros which are considered safe and, if &%-D%& only
3539 supplies macros from this list, and the values are acceptable, then Exim will
3540 not give up root privilege if the caller is root, the Exim run-time user, or
3541 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3542 to be removed in the future. Acceptable values for the macros satisfy the
3543 regexp: &`^[A-Za-z0-9_/.-]*$`&
3545 The entire option (including equals sign if present) must all be within one
3546 command line item. &%-D%& can be used to set the value of a macro to the empty
3547 string, in which case the equals sign is optional. These two commands are
3553 To include spaces in a macro definition item, quotes must be used. If you use
3554 quotes, spaces are permitted around the macro name and the equals sign. For
3557 exim '-D ABC = something' ...
3559 &%-D%& may be repeated up to 10 times on a command line.
3561 Only macro names up to 22 letters long can be set.
3565 .vitem &%-d%&<&'debug&~options'&>
3567 .cindex "debugging" "list of selectors"
3568 .cindex "debugging" "&%-d%& option"
3569 This option causes debugging information to be written to the standard
3570 error stream. It is restricted to admin users because debugging output may show
3571 database queries that contain password information. Also, the details of users'
3572 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3573 writes an error message to the standard error stream and exits with a non-zero
3576 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3577 standard debugging data is output. This can be reduced, or increased to include
3578 some more rarely needed information, by directly following &%-d%& with a string
3579 made up of names preceded by plus or minus characters. These add or remove sets
3580 of debugging data, respectively. For example, &%-d+filter%& adds filter
3581 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3582 no spaces are allowed in the debug setting. The available debugging categories
3585 &`acl `& ACL interpretation
3586 &`auth `& authenticators
3587 &`deliver `& general delivery logic
3588 &`dns `& DNS lookups (see also resolver)
3589 &`dnsbl `& DNS black list (aka RBL) code
3590 &`exec `& arguments for &[execv()]& calls
3591 &`expand `& detailed debugging for string expansions
3592 &`filter `& filter handling
3593 &`hints_lookup `& hints data lookups
3594 &`host_lookup `& all types of name-to-IP address handling
3595 &`ident `& ident lookup
3596 &`interface `& lists of local interfaces
3597 &`lists `& matching things in lists
3598 &`load `& system load checks
3599 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3600 &<<CHAPlocalscan>>&)
3601 &`lookup `& general lookup code and all lookups
3602 &`memory `& memory handling
3603 &`pid `& add pid to debug output lines
3604 &`process_info `& setting info for the process log
3605 &`queue_run `& queue runs
3606 &`receive `& general message reception logic
3607 &`resolver `& turn on the DNS resolver's debugging output
3608 &`retry `& retry handling
3609 &`rewrite `& address rewriting
3610 &`route `& address routing
3611 &`timestamp `& add timestamp to debug output lines
3613 &`transport `& transports
3614 &`uid `& changes of uid/gid and looking up uid/gid
3615 &`verify `& address verification logic
3616 &`all `& almost all of the above (see below), and also &%-v%&
3618 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3619 for &`-all`&. The reason for this is that &`+all`& is something that people
3620 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3621 is included, an awful lot of output that is very rarely of interest is
3622 generated, so it now has to be explicitly requested. However, &`-all`& does
3623 turn everything off.
3625 .cindex "resolver, debugging output"
3626 .cindex "DNS resolver, debugging output"
3627 The &`resolver`& option produces output only if the DNS resolver was compiled
3628 with DEBUG enabled. This is not the case in some operating systems. Also,
3629 unfortunately, debugging output from the DNS resolver is written to stdout
3632 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3633 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3634 However, the &`pid`& selector is forced when debugging is turned on for a
3635 daemon, which then passes it on to any re-executed Exims. Exim also
3636 automatically adds the pid to debug lines when several remote deliveries are
3639 The &`timestamp`& selector causes the current time to be inserted at the start
3640 of all debug output lines. This can be useful when trying to track down delays
3643 If the &%debug_print%& option is set in any driver, it produces output whenever
3644 any debugging is selected, or if &%-v%& is used.
3646 .vitem &%-dd%&<&'debug&~options'&>
3648 This option behaves exactly like &%-d%& except when used on a command that
3649 starts a daemon process. In that case, debugging is turned off for the
3650 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3651 behaviour of the daemon without creating as much output as full debugging does.
3654 .oindex "&%-dropcr%&"
3655 This is an obsolete option that is now a no-op. It used to affect the way Exim
3656 handled CR and LF characters in incoming messages. What happens now is
3657 described in section &<<SECTlineendings>>&.
3661 .cindex "bounce message" "generating"
3662 This option specifies that an incoming message is a locally-generated delivery
3663 failure report. It is used internally by Exim when handling delivery failures
3664 and is not intended for external use. Its only effect is to stop Exim
3665 generating certain messages to the postmaster, as otherwise message cascades
3666 could occur in some situations. As part of the same option, a message id may
3667 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3668 new message contains the id, following &"R="&, as a cross-reference.
3671 .oindex "&%-e%&&'x'&"
3672 There are a number of Sendmail options starting with &%-oe%& which seem to be
3673 called by various programs without the leading &%o%& in the option. For
3674 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3675 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3677 .vitem &%-F%&&~<&'string'&>
3679 .cindex "sender" "name"
3680 .cindex "name" "of sender"
3681 This option sets the sender's full name for use when a locally-generated
3682 message is being accepted. In the absence of this option, the user's &'gecos'&
3683 entry from the password data is used. As users are generally permitted to alter
3684 their &'gecos'& entries, no security considerations are involved. White space
3685 between &%-F%& and the <&'string'&> is optional.
3687 .vitem &%-f%&&~<&'address'&>
3689 .cindex "sender" "address"
3690 .cindex "address" "sender"
3691 .cindex "trusted users"
3692 .cindex "envelope sender"
3693 .cindex "user" "trusted"
3694 This option sets the address of the envelope sender of a locally-generated
3695 message (also known as the return path). The option can normally be used only
3696 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3699 Processes running as root or the Exim user are always trusted. Other
3700 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3701 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3702 of a local message is set to the caller's login name at the default qualify
3705 There is one exception to the restriction on the use of &%-f%&: an empty sender
3706 can be specified by any user, trusted or not, to create a message that can
3707 never provoke a bounce. An empty sender can be specified either as an empty
3708 string, or as a pair of angle brackets with nothing between them, as in these
3709 examples of shell commands:
3711 exim -f '<>' user@domain
3712 exim -f "" user@domain
3714 In addition, the use of &%-f%& is not restricted when testing a filter file
3715 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3718 Allowing untrusted users to change the sender address does not of itself make
3719 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3720 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3721 though this can be overridden by setting &%no_local_from_check%&.
3724 .cindex "&""From""& line"
3725 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3726 given as two arguments or one combined argument). The sender of a
3727 locally-generated message can also be set (when permitted) by an initial
3728 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3729 if &%-f%& is also present, it overrides &"From&~"&.
3733 .cindex "submission fixups, suppressing (command-line)"
3734 This option is equivalent to an ACL applying:
3736 control = suppress_local_fixups
3738 for every message received. Note that Sendmail will complain about such
3739 bad formatting, where Exim silently just does not fix it up. This may change
3742 As this affects audit information, the caller must be a trusted user to use
3745 .vitem &%-h%&&~<&'number'&>
3747 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3748 This option is accepted for compatibility with Sendmail, but has no effect. (In
3749 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3754 .cindex "Solaris" "&'mail'& command"
3755 .cindex "dot" "in incoming non-SMTP message"
3756 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3757 line by itself should not terminate an incoming, non-SMTP message. I can find
3758 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3759 command in Solaris 2.4 uses it. See also &%-ti%&.
3761 .vitem &%-L%&&~<&'tag'&>
3763 .cindex "syslog" "process name; set with flag"
3764 This option is equivalent to setting &%syslog_processname%& in the config
3765 file and setting &%log_file_path%& to &`syslog`&.
3766 Its use is restricted to administrators. The configuration file has to be
3767 read and parsed, to determine access rights, before this is set and takes
3768 effect, so early configuration file errors will not honour this flag.
3770 The tag should not be longer than 32 characters.
3772 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3774 .cindex "forcing delivery"
3775 .cindex "delivery" "forcing attempt"
3776 .cindex "frozen messages" "forcing delivery"
3777 This option requests Exim to run a delivery attempt on each message in turn. If
3778 any of the messages are frozen, they are automatically thawed before the
3779 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3780 and &%hold_domains%& are ignored.
3783 .cindex "hints database" "overriding retry hints"
3784 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3785 the normal retry time has not yet been reached. This option requires the caller
3786 to be an admin user. However, there is an option called &%prod_requires_admin%&
3787 which can be set false to relax this restriction (and also the same requirement
3788 for the &%-q%&, &%-R%&, and &%-S%& options).
3790 The deliveries happen synchronously, that is, the original Exim process does
3791 not terminate until all the delivery attempts have finished. No output is
3792 produced unless there is a serious error. If you want to see what is happening,
3793 use the &%-v%& option as well, or inspect Exim's main log.
3795 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3797 .cindex "message" "adding recipients"
3798 .cindex "recipient" "adding"
3799 This option requests Exim to add the addresses to the list of recipients of the
3800 message (&"ar"& for &"add recipients"&). The first argument must be a message
3801 id, and the remaining ones must be email addresses. However, if the message is
3802 active (in the middle of a delivery attempt), it is not altered. This option
3803 can be used only by an admin user.
3805 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3806 &~<&'message&~id'&>"
3808 .cindex "SMTP" "passed connection"
3809 .cindex "SMTP" "multiple deliveries"
3810 .cindex "multiple SMTP deliveries"
3811 This option is not intended for use by external callers. It is used internally
3812 by Exim to invoke another instance of itself to deliver a waiting message using
3813 an existing SMTP connection, which is passed as the standard input. Details are
3814 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3815 must be root or the Exim user in order to use it.
3819 This option is not intended for use by external callers. It is used internally
3820 by Exim in conjunction with the &%-MC%& option. It signifies that the
3821 connection to the remote host has been authenticated.
3825 This option is not intended for use by external callers. It is used internally
3826 by Exim in conjunction with the &%-MC%& option. It signifies that the
3827 remote host supports the ESMTP &_DSN_& extension.
3831 This option is not intended for use by external callers. It is used internally
3832 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3833 which Exim is connected supports pipelining.
3835 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3837 This option is not intended for use by external callers. It is used internally
3838 by Exim in conjunction with the &%-MC%& option when the original delivery was
3839 started by a queue runner. It passes on the process id of the queue runner,
3840 together with the file descriptor number of an open pipe. Closure of the pipe
3841 signals the final completion of the sequence of processes that are passing
3842 messages through the same SMTP connection.
3846 This option is not intended for use by external callers. It is used internally
3847 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3848 SMTP SIZE option should be used on messages delivered down the existing
3853 This option is not intended for use by external callers. It is used internally
3854 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3855 host to which Exim is connected supports TLS encryption.
3857 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3859 .cindex "hints database" "not overridden by &%-Mc%&"
3860 .cindex "delivery" "manually started &-- not forced"
3861 This option requests Exim to run a delivery attempt on each message in turn,
3862 but unlike the &%-M%& option, it does check for retry hints, and respects any
3863 that are found. This option is not very useful to external callers. It is
3864 provided mainly for internal use by Exim when it needs to re-invoke itself in
3865 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3866 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3867 respects retry times and other options such as &%hold_domains%& that are
3868 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3869 If you want to run a specific delivery as if in a queue run, you should use
3870 &%-q%& with a message id argument. A distinction between queue run deliveries
3871 and other deliveries is made in one or two places.
3873 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3875 .cindex "message" "changing sender"
3876 .cindex "sender" "changing"
3877 This option requests Exim to change the sender address in the message to the
3878 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3879 &"edit sender"&). There must be exactly two arguments. The first argument must
3880 be a message id, and the second one an email address. However, if the message
3881 is active (in the middle of a delivery attempt), its status is not altered.
3882 This option can be used only by an admin user.
3884 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3886 .cindex "freezing messages"
3887 .cindex "message" "manually freezing"
3888 This option requests Exim to mark each listed message as &"frozen"&. This
3889 prevents any delivery attempts taking place until the message is &"thawed"&,
3890 either manually or as a result of the &%auto_thaw%& configuration option.
3891 However, if any of the messages are active (in the middle of a delivery
3892 attempt), their status is not altered. This option can be used only by an admin
3895 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3897 .cindex "giving up on messages"
3898 .cindex "message" "abandoning delivery attempts"
3899 .cindex "delivery" "abandoning further attempts"
3900 This option requests Exim to give up trying to deliver the listed messages,
3901 including any that are frozen. However, if any of the messages are active,
3902 their status is not altered. For non-bounce messages, a delivery error message
3903 is sent to the sender, containing the text &"cancelled by administrator"&.
3904 Bounce messages are just discarded. This option can be used only by an admin
3907 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3909 .cindex "delivery" "cancelling all"
3910 This option requests Exim to mark all the recipient addresses in the messages
3911 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3912 message is active (in the middle of a delivery attempt), its status is not
3913 altered. This option can be used only by an admin user.
3915 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3917 .cindex "delivery" "cancelling by address"
3918 .cindex "recipient" "removing"
3919 .cindex "removing recipients"
3920 This option requests Exim to mark the given addresses as already delivered
3921 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3922 the remaining ones must be email addresses. These are matched to recipient
3923 addresses in the message in a case-sensitive manner. If the message is active
3924 (in the middle of a delivery attempt), its status is not altered. This option
3925 can be used only by an admin user.
3927 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3929 .cindex "removing messages"
3930 .cindex "abandoning mail"
3931 .cindex "message" "manually discarding"
3932 This option requests Exim to remove the given messages from the queue. No
3933 bounce messages are sent; each message is simply forgotten. However, if any of
3934 the messages are active, their status is not altered. This option can be used
3935 only by an admin user or by the user who originally caused the message to be
3936 placed on the queue.
3938 .vitem &%-Mset%&&~<&'message&~id'&>
3940 .cindex "testing" "string expansion"
3941 .cindex "expansion" "testing"
3942 This option is useful only in conjunction with &%-be%& (that is, when testing
3943 string expansions). Exim loads the given message from its spool before doing
3944 the test expansions, thus setting message-specific variables such as
3945 &$message_size$& and the header variables. The &$recipients$& variable is made
3946 available. This feature is provided to make it easier to test expansions that
3947 make use of these variables. However, this option can be used only by an admin
3948 user. See also &%-bem%&.
3950 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3952 .cindex "thawing messages"
3953 .cindex "unfreezing messages"
3954 .cindex "frozen messages" "thawing"
3955 .cindex "message" "thawing frozen"
3956 This option requests Exim to &"thaw"& any of the listed messages that are
3957 &"frozen"&, so that delivery attempts can resume. However, if any of the
3958 messages are active, their status is not altered. This option can be used only
3961 .vitem &%-Mvb%&&~<&'message&~id'&>
3963 .cindex "listing" "message body"
3964 .cindex "message" "listing body of"
3965 This option causes the contents of the message body (-D) spool file to be
3966 written to the standard output. This option can be used only by an admin user.
3968 .vitem &%-Mvc%&&~<&'message&~id'&>
3970 .cindex "message" "listing in RFC 2822 format"
3971 .cindex "listing" "message in RFC 2822 format"
3972 This option causes a copy of the complete message (header lines plus body) to
3973 be written to the standard output in RFC 2822 format. This option can be used
3974 only by an admin user.
3976 .vitem &%-Mvh%&&~<&'message&~id'&>
3978 .cindex "listing" "message headers"
3979 .cindex "header lines" "listing"
3980 .cindex "message" "listing header lines"
3981 This option causes the contents of the message headers (-H) spool file to be
3982 written to the standard output. This option can be used only by an admin user.
3984 .vitem &%-Mvl%&&~<&'message&~id'&>
3986 .cindex "listing" "message log"
3987 .cindex "message" "listing message log"
3988 This option causes the contents of the message log spool file to be written to
3989 the standard output. This option can be used only by an admin user.
3993 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3994 treats it that way too.
3998 .cindex "debugging" "&%-N%& option"
3999 .cindex "debugging" "suppressing delivery"
4000 This is a debugging option that inhibits delivery of a message at the transport
4001 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4002 it just doesn't actually transport the message, but instead behaves as if it
4003 had successfully done so. However, it does not make any updates to the retry
4004 database, and the log entries for deliveries are flagged with &"*>"& rather
4007 Because &%-N%& discards any message to which it applies, only root or the Exim
4008 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4009 words, an ordinary user can use it only when supplying an incoming message to
4010 which it will apply. Although transportation never fails when &%-N%& is set, an
4011 address may be deferred because of a configuration problem on a transport, or a
4012 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4013 the message, and applies to any subsequent delivery attempts that may happen
4018 This option is interpreted by Sendmail to mean &"no aliasing"&.
4019 For normal modes of operation, it is ignored by Exim.
4020 When combined with &%-bP%& it suppresses the name of an option from being output.
4022 .vitem &%-O%&&~<&'data'&>
4024 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4027 .vitem &%-oA%&&~<&'file&~name'&>
4029 .cindex "Sendmail compatibility" "&%-oA%& option"
4030 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4031 alternative alias file name. Exim handles &%-bi%& differently; see the
4034 .vitem &%-oB%&&~<&'n'&>
4036 .cindex "SMTP" "passed connection"
4037 .cindex "SMTP" "multiple deliveries"
4038 .cindex "multiple SMTP deliveries"
4039 This is a debugging option which limits the maximum number of messages that can
4040 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4041 transport. If <&'n'&> is omitted, the limit is set to 1.
4045 .cindex "background delivery"
4046 .cindex "delivery" "in the background"
4047 This option applies to all modes in which Exim accepts incoming messages,
4048 including the listening daemon. It requests &"background"& delivery of such
4049 messages, which means that the accepting process automatically starts a
4050 delivery process for each message received, but does not wait for the delivery
4051 processes to finish.
4053 When all the messages have been received, the reception process exits,
4054 leaving the delivery processes to finish in their own time. The standard output
4055 and error streams are closed at the start of each delivery process.
4056 This is the default action if none of the &%-od%& options are present.
4058 If one of the queueing options in the configuration file
4059 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4060 overrides it if &%queue_only_override%& is set true, which is the default
4061 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4065 .cindex "foreground delivery"
4066 .cindex "delivery" "in the foreground"
4067 This option requests &"foreground"& (synchronous) delivery when Exim has
4068 accepted a locally-generated message. (For the daemon it is exactly the same as
4069 &%-odb%&.) A delivery process is automatically started to deliver the message,
4070 and Exim waits for it to complete before proceeding.
4072 The original Exim reception process does not finish until the delivery
4073 process for the final message has ended. The standard error stream is left open
4076 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4077 false and one of the queueing options in the configuration file is in effect.
4079 If there is a temporary delivery error during foreground delivery, the
4080 message is left on the queue for later delivery, and the original reception
4081 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4082 restricted configuration that never queues messages.
4087 This option is synonymous with &%-odf%&. It is provided for compatibility with
4092 .cindex "non-immediate delivery"
4093 .cindex "delivery" "suppressing immediate"
4094 .cindex "queueing incoming messages"
4095 This option applies to all modes in which Exim accepts incoming messages,
4096 including the listening daemon. It specifies that the accepting process should
4097 not automatically start a delivery process for each message received. Messages
4098 are placed on the queue, and remain there until a subsequent queue runner
4099 process encounters them. There are several configuration options (such as
4100 &%queue_only%&) that can be used to queue incoming messages under certain
4101 conditions. This option overrides all of them and also &%-odqs%&. It always
4106 .cindex "SMTP" "delaying delivery"
4107 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4108 However, like &%-odb%& and &%-odi%&, this option has no effect if
4109 &%queue_only_override%& is false and one of the queueing options in the
4110 configuration file is in effect.
4112 When &%-odqs%& does operate, a delivery process is started for each incoming
4113 message, in the background by default, but in the foreground if &%-odi%& is
4114 also present. The recipient addresses are routed, and local deliveries are done
4115 in the normal way. However, if any SMTP deliveries are required, they are not
4116 done at this time, so the message remains on the queue until a subsequent queue
4117 runner process encounters it. Because routing was done, Exim knows which
4118 messages are waiting for which hosts, and so a number of messages for the same
4119 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4120 configuration option has the same effect for specific domains. See also the
4125 .cindex "error" "reporting"
4126 If an error is detected while a non-SMTP message is being received (for
4127 example, a malformed address), the error is reported to the sender in a mail
4130 .cindex "return code" "for &%-oee%&"
4132 this error message is successfully sent, the Exim receiving process
4133 exits with a return code of zero. If not, the return code is 2 if the problem
4134 is that the original message has no recipients, or 1 for any other error.
4135 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4139 .cindex "error" "reporting"
4140 .cindex "return code" "for &%-oem%&"
4141 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4142 return code, whether or not the error message was successfully sent.
4143 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4147 .cindex "error" "reporting"
4148 If an error is detected while a non-SMTP message is being received, the
4149 error is reported by writing a message to the standard error file (stderr).
4150 .cindex "return code" "for &%-oep%&"
4151 The return code is 1 for all errors.
4155 .cindex "error" "reporting"
4156 This option is supported for compatibility with Sendmail, but has the same
4161 .cindex "error" "reporting"
4162 This option is supported for compatibility with Sendmail, but has the same
4167 .cindex "dot" "in incoming non-SMTP message"
4168 This option, which has the same effect as &%-i%&, specifies that a dot on a
4169 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4170 single dot does terminate, though Exim does no special processing for other
4171 lines that start with a dot. This option is set by default if Exim is called as
4172 &'rmail'&. See also &%-ti%&.
4175 .oindex "&%-oitrue%&"
4176 This option is treated as synonymous with &%-oi%&.
4178 .vitem &%-oMa%&&~<&'host&~address'&>
4180 .cindex "sender" "host address, specifying for local message"
4181 A number of options starting with &%-oM%& can be used to set values associated
4182 with remote hosts on locally-submitted messages (that is, messages not received
4183 over TCP/IP). These options can be used by any caller in conjunction with the
4184 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4185 other circumstances, they are ignored unless the caller is trusted.
4187 The &%-oMa%& option sets the sender host address. This may include a port
4188 number at the end, after a full stop (period). For example:
4190 exim -bs -oMa 10.9.8.7.1234
4192 An alternative syntax is to enclose the IP address in square brackets,
4193 followed by a colon and the port number:
4195 exim -bs -oMa [10.9.8.7]:1234
4197 The IP address is placed in the &$sender_host_address$& variable, and the
4198 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4199 are present on the command line, the sender host IP address is taken from
4200 whichever one is last.
4202 .vitem &%-oMaa%&&~<&'name'&>
4204 .cindex "authentication" "name, specifying for local message"
4205 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4206 option sets the value of &$sender_host_authenticated$& (the authenticator
4207 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4208 This option can be used with &%-bh%& and &%-bs%& to set up an
4209 authenticated SMTP session without actually using the SMTP AUTH command.
4211 .vitem &%-oMai%&&~<&'string'&>
4213 .cindex "authentication" "id, specifying for local message"
4214 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4215 option sets the value of &$authenticated_id$& (the id that was authenticated).
4216 This overrides the default value (the caller's login id, except with &%-bh%&,
4217 where there is no default) for messages from local sources. See chapter
4218 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4220 .vitem &%-oMas%&&~<&'address'&>
4222 .cindex "authentication" "sender, specifying for local message"
4223 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4224 option sets the authenticated sender value in &$authenticated_sender$&. It
4225 overrides the sender address that is created from the caller's login id for
4226 messages from local sources, except when &%-bh%& is used, when there is no
4227 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4228 specified on a MAIL command overrides this value. See chapter
4229 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4231 .vitem &%-oMi%&&~<&'interface&~address'&>
4233 .cindex "interface" "address, specifying for local message"
4234 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4235 option sets the IP interface address value. A port number may be included,
4236 using the same syntax as for &%-oMa%&. The interface address is placed in
4237 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4239 .vitem &%-oMm%&&~<&'message&~reference'&>
4241 .cindex "message reference" "message reference, specifying for local message"
4242 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4243 option sets the message reference, e.g. message-id, and is logged during
4244 delivery. This is useful when some kind of audit trail is required to tie
4245 messages together. The format of the message reference is checked and will
4246 abort if the format is invalid. The option will only be accepted if exim is
4247 running in trusted mode, not as any regular user.
4249 The best example of a message reference is when Exim sends a bounce message.
4250 The message reference is the message-id of the original message for which Exim
4251 is sending the bounce.
4253 .vitem &%-oMr%&&~<&'protocol&~name'&>
4255 .cindex "protocol, specifying for local message"
4256 .vindex "&$received_protocol$&"
4257 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4258 option sets the received protocol value that is stored in
4259 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4260 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4261 SMTP protocol names (see the description of &$received_protocol$& in section
4262 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4263 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4266 .vitem &%-oMs%&&~<&'host&~name'&>
4268 .cindex "sender" "host name, specifying for local message"
4269 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4270 option sets the sender host name in &$sender_host_name$&. When this option is
4271 present, Exim does not attempt to look up a host name from an IP address; it
4272 uses the name it is given.
4274 .vitem &%-oMt%&&~<&'ident&~string'&>
4276 .cindex "sender" "ident string, specifying for local message"
4277 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4278 option sets the sender ident value in &$sender_ident$&. The default setting for
4279 local callers is the login id of the calling process, except when &%-bh%& is
4280 used, when there is no default.
4284 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4285 In Sendmail, this option means &"me too"&, indicating that the sender of a
4286 message should receive a copy of the message if the sender appears in an alias
4287 expansion. Exim always does this, so the option does nothing.
4291 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4292 This option is ignored. In Sendmail it specifies &"old style headers"&,
4293 whatever that means.
4295 .vitem &%-oP%&&~<&'path'&>
4297 .cindex "pid (process id)" "of daemon"
4298 .cindex "daemon" "process id (pid)"
4299 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4300 value. The option specifies the file to which the process id of the daemon is
4301 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4302 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4303 because in those cases, the normal pid file is not used.
4305 .vitem &%-or%&&~<&'time'&>
4307 .cindex "timeout" "for non-SMTP input"
4308 This option sets a timeout value for incoming non-SMTP messages. If it is not
4309 set, Exim will wait forever for the standard input. The value can also be set
4310 by the &%receive_timeout%& option. The format used for specifying times is
4311 described in section &<<SECTtimeformat>>&.
4313 .vitem &%-os%&&~<&'time'&>
4315 .cindex "timeout" "for SMTP input"
4316 .cindex "SMTP" "input timeout"
4317 This option sets a timeout value for incoming SMTP messages. The timeout
4318 applies to each SMTP command and block of data. The value can also be set by
4319 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4320 for specifying times is described in section &<<SECTtimeformat>>&.
4324 This option has exactly the same effect as &%-v%&.
4326 .vitem &%-oX%&&~<&'number&~or&~string'&>
4328 .cindex "TCP/IP" "setting listening ports"
4329 .cindex "TCP/IP" "setting listening interfaces"
4330 .cindex "port" "receiving TCP/IP"
4331 This option is relevant only when the &%-bd%& (start listening daemon) option
4332 is also given. It controls which ports and interfaces the daemon uses. Details
4333 of the syntax, and how it interacts with configuration file options, are given
4334 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4335 file is written unless &%-oP%& is also present to specify a pid file name.
4339 .cindex "Perl" "starting the interpreter"
4340 This option applies when an embedded Perl interpreter is linked with Exim (see
4341 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4342 option, forcing the starting of the interpreter to be delayed until it is
4347 .cindex "Perl" "starting the interpreter"
4348 This option applies when an embedded Perl interpreter is linked with Exim (see
4349 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4350 option, forcing the starting of the interpreter to occur as soon as Exim is
4353 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4355 For compatibility with Sendmail, this option is equivalent to
4357 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4359 It sets the incoming protocol and host name (for trusted callers). The
4360 host name and its colon can be omitted when only the protocol is to be set.
4361 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4362 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4363 or &`s`& using this option (but that does not seem a real limitation).
4367 .cindex "queue runner" "starting manually"
4368 This option is normally restricted to admin users. However, there is a
4369 configuration option called &%prod_requires_admin%& which can be set false to
4370 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4371 and &%-S%& options).
4373 .cindex "queue runner" "description of operation"
4374 The &%-q%& option starts one queue runner process. This scans the queue of
4375 waiting messages, and runs a delivery process for each one in turn. It waits
4376 for each delivery process to finish before starting the next one. A delivery
4377 process may not actually do any deliveries if the retry times for the addresses
4378 have not been reached. Use &%-qf%& (see below) if you want to override this.
4381 .cindex "SMTP" "passed connection"
4382 .cindex "SMTP" "multiple deliveries"
4383 .cindex "multiple SMTP deliveries"
4384 the delivery process spawns other processes to deliver other messages down
4385 passed SMTP connections, the queue runner waits for these to finish before
4388 When all the queued messages have been considered, the original queue runner
4389 process terminates. In other words, a single pass is made over the waiting
4390 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4391 this to be repeated periodically.
4393 Exim processes the waiting messages in an unpredictable order. It isn't very
4394 random, but it is likely to be different each time, which is all that matters.
4395 If one particular message screws up a remote MTA, other messages to the same
4396 MTA have a chance of getting through if they get tried first.
4398 It is possible to cause the messages to be processed in lexical message id
4399 order, which is essentially the order in which they arrived, by setting the
4400 &%queue_run_in_order%& option, but this is not recommended for normal use.
4402 .vitem &%-q%&<&'qflags'&>
4403 The &%-q%& option may be followed by one or more flag letters that change its
4404 behaviour. They are all optional, but if more than one is present, they must
4405 appear in the correct order. Each flag is described in a separate item below.
4409 .cindex "queue" "double scanning"
4410 .cindex "queue" "routing"
4411 .cindex "routing" "whole queue before delivery"
4412 An option starting with &%-qq%& requests a two-stage queue run. In the first
4413 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4414 every domain. Addresses are routed, local deliveries happen, but no remote
4417 .cindex "hints database" "remembering routing"
4418 The hints database that remembers which messages are waiting for specific hosts
4419 is updated, as if delivery to those hosts had been deferred. After this is
4420 complete, a second, normal queue scan happens, with routing and delivery taking
4421 place as normal. Messages that are routed to the same host should mostly be
4422 delivered down a single SMTP
4423 .cindex "SMTP" "passed connection"
4424 .cindex "SMTP" "multiple deliveries"
4425 .cindex "multiple SMTP deliveries"
4426 connection because of the hints that were set up during the first queue scan.
4427 This option may be useful for hosts that are connected to the Internet
4430 .vitem &%-q[q]i...%&
4432 .cindex "queue" "initial delivery"
4433 If the &'i'& flag is present, the queue runner runs delivery processes only for
4434 those messages that haven't previously been tried. (&'i'& stands for &"initial
4435 delivery"&.) This can be helpful if you are putting messages on the queue using
4436 &%-odq%& and want a queue runner just to process the new messages.
4438 .vitem &%-q[q][i]f...%&
4440 .cindex "queue" "forcing delivery"
4441 .cindex "delivery" "forcing in queue run"
4442 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4443 message, whereas without &'f'& only those non-frozen addresses that have passed
4444 their retry times are tried.
4446 .vitem &%-q[q][i]ff...%&
4448 .cindex "frozen messages" "forcing delivery"
4449 If &'ff'& is present, a delivery attempt is forced for every message, whether
4452 .vitem &%-q[q][i][f[f]]l%&
4454 .cindex "queue" "local deliveries only"
4455 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4456 be done. If a message requires any remote deliveries, it remains on the queue
4459 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4460 .cindex "queue" "delivering specific messages"
4461 When scanning the queue, Exim can be made to skip over messages whose ids are
4462 lexically less than a given value by following the &%-q%& option with a
4463 starting message id. For example:
4465 exim -q 0t5C6f-0000c8-00
4467 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4468 second message id is given, messages whose ids are lexically greater than it
4469 are also skipped. If the same id is given twice, for example,
4471 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4473 just one delivery process is started, for that message. This differs from
4474 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4475 that it counts as a delivery from a queue run. Note that the selection
4476 mechanism does not affect the order in which the messages are scanned. There
4477 are also other ways of selecting specific sets of messages for delivery in a
4478 queue run &-- see &%-R%& and &%-S%&.
4480 .vitem &%-q%&<&'qflags'&><&'time'&>
4481 .cindex "queue runner" "starting periodically"
4482 .cindex "periodic queue running"
4483 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4484 starting a queue runner process at intervals specified by the given time value
4485 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4486 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4487 single daemon process handles both functions. A common way of starting up a
4488 combined daemon at system boot time is to use a command such as
4490 /usr/exim/bin/exim -bd -q30m
4492 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4493 process every 30 minutes.
4495 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4496 pid file is written unless one is explicitly requested by the &%-oP%& option.
4498 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4500 This option is synonymous with &%-R%&. It is provided for Sendmail
4503 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4505 This option is synonymous with &%-S%&.
4507 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4509 .cindex "queue runner" "for specific recipients"
4510 .cindex "delivery" "to given domain"
4511 .cindex "domain" "delivery to"
4512 The <&'rsflags'&> may be empty, in which case the white space before the string
4513 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4514 which are the possible values for <&'rsflags'&>. White space is required if
4515 <&'rsflags'&> is not empty.
4517 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4518 perform a single queue run, except that, when scanning the messages on the
4519 queue, Exim processes only those that have at least one undelivered recipient
4520 address containing the given string, which is checked in a case-independent
4521 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4522 regular expression; otherwise it is a literal string.
4524 If you want to do periodic queue runs for messages with specific recipients,
4525 you can combine &%-R%& with &%-q%& and a time value. For example:
4527 exim -q25m -R @special.domain.example
4529 This example does a queue run for messages with recipients in the given domain
4530 every 25 minutes. Any additional flags that are specified with &%-q%& are
4531 applied to each queue run.
4533 Once a message is selected for delivery by this mechanism, all its addresses
4534 are processed. For the first selected message, Exim overrides any retry
4535 information and forces a delivery attempt for each undelivered address. This
4536 means that if delivery of any address in the first message is successful, any
4537 existing retry information is deleted, and so delivery attempts for that
4538 address in subsequently selected messages (which are processed without forcing)
4539 will run. However, if delivery of any address does not succeed, the retry
4540 information is updated, and in subsequently selected messages, the failing
4541 address will be skipped.
4543 .cindex "frozen messages" "forcing delivery"
4544 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4545 all selected messages, not just the first; frozen messages are included when
4548 The &%-R%& option makes it straightforward to initiate delivery of all messages
4549 to a given domain after a host has been down for some time. When the SMTP
4550 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4551 effect is to run Exim with the &%-R%& option, but it can be configured to run
4552 an arbitrary command instead.
4556 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4558 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4560 .cindex "delivery" "from given sender"
4561 .cindex "queue runner" "for specific senders"
4562 This option acts like &%-R%& except that it checks the string against each
4563 message's sender instead of against the recipients. If &%-R%& is also set, both
4564 conditions must be met for a message to be selected. If either of the options
4565 has &'f'& or &'ff'& in its flags, the associated action is taken.
4567 .vitem &%-Tqt%&&~<&'times'&>
4569 This is an option that is exclusively for use by the Exim testing suite. It is not
4570 recognized when Exim is run normally. It allows for the setting up of explicit
4571 &"queue times"& so that various warning/retry features can be tested.
4575 .cindex "recipient" "extracting from header lines"
4576 .cindex "&'Bcc:'& header line"
4577 .cindex "&'Cc:'& header line"
4578 .cindex "&'To:'& header line"
4579 When Exim is receiving a locally-generated, non-SMTP message on its standard
4580 input, the &%-t%& option causes the recipients of the message to be obtained
4581 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4582 from the command arguments. The addresses are extracted before any rewriting
4583 takes place and the &'Bcc:'& header line, if present, is then removed.
4585 .cindex "Sendmail compatibility" "&%-t%& option"
4586 If the command has any arguments, they specify addresses to which the message
4587 is &'not'& to be delivered. That is, the argument addresses are removed from
4588 the recipients list obtained from the headers. This is compatible with Smail 3
4589 and in accordance with the documented behaviour of several versions of
4590 Sendmail, as described in man pages on a number of operating systems (e.g.
4591 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4592 argument addresses to those obtained from the headers, and the O'Reilly
4593 Sendmail book documents it that way. Exim can be made to add argument addresses
4594 instead of subtracting them by setting the option
4595 &%extract_addresses_remove_arguments%& false.
4597 .cindex "&%Resent-%& header lines" "with &%-t%&"
4598 If there are any &%Resent-%& header lines in the message, Exim extracts
4599 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4600 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4601 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4602 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4604 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4605 message is resent several times). The RFC also specifies that they should be
4606 added at the front of the message, and separated by &'Received:'& lines. It is
4607 not at all clear how &%-t%& should operate in the present of multiple sets,
4608 nor indeed exactly what constitutes a &"set"&.
4609 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4610 are often added at the end of the header, and if a message is resent more than
4611 once, it is common for the original set of &%Resent-%& headers to be renamed as
4612 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4616 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4617 compatibility with Sendmail.
4619 .vitem &%-tls-on-connect%&
4620 .oindex "&%-tls-on-connect%&"
4621 .cindex "TLS" "use without STARTTLS"
4622 .cindex "TLS" "automatic start"
4623 This option is available when Exim is compiled with TLS support. It forces all
4624 incoming SMTP connections to behave as if the incoming port is listed in the
4625 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4626 &<<CHAPTLS>>& for further details.
4631 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4632 Sendmail uses this option for &"initial message submission"&, and its
4633 documentation states that in future releases, it may complain about
4634 syntactically invalid messages rather than fixing them when this flag is not
4635 set. Exim ignores this option.
4639 This option causes Exim to write information to the standard error stream,
4640 describing what it is doing. In particular, it shows the log lines for
4641 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4642 dialogue is shown. Some of the log lines shown may not actually be written to
4643 the log if the setting of &%log_selector%& discards them. Any relevant
4644 selectors are shown with each log line. If none are shown, the logging is
4649 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4650 National Language Support extended characters in the body of the mail item"&).
4651 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4654 .vitem &%-X%&&~<&'logfile'&>
4656 This option is interpreted by Sendmail to cause debug information to be sent
4657 to the named file. It is ignored by Exim.
4659 .vitem &%-z%&&~<&'log-line'&>
4661 This option writes its argument to Exim's logfile.
4662 Use is restricted to administrators; the intent is for operational notes.
4663 Quotes should be used to maintain a multi-word item as a single argument,
4671 . ////////////////////////////////////////////////////////////////////////////
4672 . Insert a stylized DocBook comment here, to identify the end of the command
4673 . line options. This is for the benefit of the Perl script that automatically
4674 . creates a man page for the options.
4675 . ////////////////////////////////////////////////////////////////////////////
4678 <!-- === End of command line options === -->
4685 . ////////////////////////////////////////////////////////////////////////////
4686 . ////////////////////////////////////////////////////////////////////////////
4689 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4690 "The runtime configuration file"
4692 .cindex "run time configuration"
4693 .cindex "configuration file" "general description"
4694 .cindex "CONFIGURE_FILE"
4695 .cindex "configuration file" "errors in"
4696 .cindex "error" "in configuration file"
4697 .cindex "return code" "for bad configuration"
4698 Exim uses a single run time configuration file that is read whenever an Exim
4699 binary is executed. Note that in normal operation, this happens frequently,
4700 because Exim is designed to operate in a distributed manner, without central
4703 If a syntax error is detected while reading the configuration file, Exim
4704 writes a message on the standard error, and exits with a non-zero return code.
4705 The message is also written to the panic log. &*Note*&: Only simple syntax
4706 errors can be detected at this time. The values of any expanded options are
4707 not checked until the expansion happens, even when the expansion does not
4708 actually alter the string.
4710 The name of the configuration file is compiled into the binary for security
4711 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4712 most configurations, this specifies a single file. However, it is permitted to
4713 give a colon-separated list of file names, in which case Exim uses the first
4714 existing file in the list.
4717 .cindex "EXIM_GROUP"
4718 .cindex "CONFIGURE_OWNER"
4719 .cindex "CONFIGURE_GROUP"
4720 .cindex "configuration file" "ownership"
4721 .cindex "ownership" "configuration file"
4722 The run time configuration file must be owned by root or by the user that is
4723 specified at compile time by the CONFIGURE_OWNER option (if set). The
4724 configuration file must not be world-writeable, or group-writeable unless its
4725 group is the root group or the one specified at compile time by the
4726 CONFIGURE_GROUP option.
4728 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4729 to root, anybody who is able to edit the run time configuration file has an
4730 easy way to run commands as root. If you specify a user or group in the
4731 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4732 who are members of that group will trivially be able to obtain root privileges.
4734 Up to Exim version 4.72, the run time configuration file was also permitted to
4735 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4736 since it offered a simple privilege escalation for any attacker who managed to
4737 compromise the Exim user account.
4739 A default configuration file, which will work correctly in simple situations,
4740 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4741 defines just one file name, the installation process copies the default
4742 configuration to a new file of that name if it did not previously exist. If
4743 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4744 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4749 .section "Using a different configuration file" "SECID40"
4750 .cindex "configuration file" "alternate"
4751 A one-off alternate configuration can be specified by the &%-C%& command line
4752 option, which may specify a single file or a list of files. However, when
4753 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4754 unless the argument for &%-C%& is identical to the built-in value from
4755 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4756 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4757 is useful mainly for checking the syntax of configuration files before
4758 installing them. No owner or group checks are done on a configuration file
4759 specified by &%-C%&, if root privilege has been dropped.
4761 Even the Exim user is not trusted to specify an arbitrary configuration file
4762 with the &%-C%& option to be used with root privileges, unless that file is
4763 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4764 testing a configuration using &%-C%& right through message reception and
4765 delivery, even if the caller is root. The reception works, but by that time,
4766 Exim is running as the Exim user, so when it re-execs to regain privilege for
4767 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4768 can test reception and delivery using two separate commands (one to put a
4769 message on the queue, using &%-odq%&, and another to do the delivery, using
4772 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4773 prefix string with which any file named in a &%-C%& command line option must
4774 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4775 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4776 name can be used with &%-C%&.
4778 One-off changes to a configuration can be specified by the &%-D%& command line
4779 option, which defines and overrides values for macros used inside the
4780 configuration file. However, like &%-C%&, the use of this option by a
4781 non-privileged user causes Exim to discard its root privilege.
4782 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4783 completely disabled, and its use causes an immediate error exit.
4785 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4786 to declare certain macro names trusted, such that root privilege will not
4787 necessarily be discarded.
4788 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4789 considered safe and, if &%-D%& only supplies macros from this list, and the
4790 values are acceptable, then Exim will not give up root privilege if the caller
4791 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4792 transition mechanism and is expected to be removed in the future. Acceptable
4793 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4795 Some sites may wish to use the same Exim binary on different machines that
4796 share a file system, but to use different configuration files on each machine.
4797 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4798 looks for a file whose name is the configuration file name followed by a dot
4799 and the machine's node name, as obtained from the &[uname()]& function. If this
4800 file does not exist, the standard name is tried. This processing occurs for
4801 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4803 In some esoteric situations different versions of Exim may be run under
4804 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4805 help with this. See the comments in &_src/EDITME_& for details.
4809 .section "Configuration file format" "SECTconffilfor"
4810 .cindex "configuration file" "format of"
4811 .cindex "format" "configuration file"
4812 Exim's configuration file is divided into a number of different parts. General
4813 option settings must always appear at the start of the file. The other parts
4814 are all optional, and may appear in any order. Each part other than the first
4815 is introduced by the word &"begin"& followed by at least one literal
4816 space, and the name of the part. The optional parts are:
4819 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4822 .cindex "AUTH" "configuration"
4823 &'authenticators'&: Configuration settings for the authenticator drivers. These
4824 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4826 &'routers'&: Configuration settings for the router drivers. Routers process
4827 addresses and determine how the message is to be delivered (see chapters
4828 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4830 &'transports'&: Configuration settings for the transport drivers. Transports
4831 define mechanisms for copying messages to destinations (see chapters
4832 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4834 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4835 If there is no retry section, or if it is empty (that is, no retry rules are
4836 defined), Exim will not retry deliveries. In this situation, temporary errors
4837 are treated the same as permanent errors. Retry rules are discussed in chapter
4840 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4841 when new addresses are generated during delivery. Rewriting is discussed in
4842 chapter &<<CHAPrewrite>>&.
4844 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4845 want to use this feature, you must set
4847 LOCAL_SCAN_HAS_OPTIONS=yes
4849 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4850 facility are given in chapter &<<CHAPlocalscan>>&.
4853 .cindex "configuration file" "leading white space in"
4854 .cindex "configuration file" "trailing white space in"
4855 .cindex "white space" "in configuration file"
4856 Leading and trailing white space in configuration lines is always ignored.
4858 Blank lines in the file, and lines starting with a # character (ignoring
4859 leading white space) are treated as comments and are ignored. &*Note*&: A
4860 # character other than at the beginning of a line is not treated specially,
4861 and does not introduce a comment.
4863 Any non-comment line can be continued by ending it with a backslash. Note that
4864 the general rule for white space means that trailing white space after the
4865 backslash and leading white space at the start of continuation
4866 lines is ignored. Comment lines beginning with # (but not empty lines) may
4867 appear in the middle of a sequence of continuation lines.
4869 A convenient way to create a configuration file is to start from the
4870 default, which is supplied in &_src/configure.default_&, and add, delete, or
4871 change settings as required.
4873 The ACLs, retry rules, and rewriting rules have their own syntax which is
4874 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4875 respectively. The other parts of the configuration file have some syntactic
4876 items in common, and these are described below, from section &<<SECTcos>>&
4877 onwards. Before that, the inclusion, macro, and conditional facilities are
4882 .section "File inclusions in the configuration file" "SECID41"
4883 .cindex "inclusions in configuration file"
4884 .cindex "configuration file" "including other files"
4885 .cindex "&`.include`& in configuration file"
4886 .cindex "&`.include_if_exists`& in configuration file"
4887 You can include other files inside Exim's run time configuration file by
4890 &`.include`& <&'file name'&>
4891 &`.include_if_exists`& <&'file name'&>
4893 on a line by itself. Double quotes round the file name are optional. If you use
4894 the first form, a configuration error occurs if the file does not exist; the
4895 second form does nothing for non-existent files. In all cases, an absolute file
4898 Includes may be nested to any depth, but remember that Exim reads its
4899 configuration file often, so it is a good idea to keep them to a minimum.
4900 If you change the contents of an included file, you must HUP the daemon,
4901 because an included file is read only when the configuration itself is read.
4903 The processing of inclusions happens early, at a physical line level, so, like
4904 comment lines, an inclusion can be used in the middle of an option setting,
4907 hosts_lookup = a.b.c \
4910 Include processing happens after macro processing (see below). Its effect is to
4911 process the lines of the included file as if they occurred inline where the
4916 .section "Macros in the configuration file" "SECTmacrodefs"
4917 .cindex "macro" "description of"
4918 .cindex "configuration file" "macros"
4919 If a line in the main part of the configuration (that is, before the first
4920 &"begin"& line) begins with an upper case letter, it is taken as a macro
4921 definition, and must be of the form
4923 <&'name'&> = <&'rest of line'&>
4925 The name must consist of letters, digits, and underscores, and need not all be
4926 in upper case, though that is recommended. The rest of the line, including any
4927 continuations, is the replacement text, and has leading and trailing white
4928 space removed. Quotes are not removed. The replacement text can never end with
4929 a backslash character, but this doesn't seem to be a serious limitation.
4931 Macros may also be defined between router, transport, authenticator, or ACL
4932 definitions. They may not, however, be defined within an individual driver or
4933 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4935 .section "Macro substitution" "SECID42"
4936 Once a macro is defined, all subsequent lines in the file (and any included
4937 files) are scanned for the macro name; if there are several macros, the line is
4938 scanned for each in turn, in the order in which the macros are defined. The
4939 replacement text is not re-scanned for the current macro, though it is scanned
4940 for subsequently defined macros. For this reason, a macro name may not contain
4941 the name of a previously defined macro as a substring. You could, for example,
4944 &`ABCD_XYZ = `&<&'something'&>
4945 &`ABCD = `&<&'something else'&>
4947 but putting the definitions in the opposite order would provoke a configuration
4948 error. Macro expansion is applied to individual physical lines from the file,
4949 before checking for line continuation or file inclusion (see above). If a line
4950 consists solely of a macro name, and the expansion of the macro is empty, the
4951 line is ignored. A macro at the start of a line may turn the line into a
4952 comment line or a &`.include`& line.
4955 .section "Redefining macros" "SECID43"
4956 Once defined, the value of a macro can be redefined later in the configuration
4957 (or in an included file). Redefinition is specified by using &'=='& instead of
4962 MAC == updated value
4964 Redefinition does not alter the order in which the macros are applied to the
4965 subsequent lines of the configuration file. It is still the same order in which
4966 the macros were originally defined. All that changes is the macro's value.
4967 Redefinition makes it possible to accumulate values. For example:
4971 MAC == MAC and something added
4973 This can be helpful in situations where the configuration file is built
4974 from a number of other files.
4976 .section "Overriding macro values" "SECID44"
4977 The values set for macros in the configuration file can be overridden by the
4978 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4979 used, unless called by root or the Exim user. A definition on the command line
4980 using the &%-D%& option causes all definitions and redefinitions within the
4985 .section "Example of macro usage" "SECID45"
4986 As an example of macro usage, consider a configuration where aliases are looked
4987 up in a MySQL database. It helps to keep the file less cluttered if long
4988 strings such as SQL statements are defined separately as macros, for example:
4990 ALIAS_QUERY = select mailbox from user where \
4991 login='${quote_mysql:$local_part}';
4993 This can then be used in a &(redirect)& router setting like this:
4995 data = ${lookup mysql{ALIAS_QUERY}}
4997 In earlier versions of Exim macros were sometimes used for domain, host, or
4998 address lists. In Exim 4 these are handled better by named lists &-- see
4999 section &<<SECTnamedlists>>&.
5002 .section "Conditional skips in the configuration file" "SECID46"
5003 .cindex "configuration file" "conditional skips"
5004 .cindex "&`.ifdef`&"
5005 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5006 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5007 portions of the configuration file. The processing happens whenever the file is
5008 read (that is, when an Exim binary starts to run).
5010 The implementation is very simple. Instances of the first four directives must
5011 be followed by text that includes the names of one or macros. The condition
5012 that is tested is whether or not any macro substitution has taken place in the
5016 message_size_limit = 50M
5018 message_size_limit = 100M
5021 sets a message size limit of 50M if the macro &`AAA`& is defined
5022 (or &`A`& or &`AA`&), and 100M
5023 otherwise. If there is more than one macro named on the line, the condition
5024 is true if any of them are defined. That is, it is an &"or"& condition. To
5025 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5027 Although you can use a macro expansion to generate one of these directives,
5028 it is not very useful, because the condition &"there was a macro substitution
5029 in this line"& will always be true.
5031 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5032 to clarify complicated nestings.
5036 .section "Common option syntax" "SECTcos"
5037 .cindex "common option syntax"
5038 .cindex "syntax of common options"
5039 .cindex "configuration file" "common option syntax"
5040 For the main set of options, driver options, and &[local_scan()]& options,
5041 each setting is on a line by itself, and starts with a name consisting of
5042 lower-case letters and underscores. Many options require a data value, and in
5043 these cases the name must be followed by an equals sign (with optional white
5044 space) and then the value. For example:
5046 qualify_domain = mydomain.example.com
5048 .cindex "hiding configuration option values"
5049 .cindex "configuration options" "hiding value of"
5050 .cindex "options" "hiding value of"
5051 Some option settings may contain sensitive data, for example, passwords for
5052 accessing databases. To stop non-admin users from using the &%-bP%& command
5053 line option to read these values, you can precede the option settings with the
5054 word &"hide"&. For example:
5056 hide mysql_servers = localhost/users/admin/secret-password
5058 For non-admin users, such options are displayed like this:
5060 mysql_servers = <value not displayable>
5062 If &"hide"& is used on a driver option, it hides the value of that option on
5063 all instances of the same driver.
5065 The following sections describe the syntax used for the different data types
5066 that are found in option settings.
5069 .section "Boolean options" "SECID47"
5070 .cindex "format" "boolean"
5071 .cindex "boolean configuration values"
5072 .oindex "&%no_%&&'xxx'&"
5073 .oindex "&%not_%&&'xxx'&"
5074 Options whose type is given as boolean are on/off switches. There are two
5075 different ways of specifying such options: with and without a data value. If
5076 the option name is specified on its own without data, the switch is turned on;
5077 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5078 boolean options may be followed by an equals sign and one of the words
5079 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5080 the following two settings have exactly the same effect:
5085 The following two lines also have the same (opposite) effect:
5090 You can use whichever syntax you prefer.
5095 .section "Integer values" "SECID48"
5096 .cindex "integer configuration values"
5097 .cindex "format" "integer"
5098 If an option's type is given as &"integer"&, the value can be given in decimal,
5099 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5100 number is assumed. Otherwise, it is treated as an octal number unless it starts
5101 with the characters &"0x"&, in which case the remainder is interpreted as a
5104 If an integer value is followed by the letter K, it is multiplied by 1024; if
5105 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5106 of integer option settings are output, values which are an exact multiple of
5107 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5108 and M. The printing style is independent of the actual input format that was
5112 .section "Octal integer values" "SECID49"
5113 .cindex "integer format"
5114 .cindex "format" "octal integer"
5115 If an option's type is given as &"octal integer"&, its value is always
5116 interpreted as an octal number, whether or not it starts with the digit zero.
5117 Such options are always output in octal.
5120 .section "Fixed point numbers" "SECID50"
5121 .cindex "fixed point configuration values"
5122 .cindex "format" "fixed point"
5123 If an option's type is given as &"fixed-point"&, its value must be a decimal
5124 integer, optionally followed by a decimal point and up to three further digits.
5128 .section "Time intervals" "SECTtimeformat"
5129 .cindex "time interval" "specifying in configuration"
5130 .cindex "format" "time interval"
5131 A time interval is specified as a sequence of numbers, each followed by one of
5132 the following letters, with no intervening white space:
5142 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5143 intervals are output in the same format. Exim does not restrict the values; it
5144 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5148 .section "String values" "SECTstrings"
5149 .cindex "string" "format of configuration values"
5150 .cindex "format" "string"
5151 If an option's type is specified as &"string"&, the value can be specified with
5152 or without double-quotes. If it does not start with a double-quote, the value
5153 consists of the remainder of the line plus any continuation lines, starting at
5154 the first character after any leading white space, with trailing white space
5155 removed, and with no interpretation of the characters in the string. Because
5156 Exim removes comment lines (those beginning with #) at an early stage, they can
5157 appear in the middle of a multi-line string. The following two settings are
5158 therefore equivalent:
5160 trusted_users = uucp:mail
5161 trusted_users = uucp:\
5162 # This comment line is ignored
5165 .cindex "string" "quoted"
5166 .cindex "escape characters in quoted strings"
5167 If a string does start with a double-quote, it must end with a closing
5168 double-quote, and any backslash characters other than those used for line
5169 continuation are interpreted as escape characters, as follows:
5172 .irow &`\\`& "single backslash"
5173 .irow &`\n`& "newline"
5174 .irow &`\r`& "carriage return"
5176 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5177 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5181 If a backslash is followed by some other character, including a double-quote
5182 character, that character replaces the pair.
5184 Quoting is necessary only if you want to make use of the backslash escapes to
5185 insert special characters, or if you need to specify a value with leading or
5186 trailing spaces. These cases are rare, so quoting is almost never needed in
5187 current versions of Exim. In versions of Exim before 3.14, quoting was required
5188 in order to continue lines, so you may come across older configuration files
5189 and examples that apparently quote unnecessarily.
5192 .section "Expanded strings" "SECID51"
5193 .cindex "expansion" "definition of"
5194 Some strings in the configuration file are subjected to &'string expansion'&,
5195 by which means various parts of the string may be changed according to the
5196 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5197 is as just described; in particular, the handling of backslashes in quoted
5198 strings is done as part of the input process, before expansion takes place.
5199 However, backslash is also an escape character for the expander, so any
5200 backslashes that are required for that reason must be doubled if they are
5201 within a quoted configuration string.
5204 .section "User and group names" "SECID52"
5205 .cindex "user name" "format of"
5206 .cindex "format" "user name"
5207 .cindex "groups" "name format"
5208 .cindex "format" "group name"
5209 User and group names are specified as strings, using the syntax described
5210 above, but the strings are interpreted specially. A user or group name must
5211 either consist entirely of digits, or be a name that can be looked up using the
5212 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5215 .section "List construction" "SECTlistconstruct"
5216 .cindex "list" "syntax of in configuration"
5217 .cindex "format" "list item in configuration"
5218 .cindex "string" "list, definition of"
5219 The data for some configuration options is a list of items, with colon as the
5220 default separator. Many of these options are shown with type &"string list"& in
5221 the descriptions later in this document. Others are listed as &"domain list"&,
5222 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5223 are all the same; however, those other than &"string list"& are subject to
5224 particular kinds of interpretation, as described in chapter
5225 &<<CHAPdomhosaddlists>>&.
5227 In all these cases, the entire list is treated as a single string as far as the
5228 input syntax is concerned. The &%trusted_users%& setting in section
5229 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5230 in a list, it must be entered as two colons. Leading and trailing white space
5231 on each item in a list is ignored. This makes it possible to include items that
5232 start with a colon, and in particular, certain forms of IPv6 address. For
5235 local_interfaces = 127.0.0.1 : ::::1
5237 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5239 &*Note*&: Although leading and trailing white space is ignored in individual
5240 list items, it is not ignored when parsing the list. The space after the first
5241 colon in the example above is necessary. If it were not there, the list would
5242 be interpreted as the two items 127.0.0.1:: and 1.
5244 .section "Changing list separators" "SECTlistsepchange"
5245 .cindex "list separator" "changing"
5246 .cindex "IPv6" "addresses in lists"
5247 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5248 introduced to allow the separator character to be changed. If a list begins
5249 with a left angle bracket, followed by any punctuation character, that
5250 character is used instead of colon as the list separator. For example, the list
5251 above can be rewritten to use a semicolon separator like this:
5253 local_interfaces = <; 127.0.0.1 ; ::1
5255 This facility applies to all lists, with the exception of the list in
5256 &%log_file_path%&. It is recommended that the use of non-colon separators be
5257 confined to circumstances where they really are needed.
5259 .cindex "list separator" "newline as"
5260 .cindex "newline" "as list separator"
5261 It is also possible to use newline and other control characters (those with
5262 code values less than 32, plus DEL) as separators in lists. Such separators
5263 must be provided literally at the time the list is processed. For options that
5264 are string-expanded, you can write the separator using a normal escape
5265 sequence. This will be processed by the expander before the string is
5266 interpreted as a list. For example, if a newline-separated list of domains is
5267 generated by a lookup, you can process it directly by a line such as this:
5269 domains = <\n ${lookup mysql{.....}}
5271 This avoids having to change the list separator in such data. You are unlikely
5272 to want to use a control character as a separator in an option that is not
5273 expanded, because the value is literal text. However, it can be done by giving
5274 the value in quotes. For example:
5276 local_interfaces = "<\n 127.0.0.1 \n ::1"
5278 Unlike printing character separators, which can be included in list items by
5279 doubling, it is not possible to include a control character as data when it is
5280 set as the separator. Two such characters in succession are interpreted as
5281 enclosing an empty list item.
5285 .section "Empty items in lists" "SECTempitelis"
5286 .cindex "list" "empty item in"
5287 An empty item at the end of a list is always ignored. In other words, trailing
5288 separator characters are ignored. Thus, the list in
5290 senders = user@domain :
5292 contains only a single item. If you want to include an empty string as one item
5293 in a list, it must not be the last item. For example, this list contains three
5294 items, the second of which is empty:
5296 senders = user1@domain : : user2@domain
5298 &*Note*&: There must be white space between the two colons, as otherwise they
5299 are interpreted as representing a single colon data character (and the list
5300 would then contain just one item). If you want to specify a list that contains
5301 just one, empty item, you can do it as in this example:
5305 In this case, the first item is empty, and the second is discarded because it
5306 is at the end of the list.
5311 .section "Format of driver configurations" "SECTfordricon"
5312 .cindex "drivers" "configuration format"
5313 There are separate parts in the configuration for defining routers, transports,
5314 and authenticators. In each part, you are defining a number of driver
5315 instances, each with its own set of options. Each driver instance is defined by
5316 a sequence of lines like this:
5318 <&'instance name'&>:
5323 In the following example, the instance name is &(localuser)&, and it is
5324 followed by three options settings:
5329 transport = local_delivery
5331 For each driver instance, you specify which Exim code module it uses &-- by the
5332 setting of the &%driver%& option &-- and (optionally) some configuration
5333 settings. For example, in the case of transports, if you want a transport to
5334 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5335 a local file you would use the &(appendfile)& driver. Each of the drivers is
5336 described in detail in its own separate chapter later in this manual.
5338 You can have several routers, transports, or authenticators that are based on
5339 the same underlying driver (each must have a different instance name).
5341 The order in which routers are defined is important, because addresses are
5342 passed to individual routers one by one, in order. The order in which
5343 transports are defined does not matter at all. The order in which
5344 authenticators are defined is used only when Exim, as a client, is searching
5345 them to find one that matches an authentication mechanism offered by the
5348 .cindex "generic options"
5349 .cindex "options" "generic &-- definition of"
5350 Within a driver instance definition, there are two kinds of option: &'generic'&
5351 and &'private'&. The generic options are those that apply to all drivers of the
5352 same type (that is, all routers, all transports or all authenticators). The
5353 &%driver%& option is a generic option that must appear in every definition.
5354 .cindex "private options"
5355 The private options are special for each driver, and none need appear, because
5356 they all have default values.
5358 The options may appear in any order, except that the &%driver%& option must
5359 precede any private options, since these depend on the particular driver. For
5360 this reason, it is recommended that &%driver%& always be the first option.
5362 Driver instance names, which are used for reference in log entries and
5363 elsewhere, can be any sequence of letters, digits, and underscores (starting
5364 with a letter) and must be unique among drivers of the same type. A router and
5365 a transport (for example) can each have the same name, but no two router
5366 instances can have the same name. The name of a driver instance should not be
5367 confused with the name of the underlying driver module. For example, the
5368 configuration lines:
5373 create an instance of the &(smtp)& transport driver whose name is
5374 &(remote_smtp)&. The same driver code can be used more than once, with
5375 different instance names and different option settings each time. A second
5376 instance of the &(smtp)& transport, with different options, might be defined
5382 command_timeout = 10s
5384 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5385 these transport instances from routers, and these names would appear in log
5388 Comment lines may be present in the middle of driver specifications. The full
5389 list of option settings for any particular driver instance, including all the
5390 defaulted values, can be extracted by making use of the &%-bP%& command line
5398 . ////////////////////////////////////////////////////////////////////////////
5399 . ////////////////////////////////////////////////////////////////////////////
5401 .chapter "The default configuration file" "CHAPdefconfil"
5402 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5403 .cindex "default" "configuration file &""walk through""&"
5404 The default configuration file supplied with Exim as &_src/configure.default_&
5405 is sufficient for a host with simple mail requirements. As an introduction to
5406 the way Exim is configured, this chapter &"walks through"& the default
5407 configuration, giving brief explanations of the settings. Detailed descriptions
5408 of the options are given in subsequent chapters. The default configuration file
5409 itself contains extensive comments about ways you might want to modify the
5410 initial settings. However, note that there are many options that are not
5411 mentioned at all in the default configuration.
5415 .section "Main configuration settings" "SECTdefconfmain"
5416 The main (global) configuration option settings must always come first in the
5417 file. The first thing you'll see in the file, after some initial comments, is
5420 # primary_hostname =
5422 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5423 to know the official, fully qualified name of your host, and this is where you
5424 can specify it. However, in most cases you do not need to set this option. When
5425 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5427 The first three non-comment configuration lines are as follows:
5429 domainlist local_domains = @
5430 domainlist relay_to_domains =
5431 hostlist relay_from_hosts = 127.0.0.1
5433 These are not, in fact, option settings. They are definitions of two named
5434 domain lists and one named host list. Exim allows you to give names to lists of
5435 domains, hosts, and email addresses, in order to make it easier to manage the
5436 configuration file (see section &<<SECTnamedlists>>&).
5438 The first line defines a domain list called &'local_domains'&; this is used
5439 later in the configuration to identify domains that are to be delivered
5442 .cindex "@ in a domain list"
5443 There is just one item in this list, the string &"@"&. This is a special form
5444 of entry which means &"the name of the local host"&. Thus, if the local host is
5445 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5446 be delivered locally. Because the local host's name is referenced indirectly,
5447 the same configuration file can be used on different hosts.
5449 The second line defines a domain list called &'relay_to_domains'&, but the
5450 list itself is empty. Later in the configuration we will come to the part that
5451 controls mail relaying through the local host; it allows relaying to any
5452 domains in this list. By default, therefore, no relaying on the basis of a mail
5453 domain is permitted.
5455 The third line defines a host list called &'relay_from_hosts'&. This list is
5456 used later in the configuration to permit relaying from any host or IP address
5457 that matches the list. The default contains just the IP address of the IPv4
5458 loopback interface, which means that processes on the local host are able to
5459 submit mail for relaying by sending it over TCP/IP to that interface. No other
5460 hosts are permitted to submit messages for relaying.
5462 Just to be sure there's no misunderstanding: at this point in the configuration
5463 we aren't actually setting up any controls. We are just defining some domains
5464 and hosts that will be used in the controls that are specified later.
5466 The next two configuration lines are genuine option settings:
5468 acl_smtp_rcpt = acl_check_rcpt
5469 acl_smtp_data = acl_check_data
5471 These options specify &'Access Control Lists'& (ACLs) that are to be used
5472 during an incoming SMTP session for every recipient of a message (every RCPT
5473 command), and after the contents of the message have been received,
5474 respectively. The names of the lists are &'acl_check_rcpt'& and
5475 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5476 section of the configuration. The RCPT ACL controls which recipients are
5477 accepted for an incoming message &-- if a configuration does not provide an ACL
5478 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5479 contents of a message to be checked.
5481 Two commented-out option settings are next:
5483 # av_scanner = clamd:/tmp/clamd
5484 # spamd_address = 127.0.0.1 783
5486 These are example settings that can be used when Exim is compiled with the
5487 content-scanning extension. The first specifies the interface to the virus
5488 scanner, and the second specifies the interface to SpamAssassin. Further
5489 details are given in chapter &<<CHAPexiscan>>&.
5491 Three more commented-out option settings follow:
5493 # tls_advertise_hosts = *
5494 # tls_certificate = /etc/ssl/exim.crt
5495 # tls_privatekey = /etc/ssl/exim.pem
5497 These are example settings that can be used when Exim is compiled with
5498 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5499 first one specifies the list of clients that are allowed to use TLS when
5500 connecting to this server; in this case the wildcard means all clients. The
5501 other options specify where Exim should find its TLS certificate and private
5502 key, which together prove the server's identity to any clients that connect.
5503 More details are given in chapter &<<CHAPTLS>>&.
5505 Another two commented-out option settings follow:
5507 # daemon_smtp_ports = 25 : 465 : 587
5508 # tls_on_connect_ports = 465
5510 .cindex "port" "465 and 587"
5511 .cindex "port" "for message submission"
5512 .cindex "message" "submission, ports for"
5513 .cindex "ssmtp protocol"
5514 .cindex "smtps protocol"
5515 .cindex "SMTP" "ssmtp protocol"
5516 .cindex "SMTP" "smtps protocol"
5517 These options provide better support for roaming users who wish to use this
5518 server for message submission. They are not much use unless you have turned on
5519 TLS (as described in the previous paragraph) and authentication (about which
5520 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5521 on end-user networks, so RFC 4409 specifies that message submission should use
5522 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5523 configured to use port 587 correctly, so these settings also enable the
5524 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5525 &<<SECTsupobssmt>>&).
5527 Two more commented-out options settings follow:
5530 # qualify_recipient =
5532 The first of these specifies a domain that Exim uses when it constructs a
5533 complete email address from a local login name. This is often needed when Exim
5534 receives a message from a local process. If you do not set &%qualify_domain%&,
5535 the value of &%primary_hostname%& is used. If you set both of these options,
5536 you can have different qualification domains for sender and recipient
5537 addresses. If you set only the first one, its value is used in both cases.
5539 .cindex "domain literal" "recognizing format"
5540 The following line must be uncommented if you want Exim to recognize
5541 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5542 (an IP address within square brackets) instead of a named domain.
5544 # allow_domain_literals
5546 The RFCs still require this form, but many people think that in the modern
5547 Internet it makes little sense to permit mail to be sent to specific hosts by
5548 quoting their IP addresses. This ancient format has been used by people who
5549 try to abuse hosts by using them for unwanted relaying. However, some
5550 people believe there are circumstances (for example, messages addressed to
5551 &'postmaster'&) where domain literals are still useful.
5553 The next configuration line is a kind of trigger guard:
5557 It specifies that no delivery must ever be run as the root user. The normal
5558 convention is to set up &'root'& as an alias for the system administrator. This
5559 setting is a guard against slips in the configuration.
5560 The list of users specified by &%never_users%& is not, however, the complete
5561 list; the build-time configuration in &_Local/Makefile_& has an option called
5562 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5563 contents of &%never_users%& are added to this list. By default
5564 FIXED_NEVER_USERS also specifies root.
5566 When a remote host connects to Exim in order to send mail, the only information
5567 Exim has about the host's identity is its IP address. The next configuration
5572 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5573 in order to get a host name. This improves the quality of the logging
5574 information, but if you feel it is too expensive, you can remove it entirely,
5575 or restrict the lookup to hosts on &"nearby"& networks.
5576 Note that it is not always possible to find a host name from an IP address,
5577 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5580 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5581 1413 (hence their names):
5584 rfc1413_query_timeout = 0s
5586 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5587 Few hosts offer RFC1413 service these days; calls have to be
5588 terminated by a timeout and this needlessly delays the startup
5589 of an incoming SMTP connection.
5590 If you have hosts for which you trust RFC1413 and need this
5591 information, you can change this.
5593 This line enables an efficiency SMTP option. It is negotiated by clients
5594 and not expected to cause problems but can be disabled if needed.
5599 When Exim receives messages over SMTP connections, it expects all addresses to
5600 be fully qualified with a domain, as required by the SMTP definition. However,
5601 if you are running a server to which simple clients submit messages, you may
5602 find that they send unqualified addresses. The two commented-out options:
5604 # sender_unqualified_hosts =
5605 # recipient_unqualified_hosts =
5607 show how you can specify hosts that are permitted to send unqualified sender
5608 and recipient addresses, respectively.
5610 The &%log_selector%& option is used to increase the detail of logging
5613 log_selector = +smtp_protocol_error +smtp_syntax_error \
5614 +tls_certificate_verified
5617 The &%percent_hack_domains%& option is also commented out:
5619 # percent_hack_domains =
5621 It provides a list of domains for which the &"percent hack"& is to operate.
5622 This is an almost obsolete form of explicit email routing. If you do not know
5623 anything about it, you can safely ignore this topic.
5625 The last two settings in the main part of the default configuration are
5626 concerned with messages that have been &"frozen"& on Exim's queue. When a
5627 message is frozen, Exim no longer continues to try to deliver it. Freezing
5628 occurs when a bounce message encounters a permanent failure because the sender
5629 address of the original message that caused the bounce is invalid, so the
5630 bounce cannot be delivered. This is probably the most common case, but there
5631 are also other conditions that cause freezing, and frozen messages are not
5632 always bounce messages.
5634 ignore_bounce_errors_after = 2d
5635 timeout_frozen_after = 7d
5637 The first of these options specifies that failing bounce messages are to be
5638 discarded after 2 days on the queue. The second specifies that any frozen
5639 message (whether a bounce message or not) is to be timed out (and discarded)
5640 after a week. In this configuration, the first setting ensures that no failing
5641 bounce message ever lasts a week.
5645 .section "ACL configuration" "SECID54"
5646 .cindex "default" "ACLs"
5647 .cindex "&ACL;" "default configuration"
5648 In the default configuration, the ACL section follows the main configuration.
5649 It starts with the line
5653 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5654 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5655 and &%acl_smtp_data%& above.
5657 .cindex "RCPT" "ACL for"
5658 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5659 RCPT command specifies one of the message's recipients. The ACL statements
5660 are considered in order, until the recipient address is either accepted or
5661 rejected. The RCPT command is then accepted or rejected, according to the
5662 result of the ACL processing.
5666 This line, consisting of a name terminated by a colon, marks the start of the
5671 This ACL statement accepts the recipient if the sending host matches the list.
5672 But what does that strange list mean? It doesn't actually contain any host
5673 names or IP addresses. The presence of the colon puts an empty item in the
5674 list; Exim matches this only if the incoming message did not come from a remote
5675 host, because in that case, the remote hostname is empty. The colon is
5676 important. Without it, the list itself is empty, and can never match anything.
5678 What this statement is doing is to accept unconditionally all recipients in
5679 messages that are submitted by SMTP from local processes using the standard
5680 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5683 deny message = Restricted characters in address
5684 domains = +local_domains
5685 local_parts = ^[.] : ^.*[@%!/|]
5687 deny message = Restricted characters in address
5688 domains = !+local_domains
5689 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5691 These statements are concerned with local parts that contain any of the
5692 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5693 Although these characters are entirely legal in local parts (in the case of
5694 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5695 in Internet mail addresses.
5697 The first three have in the past been associated with explicitly routed
5698 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5699 option). Addresses containing these characters are regularly tried by spammers
5700 in an attempt to bypass relaying restrictions, and also by open relay testing
5701 programs. Unless you really need them it is safest to reject these characters
5702 at this early stage. This configuration is heavy-handed in rejecting these
5703 characters for all messages it accepts from remote hosts. This is a deliberate
5704 policy of being as safe as possible.
5706 The first rule above is stricter, and is applied to messages that are addressed
5707 to one of the local domains handled by this host. This is implemented by the
5708 first condition, which restricts it to domains that are listed in the
5709 &'local_domains'& domain list. The &"+"& character is used to indicate a
5710 reference to a named list. In this configuration, there is just one domain in
5711 &'local_domains'&, but in general there may be many.
5713 The second condition on the first statement uses two regular expressions to
5714 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5715 or &"|"&. If you have local accounts that include these characters, you will
5716 have to modify this rule.
5718 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5719 allows them because they have been encountered in practice. (Consider the
5720 common convention of local parts constructed as
5721 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5722 the author of Exim, who has no second initial.) However, a local part starting
5723 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5724 file name (for example, for a mailing list). This is also true for local parts
5725 that contain slashes. A pipe symbol can also be troublesome if the local part
5726 is incorporated unthinkingly into a shell command line.
5728 The second rule above applies to all other domains, and is less strict. This
5729 allows your own users to send outgoing messages to sites that use slashes
5730 and vertical bars in their local parts. It blocks local parts that begin
5731 with a dot, slash, or vertical bar, but allows these characters within the
5732 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5733 and &"!"& is blocked, as before. The motivation here is to prevent your users
5734 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5736 accept local_parts = postmaster
5737 domains = +local_domains
5739 This statement, which has two conditions, accepts an incoming address if the
5740 local part is &'postmaster'& and the domain is one of those listed in the
5741 &'local_domains'& domain list. The &"+"& character is used to indicate a
5742 reference to a named list. In this configuration, there is just one domain in
5743 &'local_domains'&, but in general there may be many.
5745 The presence of this statement means that mail to postmaster is never blocked
5746 by any of the subsequent tests. This can be helpful while sorting out problems
5747 in cases where the subsequent tests are incorrectly denying access.
5749 require verify = sender
5751 This statement requires the sender address to be verified before any subsequent
5752 ACL statement can be used. If verification fails, the incoming recipient
5753 address is refused. Verification consists of trying to route the address, to
5754 see if a bounce message could be delivered to it. In the case of remote
5755 addresses, basic verification checks only the domain, but &'callouts'& can be
5756 used for more verification if required. Section &<<SECTaddressverification>>&
5757 discusses the details of address verification.
5759 accept hosts = +relay_from_hosts
5760 control = submission
5762 This statement accepts the address if the message is coming from one of the
5763 hosts that are defined as being allowed to relay through this host. Recipient
5764 verification is omitted here, because in many cases the clients are dumb MUAs
5765 that do not cope well with SMTP error responses. For the same reason, the
5766 second line specifies &"submission mode"& for messages that are accepted. This
5767 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5768 messages that are deficient in some way, for example, because they lack a
5769 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5770 probably add recipient verification here, and disable submission mode.
5772 accept authenticated = *
5773 control = submission
5775 This statement accepts the address if the client host has authenticated itself.
5776 Submission mode is again specified, on the grounds that such messages are most
5777 likely to come from MUAs. The default configuration does not define any
5778 authenticators, though it does include some nearly complete commented-out
5779 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5780 fact authenticate until you complete the authenticator definitions.
5782 require message = relay not permitted
5783 domains = +local_domains : +relay_to_domains
5785 This statement rejects the address if its domain is neither a local domain nor
5786 one of the domains for which this host is a relay.
5788 require verify = recipient
5790 This statement requires the recipient address to be verified; if verification
5791 fails, the address is rejected.
5793 # deny message = rejected because $sender_host_address \
5794 # is in a black list at $dnslist_domain\n\
5796 # dnslists = black.list.example
5798 # warn dnslists = black.list.example
5799 # add_header = X-Warning: $sender_host_address is in \
5800 # a black list at $dnslist_domain
5801 # log_message = found in $dnslist_domain
5803 These commented-out lines are examples of how you could configure Exim to check
5804 sending hosts against a DNS black list. The first statement rejects messages
5805 from blacklisted hosts, whereas the second just inserts a warning header
5808 # require verify = csa
5810 This commented-out line is an example of how you could turn on client SMTP
5811 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5816 The final statement in the first ACL unconditionally accepts any recipient
5817 address that has successfully passed all the previous tests.
5821 This line marks the start of the second ACL, and names it. Most of the contents
5822 of this ACL are commented out:
5825 # message = This message contains a virus \
5828 These lines are examples of how to arrange for messages to be scanned for
5829 viruses when Exim has been compiled with the content-scanning extension, and a
5830 suitable virus scanner is installed. If the message is found to contain a
5831 virus, it is rejected with the given custom error message.
5833 # warn spam = nobody
5834 # message = X-Spam_score: $spam_score\n\
5835 # X-Spam_score_int: $spam_score_int\n\
5836 # X-Spam_bar: $spam_bar\n\
5837 # X-Spam_report: $spam_report
5839 These lines are an example of how to arrange for messages to be scanned by
5840 SpamAssassin when Exim has been compiled with the content-scanning extension,
5841 and SpamAssassin has been installed. The SpamAssassin check is run with
5842 &`nobody`& as its user parameter, and the results are added to the message as a
5843 series of extra header line. In this case, the message is not rejected,
5844 whatever the spam score.
5848 This final line in the DATA ACL accepts the message unconditionally.
5851 .section "Router configuration" "SECID55"
5852 .cindex "default" "routers"
5853 .cindex "routers" "default"
5854 The router configuration comes next in the default configuration, introduced
5859 Routers are the modules in Exim that make decisions about where to send
5860 messages. An address is passed to each router in turn, until it is either
5861 accepted, or failed. This means that the order in which you define the routers
5862 matters. Each router is fully described in its own chapter later in this
5863 manual. Here we give only brief overviews.
5866 # driver = ipliteral
5867 # domains = !+local_domains
5868 # transport = remote_smtp
5870 .cindex "domain literal" "default router"
5871 This router is commented out because the majority of sites do not want to
5872 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5873 you uncomment this router, you also need to uncomment the setting of
5874 &%allow_domain_literals%& in the main part of the configuration.
5878 domains = ! +local_domains
5879 transport = remote_smtp
5880 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5883 The first uncommented router handles addresses that do not involve any local
5884 domains. This is specified by the line
5886 domains = ! +local_domains
5888 The &%domains%& option lists the domains to which this router applies, but the
5889 exclamation mark is a negation sign, so the router is used only for domains
5890 that are not in the domain list called &'local_domains'& (which was defined at
5891 the start of the configuration). The plus sign before &'local_domains'&
5892 indicates that it is referring to a named list. Addresses in other domains are
5893 passed on to the following routers.
5895 The name of the router driver is &(dnslookup)&,
5896 and is specified by the &%driver%& option. Do not be confused by the fact that
5897 the name of this router instance is the same as the name of the driver. The
5898 instance name is arbitrary, but the name set in the &%driver%& option must be
5899 one of the driver modules that is in the Exim binary.
5901 The &(dnslookup)& router routes addresses by looking up their domains in the
5902 DNS in order to obtain a list of hosts to which the address is routed. If the
5903 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5904 specified by the &%transport%& option. If the router does not find the domain
5905 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5906 the address fails and is bounced.
5908 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5909 be entirely ignored. This option is present because a number of cases have been
5910 encountered where MX records in the DNS point to host names
5911 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5912 Completely ignoring these IP addresses causes Exim to fail to route the
5913 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5914 continue to try to deliver the message periodically until the address timed
5921 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5923 file_transport = address_file
5924 pipe_transport = address_pipe
5926 Control reaches this and subsequent routers only for addresses in the local
5927 domains. This router checks to see whether the local part is defined as an
5928 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5929 data that it looks up from that file. If no data is found for the local part,
5930 the value of the &%data%& option is empty, causing the address to be passed to
5933 &_/etc/aliases_& is a conventional name for the system aliases file that is
5934 often used. That is why it is referenced by from the default configuration
5935 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5936 &_Local/Makefile_& before building Exim.
5941 # local_part_suffix = +* : -*
5942 # local_part_suffix_optional
5943 file = $home/.forward
5948 file_transport = address_file
5949 pipe_transport = address_pipe
5950 reply_transport = address_reply
5952 This is the most complicated router in the default configuration. It is another
5953 redirection router, but this time it is looking for forwarding data set up by
5954 individual users. The &%check_local_user%& setting specifies a check that the
5955 local part of the address is the login name of a local user. If it is not, the
5956 router is skipped. The two commented options that follow &%check_local_user%&,
5959 # local_part_suffix = +* : -*
5960 # local_part_suffix_optional
5962 .vindex "&$local_part_suffix$&"
5963 show how you can specify the recognition of local part suffixes. If the first
5964 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5965 by any sequence of characters, is removed from the local part and placed in the
5966 variable &$local_part_suffix$&. The second suffix option specifies that the
5967 presence of a suffix in the local part is optional. When a suffix is present,
5968 the check for a local login uses the local part with the suffix removed.
5970 When a local user account is found, the file called &_.forward_& in the user's
5971 home directory is consulted. If it does not exist, or is empty, the router
5972 declines. Otherwise, the contents of &_.forward_& are interpreted as
5973 redirection data (see chapter &<<CHAPredirect>>& for more details).
5975 .cindex "Sieve filter" "enabling in default router"
5976 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5977 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5978 is commented out by default), the contents of the file are interpreted as a set
5979 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5980 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5981 separate document entitled &'Exim's interfaces to mail filtering'&.
5983 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5984 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5985 There are two reasons for doing this:
5988 Whether or not a local user has a &_.forward_& file is not really relevant when
5989 checking an address for validity; it makes sense not to waste resources doing
5992 More importantly, when Exim is verifying addresses or handling an EXPN
5993 command during an SMTP session, it is running as the Exim user, not as root.
5994 The group is the Exim group, and no additional groups are set up.
5995 It may therefore not be possible for Exim to read users' &_.forward_& files at
5999 The setting of &%check_ancestor%& prevents the router from generating a new
6000 address that is the same as any previous address that was redirected. (This
6001 works round a problem concerning a bad interaction between aliasing and
6002 forwarding &-- see section &<<SECTredlocmai>>&).
6004 The final three option settings specify the transports that are to be used when
6005 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6006 auto-reply, respectively. For example, if a &_.forward_& file contains
6008 a.nother@elsewhere.example, /home/spqr/archive
6010 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6016 # local_part_suffix = +* : -*
6017 # local_part_suffix_optional
6018 transport = local_delivery
6020 The final router sets up delivery into local mailboxes, provided that the local
6021 part is the name of a local login, by accepting the address and assigning it to
6022 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6023 routers, so the address is bounced. The commented suffix settings fulfil the
6024 same purpose as they do for the &(userforward)& router.
6027 .section "Transport configuration" "SECID56"
6028 .cindex "default" "transports"
6029 .cindex "transports" "default"
6030 Transports define mechanisms for actually delivering messages. They operate
6031 only when referenced from routers, so the order in which they are defined does
6032 not matter. The transports section of the configuration starts with
6036 One remote transport and four local transports are defined.
6042 This transport is used for delivering messages over SMTP connections.
6043 The list of remote hosts comes from the router.
6044 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6045 It is negotiated between client and server
6046 and not expected to cause problems but can be disabled if needed.
6047 All other options are defaulted.
6051 file = /var/mail/$local_part
6058 This &(appendfile)& transport is used for local delivery to user mailboxes in
6059 traditional BSD mailbox format. By default it runs under the uid and gid of the
6060 local user, which requires the sticky bit to be set on the &_/var/mail_&
6061 directory. Some systems use the alternative approach of running mail deliveries
6062 under a particular group instead of using the sticky bit. The commented options
6063 show how this can be done.
6065 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6066 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6067 similarly-named options above.
6073 This transport is used for handling deliveries to pipes that are generated by
6074 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6075 option specifies that any output on stdout or stderr generated by the pipe is to
6076 be returned to the sender.
6084 This transport is used for handling deliveries to files that are generated by
6085 redirection. The name of the file is not specified in this instance of
6086 &(appendfile)&, because it comes from the &(redirect)& router.
6091 This transport is used for handling automatic replies generated by users'
6096 .section "Default retry rule" "SECID57"
6097 .cindex "retry" "default rule"
6098 .cindex "default" "retry rule"
6099 The retry section of the configuration file contains rules which affect the way
6100 Exim retries deliveries that cannot be completed at the first attempt. It is
6101 introduced by the line
6105 In the default configuration, there is just one rule, which applies to all
6108 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6110 This causes any temporarily failing address to be retried every 15 minutes for
6111 2 hours, then at intervals starting at one hour and increasing by a factor of
6112 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6113 is not delivered after 4 days of temporary failure, it is bounced.
6115 If the retry section is removed from the configuration, or is empty (that is,
6116 if no retry rules are defined), Exim will not retry deliveries. This turns
6117 temporary errors into permanent errors.
6120 .section "Rewriting configuration" "SECID58"
6121 The rewriting section of the configuration, introduced by
6125 contains rules for rewriting addresses in messages as they arrive. There are no
6126 rewriting rules in the default configuration file.
6130 .section "Authenticators configuration" "SECTdefconfauth"
6131 .cindex "AUTH" "configuration"
6132 The authenticators section of the configuration, introduced by
6134 begin authenticators
6136 defines mechanisms for the use of the SMTP AUTH command. The default
6137 configuration file contains two commented-out example authenticators
6138 which support plaintext username/password authentication using the
6139 standard PLAIN mechanism and the traditional but non-standard LOGIN
6140 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6141 to support most MUA software.
6143 The example PLAIN authenticator looks like this:
6146 # driver = plaintext
6147 # server_set_id = $auth2
6148 # server_prompts = :
6149 # server_condition = Authentication is not yet configured
6150 # server_advertise_condition = ${if def:tls_in_cipher }
6152 And the example LOGIN authenticator looks like this:
6155 # driver = plaintext
6156 # server_set_id = $auth1
6157 # server_prompts = <| Username: | Password:
6158 # server_condition = Authentication is not yet configured
6159 # server_advertise_condition = ${if def:tls_in_cipher }
6162 The &%server_set_id%& option makes Exim remember the authenticated username
6163 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6164 &%server_prompts%& option configures the &(plaintext)& authenticator so
6165 that it implements the details of the specific authentication mechanism,
6166 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6167 when Exim offers authentication to clients; in the examples, this is only
6168 when TLS or SSL has been started, so to enable the authenticators you also
6169 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6171 The &%server_condition%& setting defines how to verify that the username and
6172 password are correct. In the examples it just produces an error message.
6173 To make the authenticators work, you can use a string expansion
6174 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6176 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6177 usercode and password are in different positions.
6178 Chapter &<<CHAPplaintext>>& covers both.
6180 .ecindex IIDconfiwal
6184 . ////////////////////////////////////////////////////////////////////////////
6185 . ////////////////////////////////////////////////////////////////////////////
6187 .chapter "Regular expressions" "CHAPregexp"
6189 .cindex "regular expressions" "library"
6191 Exim supports the use of regular expressions in many of its options. It
6192 uses the PCRE regular expression library; this provides regular expression
6193 matching that is compatible with Perl 5. The syntax and semantics of
6194 regular expressions is discussed in many Perl reference books, and also in
6195 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6196 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6198 The documentation for the syntax and semantics of the regular expressions that
6199 are supported by PCRE is included in the PCRE distribution, and no further
6200 description is included here. The PCRE functions are called from Exim using
6201 the default option settings (that is, with no PCRE options set), except that
6202 the PCRE_CASELESS option is set when the matching is required to be
6205 In most cases, when a regular expression is required in an Exim configuration,
6206 it has to start with a circumflex, in order to distinguish it from plain text
6207 or an &"ends with"& wildcard. In this example of a configuration setting, the
6208 second item in the colon-separated list is a regular expression.
6210 domains = a.b.c : ^\\d{3} : *.y.z : ...
6212 The doubling of the backslash is required because of string expansion that
6213 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6214 of this issue, and a way of avoiding the need for doubling backslashes. The
6215 regular expression that is eventually used in this example contains just one
6216 backslash. The circumflex is included in the regular expression, and has the
6217 normal effect of &"anchoring"& it to the start of the string that is being
6220 There are, however, two cases where a circumflex is not required for the
6221 recognition of a regular expression: these are the &%match%& condition in a
6222 string expansion, and the &%matches%& condition in an Exim filter file. In
6223 these cases, the relevant string is always treated as a regular expression; if
6224 it does not start with a circumflex, the expression is not anchored, and can
6225 match anywhere in the subject string.
6227 In all cases, if you want a regular expression to match at the end of a string,
6228 you must code the $ metacharacter to indicate this. For example:
6230 domains = ^\\d{3}\\.example
6232 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6235 domains = ^\\d{3}\\.example\$
6237 if you want &'example'& to be the top-level domain. The backslash before the
6238 $ is needed because string expansion also interprets dollar characters.
6242 . ////////////////////////////////////////////////////////////////////////////
6243 . ////////////////////////////////////////////////////////////////////////////
6245 .chapter "File and database lookups" "CHAPfdlookup"
6246 .scindex IIDfidalo1 "file" "lookups"
6247 .scindex IIDfidalo2 "database" "lookups"
6248 .cindex "lookup" "description of"
6249 Exim can be configured to look up data in files or databases as it processes
6250 messages. Two different kinds of syntax are used:
6253 A string that is to be expanded may contain explicit lookup requests. These
6254 cause parts of the string to be replaced by data that is obtained from the
6255 lookup. Lookups of this type are conditional expansion items. Different results
6256 can be defined for the cases of lookup success and failure. See chapter
6257 &<<CHAPexpand>>&, where string expansions are described in detail.
6258 The key for the lookup is specified as part of the string expansion.
6260 Lists of domains, hosts, and email addresses can contain lookup requests as a
6261 way of avoiding excessively long linear lists. In this case, the data that is
6262 returned by the lookup is often (but not always) discarded; whether the lookup
6263 succeeds or fails is what really counts. These kinds of list are described in
6264 chapter &<<CHAPdomhosaddlists>>&.
6265 The key for the lookup is given by the context in which the list is expanded.
6268 String expansions, lists, and lookups interact with each other in such a way
6269 that there is no order in which to describe any one of them that does not
6270 involve references to the others. Each of these three chapters makes more sense
6271 if you have read the other two first. If you are reading this for the first
6272 time, be aware that some of it will make a lot more sense after you have read
6273 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6275 .section "Examples of different lookup syntax" "SECID60"
6276 It is easy to confuse the two different kinds of lookup, especially as the
6277 lists that may contain the second kind are always expanded before being
6278 processed as lists. Therefore, they may also contain lookups of the first kind.
6279 Be careful to distinguish between the following two examples:
6281 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6282 domains = lsearch;/some/file
6284 The first uses a string expansion, the result of which must be a domain list.
6285 No strings have been specified for a successful or a failing lookup; the
6286 defaults in this case are the looked-up data and an empty string, respectively.
6287 The expansion takes place before the string is processed as a list, and the
6288 file that is searched could contain lines like this:
6290 192.168.3.4: domain1:domain2:...
6291 192.168.1.9: domain3:domain4:...
6293 When the lookup succeeds, the result of the expansion is a list of domains (and
6294 possibly other types of item that are allowed in domain lists).
6296 In the second example, the lookup is a single item in a domain list. It causes
6297 Exim to use a lookup to see if the domain that is being processed can be found
6298 in the file. The file could contains lines like this:
6303 Any data that follows the keys is not relevant when checking that the domain
6304 matches the list item.
6306 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6307 Consider a file containing lines like this:
6309 192.168.5.6: lsearch;/another/file
6311 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6312 first &%domains%& setting above generates the second setting, which therefore
6313 causes a second lookup to occur.
6315 The rest of this chapter describes the different lookup types that are
6316 available. Any of them can be used in any part of the configuration where a
6317 lookup is permitted.
6320 .section "Lookup types" "SECID61"
6321 .cindex "lookup" "types of"
6322 .cindex "single-key lookup" "definition of"
6323 Two different types of data lookup are implemented:
6326 The &'single-key'& type requires the specification of a file in which to look,
6327 and a single key to search for. The key must be a non-empty string for the
6328 lookup to succeed. The lookup type determines how the file is searched.
6330 .cindex "query-style lookup" "definition of"
6331 The &'query-style'& type accepts a generalized database query. No particular
6332 key value is assumed by Exim for query-style lookups. You can use whichever
6333 Exim variables you need to construct the database query.
6336 The code for each lookup type is in a separate source file that is included in
6337 the binary of Exim only if the corresponding compile-time option is set. The
6338 default settings in &_src/EDITME_& are:
6343 which means that only linear searching and DBM lookups are included by default.
6344 For some types of lookup (e.g. SQL databases), you need to install appropriate
6345 libraries and header files before building Exim.
6350 .section "Single-key lookup types" "SECTsinglekeylookups"
6351 .cindex "lookup" "single-key types"
6352 .cindex "single-key lookup" "list of types"
6353 The following single-key lookup types are implemented:
6356 .cindex "cdb" "description of"
6357 .cindex "lookup" "cdb"
6358 .cindex "binary zero" "in lookup key"
6359 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6360 string without a terminating binary zero. The cdb format is designed for
6361 indexed files that are read frequently and never updated, except by total
6362 re-creation. As such, it is particularly suitable for large files containing
6363 aliases or other indexed data referenced by an MTA. Information about cdb can
6364 be found in several places:
6366 &url(http://www.pobox.com/~djb/cdb.html)
6367 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6368 &url(http://packages.debian.org/stable/utils/freecdb.html)
6370 A cdb distribution is not needed in order to build Exim with cdb support,
6371 because the code for reading cdb files is included directly in Exim itself.
6372 However, no means of building or testing cdb files is provided with Exim, so
6373 you need to obtain a cdb distribution in order to do this.
6375 .cindex "DBM" "lookup type"
6376 .cindex "lookup" "dbm"
6377 .cindex "binary zero" "in lookup key"
6378 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6379 DBM file by looking up the record with the given key. A terminating binary
6380 zero is included in the key that is passed to the DBM library. See section
6381 &<<SECTdb>>& for a discussion of DBM libraries.
6383 .cindex "Berkeley DB library" "file format"
6384 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6385 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6386 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6387 the DB_UNKNOWN option. This enables it to handle any of the types of database
6388 that the library supports, and can be useful for accessing DBM files created by
6389 other applications. (For earlier DB versions, DB_HASH is always used.)
6391 .cindex "lookup" "dbmjz"
6392 .cindex "lookup" "dbm &-- embedded NULs"
6394 .cindex "dbmjz lookup type"
6395 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6396 interpreted as an Exim list; the elements of the list are joined together with
6397 ASCII NUL characters to form the lookup key. An example usage would be to
6398 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6399 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6400 &(cram_md5)& authenticator.
6402 .cindex "lookup" "dbmnz"
6403 .cindex "lookup" "dbm &-- terminating zero"
6404 .cindex "binary zero" "in lookup key"
6406 .cindex "&_/etc/userdbshadow.dat_&"
6407 .cindex "dbmnz lookup type"
6408 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6409 is not included in the key that is passed to the DBM library. You may need this
6410 if you want to look up data in files that are created by or shared with some
6411 other application that does not use terminating zeros. For example, you need to
6412 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6413 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6414 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6415 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6417 .cindex "lookup" "dsearch"
6418 .cindex "dsearch lookup type"
6419 &(dsearch)&: The given file must be a directory; this is searched for an entry
6420 whose name is the key by calling the &[lstat()]& function. The key may not
6421 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6422 the lookup is the name of the entry, which may be a file, directory,
6423 symbolic link, or any other kind of directory entry. An example of how this
6424 lookup can be used to support virtual domains is given in section
6425 &<<SECTvirtualdomains>>&.
6427 .cindex "lookup" "iplsearch"
6428 .cindex "iplsearch lookup type"
6429 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6430 terminated by a colon or white space or the end of the line. The keys in the
6431 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6432 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6433 being interpreted as a key terminator. For example:
6435 1.2.3.4: data for 1.2.3.4
6436 192.168.0.0/16: data for 192.168.0.0/16
6437 "abcd::cdab": data for abcd::cdab
6438 "abcd:abcd::/32" data for abcd:abcd::/32
6440 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6441 file is searched linearly, using the CIDR masks where present, until a matching
6442 key is found. The first key that matches is used; there is no attempt to find a
6443 &"best"& match. Apart from the way the keys are matched, the processing for
6444 &(iplsearch)& is the same as for &(lsearch)&.
6446 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6447 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6448 lookup types support only literal keys.
6450 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6451 the implicit key is the host's IP address rather than its name (see section
6452 &<<SECThoslispatsikey>>&).
6454 .cindex "linear search"
6455 .cindex "lookup" "lsearch"
6456 .cindex "lsearch lookup type"
6457 .cindex "case sensitivity" "in lsearch lookup"
6458 &(lsearch)&: The given file is a text file that is searched linearly for a
6459 line beginning with the search key, terminated by a colon or white space or the
6460 end of the line. The search is case-insensitive; that is, upper and lower case
6461 letters are treated as the same. The first occurrence of the key that is found
6462 in the file is used.
6464 White space between the key and the colon is permitted. The remainder of the
6465 line, with leading and trailing white space removed, is the data. This can be
6466 continued onto subsequent lines by starting them with any amount of white
6467 space, but only a single space character is included in the data at such a
6468 junction. If the data begins with a colon, the key must be terminated by a
6473 Empty lines and lines beginning with # are ignored, even if they occur in the
6474 middle of an item. This is the traditional textual format of alias files. Note
6475 that the keys in an &(lsearch)& file are literal strings. There is no
6476 wildcarding of any kind.
6478 .cindex "lookup" "lsearch &-- colons in keys"
6479 .cindex "white space" "in lsearch key"
6480 In most &(lsearch)& files, keys are not required to contain colons or #
6481 characters, or white space. However, if you need this feature, it is available.
6482 If a key begins with a doublequote character, it is terminated only by a
6483 matching quote (or end of line), and the normal escaping rules apply to its
6484 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6485 quoted keys (exactly as for unquoted keys). There is no special handling of
6486 quotes for the data part of an &(lsearch)& line.
6489 .cindex "NIS lookup type"
6490 .cindex "lookup" "NIS"
6491 .cindex "binary zero" "in lookup key"
6492 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6493 the given key, without a terminating binary zero. There is a variant called
6494 &(nis0)& which does include the terminating binary zero in the key. This is
6495 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6496 aliases; the full map names must be used.
6499 .cindex "wildlsearch lookup type"
6500 .cindex "lookup" "wildlsearch"
6501 .cindex "nwildlsearch lookup type"
6502 .cindex "lookup" "nwildlsearch"
6503 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6504 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6505 the file may be wildcarded. The difference between these two lookup types is
6506 that for &(wildlsearch)&, each key in the file is string-expanded before being
6507 used, whereas for &(nwildlsearch)&, no expansion takes place.
6509 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6510 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6511 file that are regular expressions can be made case-sensitive by the use of
6512 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6514 . ==== As this is a nested list, any displays it contains must be indented
6515 . ==== as otherwise they are too far to the left.
6518 The string may begin with an asterisk to mean &"ends with"&. For example:
6520 *.a.b.c data for anything.a.b.c
6521 *fish data for anythingfish
6524 The string may begin with a circumflex to indicate a regular expression. For
6525 example, for &(wildlsearch)&:
6527 ^\N\d+\.a\.b\N data for <digits>.a.b
6529 Note the use of &`\N`& to disable expansion of the contents of the regular
6530 expression. If you are using &(nwildlsearch)&, where the keys are not
6531 string-expanded, the equivalent entry is:
6533 ^\d+\.a\.b data for <digits>.a.b
6535 The case-insensitive flag is set at the start of compiling the regular
6536 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6537 For example, to make the entire pattern case-sensitive:
6539 ^(?-i)\d+\.a\.b data for <digits>.a.b
6542 If the regular expression contains white space or colon characters, you must
6543 either quote it (see &(lsearch)& above), or represent these characters in other
6544 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6545 colon. This may be easier than quoting, because if you quote, you have to
6546 escape all the backslashes inside the quotes.
6548 &*Note*&: It is not possible to capture substrings in a regular expression
6549 match for later use, because the results of all lookups are cached. If a lookup
6550 is repeated, the result is taken from the cache, and no actual pattern matching
6551 takes place. The values of all the numeric variables are unset after a
6552 &((n)wildlsearch)& match.
6555 Although I cannot see it being of much use, the general matching function that
6556 is used to implement &((n)wildlsearch)& means that the string may begin with a
6557 lookup name terminated by a semicolon, and followed by lookup data. For
6560 cdb;/some/file data for keys that match the file
6562 The data that is obtained from the nested lookup is discarded.
6565 Keys that do not match any of these patterns are interpreted literally. The
6566 continuation rules for the data are the same as for &(lsearch)&, and keys may
6567 be followed by optional colons.
6569 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6570 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6571 lookup types support only literal keys.
6575 .section "Query-style lookup types" "SECID62"
6576 .cindex "lookup" "query-style types"
6577 .cindex "query-style lookup" "list of types"
6578 The supported query-style lookup types are listed below. Further details about
6579 many of them are given in later sections.
6582 .cindex "DNS" "as a lookup type"
6583 .cindex "lookup" "DNS"
6584 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6585 are given in the supplied query. The resulting data is the contents of the
6586 records. See section &<<SECTdnsdb>>&.
6588 .cindex "InterBase lookup type"
6589 .cindex "lookup" "InterBase"
6590 &(ibase)&: This does a lookup in an InterBase database.
6592 .cindex "LDAP" "lookup type"
6593 .cindex "lookup" "LDAP"
6594 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6595 returns attributes from a single entry. There is a variant called &(ldapm)&
6596 that permits values from multiple entries to be returned. A third variant
6597 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6598 any attribute values. See section &<<SECTldap>>&.
6600 .cindex "MySQL" "lookup type"
6601 .cindex "lookup" "MySQL"
6602 &(mysql)&: The format of the query is an SQL statement that is passed to a
6603 MySQL database. See section &<<SECTsql>>&.
6605 .cindex "NIS+ lookup type"
6606 .cindex "lookup" "NIS+"
6607 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6608 the field to be returned. See section &<<SECTnisplus>>&.
6610 .cindex "Oracle" "lookup type"
6611 .cindex "lookup" "Oracle"
6612 &(oracle)&: The format of the query is an SQL statement that is passed to an
6613 Oracle database. See section &<<SECTsql>>&.
6615 .cindex "lookup" "passwd"
6616 .cindex "passwd lookup type"
6617 .cindex "&_/etc/passwd_&"
6618 &(passwd)& is a query-style lookup with queries that are just user names. The
6619 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6620 success, the result string is the same as you would get from an &(lsearch)&
6621 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6622 password value. For example:
6624 *:42:42:King Rat:/home/kr:/bin/bash
6627 .cindex "PostgreSQL lookup type"
6628 .cindex "lookup" "PostgreSQL"
6629 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6630 PostgreSQL database. See section &<<SECTsql>>&.
6634 .cindex "Redis lookup type"
6635 .cindex lookup Redis
6636 &(redis)&: The format of the query is an SQL statement that is passed to a
6637 Redis database. See section &<<SECTsql>>&.
6641 .cindex "sqlite lookup type"
6642 .cindex "lookup" "sqlite"
6643 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6644 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6647 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6648 not likely to be useful in normal operation.
6650 .cindex "whoson lookup type"
6651 .cindex "lookup" "whoson"
6652 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6653 allows a server to check whether a particular (dynamically allocated) IP
6654 address is currently allocated to a known (trusted) user and, optionally, to
6655 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6656 at one time for &"POP before SMTP"& authentication, but that approach has been
6657 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6658 &"POP before SMTP"& checking using ACL statements such as
6660 require condition = \
6661 ${lookup whoson {$sender_host_address}{yes}{no}}
6663 The query consists of a single IP address. The value returned is the name of
6664 the authenticated user, which is stored in the variable &$value$&. However, in
6665 this example, the data in &$value$& is not used; the result of the lookup is
6666 one of the fixed strings &"yes"& or &"no"&.
6671 .section "Temporary errors in lookups" "SECID63"
6672 .cindex "lookup" "temporary error in"
6673 Lookup functions can return temporary error codes if the lookup cannot be
6674 completed. For example, an SQL or LDAP database might be unavailable. For this
6675 reason, it is not advisable to use a lookup that might do this for critical
6676 options such as a list of local domains.
6678 When a lookup cannot be completed in a router or transport, delivery
6679 of the message (to the relevant address) is deferred, as for any other
6680 temporary error. In other circumstances Exim may assume the lookup has failed,
6681 or may give up altogether.
6685 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6686 .cindex "wildcard lookups"
6687 .cindex "lookup" "default values"
6688 .cindex "lookup" "wildcard"
6689 .cindex "lookup" "* added to type"
6690 .cindex "default" "in single-key lookups"
6691 In this context, a &"default value"& is a value specified by the administrator
6692 that is to be used if a lookup fails.
6694 &*Note:*& This section applies only to single-key lookups. For query-style
6695 lookups, the facilities of the query language must be used. An attempt to
6696 specify a default for a query-style lookup provokes an error.
6698 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6699 and the initial lookup fails, the key &"*"& is looked up in the file to
6700 provide a default value. See also the section on partial matching below.
6702 .cindex "*@ with single-key lookup"
6703 .cindex "lookup" "*@ added to type"
6704 .cindex "alias file" "per-domain default"
6705 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6706 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6707 character, a second lookup is done with everything before the last @ replaced
6708 by *. This makes it possible to provide per-domain defaults in alias files
6709 that include the domains in the keys. If the second lookup fails (or doesn't
6710 take place because there is no @ in the key), &"*"& is looked up.
6711 For example, a &(redirect)& router might contain:
6713 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6715 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6716 looks up these keys, in this order:
6722 The data is taken from whichever key it finds first. &*Note*&: In an
6723 &(lsearch)& file, this does not mean the first of these keys in the file. A
6724 complete scan is done for each key, and only if it is not found at all does
6725 Exim move on to try the next key.
6729 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6730 .cindex "partial matching"
6731 .cindex "wildcard lookups"
6732 .cindex "lookup" "partial matching"
6733 .cindex "lookup" "wildcard"
6734 .cindex "asterisk" "in search type"
6735 The normal operation of a single-key lookup is to search the file for an exact
6736 match with the given key. However, in a number of situations where domains are
6737 being looked up, it is useful to be able to do partial matching. In this case,
6738 information in the file that has a key starting with &"*."& is matched by any
6739 domain that ends with the components that follow the full stop. For example, if
6740 a key in a DBM file is
6742 *.dates.fict.example
6744 then when partial matching is enabled this is matched by (amongst others)
6745 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6746 by &'dates.fict.example'&, if that does not appear as a separate key in the
6749 &*Note*&: Partial matching is not available for query-style lookups. It is
6750 also not available for any lookup items in address lists (see section
6751 &<<SECTaddresslist>>&).
6753 Partial matching is implemented by doing a series of separate lookups using
6754 keys constructed by modifying the original subject key. This means that it can
6755 be used with any of the single-key lookup types, provided that
6756 partial matching keys
6757 beginning with a special prefix (default &"*."&) are included in the data file.
6758 Keys in the file that do not begin with the prefix are matched only by
6759 unmodified subject keys when partial matching is in use.
6761 Partial matching is requested by adding the string &"partial-"& to the front of
6762 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6763 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6764 is added at the start of the subject key, and it is looked up again. If that
6765 fails, further lookups are tried with dot-separated components removed from the
6766 start of the subject key, one-by-one, and &"*."& added on the front of what
6769 A minimum number of two non-* components are required. This can be adjusted
6770 by including a number before the hyphen in the search type. For example,
6771 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6772 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6773 subject key is &'2250.dates.fict.example'& then the following keys are looked
6774 up when the minimum number of non-* components is two:
6776 2250.dates.fict.example
6777 *.2250.dates.fict.example
6778 *.dates.fict.example
6781 As soon as one key in the sequence is successfully looked up, the lookup
6784 .cindex "lookup" "partial matching &-- changing prefix"
6785 .cindex "prefix" "for partial matching"
6786 The use of &"*."& as the partial matching prefix is a default that can be
6787 changed. The motivation for this feature is to allow Exim to operate with file
6788 formats that are used by other MTAs. A different prefix can be supplied in
6789 parentheses instead of the hyphen after &"partial"&. For example:
6791 domains = partial(.)lsearch;/some/file
6793 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6794 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6795 components is unchanged). The prefix may consist of any punctuation characters
6796 other than a closing parenthesis. It may be empty, for example:
6798 domains = partial1()cdb;/some/file
6800 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6801 &`a.b.c`&, &`b.c`&, and &`c`&.
6803 If &"partial0"& is specified, what happens at the end (when the lookup with
6804 just one non-wild component has failed, and the original key is shortened right
6805 down to the null string) depends on the prefix:
6808 If the prefix has zero length, the whole lookup fails.
6810 If the prefix has length 1, a lookup for just the prefix is done. For
6811 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6813 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6814 remainder is looked up. With the default prefix, therefore, the final lookup is
6815 for &"*"& on its own.
6817 Otherwise, the whole prefix is looked up.
6821 If the search type ends in &"*"& or &"*@"& (see section
6822 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6823 this implies happens after all partial lookups have failed. If &"partial0"& is
6824 specified, adding &"*"& to the search type has no effect with the default
6825 prefix, because the &"*"& key is already included in the sequence of partial
6826 lookups. However, there might be a use for lookup types such as
6827 &"partial0(.)lsearch*"&.
6829 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6830 in domain lists and the like. Partial matching works only in terms of
6831 dot-separated components; a key such as &`*fict.example`&
6832 in a database file is useless, because the asterisk in a partial matching
6833 subject key is always followed by a dot.
6838 .section "Lookup caching" "SECID64"
6839 .cindex "lookup" "caching"
6840 .cindex "caching" "lookup data"
6841 Exim caches all lookup results in order to avoid needless repetition of
6842 lookups. However, because (apart from the daemon) Exim operates as a collection
6843 of independent, short-lived processes, this caching applies only within a
6844 single Exim process. There is no inter-process lookup caching facility.
6846 For single-key lookups, Exim keeps the relevant files open in case there is
6847 another lookup that needs them. In some types of configuration this can lead to
6848 many files being kept open for messages with many recipients. To avoid hitting
6849 the operating system limit on the number of simultaneously open files, Exim
6850 closes the least recently used file when it needs to open more files than its
6851 own internal limit, which can be changed via the &%lookup_open_max%& option.
6853 The single-key lookup files are closed and the lookup caches are flushed at
6854 strategic points during delivery &-- for example, after all routing is
6860 .section "Quoting lookup data" "SECID65"
6861 .cindex "lookup" "quoting"
6862 .cindex "quoting" "in lookups"
6863 When data from an incoming message is included in a query-style lookup, there
6864 is the possibility of special characters in the data messing up the syntax of
6865 the query. For example, a NIS+ query that contains
6869 will be broken if the local part happens to contain a closing square bracket.
6870 For NIS+, data can be enclosed in double quotes like this:
6872 [name="$local_part"]
6874 but this still leaves the problem of a double quote in the data. The rule for
6875 NIS+ is that double quotes must be doubled. Other lookup types have different
6876 rules, and to cope with the differing requirements, an expansion operator
6877 of the following form is provided:
6879 ${quote_<lookup-type>:<string>}
6881 For example, the safest way to write the NIS+ query is
6883 [name="${quote_nisplus:$local_part}"]
6885 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6886 operator can be used for all lookup types, but has no effect for single-key
6887 lookups, since no quoting is ever needed in their key strings.
6892 .section "More about dnsdb" "SECTdnsdb"
6893 .cindex "dnsdb lookup"
6894 .cindex "lookup" "dnsdb"
6895 .cindex "DNS" "as a lookup type"
6896 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6897 of a record type and a domain name, separated by an equals sign. For example,
6898 an expansion string could contain:
6900 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6902 If the lookup succeeds, the result is placed in &$value$&, which in this case
6903 is used on its own as the result. If the lookup does not succeed, the
6904 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6905 &<<SECTforexpfai>>& for an explanation of what this means.
6907 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
6908 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
6909 If no type is given, TXT is assumed.
6911 For any record type, if multiple records are found, the data is returned as a
6912 concatenation, with newline as the default separator. The order, of course,
6913 depends on the DNS resolver. You can specify a different separator character
6914 between multiple records by putting a right angle-bracket followed immediately
6915 by the new separator at the start of the query. For example:
6917 ${lookup dnsdb{>: a=host1.example}}
6919 It is permitted to specify a space as the separator character. Further
6920 white space is ignored.
6921 For lookup types that return multiple fields per record,
6922 an alternate field separator can be specified using a comma after the main
6923 separator character, followed immediately by the field separator.
6925 .cindex "PTR record" "in &(dnsdb)& lookup"
6926 When the type is PTR,
6927 the data can be an IP address, written as normal; inversion and the addition of
6928 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6930 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6932 If the data for a PTR record is not a syntactically valid IP address, it is not
6933 altered and nothing is added.
6935 .cindex "MX record" "in &(dnsdb)& lookup"
6936 .cindex "SRV record" "in &(dnsdb)& lookup"
6937 For an MX lookup, both the preference value and the host name are returned for
6938 each record, separated by a space. For an SRV lookup, the priority, weight,
6939 port, and host name are returned for each record, separated by spaces.
6940 The field separator can be modified as above.
6942 .cindex "TXT record" "in &(dnsdb)& lookup"
6943 .cindex "SPF record" "in &(dnsdb)& lookup"
6944 For TXT records with multiple items of data, only the first item is returned,
6945 unless a field separator is specified.
6946 To concatenate items without a separator, use a semicolon instead.
6948 default behaviour is to concatenate multiple items without using a separator.
6950 ${lookup dnsdb{>\n,: txt=a.b.example}}
6951 ${lookup dnsdb{>\n; txt=a.b.example}}
6952 ${lookup dnsdb{spf=example.org}}
6954 It is permitted to specify a space as the separator character. Further
6955 white space is ignored.
6957 .cindex "SOA record" "in &(dnsdb)& lookup"
6958 For an SOA lookup, while no result is obtained the lookup is redone with
6959 successively more leading components dropped from the given domain.
6960 Only the primary-nameserver field is returned unless a field separator is
6963 ${lookup dnsdb{>:,; soa=a.b.example.com}}
6966 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
6967 .cindex "dnsdb modifiers"
6968 .cindex "modifiers" "dnsdb"
6969 .cindex "options" "dnsdb"
6970 Modifiers for &(dnsdb)& lookups are given by optional keywords,
6971 each followed by a comma,
6972 that may appear before the record type.
6974 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6975 temporary DNS error for any of them, the behaviour is controlled by
6976 a defer-option modifier.
6977 The possible keywords are
6978 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
6979 With &"strict"& behaviour, any temporary DNS error causes the
6980 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6981 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6982 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6983 error causes the whole lookup to defer only if none of the other lookups
6984 succeed. The default is &"lax"&, so the following lookups are equivalent:
6986 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6987 ${lookup dnsdb{a=one.host.com:two.host.com}}
6989 Thus, in the default case, as long as at least one of the DNS lookups
6990 yields some data, the lookup succeeds.
6992 .cindex "DNSSEC" "dns lookup"
6993 Use of &(DNSSEC)& is controlled by a dnssec modifier.
6994 The possible keywords are
6995 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
6996 With &"strict"& or &"lax"& DNSSEC information is requested
6998 With &"strict"& a response from the DNS resolver that
6999 is not labelled as authenticated data
7000 is treated as equivalent to a temporary DNS error.
7001 The default is &"never"&.
7003 See also the &$lookup_dnssec_authenticated$& variable.
7005 .cindex timeout "dns lookup"
7006 .cindex "DNS" timeout
7007 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7008 The form is &"retrans_VAL"& where VAL is an Exim time specification
7010 The default value is set by the main configuration option &%dns_retrans%&.
7012 Retries for the dnsdb lookup can be controlled by a retry modifier.
7013 The form if &"retry_VAL"& where VAL is an integer.
7014 The default count is set by the main configuration option &%dns_retry%&.
7017 .cindex cacheing "of dns lookup"
7018 .cindex TTL "of dns lookup"
7020 Dnsdb lookup results are cached within a single process (and its children).
7021 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7022 value of the set of returned DNS records.
7026 .section "Pseudo dnsdb record types" "SECID66"
7027 .cindex "MX record" "in &(dnsdb)& lookup"
7028 By default, both the preference value and the host name are returned for
7029 each MX record, separated by a space. If you want only host names, you can use
7030 the pseudo-type MXH:
7032 ${lookup dnsdb{mxh=a.b.example}}
7034 In this case, the preference values are omitted, and just the host names are
7037 .cindex "name server for enclosing domain"
7038 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7039 records on the given domain, but if none are found, it removes the first
7040 component of the domain name, and tries again. This process continues until NS
7041 records are found or there are no more components left (or there is a DNS
7042 error). In other words, it may return the name servers for a top-level domain,
7043 but it never returns the root name servers. If there are no NS records for the
7044 top-level domain, the lookup fails. Consider these examples:
7046 ${lookup dnsdb{zns=xxx.quercite.com}}
7047 ${lookup dnsdb{zns=xxx.edu}}
7049 Assuming that in each case there are no NS records for the full domain name,
7050 the first returns the name servers for &%quercite.com%&, and the second returns
7051 the name servers for &%edu%&.
7053 You should be careful about how you use this lookup because, unless the
7054 top-level domain does not exist, the lookup always returns some host names. The
7055 sort of use to which this might be put is for seeing if the name servers for a
7056 given domain are on a blacklist. You can probably assume that the name servers
7057 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7060 .cindex "CSA" "in &(dnsdb)& lookup"
7061 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7062 records according to the CSA rules, which are described in section
7063 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7064 not sufficient because of the extra parent domain search behaviour of CSA. The
7065 result of a successful lookup such as:
7067 ${lookup dnsdb {csa=$sender_helo_name}}
7069 has two space-separated fields: an authorization code and a target host name.
7070 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7071 authorization required but absent, or &"?"& for unknown.
7073 .cindex "A+" "in &(dnsdb)& lookup"
7074 The pseudo-type A+ performs an AAAA
7075 and then an A lookup. All results are returned; defer processing
7076 (see below) is handled separately for each lookup. Example:
7078 ${lookup dnsdb {>; a+=$sender_helo_name}}
7082 .section "Multiple dnsdb lookups" "SECID67"
7083 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7084 However, you can specify a list of domains or IP addresses in a single
7085 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7086 the default separator, but with the ability to change this. For example:
7088 ${lookup dnsdb{one.domain.com:two.domain.com}}
7089 ${lookup dnsdb{a=one.host.com:two.host.com}}
7090 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7092 In order to retain backwards compatibility, there is one special case: if
7093 the lookup type is PTR and no change of separator is specified, Exim looks
7094 to see if the rest of the string is precisely one IPv6 address. In this
7095 case, it does not treat it as a list.
7097 The data from each lookup is concatenated, with newline separators by default,
7098 in the same way that multiple DNS records for a single item are handled. A
7099 different separator can be specified, as described above.
7104 .section "More about LDAP" "SECTldap"
7105 .cindex "LDAP" "lookup, more about"
7106 .cindex "lookup" "LDAP"
7107 .cindex "Solaris" "LDAP"
7108 The original LDAP implementation came from the University of Michigan; this has
7109 become &"Open LDAP"&, and there are now two different releases. Another
7110 implementation comes from Netscape, and Solaris 7 and subsequent releases
7111 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7112 the lookup function level, their error handling is different. For this reason
7113 it is necessary to set a compile-time variable when building Exim with LDAP, to
7114 indicate which LDAP library is in use. One of the following should appear in
7115 your &_Local/Makefile_&:
7117 LDAP_LIB_TYPE=UMICHIGAN
7118 LDAP_LIB_TYPE=OPENLDAP1
7119 LDAP_LIB_TYPE=OPENLDAP2
7120 LDAP_LIB_TYPE=NETSCAPE
7121 LDAP_LIB_TYPE=SOLARIS
7123 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7124 same interface as the University of Michigan version.
7126 There are three LDAP lookup types in Exim. These behave slightly differently in
7127 the way they handle the results of a query:
7130 &(ldap)& requires the result to contain just one entry; if there are more, it
7133 &(ldapdn)& also requires the result to contain just one entry, but it is the
7134 Distinguished Name that is returned rather than any attribute values.
7136 &(ldapm)& permits the result to contain more than one entry; the attributes
7137 from all of them are returned.
7141 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7142 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7143 the data returned by a successful lookup is described in the next section.
7144 First we explain how LDAP queries are coded.
7147 .section "Format of LDAP queries" "SECTforldaque"
7148 .cindex "LDAP" "query format"
7149 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7150 the configuration of a &(redirect)& router one might have this setting:
7152 data = ${lookup ldap \
7153 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7154 c=UK?mailbox?base?}}
7156 .cindex "LDAP" "with TLS"
7157 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7158 secure (encrypted) LDAP connections. The second of these ensures that an
7159 encrypted TLS connection is used.
7161 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7162 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7163 See the &%ldap_start_tls%& option.
7165 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7166 controlled. Every part of the TLS configuration can be configured by settings in
7167 &_exim.conf_&. Depending on the version of the client libraries installed on
7168 your system, some of the initialization may have required setting options in
7169 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7170 certificates. This revealed a nuance where the current UID that exim was
7171 running as could affect which config files it read. With Exim 4.83, these
7172 methods become optional, only taking effect if not specifically set in
7176 .section "LDAP quoting" "SECID68"
7177 .cindex "LDAP" "quoting"
7178 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7179 and the second because the LDAP query is represented as a URL. Furthermore,
7180 within an LDAP query, two different kinds of quoting are required. For this
7181 reason, there are two different LDAP-specific quoting operators.
7183 The &%quote_ldap%& operator is designed for use on strings that are part of
7184 filter specifications. Conceptually, it first does the following conversions on
7192 in accordance with RFC 2254. The resulting string is then quoted according
7193 to the rules for URLs, that is, all non-alphanumeric characters except
7197 are converted to their hex values, preceded by a percent sign. For example:
7199 ${quote_ldap: a(bc)*, a<yz>; }
7203 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7205 Removing the URL quoting, this is (with a leading and a trailing space):
7207 a\28bc\29\2A, a<yz>;
7209 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7210 base DN specifications in queries. Conceptually, it first converts the string
7211 by inserting a backslash in front of any of the following characters:
7215 It also inserts a backslash before any leading spaces or # characters, and
7216 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7217 is then quoted according to the rules for URLs. For example:
7219 ${quote_ldap_dn: a(bc)*, a<yz>; }
7223 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7225 Removing the URL quoting, this is (with a trailing space):
7227 \ a(bc)*\, a\<yz\>\;\
7229 There are some further comments about quoting in the section on LDAP
7230 authentication below.
7233 .section "LDAP connections" "SECID69"
7234 .cindex "LDAP" "connections"
7235 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7236 is in use, via a Unix domain socket. The example given above does not specify
7237 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7240 ldap://<hostname>:<port>/...
7242 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7243 used. When no server is specified in a query, a list of default servers is
7244 taken from the &%ldap_default_servers%& configuration option. This supplies a
7245 colon-separated list of servers which are tried in turn until one successfully
7246 handles a query, or there is a serious error. Successful handling either
7247 returns the requested data, or indicates that it does not exist. Serious errors
7248 are syntactical, or multiple values when only a single value is expected.
7249 Errors which cause the next server to be tried are connection failures, bind
7250 failures, and timeouts.
7252 For each server name in the list, a port number can be given. The standard way
7253 of specifying a host and port is to use a colon separator (RFC 1738). Because
7254 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7255 doubled. For example
7257 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7259 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7260 to the LDAP library with no server name, and the library's default (normally
7261 the local host) is used.
7263 If you are using the OpenLDAP library, you can connect to an LDAP server using
7264 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7265 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7266 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7269 For this type of connection, instead of a host name for the server, a pathname
7270 for the socket is required, and the port number is not relevant. The pathname
7271 can be specified either as an item in &%ldap_default_servers%&, or inline in
7272 the query. In the former case, you can have settings such as
7274 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7276 When the pathname is given in the query, you have to escape the slashes as
7277 &`%2F`& to fit in with the LDAP URL syntax. For example:
7279 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7281 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7282 a pathname, it uses the Unix domain socket code, even if the query actually
7283 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7284 socket connection. This behaviour means that you can use a setting of
7285 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7286 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7287 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7290 If an explicit &`ldapi`& type is given in a query when a host name is
7291 specified, an error is diagnosed. However, if there are more items in
7292 &%ldap_default_servers%&, they are tried. In other words:
7295 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7298 Using &`ldapi`& with a host name causes an error.
7302 Using &`ldapi`& with no host or path in the query, and no setting of
7303 &%ldap_default_servers%&, does whatever the library does by default.
7307 .section "LDAP authentication and control information" "SECID70"
7308 .cindex "LDAP" "authentication"
7309 The LDAP URL syntax provides no way of passing authentication and other control
7310 information to the server. To make this possible, the URL in an LDAP query may
7311 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7312 spaces. If a value contains spaces it must be enclosed in double quotes, and
7313 when double quotes are used, backslash is interpreted in the usual way inside
7314 them. The following names are recognized:
7316 &`DEREFERENCE`& set the dereferencing parameter
7317 &`NETTIME `& set a timeout for a network operation
7318 &`USER `& set the DN, for authenticating the LDAP bind
7319 &`PASS `& set the password, likewise
7320 &`REFERRALS `& set the referrals parameter
7321 &`SERVERS `& set alternate server list for this query only
7322 &`SIZE `& set the limit for the number of entries returned
7323 &`TIME `& set the maximum waiting time for a query
7325 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7326 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7327 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7328 library from trying to follow referrals issued by the LDAP server.
7330 .cindex LDAP timeout
7331 .cindex timeout "LDAP lookup"
7332 The name CONNECT is an obsolete name for NETTIME, retained for
7333 backwards compatibility. This timeout (specified as a number of seconds) is
7334 enforced from the client end for operations that can be carried out over a
7335 network. Specifically, it applies to network connections and calls to the
7336 &'ldap_result()'& function. If the value is greater than zero, it is used if
7337 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7338 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7339 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7340 Netscape SDK; for OpenLDAP no action is taken.
7342 The TIME parameter (also a number of seconds) is passed to the server to
7343 set a server-side limit on the time taken to complete a search.
7345 The SERVERS parameter allows you to specify an alternate list of ldap servers
7346 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7347 default list of ldap servers, and a single lookup can specify a single ldap
7348 server to use. But when you need to do a lookup with a list of servers that is
7349 different than the default list (maybe different order, maybe a completely
7350 different set of servers), the SERVERS parameter allows you to specify this
7351 alternate list (colon-separated).
7353 Here is an example of an LDAP query in an Exim lookup that uses some of these
7354 values. This is a single line, folded to fit on the page:
7357 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7358 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7361 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7362 any of the auxiliary data. Exim configuration settings that include lookups
7363 which contain password information should be preceded by &"hide"& to prevent
7364 non-admin users from using the &%-bP%& option to see their values.
7366 The auxiliary data items may be given in any order. The default is no
7367 connection timeout (the system timeout is used), no user or password, no limit
7368 on the number of entries returned, and no time limit on queries.
7370 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7371 removes any URL quoting that it may contain before passing it LDAP. Apparently
7372 some libraries do this for themselves, but some do not. Removing the URL
7373 quoting has two advantages:
7376 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7377 DNs as with DNs inside actual queries.
7379 It permits spaces inside USER= DNs.
7382 For example, a setting such as
7384 USER=cn=${quote_ldap_dn:$1}
7386 should work even if &$1$& contains spaces.
7388 Expanded data for the PASS= value should be quoted using the &%quote%&
7389 expansion operator, rather than the LDAP quote operators. The only reason this
7390 field needs quoting is to ensure that it conforms to the Exim syntax, which
7391 does not allow unquoted spaces. For example:
7395 The LDAP authentication mechanism can be used to check passwords as part of
7396 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7401 .section "Format of data returned by LDAP" "SECID71"
7402 .cindex "LDAP" "returned data formats"
7403 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7404 as a sequence of values, for example
7406 cn=manager,o=University of Cambridge,c=UK
7408 The &(ldap)& lookup type generates an error if more than one entry matches the
7409 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7410 the result between the data from different entries. It is possible for multiple
7411 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7412 you know that whatever values are returned all came from a single entry in the
7415 In the common case where you specify a single attribute in your LDAP query, the
7416 result is not quoted, and does not contain the attribute name. If the attribute
7417 has multiple values, they are separated by commas. Any comma that is
7418 part of an attribute's value is doubled.
7420 If you specify multiple attributes, the result contains space-separated, quoted
7421 strings, each preceded by the attribute name and an equals sign. Within the
7422 quotes, the quote character, backslash, and newline are escaped with
7423 backslashes, and commas are used to separate multiple values for the attribute.
7424 Any commas in attribute values are doubled
7425 (permitting treatment of the values as a comma-separated list).
7426 Apart from the escaping, the string within quotes takes the same form as the
7427 output when a single attribute is requested. Specifying no attributes is the
7428 same as specifying all of an entry's attributes.
7430 Here are some examples of the output format. The first line of each pair is an
7431 LDAP query, and the second is the data that is returned. The attribute called
7432 &%attr1%& has two values, one of them with an embedded comma, whereas
7433 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7434 (they have SUP &%attr%& in their schema definitions).
7437 ldap:///o=base?attr1?sub?(uid=fred)
7440 ldap:///o=base?attr2?sub?(uid=fred)
7443 ldap:///o=base?attr?sub?(uid=fred)
7444 value1.1,value1,,2,value two
7446 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7447 attr1="value1.1,value1,,2" attr2="value two"
7449 ldap:///o=base??sub?(uid=fred)
7450 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7453 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7454 results of LDAP lookups.
7455 The &%extract%& operator in string expansions can be used to pick out
7456 individual fields from data that consists of &'key'&=&'value'& pairs.
7457 The &%listextract%& operator should be used to pick out individual values
7458 of attributes, even when only a single value is expected.
7459 The doubling of embedded commas allows you to use the returned data as a
7460 comma separated list (using the "<," syntax for changing the input list separator).
7465 .section "More about NIS+" "SECTnisplus"
7466 .cindex "NIS+ lookup type"
7467 .cindex "lookup" "NIS+"
7468 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7469 and field name. If this is given, the result of a successful query is the
7470 contents of the named field; otherwise the result consists of a concatenation
7471 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7472 values containing spaces are quoted. For example, the query
7474 [name=mg1456],passwd.org_dir
7476 might return the string
7478 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7479 home=/home/mg1456 shell=/bin/bash shadow=""
7481 (split over two lines here to fit on the page), whereas
7483 [name=mg1456],passwd.org_dir:gcos
7489 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7490 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7491 operator is to double any quote characters within the text.
7495 .section "SQL lookups" "SECTsql"
7496 .cindex "SQL lookup types"
7497 .cindex "MySQL" "lookup type"
7498 .cindex "PostgreSQL lookup type"
7499 .cindex "lookup" "MySQL"
7500 .cindex "lookup" "PostgreSQL"
7501 .cindex "Oracle" "lookup type"
7502 .cindex "lookup" "Oracle"
7503 .cindex "InterBase lookup type"
7504 .cindex "lookup" "InterBase"
7505 .cindex "Redis lookup type"
7506 .cindex lookup Redis
7507 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7509 databases. Queries for these databases contain SQL statements, so an example
7512 ${lookup mysql{select mailbox from users where id='userx'}\
7515 If the result of the query contains more than one field, the data for each
7516 field in the row is returned, preceded by its name, so the result of
7518 ${lookup pgsql{select home,name from users where id='userx'}\
7523 home=/home/userx name="Mister X"
7525 Empty values and values containing spaces are double quoted, with embedded
7526 quotes escaped by a backslash. If the result of the query contains just one
7527 field, the value is passed back verbatim, without a field name, for example:
7531 If the result of the query yields more than one row, it is all concatenated,
7532 with a newline between the data for each row.
7535 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7536 .cindex "MySQL" "lookup type"
7537 .cindex "PostgreSQL lookup type"
7538 .cindex "lookup" "MySQL"
7539 .cindex "lookup" "PostgreSQL"
7540 .cindex "Oracle" "lookup type"
7541 .cindex "lookup" "Oracle"
7542 .cindex "InterBase lookup type"
7543 .cindex "lookup" "InterBase"
7544 .cindex "Redis lookup type"
7545 .cindex lookup Redis
7546 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7547 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7548 or &%redis_servers%&
7549 option (as appropriate) must be set to a colon-separated list of server
7551 (For MySQL and PostgreSQL, the global option need not be set if all
7552 queries contain their own server information &-- see section
7553 &<<SECTspeserque>>&.)
7555 each item in the list is a slash-separated list of four
7556 items: host name, database name, user name, and password. In the case of
7557 Oracle, the host name field is used for the &"service name"&, and the database
7558 name field is not used and should be empty. For example:
7560 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7562 Because password data is sensitive, you should always precede the setting with
7563 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7564 option. Here is an example where two MySQL servers are listed:
7566 hide mysql_servers = localhost/users/root/secret:\
7567 otherhost/users/root/othersecret
7569 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7570 because this is a colon-separated list, the colon has to be doubled. For each
7571 query, these parameter groups are tried in order until a connection is made and
7572 a query is successfully processed. The result of a query may be that no data is
7573 found, but that is still a successful query. In other words, the list of
7574 servers provides a backup facility, not a list of different places to look.
7577 For Redis the global option need not be specified if all queries contain their
7578 own server information &-- see section &<<SECTspeserque>>&.
7579 If specified, the option must be set to a colon-separated list of server
7581 Each item in the list is a slash-separated list of three items:
7582 host, database number, and password.
7584 The host is required and may be either an IPv4 address and optional
7585 port number (separated by a colon, which needs doubling due to the
7586 higher-level list), or a Unix socket pathname enclosed in parentheses
7588 The database number is optional; if present that number is selected in the backend
7590 The password is optional; if present it is used to authenticate to the backend
7595 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7596 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7597 respectively, and the characters single-quote, double-quote, and backslash
7598 itself are escaped with backslashes.
7600 The &%quote_redis%& expansion operator
7601 escapes whitespace and backslash characters with a backslash.
7604 .section "Specifying the server in the query" "SECTspeserque"
7605 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
7606 it is possible to specify a list of servers with an individual query. This is
7607 done by starting the query with
7609 &`servers=`&&'server1:server2:server3:...'&&`;`&
7611 Each item in the list may take one of two forms:
7613 If it contains no slashes it is assumed to be just a host name. The appropriate
7614 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7615 of the same name, and the remaining parameters (database, user, password) are
7618 If it contains any slashes, it is taken as a complete parameter set.
7620 The list of servers is used in exactly the same way as the global list.
7621 Once a connection to a server has happened and a query has been
7622 successfully executed, processing of the lookup ceases.
7624 This feature is intended for use in master/slave situations where updates
7625 are occurring and you want to update the master rather than a slave. If the
7626 master is in the list as a backup for reading, you might have a global setting
7629 mysql_servers = slave1/db/name/pw:\
7633 In an updating lookup, you could then write:
7635 ${lookup mysql{servers=master; UPDATE ...} }
7637 That query would then be sent only to the master server. If, on the other hand,
7638 the master is not to be used for reading, and so is not present in the global
7639 option, you can still update it by a query of this form:
7641 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7645 .section "Special MySQL features" "SECID73"
7646 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7647 causes a connection to the server on the local host by means of a Unix domain
7648 socket. An alternate socket can be specified in parentheses.
7650 An option group name for MySQL option files can be specified in square brackets;
7651 the default value is &"exim"&.
7653 The full syntax of each item in &%mysql_servers%& is:
7655 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7656 <&'database'&>/<&'user'&>/<&'password'&>
7658 Any of the four sub-parts of the first field can be omitted. For normal use on
7659 the local host it can be left blank or set to just &"localhost"&.
7661 No database need be supplied &-- but if it is absent here, it must be given in
7664 If a MySQL query is issued that does not request any data (an insert, update,
7665 or delete command), the result of the lookup is the number of rows affected.
7667 &*Warning*&: This can be misleading. If an update does not actually change
7668 anything (for example, setting a field to the value it already has), the result
7669 is zero because no rows are affected.
7672 .section "Special PostgreSQL features" "SECID74"
7673 PostgreSQL lookups can also use Unix domain socket connections to the database.
7674 This is usually faster and costs less CPU time than a TCP/IP connection.
7675 However it can be used only if the mail server runs on the same machine as the
7676 database server. A configuration line for PostgreSQL via Unix domain sockets
7679 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7681 In other words, instead of supplying a host name, a path to the socket is
7682 given. The path name is enclosed in parentheses so that its slashes aren't
7683 visually confused with the delimiters for the other server parameters.
7685 If a PostgreSQL query is issued that does not request any data (an insert,
7686 update, or delete command), the result of the lookup is the number of rows
7689 .section "More about SQLite" "SECTsqlite"
7690 .cindex "lookup" "SQLite"
7691 .cindex "sqlite lookup type"
7692 SQLite is different to the other SQL lookups because a file name is required in
7693 addition to the SQL query. An SQLite database is a single file, and there is no
7694 daemon as in the other SQL databases. The interface to Exim requires the name
7695 of the file, as an absolute path, to be given at the start of the query. It is
7696 separated from the query by white space. This means that the path name cannot
7697 contain white space. Here is a lookup expansion example:
7699 ${lookup sqlite {/some/thing/sqlitedb \
7700 select name from aliases where id='userx';}}
7702 In a list, the syntax is similar. For example:
7704 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7705 select * from relays where ip='$sender_host_address';
7707 The only character affected by the &%quote_sqlite%& operator is a single
7708 quote, which it doubles.
7710 .cindex timeout SQLite
7711 .cindex sqlite "lookup timeout"
7712 The SQLite library handles multiple simultaneous accesses to the database
7713 internally. Multiple readers are permitted, but only one process can
7714 update at once. Attempts to access the database while it is being updated
7715 are rejected after a timeout period, during which the SQLite library
7716 waits for the lock to be released. In Exim, the default timeout is set
7717 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7723 . ////////////////////////////////////////////////////////////////////////////
7724 . ////////////////////////////////////////////////////////////////////////////
7726 .chapter "Domain, host, address, and local part lists" &&&
7727 "CHAPdomhosaddlists" &&&
7728 "Domain, host, and address lists"
7729 .scindex IIDdohoadli "lists of domains; hosts; etc."
7730 A number of Exim configuration options contain lists of domains, hosts,
7731 email addresses, or local parts. For example, the &%hold_domains%& option
7732 contains a list of domains whose delivery is currently suspended. These lists
7733 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7734 arguments to expansion conditions such as &%match_domain%&.
7736 Each item in one of these lists is a pattern to be matched against a domain,
7737 host, email address, or local part, respectively. In the sections below, the
7738 different types of pattern for each case are described, but first we cover some
7739 general facilities that apply to all four kinds of list.
7741 Note that other parts of Exim use a &'string list'& which does not
7742 support all the complexity available in
7743 domain, host, address and local part lists.
7747 .section "Expansion of lists" "SECTlistexpand"
7748 .cindex "expansion" "of lists"
7749 Each list is expanded as a single string before it is used. The result of
7750 expansion must be a list, possibly containing empty items, which is split up
7751 into separate items for matching. By default, colon is the separator character,
7752 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7753 &<<SECTempitelis>>& for details of the list syntax; the second of these
7754 discusses the way to specify empty list items.
7757 If the string expansion is forced to fail, Exim behaves as if the item it is
7758 testing (domain, host, address, or local part) is not in the list. Other
7759 expansion failures cause temporary errors.
7761 If an item in a list is a regular expression, backslashes, dollars and possibly
7762 other special characters in the expression must be protected against
7763 misinterpretation by the string expander. The easiest way to do this is to use
7764 the &`\N`& expansion feature to indicate that the contents of the regular
7765 expression should not be expanded. For example, in an ACL you might have:
7767 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7768 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7770 The first item is a regular expression that is protected from expansion by
7771 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7772 senders based on the receiving domain.
7777 .section "Negated items in lists" "SECID76"
7778 .cindex "list" "negation"
7779 .cindex "negation" "in lists"
7780 Items in a list may be positive or negative. Negative items are indicated by a
7781 leading exclamation mark, which may be followed by optional white space. A list
7782 defines a set of items (domains, etc). When Exim processes one of these lists,
7783 it is trying to find out whether a domain, host, address, or local part
7784 (respectively) is in the set that is defined by the list. It works like this:
7786 The list is scanned from left to right. If a positive item is matched, the
7787 subject that is being checked is in the set; if a negative item is matched, the
7788 subject is not in the set. If the end of the list is reached without the
7789 subject having matched any of the patterns, it is in the set if the last item
7790 was a negative one, but not if it was a positive one. For example, the list in
7792 domainlist relay_to_domains = !a.b.c : *.b.c
7794 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7795 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7796 list is positive. However, if the setting were
7798 domainlist relay_to_domains = !a.b.c
7800 then all domains other than &'a.b.c'& would match because the last item in the
7801 list is negative. In other words, a list that ends with a negative item behaves
7802 as if it had an extra item &`:*`& on the end.
7804 Another way of thinking about positive and negative items in lists is to read
7805 the connector as &"or"& after a positive item and as &"and"& after a negative
7810 .section "File names in lists" "SECTfilnamlis"
7811 .cindex "list" "file name in"
7812 If an item in a domain, host, address, or local part list is an absolute file
7813 name (beginning with a slash character), each line of the file is read and
7814 processed as if it were an independent item in the list, except that further
7815 file names are not allowed,
7816 and no expansion of the data from the file takes place.
7817 Empty lines in the file are ignored, and the file may also contain comment
7821 For domain and host lists, if a # character appears anywhere in a line of the
7822 file, it and all following characters are ignored.
7824 Because local parts may legitimately contain # characters, a comment in an
7825 address list or local part list file is recognized only if # is preceded by
7826 white space or the start of the line. For example:
7828 not#comment@x.y.z # but this is a comment
7832 Putting a file name in a list has the same effect as inserting each line of the
7833 file as an item in the list (blank lines and comments excepted). However, there
7834 is one important difference: the file is read each time the list is processed,
7835 so if its contents vary over time, Exim's behaviour changes.
7837 If a file name is preceded by an exclamation mark, the sense of any match
7838 within the file is inverted. For example, if
7840 hold_domains = !/etc/nohold-domains
7842 and the file contains the lines
7847 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7848 any domain matching &`*.b.c`& is not.
7852 .section "An lsearch file is not an out-of-line list" "SECID77"
7853 As will be described in the sections that follow, lookups can be used in lists
7854 to provide indexed methods of checking list membership. There has been some
7855 confusion about the way &(lsearch)& lookups work in lists. Because
7856 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7857 sometimes thought that it is allowed to contain wild cards and other kinds of
7858 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7859 always fixed strings, just as for any other single-key lookup type.
7861 If you want to use a file to contain wild-card patterns that form part of a
7862 list, just give the file name on its own, without a search type, as described
7863 in the previous section. You could also use the &(wildlsearch)& or
7864 &(nwildlsearch)&, but there is no advantage in doing this.
7869 .section "Named lists" "SECTnamedlists"
7870 .cindex "named lists"
7871 .cindex "list" "named"
7872 A list of domains, hosts, email addresses, or local parts can be given a name
7873 which is then used to refer to the list elsewhere in the configuration. This is
7874 particularly convenient if the same list is required in several different
7875 places. It also allows lists to be given meaningful names, which can improve
7876 the readability of the configuration. For example, it is conventional to define
7877 a domain list called &'local_domains'& for all the domains that are handled
7878 locally on a host, using a configuration line such as
7880 domainlist local_domains = localhost:my.dom.example
7882 Named lists are referenced by giving their name preceded by a plus sign, so,
7883 for example, a router that is intended to handle local domains would be
7884 configured with the line
7886 domains = +local_domains
7888 The first router in a configuration is often one that handles all domains
7889 except the local ones, using a configuration with a negated item like this:
7893 domains = ! +local_domains
7894 transport = remote_smtp
7897 The four kinds of named list are created by configuration lines starting with
7898 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7899 respectively. Then there follows the name that you are defining, followed by an
7900 equals sign and the list itself. For example:
7902 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7903 addresslist bad_senders = cdb;/etc/badsenders
7905 A named list may refer to other named lists:
7907 domainlist dom1 = first.example : second.example
7908 domainlist dom2 = +dom1 : third.example
7909 domainlist dom3 = fourth.example : +dom2 : fifth.example
7911 &*Warning*&: If the last item in a referenced list is a negative one, the
7912 effect may not be what you intended, because the negation does not propagate
7913 out to the higher level. For example, consider:
7915 domainlist dom1 = !a.b
7916 domainlist dom2 = +dom1 : *.b
7918 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7919 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7920 means it matches the second list as well. The effect is not the same as
7922 domainlist dom2 = !a.b : *.b
7924 where &'x.y'& does not match. It's best to avoid negation altogether in
7925 referenced lists if you can.
7927 Named lists may have a performance advantage. When Exim is routing an
7928 address or checking an incoming message, it caches the result of tests on named
7929 lists. So, if you have a setting such as
7931 domains = +local_domains
7933 on several of your routers
7934 or in several ACL statements,
7935 the actual test is done only for the first one. However, the caching works only
7936 if there are no expansions within the list itself or any sublists that it
7937 references. In other words, caching happens only for lists that are known to be
7938 the same each time they are referenced.
7940 By default, there may be up to 16 named lists of each type. This limit can be
7941 extended by changing a compile-time variable. The use of domain and host lists
7942 is recommended for concepts such as local domains, relay domains, and relay
7943 hosts. The default configuration is set up like this.
7947 .section "Named lists compared with macros" "SECID78"
7948 .cindex "list" "named compared with macro"
7949 .cindex "macro" "compared with named list"
7950 At first sight, named lists might seem to be no different from macros in the
7951 configuration file. However, macros are just textual substitutions. If you
7954 ALIST = host1 : host2
7955 auth_advertise_hosts = !ALIST
7957 it probably won't do what you want, because that is exactly the same as
7959 auth_advertise_hosts = !host1 : host2
7961 Notice that the second host name is not negated. However, if you use a host
7964 hostlist alist = host1 : host2
7965 auth_advertise_hosts = ! +alist
7967 the negation applies to the whole list, and so that is equivalent to
7969 auth_advertise_hosts = !host1 : !host2
7973 .section "Named list caching" "SECID79"
7974 .cindex "list" "caching of named"
7975 .cindex "caching" "named lists"
7976 While processing a message, Exim caches the result of checking a named list if
7977 it is sure that the list is the same each time. In practice, this means that
7978 the cache operates only if the list contains no $ characters, which guarantees
7979 that it will not change when it is expanded. Sometimes, however, you may have
7980 an expanded list that you know will be the same each time within a given
7981 message. For example:
7983 domainlist special_domains = \
7984 ${lookup{$sender_host_address}cdb{/some/file}}
7986 This provides a list of domains that depends only on the sending host's IP
7987 address. If this domain list is referenced a number of times (for example,
7988 in several ACL lines, or in several routers) the result of the check is not
7989 cached by default, because Exim does not know that it is going to be the
7990 same list each time.
7992 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7993 cache the result anyway. For example:
7995 domainlist_cache special_domains = ${lookup{...
7997 If you do this, you should be absolutely sure that caching is going to do
7998 the right thing in all cases. When in doubt, leave it out.
8002 .section "Domain lists" "SECTdomainlist"
8003 .cindex "domain list" "patterns for"
8004 .cindex "list" "domain list"
8005 Domain lists contain patterns that are to be matched against a mail domain.
8006 The following types of item may appear in domain lists:
8009 .cindex "primary host name"
8010 .cindex "host name" "matched in domain list"
8011 .oindex "&%primary_hostname%&"
8012 .cindex "domain list" "matching primary host name"
8013 .cindex "@ in a domain list"
8014 If a pattern consists of a single @ character, it matches the local host name,
8015 as set by the &%primary_hostname%& option (or defaulted). This makes it
8016 possible to use the same configuration file on several different hosts that
8017 differ only in their names.
8019 .cindex "@[] in a domain list"
8020 .cindex "domain list" "matching local IP interfaces"
8021 .cindex "domain literal"
8022 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8023 in square brackets (as in an email address that contains a domain literal), but
8024 only if that IP address is recognized as local for email routing purposes. The
8025 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8026 control which of a host's several IP addresses are treated as local.
8027 In today's Internet, the use of domain literals is controversial.
8030 .cindex "@mx_primary"
8031 .cindex "@mx_secondary"
8032 .cindex "domain list" "matching MX pointers to local host"
8033 If a pattern consists of the string &`@mx_any`& it matches any domain that
8034 has an MX record pointing to the local host or to any host that is listed in
8035 .oindex "&%hosts_treat_as_local%&"
8036 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8037 are similar, except that the first matches only when a primary MX target is the
8038 local host, and the second only when no primary MX target is the local host,
8039 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8040 preference value &-- there may of course be more than one of them.
8042 The MX lookup that takes place when matching a pattern of this type is
8043 performed with the resolver options for widening names turned off. Thus, for
8044 example, a single-component domain will &'not'& be expanded by adding the
8045 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8046 options of the &(dnslookup)& router for a discussion of domain widening.
8048 Sometimes you may want to ignore certain IP addresses when using one of these
8049 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8050 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8051 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8052 on a router). For example:
8054 domains = @mx_any/ignore=127.0.0.1
8056 This example matches any domain that has an MX record pointing to one of
8057 the local host's IP addresses other than 127.0.0.1.
8059 The list of IP addresses is in fact processed by the same code that processes
8060 host lists, so it may contain CIDR-coded network specifications and it may also
8061 contain negative items.
8063 Because the list of IP addresses is a sublist within a domain list, you have to
8064 be careful about delimiters if there is more than one address. Like any other
8065 list, the default delimiter can be changed. Thus, you might have:
8067 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8068 an.other.domain : ...
8070 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8071 involved, it is easiest to change the delimiter for the main list as well:
8073 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8074 an.other.domain ? ...
8077 .cindex "asterisk" "in domain list"
8078 .cindex "domain list" "asterisk in"
8079 .cindex "domain list" "matching &""ends with""&"
8080 If a pattern starts with an asterisk, the remaining characters of the pattern
8081 are compared with the terminating characters of the domain. The use of &"*"& in
8082 domain lists differs from its use in partial matching lookups. In a domain
8083 list, the character following the asterisk need not be a dot, whereas partial
8084 matching works only in terms of dot-separated components. For example, a domain
8085 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8089 .cindex "regular expressions" "in domain list"
8090 .cindex "domain list" "matching regular expression"
8091 If a pattern starts with a circumflex character, it is treated as a regular
8092 expression, and matched against the domain using a regular expression matching
8093 function. The circumflex is treated as part of the regular expression.
8094 Email domains are case-independent, so this regular expression match is by
8095 default case-independent, but you can make it case-dependent by starting it
8096 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8097 are given in chapter &<<CHAPregexp>>&.
8099 &*Warning*&: Because domain lists are expanded before being processed, you
8100 must escape any backslash and dollar characters in the regular expression, or
8101 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8102 it is not to be expanded (unless you really do want to build a regular
8103 expression by expansion, of course).
8105 .cindex "lookup" "in domain list"
8106 .cindex "domain list" "matching by lookup"
8107 If a pattern starts with the name of a single-key lookup type followed by a
8108 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8109 must be a file name in a suitable format for the lookup type. For example, for
8110 &"cdb;"& it must be an absolute path:
8112 domains = cdb;/etc/mail/local_domains.cdb
8114 The appropriate type of lookup is done on the file using the domain name as the
8115 key. In most cases, the data that is looked up is not used; Exim is interested
8116 only in whether or not the key is present in the file. However, when a lookup
8117 is used for the &%domains%& option on a router
8118 or a &%domains%& condition in an ACL statement, the data is preserved in the
8119 &$domain_data$& variable and can be referred to in other router options or
8120 other statements in the same ACL.
8123 Any of the single-key lookup type names may be preceded by
8124 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8126 domains = partial-dbm;/partial/domains
8128 This causes partial matching logic to be invoked; a description of how this
8129 works is given in section &<<SECTpartiallookup>>&.
8132 .cindex "asterisk" "in lookup type"
8133 Any of the single-key lookup types may be followed by an asterisk. This causes
8134 a default lookup for a key consisting of a single asterisk to be done if the
8135 original lookup fails. This is not a useful feature when using a domain list to
8136 select particular domains (because any domain would match), but it might have
8137 value if the result of the lookup is being used via the &$domain_data$&
8140 If the pattern starts with the name of a query-style lookup type followed by a
8141 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8142 pattern must be an appropriate query for the lookup type, as described in
8143 chapter &<<CHAPfdlookup>>&. For example:
8145 hold_domains = mysql;select domain from holdlist \
8146 where domain = '${quote_mysql:$domain}';
8148 In most cases, the data that is looked up is not used (so for an SQL query, for
8149 example, it doesn't matter what field you select). Exim is interested only in
8150 whether or not the query succeeds. However, when a lookup is used for the
8151 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8152 variable and can be referred to in other options.
8154 .cindex "domain list" "matching literal domain name"
8155 If none of the above cases apply, a caseless textual comparison is made
8156 between the pattern and the domain.
8159 Here is an example that uses several different kinds of pattern:
8161 domainlist funny_domains = \
8164 *.foundation.fict.example : \
8165 \N^[1-2]\d{3}\.fict\.example$\N : \
8166 partial-dbm;/opt/data/penguin/book : \
8167 nis;domains.byname : \
8168 nisplus;[name=$domain,status=local],domains.org_dir
8170 There are obvious processing trade-offs among the various matching modes. Using
8171 an asterisk is faster than a regular expression, and listing a few names
8172 explicitly probably is too. The use of a file or database lookup is expensive,
8173 but may be the only option if hundreds of names are required. Because the
8174 patterns are tested in order, it makes sense to put the most commonly matched
8179 .section "Host lists" "SECThostlist"
8180 .cindex "host list" "patterns in"
8181 .cindex "list" "host list"
8182 Host lists are used to control what remote hosts are allowed to do. For
8183 example, some hosts may be allowed to use the local host as a relay, and some
8184 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8185 two different ways, by name or by IP address. In a host list, some types of
8186 pattern are matched to a host name, and some are matched to an IP address.
8187 You need to be particularly careful with this when single-key lookups are
8188 involved, to ensure that the right value is being used as the key.
8191 .section "Special host list patterns" "SECID80"
8192 .cindex "empty item in hosts list"
8193 .cindex "host list" "empty string in"
8194 If a host list item is the empty string, it matches only when no remote host is
8195 involved. This is the case when a message is being received from a local
8196 process using SMTP on the standard input, that is, when a TCP/IP connection is
8199 .cindex "asterisk" "in host list"
8200 The special pattern &"*"& in a host list matches any host or no host. Neither
8201 the IP address nor the name is actually inspected.
8205 .section "Host list patterns that match by IP address" "SECThoslispatip"
8206 .cindex "host list" "matching IP addresses"
8207 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8208 the incoming address actually appears in the IPv6 host as
8209 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8210 list, it is converted into a traditional IPv4 address first. (Not all operating
8211 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8214 The following types of pattern in a host list check the remote host by
8215 inspecting its IP address:
8218 If the pattern is a plain domain name (not a regular expression, not starting
8219 with *, not a lookup of any kind), Exim calls the operating system function
8220 to find the associated IP address(es). Exim uses the newer
8221 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8222 This typically causes a forward DNS lookup of the name. The result is compared
8223 with the IP address of the subject host.
8225 If there is a temporary problem (such as a DNS timeout) with the host name
8226 lookup, a temporary error occurs. For example, if the list is being used in an
8227 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8228 temporary SMTP error code. If no IP address can be found for the host name,
8229 what happens is described in section &<<SECTbehipnot>>& below.
8232 .cindex "@ in a host list"
8233 If the pattern is &"@"&, the primary host name is substituted and used as a
8234 domain name, as just described.
8237 If the pattern is an IP address, it is matched against the IP address of the
8238 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8239 IPv6 addresses can be given in colon-separated format, but the colons have to
8240 be doubled so as not to be taken as item separators when the default list
8241 separator is used. IPv6 addresses are recognized even when Exim is compiled
8242 without IPv6 support. This means that if they appear in a host list on an
8243 IPv4-only host, Exim will not treat them as host names. They are just addresses
8244 that can never match a client host.
8247 .cindex "@[] in a host list"
8248 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8249 the local host. For example, if the local host is an IPv4 host with one
8250 interface address 10.45.23.56, these two ACL statements have the same effect:
8252 accept hosts = 127.0.0.1 : 10.45.23.56
8256 .cindex "CIDR notation"
8257 If the pattern is an IP address followed by a slash and a mask length (for
8258 example 10.11.42.0/24), it is matched against the IP address of the subject
8259 host under the given mask. This allows, an entire network of hosts to be
8260 included (or excluded) by a single item. The mask uses CIDR notation; it
8261 specifies the number of address bits that must match, starting from the most
8262 significant end of the address.
8264 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8265 of a range of addresses. It is the number of bits in the network portion of the
8266 address. The above example specifies a 24-bit netmask, so it matches all 256
8267 addresses in the 10.11.42.0 network. An item such as
8271 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8272 32 for an IPv4 address is the same as no mask at all; just a single address
8275 Here is another example which shows an IPv4 and an IPv6 network:
8277 recipient_unqualified_hosts = 192.168.0.0/16: \
8278 3ffe::ffff::836f::::/48
8280 The doubling of list separator characters applies only when these items
8281 appear inline in a host list. It is not required when indirecting via a file.
8284 recipient_unqualified_hosts = /opt/exim/unqualnets
8286 could make use of a file containing
8291 to have exactly the same effect as the previous example. When listing IPv6
8292 addresses inline, it is usually more convenient to use the facility for
8293 changing separator characters. This list contains the same two networks:
8295 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8298 The separator is changed to semicolon by the leading &"<;"& at the start of the
8304 .section "Host list patterns for single-key lookups by host address" &&&
8305 "SECThoslispatsikey"
8306 .cindex "host list" "lookup of IP address"
8307 When a host is to be identified by a single-key lookup of its complete IP
8308 address, the pattern takes this form:
8310 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8314 hosts_lookup = net-cdb;/hosts-by-ip.db
8316 The text form of the IP address of the subject host is used as the lookup key.
8317 IPv6 addresses are converted to an unabbreviated form, using lower case
8318 letters, with dots as separators because colon is the key terminator in
8319 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8320 quoting the keys, but this is a facility that was added later.] The data
8321 returned by the lookup is not used.
8323 .cindex "IP address" "masking"
8324 .cindex "host list" "masked IP address"
8325 Single-key lookups can also be performed using masked IP addresses, using
8326 patterns of this form:
8328 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8332 net24-dbm;/networks.db
8334 The IP address of the subject host is masked using <&'number'&> as the mask
8335 length. A textual string is constructed from the masked value, followed by the
8336 mask, and this is used as the lookup key. For example, if the host's IP address
8337 is 192.168.34.6, the key that is looked up for the above example is
8338 &"192.168.34.0/24"&.
8340 When an IPv6 address is converted to a string, dots are normally used instead
8341 of colons, so that keys in &(lsearch)& files need not contain colons (which
8342 terminate &(lsearch)& keys). This was implemented some time before the ability
8343 to quote keys was made available in &(lsearch)& files. However, the more
8344 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8345 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8346 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8347 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8348 addresses are always used.
8350 Ideally, it would be nice to tidy up this anomalous situation by changing to
8351 colons in all cases, given that quoting is now available for &(lsearch)&.
8352 However, this would be an incompatible change that might break some existing
8355 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8356 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8357 the former case the key strings include the mask value, whereas in the latter
8358 case the IP address is used on its own.
8362 .section "Host list patterns that match by host name" "SECThoslispatnam"
8363 .cindex "host" "lookup failures"
8364 .cindex "unknown host name"
8365 .cindex "host list" "matching host name"
8366 There are several types of pattern that require Exim to know the name of the
8367 remote host. These are either wildcard patterns or lookups by name. (If a
8368 complete hostname is given without any wildcarding, it is used to find an IP
8369 address to match against, as described in section &<<SECThoslispatip>>&
8372 If the remote host name is not already known when Exim encounters one of these
8373 patterns, it has to be found from the IP address.
8374 Although many sites on the Internet are conscientious about maintaining reverse
8375 DNS data for their hosts, there are also many that do not do this.
8376 Consequently, a name cannot always be found, and this may lead to unwanted
8377 effects. Take care when configuring host lists with wildcarded name patterns.
8378 Consider what will happen if a name cannot be found.
8380 Because of the problems of determining host names from IP addresses, matching
8381 against host names is not as common as matching against IP addresses.
8383 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8384 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8385 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8386 are done can be changed by setting the &%host_lookup_order%& option. For
8387 security, once Exim has found one or more names, it looks up the IP addresses
8388 for these names and compares them with the IP address that it started with.
8389 Only those names whose IP addresses match are accepted. Any other names are
8390 discarded. If no names are left, Exim behaves as if the host name cannot be
8391 found. In the most common case there is only one name and one IP address.
8393 There are some options that control what happens if a host name cannot be
8394 found. These are described in section &<<SECTbehipnot>>& below.
8396 .cindex "host" "alias for"
8397 .cindex "alias for host"
8398 As a result of aliasing, hosts may have more than one name. When processing any
8399 of the following types of pattern, all the host's names are checked:
8402 .cindex "asterisk" "in host list"
8403 If a pattern starts with &"*"& the remainder of the item must match the end of
8404 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8405 &'.b.c'&. This special simple form is provided because this is a very common
8406 requirement. Other kinds of wildcarding require the use of a regular
8409 .cindex "regular expressions" "in host list"
8410 .cindex "host list" "regular expression in"
8411 If the item starts with &"^"& it is taken to be a regular expression which is
8412 matched against the host name. Host names are case-independent, so this regular
8413 expression match is by default case-independent, but you can make it
8414 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8415 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8420 is a regular expression that matches either of the two hosts &'a.c.d'& or
8421 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8422 that backslash and dollar characters are not misinterpreted as part of the
8423 string expansion. The simplest way to do this is to use &`\N`& to mark that
8424 part of the string as non-expandable. For example:
8426 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8428 &*Warning*&: If you want to match a complete host name, you must include the
8429 &`$`& terminating metacharacter in the regular expression, as in the above
8430 example. Without it, a match at the start of the host name is all that is
8437 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8438 .cindex "host" "lookup failures, permanent"
8439 While processing a host list, Exim may need to look up an IP address from a
8440 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8441 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8442 behaviour when it fails to find the information it is seeking is the same.
8444 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8445 apply to temporary DNS errors, whose handling is described in the next section.
8447 .cindex "&`+include_unknown`&"
8448 .cindex "&`+ignore_unknown`&"
8449 Exim parses a host list from left to right. If it encounters a permanent
8450 lookup failure in any item in the host list before it has found a match,
8451 Exim treats it as a failure and the default behavior is as if the host
8452 does not match the list. This may not always be what you want to happen.
8453 To change Exim's behaviour, the special items &`+include_unknown`& or
8454 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8455 not recognized in an indirected file).
8458 If any item that follows &`+include_unknown`& requires information that
8459 cannot found, Exim behaves as if the host does match the list. For example,
8461 host_reject_connection = +include_unknown:*.enemy.ex
8463 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8464 any hosts whose name it cannot find.
8467 If any item that follows &`+ignore_unknown`& requires information that cannot
8468 be found, Exim ignores that item and proceeds to the rest of the list. For
8471 accept hosts = +ignore_unknown : friend.example : \
8474 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8475 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8476 name can be found for 192.168.4.5, it is rejected.
8479 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8480 list. The effect of each one lasts until the next, or until the end of the
8483 .section "Mixing wildcarded host names and addresses in host lists" &&&
8485 .cindex "host list" "mixing names and addresses in"
8487 This section explains the host/ip processing logic with the same concepts
8488 as the previous section, but specifically addresses what happens when a
8489 wildcarded hostname is one of the items in the hostlist.
8492 If you have name lookups or wildcarded host names and
8493 IP addresses in the same host list, you should normally put the IP
8494 addresses first. For example, in an ACL you could have:
8496 accept hosts = 10.9.8.7 : *.friend.example
8498 The reason you normally would order it this way lies in the
8499 left-to-right way that Exim processes lists. It can test IP addresses
8500 without doing any DNS lookups, but when it reaches an item that requires
8501 a host name, it fails if it cannot find a host name to compare with the
8502 pattern. If the above list is given in the opposite order, the
8503 &%accept%& statement fails for a host whose name cannot be found, even
8504 if its IP address is 10.9.8.7.
8507 If you really do want to do the name check first, and still recognize the IP
8508 address, you can rewrite the ACL like this:
8510 accept hosts = *.friend.example
8511 accept hosts = 10.9.8.7
8513 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8514 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8515 &`+ignore_unknown`&, which was discussed in depth in the first example in
8520 .section "Temporary DNS errors when looking up host information" &&&
8522 .cindex "host" "lookup failures, temporary"
8523 .cindex "&`+include_defer`&"
8524 .cindex "&`+ignore_defer`&"
8525 A temporary DNS lookup failure normally causes a defer action (except when
8526 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8527 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8528 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8529 section. These options should be used with care, probably only in non-critical
8530 host lists such as whitelists.
8534 .section "Host list patterns for single-key lookups by host name" &&&
8535 "SECThoslispatnamsk"
8536 .cindex "unknown host name"
8537 .cindex "host list" "matching host name"
8538 If a pattern is of the form
8540 <&'single-key-search-type'&>;<&'search-data'&>
8544 dbm;/host/accept/list
8546 a single-key lookup is performed, using the host name as its key. If the
8547 lookup succeeds, the host matches the item. The actual data that is looked up
8550 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8551 keys in the file, not IP addresses. If you want to do lookups based on IP
8552 addresses, you must precede the search type with &"net-"& (see section
8553 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8554 two items in the same list, one doing an address lookup and one doing a name
8555 lookup, both using the same file.
8559 .section "Host list patterns for query-style lookups" "SECID81"
8560 If a pattern is of the form
8562 <&'query-style-search-type'&>;<&'query'&>
8564 the query is obeyed, and if it succeeds, the host matches the item. The actual
8565 data that is looked up is not used. The variables &$sender_host_address$& and
8566 &$sender_host_name$& can be used in the query. For example:
8568 hosts_lookup = pgsql;\
8569 select ip from hostlist where ip='$sender_host_address'
8571 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8572 can use the &%sg%& expansion item to change this if you need to. If you want to
8573 use masked IP addresses in database queries, you can use the &%mask%& expansion
8576 If the query contains a reference to &$sender_host_name$&, Exim automatically
8577 looks up the host name if it has not already done so. (See section
8578 &<<SECThoslispatnam>>& for comments on finding host names.)
8580 Historical note: prior to release 4.30, Exim would always attempt to find a
8581 host name before running the query, unless the search type was preceded by
8582 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8583 still recognized for query-style lookups, but its presence or absence has no
8584 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8585 See section &<<SECThoslispatsikey>>&.)
8591 .section "Address lists" "SECTaddresslist"
8592 .cindex "list" "address list"
8593 .cindex "address list" "empty item"
8594 .cindex "address list" "patterns"
8595 Address lists contain patterns that are matched against mail addresses. There
8596 is one special case to be considered: the sender address of a bounce message is
8597 always empty. You can test for this by providing an empty item in an address
8598 list. For example, you can set up a router to process bounce messages by
8599 using this option setting:
8603 The presence of the colon creates an empty item. If you do not provide any
8604 data, the list is empty and matches nothing. The empty sender can also be
8605 detected by a regular expression that matches an empty string,
8606 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8608 Non-empty items in an address list can be straightforward email addresses. For
8611 senders = jbc@askone.example : hs@anacreon.example
8613 A certain amount of wildcarding is permitted. If a pattern contains an @
8614 character, but is not a regular expression and does not begin with a
8615 semicolon-terminated lookup type (described below), the local part of the
8616 subject address is compared with the local part of the pattern, which may start
8617 with an asterisk. If the local parts match, the domain is checked in exactly
8618 the same way as for a pattern in a domain list. For example, the domain can be
8619 wildcarded, refer to a named list, or be a lookup:
8621 deny senders = *@*.spamming.site:\
8622 *@+hostile_domains:\
8623 bozo@partial-lsearch;/list/of/dodgy/sites:\
8624 *@dbm;/bad/domains.db
8626 .cindex "local part" "starting with !"
8627 .cindex "address list" "local part starting with !"
8628 If a local part that begins with an exclamation mark is required, it has to be
8629 specified using a regular expression, because otherwise the exclamation mark is
8630 treated as a sign of negation, as is standard in lists.
8632 If a non-empty pattern that is not a regular expression or a lookup does not
8633 contain an @ character, it is matched against the domain part of the subject
8634 address. The only two formats that are recognized this way are a literal
8635 domain, or a domain pattern that starts with *. In both these cases, the effect
8636 is the same as if &`*@`& preceded the pattern. For example:
8638 deny senders = enemy.domain : *.enemy.domain
8641 The following kinds of more complicated address list pattern can match any
8642 address, including the empty address that is characteristic of bounce message
8646 .cindex "regular expressions" "in address list"
8647 .cindex "address list" "regular expression in"
8648 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8649 done against the complete address, with the pattern as the regular expression.
8650 You must take care that backslash and dollar characters are not misinterpreted
8651 as part of the string expansion. The simplest way to do this is to use &`\N`&
8652 to mark that part of the string as non-expandable. For example:
8654 deny senders = \N^.*this.*@example\.com$\N : \
8655 \N^\d{8}.+@spamhaus.example$\N : ...
8657 The &`\N`& sequences are removed by the expansion, so these items do indeed
8658 start with &"^"& by the time they are being interpreted as address patterns.
8661 .cindex "address list" "lookup for complete address"
8662 Complete addresses can be looked up by using a pattern that starts with a
8663 lookup type terminated by a semicolon, followed by the data for the lookup. For
8666 deny senders = cdb;/etc/blocked.senders : \
8667 mysql;select address from blocked where \
8668 address='${quote_mysql:$sender_address}'
8670 Both query-style and single-key lookup types can be used. For a single-key
8671 lookup type, Exim uses the complete address as the key. However, empty keys are
8672 not supported for single-key lookups, so a match against the empty address
8673 always fails. This restriction does not apply to query-style lookups.
8675 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8676 cannot be used, and is ignored if specified, with an entry being written to the
8678 .cindex "*@ with single-key lookup"
8679 However, you can configure lookup defaults, as described in section
8680 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8681 default. For example, with this lookup:
8683 accept senders = lsearch*@;/some/file
8685 the file could contains lines like this:
8687 user1@domain1.example
8690 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8693 nimrod@jaeger.example
8697 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8698 would mean that every address matches, thus rendering the test useless.
8700 &*Warning 2*&: Do not confuse these two kinds of item:
8702 deny recipients = dbm*@;/some/file
8703 deny recipients = *@dbm;/some/file
8705 The first does a whole address lookup, with defaulting, as just described,
8706 because it starts with a lookup type. The second matches the local part and
8707 domain independently, as described in a bullet point below.
8711 The following kinds of address list pattern can match only non-empty addresses.
8712 If the subject address is empty, a match against any of these pattern types
8717 .cindex "@@ with single-key lookup"
8718 .cindex "address list" "@@ lookup type"
8719 .cindex "address list" "split local part and domain"
8720 If a pattern starts with &"@@"& followed by a single-key lookup item
8721 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8722 split into a local part and a domain. The domain is looked up in the file. If
8723 it is not found, there is no match. If it is found, the data that is looked up
8724 from the file is treated as a colon-separated list of local part patterns, each
8725 of which is matched against the subject local part in turn.
8727 .cindex "asterisk" "in address list"
8728 The lookup may be a partial one, and/or one involving a search for a default
8729 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8730 patterns that are looked up can be regular expressions or begin with &"*"&, or
8731 even be further lookups. They may also be independently negated. For example,
8734 deny senders = @@dbm;/etc/reject-by-domain
8736 the data from which the DBM file is built could contain lines like
8738 baddomain.com: !postmaster : *
8740 to reject all senders except &%postmaster%& from that domain.
8742 .cindex "local part" "starting with !"
8743 If a local part that actually begins with an exclamation mark is required, it
8744 has to be specified using a regular expression. In &(lsearch)& files, an entry
8745 may be split over several lines by indenting the second and subsequent lines,
8746 but the separating colon must still be included at line breaks. White space
8747 surrounding the colons is ignored. For example:
8749 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8752 As in all colon-separated lists in Exim, a colon can be included in an item by
8755 If the last item in the list starts with a right angle-bracket, the remainder
8756 of the item is taken as a new key to look up in order to obtain a continuation
8757 list of local parts. The new key can be any sequence of characters. Thus one
8758 might have entries like
8760 aol.com: spammer1 : spammer 2 : >*
8761 xyz.com: spammer3 : >*
8764 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8765 local parts for all domains, in addition to the specific local parts listed for
8766 each domain. Of course, using this feature costs another lookup each time a
8767 chain is followed, but the effort needed to maintain the data is reduced.
8769 .cindex "loop" "in lookups"
8770 It is possible to construct loops using this facility, and in order to catch
8771 them, the chains may be no more than fifty items long.
8774 The @@<&'lookup'&> style of item can also be used with a query-style
8775 lookup, but in this case, the chaining facility is not available. The lookup
8776 can only return a single list of local parts.
8779 &*Warning*&: There is an important difference between the address list items
8780 in these two examples:
8783 senders = *@+my_list
8785 In the first one, &`my_list`& is a named address list, whereas in the second
8786 example it is a named domain list.
8791 .section "Case of letters in address lists" "SECTcasletadd"
8792 .cindex "case of local parts"
8793 .cindex "address list" "case forcing"
8794 .cindex "case forcing in address lists"
8795 Domains in email addresses are always handled caselessly, but for local parts
8796 case may be significant on some systems (see &%caseful_local_part%& for how
8797 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8798 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8799 blocking lists should be done in a case-independent manner. Since most address
8800 lists in Exim are used for this kind of control, Exim attempts to do this by
8803 The domain portion of an address is always lowercased before matching it to an
8804 address list. The local part is lowercased by default, and any string
8805 comparisons that take place are done caselessly. This means that the data in
8806 the address list itself, in files included as plain file names, and in any file
8807 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8808 keys in files that are looked up by a search type other than &(lsearch)& (which
8809 works caselessly) must be in lower case, because these lookups are not
8812 .cindex "&`+caseful`&"
8813 To allow for the possibility of caseful address list matching, if an item in
8814 an address list is the string &"+caseful"&, the original case of the local
8815 part is restored for any comparisons that follow, and string comparisons are no
8816 longer case-independent. This does not affect the domain, which remains in
8817 lower case. However, although independent matches on the domain alone are still
8818 performed caselessly, regular expressions that match against an entire address
8819 become case-sensitive after &"+caseful"& has been seen.
8823 .section "Local part lists" "SECTlocparlis"
8824 .cindex "list" "local part list"
8825 .cindex "local part" "list"
8826 Case-sensitivity in local part lists is handled in the same way as for address
8827 lists, as just described. The &"+caseful"& item can be used if required. In a
8828 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8829 set false, the subject is lowercased and the matching is initially
8830 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8831 matching in the local part list, but not elsewhere in the router. If
8832 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8833 option is case-sensitive from the start.
8835 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8836 comments are handled in the same way as address lists &-- they are recognized
8837 only if the # is preceded by white space or the start of the line.
8838 Otherwise, local part lists are matched in the same way as domain lists, except
8839 that the special items that refer to the local host (&`@`&, &`@[]`&,
8840 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8841 Refer to section &<<SECTdomainlist>>& for details of the other available item
8843 .ecindex IIDdohoadli
8848 . ////////////////////////////////////////////////////////////////////////////
8849 . ////////////////////////////////////////////////////////////////////////////
8851 .chapter "String expansions" "CHAPexpand"
8852 .scindex IIDstrexp "expansion" "of strings"
8853 Many strings in Exim's run time configuration are expanded before use. Some of
8854 them are expanded every time they are used; others are expanded only once.
8856 When a string is being expanded it is copied verbatim from left to right except
8857 when a dollar or backslash character is encountered. A dollar specifies the
8858 start of a portion of the string that is interpreted and replaced as described
8859 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8860 escape character, as described in the following section.
8862 Whether a string is expanded depends upon the context. Usually this is solely
8863 dependent upon the option for which a value is sought; in this documentation,
8864 options for which string expansion is performed are marked with † after
8865 the data type. ACL rules always expand strings. A couple of expansion
8866 conditions do not expand some of the brace-delimited branches, for security
8871 .section "Literal text in expanded strings" "SECTlittext"
8872 .cindex "expansion" "including literal text"
8873 An uninterpreted dollar can be included in an expanded string by putting a
8874 backslash in front of it. A backslash can be used to prevent any special
8875 character being treated specially in an expansion, including backslash itself.
8876 If the string appears in quotes in the configuration file, two backslashes are
8877 required because the quotes themselves cause interpretation of backslashes when
8878 the string is read in (see section &<<SECTstrings>>&).
8880 .cindex "expansion" "non-expandable substrings"
8881 A portion of the string can specified as non-expandable by placing it between
8882 two occurrences of &`\N`&. This is particularly useful for protecting regular
8883 expressions, which often contain backslashes and dollar signs. For example:
8885 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8887 On encountering the first &`\N`&, the expander copies subsequent characters
8888 without interpretation until it reaches the next &`\N`& or the end of the
8893 .section "Character escape sequences in expanded strings" "SECID82"
8894 .cindex "expansion" "escape sequences"
8895 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8896 expanded string is recognized as an escape sequence for the character newline,
8897 carriage return, or tab, respectively. A backslash followed by up to three
8898 octal digits is recognized as an octal encoding for a single character, and a
8899 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8902 These escape sequences are also recognized in quoted strings when they are read
8903 in. Their interpretation in expansions as well is useful for unquoted strings,
8904 and for other cases such as looked-up strings that are then expanded.
8907 .section "Testing string expansions" "SECID83"
8908 .cindex "expansion" "testing"
8909 .cindex "testing" "string expansion"
8911 Many expansions can be tested by calling Exim with the &%-be%& option. This
8912 takes the command arguments, or lines from the standard input if there are no
8913 arguments, runs them through the string expansion code, and writes the results
8914 to the standard output. Variables based on configuration values are set up, but
8915 since no message is being processed, variables such as &$local_part$& have no
8916 value. Nevertheless the &%-be%& option can be useful for checking out file and
8917 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8920 Exim gives up its root privilege when it is called with the &%-be%& option, and
8921 instead runs under the uid and gid it was called with, to prevent users from
8922 using &%-be%& for reading files to which they do not have access.
8925 If you want to test expansions that include variables whose values are taken
8926 from a message, there are two other options that can be used. The &%-bem%&
8927 option is like &%-be%& except that it is followed by a file name. The file is
8928 read as a message before doing the test expansions. For example:
8930 exim -bem /tmp/test.message '$h_subject:'
8932 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8933 Exim message identifier. For example:
8935 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8937 This loads the message from Exim's spool before doing the test expansions, and
8938 is therefore restricted to admin users.
8941 .section "Forced expansion failure" "SECTforexpfai"
8942 .cindex "expansion" "forced failure"
8943 A number of expansions that are described in the following section have
8944 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8945 (which are sometimes called &"curly brackets"&). Which of the two strings is
8946 used depends on some condition that is evaluated as part of the expansion. If,
8947 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8948 the entire string expansion fails in a way that can be detected by the code
8949 that requested the expansion. This is called &"forced expansion failure"&, and
8950 its consequences depend on the circumstances. In some cases it is no different
8951 from any other expansion failure, but in others a different action may be
8952 taken. Such variations are mentioned in the documentation of the option that is
8958 .section "Expansion items" "SECTexpansionitems"
8959 The following items are recognized in expanded strings. White space may be used
8960 between sub-items that are keywords or substrings enclosed in braces inside an
8961 outer set of braces, to improve readability. &*Warning*&: Within braces,
8962 white space is significant.
8965 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8966 .cindex "expansion" "variables"
8967 Substitute the contents of the named variable, for example:
8972 The second form can be used to separate the name from subsequent alphanumeric
8973 characters. This form (using braces) is available only for variables; it does
8974 &'not'& apply to message headers. The names of the variables are given in
8975 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8976 given, the expansion fails.
8978 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8979 .cindex "expansion" "operators"
8980 The string is first itself expanded, and then the operation specified by
8981 <&'op'&> is applied to it. For example:
8985 The string starts with the first character after the colon, which may be
8986 leading white space. A list of operators is given in section &<<SECTexpop>>&
8987 below. The operator notation is used for simple expansion items that have just
8988 one argument, because it reduces the number of braces and therefore makes the
8989 string easier to understand.
8991 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8992 This item inserts &"basic"& header lines. It is described with the &%header%&
8993 expansion item below.
8996 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
8997 .cindex "expansion" "calling an acl"
8998 .cindex "&%acl%&" "call from expansion"
8999 The name and zero to nine argument strings are first expanded separately. The expanded
9000 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9001 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9002 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9003 and may use the variables; if another acl expansion is used the values
9004 are restored after it returns. If the ACL sets
9005 a value using a "message =" modifier and returns accept or deny, the value becomes
9006 the result of the expansion.
9007 If no message is set and the ACL returns accept or deny
9008 the expansion result is an empty string.
9009 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9012 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9013 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9014 .cindex "expansion" "extracting cerificate fields"
9015 .cindex "&%certextract%&" "certificate fields"
9016 .cindex "certificate" "extracting fields"
9017 The <&'certificate'&> must be a variable of type certificate.
9018 The field name is expanded and used to retrieve the relevant field from
9019 the certificate. Supported fields are:
9023 &`subject `& RFC4514 DN
9024 &`issuer `& RFC4514 DN
9029 &`subj_altname `& tagged list
9033 If the field is found,
9034 <&'string2'&> is expanded, and replaces the whole item;
9035 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9036 variable &$value$& contains the value that has been extracted. Afterwards, it
9037 is restored to any previous value it might have had.
9039 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9040 key is not found. If {<&'string2'&>} is also omitted, the value that was
9043 Some field names take optional modifiers, appended and separated by commas.
9045 The field selectors marked as "RFC4514" above
9046 output a Distinguished Name string which is
9048 parseable by Exim as a comma-separated tagged list
9049 (the exceptions being elements containing commas).
9050 RDN elements of a single type may be selected by
9051 a modifier of the type label; if so the expansion
9052 result is a list (newline-separated by default).
9053 The separator may be changed by another modifier of
9054 a right angle-bracket followed immediately by the new separator.
9055 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9057 The field selectors marked as "time" above
9058 take an optional modifier of "int"
9059 for which the result is the number of seconds since epoch.
9060 Otherwise the result is a human-readable string
9061 in the timezone selected by the main "timezone" option.
9063 The field selectors marked as "list" above return a list,
9064 newline-separated by default,
9065 (embedded separator characters in elements are doubled).
9066 The separator may be changed by a modifier of
9067 a right angle-bracket followed immediately by the new separator.
9069 The field selectors marked as "tagged" above
9070 prefix each list element with a type string and an equals sign.
9071 Elements of only one type may be selected by a modifier
9072 which is one of "dns", "uri" or "mail";
9073 if so the element tags are omitted.
9075 If not otherwise noted field values are presented in human-readable form.
9077 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9078 {*&<&'arg'&>&*}...}*&"
9080 This expansion dynamically loads and then calls a locally-written C function.
9081 This functionality is available only if Exim is compiled with
9085 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9086 object so that it doesn't reload the same object file in the same Exim process
9087 (but of course Exim does start new processes frequently).
9089 There may be from zero to eight arguments to the function. When compiling
9090 a local function that is to be called in this way, &_local_scan.h_& should be
9091 included. The Exim variables and functions that are defined by that API
9092 are also available for dynamically loaded functions. The function itself
9093 must have the following type:
9095 int dlfunction(uschar **yield, int argc, uschar *argv[])
9097 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9098 function should return one of the following values:
9100 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9101 into the expanded string that is being built.
9103 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9104 from &'yield'&, if it is set.
9106 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9107 taken from &'yield'& if it is set.
9109 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9111 When compiling a function that is to be used in this way with gcc,
9112 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9113 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9116 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9117 .cindex "expansion" "extracting value from environment"
9118 .cindex "environment" "value from"
9119 The key is first expanded separately, and leading and trailing white space
9121 This is then searched for as a name in the environment.
9122 If a variable is found then its value is placed in &$value$&
9123 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9125 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9126 appear, for example:
9128 ${env{USER}{$value} fail }
9130 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9131 {<&'string1'&>} must be present for &"fail"& to be recognized.
9133 If {<&'string2'&>} is omitted an empty string is substituted on
9135 If {<&'string1'&>} is omitted the search result is substituted on
9139 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9140 {*&<&'string3'&>&*}}*&"
9141 .cindex "expansion" "extracting substrings by key"
9142 .cindex "&%extract%&" "substrings by key"
9143 The key and <&'string1'&> are first expanded separately. Leading and trailing
9144 white space is removed from the key (but not from any of the strings). The key
9145 must not consist entirely of digits. The expanded <&'string1'&> must be of the
9148 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9151 where the equals signs and spaces (but not both) are optional. If any of the
9152 values contain white space, they must be enclosed in double quotes, and any
9153 values that are enclosed in double quotes are subject to escape processing as
9154 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9155 for the value that corresponds to the key. The search is case-insensitive. If
9156 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9157 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9158 variable &$value$& contains the value that has been extracted. Afterwards, it
9159 is restored to any previous value it might have had.
9161 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9162 key is not found. If {<&'string2'&>} is also omitted, the value that was
9163 extracted is used. Thus, for example, these two expansions are identical, and
9166 ${extract{gid}{uid=1984 gid=2001}}
9167 ${extract{gid}{uid=1984 gid=2001}{$value}}
9169 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9170 appear, for example:
9172 ${extract{Z}{A=... B=...}{$value} fail }
9174 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9175 {<&'string2'&>} must be present for &"fail"& to be recognized.
9178 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9179 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9180 .cindex "expansion" "extracting substrings by number"
9181 .cindex "&%extract%&" "substrings by number"
9182 The <&'number'&> argument must consist entirely of decimal digits,
9183 apart from leading and trailing white space, which is ignored.
9184 This is what distinguishes this form of &%extract%& from the previous kind. It
9185 behaves in the same way, except that, instead of extracting a named field, it
9186 extracts from <&'string1'&> the field whose number is given as the first
9187 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9188 <&'string3'&> as before.
9190 The fields in the string are separated by any one of the characters in the
9191 separator string. These may include space or tab characters.
9192 The first field is numbered one. If the number is negative, the fields are
9193 counted from the end of the string, with the rightmost one numbered -1. If the
9194 number given is zero, the entire string is returned. If the modulus of the
9195 number is greater than the number of fields in the string, the result is the
9196 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9197 provided. For example:
9199 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9203 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9205 yields &"99"&. Two successive separators mean that the field between them is
9206 empty (for example, the fifth field above).
9209 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9210 .cindex "list" "selecting by condition"
9211 .cindex "expansion" "selecting from list by condition"
9213 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9214 default, but the separator can be changed in the usual way. For each item
9215 in this list, its value is place in &$item$&, and then the condition is
9216 evaluated. If the condition is true, &$item$& is added to the output as an
9217 item in a new list; if the condition is false, the item is discarded. The
9218 separator used for the output list is the same as the one used for the
9219 input, but a separator setting is not included in the output. For example:
9221 ${filter{a:b:c}{!eq{$item}{b}}
9223 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9224 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9227 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9228 .cindex "hash function" "textual"
9229 .cindex "expansion" "textual hash"
9230 This is a textual hashing function, and was the first to be implemented in
9231 early versions of Exim. In current releases, there are other hashing functions
9232 (numeric, MD5, and SHA-1), which are described below.
9234 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9235 <&'n'&>. If you are using fixed values for these numbers, that is, if
9236 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9237 use the simpler operator notation that avoids some of the braces:
9239 ${hash_<n>_<m>:<string>}
9241 The second number is optional (in both notations). If <&'n'&> is greater than
9242 or equal to the length of the string, the expansion item returns the string.
9243 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9244 function to the string. The new string consists of characters taken from the
9245 first <&'m'&> characters of the string
9247 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9249 If <&'m'&> is not present the value 26 is used, so that only lower case
9250 letters appear. For example:
9252 &`$hash{3}{monty}} `& yields &`jmg`&
9253 &`$hash{5}{monty}} `& yields &`monty`&
9254 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9257 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9258 &*$h_*&<&'header&~name'&>&*:*&" &&&
9259 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9260 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9261 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9262 &*$rh_*&<&'header&~name'&>&*:*&"
9263 .cindex "expansion" "header insertion"
9264 .vindex "&$header_$&"
9265 .vindex "&$bheader_$&"
9266 .vindex "&$rheader_$&"
9267 .cindex "header lines" "in expansion strings"
9268 .cindex "header lines" "character sets"
9269 .cindex "header lines" "decoding"
9270 Substitute the contents of the named message header line, for example
9274 The newline that terminates a header line is not included in the expansion, but
9275 internal newlines (caused by splitting the header line over several physical
9276 lines) may be present.
9278 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9279 the data in the header line is interpreted.
9282 .cindex "white space" "in header lines"
9283 &%rheader%& gives the original &"raw"& content of the header line, with no
9284 processing at all, and without the removal of leading and trailing white space.
9287 .cindex "base64 encoding" "in header lines"
9288 &%bheader%& removes leading and trailing white space, and then decodes base64
9289 or quoted-printable MIME &"words"& within the header text, but does no
9290 character set translation. If decoding of what looks superficially like a MIME
9291 &"word"& fails, the raw string is returned. If decoding
9292 .cindex "binary zero" "in header line"
9293 produces a binary zero character, it is replaced by a question mark &-- this is
9294 what Exim does for binary zeros that are actually received in header lines.
9297 &%header%& tries to translate the string as decoded by &%bheader%& to a
9298 standard character set. This is an attempt to produce the same string as would
9299 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9300 returned. Translation is attempted only on operating systems that support the
9301 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9302 a system Makefile or in &_Local/Makefile_&.
9305 In a filter file, the target character set for &%header%& can be specified by a
9306 command of the following form:
9308 headers charset "UTF-8"
9310 This command affects all references to &$h_$& (or &$header_$&) expansions in
9311 subsequently obeyed filter commands. In the absence of this command, the target
9312 character set in a filter is taken from the setting of the &%headers_charset%&
9313 option in the runtime configuration. The value of this option defaults to the
9314 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9317 Header names follow the syntax of RFC 2822, which states that they may contain
9318 any printing characters except space and colon. Consequently, curly brackets
9319 &'do not'& terminate header names, and should not be used to enclose them as
9320 if they were variables. Attempting to do so causes a syntax error.
9322 Only header lines that are common to all copies of a message are visible to
9323 this mechanism. These are the original header lines that are received with the
9324 message, and any that are added by an ACL statement or by a system
9325 filter. Header lines that are added to a particular copy of a message by a
9326 router or transport are not accessible.
9328 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9329 before the DATA ACL, because the header structure is not set up until the
9330 message is received. Header lines that are added in a RCPT ACL (for example)
9331 are saved until the message's incoming header lines are available, at which
9332 point they are added. When a DATA ACL is running, however, header lines added
9333 by earlier ACLs are visible.
9335 Upper case and lower case letters are synonymous in header names. If the
9336 following character is white space, the terminating colon may be omitted, but
9337 this is not recommended, because you may then forget it when it is needed. When
9338 white space terminates the header name, this white space is included in the
9339 expanded string. If the message does not contain the given header, the
9340 expansion item is replaced by an empty string. (See the &%def%& condition in
9341 section &<<SECTexpcond>>& for a means of testing for the existence of a
9344 If there is more than one header with the same name, they are all concatenated
9345 to form the substitution string, up to a maximum length of 64K. Unless
9346 &%rheader%& is being used, leading and trailing white space is removed from
9347 each header before concatenation, and a completely empty header is ignored. A
9348 newline character is then inserted between non-empty headers, but there is no
9349 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9350 those headers that contain lists of addresses, a comma is also inserted at the
9351 junctions between headers. This does not happen for the &%rheader%& expansion.
9354 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9355 .cindex "expansion" "hmac hashing"
9357 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9358 shared secret and some text into a message authentication code, as specified in
9359 RFC 2104. This differs from &`${md5:secret_text...}`& or
9360 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9361 cryptographic hash, allowing for authentication that is not possible with MD5
9362 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9363 present. For example:
9365 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9367 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9370 dd97e3ba5d1a61b5006108f8c8252953
9372 As an example of how this might be used, you might put in the main part of
9373 an Exim configuration:
9375 SPAMSCAN_SECRET=cohgheeLei2thahw
9377 In a router or a transport you could then have:
9380 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9381 ${hmac{md5}{SPAMSCAN_SECRET}\
9382 {${primary_hostname},${message_exim_id},$h_message-id:}}
9384 Then given a message, you can check where it was scanned by looking at the
9385 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9386 this header line is authentic by recomputing the authentication code from the
9387 host name, message ID and the &'Message-id:'& header line. This can be done
9388 using Exim's &%-be%& option, or by other means, for example by using the
9389 &'hmac_md5_hex()'& function in Perl.
9392 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9393 .cindex "expansion" "conditional"
9394 .cindex "&%if%&, expansion item"
9395 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9396 item; otherwise <&'string2'&> is used. The available conditions are described
9397 in section &<<SECTexpcond>>& below. For example:
9399 ${if eq {$local_part}{postmaster} {yes}{no} }
9401 The second string need not be present; if it is not and the condition is not
9402 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9403 be present instead of the second string (without any curly brackets). In this
9404 case, the expansion is forced to fail if the condition is not true (see section
9405 &<<SECTforexpfai>>&).
9407 If both strings are omitted, the result is the string &`true`& if the condition
9408 is true, and the empty string if the condition is false. This makes it less
9409 cumbersome to write custom ACL and router conditions. For example, instead of
9411 condition = ${if >{$acl_m4}{3}{true}{false}}
9415 condition = ${if >{$acl_m4}{3}}
9421 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9422 .cindex expansion "imap folder"
9423 .cindex "&%imapfolder%& expansion item"
9424 This item converts a (possibly multilevel, or with non-ASCII characters)
9425 folder specification to a Maildir name for filesystem use.
9426 For information on internationalisation support see &<<SECTi18nMDA>>&.
9431 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9432 .cindex "expansion" "string truncation"
9433 .cindex "&%length%& expansion item"
9434 The &%length%& item is used to extract the initial portion of a string. Both
9435 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9436 you are using a fixed value for the number, that is, if <&'string1'&> does not
9437 change when expanded, you can use the simpler operator notation that avoids
9440 ${length_<n>:<string>}
9442 The result of this item is either the first <&'n'&> characters or the whole
9443 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9444 &%strlen%&, which gives the length of a string.
9447 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9448 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9449 .cindex "expansion" "extracting list elements by number"
9450 .cindex "&%listextract%&" "extract list elements by number"
9451 .cindex "list" "extracting elements by number"
9452 The <&'number'&> argument must consist entirely of decimal digits,
9453 apart from an optional leading minus,
9454 and leading and trailing white space (which is ignored).
9456 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9457 default, but the separator can be changed in the usual way.
9459 The first field of the list is numbered one.
9460 If the number is negative, the fields are
9461 counted from the end of the list, with the rightmost one numbered -1.
9462 The numbered element of the list is extracted and placed in &$value$&,
9463 then <&'string2'&> is expanded as the result.
9465 If the modulus of the
9466 number is zero or greater than the number of fields in the string,
9467 the result is the expansion of <&'string3'&>.
9471 ${listextract{2}{x:42:99}}
9475 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9477 yields &"result: 42"&.
9479 If {<&'string3'&>} is omitted, an empty string is used for string3.
9480 If {<&'string2'&>} is also omitted, the value that was
9482 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9485 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9486 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9487 This is the first of one of two different types of lookup item, which are both
9488 described in the next item.
9490 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9491 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9492 .cindex "expansion" "lookup in"
9493 .cindex "file" "lookups"
9494 .cindex "lookup" "in expanded string"
9495 The two forms of lookup item specify data lookups in files and databases, as
9496 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9497 lookups, and the second is used for query-style lookups. The <&'key'&>,
9498 <&'file'&>, and <&'query'&> strings are expanded before use.
9500 If there is any white space in a lookup item which is part of a filter command,
9501 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9502 other place where white space is significant, the lookup item must be enclosed
9503 in double quotes. The use of data lookups in users' filter files may be locked
9504 out by the system administrator.
9507 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9508 During its expansion, the variable &$value$& contains the data returned by the
9509 lookup. Afterwards it reverts to the value it had previously (at the outer
9510 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9511 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9512 string on failure. If <&'string2'&> is provided, it can itself be a nested
9513 lookup, thus providing a mechanism for looking up a default value when the
9514 original lookup fails.
9516 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9517 data for the outer lookup while the parameters of the second lookup are
9518 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9519 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9520 appear, and in this case, if the lookup fails, the entire expansion is forced
9521 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9522 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9523 successful lookup, and nothing in the case of failure.
9525 For single-key lookups, the string &"partial"& is permitted to precede the
9526 search type in order to do partial matching, and * or *@ may follow a search
9527 type to request default lookups if the key does not match (see sections
9528 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9530 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9531 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9532 and non-wild parts of the key during the expansion of the replacement text.
9533 They return to their previous values at the end of the lookup item.
9535 This example looks up the postmaster alias in the conventional alias file:
9537 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9539 This example uses NIS+ to look up the full name of the user corresponding to
9540 the local part of an address, forcing the expansion to fail if it is not found:
9542 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9547 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9548 .cindex "expansion" "list creation"
9550 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9551 default, but the separator can be changed in the usual way. For each item
9552 in this list, its value is place in &$item$&, and then <&'string2'&> is
9553 expanded and added to the output as an item in a new list. The separator used
9554 for the output list is the same as the one used for the input, but a separator
9555 setting is not included in the output. For example:
9557 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9559 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9560 value of &$item$& is restored to what it was before. See also the &*filter*&
9561 and &*reduce*& expansion items.
9563 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9564 .cindex "expansion" "numeric hash"
9565 .cindex "hash function" "numeric"
9566 The three strings are expanded; the first two must yield numbers. Call them
9567 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9568 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9569 can use the simpler operator notation that avoids some of the braces:
9571 ${nhash_<n>_<m>:<string>}
9573 The second number is optional (in both notations). If there is only one number,
9574 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9575 processed by a div/mod hash function that returns two numbers, separated by a
9576 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9579 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9581 returns the string &"6/33"&.
9585 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9586 .cindex "Perl" "use in expanded string"
9587 .cindex "expansion" "calling Perl from"
9588 This item is available only if Exim has been built to include an embedded Perl
9589 interpreter. The subroutine name and the arguments are first separately
9590 expanded, and then the Perl subroutine is called with those arguments. No
9591 additional arguments need be given; the maximum number permitted, including the
9592 name of the subroutine, is nine.
9594 The return value of the subroutine is inserted into the expanded string, unless
9595 the return value is &%undef%&. In that case, the expansion fails in the same
9596 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9597 Whatever you return is evaluated in a scalar context. For example, if you
9598 return the name of a Perl vector, the return value is the size of the vector,
9601 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9602 with the error message that was passed to &%die%&. More details of the embedded
9603 Perl facility are given in chapter &<<CHAPperl>>&.
9605 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9606 out the use of this expansion item in filter files.
9609 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9610 .cindex "&%prvs%& expansion item"
9611 The first argument is a complete email address and the second is secret
9612 keystring. The third argument, specifying a key number, is optional. If absent,
9613 it defaults to 0. The result of the expansion is a prvs-signed email address,
9614 to be typically used with the &%return_path%& option on an &(smtp)& transport
9615 as part of a bounce address tag validation (BATV) scheme. For more discussion
9616 and an example, see section &<<SECTverifyPRVS>>&.
9618 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9619 {*&<&'string'&>&*}}*&"
9620 .cindex "&%prvscheck%& expansion item"
9621 This expansion item is the complement of the &%prvs%& item. It is used for
9622 checking prvs-signed addresses. If the expansion of the first argument does not
9623 yield a syntactically valid prvs-signed address, the whole item expands to the
9624 empty string. When the first argument does expand to a syntactically valid
9625 prvs-signed address, the second argument is expanded, with the prvs-decoded
9626 version of the address and the key number extracted from the address in the
9627 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9629 These two variables can be used in the expansion of the second argument to
9630 retrieve the secret. The validity of the prvs-signed address is then checked
9631 against the secret. The result is stored in the variable &$prvscheck_result$&,
9632 which is empty for failure or &"1"& for success.
9634 The third argument is optional; if it is missing, it defaults to an empty
9635 string. This argument is now expanded. If the result is an empty string, the
9636 result of the expansion is the decoded version of the address. This is the case
9637 whether or not the signature was valid. Otherwise, the result of the expansion
9638 is the expansion of the third argument.
9640 All three variables can be used in the expansion of the third argument.
9641 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9642 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9644 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9645 .cindex "expansion" "inserting an entire file"
9646 .cindex "file" "inserting into expansion"
9647 .cindex "&%readfile%& expansion item"
9648 The file name and end-of-line string are first expanded separately. The file is
9649 then read, and its contents replace the entire item. All newline characters in
9650 the file are replaced by the end-of-line string if it is present. Otherwise,
9651 newlines are left in the string.
9652 String expansion is not applied to the contents of the file. If you want this,
9653 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9654 the string expansion fails.
9656 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9657 locks out the use of this expansion item in filter files.
9661 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9662 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9663 .cindex "expansion" "inserting from a socket"
9664 .cindex "socket, use of in expansion"
9665 .cindex "&%readsocket%& expansion item"
9666 This item inserts data from a Unix domain or TCP socket into the expanded
9667 string. The minimal way of using it uses just two arguments, as in these
9670 ${readsocket{/socket/name}{request string}}
9671 ${readsocket{inet:some.host:1234}{request string}}
9673 For a Unix domain socket, the first substring must be the path to the socket.
9674 For an Internet socket, the first substring must contain &`inet:`& followed by
9675 a host name or IP address, followed by a colon and a port, which can be a
9676 number or the name of a TCP port in &_/etc/services_&. An IP address may
9677 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9680 ${readsocket{inet:[::1]:1234}{request string}}
9682 Only a single host name may be given, but if looking it up yields more than
9683 one IP address, they are each tried in turn until a connection is made. For
9684 both kinds of socket, Exim makes a connection, writes the request string
9685 unless it is an empty string; and no terminating NUL is ever sent)
9686 and reads from the socket until an end-of-file
9687 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9688 extend what can be done. Firstly, you can vary the timeout. For example:
9690 ${readsocket{/socket/name}{request string}{3s}}
9692 A fourth argument allows you to change any newlines that are in the data
9693 that is read, in the same way as for &%readfile%& (see above). This example
9694 turns them into spaces:
9696 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9698 As with all expansions, the substrings are expanded before the processing
9699 happens. Errors in these sub-expansions cause the expansion to fail. In
9700 addition, the following errors can occur:
9703 Failure to create a socket file descriptor;
9705 Failure to connect the socket;
9707 Failure to write the request string;
9709 Timeout on reading from the socket.
9712 By default, any of these errors causes the expansion to fail. However, if
9713 you supply a fifth substring, it is expanded and used when any of the above
9714 errors occurs. For example:
9716 ${readsocket{/socket/name}{request string}{3s}{\n}\
9719 You can test for the existence of a Unix domain socket by wrapping this
9720 expansion in &`${if exists`&, but there is a race condition between that test
9721 and the actual opening of the socket, so it is safer to use the fifth argument
9722 if you want to be absolutely sure of avoiding an expansion error for a
9723 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9725 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9726 locks out the use of this expansion item in filter files.
9729 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9730 .cindex "expansion" "reducing a list to a scalar"
9731 .cindex "list" "reducing to a scalar"
9734 This operation reduces a list to a single, scalar string. After expansion,
9735 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9736 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9737 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9738 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9739 them. The result of that expansion is assigned to &$value$& before the next
9740 iteration. When the end of the list is reached, the final value of &$value$& is
9741 added to the expansion output. The &*reduce*& expansion item can be used in a
9742 number of ways. For example, to add up a list of numbers:
9744 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9746 The result of that expansion would be &`6`&. The maximum of a list of numbers
9749 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9751 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9752 restored to what they were before. See also the &*filter*& and &*map*&
9755 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9756 This item inserts &"raw"& header lines. It is described with the &%header%&
9757 expansion item above.
9759 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9760 {*&<&'string2'&>&*}}*&"
9761 .cindex "expansion" "running a command"
9762 .cindex "&%run%& expansion item"
9763 The command and its arguments are first expanded as one string. The string is
9764 split apart into individual arguments by spaces, and then the command is run
9765 in a separate process, but under the same uid and gid. As in other command
9766 executions from Exim, a shell is not used by default. If the command requires
9767 a shell, you must explicitly code it.
9769 Since the arguments are split by spaces, when there is a variable expansion
9770 which has an empty result, it will cause the situation that the argument will
9771 simply be omitted when the program is actually executed by Exim. If the
9772 script/program requires a specific number of arguments and the expanded
9773 variable could possibly result in this empty expansion, the variable must be
9774 quoted. This is more difficult if the expanded variable itself could result
9775 in a string containing quotes, because it would interfere with the quotes
9776 around the command arguments. A possible guard against this is to wrap the
9777 variable in the &%sg%& operator to change any quote marks to some other
9780 The standard input for the command exists, but is empty. The standard output
9781 and standard error are set to the same file descriptor.
9782 .cindex "return code" "from &%run%& expansion"
9784 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9785 and replaces the entire item; during this expansion, the standard output/error
9786 from the command is in the variable &$value$&. If the command fails,
9787 <&'string2'&>, if present, is expanded and used. Once again, during the
9788 expansion, the standard output/error from the command is in the variable
9791 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9792 can be the word &"fail"& (not in braces) to force expansion failure if the
9793 command does not succeed. If both strings are omitted, the result is contents
9794 of the standard output/error on success, and nothing on failure.
9796 .vindex "&$run_in_acl$&"
9797 The standard output/error of the command is put in the variable &$value$&.
9798 In this ACL example, the output of a command is logged for the admin to
9801 warn condition = ${run{/usr/bin/id}{yes}{no}}
9802 log_message = Output of id: $value
9804 If the command requires shell idioms, such as the > redirect operator, the
9805 shell must be invoked directly, such as with:
9807 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9811 The return code from the command is put in the variable &$runrc$&, and this
9812 remains set afterwards, so in a filter file you can do things like this:
9814 if "${run{x y z}{}}$runrc" is 1 then ...
9815 elif $runrc is 2 then ...
9819 If execution of the command fails (for example, the command does not exist),
9820 the return code is 127 &-- the same code that shells use for non-existent
9823 &*Warning*&: In a router or transport, you cannot assume the order in which
9824 option values are expanded, except for those preconditions whose order of
9825 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9826 by the expansion of one option, and use it in another.
9828 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9829 out the use of this expansion item in filter files.
9832 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9833 .cindex "expansion" "string substitution"
9834 .cindex "&%sg%& expansion item"
9835 This item works like Perl's substitution operator (s) with the global (/g)
9836 option; hence its name. However, unlike the Perl equivalent, Exim does not
9837 modify the subject string; instead it returns the modified string for insertion
9838 into the overall expansion. The item takes three arguments: the subject string,
9839 a regular expression, and a substitution string. For example:
9841 ${sg{abcdefabcdef}{abc}{xyz}}
9843 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9844 if any $ or \ characters are required in the regular expression or in the
9845 substitution string, they have to be escaped. For example:
9847 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9849 yields &"defabc"&, and
9851 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9853 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9854 the regular expression from string expansion.
9858 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
9859 .cindex sorting "a list"
9860 .cindex list sorting
9861 .cindex expansion "list sorting"
9862 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9863 default, but the separator can be changed in the usual way.
9864 The <&'comparator'&> argument is interpreted as the operator
9865 of a two-argument expansion condition.
9866 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
9867 The comparison should return true when applied to two values
9868 if the first value should sort before the second value.
9869 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
9870 the element being placed in &$item$&,
9871 to give values for comparison.
9873 The item result is a sorted list,
9874 with the original list separator,
9875 of the list elements (in full) of the original.
9879 ${sort{3:2:1:4}{<}{$item}}
9881 sorts a list of numbers, and
9883 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
9885 will sort an MX lookup into priority order.
9888 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9889 .cindex "&%substr%& expansion item"
9890 .cindex "substring extraction"
9891 .cindex "expansion" "substring extraction"
9892 The three strings are expanded; the first two must yield numbers. Call them
9893 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9894 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9895 can use the simpler operator notation that avoids some of the braces:
9897 ${substr_<n>_<m>:<string>}
9899 The second number is optional (in both notations).
9900 If it is absent in the simpler format, the preceding underscore must also be
9903 The &%substr%& item can be used to extract more general substrings than
9904 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9905 length required. For example
9907 ${substr{3}{2}{$local_part}}
9909 If the starting offset is greater than the string length the result is the
9910 null string; if the length plus starting offset is greater than the string
9911 length, the result is the right-hand part of the string, starting from the
9912 given offset. The first character in the string has offset zero.
9914 The &%substr%& expansion item can take negative offset values to count
9915 from the right-hand end of its operand. The last character is offset -1, the
9916 second-last is offset -2, and so on. Thus, for example,
9918 ${substr{-5}{2}{1234567}}
9920 yields &"34"&. If the absolute value of a negative offset is greater than the
9921 length of the string, the substring starts at the beginning of the string, and
9922 the length is reduced by the amount of overshoot. Thus, for example,
9924 ${substr{-5}{2}{12}}
9926 yields an empty string, but
9928 ${substr{-3}{2}{12}}
9932 When the second number is omitted from &%substr%&, the remainder of the string
9933 is taken if the offset is positive. If it is negative, all characters in the
9934 string preceding the offset point are taken. For example, an offset of -1 and
9935 no length, as in these semantically identical examples:
9938 ${substr{-1}{abcde}}
9940 yields all but the last character of the string, that is, &"abcd"&.
9944 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9945 {*&<&'replacements'&>&*}}*&"
9946 .cindex "expansion" "character translation"
9947 .cindex "&%tr%& expansion item"
9948 This item does single-character translation on its subject string. The second
9949 argument is a list of characters to be translated in the subject string. Each
9950 matching character is replaced by the corresponding character from the
9951 replacement list. For example
9953 ${tr{abcdea}{ac}{13}}
9955 yields &`1b3de1`&. If there are duplicates in the second character string, the
9956 last occurrence is used. If the third string is shorter than the second, its
9957 last character is replicated. However, if it is empty, no translation takes
9963 .section "Expansion operators" "SECTexpop"
9964 .cindex "expansion" "operators"
9965 For expansion items that perform transformations on a single argument string,
9966 the &"operator"& notation is used because it is simpler and uses fewer braces.
9967 The substring is first expanded before the operation is applied to it. The
9968 following operations can be performed:
9971 .vitem &*${address:*&<&'string'&>&*}*&
9972 .cindex "expansion" "RFC 2822 address handling"
9973 .cindex "&%address%& expansion item"
9974 The string is interpreted as an RFC 2822 address, as it might appear in a
9975 header line, and the effective address is extracted from it. If the string does
9976 not parse successfully, the result is empty.
9979 .vitem &*${addresses:*&<&'string'&>&*}*&
9980 .cindex "expansion" "RFC 2822 address handling"
9981 .cindex "&%addresses%& expansion item"
9982 The string (after expansion) is interpreted as a list of addresses in RFC
9983 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9984 operative address (&'local-part@domain'&) is extracted from each item, and the
9985 result of the expansion is a colon-separated list, with appropriate
9986 doubling of colons should any happen to be present in the email addresses.
9987 Syntactically invalid RFC2822 address items are omitted from the output.
9989 It is possible to specify a character other than colon for the output
9990 separator by starting the string with > followed by the new separator
9991 character. For example:
9993 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9995 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9996 expansion item, which extracts the working address from a single RFC2822
9997 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
10000 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10001 a strict interpretation of header line formatting. Exim parses the bare,
10002 unquoted portion of an email address and if it finds a comma, treats it as an
10003 email address separator. For the example header line:
10005 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10007 The first example below demonstrates that Q-encoded email addresses are parsed
10008 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10009 It does not see the comma because it's still encoded as "=2C". The second
10010 example below is passed the contents of &`$header_from:`&, meaning it gets
10011 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10012 The third example shows that the presence of a comma is skipped when it is
10015 # exim -be '${addresses:From: \
10016 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10018 # exim -be '${addresses:From: Last, First <user@example.com>}'
10019 Last:user@example.com
10020 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10024 .vitem &*${base62:*&<&'digits'&>&*}*&
10025 .cindex "&%base62%& expansion item"
10026 .cindex "expansion" "conversion to base 62"
10027 The string must consist entirely of decimal digits. The number is converted to
10028 base 62 and output as a string of six characters, including leading zeros. In
10029 the few operating environments where Exim uses base 36 instead of base 62 for
10030 its message identifiers (because those systems do not have case-sensitive file
10031 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
10032 be absolutely clear: this is &'not'& base64 encoding.
10034 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10035 .cindex "&%base62d%& expansion item"
10036 .cindex "expansion" "conversion to base 62"
10037 The string must consist entirely of base-62 digits, or, in operating
10038 environments where Exim uses base 36 instead of base 62 for its message
10039 identifiers, base-36 digits. The number is converted to decimal and output as a
10043 .vitem &*${base64:*&<&'string'&>&*}*&
10044 .cindex "expansion" "base64 encoding"
10045 .cindex "base64 encoding" "in string expansion"
10046 .cindex "&%base64%& expansion item"
10047 .cindex certificate "base64 of DER"
10048 This operator converts a string into one that is base64 encoded.
10050 If the string is a single variable of type certificate,
10051 returns the base64 encoding of the DER form of the certificate.
10054 .vitem &*${base64d:*&<&'string'&>&*}*&
10055 .cindex "expansion" "base64 decoding"
10056 .cindex "base64 decoding" "in string expansion"
10057 .cindex "&%base64d%& expansion item"
10058 This operator converts a base64-encoded string into the un-coded form.
10062 .vitem &*${domain:*&<&'string'&>&*}*&
10063 .cindex "domain" "extraction"
10064 .cindex "expansion" "domain extraction"
10065 The string is interpreted as an RFC 2822 address and the domain is extracted
10066 from it. If the string does not parse successfully, the result is empty.
10069 .vitem &*${escape:*&<&'string'&>&*}*&
10070 .cindex "expansion" "escaping non-printing characters"
10071 .cindex "&%escape%& expansion item"
10072 If the string contains any non-printing characters, they are converted to
10073 escape sequences starting with a backslash. Whether characters with the most
10074 significant bit set (so-called &"8-bit characters"&) count as printing or not
10075 is controlled by the &%print_topbitchars%& option.
10078 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10079 .cindex "expansion" "expression evaluation"
10080 .cindex "expansion" "arithmetic expression"
10081 .cindex "&%eval%& expansion item"
10082 These items supports simple arithmetic and bitwise logical operations in
10083 expansion strings. The string (after expansion) must be a conventional
10084 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10085 logical operators, and parentheses. All operations are carried out using
10086 integer arithmetic. The operator priorities are as follows (the same as in the
10087 C programming language):
10089 .irow &'highest:'& "not (~), negate (-)"
10090 .irow "" "multiply (*), divide (/), remainder (%)"
10091 .irow "" "plus (+), minus (-)"
10092 .irow "" "shift-left (<<), shift-right (>>)"
10093 .irow "" "and (&&)"
10095 .irow &'lowest:'& "or (|)"
10097 Binary operators with the same priority are evaluated from left to right. White
10098 space is permitted before or after operators.
10100 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10101 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10102 decimal, even if they start with a leading zero; hexadecimal numbers are not
10103 permitted. This can be useful when processing numbers extracted from dates or
10104 times, which often do have leading zeros.
10106 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10108 respectively. Negative numbers are supported. The result of the computation is
10109 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10112 &`${eval:1+1} `& yields 2
10113 &`${eval:1+2*3} `& yields 7
10114 &`${eval:(1+2)*3} `& yields 9
10115 &`${eval:2+42%5} `& yields 4
10116 &`${eval:0xc&5} `& yields 4
10117 &`${eval:0xc|5} `& yields 13
10118 &`${eval:0xc^5} `& yields 9
10119 &`${eval:0xc>>1} `& yields 6
10120 &`${eval:0xc<<1} `& yields 24
10121 &`${eval:~255&0x1234} `& yields 4608
10122 &`${eval:-(~255&0x1234)} `& yields -4608
10125 As a more realistic example, in an ACL you might have
10127 deny message = Too many bad recipients
10130 {>{$rcpt_count}{10}} \
10133 {$recipients_count} \
10134 {${eval:$rcpt_count/2}} \
10138 The condition is true if there have been more than 10 RCPT commands and
10139 fewer than half of them have resulted in a valid recipient.
10142 .vitem &*${expand:*&<&'string'&>&*}*&
10143 .cindex "expansion" "re-expansion of substring"
10144 The &%expand%& operator causes a string to be expanded for a second time. For
10147 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10149 first looks up a string in a file while expanding the operand for &%expand%&,
10150 and then re-expands what it has found.
10153 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10155 .cindex "UTF-8" "conversion from"
10156 .cindex "expansion" "UTF-8 conversion"
10157 .cindex "&%from_utf8%& expansion item"
10158 The world is slowly moving towards Unicode, although there are no standards for
10159 email yet. However, other applications (including some databases) are starting
10160 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10161 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10162 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10163 the result is an undefined sequence of bytes.
10165 Unicode code points with values less than 256 are compatible with ASCII and
10166 ISO-8859-1 (also known as Latin-1).
10167 For example, character 169 is the copyright symbol in both cases, though the
10168 way it is encoded is different. In UTF-8, more than one byte is needed for
10169 characters with code values greater than 127, whereas ISO-8859-1 is a
10170 single-byte encoding (but thereby limited to 256 characters). This makes
10171 translation from UTF-8 to ISO-8859-1 straightforward.
10174 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10175 .cindex "hash function" "textual"
10176 .cindex "expansion" "textual hash"
10177 The &%hash%& operator is a simpler interface to the hashing function that can
10178 be used when the two parameters are fixed numbers (as opposed to strings that
10179 change when expanded). The effect is the same as
10181 ${hash{<n>}{<m>}{<string>}}
10183 See the description of the general &%hash%& item above for details. The
10184 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10188 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10189 .cindex "base64 encoding" "conversion from hex"
10190 .cindex "expansion" "hex to base64"
10191 .cindex "&%hex2b64%& expansion item"
10192 This operator converts a hex string into one that is base64 encoded. This can
10193 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10197 .vitem &*${hexquote:*&<&'string'&>&*}*&
10198 .cindex "quoting" "hex-encoded unprintable characters"
10199 .cindex "&%hexquote%& expansion item"
10200 This operator converts non-printable characters in a string into a hex
10201 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10202 as is, and other byte values are converted to &`\xNN`&, for example a
10203 byte value 127 is converted to &`\x7f`&.
10207 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10208 .cindex "&%ipv6denorm%& expansion item"
10209 .cindex "IP address" normalisation
10210 This expands an IPv6 address to a full eight-element colon-separated set
10211 of hex digits including leading zeroes.
10212 A trailing ipv4-style dotted-decimal set is converted to hex.
10213 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10215 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10216 .cindex "&%ipv6norm%& expansion item"
10217 .cindex "IP address" normalisation
10218 .cindex "IP address" "canonical form"
10219 This converts an IPv6 address to canonical form.
10220 Leading zeroes of groups are omitted, and the longest
10221 set of zero-valued groups is replaced with a double colon.
10222 A trailing ipv4-style dotted-decimal set is converted to hex.
10223 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10227 .vitem &*${lc:*&<&'string'&>&*}*&
10228 .cindex "case forcing in strings"
10229 .cindex "string" "case forcing"
10230 .cindex "lower casing"
10231 .cindex "expansion" "case forcing"
10232 .cindex "&%lc%& expansion item"
10233 This forces the letters in the string into lower-case, for example:
10238 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10239 .cindex "expansion" "string truncation"
10240 .cindex "&%length%& expansion item"
10241 The &%length%& operator is a simpler interface to the &%length%& function that
10242 can be used when the parameter is a fixed number (as opposed to a string that
10243 changes when expanded). The effect is the same as
10245 ${length{<number>}{<string>}}
10247 See the description of the general &%length%& item above for details. Note that
10248 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10249 when &%length%& is used as an operator.
10252 .vitem &*${listcount:*&<&'string'&>&*}*&
10253 .cindex "expansion" "list item count"
10254 .cindex "list" "item count"
10255 .cindex "list" "count of items"
10256 .cindex "&%listcount%& expansion item"
10257 The string is interpreted as a list and the number of items is returned.
10260 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10261 .cindex "expansion" "named list"
10262 .cindex "&%listnamed%& expansion item"
10263 The name is interpreted as a named list and the content of the list is returned,
10264 expanding any referenced lists, re-quoting as needed for colon-separation.
10265 If the optional type is given it must be one of "a", "d", "h" or "l"
10266 and selects address-, domain-, host- or localpart- lists to search among respectively.
10267 Otherwise all types are searched in an undefined order and the first
10268 matching list is returned.
10271 .vitem &*${local_part:*&<&'string'&>&*}*&
10272 .cindex "expansion" "local part extraction"
10273 .cindex "&%local_part%& expansion item"
10274 The string is interpreted as an RFC 2822 address and the local part is
10275 extracted from it. If the string does not parse successfully, the result is
10279 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10280 .cindex "masked IP address"
10281 .cindex "IP address" "masking"
10282 .cindex "CIDR notation"
10283 .cindex "expansion" "IP address masking"
10284 .cindex "&%mask%& expansion item"
10285 If the form of the string to be operated on is not an IP address followed by a
10286 slash and an integer (that is, a network address in CIDR notation), the
10287 expansion fails. Otherwise, this operator converts the IP address to binary,
10288 masks off the least significant bits according to the bit count, and converts
10289 the result back to text, with mask appended. For example,
10291 ${mask:10.111.131.206/28}
10293 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10294 be mostly used for looking up masked addresses in files, the result for an IPv6
10295 address uses dots to separate components instead of colons, because colon
10296 terminates a key string in lsearch files. So, for example,
10298 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10302 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10304 Letters in IPv6 addresses are always output in lower case.
10307 .vitem &*${md5:*&<&'string'&>&*}*&
10309 .cindex "expansion" "MD5 hash"
10310 .cindex certificate fingerprint
10311 .cindex "&%md5%& expansion item"
10312 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10313 as a 32-digit hexadecimal number, in which any letters are in lower case.
10315 If the string is a single variable of type certificate,
10316 returns the MD5 hash fingerprint of the certificate.
10319 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10320 .cindex "expansion" "numeric hash"
10321 .cindex "hash function" "numeric"
10322 The &%nhash%& operator is a simpler interface to the numeric hashing function
10323 that can be used when the two parameters are fixed numbers (as opposed to
10324 strings that change when expanded). The effect is the same as
10326 ${nhash{<n>}{<m>}{<string>}}
10328 See the description of the general &%nhash%& item above for details.
10331 .vitem &*${quote:*&<&'string'&>&*}*&
10332 .cindex "quoting" "in string expansions"
10333 .cindex "expansion" "quoting"
10334 .cindex "&%quote%& expansion item"
10335 The &%quote%& operator puts its argument into double quotes if it
10336 is an empty string or
10337 contains anything other than letters, digits, underscores, dots, and hyphens.
10338 Any occurrences of double quotes and backslashes are escaped with a backslash.
10339 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10340 respectively For example,
10348 The place where this is useful is when the argument is a substitution from a
10349 variable or a message header.
10351 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10352 .cindex "&%quote_local_part%& expansion item"
10353 This operator is like &%quote%&, except that it quotes the string only if
10354 required to do so by the rules of RFC 2822 for quoting local parts. For
10355 example, a plus sign would not cause quoting (but it would for &%quote%&).
10356 If you are creating a new email address from the contents of &$local_part$&
10357 (or any other unknown data), you should always use this operator.
10360 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10361 .cindex "quoting" "lookup-specific"
10362 This operator applies lookup-specific quoting rules to the string. Each
10363 query-style lookup type has its own quoting rules which are described with
10364 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10366 ${quote_ldap:two * two}
10372 For single-key lookup types, no quoting is ever necessary and this operator
10373 yields an unchanged string.
10376 .vitem &*${randint:*&<&'n'&>&*}*&
10377 .cindex "random number"
10378 This operator returns a somewhat random number which is less than the
10379 supplied number and is at least 0. The quality of this randomness depends
10380 on how Exim was built; the values are not suitable for keying material.
10381 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10382 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10383 for versions of GnuTLS with that function.
10384 Otherwise, the implementation may be arc4random(), random() seeded by
10385 srandomdev() or srandom(), or a custom implementation even weaker than
10389 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10390 .cindex "expansion" "IP address"
10391 This operator reverses an IP address; for IPv4 addresses, the result is in
10392 dotted-quad decimal form, while for IPv6 addresses the result is in
10393 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10394 for DNS. For example,
10396 ${reverse_ip:192.0.2.4}
10397 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10402 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10406 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10407 .cindex "expansion" "RFC 2047"
10408 .cindex "RFC 2047" "expansion operator"
10409 .cindex "&%rfc2047%& expansion item"
10410 This operator encodes text according to the rules of RFC 2047. This is an
10411 encoding that is used in header lines to encode non-ASCII characters. It is
10412 assumed that the input string is in the encoding specified by the
10413 &%headers_charset%& option, which gets its default at build time. If the string
10414 contains only characters in the range 33&--126, and no instances of the
10417 ? = ( ) < > @ , ; : \ " . [ ] _
10419 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10420 string, using as many &"encoded words"& as necessary to encode all the
10424 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10425 .cindex "expansion" "RFC 2047"
10426 .cindex "RFC 2047" "decoding"
10427 .cindex "&%rfc2047d%& expansion item"
10428 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10429 bytes are replaced by question marks. Characters are converted into the
10430 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10431 not recognized unless &%check_rfc2047_length%& is set false.
10433 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10434 access a header line, RFC 2047 decoding is done automatically. You do not need
10435 to use this operator as well.
10439 .vitem &*${rxquote:*&<&'string'&>&*}*&
10440 .cindex "quoting" "in regular expressions"
10441 .cindex "regular expressions" "quoting"
10442 .cindex "&%rxquote%& expansion item"
10443 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10444 characters in its argument. This is useful when substituting the values of
10445 variables or headers inside regular expressions.
10448 .vitem &*${sha1:*&<&'string'&>&*}*&
10449 .cindex "SHA-1 hash"
10450 .cindex "expansion" "SHA-1 hashing"
10451 .cindex certificate fingerprint
10452 .cindex "&%sha2%& expansion item"
10453 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10454 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10456 If the string is a single variable of type certificate,
10457 returns the SHA-1 hash fingerprint of the certificate.
10460 .vitem &*${sha256:*&<&'certificate'&>&*}*&
10461 .cindex "SHA-256 hash"
10462 .cindex certificate fingerprint
10463 .cindex "expansion" "SHA-256 hashing"
10464 .cindex "&%sha256%& expansion item"
10465 The &%sha256%& operator computes the SHA-256 hash fingerprint of the
10468 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10469 Only arguments which are a single variable of certificate type are supported.
10472 .vitem &*${stat:*&<&'string'&>&*}*&
10473 .cindex "expansion" "statting a file"
10474 .cindex "file" "extracting characteristics"
10475 .cindex "&%stat%& expansion item"
10476 The string, after expansion, must be a file path. A call to the &[stat()]&
10477 function is made for this path. If &[stat()]& fails, an error occurs and the
10478 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10479 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10480 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10481 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10482 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10483 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10484 can extract individual fields using the &%extract%& expansion item.
10486 The use of the &%stat%& expansion in users' filter files can be locked out by
10487 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10488 systems for files larger than 2GB.
10490 .vitem &*${str2b64:*&<&'string'&>&*}*&
10491 .cindex "&%str2b64%& expansion item"
10493 Now deprecated, a synonym for the &%base64%& expansion operator.
10498 .vitem &*${strlen:*&<&'string'&>&*}*&
10499 .cindex "expansion" "string length"
10500 .cindex "string" "length in expansion"
10501 .cindex "&%strlen%& expansion item"
10502 The item is replace by the length of the expanded string, expressed as a
10503 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10506 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10507 .cindex "&%substr%& expansion item"
10508 .cindex "substring extraction"
10509 .cindex "expansion" "substring expansion"
10510 The &%substr%& operator is a simpler interface to the &%substr%& function that
10511 can be used when the two parameters are fixed numbers (as opposed to strings
10512 that change when expanded). The effect is the same as
10514 ${substr{<start>}{<length>}{<string>}}
10516 See the description of the general &%substr%& item above for details. The
10517 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10519 .vitem &*${time_eval:*&<&'string'&>&*}*&
10520 .cindex "&%time_eval%& expansion item"
10521 .cindex "time interval" "decoding"
10522 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10525 .vitem &*${time_interval:*&<&'string'&>&*}*&
10526 .cindex "&%time_interval%& expansion item"
10527 .cindex "time interval" "formatting"
10528 The argument (after sub-expansion) must be a sequence of decimal digits that
10529 represents an interval of time as a number of seconds. It is converted into a
10530 number of larger units and output in Exim's normal time format, for example,
10533 .vitem &*${uc:*&<&'string'&>&*}*&
10534 .cindex "case forcing in strings"
10535 .cindex "string" "case forcing"
10536 .cindex "upper casing"
10537 .cindex "expansion" "case forcing"
10538 .cindex "&%uc%& expansion item"
10539 This forces the letters in the string into upper-case.
10541 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10542 .cindex "correction of invalid utf-8 sequences in strings"
10543 .cindex "utf-8" "utf-8 sequences"
10544 .cindex "incorrect utf-8"
10545 .cindex "expansion" "utf-8 forcing"
10546 .cindex "&%utf8clean%& expansion item"
10547 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10550 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
10551 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
10552 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
10553 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
10554 .cindex expansion UTF-8
10555 .cindex UTF-8 expansion
10557 .cindex internationalisation
10558 .cindex "&%utf8_domain_to_alabel%& expansion item"
10559 .cindex "&%utf8_domain_from_alabel%& expansion item"
10560 .cindex "&%utf8_localpart_to_alabel%& expansion item"
10561 .cindex "&%utf8_localpart_from_alabel%& expansion item"
10562 These convert EAI mail name components between UTF-8 and a-label forms.
10563 For information on internationalisation support see &<<SECTi18nMTA>>&.
10572 .section "Expansion conditions" "SECTexpcond"
10573 .scindex IIDexpcond "expansion" "conditions"
10574 The following conditions are available for testing by the &%${if%& construct
10575 while expanding strings:
10578 .vitem &*!*&<&'condition'&>
10579 .cindex "expansion" "negating a condition"
10580 .cindex "negation" "in expansion condition"
10581 Preceding any condition with an exclamation mark negates the result of the
10584 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10585 .cindex "numeric comparison"
10586 .cindex "expansion" "numeric comparison"
10587 There are a number of symbolic operators for doing numeric comparisons. They
10593 &`>= `& greater or equal
10595 &`<= `& less or equal
10599 ${if >{$message_size}{10M} ...
10601 Note that the general negation operator provides for inequality testing. The
10602 two strings must take the form of optionally signed decimal integers,
10603 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10604 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10605 As a special case, the numerical value of an empty string is taken as
10608 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10609 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10610 10M, not if 10M is larger than &$message_size$&.
10613 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10614 {*&<&'arg2'&>&*}...}*&
10615 .cindex "expansion" "calling an acl"
10616 .cindex "&%acl%&" "expansion condition"
10617 The name and zero to nine argument strings are first expanded separately. The expanded
10618 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10619 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10620 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10621 and may use the variables; if another acl expansion is used the values
10622 are restored after it returns. If the ACL sets
10623 a value using a "message =" modifier the variable $value becomes
10624 the result of the expansion, otherwise it is empty.
10625 If the ACL returns accept the condition is true; if deny, false.
10626 If the ACL returns defer the result is a forced-fail.
10628 .vitem &*bool&~{*&<&'string'&>&*}*&
10629 .cindex "expansion" "boolean parsing"
10630 .cindex "&%bool%& expansion condition"
10631 This condition turns a string holding a true or false representation into
10632 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10633 (case-insensitively); also integer numbers map to true if non-zero,
10635 An empty string is treated as false.
10636 Leading and trailing whitespace is ignored;
10637 thus a string consisting only of whitespace is false.
10638 All other string values will result in expansion failure.
10640 When combined with ACL variables, this expansion condition will let you
10641 make decisions in one place and act on those decisions in another place.
10644 ${if bool{$acl_m_privileged_sender} ...
10648 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10649 .cindex "expansion" "boolean parsing"
10650 .cindex "&%bool_lax%& expansion condition"
10651 Like &%bool%&, this condition turns a string into a boolean state. But
10652 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10653 loose definition that the Router &%condition%& option uses. The empty string
10654 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10655 true. Leading and trailing whitespace is ignored.
10657 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10659 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10660 .cindex "expansion" "encrypted comparison"
10661 .cindex "encrypted strings, comparing"
10662 .cindex "&%crypteq%& expansion condition"
10663 This condition is included in the Exim binary if it is built to support any
10664 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10665 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10666 included in the binary.
10668 The &%crypteq%& condition has two arguments. The first is encrypted and
10669 compared against the second, which is already encrypted. The second string may
10670 be in the LDAP form for storing encrypted strings, which starts with the
10671 encryption type in curly brackets, followed by the data. If the second string
10672 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10673 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10674 Typically this will be a field from a password file. An example of an encrypted
10675 string in LDAP form is:
10677 {md5}CY9rzUYh03PK3k6DJie09g==
10679 If such a string appears directly in an expansion, the curly brackets have to
10680 be quoted, because they are part of the expansion syntax. For example:
10682 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10684 The following encryption types (whose names are matched case-independently) are
10689 .cindex "base64 encoding" "in encrypted password"
10690 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10691 printable characters to compare with the remainder of the second string. If the
10692 length of the comparison string is 24, Exim assumes that it is base64 encoded
10693 (as in the above example). If the length is 32, Exim assumes that it is a
10694 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10698 .cindex "SHA-1 hash"
10699 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10700 printable characters to compare with the remainder of the second string. If the
10701 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10702 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10703 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10706 .cindex "&[crypt()]&"
10707 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10708 only the first eight characters of the password. However, in modern operating
10709 systems this is no longer true, and in many cases the entire password is used,
10710 whatever its length.
10713 .cindex "&[crypt16()]&"
10714 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10715 use up to 16 characters of the password in some operating systems. Again, in
10716 modern operating systems, more characters may be used.
10718 Exim has its own version of &[crypt16()]&, which is just a double call to
10719 &[crypt()]&. For operating systems that have their own version, setting
10720 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10721 operating system version instead of its own. This option is set by default in
10722 the OS-dependent &_Makefile_& for those operating systems that are known to
10723 support &[crypt16()]&.
10725 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10726 it was not using the same algorithm as some operating systems' versions. It
10727 turns out that as well as &[crypt16()]& there is a function called
10728 &[bigcrypt()]& in some operating systems. This may or may not use the same
10729 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10731 However, since there is now a move away from the traditional &[crypt()]&
10732 functions towards using SHA1 and other algorithms, tidying up this area of
10733 Exim is seen as very low priority.
10735 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10736 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10737 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10738 default is &`{crypt}`&. Whatever the default, you can always use either
10739 function by specifying it explicitly in curly brackets.
10741 .vitem &*def:*&<&'variable&~name'&>
10742 .cindex "expansion" "checking for empty variable"
10743 .cindex "&%def%& expansion condition"
10744 The &%def%& condition must be followed by the name of one of the expansion
10745 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10746 variable does not contain the empty string. For example:
10748 ${if def:sender_ident {from $sender_ident}}
10750 Note that the variable name is given without a leading &%$%& character. If the
10751 variable does not exist, the expansion fails.
10753 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10754 &~&*def:h_*&<&'header&~name'&>&*:*&"
10755 .cindex "expansion" "checking header line existence"
10756 This condition is true if a message is being processed and the named header
10757 exists in the message. For example,
10759 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10761 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10762 the header name must be terminated by a colon if white space does not follow.
10764 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10765 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10766 .cindex "string" "comparison"
10767 .cindex "expansion" "string comparison"
10768 .cindex "&%eq%& expansion condition"
10769 .cindex "&%eqi%& expansion condition"
10770 The two substrings are first expanded. The condition is true if the two
10771 resulting strings are identical. For &%eq%& the comparison includes the case of
10772 letters, whereas for &%eqi%& the comparison is case-independent.
10774 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10775 .cindex "expansion" "file existence test"
10776 .cindex "file" "existence test"
10777 .cindex "&%exists%&, expansion condition"
10778 The substring is first expanded and then interpreted as an absolute path. The
10779 condition is true if the named file (or directory) exists. The existence test
10780 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10781 users' filter files may be locked out by the system administrator.
10783 .vitem &*first_delivery*&
10784 .cindex "delivery" "first"
10785 .cindex "first delivery"
10786 .cindex "expansion" "first delivery test"
10787 .cindex "&%first_delivery%& expansion condition"
10788 This condition, which has no data, is true during a message's first delivery
10789 attempt. It is false during any subsequent delivery attempts.
10792 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10793 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10794 .cindex "list" "iterative conditions"
10795 .cindex "expansion" "&*forall*& condition"
10796 .cindex "expansion" "&*forany*& condition"
10798 These conditions iterate over a list. The first argument is expanded to form
10799 the list. By default, the list separator is a colon, but it can be changed by
10800 the normal method. The second argument is interpreted as a condition that is to
10801 be applied to each item in the list in turn. During the interpretation of the
10802 condition, the current list item is placed in a variable called &$item$&.
10804 For &*forany*&, interpretation stops if the condition is true for any item, and
10805 the result of the whole condition is true. If the condition is false for all
10806 items in the list, the overall condition is false.
10808 For &*forall*&, interpretation stops if the condition is false for any item,
10809 and the result of the whole condition is false. If the condition is true for
10810 all items in the list, the overall condition is true.
10812 Note that negation of &*forany*& means that the condition must be false for all
10813 items for the overall condition to succeed, and negation of &*forall*& means
10814 that the condition must be false for at least one item. In this example, the
10815 list separator is changed to a comma:
10817 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10819 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10820 being processed, to enable these expansion items to be nested.
10822 To scan a named list, expand it with the &*listnamed*& operator.
10825 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10826 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10827 .cindex "string" "comparison"
10828 .cindex "expansion" "string comparison"
10829 .cindex "&%ge%& expansion condition"
10830 .cindex "&%gei%& expansion condition"
10831 The two substrings are first expanded. The condition is true if the first
10832 string is lexically greater than or equal to the second string. For &%ge%& the
10833 comparison includes the case of letters, whereas for &%gei%& the comparison is
10836 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10837 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10838 .cindex "string" "comparison"
10839 .cindex "expansion" "string comparison"
10840 .cindex "&%gt%& expansion condition"
10841 .cindex "&%gti%& expansion condition"
10842 The two substrings are first expanded. The condition is true if the first
10843 string is lexically greater than the second string. For &%gt%& the comparison
10844 includes the case of letters, whereas for &%gti%& the comparison is
10847 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10848 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10849 .cindex "string" "comparison"
10850 .cindex "list" "iterative conditions"
10851 Both strings are expanded; the second string is treated as a list of simple
10852 strings; if the first string is a member of the second, then the condition
10855 These are simpler to use versions of the more powerful &*forany*& condition.
10856 Examples, and the &*forany*& equivalents:
10858 ${if inlist{needle}{foo:needle:bar}}
10859 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10860 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10861 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10864 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10865 &*isip4&~{*&<&'string'&>&*}*& &&&
10866 &*isip6&~{*&<&'string'&>&*}*&
10867 .cindex "IP address" "testing string format"
10868 .cindex "string" "testing for IP address"
10869 .cindex "&%isip%& expansion condition"
10870 .cindex "&%isip4%& expansion condition"
10871 .cindex "&%isip6%& expansion condition"
10872 The substring is first expanded, and then tested to see if it has the form of
10873 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10874 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10876 For an IPv4 address, the test is for four dot-separated components, each of
10877 which consists of from one to three digits. For an IPv6 address, up to eight
10878 colon-separated components are permitted, each containing from one to four
10879 hexadecimal digits. There may be fewer than eight components if an empty
10880 component (adjacent colons) is present. Only one empty component is permitted.
10882 &*Note*&: The checks are just on the form of the address; actual numerical
10883 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10884 check. The main use of these tests is to distinguish between IP addresses and
10885 host names, or between IPv4 and IPv6 addresses. For example, you could use
10887 ${if isip4{$sender_host_address}...
10889 to test which IP version an incoming SMTP connection is using.
10891 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10892 .cindex "LDAP" "use for authentication"
10893 .cindex "expansion" "LDAP authentication test"
10894 .cindex "&%ldapauth%& expansion condition"
10895 This condition supports user authentication using LDAP. See section
10896 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10897 queries. For this use, the query must contain a user name and password. The
10898 query itself is not used, and can be empty. The condition is true if the
10899 password is not empty, and the user name and password are accepted by the LDAP
10900 server. An empty password is rejected without calling LDAP because LDAP binds
10901 with an empty password are considered anonymous regardless of the username, and
10902 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10903 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10907 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10908 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10909 .cindex "string" "comparison"
10910 .cindex "expansion" "string comparison"
10911 .cindex "&%le%& expansion condition"
10912 .cindex "&%lei%& expansion condition"
10913 The two substrings are first expanded. The condition is true if the first
10914 string is lexically less than or equal to the second string. For &%le%& the
10915 comparison includes the case of letters, whereas for &%lei%& the comparison is
10918 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10919 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10920 .cindex "string" "comparison"
10921 .cindex "expansion" "string comparison"
10922 .cindex "&%lt%& expansion condition"
10923 .cindex "&%lti%& expansion condition"
10924 The two substrings are first expanded. The condition is true if the first
10925 string is lexically less than the second string. For &%lt%& the comparison
10926 includes the case of letters, whereas for &%lti%& the comparison is
10930 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10931 .cindex "expansion" "regular expression comparison"
10932 .cindex "regular expressions" "match in expanded string"
10933 .cindex "&%match%& expansion condition"
10934 The two substrings are first expanded. The second is then treated as a regular
10935 expression and applied to the first. Because of the pre-expansion, if the
10936 regular expression contains dollar, or backslash characters, they must be
10937 escaped. Care must also be taken if the regular expression contains braces
10938 (curly brackets). A closing brace must be escaped so that it is not taken as a
10939 premature termination of <&'string2'&>. The easiest approach is to use the
10940 &`\N`& feature to disable expansion of the regular expression.
10943 ${if match {$local_part}{\N^\d{3}\N} ...
10945 If the whole expansion string is in double quotes, further escaping of
10946 backslashes is also required.
10948 The condition is true if the regular expression match succeeds.
10949 The regular expression is not required to begin with a circumflex
10950 metacharacter, but if there is no circumflex, the expression is not anchored,
10951 and it may match anywhere in the subject, not just at the start. If you want
10952 the pattern to match at the end of the subject, you must include the &`$`&
10953 metacharacter at an appropriate point.
10955 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10956 At the start of an &%if%& expansion the values of the numeric variable
10957 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10958 succeeds causes them to be reset to the substrings of that condition and they
10959 will have these values during the expansion of the success string. At the end
10960 of the &%if%& expansion, the previous values are restored. After testing a
10961 combination of conditions using &%or%&, the subsequent values of the numeric
10962 variables are those of the condition that succeeded.
10964 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10965 .cindex "&%match_address%& expansion condition"
10966 See &*match_local_part*&.
10968 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10969 .cindex "&%match_domain%& expansion condition"
10970 See &*match_local_part*&.
10972 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10973 .cindex "&%match_ip%& expansion condition"
10974 This condition matches an IP address to a list of IP address patterns. It must
10975 be followed by two argument strings. The first (after expansion) must be an IP
10976 address or an empty string. The second (not expanded) is a restricted host
10977 list that can match only an IP address, not a host name. For example:
10979 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10981 The specific types of host list item that are permitted in the list are:
10984 An IP address, optionally with a CIDR mask.
10986 A single asterisk, which matches any IP address.
10988 An empty item, which matches only if the IP address is empty. This could be
10989 useful for testing for a locally submitted message or one from specific hosts
10990 in a single test such as
10991 . ==== As this is a nested list, any displays it contains must be indented
10992 . ==== as otherwise they are too far to the left. This comment applies to
10993 . ==== the use of xmlto plus fop. There's no problem when formatting with
10994 . ==== sdop, with or without the extra indent.
10996 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10998 where the first item in the list is the empty string.
11000 The item @[] matches any of the local host's interface addresses.
11002 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11003 even if &`net-`& is not specified. There is never any attempt to turn the IP
11004 address into a host name. The most common type of linear search for
11005 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11006 masks. For example:
11008 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11010 It is of course possible to use other kinds of lookup, and in such a case, you
11011 do need to specify the &`net-`& prefix if you want to specify a specific
11012 address mask, for example:
11014 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11016 However, unless you are combining a &%match_ip%& condition with others, it is
11017 just as easy to use the fact that a lookup is itself a condition, and write:
11019 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11023 Note that <&'string2'&> is not itself subject to string expansion, unless
11024 Exim was built with the EXPAND_LISTMATCH_RHS option.
11026 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11028 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11029 .cindex "domain list" "in expansion condition"
11030 .cindex "address list" "in expansion condition"
11031 .cindex "local part" "list, in expansion condition"
11032 .cindex "&%match_local_part%& expansion condition"
11033 This condition, together with &%match_address%& and &%match_domain%&, make it
11034 possible to test domain, address, and local part lists within expansions. Each
11035 condition requires two arguments: an item and a list to match. A trivial
11038 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11040 In each case, the second argument may contain any of the allowable items for a
11041 list of the appropriate type. Also, because the second argument (after
11042 expansion) is a standard form of list, it is possible to refer to a named list.
11043 Thus, you can use conditions like this:
11045 ${if match_domain{$domain}{+local_domains}{...
11047 .cindex "&`+caseful`&"
11048 For address lists, the matching starts off caselessly, but the &`+caseful`&
11049 item can be used, as in all address lists, to cause subsequent items to
11050 have their local parts matched casefully. Domains are always matched
11053 Note that <&'string2'&> is not itself subject to string expansion, unless
11054 Exim was built with the EXPAND_LISTMATCH_RHS option.
11056 &*Note*&: Host lists are &'not'& supported in this way. This is because
11057 hosts have two identities: a name and an IP address, and it is not clear
11058 how to specify cleanly how such a test would work. However, IP addresses can be
11059 matched using &%match_ip%&.
11061 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11062 .cindex "PAM authentication"
11063 .cindex "AUTH" "with PAM"
11064 .cindex "Solaris" "PAM support"
11065 .cindex "expansion" "PAM authentication test"
11066 .cindex "&%pam%& expansion condition"
11067 &'Pluggable Authentication Modules'&
11068 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
11069 available in the latest releases of Solaris and in some GNU/Linux
11070 distributions. The Exim support, which is intended for use in conjunction with
11071 the SMTP AUTH command, is available only if Exim is compiled with
11075 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11076 in some releases of GNU/Linux &%-ldl%& is also needed.
11078 The argument string is first expanded, and the result must be a
11079 colon-separated list of strings. Leading and trailing white space is ignored.
11080 The PAM module is initialized with the service name &"exim"& and the user name
11081 taken from the first item in the colon-separated data string (<&'string1'&>).
11082 The remaining items in the data string are passed over in response to requests
11083 from the authentication function. In the simple case there will only be one
11084 request, for a password, so the data consists of just two strings.
11086 There can be problems if any of the strings are permitted to contain colon
11087 characters. In the usual way, these have to be doubled to avoid being taken as
11088 separators. If the data is being inserted from a variable, the &%sg%& expansion
11089 item can be used to double any existing colons. For example, the configuration
11090 of a LOGIN authenticator might contain this setting:
11092 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11094 For a PLAIN authenticator you could use:
11096 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11098 In some operating systems, PAM authentication can be done only from a process
11099 running as root. Since Exim is running as the Exim user when receiving
11100 messages, this means that PAM cannot be used directly in those systems.
11101 A patched version of the &'pam_unix'& module that comes with the
11102 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
11103 The patched module allows one special uid/gid combination, in addition to root,
11104 to authenticate. If you build the patched module to allow the Exim user and
11105 group, PAM can then be used from an Exim authenticator.
11108 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11109 .cindex "&'pwcheck'& daemon"
11111 .cindex "expansion" "&'pwcheck'& authentication test"
11112 .cindex "&%pwcheck%& expansion condition"
11113 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11114 This is one way of making it possible for passwords to be checked by a process
11115 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11116 deprecated. Its replacement is &'saslauthd'& (see below).
11118 The pwcheck support is not included in Exim by default. You need to specify
11119 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11120 building Exim. For example:
11122 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11124 You do not need to install the full Cyrus software suite in order to use
11125 the pwcheck daemon. You can compile and install just the daemon alone
11126 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11127 access to the &_/var/pwcheck_& directory.
11129 The &%pwcheck%& condition takes one argument, which must be the user name and
11130 password, separated by a colon. For example, in a LOGIN authenticator
11131 configuration, you might have this:
11133 server_condition = ${if pwcheck{$auth1:$auth2}}
11135 Again, for a PLAIN authenticator configuration, this would be:
11137 server_condition = ${if pwcheck{$auth2:$auth3}}
11139 .vitem &*queue_running*&
11140 .cindex "queue runner" "detecting when delivering from"
11141 .cindex "expansion" "queue runner test"
11142 .cindex "&%queue_running%& expansion condition"
11143 This condition, which has no data, is true during delivery attempts that are
11144 initiated by queue runner processes, and false otherwise.
11147 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11149 .cindex "expansion" "Radius authentication"
11150 .cindex "&%radius%& expansion condition"
11151 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11152 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11153 the Radius client configuration file in order to build Exim with Radius
11156 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11157 library, using the original API. If you are using release 0.4.0 or later of
11158 this library, you need to set
11160 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11162 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11163 &%libradius%& library that comes with FreeBSD. To do this, set
11165 RADIUS_LIB_TYPE=RADLIB
11167 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11168 You may also have to supply a suitable setting in EXTRALIBS so that the
11169 Radius library can be found when Exim is linked.
11171 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11172 Radius client library, which calls the Radius server. The condition is true if
11173 the authentication is successful. For example:
11175 server_condition = ${if radius{<arguments>}}
11179 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11180 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11181 .cindex "&'saslauthd'& daemon"
11183 .cindex "expansion" "&'saslauthd'& authentication test"
11184 .cindex "&%saslauthd%& expansion condition"
11185 This condition supports user authentication using the Cyrus &'saslauthd'&
11186 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11187 Using this daemon is one way of making it possible for passwords to be checked
11188 by a process that is not running as root.
11190 The saslauthd support is not included in Exim by default. You need to specify
11191 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11192 building Exim. For example:
11194 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11196 You do not need to install the full Cyrus software suite in order to use
11197 the saslauthd daemon. You can compile and install just the daemon alone
11198 from the Cyrus SASL library.
11200 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11201 two are mandatory. For example:
11203 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11205 The service and the realm are optional (which is why the arguments are enclosed
11206 in their own set of braces). For details of the meaning of the service and
11207 realm, and how to run the daemon, consult the Cyrus documentation.
11212 .section "Combining expansion conditions" "SECID84"
11213 .cindex "expansion" "combining conditions"
11214 Several conditions can be tested at once by combining them using the &%and%&
11215 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11216 conditions on their own, and precede their lists of sub-conditions. Each
11217 sub-condition must be enclosed in braces within the overall braces that contain
11218 the list. No repetition of &%if%& is used.
11222 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11223 .cindex "&""or""& expansion condition"
11224 .cindex "expansion" "&""or""& of conditions"
11225 The sub-conditions are evaluated from left to right. The condition is true if
11226 any one of the sub-conditions is true.
11229 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11231 When a true sub-condition is found, the following ones are parsed but not
11232 evaluated. If there are several &"match"& sub-conditions the values of the
11233 numeric variables afterwards are taken from the first one that succeeds.
11235 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11236 .cindex "&""and""& expansion condition"
11237 .cindex "expansion" "&""and""& of conditions"
11238 The sub-conditions are evaluated from left to right. The condition is true if
11239 all of the sub-conditions are true. If there are several &"match"&
11240 sub-conditions, the values of the numeric variables afterwards are taken from
11241 the last one. When a false sub-condition is found, the following ones are
11242 parsed but not evaluated.
11244 .ecindex IIDexpcond
11249 .section "Expansion variables" "SECTexpvar"
11250 .cindex "expansion" "variables, list of"
11251 This section contains an alphabetical list of all the expansion variables. Some
11252 of them are available only when Exim is compiled with specific options such as
11253 support for TLS or the content scanning extension.
11256 .vitem "&$0$&, &$1$&, etc"
11257 .cindex "numerical variables (&$1$& &$2$& etc)"
11258 When a &%match%& expansion condition succeeds, these variables contain the
11259 captured substrings identified by the regular expression during subsequent
11260 processing of the success string of the containing &%if%& expansion item.
11261 In the expansion condition case
11262 they do not retain their values afterwards; in fact, their previous
11263 values are restored at the end of processing an &%if%& item. The numerical
11264 variables may also be set externally by some other matching process which
11265 precedes the expansion of the string. For example, the commands available in
11266 Exim filter files include an &%if%& command with its own regular expression
11267 matching condition.
11269 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11270 Within an acl condition, expansion condition or expansion item
11271 any arguments are copied to these variables,
11272 any unused variables being made empty.
11274 .vitem "&$acl_c...$&"
11275 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11276 can be given any name that starts with &$acl_c$& and is at least six characters
11277 long, but the sixth character must be either a digit or an underscore. For
11278 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11279 variables persist throughout the lifetime of an SMTP connection. They can be
11280 used to pass information between ACLs and between different invocations of the
11281 same ACL. When a message is received, the values of these variables are saved
11282 with the message, and can be accessed by filters, routers, and transports
11283 during subsequent delivery.
11285 .vitem "&$acl_m...$&"
11286 These variables are like the &$acl_c...$& variables, except that their values
11287 are reset after a message has been received. Thus, if several messages are
11288 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11289 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11290 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11291 message is received, the values of these variables are saved with the message,
11292 and can be accessed by filters, routers, and transports during subsequent
11295 .vitem &$acl_narg$&
11296 Within an acl condition, expansion condition or expansion item
11297 this variable has the number of arguments.
11299 .vitem &$acl_verify_message$&
11300 .vindex "&$acl_verify_message$&"
11301 After an address verification has failed, this variable contains the failure
11302 message. It retains its value for use in subsequent modifiers. The message can
11303 be preserved by coding like this:
11305 warn !verify = sender
11306 set acl_m0 = $acl_verify_message
11308 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11309 &%log_message%& modifiers, to include information about the verification
11312 .vitem &$address_data$&
11313 .vindex "&$address_data$&"
11314 This variable is set by means of the &%address_data%& option in routers. The
11315 value then remains with the address while it is processed by subsequent routers
11316 and eventually a transport. If the transport is handling multiple addresses,
11317 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11318 for more details. &*Note*&: The contents of &$address_data$& are visible in
11321 If &$address_data$& is set when the routers are called from an ACL to verify
11322 a recipient address, the final value is still in the variable for subsequent
11323 conditions and modifiers of the ACL statement. If routing the address caused it
11324 to be redirected to just one address, the child address is also routed as part
11325 of the verification, and in this case the final value of &$address_data$& is
11326 from the child's routing.
11328 If &$address_data$& is set when the routers are called from an ACL to verify a
11329 sender address, the final value is also preserved, but this time in
11330 &$sender_address_data$&, to distinguish it from data from a recipient
11333 In both cases (recipient and sender verification), the value does not persist
11334 after the end of the current ACL statement. If you want to preserve
11335 these values for longer, you can save them in ACL variables.
11337 .vitem &$address_file$&
11338 .vindex "&$address_file$&"
11339 When, as a result of aliasing, forwarding, or filtering, a message is directed
11340 to a specific file, this variable holds the name of the file when the transport
11341 is running. At other times, the variable is empty. For example, using the
11342 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11344 /home/r2d2/savemail
11346 then when the &(address_file)& transport is running, &$address_file$&
11347 contains the text string &`/home/r2d2/savemail`&.
11348 .cindex "Sieve filter" "value of &$address_file$&"
11349 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11350 then up to the transport configuration to generate an appropriate absolute path
11351 to the relevant file.
11353 .vitem &$address_pipe$&
11354 .vindex "&$address_pipe$&"
11355 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11356 this variable holds the pipe command when the transport is running.
11358 .vitem "&$auth1$& &-- &$auth3$&"
11359 .vindex "&$auth1$&, &$auth2$&, etc"
11360 These variables are used in SMTP authenticators (see chapters
11361 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
11363 .vitem &$authenticated_id$&
11364 .cindex "authentication" "id"
11365 .vindex "&$authenticated_id$&"
11366 When a server successfully authenticates a client it may be configured to
11367 preserve some of the authentication information in the variable
11368 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11369 user/password authenticator configuration might preserve the user name for use
11370 in the routers. Note that this is not the same information that is saved in
11371 &$sender_host_authenticated$&.
11372 When a message is submitted locally (that is, not over a TCP connection)
11373 the value of &$authenticated_id$& is normally the login name of the calling
11374 process. However, a trusted user can override this by means of the &%-oMai%&
11375 command line option.
11377 .vitem &$authenticated_fail_id$&
11378 .cindex "authentication" "fail" "id"
11379 .vindex "&$authenticated_fail_id$&"
11380 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11381 will contain the failed authentication id. If more than one authentication
11382 id is attempted, it will contain only the last one. The variable is
11383 available for processing in the ACL's, generally the quit or notquit ACL.
11384 A message to a local recipient could still be accepted without requiring
11385 authentication, which means this variable could also be visible in all of
11389 .vitem &$authenticated_sender$&
11390 .cindex "sender" "authenticated"
11391 .cindex "authentication" "sender"
11392 .cindex "AUTH" "on MAIL command"
11393 .vindex "&$authenticated_sender$&"
11394 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11395 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11396 described in section &<<SECTauthparamail>>&. Unless the data is the string
11397 &"<>"&, it is set as the authenticated sender of the message, and the value is
11398 available during delivery in the &$authenticated_sender$& variable. If the
11399 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11401 .vindex "&$qualify_domain$&"
11402 When a message is submitted locally (that is, not over a TCP connection), the
11403 value of &$authenticated_sender$& is an address constructed from the login
11404 name of the calling process and &$qualify_domain$&, except that a trusted user
11405 can override this by means of the &%-oMas%& command line option.
11408 .vitem &$authentication_failed$&
11409 .cindex "authentication" "failure"
11410 .vindex "&$authentication_failed$&"
11411 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11412 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11413 possible to distinguish between &"did not try to authenticate"&
11414 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11415 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11416 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11417 negative response to an AUTH command, including (for example) an attempt to use
11418 an undefined mechanism.
11420 .vitem &$av_failed$&
11421 .cindex "content scanning" "AV scanner failure"
11422 This variable is available when Exim is compiled with the content-scanning
11423 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11424 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11425 the ACL malware condition.
11427 .vitem &$body_linecount$&
11428 .cindex "message body" "line count"
11429 .cindex "body of message" "line count"
11430 .vindex "&$body_linecount$&"
11431 When a message is being received or delivered, this variable contains the
11432 number of lines in the message's body. See also &$message_linecount$&.
11434 .vitem &$body_zerocount$&
11435 .cindex "message body" "binary zero count"
11436 .cindex "body of message" "binary zero count"
11437 .cindex "binary zero" "in message body"
11438 .vindex "&$body_zerocount$&"
11439 When a message is being received or delivered, this variable contains the
11440 number of binary zero bytes (ASCII NULs) in the message's body.
11442 .vitem &$bounce_recipient$&
11443 .vindex "&$bounce_recipient$&"
11444 This is set to the recipient address of a bounce message while Exim is creating
11445 it. It is useful if a customized bounce message text file is in use (see
11446 chapter &<<CHAPemsgcust>>&).
11448 .vitem &$bounce_return_size_limit$&
11449 .vindex "&$bounce_return_size_limit$&"
11450 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11451 up to a multiple of 1000. It is useful when a customized error message text
11452 file is in use (see chapter &<<CHAPemsgcust>>&).
11454 .vitem &$caller_gid$&
11455 .cindex "gid (group id)" "caller"
11456 .vindex "&$caller_gid$&"
11457 The real group id under which the process that called Exim was running. This is
11458 not the same as the group id of the originator of a message (see
11459 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11460 incarnation normally contains the Exim gid.
11462 .vitem &$caller_uid$&
11463 .cindex "uid (user id)" "caller"
11464 .vindex "&$caller_uid$&"
11465 The real user id under which the process that called Exim was running. This is
11466 not the same as the user id of the originator of a message (see
11467 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11468 incarnation normally contains the Exim uid.
11470 .vitem &$callout_address$&
11471 .vindex "&$callout_address$&"
11472 After a callout for verification, spamd or malware daemon service, the
11473 address that was connected to.
11475 .vitem &$compile_number$&
11476 .vindex "&$compile_number$&"
11477 The building process for Exim keeps a count of the number
11478 of times it has been compiled. This serves to distinguish different
11479 compilations of the same version of the program.
11481 .vitem &$config_dir$&
11482 .vindex "&$config_dir$&"
11483 The directory name of the main configuration file. That is, the content of
11484 &$config_file$& with the last component stripped. The value does not
11485 contain the trailing slash. If &$config_file$& does not contain a slash,
11486 &$config_dir$& is ".".
11488 .vitem &$config_file$&
11489 .vindex "&$config_file$&"
11490 The name of the main configuration file Exim is using.
11492 .vitem &$demime_errorlevel$&
11493 .vindex "&$demime_errorlevel$&"
11494 This variable is available when Exim is compiled with
11495 the content-scanning extension and the obsolete &%demime%& condition. For
11496 details, see section &<<SECTdemimecond>>&.
11498 .vitem &$demime_reason$&
11499 .vindex "&$demime_reason$&"
11500 This variable is available when Exim is compiled with the
11501 content-scanning extension and the obsolete &%demime%& condition. For details,
11502 see section &<<SECTdemimecond>>&.
11504 .vitem &$dkim_cur_signer$& &&&
11505 &$dkim_verify_status$& &&&
11506 &$dkim_verify_reason$& &&&
11507 &$dkim_domain$& &&&
11508 &$dkim_identity$& &&&
11509 &$dkim_selector$& &&&
11511 &$dkim_canon_body$& &&&
11512 &$dkim_canon_headers$& &&&
11513 &$dkim_copiedheaders$& &&&
11514 &$dkim_bodylength$& &&&
11515 &$dkim_created$& &&&
11516 &$dkim_expires$& &&&
11517 &$dkim_headernames$& &&&
11518 &$dkim_key_testing$& &&&
11519 &$dkim_key_nosubdomains$& &&&
11520 &$dkim_key_srvtype$& &&&
11521 &$dkim_key_granularity$& &&&
11522 &$dkim_key_notes$& &&&
11523 &$dkim_key_length$&
11524 These variables are only available within the DKIM ACL.
11525 For details see chapter &<<CHAPdkim>>&.
11527 .vitem &$dkim_signers$&
11528 .vindex &$dkim_signers$&
11529 When a message has been received this variable contains
11530 a colon-separated list of signer domains and identities for the message.
11531 For details see chapter &<<CHAPdkim>>&.
11533 .vitem &$dnslist_domain$& &&&
11534 &$dnslist_matched$& &&&
11535 &$dnslist_text$& &&&
11537 .vindex "&$dnslist_domain$&"
11538 .vindex "&$dnslist_matched$&"
11539 .vindex "&$dnslist_text$&"
11540 .vindex "&$dnslist_value$&"
11541 .cindex "black list (DNS)"
11542 When a DNS (black) list lookup succeeds, these variables are set to contain
11543 the following data from the lookup: the list's domain name, the key that was
11544 looked up, the contents of any associated TXT record, and the value from the
11545 main A record. See section &<<SECID204>>& for more details.
11548 .vindex "&$domain$&"
11549 When an address is being routed, or delivered on its own, this variable
11550 contains the domain. Uppercase letters in the domain are converted into lower
11551 case for &$domain$&.
11553 Global address rewriting happens when a message is received, so the value of
11554 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11555 is set during user filtering, but not during system filtering, because a
11556 message may have many recipients and the system filter is called just once.
11558 When more than one address is being delivered at once (for example, several
11559 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11560 have the same domain. Transports can be restricted to handling only one domain
11561 at a time if the value of &$domain$& is required at transport time &-- this is
11562 the default for local transports. For further details of the environment in
11563 which local transports are run, see chapter &<<CHAPenvironment>>&.
11565 .oindex "&%delay_warning_condition%&"
11566 At the end of a delivery, if all deferred addresses have the same domain, it is
11567 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11569 The &$domain$& variable is also used in some other circumstances:
11572 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11573 the recipient address. The domain of the &'sender'& address is in
11574 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11575 normally set during the running of the MAIL ACL. However, if the sender address
11576 is verified with a callout during the MAIL ACL, the sender domain is placed in
11577 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11578 the &(smtp)& transport.
11581 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11582 &$domain$& contains the domain portion of the address that is being rewritten;
11583 it can be used in the expansion of the replacement address, for example, to
11584 rewrite domains by file lookup.
11587 With one important exception, whenever a domain list is being scanned,
11588 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11589 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11590 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11591 that, in a RCPT ACL, the sender domain list can be dependent on the
11592 recipient domain (which is what is in &$domain$& at this time).
11595 .cindex "ETRN" "value of &$domain$&"
11596 .oindex "&%smtp_etrn_command%&"
11597 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11598 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11602 .vitem &$domain_data$&
11603 .vindex "&$domain_data$&"
11604 When the &%domains%& option on a router matches a domain by
11605 means of a lookup, the data read by the lookup is available during the running
11606 of the router as &$domain_data$&. In addition, if the driver routes the
11607 address to a transport, the value is available in that transport. If the
11608 transport is handling multiple addresses, the value from the first address is
11611 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11612 domain by means of a lookup. The data read by the lookup is available during
11613 the rest of the ACL statement. In all other situations, this variable expands
11616 .vitem &$exim_gid$&
11617 .vindex "&$exim_gid$&"
11618 This variable contains the numerical value of the Exim group id.
11620 .vitem &$exim_path$&
11621 .vindex "&$exim_path$&"
11622 This variable contains the path to the Exim binary.
11624 .vitem &$exim_uid$&
11625 .vindex "&$exim_uid$&"
11626 This variable contains the numerical value of the Exim user id.
11628 .vitem &$exim_version$&
11629 .vindex "&$exim_version$&"
11630 This variable contains the version string of the Exim build.
11631 The first character is a major version number, currently 4.
11632 Then after a dot, the next group of digits is a minor version number.
11633 There may be other characters following the minor version.
11635 .vitem &$found_extension$&
11636 .vindex "&$found_extension$&"
11637 This variable is available when Exim is compiled with the
11638 content-scanning extension and the obsolete &%demime%& condition. For details,
11639 see section &<<SECTdemimecond>>&.
11641 .vitem &$header_$&<&'name'&>
11642 This is not strictly an expansion variable. It is expansion syntax for
11643 inserting the message header line with the given name. Note that the name must
11644 be terminated by colon or white space, because it may contain a wide variety of
11645 characters. Note also that braces must &'not'& be used.
11647 .vitem &$headers_added$&
11648 .vindex "&$headers_added$&"
11649 Within an ACL this variable contains the headers added so far by
11650 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11651 The headers are a newline-separated list.
11655 When the &%check_local_user%& option is set for a router, the user's home
11656 directory is placed in &$home$& when the check succeeds. In particular, this
11657 means it is set during the running of users' filter files. A router may also
11658 explicitly set a home directory for use by a transport; this can be overridden
11659 by a setting on the transport itself.
11661 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11662 of the environment variable HOME.
11666 If a router assigns an address to a transport (any transport), and passes a
11667 list of hosts with the address, the value of &$host$& when the transport starts
11668 to run is the name of the first host on the list. Note that this applies both
11669 to local and remote transports.
11671 .cindex "transport" "filter"
11672 .cindex "filter" "transport filter"
11673 For the &(smtp)& transport, if there is more than one host, the value of
11674 &$host$& changes as the transport works its way through the list. In
11675 particular, when the &(smtp)& transport is expanding its options for encryption
11676 using TLS, or for specifying a transport filter (see chapter
11677 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11680 When used in the client part of an authenticator configuration (see chapter
11681 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11682 client is connected.
11685 .vitem &$host_address$&
11686 .vindex "&$host_address$&"
11687 This variable is set to the remote host's IP address whenever &$host$& is set
11688 for a remote connection. It is also set to the IP address that is being checked
11689 when the &%ignore_target_hosts%& option is being processed.
11691 .vitem &$host_data$&
11692 .vindex "&$host_data$&"
11693 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11694 result of the lookup is made available in the &$host_data$& variable. This
11695 allows you, for example, to do things like this:
11697 deny hosts = net-lsearch;/some/file
11698 message = $host_data
11700 .vitem &$host_lookup_deferred$&
11701 .cindex "host name" "lookup, failure of"
11702 .vindex "&$host_lookup_deferred$&"
11703 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11704 message comes from a remote host and there is an attempt to look up the host's
11705 name from its IP address, and the attempt is not successful, one of these
11706 variables is set to &"1"&.
11709 If the lookup receives a definite negative response (for example, a DNS lookup
11710 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11713 If there is any kind of problem during the lookup, such that Exim cannot
11714 tell whether or not the host name is defined (for example, a timeout for a DNS
11715 lookup), &$host_lookup_deferred$& is set to &"1"&.
11718 Looking up a host's name from its IP address consists of more than just a
11719 single reverse lookup. Exim checks that a forward lookup of at least one of the
11720 names it receives from a reverse lookup yields the original IP address. If this
11721 is not the case, Exim does not accept the looked up name(s), and
11722 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11723 IP address (for example, the existence of a PTR record in the DNS) is not
11724 sufficient on its own for the success of a host name lookup. If the reverse
11725 lookup succeeds, but there is a lookup problem such as a timeout when checking
11726 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11727 &"1"&. See also &$sender_host_name$&.
11729 .vitem &$host_lookup_failed$&
11730 .vindex "&$host_lookup_failed$&"
11731 See &$host_lookup_deferred$&.
11733 .vitem &$host_port$&
11734 .vindex "&$host_port$&"
11735 This variable is set to the remote host's TCP port whenever &$host$& is set
11736 for an outbound connection.
11738 .vitem &$initial_cwd$&
11739 .vindex "&$initial_cwd$&
11740 This variable contains the full path name of the initial working
11741 directory of the current Exim process. This may differ from the current
11742 working directory, as Exim changes this to "/" during early startup, and
11743 to &$spool_directory$& later.
11746 .vindex "&$inode$&"
11747 The only time this variable is set is while expanding the &%directory_file%&
11748 option in the &(appendfile)& transport. The variable contains the inode number
11749 of the temporary file which is about to be renamed. It can be used to construct
11750 a unique name for the file.
11752 .vitem &$interface_address$&
11753 .vindex "&$interface_address$&"
11754 This is an obsolete name for &$received_ip_address$&.
11756 .vitem &$interface_port$&
11757 .vindex "&$interface_port$&"
11758 This is an obsolete name for &$received_port$&.
11762 This variable is used during the expansion of &*forall*& and &*forany*&
11763 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11764 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11768 .vindex "&$ldap_dn$&"
11769 This variable, which is available only when Exim is compiled with LDAP support,
11770 contains the DN from the last entry in the most recently successful LDAP
11773 .vitem &$load_average$&
11774 .vindex "&$load_average$&"
11775 This variable contains the system load average, multiplied by 1000 so that it
11776 is an integer. For example, if the load average is 0.21, the value of the
11777 variable is 210. The value is recomputed every time the variable is referenced.
11779 .vitem &$local_part$&
11780 .vindex "&$local_part$&"
11781 When an address is being routed, or delivered on its own, this
11782 variable contains the local part. When a number of addresses are being
11783 delivered together (for example, multiple RCPT commands in an SMTP
11784 session), &$local_part$& is not set.
11786 Global address rewriting happens when a message is received, so the value of
11787 &$local_part$& during routing and delivery is the value after rewriting.
11788 &$local_part$& is set during user filtering, but not during system filtering,
11789 because a message may have many recipients and the system filter is called just
11792 .vindex "&$local_part_prefix$&"
11793 .vindex "&$local_part_suffix$&"
11794 If a local part prefix or suffix has been recognized, it is not included in the
11795 value of &$local_part$& during routing and subsequent delivery. The values of
11796 any prefix or suffix are in &$local_part_prefix$& and
11797 &$local_part_suffix$&, respectively.
11799 When a message is being delivered to a file, pipe, or autoreply transport as a
11800 result of aliasing or forwarding, &$local_part$& is set to the local part of
11801 the parent address, not to the file name or command (see &$address_file$& and
11804 When an ACL is running for a RCPT command, &$local_part$& contains the
11805 local part of the recipient address.
11807 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11808 &$local_part$& contains the local part of the address that is being rewritten;
11809 it can be used in the expansion of the replacement address, for example.
11811 In all cases, all quoting is removed from the local part. For example, for both
11814 "abc:xyz"@test.example
11815 abc\:xyz@test.example
11817 the value of &$local_part$& is
11821 If you use &$local_part$& to create another address, you should always wrap it
11822 inside a quoting operator. For example, in a &(redirect)& router you could
11825 data = ${quote_local_part:$local_part}@new.domain.example
11827 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11828 to process local parts in a case-dependent manner in a router, you can set the
11829 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11831 .vitem &$local_part_data$&
11832 .vindex "&$local_part_data$&"
11833 When the &%local_parts%& option on a router matches a local part by means of a
11834 lookup, the data read by the lookup is available during the running of the
11835 router as &$local_part_data$&. In addition, if the driver routes the address
11836 to a transport, the value is available in that transport. If the transport is
11837 handling multiple addresses, the value from the first address is used.
11839 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11840 matches a local part by means of a lookup. The data read by the lookup is
11841 available during the rest of the ACL statement. In all other situations, this
11842 variable expands to nothing.
11844 .vitem &$local_part_prefix$&
11845 .vindex "&$local_part_prefix$&"
11846 When an address is being routed or delivered, and a
11847 specific prefix for the local part was recognized, it is available in this
11848 variable, having been removed from &$local_part$&.
11850 .vitem &$local_part_suffix$&
11851 .vindex "&$local_part_suffix$&"
11852 When an address is being routed or delivered, and a
11853 specific suffix for the local part was recognized, it is available in this
11854 variable, having been removed from &$local_part$&.
11856 .vitem &$local_scan_data$&
11857 .vindex "&$local_scan_data$&"
11858 This variable contains the text returned by the &[local_scan()]& function when
11859 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11861 .vitem &$local_user_gid$&
11862 .vindex "&$local_user_gid$&"
11863 See &$local_user_uid$&.
11865 .vitem &$local_user_uid$&
11866 .vindex "&$local_user_uid$&"
11867 This variable and &$local_user_gid$& are set to the uid and gid after the
11868 &%check_local_user%& router precondition succeeds. This means that their values
11869 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11870 and &%condition%&), for the &%address_data%& expansion, and for any
11871 router-specific expansions. At all other times, the values in these variables
11872 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11874 .vitem &$localhost_number$&
11875 .vindex "&$localhost_number$&"
11876 This contains the expanded value of the
11877 &%localhost_number%& option. The expansion happens after the main options have
11880 .vitem &$log_inodes$&
11881 .vindex "&$log_inodes$&"
11882 The number of free inodes in the disk partition where Exim's
11883 log files are being written. The value is recalculated whenever the variable is
11884 referenced. If the relevant file system does not have the concept of inodes,
11885 the value of is -1. See also the &%check_log_inodes%& option.
11887 .vitem &$log_space$&
11888 .vindex "&$log_space$&"
11889 The amount of free space (as a number of kilobytes) in the disk
11890 partition where Exim's log files are being written. The value is recalculated
11891 whenever the variable is referenced. If the operating system does not have the
11892 ability to find the amount of free space (only true for experimental systems),
11893 the space value is -1. See also the &%check_log_space%& option.
11896 .vitem &$lookup_dnssec_authenticated$&
11897 .vindex "&$lookup_dnssec_authenticated$&"
11898 This variable is set after a DNS lookup done by
11899 a dnsdb lookup expansion, dnslookup router or smtp transport.
11900 .cindex "DNS" "DNSSEC"
11901 It will be empty if &(DNSSEC)& was not requested,
11902 &"no"& if the result was not labelled as authenticated data
11903 and &"yes"& if it was.
11904 Results that are labelled as authoritative answer that match
11905 the &%dns_trust_aa%& configuration variable count also
11906 as authenticated data.
11908 .vitem &$mailstore_basename$&
11909 .vindex "&$mailstore_basename$&"
11910 This variable is set only when doing deliveries in &"mailstore"& format in the
11911 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11912 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11913 contains the basename of the files that are being written, that is, the name
11914 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11917 .vitem &$malware_name$&
11918 .vindex "&$malware_name$&"
11919 This variable is available when Exim is compiled with the
11920 content-scanning extension. It is set to the name of the virus that was found
11921 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11923 .vitem &$max_received_linelength$&
11924 .vindex "&$max_received_linelength$&"
11925 .cindex "maximum" "line length"
11926 .cindex "line length" "maximum"
11927 This variable contains the number of bytes in the longest line that was
11928 received as part of the message, not counting the line termination
11931 .vitem &$message_age$&
11932 .cindex "message" "age of"
11933 .vindex "&$message_age$&"
11934 This variable is set at the start of a delivery attempt to contain the number
11935 of seconds since the message was received. It does not change during a single
11938 .vitem &$message_body$&
11939 .cindex "body of message" "expansion variable"
11940 .cindex "message body" "in expansion"
11941 .cindex "binary zero" "in message body"
11942 .vindex "&$message_body$&"
11943 .oindex "&%message_body_visible%&"
11944 This variable contains the initial portion of a message's body while it is
11945 being delivered, and is intended mainly for use in filter files. The maximum
11946 number of characters of the body that are put into the variable is set by the
11947 &%message_body_visible%& configuration option; the default is 500.
11949 .oindex "&%message_body_newlines%&"
11950 By default, newlines are converted into spaces in &$message_body$&, to make it
11951 easier to search for phrases that might be split over a line break. However,
11952 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11953 zeros are always converted into spaces.
11955 .vitem &$message_body_end$&
11956 .cindex "body of message" "expansion variable"
11957 .cindex "message body" "in expansion"
11958 .vindex "&$message_body_end$&"
11959 This variable contains the final portion of a message's
11960 body while it is being delivered. The format and maximum size are as for
11963 .vitem &$message_body_size$&
11964 .cindex "body of message" "size"
11965 .cindex "message body" "size"
11966 .vindex "&$message_body_size$&"
11967 When a message is being delivered, this variable contains the size of the body
11968 in bytes. The count starts from the character after the blank line that
11969 separates the body from the header. Newlines are included in the count. See
11970 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11972 .vitem &$message_exim_id$&
11973 .vindex "&$message_exim_id$&"
11974 When a message is being received or delivered, this variable contains the
11975 unique message id that is generated and used by Exim to identify the message.
11976 An id is not created for a message until after its header has been successfully
11977 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11978 line; it is the local id that Exim assigns to the message, for example:
11979 &`1BXTIK-0001yO-VA`&.
11981 .vitem &$message_headers$&
11982 .vindex &$message_headers$&
11983 This variable contains a concatenation of all the header lines when a message
11984 is being processed, except for lines added by routers or transports. The header
11985 lines are separated by newline characters. Their contents are decoded in the
11986 same way as a header line that is inserted by &%bheader%&.
11988 .vitem &$message_headers_raw$&
11989 .vindex &$message_headers_raw$&
11990 This variable is like &$message_headers$& except that no processing of the
11991 contents of header lines is done.
11993 .vitem &$message_id$&
11994 This is an old name for &$message_exim_id$&. It is now deprecated.
11996 .vitem &$message_linecount$&
11997 .vindex "&$message_linecount$&"
11998 This variable contains the total number of lines in the header and body of the
11999 message. Compare &$body_linecount$&, which is the count for the body only.
12000 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12001 number of lines received. Before delivery happens (that is, before filters,
12002 routers, and transports run) the count is increased to include the
12003 &'Received:'& header line that Exim standardly adds, and also any other header
12004 lines that are added by ACLs. The blank line that separates the message header
12005 from the body is not counted.
12007 As with the special case of &$message_size$&, during the expansion of the
12008 appendfile transport's maildir_tag option in maildir format, the value of
12009 &$message_linecount$& is the precise size of the number of newlines in the
12010 file that has been written (minus one for the blank line between the
12011 header and the body).
12013 Here is an example of the use of this variable in a DATA ACL:
12015 deny message = Too many lines in message header
12017 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12019 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12020 message has not yet been received.
12022 .vitem &$message_size$&
12023 .cindex "size" "of message"
12024 .cindex "message" "size"
12025 .vindex "&$message_size$&"
12026 When a message is being processed, this variable contains its size in bytes. In
12027 most cases, the size includes those headers that were received with the
12028 message, but not those (such as &'Envelope-to:'&) that are added to individual
12029 deliveries as they are written. However, there is one special case: during the
12030 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12031 doing a delivery in maildir format, the value of &$message_size$& is the
12032 precise size of the file that has been written. See also
12033 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12035 .cindex "RCPT" "value of &$message_size$&"
12036 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12037 contains the size supplied on the MAIL command, or -1 if no size was given. The
12038 value may not, of course, be truthful.
12040 .vitem &$mime_$&&'xxx'&
12041 A number of variables whose names start with &$mime$& are
12042 available when Exim is compiled with the content-scanning extension. For
12043 details, see section &<<SECTscanmimepart>>&.
12045 .vitem "&$n0$& &-- &$n9$&"
12046 These variables are counters that can be incremented by means
12047 of the &%add%& command in filter files.
12049 .vitem &$original_domain$&
12050 .vindex "&$domain$&"
12051 .vindex "&$original_domain$&"
12052 When a top-level address is being processed for delivery, this contains the
12053 same value as &$domain$&. However, if a &"child"& address (for example,
12054 generated by an alias, forward, or filter file) is being processed, this
12055 variable contains the domain of the original address (lower cased). This
12056 differs from &$parent_domain$& only when there is more than one level of
12057 aliasing or forwarding. When more than one address is being delivered in a
12058 single transport run, &$original_domain$& is not set.
12060 If a new address is created by means of a &%deliver%& command in a system
12061 filter, it is set up with an artificial &"parent"& address. This has the local
12062 part &'system-filter'& and the default qualify domain.
12064 .vitem &$original_local_part$&
12065 .vindex "&$local_part$&"
12066 .vindex "&$original_local_part$&"
12067 When a top-level address is being processed for delivery, this contains the
12068 same value as &$local_part$&, unless a prefix or suffix was removed from the
12069 local part, because &$original_local_part$& always contains the full local
12070 part. When a &"child"& address (for example, generated by an alias, forward, or
12071 filter file) is being processed, this variable contains the full local part of
12072 the original address.
12074 If the router that did the redirection processed the local part
12075 case-insensitively, the value in &$original_local_part$& is in lower case.
12076 This variable differs from &$parent_local_part$& only when there is more than
12077 one level of aliasing or forwarding. When more than one address is being
12078 delivered in a single transport run, &$original_local_part$& is not set.
12080 If a new address is created by means of a &%deliver%& command in a system
12081 filter, it is set up with an artificial &"parent"& address. This has the local
12082 part &'system-filter'& and the default qualify domain.
12084 .vitem &$originator_gid$&
12085 .cindex "gid (group id)" "of originating user"
12086 .cindex "sender" "gid"
12087 .vindex "&$caller_gid$&"
12088 .vindex "&$originator_gid$&"
12089 This variable contains the value of &$caller_gid$& that was set when the
12090 message was received. For messages received via the command line, this is the
12091 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12092 normally the gid of the Exim user.
12094 .vitem &$originator_uid$&
12095 .cindex "uid (user id)" "of originating user"
12096 .cindex "sender" "uid"
12097 .vindex "&$caller_uid$&"
12098 .vindex "&$originaltor_uid$&"
12099 The value of &$caller_uid$& that was set when the message was received. For
12100 messages received via the command line, this is the uid of the sending user.
12101 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12104 .vitem &$parent_domain$&
12105 .vindex "&$parent_domain$&"
12106 This variable is similar to &$original_domain$& (see
12107 above), except that it refers to the immediately preceding parent address.
12109 .vitem &$parent_local_part$&
12110 .vindex "&$parent_local_part$&"
12111 This variable is similar to &$original_local_part$&
12112 (see above), except that it refers to the immediately preceding parent address.
12115 .cindex "pid (process id)" "of current process"
12117 This variable contains the current process id.
12119 .vitem &$pipe_addresses$&
12120 .cindex "filter" "transport filter"
12121 .cindex "transport" "filter"
12122 .vindex "&$pipe_addresses$&"
12123 This is not an expansion variable, but is mentioned here because the string
12124 &`$pipe_addresses`& is handled specially in the command specification for the
12125 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12126 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12127 It cannot be used in general expansion strings, and provokes an &"unknown
12128 variable"& error if encountered.
12130 .vitem &$primary_hostname$&
12131 .vindex "&$primary_hostname$&"
12132 This variable contains the value set by &%primary_hostname%& in the
12133 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12134 a single-component name, Exim calls &[gethostbyname()]& (or
12135 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12136 qualified host name. See also &$smtp_active_hostname$&.
12140 .vitem &$proxy_host_address$& &&&
12141 &$proxy_host_port$& &&&
12142 &$proxy_target_address$& &&&
12143 &$proxy_target_port$& &&&
12145 These variables are only available when built with Proxy Protocol
12147 For details see chapter &<<SECTproxyInbound>>&.
12151 .vitem &$prdr_requested$&
12152 .cindex "PRDR" "variable for"
12153 This variable is set to &"yes"& if PRDR was requested by the client for the
12154 current message, otherwise &"no"&.
12157 .vitem &$prvscheck_address$&
12158 This variable is used in conjunction with the &%prvscheck%& expansion item,
12159 which is described in sections &<<SECTexpansionitems>>& and
12160 &<<SECTverifyPRVS>>&.
12162 .vitem &$prvscheck_keynum$&
12163 This variable is used in conjunction with the &%prvscheck%& expansion item,
12164 which is described in sections &<<SECTexpansionitems>>& and
12165 &<<SECTverifyPRVS>>&.
12167 .vitem &$prvscheck_result$&
12168 This variable is used in conjunction with the &%prvscheck%& expansion item,
12169 which is described in sections &<<SECTexpansionitems>>& and
12170 &<<SECTverifyPRVS>>&.
12172 .vitem &$qualify_domain$&
12173 .vindex "&$qualify_domain$&"
12174 The value set for the &%qualify_domain%& option in the configuration file.
12176 .vitem &$qualify_recipient$&
12177 .vindex "&$qualify_recipient$&"
12178 The value set for the &%qualify_recipient%& option in the configuration file,
12179 or if not set, the value of &$qualify_domain$&.
12181 .vitem &$rcpt_count$&
12182 .vindex "&$rcpt_count$&"
12183 When a message is being received by SMTP, this variable contains the number of
12184 RCPT commands received for the current message. If this variable is used in a
12185 RCPT ACL, its value includes the current command.
12187 .vitem &$rcpt_defer_count$&
12188 .vindex "&$rcpt_defer_count$&"
12189 .cindex "4&'xx'& responses" "count of"
12190 When a message is being received by SMTP, this variable contains the number of
12191 RCPT commands in the current message that have previously been rejected with a
12192 temporary (4&'xx'&) response.
12194 .vitem &$rcpt_fail_count$&
12195 .vindex "&$rcpt_fail_count$&"
12196 When a message is being received by SMTP, this variable contains the number of
12197 RCPT commands in the current message that have previously been rejected with a
12198 permanent (5&'xx'&) response.
12200 .vitem &$received_count$&
12201 .vindex "&$received_count$&"
12202 This variable contains the number of &'Received:'& header lines in the message,
12203 including the one added by Exim (so its value is always greater than zero). It
12204 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12207 .vitem &$received_for$&
12208 .vindex "&$received_for$&"
12209 If there is only a single recipient address in an incoming message, this
12210 variable contains that address when the &'Received:'& header line is being
12211 built. The value is copied after recipient rewriting has happened, but before
12212 the &[local_scan()]& function is run.
12214 .vitem &$received_ip_address$&
12215 .vindex "&$received_ip_address$&"
12216 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12217 variable is set to the address of the local IP interface, and &$received_port$&
12218 is set to the local port number. (The remote IP address and port are in
12219 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12220 the port value is -1 unless it has been set using the &%-oMi%& command line
12223 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12224 could be used, for example, to make the file name for a TLS certificate depend
12225 on which interface and/or port is being used for the incoming connection. The
12226 values of &$received_ip_address$& and &$received_port$& are saved with any
12227 messages that are received, thus making these variables available at delivery
12229 For outbound connections see &$sending_ip_address$&.
12231 .vitem &$received_port$&
12232 .vindex "&$received_port$&"
12233 See &$received_ip_address$&.
12235 .vitem &$received_protocol$&
12236 .vindex "&$received_protocol$&"
12237 When a message is being processed, this variable contains the name of the
12238 protocol by which it was received. Most of the names used by Exim are defined
12239 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12240 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12241 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12242 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12243 connection and the client was successfully authenticated.
12245 Exim uses the protocol name &"smtps"& for the case when encryption is
12246 automatically set up on connection without the use of STARTTLS (see
12247 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12248 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12249 where the client initially uses EHLO, sets up an encrypted connection using
12250 STARTTLS, and then uses HELO afterwards.
12252 The &%-oMr%& option provides a way of specifying a custom protocol name for
12253 messages that are injected locally by trusted callers. This is commonly used to
12254 identify messages that are being re-injected after some kind of scanning.
12256 .vitem &$received_time$&
12257 .vindex "&$received_time$&"
12258 This variable contains the date and time when the current message was received,
12259 as a number of seconds since the start of the Unix epoch.
12261 .vitem &$recipient_data$&
12262 .vindex "&$recipient_data$&"
12263 This variable is set after an indexing lookup success in an ACL &%recipients%&
12264 condition. It contains the data from the lookup, and the value remains set
12265 until the next &%recipients%& test. Thus, you can do things like this:
12267 &`require recipients = cdb*@;/some/file`&
12268 &`deny `&&'some further test involving'& &`$recipient_data`&
12270 &*Warning*&: This variable is set only when a lookup is used as an indexing
12271 method in the address list, using the semicolon syntax as in the example above.
12272 The variable is not set for a lookup that is used as part of the string
12273 expansion that all such lists undergo before being interpreted.
12275 .vitem &$recipient_verify_failure$&
12276 .vindex "&$recipient_verify_failure$&"
12277 In an ACL, when a recipient verification fails, this variable contains
12278 information about the failure. It is set to one of the following words:
12281 &"qualify"&: The address was unqualified (no domain), and the message
12282 was neither local nor came from an exempted host.
12285 &"route"&: Routing failed.
12288 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12289 or before the MAIL command (that is, on initial connection, HELO, or
12293 &"recipient"&: The RCPT command in a callout was rejected.
12296 &"postmaster"&: The postmaster check in a callout was rejected.
12299 The main use of this variable is expected to be to distinguish between
12300 rejections of MAIL and rejections of RCPT.
12302 .vitem &$recipients$&
12303 .vindex "&$recipients$&"
12304 This variable contains a list of envelope recipients for a message. A comma and
12305 a space separate the addresses in the replacement text. However, the variable
12306 is not generally available, to prevent exposure of Bcc recipients in
12307 unprivileged users' filter files. You can use &$recipients$& only in these
12311 In a system filter file.
12313 In the ACLs associated with the DATA command and with non-SMTP messages, that
12314 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12315 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12316 &%acl_not_smtp_mime%&.
12318 From within a &[local_scan()]& function.
12322 .vitem &$recipients_count$&
12323 .vindex "&$recipients_count$&"
12324 When a message is being processed, this variable contains the number of
12325 envelope recipients that came with the message. Duplicates are not excluded
12326 from the count. While a message is being received over SMTP, the number
12327 increases for each accepted recipient. It can be referenced in an ACL.
12330 .vitem &$regex_match_string$&
12331 .vindex "&$regex_match_string$&"
12332 This variable is set to contain the matching regular expression after a
12333 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12335 .vitem "&$regex1$&, &$regex2$&, etc"
12336 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12337 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12338 these variables contain the
12339 captured substrings identified by the regular expression.
12342 .vitem &$reply_address$&
12343 .vindex "&$reply_address$&"
12344 When a message is being processed, this variable contains the contents of the
12345 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12346 contents of the &'From:'& header line. Apart from the removal of leading
12347 white space, the value is not processed in any way. In particular, no RFC 2047
12348 decoding or character code translation takes place.
12350 .vitem &$return_path$&
12351 .vindex "&$return_path$&"
12352 When a message is being delivered, this variable contains the return path &--
12353 the sender field that will be sent as part of the envelope. It is not enclosed
12354 in <> characters. At the start of routing an address, &$return_path$& has the
12355 same value as &$sender_address$&, but if, for example, an incoming message to a
12356 mailing list has been expanded by a router which specifies a different address
12357 for bounce messages, &$return_path$& subsequently contains the new bounce
12358 address, whereas &$sender_address$& always contains the original sender address
12359 that was received with the message. In other words, &$sender_address$& contains
12360 the incoming envelope sender, and &$return_path$& contains the outgoing
12363 .vitem &$return_size_limit$&
12364 .vindex "&$return_size_limit$&"
12365 This is an obsolete name for &$bounce_return_size_limit$&.
12367 .vitem &$router_name$&
12368 .cindex "router" "name"
12369 .cindex "name" "of router"
12370 .vindex "&$router_name$&"
12371 During the running of a router this variable contains its name.
12374 .cindex "return code" "from &%run%& expansion"
12375 .vindex "&$runrc$&"
12376 This variable contains the return code from a command that is run by the
12377 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12378 assume the order in which option values are expanded, except for those
12379 preconditions whose order of testing is documented. Therefore, you cannot
12380 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12383 .vitem &$self_hostname$&
12384 .oindex "&%self%&" "value of host name"
12385 .vindex "&$self_hostname$&"
12386 When an address is routed to a supposedly remote host that turns out to be the
12387 local host, what happens is controlled by the &%self%& generic router option.
12388 One of its values causes the address to be passed to another router. When this
12389 happens, &$self_hostname$& is set to the name of the local host that the
12390 original router encountered. In other circumstances its contents are null.
12392 .vitem &$sender_address$&
12393 .vindex "&$sender_address$&"
12394 When a message is being processed, this variable contains the sender's address
12395 that was received in the message's envelope. The case of letters in the address
12396 is retained, in both the local part and the domain. For bounce messages, the
12397 value of this variable is the empty string. See also &$return_path$&.
12399 .vitem &$sender_address_data$&
12400 .vindex "&$address_data$&"
12401 .vindex "&$sender_address_data$&"
12402 If &$address_data$& is set when the routers are called from an ACL to verify a
12403 sender address, the final value is preserved in &$sender_address_data$&, to
12404 distinguish it from data from a recipient address. The value does not persist
12405 after the end of the current ACL statement. If you want to preserve it for
12406 longer, you can save it in an ACL variable.
12408 .vitem &$sender_address_domain$&
12409 .vindex "&$sender_address_domain$&"
12410 The domain portion of &$sender_address$&.
12412 .vitem &$sender_address_local_part$&
12413 .vindex "&$sender_address_local_part$&"
12414 The local part portion of &$sender_address$&.
12416 .vitem &$sender_data$&
12417 .vindex "&$sender_data$&"
12418 This variable is set after a lookup success in an ACL &%senders%& condition or
12419 in a router &%senders%& option. It contains the data from the lookup, and the
12420 value remains set until the next &%senders%& test. Thus, you can do things like
12423 &`require senders = cdb*@;/some/file`&
12424 &`deny `&&'some further test involving'& &`$sender_data`&
12426 &*Warning*&: This variable is set only when a lookup is used as an indexing
12427 method in the address list, using the semicolon syntax as in the example above.
12428 The variable is not set for a lookup that is used as part of the string
12429 expansion that all such lists undergo before being interpreted.
12431 .vitem &$sender_fullhost$&
12432 .vindex "&$sender_fullhost$&"
12433 When a message is received from a remote host, this variable contains the host
12434 name and IP address in a single string. It ends with the IP address in square
12435 brackets, followed by a colon and a port number if the logging of ports is
12436 enabled. The format of the rest of the string depends on whether the host
12437 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12438 looking up its IP address. (Looking up the IP address can be forced by the
12439 &%host_lookup%& option, independent of verification.) A plain host name at the
12440 start of the string is a verified host name; if this is not present,
12441 verification either failed or was not requested. A host name in parentheses is
12442 the argument of a HELO or EHLO command. This is omitted if it is identical to
12443 the verified host name or to the host's IP address in square brackets.
12445 .vitem &$sender_helo_dnssec$&
12446 .vindex "&$sender_helo_dnssec$&"
12447 This boolean variable is true if a successful HELO verification was
12448 .cindex "DNS" "DNSSEC"
12449 done using DNS information the resolver library stated was authenticated data.
12451 .vitem &$sender_helo_name$&
12452 .vindex "&$sender_helo_name$&"
12453 When a message is received from a remote host that has issued a HELO or EHLO
12454 command, the argument of that command is placed in this variable. It is also
12455 set if HELO or EHLO is used when a message is received using SMTP locally via
12456 the &%-bs%& or &%-bS%& options.
12458 .vitem &$sender_host_address$&
12459 .vindex "&$sender_host_address$&"
12460 When a message is received from a remote host using SMTP,
12461 this variable contains that
12462 host's IP address. For locally non-SMTP submitted messages, it is empty.
12464 .vitem &$sender_host_authenticated$&
12465 .vindex "&$sender_host_authenticated$&"
12466 This variable contains the name (not the public name) of the authenticator
12467 driver that successfully authenticated the client from which the message was
12468 received. It is empty if there was no successful authentication. See also
12469 &$authenticated_id$&.
12471 .vitem &$sender_host_dnssec$&
12472 .vindex "&$sender_host_dnssec$&"
12473 If an attempt to populate &$sender_host_name$& has been made
12474 (by reference, &%hosts_lookup%& or
12475 otherwise) then this boolean will have been set true if, and only if, the
12476 resolver library states that both
12477 the reverse and forward DNS were authenticated data. At all
12478 other times, this variable is false.
12480 .cindex "DNS" "DNSSEC"
12481 It is likely that you will need to coerce DNSSEC support on in the resolver
12482 library, by setting:
12487 Exim does not perform DNSSEC validation itself, instead leaving that to a
12488 validating resolver (e.g. unbound, or bind with suitable configuration).
12490 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12491 mechanism in the list, then this variable will be false.
12494 .vitem &$sender_host_name$&
12495 .vindex "&$sender_host_name$&"
12496 When a message is received from a remote host, this variable contains the
12497 host's name as obtained by looking up its IP address. For messages received by
12498 other means, this variable is empty.
12500 .vindex "&$host_lookup_failed$&"
12501 If the host name has not previously been looked up, a reference to
12502 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12503 A looked up name is accepted only if it leads back to the original IP address
12504 via a forward lookup. If either the reverse or the forward lookup fails to find
12505 any data, or if the forward lookup does not yield the original IP address,
12506 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12508 .vindex "&$host_lookup_deferred$&"
12509 However, if either of the lookups cannot be completed (for example, there is a
12510 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12511 &$host_lookup_failed$& remains set to &"0"&.
12513 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12514 host name again if there is a subsequent reference to &$sender_host_name$&
12515 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12518 Exim does not automatically look up every calling host's name. If you want
12519 maximum efficiency, you should arrange your configuration so that it avoids
12520 these lookups altogether. The lookup happens only if one or more of the
12521 following are true:
12524 A string containing &$sender_host_name$& is expanded.
12526 The calling host matches the list in &%host_lookup%&. In the default
12527 configuration, this option is set to *, so it must be changed if lookups are
12528 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12530 Exim needs the host name in order to test an item in a host list. The items
12531 that require this are described in sections &<<SECThoslispatnam>>& and
12532 &<<SECThoslispatnamsk>>&.
12534 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12535 In this case, the host name is required to compare with the name quoted in any
12536 EHLO or HELO commands that the client issues.
12538 The remote host issues a EHLO or HELO command that quotes one of the
12539 domains in &%helo_lookup_domains%&. The default value of this option is
12540 . ==== As this is a nested list, any displays it contains must be indented
12541 . ==== as otherwise they are too far to the left.
12543 helo_lookup_domains = @ : @[]
12545 which causes a lookup if a remote host (incorrectly) gives the server's name or
12546 IP address in an EHLO or HELO command.
12550 .vitem &$sender_host_port$&
12551 .vindex "&$sender_host_port$&"
12552 When a message is received from a remote host, this variable contains the port
12553 number that was used on the remote host.
12555 .vitem &$sender_ident$&
12556 .vindex "&$sender_ident$&"
12557 When a message is received from a remote host, this variable contains the
12558 identification received in response to an RFC 1413 request. When a message has
12559 been received locally, this variable contains the login name of the user that
12562 .vitem &$sender_rate_$&&'xxx'&
12563 A number of variables whose names begin &$sender_rate_$& are set as part of the
12564 &%ratelimit%& ACL condition. Details are given in section
12565 &<<SECTratelimiting>>&.
12567 .vitem &$sender_rcvhost$&
12568 .cindex "DNS" "reverse lookup"
12569 .cindex "reverse DNS lookup"
12570 .vindex "&$sender_rcvhost$&"
12571 This is provided specifically for use in &'Received:'& headers. It starts with
12572 either the verified host name (as obtained from a reverse DNS lookup) or, if
12573 there is no verified host name, the IP address in square brackets. After that
12574 there may be text in parentheses. When the first item is a verified host name,
12575 the first thing in the parentheses is the IP address in square brackets,
12576 followed by a colon and a port number if port logging is enabled. When the
12577 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12580 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12581 was used and its argument was not identical to the real host name or IP
12582 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12583 all three items are present in the parentheses, a newline and tab are inserted
12584 into the string, to improve the formatting of the &'Received:'& header.
12586 .vitem &$sender_verify_failure$&
12587 .vindex "&$sender_verify_failure$&"
12588 In an ACL, when a sender verification fails, this variable contains information
12589 about the failure. The details are the same as for
12590 &$recipient_verify_failure$&.
12592 .vitem &$sending_ip_address$&
12593 .vindex "&$sending_ip_address$&"
12594 This variable is set whenever an outgoing SMTP connection to another host has
12595 been set up. It contains the IP address of the local interface that is being
12596 used. This is useful if a host that has more than one IP address wants to take
12597 on different personalities depending on which one is being used. For incoming
12598 connections, see &$received_ip_address$&.
12600 .vitem &$sending_port$&
12601 .vindex "&$sending_port$&"
12602 This variable is set whenever an outgoing SMTP connection to another host has
12603 been set up. It contains the local port that is being used. For incoming
12604 connections, see &$received_port$&.
12606 .vitem &$smtp_active_hostname$&
12607 .vindex "&$smtp_active_hostname$&"
12608 During an incoming SMTP session, this variable contains the value of the active
12609 host name, as specified by the &%smtp_active_hostname%& option. The value of
12610 &$smtp_active_hostname$& is saved with any message that is received, so its
12611 value can be consulted during routing and delivery.
12613 .vitem &$smtp_command$&
12614 .vindex "&$smtp_command$&"
12615 During the processing of an incoming SMTP command, this variable contains the
12616 entire command. This makes it possible to distinguish between HELO and EHLO in
12617 the HELO ACL, and also to distinguish between commands such as these:
12622 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12623 command, the address in &$smtp_command$& is the original address before any
12624 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12625 the address after SMTP-time rewriting.
12627 .vitem &$smtp_command_argument$&
12628 .cindex "SMTP" "command, argument for"
12629 .vindex "&$smtp_command_argument$&"
12630 While an ACL is running to check an SMTP command, this variable contains the
12631 argument, that is, the text that follows the command name, with leading white
12632 space removed. Following the introduction of &$smtp_command$&, this variable is
12633 somewhat redundant, but is retained for backwards compatibility.
12635 .vitem &$smtp_count_at_connection_start$&
12636 .vindex "&$smtp_count_at_connection_start$&"
12637 This variable is set greater than zero only in processes spawned by the Exim
12638 daemon for handling incoming SMTP connections. The name is deliberately long,
12639 in order to emphasize what the contents are. When the daemon accepts a new
12640 connection, it increments this variable. A copy of the variable is passed to
12641 the child process that handles the connection, but its value is fixed, and
12642 never changes. It is only an approximation of how many incoming connections
12643 there actually are, because many other connections may come and go while a
12644 single connection is being processed. When a child process terminates, the
12645 daemon decrements its copy of the variable.
12647 .vitem "&$sn0$& &-- &$sn9$&"
12648 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12649 that were current at the end of the system filter file. This allows a system
12650 filter file to set values that can be tested in users' filter files. For
12651 example, a system filter could set a value indicating how likely it is that a
12652 message is junk mail.
12654 .vitem &$spam_$&&'xxx'&
12655 A number of variables whose names start with &$spam$& are available when Exim
12656 is compiled with the content-scanning extension. For details, see section
12657 &<<SECTscanspamass>>&.
12660 .vitem &$spool_directory$&
12661 .vindex "&$spool_directory$&"
12662 The name of Exim's spool directory.
12664 .vitem &$spool_inodes$&
12665 .vindex "&$spool_inodes$&"
12666 The number of free inodes in the disk partition where Exim's spool files are
12667 being written. The value is recalculated whenever the variable is referenced.
12668 If the relevant file system does not have the concept of inodes, the value of
12669 is -1. See also the &%check_spool_inodes%& option.
12671 .vitem &$spool_space$&
12672 .vindex "&$spool_space$&"
12673 The amount of free space (as a number of kilobytes) in the disk partition where
12674 Exim's spool files are being written. The value is recalculated whenever the
12675 variable is referenced. If the operating system does not have the ability to
12676 find the amount of free space (only true for experimental systems), the space
12677 value is -1. For example, to check in an ACL that there is at least 50
12678 megabytes free on the spool, you could write:
12680 condition = ${if > {$spool_space}{50000}}
12682 See also the &%check_spool_space%& option.
12685 .vitem &$thisaddress$&
12686 .vindex "&$thisaddress$&"
12687 This variable is set only during the processing of the &%foranyaddress%&
12688 command in a filter file. Its use is explained in the description of that
12689 command, which can be found in the separate document entitled &'Exim's
12690 interfaces to mail filtering'&.
12692 .vitem &$tls_in_bits$&
12693 .vindex "&$tls_in_bits$&"
12694 Contains an approximation of the TLS cipher's bit-strength
12695 on the inbound connection; the meaning of
12696 this depends upon the TLS implementation used.
12697 If TLS has not been negotiated, the value will be 0.
12698 The value of this is automatically fed into the Cyrus SASL authenticator
12699 when acting as a server, to specify the "external SSF" (a SASL term).
12701 The deprecated &$tls_bits$& variable refers to the inbound side
12702 except when used in the context of an outbound SMTP delivery, when it refers to
12705 .vitem &$tls_out_bits$&
12706 .vindex "&$tls_out_bits$&"
12707 Contains an approximation of the TLS cipher's bit-strength
12708 on an outbound SMTP connection; the meaning of
12709 this depends upon the TLS implementation used.
12710 If TLS has not been negotiated, the value will be 0.
12712 .vitem &$tls_in_ourcert$&
12713 .vindex "&$tls_in_ourcert$&"
12714 .cindex certificate veriables
12715 This variable refers to the certificate presented to the peer of an
12716 inbound connection when the message was received.
12717 It is only useful as the argument of a
12718 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12719 or a &%def%& condition.
12721 .vitem &$tls_in_peercert$&
12722 .vindex "&$tls_in_peercert$&"
12723 This variable refers to the certificate presented by the peer of an
12724 inbound connection when the message was received.
12725 It is only useful as the argument of a
12726 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12727 or a &%def%& condition.
12728 If certificate verification fails it may refer to a failing chain element
12729 which is not the leaf.
12731 .vitem &$tls_out_ourcert$&
12732 .vindex "&$tls_out_ourcert$&"
12733 This variable refers to the certificate presented to the peer of an
12734 outbound connection. It is only useful as the argument of a
12735 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12736 or a &%def%& condition.
12738 .vitem &$tls_out_peercert$&
12739 .vindex "&$tls_out_peercert$&"
12740 This variable refers to the certificate presented by the peer of an
12741 outbound connection. It is only useful as the argument of a
12742 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12743 or a &%def%& condition.
12744 If certificate verification fails it may refer to a failing chain element
12745 which is not the leaf.
12747 .vitem &$tls_in_certificate_verified$&
12748 .vindex "&$tls_in_certificate_verified$&"
12749 This variable is set to &"1"& if a TLS certificate was verified when the
12750 message was received, and &"0"& otherwise.
12752 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
12753 except when used in the context of an outbound SMTP delivery, when it refers to
12756 .vitem &$tls_out_certificate_verified$&
12757 .vindex "&$tls_out_certificate_verified$&"
12758 This variable is set to &"1"& if a TLS certificate was verified when an
12759 outbound SMTP connection was made,
12760 and &"0"& otherwise.
12762 .vitem &$tls_in_cipher$&
12763 .vindex "&$tls_in_cipher$&"
12764 .vindex "&$tls_cipher$&"
12765 When a message is received from a remote host over an encrypted SMTP
12766 connection, this variable is set to the cipher suite that was negotiated, for
12767 example DES-CBC3-SHA. In other circumstances, in particular, for message
12768 received over unencrypted connections, the variable is empty. Testing
12769 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
12770 non-encrypted connections during ACL processing.
12772 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12773 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12774 becomes the same as &$tls_out_cipher$&.
12776 .vitem &$tls_out_cipher$&
12777 .vindex "&$tls_out_cipher$&"
12779 cleared before any outgoing SMTP connection is made,
12780 and then set to the outgoing cipher suite if one is negotiated. See chapter
12781 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12782 details of the &(smtp)& transport.
12784 .vitem &$tls_in_ocsp$&
12785 .vindex "&$tls_in_ocsp$&"
12786 When a message is received from a remote client connection
12787 the result of any OCSP request from the client is encoded in this variable:
12789 0 OCSP proof was not requested (default value)
12790 1 No response to request
12791 2 Response not verified
12792 3 Verification failed
12793 4 Verification succeeded
12796 .vitem &$tls_out_ocsp$&
12797 .vindex "&$tls_out_ocsp$&"
12798 When a message is sent to a remote host connection
12799 the result of any OCSP request made is encoded in this variable.
12800 See &$tls_in_ocsp$& for values.
12802 .vitem &$tls_in_peerdn$&
12803 .vindex "&$tls_in_peerdn$&"
12804 .vindex "&$tls_peerdn$&"
12805 .cindex certificate "extracting fields"
12806 When a message is received from a remote host over an encrypted SMTP
12807 connection, and Exim is configured to request a certificate from the client,
12808 the value of the Distinguished Name of the certificate is made available in the
12809 &$tls_in_peerdn$& during subsequent processing.
12810 If certificate verification fails it may refer to a failing chain element
12811 which is not the leaf.
12813 The deprecated &$tls_peerdn$& variable refers to the inbound side
12814 except when used in the context of an outbound SMTP delivery, when it refers to
12817 .vitem &$tls_out_peerdn$&
12818 .vindex "&$tls_out_peerdn$&"
12819 When a message is being delivered to a remote host over an encrypted SMTP
12820 connection, and Exim is configured to request a certificate from the server,
12821 the value of the Distinguished Name of the certificate is made available in the
12822 &$tls_out_peerdn$& during subsequent processing.
12823 If certificate verification fails it may refer to a failing chain element
12824 which is not the leaf.
12826 .vitem &$tls_in_sni$&
12827 .vindex "&$tls_in_sni$&"
12828 .vindex "&$tls_sni$&"
12829 .cindex "TLS" "Server Name Indication"
12830 When a TLS session is being established, if the client sends the Server
12831 Name Indication extension, the value will be placed in this variable.
12832 If the variable appears in &%tls_certificate%& then this option and
12833 some others, described in &<<SECTtlssni>>&,
12834 will be re-expanded early in the TLS session, to permit
12835 a different certificate to be presented (and optionally a different key to be
12836 used) to the client, based upon the value of the SNI extension.
12838 The deprecated &$tls_sni$& variable refers to the inbound side
12839 except when used in the context of an outbound SMTP delivery, when it refers to
12842 .vitem &$tls_out_sni$&
12843 .vindex "&$tls_out_sni$&"
12844 .cindex "TLS" "Server Name Indication"
12846 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12849 .vitem &$tod_bsdinbox$&
12850 .vindex "&$tod_bsdinbox$&"
12851 The time of day and the date, in the format required for BSD-style mailbox
12852 files, for example: Thu Oct 17 17:14:09 1995.
12854 .vitem &$tod_epoch$&
12855 .vindex "&$tod_epoch$&"
12856 The time and date as a number of seconds since the start of the Unix epoch.
12858 .vitem &$tod_epoch_l$&
12859 .vindex "&$tod_epoch_l$&"
12860 The time and date as a number of microseconds since the start of the Unix epoch.
12862 .vitem &$tod_full$&
12863 .vindex "&$tod_full$&"
12864 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12865 +0100. The timezone is always given as a numerical offset from UTC, with
12866 positive values used for timezones that are ahead (east) of UTC, and negative
12867 values for those that are behind (west).
12870 .vindex "&$tod_log$&"
12871 The time and date in the format used for writing Exim's log files, for example:
12872 1995-10-12 15:32:29, but without a timezone.
12874 .vitem &$tod_logfile$&
12875 .vindex "&$tod_logfile$&"
12876 This variable contains the date in the format yyyymmdd. This is the format that
12877 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12880 .vitem &$tod_zone$&
12881 .vindex "&$tod_zone$&"
12882 This variable contains the numerical value of the local timezone, for example:
12885 .vitem &$tod_zulu$&
12886 .vindex "&$tod_zulu$&"
12887 This variable contains the UTC date and time in &"Zulu"& format, as specified
12888 by ISO 8601, for example: 20030221154023Z.
12890 .vitem &$transport_name$&
12891 .cindex "transport" "name"
12892 .cindex "name" "of transport"
12893 .vindex "&$transport_name$&"
12894 During the running of a transport, this variable contains its name.
12897 .vindex "&$value$&"
12898 This variable contains the result of an expansion lookup, extraction operation,
12899 or external command, as described above. It is also used during a
12900 &*reduce*& expansion.
12902 .vitem &$verify_mode$&
12903 .vindex "&$verify_mode$&"
12904 While a router or transport is being run in verify mode
12905 or for cutthrough delivery,
12906 contains "S" for sender-verification or "R" for recipient-verification.
12909 .vitem &$version_number$&
12910 .vindex "&$version_number$&"
12911 The version number of Exim.
12913 .vitem &$warn_message_delay$&
12914 .vindex "&$warn_message_delay$&"
12915 This variable is set only during the creation of a message warning about a
12916 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12918 .vitem &$warn_message_recipients$&
12919 .vindex "&$warn_message_recipients$&"
12920 This variable is set only during the creation of a message warning about a
12921 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12927 . ////////////////////////////////////////////////////////////////////////////
12928 . ////////////////////////////////////////////////////////////////////////////
12930 .chapter "Embedded Perl" "CHAPperl"
12931 .scindex IIDperl "Perl" "calling from Exim"
12932 Exim can be built to include an embedded Perl interpreter. When this is done,
12933 Perl subroutines can be called as part of the string expansion process. To make
12934 use of the Perl support, you need version 5.004 or later of Perl installed on
12935 your system. To include the embedded interpreter in the Exim binary, include
12940 in your &_Local/Makefile_& and then build Exim in the normal way.
12943 .section "Setting up so Perl can be used" "SECID85"
12944 .oindex "&%perl_startup%&"
12945 Access to Perl subroutines is via a global configuration option called
12946 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12947 no &%perl_startup%& option in the Exim configuration file then no Perl
12948 interpreter is started and there is almost no overhead for Exim (since none of
12949 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12950 option then the associated value is taken to be Perl code which is executed in
12951 a newly created Perl interpreter.
12953 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12954 need backslashes before any characters to escape special meanings. The option
12955 should usually be something like
12957 perl_startup = do '/etc/exim.pl'
12959 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12960 use from Exim. Exim can be configured either to start up a Perl interpreter as
12961 soon as it is entered, or to wait until the first time it is needed. Starting
12962 the interpreter at the beginning ensures that it is done while Exim still has
12963 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12964 fact used in a particular run. Also, note that this does not mean that Exim is
12965 necessarily running as root when Perl is called at a later time. By default,
12966 the interpreter is started only when it is needed, but this can be changed in
12970 .oindex "&%perl_at_start%&"
12971 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12972 a startup when Exim is entered.
12974 The command line option &%-ps%& also requests a startup when Exim is entered,
12975 overriding the setting of &%perl_at_start%&.
12978 There is also a command line option &%-pd%& (for delay) which suppresses the
12979 initial startup, even if &%perl_at_start%& is set.
12982 .section "Calling Perl subroutines" "SECID86"
12983 When the configuration file includes a &%perl_startup%& option you can make use
12984 of the string expansion item to call the Perl subroutines that are defined
12985 by the &%perl_startup%& code. The operator is used in any of the following
12989 ${perl{foo}{argument}}
12990 ${perl{foo}{argument1}{argument2} ... }
12992 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12993 arguments may be passed. Passing more than this results in an expansion failure
12994 with an error message of the form
12996 Too many arguments passed to Perl subroutine "foo" (max is 8)
12998 The return value of the Perl subroutine is evaluated in a scalar context before
12999 it is passed back to Exim to be inserted into the expanded string. If the
13000 return value is &'undef'&, the expansion is forced to fail in the same way as
13001 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
13002 by obeying Perl's &%die%& function, the expansion fails with the error message
13003 that was passed to &%die%&.
13006 .section "Calling Exim functions from Perl" "SECID87"
13007 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
13008 is available to call back into Exim's string expansion function. For example,
13011 my $lp = Exim::expand_string('$local_part');
13013 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
13014 Note those are single quotes and not double quotes to protect against
13015 &$local_part$& being interpolated as a Perl variable.
13017 If the string expansion is forced to fail by a &"fail"& item, the result of
13018 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
13019 expansion string, the Perl call from the original expansion string fails with
13020 an appropriate error message, in the same way as if &%die%& were used.
13022 .cindex "debugging" "from embedded Perl"
13023 .cindex "log" "writing from embedded Perl"
13024 Two other Exim functions are available for use from within Perl code.
13025 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
13026 debugging is enabled. If you want a newline at the end, you must supply it.
13027 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
13028 timestamp. In this case, you should not supply a terminating newline.
13031 .section "Use of standard output and error by Perl" "SECID88"
13032 .cindex "Perl" "standard output and error"
13033 You should not write to the standard error or output streams from within your
13034 Perl code, as it is not defined how these are set up. In versions of Exim
13035 before 4.50, it is possible for the standard output or error to refer to the
13036 SMTP connection during message reception via the daemon. Writing to this stream
13037 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
13038 error streams are connected to &_/dev/null_& in the daemon. The chaos is
13039 avoided, but the output is lost.
13041 .cindex "Perl" "use of &%warn%&"
13042 The Perl &%warn%& statement writes to the standard error stream by default.
13043 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
13044 you have no control. When Exim starts up the Perl interpreter, it arranges for
13045 output from the &%warn%& statement to be written to the Exim main log. You can
13046 change this by including appropriate Perl magic somewhere in your Perl code.
13047 For example, to discard &%warn%& output completely, you need this:
13049 $SIG{__WARN__} = sub { };
13051 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
13052 example, the code for the subroutine is empty, so it does nothing, but you can
13053 include any Perl code that you like. The text of the &%warn%& message is passed
13054 as the first subroutine argument.
13058 . ////////////////////////////////////////////////////////////////////////////
13059 . ////////////////////////////////////////////////////////////////////////////
13061 .chapter "Starting the daemon and the use of network interfaces" &&&
13062 "CHAPinterfaces" &&&
13063 "Starting the daemon"
13064 .cindex "daemon" "starting"
13065 .cindex "interface" "listening"
13066 .cindex "network interface"
13067 .cindex "interface" "network"
13068 .cindex "IP address" "for listening"
13069 .cindex "daemon" "listening IP addresses"
13070 .cindex "TCP/IP" "setting listening interfaces"
13071 .cindex "TCP/IP" "setting listening ports"
13072 A host that is connected to a TCP/IP network may have one or more physical
13073 hardware network interfaces. Each of these interfaces may be configured as one
13074 or more &"logical"& interfaces, which are the entities that a program actually
13075 works with. Each of these logical interfaces is associated with an IP address.
13076 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13077 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13078 knowledge about the host's interfaces for use in three different circumstances:
13081 When a listening daemon is started, Exim needs to know which interfaces
13082 and ports to listen on.
13084 When Exim is routing an address, it needs to know which IP addresses
13085 are associated with local interfaces. This is required for the correct
13086 processing of MX lists by removing the local host and others with the
13087 same or higher priority values. Also, Exim needs to detect cases
13088 when an address is routed to an IP address that in fact belongs to the
13089 local host. Unless the &%self%& router option or the &%allow_localhost%&
13090 option of the smtp transport is set (as appropriate), this is treated
13091 as an error situation.
13093 When Exim connects to a remote host, it may need to know which interface to use
13094 for the outgoing connection.
13098 Exim's default behaviour is likely to be appropriate in the vast majority
13099 of cases. If your host has only one interface, and you want all its IP
13100 addresses to be treated in the same way, and you are using only the
13101 standard SMTP port, you should not need to take any special action. The
13102 rest of this chapter does not apply to you.
13104 In a more complicated situation you may want to listen only on certain
13105 interfaces, or on different ports, and for this reason there are a number of
13106 options that can be used to influence Exim's behaviour. The rest of this
13107 chapter describes how they operate.
13109 When a message is received over TCP/IP, the interface and port that were
13110 actually used are set in &$received_ip_address$& and &$received_port$&.
13114 .section "Starting a listening daemon" "SECID89"
13115 When a listening daemon is started (by means of the &%-bd%& command line
13116 option), the interfaces and ports on which it listens are controlled by the
13120 &%daemon_smtp_ports%& contains a list of default ports
13122 (For backward compatibility, this option can also be specified in the singular.)
13124 &%local_interfaces%& contains list of interface IP addresses on which to
13125 listen. Each item may optionally also specify a port.
13128 The default list separator in both cases is a colon, but this can be changed as
13129 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
13130 it is usually best to change the separator to avoid having to double all the
13131 colons. For example:
13133 local_interfaces = <; 127.0.0.1 ; \
13136 3ffe:ffff:836f::fe86:a061
13138 There are two different formats for specifying a port along with an IP address
13139 in &%local_interfaces%&:
13142 The port is added onto the address with a dot separator. For example, to listen
13143 on port 1234 on two different IP addresses:
13145 local_interfaces = <; 192.168.23.65.1234 ; \
13146 3ffe:ffff:836f::fe86:a061.1234
13149 The IP address is enclosed in square brackets, and the port is added
13150 with a colon separator, for example:
13152 local_interfaces = <; [192.168.23.65]:1234 ; \
13153 [3ffe:ffff:836f::fe86:a061]:1234
13157 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13158 default setting contains just one port:
13160 daemon_smtp_ports = smtp
13162 If more than one port is listed, each interface that does not have its own port
13163 specified listens on all of them. Ports that are listed in
13164 &%daemon_smtp_ports%& can be identified either by name (defined in
13165 &_/etc/services_&) or by number. However, when ports are given with individual
13166 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13170 .section "Special IP listening addresses" "SECID90"
13171 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13172 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13173 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13174 instead of setting up separate listening sockets for each interface. The
13175 default value of &%local_interfaces%& is
13177 local_interfaces = 0.0.0.0
13179 when Exim is built without IPv6 support; otherwise it is:
13181 local_interfaces = <; ::0 ; 0.0.0.0
13183 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13187 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13188 The &%-oX%& command line option can be used to override the values of
13189 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13190 instance. Another way of doing this would be to use macros and the &%-D%&
13191 option. However, &%-oX%& can be used by any admin user, whereas modification of
13192 the runtime configuration by &%-D%& is allowed only when the caller is root or
13195 The value of &%-oX%& is a list of items. The default colon separator can be
13196 changed in the usual way if required. If there are any items that do not
13197 contain dots or colons (that is, are not IP addresses), the value of
13198 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13199 items that do contain dots or colons, the value of &%local_interfaces%& is
13200 replaced by those items. Thus, for example,
13204 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13207 -oX 192.168.34.5.1125
13209 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13210 (However, since &%local_interfaces%& now contains no items without ports, the
13211 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13215 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
13216 .cindex "ssmtp protocol"
13217 .cindex "smtps protocol"
13218 .cindex "SMTP" "ssmtp protocol"
13219 .cindex "SMTP" "smtps protocol"
13220 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
13221 before the STARTTLS command was standardized for SMTP. Some legacy clients
13222 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
13223 list of port numbers or service names,
13224 connections to those ports must use SSMTP. The most
13225 common use of this option is expected to be
13227 tls_on_connect_ports = 465
13229 because 465 is the usual port number used by the legacy clients. There is also
13230 a command line option &%-tls-on-connect%&, which forces all ports to behave in
13231 this way when a daemon is started.
13233 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13234 daemon to listen on those ports. You must still specify them in
13235 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13236 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13237 connections via the daemon.)
13242 .section "IPv6 address scopes" "SECID92"
13243 .cindex "IPv6" "address scopes"
13244 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13245 can, in principle, have the same link-local IPv6 address on different
13246 interfaces. Thus, additional information is needed, over and above the IP
13247 address, to distinguish individual interfaces. A convention of using a
13248 percent sign followed by something (often the interface name) has been
13249 adopted in some cases, leading to addresses like this:
13251 fe80::202:b3ff:fe03:45c1%eth0
13253 To accommodate this usage, a percent sign followed by an arbitrary string is
13254 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13255 to convert a textual IPv6 address for actual use. This function recognizes the
13256 percent convention in operating systems that support it, and it processes the
13257 address appropriately. Unfortunately, some older libraries have problems with
13258 &[getaddrinfo()]&. If
13260 IPV6_USE_INET_PTON=yes
13262 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13263 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13264 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13265 function.) Of course, this means that the additional functionality of
13266 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13268 .section "Disabling IPv6" "SECID93"
13269 .cindex "IPv6" "disabling"
13270 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13271 run on a host whose kernel does not support IPv6. The binary will fall back to
13272 using IPv4, but it may waste resources looking up AAAA records, and trying to
13273 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13274 .oindex "&%disable_ipv6%&"
13275 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13276 activities take place. AAAA records are never looked up, and any IPv6 addresses
13277 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13278 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13279 to handle IPv6 literal addresses.
13281 On the other hand, when IPv6 is in use, there may be times when you want to
13282 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13283 option to globally suppress the lookup of AAAA records for specified domains,
13284 and you can use the &%ignore_target_hosts%& generic router option to ignore
13285 IPv6 addresses in an individual router.
13289 .section "Examples of starting a listening daemon" "SECID94"
13290 The default case in an IPv6 environment is
13292 daemon_smtp_ports = smtp
13293 local_interfaces = <; ::0 ; 0.0.0.0
13295 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13296 Either one or two sockets may be used, depending on the characteristics of
13297 the TCP/IP stack. (This is complicated and messy; for more information,
13298 read the comments in the &_daemon.c_& source file.)
13300 To specify listening on ports 25 and 26 on all interfaces:
13302 daemon_smtp_ports = 25 : 26
13304 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13306 local_interfaces = <; ::0.25 ; ::0.26 \
13307 0.0.0.0.25 ; 0.0.0.0.26
13309 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13310 IPv4 loopback address only:
13312 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13314 To specify listening on the default port on specific interfaces only:
13316 local_interfaces = 10.0.0.67 : 192.168.34.67
13318 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13322 .section "Recognizing the local host" "SECTreclocipadd"
13323 The &%local_interfaces%& option is also used when Exim needs to determine
13324 whether or not an IP address refers to the local host. That is, the IP
13325 addresses of all the interfaces on which a daemon is listening are always
13328 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13329 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13330 available interfaces from the operating system, and extracts the relevant
13331 (that is, IPv4 or IPv6) addresses to use for checking.
13333 Some systems set up large numbers of virtual interfaces in order to provide
13334 many virtual web servers. In this situation, you may want to listen for
13335 email on only a few of the available interfaces, but nevertheless treat all
13336 interfaces as local when routing. You can do this by setting
13337 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13338 &"all"& wildcard values. These addresses are recognized as local, but are not
13339 used for listening. Consider this example:
13341 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13343 3ffe:2101:12:1:a00:20ff:fe86:a061
13345 extra_local_interfaces = <; ::0 ; 0.0.0.0
13347 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13348 address, but all available interface addresses are treated as local when
13351 In some environments the local host name may be in an MX list, but with an IP
13352 address that is not assigned to any local interface. In other cases it may be
13353 desirable to treat other host names as if they referred to the local host. Both
13354 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13355 This contains host names rather than IP addresses. When a host is referenced
13356 during routing, either via an MX record or directly, it is treated as the local
13357 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13358 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13362 .section "Delivering to a remote host" "SECID95"
13363 Delivery to a remote host is handled by the smtp transport. By default, it
13364 allows the system's TCP/IP functions to choose which interface to use (if
13365 there is more than one) when connecting to a remote host. However, the
13366 &%interface%& option can be set to specify which interface is used. See the
13367 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13373 . ////////////////////////////////////////////////////////////////////////////
13374 . ////////////////////////////////////////////////////////////////////////////
13376 .chapter "Main configuration" "CHAPmainconfig"
13377 .scindex IIDconfima "configuration file" "main section"
13378 .scindex IIDmaiconf "main configuration"
13379 The first part of the run time configuration file contains three types of item:
13382 Macro definitions: These lines start with an upper case letter. See section
13383 &<<SECTmacrodefs>>& for details of macro processing.
13385 Named list definitions: These lines start with one of the words &"domainlist"&,
13386 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13387 section &<<SECTnamedlists>>&.
13389 Main configuration settings: Each setting occupies one line of the file
13390 (with possible continuations). If any setting is preceded by the word
13391 &"hide"&, the &%-bP%& command line option displays its value to admin users
13392 only. See section &<<SECTcos>>& for a description of the syntax of these option
13396 This chapter specifies all the main configuration options, along with their
13397 types and default values. For ease of finding a particular option, they appear
13398 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13399 are now so many options, they are first listed briefly in functional groups, as
13400 an aid to finding the name of the option you are looking for. Some options are
13401 listed in more than one group.
13403 .section "Miscellaneous" "SECID96"
13405 .row &%bi_command%& "to run for &%-bi%& command line option"
13406 .row &%disable_ipv6%& "do no IPv6 processing"
13407 .row &%keep_malformed%& "for broken files &-- should not happen"
13408 .row &%localhost_number%& "for unique message ids in clusters"
13409 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13410 .row &%message_body_visible%& "how much to show in &$message_body$&"
13411 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13412 .row &%print_topbitchars%& "top-bit characters are printing"
13413 .row &%timezone%& "force time zone"
13417 .section "Exim parameters" "SECID97"
13419 .row &%exim_group%& "override compiled-in value"
13420 .row &%exim_path%& "override compiled-in value"
13421 .row &%exim_user%& "override compiled-in value"
13422 .row &%primary_hostname%& "default from &[uname()]&"
13423 .row &%split_spool_directory%& "use multiple directories"
13424 .row &%spool_directory%& "override compiled-in value"
13429 .section "Privilege controls" "SECID98"
13431 .row &%admin_groups%& "groups that are Exim admin users"
13432 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13433 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13434 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13435 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13436 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13437 .row &%never_users%& "do not run deliveries as these"
13438 .row &%prod_requires_admin%& "forced delivery requires admin user"
13439 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13440 .row &%trusted_groups%& "groups that are trusted"
13441 .row &%trusted_users%& "users that are trusted"
13446 .section "Logging" "SECID99"
13448 .row &%event_action%& "custom logging"
13449 .row &%hosts_connection_nolog%& "exemption from connect logging"
13450 .row &%log_file_path%& "override compiled-in value"
13451 .row &%log_selector%& "set/unset optional logging"
13452 .row &%log_timezone%& "add timezone to log lines"
13453 .row &%message_logs%& "create per-message logs"
13454 .row &%preserve_message_logs%& "after message completion"
13455 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13456 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13457 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13458 .row &%syslog_facility%& "set syslog &""facility""& field"
13459 .row &%syslog_processname%& "set syslog &""ident""& field"
13460 .row &%syslog_timestamp%& "timestamp syslog lines"
13461 .row &%write_rejectlog%& "control use of message log"
13466 .section "Frozen messages" "SECID100"
13468 .row &%auto_thaw%& "sets time for retrying frozen messages"
13469 .row &%freeze_tell%& "send message when freezing"
13470 .row &%move_frozen_messages%& "to another directory"
13471 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13476 .section "Data lookups" "SECID101"
13478 .row &%ibase_servers%& "InterBase servers"
13479 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13480 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13481 .row &%ldap_cert_file%& "client cert file for LDAP"
13482 .row &%ldap_cert_key%& "client key file for LDAP"
13483 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13484 .row &%ldap_default_servers%& "used if no server in query"
13485 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13486 .row &%ldap_start_tls%& "require TLS within LDAP"
13487 .row &%ldap_version%& "set protocol version"
13488 .row &%lookup_open_max%& "lookup files held open"
13489 .row &%mysql_servers%& "default MySQL servers"
13490 .row &%oracle_servers%& "Oracle servers"
13491 .row &%pgsql_servers%& "default PostgreSQL servers"
13492 .row &%sqlite_lock_timeout%& "as it says"
13497 .section "Message ids" "SECID102"
13499 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13500 .row &%message_id_header_text%& "ditto"
13505 .section "Embedded Perl Startup" "SECID103"
13507 .row &%perl_at_start%& "always start the interpreter"
13508 .row &%perl_startup%& "code to obey when starting Perl"
13513 .section "Daemon" "SECID104"
13515 .row &%daemon_smtp_ports%& "default ports"
13516 .row &%daemon_startup_retries%& "number of times to retry"
13517 .row &%daemon_startup_sleep%& "time to sleep between tries"
13518 .row &%extra_local_interfaces%& "not necessarily listened on"
13519 .row &%local_interfaces%& "on which to listen, with optional ports"
13520 .row &%pid_file_path%& "override compiled-in value"
13521 .row &%queue_run_max%& "maximum simultaneous queue runners"
13526 .section "Resource control" "SECID105"
13528 .row &%check_log_inodes%& "before accepting a message"
13529 .row &%check_log_space%& "before accepting a message"
13530 .row &%check_spool_inodes%& "before accepting a message"
13531 .row &%check_spool_space%& "before accepting a message"
13532 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13533 .row &%queue_only_load%& "queue incoming if load high"
13534 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13535 .row &%queue_run_max%& "maximum simultaneous queue runners"
13536 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13537 .row &%smtp_accept_max%& "simultaneous incoming connections"
13538 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13539 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13540 .row &%smtp_accept_max_per_connection%& "messages per connection"
13541 .row &%smtp_accept_max_per_host%& "connections from one host"
13542 .row &%smtp_accept_queue%& "queue mail if more connections"
13543 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13545 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13546 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13547 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13548 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13549 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13554 .section "Policy controls" "SECID106"
13556 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13557 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13558 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13559 .row &%acl_smtp_auth%& "ACL for AUTH"
13560 .row &%acl_smtp_connect%& "ACL for connection"
13561 .row &%acl_smtp_data%& "ACL for DATA"
13562 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13563 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13564 .row &%acl_smtp_etrn%& "ACL for ETRN"
13565 .row &%acl_smtp_expn%& "ACL for EXPN"
13566 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13567 .row &%acl_smtp_mail%& "ACL for MAIL"
13568 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13569 .row &%acl_smtp_mime%& "ACL for MIME parts"
13570 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13571 .row &%acl_smtp_predata%& "ACL for start of data"
13572 .row &%acl_smtp_quit%& "ACL for QUIT"
13573 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13574 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13575 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13576 .row &%av_scanner%& "specify virus scanner"
13577 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13579 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13580 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13581 .row &%header_maxsize%& "total size of message header"
13582 .row &%header_line_maxsize%& "individual header line limit"
13583 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13584 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13585 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13586 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13587 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13588 .row &%host_lookup%& "host name looked up for these hosts"
13589 .row &%host_lookup_order%& "order of DNS and local name lookups"
13590 .row &%hosts_proxy%& "use proxy protocol for these hosts"
13591 .row &%host_reject_connection%& "reject connection from these hosts"
13592 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13593 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13594 .row &%message_size_limit%& "for all messages"
13595 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13596 .row &%spamd_address%& "set interface to SpamAssassin"
13597 .row &%strict_acl_vars%& "object to unset ACL variables"
13602 .section "Callout cache" "SECID107"
13604 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13606 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13608 .row &%callout_negative_expire%& "timeout for negative address cache item"
13609 .row &%callout_positive_expire%& "timeout for positive address cache item"
13610 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13615 .section "TLS" "SECID108"
13617 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13618 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13619 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13620 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13621 .row &%tls_certificate%& "location of server certificate"
13622 .row &%tls_crl%& "certificate revocation list"
13623 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13624 .row &%tls_dhparam%& "DH parameters for server"
13625 .row &%tls_eccurve%& "EC curve selection for server"
13626 .row &%tls_ocsp_file%& "location of server certificate status proof"
13627 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13628 .row &%tls_privatekey%& "location of server private key"
13629 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13630 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13631 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13632 .row &%tls_verify_certificates%& "expected client certificates"
13633 .row &%tls_verify_hosts%& "insist on client certificate verify"
13638 .section "Local user handling" "SECID109"
13640 .row &%finduser_retries%& "useful in NIS environments"
13641 .row &%gecos_name%& "used when creating &'Sender:'&"
13642 .row &%gecos_pattern%& "ditto"
13643 .row &%max_username_length%& "for systems that truncate"
13644 .row &%unknown_login%& "used when no login name found"
13645 .row &%unknown_username%& "ditto"
13646 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13647 .row &%uucp_from_sender%& "ditto"
13652 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13654 .row &%header_maxsize%& "total size of message header"
13655 .row &%header_line_maxsize%& "individual header line limit"
13656 .row &%message_size_limit%& "applies to all messages"
13657 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13658 .row &%received_header_text%& "expanded to make &'Received:'&"
13659 .row &%received_headers_max%& "for mail loop detection"
13660 .row &%recipients_max%& "limit per message"
13661 .row &%recipients_max_reject%& "permanently reject excess recipients"
13667 .section "Non-SMTP incoming messages" "SECID111"
13669 .row &%receive_timeout%& "for non-SMTP messages"
13676 .section "Incoming SMTP messages" "SECID112"
13677 See also the &'Policy controls'& section above.
13680 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
13681 .row &%host_lookup%& "host name looked up for these hosts"
13682 .row &%host_lookup_order%& "order of DNS and local name lookups"
13683 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13684 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13685 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13686 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13687 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13688 .row &%smtp_accept_max%& "simultaneous incoming connections"
13689 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13690 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13691 .row &%smtp_accept_max_per_connection%& "messages per connection"
13692 .row &%smtp_accept_max_per_host%& "connections from one host"
13693 .row &%smtp_accept_queue%& "queue mail if more connections"
13694 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13696 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13697 .row &%smtp_active_hostname%& "host name to use in messages"
13698 .row &%smtp_banner%& "text for welcome banner"
13699 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13700 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13701 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13702 .row &%smtp_etrn_command%& "what to run for ETRN"
13703 .row &%smtp_etrn_serialize%& "only one at once"
13704 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13705 .row &%smtp_max_unknown_commands%& "before dropping connection"
13706 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13707 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13708 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13709 .row &%smtp_receive_timeout%& "per command or data line"
13710 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13711 .row &%smtp_return_error_details%& "give detail on rejections"
13716 .section "SMTP extensions" "SECID113"
13718 .row &%accept_8bitmime%& "advertise 8BITMIME"
13719 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13720 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
13721 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13722 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13723 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13724 .row &%prdr_enable%& "advertise PRDR to all hosts"
13725 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
13726 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13731 .section "Processing messages" "SECID114"
13733 .row &%allow_domain_literals%& "recognize domain literal syntax"
13734 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13735 .row &%allow_utf8_domains%& "in addresses"
13736 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13738 .row &%delivery_date_remove%& "from incoming messages"
13739 .row &%envelope_to_remove%& "from incoming messages"
13740 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13741 .row &%headers_charset%& "default for translations"
13742 .row &%qualify_domain%& "default for senders"
13743 .row &%qualify_recipient%& "default for recipients"
13744 .row &%return_path_remove%& "from incoming messages"
13745 .row &%strip_excess_angle_brackets%& "in addresses"
13746 .row &%strip_trailing_dot%& "at end of addresses"
13747 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13752 .section "System filter" "SECID115"
13754 .row &%system_filter%& "locate system filter"
13755 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13757 .row &%system_filter_file_transport%& "transport for delivery to a file"
13758 .row &%system_filter_group%& "group for filter running"
13759 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13760 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13761 .row &%system_filter_user%& "user for filter running"
13766 .section "Routing and delivery" "SECID116"
13768 .row &%disable_ipv6%& "do no IPv6 processing"
13769 .row &%dns_again_means_nonexist%& "for broken domains"
13770 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13771 .row &%dns_dnssec_ok%& "parameter for resolver"
13772 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13773 .row &%dns_retrans%& "parameter for resolver"
13774 .row &%dns_retry%& "parameter for resolver"
13775 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
13776 .row &%dns_use_edns0%& "parameter for resolver"
13777 .row &%hold_domains%& "hold delivery for these domains"
13778 .row &%local_interfaces%& "for routing checks"
13779 .row &%queue_domains%& "no immediate delivery for these"
13780 .row &%queue_only%& "no immediate delivery at all"
13781 .row &%queue_only_file%& "no immediate delivery if file exists"
13782 .row &%queue_only_load%& "no immediate delivery if load is high"
13783 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13784 .row &%queue_only_override%& "allow command line to override"
13785 .row &%queue_run_in_order%& "order of arrival"
13786 .row &%queue_run_max%& "of simultaneous queue runners"
13787 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13788 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13789 .row &%remote_sort_domains%& "order of remote deliveries"
13790 .row &%retry_data_expire%& "timeout for retry data"
13791 .row &%retry_interval_max%& "safety net for retry rules"
13796 .section "Bounce and warning messages" "SECID117"
13798 .row &%bounce_message_file%& "content of bounce"
13799 .row &%bounce_message_text%& "content of bounce"
13800 .row &%bounce_return_body%& "include body if returning message"
13801 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
13802 .row &%bounce_return_message%& "include original message in bounce"
13803 .row &%bounce_return_size_limit%& "limit on returned message"
13804 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13805 .row &%dsn_from%& "set &'From:'& contents in bounces"
13806 .row &%errors_copy%& "copy bounce messages"
13807 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13808 .row &%delay_warning%& "time schedule"
13809 .row &%delay_warning_condition%& "condition for warning messages"
13810 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13811 .row &%smtp_return_error_details%& "give detail on rejections"
13812 .row &%warn_message_file%& "content of warning message"
13817 .section "Alphabetical list of main options" "SECTalomo"
13818 Those options that undergo string expansion before use are marked with
13821 .option accept_8bitmime main boolean true
13823 .cindex "8-bit characters"
13824 .cindex "log" "selectors"
13825 .cindex "log" "8BITMIME"
13826 This option causes Exim to send 8BITMIME in its response to an SMTP
13827 EHLO command, and to accept the BODY= parameter on MAIL commands.
13828 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13829 takes no steps to do anything special with messages received by this route.
13831 Historically Exim kept this option off by default, but the maintainers
13832 feel that in today's Internet, this causes more problems than it solves.
13833 It now defaults to true.
13834 A more detailed analysis of the issues is provided by Dan Bernstein:
13836 &url(http://cr.yp.to/smtp/8bitmime.html)
13839 To log received 8BITMIME status use
13841 log_selector = +8bitmime
13844 .option acl_not_smtp main string&!! unset
13845 .cindex "&ACL;" "for non-SMTP messages"
13846 .cindex "non-SMTP messages" "ACLs for"
13847 This option defines the ACL that is run when a non-SMTP message has been
13848 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13851 .option acl_not_smtp_mime main string&!! unset
13852 This option defines the ACL that is run for individual MIME parts of non-SMTP
13853 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13856 .option acl_not_smtp_start main string&!! unset
13857 .cindex "&ACL;" "at start of non-SMTP message"
13858 .cindex "non-SMTP messages" "ACLs for"
13859 This option defines the ACL that is run before Exim starts reading a
13860 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13862 .option acl_smtp_auth main string&!! unset
13863 .cindex "&ACL;" "setting up for SMTP commands"
13864 .cindex "AUTH" "ACL for"
13865 This option defines the ACL that is run when an SMTP AUTH command is
13866 received. See chapter &<<CHAPACL>>& for further details.
13868 .option acl_smtp_connect main string&!! unset
13869 .cindex "&ACL;" "on SMTP connection"
13870 This option defines the ACL that is run when an SMTP connection is received.
13871 See chapter &<<CHAPACL>>& for further details.
13873 .option acl_smtp_data main string&!! unset
13874 .cindex "DATA" "ACL for"
13875 This option defines the ACL that is run after an SMTP DATA command has been
13876 processed and the message itself has been received, but before the final
13877 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13879 .option acl_smtp_data_prdr main string&!! accept
13880 .cindex "PRDR" "ACL for"
13881 .cindex "DATA" "PRDR ACL for"
13882 .cindex "&ACL;" "PRDR-related"
13883 .cindex "&ACL;" "per-user data processing"
13884 This option defines the ACL that,
13885 if the PRDR feature has been negotiated,
13886 is run for each recipient after an SMTP DATA command has been
13887 processed and the message itself has been received, but before the
13888 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13890 .option acl_smtp_dkim main string&!! unset
13891 .cindex DKIM "ACL for"
13892 This option defines the ACL that is run for each DKIM signature
13893 of a received message.
13894 See chapter &<<CHAPdkim>>& for further details.
13896 .option acl_smtp_etrn main string&!! unset
13897 .cindex "ETRN" "ACL for"
13898 This option defines the ACL that is run when an SMTP ETRN command is
13899 received. See chapter &<<CHAPACL>>& for further details.
13901 .option acl_smtp_expn main string&!! unset
13902 .cindex "EXPN" "ACL for"
13903 This option defines the ACL that is run when an SMTP EXPN command is
13904 received. See chapter &<<CHAPACL>>& for further details.
13906 .option acl_smtp_helo main string&!! unset
13907 .cindex "EHLO" "ACL for"
13908 .cindex "HELO" "ACL for"
13909 This option defines the ACL that is run when an SMTP EHLO or HELO
13910 command is received. See chapter &<<CHAPACL>>& for further details.
13913 .option acl_smtp_mail main string&!! unset
13914 .cindex "MAIL" "ACL for"
13915 This option defines the ACL that is run when an SMTP MAIL command is
13916 received. See chapter &<<CHAPACL>>& for further details.
13918 .option acl_smtp_mailauth main string&!! unset
13919 .cindex "AUTH" "on MAIL command"
13920 This option defines the ACL that is run when there is an AUTH parameter on
13921 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13922 &<<CHAPSMTPAUTH>>& for details of authentication.
13924 .option acl_smtp_mime main string&!! unset
13925 .cindex "MIME content scanning" "ACL for"
13926 This option is available when Exim is built with the content-scanning
13927 extension. It defines the ACL that is run for each MIME part in a message. See
13928 section &<<SECTscanmimepart>>& for details.
13930 .option acl_smtp_notquit main string&!! unset
13931 .cindex "not-QUIT, ACL for"
13932 This option defines the ACL that is run when an SMTP session
13933 ends without a QUIT command being received.
13934 See chapter &<<CHAPACL>>& for further details.
13936 .option acl_smtp_predata main string&!! unset
13937 This option defines the ACL that is run when an SMTP DATA command is
13938 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13941 .option acl_smtp_quit main string&!! unset
13942 .cindex "QUIT, ACL for"
13943 This option defines the ACL that is run when an SMTP QUIT command is
13944 received. See chapter &<<CHAPACL>>& for further details.
13946 .option acl_smtp_rcpt main string&!! unset
13947 .cindex "RCPT" "ACL for"
13948 This option defines the ACL that is run when an SMTP RCPT command is
13949 received. See chapter &<<CHAPACL>>& for further details.
13951 .option acl_smtp_starttls main string&!! unset
13952 .cindex "STARTTLS, ACL for"
13953 This option defines the ACL that is run when an SMTP STARTTLS command is
13954 received. See chapter &<<CHAPACL>>& for further details.
13956 .option acl_smtp_vrfy main string&!! unset
13957 .cindex "VRFY" "ACL for"
13958 This option defines the ACL that is run when an SMTP VRFY command is
13959 received. See chapter &<<CHAPACL>>& for further details.
13962 .option add_environment main "string list" empty
13963 .cindex "environment" "inherited"
13964 This option allows to set individual environment variables that the
13965 currently linked libraries and programs in child processes use. The
13966 default list is empty,
13969 .option admin_groups main "string list&!!" unset
13970 .cindex "admin user"
13971 This option is expanded just once, at the start of Exim's processing. If the
13972 current group or any of the supplementary groups of an Exim caller is in this
13973 colon-separated list, the caller has admin privileges. If all your system
13974 programmers are in a specific group, for example, you can give them all Exim
13975 admin privileges by putting that group in &%admin_groups%&. However, this does
13976 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13977 To permit this, you have to add individuals to the Exim group.
13979 .option allow_domain_literals main boolean false
13980 .cindex "domain literal"
13981 If this option is set, the RFC 2822 domain literal format is permitted in
13982 email addresses. The option is not set by default, because the domain literal
13983 format is not normally required these days, and few people know about it. It
13984 has, however, been exploited by mail abusers.
13986 Unfortunately, it seems that some DNS black list maintainers are using this
13987 format to report black listing to postmasters. If you want to accept messages
13988 addressed to your hosts by IP address, you need to set
13989 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13990 domains (defined in the named domain list &%local_domains%& in the default
13991 configuration). This &"magic string"& matches the domain literal form of all
13992 the local host's IP addresses.
13995 .option allow_mx_to_ip main boolean false
13996 .cindex "MX record" "pointing to IP address"
13997 It appears that more and more DNS zone administrators are breaking the rules
13998 and putting domain names that look like IP addresses on the right hand side of
13999 MX records. Exim follows the rules and rejects this, giving an error message
14000 that explains the misconfiguration. However, some other MTAs support this
14001 practice, so to avoid &"Why can't Exim do this?"& complaints,
14002 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
14003 recommended, except when you have no other choice.
14005 .option allow_utf8_domains main boolean false
14006 .cindex "domain" "UTF-8 characters in"
14007 .cindex "UTF-8" "in domain name"
14008 Lots of discussion is going on about internationalized domain names. One
14009 camp is strongly in favour of just using UTF-8 characters, and it seems
14010 that at least two other MTAs permit this. This option allows Exim users to
14011 experiment if they wish.
14013 If it is set true, Exim's domain parsing function allows valid
14014 UTF-8 multicharacters to appear in domain name components, in addition to
14015 letters, digits, and hyphens. However, just setting this option is not
14016 enough; if you want to look up these domain names in the DNS, you must also
14017 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
14018 suitable setting is:
14020 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
14021 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
14023 Alternatively, you can just disable this feature by setting
14025 dns_check_names_pattern =
14027 That is, set the option to an empty string so that no check is done.
14030 .option auth_advertise_hosts main "host list&!!" *
14031 .cindex "authentication" "advertising"
14032 .cindex "AUTH" "advertising"
14033 If any server authentication mechanisms are configured, Exim advertises them in
14034 response to an EHLO command only if the calling host matches this list.
14035 Otherwise, Exim does not advertise AUTH.
14036 Exim does not accept AUTH commands from clients to which it has not
14037 advertised the availability of AUTH. The advertising of individual
14038 authentication mechanisms can be controlled by the use of the
14039 &%server_advertise_condition%& generic authenticator option on the individual
14040 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
14042 Certain mail clients (for example, Netscape) require the user to provide a name
14043 and password for authentication if AUTH is advertised, even though it may
14044 not be needed (the host may accept messages from hosts on its local LAN without
14045 authentication, for example). The &%auth_advertise_hosts%& option can be used
14046 to make these clients more friendly by excluding them from the set of hosts to
14047 which Exim advertises AUTH.
14049 .cindex "AUTH" "advertising when encrypted"
14050 If you want to advertise the availability of AUTH only when the connection
14051 is encrypted using TLS, you can make use of the fact that the value of this
14052 option is expanded, with a setting like this:
14054 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
14056 .vindex "&$tls_in_cipher$&"
14057 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
14058 the expansion is empty, thus matching no hosts. Otherwise, the result of the
14059 expansion is *, which matches all hosts.
14062 .option auto_thaw main time 0s
14063 .cindex "thawing messages"
14064 .cindex "unfreezing messages"
14065 If this option is set to a time greater than zero, a queue runner will try a
14066 new delivery attempt on any frozen message, other than a bounce message, if
14067 this much time has passed since it was frozen. This may result in the message
14068 being re-frozen if nothing has changed since the last attempt. It is a way of
14069 saying &"keep on trying, even though there are big problems"&.
14071 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
14072 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
14073 thought to be very useful any more, and its use should probably be avoided.
14076 .option av_scanner main string "see below"
14077 This option is available if Exim is built with the content-scanning extension.
14078 It specifies which anti-virus scanner to use. The default value is:
14080 sophie:/var/run/sophie
14082 If the value of &%av_scanner%& starts with a dollar character, it is expanded
14083 before use. See section &<<SECTscanvirus>>& for further details.
14086 .option bi_command main string unset
14088 This option supplies the name of a command that is run when Exim is called with
14089 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14090 just the command name, it is not a complete command line. If an argument is
14091 required, it must come from the &%-oA%& command line option.
14094 .option bounce_message_file main string unset
14095 .cindex "bounce message" "customizing"
14096 .cindex "customizing" "bounce message"
14097 This option defines a template file containing paragraphs of text to be used
14098 for constructing bounce messages. Details of the file's contents are given in
14099 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14102 .option bounce_message_text main string unset
14103 When this option is set, its contents are included in the default bounce
14104 message immediately after &"This message was created automatically by mail
14105 delivery software."& It is not used if &%bounce_message_file%& is set.
14107 .option bounce_return_body main boolean true
14108 .cindex "bounce message" "including body"
14109 This option controls whether the body of an incoming message is included in a
14110 bounce message when &%bounce_return_message%& is true. The default setting
14111 causes the entire message, both header and body, to be returned (subject to the
14112 value of &%bounce_return_size_limit%&). If this option is false, only the
14113 message header is included. In the case of a non-SMTP message containing an
14114 error that is detected during reception, only those header lines preceding the
14115 point at which the error was detected are returned.
14116 .cindex "bounce message" "including original"
14118 .option bounce_return_linesize_limit main integer 998
14119 .cindex "size" "of bounce lines, limit"
14120 .cindex "bounce message" "line length limit"
14121 .cindex "limit" "bounce message line length"
14122 This option sets a limit in bytes on the line length of messages
14123 that are returned to senders due to delivery problems,
14124 when &%bounce_return_message%& is true.
14125 The default value corresponds to RFC limits.
14126 If the message being returned has lines longer than this value it is
14127 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
14129 The option also applies to bounces returned when an error is detected
14130 during reception of a messsage.
14131 In this case lines from the original are truncated.
14133 The option does not apply to messages generated by an &(autoreply)& transport.
14136 .option bounce_return_message main boolean true
14137 If this option is set false, none of the original message is included in
14138 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14139 &%bounce_return_body%&.
14142 .option bounce_return_size_limit main integer 100K
14143 .cindex "size" "of bounce, limit"
14144 .cindex "bounce message" "size limit"
14145 .cindex "limit" "bounce message size"
14146 This option sets a limit in bytes on the size of messages that are returned to
14147 senders as part of bounce messages when &%bounce_return_message%& is true. The
14148 limit should be less than the value of the global &%message_size_limit%& and of
14149 any &%message_size_limit%& settings on transports, to allow for the bounce text
14150 that Exim generates. If this option is set to zero there is no limit.
14152 When the body of any message that is to be included in a bounce message is
14153 greater than the limit, it is truncated, and a comment pointing this out is
14154 added at the top. The actual cutoff may be greater than the value given, owing
14155 to the use of buffering for transferring the message in chunks (typically 8K in
14156 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14159 .option bounce_sender_authentication main string unset
14160 .cindex "bounce message" "sender authentication"
14161 .cindex "authentication" "bounce message"
14162 .cindex "AUTH" "on bounce message"
14163 This option provides an authenticated sender address that is sent with any
14164 bounce messages generated by Exim that are sent over an authenticated SMTP
14165 connection. A typical setting might be:
14167 bounce_sender_authentication = mailer-daemon@my.domain.example
14169 which would cause bounce messages to be sent using the SMTP command:
14171 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14173 The value of &%bounce_sender_authentication%& must always be a complete email
14176 .option callout_domain_negative_expire main time 3h
14177 .cindex "caching" "callout timeouts"
14178 .cindex "callout" "caching timeouts"
14179 This option specifies the expiry time for negative callout cache data for a
14180 domain. See section &<<SECTcallver>>& for details of callout verification, and
14181 section &<<SECTcallvercache>>& for details of the caching.
14184 .option callout_domain_positive_expire main time 7d
14185 This option specifies the expiry time for positive callout cache data for a
14186 domain. See section &<<SECTcallver>>& for details of callout verification, and
14187 section &<<SECTcallvercache>>& for details of the caching.
14190 .option callout_negative_expire main time 2h
14191 This option specifies the expiry time for negative callout cache data for an
14192 address. See section &<<SECTcallver>>& for details of callout verification, and
14193 section &<<SECTcallvercache>>& for details of the caching.
14196 .option callout_positive_expire main time 24h
14197 This option specifies the expiry time for positive callout cache data for an
14198 address. See section &<<SECTcallver>>& for details of callout verification, and
14199 section &<<SECTcallvercache>>& for details of the caching.
14202 .option callout_random_local_part main string&!! "see below"
14203 This option defines the &"random"& local part that can be used as part of
14204 callout verification. The default value is
14206 $primary_hostname-$tod_epoch-testing
14208 See section &<<CALLaddparcall>>& for details of how this value is used.
14211 .option check_log_inodes main integer 0
14212 See &%check_spool_space%& below.
14215 .option check_log_space main integer 0
14216 See &%check_spool_space%& below.
14218 .oindex "&%check_rfc2047_length%&"
14219 .cindex "RFC 2047" "disabling length check"
14220 .option check_rfc2047_length main boolean true
14221 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14222 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14223 word; strings to be encoded that exceed this length are supposed to use
14224 multiple encoded words. By default, Exim does not recognize encoded words that
14225 exceed the maximum length. However, it seems that some software, in violation
14226 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14227 set false, Exim recognizes encoded words of any length.
14230 .option check_spool_inodes main integer 0
14231 See &%check_spool_space%& below.
14234 .option check_spool_space main integer 0
14235 .cindex "checking disk space"
14236 .cindex "disk space, checking"
14237 .cindex "spool directory" "checking space"
14238 The four &%check_...%& options allow for checking of disk resources before a
14239 message is accepted.
14241 .vindex "&$log_inodes$&"
14242 .vindex "&$log_space$&"
14243 .vindex "&$spool_inodes$&"
14244 .vindex "&$spool_space$&"
14245 When any of these options are set, they apply to all incoming messages. If you
14246 want to apply different checks to different kinds of message, you can do so by
14247 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14248 &$spool_space$& in an ACL with appropriate additional conditions.
14251 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14252 either value is greater than zero, for example:
14254 check_spool_space = 10M
14255 check_spool_inodes = 100
14257 The spool partition is the one that contains the directory defined by
14258 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14261 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14262 files are written if either is greater than zero. These should be set only if
14263 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14265 If there is less space or fewer inodes than requested, Exim refuses to accept
14266 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14267 error response to the MAIL command. If ESMTP is in use and there was a
14268 SIZE parameter on the MAIL command, its value is added to the
14269 &%check_spool_space%& value, and the check is performed even if
14270 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14272 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14273 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
14275 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14276 failure a message is written to stderr and Exim exits with a non-zero code, as
14277 it obviously cannot send an error message of any kind.
14279 .option daemon_smtp_ports main string &`smtp`&
14280 .cindex "port" "for daemon"
14281 .cindex "TCP/IP" "setting listening ports"
14282 This option specifies one or more default SMTP ports on which the Exim daemon
14283 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14284 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14286 .option daemon_startup_retries main integer 9
14287 .cindex "daemon startup, retrying"
14288 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14289 the daemon at startup when it cannot immediately bind a listening socket
14290 (typically because the socket is already in use): &%daemon_startup_retries%&
14291 defines the number of retries after the first failure, and
14292 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14294 .option daemon_startup_sleep main time 30s
14295 See &%daemon_startup_retries%&.
14297 .option delay_warning main "time list" 24h
14298 .cindex "warning of delay"
14299 .cindex "delay warning, specifying"
14300 When a message is delayed, Exim sends a warning message to the sender at
14301 intervals specified by this option. The data is a colon-separated list of times
14302 after which to send warning messages. If the value of the option is an empty
14303 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14304 message has been on the queue for longer than the last time, the last interval
14305 between the times is used to compute subsequent warning times. For example,
14308 delay_warning = 4h:8h:24h
14310 the first message is sent after 4 hours, the second after 8 hours, and
14311 the third one after 24 hours. After that, messages are sent every 16 hours,
14312 because that is the interval between the last two times on the list. If you set
14313 just one time, it specifies the repeat interval. For example, with:
14317 messages are repeated every six hours. To stop warnings after a given time, set
14318 a very large time at the end of the list. For example:
14320 delay_warning = 2h:12h:99d
14322 Note that the option is only evaluated at the time a delivery attempt fails,
14323 which depends on retry and queue-runner configuration.
14324 Typically retries will be configured more frequently than warning messages.
14326 .option delay_warning_condition main string&!! "see below"
14327 .vindex "&$domain$&"
14328 The string is expanded at the time a warning message might be sent. If all the
14329 deferred addresses have the same domain, it is set in &$domain$& during the
14330 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14331 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14332 &"false"& (the comparison being done caselessly) then the warning message is
14333 not sent. The default is:
14335 delay_warning_condition = ${if or {\
14336 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14337 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14338 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14341 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14342 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14343 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14344 &"auto-replied"& in an &'Auto-Submitted:'& header.
14346 .option deliver_drop_privilege main boolean false
14347 .cindex "unprivileged delivery"
14348 .cindex "delivery" "unprivileged"
14349 If this option is set true, Exim drops its root privilege at the start of a
14350 delivery process, and runs as the Exim user throughout. This severely restricts
14351 the kinds of local delivery that are possible, but is viable in certain types
14352 of configuration. There is a discussion about the use of root privilege in
14353 chapter &<<CHAPsecurity>>&.
14355 .option deliver_queue_load_max main fixed-point unset
14356 .cindex "load average"
14357 .cindex "queue runner" "abandoning"
14358 When this option is set, a queue run is abandoned if the system load average
14359 becomes greater than the value of the option. The option has no effect on
14360 ancient operating systems on which Exim cannot determine the load average.
14361 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14364 .option delivery_date_remove main boolean true
14365 .cindex "&'Delivery-date:'& header line"
14366 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14367 message when it is delivered, in exactly the same way as &'Return-path:'& is
14368 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14369 should not be present in incoming messages, and this option causes them to be
14370 removed at the time the message is received, to avoid any problems that might
14371 occur when a delivered message is subsequently sent on to some other recipient.
14373 .option disable_fsync main boolean false
14374 .cindex "&[fsync()]&, disabling"
14375 This option is available only if Exim was built with the compile-time option
14376 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14377 a runtime configuration generates an &"unknown option"& error. You should not
14378 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14379 really, really, really understand what you are doing. &'No pre-compiled
14380 distributions of Exim should ever make this option available.'&
14382 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14383 updated files' data to be written to disc before continuing. Unexpected events
14384 such as crashes and power outages may cause data to be lost or scrambled.
14385 Here be Dragons. &*Beware.*&
14388 .option disable_ipv6 main boolean false
14389 .cindex "IPv6" "disabling"
14390 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14391 activities take place. AAAA records are never looked up, and any IPv6 addresses
14392 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14393 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14394 to handle IPv6 literal addresses.
14397 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14398 .cindex DKIM "controlling calls to the ACL"
14399 This option gives a list of DKIM domains for which the DKIM ACL is run.
14400 It is expanded after the message is received; by default it runs
14401 the ACL once for each signature in the message.
14402 See chapter &<<CHAPdkim>>&.
14405 .option dns_again_means_nonexist main "domain list&!!" unset
14406 .cindex "DNS" "&""try again""& response; overriding"
14407 DNS lookups give a &"try again"& response for the DNS errors
14408 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14409 keep trying to deliver a message, or to give repeated temporary errors to
14410 incoming mail. Sometimes the effect is caused by a badly set up name server and
14411 may persist for a long time. If a domain which exhibits this problem matches
14412 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14413 This option should be used with care. You can make it apply to reverse lookups
14414 by a setting such as this:
14416 dns_again_means_nonexist = *.in-addr.arpa
14418 This option applies to all DNS lookups that Exim does. It also applies when the
14419 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14420 since these are most likely to be caused by DNS lookup problems. The
14421 &(dnslookup)& router has some options of its own for controlling what happens
14422 when lookups for MX or SRV records give temporary errors. These more specific
14423 options are applied after this global option.
14425 .option dns_check_names_pattern main string "see below"
14426 .cindex "DNS" "pre-check of name syntax"
14427 When this option is set to a non-empty string, it causes Exim to check domain
14428 names for characters that are not allowed in host names before handing them to
14429 the DNS resolver, because some resolvers give temporary errors for names that
14430 contain unusual characters. If a domain name contains any unwanted characters,
14431 a &"not found"& result is forced, and the resolver is not called. The check is
14432 done by matching the domain name against a regular expression, which is the
14433 value of this option. The default pattern is
14435 dns_check_names_pattern = \
14436 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14438 which permits only letters, digits, slashes, and hyphens in components, but
14439 they must start and end with a letter or digit. Slashes are not, in fact,
14440 permitted in host names, but they are found in certain NS records (which can be
14441 accessed in Exim by using a &%dnsdb%& lookup). If you set
14442 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14445 .option dns_csa_search_limit main integer 5
14446 This option controls the depth of parental searching for CSA SRV records in the
14447 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14449 .option dns_csa_use_reverse main boolean true
14450 This option controls whether or not an IP address, given as a CSA domain, is
14451 reversed and looked up in the reverse DNS, as described in more detail in
14452 section &<<SECTverifyCSA>>&.
14455 .option dns_dnssec_ok main integer -1
14456 .cindex "DNS" "resolver options"
14457 .cindex "DNS" "DNSSEC"
14458 If this option is set to a non-negative number then Exim will initialise the
14459 DNS resolver library to either use or not use DNSSEC, overriding the system
14460 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14462 If the resolver library does not support DNSSEC then this option has no effect.
14465 .option dns_ipv4_lookup main "domain list&!!" unset
14466 .cindex "IPv6" "DNS lookup for AAAA records"
14467 .cindex "DNS" "IPv6 lookup for AAAA records"
14468 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14469 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14470 (A records) when trying to find IP addresses for hosts, unless the host's
14471 domain matches this list.
14473 This is a fudge to help with name servers that give big delays or otherwise do
14474 not work for the AAAA record type. In due course, when the world's name
14475 servers have all been upgraded, there should be no need for this option.
14478 .option dns_retrans main time 0s
14479 .cindex "DNS" "resolver options"
14480 .cindex timeout "dns lookup"
14481 .cindex "DNS" timeout
14482 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14483 retransmission and retry parameters for DNS lookups. Values of zero (the
14484 defaults) leave the system default settings unchanged. The first value is the
14485 time between retries, and the second is the number of retries. It isn't
14486 totally clear exactly how these settings affect the total time a DNS lookup may
14487 take. I haven't found any documentation about timeouts on DNS lookups; these
14488 parameter values are available in the external resolver interface structure,
14489 but nowhere does it seem to describe how they are used or what you might want
14491 See also the &%slow_lookup_log%& option.
14494 .option dns_retry main integer 0
14495 See &%dns_retrans%& above.
14498 .option dns_trust_aa main "domain list&!!" unset
14499 .cindex "DNS" "resolver options"
14500 .cindex "DNS" "DNSSEC"
14501 If this option is set then lookup results marked with the AA bit
14502 (Authoritative Answer) are trusted the same way as if they were
14503 DNSSEC-verified. The authority section's name of the answer must
14504 match with this expanded domain list.
14506 Use this option only if you talk directly to a resolver that is
14507 authoritative for some zones and does not set the AD (Authentic Data)
14508 bit in the answer. Some DNS servers may have an configuration option to
14509 mark the answers from their own zones as verified (they set the AD bit).
14510 Others do not have this option. It is considered as poor practice using
14511 a resolver that is an authoritative server for some zones.
14513 Use this option only if you really have to (e.g. if you want
14514 to use DANE for remote delivery to a server that is listed in the DNS
14515 zones that your resolver is authoritative for).
14517 If the DNS answer packet has the AA bit set and contains resource record
14518 in the answer section, the name of the first NS record appearing in the
14519 authority section is compared against the list. If the answer packet is
14520 authoritative but the answer section is empty, the name of the first SOA
14521 record in the authoritative section is used instead.
14523 .cindex "DNS" "resolver options"
14524 .option dns_use_edns0 main integer -1
14525 .cindex "DNS" "resolver options"
14526 .cindex "DNS" "EDNS0"
14527 If this option is set to a non-negative number then Exim will initialise the
14528 DNS resolver library to either use or not use EDNS0 extensions, overriding
14529 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14532 If the resolver library does not support EDNS0 then this option has no effect.
14535 .option drop_cr main boolean false
14536 This is an obsolete option that is now a no-op. It used to affect the way Exim
14537 handled CR and LF characters in incoming messages. What happens now is
14538 described in section &<<SECTlineendings>>&.
14540 .option dsn_advertise_hosts main "host list&!!" unset
14541 .cindex "bounce messages" "success"
14542 .cindex "DSN" "success"
14543 .cindex "Delivery Status Notification" "success"
14544 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14545 and accepted from, these hosts.
14546 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14547 and RET and ORCPT options on MAIL FROM commands.
14548 A NOTIFY=SUCCESS option requests success-DSN messages.
14549 A NOTIFY= option with no argument requests that no delay or failure DSNs
14552 .option dsn_from main "string&!!" "see below"
14553 .cindex "&'From:'& header line" "in bounces"
14554 .cindex "bounce messages" "&'From:'& line, specifying"
14555 This option can be used to vary the contents of &'From:'& header lines in
14556 bounces and other automatically generated messages (&"Delivery Status
14557 Notifications"& &-- hence the name of the option). The default setting is:
14559 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14561 The value is expanded every time it is needed. If the expansion fails, a
14562 panic is logged, and the default value is used.
14564 .option envelope_to_remove main boolean true
14565 .cindex "&'Envelope-to:'& header line"
14566 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14567 message when it is delivered, in exactly the same way as &'Return-path:'& is
14568 handled. &'Envelope-to:'& records the original recipient address from the
14569 message's envelope that caused the delivery to happen. Such headers should not
14570 be present in incoming messages, and this option causes them to be removed at
14571 the time the message is received, to avoid any problems that might occur when a
14572 delivered message is subsequently sent on to some other recipient.
14575 .option errors_copy main "string list&!!" unset
14576 .cindex "bounce message" "copy to other address"
14577 .cindex "copy of bounce message"
14578 Setting this option causes Exim to send bcc copies of bounce messages that it
14579 generates to other addresses. &*Note*&: This does not apply to bounce messages
14580 coming from elsewhere. The value of the option is a colon-separated list of
14581 items. Each item consists of a pattern, terminated by white space, followed by
14582 a comma-separated list of email addresses. If a pattern contains spaces, it
14583 must be enclosed in double quotes.
14585 Each pattern is processed in the same way as a single item in an address list
14586 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14587 the bounce message, the message is copied to the addresses on the list. The
14588 items are scanned in order, and once a matching one is found, no further items
14589 are examined. For example:
14591 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14592 rqps@mydomain hostmaster@mydomain.example,\
14593 postmaster@mydomain.example
14595 .vindex "&$domain$&"
14596 .vindex "&$local_part$&"
14597 The address list is expanded before use. The expansion variables &$local_part$&
14598 and &$domain$& are set from the original recipient of the error message, and if
14599 there was any wildcard matching in the pattern, the expansion
14600 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14601 variables &$0$&, &$1$&, etc. are set in the normal way.
14604 .option errors_reply_to main string unset
14605 .cindex "bounce message" "&'Reply-to:'& in"
14606 By default, Exim's bounce and delivery warning messages contain the header line
14608 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14610 .oindex &%quota_warn_message%&
14611 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14612 A warning message that is generated by the &%quota_warn_message%& option in an
14613 &(appendfile)& transport may contain its own &'From:'& header line that
14614 overrides the default.
14616 Experience shows that people reply to bounce messages. If the
14617 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14618 and warning messages. For example:
14620 errors_reply_to = postmaster@my.domain.example
14622 The value of the option is not expanded. It must specify a valid RFC 2822
14623 address. However, if a warning message that is generated by the
14624 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14625 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14630 .option event_action main string&!! unset
14632 This option declares a string to be expanded for Exim's events mechanism.
14633 For details see &<<CHAPevents>>&.
14637 .option exim_group main string "compile-time configured"
14638 .cindex "gid (group id)" "Exim's own"
14639 .cindex "Exim group"
14640 This option changes the gid under which Exim runs when it gives up root
14641 privilege. The default value is compiled into the binary. The value of this
14642 option is used only when &%exim_user%& is also set. Unless it consists entirely
14643 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14644 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14648 .option exim_path main string "see below"
14649 .cindex "Exim binary, path name"
14650 This option specifies the path name of the Exim binary, which is used when Exim
14651 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14652 the directory configured at compile time by the BIN_DIRECTORY setting. It
14653 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14655 &*Warning*&: Do not use a macro to define the value of this option, because
14656 you will break those Exim utilities that scan the configuration file to find
14657 where the binary is. (They then use the &%-bP%& option to extract option
14658 settings such as the value of &%spool_directory%&.)
14661 .option exim_user main string "compile-time configured"
14662 .cindex "uid (user id)" "Exim's own"
14663 .cindex "Exim user"
14664 This option changes the uid under which Exim runs when it gives up root
14665 privilege. The default value is compiled into the binary. Ownership of the run
14666 time configuration file and the use of the &%-C%& and &%-D%& command line
14667 options is checked against the values in the binary, not what is set here.
14669 Unless it consists entirely of digits, the string is looked up using
14670 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14671 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14672 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14675 .option extra_local_interfaces main "string list" unset
14676 This option defines network interfaces that are to be considered local when
14677 routing, but which are not used for listening by the daemon. See section
14678 &<<SECTreclocipadd>>& for details.
14681 . Allow this long option name to split; give it unsplit as a fifth argument
14682 . for the automatic .oindex that is generated by .option.
14684 .option "extract_addresses_remove_arguments" main boolean true &&&
14685 extract_addresses_remove_arguments
14687 .cindex "command line" "addresses with &%-t%&"
14688 .cindex "Sendmail compatibility" "&%-t%& option"
14689 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14690 are present on the command line when the &%-t%& option is used to build an
14691 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14692 line addresses are removed from the recipients list. This is also how Smail
14693 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14694 command line addresses are added to those obtained from the header lines. When
14695 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14696 argument headers. If it is set false, Exim adds rather than removes argument
14700 .option finduser_retries main integer 0
14701 .cindex "NIS, retrying user lookups"
14702 On systems running NIS or other schemes in which user and group information is
14703 distributed from a remote system, there can be times when &[getpwnam()]& and
14704 related functions fail, even when given valid data, because things time out.
14705 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14706 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14707 many extra times to find a user or a group, waiting for one second between
14710 .cindex "&_/etc/passwd_&" "multiple reading of"
14711 You should not set this option greater than zero if your user information is in
14712 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14713 search the file multiple times for non-existent users, and also cause delay.
14717 .option freeze_tell main "string list, comma separated" unset
14718 .cindex "freezing messages" "sending a message when freezing"
14719 On encountering certain errors, or when configured to do so in a system filter,
14720 ACL, or special router, Exim freezes a message. This means that no further
14721 delivery attempts take place until an administrator thaws the message, or the
14722 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14723 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14724 warning message whenever it freezes something, unless the message it is
14725 freezing is a locally-generated bounce message. (Without this exception there
14726 is the possibility of looping.) The warning message is sent to the addresses
14727 supplied as the comma-separated value of this option. If several of the
14728 message's addresses cause freezing, only a single message is sent. If the
14729 freezing was automatic, the reason(s) for freezing can be found in the message
14730 log. If you configure freezing in a filter or ACL, you must arrange for any
14731 logging that you require.
14734 .option gecos_name main string&!! unset
14736 .cindex "&""gecos""& field, parsing"
14737 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14738 password file to hold other information in addition to users' real names. Exim
14739 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14740 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14741 of the field are used unchanged, except that, if an ampersand is encountered,
14742 it is replaced by the user's login name with the first character forced to
14743 upper case, since this is a convention that is observed on many systems.
14745 When these options are set, &%gecos_pattern%& is treated as a regular
14746 expression that is to be applied to the field (again with && replaced by the
14747 login name), and if it matches, &%gecos_name%& is expanded and used as the
14750 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14751 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14752 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14753 name terminates at the first comma, the following can be used:
14755 gecos_pattern = ([^,]*)
14759 .option gecos_pattern main string unset
14760 See &%gecos_name%& above.
14763 .option gnutls_compat_mode main boolean unset
14764 This option controls whether GnuTLS is used in compatibility mode in an Exim
14765 server. This reduces security slightly, but improves interworking with older
14766 implementations of TLS.
14769 option gnutls_allow_auto_pkcs11 main boolean unset
14770 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14771 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14774 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14779 .option headers_charset main string "see below"
14780 This option sets a default character set for translating from encoded MIME
14781 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14782 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14783 ultimate default is ISO-8859-1. For more details see the description of header
14784 insertions in section &<<SECTexpansionitems>>&.
14788 .option header_maxsize main integer "see below"
14789 .cindex "header section" "maximum size of"
14790 .cindex "limit" "size of message header section"
14791 This option controls the overall maximum size of a message's header
14792 section. The default is the value of HEADER_MAXSIZE in
14793 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14794 sections are rejected.
14797 .option header_line_maxsize main integer 0
14798 .cindex "header lines" "maximum size of"
14799 .cindex "limit" "size of one header line"
14800 This option limits the length of any individual header line in a message, after
14801 all the continuations have been joined together. Messages with individual
14802 header lines that are longer than the limit are rejected. The default value of
14803 zero means &"no limit"&.
14808 .option helo_accept_junk_hosts main "host list&!!" unset
14809 .cindex "HELO" "accepting junk data"
14810 .cindex "EHLO" "accepting junk data"
14811 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14812 mail, and gives an error response for invalid data. Unfortunately, there are
14813 some SMTP clients that send syntactic junk. They can be accommodated by setting
14814 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14815 if you want to do semantic checking.
14816 See also &%helo_allow_chars%& for a way of extending the permitted character
14820 .option helo_allow_chars main string unset
14821 .cindex "HELO" "underscores in"
14822 .cindex "EHLO" "underscores in"
14823 .cindex "underscore in EHLO/HELO"
14824 This option can be set to a string of rogue characters that are permitted in
14825 all EHLO and HELO names in addition to the standard letters, digits,
14826 hyphens, and dots. If you really must allow underscores, you can set
14828 helo_allow_chars = _
14830 Note that the value is one string, not a list.
14833 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14834 .cindex "HELO" "forcing reverse lookup"
14835 .cindex "EHLO" "forcing reverse lookup"
14836 If the domain given by a client in a HELO or EHLO command matches this
14837 list, a reverse lookup is done in order to establish the host's true name. The
14838 default forces a lookup if the client host gives the server's name or any of
14839 its IP addresses (in brackets), something that broken clients have been seen to
14843 .option helo_try_verify_hosts main "host list&!!" unset
14844 .cindex "HELO verifying" "optional"
14845 .cindex "EHLO" "verifying, optional"
14846 By default, Exim just checks the syntax of HELO and EHLO commands (see
14847 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14848 to do more extensive checking of the data supplied by these commands. The ACL
14849 condition &`verify = helo`& is provided to make this possible.
14850 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14851 to force the check to occur. From release 4.53 onwards, this is no longer
14852 necessary. If the check has not been done before &`verify = helo`& is
14853 encountered, it is done at that time. Consequently, this option is obsolete.
14854 Its specification is retained here for backwards compatibility.
14856 When an EHLO or HELO command is received, if the calling host matches
14857 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14858 EHLO command either:
14861 is an IP literal matching the calling address of the host, or
14863 .cindex "DNS" "reverse lookup"
14864 .cindex "reverse DNS lookup"
14865 matches the host name that Exim obtains by doing a reverse lookup of the
14866 calling host address, or
14868 when looked up in DNS yields the calling host address.
14871 However, the EHLO or HELO command is not rejected if any of the checks
14872 fail. Processing continues, but the result of the check is remembered, and can
14873 be detected later in an ACL by the &`verify = helo`& condition.
14875 If DNS was used for successful verification, the variable
14876 .cindex "DNS" "DNSSEC"
14877 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
14879 .option helo_verify_hosts main "host list&!!" unset
14880 .cindex "HELO verifying" "mandatory"
14881 .cindex "EHLO" "verifying, mandatory"
14882 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14883 backwards compatibility. For hosts that match this option, Exim checks the host
14884 name given in the HELO or EHLO in the same way as for
14885 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14886 rejected with a 550 error, and entries are written to the main and reject logs.
14887 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14890 .option hold_domains main "domain list&!!" unset
14891 .cindex "domain" "delaying delivery"
14892 .cindex "delivery" "delaying certain domains"
14893 This option allows mail for particular domains to be held on the queue
14894 manually. The option is overridden if a message delivery is forced with the
14895 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14896 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14897 item in &%hold_domains%&, no routing or delivery for that address is done, and
14898 it is deferred every time the message is looked at.
14900 This option is intended as a temporary operational measure for delaying the
14901 delivery of mail while some problem is being sorted out, or some new
14902 configuration tested. If you just want to delay the processing of some
14903 domains until a queue run occurs, you should use &%queue_domains%& or
14904 &%queue_smtp_domains%&, not &%hold_domains%&.
14906 A setting of &%hold_domains%& does not override Exim's code for removing
14907 messages from the queue if they have been there longer than the longest retry
14908 time in any retry rule. If you want to hold messages for longer than the normal
14909 retry times, insert a dummy retry rule with a long retry time.
14912 .option host_lookup main "host list&!!" unset
14913 .cindex "host name" "lookup, forcing"
14914 Exim does not look up the name of a calling host from its IP address unless it
14915 is required to compare against some host list, or the host matches
14916 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
14917 option (which normally contains IP addresses rather than host names). The
14918 default configuration file contains
14922 which causes a lookup to happen for all hosts. If the expense of these lookups
14923 is felt to be too great, the setting can be changed or removed.
14925 After a successful reverse lookup, Exim does a forward lookup on the name it
14926 has obtained, to verify that it yields the IP address that it started with. If
14927 this check fails, Exim behaves as if the name lookup failed.
14929 .vindex "&$host_lookup_failed$&"
14930 .vindex "&$sender_host_name$&"
14931 After any kind of failure, the host name (in &$sender_host_name$&) remains
14932 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
14933 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
14934 &`verify = reverse_host_lookup`& in ACLs.
14937 .option host_lookup_order main "string list" &`bydns:byaddr`&
14938 This option specifies the order of different lookup methods when Exim is trying
14939 to find a host name from an IP address. The default is to do a DNS lookup
14940 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
14941 if that fails. You can change the order of these lookups, or omit one entirely,
14944 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
14945 multiple PTR records in the DNS and the IP address is not listed in
14946 &_/etc/hosts_&. Different operating systems give different results in this
14947 case. That is why the default tries a DNS lookup first.
14951 .option host_reject_connection main "host list&!!" unset
14952 .cindex "host" "rejecting connections from"
14953 If this option is set, incoming SMTP calls from the hosts listed are rejected
14954 as soon as the connection is made.
14955 This option is obsolete, and retained only for backward compatibility, because
14956 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
14957 connections immediately.
14959 The ability to give an immediate rejection (either by this option or using an
14960 ACL) is provided for use in unusual cases. Many hosts will just try again,
14961 sometimes without much delay. Normally, it is better to use an ACL to reject
14962 incoming messages at a later stage, such as after RCPT commands. See
14963 chapter &<<CHAPACL>>&.
14966 .option hosts_connection_nolog main "host list&!!" unset
14967 .cindex "host" "not logging connections from"
14968 This option defines a list of hosts for which connection logging does not
14969 happen, even though the &%smtp_connection%& log selector is set. For example,
14970 you might want not to log SMTP connections from local processes, or from
14971 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
14972 the daemon; you should therefore strive to restrict its value to a short inline
14973 list of IP addresses and networks. To disable logging SMTP connections from
14974 local processes, you must create a host list with an empty item. For example:
14976 hosts_connection_nolog = :
14978 If the &%smtp_connection%& log selector is not set, this option has no effect.
14983 .option hosts_proxy main "host list&!!" unset
14984 .cindex proxy "proxy protocol"
14985 This option enables use of Proxy Protocol proxies for incoming
14986 connections. For details see &<<SECTproxyInbound>>&.
14990 .option hosts_treat_as_local main "domain list&!!" unset
14991 .cindex "local host" "domains treated as"
14992 .cindex "host" "treated as local"
14993 If this option is set, any host names that match the domain list are treated as
14994 if they were the local host when Exim is scanning host lists obtained from MX
14996 or other sources. Note that the value of this option is a domain list, not a
14997 host list, because it is always used to check host names, not IP addresses.
14999 This option also applies when Exim is matching the special items
15000 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
15001 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
15002 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
15003 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
15004 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
15005 interfaces and recognizing the local host.
15008 .option ibase_servers main "string list" unset
15009 .cindex "InterBase" "server list"
15010 This option provides a list of InterBase servers and associated connection data,
15011 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
15012 The option is available only if Exim has been built with InterBase support.
15016 .option ignore_bounce_errors_after main time 10w
15017 .cindex "bounce message" "discarding"
15018 .cindex "discarding bounce message"
15019 This option affects the processing of bounce messages that cannot be delivered,
15020 that is, those that suffer a permanent delivery failure. (Bounce messages that
15021 suffer temporary delivery failures are of course retried in the usual way.)
15023 After a permanent delivery failure, bounce messages are frozen,
15024 because there is no sender to whom they can be returned. When a frozen bounce
15025 message has been on the queue for more than the given time, it is unfrozen at
15026 the next queue run, and a further delivery is attempted. If delivery fails
15027 again, the bounce message is discarded. This makes it possible to keep failed
15028 bounce messages around for a shorter time than the normal maximum retry time
15029 for frozen messages. For example,
15031 ignore_bounce_errors_after = 12h
15033 retries failed bounce message deliveries after 12 hours, discarding any further
15034 failures. If the value of this option is set to a zero time period, bounce
15035 failures are discarded immediately. Setting a very long time (as in the default
15036 value) has the effect of disabling this option. For ways of automatically
15037 dealing with other kinds of frozen message, see &%auto_thaw%& and
15038 &%timeout_frozen_after%&.
15041 .option ignore_fromline_hosts main "host list&!!" unset
15042 .cindex "&""From""& line"
15043 .cindex "UUCP" "&""From""& line"
15044 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
15045 the headers of a message. By default this is treated as the start of the
15046 message's body, which means that any following headers are not recognized as
15047 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
15048 match those hosts that insist on sending it. If the sender is actually a local
15049 process rather than a remote host, and is using &%-bs%& to inject the messages,
15050 &%ignore_fromline_local%& must be set to achieve this effect.
15053 .option ignore_fromline_local main boolean false
15054 See &%ignore_fromline_hosts%& above.
15057 .option keep_environment main "string list" unset
15058 .cindex "environment" "inherited"
15059 This option contains a string list of environment variables to keep.
15060 You have to trust these variables or you have to be sure that
15061 these variables do not impose any security risk. Keep in mind that
15062 during the startup phase Exim is running with an effective UID 0 in most
15063 installations. As the default value is an empty list, the default
15064 environment for using libraries, running embedded Perl code, or running
15065 external binaries is empty, and does not not even contain PATH or HOME.
15067 Actually the list is interpreted as a list of patterns
15068 (&<<SECTlistexpand>>&), except that it is not expanded first.
15070 WARNING: Macro substitution is still done first, so having a macro
15071 FOO and having FOO_HOME in your &%keep_environment%& option may have
15072 unexpected results. You may work around this using a regular expression
15073 that does not match the macro name: ^[F]OO_HOME$.
15075 Current versions of Exim issue a warning during startupif you do not mention
15076 &%keep_environment%& or &%add_environment%& in your runtime configuration
15081 .option keep_malformed main time 4d
15082 This option specifies the length of time to keep messages whose spool files
15083 have been corrupted in some way. This should, of course, never happen. At the
15084 next attempt to deliver such a message, it gets removed. The incident is
15088 .option ldap_ca_cert_dir main string unset
15089 .cindex "LDAP", "TLS CA certificate directory"
15090 .cindex certificate "directory for LDAP"
15091 This option indicates which directory contains CA certificates for verifying
15092 a TLS certificate presented by an LDAP server.
15093 While Exim does not provide a default value, your SSL library may.
15094 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15095 and constrained to be a directory.
15098 .option ldap_ca_cert_file main string unset
15099 .cindex "LDAP", "TLS CA certificate file"
15100 .cindex certificate "file for LDAP"
15101 This option indicates which file contains CA certificates for verifying
15102 a TLS certificate presented by an LDAP server.
15103 While Exim does not provide a default value, your SSL library may.
15104 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15105 and constrained to be a file.
15108 .option ldap_cert_file main string unset
15109 .cindex "LDAP" "TLS client certificate file"
15110 .cindex certificate "file for LDAP"
15111 This option indicates which file contains an TLS client certificate which
15112 Exim should present to the LDAP server during TLS negotiation.
15113 Should be used together with &%ldap_cert_key%&.
15116 .option ldap_cert_key main string unset
15117 .cindex "LDAP" "TLS client key file"
15118 .cindex certificate "key for LDAP"
15119 This option indicates which file contains the secret/private key to use
15120 to prove identity to the LDAP server during TLS negotiation.
15121 Should be used together with &%ldap_cert_file%&, which contains the
15122 identity to be proven.
15125 .option ldap_cipher_suite main string unset
15126 .cindex "LDAP" "TLS cipher suite"
15127 This controls the TLS cipher-suite negotiation during TLS negotiation with
15128 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
15129 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15132 .option ldap_default_servers main "string list" unset
15133 .cindex "LDAP" "default servers"
15134 This option provides a list of LDAP servers which are tried in turn when an
15135 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15136 details of LDAP queries. This option is available only when Exim has been built
15140 .option ldap_require_cert main string unset.
15141 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15142 This should be one of the values "hard", "demand", "allow", "try" or "never".
15143 A value other than one of these is interpreted as "never".
15144 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15145 Although Exim does not set a default, the LDAP library probably defaults
15149 .option ldap_start_tls main boolean false
15150 .cindex "LDAP" "whether or not to negotiate TLS"
15151 If set, Exim will attempt to negotiate TLS with the LDAP server when
15152 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15153 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15155 In the event of failure to negotiate TLS, the action taken is controlled
15156 by &%ldap_require_cert%&.
15159 .option ldap_version main integer unset
15160 .cindex "LDAP" "protocol version, forcing"
15161 This option can be used to force Exim to set a specific protocol version for
15162 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15163 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15164 the LDAP headers; otherwise it is 2. This option is available only when Exim
15165 has been built with LDAP support.
15169 .option local_from_check main boolean true
15170 .cindex "&'Sender:'& header line" "disabling addition of"
15171 .cindex "&'From:'& header line" "disabling checking of"
15172 When a message is submitted locally (that is, not over a TCP/IP connection) by
15173 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15174 checks that the &'From:'& header line matches the login of the calling user and
15175 the domain specified by &%qualify_domain%&.
15177 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15178 locally submitted message is automatically qualified by Exim, unless the
15179 &%-bnq%& command line option is used.
15181 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15182 on the local part. If the &'From:'& header line does not match, Exim adds a
15183 &'Sender:'& header with an address constructed from the calling user's login
15184 and the default qualify domain.
15186 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15187 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15188 &'Sender:'& header lines supplied by untrusted users, you must also set
15189 &%local_sender_retain%& to be true.
15191 .cindex "envelope sender"
15192 These options affect only the header lines in the message. The envelope sender
15193 is still forced to be the login id at the qualify domain unless
15194 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15196 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15197 request similar header line checking. See section &<<SECTthesenhea>>&, which
15198 has more details about &'Sender:'& processing.
15203 .option local_from_prefix main string unset
15204 When Exim checks the &'From:'& header line of locally submitted messages for
15205 matching the login id (see &%local_from_check%& above), it can be configured to
15206 ignore certain prefixes and suffixes in the local part of the address. This is
15207 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15208 appropriate lists, in the same form as the &%local_part_prefix%& and
15209 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15212 local_from_prefix = *-
15214 is set, a &'From:'& line containing
15216 From: anything-user@your.domain.example
15218 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15219 matches the actual sender address that is constructed from the login name and
15223 .option local_from_suffix main string unset
15224 See &%local_from_prefix%& above.
15227 .option local_interfaces main "string list" "see below"
15228 This option controls which network interfaces are used by the daemon for
15229 listening; they are also used to identify the local host when routing. Chapter
15230 &<<CHAPinterfaces>>& contains a full description of this option and the related
15231 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15232 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15233 &%local_interfaces%& is
15235 local_interfaces = 0.0.0.0
15237 when Exim is built without IPv6 support; otherwise it is
15239 local_interfaces = <; ::0 ; 0.0.0.0
15242 .option local_scan_timeout main time 5m
15243 .cindex "timeout" "for &[local_scan()]& function"
15244 .cindex "&[local_scan()]& function" "timeout"
15245 This timeout applies to the &[local_scan()]& function (see chapter
15246 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15247 the incoming message is rejected with a temporary error if it is an SMTP
15248 message. For a non-SMTP message, the message is dropped and Exim ends with a
15249 non-zero code. The incident is logged on the main and reject logs.
15253 .option local_sender_retain main boolean false
15254 .cindex "&'Sender:'& header line" "retaining from local submission"
15255 When a message is submitted locally (that is, not over a TCP/IP connection) by
15256 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15257 do not want this to happen, you must set &%local_sender_retain%&, and you must
15258 also set &%local_from_check%& to be false (Exim will complain if you do not).
15259 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15260 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15265 .option localhost_number main string&!! unset
15266 .cindex "host" "locally unique number for"
15267 .cindex "message ids" "with multiple hosts"
15268 .vindex "&$localhost_number$&"
15269 Exim's message ids are normally unique only within the local host. If
15270 uniqueness among a set of hosts is required, each host must set a different
15271 value for the &%localhost_number%& option. The string is expanded immediately
15272 after reading the configuration file (so that a number can be computed from the
15273 host name, for example) and the result of the expansion must be a number in the
15274 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15275 systems). This is available in subsequent string expansions via the variable
15276 &$localhost_number$&. When &%localhost_number is set%&, the final two
15277 characters of the message id, instead of just being a fractional part of the
15278 time, are computed from the time and the local host number as described in
15279 section &<<SECTmessiden>>&.
15283 .option log_file_path main "string list&!!" "set at compile time"
15284 .cindex "log" "file path for"
15285 This option sets the path which is used to determine the names of Exim's log
15286 files, or indicates that logging is to be to syslog, or both. It is expanded
15287 when Exim is entered, so it can, for example, contain a reference to the host
15288 name. If no specific path is set for the log files at compile or run time,
15289 or if the option is unset at run time (i.e. &`log_file_path = `&)
15290 they are written in a sub-directory called &_log_& in Exim's spool directory.
15291 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15292 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15293 used. If this string is fixed at your installation (contains no expansion
15294 variables) it is recommended that you do not set this option in the
15295 configuration file, but instead supply the path using LOG_FILE_PATH in
15296 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15297 early on &-- in particular, failure to read the configuration file.
15300 .option log_selector main string unset
15301 .cindex "log" "selectors"
15302 This option can be used to reduce or increase the number of things that Exim
15303 writes to its log files. Its argument is made up of names preceded by plus or
15304 minus characters. For example:
15306 log_selector = +arguments -retry_defer
15308 A list of possible names and what they control is given in the chapter on
15309 logging, in section &<<SECTlogselector>>&.
15312 .option log_timezone main boolean false
15313 .cindex "log" "timezone for entries"
15314 .vindex "&$tod_log$&"
15315 .vindex "&$tod_zone$&"
15316 By default, the timestamps on log lines are in local time without the
15317 timezone. This means that if your timezone changes twice a year, the timestamps
15318 in log lines are ambiguous for an hour when the clocks go back. One way of
15319 avoiding this problem is to set the timezone to UTC. An alternative is to set
15320 &%log_timezone%& true. This turns on the addition of the timezone offset to
15321 timestamps in log lines. Turning on this option can add quite a lot to the size
15322 of log files because each line is extended by 6 characters. Note that the
15323 &$tod_log$& variable contains the log timestamp without the zone, but there is
15324 another variable called &$tod_zone$& that contains just the timezone offset.
15327 .option lookup_open_max main integer 25
15328 .cindex "too many open files"
15329 .cindex "open files, too many"
15330 .cindex "file" "too many open"
15331 .cindex "lookup" "maximum open files"
15332 .cindex "limit" "open files for lookups"
15333 This option limits the number of simultaneously open files for single-key
15334 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15335 Exim normally keeps these files open during routing, because often the same
15336 file is required several times. If the limit is reached, Exim closes the least
15337 recently used file. Note that if you are using the &'ndbm'& library, it
15338 actually opens two files for each logical DBM database, though it still counts
15339 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15340 open files"& errors with NDBM, you need to reduce the value of
15341 &%lookup_open_max%&.
15344 .option max_username_length main integer 0
15345 .cindex "length of login name"
15346 .cindex "user name" "maximum length"
15347 .cindex "limit" "user name length"
15348 Some operating systems are broken in that they truncate long arguments to
15349 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15350 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15351 an argument that is longer behaves as if &[getpwnam()]& failed.
15354 .option message_body_newlines main bool false
15355 .cindex "message body" "newlines in variables"
15356 .cindex "newline" "in message body variables"
15357 .vindex "&$message_body$&"
15358 .vindex "&$message_body_end$&"
15359 By default, newlines in the message body are replaced by spaces when setting
15360 the &$message_body$& and &$message_body_end$& expansion variables. If this
15361 option is set true, this no longer happens.
15364 .option message_body_visible main integer 500
15365 .cindex "body of message" "visible size"
15366 .cindex "message body" "visible size"
15367 .vindex "&$message_body$&"
15368 .vindex "&$message_body_end$&"
15369 This option specifies how much of a message's body is to be included in the
15370 &$message_body$& and &$message_body_end$& expansion variables.
15373 .option message_id_header_domain main string&!! unset
15374 .cindex "&'Message-ID:'& header line"
15375 If this option is set, the string is expanded and used as the right hand side
15376 (domain) of the &'Message-ID:'& header that Exim creates if a
15377 locally-originated incoming message does not have one. &"Locally-originated"&
15378 means &"not received over TCP/IP."&
15379 Otherwise, the primary host name is used.
15380 Only letters, digits, dot and hyphen are accepted; any other characters are
15381 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15382 empty string, the option is ignored.
15385 .option message_id_header_text main string&!! unset
15386 If this variable is set, the string is expanded and used to augment the text of
15387 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15388 message does not have one. The text of this header is required by RFC 2822 to
15389 take the form of an address. By default, Exim uses its internal message id as
15390 the local part, and the primary host name as the domain. If this option is set,
15391 it is expanded, and provided the expansion is not forced to fail, and does not
15392 yield an empty string, the result is inserted into the header immediately
15393 before the @, separated from the internal message id by a dot. Any characters
15394 that are illegal in an address are automatically converted into hyphens. This
15395 means that variables such as &$tod_log$& can be used, because the spaces and
15396 colons will become hyphens.
15399 .option message_logs main boolean true
15400 .cindex "message logs" "disabling"
15401 .cindex "log" "message log; disabling"
15402 If this option is turned off, per-message log files are not created in the
15403 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15404 Exim, by reducing the number of files involved in handling a message from a
15405 minimum of four (header spool file, body spool file, delivery journal, and
15406 per-message log) to three. The other major I/O activity is Exim's main log,
15407 which is not affected by this option.
15410 .option message_size_limit main string&!! 50M
15411 .cindex "message" "size limit"
15412 .cindex "limit" "message size"
15413 .cindex "size" "of message, limit"
15414 This option limits the maximum size of message that Exim will process. The
15415 value is expanded for each incoming connection so, for example, it can be made
15416 to depend on the IP address of the remote host for messages arriving via
15417 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15418 optionally followed by K or M.
15420 &*Note*&: This limit cannot be made to depend on a message's sender or any
15421 other properties of an individual message, because it has to be advertised in
15422 the server's response to EHLO. String expansion failure causes a temporary
15423 error. A value of zero means no limit, but its use is not recommended. See also
15424 &%bounce_return_size_limit%&.
15426 Incoming SMTP messages are failed with a 552 error if the limit is
15427 exceeded; locally-generated messages either get a stderr message or a delivery
15428 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15429 an oversized message is logged in both the main and the reject logs. See also
15430 the generic transport option &%message_size_limit%&, which limits the size of
15431 message that an individual transport can process.
15433 If you use a virus-scanner and set this option to to a value larger than the
15434 maximum size that your virus-scanner is configured to support, you may get
15435 failures triggered by large mails. The right size to configure for the
15436 virus-scanner depends upon what data is passed and the options in use but it's
15437 probably safest to just set it to a little larger than this value. E.g., with a
15438 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15439 some problems may result.
15441 A value of 0 will disable size limit checking; Exim will still advertise the
15442 SIZE extension in an EHLO response, but without a limit, so as to permit
15443 SMTP clients to still indicate the message size along with the MAIL verb.
15446 .option move_frozen_messages main boolean false
15447 .cindex "frozen messages" "moving"
15448 This option, which is available only if Exim has been built with the setting
15450 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15452 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15453 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15454 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15455 standard utilities for handling such moved messages, and they do not show up in
15456 lists generated by &%-bp%& or by the Exim monitor.
15459 .option mua_wrapper main boolean false
15460 Setting this option true causes Exim to run in a very restrictive mode in which
15461 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15462 contains a full description of this facility.
15466 .option mysql_servers main "string list" unset
15467 .cindex "MySQL" "server list"
15468 This option provides a list of MySQL servers and associated connection data, to
15469 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15470 option is available only if Exim has been built with MySQL support.
15473 .option never_users main "string list&!!" unset
15474 This option is expanded just once, at the start of Exim's processing. Local
15475 message deliveries are normally run in processes that are setuid to the
15476 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15477 It is usually desirable to prevent any deliveries from running as root, as a
15480 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15481 list of users that must not be used for local deliveries. This list is fixed in
15482 the binary and cannot be overridden by the configuration file. By default, it
15483 contains just the single user name &"root"&. The &%never_users%& runtime option
15484 can be used to add more users to the fixed list.
15486 If a message is to be delivered as one of the users on the fixed list or the
15487 &%never_users%& list, an error occurs, and delivery is deferred. A common
15490 never_users = root:daemon:bin
15492 Including root is redundant if it is also on the fixed list, but it does no
15493 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15497 .option openssl_options main "string list" "+no_sslv2 +single_dh_use"
15498 .cindex "OpenSSL "compatibility options"
15499 This option allows an administrator to adjust the SSL options applied
15500 by OpenSSL to connections. It is given as a space-separated list of items,
15501 each one to be +added or -subtracted from the current value.
15503 This option is only available if Exim is built against OpenSSL. The values
15504 available for this option vary according to the age of your OpenSSL install.
15505 The &"all"& value controls a subset of flags which are available, typically
15506 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15507 list the values known on your system and Exim should support all the
15508 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15509 names lose the leading &"SSL_OP_"& and are lower-cased.
15511 Note that adjusting the options can have severe impact upon the security of
15512 SSL as used by Exim. It is possible to disable safety checks and shoot
15513 yourself in the foot in various unpleasant ways. This option should not be
15514 adjusted lightly. An unrecognised item will be detected at startup, by
15515 invoking Exim with the &%-bV%& flag.
15517 The option affects Exim operating both as a server and as a client.
15519 Historical note: prior to release 4.80, Exim defaulted this value to
15520 "+dont_insert_empty_fragments", which may still be needed for compatibility
15521 with some clients, but which lowers security by increasing exposure to
15522 some now infamous attacks.
15526 # Make both old MS and old Eudora happy:
15527 openssl_options = -all +microsoft_big_sslv3_buffer \
15528 +dont_insert_empty_fragments
15530 # Disable older protocol versions:
15531 openssl_options = +no_sslv2 +no_sslv3
15534 Possible options may include:
15538 &`allow_unsafe_legacy_renegotiation`&
15540 &`cipher_server_preference`&
15542 &`dont_insert_empty_fragments`&
15546 &`legacy_server_connect`&
15548 &`microsoft_big_sslv3_buffer`&
15550 &`microsoft_sess_id_bug`&
15552 &`msie_sslv2_rsa_padding`&
15554 &`netscape_challenge_bug`&
15556 &`netscape_reuse_cipher_change_bug`&
15560 &`no_session_resumption_on_renegotiation`&
15574 &`safari_ecdhe_ecdsa_bug`&
15578 &`single_ecdh_use`&
15580 &`ssleay_080_client_dh_bug`&
15582 &`sslref2_reuse_cert_type_bug`&
15584 &`tls_block_padding_bug`&
15588 &`tls_rollback_bug`&
15591 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15592 all clients connecting using the MacOS SecureTransport TLS facility prior
15593 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15594 to negotiate TLS then this option value might help, provided that your OpenSSL
15595 release is new enough to contain this work-around. This may be a situation
15596 where you have to upgrade OpenSSL to get buggy clients working.
15599 .option oracle_servers main "string list" unset
15600 .cindex "Oracle" "server list"
15601 This option provides a list of Oracle servers and associated connection data,
15602 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15603 The option is available only if Exim has been built with Oracle support.
15606 .option percent_hack_domains main "domain list&!!" unset
15607 .cindex "&""percent hack""&"
15608 .cindex "source routing" "in email address"
15609 .cindex "address" "source-routed"
15610 The &"percent hack"& is the convention whereby a local part containing a
15611 percent sign is re-interpreted as a new email address, with the percent
15612 replaced by @. This is sometimes called &"source routing"&, though that term is
15613 also applied to RFC 2822 addresses that begin with an @ character. If this
15614 option is set, Exim implements the percent facility for those domains listed,
15615 but no others. This happens before an incoming SMTP address is tested against
15618 &*Warning*&: The &"percent hack"& has often been abused by people who are
15619 trying to get round relaying restrictions. For this reason, it is best avoided
15620 if at all possible. Unfortunately, a number of less security-conscious MTAs
15621 implement it unconditionally. If you are running Exim on a gateway host, and
15622 routing mail through to internal MTAs without processing the local parts, it is
15623 a good idea to reject recipient addresses with percent characters in their
15624 local parts. Exim's default configuration does this.
15627 .option perl_at_start main boolean false
15628 This option is available only when Exim is built with an embedded Perl
15629 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15632 .option perl_startup main string unset
15633 This option is available only when Exim is built with an embedded Perl
15634 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15637 .option pgsql_servers main "string list" unset
15638 .cindex "PostgreSQL lookup type" "server list"
15639 This option provides a list of PostgreSQL servers and associated connection
15640 data, to be used in conjunction with &(pgsql)& lookups (see section
15641 &<<SECID72>>&). The option is available only if Exim has been built with
15642 PostgreSQL support.
15645 .option pid_file_path main string&!! "set at compile time"
15646 .cindex "daemon" "pid file path"
15647 .cindex "pid file, path for"
15648 This option sets the name of the file to which the Exim daemon writes its
15649 process id. The string is expanded, so it can contain, for example, references
15652 pid_file_path = /var/log/$primary_hostname/exim.pid
15654 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15656 The value set by the option can be overridden by the &%-oP%& command line
15657 option. A pid file is not written if a &"non-standard"& daemon is run by means
15658 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15661 .option pipelining_advertise_hosts main "host list&!!" *
15662 .cindex "PIPELINING" "suppressing advertising"
15663 This option can be used to suppress the advertisement of the SMTP
15664 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15665 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15666 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15667 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15668 that clients will use it; &"out of order"& commands that are &"expected"& do
15669 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15672 .option prdr_enable main boolean false
15673 .cindex "PRDR" "enabling on server"
15674 This option can be used to enable the Per-Recipient Data Response extension
15675 to SMTP, defined by Eric Hall.
15676 If the option is set, PRDR is advertised by Exim when operating as a server.
15677 If the client requests PRDR, and more than one recipient, for a message
15678 an additional ACL is called for each recipient after the message content
15679 is received. See section &<<SECTPRDRACL>>&.
15681 .option preserve_message_logs main boolean false
15682 .cindex "message logs" "preserving"
15683 If this option is set, message log files are not deleted when messages are
15684 completed. Instead, they are moved to a sub-directory of the spool directory
15685 called &_msglog.OLD_&, where they remain available for statistical or debugging
15686 purposes. This is a dangerous option to set on systems with any appreciable
15687 volume of mail. Use with care!
15690 .option primary_hostname main string "see below"
15691 .cindex "name" "of local host"
15692 .cindex "host" "name of local"
15693 .cindex "local host" "name of"
15694 .vindex "&$primary_hostname$&"
15695 This specifies the name of the current host. It is used in the default EHLO or
15696 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15697 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15698 The value is also used by default in some SMTP response messages from an Exim
15699 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15701 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15702 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15703 contains only one component, Exim passes it to &[gethostbyname()]& (or
15704 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15705 version. The variable &$primary_hostname$& contains the host name, whether set
15706 explicitly by this option, or defaulted.
15709 .option print_topbitchars main boolean false
15710 .cindex "printing characters"
15711 .cindex "8-bit characters"
15712 By default, Exim considers only those characters whose codes lie in the range
15713 32&--126 to be printing characters. In a number of circumstances (for example,
15714 when writing log entries) non-printing characters are converted into escape
15715 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15716 is set, code values of 128 and above are also considered to be printing
15719 This option also affects the header syntax checks performed by the
15720 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15721 the user's full name when constructing From: and Sender: addresses (as
15722 described in section &<<SECTconstr>>&). Setting this option can cause
15723 Exim to generate eight bit message headers that do not conform to the
15727 .option process_log_path main string unset
15728 .cindex "process log path"
15729 .cindex "log" "process log"
15730 .cindex "&'exiwhat'&"
15731 This option sets the name of the file to which an Exim process writes its
15732 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15733 utility script. If this option is unset, the file called &_exim-process.info_&
15734 in Exim's spool directory is used. The ability to specify the name explicitly
15735 can be useful in environments where two different Exims are running, using
15736 different spool directories.
15739 .option prod_requires_admin main boolean true
15743 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15744 admin user unless &%prod_requires_admin%& is set false. See also
15745 &%queue_list_requires_admin%&.
15748 .option qualify_domain main string "see below"
15749 .cindex "domain" "for qualifying addresses"
15750 .cindex "address" "qualification"
15751 This option specifies the domain name that is added to any envelope sender
15752 addresses that do not have a domain qualification. It also applies to
15753 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15754 are accepted by default only for locally-generated messages. Qualification is
15755 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15756 locally-generated messages, unless the &%-bnq%& command line option is used.
15758 Messages from external sources must always contain fully qualified addresses,
15759 unless the sending host matches &%sender_unqualified_hosts%& or
15760 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15761 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15762 necessary. Internally, Exim always works with fully qualified envelope
15763 addresses. If &%qualify_domain%& is not set, it defaults to the
15764 &%primary_hostname%& value.
15767 .option qualify_recipient main string "see below"
15768 This option allows you to specify a different domain for qualifying recipient
15769 addresses to the one that is used for senders. See &%qualify_domain%& above.
15773 .option queue_domains main "domain list&!!" unset
15774 .cindex "domain" "specifying non-immediate delivery"
15775 .cindex "queueing incoming messages"
15776 .cindex "message" "queueing certain domains"
15777 This option lists domains for which immediate delivery is not required.
15778 A delivery process is started whenever a message is received, but only those
15779 domains that do not match are processed. All other deliveries wait until the
15780 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15783 .option queue_list_requires_admin main boolean true
15785 The &%-bp%& command-line option, which lists the messages that are on the
15786 queue, requires the caller to be an admin user unless
15787 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15790 .option queue_only main boolean false
15791 .cindex "queueing incoming messages"
15792 .cindex "message" "queueing unconditionally"
15793 If &%queue_only%& is set, a delivery process is not automatically started
15794 whenever a message is received. Instead, the message waits on the queue for the
15795 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15796 delivered immediately when certain conditions (such as heavy load) occur.
15798 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15799 and &%-odi%& command line options override &%queue_only%& unless
15800 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15801 &%queue_only_load%&, and &%smtp_accept_queue%&.
15804 .option queue_only_file main string unset
15805 .cindex "queueing incoming messages"
15806 .cindex "message" "queueing by file existence"
15807 This option can be set to a colon-separated list of absolute path names, each
15808 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15809 it tests for the existence of each listed path using a call to &[stat()]&. For
15810 each path that exists, the corresponding queueing option is set.
15811 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15812 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15814 queue_only_file = smtp/some/file
15816 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15817 &_/some/file_& exists.
15820 .option queue_only_load main fixed-point unset
15821 .cindex "load average"
15822 .cindex "queueing incoming messages"
15823 .cindex "message" "queueing by load"
15824 If the system load average is higher than this value, incoming messages from
15825 all sources are queued, and no automatic deliveries are started. If this
15826 happens during local or remote SMTP input, all subsequent messages received on
15827 the same SMTP connection are queued by default, whatever happens to the load in
15828 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15831 Deliveries will subsequently be performed by queue runner processes. This
15832 option has no effect on ancient operating systems on which Exim cannot
15833 determine the load average. See also &%deliver_queue_load_max%& and
15834 &%smtp_load_reserve%&.
15837 .option queue_only_load_latch main boolean true
15838 .cindex "load average" "re-evaluating per message"
15839 When this option is true (the default), once one message has been queued
15840 because the load average is higher than the value set by &%queue_only_load%&,
15841 all subsequent messages received on the same SMTP connection are also queued.
15842 This is a deliberate choice; even though the load average may fall below the
15843 threshold, it doesn't seem right to deliver later messages on the same
15844 connection when not delivering earlier ones. However, there are special
15845 circumstances such as very long-lived connections from scanning appliances
15846 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15847 should be set false. This causes the value of the load average to be
15848 re-evaluated for each message.
15851 .option queue_only_override main boolean true
15852 .cindex "queueing incoming messages"
15853 When this option is true, the &%-od%&&'x'& command line options override the
15854 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15855 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15856 to override; they are accepted, but ignored.
15859 .option queue_run_in_order main boolean false
15860 .cindex "queue runner" "processing messages in order"
15861 If this option is set, queue runs happen in order of message arrival instead of
15862 in an arbitrary order. For this to happen, a complete list of the entire queue
15863 must be set up before the deliveries start. When the queue is all held in a
15864 single directory (the default), a single list is created for both the ordered
15865 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15866 single list is not created when &%queue_run_in_order%& is false. In this case,
15867 the sub-directories are processed one at a time (in a random order), and this
15868 avoids setting up one huge list for the whole queue. Thus, setting
15869 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15870 when the queue is large, because of the extra work in setting up the single,
15871 large list. In most situations, &%queue_run_in_order%& should not be set.
15875 .option queue_run_max main integer 5
15876 .cindex "queue runner" "maximum number of"
15877 This controls the maximum number of queue runner processes that an Exim daemon
15878 can run simultaneously. This does not mean that it starts them all at once,
15879 but rather that if the maximum number are still running when the time comes to
15880 start another one, it refrains from starting another one. This can happen with
15881 very large queues and/or very sluggish deliveries. This option does not,
15882 however, interlock with other processes, so additional queue runners can be
15883 started by other means, or by killing and restarting the daemon.
15885 Setting this option to zero does not suppress queue runs; rather, it disables
15886 the limit, allowing any number of simultaneous queue runner processes to be
15887 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15888 the daemon's command line.
15890 .option queue_smtp_domains main "domain list&!!" unset
15891 .cindex "queueing incoming messages"
15892 .cindex "message" "queueing remote deliveries"
15893 When this option is set, a delivery process is started whenever a message is
15894 received, routing is performed, and local deliveries take place.
15895 However, if any SMTP deliveries are required for domains that match
15896 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
15897 message waits on the queue for the next queue run. Since routing of the message
15898 has taken place, Exim knows to which remote hosts it must be delivered, and so
15899 when the queue run happens, multiple messages for the same host are delivered
15900 over a single SMTP connection. The &%-odqs%& command line option causes all
15901 SMTP deliveries to be queued in this way, and is equivalent to setting
15902 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
15906 .option receive_timeout main time 0s
15907 .cindex "timeout" "for non-SMTP input"
15908 This option sets the timeout for accepting a non-SMTP message, that is, the
15909 maximum time that Exim waits when reading a message on the standard input. If
15910 the value is zero, it will wait for ever. This setting is overridden by the
15911 &%-or%& command line option. The timeout for incoming SMTP messages is
15912 controlled by &%smtp_receive_timeout%&.
15914 .option received_header_text main string&!! "see below"
15915 .cindex "customizing" "&'Received:'& header"
15916 .cindex "&'Received:'& header line" "customizing"
15917 This string defines the contents of the &'Received:'& message header that is
15918 added to each message, except for the timestamp, which is automatically added
15919 on at the end (preceded by a semicolon). The string is expanded each time it is
15920 used. If the expansion yields an empty string, no &'Received:'& header line is
15921 added to the message. Otherwise, the string should start with the text
15922 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
15923 header lines. The default setting is:
15926 received_header_text = Received: \
15927 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
15928 {${if def:sender_ident \
15929 {from ${quote_local_part:$sender_ident} }}\
15930 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
15931 by $primary_hostname \
15932 ${if def:received_protocol {with $received_protocol}} \
15933 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
15934 (Exim $version_number)\n\t\
15935 ${if def:sender_address \
15936 {(envelope-from <$sender_address>)\n\t}}\
15937 id $message_exim_id\
15938 ${if def:received_for {\n\tfor $received_for}}
15941 The reference to the TLS cipher is omitted when Exim is built without TLS
15942 support. The use of conditional expansions ensures that this works for both
15943 locally generated messages and messages received from remote hosts, giving
15944 header lines such as the following:
15946 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
15947 by marley.carol.example with esmtp (Exim 4.00)
15948 (envelope-from <bob@carol.example>)
15949 id 16IOWa-00019l-00
15950 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
15951 Received: by scrooge.carol.example with local (Exim 4.00)
15952 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
15954 Until the body of the message has been received, the timestamp is the time when
15955 the message started to be received. Once the body has arrived, and all policy
15956 checks have taken place, the timestamp is updated to the time at which the
15957 message was accepted.
15960 .option received_headers_max main integer 30
15961 .cindex "loop" "prevention"
15962 .cindex "mail loop prevention"
15963 .cindex "&'Received:'& header line" "counting"
15964 When a message is to be delivered, the number of &'Received:'& headers is
15965 counted, and if it is greater than this parameter, a mail loop is assumed to
15966 have occurred, the delivery is abandoned, and an error message is generated.
15967 This applies to both local and remote deliveries.
15970 .option recipient_unqualified_hosts main "host list&!!" unset
15971 .cindex "unqualified addresses"
15972 .cindex "host" "unqualified addresses from"
15973 This option lists those hosts from which Exim is prepared to accept unqualified
15974 recipient addresses in message envelopes. The addresses are made fully
15975 qualified by the addition of the &%qualify_recipient%& value. This option also
15976 affects message header lines. Exim does not reject unqualified recipient
15977 addresses in headers, but it qualifies them only if the message came from a
15978 host that matches &%recipient_unqualified_hosts%&,
15979 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
15980 option was not set.
15983 .option recipients_max main integer 0
15984 .cindex "limit" "number of recipients"
15985 .cindex "recipient" "maximum number"
15986 If this option is set greater than zero, it specifies the maximum number of
15987 original recipients for any message. Additional recipients that are generated
15988 by aliasing or forwarding do not count. SMTP messages get a 452 response for
15989 all recipients over the limit; earlier recipients are delivered as normal.
15990 Non-SMTP messages with too many recipients are failed, and no deliveries are
15993 .cindex "RCPT" "maximum number of incoming"
15994 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
15995 RCPT commands in a single message.
15998 .option recipients_max_reject main boolean false
15999 If this option is set true, Exim rejects SMTP messages containing too many
16000 recipients by giving 552 errors to the surplus RCPT commands, and a 554
16001 error to the eventual DATA command. Otherwise (the default) it gives a 452
16002 error to the surplus RCPT commands and accepts the message on behalf of the
16003 initial set of recipients. The remote server should then re-send the message
16004 for the remaining recipients at a later time.
16007 .option remote_max_parallel main integer 2
16008 .cindex "delivery" "parallelism for remote"
16009 This option controls parallel delivery of one message to a number of remote
16010 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
16011 does all the remote deliveries for a message one by one. Otherwise, if a single
16012 message has to be delivered to more than one remote host, or if several copies
16013 have to be sent to the same remote host, up to &%remote_max_parallel%&
16014 deliveries are done simultaneously. If more than &%remote_max_parallel%&
16015 deliveries are required, the maximum number of processes are started, and as
16016 each one finishes, another is begun. The order of starting processes is the
16017 same as if sequential delivery were being done, and can be controlled by the
16018 &%remote_sort_domains%& option. If parallel delivery takes place while running
16019 with debugging turned on, the debugging output from each delivery process is
16020 tagged with its process id.
16022 This option controls only the maximum number of parallel deliveries for one
16023 message in one Exim delivery process. Because Exim has no central queue
16024 manager, there is no way of controlling the total number of simultaneous
16025 deliveries if the configuration allows a delivery attempt as soon as a message
16028 .cindex "number of deliveries"
16029 .cindex "delivery" "maximum number of"
16030 If you want to control the total number of deliveries on the system, you
16031 need to set the &%queue_only%& option. This ensures that all incoming messages
16032 are added to the queue without starting a delivery process. Then set up an Exim
16033 daemon to start queue runner processes at appropriate intervals (probably
16034 fairly often, for example, every minute), and limit the total number of queue
16035 runners by setting the &%queue_run_max%& parameter. Because each queue runner
16036 delivers only one message at a time, the maximum number of deliveries that can
16037 then take place at once is &%queue_run_max%& multiplied by
16038 &%remote_max_parallel%&.
16040 If it is purely remote deliveries you want to control, use
16041 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
16042 doing the SMTP routing before queueing, so that several messages for the same
16043 host will eventually get delivered down the same connection.
16046 .option remote_sort_domains main "domain list&!!" unset
16047 .cindex "sorting remote deliveries"
16048 .cindex "delivery" "sorting remote"
16049 When there are a number of remote deliveries for a message, they are sorted by
16050 domain into the order given by this list. For example,
16052 remote_sort_domains = *.cam.ac.uk:*.uk
16054 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
16055 then to those in the &%uk%& domain, then to any others.
16058 .option retry_data_expire main time 7d
16059 .cindex "hints database" "data expiry"
16060 This option sets a &"use before"& time on retry information in Exim's hints
16061 database. Any older retry data is ignored. This means that, for example, once a
16062 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
16066 .option retry_interval_max main time 24h
16067 .cindex "retry" "limit on interval"
16068 .cindex "limit" "on retry interval"
16069 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
16070 intervals between delivery attempts for messages that cannot be delivered
16071 straight away. This option sets an overall limit to the length of time between
16072 retries. It cannot be set greater than 24 hours; any attempt to do so forces
16076 .option return_path_remove main boolean true
16077 .cindex "&'Return-path:'& header line" "removing"
16078 RFC 2821, section 4.4, states that an SMTP server must insert a
16079 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
16080 The &'Return-path:'& header preserves the sender address as received in the
16081 MAIL command. This description implies that this header should not be present
16082 in an incoming message. If &%return_path_remove%& is true, any existing
16083 &'Return-path:'& headers are removed from messages at the time they are
16084 received. Exim's transports have options for adding &'Return-path:'& headers at
16085 the time of delivery. They are normally used only for final local deliveries.
16088 .option return_size_limit main integer 100K
16089 This option is an obsolete synonym for &%bounce_return_size_limit%&.
16092 .option rfc1413_hosts main "host list&!!" @[]
16094 .cindex "host" "for RFC 1413 calls"
16095 RFC 1413 identification calls are made to any client host which matches
16096 an item in the list.
16097 The default value specifies just this host, being any local interface
16100 .option rfc1413_query_timeout main time 0s
16101 .cindex "RFC 1413" "query timeout"
16102 .cindex "timeout" "for RFC 1413 call"
16103 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
16104 no RFC 1413 calls are ever made.
16107 .option sender_unqualified_hosts main "host list&!!" unset
16108 .cindex "unqualified addresses"
16109 .cindex "host" "unqualified addresses from"
16110 This option lists those hosts from which Exim is prepared to accept unqualified
16111 sender addresses. The addresses are made fully qualified by the addition of
16112 &%qualify_domain%&. This option also affects message header lines. Exim does
16113 not reject unqualified addresses in headers that contain sender addresses, but
16114 it qualifies them only if the message came from a host that matches
16115 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
16116 using TCP/IP), and the &%-bnq%& option was not set.
16118 .option set_environment main "string list" empty
16119 .cindex "environment"
16120 This option allows to set individual environment variables that the
16121 currently linked libraries and programs in child processes use. The
16122 default list is empty,
16125 .option slow_lookup_log main integer 0
16126 .cindex "logging" "slow lookups"
16127 .cindex "dns" "logging slow lookups"
16128 This option controls logging of slow lookups.
16129 If the value is nonzero it is taken as a number of milliseconds
16130 and lookups taking longer than this are logged.
16131 Currently this applies only to DNS lookups.
16135 .option smtp_accept_keepalive main boolean true
16136 .cindex "keepalive" "on incoming connection"
16137 This option controls the setting of the SO_KEEPALIVE option on incoming
16138 TCP/IP socket connections. When set, it causes the kernel to probe idle
16139 connections periodically, by sending packets with &"old"& sequence numbers. The
16140 other end of the connection should send an acknowledgment if the connection is
16141 still okay or a reset if the connection has been aborted. The reason for doing
16142 this is that it has the beneficial effect of freeing up certain types of
16143 connection that can get stuck when the remote host is disconnected without
16144 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16145 hours to detect unreachable hosts.
16149 .option smtp_accept_max main integer 20
16150 .cindex "limit" "incoming SMTP connections"
16151 .cindex "SMTP" "incoming connection count"
16153 This option specifies the maximum number of simultaneous incoming SMTP calls
16154 that Exim will accept. It applies only to the listening daemon; there is no
16155 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16156 value is set to zero, no limit is applied. However, it is required to be
16157 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16158 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16160 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16161 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16162 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16163 and &%smtp_load_reserve%& are then checked before accepting the connection.
16166 .option smtp_accept_max_nonmail main integer 10
16167 .cindex "limit" "non-mail SMTP commands"
16168 .cindex "SMTP" "limiting non-mail commands"
16169 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16170 the connection if there are too many. This option defines &"too many"&. The
16171 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16172 client looping sending EHLO, for example. The check is applied only if the
16173 client host matches &%smtp_accept_max_nonmail_hosts%&.
16175 When a new message is expected, one occurrence of RSET is not counted. This
16176 allows a client to send one RSET between messages (this is not necessary,
16177 but some clients do it). Exim also allows one uncounted occurrence of HELO
16178 or EHLO, and one occurrence of STARTTLS between messages. After
16179 starting up a TLS session, another EHLO is expected, and so it too is not
16180 counted. The first occurrence of AUTH in a connection, or immediately
16181 following STARTTLS is not counted. Otherwise, all commands other than
16182 MAIL, RCPT, DATA, and QUIT are counted.
16185 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16186 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16187 check by setting this option. The default value makes it apply to all hosts. By
16188 changing the value, you can exclude any badly-behaved hosts that you have to
16192 . Allow this long option name to split; give it unsplit as a fifth argument
16193 . for the automatic .oindex that is generated by .option.
16194 . We insert " &~&~" which is both pretty nasty visually and results in
16195 . non-searchable text. HowItWorks.txt mentions an option for inserting
16196 . zero-width-space, which would be nicer visually and results in (at least)
16197 . html that Firefox will split on when it's forced to reflow (rather than
16198 . inserting a horizontal scrollbar). However, the text is still not
16199 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16200 . the option name to split.
16202 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16203 smtp_accept_max_per_connection
16204 .cindex "SMTP" "limiting incoming message count"
16205 .cindex "limit" "messages per SMTP connection"
16206 The value of this option limits the number of MAIL commands that Exim is
16207 prepared to accept over a single SMTP connection, whether or not each command
16208 results in the transfer of a message. After the limit is reached, a 421
16209 response is given to subsequent MAIL commands. This limit is a safety
16210 precaution against a client that goes mad (incidents of this type have been
16214 .option smtp_accept_max_per_host main string&!! unset
16215 .cindex "limit" "SMTP connections from one host"
16216 .cindex "host" "limiting SMTP connections from"
16217 This option restricts the number of simultaneous IP connections from a single
16218 host (strictly, from a single IP address) to the Exim daemon. The option is
16219 expanded, to enable different limits to be applied to different hosts by
16220 reference to &$sender_host_address$&. Once the limit is reached, additional
16221 connection attempts from the same host are rejected with error code 421. This
16222 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16223 of zero imposes no limit. If this option is set greater than zero, it is
16224 required that &%smtp_accept_max%& be non-zero.
16226 &*Warning*&: When setting this option you should not use any expansion
16227 constructions that take an appreciable amount of time. The expansion and test
16228 happen in the main daemon loop, in order to reject additional connections
16229 without forking additional processes (otherwise a denial-of-service attack
16230 could cause a vast number or processes to be created). While the daemon is
16231 doing this processing, it cannot accept any other incoming connections.
16235 .option smtp_accept_queue main integer 0
16236 .cindex "SMTP" "incoming connection count"
16237 .cindex "queueing incoming messages"
16238 .cindex "message" "queueing by SMTP connection count"
16239 If the number of simultaneous incoming SMTP connections being handled via the
16240 listening daemon exceeds this value, messages received by SMTP are just placed
16241 on the queue; no delivery processes are started automatically. The count is
16242 fixed at the start of an SMTP connection. It cannot be updated in the
16243 subprocess that receives messages, and so the queueing or not queueing applies
16244 to all messages received in the same connection.
16246 A value of zero implies no limit, and clearly any non-zero value is useful only
16247 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16248 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16249 various &%-od%&&'x'& command line options.
16252 . See the comment on smtp_accept_max_per_connection
16254 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16255 smtp_accept_queue_per_connection
16256 .cindex "queueing incoming messages"
16257 .cindex "message" "queueing by message count"
16258 This option limits the number of delivery processes that Exim starts
16259 automatically when receiving messages via SMTP, whether via the daemon or by
16260 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16261 and the number of messages received in a single SMTP session exceeds this
16262 number, subsequent messages are placed on the queue, but no delivery processes
16263 are started. This helps to limit the number of Exim processes when a server
16264 restarts after downtime and there is a lot of mail waiting for it on other
16265 systems. On large systems, the default should probably be increased, and on
16266 dial-in client systems it should probably be set to zero (that is, disabled).
16269 .option smtp_accept_reserve main integer 0
16270 .cindex "SMTP" "incoming call count"
16271 .cindex "host" "reserved"
16272 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16273 number of SMTP connections that are reserved for connections from the hosts
16274 that are specified in &%smtp_reserve_hosts%&. The value set in
16275 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16276 restricted to this number of connections; the option specifies a minimum number
16277 of connection slots for them, not a maximum. It is a guarantee that this group
16278 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16279 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16282 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16283 set to 5, once there are 45 active connections (from any hosts), new
16284 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16285 provided the other criteria for acceptance are met.
16288 .option smtp_active_hostname main string&!! unset
16289 .cindex "host" "name in SMTP responses"
16290 .cindex "SMTP" "host name in responses"
16291 .vindex "&$primary_hostname$&"
16292 This option is provided for multi-homed servers that want to masquerade as
16293 several different hosts. At the start of an incoming SMTP connection, its value
16294 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16295 responses. For example, it is used as domain name in the response to an
16296 incoming HELO or EHLO command.
16298 .vindex "&$smtp_active_hostname$&"
16299 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16300 is saved with any messages that are received. It is therefore available for use
16301 in routers and transports when the message is later delivered.
16303 If this option is unset, or if its expansion is forced to fail, or if the
16304 expansion results in an empty string, the value of &$primary_hostname$& is
16305 used. Other expansion failures cause a message to be written to the main and
16306 panic logs, and the SMTP command receives a temporary error. Typically, the
16307 value of &%smtp_active_hostname%& depends on the incoming interface address.
16310 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16311 {cox.mydomain}{box.mydomain}}
16314 Although &$smtp_active_hostname$& is primarily concerned with incoming
16315 messages, it is also used as the default for HELO commands in callout
16316 verification if there is no remote transport from which to obtain a
16317 &%helo_data%& value.
16319 .option smtp_banner main string&!! "see below"
16320 .cindex "SMTP" "welcome banner"
16321 .cindex "banner for SMTP"
16322 .cindex "welcome banner for SMTP"
16323 .cindex "customizing" "SMTP banner"
16324 This string, which is expanded every time it is used, is output as the initial
16325 positive response to an SMTP connection. The default setting is:
16327 smtp_banner = $smtp_active_hostname ESMTP Exim \
16328 $version_number $tod_full
16330 Failure to expand the string causes a panic error. If you want to create a
16331 multiline response to the initial SMTP connection, use &"\n"& in the string at
16332 appropriate points, but not at the end. Note that the 220 code is not included
16333 in this string. Exim adds it automatically (several times in the case of a
16334 multiline response).
16337 .option smtp_check_spool_space main boolean true
16338 .cindex "checking disk space"
16339 .cindex "disk space, checking"
16340 .cindex "spool directory" "checking space"
16341 When this option is set, if an incoming SMTP session encounters the SIZE
16342 option on a MAIL command, it checks that there is enough space in the
16343 spool directory's partition to accept a message of that size, while still
16344 leaving free the amount specified by &%check_spool_space%& (even if that value
16345 is zero). If there isn't enough space, a temporary error code is returned.
16348 .option smtp_connect_backlog main integer 20
16349 .cindex "connection backlog"
16350 .cindex "SMTP" "connection backlog"
16351 .cindex "backlog of connections"
16352 This option specifies a maximum number of waiting SMTP connections. Exim passes
16353 this value to the TCP/IP system when it sets up its listener. Once this number
16354 of connections are waiting for the daemon's attention, subsequent connection
16355 attempts are refused at the TCP/IP level. At least, that is what the manuals
16356 say; in some circumstances such connection attempts have been observed to time
16357 out instead. For large systems it is probably a good idea to increase the
16358 value (to 50, say). It also gives some protection against denial-of-service
16359 attacks by SYN flooding.
16362 .option smtp_enforce_sync main boolean true
16363 .cindex "SMTP" "synchronization checking"
16364 .cindex "synchronization checking in SMTP"
16365 The SMTP protocol specification requires the client to wait for a response from
16366 the server at certain points in the dialogue. Without PIPELINING these
16367 synchronization points are after every command; with PIPELINING they are
16368 fewer, but they still exist.
16370 Some spamming sites send out a complete set of SMTP commands without waiting
16371 for any response. Exim protects against this by rejecting a message if the
16372 client has sent further input when it should not have. The error response &"554
16373 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16374 for this error cannot be perfect because of transmission delays (unexpected
16375 input may be on its way but not yet received when Exim checks). However, it
16376 does detect many instances.
16378 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16379 If you want to disable the check selectively (for example, only for certain
16380 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16381 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16385 .option smtp_etrn_command main string&!! unset
16386 .cindex "ETRN" "command to be run"
16387 .vindex "&$domain$&"
16388 If this option is set, the given command is run whenever an SMTP ETRN
16389 command is received from a host that is permitted to issue such commands (see
16390 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16391 are independently expanded. The expansion variable &$domain$& is set to the
16392 argument of the ETRN command, and no syntax checking is done on it. For
16395 smtp_etrn_command = /etc/etrn_command $domain \
16396 $sender_host_address
16398 A new process is created to run the command, but Exim does not wait for it to
16399 complete. Consequently, its status cannot be checked. If the command cannot be
16400 run, a line is written to the panic log, but the ETRN caller still receives
16401 a 250 success response. Exim is normally running under its own uid when
16402 receiving SMTP, so it is not possible for it to change the uid before running
16406 .option smtp_etrn_serialize main boolean true
16407 .cindex "ETRN" "serializing"
16408 When this option is set, it prevents the simultaneous execution of more than
16409 one identical command as a result of ETRN in an SMTP connection. See
16410 section &<<SECTETRN>>& for details.
16413 .option smtp_load_reserve main fixed-point unset
16414 .cindex "load average"
16415 If the system load average ever gets higher than this, incoming SMTP calls are
16416 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16417 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16418 the load is over the limit. The option has no effect on ancient operating
16419 systems on which Exim cannot determine the load average. See also
16420 &%deliver_queue_load_max%& and &%queue_only_load%&.
16424 .option smtp_max_synprot_errors main integer 3
16425 .cindex "SMTP" "limiting syntax and protocol errors"
16426 .cindex "limit" "SMTP syntax and protocol errors"
16427 Exim rejects SMTP commands that contain syntax or protocol errors. In
16428 particular, a syntactically invalid email address, as in this command:
16430 RCPT TO:<abc xyz@a.b.c>
16432 causes immediate rejection of the command, before any other tests are done.
16433 (The ACL cannot be run if there is no valid address to set up for it.) An
16434 example of a protocol error is receiving RCPT before MAIL. If there are
16435 too many syntax or protocol errors in one SMTP session, the connection is
16436 dropped. The limit is set by this option.
16438 .cindex "PIPELINING" "expected errors"
16439 When the PIPELINING extension to SMTP is in use, some protocol errors are
16440 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16441 Exim assumes that PIPELINING will be used if it advertises it (see
16442 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16443 not count towards the limit.
16447 .option smtp_max_unknown_commands main integer 3
16448 .cindex "SMTP" "limiting unknown commands"
16449 .cindex "limit" "unknown SMTP commands"
16450 If there are too many unrecognized commands in an incoming SMTP session, an
16451 Exim server drops the connection. This is a defence against some kinds of abuse
16454 into making connections to SMTP ports; in these circumstances, a number of
16455 non-SMTP command lines are sent first.
16459 .option smtp_ratelimit_hosts main "host list&!!" unset
16460 .cindex "SMTP" "rate limiting"
16461 .cindex "limit" "rate of message arrival"
16462 .cindex "RCPT" "rate limiting"
16463 Some sites find it helpful to be able to limit the rate at which certain hosts
16464 can send them messages, and the rate at which an individual message can specify
16467 Exim has two rate-limiting facilities. This section describes the older
16468 facility, which can limit rates within a single connection. The newer
16469 &%ratelimit%& ACL condition can limit rates across all connections. See section
16470 &<<SECTratelimiting>>& for details of the newer facility.
16472 When a host matches &%smtp_ratelimit_hosts%&, the values of
16473 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16474 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16475 respectively. Each option, if set, must contain a set of four comma-separated
16479 A threshold, before which there is no rate limiting.
16481 An initial time delay. Unlike other times in Exim, numbers with decimal
16482 fractional parts are allowed here.
16484 A factor by which to increase the delay each time.
16486 A maximum value for the delay. This should normally be less than 5 minutes,
16487 because after that time, the client is liable to timeout the SMTP command.
16490 For example, these settings have been used successfully at the site which
16491 first suggested this feature, for controlling mail from their customers:
16493 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16494 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16496 The first setting specifies delays that are applied to MAIL commands after
16497 two have been received over a single connection. The initial delay is 0.5
16498 seconds, increasing by a factor of 1.05 each time. The second setting applies
16499 delays to RCPT commands when more than four occur in a single message.
16502 .option smtp_ratelimit_mail main string unset
16503 See &%smtp_ratelimit_hosts%& above.
16506 .option smtp_ratelimit_rcpt main string unset
16507 See &%smtp_ratelimit_hosts%& above.
16510 .option smtp_receive_timeout main time&!! 5m
16511 .cindex "timeout" "for SMTP input"
16512 .cindex "SMTP" "input timeout"
16513 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16514 input, including batch SMTP. If a line of input (either an SMTP command or a
16515 data line) is not received within this time, the SMTP connection is dropped and
16516 the message is abandoned.
16517 A line is written to the log containing one of the following messages:
16519 SMTP command timeout on connection from...
16520 SMTP data timeout on connection from...
16522 The former means that Exim was expecting to read an SMTP command; the latter
16523 means that it was in the DATA phase, reading the contents of a message.
16525 If the first character of the option is a &"$"& the option is
16526 expanded before use and may depend on
16527 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16531 The value set by this option can be overridden by the
16532 &%-os%& command-line option. A setting of zero time disables the timeout, but
16533 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16534 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16535 timeout is controlled by &%receive_timeout%& and &%-or%&.
16538 .option smtp_reserve_hosts main "host list&!!" unset
16539 This option defines hosts for which SMTP connections are reserved; see
16540 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16543 .option smtp_return_error_details main boolean false
16544 .cindex "SMTP" "details policy failures"
16545 .cindex "policy control" "rejection, returning details"
16546 In the default state, Exim uses bland messages such as
16547 &"Administrative prohibition"& when it rejects SMTP commands for policy
16548 reasons. Many sysadmins like this because it gives away little information
16549 to spammers. However, some other sysadmins who are applying strict checking
16550 policies want to give out much fuller information about failures. Setting
16551 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16552 example, instead of &"Administrative prohibition"&, it might give:
16554 550-Rejected after DATA: '>' missing at end of address:
16555 550 failing address in "From" header is: <user@dom.ain
16560 .option smtputf8_advertise_hosts main "host list&!!" *
16561 .cindex "SMTPUTF8" "advertising"
16562 When Exim is built with support for internationalised mail names,
16563 the availability therof is advertised in
16564 response to EHLO only to those client hosts that match this option. See
16565 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
16569 .option spamd_address main string "see below"
16570 This option is available when Exim is compiled with the content-scanning
16571 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16572 The default value is
16576 See section &<<SECTscanspamass>>& for more details.
16580 .option split_spool_directory main boolean false
16581 .cindex "multiple spool directories"
16582 .cindex "spool directory" "split"
16583 .cindex "directories, multiple"
16584 If this option is set, it causes Exim to split its input directory into 62
16585 subdirectories, each with a single alphanumeric character as its name. The
16586 sixth character of the message id is used to allocate messages to
16587 subdirectories; this is the least significant base-62 digit of the time of
16588 arrival of the message.
16590 Splitting up the spool in this way may provide better performance on systems
16591 where there are long mail queues, by reducing the number of files in any one
16592 directory. The msglog directory is also split up in a similar way to the input
16593 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16594 are still placed in the single directory &_msglog.OLD_&.
16596 It is not necessary to take any special action for existing messages when
16597 changing &%split_spool_directory%&. Exim notices messages that are in the
16598 &"wrong"& place, and continues to process them. If the option is turned off
16599 after a period of being on, the subdirectories will eventually empty and be
16600 automatically deleted.
16602 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16603 changes. Instead of creating a list of all messages in the queue, and then
16604 trying to deliver each one in turn, it constructs a list of those in one
16605 sub-directory and tries to deliver them, before moving on to the next
16606 sub-directory. The sub-directories are processed in a random order. This
16607 spreads out the scanning of the input directories, and uses less memory. It is
16608 particularly beneficial when there are lots of messages on the queue. However,
16609 if &%queue_run_in_order%& is set, none of this new processing happens. The
16610 entire queue has to be scanned and sorted before any deliveries can start.
16613 .option spool_directory main string&!! "set at compile time"
16614 .cindex "spool directory" "path to"
16615 This defines the directory in which Exim keeps its spool, that is, the messages
16616 it is waiting to deliver. The default value is taken from the compile-time
16617 configuration setting, if there is one. If not, this option must be set. The
16618 string is expanded, so it can contain, for example, a reference to
16619 &$primary_hostname$&.
16621 If the spool directory name is fixed on your installation, it is recommended
16622 that you set it at build time rather than from this option, particularly if the
16623 log files are being written to the spool directory (see &%log_file_path%&).
16624 Otherwise log files cannot be used for errors that are detected early on, such
16625 as failures in the configuration file.
16627 By using this option to override the compiled-in path, it is possible to run
16628 tests of Exim without using the standard spool.
16630 .option sqlite_lock_timeout main time 5s
16631 .cindex "sqlite lookup type" "lock timeout"
16632 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16633 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16635 .option strict_acl_vars main boolean false
16636 .cindex "&ACL;" "variables, handling unset"
16637 This option controls what happens if a syntactically valid but undefined ACL
16638 variable is referenced. If it is false (the default), an empty string
16639 is substituted; if it is true, an error is generated. See section
16640 &<<SECTaclvariables>>& for details of ACL variables.
16642 .option strip_excess_angle_brackets main boolean false
16643 .cindex "angle brackets, excess"
16644 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16645 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16646 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16647 passed on to another MTA, the excess angle brackets are not passed on. If this
16648 option is not set, multiple pairs of angle brackets cause a syntax error.
16651 .option strip_trailing_dot main boolean false
16652 .cindex "trailing dot on domain"
16653 .cindex "dot" "trailing on domain"
16654 If this option is set, a trailing dot at the end of a domain in an address is
16655 ignored. If this is in the envelope and the message is passed on to another
16656 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16657 domain causes a syntax error.
16658 However, addresses in header lines are checked only when an ACL requests header
16662 .option syslog_duplication main boolean true
16663 .cindex "syslog" "duplicate log lines; suppressing"
16664 When Exim is logging to syslog, it writes the log lines for its three
16665 separate logs at different syslog priorities so that they can in principle
16666 be separated on the logging hosts. Some installations do not require this
16667 separation, and in those cases, the duplication of certain log lines is a
16668 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16669 particular log line is written to syslog. For lines that normally go to
16670 both the main log and the reject log, the reject log version (possibly
16671 containing message header lines) is written, at LOG_NOTICE priority.
16672 Lines that normally go to both the main and the panic log are written at
16673 the LOG_ALERT priority.
16676 .option syslog_facility main string unset
16677 .cindex "syslog" "facility; setting"
16678 This option sets the syslog &"facility"& name, used when Exim is logging to
16679 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16680 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16681 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16682 details of Exim's logging.
16686 .option syslog_processname main string &`exim`&
16687 .cindex "syslog" "process name; setting"
16688 This option sets the syslog &"ident"& name, used when Exim is logging to
16689 syslog. The value must be no longer than 32 characters. See chapter
16690 &<<CHAPlog>>& for details of Exim's logging.
16694 .option syslog_timestamp main boolean true
16695 .cindex "syslog" "timestamps"
16696 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16697 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16698 details of Exim's logging.
16701 .option system_filter main string&!! unset
16702 .cindex "filter" "system filter"
16703 .cindex "system filter" "specifying"
16704 .cindex "Sieve filter" "not available for system filter"
16705 This option specifies an Exim filter file that is applied to all messages at
16706 the start of each delivery attempt, before any routing is done. System filters
16707 must be Exim filters; they cannot be Sieve filters. If the system filter
16708 generates any deliveries to files or pipes, or any new mail messages, the
16709 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16710 which transports are to be used. Details of this facility are given in chapter
16711 &<<CHAPsystemfilter>>&.
16714 .option system_filter_directory_transport main string&!! unset
16715 .vindex "&$address_file$&"
16716 This sets the name of the transport driver that is to be used when the
16717 &%save%& command in a system message filter specifies a path ending in &"/"&,
16718 implying delivery of each message into a separate file in some directory.
16719 During the delivery, the variable &$address_file$& contains the path name.
16722 .option system_filter_file_transport main string&!! unset
16723 .cindex "file" "transport for system filter"
16724 This sets the name of the transport driver that is to be used when the &%save%&
16725 command in a system message filter specifies a path not ending in &"/"&. During
16726 the delivery, the variable &$address_file$& contains the path name.
16728 .option system_filter_group main string unset
16729 .cindex "gid (group id)" "system filter"
16730 This option is used only when &%system_filter_user%& is also set. It sets the
16731 gid under which the system filter is run, overriding any gid that is associated
16732 with the user. The value may be numerical or symbolic.
16734 .option system_filter_pipe_transport main string&!! unset
16735 .cindex "&(pipe)& transport" "for system filter"
16736 .vindex "&$address_pipe$&"
16737 This specifies the transport driver that is to be used when a &%pipe%& command
16738 is used in a system filter. During the delivery, the variable &$address_pipe$&
16739 contains the pipe command.
16742 .option system_filter_reply_transport main string&!! unset
16743 .cindex "&(autoreply)& transport" "for system filter"
16744 This specifies the transport driver that is to be used when a &%mail%& command
16745 is used in a system filter.
16748 .option system_filter_user main string unset
16749 .cindex "uid (user id)" "system filter"
16750 If this option is set to root, the system filter is run in the main Exim
16751 delivery process, as root. Otherwise, the system filter runs in a separate
16752 process, as the given user, defaulting to the Exim run-time user.
16753 Unless the string consists entirely of digits, it
16754 is looked up in the password data. Failure to find the named user causes a
16755 configuration error. The gid is either taken from the password data, or
16756 specified by &%system_filter_group%&. When the uid is specified numerically,
16757 &%system_filter_group%& is required to be set.
16759 If the system filter generates any pipe, file, or reply deliveries, the uid
16760 under which the filter is run is used when transporting them, unless a
16761 transport option overrides.
16764 .option tcp_nodelay main boolean true
16765 .cindex "daemon" "TCP_NODELAY on sockets"
16766 .cindex "Nagle algorithm"
16767 .cindex "TCP_NODELAY on listening sockets"
16768 If this option is set false, it stops the Exim daemon setting the
16769 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16770 turns off the &"Nagle algorithm"&, which is a way of improving network
16771 performance in interactive (character-by-character) situations. Turning it off
16772 should improve Exim's performance a bit, so that is what happens by default.
16773 However, it appears that some broken clients cannot cope, and time out. Hence
16774 this option. It affects only those sockets that are set up for listening by the
16775 daemon. Sockets created by the smtp transport for delivering mail always set
16779 .option timeout_frozen_after main time 0s
16780 .cindex "frozen messages" "timing out"
16781 .cindex "timeout" "frozen messages"
16782 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16783 message of any kind that has been on the queue for longer than the given time
16784 is automatically cancelled at the next queue run. If the frozen message is a
16785 bounce message, it is just discarded; otherwise, a bounce is sent to the
16786 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16787 If you want to timeout frozen bounce messages earlier than other kinds of
16788 frozen message, see &%ignore_bounce_errors_after%&.
16790 &*Note:*& the default value of zero means no timeouts; with this setting,
16791 frozen messages remain on the queue forever (except for any frozen bounce
16792 messages that are released by &%ignore_bounce_errors_after%&).
16795 .option timezone main string unset
16796 .cindex "timezone, setting"
16797 The value of &%timezone%& is used to set the environment variable TZ while
16798 running Exim (if it is different on entry). This ensures that all timestamps
16799 created by Exim are in the required timezone. If you want all your timestamps
16800 to be in UTC (aka GMT) you should set
16804 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16805 or, if that is not set, from the value of the TZ environment variable when Exim
16806 is built. If &%timezone%& is set to the empty string, either at build or run
16807 time, any existing TZ variable is removed from the environment when Exim
16808 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16809 unfortunately not all, operating systems.
16813 .option tls_advertise_hosts main "host list&!!" *
16815 .cindex "TLS" "advertising"
16816 .cindex "encryption" "on SMTP connection"
16817 .cindex "SMTP" "encrypted connection"
16818 When Exim is built with support for TLS encrypted connections, the availability
16819 of the STARTTLS command to set up an encrypted session is advertised in
16820 response to EHLO only to those client hosts that match this option. See
16821 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16823 Note that the default value requires that a certificate be supplied
16824 using the &%tls_certificate%& option. If no certificate is available then
16825 the &%tls_advertise_hosts%& option should be set empty.
16829 .option tls_certificate main string&!! unset
16830 .cindex "TLS" "server certificate; location of"
16831 .cindex "certificate" "server, location of"
16832 The value of this option is expanded, and must then be the absolute path to a
16833 file which contains the server's certificates. The server's private key is also
16834 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16835 &<<CHAPTLS>>& for further details.
16837 &*Note*&: The certificates defined by this option are used only when Exim is
16838 receiving incoming messages as a server. If you want to supply certificates for
16839 use when sending messages as a client, you must set the &%tls_certificate%&
16840 option in the relevant &(smtp)& transport.
16842 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16843 if the OpenSSL build supports TLS extensions and the TLS client sends the
16844 Server Name Indication extension, then this option and others documented in
16845 &<<SECTtlssni>>& will be re-expanded.
16847 .option tls_crl main string&!! unset
16848 .cindex "TLS" "server certificate revocation list"
16849 .cindex "certificate" "revocation list for server"
16850 This option specifies a certificate revocation list. The expanded value must
16851 be the name of a file that contains a CRL in PEM format.
16853 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16856 .option tls_dh_max_bits main integer 2236
16857 .cindex "TLS" "D-H bit count"
16858 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16859 the chosen TLS library. That value might prove to be too high for
16860 interoperability. This option provides a maximum clamp on the value
16861 suggested, trading off security for interoperability.
16863 The value must be at least 1024.
16865 The value 2236 was chosen because, at time of adding the option, it was the
16866 hard-coded maximum value supported by the NSS cryptographic library, as used
16867 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16869 If you prefer more security and are willing to break some clients, raise this
16872 Note that the value passed to GnuTLS for *generating* a new prime may be a
16873 little less than this figure, because GnuTLS is inexact and may produce a
16874 larger prime than requested.
16877 .option tls_dhparam main string&!! unset
16878 .cindex "TLS" "D-H parameters for server"
16879 The value of this option is expanded and indicates the source of DH parameters
16880 to be used by Exim.
16882 If it is a filename starting with a &`/`&, then it names a file from which DH
16883 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16884 PKCS#3 representation of the DH prime. If the file does not exist, for
16885 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16886 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16887 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16888 and treated as though the &%tls_dhparam%& were set to "none".
16890 If this option expands to the string "none", then no DH parameters will be
16893 If this option expands to the string "historic" and Exim is using GnuTLS, then
16894 Exim will attempt to load a file from inside the spool directory. If the file
16895 does not exist, Exim will attempt to create it.
16896 See section &<<SECTgnutlsparam>>& for further details.
16898 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
16899 a default DH prime; the default is the 2048 bit prime described in section
16900 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
16901 in IKE is assigned number 23.
16903 Otherwise, the option must expand to the name used by Exim for any of a number
16904 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
16905 "ike" followed by the number used by IKE, of "default" which corresponds to
16908 The available primes are:
16909 &`ike1`&, &`ike2`&, &`ike5`&,
16910 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
16911 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
16913 Some of these will be too small to be accepted by clients.
16914 Some may be too large to be accepted by clients.
16916 The TLS protocol does not negotiate an acceptable size for this; clients tend
16917 to hard-drop connections if what is offered by the server is unacceptable,
16918 whether too large or too small, and there's no provision for the client to
16919 tell the server what these constraints are. Thus, as a server operator, you
16920 need to make an educated guess as to what is most likely to work for your
16923 Some known size constraints suggest that a bit-size in the range 2048 to 2236
16924 is most likely to maximise interoperability. The upper bound comes from
16925 applications using the Mozilla Network Security Services (NSS) library, which
16926 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
16927 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
16928 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
16929 acceptable bound from 1024 to 2048.
16932 .option tls_eccurve main string&!! prime256v1
16933 .cindex TLS "EC cryptography"
16934 If built with a recent-enough version of OpenSSL,
16935 this option selects a EC curve for use by Exim.
16937 Curve names of the form &'prime256v1'& are accepted.
16938 For even more-recent library versions, names of the form &'P-512'&
16939 are also accepted, plus the special value &'auto'&
16940 which tells the library to choose.
16942 If the option is set to an empty string, no EC curves will be enabled.
16945 .option tls_ocsp_file main string&!! unset
16946 .cindex TLS "certificate status"
16947 .cindex TLS "OCSP proof file"
16949 must if set expand to the absolute path to a file which contains a current
16950 status proof for the server's certificate, as obtained from the
16951 Certificate Authority.
16954 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
16958 .option tls_on_connect_ports main "string list" unset
16961 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
16962 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
16963 set up without waiting for the client to issue a STARTTLS command. For
16964 further details, see section &<<SECTsupobssmt>>&.
16968 .option tls_privatekey main string&!! unset
16969 .cindex "TLS" "server private key; location of"
16970 The value of this option is expanded, and must then be the absolute path to a
16971 file which contains the server's private key. If this option is unset, or if
16972 the expansion is forced to fail, or the result is an empty string, the private
16973 key is assumed to be in the same file as the server's certificates. See chapter
16974 &<<CHAPTLS>>& for further details.
16976 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16979 .option tls_remember_esmtp main boolean false
16980 .cindex "TLS" "esmtp state; remembering"
16981 .cindex "TLS" "broken clients"
16982 If this option is set true, Exim violates the RFCs by remembering that it is in
16983 &"esmtp"& state after successfully negotiating a TLS session. This provides
16984 support for broken clients that fail to send a new EHLO after starting a
16988 .option tls_require_ciphers main string&!! unset
16989 .cindex "TLS" "requiring specific ciphers"
16990 .cindex "cipher" "requiring specific"
16991 This option controls which ciphers can be used for incoming TLS connections.
16992 The &(smtp)& transport has an option of the same name for controlling outgoing
16993 connections. This option is expanded for each connection, so can be varied for
16994 different clients if required. The value of this option must be a list of
16995 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
16996 in somewhat different ways. If GnuTLS is being used, the client controls the
16997 preference order of the available ciphers. Details are given in sections
16998 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
17001 .option tls_try_verify_hosts main "host list&!!" unset
17002 .cindex "TLS" "client certificate verification"
17003 .cindex "certificate" "verification of client"
17004 See &%tls_verify_hosts%& below.
17007 .option tls_verify_certificates main string&!! system
17008 .cindex "TLS" "client certificate verification"
17009 .cindex "certificate" "verification of client"
17010 The value of this option is expanded, and must then be either the
17012 or the absolute path to
17013 a file or directory containing permitted certificates for clients that
17014 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
17016 The "system" value for the option will use a
17017 system default location compiled into the SSL library.
17018 This is not available for GnuTLS versions preceding 3.0.20,
17019 and will be taken as empty; an explicit location
17022 The use of a directory for the option value is not available for GnuTLS versions
17023 preceding 3.3.6 and a single file must be used.
17025 With OpenSSL the certificates specified
17027 either by file or directory
17028 are added to those given by the system default location.
17030 These certificates should be for the certificate authorities trusted, rather
17031 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
17032 the value is a file then the certificates are sent by Exim as a server to
17033 connecting clients, defining the list of accepted certificate authorities.
17034 Thus the values defined should be considered public data. To avoid this,
17035 use the explicit directory version.
17037 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17039 A forced expansion failure or setting to an empty string is equivalent to
17043 .option tls_verify_hosts main "host list&!!" unset
17044 .cindex "TLS" "client certificate verification"
17045 .cindex "certificate" "verification of client"
17046 This option, along with &%tls_try_verify_hosts%&, controls the checking of
17047 certificates from clients. The expected certificates are defined by
17048 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
17049 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
17050 &%tls_verify_certificates%& is not set.
17052 Any client that matches &%tls_verify_hosts%& is constrained by
17053 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
17054 present one of the listed certificates. If it does not, the connection is
17055 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
17056 the host to use TLS. It can still send SMTP commands through unencrypted
17057 connections. Forcing a client to use TLS has to be done separately using an
17058 ACL to reject inappropriate commands when the connection is not encrypted.
17060 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
17061 matches this option (but not &%tls_verify_hosts%&), Exim requests a
17062 certificate and checks it against &%tls_verify_certificates%&, but does not
17063 abort the connection if there is no certificate or if it does not match. This
17064 state can be detected in an ACL, which makes it possible to implement policies
17065 such as &"accept for relay only if a verified certificate has been received,
17066 but accept for local delivery if encrypted, even without a verified
17069 Client hosts that match neither of these lists are not asked to present
17073 .option trusted_groups main "string list&!!" unset
17074 .cindex "trusted groups"
17075 .cindex "groups" "trusted"
17076 This option is expanded just once, at the start of Exim's processing. If this
17077 option is set, any process that is running in one of the listed groups, or
17078 which has one of them as a supplementary group, is trusted. The groups can be
17079 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
17080 details of what trusted callers are permitted to do. If neither
17081 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
17084 .option trusted_users main "string list&!!" unset
17085 .cindex "trusted users"
17086 .cindex "user" "trusted"
17087 This option is expanded just once, at the start of Exim's processing. If this
17088 option is set, any process that is running as one of the listed users is
17089 trusted. The users can be specified numerically or by name. See section
17090 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
17091 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
17092 Exim user are trusted.
17094 .option unknown_login main string&!! unset
17095 .cindex "uid (user id)" "unknown caller"
17096 .vindex "&$caller_uid$&"
17097 This is a specialized feature for use in unusual configurations. By default, if
17098 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
17099 gives up. The &%unknown_login%& option can be used to set a login name to be
17100 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
17101 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
17102 is used for the user's real name (gecos field), unless this has been set by the
17105 .option unknown_username main string unset
17106 See &%unknown_login%&.
17108 .option untrusted_set_sender main "address list&!!" unset
17109 .cindex "trusted users"
17110 .cindex "sender" "setting by untrusted user"
17111 .cindex "untrusted user setting sender"
17112 .cindex "user" "untrusted setting sender"
17113 .cindex "envelope sender"
17114 When an untrusted user submits a message to Exim using the standard input, Exim
17115 normally creates an envelope sender address from the user's login and the
17116 default qualification domain. Data from the &%-f%& option (for setting envelope
17117 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
17118 is used) is ignored.
17120 However, untrusted users are permitted to set an empty envelope sender address,
17121 to declare that a message should never generate any bounces. For example:
17123 exim -f '<>' user@domain.example
17125 .vindex "&$sender_ident$&"
17126 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
17127 other envelope sender addresses in a controlled way. When it is set, untrusted
17128 users are allowed to set envelope sender addresses that match any of the
17129 patterns in the list. Like all address lists, the string is expanded. The
17130 identity of the user is in &$sender_ident$&, so you can, for example, restrict
17131 users to setting senders that start with their login ids
17132 followed by a hyphen
17133 by a setting like this:
17135 untrusted_set_sender = ^$sender_ident-
17137 If you want to allow untrusted users to set envelope sender addresses without
17138 restriction, you can use
17140 untrusted_set_sender = *
17142 The &%untrusted_set_sender%& option applies to all forms of local input, but
17143 only to the setting of the envelope sender. It does not permit untrusted users
17144 to use the other options which trusted user can use to override message
17145 parameters. Furthermore, it does not stop Exim from removing an existing
17146 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17147 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17148 overriding these actions. The handling of the &'Sender:'& header is also
17149 described in section &<<SECTthesenhea>>&.
17151 The log line for a message's arrival shows the envelope sender following
17152 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17153 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17154 envelope sender address, the user's login is shown in parentheses after the
17158 .option uucp_from_pattern main string "see below"
17159 .cindex "&""From""& line"
17160 .cindex "UUCP" "&""From""& line"
17161 Some applications that pass messages to an MTA via a command line interface use
17162 an initial line starting with &"From&~"& to pass the envelope sender. In
17163 particular, this is used by UUCP software. Exim recognizes such a line by means
17164 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17165 matches, the sender address is constructed by expanding the contents of
17166 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17167 default pattern recognizes lines in the following two forms:
17169 From ph10 Fri Jan 5 12:35 GMT 1996
17170 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17172 The pattern can be seen by running
17174 exim -bP uucp_from_pattern
17176 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17177 year in the second case. The first word after &"From&~"& is matched in the
17178 regular expression by a parenthesized subpattern. The default value for
17179 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17180 (&"ph10"& in the example above) as the message's sender. See also
17181 &%ignore_fromline_hosts%&.
17184 .option uucp_from_sender main string&!! &`$1`&
17185 See &%uucp_from_pattern%& above.
17188 .option warn_message_file main string unset
17189 .cindex "warning of delay" "customizing the message"
17190 .cindex "customizing" "warning message"
17191 This option defines a template file containing paragraphs of text to be used
17192 for constructing the warning message which is sent by Exim when a message has
17193 been on the queue for a specified amount of time, as specified by
17194 &%delay_warning%&. Details of the file's contents are given in chapter
17195 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17198 .option write_rejectlog main boolean true
17199 .cindex "reject log" "disabling"
17200 If this option is set false, Exim no longer writes anything to the reject log.
17201 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17202 .ecindex IIDconfima
17203 .ecindex IIDmaiconf
17208 . ////////////////////////////////////////////////////////////////////////////
17209 . ////////////////////////////////////////////////////////////////////////////
17211 .chapter "Generic options for routers" "CHAProutergeneric"
17212 .scindex IIDgenoprou1 "options" "generic; for routers"
17213 .scindex IIDgenoprou2 "generic options" "router"
17214 This chapter describes the generic options that apply to all routers.
17215 Those that are preconditions are marked with ‡ in the &"use"& field.
17217 For a general description of how a router operates, see sections
17218 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17219 which the preconditions are tested. The order of expansion of the options that
17220 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17221 &%headers_remove%&, &%transport%&.
17225 .option address_data routers string&!! unset
17226 .cindex "router" "data attached to address"
17227 The string is expanded just before the router is run, that is, after all the
17228 precondition tests have succeeded. If the expansion is forced to fail, the
17229 router declines, the value of &%address_data%& remains unchanged, and the
17230 &%more%& option controls what happens next. Other expansion failures cause
17231 delivery of the address to be deferred.
17233 .vindex "&$address_data$&"
17234 When the expansion succeeds, the value is retained with the address, and can be
17235 accessed using the variable &$address_data$& in the current router, subsequent
17236 routers, and the eventual transport.
17238 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17239 that runs a user's filter file, the contents of &$address_data$& are accessible
17240 in the filter. This is not normally a problem, because such data is usually
17241 either not confidential or it &"belongs"& to the current user, but if you do
17242 put confidential data into &$address_data$& you need to remember this point.
17244 Even if the router declines or passes, the value of &$address_data$& remains
17245 with the address, though it can be changed by another &%address_data%& setting
17246 on a subsequent router. If a router generates child addresses, the value of
17247 &$address_data$& propagates to them. This also applies to the special kind of
17248 &"child"& that is generated by a router with the &%unseen%& option.
17250 The idea of &%address_data%& is that you can use it to look up a lot of data
17251 for the address once, and then pick out parts of the data later. For example,
17252 you could use a single LDAP lookup to return a string of the form
17254 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17256 In the transport you could pick out the mailbox by a setting such as
17258 file = ${extract{mailbox}{$address_data}}
17260 This makes the configuration file less messy, and also reduces the number of
17261 lookups (though Exim does cache lookups).
17263 .vindex "&$sender_address_data$&"
17264 .vindex "&$address_data$&"
17265 The &%address_data%& facility is also useful as a means of passing information
17266 from one router to another, and from a router to a transport. In addition, if
17267 &$address_data$& is set by a router when verifying a recipient address from an
17268 ACL, it remains available for use in the rest of the ACL statement. After
17269 verifying a sender, the value is transferred to &$sender_address_data$&.
17273 .option address_test routers&!? boolean true
17275 .cindex "router" "skipping when address testing"
17276 If this option is set false, the router is skipped when routing is being tested
17277 by means of the &%-bt%& command line option. This can be a convenience when
17278 your first router sends messages to an external scanner, because it saves you
17279 having to set the &"already scanned"& indicator when testing real address
17284 .option cannot_route_message routers string&!! unset
17285 .cindex "router" "customizing &""cannot route""& message"
17286 .cindex "customizing" "&""cannot route""& message"
17287 This option specifies a text message that is used when an address cannot be
17288 routed because Exim has run out of routers. The default message is
17289 &"Unrouteable address"&. This option is useful only on routers that have
17290 &%more%& set false, or on the very last router in a configuration, because the
17291 value that is used is taken from the last router that is considered. This
17292 includes a router that is skipped because its preconditions are not met, as
17293 well as a router that declines. For example, using the default configuration,
17296 cannot_route_message = Remote domain not found in DNS
17298 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17301 cannot_route_message = Unknown local user
17303 on the final router that checks for local users. If string expansion fails for
17304 this option, the default message is used. Unless the expansion failure was
17305 explicitly forced, a message about the failure is written to the main and panic
17306 logs, in addition to the normal message about the routing failure.
17309 .option caseful_local_part routers boolean false
17310 .cindex "case of local parts"
17311 .cindex "router" "case of local parts"
17312 By default, routers handle the local parts of addresses in a case-insensitive
17313 manner, though the actual case is preserved for transmission with the message.
17314 If you want the case of letters to be significant in a router, you must set
17315 this option true. For individual router options that contain address or local
17316 part lists (for example, &%local_parts%&), case-sensitive matching can be
17317 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17320 .vindex "&$local_part$&"
17321 .vindex "&$original_local_part$&"
17322 .vindex "&$parent_local_part$&"
17323 The value of the &$local_part$& variable is forced to lower case while a
17324 router is running unless &%caseful_local_part%& is set. When a router assigns
17325 an address to a transport, the value of &$local_part$& when the transport runs
17326 is the same as it was in the router. Similarly, when a router generates child
17327 addresses by aliasing or forwarding, the values of &$original_local_part$&
17328 and &$parent_local_part$& are those that were used by the redirecting router.
17330 This option applies to the processing of an address by a router. When a
17331 recipient address is being processed in an ACL, there is a separate &%control%&
17332 modifier that can be used to specify case-sensitive processing within the ACL
17333 (see section &<<SECTcontrols>>&).
17337 .option check_local_user routers&!? boolean false
17338 .cindex "local user, checking in router"
17339 .cindex "router" "checking for local user"
17340 .cindex "&_/etc/passwd_&"
17342 When this option is true, Exim checks that the local part of the recipient
17343 address (with affixes removed if relevant) is the name of an account on the
17344 local system. The check is done by calling the &[getpwnam()]& function rather
17345 than trying to read &_/etc/passwd_& directly. This means that other methods of
17346 holding password data (such as NIS) are supported. If the local part is a local
17347 user, &$home$& is set from the password data, and can be tested in other
17348 preconditions that are evaluated after this one (the order of evaluation is
17349 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17350 overridden by &%router_home_directory%&. If the local part is not a local user,
17351 the router is skipped.
17353 If you want to check that the local part is either the name of a local user
17354 or matches something else, you cannot combine &%check_local_user%& with a
17355 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17356 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17357 setting to achieve this. For example:
17359 local_parts = passwd;$local_part : lsearch;/etc/other/users
17361 Note, however, that the side effects of &%check_local_user%& (such as setting
17362 up a home directory) do not occur when a &(passwd)& lookup is used in a
17363 &%local_parts%& (or any other) precondition.
17367 .option condition routers&!? string&!! unset
17368 .cindex "router" "customized precondition"
17369 This option specifies a general precondition test that has to succeed for the
17370 router to be called. The &%condition%& option is the last precondition to be
17371 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17372 result is a forced failure, or an empty string, or one of the strings &"0"& or
17373 &"no"& or &"false"& (checked without regard to the case of the letters), the
17374 router is skipped, and the address is offered to the next one.
17376 If the result is any other value, the router is run (as this is the last
17377 precondition to be evaluated, all the other preconditions must be true).
17379 This option is unusual in that multiple &%condition%& options may be present.
17380 All &%condition%& options must succeed.
17382 The &%condition%& option provides a means of applying custom conditions to the
17383 running of routers. Note that in the case of a simple conditional expansion,
17384 the default expansion values are exactly what is wanted. For example:
17386 condition = ${if >{$message_age}{600}}
17388 Because of the default behaviour of the string expansion, this is equivalent to
17390 condition = ${if >{$message_age}{600}{true}{}}
17393 A multiple condition example, which succeeds:
17395 condition = ${if >{$message_age}{600}}
17396 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17400 If the expansion fails (other than forced failure) delivery is deferred. Some
17401 of the other precondition options are common special cases that could in fact
17402 be specified using &%condition%&.
17404 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17405 are far older, and use one set of semantics. ACLs are newer and when
17406 they were created, the ACL &%condition%& process was given far stricter
17407 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17408 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17409 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17410 Router rules processing behavior.
17412 This is best illustrated in an example:
17414 # If used in an ACL condition will fail with a syntax error, but
17415 # in a router condition any extra characters are treated as a string
17417 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17420 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17423 In each example above, the &%if%& statement actually ends after
17424 &"{google.com}}"&. Since no true or false braces were defined, the
17425 default &%if%& behavior is to return a boolean true or a null answer
17426 (which evaluates to false). The rest of the line is then treated as a
17427 string. So the first example resulted in the boolean answer &"true"&
17428 with the string &" {yes} {no}}"& appended to it. The second example
17429 resulted in the null output (indicating false) with the string
17430 &" {yes} {no}}"& appended to it.
17432 In fact you can put excess forward braces in too. In the router
17433 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17434 mean something, like after a &"$"& or when required as part of a
17435 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17438 Thus, in a Router, the above expansion strings will both always evaluate
17439 true, as the result of expansion is a non-empty string which doesn't
17440 match an explicit false value. This can be tricky to debug. By
17441 contrast, in an ACL either of those strings will always result in an
17442 expansion error because the result doesn't look sufficiently boolean.
17445 .option debug_print routers string&!! unset
17446 .cindex "testing" "variables in drivers"
17447 If this option is set and debugging is enabled (see the &%-d%& command line
17448 option) or in address-testing mode (see the &%-bt%& command line option),
17449 the string is expanded and included in the debugging output.
17450 If expansion of the string fails, the error message is written to the debugging
17451 output, and Exim carries on processing.
17452 This option is provided to help with checking out the values of variables and
17453 so on when debugging router configurations. For example, if a &%condition%&
17454 option appears not to be working, &%debug_print%& can be used to output the
17455 variables it references. The output happens after checks for &%domains%&,
17456 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17457 are tested. A newline is added to the text if it does not end with one.
17458 The variable &$router_name$& contains the name of the router.
17462 .option disable_logging routers boolean false
17463 If this option is set true, nothing is logged for any routing errors
17464 or for any deliveries caused by this router. You should not set this option
17465 unless you really, really know what you are doing. See also the generic
17466 transport option of the same name.
17468 .option dnssec_request_domains routers "domain list&!!" unset
17469 .cindex "MX record" "security"
17470 .cindex "DNSSEC" "MX lookup"
17471 .cindex "security" "MX lookup"
17472 .cindex "DNS" "DNSSEC"
17473 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17474 the dnssec request bit set.
17475 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17477 .option dnssec_require_domains routers "domain list&!!" unset
17478 .cindex "MX record" "security"
17479 .cindex "DNSSEC" "MX lookup"
17480 .cindex "security" "MX lookup"
17481 .cindex "DNS" "DNSSEC"
17482 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17483 the dnssec request bit set. Any returns not having the Authenticated Data bit
17484 (AD bit) set will be ignored and logged as a host-lookup failure.
17485 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17488 .option domains routers&!? "domain list&!!" unset
17489 .cindex "router" "restricting to specific domains"
17490 .vindex "&$domain_data$&"
17491 If this option is set, the router is skipped unless the current domain matches
17492 the list. If the match is achieved by means of a file lookup, the data that the
17493 lookup returned for the domain is placed in &$domain_data$& for use in string
17494 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17495 a list of the order in which preconditions are evaluated.
17499 .option driver routers string unset
17500 This option must always be set. It specifies which of the available routers is
17504 .option dsn_lasthop routers boolean false
17505 .cindex "DSN" "success"
17506 .cindex "Delivery Status Notification" "success"
17507 If this option is set true, and extended DSN (RFC3461) processing is in effect,
17508 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
17509 instead send a success DSN as if the next hop does not support DSN.
17510 Not effective on redirect routers.
17514 .option errors_to routers string&!! unset
17515 .cindex "envelope sender"
17516 .cindex "router" "changing address for errors"
17517 If a router successfully handles an address, it may assign the address to a
17518 transport for delivery or it may generate child addresses. In both cases, if
17519 there is a delivery problem during later processing, the resulting bounce
17520 message is sent to the address that results from expanding this string,
17521 provided that the address verifies successfully. The &%errors_to%& option is
17522 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
17524 The &%errors_to%& setting associated with an address can be overridden if it
17525 subsequently passes through other routers that have their own &%errors_to%&
17526 settings, or if the message is delivered by a transport with a &%return_path%&
17529 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
17530 the expansion fails to verify, the errors address associated with the incoming
17531 address is used. At top level, this is the envelope sender. A non-forced
17532 expansion failure causes delivery to be deferred.
17534 If an address for which &%errors_to%& has been set ends up being delivered over
17535 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17536 any bounces that are generated by other MTAs on the delivery route are also
17537 sent there. You can set &%errors_to%& to the empty string by either of these
17543 An expansion item that yields an empty string has the same effect. If you do
17544 this, a locally detected delivery error for addresses processed by this router
17545 no longer gives rise to a bounce message; the error is discarded. If the
17546 address is delivered to a remote host, the return path is set to &`<>`&, unless
17547 overridden by the &%return_path%& option on the transport.
17549 .vindex "&$address_data$&"
17550 If for some reason you want to discard local errors, but use a non-empty
17551 MAIL command for remote delivery, you can preserve the original return
17552 path in &$address_data$& in the router, and reinstate it in the transport by
17553 setting &%return_path%&.
17555 The most common use of &%errors_to%& is to direct mailing list bounces to the
17556 manager of the list, as described in section &<<SECTmailinglists>>&, or to
17557 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
17561 .option expn routers&!? boolean true
17562 .cindex "address" "testing"
17563 .cindex "testing" "addresses"
17564 .cindex "EXPN" "router skipping"
17565 .cindex "router" "skipping for EXPN"
17566 If this option is turned off, the router is skipped when testing an address
17567 as a result of processing an SMTP EXPN command. You might, for example,
17568 want to turn it off on a router for users' &_.forward_& files, while leaving it
17569 on for the system alias file.
17570 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17573 The use of the SMTP EXPN command is controlled by an ACL (see chapter
17574 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
17575 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
17579 .option fail_verify routers boolean false
17580 .cindex "router" "forcing verification failure"
17581 Setting this option has the effect of setting both &%fail_verify_sender%& and
17582 &%fail_verify_recipient%& to the same value.
17586 .option fail_verify_recipient routers boolean false
17587 If this option is true and an address is accepted by this router when
17588 verifying a recipient, verification fails.
17592 .option fail_verify_sender routers boolean false
17593 If this option is true and an address is accepted by this router when
17594 verifying a sender, verification fails.
17598 .option fallback_hosts routers "string list" unset
17599 .cindex "router" "fallback hosts"
17600 .cindex "fallback" "hosts specified on router"
17601 String expansion is not applied to this option. The argument must be a
17602 colon-separated list of host names or IP addresses. The list separator can be
17603 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
17604 each name or address. In fact, the format of each item is exactly the same as
17605 defined for the list of hosts in a &(manualroute)& router (see section
17606 &<<SECTformatonehostitem>>&).
17608 If a router queues an address for a remote transport, this host list is
17609 associated with the address, and used instead of the transport's fallback host
17610 list. If &%hosts_randomize%& is set on the transport, the order of the list is
17611 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
17612 transport for further details.
17615 .option group routers string&!! "see below"
17616 .cindex "gid (group id)" "local delivery"
17617 .cindex "local transports" "uid and gid"
17618 .cindex "transport" "local"
17619 .cindex "router" "setting group"
17620 When a router queues an address for a transport, and the transport does not
17621 specify a group, the group given here is used when running the delivery
17623 The group may be specified numerically or by name. If expansion fails, the
17624 error is logged and delivery is deferred.
17625 The default is unset, unless &%check_local_user%& is set, when the default
17626 is taken from the password information. See also &%initgroups%& and &%user%&
17627 and the discussion in chapter &<<CHAPenvironment>>&.
17631 .option headers_add routers list&!! unset
17632 .cindex "header lines" "adding"
17633 .cindex "router" "adding header lines"
17634 This option specifies a list of text headers,
17635 newline-separated (by default, changeable in the usual way),
17636 that is associated with any addresses that are accepted by the router.
17637 Each item is separately expanded, at routing time. However, this
17638 option has no effect when an address is just being verified. The way in which
17639 the text is used to add header lines at transport time is described in section
17640 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
17641 message is in the process of being transported. This means that references to
17642 header lines in string expansions in the transport's configuration do not
17643 &"see"& the added header lines.
17645 The &%headers_add%& option is expanded after &%errors_to%&, but before
17646 &%headers_remove%& and &%transport%&. If an item is empty, or if
17647 an item expansion is forced to fail, the item has no effect. Other expansion
17648 failures are treated as configuration errors.
17650 Unlike most options, &%headers_add%& can be specified multiple times
17651 for a router; all listed headers are added.
17653 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
17654 router that has the &%one_time%& option set.
17656 .cindex "duplicate addresses"
17657 .oindex "&%unseen%&"
17658 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17659 additions are deleted when the address is passed on to subsequent routers.
17660 For a &%redirect%& router, if a generated address is the same as the incoming
17661 address, this can lead to duplicate addresses with different header
17662 modifications. Exim does not do duplicate deliveries (except, in certain
17663 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
17664 which of the duplicates is discarded, so this ambiguous situation should be
17665 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
17669 .option headers_remove routers list&!! unset
17670 .cindex "header lines" "removing"
17671 .cindex "router" "removing header lines"
17672 This option specifies a list of text headers,
17673 colon-separated (by default, changeable in the usual way),
17674 that is associated with any addresses that are accepted by the router.
17675 Each item is separately expanded, at routing time. However, this
17676 option has no effect when an address is just being verified. The way in which
17677 the text is used to remove header lines at transport time is described in
17678 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
17679 the message is in the process of being transported. This means that references
17680 to header lines in string expansions in the transport's configuration still
17681 &"see"& the original header lines.
17683 The &%headers_remove%& option is expanded after &%errors_to%& and
17684 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
17685 the item has no effect. Other expansion failures are treated as configuration
17688 Unlike most options, &%headers_remove%& can be specified multiple times
17689 for a router; all listed headers are removed.
17691 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
17692 router that has the &%one_time%& option set.
17694 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17695 removal requests are deleted when the address is passed on to subsequent
17696 routers, and this can lead to problems with duplicates -- see the similar
17697 warning for &%headers_add%& above.
17699 &*Warning 3*&: Because of the separate expansion of the list items,
17700 items that contain a list separator must have it doubled.
17701 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
17705 .option ignore_target_hosts routers "host list&!!" unset
17706 .cindex "IP address" "discarding"
17707 .cindex "router" "discarding IP addresses"
17708 Although this option is a host list, it should normally contain IP address
17709 entries rather than names. If any host that is looked up by the router has an
17710 IP address that matches an item in this list, Exim behaves as if that IP
17711 address did not exist. This option allows you to cope with rogue DNS entries
17714 remote.domain.example. A 127.0.0.1
17718 ignore_target_hosts = 127.0.0.1
17720 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17721 discarded in this way, the router declines. In a conventional configuration, an
17722 attempt to mail to such a domain would normally provoke the &"unrouteable
17723 domain"& error, and an attempt to verify an address in the domain would fail.
17724 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17725 router declines if presented with one of the listed addresses.
17727 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17728 means of the first or the second of the following settings, respectively:
17730 ignore_target_hosts = 0.0.0.0/0
17731 ignore_target_hosts = <; 0::0/0
17733 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17734 in the second line matches all IPv6 addresses.
17736 This option may also be useful for ignoring link-local and site-local IPv6
17737 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17738 is expanded before use as a list, it is possible to make it dependent on the
17739 domain that is being routed.
17741 .vindex "&$host_address$&"
17742 During its expansion, &$host_address$& is set to the IP address that is being
17745 .option initgroups routers boolean false
17746 .cindex "additional groups"
17747 .cindex "groups" "additional"
17748 .cindex "local transports" "uid and gid"
17749 .cindex "transport" "local"
17750 If the router queues an address for a transport, and this option is true, and
17751 the uid supplied by the router is not overridden by the transport, the
17752 &[initgroups()]& function is called when running the transport to ensure that
17753 any additional groups associated with the uid are set up. See also &%group%&
17754 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17758 .option local_part_prefix routers&!? "string list" unset
17759 .cindex "router" "prefix for local part"
17760 .cindex "prefix" "for local part, used in router"
17761 If this option is set, the router is skipped unless the local part starts with
17762 one of the given strings, or &%local_part_prefix_optional%& is true. See
17763 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17766 The list is scanned from left to right, and the first prefix that matches is
17767 used. A limited form of wildcard is available; if the prefix begins with an
17768 asterisk, it matches the longest possible sequence of arbitrary characters at
17769 the start of the local part. An asterisk should therefore always be followed by
17770 some character that does not occur in normal local parts.
17771 .cindex "multiple mailboxes"
17772 .cindex "mailbox" "multiple"
17773 Wildcarding can be used to set up multiple user mailboxes, as described in
17774 section &<<SECTmulbox>>&.
17776 .vindex "&$local_part$&"
17777 .vindex "&$local_part_prefix$&"
17778 During the testing of the &%local_parts%& option, and while the router is
17779 running, the prefix is removed from the local part, and is available in the
17780 expansion variable &$local_part_prefix$&. When a message is being delivered, if
17781 the router accepts the address, this remains true during subsequent delivery by
17782 a transport. In particular, the local part that is transmitted in the RCPT
17783 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
17784 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
17785 the relevant transport.
17787 When an address is being verified, &%local_part_prefix%& affects only the
17788 behaviour of the router. If the callout feature of verification is in use, this
17789 means that the full address, including the prefix, will be used during the
17792 The prefix facility is commonly used to handle local parts of the form
17793 &%owner-something%&. Another common use is to support local parts of the form
17794 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
17795 to tell a user their forwarding is broken &-- by placing a router like this one
17796 immediately before the router that handles &_.forward_& files:
17800 local_part_prefix = real-
17802 transport = local_delivery
17804 For security, it would probably be a good idea to restrict the use of this
17805 router to locally-generated messages, using a condition such as this:
17807 condition = ${if match {$sender_host_address}\
17808 {\N^(|127\.0\.0\.1)$\N}}
17811 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
17812 both conditions must be met if not optional. Care must be taken if wildcards
17813 are used in both a prefix and a suffix on the same router. Different
17814 separator characters must be used to avoid ambiguity.
17817 .option local_part_prefix_optional routers boolean false
17818 See &%local_part_prefix%& above.
17822 .option local_part_suffix routers&!? "string list" unset
17823 .cindex "router" "suffix for local part"
17824 .cindex "suffix for local part" "used in router"
17825 This option operates in the same way as &%local_part_prefix%&, except that the
17826 local part must end (rather than start) with the given string, the
17827 &%local_part_suffix_optional%& option determines whether the suffix is
17828 mandatory, and the wildcard * character, if present, must be the last
17829 character of the suffix. This option facility is commonly used to handle local
17830 parts of the form &%something-request%& and multiple user mailboxes of the form
17834 .option local_part_suffix_optional routers boolean false
17835 See &%local_part_suffix%& above.
17839 .option local_parts routers&!? "local part list&!!" unset
17840 .cindex "router" "restricting to specific local parts"
17841 .cindex "local part" "checking in router"
17842 The router is run only if the local part of the address matches the list.
17843 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17845 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
17846 string is expanded, it is possible to make it depend on the domain, for
17849 local_parts = dbm;/usr/local/specials/$domain
17851 .vindex "&$local_part_data$&"
17852 If the match is achieved by a lookup, the data that the lookup returned
17853 for the local part is placed in the variable &$local_part_data$& for use in
17854 expansions of the router's private options. You might use this option, for
17855 example, if you have a large number of local virtual domains, and you want to
17856 send all postmaster mail to the same place without having to set up an alias in
17857 each virtual domain:
17861 local_parts = postmaster
17862 data = postmaster@real.domain.example
17866 .option log_as_local routers boolean "see below"
17867 .cindex "log" "delivery line"
17868 .cindex "delivery" "log line format"
17869 Exim has two logging styles for delivery, the idea being to make local
17870 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17871 recipient address is given just as the local part, without a domain. The use of
17872 this style is controlled by this option. It defaults to true for the &(accept)&
17873 router, and false for all the others. This option applies only when a
17874 router assigns an address to a transport. It has no effect on routers that
17875 redirect addresses.
17879 .option more routers boolean&!! true
17880 The result of string expansion for this option must be a valid boolean value,
17881 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17882 result causes an error, and delivery is deferred. If the expansion is forced to
17883 fail, the default value for the option (true) is used. Other failures cause
17884 delivery to be deferred.
17886 If this option is set false, and the router declines to handle the address, no
17887 further routers are tried, routing fails, and the address is bounced.
17889 However, if the router explicitly passes an address to the following router by
17890 means of the setting
17894 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17895 does not affect the behaviour if one of the precondition tests fails. In that
17896 case, the address is always passed to the next router.
17898 Note that &%address_data%& is not considered to be a precondition. If its
17899 expansion is forced to fail, the router declines, and the value of &%more%&
17900 controls what happens next.
17903 .option pass_on_timeout routers boolean false
17904 .cindex "timeout" "of router"
17905 .cindex "router" "timeout"
17906 If a router times out during a host lookup, it normally causes deferral of the
17907 address. If &%pass_on_timeout%& is set, the address is passed on to the next
17908 router, overriding &%no_more%&. This may be helpful for systems that are
17909 intermittently connected to the Internet, or those that want to pass to a smart
17910 host any messages that cannot immediately be delivered.
17912 There are occasional other temporary errors that can occur while doing DNS
17913 lookups. They are treated in the same way as a timeout, and this option
17914 applies to all of them.
17918 .option pass_router routers string unset
17919 .cindex "router" "go to after &""pass""&"
17920 Routers that recognize the generic &%self%& option (&(dnslookup)&,
17921 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
17922 routing to continue, and overriding a false setting of &%more%&. When one of
17923 these routers returns &"pass"&, the address is normally handed on to the next
17924 router in sequence. This can be changed by setting &%pass_router%& to the name
17925 of another router. However (unlike &%redirect_router%&) the named router must
17926 be below the current router, to avoid loops. Note that this option applies only
17927 to the special case of &"pass"&. It does not apply when a router returns
17928 &"decline"& because it cannot handle an address.
17932 .option redirect_router routers string unset
17933 .cindex "router" "start at after redirection"
17934 Sometimes an administrator knows that it is pointless to reprocess addresses
17935 generated from alias or forward files with the same router again. For
17936 example, if an alias file translates real names into login ids there is no
17937 point searching the alias file a second time, especially if it is a large file.
17939 The &%redirect_router%& option can be set to the name of any router instance.
17940 It causes the routing of any generated addresses to start at the named router
17941 instead of at the first router. This option has no effect if the router in
17942 which it is set does not generate new addresses.
17946 .option require_files routers&!? "string list&!!" unset
17947 .cindex "file" "requiring for router"
17948 .cindex "router" "requiring file existence"
17949 This option provides a general mechanism for predicating the running of a
17950 router on the existence or non-existence of certain files or directories.
17951 Before running a router, as one of its precondition tests, Exim works its way
17952 through the &%require_files%& list, expanding each item separately.
17954 Because the list is split before expansion, any colons in expansion items must
17955 be doubled, or the facility for using a different list separator must be used.
17956 If any expansion is forced to fail, the item is ignored. Other expansion
17957 failures cause routing of the address to be deferred.
17959 If any expanded string is empty, it is ignored. Otherwise, except as described
17960 below, each string must be a fully qualified file path, optionally preceded by
17961 &"!"&. The paths are passed to the &[stat()]& function to test for the
17962 existence of the files or directories. The router is skipped if any paths not
17963 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
17966 If &[stat()]& cannot determine whether a file exists or not, delivery of
17967 the message is deferred. This can happen when NFS-mounted filesystems are
17970 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
17971 options, so you cannot use it to check for the existence of a file in which to
17972 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
17973 full list of the order in which preconditions are evaluated.) However, as
17974 these options are all expanded, you can use the &%exists%& expansion condition
17975 to make such tests. The &%require_files%& option is intended for checking files
17976 that the router may be going to use internally, or which are needed by a
17977 transport (for example &_.procmailrc_&).
17979 During delivery, the &[stat()]& function is run as root, but there is a
17980 facility for some checking of the accessibility of a file by another user.
17981 This is not a proper permissions check, but just a &"rough"& check that
17982 operates as follows:
17984 If an item in a &%require_files%& list does not contain any forward slash
17985 characters, it is taken to be the user (and optional group, separated by a
17986 comma) to be checked for subsequent files in the list. If no group is specified
17987 but the user is specified symbolically, the gid associated with the uid is
17990 require_files = mail:/some/file
17991 require_files = $local_part:$home/.procmailrc
17993 If a user or group name in a &%require_files%& list does not exist, the
17994 &%require_files%& condition fails.
17996 Exim performs the check by scanning along the components of the file path, and
17997 checking the access for the given uid and gid. It checks for &"x"& access on
17998 directories, and &"r"& access on the final file. Note that this means that file
17999 access control lists, if the operating system has them, are ignored.
18001 &*Warning 1*&: When the router is being run to verify addresses for an
18002 incoming SMTP message, Exim is not running as root, but under its own uid. This
18003 may affect the result of a &%require_files%& check. In particular, &[stat()]&
18004 may yield the error EACCES (&"Permission denied"&). This means that the Exim
18005 user is not permitted to read one of the directories on the file's path.
18007 &*Warning 2*&: Even when Exim is running as root while delivering a message,
18008 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
18009 without root access. In this case, if a check for access by a particular user
18010 is requested, Exim creates a subprocess that runs as that user, and tries the
18011 check again in that process.
18013 The default action for handling an unresolved EACCES is to consider it to
18014 be caused by a configuration error, and routing is deferred because the
18015 existence or non-existence of the file cannot be determined. However, in some
18016 circumstances it may be desirable to treat this condition as if the file did
18017 not exist. If the file name (or the exclamation mark that precedes the file
18018 name for non-existence) is preceded by a plus sign, the EACCES error is treated
18019 as if the file did not exist. For example:
18021 require_files = +/some/file
18023 If the router is not an essential part of verification (for example, it
18024 handles users' &_.forward_& files), another solution is to set the &%verify%&
18025 option false so that the router is skipped when verifying.
18029 .option retry_use_local_part routers boolean "see below"
18030 .cindex "hints database" "retry keys"
18031 .cindex "local part" "in retry keys"
18032 When a delivery suffers a temporary routing failure, a retry record is created
18033 in Exim's hints database. For addresses whose routing depends only on the
18034 domain, the key for the retry record should not involve the local part, but for
18035 other addresses, both the domain and the local part should be included.
18036 Usually, remote routing is of the former kind, and local routing is of the
18039 This option controls whether the local part is used to form the key for retry
18040 hints for addresses that suffer temporary errors while being handled by this
18041 router. The default value is true for any router that has &%check_local_user%&
18042 set, and false otherwise. Note that this option does not apply to hints keys
18043 for transport delays; they are controlled by a generic transport option of the
18046 The setting of &%retry_use_local_part%& applies only to the router on which it
18047 appears. If the router generates child addresses, they are routed
18048 independently; this setting does not become attached to them.
18052 .option router_home_directory routers string&!! unset
18053 .cindex "router" "home directory for"
18054 .cindex "home directory" "for router"
18056 This option sets a home directory for use while the router is running. (Compare
18057 &%transport_home_directory%&, which sets a home directory for later
18058 transporting.) In particular, if used on a &(redirect)& router, this option
18059 sets a value for &$home$& while a filter is running. The value is expanded;
18060 forced expansion failure causes the option to be ignored &-- other failures
18061 cause the router to defer.
18063 Expansion of &%router_home_directory%& happens immediately after the
18064 &%check_local_user%& test (if configured), before any further expansions take
18066 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18068 While the router is running, &%router_home_directory%& overrides the value of
18069 &$home$& that came from &%check_local_user%&.
18071 When a router accepts an address and assigns it to a local transport (including
18072 the cases when a &(redirect)& router generates a pipe, file, or autoreply
18073 delivery), the home directory setting for the transport is taken from the first
18074 of these values that is set:
18077 The &%home_directory%& option on the transport;
18079 The &%transport_home_directory%& option on the router;
18081 The password data if &%check_local_user%& is set on the router;
18083 The &%router_home_directory%& option on the router.
18086 In other words, &%router_home_directory%& overrides the password data for the
18087 router, but not for the transport.
18091 .option self routers string freeze
18092 .cindex "MX record" "pointing to local host"
18093 .cindex "local host" "MX pointing to"
18094 This option applies to those routers that use a recipient address to find a
18095 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
18096 and &(manualroute)& routers.
18097 Certain configurations of the &(queryprogram)& router can also specify a list
18099 Usually such routers are configured to send the message to a remote host via an
18100 &(smtp)& transport. The &%self%& option specifies what happens when the first
18101 host on the list turns out to be the local host.
18102 The way in which Exim checks for the local host is described in section
18103 &<<SECTreclocipadd>>&.
18105 Normally this situation indicates either an error in Exim's configuration (for
18106 example, the router should be configured not to process this domain), or an
18107 error in the DNS (for example, the MX should not point to this host). For this
18108 reason, the default action is to log the incident, defer the address, and
18109 freeze the message. The following alternatives are provided for use in special
18114 Delivery of the message is tried again later, but the message is not frozen.
18116 .vitem "&%reroute%&: <&'domain'&>"
18117 The domain is changed to the given domain, and the address is passed back to
18118 be reprocessed by the routers. No rewriting of headers takes place. This
18119 behaviour is essentially a redirection.
18121 .vitem "&%reroute: rewrite:%& <&'domain'&>"
18122 The domain is changed to the given domain, and the address is passed back to be
18123 reprocessed by the routers. Any headers that contain the original domain are
18128 .vindex "&$self_hostname$&"
18129 The router passes the address to the next router, or to the router named in the
18130 &%pass_router%& option if it is set. This overrides &%no_more%&. During
18131 subsequent routing and delivery, the variable &$self_hostname$& contains the
18132 name of the local host that the router encountered. This can be used to
18133 distinguish between different cases for hosts with multiple names. The
18139 ensures that only those addresses that routed to the local host are passed on.
18140 Without &%no_more%&, addresses that were declined for other reasons would also
18141 be passed to the next router.
18144 Delivery fails and an error report is generated.
18147 .cindex "local host" "sending to"
18148 The anomaly is ignored and the address is queued for the transport. This
18149 setting should be used with extreme caution. For an &(smtp)& transport, it
18150 makes sense only in cases where the program that is listening on the SMTP port
18151 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18152 different configuration file that handles the domain in another way.
18157 .option senders routers&!? "address list&!!" unset
18158 .cindex "router" "checking senders"
18159 If this option is set, the router is skipped unless the message's sender
18160 address matches something on the list.
18161 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18164 There are issues concerning verification when the running of routers is
18165 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18166 setting, it sets the sender to the null string. When using the &%-bt%& option
18167 to check a configuration file, it is necessary also to use the &%-f%& option to
18168 set an appropriate sender. For incoming mail, the sender is unset when
18169 verifying the sender, but is available when verifying any recipients. If the
18170 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18174 .option translate_ip_address routers string&!! unset
18175 .cindex "IP address" "translating"
18176 .cindex "packet radio"
18177 .cindex "router" "IP address translation"
18178 There exist some rare networking situations (for example, packet radio) where
18179 it is helpful to be able to translate IP addresses generated by normal routing
18180 mechanisms into other IP addresses, thus performing a kind of manual IP
18181 routing. This should be done only if the normal IP routing of the TCP/IP stack
18182 is inadequate or broken. Because this is an extremely uncommon requirement, the
18183 code to support this option is not included in the Exim binary unless
18184 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18186 .vindex "&$host_address$&"
18187 The &%translate_ip_address%& string is expanded for every IP address generated
18188 by the router, with the generated address set in &$host_address$&. If the
18189 expansion is forced to fail, no action is taken.
18190 For any other expansion error, delivery of the message is deferred.
18191 If the result of the expansion is an IP address, that replaces the original
18192 address; otherwise the result is assumed to be a host name &-- this is looked
18193 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18194 produce one or more replacement IP addresses. For example, to subvert all IP
18195 addresses in some specific networks, this could be added to a router:
18197 translate_ip_address = \
18198 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18201 The file would contain lines like
18203 10.2.3.128/26 some.host
18204 10.8.4.34/26 10.44.8.15
18206 You should not make use of this facility unless you really understand what you
18211 .option transport routers string&!! unset
18212 This option specifies the transport to be used when a router accepts an address
18213 and sets it up for delivery. A transport is never needed if a router is used
18214 only for verification. The value of the option is expanded at routing time,
18215 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18216 and result must be the name of one of the configured transports. If it is not,
18217 delivery is deferred.
18219 The &%transport%& option is not used by the &(redirect)& router, but it does
18220 have some private options that set up transports for pipe and file deliveries
18221 (see chapter &<<CHAPredirect>>&).
18225 .option transport_current_directory routers string&!! unset
18226 .cindex "current directory for local transport"
18227 This option associates a current directory with any address that is routed
18228 to a local transport. This can happen either because a transport is
18229 explicitly configured for the router, or because it generates a delivery to a
18230 file or a pipe. During the delivery process (that is, at transport time), this
18231 option string is expanded and is set as the current directory, unless
18232 overridden by a setting on the transport.
18233 If the expansion fails for any reason, including forced failure, an error is
18234 logged, and delivery is deferred.
18235 See chapter &<<CHAPenvironment>>& for details of the local delivery
18241 .option transport_home_directory routers string&!! "see below"
18242 .cindex "home directory" "for local transport"
18243 This option associates a home directory with any address that is routed to a
18244 local transport. This can happen either because a transport is explicitly
18245 configured for the router, or because it generates a delivery to a file or a
18246 pipe. During the delivery process (that is, at transport time), the option
18247 string is expanded and is set as the home directory, unless overridden by a
18248 setting of &%home_directory%& on the transport.
18249 If the expansion fails for any reason, including forced failure, an error is
18250 logged, and delivery is deferred.
18252 If the transport does not specify a home directory, and
18253 &%transport_home_directory%& is not set for the router, the home directory for
18254 the transport is taken from the password data if &%check_local_user%& is set for
18255 the router. Otherwise it is taken from &%router_home_directory%& if that option
18256 is set; if not, no home directory is set for the transport.
18258 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18264 .option unseen routers boolean&!! false
18265 .cindex "router" "carrying on after success"
18266 The result of string expansion for this option must be a valid boolean value,
18267 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18268 result causes an error, and delivery is deferred. If the expansion is forced to
18269 fail, the default value for the option (false) is used. Other failures cause
18270 delivery to be deferred.
18272 When this option is set true, routing does not cease if the router accepts the
18273 address. Instead, a copy of the incoming address is passed to the next router,
18274 overriding a false setting of &%more%&. There is little point in setting
18275 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18276 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18277 sometimes true and sometimes false).
18279 .cindex "copy of message (&%unseen%& option)"
18280 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18281 qualifier in filter files. It can be used to cause copies of messages to be
18282 delivered to some other destination, while also carrying out a normal delivery.
18283 In effect, the current address is made into a &"parent"& that has two children
18284 &-- one that is delivered as specified by this router, and a clone that goes on
18285 to be routed further. For this reason, &%unseen%& may not be combined with the
18286 &%one_time%& option in a &(redirect)& router.
18288 &*Warning*&: Header lines added to the address (or specified for removal) by
18289 this router or by previous routers affect the &"unseen"& copy of the message
18290 only. The clone that continues to be processed by further routers starts with
18291 no added headers and none specified for removal. For a &%redirect%& router, if
18292 a generated address is the same as the incoming address, this can lead to
18293 duplicate addresses with different header modifications. Exim does not do
18294 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18295 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18296 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18297 &%redirect%& router may be of help.
18299 Unlike the handling of header modifications, any data that was set by the
18300 &%address_data%& option in the current or previous routers &'is'& passed on to
18301 subsequent routers.
18304 .option user routers string&!! "see below"
18305 .cindex "uid (user id)" "local delivery"
18306 .cindex "local transports" "uid and gid"
18307 .cindex "transport" "local"
18308 .cindex "router" "user for filter processing"
18309 .cindex "filter" "user for processing"
18310 When a router queues an address for a transport, and the transport does not
18311 specify a user, the user given here is used when running the delivery process.
18312 The user may be specified numerically or by name. If expansion fails, the
18313 error is logged and delivery is deferred.
18314 This user is also used by the &(redirect)& router when running a filter file.
18315 The default is unset, except when &%check_local_user%& is set. In this case,
18316 the default is taken from the password information. If the user is specified as
18317 a name, and &%group%& is not set, the group associated with the user is used.
18318 See also &%initgroups%& and &%group%& and the discussion in chapter
18319 &<<CHAPenvironment>>&.
18323 .option verify routers&!? boolean true
18324 Setting this option has the effect of setting &%verify_sender%& and
18325 &%verify_recipient%& to the same value.
18328 .option verify_only routers&!? boolean false
18329 .cindex "EXPN" "with &%verify_only%&"
18331 .cindex "router" "used only when verifying"
18332 If this option is set, the router is used only when verifying an address,
18333 delivering in cutthrough mode or
18334 testing with the &%-bv%& option, not when actually doing a delivery, testing
18335 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18336 restricted to verifying only senders or recipients by means of
18337 &%verify_sender%& and &%verify_recipient%&.
18339 &*Warning*&: When the router is being run to verify addresses for an incoming
18340 SMTP message, Exim is not running as root, but under its own uid. If the router
18341 accesses any files, you need to make sure that they are accessible to the Exim
18345 .option verify_recipient routers&!? boolean true
18346 If this option is false, the router is skipped when verifying recipient
18348 delivering in cutthrough mode
18349 or testing recipient verification using &%-bv%&.
18350 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18352 See also the &$verify_mode$& variable.
18355 .option verify_sender routers&!? boolean true
18356 If this option is false, the router is skipped when verifying sender addresses
18357 or testing sender verification using &%-bvs%&.
18358 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18360 See also the &$verify_mode$& variable.
18361 .ecindex IIDgenoprou1
18362 .ecindex IIDgenoprou2
18369 . ////////////////////////////////////////////////////////////////////////////
18370 . ////////////////////////////////////////////////////////////////////////////
18372 .chapter "The accept router" "CHID4"
18373 .cindex "&(accept)& router"
18374 .cindex "routers" "&(accept)&"
18375 The &(accept)& router has no private options of its own. Unless it is being
18376 used purely for verification (see &%verify_only%&) a transport is required to
18377 be defined by the generic &%transport%& option. If the preconditions that are
18378 specified by generic options are met, the router accepts the address and queues
18379 it for the given transport. The most common use of this router is for setting
18380 up deliveries to local mailboxes. For example:
18384 domains = mydomain.example
18386 transport = local_delivery
18388 The &%domains%& condition in this example checks the domain of the address, and
18389 &%check_local_user%& checks that the local part is the login of a local user.
18390 When both preconditions are met, the &(accept)& router runs, and queues the
18391 address for the &(local_delivery)& transport.
18398 . ////////////////////////////////////////////////////////////////////////////
18399 . ////////////////////////////////////////////////////////////////////////////
18401 .chapter "The dnslookup router" "CHAPdnslookup"
18402 .scindex IIDdnsrou1 "&(dnslookup)& router"
18403 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18404 The &(dnslookup)& router looks up the hosts that handle mail for the
18405 recipient's domain in the DNS. A transport must always be set for this router,
18406 unless &%verify_only%& is set.
18408 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18409 SRV records. If none are found, or if SRV support is not configured,
18410 MX records are looked up. If no MX records exist, address records are sought.
18411 However, &%mx_domains%& can be set to disable the direct use of address
18414 MX records of equal priority are sorted by Exim into a random order. Exim then
18415 looks for address records for the host names obtained from MX or SRV records.
18416 When a host has more than one IP address, they are sorted into a random order,
18417 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
18418 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18419 generic option, the router declines.
18421 Unless they have the highest priority (lowest MX value), MX records that point
18422 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18423 are discarded, together with any other MX records of equal or lower priority.
18425 .cindex "MX record" "pointing to local host"
18426 .cindex "local host" "MX pointing to"
18427 .oindex "&%self%&" "in &(dnslookup)& router"
18428 If the host pointed to by the highest priority MX record, or looked up as an
18429 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18430 happens is controlled by the generic &%self%& option.
18433 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18434 There have been problems with DNS servers when SRV records are looked up.
18435 Some misbehaving servers return a DNS error or timeout when a non-existent
18436 SRV record is sought. Similar problems have in the past been reported for
18437 MX records. The global &%dns_again_means_nonexist%& option can help with this
18438 problem, but it is heavy-handed because it is a global option.
18440 For this reason, there are two options, &%srv_fail_domains%& and
18441 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18442 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18443 an attempt to look up an SRV or MX record causes one of these results, and the
18444 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18445 such record"&. In the case of an SRV lookup, this means that the router
18446 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18447 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18448 case routing fails.
18451 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18452 .cindex "&(dnslookup)& router" "declines"
18453 There are a few cases where a &(dnslookup)& router will decline to accept
18454 an address; if such a router is expected to handle "all remaining non-local
18455 domains", then it is important to set &%no_more%&.
18457 The router will defer rather than decline if the domain
18458 is found in the &%fail_defer_domains%& router option.
18460 Reasons for a &(dnslookup)& router to decline currently include:
18462 The domain does not exist in DNS
18464 The domain exists but the MX record's host part is just "."; this is a common
18465 convention (borrowed from SRV) used to indicate that there is no such service
18466 for this domain and to not fall back to trying A/AAAA records.
18468 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18470 MX record points to a non-existent host.
18472 MX record points to an IP address and the main section option
18473 &%allow_mx_to_ip%& is not set.
18475 MX records exist and point to valid hosts, but all hosts resolve only to
18476 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18478 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18479 &%dns_check_names_pattern%& for handling one variant of this)
18481 &%check_secondary_mx%& is set on this router but the local host can
18482 not be found in the MX records (see below)
18488 .section "Private options for dnslookup" "SECID118"
18489 .cindex "options" "&(dnslookup)& router"
18490 The private options for the &(dnslookup)& router are as follows:
18492 .option check_secondary_mx dnslookup boolean false
18493 .cindex "MX record" "checking for secondary"
18494 If this option is set, the router declines unless the local host is found in
18495 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18496 process domains for which the local host is a secondary mail exchanger
18497 differently to other domains. The way in which Exim decides whether a host is
18498 the local host is described in section &<<SECTreclocipadd>>&.
18501 .option check_srv dnslookup string&!! unset
18502 .cindex "SRV record" "enabling use of"
18503 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
18504 addition to MX and address records. The support is disabled by default. To
18505 enable SRV support, set the &%check_srv%& option to the name of the service
18506 required. For example,
18510 looks for SRV records that refer to the normal smtp service. The option is
18511 expanded, so the service name can vary from message to message or address
18512 to address. This might be helpful if SRV records are being used for a
18513 submission service. If the expansion is forced to fail, the &%check_srv%&
18514 option is ignored, and the router proceeds to look for MX records in the
18517 When the expansion succeeds, the router searches first for SRV records for
18518 the given service (it assumes TCP protocol). A single SRV record with a
18519 host name that consists of just a single dot indicates &"no such service for
18520 this domain"&; if this is encountered, the router declines. If other kinds of
18521 SRV record are found, they are used to construct a host list for delivery
18522 according to the rules of RFC 2782. MX records are not sought in this case.
18524 When no SRV records are found, MX records (and address records) are sought in
18525 the traditional way. In other words, SRV records take precedence over MX
18526 records, just as MX records take precedence over address records. Note that
18527 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
18528 defined it. It is apparently believed that MX records are sufficient for email
18529 and that SRV records should not be used for this purpose. However, SRV records
18530 have an additional &"weight"& feature which some people might find useful when
18531 trying to split an SMTP load between hosts of different power.
18533 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
18534 when there is a DNS lookup error.
18539 .option fail_defer_domains dnslookup "domain list&!!" unset
18540 .cindex "MX record" "not found"
18541 DNS lookups for domains matching &%fail_defer_domains%&
18542 which find no matching record will cause the router to defer
18543 rather than the default behaviour of decline.
18544 This maybe be useful for queueing messages for a newly created
18545 domain while the DNS configuration is not ready.
18546 However, it will result in any message with mistyped domains
18550 .option mx_domains dnslookup "domain list&!!" unset
18551 .cindex "MX record" "required to exist"
18552 .cindex "SRV record" "required to exist"
18553 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
18554 record in order to be recognized. (The name of this option could be improved.)
18555 For example, if all the mail hosts in &'fict.example'& are known to have MX
18556 records, except for those in &'discworld.fict.example'&, you could use this
18559 mx_domains = ! *.discworld.fict.example : *.fict.example
18561 This specifies that messages addressed to a domain that matches the list but
18562 has no MX record should be bounced immediately instead of being routed using
18563 the address record.
18566 .option mx_fail_domains dnslookup "domain list&!!" unset
18567 If the DNS lookup for MX records for one of the domains in this list causes a
18568 DNS lookup error, Exim behaves as if no MX records were found. See section
18569 &<<SECTprowitdnsloo>>& for more discussion.
18574 .option qualify_single dnslookup boolean true
18575 .cindex "DNS" "resolver options"
18576 .cindex "DNS" "qualifying single-component names"
18577 When this option is true, the resolver option RES_DEFNAMES is set for DNS
18578 lookups. Typically, but not standardly, this causes the resolver to qualify
18579 single-component names with the default domain. For example, on a machine
18580 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
18581 &'thesaurus.ref.example'& inside the resolver. For details of what your
18582 resolver actually does, consult your man pages for &'resolver'& and
18587 .option rewrite_headers dnslookup boolean true
18588 .cindex "rewriting" "header lines"
18589 .cindex "header lines" "rewriting"
18590 If the domain name in the address that is being processed is not fully
18591 qualified, it may be expanded to its full form by a DNS lookup. For example, if
18592 an address is specified as &'dormouse@teaparty'&, the domain might be
18593 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
18594 occur as a result of setting the &%widen_domains%& option. If
18595 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
18596 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
18597 header lines of the message are rewritten with the full domain name.
18599 This option should be turned off only when it is known that no message is
18600 ever going to be sent outside an environment where the abbreviation makes
18603 When an MX record is looked up in the DNS and matches a wildcard record, name
18604 servers normally return a record containing the name that has been looked up,
18605 making it impossible to detect whether a wildcard was present or not. However,
18606 some name servers have recently been seen to return the wildcard entry. If the
18607 name returned by a DNS lookup begins with an asterisk, it is not used for
18611 .option same_domain_copy_routing dnslookup boolean false
18612 .cindex "address" "copying routing"
18613 Addresses with the same domain are normally routed by the &(dnslookup)& router
18614 to the same list of hosts. However, this cannot be presumed, because the router
18615 options and preconditions may refer to the local part of the address. By
18616 default, therefore, Exim routes each address in a message independently. DNS
18617 servers run caches, so repeated DNS lookups are not normally expensive, and in
18618 any case, personal messages rarely have more than a few recipients.
18620 If you are running mailing lists with large numbers of subscribers at the same
18621 domain, and you are using a &(dnslookup)& router which is independent of the
18622 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18623 lookups for identical domains in one message. In this case, when &(dnslookup)&
18624 routes an address to a remote transport, any other unrouted addresses in the
18625 message that have the same domain are automatically given the same routing
18626 without processing them independently,
18627 provided the following conditions are met:
18630 No router that processed the address specified &%headers_add%& or
18631 &%headers_remove%&.
18633 The router did not change the address in any way, for example, by &"widening"&
18640 .option search_parents dnslookup boolean false
18641 .cindex "DNS" "resolver options"
18642 When this option is true, the resolver option RES_DNSRCH is set for DNS
18643 lookups. This is different from the &%qualify_single%& option in that it
18644 applies to domains containing dots. Typically, but not standardly, it causes
18645 the resolver to search for the name in the current domain and in parent
18646 domains. For example, on a machine in the &'fict.example'& domain, if looking
18647 up &'teaparty.wonderland'& failed, the resolver would try
18648 &'teaparty.wonderland.fict.example'&. For details of what your resolver
18649 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
18651 Setting this option true can cause problems in domains that have a wildcard MX
18652 record, because any domain that does not have its own MX record matches the
18657 .option srv_fail_domains dnslookup "domain list&!!" unset
18658 If the DNS lookup for SRV records for one of the domains in this list causes a
18659 DNS lookup error, Exim behaves as if no SRV records were found. See section
18660 &<<SECTprowitdnsloo>>& for more discussion.
18665 .option widen_domains dnslookup "string list" unset
18666 .cindex "domain" "partial; widening"
18667 If a DNS lookup fails and this option is set, each of its strings in turn is
18668 added onto the end of the domain, and the lookup is tried again. For example,
18671 widen_domains = fict.example:ref.example
18673 is set and a lookup of &'klingon.dictionary'& fails,
18674 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
18675 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
18676 and &%search_parents%& options can cause some widening to be undertaken inside
18677 the DNS resolver. &%widen_domains%& is not applied to sender addresses
18678 when verifying, unless &%rewrite_headers%& is false (not the default).
18681 .section "Effect of qualify_single and search_parents" "SECID119"
18682 When a domain from an envelope recipient is changed by the resolver as a result
18683 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
18684 corresponding address in the message's header lines unless &%rewrite_headers%&
18685 is set false. Exim then re-routes the address, using the full domain.
18687 These two options affect only the DNS lookup that takes place inside the router
18688 for the domain of the address that is being routed. They do not affect lookups
18689 such as that implied by
18693 that may happen while processing a router precondition before the router is
18694 entered. No widening ever takes place for these lookups.
18695 .ecindex IIDdnsrou1
18696 .ecindex IIDdnsrou2
18706 . ////////////////////////////////////////////////////////////////////////////
18707 . ////////////////////////////////////////////////////////////////////////////
18709 .chapter "The ipliteral router" "CHID5"
18710 .cindex "&(ipliteral)& router"
18711 .cindex "domain literal" "routing"
18712 .cindex "routers" "&(ipliteral)&"
18713 This router has no private options. Unless it is being used purely for
18714 verification (see &%verify_only%&) a transport is required to be defined by the
18715 generic &%transport%& option. The router accepts the address if its domain part
18716 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18717 router handles the address
18721 by setting up delivery to the host with that IP address. IPv4 domain literals
18722 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18723 are similar, but the address is preceded by &`ipv6:`&. For example:
18725 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18727 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18728 grounds that sooner or later somebody will try it.
18730 .oindex "&%self%&" "in &(ipliteral)& router"
18731 If the IP address matches something in &%ignore_target_hosts%&, the router
18732 declines. If an IP literal turns out to refer to the local host, the generic
18733 &%self%& option determines what happens.
18735 The RFCs require support for domain literals; however, their use is
18736 controversial in today's Internet. If you want to use this router, you must
18737 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18738 Exim will not recognize the domain literal syntax in addresses.
18742 . ////////////////////////////////////////////////////////////////////////////
18743 . ////////////////////////////////////////////////////////////////////////////
18745 .chapter "The iplookup router" "CHID6"
18746 .cindex "&(iplookup)& router"
18747 .cindex "routers" "&(iplookup)&"
18748 The &(iplookup)& router was written to fulfil a specific requirement in
18749 Cambridge University (which in fact no longer exists). For this reason, it is
18750 not included in the binary of Exim by default. If you want to include it, you
18753 ROUTER_IPLOOKUP=yes
18755 in your &_Local/Makefile_& configuration file.
18757 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18758 connection to one or more specific hosts. The host can then return the same or
18759 a different address &-- in effect rewriting the recipient address in the
18760 message's envelope. The new address is then passed on to subsequent routers. If
18761 this process fails, the address can be passed on to other routers, or delivery
18762 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18763 must not be specified for it.
18765 .cindex "options" "&(iplookup)& router"
18766 .option hosts iplookup string unset
18767 This option must be supplied. Its value is a colon-separated list of host
18768 names. The hosts are looked up using &[gethostbyname()]&
18769 (or &[getipnodebyname()]& when available)
18770 and are tried in order until one responds to the query. If none respond, what
18771 happens is controlled by &%optional%&.
18774 .option optional iplookup boolean false
18775 If &%optional%& is true, if no response is obtained from any host, the address
18776 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18777 delivery to the address is deferred.
18780 .option port iplookup integer 0
18781 .cindex "port" "&(iplookup)& router"
18782 This option must be supplied. It specifies the port number for the TCP or UDP
18786 .option protocol iplookup string udp
18787 This option can be set to &"udp"& or &"tcp"& to specify which of the two
18788 protocols is to be used.
18791 .option query iplookup string&!! "see below"
18792 This defines the content of the query that is sent to the remote hosts. The
18795 $local_part@$domain $local_part@$domain
18797 The repetition serves as a way of checking that a response is to the correct
18798 query in the default case (see &%response_pattern%& below).
18801 .option reroute iplookup string&!! unset
18802 If this option is not set, the rerouted address is precisely the byte string
18803 returned by the remote host, up to the first white space, if any. If set, the
18804 string is expanded to form the rerouted address. It can include parts matched
18805 in the response by &%response_pattern%& by means of numeric variables such as
18806 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
18807 whether or not a pattern is in use. In all cases, the rerouted address must end
18808 up in the form &'local_part@domain'&.
18811 .option response_pattern iplookup string unset
18812 This option can be set to a regular expression that is applied to the string
18813 returned from the remote host. If the pattern does not match the response, the
18814 router declines. If &%response_pattern%& is not set, no checking of the
18815 response is done, unless the query was defaulted, in which case there is a
18816 check that the text returned after the first white space is the original
18817 address. This checks that the answer that has been received is in response to
18818 the correct question. For example, if the response is just a new domain, the
18819 following could be used:
18821 response_pattern = ^([^@]+)$
18822 reroute = $local_part@$1
18825 .option timeout iplookup time 5s
18826 This specifies the amount of time to wait for a response from the remote
18827 machine. The same timeout is used for the &[connect()]& function for a TCP
18828 call. It does not apply to UDP.
18833 . ////////////////////////////////////////////////////////////////////////////
18834 . ////////////////////////////////////////////////////////////////////////////
18836 .chapter "The manualroute router" "CHID7"
18837 .scindex IIDmanrou1 "&(manualroute)& router"
18838 .scindex IIDmanrou2 "routers" "&(manualroute)&"
18839 .cindex "domain" "manually routing"
18840 The &(manualroute)& router is so-called because it provides a way of manually
18841 routing an address according to its domain. It is mainly used when you want to
18842 route addresses to remote hosts according to your own rules, bypassing the
18843 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18844 route to local transports, a facility that may be useful if you want to save
18845 messages for dial-in hosts in local files.
18847 The &(manualroute)& router compares a list of domain patterns with the domain
18848 it is trying to route. If there is no match, the router declines. Each pattern
18849 has associated with it a list of hosts and some other optional data, which may
18850 include a transport. The combination of a pattern and its data is called a
18851 &"routing rule"&. For patterns that do not have an associated transport, the
18852 generic &%transport%& option must specify a transport, unless the router is
18853 being used purely for verification (see &%verify_only%&).
18856 In the case of verification, matching the domain pattern is sufficient for the
18857 router to accept the address. When actually routing an address for delivery,
18858 an address that matches a domain pattern is queued for the associated
18859 transport. If the transport is not a local one, a host list must be associated
18860 with the pattern; IP addresses are looked up for the hosts, and these are
18861 passed to the transport along with the mail address. For local transports, a
18862 host list is optional. If it is present, it is passed in &$host$& as a single
18865 The list of routing rules can be provided as an inline string in
18866 &%route_list%&, or the data can be obtained by looking up the domain in a file
18867 or database by setting &%route_data%&. Only one of these settings may appear in
18868 any one instance of &(manualroute)&. The format of routing rules is described
18869 below, following the list of private options.
18872 .section "Private options for manualroute" "SECTprioptman"
18874 .cindex "options" "&(manualroute)& router"
18875 The private options for the &(manualroute)& router are as follows:
18877 .option host_all_ignored manualroute string defer
18878 See &%host_find_failed%&.
18880 .option host_find_failed manualroute string freeze
18881 This option controls what happens when &(manualroute)& tries to find an IP
18882 address for a host, and the host does not exist. The option can be set to one
18883 of the following values:
18892 The default (&"freeze"&) assumes that this state is a serious configuration
18893 error. The difference between &"pass"& and &"decline"& is that the former
18894 forces the address to be passed to the next router (or the router defined by
18897 overriding &%no_more%&, whereas the latter passes the address to the next
18898 router only if &%more%& is true.
18900 The value &"ignore"& causes Exim to completely ignore a host whose IP address
18901 cannot be found. If all the hosts in the list are ignored, the behaviour is
18902 controlled by the &%host_all_ignored%& option. This takes the same values
18903 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
18905 The &%host_find_failed%& option applies only to a definite &"does not exist"&
18906 state; if a host lookup gets a temporary error, delivery is deferred unless the
18907 generic &%pass_on_timeout%& option is set.
18910 .option hosts_randomize manualroute boolean false
18911 .cindex "randomized host list"
18912 .cindex "host" "list of; randomized"
18913 If this option is set, the order of the items in a host list in a routing rule
18914 is randomized each time the list is used, unless an option in the routing rule
18915 overrides (see below). Randomizing the order of a host list can be used to do
18916 crude load sharing. However, if more than one mail address is routed by the
18917 same router to the same host list, the host lists are considered to be the same
18918 (even though they may be randomized into different orders) for the purpose of
18919 deciding whether to batch the deliveries into a single SMTP transaction.
18921 When &%hosts_randomize%& is true, a host list may be split
18922 into groups whose order is separately randomized. This makes it possible to
18923 set up MX-like behaviour. The boundaries between groups are indicated by an
18924 item that is just &`+`& in the host list. For example:
18926 route_list = * host1:host2:host3:+:host4:host5
18928 The order of the first three hosts and the order of the last two hosts is
18929 randomized for each use, but the first three always end up before the last two.
18930 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
18931 randomized host list is passed to an &(smtp)& transport that also has
18932 &%hosts_randomize set%&, the list is not re-randomized.
18935 .option route_data manualroute string&!! unset
18936 If this option is set, it must expand to yield the data part of a routing rule.
18937 Typically, the expansion string includes a lookup based on the domain. For
18940 route_data = ${lookup{$domain}dbm{/etc/routes}}
18942 If the expansion is forced to fail, or the result is an empty string, the
18943 router declines. Other kinds of expansion failure cause delivery to be
18947 .option route_list manualroute "string list" unset
18948 This string is a list of routing rules, in the form defined below. Note that,
18949 unlike most string lists, the items are separated by semicolons. This is so
18950 that they may contain colon-separated host lists.
18953 .option same_domain_copy_routing manualroute boolean false
18954 .cindex "address" "copying routing"
18955 Addresses with the same domain are normally routed by the &(manualroute)&
18956 router to the same list of hosts. However, this cannot be presumed, because the
18957 router options and preconditions may refer to the local part of the address. By
18958 default, therefore, Exim routes each address in a message independently. DNS
18959 servers run caches, so repeated DNS lookups are not normally expensive, and in
18960 any case, personal messages rarely have more than a few recipients.
18962 If you are running mailing lists with large numbers of subscribers at the same
18963 domain, and you are using a &(manualroute)& router which is independent of the
18964 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18965 lookups for identical domains in one message. In this case, when
18966 &(manualroute)& routes an address to a remote transport, any other unrouted
18967 addresses in the message that have the same domain are automatically given the
18968 same routing without processing them independently. However, this is only done
18969 if &%headers_add%& and &%headers_remove%& are unset.
18974 .section "Routing rules in route_list" "SECID120"
18975 The value of &%route_list%& is a string consisting of a sequence of routing
18976 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
18977 entered as two semicolons. Alternatively, the list separator can be changed as
18978 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
18979 Empty rules are ignored. The format of each rule is
18981 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
18983 The following example contains two rules, each with a simple domain pattern and
18987 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
18988 thes.ref.example mail-3.ref.example:mail-4.ref.example
18990 The three parts of a rule are separated by white space. The pattern and the
18991 list of hosts can be enclosed in quotes if necessary, and if they are, the
18992 usual quoting rules apply. Each rule in a &%route_list%& must start with a
18993 single domain pattern, which is the only mandatory item in the rule. The
18994 pattern is in the same format as one item in a domain list (see section
18995 &<<SECTdomainlist>>&),
18996 except that it may not be the name of an interpolated file.
18997 That is, it may be wildcarded, or a regular expression, or a file or database
18998 lookup (with semicolons doubled, because of the use of semicolon as a separator
18999 in a &%route_list%&).
19001 The rules in &%route_list%& are searched in order until one of the patterns
19002 matches the domain that is being routed. The list of hosts and then options are
19003 then used as described below. If there is no match, the router declines. When
19004 &%route_list%& is set, &%route_data%& must not be set.
19008 .section "Routing rules in route_data" "SECID121"
19009 The use of &%route_list%& is convenient when there are only a small number of
19010 routing rules. For larger numbers, it is easier to use a file or database to
19011 hold the routing information, and use the &%route_data%& option instead.
19012 The value of &%route_data%& is a list of hosts, followed by (optional) options.
19013 Most commonly, &%route_data%& is set as a string that contains an
19014 expansion lookup. For example, suppose we place two routing rules in a file
19017 dict.ref.example: mail-1.ref.example:mail-2.ref.example
19018 thes.ref.example: mail-3.ref.example:mail-4.ref.example
19020 This data can be accessed by setting
19022 route_data = ${lookup{$domain}lsearch{/the/file/name}}
19024 Failure of the lookup results in an empty string, causing the router to
19025 decline. However, you do not have to use a lookup in &%route_data%&. The only
19026 requirement is that the result of expanding the string is a list of hosts,
19027 possibly followed by options, separated by white space. The list of hosts must
19028 be enclosed in quotes if it contains white space.
19033 .section "Format of the list of hosts" "SECID122"
19034 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
19035 always separately expanded before use. If the expansion fails, the router
19036 declines. The result of the expansion must be a colon-separated list of names
19037 and/or IP addresses, optionally also including ports. The format of each item
19038 in the list is described in the next section. The list separator can be changed
19039 as described in section &<<SECTlistconstruct>>&.
19041 If the list of hosts was obtained from a &%route_list%& item, the following
19042 variables are set during its expansion:
19045 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
19046 If the domain was matched against a regular expression, the numeric variables
19047 &$1$&, &$2$&, etc. may be set. For example:
19049 route_list = ^domain(\d+) host-$1.text.example
19052 &$0$& is always set to the entire domain.
19054 &$1$& is also set when partial matching is done in a file lookup.
19057 .vindex "&$value$&"
19058 If the pattern that matched the domain was a lookup item, the data that was
19059 looked up is available in the expansion variable &$value$&. For example:
19061 route_list = lsearch;;/some/file.routes $value
19065 Note the doubling of the semicolon in the pattern that is necessary because
19066 semicolon is the default route list separator.
19070 .section "Format of one host item" "SECTformatonehostitem"
19071 Each item in the list of hosts is either a host name or an IP address,
19072 optionally with an attached port number. When no port is given, an IP address
19073 is not enclosed in brackets. When a port is specified, it overrides the port
19074 specification on the transport. The port is separated from the name or address
19075 by a colon. This leads to some complications:
19078 Because colon is the default separator for the list of hosts, either
19079 the colon that specifies a port must be doubled, or the list separator must
19080 be changed. The following two examples have the same effect:
19082 route_list = * "host1.tld::1225 : host2.tld::1226"
19083 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
19086 When IPv6 addresses are involved, it gets worse, because they contain
19087 colons of their own. To make this case easier, it is permitted to
19088 enclose an IP address (either v4 or v6) in square brackets if a port
19089 number follows. For example:
19091 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
19095 .section "How the list of hosts is used" "SECThostshowused"
19096 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
19097 the hosts is tried, in the order specified, when carrying out the SMTP
19098 delivery. However, the order can be changed by setting the &%hosts_randomize%&
19099 option, either on the router (see section &<<SECTprioptman>>& above), or on the
19102 Hosts may be listed by name or by IP address. An unadorned name in the list of
19103 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
19104 interpreted as an indirection to a sublist of hosts obtained by looking up MX
19105 records in the DNS. For example:
19107 route_list = * x.y.z:p.q.r/MX:e.f.g
19109 If this feature is used with a port specifier, the port must come last. For
19112 route_list = * dom1.tld/mx::1225
19114 If the &%hosts_randomize%& option is set, the order of the items in the list is
19115 randomized before any lookups are done. Exim then scans the list; for any name
19116 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
19117 be an interface on the local host and the item is not the first in the list,
19118 Exim discards it and any subsequent items. If it is the first item, what
19119 happens is controlled by the
19120 .oindex "&%self%&" "in &(manualroute)& router"
19121 &%self%& option of the router.
19123 A name on the list that is followed by &`/MX`& is replaced with the list of
19124 hosts obtained by looking up MX records for the name. This is always a DNS
19125 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
19126 below) are not relevant here. The order of these hosts is determined by the
19127 preference values in the MX records, according to the usual rules. Because
19128 randomizing happens before the MX lookup, it does not affect the order that is
19129 defined by MX preferences.
19131 If the local host is present in the sublist obtained from MX records, but is
19132 not the most preferred host in that list, it and any equally or less
19133 preferred hosts are removed before the sublist is inserted into the main list.
19135 If the local host is the most preferred host in the MX list, what happens
19136 depends on where in the original list of hosts the &`/MX`& item appears. If it
19137 is not the first item (that is, there are previous hosts in the main list),
19138 Exim discards this name and any subsequent items in the main list.
19140 If the MX item is first in the list of hosts, and the local host is the
19141 most preferred host, what happens is controlled by the &%self%& option of the
19144 DNS failures when lookup up the MX records are treated in the same way as DNS
19145 failures when looking up IP addresses: &%pass_on_timeout%& and
19146 &%host_find_failed%& are used when relevant.
19148 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19149 whether obtained from an MX lookup or not.
19153 .section "How the options are used" "SECThowoptused"
19154 The options are a sequence of words; in practice no more than three are ever
19155 present. One of the words can be the name of a transport; this overrides the
19156 &%transport%& option on the router for this particular routing rule only. The
19157 other words (if present) control randomization of the list of hosts on a
19158 per-rule basis, and how the IP addresses of the hosts are to be found when
19159 routing to a remote transport. These options are as follows:
19162 &%randomize%&: randomize the order of the hosts in this list, overriding the
19163 setting of &%hosts_randomize%& for this routing rule only.
19165 &%no_randomize%&: do not randomize the order of the hosts in this list,
19166 overriding the setting of &%hosts_randomize%& for this routing rule only.
19168 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19169 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19170 also look in &_/etc/hosts_& or other sources of information.
19172 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19173 no address records are found. If there is a temporary DNS error (such as a
19174 timeout), delivery is deferred.
19179 route_list = domain1 host1:host2:host3 randomize bydns;\
19180 domain2 host4:host5
19182 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19183 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19184 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19185 or &[gethostbyname()]&, and the result of the lookup is the result of that
19188 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19189 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19190 instead of TRY_AGAIN. That is why the default action is to try a DNS
19191 lookup first. Only if that gives a definite &"no such host"& is the local
19196 If no IP address for a host can be found, what happens is controlled by the
19197 &%host_find_failed%& option.
19200 When an address is routed to a local transport, IP addresses are not looked up.
19201 The host list is passed to the transport in the &$host$& variable.
19205 .section "Manualroute examples" "SECID123"
19206 In some of the examples that follow, the presence of the &%remote_smtp%&
19207 transport, as defined in the default configuration file, is assumed:
19210 .cindex "smart host" "example router"
19211 The &(manualroute)& router can be used to forward all external mail to a
19212 &'smart host'&. If you have set up, in the main part of the configuration, a
19213 named domain list that contains your local domains, for example:
19215 domainlist local_domains = my.domain.example
19217 You can arrange for all other domains to be routed to a smart host by making
19218 your first router something like this:
19221 driver = manualroute
19222 domains = !+local_domains
19223 transport = remote_smtp
19224 route_list = * smarthost.ref.example
19226 This causes all non-local addresses to be sent to the single host
19227 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19228 they are tried in order
19229 (but you can use &%hosts_randomize%& to vary the order each time).
19230 Another way of configuring the same thing is this:
19233 driver = manualroute
19234 transport = remote_smtp
19235 route_list = !+local_domains smarthost.ref.example
19237 There is no difference in behaviour between these two routers as they stand.
19238 However, they behave differently if &%no_more%& is added to them. In the first
19239 example, the router is skipped if the domain does not match the &%domains%&
19240 precondition; the following router is always tried. If the router runs, it
19241 always matches the domain and so can never decline. Therefore, &%no_more%&
19242 would have no effect. In the second case, the router is never skipped; it
19243 always runs. However, if it doesn't match the domain, it declines. In this case
19244 &%no_more%& would prevent subsequent routers from running.
19247 .cindex "mail hub example"
19248 A &'mail hub'& is a host which receives mail for a number of domains via MX
19249 records in the DNS and delivers it via its own private routing mechanism. Often
19250 the final destinations are behind a firewall, with the mail hub being the one
19251 machine that can connect to machines both inside and outside the firewall. The
19252 &(manualroute)& router is usually used on a mail hub to route incoming messages
19253 to the correct hosts. For a small number of domains, the routing can be inline,
19254 using the &%route_list%& option, but for a larger number a file or database
19255 lookup is easier to manage.
19257 If the domain names are in fact the names of the machines to which the mail is
19258 to be sent by the mail hub, the configuration can be quite simple. For
19262 driver = manualroute
19263 transport = remote_smtp
19264 route_list = *.rhodes.tvs.example $domain
19266 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19267 whose names are the same as the mail domains. A similar approach can be taken
19268 if the host name can be obtained from the domain name by a string manipulation
19269 that the expansion facilities can handle. Otherwise, a lookup based on the
19270 domain can be used to find the host:
19273 driver = manualroute
19274 transport = remote_smtp
19275 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19277 The result of the lookup must be the name or IP address of the host (or
19278 hosts) to which the address is to be routed. If the lookup fails, the route
19279 data is empty, causing the router to decline. The address then passes to the
19283 .cindex "batched SMTP output example"
19284 .cindex "SMTP" "batched outgoing; example"
19285 You can use &(manualroute)& to deliver messages to pipes or files in batched
19286 SMTP format for onward transportation by some other means. This is one way of
19287 storing mail for a dial-up host when it is not connected. The route list entry
19288 can be as simple as a single domain name in a configuration like this:
19291 driver = manualroute
19292 transport = batchsmtp_appendfile
19293 route_list = saved.domain.example
19295 though often a pattern is used to pick up more than one domain. If there are
19296 several domains or groups of domains with different transport requirements,
19297 different transports can be listed in the routing information:
19300 driver = manualroute
19302 *.saved.domain1.example $domain batch_appendfile; \
19303 *.saved.domain2.example \
19304 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19307 .vindex "&$domain$&"
19309 The first of these just passes the domain in the &$host$& variable, which
19310 doesn't achieve much (since it is also in &$domain$&), but the second does a
19311 file lookup to find a value to pass, causing the router to decline to handle
19312 the address if the lookup fails.
19315 .cindex "UUCP" "example of router for"
19316 Routing mail directly to UUCP software is a specific case of the use of
19317 &(manualroute)& in a gateway to another mail environment. This is an example of
19318 one way it can be done:
19324 command = /usr/local/bin/uux -r - \
19325 ${substr_-5:$host}!rmail ${local_part}
19326 return_fail_output = true
19331 driver = manualroute
19333 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19335 The file &_/usr/local/exim/uucphosts_& contains entries like
19337 darksite.ethereal.example: darksite.UUCP
19339 It can be set up more simply without adding and removing &".UUCP"& but this way
19340 makes clear the distinction between the domain name
19341 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19343 .ecindex IIDmanrou1
19344 .ecindex IIDmanrou2
19353 . ////////////////////////////////////////////////////////////////////////////
19354 . ////////////////////////////////////////////////////////////////////////////
19356 .chapter "The queryprogram router" "CHAPdriverlast"
19357 .scindex IIDquerou1 "&(queryprogram)& router"
19358 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19359 .cindex "routing" "by external program"
19360 The &(queryprogram)& router routes an address by running an external command
19361 and acting on its output. This is an expensive way to route, and is intended
19362 mainly for use in lightly-loaded systems, or for performing experiments.
19363 However, if it is possible to use the precondition options (&%domains%&,
19364 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19365 be used in special cases, even on a busy host. There are the following private
19367 .cindex "options" "&(queryprogram)& router"
19369 .option command queryprogram string&!! unset
19370 This option must be set. It specifies the command that is to be run. The
19371 command is split up into a command name and arguments, and then each is
19372 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19373 &<<CHAPpipetransport>>&).
19376 .option command_group queryprogram string unset
19377 .cindex "gid (group id)" "in &(queryprogram)& router"
19378 This option specifies a gid to be set when running the command while routing an
19379 address for deliver. It must be set if &%command_user%& specifies a numerical
19380 uid. If it begins with a digit, it is interpreted as the numerical value of the
19381 gid. Otherwise it is looked up using &[getgrnam()]&.
19384 .option command_user queryprogram string unset
19385 .cindex "uid (user id)" "for &(queryprogram)&"
19386 This option must be set. It specifies the uid which is set when running the
19387 command while routing an address for delivery. If the value begins with a digit,
19388 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19389 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19390 not set, a value for the gid also.
19392 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19393 root, which it does during a normal delivery in a conventional configuration.
19394 However, when an address is being verified during message reception, Exim is
19395 usually running as the Exim user, not as root. If the &(queryprogram)& router
19396 is called from a non-root process, Exim cannot change uid or gid before running
19397 the command. In this circumstance the command runs under the current uid and
19401 .option current_directory queryprogram string /
19402 This option specifies an absolute path which is made the current directory
19403 before running the command.
19406 .option timeout queryprogram time 1h
19407 If the command does not complete within the timeout period, its process group
19408 is killed and the message is frozen. A value of zero time specifies no
19412 The standard output of the command is connected to a pipe, which is read when
19413 the command terminates. It should consist of a single line of output,
19414 containing up to five fields, separated by white space. The maximum length of
19415 the line is 1023 characters. Longer lines are silently truncated. The first
19416 field is one of the following words (case-insensitive):
19419 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19422 &'Decline'&: the router declines; pass the address to the next router, unless
19423 &%no_more%& is set.
19425 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19426 subsequent text on the line is an error message. If the router is run as part
19427 of address verification during an incoming SMTP message, the message is
19428 included in the SMTP response.
19430 &'Defer'&: routing could not be completed at this time; try again later. Any
19431 subsequent text on the line is an error message which is logged. It is not
19432 included in any SMTP response.
19434 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19436 &'Pass'&: pass the address to the next router (or the router specified by
19437 &%pass_router%&), overriding &%no_more%&.
19439 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19440 new addresses, which are routed independently, starting with the first router,
19441 or the router specified by &%redirect_router%&, if set.
19444 When the first word is &'accept'&, the remainder of the line consists of a
19445 number of keyed data values, as follows (split into two lines here, to fit on
19448 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19449 LOOKUP=byname|bydns DATA=<text>
19451 The data items can be given in any order, and all are optional. If no transport
19452 is included, the transport specified by the generic &%transport%& option is
19453 used. The list of hosts and the lookup type are needed only if the transport is
19454 an &(smtp)& transport that does not itself supply a list of hosts.
19456 The format of the list of hosts is the same as for the &(manualroute)& router.
19457 As well as host names and IP addresses with optional port numbers, as described
19458 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19459 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19460 (see section &<<SECThostshowused>>&).
19462 If the lookup type is not specified, Exim behaves as follows when trying to
19463 find an IP address for each host: First, a DNS lookup is done. If this yields
19464 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19465 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19466 result of the lookup is the result of that call.
19468 .vindex "&$address_data$&"
19469 If the DATA field is set, its value is placed in the &$address_data$&
19470 variable. For example, this return line
19472 accept hosts=x1.y.example:x2.y.example data="rule1"
19474 routes the address to the default transport, passing a list of two hosts. When
19475 the transport runs, the string &"rule1"& is in &$address_data$&.
19476 .ecindex IIDquerou1
19477 .ecindex IIDquerou2
19482 . ////////////////////////////////////////////////////////////////////////////
19483 . ////////////////////////////////////////////////////////////////////////////
19485 .chapter "The redirect router" "CHAPredirect"
19486 .scindex IIDredrou1 "&(redirect)& router"
19487 .scindex IIDredrou2 "routers" "&(redirect)&"
19488 .cindex "alias file" "in a &(redirect)& router"
19489 .cindex "address redirection" "&(redirect)& router"
19490 The &(redirect)& router handles several kinds of address redirection. Its most
19491 common uses are for resolving local part aliases from a central alias file
19492 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
19493 files, but it has many other potential uses. The incoming address can be
19494 redirected in several different ways:
19497 It can be replaced by one or more new addresses which are themselves routed
19500 It can be routed to be delivered to a given file or directory.
19502 It can be routed to be delivered to a specified pipe command.
19504 It can cause an automatic reply to be generated.
19506 It can be forced to fail, optionally with a custom error message.
19508 It can be temporarily deferred, optionally with a custom message.
19510 It can be discarded.
19513 The generic &%transport%& option must not be set for &(redirect)& routers.
19514 However, there are some private options which define transports for delivery to
19515 files and pipes, and for generating autoreplies. See the &%file_transport%&,
19516 &%pipe_transport%& and &%reply_transport%& descriptions below.
19518 If success DSNs have been requested
19519 .cindex "DSN" "success"
19520 .cindex "Delivery Status Notification" "success"
19521 redirection triggers one and the DSN options are not passed any further.
19525 .section "Redirection data" "SECID124"
19526 The router operates by interpreting a text string which it obtains either by
19527 expanding the contents of the &%data%& option, or by reading the entire
19528 contents of a file whose name is given in the &%file%& option. These two
19529 options are mutually exclusive. The first is commonly used for handling system
19530 aliases, in a configuration like this:
19534 data = ${lookup{$local_part}lsearch{/etc/aliases}}
19536 If the lookup fails, the expanded string in this example is empty. When the
19537 expansion of &%data%& results in an empty string, the router declines. A forced
19538 expansion failure also causes the router to decline; other expansion failures
19539 cause delivery to be deferred.
19541 A configuration using &%file%& is commonly used for handling users'
19542 &_.forward_& files, like this:
19547 file = $home/.forward
19550 If the file does not exist, or causes no action to be taken (for example, it is
19551 empty or consists only of comments), the router declines. &*Warning*&: This
19552 is not the case when the file contains syntactically valid items that happen to
19553 yield empty addresses, for example, items containing only RFC 2822 address
19558 .section "Forward files and address verification" "SECID125"
19559 .cindex "address redirection" "while verifying"
19560 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
19561 &_.forward_& files, as in the example above. There are two reasons for this:
19564 When Exim is receiving an incoming SMTP message from a remote host, it is
19565 running under the Exim uid, not as root. Exim is unable to change uid to read
19566 the file as the user, and it may not be able to read it as the Exim user. So in
19567 practice the router may not be able to operate.
19569 However, even when the router can operate, the existence of a &_.forward_& file
19570 is unimportant when verifying an address. What should be checked is whether the
19571 local part is a valid user name or not. Cutting out the redirection processing
19572 saves some resources.
19580 .section "Interpreting redirection data" "SECID126"
19581 .cindex "Sieve filter" "specifying in redirection data"
19582 .cindex "filter" "specifying in redirection data"
19583 The contents of the data string, whether obtained from &%data%& or &%file%&,
19584 can be interpreted in two different ways:
19587 If the &%allow_filter%& option is set true, and the data begins with the text
19588 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
19589 &'filtering'& instructions in the form of an Exim or Sieve filter file,
19590 respectively. Details of the syntax and semantics of filter files are described
19591 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
19592 document is intended for use by end users.
19594 Otherwise, the data must be a comma-separated list of redirection items, as
19595 described in the next section.
19598 When a message is redirected to a file (a &"mail folder"&), the file name given
19599 in a non-filter redirection list must always be an absolute path. A filter may
19600 generate a relative path &-- how this is handled depends on the transport's
19601 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
19602 for the &(appendfile)& transport.
19606 .section "Items in a non-filter redirection list" "SECTitenonfilred"
19607 .cindex "address redirection" "non-filter list items"
19608 When the redirection data is not an Exim or Sieve filter, for example, if it
19609 comes from a conventional alias or forward file, it consists of a list of
19610 addresses, file names, pipe commands, or certain special items (see section
19611 &<<SECTspecitredli>>& below). The special items can be individually enabled or
19612 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
19613 depending on their default values. The items in the list are separated by
19614 commas or newlines.
19615 If a comma is required in an item, the entire item must be enclosed in double
19618 Lines starting with a # character are comments, and are ignored, and # may
19619 also appear following a comma, in which case everything between the # and the
19620 next newline character is ignored.
19622 If an item is entirely enclosed in double quotes, these are removed. Otherwise
19623 double quotes are retained because some forms of mail address require their use
19624 (but never to enclose the entire address). In the following description,
19625 &"item"& refers to what remains after any surrounding double quotes have been
19628 .vindex "&$local_part$&"
19629 &*Warning*&: If you use an Exim expansion to construct a redirection address,
19630 and the expansion contains a reference to &$local_part$&, you should make use
19631 of the &%quote_local_part%& expansion operator, in case the local part contains
19632 special characters. For example, to redirect all mail for the domain
19633 &'obsolete.example'&, retaining the existing local part, you could use this
19636 data = ${quote_local_part:$local_part}@newdomain.example
19640 .section "Redirecting to a local mailbox" "SECTredlocmai"
19641 .cindex "routing" "loops in"
19642 .cindex "loop" "while routing, avoidance of"
19643 .cindex "address redirection" "to local mailbox"
19644 A redirection item may safely be the same as the address currently under
19645 consideration. This does not cause a routing loop, because a router is
19646 automatically skipped if any ancestor of the address that is being processed
19647 is the same as the current address and was processed by the current router.
19648 Such an address is therefore passed to the following routers, so it is handled
19649 as if there were no redirection. When making this loop-avoidance test, the
19650 complete local part, including any prefix or suffix, is used.
19652 .cindex "address redirection" "local part without domain"
19653 Specifying the same local part without a domain is a common usage in personal
19654 filter files when the user wants to have messages delivered to the local
19655 mailbox and also forwarded elsewhere. For example, the user whose login is
19656 &'cleo'& might have a &_.forward_& file containing this:
19658 cleo, cleopatra@egypt.example
19660 .cindex "backslash in alias file"
19661 .cindex "alias file" "backslash in"
19662 For compatibility with other MTAs, such unqualified local parts may be
19663 preceded by &"\"&, but this is not a requirement for loop prevention. However,
19664 it does make a difference if more than one domain is being handled
19667 If an item begins with &"\"& and the rest of the item parses as a valid RFC
19668 2822 address that does not include a domain, the item is qualified using the
19669 domain of the incoming address. In the absence of a leading &"\"&, unqualified
19670 addresses are qualified using the value in &%qualify_recipient%&, but you can
19671 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
19673 Care must be taken if there are alias names for local users.
19674 Consider an MTA handling a single local domain where the system alias file
19679 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
19680 messages in the local mailbox, and also forward copies elsewhere. He creates
19683 Sam.Reman, spqr@reme.elsewhere.example
19685 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
19686 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
19687 second time round, because it has previously routed it,
19688 and the following routers presumably cannot handle the alias. The forward file
19689 should really contain
19691 spqr, spqr@reme.elsewhere.example
19693 but because this is such a common error, the &%check_ancestor%& option (see
19694 below) exists to provide a way to get round it. This is normally set on a
19695 &(redirect)& router that is handling users' &_.forward_& files.
19699 .section "Special items in redirection lists" "SECTspecitredli"
19700 In addition to addresses, the following types of item may appear in redirection
19701 lists (that is, in non-filter redirection data):
19704 .cindex "pipe" "in redirection list"
19705 .cindex "address redirection" "to pipe"
19706 An item is treated as a pipe command if it begins with &"|"& and does not parse
19707 as a valid RFC 2822 address that includes a domain. A transport for running the
19708 command must be specified by the &%pipe_transport%& option.
19709 Normally, either the router or the transport specifies a user and a group under
19710 which to run the delivery. The default is to use the Exim user and group.
19712 Single or double quotes can be used for enclosing the individual arguments of
19713 the pipe command; no interpretation of escapes is done for single quotes. If
19714 the command contains a comma character, it is necessary to put the whole item
19715 in double quotes, for example:
19717 "|/some/command ready,steady,go"
19719 since items in redirection lists are terminated by commas. Do not, however,
19720 quote just the command. An item such as
19722 |"/some/command ready,steady,go"
19724 is interpreted as a pipe with a rather strange command name, and no arguments.
19726 Note that the above example assumes that the text comes from a lookup source
19727 of some sort, so that the quotes are part of the data. If composing a
19728 redirect router with a &%data%& option directly specifying this command, the
19729 quotes will be used by the configuration parser to define the extent of one
19730 string, but will not be passed down into the redirect router itself. There
19731 are two main approaches to get around this: escape quotes to be part of the
19732 data itself, or avoid using this mechanism and instead create a custom
19733 transport with the &%command%& option set and reference that transport from
19734 an &%accept%& router.
19737 .cindex "file" "in redirection list"
19738 .cindex "address redirection" "to file"
19739 An item is interpreted as a path name if it begins with &"/"& and does not
19740 parse as a valid RFC 2822 address that includes a domain. For example,
19742 /home/world/minbari
19744 is treated as a file name, but
19746 /s=molari/o=babylon/@x400gate.way
19748 is treated as an address. For a file name, a transport must be specified using
19749 the &%file_transport%& option. However, if the generated path name ends with a
19750 forward slash character, it is interpreted as a directory name rather than a
19751 file name, and &%directory_transport%& is used instead.
19753 Normally, either the router or the transport specifies a user and a group under
19754 which to run the delivery. The default is to use the Exim user and group.
19756 .cindex "&_/dev/null_&"
19757 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19758 bypassed at a high level, and the log entry shows &"**bypassed**"&
19759 instead of a transport name. In this case the user and group are not used.
19762 .cindex "included address list"
19763 .cindex "address redirection" "included external list"
19764 If an item is of the form
19766 :include:<path name>
19768 a list of further items is taken from the given file and included at that
19769 point. &*Note*&: Such a file can not be a filter file; it is just an
19770 out-of-line addition to the list. The items in the included list are separated
19771 by commas or newlines and are not subject to expansion. If this is the first
19772 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19773 the alias name. This example is incorrect:
19775 list1 :include:/opt/lists/list1
19777 It must be given as
19779 list1: :include:/opt/lists/list1
19782 .cindex "address redirection" "to black hole"
19783 Sometimes you want to throw away mail to a particular local part. Making the
19784 &%data%& option expand to an empty string does not work, because that causes
19785 the router to decline. Instead, the alias item
19786 .cindex "black hole"
19787 .cindex "abandoning mail"
19788 &':blackhole:'& can be used. It does what its name implies. No delivery is
19789 done, and no error message is generated. This has the same effect as specifying
19790 &_/dev/null_& as a destination, but it can be independently disabled.
19792 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
19793 delivery is done for the original local part, even if other redirection items
19794 are present. If you are generating a multi-item list (for example, by reading a
19795 database) and need the ability to provide a no-op item, you must use
19799 .cindex "delivery" "forcing failure"
19800 .cindex "delivery" "forcing deferral"
19801 .cindex "failing delivery" "forcing"
19802 .cindex "deferred delivery, forcing"
19803 .cindex "customizing" "failure message"
19804 An attempt to deliver a particular address can be deferred or forced to fail by
19805 redirection items of the form
19810 respectively. When a redirection list contains such an item, it applies
19811 to the entire redirection; any other items in the list are ignored. Any
19812 text following &':fail:'& or &':defer:'& is placed in the error text
19813 associated with the failure. For example, an alias file might contain:
19815 X.Employee: :fail: Gone away, no forwarding address
19817 In the case of an address that is being verified from an ACL or as the subject
19819 .cindex "VRFY" "error text, display of"
19820 VRFY command, the text is included in the SMTP error response by
19822 .cindex "EXPN" "error text, display of"
19823 The text is not included in the response to an EXPN command. In non-SMTP cases
19824 the text is included in the error message that Exim generates.
19826 .cindex "SMTP" "error codes"
19827 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
19828 &':fail:'&. However, if the message starts with three digits followed by a
19829 space, optionally followed by an extended code of the form &'n.n.n'&, also
19830 followed by a space, and the very first digit is the same as the default error
19831 code, the code from the message is used instead. If the very first digit is
19832 incorrect, a panic error is logged, and the default code is used. You can
19833 suppress the use of the supplied code in a redirect router by setting the
19834 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
19837 .vindex "&$acl_verify_message$&"
19838 In an ACL, an explicitly provided message overrides the default, but the
19839 default message is available in the variable &$acl_verify_message$& and can
19840 therefore be included in a custom message if this is desired.
19842 Normally the error text is the rest of the redirection list &-- a comma does
19843 not terminate it &-- but a newline does act as a terminator. Newlines are not
19844 normally present in alias expansions. In &(lsearch)& lookups they are removed
19845 as part of the continuation process, but they may exist in other kinds of
19846 lookup and in &':include:'& files.
19848 During routing for message delivery (as opposed to verification), a redirection
19849 containing &':fail:'& causes an immediate failure of the incoming address,
19850 whereas &':defer:'& causes the message to remain on the queue so that a
19851 subsequent delivery attempt can happen at a later time. If an address is
19852 deferred for too long, it will ultimately fail, because the normal retry
19856 .cindex "alias file" "exception to default"
19857 Sometimes it is useful to use a single-key search type with a default (see
19858 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19859 for exceptions to the default. These can be handled by aliasing them to
19860 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19861 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19862 results in an empty redirection list has the same effect.
19866 .section "Duplicate addresses" "SECTdupaddr"
19867 .cindex "duplicate addresses"
19868 .cindex "address duplicate, discarding"
19869 .cindex "pipe" "duplicated"
19870 Exim removes duplicate addresses from the list to which it is delivering, so as
19871 to deliver just one copy to each address. This does not apply to deliveries
19872 routed to pipes by different immediate parent addresses, but an indirect
19873 aliasing scheme of the type
19875 pipe: |/some/command $local_part
19879 does not work with a message that is addressed to both local parts, because
19880 when the second is aliased to the intermediate local part &"pipe"& it gets
19881 discarded as being the same as a previously handled address. However, a scheme
19884 localpart1: |/some/command $local_part
19885 localpart2: |/some/command $local_part
19887 does result in two different pipe deliveries, because the immediate parents of
19888 the pipes are distinct.
19892 .section "Repeated redirection expansion" "SECID128"
19893 .cindex "repeated redirection expansion"
19894 .cindex "address redirection" "repeated for each delivery attempt"
19895 When a message cannot be delivered to all of its recipients immediately,
19896 leading to two or more delivery attempts, redirection expansion is carried out
19897 afresh each time for those addresses whose children were not all previously
19898 delivered. If redirection is being used as a mailing list, this can lead to new
19899 members of the list receiving copies of old messages. The &%one_time%& option
19900 can be used to avoid this.
19903 .section "Errors in redirection lists" "SECID129"
19904 .cindex "address redirection" "errors"
19905 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
19906 error is skipped, and an entry is written to the main log. This may be useful
19907 for mailing lists that are automatically managed. Otherwise, if an error is
19908 detected while generating the list of new addresses, the original address is
19909 deferred. See also &%syntax_errors_to%&.
19913 .section "Private options for the redirect router" "SECID130"
19915 .cindex "options" "&(redirect)& router"
19916 The private options for the &(redirect)& router are as follows:
19919 .option allow_defer redirect boolean false
19920 Setting this option allows the use of &':defer:'& in non-filter redirection
19921 data, or the &%defer%& command in an Exim filter file.
19924 .option allow_fail redirect boolean false
19925 .cindex "failing delivery" "from filter"
19926 If this option is true, the &':fail:'& item can be used in a redirection list,
19927 and the &%fail%& command may be used in an Exim filter file.
19930 .option allow_filter redirect boolean false
19931 .cindex "filter" "enabling use of"
19932 .cindex "Sieve filter" "enabling use of"
19933 Setting this option allows Exim to interpret redirection data that starts with
19934 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
19935 are some features of Exim filter files that some administrators may wish to
19936 lock out; see the &%forbid_filter_%&&'xxx'& options below.
19938 It is also possible to lock out Exim filters or Sieve filters while allowing
19939 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
19942 The filter is run using the uid and gid set by the generic &%user%& and
19943 &%group%& options. These take their defaults from the password data if
19944 &%check_local_user%& is set, so in the normal case of users' personal filter
19945 files, the filter is run as the relevant user. When &%allow_filter%& is set
19946 true, Exim insists that either &%check_local_user%& or &%user%& is set.
19950 .option allow_freeze redirect boolean false
19951 .cindex "freezing messages" "allowing in filter"
19952 Setting this option allows the use of the &%freeze%& command in an Exim filter.
19953 This command is more normally encountered in system filters, and is disabled by
19954 default for redirection filters because it isn't something you usually want to
19955 let ordinary users do.
19959 .option check_ancestor redirect boolean false
19960 This option is concerned with handling generated addresses that are the same
19961 as some address in the list of redirection ancestors of the current address.
19962 Although it is turned off by default in the code, it is set in the default
19963 configuration file for handling users' &_.forward_& files. It is recommended
19964 for this use of the &(redirect)& router.
19966 When &%check_ancestor%& is set, if a generated address (including the domain)
19967 is the same as any ancestor of the current address, it is replaced by a copy of
19968 the current address. This helps in the case where local part A is aliased to B,
19969 and B has a &_.forward_& file pointing back to A. For example, within a single
19970 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
19971 &_&~jb/.forward_& contains:
19973 \Joe.Bloggs, <other item(s)>
19975 Without the &%check_ancestor%& setting, either local part (&"jb"& or
19976 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
19977 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
19978 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
19979 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
19980 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
19981 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
19982 original address. See also the &%repeat_use%& option below.
19985 .option check_group redirect boolean "see below"
19986 When the &%file%& option is used, the group owner of the file is checked only
19987 when this option is set. The permitted groups are those listed in the
19988 &%owngroups%& option, together with the user's default group if
19989 &%check_local_user%& is set. If the file has the wrong group, routing is
19990 deferred. The default setting for this option is true if &%check_local_user%&
19991 is set and the &%modemask%& option permits the group write bit, or if the
19992 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
19996 .option check_owner redirect boolean "see below"
19997 When the &%file%& option is used, the owner of the file is checked only when
19998 this option is set. If &%check_local_user%& is set, the local user is
19999 permitted; otherwise the owner must be one of those listed in the &%owners%&
20000 option. The default value for this option is true if &%check_local_user%& or
20001 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
20004 .option data redirect string&!! unset
20005 This option is mutually exclusive with &%file%&. One or other of them must be
20006 set, but not both. The contents of &%data%& are expanded, and then used as the
20007 list of forwarding items, or as a set of filtering instructions. If the
20008 expansion is forced to fail, or the result is an empty string or a string that
20009 has no effect (consists entirely of comments), the router declines.
20011 When filtering instructions are used, the string must begin with &"#Exim
20012 filter"&, and all comments in the string, including this initial one, must be
20013 terminated with newline characters. For example:
20015 data = #Exim filter\n\
20016 if $h_to: contains Exim then save $home/mail/exim endif
20018 If you are reading the data from a database where newlines cannot be included,
20019 you can use the &${sg}$& expansion item to turn the escape string of your
20020 choice into a newline.
20023 .option directory_transport redirect string&!! unset
20024 A &(redirect)& router sets up a direct delivery to a directory when a path name
20025 ending with a slash is specified as a new &"address"&. The transport used is
20026 specified by this option, which, after expansion, must be the name of a
20027 configured transport. This should normally be an &(appendfile)& transport.
20030 .option file redirect string&!! unset
20031 This option specifies the name of a file that contains the redirection data. It
20032 is mutually exclusive with the &%data%& option. The string is expanded before
20033 use; if the expansion is forced to fail, the router declines. Other expansion
20034 failures cause delivery to be deferred. The result of a successful expansion
20035 must be an absolute path. The entire file is read and used as the redirection
20036 data. If the data is an empty string or a string that has no effect (consists
20037 entirely of comments), the router declines.
20039 .cindex "NFS" "checking for file existence"
20040 If the attempt to open the file fails with a &"does not exist"& error, Exim
20041 runs a check on the containing directory,
20042 unless &%ignore_enotdir%& is true (see below).
20043 If the directory does not appear to exist, delivery is deferred. This can
20044 happen when users' &_.forward_& files are in NFS-mounted directories, and there
20045 is a mount problem. If the containing directory does exist, but the file does
20046 not, the router declines.
20049 .option file_transport redirect string&!! unset
20050 .vindex "&$address_file$&"
20051 A &(redirect)& router sets up a direct delivery to a file when a path name not
20052 ending in a slash is specified as a new &"address"&. The transport used is
20053 specified by this option, which, after expansion, must be the name of a
20054 configured transport. This should normally be an &(appendfile)& transport. When
20055 it is running, the file name is in &$address_file$&.
20058 .option filter_prepend_home redirect boolean true
20059 When this option is true, if a &(save)& command in an Exim filter specifies a
20060 relative path, and &$home$& is defined, it is automatically prepended to the
20061 relative path. If this option is set false, this action does not happen. The
20062 relative path is then passed to the transport unmodified.
20065 .option forbid_blackhole redirect boolean false
20066 If this option is true, the &':blackhole:'& item may not appear in a
20070 .option forbid_exim_filter redirect boolean false
20071 If this option is set true, only Sieve filters are permitted when
20072 &%allow_filter%& is true.
20077 .option forbid_file redirect boolean false
20078 .cindex "delivery" "to file; forbidding"
20079 .cindex "Sieve filter" "forbidding delivery to a file"
20080 .cindex "Sieve filter" "&""keep""& facility; disabling"
20081 If this option is true, this router may not generate a new address that
20082 specifies delivery to a local file or directory, either from a filter or from a
20083 conventional forward file. This option is forced to be true if &%one_time%& is
20084 set. It applies to Sieve filters as well as to Exim filters, but if true, it
20085 locks out the Sieve's &"keep"& facility.
20088 .option forbid_filter_dlfunc redirect boolean false
20089 .cindex "filter" "locking out certain features"
20090 If this option is true, string expansions in Exim filters are not allowed to
20091 make use of the &%dlfunc%& expansion facility to run dynamically loaded
20094 .option forbid_filter_existstest redirect boolean false
20095 .cindex "expansion" "statting a file"
20096 If this option is true, string expansions in Exim filters are not allowed to
20097 make use of the &%exists%& condition or the &%stat%& expansion item.
20099 .option forbid_filter_logwrite redirect boolean false
20100 If this option is true, use of the logging facility in Exim filters is not
20101 permitted. Logging is in any case available only if the filter is being run
20102 under some unprivileged uid (which is normally the case for ordinary users'
20103 &_.forward_& files).
20106 .option forbid_filter_lookup redirect boolean false
20107 If this option is true, string expansions in Exim filter files are not allowed
20108 to make use of &%lookup%& items.
20111 .option forbid_filter_perl redirect boolean false
20112 This option has an effect only if Exim is built with embedded Perl support. If
20113 it is true, string expansions in Exim filter files are not allowed to make use
20114 of the embedded Perl support.
20117 .option forbid_filter_readfile redirect boolean false
20118 If this option is true, string expansions in Exim filter files are not allowed
20119 to make use of &%readfile%& items.
20122 .option forbid_filter_readsocket redirect boolean false
20123 If this option is true, string expansions in Exim filter files are not allowed
20124 to make use of &%readsocket%& items.
20127 .option forbid_filter_reply redirect boolean false
20128 If this option is true, this router may not generate an automatic reply
20129 message. Automatic replies can be generated only from Exim or Sieve filter
20130 files, not from traditional forward files. This option is forced to be true if
20131 &%one_time%& is set.
20134 .option forbid_filter_run redirect boolean false
20135 If this option is true, string expansions in Exim filter files are not allowed
20136 to make use of &%run%& items.
20139 .option forbid_include redirect boolean false
20140 If this option is true, items of the form
20142 :include:<path name>
20144 are not permitted in non-filter redirection lists.
20147 .option forbid_pipe redirect boolean false
20148 .cindex "delivery" "to pipe; forbidding"
20149 If this option is true, this router may not generate a new address which
20150 specifies delivery to a pipe, either from an Exim filter or from a conventional
20151 forward file. This option is forced to be true if &%one_time%& is set.
20154 .option forbid_sieve_filter redirect boolean false
20155 If this option is set true, only Exim filters are permitted when
20156 &%allow_filter%& is true.
20159 .cindex "SMTP" "error codes"
20160 .option forbid_smtp_code redirect boolean false
20161 If this option is set true, any SMTP error codes that are present at the start
20162 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20163 the default codes (451 and 550, respectively) are always used.
20168 .option hide_child_in_errmsg redirect boolean false
20169 .cindex "bounce message" "redirection details; suppressing"
20170 If this option is true, it prevents Exim from quoting a child address if it
20171 generates a bounce or delay message for it. Instead it says &"an address
20172 generated from <&'the top level address'&>"&. Of course, this applies only to
20173 bounces generated locally. If a message is forwarded to another host, &'its'&
20174 bounce may well quote the generated address.
20177 .option ignore_eacces redirect boolean false
20179 If this option is set and an attempt to open a redirection file yields the
20180 EACCES error (permission denied), the &(redirect)& router behaves as if the
20181 file did not exist.
20184 .option ignore_enotdir redirect boolean false
20186 If this option is set and an attempt to open a redirection file yields the
20187 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20188 router behaves as if the file did not exist.
20190 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20191 router that has the &%file%& option set discovers that the file does not exist
20192 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20193 against unmounted NFS directories. If the parent can not be statted, delivery
20194 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20195 is set, because that option tells Exim to ignore &"something on the path is not
20196 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20197 that some operating systems give ENOENT where others give ENOTDIR.
20201 .option include_directory redirect string unset
20202 If this option is set, the path names of any &':include:'& items in a
20203 redirection list must start with this directory.
20206 .option modemask redirect "octal integer" 022
20207 This specifies mode bits which must not be set for a file specified by the
20208 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20211 .option one_time redirect boolean false
20212 .cindex "one-time aliasing/forwarding expansion"
20213 .cindex "alias file" "one-time expansion"
20214 .cindex "forward file" "one-time expansion"
20215 .cindex "mailing lists" "one-time expansion"
20216 .cindex "address redirection" "one-time expansion"
20217 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20218 files each time it tries to deliver a message causes a problem when one or more
20219 of the generated addresses fails be delivered at the first attempt. The problem
20220 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20221 but of what happens when the redirection list changes during the time that the
20222 message is on Exim's queue. This is particularly true in the case of mailing
20223 lists, where new subscribers might receive copies of messages that were posted
20224 before they subscribed.
20226 If &%one_time%& is set and any addresses generated by the router fail to
20227 deliver at the first attempt, the failing addresses are added to the message as
20228 &"top level"& addresses, and the parent address that generated them is marked
20229 &"delivered"&. Thus, redirection does not happen again at the next delivery
20232 &*Warning 1*&: Any header line addition or removal that is specified by this
20233 router would be lost if delivery did not succeed at the first attempt. For this
20234 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20235 permitted when &%one_time%& is set.
20237 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20238 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20239 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20241 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20244 The original top-level address is remembered with each of the generated
20245 addresses, and is output in any log messages. However, any intermediate parent
20246 addresses are not recorded. This makes a difference to the log only if
20247 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20248 typically be used for mailing lists, where there is normally just one level of
20252 .option owners redirect "string list" unset
20253 .cindex "ownership" "alias file"
20254 .cindex "ownership" "forward file"
20255 .cindex "alias file" "ownership"
20256 .cindex "forward file" "ownership"
20257 This specifies a list of permitted owners for the file specified by &%file%&.
20258 This list is in addition to the local user when &%check_local_user%& is set.
20259 See &%check_owner%& above.
20262 .option owngroups redirect "string list" unset
20263 This specifies a list of permitted groups for the file specified by &%file%&.
20264 The list is in addition to the local user's primary group when
20265 &%check_local_user%& is set. See &%check_group%& above.
20268 .option pipe_transport redirect string&!! unset
20269 .vindex "&$address_pipe$&"
20270 A &(redirect)& router sets up a direct delivery to a pipe when a string
20271 starting with a vertical bar character is specified as a new &"address"&. The
20272 transport used is specified by this option, which, after expansion, must be the
20273 name of a configured transport. This should normally be a &(pipe)& transport.
20274 When the transport is run, the pipe command is in &$address_pipe$&.
20277 .option qualify_domain redirect string&!! unset
20278 .vindex "&$qualify_recipient$&"
20279 If this option is set, and an unqualified address (one without a domain) is
20280 generated, and that address would normally be qualified by the global setting
20281 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20282 expanding this string. If the expansion fails, the router declines. If you want
20283 to revert to the default, you can have the expansion generate
20284 &$qualify_recipient$&.
20286 This option applies to all unqualified addresses generated by Exim filters,
20287 but for traditional &_.forward_& files, it applies only to addresses that are
20288 not preceded by a backslash. Sieve filters cannot generate unqualified
20291 .option qualify_preserve_domain redirect boolean false
20292 .cindex "domain" "in redirection; preserving"
20293 .cindex "preserving domain in redirection"
20294 .cindex "address redirection" "domain; preserving"
20295 If this option is set, the router's local &%qualify_domain%& option must not be
20296 set (a configuration error occurs if it is). If an unqualified address (one
20297 without a domain) is generated, it is qualified with the domain of the parent
20298 address (the immediately preceding ancestor) instead of the global
20299 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20300 this applies whether or not the address is preceded by a backslash.
20303 .option repeat_use redirect boolean true
20304 If this option is set false, the router is skipped for a child address that has
20305 any ancestor that was routed by this router. This test happens before any of
20306 the other preconditions are tested. Exim's default anti-looping rules skip
20307 only when the ancestor is the same as the current address. See also
20308 &%check_ancestor%& above and the generic &%redirect_router%& option.
20311 .option reply_transport redirect string&!! unset
20312 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20313 &%vacation%& command is used in a filter file. The transport used is specified
20314 by this option, which, after expansion, must be the name of a configured
20315 transport. This should normally be an &(autoreply)& transport. Other transports
20316 are unlikely to do anything sensible or useful.
20319 .option rewrite redirect boolean true
20320 .cindex "address redirection" "disabling rewriting"
20321 If this option is set false, addresses generated by the router are not
20322 subject to address rewriting. Otherwise, they are treated like new addresses
20323 and are rewritten according to the global rewriting rules.
20326 .option sieve_subaddress redirect string&!! unset
20327 The value of this option is passed to a Sieve filter to specify the
20328 :subaddress part of an address.
20330 .option sieve_useraddress redirect string&!! unset
20331 The value of this option is passed to a Sieve filter to specify the :user part
20332 of an address. However, if it is unset, the entire original local part
20333 (including any prefix or suffix) is used for :user.
20336 .option sieve_vacation_directory redirect string&!! unset
20337 .cindex "Sieve filter" "vacation directory"
20338 To enable the &"vacation"& extension for Sieve filters, you must set
20339 &%sieve_vacation_directory%& to the directory where vacation databases are held
20340 (do not put anything else in that directory), and ensure that the
20341 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20342 needs their own directory; Exim will create it if necessary.
20346 .option skip_syntax_errors redirect boolean false
20347 .cindex "forward file" "broken"
20348 .cindex "address redirection" "broken files"
20349 .cindex "alias file" "broken"
20350 .cindex "broken alias or forward files"
20351 .cindex "ignoring faulty addresses"
20352 .cindex "skipping faulty addresses"
20353 .cindex "error" "skipping bad syntax"
20354 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20355 non-filter redirection data are skipped, and each failing address is logged. If
20356 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20357 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20358 are expanded and placed at the head of the error message generated by
20359 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20360 be the same address as the generic &%errors_to%& option. The
20361 &%skip_syntax_errors%& option is often used when handling mailing lists.
20363 If all the addresses in a redirection list are skipped because of syntax
20364 errors, the router declines to handle the original address, and it is passed to
20365 the following routers.
20367 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20368 error in the filter causes filtering to be abandoned without any action being
20369 taken. The incident is logged, and the router declines to handle the address,
20370 so it is passed to the following routers.
20372 .cindex "Sieve filter" "syntax errors in"
20373 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20374 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20375 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20377 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20378 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20379 option, used with an address that does not get redirected, can be used to
20380 notify users of these errors, by means of a router like this:
20386 file = $home/.forward
20387 file_transport = address_file
20388 pipe_transport = address_pipe
20389 reply_transport = address_reply
20392 syntax_errors_to = real-$local_part@$domain
20393 syntax_errors_text = \
20394 This is an automatically generated message. An error has\n\
20395 been found in your .forward file. Details of the error are\n\
20396 reported below. While this error persists, you will receive\n\
20397 a copy of this message for every message that is addressed\n\
20398 to you. If your .forward file is a filter file, or if it is\n\
20399 a non-filter file containing no valid forwarding addresses,\n\
20400 a copy of each incoming message will be put in your normal\n\
20401 mailbox. If a non-filter file contains at least one valid\n\
20402 forwarding address, forwarding to the valid addresses will\n\
20403 happen, and those will be the only deliveries that occur.
20405 You also need a router to ensure that local addresses that are prefixed by
20406 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20407 put this immediately before the &(userforward)& router:
20412 local_part_prefix = real-
20413 transport = local_delivery
20415 For security, it would probably be a good idea to restrict the use of this
20416 router to locally-generated messages, using a condition such as this:
20418 condition = ${if match {$sender_host_address}\
20419 {\N^(|127\.0\.0\.1)$\N}}
20423 .option syntax_errors_text redirect string&!! unset
20424 See &%skip_syntax_errors%& above.
20427 .option syntax_errors_to redirect string unset
20428 See &%skip_syntax_errors%& above.
20429 .ecindex IIDredrou1
20430 .ecindex IIDredrou2
20437 . ////////////////////////////////////////////////////////////////////////////
20438 . ////////////////////////////////////////////////////////////////////////////
20440 .chapter "Environment for running local transports" "CHAPenvironment" &&&
20441 "Environment for local transports"
20442 .scindex IIDenvlotra1 "local transports" "environment for"
20443 .scindex IIDenvlotra2 "environment for local transports"
20444 .scindex IIDenvlotra3 "transport" "local; environment for"
20445 Local transports handle deliveries to files and pipes. (The &(autoreply)&
20446 transport can be thought of as similar to a pipe.) Exim always runs transports
20447 in subprocesses, under specified uids and gids. Typical deliveries to local
20448 mailboxes run under the uid and gid of the local user.
20450 Exim also sets a specific current directory while running the transport; for
20451 some transports a home directory setting is also relevant. The &(pipe)&
20452 transport is the only one that sets up environment variables; see section
20453 &<<SECTpipeenv>>& for details.
20455 The values used for the uid, gid, and the directories may come from several
20456 different places. In many cases, the router that handles the address associates
20457 settings with that address as a result of its &%check_local_user%&, &%group%&,
20458 or &%user%& options. However, values may also be given in the transport's own
20459 configuration, and these override anything that comes from the router.
20463 .section "Concurrent deliveries" "SECID131"
20464 .cindex "concurrent deliveries"
20465 .cindex "simultaneous deliveries"
20466 If two different messages for the same local recipient arrive more or less
20467 simultaneously, the two delivery processes are likely to run concurrently. When
20468 the &(appendfile)& transport is used to write to a file, Exim applies locking
20469 rules to stop concurrent processes from writing to the same file at the same
20472 However, when you use a &(pipe)& transport, it is up to you to arrange any
20473 locking that is needed. Here is a silly example:
20477 command = /bin/sh -c 'cat >>/some/file'
20479 This is supposed to write the message at the end of the file. However, if two
20480 messages arrive at the same time, the file will be scrambled. You can use the
20481 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
20482 file using the same algorithm that Exim itself uses.
20487 .section "Uids and gids" "SECTenvuidgid"
20488 .cindex "local transports" "uid and gid"
20489 .cindex "transport" "local; uid and gid"
20490 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
20491 overrides any group that the router set in the address, even if &%user%& is not
20492 set for the transport. This makes it possible, for example, to run local mail
20493 delivery under the uid of the recipient (set by the router), but in a special
20494 group (set by the transport). For example:
20497 # User/group are set by check_local_user in this router
20501 transport = group_delivery
20504 # This transport overrides the group
20506 driver = appendfile
20507 file = /var/spool/mail/$local_part
20510 If &%user%& is set for a transport, its value overrides what is set in the
20511 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
20512 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
20515 .oindex "&%initgroups%&"
20516 When the uid is taken from the transport's configuration, the &[initgroups()]&
20517 function is called for the groups associated with that uid if the
20518 &%initgroups%& option is set for the transport. When the uid is not specified
20519 by the transport, but is associated with the address by a router, the option
20520 for calling &[initgroups()]& is taken from the router configuration.
20522 .cindex "&(pipe)& transport" "uid for"
20523 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
20524 is set and &%user%& is not set, the uid of the process that called Exim to
20525 receive the message is used, and if &%group%& is not set, the corresponding
20526 original gid is also used.
20528 This is the detailed preference order for obtaining a gid; the first of the
20529 following that is set is used:
20532 A &%group%& setting of the transport;
20534 A &%group%& setting of the router;
20536 A gid associated with a user setting of the router, either as a result of
20537 &%check_local_user%& or an explicit non-numeric &%user%& setting;
20539 The group associated with a non-numeric &%user%& setting of the transport;
20541 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
20542 the uid is the creator's uid;
20544 The Exim gid if the Exim uid is being used as a default.
20547 If, for example, the user is specified numerically on the router and there are
20548 no group settings, no gid is available. In this situation, an error occurs.
20549 This is different for the uid, for which there always is an ultimate default.
20550 The first of the following that is set is used:
20553 A &%user%& setting of the transport;
20555 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
20557 A &%user%& setting of the router;
20559 A &%check_local_user%& setting of the router;
20564 Of course, an error will still occur if the uid that is chosen is on the
20565 &%never_users%& list.
20571 .section "Current and home directories" "SECID132"
20572 .cindex "current directory for local transport"
20573 .cindex "home directory" "for local transport"
20574 .cindex "transport" "local; home directory for"
20575 .cindex "transport" "local; current directory for"
20576 Routers may set current and home directories for local transports by means of
20577 the &%transport_current_directory%& and &%transport_home_directory%& options.
20578 However, if the transport's &%current_directory%& or &%home_directory%& options
20579 are set, they override the router's values. In detail, the home directory
20580 for a local transport is taken from the first of these values that is set:
20583 The &%home_directory%& option on the transport;
20585 The &%transport_home_directory%& option on the router;
20587 The password data if &%check_local_user%& is set on the router;
20589 The &%router_home_directory%& option on the router.
20592 The current directory is taken from the first of these values that is set:
20595 The &%current_directory%& option on the transport;
20597 The &%transport_current_directory%& option on the router.
20601 If neither the router nor the transport sets a current directory, Exim uses the
20602 value of the home directory, if it is set. Otherwise it sets the current
20603 directory to &_/_& before running a local transport.
20607 .section "Expansion variables derived from the address" "SECID133"
20608 .vindex "&$domain$&"
20609 .vindex "&$local_part$&"
20610 .vindex "&$original_domain$&"
20611 Normally a local delivery is handling a single address, and in that case the
20612 variables such as &$domain$& and &$local_part$& are set during local
20613 deliveries. However, in some circumstances more than one address may be handled
20614 at once (for example, while writing batch SMTP for onward transmission by some
20615 other means). In this case, the variables associated with the local part are
20616 never set, &$domain$& is set only if all the addresses have the same domain,
20617 and &$original_domain$& is never set.
20618 .ecindex IIDenvlotra1
20619 .ecindex IIDenvlotra2
20620 .ecindex IIDenvlotra3
20628 . ////////////////////////////////////////////////////////////////////////////
20629 . ////////////////////////////////////////////////////////////////////////////
20631 .chapter "Generic options for transports" "CHAPtransportgeneric"
20632 .scindex IIDgenoptra1 "generic options" "transport"
20633 .scindex IIDgenoptra2 "options" "generic; for transports"
20634 .scindex IIDgenoptra3 "transport" "generic options for"
20635 The following generic options apply to all transports:
20638 .option body_only transports boolean false
20639 .cindex "transport" "body only"
20640 .cindex "message" "transporting body only"
20641 .cindex "body of message" "transporting"
20642 If this option is set, the message's headers are not transported. It is
20643 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
20644 or &(pipe)& transports, the settings of &%message_prefix%& and
20645 &%message_suffix%& should be checked, because this option does not
20646 automatically suppress them.
20649 .option current_directory transports string&!! unset
20650 .cindex "transport" "current directory for"
20651 This specifies the current directory that is to be set while running the
20652 transport, overriding any value that may have been set by the router.
20653 If the expansion fails for any reason, including forced failure, an error is
20654 logged, and delivery is deferred.
20657 .option disable_logging transports boolean false
20658 If this option is set true, nothing is logged for any
20659 deliveries by the transport or for any
20660 transport errors. You should not set this option unless you really, really know
20661 what you are doing.
20664 .option debug_print transports string&!! unset
20665 .cindex "testing" "variables in drivers"
20666 If this option is set and debugging is enabled (see the &%-d%& command line
20667 option), the string is expanded and included in the debugging output when the
20669 If expansion of the string fails, the error message is written to the debugging
20670 output, and Exim carries on processing.
20671 This facility is provided to help with checking out the values of variables and
20672 so on when debugging driver configurations. For example, if a &%headers_add%&
20673 option is not working properly, &%debug_print%& could be used to output the
20674 variables it references. A newline is added to the text if it does not end with
20676 The variables &$transport_name$& and &$router_name$& contain the name of the
20677 transport and the router that called it.
20679 .option delivery_date_add transports boolean false
20680 .cindex "&'Delivery-date:'& header line"
20681 If this option is true, a &'Delivery-date:'& header is added to the message.
20682 This gives the actual time the delivery was made. As this is not a standard
20683 header, Exim has a configuration option (&%delivery_date_remove%&) which
20684 requests its removal from incoming messages, so that delivered messages can
20685 safely be resent to other recipients.
20688 .option driver transports string unset
20689 This specifies which of the available transport drivers is to be used.
20690 There is no default, and this option must be set for every transport.
20693 .option envelope_to_add transports boolean false
20694 .cindex "&'Envelope-to:'& header line"
20695 If this option is true, an &'Envelope-to:'& header is added to the message.
20696 This gives the original address(es) in the incoming envelope that caused this
20697 delivery to happen. More than one address may be present if the transport is
20698 configured to handle several addresses at once, or if more than one original
20699 address was redirected to the same final address. As this is not a standard
20700 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20701 its removal from incoming messages, so that delivered messages can safely be
20702 resent to other recipients.
20705 .option event_action transports string&!! unset
20707 This option declares a string to be expanded for Exim's events mechanism.
20708 For details see &<<CHAPevents>>&.
20712 .option group transports string&!! "Exim group"
20713 .cindex "transport" "group; specifying"
20714 This option specifies a gid for running the transport process, overriding any
20715 value that the router supplies, and also overriding any value associated with
20716 &%user%& (see below).
20719 .option headers_add transports list&!! unset
20720 .cindex "header lines" "adding in transport"
20721 .cindex "transport" "header lines; adding"
20722 This option specifies a list of text headers,
20723 newline-separated (by default, changeable in the usual way),
20724 which are (separately) expanded and added to the header
20725 portion of a message as it is transported, as described in section
20726 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20727 routers. If the result of the expansion is an empty string, or if the expansion
20728 is forced to fail, no action is taken. Other expansion failures are treated as
20729 errors and cause the delivery to be deferred.
20731 Unlike most options, &%headers_add%& can be specified multiple times
20732 for a transport; all listed headers are added.
20735 .option headers_only transports boolean false
20736 .cindex "transport" "header lines only"
20737 .cindex "message" "transporting headers only"
20738 .cindex "header lines" "transporting"
20739 If this option is set, the message's body is not transported. It is mutually
20740 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20741 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20742 checked, since this option does not automatically suppress them.
20745 .option headers_remove transports list&!! unset
20746 .cindex "header lines" "removing"
20747 .cindex "transport" "header lines; removing"
20748 This option specifies a list of header names,
20749 colon-separated (by default, changeable in the usual way);
20750 these headers are omitted from the message as it is transported, as described
20751 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20753 Each list item is separately expanded.
20754 If the result of the expansion is an empty string, or if the expansion
20755 is forced to fail, no action is taken. Other expansion failures are treated as
20756 errors and cause the delivery to be deferred.
20758 Unlike most options, &%headers_remove%& can be specified multiple times
20759 for a router; all listed headers are removed.
20761 &*Warning*&: Because of the separate expansion of the list items,
20762 items that contain a list separator must have it doubled.
20763 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
20767 .option headers_rewrite transports string unset
20768 .cindex "transport" "header lines; rewriting"
20769 .cindex "rewriting" "at transport time"
20770 This option allows addresses in header lines to be rewritten at transport time,
20771 that is, as the message is being copied to its destination. The contents of the
20772 option are a colon-separated list of rewriting rules. Each rule is in exactly
20773 the same form as one of the general rewriting rules that are applied when a
20774 message is received. These are described in chapter &<<CHAPrewrite>>&. For
20777 headers_rewrite = a@b c@d f : \
20780 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
20781 &'w@z'& in all address-bearing header lines. The rules are applied to the
20782 header lines just before they are written out at transport time, so they affect
20783 only those copies of the message that pass through the transport. However, only
20784 the message's original header lines, and any that were added by a system
20785 filter, are rewritten. If a router or transport adds header lines, they are not
20786 affected by this option. These rewriting rules are &'not'& applied to the
20787 envelope. You can change the return path using &%return_path%&, but you cannot
20788 change envelope recipients at this time.
20791 .option home_directory transports string&!! unset
20792 .cindex "transport" "home directory for"
20794 This option specifies a home directory setting for a local transport,
20795 overriding any value that may be set by the router. The home directory is
20796 placed in &$home$& while expanding the transport's private options. It is also
20797 used as the current directory if no current directory is set by the
20798 &%current_directory%& option on the transport or the
20799 &%transport_current_directory%& option on the router. If the expansion fails
20800 for any reason, including forced failure, an error is logged, and delivery is
20804 .option initgroups transports boolean false
20805 .cindex "additional groups"
20806 .cindex "groups" "additional"
20807 .cindex "transport" "group; additional"
20808 If this option is true and the uid for the delivery process is provided by the
20809 transport, the &[initgroups()]& function is called when running the transport
20810 to ensure that any additional groups associated with the uid are set up.
20814 .option max_parallel transports integer&!! unset
20815 .cindex limit "transport parallelism"
20816 .cindex transport "parallel processes"
20817 .cindex transport "concurrency limit"
20818 .cindex "delivery" "parallelism for transport"
20819 If this option is set and expands to an integer greater than zero
20820 it limits the number of concurrent runs of the transport.
20821 The control does not apply to shadow transports.
20823 .cindex "hints database" "transport concurrency control"
20824 Exim implements this control by means of a hints database in which a record is
20825 incremented whenever a transport process is beaing created. The record
20826 is decremented and possibly removed when the process terminates.
20827 Obviously there is scope for
20828 records to get left lying around if there is a system or program crash. To
20829 guard against this, Exim ignores any records that are more than six hours old.
20831 If you use this option, you should also arrange to delete the
20832 relevant hints database whenever your system reboots. The names of the files
20833 start with &_misc_& and they are kept in the &_spool/db_& directory. There
20834 may be one or two files, depending on the type of DBM in use. The same files
20835 are used for ETRN and smtp transport serialization.
20839 .option message_size_limit transports string&!! 0
20840 .cindex "limit" "message size per transport"
20841 .cindex "size" "of message, limit"
20842 .cindex "transport" "message size; limiting"
20843 This option controls the size of messages passed through the transport. It is
20844 expanded before use; the result of the expansion must be a sequence of decimal
20845 digits, optionally followed by K or M. If the expansion fails for any reason,
20846 including forced failure, or if the result is not of the required form,
20847 delivery is deferred. If the value is greater than zero and the size of a
20848 message exceeds this limit, the address is failed. If there is any chance that
20849 the resulting bounce message could be routed to the same transport, you should
20850 ensure that &%return_size_limit%& is less than the transport's
20851 &%message_size_limit%&, as otherwise the bounce message will fail to get
20856 .option rcpt_include_affixes transports boolean false
20857 .cindex "prefix" "for local part, including in envelope"
20858 .cindex "suffix for local part" "including in envelope"
20859 .cindex "local part" "prefix"
20860 .cindex "local part" "suffix"
20861 When this option is false (the default), and an address that has had any
20862 affixes (prefixes or suffixes) removed from the local part is delivered by any
20863 form of SMTP or LMTP, the affixes are not included. For example, if a router
20866 local_part_prefix = *-
20868 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
20871 RCPT TO:<xyz@some.domain>
20873 This is also the case when an ACL-time callout is being used to verify a
20874 recipient address. However, if &%rcpt_include_affixes%& is set true, the
20875 whole local part is included in the RCPT command. This option applies to BSMTP
20876 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
20877 &(lmtp)& and &(smtp)& transports.
20880 .option retry_use_local_part transports boolean "see below"
20881 .cindex "hints database" "retry keys"
20882 When a delivery suffers a temporary failure, a retry record is created
20883 in Exim's hints database. For remote deliveries, the key for the retry record
20884 is based on the name and/or IP address of the failing remote host. For local
20885 deliveries, the key is normally the entire address, including both the local
20886 part and the domain. This is suitable for most common cases of local delivery
20887 temporary failure &-- for example, exceeding a mailbox quota should delay only
20888 deliveries to that mailbox, not to the whole domain.
20890 However, in some special cases you may want to treat a temporary local delivery
20891 as a failure associated with the domain, and not with a particular local part.
20892 (For example, if you are storing all mail for some domain in files.) You can do
20893 this by setting &%retry_use_local_part%& false.
20895 For all the local transports, its default value is true. For remote transports,
20896 the default value is false for tidiness, but changing the value has no effect
20897 on a remote transport in the current implementation.
20900 .option return_path transports string&!! unset
20901 .cindex "envelope sender"
20902 .cindex "transport" "return path; changing"
20903 .cindex "return path" "changing in transport"
20904 If this option is set, the string is expanded at transport time and replaces
20905 the existing return path (envelope sender) value in the copy of the message
20906 that is being delivered. An empty return path is permitted. This feature is
20907 designed for remote deliveries, where the value of this option is used in the
20908 SMTP MAIL command. If you set &%return_path%& for a local transport, the
20909 only effect is to change the address that is placed in the &'Return-path:'&
20910 header line, if one is added to the message (see the next option).
20912 &*Note:*& A changed return path is not logged unless you add
20913 &%return_path_on_delivery%& to the log selector.
20915 .vindex "&$return_path$&"
20916 The expansion can refer to the existing value via &$return_path$&. This is
20917 either the message's envelope sender, or an address set by the
20918 &%errors_to%& option on a router. If the expansion is forced to fail, no
20919 replacement occurs; if it fails for another reason, delivery is deferred. This
20920 option can be used to support VERP (Variable Envelope Return Paths) &-- see
20921 section &<<SECTverp>>&.
20923 &*Note*&: If a delivery error is detected locally, including the case when a
20924 remote server rejects a message at SMTP time, the bounce message is not sent to
20925 the value of this option. It is sent to the previously set errors address.
20926 This defaults to the incoming sender address, but can be changed by setting
20927 &%errors_to%& in a router.
20931 .option return_path_add transports boolean false
20932 .cindex "&'Return-path:'& header line"
20933 If this option is true, a &'Return-path:'& header is added to the message.
20934 Although the return path is normally available in the prefix line of BSD
20935 mailboxes, this is commonly not displayed by MUAs, and so the user does not
20936 have easy access to it.
20938 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
20939 the delivery SMTP server makes the final delivery"&. This implies that this
20940 header should not be present in incoming messages. Exim has a configuration
20941 option, &%return_path_remove%&, which requests removal of this header from
20942 incoming messages, so that delivered messages can safely be resent to other
20946 .option shadow_condition transports string&!! unset
20947 See &%shadow_transport%& below.
20950 .option shadow_transport transports string unset
20951 .cindex "shadow transport"
20952 .cindex "transport" "shadow"
20953 A local transport may set the &%shadow_transport%& option to the name of
20954 another local transport. Shadow remote transports are not supported.
20956 Whenever a delivery to the main transport succeeds, and either
20957 &%shadow_condition%& is unset, or its expansion does not result in the empty
20958 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
20959 passed to the shadow transport, with the same delivery address or addresses. If
20960 expansion fails, no action is taken except that non-forced expansion failures
20961 cause a log line to be written.
20963 The result of the shadow transport is discarded and does not affect the
20964 subsequent processing of the message. Only a single level of shadowing is
20965 provided; the &%shadow_transport%& option is ignored on any transport when it
20966 is running as a shadow. Options concerned with output from pipes are also
20967 ignored. The log line for the successful delivery has an item added on the end,
20970 ST=<shadow transport name>
20972 If the shadow transport did not succeed, the error message is put in
20973 parentheses afterwards. Shadow transports can be used for a number of different
20974 purposes, including keeping more detailed log information than Exim normally
20975 provides, and implementing automatic acknowledgment policies based on message
20976 headers that some sites insist on.
20979 .option transport_filter transports string&!! unset
20980 .cindex "transport" "filter"
20981 .cindex "filter" "transport filter"
20982 This option sets up a filtering (in the Unix shell sense) process for messages
20983 at transport time. It should not be confused with mail filtering as set up by
20984 individual users or via a system filter.
20986 If unset, or expanding to an empty string, no filtering is done.
20989 When the message is about to be written out, the command specified by
20990 &%transport_filter%& is started up in a separate, parallel process, and
20991 the entire message, including the header lines, is passed to it on its standard
20992 input (this in fact is done from a third process, to avoid deadlock). The
20993 command must be specified as an absolute path.
20995 The lines of the message that are written to the transport filter are
20996 terminated by newline (&"\n"&). The message is passed to the filter before any
20997 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
20998 lines beginning with a dot, and also before any processing implied by the
20999 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
21000 &(pipe)& transports.
21002 The standard error for the filter process is set to the same destination as its
21003 standard output; this is read and written to the message's ultimate
21004 destination. The process that writes the message to the filter, the
21005 filter itself, and the original process that reads the result and delivers it
21006 are all run in parallel, like a shell pipeline.
21008 The filter can perform any transformations it likes, but of course should take
21009 care not to break RFC 2822 syntax. Exim does not check the result, except to
21010 test for a final newline when SMTP is in use. All messages transmitted over
21011 SMTP must end with a newline, so Exim supplies one if it is missing.
21013 .cindex "content scanning" "per user"
21014 A transport filter can be used to provide content-scanning on a per-user basis
21015 at delivery time if the only required effect of the scan is to modify the
21016 message. For example, a content scan could insert a new header line containing
21017 a spam score. This could be interpreted by a filter in the user's MUA. It is
21018 not possible to discard a message at this stage.
21020 .cindex "SMTP" "SIZE"
21021 A problem might arise if the filter increases the size of a message that is
21022 being sent down an SMTP connection. If the receiving SMTP server has indicated
21023 support for the SIZE parameter, Exim will have sent the size of the message
21024 at the start of the SMTP session. If what is actually sent is substantially
21025 more, the server might reject the message. This can be worked round by setting
21026 the &%size_addition%& option on the &(smtp)& transport, either to allow for
21027 additions to the message, or to disable the use of SIZE altogether.
21029 .vindex "&$pipe_addresses$&"
21030 The value of the &%transport_filter%& option is the command string for starting
21031 the filter, which is run directly from Exim, not under a shell. The string is
21032 parsed by Exim in the same way as a command string for the &(pipe)& transport:
21033 Exim breaks it up into arguments and then expands each argument separately (see
21034 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
21035 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
21036 of arguments, one for each address that applies to this delivery. (This isn't
21037 an ideal name for this feature here, but as it was already implemented for the
21038 &(pipe)& transport, it seemed sensible not to change it.)
21041 .vindex "&$host_address$&"
21042 The expansion variables &$host$& and &$host_address$& are available when the
21043 transport is a remote one. They contain the name and IP address of the host to
21044 which the message is being sent. For example:
21046 transport_filter = /some/directory/transport-filter.pl \
21047 $host $host_address $sender_address $pipe_addresses
21050 Two problems arise if you want to use more complicated expansion items to
21051 generate transport filter commands, both of which due to the fact that the
21052 command is split up &'before'& expansion.
21054 If an expansion item contains white space, you must quote it, so that it is all
21055 part of the same command item. If the entire option setting is one such
21056 expansion item, you have to take care what kind of quoting you use. For
21059 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
21061 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
21062 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
21063 stripped by Exim when it read the option's value. When the value is used, if
21064 the single quotes were missing, the line would be split into two items,
21065 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
21066 Exim tried to expand the first one.
21068 Except for the special case of &$pipe_addresses$& that is mentioned above, an
21069 expansion cannot generate multiple arguments, or a command name followed by
21070 arguments. Consider this example:
21072 transport_filter = ${lookup{$host}lsearch{/a/file}\
21073 {$value}{/bin/cat}}
21075 The result of the lookup is interpreted as the name of the command, even
21076 if it contains white space. The simplest way round this is to use a shell:
21078 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
21079 {$value}{/bin/cat}}
21083 The filter process is run under the same uid and gid as the normal delivery.
21084 For remote deliveries this is the Exim uid/gid by default. The command should
21085 normally yield a zero return code. Transport filters are not supposed to fail.
21086 A non-zero code is taken to mean that the transport filter encountered some
21087 serious problem. Delivery of the message is deferred; the message remains on
21088 the queue and is tried again later. It is not possible to cause a message to be
21089 bounced from a transport filter.
21091 If a transport filter is set on an autoreply transport, the original message is
21092 passed through the filter as it is being copied into the newly generated
21093 message, which happens if the &%return_message%& option is set.
21096 .option transport_filter_timeout transports time 5m
21097 .cindex "transport" "filter, timeout"
21098 When Exim is reading the output of a transport filter, it applies a timeout
21099 that can be set by this option. Exceeding the timeout is normally treated as a
21100 temporary delivery failure. However, if a transport filter is used with a
21101 &(pipe)& transport, a timeout in the transport filter is treated in the same
21102 way as a timeout in the pipe command itself. By default, a timeout is a hard
21103 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
21104 becomes a temporary error.
21107 .option user transports string&!! "Exim user"
21108 .cindex "uid (user id)" "local delivery"
21109 .cindex "transport" "user, specifying"
21110 This option specifies the user under whose uid the delivery process is to be
21111 run, overriding any uid that may have been set by the router. If the user is
21112 given as a name, the uid is looked up from the password data, and the
21113 associated group is taken as the value of the gid to be used if the &%group%&
21116 For deliveries that use local transports, a user and group are normally
21117 specified explicitly or implicitly (for example, as a result of
21118 &%check_local_user%&) by the router or transport.
21120 .cindex "hints database" "access by remote transport"
21121 For remote transports, you should leave this option unset unless you really are
21122 sure you know what you are doing. When a remote transport is running, it needs
21123 to be able to access Exim's hints databases, because each host may have its own
21125 .ecindex IIDgenoptra1
21126 .ecindex IIDgenoptra2
21127 .ecindex IIDgenoptra3
21134 . ////////////////////////////////////////////////////////////////////////////
21135 . ////////////////////////////////////////////////////////////////////////////
21137 .chapter "Address batching in local transports" "CHAPbatching" &&&
21139 .cindex "transport" "local; address batching in"
21140 The only remote transport (&(smtp)&) is normally configured to handle more than
21141 one address at a time, so that when several addresses are routed to the same
21142 remote host, just one copy of the message is sent. Local transports, however,
21143 normally handle one address at a time. That is, a separate instance of the
21144 transport is run for each address that is routed to the transport. A separate
21145 copy of the message is delivered each time.
21147 .cindex "batched local delivery"
21148 .oindex "&%batch_max%&"
21149 .oindex "&%batch_id%&"
21150 In special cases, it may be desirable to handle several addresses at once in a
21151 local transport, for example:
21154 In an &(appendfile)& transport, when storing messages in files for later
21155 delivery by some other means, a single copy of the message with multiple
21156 recipients saves space.
21158 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21159 a single copy saves time, and is the normal way LMTP is expected to work.
21161 In a &(pipe)& transport, when passing the message
21162 to a scanner program or
21163 to some other delivery mechanism such as UUCP, multiple recipients may be
21167 These three local transports all have the same options for controlling multiple
21168 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21169 repeating the information for each transport, these options are described here.
21171 The &%batch_max%& option specifies the maximum number of addresses that can be
21172 delivered together in a single run of the transport. Its default value is one
21173 (no batching). When more than one address is routed to a transport that has a
21174 &%batch_max%& value greater than one, the addresses are delivered in a batch
21175 (that is, in a single run of the transport with multiple recipients), subject
21176 to certain conditions:
21179 .vindex "&$local_part$&"
21180 If any of the transport's options contain a reference to &$local_part$&, no
21181 batching is possible.
21183 .vindex "&$domain$&"
21184 If any of the transport's options contain a reference to &$domain$&, only
21185 addresses with the same domain are batched.
21187 .cindex "customizing" "batching condition"
21188 If &%batch_id%& is set, it is expanded for each address, and only those
21189 addresses with the same expanded value are batched. This allows you to specify
21190 customized batching conditions. Failure of the expansion for any reason,
21191 including forced failure, disables batching, but it does not stop the delivery
21194 Batched addresses must also have the same errors address (where to send
21195 delivery errors), the same header additions and removals, the same user and
21196 group for the transport, and if a host list is present, the first host must
21200 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21201 both when the file or pipe command is specified in the transport, and when it
21202 is specified by a &(redirect)& router, but all the batched addresses must of
21203 course be routed to the same file or pipe command. These two transports have an
21204 option called &%use_bsmtp%&, which causes them to deliver the message in
21205 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21206 &%check_string%& and &%escape_string%& options are forced to the values
21209 escape_string = ".."
21211 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21212 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21213 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21215 .cindex "&'Envelope-to:'& header line"
21216 If the generic &%envelope_to_add%& option is set for a batching transport, the
21217 &'Envelope-to:'& header that is added to the message contains all the addresses
21218 that are being processed together. If you are using a batching &(appendfile)&
21219 transport without &%use_bsmtp%&, the only way to preserve the recipient
21220 addresses is to set the &%envelope_to_add%& option.
21222 .cindex "&(pipe)& transport" "with multiple addresses"
21223 .vindex "&$pipe_addresses$&"
21224 If you are using a &(pipe)& transport without BSMTP, and setting the
21225 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21226 the command. This is not a true variable; it is a bit of magic that causes each
21227 of the recipient addresses to be inserted into the command as a separate
21228 argument. This provides a way of accessing all the addresses that are being
21229 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21230 are specified by a &(redirect)& router.
21235 . ////////////////////////////////////////////////////////////////////////////
21236 . ////////////////////////////////////////////////////////////////////////////
21238 .chapter "The appendfile transport" "CHAPappendfile"
21239 .scindex IIDapptra1 "&(appendfile)& transport"
21240 .scindex IIDapptra2 "transports" "&(appendfile)&"
21241 .cindex "directory creation"
21242 .cindex "creating directories"
21243 The &(appendfile)& transport delivers a message by appending it to an existing
21244 file, or by creating an entirely new file in a specified directory. Single
21245 files to which messages are appended can be in the traditional Unix mailbox
21246 format, or optionally in the MBX format supported by the Pine MUA and
21247 University of Washington IMAP daemon, &'inter alia'&. When each message is
21248 being delivered as a separate file, &"maildir"& format can optionally be used
21249 to give added protection against failures that happen part-way through the
21250 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21251 supported. For all file formats, Exim attempts to create as many levels of
21252 directory as necessary, provided that &%create_directory%& is set.
21254 The code for the optional formats is not included in the Exim binary by
21255 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21256 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21259 .cindex "quota" "system"
21260 Exim recognizes system quota errors, and generates an appropriate message. Exim
21261 also supports its own quota control within the transport, for use when the
21262 system facility is unavailable or cannot be used for some reason.
21264 If there is an error while appending to a file (for example, quota exceeded or
21265 partition filled), Exim attempts to reset the file's length and last
21266 modification time back to what they were before. If there is an error while
21267 creating an entirely new file, the new file is removed.
21269 Before appending to a file, a number of security checks are made, and the
21270 file is locked. A detailed description is given below, after the list of
21273 The &(appendfile)& transport is most commonly used for local deliveries to
21274 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21275 putting messages into files for remote delivery by some means other than Exim.
21276 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21281 .section "The file and directory options" "SECTfildiropt"
21282 The &%file%& option specifies a single file, to which the message is appended;
21283 the &%directory%& option specifies a directory, in which a new file containing
21284 the message is created. Only one of these two options can be set, and for
21285 normal deliveries to mailboxes, one of them &'must'& be set.
21287 .vindex "&$address_file$&"
21288 .vindex "&$local_part$&"
21289 However, &(appendfile)& is also used for delivering messages to files or
21290 directories whose names (or parts of names) are obtained from alias,
21291 forwarding, or filtering operations (for example, a &%save%& command in a
21292 user's Exim filter). When such a transport is running, &$local_part$& contains
21293 the local part that was aliased or forwarded, and &$address_file$& contains the
21294 name (or partial name) of the file or directory generated by the redirection
21295 operation. There are two cases:
21298 If neither &%file%& nor &%directory%& is set, the redirection operation
21299 must specify an absolute path (one that begins with &`/`&). This is the most
21300 common case when users with local accounts use filtering to sort mail into
21301 different folders. See for example, the &(address_file)& transport in the
21302 default configuration. If the path ends with a slash, it is assumed to be the
21303 name of a directory. A delivery to a directory can also be forced by setting
21304 &%maildir_format%& or &%mailstore_format%&.
21306 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21307 used to determine the file or directory name for the delivery. Normally, the
21308 contents of &$address_file$& are used in some way in the string expansion.
21312 .cindex "Sieve filter" "configuring &(appendfile)&"
21313 .cindex "Sieve filter" "relative mailbox path handling"
21314 As an example of the second case, consider an environment where users do not
21315 have home directories. They may be permitted to use Exim filter commands of the
21320 or Sieve filter commands of the form:
21322 require "fileinto";
21323 fileinto "folder23";
21325 In this situation, the expansion of &%file%& or &%directory%& in the transport
21326 must transform the relative path into an appropriate absolute file name. In the
21327 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21328 is used as a result of a &"keep"& action in the filter. This example shows one
21329 way of handling this requirement:
21331 file = ${if eq{$address_file}{inbox} \
21332 {/var/mail/$local_part} \
21333 {${if eq{${substr_0_1:$address_file}}{/} \
21335 {$home/mail/$address_file} \
21339 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21340 location, absolute paths are used without change, and other folders are in the
21341 &_mail_& directory within the home directory.
21343 &*Note 1*&: While processing an Exim filter, a relative path such as
21344 &_folder23_& is turned into an absolute path if a home directory is known to
21345 the router. In particular, this is the case if &%check_local_user%& is set. If
21346 you want to prevent this happening at routing time, you can set
21347 &%router_home_directory%& empty. This forces the router to pass the relative
21348 path to the transport.
21350 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21351 the &%file%& or &%directory%& option is still used if it is set.
21356 .section "Private options for appendfile" "SECID134"
21357 .cindex "options" "&(appendfile)& transport"
21361 .option allow_fifo appendfile boolean false
21362 .cindex "fifo (named pipe)"
21363 .cindex "named pipe (fifo)"
21364 .cindex "pipe" "named (fifo)"
21365 Setting this option permits delivery to named pipes (FIFOs) as well as to
21366 regular files. If no process is reading the named pipe at delivery time, the
21367 delivery is deferred.
21370 .option allow_symlink appendfile boolean false
21371 .cindex "symbolic link" "to mailbox"
21372 .cindex "mailbox" "symbolic link"
21373 By default, &(appendfile)& will not deliver if the path name for the file is
21374 that of a symbolic link. Setting this option relaxes that constraint, but there
21375 are security issues involved in the use of symbolic links. Be sure you know
21376 what you are doing if you set this. Details of exactly what this option affects
21377 are included in the discussion which follows this list of options.
21380 .option batch_id appendfile string&!! unset
21381 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21382 However, batching is automatically disabled for &(appendfile)& deliveries that
21383 happen as a result of forwarding or aliasing or other redirection directly to a
21387 .option batch_max appendfile integer 1
21388 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21391 .option check_group appendfile boolean false
21392 When this option is set, the group owner of the file defined by the &%file%&
21393 option is checked to see that it is the same as the group under which the
21394 delivery process is running. The default setting is false because the default
21395 file mode is 0600, which means that the group is irrelevant.
21398 .option check_owner appendfile boolean true
21399 When this option is set, the owner of the file defined by the &%file%& option
21400 is checked to ensure that it is the same as the user under which the delivery
21401 process is running.
21404 .option check_string appendfile string "see below"
21405 .cindex "&""From""& line"
21406 As &(appendfile)& writes the message, the start of each line is tested for
21407 matching &%check_string%&, and if it does, the initial matching characters are
21408 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21409 a literal string, not a regular expression, and the case of any letters it
21410 contains is significant.
21412 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21413 are forced to &"."& and &".."& respectively, and any settings in the
21414 configuration are ignored. Otherwise, they default to &"From&~"& and
21415 &">From&~"& when the &%file%& option is set, and unset when any of the
21416 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21418 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21419 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21420 &"From&~"& indicates the start of a new message. All four options need changing
21421 if another format is used. For example, to deliver to mailboxes in MMDF format:
21422 .cindex "MMDF format mailbox"
21423 .cindex "mailbox" "MMDF format"
21425 check_string = "\1\1\1\1\n"
21426 escape_string = "\1\1\1\1 \n"
21427 message_prefix = "\1\1\1\1\n"
21428 message_suffix = "\1\1\1\1\n"
21430 .option create_directory appendfile boolean true
21431 .cindex "directory creation"
21432 When this option is true, Exim attempts to create any missing superior
21433 directories for the file that it is about to write. A created directory's mode
21434 is given by the &%directory_mode%& option.
21436 The group ownership of a newly created directory is highly dependent on the
21437 operating system (and possibly the file system) that is being used. For
21438 example, in Solaris, if the parent directory has the setgid bit set, its group
21439 is propagated to the child; if not, the currently set group is used. However,
21440 in FreeBSD, the parent's group is always used.
21444 .option create_file appendfile string anywhere
21445 This option constrains the location of files and directories that are created
21446 by this transport. It applies to files defined by the &%file%& option and
21447 directories defined by the &%directory%& option. In the case of maildir
21448 delivery, it applies to the top level directory, not the maildir directories
21451 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
21452 &"belowhome"&. In the second and third cases, a home directory must have been
21453 set for the transport. This option is not useful when an explicit file name is
21454 given for normal mailbox deliveries. It is intended for the case when file
21455 names are generated from users' &_.forward_& files. These are usually handled
21456 by an &(appendfile)& transport called &%address_file%&. See also
21457 &%file_must_exist%&.
21460 .option directory appendfile string&!! unset
21461 This option is mutually exclusive with the &%file%& option, but one of &%file%&
21462 or &%directory%& must be set, unless the delivery is the direct result of a
21463 redirection (see section &<<SECTfildiropt>>&).
21465 When &%directory%& is set, the string is expanded, and the message is delivered
21466 into a new file or files in or below the given directory, instead of being
21467 appended to a single mailbox file. A number of different formats are provided
21468 (see &%maildir_format%& and &%mailstore_format%&), and see section
21469 &<<SECTopdir>>& for further details of this form of delivery.
21472 .option directory_file appendfile string&!! "see below"
21474 .vindex "&$inode$&"
21475 When &%directory%& is set, but neither &%maildir_format%& nor
21476 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
21477 whose name is obtained by expanding this string. The default value is:
21479 q${base62:$tod_epoch}-$inode
21481 This generates a unique name from the current time, in base 62 form, and the
21482 inode of the file. The variable &$inode$& is available only when expanding this
21486 .option directory_mode appendfile "octal integer" 0700
21487 If &(appendfile)& creates any directories as a result of the
21488 &%create_directory%& option, their mode is specified by this option.
21491 .option escape_string appendfile string "see description"
21492 See &%check_string%& above.
21495 .option file appendfile string&!! unset
21496 This option is mutually exclusive with the &%directory%& option, but one of
21497 &%file%& or &%directory%& must be set, unless the delivery is the direct result
21498 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
21499 specifies a single file, to which the message is appended. One or more of
21500 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
21503 .cindex "NFS" "lock file"
21504 .cindex "locking files"
21505 .cindex "lock files"
21506 If you are using more than one host to deliver over NFS into the same
21507 mailboxes, you should always use lock files.
21509 The string value is expanded for each delivery, and must yield an absolute
21510 path. The most common settings of this option are variations on one of these
21513 file = /var/spool/mail/$local_part
21514 file = /home/$local_part/inbox
21517 .cindex "&""sticky""& bit"
21518 In the first example, all deliveries are done into the same directory. If Exim
21519 is configured to use lock files (see &%use_lockfile%& below) it must be able to
21520 create a file in the directory, so the &"sticky"& bit must be turned on for
21521 deliveries to be possible, or alternatively the &%group%& option can be used to
21522 run the delivery under a group id which has write access to the directory.
21526 .option file_format appendfile string unset
21527 .cindex "file" "mailbox; checking existing format"
21528 This option requests the transport to check the format of an existing file
21529 before adding to it. The check consists of matching a specific string at the
21530 start of the file. The value of the option consists of an even number of
21531 colon-separated strings. The first of each pair is the test string, and the
21532 second is the name of a transport. If the transport associated with a matched
21533 string is not the current transport, control is passed over to the other
21534 transport. For example, suppose the standard &(local_delivery)& transport has
21537 file_format = "From : local_delivery :\
21538 \1\1\1\1\n : local_mmdf_delivery"
21540 Mailboxes that begin with &"From"& are still handled by this transport, but if
21541 a mailbox begins with four binary ones followed by a newline, control is passed
21542 to a transport called &%local_mmdf_delivery%&, which presumably is configured
21543 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
21544 is assumed to match the current transport. If the start of a mailbox doesn't
21545 match any string, or if the transport named for a given string is not defined,
21546 delivery is deferred.
21549 .option file_must_exist appendfile boolean false
21550 If this option is true, the file specified by the &%file%& option must exist.
21551 A temporary error occurs if it does not, causing delivery to be deferred.
21552 If this option is false, the file is created if it does not exist.
21555 .option lock_fcntl_timeout appendfile time 0s
21556 .cindex "timeout" "mailbox locking"
21557 .cindex "mailbox" "locking, blocking and non-blocking"
21558 .cindex "locking files"
21559 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
21560 when locking an open mailbox file. If the call fails, the delivery process
21561 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
21562 Non-blocking calls are used so that the file is not kept open during the wait
21563 for the lock; the reason for this is to make it as safe as possible for
21564 deliveries over NFS in the case when processes might be accessing an NFS
21565 mailbox without using a lock file. This should not be done, but
21566 misunderstandings and hence misconfigurations are not unknown.
21568 On a busy system, however, the performance of a non-blocking lock approach is
21569 not as good as using a blocking lock with a timeout. In this case, the waiting
21570 is done inside the system call, and Exim's delivery process acquires the lock
21571 and can proceed as soon as the previous lock holder releases it.
21573 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
21574 timeout, are used. There may still be some retrying: the maximum number of
21577 (lock_retries * lock_interval) / lock_fcntl_timeout
21579 rounded up to the next whole number. In other words, the total time during
21580 which &(appendfile)& is trying to get a lock is roughly the same, unless
21581 &%lock_fcntl_timeout%& is set very large.
21583 You should consider setting this option if you are getting a lot of delayed
21584 local deliveries because of errors of the form
21586 failed to lock mailbox /some/file (fcntl)
21589 .option lock_flock_timeout appendfile time 0s
21590 This timeout applies to file locking when using &[flock()]& (see
21591 &%use_flock%&); the timeout operates in a similar manner to
21592 &%lock_fcntl_timeout%&.
21595 .option lock_interval appendfile time 3s
21596 This specifies the time to wait between attempts to lock the file. See below
21597 for details of locking.
21600 .option lock_retries appendfile integer 10
21601 This specifies the maximum number of attempts to lock the file. A value of zero
21602 is treated as 1. See below for details of locking.
21605 .option lockfile_mode appendfile "octal integer" 0600
21606 This specifies the mode of the created lock file, when a lock file is being
21607 used (see &%use_lockfile%& and &%use_mbx_lock%&).
21610 .option lockfile_timeout appendfile time 30m
21611 .cindex "timeout" "mailbox locking"
21612 When a lock file is being used (see &%use_lockfile%&), if a lock file already
21613 exists and is older than this value, it is assumed to have been left behind by
21614 accident, and Exim attempts to remove it.
21617 .option mailbox_filecount appendfile string&!! unset
21618 .cindex "mailbox" "specifying size of"
21619 .cindex "size" "of mailbox"
21620 If this option is set, it is expanded, and the result is taken as the current
21621 number of files in the mailbox. It must be a decimal number, optionally
21622 followed by K or M. This provides a way of obtaining this information from an
21623 external source that maintains the data.
21626 .option mailbox_size appendfile string&!! unset
21627 .cindex "mailbox" "specifying size of"
21628 .cindex "size" "of mailbox"
21629 If this option is set, it is expanded, and the result is taken as the current
21630 size the mailbox. It must be a decimal number, optionally followed by K or M.
21631 This provides a way of obtaining this information from an external source that
21632 maintains the data. This is likely to be helpful for maildir deliveries where
21633 it is computationally expensive to compute the size of a mailbox.
21637 .option maildir_format appendfile boolean false
21638 .cindex "maildir format" "specifying"
21639 If this option is set with the &%directory%& option, the delivery is into a new
21640 file, in the &"maildir"& format that is used by other mail software. When the
21641 transport is activated directly from a &(redirect)& router (for example, the
21642 &(address_file)& transport in the default configuration), setting
21643 &%maildir_format%& causes the path received from the router to be treated as a
21644 directory, whether or not it ends with &`/`&. This option is available only if
21645 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
21646 &<<SECTmaildirdelivery>>& below for further details.
21649 .option maildir_quota_directory_regex appendfile string "See below"
21650 .cindex "maildir format" "quota; directories included in"
21651 .cindex "quota" "maildir; directories included in"
21652 This option is relevant only when &%maildir_use_size_file%& is set. It defines
21653 a regular expression for specifying directories, relative to the quota
21654 directory (see &%quota_directory%&), that should be included in the quota
21655 calculation. The default value is:
21657 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
21659 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
21660 (directories whose names begin with a dot). If you want to exclude the
21662 folder from the count (as some sites do), you need to change this setting to
21664 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
21666 This uses a negative lookahead in the regular expression to exclude the
21667 directory whose name is &_.Trash_&. When a directory is excluded from quota
21668 calculations, quota processing is bypassed for any messages that are delivered
21669 directly into that directory.
21672 .option maildir_retries appendfile integer 10
21673 This option specifies the number of times to retry when writing a file in
21674 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
21677 .option maildir_tag appendfile string&!! unset
21678 This option applies only to deliveries in maildir format, and is described in
21679 section &<<SECTmaildirdelivery>>& below.
21682 .option maildir_use_size_file appendfile&!! boolean false
21683 .cindex "maildir format" "&_maildirsize_& file"
21684 The result of string expansion for this option must be a valid boolean value.
21685 If it is true, it enables support for &_maildirsize_& files. Exim
21686 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
21687 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
21688 value is zero. See &%maildir_quota_directory_regex%& above and section
21689 &<<SECTmaildirdelivery>>& below for further details.
21691 .option maildirfolder_create_regex appendfile string unset
21692 .cindex "maildir format" "&_maildirfolder_& file"
21693 .cindex "&_maildirfolder_&, creating"
21694 The value of this option is a regular expression. If it is unset, it has no
21695 effect. Otherwise, before a maildir delivery takes place, the pattern is
21696 matched against the name of the maildir directory, that is, the directory
21697 containing the &_new_& and &_tmp_& subdirectories that will be used for the
21698 delivery. If there is a match, Exim checks for the existence of a file called
21699 &_maildirfolder_& in the directory, and creates it if it does not exist.
21700 See section &<<SECTmaildirdelivery>>& for more details.
21703 .option mailstore_format appendfile boolean false
21704 .cindex "mailstore format" "specifying"
21705 If this option is set with the &%directory%& option, the delivery is into two
21706 new files in &"mailstore"& format. The option is available only if
21707 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
21708 below for further details.
21711 .option mailstore_prefix appendfile string&!! unset
21712 This option applies only to deliveries in mailstore format, and is described in
21713 section &<<SECTopdir>>& below.
21716 .option mailstore_suffix appendfile string&!! unset
21717 This option applies only to deliveries in mailstore format, and is described in
21718 section &<<SECTopdir>>& below.
21721 .option mbx_format appendfile boolean false
21722 .cindex "locking files"
21723 .cindex "file" "locking"
21724 .cindex "file" "MBX format"
21725 .cindex "MBX format, specifying"
21726 This option is available only if Exim has been compiled with SUPPORT_MBX
21727 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
21728 the message is appended to the mailbox file in MBX format instead of
21729 traditional Unix format. This format is supported by Pine4 and its associated
21730 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
21732 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
21733 automatically changed by the use of &%mbx_format%&. They should normally be set
21734 empty when using MBX format, so this option almost always appears in this
21741 If none of the locking options are mentioned in the configuration,
21742 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21743 is possible to specify the other kinds of locking with &%mbx_format%&, but
21744 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21745 interworks with &'c-client'&, providing for shared access to the mailbox. It
21746 should not be used if any program that does not use this form of locking is
21747 going to access the mailbox, nor should it be used if the mailbox file is NFS
21748 mounted, because it works only when the mailbox is accessed from a single host.
21750 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21751 the standard version of &'c-client'&, because as long as it has a mailbox open
21752 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21753 append messages to it.
21756 .option message_prefix appendfile string&!! "see below"
21757 .cindex "&""From""& line"
21758 The string specified here is expanded and output at the start of every message.
21759 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21760 in which case it is:
21762 message_prefix = "From ${if def:return_path{$return_path}\
21763 {MAILER-DAEMON}} $tod_bsdinbox\n"
21765 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21766 &`\n`& to &`\r\n`& in &%message_prefix%&.
21768 .option message_suffix appendfile string&!! "see below"
21769 The string specified here is expanded and output at the end of every message.
21770 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21771 in which case it is a single newline character. The suffix can be suppressed by
21776 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21777 &`\n`& to &`\r\n`& in &%message_suffix%&.
21779 .option mode appendfile "octal integer" 0600
21780 If the output file is created, it is given this mode. If it already exists and
21781 has wider permissions, they are reduced to this mode. If it has narrower
21782 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
21783 if the delivery is the result of a &%save%& command in a filter file specifying
21784 a particular mode, the mode of the output file is always forced to take that
21785 value, and this option is ignored.
21788 .option mode_fail_narrower appendfile boolean true
21789 This option applies in the case when an existing mailbox file has a narrower
21790 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
21791 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
21792 continues with the delivery attempt, using the existing mode of the file.
21795 .option notify_comsat appendfile boolean false
21796 If this option is true, the &'comsat'& daemon is notified after every
21797 successful delivery to a user mailbox. This is the daemon that notifies logged
21798 on users about incoming mail.
21801 .option quota appendfile string&!! unset
21802 .cindex "quota" "imposed by Exim"
21803 This option imposes a limit on the size of the file to which Exim is appending,
21804 or to the total space used in the directory tree when the &%directory%& option
21805 is set. In the latter case, computation of the space used is expensive, because
21806 all the files in the directory (and any sub-directories) have to be
21807 individually inspected and their sizes summed. (See &%quota_size_regex%& and
21808 &%maildir_use_size_file%& for ways to avoid this in environments where users
21809 have no shell access to their mailboxes).
21811 As there is no interlock against two simultaneous deliveries into a
21812 multi-file mailbox, it is possible for the quota to be overrun in this case.
21813 For single-file mailboxes, of course, an interlock is a necessity.
21815 A file's size is taken as its &'used'& value. Because of blocking effects, this
21816 may be a lot less than the actual amount of disk space allocated to the file.
21817 If the sizes of a number of files are being added up, the rounding effect can
21818 become quite noticeable, especially on systems that have large block sizes.
21819 Nevertheless, it seems best to stick to the &'used'& figure, because this is
21820 the obvious value which users understand most easily.
21822 The value of the option is expanded, and must then be a numerical value
21823 (decimal point allowed), optionally followed by one of the letters K, M, or G,
21824 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
21825 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
21828 &*Note*&: A value of zero is interpreted as &"no quota"&.
21830 The expansion happens while Exim is running as root, before it changes uid for
21831 the delivery. This means that files that are inaccessible to the end user can
21832 be used to hold quota values that are looked up in the expansion. When delivery
21833 fails because this quota is exceeded, the handling of the error is as for
21834 system quota failures.
21836 By default, Exim's quota checking mimics system quotas, and restricts the
21837 mailbox to the specified maximum size, though the value is not accurate to the
21838 last byte, owing to separator lines and additional headers that may get added
21839 during message delivery. When a mailbox is nearly full, large messages may get
21840 refused even though small ones are accepted, because the size of the current
21841 message is added to the quota when the check is made. This behaviour can be
21842 changed by setting &%quota_is_inclusive%& false. When this is done, the check
21843 for exceeding the quota does not include the current message. Thus, deliveries
21844 continue until the quota has been exceeded; thereafter, no further messages are
21845 delivered. See also &%quota_warn_threshold%&.
21848 .option quota_directory appendfile string&!! unset
21849 This option defines the directory to check for quota purposes when delivering
21850 into individual files. The default is the delivery directory, or, if a file
21851 called &_maildirfolder_& exists in a maildir directory, the parent of the
21852 delivery directory.
21855 .option quota_filecount appendfile string&!! 0
21856 This option applies when the &%directory%& option is set. It limits the total
21857 number of files in the directory (compare the inode limit in system quotas). It
21858 can only be used if &%quota%& is also set. The value is expanded; an expansion
21859 failure causes delivery to be deferred. A value of zero is interpreted as
21863 .option quota_is_inclusive appendfile boolean true
21864 See &%quota%& above.
21867 .option quota_size_regex appendfile string unset
21868 This option applies when one of the delivery modes that writes a separate file
21869 for each message is being used. When Exim wants to find the size of one of
21870 these files in order to test the quota, it first checks &%quota_size_regex%&.
21871 If this is set to a regular expression that matches the file name, and it
21872 captures one string, that string is interpreted as a representation of the
21873 file's size. The value of &%quota_size_regex%& is not expanded.
21875 This feature is useful only when users have no shell access to their mailboxes
21876 &-- otherwise they could defeat the quota simply by renaming the files. This
21877 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
21878 the file length to the file name. For example:
21880 maildir_tag = ,S=$message_size
21881 quota_size_regex = ,S=(\d+)
21883 An alternative to &$message_size$& is &$message_linecount$&, which contains the
21884 number of lines in the message.
21886 The regular expression should not assume that the length is at the end of the
21887 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
21888 sometimes add other information onto the ends of message file names.
21890 Section &<<SECID136>>& contains further information.
21893 .option quota_warn_message appendfile string&!! "see below"
21894 See below for the use of this option. If it is not set when
21895 &%quota_warn_threshold%& is set, it defaults to
21897 quota_warn_message = "\
21898 To: $local_part@$domain\n\
21899 Subject: Your mailbox\n\n\
21900 This message is automatically created \
21901 by mail delivery software.\n\n\
21902 The size of your mailbox has exceeded \
21903 a warning threshold that is\n\
21904 set by the system administrator.\n"
21908 .option quota_warn_threshold appendfile string&!! 0
21909 .cindex "quota" "warning threshold"
21910 .cindex "mailbox" "size warning"
21911 .cindex "size" "of mailbox"
21912 This option is expanded in the same way as &%quota%& (see above). If the
21913 resulting value is greater than zero, and delivery of the message causes the
21914 size of the file or total space in the directory tree to cross the given
21915 threshold, a warning message is sent. If &%quota%& is also set, the threshold
21916 may be specified as a percentage of it by following the value with a percent
21920 quota_warn_threshold = 75%
21922 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
21923 percent sign is ignored.
21925 The warning message itself is specified by the &%quota_warn_message%& option,
21926 and it must start with a &'To:'& header line containing the recipient(s) of the
21927 warning message. These do not necessarily have to include the recipient(s) of
21928 the original message. A &'Subject:'& line should also normally be supplied. You
21929 can include any other header lines that you want. If you do not include a
21930 &'From:'& line, the default is:
21932 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
21934 .oindex &%errors_reply_to%&
21935 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
21938 The &%quota%& option does not have to be set in order to use this option; they
21939 are independent of one another except when the threshold is specified as a
21943 .option use_bsmtp appendfile boolean false
21944 .cindex "envelope sender"
21945 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
21946 format, with the envelope sender and recipient(s) included as SMTP commands. If
21947 you want to include a leading HELO command with such messages, you can do
21948 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
21949 for details of batch SMTP.
21952 .option use_crlf appendfile boolean false
21953 .cindex "carriage return"
21955 This option causes lines to be terminated with the two-character CRLF sequence
21956 (carriage return, linefeed) instead of just a linefeed character. In the case
21957 of batched SMTP, the byte sequence written to the file is then an exact image
21958 of what would be sent down a real SMTP connection.
21960 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
21961 (which are used to supply the traditional &"From&~"& and blank line separators
21962 in Berkeley-style mailboxes) are written verbatim, so must contain their own
21963 carriage return characters if these are needed. In cases where these options
21964 have non-empty defaults, the values end with a single linefeed, so they must be
21965 changed to end with &`\r\n`& if &%use_crlf%& is set.
21968 .option use_fcntl_lock appendfile boolean "see below"
21969 This option controls the use of the &[fcntl()]& function to lock a file for
21970 exclusive use when a message is being appended. It is set by default unless
21971 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
21972 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
21973 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
21976 .option use_flock_lock appendfile boolean false
21977 This option is provided to support the use of &[flock()]& for file locking, for
21978 the few situations where it is needed. Most modern operating systems support
21979 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
21980 each other. Exim uses &[fcntl()]& locking by default.
21982 This option is required only if you are using an operating system where
21983 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
21984 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
21985 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
21987 .cindex "Solaris" "&[flock()]& support"
21988 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
21989 have it (and some, I think, provide a not quite right version built on top of
21990 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
21991 the ability to use it, and any attempt to do so will cause a configuration
21994 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
21995 is just being mapped onto &[fcntl()]& by the OS).
21998 .option use_lockfile appendfile boolean "see below"
21999 If this option is turned off, Exim does not attempt to create a lock file when
22000 appending to a mailbox file. In this situation, the only locking is by
22001 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
22002 sure that every MUA that is ever going to look at your users' mailboxes uses
22003 &[fcntl()]& rather than a lock file, and even then only when you are not
22004 delivering over NFS from more than one host.
22006 .cindex "NFS" "lock file"
22007 In order to append to an NFS file safely from more than one host, it is
22008 necessary to take out a lock &'before'& opening the file, and the lock file
22009 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
22012 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
22013 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
22014 except when &%mbx_format%& is set.
22017 .option use_mbx_lock appendfile boolean "see below"
22018 This option is available only if Exim has been compiled with SUPPORT_MBX
22019 set in &_Local/Makefile_&. Setting the option specifies that special MBX
22020 locking rules be used. It is set by default if &%mbx_format%& is set and none
22021 of the locking options are mentioned in the configuration. The locking rules
22022 are the same as are used by the &'c-client'& library that underlies Pine and
22023 the IMAP4 and POP daemons that come with it (see the discussion below). The
22024 rules allow for shared access to the mailbox. However, this kind of locking
22025 does not work when the mailbox is NFS mounted.
22027 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
22028 &%use_flock_lock%& to control what kind of locking is used in implementing the
22029 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
22030 without &%use_fcntl_lock%& or &%use_flock_lock%&.
22035 .section "Operational details for appending" "SECTopappend"
22036 .cindex "appending to a file"
22037 .cindex "file" "appending"
22038 Before appending to a file, the following preparations are made:
22041 If the name of the file is &_/dev/null_&, no action is taken, and a success
22045 .cindex "directory creation"
22046 If any directories on the file's path are missing, Exim creates them if the
22047 &%create_directory%& option is set. A created directory's mode is given by the
22048 &%directory_mode%& option.
22051 If &%file_format%& is set, the format of an existing file is checked. If this
22052 indicates that a different transport should be used, control is passed to that
22056 .cindex "file" "locking"
22057 .cindex "locking files"
22058 .cindex "NFS" "lock file"
22059 If &%use_lockfile%& is set, a lock file is built in a way that will work
22060 reliably over NFS, as follows:
22063 Create a &"hitching post"& file whose name is that of the lock file with the
22064 current time, primary host name, and process id added, by opening for writing
22065 as a new file. If this fails with an access error, delivery is deferred.
22067 Close the hitching post file, and hard link it to the lock file name.
22069 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
22070 Unlink the hitching post name.
22072 Otherwise, use &[stat()]& to get information about the hitching post file, and
22073 then unlink hitching post name. If the number of links is exactly two, creation
22074 of the lock file succeeded but something (for example, an NFS server crash and
22075 restart) caused this fact not to be communicated to the &[link()]& call.
22077 If creation of the lock file failed, wait for &%lock_interval%& and try again,
22078 up to &%lock_retries%& times. However, since any program that writes to a
22079 mailbox should complete its task very quickly, it is reasonable to time out old
22080 lock files that are normally the result of user agent and system crashes. If an
22081 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
22082 it before trying again.
22086 A call is made to &[lstat()]& to discover whether the main file exists, and if
22087 so, what its characteristics are. If &[lstat()]& fails for any reason other
22088 than non-existence, delivery is deferred.
22091 .cindex "symbolic link" "to mailbox"
22092 .cindex "mailbox" "symbolic link"
22093 If the file does exist and is a symbolic link, delivery is deferred, unless the
22094 &%allow_symlink%& option is set, in which case the ownership of the link is
22095 checked, and then &[stat()]& is called to find out about the real file, which
22096 is then subjected to the checks below. The check on the top-level link
22097 ownership prevents one user creating a link for another's mailbox in a sticky
22098 directory, though allowing symbolic links in this case is definitely not a good
22099 idea. If there is a chain of symbolic links, the intermediate ones are not
22103 If the file already exists but is not a regular file, or if the file's owner
22104 and group (if the group is being checked &-- see &%check_group%& above) are
22105 different from the user and group under which the delivery is running,
22106 delivery is deferred.
22109 If the file's permissions are more generous than specified, they are reduced.
22110 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
22111 is set false, in which case the delivery is tried using the existing
22115 The file's inode number is saved, and the file is then opened for appending.
22116 If this fails because the file has vanished, &(appendfile)& behaves as if it
22117 hadn't existed (see below). For any other failures, delivery is deferred.
22120 If the file is opened successfully, check that the inode number hasn't
22121 changed, that it is still a regular file, and that the owner and permissions
22122 have not changed. If anything is wrong, defer delivery and freeze the message.
22125 If the file did not exist originally, defer delivery if the &%file_must_exist%&
22126 option is set. Otherwise, check that the file is being created in a permitted
22127 directory if the &%create_file%& option is set (deferring on failure), and then
22128 open for writing as a new file, with the O_EXCL and O_CREAT options,
22129 except when dealing with a symbolic link (the &%allow_symlink%& option must be
22130 set). In this case, which can happen if the link points to a non-existent file,
22131 the file is opened for writing using O_CREAT but not O_EXCL, because
22132 that prevents link following.
22135 .cindex "loop" "while file testing"
22136 If opening fails because the file exists, obey the tests given above for
22137 existing files. However, to avoid looping in a situation where the file is
22138 being continuously created and destroyed, the exists/not-exists loop is broken
22139 after 10 repetitions, and the message is then frozen.
22142 If opening fails with any other error, defer delivery.
22145 .cindex "file" "locking"
22146 .cindex "locking files"
22147 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22148 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22149 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22150 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22151 file, and an exclusive lock on the file whose name is
22153 /tmp/.<device-number>.<inode-number>
22155 using the device and inode numbers of the open mailbox file, in accordance with
22156 the MBX locking rules. This file is created with a mode that is specified by
22157 the &%lockfile_mode%& option.
22159 If Exim fails to lock the file, there are two possible courses of action,
22160 depending on the value of the locking timeout. This is obtained from
22161 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22163 If the timeout value is zero, the file is closed, Exim waits for
22164 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22165 to lock it again. This happens up to &%lock_retries%& times, after which the
22166 delivery is deferred.
22168 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22169 &[flock()]& are used (with the given timeout), so there has already been some
22170 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22171 immediately. It retries up to
22173 (lock_retries * lock_interval) / <timeout>
22175 times (rounded up).
22178 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22179 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22182 .section "Operational details for delivery to a new file" "SECTopdir"
22183 .cindex "delivery" "to single file"
22184 .cindex "&""From""& line"
22185 When the &%directory%& option is set instead of &%file%&, each message is
22186 delivered into a newly-created file or set of files. When &(appendfile)& is
22187 activated directly from a &(redirect)& router, neither &%file%& nor
22188 &%directory%& is normally set, because the path for delivery is supplied by the
22189 router. (See for example, the &(address_file)& transport in the default
22190 configuration.) In this case, delivery is to a new file if either the path name
22191 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22193 No locking is required while writing the message to a new file, so the various
22194 locking options of the transport are ignored. The &"From"& line that by default
22195 separates messages in a single file is not normally needed, nor is the escaping
22196 of message lines that start with &"From"&, and there is no need to ensure a
22197 newline at the end of each message. Consequently, the default values for
22198 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22199 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22201 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22202 the files in the delivery directory by default. However, you can specify a
22203 different directory by setting &%quota_directory%&. Also, for maildir
22204 deliveries (see below) the &_maildirfolder_& convention is honoured.
22207 .cindex "maildir format"
22208 .cindex "mailstore format"
22209 There are three different ways in which delivery to individual files can be
22210 done, controlled by the settings of the &%maildir_format%& and
22211 &%mailstore_format%& options. Note that code to support maildir or mailstore
22212 formats is not included in the binary unless SUPPORT_MAILDIR or
22213 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22215 .cindex "directory creation"
22216 In all three cases an attempt is made to create the directory and any necessary
22217 sub-directories if they do not exist, provided that the &%create_directory%&
22218 option is set (the default). The location of a created directory can be
22219 constrained by setting &%create_file%&. A created directory's mode is given by
22220 the &%directory_mode%& option. If creation fails, or if the
22221 &%create_directory%& option is not set when creation is required, delivery is
22226 .section "Maildir delivery" "SECTmaildirdelivery"
22227 .cindex "maildir format" "description of"
22228 If the &%maildir_format%& option is true, Exim delivers each message by writing
22229 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22230 directory that is defined by the &%directory%& option (the &"delivery
22231 directory"&). If the delivery is successful, the file is renamed into the
22232 &_new_& subdirectory.
22234 In the file name, <&'stime'&> is the current time of day in seconds, and
22235 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22236 Exim checks that the time-of-day clock has moved on by at least one microsecond
22237 before terminating the delivery process. This guarantees uniqueness for the
22238 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22239 opening it. If any response other than ENOENT (does not exist) is given,
22240 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22242 Before Exim carries out a maildir delivery, it ensures that subdirectories
22243 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22244 do not exist, Exim tries to create them and any superior directories in their
22245 path, subject to the &%create_directory%& and &%create_file%& options. If the
22246 &%maildirfolder_create_regex%& option is set, and the regular expression it
22247 contains matches the delivery directory, Exim also ensures that a file called
22248 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22249 &_maildirfolder_& file cannot be created, delivery is deferred.
22251 These features make it possible to use Exim to create all the necessary files
22252 and directories in a maildir mailbox, including subdirectories for maildir++
22253 folders. Consider this example:
22255 maildir_format = true
22256 directory = /var/mail/$local_part\
22257 ${if eq{$local_part_suffix}{}{}\
22258 {/.${substr_1:$local_part_suffix}}}
22259 maildirfolder_create_regex = /\.[^/]+$
22261 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22262 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22263 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22264 not match this name, so Exim will not look for or create the file
22265 &_/var/mail/pimbo/maildirfolder_&, though it will create
22266 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22268 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22269 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22270 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22271 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22272 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22274 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22275 not inadvertently match the toplevel maildir directory, because a
22276 &_maildirfolder_& file at top level would completely break quota calculations.
22278 .cindex "quota" "in maildir delivery"
22279 .cindex "maildir++"
22280 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22281 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22282 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22283 Exim assumes the directory is a maildir++ folder directory, which is one level
22284 down from the user's top level mailbox directory. This causes it to start at
22285 the parent directory instead of the current directory when calculating the
22286 amount of space used.
22288 One problem with delivering into a multi-file mailbox is that it is
22289 computationally expensive to compute the size of the mailbox for quota
22290 checking. Various approaches have been taken to reduce the amount of work
22291 needed. The next two sections describe two of them. A third alternative is to
22292 use some external process for maintaining the size data, and use the expansion
22293 of the &%mailbox_size%& option as a way of importing it into Exim.
22298 .section "Using tags to record message sizes" "SECID135"
22299 If &%maildir_tag%& is set, the string is expanded for each delivery.
22300 When the maildir file is renamed into the &_new_& sub-directory, the
22301 tag is added to its name. However, if adding the tag takes the length of the
22302 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22303 the tag is dropped and the maildir file is created with no tag.
22306 .vindex "&$message_size$&"
22307 Tags can be used to encode the size of files in their names; see
22308 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22309 happens after the message has been written. The value of the &$message_size$&
22310 variable is set to the number of bytes actually written. If the expansion is
22311 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22312 be deferred. The expanded tag may contain any printing characters except &"/"&.
22313 Non-printing characters in the string are ignored; if the resulting string is
22314 empty, it is ignored. If it starts with an alphanumeric character, a leading
22315 colon is inserted; this default has not proven to be the path that popular
22316 maildir implementations have chosen (but changing it in Exim would break
22317 backwards compatibility).
22319 For one common implementation, you might set:
22321 maildir_tag = ,S=${message_size}
22323 but you should check the documentation of the other software to be sure.
22325 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22326 as this allows Exim to extract the size from your tag, instead of having to
22327 &[stat()]& each message file.
22330 .section "Using a maildirsize file" "SECID136"
22331 .cindex "quota" "in maildir delivery"
22332 .cindex "maildir format" "&_maildirsize_& file"
22333 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22334 storing quota and message size information in a file called &_maildirsize_&
22335 within the toplevel maildir directory. If this file does not exist, Exim
22336 creates it, setting the quota from the &%quota%& option of the transport. If
22337 the maildir directory itself does not exist, it is created before any attempt
22338 to write a &_maildirsize_& file.
22340 The &_maildirsize_& file is used to hold information about the sizes of
22341 messages in the maildir, thus speeding up quota calculations. The quota value
22342 in the file is just a cache; if the quota is changed in the transport, the new
22343 value overrides the cached value when the next message is delivered. The cache
22344 is maintained for the benefit of other programs that access the maildir and
22345 need to know the quota.
22347 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22348 file is maintained (with a zero quota setting), but no quota is imposed.
22350 A regular expression is available for controlling which directories in the
22351 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22352 See the description of the &%maildir_quota_directory_regex%& option above for
22356 .section "Mailstore delivery" "SECID137"
22357 .cindex "mailstore format" "description of"
22358 If the &%mailstore_format%& option is true, each message is written as two
22359 files in the given directory. A unique base name is constructed from the
22360 message id and the current delivery process, and the files that are written use
22361 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22362 contains the message's envelope, and the &_.msg_& file contains the message
22363 itself. The base name is placed in the variable &$mailstore_basename$&.
22365 During delivery, the envelope is first written to a file with the suffix
22366 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22367 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22368 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22369 file before accessing either of them. An alternative approach is to wait for
22370 the absence of a &_.tmp_& file.
22372 The envelope file starts with any text defined by the &%mailstore_prefix%&
22373 option, expanded and terminated by a newline if there isn't one. Then follows
22374 the sender address on one line, then all the recipient addresses, one per line.
22375 There can be more than one recipient only if the &%batch_max%& option is set
22376 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22377 appended to the file, followed by a newline if it does not end with one.
22379 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22380 failure, it is ignored. Other expansion errors are treated as serious
22381 configuration errors, and delivery is deferred. The variable
22382 &$mailstore_basename$& is available for use during these expansions.
22385 .section "Non-special new file delivery" "SECID138"
22386 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22387 file is created directly in the named directory. For example, when delivering
22388 messages into files in batched SMTP format for later delivery to some host (see
22389 section &<<SECTbatchSMTP>>&), a setting such as
22391 directory = /var/bsmtp/$host
22393 might be used. A message is written to a file with a temporary name, which is
22394 then renamed when the delivery is complete. The final name is obtained by
22395 expanding the contents of the &%directory_file%& option.
22396 .ecindex IIDapptra1
22397 .ecindex IIDapptra2
22404 . ////////////////////////////////////////////////////////////////////////////
22405 . ////////////////////////////////////////////////////////////////////////////
22407 .chapter "The autoreply transport" "CHID8"
22408 .scindex IIDauttra1 "transports" "&(autoreply)&"
22409 .scindex IIDauttra2 "&(autoreply)& transport"
22410 The &(autoreply)& transport is not a true transport in that it does not cause
22411 the message to be transmitted. Instead, it generates a new mail message as an
22412 automatic reply to the incoming message. &'References:'& and
22413 &'Auto-Submitted:'& header lines are included. These are constructed according
22414 to the rules in RFCs 2822 and 3834, respectively.
22416 If the router that passes the message to this transport does not have the
22417 &%unseen%& option set, the original message (for the current recipient) is not
22418 delivered anywhere. However, when the &%unseen%& option is set on the router
22419 that passes the message to this transport, routing of the address continues, so
22420 another router can set up a normal message delivery.
22423 The &(autoreply)& transport is usually run as the result of mail filtering, a
22424 &"vacation"& message being the standard example. However, it can also be run
22425 directly from a router like any other transport. To reduce the possibility of
22426 message cascades, messages created by the &(autoreply)& transport always have
22427 empty envelope sender addresses, like bounce messages.
22429 The parameters of the message to be sent can be specified in the configuration
22430 by options described below. However, these are used only when the address
22431 passed to the transport does not contain its own reply information. When the
22432 transport is run as a consequence of a
22434 or &%vacation%& command in a filter file, the parameters of the message are
22435 supplied by the filter, and passed with the address. The transport's options
22436 that define the message are then ignored (so they are not usually set in this
22437 case). The message is specified entirely by the filter or by the transport; it
22438 is never built from a mixture of options. However, the &%file_optional%&,
22439 &%mode%&, and &%return_message%& options apply in all cases.
22441 &(Autoreply)& is implemented as a local transport. When used as a result of a
22442 command in a user's filter file, &(autoreply)& normally runs under the uid and
22443 gid of the user, and with appropriate current and home directories (see chapter
22444 &<<CHAPenvironment>>&).
22446 There is a subtle difference between routing a message to a &(pipe)& transport
22447 that generates some text to be returned to the sender, and routing it to an
22448 &(autoreply)& transport. This difference is noticeable only if more than one
22449 address from the same message is so handled. In the case of a pipe, the
22450 separate outputs from the different addresses are gathered up and returned to
22451 the sender in a single message, whereas if &(autoreply)& is used, a separate
22452 message is generated for each address that is passed to it.
22454 Non-printing characters are not permitted in the header lines generated for the
22455 message that &(autoreply)& creates, with the exception of newlines that are
22456 immediately followed by white space. If any non-printing characters are found,
22457 the transport defers.
22458 Whether characters with the top bit set count as printing characters or not is
22459 controlled by the &%print_topbitchars%& global option.
22461 If any of the generic options for manipulating headers (for example,
22462 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
22463 of the original message that is included in the generated message when
22464 &%return_message%& is set. They do not apply to the generated message itself.
22466 .vindex "&$sender_address$&"
22467 If the &(autoreply)& transport receives return code 2 from Exim when it submits
22468 the message, indicating that there were no recipients, it does not treat this
22469 as an error. This means that autoreplies sent to &$sender_address$& when this
22470 is empty (because the incoming message is a bounce message) do not cause
22471 problems. They are just discarded.
22475 .section "Private options for autoreply" "SECID139"
22476 .cindex "options" "&(autoreply)& transport"
22478 .option bcc autoreply string&!! unset
22479 This specifies the addresses that are to receive &"blind carbon copies"& of the
22480 message when the message is specified by the transport.
22483 .option cc autoreply string&!! unset
22484 This specifies recipients of the message and the contents of the &'Cc:'& header
22485 when the message is specified by the transport.
22488 .option file autoreply string&!! unset
22489 The contents of the file are sent as the body of the message when the message
22490 is specified by the transport. If both &%file%& and &%text%& are set, the text
22491 string comes first.
22494 .option file_expand autoreply boolean false
22495 If this is set, the contents of the file named by the &%file%& option are
22496 subjected to string expansion as they are added to the message.
22499 .option file_optional autoreply boolean false
22500 If this option is true, no error is generated if the file named by the &%file%&
22501 option or passed with the address does not exist or cannot be read.
22504 .option from autoreply string&!! unset
22505 This specifies the contents of the &'From:'& header when the message is
22506 specified by the transport.
22509 .option headers autoreply string&!! unset
22510 This specifies additional RFC 2822 headers that are to be added to the message
22511 when the message is specified by the transport. Several can be given by using
22512 &"\n"& to separate them. There is no check on the format.
22515 .option log autoreply string&!! unset
22516 This option names a file in which a record of every message sent is logged when
22517 the message is specified by the transport.
22520 .option mode autoreply "octal integer" 0600
22521 If either the log file or the &"once"& file has to be created, this mode is
22525 .option never_mail autoreply "address list&!!" unset
22526 If any run of the transport creates a message with a recipient that matches any
22527 item in the list, that recipient is quietly discarded. If all recipients are
22528 discarded, no message is created. This applies both when the recipients are
22529 generated by a filter and when they are specified in the transport.
22533 .option once autoreply string&!! unset
22534 This option names a file or DBM database in which a record of each &'To:'&
22535 recipient is kept when the message is specified by the transport. &*Note*&:
22536 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
22538 If &%once%& is unset, or is set to an empty string, the message is always sent.
22539 By default, if &%once%& is set to a non-empty file name, the message
22540 is not sent if a potential recipient is already listed in the database.
22541 However, if the &%once_repeat%& option specifies a time greater than zero, the
22542 message is sent if that much time has elapsed since a message was last sent to
22543 this recipient. A setting of zero time for &%once_repeat%& (the default)
22544 prevents a message from being sent a second time &-- in this case, zero means
22547 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
22548 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
22549 greater than zero, it changes the way Exim implements the &%once%& option.
22550 Instead of using a DBM file to record every recipient it sends to, it uses a
22551 regular file, whose size will never get larger than the given value.
22553 In the file, Exim keeps a linear list of recipient addresses and the times at
22554 which they were sent messages. If the file is full when a new address needs to
22555 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
22556 means that a given recipient may receive multiple messages, but at
22557 unpredictable intervals that depend on the rate of turnover of addresses in the
22558 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
22561 .option once_file_size autoreply integer 0
22562 See &%once%& above.
22565 .option once_repeat autoreply time&!! 0s
22566 See &%once%& above.
22567 After expansion, the value of this option must be a valid time value.
22570 .option reply_to autoreply string&!! unset
22571 This specifies the contents of the &'Reply-To:'& header when the message is
22572 specified by the transport.
22575 .option return_message autoreply boolean false
22576 If this is set, a copy of the original message is returned with the new
22577 message, subject to the maximum size set in the &%return_size_limit%& global
22578 configuration option.
22581 .option subject autoreply string&!! unset
22582 This specifies the contents of the &'Subject:'& header when the message is
22583 specified by the transport. It is tempting to quote the original subject in
22584 automatic responses. For example:
22586 subject = Re: $h_subject:
22588 There is a danger in doing this, however. It may allow a third party to
22589 subscribe your users to an opt-in mailing list, provided that the list accepts
22590 bounce messages as subscription confirmations. Well-managed lists require a
22591 non-bounce message to confirm a subscription, so the danger is relatively
22596 .option text autoreply string&!! unset
22597 This specifies a single string to be used as the body of the message when the
22598 message is specified by the transport. If both &%text%& and &%file%& are set,
22599 the text comes first.
22602 .option to autoreply string&!! unset
22603 This specifies recipients of the message and the contents of the &'To:'& header
22604 when the message is specified by the transport.
22605 .ecindex IIDauttra1
22606 .ecindex IIDauttra2
22611 . ////////////////////////////////////////////////////////////////////////////
22612 . ////////////////////////////////////////////////////////////////////////////
22614 .chapter "The lmtp transport" "CHAPLMTP"
22615 .cindex "transports" "&(lmtp)&"
22616 .cindex "&(lmtp)& transport"
22617 .cindex "LMTP" "over a pipe"
22618 .cindex "LMTP" "over a socket"
22619 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
22621 or by interacting with a Unix domain socket.
22622 This transport is something of a cross between the &(pipe)& and &(smtp)&
22623 transports. Exim also has support for using LMTP over TCP/IP; this is
22624 implemented as an option for the &(smtp)& transport. Because LMTP is expected
22625 to be of minority interest, the default build-time configure in &_src/EDITME_&
22626 has it commented out. You need to ensure that
22630 .cindex "options" "&(lmtp)& transport"
22631 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
22632 included in the Exim binary. The private options of the &(lmtp)& transport are
22635 .option batch_id lmtp string&!! unset
22636 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22639 .option batch_max lmtp integer 1
22640 This limits the number of addresses that can be handled in a single delivery.
22641 Most LMTP servers can handle several addresses at once, so it is normally a
22642 good idea to increase this value. See the description of local delivery
22643 batching in chapter &<<CHAPbatching>>&.
22646 .option command lmtp string&!! unset
22647 This option must be set if &%socket%& is not set. The string is a command which
22648 is run in a separate process. It is split up into a command name and list of
22649 arguments, each of which is separately expanded (so expansion cannot change the
22650 number of arguments). The command is run directly, not via a shell. The message
22651 is passed to the new process using the standard input and output to operate the
22654 .option ignore_quota lmtp boolean false
22655 .cindex "LMTP" "ignoring quota errors"
22656 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
22657 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
22658 in its response to the LHLO command.
22660 .option socket lmtp string&!! unset
22661 This option must be set if &%command%& is not set. The result of expansion must
22662 be the name of a Unix domain socket. The transport connects to the socket and
22663 delivers the message to it using the LMTP protocol.
22666 .option timeout lmtp time 5m
22667 The transport is aborted if the created process or Unix domain socket does not
22668 respond to LMTP commands or message input within this timeout. Delivery
22669 is deferred, and will be tried again later. Here is an example of a typical
22674 command = /some/local/lmtp/delivery/program
22678 This delivers up to 20 addresses at a time, in a mixture of domains if
22679 necessary, running as the user &'exim'&.
22683 . ////////////////////////////////////////////////////////////////////////////
22684 . ////////////////////////////////////////////////////////////////////////////
22686 .chapter "The pipe transport" "CHAPpipetransport"
22687 .scindex IIDpiptra1 "transports" "&(pipe)&"
22688 .scindex IIDpiptra2 "&(pipe)& transport"
22689 The &(pipe)& transport is used to deliver messages via a pipe to a command
22690 running in another process. One example is the use of &(pipe)& as a
22691 pseudo-remote transport for passing messages to some other delivery mechanism
22692 (such as UUCP). Another is the use by individual users to automatically process
22693 their incoming messages. The &(pipe)& transport can be used in one of the
22697 .vindex "&$local_part$&"
22698 A router routes one address to a transport in the normal way, and the
22699 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
22700 contains the local part of the address (as usual), and the command that is run
22701 is specified by the &%command%& option on the transport.
22703 .vindex "&$pipe_addresses$&"
22704 If the &%batch_max%& option is set greater than 1 (the default is 1), the
22705 transport can handle more than one address in a single run. In this case, when
22706 more than one address is routed to the transport, &$local_part$& is not set
22707 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
22708 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
22709 that are routed to the transport.
22711 .vindex "&$address_pipe$&"
22712 A router redirects an address directly to a pipe command (for example, from an
22713 alias or forward file). In this case, &$address_pipe$& contains the text of the
22714 pipe command, and the &%command%& option on the transport is ignored unless
22715 &%force_command%& is set. If only one address is being transported
22716 (&%batch_max%& is not greater than one, or only one address was redirected to
22717 this pipe command), &$local_part$& contains the local part that was redirected.
22721 The &(pipe)& transport is a non-interactive delivery method. Exim can also
22722 deliver messages over pipes using the LMTP interactive protocol. This is
22723 implemented by the &(lmtp)& transport.
22725 In the case when &(pipe)& is run as a consequence of an entry in a local user's
22726 &_.forward_& file, the command runs under the uid and gid of that user. In
22727 other cases, the uid and gid have to be specified explicitly, either on the
22728 transport or on the router that handles the address. Current and &"home"&
22729 directories are also controllable. See chapter &<<CHAPenvironment>>& for
22730 details of the local delivery environment and chapter &<<CHAPbatching>>&
22731 for a discussion of local delivery batching.
22734 .section "Concurrent delivery" "SECID140"
22735 If two messages arrive at almost the same time, and both are routed to a pipe
22736 delivery, the two pipe transports may be run concurrently. You must ensure that
22737 any pipe commands you set up are robust against this happening. If the commands
22738 write to a file, the &%exim_lock%& utility might be of use.
22740 Alternatively the &%max_parallel%& option could be used with a value
22741 of "1" to enforce serialization.
22747 .section "Returned status and data" "SECID141"
22748 .cindex "&(pipe)& transport" "returned data"
22749 If the command exits with a non-zero return code, the delivery is deemed to
22750 have failed, unless either the &%ignore_status%& option is set (in which case
22751 the return code is treated as zero), or the return code is one of those listed
22752 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22753 later"&. In this case, delivery is deferred. Details of a permanent failure are
22754 logged, but are not included in the bounce message, which merely contains
22755 &"local delivery failed"&.
22757 If the command exits on a signal and the &%freeze_signal%& option is set then
22758 the message will be frozen in the queue. If that option is not set, a bounce
22759 will be sent as normal.
22761 If the return code is greater than 128 and the command being run is a shell
22762 script, it normally means that the script was terminated by a signal whose
22763 value is the return code minus 128. The &%freeze_signal%& option does not
22764 apply in this case.
22766 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22767 return code is set to 127. This is the value that a shell returns if it is
22768 asked to run a non-existent command. The wording for the log line suggests that
22769 a non-existent command may be the problem.
22771 The &%return_output%& option can affect the result of a pipe delivery. If it is
22772 set and the command produces any output on its standard output or standard
22773 error streams, the command is considered to have failed, even if it gave a zero
22774 return code or if &%ignore_status%& is set. The output from the command is
22775 included as part of the bounce message. The &%return_fail_output%& option is
22776 similar, except that output is returned only when the command exits with a
22777 failure return code, that is, a value other than zero or a code that matches
22782 .section "How the command is run" "SECThowcommandrun"
22783 .cindex "&(pipe)& transport" "path for command"
22784 The command line is (by default) broken down into a command name and arguments
22785 by the &(pipe)& transport itself. The &%allow_commands%& and
22786 &%restrict_to_path%& options can be used to restrict the commands that may be
22789 .cindex "quoting" "in pipe command"
22790 Unquoted arguments are delimited by white space. If an argument appears in
22791 double quotes, backslash is interpreted as an escape character in the usual
22792 way. If an argument appears in single quotes, no escaping is done.
22794 String expansion is applied to the command line except when it comes from a
22795 traditional &_.forward_& file (commands from a filter file are expanded). The
22796 expansion is applied to each argument in turn rather than to the whole line.
22797 For this reason, any string expansion item that contains white space must be
22798 quoted so as to be contained within a single argument. A setting such as
22800 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
22802 will not work, because the expansion item gets split between several
22803 arguments. You have to write
22805 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
22807 to ensure that it is all in one argument. The expansion is done in this way,
22808 argument by argument, so that the number of arguments cannot be changed as a
22809 result of expansion, and quotes or backslashes in inserted variables do not
22810 interact with external quoting. However, this leads to problems if you want to
22811 generate multiple arguments (or the command name plus arguments) from a single
22812 expansion. In this situation, the simplest solution is to use a shell. For
22815 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
22818 .cindex "transport" "filter"
22819 .cindex "filter" "transport filter"
22820 .vindex "&$pipe_addresses$&"
22821 Special handling takes place when an argument consists of precisely the text
22822 &`$pipe_addresses`&. This is not a general expansion variable; the only
22823 place this string is recognized is when it appears as an argument for a pipe or
22824 transport filter command. It causes each address that is being handled to be
22825 inserted in the argument list at that point &'as a separate argument'&. This
22826 avoids any problems with spaces or shell metacharacters, and is of use when a
22827 &(pipe)& transport is handling groups of addresses in a batch.
22829 If &%force_command%& is enabled on the transport, Special handling takes place
22830 for an argument that consists of precisely the text &`$address_pipe`&. It
22831 is handled similarly to &$pipe_addresses$& above. It is expanded and each
22832 argument is inserted in the argument list at that point
22833 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
22834 the only item in the argument; in fact, if it were then &%force_command%&
22835 should behave as a no-op. Rather, it should be used to adjust the command
22836 run while preserving the argument vector separation.
22838 After splitting up into arguments and expansion, the resulting command is run
22839 in a subprocess directly from the transport, &'not'& under a shell. The
22840 message that is being delivered is supplied on the standard input, and the
22841 standard output and standard error are both connected to a single pipe that is
22842 read by Exim. The &%max_output%& option controls how much output the command
22843 may produce, and the &%return_output%& and &%return_fail_output%& options
22844 control what is done with it.
22846 Not running the command under a shell (by default) lessens the security risks
22847 in cases when a command from a user's filter file is built out of data that was
22848 taken from an incoming message. If a shell is required, it can of course be
22849 explicitly specified as the command to be run. However, there are circumstances
22850 where existing commands (for example, in &_.forward_& files) expect to be run
22851 under a shell and cannot easily be modified. To allow for these cases, there is
22852 an option called &%use_shell%&, which changes the way the &(pipe)& transport
22853 works. Instead of breaking up the command line as just described, it expands it
22854 as a single string and passes the result to &_/bin/sh_&. The
22855 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
22856 with &%use_shell%&, and the whole mechanism is inherently less secure.
22860 .section "Environment variables" "SECTpipeenv"
22861 .cindex "&(pipe)& transport" "environment for command"
22862 .cindex "environment for pipe transport"
22863 The environment variables listed below are set up when the command is invoked.
22864 This list is a compromise for maximum compatibility with other MTAs. Note that
22865 the &%environment%& option can be used to add additional variables to this
22868 &`DOMAIN `& the domain of the address
22869 &`HOME `& the home directory, if set
22870 &`HOST `& the host name when called from a router (see below)
22871 &`LOCAL_PART `& see below
22872 &`LOCAL_PART_PREFIX `& see below
22873 &`LOCAL_PART_SUFFIX `& see below
22874 &`LOGNAME `& see below
22875 &`MESSAGE_ID `& Exim's local ID for the message
22876 &`PATH `& as specified by the &%path%& option below
22877 &`QUALIFY_DOMAIN `& the sender qualification domain
22878 &`RECIPIENT `& the complete recipient address
22879 &`SENDER `& the sender of the message (empty if a bounce)
22880 &`SHELL `& &`/bin/sh`&
22881 &`TZ `& the value of the &%timezone%& option, if set
22882 &`USER `& see below
22884 When a &(pipe)& transport is called directly from (for example) an &(accept)&
22885 router, LOCAL_PART is set to the local part of the address. When it is
22886 called as a result of a forward or alias expansion, LOCAL_PART is set to
22887 the local part of the address that was expanded. In both cases, any affixes are
22888 removed from the local part, and made available in LOCAL_PART_PREFIX and
22889 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
22890 same value as LOCAL_PART for compatibility with other MTAs.
22893 HOST is set only when a &(pipe)& transport is called from a router that
22894 associates hosts with an address, typically when using &(pipe)& as a
22895 pseudo-remote transport. HOST is set to the first host name specified by
22899 If the transport's generic &%home_directory%& option is set, its value is used
22900 for the HOME environment variable. Otherwise, a home directory may be set
22901 by the router's &%transport_home_directory%& option, which defaults to the
22902 user's home directory if &%check_local_user%& is set.
22905 .section "Private options for pipe" "SECID142"
22906 .cindex "options" "&(pipe)& transport"
22910 .option allow_commands pipe "string list&!!" unset
22911 .cindex "&(pipe)& transport" "permitted commands"
22912 The string is expanded, and is then interpreted as a colon-separated list of
22913 permitted commands. If &%restrict_to_path%& is not set, the only commands
22914 permitted are those in the &%allow_commands%& list. They need not be absolute
22915 paths; the &%path%& option is still used for relative paths. If
22916 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
22917 in the &%allow_commands%& list, or a name without any slashes that is found on
22918 the path. In other words, if neither &%allow_commands%& nor
22919 &%restrict_to_path%& is set, there is no restriction on the command, but
22920 otherwise only commands that are permitted by one or the other are allowed. For
22923 allow_commands = /usr/bin/vacation
22925 and &%restrict_to_path%& is not set, the only permitted command is
22926 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
22927 &%use_shell%& is set.
22930 .option batch_id pipe string&!! unset
22931 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22934 .option batch_max pipe integer 1
22935 This limits the number of addresses that can be handled in a single delivery.
22936 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22939 .option check_string pipe string unset
22940 As &(pipe)& writes the message, the start of each line is tested for matching
22941 &%check_string%&, and if it does, the initial matching characters are replaced
22942 by the contents of &%escape_string%&, provided both are set. The value of
22943 &%check_string%& is a literal string, not a regular expression, and the case of
22944 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
22945 of &%check_string%& and &%escape_string%& are forced to values that implement
22946 the SMTP escaping protocol. Any settings made in the configuration file are
22950 .option command pipe string&!! unset
22951 This option need not be set when &(pipe)& is being used to deliver to pipes
22952 obtained directly from address redirections. In other cases, the option must be
22953 set, to provide a command to be run. It need not yield an absolute path (see
22954 the &%path%& option below). The command is split up into separate arguments by
22955 Exim, and each argument is separately expanded, as described in section
22956 &<<SECThowcommandrun>>& above.
22959 .option environment pipe string&!! unset
22960 .cindex "&(pipe)& transport" "environment for command"
22961 .cindex "environment for &(pipe)& transport"
22962 This option is used to add additional variables to the environment in which the
22963 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
22964 a string which is expanded, and then interpreted as a colon-separated list of
22965 environment settings of the form <&'name'&>=<&'value'&>.
22968 .option escape_string pipe string unset
22969 See &%check_string%& above.
22972 .option freeze_exec_fail pipe boolean false
22973 .cindex "exec failure"
22974 .cindex "failure of exec"
22975 .cindex "&(pipe)& transport" "failure of exec"
22976 Failure to exec the command in a pipe transport is by default treated like
22977 any other failure while running the command. However, if &%freeze_exec_fail%&
22978 is set, failure to exec is treated specially, and causes the message to be
22979 frozen, whatever the setting of &%ignore_status%&.
22982 .option freeze_signal pipe boolean false
22983 .cindex "signal exit"
22984 .cindex "&(pipe)& transport", "signal exit"
22985 Normally if the process run by a command in a pipe transport exits on a signal,
22986 a bounce message is sent. If &%freeze_signal%& is set, the message will be
22987 frozen in Exim's queue instead.
22990 .option force_command pipe boolean false
22991 .cindex "force command"
22992 .cindex "&(pipe)& transport", "force command"
22993 Normally when a router redirects an address directly to a pipe command
22994 the &%command%& option on the transport is ignored. If &%force_command%&
22995 is set, the &%command%& option will used. This is especially
22996 useful for forcing a wrapper or additional argument to be added to the
22997 command. For example:
22999 command = /usr/bin/remote_exec myhost -- $address_pipe
23003 Note that &$address_pipe$& is handled specially in &%command%& when
23004 &%force_command%& is set, expanding out to the original argument vector as
23005 separate items, similarly to a Unix shell &`"$@"`& construct.
23008 .option ignore_status pipe boolean false
23009 If this option is true, the status returned by the subprocess that is set up to
23010 run the command is ignored, and Exim behaves as if zero had been returned.
23011 Otherwise, a non-zero status or termination by signal causes an error return
23012 from the transport unless the status value is one of those listed in
23013 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
23015 &*Note*&: This option does not apply to timeouts, which do not return a status.
23016 See the &%timeout_defer%& option for how timeouts are handled.
23019 .option log_defer_output pipe boolean false
23020 .cindex "&(pipe)& transport" "logging output"
23021 If this option is set, and the status returned by the command is
23022 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
23023 and any output was produced on stdout or stderr, the first line of it is
23024 written to the main log.
23027 .option log_fail_output pipe boolean false
23028 If this option is set, and the command returns any output on stdout or
23029 stderr, and also ends with a return code that is neither zero nor one of
23030 the return codes listed in &%temp_errors%& (that is, the delivery
23031 failed), the first line of output is written to the main log. This
23032 option and &%log_output%& are mutually exclusive. Only one of them may
23036 .option log_output pipe boolean false
23037 If this option is set and the command returns any output on stdout or
23038 stderr, the first line of output is written to the main log, whatever
23039 the return code. This option and &%log_fail_output%& are mutually
23040 exclusive. Only one of them may be set.
23043 .option max_output pipe integer 20K
23044 This specifies the maximum amount of output that the command may produce on its
23045 standard output and standard error file combined. If the limit is exceeded, the
23046 process running the command is killed. This is intended as a safety measure to
23047 catch runaway processes. The limit is applied independently of the settings of
23048 the options that control what is done with such output (for example,
23049 &%return_output%&). Because of buffering effects, the amount of output may
23050 exceed the limit by a small amount before Exim notices.
23053 .option message_prefix pipe string&!! "see below"
23054 The string specified here is expanded and output at the start of every message.
23055 The default is unset if &%use_bsmtp%& is set. Otherwise it is
23058 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
23062 .cindex "&%tmail%&"
23063 .cindex "&""From""& line"
23064 This is required by the commonly used &_/usr/bin/vacation_& program.
23065 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
23066 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
23071 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23072 &`\n`& to &`\r\n`& in &%message_prefix%&.
23075 .option message_suffix pipe string&!! "see below"
23076 The string specified here is expanded and output at the end of every message.
23077 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
23078 The suffix can be suppressed by setting
23082 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23083 &`\n`& to &`\r\n`& in &%message_suffix%&.
23086 .option path pipe string "see below"
23087 This option specifies the string that is set up in the PATH environment
23088 variable of the subprocess. The default is:
23092 If the &%command%& option does not yield an absolute path name, the command is
23093 sought in the PATH directories, in the usual way. &*Warning*&: This does not
23094 apply to a command specified as a transport filter.
23097 .option permit_coredump pipe boolean false
23098 Normally Exim inhibits core-dumps during delivery. If you have a need to get
23099 a core-dump of a pipe command, enable this command. This enables core-dumps
23100 during delivery and affects both the Exim binary and the pipe command run.
23101 It is recommended that this option remain off unless and until you have a need
23102 for it and that this only be enabled when needed, as the risk of excessive
23103 resource consumption can be quite high. Note also that Exim is typically
23104 installed as a setuid binary and most operating systems will inhibit coredumps
23105 of these by default, so further OS-specific action may be required.
23108 .option pipe_as_creator pipe boolean false
23109 .cindex "uid (user id)" "local delivery"
23110 If the generic &%user%& option is not set and this option is true, the delivery
23111 process is run under the uid that was in force when Exim was originally called
23112 to accept the message. If the group id is not otherwise set (via the generic
23113 &%group%& option), the gid that was in force when Exim was originally called to
23114 accept the message is used.
23117 .option restrict_to_path pipe boolean false
23118 When this option is set, any command name not listed in &%allow_commands%& must
23119 contain no slashes. The command is searched for only in the directories listed
23120 in the &%path%& option. This option is intended for use in the case when a pipe
23121 command has been generated from a user's &_.forward_& file. This is usually
23122 handled by a &(pipe)& transport called &%address_pipe%&.
23125 .option return_fail_output pipe boolean false
23126 If this option is true, and the command produced any output and ended with a
23127 return code other than zero or one of the codes listed in &%temp_errors%& (that
23128 is, the delivery failed), the output is returned in the bounce message.
23129 However, if the message has a null sender (that is, it is itself a bounce
23130 message), output from the command is discarded. This option and
23131 &%return_output%& are mutually exclusive. Only one of them may be set.
23135 .option return_output pipe boolean false
23136 If this option is true, and the command produced any output, the delivery is
23137 deemed to have failed whatever the return code from the command, and the output
23138 is returned in the bounce message. Otherwise, the output is just discarded.
23139 However, if the message has a null sender (that is, it is a bounce message),
23140 output from the command is always discarded, whatever the setting of this
23141 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23142 of them may be set.
23146 .option temp_errors pipe "string list" "see below"
23147 .cindex "&(pipe)& transport" "temporary failure"
23148 This option contains either a colon-separated list of numbers, or a single
23149 asterisk. If &%ignore_status%& is false
23150 and &%return_output%& is not set,
23151 and the command exits with a non-zero return code, the failure is treated as
23152 temporary and the delivery is deferred if the return code matches one of the
23153 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23154 codes are treated as permanent errors. The default setting contains the codes
23155 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23156 compiled on a system that does not define these macros, it assumes values of 75
23157 and 73, respectively.
23160 .option timeout pipe time 1h
23161 If the command fails to complete within this time, it is killed. This normally
23162 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23163 specifies no timeout. In order to ensure that any subprocesses created by the
23164 command are also killed, Exim makes the initial process a process group leader,
23165 and kills the whole process group on a timeout. However, this can be defeated
23166 if one of the processes starts a new process group.
23168 .option timeout_defer pipe boolean false
23169 A timeout in a &(pipe)& transport, either in the command that the transport
23170 runs, or in a transport filter that is associated with it, is by default
23171 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23172 is set true, both kinds of timeout become temporary errors, causing the
23173 delivery to be deferred.
23175 .option umask pipe "octal integer" 022
23176 This specifies the umask setting for the subprocess that runs the command.
23179 .option use_bsmtp pipe boolean false
23180 .cindex "envelope sender"
23181 If this option is set true, the &(pipe)& transport writes messages in &"batch
23182 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23183 commands. If you want to include a leading HELO command with such messages,
23184 you can do so by setting the &%message_prefix%& option. See section
23185 &<<SECTbatchSMTP>>& for details of batch SMTP.
23187 .option use_classresources pipe boolean false
23188 .cindex "class resources (BSD)"
23189 This option is available only when Exim is running on FreeBSD, NetBSD, or
23190 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23191 resource limits when a &(pipe)& transport is run to perform a delivery. The
23192 limits for the uid under which the pipe is to run are obtained from the login
23196 .option use_crlf pipe boolean false
23197 .cindex "carriage return"
23199 This option causes lines to be terminated with the two-character CRLF sequence
23200 (carriage return, linefeed) instead of just a linefeed character. In the case
23201 of batched SMTP, the byte sequence written to the pipe is then an exact image
23202 of what would be sent down a real SMTP connection.
23204 The contents of the &%message_prefix%& and &%message_suffix%& options are
23205 written verbatim, so must contain their own carriage return characters if these
23206 are needed. When &%use_bsmtp%& is not set, the default values for both
23207 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23208 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23211 .option use_shell pipe boolean false
23212 .vindex "&$pipe_addresses$&"
23213 If this option is set, it causes the command to be passed to &_/bin/sh_&
23214 instead of being run directly from the transport, as described in section
23215 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23216 where the command is expected to be run under a shell and cannot easily be
23217 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23218 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23219 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23224 .section "Using an external local delivery agent" "SECID143"
23225 .cindex "local delivery" "using an external agent"
23226 .cindex "&'procmail'&"
23227 .cindex "external local delivery"
23228 .cindex "delivery" "&'procmail'&"
23229 .cindex "delivery" "by external agent"
23230 The &(pipe)& transport can be used to pass all messages that require local
23231 delivery to a separate local delivery agent such as &%procmail%&. When doing
23232 this, care must be taken to ensure that the pipe is run under an appropriate
23233 uid and gid. In some configurations one wants this to be a uid that is trusted
23234 by the delivery agent to supply the correct sender of the message. It may be
23235 necessary to recompile or reconfigure the delivery agent so that it trusts an
23236 appropriate user. The following is an example transport and router
23237 configuration for &%procmail%&:
23242 command = /usr/local/bin/procmail -d $local_part
23246 check_string = "From "
23247 escape_string = ">From "
23256 transport = procmail_pipe
23258 In this example, the pipe is run as the local user, but with the group set to
23259 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23260 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23261 user to supply a correct sender address. If you do not specify either a
23262 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23263 home directory is the user's home directory by default.
23265 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23269 as shown in some &%procmail%& documentation, because Exim does not by default
23270 use a shell to run pipe commands.
23273 The next example shows a transport and a router for a system where local
23274 deliveries are handled by the Cyrus IMAP server.
23277 local_delivery_cyrus:
23279 command = /usr/cyrus/bin/deliver \
23280 -m ${substr_1:$local_part_suffix} -- $local_part
23292 local_part_suffix = .*
23293 transport = local_delivery_cyrus
23295 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23296 &%return_output%& to cause any text written by Cyrus to be returned to the
23298 .ecindex IIDpiptra1
23299 .ecindex IIDpiptra2
23302 . ////////////////////////////////////////////////////////////////////////////
23303 . ////////////////////////////////////////////////////////////////////////////
23305 .chapter "The smtp transport" "CHAPsmtptrans"
23306 .scindex IIDsmttra1 "transports" "&(smtp)&"
23307 .scindex IIDsmttra2 "&(smtp)& transport"
23308 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23309 or LMTP protocol. The list of hosts to try can either be taken from the address
23310 that is being processed (having been set up by the router), or specified
23311 explicitly for the transport. Timeout and retry processing (see chapter
23312 &<<CHAPretry>>&) is applied to each IP address independently.
23315 .section "Multiple messages on a single connection" "SECID144"
23316 The sending of multiple messages over a single TCP/IP connection can arise in
23320 If a message contains more than &%max_rcpt%& (see below) addresses that are
23321 routed to the same host, more than one copy of the message has to be sent to
23322 that host. In this situation, multiple copies may be sent in a single run of
23323 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23324 does when it has too many addresses to send in one message also depends on the
23325 value of the global &%remote_max_parallel%& option. Details are given in
23326 section &<<SECToutSMTPTCP>>&.)
23328 .cindex "hints database" "remembering routing"
23329 When a message has been successfully delivered over a TCP/IP connection, Exim
23330 looks in its hints database to see if there are any other messages awaiting a
23331 connection to the same host. If there are, a new delivery process is started
23332 for one of them, and the current TCP/IP connection is passed on to it. The new
23333 process may in turn send multiple copies and possibly create yet another
23338 For each copy sent over the same TCP/IP connection, a sequence counter is
23339 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23340 no further messages are sent over that connection.
23344 .section "Use of the $host and $host_address variables" "SECID145"
23346 .vindex "&$host_address$&"
23347 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23348 &$host_address$& are the name and IP address of the first host on the host list
23349 passed by the router. However, when the transport is about to connect to a
23350 specific host, and while it is connected to that host, &$host$& and
23351 &$host_address$& are set to the values for that host. These are the values
23352 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23353 &%serialize_hosts%&, and the various TLS options are expanded.
23356 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23357 .vindex &$tls_bits$&
23358 .vindex &$tls_cipher$&
23359 .vindex &$tls_peerdn$&
23360 .vindex &$tls_sni$&
23361 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23362 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23363 are the values that were set when the message was received.
23364 These are the values that are used for options that are expanded before any
23365 SMTP connections are made. Just before each connection is made, these four
23366 variables are emptied. If TLS is subsequently started, they are set to the
23367 appropriate values for the outgoing connection, and these are the values that
23368 are in force when any authenticators are run and when the
23369 &%authenticated_sender%& option is expanded.
23371 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23372 and will be removed in a future release.
23375 .section "Private options for smtp" "SECID146"
23376 .cindex "options" "&(smtp)& transport"
23377 The private options of the &(smtp)& transport are as follows:
23380 .option address_retry_include_sender smtp boolean true
23381 .cindex "4&'xx'& responses" "retrying after"
23382 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23383 is the combination of sender and recipient that is delayed in subsequent queue
23384 runs until the retry time is reached. You can delay the recipient without
23385 reference to the sender (which is what earlier versions of Exim did), by
23386 setting &%address_retry_include_sender%& false. However, this can lead to
23387 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23389 .option allow_localhost smtp boolean false
23390 .cindex "local host" "sending to"
23391 .cindex "fallback" "hosts specified on transport"
23392 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23393 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23394 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23395 the delivery anyway. This should be used only in special cases when the
23396 configuration ensures that no looping will result (for example, a differently
23397 configured Exim is listening on the port to which the message is sent).
23400 .option authenticated_sender smtp string&!! unset
23402 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23403 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23404 overriding any existing authenticated sender value. If the string expansion is
23405 forced to fail, the option is ignored. Other expansion failures cause delivery
23406 to be deferred. If the result of expansion is an empty string, that is also
23409 The expansion happens after the outgoing connection has been made and TLS
23410 started, if required. This means that the &$host$&, &$host_address$&,
23411 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23412 particular connection.
23414 If the SMTP session is not authenticated, the expansion of
23415 &%authenticated_sender%& still happens (and can cause the delivery to be
23416 deferred if it fails), but no AUTH= item is added to MAIL commands
23417 unless &%authenticated_sender_force%& is true.
23419 This option allows you to use the &(smtp)& transport in LMTP mode to
23420 deliver mail to Cyrus IMAP and provide the proper local part as the
23421 &"authenticated sender"&, via a setting such as:
23423 authenticated_sender = $local_part
23425 This removes the need for IMAP subfolders to be assigned special ACLs to
23426 allow direct delivery to those subfolders.
23428 Because of expected uses such as that just described for Cyrus (when no
23429 domain is involved), there is no checking on the syntax of the provided
23433 .option authenticated_sender_force smtp boolean false
23434 If this option is set true, the &%authenticated_sender%& option's value
23435 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23436 authenticated as a client.
23439 .option command_timeout smtp time 5m
23440 This sets a timeout for receiving a response to an SMTP command that has been
23441 sent out. It is also used when waiting for the initial banner line from the
23442 remote host. Its value must not be zero.
23445 .option connect_timeout smtp time 5m
23446 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
23447 to a remote host. A setting of zero allows the system timeout (typically
23448 several minutes) to act. To have any effect, the value of this option must be
23449 less than the system timeout. However, it has been observed that on some
23450 systems there is no system timeout, which is why the default value for this
23451 option is 5 minutes, a value recommended by RFC 1123.
23454 .option connection_max_messages smtp integer 500
23455 .cindex "SMTP" "passed connection"
23456 .cindex "SMTP" "multiple deliveries"
23457 .cindex "multiple SMTP deliveries"
23458 This controls the maximum number of separate message deliveries that are sent
23459 over a single TCP/IP connection. If the value is zero, there is no limit.
23460 For testing purposes, this value can be overridden by the &%-oB%& command line
23464 .option data_timeout smtp time 5m
23465 This sets a timeout for the transmission of each block in the data portion of
23466 the message. As a result, the overall timeout for a message depends on the size
23467 of the message. Its value must not be zero. See also &%final_timeout%&.
23470 .option dkim_domain smtp string&!! unset
23471 .option dkim_selector smtp string&!! unset
23472 .option dkim_private_key smtp string&!! unset
23473 .option dkim_canon smtp string&!! unset
23474 .option dkim_strict smtp string&!! unset
23475 .option dkim_sign_headers smtp string&!! unset
23476 DKIM signing options. For details see &<<SECDKIMSIGN>>&.
23479 .option delay_after_cutoff smtp boolean true
23480 This option controls what happens when all remote IP addresses for a given
23481 domain have been inaccessible for so long that they have passed their retry
23484 In the default state, if the next retry time has not been reached for any of
23485 them, the address is bounced without trying any deliveries. In other words,
23486 Exim delays retrying an IP address after the final cutoff time until a new
23487 retry time is reached, and can therefore bounce an address without ever trying
23488 a delivery, when machines have been down for a long time. Some people are
23489 unhappy at this prospect, so...
23491 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23492 addresses are past their final cutoff time, Exim tries to deliver to those
23493 IP addresses that have not been tried since the message arrived. If there are
23494 none, of if they all fail, the address is bounced. In other words, it does not
23495 delay when a new message arrives, but immediately tries those expired IP
23496 addresses that haven't been tried since the message arrived. If there is a
23497 continuous stream of messages for the dead hosts, unsetting
23498 &%delay_after_cutoff%& means that there will be many more attempts to deliver
23502 .option dns_qualify_single smtp boolean true
23503 If the &%hosts%& or &%fallback_hosts%& option is being used,
23504 and the &%gethostbyname%& option is false,
23505 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
23506 in chapter &<<CHAPdnslookup>>& for more details.
23509 .option dns_search_parents smtp boolean false
23510 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
23511 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
23512 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
23516 .option dnssec_request_domains smtp "domain list&!!" unset
23517 .cindex "MX record" "security"
23518 .cindex "DNSSEC" "MX lookup"
23519 .cindex "security" "MX lookup"
23520 .cindex "DNS" "DNSSEC"
23521 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23522 the dnssec request bit set.
23523 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23527 .option dnssec_require_domains smtp "domain list&!!" unset
23528 .cindex "MX record" "security"
23529 .cindex "DNSSEC" "MX lookup"
23530 .cindex "security" "MX lookup"
23531 .cindex "DNS" "DNSSEC"
23532 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23533 the dnssec request bit set. Any returns not having the Authenticated Data bit
23534 (AD bit) set will be ignored and logged as a host-lookup failure.
23535 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23539 .option dscp smtp string&!! unset
23540 .cindex "DCSP" "outbound"
23541 This option causes the DSCP value associated with a socket to be set to one
23542 of a number of fixed strings or to numeric value.
23543 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
23544 Common values include &`throughput`&, &`mincost`&, and on newer systems
23545 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
23547 The outbound packets from Exim will be marked with this value in the header
23548 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
23549 that these values will have any effect, not be stripped by networking
23550 equipment, or do much of anything without cooperation with your Network
23551 Engineer and those of all network operators between the source and destination.
23554 .option fallback_hosts smtp "string list" unset
23555 .cindex "fallback" "hosts specified on transport"
23556 String expansion is not applied to this option. The argument must be a
23557 colon-separated list of host names or IP addresses, optionally also including
23558 port numbers, though the separator can be changed, as described in section
23559 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23560 item in a &%route_list%& setting for the &(manualroute)& router, as described
23561 in section &<<SECTformatonehostitem>>&.
23563 Fallback hosts can also be specified on routers, which associate them with the
23564 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
23565 &%fallback_hosts%& specified on the transport is used only if the address does
23566 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
23567 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
23568 However, &%hosts_randomize%& does apply to fallback host lists.
23570 If Exim is unable to deliver to any of the hosts for a particular address, and
23571 the errors are not permanent rejections, the address is put on a separate
23572 transport queue with its host list replaced by the fallback hosts, unless the
23573 address was routed via MX records and the current host was in the original MX
23574 list. In that situation, the fallback host list is not used.
23576 Once normal deliveries are complete, the fallback queue is delivered by
23577 re-running the same transports with the new host lists. If several failing
23578 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
23579 copy of the message is sent.
23581 The resolution of the host names on the fallback list is controlled by the
23582 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
23583 both to cases when the host list comes with the address and when it is taken
23584 from &%hosts%&. This option provides a &"use a smart host only if delivery
23588 .option final_timeout smtp time 10m
23589 This is the timeout that applies while waiting for the response to the final
23590 line containing just &"."& that terminates a message. Its value must not be
23593 .option gethostbyname smtp boolean false
23594 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
23595 being used, names are looked up using &[gethostbyname()]&
23596 (or &[getipnodebyname()]& when available)
23597 instead of using the DNS. Of course, that function may in fact use the DNS, but
23598 it may also consult other sources of information such as &_/etc/hosts_&.
23600 .option gnutls_compat_mode smtp boolean unset
23601 This option controls whether GnuTLS is used in compatibility mode in an Exim
23602 server. This reduces security slightly, but improves interworking with older
23603 implementations of TLS.
23605 .option helo_data smtp string&!! "see below"
23606 .cindex "HELO" "argument, setting"
23607 .cindex "EHLO" "argument, setting"
23608 .cindex "LHLO argument setting"
23609 The value of this option is expanded after a connection to a another host has
23610 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
23611 command that starts the outgoing SMTP or LMTP session. The default value of the
23616 During the expansion, the variables &$host$& and &$host_address$& are set to
23617 the identity of the remote host, and the variables &$sending_ip_address$& and
23618 &$sending_port$& are set to the local IP address and port number that are being
23619 used. These variables can be used to generate different values for different
23620 servers or different local IP addresses. For example, if you want the string
23621 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
23622 interface address, you could use this:
23624 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
23625 {$primary_hostname}}
23627 The use of &%helo_data%& applies both to sending messages and when doing
23630 .option hosts smtp "string list&!!" unset
23631 Hosts are associated with an address by a router such as &(dnslookup)&, which
23632 finds the hosts by looking up the address domain in the DNS, or by
23633 &(manualroute)&, which has lists of hosts in its configuration. However,
23634 email addresses can be passed to the &(smtp)& transport by any router, and not
23635 all of them can provide an associated list of hosts.
23637 The &%hosts%& option specifies a list of hosts to be used if the address being
23638 processed does not have any hosts associated with it. The hosts specified by
23639 &%hosts%& are also used, whether or not the address has its own hosts, if
23640 &%hosts_override%& is set.
23642 The string is first expanded, before being interpreted as a colon-separated
23643 list of host names or IP addresses, possibly including port numbers. The
23644 separator may be changed to something other than colon, as described in section
23645 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23646 item in a &%route_list%& setting for the &(manualroute)& router, as described
23647 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
23648 of the &(manualroute)& router is not available here.
23650 If the expansion fails, delivery is deferred. Unless the failure was caused by
23651 the inability to complete a lookup, the error is logged to the panic log as
23652 well as the main log. Host names are looked up either by searching directly for
23653 address records in the DNS or by calling &[gethostbyname()]& (or
23654 &[getipnodebyname()]& when available), depending on the setting of the
23655 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
23656 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
23659 During delivery, the hosts are tried in order, subject to their retry status,
23660 unless &%hosts_randomize%& is set.
23663 .option hosts_avoid_esmtp smtp "host list&!!" unset
23664 .cindex "ESMTP, avoiding use of"
23665 .cindex "HELO" "forcing use of"
23666 .cindex "EHLO" "avoiding use of"
23667 .cindex "PIPELINING" "avoiding the use of"
23668 This option is for use with broken hosts that announce ESMTP facilities (for
23669 example, PIPELINING) and then fail to implement them properly. When a host
23670 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
23671 start of the SMTP session. This means that it cannot use any of the ESMTP
23672 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
23675 .option hosts_avoid_pipelining smtp "host list&!!" unset
23676 .cindex "PIPELINING" "avoiding the use of"
23677 Exim will not use the SMTP PIPELINING extension when delivering to any host
23678 that matches this list, even if the server host advertises PIPELINING support.
23681 .option hosts_avoid_tls smtp "host list&!!" unset
23682 .cindex "TLS" "avoiding for certain hosts"
23683 Exim will not try to start a TLS session when delivering to any host that
23684 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23686 .option hosts_verify_avoid_tls smtp "host list&!!" unset
23687 .cindex "TLS" "avoiding for certain hosts"
23688 Exim will not try to start a TLS session for a verify callout,
23689 or when delivering in cutthrough mode,
23690 to any host that matches this list.
23693 .option hosts_max_try smtp integer 5
23694 .cindex "host" "maximum number to try"
23695 .cindex "limit" "number of hosts tried"
23696 .cindex "limit" "number of MX tried"
23697 .cindex "MX record" "maximum tried"
23698 This option limits the number of IP addresses that are tried for any one
23699 delivery in cases where there are temporary delivery errors. Section
23700 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
23703 .option hosts_max_try_hardlimit smtp integer 50
23704 This is an additional check on the maximum number of IP addresses that Exim
23705 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
23710 .option hosts_nopass_tls smtp "host list&!!" unset
23711 .cindex "TLS" "passing connection"
23712 .cindex "multiple SMTP deliveries"
23713 .cindex "TLS" "multiple message deliveries"
23714 For any host that matches this list, a connection on which a TLS session has
23715 been started will not be passed to a new delivery process for sending another
23716 message on the same connection. See section &<<SECTmulmessam>>& for an
23717 explanation of when this might be needed.
23720 .option hosts_override smtp boolean false
23721 If this option is set and the &%hosts%& option is also set, any hosts that are
23722 attached to the address are ignored, and instead the hosts specified by the
23723 &%hosts%& option are always used. This option does not apply to
23724 &%fallback_hosts%&.
23727 .option hosts_randomize smtp boolean false
23728 .cindex "randomized host list"
23729 .cindex "host" "list of; randomized"
23730 .cindex "fallback" "randomized hosts"
23731 If this option is set, and either the list of hosts is taken from the
23732 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
23733 were not obtained from MX records (this includes fallback hosts from the
23734 router), and were not randomized by the router, the order of trying the hosts
23735 is randomized each time the transport runs. Randomizing the order of a host
23736 list can be used to do crude load sharing.
23738 When &%hosts_randomize%& is true, a host list may be split into groups whose
23739 order is separately randomized. This makes it possible to set up MX-like
23740 behaviour. The boundaries between groups are indicated by an item that is just
23741 &`+`& in the host list. For example:
23743 hosts = host1:host2:host3:+:host4:host5
23745 The order of the first three hosts and the order of the last two hosts is
23746 randomized for each use, but the first three always end up before the last two.
23747 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
23749 .option hosts_require_auth smtp "host list&!!" unset
23750 .cindex "authentication" "required by client"
23751 This option provides a list of servers for which authentication must succeed
23752 before Exim will try to transfer a message. If authentication fails for
23753 servers which are not in this list, Exim tries to send unauthenticated. If
23754 authentication fails for one of these servers, delivery is deferred. This
23755 temporary error is detectable in the retry rules, so it can be turned into a
23756 hard failure if required. See also &%hosts_try_auth%&, and chapter
23757 &<<CHAPSMTPAUTH>>& for details of authentication.
23760 .option hosts_request_ocsp smtp "host list&!!" *
23761 .cindex "TLS" "requiring for certain servers"
23762 Exim will request a Certificate Status on a
23763 TLS session for any host that matches this list.
23764 &%tls_verify_certificates%& should also be set for the transport.
23766 .option hosts_require_ocsp smtp "host list&!!" unset
23767 .cindex "TLS" "requiring for certain servers"
23768 Exim will request, and check for a valid Certificate Status being given, on a
23769 TLS session for any host that matches this list.
23770 &%tls_verify_certificates%& should also be set for the transport.
23772 .option hosts_require_tls smtp "host list&!!" unset
23773 .cindex "TLS" "requiring for certain servers"
23774 Exim will insist on using a TLS session when delivering to any host that
23775 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23776 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23777 incoming messages, use an appropriate ACL.
23779 .option hosts_try_auth smtp "host list&!!" unset
23780 .cindex "authentication" "optional in client"
23781 This option provides a list of servers to which, provided they announce
23782 authentication support, Exim will attempt to authenticate as a client when it
23783 connects. If authentication fails, Exim will try to transfer the message
23784 unauthenticated. See also &%hosts_require_auth%&, and chapter
23785 &<<CHAPSMTPAUTH>>& for details of authentication.
23787 .option hosts_try_prdr smtp "host list&!!" *
23788 .cindex "PRDR" "enabling, optional in client"
23789 This option provides a list of servers to which, provided they announce
23790 PRDR support, Exim will attempt to negotiate PRDR
23791 for multi-recipient messages.
23792 The option can usually be left as default.
23794 .option interface smtp "string list&!!" unset
23795 .cindex "bind IP address"
23796 .cindex "IP address" "binding"
23798 .vindex "&$host_address$&"
23799 This option specifies which interface to bind to when making an outgoing SMTP
23800 call. The value is an IP address, not an interface name such as
23801 &`eth0`&. Do not confuse this with the interface address that was used when a
23802 message was received, which is in &$received_ip_address$&, formerly known as
23803 &$interface_address$&. The name was changed to minimize confusion with the
23804 outgoing interface address. There is no variable that contains an outgoing
23805 interface address because, unless it is set by this option, its value is
23808 During the expansion of the &%interface%& option the variables &$host$& and
23809 &$host_address$& refer to the host to which a connection is about to be made
23810 during the expansion of the string. Forced expansion failure, or an empty
23811 string result causes the option to be ignored. Otherwise, after expansion, the
23812 string must be a list of IP addresses, colon-separated by default, but the
23813 separator can be changed in the usual way. For example:
23815 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
23817 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
23818 connection. If none of them are the correct type, the option is ignored. If
23819 &%interface%& is not set, or is ignored, the system's IP functions choose which
23820 interface to use if the host has more than one.
23823 .option keepalive smtp boolean true
23824 .cindex "keepalive" "on outgoing connection"
23825 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
23826 connections. When set, it causes the kernel to probe idle connections
23827 periodically, by sending packets with &"old"& sequence numbers. The other end
23828 of the connection should send a acknowledgment if the connection is still okay
23829 or a reset if the connection has been aborted. The reason for doing this is
23830 that it has the beneficial effect of freeing up certain types of connection
23831 that can get stuck when the remote host is disconnected without tidying up the
23832 TCP/IP call properly. The keepalive mechanism takes several hours to detect
23836 .option lmtp_ignore_quota smtp boolean false
23837 .cindex "LMTP" "ignoring quota errors"
23838 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
23839 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
23840 has advertised support for IGNOREQUOTA in its response to the LHLO command.
23842 .option max_rcpt smtp integer 100
23843 .cindex "RCPT" "maximum number of outgoing"
23844 This option limits the number of RCPT commands that are sent in a single
23845 SMTP message transaction. Each set of addresses is treated independently, and
23846 so can cause parallel connections to the same host if &%remote_max_parallel%&
23850 .option multi_domain smtp boolean&!! true
23851 .vindex "&$domain$&"
23852 When this option is set, the &(smtp)& transport can handle a number of
23853 addresses containing a mixture of different domains provided they all resolve
23854 to the same list of hosts. Turning the option off restricts the transport to
23855 handling only one domain at a time. This is useful if you want to use
23856 &$domain$& in an expansion for the transport, because it is set only when there
23857 is a single domain involved in a remote delivery.
23859 It is expanded per-address and can depend on any of
23860 &$address_data$&, &$domain_data$&, &$local_part_data$&,
23861 &$host$&, &$host_address$& and &$host_port$&.
23863 .option port smtp string&!! "see below"
23864 .cindex "port" "sending TCP/IP"
23865 .cindex "TCP/IP" "setting outgoing port"
23866 This option specifies the TCP/IP port on the server to which Exim connects.
23867 &*Note:*& Do not confuse this with the port that was used when a message was
23868 received, which is in &$received_port$&, formerly known as &$interface_port$&.
23869 The name was changed to minimize confusion with the outgoing port. There is no
23870 variable that contains an outgoing port.
23872 If the value of this option begins with a digit it is taken as a port number;
23873 otherwise it is looked up using &[getservbyname()]&. The default value is
23874 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
23875 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
23880 .option protocol smtp string smtp
23881 .cindex "LMTP" "over TCP/IP"
23882 .cindex "ssmtp protocol" "outbound"
23883 .cindex "TLS" "SSL-on-connect outbound"
23885 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
23886 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
23887 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
23888 deliveries into closed message stores. Exim also has support for running LMTP
23889 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
23891 If this option is set to &"smtps"&, the default value for the &%port%& option
23892 changes to &"smtps"&, and the transport initiates TLS immediately after
23893 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
23894 The Internet standards bodies strongly discourage use of this mode.
23897 .option retry_include_ip_address smtp boolean&!! true
23898 Exim normally includes both the host name and the IP address in the key it
23899 constructs for indexing retry data after a temporary delivery failure. This
23900 means that when one of several IP addresses for a host is failing, it gets
23901 tried periodically (controlled by the retry rules), but use of the other IP
23902 addresses is not affected.
23904 However, in some dialup environments hosts are assigned a different IP address
23905 each time they connect. In this situation the use of the IP address as part of
23906 the retry key leads to undesirable behaviour. Setting this option false causes
23907 Exim to use only the host name.
23908 Since it is expanded it can be made to depend on the host or domain.
23911 .option serialize_hosts smtp "host list&!!" unset
23912 .cindex "serializing connections"
23913 .cindex "host" "serializing connections"
23914 Because Exim operates in a distributed manner, if several messages for the same
23915 host arrive at around the same time, more than one simultaneous connection to
23916 the remote host can occur. This is not usually a problem except when there is a
23917 slow link between the hosts. In that situation it may be helpful to restrict
23918 Exim to one connection at a time. This can be done by setting
23919 &%serialize_hosts%& to match the relevant hosts.
23921 .cindex "hints database" "serializing deliveries to a host"
23922 Exim implements serialization by means of a hints database in which a record is
23923 written whenever a process connects to one of the restricted hosts. The record
23924 is deleted when the connection is completed. Obviously there is scope for
23925 records to get left lying around if there is a system or program crash. To
23926 guard against this, Exim ignores any records that are more than six hours old.
23928 If you set up this kind of serialization, you should also arrange to delete the
23929 relevant hints database whenever your system reboots. The names of the files
23930 start with &_misc_& and they are kept in the &_spool/db_& directory. There
23931 may be one or two files, depending on the type of DBM in use. The same files
23932 are used for ETRN serialization.
23935 See also the &%max_parallel%& generic transport option.
23939 .option size_addition smtp integer 1024
23940 .cindex "SMTP" "SIZE"
23941 .cindex "message" "size issue for transport filter"
23942 .cindex "size" "of message"
23943 .cindex "transport" "filter"
23944 .cindex "filter" "transport filter"
23945 If a remote SMTP server indicates that it supports the SIZE option of the
23946 MAIL command, Exim uses this to pass over the message size at the start of
23947 an SMTP transaction. It adds the value of &%size_addition%& to the value it
23948 sends, to allow for headers and other text that may be added during delivery by
23949 configuration options or in a transport filter. It may be necessary to increase
23950 this if a lot of text is added to messages.
23952 Alternatively, if the value of &%size_addition%& is set negative, it disables
23953 the use of the SIZE option altogether.
23957 .option socks_proxy smtp string&!! unset
23958 .cindex proxy SOCKS
23959 This option enables use of SOCKS proxies for connections made by the
23960 transport. For details see &<<SECTproxySOCKS>>&.
23964 .option tls_certificate smtp string&!! unset
23965 .cindex "TLS" "client certificate, location of"
23966 .cindex "certificate" "client, location of"
23968 .vindex "&$host_address$&"
23969 The value of this option must be the absolute path to a file which contains the
23970 client's certificate, for possible use when sending a message over an encrypted
23971 connection. The values of &$host$& and &$host_address$& are set to the name and
23972 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
23975 &*Note*&: This option must be set if you want Exim to be able to use a TLS
23976 certificate when sending messages as a client. The global option of the same
23977 name specifies the certificate for Exim as a server; it is not automatically
23978 assumed that the same certificate should be used when Exim is operating as a
23982 .option tls_crl smtp string&!! unset
23983 .cindex "TLS" "client certificate revocation list"
23984 .cindex "certificate" "revocation list for client"
23985 This option specifies a certificate revocation list. The expanded value must
23986 be the name of a file that contains a CRL in PEM format.
23989 .option tls_dh_min_bits smtp integer 1024
23990 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
23991 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
23992 key agreement is negotiated, the server will provide a large prime number
23993 for use. This option establishes the minimum acceptable size of that number.
23994 If the parameter offered by the server is too small, then the TLS handshake
23997 Only supported when using GnuTLS.
24000 .option tls_privatekey smtp string&!! unset
24001 .cindex "TLS" "client private key, location of"
24003 .vindex "&$host_address$&"
24004 The value of this option must be the absolute path to a file which contains the
24005 client's private key. This is used when sending a message over an encrypted
24006 connection using a client certificate. The values of &$host$& and
24007 &$host_address$& are set to the name and address of the server during the
24008 expansion. If this option is unset, or the expansion is forced to fail, or the
24009 result is an empty string, the private key is assumed to be in the same file as
24010 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
24013 .option tls_require_ciphers smtp string&!! unset
24014 .cindex "TLS" "requiring specific ciphers"
24015 .cindex "cipher" "requiring specific"
24017 .vindex "&$host_address$&"
24018 The value of this option must be a list of permitted cipher suites, for use
24019 when setting up an outgoing encrypted connection. (There is a global option of
24020 the same name for controlling incoming connections.) The values of &$host$& and
24021 &$host_address$& are set to the name and address of the server during the
24022 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
24023 is used in different ways by OpenSSL and GnuTLS (see sections
24024 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
24025 ciphers is a preference order.
24029 .option tls_sni smtp string&!! unset
24030 .cindex "TLS" "Server Name Indication"
24031 .vindex "&$tls_sni$&"
24032 If this option is set then it sets the $tls_out_sni variable and causes any
24033 TLS session to pass this value as the Server Name Indication extension to
24034 the remote side, which can be used by the remote side to select an appropriate
24035 certificate and private key for the session.
24037 See &<<SECTtlssni>>& for more information.
24039 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
24045 .option tls_tempfail_tryclear smtp boolean true
24046 .cindex "4&'xx'& responses" "to STARTTLS"
24047 When the server host is not in &%hosts_require_tls%&, and there is a problem in
24048 setting up a TLS session, this option determines whether or not Exim should try
24049 to deliver the message unencrypted. If it is set false, delivery to the
24050 current host is deferred; if there are other hosts, they are tried. If this
24051 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
24052 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
24053 TLS negotiation fails, Exim closes the current connection (because it is in an
24054 unknown state), opens a new one to the same host, and then tries the delivery
24058 .option tls_try_verify_hosts smtp "host list&!!" *
24059 .cindex "TLS" "server certificate verification"
24060 .cindex "certificate" "verification of server"
24061 This option gives a list of hosts for which, on encrypted connections,
24062 certificate verification will be tried but need not succeed.
24063 The &%tls_verify_certificates%& option must also be set.
24064 Note that unless the host is in this list
24065 TLS connections will be denied to hosts using self-signed certificates
24066 when &%tls_verify_certificates%& is matched.
24067 The &$tls_out_certificate_verified$& variable is set when
24068 certificate verification succeeds.
24071 .option tls_verify_cert_hostnames smtp "host list&!!" *
24072 .cindex "TLS" "server certificate hostname verification"
24073 .cindex "certificate" "verification of server"
24074 This option give a list of hosts for which,
24075 while verifying the server certificate,
24076 checks will be included on the host name
24077 (note that this will generally be the result of a DNS MX lookup)
24078 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
24079 limited to being the initial component of a 3-or-more component FQDN.
24081 There is no equivalent checking on client certificates.
24084 .option tls_verify_certificates smtp string&!! system
24085 .cindex "TLS" "server certificate verification"
24086 .cindex "certificate" "verification of server"
24088 .vindex "&$host_address$&"
24089 The value of this option must be either the
24091 or the absolute path to
24092 a file or directory containing permitted certificates for servers,
24093 for use when setting up an encrypted connection.
24095 The "system" value for the option will use a location compiled into the SSL library.
24096 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
24097 is taken as empty and an explicit location
24100 The use of a directory for the option value is not available for GnuTLS versions
24101 preceding 3.3.6 and a single file must be used.
24103 With OpenSSL the certificates specified
24105 either by file or directory
24106 are added to those given by the system default location.
24108 The values of &$host$& and
24109 &$host_address$& are set to the name and address of the server during the
24110 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
24112 For back-compatibility,
24113 if neither tls_verify_hosts nor tls_try_verify_hosts are set
24114 (a single-colon empty list counts as being set)
24115 and certificate verification fails the TLS connection is closed.
24118 .option tls_verify_hosts smtp "host list&!!" unset
24119 .cindex "TLS" "server certificate verification"
24120 .cindex "certificate" "verification of server"
24121 This option gives a list of hosts for which, on encrypted connections,
24122 certificate verification must succeed.
24123 The &%tls_verify_certificates%& option must also be set.
24124 If both this option and &%tls_try_verify_hosts%& are unset
24125 operation is as if this option selected all hosts.
24130 .section "How the limits for the number of hosts to try are used" &&&
24132 .cindex "host" "maximum number to try"
24133 .cindex "limit" "hosts; maximum number tried"
24134 There are two options that are concerned with the number of hosts that are
24135 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
24136 &%hosts_max_try_hardlimit%&.
24139 The &%hosts_max_try%& option limits the number of hosts that are tried
24140 for a single delivery. However, despite the term &"host"& in its name, the
24141 option actually applies to each IP address independently. In other words, a
24142 multihomed host is treated as several independent hosts, just as it is for
24145 Many of the larger ISPs have multiple MX records which often point to
24146 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
24147 created as a result of routing one of these domains.
24149 Trying every single IP address on such a long list does not seem sensible; if
24150 several at the top of the list fail, it is reasonable to assume there is some
24151 problem that is likely to affect all of them. Roughly speaking, the value of
24152 &%hosts_max_try%& is the maximum number that are tried before deferring the
24153 delivery. However, the logic cannot be quite that simple.
24155 Firstly, IP addresses that are skipped because their retry times have not
24156 arrived do not count, and in addition, addresses that are past their retry
24157 limits are also not counted, even when they are tried. This means that when
24158 some IP addresses are past their retry limits, more than the value of
24159 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
24160 that all IP addresses are considered before timing out an email address (but
24161 see below for an exception).
24163 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
24164 list to see if there is a subsequent host with a different (higher valued) MX.
24165 If there is, that host is considered next, and the current IP address is used
24166 but not counted. This behaviour helps in the case of a domain with a retry rule
24167 that hardly ever delays any hosts, as is now explained:
24169 Consider the case of a long list of hosts with one MX value, and a few with a
24170 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
24171 hosts at the top of the list are tried at first. With the default retry rule,
24172 which specifies increasing retry times, the higher MX hosts are eventually
24173 tried when those at the top of the list are skipped because they have not
24174 reached their retry times.
24176 However, it is common practice to put a fixed short retry time on domains for
24177 large ISPs, on the grounds that their servers are rarely down for very long.
24178 Unfortunately, these are exactly the domains that tend to resolve to long lists
24179 of hosts. The short retry time means that the lowest MX hosts are tried every
24180 time. The attempts may be in a different order because of random sorting, but
24181 without the special MX check, the higher MX hosts would never be tried until
24182 all the lower MX hosts had timed out (which might be several days), because
24183 there are always some lower MX hosts that have reached their retry times. With
24184 the special check, Exim considers at least one IP address from each MX value at
24185 every delivery attempt, even if the &%hosts_max_try%& limit has already been
24188 The above logic means that &%hosts_max_try%& is not a hard limit, and in
24189 particular, Exim normally eventually tries all the IP addresses before timing
24190 out an email address. When &%hosts_max_try%& was implemented, this seemed a
24191 reasonable thing to do. Recently, however, some lunatic DNS configurations have
24192 been set up with hundreds of IP addresses for some domains. It can
24193 take a very long time indeed for an address to time out in these cases.
24195 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
24196 Exim never tries more than this number of IP addresses; if it hits this limit
24197 and they are all timed out, the email address is bounced, even though not all
24198 possible IP addresses have been tried.
24199 .ecindex IIDsmttra1
24200 .ecindex IIDsmttra2
24206 . ////////////////////////////////////////////////////////////////////////////
24207 . ////////////////////////////////////////////////////////////////////////////
24209 .chapter "Address rewriting" "CHAPrewrite"
24210 .scindex IIDaddrew "rewriting" "addresses"
24211 There are some circumstances in which Exim automatically rewrites domains in
24212 addresses. The two most common are when an address is given without a domain
24213 (referred to as an &"unqualified address"&) or when an address contains an
24214 abbreviated domain that is expanded by DNS lookup.
24216 Unqualified envelope addresses are accepted only for locally submitted
24217 messages, or for messages that are received from hosts matching
24218 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24219 appropriate. Unqualified addresses in header lines are qualified if they are in
24220 locally submitted messages, or messages from hosts that are permitted to send
24221 unqualified envelope addresses. Otherwise, unqualified addresses in header
24222 lines are neither qualified nor rewritten.
24224 One situation in which Exim does &'not'& automatically rewrite a domain is
24225 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
24226 such a domain should be rewritten using the &"canonical"& name, and some MTAs
24227 do this. The new RFCs do not contain this suggestion.
24230 .section "Explicitly configured address rewriting" "SECID147"
24231 This chapter describes the rewriting rules that can be used in the
24232 main rewrite section of the configuration file, and also in the generic
24233 &%headers_rewrite%& option that can be set on any transport.
24235 Some people believe that configured address rewriting is a Mortal Sin.
24236 Others believe that life is not possible without it. Exim provides the
24237 facility; you do not have to use it.
24239 The main rewriting rules that appear in the &"rewrite"& section of the
24240 configuration file are applied to addresses in incoming messages, both envelope
24241 addresses and addresses in header lines. Each rule specifies the types of
24242 address to which it applies.
24244 Whether or not addresses in header lines are rewritten depends on the origin of
24245 the headers and the type of rewriting. Global rewriting, that is, rewriting
24246 rules from the rewrite section of the configuration file, is applied only to
24247 those headers that were received with the message. Header lines that are added
24248 by ACLs or by a system filter or by individual routers or transports (which
24249 are specific to individual recipient addresses) are not rewritten by the global
24252 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24253 applies all headers except those added by routers and transports. That is, as
24254 well as the headers that were received with the message, it also applies to
24255 headers that were added by an ACL or a system filter.
24258 In general, rewriting addresses from your own system or domain has some
24259 legitimacy. Rewriting other addresses should be done only with great care and
24260 in special circumstances. The author of Exim believes that rewriting should be
24261 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24262 Although it can sometimes be used as a routing tool, this is very strongly
24265 There are two commonly encountered circumstances where rewriting is used, as
24266 illustrated by these examples:
24269 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24270 exchange mail with each other behind a firewall, but there is only a single
24271 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24272 &'hitch.fict.example'& when sending mail off-site.
24274 A host rewrites the local parts of its own users so that, for example,
24275 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24280 .section "When does rewriting happen?" "SECID148"
24281 .cindex "rewriting" "timing of"
24282 .cindex "&ACL;" "rewriting addresses in"
24283 Configured address rewriting can take place at several different stages of a
24284 message's processing.
24286 .vindex "&$sender_address$&"
24287 At the start of an ACL for MAIL, the sender address may have been rewritten
24288 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24289 ordinary rewrite rules have yet been applied. If, however, the sender address
24290 is verified in the ACL, it is rewritten before verification, and remains
24291 rewritten thereafter. The subsequent value of &$sender_address$& is the
24292 rewritten address. This also applies if sender verification happens in a
24293 RCPT ACL. Otherwise, when the sender address is not verified, it is
24294 rewritten as soon as a message's header lines have been received.
24296 .vindex "&$domain$&"
24297 .vindex "&$local_part$&"
24298 Similarly, at the start of an ACL for RCPT, the current recipient's address
24299 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24300 rewrite rules have yet been applied to it. However, the behaviour is different
24301 from the sender address when a recipient is verified. The address is rewritten
24302 for the verification, but the rewriting is not remembered at this stage. The
24303 value of &$local_part$& and &$domain$& after verification are always the same
24304 as they were before (that is, they contain the unrewritten &-- except for
24305 SMTP-time rewriting &-- address).
24307 As soon as a message's header lines have been received, all the envelope
24308 recipient addresses are permanently rewritten, and rewriting is also applied to
24309 the addresses in the header lines (if configured). This happens before adding
24310 any header lines that were specified in MAIL or RCPT ACLs, and
24311 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24312 before the DATA ACL and &[local_scan()]& functions are run.
24314 When an address is being routed, either for delivery or for verification,
24315 rewriting is applied immediately to child addresses that are generated by
24316 redirection, unless &%no_rewrite%& is set on the router.
24318 .cindex "envelope sender" "rewriting at transport time"
24319 .cindex "rewriting" "at transport time"
24320 .cindex "header lines" "rewriting at transport time"
24321 At transport time, additional rewriting of addresses in header lines can be
24322 specified by setting the generic &%headers_rewrite%& option on a transport.
24323 This option contains rules that are identical in form to those in the rewrite
24324 section of the configuration file. They are applied to the original message
24325 header lines and any that were added by ACLs or a system filter. They are not
24326 applied to header lines that are added by routers or the transport.
24328 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24329 transport option. However, it is not possible to rewrite envelope recipients at
24335 .section "Testing the rewriting rules that apply on input" "SECID149"
24336 .cindex "rewriting" "testing"
24337 .cindex "testing" "rewriting"
24338 Exim's input rewriting configuration appears in a part of the run time
24339 configuration file headed by &"begin rewrite"&. It can be tested by the
24340 &%-brw%& command line option. This takes an address (which can be a full RFC
24341 2822 address) as its argument. The output is a list of how the address would be
24342 transformed by the rewriting rules for each of the different places it might
24343 appear in an incoming message, that is, for each different header and for the
24344 envelope sender and recipient fields. For example,
24346 exim -brw ph10@exim.workshop.example
24348 might produce the output
24350 sender: Philip.Hazel@exim.workshop.example
24351 from: Philip.Hazel@exim.workshop.example
24352 to: ph10@exim.workshop.example
24353 cc: ph10@exim.workshop.example
24354 bcc: ph10@exim.workshop.example
24355 reply-to: Philip.Hazel@exim.workshop.example
24356 env-from: Philip.Hazel@exim.workshop.example
24357 env-to: ph10@exim.workshop.example
24359 which shows that rewriting has been set up for that address when used in any of
24360 the source fields, but not when it appears as a recipient address. At the
24361 present time, there is no equivalent way of testing rewriting rules that are
24362 set for a particular transport.
24365 .section "Rewriting rules" "SECID150"
24366 .cindex "rewriting" "rules"
24367 The rewrite section of the configuration file consists of lines of rewriting
24370 <&'source pattern'&> <&'replacement'&> <&'flags'&>
24372 Rewriting rules that are specified for the &%headers_rewrite%& generic
24373 transport option are given as a colon-separated list. Each item in the list
24374 takes the same form as a line in the main rewriting configuration (except that
24375 any colons must be doubled, of course).
24377 The formats of source patterns and replacement strings are described below.
24378 Each is terminated by white space, unless enclosed in double quotes, in which
24379 case normal quoting conventions apply inside the quotes. The flags are single
24380 characters which may appear in any order. Spaces and tabs between them are
24383 For each address that could potentially be rewritten, the rules are scanned in
24384 order, and replacements for the address from earlier rules can themselves be
24385 replaced by later rules (but see the &"q"& and &"R"& flags).
24387 The order in which addresses are rewritten is undefined, may change between
24388 releases, and must not be relied on, with one exception: when a message is
24389 received, the envelope sender is always rewritten first, before any header
24390 lines are rewritten. For example, the replacement string for a rewrite of an
24391 address in &'To:'& must not assume that the message's address in &'From:'& has
24392 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
24393 that the envelope sender has already been rewritten.
24395 .vindex "&$domain$&"
24396 .vindex "&$local_part$&"
24397 The variables &$local_part$& and &$domain$& can be used in the replacement
24398 string to refer to the address that is being rewritten. Note that lookup-driven
24399 rewriting can be done by a rule of the form
24403 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
24404 refer to the address that is being rewritten.
24407 .section "Rewriting patterns" "SECID151"
24408 .cindex "rewriting" "patterns"
24409 .cindex "address list" "in a rewriting pattern"
24410 The source pattern in a rewriting rule is any item which may appear in an
24411 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
24412 single-item address list, which means that it is expanded before being tested
24413 against the address. As always, if you use a regular expression as a pattern,
24414 you must take care to escape dollar and backslash characters, or use the &`\N`&
24415 facility to suppress string expansion within the regular expression.
24417 Domains in patterns should be given in lower case. Local parts in patterns are
24418 case-sensitive. If you want to do case-insensitive matching of local parts, you
24419 can use a regular expression that starts with &`^(?i)`&.
24421 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
24422 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
24423 depending on the type of match which occurred. These can be used in the
24424 replacement string to insert portions of the incoming address. &$0$& always
24425 refers to the complete incoming address. When a regular expression is used, the
24426 numerical variables are set from its capturing subexpressions. For other types
24427 of pattern they are set as follows:
24430 If a local part or domain starts with an asterisk, the numerical variables
24431 refer to the character strings matched by asterisks, with &$1$& associated with
24432 the first asterisk, and &$2$& with the second, if present. For example, if the
24435 *queen@*.fict.example
24437 is matched against the address &'hearts-queen@wonderland.fict.example'& then
24439 $0 = hearts-queen@wonderland.fict.example
24443 Note that if the local part does not start with an asterisk, but the domain
24444 does, it is &$1$& that contains the wild part of the domain.
24447 If the domain part of the pattern is a partial lookup, the wild and fixed parts
24448 of the domain are placed in the next available numerical variables. Suppose,
24449 for example, that the address &'foo@bar.baz.example'& is processed by a
24450 rewriting rule of the form
24452 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
24454 and the key in the file that matches the domain is &`*.baz.example`&. Then
24460 If the address &'foo@baz.example'& is looked up, this matches the same
24461 wildcard file entry, and in this case &$2$& is set to the empty string, but
24462 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
24463 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
24464 whole domain. For non-partial domain lookups, no numerical variables are set.
24468 .section "Rewriting replacements" "SECID152"
24469 .cindex "rewriting" "replacements"
24470 If the replacement string for a rule is a single asterisk, addresses that
24471 match the pattern and the flags are &'not'& rewritten, and no subsequent
24472 rewriting rules are scanned. For example,
24474 hatta@lookingglass.fict.example * f
24476 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
24479 .vindex "&$domain$&"
24480 .vindex "&$local_part$&"
24481 If the replacement string is not a single asterisk, it is expanded, and must
24482 yield a fully qualified address. Within the expansion, the variables
24483 &$local_part$& and &$domain$& refer to the address that is being rewritten.
24484 Any letters they contain retain their original case &-- they are not lower
24485 cased. The numerical variables are set up according to the type of pattern that
24486 matched the address, as described above. If the expansion is forced to fail by
24487 the presence of &"fail"& in a conditional or lookup item, rewriting by the
24488 current rule is abandoned, but subsequent rules may take effect. Any other
24489 expansion failure causes the entire rewriting operation to be abandoned, and an
24490 entry written to the panic log.
24494 .section "Rewriting flags" "SECID153"
24495 There are three different kinds of flag that may appear on rewriting rules:
24498 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
24501 A flag that specifies rewriting at SMTP time: S.
24503 Flags that control the rewriting process: Q, q, R, w.
24506 For rules that are part of the &%headers_rewrite%& generic transport option,
24507 E, F, T, and S are not permitted.
24511 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
24513 .cindex "rewriting" "flags"
24514 If none of the following flag letters, nor the &"S"& flag (see section
24515 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
24516 and to both the sender and recipient fields of the envelope, whereas a
24517 transport-time rewriting rule just applies to all headers. Otherwise, the
24518 rewriting rule is skipped unless the relevant addresses are being processed.
24520 &`E`& rewrite all envelope fields
24521 &`F`& rewrite the envelope From field
24522 &`T`& rewrite the envelope To field
24523 &`b`& rewrite the &'Bcc:'& header
24524 &`c`& rewrite the &'Cc:'& header
24525 &`f`& rewrite the &'From:'& header
24526 &`h`& rewrite all headers
24527 &`r`& rewrite the &'Reply-To:'& header
24528 &`s`& rewrite the &'Sender:'& header
24529 &`t`& rewrite the &'To:'& header
24531 "All headers" means all of the headers listed above that can be selected
24532 individually, plus their &'Resent-'& versions. It does not include
24533 other headers such as &'Subject:'& etc.
24535 You should be particularly careful about rewriting &'Sender:'& headers, and
24536 restrict this to special known cases in your own domains.
24539 .section "The SMTP-time rewriting flag" "SECTrewriteS"
24540 .cindex "SMTP" "rewriting malformed addresses"
24541 .cindex "RCPT" "rewriting argument of"
24542 .cindex "MAIL" "rewriting argument of"
24543 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
24544 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
24545 before any other processing; even before syntax checking. The pattern is
24546 required to be a regular expression, and it is matched against the whole of the
24547 data for the command, including any surrounding angle brackets.
24549 .vindex "&$domain$&"
24550 .vindex "&$local_part$&"
24551 This form of rewrite rule allows for the handling of addresses that are not
24552 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
24553 input). Because the input is not required to be a syntactically valid address,
24554 the variables &$local_part$& and &$domain$& are not available during the
24555 expansion of the replacement string. The result of rewriting replaces the
24556 original address in the MAIL or RCPT command.
24559 .section "Flags controlling the rewriting process" "SECID155"
24560 There are four flags which control the way the rewriting process works. These
24561 take effect only when a rule is invoked, that is, when the address is of the
24562 correct type (matches the flags) and matches the pattern:
24565 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
24566 unqualified local part. It is qualified with &%qualify_recipient%&. In the
24567 absence of &"Q"& the rewritten address must always include a domain.
24569 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
24570 even if no rewriting actually takes place because of a &"fail"& in the
24571 expansion. The &"q"& flag is not effective if the address is of the wrong type
24572 (does not match the flags) or does not match the pattern.
24574 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
24575 address, up to ten times. It can be combined with the &"q"& flag, to stop
24576 rewriting once it fails to match (after at least one successful rewrite).
24578 .cindex "rewriting" "whole addresses"
24579 When an address in a header is rewritten, the rewriting normally applies only
24580 to the working part of the address, with any comments and RFC 2822 &"phrase"&
24581 left unchanged. For example, rewriting might change
24583 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
24587 From: Ford Prefect <prefectf@hitch.fict.example>
24590 Sometimes there is a need to replace the whole address item, and this can be
24591 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
24592 causes an address in a header line to be rewritten, the entire address is
24593 replaced, not just the working part. The replacement must be a complete RFC
24594 2822 address, including the angle brackets if necessary. If text outside angle
24595 brackets contains a character whose value is greater than 126 or less than 32
24596 (except for tab), the text is encoded according to RFC 2047. The character set
24597 is taken from &%headers_charset%&, which gets its default at build time.
24599 When the &"w"& flag is set on a rule that causes an envelope address to be
24600 rewritten, all but the working part of the replacement address is discarded.
24604 .section "Rewriting examples" "SECID156"
24605 Here is an example of the two common rewriting paradigms:
24607 *@*.hitch.fict.example $1@hitch.fict.example
24608 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
24609 {$value}fail}@hitch.fict.example bctfrF
24611 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
24612 the string expansion to fail if the lookup does not succeed. In this context it
24613 has the effect of leaving the original address unchanged, but Exim goes on to
24614 consider subsequent rewriting rules, if any, because the &"q"& flag is not
24615 present in that rule. An alternative to &"fail"& would be to supply &$1$&
24616 explicitly, which would cause the rewritten address to be the same as before,
24617 at the cost of a small bit of processing. Not supplying either of these is an
24618 error, since the rewritten address would then contain no local part.
24620 The first example above replaces the domain with a superior, more general
24621 domain. This may not be desirable for certain local parts. If the rule
24623 root@*.hitch.fict.example *
24625 were inserted before the first rule, rewriting would be suppressed for the
24626 local part &'root'& at any domain ending in &'hitch.fict.example'&.
24628 Rewriting can be made conditional on a number of tests, by making use of
24629 &${if$& in the expansion item. For example, to apply a rewriting rule only to
24630 messages that originate outside the local host:
24632 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
24633 {$1@hitch.fict.example}fail}"
24635 The replacement string is quoted in this example because it contains white
24638 .cindex "rewriting" "bang paths"
24639 .cindex "bang paths" "rewriting"
24640 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
24641 an address it treats it as an unqualified local part which it qualifies with
24642 the local qualification domain (if the source of the message is local or if the
24643 remote host is permitted to send unqualified addresses). Rewriting can
24644 sometimes be used to handle simple bang paths with a fixed number of
24645 components. For example, the rule
24647 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
24649 rewrites a two-component bang path &'host.name!user'& as the domain address
24650 &'user@host.name'&. However, there is a security implication in using this as
24651 a global rewriting rule for envelope addresses. It can provide a backdoor
24652 method for using your system as a relay, because the incoming addresses appear
24653 to be local. If the bang path addresses are received via SMTP, it is safer to
24654 use the &"S"& flag to rewrite them as they are received, so that relay checking
24655 can be done on the rewritten addresses.
24662 . ////////////////////////////////////////////////////////////////////////////
24663 . ////////////////////////////////////////////////////////////////////////////
24665 .chapter "Retry configuration" "CHAPretry"
24666 .scindex IIDretconf1 "retry" "configuration, description of"
24667 .scindex IIDregconf2 "configuration file" "retry section"
24668 The &"retry"& section of the runtime configuration file contains a list of
24669 retry rules that control how often Exim tries to deliver messages that cannot
24670 be delivered at the first attempt. If there are no retry rules (the section is
24671 empty or not present), there are no retries. In this situation, temporary
24672 errors are treated as permanent. The default configuration contains a single,
24673 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
24674 line option can be used to test which retry rule will be used for a given
24675 address, domain and error.
24677 The most common cause of retries is temporary failure to deliver to a remote
24678 host because the host is down, or inaccessible because of a network problem.
24679 Exim's retry processing in this case is applied on a per-host (strictly, per IP
24680 address) basis, not on a per-message basis. Thus, if one message has recently
24681 been delayed, delivery of a new message to the same host is not immediately
24682 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
24683 log selector is set, the message
24684 .cindex "retry" "time not reached"
24685 &"retry time not reached"& is written to the main log whenever a delivery is
24686 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
24687 the handling of errors during remote deliveries.
24689 Retry processing applies to routing as well as to delivering, except as covered
24690 in the next paragraph. The retry rules do not distinguish between these
24691 actions. It is not possible, for example, to specify different behaviour for
24692 failures to route the domain &'snark.fict.example'& and failures to deliver to
24693 the host &'snark.fict.example'&. I didn't think anyone would ever need this
24694 added complication, so did not implement it. However, although they share the
24695 same retry rule, the actual retry times for routing and transporting a given
24696 domain are maintained independently.
24698 When a delivery is not part of a queue run (typically an immediate delivery on
24699 receipt of a message), the routers are always run, and local deliveries are
24700 always attempted, even if retry times are set for them. This makes for better
24701 behaviour if one particular message is causing problems (for example, causing
24702 quota overflow, or provoking an error in a filter file). If such a delivery
24703 suffers a temporary failure, the retry data is updated as normal, and
24704 subsequent delivery attempts from queue runs occur only when the retry time for
24705 the local address is reached.
24707 .section "Changing retry rules" "SECID157"
24708 If you change the retry rules in your configuration, you should consider
24709 whether or not to delete the retry data that is stored in Exim's spool area in
24710 files with names like &_db/retry_&. Deleting any of Exim's hints files is
24711 always safe; that is why they are called &"hints"&.
24713 The hints retry data contains suggested retry times based on the previous
24714 rules. In the case of a long-running problem with a remote host, it might
24715 record the fact that the host has timed out. If your new rules increase the
24716 timeout time for such a host, you should definitely remove the old retry data
24717 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
24718 messages that it should now be retaining.
24722 .section "Format of retry rules" "SECID158"
24723 .cindex "retry" "rules"
24724 Each retry rule occupies one line and consists of three or four parts,
24725 separated by white space: a pattern, an error name, an optional list of sender
24726 addresses, and a list of retry parameters. The pattern and sender lists must be
24727 enclosed in double quotes if they contain white space. The rules are searched
24728 in order until one is found where the pattern, error name, and sender list (if
24729 present) match the failing host or address, the error that occurred, and the
24730 message's sender, respectively.
24733 The pattern is any single item that may appear in an address list (see section
24734 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
24735 which means that it is expanded before being tested against the address that
24736 has been delayed. A negated address list item is permitted. Address
24737 list processing treats a plain domain name as if it were preceded by &"*@"&,
24738 which makes it possible for many retry rules to start with just a domain. For
24741 lookingglass.fict.example * F,24h,30m;
24743 provides a rule for any address in the &'lookingglass.fict.example'& domain,
24746 alice@lookingglass.fict.example * F,24h,30m;
24748 applies only to temporary failures involving the local part &%alice%&.
24749 In practice, almost all rules start with a domain name pattern without a local
24752 .cindex "regular expressions" "in retry rules"
24753 &*Warning*&: If you use a regular expression in a retry rule pattern, it
24754 must match a complete address, not just a domain, because that is how regular
24755 expressions work in address lists.
24757 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
24758 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
24762 .section "Choosing which retry rule to use for address errors" "SECID159"
24763 When Exim is looking for a retry rule after a routing attempt has failed (for
24764 example, after a DNS timeout), each line in the retry configuration is tested
24765 against the complete address only if &%retry_use_local_part%& is set for the
24766 router. Otherwise, only the domain is used, except when matching against a
24767 regular expression, when the local part of the address is replaced with &"*"&.
24768 A domain on its own can match a domain pattern, or a pattern that starts with
24769 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
24770 &%check_local_user%& is true, and false for other routers.
24772 Similarly, when Exim is looking for a retry rule after a local delivery has
24773 failed (for example, after a mailbox full error), each line in the retry
24774 configuration is tested against the complete address only if
24775 &%retry_use_local_part%& is set for the transport (it defaults true for all
24778 .cindex "4&'xx'& responses" "retry rules for"
24779 However, when Exim is looking for a retry rule after a remote delivery attempt
24780 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
24781 whole address is always used as the key when searching the retry rules. The
24782 rule that is found is used to create a retry time for the combination of the
24783 failing address and the message's sender. It is the combination of sender and
24784 recipient that is delayed in subsequent queue runs until its retry time is
24785 reached. You can delay the recipient without regard to the sender by setting
24786 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
24787 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
24792 .section "Choosing which retry rule to use for host and message errors" &&&
24794 For a temporary error that is not related to an individual address (for
24795 example, a connection timeout), each line in the retry configuration is checked
24796 twice. First, the name of the remote host is used as a domain name (preceded by
24797 &"*@"& when matching a regular expression). If this does not match the line,
24798 the domain from the email address is tried in a similar fashion. For example,
24799 suppose the MX records for &'a.b.c.example'& are
24801 a.b.c.example MX 5 x.y.z.example
24805 and the retry rules are
24807 p.q.r.example * F,24h,30m;
24808 a.b.c.example * F,4d,45m;
24810 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
24811 first rule matches neither the host nor the domain, so Exim looks at the second
24812 rule. This does not match the host, but it does match the domain, so it is used
24813 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
24814 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
24815 first retry rule is used, because it matches the host.
24817 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
24818 first rule to determine retry times, but for all the other hosts for the domain
24819 &'a.b.c.example'&, the second rule is used. The second rule is also used if
24820 routing to &'a.b.c.example'& suffers a temporary failure.
24822 &*Note*&: The host name is used when matching the patterns, not its IP address.
24823 However, if a message is routed directly to an IP address without the use of a
24824 host name, for example, if a &(manualroute)& router contains a setting such as:
24826 route_list = *.a.example 192.168.34.23
24828 then the &"host name"& that is used when searching for a retry rule is the
24829 textual form of the IP address.
24831 .section "Retry rules for specific errors" "SECID161"
24832 .cindex "retry" "specific errors; specifying"
24833 The second field in a retry rule is the name of a particular error, or an
24834 asterisk, which matches any error. The errors that can be tested for are:
24837 .vitem &%auth_failed%&
24838 Authentication failed when trying to send to a host in the
24839 &%hosts_require_auth%& list in an &(smtp)& transport.
24841 .vitem &%data_4xx%&
24842 A 4&'xx'& error was received for an outgoing DATA command, either immediately
24843 after the command, or after sending the message's data.
24845 .vitem &%mail_4xx%&
24846 A 4&'xx'& error was received for an outgoing MAIL command.
24848 .vitem &%rcpt_4xx%&
24849 A 4&'xx'& error was received for an outgoing RCPT command.
24852 For the three 4&'xx'& errors, either the first or both of the x's can be given
24853 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
24854 recognize 452 errors given to RCPT commands for addresses in a certain domain,
24855 and have retries every ten minutes with a one-hour timeout, you could set up a
24856 retry rule of this form:
24858 the.domain.name rcpt_452 F,1h,10m
24860 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
24861 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
24864 .vitem &%lost_connection%&
24865 A server unexpectedly closed the SMTP connection. There may, of course,
24866 legitimate reasons for this (host died, network died), but if it repeats a lot
24867 for the same host, it indicates something odd.
24870 A DNS lookup for a host failed.
24871 Note that a &%dnslookup%& router will need to have matched
24872 its &%fail_defer_domains%& option for this retry type to be usable.
24873 Also note that a &%manualroute%& router will probably need
24874 its &%host_find_failed%& option set to &%defer%&.
24876 .vitem &%refused_MX%&
24877 A connection to a host obtained from an MX record was refused.
24879 .vitem &%refused_A%&
24880 A connection to a host not obtained from an MX record was refused.
24883 A connection was refused.
24885 .vitem &%timeout_connect_MX%&
24886 A connection attempt to a host obtained from an MX record timed out.
24888 .vitem &%timeout_connect_A%&
24889 A connection attempt to a host not obtained from an MX record timed out.
24891 .vitem &%timeout_connect%&
24892 A connection attempt timed out.
24894 .vitem &%timeout_MX%&
24895 There was a timeout while connecting or during an SMTP session with a host
24896 obtained from an MX record.
24898 .vitem &%timeout_A%&
24899 There was a timeout while connecting or during an SMTP session with a host not
24900 obtained from an MX record.
24903 There was a timeout while connecting or during an SMTP session.
24905 .vitem &%tls_required%&
24906 The server was required to use TLS (it matched &%hosts_require_tls%& in the
24907 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
24908 to STARTTLS, or there was a problem setting up the TLS connection.
24911 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24914 .vitem &%quota_%&<&'time'&>
24915 .cindex "quota" "error testing in retry rule"
24916 .cindex "retry" "quota error testing"
24917 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24918 transport, and the mailbox has not been accessed for <&'time'&>. For example,
24919 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
24923 .cindex "mailbox" "time of last read"
24924 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
24925 timeouts when the mailbox is full and is not being read by its owner. Ideally,
24926 it should be based on the last time that the user accessed the mailbox.
24927 However, it is not always possible to determine this. Exim uses the following
24931 If the mailbox is a single file, the time of last access (the &"atime"&) is
24932 used. As no new messages are being delivered (because the mailbox is over
24933 quota), Exim does not access the file, so this is the time of last user access.
24935 .cindex "maildir format" "time of last read"
24936 For a maildir delivery, the time of last modification of the &_new_&
24937 subdirectory is used. As the mailbox is over quota, no new files are created in
24938 the &_new_& subdirectory, because no new messages are being delivered. Any
24939 change to the &_new_& subdirectory is therefore assumed to be the result of an
24940 MUA moving a new message to the &_cur_& directory when it is first read. The
24941 time that is used is therefore the last time that the user read a new message.
24943 For other kinds of multi-file mailbox, the time of last access cannot be
24944 obtained, so a retry rule that uses this type of error field is never matched.
24947 The quota errors apply both to system-enforced quotas and to Exim's own quota
24948 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
24949 when a local delivery is deferred because a partition is full (the ENOSPC
24954 .section "Retry rules for specified senders" "SECID162"
24955 .cindex "retry" "rules; sender-specific"
24956 You can specify retry rules that apply only when the failing message has a
24957 specific sender. In particular, this can be used to define retry rules that
24958 apply only to bounce messages. The third item in a retry rule can be of this
24961 &`senders=`&<&'address list'&>
24963 The retry timings themselves are then the fourth item. For example:
24965 * rcpt_4xx senders=: F,1h,30m
24967 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
24968 host. If the address list contains white space, it must be enclosed in quotes.
24971 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
24973 &*Warning*&: This facility can be unhelpful if it is used for host errors
24974 (which do not depend on the recipient). The reason is that the sender is used
24975 only to match the retry rule. Once the rule has been found for a host error,
24976 its contents are used to set a retry time for the host, and this will apply to
24977 all messages, not just those with specific senders.
24979 When testing retry rules using &%-brt%&, you can supply a sender using the
24980 &%-f%& command line option, like this:
24982 exim -f "" -brt user@dom.ain
24984 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
24985 list is never matched.
24991 .section "Retry parameters" "SECID163"
24992 .cindex "retry" "parameters in rules"
24993 The third (or fourth, if a senders list is present) field in a retry rule is a
24994 sequence of retry parameter sets, separated by semicolons. Each set consists of
24996 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
24998 The letter identifies the algorithm for computing a new retry time; the cutoff
24999 time is the time beyond which this algorithm no longer applies, and the
25000 arguments vary the algorithm's action. The cutoff time is measured from the
25001 time that the first failure for the domain (combined with the local part if
25002 relevant) was detected, not from the time the message was received.
25004 .cindex "retry" "algorithms"
25005 .cindex "retry" "fixed intervals"
25006 .cindex "retry" "increasing intervals"
25007 .cindex "retry" "random intervals"
25008 The available algorithms are:
25011 &'F'&: retry at fixed intervals. There is a single time parameter specifying
25014 &'G'&: retry at geometrically increasing intervals. The first argument
25015 specifies a starting value for the interval, and the second a multiplier, which
25016 is used to increase the size of the interval at each retry.
25018 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
25019 retry, the previous interval is multiplied by the factor in order to get a
25020 maximum for the next interval. The minimum interval is the first argument of
25021 the parameter, and an actual interval is chosen randomly between them. Such a
25022 rule has been found to be helpful in cluster configurations when all the
25023 members of the cluster restart at once, and may therefore synchronize their
25024 queue processing times.
25027 When computing the next retry time, the algorithm definitions are scanned in
25028 order until one whose cutoff time has not yet passed is reached. This is then
25029 used to compute a new retry time that is later than the current time. In the
25030 case of fixed interval retries, this simply means adding the interval to the
25031 current time. For geometrically increasing intervals, retry intervals are
25032 computed from the rule's parameters until one that is greater than the previous
25033 interval is found. The main configuration variable
25034 .cindex "limit" "retry interval"
25035 .cindex "retry" "interval, maximum"
25036 .oindex "&%retry_interval_max%&"
25037 &%retry_interval_max%& limits the maximum interval between retries. It
25038 cannot be set greater than &`24h`&, which is its default value.
25040 A single remote domain may have a number of hosts associated with it, and each
25041 host may have more than one IP address. Retry algorithms are selected on the
25042 basis of the domain name, but are applied to each IP address independently. If,
25043 for example, a host has two IP addresses and one is unusable, Exim will
25044 generate retry times for it and will not try to use it until its next retry
25045 time comes. Thus the good IP address is likely to be tried first most of the
25048 .cindex "hints database" "use for retrying"
25049 Retry times are hints rather than promises. Exim does not make any attempt to
25050 run deliveries exactly at the computed times. Instead, a queue runner process
25051 starts delivery processes for delayed messages periodically, and these attempt
25052 new deliveries only for those addresses that have passed their next retry time.
25053 If a new message arrives for a deferred address, an immediate delivery attempt
25054 occurs only if the address has passed its retry time. In the absence of new
25055 messages, the minimum time between retries is the interval between queue runner
25056 processes. There is not much point in setting retry times of five minutes if
25057 your queue runners happen only once an hour, unless there are a significant
25058 number of incoming messages (which might be the case on a system that is
25059 sending everything to a smart host, for example).
25061 The data in the retry hints database can be inspected by using the
25062 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
25063 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
25064 &'exinext'& utility script can be used to find out what the next retry times
25065 are for the hosts associated with a particular mail domain, and also for local
25066 deliveries that have been deferred.
25069 .section "Retry rule examples" "SECID164"
25070 Here are some example retry rules:
25072 alice@wonderland.fict.example quota_5d F,7d,3h
25073 wonderland.fict.example quota_5d
25074 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
25075 lookingglass.fict.example * F,24h,30m;
25076 * refused_A F,2h,20m;
25077 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
25079 The first rule sets up special handling for mail to
25080 &'alice@wonderland.fict.example'& when there is an over-quota error and the
25081 mailbox has not been read for at least 5 days. Retries continue every three
25082 hours for 7 days. The second rule handles over-quota errors for all other local
25083 parts at &'wonderland.fict.example'&; the absence of a local part has the same
25084 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
25085 fail are bounced immediately if the mailbox has not been read for at least 5
25088 The third rule handles all other errors at &'wonderland.fict.example'&; retries
25089 happen every 15 minutes for an hour, then with geometrically increasing
25090 intervals until two days have passed since a delivery first failed. After the
25091 first hour there is a delay of one hour, then two hours, then four hours, and
25092 so on (this is a rather extreme example).
25094 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
25095 They happen every 30 minutes for 24 hours only. The remaining two rules handle
25096 all other domains, with special action for connection refusal from hosts that
25097 were not obtained from an MX record.
25099 The final rule in a retry configuration should always have asterisks in the
25100 first two fields so as to provide a general catch-all for any addresses that do
25101 not have their own special handling. This example tries every 15 minutes for 2
25102 hours, then with intervals starting at one hour and increasing by a factor of
25103 1.5 up to 16 hours, then every 8 hours up to 5 days.
25107 .section "Timeout of retry data" "SECID165"
25108 .cindex "timeout" "of retry data"
25109 .oindex "&%retry_data_expire%&"
25110 .cindex "hints database" "data expiry"
25111 .cindex "retry" "timeout of data"
25112 Exim timestamps the data that it writes to its retry hints database. When it
25113 consults the data during a delivery it ignores any that is older than the value
25114 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
25115 been tried for 7 days, Exim will try to deliver to it immediately a message
25116 arrives, and if that fails, it will calculate a retry time as if it were
25117 failing for the first time.
25119 This improves the behaviour for messages routed to rarely-used hosts such as MX
25120 backups. If such a host was down at one time, and happens to be down again when
25121 Exim tries a month later, using the old retry data would imply that it had been
25122 down all the time, which is not a justified assumption.
25124 If a host really is permanently dead, this behaviour causes a burst of retries
25125 every now and again, but only if messages routed to it are rare. If there is a
25126 message at least once every 7 days the retry data never expires.
25131 .section "Long-term failures" "SECID166"
25132 .cindex "delivery failure, long-term"
25133 .cindex "retry" "after long-term failure"
25134 Special processing happens when an email address has been failing for so long
25135 that the cutoff time for the last algorithm is reached. For example, using the
25136 default retry rule:
25138 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
25140 the cutoff time is four days. Reaching the retry cutoff is independent of how
25141 long any specific message has been failing; it is the length of continuous
25142 failure for the recipient address that counts.
25144 When the cutoff time is reached for a local delivery, or for all the IP
25145 addresses associated with a remote delivery, a subsequent delivery failure
25146 causes Exim to give up on the address, and a bounce message is generated.
25147 In order to cater for new messages that use the failing address, a next retry
25148 time is still computed from the final algorithm, and is used as follows:
25150 For local deliveries, one delivery attempt is always made for any subsequent
25151 messages. If this delivery fails, the address fails immediately. The
25152 post-cutoff retry time is not used.
25154 If the delivery is remote, there are two possibilities, controlled by the
25155 .oindex "&%delay_after_cutoff%&"
25156 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
25157 default. Until the post-cutoff retry time for one of the IP addresses is
25158 reached, the failing email address is bounced immediately, without a delivery
25159 attempt taking place. After that time, one new delivery attempt is made to
25160 those IP addresses that are past their retry times, and if that still fails,
25161 the address is bounced and new retry times are computed.
25163 In other words, when all the hosts for a given email address have been failing
25164 for a long time, Exim bounces rather then defers until one of the hosts' retry
25165 times is reached. Then it tries once, and bounces if that attempt fails. This
25166 behaviour ensures that few resources are wasted in repeatedly trying to deliver
25167 to a broken destination, but if the host does recover, Exim will eventually
25170 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25171 addresses are past their final cutoff time, Exim tries to deliver to those IP
25172 addresses that have not been tried since the message arrived. If there are
25173 no suitable IP addresses, or if they all fail, the address is bounced. In other
25174 words, it does not delay when a new message arrives, but tries the expired
25175 addresses immediately, unless they have been tried since the message arrived.
25176 If there is a continuous stream of messages for the failing domains, setting
25177 &%delay_after_cutoff%& false means that there will be many more attempts to
25178 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
25181 .section "Deliveries that work intermittently" "SECID167"
25182 .cindex "retry" "intermittently working deliveries"
25183 Some additional logic is needed to cope with cases where a host is
25184 intermittently available, or when a message has some attribute that prevents
25185 its delivery when others to the same address get through. In this situation,
25186 because some messages are successfully delivered, the &"retry clock"& for the
25187 host or address keeps getting reset by the successful deliveries, and so
25188 failing messages remain on the queue for ever because the cutoff time is never
25191 Two exceptional actions are applied to prevent this happening. The first
25192 applies to errors that are related to a message rather than a remote host.
25193 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
25194 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
25195 commands, and quota failures. For this type of error, if a message's arrival
25196 time is earlier than the &"first failed"& time for the error, the earlier time
25197 is used when scanning the retry rules to decide when to try next and when to
25198 time out the address.
25200 The exceptional second action applies in all cases. If a message has been on
25201 the queue for longer than the cutoff time of any applicable retry rule for a
25202 given address, a delivery is attempted for that address, even if it is not yet
25203 time, and if this delivery fails, the address is timed out. A new retry time is
25204 not computed in this case, so that other messages for the same address are
25205 considered immediately.
25206 .ecindex IIDretconf1
25207 .ecindex IIDregconf2
25214 . ////////////////////////////////////////////////////////////////////////////
25215 . ////////////////////////////////////////////////////////////////////////////
25217 .chapter "SMTP authentication" "CHAPSMTPAUTH"
25218 .scindex IIDauthconf1 "SMTP" "authentication configuration"
25219 .scindex IIDauthconf2 "authentication"
25220 The &"authenticators"& section of Exim's run time configuration is concerned
25221 with SMTP authentication. This facility is an extension to the SMTP protocol,
25222 described in RFC 2554, which allows a client SMTP host to authenticate itself
25223 to a server. This is a common way for a server to recognize clients that are
25224 permitted to use it as a relay. SMTP authentication is not of relevance to the
25225 transfer of mail between servers that have no managerial connection with each
25228 .cindex "AUTH" "description of"
25229 Very briefly, the way SMTP authentication works is as follows:
25232 The server advertises a number of authentication &'mechanisms'& in response to
25233 the client's EHLO command.
25235 The client issues an AUTH command, naming a specific mechanism. The command
25236 may, optionally, contain some authentication data.
25238 The server may issue one or more &'challenges'&, to which the client must send
25239 appropriate responses. In simple authentication mechanisms, the challenges are
25240 just prompts for user names and passwords. The server does not have to issue
25241 any challenges &-- in some mechanisms the relevant data may all be transmitted
25242 with the AUTH command.
25244 The server either accepts or denies authentication.
25246 If authentication succeeds, the client may optionally make use of the AUTH
25247 option on the MAIL command to pass an authenticated sender in subsequent
25248 mail transactions. Authentication lasts for the remainder of the SMTP
25251 If authentication fails, the client may give up, or it may try a different
25252 authentication mechanism, or it may try transferring mail over the
25253 unauthenticated connection.
25256 If you are setting up a client, and want to know which authentication
25257 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25258 SMTP port) on the server, and issue an EHLO command. The response to this
25259 includes the list of supported mechanisms. For example:
25261 &`$ `&&*&`telnet server.example 25`&*&
25262 &`Trying 192.168.34.25...`&
25263 &`Connected to server.example.`&
25264 &`Escape character is '^]'.`&
25265 &`220 server.example ESMTP Exim 4.20 ...`&
25266 &*&`ehlo client.example`&*&
25267 &`250-server.example Hello client.example [10.8.4.5]`&
25268 &`250-SIZE 52428800`&
25273 The second-last line of this example output shows that the server supports
25274 authentication using the PLAIN mechanism. In Exim, the different authentication
25275 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25276 routers and transports, which authenticators are included in the binary is
25277 controlled by build-time definitions. The following are currently available,
25278 included by setting
25281 AUTH_CYRUS_SASL=yes
25284 AUTH_HEIMDAL_GSSAPI=yes
25289 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25290 authentication mechanism (RFC 2195), and the second provides an interface to
25291 the Cyrus SASL authentication library.
25292 The third is an interface to Dovecot's authentication system, delegating the
25293 work via a socket interface.
25294 The fourth provides an interface to the GNU SASL authentication library, which
25295 provides mechanisms but typically not data sources.
25296 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25297 supporting setting a server keytab.
25298 The sixth can be configured to support
25299 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25300 not formally documented, but used by several MUAs. The seventh authenticator
25301 supports Microsoft's &'Secure Password Authentication'& mechanism.
25302 The eighth is an Exim authenticator but not an SMTP one;
25303 instead it can use information from a TLS negotiation.
25305 The authenticators are configured using the same syntax as other drivers (see
25306 section &<<SECTfordricon>>&). If no authenticators are required, no
25307 authentication section need be present in the configuration file. Each
25308 authenticator can in principle have both server and client functions. When Exim
25309 is receiving SMTP mail, it is acting as a server; when it is sending out
25310 messages over SMTP, it is acting as a client. Authenticator configuration
25311 options are provided for use in both these circumstances.
25313 To make it clear which options apply to which situation, the prefixes
25314 &%server_%& and &%client_%& are used on option names that are specific to
25315 either the server or the client function, respectively. Server and client
25316 functions are disabled if none of their options are set. If an authenticator is
25317 to be used for both server and client functions, a single definition, using
25318 both sets of options, is required. For example:
25322 public_name = CRAM-MD5
25323 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25325 client_secret = secret2
25327 The &%server_%& option is used when Exim is acting as a server, and the
25328 &%client_%& options when it is acting as a client.
25330 Descriptions of the individual authenticators are given in subsequent chapters.
25331 The remainder of this chapter covers the generic options for the
25332 authenticators, followed by general discussion of the way authentication works
25335 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25336 per-mechanism basis. Please read carefully to determine which variables hold
25337 account labels such as usercodes and which hold passwords or other
25338 authenticating data.
25340 Note that some mechanisms support two different identifiers for accounts: the
25341 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25342 and &'authz'& are commonly encountered. The American spelling is standard here.
25343 Conceptually, authentication data such as passwords are tied to the identifier
25344 used to authenticate; servers may have rules to permit one user to act as a
25345 second user, so that after login the session is treated as though that second
25346 user had logged in. That second user is the &'authorization id'&. A robust
25347 configuration might confirm that the &'authz'& field is empty or matches the
25348 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25349 as verified data, the &'authz'& as an unverified request which the server might
25352 A &'realm'& is a text string, typically a domain name, presented by a server
25353 to a client to help it select an account and credentials to use. In some
25354 mechanisms, the client and server provably agree on the realm, but clients
25355 typically can not treat the realm as secure data to be blindly trusted.
25359 .section "Generic options for authenticators" "SECID168"
25360 .cindex "authentication" "generic options"
25361 .cindex "options" "generic; for authenticators"
25363 .option client_condition authenticators string&!! unset
25364 When Exim is authenticating as a client, it skips any authenticator whose
25365 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
25366 used, for example, to skip plain text authenticators when the connection is not
25367 encrypted by a setting such as:
25369 client_condition = ${if !eq{$tls_out_cipher}{}}
25373 .option client_set_id authenticators string&!! unset
25374 When client authentication succeeds, this condition is expanded; the
25375 result is used in the log lines for outbound messages.
25376 Typically it will be the user name used for authentication.
25379 .option driver authenticators string unset
25380 This option must always be set. It specifies which of the available
25381 authenticators is to be used.
25384 .option public_name authenticators string unset
25385 This option specifies the name of the authentication mechanism that the driver
25386 implements, and by which it is known to the outside world. These names should
25387 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
25388 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
25389 defaults to the driver's instance name.
25392 .option server_advertise_condition authenticators string&!! unset
25393 When a server is about to advertise an authentication mechanism, the condition
25394 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
25395 mechanism is not advertised.
25396 If the expansion fails, the mechanism is not advertised. If the failure was not
25397 forced, and was not caused by a lookup defer, the incident is logged.
25398 See section &<<SECTauthexiser>>& below for further discussion.
25401 .option server_condition authenticators string&!! unset
25402 This option must be set for a &%plaintext%& server authenticator, where it
25403 is used directly to control authentication. See section &<<SECTplainserver>>&
25406 For the &(gsasl)& authenticator, this option is required for various
25407 mechanisms; see chapter &<<CHAPgsasl>>& for details.
25409 For the other authenticators, &%server_condition%& can be used as an additional
25410 authentication or authorization mechanism that is applied after the other
25411 authenticator conditions succeed. If it is set, it is expanded when the
25412 authenticator would otherwise return a success code. If the expansion is forced
25413 to fail, authentication fails. Any other expansion failure causes a temporary
25414 error code to be returned. If the result of a successful expansion is an empty
25415 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25416 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
25417 other result, a temporary error code is returned, with the expanded string as
25421 .option server_debug_print authenticators string&!! unset
25422 If this option is set and authentication debugging is enabled (see the &%-d%&
25423 command line option), the string is expanded and included in the debugging
25424 output when the authenticator is run as a server. This can help with checking
25425 out the values of variables.
25426 If expansion of the string fails, the error message is written to the debugging
25427 output, and Exim carries on processing.
25430 .option server_set_id authenticators string&!! unset
25431 .vindex "&$authenticated_id$&"
25432 When an Exim server successfully authenticates a client, this string is
25433 expanded using data from the authentication, and preserved for any incoming
25434 messages in the variable &$authenticated_id$&. It is also included in the log
25435 lines for incoming messages. For example, a user/password authenticator
25436 configuration might preserve the user name that was used to authenticate, and
25437 refer to it subsequently during delivery of the message.
25438 If expansion fails, the option is ignored.
25441 .option server_mail_auth_condition authenticators string&!! unset
25442 This option allows a server to discard authenticated sender addresses supplied
25443 as part of MAIL commands in SMTP connections that are authenticated by the
25444 driver on which &%server_mail_auth_condition%& is set. The option is not used
25445 as part of the authentication process; instead its (unexpanded) value is
25446 remembered for later use.
25447 How it is used is described in the following section.
25453 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
25454 .cindex "authentication" "sender; authenticated"
25455 .cindex "AUTH" "on MAIL command"
25456 When a client supplied an AUTH= item on a MAIL command, Exim applies
25457 the following checks before accepting it as the authenticated sender of the
25461 If the connection is not using extended SMTP (that is, HELO was used rather
25462 than EHLO), the use of AUTH= is a syntax error.
25464 If the value of the AUTH= parameter is &"<>"&, it is ignored.
25466 .vindex "&$authenticated_sender$&"
25467 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
25468 running, the value of &$authenticated_sender$& is set to the value obtained
25469 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
25470 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
25471 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
25472 given for the MAIL command.
25474 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
25475 is accepted and placed in &$authenticated_sender$& only if the client has
25478 If the AUTH= value was accepted by either of the two previous rules, and
25479 the client has authenticated, and the authenticator has a setting for the
25480 &%server_mail_auth_condition%&, the condition is checked at this point. The
25481 valued that was saved from the authenticator is expanded. If the expansion
25482 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
25483 &$authenticated_sender$& is deleted. If the expansion yields any other value,
25484 the value of &$authenticated_sender$& is retained and passed on with the
25489 When &$authenticated_sender$& is set for a message, it is passed on to other
25490 hosts to which Exim authenticates as a client. Do not confuse this value with
25491 &$authenticated_id$&, which is a string obtained from the authentication
25492 process, and which is not usually a complete email address.
25494 .vindex "&$sender_address$&"
25495 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
25496 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
25497 therefore make use of &$authenticated_sender$&. The converse is not true: the
25498 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
25503 .section "Authentication on an Exim server" "SECTauthexiser"
25504 .cindex "authentication" "on an Exim server"
25505 When Exim receives an EHLO command, it advertises the public names of those
25506 authenticators that are configured as servers, subject to the following
25510 The client host must match &%auth_advertise_hosts%& (default *).
25512 It the &%server_advertise_condition%& option is set, its expansion must not
25513 yield the empty string, &"0"&, &"no"&, or &"false"&.
25516 The order in which the authenticators are defined controls the order in which
25517 the mechanisms are advertised.
25519 Some mail clients (for example, some versions of Netscape) require the user to
25520 provide a name and password for authentication whenever AUTH is advertised,
25521 even though authentication may not in fact be needed (for example, Exim may be
25522 set up to allow unconditional relaying from the client by an IP address check).
25523 You can make such clients more friendly by not advertising AUTH to them.
25524 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
25525 that runs for RCPT) to relay without authentication, you should set
25527 auth_advertise_hosts = ! 10.9.8.0/24
25529 so that no authentication mechanisms are advertised to them.
25531 The &%server_advertise_condition%& controls the advertisement of individual
25532 authentication mechanisms. For example, it can be used to restrict the
25533 advertisement of a particular mechanism to encrypted connections, by a setting
25536 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
25538 .vindex "&$tls_in_cipher$&"
25539 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
25540 yields &"yes"&, which allows the advertisement to happen.
25542 When an Exim server receives an AUTH command from a client, it rejects it
25543 immediately if AUTH was not advertised in response to an earlier EHLO
25544 command. This is the case if
25547 The client host does not match &%auth_advertise_hosts%&; or
25549 No authenticators are configured with server options; or
25551 Expansion of &%server_advertise_condition%& blocked the advertising of all the
25552 server authenticators.
25556 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
25557 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
25558 AUTH is accepted from any client host.
25560 If AUTH is not rejected by the ACL, Exim searches its configuration for a
25561 server authentication mechanism that was advertised in response to EHLO and
25562 that matches the one named in the AUTH command. If it finds one, it runs
25563 the appropriate authentication protocol, and authentication either succeeds or
25564 fails. If there is no matching advertised mechanism, the AUTH command is
25565 rejected with a 504 error.
25567 .vindex "&$received_protocol$&"
25568 .vindex "&$sender_host_authenticated$&"
25569 When a message is received from an authenticated host, the value of
25570 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
25571 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
25572 public name) of the authenticator driver that successfully authenticated the
25573 client from which the message was received. This variable is empty if there was
25574 no successful authentication.
25579 .section "Testing server authentication" "SECID169"
25580 .cindex "authentication" "testing a server"
25581 .cindex "AUTH" "testing a server"
25582 .cindex "base64 encoding" "creating authentication test data"
25583 Exim's &%-bh%& option can be useful for testing server authentication
25584 configurations. The data for the AUTH command has to be sent using base64
25585 encoding. A quick way to produce such data for testing is the following Perl
25589 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
25591 .cindex "binary zero" "in authentication data"
25592 This interprets its argument as a Perl string, and then encodes it. The
25593 interpretation as a Perl string allows binary zeros, which are required for
25594 some kinds of authentication, to be included in the data. For example, a
25595 command line to run this script on such data might be
25597 encode '\0user\0password'
25599 Note the use of single quotes to prevent the shell interpreting the
25600 backslashes, so that they can be interpreted by Perl to specify characters
25601 whose code value is zero.
25603 &*Warning 1*&: If either of the user or password strings starts with an octal
25604 digit, you must use three zeros instead of one after the leading backslash. If
25605 you do not, the octal digit that starts your string will be incorrectly
25606 interpreted as part of the code for the first character.
25608 &*Warning 2*&: If there are characters in the strings that Perl interprets
25609 specially, you must use a Perl escape to prevent them being misinterpreted. For
25610 example, a command such as
25612 encode '\0user@domain.com\0pas$$word'
25614 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
25616 If you have the &%mimencode%& command installed, another way to do produce
25617 base64-encoded strings is to run the command
25619 echo -e -n `\0user\0password' | mimencode
25621 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
25622 in the argument, and the &%-n%& option specifies no newline at the end of its
25623 output. However, not all versions of &%echo%& recognize these options, so you
25624 should check your version before relying on this suggestion.
25628 .section "Authentication by an Exim client" "SECID170"
25629 .cindex "authentication" "on an Exim client"
25630 The &(smtp)& transport has two options called &%hosts_require_auth%& and
25631 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
25632 announces support for authentication, and the host matches an entry in either
25633 of these options, Exim (as a client) tries to authenticate as follows:
25636 For each authenticator that is configured as a client, in the order in which
25637 they are defined in the configuration, it searches the authentication
25638 mechanisms announced by the server for one whose name matches the public name
25639 of the authenticator.
25642 .vindex "&$host_address$&"
25643 When it finds one that matches, it runs the authenticator's client code. The
25644 variables &$host$& and &$host_address$& are available for any string expansions
25645 that the client might do. They are set to the server's name and IP address. If
25646 any expansion is forced to fail, the authentication attempt is abandoned, and
25647 Exim moves on to the next authenticator. Otherwise an expansion failure causes
25648 delivery to be deferred.
25650 If the result of the authentication attempt is a temporary error or a timeout,
25651 Exim abandons trying to send the message to the host for the moment. It will
25652 try again later. If there are any backup hosts available, they are tried in the
25655 If the response to authentication is a permanent error (5&'xx'& code), Exim
25656 carries on searching the list of authenticators and tries another one if
25657 possible. If all authentication attempts give permanent errors, or if there are
25658 no attempts because no mechanisms match (or option expansions force failure),
25659 what happens depends on whether the host matches &%hosts_require_auth%& or
25660 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
25661 delivery is deferred. The error can be detected in the retry rules, and thereby
25662 turned into a permanent error if you wish. In the second case, Exim tries to
25663 deliver the message unauthenticated.
25666 .cindex "AUTH" "on MAIL command"
25667 When Exim has authenticated itself to a remote server, it adds the AUTH
25668 parameter to the MAIL commands it sends, if it has an authenticated sender for
25669 the message. If the message came from a remote host, the authenticated sender
25670 is the one that was receiving on an incoming MAIL command, provided that the
25671 incoming connection was authenticated and the &%server_mail_auth%& condition
25672 allowed the authenticated sender to be retained. If a local process calls Exim
25673 to send a message, the sender address that is built from the login name and
25674 &%qualify_domain%& is treated as authenticated. However, if the
25675 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
25676 the authenticated sender that was received with the message.
25677 .ecindex IIDauthconf1
25678 .ecindex IIDauthconf2
25685 . ////////////////////////////////////////////////////////////////////////////
25686 . ////////////////////////////////////////////////////////////////////////////
25688 .chapter "The plaintext authenticator" "CHAPplaintext"
25689 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
25690 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
25691 The &(plaintext)& authenticator can be configured to support the PLAIN and
25692 LOGIN authentication mechanisms, both of which transfer authentication data as
25693 plain (unencrypted) text (though base64 encoded). The use of plain text is a
25694 security risk; you are strongly advised to insist on the use of SMTP encryption
25695 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
25696 use unencrypted plain text, you should not use the same passwords for SMTP
25697 connections as you do for login accounts.
25699 .section "Plaintext options" "SECID171"
25700 .cindex "options" "&(plaintext)& authenticator (server)"
25701 When configured as a server, &(plaintext)& uses the following options:
25703 .option server_condition authenticators string&!! unset
25704 This is actually a global authentication option, but it must be set in order to
25705 configure the &(plaintext)& driver as a server. Its use is described below.
25707 .option server_prompts plaintext string&!! unset
25708 The contents of this option, after expansion, must be a colon-separated list of
25709 prompt strings. If expansion fails, a temporary authentication rejection is
25712 .section "Using plaintext in a server" "SECTplainserver"
25713 .cindex "AUTH" "in &(plaintext)& authenticator"
25714 .cindex "binary zero" "in &(plaintext)& authenticator"
25715 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
25716 "in &(plaintext)& authenticator"
25717 .vindex "&$auth1$&, &$auth2$&, etc"
25718 .cindex "base64 encoding" "in &(plaintext)& authenticator"
25720 When running as a server, &(plaintext)& performs the authentication test by
25721 expanding a string. The data sent by the client with the AUTH command, or in
25722 response to subsequent prompts, is base64 encoded, and so may contain any byte
25723 values when decoded. If any data is supplied with the command, it is treated as
25724 a list of strings, separated by NULs (binary zeros), the first three of which
25725 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
25726 (neither LOGIN nor PLAIN uses more than three strings).
25728 For compatibility with previous releases of Exim, the values are also placed in
25729 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
25730 variables for this purpose is now deprecated, as it can lead to confusion in
25731 string expansions that also use them for other things.
25733 If there are more strings in &%server_prompts%& than the number of strings
25734 supplied with the AUTH command, the remaining prompts are used to obtain more
25735 data. Each response from the client may be a list of NUL-separated strings.
25737 .vindex "&$authenticated_id$&"
25738 Once a sufficient number of data strings have been received,
25739 &%server_condition%& is expanded. If the expansion is forced to fail,
25740 authentication fails. Any other expansion failure causes a temporary error code
25741 to be returned. If the result of a successful expansion is an empty string,
25742 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25743 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
25744 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
25745 For any other result, a temporary error code is returned, with the expanded
25746 string as the error text
25748 &*Warning*&: If you use a lookup in the expansion to find the user's
25749 password, be sure to make the authentication fail if the user is unknown.
25750 There are good and bad examples at the end of the next section.
25754 .section "The PLAIN authentication mechanism" "SECID172"
25755 .cindex "PLAIN authentication mechanism"
25756 .cindex "authentication" "PLAIN mechanism"
25757 .cindex "binary zero" "in &(plaintext)& authenticator"
25758 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
25759 sent as one item of data (that is, one combined string containing two NUL
25760 separators). The data is sent either as part of the AUTH command, or
25761 subsequently in response to an empty prompt from the server.
25763 The second and third strings are a user name and a corresponding password.
25764 Using a single fixed user name and password as an example, this could be
25765 configured as follows:
25769 public_name = PLAIN
25771 server_condition = \
25772 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
25773 server_set_id = $auth2
25775 Note that the default result strings from &%if%& (&"true"& or an empty string)
25776 are exactly what we want here, so they need not be specified. Obviously, if the
25777 password contains expansion-significant characters such as dollar, backslash,
25778 or closing brace, they have to be escaped.
25780 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
25781 the end of a string list are ignored). If all the data comes as part of the
25782 AUTH command, as is commonly the case, the prompt is not used. This
25783 authenticator is advertised in the response to EHLO as
25787 and a client host can authenticate itself by sending the command
25789 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
25791 As this contains three strings (more than the number of prompts), no further
25792 data is required from the client. Alternatively, the client may just send
25796 to initiate authentication, in which case the server replies with an empty
25797 prompt. The client must respond with the combined data string.
25799 The data string is base64 encoded, as required by the RFC. This example,
25800 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
25801 represents a zero byte. This is split up into three strings, the first of which
25802 is empty. The &%server_condition%& option in the authenticator checks that the
25803 second two are &`username`& and &`mysecret`& respectively.
25805 Having just one fixed user name and password, as in this example, is not very
25806 realistic, though for a small organization with only a handful of
25807 authenticating clients it could make sense.
25809 A more sophisticated instance of this authenticator could use the user name in
25810 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
25811 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
25812 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
25813 This is an incorrect example:
25815 server_condition = \
25816 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
25818 The expansion uses the user name (&$auth2$&) as the key to look up a password,
25819 which it then compares to the supplied password (&$auth3$&). Why is this example
25820 incorrect? It works fine for existing users, but consider what happens if a
25821 non-existent user name is given. The lookup fails, but as no success/failure
25822 strings are given for the lookup, it yields an empty string. Thus, to defeat
25823 the authentication, all a client has to do is to supply a non-existent user
25824 name and an empty password. The correct way of writing this test is:
25826 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
25827 {${if eq{$value}{$auth3}}} {false}}
25829 In this case, if the lookup succeeds, the result is checked; if the lookup
25830 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
25831 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
25832 always fails if its second argument is empty. However, the second way of
25833 writing the test makes the logic clearer.
25836 .section "The LOGIN authentication mechanism" "SECID173"
25837 .cindex "LOGIN authentication mechanism"
25838 .cindex "authentication" "LOGIN mechanism"
25839 The LOGIN authentication mechanism is not documented in any RFC, but is in use
25840 in a number of programs. No data is sent with the AUTH command. Instead, a
25841 user name and password are supplied separately, in response to prompts. The
25842 plaintext authenticator can be configured to support this as in this example:
25846 public_name = LOGIN
25847 server_prompts = User Name : Password
25848 server_condition = \
25849 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
25850 server_set_id = $auth1
25852 Because of the way plaintext operates, this authenticator accepts data supplied
25853 with the AUTH command (in contravention of the specification of LOGIN), but
25854 if the client does not supply it (as is the case for LOGIN clients), the prompt
25855 strings are used to obtain two data items.
25857 Some clients are very particular about the precise text of the prompts. For
25858 example, Outlook Express is reported to recognize only &"Username:"& and
25859 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
25860 strings. It uses the &%ldapauth%& expansion condition to check the user
25861 name and password by binding to an LDAP server:
25865 public_name = LOGIN
25866 server_prompts = Username:: : Password::
25867 server_condition = ${if and{{ \
25870 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
25871 pass=${quote:$auth2} \
25872 ldap://ldap.example.org/} }} }
25873 server_set_id = uid=$auth1,ou=people,o=example.org
25875 We have to check that the username is not empty before using it, because LDAP
25876 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
25877 operator to correctly quote the DN for authentication. However, the basic
25878 &%quote%& operator, rather than any of the LDAP quoting operators, is the
25879 correct one to use for the password, because quoting is needed only to make
25880 the password conform to the Exim syntax. At the LDAP level, the password is an
25881 uninterpreted string.
25884 .section "Support for different kinds of authentication" "SECID174"
25885 A number of string expansion features are provided for the purpose of
25886 interfacing to different ways of user authentication. These include checking
25887 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
25888 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
25894 .section "Using plaintext in a client" "SECID175"
25895 .cindex "options" "&(plaintext)& authenticator (client)"
25896 The &(plaintext)& authenticator has two client options:
25898 .option client_ignore_invalid_base64 plaintext boolean false
25899 If the client receives a server prompt that is not a valid base64 string,
25900 authentication is abandoned by default. However, if this option is set true,
25901 the error in the challenge is ignored and the client sends the response as
25904 .option client_send plaintext string&!! unset
25905 The string is a colon-separated list of authentication data strings. Each
25906 string is independently expanded before being sent to the server. The first
25907 string is sent with the AUTH command; any more strings are sent in response
25908 to prompts from the server. Before each string is expanded, the value of the
25909 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
25910 with &$auth1$& for the first prompt. Up to three prompts are stored in this
25911 way. Thus, the prompt that is received in response to sending the first string
25912 (with the AUTH command) can be used in the expansion of the second string, and
25913 so on. If an invalid base64 string is received when
25914 &%client_ignore_invalid_base64%& is set, an empty string is put in the
25915 &$auth$&<&'n'&> variable.
25917 &*Note*&: You cannot use expansion to create multiple strings, because
25918 splitting takes priority and happens first.
25920 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
25921 the data, further processing is applied to each string before it is sent. If
25922 there are any single circumflex characters in the string, they are converted to
25923 NULs. Should an actual circumflex be required as data, it must be doubled in
25926 This is an example of a client configuration that implements the PLAIN
25927 authentication mechanism with a fixed user name and password:
25931 public_name = PLAIN
25932 client_send = ^username^mysecret
25934 The lack of colons means that the entire text is sent with the AUTH
25935 command, with the circumflex characters converted to NULs. A similar example
25936 that uses the LOGIN mechanism is:
25940 public_name = LOGIN
25941 client_send = : username : mysecret
25943 The initial colon means that the first string is empty, so no data is sent with
25944 the AUTH command itself. The remaining strings are sent in response to
25946 .ecindex IIDplaiauth1
25947 .ecindex IIDplaiauth2
25952 . ////////////////////////////////////////////////////////////////////////////
25953 . ////////////////////////////////////////////////////////////////////////////
25955 .chapter "The cram_md5 authenticator" "CHID9"
25956 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
25957 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
25958 .cindex "CRAM-MD5 authentication mechanism"
25959 .cindex "authentication" "CRAM-MD5 mechanism"
25960 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
25961 sends a challenge string to the client, and the response consists of a user
25962 name and the CRAM-MD5 digest of the challenge string combined with a secret
25963 string (password) which is known to both server and client. Thus, the secret
25964 is not sent over the network as plain text, which makes this authenticator more
25965 secure than &(plaintext)&. However, the downside is that the secret has to be
25966 available in plain text at either end.
25969 .section "Using cram_md5 as a server" "SECID176"
25970 .cindex "options" "&(cram_md5)& authenticator (server)"
25971 This authenticator has one server option, which must be set to configure the
25972 authenticator as a server:
25974 .option server_secret cram_md5 string&!! unset
25975 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
25976 When the server receives the client's response, the user name is placed in
25977 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
25978 obtain the password for that user. The server then computes the CRAM-MD5 digest
25979 that the client should have sent, and checks that it received the correct
25980 string. If the expansion of &%server_secret%& is forced to fail, authentication
25981 fails. If the expansion fails for some other reason, a temporary error code is
25982 returned to the client.
25984 For compatibility with previous releases of Exim, the user name is also placed
25985 in &$1$&. However, the use of this variables for this purpose is now
25986 deprecated, as it can lead to confusion in string expansions that also use
25987 numeric variables for other things.
25989 For example, the following authenticator checks that the user name given by the
25990 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
25991 user name, authentication fails.
25995 public_name = CRAM-MD5
25996 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
25997 server_set_id = $auth1
25999 .vindex "&$authenticated_id$&"
26000 If authentication succeeds, the setting of &%server_set_id%& preserves the user
26001 name in &$authenticated_id$&. A more typical configuration might look up the
26002 secret string in a file, using the user name as the key. For example:
26006 public_name = CRAM-MD5
26007 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
26009 server_set_id = $auth1
26011 Note that this expansion explicitly forces failure if the lookup fails
26012 because &$auth1$& contains an unknown user name.
26014 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
26015 using the relevant libraries, you need to know the realm to specify in the
26016 lookup and then ask for the &"userPassword"& attribute for that user in that
26021 public_name = CRAM-MD5
26022 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
26023 dbmjz{/etc/sasldb2}{$value}fail}
26024 server_set_id = $auth1
26027 .section "Using cram_md5 as a client" "SECID177"
26028 .cindex "options" "&(cram_md5)& authenticator (client)"
26029 When used as a client, the &(cram_md5)& authenticator has two options:
26033 .option client_name cram_md5 string&!! "the primary host name"
26034 This string is expanded, and the result used as the user name data when
26035 computing the response to the server's challenge.
26038 .option client_secret cram_md5 string&!! unset
26039 This option must be set for the authenticator to work as a client. Its value is
26040 expanded and the result used as the secret string when computing the response.
26044 .vindex "&$host_address$&"
26045 Different user names and secrets can be used for different servers by referring
26046 to &$host$& or &$host_address$& in the options. Forced failure of either
26047 expansion string is treated as an indication that this authenticator is not
26048 prepared to handle this case. Exim moves on to the next configured client
26049 authenticator. Any other expansion failure causes Exim to give up trying to
26050 send the message to the current server.
26052 A simple example configuration of a &(cram_md5)& authenticator, using fixed
26057 public_name = CRAM-MD5
26059 client_secret = secret
26061 .ecindex IIDcramauth1
26062 .ecindex IIDcramauth2
26066 . ////////////////////////////////////////////////////////////////////////////
26067 . ////////////////////////////////////////////////////////////////////////////
26069 .chapter "The cyrus_sasl authenticator" "CHID10"
26070 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
26071 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
26072 .cindex "Cyrus" "SASL library"
26074 The code for this authenticator was provided by Matthew Byng-Maddick of A L
26075 Digital Ltd (&url(http://www.aldigital.co.uk)).
26077 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
26078 library implementation of the RFC 2222 (&"Simple Authentication and Security
26079 Layer"&). This library supports a number of authentication mechanisms,
26080 including PLAIN and LOGIN, but also several others that Exim does not support
26081 directly. In particular, there is support for Kerberos authentication.
26083 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
26084 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
26085 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
26086 name of the driver to determine which mechanism to support.
26088 Where access to some kind of secret file is required, for example in GSSAPI
26089 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
26090 user, and that the Cyrus SASL library has no way of escalating privileges
26091 by default. You may also find you need to set environment variables,
26092 depending on the driver you are using.
26094 The application name provided by Exim is &"exim"&, so various SASL options may
26095 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
26096 Kerberos, note that because of limitations in the GSSAPI interface,
26097 changing the server keytab might need to be communicated down to the Kerberos
26098 layer independently. The mechanism for doing so is dependent upon the Kerberos
26101 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
26102 may be set to point to an alternative keytab file. Exim will pass this
26103 variable through from its own inherited environment when started as root or the
26104 Exim user. The keytab file needs to be readable by the Exim user.
26105 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
26106 environment variable. In practice, for those releases, the Cyrus authenticator
26107 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
26108 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
26111 .section "Using cyrus_sasl as a server" "SECID178"
26112 The &(cyrus_sasl)& authenticator has four private options. It puts the username
26113 (on a successful authentication) into &$auth1$&. For compatibility with
26114 previous releases of Exim, the username is also placed in &$1$&. However, the
26115 use of this variable for this purpose is now deprecated, as it can lead to
26116 confusion in string expansions that also use numeric variables for other
26120 .option server_hostname cyrus_sasl string&!! "see below"
26121 This option selects the hostname that is used when communicating with the
26122 library. The default value is &`$primary_hostname`&. It is up to the underlying
26123 SASL plug-in what it does with this data.
26126 .option server_mech cyrus_sasl string "see below"
26127 This option selects the authentication mechanism this driver should use. The
26128 default is the value of the generic &%public_name%& option. This option allows
26129 you to use a different underlying mechanism from the advertised name. For
26133 driver = cyrus_sasl
26134 public_name = X-ANYTHING
26135 server_mech = CRAM-MD5
26136 server_set_id = $auth1
26139 .option server_realm cyrus_sasl string&!! unset
26140 This specifies the SASL realm that the server claims to be in.
26143 .option server_service cyrus_sasl string &`smtp`&
26144 This is the SASL service that the server claims to implement.
26147 For straightforward cases, you do not need to set any of the authenticator's
26148 private options. All you need to do is to specify an appropriate mechanism as
26149 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
26150 PLAIN, you could have two authenticators as follows:
26153 driver = cyrus_sasl
26154 public_name = CRAM-MD5
26155 server_set_id = $auth1
26158 driver = cyrus_sasl
26159 public_name = PLAIN
26160 server_set_id = $auth2
26162 Cyrus SASL does implement the LOGIN authentication method, even though it is
26163 not a standard method. It is disabled by default in the source distribution,
26164 but it is present in many binary distributions.
26165 .ecindex IIDcyrauth1
26166 .ecindex IIDcyrauth2
26171 . ////////////////////////////////////////////////////////////////////////////
26172 . ////////////////////////////////////////////////////////////////////////////
26173 .chapter "The dovecot authenticator" "CHAPdovecot"
26174 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
26175 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
26176 This authenticator is an interface to the authentication facility of the
26177 Dovecot POP/IMAP server, which can support a number of authentication methods.
26178 Note that Dovecot must be configured to use auth-client not auth-userdb.
26179 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
26180 to use the same mechanisms for SMTP authentication. This is a server
26181 authenticator only. There is only one option:
26183 .option server_socket dovecot string unset
26185 This option must specify the socket that is the interface to Dovecot
26186 authentication. The &%public_name%& option must specify an authentication
26187 mechanism that Dovecot is configured to support. You can have several
26188 authenticators for different mechanisms. For example:
26192 public_name = PLAIN
26193 server_socket = /var/run/dovecot/auth-client
26194 server_set_id = $auth1
26199 server_socket = /var/run/dovecot/auth-client
26200 server_set_id = $auth1
26202 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
26203 &$received_ip_address$& (that is, the connection is local), the &"secured"&
26204 option is passed in the Dovecot authentication command. If, for a TLS
26205 connection, a client certificate has been verified, the &"valid-client-cert"&
26206 option is passed. When authentication succeeds, the identity of the user
26207 who authenticated is placed in &$auth1$&.
26208 .ecindex IIDdcotauth1
26209 .ecindex IIDdcotauth2
26212 . ////////////////////////////////////////////////////////////////////////////
26213 . ////////////////////////////////////////////////////////////////////////////
26214 .chapter "The gsasl authenticator" "CHAPgsasl"
26215 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
26216 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
26217 .cindex "authentication" "GNU SASL"
26218 .cindex "authentication" "SASL"
26219 .cindex "authentication" "EXTERNAL"
26220 .cindex "authentication" "ANONYMOUS"
26221 .cindex "authentication" "PLAIN"
26222 .cindex "authentication" "LOGIN"
26223 .cindex "authentication" "DIGEST-MD5"
26224 .cindex "authentication" "CRAM-MD5"
26225 .cindex "authentication" "SCRAM-SHA-1"
26226 The &(gsasl)& authenticator provides server integration for the GNU SASL
26227 library and the mechanisms it provides. This is new as of the 4.80 release
26228 and there are a few areas where the library does not let Exim smoothly
26229 scale to handle future authentication mechanisms, so no guarantee can be
26230 made that any particular new authentication mechanism will be supported
26231 without code changes in Exim.
26234 .option server_channelbinding gsasl boolean false
26235 Some authentication mechanisms are able to use external context at both ends
26236 of the session to bind the authentication to that context, and fail the
26237 authentication process if that context differs. Specifically, some TLS
26238 ciphersuites can provide identifying information about the cryptographic
26241 This means that certificate identity and verification becomes a non-issue,
26242 as a man-in-the-middle attack will cause the correct client and server to
26243 see different identifiers and authentication will fail.
26245 This is currently only supported when using the GnuTLS library. This is
26246 only usable by mechanisms which support "channel binding"; at time of
26247 writing, that's the SCRAM family.
26249 This defaults off to ensure smooth upgrade across Exim releases, in case
26250 this option causes some clients to start failing. Some future release
26251 of Exim may switch the default to be true.
26254 .option server_hostname gsasl string&!! "see below"
26255 This option selects the hostname that is used when communicating with the
26256 library. The default value is &`$primary_hostname`&.
26257 Some mechanisms will use this data.
26260 .option server_mech gsasl string "see below"
26261 This option selects the authentication mechanism this driver should use. The
26262 default is the value of the generic &%public_name%& option. This option allows
26263 you to use a different underlying mechanism from the advertised name. For
26268 public_name = X-ANYTHING
26269 server_mech = CRAM-MD5
26270 server_set_id = $auth1
26274 .option server_password gsasl string&!! unset
26275 Various mechanisms need access to the cleartext password on the server, so
26276 that proof-of-possession can be demonstrated on the wire, without sending
26277 the password itself.
26279 The data available for lookup varies per mechanism.
26280 In all cases, &$auth1$& is set to the &'authentication id'&.
26281 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26282 if available, else the empty string.
26283 The &$auth3$& variable will always be the &'realm'& if available,
26284 else the empty string.
26286 A forced failure will cause authentication to defer.
26288 If using this option, it may make sense to set the &%server_condition%&
26289 option to be simply "true".
26292 .option server_realm gsasl string&!! unset
26293 This specifies the SASL realm that the server claims to be in.
26294 Some mechanisms will use this data.
26297 .option server_scram_iter gsasl string&!! unset
26298 This option provides data for the SCRAM family of mechanisms.
26299 &$auth1$& is not available at evaluation time.
26300 (This may change, as we receive feedback on use)
26303 .option server_scram_salt gsasl string&!! unset
26304 This option provides data for the SCRAM family of mechanisms.
26305 &$auth1$& is not available at evaluation time.
26306 (This may change, as we receive feedback on use)
26309 .option server_service gsasl string &`smtp`&
26310 This is the SASL service that the server claims to implement.
26311 Some mechanisms will use this data.
26314 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26315 .vindex "&$auth1$&, &$auth2$&, etc"
26316 These may be set when evaluating specific options, as detailed above.
26317 They will also be set when evaluating &%server_condition%&.
26319 Unless otherwise stated below, the &(gsasl)& integration will use the following
26320 meanings for these variables:
26323 .vindex "&$auth1$&"
26324 &$auth1$&: the &'authentication id'&
26326 .vindex "&$auth2$&"
26327 &$auth2$&: the &'authorization id'&
26329 .vindex "&$auth3$&"
26330 &$auth3$&: the &'realm'&
26333 On a per-mechanism basis:
26336 .cindex "authentication" "EXTERNAL"
26337 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
26338 the &%server_condition%& option must be present.
26340 .cindex "authentication" "ANONYMOUS"
26341 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
26342 the &%server_condition%& option must be present.
26344 .cindex "authentication" "GSSAPI"
26345 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
26346 &$auth2$& will be set to the &'authorization id'&,
26347 the &%server_condition%& option must be present.
26350 An &'anonymous token'& is something passed along as an unauthenticated
26351 identifier; this is analogous to FTP anonymous authentication passing an
26352 email address, or software-identifier@, as the "password".
26355 An example showing the password having the realm specified in the callback
26356 and demonstrating a Cyrus SASL to GSASL migration approach is:
26358 gsasl_cyrusless_crammd5:
26360 public_name = CRAM-MD5
26361 server_realm = imap.example.org
26362 server_password = ${lookup{$auth1:$auth3:userPassword}\
26363 dbmjz{/etc/sasldb2}{$value}fail}
26364 server_set_id = ${quote:$auth1}
26365 server_condition = yes
26369 . ////////////////////////////////////////////////////////////////////////////
26370 . ////////////////////////////////////////////////////////////////////////////
26372 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
26373 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
26374 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
26375 .cindex "authentication" "GSSAPI"
26376 .cindex "authentication" "Kerberos"
26377 The &(heimdal_gssapi)& authenticator provides server integration for the
26378 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
26381 .option server_hostname heimdal_gssapi string&!! "see below"
26382 This option selects the hostname that is used, with &%server_service%&,
26383 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
26384 identifier. The default value is &`$primary_hostname`&.
26386 .option server_keytab heimdal_gssapi string&!! unset
26387 If set, then Heimdal will not use the system default keytab (typically
26388 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
26389 The value should be a pathname, with no &"file:"& prefix.
26391 .option server_service heimdal_gssapi string&!! "smtp"
26392 This option specifies the service identifier used, in conjunction with
26393 &%server_hostname%&, for building the identifier for finding credentials
26397 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
26398 Beware that these variables will typically include a realm, thus will appear
26399 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
26400 not verified, so a malicious client can set it to anything.
26402 The &$auth1$& field should be safely trustable as a value from the Key
26403 Distribution Center. Note that these are not quite email addresses.
26404 Each identifier is for a role, and so the left-hand-side may include a
26405 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
26407 .vindex "&$auth1$&, &$auth2$&, etc"
26409 .vindex "&$auth1$&"
26410 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
26412 .vindex "&$auth2$&"
26413 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
26414 authentication. If that was empty, this will also be set to the
26419 . ////////////////////////////////////////////////////////////////////////////
26420 . ////////////////////////////////////////////////////////////////////////////
26422 .chapter "The spa authenticator" "CHAPspa"
26423 .scindex IIDspaauth1 "&(spa)& authenticator"
26424 .scindex IIDspaauth2 "authenticators" "&(spa)&"
26425 .cindex "authentication" "Microsoft Secure Password"
26426 .cindex "authentication" "NTLM"
26427 .cindex "Microsoft Secure Password Authentication"
26428 .cindex "NTLM authentication"
26429 The &(spa)& authenticator provides client support for Microsoft's &'Secure
26430 Password Authentication'& mechanism,
26431 which is also sometimes known as NTLM (NT LanMan). The code for client side of
26432 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
26433 taken from the Samba project (&url(http://www.samba.org)). The code for the
26434 server side was subsequently contributed by Tom Kistner. The mechanism works as
26438 After the AUTH command has been accepted, the client sends an SPA
26439 authentication request based on the user name and optional domain.
26441 The server sends back a challenge.
26443 The client builds a challenge response which makes use of the user's password
26444 and sends it to the server, which then accepts or rejects it.
26447 Encryption is used to protect the password in transit.
26451 .section "Using spa as a server" "SECID179"
26452 .cindex "options" "&(spa)& authenticator (server)"
26453 The &(spa)& authenticator has just one server option:
26455 .option server_password spa string&!! unset
26456 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
26457 This option is expanded, and the result must be the cleartext password for the
26458 authenticating user, whose name is at this point in &$auth1$&. For
26459 compatibility with previous releases of Exim, the user name is also placed in
26460 &$1$&. However, the use of this variable for this purpose is now deprecated, as
26461 it can lead to confusion in string expansions that also use numeric variables
26462 for other things. For example:
26467 server_password = \
26468 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
26470 If the expansion is forced to fail, authentication fails. Any other expansion
26471 failure causes a temporary error code to be returned.
26477 .section "Using spa as a client" "SECID180"
26478 .cindex "options" "&(spa)& authenticator (client)"
26479 The &(spa)& authenticator has the following client options:
26483 .option client_domain spa string&!! unset
26484 This option specifies an optional domain for the authentication.
26487 .option client_password spa string&!! unset
26488 This option specifies the user's password, and must be set.
26491 .option client_username spa string&!! unset
26492 This option specifies the user name, and must be set. Here is an example of a
26493 configuration of this authenticator for use with the mail servers at
26499 client_username = msn/msn_username
26500 client_password = msn_plaintext_password
26501 client_domain = DOMAIN_OR_UNSET
26503 .ecindex IIDspaauth1
26504 .ecindex IIDspaauth2
26510 . ////////////////////////////////////////////////////////////////////////////
26511 . ////////////////////////////////////////////////////////////////////////////
26513 .chapter "The tls authenticator" "CHAPtlsauth"
26514 .scindex IIDtlsauth1 "&(tls)& authenticator"
26515 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
26516 .cindex "authentication" "Client Certificate"
26517 .cindex "authentication" "X509"
26518 .cindex "Certificate-based authentication"
26519 The &(tls)& authenticator provides server support for
26520 authentication based on client certificates.
26522 It is not an SMTP authentication mechanism and is not
26523 advertised by the server as part of the SMTP EHLO response.
26524 It is an Exim authenticator in the sense that it affects
26525 the protocol element of the log line, can be tested for
26526 by the &%authenticated%& ACL condition, and can set
26527 the &$authenticated_id$& variable.
26529 The client must present a verifiable certificate,
26530 for which it must have been requested via the
26531 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
26532 (see &<<CHAPTLS>>&).
26534 If an authenticator of this type is configured it is
26535 run before any SMTP-level communication is done,
26536 and can authenticate the connection.
26537 If it does, SMTP authentication is not offered.
26539 A maximum of one authenticator of this type may be present.
26542 .cindex "options" "&(tls)& authenticator (server)"
26543 The &(tls)& authenticator has three server options:
26545 .option server_param1 tls string&!! unset
26546 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
26547 This option is expanded after the TLS negotiation and
26548 the result is placed in &$auth1$&.
26549 If the expansion is forced to fail, authentication fails. Any other expansion
26550 failure causes a temporary error code to be returned.
26552 .option server_param2 tls string&!! unset
26553 .option server_param3 tls string&!! unset
26554 As above, for &$auth2$& and &$auth3$&.
26556 &%server_param1%& may also be spelled &%server_param%&.
26563 server_param1 = ${certextract {subj_altname,mail,>:} \
26564 {$tls_in_peercert}}
26565 server_condition = ${if forany {$auth1} \
26567 {${lookup ldap{ldap:///\
26568 mailname=${quote_ldap_dn:${lc:$item}},\
26569 ou=users,LDAP_DC?mailid} {$value}{0} \
26571 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
26573 This accepts a client certificate that is verifiable against any
26574 of your configured trust-anchors
26575 which usually means the full set of public CAs)
26576 and which has a SAN with a good account name.
26577 Note that the client cert is on the wire in-clear, including the SAN,
26578 whereas a plaintext SMTP AUTH done inside TLS is not.
26580 . An alternative might use
26582 . server_param1 = ${sha256:$tls_in_peercert}
26584 . to require one of a set of specific certs that define a given account
26585 . (the verification is still required, but mostly irrelevant).
26586 . This would help for per-device use.
26588 . However, for the future we really need support for checking a
26589 . user cert in LDAP - which probably wants a base-64 DER.
26591 .ecindex IIDtlsauth1
26592 .ecindex IIDtlsauth2
26595 Note that because authentication is traditionally an SMTP operation,
26596 the &%authenticated%& ACL condition cannot be used in
26597 a connect- or helo-ACL.
26601 . ////////////////////////////////////////////////////////////////////////////
26602 . ////////////////////////////////////////////////////////////////////////////
26604 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
26605 "Encrypted SMTP connections"
26606 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
26607 .scindex IIDencsmtp2 "SMTP" "encryption"
26608 .cindex "TLS" "on SMTP connection"
26611 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
26612 Sockets Layer), is implemented by making use of the OpenSSL library or the
26613 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
26614 cryptographic code in the Exim distribution itself for implementing TLS. In
26615 order to use this feature you must install OpenSSL or GnuTLS, and then build a
26616 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
26617 You also need to understand the basic concepts of encryption at a managerial
26618 level, and in particular, the way that public keys, private keys, and
26619 certificates are used.
26621 RFC 3207 defines how SMTP connections can make use of encryption. Once a
26622 connection is established, the client issues a STARTTLS command. If the
26623 server accepts this, the client and the server negotiate an encryption
26624 mechanism. If the negotiation succeeds, the data that subsequently passes
26625 between them is encrypted.
26627 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
26628 and if so, what cipher suite is in use, whether the client supplied a
26629 certificate, and whether or not that certificate was verified. This makes it
26630 possible for an Exim server to deny or accept certain commands based on the
26633 &*Warning*&: Certain types of firewall and certain anti-virus products can
26634 disrupt TLS connections. You need to turn off SMTP scanning for these products
26635 in order to get TLS to work.
26639 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
26641 .cindex "ssmtp protocol"
26642 .cindex "smtps protocol"
26643 .cindex "SMTP" "ssmtp protocol"
26644 .cindex "SMTP" "smtps protocol"
26645 Early implementations of encrypted SMTP used a different TCP port from normal
26646 SMTP, and expected an encryption negotiation to start immediately, instead of
26647 waiting for a STARTTLS command from the client using the standard SMTP
26648 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
26649 allocated for this purpose.
26651 This approach was abandoned when encrypted SMTP was standardized, but there are
26652 still some legacy clients that use it. Exim supports these clients by means of
26653 the &%tls_on_connect_ports%& global option. Its value must be a list of port
26654 numbers; the most common use is expected to be:
26656 tls_on_connect_ports = 465
26658 The port numbers specified by this option apply to all SMTP connections, both
26659 via the daemon and via &'inetd'&. You still need to specify all the ports that
26660 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
26661 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
26662 an extra port &-- rather, it specifies different behaviour on a port that is
26665 There is also a &%-tls-on-connect%& command line option. This overrides
26666 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
26673 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
26674 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
26675 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
26676 followed later, when the first versions of GnuTLS were released. To build Exim
26677 to use GnuTLS, you need to set
26681 in Local/Makefile, in addition to
26685 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
26686 include files and libraries for GnuTLS can be found.
26688 There are some differences in usage when using GnuTLS instead of OpenSSL:
26691 The &%tls_verify_certificates%& option
26692 cannot be the path of a directory
26693 for GnuTLS versions before 3.3.6
26694 (for later versions, or OpenSSL, it can be either).
26696 The default value for &%tls_dhparam%& differs for historical reasons.
26698 .vindex "&$tls_in_peerdn$&"
26699 .vindex "&$tls_out_peerdn$&"
26700 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
26701 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
26702 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
26704 OpenSSL identifies cipher suites using hyphens as separators, for example:
26705 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
26706 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
26707 in a cipher list. To make life simpler, Exim changes underscores to hyphens
26708 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
26709 to handle its own older variants) when processing lists of cipher suites in the
26710 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
26713 The &%tls_require_ciphers%& options operate differently, as described in the
26714 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
26716 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
26717 When using OpenSSL, this option is ignored.
26718 (If an API is found to let OpenSSL be configured in this way,
26719 let the Exim Maintainers know and we'll likely use it).
26721 Some other recently added features may only be available in one or the other.
26722 This should be documented with the feature. If the documentation does not
26723 explicitly state that the feature is infeasible in the other TLS
26724 implementation, then patches are welcome.
26728 .section "GnuTLS parameter computation" "SECTgnutlsparam"
26729 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
26730 an explicit path; if the latter, then the text about generation still applies,
26731 but not the chosen filename.
26732 By default, as of Exim 4.80 a hard-coded D-H prime is used.
26733 See the documentation of &%tls_dhparam%& for more information.
26735 GnuTLS uses D-H parameters that may take a substantial amount of time
26736 to compute. It is unreasonable to re-compute them for every TLS session.
26737 Therefore, Exim keeps this data in a file in its spool directory, called
26738 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
26740 The file is owned by the Exim user and is readable only by
26741 its owner. Every Exim process that start up GnuTLS reads the D-H
26742 parameters from this file. If the file does not exist, the first Exim process
26743 that needs it computes the data and writes it to a temporary file which is
26744 renamed once it is complete. It does not matter if several Exim processes do
26745 this simultaneously (apart from wasting a few resources). Once a file is in
26746 place, new Exim processes immediately start using it.
26748 For maximum security, the parameters that are stored in this file should be
26749 recalculated periodically, the frequency depending on your paranoia level.
26750 If you are avoiding using the fixed D-H primes published in RFCs, then you
26751 are concerned about some advanced attacks and will wish to do this; if you do
26752 not regenerate then you might as well stick to the standard primes.
26754 Arranging this is easy in principle; just delete the file when you want new
26755 values to be computed. However, there may be a problem. The calculation of new
26756 parameters needs random numbers, and these are obtained from &_/dev/random_&.
26757 If the system is not very active, &_/dev/random_& may delay returning data
26758 until enough randomness (entropy) is available. This may cause Exim to hang for
26759 a substantial amount of time, causing timeouts on incoming connections.
26761 The solution is to generate the parameters externally to Exim. They are stored
26762 in &_gnutls-params-N_& in PEM format, which means that they can be
26763 generated externally using the &(certtool)& command that is part of GnuTLS.
26765 To replace the parameters with new ones, instead of deleting the file
26766 and letting Exim re-create it, you can generate new parameters using
26767 &(certtool)& and, when this has been done, replace Exim's cache file by
26768 renaming. The relevant commands are something like this:
26771 [ look for file; assume gnutls-params-2236 is the most recent ]
26774 # chown exim:exim new-params
26775 # chmod 0600 new-params
26776 # certtool --generate-dh-params --bits 2236 >>new-params
26777 # openssl dhparam -noout -text -in new-params | head
26778 [ check the first line, make sure it's not more than 2236;
26779 if it is, then go back to the start ("rm") and repeat
26780 until the size generated is at most the size requested ]
26781 # chmod 0400 new-params
26782 # mv new-params gnutls-params-2236
26784 If Exim never has to generate the parameters itself, the possibility of
26785 stalling is removed.
26787 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
26788 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
26789 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
26790 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
26791 and Exim does so. This attempt to remove Exim from TLS policy decisions
26792 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
26793 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
26794 which applies to all D-H usage, client or server. If the value returned by
26795 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
26796 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
26797 limit, which is still much higher than Exim historically used.
26799 The filename and bits used will change as the GnuTLS maintainers change the
26800 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
26801 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
26802 2432 bits, while NSS is limited to 2236 bits.
26804 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
26805 increase the chance of the generated prime actually being within acceptable
26806 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
26807 procedure above. There is no sane procedure available to Exim to double-check
26808 the size of the generated prime, so it might still be too large.
26811 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
26812 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
26813 .oindex "&%tls_require_ciphers%&" "OpenSSL"
26814 There is a function in the OpenSSL library that can be passed a list of cipher
26815 suites before the cipher negotiation takes place. This specifies which ciphers
26816 are acceptable. The list is colon separated and may contain names like
26817 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
26818 directly to this function call.
26819 Many systems will install the OpenSSL manual-pages, so you may have
26820 &'ciphers(1)'& available to you.
26821 The following quotation from the OpenSSL
26822 documentation specifies what forms of item are allowed in the cipher string:
26825 It can consist of a single cipher suite such as RC4-SHA.
26827 It can represent a list of cipher suites containing a certain algorithm,
26828 or cipher suites of a certain type. For example SHA1 represents all
26829 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
26832 Lists of cipher suites can be combined in a single cipher string using
26833 the + character. This is used as a logical and operation. For example
26834 SHA1+DES represents all cipher suites containing the SHA1 and the DES
26838 Each cipher string can be optionally preceded by one of the characters &`!`&,
26841 If &`!`& is used, the ciphers are permanently deleted from the list. The
26842 ciphers deleted can never reappear in the list even if they are explicitly
26845 If &`-`& is used, the ciphers are deleted from the list, but some or all
26846 of the ciphers can be added again by later options.
26848 If &`+`& is used, the ciphers are moved to the end of the list. This
26849 option does not add any new ciphers; it just moves matching existing ones.
26852 If none of these characters is present, the string is interpreted as
26853 a list of ciphers to be appended to the current preference list. If the list
26854 includes any ciphers already present they will be ignored: that is, they will
26855 not be moved to the end of the list.
26858 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
26861 # note single-quotes to get ! past any shell history expansion
26862 $ openssl ciphers 'HIGH:!MD5:!SHA1'
26865 This example will let the library defaults be permitted on the MX port, where
26866 there's probably no identity verification anyway, but ups the ante on the
26867 submission ports where the administrator might have some influence on the
26868 choice of clients used:
26870 # OpenSSL variant; see man ciphers(1)
26871 tls_require_ciphers = ${if =={$received_port}{25}\
26878 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
26880 .cindex "GnuTLS" "specifying parameters for"
26881 .cindex "TLS" "specifying ciphers (GnuTLS)"
26882 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
26883 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
26884 .cindex "TLS" "specifying protocols (GnuTLS)"
26885 .cindex "TLS" "specifying priority string (GnuTLS)"
26886 .oindex "&%tls_require_ciphers%&" "GnuTLS"
26887 The GnuTLS library allows the caller to provide a "priority string", documented
26888 as part of the &[gnutls_priority_init]& function. This is very similar to the
26889 ciphersuite specification in OpenSSL.
26891 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
26892 and controls both protocols and ciphers.
26894 The &%tls_require_ciphers%& option is available both as an global option,
26895 controlling how Exim behaves as a server, and also as an option of the
26896 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
26897 the value is string expanded. The resulting string is not an Exim list and
26898 the string is given to the GnuTLS library, so that Exim does not need to be
26899 aware of future feature enhancements of GnuTLS.
26901 Documentation of the strings accepted may be found in the GnuTLS manual, under
26902 "Priority strings". This is online as
26903 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
26904 but beware that this relates to GnuTLS 3, which may be newer than the version
26905 installed on your system. If you are using GnuTLS 3,
26906 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
26907 on that site can be used to test a given string.
26911 # Disable older versions of protocols
26912 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
26915 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
26916 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
26917 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
26919 This example will let the library defaults be permitted on the MX port, where
26920 there's probably no identity verification anyway, and lowers security further
26921 by increasing compatibility; but this ups the ante on the submission ports
26922 where the administrator might have some influence on the choice of clients
26926 tls_require_ciphers = ${if =={$received_port}{25}\
26932 .section "Configuring an Exim server to use TLS" "SECID182"
26933 .cindex "TLS" "configuring an Exim server"
26934 When Exim has been built with TLS support, it advertises the availability of
26935 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
26936 but not to any others. The default value of this option is unset, which means
26937 that STARTTLS is not advertised at all. This default is chosen because you
26938 need to set some other options in order to make TLS available, and also it is
26939 sensible for systems that want to use TLS only as a client.
26941 If a client issues a STARTTLS command and there is some configuration
26942 problem in the server, the command is rejected with a 454 error. If the client
26943 persists in trying to issue SMTP commands, all except QUIT are rejected
26946 554 Security failure
26948 If a STARTTLS command is issued within an existing TLS session, it is
26949 rejected with a 554 error code.
26951 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
26952 match some hosts. You can, of course, set it to * to match all hosts.
26953 However, this is not all you need to do. TLS sessions to a server won't work
26954 without some further configuration at the server end.
26956 It is rumoured that all existing clients that support TLS/SSL use RSA
26957 encryption. To make this work you need to set, in the server,
26959 tls_certificate = /some/file/name
26960 tls_privatekey = /some/file/name
26962 These options are, in fact, expanded strings, so you can make them depend on
26963 the identity of the client that is connected if you wish. The first file
26964 contains the server's X509 certificate, and the second contains the private key
26965 that goes with it. These files need to be
26966 PEM format and readable by the Exim user, and must
26967 always be given as full path names.
26968 The key must not be password-protected.
26969 They can be the same file if both the
26970 certificate and the key are contained within it. If &%tls_privatekey%& is not
26971 set, or if its expansion is forced to fail or results in an empty string, this
26972 is assumed to be the case. The certificate file may also contain intermediate
26973 certificates that need to be sent to the client to enable it to authenticate
26974 the server's certificate.
26976 If you do not understand about certificates and keys, please try to find a
26977 source of this background information, which is not Exim-specific. (There are a
26978 few comments below in section &<<SECTcerandall>>&.)
26980 &*Note*&: These options do not apply when Exim is operating as a client &--
26981 they apply only in the case of a server. If you need to use a certificate in an
26982 Exim client, you must set the options of the same names in an &(smtp)&
26985 With just these options, an Exim server will be able to use TLS. It does not
26986 require the client to have a certificate (but see below for how to insist on
26987 this). There is one other option that may be needed in other situations. If
26989 tls_dhparam = /some/file/name
26991 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
26992 with the parameters contained in the file.
26993 Set this to &`none`& to disable use of DH entirely, by making no prime
26998 This may also be set to a string identifying a standard prime to be used for
26999 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
27000 used is &`ike23`&. There are a few standard primes available, see the
27001 documentation for &%tls_dhparam%& for the complete list.
27007 for a way of generating file data.
27009 The strings supplied for these three options are expanded every time a client
27010 host connects. It is therefore possible to use different certificates and keys
27011 for different hosts, if you so wish, by making use of the client's IP address
27012 in &$sender_host_address$& to control the expansion. If a string expansion is
27013 forced to fail, Exim behaves as if the option is not set.
27015 .cindex "cipher" "logging"
27016 .cindex "log" "TLS cipher"
27017 .vindex "&$tls_in_cipher$&"
27018 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
27019 an incoming TLS connection. It is included in the &'Received:'& header of an
27020 incoming message (by default &-- you can, of course, change this), and it is
27021 also included in the log line that records a message's arrival, keyed by
27022 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
27023 condition can be used to test for specific cipher suites in ACLs.
27025 Once TLS has been established, the ACLs that run for subsequent SMTP commands
27026 can check the name of the cipher suite and vary their actions accordingly. The
27027 cipher suite names vary, depending on which TLS library is being used. For
27028 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
27029 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
27030 documentation for more details.
27032 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
27033 (again depending on the &%tls_cipher%& log selector).
27036 .section "Requesting and verifying client certificates" "SECID183"
27037 .cindex "certificate" "verification of client"
27038 .cindex "TLS" "client certificate verification"
27039 If you want an Exim server to request a certificate when negotiating a TLS
27040 session with a client, you must set either &%tls_verify_hosts%& or
27041 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
27042 apply to all TLS connections. For any host that matches one of these options,
27043 Exim requests a certificate as part of the setup of the TLS session. The
27044 contents of the certificate are verified by comparing it with a list of
27045 expected certificates.
27046 These may be the system default set (depending on library version),
27047 an explicit file or,
27048 depending on library version, a directory, identified by
27049 &%tls_verify_certificates%&.
27051 A file can contain multiple certificates, concatenated end to end. If a
27054 each certificate must be in a separate file, with a name (or a symbolic link)
27055 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
27056 certificate. You can compute the relevant hash by running the command
27058 openssl x509 -hash -noout -in /cert/file
27060 where &_/cert/file_& contains a single certificate.
27062 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
27063 what happens if the client does not supply a certificate, or if the certificate
27064 does not match any of the certificates in the collection named by
27065 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
27066 attempt to set up a TLS session is aborted, and the incoming connection is
27067 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
27068 session continues. ACLs that run for subsequent SMTP commands can detect the
27069 fact that no certificate was verified, and vary their actions accordingly. For
27070 example, you can insist on a certificate before accepting a message for
27071 relaying, but not when the message is destined for local delivery.
27073 .vindex "&$tls_in_peerdn$&"
27074 When a client supplies a certificate (whether it verifies or not), the value of
27075 the Distinguished Name of the certificate is made available in the variable
27076 &$tls_in_peerdn$& during subsequent processing of the message.
27078 .cindex "log" "distinguished name"
27079 Because it is often a long text string, it is not included in the log line or
27080 &'Received:'& header by default. You can arrange for it to be logged, keyed by
27081 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
27082 &%received_header_text%& to change the &'Received:'& header. When no
27083 certificate is supplied, &$tls_in_peerdn$& is empty.
27086 .section "Revoked certificates" "SECID184"
27087 .cindex "TLS" "revoked certificates"
27088 .cindex "revocation list"
27089 .cindex "certificate" "revocation list"
27090 .cindex "OCSP" "stapling"
27091 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
27092 certificates are revoked. If you have such a list, you can pass it to an Exim
27093 server using the global option called &%tls_crl%& and to an Exim client using
27094 an identically named option for the &(smtp)& transport. In each case, the value
27095 of the option is expanded and must then be the name of a file that contains a
27097 The downside is that clients have to periodically re-download a potentially huge
27098 file from every certificate authority they know of.
27100 The way with most moving parts at query time is Online Certificate
27101 Status Protocol (OCSP), where the client verifies the certificate
27102 against an OCSP server run by the CA. This lets the CA track all
27103 usage of the certs. It requires running software with access to the
27104 private key of the CA, to sign the responses to the OCSP queries. OCSP
27105 is based on HTTP and can be proxied accordingly.
27107 The only widespread OCSP server implementation (known to this writer)
27108 comes as part of OpenSSL and aborts on an invalid request, such as
27109 connecting to the port and then disconnecting. This requires
27110 re-entering the passphrase each time some random client does this.
27112 The third way is OCSP Stapling; in this, the server using a certificate
27113 issued by the CA periodically requests an OCSP proof of validity from
27114 the OCSP server, then serves it up inline as part of the TLS
27115 negotiation. This approach adds no extra round trips, does not let the
27116 CA track users, scales well with number of certs issued by the CA and is
27117 resilient to temporary OCSP server failures, as long as the server
27118 starts retrying to fetch an OCSP proof some time before its current
27119 proof expires. The downside is that it requires server support.
27121 Unless Exim is built with the support disabled,
27123 or with GnuTLS earlier than version 3.3.16 / 3.4.8
27125 support for OCSP stapling is included.
27127 There is a global option called &%tls_ocsp_file%&.
27128 The file specified therein is expected to be in DER format, and contain
27129 an OCSP proof. Exim will serve it as part of the TLS handshake. This
27130 option will be re-expanded for SNI, if the &%tls_certificate%& option
27131 contains &`tls_in_sni`&, as per other TLS options.
27133 Exim does not at this time implement any support for fetching a new OCSP
27134 proof. The burden is on the administrator to handle this, outside of
27135 Exim. The file specified should be replaced atomically, so that the
27136 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
27137 on each connection, so a new file will be handled transparently on the
27140 When built with OpenSSL Exim will check for a valid next update timestamp
27141 in the OCSP proof; if not present, or if the proof has expired, it will be
27144 For the client to be able to verify the stapled OCSP the server must
27145 also supply, in its stapled information, any intermediate
27146 certificates for the chain leading to the OCSP proof from the signer
27147 of the server certificate. There may be zero or one such. These
27148 intermediate certificates should be added to the server OCSP stapling
27149 file named by &%tls_ocsp_file%&.
27151 Note that the proof only covers the terminal server certificate,
27152 not any of the chain from CA to it.
27154 There is no current way to staple a proof for a client certificate.
27157 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
27158 OCSP server is supplied. The server URL may be included in the
27159 server certificate, if the CA is helpful.
27161 One failure mode seen was the OCSP Signer cert expiring before the end
27162 of validity of the OCSP proof. The checking done by Exim/OpenSSL
27163 noted this as invalid overall, but the re-fetch script did not.
27169 .section "Configuring an Exim client to use TLS" "SECID185"
27170 .cindex "cipher" "logging"
27171 .cindex "log" "TLS cipher"
27172 .cindex "log" "distinguished name"
27173 .cindex "TLS" "configuring an Exim client"
27174 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
27175 deliveries as well as to incoming, the latter one causing logging of the
27176 server certificate's DN. The remaining client configuration for TLS is all
27177 within the &(smtp)& transport.
27179 It is not necessary to set any options to have TLS work in the &(smtp)&
27180 transport. If Exim is built with TLS support, and TLS is advertised by a
27181 server, the &(smtp)& transport always tries to start a TLS session. However,
27182 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
27183 transport) to a list of server hosts for which TLS should not be used.
27185 If you do not want Exim to attempt to send messages unencrypted when an attempt
27186 to set up an encrypted connection fails in any way, you can set
27187 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
27188 those hosts, delivery is always deferred if an encrypted connection cannot be
27189 set up. If there are any other hosts for the address, they are tried in the
27192 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
27193 the message unencrypted. It always does this if the response to STARTTLS is
27194 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
27195 session after a success response code, what happens is controlled by the
27196 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
27197 delivery to this host is deferred, and other hosts (if available) are tried. If
27198 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
27199 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
27200 negotiation fails, Exim closes the current connection (because it is in an
27201 unknown state), opens a new one to the same host, and then tries the delivery
27204 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
27205 transport provide the client with a certificate, which is passed to the server
27206 if it requests it. If the server is Exim, it will request a certificate only if
27207 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
27209 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
27210 specifies a collection of expected server certificates.
27211 These may be the system default set (depending on library version),
27213 depending on library version, a directory,
27214 must name a file or,
27215 for OpenSSL only (not GnuTLS), a directory.
27216 The client verifies the server's certificate
27217 against this collection, taking into account any revoked certificates that are
27218 in the list defined by &%tls_crl%&.
27219 Failure to verify fails the TLS connection unless either of the
27220 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
27222 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
27223 certificate verification to the listed servers. Verification either must
27224 or need not succeed respectively.
27226 The &(smtp)& transport has two OCSP-related options:
27227 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
27228 is requested and required for the connection to proceed. The default
27230 &%hosts_request_ocsp%&; a host-list for which (additionally)
27231 a Certificate Status is requested (but not necessarily verified). The default
27232 value is "*" meaning that requests are made unless configured
27235 The host(s) should also be in &%hosts_require_tls%&, and
27236 &%tls_verify_certificates%& configured for the transport,
27237 for OCSP to be relevant.
27240 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
27241 list of permitted cipher suites. If either of these checks fails, delivery to
27242 the current host is abandoned, and the &(smtp)& transport tries to deliver to
27243 alternative hosts, if any.
27246 These options must be set in the &(smtp)& transport for Exim to use TLS when it
27247 is operating as a client. Exim does not assume that a server certificate (set
27248 by the global options of the same name) should also be used when operating as a
27252 .vindex "&$host_address$&"
27253 All the TLS options in the &(smtp)& transport are expanded before use, with
27254 &$host$& and &$host_address$& containing the name and address of the server to
27255 which the client is connected. Forced failure of an expansion causes Exim to
27256 behave as if the relevant option were unset.
27258 .vindex &$tls_out_bits$&
27259 .vindex &$tls_out_cipher$&
27260 .vindex &$tls_out_peerdn$&
27261 .vindex &$tls_out_sni$&
27262 Before an SMTP connection is established, the
27263 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27264 variables are emptied. (Until the first connection, they contain the values
27265 that were set when the message was received.) If STARTTLS is subsequently
27266 successfully obeyed, these variables are set to the relevant values for the
27267 outgoing connection.
27271 .section "Use of TLS Server Name Indication" "SECTtlssni"
27272 .cindex "TLS" "Server Name Indication"
27273 .vindex "&$tls_in_sni$&"
27274 .oindex "&%tls_in_sni%&"
27275 With TLS1.0 or above, there is an extension mechanism by which extra
27276 information can be included at various points in the protocol. One of these
27277 extensions, documented in RFC 6066 (and before that RFC 4366) is
27278 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27279 client in the initial handshake, so that the server can examine the servername
27280 within and possibly choose to use different certificates and keys (and more)
27283 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27284 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
27287 With SMTP to MX, there are the same problems here as in choosing the identity
27288 against which to validate a certificate: you can't rely on insecure DNS to
27289 provide the identity which you then cryptographically verify. So this will
27290 be of limited use in that environment.
27292 With SMTP to Submission, there is a well-defined hostname which clients are
27293 connecting to and can validate certificates against. Thus clients &*can*&
27294 choose to include this information in the TLS negotiation. If this becomes
27295 wide-spread, then hosters can choose to present different certificates to
27296 different clients. Or even negotiate different cipher suites.
27298 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
27299 if not empty, will be sent on a TLS session as part of the handshake. There's
27300 nothing more to it. Choosing a sensible value not derived insecurely is the
27301 only point of caution. The &$tls_out_sni$& variable will be set to this string
27302 for the lifetime of the client connection (including during authentication).
27304 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
27305 received from a client.
27306 It can be logged with the &%log_selector%& item &`+tls_sni`&.
27308 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
27309 option (prior to expansion) then the following options will be re-expanded
27310 during TLS session handshake, to permit alternative values to be chosen:
27313 .vindex "&%tls_certificate%&"
27314 &%tls_certificate%&
27316 .vindex "&%tls_crl%&"
27319 .vindex "&%tls_privatekey%&"
27322 .vindex "&%tls_verify_certificates%&"
27323 &%tls_verify_certificates%&
27325 .vindex "&%tls_ocsp_file%&"
27329 Great care should be taken to deal with matters of case, various injection
27330 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
27331 can always be referenced; it is important to remember that &$tls_sni$& is
27332 arbitrary unverified data provided prior to authentication.
27334 The Exim developers are proceeding cautiously and so far no other TLS options
27337 When Exim is built against OpenSSL, OpenSSL must have been built with support
27338 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
27339 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
27340 see &`-servername`& in the output, then OpenSSL has support.
27342 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
27343 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
27344 built, then you have SNI support).
27348 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
27350 .cindex "multiple SMTP deliveries with TLS"
27351 .cindex "TLS" "multiple message deliveries"
27352 Exim sends multiple messages down the same TCP/IP connection by starting up
27353 an entirely new delivery process for each message, passing the socket from
27354 one process to the next. This implementation does not fit well with the use
27355 of TLS, because there is quite a lot of state information associated with a TLS
27356 connection, not just a socket identification. Passing all the state information
27357 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
27358 session before passing the socket to a new process. The new process may then
27359 try to start a new TLS session, and if successful, may try to re-authenticate
27360 if AUTH is in use, before sending the next message.
27362 The RFC is not clear as to whether or not an SMTP session continues in clear
27363 after TLS has been shut down, or whether TLS may be restarted again later, as
27364 just described. However, if the server is Exim, this shutdown and
27365 reinitialization works. It is not known which (if any) other servers operate
27366 successfully if the client closes a TLS session and continues with unencrypted
27367 SMTP, but there are certainly some that do not work. For such servers, Exim
27368 should not pass the socket to another process, because the failure of the
27369 subsequent attempt to use it would cause Exim to record a temporary host error,
27370 and delay other deliveries to that host.
27372 To test for this case, Exim sends an EHLO command to the server after
27373 closing down the TLS session. If this fails in any way, the connection is
27374 closed instead of being passed to a new delivery process, but no retry
27375 information is recorded.
27377 There is also a manual override; you can set &%hosts_nopass_tls%& on the
27378 &(smtp)& transport to match those hosts for which Exim should not pass
27379 connections to new processes if TLS has been used.
27384 .section "Certificates and all that" "SECTcerandall"
27385 .cindex "certificate" "references to discussion"
27386 In order to understand fully how TLS works, you need to know about
27387 certificates, certificate signing, and certificate authorities. This is not the
27388 place to give a tutorial, especially as I do not know very much about it
27389 myself. Some helpful introduction can be found in the FAQ for the SSL addition
27390 to Apache, currently at
27392 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
27394 Other parts of the &'modssl'& documentation are also helpful, and have
27395 links to further files.
27396 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
27397 0-201-61598-3), contains both introductory and more in-depth descriptions.
27398 Some sample programs taken from the book are available from
27400 &url(http://www.rtfm.com/openssl-examples/)
27404 .section "Certificate chains" "SECID186"
27405 The file named by &%tls_certificate%& may contain more than one
27406 certificate. This is useful in the case where the certificate that is being
27407 sent is validated by an intermediate certificate which the other end does
27408 not have. Multiple certificates must be in the correct order in the file.
27409 First the host's certificate itself, then the first intermediate
27410 certificate to validate the issuer of the host certificate, then the next
27411 intermediate certificate to validate the issuer of the first intermediate
27412 certificate, and so on, until finally (optionally) the root certificate.
27413 The root certificate must already be trusted by the recipient for
27414 validation to succeed, of course, but if it's not preinstalled, sending the
27415 root certificate along with the rest makes it available for the user to
27416 install if the receiving end is a client MUA that can interact with a user.
27418 Note that certificates using MD5 are unlikely to work on today's Internet;
27419 even if your libraries allow loading them for use in Exim when acting as a
27420 server, increasingly clients will not accept such certificates. The error
27421 diagnostics in such a case can be frustratingly vague.
27425 .section "Self-signed certificates" "SECID187"
27426 .cindex "certificate" "self-signed"
27427 You can create a self-signed certificate using the &'req'& command provided
27428 with OpenSSL, like this:
27429 . ==== Do not shorten the duration here without reading and considering
27430 . ==== the text below. Please leave it at 9999 days.
27432 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
27435 &_file1_& and &_file2_& can be the same file; the key and the certificate are
27436 delimited and so can be identified independently. The &%-days%& option
27437 specifies a period for which the certificate is valid. The &%-nodes%& option is
27438 important: if you do not set it, the key is encrypted with a passphrase
27439 that you are prompted for, and any use that is made of the key causes more
27440 prompting for the passphrase. This is not helpful if you are going to use
27441 this certificate and key in an MTA, where prompting is not possible.
27443 . ==== I expect to still be working 26 years from now. The less technical
27444 . ==== debt I create, in terms of storing up trouble for my later years, the
27445 . ==== happier I will be then. We really have reached the point where we
27446 . ==== should start, at the very least, provoking thought and making folks
27447 . ==== pause before proceeding, instead of leaving all the fixes until two
27448 . ==== years before 2^31 seconds after the 1970 Unix epoch.
27450 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
27451 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
27452 the above command might produce a date in the past. Think carefully about
27453 the lifetime of the systems you're deploying, and either reduce the duration
27454 of the certificate or reconsider your platform deployment. (At time of
27455 writing, reducing the duration is the most likely choice, but the inexorable
27456 progression of time takes us steadily towards an era where this will not
27457 be a sensible resolution).
27459 A self-signed certificate made in this way is sufficient for testing, and
27460 may be adequate for all your requirements if you are mainly interested in
27461 encrypting transfers, and not in secure identification.
27463 However, many clients require that the certificate presented by the server be a
27464 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
27465 certificate. In this situation, the self-signed certificate described above
27466 must be installed on the client host as a trusted root &'certification
27467 authority'& (CA), and the certificate used by Exim must be a user certificate
27468 signed with that self-signed certificate.
27470 For information on creating self-signed CA certificates and using them to sign
27471 user certificates, see the &'General implementation overview'& chapter of the
27472 Open-source PKI book, available online at
27473 &url(http://ospkibook.sourceforge.net/).
27474 .ecindex IIDencsmtp1
27475 .ecindex IIDencsmtp2
27479 . ////////////////////////////////////////////////////////////////////////////
27480 . ////////////////////////////////////////////////////////////////////////////
27482 .chapter "Access control lists" "CHAPACL"
27483 .scindex IIDacl "&ACL;" "description"
27484 .cindex "control of incoming mail"
27485 .cindex "message" "controlling incoming"
27486 .cindex "policy control" "access control lists"
27487 Access Control Lists (ACLs) are defined in a separate section of the run time
27488 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
27489 name, terminated by a colon. Here is a complete ACL section that contains just
27490 one very small ACL:
27494 accept hosts = one.host.only
27496 You can have as many lists as you like in the ACL section, and the order in
27497 which they appear does not matter. The lists are self-terminating.
27499 The majority of ACLs are used to control Exim's behaviour when it receives
27500 certain SMTP commands. This applies both to incoming TCP/IP connections, and
27501 when a local process submits a message using SMTP by specifying the &%-bs%&
27502 option. The most common use is for controlling which recipients are accepted
27503 in incoming messages. In addition, you can define an ACL that is used to check
27504 local non-SMTP messages. The default configuration file contains an example of
27505 a realistic ACL for checking RCPT commands. This is discussed in chapter
27506 &<<CHAPdefconfil>>&.
27509 .section "Testing ACLs" "SECID188"
27510 The &%-bh%& command line option provides a way of testing your ACL
27511 configuration locally by running a fake SMTP session with which you interact.
27514 .section "Specifying when ACLs are used" "SECID189"
27515 .cindex "&ACL;" "options for specifying"
27516 In order to cause an ACL to be used, you have to name it in one of the relevant
27517 options in the main part of the configuration. These options are:
27518 .cindex "AUTH" "ACL for"
27519 .cindex "DATA" "ACLs for"
27520 .cindex "ETRN" "ACL for"
27521 .cindex "EXPN" "ACL for"
27522 .cindex "HELO" "ACL for"
27523 .cindex "EHLO" "ACL for"
27524 .cindex "DKIM" "ACL for"
27525 .cindex "MAIL" "ACL for"
27526 .cindex "QUIT, ACL for"
27527 .cindex "RCPT" "ACL for"
27528 .cindex "STARTTLS, ACL for"
27529 .cindex "VRFY" "ACL for"
27530 .cindex "SMTP" "connection, ACL for"
27531 .cindex "non-SMTP messages" "ACLs for"
27532 .cindex "MIME content scanning" "ACL for"
27533 .cindex "PRDR" "ACL for"
27536 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
27537 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
27538 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
27539 .irow &%acl_smtp_auth%& "ACL for AUTH"
27540 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
27541 .irow &%acl_smtp_data%& "ACL after DATA is complete"
27542 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
27543 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
27544 .irow &%acl_smtp_etrn%& "ACL for ETRN"
27545 .irow &%acl_smtp_expn%& "ACL for EXPN"
27546 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
27547 .irow &%acl_smtp_mail%& "ACL for MAIL"
27548 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
27549 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
27550 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
27551 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
27552 .irow &%acl_smtp_quit%& "ACL for QUIT"
27553 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
27554 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
27555 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
27558 For example, if you set
27560 acl_smtp_rcpt = small_acl
27562 the little ACL defined above is used whenever Exim receives a RCPT command
27563 in an SMTP dialogue. The majority of policy tests on incoming messages can be
27564 done when RCPT commands arrive. A rejection of RCPT should cause the
27565 sending MTA to give up on the recipient address contained in the RCPT
27566 command, whereas rejection at other times may cause the client MTA to keep on
27567 trying to deliver the message. It is therefore recommended that you do as much
27568 testing as possible at RCPT time.
27571 .section "The non-SMTP ACLs" "SECID190"
27572 .cindex "non-SMTP messages" "ACLs for"
27573 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
27574 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
27575 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
27576 the state of the SMTP connection such as encryption and authentication) are not
27577 relevant and are forbidden in these ACLs. However, the sender and recipients
27578 are known, so the &%senders%& and &%sender_domains%& conditions and the
27579 &$sender_address$& and &$recipients$& variables can be used. Variables such as
27580 &$authenticated_sender$& are also available. You can specify added header lines
27581 in any of these ACLs.
27583 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
27584 non-SMTP message, before any of the message has been read. (This is the
27585 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
27586 batched SMTP input, it runs after the DATA command has been reached. The
27587 result of this ACL is ignored; it cannot be used to reject a message. If you
27588 really need to, you could set a value in an ACL variable here and reject based
27589 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
27590 controls, and in particular, it can be used to set
27592 control = suppress_local_fixups
27594 This cannot be used in the other non-SMTP ACLs because by the time they are
27595 run, it is too late.
27597 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
27598 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27600 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
27601 kind of rejection is treated as permanent, because there is no way of sending a
27602 temporary error for these kinds of message.
27605 .section "The SMTP connect ACL" "SECID191"
27606 .cindex "SMTP" "connection, ACL for"
27607 .oindex &%smtp_banner%&
27608 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
27609 session, after the test specified by &%host_reject_connection%& (which is now
27610 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
27611 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
27612 the message override the banner message that is otherwise specified by the
27613 &%smtp_banner%& option.
27616 .section "The EHLO/HELO ACL" "SECID192"
27617 .cindex "EHLO" "ACL for"
27618 .cindex "HELO" "ACL for"
27619 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
27620 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
27621 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
27622 Note that a client may issue more than one EHLO or HELO command in an SMTP
27623 session, and indeed is required to issue a new EHLO or HELO after successfully
27624 setting up encryption following a STARTTLS command.
27627 Note also that a deny neither forces the client to go away nor means that
27628 mail will be refused on the connection. Consider checking for
27629 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
27632 If the command is accepted by an &%accept%& verb that has a &%message%&
27633 modifier, the message may not contain more than one line (it will be truncated
27634 at the first newline and a panic logged if it does). Such a message cannot
27635 affect the EHLO options that are listed on the second and subsequent lines of
27639 .section "The DATA ACLs" "SECID193"
27640 .cindex "DATA" "ACLs for"
27641 Two ACLs are associated with the DATA command, because it is two-stage
27642 command, with two responses being sent to the client.
27643 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
27644 is obeyed. This gives you control after all the RCPT commands, but before
27645 the message itself is received. It offers the opportunity to give a negative
27646 response to the DATA command before the data is transmitted. Header lines
27647 added by MAIL or RCPT ACLs are not visible at this time, but any that
27648 are defined here are visible when the &%acl_smtp_data%& ACL is run.
27650 You cannot test the contents of the message, for example, to verify addresses
27651 in the headers, at RCPT time or when the DATA command is received. Such
27652 tests have to appear in the ACL that is run after the message itself has been
27653 received, before the final response to the DATA command is sent. This is
27654 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
27655 associated with the DATA command.
27657 For both of these ACLs, it is not possible to reject individual recipients. An
27658 error response rejects the entire message. Unfortunately, it is known that some
27659 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
27660 before or after the data) correctly &-- they keep the message on their queues
27661 and try again later, but that is their problem, though it does waste some of
27664 The &%acl_smtp_data%& ACL is run after
27665 the &%acl_smtp_data_prdr%&,
27666 the &%acl_smtp_dkim%&
27667 and the &%acl_smtp_mime%& ACLs.
27669 .section "The SMTP DKIM ACL" "SECTDKIMACL"
27670 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
27671 enabled (which is the default).
27673 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
27674 received, and is executed for each DKIM signature found in a message. If not
27675 otherwise specified, the default action is to accept.
27677 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
27679 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
27682 .section "The SMTP MIME ACL" "SECID194"
27683 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
27684 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27686 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27689 .section "The SMTP PRDR ACL" "SECTPRDRACL"
27690 .cindex "PRDR" "ACL for"
27691 .oindex "&%prdr_enable%&"
27692 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
27693 with PRDR support enabled (which is the default).
27694 It becomes active only when the PRDR feature is negotiated between
27695 client and server for a message, and more than one recipient
27698 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
27699 has been received, and is executed once for each recipient of the message
27700 with &$local_part$& and &$domain$& valid.
27701 The test may accept, defer or deny for individual recipients.
27702 The &%acl_smtp_data%& will still be called after this ACL and
27703 can reject the message overall, even if this ACL has accepted it
27704 for some or all recipients.
27706 PRDR may be used to support per-user content filtering. Without it
27707 one must defer any recipient after the first that has a different
27708 content-filter configuration. With PRDR, the RCPT-time check
27710 .cindex "PRDR" "variable for"
27711 for this can be disabled when the variable &$prdr_requested$&
27714 Any required difference in behaviour of the main DATA-time
27715 ACL should however depend on the PRDR-time ACL having run, as Exim
27716 will avoid doing so in some situations (e.g. single-recipient mails).
27718 See also the &%prdr_enable%& global option
27719 and the &%hosts_try_prdr%& smtp transport option.
27721 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27722 If the ACL is not defined, processing completes as if
27723 the feature was not requested by the client.
27725 .section "The QUIT ACL" "SECTQUITACL"
27726 .cindex "QUIT, ACL for"
27727 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
27728 does not affect the response code to QUIT, which is always 221. Thus, the ACL
27729 does not in fact control any access.
27730 For this reason, it may only accept
27731 or warn as its final result.
27733 This ACL can be used for tasks such as custom logging at the end of an SMTP
27734 session. For example, you can use ACL variables in other ACLs to count
27735 messages, recipients, etc., and log the totals at QUIT time using one or
27736 more &%logwrite%& modifiers on a &%warn%& verb.
27738 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
27739 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
27741 You do not need to have a final &%accept%&, but if you do, you can use a
27742 &%message%& modifier to specify custom text that is sent as part of the 221
27745 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
27746 failure (for example, failure to open a log file, or when Exim is bombing out
27747 because it has detected an unrecoverable error), all SMTP commands from the
27748 client are given temporary error responses until QUIT is received or the
27749 connection is closed. In these special cases, the QUIT ACL does not run.
27752 .section "The not-QUIT ACL" "SECTNOTQUITACL"
27753 .vindex &$acl_smtp_notquit$&
27754 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
27755 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
27756 trouble, such as being unable to write to its log files, this ACL is not run,
27757 because it might try to do things (such as write to log files) that make the
27758 situation even worse.
27760 Like the QUIT ACL, this ACL is provided to make it possible to do customized
27761 logging or to gather statistics, and its outcome is ignored. The &%delay%&
27762 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
27765 .vindex &$smtp_notquit_reason$&
27766 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
27767 to a string that indicates the reason for the termination of the SMTP
27768 connection. The possible values are:
27770 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
27771 .irow &`bad-commands`& "Too many unknown or non-mail commands"
27772 .irow &`command-timeout`& "Timeout while reading SMTP commands"
27773 .irow &`connection-lost`& "The SMTP connection has been lost"
27774 .irow &`data-timeout`& "Timeout while reading message data"
27775 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
27776 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
27777 .irow &`signal-exit`& "SIGTERM or SIGINT"
27778 .irow &`synchronization-error`& "SMTP synchronization error"
27779 .irow &`tls-failed`& "TLS failed to start"
27781 In most cases when an SMTP connection is closed without having received QUIT,
27782 Exim sends an SMTP response message before actually closing the connection.
27783 With the exception of the &`acl-drop`& case, the default message can be
27784 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
27785 &%drop%& verb in another ACL, it is the message from the other ACL that is
27789 .section "Finding an ACL to use" "SECID195"
27790 .cindex "&ACL;" "finding which to use"
27791 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
27792 you can use different ACLs in different circumstances. For example,
27794 acl_smtp_rcpt = ${if ={25}{$interface_port} \
27795 {acl_check_rcpt} {acl_check_rcpt_submit} }
27797 In the default configuration file there are some example settings for
27798 providing an RFC 4409 message submission service on port 587 and a
27799 non-standard &"smtps"& service on port 465. You can use a string
27800 expansion like this to choose an ACL for MUAs on these ports which is
27801 more appropriate for this purpose than the default ACL on port 25.
27803 The expanded string does not have to be the name of an ACL in the
27804 configuration file; there are other possibilities. Having expanded the
27805 string, Exim searches for an ACL as follows:
27808 If the string begins with a slash, Exim uses it as a file name, and reads its
27809 contents as an ACL. The lines are processed in the same way as lines in the
27810 Exim configuration file. In particular, continuation lines are supported, blank
27811 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
27812 If the file does not exist or cannot be read, an error occurs (typically
27813 causing a temporary failure of whatever caused the ACL to be run). For example:
27815 acl_smtp_data = /etc/acls/\
27816 ${lookup{$sender_host_address}lsearch\
27817 {/etc/acllist}{$value}{default}}
27819 This looks up an ACL file to use on the basis of the host's IP address, falling
27820 back to a default if the lookup fails. If an ACL is successfully read from a
27821 file, it is retained in memory for the duration of the Exim process, so that it
27822 can be re-used without having to re-read the file.
27824 If the string does not start with a slash, and does not contain any spaces,
27825 Exim searches the ACL section of the configuration for an ACL whose name
27826 matches the string.
27828 If no named ACL is found, or if the string contains spaces, Exim parses
27829 the string as an inline ACL. This can save typing in cases where you just
27830 want to have something like
27832 acl_smtp_vrfy = accept
27834 in order to allow free use of the VRFY command. Such a string may contain
27835 newlines; it is processed in the same way as an ACL that is read from a file.
27841 .section "ACL return codes" "SECID196"
27842 .cindex "&ACL;" "return codes"
27843 Except for the QUIT ACL, which does not affect the SMTP return code (see
27844 section &<<SECTQUITACL>>& above), the result of running an ACL is either
27845 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
27846 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
27847 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
27848 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
27849 This also causes a 4&'xx'& return code.
27851 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
27852 &"deny"&, because there is no mechanism for passing temporary errors to the
27853 submitters of non-SMTP messages.
27856 ACLs that are relevant to message reception may also return &"discard"&. This
27857 has the effect of &"accept"&, but causes either the entire message or an
27858 individual recipient address to be discarded. In other words, it is a
27859 blackholing facility. Use it with care.
27861 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
27862 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
27863 RCPT ACL is to discard just the one recipient address. If there are no
27864 recipients left when the message's data is received, the DATA ACL is not
27865 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
27866 remaining recipients. The &"discard"& return is not permitted for the
27867 &%acl_smtp_predata%& ACL.
27870 .cindex "&[local_scan()]& function" "when all recipients discarded"
27871 The &[local_scan()]& function is always run, even if there are no remaining
27872 recipients; it may create new recipients.
27876 .section "Unset ACL options" "SECID197"
27877 .cindex "&ACL;" "unset options"
27878 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
27879 all the same. &*Note*&: These defaults apply only when the relevant ACL is
27880 not defined at all. For any defined ACL, the default action when control
27881 reaches the end of the ACL statements is &"deny"&.
27883 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
27884 these two are ACLs that are used only for their side effects. They cannot be
27885 used to accept or reject anything.
27887 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
27888 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
27889 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
27890 when the ACL is not defined is &"accept"&.
27892 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
27893 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
27894 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
27895 messages over an SMTP connection. For an example, see the ACL in the default
27896 configuration file.
27901 .section "Data for message ACLs" "SECID198"
27902 .cindex "&ACL;" "data for message ACL"
27904 .vindex &$local_part$&
27905 .vindex &$sender_address$&
27906 .vindex &$sender_host_address$&
27907 .vindex &$smtp_command$&
27908 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
27909 that contain information about the host and the message's sender (for example,
27910 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
27911 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
27912 &$local_part$& are set from the argument address. The entire SMTP command
27913 is available in &$smtp_command$&.
27915 When an ACL for the AUTH parameter of MAIL is running, the variables that
27916 contain information about the host are set, but &$sender_address$& is not yet
27917 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
27920 .vindex "&$message_size$&"
27921 The &$message_size$& variable is set to the value of the SIZE parameter on
27922 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
27923 that parameter is not given. The value is updated to the true message size by
27924 the time the final DATA ACL is run (after the message data has been
27927 .vindex "&$rcpt_count$&"
27928 .vindex "&$recipients_count$&"
27929 The &$rcpt_count$& variable increases by one for each RCPT command received.
27930 The &$recipients_count$& variable increases by one each time a RCPT command is
27931 accepted, so while an ACL for RCPT is being processed, it contains the number
27932 of previously accepted recipients. At DATA time (for both the DATA ACLs),
27933 &$rcpt_count$& contains the total number of RCPT commands, and
27934 &$recipients_count$& contains the total number of accepted recipients.
27940 .section "Data for non-message ACLs" "SECTdatfornon"
27941 .cindex "&ACL;" "data for non-message ACL"
27942 .vindex &$smtp_command_argument$&
27943 .vindex &$smtp_command$&
27944 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
27945 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
27946 and the entire SMTP command is available in &$smtp_command$&.
27947 These variables can be tested using a &%condition%& condition. For example,
27948 here is an ACL for use with AUTH, which insists that either the session is
27949 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
27950 does not permit authentication methods that use cleartext passwords on
27951 unencrypted connections.
27954 accept encrypted = *
27955 accept condition = ${if eq{${uc:$smtp_command_argument}}\
27957 deny message = TLS encryption or CRAM-MD5 required
27959 (Another way of applying this restriction is to arrange for the authenticators
27960 that use cleartext passwords not to be advertised when the connection is not
27961 encrypted. You can use the generic &%server_advertise_condition%& authenticator
27962 option to do this.)
27966 .section "Format of an ACL" "SECID199"
27967 .cindex "&ACL;" "format of"
27968 .cindex "&ACL;" "verbs, definition of"
27969 An individual ACL consists of a number of statements. Each statement starts
27970 with a verb, optionally followed by a number of conditions and &"modifiers"&.
27971 Modifiers can change the way the verb operates, define error and log messages,
27972 set variables, insert delays, and vary the processing of accepted messages.
27974 If all the conditions are met, the verb is obeyed. The same condition may be
27975 used (with different arguments) more than once in the same statement. This
27976 provides a means of specifying an &"and"& conjunction between conditions. For
27979 deny dnslists = list1.example
27980 dnslists = list2.example
27982 If there are no conditions, the verb is always obeyed. Exim stops evaluating
27983 the conditions and modifiers when it reaches a condition that fails. What
27984 happens then depends on the verb (and in one case, on a special modifier). Not
27985 all the conditions make sense at every testing point. For example, you cannot
27986 test a sender address in the ACL that is run for a VRFY command.
27989 .section "ACL verbs" "SECID200"
27990 The ACL verbs are as follows:
27993 .cindex "&%accept%& ACL verb"
27994 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
27995 of the conditions are not met, what happens depends on whether &%endpass%&
27996 appears among the conditions (for syntax see below). If the failing condition
27997 is before &%endpass%&, control is passed to the next ACL statement; if it is
27998 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
27999 check a RCPT command:
28001 accept domains = +local_domains
28005 If the recipient domain does not match the &%domains%& condition, control
28006 passes to the next statement. If it does match, the recipient is verified, and
28007 the command is accepted if verification succeeds. However, if verification
28008 fails, the ACL yields &"deny"&, because the failing condition is after
28011 The &%endpass%& feature has turned out to be confusing to many people, so its
28012 use is not recommended nowadays. It is always possible to rewrite an ACL so
28013 that &%endpass%& is not needed, and it is no longer used in the default
28016 .cindex "&%message%& ACL modifier" "with &%accept%&"
28017 If a &%message%& modifier appears on an &%accept%& statement, its action
28018 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
28019 (when an &%accept%& verb either accepts or passes control to the next
28020 statement), &%message%& can be used to vary the message that is sent when an
28021 SMTP command is accepted. For example, in a RCPT ACL you could have:
28023 &`accept `&<&'some conditions'&>
28024 &` message = OK, I will allow you through today`&
28026 You can specify an SMTP response code, optionally followed by an &"extended
28027 response code"& at the start of the message, but the first digit must be the
28028 same as would be sent by default, which is 2 for an &%accept%& verb.
28030 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
28031 an error message that is used when access is denied. This behaviour is retained
28032 for backward compatibility, but current &"best practice"& is to avoid the use
28037 .cindex "&%defer%& ACL verb"
28038 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
28039 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
28040 &%defer%& is the same as &%deny%&, because there is no way of sending a
28041 temporary error. For a RCPT command, &%defer%& is much the same as using a
28042 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
28043 be used in any ACL, and even for a recipient it might be a simpler approach.
28047 .cindex "&%deny%& ACL verb"
28048 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
28049 the conditions are not met, control is passed to the next ACL statement. For
28052 deny dnslists = blackholes.mail-abuse.org
28054 rejects commands from hosts that are on a DNS black list.
28058 .cindex "&%discard%& ACL verb"
28059 &%discard%&: This verb behaves like &%accept%&, except that it returns
28060 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
28061 that are concerned with receiving messages. When all the conditions are true,
28062 the sending entity receives a &"success"& response. However, &%discard%& causes
28063 recipients to be discarded. If it is used in an ACL for RCPT, just the one
28064 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
28065 message's recipients are discarded. Recipients that are discarded before DATA
28066 do not appear in the log line when the &%received_recipients%& log selector is set.
28068 If the &%log_message%& modifier is set when &%discard%& operates,
28069 its contents are added to the line that is automatically written to the log.
28070 The &%message%& modifier operates exactly as it does for &%accept%&.
28074 .cindex "&%drop%& ACL verb"
28075 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
28076 forcibly closed after the 5&'xx'& error message has been sent. For example:
28078 drop message = I don't take more than 20 RCPTs
28079 condition = ${if > {$rcpt_count}{20}}
28081 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
28082 The connection is always dropped after sending a 550 response.
28085 .cindex "&%require%& ACL verb"
28086 &%require%&: If all the conditions are met, control is passed to the next ACL
28087 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
28088 example, when checking a RCPT command,
28090 require message = Sender did not verify
28093 passes control to subsequent statements only if the message's sender can be
28094 verified. Otherwise, it rejects the command. Note the positioning of the
28095 &%message%& modifier, before the &%verify%& condition. The reason for this is
28096 discussed in section &<<SECTcondmodproc>>&.
28099 .cindex "&%warn%& ACL verb"
28100 &%warn%&: If all the conditions are true, a line specified by the
28101 &%log_message%& modifier is written to Exim's main log. Control always passes
28102 to the next ACL statement. If any condition is false, the log line is not
28103 written. If an identical log line is requested several times in the same
28104 message, only one copy is actually written to the log. If you want to force
28105 duplicates to be written, use the &%logwrite%& modifier instead.
28107 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
28108 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
28109 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
28110 first failing condition. There is more about adding header lines in section
28111 &<<SECTaddheadacl>>&.
28113 If any condition on a &%warn%& statement cannot be completed (that is, there is
28114 some sort of defer), the log line specified by &%log_message%& is not written.
28115 This does not include the case of a forced failure from a lookup, which
28116 is considered to be a successful completion. After a defer, no further
28117 conditions or modifiers in the &%warn%& statement are processed. The incident
28118 is logged, and the ACL continues to be processed, from the next statement
28122 .vindex "&$acl_verify_message$&"
28123 When one of the &%warn%& conditions is an address verification that fails, the
28124 text of the verification failure message is in &$acl_verify_message$&. If you
28125 want this logged, you must set it up explicitly. For example:
28127 warn !verify = sender
28128 log_message = sender verify failed: $acl_verify_message
28132 At the end of each ACL there is an implicit unconditional &%deny%&.
28134 As you can see from the examples above, the conditions and modifiers are
28135 written one to a line, with the first one on the same line as the verb, and
28136 subsequent ones on following lines. If you have a very long condition, you can
28137 continue it onto several physical lines by the usual backslash continuation
28138 mechanism. It is conventional to align the conditions vertically.
28142 .section "ACL variables" "SECTaclvariables"
28143 .cindex "&ACL;" "variables"
28144 There are some special variables that can be set during ACL processing. They
28145 can be used to pass information between different ACLs, different invocations
28146 of the same ACL in the same SMTP connection, and between ACLs and the routers,
28147 transports, and filters that are used to deliver a message. The names of these
28148 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
28149 an underscore, but the remainder of the name can be any sequence of
28150 alphanumeric characters and underscores that you choose. There is no limit on
28151 the number of ACL variables. The two sets act as follows:
28153 The values of those variables whose names begin with &$acl_c$& persist
28154 throughout an SMTP connection. They are never reset. Thus, a value that is set
28155 while receiving one message is still available when receiving the next message
28156 on the same SMTP connection.
28158 The values of those variables whose names begin with &$acl_m$& persist only
28159 while a message is being received. They are reset afterwards. They are also
28160 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
28163 When a message is accepted, the current values of all the ACL variables are
28164 preserved with the message and are subsequently made available at delivery
28165 time. The ACL variables are set by a modifier called &%set%&. For example:
28167 accept hosts = whatever
28168 set acl_m4 = some value
28169 accept authenticated = *
28170 set acl_c_auth = yes
28172 &*Note*&: A leading dollar sign is not used when naming a variable that is to
28173 be set. If you want to set a variable without taking any action, you can use a
28174 &%warn%& verb without any other modifiers or conditions.
28176 .oindex &%strict_acl_vars%&
28177 What happens if a syntactically valid but undefined ACL variable is
28178 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
28179 false (the default), an empty string is substituted; if it is true, an
28180 error is generated.
28182 Versions of Exim before 4.64 have a limited set of numbered variables, but
28183 their names are compatible, so there is no problem with upgrading.
28186 .section "Condition and modifier processing" "SECTcondmodproc"
28187 .cindex "&ACL;" "conditions; processing"
28188 .cindex "&ACL;" "modifiers; processing"
28189 An exclamation mark preceding a condition negates its result. For example:
28191 deny domains = *.dom.example
28192 !verify = recipient
28194 causes the ACL to return &"deny"& if the recipient domain ends in
28195 &'dom.example'& and the recipient address cannot be verified. Sometimes
28196 negation can be used on the right-hand side of a condition. For example, these
28197 two statements are equivalent:
28199 deny hosts = !192.168.3.4
28200 deny !hosts = 192.168.3.4
28202 However, for many conditions (&%verify%& being a good example), only left-hand
28203 side negation of the whole condition is possible.
28205 The arguments of conditions and modifiers are expanded. A forced failure
28206 of an expansion causes a condition to be ignored, that is, it behaves as if the
28207 condition is true. Consider these two statements:
28209 accept senders = ${lookup{$host_name}lsearch\
28210 {/some/file}{$value}fail}
28211 accept senders = ${lookup{$host_name}lsearch\
28212 {/some/file}{$value}{}}
28214 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
28215 the returned list is searched, but if the lookup fails the behaviour is
28216 different in the two cases. The &%fail%& in the first statement causes the
28217 condition to be ignored, leaving no further conditions. The &%accept%& verb
28218 therefore succeeds. The second statement, however, generates an empty list when
28219 the lookup fails. No sender can match an empty list, so the condition fails,
28220 and therefore the &%accept%& also fails.
28222 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
28223 specify actions that are taken as the conditions for a statement are checked;
28224 others specify text for messages that are used when access is denied or a
28225 warning is generated. The &%control%& modifier affects the way an incoming
28226 message is handled.
28228 The positioning of the modifiers in an ACL statement is important, because the
28229 processing of a verb ceases as soon as its outcome is known. Only those
28230 modifiers that have already been encountered will take effect. For example,
28231 consider this use of the &%message%& modifier:
28233 require message = Can't verify sender
28235 message = Can't verify recipient
28237 message = This message cannot be used
28239 If sender verification fails, Exim knows that the result of the statement is
28240 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
28241 so its text is used as the error message. If sender verification succeeds, but
28242 recipient verification fails, the second message is used. If recipient
28243 verification succeeds, the third message becomes &"current"&, but is never used
28244 because there are no more conditions to cause failure.
28246 For the &%deny%& verb, on the other hand, it is always the last &%message%&
28247 modifier that is used, because all the conditions must be true for rejection to
28248 happen. Specifying more than one &%message%& modifier does not make sense, and
28249 the message can even be specified after all the conditions. For example:
28252 !senders = *@my.domain.example
28253 message = Invalid sender from client host
28255 The &"deny"& result does not happen until the end of the statement is reached,
28256 by which time Exim has set up the message.
28260 .section "ACL modifiers" "SECTACLmodi"
28261 .cindex "&ACL;" "modifiers; list of"
28262 The ACL modifiers are as follows:
28265 .vitem &*add_header*&&~=&~<&'text'&>
28266 This modifier specifies one or more header lines that are to be added to an
28267 incoming message, assuming, of course, that the message is ultimately
28268 accepted. For details, see section &<<SECTaddheadacl>>&.
28270 .vitem &*continue*&&~=&~<&'text'&>
28271 .cindex "&%continue%& ACL modifier"
28272 .cindex "database" "updating in ACL"
28273 This modifier does nothing of itself, and processing of the ACL always
28274 continues with the next condition or modifier. The value of &%continue%& is in
28275 the side effects of expanding its argument. Typically this could be used to
28276 update a database. It is really just a syntactic tidiness, to avoid having to
28277 write rather ugly lines like this:
28279 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
28281 Instead, all you need is
28283 &`continue = `&<&'some expansion'&>
28286 .vitem &*control*&&~=&~<&'text'&>
28287 .cindex "&%control%& ACL modifier"
28288 This modifier affects the subsequent processing of the SMTP connection or of an
28289 incoming message that is accepted. The effect of the first type of control
28290 lasts for the duration of the connection, whereas the effect of the second type
28291 lasts only until the current message has been received. The message-specific
28292 controls always apply to the whole message, not to individual recipients,
28293 even if the &%control%& modifier appears in a RCPT ACL.
28295 As there are now quite a few controls that can be applied, they are described
28296 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
28297 in several different ways. For example:
28299 . ==== As this is a nested list, any displays it contains must be indented
28300 . ==== as otherwise they are too far to the left. That comment applies only
28301 . ==== when xmlto and fop are used; formatting with sdop gets it right either
28305 It can be at the end of an &%accept%& statement:
28307 accept ...some conditions
28308 control = queue_only
28310 In this case, the control is applied when this statement yields &"accept"&, in
28311 other words, when the conditions are all true.
28314 It can be in the middle of an &%accept%& statement:
28316 accept ...some conditions...
28317 control = queue_only
28318 ...some more conditions...
28320 If the first set of conditions are true, the control is applied, even if the
28321 statement does not accept because one of the second set of conditions is false.
28322 In this case, some subsequent statement must yield &"accept"& for the control
28326 It can be used with &%warn%& to apply the control, leaving the
28327 decision about accepting or denying to a subsequent verb. For
28330 warn ...some conditions...
28334 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
28335 &%logwrite%&, so it does not add anything to the message and does not write a
28339 If you want to apply a control unconditionally, you can use it with a
28340 &%require%& verb. For example:
28342 require control = no_multiline_responses
28346 .vitem &*delay*&&~=&~<&'time'&>
28347 .cindex "&%delay%& ACL modifier"
28349 This modifier may appear in any ACL except notquit. It causes Exim to wait for
28350 the time interval before proceeding. However, when testing Exim using the
28351 &%-bh%& option, the delay is not actually imposed (an appropriate message is
28352 output instead). The time is given in the usual Exim notation, and the delay
28353 happens as soon as the modifier is processed. In an SMTP session, pending
28354 output is flushed before the delay is imposed.
28356 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
28359 deny ...some conditions...
28362 The delay happens if all the conditions are true, before the statement returns
28363 &"deny"&. Compare this with:
28366 ...some conditions...
28368 which waits for 30s before processing the conditions. The &%delay%& modifier
28369 can also be used with &%warn%& and together with &%control%&:
28371 warn ...some conditions...
28377 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
28378 responses to several commands are no longer buffered and sent in one packet (as
28379 they would normally be) because all output is flushed before imposing the
28380 delay. This optimization is disabled so that a number of small delays do not
28381 appear to the client as one large aggregated delay that might provoke an
28382 unwanted timeout. You can, however, disable output flushing for &%delay%& by
28383 using a &%control%& modifier to set &%no_delay_flush%&.
28387 .cindex "&%endpass%& ACL modifier"
28388 This modifier, which has no argument, is recognized only in &%accept%& and
28389 &%discard%& statements. It marks the boundary between the conditions whose
28390 failure causes control to pass to the next statement, and the conditions whose
28391 failure causes the ACL to return &"deny"&. This concept has proved to be
28392 confusing to some people, so the use of &%endpass%& is no longer recommended as
28393 &"best practice"&. See the description of &%accept%& above for more details.
28396 .vitem &*log_message*&&~=&~<&'text'&>
28397 .cindex "&%log_message%& ACL modifier"
28398 This modifier sets up a message that is used as part of the log message if the
28399 ACL denies access or a &%warn%& statement's conditions are true. For example:
28401 require log_message = wrong cipher suite $tls_in_cipher
28402 encrypted = DES-CBC3-SHA
28404 &%log_message%& is also used when recipients are discarded by &%discard%&. For
28407 &`discard `&<&'some conditions'&>
28408 &` log_message = Discarded $local_part@$domain because...`&
28410 When access is denied, &%log_message%& adds to any underlying error message
28411 that may exist because of a condition failure. For example, while verifying a
28412 recipient address, a &':fail:'& redirection might have already set up a
28415 The message may be defined before the conditions to which it applies, because
28416 the string expansion does not happen until Exim decides that access is to be
28417 denied. This means that any variables that are set by the condition are
28418 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
28419 variables are set after a DNS black list lookup succeeds. If the expansion of
28420 &%log_message%& fails, or if the result is an empty string, the modifier is
28423 .vindex "&$acl_verify_message$&"
28424 If you want to use a &%warn%& statement to log the result of an address
28425 verification, you can use &$acl_verify_message$& to include the verification
28428 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
28429 the start of the logged message. If the same warning log message is requested
28430 more than once while receiving a single email message, only one copy is
28431 actually logged. If you want to log multiple copies, use &%logwrite%& instead
28432 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
28433 is logged for a successful &%warn%& statement.
28435 If &%log_message%& is not present and there is no underlying error message (for
28436 example, from the failure of address verification), but &%message%& is present,
28437 the &%message%& text is used for logging rejections. However, if any text for
28438 logging contains newlines, only the first line is logged. In the absence of
28439 both &%log_message%& and &%message%&, a default built-in message is used for
28440 logging rejections.
28443 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
28444 .cindex "&%log_reject_target%& ACL modifier"
28445 .cindex "logging in ACL" "specifying which log"
28446 This modifier makes it possible to specify which logs are used for messages
28447 about ACL rejections. Its argument is a colon-separated list of words that can
28448 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
28449 may be empty, in which case a rejection is not logged at all. For example, this
28450 ACL fragment writes no logging information when access is denied:
28452 &`deny `&<&'some conditions'&>
28453 &` log_reject_target =`&
28455 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
28456 permanent and temporary rejections. Its effect lasts for the rest of the
28460 .vitem &*logwrite*&&~=&~<&'text'&>
28461 .cindex "&%logwrite%& ACL modifier"
28462 .cindex "logging in ACL" "immediate"
28463 This modifier writes a message to a log file as soon as it is encountered when
28464 processing an ACL. (Compare &%log_message%&, which, except in the case of
28465 &%warn%& and &%discard%&, is used only if the ACL statement denies
28466 access.) The &%logwrite%& modifier can be used to log special incidents in
28469 &`accept `&<&'some special conditions'&>
28470 &` control = freeze`&
28471 &` logwrite = froze message because ...`&
28473 By default, the message is written to the main log. However, it may begin
28474 with a colon, followed by a comma-separated list of log names, and then
28475 another colon, to specify exactly which logs are to be written. For
28478 logwrite = :main,reject: text for main and reject logs
28479 logwrite = :panic: text for panic log only
28483 .vitem &*message*&&~=&~<&'text'&>
28484 .cindex "&%message%& ACL modifier"
28485 This modifier sets up a text string that is expanded and used as a response
28486 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
28487 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
28488 there is some complication if &%endpass%& is involved; see the description of
28489 &%accept%& for details.)
28491 The expansion of the message happens at the time Exim decides that the ACL is
28492 to end, not at the time it processes &%message%&. If the expansion fails, or
28493 generates an empty string, the modifier is ignored. Here is an example where
28494 &%message%& must be specified first, because the ACL ends with a rejection if
28495 the &%hosts%& condition fails:
28497 require message = Host not recognized
28500 (Once a condition has failed, no further conditions or modifiers are
28503 .cindex "SMTP" "error codes"
28504 .oindex "&%smtp_banner%&
28505 For ACLs that are triggered by SMTP commands, the message is returned as part
28506 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
28507 is meaningful only for SMTP, as no message is returned when a non-SMTP message
28508 is accepted. In the case of the connect ACL, accepting with a message modifier
28509 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
28510 accept message may not contain more than one line (otherwise it will be
28511 truncated at the first newline and a panic logged), and it cannot affect the
28514 When SMTP is involved, the message may begin with an overriding response code,
28515 consisting of three digits optionally followed by an &"extended response code"&
28516 of the form &'n.n.n'&, each code being followed by a space. For example:
28518 deny message = 599 1.2.3 Host not welcome
28519 hosts = 192.168.34.0/24
28521 The first digit of the supplied response code must be the same as would be sent
28522 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
28523 access, but for the predata ACL, note that the default success code is 354, not
28526 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
28527 the message modifier cannot override the 221 response code.
28529 The text in a &%message%& modifier is literal; any quotes are taken as
28530 literals, but because the string is expanded, backslash escapes are processed
28531 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
28534 .vindex "&$acl_verify_message$&"
28535 For ACLs that are called by an &%acl =%& ACL condition, the message is
28536 stored in &$acl_verify_message$&, from which the calling ACL may use it.
28538 If &%message%& is used on a statement that verifies an address, the message
28539 specified overrides any message that is generated by the verification process.
28540 However, the original message is available in the variable
28541 &$acl_verify_message$&, so you can incorporate it into your message if you
28542 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
28543 routers to be passed back as part of the SMTP response, you should either not
28544 use a &%message%& modifier, or make use of &$acl_verify_message$&.
28546 For compatibility with previous releases of Exim, a &%message%& modifier that
28547 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
28548 modifier, but this usage is now deprecated. However, &%message%& acts only when
28549 all the conditions are true, wherever it appears in an ACL command, whereas
28550 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
28551 &%warn%& in an ACL that is not concerned with receiving a message, it has no
28555 .vitem &*remove_header*&&~=&~<&'text'&>
28556 This modifier specifies one or more header names in a colon-separated list
28557 that are to be removed from an incoming message, assuming, of course, that
28558 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
28561 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
28562 .cindex "&%set%& ACL modifier"
28563 This modifier puts a value into one of the ACL variables (see section
28564 &<<SECTaclvariables>>&).
28567 .vitem &*udpsend*&&~=&~<&'parameters'&>
28568 This modifier sends a UDP packet, for purposes such as statistics
28569 collection or behaviour monitoring. The parameters are expanded, and
28570 the result of the expansion must be a colon-separated list consisting
28571 of a destination server, port number, and the packet contents. The
28572 server can be specified as a host name or IPv4 or IPv6 address. The
28573 separator can be changed with the usual angle bracket syntax. For
28574 example, you might want to collect information on which hosts connect
28577 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
28578 $tod_zulu $sender_host_address
28585 .section "Use of the control modifier" "SECTcontrols"
28586 .cindex "&%control%& ACL modifier"
28587 The &%control%& modifier supports the following settings:
28590 .vitem &*control&~=&~allow_auth_unadvertised*&
28591 This modifier allows a client host to use the SMTP AUTH command even when it
28592 has not been advertised in response to EHLO. Furthermore, because there are
28593 apparently some really broken clients that do this, Exim will accept AUTH after
28594 HELO (rather than EHLO) when this control is set. It should be used only if you
28595 really need it, and you should limit its use to those broken clients that do
28596 not work without it. For example:
28598 warn hosts = 192.168.34.25
28599 control = allow_auth_unadvertised
28601 Normally, when an Exim server receives an AUTH command, it checks the name of
28602 the authentication mechanism that is given in the command to ensure that it
28603 matches an advertised mechanism. When this control is set, the check that a
28604 mechanism has been advertised is bypassed. Any configured mechanism can be used
28605 by the client. This control is permitted only in the connection and HELO ACLs.
28608 .vitem &*control&~=&~caseful_local_part*& &&&
28609 &*control&~=&~caselower_local_part*&
28610 .cindex "&ACL;" "case of local part in"
28611 .cindex "case of local parts"
28612 .vindex "&$local_part$&"
28613 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
28614 (that is, during RCPT processing). By default, the contents of &$local_part$&
28615 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
28616 any uppercase letters in the original local part are restored in &$local_part$&
28617 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
28620 These controls affect only the current recipient. Moreover, they apply only to
28621 local part handling that takes place directly in the ACL (for example, as a key
28622 in lookups). If a test to verify the recipient is obeyed, the case-related
28623 handling of the local part during the verification is controlled by the router
28624 configuration (see the &%caseful_local_part%& generic router option).
28626 This facility could be used, for example, to add a spam score to local parts
28627 containing upper case letters. For example, using &$acl_m4$& to accumulate the
28630 warn control = caseful_local_part
28631 set acl_m4 = ${eval:\
28633 ${if match{$local_part}{[A-Z]}{1}{0}}\
28635 control = caselower_local_part
28637 Notice that we put back the lower cased version afterwards, assuming that
28638 is what is wanted for subsequent tests.
28641 .vitem &*control&~=&~cutthrough_delivery*&
28642 .cindex "&ACL;" "cutthrough routing"
28643 .cindex "cutthrough" "requesting"
28644 This option requests delivery be attempted while the item is being received.
28646 The option is usable in the RCPT ACL.
28647 If enabled for a message received via smtp and routed to an smtp transport,
28648 and only one transport, interface, destination host and port combination
28649 is used for all recipients of the message,
28650 then the delivery connection is made while the receiving connection is open
28651 and data is copied from one to the other.
28653 An attempt to set this option for any recipient but the first
28654 for a mail will be quietly ignored.
28655 If a recipient-verify callout
28659 connection is subsequently
28660 requested in the same ACL it is held open and used for
28661 any subsequent recipients and the data,
28662 otherwise one is made after the initial RCPT ACL completes.
28664 Note that routers are used in verify mode,
28665 and cannot depend on content of received headers.
28666 Note also that headers cannot be
28667 modified by any of the post-data ACLs (DATA, MIME and DKIM).
28668 Headers may be modified by routers (subject to the above) and transports.
28671 All the usual ACLs are called; if one results in the message being
28672 rejected, all effort spent in delivery (including the costs on
28673 the ultimate destination) will be wasted.
28674 Note that in the case of data-time ACLs this includes the entire
28678 Cutthrough delivery is not supported via transport-filters or when DKIM signing
28679 of outgoing messages is done, because it sends data to the ultimate destination
28680 before the entire message has been received from the source.
28681 It is not supported for messages received with the SMTP PRDR option in use.
28683 Should the ultimate destination system positively accept or reject the mail,
28684 a corresponding indication is given to the source system and nothing is queued.
28685 If there is a temporary error the item is queued for later delivery in the
28686 usual fashion. If the item is successfully delivered in cutthrough mode
28687 the delivery log lines are tagged with ">>" rather than "=>" and appear
28688 before the acceptance "<=" line.
28690 Delivery in this mode avoids the generation of a bounce mail to a
28692 sender when the destination system is doing content-scan based rejection.
28695 .vitem &*control&~=&~debug/*&<&'options'&>
28696 .cindex "&ACL;" "enabling debug logging"
28697 .cindex "debugging" "enabling from an ACL"
28698 This control turns on debug logging, almost as though Exim had been invoked
28699 with &`-d`&, with the output going to a new logfile, by default called
28700 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
28701 may access any variables already defined. The logging may be adjusted with
28702 the &'opts'& option, which takes the same values as the &`-d`& command-line
28703 option. Some examples (which depend on variables that don't exist in all
28707 control = debug/tag=.$sender_host_address
28708 control = debug/opts=+expand+acl
28709 control = debug/tag=.$message_exim_id/opts=+expand
28713 .vitem &*control&~=&~dkim_disable_verify*&
28714 .cindex "disable DKIM verify"
28715 .cindex "DKIM" "disable verify"
28716 This control turns off DKIM verification processing entirely. For details on
28717 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
28720 .vitem &*control&~=&~dscp/*&<&'value'&>
28721 .cindex "&ACL;" "setting DSCP value"
28722 .cindex "DSCP" "inbound"
28723 This option causes the DSCP value associated with the socket for the inbound
28724 connection to be adjusted to a given value, given as one of a number of fixed
28725 strings or to numeric value.
28726 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
28727 Common values include &`throughput`&, &`mincost`&, and on newer systems
28728 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
28730 The outbound packets from Exim will be marked with this value in the header
28731 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
28732 that these values will have any effect, not be stripped by networking
28733 equipment, or do much of anything without cooperation with your Network
28734 Engineer and those of all network operators between the source and destination.
28737 .vitem &*control&~=&~enforce_sync*& &&&
28738 &*control&~=&~no_enforce_sync*&
28739 .cindex "SMTP" "synchronization checking"
28740 .cindex "synchronization checking in SMTP"
28741 These controls make it possible to be selective about when SMTP synchronization
28742 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
28743 state of the switch (it is true by default). See the description of this option
28744 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
28746 The effect of these two controls lasts for the remainder of the SMTP
28747 connection. They can appear in any ACL except the one for the non-SMTP
28748 messages. The most straightforward place to put them is in the ACL defined by
28749 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
28750 before the first synchronization check. The expected use is to turn off the
28751 synchronization checks for badly-behaved hosts that you nevertheless need to
28755 .vitem &*control&~=&~fakedefer/*&<&'message'&>
28756 .cindex "fake defer"
28757 .cindex "defer, fake"
28758 This control works in exactly the same way as &%fakereject%& (described below)
28759 except that it causes an SMTP 450 response after the message data instead of a
28760 550 response. You must take care when using &%fakedefer%& because it causes the
28761 messages to be duplicated when the sender retries. Therefore, you should not
28762 use &%fakedefer%& if the message is to be delivered normally.
28764 .vitem &*control&~=&~fakereject/*&<&'message'&>
28765 .cindex "fake rejection"
28766 .cindex "rejection, fake"
28767 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
28768 words, only when an SMTP message is being received. If Exim accepts the
28769 message, instead the final 250 response, a 550 rejection message is sent.
28770 However, Exim proceeds to deliver the message as normal. The control applies
28771 only to the current message, not to any subsequent ones that may be received in
28772 the same SMTP connection.
28774 The text for the 550 response is taken from the &%control%& modifier. If no
28775 message is supplied, the following is used:
28777 550-Your message has been rejected but is being
28778 550-kept for evaluation.
28779 550-If it was a legitimate message, it may still be
28780 550 delivered to the target recipient(s).
28782 This facility should be used with extreme caution.
28784 .vitem &*control&~=&~freeze*&
28785 .cindex "frozen messages" "forcing in ACL"
28786 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28787 other words, only when a message is being received. If the message is accepted,
28788 it is placed on Exim's queue and frozen. The control applies only to the
28789 current message, not to any subsequent ones that may be received in the same
28792 This modifier can optionally be followed by &`/no_tell`&. If the global option
28793 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
28794 is told about the freezing), provided all the &*control=freeze*& modifiers that
28795 are obeyed for the current message have the &`/no_tell`& option.
28797 .vitem &*control&~=&~no_delay_flush*&
28798 .cindex "SMTP" "output flushing, disabling for delay"
28799 Exim normally flushes SMTP output before implementing a delay in an ACL, to
28800 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28801 use. This control, as long as it is encountered before the &%delay%& modifier,
28802 disables such output flushing.
28804 .vitem &*control&~=&~no_callout_flush*&
28805 .cindex "SMTP" "output flushing, disabling for callout"
28806 Exim normally flushes SMTP output before performing a callout in an ACL, to
28807 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28808 use. This control, as long as it is encountered before the &%verify%& condition
28809 that causes the callout, disables such output flushing.
28811 .vitem &*control&~=&~no_mbox_unspool*&
28812 This control is available when Exim is compiled with the content scanning
28813 extension. Content scanning may require a copy of the current message, or parts
28814 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
28815 or spam scanner. Normally, such copies are deleted when they are no longer
28816 needed. If this control is set, the copies are not deleted. The control applies
28817 only to the current message, not to any subsequent ones that may be received in
28818 the same SMTP connection. It is provided for debugging purposes and is unlikely
28819 to be useful in production.
28821 .vitem &*control&~=&~no_multiline_responses*&
28822 .cindex "multiline responses, suppressing"
28823 This control is permitted for any ACL except the one for non-SMTP messages.
28824 It seems that there are broken clients in use that cannot handle multiline
28825 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
28827 If this control is set, multiline SMTP responses from ACL rejections are
28828 suppressed. One way of doing this would have been to put out these responses as
28829 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
28830 (&"use multiline responses for more"& it says &-- ha!), and some of the
28831 responses might get close to that. So this facility, which is after all only a
28832 sop to broken clients, is implemented by doing two very easy things:
28835 Extra information that is normally output as part of a rejection caused by
28836 sender verification failure is omitted. Only the final line (typically &"sender
28837 verification failed"&) is sent.
28839 If a &%message%& modifier supplies a multiline response, only the first
28843 The setting of the switch can, of course, be made conditional on the
28844 calling host. Its effect lasts until the end of the SMTP connection.
28846 .vitem &*control&~=&~no_pipelining*&
28847 .cindex "PIPELINING" "suppressing advertising"
28848 This control turns off the advertising of the PIPELINING extension to SMTP in
28849 the current session. To be useful, it must be obeyed before Exim sends its
28850 response to an EHLO command. Therefore, it should normally appear in an ACL
28851 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
28852 &%pipelining_advertise_hosts%&.
28854 .vitem &*control&~=&~queue_only*&
28855 .oindex "&%queue_only%&"
28856 .cindex "queueing incoming messages"
28857 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28858 other words, only when a message is being received. If the message is accepted,
28859 it is placed on Exim's queue and left there for delivery by a subsequent queue
28860 runner. No immediate delivery process is started. In other words, it has the
28861 effect as the &%queue_only%& global option. However, the control applies only
28862 to the current message, not to any subsequent ones that may be received in the
28863 same SMTP connection.
28865 .vitem &*control&~=&~submission/*&<&'options'&>
28866 .cindex "message" "submission"
28867 .cindex "submission mode"
28868 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
28869 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
28870 the current message is a submission from a local MUA. In this case, Exim
28871 operates in &"submission mode"&, and applies certain fixups to the message if
28872 necessary. For example, it adds a &'Date:'& header line if one is not present.
28873 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
28874 late (the message has already been created).
28876 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
28877 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
28878 submission mode; the available options for this control are described there.
28879 The control applies only to the current message, not to any subsequent ones
28880 that may be received in the same SMTP connection.
28882 .vitem &*control&~=&~suppress_local_fixups*&
28883 .cindex "submission fixups, suppressing"
28884 This control applies to locally submitted (non TCP/IP) messages, and is the
28885 complement of &`control = submission`&. It disables the fixups that are
28886 normally applied to locally-submitted messages. Specifically:
28889 Any &'Sender:'& header line is left alone (in this respect, it is a
28890 dynamic version of &%local_sender_retain%&).
28892 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
28894 There is no check that &'From:'& corresponds to the actual sender.
28897 This control may be useful when a remotely-originated message is accepted,
28898 passed to some scanning program, and then re-submitted for delivery. It can be
28899 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
28900 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
28903 &*Note:*& This control applies only to the current message, not to any others
28904 that are being submitted at the same time using &%-bs%& or &%-bS%&.
28907 .vitem &*control&~=&~utf8_downconvert*&
28908 This control enables conversion of UTF-8 in message addresses
28910 For details see &<<SECTi18nMTA>>&.
28915 .section "Summary of message fixup control" "SECTsummesfix"
28916 All four possibilities for message fixups can be specified:
28919 Locally submitted, fixups applied: the default.
28921 Locally submitted, no fixups applied: use
28922 &`control = suppress_local_fixups`&.
28924 Remotely submitted, no fixups applied: the default.
28926 Remotely submitted, fixups applied: use &`control = submission`&.
28931 .section "Adding header lines in ACLs" "SECTaddheadacl"
28932 .cindex "header lines" "adding in an ACL"
28933 .cindex "header lines" "position of added lines"
28934 .cindex "&%add_header%& ACL modifier"
28935 The &%add_header%& modifier can be used to add one or more extra header lines
28936 to an incoming message, as in this example:
28938 warn dnslists = sbl.spamhaus.org : \
28939 dialup.mail-abuse.org
28940 add_header = X-blacklisted-at: $dnslist_domain
28942 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28943 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28944 receiving a message). The message must ultimately be accepted for
28945 &%add_header%& to have any significant effect. You can use &%add_header%& with
28946 any ACL verb, including &%deny%& (though this is potentially useful only in a
28949 Headers will not be added to the message if the modifier is used in
28950 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28952 Leading and trailing newlines are removed from
28953 the data for the &%add_header%& modifier; if it then
28954 contains one or more newlines that
28955 are not followed by a space or a tab, it is assumed to contain multiple header
28956 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
28957 front of any line that is not a valid header line.
28959 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28960 They are added to the message before processing the DATA and MIME ACLs.
28961 However, if an identical header line is requested more than once, only one copy
28962 is actually added to the message. Further header lines may be accumulated
28963 during the DATA and MIME ACLs, after which they are added to the message, again
28964 with duplicates suppressed. Thus, it is possible to add two identical header
28965 lines to an SMTP message, but only if one is added before DATA and one after.
28966 In the case of non-SMTP messages, new headers are accumulated during the
28967 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
28968 message is rejected after DATA or by the non-SMTP ACL, all added header lines
28969 are included in the entry that is written to the reject log.
28971 .cindex "header lines" "added; visibility of"
28972 Header lines are not visible in string expansions
28974 until they are added to the
28975 message. It follows that header lines defined in the MAIL, RCPT, and predata
28976 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
28977 header lines that are added by the DATA or MIME ACLs are not visible in those
28978 ACLs. Because of this restriction, you cannot use header lines as a way of
28979 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
28980 this, you can use ACL variables, as described in section
28981 &<<SECTaclvariables>>&.
28983 The list of headers yet to be added is given by the &%$headers_added%& variable.
28985 The &%add_header%& modifier acts immediately as it is encountered during the
28986 processing of an ACL. Notice the difference between these two cases:
28988 &`accept add_header = ADDED: some text`&
28989 &` `&<&'some condition'&>
28991 &`accept `&<&'some condition'&>
28992 &` add_header = ADDED: some text`&
28994 In the first case, the header line is always added, whether or not the
28995 condition is true. In the second case, the header line is added only if the
28996 condition is true. Multiple occurrences of &%add_header%& may occur in the same
28997 ACL statement. All those that are encountered before a condition fails are
29000 .cindex "&%warn%& ACL verb"
29001 For compatibility with previous versions of Exim, a &%message%& modifier for a
29002 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
29003 effect only if all the conditions are true, even if it appears before some of
29004 them. Furthermore, only the last occurrence of &%message%& is honoured. This
29005 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
29006 are present on a &%warn%& verb, both are processed according to their
29009 By default, new header lines are added to a message at the end of the existing
29010 header lines. However, you can specify that any particular header line should
29011 be added right at the start (before all the &'Received:'& lines), immediately
29012 after the first block of &'Received:'& lines, or immediately before any line
29013 that is not a &'Received:'& or &'Resent-something:'& header.
29015 This is done by specifying &":at_start:"&, &":after_received:"&, or
29016 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
29017 header line, respectively. (Header text cannot start with a colon, as there has
29018 to be a header name first.) For example:
29020 warn add_header = \
29021 :after_received:X-My-Header: something or other...
29023 If more than one header line is supplied in a single &%add_header%& modifier,
29024 each one is treated independently and can therefore be placed differently. If
29025 you add more than one line at the start, or after the Received: block, they end
29026 up in reverse order.
29028 &*Warning*&: This facility currently applies only to header lines that are
29029 added in an ACL. It does NOT work for header lines that are added in a
29030 system filter or in a router or transport.
29034 .section "Removing header lines in ACLs" "SECTremoveheadacl"
29035 .cindex "header lines" "removing in an ACL"
29036 .cindex "header lines" "position of removed lines"
29037 .cindex "&%remove_header%& ACL modifier"
29038 The &%remove_header%& modifier can be used to remove one or more header lines
29039 from an incoming message, as in this example:
29041 warn message = Remove internal headers
29042 remove_header = x-route-mail1 : x-route-mail2
29044 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29045 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29046 receiving a message). The message must ultimately be accepted for
29047 &%remove_header%& to have any significant effect. You can use &%remove_header%&
29048 with any ACL verb, including &%deny%&, though this is really not useful for
29049 any verb that doesn't result in a delivered message.
29051 Headers will not be removed to the message if the modifier is used in
29052 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
29054 More than one header can be removed at the same time by using a colon separated
29055 list of header names. The header matching is case insensitive. Wildcards are
29056 not permitted, nor is list expansion performed, so you cannot use hostlists to
29057 create a list of headers, however both connection and message variable expansion
29058 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
29060 warn hosts = +internal_hosts
29061 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
29062 warn message = Remove internal headers
29063 remove_header = $acl_c_ihdrs
29065 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29066 They are removed from the message before processing the DATA and MIME ACLs.
29067 There is no harm in attempting to remove the same header twice nor is removing
29068 a non-existent header. Further header lines to be removed may be accumulated
29069 during the DATA and MIME ACLs, after which they are removed from the message,
29070 if present. In the case of non-SMTP messages, headers to be removed are
29071 accumulated during the non-SMTP ACLs, and are removed from the message after
29072 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
29073 ACL, there really is no effect because there is no logging of what headers
29074 would have been removed.
29076 .cindex "header lines" "removed; visibility of"
29077 Header lines are not visible in string expansions until the DATA phase when it
29078 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
29079 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
29080 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
29081 this restriction, you cannot use header lines as a way of controlling data
29082 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
29083 you should instead use ACL variables, as described in section
29084 &<<SECTaclvariables>>&.
29086 The &%remove_header%& modifier acts immediately as it is encountered during the
29087 processing of an ACL. Notice the difference between these two cases:
29089 &`accept remove_header = X-Internal`&
29090 &` `&<&'some condition'&>
29092 &`accept `&<&'some condition'&>
29093 &` remove_header = X-Internal`&
29095 In the first case, the header line is always removed, whether or not the
29096 condition is true. In the second case, the header line is removed only if the
29097 condition is true. Multiple occurrences of &%remove_header%& may occur in the
29098 same ACL statement. All those that are encountered before a condition fails
29101 &*Warning*&: This facility currently applies only to header lines that are
29102 present during ACL processing. It does NOT remove header lines that are added
29103 in a system filter or in a router or transport.
29108 .section "ACL conditions" "SECTaclconditions"
29109 .cindex "&ACL;" "conditions; list of"
29110 Some of the conditions listed in this section are available only when Exim is
29111 compiled with the content-scanning extension. They are included here briefly
29112 for completeness. More detailed descriptions can be found in the discussion on
29113 content scanning in chapter &<<CHAPexiscan>>&.
29115 Not all conditions are relevant in all circumstances. For example, testing
29116 senders and recipients does not make sense in an ACL that is being run as the
29117 result of the arrival of an ETRN command, and checks on message headers can be
29118 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
29119 can use the same condition (with different parameters) more than once in the
29120 same ACL statement. This provides a way of specifying an &"and"& conjunction.
29121 The conditions are as follows:
29125 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
29126 .cindex "&ACL;" "nested"
29127 .cindex "&ACL;" "indirect"
29128 .cindex "&ACL;" "arguments"
29129 .cindex "&%acl%& ACL condition"
29130 The possible values of the argument are the same as for the
29131 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
29132 &"accept"& the condition is true; if it returns &"deny"& the condition is
29133 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
29134 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
29135 condition false. This means that further processing of the &%warn%& verb
29136 ceases, but processing of the ACL continues.
29138 If the argument is a named ACL, up to nine space-separated optional values
29139 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
29140 and $acl_narg is set to the count of values.
29141 Previous values of these variables are restored after the call returns.
29142 The name and values are expanded separately.
29143 Note that spaces in complex expansions which are used as arguments
29144 will act as argument separators.
29146 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
29147 the connection is dropped. If it returns &"discard"&, the verb must be
29148 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
29149 conditions are tested.
29151 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
29152 loops. This condition allows you to use different ACLs in different
29153 circumstances. For example, different ACLs can be used to handle RCPT commands
29154 for different local users or different local domains.
29156 .vitem &*authenticated&~=&~*&<&'string&~list'&>
29157 .cindex "&%authenticated%& ACL condition"
29158 .cindex "authentication" "ACL checking"
29159 .cindex "&ACL;" "testing for authentication"
29160 If the SMTP connection is not authenticated, the condition is false. Otherwise,
29161 the name of the authenticator is tested against the list. To test for
29162 authentication by any authenticator, you can set
29167 .vitem &*condition&~=&~*&<&'string'&>
29168 .cindex "&%condition%& ACL condition"
29169 .cindex "customizing" "ACL condition"
29170 .cindex "&ACL;" "customized test"
29171 .cindex "&ACL;" "testing, customized"
29172 This feature allows you to make up custom conditions. If the result of
29173 expanding the string is an empty string, the number zero, or one of the strings
29174 &"no"& or &"false"&, the condition is false. If the result is any non-zero
29175 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
29176 any other value, some error is assumed to have occurred, and the ACL returns
29177 &"defer"&. However, if the expansion is forced to fail, the condition is
29178 ignored. The effect is to treat it as true, whether it is positive or
29181 .vitem &*decode&~=&~*&<&'location'&>
29182 .cindex "&%decode%& ACL condition"
29183 This condition is available only when Exim is compiled with the
29184 content-scanning extension, and it is allowed only in the ACL defined by
29185 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
29186 If all goes well, the condition is true. It is false only if there are
29187 problems such as a syntax error or a memory shortage. For more details, see
29188 chapter &<<CHAPexiscan>>&.
29190 .vitem &*demime&~=&~*&<&'extension&~list'&>
29191 .cindex "&%demime%& ACL condition"
29192 This condition is available only when Exim is compiled with the
29193 content-scanning extension. Its use is described in section
29194 &<<SECTdemimecond>>&.
29196 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
29197 .cindex "&%dnslists%& ACL condition"
29198 .cindex "DNS list" "in ACL"
29199 .cindex "black list (DNS)"
29200 .cindex "&ACL;" "testing a DNS list"
29201 This condition checks for entries in DNS black lists. These are also known as
29202 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
29203 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
29204 different variants of this condition to describe briefly here. See sections
29205 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
29207 .vitem &*domains&~=&~*&<&'domain&~list'&>
29208 .cindex "&%domains%& ACL condition"
29209 .cindex "domain" "ACL checking"
29210 .cindex "&ACL;" "testing a recipient domain"
29211 .vindex "&$domain_data$&"
29212 This condition is relevant only after a RCPT command. It checks that the domain
29213 of the recipient address is in the domain list. If percent-hack processing is
29214 enabled, it is done before this test is done. If the check succeeds with a
29215 lookup, the result of the lookup is placed in &$domain_data$& until the next
29218 &*Note carefully*& (because many people seem to fall foul of this): you cannot
29219 use &%domains%& in a DATA ACL.
29222 .vitem &*encrypted&~=&~*&<&'string&~list'&>
29223 .cindex "&%encrypted%& ACL condition"
29224 .cindex "encryption" "checking in an ACL"
29225 .cindex "&ACL;" "testing for encryption"
29226 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
29227 name of the cipher suite in use is tested against the list. To test for
29228 encryption without testing for any specific cipher suite(s), set
29234 .vitem &*hosts&~=&~*&<&'host&~list'&>
29235 .cindex "&%hosts%& ACL condition"
29236 .cindex "host" "ACL checking"
29237 .cindex "&ACL;" "testing the client host"
29238 This condition tests that the calling host matches the host list. If you have
29239 name lookups or wildcarded host names and IP addresses in the same host list,
29240 you should normally put the IP addresses first. For example, you could have:
29242 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
29244 The lookup in this example uses the host name for its key. This is implied by
29245 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
29246 and it wouldn't matter which way round you had these two items.)
29248 The reason for the problem with host names lies in the left-to-right way that
29249 Exim processes lists. It can test IP addresses without doing any DNS lookups,
29250 but when it reaches an item that requires a host name, it fails if it cannot
29251 find a host name to compare with the pattern. If the above list is given in the
29252 opposite order, the &%accept%& statement fails for a host whose name cannot be
29253 found, even if its IP address is 10.9.8.7.
29255 If you really do want to do the name check first, and still recognize the IP
29256 address even if the name lookup fails, you can rewrite the ACL like this:
29258 accept hosts = dbm;/etc/friendly/hosts
29259 accept hosts = 10.9.8.7
29261 The default action on failing to find the host name is to assume that the host
29262 is not in the list, so the first &%accept%& statement fails. The second
29263 statement can then check the IP address.
29265 .vindex "&$host_data$&"
29266 If a &%hosts%& condition is satisfied by means of a lookup, the result
29267 of the lookup is made available in the &$host_data$& variable. This
29268 allows you, for example, to set up a statement like this:
29270 deny hosts = net-lsearch;/some/file
29271 message = $host_data
29273 which gives a custom error message for each denied host.
29275 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
29276 .cindex "&%local_parts%& ACL condition"
29277 .cindex "local part" "ACL checking"
29278 .cindex "&ACL;" "testing a local part"
29279 .vindex "&$local_part_data$&"
29280 This condition is relevant only after a RCPT command. It checks that the local
29281 part of the recipient address is in the list. If percent-hack processing is
29282 enabled, it is done before this test. If the check succeeds with a lookup, the
29283 result of the lookup is placed in &$local_part_data$&, which remains set until
29284 the next &%local_parts%& test.
29286 .vitem &*malware&~=&~*&<&'option'&>
29287 .cindex "&%malware%& ACL condition"
29288 .cindex "&ACL;" "virus scanning"
29289 .cindex "&ACL;" "scanning for viruses"
29290 This condition is available only when Exim is compiled with the
29291 content-scanning extension. It causes the incoming message to be scanned for
29292 viruses. For details, see chapter &<<CHAPexiscan>>&.
29294 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29295 .cindex "&%mime_regex%& ACL condition"
29296 .cindex "&ACL;" "testing by regex matching"
29297 This condition is available only when Exim is compiled with the
29298 content-scanning extension, and it is allowed only in the ACL defined by
29299 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
29300 with any of the regular expressions. For details, see chapter
29303 .vitem &*ratelimit&~=&~*&<&'parameters'&>
29304 .cindex "rate limiting"
29305 This condition can be used to limit the rate at which a user or host submits
29306 messages. Details are given in section &<<SECTratelimiting>>&.
29308 .vitem &*recipients&~=&~*&<&'address&~list'&>
29309 .cindex "&%recipients%& ACL condition"
29310 .cindex "recipient" "ACL checking"
29311 .cindex "&ACL;" "testing a recipient"
29312 This condition is relevant only after a RCPT command. It checks the entire
29313 recipient address against a list of recipients.
29315 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29316 .cindex "&%regex%& ACL condition"
29317 .cindex "&ACL;" "testing by regex matching"
29318 This condition is available only when Exim is compiled with the
29319 content-scanning extension, and is available only in the DATA, MIME, and
29320 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
29321 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
29323 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
29324 .cindex "&%sender_domains%& ACL condition"
29325 .cindex "sender" "ACL checking"
29326 .cindex "&ACL;" "testing a sender domain"
29327 .vindex "&$domain$&"
29328 .vindex "&$sender_address_domain$&"
29329 This condition tests the domain of the sender of the message against the given
29330 domain list. &*Note*&: The domain of the sender address is in
29331 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
29332 of this condition. This is an exception to the general rule for testing domain
29333 lists. It is done this way so that, if this condition is used in an ACL for a
29334 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
29335 influence the sender checking.
29337 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29338 relaying, because sender addresses are easily, and commonly, forged.
29340 .vitem &*senders&~=&~*&<&'address&~list'&>
29341 .cindex "&%senders%& ACL condition"
29342 .cindex "sender" "ACL checking"
29343 .cindex "&ACL;" "testing a sender"
29344 This condition tests the sender of the message against the given list. To test
29345 for a bounce message, which has an empty sender, set
29349 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29350 relaying, because sender addresses are easily, and commonly, forged.
29352 .vitem &*spam&~=&~*&<&'username'&>
29353 .cindex "&%spam%& ACL condition"
29354 .cindex "&ACL;" "scanning for spam"
29355 This condition is available only when Exim is compiled with the
29356 content-scanning extension. It causes the incoming message to be scanned by
29357 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
29359 .vitem &*verify&~=&~certificate*&
29360 .cindex "&%verify%& ACL condition"
29361 .cindex "TLS" "client certificate verification"
29362 .cindex "certificate" "verification of client"
29363 .cindex "&ACL;" "certificate verification"
29364 .cindex "&ACL;" "testing a TLS certificate"
29365 This condition is true in an SMTP session if the session is encrypted, and a
29366 certificate was received from the client, and the certificate was verified. The
29367 server requests a certificate only if the client matches &%tls_verify_hosts%&
29368 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
29370 .vitem &*verify&~=&~csa*&
29371 .cindex "CSA verification"
29372 This condition checks whether the sending host (the client) is authorized to
29373 send email. Details of how this works are given in section
29374 &<<SECTverifyCSA>>&.
29376 .vitem &*verify&~=&~header_names_ascii*&
29377 .cindex "&%verify%& ACL condition"
29378 .cindex "&ACL;" "verifying header names only ASCII"
29379 .cindex "header lines" "verifying header names only ASCII"
29380 .cindex "verifying" "header names only ASCII"
29381 This condition is relevant only in an ACL that is run after a message has been
29382 received, that is, in an ACL specified by &%acl_smtp_data%& or
29383 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
29384 there are no non-ASCII characters, also excluding control characters. The
29385 allowable characters are decimal ASCII values 33 through 126.
29387 Exim itself will handle headers with non-ASCII characters, but it can cause
29388 problems for downstream applications, so this option will allow their
29389 detection and rejection in the DATA ACL's.
29391 .vitem &*verify&~=&~header_sender/*&<&'options'&>
29392 .cindex "&%verify%& ACL condition"
29393 .cindex "&ACL;" "verifying sender in the header"
29394 .cindex "header lines" "verifying the sender in"
29395 .cindex "sender" "verifying in header"
29396 .cindex "verifying" "sender in header"
29397 This condition is relevant only in an ACL that is run after a message has been
29398 received, that is, in an ACL specified by &%acl_smtp_data%& or
29399 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
29400 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
29401 is loosely thought of as a &"sender"& address (hence the name of the test).
29402 However, an address that appears in one of these headers need not be an address
29403 that accepts bounce messages; only sender addresses in envelopes are required
29404 to accept bounces. Therefore, if you use the callout option on this check, you
29405 might want to arrange for a non-empty address in the MAIL command.
29407 Details of address verification and the options are given later, starting at
29408 section &<<SECTaddressverification>>& (callouts are described in section
29409 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
29410 condition to restrict it to bounce messages only:
29413 message = A valid sender header is required for bounces
29414 !verify = header_sender
29417 .vitem &*verify&~=&~header_syntax*&
29418 .cindex "&%verify%& ACL condition"
29419 .cindex "&ACL;" "verifying header syntax"
29420 .cindex "header lines" "verifying syntax"
29421 .cindex "verifying" "header syntax"
29422 This condition is relevant only in an ACL that is run after a message has been
29423 received, that is, in an ACL specified by &%acl_smtp_data%& or
29424 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
29425 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
29426 and &'Bcc:'&), returning true if there are no problems.
29427 Unqualified addresses (local parts without domains) are
29428 permitted only in locally generated messages and from hosts that match
29429 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
29432 Note that this condition is a syntax check only. However, a common spamming
29433 ploy used to be to send syntactically invalid headers such as
29437 and this condition can be used to reject such messages, though they are not as
29438 common as they used to be.
29440 .vitem &*verify&~=&~helo*&
29441 .cindex "&%verify%& ACL condition"
29442 .cindex "&ACL;" "verifying HELO/EHLO"
29443 .cindex "HELO" "verifying"
29444 .cindex "EHLO" "verifying"
29445 .cindex "verifying" "EHLO"
29446 .cindex "verifying" "HELO"
29447 This condition is true if a HELO or EHLO command has been received from the
29448 client host, and its contents have been verified. If there has been no previous
29449 attempt to verify the HELO/EHLO contents, it is carried out when this
29450 condition is encountered. See the description of the &%helo_verify_hosts%& and
29451 &%helo_try_verify_hosts%& options for details of how to request verification
29452 independently of this condition.
29454 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
29455 option), this condition is always true.
29458 .vitem &*verify&~=&~not_blind*&
29459 .cindex "verifying" "not blind"
29460 .cindex "bcc recipients, verifying none"
29461 This condition checks that there are no blind (bcc) recipients in the message.
29462 Every envelope recipient must appear either in a &'To:'& header line or in a
29463 &'Cc:'& header line for this condition to be true. Local parts are checked
29464 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
29465 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
29466 used only in a DATA or non-SMTP ACL.
29468 There are, of course, many legitimate messages that make use of blind (bcc)
29469 recipients. This check should not be used on its own for blocking messages.
29472 .vitem &*verify&~=&~recipient/*&<&'options'&>
29473 .cindex "&%verify%& ACL condition"
29474 .cindex "&ACL;" "verifying recipient"
29475 .cindex "recipient" "verifying"
29476 .cindex "verifying" "recipient"
29477 .vindex "&$address_data$&"
29478 This condition is relevant only after a RCPT command. It verifies the current
29479 recipient. Details of address verification are given later, starting at section
29480 &<<SECTaddressverification>>&. After a recipient has been verified, the value
29481 of &$address_data$& is the last value that was set while routing the address.
29482 This applies even if the verification fails. When an address that is being
29483 verified is redirected to a single address, verification continues with the new
29484 address, and in that case, the subsequent value of &$address_data$& is the
29485 value for the child address.
29487 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
29488 .cindex "&%verify%& ACL condition"
29489 .cindex "&ACL;" "verifying host reverse lookup"
29490 .cindex "host" "verifying reverse lookup"
29491 This condition ensures that a verified host name has been looked up from the IP
29492 address of the client host. (This may have happened already if the host name
29493 was needed for checking a host list, or if the host matched &%host_lookup%&.)
29494 Verification ensures that the host name obtained from a reverse DNS lookup, or
29495 one of its aliases, does, when it is itself looked up in the DNS, yield the
29496 original IP address.
29498 There is one possible option, &`defer_ok`&. If this is present and a
29499 DNS operation returns a temporary error, the verify condition succeeds.
29501 If this condition is used for a locally generated message (that is, when there
29502 is no client host involved), it always succeeds.
29504 .vitem &*verify&~=&~sender/*&<&'options'&>
29505 .cindex "&%verify%& ACL condition"
29506 .cindex "&ACL;" "verifying sender"
29507 .cindex "sender" "verifying"
29508 .cindex "verifying" "sender"
29509 This condition is relevant only after a MAIL or RCPT command, or after a
29510 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
29511 the message's sender is empty (that is, this is a bounce message), the
29512 condition is true. Otherwise, the sender address is verified.
29514 .vindex "&$address_data$&"
29515 .vindex "&$sender_address_data$&"
29516 If there is data in the &$address_data$& variable at the end of routing, its
29517 value is placed in &$sender_address_data$& at the end of verification. This
29518 value can be used in subsequent conditions and modifiers in the same ACL
29519 statement. It does not persist after the end of the current statement. If you
29520 want to preserve the value for longer, you can save it in an ACL variable.
29522 Details of verification are given later, starting at section
29523 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
29524 to avoid doing it more than once per message.
29526 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
29527 .cindex "&%verify%& ACL condition"
29528 This is a variation of the previous option, in which a modified address is
29529 verified as a sender.
29534 .section "Using DNS lists" "SECTmorednslists"
29535 .cindex "DNS list" "in ACL"
29536 .cindex "black list (DNS)"
29537 .cindex "&ACL;" "testing a DNS list"
29538 In its simplest form, the &%dnslists%& condition tests whether the calling host
29539 is on at least one of a number of DNS lists by looking up the inverted IP
29540 address in one or more DNS domains. (Note that DNS list domains are not mail
29541 domains, so the &`+`& syntax for named lists doesn't work - it is used for
29542 special options instead.) For example, if the calling host's IP
29543 address is 192.168.62.43, and the ACL statement is
29545 deny dnslists = blackholes.mail-abuse.org : \
29546 dialups.mail-abuse.org
29548 the following records are looked up:
29550 43.62.168.192.blackholes.mail-abuse.org
29551 43.62.168.192.dialups.mail-abuse.org
29553 As soon as Exim finds an existing DNS record, processing of the list stops.
29554 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
29555 to test that a host is on more than one list (an &"and"& conjunction), you can
29556 use two separate conditions:
29558 deny dnslists = blackholes.mail-abuse.org
29559 dnslists = dialups.mail-abuse.org
29561 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
29562 behaves as if the host does not match the list item, that is, as if the DNS
29563 record does not exist. If there are further items in the DNS list, they are
29566 This is usually the required action when &%dnslists%& is used with &%deny%&
29567 (which is the most common usage), because it prevents a DNS failure from
29568 blocking mail. However, you can change this behaviour by putting one of the
29569 following special items in the list:
29571 &`+include_unknown `& behave as if the item is on the list
29572 &`+exclude_unknown `& behave as if the item is not on the list (default)
29573 &`+defer_unknown `& give a temporary error
29575 .cindex "&`+include_unknown`&"
29576 .cindex "&`+exclude_unknown`&"
29577 .cindex "&`+defer_unknown`&"
29578 Each of these applies to any subsequent items on the list. For example:
29580 deny dnslists = +defer_unknown : foo.bar.example
29582 Testing the list of domains stops as soon as a match is found. If you want to
29583 warn for one list and block for another, you can use two different statements:
29585 deny dnslists = blackholes.mail-abuse.org
29586 warn message = X-Warn: sending host is on dialups list
29587 dnslists = dialups.mail-abuse.org
29589 .cindex cacheing "of dns lookup"
29591 DNS list lookups are cached by Exim for the duration of the SMTP session
29593 (but limited by the DNS return TTL value),
29595 so a lookup based on the IP address is done at most once for any incoming
29596 connection (assuming long-enough TTL).
29597 Exim does not share information between multiple incoming
29598 connections (but your local name server cache should be active).
29602 .section "Specifying the IP address for a DNS list lookup" "SECID201"
29603 .cindex "DNS list" "keyed by explicit IP address"
29604 By default, the IP address that is used in a DNS list lookup is the IP address
29605 of the calling host. However, you can specify another IP address by listing it
29606 after the domain name, introduced by a slash. For example:
29608 deny dnslists = black.list.tld/192.168.1.2
29610 This feature is not very helpful with explicit IP addresses; it is intended for
29611 use with IP addresses that are looked up, for example, the IP addresses of the
29612 MX hosts or nameservers of an email sender address. For an example, see section
29613 &<<SECTmulkeyfor>>& below.
29618 .section "DNS lists keyed on domain names" "SECID202"
29619 .cindex "DNS list" "keyed by domain name"
29620 There are some lists that are keyed on domain names rather than inverted IP
29621 addresses (see for example the &'domain based zones'& link at
29622 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
29623 with these lists. You can change the name that is looked up in a DNS list by
29624 listing it after the domain name, introduced by a slash. For example,
29626 deny message = Sender's domain is listed at $dnslist_domain
29627 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
29629 This particular example is useful only in ACLs that are obeyed after the
29630 RCPT or DATA commands, when a sender address is available. If (for
29631 example) the message's sender is &'user@tld.example'& the name that is looked
29632 up by this example is
29634 tld.example.dsn.rfc-ignorant.org
29636 A single &%dnslists%& condition can contain entries for both names and IP
29637 addresses. For example:
29639 deny dnslists = sbl.spamhaus.org : \
29640 dsn.rfc-ignorant.org/$sender_address_domain
29642 The first item checks the sending host's IP address; the second checks a domain
29643 name. The whole condition is true if either of the DNS lookups succeeds.
29648 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
29649 .cindex "DNS list" "multiple keys for"
29650 The syntax described above for looking up explicitly-defined values (either
29651 names or IP addresses) in a DNS blacklist is a simplification. After the domain
29652 name for the DNS list, what follows the slash can in fact be a list of items.
29653 As with all lists in Exim, the default separator is a colon. However, because
29654 this is a sublist within the list of DNS blacklist domains, it is necessary
29655 either to double the separators like this:
29657 dnslists = black.list.tld/name.1::name.2
29659 or to change the separator character, like this:
29661 dnslists = black.list.tld/<;name.1;name.2
29663 If an item in the list is an IP address, it is inverted before the DNS
29664 blacklist domain is appended. If it is not an IP address, no inversion
29665 occurs. Consider this condition:
29667 dnslists = black.list.tld/<;192.168.1.2;a.domain
29669 The DNS lookups that occur are:
29671 2.1.168.192.black.list.tld
29672 a.domain.black.list.tld
29674 Once a DNS record has been found (that matches a specific IP return
29675 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
29676 are done. If there is a temporary DNS error, the rest of the sublist of domains
29677 or IP addresses is tried. A temporary error for the whole dnslists item occurs
29678 only if no other DNS lookup in this sublist succeeds. In other words, a
29679 successful lookup for any of the items in the sublist overrides a temporary
29680 error for a previous item.
29682 The ability to supply a list of items after the slash is in some sense just a
29683 syntactic convenience. These two examples have the same effect:
29685 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
29686 dnslists = black.list.tld/a.domain::b.domain
29688 However, when the data for the list is obtained from a lookup, the second form
29689 is usually much more convenient. Consider this example:
29691 deny message = The mail servers for the domain \
29692 $sender_address_domain \
29693 are listed at $dnslist_domain ($dnslist_value); \
29695 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
29696 ${lookup dnsdb {>|mxh=\
29697 $sender_address_domain} }} }
29699 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
29700 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
29701 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
29702 of expanding the condition might be something like this:
29704 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
29706 Thus, this example checks whether or not the IP addresses of the sender
29707 domain's mail servers are on the Spamhaus black list.
29709 The key that was used for a successful DNS list lookup is put into the variable
29710 &$dnslist_matched$& (see section &<<SECID204>>&).
29715 .section "Data returned by DNS lists" "SECID203"
29716 .cindex "DNS list" "data returned from"
29717 DNS lists are constructed using address records in the DNS. The original RBL
29718 just used the address 127.0.0.1 on the right hand side of each record, but the
29719 RBL+ list and some other lists use a number of values with different meanings.
29720 The values used on the RBL+ list are:
29724 127.1.0.3 DUL and RBL
29726 127.1.0.5 RSS and RBL
29727 127.1.0.6 RSS and DUL
29728 127.1.0.7 RSS and DUL and RBL
29730 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
29731 different values. Some DNS lists may return more than one address record;
29732 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
29735 .section "Variables set from DNS lists" "SECID204"
29736 .cindex "expansion" "variables, set from DNS list"
29737 .cindex "DNS list" "variables set from"
29738 .vindex "&$dnslist_domain$&"
29739 .vindex "&$dnslist_matched$&"
29740 .vindex "&$dnslist_text$&"
29741 .vindex "&$dnslist_value$&"
29742 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
29743 the name of the overall domain that matched (for example,
29744 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
29745 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
29746 the DNS record. When the key is an IP address, it is not reversed in
29747 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
29748 cases, for example:
29750 deny dnslists = spamhaus.example
29752 the key is also available in another variable (in this case,
29753 &$sender_host_address$&). In more complicated cases, however, this is not true.
29754 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
29755 might generate a dnslists lookup like this:
29757 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
29759 If this condition succeeds, the value in &$dnslist_matched$& might be
29760 &`192.168.6.7`& (for example).
29762 If more than one address record is returned by the DNS lookup, all the IP
29763 addresses are included in &$dnslist_value$&, separated by commas and spaces.
29764 The variable &$dnslist_text$& contains the contents of any associated TXT
29765 record. For lists such as RBL+ the TXT record for a merged entry is often not
29766 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
29769 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
29770 &-- although these appear before the condition in the ACL, they are not
29771 expanded until after it has failed. For example:
29773 deny hosts = !+local_networks
29774 message = $sender_host_address is listed \
29776 dnslists = rbl-plus.mail-abuse.example
29781 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
29782 .cindex "DNS list" "matching specific returned data"
29783 You can add an equals sign and an IP address after a &%dnslists%& domain name
29784 in order to restrict its action to DNS records with a matching right hand side.
29787 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
29789 rejects only those hosts that yield 127.0.0.2. Without this additional data,
29790 any address record is considered to be a match. For the moment, we assume
29791 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
29792 describes how multiple records are handled.
29794 More than one IP address may be given for checking, using a comma as a
29795 separator. These are alternatives &-- if any one of them matches, the
29796 &%dnslists%& condition is true. For example:
29798 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29800 If you want to specify a constraining address list and also specify names or IP
29801 addresses to be looked up, the constraining address list must be specified
29802 first. For example:
29804 deny dnslists = dsn.rfc-ignorant.org\
29805 =127.0.0.2/$sender_address_domain
29808 If the character &`&&`& is used instead of &`=`&, the comparison for each
29809 listed IP address is done by a bitwise &"and"& instead of by an equality test.
29810 In other words, the listed addresses are used as bit masks. The comparison is
29811 true if all the bits in the mask are present in the address that is being
29812 tested. For example:
29814 dnslists = a.b.c&0.0.0.3
29816 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
29817 want to test whether one bit or another bit is present (as opposed to both
29818 being present), you must use multiple values. For example:
29820 dnslists = a.b.c&0.0.0.1,0.0.0.2
29822 matches if the final component of the address is an odd number or two times
29827 .section "Negated DNS matching conditions" "SECID205"
29828 You can supply a negative list of IP addresses as part of a &%dnslists%&
29831 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29833 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29834 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
29836 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
29838 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29839 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
29840 words, the result of the test is inverted if an exclamation mark appears before
29841 the &`=`& (or the &`&&`&) sign.
29843 &*Note*&: This kind of negation is not the same as negation in a domain,
29844 host, or address list (which is why the syntax is different).
29846 If you are using just one list, the negation syntax does not gain you much. The
29847 previous example is precisely equivalent to
29849 deny dnslists = a.b.c
29850 !dnslists = a.b.c=127.0.0.2,127.0.0.3
29852 However, if you are using multiple lists, the negation syntax is clearer.
29853 Consider this example:
29855 deny dnslists = sbl.spamhaus.org : \
29857 dnsbl.njabl.org!=127.0.0.3 : \
29860 Using only positive lists, this would have to be:
29862 deny dnslists = sbl.spamhaus.org : \
29864 deny dnslists = dnsbl.njabl.org
29865 !dnslists = dnsbl.njabl.org=127.0.0.3
29866 deny dnslists = relays.ordb.org
29868 which is less clear, and harder to maintain.
29873 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
29874 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
29875 thereby providing more than one IP address. When an item in a &%dnslists%& list
29876 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
29877 the match to specific results from the DNS lookup, there are two ways in which
29878 the checking can be handled. For example, consider the condition:
29880 dnslists = a.b.c=127.0.0.1
29882 What happens if the DNS lookup for the incoming IP address yields both
29883 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
29884 condition true because at least one given value was found, or is it false
29885 because at least one of the found values was not listed? And how does this
29886 affect negated conditions? Both possibilities are provided for with the help of
29887 additional separators &`==`& and &`=&&`&.
29890 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
29891 IP addresses matches one of the listed addresses. For the example above, the
29892 condition is true because 127.0.0.1 matches.
29894 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
29895 looked up IP addresses matches one of the listed addresses. If the condition is
29898 dnslists = a.b.c==127.0.0.1
29900 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29901 false because 127.0.0.2 is not listed. You would need to have:
29903 dnslists = a.b.c==127.0.0.1,127.0.0.2
29905 for the condition to be true.
29908 When &`!`& is used to negate IP address matching, it inverts the result, giving
29909 the precise opposite of the behaviour above. Thus:
29911 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
29912 addresses matches one of the listed addresses. Consider:
29914 dnslists = a.b.c!&0.0.0.1
29916 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29917 false because 127.0.0.1 matches.
29919 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
29920 looked up IP address that does not match. Consider:
29922 dnslists = a.b.c!=&0.0.0.1
29924 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29925 true, because 127.0.0.2 does not match. You would need to have:
29927 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
29929 for the condition to be false.
29931 When the DNS lookup yields only a single IP address, there is no difference
29932 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
29937 .section "Detailed information from merged DNS lists" "SECTmordetinf"
29938 .cindex "DNS list" "information from merged"
29939 When the facility for restricting the matching IP values in a DNS list is used,
29940 the text from the TXT record that is set in &$dnslist_text$& may not reflect
29941 the true reason for rejection. This happens when lists are merged and the IP
29942 address in the A record is used to distinguish them; unfortunately there is
29943 only one TXT record. One way round this is not to use merged lists, but that
29944 can be inefficient because it requires multiple DNS lookups where one would do
29945 in the vast majority of cases when the host of interest is not on any of the
29948 A less inefficient way of solving this problem is available. If
29949 two domain names, comma-separated, are given, the second is used first to
29950 do an initial check, making use of any IP value restrictions that are set.
29951 If there is a match, the first domain is used, without any IP value
29952 restrictions, to get the TXT record. As a byproduct of this, there is also
29953 a check that the IP being tested is indeed on the first list. The first
29954 domain is the one that is put in &$dnslist_domain$&. For example:
29957 rejected because $sender_host_address is blacklisted \
29958 at $dnslist_domain\n$dnslist_text
29960 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
29961 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29963 For the first blacklist item, this starts by doing a lookup in
29964 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
29965 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
29966 value, and as long as something is found, it looks for the corresponding TXT
29967 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
29968 The second blacklist item is processed similarly.
29970 If you are interested in more than one merged list, the same list must be
29971 given several times, but because the results of the DNS lookups are cached,
29972 the DNS calls themselves are not repeated. For example:
29974 reject dnslists = \
29975 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
29976 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
29977 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
29978 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29980 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
29981 values matches (or if no record is found), this is the only lookup that is
29982 done. Only if there is a match is one of the more specific lists consulted.
29986 .section "DNS lists and IPv6" "SECTmorednslistslast"
29987 .cindex "IPv6" "DNS black lists"
29988 .cindex "DNS list" "IPv6 usage"
29989 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
29990 nibble by nibble. For example, if the calling host's IP address is
29991 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
29993 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
29994 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
29996 (split over two lines here to fit on the page). Unfortunately, some of the DNS
29997 lists contain wildcard records, intended for IPv4, that interact badly with
29998 IPv6. For example, the DNS entry
30000 *.3.some.list.example. A 127.0.0.1
30002 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
30003 Unfortunately, it also matches the entire 3::/4 IPv6 network.
30005 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
30006 &%condition%& condition, as in this example:
30008 deny condition = ${if isip4{$sender_host_address}}
30009 dnslists = some.list.example
30012 If an explicit key is being used for a DNS lookup and it may be an IPv6
30013 address you should specify alternate list separators for both the outer
30014 (DNS list name) list and inner (lookup keys) list:
30016 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
30019 .section "Rate limiting incoming messages" "SECTratelimiting"
30020 .cindex "rate limiting" "client sending"
30021 .cindex "limiting client sending rates"
30022 .oindex "&%smtp_ratelimit_*%&"
30023 The &%ratelimit%& ACL condition can be used to measure and control the rate at
30024 which clients can send email. This is more powerful than the
30025 &%smtp_ratelimit_*%& options, because those options control the rate of
30026 commands in a single SMTP session only, whereas the &%ratelimit%& condition
30027 works across all connections (concurrent and sequential) from the same client
30028 host. The syntax of the &%ratelimit%& condition is:
30030 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
30032 If the average client sending rate is less than &'m'& messages per time
30033 period &'p'& then the condition is false; otherwise it is true.
30035 As a side-effect, the &%ratelimit%& condition sets the expansion variable
30036 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
30037 configured value of &'m'&, and &$sender_rate_period$& to the configured value
30040 The parameter &'p'& is the smoothing time constant, in the form of an Exim
30041 time interval, for example, &`8h`& for eight hours. A larger time constant
30042 means that it takes Exim longer to forget a client's past behaviour. The
30043 parameter &'m'& is the maximum number of messages that a client is permitted to
30044 send in each time interval. It also specifies the number of messages permitted
30045 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
30046 constant, you can allow a client to send more messages in a burst without
30047 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
30048 both small, messages must be sent at an even rate.
30050 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
30051 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
30052 when deploying the &%ratelimit%& ACL condition. The script prints usage
30053 instructions when it is run with no arguments.
30055 The key is used to look up the data for calculating the client's average
30056 sending rate. This data is stored in Exim's spool directory, alongside the
30057 retry and other hints databases. The default key is &$sender_host_address$&,
30058 which means Exim computes the sending rate of each client host IP address.
30059 By changing the key you can change how Exim identifies clients for the purpose
30060 of ratelimiting. For example, to limit the sending rate of each authenticated
30061 user, independent of the computer they are sending from, set the key to
30062 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
30063 example, &$authenticated_id$& is only meaningful if the client has
30064 authenticated (which you can check with the &%authenticated%& ACL condition).
30066 The lookup key does not have to identify clients: If you want to limit the
30067 rate at which a recipient receives messages, you can use the key
30068 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
30071 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
30072 specifies what Exim measures the rate of, for example messages or recipients
30073 or bytes. You can adjust the measurement using the &%unique=%& and/or
30074 &%count=%& options. You can also control when Exim updates the recorded rate
30075 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
30076 separated by a slash, like the other parameters. They may appear in any order.
30078 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
30079 any options that alter the meaning of the stored data. The limit &'m'& is not
30080 stored, so you can alter the configured maximum rate and Exim will still
30081 remember clients' past behaviour. If you change the &%per_*%& mode or add or
30082 remove the &%unique=%& option, the lookup key changes so Exim will forget past
30083 behaviour. The lookup key is not affected by changes to the update mode and
30084 the &%count=%& option.
30087 .section "Ratelimit options for what is being measured" "ratoptmea"
30088 .cindex "rate limiting" "per_* options"
30089 The &%per_conn%& option limits the client's connection rate. It is not
30090 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
30091 &%acl_not_smtp_start%& ACLs.
30093 The &%per_mail%& option limits the client's rate of sending messages. This is
30094 the default if none of the &%per_*%& options is specified. It can be used in
30095 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
30096 &%acl_smtp_data%&, or &%acl_not_smtp%&.
30098 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
30099 the same ACLs as the &%per_mail%& option, though it is best to use this option
30100 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
30101 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
30102 in its MAIL command, which may be inaccurate or completely missing. You can
30103 follow the limit &'m'& in the configuration with K, M, or G to specify limits
30104 in kilobytes, megabytes, or gigabytes, respectively.
30106 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
30107 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
30108 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
30109 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
30110 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
30111 in either case the rate limiting engine will see a message with many
30112 recipients as a large high-speed burst.
30114 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
30115 number of different recipients that the client has sent messages to in the
30116 last time period. That is, if the client repeatedly sends messages to the same
30117 recipient, its measured rate is not increased. This option can only be used in
30120 The &%per_cmd%& option causes Exim to recompute the rate every time the
30121 condition is processed. This can be used to limit the rate of any SMTP
30122 command. If it is used in multiple ACLs it can limit the aggregate rate of
30123 multiple different commands.
30125 The &%count=%& option can be used to alter how much Exim adds to the client's
30126 measured rate. For example, the &%per_byte%& option is equivalent to
30127 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
30128 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
30129 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
30131 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
30134 .section "Ratelimit update modes" "ratoptupd"
30135 .cindex "rate limiting" "reading data without updating"
30136 You can specify one of three options with the &%ratelimit%& condition to
30137 control when its database is updated. This section describes the &%readonly%&
30138 mode, and the next section describes the &%strict%& and &%leaky%& modes.
30140 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
30141 previously-computed rate to check against the limit.
30143 For example, you can test the client's sending rate and deny it access (when
30144 it is too fast) in the connect ACL. If the client passes this check then it
30145 can go on to send a message, in which case its recorded rate will be updated
30146 in the MAIL ACL. Subsequent connections from the same client will check this
30150 deny ratelimit = 100 / 5m / readonly
30151 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
30152 (max $sender_rate_limit)
30155 warn ratelimit = 100 / 5m / strict
30156 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
30157 (max $sender_rate_limit)
30160 If Exim encounters multiple &%ratelimit%& conditions with the same key when
30161 processing a message then it may increase the client's measured rate more than
30162 it should. For example, this will happen if you check the &%per_rcpt%& option
30163 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
30164 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
30165 multiple update problems by using the &%readonly%& option on later ratelimit
30168 The &%per_*%& options described above do not make sense in some ACLs. If you
30169 use a &%per_*%& option in an ACL where it is not normally permitted then the
30170 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
30171 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
30172 next section) so you must specify the &%readonly%& option explicitly.
30175 .section "Ratelimit options for handling fast clients" "ratoptfast"
30176 .cindex "rate limiting" "strict and leaky modes"
30177 If a client's average rate is greater than the maximum, the rate limiting
30178 engine can react in two possible ways, depending on the presence of the
30179 &%strict%& or &%leaky%& update modes. This is independent of the other
30180 counter-measures (such as rejecting the message) that may be specified by the
30183 The &%leaky%& (default) option means that the client's recorded rate is not
30184 updated if it is above the limit. The effect of this is that Exim measures the
30185 client's average rate of successfully sent email, which cannot be greater than
30186 the maximum allowed. If the client is over the limit it may suffer some
30187 counter-measures (as specified in the ACL), but it will still be able to send
30188 email at the configured maximum rate, whatever the rate of its attempts. This
30189 is generally the better choice if you have clients that retry automatically.
30190 For example, it does not prevent a sender with an over-aggressive retry rate
30191 from getting any email through.
30193 The &%strict%& option means that the client's recorded rate is always
30194 updated. The effect of this is that Exim measures the client's average rate
30195 of attempts to send email, which can be much higher than the maximum it is
30196 actually allowed. If the client is over the limit it may be subjected to
30197 counter-measures by the ACL. It must slow down and allow sufficient time to
30198 pass that its computed rate falls below the maximum before it can send email
30199 again. The time (the number of smoothing periods) it must wait and not
30200 attempt to send mail can be calculated with this formula:
30202 ln(peakrate/maxrate)
30206 .section "Limiting the rate of different events" "ratoptuniq"
30207 .cindex "rate limiting" "counting unique events"
30208 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
30209 rate of different events. For example, the &%per_addr%& option uses this
30210 mechanism to count the number of different recipients that the client has
30211 sent messages to in the last time period; it is equivalent to
30212 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
30213 measure the rate that a client uses different sender addresses with the
30214 options &`per_mail/unique=$sender_address`&.
30216 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
30217 has seen for that key. The whole set is thrown away when it is older than the
30218 rate smoothing period &'p'&, so each different event is counted at most once
30219 per period. In the &%leaky%& update mode, an event that causes the client to
30220 go over the limit is not added to the set, in the same way that the client's
30221 recorded rate is not updated in the same situation.
30223 When you combine the &%unique=%& and &%readonly%& options, the specific
30224 &%unique=%& value is ignored, and Exim just retrieves the client's stored
30227 The &%unique=%& mechanism needs more space in the ratelimit database than the
30228 other &%ratelimit%& options in order to store the event set. The number of
30229 unique values is potentially as large as the rate limit, so the extra space
30230 required increases with larger limits.
30232 The uniqueification is not perfect: there is a small probability that Exim
30233 will think a new event has happened before. If the sender's rate is less than
30234 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
30235 the measured rate can go above the limit, in which case Exim may under-count
30236 events by a significant margin. Fortunately, if the rate is high enough (2.7
30237 times the limit) that the false positive rate goes above 9%, then Exim will
30238 throw away the over-full event set before the measured rate falls below the
30239 limit. Therefore the only harm should be that exceptionally high sending rates
30240 are logged incorrectly; any countermeasures you configure will be as effective
30244 .section "Using rate limiting" "useratlim"
30245 Exim's other ACL facilities are used to define what counter-measures are taken
30246 when the rate limit is exceeded. This might be anything from logging a warning
30247 (for example, while measuring existing sending rates in order to define
30248 policy), through time delays to slow down fast senders, up to rejecting the
30249 message. For example:
30251 # Log all senders' rates
30252 warn ratelimit = 0 / 1h / strict
30253 log_message = Sender rate $sender_rate / $sender_rate_period
30255 # Slow down fast senders; note the need to truncate $sender_rate
30256 # at the decimal point.
30257 warn ratelimit = 100 / 1h / per_rcpt / strict
30258 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
30259 $sender_rate_limit }s
30261 # Keep authenticated users under control
30262 deny authenticated = *
30263 ratelimit = 100 / 1d / strict / $authenticated_id
30265 # System-wide rate limit
30266 defer message = Sorry, too busy. Try again later.
30267 ratelimit = 10 / 1s / $primary_hostname
30269 # Restrict incoming rate from each host, with a default
30270 # set using a macro and special cases looked up in a table.
30271 defer message = Sender rate exceeds $sender_rate_limit \
30272 messages per $sender_rate_period
30273 ratelimit = ${lookup {$sender_host_address} \
30274 cdb {DB/ratelimits.cdb} \
30275 {$value} {RATELIMIT} }
30277 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
30278 especially with the &%per_rcpt%& option, you may suffer from a performance
30279 bottleneck caused by locking on the ratelimit hints database. Apart from
30280 making your ACLs less complicated, you can reduce the problem by using a
30281 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
30282 this means that Exim will lose its hints data after a reboot (including retry
30283 hints, the callout cache, and ratelimit data).
30287 .section "Address verification" "SECTaddressverification"
30288 .cindex "verifying address" "options for"
30289 .cindex "policy control" "address verification"
30290 Several of the &%verify%& conditions described in section
30291 &<<SECTaclconditions>>& cause addresses to be verified. Section
30292 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
30293 The verification conditions can be followed by options that modify the
30294 verification process. The options are separated from the keyword and from each
30295 other by slashes, and some of them contain parameters. For example:
30297 verify = sender/callout
30298 verify = recipient/defer_ok/callout=10s,defer_ok
30300 The first stage of address verification, which always happens, is to run the
30301 address through the routers, in &"verify mode"&. Routers can detect the
30302 difference between verification and routing for delivery, and their actions can
30303 be varied by a number of generic options such as &%verify%& and &%verify_only%&
30304 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
30305 The available options are as follows:
30308 If the &%callout%& option is specified, successful routing to one or more
30309 remote hosts is followed by a &"callout"& to those hosts as an additional
30310 check. Callouts and their sub-options are discussed in the next section.
30312 If there is a defer error while doing verification routing, the ACL
30313 normally returns &"defer"&. However, if you include &%defer_ok%& in the
30314 options, the condition is forced to be true instead. Note that this is a main
30315 verification option as well as a suboption for callouts.
30317 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
30318 discusses the reporting of sender address verification failures.
30320 The &%success_on_redirect%& option causes verification always to succeed
30321 immediately after a successful redirection. By default, if a redirection
30322 generates just one address, that address is also verified. See further
30323 discussion in section &<<SECTredirwhilveri>>&.
30326 .cindex "verifying address" "differentiating failures"
30327 .vindex "&$recipient_verify_failure$&"
30328 .vindex "&$sender_verify_failure$&"
30329 .vindex "&$acl_verify_message$&"
30330 After an address verification failure, &$acl_verify_message$& contains the
30331 error message that is associated with the failure. It can be preserved by
30334 warn !verify = sender
30335 set acl_m0 = $acl_verify_message
30337 If you are writing your own custom rejection message or log message when
30338 denying access, you can use this variable to include information about the
30339 verification failure.
30341 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
30342 appropriate) contains one of the following words:
30345 &%qualify%&: The address was unqualified (no domain), and the message
30346 was neither local nor came from an exempted host.
30348 &%route%&: Routing failed.
30350 &%mail%&: Routing succeeded, and a callout was attempted; rejection
30351 occurred at or before the MAIL command (that is, on initial
30352 connection, HELO, or MAIL).
30354 &%recipient%&: The RCPT command in a callout was rejected.
30356 &%postmaster%&: The postmaster check in a callout was rejected.
30359 The main use of these variables is expected to be to distinguish between
30360 rejections of MAIL and rejections of RCPT in callouts.
30365 .section "Callout verification" "SECTcallver"
30366 .cindex "verifying address" "by callout"
30367 .cindex "callout" "verification"
30368 .cindex "SMTP" "callout verification"
30369 For non-local addresses, routing verifies the domain, but is unable to do any
30370 checking of the local part. There are situations where some means of verifying
30371 the local part is desirable. One way this can be done is to make an SMTP
30372 &'callback'& to a delivery host for the sender address or a &'callforward'& to
30373 a subsequent host for a recipient address, to see if the host accepts the
30374 address. We use the term &'callout'& to cover both cases. Note that for a
30375 sender address, the callback is not to the client host that is trying to
30376 deliver the message, but to one of the hosts that accepts incoming mail for the
30379 Exim does not do callouts by default. If you want them to happen, you must
30380 request them by setting appropriate options on the &%verify%& condition, as
30381 described below. This facility should be used with care, because it can add a
30382 lot of resource usage to the cost of verifying an address. However, Exim does
30383 cache the results of callouts, which helps to reduce the cost. Details of
30384 caching are in section &<<SECTcallvercache>>&.
30386 Recipient callouts are usually used only between hosts that are controlled by
30387 the same administration. For example, a corporate gateway host could use
30388 callouts to check for valid recipients on an internal mailserver. A successful
30389 callout does not guarantee that a real delivery to the address would succeed;
30390 on the other hand, a failing callout does guarantee that a delivery would fail.
30392 If the &%callout%& option is present on a condition that verifies an address, a
30393 second stage of verification occurs if the address is successfully routed to
30394 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
30395 &(manualroute)& router, where the router specifies the hosts. However, if a
30396 router that does not set up hosts routes to an &(smtp)& transport with a
30397 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
30398 &%hosts_override%& set, its hosts are always used, whether or not the router
30399 supplies a host list.
30400 Callouts are only supported on &(smtp)& transports.
30402 The port that is used is taken from the transport, if it is specified and is a
30403 remote transport. (For routers that do verification only, no transport need be
30404 specified.) Otherwise, the default SMTP port is used. If a remote transport
30405 specifies an outgoing interface, this is used; otherwise the interface is not
30406 specified. Likewise, the text that is used for the HELO command is taken from
30407 the transport's &%helo_data%& option; if there is no transport, the value of
30408 &$smtp_active_hostname$& is used.
30410 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
30411 test whether a bounce message could be delivered to the sender address. The
30412 following SMTP commands are sent:
30414 &`HELO `&<&'local host name'&>
30416 &`RCPT TO:`&<&'the address to be tested'&>
30419 LHLO is used instead of HELO if the transport's &%protocol%& option is
30422 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
30425 A recipient callout check is similar. By default, it also uses an empty address
30426 for the sender. This default is chosen because most hosts do not make use of
30427 the sender address when verifying a recipient. Using the same address means
30428 that a single cache entry can be used for each recipient. Some sites, however,
30429 do make use of the sender address when verifying. These are catered for by the
30430 &%use_sender%& and &%use_postmaster%& options, described in the next section.
30432 If the response to the RCPT command is a 2&'xx'& code, the verification
30433 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
30434 Exim tries the next host, if any. If there is a problem with all the remote
30435 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
30436 &%callout%& option is given, in which case the condition is forced to succeed.
30438 .cindex "SMTP" "output flushing, disabling for callout"
30439 A callout may take a little time. For this reason, Exim normally flushes SMTP
30440 output before performing a callout in an ACL, to avoid unexpected timeouts in
30441 clients when the SMTP PIPELINING extension is in use. The flushing can be
30442 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
30447 .section "Additional parameters for callouts" "CALLaddparcall"
30448 .cindex "callout" "additional parameters for"
30449 The &%callout%& option can be followed by an equals sign and a number of
30450 optional parameters, separated by commas. For example:
30452 verify = recipient/callout=10s,defer_ok
30454 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
30455 separate verify options, is retained for backwards compatibility, but is now
30456 deprecated. The additional parameters for &%callout%& are as follows:
30460 .vitem <&'a&~time&~interval'&>
30461 .cindex "callout" "timeout, specifying"
30462 This specifies the timeout that applies for the callout attempt to each host.
30465 verify = sender/callout=5s
30467 The default is 30 seconds. The timeout is used for each response from the
30468 remote host. It is also used for the initial connection, unless overridden by
30469 the &%connect%& parameter.
30472 .vitem &*connect&~=&~*&<&'time&~interval'&>
30473 .cindex "callout" "connection timeout, specifying"
30474 This parameter makes it possible to set a different (usually smaller) timeout
30475 for making the SMTP connection. For example:
30477 verify = sender/callout=5s,connect=1s
30479 If not specified, this timeout defaults to the general timeout value.
30481 .vitem &*defer_ok*&
30482 .cindex "callout" "defer, action on"
30483 When this parameter is present, failure to contact any host, or any other kind
30484 of temporary error, is treated as success by the ACL. However, the cache is not
30485 updated in this circumstance.
30487 .vitem &*fullpostmaster*&
30488 .cindex "callout" "full postmaster check"
30489 This operates like the &%postmaster%& option (see below), but if the check for
30490 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
30491 accordance with the specification in RFC 2821. The RFC states that the
30492 unqualified address &'postmaster'& should be accepted.
30495 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
30496 .cindex "callout" "sender when verifying header"
30497 When verifying addresses in header lines using the &%header_sender%&
30498 verification option, Exim behaves by default as if the addresses are envelope
30499 sender addresses from a message. Callout verification therefore tests to see
30500 whether a bounce message could be delivered, by using an empty address in the
30501 MAIL command. However, it is arguable that these addresses might never be used
30502 as envelope senders, and could therefore justifiably reject bounce messages
30503 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
30504 address to use in the MAIL command. For example:
30506 require verify = header_sender/callout=mailfrom=abcd@x.y.z
30508 This parameter is available only for the &%header_sender%& verification option.
30511 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
30512 .cindex "callout" "overall timeout, specifying"
30513 This parameter sets an overall timeout for performing a callout verification.
30516 verify = sender/callout=5s,maxwait=30s
30518 This timeout defaults to four times the callout timeout for individual SMTP
30519 commands. The overall timeout applies when there is more than one host that can
30520 be tried. The timeout is checked before trying the next host. This prevents
30521 very long delays if there are a large number of hosts and all are timing out
30522 (for example, when network connections are timing out).
30525 .vitem &*no_cache*&
30526 .cindex "callout" "cache, suppressing"
30527 .cindex "caching callout, suppressing"
30528 When this parameter is given, the callout cache is neither read nor updated.
30530 .vitem &*postmaster*&
30531 .cindex "callout" "postmaster; checking"
30532 When this parameter is set, a successful callout check is followed by a similar
30533 check for the local part &'postmaster'& at the same domain. If this address is
30534 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
30535 the postmaster check is recorded in a cache record; if it is a failure, this is
30536 used to fail subsequent callouts for the domain without a connection being
30537 made, until the cache record expires.
30539 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
30540 The postmaster check uses an empty sender in the MAIL command by default.
30541 You can use this parameter to do a postmaster check using a different address.
30544 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
30546 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
30547 one overrides. The &%postmaster%& parameter is equivalent to this example:
30549 require verify = sender/callout=postmaster_mailfrom=
30551 &*Warning*&: The caching arrangements for postmaster checking do not take
30552 account of the sender address. It is assumed that either the empty address or
30553 a fixed non-empty address will be used. All that Exim remembers is that the
30554 postmaster check for the domain succeeded or failed.
30558 .cindex "callout" "&""random""& check"
30559 When this parameter is set, before doing the normal callout check, Exim does a
30560 check for a &"random"& local part at the same domain. The local part is not
30561 really random &-- it is defined by the expansion of the option
30562 &%callout_random_local_part%&, which defaults to
30564 $primary_hostname-$tod_epoch-testing
30566 The idea here is to try to determine whether the remote host accepts all local
30567 parts without checking. If it does, there is no point in doing callouts for
30568 specific local parts. If the &"random"& check succeeds, the result is saved in
30569 a cache record, and used to force the current and subsequent callout checks to
30570 succeed without a connection being made, until the cache record expires.
30572 .vitem &*use_postmaster*&
30573 .cindex "callout" "sender for recipient check"
30574 This parameter applies to recipient callouts only. For example:
30576 deny !verify = recipient/callout=use_postmaster
30578 .vindex "&$qualify_domain$&"
30579 It causes a non-empty postmaster address to be used in the MAIL command when
30580 performing the callout for the recipient, and also for a &"random"& check if
30581 that is configured. The local part of the address is &`postmaster`& and the
30582 domain is the contents of &$qualify_domain$&.
30584 .vitem &*use_sender*&
30585 This option applies to recipient callouts only. For example:
30587 require verify = recipient/callout=use_sender
30589 It causes the message's actual sender address to be used in the MAIL
30590 command when performing the callout, instead of an empty address. There is no
30591 need to use this option unless you know that the called hosts make use of the
30592 sender when checking recipients. If used indiscriminately, it reduces the
30593 usefulness of callout caching.
30596 If you use any of the parameters that set a non-empty sender for the MAIL
30597 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
30598 &%use_sender%&), you should think about possible loops. Recipient checking is
30599 usually done between two hosts that are under the same management, and the host
30600 that receives the callouts is not normally configured to do callouts itself.
30601 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
30602 these circumstances.
30604 However, if you use a non-empty sender address for a callout to an arbitrary
30605 host, there is the likelihood that the remote host will itself initiate a
30606 callout check back to your host. As it is checking what appears to be a message
30607 sender, it is likely to use an empty address in MAIL, thus avoiding a
30608 callout loop. However, to be on the safe side it would be best to set up your
30609 own ACLs so that they do not do sender verification checks when the recipient
30610 is the address you use for header sender or postmaster callout checking.
30612 Another issue to think about when using non-empty senders for callouts is
30613 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
30614 by the sender/recipient combination; thus, for any given recipient, many more
30615 actual callouts are performed than when an empty sender or postmaster is used.
30620 .section "Callout caching" "SECTcallvercache"
30621 .cindex "hints database" "callout cache"
30622 .cindex "callout" "cache, description of"
30623 .cindex "caching" "callout"
30624 Exim caches the results of callouts in order to reduce the amount of resources
30625 used, unless you specify the &%no_cache%& parameter with the &%callout%&
30626 option. A hints database called &"callout"& is used for the cache. Two
30627 different record types are used: one records the result of a callout check for
30628 a specific address, and the other records information that applies to the
30629 entire domain (for example, that it accepts the local part &'postmaster'&).
30631 When an original callout fails, a detailed SMTP error message is given about
30632 the failure. However, for subsequent failures use the cache data, this message
30635 The expiry times for negative and positive address cache records are
30636 independent, and can be set by the global options &%callout_negative_expire%&
30637 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
30639 If a host gives a negative response to an SMTP connection, or rejects any
30640 commands up to and including
30644 (but not including the MAIL command with a non-empty address),
30645 any callout attempt is bound to fail. Exim remembers such failures in a
30646 domain cache record, which it uses to fail callouts for the domain without
30647 making new connections, until the domain record times out. There are two
30648 separate expiry times for domain cache records:
30649 &%callout_domain_negative_expire%& (default 3h) and
30650 &%callout_domain_positive_expire%& (default 7d).
30652 Domain records expire when the negative expiry time is reached if callouts
30653 cannot be made for the domain, or if the postmaster check failed.
30654 Otherwise, they expire when the positive expiry time is reached. This
30655 ensures that, for example, a host that stops accepting &"random"& local parts
30656 will eventually be noticed.
30658 The callout caching mechanism is based on the domain of the address that is
30659 being tested. If the domain routes to several hosts, it is assumed that their
30660 behaviour will be the same.
30664 .section "Sender address verification reporting" "SECTsenaddver"
30665 .cindex "verifying" "suppressing error details"
30666 See section &<<SECTaddressverification>>& for a general discussion of
30667 verification. When sender verification fails in an ACL, the details of the
30668 failure are given as additional output lines before the 550 response to the
30669 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
30672 MAIL FROM:<xyz@abc.example>
30674 RCPT TO:<pqr@def.example>
30675 550-Verification failed for <xyz@abc.example>
30676 550-Called: 192.168.34.43
30677 550-Sent: RCPT TO:<xyz@abc.example>
30678 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
30679 550 Sender verification failed
30681 If more than one RCPT command fails in the same way, the details are given
30682 only for the first of them. However, some administrators do not want to send
30683 out this much information. You can suppress the details by adding
30684 &`/no_details`& to the ACL statement that requests sender verification. For
30687 verify = sender/no_details
30690 .section "Redirection while verifying" "SECTredirwhilveri"
30691 .cindex "verifying" "redirection while"
30692 .cindex "address redirection" "while verifying"
30693 A dilemma arises when a local address is redirected by aliasing or forwarding
30694 during verification: should the generated addresses themselves be verified,
30695 or should the successful expansion of the original address be enough to verify
30696 it? By default, Exim takes the following pragmatic approach:
30699 When an incoming address is redirected to just one child address, verification
30700 continues with the child address, and if that fails to verify, the original
30701 verification also fails.
30703 When an incoming address is redirected to more than one child address,
30704 verification does not continue. A success result is returned.
30707 This seems the most reasonable behaviour for the common use of aliasing as a
30708 way of redirecting different local parts to the same mailbox. It means, for
30709 example, that a pair of alias entries of the form
30712 aw123: :fail: Gone away, no forwarding address
30714 work as expected, with both local parts causing verification failure. When a
30715 redirection generates more than one address, the behaviour is more like a
30716 mailing list, where the existence of the alias itself is sufficient for
30717 verification to succeed.
30719 It is possible, however, to change the default behaviour so that all successful
30720 redirections count as successful verifications, however many new addresses are
30721 generated. This is specified by the &%success_on_redirect%& verification
30722 option. For example:
30724 require verify = recipient/success_on_redirect/callout=10s
30726 In this example, verification succeeds if a router generates a new address, and
30727 the callout does not occur, because no address was routed to a remote host.
30729 When verification is being tested via the &%-bv%& option, the treatment of
30730 redirections is as just described, unless the &%-v%& or any debugging option is
30731 also specified. In that case, full verification is done for every generated
30732 address and a report is output for each of them.
30736 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
30737 .cindex "CSA" "verifying"
30738 Client SMTP Authorization is a system that allows a site to advertise
30739 which machines are and are not permitted to send email. This is done by placing
30740 special SRV records in the DNS; these are looked up using the client's HELO
30741 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
30742 Authorization checks in Exim are performed by the ACL condition:
30746 This fails if the client is not authorized. If there is a DNS problem, or if no
30747 valid CSA SRV record is found, or if the client is authorized, the condition
30748 succeeds. These three cases can be distinguished using the expansion variable
30749 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
30750 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
30751 be likely to cause problems for legitimate email.
30753 The error messages produced by the CSA code include slightly more
30754 detail. If &$csa_status$& is &"defer"&, this may be because of problems
30755 looking up the CSA SRV record, or problems looking up the CSA target
30756 address record. There are four reasons for &$csa_status$& being &"fail"&:
30759 The client's host name is explicitly not authorized.
30761 The client's IP address does not match any of the CSA target IP addresses.
30763 The client's host name is authorized but it has no valid target IP addresses
30764 (for example, the target's addresses are IPv6 and the client is using IPv4).
30766 The client's host name has no CSA SRV record but a parent domain has asserted
30767 that all subdomains must be explicitly authorized.
30770 The &%csa%& verification condition can take an argument which is the domain to
30771 use for the DNS query. The default is:
30773 verify = csa/$sender_helo_name
30775 This implementation includes an extension to CSA. If the query domain
30776 is an address literal such as [192.0.2.95], or if it is a bare IP
30777 address, Exim searches for CSA SRV records in the reverse DNS as if
30778 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
30781 verify = csa/$sender_host_address
30783 In fact, this is the check that Exim performs if the client does not say HELO.
30784 This extension can be turned off by setting the main configuration option
30785 &%dns_csa_use_reverse%& to be false.
30787 If a CSA SRV record is not found for the domain itself, a search
30788 is performed through its parent domains for a record which might be
30789 making assertions about subdomains. The maximum depth of this search is limited
30790 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
30791 default. Exim does not look for CSA SRV records in a top level domain, so the
30792 default settings handle HELO domains as long as seven
30793 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
30794 of legitimate HELO domains.
30796 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
30797 direct SRV lookups, this is not sufficient because of the extra parent domain
30798 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
30799 addresses into lookups in the reverse DNS space. The result of a successful
30802 ${lookup dnsdb {csa=$sender_helo_name}}
30804 has two space-separated fields: an authorization code and a target host name.
30805 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
30806 authorization required but absent, or &"?"& for unknown.
30811 .section "Bounce address tag validation" "SECTverifyPRVS"
30812 .cindex "BATV, verifying"
30813 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
30814 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
30815 Genuine incoming bounce messages should therefore always be addressed to
30816 recipients that have a valid tag. This scheme is a way of detecting unwanted
30817 bounce messages caused by sender address forgeries (often called &"collateral
30818 spam"&), because the recipients of such messages do not include valid tags.
30820 There are two expansion items to help with the implementation of the BATV
30821 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
30822 the original envelope sender address by using a simple key to add a hash of the
30823 address and some time-based randomizing information. The &%prvs%& expansion
30824 item creates a signed address, and the &%prvscheck%& expansion item checks one.
30825 The syntax of these expansion items is described in section
30826 &<<SECTexpansionitems>>&.
30828 As an example, suppose the secret per-address keys are stored in an MySQL
30829 database. A query to look up the key for an address could be defined as a macro
30832 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
30833 WHERE sender='${quote_mysql:$prvscheck_address}'\
30836 Suppose also that the senders who make use of BATV are defined by an address
30837 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
30840 # Bounces: drop unsigned addresses for BATV senders
30841 deny message = This address does not send an unsigned reverse path
30843 recipients = +batv_senders
30845 # Bounces: In case of prvs-signed address, check signature.
30846 deny message = Invalid reverse path signature.
30848 condition = ${prvscheck {$local_part@$domain}\
30849 {PRVSCHECK_SQL}{1}}
30850 !condition = $prvscheck_result
30852 The first statement rejects recipients for bounce messages that are addressed
30853 to plain BATV sender addresses, because it is known that BATV senders do not
30854 send out messages with plain sender addresses. The second statement rejects
30855 recipients that are prvs-signed, but with invalid signatures (either because
30856 the key is wrong, or the signature has timed out).
30858 A non-prvs-signed address is not rejected by the second statement, because the
30859 &%prvscheck%& expansion yields an empty string if its first argument is not a
30860 prvs-signed address, thus causing the &%condition%& condition to be false. If
30861 the first argument is a syntactically valid prvs-signed address, the yield is
30862 the third string (in this case &"1"&), whether or not the cryptographic and
30863 timeout checks succeed. The &$prvscheck_result$& variable contains the result
30864 of the checks (empty for failure, &"1"& for success).
30866 There is one more issue you must consider when implementing prvs-signing:
30867 you have to ensure that the routers accept prvs-signed addresses and
30868 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
30869 router to remove the signature with a configuration along these lines:
30873 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
30875 This works because, if the third argument of &%prvscheck%& is empty, the result
30876 of the expansion of a prvs-signed address is the decoded value of the original
30877 address. This router should probably be the first of your routers that handles
30880 To create BATV-signed addresses in the first place, a transport of this form
30883 external_smtp_batv:
30885 return_path = ${prvs {$return_path} \
30886 {${lookup mysql{SELECT \
30887 secret FROM batv_prvs WHERE \
30888 sender='${quote_mysql:$sender_address}'} \
30891 If no key can be found for the existing return path, no signing takes place.
30895 .section "Using an ACL to control relaying" "SECTrelaycontrol"
30896 .cindex "&ACL;" "relay control"
30897 .cindex "relaying" "control by ACL"
30898 .cindex "policy control" "relay control"
30899 An MTA is said to &'relay'& a message if it receives it from some host and
30900 delivers it directly to another host as a result of a remote address contained
30901 within it. Redirecting a local address via an alias or forward file and then
30902 passing the message on to another host is not relaying,
30903 .cindex "&""percent hack""&"
30904 but a redirection as a result of the &"percent hack"& is.
30906 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
30907 A host which is acting as a gateway or an MX backup is concerned with incoming
30908 relaying from arbitrary hosts to a specific set of domains. On the other hand,
30909 a host which is acting as a smart host for a number of clients is concerned
30910 with outgoing relaying from those clients to the Internet at large. Often the
30911 same host is fulfilling both functions,
30913 . as illustrated in the diagram below,
30915 but in principle these two kinds of relaying are entirely independent. What is
30916 not wanted is the transmission of mail from arbitrary remote hosts through your
30917 system to arbitrary domains.
30920 You can implement relay control by means of suitable statements in the ACL that
30921 runs for each RCPT command. For convenience, it is often easiest to use
30922 Exim's named list facility to define the domains and hosts involved. For
30923 example, suppose you want to do the following:
30926 Deliver a number of domains to mailboxes on the local host (or process them
30927 locally in some other way). Let's say these are &'my.dom1.example'& and
30928 &'my.dom2.example'&.
30930 Relay mail for a number of other domains for which you are the secondary MX.
30931 These might be &'friend1.example'& and &'friend2.example'&.
30933 Relay mail from the hosts on your local LAN, to whatever domains are involved.
30934 Suppose your LAN is 192.168.45.0/24.
30938 In the main part of the configuration, you put the following definitions:
30940 domainlist local_domains = my.dom1.example : my.dom2.example
30941 domainlist relay_to_domains = friend1.example : friend2.example
30942 hostlist relay_from_hosts = 192.168.45.0/24
30944 Now you can use these definitions in the ACL that is run for every RCPT
30948 accept domains = +local_domains : +relay_to_domains
30949 accept hosts = +relay_from_hosts
30951 The first statement accepts any RCPT command that contains an address in
30952 the local or relay domains. For any other domain, control passes to the second
30953 statement, which accepts the command only if it comes from one of the relay
30954 hosts. In practice, you will probably want to make your ACL more sophisticated
30955 than this, for example, by including sender and recipient verification. The
30956 default configuration includes a more comprehensive example, which is described
30957 in chapter &<<CHAPdefconfil>>&.
30961 .section "Checking a relay configuration" "SECTcheralcon"
30962 .cindex "relaying" "checking control of"
30963 You can check the relay characteristics of your configuration in the same way
30964 that you can test any ACL behaviour for an incoming SMTP connection, by using
30965 the &%-bh%& option to run a fake SMTP session with which you interact.
30970 . ////////////////////////////////////////////////////////////////////////////
30971 . ////////////////////////////////////////////////////////////////////////////
30973 .chapter "Content scanning at ACL time" "CHAPexiscan"
30974 .scindex IIDcosca "content scanning" "at ACL time"
30975 The extension of Exim to include content scanning at ACL time, formerly known
30976 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
30977 was integrated into the main source for Exim release 4.50, and Tom continues to
30978 maintain it. Most of the wording of this chapter is taken from Tom's
30981 It is also possible to scan the content of messages at other times. The
30982 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
30983 scanning after all the ACLs have run. A transport filter can be used to scan
30984 messages at delivery time (see the &%transport_filter%& option, described in
30985 chapter &<<CHAPtransportgeneric>>&).
30987 If you want to include the ACL-time content-scanning features when you compile
30988 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
30989 &_Local/Makefile_&. When you do that, the Exim binary is built with:
30992 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
30993 for all MIME parts for SMTP and non-SMTP messages, respectively.
30995 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
30996 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
30997 run at the end of message reception (the &%acl_smtp_data%& ACL).
30999 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
31000 of messages, or parts of messages, for debugging purposes.
31002 Additional expansion variables that are set in the new ACL and by the new
31005 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
31008 There is another content-scanning configuration option for &_Local/Makefile_&,
31009 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
31010 condition is compiled, in addition to all the other content-scanning features.
31012 Content-scanning is continually evolving, and new features are still being
31013 added. While such features are still unstable and liable to incompatible
31014 changes, they are made available in Exim by setting options whose names begin
31015 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
31016 this manual. You can find out about them by reading the file called
31017 &_doc/experimental.txt_&.
31019 All the content-scanning facilities work on a MBOX copy of the message that is
31020 temporarily created in a file called:
31022 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
31024 The &_.eml_& extension is a friendly hint to virus scanners that they can
31025 expect an MBOX-like structure inside that file. The file is created when the
31026 first content scanning facility is called. Subsequent calls to content
31027 scanning conditions open the same file again. The directory is recursively
31028 removed when the &%acl_smtp_data%& ACL has finished running, unless
31030 control = no_mbox_unspool
31032 has been encountered. When the MIME ACL decodes files, they are put into the
31033 same directory by default.
31037 .section "Scanning for viruses" "SECTscanvirus"
31038 .cindex "virus scanning"
31039 .cindex "content scanning" "for viruses"
31040 .cindex "content scanning" "the &%malware%& condition"
31041 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
31042 It supports a &"generic"& interface to scanners called via the shell, and
31043 specialized interfaces for &"daemon"& type virus scanners, which are resident
31044 in memory and thus are much faster.
31046 A timeout of 2 minutes is applied to a scanner call (by default);
31047 if it expires then a defer action is taken.
31049 .oindex "&%av_scanner%&"
31050 You can set the &%av_scanner%& option in the main part of the configuration
31051 to specify which scanner to use, together with any additional options that
31052 are needed. The basic syntax is as follows:
31054 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
31056 If you do not set &%av_scanner%&, it defaults to
31058 av_scanner = sophie:/var/run/sophie
31060 If the value of &%av_scanner%& starts with a dollar character, it is expanded
31062 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
31063 The following scanner types are supported in this release:
31067 .cindex "virus scanners" "avast"
31068 This is the scanner daemon of Avast. It has been tested with Avast Core
31069 Security (currently at version 1.1.7).
31070 You can get a trial version at &url(http://www.avast.com) or for Linux
31071 at &url(http://www.avast.com/linux-server-antivirus).
31072 This scanner type takes one option,
31073 which can be either a full path to a UNIX socket,
31074 or host and port specifiers separated by white space.
31075 The host may be a name or an IP address; the port is either a
31076 single number or a pair of numbers with a dash between.
31077 Any further options are given, on separate lines,
31078 to the daemon as options before the main scan command.
31081 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
31082 av_scanner = avast:192.168.2.22 5036
31084 If you omit the argument, the default path
31085 &_/var/run/avast/scan.sock_&
31087 If you use a remote host,
31088 you need to make Exim's spool directory available to it,
31089 as the scanner is passed a file path, not file contents.
31090 For information about available commands and their options you may use
31092 $ socat UNIX:/var/run/avast/scan.sock STDIO:
31099 .vitem &%aveserver%&
31100 .cindex "virus scanners" "Kaspersky"
31101 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
31102 at &url(http://www.kaspersky.com). This scanner type takes one option,
31103 which is the path to the daemon's UNIX socket. The default is shown in this
31106 av_scanner = aveserver:/var/run/aveserver
31111 .cindex "virus scanners" "clamd"
31112 This daemon-type scanner is GPL and free. You can get it at
31113 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
31114 unpack MIME containers, so it used to be recommended to unpack MIME attachments
31115 in the MIME ACL. This is no longer believed to be necessary.
31117 The options are a list of server specifiers, which may be
31118 a UNIX socket specification,
31119 a TCP socket specification,
31120 or a (global) option.
31122 A socket specification consists of a space-separated list.
31123 For a Unix socket the first element is a full path for the socket,
31124 for a TCP socket the first element is the IP address
31125 and the second a port number,
31126 Any further elements are per-server (non-global) options.
31127 These per-server options are supported:
31129 retry=<timespec> Retry on connect fail
31132 The &`retry`& option specifies a time after which a single retry for
31133 a failed connect is made. The default is to not retry.
31135 If a Unix socket file is specified, only one server is supported.
31139 av_scanner = clamd:/opt/clamd/socket
31140 av_scanner = clamd:192.0.2.3 1234
31141 av_scanner = clamd:192.0.2.3 1234:local
31142 av_scanner = clamd:192.0.2.3 1234 retry=10s
31143 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
31145 If the value of av_scanner points to a UNIX socket file or contains the
31147 option, then the ClamAV interface will pass a filename containing the data
31148 to be scanned, which will should normally result in less I/O happening and be
31149 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
31150 Exim does not assume that there is a common filesystem with the remote host.
31151 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
31152 you be running a version of ClamAV prior to 0.95.
31154 The final example shows that multiple TCP targets can be specified. Exim will
31155 randomly use one for each incoming email (i.e. it load balances them). Note
31156 that only TCP targets may be used if specifying a list of scanners; a UNIX
31157 socket cannot be mixed in with TCP targets. If one of the servers becomes
31158 unavailable, Exim will try the remaining one(s) until it finds one that works.
31159 When a clamd server becomes unreachable, Exim will log a message. Exim does
31160 not keep track of scanner state between multiple messages, and the scanner
31161 selection is random, so the message will get logged in the mainlog for each
31162 email that the down scanner gets chosen first (message wrapped to be readable):
31164 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
31165 clamd: connection to localhost, port 3310 failed
31166 (Connection refused)
31169 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
31170 contributing the code for this scanner.
31173 .cindex "virus scanners" "command line interface"
31174 This is the keyword for the generic command line scanner interface. It can be
31175 used to attach virus scanners that are invoked from the shell. This scanner
31176 type takes 3 mandatory options:
31179 The full path and name of the scanner binary, with all command line options,
31180 and a placeholder (&`%s`&) for the directory to scan.
31183 A regular expression to match against the STDOUT and STDERR output of the
31184 virus scanner. If the expression matches, a virus was found. You must make
31185 absolutely sure that this expression matches on &"virus found"&. This is called
31186 the &"trigger"& expression.
31189 Another regular expression, containing exactly one pair of parentheses, to
31190 match the name of the virus found in the scanners output. This is called the
31191 &"name"& expression.
31194 For example, Sophos Sweep reports a virus on a line like this:
31196 Virus 'W32/Magistr-B' found in file ./those.bat
31198 For the trigger expression, we can match the phrase &"found in file"&. For the
31199 name expression, we want to extract the W32/Magistr-B string, so we can match
31200 for the single quotes left and right of it. Altogether, this makes the
31201 configuration setting:
31203 av_scanner = cmdline:\
31204 /path/to/sweep -ss -all -rec -archive %s:\
31205 found in file:'(.+)'
31208 .cindex "virus scanners" "DrWeb"
31209 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
31211 either a full path to a UNIX socket,
31212 or host and port specifiers separated by white space.
31213 The host may be a name or an IP address; the port is either a
31214 single number or a pair of numbers with a dash between.
31217 av_scanner = drweb:/var/run/drwebd.sock
31218 av_scanner = drweb:192.168.2.20 31337
31220 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
31221 is used. Thanks to Alex Miller for contributing the code for this scanner.
31224 .cindex "virus scanners" "f-protd"
31225 The f-protd scanner is accessed via HTTP over TCP.
31226 One argument is taken, being a space-separated hostname and port number
31230 av_scanner = f-protd:localhost 10200-10204
31232 If you omit the argument, the default values show above are used.
31235 .cindex "virus scanners" "F-Secure"
31236 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
31237 argument which is the path to a UNIX socket. For example:
31239 av_scanner = fsecure:/path/to/.fsav
31241 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
31242 Thelmen for contributing the code for this scanner.
31244 .vitem &%kavdaemon%&
31245 .cindex "virus scanners" "Kaspersky"
31246 This is the scanner daemon of Kaspersky Version 4. This version of the
31247 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
31248 scanner type takes one option, which is the path to the daemon's UNIX socket.
31251 av_scanner = kavdaemon:/opt/AVP/AvpCtl
31253 The default path is &_/var/run/AvpCtl_&.
31256 .cindex "virus scanners" "mksd"
31257 This is a daemon type scanner that is aimed mainly at Polish users, though some
31258 parts of documentation are now available in English. You can get it at
31259 &url(http://linux.mks.com.pl/). The only option for this scanner type is
31260 the maximum number of processes used simultaneously to scan the attachments,
31261 provided that the demime facility is employed and also provided that mksd has
31262 been run with at least the same number of child processes. For example:
31264 av_scanner = mksd:2
31266 You can safely omit this option (the default value is 1).
31269 .cindex "virus scanners" "simple socket-connected"
31270 This is a general-purpose way of talking to simple scanner daemons
31271 running on the local machine.
31272 There are four options:
31273 an address (which may be an IP address and port, or the path of a Unix socket),
31274 a commandline to send (may include a single %s which will be replaced with
31275 the path to the mail file to be scanned),
31276 an RE to trigger on from the returned data,
31277 an RE to extract malware_name from the returned data.
31280 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
31282 Default for the socket specifier is &_/tmp/malware.sock_&.
31283 Default for the commandline is &_%s\n_&.
31284 Both regular-expressions are required.
31287 .cindex "virus scanners" "Sophos and Sophie"
31288 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
31289 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
31290 for this scanner type is the path to the UNIX socket that Sophie uses for
31291 client communication. For example:
31293 av_scanner = sophie:/tmp/sophie
31295 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
31299 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
31300 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
31303 The &%av_scanner%& option is expanded each time &%malware%& is called. This
31304 makes it possible to use different scanners. See further below for an example.
31305 The &%malware%& condition caches its results, so when you use it multiple times
31306 for the same message, the actual scanning process is only carried out once.
31307 However, using expandable items in &%av_scanner%& disables this caching, in
31308 which case each use of the &%malware%& condition causes a new scan of the
31311 The &%malware%& condition takes a right-hand argument that is expanded before
31312 use and taken as a list, slash-separated by default.
31313 The first element can then be one of
31316 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
31317 The condition succeeds if a virus was found, and fail otherwise. This is the
31320 &"false"& or &"0"& or an empty string, in which case no scanning is done and
31321 the condition fails immediately.
31323 A regular expression, in which case the message is scanned for viruses. The
31324 condition succeeds if a virus is found and its name matches the regular
31325 expression. This allows you to take special actions on certain types of virus.
31326 Note that &"/"& characters in the RE must be doubled due to the list-processing,
31327 unless the separator is changed (in the usual way).
31330 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
31331 messages even if there is a problem with the virus scanner.
31332 Otherwise, such a problem causes the ACL to defer.
31334 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
31335 specify a non-default timeout. The default is two minutes.
31338 malware = * / defer_ok / tmo=10s
31340 A timeout causes the ACL to defer.
31342 .vindex "&$callout_address$&"
31343 When a connection is made to the scanner the expansion variable &$callout_address$&
31344 is set to record the actual address used.
31346 .vindex "&$malware_name$&"
31347 When a virus is found, the condition sets up an expansion variable called
31348 &$malware_name$& that contains the name of the virus. You can use it in a
31349 &%message%& modifier that specifies the error returned to the sender, and/or in
31352 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
31353 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
31354 &%malware%& condition.
31356 Beware the interaction of Exim's &%message_size_limit%& with any size limits
31357 imposed by your anti-virus scanner.
31359 Here is a very simple scanning example:
31361 deny message = This message contains malware ($malware_name)
31365 The next example accepts messages when there is a problem with the scanner:
31367 deny message = This message contains malware ($malware_name)
31369 malware = */defer_ok
31371 The next example shows how to use an ACL variable to scan with both sophie and
31372 aveserver. It assumes you have set:
31374 av_scanner = $acl_m0
31376 in the main Exim configuration.
31378 deny message = This message contains malware ($malware_name)
31379 set acl_m0 = sophie
31382 deny message = This message contains malware ($malware_name)
31383 set acl_m0 = aveserver
31388 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
31389 .cindex "content scanning" "for spam"
31390 .cindex "spam scanning"
31391 .cindex "SpamAssassin"
31393 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
31394 score and a report for the message.
31395 Support is also provided for Rspamd.
31397 For more information about installation and configuration of SpamAssassin or
31398 Rspamd refer to their respective websites at
31399 &url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
31401 SpamAssassin can be installed with CPAN by running:
31403 perl -MCPAN -e 'install Mail::SpamAssassin'
31405 SpamAssassin has its own set of configuration files. Please review its
31406 documentation to see how you can tweak it. The default installation should work
31409 .oindex "&%spamd_address%&"
31410 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
31411 intend to use an instance running on the local host you do not need to set
31412 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
31413 you must set the &%spamd_address%& option in the global part of the Exim
31414 configuration as follows (example):
31416 spamd_address = 192.168.99.45 387
31419 To use Rspamd (which by default listens on all local addresses
31421 you should add &%variant=rspamd%& after the address/port pair, for example:
31423 spamd_address = 127.0.0.1 11333 variant=rspamd
31426 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
31427 sockets. If you want to us these, supply &%spamd_address%& with an absolute
31428 file name instead of an address/port pair:
31430 spamd_address = /var/run/spamd_socket
31432 You can have multiple &%spamd%& servers to improve scalability. These can
31433 reside on other hardware reachable over the network. To specify multiple
31434 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
31435 option, separated with colons (the separator can be changed in the usual way):
31437 spamd_address = 192.168.2.10 783 : \
31438 192.168.2.11 783 : \
31441 Up to 32 &%spamd%& servers are supported.
31442 When a server fails to respond to the connection attempt, all other
31443 servers are tried until one succeeds. If no server responds, the &%spam%&
31446 Unix and TCP socket specifications may be mixed in any order.
31447 Each element of the list is a list itself, space-separated by default
31448 and changeable in the usual way.
31450 For TCP socket specifications a host name or IP (v4 or v6, but
31451 subject to list-separator quoting rules) address can be used,
31452 and the port can be one or a dash-separated pair.
31453 In the latter case, the range is tried in strict order.
31455 Elements after the first for Unix sockets, or second for TCP socket,
31457 The supported options are:
31459 pri=<priority> Selection priority
31460 weight=<value> Selection bias
31461 time=<start>-<end> Use only between these times of day
31462 retry=<timespec> Retry on connect fail
31463 tmo=<timespec> Connection time limit
31464 variant=rspamd Use Rspamd rather than SpamAssassin protocol
31467 The &`pri`& option specifies a priority for the server within the list,
31468 higher values being tried first.
31469 The default priority is 1.
31471 The &`weight`& option specifies a selection bias.
31472 Within a priority set
31473 servers are queried in a random fashion, weighted by this value.
31474 The default value for selection bias is 1.
31476 Time specifications for the &`time`& option are <hour>.<minute>.<second>
31477 in the local time zone; each element being one or more digits.
31478 Either the seconds or both minutes and seconds, plus the leading &`.`&
31479 characters, may be omitted and will be taken as zero.
31481 Timeout specifications for the &`retry`& and &`tmo`& options
31482 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
31484 The &`tmo`& option specifies an overall timeout for communication.
31485 The default value is two minutes.
31487 The &`retry`& option specifies a time after which a single retry for
31488 a failed connect is made.
31489 The default is to not retry.
31491 The &%spamd_address%& variable is expanded before use if it starts with
31492 a dollar sign. In this case, the expansion may return a string that is
31493 used as the list so that multiple spamd servers can be the result of an
31496 .vindex "&$callout_address$&"
31497 When a connection is made to the server the expansion variable &$callout_address$&
31498 is set to record the actual address used.
31500 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
31501 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
31503 deny message = This message was classified as SPAM
31506 The right-hand side of the &%spam%& condition specifies a name. This is
31507 relevant if you have set up multiple SpamAssassin profiles. If you do not want
31508 to scan using a specific profile, but rather use the SpamAssassin system-wide
31509 default profile, you can scan for an unknown name, or simply use &"nobody"&.
31510 Rspamd does not use this setting. However, you must put something on the
31513 The name allows you to use per-domain or per-user antispam profiles in
31514 principle, but this is not straightforward in practice, because a message may
31515 have multiple recipients, not necessarily all in the same domain. Because the
31516 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
31517 read the contents of the message, the variables &$local_part$& and &$domain$&
31519 Careful enforcement of single-recipient messages
31520 (e.g. by responding with defer in the recipient ACL for all recipients
31522 or the use of PRDR,
31523 .cindex "PRDR" "use for per-user SpamAssassin profiles"
31524 are needed to use this feature.
31526 The right-hand side of the &%spam%& condition is expanded before being used, so
31527 you can put lookups or conditions there. When the right-hand side evaluates to
31528 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
31531 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
31532 large ones may cause significant performance degradation. As most spam messages
31533 are quite small, it is recommended that you do not scan the big ones. For
31536 deny message = This message was classified as SPAM
31537 condition = ${if < {$message_size}{10K}}
31541 The &%spam%& condition returns true if the threshold specified in the user's
31542 SpamAssassin profile has been matched or exceeded. If you want to use the
31543 &%spam%& condition for its side effects (see the variables below), you can make
31544 it always return &"true"& by appending &`:true`& to the username.
31546 .cindex "spam scanning" "returned variables"
31547 When the &%spam%& condition is run, it sets up a number of expansion
31549 Except for &$spam_report$&,
31550 these variables are saved with the received message so are
31551 available for use at delivery time.
31554 .vitem &$spam_score$&
31555 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
31556 for inclusion in log or reject messages.
31558 .vitem &$spam_score_int$&
31559 The spam score of the message, multiplied by ten, as an integer value. For
31560 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
31561 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
31562 The integer value is useful for numeric comparisons in conditions.
31564 .vitem &$spam_bar$&
31565 A string consisting of a number of &"+"& or &"-"& characters, representing the
31566 integer part of the spam score value. A spam score of 4.4 would have a
31567 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
31568 headers, since MUAs can match on such strings. The maximum length of the
31569 spam bar is 50 characters.
31571 .vitem &$spam_report$&
31572 A multiline text table, containing the full SpamAssassin report for the
31573 message. Useful for inclusion in headers or reject messages.
31574 This variable is only usable in a DATA-time ACL.
31576 .vitem &$spam_action$&
31577 For SpamAssassin either 'reject' or 'no action' depending on the
31578 spam score versus threshold.
31579 For Rspamd, the recommended action.
31583 The &%spam%& condition caches its results unless expansion in
31584 spamd_address was used. If you call it again with the same user name, it
31585 does not scan again, but rather returns the same values as before.
31587 The &%spam%& condition returns DEFER if there is any error while running
31588 the message through SpamAssassin or if the expansion of spamd_address
31589 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
31590 statement block), append &`/defer_ok`& to the right-hand side of the
31591 spam condition, like this:
31593 deny message = This message was classified as SPAM
31594 spam = joe/defer_ok
31596 This causes messages to be accepted even if there is a problem with &%spamd%&.
31598 Here is a longer, commented example of the use of the &%spam%&
31601 # put headers in all messages (no matter if spam or not)
31602 warn spam = nobody:true
31603 add_header = X-Spam-Score: $spam_score ($spam_bar)
31604 add_header = X-Spam-Report: $spam_report
31606 # add second subject line with *SPAM* marker when message
31607 # is over threshold
31609 add_header = Subject: *SPAM* $h_Subject:
31611 # reject spam at high scores (> 12)
31612 deny message = This message scored $spam_score spam points.
31614 condition = ${if >{$spam_score_int}{120}{1}{0}}
31619 .section "Scanning MIME parts" "SECTscanmimepart"
31620 .cindex "content scanning" "MIME parts"
31621 .cindex "MIME content scanning"
31622 .oindex "&%acl_smtp_mime%&"
31623 .oindex "&%acl_not_smtp_mime%&"
31624 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
31625 each MIME part of an SMTP message, including multipart types, in the sequence
31626 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
31627 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
31628 options may both refer to the same ACL if you want the same processing in both
31631 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
31632 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
31633 the case of a non-SMTP message. However, a MIME ACL is called only if the
31634 message contains a &'Content-Type:'& header line. When a call to a MIME
31635 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
31636 result code is sent to the client. In the case of an SMTP message, the
31637 &%acl_smtp_data%& ACL is not called when this happens.
31639 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
31640 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
31641 condition to match against the raw MIME part. You can also use the
31642 &%mime_regex%& condition to match against the decoded MIME part (see section
31643 &<<SECTscanregex>>&).
31645 At the start of a MIME ACL, a number of variables are set from the header
31646 information for the relevant MIME part. These are described below. The contents
31647 of the MIME part are not by default decoded into a disk file except for MIME
31648 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
31649 part into a disk file, you can use the &%decode%& condition. The general
31652 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
31654 The right hand side is expanded before use. After expansion,
31658 &"0"& or &"false"&, in which case no decoding is done.
31660 The string &"default"&. In that case, the file is put in the temporary
31661 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
31662 a sequential file name consisting of the message id and a sequence number. The
31663 full path and name is available in &$mime_decoded_filename$& after decoding.
31665 A full path name starting with a slash. If the full name is an existing
31666 directory, it is used as a replacement for the default directory. The filename
31667 is then sequentially assigned. If the path does not exist, it is used as
31668 the full path and file name.
31670 If the string does not start with a slash, it is used as the
31671 filename, and the default path is then used.
31673 The &%decode%& condition normally succeeds. It is only false for syntax
31674 errors or unusual circumstances such as memory shortages. You can easily decode
31675 a file with its original, proposed filename using
31677 decode = $mime_filename
31679 However, you should keep in mind that &$mime_filename$& might contain
31680 anything. If you place files outside of the default path, they are not
31681 automatically unlinked.
31683 For RFC822 attachments (these are messages attached to messages, with a
31684 content-type of &"message/rfc822"&), the ACL is called again in the same manner
31685 as for the primary message, only that the &$mime_is_rfc822$& expansion
31686 variable is set (see below). Attached messages are always decoded to disk
31687 before being checked, and the files are unlinked once the check is done.
31689 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
31690 used to match regular expressions against raw and decoded MIME parts,
31691 respectively. They are described in section &<<SECTscanregex>>&.
31693 .cindex "MIME content scanning" "returned variables"
31694 The following list describes all expansion variables that are
31695 available in the MIME ACL:
31698 .vitem &$mime_boundary$&
31699 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
31700 have a boundary string, which is stored in this variable. If the current part
31701 has no boundary parameter in the &'Content-Type:'& header, this variable
31702 contains the empty string.
31704 .vitem &$mime_charset$&
31705 This variable contains the character set identifier, if one was found in the
31706 &'Content-Type:'& header. Examples for charset identifiers are:
31712 Please note that this value is not normalized, so you should do matches
31713 case-insensitively.
31715 .vitem &$mime_content_description$&
31716 This variable contains the normalized content of the &'Content-Description:'&
31717 header. It can contain a human-readable description of the parts content. Some
31718 implementations repeat the filename for attachments here, but they are usually
31719 only used for display purposes.
31721 .vitem &$mime_content_disposition$&
31722 This variable contains the normalized content of the &'Content-Disposition:'&
31723 header. You can expect strings like &"attachment"& or &"inline"& here.
31725 .vitem &$mime_content_id$&
31726 This variable contains the normalized content of the &'Content-ID:'& header.
31727 This is a unique ID that can be used to reference a part from another part.
31729 .vitem &$mime_content_size$&
31730 This variable is set only after the &%decode%& modifier (see above) has been
31731 successfully run. It contains the size of the decoded part in kilobytes. The
31732 size is always rounded up to full kilobytes, so only a completely empty part
31733 has a &$mime_content_size$& of zero.
31735 .vitem &$mime_content_transfer_encoding$&
31736 This variable contains the normalized content of the
31737 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
31738 type. Typical values are &"base64"& and &"quoted-printable"&.
31740 .vitem &$mime_content_type$&
31741 If the MIME part has a &'Content-Type:'& header, this variable contains its
31742 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
31743 are some examples of popular MIME types, as they may appear in this variable:
31747 application/octet-stream
31751 If the MIME part has no &'Content-Type:'& header, this variable contains the
31754 .vitem &$mime_decoded_filename$&
31755 This variable is set only after the &%decode%& modifier (see above) has been
31756 successfully run. It contains the full path and file name of the file
31757 containing the decoded data.
31762 .vitem &$mime_filename$&
31763 This is perhaps the most important of the MIME variables. It contains a
31764 proposed filename for an attachment, if one was found in either the
31765 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
31768 decoded, but no additional sanity checks are done.
31770 found, this variable contains the empty string.
31772 .vitem &$mime_is_coverletter$&
31773 This variable attempts to differentiate the &"cover letter"& of an e-mail from
31774 attached data. It can be used to clamp down on flashy or unnecessarily encoded
31775 content in the cover letter, while not restricting attachments at all.
31777 The variable contains 1 (true) for a MIME part believed to be part of the
31778 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
31782 The outermost MIME part of a message is always a cover letter.
31785 If a multipart/alternative or multipart/related MIME part is a cover letter,
31786 so are all MIME subparts within that multipart.
31789 If any other multipart is a cover letter, the first subpart is a cover letter,
31790 and the rest are attachments.
31793 All parts contained within an attachment multipart are attachments.
31796 As an example, the following will ban &"HTML mail"& (including that sent with
31797 alternative plain text), while allowing HTML files to be attached. HTML
31798 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
31800 deny message = HTML mail is not accepted here
31801 !condition = $mime_is_rfc822
31802 condition = $mime_is_coverletter
31803 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
31805 .vitem &$mime_is_multipart$&
31806 This variable has the value 1 (true) when the current part has the main type
31807 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
31808 Since multipart entities only serve as containers for other parts, you may not
31809 want to carry out specific actions on them.
31811 .vitem &$mime_is_rfc822$&
31812 This variable has the value 1 (true) if the current part is not a part of the
31813 checked message itself, but part of an attached message. Attached message
31814 decoding is fully recursive.
31816 .vitem &$mime_part_count$&
31817 This variable is a counter that is raised for each processed MIME part. It
31818 starts at zero for the very first part (which is usually a multipart). The
31819 counter is per-message, so it is reset when processing RFC822 attachments (see
31820 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
31821 complete, so you can use it in the DATA ACL to determine the number of MIME
31822 parts of a message. For non-MIME messages, this variable contains the value -1.
31827 .section "Scanning with regular expressions" "SECTscanregex"
31828 .cindex "content scanning" "with regular expressions"
31829 .cindex "regular expressions" "content scanning with"
31830 You can specify your own custom regular expression matches on the full body of
31831 the message, or on individual MIME parts.
31833 The &%regex%& condition takes one or more regular expressions as arguments and
31834 matches them against the full message (when called in the DATA ACL) or a raw
31835 MIME part (when called in the MIME ACL). The &%regex%& condition matches
31836 linewise, with a maximum line length of 32K characters. That means you cannot
31837 have multiline matches with the &%regex%& condition.
31839 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
31840 to 32K of decoded content (the whole content at once, not linewise). If the
31841 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
31842 is decoded automatically when &%mime_regex%& is executed (using default path
31843 and filename values). If the decoded data is larger than 32K, only the first
31844 32K characters are checked.
31846 The regular expressions are passed as a colon-separated list. To include a
31847 literal colon, you must double it. Since the whole right-hand side string is
31848 expanded before being used, you must also escape dollar signs and backslashes
31849 with more backslashes, or use the &`\N`& facility to disable expansion.
31850 Here is a simple example that contains two regular expressions:
31852 deny message = contains blacklisted regex ($regex_match_string)
31853 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
31855 The conditions returns true if any one of the regular expressions matches. The
31856 &$regex_match_string$& expansion variable is then set up and contains the
31857 matching regular expression.
31858 The expansion variables &$regex1$& &$regex2$& etc
31859 are set to any substrings captured by the regular expression.
31861 &*Warning*&: With large messages, these conditions can be fairly
31867 .section "The demime condition" "SECTdemimecond"
31868 .cindex "content scanning" "MIME checking"
31869 .cindex "MIME content scanning"
31870 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
31871 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
31872 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
31873 ACL functionality, but provides no additional facilities. Please note that this
31874 condition is deprecated and kept only for backward compatibility. You must set
31875 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
31876 use the &%demime%& condition.
31878 The &%demime%& condition unpacks MIME containers in the message. It detects
31879 errors in MIME containers and can match file extensions found in the message
31880 against a list. Using this facility produces files containing the unpacked MIME
31881 parts of the message in the temporary scan directory. If you do antivirus
31882 scanning, it is recommended that you use the &%demime%& condition before the
31883 antivirus (&%malware%&) condition.
31885 On the right-hand side of the &%demime%& condition you can pass a
31886 colon-separated list of file extensions that it should match against. For
31889 deny message = Found blacklisted file attachment
31890 demime = vbs:com:bat:pif:prf:lnk
31892 If one of the file extensions is found, the condition is true, otherwise it is
31893 false. If there is a temporary error while demimeing (for example, &"disk
31894 full"&), the condition defers, and the message is temporarily rejected (unless
31895 the condition is on a &%warn%& verb).
31897 The right-hand side is expanded before being treated as a list, so you can have
31898 conditions and lookups there. If it expands to an empty string, &"false"&, or
31899 zero (&"0"&), no demimeing is done and the condition is false.
31901 The &%demime%& condition set the following variables:
31904 .vitem &$demime_errorlevel$&
31905 .vindex "&$demime_errorlevel$&"
31906 When an error is detected in a MIME container, this variable contains the
31907 severity of the error, as an integer number. The higher the value, the more
31908 severe the error (the current maximum value is 3). If this variable is unset or
31909 zero, no error occurred.
31911 .vitem &$demime_reason$&
31912 .vindex "&$demime_reason$&"
31913 When &$demime_errorlevel$& is greater than zero, this variable contains a
31914 human-readable text string describing the MIME error that occurred.
31918 .vitem &$found_extension$&
31919 .vindex "&$found_extension$&"
31920 When the &%demime%& condition is true, this variable contains the file
31921 extension it found.
31924 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
31925 the &%demime%& condition, and are not changed on subsequent calls.
31927 If you do not want to check for file extensions, but rather use the &%demime%&
31928 condition for unpacking or error checking purposes, pass &"*"& as the
31929 right-hand side value. Here is a more elaborate example of how to use this
31932 # Reject messages with serious MIME container errors
31933 deny message = Found MIME error ($demime_reason).
31935 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
31937 # Reject known virus spreading file extensions.
31938 # Accepting these is pretty much braindead.
31939 deny message = contains $found_extension file (blacklisted).
31940 demime = com:vbs:bat:pif:scr
31942 # Freeze .exe and .doc files. Postmaster can
31943 # examine them and eventually thaw them.
31944 deny log_message = Another $found_extension file.
31953 . ////////////////////////////////////////////////////////////////////////////
31954 . ////////////////////////////////////////////////////////////////////////////
31956 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
31957 "Local scan function"
31958 .scindex IIDlosca "&[local_scan()]& function" "description of"
31959 .cindex "customizing" "input scan using C function"
31960 .cindex "policy control" "by local scan function"
31961 In these days of email worms, viruses, and ever-increasing spam, some sites
31962 want to apply a lot of checking to messages before accepting them.
31964 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
31965 passing messages to external virus and spam scanning software. You can also do
31966 a certain amount in Exim itself through string expansions and the &%condition%&
31967 condition in the ACL that runs after the SMTP DATA command or the ACL for
31968 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
31970 To allow for further customization to a site's own requirements, there is the
31971 possibility of linking Exim with a private message scanning function, written
31972 in C. If you want to run code that is written in something other than C, you
31973 can of course use a little C stub to call it.
31975 The local scan function is run once for every incoming message, at the point
31976 when Exim is just about to accept the message.
31977 It can therefore be used to control non-SMTP messages from local processes as
31978 well as messages arriving via SMTP.
31980 Exim applies a timeout to calls of the local scan function, and there is an
31981 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
31982 Zero means &"no timeout"&.
31983 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
31984 before calling the local scan function, so that the most common types of crash
31985 are caught. If the timeout is exceeded or one of those signals is caught, the
31986 incoming message is rejected with a temporary error if it is an SMTP message.
31987 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
31988 code. The incident is logged on the main and reject logs.
31992 .section "Building Exim to use a local scan function" "SECID207"
31993 .cindex "&[local_scan()]& function" "building Exim to use"
31994 To make use of the local scan function feature, you must tell Exim where your
31995 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
31996 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
31997 directory, so you might set
31999 LOCAL_SCAN_SOURCE=Local/local_scan.c
32001 for example. The function must be called &[local_scan()]&. It is called by
32002 Exim after it has received a message, when the success return code is about to
32003 be sent. This is after all the ACLs have been run. The return code from your
32004 function controls whether the message is actually accepted or not. There is a
32005 commented template function (that just accepts the message) in the file
32006 _src/local_scan.c_.
32008 If you want to make use of Exim's run time configuration file to set options
32009 for your &[local_scan()]& function, you must also set
32011 LOCAL_SCAN_HAS_OPTIONS=yes
32013 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
32018 .section "API for local_scan()" "SECTapiforloc"
32019 .cindex "&[local_scan()]& function" "API description"
32020 You must include this line near the start of your code:
32022 #include "local_scan.h"
32024 This header file defines a number of variables and other values, and the
32025 prototype for the function itself. Exim is coded to use unsigned char values
32026 almost exclusively, and one of the things this header defines is a shorthand
32027 for &`unsigned char`& called &`uschar`&.
32028 It also contains the following macro definitions, to simplify casting character
32029 strings and pointers to character strings:
32031 #define CS (char *)
32032 #define CCS (const char *)
32033 #define CSS (char **)
32034 #define US (unsigned char *)
32035 #define CUS (const unsigned char *)
32036 #define USS (unsigned char **)
32038 The function prototype for &[local_scan()]& is:
32040 extern int local_scan(int fd, uschar **return_text);
32042 The arguments are as follows:
32045 &%fd%& is a file descriptor for the file that contains the body of the message
32046 (the -D file). The file is open for reading and writing, but updating it is not
32047 recommended. &*Warning*&: You must &'not'& close this file descriptor.
32049 The descriptor is positioned at character 19 of the file, which is the first
32050 character of the body itself, because the first 19 characters are the message
32051 id followed by &`-D`& and a newline. If you rewind the file, you should use the
32052 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
32053 case this changes in some future version.
32055 &%return_text%& is an address which you can use to return a pointer to a text
32056 string at the end of the function. The value it points to on entry is NULL.
32059 The function must return an &%int%& value which is one of the following macros:
32062 .vitem &`LOCAL_SCAN_ACCEPT`&
32063 .vindex "&$local_scan_data$&"
32064 The message is accepted. If you pass back a string of text, it is saved with
32065 the message, and made available in the variable &$local_scan_data$&. No
32066 newlines are permitted (if there are any, they are turned into spaces) and the
32067 maximum length of text is 1000 characters.
32069 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
32070 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32071 queued without immediate delivery, and is frozen.
32073 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
32074 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32075 queued without immediate delivery.
32077 .vitem &`LOCAL_SCAN_REJECT`&
32078 The message is rejected; the returned text is used as an error message which is
32079 passed back to the sender and which is also logged. Newlines are permitted &--
32080 they cause a multiline response for SMTP rejections, but are converted to
32081 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
32084 .vitem &`LOCAL_SCAN_TEMPREJECT`&
32085 The message is temporarily rejected; the returned text is used as an error
32086 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
32089 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
32090 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
32091 message is not written to the reject log. It has the effect of unsetting the
32092 &%rejected_header%& log selector for just this rejection. If
32093 &%rejected_header%& is already unset (see the discussion of the
32094 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
32095 same as LOCAL_SCAN_REJECT.
32097 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
32098 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
32099 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
32102 If the message is not being received by interactive SMTP, rejections are
32103 reported by writing to &%stderr%& or by sending an email, as configured by the
32104 &%-oe%& command line options.
32108 .section "Configuration options for local_scan()" "SECTconoptloc"
32109 .cindex "&[local_scan()]& function" "configuration options"
32110 It is possible to have option settings in the main configuration file
32111 that set values in static variables in the &[local_scan()]& module. If you
32112 want to do this, you must have the line
32114 LOCAL_SCAN_HAS_OPTIONS=yes
32116 in your &_Local/Makefile_& when you build Exim. (This line is in
32117 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
32118 file, you must define static variables to hold the option values, and a table
32121 The table must be a vector called &%local_scan_options%&, of type
32122 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
32123 and a pointer to the variable that holds the value. The entries must appear in
32124 alphabetical order. Following &%local_scan_options%& you must also define a
32125 variable called &%local_scan_options_count%& that contains the number of
32126 entries in the table. Here is a short example, showing two kinds of option:
32128 static int my_integer_option = 42;
32129 static uschar *my_string_option = US"a default string";
32131 optionlist local_scan_options[] = {
32132 { "my_integer", opt_int, &my_integer_option },
32133 { "my_string", opt_stringptr, &my_string_option }
32136 int local_scan_options_count =
32137 sizeof(local_scan_options)/sizeof(optionlist);
32139 The values of the variables can now be changed from Exim's runtime
32140 configuration file by including a local scan section as in this example:
32144 my_string = some string of text...
32146 The available types of option data are as follows:
32149 .vitem &*opt_bool*&
32150 This specifies a boolean (true/false) option. The address should point to a
32151 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
32152 that are defined as &"1"& and &"0"&, respectively. If you want to detect
32153 whether such a variable has been set at all, you can initialize it to
32154 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
32157 .vitem &*opt_fixed*&
32158 This specifies a fixed point number, such as is used for load averages.
32159 The address should point to a variable of type &`int`&. The value is stored
32160 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
32163 This specifies an integer; the address should point to a variable of type
32164 &`int`&. The value may be specified in any of the integer formats accepted by
32167 .vitem &*opt_mkint*&
32168 This is the same as &%opt_int%&, except that when such a value is output in a
32169 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
32170 printed with the suffix K or M.
32172 .vitem &*opt_octint*&
32173 This also specifies an integer, but the value is always interpreted as an
32174 octal integer, whether or not it starts with the digit zero, and it is
32175 always output in octal.
32177 .vitem &*opt_stringptr*&
32178 This specifies a string value; the address must be a pointer to a
32179 variable that points to a string (for example, of type &`uschar *`&).
32181 .vitem &*opt_time*&
32182 This specifies a time interval value. The address must point to a variable of
32183 type &`int`&. The value that is placed there is a number of seconds.
32186 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
32187 out the values of all the &[local_scan()]& options.
32191 .section "Available Exim variables" "SECID208"
32192 .cindex "&[local_scan()]& function" "available Exim variables"
32193 The header &_local_scan.h_& gives you access to a number of C variables. These
32194 are the only ones that are guaranteed to be maintained from release to release.
32195 Note, however, that you can obtain the value of any Exim expansion variable,
32196 including &$recipients$&, by calling &'expand_string()'&. The exported
32197 C variables are as follows:
32200 .vitem &*int&~body_linecount*&
32201 This variable contains the number of lines in the message's body.
32203 .vitem &*int&~body_zerocount*&
32204 This variable contains the number of binary zero bytes in the message's body.
32206 .vitem &*unsigned&~int&~debug_selector*&
32207 This variable is set to zero when no debugging is taking place. Otherwise, it
32208 is a bitmap of debugging selectors. Two bits are identified for use in
32209 &[local_scan()]&; they are defined as macros:
32212 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
32213 testing option that is not privileged &-- any caller may set it. All the
32214 other selector bits can be set only by admin users.
32217 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
32218 by the &`+local_scan`& debug selector. It is not included in the default set
32222 Thus, to write to the debugging output only when &`+local_scan`& has been
32223 selected, you should use code like this:
32225 if ((debug_selector & D_local_scan) != 0)
32226 debug_printf("xxx", ...);
32228 .vitem &*uschar&~*expand_string_message*&
32229 After a failing call to &'expand_string()'& (returned value NULL), the
32230 variable &%expand_string_message%& contains the error message, zero-terminated.
32232 .vitem &*header_line&~*header_list*&
32233 A pointer to a chain of header lines. The &%header_line%& structure is
32236 .vitem &*header_line&~*header_last*&
32237 A pointer to the last of the header lines.
32239 .vitem &*uschar&~*headers_charset*&
32240 The value of the &%headers_charset%& configuration option.
32242 .vitem &*BOOL&~host_checking*&
32243 This variable is TRUE during a host checking session that is initiated by the
32244 &%-bh%& command line option.
32246 .vitem &*uschar&~*interface_address*&
32247 The IP address of the interface that received the message, as a string. This
32248 is NULL for locally submitted messages.
32250 .vitem &*int&~interface_port*&
32251 The port on which this message was received. When testing with the &%-bh%&
32252 command line option, the value of this variable is -1 unless a port has been
32253 specified via the &%-oMi%& option.
32255 .vitem &*uschar&~*message_id*&
32256 This variable contains Exim's message id for the incoming message (the value of
32257 &$message_exim_id$&) as a zero-terminated string.
32259 .vitem &*uschar&~*received_protocol*&
32260 The name of the protocol by which the message was received.
32262 .vitem &*int&~recipients_count*&
32263 The number of accepted recipients.
32265 .vitem &*recipient_item&~*recipients_list*&
32266 .cindex "recipient" "adding in local scan"
32267 .cindex "recipient" "removing in local scan"
32268 The list of accepted recipients, held in a vector of length
32269 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
32270 can add additional recipients by calling &'receive_add_recipient()'& (see
32271 below). You can delete recipients by removing them from the vector and
32272 adjusting the value in &%recipients_count%&. In particular, by setting
32273 &%recipients_count%& to zero you remove all recipients. If you then return the
32274 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
32275 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
32276 and then call &'receive_add_recipient()'& as often as needed.
32278 .vitem &*uschar&~*sender_address*&
32279 The envelope sender address. For bounce messages this is the empty string.
32281 .vitem &*uschar&~*sender_host_address*&
32282 The IP address of the sending host, as a string. This is NULL for
32283 locally-submitted messages.
32285 .vitem &*uschar&~*sender_host_authenticated*&
32286 The name of the authentication mechanism that was used, or NULL if the message
32287 was not received over an authenticated SMTP connection.
32289 .vitem &*uschar&~*sender_host_name*&
32290 The name of the sending host, if known.
32292 .vitem &*int&~sender_host_port*&
32293 The port on the sending host.
32295 .vitem &*BOOL&~smtp_input*&
32296 This variable is TRUE for all SMTP input, including BSMTP.
32298 .vitem &*BOOL&~smtp_batched_input*&
32299 This variable is TRUE for BSMTP input.
32301 .vitem &*int&~store_pool*&
32302 The contents of this variable control which pool of memory is used for new
32303 requests. See section &<<SECTmemhanloc>>& for details.
32307 .section "Structure of header lines" "SECID209"
32308 The &%header_line%& structure contains the members listed below.
32309 You can add additional header lines by calling the &'header_add()'& function
32310 (see below). You can cause header lines to be ignored (deleted) by setting
32315 .vitem &*struct&~header_line&~*next*&
32316 A pointer to the next header line, or NULL for the last line.
32318 .vitem &*int&~type*&
32319 A code identifying certain headers that Exim recognizes. The codes are printing
32320 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
32321 Notice in particular that any header line whose type is * is not transmitted
32322 with the message. This flagging is used for header lines that have been
32323 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
32324 lines.) Effectively, * means &"deleted"&.
32326 .vitem &*int&~slen*&
32327 The number of characters in the header line, including the terminating and any
32330 .vitem &*uschar&~*text*&
32331 A pointer to the text of the header. It always ends with a newline, followed by
32332 a zero byte. Internal newlines are preserved.
32337 .section "Structure of recipient items" "SECID210"
32338 The &%recipient_item%& structure contains these members:
32341 .vitem &*uschar&~*address*&
32342 This is a pointer to the recipient address as it was received.
32344 .vitem &*int&~pno*&
32345 This is used in later Exim processing when top level addresses are created by
32346 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
32347 and must always contain -1 at this stage.
32349 .vitem &*uschar&~*errors_to*&
32350 If this value is not NULL, bounce messages caused by failing to deliver to the
32351 recipient are sent to the address it contains. In other words, it overrides the
32352 envelope sender for this one recipient. (Compare the &%errors_to%& generic
32353 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
32354 an unqualified address, Exim qualifies it using the domain from
32355 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
32356 is NULL for all recipients.
32361 .section "Available Exim functions" "SECID211"
32362 .cindex "&[local_scan()]& function" "available Exim functions"
32363 The header &_local_scan.h_& gives you access to a number of Exim functions.
32364 These are the only ones that are guaranteed to be maintained from release to
32368 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
32369 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
32371 This function creates a child process that runs the command specified by
32372 &%argv%&. The environment for the process is specified by &%envp%&, which can
32373 be NULL if no environment variables are to be passed. A new umask is supplied
32374 for the process in &%newumask%&.
32376 Pipes to the standard input and output of the new process are set up
32377 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
32378 standard error is cloned to the standard output. If there are any file
32379 descriptors &"in the way"& in the new process, they are closed. If the final
32380 argument is TRUE, the new process is made into a process group leader.
32382 The function returns the pid of the new process, or -1 if things go wrong.
32384 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
32385 This function waits for a child process to terminate, or for a timeout (in
32386 seconds) to expire. A timeout value of zero means wait as long as it takes. The
32387 return value is as follows:
32392 The process terminated by a normal exit and the value is the process
32398 The process was terminated by a signal and the value is the negation of the
32404 The process timed out.
32408 The was some other error in wait(); &%errno%& is still set.
32411 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
32412 This function provide you with a means of submitting a new message to
32413 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
32414 want, but this packages it all up for you.) The function creates a pipe,
32415 forks a subprocess that is running
32417 exim -t -oem -oi -f <>
32419 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
32420 that is connected to the standard input. The yield of the function is the PID
32421 of the subprocess. You can then write a message to the file descriptor, with
32422 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
32424 When you have finished, call &'child_close()'& to wait for the process to
32425 finish and to collect its ending status. A timeout value of zero is usually
32426 fine in this circumstance. Unless you have made a mistake with the recipient
32427 addresses, you should get a return code of zero.
32430 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
32431 *sender_authentication)*&
32432 This function is a more sophisticated version of &'child_open()'&. The command
32435 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
32437 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
32440 .vitem &*void&~debug_printf(char&~*,&~...)*&
32441 This is Exim's debugging function, with arguments as for &'(printf()'&. The
32442 output is written to the standard error stream. If no debugging is selected,
32443 calls to &'debug_printf()'& have no effect. Normally, you should make calls
32444 conditional on the &`local_scan`& debug selector by coding like this:
32446 if ((debug_selector & D_local_scan) != 0)
32447 debug_printf("xxx", ...);
32450 .vitem &*uschar&~*expand_string(uschar&~*string)*&
32451 This is an interface to Exim's string expansion code. The return value is the
32452 expanded string, or NULL if there was an expansion failure.
32453 The C variable &%expand_string_message%& contains an error message after an
32454 expansion failure. If expansion does not change the string, the return value is
32455 the pointer to the input string. Otherwise, the return value points to a new
32456 block of memory that was obtained by a call to &'store_get()'&. See section
32457 &<<SECTmemhanloc>>& below for a discussion of memory handling.
32459 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
32460 This function allows you to an add additional header line at the end of the
32461 existing ones. The first argument is the type, and should normally be a space
32462 character. The second argument is a format string and any number of
32463 substitution arguments as for &[sprintf()]&. You may include internal newlines
32464 if you want, and you must ensure that the string ends with a newline.
32466 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
32467 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
32468 This function adds a new header line at a specified point in the header
32469 chain. The header itself is specified as for &'header_add()'&.
32471 If &%name%& is NULL, the new header is added at the end of the chain if
32472 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
32473 NULL, the header lines are searched for the first non-deleted header that
32474 matches the name. If one is found, the new header is added before it if
32475 &%after%& is false. If &%after%& is true, the new header is added after the
32476 found header and any adjacent subsequent ones with the same name (even if
32477 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
32478 option controls where the header is added. If it is true, addition is at the
32479 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
32480 headers, or at the top if there are no &'Received:'& headers, you could use
32482 header_add_at_position(TRUE, US"Received", TRUE,
32483 ' ', "X-xxx: ...");
32485 Normally, there is always at least one non-deleted &'Received:'& header, but
32486 there may not be if &%received_header_text%& expands to an empty string.
32489 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
32490 This function removes header lines. If &%occurrence%& is zero or negative, all
32491 occurrences of the header are removed. If occurrence is greater than zero, that
32492 particular instance of the header is removed. If no header(s) can be found that
32493 match the specification, the function does nothing.
32496 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
32497 int&~length,&~BOOL&~notdel)*&"
32498 This function tests whether the given header has the given name. It is not just
32499 a string comparison, because white space is permitted between the name and the
32500 colon. If the &%notdel%& argument is true, a false return is forced for all
32501 &"deleted"& headers; otherwise they are not treated specially. For example:
32503 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
32505 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
32506 .cindex "base64 encoding" "functions for &[local_scan()]& use"
32507 This function base64-encodes a string, which is passed by address and length.
32508 The text may contain bytes of any value, including zero. The result is passed
32509 back in dynamic memory that is obtained by calling &'store_get()'&. It is
32512 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
32513 This function decodes a base64-encoded string. Its arguments are a
32514 zero-terminated base64-encoded string and the address of a variable that is set
32515 to point to the result, which is in dynamic memory. The length of the decoded
32516 string is the yield of the function. If the input is invalid base64 data, the
32517 yield is -1. A zero byte is added to the end of the output string to make it
32518 easy to interpret as a C string (assuming it contains no zeros of its own). The
32519 added zero byte is not included in the returned count.
32521 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
32522 This function checks for a match in a domain list. Domains are always
32523 matched caselessly. The return value is one of the following:
32525 &`OK `& match succeeded
32526 &`FAIL `& match failed
32527 &`DEFER `& match deferred
32529 DEFER is usually caused by some kind of lookup defer, such as the
32530 inability to contact a database.
32532 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
32534 This function checks for a match in a local part list. The third argument
32535 controls case-sensitivity. The return values are as for
32536 &'lss_match_domain()'&.
32538 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
32540 This function checks for a match in an address list. The third argument
32541 controls the case-sensitivity of the local part match. The domain is always
32542 matched caselessly. The return values are as for &'lss_match_domain()'&.
32544 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
32546 This function checks for a match in a host list. The most common usage is
32549 lss_match_host(sender_host_name, sender_host_address, ...)
32551 .vindex "&$sender_host_address$&"
32552 An empty address field matches an empty item in the host list. If the host name
32553 is NULL, the name corresponding to &$sender_host_address$& is automatically
32554 looked up if a host name is required to match an item in the list. The return
32555 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
32556 returns ERROR in the case when it had to look up a host name, but the lookup
32559 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
32561 This function writes to Exim's log files. The first argument should be zero (it
32562 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
32563 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
32564 them. It specifies to which log or logs the message is written. The remaining
32565 arguments are a format and relevant insertion arguments. The string should not
32566 contain any newlines, not even at the end.
32569 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
32570 This function adds an additional recipient to the message. The first argument
32571 is the recipient address. If it is unqualified (has no domain), it is qualified
32572 with the &%qualify_recipient%& domain. The second argument must always be -1.
32574 This function does not allow you to specify a private &%errors_to%& address (as
32575 described with the structure of &%recipient_item%& above), because it pre-dates
32576 the addition of that field to the structure. However, it is easy to add such a
32577 value afterwards. For example:
32579 receive_add_recipient(US"monitor@mydom.example", -1);
32580 recipients_list[recipients_count-1].errors_to =
32581 US"postmaster@mydom.example";
32584 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
32585 This is a convenience function to remove a named recipient from the list of
32586 recipients. It returns true if a recipient was removed, and false if no
32587 matching recipient could be found. The argument must be a complete email
32594 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
32595 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
32596 This function decodes strings that are encoded according to RFC 2047. Typically
32597 these are the contents of header lines. First, each &"encoded word"& is decoded
32598 from the Q or B encoding into a byte-string. Then, if provided with the name of
32599 a charset encoding, and if the &[iconv()]& function is available, an attempt is
32600 made to translate the result to the named character set. If this fails, the
32601 binary string is returned with an error message.
32603 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
32604 maximum MIME word length is enforced. The third argument is the target
32605 encoding, or NULL if no translation is wanted.
32607 .cindex "binary zero" "in RFC 2047 decoding"
32608 .cindex "RFC 2047" "binary zero in"
32609 If a binary zero is encountered in the decoded string, it is replaced by the
32610 contents of the &%zeroval%& argument. For use with Exim headers, the value must
32611 not be 0 because header lines are handled as zero-terminated strings.
32613 The function returns the result of processing the string, zero-terminated; if
32614 &%lenptr%& is not NULL, the length of the result is set in the variable to
32615 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
32617 If an error is encountered, the function returns NULL and uses the &%error%&
32618 argument to return an error message. The variable pointed to by &%error%& is
32619 set to NULL if there is no error; it may be set non-NULL even when the function
32620 returns a non-NULL value if decoding was successful, but there was a problem
32624 .vitem &*int&~smtp_fflush(void)*&
32625 This function is used in conjunction with &'smtp_printf()'&, as described
32628 .vitem &*void&~smtp_printf(char&~*,&~...)*&
32629 The arguments of this function are like &[printf()]&; it writes to the SMTP
32630 output stream. You should use this function only when there is an SMTP output
32631 stream, that is, when the incoming message is being received via interactive
32632 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
32633 is FALSE. If you want to test for an incoming message from another host (as
32634 opposed to a local process that used the &%-bs%& command line option), you can
32635 test the value of &%sender_host_address%&, which is non-NULL when a remote host
32638 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
32639 output function, so it can be used for all forms of SMTP connection.
32641 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
32642 must start with an appropriate response code: 550 if you are going to return
32643 LOCAL_SCAN_REJECT, 451 if you are going to return
32644 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
32645 initial lines of a multi-line response, the code must be followed by a hyphen
32646 to indicate that the line is not the final response line. You must also ensure
32647 that the lines you write terminate with CRLF. For example:
32649 smtp_printf("550-this is some extra info\r\n");
32650 return LOCAL_SCAN_REJECT;
32652 Note that you can also create multi-line responses by including newlines in
32653 the data returned via the &%return_text%& argument. The added value of using
32654 &'smtp_printf()'& is that, for instance, you could introduce delays between
32655 multiple output lines.
32657 The &'smtp_printf()'& function does not return any error indication, because it
32658 does not automatically flush pending output, and therefore does not test
32659 the state of the stream. (In the main code of Exim, flushing and error
32660 detection is done when Exim is ready for the next SMTP input command.) If
32661 you want to flush the output and check for an error (for example, the
32662 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
32663 arguments. It flushes the output stream, and returns a non-zero value if there
32666 .vitem &*void&~*store_get(int)*&
32667 This function accesses Exim's internal store (memory) manager. It gets a new
32668 chunk of memory whose size is given by the argument. Exim bombs out if it ever
32669 runs out of memory. See the next section for a discussion of memory handling.
32671 .vitem &*void&~*store_get_perm(int)*&
32672 This function is like &'store_get()'&, but it always gets memory from the
32673 permanent pool. See the next section for a discussion of memory handling.
32675 .vitem &*uschar&~*string_copy(uschar&~*string)*&
32678 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
32681 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
32682 These three functions create strings using Exim's dynamic memory facilities.
32683 The first makes a copy of an entire string. The second copies up to a maximum
32684 number of characters, indicated by the second argument. The third uses a format
32685 and insertion arguments to create a new string. In each case, the result is a
32686 pointer to a new string in the current memory pool. See the next section for
32692 .section "More about Exim's memory handling" "SECTmemhanloc"
32693 .cindex "&[local_scan()]& function" "memory handling"
32694 No function is provided for freeing memory, because that is never needed.
32695 The dynamic memory that Exim uses when receiving a message is automatically
32696 recycled if another message is received by the same process (this applies only
32697 to incoming SMTP connections &-- other input methods can supply only one
32698 message at a time). After receiving the last message, a reception process
32701 Because it is recycled, the normal dynamic memory cannot be used for holding
32702 data that must be preserved over a number of incoming messages on the same SMTP
32703 connection. However, Exim in fact uses two pools of dynamic memory; the second
32704 one is not recycled, and can be used for this purpose.
32706 If you want to allocate memory that remains available for subsequent messages
32707 in the same SMTP connection, you should set
32709 store_pool = POOL_PERM
32711 before calling the function that does the allocation. There is no need to
32712 restore the value if you do not need to; however, if you do want to revert to
32713 the normal pool, you can either restore the previous value of &%store_pool%& or
32714 set it explicitly to POOL_MAIN.
32716 The pool setting applies to all functions that get dynamic memory, including
32717 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
32718 There is also a convenience function called &'store_get_perm()'& that gets a
32719 block of memory from the permanent pool while preserving the value of
32726 . ////////////////////////////////////////////////////////////////////////////
32727 . ////////////////////////////////////////////////////////////////////////////
32729 .chapter "System-wide message filtering" "CHAPsystemfilter"
32730 .scindex IIDsysfil1 "filter" "system filter"
32731 .scindex IIDsysfil2 "filtering all mail"
32732 .scindex IIDsysfil3 "system filter"
32733 The previous chapters (on ACLs and the local scan function) describe checks
32734 that can be applied to messages before they are accepted by a host. There is
32735 also a mechanism for checking messages once they have been received, but before
32736 they are delivered. This is called the &'system filter'&.
32738 The system filter operates in a similar manner to users' filter files, but it
32739 is run just once per message (however many recipients the message has).
32740 It should not normally be used as a substitute for routing, because &%deliver%&
32741 commands in a system router provide new envelope recipient addresses.
32742 The system filter must be an Exim filter. It cannot be a Sieve filter.
32744 The system filter is run at the start of a delivery attempt, before any routing
32745 is done. If a message fails to be completely delivered at the first attempt,
32746 the system filter is run again at the start of every retry.
32747 If you want your filter to do something only once per message, you can make use
32748 of the &%first_delivery%& condition in an &%if%& command in the filter to
32749 prevent it happening on retries.
32751 .vindex "&$domain$&"
32752 .vindex "&$local_part$&"
32753 &*Warning*&: Because the system filter runs just once, variables that are
32754 specific to individual recipient addresses, such as &$local_part$& and
32755 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
32756 you want to run a centrally-specified filter for each recipient address
32757 independently, you can do so by setting up a suitable &(redirect)& router, as
32758 described in section &<<SECTperaddfil>>& below.
32761 .section "Specifying a system filter" "SECID212"
32762 .cindex "uid (user id)" "system filter"
32763 .cindex "gid (group id)" "system filter"
32764 The name of the file that contains the system filter must be specified by
32765 setting &%system_filter%&. If you want the filter to run under a uid and gid
32766 other than root, you must also set &%system_filter_user%& and
32767 &%system_filter_group%& as appropriate. For example:
32769 system_filter = /etc/mail/exim.filter
32770 system_filter_user = exim
32772 If a system filter generates any deliveries directly to files or pipes (via the
32773 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
32774 specified by setting &%system_filter_file_transport%& and
32775 &%system_filter_pipe_transport%&, respectively. Similarly,
32776 &%system_filter_reply_transport%& must be set to handle any messages generated
32777 by the &%reply%& command.
32780 .section "Testing a system filter" "SECID213"
32781 You can run simple tests of a system filter in the same way as for a user
32782 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
32783 are permitted only in system filters are recognized.
32785 If you want to test the combined effect of a system filter and a user filter,
32786 you can use both &%-bF%& and &%-bf%& on the same command line.
32790 .section "Contents of a system filter" "SECID214"
32791 The language used to specify system filters is the same as for users' filter
32792 files. It is described in the separate end-user document &'Exim's interface to
32793 mail filtering'&. However, there are some additional features that are
32794 available only in system filters; these are described in subsequent sections.
32795 If they are encountered in a user's filter file or when testing with &%-bf%&,
32798 .cindex "frozen messages" "manual thaw; testing in filter"
32799 There are two special conditions which, though available in users' filter
32800 files, are designed for use in system filters. The condition &%first_delivery%&
32801 is true only for the first attempt at delivering a message, and
32802 &%manually_thawed%& is true only if the message has been frozen, and
32803 subsequently thawed by an admin user. An explicit forced delivery counts as a
32804 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
32806 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
32807 specify an &"unseen"& (non-significant) delivery, and that delivery does not
32808 succeed, it will not be tried again.
32809 If you want Exim to retry an unseen delivery until it succeeds, you should
32810 arrange to set it up every time the filter runs.
32812 When a system filter finishes running, the values of the variables &$n0$& &--
32813 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
32814 users' filter files. Thus a system filter can, for example, set up &"scores"&
32815 to which users' filter files can refer.
32819 .section "Additional variable for system filters" "SECID215"
32820 .vindex "&$recipients$&"
32821 The expansion variable &$recipients$&, containing a list of all the recipients
32822 of the message (separated by commas and white space), is available in system
32823 filters. It is not available in users' filters for privacy reasons.
32827 .section "Defer, freeze, and fail commands for system filters" "SECID216"
32828 .cindex "freezing messages"
32829 .cindex "message" "freezing"
32830 .cindex "message" "forced failure"
32831 .cindex "&%fail%&" "in system filter"
32832 .cindex "&%freeze%& in system filter"
32833 .cindex "&%defer%& in system filter"
32834 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
32835 always available in system filters, but are not normally enabled in users'
32836 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
32837 for the &(redirect)& router.) These commands can optionally be followed by the
32838 word &%text%& and a string containing an error message, for example:
32840 fail text "this message looks like spam to me"
32842 The keyword &%text%& is optional if the next character is a double quote.
32844 The &%defer%& command defers delivery of the original recipients of the
32845 message. The &%fail%& command causes all the original recipients to be failed,
32846 and a bounce message to be created. The &%freeze%& command suspends all
32847 delivery attempts for the original recipients. In all cases, any new deliveries
32848 that are specified by the filter are attempted as normal after the filter has
32851 The &%freeze%& command is ignored if the message has been manually unfrozen and
32852 not manually frozen since. This means that automatic freezing by a system
32853 filter can be used as a way of checking out suspicious messages. If a message
32854 is found to be all right, manually unfreezing it allows it to be delivered.
32856 .cindex "log" "&%fail%& command log line"
32857 .cindex "&%fail%&" "log line; reducing"
32858 The text given with a fail command is used as part of the bounce message as
32859 well as being written to the log. If the message is quite long, this can fill
32860 up a lot of log space when such failures are common. To reduce the size of the
32861 log message, Exim interprets the text in a special way if it starts with the
32862 two characters &`<<`& and contains &`>>`& later. The text between these two
32863 strings is written to the log, and the rest of the text is used in the bounce
32864 message. For example:
32866 fail "<<filter test 1>>Your message is rejected \
32867 because it contains attachments that we are \
32868 not prepared to receive."
32871 .cindex "loop" "caused by &%fail%&"
32872 Take great care with the &%fail%& command when basing the decision to fail on
32873 the contents of the message, because the bounce message will of course include
32874 the contents of the original message and will therefore trigger the &%fail%&
32875 command again (causing a mail loop) unless steps are taken to prevent this.
32876 Testing the &%error_message%& condition is one way to prevent this. You could
32879 if $message_body contains "this is spam" and not error_message
32880 then fail text "spam is not wanted here" endif
32882 though of course that might let through unwanted bounce messages. The
32883 alternative is clever checking of the body and/or headers to detect bounces
32884 generated by the filter.
32886 The interpretation of a system filter file ceases after a
32888 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
32889 set up earlier in the filter file are honoured, so you can use a sequence such
32895 to send a specified message when the system filter is freezing (or deferring or
32896 failing) a message. The normal deliveries for the message do not, of course,
32901 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
32902 .cindex "header lines" "adding; in system filter"
32903 .cindex "header lines" "removing; in system filter"
32904 .cindex "filter" "header lines; adding/removing"
32905 Two filter commands that are available only in system filters are:
32907 headers add <string>
32908 headers remove <string>
32910 The argument for the &%headers add%& is a string that is expanded and then
32911 added to the end of the message's headers. It is the responsibility of the
32912 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
32913 space is ignored, and if the string is otherwise empty, or if the expansion is
32914 forced to fail, the command has no effect.
32916 You can use &"\n"& within the string, followed by white space, to specify
32917 continued header lines. More than one header may be added in one command by
32918 including &"\n"& within the string without any following white space. For
32921 headers add "X-header-1: ....\n \
32922 continuation of X-header-1 ...\n\
32925 Note that the header line continuation white space after the first newline must
32926 be placed before the backslash that continues the input string, because white
32927 space after input continuations is ignored.
32929 The argument for &%headers remove%& is a colon-separated list of header names.
32930 This command applies only to those headers that are stored with the message;
32931 those that are added at delivery time (such as &'Envelope-To:'& and
32932 &'Return-Path:'&) cannot be removed by this means. If there is more than one
32933 header with the same name, they are all removed.
32935 The &%headers%& command in a system filter makes an immediate change to the set
32936 of header lines that was received with the message (with possible additions
32937 from ACL processing). Subsequent commands in the system filter operate on the
32938 modified set, which also forms the basis for subsequent message delivery.
32939 Unless further modified during routing or transporting, this set of headers is
32940 used for all recipients of the message.
32942 During routing and transporting, the variables that refer to the contents of
32943 header lines refer only to those lines that are in this set. Thus, header lines
32944 that are added by a system filter are visible to users' filter files and to all
32945 routers and transports. This contrasts with the manipulation of header lines by
32946 routers and transports, which is not immediate, but which instead is saved up
32947 until the message is actually being written (see section
32948 &<<SECTheadersaddrem>>&).
32950 If the message is not delivered at the first attempt, header lines that were
32951 added by the system filter are stored with the message, and so are still
32952 present at the next delivery attempt. Header lines that were removed are still
32953 present, but marked &"deleted"& so that they are not transported with the
32954 message. For this reason, it is usual to make the &%headers%& command
32955 conditional on &%first_delivery%& so that the set of header lines is not
32956 modified more than once.
32958 Because header modification in a system filter acts immediately, you have to
32959 use an indirect approach if you want to modify the contents of a header line.
32962 headers add "Old-Subject: $h_subject:"
32963 headers remove "Subject"
32964 headers add "Subject: new subject (was: $h_old-subject:)"
32965 headers remove "Old-Subject"
32970 .section "Setting an errors address in a system filter" "SECID217"
32971 .cindex "envelope sender"
32972 In a system filter, if a &%deliver%& command is followed by
32974 errors_to <some address>
32976 in order to change the envelope sender (and hence the error reporting) for that
32977 delivery, any address may be specified. (In a user filter, only the current
32978 user's address can be set.) For example, if some mail is being monitored, you
32981 unseen deliver monitor@spying.example errors_to root@local.example
32983 to take a copy which would not be sent back to the normal error reporting
32984 address if its delivery failed.
32988 .section "Per-address filtering" "SECTperaddfil"
32989 .vindex "&$domain$&"
32990 .vindex "&$local_part$&"
32991 In contrast to the system filter, which is run just once per message for each
32992 delivery attempt, it is also possible to set up a system-wide filtering
32993 operation that runs once for each recipient address. In this case, variables
32994 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
32995 filter file could be made dependent on them. This is an example of a router
32996 which implements such a filter:
33001 domains = +local_domains
33002 file = /central/filters/$local_part
33007 The filter is run in a separate process under its own uid. Therefore, either
33008 &%check_local_user%& must be set (as above), in which case the filter is run as
33009 the local user, or the &%user%& option must be used to specify which user to
33010 use. If both are set, &%user%& overrides.
33012 Care should be taken to ensure that none of the commands in the filter file
33013 specify a significant delivery if the message is to go on to be delivered to
33014 its intended recipient. The router will not then claim to have dealt with the
33015 address, so it will be passed on to subsequent routers to be delivered in the
33017 .ecindex IIDsysfil1
33018 .ecindex IIDsysfil2
33019 .ecindex IIDsysfil3
33026 . ////////////////////////////////////////////////////////////////////////////
33027 . ////////////////////////////////////////////////////////////////////////////
33029 .chapter "Message processing" "CHAPmsgproc"
33030 .scindex IIDmesproc "message" "general processing"
33031 Exim performs various transformations on the sender and recipient addresses of
33032 all messages that it handles, and also on the messages' header lines. Some of
33033 these are optional and configurable, while others always take place. All of
33034 this processing, except rewriting as a result of routing, and the addition or
33035 removal of header lines while delivering, happens when a message is received,
33036 before it is placed on Exim's queue.
33038 Some of the automatic processing takes place by default only for
33039 &"locally-originated"& messages. This adjective is used to describe messages
33040 that are not received over TCP/IP, but instead are passed to an Exim process on
33041 its standard input. This includes the interactive &"local SMTP"& case that is
33042 set up by the &%-bs%& command line option.
33044 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
33045 or ::1) are not considered to be locally-originated. Exim does not treat the
33046 loopback interface specially in any way.
33048 If you want the loopback interface to be treated specially, you must ensure
33049 that there are appropriate entries in your ACLs.
33054 .section "Submission mode for non-local messages" "SECTsubmodnon"
33055 .cindex "message" "submission"
33056 .cindex "submission mode"
33057 Processing that happens automatically for locally-originated messages (unless
33058 &%suppress_local_fixups%& is set) can also be requested for messages that are
33059 received over TCP/IP. The term &"submission mode"& is used to describe this
33060 state. Submission mode is set by the modifier
33062 control = submission
33064 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
33065 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
33066 a local submission, and is normally used when the source of the message is
33067 known to be an MUA running on a client host (as opposed to an MTA). For
33068 example, to set submission mode for messages originating on the IPv4 loopback
33069 interface, you could include the following in the MAIL ACL:
33071 warn hosts = 127.0.0.1
33072 control = submission
33074 .cindex "&%sender_retain%& submission option"
33075 There are some options that can be used when setting submission mode. A slash
33076 is used to separate options. For example:
33078 control = submission/sender_retain
33080 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
33081 true and &%local_from_check%& false for the current incoming message. The first
33082 of these allows an existing &'Sender:'& header in the message to remain, and
33083 the second suppresses the check to ensure that &'From:'& matches the
33084 authenticated sender. With this setting, Exim still fixes up messages by adding
33085 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
33086 attempt to check sender authenticity in header lines.
33088 When &%sender_retain%& is not set, a submission mode setting may specify a
33089 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
33092 control = submission/domain=some.domain
33094 The domain may be empty. How this value is used is described in sections
33095 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
33096 that allows you to specify the user's full name for inclusion in a created
33097 &'Sender:'& or &'From:'& header line. For example:
33099 accept authenticated = *
33100 control = submission/domain=wonderland.example/\
33101 name=${lookup {$authenticated_id} \
33102 lsearch {/etc/exim/namelist}}
33104 Because the name may contain any characters, including slashes, the &%name%&
33105 option must be given last. The remainder of the string is used as the name. For
33106 the example above, if &_/etc/exim/namelist_& contains:
33108 bigegg: Humpty Dumpty
33110 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
33113 Sender: Humpty Dumpty <bigegg@wonderland.example>
33115 .cindex "return path" "in submission mode"
33116 By default, submission mode forces the return path to the same address as is
33117 used to create the &'Sender:'& header. However, if &%sender_retain%& is
33118 specified, the return path is also left unchanged.
33120 &*Note*&: The changes caused by submission mode take effect after the predata
33121 ACL. This means that any sender checks performed before the fix-ups use the
33122 untrusted sender address specified by the user, not the trusted sender address
33123 specified by submission mode. Although this might be slightly unexpected, it
33124 does mean that you can configure ACL checks to spot that a user is trying to
33125 spoof another's address.
33127 .section "Line endings" "SECTlineendings"
33128 .cindex "line endings"
33129 .cindex "carriage return"
33131 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
33132 linefeed) is the line ending for messages transmitted over the Internet using
33133 SMTP over TCP/IP. However, within individual operating systems, different
33134 conventions are used. For example, Unix-like systems use just LF, but others
33135 use CRLF or just CR.
33137 Exim was designed for Unix-like systems, and internally, it stores messages
33138 using the system's convention of a single LF as a line terminator. When
33139 receiving a message, all line endings are translated to this standard format.
33140 Originally, it was thought that programs that passed messages directly to an
33141 MTA within an operating system would use that system's convention. Experience
33142 has shown that this is not the case; for example, there are Unix applications
33143 that use CRLF in this circumstance. For this reason, and for compatibility with
33144 other MTAs, the way Exim handles line endings for all messages is now as
33148 LF not preceded by CR is treated as a line ending.
33150 CR is treated as a line ending; if it is immediately followed by LF, the LF
33153 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
33154 nor a local message in the state where a line containing only a dot is a
33157 If a bare CR is encountered within a header line, an extra space is added after
33158 the line terminator so as not to end the header line. The reasoning behind this
33159 is that bare CRs in header lines are most likely either to be mistakes, or
33160 people trying to play silly games.
33162 If the first header line received in a message ends with CRLF, a subsequent
33163 bare LF in a header line is treated in the same way as a bare CR in a header
33171 .section "Unqualified addresses" "SECID218"
33172 .cindex "unqualified addresses"
33173 .cindex "address" "qualification"
33174 By default, Exim expects every envelope address it receives from an external
33175 host to be fully qualified. Unqualified addresses cause negative responses to
33176 SMTP commands. However, because SMTP is used as a means of transporting
33177 messages from MUAs running on personal workstations, there is sometimes a
33178 requirement to accept unqualified addresses from specific hosts or IP networks.
33180 Exim has two options that separately control which hosts may send unqualified
33181 sender or recipient addresses in SMTP commands, namely
33182 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
33183 cases, if an unqualified address is accepted, it is qualified by adding the
33184 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
33186 .oindex "&%qualify_domain%&"
33187 .oindex "&%qualify_recipient%&"
33188 Unqualified addresses in header lines are automatically qualified for messages
33189 that are locally originated, unless the &%-bnq%& option is given on the command
33190 line. For messages received over SMTP, unqualified addresses in header lines
33191 are qualified only if unqualified addresses are permitted in SMTP commands. In
33192 other words, such qualification is also controlled by
33193 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
33198 .section "The UUCP From line" "SECID219"
33199 .cindex "&""From""& line"
33200 .cindex "UUCP" "&""From""& line"
33201 .cindex "sender" "address"
33202 .oindex "&%uucp_from_pattern%&"
33203 .oindex "&%uucp_from_sender%&"
33204 .cindex "envelope sender"
33205 .cindex "Sendmail compatibility" "&""From""& line"
33206 Messages that have come from UUCP (and some other applications) often begin
33207 with a line containing the envelope sender and a timestamp, following the word
33208 &"From"&. Examples of two common formats are:
33210 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
33211 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
33213 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
33214 Exim recognizes such lines at the start of messages that are submitted to it
33215 via the command line (that is, on the standard input). It does not recognize
33216 such lines in incoming SMTP messages, unless the sending host matches
33217 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
33218 and &%ignore_fromline_local%& is set. The recognition is controlled by a
33219 regular expression that is defined by the &%uucp_from_pattern%& option, whose
33220 default value matches the two common cases shown above and puts the address
33221 that follows &"From"& into &$1$&.
33223 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
33224 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
33225 a trusted user, the message's sender address is constructed by expanding the
33226 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
33227 then parsed as an RFC 2822 address. If there is no domain, the local part is
33228 qualified with &%qualify_domain%& unless it is the empty string. However, if
33229 the command line &%-f%& option is used, it overrides the &"From"& line.
33231 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
33232 sender address is not changed. This is also the case for incoming SMTP messages
33233 that are permitted to contain &"From"& lines.
33235 Only one &"From"& line is recognized. If there is more than one, the second is
33236 treated as a data line that starts the body of the message, as it is not valid
33237 as a header line. This also happens if a &"From"& line is present in an
33238 incoming SMTP message from a source that is not permitted to send them.
33242 .section "Resent- header lines" "SECID220"
33243 .cindex "&%Resent-%& header lines"
33244 RFC 2822 makes provision for sets of header lines starting with the string
33245 &`Resent-`& to be added to a message when it is resent by the original
33246 recipient to somebody else. These headers are &'Resent-Date:'&,
33247 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
33248 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
33251 &'Resent fields are strictly informational. They MUST NOT be used in the normal
33252 processing of replies or other such automatic actions on messages.'&
33255 This leaves things a bit vague as far as other processing actions such as
33256 address rewriting are concerned. Exim treats &%Resent-%& header lines as
33260 A &'Resent-From:'& line that just contains the login id of the submitting user
33261 is automatically rewritten in the same way as &'From:'& (see below).
33263 If there's a rewriting rule for a particular header line, it is also applied to
33264 &%Resent-%& header lines of the same type. For example, a rule that rewrites
33265 &'From:'& also rewrites &'Resent-From:'&.
33267 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
33270 For a locally-submitted message,
33271 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
33272 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
33273 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
33274 included in log lines in this case.
33276 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
33277 &%Resent-%& header lines are present.
33283 .section "The Auto-Submitted: header line" "SECID221"
33284 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
33285 includes the header line:
33287 Auto-Submitted: auto-replied
33290 .section "The Bcc: header line" "SECID222"
33291 .cindex "&'Bcc:'& header line"
33292 If Exim is called with the &%-t%& option, to take recipient addresses from a
33293 message's header, it removes any &'Bcc:'& header line that may exist (after
33294 extracting its addresses). If &%-t%& is not present on the command line, any
33295 existing &'Bcc:'& is not removed.
33298 .section "The Date: header line" "SECID223"
33299 .cindex "&'Date:'& header line"
33300 If a locally-generated or submission-mode message has no &'Date:'& header line,
33301 Exim adds one, using the current date and time, unless the
33302 &%suppress_local_fixups%& control has been specified.
33304 .section "The Delivery-date: header line" "SECID224"
33305 .cindex "&'Delivery-date:'& header line"
33306 .oindex "&%delivery_date_remove%&"
33307 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
33308 set. Exim can be configured to add them to the final delivery of messages. (See
33309 the generic &%delivery_date_add%& transport option.) They should not be present
33310 in messages in transit. If the &%delivery_date_remove%& configuration option is
33311 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
33315 .section "The Envelope-to: header line" "SECID225"
33316 .cindex "&'Envelope-to:'& header line"
33317 .oindex "&%envelope_to_remove%&"
33318 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
33319 Exim can be configured to add them to the final delivery of messages. (See the
33320 generic &%envelope_to_add%& transport option.) They should not be present in
33321 messages in transit. If the &%envelope_to_remove%& configuration option is set
33322 (the default), Exim removes &'Envelope-to:'& header lines from incoming
33326 .section "The From: header line" "SECTthefrohea"
33327 .cindex "&'From:'& header line"
33328 .cindex "Sendmail compatibility" "&""From""& line"
33329 .cindex "message" "submission"
33330 .cindex "submission mode"
33331 If a submission-mode message does not contain a &'From:'& header line, Exim
33332 adds one if either of the following conditions is true:
33335 The envelope sender address is not empty (that is, this is not a bounce
33336 message). The added header line copies the envelope sender address.
33338 .vindex "&$authenticated_id$&"
33339 The SMTP session is authenticated and &$authenticated_id$& is not empty.
33341 .vindex "&$qualify_domain$&"
33342 If no domain is specified by the submission control, the local part is
33343 &$authenticated_id$& and the domain is &$qualify_domain$&.
33345 If a non-empty domain is specified by the submission control, the local
33346 part is &$authenticated_id$&, and the domain is the specified domain.
33348 If an empty domain is specified by the submission control,
33349 &$authenticated_id$& is assumed to be the complete address.
33353 A non-empty envelope sender takes precedence.
33355 If a locally-generated incoming message does not contain a &'From:'& header
33356 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
33357 containing the sender's address. The calling user's login name and full name
33358 are used to construct the address, as described in section &<<SECTconstr>>&.
33359 They are obtained from the password data by calling &[getpwuid()]& (but see the
33360 &%unknown_login%& configuration option). The address is qualified with
33361 &%qualify_domain%&.
33363 For compatibility with Sendmail, if an incoming, non-SMTP message has a
33364 &'From:'& header line containing just the unqualified login name of the calling
33365 user, this is replaced by an address containing the user's login name and full
33366 name as described in section &<<SECTconstr>>&.
33369 .section "The Message-ID: header line" "SECID226"
33370 .cindex "&'Message-ID:'& header line"
33371 .cindex "message" "submission"
33372 .oindex "&%message_id_header_text%&"
33373 If a locally-generated or submission-mode incoming message does not contain a
33374 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
33375 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
33376 to the message. If there are any &'Resent-:'& headers in the message, it
33377 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
33378 message id, preceded by the letter E to ensure it starts with a letter, and
33379 followed by @ and the primary host name. Additional information can be included
33380 in this header line by setting the &%message_id_header_text%& and/or
33381 &%message_id_header_domain%& options.
33384 .section "The Received: header line" "SECID227"
33385 .cindex "&'Received:'& header line"
33386 A &'Received:'& header line is added at the start of every message. The
33387 contents are defined by the &%received_header_text%& configuration option, and
33388 Exim automatically adds a semicolon and a timestamp to the configured string.
33390 The &'Received:'& header is generated as soon as the message's header lines
33391 have been received. At this stage, the timestamp in the &'Received:'& header
33392 line is the time that the message started to be received. This is the value
33393 that is seen by the DATA ACL and by the &[local_scan()]& function.
33395 Once a message is accepted, the timestamp in the &'Received:'& header line is
33396 changed to the time of acceptance, which is (apart from a small delay while the
33397 -H spool file is written) the earliest time at which delivery could start.
33400 .section "The References: header line" "SECID228"
33401 .cindex "&'References:'& header line"
33402 Messages created by the &(autoreply)& transport include a &'References:'&
33403 header line. This is constructed according to the rules that are described in
33404 section 3.64 of RFC 2822 (which states that replies should contain such a
33405 header line), and section 3.14 of RFC 3834 (which states that automatic
33406 responses are not different in this respect). However, because some mail
33407 processing software does not cope well with very long header lines, no more
33408 than 12 message IDs are copied from the &'References:'& header line in the
33409 incoming message. If there are more than 12, the first one and then the final
33410 11 are copied, before adding the message ID of the incoming message.
33414 .section "The Return-path: header line" "SECID229"
33415 .cindex "&'Return-path:'& header line"
33416 .oindex "&%return_path_remove%&"
33417 &'Return-path:'& header lines are defined as something an MTA may insert when
33418 it does the final delivery of messages. (See the generic &%return_path_add%&
33419 transport option.) Therefore, they should not be present in messages in
33420 transit. If the &%return_path_remove%& configuration option is set (the
33421 default), Exim removes &'Return-path:'& header lines from incoming messages.
33425 .section "The Sender: header line" "SECTthesenhea"
33426 .cindex "&'Sender:'& header line"
33427 .cindex "message" "submission"
33428 For a locally-originated message from an untrusted user, Exim may remove an
33429 existing &'Sender:'& header line, and it may add a new one. You can modify
33430 these actions by setting the &%local_sender_retain%& option true, the
33431 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
33434 When a local message is received from an untrusted user and
33435 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
33436 control has not been set, a check is made to see if the address given in the
33437 &'From:'& header line is the correct (local) sender of the message. The address
33438 that is expected has the login name as the local part and the value of
33439 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
33440 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
33441 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
33442 line is added to the message.
33444 If you set &%local_from_check%& false, this checking does not occur. However,
33445 the removal of an existing &'Sender:'& line still happens, unless you also set
33446 &%local_sender_retain%& to be true. It is not possible to set both of these
33447 options true at the same time.
33449 .cindex "submission mode"
33450 By default, no processing of &'Sender:'& header lines is done for messages
33451 received over TCP/IP or for messages submitted by trusted users. However, when
33452 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
33453 not specified on the submission control, the following processing takes place:
33455 .vindex "&$authenticated_id$&"
33456 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
33457 authenticated, and &$authenticated_id$& is not empty, a sender address is
33458 created as follows:
33461 .vindex "&$qualify_domain$&"
33462 If no domain is specified by the submission control, the local part is
33463 &$authenticated_id$& and the domain is &$qualify_domain$&.
33465 If a non-empty domain is specified by the submission control, the local part
33466 is &$authenticated_id$&, and the domain is the specified domain.
33468 If an empty domain is specified by the submission control,
33469 &$authenticated_id$& is assumed to be the complete address.
33472 This address is compared with the address in the &'From:'& header line. If they
33473 are different, a &'Sender:'& header line containing the created address is
33474 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
33475 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
33477 .cindex "return path" "created from &'Sender:'&"
33478 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
33479 the message (the envelope sender address) is changed to be the same address,
33480 except in the case of submission mode when &%sender_retain%& is specified.
33484 .section "Adding and removing header lines in routers and transports" &&&
33485 "SECTheadersaddrem"
33486 .cindex "header lines" "adding; in router or transport"
33487 .cindex "header lines" "removing; in router or transport"
33488 When a message is delivered, the addition and removal of header lines can be
33489 specified in a system filter, or on any of the routers and transports that
33490 process the message. Section &<<SECTaddremheasys>>& contains details about
33491 modifying headers in a system filter. Header lines can also be added in an ACL
33492 as a message is received (see section &<<SECTaddheadacl>>&).
33494 In contrast to what happens in a system filter, header modifications that are
33495 specified on routers and transports apply only to the particular recipient
33496 addresses that are being processed by those routers and transports. These
33497 changes do not actually take place until a copy of the message is being
33498 transported. Therefore, they do not affect the basic set of header lines, and
33499 they do not affect the values of the variables that refer to header lines.
33501 &*Note*&: In particular, this means that any expansions in the configuration of
33502 the transport cannot refer to the modified header lines, because such
33503 expansions all occur before the message is actually transported.
33505 For both routers and transports, the argument of a &%headers_add%&
33506 option must be in the form of one or more RFC 2822 header lines, separated by
33507 newlines (coded as &"\n"&). For example:
33509 headers_add = X-added-header: added by $primary_hostname\n\
33510 X-added-second: another added header line
33512 Exim does not check the syntax of these added header lines.
33514 Multiple &%headers_add%& options for a single router or transport can be
33515 specified; the values will append to a single list of header lines.
33516 Each header-line is separately expanded.
33518 The argument of a &%headers_remove%& option must consist of a colon-separated
33519 list of header names. This is confusing, because header names themselves are
33520 often terminated by colons. In this case, the colons are the list separators,
33521 not part of the names. For example:
33523 headers_remove = return-receipt-to:acknowledge-to
33526 Multiple &%headers_remove%& options for a single router or transport can be
33527 specified; the arguments will append to a single header-names list.
33528 Each item is separately expanded.
33529 Note that colons in complex expansions which are used to
33530 form all or part of a &%headers_remove%& list
33531 will act as list separators.
33533 When &%headers_add%& or &%headers_remove%& is specified on a router,
33534 items are expanded at routing time,
33535 and then associated with all addresses that are
33536 accepted by that router, and also with any new addresses that it generates. If
33537 an address passes through several routers as a result of aliasing or
33538 forwarding, the changes are cumulative.
33540 .oindex "&%unseen%&"
33541 However, this does not apply to multiple routers that result from the use of
33542 the &%unseen%& option. Any header modifications that were specified by the
33543 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
33545 Addresses that end up with different &%headers_add%& or &%headers_remove%&
33546 settings cannot be delivered together in a batch, so a transport is always
33547 dealing with a set of addresses that have the same header-processing
33550 The transport starts by writing the original set of header lines that arrived
33551 with the message, possibly modified by the system filter. As it writes out
33552 these lines, it consults the list of header names that were attached to the
33553 recipient address(es) by &%headers_remove%& options in routers, and it also
33554 consults the transport's own &%headers_remove%& option. Header lines whose
33555 names are on either of these lists are not written out. If there are multiple
33556 instances of any listed header, they are all skipped.
33558 After the remaining original header lines have been written, new header
33559 lines that were specified by routers' &%headers_add%& options are written, in
33560 the order in which they were attached to the address. These are followed by any
33561 header lines specified by the transport's &%headers_add%& option.
33563 This way of handling header line modifications in routers and transports has
33564 the following consequences:
33567 The original set of header lines, possibly modified by the system filter,
33568 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
33569 to it, at all times.
33571 Header lines that are added by a router's
33572 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
33573 expansion syntax in subsequent routers or the transport.
33575 Conversely, header lines that are specified for removal by &%headers_remove%&
33576 in a router remain visible to subsequent routers and the transport.
33578 Headers added to an address by &%headers_add%& in a router cannot be removed by
33579 a later router or by a transport.
33581 An added header can refer to the contents of an original header that is to be
33582 removed, even it has the same name as the added header. For example:
33584 headers_remove = subject
33585 headers_add = Subject: new subject (was: $h_subject:)
33589 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
33590 for a &(redirect)& router that has the &%one_time%& option set.
33596 .section "Constructed addresses" "SECTconstr"
33597 .cindex "address" "constructed"
33598 .cindex "constructed address"
33599 When Exim constructs a sender address for a locally-generated message, it uses
33602 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
33606 Zaphod Beeblebrox <zaphod@end.univ.example>
33608 The user name is obtained from the &%-F%& command line option if set, or
33609 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
33610 &"gecos"& field from the password entry. If the &"gecos"& field contains an
33611 ampersand character, this is replaced by the login name with the first letter
33612 upper cased, as is conventional in a number of operating systems. See the
33613 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
33614 The &%unknown_username%& option can be used to specify user names in cases when
33615 there is no password file entry.
33618 In all cases, the user name is made to conform to RFC 2822 by quoting all or
33619 parts of it if necessary. In addition, if it contains any non-printing
33620 characters, it is encoded as described in RFC 2047, which defines a way of
33621 including non-ASCII characters in header lines. The value of the
33622 &%headers_charset%& option specifies the name of the encoding that is used (the
33623 characters are assumed to be in this encoding). The setting of
33624 &%print_topbitchars%& controls whether characters with the top bit set (that
33625 is, with codes greater than 127) count as printing characters or not.
33629 .section "Case of local parts" "SECID230"
33630 .cindex "case of local parts"
33631 .cindex "local part" "case of"
33632 RFC 2822 states that the case of letters in the local parts of addresses cannot
33633 be assumed to be non-significant. Exim preserves the case of local parts of
33634 addresses, but by default it uses a lower-cased form when it is routing,
33635 because on most Unix systems, usernames are in lower case and case-insensitive
33636 routing is required. However, any particular router can be made to use the
33637 original case for local parts by setting the &%caseful_local_part%& generic
33640 .cindex "mixed-case login names"
33641 If you must have mixed-case user names on your system, the best way to proceed,
33642 assuming you want case-independent handling of incoming email, is to set up
33643 your first router to convert incoming local parts in your domains to the
33644 correct case by means of a file lookup. For example:
33648 domains = +local_domains
33649 data = ${lookup{$local_part}cdb\
33650 {/etc/usercased.cdb}{$value}fail}\
33653 For this router, the local part is forced to lower case by the default action
33654 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
33655 up a new local part in the correct case. If you then set &%caseful_local_part%&
33656 on any subsequent routers which process your domains, they will operate on
33657 local parts with the correct case in a case-sensitive manner.
33661 .section "Dots in local parts" "SECID231"
33662 .cindex "dot" "in local part"
33663 .cindex "local part" "dots in"
33664 RFC 2822 forbids empty components in local parts. That is, an unquoted local
33665 part may not begin or end with a dot, nor have two consecutive dots in the
33666 middle. However, it seems that many MTAs do not enforce this, so Exim permits
33667 empty components for compatibility.
33671 .section "Rewriting addresses" "SECID232"
33672 .cindex "rewriting" "addresses"
33673 Rewriting of sender and recipient addresses, and addresses in headers, can
33674 happen automatically, or as the result of configuration options, as described
33675 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
33676 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
33678 Automatic rewriting includes qualification, as mentioned above. The other case
33679 in which it can happen is when an incomplete non-local domain is given. The
33680 routing process may cause this to be expanded into the full domain name. For
33681 example, a header such as
33685 might get rewritten as
33687 To: hare@teaparty.wonderland.fict.example
33689 Rewriting as a result of routing is the one kind of message processing that
33690 does not happen at input time, as it cannot be done until the address has
33693 Strictly, one should not do &'any'& deliveries of a message until all its
33694 addresses have been routed, in case any of the headers get changed as a
33695 result of routing. However, doing this in practice would hold up many
33696 deliveries for unreasonable amounts of time, just because one address could not
33697 immediately be routed. Exim therefore does not delay other deliveries when
33698 routing of one or more addresses is deferred.
33699 .ecindex IIDmesproc
33703 . ////////////////////////////////////////////////////////////////////////////
33704 . ////////////////////////////////////////////////////////////////////////////
33706 .chapter "SMTP processing" "CHAPSMTP"
33707 .scindex IIDsmtpproc1 "SMTP" "processing details"
33708 .scindex IIDsmtpproc2 "LMTP" "processing details"
33709 Exim supports a number of different ways of using the SMTP protocol, and its
33710 LMTP variant, which is an interactive protocol for transferring messages into a
33711 closed mail store application. This chapter contains details of how SMTP is
33712 processed. For incoming mail, the following are available:
33715 SMTP over TCP/IP (Exim daemon or &'inetd'&);
33717 SMTP over the standard input and output (the &%-bs%& option);
33719 Batched SMTP on the standard input (the &%-bS%& option).
33722 For mail delivery, the following are available:
33725 SMTP over TCP/IP (the &(smtp)& transport);
33727 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
33730 LMTP over a pipe to a process running in the local host (the &(lmtp)&
33733 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
33734 the &%use_bsmtp%& option set).
33737 &'Batched SMTP'& is the name for a process in which batches of messages are
33738 stored in or read from files (or pipes), in a format in which SMTP commands are
33739 used to contain the envelope information.
33743 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
33744 .cindex "SMTP" "outgoing over TCP/IP"
33745 .cindex "outgoing SMTP over TCP/IP"
33746 .cindex "LMTP" "over TCP/IP"
33747 .cindex "outgoing LMTP over TCP/IP"
33750 .cindex "SIZE option on MAIL command"
33751 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
33752 The &%protocol%& option selects which protocol is to be used, but the actual
33753 processing is the same in both cases.
33755 If, in response to its EHLO command, Exim is told that the SIZE
33756 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
33757 command. The value of <&'n'&> is the message size plus the value of the
33758 &%size_addition%& option (default 1024) to allow for additions to the message
33759 such as per-transport header lines, or changes made in a
33760 .cindex "transport" "filter"
33761 .cindex "filter" "transport filter"
33762 transport filter. If &%size_addition%& is set negative, the use of SIZE is
33765 If the remote server advertises support for PIPELINING, Exim uses the
33766 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
33767 required for the transaction.
33769 If the remote server advertises support for the STARTTLS command, and Exim
33770 was built to support TLS encryption, it tries to start a TLS session unless the
33771 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
33772 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
33773 is called for verification.
33775 If the remote server advertises support for the AUTH command, Exim scans
33776 the authenticators configuration for any suitable client settings, as described
33777 in chapter &<<CHAPSMTPAUTH>>&.
33779 .cindex "carriage return"
33781 Responses from the remote host are supposed to be terminated by CR followed by
33782 LF. However, there are known to be hosts that do not send CR characters, so in
33783 order to be able to interwork with such hosts, Exim treats LF on its own as a
33786 If a message contains a number of different addresses, all those with the same
33787 characteristics (for example, the same envelope sender) that resolve to the
33788 same set of hosts, in the same order, are sent in a single SMTP transaction,
33789 even if they are for different domains, unless there are more than the setting
33790 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
33791 they are split into groups containing no more than &%max_rcpt%&s addresses
33792 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
33793 in parallel sessions. The order of hosts with identical MX values is not
33794 significant when checking whether addresses can be batched in this way.
33796 When the &(smtp)& transport suffers a temporary failure that is not
33797 message-related, Exim updates its transport-specific database, which contains
33798 records indexed by host name that remember which messages are waiting for each
33799 particular host. It also updates the retry database with new retry times.
33801 .cindex "hints database" "retry keys"
33802 Exim's retry hints are based on host name plus IP address, so if one address of
33803 a multi-homed host is broken, it will soon be skipped most of the time.
33804 See the next section for more detail about error handling.
33806 .cindex "SMTP" "passed connection"
33807 .cindex "SMTP" "batching over TCP/IP"
33808 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
33809 looks in the hints database for the transport to see if there are any queued
33810 messages waiting for the host to which it is connected. If it finds one, it
33811 creates a new Exim process using the &%-MC%& option (which can only be used by
33812 a process running as root or the Exim user) and passes the TCP/IP socket to it
33813 so that it can deliver another message using the same socket. The new process
33814 does only those deliveries that are routed to the connected host, and may in
33815 turn pass the socket on to a third process, and so on.
33817 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
33818 limit the number of messages sent down a single TCP/IP connection.
33820 .cindex "asterisk" "after IP address"
33821 The second and subsequent messages delivered down an existing connection are
33822 identified in the main log by the addition of an asterisk after the closing
33823 square bracket of the IP address.
33828 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
33829 .cindex "error" "in outgoing SMTP"
33830 .cindex "SMTP" "errors in outgoing"
33831 .cindex "host" "error"
33832 Three different kinds of error are recognized for outgoing SMTP: host errors,
33833 message errors, and recipient errors.
33836 .vitem "&*Host errors*&"
33837 A host error is not associated with a particular message or with a
33838 particular recipient of a message. The host errors are:
33841 Connection refused or timed out,
33843 Any error response code on connection,
33845 Any error response code to EHLO or HELO,
33847 Loss of connection at any time, except after &"."&,
33849 I/O errors at any time,
33851 Timeouts during the session, other than in response to MAIL, RCPT or
33852 the &"."& at the end of the data.
33855 For a host error, a permanent error response on connection, or in response to
33856 EHLO, causes all addresses routed to the host to be failed. Any other host
33857 error causes all addresses to be deferred, and retry data to be created for the
33858 host. It is not tried again, for any message, until its retry time arrives. If
33859 the current set of addresses are not all delivered in this run (to some
33860 alternative host), the message is added to the list of those waiting for this
33861 host, so if it is still undelivered when a subsequent successful delivery is
33862 made to the host, it will be sent down the same SMTP connection.
33864 .vitem "&*Message errors*&"
33865 .cindex "message" "error"
33866 A message error is associated with a particular message when sent to a
33867 particular host, but not with a particular recipient of the message. The
33868 message errors are:
33871 Any error response code to MAIL, DATA, or the &"."& that terminates
33874 Timeout after MAIL,
33876 Timeout or loss of connection after the &"."& that terminates the data. A
33877 timeout after the DATA command itself is treated as a host error, as is loss of
33878 connection at any other time.
33881 For a message error, a permanent error response (5&'xx'&) causes all addresses
33882 to be failed, and a delivery error report to be returned to the sender. A
33883 temporary error response (4&'xx'&), or one of the timeouts, causes all
33884 addresses to be deferred. Retry data is not created for the host, but instead,
33885 a retry record for the combination of host plus message id is created. The
33886 message is not added to the list of those waiting for this host. This ensures
33887 that the failing message will not be sent to this host again until the retry
33888 time arrives. However, other messages that are routed to the host are not
33889 affected, so if it is some property of the message that is causing the error,
33890 it will not stop the delivery of other mail.
33892 If the remote host specified support for the SIZE parameter in its response
33893 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
33894 over-large message will cause a message error because the error arrives as a
33897 .vitem "&*Recipient errors*&"
33898 .cindex "recipient" "error"
33899 A recipient error is associated with a particular recipient of a message. The
33900 recipient errors are:
33903 Any error response to RCPT,
33905 Timeout after RCPT.
33908 For a recipient error, a permanent error response (5&'xx'&) causes the
33909 recipient address to be failed, and a bounce message to be returned to the
33910 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
33911 address to be deferred, and routing retry data to be created for it. This is
33912 used to delay processing of the address in subsequent queue runs, until its
33913 routing retry time arrives. This applies to all messages, but because it
33914 operates only in queue runs, one attempt will be made to deliver a new message
33915 to the failing address before the delay starts to operate. This ensures that,
33916 if the failure is really related to the message rather than the recipient
33917 (&"message too big for this recipient"& is a possible example), other messages
33918 have a chance of getting delivered. If a delivery to the address does succeed,
33919 the retry information gets cleared, so all stuck messages get tried again, and
33920 the retry clock is reset.
33922 The message is not added to the list of those waiting for this host. Use of the
33923 host for other messages is unaffected, and except in the case of a timeout,
33924 other recipients are processed independently, and may be successfully delivered
33925 in the current SMTP session. After a timeout it is of course impossible to
33926 proceed with the session, so all addresses get deferred. However, those other
33927 than the one that failed do not suffer any subsequent retry delays. Therefore,
33928 if one recipient is causing trouble, the others have a chance of getting
33929 through when a subsequent delivery attempt occurs before the failing
33930 recipient's retry time.
33933 In all cases, if there are other hosts (or IP addresses) available for the
33934 current set of addresses (for example, from multiple MX records), they are
33935 tried in this run for any undelivered addresses, subject of course to their
33936 own retry data. In other words, recipient error retry data does not take effect
33937 until the next delivery attempt.
33939 Some hosts have been observed to give temporary error responses to every
33940 MAIL command at certain times (&"insufficient space"& has been seen). It
33941 would be nice if such circumstances could be recognized, and defer data for the
33942 host itself created, but this is not possible within the current Exim design.
33943 What actually happens is that retry data for every (host, message) combination
33946 The reason that timeouts after MAIL and RCPT are treated specially is that
33947 these can sometimes arise as a result of the remote host's verification
33948 procedures. Exim makes this assumption, and treats them as if a temporary error
33949 response had been received. A timeout after &"."& is treated specially because
33950 it is known that some broken implementations fail to recognize the end of the
33951 message if the last character of the last line is a binary zero. Thus, it is
33952 helpful to treat this case as a message error.
33954 Timeouts at other times are treated as host errors, assuming a problem with the
33955 host, or the connection to it. If a timeout after MAIL, RCPT,
33956 or &"."& is really a connection problem, the assumption is that at the next try
33957 the timeout is likely to occur at some other point in the dialogue, causing it
33958 then to be treated as a host error.
33960 There is experimental evidence that some MTAs drop the connection after the
33961 terminating &"."& if they do not like the contents of the message for some
33962 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
33963 should be given. That is why Exim treats this case as a message rather than a
33964 host error, in order not to delay other messages to the same host.
33969 .section "Incoming SMTP messages over TCP/IP" "SECID233"
33970 .cindex "SMTP" "incoming over TCP/IP"
33971 .cindex "incoming SMTP over TCP/IP"
33974 Incoming SMTP messages can be accepted in one of two ways: by running a
33975 listening daemon, or by using &'inetd'&. In the latter case, the entry in
33976 &_/etc/inetd.conf_& should be like this:
33978 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
33980 Exim distinguishes between this case and the case of a locally running user
33981 agent using the &%-bs%& option by checking whether or not the standard input is
33982 a socket. When it is, either the port must be privileged (less than 1024), or
33983 the caller must be root or the Exim user. If any other user passes a socket
33984 with an unprivileged port number, Exim prints a message on the standard error
33985 stream and exits with an error code.
33987 By default, Exim does not make a log entry when a remote host connects or
33988 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
33989 unexpected. It can be made to write such log entries by setting the
33990 &%smtp_connection%& log selector.
33992 .cindex "carriage return"
33994 Commands from the remote host are supposed to be terminated by CR followed by
33995 LF. However, there are known to be hosts that do not send CR characters. In
33996 order to be able to interwork with such hosts, Exim treats LF on its own as a
33998 Furthermore, because common code is used for receiving messages from all
33999 sources, a CR on its own is also interpreted as a line terminator. However, the
34000 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
34002 .cindex "EHLO" "invalid data"
34003 .cindex "HELO" "invalid data"
34004 One area that sometimes gives rise to problems concerns the EHLO or
34005 HELO commands. Some clients send syntactically invalid versions of these
34006 commands, which Exim rejects by default. (This is nothing to do with verifying
34007 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
34008 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
34009 match the broken hosts that send invalid commands.
34011 .cindex "SIZE option on MAIL command"
34012 .cindex "MAIL" "SIZE option"
34013 The amount of disk space available is checked whenever SIZE is received on
34014 a MAIL command, independently of whether &%message_size_limit%& or
34015 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
34016 false. A temporary error is given if there is not enough space. If
34017 &%check_spool_space%& is set, the check is for that amount of space plus the
34018 value given with SIZE, that is, it checks that the addition of the incoming
34019 message will not reduce the space below the threshold.
34021 When a message is successfully received, Exim includes the local message id in
34022 its response to the final &"."& that terminates the data. If the remote host
34023 logs this text it can help with tracing what has happened to a message.
34025 The Exim daemon can limit the number of simultaneous incoming connections it is
34026 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
34027 number of simultaneous incoming connections from a single remote host (see the
34028 &%smtp_accept_max_per_host%& option). Additional connection attempts are
34029 rejected using the SMTP temporary error code 421.
34031 The Exim daemon does not rely on the SIGCHLD signal to detect when a
34032 subprocess has finished, as this can get lost at busy times. Instead, it looks
34033 for completed subprocesses every time it wakes up. Provided there are other
34034 things happening (new incoming calls, starts of queue runs), completed
34035 processes will be noticed and tidied away. On very quiet systems you may
34036 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
34037 it will be noticed when the daemon next wakes up.
34039 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
34040 and can also be set up to reject SMTP calls from non-reserved hosts at times of
34041 high system load &-- for details see the &%smtp_accept_reserve%&,
34042 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
34043 applies in both the daemon and &'inetd'& cases.
34045 Exim normally starts a delivery process for each message received, though this
34046 can be varied by means of the &%-odq%& command line option and the
34047 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
34048 number of simultaneously running delivery processes started in this way from
34049 SMTP input can be limited by the &%smtp_accept_queue%& and
34050 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
34051 subsequently received messages are just put on the input queue without starting
34052 a delivery process.
34054 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
34055 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
34056 started up from the &'inetd'& daemon, because in that case each connection is
34057 handled by an entirely independent Exim process. Control by load average is,
34058 however, available with &'inetd'&.
34060 Exim can be configured to verify addresses in incoming SMTP commands as they
34061 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
34062 to rewrite addresses at this time &-- before any syntax checking is done. See
34063 section &<<SECTrewriteS>>&.
34065 Exim can also be configured to limit the rate at which a client host submits
34066 MAIL and RCPT commands in a single SMTP session. See the
34067 &%smtp_ratelimit_hosts%& option.
34071 .section "Unrecognized SMTP commands" "SECID234"
34072 .cindex "SMTP" "unrecognized commands"
34073 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
34074 commands during a single SMTP connection, it drops the connection after sending
34075 the error response to the last command. The default value for
34076 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
34077 abuse that subvert web servers into making connections to SMTP ports; in these
34078 circumstances, a number of non-SMTP lines are sent first.
34081 .section "Syntax and protocol errors in SMTP commands" "SECID235"
34082 .cindex "SMTP" "syntax errors"
34083 .cindex "SMTP" "protocol errors"
34084 A syntax error is detected if an SMTP command is recognized, but there is
34085 something syntactically wrong with its data, for example, a malformed email
34086 address in a RCPT command. Protocol errors include invalid command
34087 sequencing such as RCPT before MAIL. If Exim receives more than
34088 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
34089 drops the connection after sending the error response to the last command. The
34090 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
34091 broken clients that loop sending bad commands (yes, it has been seen).
34095 .section "Use of non-mail SMTP commands" "SECID236"
34096 .cindex "SMTP" "non-mail commands"
34097 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
34098 DATA. Exim counts such commands, and drops the connection if there are too
34099 many of them in a single SMTP session. This action catches some
34100 denial-of-service attempts and things like repeated failing AUTHs, or a mad
34101 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
34102 defines what &"too many"& means. Its default value is 10.
34104 When a new message is expected, one occurrence of RSET is not counted. This
34105 allows a client to send one RSET between messages (this is not necessary,
34106 but some clients do it). Exim also allows one uncounted occurrence of HELO
34107 or EHLO, and one occurrence of STARTTLS between messages. After
34108 starting up a TLS session, another EHLO is expected, and so it too is not
34111 The first occurrence of AUTH in a connection, or immediately following
34112 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
34113 RCPT, DATA, and QUIT are counted.
34115 You can control which hosts are subject to the limit set by
34116 &%smtp_accept_max_nonmail%& by setting
34117 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
34118 the limit apply to all hosts. This option means that you can exclude any
34119 specific badly-behaved hosts that you have to live with.
34124 .section "The VRFY and EXPN commands" "SECID237"
34125 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
34126 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
34127 appropriate) in order to decide whether the command should be accepted or not.
34130 .cindex "VRFY" "processing"
34131 When no ACL is defined for VRFY, or if it rejects without
34132 setting an explicit response code, the command is accepted
34133 (with a 252 SMTP response code)
34134 in order to support awkward clients that do a VRFY before every RCPT.
34136 When VRFY is accepted, it runs exactly the same code as when Exim is
34137 called with the &%-bv%& option, and returns 250/451/550
34138 SMTP response codes.
34140 .cindex "EXPN" "processing"
34141 If no ACL for EXPN is defined, the command is rejected.
34142 When EXPN is accepted, a single-level expansion of the address is done.
34143 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
34144 than a verification (the &%-bv%& option). If an unqualified local part is given
34145 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
34146 of VRFY and EXPN commands are logged on the main and reject logs, and
34147 VRFY verification failures are logged on the main log for consistency with
34152 .section "The ETRN command" "SECTETRN"
34153 .cindex "ETRN" "processing"
34154 RFC 1985 describes an SMTP command called ETRN that is designed to
34155 overcome the security problems of the TURN command (which has fallen into
34156 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
34157 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
34158 should be accepted or not. If no ACL is defined, the command is rejected.
34160 The ETRN command is concerned with &"releasing"& messages that are awaiting
34161 delivery to certain hosts. As Exim does not organize its message queue by host,
34162 the only form of ETRN that is supported by default is the one where the
34163 text starts with the &"#"& prefix, in which case the remainder of the text is
34164 specific to the SMTP server. A valid ETRN command causes a run of Exim with
34165 the &%-R%& option to happen, with the remainder of the ETRN text as its
34166 argument. For example,
34174 which causes a delivery attempt on all messages with undelivered addresses
34175 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
34176 default), Exim prevents the simultaneous execution of more than one queue run
34177 for the same argument string as a result of an ETRN command. This stops
34178 a misbehaving client from starting more than one queue runner at once.
34180 .cindex "hints database" "ETRN serialization"
34181 Exim implements the serialization by means of a hints database in which a
34182 record is written whenever a process is started by ETRN, and deleted when
34183 the process completes. However, Exim does not keep the SMTP session waiting for
34184 the ETRN process to complete. Once ETRN is accepted, the client is sent
34185 a &"success"& return code. Obviously there is scope for hints records to get
34186 left lying around if there is a system or program crash. To guard against this,
34187 Exim ignores any records that are more than six hours old.
34189 .oindex "&%smtp_etrn_command%&"
34190 For more control over what ETRN does, the &%smtp_etrn_command%& option can
34191 used. This specifies a command that is run whenever ETRN is received,
34192 whatever the form of its argument. For
34195 smtp_etrn_command = /etc/etrn_command $domain \
34196 $sender_host_address
34198 .vindex "&$domain$&"
34199 The string is split up into arguments which are independently expanded. The
34200 expansion variable &$domain$& is set to the argument of the ETRN command,
34201 and no syntax checking is done on the contents of this argument. Exim does not
34202 wait for the command to complete, so its status code is not checked. Exim runs
34203 under its own uid and gid when receiving incoming SMTP, so it is not possible
34204 for it to change them before running the command.
34208 .section "Incoming local SMTP" "SECID238"
34209 .cindex "SMTP" "local incoming"
34210 Some user agents use SMTP to pass messages to their local MTA using the
34211 standard input and output, as opposed to passing the envelope on the command
34212 line and writing the message to the standard input. This is supported by the
34213 &%-bs%& option. This form of SMTP is handled in the same way as incoming
34214 messages over TCP/IP (including the use of ACLs), except that the envelope
34215 sender given in a MAIL command is ignored unless the caller is trusted. In
34216 an ACL you can detect this form of SMTP input by testing for an empty host
34217 identification. It is common to have this as the first line in the ACL that
34218 runs for RCPT commands:
34222 This accepts SMTP messages from local processes without doing any other tests.
34226 .section "Outgoing batched SMTP" "SECTbatchSMTP"
34227 .cindex "SMTP" "batched outgoing"
34228 .cindex "batched SMTP output"
34229 Both the &(appendfile)& and &(pipe)& transports can be used for handling
34230 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
34231 be output in BSMTP format. No SMTP responses are possible for this form of
34232 delivery. All it is doing is using SMTP commands as a way of transmitting the
34233 envelope along with the message.
34235 The message is written to the file or pipe preceded by the SMTP commands
34236 MAIL and RCPT, and followed by a line containing a single dot. Lines in
34237 the message that start with a dot have an extra dot added. The SMTP command
34238 HELO is not normally used. If it is required, the &%message_prefix%& option
34239 can be used to specify it.
34241 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
34242 one recipient address at a time by default. However, you can arrange for them
34243 to handle several addresses at once by setting the &%batch_max%& option. When
34244 this is done for BSMTP, messages may contain multiple RCPT commands. See
34245 chapter &<<CHAPbatching>>& for more details.
34248 When one or more addresses are routed to a BSMTP transport by a router that
34249 sets up a host list, the name of the first host on the list is available to the
34250 transport in the variable &$host$&. Here is an example of such a transport and
34255 driver = manualroute
34256 transport = smtp_appendfile
34257 route_list = domain.example batch.host.example
34261 driver = appendfile
34262 directory = /var/bsmtp/$host
34267 This causes messages addressed to &'domain.example'& to be written in BSMTP
34268 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
34269 message (unless there are more than 1000 recipients).
34273 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
34274 .cindex "SMTP" "batched incoming"
34275 .cindex "batched SMTP input"
34276 The &%-bS%& command line option causes Exim to accept one or more messages by
34277 reading SMTP on the standard input, but to generate no responses. If the caller
34278 is trusted, the senders in the MAIL commands are believed; otherwise the
34279 sender is always the caller of Exim. Unqualified senders and receivers are not
34280 rejected (there seems little point) but instead just get qualified. HELO
34281 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
34282 as NOOP; QUIT quits.
34284 Minimal policy checking is done for BSMTP input. Only the non-SMTP
34285 ACL is run in the same way as for non-SMTP local input.
34287 If an error is detected while reading a message, including a missing &"."& at
34288 the end, Exim gives up immediately. It writes details of the error to the
34289 standard output in a stylized way that the calling program should be able to
34290 make some use of automatically, for example:
34292 554 Unexpected end of file
34293 Transaction started in line 10
34294 Error detected in line 14
34296 It writes a more verbose version, for human consumption, to the standard error
34299 An error was detected while processing a file of BSMTP input.
34300 The error message was:
34302 501 '>' missing at end of address
34304 The SMTP transaction started in line 10.
34305 The error was detected in line 12.
34306 The SMTP command at fault was:
34308 rcpt to:<malformed@in.com.plete
34310 1 previous message was successfully processed.
34311 The rest of the batch was abandoned.
34313 The return code from Exim is zero only if there were no errors. It is 1 if some
34314 messages were accepted before an error was detected, and 2 if no messages were
34316 .ecindex IIDsmtpproc1
34317 .ecindex IIDsmtpproc2
34321 . ////////////////////////////////////////////////////////////////////////////
34322 . ////////////////////////////////////////////////////////////////////////////
34324 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
34325 "Customizing messages"
34326 When a message fails to be delivered, or remains on the queue for more than a
34327 configured amount of time, Exim sends a message to the original sender, or
34328 to an alternative configured address. The text of these messages is built into
34329 the code of Exim, but it is possible to change it, either by adding a single
34330 string, or by replacing each of the paragraphs by text supplied in a file.
34332 The &'From:'& and &'To:'& header lines are automatically generated; you can
34333 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
34334 option. Exim also adds the line
34336 Auto-Submitted: auto-generated
34338 to all warning and bounce messages,
34341 .section "Customizing bounce messages" "SECID239"
34342 .cindex "customizing" "bounce message"
34343 .cindex "bounce message" "customizing"
34344 If &%bounce_message_text%& is set, its contents are included in the default
34345 message immediately after &"This message was created automatically by mail
34346 delivery software."& The string is not expanded. It is not used if
34347 &%bounce_message_file%& is set.
34349 When &%bounce_message_file%& is set, it must point to a template file for
34350 constructing error messages. The file consists of a series of text items,
34351 separated by lines consisting of exactly four asterisks. If the file cannot be
34352 opened, default text is used and a message is written to the main and panic
34353 logs. If any text item in the file is empty, default text is used for that
34356 .vindex "&$bounce_recipient$&"
34357 .vindex "&$bounce_return_size_limit$&"
34358 Each item of text that is read from the file is expanded, and there are two
34359 expansion variables which can be of use here: &$bounce_recipient$& is set to
34360 the recipient of an error message while it is being created, and
34361 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
34362 option, rounded to a whole number.
34364 The items must appear in the file in the following order:
34367 The first item is included in the headers, and should include at least a
34368 &'Subject:'& header. Exim does not check the syntax of these headers.
34370 The second item forms the start of the error message. After it, Exim lists the
34371 failing addresses with their error messages.
34373 The third item is used to introduce any text from pipe transports that is to be
34374 returned to the sender. It is omitted if there is no such text.
34376 The fourth, fifth and sixth items will be ignored and may be empty.
34377 The fields exist for back-compatibility
34380 The default state (&%bounce_message_file%& unset) is equivalent to the
34381 following file, in which the sixth item is empty. The &'Subject:'& and some
34382 other lines have been split in order to fit them on the page:
34384 Subject: Mail delivery failed
34385 ${if eq{$sender_address}{$bounce_recipient}
34386 {: returning message to sender}}
34388 This message was created automatically by mail delivery software.
34390 A message ${if eq{$sender_address}{$bounce_recipient}
34391 {that you sent }{sent by
34395 }}could not be delivered to all of its recipients.
34396 This is a permanent error. The following address(es) failed:
34398 The following text was generated during the delivery attempt(s):
34400 ------ This is a copy of the message, including all the headers.
34403 ------ The body of the message is $message_size characters long;
34405 ------ $bounce_return_size_limit or so are included here.
34408 .section "Customizing warning messages" "SECTcustwarn"
34409 .cindex "customizing" "warning message"
34410 .cindex "warning of delay" "customizing the message"
34411 The option &%warn_message_file%& can be pointed at a template file for use when
34412 warnings about message delays are created. In this case there are only three
34416 The first item is included in the headers, and should include at least a
34417 &'Subject:'& header. Exim does not check the syntax of these headers.
34419 The second item forms the start of the warning message. After it, Exim lists
34420 the delayed addresses.
34422 The third item then ends the message.
34425 The default state is equivalent to the following file, except that some lines
34426 have been split here, in order to fit them on the page:
34428 Subject: Warning: message $message_exim_id delayed
34429 $warn_message_delay
34431 This message was created automatically by mail delivery software.
34433 A message ${if eq{$sender_address}{$warn_message_recipients}
34434 {that you sent }{sent by
34438 }}has not been delivered to all of its recipients after
34439 more than $warn_message_delay on the queue on $primary_hostname.
34441 The message identifier is: $message_exim_id
34442 The subject of the message is: $h_subject
34443 The date of the message is: $h_date
34445 The following address(es) have not yet been delivered:
34447 No action is required on your part. Delivery attempts will
34448 continue for some time, and this warning may be repeated at
34449 intervals if the message remains undelivered. Eventually the
34450 mail delivery software will give up, and when that happens,
34451 the message will be returned to you.
34453 .vindex "&$warn_message_delay$&"
34454 .vindex "&$warn_message_recipients$&"
34455 However, in the default state the subject and date lines are omitted if no
34456 appropriate headers exist. During the expansion of this file,
34457 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
34458 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
34459 of recipients for the warning message. There may be more than one if there are
34460 multiple addresses with different &%errors_to%& settings on the routers that
34466 . ////////////////////////////////////////////////////////////////////////////
34467 . ////////////////////////////////////////////////////////////////////////////
34469 .chapter "Some common configuration settings" "CHAPcomconreq"
34470 This chapter discusses some configuration settings that seem to be fairly
34471 common. More examples and discussion can be found in the Exim book.
34475 .section "Sending mail to a smart host" "SECID240"
34476 .cindex "smart host" "example router"
34477 If you want to send all mail for non-local domains to a &"smart host"&, you
34478 should replace the default &(dnslookup)& router with a router which does the
34479 routing explicitly:
34481 send_to_smart_host:
34482 driver = manualroute
34483 route_list = !+local_domains smart.host.name
34484 transport = remote_smtp
34486 You can use the smart host's IP address instead of the name if you wish.
34487 If you are using Exim only to submit messages to a smart host, and not for
34488 receiving incoming messages, you can arrange for it to do the submission
34489 synchronously by setting the &%mua_wrapper%& option (see chapter
34490 &<<CHAPnonqueueing>>&).
34495 .section "Using Exim to handle mailing lists" "SECTmailinglists"
34496 .cindex "mailing lists"
34497 Exim can be used to run simple mailing lists, but for large and/or complicated
34498 requirements, the use of additional specialized mailing list software such as
34499 Majordomo or Mailman is recommended.
34501 The &(redirect)& router can be used to handle mailing lists where each list
34502 is maintained in a separate file, which can therefore be managed by an
34503 independent manager. The &%domains%& router option can be used to run these
34504 lists in a separate domain from normal mail. For example:
34508 domains = lists.example
34509 file = /usr/lists/$local_part
34512 errors_to = $local_part-request@lists.example
34515 This router is skipped for domains other than &'lists.example'&. For addresses
34516 in that domain, it looks for a file that matches the local part. If there is no
34517 such file, the router declines, but because &%no_more%& is set, no subsequent
34518 routers are tried, and so the whole delivery fails.
34520 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
34521 expanded into a file name or a pipe delivery, which is usually inappropriate in
34524 .oindex "&%errors_to%&"
34525 The &%errors_to%& option specifies that any delivery errors caused by addresses
34526 taken from a mailing list are to be sent to the given address rather than the
34527 original sender of the message. However, before acting on this, Exim verifies
34528 the error address, and ignores it if verification fails.
34530 For example, using the configuration above, mail sent to
34531 &'dicts@lists.example'& is passed on to those addresses contained in
34532 &_/usr/lists/dicts_&, with error reports directed to
34533 &'dicts-request@lists.example'&, provided that this address can be verified.
34534 There could be a file called &_/usr/lists/dicts-request_& containing
34535 the address(es) of this particular list's manager(s), but other approaches,
34536 such as setting up an earlier router (possibly using the &%local_part_prefix%&
34537 or &%local_part_suffix%& options) to handle addresses of the form
34538 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
34542 .section "Syntax errors in mailing lists" "SECID241"
34543 .cindex "mailing lists" "syntax errors in"
34544 If an entry in redirection data contains a syntax error, Exim normally defers
34545 delivery of the original address. That means that a syntax error in a mailing
34546 list holds up all deliveries to the list. This may not be appropriate when a
34547 list is being maintained automatically from data supplied by users, and the
34548 addresses are not rigorously checked.
34550 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
34551 entries that fail to parse, noting the incident in the log. If in addition
34552 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
34553 whenever a broken address is skipped. It is usually appropriate to set
34554 &%syntax_errors_to%& to the same address as &%errors_to%&.
34558 .section "Re-expansion of mailing lists" "SECID242"
34559 .cindex "mailing lists" "re-expansion of"
34560 Exim remembers every individual address to which a message has been delivered,
34561 in order to avoid duplication, but it normally stores only the original
34562 recipient addresses with a message. If all the deliveries to a mailing list
34563 cannot be done at the first attempt, the mailing list is re-expanded when the
34564 delivery is next tried. This means that alterations to the list are taken into
34565 account at each delivery attempt, so addresses that have been added to
34566 the list since the message arrived will therefore receive a copy of the
34567 message, even though it pre-dates their subscription.
34569 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
34570 on the &(redirect)& router. If this is done, any addresses generated by the
34571 router that fail to deliver at the first attempt are added to the message as
34572 &"top level"& addresses, and the parent address that generated them is marked
34573 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
34574 subsequent delivery attempts. The disadvantage of this is that if any of the
34575 failing addresses are incorrect, correcting them in the file has no effect on
34576 pre-existing messages.
34578 The original top-level address is remembered with each of the generated
34579 addresses, and is output in any log messages. However, any intermediate parent
34580 addresses are not recorded. This makes a difference to the log only if the
34581 &%all_parents%& selector is set, but for mailing lists there is normally only
34582 one level of expansion anyway.
34586 .section "Closed mailing lists" "SECID243"
34587 .cindex "mailing lists" "closed"
34588 The examples so far have assumed open mailing lists, to which anybody may
34589 send mail. It is also possible to set up closed lists, where mail is accepted
34590 from specified senders only. This is done by making use of the generic
34591 &%senders%& option to restrict the router that handles the list.
34593 The following example uses the same file as a list of recipients and as a list
34594 of permitted senders. It requires three routers:
34598 domains = lists.example
34599 local_part_suffix = -request
34600 file = /usr/lists/$local_part$local_part_suffix
34605 domains = lists.example
34606 senders = ${if exists {/usr/lists/$local_part}\
34607 {lsearch;/usr/lists/$local_part}{*}}
34608 file = /usr/lists/$local_part
34611 errors_to = $local_part-request@lists.example
34616 domains = lists.example
34618 data = :fail: $local_part@lists.example is a closed mailing list
34620 All three routers have the same &%domains%& setting, so for any other domains,
34621 they are all skipped. The first router runs only if the local part ends in
34622 &%-request%&. It handles messages to the list manager(s) by means of an open
34625 The second router runs only if the &%senders%& precondition is satisfied. It
34626 checks for the existence of a list that corresponds to the local part, and then
34627 checks that the sender is on the list by means of a linear search. It is
34628 necessary to check for the existence of the file before trying to search it,
34629 because otherwise Exim thinks there is a configuration error. If the file does
34630 not exist, the expansion of &%senders%& is *, which matches all senders. This
34631 means that the router runs, but because there is no list, declines, and
34632 &%no_more%& ensures that no further routers are run. The address fails with an
34633 &"unrouteable address"& error.
34635 The third router runs only if the second router is skipped, which happens when
34636 a mailing list exists, but the sender is not on it. This router forcibly fails
34637 the address, giving a suitable error message.
34642 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
34644 .cindex "Variable Envelope Return Paths"
34645 .cindex "envelope sender"
34646 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
34647 are a way of helping mailing list administrators discover which subscription
34648 address is the cause of a particular delivery failure. The idea is to encode
34649 the original recipient address in the outgoing envelope sender address, so that
34650 if the message is forwarded by another host and then subsequently bounces, the
34651 original recipient can be extracted from the recipient address of the bounce.
34653 .oindex &%errors_to%&
34654 .oindex &%return_path%&
34655 Envelope sender addresses can be modified by Exim using two different
34656 facilities: the &%errors_to%& option on a router (as shown in previous mailing
34657 list examples), or the &%return_path%& option on a transport. The second of
34658 these is effective only if the message is successfully delivered to another
34659 host; it is not used for errors detected on the local host (see the description
34660 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
34661 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
34667 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34668 {$1-request+$local_part=$domain@your.dom.example}fail}
34670 This has the effect of rewriting the return path (envelope sender) on outgoing
34671 SMTP messages, if the local part of the original return path ends in
34672 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
34673 local part and domain of the recipient into the return path. Suppose, for
34674 example, that a message whose return path has been set to
34675 &'somelist-request@your.dom.example'& is sent to
34676 &'subscriber@other.dom.example'&. In the transport, the return path is
34679 somelist-request+subscriber=other.dom.example@your.dom.example
34681 .vindex "&$local_part$&"
34682 For this to work, you must tell Exim to send multiple copies of messages that
34683 have more than one recipient, so that each copy has just one recipient. This is
34684 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
34685 might be sent to several different recipients in the same domain, in which case
34686 &$local_part$& is not available in the transport, because it is not unique.
34688 Unless your host is doing nothing but mailing list deliveries, you should
34689 probably use a separate transport for the VERP deliveries, so as not to use
34690 extra resources in making one-per-recipient copies for other deliveries. This
34691 can easily be done by expanding the &%transport%& option in the router:
34695 domains = ! +local_domains
34697 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34698 {verp_smtp}{remote_smtp}}
34701 If you want to change the return path using &%errors_to%& in a router instead
34702 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
34703 routers that handle mailing list addresses. This will ensure that all delivery
34704 errors, including those detected on the local host, are sent to the VERP
34707 On a host that does no local deliveries and has no manual routing, only the
34708 &(dnslookup)& router needs to be changed. A special transport is not needed for
34709 SMTP deliveries. Every mailing list recipient has its own return path value,
34710 and so Exim must hand them to the transport one at a time. Here is an example
34711 of a &(dnslookup)& router that implements VERP:
34715 domains = ! +local_domains
34716 transport = remote_smtp
34718 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
34719 {$1-request+$local_part=$domain@your.dom.example}fail}
34722 Before you start sending out messages with VERPed return paths, you must also
34723 configure Exim to accept the bounce messages that come back to those paths.
34724 Typically this is done by setting a &%local_part_suffix%& option for a
34725 router, and using this to route the messages to wherever you want to handle
34728 The overhead incurred in using VERP depends very much on the size of the
34729 message, the number of recipient addresses that resolve to the same remote
34730 host, and the speed of the connection over which the message is being sent. If
34731 a lot of addresses resolve to the same host and the connection is slow, sending
34732 a separate copy of the message for each address may take substantially longer
34733 than sending a single copy with many recipients (for which VERP cannot be
34741 .section "Virtual domains" "SECTvirtualdomains"
34742 .cindex "virtual domains"
34743 .cindex "domain" "virtual"
34744 The phrase &'virtual domain'& is unfortunately used with two rather different
34748 A domain for which there are no real mailboxes; all valid local parts are
34749 aliases for other email addresses. Common examples are organizational
34750 top-level domains and &"vanity"& domains.
34752 One of a number of independent domains that are all handled by the same host,
34753 with mailboxes on that host, but where the mailbox owners do not necessarily
34754 have login accounts on that host.
34757 The first usage is probably more common, and does seem more &"virtual"& than
34758 the second. This kind of domain can be handled in Exim with a straightforward
34759 aliasing router. One approach is to create a separate alias file for each
34760 virtual domain. Exim can test for the existence of the alias file to determine
34761 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
34762 to a router of this form:
34766 domains = dsearch;/etc/mail/virtual
34767 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
34770 The &%domains%& option specifies that the router is to be skipped, unless there
34771 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
34772 domain that is being processed. When the router runs, it looks up the local
34773 part in the file to find a new address (or list of addresses). The &%no_more%&
34774 setting ensures that if the lookup fails (leading to &%data%& being an empty
34775 string), Exim gives up on the address without trying any subsequent routers.
34777 This one router can handle all the virtual domains because the alias file names
34778 follow a fixed pattern. Permissions can be arranged so that appropriate people
34779 can edit the different alias files. A successful aliasing operation results in
34780 a new envelope recipient address, which is then routed from scratch.
34782 The other kind of &"virtual"& domain can also be handled in a straightforward
34783 way. One approach is to create a file for each domain containing a list of
34784 valid local parts, and use it in a router like this:
34788 domains = dsearch;/etc/mail/domains
34789 local_parts = lsearch;/etc/mail/domains/$domain
34790 transport = my_mailboxes
34792 The address is accepted if there is a file for the domain, and the local part
34793 can be found in the file. The &%domains%& option is used to check for the
34794 file's existence because &%domains%& is tested before the &%local_parts%&
34795 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
34796 because that option is tested after &%local_parts%&. The transport is as
34800 driver = appendfile
34801 file = /var/mail/$domain/$local_part
34804 This uses a directory of mailboxes for each domain. The &%user%& setting is
34805 required, to specify which uid is to be used for writing to the mailboxes.
34807 The configuration shown here is just one example of how you might support this
34808 requirement. There are many other ways this kind of configuration can be set
34809 up, for example, by using a database instead of separate files to hold all the
34810 information about the domains.
34814 .section "Multiple user mailboxes" "SECTmulbox"
34815 .cindex "multiple mailboxes"
34816 .cindex "mailbox" "multiple"
34817 .cindex "local part" "prefix"
34818 .cindex "local part" "suffix"
34819 Heavy email users often want to operate with multiple mailboxes, into which
34820 incoming mail is automatically sorted. A popular way of handling this is to
34821 allow users to use multiple sender addresses, so that replies can easily be
34822 identified. Users are permitted to add prefixes or suffixes to their local
34823 parts for this purpose. The wildcard facility of the generic router options
34824 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
34825 example, consider this router:
34830 file = $home/.forward
34831 local_part_suffix = -*
34832 local_part_suffix_optional
34835 .vindex "&$local_part_suffix$&"
34836 It runs a user's &_.forward_& file for all local parts of the form
34837 &'username-*'&. Within the filter file the user can distinguish different
34838 cases by testing the variable &$local_part_suffix$&. For example:
34840 if $local_part_suffix contains -special then
34841 save /home/$local_part/Mail/special
34844 If the filter file does not exist, or does not deal with such addresses, they
34845 fall through to subsequent routers, and, assuming no subsequent use of the
34846 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
34847 control over which suffixes are valid.
34849 Alternatively, a suffix can be used to trigger the use of a different
34850 &_.forward_& file &-- which is the way a similar facility is implemented in
34856 file = $home/.forward$local_part_suffix
34857 local_part_suffix = -*
34858 local_part_suffix_optional
34861 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
34862 example, &_.forward-special_& is used. Once again, if the appropriate file
34863 does not exist, or does not deal with the address, it is passed on to
34864 subsequent routers, which could, if required, look for an unqualified
34865 &_.forward_& file to use as a default.
34869 .section "Simplified vacation processing" "SECID244"
34870 .cindex "vacation processing"
34871 The traditional way of running the &'vacation'& program is for a user to set up
34872 a pipe command in a &_.forward_& file
34873 (see section &<<SECTspecitredli>>& for syntax details).
34874 This is prone to error by inexperienced users. There are two features of Exim
34875 that can be used to make this process simpler for users:
34878 A local part prefix such as &"vacation-"& can be specified on a router which
34879 can cause the message to be delivered directly to the &'vacation'& program, or
34880 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
34881 &_.forward_& file are then much simpler. For example:
34883 spqr, vacation-spqr
34886 The &%require_files%& generic router option can be used to trigger a
34887 vacation delivery by checking for the existence of a certain file in the
34888 user's home directory. The &%unseen%& generic option should also be used, to
34889 ensure that the original delivery also proceeds. In this case, all the user has
34890 to do is to create a file called, say, &_.vacation_&, containing a vacation
34894 Another advantage of both these methods is that they both work even when the
34895 use of arbitrary pipes by users is locked out.
34899 .section "Taking copies of mail" "SECID245"
34900 .cindex "message" "copying every"
34901 Some installations have policies that require archive copies of all messages to
34902 be made. A single copy of each message can easily be taken by an appropriate
34903 command in a system filter, which could, for example, use a different file for
34904 each day's messages.
34906 There is also a shadow transport mechanism that can be used to take copies of
34907 messages that are successfully delivered by local transports, one copy per
34908 delivery. This could be used, &'inter alia'&, to implement automatic
34909 notification of delivery by sites that insist on doing such things.
34913 .section "Intermittently connected hosts" "SECID246"
34914 .cindex "intermittently connected hosts"
34915 It has become quite common (because it is cheaper) for hosts to connect to the
34916 Internet periodically rather than remain connected all the time. The normal
34917 arrangement is that mail for such hosts accumulates on a system that is
34918 permanently connected.
34920 Exim was designed for use on permanently connected hosts, and so it is not
34921 particularly well-suited to use in an intermittently connected environment.
34922 Nevertheless there are some features that can be used.
34925 .section "Exim on the upstream server host" "SECID247"
34926 It is tempting to arrange for incoming mail for the intermittently connected
34927 host to remain on Exim's queue until the client connects. However, this
34928 approach does not scale very well. Two different kinds of waiting message are
34929 being mixed up in the same queue &-- those that cannot be delivered because of
34930 some temporary problem, and those that are waiting for their destination host
34931 to connect. This makes it hard to manage the queue, as well as wasting
34932 resources, because each queue runner scans the entire queue.
34934 A better approach is to separate off those messages that are waiting for an
34935 intermittently connected host. This can be done by delivering these messages
34936 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
34937 format, from where they are transmitted by other software when their
34938 destination connects. This makes it easy to collect all the mail for one host
34939 in a single directory, and to apply local timeout rules on a per-message basis
34942 On a very small scale, leaving the mail on Exim's queue can be made to work. If
34943 you are doing this, you should configure Exim with a long retry period for the
34944 intermittent host. For example:
34946 cheshire.wonderland.fict.example * F,5d,24h
34948 This stops a lot of failed delivery attempts from occurring, but Exim remembers
34949 which messages it has queued up for that host. Once the intermittent host comes
34950 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
34951 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
34952 causes all the queued up messages to be delivered, often down a single SMTP
34953 connection. While the host remains connected, any new messages get delivered
34956 If the connecting hosts do not have fixed IP addresses, that is, if a host is
34957 issued with a different IP address each time it connects, Exim's retry
34958 mechanisms on the holding host get confused, because the IP address is normally
34959 used as part of the key string for holding retry information. This can be
34960 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
34961 Since this has disadvantages for permanently connected hosts, it is best to
34962 arrange a separate transport for the intermittently connected ones.
34966 .section "Exim on the intermittently connected client host" "SECID248"
34967 The value of &%smtp_accept_queue_per_connection%& should probably be
34968 increased, or even set to zero (that is, disabled) on the intermittently
34969 connected host, so that all incoming messages down a single connection get
34970 delivered immediately.
34972 .cindex "SMTP" "passed connection"
34973 .cindex "SMTP" "multiple deliveries"
34974 .cindex "multiple SMTP deliveries"
34975 Mail waiting to be sent from an intermittently connected host will probably
34976 not have been routed, because without a connection DNS lookups are not
34977 possible. This means that if a normal queue run is done at connection time,
34978 each message is likely to be sent in a separate SMTP session. This can be
34979 avoided by starting the queue run with a command line option beginning with
34980 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
34981 first pass, routing is done but no deliveries take place. The second pass is a
34982 normal queue run; since all the messages have been previously routed, those
34983 destined for the same host are likely to get sent as multiple deliveries in a
34984 single SMTP connection.
34988 . ////////////////////////////////////////////////////////////////////////////
34989 . ////////////////////////////////////////////////////////////////////////////
34991 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
34992 "Exim as a non-queueing client"
34993 .cindex "client, non-queueing"
34994 .cindex "smart host" "suppressing queueing"
34995 On a personal computer, it is a common requirement for all
34996 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
34997 configured to operate that way, for all the popular operating systems.
34998 However, there are some MUAs for Unix-like systems that cannot be so
34999 configured: they submit messages using the command line interface of
35000 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
35003 If the personal computer runs continuously, there is no problem, because it can
35004 run a conventional MTA that handles delivery to the smart host, and deal with
35005 any delays via its queueing mechanism. However, if the computer does not run
35006 continuously or runs different operating systems at different times, queueing
35007 email is not desirable.
35009 There is therefore a requirement for something that can provide the
35010 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
35011 any queueing or retrying facilities. Furthermore, the delivery to the smart
35012 host should be synchronous, so that if it fails, the sending MUA is immediately
35013 informed. In other words, we want something that extends an MUA that submits
35014 to a local MTA via the command line so that it behaves like one that submits
35015 to a remote smart host using TCP/SMTP.
35017 There are a number of applications (for example, there is one called &'ssmtp'&)
35018 that do this job. However, people have found them to be lacking in various
35019 ways. For instance, you might want to allow aliasing and forwarding to be done
35020 before sending a message to the smart host.
35022 Exim already had the necessary infrastructure for doing this job. Just a few
35023 tweaks were needed to make it behave as required, though it is somewhat of an
35024 overkill to use a fully-featured MTA for this purpose.
35026 .oindex "&%mua_wrapper%&"
35027 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
35028 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
35029 assumes that it is being used to &"wrap"& a command-line MUA in the manner
35030 just described. As well as setting &%mua_wrapper%&, you also need to provide a
35031 compatible router and transport configuration. Typically there will be just one
35032 router and one transport, sending everything to a smart host.
35034 When run in MUA wrapping mode, the behaviour of Exim changes in the
35038 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
35039 In other words, the only way to submit messages is via the command line.
35041 Each message is synchronously delivered as soon as it is received (&%-odi%& is
35042 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
35043 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
35044 does not finish until the delivery attempt is complete. If the delivery is
35045 successful, a zero return code is given.
35047 Address redirection is permitted, but the final routing for all addresses must
35048 be to the same remote transport, and to the same list of hosts. Furthermore,
35049 the return address (envelope sender) must be the same for all recipients, as
35050 must any added or deleted header lines. In other words, it must be possible to
35051 deliver the message in a single SMTP transaction, however many recipients there
35054 If these conditions are not met, or if routing any address results in a
35055 failure or defer status, or if Exim is unable to deliver all the recipients
35056 successfully to one of the smart hosts, delivery of the entire message fails.
35058 Because no queueing is allowed, all failures are treated as permanent; there
35059 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
35060 smart host. Furthermore, because only a single yes/no response can be given to
35061 the caller, it is not possible to deliver to some recipients and not others. If
35062 there is an error (temporary or permanent) for any recipient, all are failed.
35064 If more than one smart host is listed, Exim will try another host after a
35065 connection failure or a timeout, in the normal way. However, if this kind of
35066 failure happens for all the hosts, the delivery fails.
35068 When delivery fails, an error message is written to the standard error stream
35069 (as well as to Exim's log), and Exim exits to the caller with a return code
35070 value 1. The message is expunged from Exim's spool files. No bounce messages
35071 are ever generated.
35073 No retry data is maintained, and any retry rules are ignored.
35075 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
35076 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
35077 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
35080 The overall effect is that Exim makes a single synchronous attempt to deliver
35081 the message, failing if there is any kind of problem. Because no local
35082 deliveries are done and no daemon can be run, Exim does not need root
35083 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
35084 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
35085 the advantages and disadvantages of running without root privilege.
35090 . ////////////////////////////////////////////////////////////////////////////
35091 . ////////////////////////////////////////////////////////////////////////////
35093 .chapter "Log files" "CHAPlog"
35094 .scindex IIDloggen "log" "general description"
35095 .cindex "log" "types of"
35096 Exim writes three different logs, referred to as the main log, the reject log,
35101 The main log records the arrival of each message and each delivery in a single
35102 line in each case. The format is as compact as possible, in an attempt to keep
35103 down the size of log files. Two-character flag sequences make it easy to pick
35104 out these lines. A number of other events are recorded in the main log. Some of
35105 them are optional, in which case the &%log_selector%& option controls whether
35106 they are included or not. A Perl script called &'eximstats'&, which does simple
35107 analysis of main log files, is provided in the Exim distribution (see section
35108 &<<SECTmailstat>>&).
35110 .cindex "reject log"
35111 The reject log records information from messages that are rejected as a result
35112 of a configuration option (that is, for policy reasons).
35113 The first line of each rejection is a copy of the line that is also written to
35114 the main log. Then, if the message's header has been read at the time the log
35115 is written, its contents are written to this log. Only the original header
35116 lines are available; header lines added by ACLs are not logged. You can use the
35117 reject log to check that your policy controls are working correctly; on a busy
35118 host this may be easier than scanning the main log for rejection messages. You
35119 can suppress the writing of the reject log by setting &%write_rejectlog%&
35122 .cindex "panic log"
35123 .cindex "system log"
35124 When certain serious errors occur, Exim writes entries to its panic log. If the
35125 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
35126 are usually written to the main log as well, but can get lost amid the mass of
35127 other entries. The panic log should be empty under normal circumstances. It is
35128 therefore a good idea to check it (or to have a &'cron'& script check it)
35129 regularly, in order to become aware of any problems. When Exim cannot open its
35130 panic log, it tries as a last resort to write to the system log (syslog). This
35131 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
35132 message itself is written at priority LOG_CRIT.
35135 Every log line starts with a timestamp, in the format shown in the following
35136 example. Note that many of the examples shown in this chapter are line-wrapped.
35137 In the log file, this would be all on one line:
35139 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
35142 By default, the timestamps are in the local timezone. There are two
35143 ways of changing this:
35146 You can set the &%timezone%& option to a different time zone; in particular, if
35151 the timestamps will be in UTC (aka GMT).
35153 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
35156 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
35160 .cindex "log" "process ids in"
35161 .cindex "pid (process id)" "in log lines"
35162 Exim does not include its process id in log lines by default, but you can
35163 request that it does so by specifying the &`pid`& log selector (see section
35164 &<<SECTlogselector>>&). When this is set, the process id is output, in square
35165 brackets, immediately after the time and date.
35170 .section "Where the logs are written" "SECTwhelogwri"
35171 .cindex "log" "destination"
35172 .cindex "log" "to file"
35173 .cindex "log" "to syslog"
35175 The logs may be written to local files, or to syslog, or both. However, it
35176 should be noted that many syslog implementations use UDP as a transport, and
35177 are therefore unreliable in the sense that messages are not guaranteed to
35178 arrive at the loghost, nor is the ordering of messages necessarily maintained.
35179 It has also been reported that on large log files (tens of megabytes) you may
35180 need to tweak syslog to prevent it syncing the file with each write &-- on
35181 Linux this has been seen to make syslog take 90% plus of CPU time.
35183 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
35184 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
35185 configuration. This latter string is expanded, so it can contain, for example,
35186 references to the host name:
35188 log_file_path = /var/log/$primary_hostname/exim_%slog
35190 It is generally advisable, however, to set the string in &_Local/Makefile_&
35191 rather than at run time, because then the setting is available right from the
35192 start of Exim's execution. Otherwise, if there's something it wants to log
35193 before it has read the configuration file (for example, an error in the
35194 configuration file) it will not use the path you want, and may not be able to
35197 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
35198 list, currently limited to at most two items. This is one option where the
35199 facility for changing a list separator may not be used. The list must always be
35200 colon-separated. If an item in the list is &"syslog"& then syslog is used;
35201 otherwise the item must either be an absolute path, containing &`%s`& at the
35202 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
35203 implying the use of a default path.
35205 When Exim encounters an empty item in the list, it searches the list defined by
35206 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
35207 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
35208 mean &"use the path specified at build time"&. It no such item exists, log
35209 files are written in the &_log_& subdirectory of the spool directory. This is
35210 equivalent to the setting:
35212 log_file_path = $spool_directory/log/%slog
35214 If you do not specify anything at build time or run time,
35215 or if you unset the option at run time (i.e. &`log_file_path = `&),
35216 that is where the logs are written.
35218 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
35219 are in use &-- see section &<<SECTdatlogfil>>& below.
35221 Here are some examples of possible settings:
35223 &`LOG_FILE_PATH=syslog `& syslog only
35224 &`LOG_FILE_PATH=:syslog `& syslog and default path
35225 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
35226 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
35228 If there are more than two paths in the list, the first is used and a panic
35233 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
35234 .cindex "log" "cycling local files"
35235 .cindex "cycling logs"
35236 .cindex "&'exicyclog'&"
35237 .cindex "log" "local files; writing to"
35238 Some operating systems provide centralized and standardized methods for cycling
35239 log files. For those that do not, a utility script called &'exicyclog'& is
35240 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
35241 main and reject logs each time it is called. The maximum number of old logs to
35242 keep can be set. It is suggested this script is run as a daily &'cron'& job.
35244 An Exim delivery process opens the main log when it first needs to write to it,
35245 and it keeps the file open in case subsequent entries are required &-- for
35246 example, if a number of different deliveries are being done for the same
35247 message. However, remote SMTP deliveries can take a long time, and this means
35248 that the file may be kept open long after it is renamed if &'exicyclog'& or
35249 something similar is being used to rename log files on a regular basis. To
35250 ensure that a switch of log files is noticed as soon as possible, Exim calls
35251 &[stat()]& on the main log's name before reusing an open file, and if the file
35252 does not exist, or its inode has changed, the old file is closed and Exim
35253 tries to open the main log from scratch. Thus, an old log file may remain open
35254 for quite some time, but no Exim processes should write to it once it has been
35259 .section "Datestamped log files" "SECTdatlogfil"
35260 .cindex "log" "datestamped files"
35261 Instead of cycling the main and reject log files by renaming them
35262 periodically, some sites like to use files whose names contain a datestamp,
35263 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
35264 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
35265 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
35266 point where the datestamp is required. For example:
35268 log_file_path = /var/spool/exim/log/%slog-%D
35269 log_file_path = /var/log/exim-%s-%D.log
35270 log_file_path = /var/spool/exim/log/%D-%slog
35271 log_file_path = /var/log/exim/%s.%M
35273 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
35274 examples of names generated by the above examples:
35276 /var/spool/exim/log/mainlog-20021225
35277 /var/log/exim-reject-20021225.log
35278 /var/spool/exim/log/20021225-mainlog
35279 /var/log/exim/main.200212
35281 When this form of log file is specified, Exim automatically switches to new
35282 files at midnight. It does not make any attempt to compress old logs; you
35283 will need to write your own script if you require this. You should not
35284 run &'exicyclog'& with this form of logging.
35286 The location of the panic log is also determined by &%log_file_path%&, but it
35287 is not datestamped, because rotation of the panic log does not make sense.
35288 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
35289 the string. In addition, if it immediately follows a slash, a following
35290 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
35291 character is removed. Thus, the four examples above would give these panic
35294 /var/spool/exim/log/paniclog
35295 /var/log/exim-panic.log
35296 /var/spool/exim/log/paniclog
35297 /var/log/exim/panic
35301 .section "Logging to syslog" "SECID249"
35302 .cindex "log" "syslog; writing to"
35303 The use of syslog does not change what Exim logs or the format of its messages,
35304 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
35305 Exim's log lines are omitted when these lines are sent to syslog. Apart from
35306 that, the same strings are written to syslog as to log files. The syslog
35307 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
35308 by default, but you can change these by setting the &%syslog_facility%& and
35309 &%syslog_processname%& options, respectively. If Exim was compiled with
35310 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
35311 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
35312 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
35313 the time and host name to each line.
35314 The three log streams are mapped onto syslog priorities as follows:
35317 &'mainlog'& is mapped to LOG_INFO
35319 &'rejectlog'& is mapped to LOG_NOTICE
35321 &'paniclog'& is mapped to LOG_ALERT
35324 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
35325 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
35326 these are routed by syslog to the same place. You can suppress this duplication
35327 by setting &%syslog_duplication%& false.
35329 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
35330 entries contain multiple lines when headers are included. To cope with both
35331 these cases, entries written to syslog are split into separate &[syslog()]&
35332 calls at each internal newline, and also after a maximum of
35333 870 data characters. (This allows for a total syslog line length of 1024, when
35334 additions such as timestamps are added.) If you are running a syslog
35335 replacement that can handle lines longer than the 1024 characters allowed by
35336 RFC 3164, you should set
35338 SYSLOG_LONG_LINES=yes
35340 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
35341 lines, but it still splits at internal newlines in &'reject'& log entries.
35343 To make it easy to re-assemble split lines later, each component of a split
35344 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
35345 where <&'n'&> is the component number and <&'m'&> is the total number of
35346 components in the entry. The / delimiter is used when the line was split
35347 because it was too long; if it was split because of an internal newline, the \
35348 delimiter is used. For example, supposing the length limit to be 50 instead of
35349 870, the following would be the result of a typical rejection message to
35350 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
35351 name, and pid as added by syslog:
35353 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
35354 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
35355 [3/5] when scanning for sender: missing or malformed lo
35356 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
35359 The same error might cause the following lines to be written to &"rejectlog"&
35362 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
35363 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
35364 [3/18] er when scanning for sender: missing or malformed
35365 [4/18] local part in "<>" (envelope sender is <ph10@cam
35367 [6\18] Recipients: ph10@some.domain.cam.example
35368 [7\18] P Received: from [127.0.0.1] (ident=ph10)
35369 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
35370 [9\18] id 16RdAL-0006pc-00
35371 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
35372 [11\18] 09:43 +0100
35374 [13\18] Subject: this is a test header
35375 [18\18] X-something: this is another header
35376 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
35379 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
35381 Log lines that are neither too long nor contain newlines are written to syslog
35382 without modification.
35384 If only syslog is being used, the Exim monitor is unable to provide a log tail
35385 display, unless syslog is routing &'mainlog'& to a file on the local host and
35386 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
35391 .section "Log line flags" "SECID250"
35392 One line is written to the main log for each message received, and for each
35393 successful, unsuccessful, and delayed delivery. These lines can readily be
35394 picked out by the distinctive two-character flags that immediately follow the
35395 timestamp. The flags are:
35397 &`<=`& message arrival
35398 &`=>`& normal message delivery
35399 &`->`& additional address in same delivery
35400 &`>>`& cutthrough message delivery
35401 &`*>`& delivery suppressed by &%-N%&
35402 &`**`& delivery failed; address bounced
35403 &`==`& delivery deferred; temporary problem
35407 .section "Logging message reception" "SECID251"
35408 .cindex "log" "reception line"
35409 The format of the single-line entry in the main log that is written for every
35410 message received is shown in the basic example below, which is split over
35411 several lines in order to fit it on the page:
35413 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
35414 H=mailer.fict.example [192.168.123.123] U=exim
35415 P=smtp S=5678 id=<incoming message id>
35417 The address immediately following &"<="& is the envelope sender address. A
35418 bounce message is shown with the sender address &"<>"&, and if it is locally
35419 generated, this is followed by an item of the form
35423 which is a reference to the message that caused the bounce to be sent.
35427 For messages from other hosts, the H and U fields identify the remote host and
35428 record the RFC 1413 identity of the user that sent the message, if one was
35429 received. The number given in square brackets is the IP address of the sending
35430 host. If there is a single, unparenthesized host name in the H field, as
35431 above, it has been verified to correspond to the IP address (see the
35432 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
35433 by the remote host in the SMTP HELO or EHLO command, and has not been
35434 verified. If verification yields a different name to that given for HELO or
35435 EHLO, the verified name appears first, followed by the HELO or EHLO
35436 name in parentheses.
35438 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
35439 without brackets, in the HELO or EHLO command, leading to entries in
35440 the log containing text like these examples:
35442 H=(10.21.32.43) [192.168.8.34]
35443 H=([10.21.32.43]) [192.168.8.34]
35445 This can be confusing. Only the final address in square brackets can be relied
35448 For locally generated messages (that is, messages not received over TCP/IP),
35449 the H field is omitted, and the U field contains the login name of the caller
35452 .cindex "authentication" "logging"
35453 .cindex "AUTH" "logging"
35454 For all messages, the P field specifies the protocol used to receive the
35455 message. This is the value that is stored in &$received_protocol$&. In the case
35456 of incoming SMTP messages, the value indicates whether or not any SMTP
35457 extensions (ESMTP), encryption, or authentication were used. If the SMTP
35458 session was encrypted, there is an additional X field that records the cipher
35459 suite that was used.
35461 .cindex log protocol
35462 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
35463 hosts that have authenticated themselves using the SMTP AUTH command. The first
35464 value is used when the SMTP connection was encrypted (&"secure"&). In this case
35465 there is an additional item A= followed by the name of the authenticator that
35466 was used. If an authenticated identification was set up by the authenticator's
35467 &%server_set_id%& option, this is logged too, separated by a colon from the
35468 authenticator name.
35470 .cindex "size" "of message"
35471 The id field records the existing message id, if present. The size of the
35472 received message is given by the S field. When the message is delivered,
35473 headers may be removed or added, so that the size of delivered copies of the
35474 message may not correspond with this value (and indeed may be different to each
35477 The &%log_selector%& option can be used to request the logging of additional
35478 data when a message is received. See section &<<SECTlogselector>>& below.
35482 .section "Logging deliveries" "SECID252"
35483 .cindex "log" "delivery line"
35484 The format of the single-line entry in the main log that is written for every
35485 delivery is shown in one of the examples below, for local and remote
35486 deliveries, respectively. Each example has been split into multiple lines in order
35487 to fit it on the page:
35489 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
35490 <marv@hitch.fict.example> R=localuser T=local_delivery
35491 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
35492 monk@holistic.fict.example R=dnslookup T=remote_smtp
35493 H=holistic.fict.example [192.168.234.234]
35495 For ordinary local deliveries, the original address is given in angle brackets
35496 after the final delivery address, which might be a pipe or a file. If
35497 intermediate address(es) exist between the original and the final address, the
35498 last of these is given in parentheses after the final address. The R and T
35499 fields record the router and transport that were used to process the address.
35501 If SMTP AUTH was used for the delivery there is an additional item A=
35502 followed by the name of the authenticator that was used.
35503 If an authenticated identification was set up by the authenticator's &%client_set_id%&
35504 option, this is logged too, separated by a colon from the authenticator name.
35506 If a shadow transport was run after a successful local delivery, the log line
35507 for the successful delivery has an item added on the end, of the form
35509 &`ST=<`&&'shadow transport name'&&`>`&
35511 If the shadow transport did not succeed, the error message is put in
35512 parentheses afterwards.
35514 .cindex "asterisk" "after IP address"
35515 When more than one address is included in a single delivery (for example, two
35516 SMTP RCPT commands in one transaction) the second and subsequent addresses are
35517 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
35518 down a single SMTP connection, an asterisk follows the IP address in the log
35519 lines for the second and subsequent messages.
35521 .cindex "delivery" "cutthrough; logging"
35522 .cindex "cutthrough" "logging"
35523 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
35524 line precedes the reception line, since cutthrough waits for a possible
35525 rejection from the destination in case it can reject the sourced item.
35527 The generation of a reply message by a filter file gets logged as a
35528 &"delivery"& to the addressee, preceded by &">"&.
35530 The &%log_selector%& option can be used to request the logging of additional
35531 data when a message is delivered. See section &<<SECTlogselector>>& below.
35534 .section "Discarded deliveries" "SECID253"
35535 .cindex "discarded messages"
35536 .cindex "message" "discarded"
35537 .cindex "delivery" "discarded; logging"
35538 When a message is discarded as a result of the command &"seen finish"& being
35539 obeyed in a filter file which generates no deliveries, a log entry of the form
35541 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
35542 <low.club@bridge.example> R=userforward
35544 is written, to record why no deliveries are logged. When a message is discarded
35545 because it is aliased to &":blackhole:"& the log line is like this:
35547 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
35548 <hole@nowhere.example> R=blackhole_router
35552 .section "Deferred deliveries" "SECID254"
35553 When a delivery is deferred, a line of the following form is logged:
35555 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
35556 R=dnslookup T=smtp defer (146): Connection refused
35558 In the case of remote deliveries, the error is the one that was given for the
35559 last IP address that was tried. Details of individual SMTP failures are also
35560 written to the log, so the above line would be preceded by something like
35562 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
35563 mail1.endrest.example [192.168.239.239]: Connection refused
35565 When a deferred address is skipped because its retry time has not been reached,
35566 a message is written to the log, but this can be suppressed by setting an
35567 appropriate value in &%log_selector%&.
35571 .section "Delivery failures" "SECID255"
35572 .cindex "delivery" "failure; logging"
35573 If a delivery fails because an address cannot be routed, a line of the
35574 following form is logged:
35576 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
35577 <jim@trek99.example>: unknown mail domain
35579 If a delivery fails at transport time, the router and transport are shown, and
35580 the response from the remote host is included, as in this example:
35582 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
35583 R=dnslookup T=remote_smtp: SMTP error from remote mailer
35584 after pipelined RCPT TO:<ace400@pb.example>: host
35585 pbmail3.py.example [192.168.63.111]: 553 5.3.0
35586 <ace400@pb.example>...Addressee unknown
35588 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
35589 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
35590 disabling PIPELINING. The log lines for all forms of delivery failure are
35591 flagged with &`**`&.
35595 .section "Fake deliveries" "SECID256"
35596 .cindex "delivery" "fake; logging"
35597 If a delivery does not actually take place because the &%-N%& option has been
35598 used to suppress it, a normal delivery line is written to the log, except that
35599 &"=>"& is replaced by &"*>"&.
35603 .section "Completion" "SECID257"
35606 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
35608 is written to the main log when a message is about to be removed from the spool
35609 at the end of its processing.
35614 .section "Summary of Fields in Log Lines" "SECID258"
35615 .cindex "log" "summary of fields"
35616 A summary of the field identifiers that are used in log lines is shown in
35617 the following table:
35619 &`A `& authenticator name (and optional id and sender)
35620 &`C `& SMTP confirmation on delivery
35621 &` `& command list for &"no mail in SMTP session"&
35622 &`CV `& certificate verification status
35623 &`D `& duration of &"no mail in SMTP session"&
35624 &`DN `& distinguished name from peer certificate
35625 &`DT `& on &`=>`& lines: time taken for a delivery
35626 &`F `& sender address (on delivery lines)
35627 &`H `& host name and IP address
35628 &`I `& local interface used
35629 &`id `& message id for incoming message
35630 &`P `& on &`<=`& lines: protocol used
35631 &` `& on &`=>`& and &`**`& lines: return path
35632 &`PRX `& on &'<='& and&`=>`& lines: proxy address
35633 &`QT `& on &`=>`& lines: time spent on queue so far
35634 &` `& on &"Completed"& lines: time spent on queue
35635 &`R `& on &`<=`& lines: reference for local bounce
35636 &` `& on &`=>`& &`**`& and &`==`& lines: router name
35637 &`S `& size of message in bytes
35638 &`SNI `& server name indication from TLS client hello
35639 &`ST `& shadow transport name
35640 &`T `& on &`<=`& lines: message subject (topic)
35641 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
35642 &`U `& local user or RFC 1413 identity
35643 &`X `& TLS cipher suite
35647 .section "Other log entries" "SECID259"
35648 Various other types of log entry are written from time to time. Most should be
35649 self-explanatory. Among the more common are:
35652 .cindex "retry" "time not reached"
35653 &'retry time not reached'&&~&~An address previously suffered a temporary error
35654 during routing or local delivery, and the time to retry has not yet arrived.
35655 This message is not written to an individual message log file unless it happens
35656 during the first delivery attempt.
35658 &'retry time not reached for any host'&&~&~An address previously suffered
35659 temporary errors during remote delivery, and the retry time has not yet arrived
35660 for any of the hosts to which it is routed.
35662 .cindex "spool directory" "file locked"
35663 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
35664 some other Exim process is already working on the message. This can be quite
35665 common if queue running processes are started at frequent intervals. The
35666 &'exiwhat'& utility script can be used to find out what Exim processes are
35669 .cindex "error" "ignored"
35670 &'error ignored'&&~&~There are several circumstances that give rise to this
35673 Exim failed to deliver a bounce message whose age was greater than
35674 &%ignore_bounce_errors_after%&. The bounce was discarded.
35676 A filter file set up a delivery using the &"noerror"& option, and the delivery
35677 failed. The delivery was discarded.
35679 A delivery set up by a router configured with
35680 . ==== As this is a nested list, any displays it contains must be indented
35681 . ==== as otherwise they are too far to the left.
35685 failed. The delivery was discarded.
35693 .section "Reducing or increasing what is logged" "SECTlogselector"
35694 .cindex "log" "selectors"
35695 By setting the &%log_selector%& global option, you can disable some of Exim's
35696 default logging, or you can request additional logging. The value of
35697 &%log_selector%& is made up of names preceded by plus or minus characters. For
35700 log_selector = +arguments -retry_defer
35702 The list of optional log items is in the following table, with the default
35703 selection marked by asterisks:
35705 &` 8bitmime `& received 8BITMIME status
35706 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
35707 &` address_rewrite `& address rewriting
35708 &` all_parents `& all parents in => lines
35709 &` arguments `& command line arguments
35710 &`*connection_reject `& connection rejections
35711 &`*delay_delivery `& immediate delivery delayed
35712 &` deliver_time `& time taken to perform delivery
35713 &` delivery_size `& add &`S=`&&'nnn'& to => lines
35714 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
35715 &`*etrn `& ETRN commands
35716 &`*host_lookup_failed `& as it says
35717 &` ident_timeout `& timeout for ident connection
35718 &` incoming_interface `& local interface on <= and => lines
35719 &` incoming_port `& remote port on <= lines
35720 &`*lost_incoming_connection `& as it says (includes timeouts)
35722 &` outgoing_interface `& local interface on => lines
35724 &` outgoing_port `& add remote port to => lines
35725 &`*queue_run `& start and end queue runs
35726 &` queue_time `& time on queue for one recipient
35727 &` queue_time_overall `& time on queue for whole message
35728 &` pid `& Exim process id
35730 &` proxy `& proxy address on <= and => lines
35732 &` received_recipients `& recipients on <= lines
35733 &` received_sender `& sender on <= lines
35734 &`*rejected_header `& header contents on reject log
35735 &`*retry_defer `& &"retry time not reached"&
35736 &` return_path_on_delivery `& put return path on => and ** lines
35737 &` sender_on_delivery `& add sender to => lines
35738 &`*sender_verify_fail `& sender verification failures
35739 &`*size_reject `& rejection because too big
35740 &`*skip_delivery `& delivery skipped in a queue run
35741 &`*smtp_confirmation `& SMTP confirmation on => lines
35742 &` smtp_connection `& incoming SMTP connections
35743 &` smtp_incomplete_transaction`& incomplete SMTP transactions
35744 &` smtp_mailauth `& AUTH argument to MAIL commands
35745 &` smtp_no_mail `& session with no MAIL commands
35746 &` smtp_protocol_error `& SMTP protocol errors
35747 &` smtp_syntax_error `& SMTP syntax errors
35748 &` subject `& contents of &'Subject:'& on <= lines
35749 &`*tls_certificate_verified `& certificate verification status
35750 &`*tls_cipher `& TLS cipher suite on <= and => lines
35751 &` tls_peerdn `& TLS peer DN on <= and => lines
35752 &` tls_sni `& TLS SNI on <= lines
35753 &` unknown_in_list `& DNS lookup failed in list match
35755 &` all `& all of the above
35757 See also the &%slow_lookup_log%& main configuration option,
35758 section &<<SECID99>>&
35760 More details on each of these items follows:
35764 .cindex "log" "8BITMIME"
35765 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
35766 which may help in tracking down interoperability issues with ancient MTAs
35767 that are not 8bit clean. This is added to the &"<="& line, tagged with
35768 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
35769 &`7BIT`& and &`8BITMIME`& respectively.
35771 .cindex "&%warn%& ACL verb" "log when skipping"
35772 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
35773 its conditions cannot be evaluated, a log line to this effect is written if
35774 this log selector is set.
35776 .cindex "log" "rewriting"
35777 .cindex "rewriting" "logging"
35778 &%address_rewrite%&: This applies both to global rewrites and per-transport
35779 rewrites, but not to rewrites in filters run as an unprivileged user (because
35780 such users cannot access the log).
35782 .cindex "log" "full parentage"
35783 &%all_parents%&: Normally only the original and final addresses are logged on
35784 delivery lines; with this selector, intermediate parents are given in
35785 parentheses between them.
35787 .cindex "log" "Exim arguments"
35788 .cindex "Exim arguments, logging"
35789 &%arguments%&: This causes Exim to write the arguments with which it was called
35790 to the main log, preceded by the current working directory. This is a debugging
35791 feature, added to make it easier to find out how certain MUAs call
35792 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
35793 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
35794 that are empty or that contain white space are quoted. Non-printing characters
35795 are shown as escape sequences. This facility cannot log unrecognized arguments,
35796 because the arguments are checked before the configuration file is read. The
35797 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
35798 between the caller and Exim.
35800 .cindex "log" "connection rejections"
35801 &%connection_reject%&: A log entry is written whenever an incoming SMTP
35802 connection is rejected, for whatever reason.
35804 .cindex "log" "delayed delivery"
35805 .cindex "delayed delivery, logging"
35806 &%delay_delivery%&: A log entry is written whenever a delivery process is not
35807 started for an incoming message because the load is too high or too many
35808 messages were received on one connection. Logging does not occur if no delivery
35809 process is started because &%queue_only%& is set or &%-odq%& was used.
35811 .cindex "log" "delivery duration"
35812 &%deliver_time%&: For each delivery, the amount of real time it has taken to
35813 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
35815 .cindex "log" "message size on delivery"
35816 .cindex "size" "of message"
35817 &%delivery_size%&: For each delivery, the size of message delivered is added to
35818 the &"=>"& line, tagged with S=.
35820 .cindex "log" "dnslist defer"
35821 .cindex "DNS list" "logging defer"
35822 .cindex "black list (DNS)"
35823 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
35824 DNS black list suffers a temporary error.
35826 .cindex "log" "ETRN commands"
35827 .cindex "ETRN" "logging"
35828 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
35829 is run to determine whether or not it is actually accepted. An invalid ETRN
35830 command, or one received within a message transaction is not logged by this
35831 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
35833 .cindex "log" "host lookup failure"
35834 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
35835 any addresses, or when a lookup of an IP address fails to find a host name, a
35836 log line is written. This logging does not apply to direct DNS lookups when
35837 routing email addresses, but it does apply to &"byname"& lookups.
35839 .cindex "log" "ident timeout"
35840 .cindex "RFC 1413" "logging timeout"
35841 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
35842 client's ident port times out.
35844 .cindex "log" "incoming interface"
35845 .cindex "log" "local interface"
35846 .cindex "log" "local address and port"
35847 .cindex "TCP/IP" "logging local address and port"
35848 .cindex "interface" "logging"
35849 &%incoming_interface%&: The interface on which a message was received is added
35850 to the &"<="& line as an IP address in square brackets, tagged by I= and
35851 followed by a colon and the port number. The local interface and port are also
35852 added to other SMTP log lines, for example &"SMTP connection from"&, to
35853 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
35855 The latter can be disabled by turning off the &%outgoing_interface%& option.
35859 .cindex log "incoming proxy address"
35860 .cindex proxy "logging proxy address"
35861 .cindex "TCP/IP" "logging proxy address"
35862 &%proxy%&: The internal (closest to the system running Exim) IP address
35863 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
35864 on a proxied connection
35865 or the &"=>"& line for a message delivered on a proxied connection..
35866 See &<<SECTproxyInbound>>& for more information.
35869 .cindex "log" "incoming remote port"
35870 .cindex "port" "logging remote"
35871 .cindex "TCP/IP" "logging incoming remote port"
35872 .vindex "&$sender_fullhost$&"
35873 .vindex "&$sender_rcvhost$&"
35874 &%incoming_port%&: The remote port number from which a message was received is
35875 added to log entries and &'Received:'& header lines, following the IP address
35876 in square brackets, and separated from it by a colon. This is implemented by
35877 changing the value that is put in the &$sender_fullhost$& and
35878 &$sender_rcvhost$& variables. Recording the remote port number has become more
35879 important with the widening use of NAT (see RFC 2505).
35881 .cindex "log" "dropped connection"
35882 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
35883 connection is unexpectedly dropped.
35885 .cindex "log" "outgoing interface"
35886 .cindex "log" "local interface"
35887 .cindex "log" "local address and port"
35888 .cindex "TCP/IP" "logging local address and port"
35889 .cindex "interface" "logging"
35891 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
35892 interface on which a message was sent is added to delivery lines as an I= tag
35893 followed by IP address in square brackets. You can disable this by turning
35894 off the &%outgoing_interface%& option.
35897 .cindex "log" "outgoing remote port"
35898 .cindex "port" "logging outgoint remote"
35899 .cindex "TCP/IP" "logging ougtoing remote port"
35900 &%outgoing_port%&: The remote port number is added to delivery log lines (those
35901 containing => tags) following the IP address.
35903 The local port is also added if &%incoming_interface%& and
35904 &%outgoing_interface%& are both enabled.
35906 This option is not included in the default setting, because for most ordinary
35907 configurations, the remote port number is always 25 (the SMTP port), and the
35908 local port is a random ephemeral port.
35910 .cindex "log" "process ids in"
35911 .cindex "pid (process id)" "in log lines"
35912 &%pid%&: The current process id is added to every log line, in square brackets,
35913 immediately after the time and date.
35915 .cindex "log" "queue run"
35916 .cindex "queue runner" "logging"
35917 &%queue_run%&: The start and end of every queue run are logged.
35919 .cindex "log" "queue time"
35920 &%queue_time%&: The amount of time the message has been in the queue on the
35921 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
35922 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
35923 includes reception time as well as the delivery time for the current address.
35924 This means that it may be longer than the difference between the arrival and
35925 delivery log line times, because the arrival log line is not written until the
35926 message has been successfully received.
35928 &%queue_time_overall%&: The amount of time the message has been in the queue on
35929 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
35930 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
35931 message, so it includes reception time as well as the total delivery time.
35933 .cindex "log" "recipients"
35934 &%received_recipients%&: The recipients of a message are listed in the main log
35935 as soon as the message is received. The list appears at the end of the log line
35936 that is written when a message is received, preceded by the word &"for"&. The
35937 addresses are listed after they have been qualified, but before any rewriting
35939 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
35942 .cindex "log" "sender reception"
35943 &%received_sender%&: The unrewritten original sender of a message is added to
35944 the end of the log line that records the message's arrival, after the word
35945 &"from"& (before the recipients if &%received_recipients%& is also set).
35947 .cindex "log" "header lines for rejection"
35948 &%rejected_header%&: If a message's header has been received at the time a
35949 rejection is written to the reject log, the complete header is added to the
35950 log. Header logging can be turned off individually for messages that are
35951 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
35953 .cindex "log" "retry defer"
35954 &%retry_defer%&: A log line is written if a delivery is deferred because a
35955 retry time has not yet been reached. However, this &"retry time not reached"&
35956 message is always omitted from individual message logs after the first delivery
35959 .cindex "log" "return path"
35960 &%return_path_on_delivery%&: The return path that is being transmitted with
35961 the message is included in delivery and bounce lines, using the tag P=.
35962 This is omitted if no delivery actually happens, for example, if routing fails,
35963 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
35965 .cindex "log" "sender on delivery"
35966 &%sender_on_delivery%&: The message's sender address is added to every delivery
35967 and bounce line, tagged by F= (for &"from"&).
35968 This is the original sender that was received with the message; it is not
35969 necessarily the same as the outgoing return path.
35971 .cindex "log" "sender verify failure"
35972 &%sender_verify_fail%&: If this selector is unset, the separate log line that
35973 gives details of a sender verification failure is not written. Log lines for
35974 the rejection of SMTP commands contain just &"sender verify failed"&, so some
35977 .cindex "log" "size rejection"
35978 &%size_reject%&: A log line is written whenever a message is rejected because
35981 .cindex "log" "frozen messages; skipped"
35982 .cindex "frozen messages" "logging skipping"
35983 &%skip_delivery%&: A log line is written whenever a message is skipped during a
35984 queue run because it is frozen or because another process is already delivering
35986 .cindex "&""spool file is locked""&"
35987 The message that is written is &"spool file is locked"&.
35989 .cindex "log" "smtp confirmation"
35990 .cindex "SMTP" "logging confirmation"
35991 .cindex "LMTP" "logging confirmation"
35992 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
35993 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
35994 A number of MTAs (including Exim) return an identifying string in this
35997 .cindex "log" "SMTP connections"
35998 .cindex "SMTP" "logging connections"
35999 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
36000 established or closed, unless the connection is from a host that matches
36001 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
36002 only when the closure is unexpected.) This applies to connections from local
36003 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
36004 dropped in the middle of a message, a log line is always written, whether or
36005 not this selector is set, but otherwise nothing is written at the start and end
36006 of connections unless this selector is enabled.
36008 For TCP/IP connections to an Exim daemon, the current number of connections is
36009 included in the log message for each new connection, but note that the count is
36010 reset if the daemon is restarted.
36011 Also, because connections are closed (and the closure is logged) in
36012 subprocesses, the count may not include connections that have been closed but
36013 whose termination the daemon has not yet noticed. Thus, while it is possible to
36014 match up the opening and closing of connections in the log, the value of the
36015 logged counts may not be entirely accurate.
36017 .cindex "log" "SMTP transaction; incomplete"
36018 .cindex "SMTP" "logging incomplete transactions"
36019 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
36020 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
36021 and the message sender plus any accepted recipients are included in the log
36022 line. This can provide evidence of dictionary attacks.
36024 .cindex "log" "non-MAIL SMTP sessions"
36025 .cindex "MAIL" "logging session without"
36026 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
36027 connection terminates without having issued a MAIL command. This includes both
36028 the case when the connection is dropped, and the case when QUIT is used. It
36029 does not include cases where the connection is rejected right at the start (by
36030 an ACL, or because there are too many connections, or whatever). These cases
36031 already have their own log lines.
36033 The log line that is written contains the identity of the client in the usual
36034 way, followed by D= and a time, which records the duration of the connection.
36035 If the connection was authenticated, this fact is logged exactly as it is for
36036 an incoming message, with an A= item. If the connection was encrypted, CV=,
36037 DN=, and X= items may appear as they do for an incoming message, controlled by
36038 the same logging options.
36040 Finally, if any SMTP commands were issued during the connection, a C= item
36041 is added to the line, listing the commands that were used. For example,
36045 shows that the client issued QUIT straight after EHLO. If there were fewer
36046 than 20 commands, they are all listed. If there were more than 20 commands,
36047 the last 20 are listed, preceded by &"..."&. However, with the default
36048 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
36049 have been aborted before 20 non-mail commands are processed.
36051 &%smtp_mailauth%&: A third subfield with the authenticated sender,
36052 colon-separated, is appended to the A= item for a message arrival or delivery
36053 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
36054 was accepted or used.
36056 .cindex "log" "SMTP protocol error"
36057 .cindex "SMTP" "logging protocol error"
36058 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
36059 encountered. Exim does not have perfect detection of all protocol errors
36060 because of transmission delays and the use of pipelining. If PIPELINING has
36061 been advertised to a client, an Exim server assumes that the client will use
36062 it, and therefore it does not count &"expected"& errors (for example, RCPT
36063 received after rejecting MAIL) as protocol errors.
36065 .cindex "SMTP" "logging syntax errors"
36066 .cindex "SMTP" "syntax errors; logging"
36067 .cindex "SMTP" "unknown command; logging"
36068 .cindex "log" "unknown SMTP command"
36069 .cindex "log" "SMTP syntax error"
36070 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
36071 encountered. An unrecognized command is treated as a syntax error. For an
36072 external connection, the host identity is given; for an internal connection
36073 using &%-bs%& the sender identification (normally the calling user) is given.
36075 .cindex "log" "subject"
36076 .cindex "subject, logging"
36077 &%subject%&: The subject of the message is added to the arrival log line,
36078 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
36079 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
36080 specifies whether characters with values greater than 127 should be logged
36081 unchanged, or whether they should be rendered as escape sequences.
36083 .cindex "log" "certificate verification"
36084 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
36085 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
36086 verified, and &`CV=no`& if not.
36088 .cindex "log" "TLS cipher"
36089 .cindex "TLS" "logging cipher"
36090 &%tls_cipher%&: When a message is sent or received over an encrypted
36091 connection, the cipher suite used is added to the log line, preceded by X=.
36093 .cindex "log" "TLS peer DN"
36094 .cindex "TLS" "logging peer DN"
36095 &%tls_peerdn%&: When a message is sent or received over an encrypted
36096 connection, and a certificate is supplied by the remote host, the peer DN is
36097 added to the log line, preceded by DN=.
36099 .cindex "log" "TLS SNI"
36100 .cindex "TLS" "logging SNI"
36101 &%tls_sni%&: When a message is received over an encrypted connection, and
36102 the remote host provided the Server Name Indication extension, the SNI is
36103 added to the log line, preceded by SNI=.
36105 .cindex "log" "DNS failure in list"
36106 &%unknown_in_list%&: This setting causes a log entry to be written when the
36107 result of a list match is failure because a DNS lookup failed.
36111 .section "Message log" "SECID260"
36112 .cindex "message" "log file for"
36113 .cindex "log" "message log; description of"
36114 .cindex "&_msglog_& directory"
36115 .oindex "&%preserve_message_logs%&"
36116 In addition to the general log files, Exim writes a log file for each message
36117 that it handles. The names of these per-message logs are the message ids, and
36118 they are kept in the &_msglog_& sub-directory of the spool directory. Each
36119 message log contains copies of the log lines that apply to the message. This
36120 makes it easier to inspect the status of an individual message without having
36121 to search the main log. A message log is deleted when processing of the message
36122 is complete, unless &%preserve_message_logs%& is set, but this should be used
36123 only with great care because they can fill up your disk very quickly.
36125 On a heavily loaded system, it may be desirable to disable the use of
36126 per-message logs, in order to reduce disk I/O. This can be done by setting the
36127 &%message_logs%& option false.
36133 . ////////////////////////////////////////////////////////////////////////////
36134 . ////////////////////////////////////////////////////////////////////////////
36136 .chapter "Exim utilities" "CHAPutils"
36137 .scindex IIDutils "utilities"
36138 A number of utility scripts and programs are supplied with Exim and are
36139 described in this chapter. There is also the Exim Monitor, which is covered in
36140 the next chapter. The utilities described here are:
36142 .itable none 0 0 3 7* left 15* left 40* left
36143 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
36144 "list what Exim processes are doing"
36145 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
36146 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
36147 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
36148 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
36150 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
36151 .irow &<<SECTmailstat>>& &'eximstats'& &&&
36152 "extract statistics from the log"
36153 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
36154 "check address acceptance from given IP"
36155 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
36156 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
36157 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
36158 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
36159 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
36160 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
36163 Another utility that might be of use to sites with many MTAs is Tom Kistner's
36164 &'exilog'&. It provides log visualizations across multiple Exim servers. See
36165 &url(http://duncanthrax.net/exilog/) for details.
36170 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
36171 .cindex "&'exiwhat'&"
36172 .cindex "process, querying"
36174 On operating systems that can restart a system call after receiving a signal
36175 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
36176 a line describing what it is doing to the file &_exim-process.info_& in the
36177 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
36178 processes it can find, having first emptied the file. It then waits for one
36179 second to allow the Exim processes to react before displaying the results. In
36180 order to run &'exiwhat'& successfully you have to have sufficient privilege to
36181 send the signal to the Exim processes, so it is normally run as root.
36183 &*Warning*&: This is not an efficient process. It is intended for occasional
36184 use by system administrators. It is not sensible, for example, to set up a
36185 script that sends SIGUSR1 signals to Exim processes at short intervals.
36188 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
36189 varies in different operating systems. Not only are different options used,
36190 but the format of the output is different. For this reason, there are some
36191 system configuration options that configure exactly how &'exiwhat'& works. If
36192 it doesn't seem to be working for you, check the following compile-time
36195 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
36196 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
36197 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
36198 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
36200 An example of typical output from &'exiwhat'& is
36202 164 daemon: -q1h, listening on port 25
36203 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
36204 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
36205 [10.19.42.42] (editor@ref.example)
36206 10592 handling incoming call from [192.168.243.242]
36207 10628 accepting a local non-SMTP message
36209 The first number in the output line is the process number. The third line has
36210 been split here, in order to fit it on the page.
36214 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
36215 .cindex "&'exiqgrep'&"
36216 .cindex "queue" "grepping"
36217 This utility is a Perl script contributed by Matt Hubbard. It runs
36221 or (in case &*-a*& switch is specified)
36225 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
36226 contain alternate exim configuration the queue management might be using.
36228 to obtain a queue listing, and then greps the output to select messages
36229 that match given criteria. The following selection options are available:
36232 .vitem &*-f*&&~<&'regex'&>
36233 Match the sender address using a case-insensitive search. The field that is
36234 tested is enclosed in angle brackets, so you can test for bounce messages with
36238 .vitem &*-r*&&~<&'regex'&>
36239 Match a recipient address using a case-insensitive search. The field that is
36240 tested is not enclosed in angle brackets.
36242 .vitem &*-s*&&~<&'regex'&>
36243 Match against the size field.
36245 .vitem &*-y*&&~<&'seconds'&>
36246 Match messages that are younger than the given time.
36248 .vitem &*-o*&&~<&'seconds'&>
36249 Match messages that are older than the given time.
36252 Match only frozen messages.
36255 Match only non-frozen messages.
36258 The following options control the format of the output:
36262 Display only the count of matching messages.
36265 Long format &-- display the full message information as output by Exim. This is
36269 Display message ids only.
36272 Brief format &-- one line per message.
36275 Display messages in reverse order.
36278 Include delivered recipients in queue listing.
36281 There is one more option, &%-h%&, which outputs a list of options.
36285 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
36286 .cindex "&'exiqsumm'&"
36287 .cindex "queue" "summary"
36288 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
36289 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
36290 running a command such as
36292 exim -bp | exiqsumm
36294 The output consists of one line for each domain that has messages waiting for
36295 it, as in the following example:
36297 3 2322 74m 66m msn.com.example
36299 Each line lists the number of pending deliveries for a domain, their total
36300 volume, and the length of time that the oldest and the newest messages have
36301 been waiting. Note that the number of pending deliveries is greater than the
36302 number of messages when messages have more than one recipient.
36304 A summary line is output at the end. By default the output is sorted on the
36305 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
36306 the output to be sorted by oldest message and by count of messages,
36307 respectively. There are also three options that split the messages for each
36308 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
36309 separates frozen messages, and &%-s%& separates messages according to their
36312 The output of &'exim -bp'& contains the original addresses in the message, so
36313 this also applies to the output from &'exiqsumm'&. No domains from addresses
36314 generated by aliasing or forwarding are included (unless the &%one_time%&
36315 option of the &(redirect)& router has been used to convert them into &"top
36316 level"& addresses).
36321 .section "Extracting specific information from the log (exigrep)" &&&
36323 .cindex "&'exigrep'&"
36324 .cindex "log" "extracts; grepping for"
36325 The &'exigrep'& utility is a Perl script that searches one or more main log
36326 files for entries that match a given pattern. When it finds a match, it
36327 extracts all the log entries for the relevant message, not just those that
36328 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
36329 given message, or all mail for a given user, or for a given host, for example.
36330 The input files can be in Exim log format or syslog format.
36331 If a matching log line is not associated with a specific message, it is
36332 included in &'exigrep'&'s output without any additional lines. The usage is:
36334 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
36336 If no log file names are given on the command line, the standard input is read.
36338 The &%-t%& argument specifies a number of seconds. It adds an additional
36339 condition for message selection. Messages that are complete are shown only if
36340 they spent more than <&'n'&> seconds on the queue.
36342 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
36343 makes it case-sensitive. This may give a performance improvement when searching
36344 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
36345 option; with &%-I%& they do not. In both cases it is possible to change the
36346 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
36348 The &%-l%& option means &"literal"&, that is, treat all characters in the
36349 pattern as standing for themselves. Otherwise the pattern must be a Perl
36350 regular expression.
36352 The &%-v%& option inverts the matching condition. That is, a line is selected
36353 if it does &'not'& match the pattern.
36355 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
36356 that are generated as a result/response to a message that &'exigrep'& matched
36360 user_a sends a message to user_b, which generates a bounce back to user_b. If
36361 &'exigrep'& is used to search for &"user_a"&, only the first message will be
36362 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
36363 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
36364 when searching for &"user_a"& will show both messages since the bounce is
36365 &"related"& to or a &"result"& of the first message that was found by the
36368 If the location of a &'zcat'& command is known from the definition of
36369 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
36370 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
36371 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
36372 autodetection of some well known compression extensions.
36375 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
36376 .cindex "&'exipick'&"
36377 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
36378 lists messages from the queue according to a variety of criteria. For details
36379 of &'exipick'&'s facilities, visit the web page at
36380 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
36381 the &%--help%& option.
36384 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
36385 .cindex "log" "cycling local files"
36386 .cindex "cycling logs"
36387 .cindex "&'exicyclog'&"
36388 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
36389 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
36390 you are using log files with datestamps in their names (see section
36391 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
36392 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
36393 There are two command line options for &'exicyclog'&:
36395 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
36396 default that is set when Exim is built. The default default is 10.
36398 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
36399 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
36400 overriding the script's default, which is to find the setting from Exim's
36404 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
36405 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
36406 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
36407 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
36408 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
36409 logs are handled similarly.
36411 If the limit is greater than 99, the script uses 3-digit numbers such as
36412 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
36413 to one that is greater, or &'vice versa'&, you will have to fix the names of
36414 any existing log files.
36416 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
36417 the end are deleted. All files with numbers greater than 01 are compressed,
36418 using a compression command which is configured by the COMPRESS_COMMAND
36419 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
36420 root &%crontab%& entry of the form
36422 1 0 * * * su exim -c /usr/exim/bin/exicyclog
36424 assuming you have used the name &"exim"& for the Exim user. You can run
36425 &'exicyclog'& as root if you wish, but there is no need.
36429 .section "Mail statistics (eximstats)" "SECTmailstat"
36430 .cindex "statistics"
36431 .cindex "&'eximstats'&"
36432 A Perl script called &'eximstats'& is provided for extracting statistical
36433 information from log files. The output is either plain text, or HTML.
36434 Exim log files are also supported by the &'Lire'& system produced by the
36435 LogReport Foundation &url(http://www.logreport.org).
36437 The &'eximstats'& script has been hacked about quite a bit over time. The
36438 latest version is the result of some extensive revision by Steve Campbell. A
36439 lot of information is given by default, but there are options for suppressing
36440 various parts of it. Following any options, the arguments to the script are a
36441 list of files, which should be main log files. For example:
36443 eximstats -nr /var/spool/exim/log/mainlog.01
36445 By default, &'eximstats'& extracts information about the number and volume of
36446 messages received from or delivered to various hosts. The information is sorted
36447 both by message count and by volume, and the top fifty hosts in each category
36448 are listed on the standard output. Similar information, based on email
36449 addresses or domains instead of hosts can be requested by means of various
36450 options. For messages delivered and received locally, similar statistics are
36451 also produced per user.
36453 The output also includes total counts and statistics about delivery errors, and
36454 histograms showing the number of messages received and deliveries made in each
36455 hour of the day. A delivery with more than one address in its envelope (for
36456 example, an SMTP transaction with more than one RCPT command) is counted
36457 as a single delivery by &'eximstats'&.
36459 Though normally more deliveries than receipts are reported (as messages may
36460 have multiple recipients), it is possible for &'eximstats'& to report more
36461 messages received than delivered, even though the queue is empty at the start
36462 and end of the period in question. If an incoming message contains no valid
36463 recipients, no deliveries are recorded for it. A bounce message is handled as
36464 an entirely separate message.
36466 &'eximstats'& always outputs a grand total summary giving the volume and number
36467 of messages received and deliveries made, and the number of hosts involved in
36468 each case. It also outputs the number of messages that were delayed (that is,
36469 not completely delivered at the first attempt), and the number that had at
36470 least one address that failed.
36472 The remainder of the output is in sections that can be independently disabled
36473 or modified by various options. It consists of a summary of deliveries by
36474 transport, histograms of messages received and delivered per time interval
36475 (default per hour), information about the time messages spent on the queue,
36476 a list of relayed messages, lists of the top fifty sending hosts, local
36477 senders, destination hosts, and destination local users by count and by volume,
36478 and a list of delivery errors that occurred.
36480 The relay information lists messages that were actually relayed, that is, they
36481 came from a remote host and were directly delivered to some other remote host,
36482 without being processed (for example, for aliasing or forwarding) locally.
36484 There are quite a few options for &'eximstats'& to control exactly what it
36485 outputs. These are documented in the Perl script itself, and can be extracted
36486 by running the command &(perldoc)& on the script. For example:
36488 perldoc /usr/exim/bin/eximstats
36491 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
36492 .cindex "&'exim_checkaccess'&"
36493 .cindex "policy control" "checking access"
36494 .cindex "checking access"
36495 The &%-bh%& command line argument allows you to run a fake SMTP session with
36496 debugging output, in order to check what Exim is doing when it is applying
36497 policy controls to incoming SMTP mail. However, not everybody is sufficiently
36498 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
36499 sometimes you just want to answer the question &"Does this address have
36500 access?"& without bothering with any further details.
36502 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
36503 two arguments, an IP address and an email address:
36505 exim_checkaccess 10.9.8.7 A.User@a.domain.example
36507 The utility runs a call to Exim with the &%-bh%& option, to test whether the
36508 given email address would be accepted in a RCPT command in a TCP/IP
36509 connection from the host with the given IP address. The output of the utility
36510 is either the word &"accepted"&, or the SMTP error response, for example:
36513 550 Relay not permitted
36515 When running this test, the utility uses &`<>`& as the envelope sender address
36516 for the MAIL command, but you can change this by providing additional
36517 options. These are passed directly to the Exim command. For example, to specify
36518 that the test is to be run with the sender address &'himself@there.example'&
36521 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
36522 -f himself@there.example
36524 Note that these additional Exim command line items must be given after the two
36525 mandatory arguments.
36527 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
36528 while running its checks. You can run checks that include callouts by using
36529 &%-bhc%&, but this is not yet available in a &"packaged"& form.
36533 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
36534 .cindex "DBM" "building dbm files"
36535 .cindex "building DBM files"
36536 .cindex "&'exim_dbmbuild'&"
36537 .cindex "lower casing"
36538 .cindex "binary zero" "in lookup key"
36539 The &'exim_dbmbuild'& program reads an input file containing keys and data in
36540 the format used by the &(lsearch)& lookup (see section
36541 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
36542 names as keys and the remainder of the information as data. The lower-casing
36543 can be prevented by calling the program with the &%-nolc%& option.
36545 A terminating zero is included as part of the key string. This is expected by
36546 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
36547 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
36548 strings or the data strings. The &(dbmnz)& lookup type can be used with such
36551 The program requires two arguments: the name of the input file (which can be a
36552 single hyphen to indicate the standard input), and the name of the output file.
36553 It creates the output under a temporary name, and then renames it if all went
36557 If the native DB interface is in use (USE_DB is set in a compile-time
36558 configuration file &-- this is common in free versions of Unix) the two file
36559 names must be different, because in this mode the Berkeley DB functions create
36560 a single output file using exactly the name given. For example,
36562 exim_dbmbuild /etc/aliases /etc/aliases.db
36564 reads the system alias file and creates a DBM version of it in
36565 &_/etc/aliases.db_&.
36567 In systems that use the &'ndbm'& routines (mostly proprietary versions of
36568 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
36569 environment, the suffixes are added to the second argument of
36570 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
36571 when the Berkeley functions are used in compatibility mode (though this is not
36572 recommended), because in that case it adds a &_.db_& suffix to the file name.
36574 If a duplicate key is encountered, the program outputs a warning, and when it
36575 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
36576 option is used. By default, only the first of a set of duplicates is used &--
36577 this makes it compatible with &(lsearch)& lookups. There is an option
36578 &%-lastdup%& which causes it to use the data for the last duplicate instead.
36579 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
36580 &%stderr%&. For other errors, where it doesn't actually make a new file, the
36586 .section "Finding individual retry times (exinext)" "SECTfinindret"
36587 .cindex "retry" "times"
36588 .cindex "&'exinext'&"
36589 A utility called &'exinext'& (mostly a Perl script) provides the ability to
36590 fish specific information out of the retry database. Given a mail domain (or a
36591 complete address), it looks up the hosts for that domain, and outputs any retry
36592 information for the hosts or for the domain. At present, the retry information
36593 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
36594 output. For example:
36596 $ exinext piglet@milne.fict.example
36597 kanga.milne.example:192.168.8.1 error 146: Connection refused
36598 first failed: 21-Feb-1996 14:57:34
36599 last tried: 21-Feb-1996 14:57:34
36600 next try at: 21-Feb-1996 15:02:34
36601 roo.milne.example:192.168.8.3 error 146: Connection refused
36602 first failed: 20-Jan-1996 13:12:08
36603 last tried: 21-Feb-1996 11:42:03
36604 next try at: 21-Feb-1996 19:42:03
36605 past final cutoff time
36607 You can also give &'exinext'& a local part, without a domain, and it
36608 will give any retry information for that local part in your default domain.
36609 A message id can be used to obtain retry information pertaining to a specific
36610 message. This exists only when an attempt to deliver a message to a remote host
36611 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
36612 &'exinext'& is not particularly efficient, but then it is not expected to be
36615 The &'exinext'& utility calls Exim to find out information such as the location
36616 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
36617 passed on to the &'exim'& commands. The first specifies an alternate Exim
36618 configuration file, and the second sets macros for use within the configuration
36619 file. These features are mainly to help in testing, but might also be useful in
36620 environments where more than one configuration file is in use.
36624 .section "Hints database maintenance" "SECThindatmai"
36625 .cindex "hints database" "maintenance"
36626 .cindex "maintaining Exim's hints database"
36627 Three utility programs are provided for maintaining the DBM files that Exim
36628 uses to contain its delivery hint information. Each program requires two
36629 arguments. The first specifies the name of Exim's spool directory, and the
36630 second is the name of the database it is to operate on. These are as follows:
36633 &'retry'&: the database of retry information
36635 &'wait-'&<&'transport name'&>: databases of information about messages waiting
36638 &'callout'&: the callout cache
36640 &'ratelimit'&: the data for implementing the ratelimit ACL condition
36642 &'misc'&: other hints data
36645 The &'misc'& database is used for
36648 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
36650 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
36651 &(smtp)& transport)
36653 Limiting the concurrency of specific transports (when &%max_parallel%& is set
36659 .section "exim_dumpdb" "SECID261"
36660 .cindex "&'exim_dumpdb'&"
36661 The entire contents of a database are written to the standard output by the
36662 &'exim_dumpdb'& program, which has no options or arguments other than the
36663 spool and database names. For example, to dump the retry database:
36665 exim_dumpdb /var/spool/exim retry
36667 Two lines of output are produced for each entry:
36669 T:mail.ref.example:192.168.242.242 146 77 Connection refused
36670 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
36672 The first item on the first line is the key of the record. It starts with one
36673 of the letters R, or T, depending on whether it refers to a routing or
36674 transport retry. For a local delivery, the next part is the local address; for
36675 a remote delivery it is the name of the remote host, followed by its failing IP
36676 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
36677 transport). If the remote port is not the standard one (port 25), it is added
36678 to the IP address. Then there follows an error code, an additional error code,
36679 and a textual description of the error.
36681 The three times on the second line are the time of first failure, the time of
36682 the last delivery attempt, and the computed time for the next attempt. The line
36683 ends with an asterisk if the cutoff time for the last retry rule has been
36686 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
36687 consists of a host name followed by a list of ids for messages that are or were
36688 waiting to be delivered to that host. If there are a very large number for any
36689 one host, continuation records, with a sequence number added to the host name,
36690 may be seen. The data in these records is often out of date, because a message
36691 may be routed to several alternative hosts, and Exim makes no effort to keep
36696 .section "exim_tidydb" "SECID262"
36697 .cindex "&'exim_tidydb'&"
36698 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
36699 database. If run with no options, it removes all records that are more than 30
36700 days old. The age is calculated from the date and time that the record was last
36701 updated. Note that, in the case of the retry database, it is &'not'& the time
36702 since the first delivery failure. Information about a host that has been down
36703 for more than 30 days will remain in the database, provided that the record is
36704 updated sufficiently often.
36706 The cutoff date can be altered by means of the &%-t%& option, which must be
36707 followed by a time. For example, to remove all records older than a week from
36708 the retry database:
36710 exim_tidydb -t 7d /var/spool/exim retry
36712 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
36713 message ids. In the former these appear as data in records keyed by host &--
36714 they were messages that were waiting for that host &-- and in the latter they
36715 are the keys for retry information for messages that have suffered certain
36716 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
36717 message ids in database records are those of messages that are still on the
36718 queue. Message ids for messages that no longer exist are removed from
36719 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
36720 For the &'retry'& database, records whose keys are non-existent message ids are
36721 removed. The &'exim_tidydb'& utility outputs comments on the standard output
36722 whenever it removes information from the database.
36724 Certain records are automatically removed by Exim when they are no longer
36725 needed, but others are not. For example, if all the MX hosts for a domain are
36726 down, a retry record is created for each one. If the primary MX host comes back
36727 first, its record is removed when Exim successfully delivers to it, but the
36728 records for the others remain because Exim has not tried to use those hosts.
36730 It is important, therefore, to run &'exim_tidydb'& periodically on all the
36731 hints databases. You should do this at a quiet time of day, because it requires
36732 a database to be locked (and therefore inaccessible to Exim) while it does its
36733 work. Removing records from a DBM file does not normally make the file smaller,
36734 but all the common DBM libraries are able to re-use the space that is released.
36735 After an initial phase of increasing in size, the databases normally reach a
36736 point at which they no longer get any bigger, as long as they are regularly
36739 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
36740 databases is likely to keep on increasing.
36745 .section "exim_fixdb" "SECID263"
36746 .cindex "&'exim_fixdb'&"
36747 The &'exim_fixdb'& program is a utility for interactively modifying databases.
36748 Its main use is for testing Exim, but it might also be occasionally useful for
36749 getting round problems in a live system. It has no options, and its interface
36750 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
36751 key of a database record can then be entered, and the data for that record is
36754 If &"d"& is typed at the next prompt, the entire record is deleted. For all
36755 except the &'retry'& database, that is the only operation that can be carried
36756 out. For the &'retry'& database, each field is output preceded by a number, and
36757 data for individual fields can be changed by typing the field number followed
36758 by new data, for example:
36762 resets the time of the next delivery attempt. Time values are given as a
36763 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
36764 used as optional separators.
36769 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
36770 .cindex "mailbox" "maintenance"
36771 .cindex "&'exim_lock'&"
36772 .cindex "locking mailboxes"
36773 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
36774 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
36775 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
36776 a user agent while investigating a problem. The utility requires the name of
36777 the file as its first argument. If the locking is successful, the second
36778 argument is run as a command (using C's &[system()]& function); if there is no
36779 second argument, the value of the SHELL environment variable is used; if this
36780 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
36781 is unlocked and the utility ends. The following options are available:
36785 Use &[fcntl()]& locking on the open mailbox.
36788 Use &[flock()]& locking on the open mailbox, provided the operating system
36791 .vitem &%-interval%&
36792 This must be followed by a number, which is a number of seconds; it sets the
36793 interval to sleep between retries (default 3).
36795 .vitem &%-lockfile%&
36796 Create a lock file before opening the mailbox.
36799 Lock the mailbox using MBX rules.
36802 Suppress verification output.
36804 .vitem &%-retries%&
36805 This must be followed by a number; it sets the number of times to try to get
36806 the lock (default 10).
36808 .vitem &%-restore_time%&
36809 This option causes &%exim_lock%& to restore the modified and read times to the
36810 locked file before exiting. This allows you to access a locked mailbox (for
36811 example, to take a backup copy) without disturbing the times that the user
36814 .vitem &%-timeout%&
36815 This must be followed by a number, which is a number of seconds; it sets a
36816 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
36817 default), a non-blocking call is used.
36820 Generate verbose output.
36823 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
36824 default is to create a lock file and also to use &[fcntl()]& locking on the
36825 mailbox, which is the same as Exim's default. The use of &%-flock%& or
36826 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
36827 requires that the directory containing the file be writeable. Locking by lock
36828 file does not last for ever; Exim assumes that a lock file is expired if it is
36829 more than 30 minutes old.
36831 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
36832 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
36833 to be taken out on the open mailbox, and an exclusive lock on the file
36834 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
36835 number of the mailbox file. When the locking is released, if an exclusive lock
36836 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
36838 The default output contains verification of the locking that takes place. The
36839 &%-v%& option causes some additional information to be given. The &%-q%& option
36840 suppresses all output except error messages.
36844 exim_lock /var/spool/mail/spqr
36846 runs an interactive shell while the file is locked, whereas
36848 &`exim_lock -q /var/spool/mail/spqr <<End`&
36849 <&'some commands'&>
36852 runs a specific non-interactive sequence of commands while the file is locked,
36853 suppressing all verification output. A single command can be run by a command
36856 exim_lock -q /var/spool/mail/spqr \
36857 "cp /var/spool/mail/spqr /some/where"
36859 Note that if a command is supplied, it must be entirely contained within the
36860 second argument &-- hence the quotes.
36864 . ////////////////////////////////////////////////////////////////////////////
36865 . ////////////////////////////////////////////////////////////////////////////
36867 .chapter "The Exim monitor" "CHAPeximon"
36868 .scindex IIDeximon "Exim monitor" "description"
36869 .cindex "X-windows"
36870 .cindex "&'eximon'&"
36871 .cindex "Local/eximon.conf"
36872 .cindex "&_exim_monitor/EDITME_&"
36873 The Exim monitor is an application which displays in an X window information
36874 about the state of Exim's queue and what Exim is doing. An admin user can
36875 perform certain operations on messages from this GUI interface; however all
36876 such facilities are also available from the command line, and indeed, the
36877 monitor itself makes use of the command line to perform any actions requested.
36881 .section "Running the monitor" "SECID264"
36882 The monitor is started by running the script called &'eximon'&. This is a shell
36883 script that sets up a number of environment variables, and then runs the
36884 binary called &_eximon.bin_&. The default appearance of the monitor window can
36885 be changed by editing the &_Local/eximon.conf_& file created by editing
36886 &_exim_monitor/EDITME_&. Comments in that file describe what the various
36887 parameters are for.
36889 The parameters that get built into the &'eximon'& script can be overridden for
36890 a particular invocation by setting up environment variables of the same names,
36891 preceded by &`EXIMON_`&. For example, a shell command such as
36893 EXIMON_LOG_DEPTH=400 eximon
36895 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
36896 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
36897 overrides the Exim log file configuration. This makes it possible to have
36898 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
36899 syslog messages are routed to a file on the local host.
36901 X resources can be used to change the appearance of the window in the normal
36902 way. For example, a resource setting of the form
36904 Eximon*background: gray94
36906 changes the colour of the background to light grey rather than white. The
36907 stripcharts are drawn with both the data lines and the reference lines in
36908 black. This means that the reference lines are not visible when on top of the
36909 data. However, their colour can be changed by setting a resource called
36910 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
36911 For example, if your X server is running Unix, you could set up lighter
36912 reference lines in the stripcharts by obeying
36915 Eximon*highlight: gray
36918 .cindex "admin user"
36919 In order to see the contents of messages on the queue, and to operate on them,
36920 &'eximon'& must either be run as root or by an admin user.
36922 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
36923 contain X11 resource parameters interpreted by the X11 library. In addition,
36924 if the first parameter starts with the string "gdb" then it is removed and the
36925 binary is invoked under gdb (the parameter is used as the gdb command-name, so
36926 versioned variants of gdb can be invoked).
36928 The monitor's window is divided into three parts. The first contains one or
36929 more stripcharts and two action buttons, the second contains a &"tail"& of the
36930 main log file, and the third is a display of the queue of messages awaiting
36931 delivery, with two more action buttons. The following sections describe these
36932 different parts of the display.
36937 .section "The stripcharts" "SECID265"
36938 .cindex "stripchart"
36939 The first stripchart is always a count of messages on the queue. Its name can
36940 be configured by setting QUEUE_STRIPCHART_NAME in the
36941 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
36942 configuration script by regular expression matches on log file entries, making
36943 it possible to display, for example, counts of messages delivered to certain
36944 hosts or using certain transports. The supplied defaults display counts of
36945 received and delivered messages, and of local and SMTP deliveries. The default
36946 period between stripchart updates is one minute; this can be adjusted by a
36947 parameter in the &_Local/eximon.conf_& file.
36949 The stripchart displays rescale themselves automatically as the value they are
36950 displaying changes. There are always 10 horizontal lines in each chart; the
36951 title string indicates the value of each division when it is greater than one.
36952 For example, &"x2"& means that each division represents a value of 2.
36954 It is also possible to have a stripchart which shows the percentage fullness of
36955 a particular disk partition, which is useful when local deliveries are confined
36956 to a single partition.
36958 .cindex "&%statvfs%& function"
36959 This relies on the availability of the &[statvfs()]& function or equivalent in
36960 the operating system. Most, but not all versions of Unix that support Exim have
36961 this. For this particular stripchart, the top of the chart always represents
36962 100%, and the scale is given as &"x10%"&. This chart is configured by setting
36963 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
36964 &_Local/eximon.conf_& file.
36969 .section "Main action buttons" "SECID266"
36970 .cindex "size" "of monitor window"
36971 .cindex "Exim monitor" "window size"
36972 .cindex "window size"
36973 Below the stripcharts there is an action button for quitting the monitor. Next
36974 to this is another button marked &"Size"&. They are placed here so that
36975 shrinking the window to its default minimum size leaves just the queue count
36976 stripchart and these two buttons visible. Pressing the &"Size"& button causes
36977 the window to expand to its maximum size, unless it is already at the maximum,
36978 in which case it is reduced to its minimum.
36980 When expanding to the maximum, if the window cannot be fully seen where it
36981 currently is, it is moved back to where it was the last time it was at full
36982 size. When it is expanding from its minimum size, the old position is
36983 remembered, and next time it is reduced to the minimum it is moved back there.
36985 The idea is that you can keep a reduced window just showing one or two
36986 stripcharts at a convenient place on your screen, easily expand it to show
36987 the full window when required, and just as easily put it back to what it was.
36988 The idea is copied from what the &'twm'& window manager does for its
36989 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
36990 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
36992 Normally, the monitor starts up with the window at its full size, but it can be
36993 built so that it starts up with the window at its smallest size, by setting
36994 START_SMALL=yes in &_Local/eximon.conf_&.
36998 .section "The log display" "SECID267"
36999 .cindex "log" "tail of; in monitor"
37000 The second section of the window is an area in which a display of the tail of
37001 the main log is maintained.
37002 To save space on the screen, the timestamp on each log line is shortened by
37003 removing the date and, if &%log_timezone%& is set, the timezone.
37004 The log tail is not available when the only destination for logging data is
37005 syslog, unless the syslog lines are routed to a local file whose name is passed
37006 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
37008 The log sub-window has a scroll bar at its lefthand side which can be used to
37009 move back to look at earlier text, and the up and down arrow keys also have a
37010 scrolling effect. The amount of log that is kept depends on the setting of
37011 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
37012 to use. When this is full, the earlier 50% of data is discarded &-- this is
37013 much more efficient than throwing it away line by line. The sub-window also has
37014 a horizontal scroll bar for accessing the ends of long log lines. This is the
37015 only means of horizontal scrolling; the right and left arrow keys are not
37016 available. Text can be cut from this part of the window using the mouse in the
37017 normal way. The size of this subwindow is controlled by parameters in the
37018 configuration file &_Local/eximon.conf_&.
37020 Searches of the text in the log window can be carried out by means of the ^R
37021 and ^S keystrokes, which default to a reverse and a forward search,
37022 respectively. The search covers only the text that is displayed in the window.
37023 It cannot go further back up the log.
37025 The point from which the search starts is indicated by a caret marker. This is
37026 normally at the end of the text in the window, but can be positioned explicitly
37027 by pointing and clicking with the left mouse button, and is moved automatically
37028 by a successful search. If new text arrives in the window when it is scrolled
37029 back, the caret remains where it is, but if the window is not scrolled back,
37030 the caret is moved to the end of the new text.
37032 Pressing ^R or ^S pops up a window into which the search text can be typed.
37033 There are buttons for selecting forward or reverse searching, for carrying out
37034 the search, and for cancelling. If the &"Search"& button is pressed, the search
37035 happens and the window remains so that further searches can be done. If the
37036 &"Return"& key is pressed, a single search is done and the window is closed. If
37037 ^C is typed the search is cancelled.
37039 The searching facility is implemented using the facilities of the Athena text
37040 widget. By default this pops up a window containing both &"search"& and
37041 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
37042 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
37043 However, the linkers in BSDI and HP-UX seem unable to handle an externally
37044 provided version of &%TextPop%& when the remaining parts of the text widget
37045 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
37046 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
37047 on these systems, at the expense of having unwanted items in the search popup
37052 .section "The queue display" "SECID268"
37053 .cindex "queue" "display in monitor"
37054 The bottom section of the monitor window contains a list of all messages that
37055 are on the queue, which includes those currently being received or delivered,
37056 as well as those awaiting delivery. The size of this subwindow is controlled by
37057 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
37058 at which it is updated is controlled by another parameter in the same file &--
37059 the default is 5 minutes, since queue scans can be quite expensive. However,
37060 there is an &"Update"& action button just above the display which can be used
37061 to force an update of the queue display at any time.
37063 When a host is down for some time, a lot of pending mail can build up for it,
37064 and this can make it hard to deal with other messages on the queue. To help
37065 with this situation there is a button next to &"Update"& called &"Hide"&. If
37066 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
37067 type anything in here and press &"Return"&, the text is added to a chain of
37068 such texts, and if every undelivered address in a message matches at least one
37069 of the texts, the message is not displayed.
37071 If there is an address that does not match any of the texts, all the addresses
37072 are displayed as normal. The matching happens on the ends of addresses so, for
37073 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
37074 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
37075 has been set up, a button called &"Unhide"& is displayed. If pressed, it
37076 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
37077 a hide request is automatically cancelled after one hour.
37079 While the dialogue box is displayed, you can't press any buttons or do anything
37080 else to the monitor window. For this reason, if you want to cut text from the
37081 queue display to use in the dialogue box, you have to do the cutting before
37082 pressing the &"Hide"& button.
37084 The queue display contains, for each unhidden queued message, the length of
37085 time it has been on the queue, the size of the message, the message id, the
37086 message sender, and the first undelivered recipient, all on one line. If it is
37087 a bounce message, the sender is shown as &"<>"&. If there is more than one
37088 recipient to which the message has not yet been delivered, subsequent ones are
37089 listed on additional lines, up to a maximum configured number, following which
37090 an ellipsis is displayed. Recipients that have already received the message are
37093 .cindex "frozen messages" "display"
37094 If a message is frozen, an asterisk is displayed at the left-hand side.
37096 The queue display has a vertical scroll bar, and can also be scrolled by means
37097 of the arrow keys. Text can be cut from it using the mouse in the normal way.
37098 The text searching facilities, as described above for the log window, are also
37099 available, but the caret is always moved to the end of the text when the queue
37100 display is updated.
37104 .section "The queue menu" "SECID269"
37105 .cindex "queue" "menu in monitor"
37106 If the &%shift%& key is held down and the left button is clicked when the mouse
37107 pointer is over the text for any message, an action menu pops up, and the first
37108 line of the queue display for the message is highlighted. This does not affect
37111 If you want to use some other event for popping up the menu, you can set the
37112 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
37113 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
37114 value set in this parameter is a standard X event description. For example, to
37115 run eximon using &%ctrl%& rather than &%shift%& you could use
37117 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
37119 The title of the menu is the message id, and it contains entries which act as
37123 &'message log'&: The contents of the message log for the message are displayed
37124 in a new text window.
37126 &'headers'&: Information from the spool file that contains the envelope
37127 information and headers is displayed in a new text window. See chapter
37128 &<<CHAPspool>>& for a description of the format of spool files.
37130 &'body'&: The contents of the spool file containing the body of the message are
37131 displayed in a new text window. There is a default limit of 20,000 bytes to the
37132 amount of data displayed. This can be changed by setting the BODY_MAX
37133 option at compile time, or the EXIMON_BODY_MAX option at run time.
37135 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
37136 delivery of the message. This causes an automatic thaw if the message is
37137 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
37138 a new text window. The delivery is run in a separate process, to avoid holding
37139 up the monitor while the delivery proceeds.
37141 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
37142 that the message be frozen.
37144 .cindex "thawing messages"
37145 .cindex "unfreezing messages"
37146 .cindex "frozen messages" "thawing"
37147 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
37148 that the message be thawed.
37150 .cindex "delivery" "forcing failure"
37151 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
37152 that Exim gives up trying to deliver the message. A bounce message is generated
37153 for any remaining undelivered addresses.
37155 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
37156 that the message be deleted from the system without generating a bounce
37159 &'add recipient'&: A dialog box is displayed into which a recipient address can
37160 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
37161 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
37162 Otherwise it must be entered as a fully qualified address. Pressing RETURN
37163 causes a call to Exim to be made using the &%-Mar%& option to request that an
37164 additional recipient be added to the message, unless the entry box is empty, in
37165 which case no action is taken.
37167 &'mark delivered'&: A dialog box is displayed into which a recipient address
37168 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
37169 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
37170 Otherwise it must be entered as a fully qualified address. Pressing RETURN
37171 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
37172 recipient address as already delivered, unless the entry box is empty, in which
37173 case no action is taken.
37175 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
37176 mark all recipient addresses as already delivered.
37178 &'edit sender'&: A dialog box is displayed initialized with the current
37179 sender's address. Pressing RETURN causes a call to Exim to be made using the
37180 &%-Mes%& option to replace the sender address, unless the entry box is empty,
37181 in which case no action is taken. If you want to set an empty sender (as in
37182 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
37183 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
37184 the address is qualified with that domain.
37187 When a delivery is forced, a window showing the &%-v%& output is displayed. In
37188 other cases when a call to Exim is made, if there is any output from Exim (in
37189 particular, if the command fails) a window containing the command and the
37190 output is displayed. Otherwise, the results of the action are normally apparent
37191 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
37192 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
37193 if no output is generated.
37195 The queue display is automatically updated for actions such as freezing and
37196 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
37197 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
37198 force an update of the display after one of these actions.
37200 In any text window that is displayed as result of a menu action, the normal
37201 cut-and-paste facility is available, and searching can be carried out using ^R
37202 and ^S, as described above for the log tail window.
37209 . ////////////////////////////////////////////////////////////////////////////
37210 . ////////////////////////////////////////////////////////////////////////////
37212 .chapter "Security considerations" "CHAPsecurity"
37213 .scindex IIDsecurcon "security" "discussion of"
37214 This chapter discusses a number of issues concerned with security, some of
37215 which are also covered in other parts of this manual.
37217 For reasons that this author does not understand, some people have promoted
37218 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
37219 existence of this chapter in the documentation. However, the intent of the
37220 chapter is simply to describe the way Exim works in relation to certain
37221 security concerns, not to make any specific claims about the effectiveness of
37222 its security as compared with other MTAs.
37224 What follows is a description of the way Exim is supposed to be. Best efforts
37225 have been made to try to ensure that the code agrees with the theory, but an
37226 absence of bugs can never be guaranteed. Any that are reported will get fixed
37227 as soon as possible.
37230 .section "Building a more &""hardened""& Exim" "SECID286"
37231 .cindex "security" "build-time features"
37232 There are a number of build-time options that can be set in &_Local/Makefile_&
37233 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
37234 Exim administrator who does not have the root password, or by someone who has
37235 penetrated the Exim (but not the root) account. These options are as follows:
37238 ALT_CONFIG_PREFIX can be set to a string that is required to match the
37239 start of any file names used with the &%-C%& option. When it is set, these file
37240 names are also not allowed to contain the sequence &"/../"&. (However, if the
37241 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
37242 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
37243 default setting for &%ALT_CONFIG_PREFIX%&.
37245 If the permitted configuration files are confined to a directory to
37246 which only root has access, this guards against someone who has broken
37247 into the Exim account from running a privileged Exim with an arbitrary
37248 configuration file, and using it to break into other accounts.
37251 If a non-trusted configuration file (i.e. not the default configuration file
37252 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
37253 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
37254 the next item), then root privilege is retained only if the caller of Exim is
37255 root. This locks out the possibility of testing a configuration using &%-C%&
37256 right through message reception and delivery, even if the caller is root. The
37257 reception works, but by that time, Exim is running as the Exim user, so when
37258 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
37259 privilege to be lost. However, root can test reception and delivery using two
37263 The WHITELIST_D_MACROS build option declares some macros to be safe to override
37264 with &%-D%& if the real uid is one of root, the Exim run-time user or the
37265 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
37266 requiring the run-time value supplied to &%-D%& to match a regex that errs on
37267 the restrictive side. Requiring build-time selection of safe macros is onerous
37268 but this option is intended solely as a transition mechanism to permit
37269 previously-working configurations to continue to work after release 4.73.
37271 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
37274 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
37275 never to be used for any deliveries. This is like the &%never_users%& runtime
37276 option, but it cannot be overridden; the runtime option adds additional users
37277 to the list. The default setting is &"root"&; this prevents a non-root user who
37278 is permitted to modify the runtime file from using Exim as a way to get root.
37283 .section "Root privilege" "SECID270"
37285 .cindex "root privilege"
37286 The Exim binary is normally setuid to root, which means that it gains root
37287 privilege (runs as root) when it starts execution. In some special cases (for
37288 example, when the daemon is not in use and there are no local deliveries), it
37289 may be possible to run Exim setuid to some user other than root. This is
37290 discussed in the next section. However, in most installations, root privilege
37291 is required for two things:
37294 To set up a socket connected to the standard SMTP port (25) when initialising
37295 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
37298 To be able to change uid and gid in order to read users' &_.forward_& files and
37299 perform local deliveries as the receiving user or as specified in the
37303 It is not necessary to be root to do any of the other things Exim does, such as
37304 receiving messages and delivering them externally over SMTP, and it is
37305 obviously more secure if Exim does not run as root except when necessary.
37306 For this reason, a user and group for Exim to use must be defined in
37307 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
37308 group"&. Their values can be changed by the run time configuration, though this
37309 is not recommended. Often a user called &'exim'& is used, but some sites use
37310 &'mail'& or another user name altogether.
37312 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
37313 abdication; the process cannot regain root afterwards. Prior to release 4.00,
37314 &[seteuid()]& was used in some circumstances, but this is no longer the case.
37316 After a new Exim process has interpreted its command line options, it changes
37317 uid and gid in the following cases:
37322 If the &%-C%& option is used to specify an alternate configuration file, or if
37323 the &%-D%& option is used to define macro values for the configuration, and the
37324 calling process is not running as root, the uid and gid are changed to those of
37325 the calling process.
37326 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
37327 option may not be used at all.
37328 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
37329 can be supplied if the calling process is running as root, the Exim run-time
37330 user or CONFIGURE_OWNER, if defined.
37335 If the expansion test option (&%-be%&) or one of the filter testing options
37336 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
37339 If the process is not a daemon process or a queue runner process or a delivery
37340 process or a process for testing address routing (started with &%-bt%&), the
37341 uid and gid are changed to the Exim user and group. This means that Exim always
37342 runs under its own uid and gid when receiving messages. This also applies when
37343 testing address verification
37346 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
37349 For a daemon, queue runner, delivery, or address testing process, the uid
37350 remains as root at this stage, but the gid is changed to the Exim group.
37353 The processes that initially retain root privilege behave as follows:
37356 A daemon process changes the gid to the Exim group and the uid to the Exim
37357 user after setting up one or more listening sockets. The &[initgroups()]&
37358 function is called, so that if the Exim user is in any additional groups, they
37359 will be used during message reception.
37361 A queue runner process retains root privilege throughout its execution. Its
37362 job is to fork a controlled sequence of delivery processes.
37364 A delivery process retains root privilege throughout most of its execution,
37365 but any actual deliveries (that is, the transports themselves) are run in
37366 subprocesses which always change to a non-root uid and gid. For local
37367 deliveries this is typically the uid and gid of the owner of the mailbox; for
37368 remote deliveries, the Exim uid and gid are used. Once all the delivery
37369 subprocesses have been run, a delivery process changes to the Exim uid and gid
37370 while doing post-delivery tidying up such as updating the retry database and
37371 generating bounce and warning messages.
37373 While the recipient addresses in a message are being routed, the delivery
37374 process runs as root. However, if a user's filter file has to be processed,
37375 this is done in a subprocess that runs under the individual user's uid and
37376 gid. A system filter is run as root unless &%system_filter_user%& is set.
37378 A process that is testing addresses (the &%-bt%& option) runs as root so that
37379 the routing is done in the same environment as a message delivery.
37385 .section "Running Exim without privilege" "SECTrunexiwitpri"
37386 .cindex "privilege, running without"
37387 .cindex "unprivileged running"
37388 .cindex "root privilege" "running without"
37389 Some installations like to run Exim in an unprivileged state for more of its
37390 operation, for added security. Support for this mode of operation is provided
37391 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
37392 gid are changed to the Exim user and group at the start of a delivery process
37393 (and also queue runner and address testing processes). This means that address
37394 routing is no longer run as root, and the deliveries themselves cannot change
37398 .cindex "daemon" "restarting"
37399 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
37400 that the daemon can still be started in the usual way, and it can respond
37401 correctly to SIGHUP because the re-invocation regains root privilege.
37403 An alternative approach is to make Exim setuid to the Exim user and also setgid
37404 to the Exim group. If you do this, the daemon must be started from a root
37405 process. (Calling Exim from a root process makes it behave in the way it does
37406 when it is setuid root.) However, the daemon cannot restart itself after a
37407 SIGHUP signal because it cannot regain privilege.
37409 It is still useful to set &%deliver_drop_privilege%& in this case, because it
37410 stops Exim from trying to re-invoke itself to do a delivery after a message has
37411 been received. Such a re-invocation is a waste of resources because it has no
37414 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
37415 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
37416 to the Exim user seems a clean approach, but there is one complication:
37418 In this style of operation, Exim is running with the real uid and gid set to
37419 those of the calling process, and the effective uid/gid set to Exim's values.
37420 Ideally, any association with the calling process' uid/gid should be dropped,
37421 that is, the real uid/gid should be reset to the effective values so as to
37422 discard any privileges that the caller may have. While some operating systems
37423 have a function that permits this action for a non-root effective uid, quite a
37424 number of them do not. Because of this lack of standardization, Exim does not
37425 address this problem at this time.
37427 For this reason, the recommended approach for &"mostly unprivileged"& running
37428 is to keep the Exim binary setuid to root, and to set
37429 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
37430 be used in the most straightforward way.
37432 If you configure Exim not to run delivery processes as root, there are a
37433 number of restrictions on what you can do:
37436 You can deliver only as the Exim user/group. You should explicitly use the
37437 &%user%& and &%group%& options to override routers or local transports that
37438 normally deliver as the recipient. This makes sure that configurations that
37439 work in this mode function the same way in normal mode. Any implicit or
37440 explicit specification of another user causes an error.
37442 Use of &_.forward_& files is severely restricted, such that it is usually
37443 not worthwhile to include them in the configuration.
37445 Users who wish to use &_.forward_& would have to make their home directory and
37446 the file itself accessible to the Exim user. Pipe and append-to-file entries,
37447 and their equivalents in Exim filters, cannot be used. While they could be
37448 enabled in the Exim user's name, that would be insecure and not very useful.
37450 Unless the local user mailboxes are all owned by the Exim user (possible in
37451 some POP3 or IMAP-only environments):
37454 They must be owned by the Exim group and be writeable by that group. This
37455 implies you must set &%mode%& in the appendfile configuration, as well as the
37456 mode of the mailbox files themselves.
37458 You must set &%no_check_owner%&, since most or all of the files will not be
37459 owned by the Exim user.
37461 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
37462 on a newly created mailbox when unprivileged. This also implies that new
37463 mailboxes need to be created manually.
37468 These restrictions severely restrict what can be done in local deliveries.
37469 However, there are no restrictions on remote deliveries. If you are running a
37470 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
37471 gives more security at essentially no cost.
37473 If you are using the &%mua_wrapper%& facility (see chapter
37474 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
37479 .section "Delivering to local files" "SECID271"
37480 Full details of the checks applied by &(appendfile)& before it writes to a file
37481 are given in chapter &<<CHAPappendfile>>&.
37485 .section "Running local commands" "SECTsecconslocalcmds"
37486 .cindex "security" "local commands"
37487 .cindex "security" "command injection attacks"
37488 There are a number of ways in which an administrator can configure Exim to run
37489 commands based upon received, untrustworthy, data. Further, in some
37490 configurations a user who can control a &_.forward_& file can also arrange to
37491 run commands. Configuration to check includes, but is not limited to:
37494 Use of &%use_shell%& in the pipe transport: various forms of shell command
37495 injection may be possible with this option present. It is dangerous and should
37496 be used only with considerable caution. Consider constraints which whitelist
37497 allowed characters in a variable which is to be used in a pipe transport that
37498 has &%use_shell%& enabled.
37500 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
37501 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
37502 &_.forward_& files in a redirect router. If Exim is running on a central mail
37503 hub to which ordinary users do not have shell access, but home directories are
37504 NFS mounted (for instance) then administrators should review the list of these
37505 forbid options available, and should bear in mind that the options that may
37506 need forbidding can change as new features are added between releases.
37508 The &%${run...}%& expansion item does not use a shell by default, but
37509 administrators can configure use of &_/bin/sh_& as part of the command.
37510 Such invocations should be viewed with prejudicial suspicion.
37512 Administrators who use embedded Perl are advised to explore how Perl's
37513 taint checking might apply to their usage.
37515 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
37516 administrators are well advised to view its use with suspicion, in case (for
37517 instance) it allows a local-part to contain embedded Exim directives.
37519 Use of &%${match_local_part...}%& and friends becomes more dangerous if
37520 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
37521 each can reference arbitrary lists and files, rather than just being a list
37523 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
37524 real-world security vulnerabilities caused by its use with untrustworthy data
37525 injected in, for SQL injection attacks.
37526 Consider the use of the &%inlisti%& expansion condition instead.
37532 .section "Trust in configuration data" "SECTsecconfdata"
37533 .cindex "security" "data sources"
37534 .cindex "security" "regular expressions"
37535 .cindex "regular expressions" "security"
37536 .cindex "PCRE" "security"
37537 If configuration data for Exim can come from untrustworthy sources, there
37538 are some issues to be aware of:
37541 Use of &%${expand...}%& may provide a path for shell injection attacks.
37543 Letting untrusted data provide a regular expression is unwise.
37545 Using &%${match...}%& to apply a fixed regular expression against untrusted
37546 data may result in pathological behaviour within PCRE. Be aware of what
37547 "backtracking" means and consider options for being more strict with a regular
37548 expression. Avenues to explore include limiting what can match (avoiding &`.`&
37549 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
37550 possessive quantifiers or just not using regular expressions against untrusted
37553 It can be important to correctly use &%${quote:...}%&,
37554 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
37555 items to ensure that data is correctly constructed.
37557 Some lookups might return multiple results, even though normal usage is only
37558 expected to yield one result.
37564 .section "IPv4 source routing" "SECID272"
37565 .cindex "source routing" "in IP packets"
37566 .cindex "IP source routing"
37567 Many operating systems suppress IP source-routed packets in the kernel, but
37568 some cannot be made to do this, so Exim does its own check. It logs incoming
37569 IPv4 source-routed TCP calls, and then drops them. Things are all different in
37570 IPv6. No special checking is currently done.
37574 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
37575 Support for these SMTP commands is disabled by default. If required, they can
37576 be enabled by defining suitable ACLs.
37581 .section "Privileged users" "SECID274"
37582 .cindex "trusted users"
37583 .cindex "admin user"
37584 .cindex "privileged user"
37585 .cindex "user" "trusted"
37586 .cindex "user" "admin"
37587 Exim recognizes two sets of users with special privileges. Trusted users are
37588 able to submit new messages to Exim locally, but supply their own sender
37589 addresses and information about a sending host. For other users submitting
37590 local messages, Exim sets up the sender address from the uid, and doesn't
37591 permit a remote host to be specified.
37594 However, an untrusted user is permitted to use the &%-f%& command line option
37595 in the special form &%-f <>%& to indicate that a delivery failure for the
37596 message should not cause an error report. This affects the message's envelope,
37597 but it does not affect the &'Sender:'& header. Untrusted users may also be
37598 permitted to use specific forms of address with the &%-f%& option by setting
37599 the &%untrusted_set_sender%& option.
37601 Trusted users are used to run processes that receive mail messages from some
37602 other mail domain and pass them on to Exim for delivery either locally, or over
37603 the Internet. Exim trusts a caller that is running as root, as the Exim user,
37604 as any user listed in the &%trusted_users%& configuration option, or under any
37605 group listed in the &%trusted_groups%& option.
37607 Admin users are permitted to do things to the messages on Exim's queue. They
37608 can freeze or thaw messages, cause them to be returned to their senders, remove
37609 them entirely, or modify them in various ways. In addition, admin users can run
37610 the Exim monitor and see all the information it is capable of providing, which
37611 includes the contents of files on the spool.
37615 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
37616 delivery of messages on its queue is restricted to admin users. This
37617 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
37618 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
37619 queue is also restricted to admin users. This restriction can be relaxed by
37620 setting &%no_queue_list_requires_admin%&.
37622 Exim recognizes an admin user if the calling process is running as root or as
37623 the Exim user or if any of the groups associated with the calling process is
37624 the Exim group. It is not necessary actually to be running under the Exim
37625 group. However, if admin users who are not root or the Exim user are to access
37626 the contents of files on the spool via the Exim monitor (which runs
37627 unprivileged), Exim must be built to allow group read access to its spool
37632 .section "Spool files" "SECID275"
37633 .cindex "spool directory" "files"
37634 Exim's spool directory and everything it contains is owned by the Exim user and
37635 set to the Exim group. The mode for spool files is defined in the
37636 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
37637 any user who is a member of the Exim group can access these files.
37641 .section "Use of argv[0]" "SECID276"
37642 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
37643 of specific strings, Exim assumes certain options. For example, calling Exim
37644 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
37645 to calling it with the option &%-bS%&. There are no security implications in
37650 .section "Use of %f formatting" "SECID277"
37651 The only use made of &"%f"& by Exim is in formatting load average values. These
37652 are actually stored in integer variables as 1000 times the load average.
37653 Consequently, their range is limited and so therefore is the length of the
37658 .section "Embedded Exim path" "SECID278"
37659 Exim uses its own path name, which is embedded in the code, only when it needs
37660 to re-exec in order to regain root privilege. Therefore, it is not root when it
37661 does so. If some bug allowed the path to get overwritten, it would lead to an
37662 arbitrary program's being run as exim, not as root.
37666 .section "Dynamic module directory" "SECTdynmoddir"
37667 Any dynamically loadable modules must be installed into the directory
37668 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
37672 .section "Use of sprintf()" "SECID279"
37673 .cindex "&[sprintf()]&"
37674 A large number of occurrences of &"sprintf"& in the code are actually calls to
37675 &'string_sprintf()'&, a function that returns the result in malloc'd store.
37676 The intermediate formatting is done into a large fixed buffer by a function
37677 that runs through the format string itself, and checks the length of each
37678 conversion before performing it, thus preventing buffer overruns.
37680 The remaining uses of &[sprintf()]& happen in controlled circumstances where
37681 the output buffer is known to be sufficiently long to contain the converted
37686 .section "Use of debug_printf() and log_write()" "SECID280"
37687 Arbitrary strings are passed to both these functions, but they do their
37688 formatting by calling the function &'string_vformat()'&, which runs through
37689 the format string itself, and checks the length of each conversion.
37693 .section "Use of strcat() and strcpy()" "SECID281"
37694 These are used only in cases where the output buffer is known to be large
37695 enough to hold the result.
37696 .ecindex IIDsecurcon
37701 . ////////////////////////////////////////////////////////////////////////////
37702 . ////////////////////////////////////////////////////////////////////////////
37704 .chapter "Format of spool files" "CHAPspool"
37705 .scindex IIDforspo1 "format" "spool files"
37706 .scindex IIDforspo2 "spool directory" "format of files"
37707 .scindex IIDforspo3 "spool files" "format of"
37708 .cindex "spool files" "editing"
37709 A message on Exim's queue consists of two files, whose names are the message id
37710 followed by -D and -H, respectively. The data portion of the message is kept in
37711 the -D file on its own. The message's envelope, status, and headers are all
37712 kept in the -H file, whose format is described in this chapter. Each of these
37713 two files contains the final component of its own name as its first line. This
37714 is insurance against disk crashes where the directory is lost but the files
37715 themselves are recoverable.
37717 Some people are tempted into editing -D files in order to modify messages. You
37718 need to be extremely careful if you do this; it is not recommended and you are
37719 on your own if you do it. Here are some of the pitfalls:
37722 You must ensure that Exim does not try to deliver the message while you are
37723 fiddling with it. The safest way is to take out a write lock on the -D file,
37724 which is what Exim itself does, using &[fcntl()]&. If you update the file in
37725 place, the lock will be retained. If you write a new file and rename it, the
37726 lock will be lost at the instant of rename.
37728 .vindex "&$body_linecount$&"
37729 If you change the number of lines in the file, the value of
37730 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
37731 present, this value is not used by Exim, but there is no guarantee that this
37732 will always be the case.
37734 If the message is in MIME format, you must take care not to break it.
37736 If the message is cryptographically signed, any change will invalidate the
37739 All in all, modifying -D files is fraught with danger.
37741 Files whose names end with -J may also be seen in the &_input_& directory (or
37742 its subdirectories when &%split_spool_directory%& is set). These are journal
37743 files, used to record addresses to which the message has been delivered during
37744 the course of a delivery attempt. If there are still undelivered recipients at
37745 the end, the -H file is updated, and the -J file is deleted. If, however, there
37746 is some kind of crash (for example, a power outage) before this happens, the -J
37747 file remains in existence. When Exim next processes the message, it notices the
37748 -J file and uses it to update the -H file before starting the next delivery
37751 .section "Format of the -H file" "SECID282"
37752 .cindex "uid (user id)" "in spool file"
37753 .cindex "gid (group id)" "in spool file"
37754 The second line of the -H file contains the login name for the uid of the
37755 process that called Exim to read the message, followed by the numerical uid and
37756 gid. For a locally generated message, this is normally the user who sent the
37757 message. For a message received over TCP/IP via the daemon, it is
37758 normally the Exim user.
37760 The third line of the file contains the address of the message's sender as
37761 transmitted in the envelope, contained in angle brackets. The sender address is
37762 empty for bounce messages. For incoming SMTP mail, the sender address is given
37763 in the MAIL command. For locally generated mail, the sender address is
37764 created by Exim from the login name of the current user and the configured
37765 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
37766 leading &"From&~"& line if the caller is trusted, or if the supplied address is
37767 &"<>"& or an address that matches &%untrusted_set_senders%&.
37769 The fourth line contains two numbers. The first is the time that the message
37770 was received, in the conventional Unix form &-- the number of seconds since the
37771 start of the epoch. The second number is a count of the number of messages
37772 warning of delayed delivery that have been sent to the sender.
37774 There follow a number of lines starting with a hyphen. These can appear in any
37775 order, and are omitted when not relevant:
37778 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
37779 This item is obsolete, and is not generated from Exim release 4.61 onwards;
37780 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
37781 recognized, to provide backward compatibility. In the old format, a line of
37782 this form is present for every ACL variable that is not empty. The number
37783 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
37784 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
37785 the data string for the variable. The string itself starts at the beginning of
37786 the next line, and is followed by a newline character. It may contain internal
37789 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
37790 A line of this form is present for every ACL connection variable that is
37791 defined. Note that there is a space between &%-aclc%& and the rest of the name.
37792 The length is the length of the data string for the variable. The string itself
37793 starts at the beginning of the next line, and is followed by a newline
37794 character. It may contain internal newlines.
37796 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
37797 A line of this form is present for every ACL message variable that is defined.
37798 Note that there is a space between &%-aclm%& and the rest of the name. The
37799 length is the length of the data string for the variable. The string itself
37800 starts at the beginning of the next line, and is followed by a newline
37801 character. It may contain internal newlines.
37803 .vitem "&%-active_hostname%&&~<&'hostname'&>"
37804 This is present if, when the message was received over SMTP, the value of
37805 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
37807 .vitem &%-allow_unqualified_recipient%&
37808 This is present if unqualified recipient addresses are permitted in header
37809 lines (to stop such addresses from being qualified if rewriting occurs at
37810 transport time). Local messages that were input using &%-bnq%& and remote
37811 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
37813 .vitem &%-allow_unqualified_sender%&
37814 This is present if unqualified sender addresses are permitted in header lines
37815 (to stop such addresses from being qualified if rewriting occurs at transport
37816 time). Local messages that were input using &%-bnq%& and remote messages from
37817 hosts that match &%sender_unqualified_hosts%& set this flag.
37819 .vitem "&%-auth_id%&&~<&'text'&>"
37820 The id information for a message received on an authenticated SMTP connection
37821 &-- the value of the &$authenticated_id$& variable.
37823 .vitem "&%-auth_sender%&&~<&'address'&>"
37824 The address of an authenticated sender &-- the value of the
37825 &$authenticated_sender$& variable.
37827 .vitem "&%-body_linecount%&&~<&'number'&>"
37828 This records the number of lines in the body of the message, and is always
37831 .vitem "&%-body_zerocount%&&~<&'number'&>"
37832 This records the number of binary zero bytes in the body of the message, and is
37833 present if the number is greater than zero.
37835 .vitem &%-deliver_firsttime%&
37836 This is written when a new message is first added to the spool. When the spool
37837 file is updated after a deferral, it is omitted.
37839 .vitem "&%-frozen%&&~<&'time'&>"
37840 .cindex "frozen messages" "spool data"
37841 The message is frozen, and the freezing happened at <&'time'&>.
37843 .vitem "&%-helo_name%&&~<&'text'&>"
37844 This records the host name as specified by a remote host in a HELO or EHLO
37847 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
37848 This records the IP address of the host from which the message was received and
37849 the remote port number that was used. It is omitted for locally generated
37852 .vitem "&%-host_auth%&&~<&'text'&>"
37853 If the message was received on an authenticated SMTP connection, this records
37854 the name of the authenticator &-- the value of the
37855 &$sender_host_authenticated$& variable.
37857 .vitem &%-host_lookup_failed%&
37858 This is present if an attempt to look up the sending host's name from its IP
37859 address failed. It corresponds to the &$host_lookup_failed$& variable.
37861 .vitem "&%-host_name%&&~<&'text'&>"
37862 .cindex "reverse DNS lookup"
37863 .cindex "DNS" "reverse lookup"
37864 This records the name of the remote host from which the message was received,
37865 if the host name was looked up from the IP address when the message was being
37866 received. It is not present if no reverse lookup was done.
37868 .vitem "&%-ident%&&~<&'text'&>"
37869 For locally submitted messages, this records the login of the originating user,
37870 unless it was a trusted user and the &%-oMt%& option was used to specify an
37871 ident value. For messages received over TCP/IP, this records the ident string
37872 supplied by the remote host, if any.
37874 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
37875 This records the IP address of the local interface and the port number through
37876 which a message was received from a remote host. It is omitted for locally
37877 generated messages.
37880 The message is from a local sender.
37882 .vitem &%-localerror%&
37883 The message is a locally-generated bounce message.
37885 .vitem "&%-local_scan%&&~<&'string'&>"
37886 This records the data string that was returned by the &[local_scan()]& function
37887 when the message was received &-- the value of the &$local_scan_data$&
37888 variable. It is omitted if no data was returned.
37890 .vitem &%-manual_thaw%&
37891 The message was frozen but has been thawed manually, that is, by an explicit
37892 Exim command rather than via the auto-thaw process.
37895 A testing delivery process was started using the &%-N%& option to suppress any
37896 actual deliveries, but delivery was deferred. At any further delivery attempts,
37899 .vitem &%-received_protocol%&
37900 This records the value of the &$received_protocol$& variable, which contains
37901 the name of the protocol by which the message was received.
37903 .vitem &%-sender_set_untrusted%&
37904 The envelope sender of this message was set by an untrusted local caller (used
37905 to ensure that the caller is displayed in queue listings).
37907 .vitem "&%-spam_score_int%&&~<&'number'&>"
37908 If a message was scanned by SpamAssassin, this is present. It records the value
37909 of &$spam_score_int$&.
37911 .vitem &%-tls_certificate_verified%&
37912 A TLS certificate was received from the client that sent this message, and the
37913 certificate was verified by the server.
37915 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
37916 When the message was received over an encrypted connection, this records the
37917 name of the cipher suite that was used.
37919 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
37920 When the message was received over an encrypted connection, and a certificate
37921 was received from the client, this records the Distinguished Name from that
37925 Following the options there is a list of those addresses to which the message
37926 is not to be delivered. This set of addresses is initialized from the command
37927 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
37928 is set; otherwise it starts out empty. Whenever a successful delivery is made,
37929 the address is added to this set. The addresses are kept internally as a
37930 balanced binary tree, and it is a representation of that tree which is written
37931 to the spool file. If an address is expanded via an alias or forward file, the
37932 original address is added to the tree when deliveries to all its child
37933 addresses are complete.
37935 If the tree is empty, there is a single line in the spool file containing just
37936 the text &"XX"&. Otherwise, each line consists of two letters, which are either
37937 Y or N, followed by an address. The address is the value for the node of the
37938 tree, and the letters indicate whether the node has a left branch and/or a
37939 right branch attached to it, respectively. If branches exist, they immediately
37940 follow. Here is an example of a three-node tree:
37942 YY darcy@austen.fict.example
37943 NN alice@wonderland.fict.example
37944 NN editor@thesaurus.ref.example
37946 After the non-recipients tree, there is a list of the message's recipients.
37947 This is a simple list, preceded by a count. It includes all the original
37948 recipients of the message, including those to whom the message has already been
37949 delivered. In the simplest case, the list contains one address per line. For
37953 editor@thesaurus.ref.example
37954 darcy@austen.fict.example
37956 alice@wonderland.fict.example
37958 However, when a child address has been added to the top-level addresses as a
37959 result of the use of the &%one_time%& option on a &(redirect)& router, each
37960 line is of the following form:
37962 <&'top-level address'&> <&'errors_to address'&> &&&
37963 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
37965 The 01 flag bit indicates the presence of the three other fields that follow
37966 the top-level address. Other bits may be used in future to support additional
37967 fields. The <&'parent number'&> is the offset in the recipients list of the
37968 original parent of the &"one time"& address. The first two fields are the
37969 envelope sender that is associated with this address and its length. If the
37970 length is zero, there is no special envelope sender (there are then two space
37971 characters in the line). A non-empty field can arise from a &(redirect)& router
37972 that has an &%errors_to%& setting.
37975 A blank line separates the envelope and status information from the headers
37976 which follow. A header may occupy several lines of the file, and to save effort
37977 when reading it in, each header is preceded by a number and an identifying
37978 character. The number is the number of characters in the header, including any
37979 embedded newlines and the terminating newline. The character is one of the
37983 .row <&'blank'&> "header in which Exim has no special interest"
37984 .row &`B`& "&'Bcc:'& header"
37985 .row &`C`& "&'Cc:'& header"
37986 .row &`F`& "&'From:'& header"
37987 .row &`I`& "&'Message-id:'& header"
37988 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
37989 .row &`R`& "&'Reply-To:'& header"
37990 .row &`S`& "&'Sender:'& header"
37991 .row &`T`& "&'To:'& header"
37992 .row &`*`& "replaced or deleted header"
37995 Deleted or replaced (rewritten) headers remain in the spool file for debugging
37996 purposes. They are not transmitted when the message is delivered. Here is a
37997 typical set of headers:
37999 111P Received: by hobbit.fict.example with local (Exim 4.00)
38000 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
38001 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
38002 038* X-rewrote-sender: bb@hobbit.fict.example
38003 042* From: Bilbo Baggins <bb@hobbit.fict.example>
38004 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
38005 099* To: alice@wonderland.fict.example, rdo@foundation,
38006 darcy@austen.fict.example, editor@thesaurus.ref.example
38007 104T To: alice@wonderland.fict.example, rdo@foundation.example,
38008 darcy@austen.fict.example, editor@thesaurus.ref.example
38009 038 Date: Fri, 11 May 2001 10:28:59 +0100
38011 The asterisked headers indicate that the envelope sender, &'From:'& header, and
38012 &'To:'& header have been rewritten, the last one because routing expanded the
38013 unqualified domain &'foundation'&.
38014 .ecindex IIDforspo1
38015 .ecindex IIDforspo2
38016 .ecindex IIDforspo3
38018 . ////////////////////////////////////////////////////////////////////////////
38019 . ////////////////////////////////////////////////////////////////////////////
38021 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
38025 DKIM is a mechanism by which messages sent by some entity can be provably
38026 linked to a domain which that entity controls. It permits reputation to
38027 be tracked on a per-domain basis, rather than merely upon source IP address.
38028 DKIM is documented in RFC 4871.
38031 DKIM support is compiled into Exim by default if TLS support is present.
38033 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
38035 Exim's DKIM implementation allows to
38037 Sign outgoing messages: This function is implemented in the SMTP transport.
38038 It can co-exist with all other Exim features
38039 (including transport filters)
38040 except cutthrough delivery.
38042 Verify signatures in incoming messages: This is implemented by an additional
38043 ACL (acl_smtp_dkim), which can be called several times per message, with
38044 different signature contexts.
38047 In typical Exim style, the verification implementation does not include any
38048 default "policy". Instead it enables you to build your own policy using
38049 Exim's standard controls.
38051 Please note that verification of DKIM signatures in incoming mail is turned
38052 on by default for logging purposes. For each signature in incoming email,
38053 exim will log a line displaying the most important signature details, and the
38054 signature status. Here is an example (with line-breaks added for clarity):
38056 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
38057 d=facebookmail.com s=q1-2009b
38058 c=relaxed/relaxed a=rsa-sha1
38059 i=@facebookmail.com t=1252484542 [verification succeeded]
38061 You might want to turn off DKIM verification processing entirely for internal
38062 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
38063 control modifier. This should typically be done in the RCPT ACL, at points
38064 where you accept mail from relay sources (internal hosts or authenticated
38068 .section "Signing outgoing messages" "SECDKIMSIGN"
38069 .cindex "DKIM" "signing"
38071 Signing is implemented by setting private options on the SMTP transport.
38072 These options take (expandable) strings as arguments.
38074 .option dkim_domain smtp string&!! unset
38076 The domain you want to sign with. The result of this expanded
38077 option is put into the &%$dkim_domain%& expansion variable.
38079 .option dkim_selector smtp string&!! unset
38081 This sets the key selector string. You can use the &%$dkim_domain%& expansion
38082 variable to look up a matching selector. The result is put in the expansion
38083 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
38084 option along with &%$dkim_domain%&.
38086 .option dkim_private_key smtp string&!! unset
38088 This sets the private key to use. You can use the &%$dkim_domain%& and
38089 &%$dkim_selector%& expansion variables to determine the private key to use.
38090 The result can either
38092 be a valid RSA private key in ASCII armor, including line breaks.
38094 start with a slash, in which case it is treated as a file that contains
38097 be "0", "false" or the empty string, in which case the message will not
38098 be signed. This case will not result in an error, even if &%dkim_strict%&
38102 .option dkim_canon smtp string&!! unset
38104 This option sets the canonicalization method used when signing a message.
38105 The DKIM RFC currently supports two methods: "simple" and "relaxed".
38106 The option defaults to "relaxed" when unset. Note: the current implementation
38107 only supports using the same canonicalization method for both headers and body.
38109 .option dkim_strict smtp string&!! unset
38111 This option defines how Exim behaves when signing a message that
38112 should be signed fails for some reason. When the expansion evaluates to
38113 either "1" or "true", Exim will defer. Otherwise Exim will send the message
38114 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
38117 .option dkim_sign_headers smtp string&!! unset
38119 When set, this option must expand to (or be specified as) a colon-separated
38120 list of header names. Headers with these names will be included in the message
38121 signature. When unspecified, the header names recommended in RFC4871 will be
38125 .section "Verifying DKIM signatures in incoming mail" "SECID514"
38126 .cindex "DKIM" "verification"
38128 Verification of DKIM signatures in incoming email is implemented via the
38129 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
38130 syntactically(!) correct signature in the incoming message.
38131 A missing ACL definition defaults to accept.
38132 If any ACL call does not accept, the message is not accepted.
38133 If a cutthrough delivery was in progress for the message it is
38134 summarily dropped (having wasted the transmission effort).
38136 To evaluate the signature in the ACL a large number of expansion variables
38137 containing the signature status and its details are set up during the
38138 runtime of the ACL.
38140 Calling the ACL only for existing signatures is not sufficient to build
38141 more advanced policies. For that reason, the global option
38142 &%dkim_verify_signers%&, and a global expansion variable
38143 &%$dkim_signers%& exist.
38145 The global option &%dkim_verify_signers%& can be set to a colon-separated
38146 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
38147 called. It is expanded when the message has been received. At this point,
38148 the expansion variable &%$dkim_signers%& already contains a colon-separated
38149 list of signer domains and identities for the message. When
38150 &%dkim_verify_signers%& is not specified in the main configuration,
38153 dkim_verify_signers = $dkim_signers
38155 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
38156 DKIM signature in the message. Current DKIM verifiers may want to explicitly
38157 call the ACL for known domains or identities. This would be achieved as follows:
38159 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
38161 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
38162 and "ebay.com", plus all domains and identities that have signatures in the message.
38163 You can also be more creative in constructing your policy. For example:
38165 dkim_verify_signers = $sender_address_domain:$dkim_signers
38168 If a domain or identity is listed several times in the (expanded) value of
38169 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
38172 Inside the &%acl_smtp_dkim%&, the following expansion variables are
38173 available (from most to least important):
38177 .vitem &%$dkim_cur_signer%&
38178 The signer that is being evaluated in this ACL run. This can be a domain or
38179 an identity. This is one of the list items from the expanded main option
38180 &%dkim_verify_signers%& (see above).
38181 .vitem &%$dkim_verify_status%&
38182 A string describing the general status of the signature. One of
38184 &%none%&: There is no signature in the message for the current domain or
38185 identity (as reflected by &%$dkim_cur_signer%&).
38187 &%invalid%&: The signature could not be verified due to a processing error.
38188 More detail is available in &%$dkim_verify_reason%&.
38190 &%fail%&: Verification of the signature failed. More detail is
38191 available in &%$dkim_verify_reason%&.
38193 &%pass%&: The signature passed verification. It is valid.
38195 .vitem &%$dkim_verify_reason%&
38196 A string giving a little bit more detail when &%$dkim_verify_status%& is either
38197 "fail" or "invalid". One of
38199 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
38200 key for the domain could not be retrieved. This may be a temporary problem.
38202 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
38203 record for the domain is syntactically invalid.
38205 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
38206 body hash does not match the one specified in the signature header. This
38207 means that the message body was modified in transit.
38209 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
38210 could not be verified. This may mean that headers were modified,
38211 re-written or otherwise changed in a way which is incompatible with
38212 DKIM verification. It may of course also mean that the signature is forged.
38214 .vitem &%$dkim_domain%&
38215 The signing domain. IMPORTANT: This variable is only populated if there is
38216 an actual signature in the message for the current domain or identity (as
38217 reflected by &%$dkim_cur_signer%&).
38218 .vitem &%$dkim_identity%&
38219 The signing identity, if present. IMPORTANT: This variable is only populated
38220 if there is an actual signature in the message for the current domain or
38221 identity (as reflected by &%$dkim_cur_signer%&).
38222 .vitem &%$dkim_selector%&
38223 The key record selector string.
38224 .vitem &%$dkim_algo%&
38225 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
38226 .vitem &%$dkim_canon_body%&
38227 The body canonicalization method. One of 'relaxed' or 'simple'.
38228 .vitem &%dkim_canon_headers%&
38229 The header canonicalization method. One of 'relaxed' or 'simple'.
38230 .vitem &%$dkim_copiedheaders%&
38231 A transcript of headers and their values which are included in the signature
38232 (copied from the 'z=' tag of the signature).
38233 .vitem &%$dkim_bodylength%&
38234 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
38235 limit was set by the signer, "9999999999999" is returned. This makes sure
38236 that this variable always expands to an integer value.
38237 .vitem &%$dkim_created%&
38238 UNIX timestamp reflecting the date and time when the signature was created.
38239 When this was not specified by the signer, "0" is returned.
38240 .vitem &%$dkim_expires%&
38241 UNIX timestamp reflecting the date and time when the signer wants the
38242 signature to be treated as "expired". When this was not specified by the
38243 signer, "9999999999999" is returned. This makes it possible to do useful
38244 integer size comparisons against this value.
38245 .vitem &%$dkim_headernames%&
38246 A colon-separated list of names of headers included in the signature.
38247 .vitem &%$dkim_key_testing%&
38248 "1" if the key record has the "testing" flag set, "0" if not.
38249 .vitem &%$dkim_key_nosubdomains%&
38250 "1" if the key record forbids subdomaining, "0" otherwise.
38251 .vitem &%$dkim_key_srvtype%&
38252 Service type (tag s=) from the key record. Defaults to "*" if not specified
38254 .vitem &%$dkim_key_granularity%&
38255 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
38257 .vitem &%$dkim_key_notes%&
38258 Notes from the key record (tag n=).
38259 .vitem &%$dkim_key_length%&
38260 Number of bits in the key.
38263 In addition, two ACL conditions are provided:
38266 .vitem &%dkim_signers%&
38267 ACL condition that checks a colon-separated list of domains or identities
38268 for a match against the domain or identity that the ACL is currently verifying
38269 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
38270 verb to a group of domains or identities. For example:
38273 # Warn when Mail purportedly from GMail has no signature at all
38274 warn log_message = GMail sender without DKIM signature
38275 sender_domains = gmail.com
38276 dkim_signers = gmail.com
38280 .vitem &%dkim_status%&
38281 ACL condition that checks a colon-separated list of possible DKIM verification
38282 results against the actual result of verification. This is typically used
38283 to restrict an ACL verb to a list of verification outcomes, for example:
38286 deny message = Mail from Paypal with invalid/missing signature
38287 sender_domains = paypal.com:paypal.de
38288 dkim_signers = paypal.com:paypal.de
38289 dkim_status = none:invalid:fail
38292 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
38293 see the documentation of the &%$dkim_verify_status%& expansion variable above
38294 for more information of what they mean.
38297 . ////////////////////////////////////////////////////////////////////////////
38298 . ////////////////////////////////////////////////////////////////////////////
38300 .chapter "Proxies" "CHAPproxies" &&&
38302 .cindex "proxy support"
38303 .cindex "proxy" "access via"
38306 A proxy is an intermediate system through which communication is passed.
38307 Proxies may provide a security, availability or load-distribution function.
38310 .section "Inbound proxies" SECTproxyInbound
38311 .cindex proxy inbound
38312 .cindex proxy "server side"
38313 .cindex proxy "Proxy protocol"
38314 .cindex "Proxy protocol" proxy
38316 Exim has support for receiving inbound SMTP connections via a proxy
38317 that uses &"Proxy Protocol"& to speak to it.
38318 To include this support, include &"SUPPORT_PROXY=yes"&
38321 It was built on specifications from:
38322 http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
38323 That URL was revised in May 2014 to version 2 spec:
38324 http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
38326 The purpose of this facility is so that an application load balancer,
38327 such as HAProxy, can sit in front of several Exim servers
38328 to distribute load.
38329 Exim uses the local protocol communication with the proxy to obtain
38330 the remote SMTP system IP address and port information.
38331 There is no logging if a host passes or
38332 fails Proxy Protocol negotiation, but it can easily be determined and
38333 recorded in an ACL (example is below).
38335 Use of a proxy is enabled by setting the &%hosts_proxy%&
38336 main configuration option to a hostlist; connections from these
38337 hosts will use Proxy Protocol.
38339 The following expansion variables are usable
38340 (&"internal"& and &"external"& here refer to the interfaces
38343 &'proxy_host_address '& internal IP address of the proxy
38344 &'proxy_host_port '& internal TCP port of the proxy
38345 &'proxy_target_address '& external IP address of the proxy
38346 &'proxy_target_port '& external TCP port of the proxy
38347 &'proxy_session '& boolean: SMTP connection via proxy
38349 If &$proxy_session$& is set but &$proxy_host_address$& is empty
38350 there was a protocol error.
38352 Since the real connections are all coming from the proxy, and the
38353 per host connection tracking is done before Proxy Protocol is
38354 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
38355 handle all of the parallel volume you expect per inbound proxy.
38356 With the option set so high, you lose the ability
38357 to protect your server from many connections from one IP.
38358 In order to prevent your server from overload, you
38359 need to add a per connection ratelimit to your connect ACL.
38360 A possible solution is:
38362 # Set max number of connections per host
38364 # Or do some kind of IP lookup in a flat file or database
38365 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
38367 defer message = Too many connections from this IP right now
38368 ratelimit = LIMIT / 5s / per_conn / strict
38373 .section "Outbound proxies" SECTproxySOCKS
38374 .cindex proxy outbound
38375 .cindex proxy "client side"
38376 .cindex proxy SOCKS
38377 .cindex SOCKS proxy
38378 Exim has support for sending outbound SMTP via a proxy
38379 using a protocol called SOCKS5 (defined by RFC1928).
38380 The support can be optionally included by defining SUPPORT_SOCKS=yes in
38383 Use of a proxy is enabled by setting the &%socks_proxy%& option
38384 on an smtp transport.
38385 The option value is expanded and should then be a list
38386 (colon-separated by default) of proxy specifiers.
38387 Each proxy specifier is a list
38388 (space-separated by default) where the initial element
38389 is an IP address and any subsequent elements are options.
38391 Options are a string <name>=<value>.
38392 The list of options is in the following table:
38394 &'auth '& authentication method
38395 &'name '& authentication username
38396 &'pass '& authentication password
38398 &'tmo '& connection timeout
38400 &'weight '& selection bias
38403 More details on each of these options follows:
38406 .cindex authentication "to proxy"
38407 .cindex proxy authentication
38408 &%auth%&: Either &"none"& (default) or &"name"&.
38409 Using &"name"& selects username/password authentication per RFC 1929
38410 for access to the proxy.
38411 Default is &"none"&.
38413 &%name%&: sets the username for the &"name"& authentication method.
38416 &%pass%&: sets the password for the &"name"& authentication method.
38419 &%port%&: the TCP port number to use for the connection to the proxy.
38422 &%tmo%&: sets a connection timeout in seconds for this proxy.
38425 &%pri%&: specifies a priority for the proxy within the list,
38426 higher values being tried first.
38427 The default priority is 1.
38429 &%weight%&: specifies a selection bias.
38430 Within a priority set servers are queried in a random fashion,
38431 weighted by this value.
38432 The default value for selection bias is 1.
38435 Proxies from the list are tried according to their priority
38436 and weight settings until one responds. The timeout for the
38437 overall connection applies to the set of proxied attempts.
38439 .section Logging SECTproxyLog
38440 To log the (local) IP of a proxy in the incoming or delivery logline,
38441 add &"+proxy"& to the &%log_selector%& option.
38442 This will add a component tagged with &"PRX="& to the line.
38445 . ////////////////////////////////////////////////////////////////////////////
38446 . ////////////////////////////////////////////////////////////////////////////
38448 .chapter "Internationalisation" "CHAPi18n" &&&
38449 "Internationalisation""
38450 .cindex internationalisation "email address"
38453 .cindex UTF-8 "mail name handling"
38456 Exim has support for Internationalised mail names.
38457 To include this it must be built with SUPPORT_I18N and the libidn library.
38458 Standards supported are RFCs 2060, 5890, 6530 and 6533.
38460 .section "MTA operations" SECTi18nMTA
38461 .cindex SMTPUTF8 "ESMTP option"
38462 The main configuration option &%smtputf8_advertise_hosts%& specifies
38463 a host list. If this matches the sending host and
38464 accept_8bitmime is true (the default) then the ESMTP option
38465 SMTPUTF8 will be advertised.
38467 If the sender specifies the SMTPUTF8 option on a MAIL command
38468 international handling for the message is enabled and
38469 the expansion variable &$message_smtputf8$& will have value TRUE.
38471 The option &%allow_utf8_domains%& is set to true for this
38472 message. All DNS lookups are converted to a-label form
38473 whatever the setting of &%allow_utf8_domains%&
38474 when Exim is built with SUPPORT_I18N.
38476 Both localparts and domain are maintained as the original
38477 UTF-8 form internally; any comparison or regular-expression use will
38478 require appropriate care. Filenames created, eg. by
38479 the appendfile transport, will have UTF-8 names.
38481 HELO names sent by the smtp transport will have any UTF-8
38482 components expanded to a-label form,
38483 and any certificate name checks will be done using the a-label
38486 .cindex log protocol
38487 .cindex SMTPUTF8 logging
38488 Log lines and Received-by: header lines will acquire a "utf8"
38489 prefix on the protocol element, eg. utf8esmtp.
38491 The following expansion operator can be used:
38493 ${utf8_domain_to_alabel:str}
38494 ${utf8_domain_from_alabel:str}
38495 ${utf8_localpart_to_alabel:str}
38496 ${utf8_localpart_from_alabel:str}
38499 ACLs may use the following modifier:
38501 control = utf8_downconvert
38502 control = utf8_downconvert/<value>
38504 This sets a flag requiring that addresses are converted to
38505 a-label form before smtp delivery, for use in a
38506 Message Submission Agent context.
38507 If a value is appended it may be:
38509 &`1 `& (default) mandatory downconversion
38510 &`0 `& no downconversion
38511 &`-1 `& if SMTPUTF8 not supported by destination host
38514 If mua_wrapper is set, the utf8_downconvert control
38515 is initially set to -1.
38518 There is no explicit support for VRFY and EXPN.
38519 Configurations supporting these should inspect
38520 &$smtp_command_argument$& for an SMTPUTF8 argument.
38522 There is no support for LMTP on Unix sockets.
38523 Using the "lmtp" protocol option on an smtp transport,
38524 for LMTP over TCP, should work as expected.
38526 There is no support for DSN unitext handling,
38527 and no provision for converting logging from or to UTF-8.
38531 .section "MDA operations" SECTi18nMDA
38532 To aid in constructing names suitable for IMAP folders
38533 the following expansion operator can be used:
38535 ${imapfolder {<string>} {<sep>} {<specials>}}
38538 The string is converted from the charset specified by
38539 the "headers charset" command (in a filter file)
38540 or &%headers_charset%& main configuration option (otherwise),
38542 modified UTF-7 encoding specified by RFC 2060,
38543 with the following exception: All occurences of <sep>
38544 (which has to be a single character)
38545 are replaced with periods ("."), and all periods and slashes that are not
38546 <sep> and are not in the <specials> string are BASE64 encoded.
38548 The third argument can be omitted, defaulting to an empty string.
38549 The second argument can be omitted, defaulting to "/".
38551 This is the encoding used by Courier for Maildir names on disk, and followed
38552 by many other IMAP servers.
38556 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
38557 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
38558 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
38561 Note that the source charset setting is vital, and also that characters
38562 must be representable in UTF-16.
38566 . ////////////////////////////////////////////////////////////////////////////
38567 . ////////////////////////////////////////////////////////////////////////////
38569 .chapter "Events" "CHAPevents" &&&
38574 The events mechanism in Exim can be used to intercept processing at a number
38575 of points. It was originally invented to giave a way to do customised logging
38576 actions (for example, to a database) but can also be used to modify some
38577 processing actions.
38579 Most installations will never need to use Events.
38580 The support can be left out of a build by defining DISABLE_EVENT=yes
38581 in &_Local/Makefile_&.
38583 There are two major classes of events: main and transport.
38584 The main configuration option &%event_action%& controls reception events;
38585 a transport option &%event_action%& controls delivery events.
38587 Both options are a string which is expanded when the event fires.
38588 An example might look like:
38589 .cindex logging custom
38591 event_action = ${if eq {msg:delivery}{$event_name} \
38592 {${lookup pgsql {SELECT * FROM record_Delivery( \
38593 '${quote_pgsql:$sender_address_domain}',\
38594 '${quote_pgsql:${lc:$sender_address_local_part}}', \
38595 '${quote_pgsql:$domain}', \
38596 '${quote_pgsql:${lc:$local_part}}', \
38597 '${quote_pgsql:$host_address}', \
38598 '${quote_pgsql:${lc:$host}}', \
38599 '${quote_pgsql:$message_exim_id}')}} \
38603 Events have names which correspond to the point in process at which they fire.
38604 The name is placed in the variable &$event_name$& and the event action
38605 expansion must check this, as it will be called for every possible event type.
38607 The current list of events is:
38609 &`msg:complete after main `& per message
38610 &`msg:delivery after transport `& per recipient
38611 &`msg:rcpt:host:defer after transport `& per recipient per host
38612 &`msg:rcpt:defer after transport `& per recipient
38613 &`msg:host:defer after transport `& per attempt
38614 &`msg:fail:delivery after main `& per recipient
38615 &`msg:fail:internal after main `& per recipient
38616 &`tcp:connect before transport `& per connection
38617 &`tcp:close after transport `& per connection
38618 &`tls:cert before both `& per certificate in verification chain
38619 &`smtp:connect after transport `& per connection
38621 New event types may be added in future.
38623 The event name is a colon-separated list, defining the type of
38624 event in a tree of possibilities. It may be used as a list
38625 or just matched on as a whole. There will be no spaces in the name.
38627 The second column in the table above describes whether the event fires
38628 before or after the action is associates with. Those which fire before
38629 can be used to affect that action (more on this below).
38631 An additional variable, &$event_data$&, is filled with information varying
38632 with the event type:
38634 &`msg:delivery `& smtp confirmation mssage
38635 &`msg:rcpt:host:defer `& error string
38636 &`msg:rcpt:defer `& error string
38637 &`msg:host:defer `& error string
38638 &`tls:cert `& verification chain depth
38639 &`smtp:connect `& smtp banner
38642 The :defer events populate one extra variable: &$event_defer_errno$&.
38644 For complex operations an ACL expansion can be used in &%event_action%&
38645 however due to the multiple contextx that Exim operates in during
38646 the course of its processing:
38648 variables set in transport events will not be visible outside that
38651 acl_m variables in a server context are lost on a new connection,
38652 and after smtp helo/ehlo/mail/starttls/rset commands
38654 Using an ACL expansion with the logwrite modifier can be
38655 a useful way of writing to the main log.
38657 The expansion of the event_action option should normally
38658 return an empty string. Should it return anything else the
38659 following will be forced:
38661 &`msg:delivery `& (ignored)
38662 &`msg:host:defer `& (ignored)
38663 &`msg:fail:delivery`& (ignored)
38664 &`tcp:connect `& do not connect
38665 &`tcp:close `& (ignored)
38666 &`tls:cert `& refuse verification
38667 &`smtp:connect `& close connection
38669 No other use is made of the result string.
38671 For a tcp:connect event, if the connection is being made to a proxy
38672 then the address and port variables will be that of the proxy and not
38675 For tls:cert events, if GnuTLS is in use this will trigger only per
38676 chain element received on the connection.
38677 For OpenSSL it will trigger for every chain element including those
38681 . ////////////////////////////////////////////////////////////////////////////
38682 . ////////////////////////////////////////////////////////////////////////////
38684 .chapter "Adding new drivers or lookup types" "CHID13" &&&
38685 "Adding drivers or lookups"
38686 .cindex "adding drivers"
38687 .cindex "new drivers, adding"
38688 .cindex "drivers" "adding new"
38689 The following actions have to be taken in order to add a new router, transport,
38690 authenticator, or lookup type to Exim:
38693 Choose a name for the driver or lookup type that does not conflict with any
38694 existing name; I will use &"newdriver"& in what follows.
38696 Add to &_src/EDITME_& the line:
38698 <&'type'&>&`_NEWDRIVER=yes`&
38700 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
38701 code is not to be included in the binary by default, comment this line out. You
38702 should also add any relevant comments about the driver or lookup type.
38704 Add to &_src/config.h.defaults_& the line:
38706 #define <type>_NEWDRIVER
38709 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
38710 and create a table entry as is done for all the other drivers and lookup types.
38712 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
38713 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
38714 Add your &`NEWDRIVER`& to that list.
38715 As long as the dynamic module would be named &_newdriver.so_&, you can use the
38716 simple form that most lookups have.
38718 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
38719 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
38720 driver or lookup type and add it to the definition of OBJ.
38722 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
38725 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
38726 as for other drivers and lookups.
38729 Then all you need to do is write the code! A good way to start is to make a
38730 proforma by copying an existing module of the same type, globally changing all
38731 occurrences of the name, and cutting out most of the code. Note that any
38732 options you create must be listed in alphabetical order, because the tables are
38733 searched using a binary chop procedure.
38735 There is a &_README_& file in each of the sub-directories of &_src_& describing
38736 the interface that is expected.
38741 . ////////////////////////////////////////////////////////////////////////////
38742 . ////////////////////////////////////////////////////////////////////////////
38744 . /////////////////////////////////////////////////////////////////////////////
38745 . These lines are processing instructions for the Simple DocBook Processor that
38746 . Philip Hazel has developed as a less cumbersome way of making PostScript and
38747 . PDFs than using xmlto and fop. They will be ignored by all other XML
38749 . /////////////////////////////////////////////////////////////////////////////
38754 foot_right_recto="&chaptertitle;"
38755 foot_right_verso="&chaptertitle;"
38759 .makeindex "Options index" "option"
38760 .makeindex "Variables index" "variable"
38761 .makeindex "Concept index" "concept"
38764 . /////////////////////////////////////////////////////////////////////////////
38765 . /////////////////////////////////////////////////////////////////////////////