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 "4.87"
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$&) are available, but no
2791 message-specific values (such as &$message_exim_id$&) are set, because no message
2792 is being processed (but see &%-bem%& and &%-Mset%&).
2794 &*Note*&: If you use this mechanism to test lookups, and you change the data
2795 files or databases you are using, you must exit and restart Exim before trying
2796 the same lookup again. Otherwise, because each Exim process caches the results
2797 of lookups, you will just get the same result as before.
2799 .vitem &%-bem%&&~<&'filename'&>
2801 .cindex "testing" "string expansion"
2802 .cindex "expansion" "testing"
2803 This option operates like &%-be%& except that it must be followed by the name
2804 of a file. For example:
2806 exim -bem /tmp/testmessage
2808 The file is read as a message (as if receiving a locally-submitted non-SMTP
2809 message) before any of the test expansions are done. Thus, message-specific
2810 variables such as &$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 or directory
3053 (depending on the used scanner interface),
3054 using the malware scanning framework. The option of &%av_scanner%& influences
3055 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3056 the expansion should have defaults which apply to this invocation. ACLs are
3057 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3058 will never be populated and &%-bmalware%& will fail.
3060 Exim will have changed working directory before resolving the filename, so
3061 using fully qualified pathnames is advisable. Exim will be running as the Exim
3062 user when it tries to open the file, rather than as the invoking user.
3063 This option requires admin privileges.
3065 The &%-bmalware%& option will not be extended to be more generally useful,
3066 there are better tools for file-scanning. This option exists to help
3067 administrators verify their Exim and AV scanner configuration.
3071 .cindex "address qualification, suppressing"
3072 By default, Exim automatically qualifies unqualified addresses (those
3073 without domains) that appear in messages that are submitted locally (that
3074 is, not over TCP/IP). This qualification applies both to addresses in
3075 envelopes, and addresses in header lines. Sender addresses are qualified using
3076 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3077 defaults to the value of &%qualify_domain%&).
3079 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3080 being used to re-submit messages that originally came from remote hosts after
3081 content scanning, you probably do not want to qualify unqualified addresses in
3082 header lines. (Such lines will be present only if you have not enabled a header
3083 syntax check in the appropriate ACL.)
3085 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3086 messages that originate on the local host. When this is used, unqualified
3087 addresses in the envelope provoke errors (causing message rejection) and
3088 unqualified addresses in header lines are left alone.
3093 .cindex "configuration options" "extracting"
3094 .cindex "options" "configuration &-- extracting"
3095 If this option is given with no arguments, it causes the values of all Exim's
3096 main configuration options to be written to the standard output. The values
3097 of one or more specific options can be requested by giving their names as
3098 arguments, for example:
3100 exim -bP qualify_domain hold_domains
3102 .cindex "hiding configuration option values"
3103 .cindex "configuration options" "hiding value of"
3104 .cindex "options" "hiding value of"
3105 However, any option setting that is preceded by the word &"hide"& in the
3106 configuration file is not shown in full, except to an admin user. For other
3107 users, the output is as in this example:
3109 mysql_servers = <value not displayable>
3111 If &%config%& is given as an argument, the config is
3112 output, as it was parsed, any include file resolved, any comment removed.
3114 If &%config_file%& is given as an argument, the name of the run time
3115 configuration file is output. (&%configure_file%& works too, for
3116 backward compatibility.)
3117 If a list of configuration files was supplied, the value that is output here
3118 is the name of the file that was actually used.
3120 .cindex "options" "hiding name of"
3121 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3122 name will not be output.
3124 .cindex "daemon" "process id (pid)"
3125 .cindex "pid (process id)" "of daemon"
3126 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3127 directories where log files and daemon pid files are written are output,
3128 respectively. If these values are unset, log files are written in a
3129 sub-directory of the spool directory called &%log%&, and the pid file is
3130 written directly into the spool directory.
3132 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3134 exim -bP +local_domains
3136 it searches for a matching named list of any type (domain, host, address, or
3137 local part) and outputs what it finds.
3139 .cindex "options" "router &-- extracting"
3140 .cindex "options" "transport &-- extracting"
3141 .cindex "options" "authenticator &-- extracting"
3142 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3143 followed by the name of an appropriate driver instance, the option settings for
3144 that driver are output. For example:
3146 exim -bP transport local_delivery
3148 The generic driver options are output first, followed by the driver's private
3149 options. A list of the names of drivers of a particular type can be obtained by
3150 using one of the words &%router_list%&, &%transport_list%&, or
3151 &%authenticator_list%&, and a complete list of all drivers with their option
3152 settings can be obtained by using &%routers%&, &%transports%&, or
3155 .cindex "environment"
3156 If &%environment%& is given as an argument, the set of environment
3157 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3160 .cindex "options" "macro &-- extracting"
3161 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3162 are available, similarly to the drivers. Because macros are sometimes used
3163 for storing passwords, this option is restricted.
3164 The output format is one item per line.
3168 .cindex "queue" "listing messages on"
3169 .cindex "listing" "messages on the queue"
3170 This option requests a listing of the contents of the mail queue on the
3171 standard output. If the &%-bp%& option is followed by a list of message ids,
3172 just those messages are listed. By default, this option can be used only by an
3173 admin user. However, the &%queue_list_requires_admin%& option can be set false
3174 to allow any user to see the queue.
3176 Each message on the queue is displayed as in the following example:
3178 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3179 red.king@looking-glass.fict.example
3182 .cindex "message" "size in queue listing"
3183 .cindex "size" "of message"
3184 The first line contains the length of time the message has been on the queue
3185 (in this case 25 minutes), the size of the message (2.9K), the unique local
3186 identifier for the message, and the message sender, as contained in the
3187 envelope. For bounce messages, the sender address is empty, and appears as
3188 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3189 the default sender address, the user's login name is shown in parentheses
3190 before the sender address.
3192 .cindex "frozen messages" "in queue listing"
3193 If the message is frozen (attempts to deliver it are suspended) then the text
3194 &"*** frozen ***"& is displayed at the end of this line.
3196 The recipients of the message (taken from the envelope, not the headers) are
3197 displayed on subsequent lines. Those addresses to which the message has already
3198 been delivered are marked with the letter D. If an original address gets
3199 expanded into several addresses via an alias or forward file, the original is
3200 displayed with a D only when deliveries for all of its child addresses are
3206 This option operates like &%-bp%&, but in addition it shows delivered addresses
3207 that were generated from the original top level address(es) in each message by
3208 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3214 .cindex "queue" "count of messages on"
3215 This option counts the number of messages on the queue, and writes the total
3216 to the standard output. It is restricted to admin users, unless
3217 &%queue_list_requires_admin%& is set false.
3222 This option operates like &%-bp%&, but the output is not sorted into
3223 chronological order of message arrival. This can speed it up when there are
3224 lots of messages on the queue, and is particularly useful if the output is
3225 going to be post-processed in a way that doesn't need the sorting.
3229 This option is a combination of &%-bpr%& and &%-bpa%&.
3233 This option is a combination of &%-bpr%& and &%-bpu%&.
3238 This option operates like &%-bp%& but shows only undelivered top-level
3239 addresses for each message displayed. Addresses generated by aliasing or
3240 forwarding are not shown, unless the message was deferred after processing by a
3241 router with the &%one_time%& option set.
3246 .cindex "testing" "retry configuration"
3247 .cindex "retry" "configuration testing"
3248 This option is for testing retry rules, and it must be followed by up to three
3249 arguments. It causes Exim to look for a retry rule that matches the values
3250 and to write it to the standard output. For example:
3252 exim -brt bach.comp.mus.example
3253 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3255 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3256 argument, which is required, can be a complete address in the form
3257 &'local_part@domain'&, or it can be just a domain name. If the second argument
3258 contains a dot, it is interpreted as an optional second domain name; if no
3259 retry rule is found for the first argument, the second is tried. This ties in
3260 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3261 rule is found that matches the host, one that matches the mail domain is
3262 sought. Finally, an argument that is the name of a specific delivery error, as
3263 used in setting up retry rules, can be given. For example:
3265 exim -brt haydn.comp.mus.example quota_3d
3266 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3271 .cindex "testing" "rewriting"
3272 .cindex "rewriting" "testing"
3273 This option is for testing address rewriting rules, and it must be followed by
3274 a single argument, consisting of either a local part without a domain, or a
3275 complete address with a fully qualified domain. Exim outputs how this address
3276 would be rewritten for each possible place it might appear. See chapter
3277 &<<CHAPrewrite>>& for further details.
3281 .cindex "SMTP" "batched incoming"
3282 .cindex "batched SMTP input"
3283 This option is used for batched SMTP input, which is an alternative interface
3284 for non-interactive local message submission. A number of messages can be
3285 submitted in a single run. However, despite its name, this is not really SMTP
3286 input. Exim reads each message's envelope from SMTP commands on the standard
3287 input, but generates no responses. If the caller is trusted, or
3288 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3289 believed; otherwise the sender is always the caller of Exim.
3291 The message itself is read from the standard input, in SMTP format (leading
3292 dots doubled), terminated by a line containing just a single dot. An error is
3293 provoked if the terminating dot is missing. A further message may then follow.
3295 As for other local message submissions, the contents of incoming batch SMTP
3296 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3297 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3298 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3300 Some other SMTP commands are recognized in the input. HELO and EHLO act
3301 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3302 QUIT quits, ignoring the rest of the standard input.
3304 .cindex "return code" "for &%-bS%&"
3305 If any error is encountered, reports are written to the standard output and
3306 error streams, and Exim gives up immediately. The return code is 0 if no error
3307 was detected; it is 1 if one or more messages were accepted before the error
3308 was detected; otherwise it is 2.
3310 More details of input using batched SMTP are given in section
3311 &<<SECTincomingbatchedSMTP>>&.
3315 .cindex "SMTP" "local input"
3316 .cindex "local SMTP input"
3317 This option causes Exim to accept one or more messages by reading SMTP commands
3318 on the standard input, and producing SMTP replies on the standard output. SMTP
3319 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3320 Some user agents use this interface as a way of passing locally-generated
3321 messages to the MTA.
3324 .cindex "sender" "source of"
3325 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3326 set, the senders of messages are taken from the SMTP MAIL commands.
3327 Otherwise the content of these commands is ignored and the sender is set up as
3328 the calling user. Unqualified addresses are automatically qualified using
3329 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3330 &%-bnq%& option is used.
3334 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3335 using a listening daemon. Exim can distinguish the two cases by checking
3336 whether the standard input is a TCP/IP socket. When Exim is called from
3337 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3338 above concerning senders and qualification do not apply. In this situation,
3339 Exim behaves in exactly the same way as it does when receiving a message via
3340 the listening daemon.
3344 .cindex "testing" "addresses"
3345 .cindex "address" "testing"
3346 This option runs Exim in address testing mode, in which each argument is taken
3347 as a recipient address to be tested for deliverability. The results are
3348 written to the standard output. If a test fails, and the caller is not an admin
3349 user, no details of the failure are output, because these might contain
3350 sensitive information such as usernames and passwords for database lookups.
3352 If no arguments are given, Exim runs in an interactive manner, prompting with a
3353 right angle bracket for addresses to be tested.
3355 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3356 &[readline()]& function, because it is running as &'root'& and there are
3359 Each address is handled as if it were the recipient address of a message
3360 (compare the &%-bv%& option). It is passed to the routers and the result is
3361 written to the standard output. However, any router that has
3362 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3363 genuine routing tests if your first router passes everything to a scanner
3366 .cindex "return code" "for &%-bt%&"
3367 The return code is 2 if any address failed outright; it is 1 if no address
3368 failed outright but at least one could not be resolved for some reason. Return
3369 code 0 is given only when all addresses succeed.
3371 .cindex "duplicate addresses"
3372 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3373 addresses after routing is complete, so that only one delivery takes place.
3374 This does not happen when testing with &%-bt%&; the full results of routing are
3377 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3378 routers in the configuration makes any tests on the sender address of a
3380 .oindex "&%-f%&" "for address testing"
3381 you can use the &%-f%& option to set an appropriate sender when running
3382 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3383 default qualifying domain. However, if you have set up (for example) routers
3384 whose behaviour depends on the contents of an incoming message, you cannot test
3385 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3390 .cindex "version number of Exim"
3391 This option causes Exim to write the current version number, compilation
3392 number, and compilation date of the &'exim'& binary to the standard output.
3393 It also lists the DBM library that is being used, the optional modules (such as
3394 specific lookup types), the drivers that are included in the binary, and the
3395 name of the run time configuration file that is in use.
3397 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3398 configuration file. However, this is a static check only. It cannot check
3399 values that are to be expanded. For example, although a misspelt ACL verb is
3400 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3401 alone to discover (for example) all the typos in the configuration; some
3402 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3403 dynamic testing facilities.
3407 .cindex "verifying address" "using &%-bv%&"
3408 .cindex "address" "verification"
3409 This option runs Exim in address verification mode, in which each argument is
3410 taken as a recipient address to be verified by the routers. (This does
3411 not involve any verification callouts). During normal operation, verification
3412 happens mostly as a consequence processing a &%verify%& condition in an ACL
3413 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3414 including callouts, see the &%-bh%& and &%-bhc%& options.
3416 If verification fails, and the caller is not an admin user, no details of the
3417 failure are output, because these might contain sensitive information such as
3418 usernames and passwords for database lookups.
3420 If no arguments are given, Exim runs in an interactive manner, prompting with a
3421 right angle bracket for addresses to be verified.
3423 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3424 &[readline()]& function, because it is running as &'exim'& and there are
3427 Verification differs from address testing (the &%-bt%& option) in that routers
3428 that have &%no_verify%& set are skipped, and if the address is accepted by a
3429 router that has &%fail_verify%& set, verification fails. The address is
3430 verified as a recipient if &%-bv%& is used; to test verification for a sender
3431 address, &%-bvs%& should be used.
3433 If the &%-v%& option is not set, the output consists of a single line for each
3434 address, stating whether it was verified or not, and giving a reason in the
3435 latter case. Without &%-v%&, generating more than one address by redirection
3436 causes verification to end successfully, without considering the generated
3437 addresses. However, if just one address is generated, processing continues,
3438 and the generated address must verify successfully for the overall verification
3441 When &%-v%& is set, more details are given of how the address has been handled,
3442 and in the case of address redirection, all the generated addresses are also
3443 considered. Verification may succeed for some and fail for others.
3446 .cindex "return code" "for &%-bv%&"
3447 return code is 2 if any address failed outright; it is 1 if no address
3448 failed outright but at least one could not be resolved for some reason. Return
3449 code 0 is given only when all addresses succeed.
3451 If any of the routers in the configuration makes any tests on the sender
3452 address of a message, you should use the &%-f%& option to set an appropriate
3453 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3454 calling user at the default qualifying domain.
3458 This option acts like &%-bv%&, but verifies the address as a sender rather
3459 than a recipient address. This affects any rewriting and qualification that
3466 .cindex "inetd" "wait mode"
3467 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3468 similarly to the &%-bd%& option. All port specifications on the command-line
3469 and in the configuration file are ignored. Queue-running may not be specified.
3471 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3472 listening for connections. This permits the system to start up and have
3473 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3474 each port only when the first connection is received.
3476 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3477 which the daemon will exit, which should cause inetd to listen once more.
3479 .vitem &%-C%&&~<&'filelist'&>
3481 .cindex "configuration file" "alternate"
3482 .cindex "CONFIGURE_FILE"
3483 .cindex "alternate configuration file"
3484 This option causes Exim to find the run time configuration file from the given
3485 list instead of from the list specified by the CONFIGURE_FILE
3486 compile-time setting. Usually, the list will consist of just a single file
3487 name, but it can be a colon-separated list of names. In this case, the first
3488 file that exists is used. Failure to open an existing file stops Exim from
3489 proceeding any further along the list, and an error is generated.
3491 When this option is used by a caller other than root, and the list is different
3492 from the compiled-in list, Exim gives up its root privilege immediately, and
3493 runs with the real and effective uid and gid set to those of the caller.
3494 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3495 file contains a list of full pathnames, one per line, for configuration files
3496 which are trusted. Root privilege is retained for any configuration file so
3497 listed, as long as the caller is the Exim user (or the user specified in the
3498 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3499 not writeable by inappropriate users or groups.
3501 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3502 configuration using &%-C%& right through message reception and delivery,
3503 even if the caller is root. The reception works, but by that time, Exim is
3504 running as the Exim user, so when it re-executes to regain privilege for the
3505 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3506 test reception and delivery using two separate commands (one to put a message
3507 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3509 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3510 prefix string with which any file named in a &%-C%& command line option
3511 must start. In addition, the file name must not contain the sequence &`/../`&.
3512 However, if the value of the &%-C%& option is identical to the value of
3513 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3514 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3515 unset, any file name can be used with &%-C%&.
3517 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3518 to a directory to which only root has access. This prevents someone who has
3519 broken into the Exim account from running a privileged Exim with an arbitrary
3522 The &%-C%& facility is useful for ensuring that configuration files are
3523 syntactically correct, but cannot be used for test deliveries, unless the
3524 caller is privileged, or unless it is an exotic configuration that does not
3525 require privilege. No check is made on the owner or group of the files
3526 specified by this option.
3529 .vitem &%-D%&<&'macro'&>=<&'value'&>
3531 .cindex "macro" "setting on command line"
3532 This option can be used to override macro definitions in the configuration file
3533 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3534 unprivileged caller, it causes Exim to give up its root privilege.
3535 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3536 completely disabled, and its use causes an immediate error exit.
3538 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3539 colon-separated list of macros which are considered safe and, if &%-D%& only
3540 supplies macros from this list, and the values are acceptable, then Exim will
3541 not give up root privilege if the caller is root, the Exim run-time user, or
3542 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3543 to be removed in the future. Acceptable values for the macros satisfy the
3544 regexp: &`^[A-Za-z0-9_/.-]*$`&
3546 The entire option (including equals sign if present) must all be within one
3547 command line item. &%-D%& can be used to set the value of a macro to the empty
3548 string, in which case the equals sign is optional. These two commands are
3554 To include spaces in a macro definition item, quotes must be used. If you use
3555 quotes, spaces are permitted around the macro name and the equals sign. For
3558 exim '-D ABC = something' ...
3560 &%-D%& may be repeated up to 10 times on a command line.
3561 Only macro names up to 22 letters long can be set.
3564 .vitem &%-d%&<&'debug&~options'&>
3566 .cindex "debugging" "list of selectors"
3567 .cindex "debugging" "&%-d%& option"
3568 This option causes debugging information to be written to the standard
3569 error stream. It is restricted to admin users because debugging output may show
3570 database queries that contain password information. Also, the details of users'
3571 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3572 writes an error message to the standard error stream and exits with a non-zero
3575 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3576 standard debugging data is output. This can be reduced, or increased to include
3577 some more rarely needed information, by directly following &%-d%& with a string
3578 made up of names preceded by plus or minus characters. These add or remove sets
3579 of debugging data, respectively. For example, &%-d+filter%& adds filter
3580 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3581 no spaces are allowed in the debug setting. The available debugging categories
3584 &`acl `& ACL interpretation
3585 &`auth `& authenticators
3586 &`deliver `& general delivery logic
3587 &`dns `& DNS lookups (see also resolver)
3588 &`dnsbl `& DNS black list (aka RBL) code
3589 &`exec `& arguments for &[execv()]& calls
3590 &`expand `& detailed debugging for string expansions
3591 &`filter `& filter handling
3592 &`hints_lookup `& hints data lookups
3593 &`host_lookup `& all types of name-to-IP address handling
3594 &`ident `& ident lookup
3595 &`interface `& lists of local interfaces
3596 &`lists `& matching things in lists
3597 &`load `& system load checks
3598 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3599 &<<CHAPlocalscan>>&)
3600 &`lookup `& general lookup code and all lookups
3601 &`memory `& memory handling
3602 &`pid `& add pid to debug output lines
3603 &`process_info `& setting info for the process log
3604 &`queue_run `& queue runs
3605 &`receive `& general message reception logic
3606 &`resolver `& turn on the DNS resolver's debugging output
3607 &`retry `& retry handling
3608 &`rewrite `& address rewriting
3609 &`route `& address routing
3610 &`timestamp `& add timestamp to debug output lines
3612 &`transport `& transports
3613 &`uid `& changes of uid/gid and looking up uid/gid
3614 &`verify `& address verification logic
3615 &`all `& almost all of the above (see below), and also &%-v%&
3617 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3618 for &`-all`&. The reason for this is that &`+all`& is something that people
3619 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3620 is included, an awful lot of output that is very rarely of interest is
3621 generated, so it now has to be explicitly requested. However, &`-all`& does
3622 turn everything off.
3624 .cindex "resolver, debugging output"
3625 .cindex "DNS resolver, debugging output"
3626 The &`resolver`& option produces output only if the DNS resolver was compiled
3627 with DEBUG enabled. This is not the case in some operating systems. Also,
3628 unfortunately, debugging output from the DNS resolver is written to stdout
3631 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3632 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3633 However, the &`pid`& selector is forced when debugging is turned on for a
3634 daemon, which then passes it on to any re-executed Exims. Exim also
3635 automatically adds the pid to debug lines when several remote deliveries are
3638 The &`timestamp`& selector causes the current time to be inserted at the start
3639 of all debug output lines. This can be useful when trying to track down delays
3642 If the &%debug_print%& option is set in any driver, it produces output whenever
3643 any debugging is selected, or if &%-v%& is used.
3645 .vitem &%-dd%&<&'debug&~options'&>
3647 This option behaves exactly like &%-d%& except when used on a command that
3648 starts a daemon process. In that case, debugging is turned off for the
3649 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3650 behaviour of the daemon without creating as much output as full debugging does.
3653 .oindex "&%-dropcr%&"
3654 This is an obsolete option that is now a no-op. It used to affect the way Exim
3655 handled CR and LF characters in incoming messages. What happens now is
3656 described in section &<<SECTlineendings>>&.
3660 .cindex "bounce message" "generating"
3661 This option specifies that an incoming message is a locally-generated delivery
3662 failure report. It is used internally by Exim when handling delivery failures
3663 and is not intended for external use. Its only effect is to stop Exim
3664 generating certain messages to the postmaster, as otherwise message cascades
3665 could occur in some situations. As part of the same option, a message id may
3666 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3667 new message contains the id, following &"R="&, as a cross-reference.
3670 .oindex "&%-e%&&'x'&"
3671 There are a number of Sendmail options starting with &%-oe%& which seem to be
3672 called by various programs without the leading &%o%& in the option. For
3673 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3674 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3676 .vitem &%-F%&&~<&'string'&>
3678 .cindex "sender" "name"
3679 .cindex "name" "of sender"
3680 This option sets the sender's full name for use when a locally-generated
3681 message is being accepted. In the absence of this option, the user's &'gecos'&
3682 entry from the password data is used. As users are generally permitted to alter
3683 their &'gecos'& entries, no security considerations are involved. White space
3684 between &%-F%& and the <&'string'&> is optional.
3686 .vitem &%-f%&&~<&'address'&>
3688 .cindex "sender" "address"
3689 .cindex "address" "sender"
3690 .cindex "trusted users"
3691 .cindex "envelope sender"
3692 .cindex "user" "trusted"
3693 This option sets the address of the envelope sender of a locally-generated
3694 message (also known as the return path). The option can normally be used only
3695 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3698 Processes running as root or the Exim user are always trusted. Other
3699 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3700 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3701 of a local message is set to the caller's login name at the default qualify
3704 There is one exception to the restriction on the use of &%-f%&: an empty sender
3705 can be specified by any user, trusted or not, to create a message that can
3706 never provoke a bounce. An empty sender can be specified either as an empty
3707 string, or as a pair of angle brackets with nothing between them, as in these
3708 examples of shell commands:
3710 exim -f '<>' user@domain
3711 exim -f "" user@domain
3713 In addition, the use of &%-f%& is not restricted when testing a filter file
3714 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3717 Allowing untrusted users to change the sender address does not of itself make
3718 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3719 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3720 though this can be overridden by setting &%no_local_from_check%&.
3723 .cindex "&""From""& line"
3724 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3725 given as two arguments or one combined argument). The sender of a
3726 locally-generated message can also be set (when permitted) by an initial
3727 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3728 if &%-f%& is also present, it overrides &"From&~"&.
3732 .cindex "submission fixups, suppressing (command-line)"
3733 This option is equivalent to an ACL applying:
3735 control = suppress_local_fixups
3737 for every message received. Note that Sendmail will complain about such
3738 bad formatting, where Exim silently just does not fix it up. This may change
3741 As this affects audit information, the caller must be a trusted user to use
3744 .vitem &%-h%&&~<&'number'&>
3746 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3747 This option is accepted for compatibility with Sendmail, but has no effect. (In
3748 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3753 .cindex "Solaris" "&'mail'& command"
3754 .cindex "dot" "in incoming non-SMTP message"
3755 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3756 line by itself should not terminate an incoming, non-SMTP message. I can find
3757 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3758 command in Solaris 2.4 uses it. See also &%-ti%&.
3760 .vitem &%-L%&&~<&'tag'&>
3762 .cindex "syslog" "process name; set with flag"
3763 This option is equivalent to setting &%syslog_processname%& in the config
3764 file and setting &%log_file_path%& to &`syslog`&.
3765 Its use is restricted to administrators. The configuration file has to be
3766 read and parsed, to determine access rights, before this is set and takes
3767 effect, so early configuration file errors will not honour this flag.
3769 The tag should not be longer than 32 characters.
3771 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3773 .cindex "forcing delivery"
3774 .cindex "delivery" "forcing attempt"
3775 .cindex "frozen messages" "forcing delivery"
3776 This option requests Exim to run a delivery attempt on each message in turn. If
3777 any of the messages are frozen, they are automatically thawed before the
3778 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3779 and &%hold_domains%& are ignored.
3782 .cindex "hints database" "overriding retry hints"
3783 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3784 the normal retry time has not yet been reached. This option requires the caller
3785 to be an admin user. However, there is an option called &%prod_requires_admin%&
3786 which can be set false to relax this restriction (and also the same requirement
3787 for the &%-q%&, &%-R%&, and &%-S%& options).
3789 The deliveries happen synchronously, that is, the original Exim process does
3790 not terminate until all the delivery attempts have finished. No output is
3791 produced unless there is a serious error. If you want to see what is happening,
3792 use the &%-v%& option as well, or inspect Exim's main log.
3794 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3796 .cindex "message" "adding recipients"
3797 .cindex "recipient" "adding"
3798 This option requests Exim to add the addresses to the list of recipients of the
3799 message (&"ar"& for &"add recipients"&). The first argument must be a message
3800 id, and the remaining ones must be email addresses. However, if the message is
3801 active (in the middle of a delivery attempt), it is not altered. This option
3802 can be used only by an admin user.
3804 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3805 &~<&'message&~id'&>"
3807 .cindex "SMTP" "passed connection"
3808 .cindex "SMTP" "multiple deliveries"
3809 .cindex "multiple SMTP deliveries"
3810 This option is not intended for use by external callers. It is used internally
3811 by Exim to invoke another instance of itself to deliver a waiting message using
3812 an existing SMTP connection, which is passed as the standard input. Details are
3813 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3814 must be root or the Exim user in order to use it.
3818 This option is not intended for use by external callers. It is used internally
3819 by Exim in conjunction with the &%-MC%& option. It signifies that the
3820 connection to the remote host has been authenticated.
3824 This option is not intended for use by external callers. It is used internally
3825 by Exim in conjunction with the &%-MC%& option. It signifies that the
3826 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 an
3833 alternate queue is used, named by the following option.
3838 This option is not intended for use by external callers. It is used internally
3839 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3840 which Exim is connected supports pipelining.
3842 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3844 This option is not intended for use by external callers. It is used internally
3845 by Exim in conjunction with the &%-MC%& option when the original delivery was
3846 started by a queue runner. It passes on the process id of the queue runner,
3847 together with the file descriptor number of an open pipe. Closure of the pipe
3848 signals the final completion of the sequence of processes that are passing
3849 messages through the same SMTP connection.
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 SMTP SIZE option should be used on messages delivered down the existing
3860 This option is not intended for use by external callers. It is used internally
3861 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3862 host to which Exim is connected supports TLS encryption.
3864 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3866 .cindex "hints database" "not overridden by &%-Mc%&"
3867 .cindex "delivery" "manually started &-- not forced"
3868 This option requests Exim to run a delivery attempt on each message in turn,
3869 but unlike the &%-M%& option, it does check for retry hints, and respects any
3870 that are found. This option is not very useful to external callers. It is
3871 provided mainly for internal use by Exim when it needs to re-invoke itself in
3872 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3873 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3874 respects retry times and other options such as &%hold_domains%& that are
3875 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3876 If you want to run a specific delivery as if in a queue run, you should use
3877 &%-q%& with a message id argument. A distinction between queue run deliveries
3878 and other deliveries is made in one or two places.
3880 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3882 .cindex "message" "changing sender"
3883 .cindex "sender" "changing"
3884 This option requests Exim to change the sender address in the message to the
3885 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3886 &"edit sender"&). There must be exactly two arguments. The first argument must
3887 be a message id, and the second one an email address. However, if the message
3888 is active (in the middle of a delivery attempt), its status is not altered.
3889 This option can be used only by an admin user.
3891 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3893 .cindex "freezing messages"
3894 .cindex "message" "manually freezing"
3895 This option requests Exim to mark each listed message as &"frozen"&. This
3896 prevents any delivery attempts taking place until the message is &"thawed"&,
3897 either manually or as a result of the &%auto_thaw%& configuration option.
3898 However, if any of the messages are active (in the middle of a delivery
3899 attempt), their status is not altered. This option can be used only by an admin
3902 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3904 .cindex "giving up on messages"
3905 .cindex "message" "abandoning delivery attempts"
3906 .cindex "delivery" "abandoning further attempts"
3907 This option requests Exim to give up trying to deliver the listed messages,
3908 including any that are frozen. However, if any of the messages are active,
3909 their status is not altered. For non-bounce messages, a delivery error message
3910 is sent to the sender, containing the text &"cancelled by administrator"&.
3911 Bounce messages are just discarded. This option can be used only by an admin
3914 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3916 .cindex "delivery" "cancelling all"
3917 This option requests Exim to mark all the recipient addresses in the messages
3918 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3919 message is active (in the middle of a delivery attempt), its status is not
3920 altered. This option can be used only by an admin user.
3922 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3924 .cindex "delivery" "cancelling by address"
3925 .cindex "recipient" "removing"
3926 .cindex "removing recipients"
3927 This option requests Exim to mark the given addresses as already delivered
3928 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3929 the remaining ones must be email addresses. These are matched to recipient
3930 addresses in the message in a case-sensitive manner. If the message is active
3931 (in the middle of a delivery attempt), its status is not altered. This option
3932 can be used only by an admin user.
3934 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3936 .cindex "removing messages"
3937 .cindex "abandoning mail"
3938 .cindex "message" "manually discarding"
3939 This option requests Exim to remove the given messages from the queue. No
3940 bounce messages are sent; each message is simply forgotten. However, if any of
3941 the messages are active, their status is not altered. This option can be used
3942 only by an admin user or by the user who originally caused the message to be
3943 placed on the queue.
3945 .vitem &%-Mset%&&~<&'message&~id'&>
3947 .cindex "testing" "string expansion"
3948 .cindex "expansion" "testing"
3949 This option is useful only in conjunction with &%-be%& (that is, when testing
3950 string expansions). Exim loads the given message from its spool before doing
3951 the test expansions, thus setting message-specific variables such as
3952 &$message_size$& and the header variables. The &$recipients$& variable is made
3953 available. This feature is provided to make it easier to test expansions that
3954 make use of these variables. However, this option can be used only by an admin
3955 user. See also &%-bem%&.
3957 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3959 .cindex "thawing messages"
3960 .cindex "unfreezing messages"
3961 .cindex "frozen messages" "thawing"
3962 .cindex "message" "thawing frozen"
3963 This option requests Exim to &"thaw"& any of the listed messages that are
3964 &"frozen"&, so that delivery attempts can resume. However, if any of the
3965 messages are active, their status is not altered. This option can be used only
3968 .vitem &%-Mvb%&&~<&'message&~id'&>
3970 .cindex "listing" "message body"
3971 .cindex "message" "listing body of"
3972 This option causes the contents of the message body (-D) spool file to be
3973 written to the standard output. This option can be used only by an admin user.
3975 .vitem &%-Mvc%&&~<&'message&~id'&>
3977 .cindex "message" "listing in RFC 2822 format"
3978 .cindex "listing" "message in RFC 2822 format"
3979 This option causes a copy of the complete message (header lines plus body) to
3980 be written to the standard output in RFC 2822 format. This option can be used
3981 only by an admin user.
3983 .vitem &%-Mvh%&&~<&'message&~id'&>
3985 .cindex "listing" "message headers"
3986 .cindex "header lines" "listing"
3987 .cindex "message" "listing header lines"
3988 This option causes the contents of the message headers (-H) spool file to be
3989 written to the standard output. This option can be used only by an admin user.
3991 .vitem &%-Mvl%&&~<&'message&~id'&>
3993 .cindex "listing" "message log"
3994 .cindex "message" "listing message log"
3995 This option causes the contents of the message log spool file to be written to
3996 the standard output. This option can be used only by an admin user.
4000 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4001 treats it that way too.
4005 .cindex "debugging" "&%-N%& option"
4006 .cindex "debugging" "suppressing delivery"
4007 This is a debugging option that inhibits delivery of a message at the transport
4008 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4009 it just doesn't actually transport the message, but instead behaves as if it
4010 had successfully done so. However, it does not make any updates to the retry
4011 database, and the log entries for deliveries are flagged with &"*>"& rather
4014 Because &%-N%& discards any message to which it applies, only root or the Exim
4015 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4016 words, an ordinary user can use it only when supplying an incoming message to
4017 which it will apply. Although transportation never fails when &%-N%& is set, an
4018 address may be deferred because of a configuration problem on a transport, or a
4019 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4020 the message, and applies to any subsequent delivery attempts that may happen
4025 This option is interpreted by Sendmail to mean &"no aliasing"&.
4026 For normal modes of operation, it is ignored by Exim.
4027 When combined with &%-bP%& it makes the output more terse (suppresses
4028 option names, environment values and config pretty printing).
4030 .vitem &%-O%&&~<&'data'&>
4032 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4035 .vitem &%-oA%&&~<&'file&~name'&>
4037 .cindex "Sendmail compatibility" "&%-oA%& option"
4038 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4039 alternative alias file name. Exim handles &%-bi%& differently; see the
4042 .vitem &%-oB%&&~<&'n'&>
4044 .cindex "SMTP" "passed connection"
4045 .cindex "SMTP" "multiple deliveries"
4046 .cindex "multiple SMTP deliveries"
4047 This is a debugging option which limits the maximum number of messages that can
4048 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4049 transport. If <&'n'&> is omitted, the limit is set to 1.
4053 .cindex "background delivery"
4054 .cindex "delivery" "in the background"
4055 This option applies to all modes in which Exim accepts incoming messages,
4056 including the listening daemon. It requests &"background"& delivery of such
4057 messages, which means that the accepting process automatically starts a
4058 delivery process for each message received, but does not wait for the delivery
4059 processes to finish.
4061 When all the messages have been received, the reception process exits,
4062 leaving the delivery processes to finish in their own time. The standard output
4063 and error streams are closed at the start of each delivery process.
4064 This is the default action if none of the &%-od%& options are present.
4066 If one of the queueing options in the configuration file
4067 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4068 overrides it if &%queue_only_override%& is set true, which is the default
4069 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4073 .cindex "foreground delivery"
4074 .cindex "delivery" "in the foreground"
4075 This option requests &"foreground"& (synchronous) delivery when Exim has
4076 accepted a locally-generated message. (For the daemon it is exactly the same as
4077 &%-odb%&.) A delivery process is automatically started to deliver the message,
4078 and Exim waits for it to complete before proceeding.
4080 The original Exim reception process does not finish until the delivery
4081 process for the final message has ended. The standard error stream is left open
4084 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4085 false and one of the queueing options in the configuration file is in effect.
4087 If there is a temporary delivery error during foreground delivery, the
4088 message is left on the queue for later delivery, and the original reception
4089 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4090 restricted configuration that never queues messages.
4095 This option is synonymous with &%-odf%&. It is provided for compatibility with
4100 .cindex "non-immediate delivery"
4101 .cindex "delivery" "suppressing immediate"
4102 .cindex "queueing incoming messages"
4103 This option applies to all modes in which Exim accepts incoming messages,
4104 including the listening daemon. It specifies that the accepting process should
4105 not automatically start a delivery process for each message received. Messages
4106 are placed on the queue, and remain there until a subsequent queue runner
4107 process encounters them. There are several configuration options (such as
4108 &%queue_only%&) that can be used to queue incoming messages under certain
4109 conditions. This option overrides all of them and also &%-odqs%&. It always
4114 .cindex "SMTP" "delaying delivery"
4115 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4116 However, like &%-odb%& and &%-odi%&, this option has no effect if
4117 &%queue_only_override%& is false and one of the queueing options in the
4118 configuration file is in effect.
4120 When &%-odqs%& does operate, a delivery process is started for each incoming
4121 message, in the background by default, but in the foreground if &%-odi%& is
4122 also present. The recipient addresses are routed, and local deliveries are done
4123 in the normal way. However, if any SMTP deliveries are required, they are not
4124 done at this time, so the message remains on the queue until a subsequent queue
4125 runner process encounters it. Because routing was done, Exim knows which
4126 messages are waiting for which hosts, and so a number of messages for the same
4127 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4128 configuration option has the same effect for specific domains. See also the
4133 .cindex "error" "reporting"
4134 If an error is detected while a non-SMTP message is being received (for
4135 example, a malformed address), the error is reported to the sender in a mail
4138 .cindex "return code" "for &%-oee%&"
4140 this error message is successfully sent, the Exim receiving process
4141 exits with a return code of zero. If not, the return code is 2 if the problem
4142 is that the original message has no recipients, or 1 for any other error.
4143 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4147 .cindex "error" "reporting"
4148 .cindex "return code" "for &%-oem%&"
4149 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4150 return code, whether or not the error message was successfully sent.
4151 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4155 .cindex "error" "reporting"
4156 If an error is detected while a non-SMTP message is being received, the
4157 error is reported by writing a message to the standard error file (stderr).
4158 .cindex "return code" "for &%-oep%&"
4159 The return code is 1 for all errors.
4163 .cindex "error" "reporting"
4164 This option is supported for compatibility with Sendmail, but has the same
4169 .cindex "error" "reporting"
4170 This option is supported for compatibility with Sendmail, but has the same
4175 .cindex "dot" "in incoming non-SMTP message"
4176 This option, which has the same effect as &%-i%&, specifies that a dot on a
4177 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4178 single dot does terminate, though Exim does no special processing for other
4179 lines that start with a dot. This option is set by default if Exim is called as
4180 &'rmail'&. See also &%-ti%&.
4183 .oindex "&%-oitrue%&"
4184 This option is treated as synonymous with &%-oi%&.
4186 .vitem &%-oMa%&&~<&'host&~address'&>
4188 .cindex "sender" "host address, specifying for local message"
4189 A number of options starting with &%-oM%& can be used to set values associated
4190 with remote hosts on locally-submitted messages (that is, messages not received
4191 over TCP/IP). These options can be used by any caller in conjunction with the
4192 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4193 other circumstances, they are ignored unless the caller is trusted.
4195 The &%-oMa%& option sets the sender host address. This may include a port
4196 number at the end, after a full stop (period). For example:
4198 exim -bs -oMa 10.9.8.7.1234
4200 An alternative syntax is to enclose the IP address in square brackets,
4201 followed by a colon and the port number:
4203 exim -bs -oMa [10.9.8.7]:1234
4205 The IP address is placed in the &$sender_host_address$& variable, and the
4206 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4207 are present on the command line, the sender host IP address is taken from
4208 whichever one is last.
4210 .vitem &%-oMaa%&&~<&'name'&>
4212 .cindex "authentication" "name, specifying for local message"
4213 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4214 option sets the value of &$sender_host_authenticated$& (the authenticator
4215 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4216 This option can be used with &%-bh%& and &%-bs%& to set up an
4217 authenticated SMTP session without actually using the SMTP AUTH command.
4219 .vitem &%-oMai%&&~<&'string'&>
4221 .cindex "authentication" "id, specifying for local message"
4222 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4223 option sets the value of &$authenticated_id$& (the id that was authenticated).
4224 This overrides the default value (the caller's login id, except with &%-bh%&,
4225 where there is no default) for messages from local sources. See chapter
4226 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4228 .vitem &%-oMas%&&~<&'address'&>
4230 .cindex "authentication" "sender, specifying for local message"
4231 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4232 option sets the authenticated sender value in &$authenticated_sender$&. It
4233 overrides the sender address that is created from the caller's login id for
4234 messages from local sources, except when &%-bh%& is used, when there is no
4235 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4236 specified on a MAIL command overrides this value. See chapter
4237 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4239 .vitem &%-oMi%&&~<&'interface&~address'&>
4241 .cindex "interface" "address, specifying for local message"
4242 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4243 option sets the IP interface address value. A port number may be included,
4244 using the same syntax as for &%-oMa%&. The interface address is placed in
4245 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4247 .vitem &%-oMm%&&~<&'message&~reference'&>
4249 .cindex "message reference" "message reference, specifying for local message"
4250 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4251 option sets the message reference, e.g. message-id, and is logged during
4252 delivery. This is useful when some kind of audit trail is required to tie
4253 messages together. The format of the message reference is checked and will
4254 abort if the format is invalid. The option will only be accepted if exim is
4255 running in trusted mode, not as any regular user.
4257 The best example of a message reference is when Exim sends a bounce message.
4258 The message reference is the message-id of the original message for which Exim
4259 is sending the bounce.
4261 .vitem &%-oMr%&&~<&'protocol&~name'&>
4263 .cindex "protocol, specifying for local message"
4264 .vindex "&$received_protocol$&"
4265 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4266 option sets the received protocol value that is stored in
4267 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4268 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4269 SMTP protocol names (see the description of &$received_protocol$& in section
4270 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4271 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4274 .vitem &%-oMs%&&~<&'host&~name'&>
4276 .cindex "sender" "host name, specifying for local message"
4277 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4278 option sets the sender host name in &$sender_host_name$&. When this option is
4279 present, Exim does not attempt to look up a host name from an IP address; it
4280 uses the name it is given.
4282 .vitem &%-oMt%&&~<&'ident&~string'&>
4284 .cindex "sender" "ident string, specifying for local message"
4285 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4286 option sets the sender ident value in &$sender_ident$&. The default setting for
4287 local callers is the login id of the calling process, except when &%-bh%& is
4288 used, when there is no default.
4292 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4293 In Sendmail, this option means &"me too"&, indicating that the sender of a
4294 message should receive a copy of the message if the sender appears in an alias
4295 expansion. Exim always does this, so the option does nothing.
4299 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4300 This option is ignored. In Sendmail it specifies &"old style headers"&,
4301 whatever that means.
4303 .vitem &%-oP%&&~<&'path'&>
4305 .cindex "pid (process id)" "of daemon"
4306 .cindex "daemon" "process id (pid)"
4307 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4308 value. The option specifies the file to which the process id of the daemon is
4309 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4310 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4311 because in those cases, the normal pid file is not used.
4313 .vitem &%-or%&&~<&'time'&>
4315 .cindex "timeout" "for non-SMTP input"
4316 This option sets a timeout value for incoming non-SMTP messages. If it is not
4317 set, Exim will wait forever for the standard input. The value can also be set
4318 by the &%receive_timeout%& option. The format used for specifying times is
4319 described in section &<<SECTtimeformat>>&.
4321 .vitem &%-os%&&~<&'time'&>
4323 .cindex "timeout" "for SMTP input"
4324 .cindex "SMTP" "input timeout"
4325 This option sets a timeout value for incoming SMTP messages. The timeout
4326 applies to each SMTP command and block of data. The value can also be set by
4327 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4328 for specifying times is described in section &<<SECTtimeformat>>&.
4332 This option has exactly the same effect as &%-v%&.
4334 .vitem &%-oX%&&~<&'number&~or&~string'&>
4336 .cindex "TCP/IP" "setting listening ports"
4337 .cindex "TCP/IP" "setting listening interfaces"
4338 .cindex "port" "receiving TCP/IP"
4339 This option is relevant only when the &%-bd%& (start listening daemon) option
4340 is also given. It controls which ports and interfaces the daemon uses. Details
4341 of the syntax, and how it interacts with configuration file options, are given
4342 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4343 file is written unless &%-oP%& is also present to specify a pid file name.
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 be delayed until it is
4355 .cindex "Perl" "starting the interpreter"
4356 This option applies when an embedded Perl interpreter is linked with Exim (see
4357 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4358 option, forcing the starting of the interpreter to occur as soon as Exim is
4361 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4363 For compatibility with Sendmail, this option is equivalent to
4365 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4367 It sets the incoming protocol and host name (for trusted callers). The
4368 host name and its colon can be omitted when only the protocol is to be set.
4369 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4370 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4371 or &`s`& using this option (but that does not seem a real limitation).
4375 .cindex "queue runner" "starting manually"
4376 This option is normally restricted to admin users. However, there is a
4377 configuration option called &%prod_requires_admin%& which can be set false to
4378 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4379 and &%-S%& options).
4381 .cindex "queue runner" "description of operation"
4383 If other commandline options do not specify an action,
4385 the &%-q%& option starts one queue runner process. This scans the queue of
4386 waiting messages, and runs a delivery process for each one in turn. It waits
4387 for each delivery process to finish before starting the next one. A delivery
4388 process may not actually do any deliveries if the retry times for the addresses
4389 have not been reached. Use &%-qf%& (see below) if you want to override this.
4392 .cindex "SMTP" "passed connection"
4393 .cindex "SMTP" "multiple deliveries"
4394 .cindex "multiple SMTP deliveries"
4395 the delivery process spawns other processes to deliver other messages down
4396 passed SMTP connections, the queue runner waits for these to finish before
4399 When all the queued messages have been considered, the original queue runner
4400 process terminates. In other words, a single pass is made over the waiting
4401 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4402 this to be repeated periodically.
4404 Exim processes the waiting messages in an unpredictable order. It isn't very
4405 random, but it is likely to be different each time, which is all that matters.
4406 If one particular message screws up a remote MTA, other messages to the same
4407 MTA have a chance of getting through if they get tried first.
4409 It is possible to cause the messages to be processed in lexical message id
4410 order, which is essentially the order in which they arrived, by setting the
4411 &%queue_run_in_order%& option, but this is not recommended for normal use.
4413 .vitem &%-q%&<&'qflags'&>
4414 The &%-q%& option may be followed by one or more flag letters that change its
4415 behaviour. They are all optional, but if more than one is present, they must
4416 appear in the correct order. Each flag is described in a separate item below.
4420 .cindex "queue" "double scanning"
4421 .cindex "queue" "routing"
4422 .cindex "routing" "whole queue before delivery"
4423 An option starting with &%-qq%& requests a two-stage queue run. In the first
4424 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4425 every domain. Addresses are routed, local deliveries happen, but no remote
4428 .cindex "hints database" "remembering routing"
4429 The hints database that remembers which messages are waiting for specific hosts
4430 is updated, as if delivery to those hosts had been deferred. After this is
4431 complete, a second, normal queue scan happens, with routing and delivery taking
4432 place as normal. Messages that are routed to the same host should mostly be
4433 delivered down a single SMTP
4434 .cindex "SMTP" "passed connection"
4435 .cindex "SMTP" "multiple deliveries"
4436 .cindex "multiple SMTP deliveries"
4437 connection because of the hints that were set up during the first queue scan.
4438 This option may be useful for hosts that are connected to the Internet
4441 .vitem &%-q[q]i...%&
4443 .cindex "queue" "initial delivery"
4444 If the &'i'& flag is present, the queue runner runs delivery processes only for
4445 those messages that haven't previously been tried. (&'i'& stands for &"initial
4446 delivery"&.) This can be helpful if you are putting messages on the queue using
4447 &%-odq%& and want a queue runner just to process the new messages.
4449 .vitem &%-q[q][i]f...%&
4451 .cindex "queue" "forcing delivery"
4452 .cindex "delivery" "forcing in queue run"
4453 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4454 message, whereas without &'f'& only those non-frozen addresses that have passed
4455 their retry times are tried.
4457 .vitem &%-q[q][i]ff...%&
4459 .cindex "frozen messages" "forcing delivery"
4460 If &'ff'& is present, a delivery attempt is forced for every message, whether
4463 .vitem &%-q[q][i][f[f]]l%&
4465 .cindex "queue" "local deliveries only"
4466 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4467 be done. If a message requires any remote deliveries, it remains on the queue
4471 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4474 .cindex "named queues"
4475 .cindex "queue" "delivering specific messages"
4476 If the &'G'& flag and a name is present, the queue runner operates on the
4477 queue with the given name rather than the default queue.
4478 The name should not contain a &'/'& character.
4479 For a periodic queue run (see below)
4480 append to the name a slash and a time value.
4482 If other commandline options speicify an action, a &'-qG<name>'& option
4483 will specify a queue to operate on.
4486 exim -bp -qGquarantine
4488 exim -qGoffpeak -Rf @special.domain.example
4492 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4493 When scanning the queue, Exim can be made to skip over messages whose ids are
4494 lexically less than a given value by following the &%-q%& option with a
4495 starting message id. For example:
4497 exim -q 0t5C6f-0000c8-00
4499 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4500 second message id is given, messages whose ids are lexically greater than it
4501 are also skipped. If the same id is given twice, for example,
4503 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4505 just one delivery process is started, for that message. This differs from
4506 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4507 that it counts as a delivery from a queue run. Note that the selection
4508 mechanism does not affect the order in which the messages are scanned. There
4509 are also other ways of selecting specific sets of messages for delivery in a
4510 queue run &-- see &%-R%& and &%-S%&.
4512 .vitem &%-q%&<&'qflags'&><&'time'&>
4513 .cindex "queue runner" "starting periodically"
4514 .cindex "periodic queue running"
4515 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4516 starting a queue runner process at intervals specified by the given time value
4517 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4518 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4519 single daemon process handles both functions. A common way of starting up a
4520 combined daemon at system boot time is to use a command such as
4522 /usr/exim/bin/exim -bd -q30m
4524 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4525 process every 30 minutes.
4527 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4528 pid file is written unless one is explicitly requested by the &%-oP%& option.
4530 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4532 This option is synonymous with &%-R%&. It is provided for Sendmail
4535 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4537 This option is synonymous with &%-S%&.
4539 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4541 .cindex "queue runner" "for specific recipients"
4542 .cindex "delivery" "to given domain"
4543 .cindex "domain" "delivery to"
4544 The <&'rsflags'&> may be empty, in which case the white space before the string
4545 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4546 which are the possible values for <&'rsflags'&>. White space is required if
4547 <&'rsflags'&> is not empty.
4549 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4550 perform a single queue run, except that, when scanning the messages on the
4551 queue, Exim processes only those that have at least one undelivered recipient
4552 address containing the given string, which is checked in a case-independent
4553 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4554 regular expression; otherwise it is a literal string.
4556 If you want to do periodic queue runs for messages with specific recipients,
4557 you can combine &%-R%& with &%-q%& and a time value. For example:
4559 exim -q25m -R @special.domain.example
4561 This example does a queue run for messages with recipients in the given domain
4562 every 25 minutes. Any additional flags that are specified with &%-q%& are
4563 applied to each queue run.
4565 Once a message is selected for delivery by this mechanism, all its addresses
4566 are processed. For the first selected message, Exim overrides any retry
4567 information and forces a delivery attempt for each undelivered address. This
4568 means that if delivery of any address in the first message is successful, any
4569 existing retry information is deleted, and so delivery attempts for that
4570 address in subsequently selected messages (which are processed without forcing)
4571 will run. However, if delivery of any address does not succeed, the retry
4572 information is updated, and in subsequently selected messages, the failing
4573 address will be skipped.
4575 .cindex "frozen messages" "forcing delivery"
4576 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4577 all selected messages, not just the first; frozen messages are included when
4580 The &%-R%& option makes it straightforward to initiate delivery of all messages
4581 to a given domain after a host has been down for some time. When the SMTP
4582 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4583 effect is to run Exim with the &%-R%& option, but it can be configured to run
4584 an arbitrary command instead.
4588 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4590 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4592 .cindex "delivery" "from given sender"
4593 .cindex "queue runner" "for specific senders"
4594 This option acts like &%-R%& except that it checks the string against each
4595 message's sender instead of against the recipients. If &%-R%& is also set, both
4596 conditions must be met for a message to be selected. If either of the options
4597 has &'f'& or &'ff'& in its flags, the associated action is taken.
4599 .vitem &%-Tqt%&&~<&'times'&>
4601 This is an option that is exclusively for use by the Exim testing suite. It is not
4602 recognized when Exim is run normally. It allows for the setting up of explicit
4603 &"queue times"& so that various warning/retry features can be tested.
4607 .cindex "recipient" "extracting from header lines"
4608 .cindex "&'Bcc:'& header line"
4609 .cindex "&'Cc:'& header line"
4610 .cindex "&'To:'& header line"
4611 When Exim is receiving a locally-generated, non-SMTP message on its standard
4612 input, the &%-t%& option causes the recipients of the message to be obtained
4613 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4614 from the command arguments. The addresses are extracted before any rewriting
4615 takes place and the &'Bcc:'& header line, if present, is then removed.
4617 .cindex "Sendmail compatibility" "&%-t%& option"
4618 If the command has any arguments, they specify addresses to which the message
4619 is &'not'& to be delivered. That is, the argument addresses are removed from
4620 the recipients list obtained from the headers. This is compatible with Smail 3
4621 and in accordance with the documented behaviour of several versions of
4622 Sendmail, as described in man pages on a number of operating systems (e.g.
4623 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4624 argument addresses to those obtained from the headers, and the O'Reilly
4625 Sendmail book documents it that way. Exim can be made to add argument addresses
4626 instead of subtracting them by setting the option
4627 &%extract_addresses_remove_arguments%& false.
4629 .cindex "&%Resent-%& header lines" "with &%-t%&"
4630 If there are any &%Resent-%& header lines in the message, Exim extracts
4631 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4632 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4633 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4634 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4636 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4637 message is resent several times). The RFC also specifies that they should be
4638 added at the front of the message, and separated by &'Received:'& lines. It is
4639 not at all clear how &%-t%& should operate in the present of multiple sets,
4640 nor indeed exactly what constitutes a &"set"&.
4641 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4642 are often added at the end of the header, and if a message is resent more than
4643 once, it is common for the original set of &%Resent-%& headers to be renamed as
4644 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4648 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4649 compatibility with Sendmail.
4651 .vitem &%-tls-on-connect%&
4652 .oindex "&%-tls-on-connect%&"
4653 .cindex "TLS" "use without STARTTLS"
4654 .cindex "TLS" "automatic start"
4655 This option is available when Exim is compiled with TLS support. It forces all
4656 incoming SMTP connections to behave as if the incoming port is listed in the
4657 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4658 &<<CHAPTLS>>& for further details.
4663 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4664 Sendmail uses this option for &"initial message submission"&, and its
4665 documentation states that in future releases, it may complain about
4666 syntactically invalid messages rather than fixing them when this flag is not
4667 set. Exim ignores this option.
4671 This option causes Exim to write information to the standard error stream,
4672 describing what it is doing. In particular, it shows the log lines for
4673 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4674 dialogue is shown. Some of the log lines shown may not actually be written to
4675 the log if the setting of &%log_selector%& discards them. Any relevant
4676 selectors are shown with each log line. If none are shown, the logging is
4681 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4682 National Language Support extended characters in the body of the mail item"&).
4683 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4686 .vitem &%-X%&&~<&'logfile'&>
4688 This option is interpreted by Sendmail to cause debug information to be sent
4689 to the named file. It is ignored by Exim.
4691 .vitem &%-z%&&~<&'log-line'&>
4693 This option writes its argument to Exim's logfile.
4694 Use is restricted to administrators; the intent is for operational notes.
4695 Quotes should be used to maintain a multi-word item as a single argument,
4703 . ////////////////////////////////////////////////////////////////////////////
4704 . Insert a stylized DocBook comment here, to identify the end of the command
4705 . line options. This is for the benefit of the Perl script that automatically
4706 . creates a man page for the options.
4707 . ////////////////////////////////////////////////////////////////////////////
4710 <!-- === End of command line options === -->
4717 . ////////////////////////////////////////////////////////////////////////////
4718 . ////////////////////////////////////////////////////////////////////////////
4721 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4722 "The runtime configuration file"
4724 .cindex "run time configuration"
4725 .cindex "configuration file" "general description"
4726 .cindex "CONFIGURE_FILE"
4727 .cindex "configuration file" "errors in"
4728 .cindex "error" "in configuration file"
4729 .cindex "return code" "for bad configuration"
4730 Exim uses a single run time configuration file that is read whenever an Exim
4731 binary is executed. Note that in normal operation, this happens frequently,
4732 because Exim is designed to operate in a distributed manner, without central
4735 If a syntax error is detected while reading the configuration file, Exim
4736 writes a message on the standard error, and exits with a non-zero return code.
4737 The message is also written to the panic log. &*Note*&: Only simple syntax
4738 errors can be detected at this time. The values of any expanded options are
4739 not checked until the expansion happens, even when the expansion does not
4740 actually alter the string.
4742 The name of the configuration file is compiled into the binary for security
4743 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4744 most configurations, this specifies a single file. However, it is permitted to
4745 give a colon-separated list of file names, in which case Exim uses the first
4746 existing file in the list.
4749 .cindex "EXIM_GROUP"
4750 .cindex "CONFIGURE_OWNER"
4751 .cindex "CONFIGURE_GROUP"
4752 .cindex "configuration file" "ownership"
4753 .cindex "ownership" "configuration file"
4754 The run time configuration file must be owned by root or by the user that is
4755 specified at compile time by the CONFIGURE_OWNER option (if set). The
4756 configuration file must not be world-writeable, or group-writeable unless its
4757 group is the root group or the one specified at compile time by the
4758 CONFIGURE_GROUP option.
4760 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4761 to root, anybody who is able to edit the run time configuration file has an
4762 easy way to run commands as root. If you specify a user or group in the
4763 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4764 who are members of that group will trivially be able to obtain root privileges.
4766 Up to Exim version 4.72, the run time configuration file was also permitted to
4767 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4768 since it offered a simple privilege escalation for any attacker who managed to
4769 compromise the Exim user account.
4771 A default configuration file, which will work correctly in simple situations,
4772 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4773 defines just one file name, the installation process copies the default
4774 configuration to a new file of that name if it did not previously exist. If
4775 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4776 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4781 .section "Using a different configuration file" "SECID40"
4782 .cindex "configuration file" "alternate"
4783 A one-off alternate configuration can be specified by the &%-C%& command line
4784 option, which may specify a single file or a list of files. However, when
4785 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4786 unless the argument for &%-C%& is identical to the built-in value from
4787 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4788 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4789 is useful mainly for checking the syntax of configuration files before
4790 installing them. No owner or group checks are done on a configuration file
4791 specified by &%-C%&, if root privilege has been dropped.
4793 Even the Exim user is not trusted to specify an arbitrary configuration file
4794 with the &%-C%& option to be used with root privileges, unless that file is
4795 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4796 testing a configuration using &%-C%& right through message reception and
4797 delivery, even if the caller is root. The reception works, but by that time,
4798 Exim is running as the Exim user, so when it re-execs to regain privilege for
4799 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4800 can test reception and delivery using two separate commands (one to put a
4801 message on the queue, using &%-odq%&, and another to do the delivery, using
4804 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4805 prefix string with which any file named in a &%-C%& command line option must
4806 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4807 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4808 name can be used with &%-C%&.
4810 One-off changes to a configuration can be specified by the &%-D%& command line
4811 option, which defines and overrides values for macros used inside the
4812 configuration file. However, like &%-C%&, the use of this option by a
4813 non-privileged user causes Exim to discard its root privilege.
4814 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4815 completely disabled, and its use causes an immediate error exit.
4817 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4818 to declare certain macro names trusted, such that root privilege will not
4819 necessarily be discarded.
4820 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4821 considered safe and, if &%-D%& only supplies macros from this list, and the
4822 values are acceptable, then Exim will not give up root privilege if the caller
4823 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4824 transition mechanism and is expected to be removed in the future. Acceptable
4825 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4827 Some sites may wish to use the same Exim binary on different machines that
4828 share a file system, but to use different configuration files on each machine.
4829 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4830 looks for a file whose name is the configuration file name followed by a dot
4831 and the machine's node name, as obtained from the &[uname()]& function. If this
4832 file does not exist, the standard name is tried. This processing occurs for
4833 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4835 In some esoteric situations different versions of Exim may be run under
4836 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4837 help with this. See the comments in &_src/EDITME_& for details.
4841 .section "Configuration file format" "SECTconffilfor"
4842 .cindex "configuration file" "format of"
4843 .cindex "format" "configuration file"
4844 Exim's configuration file is divided into a number of different parts. General
4845 option settings must always appear at the start of the file. The other parts
4846 are all optional, and may appear in any order. Each part other than the first
4847 is introduced by the word &"begin"& followed by at least one literal
4848 space, and the name of the part. The optional parts are:
4851 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4854 .cindex "AUTH" "configuration"
4855 &'authenticators'&: Configuration settings for the authenticator drivers. These
4856 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4858 &'routers'&: Configuration settings for the router drivers. Routers process
4859 addresses and determine how the message is to be delivered (see chapters
4860 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4862 &'transports'&: Configuration settings for the transport drivers. Transports
4863 define mechanisms for copying messages to destinations (see chapters
4864 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4866 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4867 If there is no retry section, or if it is empty (that is, no retry rules are
4868 defined), Exim will not retry deliveries. In this situation, temporary errors
4869 are treated the same as permanent errors. Retry rules are discussed in chapter
4872 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4873 when new addresses are generated during delivery. Rewriting is discussed in
4874 chapter &<<CHAPrewrite>>&.
4876 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4877 want to use this feature, you must set
4879 LOCAL_SCAN_HAS_OPTIONS=yes
4881 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4882 facility are given in chapter &<<CHAPlocalscan>>&.
4885 .cindex "configuration file" "leading white space in"
4886 .cindex "configuration file" "trailing white space in"
4887 .cindex "white space" "in configuration file"
4888 Leading and trailing white space in configuration lines is always ignored.
4890 Blank lines in the file, and lines starting with a # character (ignoring
4891 leading white space) are treated as comments and are ignored. &*Note*&: A
4892 # character other than at the beginning of a line is not treated specially,
4893 and does not introduce a comment.
4895 Any non-comment line can be continued by ending it with a backslash. Note that
4896 the general rule for white space means that trailing white space after the
4897 backslash and leading white space at the start of continuation
4898 lines is ignored. Comment lines beginning with # (but not empty lines) may
4899 appear in the middle of a sequence of continuation lines.
4901 A convenient way to create a configuration file is to start from the
4902 default, which is supplied in &_src/configure.default_&, and add, delete, or
4903 change settings as required.
4905 The ACLs, retry rules, and rewriting rules have their own syntax which is
4906 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4907 respectively. The other parts of the configuration file have some syntactic
4908 items in common, and these are described below, from section &<<SECTcos>>&
4909 onwards. Before that, the inclusion, macro, and conditional facilities are
4914 .section "File inclusions in the configuration file" "SECID41"
4915 .cindex "inclusions in configuration file"
4916 .cindex "configuration file" "including other files"
4917 .cindex "&`.include`& in configuration file"
4918 .cindex "&`.include_if_exists`& in configuration file"
4919 You can include other files inside Exim's run time configuration file by
4922 &`.include`& <&'file name'&>
4923 &`.include_if_exists`& <&'file name'&>
4925 on a line by itself. Double quotes round the file name are optional. If you use
4926 the first form, a configuration error occurs if the file does not exist; the
4927 second form does nothing for non-existent files. In all cases, an absolute file
4930 Includes may be nested to any depth, but remember that Exim reads its
4931 configuration file often, so it is a good idea to keep them to a minimum.
4932 If you change the contents of an included file, you must HUP the daemon,
4933 because an included file is read only when the configuration itself is read.
4935 The processing of inclusions happens early, at a physical line level, so, like
4936 comment lines, an inclusion can be used in the middle of an option setting,
4939 hosts_lookup = a.b.c \
4942 Include processing happens after macro processing (see below). Its effect is to
4943 process the lines of the included file as if they occurred inline where the
4948 .section "Macros in the configuration file" "SECTmacrodefs"
4949 .cindex "macro" "description of"
4950 .cindex "configuration file" "macros"
4951 If a line in the main part of the configuration (that is, before the first
4952 &"begin"& line) begins with an upper case letter, it is taken as a macro
4953 definition, and must be of the form
4955 <&'name'&> = <&'rest of line'&>
4957 The name must consist of letters, digits, and underscores, and need not all be
4958 in upper case, though that is recommended. The rest of the line, including any
4959 continuations, is the replacement text, and has leading and trailing white
4960 space removed. Quotes are not removed. The replacement text can never end with
4961 a backslash character, but this doesn't seem to be a serious limitation.
4963 Macros may also be defined between router, transport, authenticator, or ACL
4964 definitions. They may not, however, be defined within an individual driver or
4965 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4967 .section "Macro substitution" "SECID42"
4968 Once a macro is defined, all subsequent lines in the file (and any included
4969 files) are scanned for the macro name; if there are several macros, the line is
4970 scanned for each in turn, in the order in which the macros are defined. The
4971 replacement text is not re-scanned for the current macro, though it is scanned
4972 for subsequently defined macros. For this reason, a macro name may not contain
4973 the name of a previously defined macro as a substring. You could, for example,
4976 &`ABCD_XYZ = `&<&'something'&>
4977 &`ABCD = `&<&'something else'&>
4979 but putting the definitions in the opposite order would provoke a configuration
4980 error. Macro expansion is applied to individual physical lines from the file,
4981 before checking for line continuation or file inclusion (see above). If a line
4982 consists solely of a macro name, and the expansion of the macro is empty, the
4983 line is ignored. A macro at the start of a line may turn the line into a
4984 comment line or a &`.include`& line.
4987 .section "Redefining macros" "SECID43"
4988 Once defined, the value of a macro can be redefined later in the configuration
4989 (or in an included file). Redefinition is specified by using &'=='& instead of
4994 MAC == updated value
4996 Redefinition does not alter the order in which the macros are applied to the
4997 subsequent lines of the configuration file. It is still the same order in which
4998 the macros were originally defined. All that changes is the macro's value.
4999 Redefinition makes it possible to accumulate values. For example:
5003 MAC == MAC and something added
5005 This can be helpful in situations where the configuration file is built
5006 from a number of other files.
5008 .section "Overriding macro values" "SECID44"
5009 The values set for macros in the configuration file can be overridden by the
5010 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5011 used, unless called by root or the Exim user. A definition on the command line
5012 using the &%-D%& option causes all definitions and redefinitions within the
5017 .section "Example of macro usage" "SECID45"
5018 As an example of macro usage, consider a configuration where aliases are looked
5019 up in a MySQL database. It helps to keep the file less cluttered if long
5020 strings such as SQL statements are defined separately as macros, for example:
5022 ALIAS_QUERY = select mailbox from user where \
5023 login='${quote_mysql:$local_part}';
5025 This can then be used in a &(redirect)& router setting like this:
5027 data = ${lookup mysql{ALIAS_QUERY}}
5029 In earlier versions of Exim macros were sometimes used for domain, host, or
5030 address lists. In Exim 4 these are handled better by named lists &-- see
5031 section &<<SECTnamedlists>>&.
5034 .section "Conditional skips in the configuration file" "SECID46"
5035 .cindex "configuration file" "conditional skips"
5036 .cindex "&`.ifdef`&"
5037 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5038 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5039 portions of the configuration file. The processing happens whenever the file is
5040 read (that is, when an Exim binary starts to run).
5042 The implementation is very simple. Instances of the first four directives must
5043 be followed by text that includes the names of one or macros. The condition
5044 that is tested is whether or not any macro substitution has taken place in the
5048 message_size_limit = 50M
5050 message_size_limit = 100M
5053 sets a message size limit of 50M if the macro &`AAA`& is defined
5054 (or &`A`& or &`AA`&), and 100M
5055 otherwise. If there is more than one macro named on the line, the condition
5056 is true if any of them are defined. That is, it is an &"or"& condition. To
5057 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5059 Although you can use a macro expansion to generate one of these directives,
5060 it is not very useful, because the condition &"there was a macro substitution
5061 in this line"& will always be true.
5063 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5064 to clarify complicated nestings.
5068 .section "Common option syntax" "SECTcos"
5069 .cindex "common option syntax"
5070 .cindex "syntax of common options"
5071 .cindex "configuration file" "common option syntax"
5072 For the main set of options, driver options, and &[local_scan()]& options,
5073 each setting is on a line by itself, and starts with a name consisting of
5074 lower-case letters and underscores. Many options require a data value, and in
5075 these cases the name must be followed by an equals sign (with optional white
5076 space) and then the value. For example:
5078 qualify_domain = mydomain.example.com
5080 .cindex "hiding configuration option values"
5081 .cindex "configuration options" "hiding value of"
5082 .cindex "options" "hiding value of"
5083 Some option settings may contain sensitive data, for example, passwords for
5084 accessing databases. To stop non-admin users from using the &%-bP%& command
5085 line option to read these values, you can precede the option settings with the
5086 word &"hide"&. For example:
5088 hide mysql_servers = localhost/users/admin/secret-password
5090 For non-admin users, such options are displayed like this:
5092 mysql_servers = <value not displayable>
5094 If &"hide"& is used on a driver option, it hides the value of that option on
5095 all instances of the same driver.
5097 The following sections describe the syntax used for the different data types
5098 that are found in option settings.
5101 .section "Boolean options" "SECID47"
5102 .cindex "format" "boolean"
5103 .cindex "boolean configuration values"
5104 .oindex "&%no_%&&'xxx'&"
5105 .oindex "&%not_%&&'xxx'&"
5106 Options whose type is given as boolean are on/off switches. There are two
5107 different ways of specifying such options: with and without a data value. If
5108 the option name is specified on its own without data, the switch is turned on;
5109 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5110 boolean options may be followed by an equals sign and one of the words
5111 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5112 the following two settings have exactly the same effect:
5117 The following two lines also have the same (opposite) effect:
5122 You can use whichever syntax you prefer.
5127 .section "Integer values" "SECID48"
5128 .cindex "integer configuration values"
5129 .cindex "format" "integer"
5130 If an option's type is given as &"integer"&, the value can be given in decimal,
5131 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5132 number is assumed. Otherwise, it is treated as an octal number unless it starts
5133 with the characters &"0x"&, in which case the remainder is interpreted as a
5136 If an integer value is followed by the letter K, it is multiplied by 1024; if
5137 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5138 of integer option settings are output, values which are an exact multiple of
5139 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5140 and M. The printing style is independent of the actual input format that was
5144 .section "Octal integer values" "SECID49"
5145 .cindex "integer format"
5146 .cindex "format" "octal integer"
5147 If an option's type is given as &"octal integer"&, its value is always
5148 interpreted as an octal number, whether or not it starts with the digit zero.
5149 Such options are always output in octal.
5152 .section "Fixed point numbers" "SECID50"
5153 .cindex "fixed point configuration values"
5154 .cindex "format" "fixed point"
5155 If an option's type is given as &"fixed-point"&, its value must be a decimal
5156 integer, optionally followed by a decimal point and up to three further digits.
5160 .section "Time intervals" "SECTtimeformat"
5161 .cindex "time interval" "specifying in configuration"
5162 .cindex "format" "time interval"
5163 A time interval is specified as a sequence of numbers, each followed by one of
5164 the following letters, with no intervening white space:
5174 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5175 intervals are output in the same format. Exim does not restrict the values; it
5176 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5180 .section "String values" "SECTstrings"
5181 .cindex "string" "format of configuration values"
5182 .cindex "format" "string"
5183 If an option's type is specified as &"string"&, the value can be specified with
5184 or without double-quotes. If it does not start with a double-quote, the value
5185 consists of the remainder of the line plus any continuation lines, starting at
5186 the first character after any leading white space, with trailing white space
5187 removed, and with no interpretation of the characters in the string. Because
5188 Exim removes comment lines (those beginning with #) at an early stage, they can
5189 appear in the middle of a multi-line string. The following two settings are
5190 therefore equivalent:
5192 trusted_users = uucp:mail
5193 trusted_users = uucp:\
5194 # This comment line is ignored
5197 .cindex "string" "quoted"
5198 .cindex "escape characters in quoted strings"
5199 If a string does start with a double-quote, it must end with a closing
5200 double-quote, and any backslash characters other than those used for line
5201 continuation are interpreted as escape characters, as follows:
5204 .irow &`\\`& "single backslash"
5205 .irow &`\n`& "newline"
5206 .irow &`\r`& "carriage return"
5208 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5209 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5213 If a backslash is followed by some other character, including a double-quote
5214 character, that character replaces the pair.
5216 Quoting is necessary only if you want to make use of the backslash escapes to
5217 insert special characters, or if you need to specify a value with leading or
5218 trailing spaces. These cases are rare, so quoting is almost never needed in
5219 current versions of Exim. In versions of Exim before 3.14, quoting was required
5220 in order to continue lines, so you may come across older configuration files
5221 and examples that apparently quote unnecessarily.
5224 .section "Expanded strings" "SECID51"
5225 .cindex "expansion" "definition of"
5226 Some strings in the configuration file are subjected to &'string expansion'&,
5227 by which means various parts of the string may be changed according to the
5228 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5229 is as just described; in particular, the handling of backslashes in quoted
5230 strings is done as part of the input process, before expansion takes place.
5231 However, backslash is also an escape character for the expander, so any
5232 backslashes that are required for that reason must be doubled if they are
5233 within a quoted configuration string.
5236 .section "User and group names" "SECID52"
5237 .cindex "user name" "format of"
5238 .cindex "format" "user name"
5239 .cindex "groups" "name format"
5240 .cindex "format" "group name"
5241 User and group names are specified as strings, using the syntax described
5242 above, but the strings are interpreted specially. A user or group name must
5243 either consist entirely of digits, or be a name that can be looked up using the
5244 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5247 .section "List construction" "SECTlistconstruct"
5248 .cindex "list" "syntax of in configuration"
5249 .cindex "format" "list item in configuration"
5250 .cindex "string" "list, definition of"
5251 The data for some configuration options is a list of items, with colon as the
5252 default separator. Many of these options are shown with type &"string list"& in
5253 the descriptions later in this document. Others are listed as &"domain list"&,
5254 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5255 are all the same; however, those other than &"string list"& are subject to
5256 particular kinds of interpretation, as described in chapter
5257 &<<CHAPdomhosaddlists>>&.
5259 In all these cases, the entire list is treated as a single string as far as the
5260 input syntax is concerned. The &%trusted_users%& setting in section
5261 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5262 in a list, it must be entered as two colons. Leading and trailing white space
5263 on each item in a list is ignored. This makes it possible to include items that
5264 start with a colon, and in particular, certain forms of IPv6 address. For
5267 local_interfaces = 127.0.0.1 : ::::1
5269 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5271 &*Note*&: Although leading and trailing white space is ignored in individual
5272 list items, it is not ignored when parsing the list. The space after the first
5273 colon in the example above is necessary. If it were not there, the list would
5274 be interpreted as the two items 127.0.0.1:: and 1.
5276 .section "Changing list separators" "SECTlistsepchange"
5277 .cindex "list separator" "changing"
5278 .cindex "IPv6" "addresses in lists"
5279 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5280 introduced to allow the separator character to be changed. If a list begins
5281 with a left angle bracket, followed by any punctuation character, that
5282 character is used instead of colon as the list separator. For example, the list
5283 above can be rewritten to use a semicolon separator like this:
5285 local_interfaces = <; 127.0.0.1 ; ::1
5287 This facility applies to all lists, with the exception of the list in
5288 &%log_file_path%&. It is recommended that the use of non-colon separators be
5289 confined to circumstances where they really are needed.
5291 .cindex "list separator" "newline as"
5292 .cindex "newline" "as list separator"
5293 It is also possible to use newline and other control characters (those with
5294 code values less than 32, plus DEL) as separators in lists. Such separators
5295 must be provided literally at the time the list is processed. For options that
5296 are string-expanded, you can write the separator using a normal escape
5297 sequence. This will be processed by the expander before the string is
5298 interpreted as a list. For example, if a newline-separated list of domains is
5299 generated by a lookup, you can process it directly by a line such as this:
5301 domains = <\n ${lookup mysql{.....}}
5303 This avoids having to change the list separator in such data. You are unlikely
5304 to want to use a control character as a separator in an option that is not
5305 expanded, because the value is literal text. However, it can be done by giving
5306 the value in quotes. For example:
5308 local_interfaces = "<\n 127.0.0.1 \n ::1"
5310 Unlike printing character separators, which can be included in list items by
5311 doubling, it is not possible to include a control character as data when it is
5312 set as the separator. Two such characters in succession are interpreted as
5313 enclosing an empty list item.
5317 .section "Empty items in lists" "SECTempitelis"
5318 .cindex "list" "empty item in"
5319 An empty item at the end of a list is always ignored. In other words, trailing
5320 separator characters are ignored. Thus, the list in
5322 senders = user@domain :
5324 contains only a single item. If you want to include an empty string as one item
5325 in a list, it must not be the last item. For example, this list contains three
5326 items, the second of which is empty:
5328 senders = user1@domain : : user2@domain
5330 &*Note*&: There must be white space between the two colons, as otherwise they
5331 are interpreted as representing a single colon data character (and the list
5332 would then contain just one item). If you want to specify a list that contains
5333 just one, empty item, you can do it as in this example:
5337 In this case, the first item is empty, and the second is discarded because it
5338 is at the end of the list.
5343 .section "Format of driver configurations" "SECTfordricon"
5344 .cindex "drivers" "configuration format"
5345 There are separate parts in the configuration for defining routers, transports,
5346 and authenticators. In each part, you are defining a number of driver
5347 instances, each with its own set of options. Each driver instance is defined by
5348 a sequence of lines like this:
5350 <&'instance name'&>:
5355 In the following example, the instance name is &(localuser)&, and it is
5356 followed by three options settings:
5361 transport = local_delivery
5363 For each driver instance, you specify which Exim code module it uses &-- by the
5364 setting of the &%driver%& option &-- and (optionally) some configuration
5365 settings. For example, in the case of transports, if you want a transport to
5366 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5367 a local file you would use the &(appendfile)& driver. Each of the drivers is
5368 described in detail in its own separate chapter later in this manual.
5370 You can have several routers, transports, or authenticators that are based on
5371 the same underlying driver (each must have a different instance name).
5373 The order in which routers are defined is important, because addresses are
5374 passed to individual routers one by one, in order. The order in which
5375 transports are defined does not matter at all. The order in which
5376 authenticators are defined is used only when Exim, as a client, is searching
5377 them to find one that matches an authentication mechanism offered by the
5380 .cindex "generic options"
5381 .cindex "options" "generic &-- definition of"
5382 Within a driver instance definition, there are two kinds of option: &'generic'&
5383 and &'private'&. The generic options are those that apply to all drivers of the
5384 same type (that is, all routers, all transports or all authenticators). The
5385 &%driver%& option is a generic option that must appear in every definition.
5386 .cindex "private options"
5387 The private options are special for each driver, and none need appear, because
5388 they all have default values.
5390 The options may appear in any order, except that the &%driver%& option must
5391 precede any private options, since these depend on the particular driver. For
5392 this reason, it is recommended that &%driver%& always be the first option.
5394 Driver instance names, which are used for reference in log entries and
5395 elsewhere, can be any sequence of letters, digits, and underscores (starting
5396 with a letter) and must be unique among drivers of the same type. A router and
5397 a transport (for example) can each have the same name, but no two router
5398 instances can have the same name. The name of a driver instance should not be
5399 confused with the name of the underlying driver module. For example, the
5400 configuration lines:
5405 create an instance of the &(smtp)& transport driver whose name is
5406 &(remote_smtp)&. The same driver code can be used more than once, with
5407 different instance names and different option settings each time. A second
5408 instance of the &(smtp)& transport, with different options, might be defined
5414 command_timeout = 10s
5416 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5417 these transport instances from routers, and these names would appear in log
5420 Comment lines may be present in the middle of driver specifications. The full
5421 list of option settings for any particular driver instance, including all the
5422 defaulted values, can be extracted by making use of the &%-bP%& command line
5430 . ////////////////////////////////////////////////////////////////////////////
5431 . ////////////////////////////////////////////////////////////////////////////
5433 .chapter "The default configuration file" "CHAPdefconfil"
5434 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5435 .cindex "default" "configuration file &""walk through""&"
5436 The default configuration file supplied with Exim as &_src/configure.default_&
5437 is sufficient for a host with simple mail requirements. As an introduction to
5438 the way Exim is configured, this chapter &"walks through"& the default
5439 configuration, giving brief explanations of the settings. Detailed descriptions
5440 of the options are given in subsequent chapters. The default configuration file
5441 itself contains extensive comments about ways you might want to modify the
5442 initial settings. However, note that there are many options that are not
5443 mentioned at all in the default configuration.
5447 .section "Main configuration settings" "SECTdefconfmain"
5448 The main (global) configuration option settings must always come first in the
5449 file. The first thing you'll see in the file, after some initial comments, is
5452 # primary_hostname =
5454 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5455 to know the official, fully qualified name of your host, and this is where you
5456 can specify it. However, in most cases you do not need to set this option. When
5457 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5459 The first three non-comment configuration lines are as follows:
5461 domainlist local_domains = @
5462 domainlist relay_to_domains =
5463 hostlist relay_from_hosts = 127.0.0.1
5465 These are not, in fact, option settings. They are definitions of two named
5466 domain lists and one named host list. Exim allows you to give names to lists of
5467 domains, hosts, and email addresses, in order to make it easier to manage the
5468 configuration file (see section &<<SECTnamedlists>>&).
5470 The first line defines a domain list called &'local_domains'&; this is used
5471 later in the configuration to identify domains that are to be delivered
5474 .cindex "@ in a domain list"
5475 There is just one item in this list, the string &"@"&. This is a special form
5476 of entry which means &"the name of the local host"&. Thus, if the local host is
5477 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5478 be delivered locally. Because the local host's name is referenced indirectly,
5479 the same configuration file can be used on different hosts.
5481 The second line defines a domain list called &'relay_to_domains'&, but the
5482 list itself is empty. Later in the configuration we will come to the part that
5483 controls mail relaying through the local host; it allows relaying to any
5484 domains in this list. By default, therefore, no relaying on the basis of a mail
5485 domain is permitted.
5487 The third line defines a host list called &'relay_from_hosts'&. This list is
5488 used later in the configuration to permit relaying from any host or IP address
5489 that matches the list. The default contains just the IP address of the IPv4
5490 loopback interface, which means that processes on the local host are able to
5491 submit mail for relaying by sending it over TCP/IP to that interface. No other
5492 hosts are permitted to submit messages for relaying.
5494 Just to be sure there's no misunderstanding: at this point in the configuration
5495 we aren't actually setting up any controls. We are just defining some domains
5496 and hosts that will be used in the controls that are specified later.
5498 The next two configuration lines are genuine option settings:
5500 acl_smtp_rcpt = acl_check_rcpt
5501 acl_smtp_data = acl_check_data
5503 These options specify &'Access Control Lists'& (ACLs) that are to be used
5504 during an incoming SMTP session for every recipient of a message (every RCPT
5505 command), and after the contents of the message have been received,
5506 respectively. The names of the lists are &'acl_check_rcpt'& and
5507 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5508 section of the configuration. The RCPT ACL controls which recipients are
5509 accepted for an incoming message &-- if a configuration does not provide an ACL
5510 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5511 contents of a message to be checked.
5513 Two commented-out option settings are next:
5515 # av_scanner = clamd:/tmp/clamd
5516 # spamd_address = 127.0.0.1 783
5518 These are example settings that can be used when Exim is compiled with the
5519 content-scanning extension. The first specifies the interface to the virus
5520 scanner, and the second specifies the interface to SpamAssassin. Further
5521 details are given in chapter &<<CHAPexiscan>>&.
5523 Three more commented-out option settings follow:
5525 # tls_advertise_hosts = *
5526 # tls_certificate = /etc/ssl/exim.crt
5527 # tls_privatekey = /etc/ssl/exim.pem
5529 These are example settings that can be used when Exim is compiled with
5530 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5531 first one specifies the list of clients that are allowed to use TLS when
5532 connecting to this server; in this case the wildcard means all clients. The
5533 other options specify where Exim should find its TLS certificate and private
5534 key, which together prove the server's identity to any clients that connect.
5535 More details are given in chapter &<<CHAPTLS>>&.
5537 Another two commented-out option settings follow:
5539 # daemon_smtp_ports = 25 : 465 : 587
5540 # tls_on_connect_ports = 465
5542 .cindex "port" "465 and 587"
5543 .cindex "port" "for message submission"
5544 .cindex "message" "submission, ports for"
5545 .cindex "ssmtp protocol"
5546 .cindex "smtps protocol"
5547 .cindex "SMTP" "ssmtp protocol"
5548 .cindex "SMTP" "smtps protocol"
5549 These options provide better support for roaming users who wish to use this
5550 server for message submission. They are not much use unless you have turned on
5551 TLS (as described in the previous paragraph) and authentication (about which
5552 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5553 on end-user networks, so RFC 4409 specifies that message submission should use
5554 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5555 configured to use port 587 correctly, so these settings also enable the
5556 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5557 &<<SECTsupobssmt>>&).
5559 Two more commented-out options settings follow:
5562 # qualify_recipient =
5564 The first of these specifies a domain that Exim uses when it constructs a
5565 complete email address from a local login name. This is often needed when Exim
5566 receives a message from a local process. If you do not set &%qualify_domain%&,
5567 the value of &%primary_hostname%& is used. If you set both of these options,
5568 you can have different qualification domains for sender and recipient
5569 addresses. If you set only the first one, its value is used in both cases.
5571 .cindex "domain literal" "recognizing format"
5572 The following line must be uncommented if you want Exim to recognize
5573 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5574 (an IP address within square brackets) instead of a named domain.
5576 # allow_domain_literals
5578 The RFCs still require this form, but many people think that in the modern
5579 Internet it makes little sense to permit mail to be sent to specific hosts by
5580 quoting their IP addresses. This ancient format has been used by people who
5581 try to abuse hosts by using them for unwanted relaying. However, some
5582 people believe there are circumstances (for example, messages addressed to
5583 &'postmaster'&) where domain literals are still useful.
5585 The next configuration line is a kind of trigger guard:
5589 It specifies that no delivery must ever be run as the root user. The normal
5590 convention is to set up &'root'& as an alias for the system administrator. This
5591 setting is a guard against slips in the configuration.
5592 The list of users specified by &%never_users%& is not, however, the complete
5593 list; the build-time configuration in &_Local/Makefile_& has an option called
5594 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5595 contents of &%never_users%& are added to this list. By default
5596 FIXED_NEVER_USERS also specifies root.
5598 When a remote host connects to Exim in order to send mail, the only information
5599 Exim has about the host's identity is its IP address. The next configuration
5604 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5605 in order to get a host name. This improves the quality of the logging
5606 information, but if you feel it is too expensive, you can remove it entirely,
5607 or restrict the lookup to hosts on &"nearby"& networks.
5608 Note that it is not always possible to find a host name from an IP address,
5609 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5612 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5613 1413 (hence their names):
5616 rfc1413_query_timeout = 0s
5618 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5619 Few hosts offer RFC1413 service these days; calls have to be
5620 terminated by a timeout and this needlessly delays the startup
5621 of an incoming SMTP connection.
5622 If you have hosts for which you trust RFC1413 and need this
5623 information, you can change this.
5625 This line enables an efficiency SMTP option. It is negotiated by clients
5626 and not expected to cause problems but can be disabled if needed.
5631 When Exim receives messages over SMTP connections, it expects all addresses to
5632 be fully qualified with a domain, as required by the SMTP definition. However,
5633 if you are running a server to which simple clients submit messages, you may
5634 find that they send unqualified addresses. The two commented-out options:
5636 # sender_unqualified_hosts =
5637 # recipient_unqualified_hosts =
5639 show how you can specify hosts that are permitted to send unqualified sender
5640 and recipient addresses, respectively.
5642 The &%log_selector%& option is used to increase the detail of logging
5645 log_selector = +smtp_protocol_error +smtp_syntax_error \
5646 +tls_certificate_verified
5649 The &%percent_hack_domains%& option is also commented out:
5651 # percent_hack_domains =
5653 It provides a list of domains for which the &"percent hack"& is to operate.
5654 This is an almost obsolete form of explicit email routing. If you do not know
5655 anything about it, you can safely ignore this topic.
5657 The next two settings in the main part of the default configuration are
5658 concerned with messages that have been &"frozen"& on Exim's queue. When a
5659 message is frozen, Exim no longer continues to try to deliver it. Freezing
5660 occurs when a bounce message encounters a permanent failure because the sender
5661 address of the original message that caused the bounce is invalid, so the
5662 bounce cannot be delivered. This is probably the most common case, but there
5663 are also other conditions that cause freezing, and frozen messages are not
5664 always bounce messages.
5666 ignore_bounce_errors_after = 2d
5667 timeout_frozen_after = 7d
5669 The first of these options specifies that failing bounce messages are to be
5670 discarded after 2 days on the queue. The second specifies that any frozen
5671 message (whether a bounce message or not) is to be timed out (and discarded)
5672 after a week. In this configuration, the first setting ensures that no failing
5673 bounce message ever lasts a week.
5675 Exim queues it's messages in a spool directory. If you expect to have
5676 large queues, you may consider using this option. It splits the spool
5677 directory into subdirectories to avoid file system degradation from
5678 many files in a single directory, resulting in better performance.
5679 Manual manipulation of queued messages becomes more complex (though fortunately
5682 # split_spool_directory = true
5685 In an ideal world everybody follows the standards. For non-ASCII
5686 messages RFC 2047 is a standard, allowing a maximum line length of 76
5687 characters. Exim adheres that standard and won't process messages which
5688 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5689 In particular, the Exim maintainers have had multiple reports of
5690 problems from Russian administrators of issues until they disable this
5691 check, because of some popular, yet buggy, mail composition software.
5693 # check_rfc2047_length = false
5696 If you need to be strictly RFC compliant you may wish to disable the
5697 8BITMIME advertisement. Use this, if you exchange mails with systems
5698 that are not 8-bit clean.
5700 # accept_8bitmime = false
5703 Libraries you use may depend on specific environment settings. This
5704 imposes a security risk (e.g. PATH). There are two lists:
5705 &%keep_environment%& for the variables to import as they are, and
5706 &%add_environment%& for variables we want to set to a fixed value.
5707 Note that TZ is handled separately, by the $%timezone%$ runtime
5708 option and by the TIMEZONE_DEFAULT buildtime option.
5710 # keep_environment = ^LDAP
5711 # add_environment = PATH=/usr/bin::/bin
5715 .section "ACL configuration" "SECID54"
5716 .cindex "default" "ACLs"
5717 .cindex "&ACL;" "default configuration"
5718 In the default configuration, the ACL section follows the main configuration.
5719 It starts with the line
5723 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5724 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5725 and &%acl_smtp_data%& above.
5727 .cindex "RCPT" "ACL for"
5728 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5729 RCPT command specifies one of the message's recipients. The ACL statements
5730 are considered in order, until the recipient address is either accepted or
5731 rejected. The RCPT command is then accepted or rejected, according to the
5732 result of the ACL processing.
5736 This line, consisting of a name terminated by a colon, marks the start of the
5741 This ACL statement accepts the recipient if the sending host matches the list.
5742 But what does that strange list mean? It doesn't actually contain any host
5743 names or IP addresses. The presence of the colon puts an empty item in the
5744 list; Exim matches this only if the incoming message did not come from a remote
5745 host, because in that case, the remote hostname is empty. The colon is
5746 important. Without it, the list itself is empty, and can never match anything.
5748 What this statement is doing is to accept unconditionally all recipients in
5749 messages that are submitted by SMTP from local processes using the standard
5750 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5753 deny message = Restricted characters in address
5754 domains = +local_domains
5755 local_parts = ^[.] : ^.*[@%!/|]
5757 deny message = Restricted characters in address
5758 domains = !+local_domains
5759 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5761 These statements are concerned with local parts that contain any of the
5762 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5763 Although these characters are entirely legal in local parts (in the case of
5764 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5765 in Internet mail addresses.
5767 The first three have in the past been associated with explicitly routed
5768 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5769 option). Addresses containing these characters are regularly tried by spammers
5770 in an attempt to bypass relaying restrictions, and also by open relay testing
5771 programs. Unless you really need them it is safest to reject these characters
5772 at this early stage. This configuration is heavy-handed in rejecting these
5773 characters for all messages it accepts from remote hosts. This is a deliberate
5774 policy of being as safe as possible.
5776 The first rule above is stricter, and is applied to messages that are addressed
5777 to one of the local domains handled by this host. This is implemented by the
5778 first condition, which restricts it to domains that are listed in the
5779 &'local_domains'& domain list. The &"+"& character is used to indicate a
5780 reference to a named list. In this configuration, there is just one domain in
5781 &'local_domains'&, but in general there may be many.
5783 The second condition on the first statement uses two regular expressions to
5784 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5785 or &"|"&. If you have local accounts that include these characters, you will
5786 have to modify this rule.
5788 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5789 allows them because they have been encountered in practice. (Consider the
5790 common convention of local parts constructed as
5791 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5792 the author of Exim, who has no second initial.) However, a local part starting
5793 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5794 file name (for example, for a mailing list). This is also true for local parts
5795 that contain slashes. A pipe symbol can also be troublesome if the local part
5796 is incorporated unthinkingly into a shell command line.
5798 The second rule above applies to all other domains, and is less strict. This
5799 allows your own users to send outgoing messages to sites that use slashes
5800 and vertical bars in their local parts. It blocks local parts that begin
5801 with a dot, slash, or vertical bar, but allows these characters within the
5802 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5803 and &"!"& is blocked, as before. The motivation here is to prevent your users
5804 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5806 accept local_parts = postmaster
5807 domains = +local_domains
5809 This statement, which has two conditions, accepts an incoming address if the
5810 local part is &'postmaster'& and the domain is one of those listed in the
5811 &'local_domains'& domain list. The &"+"& character is used to indicate a
5812 reference to a named list. In this configuration, there is just one domain in
5813 &'local_domains'&, but in general there may be many.
5815 The presence of this statement means that mail to postmaster is never blocked
5816 by any of the subsequent tests. This can be helpful while sorting out problems
5817 in cases where the subsequent tests are incorrectly denying access.
5819 require verify = sender
5821 This statement requires the sender address to be verified before any subsequent
5822 ACL statement can be used. If verification fails, the incoming recipient
5823 address is refused. Verification consists of trying to route the address, to
5824 see if a bounce message could be delivered to it. In the case of remote
5825 addresses, basic verification checks only the domain, but &'callouts'& can be
5826 used for more verification if required. Section &<<SECTaddressverification>>&
5827 discusses the details of address verification.
5829 accept hosts = +relay_from_hosts
5830 control = submission
5832 This statement accepts the address if the message is coming from one of the
5833 hosts that are defined as being allowed to relay through this host. Recipient
5834 verification is omitted here, because in many cases the clients are dumb MUAs
5835 that do not cope well with SMTP error responses. For the same reason, the
5836 second line specifies &"submission mode"& for messages that are accepted. This
5837 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5838 messages that are deficient in some way, for example, because they lack a
5839 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5840 probably add recipient verification here, and disable submission mode.
5842 accept authenticated = *
5843 control = submission
5845 This statement accepts the address if the client host has authenticated itself.
5846 Submission mode is again specified, on the grounds that such messages are most
5847 likely to come from MUAs. The default configuration does not define any
5848 authenticators, though it does include some nearly complete commented-out
5849 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5850 fact authenticate until you complete the authenticator definitions.
5852 require message = relay not permitted
5853 domains = +local_domains : +relay_to_domains
5855 This statement rejects the address if its domain is neither a local domain nor
5856 one of the domains for which this host is a relay.
5858 require verify = recipient
5860 This statement requires the recipient address to be verified; if verification
5861 fails, the address is rejected.
5863 # deny message = rejected because $sender_host_address \
5864 # is in a black list at $dnslist_domain\n\
5866 # dnslists = black.list.example
5868 # warn dnslists = black.list.example
5869 # add_header = X-Warning: $sender_host_address is in \
5870 # a black list at $dnslist_domain
5871 # log_message = found in $dnslist_domain
5873 These commented-out lines are examples of how you could configure Exim to check
5874 sending hosts against a DNS black list. The first statement rejects messages
5875 from blacklisted hosts, whereas the second just inserts a warning header
5878 # require verify = csa
5880 This commented-out line is an example of how you could turn on client SMTP
5881 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5886 The final statement in the first ACL unconditionally accepts any recipient
5887 address that has successfully passed all the previous tests.
5891 This line marks the start of the second ACL, and names it. Most of the contents
5892 of this ACL are commented out:
5895 # message = This message contains a virus \
5898 These lines are examples of how to arrange for messages to be scanned for
5899 viruses when Exim has been compiled with the content-scanning extension, and a
5900 suitable virus scanner is installed. If the message is found to contain a
5901 virus, it is rejected with the given custom error message.
5903 # warn spam = nobody
5904 # message = X-Spam_score: $spam_score\n\
5905 # X-Spam_score_int: $spam_score_int\n\
5906 # X-Spam_bar: $spam_bar\n\
5907 # X-Spam_report: $spam_report
5909 These lines are an example of how to arrange for messages to be scanned by
5910 SpamAssassin when Exim has been compiled with the content-scanning extension,
5911 and SpamAssassin has been installed. The SpamAssassin check is run with
5912 &`nobody`& as its user parameter, and the results are added to the message as a
5913 series of extra header line. In this case, the message is not rejected,
5914 whatever the spam score.
5918 This final line in the DATA ACL accepts the message unconditionally.
5921 .section "Router configuration" "SECID55"
5922 .cindex "default" "routers"
5923 .cindex "routers" "default"
5924 The router configuration comes next in the default configuration, introduced
5929 Routers are the modules in Exim that make decisions about where to send
5930 messages. An address is passed to each router in turn, until it is either
5931 accepted, or failed. This means that the order in which you define the routers
5932 matters. Each router is fully described in its own chapter later in this
5933 manual. Here we give only brief overviews.
5936 # driver = ipliteral
5937 # domains = !+local_domains
5938 # transport = remote_smtp
5940 .cindex "domain literal" "default router"
5941 This router is commented out because the majority of sites do not want to
5942 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5943 you uncomment this router, you also need to uncomment the setting of
5944 &%allow_domain_literals%& in the main part of the configuration.
5948 domains = ! +local_domains
5949 transport = remote_smtp
5950 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5953 The first uncommented router handles addresses that do not involve any local
5954 domains. This is specified by the line
5956 domains = ! +local_domains
5958 The &%domains%& option lists the domains to which this router applies, but the
5959 exclamation mark is a negation sign, so the router is used only for domains
5960 that are not in the domain list called &'local_domains'& (which was defined at
5961 the start of the configuration). The plus sign before &'local_domains'&
5962 indicates that it is referring to a named list. Addresses in other domains are
5963 passed on to the following routers.
5965 The name of the router driver is &(dnslookup)&,
5966 and is specified by the &%driver%& option. Do not be confused by the fact that
5967 the name of this router instance is the same as the name of the driver. The
5968 instance name is arbitrary, but the name set in the &%driver%& option must be
5969 one of the driver modules that is in the Exim binary.
5971 The &(dnslookup)& router routes addresses by looking up their domains in the
5972 DNS in order to obtain a list of hosts to which the address is routed. If the
5973 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5974 specified by the &%transport%& option. If the router does not find the domain
5975 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5976 the address fails and is bounced.
5978 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5979 be entirely ignored. This option is present because a number of cases have been
5980 encountered where MX records in the DNS point to host names
5981 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5982 Completely ignoring these IP addresses causes Exim to fail to route the
5983 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5984 continue to try to deliver the message periodically until the address timed
5991 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5993 file_transport = address_file
5994 pipe_transport = address_pipe
5996 Control reaches this and subsequent routers only for addresses in the local
5997 domains. This router checks to see whether the local part is defined as an
5998 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5999 data that it looks up from that file. If no data is found for the local part,
6000 the value of the &%data%& option is empty, causing the address to be passed to
6003 &_/etc/aliases_& is a conventional name for the system aliases file that is
6004 often used. That is why it is referenced by from the default configuration
6005 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6006 &_Local/Makefile_& before building Exim.
6011 # local_part_suffix = +* : -*
6012 # local_part_suffix_optional
6013 file = $home/.forward
6018 file_transport = address_file
6019 pipe_transport = address_pipe
6020 reply_transport = address_reply
6022 This is the most complicated router in the default configuration. It is another
6023 redirection router, but this time it is looking for forwarding data set up by
6024 individual users. The &%check_local_user%& setting specifies a check that the
6025 local part of the address is the login name of a local user. If it is not, the
6026 router is skipped. The two commented options that follow &%check_local_user%&,
6029 # local_part_suffix = +* : -*
6030 # local_part_suffix_optional
6032 .vindex "&$local_part_suffix$&"
6033 show how you can specify the recognition of local part suffixes. If the first
6034 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6035 by any sequence of characters, is removed from the local part and placed in the
6036 variable &$local_part_suffix$&. The second suffix option specifies that the
6037 presence of a suffix in the local part is optional. When a suffix is present,
6038 the check for a local login uses the local part with the suffix removed.
6040 When a local user account is found, the file called &_.forward_& in the user's
6041 home directory is consulted. If it does not exist, or is empty, the router
6042 declines. Otherwise, the contents of &_.forward_& are interpreted as
6043 redirection data (see chapter &<<CHAPredirect>>& for more details).
6045 .cindex "Sieve filter" "enabling in default router"
6046 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6047 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6048 is commented out by default), the contents of the file are interpreted as a set
6049 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6050 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6051 separate document entitled &'Exim's interfaces to mail filtering'&.
6053 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6054 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6055 There are two reasons for doing this:
6058 Whether or not a local user has a &_.forward_& file is not really relevant when
6059 checking an address for validity; it makes sense not to waste resources doing
6062 More importantly, when Exim is verifying addresses or handling an EXPN
6063 command during an SMTP session, it is running as the Exim user, not as root.
6064 The group is the Exim group, and no additional groups are set up.
6065 It may therefore not be possible for Exim to read users' &_.forward_& files at
6069 The setting of &%check_ancestor%& prevents the router from generating a new
6070 address that is the same as any previous address that was redirected. (This
6071 works round a problem concerning a bad interaction between aliasing and
6072 forwarding &-- see section &<<SECTredlocmai>>&).
6074 The final three option settings specify the transports that are to be used when
6075 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6076 auto-reply, respectively. For example, if a &_.forward_& file contains
6078 a.nother@elsewhere.example, /home/spqr/archive
6080 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6086 # local_part_suffix = +* : -*
6087 # local_part_suffix_optional
6088 transport = local_delivery
6090 The final router sets up delivery into local mailboxes, provided that the local
6091 part is the name of a local login, by accepting the address and assigning it to
6092 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6093 routers, so the address is bounced. The commented suffix settings fulfil the
6094 same purpose as they do for the &(userforward)& router.
6097 .section "Transport configuration" "SECID56"
6098 .cindex "default" "transports"
6099 .cindex "transports" "default"
6100 Transports define mechanisms for actually delivering messages. They operate
6101 only when referenced from routers, so the order in which they are defined does
6102 not matter. The transports section of the configuration starts with
6106 One remote transport and four local transports are defined.
6112 This transport is used for delivering messages over SMTP connections.
6113 The list of remote hosts comes from the router.
6114 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6115 It is negotiated between client and server
6116 and not expected to cause problems but can be disabled if needed.
6117 All other options are defaulted.
6121 file = /var/mail/$local_part
6128 This &(appendfile)& transport is used for local delivery to user mailboxes in
6129 traditional BSD mailbox format. By default it runs under the uid and gid of the
6130 local user, which requires the sticky bit to be set on the &_/var/mail_&
6131 directory. Some systems use the alternative approach of running mail deliveries
6132 under a particular group instead of using the sticky bit. The commented options
6133 show how this can be done.
6135 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6136 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6137 similarly-named options above.
6143 This transport is used for handling deliveries to pipes that are generated by
6144 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6145 option specifies that any output on stdout or stderr generated by the pipe is to
6146 be returned to the sender.
6154 This transport is used for handling deliveries to files that are generated by
6155 redirection. The name of the file is not specified in this instance of
6156 &(appendfile)&, because it comes from the &(redirect)& router.
6161 This transport is used for handling automatic replies generated by users'
6166 .section "Default retry rule" "SECID57"
6167 .cindex "retry" "default rule"
6168 .cindex "default" "retry rule"
6169 The retry section of the configuration file contains rules which affect the way
6170 Exim retries deliveries that cannot be completed at the first attempt. It is
6171 introduced by the line
6175 In the default configuration, there is just one rule, which applies to all
6178 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6180 This causes any temporarily failing address to be retried every 15 minutes for
6181 2 hours, then at intervals starting at one hour and increasing by a factor of
6182 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6183 is not delivered after 4 days of temporary failure, it is bounced. The time is
6184 measured from first failure, not from the time the message was received.
6186 If the retry section is removed from the configuration, or is empty (that is,
6187 if no retry rules are defined), Exim will not retry deliveries. This turns
6188 temporary errors into permanent errors.
6191 .section "Rewriting configuration" "SECID58"
6192 The rewriting section of the configuration, introduced by
6196 contains rules for rewriting addresses in messages as they arrive. There are no
6197 rewriting rules in the default configuration file.
6201 .section "Authenticators configuration" "SECTdefconfauth"
6202 .cindex "AUTH" "configuration"
6203 The authenticators section of the configuration, introduced by
6205 begin authenticators
6207 defines mechanisms for the use of the SMTP AUTH command. The default
6208 configuration file contains two commented-out example authenticators
6209 which support plaintext username/password authentication using the
6210 standard PLAIN mechanism and the traditional but non-standard LOGIN
6211 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6212 to support most MUA software.
6214 The example PLAIN authenticator looks like this:
6217 # driver = plaintext
6218 # server_set_id = $auth2
6219 # server_prompts = :
6220 # server_condition = Authentication is not yet configured
6221 # server_advertise_condition = ${if def:tls_in_cipher }
6223 And the example LOGIN authenticator looks like this:
6226 # driver = plaintext
6227 # server_set_id = $auth1
6228 # server_prompts = <| Username: | Password:
6229 # server_condition = Authentication is not yet configured
6230 # server_advertise_condition = ${if def:tls_in_cipher }
6233 The &%server_set_id%& option makes Exim remember the authenticated username
6234 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6235 &%server_prompts%& option configures the &(plaintext)& authenticator so
6236 that it implements the details of the specific authentication mechanism,
6237 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6238 when Exim offers authentication to clients; in the examples, this is only
6239 when TLS or SSL has been started, so to enable the authenticators you also
6240 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6242 The &%server_condition%& setting defines how to verify that the username and
6243 password are correct. In the examples it just produces an error message.
6244 To make the authenticators work, you can use a string expansion
6245 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6247 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6248 usercode and password are in different positions.
6249 Chapter &<<CHAPplaintext>>& covers both.
6251 .ecindex IIDconfiwal
6255 . ////////////////////////////////////////////////////////////////////////////
6256 . ////////////////////////////////////////////////////////////////////////////
6258 .chapter "Regular expressions" "CHAPregexp"
6260 .cindex "regular expressions" "library"
6262 Exim supports the use of regular expressions in many of its options. It
6263 uses the PCRE regular expression library; this provides regular expression
6264 matching that is compatible with Perl 5. The syntax and semantics of
6265 regular expressions is discussed in many Perl reference books, and also in
6266 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6267 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6269 The documentation for the syntax and semantics of the regular expressions that
6270 are supported by PCRE is included in the PCRE distribution, and no further
6271 description is included here. The PCRE functions are called from Exim using
6272 the default option settings (that is, with no PCRE options set), except that
6273 the PCRE_CASELESS option is set when the matching is required to be
6276 In most cases, when a regular expression is required in an Exim configuration,
6277 it has to start with a circumflex, in order to distinguish it from plain text
6278 or an &"ends with"& wildcard. In this example of a configuration setting, the
6279 second item in the colon-separated list is a regular expression.
6281 domains = a.b.c : ^\\d{3} : *.y.z : ...
6283 The doubling of the backslash is required because of string expansion that
6284 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6285 of this issue, and a way of avoiding the need for doubling backslashes. The
6286 regular expression that is eventually used in this example contains just one
6287 backslash. The circumflex is included in the regular expression, and has the
6288 normal effect of &"anchoring"& it to the start of the string that is being
6291 There are, however, two cases where a circumflex is not required for the
6292 recognition of a regular expression: these are the &%match%& condition in a
6293 string expansion, and the &%matches%& condition in an Exim filter file. In
6294 these cases, the relevant string is always treated as a regular expression; if
6295 it does not start with a circumflex, the expression is not anchored, and can
6296 match anywhere in the subject string.
6298 In all cases, if you want a regular expression to match at the end of a string,
6299 you must code the $ metacharacter to indicate this. For example:
6301 domains = ^\\d{3}\\.example
6303 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6306 domains = ^\\d{3}\\.example\$
6308 if you want &'example'& to be the top-level domain. The backslash before the
6309 $ is needed because string expansion also interprets dollar characters.
6313 . ////////////////////////////////////////////////////////////////////////////
6314 . ////////////////////////////////////////////////////////////////////////////
6316 .chapter "File and database lookups" "CHAPfdlookup"
6317 .scindex IIDfidalo1 "file" "lookups"
6318 .scindex IIDfidalo2 "database" "lookups"
6319 .cindex "lookup" "description of"
6320 Exim can be configured to look up data in files or databases as it processes
6321 messages. Two different kinds of syntax are used:
6324 A string that is to be expanded may contain explicit lookup requests. These
6325 cause parts of the string to be replaced by data that is obtained from the
6326 lookup. Lookups of this type are conditional expansion items. Different results
6327 can be defined for the cases of lookup success and failure. See chapter
6328 &<<CHAPexpand>>&, where string expansions are described in detail.
6329 The key for the lookup is specified as part of the string expansion.
6331 Lists of domains, hosts, and email addresses can contain lookup requests as a
6332 way of avoiding excessively long linear lists. In this case, the data that is
6333 returned by the lookup is often (but not always) discarded; whether the lookup
6334 succeeds or fails is what really counts. These kinds of list are described in
6335 chapter &<<CHAPdomhosaddlists>>&.
6336 The key for the lookup is given by the context in which the list is expanded.
6339 String expansions, lists, and lookups interact with each other in such a way
6340 that there is no order in which to describe any one of them that does not
6341 involve references to the others. Each of these three chapters makes more sense
6342 if you have read the other two first. If you are reading this for the first
6343 time, be aware that some of it will make a lot more sense after you have read
6344 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6346 .section "Examples of different lookup syntax" "SECID60"
6347 It is easy to confuse the two different kinds of lookup, especially as the
6348 lists that may contain the second kind are always expanded before being
6349 processed as lists. Therefore, they may also contain lookups of the first kind.
6350 Be careful to distinguish between the following two examples:
6352 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6353 domains = lsearch;/some/file
6355 The first uses a string expansion, the result of which must be a domain list.
6356 No strings have been specified for a successful or a failing lookup; the
6357 defaults in this case are the looked-up data and an empty string, respectively.
6358 The expansion takes place before the string is processed as a list, and the
6359 file that is searched could contain lines like this:
6361 192.168.3.4: domain1:domain2:...
6362 192.168.1.9: domain3:domain4:...
6364 When the lookup succeeds, the result of the expansion is a list of domains (and
6365 possibly other types of item that are allowed in domain lists).
6367 In the second example, the lookup is a single item in a domain list. It causes
6368 Exim to use a lookup to see if the domain that is being processed can be found
6369 in the file. The file could contains lines like this:
6374 Any data that follows the keys is not relevant when checking that the domain
6375 matches the list item.
6377 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6378 Consider a file containing lines like this:
6380 192.168.5.6: lsearch;/another/file
6382 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6383 first &%domains%& setting above generates the second setting, which therefore
6384 causes a second lookup to occur.
6386 The rest of this chapter describes the different lookup types that are
6387 available. Any of them can be used in any part of the configuration where a
6388 lookup is permitted.
6391 .section "Lookup types" "SECID61"
6392 .cindex "lookup" "types of"
6393 .cindex "single-key lookup" "definition of"
6394 Two different types of data lookup are implemented:
6397 The &'single-key'& type requires the specification of a file in which to look,
6398 and a single key to search for. The key must be a non-empty string for the
6399 lookup to succeed. The lookup type determines how the file is searched.
6401 .cindex "query-style lookup" "definition of"
6402 The &'query-style'& type accepts a generalized database query. No particular
6403 key value is assumed by Exim for query-style lookups. You can use whichever
6404 Exim variables you need to construct the database query.
6407 The code for each lookup type is in a separate source file that is included in
6408 the binary of Exim only if the corresponding compile-time option is set. The
6409 default settings in &_src/EDITME_& are:
6414 which means that only linear searching and DBM lookups are included by default.
6415 For some types of lookup (e.g. SQL databases), you need to install appropriate
6416 libraries and header files before building Exim.
6421 .section "Single-key lookup types" "SECTsinglekeylookups"
6422 .cindex "lookup" "single-key types"
6423 .cindex "single-key lookup" "list of types"
6424 The following single-key lookup types are implemented:
6427 .cindex "cdb" "description of"
6428 .cindex "lookup" "cdb"
6429 .cindex "binary zero" "in lookup key"
6430 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6431 string without a terminating binary zero. The cdb format is designed for
6432 indexed files that are read frequently and never updated, except by total
6433 re-creation. As such, it is particularly suitable for large files containing
6434 aliases or other indexed data referenced by an MTA. Information about cdb can
6435 be found in several places:
6437 &url(http://www.pobox.com/~djb/cdb.html)
6438 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6439 &url(http://packages.debian.org/stable/utils/freecdb.html)
6441 A cdb distribution is not needed in order to build Exim with cdb support,
6442 because the code for reading cdb files is included directly in Exim itself.
6443 However, no means of building or testing cdb files is provided with Exim, so
6444 you need to obtain a cdb distribution in order to do this.
6446 .cindex "DBM" "lookup type"
6447 .cindex "lookup" "dbm"
6448 .cindex "binary zero" "in lookup key"
6449 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6450 DBM file by looking up the record with the given key. A terminating binary
6451 zero is included in the key that is passed to the DBM library. See section
6452 &<<SECTdb>>& for a discussion of DBM libraries.
6454 .cindex "Berkeley DB library" "file format"
6455 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6456 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6457 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6458 the DB_UNKNOWN option. This enables it to handle any of the types of database
6459 that the library supports, and can be useful for accessing DBM files created by
6460 other applications. (For earlier DB versions, DB_HASH is always used.)
6462 .cindex "lookup" "dbmjz"
6463 .cindex "lookup" "dbm &-- embedded NULs"
6465 .cindex "dbmjz lookup type"
6466 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6467 interpreted as an Exim list; the elements of the list are joined together with
6468 ASCII NUL characters to form the lookup key. An example usage would be to
6469 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6470 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6471 &(cram_md5)& authenticator.
6473 .cindex "lookup" "dbmnz"
6474 .cindex "lookup" "dbm &-- terminating zero"
6475 .cindex "binary zero" "in lookup key"
6477 .cindex "&_/etc/userdbshadow.dat_&"
6478 .cindex "dbmnz lookup type"
6479 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6480 is not included in the key that is passed to the DBM library. You may need this
6481 if you want to look up data in files that are created by or shared with some
6482 other application that does not use terminating zeros. For example, you need to
6483 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6484 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6485 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6486 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6488 .cindex "lookup" "dsearch"
6489 .cindex "dsearch lookup type"
6490 &(dsearch)&: The given file must be a directory; this is searched for an entry
6491 whose name is the key by calling the &[lstat()]& function. The key may not
6492 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6493 the lookup is the name of the entry, which may be a file, directory,
6494 symbolic link, or any other kind of directory entry. An example of how this
6495 lookup can be used to support virtual domains is given in section
6496 &<<SECTvirtualdomains>>&.
6498 .cindex "lookup" "iplsearch"
6499 .cindex "iplsearch lookup type"
6500 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6501 terminated by a colon or white space or the end of the line. The keys in the
6502 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6503 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6504 being interpreted as a key terminator. For example:
6506 1.2.3.4: data for 1.2.3.4
6507 192.168.0.0/16: data for 192.168.0.0/16
6508 "abcd::cdab": data for abcd::cdab
6509 "abcd:abcd::/32" data for abcd:abcd::/32
6511 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6512 file is searched linearly, using the CIDR masks where present, until a matching
6513 key is found. The first key that matches is used; there is no attempt to find a
6514 &"best"& match. Apart from the way the keys are matched, the processing for
6515 &(iplsearch)& is the same as for &(lsearch)&.
6517 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6518 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6519 lookup types support only literal keys.
6521 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6522 the implicit key is the host's IP address rather than its name (see section
6523 &<<SECThoslispatsikey>>&).
6525 .cindex "linear search"
6526 .cindex "lookup" "lsearch"
6527 .cindex "lsearch lookup type"
6528 .cindex "case sensitivity" "in lsearch lookup"
6529 &(lsearch)&: The given file is a text file that is searched linearly for a
6530 line beginning with the search key, terminated by a colon or white space or the
6531 end of the line. The search is case-insensitive; that is, upper and lower case
6532 letters are treated as the same. The first occurrence of the key that is found
6533 in the file is used.
6535 White space between the key and the colon is permitted. The remainder of the
6536 line, with leading and trailing white space removed, is the data. This can be
6537 continued onto subsequent lines by starting them with any amount of white
6538 space, but only a single space character is included in the data at such a
6539 junction. If the data begins with a colon, the key must be terminated by a
6544 Empty lines and lines beginning with # are ignored, even if they occur in the
6545 middle of an item. This is the traditional textual format of alias files. Note
6546 that the keys in an &(lsearch)& file are literal strings. There is no
6547 wildcarding of any kind.
6549 .cindex "lookup" "lsearch &-- colons in keys"
6550 .cindex "white space" "in lsearch key"
6551 In most &(lsearch)& files, keys are not required to contain colons or #
6552 characters, or white space. However, if you need this feature, it is available.
6553 If a key begins with a doublequote character, it is terminated only by a
6554 matching quote (or end of line), and the normal escaping rules apply to its
6555 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6556 quoted keys (exactly as for unquoted keys). There is no special handling of
6557 quotes for the data part of an &(lsearch)& line.
6560 .cindex "NIS lookup type"
6561 .cindex "lookup" "NIS"
6562 .cindex "binary zero" "in lookup key"
6563 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6564 the given key, without a terminating binary zero. There is a variant called
6565 &(nis0)& which does include the terminating binary zero in the key. This is
6566 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6567 aliases; the full map names must be used.
6570 .cindex "wildlsearch lookup type"
6571 .cindex "lookup" "wildlsearch"
6572 .cindex "nwildlsearch lookup type"
6573 .cindex "lookup" "nwildlsearch"
6574 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6575 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6576 the file may be wildcarded. The difference between these two lookup types is
6577 that for &(wildlsearch)&, each key in the file is string-expanded before being
6578 used, whereas for &(nwildlsearch)&, no expansion takes place.
6580 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6581 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6582 file that are regular expressions can be made case-sensitive by the use of
6583 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6585 . ==== As this is a nested list, any displays it contains must be indented
6586 . ==== as otherwise they are too far to the left.
6589 The string may begin with an asterisk to mean &"ends with"&. For example:
6591 *.a.b.c data for anything.a.b.c
6592 *fish data for anythingfish
6595 The string may begin with a circumflex to indicate a regular expression. For
6596 example, for &(wildlsearch)&:
6598 ^\N\d+\.a\.b\N data for <digits>.a.b
6600 Note the use of &`\N`& to disable expansion of the contents of the regular
6601 expression. If you are using &(nwildlsearch)&, where the keys are not
6602 string-expanded, the equivalent entry is:
6604 ^\d+\.a\.b data for <digits>.a.b
6606 The case-insensitive flag is set at the start of compiling the regular
6607 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6608 For example, to make the entire pattern case-sensitive:
6610 ^(?-i)\d+\.a\.b data for <digits>.a.b
6613 If the regular expression contains white space or colon characters, you must
6614 either quote it (see &(lsearch)& above), or represent these characters in other
6615 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6616 colon. This may be easier than quoting, because if you quote, you have to
6617 escape all the backslashes inside the quotes.
6619 &*Note*&: It is not possible to capture substrings in a regular expression
6620 match for later use, because the results of all lookups are cached. If a lookup
6621 is repeated, the result is taken from the cache, and no actual pattern matching
6622 takes place. The values of all the numeric variables are unset after a
6623 &((n)wildlsearch)& match.
6626 Although I cannot see it being of much use, the general matching function that
6627 is used to implement &((n)wildlsearch)& means that the string may begin with a
6628 lookup name terminated by a semicolon, and followed by lookup data. For
6631 cdb;/some/file data for keys that match the file
6633 The data that is obtained from the nested lookup is discarded.
6636 Keys that do not match any of these patterns are interpreted literally. The
6637 continuation rules for the data are the same as for &(lsearch)&, and keys may
6638 be followed by optional colons.
6640 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6641 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6642 lookup types support only literal keys.
6646 .section "Query-style lookup types" "SECTquerystylelookups"
6647 .cindex "lookup" "query-style types"
6648 .cindex "query-style lookup" "list of types"
6649 The supported query-style lookup types are listed below. Further details about
6650 many of them are given in later sections.
6653 .cindex "DNS" "as a lookup type"
6654 .cindex "lookup" "DNS"
6655 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6656 are given in the supplied query. The resulting data is the contents of the
6657 records. See section &<<SECTdnsdb>>&.
6659 .cindex "InterBase lookup type"
6660 .cindex "lookup" "InterBase"
6661 &(ibase)&: This does a lookup in an InterBase database.
6663 .cindex "LDAP" "lookup type"
6664 .cindex "lookup" "LDAP"
6665 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6666 returns attributes from a single entry. There is a variant called &(ldapm)&
6667 that permits values from multiple entries to be returned. A third variant
6668 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6669 any attribute values. See section &<<SECTldap>>&.
6671 .cindex "MySQL" "lookup type"
6672 .cindex "lookup" "MySQL"
6673 &(mysql)&: The format of the query is an SQL statement that is passed to a
6674 MySQL database. See section &<<SECTsql>>&.
6676 .cindex "NIS+ lookup type"
6677 .cindex "lookup" "NIS+"
6678 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6679 the field to be returned. See section &<<SECTnisplus>>&.
6681 .cindex "Oracle" "lookup type"
6682 .cindex "lookup" "Oracle"
6683 &(oracle)&: The format of the query is an SQL statement that is passed to an
6684 Oracle database. See section &<<SECTsql>>&.
6686 .cindex "lookup" "passwd"
6687 .cindex "passwd lookup type"
6688 .cindex "&_/etc/passwd_&"
6689 &(passwd)& is a query-style lookup with queries that are just user names. The
6690 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6691 success, the result string is the same as you would get from an &(lsearch)&
6692 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6693 password value. For example:
6695 *:42:42:King Rat:/home/kr:/bin/bash
6698 .cindex "PostgreSQL lookup type"
6699 .cindex "lookup" "PostgreSQL"
6700 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6701 PostgreSQL database. See section &<<SECTsql>>&.
6704 .cindex "Redis lookup type"
6705 .cindex lookup Redis
6706 &(redis)&: The format of the query is an SQL statement that is passed to a
6707 Redis database. See section &<<SECTsql>>&.
6710 .cindex "sqlite lookup type"
6711 .cindex "lookup" "sqlite"
6712 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6713 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6716 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6717 not likely to be useful in normal operation.
6719 .cindex "whoson lookup type"
6720 .cindex "lookup" "whoson"
6721 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6722 allows a server to check whether a particular (dynamically allocated) IP
6723 address is currently allocated to a known (trusted) user and, optionally, to
6724 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6725 at one time for &"POP before SMTP"& authentication, but that approach has been
6726 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6727 &"POP before SMTP"& checking using ACL statements such as
6729 require condition = \
6730 ${lookup whoson {$sender_host_address}{yes}{no}}
6732 The query consists of a single IP address. The value returned is the name of
6733 the authenticated user, which is stored in the variable &$value$&. However, in
6734 this example, the data in &$value$& is not used; the result of the lookup is
6735 one of the fixed strings &"yes"& or &"no"&.
6740 .section "Temporary errors in lookups" "SECID63"
6741 .cindex "lookup" "temporary error in"
6742 Lookup functions can return temporary error codes if the lookup cannot be
6743 completed. For example, an SQL or LDAP database might be unavailable. For this
6744 reason, it is not advisable to use a lookup that might do this for critical
6745 options such as a list of local domains.
6747 When a lookup cannot be completed in a router or transport, delivery
6748 of the message (to the relevant address) is deferred, as for any other
6749 temporary error. In other circumstances Exim may assume the lookup has failed,
6750 or may give up altogether.
6754 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6755 .cindex "wildcard lookups"
6756 .cindex "lookup" "default values"
6757 .cindex "lookup" "wildcard"
6758 .cindex "lookup" "* added to type"
6759 .cindex "default" "in single-key lookups"
6760 In this context, a &"default value"& is a value specified by the administrator
6761 that is to be used if a lookup fails.
6763 &*Note:*& This section applies only to single-key lookups. For query-style
6764 lookups, the facilities of the query language must be used. An attempt to
6765 specify a default for a query-style lookup provokes an error.
6767 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6768 and the initial lookup fails, the key &"*"& is looked up in the file to
6769 provide a default value. See also the section on partial matching below.
6771 .cindex "*@ with single-key lookup"
6772 .cindex "lookup" "*@ added to type"
6773 .cindex "alias file" "per-domain default"
6774 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6775 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6776 character, a second lookup is done with everything before the last @ replaced
6777 by *. This makes it possible to provide per-domain defaults in alias files
6778 that include the domains in the keys. If the second lookup fails (or doesn't
6779 take place because there is no @ in the key), &"*"& is looked up.
6780 For example, a &(redirect)& router might contain:
6782 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6784 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6785 looks up these keys, in this order:
6791 The data is taken from whichever key it finds first. &*Note*&: In an
6792 &(lsearch)& file, this does not mean the first of these keys in the file. A
6793 complete scan is done for each key, and only if it is not found at all does
6794 Exim move on to try the next key.
6798 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6799 .cindex "partial matching"
6800 .cindex "wildcard lookups"
6801 .cindex "lookup" "partial matching"
6802 .cindex "lookup" "wildcard"
6803 .cindex "asterisk" "in search type"
6804 The normal operation of a single-key lookup is to search the file for an exact
6805 match with the given key. However, in a number of situations where domains are
6806 being looked up, it is useful to be able to do partial matching. In this case,
6807 information in the file that has a key starting with &"*."& is matched by any
6808 domain that ends with the components that follow the full stop. For example, if
6809 a key in a DBM file is
6811 *.dates.fict.example
6813 then when partial matching is enabled this is matched by (amongst others)
6814 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6815 by &'dates.fict.example'&, if that does not appear as a separate key in the
6818 &*Note*&: Partial matching is not available for query-style lookups. It is
6819 also not available for any lookup items in address lists (see section
6820 &<<SECTaddresslist>>&).
6822 Partial matching is implemented by doing a series of separate lookups using
6823 keys constructed by modifying the original subject key. This means that it can
6824 be used with any of the single-key lookup types, provided that
6825 partial matching keys
6826 beginning with a special prefix (default &"*."&) are included in the data file.
6827 Keys in the file that do not begin with the prefix are matched only by
6828 unmodified subject keys when partial matching is in use.
6830 Partial matching is requested by adding the string &"partial-"& to the front of
6831 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6832 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6833 is added at the start of the subject key, and it is looked up again. If that
6834 fails, further lookups are tried with dot-separated components removed from the
6835 start of the subject key, one-by-one, and &"*."& added on the front of what
6838 A minimum number of two non-* components are required. This can be adjusted
6839 by including a number before the hyphen in the search type. For example,
6840 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6841 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6842 subject key is &'2250.dates.fict.example'& then the following keys are looked
6843 up when the minimum number of non-* components is two:
6845 2250.dates.fict.example
6846 *.2250.dates.fict.example
6847 *.dates.fict.example
6850 As soon as one key in the sequence is successfully looked up, the lookup
6853 .cindex "lookup" "partial matching &-- changing prefix"
6854 .cindex "prefix" "for partial matching"
6855 The use of &"*."& as the partial matching prefix is a default that can be
6856 changed. The motivation for this feature is to allow Exim to operate with file
6857 formats that are used by other MTAs. A different prefix can be supplied in
6858 parentheses instead of the hyphen after &"partial"&. For example:
6860 domains = partial(.)lsearch;/some/file
6862 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6863 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6864 components is unchanged). The prefix may consist of any punctuation characters
6865 other than a closing parenthesis. It may be empty, for example:
6867 domains = partial1()cdb;/some/file
6869 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6870 &`a.b.c`&, &`b.c`&, and &`c`&.
6872 If &"partial0"& is specified, what happens at the end (when the lookup with
6873 just one non-wild component has failed, and the original key is shortened right
6874 down to the null string) depends on the prefix:
6877 If the prefix has zero length, the whole lookup fails.
6879 If the prefix has length 1, a lookup for just the prefix is done. For
6880 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6882 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6883 remainder is looked up. With the default prefix, therefore, the final lookup is
6884 for &"*"& on its own.
6886 Otherwise, the whole prefix is looked up.
6890 If the search type ends in &"*"& or &"*@"& (see section
6891 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6892 this implies happens after all partial lookups have failed. If &"partial0"& is
6893 specified, adding &"*"& to the search type has no effect with the default
6894 prefix, because the &"*"& key is already included in the sequence of partial
6895 lookups. However, there might be a use for lookup types such as
6896 &"partial0(.)lsearch*"&.
6898 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6899 in domain lists and the like. Partial matching works only in terms of
6900 dot-separated components; a key such as &`*fict.example`&
6901 in a database file is useless, because the asterisk in a partial matching
6902 subject key is always followed by a dot.
6907 .section "Lookup caching" "SECID64"
6908 .cindex "lookup" "caching"
6909 .cindex "caching" "lookup data"
6910 Exim caches all lookup results in order to avoid needless repetition of
6911 lookups. However, because (apart from the daemon) Exim operates as a collection
6912 of independent, short-lived processes, this caching applies only within a
6913 single Exim process. There is no inter-process lookup caching facility.
6915 For single-key lookups, Exim keeps the relevant files open in case there is
6916 another lookup that needs them. In some types of configuration this can lead to
6917 many files being kept open for messages with many recipients. To avoid hitting
6918 the operating system limit on the number of simultaneously open files, Exim
6919 closes the least recently used file when it needs to open more files than its
6920 own internal limit, which can be changed via the &%lookup_open_max%& option.
6922 The single-key lookup files are closed and the lookup caches are flushed at
6923 strategic points during delivery &-- for example, after all routing is
6929 .section "Quoting lookup data" "SECID65"
6930 .cindex "lookup" "quoting"
6931 .cindex "quoting" "in lookups"
6932 When data from an incoming message is included in a query-style lookup, there
6933 is the possibility of special characters in the data messing up the syntax of
6934 the query. For example, a NIS+ query that contains
6938 will be broken if the local part happens to contain a closing square bracket.
6939 For NIS+, data can be enclosed in double quotes like this:
6941 [name="$local_part"]
6943 but this still leaves the problem of a double quote in the data. The rule for
6944 NIS+ is that double quotes must be doubled. Other lookup types have different
6945 rules, and to cope with the differing requirements, an expansion operator
6946 of the following form is provided:
6948 ${quote_<lookup-type>:<string>}
6950 For example, the safest way to write the NIS+ query is
6952 [name="${quote_nisplus:$local_part}"]
6954 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6955 operator can be used for all lookup types, but has no effect for single-key
6956 lookups, since no quoting is ever needed in their key strings.
6961 .section "More about dnsdb" "SECTdnsdb"
6962 .cindex "dnsdb lookup"
6963 .cindex "lookup" "dnsdb"
6964 .cindex "DNS" "as a lookup type"
6965 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6966 of a record type and a domain name, separated by an equals sign. For example,
6967 an expansion string could contain:
6969 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6971 If the lookup succeeds, the result is placed in &$value$&, which in this case
6972 is used on its own as the result. If the lookup does not succeed, the
6973 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6974 &<<SECTforexpfai>>& for an explanation of what this means.
6976 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
6977 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
6978 If no type is given, TXT is assumed.
6980 For any record type, if multiple records are found, the data is returned as a
6981 concatenation, with newline as the default separator. The order, of course,
6982 depends on the DNS resolver. You can specify a different separator character
6983 between multiple records by putting a right angle-bracket followed immediately
6984 by the new separator at the start of the query. For example:
6986 ${lookup dnsdb{>: a=host1.example}}
6988 It is permitted to specify a space as the separator character. Further
6989 white space is ignored.
6990 For lookup types that return multiple fields per record,
6991 an alternate field separator can be specified using a comma after the main
6992 separator character, followed immediately by the field separator.
6994 .cindex "PTR record" "in &(dnsdb)& lookup"
6995 When the type is PTR,
6996 the data can be an IP address, written as normal; inversion and the addition of
6997 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6999 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7001 If the data for a PTR record is not a syntactically valid IP address, it is not
7002 altered and nothing is added.
7004 .cindex "MX record" "in &(dnsdb)& lookup"
7005 .cindex "SRV record" "in &(dnsdb)& lookup"
7006 For an MX lookup, both the preference value and the host name are returned for
7007 each record, separated by a space. For an SRV lookup, the priority, weight,
7008 port, and host name are returned for each record, separated by spaces.
7009 The field separator can be modified as above.
7011 .cindex "TXT record" "in &(dnsdb)& lookup"
7012 .cindex "SPF record" "in &(dnsdb)& lookup"
7013 For TXT records with multiple items of data, only the first item is returned,
7014 unless a field separator is specified.
7015 To concatenate items without a separator, use a semicolon instead.
7017 default behaviour is to concatenate multiple items without using a separator.
7019 ${lookup dnsdb{>\n,: txt=a.b.example}}
7020 ${lookup dnsdb{>\n; txt=a.b.example}}
7021 ${lookup dnsdb{spf=example.org}}
7023 It is permitted to specify a space as the separator character. Further
7024 white space is ignored.
7026 .cindex "SOA record" "in &(dnsdb)& lookup"
7027 For an SOA lookup, while no result is obtained the lookup is redone with
7028 successively more leading components dropped from the given domain.
7029 Only the primary-nameserver field is returned unless a field separator is
7032 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7035 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7036 .cindex "dnsdb modifiers"
7037 .cindex "modifiers" "dnsdb"
7038 .cindex "options" "dnsdb"
7039 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7040 each followed by a comma,
7041 that may appear before the record type.
7043 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7044 temporary DNS error for any of them, the behaviour is controlled by
7045 a defer-option modifier.
7046 The possible keywords are
7047 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7048 With &"strict"& behaviour, any temporary DNS error causes the
7049 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7050 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7051 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7052 error causes the whole lookup to defer only if none of the other lookups
7053 succeed. The default is &"lax"&, so the following lookups are equivalent:
7055 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7056 ${lookup dnsdb{a=one.host.com:two.host.com}}
7058 Thus, in the default case, as long as at least one of the DNS lookups
7059 yields some data, the lookup succeeds.
7061 .cindex "DNSSEC" "dns lookup"
7062 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7063 The possible keywords are
7064 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7065 With &"strict"& or &"lax"& DNSSEC information is requested
7067 With &"strict"& a response from the DNS resolver that
7068 is not labelled as authenticated data
7069 is treated as equivalent to a temporary DNS error.
7070 The default is &"never"&.
7072 See also the &$lookup_dnssec_authenticated$& variable.
7074 .cindex timeout "dns lookup"
7075 .cindex "DNS" timeout
7076 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7077 The form is &"retrans_VAL"& where VAL is an Exim time specification
7079 The default value is set by the main configuration option &%dns_retrans%&.
7081 Retries for the dnsdb lookup can be controlled by a retry modifier.
7082 The form if &"retry_VAL"& where VAL is an integer.
7083 The default count is set by the main configuration option &%dns_retry%&.
7085 .cindex cacheing "of dns lookup"
7086 .cindex TTL "of dns lookup"
7088 Dnsdb lookup results are cached within a single process (and its children).
7089 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7090 value of the set of returned DNS records.
7093 .section "Pseudo dnsdb record types" "SECID66"
7094 .cindex "MX record" "in &(dnsdb)& lookup"
7095 By default, both the preference value and the host name are returned for
7096 each MX record, separated by a space. If you want only host names, you can use
7097 the pseudo-type MXH:
7099 ${lookup dnsdb{mxh=a.b.example}}
7101 In this case, the preference values are omitted, and just the host names are
7104 .cindex "name server for enclosing domain"
7105 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7106 records on the given domain, but if none are found, it removes the first
7107 component of the domain name, and tries again. This process continues until NS
7108 records are found or there are no more components left (or there is a DNS
7109 error). In other words, it may return the name servers for a top-level domain,
7110 but it never returns the root name servers. If there are no NS records for the
7111 top-level domain, the lookup fails. Consider these examples:
7113 ${lookup dnsdb{zns=xxx.quercite.com}}
7114 ${lookup dnsdb{zns=xxx.edu}}
7116 Assuming that in each case there are no NS records for the full domain name,
7117 the first returns the name servers for &%quercite.com%&, and the second returns
7118 the name servers for &%edu%&.
7120 You should be careful about how you use this lookup because, unless the
7121 top-level domain does not exist, the lookup always returns some host names. The
7122 sort of use to which this might be put is for seeing if the name servers for a
7123 given domain are on a blacklist. You can probably assume that the name servers
7124 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7127 .cindex "CSA" "in &(dnsdb)& lookup"
7128 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7129 records according to the CSA rules, which are described in section
7130 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7131 not sufficient because of the extra parent domain search behaviour of CSA. The
7132 result of a successful lookup such as:
7134 ${lookup dnsdb {csa=$sender_helo_name}}
7136 has two space-separated fields: an authorization code and a target host name.
7137 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7138 authorization required but absent, or &"?"& for unknown.
7140 .cindex "A+" "in &(dnsdb)& lookup"
7141 The pseudo-type A+ performs an AAAA
7142 and then an A lookup. All results are returned; defer processing
7143 (see below) is handled separately for each lookup. Example:
7145 ${lookup dnsdb {>; a+=$sender_helo_name}}
7149 .section "Multiple dnsdb lookups" "SECID67"
7150 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7151 However, you can specify a list of domains or IP addresses in a single
7152 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7153 the default separator, but with the ability to change this. For example:
7155 ${lookup dnsdb{one.domain.com:two.domain.com}}
7156 ${lookup dnsdb{a=one.host.com:two.host.com}}
7157 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7159 In order to retain backwards compatibility, there is one special case: if
7160 the lookup type is PTR and no change of separator is specified, Exim looks
7161 to see if the rest of the string is precisely one IPv6 address. In this
7162 case, it does not treat it as a list.
7164 The data from each lookup is concatenated, with newline separators by default,
7165 in the same way that multiple DNS records for a single item are handled. A
7166 different separator can be specified, as described above.
7171 .section "More about LDAP" "SECTldap"
7172 .cindex "LDAP" "lookup, more about"
7173 .cindex "lookup" "LDAP"
7174 .cindex "Solaris" "LDAP"
7175 The original LDAP implementation came from the University of Michigan; this has
7176 become &"Open LDAP"&, and there are now two different releases. Another
7177 implementation comes from Netscape, and Solaris 7 and subsequent releases
7178 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7179 the lookup function level, their error handling is different. For this reason
7180 it is necessary to set a compile-time variable when building Exim with LDAP, to
7181 indicate which LDAP library is in use. One of the following should appear in
7182 your &_Local/Makefile_&:
7184 LDAP_LIB_TYPE=UMICHIGAN
7185 LDAP_LIB_TYPE=OPENLDAP1
7186 LDAP_LIB_TYPE=OPENLDAP2
7187 LDAP_LIB_TYPE=NETSCAPE
7188 LDAP_LIB_TYPE=SOLARIS
7190 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7191 same interface as the University of Michigan version.
7193 There are three LDAP lookup types in Exim. These behave slightly differently in
7194 the way they handle the results of a query:
7197 &(ldap)& requires the result to contain just one entry; if there are more, it
7200 &(ldapdn)& also requires the result to contain just one entry, but it is the
7201 Distinguished Name that is returned rather than any attribute values.
7203 &(ldapm)& permits the result to contain more than one entry; the attributes
7204 from all of them are returned.
7208 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7209 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7210 the data returned by a successful lookup is described in the next section.
7211 First we explain how LDAP queries are coded.
7214 .section "Format of LDAP queries" "SECTforldaque"
7215 .cindex "LDAP" "query format"
7216 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7217 the configuration of a &(redirect)& router one might have this setting:
7219 data = ${lookup ldap \
7220 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7221 c=UK?mailbox?base?}}
7223 .cindex "LDAP" "with TLS"
7224 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7225 secure (encrypted) LDAP connections. The second of these ensures that an
7226 encrypted TLS connection is used.
7228 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7229 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7230 See the &%ldap_start_tls%& option.
7232 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7233 controlled. Every part of the TLS configuration can be configured by settings in
7234 &_exim.conf_&. Depending on the version of the client libraries installed on
7235 your system, some of the initialization may have required setting options in
7236 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7237 certificates. This revealed a nuance where the current UID that exim was
7238 running as could affect which config files it read. With Exim 4.83, these
7239 methods become optional, only taking effect if not specifically set in
7243 .section "LDAP quoting" "SECID68"
7244 .cindex "LDAP" "quoting"
7245 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7246 and the second because the LDAP query is represented as a URL. Furthermore,
7247 within an LDAP query, two different kinds of quoting are required. For this
7248 reason, there are two different LDAP-specific quoting operators.
7250 The &%quote_ldap%& operator is designed for use on strings that are part of
7251 filter specifications. Conceptually, it first does the following conversions on
7259 in accordance with RFC 2254. The resulting string is then quoted according
7260 to the rules for URLs, that is, all non-alphanumeric characters except
7264 are converted to their hex values, preceded by a percent sign. For example:
7266 ${quote_ldap: a(bc)*, a<yz>; }
7270 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7272 Removing the URL quoting, this is (with a leading and a trailing space):
7274 a\28bc\29\2A, a<yz>;
7276 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7277 base DN specifications in queries. Conceptually, it first converts the string
7278 by inserting a backslash in front of any of the following characters:
7282 It also inserts a backslash before any leading spaces or # characters, and
7283 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7284 is then quoted according to the rules for URLs. For example:
7286 ${quote_ldap_dn: a(bc)*, a<yz>; }
7290 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7292 Removing the URL quoting, this is (with a trailing space):
7294 \ a(bc)*\, a\<yz\>\;\
7296 There are some further comments about quoting in the section on LDAP
7297 authentication below.
7300 .section "LDAP connections" "SECID69"
7301 .cindex "LDAP" "connections"
7302 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7303 is in use, via a Unix domain socket. The example given above does not specify
7304 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7307 ldap://<hostname>:<port>/...
7309 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7310 used. When no server is specified in a query, a list of default servers is
7311 taken from the &%ldap_default_servers%& configuration option. This supplies a
7312 colon-separated list of servers which are tried in turn until one successfully
7313 handles a query, or there is a serious error. Successful handling either
7314 returns the requested data, or indicates that it does not exist. Serious errors
7315 are syntactical, or multiple values when only a single value is expected.
7316 Errors which cause the next server to be tried are connection failures, bind
7317 failures, and timeouts.
7319 For each server name in the list, a port number can be given. The standard way
7320 of specifying a host and port is to use a colon separator (RFC 1738). Because
7321 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7322 doubled. For example
7324 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7326 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7327 to the LDAP library with no server name, and the library's default (normally
7328 the local host) is used.
7330 If you are using the OpenLDAP library, you can connect to an LDAP server using
7331 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7332 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7333 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7336 For this type of connection, instead of a host name for the server, a pathname
7337 for the socket is required, and the port number is not relevant. The pathname
7338 can be specified either as an item in &%ldap_default_servers%&, or inline in
7339 the query. In the former case, you can have settings such as
7341 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7343 When the pathname is given in the query, you have to escape the slashes as
7344 &`%2F`& to fit in with the LDAP URL syntax. For example:
7346 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7348 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7349 a pathname, it uses the Unix domain socket code, even if the query actually
7350 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7351 socket connection. This behaviour means that you can use a setting of
7352 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7353 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7354 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7357 If an explicit &`ldapi`& type is given in a query when a host name is
7358 specified, an error is diagnosed. However, if there are more items in
7359 &%ldap_default_servers%&, they are tried. In other words:
7362 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7365 Using &`ldapi`& with a host name causes an error.
7369 Using &`ldapi`& with no host or path in the query, and no setting of
7370 &%ldap_default_servers%&, does whatever the library does by default.
7374 .section "LDAP authentication and control information" "SECID70"
7375 .cindex "LDAP" "authentication"
7376 The LDAP URL syntax provides no way of passing authentication and other control
7377 information to the server. To make this possible, the URL in an LDAP query may
7378 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7379 spaces. If a value contains spaces it must be enclosed in double quotes, and
7380 when double quotes are used, backslash is interpreted in the usual way inside
7381 them. The following names are recognized:
7383 &`DEREFERENCE`& set the dereferencing parameter
7384 &`NETTIME `& set a timeout for a network operation
7385 &`USER `& set the DN, for authenticating the LDAP bind
7386 &`PASS `& set the password, likewise
7387 &`REFERRALS `& set the referrals parameter
7388 &`SERVERS `& set alternate server list for this query only
7389 &`SIZE `& set the limit for the number of entries returned
7390 &`TIME `& set the maximum waiting time for a query
7392 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7393 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7394 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7395 library from trying to follow referrals issued by the LDAP server.
7397 .cindex LDAP timeout
7398 .cindex timeout "LDAP lookup"
7399 The name CONNECT is an obsolete name for NETTIME, retained for
7400 backwards compatibility. This timeout (specified as a number of seconds) is
7401 enforced from the client end for operations that can be carried out over a
7402 network. Specifically, it applies to network connections and calls to the
7403 &'ldap_result()'& function. If the value is greater than zero, it is used if
7404 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7405 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7406 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7407 Netscape SDK; for OpenLDAP no action is taken.
7409 The TIME parameter (also a number of seconds) is passed to the server to
7410 set a server-side limit on the time taken to complete a search.
7412 The SERVERS parameter allows you to specify an alternate list of ldap servers
7413 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7414 default list of ldap servers, and a single lookup can specify a single ldap
7415 server to use. But when you need to do a lookup with a list of servers that is
7416 different than the default list (maybe different order, maybe a completely
7417 different set of servers), the SERVERS parameter allows you to specify this
7418 alternate list (colon-separated).
7420 Here is an example of an LDAP query in an Exim lookup that uses some of these
7421 values. This is a single line, folded to fit on the page:
7424 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7425 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7428 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7429 any of the auxiliary data. Exim configuration settings that include lookups
7430 which contain password information should be preceded by &"hide"& to prevent
7431 non-admin users from using the &%-bP%& option to see their values.
7433 The auxiliary data items may be given in any order. The default is no
7434 connection timeout (the system timeout is used), no user or password, no limit
7435 on the number of entries returned, and no time limit on queries.
7437 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7438 removes any URL quoting that it may contain before passing it LDAP. Apparently
7439 some libraries do this for themselves, but some do not. Removing the URL
7440 quoting has two advantages:
7443 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7444 DNs as with DNs inside actual queries.
7446 It permits spaces inside USER= DNs.
7449 For example, a setting such as
7451 USER=cn=${quote_ldap_dn:$1}
7453 should work even if &$1$& contains spaces.
7455 Expanded data for the PASS= value should be quoted using the &%quote%&
7456 expansion operator, rather than the LDAP quote operators. The only reason this
7457 field needs quoting is to ensure that it conforms to the Exim syntax, which
7458 does not allow unquoted spaces. For example:
7462 The LDAP authentication mechanism can be used to check passwords as part of
7463 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7468 .section "Format of data returned by LDAP" "SECID71"
7469 .cindex "LDAP" "returned data formats"
7470 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7471 as a sequence of values, for example
7473 cn=manager,o=University of Cambridge,c=UK
7475 The &(ldap)& lookup type generates an error if more than one entry matches the
7476 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7477 the result between the data from different entries. It is possible for multiple
7478 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7479 you know that whatever values are returned all came from a single entry in the
7482 In the common case where you specify a single attribute in your LDAP query, the
7483 result is not quoted, and does not contain the attribute name. If the attribute
7484 has multiple values, they are separated by commas. Any comma that is
7485 part of an attribute's value is doubled.
7487 If you specify multiple attributes, the result contains space-separated, quoted
7488 strings, each preceded by the attribute name and an equals sign. Within the
7489 quotes, the quote character, backslash, and newline are escaped with
7490 backslashes, and commas are used to separate multiple values for the attribute.
7491 Any commas in attribute values are doubled
7492 (permitting treatment of the values as a comma-separated list).
7493 Apart from the escaping, the string within quotes takes the same form as the
7494 output when a single attribute is requested. Specifying no attributes is the
7495 same as specifying all of an entry's attributes.
7497 Here are some examples of the output format. The first line of each pair is an
7498 LDAP query, and the second is the data that is returned. The attribute called
7499 &%attr1%& has two values, one of them with an embedded comma, whereas
7500 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7501 (they have SUP &%attr%& in their schema definitions).
7504 ldap:///o=base?attr1?sub?(uid=fred)
7507 ldap:///o=base?attr2?sub?(uid=fred)
7510 ldap:///o=base?attr?sub?(uid=fred)
7511 value1.1,value1,,2,value two
7513 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7514 attr1="value1.1,value1,,2" attr2="value two"
7516 ldap:///o=base??sub?(uid=fred)
7517 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7520 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7521 results of LDAP lookups.
7522 The &%extract%& operator in string expansions can be used to pick out
7523 individual fields from data that consists of &'key'&=&'value'& pairs.
7524 The &%listextract%& operator should be used to pick out individual values
7525 of attributes, even when only a single value is expected.
7526 The doubling of embedded commas allows you to use the returned data as a
7527 comma separated list (using the "<," syntax for changing the input list separator).
7532 .section "More about NIS+" "SECTnisplus"
7533 .cindex "NIS+ lookup type"
7534 .cindex "lookup" "NIS+"
7535 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7536 and field name. If this is given, the result of a successful query is the
7537 contents of the named field; otherwise the result consists of a concatenation
7538 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7539 values containing spaces are quoted. For example, the query
7541 [name=mg1456],passwd.org_dir
7543 might return the string
7545 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7546 home=/home/mg1456 shell=/bin/bash shadow=""
7548 (split over two lines here to fit on the page), whereas
7550 [name=mg1456],passwd.org_dir:gcos
7556 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7557 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7558 operator is to double any quote characters within the text.
7562 .section "SQL lookups" "SECTsql"
7563 .cindex "SQL lookup types"
7564 .cindex "MySQL" "lookup type"
7565 .cindex "PostgreSQL lookup type"
7566 .cindex "lookup" "MySQL"
7567 .cindex "lookup" "PostgreSQL"
7568 .cindex "Oracle" "lookup type"
7569 .cindex "lookup" "Oracle"
7570 .cindex "InterBase lookup type"
7571 .cindex "lookup" "InterBase"
7572 .cindex "Redis lookup type"
7573 .cindex lookup Redis
7574 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7576 databases. Queries for these databases contain SQL statements, so an example
7579 ${lookup mysql{select mailbox from users where id='userx'}\
7582 If the result of the query contains more than one field, the data for each
7583 field in the row is returned, preceded by its name, so the result of
7585 ${lookup pgsql{select home,name from users where id='userx'}\
7590 home=/home/userx name="Mister X"
7592 Empty values and values containing spaces are double quoted, with embedded
7593 quotes escaped by a backslash. If the result of the query contains just one
7594 field, the value is passed back verbatim, without a field name, for example:
7598 If the result of the query yields more than one row, it is all concatenated,
7599 with a newline between the data for each row.
7602 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7603 .cindex "MySQL" "lookup type"
7604 .cindex "PostgreSQL lookup type"
7605 .cindex "lookup" "MySQL"
7606 .cindex "lookup" "PostgreSQL"
7607 .cindex "Oracle" "lookup type"
7608 .cindex "lookup" "Oracle"
7609 .cindex "InterBase lookup type"
7610 .cindex "lookup" "InterBase"
7611 .cindex "Redis lookup type"
7612 .cindex lookup Redis
7613 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7614 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7615 or &%redis_servers%&
7616 option (as appropriate) must be set to a colon-separated list of server
7618 (For MySQL and PostgreSQL, the global option need not be set if all
7619 queries contain their own server information &-- see section
7620 &<<SECTspeserque>>&.)
7622 each item in the list is a slash-separated list of four
7623 items: host name, database name, user name, and password. In the case of
7624 Oracle, the host name field is used for the &"service name"&, and the database
7625 name field is not used and should be empty. For example:
7627 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7629 Because password data is sensitive, you should always precede the setting with
7630 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7631 option. Here is an example where two MySQL servers are listed:
7633 hide mysql_servers = localhost/users/root/secret:\
7634 otherhost/users/root/othersecret
7636 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7637 because this is a colon-separated list, the colon has to be doubled. For each
7638 query, these parameter groups are tried in order until a connection is made and
7639 a query is successfully processed. The result of a query may be that no data is
7640 found, but that is still a successful query. In other words, the list of
7641 servers provides a backup facility, not a list of different places to look.
7643 For Redis the global option need not be specified if all queries contain their
7644 own server information &-- see section &<<SECTspeserque>>&.
7645 If specified, the option must be set to a colon-separated list of server
7647 Each item in the list is a slash-separated list of three items:
7648 host, database number, and password.
7650 The host is required and may be either an IPv4 address and optional
7651 port number (separated by a colon, which needs doubling due to the
7652 higher-level list), or a Unix socket pathname enclosed in parentheses
7654 The database number is optional; if present that number is selected in the backend
7656 The password is optional; if present it is used to authenticate to the backend
7659 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7660 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7661 respectively, and the characters single-quote, double-quote, and backslash
7662 itself are escaped with backslashes.
7664 The &%quote_redis%& expansion operator
7665 escapes whitespace and backslash characters with a backslash.
7667 .section "Specifying the server in the query" "SECTspeserque"
7668 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
7669 it is possible to specify a list of servers with an individual query. This is
7670 done by starting the query with
7672 &`servers=`&&'server1:server2:server3:...'&&`;`&
7674 Each item in the list may take one of two forms:
7676 If it contains no slashes it is assumed to be just a host name. The appropriate
7677 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7678 of the same name, and the remaining parameters (database, user, password) are
7681 If it contains any slashes, it is taken as a complete parameter set.
7683 The list of servers is used in exactly the same way as the global list.
7684 Once a connection to a server has happened and a query has been
7685 successfully executed, processing of the lookup ceases.
7687 This feature is intended for use in master/slave situations where updates
7688 are occurring and you want to update the master rather than a slave. If the
7689 master is in the list as a backup for reading, you might have a global setting
7692 mysql_servers = slave1/db/name/pw:\
7696 In an updating lookup, you could then write:
7698 ${lookup mysql{servers=master; UPDATE ...} }
7700 That query would then be sent only to the master server. If, on the other hand,
7701 the master is not to be used for reading, and so is not present in the global
7702 option, you can still update it by a query of this form:
7704 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7708 .section "Special MySQL features" "SECID73"
7709 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7710 causes a connection to the server on the local host by means of a Unix domain
7711 socket. An alternate socket can be specified in parentheses.
7712 An option group name for MySQL option files can be specified in square brackets;
7713 the default value is &"exim"&.
7714 The full syntax of each item in &%mysql_servers%& is:
7716 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7717 <&'database'&>/<&'user'&>/<&'password'&>
7719 Any of the four sub-parts of the first field can be omitted. For normal use on
7720 the local host it can be left blank or set to just &"localhost"&.
7722 No database need be supplied &-- but if it is absent here, it must be given in
7725 If a MySQL query is issued that does not request any data (an insert, update,
7726 or delete command), the result of the lookup is the number of rows affected.
7728 &*Warning*&: This can be misleading. If an update does not actually change
7729 anything (for example, setting a field to the value it already has), the result
7730 is zero because no rows are affected.
7733 .section "Special PostgreSQL features" "SECID74"
7734 PostgreSQL lookups can also use Unix domain socket connections to the database.
7735 This is usually faster and costs less CPU time than a TCP/IP connection.
7736 However it can be used only if the mail server runs on the same machine as the
7737 database server. A configuration line for PostgreSQL via Unix domain sockets
7740 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7742 In other words, instead of supplying a host name, a path to the socket is
7743 given. The path name is enclosed in parentheses so that its slashes aren't
7744 visually confused with the delimiters for the other server parameters.
7746 If a PostgreSQL query is issued that does not request any data (an insert,
7747 update, or delete command), the result of the lookup is the number of rows
7750 .section "More about SQLite" "SECTsqlite"
7751 .cindex "lookup" "SQLite"
7752 .cindex "sqlite lookup type"
7753 SQLite is different to the other SQL lookups because a file name is required in
7754 addition to the SQL query. An SQLite database is a single file, and there is no
7755 daemon as in the other SQL databases. The interface to Exim requires the name
7756 of the file, as an absolute path, to be given at the start of the query. It is
7757 separated from the query by white space. This means that the path name cannot
7758 contain white space. Here is a lookup expansion example:
7760 ${lookup sqlite {/some/thing/sqlitedb \
7761 select name from aliases where id='userx';}}
7763 In a list, the syntax is similar. For example:
7765 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7766 select * from relays where ip='$sender_host_address';
7768 The only character affected by the &%quote_sqlite%& operator is a single
7769 quote, which it doubles.
7771 .cindex timeout SQLite
7772 .cindex sqlite "lookup timeout"
7773 The SQLite library handles multiple simultaneous accesses to the database
7774 internally. Multiple readers are permitted, but only one process can
7775 update at once. Attempts to access the database while it is being updated
7776 are rejected after a timeout period, during which the SQLite library
7777 waits for the lock to be released. In Exim, the default timeout is set
7778 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7784 . ////////////////////////////////////////////////////////////////////////////
7785 . ////////////////////////////////////////////////////////////////////////////
7787 .chapter "Domain, host, address, and local part lists" &&&
7788 "CHAPdomhosaddlists" &&&
7789 "Domain, host, and address lists"
7790 .scindex IIDdohoadli "lists of domains; hosts; etc."
7791 A number of Exim configuration options contain lists of domains, hosts,
7792 email addresses, or local parts. For example, the &%hold_domains%& option
7793 contains a list of domains whose delivery is currently suspended. These lists
7794 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7795 arguments to expansion conditions such as &%match_domain%&.
7797 Each item in one of these lists is a pattern to be matched against a domain,
7798 host, email address, or local part, respectively. In the sections below, the
7799 different types of pattern for each case are described, but first we cover some
7800 general facilities that apply to all four kinds of list.
7802 Note that other parts of Exim use a &'string list'& which does not
7803 support all the complexity available in
7804 domain, host, address and local part lists.
7808 .section "Expansion of lists" "SECTlistexpand"
7809 .cindex "expansion" "of lists"
7810 Each list is expanded as a single string before it is used.
7813 &'Exception: the router headers_remove option, where list-item
7814 splitting is done before string-expansion.'&
7818 expansion must be a list, possibly containing empty items, which is split up
7819 into separate items for matching. By default, colon is the separator character,
7820 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7821 &<<SECTempitelis>>& for details of the list syntax; the second of these
7822 discusses the way to specify empty list items.
7825 If the string expansion is forced to fail, Exim behaves as if the item it is
7826 testing (domain, host, address, or local part) is not in the list. Other
7827 expansion failures cause temporary errors.
7829 If an item in a list is a regular expression, backslashes, dollars and possibly
7830 other special characters in the expression must be protected against
7831 misinterpretation by the string expander. The easiest way to do this is to use
7832 the &`\N`& expansion feature to indicate that the contents of the regular
7833 expression should not be expanded. For example, in an ACL you might have:
7835 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7836 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7838 The first item is a regular expression that is protected from expansion by
7839 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7840 senders based on the receiving domain.
7845 .section "Negated items in lists" "SECID76"
7846 .cindex "list" "negation"
7847 .cindex "negation" "in lists"
7848 Items in a list may be positive or negative. Negative items are indicated by a
7849 leading exclamation mark, which may be followed by optional white space. A list
7850 defines a set of items (domains, etc). When Exim processes one of these lists,
7851 it is trying to find out whether a domain, host, address, or local part
7852 (respectively) is in the set that is defined by the list. It works like this:
7854 The list is scanned from left to right. If a positive item is matched, the
7855 subject that is being checked is in the set; if a negative item is matched, the
7856 subject is not in the set. If the end of the list is reached without the
7857 subject having matched any of the patterns, it is in the set if the last item
7858 was a negative one, but not if it was a positive one. For example, the list in
7860 domainlist relay_to_domains = !a.b.c : *.b.c
7862 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7863 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7864 list is positive. However, if the setting were
7866 domainlist relay_to_domains = !a.b.c
7868 then all domains other than &'a.b.c'& would match because the last item in the
7869 list is negative. In other words, a list that ends with a negative item behaves
7870 as if it had an extra item &`:*`& on the end.
7872 Another way of thinking about positive and negative items in lists is to read
7873 the connector as &"or"& after a positive item and as &"and"& after a negative
7878 .section "File names in lists" "SECTfilnamlis"
7879 .cindex "list" "file name in"
7880 If an item in a domain, host, address, or local part list is an absolute file
7881 name (beginning with a slash character), each line of the file is read and
7882 processed as if it were an independent item in the list, except that further
7883 file names are not allowed,
7884 and no expansion of the data from the file takes place.
7885 Empty lines in the file are ignored, and the file may also contain comment
7889 For domain and host lists, if a # character appears anywhere in a line of the
7890 file, it and all following characters are ignored.
7892 Because local parts may legitimately contain # characters, a comment in an
7893 address list or local part list file is recognized only if # is preceded by
7894 white space or the start of the line. For example:
7896 not#comment@x.y.z # but this is a comment
7900 Putting a file name in a list has the same effect as inserting each line of the
7901 file as an item in the list (blank lines and comments excepted). However, there
7902 is one important difference: the file is read each time the list is processed,
7903 so if its contents vary over time, Exim's behaviour changes.
7905 If a file name is preceded by an exclamation mark, the sense of any match
7906 within the file is inverted. For example, if
7908 hold_domains = !/etc/nohold-domains
7910 and the file contains the lines
7915 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7916 any domain matching &`*.b.c`& is not.
7920 .section "An lsearch file is not an out-of-line list" "SECID77"
7921 As will be described in the sections that follow, lookups can be used in lists
7922 to provide indexed methods of checking list membership. There has been some
7923 confusion about the way &(lsearch)& lookups work in lists. Because
7924 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7925 sometimes thought that it is allowed to contain wild cards and other kinds of
7926 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7927 always fixed strings, just as for any other single-key lookup type.
7929 If you want to use a file to contain wild-card patterns that form part of a
7930 list, just give the file name on its own, without a search type, as described
7931 in the previous section. You could also use the &(wildlsearch)& or
7932 &(nwildlsearch)&, but there is no advantage in doing this.
7937 .section "Named lists" "SECTnamedlists"
7938 .cindex "named lists"
7939 .cindex "list" "named"
7940 A list of domains, hosts, email addresses, or local parts can be given a name
7941 which is then used to refer to the list elsewhere in the configuration. This is
7942 particularly convenient if the same list is required in several different
7943 places. It also allows lists to be given meaningful names, which can improve
7944 the readability of the configuration. For example, it is conventional to define
7945 a domain list called &'local_domains'& for all the domains that are handled
7946 locally on a host, using a configuration line such as
7948 domainlist local_domains = localhost:my.dom.example
7950 Named lists are referenced by giving their name preceded by a plus sign, so,
7951 for example, a router that is intended to handle local domains would be
7952 configured with the line
7954 domains = +local_domains
7956 The first router in a configuration is often one that handles all domains
7957 except the local ones, using a configuration with a negated item like this:
7961 domains = ! +local_domains
7962 transport = remote_smtp
7965 The four kinds of named list are created by configuration lines starting with
7966 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7967 respectively. Then there follows the name that you are defining, followed by an
7968 equals sign and the list itself. For example:
7970 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7971 addresslist bad_senders = cdb;/etc/badsenders
7973 A named list may refer to other named lists:
7975 domainlist dom1 = first.example : second.example
7976 domainlist dom2 = +dom1 : third.example
7977 domainlist dom3 = fourth.example : +dom2 : fifth.example
7979 &*Warning*&: If the last item in a referenced list is a negative one, the
7980 effect may not be what you intended, because the negation does not propagate
7981 out to the higher level. For example, consider:
7983 domainlist dom1 = !a.b
7984 domainlist dom2 = +dom1 : *.b
7986 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7987 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7988 means it matches the second list as well. The effect is not the same as
7990 domainlist dom2 = !a.b : *.b
7992 where &'x.y'& does not match. It's best to avoid negation altogether in
7993 referenced lists if you can.
7995 Named lists may have a performance advantage. When Exim is routing an
7996 address or checking an incoming message, it caches the result of tests on named
7997 lists. So, if you have a setting such as
7999 domains = +local_domains
8001 on several of your routers
8002 or in several ACL statements,
8003 the actual test is done only for the first one. However, the caching works only
8004 if there are no expansions within the list itself or any sublists that it
8005 references. In other words, caching happens only for lists that are known to be
8006 the same each time they are referenced.
8008 By default, there may be up to 16 named lists of each type. This limit can be
8009 extended by changing a compile-time variable. The use of domain and host lists
8010 is recommended for concepts such as local domains, relay domains, and relay
8011 hosts. The default configuration is set up like this.
8015 .section "Named lists compared with macros" "SECID78"
8016 .cindex "list" "named compared with macro"
8017 .cindex "macro" "compared with named list"
8018 At first sight, named lists might seem to be no different from macros in the
8019 configuration file. However, macros are just textual substitutions. If you
8022 ALIST = host1 : host2
8023 auth_advertise_hosts = !ALIST
8025 it probably won't do what you want, because that is exactly the same as
8027 auth_advertise_hosts = !host1 : host2
8029 Notice that the second host name is not negated. However, if you use a host
8032 hostlist alist = host1 : host2
8033 auth_advertise_hosts = ! +alist
8035 the negation applies to the whole list, and so that is equivalent to
8037 auth_advertise_hosts = !host1 : !host2
8041 .section "Named list caching" "SECID79"
8042 .cindex "list" "caching of named"
8043 .cindex "caching" "named lists"
8044 While processing a message, Exim caches the result of checking a named list if
8045 it is sure that the list is the same each time. In practice, this means that
8046 the cache operates only if the list contains no $ characters, which guarantees
8047 that it will not change when it is expanded. Sometimes, however, you may have
8048 an expanded list that you know will be the same each time within a given
8049 message. For example:
8051 domainlist special_domains = \
8052 ${lookup{$sender_host_address}cdb{/some/file}}
8054 This provides a list of domains that depends only on the sending host's IP
8055 address. If this domain list is referenced a number of times (for example,
8056 in several ACL lines, or in several routers) the result of the check is not
8057 cached by default, because Exim does not know that it is going to be the
8058 same list each time.
8060 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8061 cache the result anyway. For example:
8063 domainlist_cache special_domains = ${lookup{...
8065 If you do this, you should be absolutely sure that caching is going to do
8066 the right thing in all cases. When in doubt, leave it out.
8070 .section "Domain lists" "SECTdomainlist"
8071 .cindex "domain list" "patterns for"
8072 .cindex "list" "domain list"
8073 Domain lists contain patterns that are to be matched against a mail domain.
8074 The following types of item may appear in domain lists:
8077 .cindex "primary host name"
8078 .cindex "host name" "matched in domain list"
8079 .oindex "&%primary_hostname%&"
8080 .cindex "domain list" "matching primary host name"
8081 .cindex "@ in a domain list"
8082 If a pattern consists of a single @ character, it matches the local host name,
8083 as set by the &%primary_hostname%& option (or defaulted). This makes it
8084 possible to use the same configuration file on several different hosts that
8085 differ only in their names.
8087 .cindex "@[] in a domain list"
8088 .cindex "domain list" "matching local IP interfaces"
8089 .cindex "domain literal"
8090 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8091 in square brackets (as in an email address that contains a domain literal), but
8092 only if that IP address is recognized as local for email routing purposes. The
8093 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8094 control which of a host's several IP addresses are treated as local.
8095 In today's Internet, the use of domain literals is controversial.
8098 .cindex "@mx_primary"
8099 .cindex "@mx_secondary"
8100 .cindex "domain list" "matching MX pointers to local host"
8101 If a pattern consists of the string &`@mx_any`& it matches any domain that
8102 has an MX record pointing to the local host or to any host that is listed in
8103 .oindex "&%hosts_treat_as_local%&"
8104 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8105 are similar, except that the first matches only when a primary MX target is the
8106 local host, and the second only when no primary MX target is the local host,
8107 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8108 preference value &-- there may of course be more than one of them.
8110 The MX lookup that takes place when matching a pattern of this type is
8111 performed with the resolver options for widening names turned off. Thus, for
8112 example, a single-component domain will &'not'& be expanded by adding the
8113 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8114 options of the &(dnslookup)& router for a discussion of domain widening.
8116 Sometimes you may want to ignore certain IP addresses when using one of these
8117 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8118 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8119 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8120 on a router). For example:
8122 domains = @mx_any/ignore=127.0.0.1
8124 This example matches any domain that has an MX record pointing to one of
8125 the local host's IP addresses other than 127.0.0.1.
8127 The list of IP addresses is in fact processed by the same code that processes
8128 host lists, so it may contain CIDR-coded network specifications and it may also
8129 contain negative items.
8131 Because the list of IP addresses is a sublist within a domain list, you have to
8132 be careful about delimiters if there is more than one address. Like any other
8133 list, the default delimiter can be changed. Thus, you might have:
8135 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8136 an.other.domain : ...
8138 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8139 involved, it is easiest to change the delimiter for the main list as well:
8141 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8142 an.other.domain ? ...
8145 .cindex "asterisk" "in domain list"
8146 .cindex "domain list" "asterisk in"
8147 .cindex "domain list" "matching &""ends with""&"
8148 If a pattern starts with an asterisk, the remaining characters of the pattern
8149 are compared with the terminating characters of the domain. The use of &"*"& in
8150 domain lists differs from its use in partial matching lookups. In a domain
8151 list, the character following the asterisk need not be a dot, whereas partial
8152 matching works only in terms of dot-separated components. For example, a domain
8153 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8157 .cindex "regular expressions" "in domain list"
8158 .cindex "domain list" "matching regular expression"
8159 If a pattern starts with a circumflex character, it is treated as a regular
8160 expression, and matched against the domain using a regular expression matching
8161 function. The circumflex is treated as part of the regular expression.
8162 Email domains are case-independent, so this regular expression match is by
8163 default case-independent, but you can make it case-dependent by starting it
8164 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8165 are given in chapter &<<CHAPregexp>>&.
8167 &*Warning*&: Because domain lists are expanded before being processed, you
8168 must escape any backslash and dollar characters in the regular expression, or
8169 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8170 it is not to be expanded (unless you really do want to build a regular
8171 expression by expansion, of course).
8173 .cindex "lookup" "in domain list"
8174 .cindex "domain list" "matching by lookup"
8175 If a pattern starts with the name of a single-key lookup type followed by a
8176 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8177 must be a file name in a suitable format for the lookup type. For example, for
8178 &"cdb;"& it must be an absolute path:
8180 domains = cdb;/etc/mail/local_domains.cdb
8182 The appropriate type of lookup is done on the file using the domain name as the
8183 key. In most cases, the data that is looked up is not used; Exim is interested
8184 only in whether or not the key is present in the file. However, when a lookup
8185 is used for the &%domains%& option on a router
8186 or a &%domains%& condition in an ACL statement, the data is preserved in the
8187 &$domain_data$& variable and can be referred to in other router options or
8188 other statements in the same ACL.
8191 Any of the single-key lookup type names may be preceded by
8192 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8194 domains = partial-dbm;/partial/domains
8196 This causes partial matching logic to be invoked; a description of how this
8197 works is given in section &<<SECTpartiallookup>>&.
8200 .cindex "asterisk" "in lookup type"
8201 Any of the single-key lookup types may be followed by an asterisk. This causes
8202 a default lookup for a key consisting of a single asterisk to be done if the
8203 original lookup fails. This is not a useful feature when using a domain list to
8204 select particular domains (because any domain would match), but it might have
8205 value if the result of the lookup is being used via the &$domain_data$&
8208 If the pattern starts with the name of a query-style lookup type followed by a
8209 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8210 pattern must be an appropriate query for the lookup type, as described in
8211 chapter &<<CHAPfdlookup>>&. For example:
8213 hold_domains = mysql;select domain from holdlist \
8214 where domain = '${quote_mysql:$domain}';
8216 In most cases, the data that is looked up is not used (so for an SQL query, for
8217 example, it doesn't matter what field you select). Exim is interested only in
8218 whether or not the query succeeds. However, when a lookup is used for the
8219 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8220 variable and can be referred to in other options.
8222 .cindex "domain list" "matching literal domain name"
8223 If none of the above cases apply, a caseless textual comparison is made
8224 between the pattern and the domain.
8227 Here is an example that uses several different kinds of pattern:
8229 domainlist funny_domains = \
8232 *.foundation.fict.example : \
8233 \N^[1-2]\d{3}\.fict\.example$\N : \
8234 partial-dbm;/opt/data/penguin/book : \
8235 nis;domains.byname : \
8236 nisplus;[name=$domain,status=local],domains.org_dir
8238 There are obvious processing trade-offs among the various matching modes. Using
8239 an asterisk is faster than a regular expression, and listing a few names
8240 explicitly probably is too. The use of a file or database lookup is expensive,
8241 but may be the only option if hundreds of names are required. Because the
8242 patterns are tested in order, it makes sense to put the most commonly matched
8247 .section "Host lists" "SECThostlist"
8248 .cindex "host list" "patterns in"
8249 .cindex "list" "host list"
8250 Host lists are used to control what remote hosts are allowed to do. For
8251 example, some hosts may be allowed to use the local host as a relay, and some
8252 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8253 two different ways, by name or by IP address. In a host list, some types of
8254 pattern are matched to a host name, and some are matched to an IP address.
8255 You need to be particularly careful with this when single-key lookups are
8256 involved, to ensure that the right value is being used as the key.
8259 .section "Special host list patterns" "SECID80"
8260 .cindex "empty item in hosts list"
8261 .cindex "host list" "empty string in"
8262 If a host list item is the empty string, it matches only when no remote host is
8263 involved. This is the case when a message is being received from a local
8264 process using SMTP on the standard input, that is, when a TCP/IP connection is
8267 .cindex "asterisk" "in host list"
8268 The special pattern &"*"& in a host list matches any host or no host. Neither
8269 the IP address nor the name is actually inspected.
8273 .section "Host list patterns that match by IP address" "SECThoslispatip"
8274 .cindex "host list" "matching IP addresses"
8275 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8276 the incoming address actually appears in the IPv6 host as
8277 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8278 list, it is converted into a traditional IPv4 address first. (Not all operating
8279 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8282 The following types of pattern in a host list check the remote host by
8283 inspecting its IP address:
8286 If the pattern is a plain domain name (not a regular expression, not starting
8287 with *, not a lookup of any kind), Exim calls the operating system function
8288 to find the associated IP address(es). Exim uses the newer
8289 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8290 This typically causes a forward DNS lookup of the name. The result is compared
8291 with the IP address of the subject host.
8293 If there is a temporary problem (such as a DNS timeout) with the host name
8294 lookup, a temporary error occurs. For example, if the list is being used in an
8295 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8296 temporary SMTP error code. If no IP address can be found for the host name,
8297 what happens is described in section &<<SECTbehipnot>>& below.
8300 .cindex "@ in a host list"
8301 If the pattern is &"@"&, the primary host name is substituted and used as a
8302 domain name, as just described.
8305 If the pattern is an IP address, it is matched against the IP address of the
8306 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8307 IPv6 addresses can be given in colon-separated format, but the colons have to
8308 be doubled so as not to be taken as item separators when the default list
8309 separator is used. IPv6 addresses are recognized even when Exim is compiled
8310 without IPv6 support. This means that if they appear in a host list on an
8311 IPv4-only host, Exim will not treat them as host names. They are just addresses
8312 that can never match a client host.
8315 .cindex "@[] in a host list"
8316 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8317 the local host. For example, if the local host is an IPv4 host with one
8318 interface address 10.45.23.56, these two ACL statements have the same effect:
8320 accept hosts = 127.0.0.1 : 10.45.23.56
8324 .cindex "CIDR notation"
8325 If the pattern is an IP address followed by a slash and a mask length (for
8326 example 10.11.42.0/24), it is matched against the IP address of the subject
8327 host under the given mask. This allows, an entire network of hosts to be
8328 included (or excluded) by a single item. The mask uses CIDR notation; it
8329 specifies the number of address bits that must match, starting from the most
8330 significant end of the address.
8332 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8333 of a range of addresses. It is the number of bits in the network portion of the
8334 address. The above example specifies a 24-bit netmask, so it matches all 256
8335 addresses in the 10.11.42.0 network. An item such as
8339 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8340 32 for an IPv4 address is the same as no mask at all; just a single address
8343 Here is another example which shows an IPv4 and an IPv6 network:
8345 recipient_unqualified_hosts = 192.168.0.0/16: \
8346 3ffe::ffff::836f::::/48
8348 The doubling of list separator characters applies only when these items
8349 appear inline in a host list. It is not required when indirecting via a file.
8352 recipient_unqualified_hosts = /opt/exim/unqualnets
8354 could make use of a file containing
8359 to have exactly the same effect as the previous example. When listing IPv6
8360 addresses inline, it is usually more convenient to use the facility for
8361 changing separator characters. This list contains the same two networks:
8363 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8366 The separator is changed to semicolon by the leading &"<;"& at the start of the
8372 .section "Host list patterns for single-key lookups by host address" &&&
8373 "SECThoslispatsikey"
8374 .cindex "host list" "lookup of IP address"
8375 When a host is to be identified by a single-key lookup of its complete IP
8376 address, the pattern takes this form:
8378 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8382 hosts_lookup = net-cdb;/hosts-by-ip.db
8384 The text form of the IP address of the subject host is used as the lookup key.
8385 IPv6 addresses are converted to an unabbreviated form, using lower case
8386 letters, with dots as separators because colon is the key terminator in
8387 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8388 quoting the keys, but this is a facility that was added later.] The data
8389 returned by the lookup is not used.
8391 .cindex "IP address" "masking"
8392 .cindex "host list" "masked IP address"
8393 Single-key lookups can also be performed using masked IP addresses, using
8394 patterns of this form:
8396 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8400 net24-dbm;/networks.db
8402 The IP address of the subject host is masked using <&'number'&> as the mask
8403 length. A textual string is constructed from the masked value, followed by the
8404 mask, and this is used as the lookup key. For example, if the host's IP address
8405 is 192.168.34.6, the key that is looked up for the above example is
8406 &"192.168.34.0/24"&.
8408 When an IPv6 address is converted to a string, dots are normally used instead
8409 of colons, so that keys in &(lsearch)& files need not contain colons (which
8410 terminate &(lsearch)& keys). This was implemented some time before the ability
8411 to quote keys was made available in &(lsearch)& files. However, the more
8412 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8413 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8414 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8415 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8416 addresses are always used.
8418 Ideally, it would be nice to tidy up this anomalous situation by changing to
8419 colons in all cases, given that quoting is now available for &(lsearch)&.
8420 However, this would be an incompatible change that might break some existing
8423 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8424 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8425 the former case the key strings include the mask value, whereas in the latter
8426 case the IP address is used on its own.
8430 .section "Host list patterns that match by host name" "SECThoslispatnam"
8431 .cindex "host" "lookup failures"
8432 .cindex "unknown host name"
8433 .cindex "host list" "matching host name"
8434 There are several types of pattern that require Exim to know the name of the
8435 remote host. These are either wildcard patterns or lookups by name. (If a
8436 complete hostname is given without any wildcarding, it is used to find an IP
8437 address to match against, as described in section &<<SECThoslispatip>>&
8440 If the remote host name is not already known when Exim encounters one of these
8441 patterns, it has to be found from the IP address.
8442 Although many sites on the Internet are conscientious about maintaining reverse
8443 DNS data for their hosts, there are also many that do not do this.
8444 Consequently, a name cannot always be found, and this may lead to unwanted
8445 effects. Take care when configuring host lists with wildcarded name patterns.
8446 Consider what will happen if a name cannot be found.
8448 Because of the problems of determining host names from IP addresses, matching
8449 against host names is not as common as matching against IP addresses.
8451 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8452 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8453 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8454 are done can be changed by setting the &%host_lookup_order%& option. For
8455 security, once Exim has found one or more names, it looks up the IP addresses
8456 for these names and compares them with the IP address that it started with.
8457 Only those names whose IP addresses match are accepted. Any other names are
8458 discarded. If no names are left, Exim behaves as if the host name cannot be
8459 found. In the most common case there is only one name and one IP address.
8461 There are some options that control what happens if a host name cannot be
8462 found. These are described in section &<<SECTbehipnot>>& below.
8464 .cindex "host" "alias for"
8465 .cindex "alias for host"
8466 As a result of aliasing, hosts may have more than one name. When processing any
8467 of the following types of pattern, all the host's names are checked:
8470 .cindex "asterisk" "in host list"
8471 If a pattern starts with &"*"& the remainder of the item must match the end of
8472 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8473 &'.b.c'&. This special simple form is provided because this is a very common
8474 requirement. Other kinds of wildcarding require the use of a regular
8477 .cindex "regular expressions" "in host list"
8478 .cindex "host list" "regular expression in"
8479 If the item starts with &"^"& it is taken to be a regular expression which is
8480 matched against the host name. Host names are case-independent, so this regular
8481 expression match is by default case-independent, but you can make it
8482 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8483 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8488 is a regular expression that matches either of the two hosts &'a.c.d'& or
8489 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8490 that backslash and dollar characters are not misinterpreted as part of the
8491 string expansion. The simplest way to do this is to use &`\N`& to mark that
8492 part of the string as non-expandable. For example:
8494 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8496 &*Warning*&: If you want to match a complete host name, you must include the
8497 &`$`& terminating metacharacter in the regular expression, as in the above
8498 example. Without it, a match at the start of the host name is all that is
8505 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8506 .cindex "host" "lookup failures, permanent"
8507 While processing a host list, Exim may need to look up an IP address from a
8508 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8509 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8510 behaviour when it fails to find the information it is seeking is the same.
8512 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8513 apply to temporary DNS errors, whose handling is described in the next section.
8515 .cindex "&`+include_unknown`&"
8516 .cindex "&`+ignore_unknown`&"
8517 Exim parses a host list from left to right. If it encounters a permanent
8518 lookup failure in any item in the host list before it has found a match,
8519 Exim treats it as a failure and the default behavior is as if the host
8520 does not match the list. This may not always be what you want to happen.
8521 To change Exim's behaviour, the special items &`+include_unknown`& or
8522 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8523 not recognized in an indirected file).
8526 If any item that follows &`+include_unknown`& requires information that
8527 cannot found, Exim behaves as if the host does match the list. For example,
8529 host_reject_connection = +include_unknown:*.enemy.ex
8531 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8532 any hosts whose name it cannot find.
8535 If any item that follows &`+ignore_unknown`& requires information that cannot
8536 be found, Exim ignores that item and proceeds to the rest of the list. For
8539 accept hosts = +ignore_unknown : friend.example : \
8542 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8543 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8544 name can be found for 192.168.4.5, it is rejected.
8547 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8548 list. The effect of each one lasts until the next, or until the end of the
8551 .section "Mixing wildcarded host names and addresses in host lists" &&&
8553 .cindex "host list" "mixing names and addresses in"
8555 This section explains the host/ip processing logic with the same concepts
8556 as the previous section, but specifically addresses what happens when a
8557 wildcarded hostname is one of the items in the hostlist.
8560 If you have name lookups or wildcarded host names and
8561 IP addresses in the same host list, you should normally put the IP
8562 addresses first. For example, in an ACL you could have:
8564 accept hosts = 10.9.8.7 : *.friend.example
8566 The reason you normally would order it this way lies in the
8567 left-to-right way that Exim processes lists. It can test IP addresses
8568 without doing any DNS lookups, but when it reaches an item that requires
8569 a host name, it fails if it cannot find a host name to compare with the
8570 pattern. If the above list is given in the opposite order, the
8571 &%accept%& statement fails for a host whose name cannot be found, even
8572 if its IP address is 10.9.8.7.
8575 If you really do want to do the name check first, and still recognize the IP
8576 address, you can rewrite the ACL like this:
8578 accept hosts = *.friend.example
8579 accept hosts = 10.9.8.7
8581 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8582 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8583 &`+ignore_unknown`&, which was discussed in depth in the first example in
8588 .section "Temporary DNS errors when looking up host information" &&&
8590 .cindex "host" "lookup failures, temporary"
8591 .cindex "&`+include_defer`&"
8592 .cindex "&`+ignore_defer`&"
8593 A temporary DNS lookup failure normally causes a defer action (except when
8594 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8595 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8596 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8597 section. These options should be used with care, probably only in non-critical
8598 host lists such as whitelists.
8602 .section "Host list patterns for single-key lookups by host name" &&&
8603 "SECThoslispatnamsk"
8604 .cindex "unknown host name"
8605 .cindex "host list" "matching host name"
8606 If a pattern is of the form
8608 <&'single-key-search-type'&>;<&'search-data'&>
8612 dbm;/host/accept/list
8614 a single-key lookup is performed, using the host name as its key. If the
8615 lookup succeeds, the host matches the item. The actual data that is looked up
8618 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8619 keys in the file, not IP addresses. If you want to do lookups based on IP
8620 addresses, you must precede the search type with &"net-"& (see section
8621 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8622 two items in the same list, one doing an address lookup and one doing a name
8623 lookup, both using the same file.
8627 .section "Host list patterns for query-style lookups" "SECID81"
8628 If a pattern is of the form
8630 <&'query-style-search-type'&>;<&'query'&>
8632 the query is obeyed, and if it succeeds, the host matches the item. The actual
8633 data that is looked up is not used. The variables &$sender_host_address$& and
8634 &$sender_host_name$& can be used in the query. For example:
8636 hosts_lookup = pgsql;\
8637 select ip from hostlist where ip='$sender_host_address'
8639 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8640 can use the &%sg%& expansion item to change this if you need to. If you want to
8641 use masked IP addresses in database queries, you can use the &%mask%& expansion
8644 If the query contains a reference to &$sender_host_name$&, Exim automatically
8645 looks up the host name if it has not already done so. (See section
8646 &<<SECThoslispatnam>>& for comments on finding host names.)
8648 Historical note: prior to release 4.30, Exim would always attempt to find a
8649 host name before running the query, unless the search type was preceded by
8650 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8651 still recognized for query-style lookups, but its presence or absence has no
8652 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8653 See section &<<SECThoslispatsikey>>&.)
8659 .section "Address lists" "SECTaddresslist"
8660 .cindex "list" "address list"
8661 .cindex "address list" "empty item"
8662 .cindex "address list" "patterns"
8663 Address lists contain patterns that are matched against mail addresses. There
8664 is one special case to be considered: the sender address of a bounce message is
8665 always empty. You can test for this by providing an empty item in an address
8666 list. For example, you can set up a router to process bounce messages by
8667 using this option setting:
8671 The presence of the colon creates an empty item. If you do not provide any
8672 data, the list is empty and matches nothing. The empty sender can also be
8673 detected by a regular expression that matches an empty string,
8674 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8676 Non-empty items in an address list can be straightforward email addresses. For
8679 senders = jbc@askone.example : hs@anacreon.example
8681 A certain amount of wildcarding is permitted. If a pattern contains an @
8682 character, but is not a regular expression and does not begin with a
8683 semicolon-terminated lookup type (described below), the local part of the
8684 subject address is compared with the local part of the pattern, which may start
8685 with an asterisk. If the local parts match, the domain is checked in exactly
8686 the same way as for a pattern in a domain list. For example, the domain can be
8687 wildcarded, refer to a named list, or be a lookup:
8689 deny senders = *@*.spamming.site:\
8690 *@+hostile_domains:\
8691 bozo@partial-lsearch;/list/of/dodgy/sites:\
8692 *@dbm;/bad/domains.db
8694 .cindex "local part" "starting with !"
8695 .cindex "address list" "local part starting with !"
8696 If a local part that begins with an exclamation mark is required, it has to be
8697 specified using a regular expression, because otherwise the exclamation mark is
8698 treated as a sign of negation, as is standard in lists.
8700 If a non-empty pattern that is not a regular expression or a lookup does not
8701 contain an @ character, it is matched against the domain part of the subject
8702 address. The only two formats that are recognized this way are a literal
8703 domain, or a domain pattern that starts with *. In both these cases, the effect
8704 is the same as if &`*@`& preceded the pattern. For example:
8706 deny senders = enemy.domain : *.enemy.domain
8709 The following kinds of more complicated address list pattern can match any
8710 address, including the empty address that is characteristic of bounce message
8714 .cindex "regular expressions" "in address list"
8715 .cindex "address list" "regular expression in"
8716 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8717 done against the complete address, with the pattern as the regular expression.
8718 You must take care that backslash and dollar characters are not misinterpreted
8719 as part of the string expansion. The simplest way to do this is to use &`\N`&
8720 to mark that part of the string as non-expandable. For example:
8722 deny senders = \N^.*this.*@example\.com$\N : \
8723 \N^\d{8}.+@spamhaus.example$\N : ...
8725 The &`\N`& sequences are removed by the expansion, so these items do indeed
8726 start with &"^"& by the time they are being interpreted as address patterns.
8729 .cindex "address list" "lookup for complete address"
8730 Complete addresses can be looked up by using a pattern that starts with a
8731 lookup type terminated by a semicolon, followed by the data for the lookup. For
8734 deny senders = cdb;/etc/blocked.senders : \
8735 mysql;select address from blocked where \
8736 address='${quote_mysql:$sender_address}'
8738 Both query-style and single-key lookup types can be used. For a single-key
8739 lookup type, Exim uses the complete address as the key. However, empty keys are
8740 not supported for single-key lookups, so a match against the empty address
8741 always fails. This restriction does not apply to query-style lookups.
8743 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8744 cannot be used, and is ignored if specified, with an entry being written to the
8746 .cindex "*@ with single-key lookup"
8747 However, you can configure lookup defaults, as described in section
8748 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8749 default. For example, with this lookup:
8751 accept senders = lsearch*@;/some/file
8753 the file could contains lines like this:
8755 user1@domain1.example
8758 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8761 nimrod@jaeger.example
8765 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8766 would mean that every address matches, thus rendering the test useless.
8768 &*Warning 2*&: Do not confuse these two kinds of item:
8770 deny recipients = dbm*@;/some/file
8771 deny recipients = *@dbm;/some/file
8773 The first does a whole address lookup, with defaulting, as just described,
8774 because it starts with a lookup type. The second matches the local part and
8775 domain independently, as described in a bullet point below.
8779 The following kinds of address list pattern can match only non-empty addresses.
8780 If the subject address is empty, a match against any of these pattern types
8785 .cindex "@@ with single-key lookup"
8786 .cindex "address list" "@@ lookup type"
8787 .cindex "address list" "split local part and domain"
8788 If a pattern starts with &"@@"& followed by a single-key lookup item
8789 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8790 split into a local part and a domain. The domain is looked up in the file. If
8791 it is not found, there is no match. If it is found, the data that is looked up
8792 from the file is treated as a colon-separated list of local part patterns, each
8793 of which is matched against the subject local part in turn.
8795 .cindex "asterisk" "in address list"
8796 The lookup may be a partial one, and/or one involving a search for a default
8797 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8798 patterns that are looked up can be regular expressions or begin with &"*"&, or
8799 even be further lookups. They may also be independently negated. For example,
8802 deny senders = @@dbm;/etc/reject-by-domain
8804 the data from which the DBM file is built could contain lines like
8806 baddomain.com: !postmaster : *
8808 to reject all senders except &%postmaster%& from that domain.
8810 .cindex "local part" "starting with !"
8811 If a local part that actually begins with an exclamation mark is required, it
8812 has to be specified using a regular expression. In &(lsearch)& files, an entry
8813 may be split over several lines by indenting the second and subsequent lines,
8814 but the separating colon must still be included at line breaks. White space
8815 surrounding the colons is ignored. For example:
8817 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8820 As in all colon-separated lists in Exim, a colon can be included in an item by
8823 If the last item in the list starts with a right angle-bracket, the remainder
8824 of the item is taken as a new key to look up in order to obtain a continuation
8825 list of local parts. The new key can be any sequence of characters. Thus one
8826 might have entries like
8828 aol.com: spammer1 : spammer 2 : >*
8829 xyz.com: spammer3 : >*
8832 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8833 local parts for all domains, in addition to the specific local parts listed for
8834 each domain. Of course, using this feature costs another lookup each time a
8835 chain is followed, but the effort needed to maintain the data is reduced.
8837 .cindex "loop" "in lookups"
8838 It is possible to construct loops using this facility, and in order to catch
8839 them, the chains may be no more than fifty items long.
8842 The @@<&'lookup'&> style of item can also be used with a query-style
8843 lookup, but in this case, the chaining facility is not available. The lookup
8844 can only return a single list of local parts.
8847 &*Warning*&: There is an important difference between the address list items
8848 in these two examples:
8851 senders = *@+my_list
8853 In the first one, &`my_list`& is a named address list, whereas in the second
8854 example it is a named domain list.
8859 .section "Case of letters in address lists" "SECTcasletadd"
8860 .cindex "case of local parts"
8861 .cindex "address list" "case forcing"
8862 .cindex "case forcing in address lists"
8863 Domains in email addresses are always handled caselessly, but for local parts
8864 case may be significant on some systems (see &%caseful_local_part%& for how
8865 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8866 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8867 blocking lists should be done in a case-independent manner. Since most address
8868 lists in Exim are used for this kind of control, Exim attempts to do this by
8871 The domain portion of an address is always lowercased before matching it to an
8872 address list. The local part is lowercased by default, and any string
8873 comparisons that take place are done caselessly. This means that the data in
8874 the address list itself, in files included as plain file names, and in any file
8875 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8876 keys in files that are looked up by a search type other than &(lsearch)& (which
8877 works caselessly) must be in lower case, because these lookups are not
8880 .cindex "&`+caseful`&"
8881 To allow for the possibility of caseful address list matching, if an item in
8882 an address list is the string &"+caseful"&, the original case of the local
8883 part is restored for any comparisons that follow, and string comparisons are no
8884 longer case-independent. This does not affect the domain, which remains in
8885 lower case. However, although independent matches on the domain alone are still
8886 performed caselessly, regular expressions that match against an entire address
8887 become case-sensitive after &"+caseful"& has been seen.
8891 .section "Local part lists" "SECTlocparlis"
8892 .cindex "list" "local part list"
8893 .cindex "local part" "list"
8894 Case-sensitivity in local part lists is handled in the same way as for address
8895 lists, as just described. The &"+caseful"& item can be used if required. In a
8896 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8897 set false, the subject is lowercased and the matching is initially
8898 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8899 matching in the local part list, but not elsewhere in the router. If
8900 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8901 option is case-sensitive from the start.
8903 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8904 comments are handled in the same way as address lists &-- they are recognized
8905 only if the # is preceded by white space or the start of the line.
8906 Otherwise, local part lists are matched in the same way as domain lists, except
8907 that the special items that refer to the local host (&`@`&, &`@[]`&,
8908 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8909 Refer to section &<<SECTdomainlist>>& for details of the other available item
8911 .ecindex IIDdohoadli
8916 . ////////////////////////////////////////////////////////////////////////////
8917 . ////////////////////////////////////////////////////////////////////////////
8919 .chapter "String expansions" "CHAPexpand"
8920 .scindex IIDstrexp "expansion" "of strings"
8921 Many strings in Exim's run time configuration are expanded before use. Some of
8922 them are expanded every time they are used; others are expanded only once.
8924 When a string is being expanded it is copied verbatim from left to right except
8925 when a dollar or backslash character is encountered. A dollar specifies the
8926 start of a portion of the string that is interpreted and replaced as described
8927 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8928 escape character, as described in the following section.
8930 Whether a string is expanded depends upon the context. Usually this is solely
8931 dependent upon the option for which a value is sought; in this documentation,
8932 options for which string expansion is performed are marked with † after
8933 the data type. ACL rules always expand strings. A couple of expansion
8934 conditions do not expand some of the brace-delimited branches, for security
8939 .section "Literal text in expanded strings" "SECTlittext"
8940 .cindex "expansion" "including literal text"
8941 An uninterpreted dollar can be included in an expanded string by putting a
8942 backslash in front of it. A backslash can be used to prevent any special
8943 character being treated specially in an expansion, including backslash itself.
8944 If the string appears in quotes in the configuration file, two backslashes are
8945 required because the quotes themselves cause interpretation of backslashes when
8946 the string is read in (see section &<<SECTstrings>>&).
8948 .cindex "expansion" "non-expandable substrings"
8949 A portion of the string can specified as non-expandable by placing it between
8950 two occurrences of &`\N`&. This is particularly useful for protecting regular
8951 expressions, which often contain backslashes and dollar signs. For example:
8953 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8955 On encountering the first &`\N`&, the expander copies subsequent characters
8956 without interpretation until it reaches the next &`\N`& or the end of the
8961 .section "Character escape sequences in expanded strings" "SECID82"
8962 .cindex "expansion" "escape sequences"
8963 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8964 expanded string is recognized as an escape sequence for the character newline,
8965 carriage return, or tab, respectively. A backslash followed by up to three
8966 octal digits is recognized as an octal encoding for a single character, and a
8967 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8970 These escape sequences are also recognized in quoted strings when they are read
8971 in. Their interpretation in expansions as well is useful for unquoted strings,
8972 and for other cases such as looked-up strings that are then expanded.
8975 .section "Testing string expansions" "SECID83"
8976 .cindex "expansion" "testing"
8977 .cindex "testing" "string expansion"
8979 Many expansions can be tested by calling Exim with the &%-be%& option. This
8980 takes the command arguments, or lines from the standard input if there are no
8981 arguments, runs them through the string expansion code, and writes the results
8982 to the standard output. Variables based on configuration values are set up, but
8983 since no message is being processed, variables such as &$local_part$& have no
8984 value. Nevertheless the &%-be%& option can be useful for checking out file and
8985 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8988 Exim gives up its root privilege when it is called with the &%-be%& option, and
8989 instead runs under the uid and gid it was called with, to prevent users from
8990 using &%-be%& for reading files to which they do not have access.
8993 If you want to test expansions that include variables whose values are taken
8994 from a message, there are two other options that can be used. The &%-bem%&
8995 option is like &%-be%& except that it is followed by a file name. The file is
8996 read as a message before doing the test expansions. For example:
8998 exim -bem /tmp/test.message '$h_subject:'
9000 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9001 Exim message identifier. For example:
9003 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9005 This loads the message from Exim's spool before doing the test expansions, and
9006 is therefore restricted to admin users.
9009 .section "Forced expansion failure" "SECTforexpfai"
9010 .cindex "expansion" "forced failure"
9011 A number of expansions that are described in the following section have
9012 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9013 (which are sometimes called &"curly brackets"&). Which of the two strings is
9014 used depends on some condition that is evaluated as part of the expansion. If,
9015 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9016 the entire string expansion fails in a way that can be detected by the code
9017 that requested the expansion. This is called &"forced expansion failure"&, and
9018 its consequences depend on the circumstances. In some cases it is no different
9019 from any other expansion failure, but in others a different action may be
9020 taken. Such variations are mentioned in the documentation of the option that is
9026 .section "Expansion items" "SECTexpansionitems"
9027 The following items are recognized in expanded strings. White space may be used
9028 between sub-items that are keywords or substrings enclosed in braces inside an
9029 outer set of braces, to improve readability. &*Warning*&: Within braces,
9030 white space is significant.
9033 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9034 .cindex "expansion" "variables"
9035 Substitute the contents of the named variable, for example:
9040 The second form can be used to separate the name from subsequent alphanumeric
9041 characters. This form (using braces) is available only for variables; it does
9042 &'not'& apply to message headers. The names of the variables are given in
9043 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9044 given, the expansion fails.
9046 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9047 .cindex "expansion" "operators"
9048 The string is first itself expanded, and then the operation specified by
9049 <&'op'&> is applied to it. For example:
9053 The string starts with the first character after the colon, which may be
9054 leading white space. A list of operators is given in section &<<SECTexpop>>&
9055 below. The operator notation is used for simple expansion items that have just
9056 one argument, because it reduces the number of braces and therefore makes the
9057 string easier to understand.
9059 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9060 This item inserts &"basic"& header lines. It is described with the &%header%&
9061 expansion item below.
9064 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9065 .cindex "expansion" "calling an acl"
9066 .cindex "&%acl%&" "call from expansion"
9067 The name and zero to nine argument strings are first expanded separately. The expanded
9068 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9069 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9070 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9071 and may use the variables; if another acl expansion is used the values
9072 are restored after it returns. If the ACL sets
9073 a value using a "message =" modifier and returns accept or deny, the value becomes
9074 the result of the expansion.
9075 If no message is set and the ACL returns accept or deny
9076 the expansion result is an empty string.
9077 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9080 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9081 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9082 .cindex "expansion" "extracting cerificate fields"
9083 .cindex "&%certextract%&" "certificate fields"
9084 .cindex "certificate" "extracting fields"
9085 The <&'certificate'&> must be a variable of type certificate.
9086 The field name is expanded and used to retrieve the relevant field from
9087 the certificate. Supported fields are:
9091 &`subject `& RFC4514 DN
9092 &`issuer `& RFC4514 DN
9097 &`subj_altname `& tagged list
9101 If the field is found,
9102 <&'string2'&> is expanded, and replaces the whole item;
9103 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9104 variable &$value$& contains the value that has been extracted. Afterwards, it
9105 is restored to any previous value it might have had.
9107 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9108 key is not found. If {<&'string2'&>} is also omitted, the value that was
9111 Some field names take optional modifiers, appended and separated by commas.
9113 The field selectors marked as "RFC4514" above
9114 output a Distinguished Name string which is
9116 parseable by Exim as a comma-separated tagged list
9117 (the exceptions being elements containing commas).
9118 RDN elements of a single type may be selected by
9119 a modifier of the type label; if so the expansion
9120 result is a list (newline-separated by default).
9121 The separator may be changed by another modifier of
9122 a right angle-bracket followed immediately by the new separator.
9123 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9125 The field selectors marked as "time" above
9126 take an optional modifier of "int"
9127 for which the result is the number of seconds since epoch.
9128 Otherwise the result is a human-readable string
9129 in the timezone selected by the main "timezone" option.
9131 The field selectors marked as "list" above return a list,
9132 newline-separated by default,
9133 (embedded separator characters in elements are doubled).
9134 The separator may be changed by a modifier of
9135 a right angle-bracket followed immediately by the new separator.
9137 The field selectors marked as "tagged" above
9138 prefix each list element with a type string and an equals sign.
9139 Elements of only one type may be selected by a modifier
9140 which is one of "dns", "uri" or "mail";
9141 if so the element tags are omitted.
9143 If not otherwise noted field values are presented in human-readable form.
9145 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9146 {*&<&'arg'&>&*}...}*&"
9148 This expansion dynamically loads and then calls a locally-written C function.
9149 This functionality is available only if Exim is compiled with
9153 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9154 object so that it doesn't reload the same object file in the same Exim process
9155 (but of course Exim does start new processes frequently).
9157 There may be from zero to eight arguments to the function. When compiling
9158 a local function that is to be called in this way, &_local_scan.h_& should be
9159 included. The Exim variables and functions that are defined by that API
9160 are also available for dynamically loaded functions. The function itself
9161 must have the following type:
9163 int dlfunction(uschar **yield, int argc, uschar *argv[])
9165 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9166 function should return one of the following values:
9168 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9169 into the expanded string that is being built.
9171 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9172 from &'yield'&, if it is set.
9174 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9175 taken from &'yield'& if it is set.
9177 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9179 When compiling a function that is to be used in this way with gcc,
9180 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9181 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9184 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9185 .cindex "expansion" "extracting value from environment"
9186 .cindex "environment" "values from"
9187 The key is first expanded separately, and leading and trailing white space
9189 This is then searched for as a name in the environment.
9190 If a variable is found then its value is placed in &$value$&
9191 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9193 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9194 appear, for example:
9196 ${env{USER}{$value} fail }
9198 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9199 {<&'string1'&>} must be present for &"fail"& to be recognized.
9201 If {<&'string2'&>} is omitted an empty string is substituted on
9203 If {<&'string1'&>} is omitted the search result is substituted on
9206 The environment is adjusted by the &%keep_environment%& and
9207 &%add_environment%& main section options.
9210 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9211 {*&<&'string3'&>&*}}*&"
9212 .cindex "expansion" "extracting substrings by key"
9213 .cindex "&%extract%&" "substrings by key"
9214 The key and <&'string1'&> are first expanded separately. Leading and trailing
9215 white space is removed from the key (but not from any of the strings). The key
9216 must not be empty and must not consist entirely of digits.
9217 The expanded <&'string1'&> must be of the form:
9219 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9222 where the equals signs and spaces (but not both) are optional. If any of the
9223 values contain white space, they must be enclosed in double quotes, and any
9224 values that are enclosed in double quotes are subject to escape processing as
9225 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9226 for the value that corresponds to the key. The search is case-insensitive. If
9227 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9228 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9229 variable &$value$& contains the value that has been extracted. Afterwards, it
9230 is restored to any previous value it might have had.
9232 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9233 key is not found. If {<&'string2'&>} is also omitted, the value that was
9234 extracted is used. Thus, for example, these two expansions are identical, and
9237 ${extract{gid}{uid=1984 gid=2001}}
9238 ${extract{gid}{uid=1984 gid=2001}{$value}}
9240 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9241 appear, for example:
9243 ${extract{Z}{A=... B=...}{$value} fail }
9245 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9246 {<&'string2'&>} must be present for &"fail"& to be recognized.
9249 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9250 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9251 .cindex "expansion" "extracting substrings by number"
9252 .cindex "&%extract%&" "substrings by number"
9253 The <&'number'&> argument must consist entirely of decimal digits,
9254 apart from leading and trailing white space, which is ignored.
9255 This is what distinguishes this form of &%extract%& from the previous kind. It
9256 behaves in the same way, except that, instead of extracting a named field, it
9257 extracts from <&'string1'&> the field whose number is given as the first
9258 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9259 <&'string3'&> as before.
9261 The fields in the string are separated by any one of the characters in the
9262 separator string. These may include space or tab characters.
9263 The first field is numbered one. If the number is negative, the fields are
9264 counted from the end of the string, with the rightmost one numbered -1. If the
9265 number given is zero, the entire string is returned. If the modulus of the
9266 number is greater than the number of fields in the string, the result is the
9267 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9268 provided. For example:
9270 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9274 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9276 yields &"99"&. Two successive separators mean that the field between them is
9277 empty (for example, the fifth field above).
9280 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9281 .cindex "list" "selecting by condition"
9282 .cindex "expansion" "selecting from list by condition"
9284 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9285 default, but the separator can be changed in the usual way. For each item
9286 in this list, its value is place in &$item$&, and then the condition is
9287 evaluated. If the condition is true, &$item$& is added to the output as an
9288 item in a new list; if the condition is false, the item is discarded. The
9289 separator used for the output list is the same as the one used for the
9290 input, but a separator setting is not included in the output. For example:
9292 ${filter{a:b:c}{!eq{$item}{b}}
9294 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9295 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9298 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9299 .cindex "hash function" "textual"
9300 .cindex "expansion" "textual hash"
9301 This is a textual hashing function, and was the first to be implemented in
9302 early versions of Exim. In current releases, there are other hashing functions
9303 (numeric, MD5, and SHA-1), which are described below.
9305 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9306 <&'n'&>. If you are using fixed values for these numbers, that is, if
9307 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9308 use the simpler operator notation that avoids some of the braces:
9310 ${hash_<n>_<m>:<string>}
9312 The second number is optional (in both notations). If <&'n'&> is greater than
9313 or equal to the length of the string, the expansion item returns the string.
9314 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9315 function to the string. The new string consists of characters taken from the
9316 first <&'m'&> characters of the string
9318 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9320 If <&'m'&> is not present the value 26 is used, so that only lower case
9321 letters appear. For example:
9323 &`$hash{3}{monty}} `& yields &`jmg`&
9324 &`$hash{5}{monty}} `& yields &`monty`&
9325 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9328 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9329 &*$h_*&<&'header&~name'&>&*:*&" &&&
9330 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9331 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9332 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9333 &*$rh_*&<&'header&~name'&>&*:*&"
9334 .cindex "expansion" "header insertion"
9335 .vindex "&$header_$&"
9336 .vindex "&$bheader_$&"
9337 .vindex "&$rheader_$&"
9338 .cindex "header lines" "in expansion strings"
9339 .cindex "header lines" "character sets"
9340 .cindex "header lines" "decoding"
9341 Substitute the contents of the named message header line, for example
9345 The newline that terminates a header line is not included in the expansion, but
9346 internal newlines (caused by splitting the header line over several physical
9347 lines) may be present.
9349 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9350 the data in the header line is interpreted.
9353 .cindex "white space" "in header lines"
9354 &%rheader%& gives the original &"raw"& content of the header line, with no
9355 processing at all, and without the removal of leading and trailing white space.
9358 .cindex "base64 encoding" "in header lines"
9359 &%bheader%& removes leading and trailing white space, and then decodes base64
9360 or quoted-printable MIME &"words"& within the header text, but does no
9361 character set translation. If decoding of what looks superficially like a MIME
9362 &"word"& fails, the raw string is returned. If decoding
9363 .cindex "binary zero" "in header line"
9364 produces a binary zero character, it is replaced by a question mark &-- this is
9365 what Exim does for binary zeros that are actually received in header lines.
9368 &%header%& tries to translate the string as decoded by &%bheader%& to a
9369 standard character set. This is an attempt to produce the same string as would
9370 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9371 returned. Translation is attempted only on operating systems that support the
9372 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9373 a system Makefile or in &_Local/Makefile_&.
9376 In a filter file, the target character set for &%header%& can be specified by a
9377 command of the following form:
9379 headers charset "UTF-8"
9381 This command affects all references to &$h_$& (or &$header_$&) expansions in
9382 subsequently obeyed filter commands. In the absence of this command, the target
9383 character set in a filter is taken from the setting of the &%headers_charset%&
9384 option in the runtime configuration. The value of this option defaults to the
9385 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9388 Header names follow the syntax of RFC 2822, which states that they may contain
9389 any printing characters except space and colon. Consequently, curly brackets
9390 &'do not'& terminate header names, and should not be used to enclose them as
9391 if they were variables. Attempting to do so causes a syntax error.
9393 Only header lines that are common to all copies of a message are visible to
9394 this mechanism. These are the original header lines that are received with the
9395 message, and any that are added by an ACL statement or by a system
9396 filter. Header lines that are added to a particular copy of a message by a
9397 router or transport are not accessible.
9399 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9400 before the DATA ACL, because the header structure is not set up until the
9401 message is received. Header lines that are added in a RCPT ACL (for example)
9402 are saved until the message's incoming header lines are available, at which
9403 point they are added. When a DATA ACL is running, however, header lines added
9404 by earlier ACLs are visible.
9406 Upper case and lower case letters are synonymous in header names. If the
9407 following character is white space, the terminating colon may be omitted, but
9408 this is not recommended, because you may then forget it when it is needed. When
9409 white space terminates the header name, this white space is included in the
9410 expanded string. If the message does not contain the given header, the
9411 expansion item is replaced by an empty string. (See the &%def%& condition in
9412 section &<<SECTexpcond>>& for a means of testing for the existence of a
9415 If there is more than one header with the same name, they are all concatenated
9416 to form the substitution string, up to a maximum length of 64K. Unless
9417 &%rheader%& is being used, leading and trailing white space is removed from
9418 each header before concatenation, and a completely empty header is ignored. A
9419 newline character is then inserted between non-empty headers, but there is no
9420 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9421 those headers that contain lists of addresses, a comma is also inserted at the
9422 junctions between headers. This does not happen for the &%rheader%& expansion.
9425 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9426 .cindex "expansion" "hmac hashing"
9428 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9429 shared secret and some text into a message authentication code, as specified in
9430 RFC 2104. This differs from &`${md5:secret_text...}`& or
9431 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9432 cryptographic hash, allowing for authentication that is not possible with MD5
9433 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9434 present. For example:
9436 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9438 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9441 dd97e3ba5d1a61b5006108f8c8252953
9443 As an example of how this might be used, you might put in the main part of
9444 an Exim configuration:
9446 SPAMSCAN_SECRET=cohgheeLei2thahw
9448 In a router or a transport you could then have:
9451 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9452 ${hmac{md5}{SPAMSCAN_SECRET}\
9453 {${primary_hostname},${message_exim_id},$h_message-id:}}
9455 Then given a message, you can check where it was scanned by looking at the
9456 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9457 this header line is authentic by recomputing the authentication code from the
9458 host name, message ID and the &'Message-id:'& header line. This can be done
9459 using Exim's &%-be%& option, or by other means, for example by using the
9460 &'hmac_md5_hex()'& function in Perl.
9463 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9464 .cindex "expansion" "conditional"
9465 .cindex "&%if%&, expansion item"
9466 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9467 item; otherwise <&'string2'&> is used. The available conditions are described
9468 in section &<<SECTexpcond>>& below. For example:
9470 ${if eq {$local_part}{postmaster} {yes}{no} }
9472 The second string need not be present; if it is not and the condition is not
9473 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9474 be present instead of the second string (without any curly brackets). In this
9475 case, the expansion is forced to fail if the condition is not true (see section
9476 &<<SECTforexpfai>>&).
9478 If both strings are omitted, the result is the string &`true`& if the condition
9479 is true, and the empty string if the condition is false. This makes it less
9480 cumbersome to write custom ACL and router conditions. For example, instead of
9482 condition = ${if >{$acl_m4}{3}{true}{false}}
9486 condition = ${if >{$acl_m4}{3}}
9491 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9492 .cindex expansion "imap folder"
9493 .cindex "&%imapfolder%& expansion item"
9494 This item converts a (possibly multilevel, or with non-ASCII characters)
9495 folder specification to a Maildir name for filesystem use.
9496 For information on internationalisation support see &<<SECTi18nMDA>>&.
9500 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9501 .cindex "expansion" "string truncation"
9502 .cindex "&%length%& expansion item"
9503 The &%length%& item is used to extract the initial portion of a string. Both
9504 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9505 you are using a fixed value for the number, that is, if <&'string1'&> does not
9506 change when expanded, you can use the simpler operator notation that avoids
9509 ${length_<n>:<string>}
9511 The result of this item is either the first <&'n'&> characters or the whole
9512 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9513 &%strlen%&, which gives the length of a string.
9516 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9517 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9518 .cindex "expansion" "extracting list elements by number"
9519 .cindex "&%listextract%&" "extract list elements by number"
9520 .cindex "list" "extracting elements by number"
9521 The <&'number'&> argument must consist entirely of decimal digits,
9522 apart from an optional leading minus,
9523 and leading and trailing white space (which is ignored).
9525 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9526 default, but the separator can be changed in the usual way.
9528 The first field of the list is numbered one.
9529 If the number is negative, the fields are
9530 counted from the end of the list, with the rightmost one numbered -1.
9531 The numbered element of the list is extracted and placed in &$value$&,
9532 then <&'string2'&> is expanded as the result.
9534 If the modulus of the
9535 number is zero or greater than the number of fields in the string,
9536 the result is the expansion of <&'string3'&>.
9540 ${listextract{2}{x:42:99}}
9544 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9546 yields &"result: 42"&.
9548 If {<&'string3'&>} is omitted, an empty string is used for string3.
9549 If {<&'string2'&>} is also omitted, the value that was
9551 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9554 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9555 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9556 This is the first of one of two different types of lookup item, which are both
9557 described in the next item.
9559 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9560 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9561 .cindex "expansion" "lookup in"
9562 .cindex "file" "lookups"
9563 .cindex "lookup" "in expanded string"
9564 The two forms of lookup item specify data lookups in files and databases, as
9565 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9566 lookups, and the second is used for query-style lookups. The <&'key'&>,
9567 <&'file'&>, and <&'query'&> strings are expanded before use.
9569 If there is any white space in a lookup item which is part of a filter command,
9570 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9571 other place where white space is significant, the lookup item must be enclosed
9572 in double quotes. The use of data lookups in users' filter files may be locked
9573 out by the system administrator.
9576 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9577 During its expansion, the variable &$value$& contains the data returned by the
9578 lookup. Afterwards it reverts to the value it had previously (at the outer
9579 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9580 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9581 string on failure. If <&'string2'&> is provided, it can itself be a nested
9582 lookup, thus providing a mechanism for looking up a default value when the
9583 original lookup fails.
9585 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9586 data for the outer lookup while the parameters of the second lookup are
9587 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9588 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9589 appear, and in this case, if the lookup fails, the entire expansion is forced
9590 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9591 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9592 successful lookup, and nothing in the case of failure.
9594 For single-key lookups, the string &"partial"& is permitted to precede the
9595 search type in order to do partial matching, and * or *@ may follow a search
9596 type to request default lookups if the key does not match (see sections
9597 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9599 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9600 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9601 and non-wild parts of the key during the expansion of the replacement text.
9602 They return to their previous values at the end of the lookup item.
9604 This example looks up the postmaster alias in the conventional alias file:
9606 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9608 This example uses NIS+ to look up the full name of the user corresponding to
9609 the local part of an address, forcing the expansion to fail if it is not found:
9611 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9616 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9617 .cindex "expansion" "list creation"
9619 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9620 default, but the separator can be changed in the usual way. For each item
9621 in this list, its value is place in &$item$&, and then <&'string2'&> is
9622 expanded and added to the output as an item in a new list. The separator used
9623 for the output list is the same as the one used for the input, but a separator
9624 setting is not included in the output. For example:
9626 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9628 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9629 value of &$item$& is restored to what it was before. See also the &*filter*&
9630 and &*reduce*& expansion items.
9632 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9633 .cindex "expansion" "numeric hash"
9634 .cindex "hash function" "numeric"
9635 The three strings are expanded; the first two must yield numbers. Call them
9636 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9637 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9638 can use the simpler operator notation that avoids some of the braces:
9640 ${nhash_<n>_<m>:<string>}
9642 The second number is optional (in both notations). If there is only one number,
9643 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9644 processed by a div/mod hash function that returns two numbers, separated by a
9645 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9648 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9650 returns the string &"6/33"&.
9654 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9655 .cindex "Perl" "use in expanded string"
9656 .cindex "expansion" "calling Perl from"
9657 This item is available only if Exim has been built to include an embedded Perl
9658 interpreter. The subroutine name and the arguments are first separately
9659 expanded, and then the Perl subroutine is called with those arguments. No
9660 additional arguments need be given; the maximum number permitted, including the
9661 name of the subroutine, is nine.
9663 The return value of the subroutine is inserted into the expanded string, unless
9664 the return value is &%undef%&. In that case, the expansion fails in the same
9665 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9666 Whatever you return is evaluated in a scalar context. For example, if you
9667 return the name of a Perl vector, the return value is the size of the vector,
9670 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9671 with the error message that was passed to &%die%&. More details of the embedded
9672 Perl facility are given in chapter &<<CHAPperl>>&.
9674 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9675 out the use of this expansion item in filter files.
9678 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9679 .cindex "&%prvs%& expansion item"
9680 The first argument is a complete email address and the second is secret
9681 keystring. The third argument, specifying a key number, is optional. If absent,
9682 it defaults to 0. The result of the expansion is a prvs-signed email address,
9683 to be typically used with the &%return_path%& option on an &(smtp)& transport
9684 as part of a bounce address tag validation (BATV) scheme. For more discussion
9685 and an example, see section &<<SECTverifyPRVS>>&.
9687 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9688 {*&<&'string'&>&*}}*&"
9689 .cindex "&%prvscheck%& expansion item"
9690 This expansion item is the complement of the &%prvs%& item. It is used for
9691 checking prvs-signed addresses. If the expansion of the first argument does not
9692 yield a syntactically valid prvs-signed address, the whole item expands to the
9693 empty string. When the first argument does expand to a syntactically valid
9694 prvs-signed address, the second argument is expanded, with the prvs-decoded
9695 version of the address and the key number extracted from the address in the
9696 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9698 These two variables can be used in the expansion of the second argument to
9699 retrieve the secret. The validity of the prvs-signed address is then checked
9700 against the secret. The result is stored in the variable &$prvscheck_result$&,
9701 which is empty for failure or &"1"& for success.
9703 The third argument is optional; if it is missing, it defaults to an empty
9704 string. This argument is now expanded. If the result is an empty string, the
9705 result of the expansion is the decoded version of the address. This is the case
9706 whether or not the signature was valid. Otherwise, the result of the expansion
9707 is the expansion of the third argument.
9709 All three variables can be used in the expansion of the third argument.
9710 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9711 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9713 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9714 .cindex "expansion" "inserting an entire file"
9715 .cindex "file" "inserting into expansion"
9716 .cindex "&%readfile%& expansion item"
9717 The file name and end-of-line string are first expanded separately. The file is
9718 then read, and its contents replace the entire item. All newline characters in
9719 the file are replaced by the end-of-line string if it is present. Otherwise,
9720 newlines are left in the string.
9721 String expansion is not applied to the contents of the file. If you want this,
9722 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9723 the string expansion fails.
9725 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9726 locks out the use of this expansion item in filter files.
9730 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9731 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9732 .cindex "expansion" "inserting from a socket"
9733 .cindex "socket, use of in expansion"
9734 .cindex "&%readsocket%& expansion item"
9735 This item inserts data from a Unix domain or TCP socket into the expanded
9736 string. The minimal way of using it uses just two arguments, as in these
9739 ${readsocket{/socket/name}{request string}}
9740 ${readsocket{inet:some.host:1234}{request string}}
9742 For a Unix domain socket, the first substring must be the path to the socket.
9743 For an Internet socket, the first substring must contain &`inet:`& followed by
9744 a host name or IP address, followed by a colon and a port, which can be a
9745 number or the name of a TCP port in &_/etc/services_&. An IP address may
9746 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9749 ${readsocket{inet:[::1]:1234}{request string}}
9751 Only a single host name may be given, but if looking it up yields more than
9752 one IP address, they are each tried in turn until a connection is made. For
9753 both kinds of socket, Exim makes a connection, writes the request string
9754 unless it is an empty string; and no terminating NUL is ever sent)
9755 and reads from the socket until an end-of-file
9756 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9757 extend what can be done. Firstly, you can vary the timeout. For example:
9759 ${readsocket{/socket/name}{request string}{3s}}
9761 A fourth argument allows you to change any newlines that are in the data
9762 that is read, in the same way as for &%readfile%& (see above). This example
9763 turns them into spaces:
9765 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9767 As with all expansions, the substrings are expanded before the processing
9768 happens. Errors in these sub-expansions cause the expansion to fail. In
9769 addition, the following errors can occur:
9772 Failure to create a socket file descriptor;
9774 Failure to connect the socket;
9776 Failure to write the request string;
9778 Timeout on reading from the socket.
9781 By default, any of these errors causes the expansion to fail. However, if
9782 you supply a fifth substring, it is expanded and used when any of the above
9783 errors occurs. For example:
9785 ${readsocket{/socket/name}{request string}{3s}{\n}\
9788 You can test for the existence of a Unix domain socket by wrapping this
9789 expansion in &`${if exists`&, but there is a race condition between that test
9790 and the actual opening of the socket, so it is safer to use the fifth argument
9791 if you want to be absolutely sure of avoiding an expansion error for a
9792 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9794 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9795 locks out the use of this expansion item in filter files.
9798 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9799 .cindex "expansion" "reducing a list to a scalar"
9800 .cindex "list" "reducing to a scalar"
9803 This operation reduces a list to a single, scalar string. After expansion,
9804 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9805 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9806 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9807 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9808 them. The result of that expansion is assigned to &$value$& before the next
9809 iteration. When the end of the list is reached, the final value of &$value$& is
9810 added to the expansion output. The &*reduce*& expansion item can be used in a
9811 number of ways. For example, to add up a list of numbers:
9813 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9815 The result of that expansion would be &`6`&. The maximum of a list of numbers
9818 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9820 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9821 restored to what they were before. See also the &*filter*& and &*map*&
9824 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9825 This item inserts &"raw"& header lines. It is described with the &%header%&
9826 expansion item above.
9828 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9829 {*&<&'string2'&>&*}}*&"
9830 .cindex "expansion" "running a command"
9831 .cindex "&%run%& expansion item"
9832 The command and its arguments are first expanded as one string. The string is
9833 split apart into individual arguments by spaces, and then the command is run
9834 in a separate process, but under the same uid and gid. As in other command
9835 executions from Exim, a shell is not used by default. If the command requires
9836 a shell, you must explicitly code it.
9838 Since the arguments are split by spaces, when there is a variable expansion
9839 which has an empty result, it will cause the situation that the argument will
9840 simply be omitted when the program is actually executed by Exim. If the
9841 script/program requires a specific number of arguments and the expanded
9842 variable could possibly result in this empty expansion, the variable must be
9843 quoted. This is more difficult if the expanded variable itself could result
9844 in a string containing quotes, because it would interfere with the quotes
9845 around the command arguments. A possible guard against this is to wrap the
9846 variable in the &%sg%& operator to change any quote marks to some other
9849 The standard input for the command exists, but is empty. The standard output
9850 and standard error are set to the same file descriptor.
9851 .cindex "return code" "from &%run%& expansion"
9853 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9854 and replaces the entire item; during this expansion, the standard output/error
9855 from the command is in the variable &$value$&. If the command fails,
9856 <&'string2'&>, if present, is expanded and used. Once again, during the
9857 expansion, the standard output/error from the command is in the variable
9860 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9861 can be the word &"fail"& (not in braces) to force expansion failure if the
9862 command does not succeed. If both strings are omitted, the result is contents
9863 of the standard output/error on success, and nothing on failure.
9865 .vindex "&$run_in_acl$&"
9866 The standard output/error of the command is put in the variable &$value$&.
9867 In this ACL example, the output of a command is logged for the admin to
9870 warn condition = ${run{/usr/bin/id}{yes}{no}}
9871 log_message = Output of id: $value
9873 If the command requires shell idioms, such as the > redirect operator, the
9874 shell must be invoked directly, such as with:
9876 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9880 The return code from the command is put in the variable &$runrc$&, and this
9881 remains set afterwards, so in a filter file you can do things like this:
9883 if "${run{x y z}{}}$runrc" is 1 then ...
9884 elif $runrc is 2 then ...
9888 If execution of the command fails (for example, the command does not exist),
9889 the return code is 127 &-- the same code that shells use for non-existent
9892 &*Warning*&: In a router or transport, you cannot assume the order in which
9893 option values are expanded, except for those preconditions whose order of
9894 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9895 by the expansion of one option, and use it in another.
9897 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9898 out the use of this expansion item in filter files.
9901 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9902 .cindex "expansion" "string substitution"
9903 .cindex "&%sg%& expansion item"
9904 This item works like Perl's substitution operator (s) with the global (/g)
9905 option; hence its name. However, unlike the Perl equivalent, Exim does not
9906 modify the subject string; instead it returns the modified string for insertion
9907 into the overall expansion. The item takes three arguments: the subject string,
9908 a regular expression, and a substitution string. For example:
9910 ${sg{abcdefabcdef}{abc}{xyz}}
9912 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9913 if any $ or \ characters are required in the regular expression or in the
9914 substitution string, they have to be escaped. For example:
9916 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9918 yields &"defabc"&, and
9920 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9922 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9923 the regular expression from string expansion.
9927 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
9928 .cindex sorting "a list"
9929 .cindex list sorting
9930 .cindex expansion "list sorting"
9931 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9932 default, but the separator can be changed in the usual way.
9933 The <&'comparator'&> argument is interpreted as the operator
9934 of a two-argument expansion condition.
9935 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
9936 The comparison should return true when applied to two values
9937 if the first value should sort before the second value.
9938 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
9939 the element being placed in &$item$&,
9940 to give values for comparison.
9942 The item result is a sorted list,
9943 with the original list separator,
9944 of the list elements (in full) of the original.
9948 ${sort{3:2:1:4}{<}{$item}}
9950 sorts a list of numbers, and
9952 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
9954 will sort an MX lookup into priority order.
9957 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9958 .cindex "&%substr%& expansion item"
9959 .cindex "substring extraction"
9960 .cindex "expansion" "substring extraction"
9961 The three strings are expanded; the first two must yield numbers. Call them
9962 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9963 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9964 can use the simpler operator notation that avoids some of the braces:
9966 ${substr_<n>_<m>:<string>}
9968 The second number is optional (in both notations).
9969 If it is absent in the simpler format, the preceding underscore must also be
9972 The &%substr%& item can be used to extract more general substrings than
9973 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9974 length required. For example
9976 ${substr{3}{2}{$local_part}}
9978 If the starting offset is greater than the string length the result is the
9979 null string; if the length plus starting offset is greater than the string
9980 length, the result is the right-hand part of the string, starting from the
9981 given offset. The first character in the string has offset zero.
9983 The &%substr%& expansion item can take negative offset values to count
9984 from the right-hand end of its operand. The last character is offset -1, the
9985 second-last is offset -2, and so on. Thus, for example,
9987 ${substr{-5}{2}{1234567}}
9989 yields &"34"&. If the absolute value of a negative offset is greater than the
9990 length of the string, the substring starts at the beginning of the string, and
9991 the length is reduced by the amount of overshoot. Thus, for example,
9993 ${substr{-5}{2}{12}}
9995 yields an empty string, but
9997 ${substr{-3}{2}{12}}
10001 When the second number is omitted from &%substr%&, the remainder of the string
10002 is taken if the offset is positive. If it is negative, all characters in the
10003 string preceding the offset point are taken. For example, an offset of -1 and
10004 no length, as in these semantically identical examples:
10007 ${substr{-1}{abcde}}
10009 yields all but the last character of the string, that is, &"abcd"&.
10013 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10014 {*&<&'replacements'&>&*}}*&"
10015 .cindex "expansion" "character translation"
10016 .cindex "&%tr%& expansion item"
10017 This item does single-character translation on its subject string. The second
10018 argument is a list of characters to be translated in the subject string. Each
10019 matching character is replaced by the corresponding character from the
10020 replacement list. For example
10022 ${tr{abcdea}{ac}{13}}
10024 yields &`1b3de1`&. If there are duplicates in the second character string, the
10025 last occurrence is used. If the third string is shorter than the second, its
10026 last character is replicated. However, if it is empty, no translation takes
10032 .section "Expansion operators" "SECTexpop"
10033 .cindex "expansion" "operators"
10034 For expansion items that perform transformations on a single argument string,
10035 the &"operator"& notation is used because it is simpler and uses fewer braces.
10036 The substring is first expanded before the operation is applied to it. The
10037 following operations can be performed:
10040 .vitem &*${address:*&<&'string'&>&*}*&
10041 .cindex "expansion" "RFC 2822 address handling"
10042 .cindex "&%address%& expansion item"
10043 The string is interpreted as an RFC 2822 address, as it might appear in a
10044 header line, and the effective address is extracted from it. If the string does
10045 not parse successfully, the result is empty.
10048 .vitem &*${addresses:*&<&'string'&>&*}*&
10049 .cindex "expansion" "RFC 2822 address handling"
10050 .cindex "&%addresses%& expansion item"
10051 The string (after expansion) is interpreted as a list of addresses in RFC
10052 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10053 operative address (&'local-part@domain'&) is extracted from each item, and the
10054 result of the expansion is a colon-separated list, with appropriate
10055 doubling of colons should any happen to be present in the email addresses.
10056 Syntactically invalid RFC2822 address items are omitted from the output.
10058 It is possible to specify a character other than colon for the output
10059 separator by starting the string with > followed by the new separator
10060 character. For example:
10062 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10064 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
10065 expansion item, which extracts the working address from a single RFC2822
10066 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
10069 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10070 a strict interpretation of header line formatting. Exim parses the bare,
10071 unquoted portion of an email address and if it finds a comma, treats it as an
10072 email address separator. For the example header line:
10074 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10076 The first example below demonstrates that Q-encoded email addresses are parsed
10077 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10078 It does not see the comma because it's still encoded as "=2C". The second
10079 example below is passed the contents of &`$header_from:`&, meaning it gets
10080 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10081 The third example shows that the presence of a comma is skipped when it is
10084 # exim -be '${addresses:From: \
10085 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10087 # exim -be '${addresses:From: Last, First <user@example.com>}'
10088 Last:user@example.com
10089 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10093 .vitem &*${base62:*&<&'digits'&>&*}*&
10094 .cindex "&%base62%& expansion item"
10095 .cindex "expansion" "conversion to base 62"
10096 The string must consist entirely of decimal digits. The number is converted to
10097 base 62 and output as a string of six characters, including leading zeros. In
10098 the few operating environments where Exim uses base 36 instead of base 62 for
10099 its message identifiers (because those systems do not have case-sensitive file
10100 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
10101 be absolutely clear: this is &'not'& base64 encoding.
10103 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10104 .cindex "&%base62d%& expansion item"
10105 .cindex "expansion" "conversion to base 62"
10106 The string must consist entirely of base-62 digits, or, in operating
10107 environments where Exim uses base 36 instead of base 62 for its message
10108 identifiers, base-36 digits. The number is converted to decimal and output as a
10111 .vitem &*${base64:*&<&'string'&>&*}*&
10112 .cindex "expansion" "base64 encoding"
10113 .cindex "base64 encoding" "in string expansion"
10114 .cindex "&%base64%& expansion item"
10115 .cindex certificate "base64 of DER"
10116 This operator converts a string into one that is base64 encoded.
10118 If the string is a single variable of type certificate,
10119 returns the base64 encoding of the DER form of the certificate.
10122 .vitem &*${base64d:*&<&'string'&>&*}*&
10123 .cindex "expansion" "base64 decoding"
10124 .cindex "base64 decoding" "in string expansion"
10125 .cindex "&%base64d%& expansion item"
10126 This operator converts a base64-encoded string into the un-coded form.
10129 .vitem &*${domain:*&<&'string'&>&*}*&
10130 .cindex "domain" "extraction"
10131 .cindex "expansion" "domain extraction"
10132 The string is interpreted as an RFC 2822 address and the domain is extracted
10133 from it. If the string does not parse successfully, the result is empty.
10136 .vitem &*${escape:*&<&'string'&>&*}*&
10137 .cindex "expansion" "escaping non-printing characters"
10138 .cindex "&%escape%& expansion item"
10139 If the string contains any non-printing characters, they are converted to
10140 escape sequences starting with a backslash. Whether characters with the most
10141 significant bit set (so-called &"8-bit characters"&) count as printing or not
10142 is controlled by the &%print_topbitchars%& option.
10145 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10146 .cindex "expansion" "expression evaluation"
10147 .cindex "expansion" "arithmetic expression"
10148 .cindex "&%eval%& expansion item"
10149 These items supports simple arithmetic and bitwise logical operations in
10150 expansion strings. The string (after expansion) must be a conventional
10151 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10152 logical operators, and parentheses. All operations are carried out using
10153 integer arithmetic. The operator priorities are as follows (the same as in the
10154 C programming language):
10156 .irow &'highest:'& "not (~), negate (-)"
10157 .irow "" "multiply (*), divide (/), remainder (%)"
10158 .irow "" "plus (+), minus (-)"
10159 .irow "" "shift-left (<<), shift-right (>>)"
10160 .irow "" "and (&&)"
10162 .irow &'lowest:'& "or (|)"
10164 Binary operators with the same priority are evaluated from left to right. White
10165 space is permitted before or after operators.
10167 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10168 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10169 decimal, even if they start with a leading zero; hexadecimal numbers are not
10170 permitted. This can be useful when processing numbers extracted from dates or
10171 times, which often do have leading zeros.
10173 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10175 respectively. Negative numbers are supported. The result of the computation is
10176 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10179 &`${eval:1+1} `& yields 2
10180 &`${eval:1+2*3} `& yields 7
10181 &`${eval:(1+2)*3} `& yields 9
10182 &`${eval:2+42%5} `& yields 4
10183 &`${eval:0xc&5} `& yields 4
10184 &`${eval:0xc|5} `& yields 13
10185 &`${eval:0xc^5} `& yields 9
10186 &`${eval:0xc>>1} `& yields 6
10187 &`${eval:0xc<<1} `& yields 24
10188 &`${eval:~255&0x1234} `& yields 4608
10189 &`${eval:-(~255&0x1234)} `& yields -4608
10192 As a more realistic example, in an ACL you might have
10194 deny message = Too many bad recipients
10197 {>{$rcpt_count}{10}} \
10200 {$recipients_count} \
10201 {${eval:$rcpt_count/2}} \
10205 The condition is true if there have been more than 10 RCPT commands and
10206 fewer than half of them have resulted in a valid recipient.
10209 .vitem &*${expand:*&<&'string'&>&*}*&
10210 .cindex "expansion" "re-expansion of substring"
10211 The &%expand%& operator causes a string to be expanded for a second time. For
10214 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10216 first looks up a string in a file while expanding the operand for &%expand%&,
10217 and then re-expands what it has found.
10220 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10222 .cindex "UTF-8" "conversion from"
10223 .cindex "expansion" "UTF-8 conversion"
10224 .cindex "&%from_utf8%& expansion item"
10225 The world is slowly moving towards Unicode, although there are no standards for
10226 email yet. However, other applications (including some databases) are starting
10227 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10228 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10229 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10230 the result is an undefined sequence of bytes.
10232 Unicode code points with values less than 256 are compatible with ASCII and
10233 ISO-8859-1 (also known as Latin-1).
10234 For example, character 169 is the copyright symbol in both cases, though the
10235 way it is encoded is different. In UTF-8, more than one byte is needed for
10236 characters with code values greater than 127, whereas ISO-8859-1 is a
10237 single-byte encoding (but thereby limited to 256 characters). This makes
10238 translation from UTF-8 to ISO-8859-1 straightforward.
10241 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10242 .cindex "hash function" "textual"
10243 .cindex "expansion" "textual hash"
10244 The &%hash%& operator is a simpler interface to the hashing function that can
10245 be used when the two parameters are fixed numbers (as opposed to strings that
10246 change when expanded). The effect is the same as
10248 ${hash{<n>}{<m>}{<string>}}
10250 See the description of the general &%hash%& item above for details. The
10251 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10255 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10256 .cindex "base64 encoding" "conversion from hex"
10257 .cindex "expansion" "hex to base64"
10258 .cindex "&%hex2b64%& expansion item"
10259 This operator converts a hex string into one that is base64 encoded. This can
10260 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10264 .vitem &*${hexquote:*&<&'string'&>&*}*&
10265 .cindex "quoting" "hex-encoded unprintable characters"
10266 .cindex "&%hexquote%& expansion item"
10267 This operator converts non-printable characters in a string into a hex
10268 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10269 as is, and other byte values are converted to &`\xNN`&, for example a
10270 byte value 127 is converted to &`\x7f`&.
10273 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10274 .cindex "&%ipv6denorm%& expansion item"
10275 .cindex "IP address" normalisation
10276 This expands an IPv6 address to a full eight-element colon-separated set
10277 of hex digits including leading zeroes.
10278 A trailing ipv4-style dotted-decimal set is converted to hex.
10279 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10281 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10282 .cindex "&%ipv6norm%& expansion item"
10283 .cindex "IP address" normalisation
10284 .cindex "IP address" "canonical form"
10285 This converts an IPv6 address to canonical form.
10286 Leading zeroes of groups are omitted, and the longest
10287 set of zero-valued groups is replaced with a double colon.
10288 A trailing ipv4-style dotted-decimal set is converted to hex.
10289 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10292 .vitem &*${lc:*&<&'string'&>&*}*&
10293 .cindex "case forcing in strings"
10294 .cindex "string" "case forcing"
10295 .cindex "lower casing"
10296 .cindex "expansion" "case forcing"
10297 .cindex "&%lc%& expansion item"
10298 This forces the letters in the string into lower-case, for example:
10303 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10304 .cindex "expansion" "string truncation"
10305 .cindex "&%length%& expansion item"
10306 The &%length%& operator is a simpler interface to the &%length%& function that
10307 can be used when the parameter is a fixed number (as opposed to a string that
10308 changes when expanded). The effect is the same as
10310 ${length{<number>}{<string>}}
10312 See the description of the general &%length%& item above for details. Note that
10313 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10314 when &%length%& is used as an operator.
10317 .vitem &*${listcount:*&<&'string'&>&*}*&
10318 .cindex "expansion" "list item count"
10319 .cindex "list" "item count"
10320 .cindex "list" "count of items"
10321 .cindex "&%listcount%& expansion item"
10322 The string is interpreted as a list and the number of items is returned.
10325 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10326 .cindex "expansion" "named list"
10327 .cindex "&%listnamed%& expansion item"
10328 The name is interpreted as a named list and the content of the list is returned,
10329 expanding any referenced lists, re-quoting as needed for colon-separation.
10330 If the optional type is given it must be one of "a", "d", "h" or "l"
10331 and selects address-, domain-, host- or localpart- lists to search among respectively.
10332 Otherwise all types are searched in an undefined order and the first
10333 matching list is returned.
10336 .vitem &*${local_part:*&<&'string'&>&*}*&
10337 .cindex "expansion" "local part extraction"
10338 .cindex "&%local_part%& expansion item"
10339 The string is interpreted as an RFC 2822 address and the local part is
10340 extracted from it. If the string does not parse successfully, the result is
10344 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10345 .cindex "masked IP address"
10346 .cindex "IP address" "masking"
10347 .cindex "CIDR notation"
10348 .cindex "expansion" "IP address masking"
10349 .cindex "&%mask%& expansion item"
10350 If the form of the string to be operated on is not an IP address followed by a
10351 slash and an integer (that is, a network address in CIDR notation), the
10352 expansion fails. Otherwise, this operator converts the IP address to binary,
10353 masks off the least significant bits according to the bit count, and converts
10354 the result back to text, with mask appended. For example,
10356 ${mask:10.111.131.206/28}
10358 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10359 be mostly used for looking up masked addresses in files, the result for an IPv6
10360 address uses dots to separate components instead of colons, because colon
10361 terminates a key string in lsearch files. So, for example,
10363 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10367 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10369 Letters in IPv6 addresses are always output in lower case.
10372 .vitem &*${md5:*&<&'string'&>&*}*&
10374 .cindex "expansion" "MD5 hash"
10375 .cindex certificate fingerprint
10376 .cindex "&%md5%& expansion item"
10377 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10378 as a 32-digit hexadecimal number, in which any letters are in lower case.
10380 If the string is a single variable of type certificate,
10381 returns the MD5 hash fingerprint of the certificate.
10384 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10385 .cindex "expansion" "numeric hash"
10386 .cindex "hash function" "numeric"
10387 The &%nhash%& operator is a simpler interface to the numeric hashing function
10388 that can be used when the two parameters are fixed numbers (as opposed to
10389 strings that change when expanded). The effect is the same as
10391 ${nhash{<n>}{<m>}{<string>}}
10393 See the description of the general &%nhash%& item above for details.
10396 .vitem &*${quote:*&<&'string'&>&*}*&
10397 .cindex "quoting" "in string expansions"
10398 .cindex "expansion" "quoting"
10399 .cindex "&%quote%& expansion item"
10400 The &%quote%& operator puts its argument into double quotes if it
10401 is an empty string or
10402 contains anything other than letters, digits, underscores, dots, and hyphens.
10403 Any occurrences of double quotes and backslashes are escaped with a backslash.
10404 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10405 respectively For example,
10413 The place where this is useful is when the argument is a substitution from a
10414 variable or a message header.
10416 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10417 .cindex "&%quote_local_part%& expansion item"
10418 This operator is like &%quote%&, except that it quotes the string only if
10419 required to do so by the rules of RFC 2822 for quoting local parts. For
10420 example, a plus sign would not cause quoting (but it would for &%quote%&).
10421 If you are creating a new email address from the contents of &$local_part$&
10422 (or any other unknown data), you should always use this operator.
10425 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10426 .cindex "quoting" "lookup-specific"
10427 This operator applies lookup-specific quoting rules to the string. Each
10428 query-style lookup type has its own quoting rules which are described with
10429 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10431 ${quote_ldap:two * two}
10437 For single-key lookup types, no quoting is ever necessary and this operator
10438 yields an unchanged string.
10441 .vitem &*${randint:*&<&'n'&>&*}*&
10442 .cindex "random number"
10443 This operator returns a somewhat random number which is less than the
10444 supplied number and is at least 0. The quality of this randomness depends
10445 on how Exim was built; the values are not suitable for keying material.
10446 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10447 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10448 for versions of GnuTLS with that function.
10449 Otherwise, the implementation may be arc4random(), random() seeded by
10450 srandomdev() or srandom(), or a custom implementation even weaker than
10454 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10455 .cindex "expansion" "IP address"
10456 This operator reverses an IP address; for IPv4 addresses, the result is in
10457 dotted-quad decimal form, while for IPv6 addresses the result is in
10458 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10459 for DNS. For example,
10461 ${reverse_ip:192.0.2.4}
10462 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10467 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10471 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10472 .cindex "expansion" "RFC 2047"
10473 .cindex "RFC 2047" "expansion operator"
10474 .cindex "&%rfc2047%& expansion item"
10475 This operator encodes text according to the rules of RFC 2047. This is an
10476 encoding that is used in header lines to encode non-ASCII characters. It is
10477 assumed that the input string is in the encoding specified by the
10478 &%headers_charset%& option, which gets its default at build time. If the string
10479 contains only characters in the range 33&--126, and no instances of the
10482 ? = ( ) < > @ , ; : \ " . [ ] _
10484 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10485 string, using as many &"encoded words"& as necessary to encode all the
10489 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10490 .cindex "expansion" "RFC 2047"
10491 .cindex "RFC 2047" "decoding"
10492 .cindex "&%rfc2047d%& expansion item"
10493 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10494 bytes are replaced by question marks. Characters are converted into the
10495 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10496 not recognized unless &%check_rfc2047_length%& is set false.
10498 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10499 access a header line, RFC 2047 decoding is done automatically. You do not need
10500 to use this operator as well.
10504 .vitem &*${rxquote:*&<&'string'&>&*}*&
10505 .cindex "quoting" "in regular expressions"
10506 .cindex "regular expressions" "quoting"
10507 .cindex "&%rxquote%& expansion item"
10508 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10509 characters in its argument. This is useful when substituting the values of
10510 variables or headers inside regular expressions.
10513 .vitem &*${sha1:*&<&'string'&>&*}*&
10514 .cindex "SHA-1 hash"
10515 .cindex "expansion" "SHA-1 hashing"
10516 .cindex certificate fingerprint
10517 .cindex "&%sha1%& expansion item"
10518 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10519 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10521 If the string is a single variable of type certificate,
10522 returns the SHA-1 hash fingerprint of the certificate.
10525 .vitem &*${sha256:*&<&'string'&>&*}*&
10526 .cindex "SHA-256 hash"
10527 .cindex certificate fingerprint
10528 .cindex "expansion" "SHA-256 hashing"
10529 .cindex "&%sha256%& expansion item"
10531 The &%sha256%& operator computes the SHA-256 hash value of the string
10533 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10536 If the string is a single variable of type certificate,
10537 returns the SHA-256 hash fingerprint of the certificate.
10541 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
10542 &*${sha3_<n>:*&<&'string'&>&*}*&
10543 .cindex "SHA3 hash"
10544 .cindex "expansion" "SHA3 hashing"
10545 .cindex "&%sha3%& expansion item"
10546 The &%sha3%& operator computes the SHA3-256 hash value of the string
10548 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10550 If a number is appended, separated by an underbar, it specifies
10551 the output length. Values of 224, 256, 384 and 512 are accepted;
10552 with 256 being the default.
10554 The &%sha3%& expansion item is only supported if Exim has been
10555 compiled with GnuTLS 3.5.0 or later.
10559 .vitem &*${stat:*&<&'string'&>&*}*&
10560 .cindex "expansion" "statting a file"
10561 .cindex "file" "extracting characteristics"
10562 .cindex "&%stat%& expansion item"
10563 The string, after expansion, must be a file path. A call to the &[stat()]&
10564 function is made for this path. If &[stat()]& fails, an error occurs and the
10565 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10566 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10567 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10568 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10569 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10570 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10571 can extract individual fields using the &%extract%& expansion item.
10573 The use of the &%stat%& expansion in users' filter files can be locked out by
10574 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10575 systems for files larger than 2GB.
10577 .vitem &*${str2b64:*&<&'string'&>&*}*&
10578 .cindex "&%str2b64%& expansion item"
10579 Now deprecated, a synonym for the &%base64%& expansion operator.
10583 .vitem &*${strlen:*&<&'string'&>&*}*&
10584 .cindex "expansion" "string length"
10585 .cindex "string" "length in expansion"
10586 .cindex "&%strlen%& expansion item"
10587 The item is replace by the length of the expanded string, expressed as a
10588 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10591 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10592 .cindex "&%substr%& expansion item"
10593 .cindex "substring extraction"
10594 .cindex "expansion" "substring expansion"
10595 The &%substr%& operator is a simpler interface to the &%substr%& function that
10596 can be used when the two parameters are fixed numbers (as opposed to strings
10597 that change when expanded). The effect is the same as
10599 ${substr{<start>}{<length>}{<string>}}
10601 See the description of the general &%substr%& item above for details. The
10602 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10604 .vitem &*${time_eval:*&<&'string'&>&*}*&
10605 .cindex "&%time_eval%& expansion item"
10606 .cindex "time interval" "decoding"
10607 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10610 .vitem &*${time_interval:*&<&'string'&>&*}*&
10611 .cindex "&%time_interval%& expansion item"
10612 .cindex "time interval" "formatting"
10613 The argument (after sub-expansion) must be a sequence of decimal digits that
10614 represents an interval of time as a number of seconds. It is converted into a
10615 number of larger units and output in Exim's normal time format, for example,
10618 .vitem &*${uc:*&<&'string'&>&*}*&
10619 .cindex "case forcing in strings"
10620 .cindex "string" "case forcing"
10621 .cindex "upper casing"
10622 .cindex "expansion" "case forcing"
10623 .cindex "&%uc%& expansion item"
10624 This forces the letters in the string into upper-case.
10626 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10627 .cindex "correction of invalid utf-8 sequences in strings"
10628 .cindex "utf-8" "utf-8 sequences"
10629 .cindex "incorrect utf-8"
10630 .cindex "expansion" "utf-8 forcing"
10631 .cindex "&%utf8clean%& expansion item"
10632 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10634 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
10635 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
10636 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
10637 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
10638 .cindex expansion UTF-8
10639 .cindex UTF-8 expansion
10641 .cindex internationalisation
10642 .cindex "&%utf8_domain_to_alabel%& expansion item"
10643 .cindex "&%utf8_domain_from_alabel%& expansion item"
10644 .cindex "&%utf8_localpart_to_alabel%& expansion item"
10645 .cindex "&%utf8_localpart_from_alabel%& expansion item"
10646 These convert EAI mail name components between UTF-8 and a-label forms.
10647 For information on internationalisation support see &<<SECTi18nMTA>>&.
10655 .section "Expansion conditions" "SECTexpcond"
10656 .scindex IIDexpcond "expansion" "conditions"
10657 The following conditions are available for testing by the &%${if%& construct
10658 while expanding strings:
10661 .vitem &*!*&<&'condition'&>
10662 .cindex "expansion" "negating a condition"
10663 .cindex "negation" "in expansion condition"
10664 Preceding any condition with an exclamation mark negates the result of the
10667 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10668 .cindex "numeric comparison"
10669 .cindex "expansion" "numeric comparison"
10670 There are a number of symbolic operators for doing numeric comparisons. They
10676 &`>= `& greater or equal
10678 &`<= `& less or equal
10682 ${if >{$message_size}{10M} ...
10684 Note that the general negation operator provides for inequality testing. The
10685 two strings must take the form of optionally signed decimal integers,
10686 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10687 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10688 As a special case, the numerical value of an empty string is taken as
10691 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10692 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10693 10M, not if 10M is larger than &$message_size$&.
10696 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10697 {*&<&'arg2'&>&*}...}*&
10698 .cindex "expansion" "calling an acl"
10699 .cindex "&%acl%&" "expansion condition"
10700 The name and zero to nine argument strings are first expanded separately. The expanded
10701 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10702 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10703 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10704 and may use the variables; if another acl expansion is used the values
10705 are restored after it returns. If the ACL sets
10706 a value using a "message =" modifier the variable $value becomes
10707 the result of the expansion, otherwise it is empty.
10708 If the ACL returns accept the condition is true; if deny, false.
10709 If the ACL returns defer the result is a forced-fail.
10711 .vitem &*bool&~{*&<&'string'&>&*}*&
10712 .cindex "expansion" "boolean parsing"
10713 .cindex "&%bool%& expansion condition"
10714 This condition turns a string holding a true or false representation into
10715 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10716 (case-insensitively); also integer numbers map to true if non-zero,
10718 An empty string is treated as false.
10719 Leading and trailing whitespace is ignored;
10720 thus a string consisting only of whitespace is false.
10721 All other string values will result in expansion failure.
10723 When combined with ACL variables, this expansion condition will let you
10724 make decisions in one place and act on those decisions in another place.
10727 ${if bool{$acl_m_privileged_sender} ...
10731 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10732 .cindex "expansion" "boolean parsing"
10733 .cindex "&%bool_lax%& expansion condition"
10734 Like &%bool%&, this condition turns a string into a boolean state. But
10735 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10736 loose definition that the Router &%condition%& option uses. The empty string
10737 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10738 true. Leading and trailing whitespace is ignored.
10740 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10742 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10743 .cindex "expansion" "encrypted comparison"
10744 .cindex "encrypted strings, comparing"
10745 .cindex "&%crypteq%& expansion condition"
10746 This condition is included in the Exim binary if it is built to support any
10747 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10748 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10749 included in the binary.
10751 The &%crypteq%& condition has two arguments. The first is encrypted and
10752 compared against the second, which is already encrypted. The second string may
10753 be in the LDAP form for storing encrypted strings, which starts with the
10754 encryption type in curly brackets, followed by the data. If the second string
10755 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10756 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10757 Typically this will be a field from a password file. An example of an encrypted
10758 string in LDAP form is:
10760 {md5}CY9rzUYh03PK3k6DJie09g==
10762 If such a string appears directly in an expansion, the curly brackets have to
10763 be quoted, because they are part of the expansion syntax. For example:
10765 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10767 The following encryption types (whose names are matched case-independently) are
10772 .cindex "base64 encoding" "in encrypted password"
10773 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10774 printable characters to compare with the remainder of the second string. If the
10775 length of the comparison string is 24, Exim assumes that it is base64 encoded
10776 (as in the above example). If the length is 32, Exim assumes that it is a
10777 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10781 .cindex "SHA-1 hash"
10782 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10783 printable characters to compare with the remainder of the second string. If the
10784 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10785 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10786 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10789 .cindex "&[crypt()]&"
10790 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10791 only the first eight characters of the password. However, in modern operating
10792 systems this is no longer true, and in many cases the entire password is used,
10793 whatever its length.
10796 .cindex "&[crypt16()]&"
10797 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10798 use up to 16 characters of the password in some operating systems. Again, in
10799 modern operating systems, more characters may be used.
10801 Exim has its own version of &[crypt16()]&, which is just a double call to
10802 &[crypt()]&. For operating systems that have their own version, setting
10803 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10804 operating system version instead of its own. This option is set by default in
10805 the OS-dependent &_Makefile_& for those operating systems that are known to
10806 support &[crypt16()]&.
10808 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10809 it was not using the same algorithm as some operating systems' versions. It
10810 turns out that as well as &[crypt16()]& there is a function called
10811 &[bigcrypt()]& in some operating systems. This may or may not use the same
10812 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10814 However, since there is now a move away from the traditional &[crypt()]&
10815 functions towards using SHA1 and other algorithms, tidying up this area of
10816 Exim is seen as very low priority.
10818 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10819 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10820 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10821 default is &`{crypt}`&. Whatever the default, you can always use either
10822 function by specifying it explicitly in curly brackets.
10824 .vitem &*def:*&<&'variable&~name'&>
10825 .cindex "expansion" "checking for empty variable"
10826 .cindex "&%def%& expansion condition"
10827 The &%def%& condition must be followed by the name of one of the expansion
10828 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10829 variable does not contain the empty string. For example:
10831 ${if def:sender_ident {from $sender_ident}}
10833 Note that the variable name is given without a leading &%$%& character. If the
10834 variable does not exist, the expansion fails.
10836 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10837 &~&*def:h_*&<&'header&~name'&>&*:*&"
10838 .cindex "expansion" "checking header line existence"
10839 This condition is true if a message is being processed and the named header
10840 exists in the message. For example,
10842 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10844 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10845 the header name must be terminated by a colon if white space does not follow.
10847 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10848 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10849 .cindex "string" "comparison"
10850 .cindex "expansion" "string comparison"
10851 .cindex "&%eq%& expansion condition"
10852 .cindex "&%eqi%& expansion condition"
10853 The two substrings are first expanded. The condition is true if the two
10854 resulting strings are identical. For &%eq%& the comparison includes the case of
10855 letters, whereas for &%eqi%& the comparison is case-independent.
10857 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10858 .cindex "expansion" "file existence test"
10859 .cindex "file" "existence test"
10860 .cindex "&%exists%&, expansion condition"
10861 The substring is first expanded and then interpreted as an absolute path. The
10862 condition is true if the named file (or directory) exists. The existence test
10863 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10864 users' filter files may be locked out by the system administrator.
10866 .vitem &*first_delivery*&
10867 .cindex "delivery" "first"
10868 .cindex "first delivery"
10869 .cindex "expansion" "first delivery test"
10870 .cindex "&%first_delivery%& expansion condition"
10871 This condition, which has no data, is true during a message's first delivery
10872 attempt. It is false during any subsequent delivery attempts.
10875 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10876 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10877 .cindex "list" "iterative conditions"
10878 .cindex "expansion" "&*forall*& condition"
10879 .cindex "expansion" "&*forany*& condition"
10881 These conditions iterate over a list. The first argument is expanded to form
10882 the list. By default, the list separator is a colon, but it can be changed by
10883 the normal method. The second argument is interpreted as a condition that is to
10884 be applied to each item in the list in turn. During the interpretation of the
10885 condition, the current list item is placed in a variable called &$item$&.
10887 For &*forany*&, interpretation stops if the condition is true for any item, and
10888 the result of the whole condition is true. If the condition is false for all
10889 items in the list, the overall condition is false.
10891 For &*forall*&, interpretation stops if the condition is false for any item,
10892 and the result of the whole condition is false. If the condition is true for
10893 all items in the list, the overall condition is true.
10895 Note that negation of &*forany*& means that the condition must be false for all
10896 items for the overall condition to succeed, and negation of &*forall*& means
10897 that the condition must be false for at least one item. In this example, the
10898 list separator is changed to a comma:
10900 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10902 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10903 being processed, to enable these expansion items to be nested.
10905 To scan a named list, expand it with the &*listnamed*& operator.
10908 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10909 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10910 .cindex "string" "comparison"
10911 .cindex "expansion" "string comparison"
10912 .cindex "&%ge%& expansion condition"
10913 .cindex "&%gei%& expansion condition"
10914 The two substrings are first expanded. The condition is true if the first
10915 string is lexically greater than or equal to the second string. For &%ge%& the
10916 comparison includes the case of letters, whereas for &%gei%& the comparison is
10919 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10920 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10921 .cindex "string" "comparison"
10922 .cindex "expansion" "string comparison"
10923 .cindex "&%gt%& expansion condition"
10924 .cindex "&%gti%& expansion condition"
10925 The two substrings are first expanded. The condition is true if the first
10926 string is lexically greater than the second string. For &%gt%& the comparison
10927 includes the case of letters, whereas for &%gti%& the comparison is
10930 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10931 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10932 .cindex "string" "comparison"
10933 .cindex "list" "iterative conditions"
10934 Both strings are expanded; the second string is treated as a list of simple
10935 strings; if the first string is a member of the second, then the condition
10938 These are simpler to use versions of the more powerful &*forany*& condition.
10939 Examples, and the &*forany*& equivalents:
10941 ${if inlist{needle}{foo:needle:bar}}
10942 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10943 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10944 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10947 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10948 &*isip4&~{*&<&'string'&>&*}*& &&&
10949 &*isip6&~{*&<&'string'&>&*}*&
10950 .cindex "IP address" "testing string format"
10951 .cindex "string" "testing for IP address"
10952 .cindex "&%isip%& expansion condition"
10953 .cindex "&%isip4%& expansion condition"
10954 .cindex "&%isip6%& expansion condition"
10955 The substring is first expanded, and then tested to see if it has the form of
10956 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10957 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10959 For an IPv4 address, the test is for four dot-separated components, each of
10960 which consists of from one to three digits. For an IPv6 address, up to eight
10961 colon-separated components are permitted, each containing from one to four
10962 hexadecimal digits. There may be fewer than eight components if an empty
10963 component (adjacent colons) is present. Only one empty component is permitted.
10965 &*Note*&: The checks are just on the form of the address; actual numerical
10966 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10967 check. The main use of these tests is to distinguish between IP addresses and
10968 host names, or between IPv4 and IPv6 addresses. For example, you could use
10970 ${if isip4{$sender_host_address}...
10972 to test which IP version an incoming SMTP connection is using.
10974 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10975 .cindex "LDAP" "use for authentication"
10976 .cindex "expansion" "LDAP authentication test"
10977 .cindex "&%ldapauth%& expansion condition"
10978 This condition supports user authentication using LDAP. See section
10979 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10980 queries. For this use, the query must contain a user name and password. The
10981 query itself is not used, and can be empty. The condition is true if the
10982 password is not empty, and the user name and password are accepted by the LDAP
10983 server. An empty password is rejected without calling LDAP because LDAP binds
10984 with an empty password are considered anonymous regardless of the username, and
10985 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10986 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10990 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10991 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10992 .cindex "string" "comparison"
10993 .cindex "expansion" "string comparison"
10994 .cindex "&%le%& expansion condition"
10995 .cindex "&%lei%& expansion condition"
10996 The two substrings are first expanded. The condition is true if the first
10997 string is lexically less than or equal to the second string. For &%le%& the
10998 comparison includes the case of letters, whereas for &%lei%& the comparison is
11001 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11002 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11003 .cindex "string" "comparison"
11004 .cindex "expansion" "string comparison"
11005 .cindex "&%lt%& expansion condition"
11006 .cindex "&%lti%& expansion condition"
11007 The two substrings are first expanded. The condition is true if the first
11008 string is lexically less than the second string. For &%lt%& the comparison
11009 includes the case of letters, whereas for &%lti%& the comparison is
11013 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11014 .cindex "expansion" "regular expression comparison"
11015 .cindex "regular expressions" "match in expanded string"
11016 .cindex "&%match%& expansion condition"
11017 The two substrings are first expanded. The second is then treated as a regular
11018 expression and applied to the first. Because of the pre-expansion, if the
11019 regular expression contains dollar, or backslash characters, they must be
11020 escaped. Care must also be taken if the regular expression contains braces
11021 (curly brackets). A closing brace must be escaped so that it is not taken as a
11022 premature termination of <&'string2'&>. The easiest approach is to use the
11023 &`\N`& feature to disable expansion of the regular expression.
11026 ${if match {$local_part}{\N^\d{3}\N} ...
11028 If the whole expansion string is in double quotes, further escaping of
11029 backslashes is also required.
11031 The condition is true if the regular expression match succeeds.
11032 The regular expression is not required to begin with a circumflex
11033 metacharacter, but if there is no circumflex, the expression is not anchored,
11034 and it may match anywhere in the subject, not just at the start. If you want
11035 the pattern to match at the end of the subject, you must include the &`$`&
11036 metacharacter at an appropriate point.
11038 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11039 At the start of an &%if%& expansion the values of the numeric variable
11040 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11041 succeeds causes them to be reset to the substrings of that condition and they
11042 will have these values during the expansion of the success string. At the end
11043 of the &%if%& expansion, the previous values are restored. After testing a
11044 combination of conditions using &%or%&, the subsequent values of the numeric
11045 variables are those of the condition that succeeded.
11047 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11048 .cindex "&%match_address%& expansion condition"
11049 See &*match_local_part*&.
11051 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11052 .cindex "&%match_domain%& expansion condition"
11053 See &*match_local_part*&.
11055 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11056 .cindex "&%match_ip%& expansion condition"
11057 This condition matches an IP address to a list of IP address patterns. It must
11058 be followed by two argument strings. The first (after expansion) must be an IP
11059 address or an empty string. The second (not expanded) is a restricted host
11060 list that can match only an IP address, not a host name. For example:
11062 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11064 The specific types of host list item that are permitted in the list are:
11067 An IP address, optionally with a CIDR mask.
11069 A single asterisk, which matches any IP address.
11071 An empty item, which matches only if the IP address is empty. This could be
11072 useful for testing for a locally submitted message or one from specific hosts
11073 in a single test such as
11074 . ==== As this is a nested list, any displays it contains must be indented
11075 . ==== as otherwise they are too far to the left. This comment applies to
11076 . ==== the use of xmlto plus fop. There's no problem when formatting with
11077 . ==== sdop, with or without the extra indent.
11079 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11081 where the first item in the list is the empty string.
11083 The item @[] matches any of the local host's interface addresses.
11085 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11086 even if &`net-`& is not specified. There is never any attempt to turn the IP
11087 address into a host name. The most common type of linear search for
11088 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11089 masks. For example:
11091 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11093 It is of course possible to use other kinds of lookup, and in such a case, you
11094 do need to specify the &`net-`& prefix if you want to specify a specific
11095 address mask, for example:
11097 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11099 However, unless you are combining a &%match_ip%& condition with others, it is
11100 just as easy to use the fact that a lookup is itself a condition, and write:
11102 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11106 Note that <&'string2'&> is not itself subject to string expansion, unless
11107 Exim was built with the EXPAND_LISTMATCH_RHS option.
11109 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11111 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11112 .cindex "domain list" "in expansion condition"
11113 .cindex "address list" "in expansion condition"
11114 .cindex "local part" "list, in expansion condition"
11115 .cindex "&%match_local_part%& expansion condition"
11116 This condition, together with &%match_address%& and &%match_domain%&, make it
11117 possible to test domain, address, and local part lists within expansions. Each
11118 condition requires two arguments: an item and a list to match. A trivial
11121 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11123 In each case, the second argument may contain any of the allowable items for a
11124 list of the appropriate type. Also, because the second argument (after
11125 expansion) is a standard form of list, it is possible to refer to a named list.
11126 Thus, you can use conditions like this:
11128 ${if match_domain{$domain}{+local_domains}{...
11130 .cindex "&`+caseful`&"
11131 For address lists, the matching starts off caselessly, but the &`+caseful`&
11132 item can be used, as in all address lists, to cause subsequent items to
11133 have their local parts matched casefully. Domains are always matched
11136 Note that <&'string2'&> is not itself subject to string expansion, unless
11137 Exim was built with the EXPAND_LISTMATCH_RHS option.
11139 &*Note*&: Host lists are &'not'& supported in this way. This is because
11140 hosts have two identities: a name and an IP address, and it is not clear
11141 how to specify cleanly how such a test would work. However, IP addresses can be
11142 matched using &%match_ip%&.
11144 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11145 .cindex "PAM authentication"
11146 .cindex "AUTH" "with PAM"
11147 .cindex "Solaris" "PAM support"
11148 .cindex "expansion" "PAM authentication test"
11149 .cindex "&%pam%& expansion condition"
11150 &'Pluggable Authentication Modules'&
11151 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
11152 available in the latest releases of Solaris and in some GNU/Linux
11153 distributions. The Exim support, which is intended for use in conjunction with
11154 the SMTP AUTH command, is available only if Exim is compiled with
11158 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11159 in some releases of GNU/Linux &%-ldl%& is also needed.
11161 The argument string is first expanded, and the result must be a
11162 colon-separated list of strings. Leading and trailing white space is ignored.
11163 The PAM module is initialized with the service name &"exim"& and the user name
11164 taken from the first item in the colon-separated data string (<&'string1'&>).
11165 The remaining items in the data string are passed over in response to requests
11166 from the authentication function. In the simple case there will only be one
11167 request, for a password, so the data consists of just two strings.
11169 There can be problems if any of the strings are permitted to contain colon
11170 characters. In the usual way, these have to be doubled to avoid being taken as
11171 separators. If the data is being inserted from a variable, the &%sg%& expansion
11172 item can be used to double any existing colons. For example, the configuration
11173 of a LOGIN authenticator might contain this setting:
11175 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11177 For a PLAIN authenticator you could use:
11179 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11181 In some operating systems, PAM authentication can be done only from a process
11182 running as root. Since Exim is running as the Exim user when receiving
11183 messages, this means that PAM cannot be used directly in those systems.
11184 A patched version of the &'pam_unix'& module that comes with the
11185 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
11186 The patched module allows one special uid/gid combination, in addition to root,
11187 to authenticate. If you build the patched module to allow the Exim user and
11188 group, PAM can then be used from an Exim authenticator.
11191 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11192 .cindex "&'pwcheck'& daemon"
11194 .cindex "expansion" "&'pwcheck'& authentication test"
11195 .cindex "&%pwcheck%& expansion condition"
11196 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11197 This is one way of making it possible for passwords to be checked by a process
11198 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11199 deprecated. Its replacement is &'saslauthd'& (see below).
11201 The pwcheck support is not included in Exim by default. You need to specify
11202 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11203 building Exim. For example:
11205 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11207 You do not need to install the full Cyrus software suite in order to use
11208 the pwcheck daemon. You can compile and install just the daemon alone
11209 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11210 access to the &_/var/pwcheck_& directory.
11212 The &%pwcheck%& condition takes one argument, which must be the user name and
11213 password, separated by a colon. For example, in a LOGIN authenticator
11214 configuration, you might have this:
11216 server_condition = ${if pwcheck{$auth1:$auth2}}
11218 Again, for a PLAIN authenticator configuration, this would be:
11220 server_condition = ${if pwcheck{$auth2:$auth3}}
11222 .vitem &*queue_running*&
11223 .cindex "queue runner" "detecting when delivering from"
11224 .cindex "expansion" "queue runner test"
11225 .cindex "&%queue_running%& expansion condition"
11226 This condition, which has no data, is true during delivery attempts that are
11227 initiated by queue runner processes, and false otherwise.
11230 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11232 .cindex "expansion" "Radius authentication"
11233 .cindex "&%radius%& expansion condition"
11234 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11235 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11236 the Radius client configuration file in order to build Exim with Radius
11239 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11240 library, using the original API. If you are using release 0.4.0 or later of
11241 this library, you need to set
11243 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11245 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11246 &%libradius%& library that comes with FreeBSD. To do this, set
11248 RADIUS_LIB_TYPE=RADLIB
11250 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11251 You may also have to supply a suitable setting in EXTRALIBS so that the
11252 Radius library can be found when Exim is linked.
11254 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11255 Radius client library, which calls the Radius server. The condition is true if
11256 the authentication is successful. For example:
11258 server_condition = ${if radius{<arguments>}}
11262 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11263 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11264 .cindex "&'saslauthd'& daemon"
11266 .cindex "expansion" "&'saslauthd'& authentication test"
11267 .cindex "&%saslauthd%& expansion condition"
11268 This condition supports user authentication using the Cyrus &'saslauthd'&
11269 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11270 Using this daemon is one way of making it possible for passwords to be checked
11271 by a process that is not running as root.
11273 The saslauthd support is not included in Exim by default. You need to specify
11274 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11275 building Exim. For example:
11277 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11279 You do not need to install the full Cyrus software suite in order to use
11280 the saslauthd daemon. You can compile and install just the daemon alone
11281 from the Cyrus SASL library.
11283 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11284 two are mandatory. For example:
11286 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11288 The service and the realm are optional (which is why the arguments are enclosed
11289 in their own set of braces). For details of the meaning of the service and
11290 realm, and how to run the daemon, consult the Cyrus documentation.
11295 .section "Combining expansion conditions" "SECID84"
11296 .cindex "expansion" "combining conditions"
11297 Several conditions can be tested at once by combining them using the &%and%&
11298 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11299 conditions on their own, and precede their lists of sub-conditions. Each
11300 sub-condition must be enclosed in braces within the overall braces that contain
11301 the list. No repetition of &%if%& is used.
11305 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11306 .cindex "&""or""& expansion condition"
11307 .cindex "expansion" "&""or""& of conditions"
11308 The sub-conditions are evaluated from left to right. The condition is true if
11309 any one of the sub-conditions is true.
11312 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11314 When a true sub-condition is found, the following ones are parsed but not
11315 evaluated. If there are several &"match"& sub-conditions the values of the
11316 numeric variables afterwards are taken from the first one that succeeds.
11318 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11319 .cindex "&""and""& expansion condition"
11320 .cindex "expansion" "&""and""& of conditions"
11321 The sub-conditions are evaluated from left to right. The condition is true if
11322 all of the sub-conditions are true. If there are several &"match"&
11323 sub-conditions, the values of the numeric variables afterwards are taken from
11324 the last one. When a false sub-condition is found, the following ones are
11325 parsed but not evaluated.
11327 .ecindex IIDexpcond
11332 .section "Expansion variables" "SECTexpvar"
11333 .cindex "expansion" "variables, list of"
11334 This section contains an alphabetical list of all the expansion variables. Some
11335 of them are available only when Exim is compiled with specific options such as
11336 support for TLS or the content scanning extension.
11339 .vitem "&$0$&, &$1$&, etc"
11340 .cindex "numerical variables (&$1$& &$2$& etc)"
11341 When a &%match%& expansion condition succeeds, these variables contain the
11342 captured substrings identified by the regular expression during subsequent
11343 processing of the success string of the containing &%if%& expansion item.
11344 In the expansion condition case
11345 they do not retain their values afterwards; in fact, their previous
11346 values are restored at the end of processing an &%if%& item. The numerical
11347 variables may also be set externally by some other matching process which
11348 precedes the expansion of the string. For example, the commands available in
11349 Exim filter files include an &%if%& command with its own regular expression
11350 matching condition.
11352 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11353 Within an acl condition, expansion condition or expansion item
11354 any arguments are copied to these variables,
11355 any unused variables being made empty.
11357 .vitem "&$acl_c...$&"
11358 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11359 can be given any name that starts with &$acl_c$& and is at least six characters
11360 long, but the sixth character must be either a digit or an underscore. For
11361 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11362 variables persist throughout the lifetime of an SMTP connection. They can be
11363 used to pass information between ACLs and between different invocations of the
11364 same ACL. When a message is received, the values of these variables are saved
11365 with the message, and can be accessed by filters, routers, and transports
11366 during subsequent delivery.
11368 .vitem "&$acl_m...$&"
11369 These variables are like the &$acl_c...$& variables, except that their values
11370 are reset after a message has been received. Thus, if several messages are
11371 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11372 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11373 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11374 message is received, the values of these variables are saved with the message,
11375 and can be accessed by filters, routers, and transports during subsequent
11378 .vitem &$acl_narg$&
11379 Within an acl condition, expansion condition or expansion item
11380 this variable has the number of arguments.
11382 .vitem &$acl_verify_message$&
11383 .vindex "&$acl_verify_message$&"
11384 After an address verification has failed, this variable contains the failure
11385 message. It retains its value for use in subsequent modifiers. The message can
11386 be preserved by coding like this:
11388 warn !verify = sender
11389 set acl_m0 = $acl_verify_message
11391 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11392 &%log_message%& modifiers, to include information about the verification
11395 .vitem &$address_data$&
11396 .vindex "&$address_data$&"
11397 This variable is set by means of the &%address_data%& option in routers. The
11398 value then remains with the address while it is processed by subsequent routers
11399 and eventually a transport. If the transport is handling multiple addresses,
11400 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11401 for more details. &*Note*&: The contents of &$address_data$& are visible in
11404 If &$address_data$& is set when the routers are called from an ACL to verify
11405 a recipient address, the final value is still in the variable for subsequent
11406 conditions and modifiers of the ACL statement. If routing the address caused it
11407 to be redirected to just one address, the child address is also routed as part
11408 of the verification, and in this case the final value of &$address_data$& is
11409 from the child's routing.
11411 If &$address_data$& is set when the routers are called from an ACL to verify a
11412 sender address, the final value is also preserved, but this time in
11413 &$sender_address_data$&, to distinguish it from data from a recipient
11416 In both cases (recipient and sender verification), the value does not persist
11417 after the end of the current ACL statement. If you want to preserve
11418 these values for longer, you can save them in ACL variables.
11420 .vitem &$address_file$&
11421 .vindex "&$address_file$&"
11422 When, as a result of aliasing, forwarding, or filtering, a message is directed
11423 to a specific file, this variable holds the name of the file when the transport
11424 is running. At other times, the variable is empty. For example, using the
11425 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11427 /home/r2d2/savemail
11429 then when the &(address_file)& transport is running, &$address_file$&
11430 contains the text string &`/home/r2d2/savemail`&.
11431 .cindex "Sieve filter" "value of &$address_file$&"
11432 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11433 then up to the transport configuration to generate an appropriate absolute path
11434 to the relevant file.
11436 .vitem &$address_pipe$&
11437 .vindex "&$address_pipe$&"
11438 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11439 this variable holds the pipe command when the transport is running.
11441 .vitem "&$auth1$& &-- &$auth3$&"
11442 .vindex "&$auth1$&, &$auth2$&, etc"
11443 These variables are used in SMTP authenticators (see chapters
11444 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
11446 .vitem &$authenticated_id$&
11447 .cindex "authentication" "id"
11448 .vindex "&$authenticated_id$&"
11449 When a server successfully authenticates a client it may be configured to
11450 preserve some of the authentication information in the variable
11451 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11452 user/password authenticator configuration might preserve the user name for use
11453 in the routers. Note that this is not the same information that is saved in
11454 &$sender_host_authenticated$&.
11455 When a message is submitted locally (that is, not over a TCP connection)
11456 the value of &$authenticated_id$& is normally the login name of the calling
11457 process. However, a trusted user can override this by means of the &%-oMai%&
11458 command line option.
11460 .vitem &$authenticated_fail_id$&
11461 .cindex "authentication" "fail" "id"
11462 .vindex "&$authenticated_fail_id$&"
11463 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11464 will contain the failed authentication id. If more than one authentication
11465 id is attempted, it will contain only the last one. The variable is
11466 available for processing in the ACL's, generally the quit or notquit ACL.
11467 A message to a local recipient could still be accepted without requiring
11468 authentication, which means this variable could also be visible in all of
11472 .vitem &$authenticated_sender$&
11473 .cindex "sender" "authenticated"
11474 .cindex "authentication" "sender"
11475 .cindex "AUTH" "on MAIL command"
11476 .vindex "&$authenticated_sender$&"
11477 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11478 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11479 described in section &<<SECTauthparamail>>&. Unless the data is the string
11480 &"<>"&, it is set as the authenticated sender of the message, and the value is
11481 available during delivery in the &$authenticated_sender$& variable. If the
11482 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11484 .vindex "&$qualify_domain$&"
11485 When a message is submitted locally (that is, not over a TCP connection), the
11486 value of &$authenticated_sender$& is an address constructed from the login
11487 name of the calling process and &$qualify_domain$&, except that a trusted user
11488 can override this by means of the &%-oMas%& command line option.
11491 .vitem &$authentication_failed$&
11492 .cindex "authentication" "failure"
11493 .vindex "&$authentication_failed$&"
11494 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11495 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11496 possible to distinguish between &"did not try to authenticate"&
11497 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11498 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11499 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11500 negative response to an AUTH command, including (for example) an attempt to use
11501 an undefined mechanism.
11503 .vitem &$av_failed$&
11504 .cindex "content scanning" "AV scanner failure"
11505 This variable is available when Exim is compiled with the content-scanning
11506 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11507 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11508 the ACL malware condition.
11510 .vitem &$body_linecount$&
11511 .cindex "message body" "line count"
11512 .cindex "body of message" "line count"
11513 .vindex "&$body_linecount$&"
11514 When a message is being received or delivered, this variable contains the
11515 number of lines in the message's body. See also &$message_linecount$&.
11517 .vitem &$body_zerocount$&
11518 .cindex "message body" "binary zero count"
11519 .cindex "body of message" "binary zero count"
11520 .cindex "binary zero" "in message body"
11521 .vindex "&$body_zerocount$&"
11522 When a message is being received or delivered, this variable contains the
11523 number of binary zero bytes (ASCII NULs) in the message's body.
11525 .vitem &$bounce_recipient$&
11526 .vindex "&$bounce_recipient$&"
11527 This is set to the recipient address of a bounce message while Exim is creating
11528 it. It is useful if a customized bounce message text file is in use (see
11529 chapter &<<CHAPemsgcust>>&).
11531 .vitem &$bounce_return_size_limit$&
11532 .vindex "&$bounce_return_size_limit$&"
11533 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11534 up to a multiple of 1000. It is useful when a customized error message text
11535 file is in use (see chapter &<<CHAPemsgcust>>&).
11537 .vitem &$caller_gid$&
11538 .cindex "gid (group id)" "caller"
11539 .vindex "&$caller_gid$&"
11540 The real group id under which the process that called Exim was running. This is
11541 not the same as the group id of the originator of a message (see
11542 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11543 incarnation normally contains the Exim gid.
11545 .vitem &$caller_uid$&
11546 .cindex "uid (user id)" "caller"
11547 .vindex "&$caller_uid$&"
11548 The real user id under which the process that called Exim was running. This is
11549 not the same as the user id of the originator of a message (see
11550 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11551 incarnation normally contains the Exim uid.
11553 .vitem &$callout_address$&
11554 .vindex "&$callout_address$&"
11555 After a callout for verification, spamd or malware daemon service, the
11556 address that was connected to.
11558 .vitem &$compile_number$&
11559 .vindex "&$compile_number$&"
11560 The building process for Exim keeps a count of the number
11561 of times it has been compiled. This serves to distinguish different
11562 compilations of the same version of the program.
11564 .vitem &$config_dir$&
11565 .vindex "&$config_dir$&"
11566 The directory name of the main configuration file. That is, the content of
11567 &$config_file$& with the last component stripped. The value does not
11568 contain the trailing slash. If &$config_file$& does not contain a slash,
11569 &$config_dir$& is ".".
11571 .vitem &$config_file$&
11572 .vindex "&$config_file$&"
11573 The name of the main configuration file Exim is using.
11575 .vitem &$dkim_cur_signer$& &&&
11576 &$dkim_verify_status$& &&&
11577 &$dkim_verify_reason$& &&&
11578 &$dkim_domain$& &&&
11579 &$dkim_identity$& &&&
11580 &$dkim_selector$& &&&
11582 &$dkim_canon_body$& &&&
11583 &$dkim_canon_headers$& &&&
11584 &$dkim_copiedheaders$& &&&
11585 &$dkim_bodylength$& &&&
11586 &$dkim_created$& &&&
11587 &$dkim_expires$& &&&
11588 &$dkim_headernames$& &&&
11589 &$dkim_key_testing$& &&&
11590 &$dkim_key_nosubdomains$& &&&
11591 &$dkim_key_srvtype$& &&&
11592 &$dkim_key_granularity$& &&&
11593 &$dkim_key_notes$& &&&
11594 &$dkim_key_length$&
11595 These variables are only available within the DKIM ACL.
11596 For details see chapter &<<CHAPdkim>>&.
11598 .vitem &$dkim_signers$&
11599 .vindex &$dkim_signers$&
11600 When a message has been received this variable contains
11601 a colon-separated list of signer domains and identities for the message.
11602 For details see chapter &<<CHAPdkim>>&.
11604 .vitem &$dnslist_domain$& &&&
11605 &$dnslist_matched$& &&&
11606 &$dnslist_text$& &&&
11608 .vindex "&$dnslist_domain$&"
11609 .vindex "&$dnslist_matched$&"
11610 .vindex "&$dnslist_text$&"
11611 .vindex "&$dnslist_value$&"
11612 .cindex "black list (DNS)"
11613 When a DNS (black) list lookup succeeds, these variables are set to contain
11614 the following data from the lookup: the list's domain name, the key that was
11615 looked up, the contents of any associated TXT record, and the value from the
11616 main A record. See section &<<SECID204>>& for more details.
11619 .vindex "&$domain$&"
11620 When an address is being routed, or delivered on its own, this variable
11621 contains the domain. Uppercase letters in the domain are converted into lower
11622 case for &$domain$&.
11624 Global address rewriting happens when a message is received, so the value of
11625 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11626 is set during user filtering, but not during system filtering, because a
11627 message may have many recipients and the system filter is called just once.
11629 When more than one address is being delivered at once (for example, several
11630 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11631 have the same domain. Transports can be restricted to handling only one domain
11632 at a time if the value of &$domain$& is required at transport time &-- this is
11633 the default for local transports. For further details of the environment in
11634 which local transports are run, see chapter &<<CHAPenvironment>>&.
11636 .oindex "&%delay_warning_condition%&"
11637 At the end of a delivery, if all deferred addresses have the same domain, it is
11638 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11640 The &$domain$& variable is also used in some other circumstances:
11643 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11644 the recipient address. The domain of the &'sender'& address is in
11645 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11646 normally set during the running of the MAIL ACL. However, if the sender address
11647 is verified with a callout during the MAIL ACL, the sender domain is placed in
11648 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11649 the &(smtp)& transport.
11652 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11653 &$domain$& contains the domain portion of the address that is being rewritten;
11654 it can be used in the expansion of the replacement address, for example, to
11655 rewrite domains by file lookup.
11658 With one important exception, whenever a domain list is being scanned,
11659 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11660 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11661 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11662 that, in a RCPT ACL, the sender domain list can be dependent on the
11663 recipient domain (which is what is in &$domain$& at this time).
11666 .cindex "ETRN" "value of &$domain$&"
11667 .oindex "&%smtp_etrn_command%&"
11668 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11669 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11673 .vitem &$domain_data$&
11674 .vindex "&$domain_data$&"
11675 When the &%domains%& option on a router matches a domain by
11676 means of a lookup, the data read by the lookup is available during the running
11677 of the router as &$domain_data$&. In addition, if the driver routes the
11678 address to a transport, the value is available in that transport. If the
11679 transport is handling multiple addresses, the value from the first address is
11682 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11683 domain by means of a lookup. The data read by the lookup is available during
11684 the rest of the ACL statement. In all other situations, this variable expands
11687 .vitem &$exim_gid$&
11688 .vindex "&$exim_gid$&"
11689 This variable contains the numerical value of the Exim group id.
11691 .vitem &$exim_path$&
11692 .vindex "&$exim_path$&"
11693 This variable contains the path to the Exim binary.
11695 .vitem &$exim_uid$&
11696 .vindex "&$exim_uid$&"
11697 This variable contains the numerical value of the Exim user id.
11699 .vitem &$exim_version$&
11700 .vindex "&$exim_version$&"
11701 This variable contains the version string of the Exim build.
11702 The first character is a major version number, currently 4.
11703 Then after a dot, the next group of digits is a minor version number.
11704 There may be other characters following the minor version.
11706 .vitem &$header_$&<&'name'&>
11707 This is not strictly an expansion variable. It is expansion syntax for
11708 inserting the message header line with the given name. Note that the name must
11709 be terminated by colon or white space, because it may contain a wide variety of
11710 characters. Note also that braces must &'not'& be used.
11712 .vitem &$headers_added$&
11713 .vindex "&$headers_added$&"
11714 Within an ACL this variable contains the headers added so far by
11715 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11716 The headers are a newline-separated list.
11720 When the &%check_local_user%& option is set for a router, the user's home
11721 directory is placed in &$home$& when the check succeeds. In particular, this
11722 means it is set during the running of users' filter files. A router may also
11723 explicitly set a home directory for use by a transport; this can be overridden
11724 by a setting on the transport itself.
11726 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11727 of the environment variable HOME, which is subject to the
11728 &%keep_environment%& and &%add_environment%& main config options.
11732 If a router assigns an address to a transport (any transport), and passes a
11733 list of hosts with the address, the value of &$host$& when the transport starts
11734 to run is the name of the first host on the list. Note that this applies both
11735 to local and remote transports.
11737 .cindex "transport" "filter"
11738 .cindex "filter" "transport filter"
11739 For the &(smtp)& transport, if there is more than one host, the value of
11740 &$host$& changes as the transport works its way through the list. In
11741 particular, when the &(smtp)& transport is expanding its options for encryption
11742 using TLS, or for specifying a transport filter (see chapter
11743 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11746 When used in the client part of an authenticator configuration (see chapter
11747 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11748 client is connected.
11751 .vitem &$host_address$&
11752 .vindex "&$host_address$&"
11753 This variable is set to the remote host's IP address whenever &$host$& is set
11754 for a remote connection. It is also set to the IP address that is being checked
11755 when the &%ignore_target_hosts%& option is being processed.
11757 .vitem &$host_data$&
11758 .vindex "&$host_data$&"
11759 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11760 result of the lookup is made available in the &$host_data$& variable. This
11761 allows you, for example, to do things like this:
11763 deny hosts = net-lsearch;/some/file
11764 message = $host_data
11766 .vitem &$host_lookup_deferred$&
11767 .cindex "host name" "lookup, failure of"
11768 .vindex "&$host_lookup_deferred$&"
11769 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11770 message comes from a remote host and there is an attempt to look up the host's
11771 name from its IP address, and the attempt is not successful, one of these
11772 variables is set to &"1"&.
11775 If the lookup receives a definite negative response (for example, a DNS lookup
11776 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11779 If there is any kind of problem during the lookup, such that Exim cannot
11780 tell whether or not the host name is defined (for example, a timeout for a DNS
11781 lookup), &$host_lookup_deferred$& is set to &"1"&.
11784 Looking up a host's name from its IP address consists of more than just a
11785 single reverse lookup. Exim checks that a forward lookup of at least one of the
11786 names it receives from a reverse lookup yields the original IP address. If this
11787 is not the case, Exim does not accept the looked up name(s), and
11788 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11789 IP address (for example, the existence of a PTR record in the DNS) is not
11790 sufficient on its own for the success of a host name lookup. If the reverse
11791 lookup succeeds, but there is a lookup problem such as a timeout when checking
11792 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11793 &"1"&. See also &$sender_host_name$&.
11795 .vitem &$host_lookup_failed$&
11796 .vindex "&$host_lookup_failed$&"
11797 See &$host_lookup_deferred$&.
11799 .vitem &$host_port$&
11800 .vindex "&$host_port$&"
11801 This variable is set to the remote host's TCP port whenever &$host$& is set
11802 for an outbound connection.
11804 .vitem &$initial_cwd$&
11805 .vindex "&$initial_cwd$&
11806 This variable contains the full path name of the initial working
11807 directory of the current Exim process. This may differ from the current
11808 working directory, as Exim changes this to "/" during early startup, and
11809 to &$spool_directory$& later.
11812 .vindex "&$inode$&"
11813 The only time this variable is set is while expanding the &%directory_file%&
11814 option in the &(appendfile)& transport. The variable contains the inode number
11815 of the temporary file which is about to be renamed. It can be used to construct
11816 a unique name for the file.
11818 .vitem &$interface_address$&
11819 .vindex "&$interface_address$&"
11820 This is an obsolete name for &$received_ip_address$&.
11822 .vitem &$interface_port$&
11823 .vindex "&$interface_port$&"
11824 This is an obsolete name for &$received_port$&.
11828 This variable is used during the expansion of &*forall*& and &*forany*&
11829 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11830 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11834 .vindex "&$ldap_dn$&"
11835 This variable, which is available only when Exim is compiled with LDAP support,
11836 contains the DN from the last entry in the most recently successful LDAP
11839 .vitem &$load_average$&
11840 .vindex "&$load_average$&"
11841 This variable contains the system load average, multiplied by 1000 so that it
11842 is an integer. For example, if the load average is 0.21, the value of the
11843 variable is 210. The value is recomputed every time the variable is referenced.
11845 .vitem &$local_part$&
11846 .vindex "&$local_part$&"
11847 When an address is being routed, or delivered on its own, this
11848 variable contains the local part. When a number of addresses are being
11849 delivered together (for example, multiple RCPT commands in an SMTP
11850 session), &$local_part$& is not set.
11852 Global address rewriting happens when a message is received, so the value of
11853 &$local_part$& during routing and delivery is the value after rewriting.
11854 &$local_part$& is set during user filtering, but not during system filtering,
11855 because a message may have many recipients and the system filter is called just
11858 .vindex "&$local_part_prefix$&"
11859 .vindex "&$local_part_suffix$&"
11860 If a local part prefix or suffix has been recognized, it is not included in the
11861 value of &$local_part$& during routing and subsequent delivery. The values of
11862 any prefix or suffix are in &$local_part_prefix$& and
11863 &$local_part_suffix$&, respectively.
11865 When a message is being delivered to a file, pipe, or autoreply transport as a
11866 result of aliasing or forwarding, &$local_part$& is set to the local part of
11867 the parent address, not to the file name or command (see &$address_file$& and
11870 When an ACL is running for a RCPT command, &$local_part$& contains the
11871 local part of the recipient address.
11873 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11874 &$local_part$& contains the local part of the address that is being rewritten;
11875 it can be used in the expansion of the replacement address, for example.
11877 In all cases, all quoting is removed from the local part. For example, for both
11880 "abc:xyz"@test.example
11881 abc\:xyz@test.example
11883 the value of &$local_part$& is
11887 If you use &$local_part$& to create another address, you should always wrap it
11888 inside a quoting operator. For example, in a &(redirect)& router you could
11891 data = ${quote_local_part:$local_part}@new.domain.example
11893 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11894 to process local parts in a case-dependent manner in a router, you can set the
11895 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11897 .vitem &$local_part_data$&
11898 .vindex "&$local_part_data$&"
11899 When the &%local_parts%& option on a router matches a local part by means of a
11900 lookup, the data read by the lookup is available during the running of the
11901 router as &$local_part_data$&. In addition, if the driver routes the address
11902 to a transport, the value is available in that transport. If the transport is
11903 handling multiple addresses, the value from the first address is used.
11905 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11906 matches a local part by means of a lookup. The data read by the lookup is
11907 available during the rest of the ACL statement. In all other situations, this
11908 variable expands to nothing.
11910 .vitem &$local_part_prefix$&
11911 .vindex "&$local_part_prefix$&"
11912 When an address is being routed or delivered, and a
11913 specific prefix for the local part was recognized, it is available in this
11914 variable, having been removed from &$local_part$&.
11916 .vitem &$local_part_suffix$&
11917 .vindex "&$local_part_suffix$&"
11918 When an address is being routed or delivered, and a
11919 specific suffix for the local part was recognized, it is available in this
11920 variable, having been removed from &$local_part$&.
11922 .vitem &$local_scan_data$&
11923 .vindex "&$local_scan_data$&"
11924 This variable contains the text returned by the &[local_scan()]& function when
11925 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11927 .vitem &$local_user_gid$&
11928 .vindex "&$local_user_gid$&"
11929 See &$local_user_uid$&.
11931 .vitem &$local_user_uid$&
11932 .vindex "&$local_user_uid$&"
11933 This variable and &$local_user_gid$& are set to the uid and gid after the
11934 &%check_local_user%& router precondition succeeds. This means that their values
11935 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11936 and &%condition%&), for the &%address_data%& expansion, and for any
11937 router-specific expansions. At all other times, the values in these variables
11938 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11940 .vitem &$localhost_number$&
11941 .vindex "&$localhost_number$&"
11942 This contains the expanded value of the
11943 &%localhost_number%& option. The expansion happens after the main options have
11946 .vitem &$log_inodes$&
11947 .vindex "&$log_inodes$&"
11948 The number of free inodes in the disk partition where Exim's
11949 log files are being written. The value is recalculated whenever the variable is
11950 referenced. If the relevant file system does not have the concept of inodes,
11951 the value of is -1. See also the &%check_log_inodes%& option.
11953 .vitem &$log_space$&
11954 .vindex "&$log_space$&"
11955 The amount of free space (as a number of kilobytes) in the disk
11956 partition where Exim's log files are being written. The value is recalculated
11957 whenever the variable is referenced. If the operating system does not have the
11958 ability to find the amount of free space (only true for experimental systems),
11959 the space value is -1. See also the &%check_log_space%& option.
11962 .vitem &$lookup_dnssec_authenticated$&
11963 .vindex "&$lookup_dnssec_authenticated$&"
11964 This variable is set after a DNS lookup done by
11965 a dnsdb lookup expansion, dnslookup router or smtp transport.
11966 .cindex "DNS" "DNSSEC"
11967 It will be empty if &(DNSSEC)& was not requested,
11968 &"no"& if the result was not labelled as authenticated data
11969 and &"yes"& if it was.
11970 Results that are labelled as authoritative answer that match
11971 the &%dns_trust_aa%& configuration variable count also
11972 as authenticated data.
11974 .vitem &$mailstore_basename$&
11975 .vindex "&$mailstore_basename$&"
11976 This variable is set only when doing deliveries in &"mailstore"& format in the
11977 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11978 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11979 contains the basename of the files that are being written, that is, the name
11980 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11983 .vitem &$malware_name$&
11984 .vindex "&$malware_name$&"
11985 This variable is available when Exim is compiled with the
11986 content-scanning extension. It is set to the name of the virus that was found
11987 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11989 .vitem &$max_received_linelength$&
11990 .vindex "&$max_received_linelength$&"
11991 .cindex "maximum" "line length"
11992 .cindex "line length" "maximum"
11993 This variable contains the number of bytes in the longest line that was
11994 received as part of the message, not counting the line termination
11997 .vitem &$message_age$&
11998 .cindex "message" "age of"
11999 .vindex "&$message_age$&"
12000 This variable is set at the start of a delivery attempt to contain the number
12001 of seconds since the message was received. It does not change during a single
12004 .vitem &$message_body$&
12005 .cindex "body of message" "expansion variable"
12006 .cindex "message body" "in expansion"
12007 .cindex "binary zero" "in message body"
12008 .vindex "&$message_body$&"
12009 .oindex "&%message_body_visible%&"
12010 This variable contains the initial portion of a message's body while it is
12011 being delivered, and is intended mainly for use in filter files. The maximum
12012 number of characters of the body that are put into the variable is set by the
12013 &%message_body_visible%& configuration option; the default is 500.
12015 .oindex "&%message_body_newlines%&"
12016 By default, newlines are converted into spaces in &$message_body$&, to make it
12017 easier to search for phrases that might be split over a line break. However,
12018 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12019 zeros are always converted into spaces.
12021 .vitem &$message_body_end$&
12022 .cindex "body of message" "expansion variable"
12023 .cindex "message body" "in expansion"
12024 .vindex "&$message_body_end$&"
12025 This variable contains the final portion of a message's
12026 body while it is being delivered. The format and maximum size are as for
12029 .vitem &$message_body_size$&
12030 .cindex "body of message" "size"
12031 .cindex "message body" "size"
12032 .vindex "&$message_body_size$&"
12033 When a message is being delivered, this variable contains the size of the body
12034 in bytes. The count starts from the character after the blank line that
12035 separates the body from the header. Newlines are included in the count. See
12036 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12038 .vitem &$message_exim_id$&
12039 .vindex "&$message_exim_id$&"
12040 When a message is being received or delivered, this variable contains the
12041 unique message id that is generated and used by Exim to identify the message.
12042 An id is not created for a message until after its header has been successfully
12043 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12044 line; it is the local id that Exim assigns to the message, for example:
12045 &`1BXTIK-0001yO-VA`&.
12047 .vitem &$message_headers$&
12048 .vindex &$message_headers$&
12049 This variable contains a concatenation of all the header lines when a message
12050 is being processed, except for lines added by routers or transports. The header
12051 lines are separated by newline characters. Their contents are decoded in the
12052 same way as a header line that is inserted by &%bheader%&.
12054 .vitem &$message_headers_raw$&
12055 .vindex &$message_headers_raw$&
12056 This variable is like &$message_headers$& except that no processing of the
12057 contents of header lines is done.
12059 .vitem &$message_id$&
12060 This is an old name for &$message_exim_id$&. It is now deprecated.
12062 .vitem &$message_linecount$&
12063 .vindex "&$message_linecount$&"
12064 This variable contains the total number of lines in the header and body of the
12065 message. Compare &$body_linecount$&, which is the count for the body only.
12066 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12067 number of lines received. Before delivery happens (that is, before filters,
12068 routers, and transports run) the count is increased to include the
12069 &'Received:'& header line that Exim standardly adds, and also any other header
12070 lines that are added by ACLs. The blank line that separates the message header
12071 from the body is not counted.
12073 As with the special case of &$message_size$&, during the expansion of the
12074 appendfile transport's maildir_tag option in maildir format, the value of
12075 &$message_linecount$& is the precise size of the number of newlines in the
12076 file that has been written (minus one for the blank line between the
12077 header and the body).
12079 Here is an example of the use of this variable in a DATA ACL:
12081 deny message = Too many lines in message header
12083 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12085 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12086 message has not yet been received.
12088 .vitem &$message_size$&
12089 .cindex "size" "of message"
12090 .cindex "message" "size"
12091 .vindex "&$message_size$&"
12092 When a message is being processed, this variable contains its size in bytes. In
12093 most cases, the size includes those headers that were received with the
12094 message, but not those (such as &'Envelope-to:'&) that are added to individual
12095 deliveries as they are written. However, there is one special case: during the
12096 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12097 doing a delivery in maildir format, the value of &$message_size$& is the
12098 precise size of the file that has been written. See also
12099 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12101 .cindex "RCPT" "value of &$message_size$&"
12102 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12103 contains the size supplied on the MAIL command, or -1 if no size was given. The
12104 value may not, of course, be truthful.
12106 .vitem &$mime_$&&'xxx'&
12107 A number of variables whose names start with &$mime$& are
12108 available when Exim is compiled with the content-scanning extension. For
12109 details, see section &<<SECTscanmimepart>>&.
12111 .vitem "&$n0$& &-- &$n9$&"
12112 These variables are counters that can be incremented by means
12113 of the &%add%& command in filter files.
12115 .vitem &$original_domain$&
12116 .vindex "&$domain$&"
12117 .vindex "&$original_domain$&"
12118 When a top-level address is being processed for delivery, this contains the
12119 same value as &$domain$&. However, if a &"child"& address (for example,
12120 generated by an alias, forward, or filter file) is being processed, this
12121 variable contains the domain of the original address (lower cased). This
12122 differs from &$parent_domain$& only when there is more than one level of
12123 aliasing or forwarding. When more than one address is being delivered in a
12124 single transport run, &$original_domain$& is not set.
12126 If a new address is created by means of a &%deliver%& command in a system
12127 filter, it is set up with an artificial &"parent"& address. This has the local
12128 part &'system-filter'& and the default qualify domain.
12130 .vitem &$original_local_part$&
12131 .vindex "&$local_part$&"
12132 .vindex "&$original_local_part$&"
12133 When a top-level address is being processed for delivery, this contains the
12134 same value as &$local_part$&, unless a prefix or suffix was removed from the
12135 local part, because &$original_local_part$& always contains the full local
12136 part. When a &"child"& address (for example, generated by an alias, forward, or
12137 filter file) is being processed, this variable contains the full local part of
12138 the original address.
12140 If the router that did the redirection processed the local part
12141 case-insensitively, the value in &$original_local_part$& is in lower case.
12142 This variable differs from &$parent_local_part$& only when there is more than
12143 one level of aliasing or forwarding. When more than one address is being
12144 delivered in a single transport run, &$original_local_part$& is not set.
12146 If a new address is created by means of a &%deliver%& command in a system
12147 filter, it is set up with an artificial &"parent"& address. This has the local
12148 part &'system-filter'& and the default qualify domain.
12150 .vitem &$originator_gid$&
12151 .cindex "gid (group id)" "of originating user"
12152 .cindex "sender" "gid"
12153 .vindex "&$caller_gid$&"
12154 .vindex "&$originator_gid$&"
12155 This variable contains the value of &$caller_gid$& that was set when the
12156 message was received. For messages received via the command line, this is the
12157 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12158 normally the gid of the Exim user.
12160 .vitem &$originator_uid$&
12161 .cindex "uid (user id)" "of originating user"
12162 .cindex "sender" "uid"
12163 .vindex "&$caller_uid$&"
12164 .vindex "&$originaltor_uid$&"
12165 The value of &$caller_uid$& that was set when the message was received. For
12166 messages received via the command line, this is the uid of the sending user.
12167 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12170 .vitem &$parent_domain$&
12171 .vindex "&$parent_domain$&"
12172 This variable is similar to &$original_domain$& (see
12173 above), except that it refers to the immediately preceding parent address.
12175 .vitem &$parent_local_part$&
12176 .vindex "&$parent_local_part$&"
12177 This variable is similar to &$original_local_part$&
12178 (see above), except that it refers to the immediately preceding parent address.
12181 .cindex "pid (process id)" "of current process"
12183 This variable contains the current process id.
12185 .vitem &$pipe_addresses$&
12186 .cindex "filter" "transport filter"
12187 .cindex "transport" "filter"
12188 .vindex "&$pipe_addresses$&"
12189 This is not an expansion variable, but is mentioned here because the string
12190 &`$pipe_addresses`& is handled specially in the command specification for the
12191 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12192 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12193 It cannot be used in general expansion strings, and provokes an &"unknown
12194 variable"& error if encountered.
12196 .vitem &$primary_hostname$&
12197 .vindex "&$primary_hostname$&"
12198 This variable contains the value set by &%primary_hostname%& in the
12199 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12200 a single-component name, Exim calls &[gethostbyname()]& (or
12201 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12202 qualified host name. See also &$smtp_active_hostname$&.
12206 .vitem &$proxy_external_address$& &&&
12207 &$proxy_external_port$& &&&
12208 &$proxy_local_address$& &&&
12209 &$proxy_local_port$& &&&
12211 These variables are only available when built with Proxy Protocol
12213 For details see chapter &<<SECTproxyInbound>>&.
12216 .vitem &$prdr_requested$&
12217 .cindex "PRDR" "variable for"
12218 This variable is set to &"yes"& if PRDR was requested by the client for the
12219 current message, otherwise &"no"&.
12221 .vitem &$prvscheck_address$&
12222 This variable is used in conjunction with the &%prvscheck%& expansion item,
12223 which is described in sections &<<SECTexpansionitems>>& and
12224 &<<SECTverifyPRVS>>&.
12226 .vitem &$prvscheck_keynum$&
12227 This variable is used in conjunction with the &%prvscheck%& expansion item,
12228 which is described in sections &<<SECTexpansionitems>>& and
12229 &<<SECTverifyPRVS>>&.
12231 .vitem &$prvscheck_result$&
12232 This variable is used in conjunction with the &%prvscheck%& expansion item,
12233 which is described in sections &<<SECTexpansionitems>>& and
12234 &<<SECTverifyPRVS>>&.
12236 .vitem &$qualify_domain$&
12237 .vindex "&$qualify_domain$&"
12238 The value set for the &%qualify_domain%& option in the configuration file.
12240 .vitem &$qualify_recipient$&
12241 .vindex "&$qualify_recipient$&"
12242 The value set for the &%qualify_recipient%& option in the configuration file,
12243 or if not set, the value of &$qualify_domain$&.
12246 .vitem &$queue_name$&
12247 .vindex &$queue_name$&
12248 .cindex "named queues"
12249 .cindex queues named
12250 The name of the spool queue in use; empty for the default queue.
12253 .vitem &$rcpt_count$&
12254 .vindex "&$rcpt_count$&"
12255 When a message is being received by SMTP, this variable contains the number of
12256 RCPT commands received for the current message. If this variable is used in a
12257 RCPT ACL, its value includes the current command.
12259 .vitem &$rcpt_defer_count$&
12260 .vindex "&$rcpt_defer_count$&"
12261 .cindex "4&'xx'& responses" "count of"
12262 When a message is being received by SMTP, this variable contains the number of
12263 RCPT commands in the current message that have previously been rejected with a
12264 temporary (4&'xx'&) response.
12266 .vitem &$rcpt_fail_count$&
12267 .vindex "&$rcpt_fail_count$&"
12268 When a message is being received by SMTP, this variable contains the number of
12269 RCPT commands in the current message that have previously been rejected with a
12270 permanent (5&'xx'&) response.
12272 .vitem &$received_count$&
12273 .vindex "&$received_count$&"
12274 This variable contains the number of &'Received:'& header lines in the message,
12275 including the one added by Exim (so its value is always greater than zero). It
12276 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12279 .vitem &$received_for$&
12280 .vindex "&$received_for$&"
12281 If there is only a single recipient address in an incoming message, this
12282 variable contains that address when the &'Received:'& header line is being
12283 built. The value is copied after recipient rewriting has happened, but before
12284 the &[local_scan()]& function is run.
12286 .vitem &$received_ip_address$&
12287 .vindex "&$received_ip_address$&"
12288 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12289 variable is set to the address of the local IP interface, and &$received_port$&
12290 is set to the local port number. (The remote IP address and port are in
12291 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12292 the port value is -1 unless it has been set using the &%-oMi%& command line
12295 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12296 could be used, for example, to make the file name for a TLS certificate depend
12297 on which interface and/or port is being used for the incoming connection. The
12298 values of &$received_ip_address$& and &$received_port$& are saved with any
12299 messages that are received, thus making these variables available at delivery
12301 For outbound connections see &$sending_ip_address$&.
12303 .vitem &$received_port$&
12304 .vindex "&$received_port$&"
12305 See &$received_ip_address$&.
12307 .vitem &$received_protocol$&
12308 .vindex "&$received_protocol$&"
12309 When a message is being processed, this variable contains the name of the
12310 protocol by which it was received. Most of the names used by Exim are defined
12311 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12312 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12313 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12314 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12315 connection and the client was successfully authenticated.
12317 Exim uses the protocol name &"smtps"& for the case when encryption is
12318 automatically set up on connection without the use of STARTTLS (see
12319 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12320 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12321 where the client initially uses EHLO, sets up an encrypted connection using
12322 STARTTLS, and then uses HELO afterwards.
12324 The &%-oMr%& option provides a way of specifying a custom protocol name for
12325 messages that are injected locally by trusted callers. This is commonly used to
12326 identify messages that are being re-injected after some kind of scanning.
12328 .vitem &$received_time$&
12329 .vindex "&$received_time$&"
12330 This variable contains the date and time when the current message was received,
12331 as a number of seconds since the start of the Unix epoch.
12333 .vitem &$recipient_data$&
12334 .vindex "&$recipient_data$&"
12335 This variable is set after an indexing lookup success in an ACL &%recipients%&
12336 condition. It contains the data from the lookup, and the value remains set
12337 until the next &%recipients%& test. Thus, you can do things like this:
12339 &`require recipients = cdb*@;/some/file`&
12340 &`deny `&&'some further test involving'& &`$recipient_data`&
12342 &*Warning*&: This variable is set only when a lookup is used as an indexing
12343 method in the address list, using the semicolon syntax as in the example above.
12344 The variable is not set for a lookup that is used as part of the string
12345 expansion that all such lists undergo before being interpreted.
12347 .vitem &$recipient_verify_failure$&
12348 .vindex "&$recipient_verify_failure$&"
12349 In an ACL, when a recipient verification fails, this variable contains
12350 information about the failure. It is set to one of the following words:
12353 &"qualify"&: The address was unqualified (no domain), and the message
12354 was neither local nor came from an exempted host.
12357 &"route"&: Routing failed.
12360 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12361 or before the MAIL command (that is, on initial connection, HELO, or
12365 &"recipient"&: The RCPT command in a callout was rejected.
12368 &"postmaster"&: The postmaster check in a callout was rejected.
12371 The main use of this variable is expected to be to distinguish between
12372 rejections of MAIL and rejections of RCPT.
12374 .vitem &$recipients$&
12375 .vindex "&$recipients$&"
12376 This variable contains a list of envelope recipients for a message. A comma and
12377 a space separate the addresses in the replacement text. However, the variable
12378 is not generally available, to prevent exposure of Bcc recipients in
12379 unprivileged users' filter files. You can use &$recipients$& only in these
12383 In a system filter file.
12385 In the ACLs associated with the DATA command and with non-SMTP messages, that
12386 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12387 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12388 &%acl_not_smtp_mime%&.
12390 From within a &[local_scan()]& function.
12394 .vitem &$recipients_count$&
12395 .vindex "&$recipients_count$&"
12396 When a message is being processed, this variable contains the number of
12397 envelope recipients that came with the message. Duplicates are not excluded
12398 from the count. While a message is being received over SMTP, the number
12399 increases for each accepted recipient. It can be referenced in an ACL.
12402 .vitem &$regex_match_string$&
12403 .vindex "&$regex_match_string$&"
12404 This variable is set to contain the matching regular expression after a
12405 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12407 .vitem "&$regex1$&, &$regex2$&, etc"
12408 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12409 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12410 these variables contain the
12411 captured substrings identified by the regular expression.
12414 .vitem &$reply_address$&
12415 .vindex "&$reply_address$&"
12416 When a message is being processed, this variable contains the contents of the
12417 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12418 contents of the &'From:'& header line. Apart from the removal of leading
12419 white space, the value is not processed in any way. In particular, no RFC 2047
12420 decoding or character code translation takes place.
12422 .vitem &$return_path$&
12423 .vindex "&$return_path$&"
12424 When a message is being delivered, this variable contains the return path &--
12425 the sender field that will be sent as part of the envelope. It is not enclosed
12426 in <> characters. At the start of routing an address, &$return_path$& has the
12427 same value as &$sender_address$&, but if, for example, an incoming message to a
12428 mailing list has been expanded by a router which specifies a different address
12429 for bounce messages, &$return_path$& subsequently contains the new bounce
12430 address, whereas &$sender_address$& always contains the original sender address
12431 that was received with the message. In other words, &$sender_address$& contains
12432 the incoming envelope sender, and &$return_path$& contains the outgoing
12435 .vitem &$return_size_limit$&
12436 .vindex "&$return_size_limit$&"
12437 This is an obsolete name for &$bounce_return_size_limit$&.
12439 .vitem &$router_name$&
12440 .cindex "router" "name"
12441 .cindex "name" "of router"
12442 .vindex "&$router_name$&"
12443 During the running of a router this variable contains its name.
12446 .cindex "return code" "from &%run%& expansion"
12447 .vindex "&$runrc$&"
12448 This variable contains the return code from a command that is run by the
12449 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12450 assume the order in which option values are expanded, except for those
12451 preconditions whose order of testing is documented. Therefore, you cannot
12452 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12455 .vitem &$self_hostname$&
12456 .oindex "&%self%&" "value of host name"
12457 .vindex "&$self_hostname$&"
12458 When an address is routed to a supposedly remote host that turns out to be the
12459 local host, what happens is controlled by the &%self%& generic router option.
12460 One of its values causes the address to be passed to another router. When this
12461 happens, &$self_hostname$& is set to the name of the local host that the
12462 original router encountered. In other circumstances its contents are null.
12464 .vitem &$sender_address$&
12465 .vindex "&$sender_address$&"
12466 When a message is being processed, this variable contains the sender's address
12467 that was received in the message's envelope. The case of letters in the address
12468 is retained, in both the local part and the domain. For bounce messages, the
12469 value of this variable is the empty string. See also &$return_path$&.
12471 .vitem &$sender_address_data$&
12472 .vindex "&$address_data$&"
12473 .vindex "&$sender_address_data$&"
12474 If &$address_data$& is set when the routers are called from an ACL to verify a
12475 sender address, the final value is preserved in &$sender_address_data$&, to
12476 distinguish it from data from a recipient address. The value does not persist
12477 after the end of the current ACL statement. If you want to preserve it for
12478 longer, you can save it in an ACL variable.
12480 .vitem &$sender_address_domain$&
12481 .vindex "&$sender_address_domain$&"
12482 The domain portion of &$sender_address$&.
12484 .vitem &$sender_address_local_part$&
12485 .vindex "&$sender_address_local_part$&"
12486 The local part portion of &$sender_address$&.
12488 .vitem &$sender_data$&
12489 .vindex "&$sender_data$&"
12490 This variable is set after a lookup success in an ACL &%senders%& condition or
12491 in a router &%senders%& option. It contains the data from the lookup, and the
12492 value remains set until the next &%senders%& test. Thus, you can do things like
12495 &`require senders = cdb*@;/some/file`&
12496 &`deny `&&'some further test involving'& &`$sender_data`&
12498 &*Warning*&: This variable is set only when a lookup is used as an indexing
12499 method in the address list, using the semicolon syntax as in the example above.
12500 The variable is not set for a lookup that is used as part of the string
12501 expansion that all such lists undergo before being interpreted.
12503 .vitem &$sender_fullhost$&
12504 .vindex "&$sender_fullhost$&"
12505 When a message is received from a remote host, this variable contains the host
12506 name and IP address in a single string. It ends with the IP address in square
12507 brackets, followed by a colon and a port number if the logging of ports is
12508 enabled. The format of the rest of the string depends on whether the host
12509 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12510 looking up its IP address. (Looking up the IP address can be forced by the
12511 &%host_lookup%& option, independent of verification.) A plain host name at the
12512 start of the string is a verified host name; if this is not present,
12513 verification either failed or was not requested. A host name in parentheses is
12514 the argument of a HELO or EHLO command. This is omitted if it is identical to
12515 the verified host name or to the host's IP address in square brackets.
12517 .vitem &$sender_helo_dnssec$&
12518 .vindex "&$sender_helo_dnssec$&"
12519 This boolean variable is true if a successful HELO verification was
12520 .cindex "DNS" "DNSSEC"
12521 done using DNS information the resolver library stated was authenticated data.
12523 .vitem &$sender_helo_name$&
12524 .vindex "&$sender_helo_name$&"
12525 When a message is received from a remote host that has issued a HELO or EHLO
12526 command, the argument of that command is placed in this variable. It is also
12527 set if HELO or EHLO is used when a message is received using SMTP locally via
12528 the &%-bs%& or &%-bS%& options.
12530 .vitem &$sender_host_address$&
12531 .vindex "&$sender_host_address$&"
12532 When a message is received from a remote host using SMTP,
12533 this variable contains that
12534 host's IP address. For locally non-SMTP submitted messages, it is empty.
12536 .vitem &$sender_host_authenticated$&
12537 .vindex "&$sender_host_authenticated$&"
12538 This variable contains the name (not the public name) of the authenticator
12539 driver that successfully authenticated the client from which the message was
12540 received. It is empty if there was no successful authentication. See also
12541 &$authenticated_id$&.
12543 .vitem &$sender_host_dnssec$&
12544 .vindex "&$sender_host_dnssec$&"
12545 If an attempt to populate &$sender_host_name$& has been made
12546 (by reference, &%hosts_lookup%& or
12547 otherwise) then this boolean will have been set true if, and only if, the
12548 resolver library states that both
12549 the reverse and forward DNS were authenticated data. At all
12550 other times, this variable is false.
12552 .cindex "DNS" "DNSSEC"
12553 It is likely that you will need to coerce DNSSEC support on in the resolver
12554 library, by setting:
12559 Exim does not perform DNSSEC validation itself, instead leaving that to a
12560 validating resolver (e.g. unbound, or bind with suitable configuration).
12562 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12563 mechanism in the list, then this variable will be false.
12566 .vitem &$sender_host_name$&
12567 .vindex "&$sender_host_name$&"
12568 When a message is received from a remote host, this variable contains the
12569 host's name as obtained by looking up its IP address. For messages received by
12570 other means, this variable is empty.
12572 .vindex "&$host_lookup_failed$&"
12573 If the host name has not previously been looked up, a reference to
12574 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12575 A looked up name is accepted only if it leads back to the original IP address
12576 via a forward lookup. If either the reverse or the forward lookup fails to find
12577 any data, or if the forward lookup does not yield the original IP address,
12578 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12580 .vindex "&$host_lookup_deferred$&"
12581 However, if either of the lookups cannot be completed (for example, there is a
12582 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12583 &$host_lookup_failed$& remains set to &"0"&.
12585 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12586 host name again if there is a subsequent reference to &$sender_host_name$&
12587 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12590 Exim does not automatically look up every calling host's name. If you want
12591 maximum efficiency, you should arrange your configuration so that it avoids
12592 these lookups altogether. The lookup happens only if one or more of the
12593 following are true:
12596 A string containing &$sender_host_name$& is expanded.
12598 The calling host matches the list in &%host_lookup%&. In the default
12599 configuration, this option is set to *, so it must be changed if lookups are
12600 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12602 Exim needs the host name in order to test an item in a host list. The items
12603 that require this are described in sections &<<SECThoslispatnam>>& and
12604 &<<SECThoslispatnamsk>>&.
12606 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12607 In this case, the host name is required to compare with the name quoted in any
12608 EHLO or HELO commands that the client issues.
12610 The remote host issues a EHLO or HELO command that quotes one of the
12611 domains in &%helo_lookup_domains%&. The default value of this option is
12612 . ==== As this is a nested list, any displays it contains must be indented
12613 . ==== as otherwise they are too far to the left.
12615 helo_lookup_domains = @ : @[]
12617 which causes a lookup if a remote host (incorrectly) gives the server's name or
12618 IP address in an EHLO or HELO command.
12622 .vitem &$sender_host_port$&
12623 .vindex "&$sender_host_port$&"
12624 When a message is received from a remote host, this variable contains the port
12625 number that was used on the remote host.
12627 .vitem &$sender_ident$&
12628 .vindex "&$sender_ident$&"
12629 When a message is received from a remote host, this variable contains the
12630 identification received in response to an RFC 1413 request. When a message has
12631 been received locally, this variable contains the login name of the user that
12634 .vitem &$sender_rate_$&&'xxx'&
12635 A number of variables whose names begin &$sender_rate_$& are set as part of the
12636 &%ratelimit%& ACL condition. Details are given in section
12637 &<<SECTratelimiting>>&.
12639 .vitem &$sender_rcvhost$&
12640 .cindex "DNS" "reverse lookup"
12641 .cindex "reverse DNS lookup"
12642 .vindex "&$sender_rcvhost$&"
12643 This is provided specifically for use in &'Received:'& headers. It starts with
12644 either the verified host name (as obtained from a reverse DNS lookup) or, if
12645 there is no verified host name, the IP address in square brackets. After that
12646 there may be text in parentheses. When the first item is a verified host name,
12647 the first thing in the parentheses is the IP address in square brackets,
12648 followed by a colon and a port number if port logging is enabled. When the
12649 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12652 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12653 was used and its argument was not identical to the real host name or IP
12654 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12655 all three items are present in the parentheses, a newline and tab are inserted
12656 into the string, to improve the formatting of the &'Received:'& header.
12658 .vitem &$sender_verify_failure$&
12659 .vindex "&$sender_verify_failure$&"
12660 In an ACL, when a sender verification fails, this variable contains information
12661 about the failure. The details are the same as for
12662 &$recipient_verify_failure$&.
12664 .vitem &$sending_ip_address$&
12665 .vindex "&$sending_ip_address$&"
12666 This variable is set whenever an outgoing SMTP connection to another host has
12667 been set up. It contains the IP address of the local interface that is being
12668 used. This is useful if a host that has more than one IP address wants to take
12669 on different personalities depending on which one is being used. For incoming
12670 connections, see &$received_ip_address$&.
12672 .vitem &$sending_port$&
12673 .vindex "&$sending_port$&"
12674 This variable is set whenever an outgoing SMTP connection to another host has
12675 been set up. It contains the local port that is being used. For incoming
12676 connections, see &$received_port$&.
12678 .vitem &$smtp_active_hostname$&
12679 .vindex "&$smtp_active_hostname$&"
12680 During an incoming SMTP session, this variable contains the value of the active
12681 host name, as specified by the &%smtp_active_hostname%& option. The value of
12682 &$smtp_active_hostname$& is saved with any message that is received, so its
12683 value can be consulted during routing and delivery.
12685 .vitem &$smtp_command$&
12686 .vindex "&$smtp_command$&"
12687 During the processing of an incoming SMTP command, this variable contains the
12688 entire command. This makes it possible to distinguish between HELO and EHLO in
12689 the HELO ACL, and also to distinguish between commands such as these:
12694 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12695 command, the address in &$smtp_command$& is the original address before any
12696 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12697 the address after SMTP-time rewriting.
12699 .vitem &$smtp_command_argument$&
12700 .cindex "SMTP" "command, argument for"
12701 .vindex "&$smtp_command_argument$&"
12702 While an ACL is running to check an SMTP command, this variable contains the
12703 argument, that is, the text that follows the command name, with leading white
12704 space removed. Following the introduction of &$smtp_command$&, this variable is
12705 somewhat redundant, but is retained for backwards compatibility.
12707 .vitem &$smtp_count_at_connection_start$&
12708 .vindex "&$smtp_count_at_connection_start$&"
12709 This variable is set greater than zero only in processes spawned by the Exim
12710 daemon for handling incoming SMTP connections. The name is deliberately long,
12711 in order to emphasize what the contents are. When the daemon accepts a new
12712 connection, it increments this variable. A copy of the variable is passed to
12713 the child process that handles the connection, but its value is fixed, and
12714 never changes. It is only an approximation of how many incoming connections
12715 there actually are, because many other connections may come and go while a
12716 single connection is being processed. When a child process terminates, the
12717 daemon decrements its copy of the variable.
12719 .vitem "&$sn0$& &-- &$sn9$&"
12720 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12721 that were current at the end of the system filter file. This allows a system
12722 filter file to set values that can be tested in users' filter files. For
12723 example, a system filter could set a value indicating how likely it is that a
12724 message is junk mail.
12726 .vitem &$spam_$&&'xxx'&
12727 A number of variables whose names start with &$spam$& are available when Exim
12728 is compiled with the content-scanning extension. For details, see section
12729 &<<SECTscanspamass>>&.
12732 .vitem &$spool_directory$&
12733 .vindex "&$spool_directory$&"
12734 The name of Exim's spool directory.
12736 .vitem &$spool_inodes$&
12737 .vindex "&$spool_inodes$&"
12738 The number of free inodes in the disk partition where Exim's spool files are
12739 being written. The value is recalculated whenever the variable is referenced.
12740 If the relevant file system does not have the concept of inodes, the value of
12741 is -1. See also the &%check_spool_inodes%& option.
12743 .vitem &$spool_space$&
12744 .vindex "&$spool_space$&"
12745 The amount of free space (as a number of kilobytes) in the disk partition where
12746 Exim's spool files are being written. The value is recalculated whenever the
12747 variable is referenced. If the operating system does not have the ability to
12748 find the amount of free space (only true for experimental systems), the space
12749 value is -1. For example, to check in an ACL that there is at least 50
12750 megabytes free on the spool, you could write:
12752 condition = ${if > {$spool_space}{50000}}
12754 See also the &%check_spool_space%& option.
12757 .vitem &$thisaddress$&
12758 .vindex "&$thisaddress$&"
12759 This variable is set only during the processing of the &%foranyaddress%&
12760 command in a filter file. Its use is explained in the description of that
12761 command, which can be found in the separate document entitled &'Exim's
12762 interfaces to mail filtering'&.
12764 .vitem &$tls_in_bits$&
12765 .vindex "&$tls_in_bits$&"
12766 Contains an approximation of the TLS cipher's bit-strength
12767 on the inbound connection; the meaning of
12768 this depends upon the TLS implementation used.
12769 If TLS has not been negotiated, the value will be 0.
12770 The value of this is automatically fed into the Cyrus SASL authenticator
12771 when acting as a server, to specify the "external SSF" (a SASL term).
12773 The deprecated &$tls_bits$& variable refers to the inbound side
12774 except when used in the context of an outbound SMTP delivery, when it refers to
12777 .vitem &$tls_out_bits$&
12778 .vindex "&$tls_out_bits$&"
12779 Contains an approximation of the TLS cipher's bit-strength
12780 on an outbound SMTP connection; the meaning of
12781 this depends upon the TLS implementation used.
12782 If TLS has not been negotiated, the value will be 0.
12784 .vitem &$tls_in_ourcert$&
12785 .vindex "&$tls_in_ourcert$&"
12786 .cindex certificate veriables
12787 This variable refers to the certificate presented to the peer of an
12788 inbound connection when the message was received.
12789 It is only useful as the argument of a
12790 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12791 or a &%def%& condition.
12793 .vitem &$tls_in_peercert$&
12794 .vindex "&$tls_in_peercert$&"
12795 This variable refers to the certificate presented by the peer of an
12796 inbound connection when the message was received.
12797 It is only useful as the argument of a
12798 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12799 or a &%def%& condition.
12800 If certificate verification fails it may refer to a failing chain element
12801 which is not the leaf.
12803 .vitem &$tls_out_ourcert$&
12804 .vindex "&$tls_out_ourcert$&"
12805 This variable refers to the certificate presented to the peer of an
12806 outbound connection. It is only useful as the argument of a
12807 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12808 or a &%def%& condition.
12810 .vitem &$tls_out_peercert$&
12811 .vindex "&$tls_out_peercert$&"
12812 This variable refers to the certificate presented by the peer of an
12813 outbound connection. It is only useful as the argument of a
12814 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12815 or a &%def%& condition.
12816 If certificate verification fails it may refer to a failing chain element
12817 which is not the leaf.
12819 .vitem &$tls_in_certificate_verified$&
12820 .vindex "&$tls_in_certificate_verified$&"
12821 This variable is set to &"1"& if a TLS certificate was verified when the
12822 message was received, and &"0"& otherwise.
12824 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
12825 except when used in the context of an outbound SMTP delivery, when it refers to
12828 .vitem &$tls_out_certificate_verified$&
12829 .vindex "&$tls_out_certificate_verified$&"
12830 This variable is set to &"1"& if a TLS certificate was verified when an
12831 outbound SMTP connection was made,
12832 and &"0"& otherwise.
12834 .vitem &$tls_in_cipher$&
12835 .vindex "&$tls_in_cipher$&"
12836 .vindex "&$tls_cipher$&"
12837 When a message is received from a remote host over an encrypted SMTP
12838 connection, this variable is set to the cipher suite that was negotiated, for
12839 example DES-CBC3-SHA. In other circumstances, in particular, for message
12840 received over unencrypted connections, the variable is empty. Testing
12841 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
12842 non-encrypted connections during ACL processing.
12844 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12845 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12846 becomes the same as &$tls_out_cipher$&.
12848 .vitem &$tls_out_cipher$&
12849 .vindex "&$tls_out_cipher$&"
12851 cleared before any outgoing SMTP connection is made,
12852 and then set to the outgoing cipher suite if one is negotiated. See chapter
12853 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12854 details of the &(smtp)& transport.
12856 .vitem &$tls_in_ocsp$&
12857 .vindex "&$tls_in_ocsp$&"
12858 When a message is received from a remote client connection
12859 the result of any OCSP request from the client is encoded in this variable:
12861 0 OCSP proof was not requested (default value)
12862 1 No response to request
12863 2 Response not verified
12864 3 Verification failed
12865 4 Verification succeeded
12868 .vitem &$tls_out_ocsp$&
12869 .vindex "&$tls_out_ocsp$&"
12870 When a message is sent to a remote host connection
12871 the result of any OCSP request made is encoded in this variable.
12872 See &$tls_in_ocsp$& for values.
12874 .vitem &$tls_in_peerdn$&
12875 .vindex "&$tls_in_peerdn$&"
12876 .vindex "&$tls_peerdn$&"
12877 .cindex certificate "extracting fields"
12878 When a message is received from a remote host over an encrypted SMTP
12879 connection, and Exim is configured to request a certificate from the client,
12880 the value of the Distinguished Name of the certificate is made available in the
12881 &$tls_in_peerdn$& during subsequent processing.
12882 If certificate verification fails it may refer to a failing chain element
12883 which is not the leaf.
12885 The deprecated &$tls_peerdn$& variable refers to the inbound side
12886 except when used in the context of an outbound SMTP delivery, when it refers to
12889 .vitem &$tls_out_peerdn$&
12890 .vindex "&$tls_out_peerdn$&"
12891 When a message is being delivered to a remote host over an encrypted SMTP
12892 connection, and Exim is configured to request a certificate from the server,
12893 the value of the Distinguished Name of the certificate is made available in the
12894 &$tls_out_peerdn$& during subsequent processing.
12895 If certificate verification fails it may refer to a failing chain element
12896 which is not the leaf.
12898 .vitem &$tls_in_sni$&
12899 .vindex "&$tls_in_sni$&"
12900 .vindex "&$tls_sni$&"
12901 .cindex "TLS" "Server Name Indication"
12902 When a TLS session is being established, if the client sends the Server
12903 Name Indication extension, the value will be placed in this variable.
12904 If the variable appears in &%tls_certificate%& then this option and
12905 some others, described in &<<SECTtlssni>>&,
12906 will be re-expanded early in the TLS session, to permit
12907 a different certificate to be presented (and optionally a different key to be
12908 used) to the client, based upon the value of the SNI extension.
12910 The deprecated &$tls_sni$& variable refers to the inbound side
12911 except when used in the context of an outbound SMTP delivery, when it refers to
12914 .vitem &$tls_out_sni$&
12915 .vindex "&$tls_out_sni$&"
12916 .cindex "TLS" "Server Name Indication"
12918 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12921 .vitem &$tod_bsdinbox$&
12922 .vindex "&$tod_bsdinbox$&"
12923 The time of day and the date, in the format required for BSD-style mailbox
12924 files, for example: Thu Oct 17 17:14:09 1995.
12926 .vitem &$tod_epoch$&
12927 .vindex "&$tod_epoch$&"
12928 The time and date as a number of seconds since the start of the Unix epoch.
12930 .vitem &$tod_epoch_l$&
12931 .vindex "&$tod_epoch_l$&"
12932 The time and date as a number of microseconds since the start of the Unix epoch.
12934 .vitem &$tod_full$&
12935 .vindex "&$tod_full$&"
12936 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12937 +0100. The timezone is always given as a numerical offset from UTC, with
12938 positive values used for timezones that are ahead (east) of UTC, and negative
12939 values for those that are behind (west).
12942 .vindex "&$tod_log$&"
12943 The time and date in the format used for writing Exim's log files, for example:
12944 1995-10-12 15:32:29, but without a timezone.
12946 .vitem &$tod_logfile$&
12947 .vindex "&$tod_logfile$&"
12948 This variable contains the date in the format yyyymmdd. This is the format that
12949 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12952 .vitem &$tod_zone$&
12953 .vindex "&$tod_zone$&"
12954 This variable contains the numerical value of the local timezone, for example:
12957 .vitem &$tod_zulu$&
12958 .vindex "&$tod_zulu$&"
12959 This variable contains the UTC date and time in &"Zulu"& format, as specified
12960 by ISO 8601, for example: 20030221154023Z.
12962 .vitem &$transport_name$&
12963 .cindex "transport" "name"
12964 .cindex "name" "of transport"
12965 .vindex "&$transport_name$&"
12966 During the running of a transport, this variable contains its name.
12969 .vindex "&$value$&"
12970 This variable contains the result of an expansion lookup, extraction operation,
12971 or external command, as described above. It is also used during a
12972 &*reduce*& expansion.
12974 .vitem &$verify_mode$&
12975 .vindex "&$verify_mode$&"
12976 While a router or transport is being run in verify mode
12977 or for cutthrough delivery,
12978 contains "S" for sender-verification or "R" for recipient-verification.
12981 .vitem &$version_number$&
12982 .vindex "&$version_number$&"
12983 The version number of Exim.
12985 .vitem &$warn_message_delay$&
12986 .vindex "&$warn_message_delay$&"
12987 This variable is set only during the creation of a message warning about a
12988 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12990 .vitem &$warn_message_recipients$&
12991 .vindex "&$warn_message_recipients$&"
12992 This variable is set only during the creation of a message warning about a
12993 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12999 . ////////////////////////////////////////////////////////////////////////////
13000 . ////////////////////////////////////////////////////////////////////////////
13002 .chapter "Embedded Perl" "CHAPperl"
13003 .scindex IIDperl "Perl" "calling from Exim"
13004 Exim can be built to include an embedded Perl interpreter. When this is done,
13005 Perl subroutines can be called as part of the string expansion process. To make
13006 use of the Perl support, you need version 5.004 or later of Perl installed on
13007 your system. To include the embedded interpreter in the Exim binary, include
13012 in your &_Local/Makefile_& and then build Exim in the normal way.
13015 .section "Setting up so Perl can be used" "SECID85"
13016 .oindex "&%perl_startup%&"
13017 Access to Perl subroutines is via a global configuration option called
13018 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13019 no &%perl_startup%& option in the Exim configuration file then no Perl
13020 interpreter is started and there is almost no overhead for Exim (since none of
13021 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13022 option then the associated value is taken to be Perl code which is executed in
13023 a newly created Perl interpreter.
13025 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13026 need backslashes before any characters to escape special meanings. The option
13027 should usually be something like
13029 perl_startup = do '/etc/exim.pl'
13031 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13032 use from Exim. Exim can be configured either to start up a Perl interpreter as
13033 soon as it is entered, or to wait until the first time it is needed. Starting
13034 the interpreter at the beginning ensures that it is done while Exim still has
13035 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13036 fact used in a particular run. Also, note that this does not mean that Exim is
13037 necessarily running as root when Perl is called at a later time. By default,
13038 the interpreter is started only when it is needed, but this can be changed in
13042 .oindex "&%perl_at_start%&"
13043 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13044 a startup when Exim is entered.
13046 The command line option &%-ps%& also requests a startup when Exim is entered,
13047 overriding the setting of &%perl_at_start%&.
13050 There is also a command line option &%-pd%& (for delay) which suppresses the
13051 initial startup, even if &%perl_at_start%& is set.
13055 .oindex "&%perl_taintmode%&"
13056 .cindex "Perl" "taintmode"
13057 To provide more security executing Perl code via the embedded Perl
13058 interpeter, the &%perl_taintmode%& option can be set. This enables the
13059 taint mode of the Perl interpreter. You are encouraged to set this
13060 option to a true value. To avoid breaking existing installations, it
13065 .section "Calling Perl subroutines" "SECID86"
13066 When the configuration file includes a &%perl_startup%& option you can make use
13067 of the string expansion item to call the Perl subroutines that are defined
13068 by the &%perl_startup%& code. The operator is used in any of the following
13072 ${perl{foo}{argument}}
13073 ${perl{foo}{argument1}{argument2} ... }
13075 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
13076 arguments may be passed. Passing more than this results in an expansion failure
13077 with an error message of the form
13079 Too many arguments passed to Perl subroutine "foo" (max is 8)
13081 The return value of the Perl subroutine is evaluated in a scalar context before
13082 it is passed back to Exim to be inserted into the expanded string. If the
13083 return value is &'undef'&, the expansion is forced to fail in the same way as
13084 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
13085 by obeying Perl's &%die%& function, the expansion fails with the error message
13086 that was passed to &%die%&.
13089 .section "Calling Exim functions from Perl" "SECID87"
13090 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
13091 is available to call back into Exim's string expansion function. For example,
13094 my $lp = Exim::expand_string('$local_part');
13096 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
13097 Note those are single quotes and not double quotes to protect against
13098 &$local_part$& being interpolated as a Perl variable.
13100 If the string expansion is forced to fail by a &"fail"& item, the result of
13101 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
13102 expansion string, the Perl call from the original expansion string fails with
13103 an appropriate error message, in the same way as if &%die%& were used.
13105 .cindex "debugging" "from embedded Perl"
13106 .cindex "log" "writing from embedded Perl"
13107 Two other Exim functions are available for use from within Perl code.
13108 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
13109 debugging is enabled. If you want a newline at the end, you must supply it.
13110 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
13111 timestamp. In this case, you should not supply a terminating newline.
13114 .section "Use of standard output and error by Perl" "SECID88"
13115 .cindex "Perl" "standard output and error"
13116 You should not write to the standard error or output streams from within your
13117 Perl code, as it is not defined how these are set up. In versions of Exim
13118 before 4.50, it is possible for the standard output or error to refer to the
13119 SMTP connection during message reception via the daemon. Writing to this stream
13120 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
13121 error streams are connected to &_/dev/null_& in the daemon. The chaos is
13122 avoided, but the output is lost.
13124 .cindex "Perl" "use of &%warn%&"
13125 The Perl &%warn%& statement writes to the standard error stream by default.
13126 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
13127 you have no control. When Exim starts up the Perl interpreter, it arranges for
13128 output from the &%warn%& statement to be written to the Exim main log. You can
13129 change this by including appropriate Perl magic somewhere in your Perl code.
13130 For example, to discard &%warn%& output completely, you need this:
13132 $SIG{__WARN__} = sub { };
13134 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
13135 example, the code for the subroutine is empty, so it does nothing, but you can
13136 include any Perl code that you like. The text of the &%warn%& message is passed
13137 as the first subroutine argument.
13141 . ////////////////////////////////////////////////////////////////////////////
13142 . ////////////////////////////////////////////////////////////////////////////
13144 .chapter "Starting the daemon and the use of network interfaces" &&&
13145 "CHAPinterfaces" &&&
13146 "Starting the daemon"
13147 .cindex "daemon" "starting"
13148 .cindex "interface" "listening"
13149 .cindex "network interface"
13150 .cindex "interface" "network"
13151 .cindex "IP address" "for listening"
13152 .cindex "daemon" "listening IP addresses"
13153 .cindex "TCP/IP" "setting listening interfaces"
13154 .cindex "TCP/IP" "setting listening ports"
13155 A host that is connected to a TCP/IP network may have one or more physical
13156 hardware network interfaces. Each of these interfaces may be configured as one
13157 or more &"logical"& interfaces, which are the entities that a program actually
13158 works with. Each of these logical interfaces is associated with an IP address.
13159 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13160 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13161 knowledge about the host's interfaces for use in three different circumstances:
13164 When a listening daemon is started, Exim needs to know which interfaces
13165 and ports to listen on.
13167 When Exim is routing an address, it needs to know which IP addresses
13168 are associated with local interfaces. This is required for the correct
13169 processing of MX lists by removing the local host and others with the
13170 same or higher priority values. Also, Exim needs to detect cases
13171 when an address is routed to an IP address that in fact belongs to the
13172 local host. Unless the &%self%& router option or the &%allow_localhost%&
13173 option of the smtp transport is set (as appropriate), this is treated
13174 as an error situation.
13176 When Exim connects to a remote host, it may need to know which interface to use
13177 for the outgoing connection.
13181 Exim's default behaviour is likely to be appropriate in the vast majority
13182 of cases. If your host has only one interface, and you want all its IP
13183 addresses to be treated in the same way, and you are using only the
13184 standard SMTP port, you should not need to take any special action. The
13185 rest of this chapter does not apply to you.
13187 In a more complicated situation you may want to listen only on certain
13188 interfaces, or on different ports, and for this reason there are a number of
13189 options that can be used to influence Exim's behaviour. The rest of this
13190 chapter describes how they operate.
13192 When a message is received over TCP/IP, the interface and port that were
13193 actually used are set in &$received_ip_address$& and &$received_port$&.
13197 .section "Starting a listening daemon" "SECID89"
13198 When a listening daemon is started (by means of the &%-bd%& command line
13199 option), the interfaces and ports on which it listens are controlled by the
13203 &%daemon_smtp_ports%& contains a list of default ports
13205 (For backward compatibility, this option can also be specified in the singular.)
13207 &%local_interfaces%& contains list of interface IP addresses on which to
13208 listen. Each item may optionally also specify a port.
13211 The default list separator in both cases is a colon, but this can be changed as
13212 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
13213 it is usually best to change the separator to avoid having to double all the
13214 colons. For example:
13216 local_interfaces = <; 127.0.0.1 ; \
13219 3ffe:ffff:836f::fe86:a061
13221 There are two different formats for specifying a port along with an IP address
13222 in &%local_interfaces%&:
13225 The port is added onto the address with a dot separator. For example, to listen
13226 on port 1234 on two different IP addresses:
13228 local_interfaces = <; 192.168.23.65.1234 ; \
13229 3ffe:ffff:836f::fe86:a061.1234
13232 The IP address is enclosed in square brackets, and the port is added
13233 with a colon separator, for example:
13235 local_interfaces = <; [192.168.23.65]:1234 ; \
13236 [3ffe:ffff:836f::fe86:a061]:1234
13240 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13241 default setting contains just one port:
13243 daemon_smtp_ports = smtp
13245 If more than one port is listed, each interface that does not have its own port
13246 specified listens on all of them. Ports that are listed in
13247 &%daemon_smtp_ports%& can be identified either by name (defined in
13248 &_/etc/services_&) or by number. However, when ports are given with individual
13249 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13253 .section "Special IP listening addresses" "SECID90"
13254 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13255 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13256 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13257 instead of setting up separate listening sockets for each interface. The
13258 default value of &%local_interfaces%& is
13260 local_interfaces = 0.0.0.0
13262 when Exim is built without IPv6 support; otherwise it is:
13264 local_interfaces = <; ::0 ; 0.0.0.0
13266 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13270 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13271 The &%-oX%& command line option can be used to override the values of
13272 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13273 instance. Another way of doing this would be to use macros and the &%-D%&
13274 option. However, &%-oX%& can be used by any admin user, whereas modification of
13275 the runtime configuration by &%-D%& is allowed only when the caller is root or
13278 The value of &%-oX%& is a list of items. The default colon separator can be
13279 changed in the usual way if required. If there are any items that do not
13280 contain dots or colons (that is, are not IP addresses), the value of
13281 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13282 items that do contain dots or colons, the value of &%local_interfaces%& is
13283 replaced by those items. Thus, for example,
13287 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13290 -oX 192.168.34.5.1125
13292 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13293 (However, since &%local_interfaces%& now contains no items without ports, the
13294 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13298 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
13299 .cindex "ssmtp protocol"
13300 .cindex "smtps protocol"
13301 .cindex "SMTP" "ssmtp protocol"
13302 .cindex "SMTP" "smtps protocol"
13303 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
13304 before the STARTTLS command was standardized for SMTP. Some legacy clients
13305 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
13306 list of port numbers or service names,
13307 connections to those ports must use SSMTP. The most
13308 common use of this option is expected to be
13310 tls_on_connect_ports = 465
13312 because 465 is the usual port number used by the legacy clients. There is also
13313 a command line option &%-tls-on-connect%&, which forces all ports to behave in
13314 this way when a daemon is started.
13316 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13317 daemon to listen on those ports. You must still specify them in
13318 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13319 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13320 connections via the daemon.)
13325 .section "IPv6 address scopes" "SECID92"
13326 .cindex "IPv6" "address scopes"
13327 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13328 can, in principle, have the same link-local IPv6 address on different
13329 interfaces. Thus, additional information is needed, over and above the IP
13330 address, to distinguish individual interfaces. A convention of using a
13331 percent sign followed by something (often the interface name) has been
13332 adopted in some cases, leading to addresses like this:
13334 fe80::202:b3ff:fe03:45c1%eth0
13336 To accommodate this usage, a percent sign followed by an arbitrary string is
13337 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13338 to convert a textual IPv6 address for actual use. This function recognizes the
13339 percent convention in operating systems that support it, and it processes the
13340 address appropriately. Unfortunately, some older libraries have problems with
13341 &[getaddrinfo()]&. If
13343 IPV6_USE_INET_PTON=yes
13345 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13346 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13347 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13348 function.) Of course, this means that the additional functionality of
13349 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13351 .section "Disabling IPv6" "SECID93"
13352 .cindex "IPv6" "disabling"
13353 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13354 run on a host whose kernel does not support IPv6. The binary will fall back to
13355 using IPv4, but it may waste resources looking up AAAA records, and trying to
13356 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13357 .oindex "&%disable_ipv6%&"
13358 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13359 activities take place. AAAA records are never looked up, and any IPv6 addresses
13360 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13361 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13362 to handle IPv6 literal addresses.
13364 On the other hand, when IPv6 is in use, there may be times when you want to
13365 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13366 option to globally suppress the lookup of AAAA records for specified domains,
13367 and you can use the &%ignore_target_hosts%& generic router option to ignore
13368 IPv6 addresses in an individual router.
13372 .section "Examples of starting a listening daemon" "SECID94"
13373 The default case in an IPv6 environment is
13375 daemon_smtp_ports = smtp
13376 local_interfaces = <; ::0 ; 0.0.0.0
13378 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13379 Either one or two sockets may be used, depending on the characteristics of
13380 the TCP/IP stack. (This is complicated and messy; for more information,
13381 read the comments in the &_daemon.c_& source file.)
13383 To specify listening on ports 25 and 26 on all interfaces:
13385 daemon_smtp_ports = 25 : 26
13387 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13389 local_interfaces = <; ::0.25 ; ::0.26 \
13390 0.0.0.0.25 ; 0.0.0.0.26
13392 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13393 IPv4 loopback address only:
13395 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13397 To specify listening on the default port on specific interfaces only:
13399 local_interfaces = 10.0.0.67 : 192.168.34.67
13401 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13405 .section "Recognizing the local host" "SECTreclocipadd"
13406 The &%local_interfaces%& option is also used when Exim needs to determine
13407 whether or not an IP address refers to the local host. That is, the IP
13408 addresses of all the interfaces on which a daemon is listening are always
13411 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13412 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13413 available interfaces from the operating system, and extracts the relevant
13414 (that is, IPv4 or IPv6) addresses to use for checking.
13416 Some systems set up large numbers of virtual interfaces in order to provide
13417 many virtual web servers. In this situation, you may want to listen for
13418 email on only a few of the available interfaces, but nevertheless treat all
13419 interfaces as local when routing. You can do this by setting
13420 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13421 &"all"& wildcard values. These addresses are recognized as local, but are not
13422 used for listening. Consider this example:
13424 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13426 3ffe:2101:12:1:a00:20ff:fe86:a061
13428 extra_local_interfaces = <; ::0 ; 0.0.0.0
13430 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13431 address, but all available interface addresses are treated as local when
13434 In some environments the local host name may be in an MX list, but with an IP
13435 address that is not assigned to any local interface. In other cases it may be
13436 desirable to treat other host names as if they referred to the local host. Both
13437 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13438 This contains host names rather than IP addresses. When a host is referenced
13439 during routing, either via an MX record or directly, it is treated as the local
13440 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13441 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13445 .section "Delivering to a remote host" "SECID95"
13446 Delivery to a remote host is handled by the smtp transport. By default, it
13447 allows the system's TCP/IP functions to choose which interface to use (if
13448 there is more than one) when connecting to a remote host. However, the
13449 &%interface%& option can be set to specify which interface is used. See the
13450 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13456 . ////////////////////////////////////////////////////////////////////////////
13457 . ////////////////////////////////////////////////////////////////////////////
13459 .chapter "Main configuration" "CHAPmainconfig"
13460 .scindex IIDconfima "configuration file" "main section"
13461 .scindex IIDmaiconf "main configuration"
13462 The first part of the run time configuration file contains three types of item:
13465 Macro definitions: These lines start with an upper case letter. See section
13466 &<<SECTmacrodefs>>& for details of macro processing.
13468 Named list definitions: These lines start with one of the words &"domainlist"&,
13469 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13470 section &<<SECTnamedlists>>&.
13472 Main configuration settings: Each setting occupies one line of the file
13473 (with possible continuations). If any setting is preceded by the word
13474 &"hide"&, the &%-bP%& command line option displays its value to admin users
13475 only. See section &<<SECTcos>>& for a description of the syntax of these option
13479 This chapter specifies all the main configuration options, along with their
13480 types and default values. For ease of finding a particular option, they appear
13481 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13482 are now so many options, they are first listed briefly in functional groups, as
13483 an aid to finding the name of the option you are looking for. Some options are
13484 listed in more than one group.
13486 .section "Miscellaneous" "SECID96"
13488 .row &%bi_command%& "to run for &%-bi%& command line option"
13489 .row &%disable_ipv6%& "do no IPv6 processing"
13490 .row &%keep_malformed%& "for broken files &-- should not happen"
13491 .row &%localhost_number%& "for unique message ids in clusters"
13492 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13493 .row &%message_body_visible%& "how much to show in &$message_body$&"
13494 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13495 .row &%print_topbitchars%& "top-bit characters are printing"
13496 .row &%timezone%& "force time zone"
13500 .section "Exim parameters" "SECID97"
13502 .row &%exim_group%& "override compiled-in value"
13503 .row &%exim_path%& "override compiled-in value"
13504 .row &%exim_user%& "override compiled-in value"
13505 .row &%primary_hostname%& "default from &[uname()]&"
13506 .row &%split_spool_directory%& "use multiple directories"
13507 .row &%spool_directory%& "override compiled-in value"
13512 .section "Privilege controls" "SECID98"
13514 .row &%admin_groups%& "groups that are Exim admin users"
13515 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13516 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13517 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13518 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13519 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13520 .row &%never_users%& "do not run deliveries as these"
13521 .row &%prod_requires_admin%& "forced delivery requires admin user"
13522 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13523 .row &%trusted_groups%& "groups that are trusted"
13524 .row &%trusted_users%& "users that are trusted"
13529 .section "Logging" "SECID99"
13531 .row &%event_action%& "custom logging"
13532 .row &%hosts_connection_nolog%& "exemption from connect logging"
13533 .row &%log_file_path%& "override compiled-in value"
13534 .row &%log_selector%& "set/unset optional logging"
13535 .row &%log_timezone%& "add timezone to log lines"
13536 .row &%message_logs%& "create per-message logs"
13537 .row &%preserve_message_logs%& "after message completion"
13538 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13539 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13540 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13541 .row &%syslog_facility%& "set syslog &""facility""& field"
13542 .row &%syslog_processname%& "set syslog &""ident""& field"
13543 .row &%syslog_timestamp%& "timestamp syslog lines"
13544 .row &%write_rejectlog%& "control use of message log"
13549 .section "Frozen messages" "SECID100"
13551 .row &%auto_thaw%& "sets time for retrying frozen messages"
13552 .row &%freeze_tell%& "send message when freezing"
13553 .row &%move_frozen_messages%& "to another directory"
13554 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13559 .section "Data lookups" "SECID101"
13561 .row &%ibase_servers%& "InterBase servers"
13562 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13563 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13564 .row &%ldap_cert_file%& "client cert file for LDAP"
13565 .row &%ldap_cert_key%& "client key file for LDAP"
13566 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13567 .row &%ldap_default_servers%& "used if no server in query"
13568 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13569 .row &%ldap_start_tls%& "require TLS within LDAP"
13570 .row &%ldap_version%& "set protocol version"
13571 .row &%lookup_open_max%& "lookup files held open"
13572 .row &%mysql_servers%& "default MySQL servers"
13573 .row &%oracle_servers%& "Oracle servers"
13574 .row &%pgsql_servers%& "default PostgreSQL servers"
13575 .row &%sqlite_lock_timeout%& "as it says"
13580 .section "Message ids" "SECID102"
13582 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13583 .row &%message_id_header_text%& "ditto"
13588 .section "Embedded Perl Startup" "SECID103"
13590 .row &%perl_at_start%& "always start the interpreter"
13591 .row &%perl_startup%& "code to obey when starting Perl"
13592 .row &%perl_taintmode%& "enable taint mode in Perl"
13597 .section "Daemon" "SECID104"
13599 .row &%daemon_smtp_ports%& "default ports"
13600 .row &%daemon_startup_retries%& "number of times to retry"
13601 .row &%daemon_startup_sleep%& "time to sleep between tries"
13602 .row &%extra_local_interfaces%& "not necessarily listened on"
13603 .row &%local_interfaces%& "on which to listen, with optional ports"
13604 .row &%pid_file_path%& "override compiled-in value"
13605 .row &%queue_run_max%& "maximum simultaneous queue runners"
13610 .section "Resource control" "SECID105"
13612 .row &%check_log_inodes%& "before accepting a message"
13613 .row &%check_log_space%& "before accepting a message"
13614 .row &%check_spool_inodes%& "before accepting a message"
13615 .row &%check_spool_space%& "before accepting a message"
13616 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13617 .row &%queue_only_load%& "queue incoming if load high"
13618 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13619 .row &%queue_run_max%& "maximum simultaneous queue runners"
13620 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13621 .row &%smtp_accept_max%& "simultaneous incoming connections"
13622 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13623 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13624 .row &%smtp_accept_max_per_connection%& "messages per connection"
13625 .row &%smtp_accept_max_per_host%& "connections from one host"
13626 .row &%smtp_accept_queue%& "queue mail if more connections"
13627 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13629 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13630 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13631 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13632 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13633 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13638 .section "Policy controls" "SECID106"
13640 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13641 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13642 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13643 .row &%acl_smtp_auth%& "ACL for AUTH"
13644 .row &%acl_smtp_connect%& "ACL for connection"
13645 .row &%acl_smtp_data%& "ACL for DATA"
13646 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13647 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13648 .row &%acl_smtp_etrn%& "ACL for ETRN"
13649 .row &%acl_smtp_expn%& "ACL for EXPN"
13650 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13651 .row &%acl_smtp_mail%& "ACL for MAIL"
13652 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13653 .row &%acl_smtp_mime%& "ACL for MIME parts"
13654 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13655 .row &%acl_smtp_predata%& "ACL for start of data"
13656 .row &%acl_smtp_quit%& "ACL for QUIT"
13657 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13658 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13659 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13660 .row &%av_scanner%& "specify virus scanner"
13661 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13663 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13664 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13665 .row &%header_maxsize%& "total size of message header"
13666 .row &%header_line_maxsize%& "individual header line limit"
13667 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13668 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13669 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13670 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13671 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13672 .row &%host_lookup%& "host name looked up for these hosts"
13673 .row &%host_lookup_order%& "order of DNS and local name lookups"
13674 .row &%hosts_proxy%& "use proxy protocol for these hosts"
13675 .row &%host_reject_connection%& "reject connection from these hosts"
13676 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13677 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13678 .row &%message_size_limit%& "for all messages"
13679 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13680 .row &%spamd_address%& "set interface to SpamAssassin"
13681 .row &%strict_acl_vars%& "object to unset ACL variables"
13686 .section "Callout cache" "SECID107"
13688 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13690 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13692 .row &%callout_negative_expire%& "timeout for negative address cache item"
13693 .row &%callout_positive_expire%& "timeout for positive address cache item"
13694 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13699 .section "TLS" "SECID108"
13701 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13702 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13703 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13704 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13705 .row &%tls_certificate%& "location of server certificate"
13706 .row &%tls_crl%& "certificate revocation list"
13707 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13708 .row &%tls_dhparam%& "DH parameters for server"
13709 .row &%tls_eccurve%& "EC curve selection for server"
13710 .row &%tls_ocsp_file%& "location of server certificate status proof"
13711 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13712 .row &%tls_privatekey%& "location of server private key"
13713 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13714 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13715 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13716 .row &%tls_verify_certificates%& "expected client certificates"
13717 .row &%tls_verify_hosts%& "insist on client certificate verify"
13722 .section "Local user handling" "SECID109"
13724 .row &%finduser_retries%& "useful in NIS environments"
13725 .row &%gecos_name%& "used when creating &'Sender:'&"
13726 .row &%gecos_pattern%& "ditto"
13727 .row &%max_username_length%& "for systems that truncate"
13728 .row &%unknown_login%& "used when no login name found"
13729 .row &%unknown_username%& "ditto"
13730 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13731 .row &%uucp_from_sender%& "ditto"
13736 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13738 .row &%header_maxsize%& "total size of message header"
13739 .row &%header_line_maxsize%& "individual header line limit"
13740 .row &%message_size_limit%& "applies to all messages"
13741 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13742 .row &%received_header_text%& "expanded to make &'Received:'&"
13743 .row &%received_headers_max%& "for mail loop detection"
13744 .row &%recipients_max%& "limit per message"
13745 .row &%recipients_max_reject%& "permanently reject excess recipients"
13751 .section "Non-SMTP incoming messages" "SECID111"
13753 .row &%receive_timeout%& "for non-SMTP messages"
13760 .section "Incoming SMTP messages" "SECID112"
13761 See also the &'Policy controls'& section above.
13764 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
13765 .row &%host_lookup%& "host name looked up for these hosts"
13766 .row &%host_lookup_order%& "order of DNS and local name lookups"
13767 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13768 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13769 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13770 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13771 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13772 .row &%smtp_accept_max%& "simultaneous incoming connections"
13773 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13774 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13775 .row &%smtp_accept_max_per_connection%& "messages per connection"
13776 .row &%smtp_accept_max_per_host%& "connections from one host"
13777 .row &%smtp_accept_queue%& "queue mail if more connections"
13778 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13780 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13781 .row &%smtp_active_hostname%& "host name to use in messages"
13782 .row &%smtp_banner%& "text for welcome banner"
13783 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13784 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13785 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13786 .row &%smtp_etrn_command%& "what to run for ETRN"
13787 .row &%smtp_etrn_serialize%& "only one at once"
13788 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13789 .row &%smtp_max_unknown_commands%& "before dropping connection"
13790 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13791 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13792 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13793 .row &%smtp_receive_timeout%& "per command or data line"
13794 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13795 .row &%smtp_return_error_details%& "give detail on rejections"
13800 .section "SMTP extensions" "SECID113"
13802 .row &%accept_8bitmime%& "advertise 8BITMIME"
13803 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13804 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
13805 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
13806 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13807 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13808 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13809 .row &%prdr_enable%& "advertise PRDR to all hosts"
13810 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
13811 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13816 .section "Processing messages" "SECID114"
13818 .row &%allow_domain_literals%& "recognize domain literal syntax"
13819 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13820 .row &%allow_utf8_domains%& "in addresses"
13821 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13823 .row &%delivery_date_remove%& "from incoming messages"
13824 .row &%envelope_to_remove%& "from incoming messages"
13825 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13826 .row &%headers_charset%& "default for translations"
13827 .row &%qualify_domain%& "default for senders"
13828 .row &%qualify_recipient%& "default for recipients"
13829 .row &%return_path_remove%& "from incoming messages"
13830 .row &%strip_excess_angle_brackets%& "in addresses"
13831 .row &%strip_trailing_dot%& "at end of addresses"
13832 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13837 .section "System filter" "SECID115"
13839 .row &%system_filter%& "locate system filter"
13840 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13842 .row &%system_filter_file_transport%& "transport for delivery to a file"
13843 .row &%system_filter_group%& "group for filter running"
13844 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13845 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13846 .row &%system_filter_user%& "user for filter running"
13851 .section "Routing and delivery" "SECID116"
13853 .row &%disable_ipv6%& "do no IPv6 processing"
13854 .row &%dns_again_means_nonexist%& "for broken domains"
13855 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13856 .row &%dns_dnssec_ok%& "parameter for resolver"
13857 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13858 .row &%dns_retrans%& "parameter for resolver"
13859 .row &%dns_retry%& "parameter for resolver"
13860 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
13861 .row &%dns_use_edns0%& "parameter for resolver"
13862 .row &%hold_domains%& "hold delivery for these domains"
13863 .row &%local_interfaces%& "for routing checks"
13864 .row &%queue_domains%& "no immediate delivery for these"
13865 .row &%queue_only%& "no immediate delivery at all"
13866 .row &%queue_only_file%& "no immediate delivery if file exists"
13867 .row &%queue_only_load%& "no immediate delivery if load is high"
13868 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13869 .row &%queue_only_override%& "allow command line to override"
13870 .row &%queue_run_in_order%& "order of arrival"
13871 .row &%queue_run_max%& "of simultaneous queue runners"
13872 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13873 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13874 .row &%remote_sort_domains%& "order of remote deliveries"
13875 .row &%retry_data_expire%& "timeout for retry data"
13876 .row &%retry_interval_max%& "safety net for retry rules"
13881 .section "Bounce and warning messages" "SECID117"
13883 .row &%bounce_message_file%& "content of bounce"
13884 .row &%bounce_message_text%& "content of bounce"
13885 .row &%bounce_return_body%& "include body if returning message"
13886 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
13887 .row &%bounce_return_message%& "include original message in bounce"
13888 .row &%bounce_return_size_limit%& "limit on returned message"
13889 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13890 .row &%dsn_from%& "set &'From:'& contents in bounces"
13891 .row &%errors_copy%& "copy bounce messages"
13892 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13893 .row &%delay_warning%& "time schedule"
13894 .row &%delay_warning_condition%& "condition for warning messages"
13895 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13896 .row &%smtp_return_error_details%& "give detail on rejections"
13897 .row &%warn_message_file%& "content of warning message"
13902 .section "Alphabetical list of main options" "SECTalomo"
13903 Those options that undergo string expansion before use are marked with
13906 .option accept_8bitmime main boolean true
13908 .cindex "8-bit characters"
13909 .cindex "log" "selectors"
13910 .cindex "log" "8BITMIME"
13911 This option causes Exim to send 8BITMIME in its response to an SMTP
13912 EHLO command, and to accept the BODY= parameter on MAIL commands.
13913 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13914 takes no steps to do anything special with messages received by this route.
13916 Historically Exim kept this option off by default, but the maintainers
13917 feel that in today's Internet, this causes more problems than it solves.
13918 It now defaults to true.
13919 A more detailed analysis of the issues is provided by Dan Bernstein:
13921 &url(http://cr.yp.to/smtp/8bitmime.html)
13924 To log received 8BITMIME status use
13926 log_selector = +8bitmime
13929 .option acl_not_smtp main string&!! unset
13930 .cindex "&ACL;" "for non-SMTP messages"
13931 .cindex "non-SMTP messages" "ACLs for"
13932 This option defines the ACL that is run when a non-SMTP message has been
13933 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13936 .option acl_not_smtp_mime main string&!! unset
13937 This option defines the ACL that is run for individual MIME parts of non-SMTP
13938 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13941 .option acl_not_smtp_start main string&!! unset
13942 .cindex "&ACL;" "at start of non-SMTP message"
13943 .cindex "non-SMTP messages" "ACLs for"
13944 This option defines the ACL that is run before Exim starts reading a
13945 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13947 .option acl_smtp_auth main string&!! unset
13948 .cindex "&ACL;" "setting up for SMTP commands"
13949 .cindex "AUTH" "ACL for"
13950 This option defines the ACL that is run when an SMTP AUTH command is
13951 received. See chapter &<<CHAPACL>>& for further details.
13953 .option acl_smtp_connect main string&!! unset
13954 .cindex "&ACL;" "on SMTP connection"
13955 This option defines the ACL that is run when an SMTP connection is received.
13956 See chapter &<<CHAPACL>>& for further details.
13958 .option acl_smtp_data main string&!! unset
13959 .cindex "DATA" "ACL for"
13960 This option defines the ACL that is run after an SMTP DATA command has been
13961 processed and the message itself has been received, but before the final
13962 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13964 .option acl_smtp_data_prdr main string&!! accept
13965 .cindex "PRDR" "ACL for"
13966 .cindex "DATA" "PRDR ACL for"
13967 .cindex "&ACL;" "PRDR-related"
13968 .cindex "&ACL;" "per-user data processing"
13969 This option defines the ACL that,
13970 if the PRDR feature has been negotiated,
13971 is run for each recipient after an SMTP DATA command has been
13972 processed and the message itself has been received, but before the
13973 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13975 .option acl_smtp_dkim main string&!! unset
13976 .cindex DKIM "ACL for"
13977 This option defines the ACL that is run for each DKIM signature
13978 of a received message.
13979 See chapter &<<CHAPdkim>>& for further details.
13981 .option acl_smtp_etrn main string&!! unset
13982 .cindex "ETRN" "ACL for"
13983 This option defines the ACL that is run when an SMTP ETRN command is
13984 received. See chapter &<<CHAPACL>>& for further details.
13986 .option acl_smtp_expn main string&!! unset
13987 .cindex "EXPN" "ACL for"
13988 This option defines the ACL that is run when an SMTP EXPN command is
13989 received. See chapter &<<CHAPACL>>& for further details.
13991 .option acl_smtp_helo main string&!! unset
13992 .cindex "EHLO" "ACL for"
13993 .cindex "HELO" "ACL for"
13994 This option defines the ACL that is run when an SMTP EHLO or HELO
13995 command is received. See chapter &<<CHAPACL>>& for further details.
13998 .option acl_smtp_mail main string&!! unset
13999 .cindex "MAIL" "ACL for"
14000 This option defines the ACL that is run when an SMTP MAIL command is
14001 received. See chapter &<<CHAPACL>>& for further details.
14003 .option acl_smtp_mailauth main string&!! unset
14004 .cindex "AUTH" "on MAIL command"
14005 This option defines the ACL that is run when there is an AUTH parameter on
14006 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14007 &<<CHAPSMTPAUTH>>& for details of authentication.
14009 .option acl_smtp_mime main string&!! unset
14010 .cindex "MIME content scanning" "ACL for"
14011 This option is available when Exim is built with the content-scanning
14012 extension. It defines the ACL that is run for each MIME part in a message. See
14013 section &<<SECTscanmimepart>>& for details.
14015 .option acl_smtp_notquit main string&!! unset
14016 .cindex "not-QUIT, ACL for"
14017 This option defines the ACL that is run when an SMTP session
14018 ends without a QUIT command being received.
14019 See chapter &<<CHAPACL>>& for further details.
14021 .option acl_smtp_predata main string&!! unset
14022 This option defines the ACL that is run when an SMTP DATA command is
14023 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14026 .option acl_smtp_quit main string&!! unset
14027 .cindex "QUIT, ACL for"
14028 This option defines the ACL that is run when an SMTP QUIT command is
14029 received. See chapter &<<CHAPACL>>& for further details.
14031 .option acl_smtp_rcpt main string&!! unset
14032 .cindex "RCPT" "ACL for"
14033 This option defines the ACL that is run when an SMTP RCPT command is
14034 received. See chapter &<<CHAPACL>>& for further details.
14036 .option acl_smtp_starttls main string&!! unset
14037 .cindex "STARTTLS, ACL for"
14038 This option defines the ACL that is run when an SMTP STARTTLS command is
14039 received. See chapter &<<CHAPACL>>& for further details.
14041 .option acl_smtp_vrfy main string&!! unset
14042 .cindex "VRFY" "ACL for"
14043 This option defines the ACL that is run when an SMTP VRFY command is
14044 received. See chapter &<<CHAPACL>>& for further details.
14046 .option add_environment main "string list" empty
14047 .cindex "environment" "set values"
14048 This option allows to set individual environment variables that the
14049 currently linked libraries and programs in child processes use.
14050 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
14052 .option admin_groups main "string list&!!" unset
14053 .cindex "admin user"
14054 This option is expanded just once, at the start of Exim's processing. If the
14055 current group or any of the supplementary groups of an Exim caller is in this
14056 colon-separated list, the caller has admin privileges. If all your system
14057 programmers are in a specific group, for example, you can give them all Exim
14058 admin privileges by putting that group in &%admin_groups%&. However, this does
14059 not permit them to read Exim's spool files (whose group owner is the Exim gid).
14060 To permit this, you have to add individuals to the Exim group.
14062 .option allow_domain_literals main boolean false
14063 .cindex "domain literal"
14064 If this option is set, the RFC 2822 domain literal format is permitted in
14065 email addresses. The option is not set by default, because the domain literal
14066 format is not normally required these days, and few people know about it. It
14067 has, however, been exploited by mail abusers.
14069 Unfortunately, it seems that some DNS black list maintainers are using this
14070 format to report black listing to postmasters. If you want to accept messages
14071 addressed to your hosts by IP address, you need to set
14072 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
14073 domains (defined in the named domain list &%local_domains%& in the default
14074 configuration). This &"magic string"& matches the domain literal form of all
14075 the local host's IP addresses.
14078 .option allow_mx_to_ip main boolean false
14079 .cindex "MX record" "pointing to IP address"
14080 It appears that more and more DNS zone administrators are breaking the rules
14081 and putting domain names that look like IP addresses on the right hand side of
14082 MX records. Exim follows the rules and rejects this, giving an error message
14083 that explains the misconfiguration. However, some other MTAs support this
14084 practice, so to avoid &"Why can't Exim do this?"& complaints,
14085 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
14086 recommended, except when you have no other choice.
14088 .option allow_utf8_domains main boolean false
14089 .cindex "domain" "UTF-8 characters in"
14090 .cindex "UTF-8" "in domain name"
14091 Lots of discussion is going on about internationalized domain names. One
14092 camp is strongly in favour of just using UTF-8 characters, and it seems
14093 that at least two other MTAs permit this. This option allows Exim users to
14094 experiment if they wish.
14096 If it is set true, Exim's domain parsing function allows valid
14097 UTF-8 multicharacters to appear in domain name components, in addition to
14098 letters, digits, and hyphens. However, just setting this option is not
14099 enough; if you want to look up these domain names in the DNS, you must also
14100 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
14101 suitable setting is:
14103 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
14104 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
14106 Alternatively, you can just disable this feature by setting
14108 dns_check_names_pattern =
14110 That is, set the option to an empty string so that no check is done.
14113 .option auth_advertise_hosts main "host list&!!" *
14114 .cindex "authentication" "advertising"
14115 .cindex "AUTH" "advertising"
14116 If any server authentication mechanisms are configured, Exim advertises them in
14117 response to an EHLO command only if the calling host matches this list.
14118 Otherwise, Exim does not advertise AUTH.
14119 Exim does not accept AUTH commands from clients to which it has not
14120 advertised the availability of AUTH. The advertising of individual
14121 authentication mechanisms can be controlled by the use of the
14122 &%server_advertise_condition%& generic authenticator option on the individual
14123 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
14125 Certain mail clients (for example, Netscape) require the user to provide a name
14126 and password for authentication if AUTH is advertised, even though it may
14127 not be needed (the host may accept messages from hosts on its local LAN without
14128 authentication, for example). The &%auth_advertise_hosts%& option can be used
14129 to make these clients more friendly by excluding them from the set of hosts to
14130 which Exim advertises AUTH.
14132 .cindex "AUTH" "advertising when encrypted"
14133 If you want to advertise the availability of AUTH only when the connection
14134 is encrypted using TLS, you can make use of the fact that the value of this
14135 option is expanded, with a setting like this:
14137 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
14139 .vindex "&$tls_in_cipher$&"
14140 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
14141 the expansion is empty, thus matching no hosts. Otherwise, the result of the
14142 expansion is *, which matches all hosts.
14145 .option auto_thaw main time 0s
14146 .cindex "thawing messages"
14147 .cindex "unfreezing messages"
14148 If this option is set to a time greater than zero, a queue runner will try a
14149 new delivery attempt on any frozen message, other than a bounce message, if
14150 this much time has passed since it was frozen. This may result in the message
14151 being re-frozen if nothing has changed since the last attempt. It is a way of
14152 saying &"keep on trying, even though there are big problems"&.
14154 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
14155 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
14156 thought to be very useful any more, and its use should probably be avoided.
14159 .option av_scanner main string "see below"
14160 This option is available if Exim is built with the content-scanning extension.
14161 It specifies which anti-virus scanner to use. The default value is:
14163 sophie:/var/run/sophie
14165 If the value of &%av_scanner%& starts with a dollar character, it is expanded
14166 before use. See section &<<SECTscanvirus>>& for further details.
14169 .option bi_command main string unset
14171 This option supplies the name of a command that is run when Exim is called with
14172 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14173 just the command name, it is not a complete command line. If an argument is
14174 required, it must come from the &%-oA%& command line option.
14177 .option bounce_message_file main string unset
14178 .cindex "bounce message" "customizing"
14179 .cindex "customizing" "bounce message"
14180 This option defines a template file containing paragraphs of text to be used
14181 for constructing bounce messages. Details of the file's contents are given in
14182 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14185 .option bounce_message_text main string unset
14186 When this option is set, its contents are included in the default bounce
14187 message immediately after &"This message was created automatically by mail
14188 delivery software."& It is not used if &%bounce_message_file%& is set.
14190 .option bounce_return_body main boolean true
14191 .cindex "bounce message" "including body"
14192 This option controls whether the body of an incoming message is included in a
14193 bounce message when &%bounce_return_message%& is true. The default setting
14194 causes the entire message, both header and body, to be returned (subject to the
14195 value of &%bounce_return_size_limit%&). If this option is false, only the
14196 message header is included. In the case of a non-SMTP message containing an
14197 error that is detected during reception, only those header lines preceding the
14198 point at which the error was detected are returned.
14199 .cindex "bounce message" "including original"
14201 .option bounce_return_linesize_limit main integer 998
14202 .cindex "size" "of bounce lines, limit"
14203 .cindex "bounce message" "line length limit"
14204 .cindex "limit" "bounce message line length"
14205 This option sets a limit in bytes on the line length of messages
14206 that are returned to senders due to delivery problems,
14207 when &%bounce_return_message%& is true.
14208 The default value corresponds to RFC limits.
14209 If the message being returned has lines longer than this value it is
14210 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
14212 The option also applies to bounces returned when an error is detected
14213 during reception of a message.
14214 In this case lines from the original are truncated.
14216 The option does not apply to messages generated by an &(autoreply)& transport.
14219 .option bounce_return_message main boolean true
14220 If this option is set false, none of the original message is included in
14221 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14222 &%bounce_return_body%&.
14225 .option bounce_return_size_limit main integer 100K
14226 .cindex "size" "of bounce, limit"
14227 .cindex "bounce message" "size limit"
14228 .cindex "limit" "bounce message size"
14229 This option sets a limit in bytes on the size of messages that are returned to
14230 senders as part of bounce messages when &%bounce_return_message%& is true. The
14231 limit should be less than the value of the global &%message_size_limit%& and of
14232 any &%message_size_limit%& settings on transports, to allow for the bounce text
14233 that Exim generates. If this option is set to zero there is no limit.
14235 When the body of any message that is to be included in a bounce message is
14236 greater than the limit, it is truncated, and a comment pointing this out is
14237 added at the top. The actual cutoff may be greater than the value given, owing
14238 to the use of buffering for transferring the message in chunks (typically 8K in
14239 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14242 .option bounce_sender_authentication main string unset
14243 .cindex "bounce message" "sender authentication"
14244 .cindex "authentication" "bounce message"
14245 .cindex "AUTH" "on bounce message"
14246 This option provides an authenticated sender address that is sent with any
14247 bounce messages generated by Exim that are sent over an authenticated SMTP
14248 connection. A typical setting might be:
14250 bounce_sender_authentication = mailer-daemon@my.domain.example
14252 which would cause bounce messages to be sent using the SMTP command:
14254 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14256 The value of &%bounce_sender_authentication%& must always be a complete email
14259 .option callout_domain_negative_expire main time 3h
14260 .cindex "caching" "callout timeouts"
14261 .cindex "callout" "caching timeouts"
14262 This option specifies the expiry time for negative callout cache data for a
14263 domain. See section &<<SECTcallver>>& for details of callout verification, and
14264 section &<<SECTcallvercache>>& for details of the caching.
14267 .option callout_domain_positive_expire main time 7d
14268 This option specifies the expiry time for positive callout cache data for a
14269 domain. See section &<<SECTcallver>>& for details of callout verification, and
14270 section &<<SECTcallvercache>>& for details of the caching.
14273 .option callout_negative_expire main time 2h
14274 This option specifies the expiry time for negative callout cache data for an
14275 address. See section &<<SECTcallver>>& for details of callout verification, and
14276 section &<<SECTcallvercache>>& for details of the caching.
14279 .option callout_positive_expire main time 24h
14280 This option specifies the expiry time for positive callout cache data for an
14281 address. See section &<<SECTcallver>>& for details of callout verification, and
14282 section &<<SECTcallvercache>>& for details of the caching.
14285 .option callout_random_local_part main string&!! "see below"
14286 This option defines the &"random"& local part that can be used as part of
14287 callout verification. The default value is
14289 $primary_hostname-$tod_epoch-testing
14291 See section &<<CALLaddparcall>>& for details of how this value is used.
14294 .option check_log_inodes main integer 0
14295 See &%check_spool_space%& below.
14298 .option check_log_space main integer 0
14299 See &%check_spool_space%& below.
14301 .oindex "&%check_rfc2047_length%&"
14302 .cindex "RFC 2047" "disabling length check"
14303 .option check_rfc2047_length main boolean true
14304 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14305 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14306 word; strings to be encoded that exceed this length are supposed to use
14307 multiple encoded words. By default, Exim does not recognize encoded words that
14308 exceed the maximum length. However, it seems that some software, in violation
14309 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14310 set false, Exim recognizes encoded words of any length.
14313 .option check_spool_inodes main integer 0
14314 See &%check_spool_space%& below.
14317 .option check_spool_space main integer 0
14318 .cindex "checking disk space"
14319 .cindex "disk space, checking"
14320 .cindex "spool directory" "checking space"
14321 The four &%check_...%& options allow for checking of disk resources before a
14322 message is accepted.
14324 .vindex "&$log_inodes$&"
14325 .vindex "&$log_space$&"
14326 .vindex "&$spool_inodes$&"
14327 .vindex "&$spool_space$&"
14328 When any of these options are set, they apply to all incoming messages. If you
14329 want to apply different checks to different kinds of message, you can do so by
14330 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14331 &$spool_space$& in an ACL with appropriate additional conditions.
14334 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14335 either value is greater than zero, for example:
14337 check_spool_space = 10M
14338 check_spool_inodes = 100
14340 The spool partition is the one that contains the directory defined by
14341 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14344 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14345 files are written if either is greater than zero. These should be set only if
14346 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14348 If there is less space or fewer inodes than requested, Exim refuses to accept
14349 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14350 error response to the MAIL command. If ESMTP is in use and there was a
14351 SIZE parameter on the MAIL command, its value is added to the
14352 &%check_spool_space%& value, and the check is performed even if
14353 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14355 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14356 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
14358 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14359 failure a message is written to stderr and Exim exits with a non-zero code, as
14360 it obviously cannot send an error message of any kind.
14362 .option chunking_advertise_hosts main "host list&!!" *
14363 .cindex CHUNKING advertisement
14364 .cindex "RFC 3030" "CHUNKING"
14365 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
14367 Hosts may use the BDAT command as an alternate to DATA.
14369 .option daemon_smtp_ports main string &`smtp`&
14370 .cindex "port" "for daemon"
14371 .cindex "TCP/IP" "setting listening ports"
14372 This option specifies one or more default SMTP ports on which the Exim daemon
14373 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14374 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14376 .option daemon_startup_retries main integer 9
14377 .cindex "daemon startup, retrying"
14378 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14379 the daemon at startup when it cannot immediately bind a listening socket
14380 (typically because the socket is already in use): &%daemon_startup_retries%&
14381 defines the number of retries after the first failure, and
14382 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14384 .option daemon_startup_sleep main time 30s
14385 See &%daemon_startup_retries%&.
14387 .option delay_warning main "time list" 24h
14388 .cindex "warning of delay"
14389 .cindex "delay warning, specifying"
14390 When a message is delayed, Exim sends a warning message to the sender at
14391 intervals specified by this option. The data is a colon-separated list of times
14392 after which to send warning messages. If the value of the option is an empty
14393 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14394 message has been on the queue for longer than the last time, the last interval
14395 between the times is used to compute subsequent warning times. For example,
14398 delay_warning = 4h:8h:24h
14400 the first message is sent after 4 hours, the second after 8 hours, and
14401 the third one after 24 hours. After that, messages are sent every 16 hours,
14402 because that is the interval between the last two times on the list. If you set
14403 just one time, it specifies the repeat interval. For example, with:
14407 messages are repeated every six hours. To stop warnings after a given time, set
14408 a very large time at the end of the list. For example:
14410 delay_warning = 2h:12h:99d
14412 Note that the option is only evaluated at the time a delivery attempt fails,
14413 which depends on retry and queue-runner configuration.
14414 Typically retries will be configured more frequently than warning messages.
14416 .option delay_warning_condition main string&!! "see below"
14417 .vindex "&$domain$&"
14418 The string is expanded at the time a warning message might be sent. If all the
14419 deferred addresses have the same domain, it is set in &$domain$& during the
14420 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14421 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14422 &"false"& (the comparison being done caselessly) then the warning message is
14423 not sent. The default is:
14425 delay_warning_condition = ${if or {\
14426 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14427 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14428 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14431 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14432 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14433 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14434 &"auto-replied"& in an &'Auto-Submitted:'& header.
14436 .option deliver_drop_privilege main boolean false
14437 .cindex "unprivileged delivery"
14438 .cindex "delivery" "unprivileged"
14439 If this option is set true, Exim drops its root privilege at the start of a
14440 delivery process, and runs as the Exim user throughout. This severely restricts
14441 the kinds of local delivery that are possible, but is viable in certain types
14442 of configuration. There is a discussion about the use of root privilege in
14443 chapter &<<CHAPsecurity>>&.
14445 .option deliver_queue_load_max main fixed-point unset
14446 .cindex "load average"
14447 .cindex "queue runner" "abandoning"
14448 When this option is set, a queue run is abandoned if the system load average
14449 becomes greater than the value of the option. The option has no effect on
14450 ancient operating systems on which Exim cannot determine the load average.
14451 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14454 .option delivery_date_remove main boolean true
14455 .cindex "&'Delivery-date:'& header line"
14456 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14457 message when it is delivered, in exactly the same way as &'Return-path:'& is
14458 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14459 should not be present in incoming messages, and this option causes them to be
14460 removed at the time the message is received, to avoid any problems that might
14461 occur when a delivered message is subsequently sent on to some other recipient.
14463 .option disable_fsync main boolean false
14464 .cindex "&[fsync()]&, disabling"
14465 This option is available only if Exim was built with the compile-time option
14466 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14467 a runtime configuration generates an &"unknown option"& error. You should not
14468 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14469 really, really, really understand what you are doing. &'No pre-compiled
14470 distributions of Exim should ever make this option available.'&
14472 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14473 updated files' data to be written to disc before continuing. Unexpected events
14474 such as crashes and power outages may cause data to be lost or scrambled.
14475 Here be Dragons. &*Beware.*&
14478 .option disable_ipv6 main boolean false
14479 .cindex "IPv6" "disabling"
14480 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14481 activities take place. AAAA records are never looked up, and any IPv6 addresses
14482 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14483 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14484 to handle IPv6 literal addresses.
14487 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14488 .cindex DKIM "controlling calls to the ACL"
14489 This option gives a list of DKIM domains for which the DKIM ACL is run.
14490 It is expanded after the message is received; by default it runs
14491 the ACL once for each signature in the message.
14492 See chapter &<<CHAPdkim>>&.
14495 .option dns_again_means_nonexist main "domain list&!!" unset
14496 .cindex "DNS" "&""try again""& response; overriding"
14497 DNS lookups give a &"try again"& response for the DNS errors
14498 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14499 keep trying to deliver a message, or to give repeated temporary errors to
14500 incoming mail. Sometimes the effect is caused by a badly set up name server and
14501 may persist for a long time. If a domain which exhibits this problem matches
14502 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14503 This option should be used with care. You can make it apply to reverse lookups
14504 by a setting such as this:
14506 dns_again_means_nonexist = *.in-addr.arpa
14508 This option applies to all DNS lookups that Exim does. It also applies when the
14509 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14510 since these are most likely to be caused by DNS lookup problems. The
14511 &(dnslookup)& router has some options of its own for controlling what happens
14512 when lookups for MX or SRV records give temporary errors. These more specific
14513 options are applied after this global option.
14515 .option dns_check_names_pattern main string "see below"
14516 .cindex "DNS" "pre-check of name syntax"
14517 When this option is set to a non-empty string, it causes Exim to check domain
14518 names for characters that are not allowed in host names before handing them to
14519 the DNS resolver, because some resolvers give temporary errors for names that
14520 contain unusual characters. If a domain name contains any unwanted characters,
14521 a &"not found"& result is forced, and the resolver is not called. The check is
14522 done by matching the domain name against a regular expression, which is the
14523 value of this option. The default pattern is
14525 dns_check_names_pattern = \
14526 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14528 which permits only letters, digits, slashes, and hyphens in components, but
14529 they must start and end with a letter or digit. Slashes are not, in fact,
14530 permitted in host names, but they are found in certain NS records (which can be
14531 accessed in Exim by using a &%dnsdb%& lookup). If you set
14532 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14535 .option dns_csa_search_limit main integer 5
14536 This option controls the depth of parental searching for CSA SRV records in the
14537 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14539 .option dns_csa_use_reverse main boolean true
14540 This option controls whether or not an IP address, given as a CSA domain, is
14541 reversed and looked up in the reverse DNS, as described in more detail in
14542 section &<<SECTverifyCSA>>&.
14545 .option dns_dnssec_ok main integer -1
14546 .cindex "DNS" "resolver options"
14547 .cindex "DNS" "DNSSEC"
14548 If this option is set to a non-negative number then Exim will initialise the
14549 DNS resolver library to either use or not use DNSSEC, overriding the system
14550 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14552 If the resolver library does not support DNSSEC then this option has no effect.
14555 .option dns_ipv4_lookup main "domain list&!!" unset
14556 .cindex "IPv6" "DNS lookup for AAAA records"
14557 .cindex "DNS" "IPv6 lookup for AAAA records"
14558 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14559 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14560 (A records) when trying to find IP addresses for hosts, unless the host's
14561 domain matches this list.
14563 This is a fudge to help with name servers that give big delays or otherwise do
14564 not work for the AAAA record type. In due course, when the world's name
14565 servers have all been upgraded, there should be no need for this option.
14568 .option dns_retrans main time 0s
14569 .cindex "DNS" "resolver options"
14570 .cindex timeout "dns lookup"
14571 .cindex "DNS" timeout
14572 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14573 retransmission and retry parameters for DNS lookups. Values of zero (the
14574 defaults) leave the system default settings unchanged. The first value is the
14575 time between retries, and the second is the number of retries. It isn't
14576 totally clear exactly how these settings affect the total time a DNS lookup may
14577 take. I haven't found any documentation about timeouts on DNS lookups; these
14578 parameter values are available in the external resolver interface structure,
14579 but nowhere does it seem to describe how they are used or what you might want
14581 See also the &%slow_lookup_log%& option.
14584 .option dns_retry main integer 0
14585 See &%dns_retrans%& above.
14588 .option dns_trust_aa main "domain list&!!" unset
14589 .cindex "DNS" "resolver options"
14590 .cindex "DNS" "DNSSEC"
14591 If this option is set then lookup results marked with the AA bit
14592 (Authoritative Answer) are trusted the same way as if they were
14593 DNSSEC-verified. The authority section's name of the answer must
14594 match with this expanded domain list.
14596 Use this option only if you talk directly to a resolver that is
14597 authoritative for some zones and does not set the AD (Authentic Data)
14598 bit in the answer. Some DNS servers may have an configuration option to
14599 mark the answers from their own zones as verified (they set the AD bit).
14600 Others do not have this option. It is considered as poor practice using
14601 a resolver that is an authoritative server for some zones.
14603 Use this option only if you really have to (e.g. if you want
14604 to use DANE for remote delivery to a server that is listed in the DNS
14605 zones that your resolver is authoritative for).
14607 If the DNS answer packet has the AA bit set and contains resource record
14608 in the answer section, the name of the first NS record appearing in the
14609 authority section is compared against the list. If the answer packet is
14610 authoritative but the answer section is empty, the name of the first SOA
14611 record in the authoritative section is used instead.
14613 .cindex "DNS" "resolver options"
14614 .option dns_use_edns0 main integer -1
14615 .cindex "DNS" "resolver options"
14616 .cindex "DNS" "EDNS0"
14617 If this option is set to a non-negative number then Exim will initialise the
14618 DNS resolver library to either use or not use EDNS0 extensions, overriding
14619 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14622 If the resolver library does not support EDNS0 then this option has no effect.
14625 .option drop_cr main boolean false
14626 This is an obsolete option that is now a no-op. It used to affect the way Exim
14627 handled CR and LF characters in incoming messages. What happens now is
14628 described in section &<<SECTlineendings>>&.
14630 .option dsn_advertise_hosts main "host list&!!" unset
14631 .cindex "bounce messages" "success"
14632 .cindex "DSN" "success"
14633 .cindex "Delivery Status Notification" "success"
14634 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14635 and accepted from, these hosts.
14636 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14637 and RET and ORCPT options on MAIL FROM commands.
14638 A NOTIFY=SUCCESS option requests success-DSN messages.
14639 A NOTIFY= option with no argument requests that no delay or failure DSNs
14642 .option dsn_from main "string&!!" "see below"
14643 .cindex "&'From:'& header line" "in bounces"
14644 .cindex "bounce messages" "&'From:'& line, specifying"
14645 This option can be used to vary the contents of &'From:'& header lines in
14646 bounces and other automatically generated messages (&"Delivery Status
14647 Notifications"& &-- hence the name of the option). The default setting is:
14649 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14651 The value is expanded every time it is needed. If the expansion fails, a
14652 panic is logged, and the default value is used.
14654 .option envelope_to_remove main boolean true
14655 .cindex "&'Envelope-to:'& header line"
14656 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14657 message when it is delivered, in exactly the same way as &'Return-path:'& is
14658 handled. &'Envelope-to:'& records the original recipient address from the
14659 message's envelope that caused the delivery to happen. Such headers should not
14660 be present in incoming messages, and this option causes them to be removed at
14661 the time the message is received, to avoid any problems that might occur when a
14662 delivered message is subsequently sent on to some other recipient.
14665 .option errors_copy main "string list&!!" unset
14666 .cindex "bounce message" "copy to other address"
14667 .cindex "copy of bounce message"
14668 Setting this option causes Exim to send bcc copies of bounce messages that it
14669 generates to other addresses. &*Note*&: This does not apply to bounce messages
14670 coming from elsewhere. The value of the option is a colon-separated list of
14671 items. Each item consists of a pattern, terminated by white space, followed by
14672 a comma-separated list of email addresses. If a pattern contains spaces, it
14673 must be enclosed in double quotes.
14675 Each pattern is processed in the same way as a single item in an address list
14676 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14677 the bounce message, the message is copied to the addresses on the list. The
14678 items are scanned in order, and once a matching one is found, no further items
14679 are examined. For example:
14681 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14682 rqps@mydomain hostmaster@mydomain.example,\
14683 postmaster@mydomain.example
14685 .vindex "&$domain$&"
14686 .vindex "&$local_part$&"
14687 The address list is expanded before use. The expansion variables &$local_part$&
14688 and &$domain$& are set from the original recipient of the error message, and if
14689 there was any wildcard matching in the pattern, the expansion
14690 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14691 variables &$0$&, &$1$&, etc. are set in the normal way.
14694 .option errors_reply_to main string unset
14695 .cindex "bounce message" "&'Reply-to:'& in"
14696 By default, Exim's bounce and delivery warning messages contain the header line
14698 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14700 .oindex &%quota_warn_message%&
14701 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14702 A warning message that is generated by the &%quota_warn_message%& option in an
14703 &(appendfile)& transport may contain its own &'From:'& header line that
14704 overrides the default.
14706 Experience shows that people reply to bounce messages. If the
14707 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14708 and warning messages. For example:
14710 errors_reply_to = postmaster@my.domain.example
14712 The value of the option is not expanded. It must specify a valid RFC 2822
14713 address. However, if a warning message that is generated by the
14714 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14715 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14719 .option event_action main string&!! unset
14721 This option declares a string to be expanded for Exim's events mechanism.
14722 For details see &<<CHAPevents>>&.
14725 .option exim_group main string "compile-time configured"
14726 .cindex "gid (group id)" "Exim's own"
14727 .cindex "Exim group"
14728 This option changes the gid under which Exim runs when it gives up root
14729 privilege. The default value is compiled into the binary. The value of this
14730 option is used only when &%exim_user%& is also set. Unless it consists entirely
14731 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14732 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14736 .option exim_path main string "see below"
14737 .cindex "Exim binary, path name"
14738 This option specifies the path name of the Exim binary, which is used when Exim
14739 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14740 the directory configured at compile time by the BIN_DIRECTORY setting. It
14741 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14743 &*Warning*&: Do not use a macro to define the value of this option, because
14744 you will break those Exim utilities that scan the configuration file to find
14745 where the binary is. (They then use the &%-bP%& option to extract option
14746 settings such as the value of &%spool_directory%&.)
14749 .option exim_user main string "compile-time configured"
14750 .cindex "uid (user id)" "Exim's own"
14751 .cindex "Exim user"
14752 This option changes the uid under which Exim runs when it gives up root
14753 privilege. The default value is compiled into the binary. Ownership of the run
14754 time configuration file and the use of the &%-C%& and &%-D%& command line
14755 options is checked against the values in the binary, not what is set here.
14757 Unless it consists entirely of digits, the string is looked up using
14758 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14759 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14760 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14763 .option extra_local_interfaces main "string list" unset
14764 This option defines network interfaces that are to be considered local when
14765 routing, but which are not used for listening by the daemon. See section
14766 &<<SECTreclocipadd>>& for details.
14769 . Allow this long option name to split; give it unsplit as a fifth argument
14770 . for the automatic .oindex that is generated by .option.
14772 .option "extract_addresses_remove_arguments" main boolean true &&&
14773 extract_addresses_remove_arguments
14775 .cindex "command line" "addresses with &%-t%&"
14776 .cindex "Sendmail compatibility" "&%-t%& option"
14777 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14778 are present on the command line when the &%-t%& option is used to build an
14779 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14780 line addresses are removed from the recipients list. This is also how Smail
14781 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14782 command line addresses are added to those obtained from the header lines. When
14783 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14784 argument headers. If it is set false, Exim adds rather than removes argument
14788 .option finduser_retries main integer 0
14789 .cindex "NIS, retrying user lookups"
14790 On systems running NIS or other schemes in which user and group information is
14791 distributed from a remote system, there can be times when &[getpwnam()]& and
14792 related functions fail, even when given valid data, because things time out.
14793 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14794 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14795 many extra times to find a user or a group, waiting for one second between
14798 .cindex "&_/etc/passwd_&" "multiple reading of"
14799 You should not set this option greater than zero if your user information is in
14800 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14801 search the file multiple times for non-existent users, and also cause delay.
14805 .option freeze_tell main "string list, comma separated" unset
14806 .cindex "freezing messages" "sending a message when freezing"
14807 On encountering certain errors, or when configured to do so in a system filter,
14808 ACL, or special router, Exim freezes a message. This means that no further
14809 delivery attempts take place until an administrator thaws the message, or the
14810 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14811 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14812 warning message whenever it freezes something, unless the message it is
14813 freezing is a locally-generated bounce message. (Without this exception there
14814 is the possibility of looping.) The warning message is sent to the addresses
14815 supplied as the comma-separated value of this option. If several of the
14816 message's addresses cause freezing, only a single message is sent. If the
14817 freezing was automatic, the reason(s) for freezing can be found in the message
14818 log. If you configure freezing in a filter or ACL, you must arrange for any
14819 logging that you require.
14822 .option gecos_name main string&!! unset
14824 .cindex "&""gecos""& field, parsing"
14825 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14826 password file to hold other information in addition to users' real names. Exim
14827 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14828 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14829 of the field are used unchanged, except that, if an ampersand is encountered,
14830 it is replaced by the user's login name with the first character forced to
14831 upper case, since this is a convention that is observed on many systems.
14833 When these options are set, &%gecos_pattern%& is treated as a regular
14834 expression that is to be applied to the field (again with && replaced by the
14835 login name), and if it matches, &%gecos_name%& is expanded and used as the
14838 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14839 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14840 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14841 name terminates at the first comma, the following can be used:
14843 gecos_pattern = ([^,]*)
14847 .option gecos_pattern main string unset
14848 See &%gecos_name%& above.
14851 .option gnutls_compat_mode main boolean unset
14852 This option controls whether GnuTLS is used in compatibility mode in an Exim
14853 server. This reduces security slightly, but improves interworking with older
14854 implementations of TLS.
14857 option gnutls_allow_auto_pkcs11 main boolean unset
14858 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14859 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14862 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14867 .option headers_charset main string "see below"
14868 This option sets a default character set for translating from encoded MIME
14869 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14870 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14871 ultimate default is ISO-8859-1. For more details see the description of header
14872 insertions in section &<<SECTexpansionitems>>&.
14876 .option header_maxsize main integer "see below"
14877 .cindex "header section" "maximum size of"
14878 .cindex "limit" "size of message header section"
14879 This option controls the overall maximum size of a message's header
14880 section. The default is the value of HEADER_MAXSIZE in
14881 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14882 sections are rejected.
14885 .option header_line_maxsize main integer 0
14886 .cindex "header lines" "maximum size of"
14887 .cindex "limit" "size of one header line"
14888 This option limits the length of any individual header line in a message, after
14889 all the continuations have been joined together. Messages with individual
14890 header lines that are longer than the limit are rejected. The default value of
14891 zero means &"no limit"&.
14896 .option helo_accept_junk_hosts main "host list&!!" unset
14897 .cindex "HELO" "accepting junk data"
14898 .cindex "EHLO" "accepting junk data"
14899 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14900 mail, and gives an error response for invalid data. Unfortunately, there are
14901 some SMTP clients that send syntactic junk. They can be accommodated by setting
14902 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14903 if you want to do semantic checking.
14904 See also &%helo_allow_chars%& for a way of extending the permitted character
14908 .option helo_allow_chars main string unset
14909 .cindex "HELO" "underscores in"
14910 .cindex "EHLO" "underscores in"
14911 .cindex "underscore in EHLO/HELO"
14912 This option can be set to a string of rogue characters that are permitted in
14913 all EHLO and HELO names in addition to the standard letters, digits,
14914 hyphens, and dots. If you really must allow underscores, you can set
14916 helo_allow_chars = _
14918 Note that the value is one string, not a list.
14921 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14922 .cindex "HELO" "forcing reverse lookup"
14923 .cindex "EHLO" "forcing reverse lookup"
14924 If the domain given by a client in a HELO or EHLO command matches this
14925 list, a reverse lookup is done in order to establish the host's true name. The
14926 default forces a lookup if the client host gives the server's name or any of
14927 its IP addresses (in brackets), something that broken clients have been seen to
14931 .option helo_try_verify_hosts main "host list&!!" unset
14932 .cindex "HELO verifying" "optional"
14933 .cindex "EHLO" "verifying, optional"
14934 By default, Exim just checks the syntax of HELO and EHLO commands (see
14935 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14936 to do more extensive checking of the data supplied by these commands. The ACL
14937 condition &`verify = helo`& is provided to make this possible.
14938 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14939 to force the check to occur. From release 4.53 onwards, this is no longer
14940 necessary. If the check has not been done before &`verify = helo`& is
14941 encountered, it is done at that time. Consequently, this option is obsolete.
14942 Its specification is retained here for backwards compatibility.
14944 When an EHLO or HELO command is received, if the calling host matches
14945 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14946 EHLO command either:
14949 is an IP literal matching the calling address of the host, or
14951 .cindex "DNS" "reverse lookup"
14952 .cindex "reverse DNS lookup"
14953 matches the host name that Exim obtains by doing a reverse lookup of the
14954 calling host address, or
14956 when looked up in DNS yields the calling host address.
14959 However, the EHLO or HELO command is not rejected if any of the checks
14960 fail. Processing continues, but the result of the check is remembered, and can
14961 be detected later in an ACL by the &`verify = helo`& condition.
14963 If DNS was used for successful verification, the variable
14964 .cindex "DNS" "DNSSEC"
14965 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
14967 .option helo_verify_hosts main "host list&!!" unset
14968 .cindex "HELO verifying" "mandatory"
14969 .cindex "EHLO" "verifying, mandatory"
14970 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14971 backwards compatibility. For hosts that match this option, Exim checks the host
14972 name given in the HELO or EHLO in the same way as for
14973 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14974 rejected with a 550 error, and entries are written to the main and reject logs.
14975 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14978 .option hold_domains main "domain list&!!" unset
14979 .cindex "domain" "delaying delivery"
14980 .cindex "delivery" "delaying certain domains"
14981 This option allows mail for particular domains to be held on the queue
14982 manually. The option is overridden if a message delivery is forced with the
14983 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14984 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14985 item in &%hold_domains%&, no routing or delivery for that address is done, and
14986 it is deferred every time the message is looked at.
14988 This option is intended as a temporary operational measure for delaying the
14989 delivery of mail while some problem is being sorted out, or some new
14990 configuration tested. If you just want to delay the processing of some
14991 domains until a queue run occurs, you should use &%queue_domains%& or
14992 &%queue_smtp_domains%&, not &%hold_domains%&.
14994 A setting of &%hold_domains%& does not override Exim's code for removing
14995 messages from the queue if they have been there longer than the longest retry
14996 time in any retry rule. If you want to hold messages for longer than the normal
14997 retry times, insert a dummy retry rule with a long retry time.
15000 .option host_lookup main "host list&!!" unset
15001 .cindex "host name" "lookup, forcing"
15002 Exim does not look up the name of a calling host from its IP address unless it
15003 is required to compare against some host list, or the host matches
15004 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
15005 option (which normally contains IP addresses rather than host names). The
15006 default configuration file contains
15010 which causes a lookup to happen for all hosts. If the expense of these lookups
15011 is felt to be too great, the setting can be changed or removed.
15013 After a successful reverse lookup, Exim does a forward lookup on the name it
15014 has obtained, to verify that it yields the IP address that it started with. If
15015 this check fails, Exim behaves as if the name lookup failed.
15017 .vindex "&$host_lookup_failed$&"
15018 .vindex "&$sender_host_name$&"
15019 After any kind of failure, the host name (in &$sender_host_name$&) remains
15020 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
15021 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
15022 &`verify = reverse_host_lookup`& in ACLs.
15025 .option host_lookup_order main "string list" &`bydns:byaddr`&
15026 This option specifies the order of different lookup methods when Exim is trying
15027 to find a host name from an IP address. The default is to do a DNS lookup
15028 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
15029 if that fails. You can change the order of these lookups, or omit one entirely,
15032 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
15033 multiple PTR records in the DNS and the IP address is not listed in
15034 &_/etc/hosts_&. Different operating systems give different results in this
15035 case. That is why the default tries a DNS lookup first.
15039 .option host_reject_connection main "host list&!!" unset
15040 .cindex "host" "rejecting connections from"
15041 If this option is set, incoming SMTP calls from the hosts listed are rejected
15042 as soon as the connection is made.
15043 This option is obsolete, and retained only for backward compatibility, because
15044 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
15045 connections immediately.
15047 The ability to give an immediate rejection (either by this option or using an
15048 ACL) is provided for use in unusual cases. Many hosts will just try again,
15049 sometimes without much delay. Normally, it is better to use an ACL to reject
15050 incoming messages at a later stage, such as after RCPT commands. See
15051 chapter &<<CHAPACL>>&.
15054 .option hosts_connection_nolog main "host list&!!" unset
15055 .cindex "host" "not logging connections from"
15056 This option defines a list of hosts for which connection logging does not
15057 happen, even though the &%smtp_connection%& log selector is set. For example,
15058 you might want not to log SMTP connections from local processes, or from
15059 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
15060 the daemon; you should therefore strive to restrict its value to a short inline
15061 list of IP addresses and networks. To disable logging SMTP connections from
15062 local processes, you must create a host list with an empty item. For example:
15064 hosts_connection_nolog = :
15066 If the &%smtp_connection%& log selector is not set, this option has no effect.
15070 .option hosts_proxy main "host list&!!" unset
15071 .cindex proxy "proxy protocol"
15072 This option enables use of Proxy Protocol proxies for incoming
15073 connections. For details see &<<SECTproxyInbound>>&.
15076 .option hosts_treat_as_local main "domain list&!!" unset
15077 .cindex "local host" "domains treated as"
15078 .cindex "host" "treated as local"
15079 If this option is set, any host names that match the domain list are treated as
15080 if they were the local host when Exim is scanning host lists obtained from MX
15082 or other sources. Note that the value of this option is a domain list, not a
15083 host list, because it is always used to check host names, not IP addresses.
15085 This option also applies when Exim is matching the special items
15086 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
15087 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
15088 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
15089 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
15090 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
15091 interfaces and recognizing the local host.
15094 .option ibase_servers main "string list" unset
15095 .cindex "InterBase" "server list"
15096 This option provides a list of InterBase servers and associated connection data,
15097 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
15098 The option is available only if Exim has been built with InterBase support.
15102 .option ignore_bounce_errors_after main time 10w
15103 .cindex "bounce message" "discarding"
15104 .cindex "discarding bounce message"
15105 This option affects the processing of bounce messages that cannot be delivered,
15106 that is, those that suffer a permanent delivery failure. (Bounce messages that
15107 suffer temporary delivery failures are of course retried in the usual way.)
15109 After a permanent delivery failure, bounce messages are frozen,
15110 because there is no sender to whom they can be returned. When a frozen bounce
15111 message has been on the queue for more than the given time, it is unfrozen at
15112 the next queue run, and a further delivery is attempted. If delivery fails
15113 again, the bounce message is discarded. This makes it possible to keep failed
15114 bounce messages around for a shorter time than the normal maximum retry time
15115 for frozen messages. For example,
15117 ignore_bounce_errors_after = 12h
15119 retries failed bounce message deliveries after 12 hours, discarding any further
15120 failures. If the value of this option is set to a zero time period, bounce
15121 failures are discarded immediately. Setting a very long time (as in the default
15122 value) has the effect of disabling this option. For ways of automatically
15123 dealing with other kinds of frozen message, see &%auto_thaw%& and
15124 &%timeout_frozen_after%&.
15127 .option ignore_fromline_hosts main "host list&!!" unset
15128 .cindex "&""From""& line"
15129 .cindex "UUCP" "&""From""& line"
15130 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
15131 the headers of a message. By default this is treated as the start of the
15132 message's body, which means that any following headers are not recognized as
15133 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
15134 match those hosts that insist on sending it. If the sender is actually a local
15135 process rather than a remote host, and is using &%-bs%& to inject the messages,
15136 &%ignore_fromline_local%& must be set to achieve this effect.
15139 .option ignore_fromline_local main boolean false
15140 See &%ignore_fromline_hosts%& above.
15142 .option keep_environment main "string list" unset
15143 .cindex "environment" "values from"
15144 This option contains a string list of environment variables to keep.
15145 You have to trust these variables or you have to be sure that
15146 these variables do not impose any security risk. Keep in mind that
15147 during the startup phase Exim is running with an effective UID 0 in most
15148 installations. As the default value is an empty list, the default
15149 environment for using libraries, running embedded Perl code, or running
15150 external binaries is empty, and does not not even contain PATH or HOME.
15152 Actually the list is interpreted as a list of patterns
15153 (&<<SECTlistexpand>>&), except that it is not expanded first.
15155 WARNING: Macro substitution is still done first, so having a macro
15156 FOO and having FOO_HOME in your &%keep_environment%& option may have
15157 unexpected results. You may work around this using a regular expression
15158 that does not match the macro name: ^[F]OO_HOME$.
15160 Current versions of Exim issue a warning during startup if you do not mention
15161 &%keep_environment%& in your runtime configuration file and if your
15162 current environment is not empty. Future versions may not issue that warning
15165 See the &%add_environment%& main config option for a way to set
15166 environment variables to a fixed value. The environment for &(pipe)&
15167 transports is handled separately, see section &<<SECTpipeenv>>& for
15171 .option keep_malformed main time 4d
15172 This option specifies the length of time to keep messages whose spool files
15173 have been corrupted in some way. This should, of course, never happen. At the
15174 next attempt to deliver such a message, it gets removed. The incident is
15178 .option ldap_ca_cert_dir main string unset
15179 .cindex "LDAP", "TLS CA certificate directory"
15180 .cindex certificate "directory for LDAP"
15181 This option indicates which directory contains CA certificates for verifying
15182 a TLS certificate presented by an LDAP server.
15183 While Exim does not provide a default value, your SSL library may.
15184 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15185 and constrained to be a directory.
15188 .option ldap_ca_cert_file main string unset
15189 .cindex "LDAP", "TLS CA certificate file"
15190 .cindex certificate "file for LDAP"
15191 This option indicates which file contains CA certificates for verifying
15192 a TLS certificate presented by an LDAP server.
15193 While Exim does not provide a default value, your SSL library may.
15194 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15195 and constrained to be a file.
15198 .option ldap_cert_file main string unset
15199 .cindex "LDAP" "TLS client certificate file"
15200 .cindex certificate "file for LDAP"
15201 This option indicates which file contains an TLS client certificate which
15202 Exim should present to the LDAP server during TLS negotiation.
15203 Should be used together with &%ldap_cert_key%&.
15206 .option ldap_cert_key main string unset
15207 .cindex "LDAP" "TLS client key file"
15208 .cindex certificate "key for LDAP"
15209 This option indicates which file contains the secret/private key to use
15210 to prove identity to the LDAP server during TLS negotiation.
15211 Should be used together with &%ldap_cert_file%&, which contains the
15212 identity to be proven.
15215 .option ldap_cipher_suite main string unset
15216 .cindex "LDAP" "TLS cipher suite"
15217 This controls the TLS cipher-suite negotiation during TLS negotiation with
15218 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
15219 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15222 .option ldap_default_servers main "string list" unset
15223 .cindex "LDAP" "default servers"
15224 This option provides a list of LDAP servers which are tried in turn when an
15225 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15226 details of LDAP queries. This option is available only when Exim has been built
15230 .option ldap_require_cert main string unset.
15231 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15232 This should be one of the values "hard", "demand", "allow", "try" or "never".
15233 A value other than one of these is interpreted as "never".
15234 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15235 Although Exim does not set a default, the LDAP library probably defaults
15239 .option ldap_start_tls main boolean false
15240 .cindex "LDAP" "whether or not to negotiate TLS"
15241 If set, Exim will attempt to negotiate TLS with the LDAP server when
15242 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15243 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15245 In the event of failure to negotiate TLS, the action taken is controlled
15246 by &%ldap_require_cert%&.
15249 .option ldap_version main integer unset
15250 .cindex "LDAP" "protocol version, forcing"
15251 This option can be used to force Exim to set a specific protocol version for
15252 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15253 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15254 the LDAP headers; otherwise it is 2. This option is available only when Exim
15255 has been built with LDAP support.
15259 .option local_from_check main boolean true
15260 .cindex "&'Sender:'& header line" "disabling addition of"
15261 .cindex "&'From:'& header line" "disabling checking of"
15262 When a message is submitted locally (that is, not over a TCP/IP connection) by
15263 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15264 checks that the &'From:'& header line matches the login of the calling user and
15265 the domain specified by &%qualify_domain%&.
15267 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15268 locally submitted message is automatically qualified by Exim, unless the
15269 &%-bnq%& command line option is used.
15271 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15272 on the local part. If the &'From:'& header line does not match, Exim adds a
15273 &'Sender:'& header with an address constructed from the calling user's login
15274 and the default qualify domain.
15276 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15277 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15278 &'Sender:'& header lines supplied by untrusted users, you must also set
15279 &%local_sender_retain%& to be true.
15281 .cindex "envelope sender"
15282 These options affect only the header lines in the message. The envelope sender
15283 is still forced to be the login id at the qualify domain unless
15284 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15286 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15287 request similar header line checking. See section &<<SECTthesenhea>>&, which
15288 has more details about &'Sender:'& processing.
15293 .option local_from_prefix main string unset
15294 When Exim checks the &'From:'& header line of locally submitted messages for
15295 matching the login id (see &%local_from_check%& above), it can be configured to
15296 ignore certain prefixes and suffixes in the local part of the address. This is
15297 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15298 appropriate lists, in the same form as the &%local_part_prefix%& and
15299 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15302 local_from_prefix = *-
15304 is set, a &'From:'& line containing
15306 From: anything-user@your.domain.example
15308 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15309 matches the actual sender address that is constructed from the login name and
15313 .option local_from_suffix main string unset
15314 See &%local_from_prefix%& above.
15317 .option local_interfaces main "string list" "see below"
15318 This option controls which network interfaces are used by the daemon for
15319 listening; they are also used to identify the local host when routing. Chapter
15320 &<<CHAPinterfaces>>& contains a full description of this option and the related
15321 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15322 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15323 &%local_interfaces%& is
15325 local_interfaces = 0.0.0.0
15327 when Exim is built without IPv6 support; otherwise it is
15329 local_interfaces = <; ::0 ; 0.0.0.0
15332 .option local_scan_timeout main time 5m
15333 .cindex "timeout" "for &[local_scan()]& function"
15334 .cindex "&[local_scan()]& function" "timeout"
15335 This timeout applies to the &[local_scan()]& function (see chapter
15336 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15337 the incoming message is rejected with a temporary error if it is an SMTP
15338 message. For a non-SMTP message, the message is dropped and Exim ends with a
15339 non-zero code. The incident is logged on the main and reject logs.
15343 .option local_sender_retain main boolean false
15344 .cindex "&'Sender:'& header line" "retaining from local submission"
15345 When a message is submitted locally (that is, not over a TCP/IP connection) by
15346 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15347 do not want this to happen, you must set &%local_sender_retain%&, and you must
15348 also set &%local_from_check%& to be false (Exim will complain if you do not).
15349 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15350 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15355 .option localhost_number main string&!! unset
15356 .cindex "host" "locally unique number for"
15357 .cindex "message ids" "with multiple hosts"
15358 .vindex "&$localhost_number$&"
15359 Exim's message ids are normally unique only within the local host. If
15360 uniqueness among a set of hosts is required, each host must set a different
15361 value for the &%localhost_number%& option. The string is expanded immediately
15362 after reading the configuration file (so that a number can be computed from the
15363 host name, for example) and the result of the expansion must be a number in the
15364 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15365 systems). This is available in subsequent string expansions via the variable
15366 &$localhost_number$&. When &%localhost_number is set%&, the final two
15367 characters of the message id, instead of just being a fractional part of the
15368 time, are computed from the time and the local host number as described in
15369 section &<<SECTmessiden>>&.
15373 .option log_file_path main "string list&!!" "set at compile time"
15374 .cindex "log" "file path for"
15375 This option sets the path which is used to determine the names of Exim's log
15376 files, or indicates that logging is to be to syslog, or both. It is expanded
15377 when Exim is entered, so it can, for example, contain a reference to the host
15378 name. If no specific path is set for the log files at compile or run time,
15379 or if the option is unset at run time (i.e. &`log_file_path = `&)
15380 they are written in a sub-directory called &_log_& in Exim's spool directory.
15381 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15382 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15383 used. If this string is fixed at your installation (contains no expansion
15384 variables) it is recommended that you do not set this option in the
15385 configuration file, but instead supply the path using LOG_FILE_PATH in
15386 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15387 early on &-- in particular, failure to read the configuration file.
15390 .option log_selector main string unset
15391 .cindex "log" "selectors"
15392 This option can be used to reduce or increase the number of things that Exim
15393 writes to its log files. Its argument is made up of names preceded by plus or
15394 minus characters. For example:
15396 log_selector = +arguments -retry_defer
15398 A list of possible names and what they control is given in the chapter on
15399 logging, in section &<<SECTlogselector>>&.
15402 .option log_timezone main boolean false
15403 .cindex "log" "timezone for entries"
15404 .vindex "&$tod_log$&"
15405 .vindex "&$tod_zone$&"
15406 By default, the timestamps on log lines are in local time without the
15407 timezone. This means that if your timezone changes twice a year, the timestamps
15408 in log lines are ambiguous for an hour when the clocks go back. One way of
15409 avoiding this problem is to set the timezone to UTC. An alternative is to set
15410 &%log_timezone%& true. This turns on the addition of the timezone offset to
15411 timestamps in log lines. Turning on this option can add quite a lot to the size
15412 of log files because each line is extended by 6 characters. Note that the
15413 &$tod_log$& variable contains the log timestamp without the zone, but there is
15414 another variable called &$tod_zone$& that contains just the timezone offset.
15417 .option lookup_open_max main integer 25
15418 .cindex "too many open files"
15419 .cindex "open files, too many"
15420 .cindex "file" "too many open"
15421 .cindex "lookup" "maximum open files"
15422 .cindex "limit" "open files for lookups"
15423 This option limits the number of simultaneously open files for single-key
15424 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15425 Exim normally keeps these files open during routing, because often the same
15426 file is required several times. If the limit is reached, Exim closes the least
15427 recently used file. Note that if you are using the &'ndbm'& library, it
15428 actually opens two files for each logical DBM database, though it still counts
15429 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15430 open files"& errors with NDBM, you need to reduce the value of
15431 &%lookup_open_max%&.
15434 .option max_username_length main integer 0
15435 .cindex "length of login name"
15436 .cindex "user name" "maximum length"
15437 .cindex "limit" "user name length"
15438 Some operating systems are broken in that they truncate long arguments to
15439 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15440 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15441 an argument that is longer behaves as if &[getpwnam()]& failed.
15444 .option message_body_newlines main bool false
15445 .cindex "message body" "newlines in variables"
15446 .cindex "newline" "in message body variables"
15447 .vindex "&$message_body$&"
15448 .vindex "&$message_body_end$&"
15449 By default, newlines in the message body are replaced by spaces when setting
15450 the &$message_body$& and &$message_body_end$& expansion variables. If this
15451 option is set true, this no longer happens.
15454 .option message_body_visible main integer 500
15455 .cindex "body of message" "visible size"
15456 .cindex "message body" "visible size"
15457 .vindex "&$message_body$&"
15458 .vindex "&$message_body_end$&"
15459 This option specifies how much of a message's body is to be included in the
15460 &$message_body$& and &$message_body_end$& expansion variables.
15463 .option message_id_header_domain main string&!! unset
15464 .cindex "&'Message-ID:'& header line"
15465 If this option is set, the string is expanded and used as the right hand side
15466 (domain) of the &'Message-ID:'& header that Exim creates if a
15467 locally-originated incoming message does not have one. &"Locally-originated"&
15468 means &"not received over TCP/IP."&
15469 Otherwise, the primary host name is used.
15470 Only letters, digits, dot and hyphen are accepted; any other characters are
15471 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15472 empty string, the option is ignored.
15475 .option message_id_header_text main string&!! unset
15476 If this variable is set, the string is expanded and used to augment the text of
15477 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15478 message does not have one. The text of this header is required by RFC 2822 to
15479 take the form of an address. By default, Exim uses its internal message id as
15480 the local part, and the primary host name as the domain. If this option is set,
15481 it is expanded, and provided the expansion is not forced to fail, and does not
15482 yield an empty string, the result is inserted into the header immediately
15483 before the @, separated from the internal message id by a dot. Any characters
15484 that are illegal in an address are automatically converted into hyphens. This
15485 means that variables such as &$tod_log$& can be used, because the spaces and
15486 colons will become hyphens.
15489 .option message_logs main boolean true
15490 .cindex "message logs" "disabling"
15491 .cindex "log" "message log; disabling"
15492 If this option is turned off, per-message log files are not created in the
15493 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15494 Exim, by reducing the number of files involved in handling a message from a
15495 minimum of four (header spool file, body spool file, delivery journal, and
15496 per-message log) to three. The other major I/O activity is Exim's main log,
15497 which is not affected by this option.
15500 .option message_size_limit main string&!! 50M
15501 .cindex "message" "size limit"
15502 .cindex "limit" "message size"
15503 .cindex "size" "of message, limit"
15504 This option limits the maximum size of message that Exim will process. The
15505 value is expanded for each incoming connection so, for example, it can be made
15506 to depend on the IP address of the remote host for messages arriving via
15507 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15508 optionally followed by K or M.
15510 &*Note*&: This limit cannot be made to depend on a message's sender or any
15511 other properties of an individual message, because it has to be advertised in
15512 the server's response to EHLO. String expansion failure causes a temporary
15513 error. A value of zero means no limit, but its use is not recommended. See also
15514 &%bounce_return_size_limit%&.
15516 Incoming SMTP messages are failed with a 552 error if the limit is
15517 exceeded; locally-generated messages either get a stderr message or a delivery
15518 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15519 an oversized message is logged in both the main and the reject logs. See also
15520 the generic transport option &%message_size_limit%&, which limits the size of
15521 message that an individual transport can process.
15523 If you use a virus-scanner and set this option to to a value larger than the
15524 maximum size that your virus-scanner is configured to support, you may get
15525 failures triggered by large mails. The right size to configure for the
15526 virus-scanner depends upon what data is passed and the options in use but it's
15527 probably safest to just set it to a little larger than this value. E.g., with a
15528 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15529 some problems may result.
15531 A value of 0 will disable size limit checking; Exim will still advertise the
15532 SIZE extension in an EHLO response, but without a limit, so as to permit
15533 SMTP clients to still indicate the message size along with the MAIL verb.
15536 .option move_frozen_messages main boolean false
15537 .cindex "frozen messages" "moving"
15538 This option, which is available only if Exim has been built with the setting
15540 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15542 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15543 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15544 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15545 standard utilities for handling such moved messages, and they do not show up in
15546 lists generated by &%-bp%& or by the Exim monitor.
15549 .option mua_wrapper main boolean false
15550 Setting this option true causes Exim to run in a very restrictive mode in which
15551 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15552 contains a full description of this facility.
15556 .option mysql_servers main "string list" unset
15557 .cindex "MySQL" "server list"
15558 This option provides a list of MySQL servers and associated connection data, to
15559 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15560 option is available only if Exim has been built with MySQL support.
15563 .option never_users main "string list&!!" unset
15564 This option is expanded just once, at the start of Exim's processing. Local
15565 message deliveries are normally run in processes that are setuid to the
15566 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15567 It is usually desirable to prevent any deliveries from running as root, as a
15570 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15571 list of users that must not be used for local deliveries. This list is fixed in
15572 the binary and cannot be overridden by the configuration file. By default, it
15573 contains just the single user name &"root"&. The &%never_users%& runtime option
15574 can be used to add more users to the fixed list.
15576 If a message is to be delivered as one of the users on the fixed list or the
15577 &%never_users%& list, an error occurs, and delivery is deferred. A common
15580 never_users = root:daemon:bin
15582 Including root is redundant if it is also on the fixed list, but it does no
15583 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15587 .option openssl_options main "string list" "+no_sslv2 +single_dh_use"
15588 .cindex "OpenSSL "compatibility options"
15589 This option allows an administrator to adjust the SSL options applied
15590 by OpenSSL to connections. It is given as a space-separated list of items,
15591 each one to be +added or -subtracted from the current value.
15593 This option is only available if Exim is built against OpenSSL. The values
15594 available for this option vary according to the age of your OpenSSL install.
15595 The &"all"& value controls a subset of flags which are available, typically
15596 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15597 list the values known on your system and Exim should support all the
15598 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15599 names lose the leading &"SSL_OP_"& and are lower-cased.
15601 Note that adjusting the options can have severe impact upon the security of
15602 SSL as used by Exim. It is possible to disable safety checks and shoot
15603 yourself in the foot in various unpleasant ways. This option should not be
15604 adjusted lightly. An unrecognised item will be detected at startup, by
15605 invoking Exim with the &%-bV%& flag.
15607 The option affects Exim operating both as a server and as a client.
15609 Historical note: prior to release 4.80, Exim defaulted this value to
15610 "+dont_insert_empty_fragments", which may still be needed for compatibility
15611 with some clients, but which lowers security by increasing exposure to
15612 some now infamous attacks.
15616 # Make both old MS and old Eudora happy:
15617 openssl_options = -all +microsoft_big_sslv3_buffer \
15618 +dont_insert_empty_fragments
15620 # Disable older protocol versions:
15621 openssl_options = +no_sslv2 +no_sslv3
15624 Possible options may include:
15628 &`allow_unsafe_legacy_renegotiation`&
15630 &`cipher_server_preference`&
15632 &`dont_insert_empty_fragments`&
15636 &`legacy_server_connect`&
15638 &`microsoft_big_sslv3_buffer`&
15640 &`microsoft_sess_id_bug`&
15642 &`msie_sslv2_rsa_padding`&
15644 &`netscape_challenge_bug`&
15646 &`netscape_reuse_cipher_change_bug`&
15650 &`no_session_resumption_on_renegotiation`&
15664 &`safari_ecdhe_ecdsa_bug`&
15668 &`single_ecdh_use`&
15670 &`ssleay_080_client_dh_bug`&
15672 &`sslref2_reuse_cert_type_bug`&
15674 &`tls_block_padding_bug`&
15678 &`tls_rollback_bug`&
15681 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15682 all clients connecting using the MacOS SecureTransport TLS facility prior
15683 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15684 to negotiate TLS then this option value might help, provided that your OpenSSL
15685 release is new enough to contain this work-around. This may be a situation
15686 where you have to upgrade OpenSSL to get buggy clients working.
15689 .option oracle_servers main "string list" unset
15690 .cindex "Oracle" "server list"
15691 This option provides a list of Oracle servers and associated connection data,
15692 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15693 The option is available only if Exim has been built with Oracle support.
15696 .option percent_hack_domains main "domain list&!!" unset
15697 .cindex "&""percent hack""&"
15698 .cindex "source routing" "in email address"
15699 .cindex "address" "source-routed"
15700 The &"percent hack"& is the convention whereby a local part containing a
15701 percent sign is re-interpreted as a new email address, with the percent
15702 replaced by @. This is sometimes called &"source routing"&, though that term is
15703 also applied to RFC 2822 addresses that begin with an @ character. If this
15704 option is set, Exim implements the percent facility for those domains listed,
15705 but no others. This happens before an incoming SMTP address is tested against
15708 &*Warning*&: The &"percent hack"& has often been abused by people who are
15709 trying to get round relaying restrictions. For this reason, it is best avoided
15710 if at all possible. Unfortunately, a number of less security-conscious MTAs
15711 implement it unconditionally. If you are running Exim on a gateway host, and
15712 routing mail through to internal MTAs without processing the local parts, it is
15713 a good idea to reject recipient addresses with percent characters in their
15714 local parts. Exim's default configuration does this.
15717 .option perl_at_start main boolean false
15719 This option is available only when Exim is built with an embedded Perl
15720 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15723 .option perl_startup main string unset
15725 This option is available only when Exim is built with an embedded Perl
15726 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15728 .option perl_startup main boolean false
15730 This Option enables the taint mode of the embedded Perl interpreter.
15733 .option pgsql_servers main "string list" unset
15734 .cindex "PostgreSQL lookup type" "server list"
15735 This option provides a list of PostgreSQL servers and associated connection
15736 data, to be used in conjunction with &(pgsql)& lookups (see section
15737 &<<SECID72>>&). The option is available only if Exim has been built with
15738 PostgreSQL support.
15741 .option pid_file_path main string&!! "set at compile time"
15742 .cindex "daemon" "pid file path"
15743 .cindex "pid file, path for"
15744 This option sets the name of the file to which the Exim daemon writes its
15745 process id. The string is expanded, so it can contain, for example, references
15748 pid_file_path = /var/log/$primary_hostname/exim.pid
15750 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15752 The value set by the option can be overridden by the &%-oP%& command line
15753 option. A pid file is not written if a &"non-standard"& daemon is run by means
15754 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15757 .option pipelining_advertise_hosts main "host list&!!" *
15758 .cindex "PIPELINING" "suppressing advertising"
15759 This option can be used to suppress the advertisement of the SMTP
15760 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15761 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15762 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15763 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15764 that clients will use it; &"out of order"& commands that are &"expected"& do
15765 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15768 .option prdr_enable main boolean false
15769 .cindex "PRDR" "enabling on server"
15770 This option can be used to enable the Per-Recipient Data Response extension
15771 to SMTP, defined by Eric Hall.
15772 If the option is set, PRDR is advertised by Exim when operating as a server.
15773 If the client requests PRDR, and more than one recipient, for a message
15774 an additional ACL is called for each recipient after the message content
15775 is received. See section &<<SECTPRDRACL>>&.
15777 .option preserve_message_logs main boolean false
15778 .cindex "message logs" "preserving"
15779 If this option is set, message log files are not deleted when messages are
15780 completed. Instead, they are moved to a sub-directory of the spool directory
15781 called &_msglog.OLD_&, where they remain available for statistical or debugging
15782 purposes. This is a dangerous option to set on systems with any appreciable
15783 volume of mail. Use with care!
15786 .option primary_hostname main string "see below"
15787 .cindex "name" "of local host"
15788 .cindex "host" "name of local"
15789 .cindex "local host" "name of"
15790 .vindex "&$primary_hostname$&"
15791 This specifies the name of the current host. It is used in the default EHLO or
15792 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15793 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15794 The value is also used by default in some SMTP response messages from an Exim
15795 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15797 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15798 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15799 contains only one component, Exim passes it to &[gethostbyname()]& (or
15800 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15801 version. The variable &$primary_hostname$& contains the host name, whether set
15802 explicitly by this option, or defaulted.
15805 .option print_topbitchars main boolean false
15806 .cindex "printing characters"
15807 .cindex "8-bit characters"
15808 By default, Exim considers only those characters whose codes lie in the range
15809 32&--126 to be printing characters. In a number of circumstances (for example,
15810 when writing log entries) non-printing characters are converted into escape
15811 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15812 is set, code values of 128 and above are also considered to be printing
15815 This option also affects the header syntax checks performed by the
15816 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15817 the user's full name when constructing From: and Sender: addresses (as
15818 described in section &<<SECTconstr>>&). Setting this option can cause
15819 Exim to generate eight bit message headers that do not conform to the
15823 .option process_log_path main string unset
15824 .cindex "process log path"
15825 .cindex "log" "process log"
15826 .cindex "&'exiwhat'&"
15827 This option sets the name of the file to which an Exim process writes its
15828 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15829 utility script. If this option is unset, the file called &_exim-process.info_&
15830 in Exim's spool directory is used. The ability to specify the name explicitly
15831 can be useful in environments where two different Exims are running, using
15832 different spool directories.
15835 .option prod_requires_admin main boolean true
15839 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15840 admin user unless &%prod_requires_admin%& is set false. See also
15841 &%queue_list_requires_admin%&.
15844 .option qualify_domain main string "see below"
15845 .cindex "domain" "for qualifying addresses"
15846 .cindex "address" "qualification"
15847 This option specifies the domain name that is added to any envelope sender
15848 addresses that do not have a domain qualification. It also applies to
15849 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15850 are accepted by default only for locally-generated messages. Qualification is
15851 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15852 locally-generated messages, unless the &%-bnq%& command line option is used.
15854 Messages from external sources must always contain fully qualified addresses,
15855 unless the sending host matches &%sender_unqualified_hosts%& or
15856 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15857 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15858 necessary. Internally, Exim always works with fully qualified envelope
15859 addresses. If &%qualify_domain%& is not set, it defaults to the
15860 &%primary_hostname%& value.
15863 .option qualify_recipient main string "see below"
15864 This option allows you to specify a different domain for qualifying recipient
15865 addresses to the one that is used for senders. See &%qualify_domain%& above.
15869 .option queue_domains main "domain list&!!" unset
15870 .cindex "domain" "specifying non-immediate delivery"
15871 .cindex "queueing incoming messages"
15872 .cindex "message" "queueing certain domains"
15873 This option lists domains for which immediate delivery is not required.
15874 A delivery process is started whenever a message is received, but only those
15875 domains that do not match are processed. All other deliveries wait until the
15876 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15879 .option queue_list_requires_admin main boolean true
15881 The &%-bp%& command-line option, which lists the messages that are on the
15882 queue, requires the caller to be an admin user unless
15883 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15886 .option queue_only main boolean false
15887 .cindex "queueing incoming messages"
15888 .cindex "message" "queueing unconditionally"
15889 If &%queue_only%& is set, a delivery process is not automatically started
15890 whenever a message is received. Instead, the message waits on the queue for the
15891 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15892 delivered immediately when certain conditions (such as heavy load) occur.
15894 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15895 and &%-odi%& command line options override &%queue_only%& unless
15896 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15897 &%queue_only_load%&, and &%smtp_accept_queue%&.
15900 .option queue_only_file main string unset
15901 .cindex "queueing incoming messages"
15902 .cindex "message" "queueing by file existence"
15903 This option can be set to a colon-separated list of absolute path names, each
15904 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15905 it tests for the existence of each listed path using a call to &[stat()]&. For
15906 each path that exists, the corresponding queueing option is set.
15907 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15908 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15910 queue_only_file = smtp/some/file
15912 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15913 &_/some/file_& exists.
15916 .option queue_only_load main fixed-point unset
15917 .cindex "load average"
15918 .cindex "queueing incoming messages"
15919 .cindex "message" "queueing by load"
15920 If the system load average is higher than this value, incoming messages from
15921 all sources are queued, and no automatic deliveries are started. If this
15922 happens during local or remote SMTP input, all subsequent messages received on
15923 the same SMTP connection are queued by default, whatever happens to the load in
15924 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15927 Deliveries will subsequently be performed by queue runner processes. This
15928 option has no effect on ancient operating systems on which Exim cannot
15929 determine the load average. See also &%deliver_queue_load_max%& and
15930 &%smtp_load_reserve%&.
15933 .option queue_only_load_latch main boolean true
15934 .cindex "load average" "re-evaluating per message"
15935 When this option is true (the default), once one message has been queued
15936 because the load average is higher than the value set by &%queue_only_load%&,
15937 all subsequent messages received on the same SMTP connection are also queued.
15938 This is a deliberate choice; even though the load average may fall below the
15939 threshold, it doesn't seem right to deliver later messages on the same
15940 connection when not delivering earlier ones. However, there are special
15941 circumstances such as very long-lived connections from scanning appliances
15942 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15943 should be set false. This causes the value of the load average to be
15944 re-evaluated for each message.
15947 .option queue_only_override main boolean true
15948 .cindex "queueing incoming messages"
15949 When this option is true, the &%-od%&&'x'& command line options override the
15950 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15951 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15952 to override; they are accepted, but ignored.
15955 .option queue_run_in_order main boolean false
15956 .cindex "queue runner" "processing messages in order"
15957 If this option is set, queue runs happen in order of message arrival instead of
15958 in an arbitrary order. For this to happen, a complete list of the entire queue
15959 must be set up before the deliveries start. When the queue is all held in a
15960 single directory (the default), a single list is created for both the ordered
15961 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15962 single list is not created when &%queue_run_in_order%& is false. In this case,
15963 the sub-directories are processed one at a time (in a random order), and this
15964 avoids setting up one huge list for the whole queue. Thus, setting
15965 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15966 when the queue is large, because of the extra work in setting up the single,
15967 large list. In most situations, &%queue_run_in_order%& should not be set.
15971 .option queue_run_max main integer&!! 5
15972 .cindex "queue runner" "maximum number of"
15973 This controls the maximum number of queue runner processes that an Exim daemon
15974 can run simultaneously. This does not mean that it starts them all at once,
15975 but rather that if the maximum number are still running when the time comes to
15976 start another one, it refrains from starting another one. This can happen with
15977 very large queues and/or very sluggish deliveries. This option does not,
15978 however, interlock with other processes, so additional queue runners can be
15979 started by other means, or by killing and restarting the daemon.
15981 Setting this option to zero does not suppress queue runs; rather, it disables
15982 the limit, allowing any number of simultaneous queue runner processes to be
15983 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15984 the daemon's command line.
15987 .cindex queues named
15988 .cindex "named queues"
15989 To set limits for different named queues use
15990 an expansion depending on the &$queue_name$& variable.
15993 .option queue_smtp_domains main "domain list&!!" unset
15994 .cindex "queueing incoming messages"
15995 .cindex "message" "queueing remote deliveries"
15996 When this option is set, a delivery process is started whenever a message is
15997 received, routing is performed, and local deliveries take place.
15998 However, if any SMTP deliveries are required for domains that match
15999 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
16000 message waits on the queue for the next queue run. Since routing of the message
16001 has taken place, Exim knows to which remote hosts it must be delivered, and so
16002 when the queue run happens, multiple messages for the same host are delivered
16003 over a single SMTP connection. The &%-odqs%& command line option causes all
16004 SMTP deliveries to be queued in this way, and is equivalent to setting
16005 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
16009 .option receive_timeout main time 0s
16010 .cindex "timeout" "for non-SMTP input"
16011 This option sets the timeout for accepting a non-SMTP message, that is, the
16012 maximum time that Exim waits when reading a message on the standard input. If
16013 the value is zero, it will wait for ever. This setting is overridden by the
16014 &%-or%& command line option. The timeout for incoming SMTP messages is
16015 controlled by &%smtp_receive_timeout%&.
16017 .option received_header_text main string&!! "see below"
16018 .cindex "customizing" "&'Received:'& header"
16019 .cindex "&'Received:'& header line" "customizing"
16020 This string defines the contents of the &'Received:'& message header that is
16021 added to each message, except for the timestamp, which is automatically added
16022 on at the end (preceded by a semicolon). The string is expanded each time it is
16023 used. If the expansion yields an empty string, no &'Received:'& header line is
16024 added to the message. Otherwise, the string should start with the text
16025 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
16026 header lines. The default setting is:
16029 received_header_text = Received: \
16030 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
16031 {${if def:sender_ident \
16032 {from ${quote_local_part:$sender_ident} }}\
16033 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
16034 by $primary_hostname \
16035 ${if def:received_protocol {with $received_protocol}} \
16036 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
16037 (Exim $version_number)\n\t\
16038 ${if def:sender_address \
16039 {(envelope-from <$sender_address>)\n\t}}\
16040 id $message_exim_id\
16041 ${if def:received_for {\n\tfor $received_for}}
16044 The reference to the TLS cipher is omitted when Exim is built without TLS
16045 support. The use of conditional expansions ensures that this works for both
16046 locally generated messages and messages received from remote hosts, giving
16047 header lines such as the following:
16049 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
16050 by marley.carol.example with esmtp (Exim 4.00)
16051 (envelope-from <bob@carol.example>)
16052 id 16IOWa-00019l-00
16053 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
16054 Received: by scrooge.carol.example with local (Exim 4.00)
16055 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
16057 Until the body of the message has been received, the timestamp is the time when
16058 the message started to be received. Once the body has arrived, and all policy
16059 checks have taken place, the timestamp is updated to the time at which the
16060 message was accepted.
16063 .option received_headers_max main integer 30
16064 .cindex "loop" "prevention"
16065 .cindex "mail loop prevention"
16066 .cindex "&'Received:'& header line" "counting"
16067 When a message is to be delivered, the number of &'Received:'& headers is
16068 counted, and if it is greater than this parameter, a mail loop is assumed to
16069 have occurred, the delivery is abandoned, and an error message is generated.
16070 This applies to both local and remote deliveries.
16073 .option recipient_unqualified_hosts main "host list&!!" unset
16074 .cindex "unqualified addresses"
16075 .cindex "host" "unqualified addresses from"
16076 This option lists those hosts from which Exim is prepared to accept unqualified
16077 recipient addresses in message envelopes. The addresses are made fully
16078 qualified by the addition of the &%qualify_recipient%& value. This option also
16079 affects message header lines. Exim does not reject unqualified recipient
16080 addresses in headers, but it qualifies them only if the message came from a
16081 host that matches &%recipient_unqualified_hosts%&,
16082 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
16083 option was not set.
16086 .option recipients_max main integer 0
16087 .cindex "limit" "number of recipients"
16088 .cindex "recipient" "maximum number"
16089 If this option is set greater than zero, it specifies the maximum number of
16090 original recipients for any message. Additional recipients that are generated
16091 by aliasing or forwarding do not count. SMTP messages get a 452 response for
16092 all recipients over the limit; earlier recipients are delivered as normal.
16093 Non-SMTP messages with too many recipients are failed, and no deliveries are
16096 .cindex "RCPT" "maximum number of incoming"
16097 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
16098 RCPT commands in a single message.
16101 .option recipients_max_reject main boolean false
16102 If this option is set true, Exim rejects SMTP messages containing too many
16103 recipients by giving 552 errors to the surplus RCPT commands, and a 554
16104 error to the eventual DATA command. Otherwise (the default) it gives a 452
16105 error to the surplus RCPT commands and accepts the message on behalf of the
16106 initial set of recipients. The remote server should then re-send the message
16107 for the remaining recipients at a later time.
16110 .option remote_max_parallel main integer 2
16111 .cindex "delivery" "parallelism for remote"
16112 This option controls parallel delivery of one message to a number of remote
16113 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
16114 does all the remote deliveries for a message one by one. Otherwise, if a single
16115 message has to be delivered to more than one remote host, or if several copies
16116 have to be sent to the same remote host, up to &%remote_max_parallel%&
16117 deliveries are done simultaneously. If more than &%remote_max_parallel%&
16118 deliveries are required, the maximum number of processes are started, and as
16119 each one finishes, another is begun. The order of starting processes is the
16120 same as if sequential delivery were being done, and can be controlled by the
16121 &%remote_sort_domains%& option. If parallel delivery takes place while running
16122 with debugging turned on, the debugging output from each delivery process is
16123 tagged with its process id.
16125 This option controls only the maximum number of parallel deliveries for one
16126 message in one Exim delivery process. Because Exim has no central queue
16127 manager, there is no way of controlling the total number of simultaneous
16128 deliveries if the configuration allows a delivery attempt as soon as a message
16131 .cindex "number of deliveries"
16132 .cindex "delivery" "maximum number of"
16133 If you want to control the total number of deliveries on the system, you
16134 need to set the &%queue_only%& option. This ensures that all incoming messages
16135 are added to the queue without starting a delivery process. Then set up an Exim
16136 daemon to start queue runner processes at appropriate intervals (probably
16137 fairly often, for example, every minute), and limit the total number of queue
16138 runners by setting the &%queue_run_max%& parameter. Because each queue runner
16139 delivers only one message at a time, the maximum number of deliveries that can
16140 then take place at once is &%queue_run_max%& multiplied by
16141 &%remote_max_parallel%&.
16143 If it is purely remote deliveries you want to control, use
16144 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
16145 doing the SMTP routing before queueing, so that several messages for the same
16146 host will eventually get delivered down the same connection.
16149 .option remote_sort_domains main "domain list&!!" unset
16150 .cindex "sorting remote deliveries"
16151 .cindex "delivery" "sorting remote"
16152 When there are a number of remote deliveries for a message, they are sorted by
16153 domain into the order given by this list. For example,
16155 remote_sort_domains = *.cam.ac.uk:*.uk
16157 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
16158 then to those in the &%uk%& domain, then to any others.
16161 .option retry_data_expire main time 7d
16162 .cindex "hints database" "data expiry"
16163 This option sets a &"use before"& time on retry information in Exim's hints
16164 database. Any older retry data is ignored. This means that, for example, once a
16165 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
16169 .option retry_interval_max main time 24h
16170 .cindex "retry" "limit on interval"
16171 .cindex "limit" "on retry interval"
16172 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
16173 intervals between delivery attempts for messages that cannot be delivered
16174 straight away. This option sets an overall limit to the length of time between
16175 retries. It cannot be set greater than 24 hours; any attempt to do so forces
16179 .option return_path_remove main boolean true
16180 .cindex "&'Return-path:'& header line" "removing"
16181 RFC 2821, section 4.4, states that an SMTP server must insert a
16182 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
16183 The &'Return-path:'& header preserves the sender address as received in the
16184 MAIL command. This description implies that this header should not be present
16185 in an incoming message. If &%return_path_remove%& is true, any existing
16186 &'Return-path:'& headers are removed from messages at the time they are
16187 received. Exim's transports have options for adding &'Return-path:'& headers at
16188 the time of delivery. They are normally used only for final local deliveries.
16191 .option return_size_limit main integer 100K
16192 This option is an obsolete synonym for &%bounce_return_size_limit%&.
16195 .option rfc1413_hosts main "host list&!!" @[]
16197 .cindex "host" "for RFC 1413 calls"
16198 RFC 1413 identification calls are made to any client host which matches
16199 an item in the list.
16200 The default value specifies just this host, being any local interface
16203 .option rfc1413_query_timeout main time 0s
16204 .cindex "RFC 1413" "query timeout"
16205 .cindex "timeout" "for RFC 1413 call"
16206 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
16207 no RFC 1413 calls are ever made.
16210 .option sender_unqualified_hosts main "host list&!!" unset
16211 .cindex "unqualified addresses"
16212 .cindex "host" "unqualified addresses from"
16213 This option lists those hosts from which Exim is prepared to accept unqualified
16214 sender addresses. The addresses are made fully qualified by the addition of
16215 &%qualify_domain%&. This option also affects message header lines. Exim does
16216 not reject unqualified addresses in headers that contain sender addresses, but
16217 it qualifies them only if the message came from a host that matches
16218 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
16219 using TCP/IP), and the &%-bnq%& option was not set.
16221 .option set_environment main "string list" empty
16222 .cindex "environment"
16223 This option allows to set individual environment variables that the
16224 currently linked libraries and programs in child processes use. The
16225 default list is empty,
16228 .option slow_lookup_log main integer 0
16229 .cindex "logging" "slow lookups"
16230 .cindex "dns" "logging slow lookups"
16231 This option controls logging of slow lookups.
16232 If the value is nonzero it is taken as a number of milliseconds
16233 and lookups taking longer than this are logged.
16234 Currently this applies only to DNS lookups.
16238 .option smtp_accept_keepalive main boolean true
16239 .cindex "keepalive" "on incoming connection"
16240 This option controls the setting of the SO_KEEPALIVE option on incoming
16241 TCP/IP socket connections. When set, it causes the kernel to probe idle
16242 connections periodically, by sending packets with &"old"& sequence numbers. The
16243 other end of the connection should send an acknowledgment if the connection is
16244 still okay or a reset if the connection has been aborted. The reason for doing
16245 this is that it has the beneficial effect of freeing up certain types of
16246 connection that can get stuck when the remote host is disconnected without
16247 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16248 hours to detect unreachable hosts.
16252 .option smtp_accept_max main integer 20
16253 .cindex "limit" "incoming SMTP connections"
16254 .cindex "SMTP" "incoming connection count"
16256 This option specifies the maximum number of simultaneous incoming SMTP calls
16257 that Exim will accept. It applies only to the listening daemon; there is no
16258 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16259 value is set to zero, no limit is applied. However, it is required to be
16260 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16261 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16263 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16264 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16265 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16266 and &%smtp_load_reserve%& are then checked before accepting the connection.
16269 .option smtp_accept_max_nonmail main integer 10
16270 .cindex "limit" "non-mail SMTP commands"
16271 .cindex "SMTP" "limiting non-mail commands"
16272 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16273 the connection if there are too many. This option defines &"too many"&. The
16274 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16275 client looping sending EHLO, for example. The check is applied only if the
16276 client host matches &%smtp_accept_max_nonmail_hosts%&.
16278 When a new message is expected, one occurrence of RSET is not counted. This
16279 allows a client to send one RSET between messages (this is not necessary,
16280 but some clients do it). Exim also allows one uncounted occurrence of HELO
16281 or EHLO, and one occurrence of STARTTLS between messages. After
16282 starting up a TLS session, another EHLO is expected, and so it too is not
16283 counted. The first occurrence of AUTH in a connection, or immediately
16284 following STARTTLS is not counted. Otherwise, all commands other than
16285 MAIL, RCPT, DATA, and QUIT are counted.
16288 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16289 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16290 check by setting this option. The default value makes it apply to all hosts. By
16291 changing the value, you can exclude any badly-behaved hosts that you have to
16295 . Allow this long option name to split; give it unsplit as a fifth argument
16296 . for the automatic .oindex that is generated by .option.
16297 . We insert " &~&~" which is both pretty nasty visually and results in
16298 . non-searchable text. HowItWorks.txt mentions an option for inserting
16299 . zero-width-space, which would be nicer visually and results in (at least)
16300 . html that Firefox will split on when it's forced to reflow (rather than
16301 . inserting a horizontal scrollbar). However, the text is still not
16302 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16303 . the option name to split.
16305 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16306 smtp_accept_max_per_connection
16307 .cindex "SMTP" "limiting incoming message count"
16308 .cindex "limit" "messages per SMTP connection"
16309 The value of this option limits the number of MAIL commands that Exim is
16310 prepared to accept over a single SMTP connection, whether or not each command
16311 results in the transfer of a message. After the limit is reached, a 421
16312 response is given to subsequent MAIL commands. This limit is a safety
16313 precaution against a client that goes mad (incidents of this type have been
16317 .option smtp_accept_max_per_host main string&!! unset
16318 .cindex "limit" "SMTP connections from one host"
16319 .cindex "host" "limiting SMTP connections from"
16320 This option restricts the number of simultaneous IP connections from a single
16321 host (strictly, from a single IP address) to the Exim daemon. The option is
16322 expanded, to enable different limits to be applied to different hosts by
16323 reference to &$sender_host_address$&. Once the limit is reached, additional
16324 connection attempts from the same host are rejected with error code 421. This
16325 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16326 of zero imposes no limit. If this option is set greater than zero, it is
16327 required that &%smtp_accept_max%& be non-zero.
16329 &*Warning*&: When setting this option you should not use any expansion
16330 constructions that take an appreciable amount of time. The expansion and test
16331 happen in the main daemon loop, in order to reject additional connections
16332 without forking additional processes (otherwise a denial-of-service attack
16333 could cause a vast number or processes to be created). While the daemon is
16334 doing this processing, it cannot accept any other incoming connections.
16338 .option smtp_accept_queue main integer 0
16339 .cindex "SMTP" "incoming connection count"
16340 .cindex "queueing incoming messages"
16341 .cindex "message" "queueing by SMTP connection count"
16342 If the number of simultaneous incoming SMTP connections being handled via the
16343 listening daemon exceeds this value, messages received by SMTP are just placed
16344 on the queue; no delivery processes are started automatically. The count is
16345 fixed at the start of an SMTP connection. It cannot be updated in the
16346 subprocess that receives messages, and so the queueing or not queueing applies
16347 to all messages received in the same connection.
16349 A value of zero implies no limit, and clearly any non-zero value is useful only
16350 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16351 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16352 various &%-od%&&'x'& command line options.
16355 . See the comment on smtp_accept_max_per_connection
16357 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16358 smtp_accept_queue_per_connection
16359 .cindex "queueing incoming messages"
16360 .cindex "message" "queueing by message count"
16361 This option limits the number of delivery processes that Exim starts
16362 automatically when receiving messages via SMTP, whether via the daemon or by
16363 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16364 and the number of messages received in a single SMTP session exceeds this
16365 number, subsequent messages are placed on the queue, but no delivery processes
16366 are started. This helps to limit the number of Exim processes when a server
16367 restarts after downtime and there is a lot of mail waiting for it on other
16368 systems. On large systems, the default should probably be increased, and on
16369 dial-in client systems it should probably be set to zero (that is, disabled).
16372 .option smtp_accept_reserve main integer 0
16373 .cindex "SMTP" "incoming call count"
16374 .cindex "host" "reserved"
16375 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16376 number of SMTP connections that are reserved for connections from the hosts
16377 that are specified in &%smtp_reserve_hosts%&. The value set in
16378 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16379 restricted to this number of connections; the option specifies a minimum number
16380 of connection slots for them, not a maximum. It is a guarantee that this group
16381 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16382 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16385 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16386 set to 5, once there are 45 active connections (from any hosts), new
16387 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16388 provided the other criteria for acceptance are met.
16391 .option smtp_active_hostname main string&!! unset
16392 .cindex "host" "name in SMTP responses"
16393 .cindex "SMTP" "host name in responses"
16394 .vindex "&$primary_hostname$&"
16395 This option is provided for multi-homed servers that want to masquerade as
16396 several different hosts. At the start of an incoming SMTP connection, its value
16397 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16398 responses. For example, it is used as domain name in the response to an
16399 incoming HELO or EHLO command.
16401 .vindex "&$smtp_active_hostname$&"
16402 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16403 is saved with any messages that are received. It is therefore available for use
16404 in routers and transports when the message is later delivered.
16406 If this option is unset, or if its expansion is forced to fail, or if the
16407 expansion results in an empty string, the value of &$primary_hostname$& is
16408 used. Other expansion failures cause a message to be written to the main and
16409 panic logs, and the SMTP command receives a temporary error. Typically, the
16410 value of &%smtp_active_hostname%& depends on the incoming interface address.
16413 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16414 {cox.mydomain}{box.mydomain}}
16417 Although &$smtp_active_hostname$& is primarily concerned with incoming
16418 messages, it is also used as the default for HELO commands in callout
16419 verification if there is no remote transport from which to obtain a
16420 &%helo_data%& value.
16422 .option smtp_banner main string&!! "see below"
16423 .cindex "SMTP" "welcome banner"
16424 .cindex "banner for SMTP"
16425 .cindex "welcome banner for SMTP"
16426 .cindex "customizing" "SMTP banner"
16427 This string, which is expanded every time it is used, is output as the initial
16428 positive response to an SMTP connection. The default setting is:
16430 smtp_banner = $smtp_active_hostname ESMTP Exim \
16431 $version_number $tod_full
16433 Failure to expand the string causes a panic error. If you want to create a
16434 multiline response to the initial SMTP connection, use &"\n"& in the string at
16435 appropriate points, but not at the end. Note that the 220 code is not included
16436 in this string. Exim adds it automatically (several times in the case of a
16437 multiline response).
16440 .option smtp_check_spool_space main boolean true
16441 .cindex "checking disk space"
16442 .cindex "disk space, checking"
16443 .cindex "spool directory" "checking space"
16444 When this option is set, if an incoming SMTP session encounters the SIZE
16445 option on a MAIL command, it checks that there is enough space in the
16446 spool directory's partition to accept a message of that size, while still
16447 leaving free the amount specified by &%check_spool_space%& (even if that value
16448 is zero). If there isn't enough space, a temporary error code is returned.
16451 .option smtp_connect_backlog main integer 20
16452 .cindex "connection backlog"
16453 .cindex "SMTP" "connection backlog"
16454 .cindex "backlog of connections"
16455 This option specifies a maximum number of waiting SMTP connections. Exim passes
16456 this value to the TCP/IP system when it sets up its listener. Once this number
16457 of connections are waiting for the daemon's attention, subsequent connection
16458 attempts are refused at the TCP/IP level. At least, that is what the manuals
16459 say; in some circumstances such connection attempts have been observed to time
16460 out instead. For large systems it is probably a good idea to increase the
16461 value (to 50, say). It also gives some protection against denial-of-service
16462 attacks by SYN flooding.
16465 .option smtp_enforce_sync main boolean true
16466 .cindex "SMTP" "synchronization checking"
16467 .cindex "synchronization checking in SMTP"
16468 The SMTP protocol specification requires the client to wait for a response from
16469 the server at certain points in the dialogue. Without PIPELINING these
16470 synchronization points are after every command; with PIPELINING they are
16471 fewer, but they still exist.
16473 Some spamming sites send out a complete set of SMTP commands without waiting
16474 for any response. Exim protects against this by rejecting a message if the
16475 client has sent further input when it should not have. The error response &"554
16476 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16477 for this error cannot be perfect because of transmission delays (unexpected
16478 input may be on its way but not yet received when Exim checks). However, it
16479 does detect many instances.
16481 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16482 If you want to disable the check selectively (for example, only for certain
16483 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16484 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16488 .option smtp_etrn_command main string&!! unset
16489 .cindex "ETRN" "command to be run"
16490 .vindex "&$domain$&"
16491 If this option is set, the given command is run whenever an SMTP ETRN
16492 command is received from a host that is permitted to issue such commands (see
16493 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16494 are independently expanded. The expansion variable &$domain$& is set to the
16495 argument of the ETRN command, and no syntax checking is done on it. For
16498 smtp_etrn_command = /etc/etrn_command $domain \
16499 $sender_host_address
16501 A new process is created to run the command, but Exim does not wait for it to
16502 complete. Consequently, its status cannot be checked. If the command cannot be
16503 run, a line is written to the panic log, but the ETRN caller still receives
16504 a 250 success response. Exim is normally running under its own uid when
16505 receiving SMTP, so it is not possible for it to change the uid before running
16509 .option smtp_etrn_serialize main boolean true
16510 .cindex "ETRN" "serializing"
16511 When this option is set, it prevents the simultaneous execution of more than
16512 one identical command as a result of ETRN in an SMTP connection. See
16513 section &<<SECTETRN>>& for details.
16516 .option smtp_load_reserve main fixed-point unset
16517 .cindex "load average"
16518 If the system load average ever gets higher than this, incoming SMTP calls are
16519 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16520 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16521 the load is over the limit. The option has no effect on ancient operating
16522 systems on which Exim cannot determine the load average. See also
16523 &%deliver_queue_load_max%& and &%queue_only_load%&.
16527 .option smtp_max_synprot_errors main integer 3
16528 .cindex "SMTP" "limiting syntax and protocol errors"
16529 .cindex "limit" "SMTP syntax and protocol errors"
16530 Exim rejects SMTP commands that contain syntax or protocol errors. In
16531 particular, a syntactically invalid email address, as in this command:
16533 RCPT TO:<abc xyz@a.b.c>
16535 causes immediate rejection of the command, before any other tests are done.
16536 (The ACL cannot be run if there is no valid address to set up for it.) An
16537 example of a protocol error is receiving RCPT before MAIL. If there are
16538 too many syntax or protocol errors in one SMTP session, the connection is
16539 dropped. The limit is set by this option.
16541 .cindex "PIPELINING" "expected errors"
16542 When the PIPELINING extension to SMTP is in use, some protocol errors are
16543 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16544 Exim assumes that PIPELINING will be used if it advertises it (see
16545 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16546 not count towards the limit.
16550 .option smtp_max_unknown_commands main integer 3
16551 .cindex "SMTP" "limiting unknown commands"
16552 .cindex "limit" "unknown SMTP commands"
16553 If there are too many unrecognized commands in an incoming SMTP session, an
16554 Exim server drops the connection. This is a defence against some kinds of abuse
16557 into making connections to SMTP ports; in these circumstances, a number of
16558 non-SMTP command lines are sent first.
16562 .option smtp_ratelimit_hosts main "host list&!!" unset
16563 .cindex "SMTP" "rate limiting"
16564 .cindex "limit" "rate of message arrival"
16565 .cindex "RCPT" "rate limiting"
16566 Some sites find it helpful to be able to limit the rate at which certain hosts
16567 can send them messages, and the rate at which an individual message can specify
16570 Exim has two rate-limiting facilities. This section describes the older
16571 facility, which can limit rates within a single connection. The newer
16572 &%ratelimit%& ACL condition can limit rates across all connections. See section
16573 &<<SECTratelimiting>>& for details of the newer facility.
16575 When a host matches &%smtp_ratelimit_hosts%&, the values of
16576 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16577 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16578 respectively. Each option, if set, must contain a set of four comma-separated
16582 A threshold, before which there is no rate limiting.
16584 An initial time delay. Unlike other times in Exim, numbers with decimal
16585 fractional parts are allowed here.
16587 A factor by which to increase the delay each time.
16589 A maximum value for the delay. This should normally be less than 5 minutes,
16590 because after that time, the client is liable to timeout the SMTP command.
16593 For example, these settings have been used successfully at the site which
16594 first suggested this feature, for controlling mail from their customers:
16596 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16597 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16599 The first setting specifies delays that are applied to MAIL commands after
16600 two have been received over a single connection. The initial delay is 0.5
16601 seconds, increasing by a factor of 1.05 each time. The second setting applies
16602 delays to RCPT commands when more than four occur in a single message.
16605 .option smtp_ratelimit_mail main string unset
16606 See &%smtp_ratelimit_hosts%& above.
16609 .option smtp_ratelimit_rcpt main string unset
16610 See &%smtp_ratelimit_hosts%& above.
16613 .option smtp_receive_timeout main time&!! 5m
16614 .cindex "timeout" "for SMTP input"
16615 .cindex "SMTP" "input timeout"
16616 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16617 input, including batch SMTP. If a line of input (either an SMTP command or a
16618 data line) is not received within this time, the SMTP connection is dropped and
16619 the message is abandoned.
16620 A line is written to the log containing one of the following messages:
16622 SMTP command timeout on connection from...
16623 SMTP data timeout on connection from...
16625 The former means that Exim was expecting to read an SMTP command; the latter
16626 means that it was in the DATA phase, reading the contents of a message.
16628 If the first character of the option is a &"$"& the option is
16629 expanded before use and may depend on
16630 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16634 The value set by this option can be overridden by the
16635 &%-os%& command-line option. A setting of zero time disables the timeout, but
16636 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16637 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16638 timeout is controlled by &%receive_timeout%& and &%-or%&.
16641 .option smtp_reserve_hosts main "host list&!!" unset
16642 This option defines hosts for which SMTP connections are reserved; see
16643 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16646 .option smtp_return_error_details main boolean false
16647 .cindex "SMTP" "details policy failures"
16648 .cindex "policy control" "rejection, returning details"
16649 In the default state, Exim uses bland messages such as
16650 &"Administrative prohibition"& when it rejects SMTP commands for policy
16651 reasons. Many sysadmins like this because it gives away little information
16652 to spammers. However, some other sysadmins who are applying strict checking
16653 policies want to give out much fuller information about failures. Setting
16654 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16655 example, instead of &"Administrative prohibition"&, it might give:
16657 550-Rejected after DATA: '>' missing at end of address:
16658 550 failing address in "From" header is: <user@dom.ain
16662 .option smtputf8_advertise_hosts main "host list&!!" *
16663 .cindex "SMTPUTF8" "advertising"
16664 When Exim is built with support for internationalised mail names,
16665 the availability therof is advertised in
16666 response to EHLO only to those client hosts that match this option. See
16667 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
16670 .option spamd_address main string "see below"
16671 This option is available when Exim is compiled with the content-scanning
16672 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16673 The default value is
16677 See section &<<SECTscanspamass>>& for more details.
16681 .option split_spool_directory main boolean false
16682 .cindex "multiple spool directories"
16683 .cindex "spool directory" "split"
16684 .cindex "directories, multiple"
16685 If this option is set, it causes Exim to split its input directory into 62
16686 subdirectories, each with a single alphanumeric character as its name. The
16687 sixth character of the message id is used to allocate messages to
16688 subdirectories; this is the least significant base-62 digit of the time of
16689 arrival of the message.
16691 Splitting up the spool in this way may provide better performance on systems
16692 where there are long mail queues, by reducing the number of files in any one
16693 directory. The msglog directory is also split up in a similar way to the input
16694 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16695 are still placed in the single directory &_msglog.OLD_&.
16697 It is not necessary to take any special action for existing messages when
16698 changing &%split_spool_directory%&. Exim notices messages that are in the
16699 &"wrong"& place, and continues to process them. If the option is turned off
16700 after a period of being on, the subdirectories will eventually empty and be
16701 automatically deleted.
16703 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16704 changes. Instead of creating a list of all messages in the queue, and then
16705 trying to deliver each one in turn, it constructs a list of those in one
16706 sub-directory and tries to deliver them, before moving on to the next
16707 sub-directory. The sub-directories are processed in a random order. This
16708 spreads out the scanning of the input directories, and uses less memory. It is
16709 particularly beneficial when there are lots of messages on the queue. However,
16710 if &%queue_run_in_order%& is set, none of this new processing happens. The
16711 entire queue has to be scanned and sorted before any deliveries can start.
16714 .option spool_directory main string&!! "set at compile time"
16715 .cindex "spool directory" "path to"
16716 This defines the directory in which Exim keeps its spool, that is, the messages
16717 it is waiting to deliver. The default value is taken from the compile-time
16718 configuration setting, if there is one. If not, this option must be set. The
16719 string is expanded, so it can contain, for example, a reference to
16720 &$primary_hostname$&.
16722 If the spool directory name is fixed on your installation, it is recommended
16723 that you set it at build time rather than from this option, particularly if the
16724 log files are being written to the spool directory (see &%log_file_path%&).
16725 Otherwise log files cannot be used for errors that are detected early on, such
16726 as failures in the configuration file.
16728 By using this option to override the compiled-in path, it is possible to run
16729 tests of Exim without using the standard spool.
16731 .option sqlite_lock_timeout main time 5s
16732 .cindex "sqlite lookup type" "lock timeout"
16733 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16734 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16736 .option strict_acl_vars main boolean false
16737 .cindex "&ACL;" "variables, handling unset"
16738 This option controls what happens if a syntactically valid but undefined ACL
16739 variable is referenced. If it is false (the default), an empty string
16740 is substituted; if it is true, an error is generated. See section
16741 &<<SECTaclvariables>>& for details of ACL variables.
16743 .option strip_excess_angle_brackets main boolean false
16744 .cindex "angle brackets, excess"
16745 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16746 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16747 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16748 passed on to another MTA, the excess angle brackets are not passed on. If this
16749 option is not set, multiple pairs of angle brackets cause a syntax error.
16752 .option strip_trailing_dot main boolean false
16753 .cindex "trailing dot on domain"
16754 .cindex "dot" "trailing on domain"
16755 If this option is set, a trailing dot at the end of a domain in an address is
16756 ignored. If this is in the envelope and the message is passed on to another
16757 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16758 domain causes a syntax error.
16759 However, addresses in header lines are checked only when an ACL requests header
16763 .option syslog_duplication main boolean true
16764 .cindex "syslog" "duplicate log lines; suppressing"
16765 When Exim is logging to syslog, it writes the log lines for its three
16766 separate logs at different syslog priorities so that they can in principle
16767 be separated on the logging hosts. Some installations do not require this
16768 separation, and in those cases, the duplication of certain log lines is a
16769 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16770 particular log line is written to syslog. For lines that normally go to
16771 both the main log and the reject log, the reject log version (possibly
16772 containing message header lines) is written, at LOG_NOTICE priority.
16773 Lines that normally go to both the main and the panic log are written at
16774 the LOG_ALERT priority.
16777 .option syslog_facility main string unset
16778 .cindex "syslog" "facility; setting"
16779 This option sets the syslog &"facility"& name, used when Exim is logging to
16780 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16781 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16782 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16783 details of Exim's logging.
16787 .option syslog_processname main string &`exim`&
16788 .cindex "syslog" "process name; setting"
16789 This option sets the syslog &"ident"& name, used when Exim is logging to
16790 syslog. The value must be no longer than 32 characters. See chapter
16791 &<<CHAPlog>>& for details of Exim's logging.
16795 .option syslog_timestamp main boolean true
16796 .cindex "syslog" "timestamps"
16797 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16798 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16799 details of Exim's logging.
16802 .option system_filter main string&!! unset
16803 .cindex "filter" "system filter"
16804 .cindex "system filter" "specifying"
16805 .cindex "Sieve filter" "not available for system filter"
16806 This option specifies an Exim filter file that is applied to all messages at
16807 the start of each delivery attempt, before any routing is done. System filters
16808 must be Exim filters; they cannot be Sieve filters. If the system filter
16809 generates any deliveries to files or pipes, or any new mail messages, the
16810 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16811 which transports are to be used. Details of this facility are given in chapter
16812 &<<CHAPsystemfilter>>&.
16815 .option system_filter_directory_transport main string&!! unset
16816 .vindex "&$address_file$&"
16817 This sets the name of the transport driver that is to be used when the
16818 &%save%& command in a system message filter specifies a path ending in &"/"&,
16819 implying delivery of each message into a separate file in some directory.
16820 During the delivery, the variable &$address_file$& contains the path name.
16823 .option system_filter_file_transport main string&!! unset
16824 .cindex "file" "transport for system filter"
16825 This sets the name of the transport driver that is to be used when the &%save%&
16826 command in a system message filter specifies a path not ending in &"/"&. During
16827 the delivery, the variable &$address_file$& contains the path name.
16829 .option system_filter_group main string unset
16830 .cindex "gid (group id)" "system filter"
16831 This option is used only when &%system_filter_user%& is also set. It sets the
16832 gid under which the system filter is run, overriding any gid that is associated
16833 with the user. The value may be numerical or symbolic.
16835 .option system_filter_pipe_transport main string&!! unset
16836 .cindex "&(pipe)& transport" "for system filter"
16837 .vindex "&$address_pipe$&"
16838 This specifies the transport driver that is to be used when a &%pipe%& command
16839 is used in a system filter. During the delivery, the variable &$address_pipe$&
16840 contains the pipe command.
16843 .option system_filter_reply_transport main string&!! unset
16844 .cindex "&(autoreply)& transport" "for system filter"
16845 This specifies the transport driver that is to be used when a &%mail%& command
16846 is used in a system filter.
16849 .option system_filter_user main string unset
16850 .cindex "uid (user id)" "system filter"
16851 If this option is set to root, the system filter is run in the main Exim
16852 delivery process, as root. Otherwise, the system filter runs in a separate
16853 process, as the given user, defaulting to the Exim run-time user.
16854 Unless the string consists entirely of digits, it
16855 is looked up in the password data. Failure to find the named user causes a
16856 configuration error. The gid is either taken from the password data, or
16857 specified by &%system_filter_group%&. When the uid is specified numerically,
16858 &%system_filter_group%& is required to be set.
16860 If the system filter generates any pipe, file, or reply deliveries, the uid
16861 under which the filter is run is used when transporting them, unless a
16862 transport option overrides.
16865 .option tcp_nodelay main boolean true
16866 .cindex "daemon" "TCP_NODELAY on sockets"
16867 .cindex "Nagle algorithm"
16868 .cindex "TCP_NODELAY on listening sockets"
16869 If this option is set false, it stops the Exim daemon setting the
16870 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16871 turns off the &"Nagle algorithm"&, which is a way of improving network
16872 performance in interactive (character-by-character) situations. Turning it off
16873 should improve Exim's performance a bit, so that is what happens by default.
16874 However, it appears that some broken clients cannot cope, and time out. Hence
16875 this option. It affects only those sockets that are set up for listening by the
16876 daemon. Sockets created by the smtp transport for delivering mail always set
16880 .option timeout_frozen_after main time 0s
16881 .cindex "frozen messages" "timing out"
16882 .cindex "timeout" "frozen messages"
16883 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16884 message of any kind that has been on the queue for longer than the given time
16885 is automatically cancelled at the next queue run. If the frozen message is a
16886 bounce message, it is just discarded; otherwise, a bounce is sent to the
16887 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16888 If you want to timeout frozen bounce messages earlier than other kinds of
16889 frozen message, see &%ignore_bounce_errors_after%&.
16891 &*Note:*& the default value of zero means no timeouts; with this setting,
16892 frozen messages remain on the queue forever (except for any frozen bounce
16893 messages that are released by &%ignore_bounce_errors_after%&).
16896 .option timezone main string unset
16897 .cindex "timezone, setting"
16898 .cindex "environment" "values from"
16899 The value of &%timezone%& is used to set the environment variable TZ while
16900 running Exim (if it is different on entry). This ensures that all timestamps
16901 created by Exim are in the required timezone. If you want all your timestamps
16902 to be in UTC (aka GMT) you should set
16906 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16907 or, if that is not set, from the value of the TZ environment variable when Exim
16908 is built. If &%timezone%& is set to the empty string, either at build or run
16909 time, any existing TZ variable is removed from the environment when Exim
16910 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16911 unfortunately not all, operating systems.
16914 .option tls_advertise_hosts main "host list&!!" *
16915 .cindex "TLS" "advertising"
16916 .cindex "encryption" "on SMTP connection"
16917 .cindex "SMTP" "encrypted connection"
16918 When Exim is built with support for TLS encrypted connections, the availability
16919 of the STARTTLS command to set up an encrypted session is advertised in
16920 response to EHLO only to those client hosts that match this option. See
16921 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16922 Note that the default value requires that a certificate be supplied
16923 using the &%tls_certificate%& option. If TLS support for incoming connections
16924 is not required the &%tls_advertise_hosts%& option should be set empty.
16927 .option tls_certificate main string&!! unset
16928 .cindex "TLS" "server certificate; location of"
16929 .cindex "certificate" "server, location of"
16930 The value of this option is expanded, and must then be the absolute path to a
16931 file which contains the server's certificates. The server's private key is also
16932 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16933 &<<CHAPTLS>>& for further details.
16935 &*Note*&: The certificates defined by this option are used only when Exim is
16936 receiving incoming messages as a server. If you want to supply certificates for
16937 use when sending messages as a client, you must set the &%tls_certificate%&
16938 option in the relevant &(smtp)& transport.
16940 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16941 if the OpenSSL build supports TLS extensions and the TLS client sends the
16942 Server Name Indication extension, then this option and others documented in
16943 &<<SECTtlssni>>& will be re-expanded.
16946 If this option is unset or empty a fresh self-signed certificate will be
16947 generated for every connection.
16950 .option tls_crl main string&!! unset
16951 .cindex "TLS" "server certificate revocation list"
16952 .cindex "certificate" "revocation list for server"
16953 This option specifies a certificate revocation list. The expanded value must
16954 be the name of a file that contains a CRL in PEM format.
16956 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16959 .option tls_dh_max_bits main integer 2236
16960 .cindex "TLS" "D-H bit count"
16961 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16962 the chosen TLS library. That value might prove to be too high for
16963 interoperability. This option provides a maximum clamp on the value
16964 suggested, trading off security for interoperability.
16966 The value must be at least 1024.
16968 The value 2236 was chosen because, at time of adding the option, it was the
16969 hard-coded maximum value supported by the NSS cryptographic library, as used
16970 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16972 If you prefer more security and are willing to break some clients, raise this
16975 Note that the value passed to GnuTLS for *generating* a new prime may be a
16976 little less than this figure, because GnuTLS is inexact and may produce a
16977 larger prime than requested.
16980 .option tls_dhparam main string&!! unset
16981 .cindex "TLS" "D-H parameters for server"
16982 The value of this option is expanded and indicates the source of DH parameters
16983 to be used by Exim.
16985 If it is a filename starting with a &`/`&, then it names a file from which DH
16986 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16987 PKCS#3 representation of the DH prime. If the file does not exist, for
16988 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16989 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16990 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16991 and treated as though the &%tls_dhparam%& were set to "none".
16993 If this option expands to the string "none", then no DH parameters will be
16996 If this option expands to the string "historic" and Exim is using GnuTLS, then
16997 Exim will attempt to load a file from inside the spool directory. If the file
16998 does not exist, Exim will attempt to create it.
16999 See section &<<SECTgnutlsparam>>& for further details.
17001 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
17002 a default DH prime; the default is the 2048 bit prime described in section
17003 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
17004 in IKE is assigned number 23.
17006 Otherwise, the option must expand to the name used by Exim for any of a number
17007 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
17008 "ike" followed by the number used by IKE, or "default" which corresponds to
17011 The available primes are:
17012 &`ike1`&, &`ike2`&, &`ike5`&,
17013 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
17014 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
17016 Some of these will be too small to be accepted by clients.
17017 Some may be too large to be accepted by clients.
17019 The TLS protocol does not negotiate an acceptable size for this; clients tend
17020 to hard-drop connections if what is offered by the server is unacceptable,
17021 whether too large or too small, and there's no provision for the client to
17022 tell the server what these constraints are. Thus, as a server operator, you
17023 need to make an educated guess as to what is most likely to work for your
17026 Some known size constraints suggest that a bit-size in the range 2048 to 2236
17027 is most likely to maximise interoperability. The upper bound comes from
17028 applications using the Mozilla Network Security Services (NSS) library, which
17029 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
17030 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
17031 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
17032 acceptable bound from 1024 to 2048.
17035 .option tls_eccurve main string&!! prime256v1
17036 .cindex TLS "EC cryptography"
17037 If built with a recent-enough version of OpenSSL,
17038 this option selects a EC curve for use by Exim.
17040 Curve names of the form &'prime256v1'& are accepted.
17041 For even more-recent library versions, names of the form &'P-512'&
17042 are also accepted, plus the special value &'auto'&
17043 which tells the library to choose.
17045 If the option is set to an empty string, no EC curves will be enabled.
17048 .option tls_ocsp_file main string&!! unset
17049 .cindex TLS "certificate status"
17050 .cindex TLS "OCSP proof file"
17052 must if set expand to the absolute path to a file which contains a current
17053 status proof for the server's certificate, as obtained from the
17054 Certificate Authority.
17056 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
17059 .option tls_on_connect_ports main "string list" unset
17062 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
17063 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
17064 set up without waiting for the client to issue a STARTTLS command. For
17065 further details, see section &<<SECTsupobssmt>>&.
17069 .option tls_privatekey main string&!! unset
17070 .cindex "TLS" "server private key; location of"
17071 The value of this option is expanded, and must then be the absolute path to a
17072 file which contains the server's private key. If this option is unset, or if
17073 the expansion is forced to fail, or the result is an empty string, the private
17074 key is assumed to be in the same file as the server's certificates. See chapter
17075 &<<CHAPTLS>>& for further details.
17077 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17080 .option tls_remember_esmtp main boolean false
17081 .cindex "TLS" "esmtp state; remembering"
17082 .cindex "TLS" "broken clients"
17083 If this option is set true, Exim violates the RFCs by remembering that it is in
17084 &"esmtp"& state after successfully negotiating a TLS session. This provides
17085 support for broken clients that fail to send a new EHLO after starting a
17089 .option tls_require_ciphers main string&!! unset
17090 .cindex "TLS" "requiring specific ciphers"
17091 .cindex "cipher" "requiring specific"
17092 This option controls which ciphers can be used for incoming TLS connections.
17093 The &(smtp)& transport has an option of the same name for controlling outgoing
17094 connections. This option is expanded for each connection, so can be varied for
17095 different clients if required. The value of this option must be a list of
17096 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
17097 in somewhat different ways. If GnuTLS is being used, the client controls the
17098 preference order of the available ciphers. Details are given in sections
17099 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
17102 .option tls_try_verify_hosts main "host list&!!" unset
17103 .cindex "TLS" "client certificate verification"
17104 .cindex "certificate" "verification of client"
17105 See &%tls_verify_hosts%& below.
17108 .option tls_verify_certificates main string&!! system
17109 .cindex "TLS" "client certificate verification"
17110 .cindex "certificate" "verification of client"
17111 The value of this option is expanded, and must then be either the
17113 or the absolute path to
17114 a file or directory containing permitted certificates for clients that
17115 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
17117 The "system" value for the option will use a
17118 system default location compiled into the SSL library.
17119 This is not available for GnuTLS versions preceding 3.0.20,
17120 and will be taken as empty; an explicit location
17123 The use of a directory for the option value is not available for GnuTLS versions
17124 preceding 3.3.6 and a single file must be used.
17126 With OpenSSL the certificates specified
17128 either by file or directory
17129 are added to those given by the system default location.
17131 These certificates should be for the certificate authorities trusted, rather
17132 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
17133 the value is a file then the certificates are sent by Exim as a server to
17134 connecting clients, defining the list of accepted certificate authorities.
17135 Thus the values defined should be considered public data. To avoid this,
17136 use the explicit directory version.
17138 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17140 A forced expansion failure or setting to an empty string is equivalent to
17144 .option tls_verify_hosts main "host list&!!" unset
17145 .cindex "TLS" "client certificate verification"
17146 .cindex "certificate" "verification of client"
17147 This option, along with &%tls_try_verify_hosts%&, controls the checking of
17148 certificates from clients. The expected certificates are defined by
17149 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
17150 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
17151 &%tls_verify_certificates%& is not set.
17153 Any client that matches &%tls_verify_hosts%& is constrained by
17154 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
17155 present one of the listed certificates. If it does not, the connection is
17156 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
17157 the host to use TLS. It can still send SMTP commands through unencrypted
17158 connections. Forcing a client to use TLS has to be done separately using an
17159 ACL to reject inappropriate commands when the connection is not encrypted.
17161 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
17162 matches this option (but not &%tls_verify_hosts%&), Exim requests a
17163 certificate and checks it against &%tls_verify_certificates%&, but does not
17164 abort the connection if there is no certificate or if it does not match. This
17165 state can be detected in an ACL, which makes it possible to implement policies
17166 such as &"accept for relay only if a verified certificate has been received,
17167 but accept for local delivery if encrypted, even without a verified
17170 Client hosts that match neither of these lists are not asked to present
17174 .option trusted_groups main "string list&!!" unset
17175 .cindex "trusted groups"
17176 .cindex "groups" "trusted"
17177 This option is expanded just once, at the start of Exim's processing. If this
17178 option is set, any process that is running in one of the listed groups, or
17179 which has one of them as a supplementary group, is trusted. The groups can be
17180 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
17181 details of what trusted callers are permitted to do. If neither
17182 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
17185 .option trusted_users main "string list&!!" unset
17186 .cindex "trusted users"
17187 .cindex "user" "trusted"
17188 This option is expanded just once, at the start of Exim's processing. If this
17189 option is set, any process that is running as one of the listed users is
17190 trusted. The users can be specified numerically or by name. See section
17191 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
17192 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
17193 Exim user are trusted.
17195 .option unknown_login main string&!! unset
17196 .cindex "uid (user id)" "unknown caller"
17197 .vindex "&$caller_uid$&"
17198 This is a specialized feature for use in unusual configurations. By default, if
17199 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
17200 gives up. The &%unknown_login%& option can be used to set a login name to be
17201 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
17202 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
17203 is used for the user's real name (gecos field), unless this has been set by the
17206 .option unknown_username main string unset
17207 See &%unknown_login%&.
17209 .option untrusted_set_sender main "address list&!!" unset
17210 .cindex "trusted users"
17211 .cindex "sender" "setting by untrusted user"
17212 .cindex "untrusted user setting sender"
17213 .cindex "user" "untrusted setting sender"
17214 .cindex "envelope sender"
17215 When an untrusted user submits a message to Exim using the standard input, Exim
17216 normally creates an envelope sender address from the user's login and the
17217 default qualification domain. Data from the &%-f%& option (for setting envelope
17218 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
17219 is used) is ignored.
17221 However, untrusted users are permitted to set an empty envelope sender address,
17222 to declare that a message should never generate any bounces. For example:
17224 exim -f '<>' user@domain.example
17226 .vindex "&$sender_ident$&"
17227 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
17228 other envelope sender addresses in a controlled way. When it is set, untrusted
17229 users are allowed to set envelope sender addresses that match any of the
17230 patterns in the list. Like all address lists, the string is expanded. The
17231 identity of the user is in &$sender_ident$&, so you can, for example, restrict
17232 users to setting senders that start with their login ids
17233 followed by a hyphen
17234 by a setting like this:
17236 untrusted_set_sender = ^$sender_ident-
17238 If you want to allow untrusted users to set envelope sender addresses without
17239 restriction, you can use
17241 untrusted_set_sender = *
17243 The &%untrusted_set_sender%& option applies to all forms of local input, but
17244 only to the setting of the envelope sender. It does not permit untrusted users
17245 to use the other options which trusted user can use to override message
17246 parameters. Furthermore, it does not stop Exim from removing an existing
17247 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17248 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17249 overriding these actions. The handling of the &'Sender:'& header is also
17250 described in section &<<SECTthesenhea>>&.
17252 The log line for a message's arrival shows the envelope sender following
17253 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17254 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17255 envelope sender address, the user's login is shown in parentheses after the
17259 .option uucp_from_pattern main string "see below"
17260 .cindex "&""From""& line"
17261 .cindex "UUCP" "&""From""& line"
17262 Some applications that pass messages to an MTA via a command line interface use
17263 an initial line starting with &"From&~"& to pass the envelope sender. In
17264 particular, this is used by UUCP software. Exim recognizes such a line by means
17265 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17266 matches, the sender address is constructed by expanding the contents of
17267 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17268 default pattern recognizes lines in the following two forms:
17270 From ph10 Fri Jan 5 12:35 GMT 1996
17271 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17273 The pattern can be seen by running
17275 exim -bP uucp_from_pattern
17277 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17278 year in the second case. The first word after &"From&~"& is matched in the
17279 regular expression by a parenthesized subpattern. The default value for
17280 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17281 (&"ph10"& in the example above) as the message's sender. See also
17282 &%ignore_fromline_hosts%&.
17285 .option uucp_from_sender main string&!! &`$1`&
17286 See &%uucp_from_pattern%& above.
17289 .option warn_message_file main string unset
17290 .cindex "warning of delay" "customizing the message"
17291 .cindex "customizing" "warning message"
17292 This option defines a template file containing paragraphs of text to be used
17293 for constructing the warning message which is sent by Exim when a message has
17294 been on the queue for a specified amount of time, as specified by
17295 &%delay_warning%&. Details of the file's contents are given in chapter
17296 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17299 .option write_rejectlog main boolean true
17300 .cindex "reject log" "disabling"
17301 If this option is set false, Exim no longer writes anything to the reject log.
17302 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17303 .ecindex IIDconfima
17304 .ecindex IIDmaiconf
17309 . ////////////////////////////////////////////////////////////////////////////
17310 . ////////////////////////////////////////////////////////////////////////////
17312 .chapter "Generic options for routers" "CHAProutergeneric"
17313 .scindex IIDgenoprou1 "options" "generic; for routers"
17314 .scindex IIDgenoprou2 "generic options" "router"
17315 This chapter describes the generic options that apply to all routers.
17316 Those that are preconditions are marked with ‡ in the &"use"& field.
17318 For a general description of how a router operates, see sections
17319 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17320 which the preconditions are tested. The order of expansion of the options that
17321 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17322 &%headers_remove%&, &%transport%&.
17326 .option address_data routers string&!! unset
17327 .cindex "router" "data attached to address"
17328 The string is expanded just before the router is run, that is, after all the
17329 precondition tests have succeeded. If the expansion is forced to fail, the
17330 router declines, the value of &%address_data%& remains unchanged, and the
17331 &%more%& option controls what happens next. Other expansion failures cause
17332 delivery of the address to be deferred.
17334 .vindex "&$address_data$&"
17335 When the expansion succeeds, the value is retained with the address, and can be
17336 accessed using the variable &$address_data$& in the current router, subsequent
17337 routers, and the eventual transport.
17339 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17340 that runs a user's filter file, the contents of &$address_data$& are accessible
17341 in the filter. This is not normally a problem, because such data is usually
17342 either not confidential or it &"belongs"& to the current user, but if you do
17343 put confidential data into &$address_data$& you need to remember this point.
17345 Even if the router declines or passes, the value of &$address_data$& remains
17346 with the address, though it can be changed by another &%address_data%& setting
17347 on a subsequent router. If a router generates child addresses, the value of
17348 &$address_data$& propagates to them. This also applies to the special kind of
17349 &"child"& that is generated by a router with the &%unseen%& option.
17351 The idea of &%address_data%& is that you can use it to look up a lot of data
17352 for the address once, and then pick out parts of the data later. For example,
17353 you could use a single LDAP lookup to return a string of the form
17355 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17357 In the transport you could pick out the mailbox by a setting such as
17359 file = ${extract{mailbox}{$address_data}}
17361 This makes the configuration file less messy, and also reduces the number of
17362 lookups (though Exim does cache lookups).
17364 .vindex "&$sender_address_data$&"
17365 .vindex "&$address_data$&"
17366 The &%address_data%& facility is also useful as a means of passing information
17367 from one router to another, and from a router to a transport. In addition, if
17368 &$address_data$& is set by a router when verifying a recipient address from an
17369 ACL, it remains available for use in the rest of the ACL statement. After
17370 verifying a sender, the value is transferred to &$sender_address_data$&.
17374 .option address_test routers&!? boolean true
17376 .cindex "router" "skipping when address testing"
17377 If this option is set false, the router is skipped when routing is being tested
17378 by means of the &%-bt%& command line option. This can be a convenience when
17379 your first router sends messages to an external scanner, because it saves you
17380 having to set the &"already scanned"& indicator when testing real address
17385 .option cannot_route_message routers string&!! unset
17386 .cindex "router" "customizing &""cannot route""& message"
17387 .cindex "customizing" "&""cannot route""& message"
17388 This option specifies a text message that is used when an address cannot be
17389 routed because Exim has run out of routers. The default message is
17390 &"Unrouteable address"&. This option is useful only on routers that have
17391 &%more%& set false, or on the very last router in a configuration, because the
17392 value that is used is taken from the last router that is considered. This
17393 includes a router that is skipped because its preconditions are not met, as
17394 well as a router that declines. For example, using the default configuration,
17397 cannot_route_message = Remote domain not found in DNS
17399 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17402 cannot_route_message = Unknown local user
17404 on the final router that checks for local users. If string expansion fails for
17405 this option, the default message is used. Unless the expansion failure was
17406 explicitly forced, a message about the failure is written to the main and panic
17407 logs, in addition to the normal message about the routing failure.
17410 .option caseful_local_part routers boolean false
17411 .cindex "case of local parts"
17412 .cindex "router" "case of local parts"
17413 By default, routers handle the local parts of addresses in a case-insensitive
17414 manner, though the actual case is preserved for transmission with the message.
17415 If you want the case of letters to be significant in a router, you must set
17416 this option true. For individual router options that contain address or local
17417 part lists (for example, &%local_parts%&), case-sensitive matching can be
17418 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17421 .vindex "&$local_part$&"
17422 .vindex "&$original_local_part$&"
17423 .vindex "&$parent_local_part$&"
17424 The value of the &$local_part$& variable is forced to lower case while a
17425 router is running unless &%caseful_local_part%& is set. When a router assigns
17426 an address to a transport, the value of &$local_part$& when the transport runs
17427 is the same as it was in the router. Similarly, when a router generates child
17428 addresses by aliasing or forwarding, the values of &$original_local_part$&
17429 and &$parent_local_part$& are those that were used by the redirecting router.
17431 This option applies to the processing of an address by a router. When a
17432 recipient address is being processed in an ACL, there is a separate &%control%&
17433 modifier that can be used to specify case-sensitive processing within the ACL
17434 (see section &<<SECTcontrols>>&).
17438 .option check_local_user routers&!? boolean false
17439 .cindex "local user, checking in router"
17440 .cindex "router" "checking for local user"
17441 .cindex "&_/etc/passwd_&"
17443 When this option is true, Exim checks that the local part of the recipient
17444 address (with affixes removed if relevant) is the name of an account on the
17445 local system. The check is done by calling the &[getpwnam()]& function rather
17446 than trying to read &_/etc/passwd_& directly. This means that other methods of
17447 holding password data (such as NIS) are supported. If the local part is a local
17448 user, &$home$& is set from the password data, and can be tested in other
17449 preconditions that are evaluated after this one (the order of evaluation is
17450 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17451 overridden by &%router_home_directory%&. If the local part is not a local user,
17452 the router is skipped.
17454 If you want to check that the local part is either the name of a local user
17455 or matches something else, you cannot combine &%check_local_user%& with a
17456 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17457 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17458 setting to achieve this. For example:
17460 local_parts = passwd;$local_part : lsearch;/etc/other/users
17462 Note, however, that the side effects of &%check_local_user%& (such as setting
17463 up a home directory) do not occur when a &(passwd)& lookup is used in a
17464 &%local_parts%& (or any other) precondition.
17468 .option condition routers&!? string&!! unset
17469 .cindex "router" "customized precondition"
17470 This option specifies a general precondition test that has to succeed for the
17471 router to be called. The &%condition%& option is the last precondition to be
17472 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17473 result is a forced failure, or an empty string, or one of the strings &"0"& or
17474 &"no"& or &"false"& (checked without regard to the case of the letters), the
17475 router is skipped, and the address is offered to the next one.
17477 If the result is any other value, the router is run (as this is the last
17478 precondition to be evaluated, all the other preconditions must be true).
17480 This option is unusual in that multiple &%condition%& options may be present.
17481 All &%condition%& options must succeed.
17483 The &%condition%& option provides a means of applying custom conditions to the
17484 running of routers. Note that in the case of a simple conditional expansion,
17485 the default expansion values are exactly what is wanted. For example:
17487 condition = ${if >{$message_age}{600}}
17489 Because of the default behaviour of the string expansion, this is equivalent to
17491 condition = ${if >{$message_age}{600}{true}{}}
17494 A multiple condition example, which succeeds:
17496 condition = ${if >{$message_age}{600}}
17497 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17501 If the expansion fails (other than forced failure) delivery is deferred. Some
17502 of the other precondition options are common special cases that could in fact
17503 be specified using &%condition%&.
17505 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17506 are far older, and use one set of semantics. ACLs are newer and when
17507 they were created, the ACL &%condition%& process was given far stricter
17508 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17509 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17510 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17511 Router rules processing behavior.
17513 This is best illustrated in an example:
17515 # If used in an ACL condition will fail with a syntax error, but
17516 # in a router condition any extra characters are treated as a string
17518 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17521 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17524 In each example above, the &%if%& statement actually ends after
17525 &"{google.com}}"&. Since no true or false braces were defined, the
17526 default &%if%& behavior is to return a boolean true or a null answer
17527 (which evaluates to false). The rest of the line is then treated as a
17528 string. So the first example resulted in the boolean answer &"true"&
17529 with the string &" {yes} {no}}"& appended to it. The second example
17530 resulted in the null output (indicating false) with the string
17531 &" {yes} {no}}"& appended to it.
17533 In fact you can put excess forward braces in too. In the router
17534 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17535 mean something, like after a &"$"& or when required as part of a
17536 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17539 Thus, in a Router, the above expansion strings will both always evaluate
17540 true, as the result of expansion is a non-empty string which doesn't
17541 match an explicit false value. This can be tricky to debug. By
17542 contrast, in an ACL either of those strings will always result in an
17543 expansion error because the result doesn't look sufficiently boolean.
17546 .option debug_print routers string&!! unset
17547 .cindex "testing" "variables in drivers"
17548 If this option is set and debugging is enabled (see the &%-d%& command line
17549 option) or in address-testing mode (see the &%-bt%& command line option),
17550 the string is expanded and included in the debugging output.
17551 If expansion of the string fails, the error message is written to the debugging
17552 output, and Exim carries on processing.
17553 This option is provided to help with checking out the values of variables and
17554 so on when debugging router configurations. For example, if a &%condition%&
17555 option appears not to be working, &%debug_print%& can be used to output the
17556 variables it references. The output happens after checks for &%domains%&,
17557 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17558 are tested. A newline is added to the text if it does not end with one.
17559 The variable &$router_name$& contains the name of the router.
17563 .option disable_logging routers boolean false
17564 If this option is set true, nothing is logged for any routing errors
17565 or for any deliveries caused by this router. You should not set this option
17566 unless you really, really know what you are doing. See also the generic
17567 transport option of the same name.
17569 .option dnssec_request_domains routers "domain list&!!" unset
17570 .cindex "MX record" "security"
17571 .cindex "DNSSEC" "MX lookup"
17572 .cindex "security" "MX lookup"
17573 .cindex "DNS" "DNSSEC"
17574 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17575 the dnssec request bit set.
17576 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17578 .option dnssec_require_domains routers "domain list&!!" unset
17579 .cindex "MX record" "security"
17580 .cindex "DNSSEC" "MX lookup"
17581 .cindex "security" "MX lookup"
17582 .cindex "DNS" "DNSSEC"
17583 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
17584 the dnssec request bit set. Any returns not having the Authenticated Data bit
17585 (AD bit) set will be ignored and logged as a host-lookup failure.
17586 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17589 .option domains routers&!? "domain list&!!" unset
17590 .cindex "router" "restricting to specific domains"
17591 .vindex "&$domain_data$&"
17592 If this option is set, the router is skipped unless the current domain matches
17593 the list. If the match is achieved by means of a file lookup, the data that the
17594 lookup returned for the domain is placed in &$domain_data$& for use in string
17595 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17596 a list of the order in which preconditions are evaluated.
17600 .option driver routers string unset
17601 This option must always be set. It specifies which of the available routers is
17605 .option dsn_lasthop routers boolean false
17606 .cindex "DSN" "success"
17607 .cindex "Delivery Status Notification" "success"
17608 If this option is set true, and extended DSN (RFC3461) processing is in effect,
17609 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
17610 instead send a success DSN as if the next hop does not support DSN.
17611 Not effective on redirect routers.
17615 .option errors_to routers string&!! unset
17616 .cindex "envelope sender"
17617 .cindex "router" "changing address for errors"
17618 If a router successfully handles an address, it may assign the address to a
17619 transport for delivery or it may generate child addresses. In both cases, if
17620 there is a delivery problem during later processing, the resulting bounce
17621 message is sent to the address that results from expanding this string,
17622 provided that the address verifies successfully. The &%errors_to%& option is
17623 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
17625 The &%errors_to%& setting associated with an address can be overridden if it
17626 subsequently passes through other routers that have their own &%errors_to%&
17627 settings, or if the message is delivered by a transport with a &%return_path%&
17630 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
17631 the expansion fails to verify, the errors address associated with the incoming
17632 address is used. At top level, this is the envelope sender. A non-forced
17633 expansion failure causes delivery to be deferred.
17635 If an address for which &%errors_to%& has been set ends up being delivered over
17636 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17637 any bounces that are generated by other MTAs on the delivery route are also
17638 sent there. You can set &%errors_to%& to the empty string by either of these
17644 An expansion item that yields an empty string has the same effect. If you do
17645 this, a locally detected delivery error for addresses processed by this router
17646 no longer gives rise to a bounce message; the error is discarded. If the
17647 address is delivered to a remote host, the return path is set to &`<>`&, unless
17648 overridden by the &%return_path%& option on the transport.
17650 .vindex "&$address_data$&"
17651 If for some reason you want to discard local errors, but use a non-empty
17652 MAIL command for remote delivery, you can preserve the original return
17653 path in &$address_data$& in the router, and reinstate it in the transport by
17654 setting &%return_path%&.
17656 The most common use of &%errors_to%& is to direct mailing list bounces to the
17657 manager of the list, as described in section &<<SECTmailinglists>>&, or to
17658 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
17662 .option expn routers&!? boolean true
17663 .cindex "address" "testing"
17664 .cindex "testing" "addresses"
17665 .cindex "EXPN" "router skipping"
17666 .cindex "router" "skipping for EXPN"
17667 If this option is turned off, the router is skipped when testing an address
17668 as a result of processing an SMTP EXPN command. You might, for example,
17669 want to turn it off on a router for users' &_.forward_& files, while leaving it
17670 on for the system alias file.
17671 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17674 The use of the SMTP EXPN command is controlled by an ACL (see chapter
17675 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
17676 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
17680 .option fail_verify routers boolean false
17681 .cindex "router" "forcing verification failure"
17682 Setting this option has the effect of setting both &%fail_verify_sender%& and
17683 &%fail_verify_recipient%& to the same value.
17687 .option fail_verify_recipient routers boolean false
17688 If this option is true and an address is accepted by this router when
17689 verifying a recipient, verification fails.
17693 .option fail_verify_sender routers boolean false
17694 If this option is true and an address is accepted by this router when
17695 verifying a sender, verification fails.
17699 .option fallback_hosts routers "string list" unset
17700 .cindex "router" "fallback hosts"
17701 .cindex "fallback" "hosts specified on router"
17702 String expansion is not applied to this option. The argument must be a
17703 colon-separated list of host names or IP addresses. The list separator can be
17704 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
17705 each name or address. In fact, the format of each item is exactly the same as
17706 defined for the list of hosts in a &(manualroute)& router (see section
17707 &<<SECTformatonehostitem>>&).
17709 If a router queues an address for a remote transport, this host list is
17710 associated with the address, and used instead of the transport's fallback host
17711 list. If &%hosts_randomize%& is set on the transport, the order of the list is
17712 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
17713 transport for further details.
17716 .option group routers string&!! "see below"
17717 .cindex "gid (group id)" "local delivery"
17718 .cindex "local transports" "uid and gid"
17719 .cindex "transport" "local"
17720 .cindex "router" "setting group"
17721 When a router queues an address for a transport, and the transport does not
17722 specify a group, the group given here is used when running the delivery
17724 The group may be specified numerically or by name. If expansion fails, the
17725 error is logged and delivery is deferred.
17726 The default is unset, unless &%check_local_user%& is set, when the default
17727 is taken from the password information. See also &%initgroups%& and &%user%&
17728 and the discussion in chapter &<<CHAPenvironment>>&.
17732 .option headers_add routers list&!! unset
17733 .cindex "header lines" "adding"
17734 .cindex "router" "adding header lines"
17735 This option specifies a list of text headers,
17736 newline-separated (by default, changeable in the usual way),
17737 that is associated with any addresses that are accepted by the router.
17738 Each item is separately expanded, at routing time. However, this
17739 option has no effect when an address is just being verified. The way in which
17740 the text is used to add header lines at transport time is described in section
17741 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
17742 message is in the process of being transported. This means that references to
17743 header lines in string expansions in the transport's configuration do not
17744 &"see"& the added header lines.
17746 The &%headers_add%& option is expanded after &%errors_to%&, but before
17747 &%headers_remove%& and &%transport%&. If an item is empty, or if
17748 an item expansion is forced to fail, the item has no effect. Other expansion
17749 failures are treated as configuration errors.
17751 Unlike most options, &%headers_add%& can be specified multiple times
17752 for a router; all listed headers are added.
17754 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
17755 router that has the &%one_time%& option set.
17757 .cindex "duplicate addresses"
17758 .oindex "&%unseen%&"
17759 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17760 additions are deleted when the address is passed on to subsequent routers.
17761 For a &%redirect%& router, if a generated address is the same as the incoming
17762 address, this can lead to duplicate addresses with different header
17763 modifications. Exim does not do duplicate deliveries (except, in certain
17764 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
17765 which of the duplicates is discarded, so this ambiguous situation should be
17766 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
17770 .option headers_remove routers list&!! unset
17771 .cindex "header lines" "removing"
17772 .cindex "router" "removing header lines"
17773 This option specifies a list of text headers,
17774 colon-separated (by default, changeable in the usual way),
17775 that is associated with any addresses that are accepted by the router.
17776 Each item is separately expanded, at routing time. However, this
17777 option has no effect when an address is just being verified. The way in which
17778 the text is used to remove header lines at transport time is described in
17779 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
17780 the message is in the process of being transported. This means that references
17781 to header lines in string expansions in the transport's configuration still
17782 &"see"& the original header lines.
17784 The &%headers_remove%& option is expanded after &%errors_to%& and
17785 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
17786 the item has no effect. Other expansion failures are treated as configuration
17789 Unlike most options, &%headers_remove%& can be specified multiple times
17790 for a router; all listed headers are removed.
17792 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
17793 router that has the &%one_time%& option set.
17795 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17796 removal requests are deleted when the address is passed on to subsequent
17797 routers, and this can lead to problems with duplicates -- see the similar
17798 warning for &%headers_add%& above.
17800 &*Warning 3*&: Because of the separate expansion of the list items,
17801 items that contain a list separator must have it doubled.
17802 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
17806 .option ignore_target_hosts routers "host list&!!" unset
17807 .cindex "IP address" "discarding"
17808 .cindex "router" "discarding IP addresses"
17809 Although this option is a host list, it should normally contain IP address
17810 entries rather than names. If any host that is looked up by the router has an
17811 IP address that matches an item in this list, Exim behaves as if that IP
17812 address did not exist. This option allows you to cope with rogue DNS entries
17815 remote.domain.example. A 127.0.0.1
17819 ignore_target_hosts = 127.0.0.1
17821 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17822 discarded in this way, the router declines. In a conventional configuration, an
17823 attempt to mail to such a domain would normally provoke the &"unrouteable
17824 domain"& error, and an attempt to verify an address in the domain would fail.
17825 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17826 router declines if presented with one of the listed addresses.
17828 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17829 means of the first or the second of the following settings, respectively:
17831 ignore_target_hosts = 0.0.0.0/0
17832 ignore_target_hosts = <; 0::0/0
17834 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17835 in the second line matches all IPv6 addresses.
17837 This option may also be useful for ignoring link-local and site-local IPv6
17838 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17839 is expanded before use as a list, it is possible to make it dependent on the
17840 domain that is being routed.
17842 .vindex "&$host_address$&"
17843 During its expansion, &$host_address$& is set to the IP address that is being
17846 .option initgroups routers boolean false
17847 .cindex "additional groups"
17848 .cindex "groups" "additional"
17849 .cindex "local transports" "uid and gid"
17850 .cindex "transport" "local"
17851 If the router queues an address for a transport, and this option is true, and
17852 the uid supplied by the router is not overridden by the transport, the
17853 &[initgroups()]& function is called when running the transport to ensure that
17854 any additional groups associated with the uid are set up. See also &%group%&
17855 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17859 .option local_part_prefix routers&!? "string list" unset
17860 .cindex "router" "prefix for local part"
17861 .cindex "prefix" "for local part, used in router"
17862 If this option is set, the router is skipped unless the local part starts with
17863 one of the given strings, or &%local_part_prefix_optional%& is true. See
17864 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17867 The list is scanned from left to right, and the first prefix that matches is
17868 used. A limited form of wildcard is available; if the prefix begins with an
17869 asterisk, it matches the longest possible sequence of arbitrary characters at
17870 the start of the local part. An asterisk should therefore always be followed by
17871 some character that does not occur in normal local parts.
17872 .cindex "multiple mailboxes"
17873 .cindex "mailbox" "multiple"
17874 Wildcarding can be used to set up multiple user mailboxes, as described in
17875 section &<<SECTmulbox>>&.
17877 .vindex "&$local_part$&"
17878 .vindex "&$local_part_prefix$&"
17879 During the testing of the &%local_parts%& option, and while the router is
17880 running, the prefix is removed from the local part, and is available in the
17881 expansion variable &$local_part_prefix$&. When a message is being delivered, if
17882 the router accepts the address, this remains true during subsequent delivery by
17883 a transport. In particular, the local part that is transmitted in the RCPT
17884 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
17885 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
17886 the relevant transport.
17888 When an address is being verified, &%local_part_prefix%& affects only the
17889 behaviour of the router. If the callout feature of verification is in use, this
17890 means that the full address, including the prefix, will be used during the
17893 The prefix facility is commonly used to handle local parts of the form
17894 &%owner-something%&. Another common use is to support local parts of the form
17895 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
17896 to tell a user their forwarding is broken &-- by placing a router like this one
17897 immediately before the router that handles &_.forward_& files:
17901 local_part_prefix = real-
17903 transport = local_delivery
17905 For security, it would probably be a good idea to restrict the use of this
17906 router to locally-generated messages, using a condition such as this:
17908 condition = ${if match {$sender_host_address}\
17909 {\N^(|127\.0\.0\.1)$\N}}
17912 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
17913 both conditions must be met if not optional. Care must be taken if wildcards
17914 are used in both a prefix and a suffix on the same router. Different
17915 separator characters must be used to avoid ambiguity.
17918 .option local_part_prefix_optional routers boolean false
17919 See &%local_part_prefix%& above.
17923 .option local_part_suffix routers&!? "string list" unset
17924 .cindex "router" "suffix for local part"
17925 .cindex "suffix for local part" "used in router"
17926 This option operates in the same way as &%local_part_prefix%&, except that the
17927 local part must end (rather than start) with the given string, the
17928 &%local_part_suffix_optional%& option determines whether the suffix is
17929 mandatory, and the wildcard * character, if present, must be the last
17930 character of the suffix. This option facility is commonly used to handle local
17931 parts of the form &%something-request%& and multiple user mailboxes of the form
17935 .option local_part_suffix_optional routers boolean false
17936 See &%local_part_suffix%& above.
17940 .option local_parts routers&!? "local part list&!!" unset
17941 .cindex "router" "restricting to specific local parts"
17942 .cindex "local part" "checking in router"
17943 The router is run only if the local part of the address matches the list.
17944 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17946 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
17947 string is expanded, it is possible to make it depend on the domain, for
17950 local_parts = dbm;/usr/local/specials/$domain
17952 .vindex "&$local_part_data$&"
17953 If the match is achieved by a lookup, the data that the lookup returned
17954 for the local part is placed in the variable &$local_part_data$& for use in
17955 expansions of the router's private options. You might use this option, for
17956 example, if you have a large number of local virtual domains, and you want to
17957 send all postmaster mail to the same place without having to set up an alias in
17958 each virtual domain:
17962 local_parts = postmaster
17963 data = postmaster@real.domain.example
17967 .option log_as_local routers boolean "see below"
17968 .cindex "log" "delivery line"
17969 .cindex "delivery" "log line format"
17970 Exim has two logging styles for delivery, the idea being to make local
17971 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17972 recipient address is given just as the local part, without a domain. The use of
17973 this style is controlled by this option. It defaults to true for the &(accept)&
17974 router, and false for all the others. This option applies only when a
17975 router assigns an address to a transport. It has no effect on routers that
17976 redirect addresses.
17980 .option more routers boolean&!! true
17981 The result of string expansion for this option must be a valid boolean value,
17982 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17983 result causes an error, and delivery is deferred. If the expansion is forced to
17984 fail, the default value for the option (true) is used. Other failures cause
17985 delivery to be deferred.
17987 If this option is set false, and the router declines to handle the address, no
17988 further routers are tried, routing fails, and the address is bounced.
17990 However, if the router explicitly passes an address to the following router by
17991 means of the setting
17995 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17996 does not affect the behaviour if one of the precondition tests fails. In that
17997 case, the address is always passed to the next router.
17999 Note that &%address_data%& is not considered to be a precondition. If its
18000 expansion is forced to fail, the router declines, and the value of &%more%&
18001 controls what happens next.
18004 .option pass_on_timeout routers boolean false
18005 .cindex "timeout" "of router"
18006 .cindex "router" "timeout"
18007 If a router times out during a host lookup, it normally causes deferral of the
18008 address. If &%pass_on_timeout%& is set, the address is passed on to the next
18009 router, overriding &%no_more%&. This may be helpful for systems that are
18010 intermittently connected to the Internet, or those that want to pass to a smart
18011 host any messages that cannot immediately be delivered.
18013 There are occasional other temporary errors that can occur while doing DNS
18014 lookups. They are treated in the same way as a timeout, and this option
18015 applies to all of them.
18019 .option pass_router routers string unset
18020 .cindex "router" "go to after &""pass""&"
18021 Routers that recognize the generic &%self%& option (&(dnslookup)&,
18022 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
18023 routing to continue, and overriding a false setting of &%more%&. When one of
18024 these routers returns &"pass"&, the address is normally handed on to the next
18025 router in sequence. This can be changed by setting &%pass_router%& to the name
18026 of another router. However (unlike &%redirect_router%&) the named router must
18027 be below the current router, to avoid loops. Note that this option applies only
18028 to the special case of &"pass"&. It does not apply when a router returns
18029 &"decline"& because it cannot handle an address.
18033 .option redirect_router routers string unset
18034 .cindex "router" "start at after redirection"
18035 Sometimes an administrator knows that it is pointless to reprocess addresses
18036 generated from alias or forward files with the same router again. For
18037 example, if an alias file translates real names into login ids there is no
18038 point searching the alias file a second time, especially if it is a large file.
18040 The &%redirect_router%& option can be set to the name of any router instance.
18041 It causes the routing of any generated addresses to start at the named router
18042 instead of at the first router. This option has no effect if the router in
18043 which it is set does not generate new addresses.
18047 .option require_files routers&!? "string list&!!" unset
18048 .cindex "file" "requiring for router"
18049 .cindex "router" "requiring file existence"
18050 This option provides a general mechanism for predicating the running of a
18051 router on the existence or non-existence of certain files or directories.
18052 Before running a router, as one of its precondition tests, Exim works its way
18053 through the &%require_files%& list, expanding each item separately.
18055 Because the list is split before expansion, any colons in expansion items must
18056 be doubled, or the facility for using a different list separator must be used.
18057 If any expansion is forced to fail, the item is ignored. Other expansion
18058 failures cause routing of the address to be deferred.
18060 If any expanded string is empty, it is ignored. Otherwise, except as described
18061 below, each string must be a fully qualified file path, optionally preceded by
18062 &"!"&. The paths are passed to the &[stat()]& function to test for the
18063 existence of the files or directories. The router is skipped if any paths not
18064 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
18067 If &[stat()]& cannot determine whether a file exists or not, delivery of
18068 the message is deferred. This can happen when NFS-mounted filesystems are
18071 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
18072 options, so you cannot use it to check for the existence of a file in which to
18073 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
18074 full list of the order in which preconditions are evaluated.) However, as
18075 these options are all expanded, you can use the &%exists%& expansion condition
18076 to make such tests. The &%require_files%& option is intended for checking files
18077 that the router may be going to use internally, or which are needed by a
18078 transport (for example &_.procmailrc_&).
18080 During delivery, the &[stat()]& function is run as root, but there is a
18081 facility for some checking of the accessibility of a file by another user.
18082 This is not a proper permissions check, but just a &"rough"& check that
18083 operates as follows:
18085 If an item in a &%require_files%& list does not contain any forward slash
18086 characters, it is taken to be the user (and optional group, separated by a
18087 comma) to be checked for subsequent files in the list. If no group is specified
18088 but the user is specified symbolically, the gid associated with the uid is
18091 require_files = mail:/some/file
18092 require_files = $local_part:$home/.procmailrc
18094 If a user or group name in a &%require_files%& list does not exist, the
18095 &%require_files%& condition fails.
18097 Exim performs the check by scanning along the components of the file path, and
18098 checking the access for the given uid and gid. It checks for &"x"& access on
18099 directories, and &"r"& access on the final file. Note that this means that file
18100 access control lists, if the operating system has them, are ignored.
18102 &*Warning 1*&: When the router is being run to verify addresses for an
18103 incoming SMTP message, Exim is not running as root, but under its own uid. This
18104 may affect the result of a &%require_files%& check. In particular, &[stat()]&
18105 may yield the error EACCES (&"Permission denied"&). This means that the Exim
18106 user is not permitted to read one of the directories on the file's path.
18108 &*Warning 2*&: Even when Exim is running as root while delivering a message,
18109 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
18110 without root access. In this case, if a check for access by a particular user
18111 is requested, Exim creates a subprocess that runs as that user, and tries the
18112 check again in that process.
18114 The default action for handling an unresolved EACCES is to consider it to
18115 be caused by a configuration error, and routing is deferred because the
18116 existence or non-existence of the file cannot be determined. However, in some
18117 circumstances it may be desirable to treat this condition as if the file did
18118 not exist. If the file name (or the exclamation mark that precedes the file
18119 name for non-existence) is preceded by a plus sign, the EACCES error is treated
18120 as if the file did not exist. For example:
18122 require_files = +/some/file
18124 If the router is not an essential part of verification (for example, it
18125 handles users' &_.forward_& files), another solution is to set the &%verify%&
18126 option false so that the router is skipped when verifying.
18130 .option retry_use_local_part routers boolean "see below"
18131 .cindex "hints database" "retry keys"
18132 .cindex "local part" "in retry keys"
18133 When a delivery suffers a temporary routing failure, a retry record is created
18134 in Exim's hints database. For addresses whose routing depends only on the
18135 domain, the key for the retry record should not involve the local part, but for
18136 other addresses, both the domain and the local part should be included.
18137 Usually, remote routing is of the former kind, and local routing is of the
18140 This option controls whether the local part is used to form the key for retry
18141 hints for addresses that suffer temporary errors while being handled by this
18142 router. The default value is true for any router that has &%check_local_user%&
18143 set, and false otherwise. Note that this option does not apply to hints keys
18144 for transport delays; they are controlled by a generic transport option of the
18147 The setting of &%retry_use_local_part%& applies only to the router on which it
18148 appears. If the router generates child addresses, they are routed
18149 independently; this setting does not become attached to them.
18153 .option router_home_directory routers string&!! unset
18154 .cindex "router" "home directory for"
18155 .cindex "home directory" "for router"
18157 This option sets a home directory for use while the router is running. (Compare
18158 &%transport_home_directory%&, which sets a home directory for later
18159 transporting.) In particular, if used on a &(redirect)& router, this option
18160 sets a value for &$home$& while a filter is running. The value is expanded;
18161 forced expansion failure causes the option to be ignored &-- other failures
18162 cause the router to defer.
18164 Expansion of &%router_home_directory%& happens immediately after the
18165 &%check_local_user%& test (if configured), before any further expansions take
18167 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18169 While the router is running, &%router_home_directory%& overrides the value of
18170 &$home$& that came from &%check_local_user%&.
18172 When a router accepts an address and assigns it to a local transport (including
18173 the cases when a &(redirect)& router generates a pipe, file, or autoreply
18174 delivery), the home directory setting for the transport is taken from the first
18175 of these values that is set:
18178 The &%home_directory%& option on the transport;
18180 The &%transport_home_directory%& option on the router;
18182 The password data if &%check_local_user%& is set on the router;
18184 The &%router_home_directory%& option on the router.
18187 In other words, &%router_home_directory%& overrides the password data for the
18188 router, but not for the transport.
18192 .option self routers string freeze
18193 .cindex "MX record" "pointing to local host"
18194 .cindex "local host" "MX pointing to"
18195 This option applies to those routers that use a recipient address to find a
18196 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
18197 and &(manualroute)& routers.
18198 Certain configurations of the &(queryprogram)& router can also specify a list
18200 Usually such routers are configured to send the message to a remote host via an
18201 &(smtp)& transport. The &%self%& option specifies what happens when the first
18202 host on the list turns out to be the local host.
18203 The way in which Exim checks for the local host is described in section
18204 &<<SECTreclocipadd>>&.
18206 Normally this situation indicates either an error in Exim's configuration (for
18207 example, the router should be configured not to process this domain), or an
18208 error in the DNS (for example, the MX should not point to this host). For this
18209 reason, the default action is to log the incident, defer the address, and
18210 freeze the message. The following alternatives are provided for use in special
18215 Delivery of the message is tried again later, but the message is not frozen.
18217 .vitem "&%reroute%&: <&'domain'&>"
18218 The domain is changed to the given domain, and the address is passed back to
18219 be reprocessed by the routers. No rewriting of headers takes place. This
18220 behaviour is essentially a redirection.
18222 .vitem "&%reroute: rewrite:%& <&'domain'&>"
18223 The domain is changed to the given domain, and the address is passed back to be
18224 reprocessed by the routers. Any headers that contain the original domain are
18229 .vindex "&$self_hostname$&"
18230 The router passes the address to the next router, or to the router named in the
18231 &%pass_router%& option if it is set. This overrides &%no_more%&. During
18232 subsequent routing and delivery, the variable &$self_hostname$& contains the
18233 name of the local host that the router encountered. This can be used to
18234 distinguish between different cases for hosts with multiple names. The
18240 ensures that only those addresses that routed to the local host are passed on.
18241 Without &%no_more%&, addresses that were declined for other reasons would also
18242 be passed to the next router.
18245 Delivery fails and an error report is generated.
18248 .cindex "local host" "sending to"
18249 The anomaly is ignored and the address is queued for the transport. This
18250 setting should be used with extreme caution. For an &(smtp)& transport, it
18251 makes sense only in cases where the program that is listening on the SMTP port
18252 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18253 different configuration file that handles the domain in another way.
18258 .option senders routers&!? "address list&!!" unset
18259 .cindex "router" "checking senders"
18260 If this option is set, the router is skipped unless the message's sender
18261 address matches something on the list.
18262 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18265 There are issues concerning verification when the running of routers is
18266 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18267 setting, it sets the sender to the null string. When using the &%-bt%& option
18268 to check a configuration file, it is necessary also to use the &%-f%& option to
18269 set an appropriate sender. For incoming mail, the sender is unset when
18270 verifying the sender, but is available when verifying any recipients. If the
18271 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18275 .option translate_ip_address routers string&!! unset
18276 .cindex "IP address" "translating"
18277 .cindex "packet radio"
18278 .cindex "router" "IP address translation"
18279 There exist some rare networking situations (for example, packet radio) where
18280 it is helpful to be able to translate IP addresses generated by normal routing
18281 mechanisms into other IP addresses, thus performing a kind of manual IP
18282 routing. This should be done only if the normal IP routing of the TCP/IP stack
18283 is inadequate or broken. Because this is an extremely uncommon requirement, the
18284 code to support this option is not included in the Exim binary unless
18285 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18287 .vindex "&$host_address$&"
18288 The &%translate_ip_address%& string is expanded for every IP address generated
18289 by the router, with the generated address set in &$host_address$&. If the
18290 expansion is forced to fail, no action is taken.
18291 For any other expansion error, delivery of the message is deferred.
18292 If the result of the expansion is an IP address, that replaces the original
18293 address; otherwise the result is assumed to be a host name &-- this is looked
18294 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18295 produce one or more replacement IP addresses. For example, to subvert all IP
18296 addresses in some specific networks, this could be added to a router:
18298 translate_ip_address = \
18299 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18302 The file would contain lines like
18304 10.2.3.128/26 some.host
18305 10.8.4.34/26 10.44.8.15
18307 You should not make use of this facility unless you really understand what you
18312 .option transport routers string&!! unset
18313 This option specifies the transport to be used when a router accepts an address
18314 and sets it up for delivery. A transport is never needed if a router is used
18315 only for verification. The value of the option is expanded at routing time,
18316 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18317 and result must be the name of one of the configured transports. If it is not,
18318 delivery is deferred.
18320 The &%transport%& option is not used by the &(redirect)& router, but it does
18321 have some private options that set up transports for pipe and file deliveries
18322 (see chapter &<<CHAPredirect>>&).
18326 .option transport_current_directory routers string&!! unset
18327 .cindex "current directory for local transport"
18328 This option associates a current directory with any address that is routed
18329 to a local transport. This can happen either because a transport is
18330 explicitly configured for the router, or because it generates a delivery to a
18331 file or a pipe. During the delivery process (that is, at transport time), this
18332 option string is expanded and is set as the current directory, unless
18333 overridden by a setting on the transport.
18334 If the expansion fails for any reason, including forced failure, an error is
18335 logged, and delivery is deferred.
18336 See chapter &<<CHAPenvironment>>& for details of the local delivery
18342 .option transport_home_directory routers string&!! "see below"
18343 .cindex "home directory" "for local transport"
18344 This option associates a home directory with any address that is routed to a
18345 local transport. This can happen either because a transport is explicitly
18346 configured for the router, or because it generates a delivery to a file or a
18347 pipe. During the delivery process (that is, at transport time), the option
18348 string is expanded and is set as the home directory, unless overridden by a
18349 setting of &%home_directory%& on the transport.
18350 If the expansion fails for any reason, including forced failure, an error is
18351 logged, and delivery is deferred.
18353 If the transport does not specify a home directory, and
18354 &%transport_home_directory%& is not set for the router, the home directory for
18355 the transport is taken from the password data if &%check_local_user%& is set for
18356 the router. Otherwise it is taken from &%router_home_directory%& if that option
18357 is set; if not, no home directory is set for the transport.
18359 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18365 .option unseen routers boolean&!! false
18366 .cindex "router" "carrying on after success"
18367 The result of string expansion for this option must be a valid boolean value,
18368 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18369 result causes an error, and delivery is deferred. If the expansion is forced to
18370 fail, the default value for the option (false) is used. Other failures cause
18371 delivery to be deferred.
18373 When this option is set true, routing does not cease if the router accepts the
18374 address. Instead, a copy of the incoming address is passed to the next router,
18375 overriding a false setting of &%more%&. There is little point in setting
18376 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18377 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18378 sometimes true and sometimes false).
18380 .cindex "copy of message (&%unseen%& option)"
18381 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18382 qualifier in filter files. It can be used to cause copies of messages to be
18383 delivered to some other destination, while also carrying out a normal delivery.
18384 In effect, the current address is made into a &"parent"& that has two children
18385 &-- one that is delivered as specified by this router, and a clone that goes on
18386 to be routed further. For this reason, &%unseen%& may not be combined with the
18387 &%one_time%& option in a &(redirect)& router.
18389 &*Warning*&: Header lines added to the address (or specified for removal) by
18390 this router or by previous routers affect the &"unseen"& copy of the message
18391 only. The clone that continues to be processed by further routers starts with
18392 no added headers and none specified for removal. For a &%redirect%& router, if
18393 a generated address is the same as the incoming address, this can lead to
18394 duplicate addresses with different header modifications. Exim does not do
18395 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18396 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18397 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18398 &%redirect%& router may be of help.
18400 Unlike the handling of header modifications, any data that was set by the
18401 &%address_data%& option in the current or previous routers &'is'& passed on to
18402 subsequent routers.
18405 .option user routers string&!! "see below"
18406 .cindex "uid (user id)" "local delivery"
18407 .cindex "local transports" "uid and gid"
18408 .cindex "transport" "local"
18409 .cindex "router" "user for filter processing"
18410 .cindex "filter" "user for processing"
18411 When a router queues an address for a transport, and the transport does not
18412 specify a user, the user given here is used when running the delivery process.
18413 The user may be specified numerically or by name. If expansion fails, the
18414 error is logged and delivery is deferred.
18415 This user is also used by the &(redirect)& router when running a filter file.
18416 The default is unset, except when &%check_local_user%& is set. In this case,
18417 the default is taken from the password information. If the user is specified as
18418 a name, and &%group%& is not set, the group associated with the user is used.
18419 See also &%initgroups%& and &%group%& and the discussion in chapter
18420 &<<CHAPenvironment>>&.
18424 .option verify routers&!? boolean true
18425 Setting this option has the effect of setting &%verify_sender%& and
18426 &%verify_recipient%& to the same value.
18429 .option verify_only routers&!? boolean false
18430 .cindex "EXPN" "with &%verify_only%&"
18432 .cindex "router" "used only when verifying"
18433 If this option is set, the router is used only when verifying an address,
18434 delivering in cutthrough mode or
18435 testing with the &%-bv%& option, not when actually doing a delivery, testing
18436 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18437 restricted to verifying only senders or recipients by means of
18438 &%verify_sender%& and &%verify_recipient%&.
18440 &*Warning*&: When the router is being run to verify addresses for an incoming
18441 SMTP message, Exim is not running as root, but under its own uid. If the router
18442 accesses any files, you need to make sure that they are accessible to the Exim
18446 .option verify_recipient routers&!? boolean true
18447 If this option is false, the router is skipped when verifying recipient
18449 delivering in cutthrough mode
18450 or testing recipient verification using &%-bv%&.
18451 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18453 See also the &$verify_mode$& variable.
18456 .option verify_sender routers&!? boolean true
18457 If this option is false, the router is skipped when verifying sender addresses
18458 or testing sender verification using &%-bvs%&.
18459 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18461 See also the &$verify_mode$& variable.
18462 .ecindex IIDgenoprou1
18463 .ecindex IIDgenoprou2
18470 . ////////////////////////////////////////////////////////////////////////////
18471 . ////////////////////////////////////////////////////////////////////////////
18473 .chapter "The accept router" "CHID4"
18474 .cindex "&(accept)& router"
18475 .cindex "routers" "&(accept)&"
18476 The &(accept)& router has no private options of its own. Unless it is being
18477 used purely for verification (see &%verify_only%&) a transport is required to
18478 be defined by the generic &%transport%& option. If the preconditions that are
18479 specified by generic options are met, the router accepts the address and queues
18480 it for the given transport. The most common use of this router is for setting
18481 up deliveries to local mailboxes. For example:
18485 domains = mydomain.example
18487 transport = local_delivery
18489 The &%domains%& condition in this example checks the domain of the address, and
18490 &%check_local_user%& checks that the local part is the login of a local user.
18491 When both preconditions are met, the &(accept)& router runs, and queues the
18492 address for the &(local_delivery)& transport.
18499 . ////////////////////////////////////////////////////////////////////////////
18500 . ////////////////////////////////////////////////////////////////////////////
18502 .chapter "The dnslookup router" "CHAPdnslookup"
18503 .scindex IIDdnsrou1 "&(dnslookup)& router"
18504 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18505 The &(dnslookup)& router looks up the hosts that handle mail for the
18506 recipient's domain in the DNS. A transport must always be set for this router,
18507 unless &%verify_only%& is set.
18509 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18510 SRV records. If none are found, or if SRV support is not configured,
18511 MX records are looked up. If no MX records exist, address records are sought.
18512 However, &%mx_domains%& can be set to disable the direct use of address
18515 MX records of equal priority are sorted by Exim into a random order. Exim then
18516 looks for address records for the host names obtained from MX or SRV records.
18517 When a host has more than one IP address, they are sorted into a random order,
18518 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
18519 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18520 generic option, the router declines.
18522 Unless they have the highest priority (lowest MX value), MX records that point
18523 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18524 are discarded, together with any other MX records of equal or lower priority.
18526 .cindex "MX record" "pointing to local host"
18527 .cindex "local host" "MX pointing to"
18528 .oindex "&%self%&" "in &(dnslookup)& router"
18529 If the host pointed to by the highest priority MX record, or looked up as an
18530 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18531 happens is controlled by the generic &%self%& option.
18534 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18535 There have been problems with DNS servers when SRV records are looked up.
18536 Some misbehaving servers return a DNS error or timeout when a non-existent
18537 SRV record is sought. Similar problems have in the past been reported for
18538 MX records. The global &%dns_again_means_nonexist%& option can help with this
18539 problem, but it is heavy-handed because it is a global option.
18541 For this reason, there are two options, &%srv_fail_domains%& and
18542 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18543 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18544 an attempt to look up an SRV or MX record causes one of these results, and the
18545 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18546 such record"&. In the case of an SRV lookup, this means that the router
18547 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18548 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18549 case routing fails.
18552 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18553 .cindex "&(dnslookup)& router" "declines"
18554 There are a few cases where a &(dnslookup)& router will decline to accept
18555 an address; if such a router is expected to handle "all remaining non-local
18556 domains", then it is important to set &%no_more%&.
18558 The router will defer rather than decline if the domain
18559 is found in the &%fail_defer_domains%& router option.
18561 Reasons for a &(dnslookup)& router to decline currently include:
18563 The domain does not exist in DNS
18565 The domain exists but the MX record's host part is just "."; this is a common
18566 convention (borrowed from SRV) used to indicate that there is no such service
18567 for this domain and to not fall back to trying A/AAAA records.
18569 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18571 MX record points to a non-existent host.
18573 MX record points to an IP address and the main section option
18574 &%allow_mx_to_ip%& is not set.
18576 MX records exist and point to valid hosts, but all hosts resolve only to
18577 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18579 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18580 &%dns_check_names_pattern%& for handling one variant of this)
18582 &%check_secondary_mx%& is set on this router but the local host can
18583 not be found in the MX records (see below)
18589 .section "Private options for dnslookup" "SECID118"
18590 .cindex "options" "&(dnslookup)& router"
18591 The private options for the &(dnslookup)& router are as follows:
18593 .option check_secondary_mx dnslookup boolean false
18594 .cindex "MX record" "checking for secondary"
18595 If this option is set, the router declines unless the local host is found in
18596 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18597 process domains for which the local host is a secondary mail exchanger
18598 differently to other domains. The way in which Exim decides whether a host is
18599 the local host is described in section &<<SECTreclocipadd>>&.
18602 .option check_srv dnslookup string&!! unset
18603 .cindex "SRV record" "enabling use of"
18604 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
18605 addition to MX and address records. The support is disabled by default. To
18606 enable SRV support, set the &%check_srv%& option to the name of the service
18607 required. For example,
18611 looks for SRV records that refer to the normal smtp service. The option is
18612 expanded, so the service name can vary from message to message or address
18613 to address. This might be helpful if SRV records are being used for a
18614 submission service. If the expansion is forced to fail, the &%check_srv%&
18615 option is ignored, and the router proceeds to look for MX records in the
18618 When the expansion succeeds, the router searches first for SRV records for
18619 the given service (it assumes TCP protocol). A single SRV record with a
18620 host name that consists of just a single dot indicates &"no such service for
18621 this domain"&; if this is encountered, the router declines. If other kinds of
18622 SRV record are found, they are used to construct a host list for delivery
18623 according to the rules of RFC 2782. MX records are not sought in this case.
18625 When no SRV records are found, MX records (and address records) are sought in
18626 the traditional way. In other words, SRV records take precedence over MX
18627 records, just as MX records take precedence over address records. Note that
18628 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
18629 defined it. It is apparently believed that MX records are sufficient for email
18630 and that SRV records should not be used for this purpose. However, SRV records
18631 have an additional &"weight"& feature which some people might find useful when
18632 trying to split an SMTP load between hosts of different power.
18634 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
18635 when there is a DNS lookup error.
18640 .option fail_defer_domains dnslookup "domain list&!!" unset
18641 .cindex "MX record" "not found"
18642 DNS lookups for domains matching &%fail_defer_domains%&
18643 which find no matching record will cause the router to defer
18644 rather than the default behaviour of decline.
18645 This maybe be useful for queueing messages for a newly created
18646 domain while the DNS configuration is not ready.
18647 However, it will result in any message with mistyped domains
18651 .option mx_domains dnslookup "domain list&!!" unset
18652 .cindex "MX record" "required to exist"
18653 .cindex "SRV record" "required to exist"
18654 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
18655 record in order to be recognized. (The name of this option could be improved.)
18656 For example, if all the mail hosts in &'fict.example'& are known to have MX
18657 records, except for those in &'discworld.fict.example'&, you could use this
18660 mx_domains = ! *.discworld.fict.example : *.fict.example
18662 This specifies that messages addressed to a domain that matches the list but
18663 has no MX record should be bounced immediately instead of being routed using
18664 the address record.
18667 .option mx_fail_domains dnslookup "domain list&!!" unset
18668 If the DNS lookup for MX records for one of the domains in this list causes a
18669 DNS lookup error, Exim behaves as if no MX records were found. See section
18670 &<<SECTprowitdnsloo>>& for more discussion.
18675 .option qualify_single dnslookup boolean true
18676 .cindex "DNS" "resolver options"
18677 .cindex "DNS" "qualifying single-component names"
18678 When this option is true, the resolver option RES_DEFNAMES is set for DNS
18679 lookups. Typically, but not standardly, this causes the resolver to qualify
18680 single-component names with the default domain. For example, on a machine
18681 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
18682 &'thesaurus.ref.example'& inside the resolver. For details of what your
18683 resolver actually does, consult your man pages for &'resolver'& and
18688 .option rewrite_headers dnslookup boolean true
18689 .cindex "rewriting" "header lines"
18690 .cindex "header lines" "rewriting"
18691 If the domain name in the address that is being processed is not fully
18692 qualified, it may be expanded to its full form by a DNS lookup. For example, if
18693 an address is specified as &'dormouse@teaparty'&, the domain might be
18694 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
18695 occur as a result of setting the &%widen_domains%& option. If
18696 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
18697 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
18698 header lines of the message are rewritten with the full domain name.
18700 This option should be turned off only when it is known that no message is
18701 ever going to be sent outside an environment where the abbreviation makes
18704 When an MX record is looked up in the DNS and matches a wildcard record, name
18705 servers normally return a record containing the name that has been looked up,
18706 making it impossible to detect whether a wildcard was present or not. However,
18707 some name servers have recently been seen to return the wildcard entry. If the
18708 name returned by a DNS lookup begins with an asterisk, it is not used for
18712 .option same_domain_copy_routing dnslookup boolean false
18713 .cindex "address" "copying routing"
18714 Addresses with the same domain are normally routed by the &(dnslookup)& router
18715 to the same list of hosts. However, this cannot be presumed, because the router
18716 options and preconditions may refer to the local part of the address. By
18717 default, therefore, Exim routes each address in a message independently. DNS
18718 servers run caches, so repeated DNS lookups are not normally expensive, and in
18719 any case, personal messages rarely have more than a few recipients.
18721 If you are running mailing lists with large numbers of subscribers at the same
18722 domain, and you are using a &(dnslookup)& router which is independent of the
18723 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18724 lookups for identical domains in one message. In this case, when &(dnslookup)&
18725 routes an address to a remote transport, any other unrouted addresses in the
18726 message that have the same domain are automatically given the same routing
18727 without processing them independently,
18728 provided the following conditions are met:
18731 No router that processed the address specified &%headers_add%& or
18732 &%headers_remove%&.
18734 The router did not change the address in any way, for example, by &"widening"&
18741 .option search_parents dnslookup boolean false
18742 .cindex "DNS" "resolver options"
18743 When this option is true, the resolver option RES_DNSRCH is set for DNS
18744 lookups. This is different from the &%qualify_single%& option in that it
18745 applies to domains containing dots. Typically, but not standardly, it causes
18746 the resolver to search for the name in the current domain and in parent
18747 domains. For example, on a machine in the &'fict.example'& domain, if looking
18748 up &'teaparty.wonderland'& failed, the resolver would try
18749 &'teaparty.wonderland.fict.example'&. For details of what your resolver
18750 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
18752 Setting this option true can cause problems in domains that have a wildcard MX
18753 record, because any domain that does not have its own MX record matches the
18758 .option srv_fail_domains dnslookup "domain list&!!" unset
18759 If the DNS lookup for SRV records for one of the domains in this list causes a
18760 DNS lookup error, Exim behaves as if no SRV records were found. See section
18761 &<<SECTprowitdnsloo>>& for more discussion.
18766 .option widen_domains dnslookup "string list" unset
18767 .cindex "domain" "partial; widening"
18768 If a DNS lookup fails and this option is set, each of its strings in turn is
18769 added onto the end of the domain, and the lookup is tried again. For example,
18772 widen_domains = fict.example:ref.example
18774 is set and a lookup of &'klingon.dictionary'& fails,
18775 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
18776 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
18777 and &%search_parents%& options can cause some widening to be undertaken inside
18778 the DNS resolver. &%widen_domains%& is not applied to sender addresses
18779 when verifying, unless &%rewrite_headers%& is false (not the default).
18782 .section "Effect of qualify_single and search_parents" "SECID119"
18783 When a domain from an envelope recipient is changed by the resolver as a result
18784 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
18785 corresponding address in the message's header lines unless &%rewrite_headers%&
18786 is set false. Exim then re-routes the address, using the full domain.
18788 These two options affect only the DNS lookup that takes place inside the router
18789 for the domain of the address that is being routed. They do not affect lookups
18790 such as that implied by
18794 that may happen while processing a router precondition before the router is
18795 entered. No widening ever takes place for these lookups.
18796 .ecindex IIDdnsrou1
18797 .ecindex IIDdnsrou2
18807 . ////////////////////////////////////////////////////////////////////////////
18808 . ////////////////////////////////////////////////////////////////////////////
18810 .chapter "The ipliteral router" "CHID5"
18811 .cindex "&(ipliteral)& router"
18812 .cindex "domain literal" "routing"
18813 .cindex "routers" "&(ipliteral)&"
18814 This router has no private options. Unless it is being used purely for
18815 verification (see &%verify_only%&) a transport is required to be defined by the
18816 generic &%transport%& option. The router accepts the address if its domain part
18817 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18818 router handles the address
18822 by setting up delivery to the host with that IP address. IPv4 domain literals
18823 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18824 are similar, but the address is preceded by &`ipv6:`&. For example:
18826 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18828 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18829 grounds that sooner or later somebody will try it.
18831 .oindex "&%self%&" "in &(ipliteral)& router"
18832 If the IP address matches something in &%ignore_target_hosts%&, the router
18833 declines. If an IP literal turns out to refer to the local host, the generic
18834 &%self%& option determines what happens.
18836 The RFCs require support for domain literals; however, their use is
18837 controversial in today's Internet. If you want to use this router, you must
18838 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18839 Exim will not recognize the domain literal syntax in addresses.
18843 . ////////////////////////////////////////////////////////////////////////////
18844 . ////////////////////////////////////////////////////////////////////////////
18846 .chapter "The iplookup router" "CHID6"
18847 .cindex "&(iplookup)& router"
18848 .cindex "routers" "&(iplookup)&"
18849 The &(iplookup)& router was written to fulfil a specific requirement in
18850 Cambridge University (which in fact no longer exists). For this reason, it is
18851 not included in the binary of Exim by default. If you want to include it, you
18854 ROUTER_IPLOOKUP=yes
18856 in your &_Local/Makefile_& configuration file.
18858 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18859 connection to one or more specific hosts. The host can then return the same or
18860 a different address &-- in effect rewriting the recipient address in the
18861 message's envelope. The new address is then passed on to subsequent routers. If
18862 this process fails, the address can be passed on to other routers, or delivery
18863 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18864 must not be specified for it.
18866 .cindex "options" "&(iplookup)& router"
18867 .option hosts iplookup string unset
18868 This option must be supplied. Its value is a colon-separated list of host
18869 names. The hosts are looked up using &[gethostbyname()]&
18870 (or &[getipnodebyname()]& when available)
18871 and are tried in order until one responds to the query. If none respond, what
18872 happens is controlled by &%optional%&.
18875 .option optional iplookup boolean false
18876 If &%optional%& is true, if no response is obtained from any host, the address
18877 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18878 delivery to the address is deferred.
18881 .option port iplookup integer 0
18882 .cindex "port" "&(iplookup)& router"
18883 This option must be supplied. It specifies the port number for the TCP or UDP
18887 .option protocol iplookup string udp
18888 This option can be set to &"udp"& or &"tcp"& to specify which of the two
18889 protocols is to be used.
18892 .option query iplookup string&!! "see below"
18893 This defines the content of the query that is sent to the remote hosts. The
18896 $local_part@$domain $local_part@$domain
18898 The repetition serves as a way of checking that a response is to the correct
18899 query in the default case (see &%response_pattern%& below).
18902 .option reroute iplookup string&!! unset
18903 If this option is not set, the rerouted address is precisely the byte string
18904 returned by the remote host, up to the first white space, if any. If set, the
18905 string is expanded to form the rerouted address. It can include parts matched
18906 in the response by &%response_pattern%& by means of numeric variables such as
18907 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
18908 whether or not a pattern is in use. In all cases, the rerouted address must end
18909 up in the form &'local_part@domain'&.
18912 .option response_pattern iplookup string unset
18913 This option can be set to a regular expression that is applied to the string
18914 returned from the remote host. If the pattern does not match the response, the
18915 router declines. If &%response_pattern%& is not set, no checking of the
18916 response is done, unless the query was defaulted, in which case there is a
18917 check that the text returned after the first white space is the original
18918 address. This checks that the answer that has been received is in response to
18919 the correct question. For example, if the response is just a new domain, the
18920 following could be used:
18922 response_pattern = ^([^@]+)$
18923 reroute = $local_part@$1
18926 .option timeout iplookup time 5s
18927 This specifies the amount of time to wait for a response from the remote
18928 machine. The same timeout is used for the &[connect()]& function for a TCP
18929 call. It does not apply to UDP.
18934 . ////////////////////////////////////////////////////////////////////////////
18935 . ////////////////////////////////////////////////////////////////////////////
18937 .chapter "The manualroute router" "CHID7"
18938 .scindex IIDmanrou1 "&(manualroute)& router"
18939 .scindex IIDmanrou2 "routers" "&(manualroute)&"
18940 .cindex "domain" "manually routing"
18941 The &(manualroute)& router is so-called because it provides a way of manually
18942 routing an address according to its domain. It is mainly used when you want to
18943 route addresses to remote hosts according to your own rules, bypassing the
18944 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18945 route to local transports, a facility that may be useful if you want to save
18946 messages for dial-in hosts in local files.
18948 The &(manualroute)& router compares a list of domain patterns with the domain
18949 it is trying to route. If there is no match, the router declines. Each pattern
18950 has associated with it a list of hosts and some other optional data, which may
18951 include a transport. The combination of a pattern and its data is called a
18952 &"routing rule"&. For patterns that do not have an associated transport, the
18953 generic &%transport%& option must specify a transport, unless the router is
18954 being used purely for verification (see &%verify_only%&).
18957 In the case of verification, matching the domain pattern is sufficient for the
18958 router to accept the address. When actually routing an address for delivery,
18959 an address that matches a domain pattern is queued for the associated
18960 transport. If the transport is not a local one, a host list must be associated
18961 with the pattern; IP addresses are looked up for the hosts, and these are
18962 passed to the transport along with the mail address. For local transports, a
18963 host list is optional. If it is present, it is passed in &$host$& as a single
18966 The list of routing rules can be provided as an inline string in
18967 &%route_list%&, or the data can be obtained by looking up the domain in a file
18968 or database by setting &%route_data%&. Only one of these settings may appear in
18969 any one instance of &(manualroute)&. The format of routing rules is described
18970 below, following the list of private options.
18973 .section "Private options for manualroute" "SECTprioptman"
18975 .cindex "options" "&(manualroute)& router"
18976 The private options for the &(manualroute)& router are as follows:
18978 .option host_all_ignored manualroute string defer
18979 See &%host_find_failed%&.
18981 .option host_find_failed manualroute string freeze
18982 This option controls what happens when &(manualroute)& tries to find an IP
18983 address for a host, and the host does not exist. The option can be set to one
18984 of the following values:
18993 The default (&"freeze"&) assumes that this state is a serious configuration
18994 error. The difference between &"pass"& and &"decline"& is that the former
18995 forces the address to be passed to the next router (or the router defined by
18998 overriding &%no_more%&, whereas the latter passes the address to the next
18999 router only if &%more%& is true.
19001 The value &"ignore"& causes Exim to completely ignore a host whose IP address
19002 cannot be found. If all the hosts in the list are ignored, the behaviour is
19003 controlled by the &%host_all_ignored%& option. This takes the same values
19004 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
19006 The &%host_find_failed%& option applies only to a definite &"does not exist"&
19007 state; if a host lookup gets a temporary error, delivery is deferred unless the
19008 generic &%pass_on_timeout%& option is set.
19011 .option hosts_randomize manualroute boolean false
19012 .cindex "randomized host list"
19013 .cindex "host" "list of; randomized"
19014 If this option is set, the order of the items in a host list in a routing rule
19015 is randomized each time the list is used, unless an option in the routing rule
19016 overrides (see below). Randomizing the order of a host list can be used to do
19017 crude load sharing. However, if more than one mail address is routed by the
19018 same router to the same host list, the host lists are considered to be the same
19019 (even though they may be randomized into different orders) for the purpose of
19020 deciding whether to batch the deliveries into a single SMTP transaction.
19022 When &%hosts_randomize%& is true, a host list may be split
19023 into groups whose order is separately randomized. This makes it possible to
19024 set up MX-like behaviour. The boundaries between groups are indicated by an
19025 item that is just &`+`& in the host list. For example:
19027 route_list = * host1:host2:host3:+:host4:host5
19029 The order of the first three hosts and the order of the last two hosts is
19030 randomized for each use, but the first three always end up before the last two.
19031 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
19032 randomized host list is passed to an &(smtp)& transport that also has
19033 &%hosts_randomize set%&, the list is not re-randomized.
19036 .option route_data manualroute string&!! unset
19037 If this option is set, it must expand to yield the data part of a routing rule.
19038 Typically, the expansion string includes a lookup based on the domain. For
19041 route_data = ${lookup{$domain}dbm{/etc/routes}}
19043 If the expansion is forced to fail, or the result is an empty string, the
19044 router declines. Other kinds of expansion failure cause delivery to be
19048 .option route_list manualroute "string list" unset
19049 This string is a list of routing rules, in the form defined below. Note that,
19050 unlike most string lists, the items are separated by semicolons. This is so
19051 that they may contain colon-separated host lists.
19054 .option same_domain_copy_routing manualroute boolean false
19055 .cindex "address" "copying routing"
19056 Addresses with the same domain are normally routed by the &(manualroute)&
19057 router to the same list of hosts. However, this cannot be presumed, because the
19058 router options and preconditions may refer to the local part of the address. By
19059 default, therefore, Exim routes each address in a message independently. DNS
19060 servers run caches, so repeated DNS lookups are not normally expensive, and in
19061 any case, personal messages rarely have more than a few recipients.
19063 If you are running mailing lists with large numbers of subscribers at the same
19064 domain, and you are using a &(manualroute)& router which is independent of the
19065 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19066 lookups for identical domains in one message. In this case, when
19067 &(manualroute)& routes an address to a remote transport, any other unrouted
19068 addresses in the message that have the same domain are automatically given the
19069 same routing without processing them independently. However, this is only done
19070 if &%headers_add%& and &%headers_remove%& are unset.
19075 .section "Routing rules in route_list" "SECID120"
19076 The value of &%route_list%& is a string consisting of a sequence of routing
19077 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
19078 entered as two semicolons. Alternatively, the list separator can be changed as
19079 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
19080 Empty rules are ignored. The format of each rule is
19082 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
19084 The following example contains two rules, each with a simple domain pattern and
19088 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
19089 thes.ref.example mail-3.ref.example:mail-4.ref.example
19091 The three parts of a rule are separated by white space. The pattern and the
19092 list of hosts can be enclosed in quotes if necessary, and if they are, the
19093 usual quoting rules apply. Each rule in a &%route_list%& must start with a
19094 single domain pattern, which is the only mandatory item in the rule. The
19095 pattern is in the same format as one item in a domain list (see section
19096 &<<SECTdomainlist>>&),
19097 except that it may not be the name of an interpolated file.
19098 That is, it may be wildcarded, or a regular expression, or a file or database
19099 lookup (with semicolons doubled, because of the use of semicolon as a separator
19100 in a &%route_list%&).
19102 The rules in &%route_list%& are searched in order until one of the patterns
19103 matches the domain that is being routed. The list of hosts and then options are
19104 then used as described below. If there is no match, the router declines. When
19105 &%route_list%& is set, &%route_data%& must not be set.
19109 .section "Routing rules in route_data" "SECID121"
19110 The use of &%route_list%& is convenient when there are only a small number of
19111 routing rules. For larger numbers, it is easier to use a file or database to
19112 hold the routing information, and use the &%route_data%& option instead.
19113 The value of &%route_data%& is a list of hosts, followed by (optional) options.
19114 Most commonly, &%route_data%& is set as a string that contains an
19115 expansion lookup. For example, suppose we place two routing rules in a file
19118 dict.ref.example: mail-1.ref.example:mail-2.ref.example
19119 thes.ref.example: mail-3.ref.example:mail-4.ref.example
19121 This data can be accessed by setting
19123 route_data = ${lookup{$domain}lsearch{/the/file/name}}
19125 Failure of the lookup results in an empty string, causing the router to
19126 decline. However, you do not have to use a lookup in &%route_data%&. The only
19127 requirement is that the result of expanding the string is a list of hosts,
19128 possibly followed by options, separated by white space. The list of hosts must
19129 be enclosed in quotes if it contains white space.
19134 .section "Format of the list of hosts" "SECID122"
19135 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
19136 always separately expanded before use. If the expansion fails, the router
19137 declines. The result of the expansion must be a colon-separated list of names
19138 and/or IP addresses, optionally also including ports. The format of each item
19139 in the list is described in the next section. The list separator can be changed
19140 as described in section &<<SECTlistconstruct>>&.
19142 If the list of hosts was obtained from a &%route_list%& item, the following
19143 variables are set during its expansion:
19146 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
19147 If the domain was matched against a regular expression, the numeric variables
19148 &$1$&, &$2$&, etc. may be set. For example:
19150 route_list = ^domain(\d+) host-$1.text.example
19153 &$0$& is always set to the entire domain.
19155 &$1$& is also set when partial matching is done in a file lookup.
19158 .vindex "&$value$&"
19159 If the pattern that matched the domain was a lookup item, the data that was
19160 looked up is available in the expansion variable &$value$&. For example:
19162 route_list = lsearch;;/some/file.routes $value
19166 Note the doubling of the semicolon in the pattern that is necessary because
19167 semicolon is the default route list separator.
19171 .section "Format of one host item" "SECTformatonehostitem"
19172 Each item in the list of hosts is either a host name or an IP address,
19173 optionally with an attached port number. When no port is given, an IP address
19174 is not enclosed in brackets. When a port is specified, it overrides the port
19175 specification on the transport. The port is separated from the name or address
19176 by a colon. This leads to some complications:
19179 Because colon is the default separator for the list of hosts, either
19180 the colon that specifies a port must be doubled, or the list separator must
19181 be changed. The following two examples have the same effect:
19183 route_list = * "host1.tld::1225 : host2.tld::1226"
19184 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
19187 When IPv6 addresses are involved, it gets worse, because they contain
19188 colons of their own. To make this case easier, it is permitted to
19189 enclose an IP address (either v4 or v6) in square brackets if a port
19190 number follows. For example:
19192 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
19196 .section "How the list of hosts is used" "SECThostshowused"
19197 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
19198 the hosts is tried, in the order specified, when carrying out the SMTP
19199 delivery. However, the order can be changed by setting the &%hosts_randomize%&
19200 option, either on the router (see section &<<SECTprioptman>>& above), or on the
19203 Hosts may be listed by name or by IP address. An unadorned name in the list of
19204 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
19205 interpreted as an indirection to a sublist of hosts obtained by looking up MX
19206 records in the DNS. For example:
19208 route_list = * x.y.z:p.q.r/MX:e.f.g
19210 If this feature is used with a port specifier, the port must come last. For
19213 route_list = * dom1.tld/mx::1225
19215 If the &%hosts_randomize%& option is set, the order of the items in the list is
19216 randomized before any lookups are done. Exim then scans the list; for any name
19217 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
19218 be an interface on the local host and the item is not the first in the list,
19219 Exim discards it and any subsequent items. If it is the first item, what
19220 happens is controlled by the
19221 .oindex "&%self%&" "in &(manualroute)& router"
19222 &%self%& option of the router.
19224 A name on the list that is followed by &`/MX`& is replaced with the list of
19225 hosts obtained by looking up MX records for the name. This is always a DNS
19226 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
19227 below) are not relevant here. The order of these hosts is determined by the
19228 preference values in the MX records, according to the usual rules. Because
19229 randomizing happens before the MX lookup, it does not affect the order that is
19230 defined by MX preferences.
19232 If the local host is present in the sublist obtained from MX records, but is
19233 not the most preferred host in that list, it and any equally or less
19234 preferred hosts are removed before the sublist is inserted into the main list.
19236 If the local host is the most preferred host in the MX list, what happens
19237 depends on where in the original list of hosts the &`/MX`& item appears. If it
19238 is not the first item (that is, there are previous hosts in the main list),
19239 Exim discards this name and any subsequent items in the main list.
19241 If the MX item is first in the list of hosts, and the local host is the
19242 most preferred host, what happens is controlled by the &%self%& option of the
19245 DNS failures when lookup up the MX records are treated in the same way as DNS
19246 failures when looking up IP addresses: &%pass_on_timeout%& and
19247 &%host_find_failed%& are used when relevant.
19249 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19250 whether obtained from an MX lookup or not.
19254 .section "How the options are used" "SECThowoptused"
19255 The options are a sequence of words; in practice no more than three are ever
19256 present. One of the words can be the name of a transport; this overrides the
19257 &%transport%& option on the router for this particular routing rule only. The
19258 other words (if present) control randomization of the list of hosts on a
19259 per-rule basis, and how the IP addresses of the hosts are to be found when
19260 routing to a remote transport. These options are as follows:
19263 &%randomize%&: randomize the order of the hosts in this list, overriding the
19264 setting of &%hosts_randomize%& for this routing rule only.
19266 &%no_randomize%&: do not randomize the order of the hosts in this list,
19267 overriding the setting of &%hosts_randomize%& for this routing rule only.
19269 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19270 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19271 also look in &_/etc/hosts_& or other sources of information.
19273 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19274 no address records are found. If there is a temporary DNS error (such as a
19275 timeout), delivery is deferred.
19280 route_list = domain1 host1:host2:host3 randomize bydns;\
19281 domain2 host4:host5
19283 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19284 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19285 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19286 or &[gethostbyname()]&, and the result of the lookup is the result of that
19289 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19290 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19291 instead of TRY_AGAIN. That is why the default action is to try a DNS
19292 lookup first. Only if that gives a definite &"no such host"& is the local
19297 If no IP address for a host can be found, what happens is controlled by the
19298 &%host_find_failed%& option.
19301 When an address is routed to a local transport, IP addresses are not looked up.
19302 The host list is passed to the transport in the &$host$& variable.
19306 .section "Manualroute examples" "SECID123"
19307 In some of the examples that follow, the presence of the &%remote_smtp%&
19308 transport, as defined in the default configuration file, is assumed:
19311 .cindex "smart host" "example router"
19312 The &(manualroute)& router can be used to forward all external mail to a
19313 &'smart host'&. If you have set up, in the main part of the configuration, a
19314 named domain list that contains your local domains, for example:
19316 domainlist local_domains = my.domain.example
19318 You can arrange for all other domains to be routed to a smart host by making
19319 your first router something like this:
19322 driver = manualroute
19323 domains = !+local_domains
19324 transport = remote_smtp
19325 route_list = * smarthost.ref.example
19327 This causes all non-local addresses to be sent to the single host
19328 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19329 they are tried in order
19330 (but you can use &%hosts_randomize%& to vary the order each time).
19331 Another way of configuring the same thing is this:
19334 driver = manualroute
19335 transport = remote_smtp
19336 route_list = !+local_domains smarthost.ref.example
19338 There is no difference in behaviour between these two routers as they stand.
19339 However, they behave differently if &%no_more%& is added to them. In the first
19340 example, the router is skipped if the domain does not match the &%domains%&
19341 precondition; the following router is always tried. If the router runs, it
19342 always matches the domain and so can never decline. Therefore, &%no_more%&
19343 would have no effect. In the second case, the router is never skipped; it
19344 always runs. However, if it doesn't match the domain, it declines. In this case
19345 &%no_more%& would prevent subsequent routers from running.
19348 .cindex "mail hub example"
19349 A &'mail hub'& is a host which receives mail for a number of domains via MX
19350 records in the DNS and delivers it via its own private routing mechanism. Often
19351 the final destinations are behind a firewall, with the mail hub being the one
19352 machine that can connect to machines both inside and outside the firewall. The
19353 &(manualroute)& router is usually used on a mail hub to route incoming messages
19354 to the correct hosts. For a small number of domains, the routing can be inline,
19355 using the &%route_list%& option, but for a larger number a file or database
19356 lookup is easier to manage.
19358 If the domain names are in fact the names of the machines to which the mail is
19359 to be sent by the mail hub, the configuration can be quite simple. For
19363 driver = manualroute
19364 transport = remote_smtp
19365 route_list = *.rhodes.tvs.example $domain
19367 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19368 whose names are the same as the mail domains. A similar approach can be taken
19369 if the host name can be obtained from the domain name by a string manipulation
19370 that the expansion facilities can handle. Otherwise, a lookup based on the
19371 domain can be used to find the host:
19374 driver = manualroute
19375 transport = remote_smtp
19376 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19378 The result of the lookup must be the name or IP address of the host (or
19379 hosts) to which the address is to be routed. If the lookup fails, the route
19380 data is empty, causing the router to decline. The address then passes to the
19384 .cindex "batched SMTP output example"
19385 .cindex "SMTP" "batched outgoing; example"
19386 You can use &(manualroute)& to deliver messages to pipes or files in batched
19387 SMTP format for onward transportation by some other means. This is one way of
19388 storing mail for a dial-up host when it is not connected. The route list entry
19389 can be as simple as a single domain name in a configuration like this:
19392 driver = manualroute
19393 transport = batchsmtp_appendfile
19394 route_list = saved.domain.example
19396 though often a pattern is used to pick up more than one domain. If there are
19397 several domains or groups of domains with different transport requirements,
19398 different transports can be listed in the routing information:
19401 driver = manualroute
19403 *.saved.domain1.example $domain batch_appendfile; \
19404 *.saved.domain2.example \
19405 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19408 .vindex "&$domain$&"
19410 The first of these just passes the domain in the &$host$& variable, which
19411 doesn't achieve much (since it is also in &$domain$&), but the second does a
19412 file lookup to find a value to pass, causing the router to decline to handle
19413 the address if the lookup fails.
19416 .cindex "UUCP" "example of router for"
19417 Routing mail directly to UUCP software is a specific case of the use of
19418 &(manualroute)& in a gateway to another mail environment. This is an example of
19419 one way it can be done:
19425 command = /usr/local/bin/uux -r - \
19426 ${substr_-5:$host}!rmail ${local_part}
19427 return_fail_output = true
19432 driver = manualroute
19434 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19436 The file &_/usr/local/exim/uucphosts_& contains entries like
19438 darksite.ethereal.example: darksite.UUCP
19440 It can be set up more simply without adding and removing &".UUCP"& but this way
19441 makes clear the distinction between the domain name
19442 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19444 .ecindex IIDmanrou1
19445 .ecindex IIDmanrou2
19454 . ////////////////////////////////////////////////////////////////////////////
19455 . ////////////////////////////////////////////////////////////////////////////
19457 .chapter "The queryprogram router" "CHAPdriverlast"
19458 .scindex IIDquerou1 "&(queryprogram)& router"
19459 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19460 .cindex "routing" "by external program"
19461 The &(queryprogram)& router routes an address by running an external command
19462 and acting on its output. This is an expensive way to route, and is intended
19463 mainly for use in lightly-loaded systems, or for performing experiments.
19464 However, if it is possible to use the precondition options (&%domains%&,
19465 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19466 be used in special cases, even on a busy host. There are the following private
19468 .cindex "options" "&(queryprogram)& router"
19470 .option command queryprogram string&!! unset
19471 This option must be set. It specifies the command that is to be run. The
19472 command is split up into a command name and arguments, and then each is
19473 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19474 &<<CHAPpipetransport>>&).
19477 .option command_group queryprogram string unset
19478 .cindex "gid (group id)" "in &(queryprogram)& router"
19479 This option specifies a gid to be set when running the command while routing an
19480 address for deliver. It must be set if &%command_user%& specifies a numerical
19481 uid. If it begins with a digit, it is interpreted as the numerical value of the
19482 gid. Otherwise it is looked up using &[getgrnam()]&.
19485 .option command_user queryprogram string unset
19486 .cindex "uid (user id)" "for &(queryprogram)&"
19487 This option must be set. It specifies the uid which is set when running the
19488 command while routing an address for delivery. If the value begins with a digit,
19489 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19490 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19491 not set, a value for the gid also.
19493 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19494 root, which it does during a normal delivery in a conventional configuration.
19495 However, when an address is being verified during message reception, Exim is
19496 usually running as the Exim user, not as root. If the &(queryprogram)& router
19497 is called from a non-root process, Exim cannot change uid or gid before running
19498 the command. In this circumstance the command runs under the current uid and
19502 .option current_directory queryprogram string /
19503 This option specifies an absolute path which is made the current directory
19504 before running the command.
19507 .option timeout queryprogram time 1h
19508 If the command does not complete within the timeout period, its process group
19509 is killed and the message is frozen. A value of zero time specifies no
19513 The standard output of the command is connected to a pipe, which is read when
19514 the command terminates. It should consist of a single line of output,
19515 containing up to five fields, separated by white space. The maximum length of
19516 the line is 1023 characters. Longer lines are silently truncated. The first
19517 field is one of the following words (case-insensitive):
19520 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19523 &'Decline'&: the router declines; pass the address to the next router, unless
19524 &%no_more%& is set.
19526 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19527 subsequent text on the line is an error message. If the router is run as part
19528 of address verification during an incoming SMTP message, the message is
19529 included in the SMTP response.
19531 &'Defer'&: routing could not be completed at this time; try again later. Any
19532 subsequent text on the line is an error message which is logged. It is not
19533 included in any SMTP response.
19535 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19537 &'Pass'&: pass the address to the next router (or the router specified by
19538 &%pass_router%&), overriding &%no_more%&.
19540 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19541 new addresses, which are routed independently, starting with the first router,
19542 or the router specified by &%redirect_router%&, if set.
19545 When the first word is &'accept'&, the remainder of the line consists of a
19546 number of keyed data values, as follows (split into two lines here, to fit on
19549 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19550 LOOKUP=byname|bydns DATA=<text>
19552 The data items can be given in any order, and all are optional. If no transport
19553 is included, the transport specified by the generic &%transport%& option is
19554 used. The list of hosts and the lookup type are needed only if the transport is
19555 an &(smtp)& transport that does not itself supply a list of hosts.
19557 The format of the list of hosts is the same as for the &(manualroute)& router.
19558 As well as host names and IP addresses with optional port numbers, as described
19559 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19560 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19561 (see section &<<SECThostshowused>>&).
19563 If the lookup type is not specified, Exim behaves as follows when trying to
19564 find an IP address for each host: First, a DNS lookup is done. If this yields
19565 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19566 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19567 result of the lookup is the result of that call.
19569 .vindex "&$address_data$&"
19570 If the DATA field is set, its value is placed in the &$address_data$&
19571 variable. For example, this return line
19573 accept hosts=x1.y.example:x2.y.example data="rule1"
19575 routes the address to the default transport, passing a list of two hosts. When
19576 the transport runs, the string &"rule1"& is in &$address_data$&.
19577 .ecindex IIDquerou1
19578 .ecindex IIDquerou2
19583 . ////////////////////////////////////////////////////////////////////////////
19584 . ////////////////////////////////////////////////////////////////////////////
19586 .chapter "The redirect router" "CHAPredirect"
19587 .scindex IIDredrou1 "&(redirect)& router"
19588 .scindex IIDredrou2 "routers" "&(redirect)&"
19589 .cindex "alias file" "in a &(redirect)& router"
19590 .cindex "address redirection" "&(redirect)& router"
19591 The &(redirect)& router handles several kinds of address redirection. Its most
19592 common uses are for resolving local part aliases from a central alias file
19593 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
19594 files, but it has many other potential uses. The incoming address can be
19595 redirected in several different ways:
19598 It can be replaced by one or more new addresses which are themselves routed
19601 It can be routed to be delivered to a given file or directory.
19603 It can be routed to be delivered to a specified pipe command.
19605 It can cause an automatic reply to be generated.
19607 It can be forced to fail, optionally with a custom error message.
19609 It can be temporarily deferred, optionally with a custom message.
19611 It can be discarded.
19614 The generic &%transport%& option must not be set for &(redirect)& routers.
19615 However, there are some private options which define transports for delivery to
19616 files and pipes, and for generating autoreplies. See the &%file_transport%&,
19617 &%pipe_transport%& and &%reply_transport%& descriptions below.
19619 If success DSNs have been requested
19620 .cindex "DSN" "success"
19621 .cindex "Delivery Status Notification" "success"
19622 redirection triggers one and the DSN options are not passed any further.
19626 .section "Redirection data" "SECID124"
19627 The router operates by interpreting a text string which it obtains either by
19628 expanding the contents of the &%data%& option, or by reading the entire
19629 contents of a file whose name is given in the &%file%& option. These two
19630 options are mutually exclusive. The first is commonly used for handling system
19631 aliases, in a configuration like this:
19635 data = ${lookup{$local_part}lsearch{/etc/aliases}}
19637 If the lookup fails, the expanded string in this example is empty. When the
19638 expansion of &%data%& results in an empty string, the router declines. A forced
19639 expansion failure also causes the router to decline; other expansion failures
19640 cause delivery to be deferred.
19642 A configuration using &%file%& is commonly used for handling users'
19643 &_.forward_& files, like this:
19648 file = $home/.forward
19651 If the file does not exist, or causes no action to be taken (for example, it is
19652 empty or consists only of comments), the router declines. &*Warning*&: This
19653 is not the case when the file contains syntactically valid items that happen to
19654 yield empty addresses, for example, items containing only RFC 2822 address
19659 .section "Forward files and address verification" "SECID125"
19660 .cindex "address redirection" "while verifying"
19661 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
19662 &_.forward_& files, as in the example above. There are two reasons for this:
19665 When Exim is receiving an incoming SMTP message from a remote host, it is
19666 running under the Exim uid, not as root. Exim is unable to change uid to read
19667 the file as the user, and it may not be able to read it as the Exim user. So in
19668 practice the router may not be able to operate.
19670 However, even when the router can operate, the existence of a &_.forward_& file
19671 is unimportant when verifying an address. What should be checked is whether the
19672 local part is a valid user name or not. Cutting out the redirection processing
19673 saves some resources.
19681 .section "Interpreting redirection data" "SECID126"
19682 .cindex "Sieve filter" "specifying in redirection data"
19683 .cindex "filter" "specifying in redirection data"
19684 The contents of the data string, whether obtained from &%data%& or &%file%&,
19685 can be interpreted in two different ways:
19688 If the &%allow_filter%& option is set true, and the data begins with the text
19689 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
19690 &'filtering'& instructions in the form of an Exim or Sieve filter file,
19691 respectively. Details of the syntax and semantics of filter files are described
19692 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
19693 document is intended for use by end users.
19695 Otherwise, the data must be a comma-separated list of redirection items, as
19696 described in the next section.
19699 When a message is redirected to a file (a &"mail folder"&), the file name given
19700 in a non-filter redirection list must always be an absolute path. A filter may
19701 generate a relative path &-- how this is handled depends on the transport's
19702 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
19703 for the &(appendfile)& transport.
19707 .section "Items in a non-filter redirection list" "SECTitenonfilred"
19708 .cindex "address redirection" "non-filter list items"
19709 When the redirection data is not an Exim or Sieve filter, for example, if it
19710 comes from a conventional alias or forward file, it consists of a list of
19711 addresses, file names, pipe commands, or certain special items (see section
19712 &<<SECTspecitredli>>& below). The special items can be individually enabled or
19713 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
19714 depending on their default values. The items in the list are separated by
19715 commas or newlines.
19716 If a comma is required in an item, the entire item must be enclosed in double
19719 Lines starting with a # character are comments, and are ignored, and # may
19720 also appear following a comma, in which case everything between the # and the
19721 next newline character is ignored.
19723 If an item is entirely enclosed in double quotes, these are removed. Otherwise
19724 double quotes are retained because some forms of mail address require their use
19725 (but never to enclose the entire address). In the following description,
19726 &"item"& refers to what remains after any surrounding double quotes have been
19729 .vindex "&$local_part$&"
19730 &*Warning*&: If you use an Exim expansion to construct a redirection address,
19731 and the expansion contains a reference to &$local_part$&, you should make use
19732 of the &%quote_local_part%& expansion operator, in case the local part contains
19733 special characters. For example, to redirect all mail for the domain
19734 &'obsolete.example'&, retaining the existing local part, you could use this
19737 data = ${quote_local_part:$local_part}@newdomain.example
19741 .section "Redirecting to a local mailbox" "SECTredlocmai"
19742 .cindex "routing" "loops in"
19743 .cindex "loop" "while routing, avoidance of"
19744 .cindex "address redirection" "to local mailbox"
19745 A redirection item may safely be the same as the address currently under
19746 consideration. This does not cause a routing loop, because a router is
19747 automatically skipped if any ancestor of the address that is being processed
19748 is the same as the current address and was processed by the current router.
19749 Such an address is therefore passed to the following routers, so it is handled
19750 as if there were no redirection. When making this loop-avoidance test, the
19751 complete local part, including any prefix or suffix, is used.
19753 .cindex "address redirection" "local part without domain"
19754 Specifying the same local part without a domain is a common usage in personal
19755 filter files when the user wants to have messages delivered to the local
19756 mailbox and also forwarded elsewhere. For example, the user whose login is
19757 &'cleo'& might have a &_.forward_& file containing this:
19759 cleo, cleopatra@egypt.example
19761 .cindex "backslash in alias file"
19762 .cindex "alias file" "backslash in"
19763 For compatibility with other MTAs, such unqualified local parts may be
19764 preceded by &"\"&, but this is not a requirement for loop prevention. However,
19765 it does make a difference if more than one domain is being handled
19768 If an item begins with &"\"& and the rest of the item parses as a valid RFC
19769 2822 address that does not include a domain, the item is qualified using the
19770 domain of the incoming address. In the absence of a leading &"\"&, unqualified
19771 addresses are qualified using the value in &%qualify_recipient%&, but you can
19772 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
19774 Care must be taken if there are alias names for local users.
19775 Consider an MTA handling a single local domain where the system alias file
19780 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
19781 messages in the local mailbox, and also forward copies elsewhere. He creates
19784 Sam.Reman, spqr@reme.elsewhere.example
19786 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
19787 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
19788 second time round, because it has previously routed it,
19789 and the following routers presumably cannot handle the alias. The forward file
19790 should really contain
19792 spqr, spqr@reme.elsewhere.example
19794 but because this is such a common error, the &%check_ancestor%& option (see
19795 below) exists to provide a way to get round it. This is normally set on a
19796 &(redirect)& router that is handling users' &_.forward_& files.
19800 .section "Special items in redirection lists" "SECTspecitredli"
19801 In addition to addresses, the following types of item may appear in redirection
19802 lists (that is, in non-filter redirection data):
19805 .cindex "pipe" "in redirection list"
19806 .cindex "address redirection" "to pipe"
19807 An item is treated as a pipe command if it begins with &"|"& and does not parse
19808 as a valid RFC 2822 address that includes a domain. A transport for running the
19809 command must be specified by the &%pipe_transport%& option.
19810 Normally, either the router or the transport specifies a user and a group under
19811 which to run the delivery. The default is to use the Exim user and group.
19813 Single or double quotes can be used for enclosing the individual arguments of
19814 the pipe command; no interpretation of escapes is done for single quotes. If
19815 the command contains a comma character, it is necessary to put the whole item
19816 in double quotes, for example:
19818 "|/some/command ready,steady,go"
19820 since items in redirection lists are terminated by commas. Do not, however,
19821 quote just the command. An item such as
19823 |"/some/command ready,steady,go"
19825 is interpreted as a pipe with a rather strange command name, and no arguments.
19827 Note that the above example assumes that the text comes from a lookup source
19828 of some sort, so that the quotes are part of the data. If composing a
19829 redirect router with a &%data%& option directly specifying this command, the
19830 quotes will be used by the configuration parser to define the extent of one
19831 string, but will not be passed down into the redirect router itself. There
19832 are two main approaches to get around this: escape quotes to be part of the
19833 data itself, or avoid using this mechanism and instead create a custom
19834 transport with the &%command%& option set and reference that transport from
19835 an &%accept%& router.
19838 .cindex "file" "in redirection list"
19839 .cindex "address redirection" "to file"
19840 An item is interpreted as a path name if it begins with &"/"& and does not
19841 parse as a valid RFC 2822 address that includes a domain. For example,
19843 /home/world/minbari
19845 is treated as a file name, but
19847 /s=molari/o=babylon/@x400gate.way
19849 is treated as an address. For a file name, a transport must be specified using
19850 the &%file_transport%& option. However, if the generated path name ends with a
19851 forward slash character, it is interpreted as a directory name rather than a
19852 file name, and &%directory_transport%& is used instead.
19854 Normally, either the router or the transport specifies a user and a group under
19855 which to run the delivery. The default is to use the Exim user and group.
19857 .cindex "&_/dev/null_&"
19858 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19859 bypassed at a high level, and the log entry shows &"**bypassed**"&
19860 instead of a transport name. In this case the user and group are not used.
19863 .cindex "included address list"
19864 .cindex "address redirection" "included external list"
19865 If an item is of the form
19867 :include:<path name>
19869 a list of further items is taken from the given file and included at that
19870 point. &*Note*&: Such a file can not be a filter file; it is just an
19871 out-of-line addition to the list. The items in the included list are separated
19872 by commas or newlines and are not subject to expansion. If this is the first
19873 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19874 the alias name. This example is incorrect:
19876 list1 :include:/opt/lists/list1
19878 It must be given as
19880 list1: :include:/opt/lists/list1
19883 .cindex "address redirection" "to black hole"
19884 Sometimes you want to throw away mail to a particular local part. Making the
19885 &%data%& option expand to an empty string does not work, because that causes
19886 the router to decline. Instead, the alias item
19887 .cindex "black hole"
19888 .cindex "abandoning mail"
19889 &':blackhole:'& can be used. It does what its name implies. No delivery is
19890 done, and no error message is generated. This has the same effect as specifying
19891 &_/dev/null_& as a destination, but it can be independently disabled.
19893 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
19894 delivery is done for the original local part, even if other redirection items
19895 are present. If you are generating a multi-item list (for example, by reading a
19896 database) and need the ability to provide a no-op item, you must use
19900 .cindex "delivery" "forcing failure"
19901 .cindex "delivery" "forcing deferral"
19902 .cindex "failing delivery" "forcing"
19903 .cindex "deferred delivery, forcing"
19904 .cindex "customizing" "failure message"
19905 An attempt to deliver a particular address can be deferred or forced to fail by
19906 redirection items of the form
19911 respectively. When a redirection list contains such an item, it applies
19912 to the entire redirection; any other items in the list are ignored. Any
19913 text following &':fail:'& or &':defer:'& is placed in the error text
19914 associated with the failure. For example, an alias file might contain:
19916 X.Employee: :fail: Gone away, no forwarding address
19918 In the case of an address that is being verified from an ACL or as the subject
19920 .cindex "VRFY" "error text, display of"
19921 VRFY command, the text is included in the SMTP error response by
19923 .cindex "EXPN" "error text, display of"
19924 The text is not included in the response to an EXPN command. In non-SMTP cases
19925 the text is included in the error message that Exim generates.
19927 .cindex "SMTP" "error codes"
19928 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
19929 &':fail:'&. However, if the message starts with three digits followed by a
19930 space, optionally followed by an extended code of the form &'n.n.n'&, also
19931 followed by a space, and the very first digit is the same as the default error
19932 code, the code from the message is used instead. If the very first digit is
19933 incorrect, a panic error is logged, and the default code is used. You can
19934 suppress the use of the supplied code in a redirect router by setting the
19935 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
19938 .vindex "&$acl_verify_message$&"
19939 In an ACL, an explicitly provided message overrides the default, but the
19940 default message is available in the variable &$acl_verify_message$& and can
19941 therefore be included in a custom message if this is desired.
19943 Normally the error text is the rest of the redirection list &-- a comma does
19944 not terminate it &-- but a newline does act as a terminator. Newlines are not
19945 normally present in alias expansions. In &(lsearch)& lookups they are removed
19946 as part of the continuation process, but they may exist in other kinds of
19947 lookup and in &':include:'& files.
19949 During routing for message delivery (as opposed to verification), a redirection
19950 containing &':fail:'& causes an immediate failure of the incoming address,
19951 whereas &':defer:'& causes the message to remain on the queue so that a
19952 subsequent delivery attempt can happen at a later time. If an address is
19953 deferred for too long, it will ultimately fail, because the normal retry
19957 .cindex "alias file" "exception to default"
19958 Sometimes it is useful to use a single-key search type with a default (see
19959 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19960 for exceptions to the default. These can be handled by aliasing them to
19961 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19962 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19963 results in an empty redirection list has the same effect.
19967 .section "Duplicate addresses" "SECTdupaddr"
19968 .cindex "duplicate addresses"
19969 .cindex "address duplicate, discarding"
19970 .cindex "pipe" "duplicated"
19971 Exim removes duplicate addresses from the list to which it is delivering, so as
19972 to deliver just one copy to each address. This does not apply to deliveries
19973 routed to pipes by different immediate parent addresses, but an indirect
19974 aliasing scheme of the type
19976 pipe: |/some/command $local_part
19980 does not work with a message that is addressed to both local parts, because
19981 when the second is aliased to the intermediate local part &"pipe"& it gets
19982 discarded as being the same as a previously handled address. However, a scheme
19985 localpart1: |/some/command $local_part
19986 localpart2: |/some/command $local_part
19988 does result in two different pipe deliveries, because the immediate parents of
19989 the pipes are distinct.
19993 .section "Repeated redirection expansion" "SECID128"
19994 .cindex "repeated redirection expansion"
19995 .cindex "address redirection" "repeated for each delivery attempt"
19996 When a message cannot be delivered to all of its recipients immediately,
19997 leading to two or more delivery attempts, redirection expansion is carried out
19998 afresh each time for those addresses whose children were not all previously
19999 delivered. If redirection is being used as a mailing list, this can lead to new
20000 members of the list receiving copies of old messages. The &%one_time%& option
20001 can be used to avoid this.
20004 .section "Errors in redirection lists" "SECID129"
20005 .cindex "address redirection" "errors"
20006 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
20007 error is skipped, and an entry is written to the main log. This may be useful
20008 for mailing lists that are automatically managed. Otherwise, if an error is
20009 detected while generating the list of new addresses, the original address is
20010 deferred. See also &%syntax_errors_to%&.
20014 .section "Private options for the redirect router" "SECID130"
20016 .cindex "options" "&(redirect)& router"
20017 The private options for the &(redirect)& router are as follows:
20020 .option allow_defer redirect boolean false
20021 Setting this option allows the use of &':defer:'& in non-filter redirection
20022 data, or the &%defer%& command in an Exim filter file.
20025 .option allow_fail redirect boolean false
20026 .cindex "failing delivery" "from filter"
20027 If this option is true, the &':fail:'& item can be used in a redirection list,
20028 and the &%fail%& command may be used in an Exim filter file.
20031 .option allow_filter redirect boolean false
20032 .cindex "filter" "enabling use of"
20033 .cindex "Sieve filter" "enabling use of"
20034 Setting this option allows Exim to interpret redirection data that starts with
20035 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
20036 are some features of Exim filter files that some administrators may wish to
20037 lock out; see the &%forbid_filter_%&&'xxx'& options below.
20039 It is also possible to lock out Exim filters or Sieve filters while allowing
20040 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
20043 The filter is run using the uid and gid set by the generic &%user%& and
20044 &%group%& options. These take their defaults from the password data if
20045 &%check_local_user%& is set, so in the normal case of users' personal filter
20046 files, the filter is run as the relevant user. When &%allow_filter%& is set
20047 true, Exim insists that either &%check_local_user%& or &%user%& is set.
20051 .option allow_freeze redirect boolean false
20052 .cindex "freezing messages" "allowing in filter"
20053 Setting this option allows the use of the &%freeze%& command in an Exim filter.
20054 This command is more normally encountered in system filters, and is disabled by
20055 default for redirection filters because it isn't something you usually want to
20056 let ordinary users do.
20060 .option check_ancestor redirect boolean false
20061 This option is concerned with handling generated addresses that are the same
20062 as some address in the list of redirection ancestors of the current address.
20063 Although it is turned off by default in the code, it is set in the default
20064 configuration file for handling users' &_.forward_& files. It is recommended
20065 for this use of the &(redirect)& router.
20067 When &%check_ancestor%& is set, if a generated address (including the domain)
20068 is the same as any ancestor of the current address, it is replaced by a copy of
20069 the current address. This helps in the case where local part A is aliased to B,
20070 and B has a &_.forward_& file pointing back to A. For example, within a single
20071 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
20072 &_&~jb/.forward_& contains:
20074 \Joe.Bloggs, <other item(s)>
20076 Without the &%check_ancestor%& setting, either local part (&"jb"& or
20077 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
20078 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
20079 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
20080 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
20081 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
20082 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
20083 original address. See also the &%repeat_use%& option below.
20086 .option check_group redirect boolean "see below"
20087 When the &%file%& option is used, the group owner of the file is checked only
20088 when this option is set. The permitted groups are those listed in the
20089 &%owngroups%& option, together with the user's default group if
20090 &%check_local_user%& is set. If the file has the wrong group, routing is
20091 deferred. The default setting for this option is true if &%check_local_user%&
20092 is set and the &%modemask%& option permits the group write bit, or if the
20093 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
20097 .option check_owner redirect boolean "see below"
20098 When the &%file%& option is used, the owner of the file is checked only when
20099 this option is set. If &%check_local_user%& is set, the local user is
20100 permitted; otherwise the owner must be one of those listed in the &%owners%&
20101 option. The default value for this option is true if &%check_local_user%& or
20102 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
20105 .option data redirect string&!! unset
20106 This option is mutually exclusive with &%file%&. One or other of them must be
20107 set, but not both. The contents of &%data%& are expanded, and then used as the
20108 list of forwarding items, or as a set of filtering instructions. If the
20109 expansion is forced to fail, or the result is an empty string or a string that
20110 has no effect (consists entirely of comments), the router declines.
20112 When filtering instructions are used, the string must begin with &"#Exim
20113 filter"&, and all comments in the string, including this initial one, must be
20114 terminated with newline characters. For example:
20116 data = #Exim filter\n\
20117 if $h_to: contains Exim then save $home/mail/exim endif
20119 If you are reading the data from a database where newlines cannot be included,
20120 you can use the &${sg}$& expansion item to turn the escape string of your
20121 choice into a newline.
20124 .option directory_transport redirect string&!! unset
20125 A &(redirect)& router sets up a direct delivery to a directory when a path name
20126 ending with a slash is specified as a new &"address"&. The transport used is
20127 specified by this option, which, after expansion, must be the name of a
20128 configured transport. This should normally be an &(appendfile)& transport.
20131 .option file redirect string&!! unset
20132 This option specifies the name of a file that contains the redirection data. It
20133 is mutually exclusive with the &%data%& option. The string is expanded before
20134 use; if the expansion is forced to fail, the router declines. Other expansion
20135 failures cause delivery to be deferred. The result of a successful expansion
20136 must be an absolute path. The entire file is read and used as the redirection
20137 data. If the data is an empty string or a string that has no effect (consists
20138 entirely of comments), the router declines.
20140 .cindex "NFS" "checking for file existence"
20141 If the attempt to open the file fails with a &"does not exist"& error, Exim
20142 runs a check on the containing directory,
20143 unless &%ignore_enotdir%& is true (see below).
20144 If the directory does not appear to exist, delivery is deferred. This can
20145 happen when users' &_.forward_& files are in NFS-mounted directories, and there
20146 is a mount problem. If the containing directory does exist, but the file does
20147 not, the router declines.
20150 .option file_transport redirect string&!! unset
20151 .vindex "&$address_file$&"
20152 A &(redirect)& router sets up a direct delivery to a file when a path name not
20153 ending in a slash is specified as a new &"address"&. The transport used is
20154 specified by this option, which, after expansion, must be the name of a
20155 configured transport. This should normally be an &(appendfile)& transport. When
20156 it is running, the file name is in &$address_file$&.
20159 .option filter_prepend_home redirect boolean true
20160 When this option is true, if a &(save)& command in an Exim filter specifies a
20161 relative path, and &$home$& is defined, it is automatically prepended to the
20162 relative path. If this option is set false, this action does not happen. The
20163 relative path is then passed to the transport unmodified.
20166 .option forbid_blackhole redirect boolean false
20167 If this option is true, the &':blackhole:'& item may not appear in a
20171 .option forbid_exim_filter redirect boolean false
20172 If this option is set true, only Sieve filters are permitted when
20173 &%allow_filter%& is true.
20178 .option forbid_file redirect boolean false
20179 .cindex "delivery" "to file; forbidding"
20180 .cindex "Sieve filter" "forbidding delivery to a file"
20181 .cindex "Sieve filter" "&""keep""& facility; disabling"
20182 If this option is true, this router may not generate a new address that
20183 specifies delivery to a local file or directory, either from a filter or from a
20184 conventional forward file. This option is forced to be true if &%one_time%& is
20185 set. It applies to Sieve filters as well as to Exim filters, but if true, it
20186 locks out the Sieve's &"keep"& facility.
20189 .option forbid_filter_dlfunc redirect boolean false
20190 .cindex "filter" "locking out certain features"
20191 If this option is true, string expansions in Exim filters are not allowed to
20192 make use of the &%dlfunc%& expansion facility to run dynamically loaded
20195 .option forbid_filter_existstest redirect boolean false
20196 .cindex "expansion" "statting a file"
20197 If this option is true, string expansions in Exim filters are not allowed to
20198 make use of the &%exists%& condition or the &%stat%& expansion item.
20200 .option forbid_filter_logwrite redirect boolean false
20201 If this option is true, use of the logging facility in Exim filters is not
20202 permitted. Logging is in any case available only if the filter is being run
20203 under some unprivileged uid (which is normally the case for ordinary users'
20204 &_.forward_& files).
20207 .option forbid_filter_lookup redirect boolean false
20208 If this option is true, string expansions in Exim filter files are not allowed
20209 to make use of &%lookup%& items.
20212 .option forbid_filter_perl redirect boolean false
20213 This option has an effect only if Exim is built with embedded Perl support. If
20214 it is true, string expansions in Exim filter files are not allowed to make use
20215 of the embedded Perl support.
20218 .option forbid_filter_readfile redirect boolean false
20219 If this option is true, string expansions in Exim filter files are not allowed
20220 to make use of &%readfile%& items.
20223 .option forbid_filter_readsocket redirect boolean false
20224 If this option is true, string expansions in Exim filter files are not allowed
20225 to make use of &%readsocket%& items.
20228 .option forbid_filter_reply redirect boolean false
20229 If this option is true, this router may not generate an automatic reply
20230 message. Automatic replies can be generated only from Exim or Sieve filter
20231 files, not from traditional forward files. This option is forced to be true if
20232 &%one_time%& is set.
20235 .option forbid_filter_run redirect boolean false
20236 If this option is true, string expansions in Exim filter files are not allowed
20237 to make use of &%run%& items.
20240 .option forbid_include redirect boolean false
20241 If this option is true, items of the form
20243 :include:<path name>
20245 are not permitted in non-filter redirection lists.
20248 .option forbid_pipe redirect boolean false
20249 .cindex "delivery" "to pipe; forbidding"
20250 If this option is true, this router may not generate a new address which
20251 specifies delivery to a pipe, either from an Exim filter or from a conventional
20252 forward file. This option is forced to be true if &%one_time%& is set.
20255 .option forbid_sieve_filter redirect boolean false
20256 If this option is set true, only Exim filters are permitted when
20257 &%allow_filter%& is true.
20260 .cindex "SMTP" "error codes"
20261 .option forbid_smtp_code redirect boolean false
20262 If this option is set true, any SMTP error codes that are present at the start
20263 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20264 the default codes (451 and 550, respectively) are always used.
20269 .option hide_child_in_errmsg redirect boolean false
20270 .cindex "bounce message" "redirection details; suppressing"
20271 If this option is true, it prevents Exim from quoting a child address if it
20272 generates a bounce or delay message for it. Instead it says &"an address
20273 generated from <&'the top level address'&>"&. Of course, this applies only to
20274 bounces generated locally. If a message is forwarded to another host, &'its'&
20275 bounce may well quote the generated address.
20278 .option ignore_eacces redirect boolean false
20280 If this option is set and an attempt to open a redirection file yields the
20281 EACCES error (permission denied), the &(redirect)& router behaves as if the
20282 file did not exist.
20285 .option ignore_enotdir redirect boolean false
20287 If this option is set and an attempt to open a redirection file yields the
20288 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20289 router behaves as if the file did not exist.
20291 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20292 router that has the &%file%& option set discovers that the file does not exist
20293 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20294 against unmounted NFS directories. If the parent can not be statted, delivery
20295 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20296 is set, because that option tells Exim to ignore &"something on the path is not
20297 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20298 that some operating systems give ENOENT where others give ENOTDIR.
20302 .option include_directory redirect string unset
20303 If this option is set, the path names of any &':include:'& items in a
20304 redirection list must start with this directory.
20307 .option modemask redirect "octal integer" 022
20308 This specifies mode bits which must not be set for a file specified by the
20309 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20312 .option one_time redirect boolean false
20313 .cindex "one-time aliasing/forwarding expansion"
20314 .cindex "alias file" "one-time expansion"
20315 .cindex "forward file" "one-time expansion"
20316 .cindex "mailing lists" "one-time expansion"
20317 .cindex "address redirection" "one-time expansion"
20318 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20319 files each time it tries to deliver a message causes a problem when one or more
20320 of the generated addresses fails be delivered at the first attempt. The problem
20321 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20322 but of what happens when the redirection list changes during the time that the
20323 message is on Exim's queue. This is particularly true in the case of mailing
20324 lists, where new subscribers might receive copies of messages that were posted
20325 before they subscribed.
20327 If &%one_time%& is set and any addresses generated by the router fail to
20328 deliver at the first attempt, the failing addresses are added to the message as
20329 &"top level"& addresses, and the parent address that generated them is marked
20330 &"delivered"&. Thus, redirection does not happen again at the next delivery
20333 &*Warning 1*&: Any header line addition or removal that is specified by this
20334 router would be lost if delivery did not succeed at the first attempt. For this
20335 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20336 permitted when &%one_time%& is set.
20338 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20339 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20340 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20342 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20345 The original top-level address is remembered with each of the generated
20346 addresses, and is output in any log messages. However, any intermediate parent
20347 addresses are not recorded. This makes a difference to the log only if
20348 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20349 typically be used for mailing lists, where there is normally just one level of
20353 .option owners redirect "string list" unset
20354 .cindex "ownership" "alias file"
20355 .cindex "ownership" "forward file"
20356 .cindex "alias file" "ownership"
20357 .cindex "forward file" "ownership"
20358 This specifies a list of permitted owners for the file specified by &%file%&.
20359 This list is in addition to the local user when &%check_local_user%& is set.
20360 See &%check_owner%& above.
20363 .option owngroups redirect "string list" unset
20364 This specifies a list of permitted groups for the file specified by &%file%&.
20365 The list is in addition to the local user's primary group when
20366 &%check_local_user%& is set. See &%check_group%& above.
20369 .option pipe_transport redirect string&!! unset
20370 .vindex "&$address_pipe$&"
20371 A &(redirect)& router sets up a direct delivery to a pipe when a string
20372 starting with a vertical bar character is specified as a new &"address"&. The
20373 transport used is specified by this option, which, after expansion, must be the
20374 name of a configured transport. This should normally be a &(pipe)& transport.
20375 When the transport is run, the pipe command is in &$address_pipe$&.
20378 .option qualify_domain redirect string&!! unset
20379 .vindex "&$qualify_recipient$&"
20380 If this option is set, and an unqualified address (one without a domain) is
20381 generated, and that address would normally be qualified by the global setting
20382 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20383 expanding this string. If the expansion fails, the router declines. If you want
20384 to revert to the default, you can have the expansion generate
20385 &$qualify_recipient$&.
20387 This option applies to all unqualified addresses generated by Exim filters,
20388 but for traditional &_.forward_& files, it applies only to addresses that are
20389 not preceded by a backslash. Sieve filters cannot generate unqualified
20392 .option qualify_preserve_domain redirect boolean false
20393 .cindex "domain" "in redirection; preserving"
20394 .cindex "preserving domain in redirection"
20395 .cindex "address redirection" "domain; preserving"
20396 If this option is set, the router's local &%qualify_domain%& option must not be
20397 set (a configuration error occurs if it is). If an unqualified address (one
20398 without a domain) is generated, it is qualified with the domain of the parent
20399 address (the immediately preceding ancestor) instead of the global
20400 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20401 this applies whether or not the address is preceded by a backslash.
20404 .option repeat_use redirect boolean true
20405 If this option is set false, the router is skipped for a child address that has
20406 any ancestor that was routed by this router. This test happens before any of
20407 the other preconditions are tested. Exim's default anti-looping rules skip
20408 only when the ancestor is the same as the current address. See also
20409 &%check_ancestor%& above and the generic &%redirect_router%& option.
20412 .option reply_transport redirect string&!! unset
20413 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20414 &%vacation%& command is used in a filter file. The transport used is specified
20415 by this option, which, after expansion, must be the name of a configured
20416 transport. This should normally be an &(autoreply)& transport. Other transports
20417 are unlikely to do anything sensible or useful.
20420 .option rewrite redirect boolean true
20421 .cindex "address redirection" "disabling rewriting"
20422 If this option is set false, addresses generated by the router are not
20423 subject to address rewriting. Otherwise, they are treated like new addresses
20424 and are rewritten according to the global rewriting rules.
20427 .option sieve_subaddress redirect string&!! unset
20428 The value of this option is passed to a Sieve filter to specify the
20429 :subaddress part of an address.
20431 .option sieve_useraddress redirect string&!! unset
20432 The value of this option is passed to a Sieve filter to specify the :user part
20433 of an address. However, if it is unset, the entire original local part
20434 (including any prefix or suffix) is used for :user.
20437 .option sieve_vacation_directory redirect string&!! unset
20438 .cindex "Sieve filter" "vacation directory"
20439 To enable the &"vacation"& extension for Sieve filters, you must set
20440 &%sieve_vacation_directory%& to the directory where vacation databases are held
20441 (do not put anything else in that directory), and ensure that the
20442 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20443 needs their own directory; Exim will create it if necessary.
20447 .option skip_syntax_errors redirect boolean false
20448 .cindex "forward file" "broken"
20449 .cindex "address redirection" "broken files"
20450 .cindex "alias file" "broken"
20451 .cindex "broken alias or forward files"
20452 .cindex "ignoring faulty addresses"
20453 .cindex "skipping faulty addresses"
20454 .cindex "error" "skipping bad syntax"
20455 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20456 non-filter redirection data are skipped, and each failing address is logged. If
20457 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20458 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20459 are expanded and placed at the head of the error message generated by
20460 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20461 be the same address as the generic &%errors_to%& option. The
20462 &%skip_syntax_errors%& option is often used when handling mailing lists.
20464 If all the addresses in a redirection list are skipped because of syntax
20465 errors, the router declines to handle the original address, and it is passed to
20466 the following routers.
20468 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20469 error in the filter causes filtering to be abandoned without any action being
20470 taken. The incident is logged, and the router declines to handle the address,
20471 so it is passed to the following routers.
20473 .cindex "Sieve filter" "syntax errors in"
20474 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20475 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20476 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20478 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20479 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20480 option, used with an address that does not get redirected, can be used to
20481 notify users of these errors, by means of a router like this:
20487 file = $home/.forward
20488 file_transport = address_file
20489 pipe_transport = address_pipe
20490 reply_transport = address_reply
20493 syntax_errors_to = real-$local_part@$domain
20494 syntax_errors_text = \
20495 This is an automatically generated message. An error has\n\
20496 been found in your .forward file. Details of the error are\n\
20497 reported below. While this error persists, you will receive\n\
20498 a copy of this message for every message that is addressed\n\
20499 to you. If your .forward file is a filter file, or if it is\n\
20500 a non-filter file containing no valid forwarding addresses,\n\
20501 a copy of each incoming message will be put in your normal\n\
20502 mailbox. If a non-filter file contains at least one valid\n\
20503 forwarding address, forwarding to the valid addresses will\n\
20504 happen, and those will be the only deliveries that occur.
20506 You also need a router to ensure that local addresses that are prefixed by
20507 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20508 put this immediately before the &(userforward)& router:
20513 local_part_prefix = real-
20514 transport = local_delivery
20516 For security, it would probably be a good idea to restrict the use of this
20517 router to locally-generated messages, using a condition such as this:
20519 condition = ${if match {$sender_host_address}\
20520 {\N^(|127\.0\.0\.1)$\N}}
20524 .option syntax_errors_text redirect string&!! unset
20525 See &%skip_syntax_errors%& above.
20528 .option syntax_errors_to redirect string unset
20529 See &%skip_syntax_errors%& above.
20530 .ecindex IIDredrou1
20531 .ecindex IIDredrou2
20538 . ////////////////////////////////////////////////////////////////////////////
20539 . ////////////////////////////////////////////////////////////////////////////
20541 .chapter "Environment for running local transports" "CHAPenvironment" &&&
20542 "Environment for local transports"
20543 .scindex IIDenvlotra1 "local transports" "environment for"
20544 .scindex IIDenvlotra2 "environment" "local transports"
20545 .scindex IIDenvlotra3 "transport" "local; environment for"
20546 Local transports handle deliveries to files and pipes. (The &(autoreply)&
20547 transport can be thought of as similar to a pipe.) Exim always runs transports
20548 in subprocesses, under specified uids and gids. Typical deliveries to local
20549 mailboxes run under the uid and gid of the local user.
20551 Exim also sets a specific current directory while running the transport; for
20552 some transports a home directory setting is also relevant. The &(pipe)&
20553 transport is the only one that sets up environment variables; see section
20554 &<<SECTpipeenv>>& for details.
20556 The values used for the uid, gid, and the directories may come from several
20557 different places. In many cases, the router that handles the address associates
20558 settings with that address as a result of its &%check_local_user%&, &%group%&,
20559 or &%user%& options. However, values may also be given in the transport's own
20560 configuration, and these override anything that comes from the router.
20564 .section "Concurrent deliveries" "SECID131"
20565 .cindex "concurrent deliveries"
20566 .cindex "simultaneous deliveries"
20567 If two different messages for the same local recipient arrive more or less
20568 simultaneously, the two delivery processes are likely to run concurrently. When
20569 the &(appendfile)& transport is used to write to a file, Exim applies locking
20570 rules to stop concurrent processes from writing to the same file at the same
20573 However, when you use a &(pipe)& transport, it is up to you to arrange any
20574 locking that is needed. Here is a silly example:
20578 command = /bin/sh -c 'cat >>/some/file'
20580 This is supposed to write the message at the end of the file. However, if two
20581 messages arrive at the same time, the file will be scrambled. You can use the
20582 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
20583 file using the same algorithm that Exim itself uses.
20588 .section "Uids and gids" "SECTenvuidgid"
20589 .cindex "local transports" "uid and gid"
20590 .cindex "transport" "local; uid and gid"
20591 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
20592 overrides any group that the router set in the address, even if &%user%& is not
20593 set for the transport. This makes it possible, for example, to run local mail
20594 delivery under the uid of the recipient (set by the router), but in a special
20595 group (set by the transport). For example:
20598 # User/group are set by check_local_user in this router
20602 transport = group_delivery
20605 # This transport overrides the group
20607 driver = appendfile
20608 file = /var/spool/mail/$local_part
20611 If &%user%& is set for a transport, its value overrides what is set in the
20612 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
20613 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
20616 .oindex "&%initgroups%&"
20617 When the uid is taken from the transport's configuration, the &[initgroups()]&
20618 function is called for the groups associated with that uid if the
20619 &%initgroups%& option is set for the transport. When the uid is not specified
20620 by the transport, but is associated with the address by a router, the option
20621 for calling &[initgroups()]& is taken from the router configuration.
20623 .cindex "&(pipe)& transport" "uid for"
20624 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
20625 is set and &%user%& is not set, the uid of the process that called Exim to
20626 receive the message is used, and if &%group%& is not set, the corresponding
20627 original gid is also used.
20629 This is the detailed preference order for obtaining a gid; the first of the
20630 following that is set is used:
20633 A &%group%& setting of the transport;
20635 A &%group%& setting of the router;
20637 A gid associated with a user setting of the router, either as a result of
20638 &%check_local_user%& or an explicit non-numeric &%user%& setting;
20640 The group associated with a non-numeric &%user%& setting of the transport;
20642 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
20643 the uid is the creator's uid;
20645 The Exim gid if the Exim uid is being used as a default.
20648 If, for example, the user is specified numerically on the router and there are
20649 no group settings, no gid is available. In this situation, an error occurs.
20650 This is different for the uid, for which there always is an ultimate default.
20651 The first of the following that is set is used:
20654 A &%user%& setting of the transport;
20656 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
20658 A &%user%& setting of the router;
20660 A &%check_local_user%& setting of the router;
20665 Of course, an error will still occur if the uid that is chosen is on the
20666 &%never_users%& list.
20672 .section "Current and home directories" "SECID132"
20673 .cindex "current directory for local transport"
20674 .cindex "home directory" "for local transport"
20675 .cindex "transport" "local; home directory for"
20676 .cindex "transport" "local; current directory for"
20677 Routers may set current and home directories for local transports by means of
20678 the &%transport_current_directory%& and &%transport_home_directory%& options.
20679 However, if the transport's &%current_directory%& or &%home_directory%& options
20680 are set, they override the router's values. In detail, the home directory
20681 for a local transport is taken from the first of these values that is set:
20684 The &%home_directory%& option on the transport;
20686 The &%transport_home_directory%& option on the router;
20688 The password data if &%check_local_user%& is set on the router;
20690 The &%router_home_directory%& option on the router.
20693 The current directory is taken from the first of these values that is set:
20696 The &%current_directory%& option on the transport;
20698 The &%transport_current_directory%& option on the router.
20702 If neither the router nor the transport sets a current directory, Exim uses the
20703 value of the home directory, if it is set. Otherwise it sets the current
20704 directory to &_/_& before running a local transport.
20708 .section "Expansion variables derived from the address" "SECID133"
20709 .vindex "&$domain$&"
20710 .vindex "&$local_part$&"
20711 .vindex "&$original_domain$&"
20712 Normally a local delivery is handling a single address, and in that case the
20713 variables such as &$domain$& and &$local_part$& are set during local
20714 deliveries. However, in some circumstances more than one address may be handled
20715 at once (for example, while writing batch SMTP for onward transmission by some
20716 other means). In this case, the variables associated with the local part are
20717 never set, &$domain$& is set only if all the addresses have the same domain,
20718 and &$original_domain$& is never set.
20719 .ecindex IIDenvlotra1
20720 .ecindex IIDenvlotra2
20721 .ecindex IIDenvlotra3
20729 . ////////////////////////////////////////////////////////////////////////////
20730 . ////////////////////////////////////////////////////////////////////////////
20732 .chapter "Generic options for transports" "CHAPtransportgeneric"
20733 .scindex IIDgenoptra1 "generic options" "transport"
20734 .scindex IIDgenoptra2 "options" "generic; for transports"
20735 .scindex IIDgenoptra3 "transport" "generic options for"
20736 The following generic options apply to all transports:
20739 .option body_only transports boolean false
20740 .cindex "transport" "body only"
20741 .cindex "message" "transporting body only"
20742 .cindex "body of message" "transporting"
20743 If this option is set, the message's headers are not transported. It is
20744 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
20745 or &(pipe)& transports, the settings of &%message_prefix%& and
20746 &%message_suffix%& should be checked, because this option does not
20747 automatically suppress them.
20750 .option current_directory transports string&!! unset
20751 .cindex "transport" "current directory for"
20752 This specifies the current directory that is to be set while running the
20753 transport, overriding any value that may have been set by the router.
20754 If the expansion fails for any reason, including forced failure, an error is
20755 logged, and delivery is deferred.
20758 .option disable_logging transports boolean false
20759 If this option is set true, nothing is logged for any
20760 deliveries by the transport or for any
20761 transport errors. You should not set this option unless you really, really know
20762 what you are doing.
20765 .option debug_print transports string&!! unset
20766 .cindex "testing" "variables in drivers"
20767 If this option is set and debugging is enabled (see the &%-d%& command line
20768 option), the string is expanded and included in the debugging output when the
20770 If expansion of the string fails, the error message is written to the debugging
20771 output, and Exim carries on processing.
20772 This facility is provided to help with checking out the values of variables and
20773 so on when debugging driver configurations. For example, if a &%headers_add%&
20774 option is not working properly, &%debug_print%& could be used to output the
20775 variables it references. A newline is added to the text if it does not end with
20777 The variables &$transport_name$& and &$router_name$& contain the name of the
20778 transport and the router that called it.
20780 .option delivery_date_add transports boolean false
20781 .cindex "&'Delivery-date:'& header line"
20782 If this option is true, a &'Delivery-date:'& header is added to the message.
20783 This gives the actual time the delivery was made. As this is not a standard
20784 header, Exim has a configuration option (&%delivery_date_remove%&) which
20785 requests its removal from incoming messages, so that delivered messages can
20786 safely be resent to other recipients.
20789 .option driver transports string unset
20790 This specifies which of the available transport drivers is to be used.
20791 There is no default, and this option must be set for every transport.
20794 .option envelope_to_add transports boolean false
20795 .cindex "&'Envelope-to:'& header line"
20796 If this option is true, an &'Envelope-to:'& header is added to the message.
20797 This gives the original address(es) in the incoming envelope that caused this
20798 delivery to happen. More than one address may be present if the transport is
20799 configured to handle several addresses at once, or if more than one original
20800 address was redirected to the same final address. As this is not a standard
20801 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20802 its removal from incoming messages, so that delivered messages can safely be
20803 resent to other recipients.
20806 .option event_action transports string&!! unset
20808 This option declares a string to be expanded for Exim's events mechanism.
20809 For details see &<<CHAPevents>>&.
20812 .option group transports string&!! "Exim group"
20813 .cindex "transport" "group; specifying"
20814 This option specifies a gid for running the transport process, overriding any
20815 value that the router supplies, and also overriding any value associated with
20816 &%user%& (see below).
20819 .option headers_add transports list&!! unset
20820 .cindex "header lines" "adding in transport"
20821 .cindex "transport" "header lines; adding"
20822 This option specifies a list of text headers,
20823 newline-separated (by default, changeable in the usual way),
20824 which are (separately) expanded and added to the header
20825 portion of a message as it is transported, as described in section
20826 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20827 routers. If the result of the expansion is an empty string, or if the expansion
20828 is forced to fail, no action is taken. Other expansion failures are treated as
20829 errors and cause the delivery to be deferred.
20831 Unlike most options, &%headers_add%& can be specified multiple times
20832 for a transport; all listed headers are added.
20835 .option headers_only transports boolean false
20836 .cindex "transport" "header lines only"
20837 .cindex "message" "transporting headers only"
20838 .cindex "header lines" "transporting"
20839 If this option is set, the message's body is not transported. It is mutually
20840 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20841 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20842 checked, since this option does not automatically suppress them.
20845 .option headers_remove transports list&!! unset
20846 .cindex "header lines" "removing"
20847 .cindex "transport" "header lines; removing"
20848 This option specifies a list of header names,
20849 colon-separated (by default, changeable in the usual way);
20850 these headers are omitted from the message as it is transported, as described
20851 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20853 Each list item is separately expanded.
20854 If the result of the expansion is an empty string, or if the expansion
20855 is forced to fail, no action is taken. Other expansion failures are treated as
20856 errors and cause the delivery to be deferred.
20858 Unlike most options, &%headers_remove%& can be specified multiple times
20859 for a transport; all listed headers are removed.
20861 &*Warning*&: Because of the separate expansion of the list items,
20862 items that contain a list separator must have it doubled.
20863 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
20867 .option headers_rewrite transports string unset
20868 .cindex "transport" "header lines; rewriting"
20869 .cindex "rewriting" "at transport time"
20870 This option allows addresses in header lines to be rewritten at transport time,
20871 that is, as the message is being copied to its destination. The contents of the
20872 option are a colon-separated list of rewriting rules. Each rule is in exactly
20873 the same form as one of the general rewriting rules that are applied when a
20874 message is received. These are described in chapter &<<CHAPrewrite>>&. For
20877 headers_rewrite = a@b c@d f : \
20880 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
20881 &'w@z'& in all address-bearing header lines. The rules are applied to the
20882 header lines just before they are written out at transport time, so they affect
20883 only those copies of the message that pass through the transport. However, only
20884 the message's original header lines, and any that were added by a system
20885 filter, are rewritten. If a router or transport adds header lines, they are not
20886 affected by this option. These rewriting rules are &'not'& applied to the
20887 envelope. You can change the return path using &%return_path%&, but you cannot
20888 change envelope recipients at this time.
20891 .option home_directory transports string&!! unset
20892 .cindex "transport" "home directory for"
20894 This option specifies a home directory setting for a local transport,
20895 overriding any value that may be set by the router. The home directory is
20896 placed in &$home$& while expanding the transport's private options. It is also
20897 used as the current directory if no current directory is set by the
20898 &%current_directory%& option on the transport or the
20899 &%transport_current_directory%& option on the router. If the expansion fails
20900 for any reason, including forced failure, an error is logged, and delivery is
20904 .option initgroups transports boolean false
20905 .cindex "additional groups"
20906 .cindex "groups" "additional"
20907 .cindex "transport" "group; additional"
20908 If this option is true and the uid for the delivery process is provided by the
20909 transport, the &[initgroups()]& function is called when running the transport
20910 to ensure that any additional groups associated with the uid are set up.
20913 .option max_parallel transports integer&!! unset
20914 .cindex limit "transport parallelism"
20915 .cindex transport "parallel processes"
20916 .cindex transport "concurrency limit"
20917 .cindex "delivery" "parallelism for transport"
20918 If this option is set and expands to an integer greater than zero
20919 it limits the number of concurrent runs of the transport.
20920 The control does not apply to shadow transports.
20922 .cindex "hints database" "transport concurrency control"
20923 Exim implements this control by means of a hints database in which a record is
20924 incremented whenever a transport process is beaing created. The record
20925 is decremented and possibly removed when the process terminates.
20926 Obviously there is scope for
20927 records to get left lying around if there is a system or program crash. To
20928 guard against this, Exim ignores any records that are more than six hours old.
20930 If you use this option, you should also arrange to delete the
20931 relevant hints database whenever your system reboots. The names of the files
20932 start with &_misc_& and they are kept in the &_spool/db_& directory. There
20933 may be one or two files, depending on the type of DBM in use. The same files
20934 are used for ETRN and smtp transport serialization.
20937 .option message_size_limit transports string&!! 0
20938 .cindex "limit" "message size per transport"
20939 .cindex "size" "of message, limit"
20940 .cindex "transport" "message size; limiting"
20941 This option controls the size of messages passed through the transport. It is
20942 expanded before use; the result of the expansion must be a sequence of decimal
20943 digits, optionally followed by K or M. If the expansion fails for any reason,
20944 including forced failure, or if the result is not of the required form,
20945 delivery is deferred. If the value is greater than zero and the size of a
20946 message exceeds this limit, the address is failed. If there is any chance that
20947 the resulting bounce message could be routed to the same transport, you should
20948 ensure that &%return_size_limit%& is less than the transport's
20949 &%message_size_limit%&, as otherwise the bounce message will fail to get
20954 .option rcpt_include_affixes transports boolean false
20955 .cindex "prefix" "for local part, including in envelope"
20956 .cindex "suffix for local part" "including in envelope"
20957 .cindex "local part" "prefix"
20958 .cindex "local part" "suffix"
20959 When this option is false (the default), and an address that has had any
20960 affixes (prefixes or suffixes) removed from the local part is delivered by any
20961 form of SMTP or LMTP, the affixes are not included. For example, if a router
20964 local_part_prefix = *-
20966 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
20969 RCPT TO:<xyz@some.domain>
20971 This is also the case when an ACL-time callout is being used to verify a
20972 recipient address. However, if &%rcpt_include_affixes%& is set true, the
20973 whole local part is included in the RCPT command. This option applies to BSMTP
20974 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
20975 &(lmtp)& and &(smtp)& transports.
20978 .option retry_use_local_part transports boolean "see below"
20979 .cindex "hints database" "retry keys"
20980 When a delivery suffers a temporary failure, a retry record is created
20981 in Exim's hints database. For remote deliveries, the key for the retry record
20982 is based on the name and/or IP address of the failing remote host. For local
20983 deliveries, the key is normally the entire address, including both the local
20984 part and the domain. This is suitable for most common cases of local delivery
20985 temporary failure &-- for example, exceeding a mailbox quota should delay only
20986 deliveries to that mailbox, not to the whole domain.
20988 However, in some special cases you may want to treat a temporary local delivery
20989 as a failure associated with the domain, and not with a particular local part.
20990 (For example, if you are storing all mail for some domain in files.) You can do
20991 this by setting &%retry_use_local_part%& false.
20993 For all the local transports, its default value is true. For remote transports,
20994 the default value is false for tidiness, but changing the value has no effect
20995 on a remote transport in the current implementation.
20998 .option return_path transports string&!! unset
20999 .cindex "envelope sender"
21000 .cindex "transport" "return path; changing"
21001 .cindex "return path" "changing in transport"
21002 If this option is set, the string is expanded at transport time and replaces
21003 the existing return path (envelope sender) value in the copy of the message
21004 that is being delivered. An empty return path is permitted. This feature is
21005 designed for remote deliveries, where the value of this option is used in the
21006 SMTP MAIL command. If you set &%return_path%& for a local transport, the
21007 only effect is to change the address that is placed in the &'Return-path:'&
21008 header line, if one is added to the message (see the next option).
21010 &*Note:*& A changed return path is not logged unless you add
21011 &%return_path_on_delivery%& to the log selector.
21013 .vindex "&$return_path$&"
21014 The expansion can refer to the existing value via &$return_path$&. This is
21015 either the message's envelope sender, or an address set by the
21016 &%errors_to%& option on a router. If the expansion is forced to fail, no
21017 replacement occurs; if it fails for another reason, delivery is deferred. This
21018 option can be used to support VERP (Variable Envelope Return Paths) &-- see
21019 section &<<SECTverp>>&.
21021 &*Note*&: If a delivery error is detected locally, including the case when a
21022 remote server rejects a message at SMTP time, the bounce message is not sent to
21023 the value of this option. It is sent to the previously set errors address.
21024 This defaults to the incoming sender address, but can be changed by setting
21025 &%errors_to%& in a router.
21029 .option return_path_add transports boolean false
21030 .cindex "&'Return-path:'& header line"
21031 If this option is true, a &'Return-path:'& header is added to the message.
21032 Although the return path is normally available in the prefix line of BSD
21033 mailboxes, this is commonly not displayed by MUAs, and so the user does not
21034 have easy access to it.
21036 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
21037 the delivery SMTP server makes the final delivery"&. This implies that this
21038 header should not be present in incoming messages. Exim has a configuration
21039 option, &%return_path_remove%&, which requests removal of this header from
21040 incoming messages, so that delivered messages can safely be resent to other
21044 .option shadow_condition transports string&!! unset
21045 See &%shadow_transport%& below.
21048 .option shadow_transport transports string unset
21049 .cindex "shadow transport"
21050 .cindex "transport" "shadow"
21051 A local transport may set the &%shadow_transport%& option to the name of
21052 another local transport. Shadow remote transports are not supported.
21054 Whenever a delivery to the main transport succeeds, and either
21055 &%shadow_condition%& is unset, or its expansion does not result in the empty
21056 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
21057 passed to the shadow transport, with the same delivery address or addresses. If
21058 expansion fails, no action is taken except that non-forced expansion failures
21059 cause a log line to be written.
21061 The result of the shadow transport is discarded and does not affect the
21062 subsequent processing of the message. Only a single level of shadowing is
21063 provided; the &%shadow_transport%& option is ignored on any transport when it
21064 is running as a shadow. Options concerned with output from pipes are also
21065 ignored. The log line for the successful delivery has an item added on the end,
21068 ST=<shadow transport name>
21070 If the shadow transport did not succeed, the error message is put in
21071 parentheses afterwards. Shadow transports can be used for a number of different
21072 purposes, including keeping more detailed log information than Exim normally
21073 provides, and implementing automatic acknowledgment policies based on message
21074 headers that some sites insist on.
21077 .option transport_filter transports string&!! unset
21078 .cindex "transport" "filter"
21079 .cindex "filter" "transport filter"
21080 This option sets up a filtering (in the Unix shell sense) process for messages
21081 at transport time. It should not be confused with mail filtering as set up by
21082 individual users or via a system filter.
21083 If unset, or expanding to an empty string, no filtering is done.
21085 When the message is about to be written out, the command specified by
21086 &%transport_filter%& is started up in a separate, parallel process, and
21087 the entire message, including the header lines, is passed to it on its standard
21088 input (this in fact is done from a third process, to avoid deadlock). The
21089 command must be specified as an absolute path.
21091 The lines of the message that are written to the transport filter are
21092 terminated by newline (&"\n"&). The message is passed to the filter before any
21093 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
21094 lines beginning with a dot, and also before any processing implied by the
21095 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
21096 &(pipe)& transports.
21098 The standard error for the filter process is set to the same destination as its
21099 standard output; this is read and written to the message's ultimate
21100 destination. The process that writes the message to the filter, the
21101 filter itself, and the original process that reads the result and delivers it
21102 are all run in parallel, like a shell pipeline.
21104 The filter can perform any transformations it likes, but of course should take
21105 care not to break RFC 2822 syntax. Exim does not check the result, except to
21106 test for a final newline when SMTP is in use. All messages transmitted over
21107 SMTP must end with a newline, so Exim supplies one if it is missing.
21109 .cindex "content scanning" "per user"
21110 A transport filter can be used to provide content-scanning on a per-user basis
21111 at delivery time if the only required effect of the scan is to modify the
21112 message. For example, a content scan could insert a new header line containing
21113 a spam score. This could be interpreted by a filter in the user's MUA. It is
21114 not possible to discard a message at this stage.
21116 .cindex "SMTP" "SIZE"
21117 A problem might arise if the filter increases the size of a message that is
21118 being sent down an SMTP connection. If the receiving SMTP server has indicated
21119 support for the SIZE parameter, Exim will have sent the size of the message
21120 at the start of the SMTP session. If what is actually sent is substantially
21121 more, the server might reject the message. This can be worked round by setting
21122 the &%size_addition%& option on the &(smtp)& transport, either to allow for
21123 additions to the message, or to disable the use of SIZE altogether.
21125 .vindex "&$pipe_addresses$&"
21126 The value of the &%transport_filter%& option is the command string for starting
21127 the filter, which is run directly from Exim, not under a shell. The string is
21128 parsed by Exim in the same way as a command string for the &(pipe)& transport:
21129 Exim breaks it up into arguments and then expands each argument separately (see
21130 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
21131 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
21132 of arguments, one for each address that applies to this delivery. (This isn't
21133 an ideal name for this feature here, but as it was already implemented for the
21134 &(pipe)& transport, it seemed sensible not to change it.)
21137 .vindex "&$host_address$&"
21138 The expansion variables &$host$& and &$host_address$& are available when the
21139 transport is a remote one. They contain the name and IP address of the host to
21140 which the message is being sent. For example:
21142 transport_filter = /some/directory/transport-filter.pl \
21143 $host $host_address $sender_address $pipe_addresses
21146 Two problems arise if you want to use more complicated expansion items to
21147 generate transport filter commands, both of which due to the fact that the
21148 command is split up &'before'& expansion.
21150 If an expansion item contains white space, you must quote it, so that it is all
21151 part of the same command item. If the entire option setting is one such
21152 expansion item, you have to take care what kind of quoting you use. For
21155 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
21157 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
21158 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
21159 stripped by Exim when it read the option's value. When the value is used, if
21160 the single quotes were missing, the line would be split into two items,
21161 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
21162 Exim tried to expand the first one.
21164 Except for the special case of &$pipe_addresses$& that is mentioned above, an
21165 expansion cannot generate multiple arguments, or a command name followed by
21166 arguments. Consider this example:
21168 transport_filter = ${lookup{$host}lsearch{/a/file}\
21169 {$value}{/bin/cat}}
21171 The result of the lookup is interpreted as the name of the command, even
21172 if it contains white space. The simplest way round this is to use a shell:
21174 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
21175 {$value}{/bin/cat}}
21179 The filter process is run under the same uid and gid as the normal delivery.
21180 For remote deliveries this is the Exim uid/gid by default. The command should
21181 normally yield a zero return code. Transport filters are not supposed to fail.
21182 A non-zero code is taken to mean that the transport filter encountered some
21183 serious problem. Delivery of the message is deferred; the message remains on
21184 the queue and is tried again later. It is not possible to cause a message to be
21185 bounced from a transport filter.
21187 If a transport filter is set on an autoreply transport, the original message is
21188 passed through the filter as it is being copied into the newly generated
21189 message, which happens if the &%return_message%& option is set.
21192 .option transport_filter_timeout transports time 5m
21193 .cindex "transport" "filter, timeout"
21194 When Exim is reading the output of a transport filter, it applies a timeout
21195 that can be set by this option. Exceeding the timeout is normally treated as a
21196 temporary delivery failure. However, if a transport filter is used with a
21197 &(pipe)& transport, a timeout in the transport filter is treated in the same
21198 way as a timeout in the pipe command itself. By default, a timeout is a hard
21199 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
21200 becomes a temporary error.
21203 .option user transports string&!! "Exim user"
21204 .cindex "uid (user id)" "local delivery"
21205 .cindex "transport" "user, specifying"
21206 This option specifies the user under whose uid the delivery process is to be
21207 run, overriding any uid that may have been set by the router. If the user is
21208 given as a name, the uid is looked up from the password data, and the
21209 associated group is taken as the value of the gid to be used if the &%group%&
21212 For deliveries that use local transports, a user and group are normally
21213 specified explicitly or implicitly (for example, as a result of
21214 &%check_local_user%&) by the router or transport.
21216 .cindex "hints database" "access by remote transport"
21217 For remote transports, you should leave this option unset unless you really are
21218 sure you know what you are doing. When a remote transport is running, it needs
21219 to be able to access Exim's hints databases, because each host may have its own
21221 .ecindex IIDgenoptra1
21222 .ecindex IIDgenoptra2
21223 .ecindex IIDgenoptra3
21230 . ////////////////////////////////////////////////////////////////////////////
21231 . ////////////////////////////////////////////////////////////////////////////
21233 .chapter "Address batching in local transports" "CHAPbatching" &&&
21235 .cindex "transport" "local; address batching in"
21236 The only remote transport (&(smtp)&) is normally configured to handle more than
21237 one address at a time, so that when several addresses are routed to the same
21238 remote host, just one copy of the message is sent. Local transports, however,
21239 normally handle one address at a time. That is, a separate instance of the
21240 transport is run for each address that is routed to the transport. A separate
21241 copy of the message is delivered each time.
21243 .cindex "batched local delivery"
21244 .oindex "&%batch_max%&"
21245 .oindex "&%batch_id%&"
21246 In special cases, it may be desirable to handle several addresses at once in a
21247 local transport, for example:
21250 In an &(appendfile)& transport, when storing messages in files for later
21251 delivery by some other means, a single copy of the message with multiple
21252 recipients saves space.
21254 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21255 a single copy saves time, and is the normal way LMTP is expected to work.
21257 In a &(pipe)& transport, when passing the message
21258 to a scanner program or
21259 to some other delivery mechanism such as UUCP, multiple recipients may be
21263 These three local transports all have the same options for controlling multiple
21264 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21265 repeating the information for each transport, these options are described here.
21267 The &%batch_max%& option specifies the maximum number of addresses that can be
21268 delivered together in a single run of the transport. Its default value is one
21269 (no batching). When more than one address is routed to a transport that has a
21270 &%batch_max%& value greater than one, the addresses are delivered in a batch
21271 (that is, in a single run of the transport with multiple recipients), subject
21272 to certain conditions:
21275 .vindex "&$local_part$&"
21276 If any of the transport's options contain a reference to &$local_part$&, no
21277 batching is possible.
21279 .vindex "&$domain$&"
21280 If any of the transport's options contain a reference to &$domain$&, only
21281 addresses with the same domain are batched.
21283 .cindex "customizing" "batching condition"
21284 If &%batch_id%& is set, it is expanded for each address, and only those
21285 addresses with the same expanded value are batched. This allows you to specify
21286 customized batching conditions. Failure of the expansion for any reason,
21287 including forced failure, disables batching, but it does not stop the delivery
21290 Batched addresses must also have the same errors address (where to send
21291 delivery errors), the same header additions and removals, the same user and
21292 group for the transport, and if a host list is present, the first host must
21296 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21297 both when the file or pipe command is specified in the transport, and when it
21298 is specified by a &(redirect)& router, but all the batched addresses must of
21299 course be routed to the same file or pipe command. These two transports have an
21300 option called &%use_bsmtp%&, which causes them to deliver the message in
21301 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21302 &%check_string%& and &%escape_string%& options are forced to the values
21305 escape_string = ".."
21307 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21308 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21309 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21311 .cindex "&'Envelope-to:'& header line"
21312 If the generic &%envelope_to_add%& option is set for a batching transport, the
21313 &'Envelope-to:'& header that is added to the message contains all the addresses
21314 that are being processed together. If you are using a batching &(appendfile)&
21315 transport without &%use_bsmtp%&, the only way to preserve the recipient
21316 addresses is to set the &%envelope_to_add%& option.
21318 .cindex "&(pipe)& transport" "with multiple addresses"
21319 .vindex "&$pipe_addresses$&"
21320 If you are using a &(pipe)& transport without BSMTP, and setting the
21321 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21322 the command. This is not a true variable; it is a bit of magic that causes each
21323 of the recipient addresses to be inserted into the command as a separate
21324 argument. This provides a way of accessing all the addresses that are being
21325 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21326 are specified by a &(redirect)& router.
21331 . ////////////////////////////////////////////////////////////////////////////
21332 . ////////////////////////////////////////////////////////////////////////////
21334 .chapter "The appendfile transport" "CHAPappendfile"
21335 .scindex IIDapptra1 "&(appendfile)& transport"
21336 .scindex IIDapptra2 "transports" "&(appendfile)&"
21337 .cindex "directory creation"
21338 .cindex "creating directories"
21339 The &(appendfile)& transport delivers a message by appending it to an existing
21340 file, or by creating an entirely new file in a specified directory. Single
21341 files to which messages are appended can be in the traditional Unix mailbox
21342 format, or optionally in the MBX format supported by the Pine MUA and
21343 University of Washington IMAP daemon, &'inter alia'&. When each message is
21344 being delivered as a separate file, &"maildir"& format can optionally be used
21345 to give added protection against failures that happen part-way through the
21346 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21347 supported. For all file formats, Exim attempts to create as many levels of
21348 directory as necessary, provided that &%create_directory%& is set.
21350 The code for the optional formats is not included in the Exim binary by
21351 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21352 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21355 .cindex "quota" "system"
21356 Exim recognizes system quota errors, and generates an appropriate message. Exim
21357 also supports its own quota control within the transport, for use when the
21358 system facility is unavailable or cannot be used for some reason.
21360 If there is an error while appending to a file (for example, quota exceeded or
21361 partition filled), Exim attempts to reset the file's length and last
21362 modification time back to what they were before. If there is an error while
21363 creating an entirely new file, the new file is removed.
21365 Before appending to a file, a number of security checks are made, and the
21366 file is locked. A detailed description is given below, after the list of
21369 The &(appendfile)& transport is most commonly used for local deliveries to
21370 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21371 putting messages into files for remote delivery by some means other than Exim.
21372 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21377 .section "The file and directory options" "SECTfildiropt"
21378 The &%file%& option specifies a single file, to which the message is appended;
21379 the &%directory%& option specifies a directory, in which a new file containing
21380 the message is created. Only one of these two options can be set, and for
21381 normal deliveries to mailboxes, one of them &'must'& be set.
21383 .vindex "&$address_file$&"
21384 .vindex "&$local_part$&"
21385 However, &(appendfile)& is also used for delivering messages to files or
21386 directories whose names (or parts of names) are obtained from alias,
21387 forwarding, or filtering operations (for example, a &%save%& command in a
21388 user's Exim filter). When such a transport is running, &$local_part$& contains
21389 the local part that was aliased or forwarded, and &$address_file$& contains the
21390 name (or partial name) of the file or directory generated by the redirection
21391 operation. There are two cases:
21394 If neither &%file%& nor &%directory%& is set, the redirection operation
21395 must specify an absolute path (one that begins with &`/`&). This is the most
21396 common case when users with local accounts use filtering to sort mail into
21397 different folders. See for example, the &(address_file)& transport in the
21398 default configuration. If the path ends with a slash, it is assumed to be the
21399 name of a directory. A delivery to a directory can also be forced by setting
21400 &%maildir_format%& or &%mailstore_format%&.
21402 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21403 used to determine the file or directory name for the delivery. Normally, the
21404 contents of &$address_file$& are used in some way in the string expansion.
21408 .cindex "Sieve filter" "configuring &(appendfile)&"
21409 .cindex "Sieve filter" "relative mailbox path handling"
21410 As an example of the second case, consider an environment where users do not
21411 have home directories. They may be permitted to use Exim filter commands of the
21416 or Sieve filter commands of the form:
21418 require "fileinto";
21419 fileinto "folder23";
21421 In this situation, the expansion of &%file%& or &%directory%& in the transport
21422 must transform the relative path into an appropriate absolute file name. In the
21423 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21424 is used as a result of a &"keep"& action in the filter. This example shows one
21425 way of handling this requirement:
21427 file = ${if eq{$address_file}{inbox} \
21428 {/var/mail/$local_part} \
21429 {${if eq{${substr_0_1:$address_file}}{/} \
21431 {$home/mail/$address_file} \
21435 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21436 location, absolute paths are used without change, and other folders are in the
21437 &_mail_& directory within the home directory.
21439 &*Note 1*&: While processing an Exim filter, a relative path such as
21440 &_folder23_& is turned into an absolute path if a home directory is known to
21441 the router. In particular, this is the case if &%check_local_user%& is set. If
21442 you want to prevent this happening at routing time, you can set
21443 &%router_home_directory%& empty. This forces the router to pass the relative
21444 path to the transport.
21446 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21447 the &%file%& or &%directory%& option is still used if it is set.
21452 .section "Private options for appendfile" "SECID134"
21453 .cindex "options" "&(appendfile)& transport"
21457 .option allow_fifo appendfile boolean false
21458 .cindex "fifo (named pipe)"
21459 .cindex "named pipe (fifo)"
21460 .cindex "pipe" "named (fifo)"
21461 Setting this option permits delivery to named pipes (FIFOs) as well as to
21462 regular files. If no process is reading the named pipe at delivery time, the
21463 delivery is deferred.
21466 .option allow_symlink appendfile boolean false
21467 .cindex "symbolic link" "to mailbox"
21468 .cindex "mailbox" "symbolic link"
21469 By default, &(appendfile)& will not deliver if the path name for the file is
21470 that of a symbolic link. Setting this option relaxes that constraint, but there
21471 are security issues involved in the use of symbolic links. Be sure you know
21472 what you are doing if you set this. Details of exactly what this option affects
21473 are included in the discussion which follows this list of options.
21476 .option batch_id appendfile string&!! unset
21477 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21478 However, batching is automatically disabled for &(appendfile)& deliveries that
21479 happen as a result of forwarding or aliasing or other redirection directly to a
21483 .option batch_max appendfile integer 1
21484 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21487 .option check_group appendfile boolean false
21488 When this option is set, the group owner of the file defined by the &%file%&
21489 option is checked to see that it is the same as the group under which the
21490 delivery process is running. The default setting is false because the default
21491 file mode is 0600, which means that the group is irrelevant.
21494 .option check_owner appendfile boolean true
21495 When this option is set, the owner of the file defined by the &%file%& option
21496 is checked to ensure that it is the same as the user under which the delivery
21497 process is running.
21500 .option check_string appendfile string "see below"
21501 .cindex "&""From""& line"
21502 As &(appendfile)& writes the message, the start of each line is tested for
21503 matching &%check_string%&, and if it does, the initial matching characters are
21504 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21505 a literal string, not a regular expression, and the case of any letters it
21506 contains is significant.
21508 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21509 are forced to &"."& and &".."& respectively, and any settings in the
21510 configuration are ignored. Otherwise, they default to &"From&~"& and
21511 &">From&~"& when the &%file%& option is set, and unset when any of the
21512 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21514 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21515 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21516 &"From&~"& indicates the start of a new message. All four options need changing
21517 if another format is used. For example, to deliver to mailboxes in MMDF format:
21518 .cindex "MMDF format mailbox"
21519 .cindex "mailbox" "MMDF format"
21521 check_string = "\1\1\1\1\n"
21522 escape_string = "\1\1\1\1 \n"
21523 message_prefix = "\1\1\1\1\n"
21524 message_suffix = "\1\1\1\1\n"
21526 .option create_directory appendfile boolean true
21527 .cindex "directory creation"
21528 When this option is true, Exim attempts to create any missing superior
21529 directories for the file that it is about to write. A created directory's mode
21530 is given by the &%directory_mode%& option.
21532 The group ownership of a newly created directory is highly dependent on the
21533 operating system (and possibly the file system) that is being used. For
21534 example, in Solaris, if the parent directory has the setgid bit set, its group
21535 is propagated to the child; if not, the currently set group is used. However,
21536 in FreeBSD, the parent's group is always used.
21540 .option create_file appendfile string anywhere
21541 This option constrains the location of files and directories that are created
21542 by this transport. It applies to files defined by the &%file%& option and
21543 directories defined by the &%directory%& option. In the case of maildir
21544 delivery, it applies to the top level directory, not the maildir directories
21547 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
21548 &"belowhome"&. In the second and third cases, a home directory must have been
21549 set for the transport. This option is not useful when an explicit file name is
21550 given for normal mailbox deliveries. It is intended for the case when file
21551 names are generated from users' &_.forward_& files. These are usually handled
21552 by an &(appendfile)& transport called &%address_file%&. See also
21553 &%file_must_exist%&.
21556 .option directory appendfile string&!! unset
21557 This option is mutually exclusive with the &%file%& option, but one of &%file%&
21558 or &%directory%& must be set, unless the delivery is the direct result of a
21559 redirection (see section &<<SECTfildiropt>>&).
21561 When &%directory%& is set, the string is expanded, and the message is delivered
21562 into a new file or files in or below the given directory, instead of being
21563 appended to a single mailbox file. A number of different formats are provided
21564 (see &%maildir_format%& and &%mailstore_format%&), and see section
21565 &<<SECTopdir>>& for further details of this form of delivery.
21568 .option directory_file appendfile string&!! "see below"
21570 .vindex "&$inode$&"
21571 When &%directory%& is set, but neither &%maildir_format%& nor
21572 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
21573 whose name is obtained by expanding this string. The default value is:
21575 q${base62:$tod_epoch}-$inode
21577 This generates a unique name from the current time, in base 62 form, and the
21578 inode of the file. The variable &$inode$& is available only when expanding this
21582 .option directory_mode appendfile "octal integer" 0700
21583 If &(appendfile)& creates any directories as a result of the
21584 &%create_directory%& option, their mode is specified by this option.
21587 .option escape_string appendfile string "see description"
21588 See &%check_string%& above.
21591 .option file appendfile string&!! unset
21592 This option is mutually exclusive with the &%directory%& option, but one of
21593 &%file%& or &%directory%& must be set, unless the delivery is the direct result
21594 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
21595 specifies a single file, to which the message is appended. One or more of
21596 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
21599 .cindex "NFS" "lock file"
21600 .cindex "locking files"
21601 .cindex "lock files"
21602 If you are using more than one host to deliver over NFS into the same
21603 mailboxes, you should always use lock files.
21605 The string value is expanded for each delivery, and must yield an absolute
21606 path. The most common settings of this option are variations on one of these
21609 file = /var/spool/mail/$local_part
21610 file = /home/$local_part/inbox
21613 .cindex "&""sticky""& bit"
21614 In the first example, all deliveries are done into the same directory. If Exim
21615 is configured to use lock files (see &%use_lockfile%& below) it must be able to
21616 create a file in the directory, so the &"sticky"& bit must be turned on for
21617 deliveries to be possible, or alternatively the &%group%& option can be used to
21618 run the delivery under a group id which has write access to the directory.
21622 .option file_format appendfile string unset
21623 .cindex "file" "mailbox; checking existing format"
21624 This option requests the transport to check the format of an existing file
21625 before adding to it. The check consists of matching a specific string at the
21626 start of the file. The value of the option consists of an even number of
21627 colon-separated strings. The first of each pair is the test string, and the
21628 second is the name of a transport. If the transport associated with a matched
21629 string is not the current transport, control is passed over to the other
21630 transport. For example, suppose the standard &(local_delivery)& transport has
21633 file_format = "From : local_delivery :\
21634 \1\1\1\1\n : local_mmdf_delivery"
21636 Mailboxes that begin with &"From"& are still handled by this transport, but if
21637 a mailbox begins with four binary ones followed by a newline, control is passed
21638 to a transport called &%local_mmdf_delivery%&, which presumably is configured
21639 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
21640 is assumed to match the current transport. If the start of a mailbox doesn't
21641 match any string, or if the transport named for a given string is not defined,
21642 delivery is deferred.
21645 .option file_must_exist appendfile boolean false
21646 If this option is true, the file specified by the &%file%& option must exist.
21647 A temporary error occurs if it does not, causing delivery to be deferred.
21648 If this option is false, the file is created if it does not exist.
21651 .option lock_fcntl_timeout appendfile time 0s
21652 .cindex "timeout" "mailbox locking"
21653 .cindex "mailbox" "locking, blocking and non-blocking"
21654 .cindex "locking files"
21655 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
21656 when locking an open mailbox file. If the call fails, the delivery process
21657 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
21658 Non-blocking calls are used so that the file is not kept open during the wait
21659 for the lock; the reason for this is to make it as safe as possible for
21660 deliveries over NFS in the case when processes might be accessing an NFS
21661 mailbox without using a lock file. This should not be done, but
21662 misunderstandings and hence misconfigurations are not unknown.
21664 On a busy system, however, the performance of a non-blocking lock approach is
21665 not as good as using a blocking lock with a timeout. In this case, the waiting
21666 is done inside the system call, and Exim's delivery process acquires the lock
21667 and can proceed as soon as the previous lock holder releases it.
21669 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
21670 timeout, are used. There may still be some retrying: the maximum number of
21673 (lock_retries * lock_interval) / lock_fcntl_timeout
21675 rounded up to the next whole number. In other words, the total time during
21676 which &(appendfile)& is trying to get a lock is roughly the same, unless
21677 &%lock_fcntl_timeout%& is set very large.
21679 You should consider setting this option if you are getting a lot of delayed
21680 local deliveries because of errors of the form
21682 failed to lock mailbox /some/file (fcntl)
21685 .option lock_flock_timeout appendfile time 0s
21686 This timeout applies to file locking when using &[flock()]& (see
21687 &%use_flock%&); the timeout operates in a similar manner to
21688 &%lock_fcntl_timeout%&.
21691 .option lock_interval appendfile time 3s
21692 This specifies the time to wait between attempts to lock the file. See below
21693 for details of locking.
21696 .option lock_retries appendfile integer 10
21697 This specifies the maximum number of attempts to lock the file. A value of zero
21698 is treated as 1. See below for details of locking.
21701 .option lockfile_mode appendfile "octal integer" 0600
21702 This specifies the mode of the created lock file, when a lock file is being
21703 used (see &%use_lockfile%& and &%use_mbx_lock%&).
21706 .option lockfile_timeout appendfile time 30m
21707 .cindex "timeout" "mailbox locking"
21708 When a lock file is being used (see &%use_lockfile%&), if a lock file already
21709 exists and is older than this value, it is assumed to have been left behind by
21710 accident, and Exim attempts to remove it.
21713 .option mailbox_filecount appendfile string&!! unset
21714 .cindex "mailbox" "specifying size of"
21715 .cindex "size" "of mailbox"
21716 If this option is set, it is expanded, and the result is taken as the current
21717 number of files in the mailbox. It must be a decimal number, optionally
21718 followed by K or M. This provides a way of obtaining this information from an
21719 external source that maintains the data.
21722 .option mailbox_size appendfile string&!! unset
21723 .cindex "mailbox" "specifying size of"
21724 .cindex "size" "of mailbox"
21725 If this option is set, it is expanded, and the result is taken as the current
21726 size the mailbox. It must be a decimal number, optionally followed by K or M.
21727 This provides a way of obtaining this information from an external source that
21728 maintains the data. This is likely to be helpful for maildir deliveries where
21729 it is computationally expensive to compute the size of a mailbox.
21733 .option maildir_format appendfile boolean false
21734 .cindex "maildir format" "specifying"
21735 If this option is set with the &%directory%& option, the delivery is into a new
21736 file, in the &"maildir"& format that is used by other mail software. When the
21737 transport is activated directly from a &(redirect)& router (for example, the
21738 &(address_file)& transport in the default configuration), setting
21739 &%maildir_format%& causes the path received from the router to be treated as a
21740 directory, whether or not it ends with &`/`&. This option is available only if
21741 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
21742 &<<SECTmaildirdelivery>>& below for further details.
21745 .option maildir_quota_directory_regex appendfile string "See below"
21746 .cindex "maildir format" "quota; directories included in"
21747 .cindex "quota" "maildir; directories included in"
21748 This option is relevant only when &%maildir_use_size_file%& is set. It defines
21749 a regular expression for specifying directories, relative to the quota
21750 directory (see &%quota_directory%&), that should be included in the quota
21751 calculation. The default value is:
21753 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
21755 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
21756 (directories whose names begin with a dot). If you want to exclude the
21758 folder from the count (as some sites do), you need to change this setting to
21760 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
21762 This uses a negative lookahead in the regular expression to exclude the
21763 directory whose name is &_.Trash_&. When a directory is excluded from quota
21764 calculations, quota processing is bypassed for any messages that are delivered
21765 directly into that directory.
21768 .option maildir_retries appendfile integer 10
21769 This option specifies the number of times to retry when writing a file in
21770 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
21773 .option maildir_tag appendfile string&!! unset
21774 This option applies only to deliveries in maildir format, and is described in
21775 section &<<SECTmaildirdelivery>>& below.
21778 .option maildir_use_size_file appendfile&!! boolean false
21779 .cindex "maildir format" "&_maildirsize_& file"
21780 The result of string expansion for this option must be a valid boolean value.
21781 If it is true, it enables support for &_maildirsize_& files. Exim
21782 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
21783 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
21784 value is zero. See &%maildir_quota_directory_regex%& above and section
21785 &<<SECTmaildirdelivery>>& below for further details.
21787 .option maildirfolder_create_regex appendfile string unset
21788 .cindex "maildir format" "&_maildirfolder_& file"
21789 .cindex "&_maildirfolder_&, creating"
21790 The value of this option is a regular expression. If it is unset, it has no
21791 effect. Otherwise, before a maildir delivery takes place, the pattern is
21792 matched against the name of the maildir directory, that is, the directory
21793 containing the &_new_& and &_tmp_& subdirectories that will be used for the
21794 delivery. If there is a match, Exim checks for the existence of a file called
21795 &_maildirfolder_& in the directory, and creates it if it does not exist.
21796 See section &<<SECTmaildirdelivery>>& for more details.
21799 .option mailstore_format appendfile boolean false
21800 .cindex "mailstore format" "specifying"
21801 If this option is set with the &%directory%& option, the delivery is into two
21802 new files in &"mailstore"& format. The option is available only if
21803 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
21804 below for further details.
21807 .option mailstore_prefix appendfile string&!! unset
21808 This option applies only to deliveries in mailstore format, and is described in
21809 section &<<SECTopdir>>& below.
21812 .option mailstore_suffix appendfile string&!! unset
21813 This option applies only to deliveries in mailstore format, and is described in
21814 section &<<SECTopdir>>& below.
21817 .option mbx_format appendfile boolean false
21818 .cindex "locking files"
21819 .cindex "file" "locking"
21820 .cindex "file" "MBX format"
21821 .cindex "MBX format, specifying"
21822 This option is available only if Exim has been compiled with SUPPORT_MBX
21823 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
21824 the message is appended to the mailbox file in MBX format instead of
21825 traditional Unix format. This format is supported by Pine4 and its associated
21826 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
21828 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
21829 automatically changed by the use of &%mbx_format%&. They should normally be set
21830 empty when using MBX format, so this option almost always appears in this
21837 If none of the locking options are mentioned in the configuration,
21838 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21839 is possible to specify the other kinds of locking with &%mbx_format%&, but
21840 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21841 interworks with &'c-client'&, providing for shared access to the mailbox. It
21842 should not be used if any program that does not use this form of locking is
21843 going to access the mailbox, nor should it be used if the mailbox file is NFS
21844 mounted, because it works only when the mailbox is accessed from a single host.
21846 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21847 the standard version of &'c-client'&, because as long as it has a mailbox open
21848 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21849 append messages to it.
21852 .option message_prefix appendfile string&!! "see below"
21853 .cindex "&""From""& line"
21854 The string specified here is expanded and output at the start of every message.
21855 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21856 in which case it is:
21858 message_prefix = "From ${if def:return_path{$return_path}\
21859 {MAILER-DAEMON}} $tod_bsdinbox\n"
21861 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21862 &`\n`& to &`\r\n`& in &%message_prefix%&.
21864 .option message_suffix appendfile string&!! "see below"
21865 The string specified here is expanded and output at the end of every message.
21866 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21867 in which case it is a single newline character. The suffix can be suppressed by
21872 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21873 &`\n`& to &`\r\n`& in &%message_suffix%&.
21875 .option mode appendfile "octal integer" 0600
21876 If the output file is created, it is given this mode. If it already exists and
21877 has wider permissions, they are reduced to this mode. If it has narrower
21878 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
21879 if the delivery is the result of a &%save%& command in a filter file specifying
21880 a particular mode, the mode of the output file is always forced to take that
21881 value, and this option is ignored.
21884 .option mode_fail_narrower appendfile boolean true
21885 This option applies in the case when an existing mailbox file has a narrower
21886 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
21887 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
21888 continues with the delivery attempt, using the existing mode of the file.
21891 .option notify_comsat appendfile boolean false
21892 If this option is true, the &'comsat'& daemon is notified after every
21893 successful delivery to a user mailbox. This is the daemon that notifies logged
21894 on users about incoming mail.
21897 .option quota appendfile string&!! unset
21898 .cindex "quota" "imposed by Exim"
21899 This option imposes a limit on the size of the file to which Exim is appending,
21900 or to the total space used in the directory tree when the &%directory%& option
21901 is set. In the latter case, computation of the space used is expensive, because
21902 all the files in the directory (and any sub-directories) have to be
21903 individually inspected and their sizes summed. (See &%quota_size_regex%& and
21904 &%maildir_use_size_file%& for ways to avoid this in environments where users
21905 have no shell access to their mailboxes).
21907 As there is no interlock against two simultaneous deliveries into a
21908 multi-file mailbox, it is possible for the quota to be overrun in this case.
21909 For single-file mailboxes, of course, an interlock is a necessity.
21911 A file's size is taken as its &'used'& value. Because of blocking effects, this
21912 may be a lot less than the actual amount of disk space allocated to the file.
21913 If the sizes of a number of files are being added up, the rounding effect can
21914 become quite noticeable, especially on systems that have large block sizes.
21915 Nevertheless, it seems best to stick to the &'used'& figure, because this is
21916 the obvious value which users understand most easily.
21918 The value of the option is expanded, and must then be a numerical value
21919 (decimal point allowed), optionally followed by one of the letters K, M, or G,
21920 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
21921 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
21924 &*Note*&: A value of zero is interpreted as &"no quota"&.
21926 The expansion happens while Exim is running as root, before it changes uid for
21927 the delivery. This means that files that are inaccessible to the end user can
21928 be used to hold quota values that are looked up in the expansion. When delivery
21929 fails because this quota is exceeded, the handling of the error is as for
21930 system quota failures.
21932 By default, Exim's quota checking mimics system quotas, and restricts the
21933 mailbox to the specified maximum size, though the value is not accurate to the
21934 last byte, owing to separator lines and additional headers that may get added
21935 during message delivery. When a mailbox is nearly full, large messages may get
21936 refused even though small ones are accepted, because the size of the current
21937 message is added to the quota when the check is made. This behaviour can be
21938 changed by setting &%quota_is_inclusive%& false. When this is done, the check
21939 for exceeding the quota does not include the current message. Thus, deliveries
21940 continue until the quota has been exceeded; thereafter, no further messages are
21941 delivered. See also &%quota_warn_threshold%&.
21944 .option quota_directory appendfile string&!! unset
21945 This option defines the directory to check for quota purposes when delivering
21946 into individual files. The default is the delivery directory, or, if a file
21947 called &_maildirfolder_& exists in a maildir directory, the parent of the
21948 delivery directory.
21951 .option quota_filecount appendfile string&!! 0
21952 This option applies when the &%directory%& option is set. It limits the total
21953 number of files in the directory (compare the inode limit in system quotas). It
21954 can only be used if &%quota%& is also set. The value is expanded; an expansion
21955 failure causes delivery to be deferred. A value of zero is interpreted as
21959 .option quota_is_inclusive appendfile boolean true
21960 See &%quota%& above.
21963 .option quota_size_regex appendfile string unset
21964 This option applies when one of the delivery modes that writes a separate file
21965 for each message is being used. When Exim wants to find the size of one of
21966 these files in order to test the quota, it first checks &%quota_size_regex%&.
21967 If this is set to a regular expression that matches the file name, and it
21968 captures one string, that string is interpreted as a representation of the
21969 file's size. The value of &%quota_size_regex%& is not expanded.
21971 This feature is useful only when users have no shell access to their mailboxes
21972 &-- otherwise they could defeat the quota simply by renaming the files. This
21973 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
21974 the file length to the file name. For example:
21976 maildir_tag = ,S=$message_size
21977 quota_size_regex = ,S=(\d+)
21979 An alternative to &$message_size$& is &$message_linecount$&, which contains the
21980 number of lines in the message.
21982 The regular expression should not assume that the length is at the end of the
21983 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
21984 sometimes add other information onto the ends of message file names.
21986 Section &<<SECID136>>& contains further information.
21989 .option quota_warn_message appendfile string&!! "see below"
21990 See below for the use of this option. If it is not set when
21991 &%quota_warn_threshold%& is set, it defaults to
21993 quota_warn_message = "\
21994 To: $local_part@$domain\n\
21995 Subject: Your mailbox\n\n\
21996 This message is automatically created \
21997 by mail delivery software.\n\n\
21998 The size of your mailbox has exceeded \
21999 a warning threshold that is\n\
22000 set by the system administrator.\n"
22004 .option quota_warn_threshold appendfile string&!! 0
22005 .cindex "quota" "warning threshold"
22006 .cindex "mailbox" "size warning"
22007 .cindex "size" "of mailbox"
22008 This option is expanded in the same way as &%quota%& (see above). If the
22009 resulting value is greater than zero, and delivery of the message causes the
22010 size of the file or total space in the directory tree to cross the given
22011 threshold, a warning message is sent. If &%quota%& is also set, the threshold
22012 may be specified as a percentage of it by following the value with a percent
22016 quota_warn_threshold = 75%
22018 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
22019 percent sign is ignored.
22021 The warning message itself is specified by the &%quota_warn_message%& option,
22022 and it must start with a &'To:'& header line containing the recipient(s) of the
22023 warning message. These do not necessarily have to include the recipient(s) of
22024 the original message. A &'Subject:'& line should also normally be supplied. You
22025 can include any other header lines that you want. If you do not include a
22026 &'From:'& line, the default is:
22028 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
22030 .oindex &%errors_reply_to%&
22031 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
22034 The &%quota%& option does not have to be set in order to use this option; they
22035 are independent of one another except when the threshold is specified as a
22039 .option use_bsmtp appendfile boolean false
22040 .cindex "envelope sender"
22041 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
22042 format, with the envelope sender and recipient(s) included as SMTP commands. If
22043 you want to include a leading HELO command with such messages, you can do
22044 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
22045 for details of batch SMTP.
22048 .option use_crlf appendfile boolean false
22049 .cindex "carriage return"
22051 This option causes lines to be terminated with the two-character CRLF sequence
22052 (carriage return, linefeed) instead of just a linefeed character. In the case
22053 of batched SMTP, the byte sequence written to the file is then an exact image
22054 of what would be sent down a real SMTP connection.
22056 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
22057 (which are used to supply the traditional &"From&~"& and blank line separators
22058 in Berkeley-style mailboxes) are written verbatim, so must contain their own
22059 carriage return characters if these are needed. In cases where these options
22060 have non-empty defaults, the values end with a single linefeed, so they must be
22061 changed to end with &`\r\n`& if &%use_crlf%& is set.
22064 .option use_fcntl_lock appendfile boolean "see below"
22065 This option controls the use of the &[fcntl()]& function to lock a file for
22066 exclusive use when a message is being appended. It is set by default unless
22067 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
22068 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
22069 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
22072 .option use_flock_lock appendfile boolean false
22073 This option is provided to support the use of &[flock()]& for file locking, for
22074 the few situations where it is needed. Most modern operating systems support
22075 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
22076 each other. Exim uses &[fcntl()]& locking by default.
22078 This option is required only if you are using an operating system where
22079 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
22080 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
22081 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
22083 .cindex "Solaris" "&[flock()]& support"
22084 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
22085 have it (and some, I think, provide a not quite right version built on top of
22086 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
22087 the ability to use it, and any attempt to do so will cause a configuration
22090 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
22091 is just being mapped onto &[fcntl()]& by the OS).
22094 .option use_lockfile appendfile boolean "see below"
22095 If this option is turned off, Exim does not attempt to create a lock file when
22096 appending to a mailbox file. In this situation, the only locking is by
22097 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
22098 sure that every MUA that is ever going to look at your users' mailboxes uses
22099 &[fcntl()]& rather than a lock file, and even then only when you are not
22100 delivering over NFS from more than one host.
22102 .cindex "NFS" "lock file"
22103 In order to append to an NFS file safely from more than one host, it is
22104 necessary to take out a lock &'before'& opening the file, and the lock file
22105 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
22108 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
22109 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
22110 except when &%mbx_format%& is set.
22113 .option use_mbx_lock appendfile boolean "see below"
22114 This option is available only if Exim has been compiled with SUPPORT_MBX
22115 set in &_Local/Makefile_&. Setting the option specifies that special MBX
22116 locking rules be used. It is set by default if &%mbx_format%& is set and none
22117 of the locking options are mentioned in the configuration. The locking rules
22118 are the same as are used by the &'c-client'& library that underlies Pine and
22119 the IMAP4 and POP daemons that come with it (see the discussion below). The
22120 rules allow for shared access to the mailbox. However, this kind of locking
22121 does not work when the mailbox is NFS mounted.
22123 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
22124 &%use_flock_lock%& to control what kind of locking is used in implementing the
22125 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
22126 without &%use_fcntl_lock%& or &%use_flock_lock%&.
22131 .section "Operational details for appending" "SECTopappend"
22132 .cindex "appending to a file"
22133 .cindex "file" "appending"
22134 Before appending to a file, the following preparations are made:
22137 If the name of the file is &_/dev/null_&, no action is taken, and a success
22141 .cindex "directory creation"
22142 If any directories on the file's path are missing, Exim creates them if the
22143 &%create_directory%& option is set. A created directory's mode is given by the
22144 &%directory_mode%& option.
22147 If &%file_format%& is set, the format of an existing file is checked. If this
22148 indicates that a different transport should be used, control is passed to that
22152 .cindex "file" "locking"
22153 .cindex "locking files"
22154 .cindex "NFS" "lock file"
22155 If &%use_lockfile%& is set, a lock file is built in a way that will work
22156 reliably over NFS, as follows:
22159 Create a &"hitching post"& file whose name is that of the lock file with the
22160 current time, primary host name, and process id added, by opening for writing
22161 as a new file. If this fails with an access error, delivery is deferred.
22163 Close the hitching post file, and hard link it to the lock file name.
22165 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
22166 Unlink the hitching post name.
22168 Otherwise, use &[stat()]& to get information about the hitching post file, and
22169 then unlink hitching post name. If the number of links is exactly two, creation
22170 of the lock file succeeded but something (for example, an NFS server crash and
22171 restart) caused this fact not to be communicated to the &[link()]& call.
22173 If creation of the lock file failed, wait for &%lock_interval%& and try again,
22174 up to &%lock_retries%& times. However, since any program that writes to a
22175 mailbox should complete its task very quickly, it is reasonable to time out old
22176 lock files that are normally the result of user agent and system crashes. If an
22177 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
22178 it before trying again.
22182 A call is made to &[lstat()]& to discover whether the main file exists, and if
22183 so, what its characteristics are. If &[lstat()]& fails for any reason other
22184 than non-existence, delivery is deferred.
22187 .cindex "symbolic link" "to mailbox"
22188 .cindex "mailbox" "symbolic link"
22189 If the file does exist and is a symbolic link, delivery is deferred, unless the
22190 &%allow_symlink%& option is set, in which case the ownership of the link is
22191 checked, and then &[stat()]& is called to find out about the real file, which
22192 is then subjected to the checks below. The check on the top-level link
22193 ownership prevents one user creating a link for another's mailbox in a sticky
22194 directory, though allowing symbolic links in this case is definitely not a good
22195 idea. If there is a chain of symbolic links, the intermediate ones are not
22199 If the file already exists but is not a regular file, or if the file's owner
22200 and group (if the group is being checked &-- see &%check_group%& above) are
22201 different from the user and group under which the delivery is running,
22202 delivery is deferred.
22205 If the file's permissions are more generous than specified, they are reduced.
22206 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
22207 is set false, in which case the delivery is tried using the existing
22211 The file's inode number is saved, and the file is then opened for appending.
22212 If this fails because the file has vanished, &(appendfile)& behaves as if it
22213 hadn't existed (see below). For any other failures, delivery is deferred.
22216 If the file is opened successfully, check that the inode number hasn't
22217 changed, that it is still a regular file, and that the owner and permissions
22218 have not changed. If anything is wrong, defer delivery and freeze the message.
22221 If the file did not exist originally, defer delivery if the &%file_must_exist%&
22222 option is set. Otherwise, check that the file is being created in a permitted
22223 directory if the &%create_file%& option is set (deferring on failure), and then
22224 open for writing as a new file, with the O_EXCL and O_CREAT options,
22225 except when dealing with a symbolic link (the &%allow_symlink%& option must be
22226 set). In this case, which can happen if the link points to a non-existent file,
22227 the file is opened for writing using O_CREAT but not O_EXCL, because
22228 that prevents link following.
22231 .cindex "loop" "while file testing"
22232 If opening fails because the file exists, obey the tests given above for
22233 existing files. However, to avoid looping in a situation where the file is
22234 being continuously created and destroyed, the exists/not-exists loop is broken
22235 after 10 repetitions, and the message is then frozen.
22238 If opening fails with any other error, defer delivery.
22241 .cindex "file" "locking"
22242 .cindex "locking files"
22243 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22244 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22245 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22246 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22247 file, and an exclusive lock on the file whose name is
22249 /tmp/.<device-number>.<inode-number>
22251 using the device and inode numbers of the open mailbox file, in accordance with
22252 the MBX locking rules. This file is created with a mode that is specified by
22253 the &%lockfile_mode%& option.
22255 If Exim fails to lock the file, there are two possible courses of action,
22256 depending on the value of the locking timeout. This is obtained from
22257 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22259 If the timeout value is zero, the file is closed, Exim waits for
22260 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22261 to lock it again. This happens up to &%lock_retries%& times, after which the
22262 delivery is deferred.
22264 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22265 &[flock()]& are used (with the given timeout), so there has already been some
22266 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22267 immediately. It retries up to
22269 (lock_retries * lock_interval) / <timeout>
22271 times (rounded up).
22274 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22275 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22278 .section "Operational details for delivery to a new file" "SECTopdir"
22279 .cindex "delivery" "to single file"
22280 .cindex "&""From""& line"
22281 When the &%directory%& option is set instead of &%file%&, each message is
22282 delivered into a newly-created file or set of files. When &(appendfile)& is
22283 activated directly from a &(redirect)& router, neither &%file%& nor
22284 &%directory%& is normally set, because the path for delivery is supplied by the
22285 router. (See for example, the &(address_file)& transport in the default
22286 configuration.) In this case, delivery is to a new file if either the path name
22287 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22289 No locking is required while writing the message to a new file, so the various
22290 locking options of the transport are ignored. The &"From"& line that by default
22291 separates messages in a single file is not normally needed, nor is the escaping
22292 of message lines that start with &"From"&, and there is no need to ensure a
22293 newline at the end of each message. Consequently, the default values for
22294 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22295 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22297 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22298 the files in the delivery directory by default. However, you can specify a
22299 different directory by setting &%quota_directory%&. Also, for maildir
22300 deliveries (see below) the &_maildirfolder_& convention is honoured.
22303 .cindex "maildir format"
22304 .cindex "mailstore format"
22305 There are three different ways in which delivery to individual files can be
22306 done, controlled by the settings of the &%maildir_format%& and
22307 &%mailstore_format%& options. Note that code to support maildir or mailstore
22308 formats is not included in the binary unless SUPPORT_MAILDIR or
22309 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22311 .cindex "directory creation"
22312 In all three cases an attempt is made to create the directory and any necessary
22313 sub-directories if they do not exist, provided that the &%create_directory%&
22314 option is set (the default). The location of a created directory can be
22315 constrained by setting &%create_file%&. A created directory's mode is given by
22316 the &%directory_mode%& option. If creation fails, or if the
22317 &%create_directory%& option is not set when creation is required, delivery is
22322 .section "Maildir delivery" "SECTmaildirdelivery"
22323 .cindex "maildir format" "description of"
22324 If the &%maildir_format%& option is true, Exim delivers each message by writing
22325 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22326 directory that is defined by the &%directory%& option (the &"delivery
22327 directory"&). If the delivery is successful, the file is renamed into the
22328 &_new_& subdirectory.
22330 In the file name, <&'stime'&> is the current time of day in seconds, and
22331 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22332 Exim checks that the time-of-day clock has moved on by at least one microsecond
22333 before terminating the delivery process. This guarantees uniqueness for the
22334 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22335 opening it. If any response other than ENOENT (does not exist) is given,
22336 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22338 Before Exim carries out a maildir delivery, it ensures that subdirectories
22339 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22340 do not exist, Exim tries to create them and any superior directories in their
22341 path, subject to the &%create_directory%& and &%create_file%& options. If the
22342 &%maildirfolder_create_regex%& option is set, and the regular expression it
22343 contains matches the delivery directory, Exim also ensures that a file called
22344 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22345 &_maildirfolder_& file cannot be created, delivery is deferred.
22347 These features make it possible to use Exim to create all the necessary files
22348 and directories in a maildir mailbox, including subdirectories for maildir++
22349 folders. Consider this example:
22351 maildir_format = true
22352 directory = /var/mail/$local_part\
22353 ${if eq{$local_part_suffix}{}{}\
22354 {/.${substr_1:$local_part_suffix}}}
22355 maildirfolder_create_regex = /\.[^/]+$
22357 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22358 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22359 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22360 not match this name, so Exim will not look for or create the file
22361 &_/var/mail/pimbo/maildirfolder_&, though it will create
22362 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22364 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22365 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22366 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22367 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22368 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22370 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22371 not inadvertently match the toplevel maildir directory, because a
22372 &_maildirfolder_& file at top level would completely break quota calculations.
22374 .cindex "quota" "in maildir delivery"
22375 .cindex "maildir++"
22376 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22377 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22378 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22379 Exim assumes the directory is a maildir++ folder directory, which is one level
22380 down from the user's top level mailbox directory. This causes it to start at
22381 the parent directory instead of the current directory when calculating the
22382 amount of space used.
22384 One problem with delivering into a multi-file mailbox is that it is
22385 computationally expensive to compute the size of the mailbox for quota
22386 checking. Various approaches have been taken to reduce the amount of work
22387 needed. The next two sections describe two of them. A third alternative is to
22388 use some external process for maintaining the size data, and use the expansion
22389 of the &%mailbox_size%& option as a way of importing it into Exim.
22394 .section "Using tags to record message sizes" "SECID135"
22395 If &%maildir_tag%& is set, the string is expanded for each delivery.
22396 When the maildir file is renamed into the &_new_& sub-directory, the
22397 tag is added to its name. However, if adding the tag takes the length of the
22398 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22399 the tag is dropped and the maildir file is created with no tag.
22402 .vindex "&$message_size$&"
22403 Tags can be used to encode the size of files in their names; see
22404 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22405 happens after the message has been written. The value of the &$message_size$&
22406 variable is set to the number of bytes actually written. If the expansion is
22407 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22408 be deferred. The expanded tag may contain any printing characters except &"/"&.
22409 Non-printing characters in the string are ignored; if the resulting string is
22410 empty, it is ignored. If it starts with an alphanumeric character, a leading
22411 colon is inserted; this default has not proven to be the path that popular
22412 maildir implementations have chosen (but changing it in Exim would break
22413 backwards compatibility).
22415 For one common implementation, you might set:
22417 maildir_tag = ,S=${message_size}
22419 but you should check the documentation of the other software to be sure.
22421 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22422 as this allows Exim to extract the size from your tag, instead of having to
22423 &[stat()]& each message file.
22426 .section "Using a maildirsize file" "SECID136"
22427 .cindex "quota" "in maildir delivery"
22428 .cindex "maildir format" "&_maildirsize_& file"
22429 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22430 storing quota and message size information in a file called &_maildirsize_&
22431 within the toplevel maildir directory. If this file does not exist, Exim
22432 creates it, setting the quota from the &%quota%& option of the transport. If
22433 the maildir directory itself does not exist, it is created before any attempt
22434 to write a &_maildirsize_& file.
22436 The &_maildirsize_& file is used to hold information about the sizes of
22437 messages in the maildir, thus speeding up quota calculations. The quota value
22438 in the file is just a cache; if the quota is changed in the transport, the new
22439 value overrides the cached value when the next message is delivered. The cache
22440 is maintained for the benefit of other programs that access the maildir and
22441 need to know the quota.
22443 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22444 file is maintained (with a zero quota setting), but no quota is imposed.
22446 A regular expression is available for controlling which directories in the
22447 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22448 See the description of the &%maildir_quota_directory_regex%& option above for
22452 .section "Mailstore delivery" "SECID137"
22453 .cindex "mailstore format" "description of"
22454 If the &%mailstore_format%& option is true, each message is written as two
22455 files in the given directory. A unique base name is constructed from the
22456 message id and the current delivery process, and the files that are written use
22457 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22458 contains the message's envelope, and the &_.msg_& file contains the message
22459 itself. The base name is placed in the variable &$mailstore_basename$&.
22461 During delivery, the envelope is first written to a file with the suffix
22462 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22463 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22464 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22465 file before accessing either of them. An alternative approach is to wait for
22466 the absence of a &_.tmp_& file.
22468 The envelope file starts with any text defined by the &%mailstore_prefix%&
22469 option, expanded and terminated by a newline if there isn't one. Then follows
22470 the sender address on one line, then all the recipient addresses, one per line.
22471 There can be more than one recipient only if the &%batch_max%& option is set
22472 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22473 appended to the file, followed by a newline if it does not end with one.
22475 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22476 failure, it is ignored. Other expansion errors are treated as serious
22477 configuration errors, and delivery is deferred. The variable
22478 &$mailstore_basename$& is available for use during these expansions.
22481 .section "Non-special new file delivery" "SECID138"
22482 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22483 file is created directly in the named directory. For example, when delivering
22484 messages into files in batched SMTP format for later delivery to some host (see
22485 section &<<SECTbatchSMTP>>&), a setting such as
22487 directory = /var/bsmtp/$host
22489 might be used. A message is written to a file with a temporary name, which is
22490 then renamed when the delivery is complete. The final name is obtained by
22491 expanding the contents of the &%directory_file%& option.
22492 .ecindex IIDapptra1
22493 .ecindex IIDapptra2
22500 . ////////////////////////////////////////////////////////////////////////////
22501 . ////////////////////////////////////////////////////////////////////////////
22503 .chapter "The autoreply transport" "CHID8"
22504 .scindex IIDauttra1 "transports" "&(autoreply)&"
22505 .scindex IIDauttra2 "&(autoreply)& transport"
22506 The &(autoreply)& transport is not a true transport in that it does not cause
22507 the message to be transmitted. Instead, it generates a new mail message as an
22508 automatic reply to the incoming message. &'References:'& and
22509 &'Auto-Submitted:'& header lines are included. These are constructed according
22510 to the rules in RFCs 2822 and 3834, respectively.
22512 If the router that passes the message to this transport does not have the
22513 &%unseen%& option set, the original message (for the current recipient) is not
22514 delivered anywhere. However, when the &%unseen%& option is set on the router
22515 that passes the message to this transport, routing of the address continues, so
22516 another router can set up a normal message delivery.
22519 The &(autoreply)& transport is usually run as the result of mail filtering, a
22520 &"vacation"& message being the standard example. However, it can also be run
22521 directly from a router like any other transport. To reduce the possibility of
22522 message cascades, messages created by the &(autoreply)& transport always have
22523 empty envelope sender addresses, like bounce messages.
22525 The parameters of the message to be sent can be specified in the configuration
22526 by options described below. However, these are used only when the address
22527 passed to the transport does not contain its own reply information. When the
22528 transport is run as a consequence of a
22530 or &%vacation%& command in a filter file, the parameters of the message are
22531 supplied by the filter, and passed with the address. The transport's options
22532 that define the message are then ignored (so they are not usually set in this
22533 case). The message is specified entirely by the filter or by the transport; it
22534 is never built from a mixture of options. However, the &%file_optional%&,
22535 &%mode%&, and &%return_message%& options apply in all cases.
22537 &(Autoreply)& is implemented as a local transport. When used as a result of a
22538 command in a user's filter file, &(autoreply)& normally runs under the uid and
22539 gid of the user, and with appropriate current and home directories (see chapter
22540 &<<CHAPenvironment>>&).
22542 There is a subtle difference between routing a message to a &(pipe)& transport
22543 that generates some text to be returned to the sender, and routing it to an
22544 &(autoreply)& transport. This difference is noticeable only if more than one
22545 address from the same message is so handled. In the case of a pipe, the
22546 separate outputs from the different addresses are gathered up and returned to
22547 the sender in a single message, whereas if &(autoreply)& is used, a separate
22548 message is generated for each address that is passed to it.
22550 Non-printing characters are not permitted in the header lines generated for the
22551 message that &(autoreply)& creates, with the exception of newlines that are
22552 immediately followed by white space. If any non-printing characters are found,
22553 the transport defers.
22554 Whether characters with the top bit set count as printing characters or not is
22555 controlled by the &%print_topbitchars%& global option.
22557 If any of the generic options for manipulating headers (for example,
22558 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
22559 of the original message that is included in the generated message when
22560 &%return_message%& is set. They do not apply to the generated message itself.
22562 .vindex "&$sender_address$&"
22563 If the &(autoreply)& transport receives return code 2 from Exim when it submits
22564 the message, indicating that there were no recipients, it does not treat this
22565 as an error. This means that autoreplies sent to &$sender_address$& when this
22566 is empty (because the incoming message is a bounce message) do not cause
22567 problems. They are just discarded.
22571 .section "Private options for autoreply" "SECID139"
22572 .cindex "options" "&(autoreply)& transport"
22574 .option bcc autoreply string&!! unset
22575 This specifies the addresses that are to receive &"blind carbon copies"& of the
22576 message when the message is specified by the transport.
22579 .option cc autoreply string&!! unset
22580 This specifies recipients of the message and the contents of the &'Cc:'& header
22581 when the message is specified by the transport.
22584 .option file autoreply string&!! unset
22585 The contents of the file are sent as the body of the message when the message
22586 is specified by the transport. If both &%file%& and &%text%& are set, the text
22587 string comes first.
22590 .option file_expand autoreply boolean false
22591 If this is set, the contents of the file named by the &%file%& option are
22592 subjected to string expansion as they are added to the message.
22595 .option file_optional autoreply boolean false
22596 If this option is true, no error is generated if the file named by the &%file%&
22597 option or passed with the address does not exist or cannot be read.
22600 .option from autoreply string&!! unset
22601 This specifies the contents of the &'From:'& header when the message is
22602 specified by the transport.
22605 .option headers autoreply string&!! unset
22606 This specifies additional RFC 2822 headers that are to be added to the message
22607 when the message is specified by the transport. Several can be given by using
22608 &"\n"& to separate them. There is no check on the format.
22611 .option log autoreply string&!! unset
22612 This option names a file in which a record of every message sent is logged when
22613 the message is specified by the transport.
22616 .option mode autoreply "octal integer" 0600
22617 If either the log file or the &"once"& file has to be created, this mode is
22621 .option never_mail autoreply "address list&!!" unset
22622 If any run of the transport creates a message with a recipient that matches any
22623 item in the list, that recipient is quietly discarded. If all recipients are
22624 discarded, no message is created. This applies both when the recipients are
22625 generated by a filter and when they are specified in the transport.
22629 .option once autoreply string&!! unset
22630 This option names a file or DBM database in which a record of each &'To:'&
22631 recipient is kept when the message is specified by the transport. &*Note*&:
22632 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
22634 If &%once%& is unset, or is set to an empty string, the message is always sent.
22635 By default, if &%once%& is set to a non-empty file name, the message
22636 is not sent if a potential recipient is already listed in the database.
22637 However, if the &%once_repeat%& option specifies a time greater than zero, the
22638 message is sent if that much time has elapsed since a message was last sent to
22639 this recipient. A setting of zero time for &%once_repeat%& (the default)
22640 prevents a message from being sent a second time &-- in this case, zero means
22643 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
22644 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
22645 greater than zero, it changes the way Exim implements the &%once%& option.
22646 Instead of using a DBM file to record every recipient it sends to, it uses a
22647 regular file, whose size will never get larger than the given value.
22649 In the file, Exim keeps a linear list of recipient addresses and the times at
22650 which they were sent messages. If the file is full when a new address needs to
22651 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
22652 means that a given recipient may receive multiple messages, but at
22653 unpredictable intervals that depend on the rate of turnover of addresses in the
22654 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
22657 .option once_file_size autoreply integer 0
22658 See &%once%& above.
22661 .option once_repeat autoreply time&!! 0s
22662 See &%once%& above.
22663 After expansion, the value of this option must be a valid time value.
22666 .option reply_to autoreply string&!! unset
22667 This specifies the contents of the &'Reply-To:'& header when the message is
22668 specified by the transport.
22671 .option return_message autoreply boolean false
22672 If this is set, a copy of the original message is returned with the new
22673 message, subject to the maximum size set in the &%return_size_limit%& global
22674 configuration option.
22677 .option subject autoreply string&!! unset
22678 This specifies the contents of the &'Subject:'& header when the message is
22679 specified by the transport. It is tempting to quote the original subject in
22680 automatic responses. For example:
22682 subject = Re: $h_subject:
22684 There is a danger in doing this, however. It may allow a third party to
22685 subscribe your users to an opt-in mailing list, provided that the list accepts
22686 bounce messages as subscription confirmations. Well-managed lists require a
22687 non-bounce message to confirm a subscription, so the danger is relatively
22692 .option text autoreply string&!! unset
22693 This specifies a single string to be used as the body of the message when the
22694 message is specified by the transport. If both &%text%& and &%file%& are set,
22695 the text comes first.
22698 .option to autoreply string&!! unset
22699 This specifies recipients of the message and the contents of the &'To:'& header
22700 when the message is specified by the transport.
22701 .ecindex IIDauttra1
22702 .ecindex IIDauttra2
22707 . ////////////////////////////////////////////////////////////////////////////
22708 . ////////////////////////////////////////////////////////////////////////////
22710 .chapter "The lmtp transport" "CHAPLMTP"
22711 .cindex "transports" "&(lmtp)&"
22712 .cindex "&(lmtp)& transport"
22713 .cindex "LMTP" "over a pipe"
22714 .cindex "LMTP" "over a socket"
22715 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
22717 or by interacting with a Unix domain socket.
22718 This transport is something of a cross between the &(pipe)& and &(smtp)&
22719 transports. Exim also has support for using LMTP over TCP/IP; this is
22720 implemented as an option for the &(smtp)& transport. Because LMTP is expected
22721 to be of minority interest, the default build-time configure in &_src/EDITME_&
22722 has it commented out. You need to ensure that
22726 .cindex "options" "&(lmtp)& transport"
22727 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
22728 included in the Exim binary. The private options of the &(lmtp)& transport are
22731 .option batch_id lmtp string&!! unset
22732 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22735 .option batch_max lmtp integer 1
22736 This limits the number of addresses that can be handled in a single delivery.
22737 Most LMTP servers can handle several addresses at once, so it is normally a
22738 good idea to increase this value. See the description of local delivery
22739 batching in chapter &<<CHAPbatching>>&.
22742 .option command lmtp string&!! unset
22743 This option must be set if &%socket%& is not set. The string is a command which
22744 is run in a separate process. It is split up into a command name and list of
22745 arguments, each of which is separately expanded (so expansion cannot change the
22746 number of arguments). The command is run directly, not via a shell. The message
22747 is passed to the new process using the standard input and output to operate the
22750 .option ignore_quota lmtp boolean false
22751 .cindex "LMTP" "ignoring quota errors"
22752 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
22753 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
22754 in its response to the LHLO command.
22756 .option socket lmtp string&!! unset
22757 This option must be set if &%command%& is not set. The result of expansion must
22758 be the name of a Unix domain socket. The transport connects to the socket and
22759 delivers the message to it using the LMTP protocol.
22762 .option timeout lmtp time 5m
22763 The transport is aborted if the created process or Unix domain socket does not
22764 respond to LMTP commands or message input within this timeout. Delivery
22765 is deferred, and will be tried again later. Here is an example of a typical
22770 command = /some/local/lmtp/delivery/program
22774 This delivers up to 20 addresses at a time, in a mixture of domains if
22775 necessary, running as the user &'exim'&.
22779 . ////////////////////////////////////////////////////////////////////////////
22780 . ////////////////////////////////////////////////////////////////////////////
22782 .chapter "The pipe transport" "CHAPpipetransport"
22783 .scindex IIDpiptra1 "transports" "&(pipe)&"
22784 .scindex IIDpiptra2 "&(pipe)& transport"
22785 The &(pipe)& transport is used to deliver messages via a pipe to a command
22786 running in another process. One example is the use of &(pipe)& as a
22787 pseudo-remote transport for passing messages to some other delivery mechanism
22788 (such as UUCP). Another is the use by individual users to automatically process
22789 their incoming messages. The &(pipe)& transport can be used in one of the
22793 .vindex "&$local_part$&"
22794 A router routes one address to a transport in the normal way, and the
22795 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
22796 contains the local part of the address (as usual), and the command that is run
22797 is specified by the &%command%& option on the transport.
22799 .vindex "&$pipe_addresses$&"
22800 If the &%batch_max%& option is set greater than 1 (the default is 1), the
22801 transport can handle more than one address in a single run. In this case, when
22802 more than one address is routed to the transport, &$local_part$& is not set
22803 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
22804 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
22805 that are routed to the transport.
22807 .vindex "&$address_pipe$&"
22808 A router redirects an address directly to a pipe command (for example, from an
22809 alias or forward file). In this case, &$address_pipe$& contains the text of the
22810 pipe command, and the &%command%& option on the transport is ignored unless
22811 &%force_command%& is set. If only one address is being transported
22812 (&%batch_max%& is not greater than one, or only one address was redirected to
22813 this pipe command), &$local_part$& contains the local part that was redirected.
22817 The &(pipe)& transport is a non-interactive delivery method. Exim can also
22818 deliver messages over pipes using the LMTP interactive protocol. This is
22819 implemented by the &(lmtp)& transport.
22821 In the case when &(pipe)& is run as a consequence of an entry in a local user's
22822 &_.forward_& file, the command runs under the uid and gid of that user. In
22823 other cases, the uid and gid have to be specified explicitly, either on the
22824 transport or on the router that handles the address. Current and &"home"&
22825 directories are also controllable. See chapter &<<CHAPenvironment>>& for
22826 details of the local delivery environment and chapter &<<CHAPbatching>>&
22827 for a discussion of local delivery batching.
22830 .section "Concurrent delivery" "SECID140"
22831 If two messages arrive at almost the same time, and both are routed to a pipe
22832 delivery, the two pipe transports may be run concurrently. You must ensure that
22833 any pipe commands you set up are robust against this happening. If the commands
22834 write to a file, the &%exim_lock%& utility might be of use.
22835 Alternatively the &%max_parallel%& option could be used with a value
22836 of "1" to enforce serialization.
22841 .section "Returned status and data" "SECID141"
22842 .cindex "&(pipe)& transport" "returned data"
22843 If the command exits with a non-zero return code, the delivery is deemed to
22844 have failed, unless either the &%ignore_status%& option is set (in which case
22845 the return code is treated as zero), or the return code is one of those listed
22846 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22847 later"&. In this case, delivery is deferred. Details of a permanent failure are
22848 logged, but are not included in the bounce message, which merely contains
22849 &"local delivery failed"&.
22851 If the command exits on a signal and the &%freeze_signal%& option is set then
22852 the message will be frozen in the queue. If that option is not set, a bounce
22853 will be sent as normal.
22855 If the return code is greater than 128 and the command being run is a shell
22856 script, it normally means that the script was terminated by a signal whose
22857 value is the return code minus 128. The &%freeze_signal%& option does not
22858 apply in this case.
22860 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22861 return code is set to 127. This is the value that a shell returns if it is
22862 asked to run a non-existent command. The wording for the log line suggests that
22863 a non-existent command may be the problem.
22865 The &%return_output%& option can affect the result of a pipe delivery. If it is
22866 set and the command produces any output on its standard output or standard
22867 error streams, the command is considered to have failed, even if it gave a zero
22868 return code or if &%ignore_status%& is set. The output from the command is
22869 included as part of the bounce message. The &%return_fail_output%& option is
22870 similar, except that output is returned only when the command exits with a
22871 failure return code, that is, a value other than zero or a code that matches
22876 .section "How the command is run" "SECThowcommandrun"
22877 .cindex "&(pipe)& transport" "path for command"
22878 The command line is (by default) broken down into a command name and arguments
22879 by the &(pipe)& transport itself. The &%allow_commands%& and
22880 &%restrict_to_path%& options can be used to restrict the commands that may be
22883 .cindex "quoting" "in pipe command"
22884 Unquoted arguments are delimited by white space. If an argument appears in
22885 double quotes, backslash is interpreted as an escape character in the usual
22886 way. If an argument appears in single quotes, no escaping is done.
22888 String expansion is applied to the command line except when it comes from a
22889 traditional &_.forward_& file (commands from a filter file are expanded). The
22890 expansion is applied to each argument in turn rather than to the whole line.
22891 For this reason, any string expansion item that contains white space must be
22892 quoted so as to be contained within a single argument. A setting such as
22894 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
22896 will not work, because the expansion item gets split between several
22897 arguments. You have to write
22899 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
22901 to ensure that it is all in one argument. The expansion is done in this way,
22902 argument by argument, so that the number of arguments cannot be changed as a
22903 result of expansion, and quotes or backslashes in inserted variables do not
22904 interact with external quoting. However, this leads to problems if you want to
22905 generate multiple arguments (or the command name plus arguments) from a single
22906 expansion. In this situation, the simplest solution is to use a shell. For
22909 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
22912 .cindex "transport" "filter"
22913 .cindex "filter" "transport filter"
22914 .vindex "&$pipe_addresses$&"
22915 Special handling takes place when an argument consists of precisely the text
22916 &`$pipe_addresses`&. This is not a general expansion variable; the only
22917 place this string is recognized is when it appears as an argument for a pipe or
22918 transport filter command. It causes each address that is being handled to be
22919 inserted in the argument list at that point &'as a separate argument'&. This
22920 avoids any problems with spaces or shell metacharacters, and is of use when a
22921 &(pipe)& transport is handling groups of addresses in a batch.
22923 If &%force_command%& is enabled on the transport, Special handling takes place
22924 for an argument that consists of precisely the text &`$address_pipe`&. It
22925 is handled similarly to &$pipe_addresses$& above. It is expanded and each
22926 argument is inserted in the argument list at that point
22927 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
22928 the only item in the argument; in fact, if it were then &%force_command%&
22929 should behave as a no-op. Rather, it should be used to adjust the command
22930 run while preserving the argument vector separation.
22932 After splitting up into arguments and expansion, the resulting command is run
22933 in a subprocess directly from the transport, &'not'& under a shell. The
22934 message that is being delivered is supplied on the standard input, and the
22935 standard output and standard error are both connected to a single pipe that is
22936 read by Exim. The &%max_output%& option controls how much output the command
22937 may produce, and the &%return_output%& and &%return_fail_output%& options
22938 control what is done with it.
22940 Not running the command under a shell (by default) lessens the security risks
22941 in cases when a command from a user's filter file is built out of data that was
22942 taken from an incoming message. If a shell is required, it can of course be
22943 explicitly specified as the command to be run. However, there are circumstances
22944 where existing commands (for example, in &_.forward_& files) expect to be run
22945 under a shell and cannot easily be modified. To allow for these cases, there is
22946 an option called &%use_shell%&, which changes the way the &(pipe)& transport
22947 works. Instead of breaking up the command line as just described, it expands it
22948 as a single string and passes the result to &_/bin/sh_&. The
22949 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
22950 with &%use_shell%&, and the whole mechanism is inherently less secure.
22954 .section "Environment variables" "SECTpipeenv"
22955 .cindex "&(pipe)& transport" "environment for command"
22956 .cindex "environment" "&(pipe)& transport"
22957 The environment variables listed below are set up when the command is invoked.
22958 This list is a compromise for maximum compatibility with other MTAs. Note that
22959 the &%environment%& option can be used to add additional variables to this
22960 environment. The environment for the &(pipe)& transport is not subject
22961 to the &%add_environment%& and &%keep_environment%& main config options.
22963 &`DOMAIN `& the domain of the address
22964 &`HOME `& the home directory, if set
22965 &`HOST `& the host name when called from a router (see below)
22966 &`LOCAL_PART `& see below
22967 &`LOCAL_PART_PREFIX `& see below
22968 &`LOCAL_PART_SUFFIX `& see below
22969 &`LOGNAME `& see below
22970 &`MESSAGE_ID `& Exim's local ID for the message
22971 &`PATH `& as specified by the &%path%& option below
22972 &`QUALIFY_DOMAIN `& the sender qualification domain
22973 &`RECIPIENT `& the complete recipient address
22974 &`SENDER `& the sender of the message (empty if a bounce)
22975 &`SHELL `& &`/bin/sh`&
22976 &`TZ `& the value of the &%timezone%& option, if set
22977 &`USER `& see below
22979 When a &(pipe)& transport is called directly from (for example) an &(accept)&
22980 router, LOCAL_PART is set to the local part of the address. When it is
22981 called as a result of a forward or alias expansion, LOCAL_PART is set to
22982 the local part of the address that was expanded. In both cases, any affixes are
22983 removed from the local part, and made available in LOCAL_PART_PREFIX and
22984 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
22985 same value as LOCAL_PART for compatibility with other MTAs.
22988 HOST is set only when a &(pipe)& transport is called from a router that
22989 associates hosts with an address, typically when using &(pipe)& as a
22990 pseudo-remote transport. HOST is set to the first host name specified by
22994 If the transport's generic &%home_directory%& option is set, its value is used
22995 for the HOME environment variable. Otherwise, a home directory may be set
22996 by the router's &%transport_home_directory%& option, which defaults to the
22997 user's home directory if &%check_local_user%& is set.
23000 .section "Private options for pipe" "SECID142"
23001 .cindex "options" "&(pipe)& transport"
23005 .option allow_commands pipe "string list&!!" unset
23006 .cindex "&(pipe)& transport" "permitted commands"
23007 The string is expanded, and is then interpreted as a colon-separated list of
23008 permitted commands. If &%restrict_to_path%& is not set, the only commands
23009 permitted are those in the &%allow_commands%& list. They need not be absolute
23010 paths; the &%path%& option is still used for relative paths. If
23011 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
23012 in the &%allow_commands%& list, or a name without any slashes that is found on
23013 the path. In other words, if neither &%allow_commands%& nor
23014 &%restrict_to_path%& is set, there is no restriction on the command, but
23015 otherwise only commands that are permitted by one or the other are allowed. For
23018 allow_commands = /usr/bin/vacation
23020 and &%restrict_to_path%& is not set, the only permitted command is
23021 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
23022 &%use_shell%& is set.
23025 .option batch_id pipe string&!! unset
23026 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23029 .option batch_max pipe integer 1
23030 This limits the number of addresses that can be handled in a single delivery.
23031 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23034 .option check_string pipe string unset
23035 As &(pipe)& writes the message, the start of each line is tested for matching
23036 &%check_string%&, and if it does, the initial matching characters are replaced
23037 by the contents of &%escape_string%&, provided both are set. The value of
23038 &%check_string%& is a literal string, not a regular expression, and the case of
23039 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
23040 of &%check_string%& and &%escape_string%& are forced to values that implement
23041 the SMTP escaping protocol. Any settings made in the configuration file are
23045 .option command pipe string&!! unset
23046 This option need not be set when &(pipe)& is being used to deliver to pipes
23047 obtained directly from address redirections. In other cases, the option must be
23048 set, to provide a command to be run. It need not yield an absolute path (see
23049 the &%path%& option below). The command is split up into separate arguments by
23050 Exim, and each argument is separately expanded, as described in section
23051 &<<SECThowcommandrun>>& above.
23054 .option environment pipe string&!! unset
23055 .cindex "&(pipe)& transport" "environment for command"
23056 .cindex "environment" "&(pipe)& transport"
23057 This option is used to add additional variables to the environment in which the
23058 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
23059 a string which is expanded, and then interpreted as a colon-separated list of
23060 environment settings of the form <&'name'&>=<&'value'&>.
23063 .option escape_string pipe string unset
23064 See &%check_string%& above.
23067 .option freeze_exec_fail pipe boolean false
23068 .cindex "exec failure"
23069 .cindex "failure of exec"
23070 .cindex "&(pipe)& transport" "failure of exec"
23071 Failure to exec the command in a pipe transport is by default treated like
23072 any other failure while running the command. However, if &%freeze_exec_fail%&
23073 is set, failure to exec is treated specially, and causes the message to be
23074 frozen, whatever the setting of &%ignore_status%&.
23077 .option freeze_signal pipe boolean false
23078 .cindex "signal exit"
23079 .cindex "&(pipe)& transport", "signal exit"
23080 Normally if the process run by a command in a pipe transport exits on a signal,
23081 a bounce message is sent. If &%freeze_signal%& is set, the message will be
23082 frozen in Exim's queue instead.
23085 .option force_command pipe boolean false
23086 .cindex "force command"
23087 .cindex "&(pipe)& transport", "force command"
23088 Normally when a router redirects an address directly to a pipe command
23089 the &%command%& option on the transport is ignored. If &%force_command%&
23090 is set, the &%command%& option will used. This is especially
23091 useful for forcing a wrapper or additional argument to be added to the
23092 command. For example:
23094 command = /usr/bin/remote_exec myhost -- $address_pipe
23098 Note that &$address_pipe$& is handled specially in &%command%& when
23099 &%force_command%& is set, expanding out to the original argument vector as
23100 separate items, similarly to a Unix shell &`"$@"`& construct.
23103 .option ignore_status pipe boolean false
23104 If this option is true, the status returned by the subprocess that is set up to
23105 run the command is ignored, and Exim behaves as if zero had been returned.
23106 Otherwise, a non-zero status or termination by signal causes an error return
23107 from the transport unless the status value is one of those listed in
23108 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
23110 &*Note*&: This option does not apply to timeouts, which do not return a status.
23111 See the &%timeout_defer%& option for how timeouts are handled.
23114 .option log_defer_output pipe boolean false
23115 .cindex "&(pipe)& transport" "logging output"
23116 If this option is set, and the status returned by the command is
23117 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
23118 and any output was produced on stdout or stderr, the first line of it is
23119 written to the main log.
23122 .option log_fail_output pipe boolean false
23123 If this option is set, and the command returns any output on stdout or
23124 stderr, and also ends with a return code that is neither zero nor one of
23125 the return codes listed in &%temp_errors%& (that is, the delivery
23126 failed), the first line of output is written to the main log. This
23127 option and &%log_output%& are mutually exclusive. Only one of them may
23131 .option log_output pipe boolean false
23132 If this option is set and the command returns any output on stdout or
23133 stderr, the first line of output is written to the main log, whatever
23134 the return code. This option and &%log_fail_output%& are mutually
23135 exclusive. Only one of them may be set.
23138 .option max_output pipe integer 20K
23139 This specifies the maximum amount of output that the command may produce on its
23140 standard output and standard error file combined. If the limit is exceeded, the
23141 process running the command is killed. This is intended as a safety measure to
23142 catch runaway processes. The limit is applied independently of the settings of
23143 the options that control what is done with such output (for example,
23144 &%return_output%&). Because of buffering effects, the amount of output may
23145 exceed the limit by a small amount before Exim notices.
23148 .option message_prefix pipe string&!! "see below"
23149 The string specified here is expanded and output at the start of every message.
23150 The default is unset if &%use_bsmtp%& is set. Otherwise it is
23153 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
23157 .cindex "&%tmail%&"
23158 .cindex "&""From""& line"
23159 This is required by the commonly used &_/usr/bin/vacation_& program.
23160 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
23161 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
23166 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23167 &`\n`& to &`\r\n`& in &%message_prefix%&.
23170 .option message_suffix pipe string&!! "see below"
23171 The string specified here is expanded and output at the end of every message.
23172 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
23173 The suffix can be suppressed by setting
23177 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23178 &`\n`& to &`\r\n`& in &%message_suffix%&.
23181 .option path pipe string "see below"
23182 This option specifies the string that is set up in the PATH environment
23183 variable of the subprocess. The default is:
23187 If the &%command%& option does not yield an absolute path name, the command is
23188 sought in the PATH directories, in the usual way. &*Warning*&: This does not
23189 apply to a command specified as a transport filter.
23192 .option permit_coredump pipe boolean false
23193 Normally Exim inhibits core-dumps during delivery. If you have a need to get
23194 a core-dump of a pipe command, enable this command. This enables core-dumps
23195 during delivery and affects both the Exim binary and the pipe command run.
23196 It is recommended that this option remain off unless and until you have a need
23197 for it and that this only be enabled when needed, as the risk of excessive
23198 resource consumption can be quite high. Note also that Exim is typically
23199 installed as a setuid binary and most operating systems will inhibit coredumps
23200 of these by default, so further OS-specific action may be required.
23203 .option pipe_as_creator pipe boolean false
23204 .cindex "uid (user id)" "local delivery"
23205 If the generic &%user%& option is not set and this option is true, the delivery
23206 process is run under the uid that was in force when Exim was originally called
23207 to accept the message. If the group id is not otherwise set (via the generic
23208 &%group%& option), the gid that was in force when Exim was originally called to
23209 accept the message is used.
23212 .option restrict_to_path pipe boolean false
23213 When this option is set, any command name not listed in &%allow_commands%& must
23214 contain no slashes. The command is searched for only in the directories listed
23215 in the &%path%& option. This option is intended for use in the case when a pipe
23216 command has been generated from a user's &_.forward_& file. This is usually
23217 handled by a &(pipe)& transport called &%address_pipe%&.
23220 .option return_fail_output pipe boolean false
23221 If this option is true, and the command produced any output and ended with a
23222 return code other than zero or one of the codes listed in &%temp_errors%& (that
23223 is, the delivery failed), the output is returned in the bounce message.
23224 However, if the message has a null sender (that is, it is itself a bounce
23225 message), output from the command is discarded. This option and
23226 &%return_output%& are mutually exclusive. Only one of them may be set.
23230 .option return_output pipe boolean false
23231 If this option is true, and the command produced any output, the delivery is
23232 deemed to have failed whatever the return code from the command, and the output
23233 is returned in the bounce message. Otherwise, the output is just discarded.
23234 However, if the message has a null sender (that is, it is a bounce message),
23235 output from the command is always discarded, whatever the setting of this
23236 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23237 of them may be set.
23241 .option temp_errors pipe "string list" "see below"
23242 .cindex "&(pipe)& transport" "temporary failure"
23243 This option contains either a colon-separated list of numbers, or a single
23244 asterisk. If &%ignore_status%& is false
23245 and &%return_output%& is not set,
23246 and the command exits with a non-zero return code, the failure is treated as
23247 temporary and the delivery is deferred if the return code matches one of the
23248 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23249 codes are treated as permanent errors. The default setting contains the codes
23250 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23251 compiled on a system that does not define these macros, it assumes values of 75
23252 and 73, respectively.
23255 .option timeout pipe time 1h
23256 If the command fails to complete within this time, it is killed. This normally
23257 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23258 specifies no timeout. In order to ensure that any subprocesses created by the
23259 command are also killed, Exim makes the initial process a process group leader,
23260 and kills the whole process group on a timeout. However, this can be defeated
23261 if one of the processes starts a new process group.
23263 .option timeout_defer pipe boolean false
23264 A timeout in a &(pipe)& transport, either in the command that the transport
23265 runs, or in a transport filter that is associated with it, is by default
23266 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23267 is set true, both kinds of timeout become temporary errors, causing the
23268 delivery to be deferred.
23270 .option umask pipe "octal integer" 022
23271 This specifies the umask setting for the subprocess that runs the command.
23274 .option use_bsmtp pipe boolean false
23275 .cindex "envelope sender"
23276 If this option is set true, the &(pipe)& transport writes messages in &"batch
23277 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23278 commands. If you want to include a leading HELO command with such messages,
23279 you can do so by setting the &%message_prefix%& option. See section
23280 &<<SECTbatchSMTP>>& for details of batch SMTP.
23282 .option use_classresources pipe boolean false
23283 .cindex "class resources (BSD)"
23284 This option is available only when Exim is running on FreeBSD, NetBSD, or
23285 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23286 resource limits when a &(pipe)& transport is run to perform a delivery. The
23287 limits for the uid under which the pipe is to run are obtained from the login
23291 .option use_crlf pipe boolean false
23292 .cindex "carriage return"
23294 This option causes lines to be terminated with the two-character CRLF sequence
23295 (carriage return, linefeed) instead of just a linefeed character. In the case
23296 of batched SMTP, the byte sequence written to the pipe is then an exact image
23297 of what would be sent down a real SMTP connection.
23299 The contents of the &%message_prefix%& and &%message_suffix%& options are
23300 written verbatim, so must contain their own carriage return characters if these
23301 are needed. When &%use_bsmtp%& is not set, the default values for both
23302 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23303 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23306 .option use_shell pipe boolean false
23307 .vindex "&$pipe_addresses$&"
23308 If this option is set, it causes the command to be passed to &_/bin/sh_&
23309 instead of being run directly from the transport, as described in section
23310 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23311 where the command is expected to be run under a shell and cannot easily be
23312 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23313 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23314 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23319 .section "Using an external local delivery agent" "SECID143"
23320 .cindex "local delivery" "using an external agent"
23321 .cindex "&'procmail'&"
23322 .cindex "external local delivery"
23323 .cindex "delivery" "&'procmail'&"
23324 .cindex "delivery" "by external agent"
23325 The &(pipe)& transport can be used to pass all messages that require local
23326 delivery to a separate local delivery agent such as &%procmail%&. When doing
23327 this, care must be taken to ensure that the pipe is run under an appropriate
23328 uid and gid. In some configurations one wants this to be a uid that is trusted
23329 by the delivery agent to supply the correct sender of the message. It may be
23330 necessary to recompile or reconfigure the delivery agent so that it trusts an
23331 appropriate user. The following is an example transport and router
23332 configuration for &%procmail%&:
23337 command = /usr/local/bin/procmail -d $local_part
23341 check_string = "From "
23342 escape_string = ">From "
23351 transport = procmail_pipe
23353 In this example, the pipe is run as the local user, but with the group set to
23354 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23355 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23356 user to supply a correct sender address. If you do not specify either a
23357 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23358 home directory is the user's home directory by default.
23360 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23364 as shown in some &%procmail%& documentation, because Exim does not by default
23365 use a shell to run pipe commands.
23368 The next example shows a transport and a router for a system where local
23369 deliveries are handled by the Cyrus IMAP server.
23372 local_delivery_cyrus:
23374 command = /usr/cyrus/bin/deliver \
23375 -m ${substr_1:$local_part_suffix} -- $local_part
23387 local_part_suffix = .*
23388 transport = local_delivery_cyrus
23390 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23391 &%return_output%& to cause any text written by Cyrus to be returned to the
23393 .ecindex IIDpiptra1
23394 .ecindex IIDpiptra2
23397 . ////////////////////////////////////////////////////////////////////////////
23398 . ////////////////////////////////////////////////////////////////////////////
23400 .chapter "The smtp transport" "CHAPsmtptrans"
23401 .scindex IIDsmttra1 "transports" "&(smtp)&"
23402 .scindex IIDsmttra2 "&(smtp)& transport"
23403 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23404 or LMTP protocol. The list of hosts to try can either be taken from the address
23405 that is being processed (having been set up by the router), or specified
23406 explicitly for the transport. Timeout and retry processing (see chapter
23407 &<<CHAPretry>>&) is applied to each IP address independently.
23410 .section "Multiple messages on a single connection" "SECID144"
23411 The sending of multiple messages over a single TCP/IP connection can arise in
23415 If a message contains more than &%max_rcpt%& (see below) addresses that are
23416 routed to the same host, more than one copy of the message has to be sent to
23417 that host. In this situation, multiple copies may be sent in a single run of
23418 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23419 does when it has too many addresses to send in one message also depends on the
23420 value of the global &%remote_max_parallel%& option. Details are given in
23421 section &<<SECToutSMTPTCP>>&.)
23423 .cindex "hints database" "remembering routing"
23424 When a message has been successfully delivered over a TCP/IP connection, Exim
23425 looks in its hints database to see if there are any other messages awaiting a
23426 connection to the same host. If there are, a new delivery process is started
23427 for one of them, and the current TCP/IP connection is passed on to it. The new
23428 process may in turn send multiple copies and possibly create yet another
23433 For each copy sent over the same TCP/IP connection, a sequence counter is
23434 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23435 no further messages are sent over that connection.
23439 .section "Use of the $host and $host_address variables" "SECID145"
23441 .vindex "&$host_address$&"
23442 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23443 &$host_address$& are the name and IP address of the first host on the host list
23444 passed by the router. However, when the transport is about to connect to a
23445 specific host, and while it is connected to that host, &$host$& and
23446 &$host_address$& are set to the values for that host. These are the values
23447 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23448 &%serialize_hosts%&, and the various TLS options are expanded.
23451 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23452 .vindex &$tls_bits$&
23453 .vindex &$tls_cipher$&
23454 .vindex &$tls_peerdn$&
23455 .vindex &$tls_sni$&
23456 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23457 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23458 are the values that were set when the message was received.
23459 These are the values that are used for options that are expanded before any
23460 SMTP connections are made. Just before each connection is made, these four
23461 variables are emptied. If TLS is subsequently started, they are set to the
23462 appropriate values for the outgoing connection, and these are the values that
23463 are in force when any authenticators are run and when the
23464 &%authenticated_sender%& option is expanded.
23466 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23467 and will be removed in a future release.
23470 .section "Private options for smtp" "SECID146"
23471 .cindex "options" "&(smtp)& transport"
23472 The private options of the &(smtp)& transport are as follows:
23475 .option address_retry_include_sender smtp boolean true
23476 .cindex "4&'xx'& responses" "retrying after"
23477 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23478 is the combination of sender and recipient that is delayed in subsequent queue
23479 runs until the retry time is reached. You can delay the recipient without
23480 reference to the sender (which is what earlier versions of Exim did), by
23481 setting &%address_retry_include_sender%& false. However, this can lead to
23482 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23484 .option allow_localhost smtp boolean false
23485 .cindex "local host" "sending to"
23486 .cindex "fallback" "hosts specified on transport"
23487 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23488 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23489 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23490 the delivery anyway. This should be used only in special cases when the
23491 configuration ensures that no looping will result (for example, a differently
23492 configured Exim is listening on the port to which the message is sent).
23495 .option authenticated_sender smtp string&!! unset
23497 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23498 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23499 overriding any existing authenticated sender value. If the string expansion is
23500 forced to fail, the option is ignored. Other expansion failures cause delivery
23501 to be deferred. If the result of expansion is an empty string, that is also
23504 The expansion happens after the outgoing connection has been made and TLS
23505 started, if required. This means that the &$host$&, &$host_address$&,
23506 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23507 particular connection.
23509 If the SMTP session is not authenticated, the expansion of
23510 &%authenticated_sender%& still happens (and can cause the delivery to be
23511 deferred if it fails), but no AUTH= item is added to MAIL commands
23512 unless &%authenticated_sender_force%& is true.
23514 This option allows you to use the &(smtp)& transport in LMTP mode to
23515 deliver mail to Cyrus IMAP and provide the proper local part as the
23516 &"authenticated sender"&, via a setting such as:
23518 authenticated_sender = $local_part
23520 This removes the need for IMAP subfolders to be assigned special ACLs to
23521 allow direct delivery to those subfolders.
23523 Because of expected uses such as that just described for Cyrus (when no
23524 domain is involved), there is no checking on the syntax of the provided
23528 .option authenticated_sender_force smtp boolean false
23529 If this option is set true, the &%authenticated_sender%& option's value
23530 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23531 authenticated as a client.
23534 .option command_timeout smtp time 5m
23535 This sets a timeout for receiving a response to an SMTP command that has been
23536 sent out. It is also used when waiting for the initial banner line from the
23537 remote host. Its value must not be zero.
23540 .option connect_timeout smtp time 5m
23541 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
23542 to a remote host. A setting of zero allows the system timeout (typically
23543 several minutes) to act. To have any effect, the value of this option must be
23544 less than the system timeout. However, it has been observed that on some
23545 systems there is no system timeout, which is why the default value for this
23546 option is 5 minutes, a value recommended by RFC 1123.
23549 .option connection_max_messages smtp integer 500
23550 .cindex "SMTP" "passed connection"
23551 .cindex "SMTP" "multiple deliveries"
23552 .cindex "multiple SMTP deliveries"
23553 This controls the maximum number of separate message deliveries that are sent
23554 over a single TCP/IP connection. If the value is zero, there is no limit.
23555 For testing purposes, this value can be overridden by the &%-oB%& command line
23559 .option data_timeout smtp time 5m
23560 This sets a timeout for the transmission of each block in the data portion of
23561 the message. As a result, the overall timeout for a message depends on the size
23562 of the message. Its value must not be zero. See also &%final_timeout%&.
23565 .option dkim_domain smtp string&!! unset
23566 .option dkim_selector smtp string&!! unset
23567 .option dkim_private_key smtp string&!! unset
23568 .option dkim_canon smtp string&!! unset
23569 .option dkim_strict smtp string&!! unset
23570 .option dkim_sign_headers smtp string&!! unset
23571 DKIM signing options. For details see &<<SECDKIMSIGN>>&.
23574 .option delay_after_cutoff smtp boolean true
23575 This option controls what happens when all remote IP addresses for a given
23576 domain have been inaccessible for so long that they have passed their retry
23579 In the default state, if the next retry time has not been reached for any of
23580 them, the address is bounced without trying any deliveries. In other words,
23581 Exim delays retrying an IP address after the final cutoff time until a new
23582 retry time is reached, and can therefore bounce an address without ever trying
23583 a delivery, when machines have been down for a long time. Some people are
23584 unhappy at this prospect, so...
23586 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23587 addresses are past their final cutoff time, Exim tries to deliver to those
23588 IP addresses that have not been tried since the message arrived. If there are
23589 none, of if they all fail, the address is bounced. In other words, it does not
23590 delay when a new message arrives, but immediately tries those expired IP
23591 addresses that haven't been tried since the message arrived. If there is a
23592 continuous stream of messages for the dead hosts, unsetting
23593 &%delay_after_cutoff%& means that there will be many more attempts to deliver
23597 .option dns_qualify_single smtp boolean true
23598 If the &%hosts%& or &%fallback_hosts%& option is being used,
23599 and the &%gethostbyname%& option is false,
23600 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
23601 in chapter &<<CHAPdnslookup>>& for more details.
23604 .option dns_search_parents smtp boolean false
23605 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
23606 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
23607 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
23611 .option dnssec_request_domains smtp "domain list&!!" unset
23612 .cindex "MX record" "security"
23613 .cindex "DNSSEC" "MX lookup"
23614 .cindex "security" "MX lookup"
23615 .cindex "DNS" "DNSSEC"
23616 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23617 the dnssec request bit set.
23618 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23622 .option dnssec_require_domains smtp "domain list&!!" unset
23623 .cindex "MX record" "security"
23624 .cindex "DNSSEC" "MX lookup"
23625 .cindex "security" "MX lookup"
23626 .cindex "DNS" "DNSSEC"
23627 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
23628 the dnssec request bit set. Any returns not having the Authenticated Data bit
23629 (AD bit) set will be ignored and logged as a host-lookup failure.
23630 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23634 .option dscp smtp string&!! unset
23635 .cindex "DCSP" "outbound"
23636 This option causes the DSCP value associated with a socket to be set to one
23637 of a number of fixed strings or to numeric value.
23638 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
23639 Common values include &`throughput`&, &`mincost`&, and on newer systems
23640 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
23642 The outbound packets from Exim will be marked with this value in the header
23643 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
23644 that these values will have any effect, not be stripped by networking
23645 equipment, or do much of anything without cooperation with your Network
23646 Engineer and those of all network operators between the source and destination.
23649 .option fallback_hosts smtp "string list" unset
23650 .cindex "fallback" "hosts specified on transport"
23651 String expansion is not applied to this option. The argument must be a
23652 colon-separated list of host names or IP addresses, optionally also including
23653 port numbers, though the separator can be changed, as described in section
23654 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23655 item in a &%route_list%& setting for the &(manualroute)& router, as described
23656 in section &<<SECTformatonehostitem>>&.
23658 Fallback hosts can also be specified on routers, which associate them with the
23659 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
23660 &%fallback_hosts%& specified on the transport is used only if the address does
23661 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
23662 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
23663 However, &%hosts_randomize%& does apply to fallback host lists.
23665 If Exim is unable to deliver to any of the hosts for a particular address, and
23666 the errors are not permanent rejections, the address is put on a separate
23667 transport queue with its host list replaced by the fallback hosts, unless the
23668 address was routed via MX records and the current host was in the original MX
23669 list. In that situation, the fallback host list is not used.
23671 Once normal deliveries are complete, the fallback queue is delivered by
23672 re-running the same transports with the new host lists. If several failing
23673 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
23674 copy of the message is sent.
23676 The resolution of the host names on the fallback list is controlled by the
23677 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
23678 both to cases when the host list comes with the address and when it is taken
23679 from &%hosts%&. This option provides a &"use a smart host only if delivery
23683 .option final_timeout smtp time 10m
23684 This is the timeout that applies while waiting for the response to the final
23685 line containing just &"."& that terminates a message. Its value must not be
23688 .option gethostbyname smtp boolean false
23689 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
23690 being used, names are looked up using &[gethostbyname()]&
23691 (or &[getipnodebyname()]& when available)
23692 instead of using the DNS. Of course, that function may in fact use the DNS, but
23693 it may also consult other sources of information such as &_/etc/hosts_&.
23695 .option gnutls_compat_mode smtp boolean unset
23696 This option controls whether GnuTLS is used in compatibility mode in an Exim
23697 server. This reduces security slightly, but improves interworking with older
23698 implementations of TLS.
23700 .option helo_data smtp string&!! "see below"
23701 .cindex "HELO" "argument, setting"
23702 .cindex "EHLO" "argument, setting"
23703 .cindex "LHLO argument setting"
23704 The value of this option is expanded after a connection to a another host has
23705 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
23706 command that starts the outgoing SMTP or LMTP session. The default value of the
23711 During the expansion, the variables &$host$& and &$host_address$& are set to
23712 the identity of the remote host, and the variables &$sending_ip_address$& and
23713 &$sending_port$& are set to the local IP address and port number that are being
23714 used. These variables can be used to generate different values for different
23715 servers or different local IP addresses. For example, if you want the string
23716 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
23717 interface address, you could use this:
23719 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
23720 {$primary_hostname}}
23722 The use of &%helo_data%& applies both to sending messages and when doing
23725 .option hosts smtp "string list&!!" unset
23726 Hosts are associated with an address by a router such as &(dnslookup)&, which
23727 finds the hosts by looking up the address domain in the DNS, or by
23728 &(manualroute)&, which has lists of hosts in its configuration. However,
23729 email addresses can be passed to the &(smtp)& transport by any router, and not
23730 all of them can provide an associated list of hosts.
23732 The &%hosts%& option specifies a list of hosts to be used if the address being
23733 processed does not have any hosts associated with it. The hosts specified by
23734 &%hosts%& are also used, whether or not the address has its own hosts, if
23735 &%hosts_override%& is set.
23737 The string is first expanded, before being interpreted as a colon-separated
23738 list of host names or IP addresses, possibly including port numbers. The
23739 separator may be changed to something other than colon, as described in section
23740 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23741 item in a &%route_list%& setting for the &(manualroute)& router, as described
23742 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
23743 of the &(manualroute)& router is not available here.
23745 If the expansion fails, delivery is deferred. Unless the failure was caused by
23746 the inability to complete a lookup, the error is logged to the panic log as
23747 well as the main log. Host names are looked up either by searching directly for
23748 address records in the DNS or by calling &[gethostbyname()]& (or
23749 &[getipnodebyname()]& when available), depending on the setting of the
23750 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
23751 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
23754 During delivery, the hosts are tried in order, subject to their retry status,
23755 unless &%hosts_randomize%& is set.
23758 .option hosts_avoid_esmtp smtp "host list&!!" unset
23759 .cindex "ESMTP, avoiding use of"
23760 .cindex "HELO" "forcing use of"
23761 .cindex "EHLO" "avoiding use of"
23762 .cindex "PIPELINING" "avoiding the use of"
23763 This option is for use with broken hosts that announce ESMTP facilities (for
23764 example, PIPELINING) and then fail to implement them properly. When a host
23765 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
23766 start of the SMTP session. This means that it cannot use any of the ESMTP
23767 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
23770 .option hosts_avoid_pipelining smtp "host list&!!" unset
23771 .cindex "PIPELINING" "avoiding the use of"
23772 Exim will not use the SMTP PIPELINING extension when delivering to any host
23773 that matches this list, even if the server host advertises PIPELINING support.
23776 .option hosts_avoid_tls smtp "host list&!!" unset
23777 .cindex "TLS" "avoiding for certain hosts"
23778 Exim will not try to start a TLS session when delivering to any host that
23779 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23781 .option hosts_verify_avoid_tls smtp "host list&!!" unset
23782 .cindex "TLS" "avoiding for certain hosts"
23783 Exim will not try to start a TLS session for a verify callout,
23784 or when delivering in cutthrough mode,
23785 to any host that matches this list.
23788 .option hosts_max_try smtp integer 5
23789 .cindex "host" "maximum number to try"
23790 .cindex "limit" "number of hosts tried"
23791 .cindex "limit" "number of MX tried"
23792 .cindex "MX record" "maximum tried"
23793 This option limits the number of IP addresses that are tried for any one
23794 delivery in cases where there are temporary delivery errors. Section
23795 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
23798 .option hosts_max_try_hardlimit smtp integer 50
23799 This is an additional check on the maximum number of IP addresses that Exim
23800 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
23805 .option hosts_nopass_tls smtp "host list&!!" unset
23806 .cindex "TLS" "passing connection"
23807 .cindex "multiple SMTP deliveries"
23808 .cindex "TLS" "multiple message deliveries"
23809 For any host that matches this list, a connection on which a TLS session has
23810 been started will not be passed to a new delivery process for sending another
23811 message on the same connection. See section &<<SECTmulmessam>>& for an
23812 explanation of when this might be needed.
23815 .option hosts_override smtp boolean false
23816 If this option is set and the &%hosts%& option is also set, any hosts that are
23817 attached to the address are ignored, and instead the hosts specified by the
23818 &%hosts%& option are always used. This option does not apply to
23819 &%fallback_hosts%&.
23822 .option hosts_randomize smtp boolean false
23823 .cindex "randomized host list"
23824 .cindex "host" "list of; randomized"
23825 .cindex "fallback" "randomized hosts"
23826 If this option is set, and either the list of hosts is taken from the
23827 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
23828 were not obtained from MX records (this includes fallback hosts from the
23829 router), and were not randomized by the router, the order of trying the hosts
23830 is randomized each time the transport runs. Randomizing the order of a host
23831 list can be used to do crude load sharing.
23833 When &%hosts_randomize%& is true, a host list may be split into groups whose
23834 order is separately randomized. This makes it possible to set up MX-like
23835 behaviour. The boundaries between groups are indicated by an item that is just
23836 &`+`& in the host list. For example:
23838 hosts = host1:host2:host3:+:host4:host5
23840 The order of the first three hosts and the order of the last two hosts is
23841 randomized for each use, but the first three always end up before the last two.
23842 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
23844 .option hosts_require_auth smtp "host list&!!" unset
23845 .cindex "authentication" "required by client"
23846 This option provides a list of servers for which authentication must succeed
23847 before Exim will try to transfer a message. If authentication fails for
23848 servers which are not in this list, Exim tries to send unauthenticated. If
23849 authentication fails for one of these servers, delivery is deferred. This
23850 temporary error is detectable in the retry rules, so it can be turned into a
23851 hard failure if required. See also &%hosts_try_auth%&, and chapter
23852 &<<CHAPSMTPAUTH>>& for details of authentication.
23855 .option hosts_request_ocsp smtp "host list&!!" *
23856 .cindex "TLS" "requiring for certain servers"
23857 Exim will request a Certificate Status on a
23858 TLS session for any host that matches this list.
23859 &%tls_verify_certificates%& should also be set for the transport.
23861 .option hosts_require_ocsp smtp "host list&!!" unset
23862 .cindex "TLS" "requiring for certain servers"
23863 Exim will request, and check for a valid Certificate Status being given, on a
23864 TLS session for any host that matches this list.
23865 &%tls_verify_certificates%& should also be set for the transport.
23867 .option hosts_require_tls smtp "host list&!!" unset
23868 .cindex "TLS" "requiring for certain servers"
23869 Exim will insist on using a TLS session when delivering to any host that
23870 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23871 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23872 incoming messages, use an appropriate ACL.
23874 .option hosts_try_auth smtp "host list&!!" unset
23875 .cindex "authentication" "optional in client"
23876 This option provides a list of servers to which, provided they announce
23877 authentication support, Exim will attempt to authenticate as a client when it
23878 connects. If authentication fails, Exim will try to transfer the message
23879 unauthenticated. See also &%hosts_require_auth%&, and chapter
23880 &<<CHAPSMTPAUTH>>& for details of authentication.
23882 .option hosts_try_prdr smtp "host list&!!" *
23883 .cindex "PRDR" "enabling, optional in client"
23884 This option provides a list of servers to which, provided they announce
23885 PRDR support, Exim will attempt to negotiate PRDR
23886 for multi-recipient messages.
23887 The option can usually be left as default.
23889 .option interface smtp "string list&!!" unset
23890 .cindex "bind IP address"
23891 .cindex "IP address" "binding"
23893 .vindex "&$host_address$&"
23894 This option specifies which interface to bind to when making an outgoing SMTP
23895 call. The value is an IP address, not an interface name such as
23896 &`eth0`&. Do not confuse this with the interface address that was used when a
23897 message was received, which is in &$received_ip_address$&, formerly known as
23898 &$interface_address$&. The name was changed to minimize confusion with the
23899 outgoing interface address. There is no variable that contains an outgoing
23900 interface address because, unless it is set by this option, its value is
23903 During the expansion of the &%interface%& option the variables &$host$& and
23904 &$host_address$& refer to the host to which a connection is about to be made
23905 during the expansion of the string. Forced expansion failure, or an empty
23906 string result causes the option to be ignored. Otherwise, after expansion, the
23907 string must be a list of IP addresses, colon-separated by default, but the
23908 separator can be changed in the usual way. For example:
23910 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
23912 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
23913 connection. If none of them are the correct type, the option is ignored. If
23914 &%interface%& is not set, or is ignored, the system's IP functions choose which
23915 interface to use if the host has more than one.
23918 .option keepalive smtp boolean true
23919 .cindex "keepalive" "on outgoing connection"
23920 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
23921 connections. When set, it causes the kernel to probe idle connections
23922 periodically, by sending packets with &"old"& sequence numbers. The other end
23923 of the connection should send a acknowledgment if the connection is still okay
23924 or a reset if the connection has been aborted. The reason for doing this is
23925 that it has the beneficial effect of freeing up certain types of connection
23926 that can get stuck when the remote host is disconnected without tidying up the
23927 TCP/IP call properly. The keepalive mechanism takes several hours to detect
23931 .option lmtp_ignore_quota smtp boolean false
23932 .cindex "LMTP" "ignoring quota errors"
23933 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
23934 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
23935 has advertised support for IGNOREQUOTA in its response to the LHLO command.
23937 .option max_rcpt smtp integer 100
23938 .cindex "RCPT" "maximum number of outgoing"
23939 This option limits the number of RCPT commands that are sent in a single
23940 SMTP message transaction. Each set of addresses is treated independently, and
23941 so can cause parallel connections to the same host if &%remote_max_parallel%&
23945 .option multi_domain smtp boolean&!! true
23946 .vindex "&$domain$&"
23947 When this option is set, the &(smtp)& transport can handle a number of
23948 addresses containing a mixture of different domains provided they all resolve
23949 to the same list of hosts. Turning the option off restricts the transport to
23950 handling only one domain at a time. This is useful if you want to use
23951 &$domain$& in an expansion for the transport, because it is set only when there
23952 is a single domain involved in a remote delivery.
23954 It is expanded per-address and can depend on any of
23955 &$address_data$&, &$domain_data$&, &$local_part_data$&,
23956 &$host$&, &$host_address$& and &$host_port$&.
23958 .option port smtp string&!! "see below"
23959 .cindex "port" "sending TCP/IP"
23960 .cindex "TCP/IP" "setting outgoing port"
23961 This option specifies the TCP/IP port on the server to which Exim connects.
23962 &*Note:*& Do not confuse this with the port that was used when a message was
23963 received, which is in &$received_port$&, formerly known as &$interface_port$&.
23964 The name was changed to minimize confusion with the outgoing port. There is no
23965 variable that contains an outgoing port.
23967 If the value of this option begins with a digit it is taken as a port number;
23968 otherwise it is looked up using &[getservbyname()]&. The default value is
23969 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
23970 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
23975 .option protocol smtp string smtp
23976 .cindex "LMTP" "over TCP/IP"
23977 .cindex "ssmtp protocol" "outbound"
23978 .cindex "TLS" "SSL-on-connect outbound"
23980 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
23981 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
23982 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
23983 deliveries into closed message stores. Exim also has support for running LMTP
23984 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
23986 If this option is set to &"smtps"&, the default value for the &%port%& option
23987 changes to &"smtps"&, and the transport initiates TLS immediately after
23988 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
23989 The Internet standards bodies strongly discourage use of this mode.
23992 .option retry_include_ip_address smtp boolean&!! true
23993 Exim normally includes both the host name and the IP address in the key it
23994 constructs for indexing retry data after a temporary delivery failure. This
23995 means that when one of several IP addresses for a host is failing, it gets
23996 tried periodically (controlled by the retry rules), but use of the other IP
23997 addresses is not affected.
23999 However, in some dialup environments hosts are assigned a different IP address
24000 each time they connect. In this situation the use of the IP address as part of
24001 the retry key leads to undesirable behaviour. Setting this option false causes
24002 Exim to use only the host name.
24003 Since it is expanded it can be made to depend on the host or domain.
24006 .option serialize_hosts smtp "host list&!!" unset
24007 .cindex "serializing connections"
24008 .cindex "host" "serializing connections"
24009 Because Exim operates in a distributed manner, if several messages for the same
24010 host arrive at around the same time, more than one simultaneous connection to
24011 the remote host can occur. This is not usually a problem except when there is a
24012 slow link between the hosts. In that situation it may be helpful to restrict
24013 Exim to one connection at a time. This can be done by setting
24014 &%serialize_hosts%& to match the relevant hosts.
24016 .cindex "hints database" "serializing deliveries to a host"
24017 Exim implements serialization by means of a hints database in which a record is
24018 written whenever a process connects to one of the restricted hosts. The record
24019 is deleted when the connection is completed. Obviously there is scope for
24020 records to get left lying around if there is a system or program crash. To
24021 guard against this, Exim ignores any records that are more than six hours old.
24023 If you set up this kind of serialization, you should also arrange to delete the
24024 relevant hints database whenever your system reboots. The names of the files
24025 start with &_misc_& and they are kept in the &_spool/db_& directory. There
24026 may be one or two files, depending on the type of DBM in use. The same files
24027 are used for ETRN serialization.
24029 See also the &%max_parallel%& generic transport option.
24032 .option size_addition smtp integer 1024
24033 .cindex "SMTP" "SIZE"
24034 .cindex "message" "size issue for transport filter"
24035 .cindex "size" "of message"
24036 .cindex "transport" "filter"
24037 .cindex "filter" "transport filter"
24038 If a remote SMTP server indicates that it supports the SIZE option of the
24039 MAIL command, Exim uses this to pass over the message size at the start of
24040 an SMTP transaction. It adds the value of &%size_addition%& to the value it
24041 sends, to allow for headers and other text that may be added during delivery by
24042 configuration options or in a transport filter. It may be necessary to increase
24043 this if a lot of text is added to messages.
24045 Alternatively, if the value of &%size_addition%& is set negative, it disables
24046 the use of the SIZE option altogether.
24049 .option socks_proxy smtp string&!! unset
24050 .cindex proxy SOCKS
24051 This option enables use of SOCKS proxies for connections made by the
24052 transport. For details see &<<SECTproxySOCKS>>&.
24055 .option tls_certificate smtp string&!! unset
24056 .cindex "TLS" "client certificate, location of"
24057 .cindex "certificate" "client, location of"
24059 .vindex "&$host_address$&"
24060 The value of this option must be the absolute path to a file which contains the
24061 client's certificate, for possible use when sending a message over an encrypted
24062 connection. The values of &$host$& and &$host_address$& are set to the name and
24063 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
24066 &*Note*&: This option must be set if you want Exim to be able to use a TLS
24067 certificate when sending messages as a client. The global option of the same
24068 name specifies the certificate for Exim as a server; it is not automatically
24069 assumed that the same certificate should be used when Exim is operating as a
24073 .option tls_crl smtp string&!! unset
24074 .cindex "TLS" "client certificate revocation list"
24075 .cindex "certificate" "revocation list for client"
24076 This option specifies a certificate revocation list. The expanded value must
24077 be the name of a file that contains a CRL in PEM format.
24080 .option tls_dh_min_bits smtp integer 1024
24081 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
24082 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
24083 key agreement is negotiated, the server will provide a large prime number
24084 for use. This option establishes the minimum acceptable size of that number.
24085 If the parameter offered by the server is too small, then the TLS handshake
24088 Only supported when using GnuTLS.
24091 .option tls_privatekey smtp string&!! unset
24092 .cindex "TLS" "client private key, location of"
24094 .vindex "&$host_address$&"
24095 The value of this option must be the absolute path to a file which contains the
24096 client's private key. This is used when sending a message over an encrypted
24097 connection using a client certificate. The values of &$host$& and
24098 &$host_address$& are set to the name and address of the server during the
24099 expansion. If this option is unset, or the expansion is forced to fail, or the
24100 result is an empty string, the private key is assumed to be in the same file as
24101 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
24104 .option tls_require_ciphers smtp string&!! unset
24105 .cindex "TLS" "requiring specific ciphers"
24106 .cindex "cipher" "requiring specific"
24108 .vindex "&$host_address$&"
24109 The value of this option must be a list of permitted cipher suites, for use
24110 when setting up an outgoing encrypted connection. (There is a global option of
24111 the same name for controlling incoming connections.) The values of &$host$& and
24112 &$host_address$& are set to the name and address of the server during the
24113 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
24114 is used in different ways by OpenSSL and GnuTLS (see sections
24115 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
24116 ciphers is a preference order.
24120 .option tls_sni smtp string&!! unset
24121 .cindex "TLS" "Server Name Indication"
24122 .vindex "&$tls_sni$&"
24123 If this option is set then it sets the $tls_out_sni variable and causes any
24124 TLS session to pass this value as the Server Name Indication extension to
24125 the remote side, which can be used by the remote side to select an appropriate
24126 certificate and private key for the session.
24128 See &<<SECTtlssni>>& for more information.
24130 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
24136 .option tls_tempfail_tryclear smtp boolean true
24137 .cindex "4&'xx'& responses" "to STARTTLS"
24138 When the server host is not in &%hosts_require_tls%&, and there is a problem in
24139 setting up a TLS session, this option determines whether or not Exim should try
24140 to deliver the message unencrypted. If it is set false, delivery to the
24141 current host is deferred; if there are other hosts, they are tried. If this
24142 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
24143 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
24144 TLS negotiation fails, Exim closes the current connection (because it is in an
24145 unknown state), opens a new one to the same host, and then tries the delivery
24149 .option tls_try_verify_hosts smtp "host list&!!" *
24150 .cindex "TLS" "server certificate verification"
24151 .cindex "certificate" "verification of server"
24152 This option gives a list of hosts for which, on encrypted connections,
24153 certificate verification will be tried but need not succeed.
24154 The &%tls_verify_certificates%& option must also be set.
24155 Note that unless the host is in this list
24156 TLS connections will be denied to hosts using self-signed certificates
24157 when &%tls_verify_certificates%& is matched.
24158 The &$tls_out_certificate_verified$& variable is set when
24159 certificate verification succeeds.
24162 .option tls_verify_cert_hostnames smtp "host list&!!" *
24163 .cindex "TLS" "server certificate hostname verification"
24164 .cindex "certificate" "verification of server"
24165 This option give a list of hosts for which,
24166 while verifying the server certificate,
24167 checks will be included on the host name
24168 (note that this will generally be the result of a DNS MX lookup)
24169 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
24170 limited to being the initial component of a 3-or-more component FQDN.
24172 There is no equivalent checking on client certificates.
24175 .option tls_verify_certificates smtp string&!! system
24176 .cindex "TLS" "server certificate verification"
24177 .cindex "certificate" "verification of server"
24179 .vindex "&$host_address$&"
24180 The value of this option must be either the
24182 or the absolute path to
24183 a file or directory containing permitted certificates for servers,
24184 for use when setting up an encrypted connection.
24186 The "system" value for the option will use a location compiled into the SSL library.
24187 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
24188 is taken as empty and an explicit location
24191 The use of a directory for the option value is not available for GnuTLS versions
24192 preceding 3.3.6 and a single file must be used.
24194 With OpenSSL the certificates specified
24196 either by file or directory
24197 are added to those given by the system default location.
24199 The values of &$host$& and
24200 &$host_address$& are set to the name and address of the server during the
24201 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
24203 For back-compatibility,
24204 if neither tls_verify_hosts nor tls_try_verify_hosts are set
24205 (a single-colon empty list counts as being set)
24206 and certificate verification fails the TLS connection is closed.
24209 .option tls_verify_hosts smtp "host list&!!" unset
24210 .cindex "TLS" "server certificate verification"
24211 .cindex "certificate" "verification of server"
24212 This option gives a list of hosts for which, on encrypted connections,
24213 certificate verification must succeed.
24214 The &%tls_verify_certificates%& option must also be set.
24215 If both this option and &%tls_try_verify_hosts%& are unset
24216 operation is as if this option selected all hosts.
24221 .section "How the limits for the number of hosts to try are used" &&&
24223 .cindex "host" "maximum number to try"
24224 .cindex "limit" "hosts; maximum number tried"
24225 There are two options that are concerned with the number of hosts that are
24226 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
24227 &%hosts_max_try_hardlimit%&.
24230 The &%hosts_max_try%& option limits the number of hosts that are tried
24231 for a single delivery. However, despite the term &"host"& in its name, the
24232 option actually applies to each IP address independently. In other words, a
24233 multihomed host is treated as several independent hosts, just as it is for
24236 Many of the larger ISPs have multiple MX records which often point to
24237 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
24238 created as a result of routing one of these domains.
24240 Trying every single IP address on such a long list does not seem sensible; if
24241 several at the top of the list fail, it is reasonable to assume there is some
24242 problem that is likely to affect all of them. Roughly speaking, the value of
24243 &%hosts_max_try%& is the maximum number that are tried before deferring the
24244 delivery. However, the logic cannot be quite that simple.
24246 Firstly, IP addresses that are skipped because their retry times have not
24247 arrived do not count, and in addition, addresses that are past their retry
24248 limits are also not counted, even when they are tried. This means that when
24249 some IP addresses are past their retry limits, more than the value of
24250 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
24251 that all IP addresses are considered before timing out an email address (but
24252 see below for an exception).
24254 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
24255 list to see if there is a subsequent host with a different (higher valued) MX.
24256 If there is, that host is considered next, and the current IP address is used
24257 but not counted. This behaviour helps in the case of a domain with a retry rule
24258 that hardly ever delays any hosts, as is now explained:
24260 Consider the case of a long list of hosts with one MX value, and a few with a
24261 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
24262 hosts at the top of the list are tried at first. With the default retry rule,
24263 which specifies increasing retry times, the higher MX hosts are eventually
24264 tried when those at the top of the list are skipped because they have not
24265 reached their retry times.
24267 However, it is common practice to put a fixed short retry time on domains for
24268 large ISPs, on the grounds that their servers are rarely down for very long.
24269 Unfortunately, these are exactly the domains that tend to resolve to long lists
24270 of hosts. The short retry time means that the lowest MX hosts are tried every
24271 time. The attempts may be in a different order because of random sorting, but
24272 without the special MX check, the higher MX hosts would never be tried until
24273 all the lower MX hosts had timed out (which might be several days), because
24274 there are always some lower MX hosts that have reached their retry times. With
24275 the special check, Exim considers at least one IP address from each MX value at
24276 every delivery attempt, even if the &%hosts_max_try%& limit has already been
24279 The above logic means that &%hosts_max_try%& is not a hard limit, and in
24280 particular, Exim normally eventually tries all the IP addresses before timing
24281 out an email address. When &%hosts_max_try%& was implemented, this seemed a
24282 reasonable thing to do. Recently, however, some lunatic DNS configurations have
24283 been set up with hundreds of IP addresses for some domains. It can
24284 take a very long time indeed for an address to time out in these cases.
24286 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
24287 Exim never tries more than this number of IP addresses; if it hits this limit
24288 and they are all timed out, the email address is bounced, even though not all
24289 possible IP addresses have been tried.
24290 .ecindex IIDsmttra1
24291 .ecindex IIDsmttra2
24297 . ////////////////////////////////////////////////////////////////////////////
24298 . ////////////////////////////////////////////////////////////////////////////
24300 .chapter "Address rewriting" "CHAPrewrite"
24301 .scindex IIDaddrew "rewriting" "addresses"
24302 There are some circumstances in which Exim automatically rewrites domains in
24303 addresses. The two most common are when an address is given without a domain
24304 (referred to as an &"unqualified address"&) or when an address contains an
24305 abbreviated domain that is expanded by DNS lookup.
24307 Unqualified envelope addresses are accepted only for locally submitted
24308 messages, or for messages that are received from hosts matching
24309 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24310 appropriate. Unqualified addresses in header lines are qualified if they are in
24311 locally submitted messages, or messages from hosts that are permitted to send
24312 unqualified envelope addresses. Otherwise, unqualified addresses in header
24313 lines are neither qualified nor rewritten.
24315 One situation in which Exim does &'not'& automatically rewrite a domain is
24316 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
24317 such a domain should be rewritten using the &"canonical"& name, and some MTAs
24318 do this. The new RFCs do not contain this suggestion.
24321 .section "Explicitly configured address rewriting" "SECID147"
24322 This chapter describes the rewriting rules that can be used in the
24323 main rewrite section of the configuration file, and also in the generic
24324 &%headers_rewrite%& option that can be set on any transport.
24326 Some people believe that configured address rewriting is a Mortal Sin.
24327 Others believe that life is not possible without it. Exim provides the
24328 facility; you do not have to use it.
24330 The main rewriting rules that appear in the &"rewrite"& section of the
24331 configuration file are applied to addresses in incoming messages, both envelope
24332 addresses and addresses in header lines. Each rule specifies the types of
24333 address to which it applies.
24335 Whether or not addresses in header lines are rewritten depends on the origin of
24336 the headers and the type of rewriting. Global rewriting, that is, rewriting
24337 rules from the rewrite section of the configuration file, is applied only to
24338 those headers that were received with the message. Header lines that are added
24339 by ACLs or by a system filter or by individual routers or transports (which
24340 are specific to individual recipient addresses) are not rewritten by the global
24343 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24344 applies all headers except those added by routers and transports. That is, as
24345 well as the headers that were received with the message, it also applies to
24346 headers that were added by an ACL or a system filter.
24349 In general, rewriting addresses from your own system or domain has some
24350 legitimacy. Rewriting other addresses should be done only with great care and
24351 in special circumstances. The author of Exim believes that rewriting should be
24352 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24353 Although it can sometimes be used as a routing tool, this is very strongly
24356 There are two commonly encountered circumstances where rewriting is used, as
24357 illustrated by these examples:
24360 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24361 exchange mail with each other behind a firewall, but there is only a single
24362 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24363 &'hitch.fict.example'& when sending mail off-site.
24365 A host rewrites the local parts of its own users so that, for example,
24366 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24371 .section "When does rewriting happen?" "SECID148"
24372 .cindex "rewriting" "timing of"
24373 .cindex "&ACL;" "rewriting addresses in"
24374 Configured address rewriting can take place at several different stages of a
24375 message's processing.
24377 .vindex "&$sender_address$&"
24378 At the start of an ACL for MAIL, the sender address may have been rewritten
24379 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24380 ordinary rewrite rules have yet been applied. If, however, the sender address
24381 is verified in the ACL, it is rewritten before verification, and remains
24382 rewritten thereafter. The subsequent value of &$sender_address$& is the
24383 rewritten address. This also applies if sender verification happens in a
24384 RCPT ACL. Otherwise, when the sender address is not verified, it is
24385 rewritten as soon as a message's header lines have been received.
24387 .vindex "&$domain$&"
24388 .vindex "&$local_part$&"
24389 Similarly, at the start of an ACL for RCPT, the current recipient's address
24390 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24391 rewrite rules have yet been applied to it. However, the behaviour is different
24392 from the sender address when a recipient is verified. The address is rewritten
24393 for the verification, but the rewriting is not remembered at this stage. The
24394 value of &$local_part$& and &$domain$& after verification are always the same
24395 as they were before (that is, they contain the unrewritten &-- except for
24396 SMTP-time rewriting &-- address).
24398 As soon as a message's header lines have been received, all the envelope
24399 recipient addresses are permanently rewritten, and rewriting is also applied to
24400 the addresses in the header lines (if configured). This happens before adding
24401 any header lines that were specified in MAIL or RCPT ACLs, and
24402 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24403 before the DATA ACL and &[local_scan()]& functions are run.
24405 When an address is being routed, either for delivery or for verification,
24406 rewriting is applied immediately to child addresses that are generated by
24407 redirection, unless &%no_rewrite%& is set on the router.
24409 .cindex "envelope sender" "rewriting at transport time"
24410 .cindex "rewriting" "at transport time"
24411 .cindex "header lines" "rewriting at transport time"
24412 At transport time, additional rewriting of addresses in header lines can be
24413 specified by setting the generic &%headers_rewrite%& option on a transport.
24414 This option contains rules that are identical in form to those in the rewrite
24415 section of the configuration file. They are applied to the original message
24416 header lines and any that were added by ACLs or a system filter. They are not
24417 applied to header lines that are added by routers or the transport.
24419 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24420 transport option. However, it is not possible to rewrite envelope recipients at
24426 .section "Testing the rewriting rules that apply on input" "SECID149"
24427 .cindex "rewriting" "testing"
24428 .cindex "testing" "rewriting"
24429 Exim's input rewriting configuration appears in a part of the run time
24430 configuration file headed by &"begin rewrite"&. It can be tested by the
24431 &%-brw%& command line option. This takes an address (which can be a full RFC
24432 2822 address) as its argument. The output is a list of how the address would be
24433 transformed by the rewriting rules for each of the different places it might
24434 appear in an incoming message, that is, for each different header and for the
24435 envelope sender and recipient fields. For example,
24437 exim -brw ph10@exim.workshop.example
24439 might produce the output
24441 sender: Philip.Hazel@exim.workshop.example
24442 from: Philip.Hazel@exim.workshop.example
24443 to: ph10@exim.workshop.example
24444 cc: ph10@exim.workshop.example
24445 bcc: ph10@exim.workshop.example
24446 reply-to: Philip.Hazel@exim.workshop.example
24447 env-from: Philip.Hazel@exim.workshop.example
24448 env-to: ph10@exim.workshop.example
24450 which shows that rewriting has been set up for that address when used in any of
24451 the source fields, but not when it appears as a recipient address. At the
24452 present time, there is no equivalent way of testing rewriting rules that are
24453 set for a particular transport.
24456 .section "Rewriting rules" "SECID150"
24457 .cindex "rewriting" "rules"
24458 The rewrite section of the configuration file consists of lines of rewriting
24461 <&'source pattern'&> <&'replacement'&> <&'flags'&>
24463 Rewriting rules that are specified for the &%headers_rewrite%& generic
24464 transport option are given as a colon-separated list. Each item in the list
24465 takes the same form as a line in the main rewriting configuration (except that
24466 any colons must be doubled, of course).
24468 The formats of source patterns and replacement strings are described below.
24469 Each is terminated by white space, unless enclosed in double quotes, in which
24470 case normal quoting conventions apply inside the quotes. The flags are single
24471 characters which may appear in any order. Spaces and tabs between them are
24474 For each address that could potentially be rewritten, the rules are scanned in
24475 order, and replacements for the address from earlier rules can themselves be
24476 replaced by later rules (but see the &"q"& and &"R"& flags).
24478 The order in which addresses are rewritten is undefined, may change between
24479 releases, and must not be relied on, with one exception: when a message is
24480 received, the envelope sender is always rewritten first, before any header
24481 lines are rewritten. For example, the replacement string for a rewrite of an
24482 address in &'To:'& must not assume that the message's address in &'From:'& has
24483 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
24484 that the envelope sender has already been rewritten.
24486 .vindex "&$domain$&"
24487 .vindex "&$local_part$&"
24488 The variables &$local_part$& and &$domain$& can be used in the replacement
24489 string to refer to the address that is being rewritten. Note that lookup-driven
24490 rewriting can be done by a rule of the form
24494 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
24495 refer to the address that is being rewritten.
24498 .section "Rewriting patterns" "SECID151"
24499 .cindex "rewriting" "patterns"
24500 .cindex "address list" "in a rewriting pattern"
24501 The source pattern in a rewriting rule is any item which may appear in an
24502 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
24503 single-item address list, which means that it is expanded before being tested
24504 against the address. As always, if you use a regular expression as a pattern,
24505 you must take care to escape dollar and backslash characters, or use the &`\N`&
24506 facility to suppress string expansion within the regular expression.
24508 Domains in patterns should be given in lower case. Local parts in patterns are
24509 case-sensitive. If you want to do case-insensitive matching of local parts, you
24510 can use a regular expression that starts with &`^(?i)`&.
24512 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
24513 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
24514 depending on the type of match which occurred. These can be used in the
24515 replacement string to insert portions of the incoming address. &$0$& always
24516 refers to the complete incoming address. When a regular expression is used, the
24517 numerical variables are set from its capturing subexpressions. For other types
24518 of pattern they are set as follows:
24521 If a local part or domain starts with an asterisk, the numerical variables
24522 refer to the character strings matched by asterisks, with &$1$& associated with
24523 the first asterisk, and &$2$& with the second, if present. For example, if the
24526 *queen@*.fict.example
24528 is matched against the address &'hearts-queen@wonderland.fict.example'& then
24530 $0 = hearts-queen@wonderland.fict.example
24534 Note that if the local part does not start with an asterisk, but the domain
24535 does, it is &$1$& that contains the wild part of the domain.
24538 If the domain part of the pattern is a partial lookup, the wild and fixed parts
24539 of the domain are placed in the next available numerical variables. Suppose,
24540 for example, that the address &'foo@bar.baz.example'& is processed by a
24541 rewriting rule of the form
24543 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
24545 and the key in the file that matches the domain is &`*.baz.example`&. Then
24551 If the address &'foo@baz.example'& is looked up, this matches the same
24552 wildcard file entry, and in this case &$2$& is set to the empty string, but
24553 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
24554 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
24555 whole domain. For non-partial domain lookups, no numerical variables are set.
24559 .section "Rewriting replacements" "SECID152"
24560 .cindex "rewriting" "replacements"
24561 If the replacement string for a rule is a single asterisk, addresses that
24562 match the pattern and the flags are &'not'& rewritten, and no subsequent
24563 rewriting rules are scanned. For example,
24565 hatta@lookingglass.fict.example * f
24567 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
24570 .vindex "&$domain$&"
24571 .vindex "&$local_part$&"
24572 If the replacement string is not a single asterisk, it is expanded, and must
24573 yield a fully qualified address. Within the expansion, the variables
24574 &$local_part$& and &$domain$& refer to the address that is being rewritten.
24575 Any letters they contain retain their original case &-- they are not lower
24576 cased. The numerical variables are set up according to the type of pattern that
24577 matched the address, as described above. If the expansion is forced to fail by
24578 the presence of &"fail"& in a conditional or lookup item, rewriting by the
24579 current rule is abandoned, but subsequent rules may take effect. Any other
24580 expansion failure causes the entire rewriting operation to be abandoned, and an
24581 entry written to the panic log.
24585 .section "Rewriting flags" "SECID153"
24586 There are three different kinds of flag that may appear on rewriting rules:
24589 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
24592 A flag that specifies rewriting at SMTP time: S.
24594 Flags that control the rewriting process: Q, q, R, w.
24597 For rules that are part of the &%headers_rewrite%& generic transport option,
24598 E, F, T, and S are not permitted.
24602 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
24604 .cindex "rewriting" "flags"
24605 If none of the following flag letters, nor the &"S"& flag (see section
24606 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
24607 and to both the sender and recipient fields of the envelope, whereas a
24608 transport-time rewriting rule just applies to all headers. Otherwise, the
24609 rewriting rule is skipped unless the relevant addresses are being processed.
24611 &`E`& rewrite all envelope fields
24612 &`F`& rewrite the envelope From field
24613 &`T`& rewrite the envelope To field
24614 &`b`& rewrite the &'Bcc:'& header
24615 &`c`& rewrite the &'Cc:'& header
24616 &`f`& rewrite the &'From:'& header
24617 &`h`& rewrite all headers
24618 &`r`& rewrite the &'Reply-To:'& header
24619 &`s`& rewrite the &'Sender:'& header
24620 &`t`& rewrite the &'To:'& header
24622 "All headers" means all of the headers listed above that can be selected
24623 individually, plus their &'Resent-'& versions. It does not include
24624 other headers such as &'Subject:'& etc.
24626 You should be particularly careful about rewriting &'Sender:'& headers, and
24627 restrict this to special known cases in your own domains.
24630 .section "The SMTP-time rewriting flag" "SECTrewriteS"
24631 .cindex "SMTP" "rewriting malformed addresses"
24632 .cindex "RCPT" "rewriting argument of"
24633 .cindex "MAIL" "rewriting argument of"
24634 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
24635 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
24636 before any other processing; even before syntax checking. The pattern is
24637 required to be a regular expression, and it is matched against the whole of the
24638 data for the command, including any surrounding angle brackets.
24640 .vindex "&$domain$&"
24641 .vindex "&$local_part$&"
24642 This form of rewrite rule allows for the handling of addresses that are not
24643 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
24644 input). Because the input is not required to be a syntactically valid address,
24645 the variables &$local_part$& and &$domain$& are not available during the
24646 expansion of the replacement string. The result of rewriting replaces the
24647 original address in the MAIL or RCPT command.
24650 .section "Flags controlling the rewriting process" "SECID155"
24651 There are four flags which control the way the rewriting process works. These
24652 take effect only when a rule is invoked, that is, when the address is of the
24653 correct type (matches the flags) and matches the pattern:
24656 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
24657 unqualified local part. It is qualified with &%qualify_recipient%&. In the
24658 absence of &"Q"& the rewritten address must always include a domain.
24660 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
24661 even if no rewriting actually takes place because of a &"fail"& in the
24662 expansion. The &"q"& flag is not effective if the address is of the wrong type
24663 (does not match the flags) or does not match the pattern.
24665 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
24666 address, up to ten times. It can be combined with the &"q"& flag, to stop
24667 rewriting once it fails to match (after at least one successful rewrite).
24669 .cindex "rewriting" "whole addresses"
24670 When an address in a header is rewritten, the rewriting normally applies only
24671 to the working part of the address, with any comments and RFC 2822 &"phrase"&
24672 left unchanged. For example, rewriting might change
24674 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
24678 From: Ford Prefect <prefectf@hitch.fict.example>
24681 Sometimes there is a need to replace the whole address item, and this can be
24682 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
24683 causes an address in a header line to be rewritten, the entire address is
24684 replaced, not just the working part. The replacement must be a complete RFC
24685 2822 address, including the angle brackets if necessary. If text outside angle
24686 brackets contains a character whose value is greater than 126 or less than 32
24687 (except for tab), the text is encoded according to RFC 2047. The character set
24688 is taken from &%headers_charset%&, which gets its default at build time.
24690 When the &"w"& flag is set on a rule that causes an envelope address to be
24691 rewritten, all but the working part of the replacement address is discarded.
24695 .section "Rewriting examples" "SECID156"
24696 Here is an example of the two common rewriting paradigms:
24698 *@*.hitch.fict.example $1@hitch.fict.example
24699 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
24700 {$value}fail}@hitch.fict.example bctfrF
24702 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
24703 the string expansion to fail if the lookup does not succeed. In this context it
24704 has the effect of leaving the original address unchanged, but Exim goes on to
24705 consider subsequent rewriting rules, if any, because the &"q"& flag is not
24706 present in that rule. An alternative to &"fail"& would be to supply &$1$&
24707 explicitly, which would cause the rewritten address to be the same as before,
24708 at the cost of a small bit of processing. Not supplying either of these is an
24709 error, since the rewritten address would then contain no local part.
24711 The first example above replaces the domain with a superior, more general
24712 domain. This may not be desirable for certain local parts. If the rule
24714 root@*.hitch.fict.example *
24716 were inserted before the first rule, rewriting would be suppressed for the
24717 local part &'root'& at any domain ending in &'hitch.fict.example'&.
24719 Rewriting can be made conditional on a number of tests, by making use of
24720 &${if$& in the expansion item. For example, to apply a rewriting rule only to
24721 messages that originate outside the local host:
24723 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
24724 {$1@hitch.fict.example}fail}"
24726 The replacement string is quoted in this example because it contains white
24729 .cindex "rewriting" "bang paths"
24730 .cindex "bang paths" "rewriting"
24731 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
24732 an address it treats it as an unqualified local part which it qualifies with
24733 the local qualification domain (if the source of the message is local or if the
24734 remote host is permitted to send unqualified addresses). Rewriting can
24735 sometimes be used to handle simple bang paths with a fixed number of
24736 components. For example, the rule
24738 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
24740 rewrites a two-component bang path &'host.name!user'& as the domain address
24741 &'user@host.name'&. However, there is a security implication in using this as
24742 a global rewriting rule for envelope addresses. It can provide a backdoor
24743 method for using your system as a relay, because the incoming addresses appear
24744 to be local. If the bang path addresses are received via SMTP, it is safer to
24745 use the &"S"& flag to rewrite them as they are received, so that relay checking
24746 can be done on the rewritten addresses.
24753 . ////////////////////////////////////////////////////////////////////////////
24754 . ////////////////////////////////////////////////////////////////////////////
24756 .chapter "Retry configuration" "CHAPretry"
24757 .scindex IIDretconf1 "retry" "configuration, description of"
24758 .scindex IIDregconf2 "configuration file" "retry section"
24759 The &"retry"& section of the runtime configuration file contains a list of
24760 retry rules that control how often Exim tries to deliver messages that cannot
24761 be delivered at the first attempt. If there are no retry rules (the section is
24762 empty or not present), there are no retries. In this situation, temporary
24763 errors are treated as permanent. The default configuration contains a single,
24764 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
24765 line option can be used to test which retry rule will be used for a given
24766 address, domain and error.
24768 The most common cause of retries is temporary failure to deliver to a remote
24769 host because the host is down, or inaccessible because of a network problem.
24770 Exim's retry processing in this case is applied on a per-host (strictly, per IP
24771 address) basis, not on a per-message basis. Thus, if one message has recently
24772 been delayed, delivery of a new message to the same host is not immediately
24773 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
24774 log selector is set, the message
24775 .cindex "retry" "time not reached"
24776 &"retry time not reached"& is written to the main log whenever a delivery is
24777 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
24778 the handling of errors during remote deliveries.
24780 Retry processing applies to routing as well as to delivering, except as covered
24781 in the next paragraph. The retry rules do not distinguish between these
24782 actions. It is not possible, for example, to specify different behaviour for
24783 failures to route the domain &'snark.fict.example'& and failures to deliver to
24784 the host &'snark.fict.example'&. I didn't think anyone would ever need this
24785 added complication, so did not implement it. However, although they share the
24786 same retry rule, the actual retry times for routing and transporting a given
24787 domain are maintained independently.
24789 When a delivery is not part of a queue run (typically an immediate delivery on
24790 receipt of a message), the routers are always run, and local deliveries are
24791 always attempted, even if retry times are set for them. This makes for better
24792 behaviour if one particular message is causing problems (for example, causing
24793 quota overflow, or provoking an error in a filter file). If such a delivery
24794 suffers a temporary failure, the retry data is updated as normal, and
24795 subsequent delivery attempts from queue runs occur only when the retry time for
24796 the local address is reached.
24798 .section "Changing retry rules" "SECID157"
24799 If you change the retry rules in your configuration, you should consider
24800 whether or not to delete the retry data that is stored in Exim's spool area in
24801 files with names like &_db/retry_&. Deleting any of Exim's hints files is
24802 always safe; that is why they are called &"hints"&.
24804 The hints retry data contains suggested retry times based on the previous
24805 rules. In the case of a long-running problem with a remote host, it might
24806 record the fact that the host has timed out. If your new rules increase the
24807 timeout time for such a host, you should definitely remove the old retry data
24808 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
24809 messages that it should now be retaining.
24813 .section "Format of retry rules" "SECID158"
24814 .cindex "retry" "rules"
24815 Each retry rule occupies one line and consists of three or four parts,
24816 separated by white space: a pattern, an error name, an optional list of sender
24817 addresses, and a list of retry parameters. The pattern and sender lists must be
24818 enclosed in double quotes if they contain white space. The rules are searched
24819 in order until one is found where the pattern, error name, and sender list (if
24820 present) match the failing host or address, the error that occurred, and the
24821 message's sender, respectively.
24824 The pattern is any single item that may appear in an address list (see section
24825 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
24826 which means that it is expanded before being tested against the address that
24827 has been delayed. A negated address list item is permitted. Address
24828 list processing treats a plain domain name as if it were preceded by &"*@"&,
24829 which makes it possible for many retry rules to start with just a domain. For
24832 lookingglass.fict.example * F,24h,30m;
24834 provides a rule for any address in the &'lookingglass.fict.example'& domain,
24837 alice@lookingglass.fict.example * F,24h,30m;
24839 applies only to temporary failures involving the local part &%alice%&.
24840 In practice, almost all rules start with a domain name pattern without a local
24843 .cindex "regular expressions" "in retry rules"
24844 &*Warning*&: If you use a regular expression in a retry rule pattern, it
24845 must match a complete address, not just a domain, because that is how regular
24846 expressions work in address lists.
24848 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
24849 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
24853 .section "Choosing which retry rule to use for address errors" "SECID159"
24854 When Exim is looking for a retry rule after a routing attempt has failed (for
24855 example, after a DNS timeout), each line in the retry configuration is tested
24856 against the complete address only if &%retry_use_local_part%& is set for the
24857 router. Otherwise, only the domain is used, except when matching against a
24858 regular expression, when the local part of the address is replaced with &"*"&.
24859 A domain on its own can match a domain pattern, or a pattern that starts with
24860 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
24861 &%check_local_user%& is true, and false for other routers.
24863 Similarly, when Exim is looking for a retry rule after a local delivery has
24864 failed (for example, after a mailbox full error), each line in the retry
24865 configuration is tested against the complete address only if
24866 &%retry_use_local_part%& is set for the transport (it defaults true for all
24869 .cindex "4&'xx'& responses" "retry rules for"
24870 However, when Exim is looking for a retry rule after a remote delivery attempt
24871 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
24872 whole address is always used as the key when searching the retry rules. The
24873 rule that is found is used to create a retry time for the combination of the
24874 failing address and the message's sender. It is the combination of sender and
24875 recipient that is delayed in subsequent queue runs until its retry time is
24876 reached. You can delay the recipient without regard to the sender by setting
24877 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
24878 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
24883 .section "Choosing which retry rule to use for host and message errors" &&&
24885 For a temporary error that is not related to an individual address (for
24886 example, a connection timeout), each line in the retry configuration is checked
24887 twice. First, the name of the remote host is used as a domain name (preceded by
24888 &"*@"& when matching a regular expression). If this does not match the line,
24889 the domain from the email address is tried in a similar fashion. For example,
24890 suppose the MX records for &'a.b.c.example'& are
24892 a.b.c.example MX 5 x.y.z.example
24896 and the retry rules are
24898 p.q.r.example * F,24h,30m;
24899 a.b.c.example * F,4d,45m;
24901 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
24902 first rule matches neither the host nor the domain, so Exim looks at the second
24903 rule. This does not match the host, but it does match the domain, so it is used
24904 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
24905 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
24906 first retry rule is used, because it matches the host.
24908 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
24909 first rule to determine retry times, but for all the other hosts for the domain
24910 &'a.b.c.example'&, the second rule is used. The second rule is also used if
24911 routing to &'a.b.c.example'& suffers a temporary failure.
24913 &*Note*&: The host name is used when matching the patterns, not its IP address.
24914 However, if a message is routed directly to an IP address without the use of a
24915 host name, for example, if a &(manualroute)& router contains a setting such as:
24917 route_list = *.a.example 192.168.34.23
24919 then the &"host name"& that is used when searching for a retry rule is the
24920 textual form of the IP address.
24922 .section "Retry rules for specific errors" "SECID161"
24923 .cindex "retry" "specific errors; specifying"
24924 The second field in a retry rule is the name of a particular error, or an
24925 asterisk, which matches any error. The errors that can be tested for are:
24928 .vitem &%auth_failed%&
24929 Authentication failed when trying to send to a host in the
24930 &%hosts_require_auth%& list in an &(smtp)& transport.
24932 .vitem &%data_4xx%&
24933 A 4&'xx'& error was received for an outgoing DATA command, either immediately
24934 after the command, or after sending the message's data.
24936 .vitem &%mail_4xx%&
24937 A 4&'xx'& error was received for an outgoing MAIL command.
24939 .vitem &%rcpt_4xx%&
24940 A 4&'xx'& error was received for an outgoing RCPT command.
24943 For the three 4&'xx'& errors, either the first or both of the x's can be given
24944 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
24945 recognize 452 errors given to RCPT commands for addresses in a certain domain,
24946 and have retries every ten minutes with a one-hour timeout, you could set up a
24947 retry rule of this form:
24949 the.domain.name rcpt_452 F,1h,10m
24951 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
24952 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
24955 .vitem &%lost_connection%&
24956 A server unexpectedly closed the SMTP connection. There may, of course,
24957 legitimate reasons for this (host died, network died), but if it repeats a lot
24958 for the same host, it indicates something odd.
24961 A DNS lookup for a host failed.
24962 Note that a &%dnslookup%& router will need to have matched
24963 its &%fail_defer_domains%& option for this retry type to be usable.
24964 Also note that a &%manualroute%& router will probably need
24965 its &%host_find_failed%& option set to &%defer%&.
24967 .vitem &%refused_MX%&
24968 A connection to a host obtained from an MX record was refused.
24970 .vitem &%refused_A%&
24971 A connection to a host not obtained from an MX record was refused.
24974 A connection was refused.
24976 .vitem &%timeout_connect_MX%&
24977 A connection attempt to a host obtained from an MX record timed out.
24979 .vitem &%timeout_connect_A%&
24980 A connection attempt to a host not obtained from an MX record timed out.
24982 .vitem &%timeout_connect%&
24983 A connection attempt timed out.
24985 .vitem &%timeout_MX%&
24986 There was a timeout while connecting or during an SMTP session with a host
24987 obtained from an MX record.
24989 .vitem &%timeout_A%&
24990 There was a timeout while connecting or during an SMTP session with a host not
24991 obtained from an MX record.
24994 There was a timeout while connecting or during an SMTP session.
24996 .vitem &%tls_required%&
24997 The server was required to use TLS (it matched &%hosts_require_tls%& in the
24998 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
24999 to STARTTLS, or there was a problem setting up the TLS connection.
25002 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25005 .vitem &%quota_%&<&'time'&>
25006 .cindex "quota" "error testing in retry rule"
25007 .cindex "retry" "quota error testing"
25008 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25009 transport, and the mailbox has not been accessed for <&'time'&>. For example,
25010 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
25014 .cindex "mailbox" "time of last read"
25015 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
25016 timeouts when the mailbox is full and is not being read by its owner. Ideally,
25017 it should be based on the last time that the user accessed the mailbox.
25018 However, it is not always possible to determine this. Exim uses the following
25022 If the mailbox is a single file, the time of last access (the &"atime"&) is
25023 used. As no new messages are being delivered (because the mailbox is over
25024 quota), Exim does not access the file, so this is the time of last user access.
25026 .cindex "maildir format" "time of last read"
25027 For a maildir delivery, the time of last modification of the &_new_&
25028 subdirectory is used. As the mailbox is over quota, no new files are created in
25029 the &_new_& subdirectory, because no new messages are being delivered. Any
25030 change to the &_new_& subdirectory is therefore assumed to be the result of an
25031 MUA moving a new message to the &_cur_& directory when it is first read. The
25032 time that is used is therefore the last time that the user read a new message.
25034 For other kinds of multi-file mailbox, the time of last access cannot be
25035 obtained, so a retry rule that uses this type of error field is never matched.
25038 The quota errors apply both to system-enforced quotas and to Exim's own quota
25039 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
25040 when a local delivery is deferred because a partition is full (the ENOSPC
25045 .section "Retry rules for specified senders" "SECID162"
25046 .cindex "retry" "rules; sender-specific"
25047 You can specify retry rules that apply only when the failing message has a
25048 specific sender. In particular, this can be used to define retry rules that
25049 apply only to bounce messages. The third item in a retry rule can be of this
25052 &`senders=`&<&'address list'&>
25054 The retry timings themselves are then the fourth item. For example:
25056 * rcpt_4xx senders=: F,1h,30m
25058 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
25059 host. If the address list contains white space, it must be enclosed in quotes.
25062 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
25064 &*Warning*&: This facility can be unhelpful if it is used for host errors
25065 (which do not depend on the recipient). The reason is that the sender is used
25066 only to match the retry rule. Once the rule has been found for a host error,
25067 its contents are used to set a retry time for the host, and this will apply to
25068 all messages, not just those with specific senders.
25070 When testing retry rules using &%-brt%&, you can supply a sender using the
25071 &%-f%& command line option, like this:
25073 exim -f "" -brt user@dom.ain
25075 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
25076 list is never matched.
25082 .section "Retry parameters" "SECID163"
25083 .cindex "retry" "parameters in rules"
25084 The third (or fourth, if a senders list is present) field in a retry rule is a
25085 sequence of retry parameter sets, separated by semicolons. Each set consists of
25087 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
25089 The letter identifies the algorithm for computing a new retry time; the cutoff
25090 time is the time beyond which this algorithm no longer applies, and the
25091 arguments vary the algorithm's action. The cutoff time is measured from the
25092 time that the first failure for the domain (combined with the local part if
25093 relevant) was detected, not from the time the message was received.
25095 .cindex "retry" "algorithms"
25096 .cindex "retry" "fixed intervals"
25097 .cindex "retry" "increasing intervals"
25098 .cindex "retry" "random intervals"
25099 The available algorithms are:
25102 &'F'&: retry at fixed intervals. There is a single time parameter specifying
25105 &'G'&: retry at geometrically increasing intervals. The first argument
25106 specifies a starting value for the interval, and the second a multiplier, which
25107 is used to increase the size of the interval at each retry.
25109 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
25110 retry, the previous interval is multiplied by the factor in order to get a
25111 maximum for the next interval. The minimum interval is the first argument of
25112 the parameter, and an actual interval is chosen randomly between them. Such a
25113 rule has been found to be helpful in cluster configurations when all the
25114 members of the cluster restart at once, and may therefore synchronize their
25115 queue processing times.
25118 When computing the next retry time, the algorithm definitions are scanned in
25119 order until one whose cutoff time has not yet passed is reached. This is then
25120 used to compute a new retry time that is later than the current time. In the
25121 case of fixed interval retries, this simply means adding the interval to the
25122 current time. For geometrically increasing intervals, retry intervals are
25123 computed from the rule's parameters until one that is greater than the previous
25124 interval is found. The main configuration variable
25125 .cindex "limit" "retry interval"
25126 .cindex "retry" "interval, maximum"
25127 .oindex "&%retry_interval_max%&"
25128 &%retry_interval_max%& limits the maximum interval between retries. It
25129 cannot be set greater than &`24h`&, which is its default value.
25131 A single remote domain may have a number of hosts associated with it, and each
25132 host may have more than one IP address. Retry algorithms are selected on the
25133 basis of the domain name, but are applied to each IP address independently. If,
25134 for example, a host has two IP addresses and one is unusable, Exim will
25135 generate retry times for it and will not try to use it until its next retry
25136 time comes. Thus the good IP address is likely to be tried first most of the
25139 .cindex "hints database" "use for retrying"
25140 Retry times are hints rather than promises. Exim does not make any attempt to
25141 run deliveries exactly at the computed times. Instead, a queue runner process
25142 starts delivery processes for delayed messages periodically, and these attempt
25143 new deliveries only for those addresses that have passed their next retry time.
25144 If a new message arrives for a deferred address, an immediate delivery attempt
25145 occurs only if the address has passed its retry time. In the absence of new
25146 messages, the minimum time between retries is the interval between queue runner
25147 processes. There is not much point in setting retry times of five minutes if
25148 your queue runners happen only once an hour, unless there are a significant
25149 number of incoming messages (which might be the case on a system that is
25150 sending everything to a smart host, for example).
25152 The data in the retry hints database can be inspected by using the
25153 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
25154 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
25155 &'exinext'& utility script can be used to find out what the next retry times
25156 are for the hosts associated with a particular mail domain, and also for local
25157 deliveries that have been deferred.
25160 .section "Retry rule examples" "SECID164"
25161 Here are some example retry rules:
25163 alice@wonderland.fict.example quota_5d F,7d,3h
25164 wonderland.fict.example quota_5d
25165 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
25166 lookingglass.fict.example * F,24h,30m;
25167 * refused_A F,2h,20m;
25168 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
25170 The first rule sets up special handling for mail to
25171 &'alice@wonderland.fict.example'& when there is an over-quota error and the
25172 mailbox has not been read for at least 5 days. Retries continue every three
25173 hours for 7 days. The second rule handles over-quota errors for all other local
25174 parts at &'wonderland.fict.example'&; the absence of a local part has the same
25175 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
25176 fail are bounced immediately if the mailbox has not been read for at least 5
25179 The third rule handles all other errors at &'wonderland.fict.example'&; retries
25180 happen every 15 minutes for an hour, then with geometrically increasing
25181 intervals until two days have passed since a delivery first failed. After the
25182 first hour there is a delay of one hour, then two hours, then four hours, and
25183 so on (this is a rather extreme example).
25185 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
25186 They happen every 30 minutes for 24 hours only. The remaining two rules handle
25187 all other domains, with special action for connection refusal from hosts that
25188 were not obtained from an MX record.
25190 The final rule in a retry configuration should always have asterisks in the
25191 first two fields so as to provide a general catch-all for any addresses that do
25192 not have their own special handling. This example tries every 15 minutes for 2
25193 hours, then with intervals starting at one hour and increasing by a factor of
25194 1.5 up to 16 hours, then every 8 hours up to 5 days.
25198 .section "Timeout of retry data" "SECID165"
25199 .cindex "timeout" "of retry data"
25200 .oindex "&%retry_data_expire%&"
25201 .cindex "hints database" "data expiry"
25202 .cindex "retry" "timeout of data"
25203 Exim timestamps the data that it writes to its retry hints database. When it
25204 consults the data during a delivery it ignores any that is older than the value
25205 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
25206 been tried for 7 days, Exim will try to deliver to it immediately a message
25207 arrives, and if that fails, it will calculate a retry time as if it were
25208 failing for the first time.
25210 This improves the behaviour for messages routed to rarely-used hosts such as MX
25211 backups. If such a host was down at one time, and happens to be down again when
25212 Exim tries a month later, using the old retry data would imply that it had been
25213 down all the time, which is not a justified assumption.
25215 If a host really is permanently dead, this behaviour causes a burst of retries
25216 every now and again, but only if messages routed to it are rare. If there is a
25217 message at least once every 7 days the retry data never expires.
25222 .section "Long-term failures" "SECID166"
25223 .cindex "delivery failure, long-term"
25224 .cindex "retry" "after long-term failure"
25225 Special processing happens when an email address has been failing for so long
25226 that the cutoff time for the last algorithm is reached. For example, using the
25227 default retry rule:
25229 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
25231 the cutoff time is four days. Reaching the retry cutoff is independent of how
25232 long any specific message has been failing; it is the length of continuous
25233 failure for the recipient address that counts.
25235 When the cutoff time is reached for a local delivery, or for all the IP
25236 addresses associated with a remote delivery, a subsequent delivery failure
25237 causes Exim to give up on the address, and a bounce message is generated.
25238 In order to cater for new messages that use the failing address, a next retry
25239 time is still computed from the final algorithm, and is used as follows:
25241 For local deliveries, one delivery attempt is always made for any subsequent
25242 messages. If this delivery fails, the address fails immediately. The
25243 post-cutoff retry time is not used.
25245 If the delivery is remote, there are two possibilities, controlled by the
25246 .oindex "&%delay_after_cutoff%&"
25247 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
25248 default. Until the post-cutoff retry time for one of the IP addresses is
25249 reached, the failing email address is bounced immediately, without a delivery
25250 attempt taking place. After that time, one new delivery attempt is made to
25251 those IP addresses that are past their retry times, and if that still fails,
25252 the address is bounced and new retry times are computed.
25254 In other words, when all the hosts for a given email address have been failing
25255 for a long time, Exim bounces rather then defers until one of the hosts' retry
25256 times is reached. Then it tries once, and bounces if that attempt fails. This
25257 behaviour ensures that few resources are wasted in repeatedly trying to deliver
25258 to a broken destination, but if the host does recover, Exim will eventually
25261 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25262 addresses are past their final cutoff time, Exim tries to deliver to those IP
25263 addresses that have not been tried since the message arrived. If there are
25264 no suitable IP addresses, or if they all fail, the address is bounced. In other
25265 words, it does not delay when a new message arrives, but tries the expired
25266 addresses immediately, unless they have been tried since the message arrived.
25267 If there is a continuous stream of messages for the failing domains, setting
25268 &%delay_after_cutoff%& false means that there will be many more attempts to
25269 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
25272 .section "Deliveries that work intermittently" "SECID167"
25273 .cindex "retry" "intermittently working deliveries"
25274 Some additional logic is needed to cope with cases where a host is
25275 intermittently available, or when a message has some attribute that prevents
25276 its delivery when others to the same address get through. In this situation,
25277 because some messages are successfully delivered, the &"retry clock"& for the
25278 host or address keeps getting reset by the successful deliveries, and so
25279 failing messages remain on the queue for ever because the cutoff time is never
25282 Two exceptional actions are applied to prevent this happening. The first
25283 applies to errors that are related to a message rather than a remote host.
25284 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
25285 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
25286 commands, and quota failures. For this type of error, if a message's arrival
25287 time is earlier than the &"first failed"& time for the error, the earlier time
25288 is used when scanning the retry rules to decide when to try next and when to
25289 time out the address.
25291 The exceptional second action applies in all cases. If a message has been on
25292 the queue for longer than the cutoff time of any applicable retry rule for a
25293 given address, a delivery is attempted for that address, even if it is not yet
25294 time, and if this delivery fails, the address is timed out. A new retry time is
25295 not computed in this case, so that other messages for the same address are
25296 considered immediately.
25297 .ecindex IIDretconf1
25298 .ecindex IIDregconf2
25305 . ////////////////////////////////////////////////////////////////////////////
25306 . ////////////////////////////////////////////////////////////////////////////
25308 .chapter "SMTP authentication" "CHAPSMTPAUTH"
25309 .scindex IIDauthconf1 "SMTP" "authentication configuration"
25310 .scindex IIDauthconf2 "authentication"
25311 The &"authenticators"& section of Exim's run time configuration is concerned
25312 with SMTP authentication. This facility is an extension to the SMTP protocol,
25313 described in RFC 2554, which allows a client SMTP host to authenticate itself
25314 to a server. This is a common way for a server to recognize clients that are
25315 permitted to use it as a relay. SMTP authentication is not of relevance to the
25316 transfer of mail between servers that have no managerial connection with each
25319 .cindex "AUTH" "description of"
25320 Very briefly, the way SMTP authentication works is as follows:
25323 The server advertises a number of authentication &'mechanisms'& in response to
25324 the client's EHLO command.
25326 The client issues an AUTH command, naming a specific mechanism. The command
25327 may, optionally, contain some authentication data.
25329 The server may issue one or more &'challenges'&, to which the client must send
25330 appropriate responses. In simple authentication mechanisms, the challenges are
25331 just prompts for user names and passwords. The server does not have to issue
25332 any challenges &-- in some mechanisms the relevant data may all be transmitted
25333 with the AUTH command.
25335 The server either accepts or denies authentication.
25337 If authentication succeeds, the client may optionally make use of the AUTH
25338 option on the MAIL command to pass an authenticated sender in subsequent
25339 mail transactions. Authentication lasts for the remainder of the SMTP
25342 If authentication fails, the client may give up, or it may try a different
25343 authentication mechanism, or it may try transferring mail over the
25344 unauthenticated connection.
25347 If you are setting up a client, and want to know which authentication
25348 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25349 SMTP port) on the server, and issue an EHLO command. The response to this
25350 includes the list of supported mechanisms. For example:
25352 &`$ `&&*&`telnet server.example 25`&*&
25353 &`Trying 192.168.34.25...`&
25354 &`Connected to server.example.`&
25355 &`Escape character is '^]'.`&
25356 &`220 server.example ESMTP Exim 4.20 ...`&
25357 &*&`ehlo client.example`&*&
25358 &`250-server.example Hello client.example [10.8.4.5]`&
25359 &`250-SIZE 52428800`&
25364 The second-last line of this example output shows that the server supports
25365 authentication using the PLAIN mechanism. In Exim, the different authentication
25366 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25367 routers and transports, which authenticators are included in the binary is
25368 controlled by build-time definitions. The following are currently available,
25369 included by setting
25372 AUTH_CYRUS_SASL=yes
25375 AUTH_HEIMDAL_GSSAPI=yes
25380 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25381 authentication mechanism (RFC 2195), and the second provides an interface to
25382 the Cyrus SASL authentication library.
25383 The third is an interface to Dovecot's authentication system, delegating the
25384 work via a socket interface.
25385 The fourth provides an interface to the GNU SASL authentication library, which
25386 provides mechanisms but typically not data sources.
25387 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25388 supporting setting a server keytab.
25389 The sixth can be configured to support
25390 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25391 not formally documented, but used by several MUAs. The seventh authenticator
25392 supports Microsoft's &'Secure Password Authentication'& mechanism.
25393 The eighth is an Exim authenticator but not an SMTP one;
25394 instead it can use information from a TLS negotiation.
25396 The authenticators are configured using the same syntax as other drivers (see
25397 section &<<SECTfordricon>>&). If no authenticators are required, no
25398 authentication section need be present in the configuration file. Each
25399 authenticator can in principle have both server and client functions. When Exim
25400 is receiving SMTP mail, it is acting as a server; when it is sending out
25401 messages over SMTP, it is acting as a client. Authenticator configuration
25402 options are provided for use in both these circumstances.
25404 To make it clear which options apply to which situation, the prefixes
25405 &%server_%& and &%client_%& are used on option names that are specific to
25406 either the server or the client function, respectively. Server and client
25407 functions are disabled if none of their options are set. If an authenticator is
25408 to be used for both server and client functions, a single definition, using
25409 both sets of options, is required. For example:
25413 public_name = CRAM-MD5
25414 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25416 client_secret = secret2
25418 The &%server_%& option is used when Exim is acting as a server, and the
25419 &%client_%& options when it is acting as a client.
25421 Descriptions of the individual authenticators are given in subsequent chapters.
25422 The remainder of this chapter covers the generic options for the
25423 authenticators, followed by general discussion of the way authentication works
25426 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25427 per-mechanism basis. Please read carefully to determine which variables hold
25428 account labels such as usercodes and which hold passwords or other
25429 authenticating data.
25431 Note that some mechanisms support two different identifiers for accounts: the
25432 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25433 and &'authz'& are commonly encountered. The American spelling is standard here.
25434 Conceptually, authentication data such as passwords are tied to the identifier
25435 used to authenticate; servers may have rules to permit one user to act as a
25436 second user, so that after login the session is treated as though that second
25437 user had logged in. That second user is the &'authorization id'&. A robust
25438 configuration might confirm that the &'authz'& field is empty or matches the
25439 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25440 as verified data, the &'authz'& as an unverified request which the server might
25443 A &'realm'& is a text string, typically a domain name, presented by a server
25444 to a client to help it select an account and credentials to use. In some
25445 mechanisms, the client and server provably agree on the realm, but clients
25446 typically can not treat the realm as secure data to be blindly trusted.
25450 .section "Generic options for authenticators" "SECID168"
25451 .cindex "authentication" "generic options"
25452 .cindex "options" "generic; for authenticators"
25454 .option client_condition authenticators string&!! unset
25455 When Exim is authenticating as a client, it skips any authenticator whose
25456 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
25457 used, for example, to skip plain text authenticators when the connection is not
25458 encrypted by a setting such as:
25460 client_condition = ${if !eq{$tls_out_cipher}{}}
25464 .option client_set_id authenticators string&!! unset
25465 When client authentication succeeds, this condition is expanded; the
25466 result is used in the log lines for outbound messages.
25467 Typically it will be the user name used for authentication.
25470 .option driver authenticators string unset
25471 This option must always be set. It specifies which of the available
25472 authenticators is to be used.
25475 .option public_name authenticators string unset
25476 This option specifies the name of the authentication mechanism that the driver
25477 implements, and by which it is known to the outside world. These names should
25478 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
25479 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
25480 defaults to the driver's instance name.
25483 .option server_advertise_condition authenticators string&!! unset
25484 When a server is about to advertise an authentication mechanism, the condition
25485 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
25486 mechanism is not advertised.
25487 If the expansion fails, the mechanism is not advertised. If the failure was not
25488 forced, and was not caused by a lookup defer, the incident is logged.
25489 See section &<<SECTauthexiser>>& below for further discussion.
25492 .option server_condition authenticators string&!! unset
25493 This option must be set for a &%plaintext%& server authenticator, where it
25494 is used directly to control authentication. See section &<<SECTplainserver>>&
25497 For the &(gsasl)& authenticator, this option is required for various
25498 mechanisms; see chapter &<<CHAPgsasl>>& for details.
25500 For the other authenticators, &%server_condition%& can be used as an additional
25501 authentication or authorization mechanism that is applied after the other
25502 authenticator conditions succeed. If it is set, it is expanded when the
25503 authenticator would otherwise return a success code. If the expansion is forced
25504 to fail, authentication fails. Any other expansion failure causes a temporary
25505 error code to be returned. If the result of a successful expansion is an empty
25506 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25507 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
25508 other result, a temporary error code is returned, with the expanded string as
25512 .option server_debug_print authenticators string&!! unset
25513 If this option is set and authentication debugging is enabled (see the &%-d%&
25514 command line option), the string is expanded and included in the debugging
25515 output when the authenticator is run as a server. This can help with checking
25516 out the values of variables.
25517 If expansion of the string fails, the error message is written to the debugging
25518 output, and Exim carries on processing.
25521 .option server_set_id authenticators string&!! unset
25522 .vindex "&$authenticated_id$&"
25523 When an Exim server successfully authenticates a client, this string is
25524 expanded using data from the authentication, and preserved for any incoming
25525 messages in the variable &$authenticated_id$&. It is also included in the log
25526 lines for incoming messages. For example, a user/password authenticator
25527 configuration might preserve the user name that was used to authenticate, and
25528 refer to it subsequently during delivery of the message.
25529 If expansion fails, the option is ignored.
25532 .option server_mail_auth_condition authenticators string&!! unset
25533 This option allows a server to discard authenticated sender addresses supplied
25534 as part of MAIL commands in SMTP connections that are authenticated by the
25535 driver on which &%server_mail_auth_condition%& is set. The option is not used
25536 as part of the authentication process; instead its (unexpanded) value is
25537 remembered for later use.
25538 How it is used is described in the following section.
25544 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
25545 .cindex "authentication" "sender; authenticated"
25546 .cindex "AUTH" "on MAIL command"
25547 When a client supplied an AUTH= item on a MAIL command, Exim applies
25548 the following checks before accepting it as the authenticated sender of the
25552 If the connection is not using extended SMTP (that is, HELO was used rather
25553 than EHLO), the use of AUTH= is a syntax error.
25555 If the value of the AUTH= parameter is &"<>"&, it is ignored.
25557 .vindex "&$authenticated_sender$&"
25558 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
25559 running, the value of &$authenticated_sender$& is set to the value obtained
25560 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
25561 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
25562 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
25563 given for the MAIL command.
25565 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
25566 is accepted and placed in &$authenticated_sender$& only if the client has
25569 If the AUTH= value was accepted by either of the two previous rules, and
25570 the client has authenticated, and the authenticator has a setting for the
25571 &%server_mail_auth_condition%&, the condition is checked at this point. The
25572 valued that was saved from the authenticator is expanded. If the expansion
25573 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
25574 &$authenticated_sender$& is deleted. If the expansion yields any other value,
25575 the value of &$authenticated_sender$& is retained and passed on with the
25580 When &$authenticated_sender$& is set for a message, it is passed on to other
25581 hosts to which Exim authenticates as a client. Do not confuse this value with
25582 &$authenticated_id$&, which is a string obtained from the authentication
25583 process, and which is not usually a complete email address.
25585 .vindex "&$sender_address$&"
25586 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
25587 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
25588 therefore make use of &$authenticated_sender$&. The converse is not true: the
25589 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
25594 .section "Authentication on an Exim server" "SECTauthexiser"
25595 .cindex "authentication" "on an Exim server"
25596 When Exim receives an EHLO command, it advertises the public names of those
25597 authenticators that are configured as servers, subject to the following
25601 The client host must match &%auth_advertise_hosts%& (default *).
25603 It the &%server_advertise_condition%& option is set, its expansion must not
25604 yield the empty string, &"0"&, &"no"&, or &"false"&.
25607 The order in which the authenticators are defined controls the order in which
25608 the mechanisms are advertised.
25610 Some mail clients (for example, some versions of Netscape) require the user to
25611 provide a name and password for authentication whenever AUTH is advertised,
25612 even though authentication may not in fact be needed (for example, Exim may be
25613 set up to allow unconditional relaying from the client by an IP address check).
25614 You can make such clients more friendly by not advertising AUTH to them.
25615 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
25616 that runs for RCPT) to relay without authentication, you should set
25618 auth_advertise_hosts = ! 10.9.8.0/24
25620 so that no authentication mechanisms are advertised to them.
25622 The &%server_advertise_condition%& controls the advertisement of individual
25623 authentication mechanisms. For example, it can be used to restrict the
25624 advertisement of a particular mechanism to encrypted connections, by a setting
25627 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
25629 .vindex "&$tls_in_cipher$&"
25630 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
25631 yields &"yes"&, which allows the advertisement to happen.
25633 When an Exim server receives an AUTH command from a client, it rejects it
25634 immediately if AUTH was not advertised in response to an earlier EHLO
25635 command. This is the case if
25638 The client host does not match &%auth_advertise_hosts%&; or
25640 No authenticators are configured with server options; or
25642 Expansion of &%server_advertise_condition%& blocked the advertising of all the
25643 server authenticators.
25647 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
25648 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
25649 AUTH is accepted from any client host.
25651 If AUTH is not rejected by the ACL, Exim searches its configuration for a
25652 server authentication mechanism that was advertised in response to EHLO and
25653 that matches the one named in the AUTH command. If it finds one, it runs
25654 the appropriate authentication protocol, and authentication either succeeds or
25655 fails. If there is no matching advertised mechanism, the AUTH command is
25656 rejected with a 504 error.
25658 .vindex "&$received_protocol$&"
25659 .vindex "&$sender_host_authenticated$&"
25660 When a message is received from an authenticated host, the value of
25661 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
25662 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
25663 public name) of the authenticator driver that successfully authenticated the
25664 client from which the message was received. This variable is empty if there was
25665 no successful authentication.
25670 .section "Testing server authentication" "SECID169"
25671 .cindex "authentication" "testing a server"
25672 .cindex "AUTH" "testing a server"
25673 .cindex "base64 encoding" "creating authentication test data"
25674 Exim's &%-bh%& option can be useful for testing server authentication
25675 configurations. The data for the AUTH command has to be sent using base64
25676 encoding. A quick way to produce such data for testing is the following Perl
25680 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
25682 .cindex "binary zero" "in authentication data"
25683 This interprets its argument as a Perl string, and then encodes it. The
25684 interpretation as a Perl string allows binary zeros, which are required for
25685 some kinds of authentication, to be included in the data. For example, a
25686 command line to run this script on such data might be
25688 encode '\0user\0password'
25690 Note the use of single quotes to prevent the shell interpreting the
25691 backslashes, so that they can be interpreted by Perl to specify characters
25692 whose code value is zero.
25694 &*Warning 1*&: If either of the user or password strings starts with an octal
25695 digit, you must use three zeros instead of one after the leading backslash. If
25696 you do not, the octal digit that starts your string will be incorrectly
25697 interpreted as part of the code for the first character.
25699 &*Warning 2*&: If there are characters in the strings that Perl interprets
25700 specially, you must use a Perl escape to prevent them being misinterpreted. For
25701 example, a command such as
25703 encode '\0user@domain.com\0pas$$word'
25705 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
25707 If you have the &%mimencode%& command installed, another way to do produce
25708 base64-encoded strings is to run the command
25710 echo -e -n `\0user\0password' | mimencode
25712 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
25713 in the argument, and the &%-n%& option specifies no newline at the end of its
25714 output. However, not all versions of &%echo%& recognize these options, so you
25715 should check your version before relying on this suggestion.
25719 .section "Authentication by an Exim client" "SECID170"
25720 .cindex "authentication" "on an Exim client"
25721 The &(smtp)& transport has two options called &%hosts_require_auth%& and
25722 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
25723 announces support for authentication, and the host matches an entry in either
25724 of these options, Exim (as a client) tries to authenticate as follows:
25727 For each authenticator that is configured as a client, in the order in which
25728 they are defined in the configuration, it searches the authentication
25729 mechanisms announced by the server for one whose name matches the public name
25730 of the authenticator.
25733 .vindex "&$host_address$&"
25734 When it finds one that matches, it runs the authenticator's client code. The
25735 variables &$host$& and &$host_address$& are available for any string expansions
25736 that the client might do. They are set to the server's name and IP address. If
25737 any expansion is forced to fail, the authentication attempt is abandoned, and
25738 Exim moves on to the next authenticator. Otherwise an expansion failure causes
25739 delivery to be deferred.
25741 If the result of the authentication attempt is a temporary error or a timeout,
25742 Exim abandons trying to send the message to the host for the moment. It will
25743 try again later. If there are any backup hosts available, they are tried in the
25746 If the response to authentication is a permanent error (5&'xx'& code), Exim
25747 carries on searching the list of authenticators and tries another one if
25748 possible. If all authentication attempts give permanent errors, or if there are
25749 no attempts because no mechanisms match (or option expansions force failure),
25750 what happens depends on whether the host matches &%hosts_require_auth%& or
25751 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
25752 delivery is deferred. The error can be detected in the retry rules, and thereby
25753 turned into a permanent error if you wish. In the second case, Exim tries to
25754 deliver the message unauthenticated.
25757 .cindex "AUTH" "on MAIL command"
25758 When Exim has authenticated itself to a remote server, it adds the AUTH
25759 parameter to the MAIL commands it sends, if it has an authenticated sender for
25760 the message. If the message came from a remote host, the authenticated sender
25761 is the one that was receiving on an incoming MAIL command, provided that the
25762 incoming connection was authenticated and the &%server_mail_auth%& condition
25763 allowed the authenticated sender to be retained. If a local process calls Exim
25764 to send a message, the sender address that is built from the login name and
25765 &%qualify_domain%& is treated as authenticated. However, if the
25766 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
25767 the authenticated sender that was received with the message.
25768 .ecindex IIDauthconf1
25769 .ecindex IIDauthconf2
25776 . ////////////////////////////////////////////////////////////////////////////
25777 . ////////////////////////////////////////////////////////////////////////////
25779 .chapter "The plaintext authenticator" "CHAPplaintext"
25780 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
25781 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
25782 The &(plaintext)& authenticator can be configured to support the PLAIN and
25783 LOGIN authentication mechanisms, both of which transfer authentication data as
25784 plain (unencrypted) text (though base64 encoded). The use of plain text is a
25785 security risk; you are strongly advised to insist on the use of SMTP encryption
25786 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
25787 use unencrypted plain text, you should not use the same passwords for SMTP
25788 connections as you do for login accounts.
25790 .section "Plaintext options" "SECID171"
25791 .cindex "options" "&(plaintext)& authenticator (server)"
25792 When configured as a server, &(plaintext)& uses the following options:
25794 .option server_condition authenticators string&!! unset
25795 This is actually a global authentication option, but it must be set in order to
25796 configure the &(plaintext)& driver as a server. Its use is described below.
25798 .option server_prompts plaintext string&!! unset
25799 The contents of this option, after expansion, must be a colon-separated list of
25800 prompt strings. If expansion fails, a temporary authentication rejection is
25803 .section "Using plaintext in a server" "SECTplainserver"
25804 .cindex "AUTH" "in &(plaintext)& authenticator"
25805 .cindex "binary zero" "in &(plaintext)& authenticator"
25806 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
25807 "in &(plaintext)& authenticator"
25808 .vindex "&$auth1$&, &$auth2$&, etc"
25809 .cindex "base64 encoding" "in &(plaintext)& authenticator"
25811 When running as a server, &(plaintext)& performs the authentication test by
25812 expanding a string. The data sent by the client with the AUTH command, or in
25813 response to subsequent prompts, is base64 encoded, and so may contain any byte
25814 values when decoded. If any data is supplied with the command, it is treated as
25815 a list of strings, separated by NULs (binary zeros), the first three of which
25816 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
25817 (neither LOGIN nor PLAIN uses more than three strings).
25819 For compatibility with previous releases of Exim, the values are also placed in
25820 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
25821 variables for this purpose is now deprecated, as it can lead to confusion in
25822 string expansions that also use them for other things.
25824 If there are more strings in &%server_prompts%& than the number of strings
25825 supplied with the AUTH command, the remaining prompts are used to obtain more
25826 data. Each response from the client may be a list of NUL-separated strings.
25828 .vindex "&$authenticated_id$&"
25829 Once a sufficient number of data strings have been received,
25830 &%server_condition%& is expanded. If the expansion is forced to fail,
25831 authentication fails. Any other expansion failure causes a temporary error code
25832 to be returned. If the result of a successful expansion is an empty string,
25833 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25834 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
25835 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
25836 For any other result, a temporary error code is returned, with the expanded
25837 string as the error text
25839 &*Warning*&: If you use a lookup in the expansion to find the user's
25840 password, be sure to make the authentication fail if the user is unknown.
25841 There are good and bad examples at the end of the next section.
25845 .section "The PLAIN authentication mechanism" "SECID172"
25846 .cindex "PLAIN authentication mechanism"
25847 .cindex "authentication" "PLAIN mechanism"
25848 .cindex "binary zero" "in &(plaintext)& authenticator"
25849 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
25850 sent as one item of data (that is, one combined string containing two NUL
25851 separators). The data is sent either as part of the AUTH command, or
25852 subsequently in response to an empty prompt from the server.
25854 The second and third strings are a user name and a corresponding password.
25855 Using a single fixed user name and password as an example, this could be
25856 configured as follows:
25860 public_name = PLAIN
25862 server_condition = \
25863 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
25864 server_set_id = $auth2
25866 Note that the default result strings from &%if%& (&"true"& or an empty string)
25867 are exactly what we want here, so they need not be specified. Obviously, if the
25868 password contains expansion-significant characters such as dollar, backslash,
25869 or closing brace, they have to be escaped.
25871 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
25872 the end of a string list are ignored). If all the data comes as part of the
25873 AUTH command, as is commonly the case, the prompt is not used. This
25874 authenticator is advertised in the response to EHLO as
25878 and a client host can authenticate itself by sending the command
25880 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
25882 As this contains three strings (more than the number of prompts), no further
25883 data is required from the client. Alternatively, the client may just send
25887 to initiate authentication, in which case the server replies with an empty
25888 prompt. The client must respond with the combined data string.
25890 The data string is base64 encoded, as required by the RFC. This example,
25891 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
25892 represents a zero byte. This is split up into three strings, the first of which
25893 is empty. The &%server_condition%& option in the authenticator checks that the
25894 second two are &`username`& and &`mysecret`& respectively.
25896 Having just one fixed user name and password, as in this example, is not very
25897 realistic, though for a small organization with only a handful of
25898 authenticating clients it could make sense.
25900 A more sophisticated instance of this authenticator could use the user name in
25901 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
25902 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
25903 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
25904 This is an incorrect example:
25906 server_condition = \
25907 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
25909 The expansion uses the user name (&$auth2$&) as the key to look up a password,
25910 which it then compares to the supplied password (&$auth3$&). Why is this example
25911 incorrect? It works fine for existing users, but consider what happens if a
25912 non-existent user name is given. The lookup fails, but as no success/failure
25913 strings are given for the lookup, it yields an empty string. Thus, to defeat
25914 the authentication, all a client has to do is to supply a non-existent user
25915 name and an empty password. The correct way of writing this test is:
25917 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
25918 {${if eq{$value}{$auth3}}} {false}}
25920 In this case, if the lookup succeeds, the result is checked; if the lookup
25921 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
25922 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
25923 always fails if its second argument is empty. However, the second way of
25924 writing the test makes the logic clearer.
25927 .section "The LOGIN authentication mechanism" "SECID173"
25928 .cindex "LOGIN authentication mechanism"
25929 .cindex "authentication" "LOGIN mechanism"
25930 The LOGIN authentication mechanism is not documented in any RFC, but is in use
25931 in a number of programs. No data is sent with the AUTH command. Instead, a
25932 user name and password are supplied separately, in response to prompts. The
25933 plaintext authenticator can be configured to support this as in this example:
25937 public_name = LOGIN
25938 server_prompts = User Name : Password
25939 server_condition = \
25940 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
25941 server_set_id = $auth1
25943 Because of the way plaintext operates, this authenticator accepts data supplied
25944 with the AUTH command (in contravention of the specification of LOGIN), but
25945 if the client does not supply it (as is the case for LOGIN clients), the prompt
25946 strings are used to obtain two data items.
25948 Some clients are very particular about the precise text of the prompts. For
25949 example, Outlook Express is reported to recognize only &"Username:"& and
25950 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
25951 strings. It uses the &%ldapauth%& expansion condition to check the user
25952 name and password by binding to an LDAP server:
25956 public_name = LOGIN
25957 server_prompts = Username:: : Password::
25958 server_condition = ${if and{{ \
25961 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
25962 pass=${quote:$auth2} \
25963 ldap://ldap.example.org/} }} }
25964 server_set_id = uid=$auth1,ou=people,o=example.org
25966 We have to check that the username is not empty before using it, because LDAP
25967 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
25968 operator to correctly quote the DN for authentication. However, the basic
25969 &%quote%& operator, rather than any of the LDAP quoting operators, is the
25970 correct one to use for the password, because quoting is needed only to make
25971 the password conform to the Exim syntax. At the LDAP level, the password is an
25972 uninterpreted string.
25975 .section "Support for different kinds of authentication" "SECID174"
25976 A number of string expansion features are provided for the purpose of
25977 interfacing to different ways of user authentication. These include checking
25978 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
25979 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
25985 .section "Using plaintext in a client" "SECID175"
25986 .cindex "options" "&(plaintext)& authenticator (client)"
25987 The &(plaintext)& authenticator has two client options:
25989 .option client_ignore_invalid_base64 plaintext boolean false
25990 If the client receives a server prompt that is not a valid base64 string,
25991 authentication is abandoned by default. However, if this option is set true,
25992 the error in the challenge is ignored and the client sends the response as
25995 .option client_send plaintext string&!! unset
25996 The string is a colon-separated list of authentication data strings. Each
25997 string is independently expanded before being sent to the server. The first
25998 string is sent with the AUTH command; any more strings are sent in response
25999 to prompts from the server. Before each string is expanded, the value of the
26000 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
26001 with &$auth1$& for the first prompt. Up to three prompts are stored in this
26002 way. Thus, the prompt that is received in response to sending the first string
26003 (with the AUTH command) can be used in the expansion of the second string, and
26004 so on. If an invalid base64 string is received when
26005 &%client_ignore_invalid_base64%& is set, an empty string is put in the
26006 &$auth$&<&'n'&> variable.
26008 &*Note*&: You cannot use expansion to create multiple strings, because
26009 splitting takes priority and happens first.
26011 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
26012 the data, further processing is applied to each string before it is sent. If
26013 there are any single circumflex characters in the string, they are converted to
26014 NULs. Should an actual circumflex be required as data, it must be doubled in
26017 This is an example of a client configuration that implements the PLAIN
26018 authentication mechanism with a fixed user name and password:
26022 public_name = PLAIN
26023 client_send = ^username^mysecret
26025 The lack of colons means that the entire text is sent with the AUTH
26026 command, with the circumflex characters converted to NULs. A similar example
26027 that uses the LOGIN mechanism is:
26031 public_name = LOGIN
26032 client_send = : username : mysecret
26034 The initial colon means that the first string is empty, so no data is sent with
26035 the AUTH command itself. The remaining strings are sent in response to
26037 .ecindex IIDplaiauth1
26038 .ecindex IIDplaiauth2
26043 . ////////////////////////////////////////////////////////////////////////////
26044 . ////////////////////////////////////////////////////////////////////////////
26046 .chapter "The cram_md5 authenticator" "CHID9"
26047 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
26048 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
26049 .cindex "CRAM-MD5 authentication mechanism"
26050 .cindex "authentication" "CRAM-MD5 mechanism"
26051 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
26052 sends a challenge string to the client, and the response consists of a user
26053 name and the CRAM-MD5 digest of the challenge string combined with a secret
26054 string (password) which is known to both server and client. Thus, the secret
26055 is not sent over the network as plain text, which makes this authenticator more
26056 secure than &(plaintext)&. However, the downside is that the secret has to be
26057 available in plain text at either end.
26060 .section "Using cram_md5 as a server" "SECID176"
26061 .cindex "options" "&(cram_md5)& authenticator (server)"
26062 This authenticator has one server option, which must be set to configure the
26063 authenticator as a server:
26065 .option server_secret cram_md5 string&!! unset
26066 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
26067 When the server receives the client's response, the user name is placed in
26068 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
26069 obtain the password for that user. The server then computes the CRAM-MD5 digest
26070 that the client should have sent, and checks that it received the correct
26071 string. If the expansion of &%server_secret%& is forced to fail, authentication
26072 fails. If the expansion fails for some other reason, a temporary error code is
26073 returned to the client.
26075 For compatibility with previous releases of Exim, the user name is also placed
26076 in &$1$&. However, the use of this variables for this purpose is now
26077 deprecated, as it can lead to confusion in string expansions that also use
26078 numeric variables for other things.
26080 For example, the following authenticator checks that the user name given by the
26081 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
26082 user name, authentication fails.
26086 public_name = CRAM-MD5
26087 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
26088 server_set_id = $auth1
26090 .vindex "&$authenticated_id$&"
26091 If authentication succeeds, the setting of &%server_set_id%& preserves the user
26092 name in &$authenticated_id$&. A more typical configuration might look up the
26093 secret string in a file, using the user name as the key. For example:
26097 public_name = CRAM-MD5
26098 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
26100 server_set_id = $auth1
26102 Note that this expansion explicitly forces failure if the lookup fails
26103 because &$auth1$& contains an unknown user name.
26105 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
26106 using the relevant libraries, you need to know the realm to specify in the
26107 lookup and then ask for the &"userPassword"& attribute for that user in that
26112 public_name = CRAM-MD5
26113 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
26114 dbmjz{/etc/sasldb2}{$value}fail}
26115 server_set_id = $auth1
26118 .section "Using cram_md5 as a client" "SECID177"
26119 .cindex "options" "&(cram_md5)& authenticator (client)"
26120 When used as a client, the &(cram_md5)& authenticator has two options:
26124 .option client_name cram_md5 string&!! "the primary host name"
26125 This string is expanded, and the result used as the user name data when
26126 computing the response to the server's challenge.
26129 .option client_secret cram_md5 string&!! unset
26130 This option must be set for the authenticator to work as a client. Its value is
26131 expanded and the result used as the secret string when computing the response.
26135 .vindex "&$host_address$&"
26136 Different user names and secrets can be used for different servers by referring
26137 to &$host$& or &$host_address$& in the options. Forced failure of either
26138 expansion string is treated as an indication that this authenticator is not
26139 prepared to handle this case. Exim moves on to the next configured client
26140 authenticator. Any other expansion failure causes Exim to give up trying to
26141 send the message to the current server.
26143 A simple example configuration of a &(cram_md5)& authenticator, using fixed
26148 public_name = CRAM-MD5
26150 client_secret = secret
26152 .ecindex IIDcramauth1
26153 .ecindex IIDcramauth2
26157 . ////////////////////////////////////////////////////////////////////////////
26158 . ////////////////////////////////////////////////////////////////////////////
26160 .chapter "The cyrus_sasl authenticator" "CHID10"
26161 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
26162 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
26163 .cindex "Cyrus" "SASL library"
26165 The code for this authenticator was provided by Matthew Byng-Maddick of A L
26166 Digital Ltd (&url(http://www.aldigital.co.uk)).
26168 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
26169 library implementation of the RFC 2222 (&"Simple Authentication and Security
26170 Layer"&). This library supports a number of authentication mechanisms,
26171 including PLAIN and LOGIN, but also several others that Exim does not support
26172 directly. In particular, there is support for Kerberos authentication.
26174 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
26175 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
26176 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
26177 name of the driver to determine which mechanism to support.
26179 Where access to some kind of secret file is required, for example in GSSAPI
26180 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
26181 user, and that the Cyrus SASL library has no way of escalating privileges
26182 by default. You may also find you need to set environment variables,
26183 depending on the driver you are using.
26185 The application name provided by Exim is &"exim"&, so various SASL options may
26186 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
26187 Kerberos, note that because of limitations in the GSSAPI interface,
26188 changing the server keytab might need to be communicated down to the Kerberos
26189 layer independently. The mechanism for doing so is dependent upon the Kerberos
26192 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
26193 may be set to point to an alternative keytab file. Exim will pass this
26194 variable through from its own inherited environment when started as root or the
26195 Exim user. The keytab file needs to be readable by the Exim user.
26196 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
26197 environment variable. In practice, for those releases, the Cyrus authenticator
26198 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
26199 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
26202 .section "Using cyrus_sasl as a server" "SECID178"
26203 The &(cyrus_sasl)& authenticator has four private options. It puts the username
26204 (on a successful authentication) into &$auth1$&. For compatibility with
26205 previous releases of Exim, the username is also placed in &$1$&. However, the
26206 use of this variable for this purpose is now deprecated, as it can lead to
26207 confusion in string expansions that also use numeric variables for other
26211 .option server_hostname cyrus_sasl string&!! "see below"
26212 This option selects the hostname that is used when communicating with the
26213 library. The default value is &`$primary_hostname`&. It is up to the underlying
26214 SASL plug-in what it does with this data.
26217 .option server_mech cyrus_sasl string "see below"
26218 This option selects the authentication mechanism this driver should use. The
26219 default is the value of the generic &%public_name%& option. This option allows
26220 you to use a different underlying mechanism from the advertised name. For
26224 driver = cyrus_sasl
26225 public_name = X-ANYTHING
26226 server_mech = CRAM-MD5
26227 server_set_id = $auth1
26230 .option server_realm cyrus_sasl string&!! unset
26231 This specifies the SASL realm that the server claims to be in.
26234 .option server_service cyrus_sasl string &`smtp`&
26235 This is the SASL service that the server claims to implement.
26238 For straightforward cases, you do not need to set any of the authenticator's
26239 private options. All you need to do is to specify an appropriate mechanism as
26240 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
26241 PLAIN, you could have two authenticators as follows:
26244 driver = cyrus_sasl
26245 public_name = CRAM-MD5
26246 server_set_id = $auth1
26249 driver = cyrus_sasl
26250 public_name = PLAIN
26251 server_set_id = $auth2
26253 Cyrus SASL does implement the LOGIN authentication method, even though it is
26254 not a standard method. It is disabled by default in the source distribution,
26255 but it is present in many binary distributions.
26256 .ecindex IIDcyrauth1
26257 .ecindex IIDcyrauth2
26262 . ////////////////////////////////////////////////////////////////////////////
26263 . ////////////////////////////////////////////////////////////////////////////
26264 .chapter "The dovecot authenticator" "CHAPdovecot"
26265 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
26266 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
26267 This authenticator is an interface to the authentication facility of the
26268 Dovecot POP/IMAP server, which can support a number of authentication methods.
26269 Note that Dovecot must be configured to use auth-client not auth-userdb.
26270 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
26271 to use the same mechanisms for SMTP authentication. This is a server
26272 authenticator only. There is only one option:
26274 .option server_socket dovecot string unset
26276 This option must specify the socket that is the interface to Dovecot
26277 authentication. The &%public_name%& option must specify an authentication
26278 mechanism that Dovecot is configured to support. You can have several
26279 authenticators for different mechanisms. For example:
26283 public_name = PLAIN
26284 server_socket = /var/run/dovecot/auth-client
26285 server_set_id = $auth1
26290 server_socket = /var/run/dovecot/auth-client
26291 server_set_id = $auth1
26293 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
26294 &$received_ip_address$& (that is, the connection is local), the &"secured"&
26295 option is passed in the Dovecot authentication command. If, for a TLS
26296 connection, a client certificate has been verified, the &"valid-client-cert"&
26297 option is passed. When authentication succeeds, the identity of the user
26298 who authenticated is placed in &$auth1$&.
26299 .ecindex IIDdcotauth1
26300 .ecindex IIDdcotauth2
26303 . ////////////////////////////////////////////////////////////////////////////
26304 . ////////////////////////////////////////////////////////////////////////////
26305 .chapter "The gsasl authenticator" "CHAPgsasl"
26306 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
26307 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
26308 .cindex "authentication" "GNU SASL"
26309 .cindex "authentication" "SASL"
26310 .cindex "authentication" "EXTERNAL"
26311 .cindex "authentication" "ANONYMOUS"
26312 .cindex "authentication" "PLAIN"
26313 .cindex "authentication" "LOGIN"
26314 .cindex "authentication" "DIGEST-MD5"
26315 .cindex "authentication" "CRAM-MD5"
26316 .cindex "authentication" "SCRAM-SHA-1"
26317 The &(gsasl)& authenticator provides server integration for the GNU SASL
26318 library and the mechanisms it provides. This is new as of the 4.80 release
26319 and there are a few areas where the library does not let Exim smoothly
26320 scale to handle future authentication mechanisms, so no guarantee can be
26321 made that any particular new authentication mechanism will be supported
26322 without code changes in Exim.
26325 .option server_channelbinding gsasl boolean false
26326 Some authentication mechanisms are able to use external context at both ends
26327 of the session to bind the authentication to that context, and fail the
26328 authentication process if that context differs. Specifically, some TLS
26329 ciphersuites can provide identifying information about the cryptographic
26332 This means that certificate identity and verification becomes a non-issue,
26333 as a man-in-the-middle attack will cause the correct client and server to
26334 see different identifiers and authentication will fail.
26336 This is currently only supported when using the GnuTLS library. This is
26337 only usable by mechanisms which support "channel binding"; at time of
26338 writing, that's the SCRAM family.
26340 This defaults off to ensure smooth upgrade across Exim releases, in case
26341 this option causes some clients to start failing. Some future release
26342 of Exim may switch the default to be true.
26345 .option server_hostname gsasl string&!! "see below"
26346 This option selects the hostname that is used when communicating with the
26347 library. The default value is &`$primary_hostname`&.
26348 Some mechanisms will use this data.
26351 .option server_mech gsasl string "see below"
26352 This option selects the authentication mechanism this driver should use. The
26353 default is the value of the generic &%public_name%& option. This option allows
26354 you to use a different underlying mechanism from the advertised name. For
26359 public_name = X-ANYTHING
26360 server_mech = CRAM-MD5
26361 server_set_id = $auth1
26365 .option server_password gsasl string&!! unset
26366 Various mechanisms need access to the cleartext password on the server, so
26367 that proof-of-possession can be demonstrated on the wire, without sending
26368 the password itself.
26370 The data available for lookup varies per mechanism.
26371 In all cases, &$auth1$& is set to the &'authentication id'&.
26372 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26373 if available, else the empty string.
26374 The &$auth3$& variable will always be the &'realm'& if available,
26375 else the empty string.
26377 A forced failure will cause authentication to defer.
26379 If using this option, it may make sense to set the &%server_condition%&
26380 option to be simply "true".
26383 .option server_realm gsasl string&!! unset
26384 This specifies the SASL realm that the server claims to be in.
26385 Some mechanisms will use this data.
26388 .option server_scram_iter gsasl string&!! unset
26389 This option provides data for the SCRAM family of mechanisms.
26390 &$auth1$& is not available at evaluation time.
26391 (This may change, as we receive feedback on use)
26394 .option server_scram_salt gsasl string&!! unset
26395 This option provides data for the SCRAM family of mechanisms.
26396 &$auth1$& is not available at evaluation time.
26397 (This may change, as we receive feedback on use)
26400 .option server_service gsasl string &`smtp`&
26401 This is the SASL service that the server claims to implement.
26402 Some mechanisms will use this data.
26405 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26406 .vindex "&$auth1$&, &$auth2$&, etc"
26407 These may be set when evaluating specific options, as detailed above.
26408 They will also be set when evaluating &%server_condition%&.
26410 Unless otherwise stated below, the &(gsasl)& integration will use the following
26411 meanings for these variables:
26414 .vindex "&$auth1$&"
26415 &$auth1$&: the &'authentication id'&
26417 .vindex "&$auth2$&"
26418 &$auth2$&: the &'authorization id'&
26420 .vindex "&$auth3$&"
26421 &$auth3$&: the &'realm'&
26424 On a per-mechanism basis:
26427 .cindex "authentication" "EXTERNAL"
26428 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
26429 the &%server_condition%& option must be present.
26431 .cindex "authentication" "ANONYMOUS"
26432 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
26433 the &%server_condition%& option must be present.
26435 .cindex "authentication" "GSSAPI"
26436 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
26437 &$auth2$& will be set to the &'authorization id'&,
26438 the &%server_condition%& option must be present.
26441 An &'anonymous token'& is something passed along as an unauthenticated
26442 identifier; this is analogous to FTP anonymous authentication passing an
26443 email address, or software-identifier@, as the "password".
26446 An example showing the password having the realm specified in the callback
26447 and demonstrating a Cyrus SASL to GSASL migration approach is:
26449 gsasl_cyrusless_crammd5:
26451 public_name = CRAM-MD5
26452 server_realm = imap.example.org
26453 server_password = ${lookup{$auth1:$auth3:userPassword}\
26454 dbmjz{/etc/sasldb2}{$value}fail}
26455 server_set_id = ${quote:$auth1}
26456 server_condition = yes
26460 . ////////////////////////////////////////////////////////////////////////////
26461 . ////////////////////////////////////////////////////////////////////////////
26463 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
26464 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
26465 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
26466 .cindex "authentication" "GSSAPI"
26467 .cindex "authentication" "Kerberos"
26468 The &(heimdal_gssapi)& authenticator provides server integration for the
26469 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
26472 .option server_hostname heimdal_gssapi string&!! "see below"
26473 This option selects the hostname that is used, with &%server_service%&,
26474 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
26475 identifier. The default value is &`$primary_hostname`&.
26477 .option server_keytab heimdal_gssapi string&!! unset
26478 If set, then Heimdal will not use the system default keytab (typically
26479 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
26480 The value should be a pathname, with no &"file:"& prefix.
26482 .option server_service heimdal_gssapi string&!! "smtp"
26483 This option specifies the service identifier used, in conjunction with
26484 &%server_hostname%&, for building the identifier for finding credentials
26488 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
26489 Beware that these variables will typically include a realm, thus will appear
26490 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
26491 not verified, so a malicious client can set it to anything.
26493 The &$auth1$& field should be safely trustable as a value from the Key
26494 Distribution Center. Note that these are not quite email addresses.
26495 Each identifier is for a role, and so the left-hand-side may include a
26496 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
26498 .vindex "&$auth1$&, &$auth2$&, etc"
26500 .vindex "&$auth1$&"
26501 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
26503 .vindex "&$auth2$&"
26504 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
26505 authentication. If that was empty, this will also be set to the
26510 . ////////////////////////////////////////////////////////////////////////////
26511 . ////////////////////////////////////////////////////////////////////////////
26513 .chapter "The spa authenticator" "CHAPspa"
26514 .scindex IIDspaauth1 "&(spa)& authenticator"
26515 .scindex IIDspaauth2 "authenticators" "&(spa)&"
26516 .cindex "authentication" "Microsoft Secure Password"
26517 .cindex "authentication" "NTLM"
26518 .cindex "Microsoft Secure Password Authentication"
26519 .cindex "NTLM authentication"
26520 The &(spa)& authenticator provides client support for Microsoft's &'Secure
26521 Password Authentication'& mechanism,
26522 which is also sometimes known as NTLM (NT LanMan). The code for client side of
26523 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
26524 taken from the Samba project (&url(http://www.samba.org)). The code for the
26525 server side was subsequently contributed by Tom Kistner. The mechanism works as
26529 After the AUTH command has been accepted, the client sends an SPA
26530 authentication request based on the user name and optional domain.
26532 The server sends back a challenge.
26534 The client builds a challenge response which makes use of the user's password
26535 and sends it to the server, which then accepts or rejects it.
26538 Encryption is used to protect the password in transit.
26542 .section "Using spa as a server" "SECID179"
26543 .cindex "options" "&(spa)& authenticator (server)"
26544 The &(spa)& authenticator has just one server option:
26546 .option server_password spa string&!! unset
26547 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
26548 This option is expanded, and the result must be the cleartext password for the
26549 authenticating user, whose name is at this point in &$auth1$&. For
26550 compatibility with previous releases of Exim, the user name is also placed in
26551 &$1$&. However, the use of this variable for this purpose is now deprecated, as
26552 it can lead to confusion in string expansions that also use numeric variables
26553 for other things. For example:
26558 server_password = \
26559 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
26561 If the expansion is forced to fail, authentication fails. Any other expansion
26562 failure causes a temporary error code to be returned.
26568 .section "Using spa as a client" "SECID180"
26569 .cindex "options" "&(spa)& authenticator (client)"
26570 The &(spa)& authenticator has the following client options:
26574 .option client_domain spa string&!! unset
26575 This option specifies an optional domain for the authentication.
26578 .option client_password spa string&!! unset
26579 This option specifies the user's password, and must be set.
26582 .option client_username spa string&!! unset
26583 This option specifies the user name, and must be set. Here is an example of a
26584 configuration of this authenticator for use with the mail servers at
26590 client_username = msn/msn_username
26591 client_password = msn_plaintext_password
26592 client_domain = DOMAIN_OR_UNSET
26594 .ecindex IIDspaauth1
26595 .ecindex IIDspaauth2
26601 . ////////////////////////////////////////////////////////////////////////////
26602 . ////////////////////////////////////////////////////////////////////////////
26604 .chapter "The tls authenticator" "CHAPtlsauth"
26605 .scindex IIDtlsauth1 "&(tls)& authenticator"
26606 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
26607 .cindex "authentication" "Client Certificate"
26608 .cindex "authentication" "X509"
26609 .cindex "Certificate-based authentication"
26610 The &(tls)& authenticator provides server support for
26611 authentication based on client certificates.
26613 It is not an SMTP authentication mechanism and is not
26614 advertised by the server as part of the SMTP EHLO response.
26615 It is an Exim authenticator in the sense that it affects
26616 the protocol element of the log line, can be tested for
26617 by the &%authenticated%& ACL condition, and can set
26618 the &$authenticated_id$& variable.
26620 The client must present a verifiable certificate,
26621 for which it must have been requested via the
26622 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
26623 (see &<<CHAPTLS>>&).
26625 If an authenticator of this type is configured it is
26626 run before any SMTP-level communication is done,
26627 and can authenticate the connection.
26628 If it does, SMTP authentication is not offered.
26630 A maximum of one authenticator of this type may be present.
26633 .cindex "options" "&(tls)& authenticator (server)"
26634 The &(tls)& authenticator has three server options:
26636 .option server_param1 tls string&!! unset
26637 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
26638 This option is expanded after the TLS negotiation and
26639 the result is placed in &$auth1$&.
26640 If the expansion is forced to fail, authentication fails. Any other expansion
26641 failure causes a temporary error code to be returned.
26643 .option server_param2 tls string&!! unset
26644 .option server_param3 tls string&!! unset
26645 As above, for &$auth2$& and &$auth3$&.
26647 &%server_param1%& may also be spelled &%server_param%&.
26654 server_param1 = ${certextract {subj_altname,mail,>:} \
26655 {$tls_in_peercert}}
26656 server_condition = ${if forany {$auth1} \
26658 {${lookup ldap{ldap:///\
26659 mailname=${quote_ldap_dn:${lc:$item}},\
26660 ou=users,LDAP_DC?mailid} {$value}{0} \
26662 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
26664 This accepts a client certificate that is verifiable against any
26665 of your configured trust-anchors
26666 which usually means the full set of public CAs)
26667 and which has a SAN with a good account name.
26668 Note that the client cert is on the wire in-clear, including the SAN,
26669 whereas a plaintext SMTP AUTH done inside TLS is not.
26671 . An alternative might use
26673 . server_param1 = ${sha256:$tls_in_peercert}
26675 . to require one of a set of specific certs that define a given account
26676 . (the verification is still required, but mostly irrelevant).
26677 . This would help for per-device use.
26679 . However, for the future we really need support for checking a
26680 . user cert in LDAP - which probably wants a base-64 DER.
26682 .ecindex IIDtlsauth1
26683 .ecindex IIDtlsauth2
26686 Note that because authentication is traditionally an SMTP operation,
26687 the &%authenticated%& ACL condition cannot be used in
26688 a connect- or helo-ACL.
26692 . ////////////////////////////////////////////////////////////////////////////
26693 . ////////////////////////////////////////////////////////////////////////////
26695 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
26696 "Encrypted SMTP connections"
26697 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
26698 .scindex IIDencsmtp2 "SMTP" "encryption"
26699 .cindex "TLS" "on SMTP connection"
26702 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
26703 Sockets Layer), is implemented by making use of the OpenSSL library or the
26704 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
26705 cryptographic code in the Exim distribution itself for implementing TLS. In
26706 order to use this feature you must install OpenSSL or GnuTLS, and then build a
26707 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
26708 You also need to understand the basic concepts of encryption at a managerial
26709 level, and in particular, the way that public keys, private keys, and
26710 certificates are used.
26712 RFC 3207 defines how SMTP connections can make use of encryption. Once a
26713 connection is established, the client issues a STARTTLS command. If the
26714 server accepts this, the client and the server negotiate an encryption
26715 mechanism. If the negotiation succeeds, the data that subsequently passes
26716 between them is encrypted.
26718 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
26719 and if so, what cipher suite is in use, whether the client supplied a
26720 certificate, and whether or not that certificate was verified. This makes it
26721 possible for an Exim server to deny or accept certain commands based on the
26724 &*Warning*&: Certain types of firewall and certain anti-virus products can
26725 disrupt TLS connections. You need to turn off SMTP scanning for these products
26726 in order to get TLS to work.
26730 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
26732 .cindex "ssmtp protocol"
26733 .cindex "smtps protocol"
26734 .cindex "SMTP" "ssmtp protocol"
26735 .cindex "SMTP" "smtps protocol"
26736 Early implementations of encrypted SMTP used a different TCP port from normal
26737 SMTP, and expected an encryption negotiation to start immediately, instead of
26738 waiting for a STARTTLS command from the client using the standard SMTP
26739 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
26740 allocated for this purpose.
26742 This approach was abandoned when encrypted SMTP was standardized, but there are
26743 still some legacy clients that use it. Exim supports these clients by means of
26744 the &%tls_on_connect_ports%& global option. Its value must be a list of port
26745 numbers; the most common use is expected to be:
26747 tls_on_connect_ports = 465
26749 The port numbers specified by this option apply to all SMTP connections, both
26750 via the daemon and via &'inetd'&. You still need to specify all the ports that
26751 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
26752 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
26753 an extra port &-- rather, it specifies different behaviour on a port that is
26756 There is also a &%-tls-on-connect%& command line option. This overrides
26757 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
26764 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
26765 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
26766 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
26767 followed later, when the first versions of GnuTLS were released. To build Exim
26768 to use GnuTLS, you need to set
26772 in Local/Makefile, in addition to
26776 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
26777 include files and libraries for GnuTLS can be found.
26779 There are some differences in usage when using GnuTLS instead of OpenSSL:
26782 The &%tls_verify_certificates%& option
26783 cannot be the path of a directory
26784 for GnuTLS versions before 3.3.6
26785 (for later versions, or OpenSSL, it can be either).
26787 The default value for &%tls_dhparam%& differs for historical reasons.
26789 .vindex "&$tls_in_peerdn$&"
26790 .vindex "&$tls_out_peerdn$&"
26791 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
26792 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
26793 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
26795 OpenSSL identifies cipher suites using hyphens as separators, for example:
26796 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
26797 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
26798 in a cipher list. To make life simpler, Exim changes underscores to hyphens
26799 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
26800 to handle its own older variants) when processing lists of cipher suites in the
26801 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
26804 The &%tls_require_ciphers%& options operate differently, as described in the
26805 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
26807 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
26808 When using OpenSSL, this option is ignored.
26809 (If an API is found to let OpenSSL be configured in this way,
26810 let the Exim Maintainers know and we'll likely use it).
26812 Some other recently added features may only be available in one or the other.
26813 This should be documented with the feature. If the documentation does not
26814 explicitly state that the feature is infeasible in the other TLS
26815 implementation, then patches are welcome.
26819 .section "GnuTLS parameter computation" "SECTgnutlsparam"
26820 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
26821 an explicit path; if the latter, then the text about generation still applies,
26822 but not the chosen filename.
26823 By default, as of Exim 4.80 a hard-coded D-H prime is used.
26824 See the documentation of &%tls_dhparam%& for more information.
26826 GnuTLS uses D-H parameters that may take a substantial amount of time
26827 to compute. It is unreasonable to re-compute them for every TLS session.
26828 Therefore, Exim keeps this data in a file in its spool directory, called
26829 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
26831 The file is owned by the Exim user and is readable only by
26832 its owner. Every Exim process that start up GnuTLS reads the D-H
26833 parameters from this file. If the file does not exist, the first Exim process
26834 that needs it computes the data and writes it to a temporary file which is
26835 renamed once it is complete. It does not matter if several Exim processes do
26836 this simultaneously (apart from wasting a few resources). Once a file is in
26837 place, new Exim processes immediately start using it.
26839 For maximum security, the parameters that are stored in this file should be
26840 recalculated periodically, the frequency depending on your paranoia level.
26841 If you are avoiding using the fixed D-H primes published in RFCs, then you
26842 are concerned about some advanced attacks and will wish to do this; if you do
26843 not regenerate then you might as well stick to the standard primes.
26845 Arranging this is easy in principle; just delete the file when you want new
26846 values to be computed. However, there may be a problem. The calculation of new
26847 parameters needs random numbers, and these are obtained from &_/dev/random_&.
26848 If the system is not very active, &_/dev/random_& may delay returning data
26849 until enough randomness (entropy) is available. This may cause Exim to hang for
26850 a substantial amount of time, causing timeouts on incoming connections.
26852 The solution is to generate the parameters externally to Exim. They are stored
26853 in &_gnutls-params-N_& in PEM format, which means that they can be
26854 generated externally using the &(certtool)& command that is part of GnuTLS.
26856 To replace the parameters with new ones, instead of deleting the file
26857 and letting Exim re-create it, you can generate new parameters using
26858 &(certtool)& and, when this has been done, replace Exim's cache file by
26859 renaming. The relevant commands are something like this:
26862 [ look for file; assume gnutls-params-2236 is the most recent ]
26865 # chown exim:exim new-params
26866 # chmod 0600 new-params
26867 # certtool --generate-dh-params --bits 2236 >>new-params
26868 # openssl dhparam -noout -text -in new-params | head
26869 [ check the first line, make sure it's not more than 2236;
26870 if it is, then go back to the start ("rm") and repeat
26871 until the size generated is at most the size requested ]
26872 # chmod 0400 new-params
26873 # mv new-params gnutls-params-2236
26875 If Exim never has to generate the parameters itself, the possibility of
26876 stalling is removed.
26878 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
26879 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
26880 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
26881 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
26882 and Exim does so. This attempt to remove Exim from TLS policy decisions
26883 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
26884 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
26885 which applies to all D-H usage, client or server. If the value returned by
26886 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
26887 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
26888 limit, which is still much higher than Exim historically used.
26890 The filename and bits used will change as the GnuTLS maintainers change the
26891 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
26892 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
26893 2432 bits, while NSS is limited to 2236 bits.
26895 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
26896 increase the chance of the generated prime actually being within acceptable
26897 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
26898 procedure above. There is no sane procedure available to Exim to double-check
26899 the size of the generated prime, so it might still be too large.
26902 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
26903 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
26904 .oindex "&%tls_require_ciphers%&" "OpenSSL"
26905 There is a function in the OpenSSL library that can be passed a list of cipher
26906 suites before the cipher negotiation takes place. This specifies which ciphers
26907 are acceptable. The list is colon separated and may contain names like
26908 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
26909 directly to this function call.
26910 Many systems will install the OpenSSL manual-pages, so you may have
26911 &'ciphers(1)'& available to you.
26912 The following quotation from the OpenSSL
26913 documentation specifies what forms of item are allowed in the cipher string:
26916 It can consist of a single cipher suite such as RC4-SHA.
26918 It can represent a list of cipher suites containing a certain algorithm,
26919 or cipher suites of a certain type. For example SHA1 represents all
26920 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
26923 Lists of cipher suites can be combined in a single cipher string using
26924 the + character. This is used as a logical and operation. For example
26925 SHA1+DES represents all cipher suites containing the SHA1 and the DES
26929 Each cipher string can be optionally preceded by one of the characters &`!`&,
26932 If &`!`& is used, the ciphers are permanently deleted from the list. The
26933 ciphers deleted can never reappear in the list even if they are explicitly
26936 If &`-`& is used, the ciphers are deleted from the list, but some or all
26937 of the ciphers can be added again by later options.
26939 If &`+`& is used, the ciphers are moved to the end of the list. This
26940 option does not add any new ciphers; it just moves matching existing ones.
26943 If none of these characters is present, the string is interpreted as
26944 a list of ciphers to be appended to the current preference list. If the list
26945 includes any ciphers already present they will be ignored: that is, they will
26946 not be moved to the end of the list.
26949 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
26952 # note single-quotes to get ! past any shell history expansion
26953 $ openssl ciphers 'HIGH:!MD5:!SHA1'
26956 This example will let the library defaults be permitted on the MX port, where
26957 there's probably no identity verification anyway, but ups the ante on the
26958 submission ports where the administrator might have some influence on the
26959 choice of clients used:
26961 # OpenSSL variant; see man ciphers(1)
26962 tls_require_ciphers = ${if =={$received_port}{25}\
26969 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
26971 .cindex "GnuTLS" "specifying parameters for"
26972 .cindex "TLS" "specifying ciphers (GnuTLS)"
26973 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
26974 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
26975 .cindex "TLS" "specifying protocols (GnuTLS)"
26976 .cindex "TLS" "specifying priority string (GnuTLS)"
26977 .oindex "&%tls_require_ciphers%&" "GnuTLS"
26978 The GnuTLS library allows the caller to provide a "priority string", documented
26979 as part of the &[gnutls_priority_init]& function. This is very similar to the
26980 ciphersuite specification in OpenSSL.
26982 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
26983 and controls both protocols and ciphers.
26985 The &%tls_require_ciphers%& option is available both as an global option,
26986 controlling how Exim behaves as a server, and also as an option of the
26987 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
26988 the value is string expanded. The resulting string is not an Exim list and
26989 the string is given to the GnuTLS library, so that Exim does not need to be
26990 aware of future feature enhancements of GnuTLS.
26992 Documentation of the strings accepted may be found in the GnuTLS manual, under
26993 "Priority strings". This is online as
26994 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
26995 but beware that this relates to GnuTLS 3, which may be newer than the version
26996 installed on your system. If you are using GnuTLS 3,
26997 then the example code
26998 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
26999 on that site can be used to test a given string.
27003 # Disable older versions of protocols
27004 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
27007 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
27008 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
27009 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
27011 This example will let the library defaults be permitted on the MX port, where
27012 there's probably no identity verification anyway, and lowers security further
27013 by increasing compatibility; but this ups the ante on the submission ports
27014 where the administrator might have some influence on the choice of clients
27018 tls_require_ciphers = ${if =={$received_port}{25}\
27024 .section "Configuring an Exim server to use TLS" "SECID182"
27025 .cindex "TLS" "configuring an Exim server"
27026 When Exim has been built with TLS support, it advertises the availability of
27027 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
27028 but not to any others. The default value of this option is unset, which means
27029 that STARTTLS is not advertised at all. This default is chosen because you
27030 need to set some other options in order to make TLS available, and also it is
27031 sensible for systems that want to use TLS only as a client.
27033 If a client issues a STARTTLS command and there is some configuration
27034 problem in the server, the command is rejected with a 454 error. If the client
27035 persists in trying to issue SMTP commands, all except QUIT are rejected
27038 554 Security failure
27040 If a STARTTLS command is issued within an existing TLS session, it is
27041 rejected with a 554 error code.
27043 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
27044 must be set to match some hosts. The default is * which matches all hosts.
27047 If this is all you do, TLS encryption will be enabled but not authentication -
27048 meaning that the peer has no assurance it is actually you he is talking to.
27049 You gain protection from a passive sniffer listening on the wire but not
27050 from someone able to intercept the communication.
27053 Further protection requires some further configuration at the server end.
27055 It is rumoured that all existing clients that support TLS/SSL use RSA
27056 encryption. To make this work you need to set, in the server,
27058 tls_certificate = /some/file/name
27059 tls_privatekey = /some/file/name
27061 These options are, in fact, expanded strings, so you can make them depend on
27062 the identity of the client that is connected if you wish. The first file
27063 contains the server's X509 certificate, and the second contains the private key
27064 that goes with it. These files need to be
27065 PEM format and readable by the Exim user, and must
27066 always be given as full path names.
27067 The key must not be password-protected.
27068 They can be the same file if both the
27069 certificate and the key are contained within it. If &%tls_privatekey%& is not
27070 set, or if its expansion is forced to fail or results in an empty string, this
27071 is assumed to be the case. The certificate file may also contain intermediate
27072 certificates that need to be sent to the client to enable it to authenticate
27073 the server's certificate.
27075 If you do not understand about certificates and keys, please try to find a
27076 source of this background information, which is not Exim-specific. (There are a
27077 few comments below in section &<<SECTcerandall>>&.)
27079 &*Note*&: These options do not apply when Exim is operating as a client &--
27080 they apply only in the case of a server. If you need to use a certificate in an
27081 Exim client, you must set the options of the same names in an &(smtp)&
27084 With just these options, an Exim server will be able to use TLS. It does not
27085 require the client to have a certificate (but see below for how to insist on
27086 this). There is one other option that may be needed in other situations. If
27088 tls_dhparam = /some/file/name
27090 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
27091 with the parameters contained in the file.
27092 Set this to &`none`& to disable use of DH entirely, by making no prime
27097 This may also be set to a string identifying a standard prime to be used for
27098 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
27099 used is &`ike23`&. There are a few standard primes available, see the
27100 documentation for &%tls_dhparam%& for the complete list.
27106 for a way of generating file data.
27108 The strings supplied for these three options are expanded every time a client
27109 host connects. It is therefore possible to use different certificates and keys
27110 for different hosts, if you so wish, by making use of the client's IP address
27111 in &$sender_host_address$& to control the expansion. If a string expansion is
27112 forced to fail, Exim behaves as if the option is not set.
27114 .cindex "cipher" "logging"
27115 .cindex "log" "TLS cipher"
27116 .vindex "&$tls_in_cipher$&"
27117 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
27118 an incoming TLS connection. It is included in the &'Received:'& header of an
27119 incoming message (by default &-- you can, of course, change this), and it is
27120 also included in the log line that records a message's arrival, keyed by
27121 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
27122 condition can be used to test for specific cipher suites in ACLs.
27124 Once TLS has been established, the ACLs that run for subsequent SMTP commands
27125 can check the name of the cipher suite and vary their actions accordingly. The
27126 cipher suite names vary, depending on which TLS library is being used. For
27127 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
27128 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
27129 documentation for more details.
27131 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
27132 (again depending on the &%tls_cipher%& log selector).
27135 .section "Requesting and verifying client certificates" "SECID183"
27136 .cindex "certificate" "verification of client"
27137 .cindex "TLS" "client certificate verification"
27138 If you want an Exim server to request a certificate when negotiating a TLS
27139 session with a client, you must set either &%tls_verify_hosts%& or
27140 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
27141 apply to all TLS connections. For any host that matches one of these options,
27142 Exim requests a certificate as part of the setup of the TLS session. The
27143 contents of the certificate are verified by comparing it with a list of
27144 expected certificates.
27145 These may be the system default set (depending on library version),
27146 an explicit file or,
27147 depending on library version, a directory, identified by
27148 &%tls_verify_certificates%&.
27150 A file can contain multiple certificates, concatenated end to end. If a
27153 each certificate must be in a separate file, with a name (or a symbolic link)
27154 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
27155 certificate. You can compute the relevant hash by running the command
27157 openssl x509 -hash -noout -in /cert/file
27159 where &_/cert/file_& contains a single certificate.
27161 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
27162 what happens if the client does not supply a certificate, or if the certificate
27163 does not match any of the certificates in the collection named by
27164 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
27165 attempt to set up a TLS session is aborted, and the incoming connection is
27166 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
27167 session continues. ACLs that run for subsequent SMTP commands can detect the
27168 fact that no certificate was verified, and vary their actions accordingly. For
27169 example, you can insist on a certificate before accepting a message for
27170 relaying, but not when the message is destined for local delivery.
27172 .vindex "&$tls_in_peerdn$&"
27173 When a client supplies a certificate (whether it verifies or not), the value of
27174 the Distinguished Name of the certificate is made available in the variable
27175 &$tls_in_peerdn$& during subsequent processing of the message.
27177 .cindex "log" "distinguished name"
27178 Because it is often a long text string, it is not included in the log line or
27179 &'Received:'& header by default. You can arrange for it to be logged, keyed by
27180 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
27181 &%received_header_text%& to change the &'Received:'& header. When no
27182 certificate is supplied, &$tls_in_peerdn$& is empty.
27185 .section "Revoked certificates" "SECID184"
27186 .cindex "TLS" "revoked certificates"
27187 .cindex "revocation list"
27188 .cindex "certificate" "revocation list"
27189 .cindex "OCSP" "stapling"
27190 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
27191 certificates are revoked. If you have such a list, you can pass it to an Exim
27192 server using the global option called &%tls_crl%& and to an Exim client using
27193 an identically named option for the &(smtp)& transport. In each case, the value
27194 of the option is expanded and must then be the name of a file that contains a
27196 The downside is that clients have to periodically re-download a potentially huge
27197 file from every certificate authority they know of.
27199 The way with most moving parts at query time is Online Certificate
27200 Status Protocol (OCSP), where the client verifies the certificate
27201 against an OCSP server run by the CA. This lets the CA track all
27202 usage of the certs. It requires running software with access to the
27203 private key of the CA, to sign the responses to the OCSP queries. OCSP
27204 is based on HTTP and can be proxied accordingly.
27206 The only widespread OCSP server implementation (known to this writer)
27207 comes as part of OpenSSL and aborts on an invalid request, such as
27208 connecting to the port and then disconnecting. This requires
27209 re-entering the passphrase each time some random client does this.
27211 The third way is OCSP Stapling; in this, the server using a certificate
27212 issued by the CA periodically requests an OCSP proof of validity from
27213 the OCSP server, then serves it up inline as part of the TLS
27214 negotiation. This approach adds no extra round trips, does not let the
27215 CA track users, scales well with number of certs issued by the CA and is
27216 resilient to temporary OCSP server failures, as long as the server
27217 starts retrying to fetch an OCSP proof some time before its current
27218 proof expires. The downside is that it requires server support.
27220 Unless Exim is built with the support disabled,
27221 or with GnuTLS earlier than version 3.3.16 / 3.4.8
27222 support for OCSP stapling is included.
27224 There is a global option called &%tls_ocsp_file%&.
27225 The file specified therein is expected to be in DER format, and contain
27226 an OCSP proof. Exim will serve it as part of the TLS handshake. This
27227 option will be re-expanded for SNI, if the &%tls_certificate%& option
27228 contains &`tls_in_sni`&, as per other TLS options.
27230 Exim does not at this time implement any support for fetching a new OCSP
27231 proof. The burden is on the administrator to handle this, outside of
27232 Exim. The file specified should be replaced atomically, so that the
27233 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
27234 on each connection, so a new file will be handled transparently on the
27237 When built with OpenSSL Exim will check for a valid next update timestamp
27238 in the OCSP proof; if not present, or if the proof has expired, it will be
27241 For the client to be able to verify the stapled OCSP the server must
27242 also supply, in its stapled information, any intermediate
27243 certificates for the chain leading to the OCSP proof from the signer
27244 of the server certificate. There may be zero or one such. These
27245 intermediate certificates should be added to the server OCSP stapling
27246 file named by &%tls_ocsp_file%&.
27248 Note that the proof only covers the terminal server certificate,
27249 not any of the chain from CA to it.
27251 There is no current way to staple a proof for a client certificate.
27254 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
27255 OCSP server is supplied. The server URL may be included in the
27256 server certificate, if the CA is helpful.
27258 One failure mode seen was the OCSP Signer cert expiring before the end
27259 of validity of the OCSP proof. The checking done by Exim/OpenSSL
27260 noted this as invalid overall, but the re-fetch script did not.
27266 .section "Configuring an Exim client to use TLS" "SECID185"
27267 .cindex "cipher" "logging"
27268 .cindex "log" "TLS cipher"
27269 .cindex "log" "distinguished name"
27270 .cindex "TLS" "configuring an Exim client"
27271 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
27272 deliveries as well as to incoming, the latter one causing logging of the
27273 server certificate's DN. The remaining client configuration for TLS is all
27274 within the &(smtp)& transport.
27276 It is not necessary to set any options to have TLS work in the &(smtp)&
27277 transport. If Exim is built with TLS support, and TLS is advertised by a
27278 server, the &(smtp)& transport always tries to start a TLS session. However,
27279 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
27280 transport) to a list of server hosts for which TLS should not be used.
27282 If you do not want Exim to attempt to send messages unencrypted when an attempt
27283 to set up an encrypted connection fails in any way, you can set
27284 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
27285 those hosts, delivery is always deferred if an encrypted connection cannot be
27286 set up. If there are any other hosts for the address, they are tried in the
27289 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
27290 the message unencrypted. It always does this if the response to STARTTLS is
27291 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
27292 session after a success response code, what happens is controlled by the
27293 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
27294 delivery to this host is deferred, and other hosts (if available) are tried. If
27295 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
27296 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
27297 negotiation fails, Exim closes the current connection (because it is in an
27298 unknown state), opens a new one to the same host, and then tries the delivery
27301 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
27302 transport provide the client with a certificate, which is passed to the server
27303 if it requests it. If the server is Exim, it will request a certificate only if
27304 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
27306 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
27307 specifies a collection of expected server certificates.
27308 These may be the system default set (depending on library version),
27310 depending on library version, a directory,
27311 must name a file or,
27312 for OpenSSL only (not GnuTLS), a directory.
27313 The client verifies the server's certificate
27314 against this collection, taking into account any revoked certificates that are
27315 in the list defined by &%tls_crl%&.
27316 Failure to verify fails the TLS connection unless either of the
27317 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
27319 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
27320 certificate verification to the listed servers. Verification either must
27321 or need not succeed respectively.
27323 The &(smtp)& transport has two OCSP-related options:
27324 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
27325 is requested and required for the connection to proceed. The default
27327 &%hosts_request_ocsp%&; a host-list for which (additionally)
27328 a Certificate Status is requested (but not necessarily verified). The default
27329 value is "*" meaning that requests are made unless configured
27332 The host(s) should also be in &%hosts_require_tls%&, and
27333 &%tls_verify_certificates%& configured for the transport,
27334 for OCSP to be relevant.
27337 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
27338 list of permitted cipher suites. If either of these checks fails, delivery to
27339 the current host is abandoned, and the &(smtp)& transport tries to deliver to
27340 alternative hosts, if any.
27343 These options must be set in the &(smtp)& transport for Exim to use TLS when it
27344 is operating as a client. Exim does not assume that a server certificate (set
27345 by the global options of the same name) should also be used when operating as a
27349 .vindex "&$host_address$&"
27350 All the TLS options in the &(smtp)& transport are expanded before use, with
27351 &$host$& and &$host_address$& containing the name and address of the server to
27352 which the client is connected. Forced failure of an expansion causes Exim to
27353 behave as if the relevant option were unset.
27355 .vindex &$tls_out_bits$&
27356 .vindex &$tls_out_cipher$&
27357 .vindex &$tls_out_peerdn$&
27358 .vindex &$tls_out_sni$&
27359 Before an SMTP connection is established, the
27360 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27361 variables are emptied. (Until the first connection, they contain the values
27362 that were set when the message was received.) If STARTTLS is subsequently
27363 successfully obeyed, these variables are set to the relevant values for the
27364 outgoing connection.
27368 .section "Use of TLS Server Name Indication" "SECTtlssni"
27369 .cindex "TLS" "Server Name Indication"
27370 .vindex "&$tls_in_sni$&"
27371 .oindex "&%tls_in_sni%&"
27372 With TLS1.0 or above, there is an extension mechanism by which extra
27373 information can be included at various points in the protocol. One of these
27374 extensions, documented in RFC 6066 (and before that RFC 4366) is
27375 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27376 client in the initial handshake, so that the server can examine the servername
27377 within and possibly choose to use different certificates and keys (and more)
27380 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27381 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
27384 With SMTP to MX, there are the same problems here as in choosing the identity
27385 against which to validate a certificate: you can't rely on insecure DNS to
27386 provide the identity which you then cryptographically verify. So this will
27387 be of limited use in that environment.
27389 With SMTP to Submission, there is a well-defined hostname which clients are
27390 connecting to and can validate certificates against. Thus clients &*can*&
27391 choose to include this information in the TLS negotiation. If this becomes
27392 wide-spread, then hosters can choose to present different certificates to
27393 different clients. Or even negotiate different cipher suites.
27395 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
27396 if not empty, will be sent on a TLS session as part of the handshake. There's
27397 nothing more to it. Choosing a sensible value not derived insecurely is the
27398 only point of caution. The &$tls_out_sni$& variable will be set to this string
27399 for the lifetime of the client connection (including during authentication).
27401 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
27402 received from a client.
27403 It can be logged with the &%log_selector%& item &`+tls_sni`&.
27405 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
27406 option (prior to expansion) then the following options will be re-expanded
27407 during TLS session handshake, to permit alternative values to be chosen:
27410 .vindex "&%tls_certificate%&"
27411 &%tls_certificate%&
27413 .vindex "&%tls_crl%&"
27416 .vindex "&%tls_privatekey%&"
27419 .vindex "&%tls_verify_certificates%&"
27420 &%tls_verify_certificates%&
27422 .vindex "&%tls_ocsp_file%&"
27426 Great care should be taken to deal with matters of case, various injection
27427 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
27428 can always be referenced; it is important to remember that &$tls_sni$& is
27429 arbitrary unverified data provided prior to authentication.
27431 The Exim developers are proceeding cautiously and so far no other TLS options
27434 When Exim is built against OpenSSL, OpenSSL must have been built with support
27435 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
27436 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
27437 see &`-servername`& in the output, then OpenSSL has support.
27439 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
27440 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
27441 built, then you have SNI support).
27445 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
27447 .cindex "multiple SMTP deliveries with TLS"
27448 .cindex "TLS" "multiple message deliveries"
27449 Exim sends multiple messages down the same TCP/IP connection by starting up
27450 an entirely new delivery process for each message, passing the socket from
27451 one process to the next. This implementation does not fit well with the use
27452 of TLS, because there is quite a lot of state information associated with a TLS
27453 connection, not just a socket identification. Passing all the state information
27454 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
27455 session before passing the socket to a new process. The new process may then
27456 try to start a new TLS session, and if successful, may try to re-authenticate
27457 if AUTH is in use, before sending the next message.
27459 The RFC is not clear as to whether or not an SMTP session continues in clear
27460 after TLS has been shut down, or whether TLS may be restarted again later, as
27461 just described. However, if the server is Exim, this shutdown and
27462 reinitialization works. It is not known which (if any) other servers operate
27463 successfully if the client closes a TLS session and continues with unencrypted
27464 SMTP, but there are certainly some that do not work. For such servers, Exim
27465 should not pass the socket to another process, because the failure of the
27466 subsequent attempt to use it would cause Exim to record a temporary host error,
27467 and delay other deliveries to that host.
27469 To test for this case, Exim sends an EHLO command to the server after
27470 closing down the TLS session. If this fails in any way, the connection is
27471 closed instead of being passed to a new delivery process, but no retry
27472 information is recorded.
27474 There is also a manual override; you can set &%hosts_nopass_tls%& on the
27475 &(smtp)& transport to match those hosts for which Exim should not pass
27476 connections to new processes if TLS has been used.
27481 .section "Certificates and all that" "SECTcerandall"
27482 .cindex "certificate" "references to discussion"
27483 In order to understand fully how TLS works, you need to know about
27484 certificates, certificate signing, and certificate authorities. This is not the
27485 place to give a tutorial, especially as I do not know very much about it
27486 myself. Some helpful introduction can be found in the FAQ for the SSL addition
27487 to Apache, currently at
27489 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
27491 Other parts of the &'modssl'& documentation are also helpful, and have
27492 links to further files.
27493 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
27494 0-201-61598-3), contains both introductory and more in-depth descriptions.
27495 Some sample programs taken from the book are available from
27497 &url(http://www.rtfm.com/openssl-examples/)
27501 .section "Certificate chains" "SECID186"
27502 The file named by &%tls_certificate%& may contain more than one
27503 certificate. This is useful in the case where the certificate that is being
27504 sent is validated by an intermediate certificate which the other end does
27505 not have. Multiple certificates must be in the correct order in the file.
27506 First the host's certificate itself, then the first intermediate
27507 certificate to validate the issuer of the host certificate, then the next
27508 intermediate certificate to validate the issuer of the first intermediate
27509 certificate, and so on, until finally (optionally) the root certificate.
27510 The root certificate must already be trusted by the recipient for
27511 validation to succeed, of course, but if it's not preinstalled, sending the
27512 root certificate along with the rest makes it available for the user to
27513 install if the receiving end is a client MUA that can interact with a user.
27515 Note that certificates using MD5 are unlikely to work on today's Internet;
27516 even if your libraries allow loading them for use in Exim when acting as a
27517 server, increasingly clients will not accept such certificates. The error
27518 diagnostics in such a case can be frustratingly vague.
27522 .section "Self-signed certificates" "SECID187"
27523 .cindex "certificate" "self-signed"
27524 You can create a self-signed certificate using the &'req'& command provided
27525 with OpenSSL, like this:
27526 . ==== Do not shorten the duration here without reading and considering
27527 . ==== the text below. Please leave it at 9999 days.
27529 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
27532 &_file1_& and &_file2_& can be the same file; the key and the certificate are
27533 delimited and so can be identified independently. The &%-days%& option
27534 specifies a period for which the certificate is valid. The &%-nodes%& option is
27535 important: if you do not set it, the key is encrypted with a passphrase
27536 that you are prompted for, and any use that is made of the key causes more
27537 prompting for the passphrase. This is not helpful if you are going to use
27538 this certificate and key in an MTA, where prompting is not possible.
27540 . ==== I expect to still be working 26 years from now. The less technical
27541 . ==== debt I create, in terms of storing up trouble for my later years, the
27542 . ==== happier I will be then. We really have reached the point where we
27543 . ==== should start, at the very least, provoking thought and making folks
27544 . ==== pause before proceeding, instead of leaving all the fixes until two
27545 . ==== years before 2^31 seconds after the 1970 Unix epoch.
27547 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
27548 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
27549 the above command might produce a date in the past. Think carefully about
27550 the lifetime of the systems you're deploying, and either reduce the duration
27551 of the certificate or reconsider your platform deployment. (At time of
27552 writing, reducing the duration is the most likely choice, but the inexorable
27553 progression of time takes us steadily towards an era where this will not
27554 be a sensible resolution).
27556 A self-signed certificate made in this way is sufficient for testing, and
27557 may be adequate for all your requirements if you are mainly interested in
27558 encrypting transfers, and not in secure identification.
27560 However, many clients require that the certificate presented by the server be a
27561 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
27562 certificate. In this situation, the self-signed certificate described above
27563 must be installed on the client host as a trusted root &'certification
27564 authority'& (CA), and the certificate used by Exim must be a user certificate
27565 signed with that self-signed certificate.
27567 For information on creating self-signed CA certificates and using them to sign
27568 user certificates, see the &'General implementation overview'& chapter of the
27569 Open-source PKI book, available online at
27570 &url(http://ospkibook.sourceforge.net/).
27571 .ecindex IIDencsmtp1
27572 .ecindex IIDencsmtp2
27576 . ////////////////////////////////////////////////////////////////////////////
27577 . ////////////////////////////////////////////////////////////////////////////
27579 .chapter "Access control lists" "CHAPACL"
27580 .scindex IIDacl "&ACL;" "description"
27581 .cindex "control of incoming mail"
27582 .cindex "message" "controlling incoming"
27583 .cindex "policy control" "access control lists"
27584 Access Control Lists (ACLs) are defined in a separate section of the run time
27585 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
27586 name, terminated by a colon. Here is a complete ACL section that contains just
27587 one very small ACL:
27591 accept hosts = one.host.only
27593 You can have as many lists as you like in the ACL section, and the order in
27594 which they appear does not matter. The lists are self-terminating.
27596 The majority of ACLs are used to control Exim's behaviour when it receives
27597 certain SMTP commands. This applies both to incoming TCP/IP connections, and
27598 when a local process submits a message using SMTP by specifying the &%-bs%&
27599 option. The most common use is for controlling which recipients are accepted
27600 in incoming messages. In addition, you can define an ACL that is used to check
27601 local non-SMTP messages. The default configuration file contains an example of
27602 a realistic ACL for checking RCPT commands. This is discussed in chapter
27603 &<<CHAPdefconfil>>&.
27606 .section "Testing ACLs" "SECID188"
27607 The &%-bh%& command line option provides a way of testing your ACL
27608 configuration locally by running a fake SMTP session with which you interact.
27611 .section "Specifying when ACLs are used" "SECID189"
27612 .cindex "&ACL;" "options for specifying"
27613 In order to cause an ACL to be used, you have to name it in one of the relevant
27614 options in the main part of the configuration. These options are:
27615 .cindex "AUTH" "ACL for"
27616 .cindex "DATA" "ACLs for"
27617 .cindex "ETRN" "ACL for"
27618 .cindex "EXPN" "ACL for"
27619 .cindex "HELO" "ACL for"
27620 .cindex "EHLO" "ACL for"
27621 .cindex "DKIM" "ACL for"
27622 .cindex "MAIL" "ACL for"
27623 .cindex "QUIT, ACL for"
27624 .cindex "RCPT" "ACL for"
27625 .cindex "STARTTLS, ACL for"
27626 .cindex "VRFY" "ACL for"
27627 .cindex "SMTP" "connection, ACL for"
27628 .cindex "non-SMTP messages" "ACLs for"
27629 .cindex "MIME content scanning" "ACL for"
27630 .cindex "PRDR" "ACL for"
27633 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
27634 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
27635 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
27636 .irow &%acl_smtp_auth%& "ACL for AUTH"
27637 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
27638 .irow &%acl_smtp_data%& "ACL after DATA is complete"
27639 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
27640 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
27641 .irow &%acl_smtp_etrn%& "ACL for ETRN"
27642 .irow &%acl_smtp_expn%& "ACL for EXPN"
27643 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
27644 .irow &%acl_smtp_mail%& "ACL for MAIL"
27645 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
27646 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
27647 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
27648 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
27649 .irow &%acl_smtp_quit%& "ACL for QUIT"
27650 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
27651 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
27652 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
27655 For example, if you set
27657 acl_smtp_rcpt = small_acl
27659 the little ACL defined above is used whenever Exim receives a RCPT command
27660 in an SMTP dialogue. The majority of policy tests on incoming messages can be
27661 done when RCPT commands arrive. A rejection of RCPT should cause the
27662 sending MTA to give up on the recipient address contained in the RCPT
27663 command, whereas rejection at other times may cause the client MTA to keep on
27664 trying to deliver the message. It is therefore recommended that you do as much
27665 testing as possible at RCPT time.
27668 .section "The non-SMTP ACLs" "SECID190"
27669 .cindex "non-SMTP messages" "ACLs for"
27670 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
27671 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
27672 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
27673 the state of the SMTP connection such as encryption and authentication) are not
27674 relevant and are forbidden in these ACLs. However, the sender and recipients
27675 are known, so the &%senders%& and &%sender_domains%& conditions and the
27676 &$sender_address$& and &$recipients$& variables can be used. Variables such as
27677 &$authenticated_sender$& are also available. You can specify added header lines
27678 in any of these ACLs.
27680 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
27681 non-SMTP message, before any of the message has been read. (This is the
27682 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
27683 batched SMTP input, it runs after the DATA command has been reached. The
27684 result of this ACL is ignored; it cannot be used to reject a message. If you
27685 really need to, you could set a value in an ACL variable here and reject based
27686 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
27687 controls, and in particular, it can be used to set
27689 control = suppress_local_fixups
27691 This cannot be used in the other non-SMTP ACLs because by the time they are
27692 run, it is too late.
27694 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
27695 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27697 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
27698 kind of rejection is treated as permanent, because there is no way of sending a
27699 temporary error for these kinds of message.
27702 .section "The SMTP connect ACL" "SECID191"
27703 .cindex "SMTP" "connection, ACL for"
27704 .oindex &%smtp_banner%&
27705 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
27706 session, after the test specified by &%host_reject_connection%& (which is now
27707 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
27708 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
27709 the message override the banner message that is otherwise specified by the
27710 &%smtp_banner%& option.
27713 .section "The EHLO/HELO ACL" "SECID192"
27714 .cindex "EHLO" "ACL for"
27715 .cindex "HELO" "ACL for"
27716 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
27717 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
27718 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
27719 Note that a client may issue more than one EHLO or HELO command in an SMTP
27720 session, and indeed is required to issue a new EHLO or HELO after successfully
27721 setting up encryption following a STARTTLS command.
27723 Note also that a deny neither forces the client to go away nor means that
27724 mail will be refused on the connection. Consider checking for
27725 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
27727 If the command is accepted by an &%accept%& verb that has a &%message%&
27728 modifier, the message may not contain more than one line (it will be truncated
27729 at the first newline and a panic logged if it does). Such a message cannot
27730 affect the EHLO options that are listed on the second and subsequent lines of
27734 .section "The DATA ACLs" "SECID193"
27735 .cindex "DATA" "ACLs for"
27736 Two ACLs are associated with the DATA command, because it is two-stage
27737 command, with two responses being sent to the client.
27738 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
27739 is obeyed. This gives you control after all the RCPT commands, but before
27740 the message itself is received. It offers the opportunity to give a negative
27741 response to the DATA command before the data is transmitted. Header lines
27742 added by MAIL or RCPT ACLs are not visible at this time, but any that
27743 are defined here are visible when the &%acl_smtp_data%& ACL is run.
27745 You cannot test the contents of the message, for example, to verify addresses
27746 in the headers, at RCPT time or when the DATA command is received. Such
27747 tests have to appear in the ACL that is run after the message itself has been
27748 received, before the final response to the DATA command is sent. This is
27749 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
27750 associated with the DATA command.
27752 .cindex CHUNKING "BDAT command"
27753 .cindex BDAT "SMTP command"
27754 .cindex "RFC 3030" CHUNKING
27755 If CHUNKING was advertised and a BDAT command sequence is received,
27756 the &%acl_smtp_predata%& ACL is not run.
27757 .XXX why not? It should be possible, for the first BDAT.
27758 The &%acl_smtp_data%& is run after the last BDAT command and all of
27759 the data specified is received.
27761 For both of these ACLs, it is not possible to reject individual recipients. An
27762 error response rejects the entire message. Unfortunately, it is known that some
27763 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
27764 before or after the data) correctly &-- they keep the message on their queues
27765 and try again later, but that is their problem, though it does waste some of
27768 The &%acl_smtp_data%& ACL is run after
27769 the &%acl_smtp_data_prdr%&,
27770 the &%acl_smtp_dkim%&
27771 and the &%acl_smtp_mime%& ACLs.
27773 .section "The SMTP DKIM ACL" "SECTDKIMACL"
27774 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
27775 enabled (which is the default).
27777 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
27778 received, and is executed for each DKIM signature found in a message. If not
27779 otherwise specified, the default action is to accept.
27781 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
27783 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
27786 .section "The SMTP MIME ACL" "SECID194"
27787 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
27788 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27790 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27793 .section "The SMTP PRDR ACL" "SECTPRDRACL"
27794 .cindex "PRDR" "ACL for"
27795 .oindex "&%prdr_enable%&"
27796 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
27797 with PRDR support enabled (which is the default).
27798 It becomes active only when the PRDR feature is negotiated between
27799 client and server for a message, and more than one recipient
27802 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
27803 has been received, and is executed once for each recipient of the message
27804 with &$local_part$& and &$domain$& valid.
27805 The test may accept, defer or deny for individual recipients.
27806 The &%acl_smtp_data%& will still be called after this ACL and
27807 can reject the message overall, even if this ACL has accepted it
27808 for some or all recipients.
27810 PRDR may be used to support per-user content filtering. Without it
27811 one must defer any recipient after the first that has a different
27812 content-filter configuration. With PRDR, the RCPT-time check
27813 .cindex "PRDR" "variable for"
27814 for this can be disabled when the variable &$prdr_requested$&
27816 Any required difference in behaviour of the main DATA-time
27817 ACL should however depend on the PRDR-time ACL having run, as Exim
27818 will avoid doing so in some situations (e.g. single-recipient mails).
27820 See also the &%prdr_enable%& global option
27821 and the &%hosts_try_prdr%& smtp transport option.
27823 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27824 If the ACL is not defined, processing completes as if
27825 the feature was not requested by the client.
27827 .section "The QUIT ACL" "SECTQUITACL"
27828 .cindex "QUIT, ACL for"
27829 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
27830 does not affect the response code to QUIT, which is always 221. Thus, the ACL
27831 does not in fact control any access.
27832 For this reason, it may only accept
27833 or warn as its final result.
27835 This ACL can be used for tasks such as custom logging at the end of an SMTP
27836 session. For example, you can use ACL variables in other ACLs to count
27837 messages, recipients, etc., and log the totals at QUIT time using one or
27838 more &%logwrite%& modifiers on a &%warn%& verb.
27840 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
27841 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
27843 You do not need to have a final &%accept%&, but if you do, you can use a
27844 &%message%& modifier to specify custom text that is sent as part of the 221
27847 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
27848 failure (for example, failure to open a log file, or when Exim is bombing out
27849 because it has detected an unrecoverable error), all SMTP commands from the
27850 client are given temporary error responses until QUIT is received or the
27851 connection is closed. In these special cases, the QUIT ACL does not run.
27854 .section "The not-QUIT ACL" "SECTNOTQUITACL"
27855 .vindex &$acl_smtp_notquit$&
27856 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
27857 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
27858 trouble, such as being unable to write to its log files, this ACL is not run,
27859 because it might try to do things (such as write to log files) that make the
27860 situation even worse.
27862 Like the QUIT ACL, this ACL is provided to make it possible to do customized
27863 logging or to gather statistics, and its outcome is ignored. The &%delay%&
27864 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
27867 .vindex &$smtp_notquit_reason$&
27868 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
27869 to a string that indicates the reason for the termination of the SMTP
27870 connection. The possible values are:
27872 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
27873 .irow &`bad-commands`& "Too many unknown or non-mail commands"
27874 .irow &`command-timeout`& "Timeout while reading SMTP commands"
27875 .irow &`connection-lost`& "The SMTP connection has been lost"
27876 .irow &`data-timeout`& "Timeout while reading message data"
27877 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
27878 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
27879 .irow &`signal-exit`& "SIGTERM or SIGINT"
27880 .irow &`synchronization-error`& "SMTP synchronization error"
27881 .irow &`tls-failed`& "TLS failed to start"
27883 In most cases when an SMTP connection is closed without having received QUIT,
27884 Exim sends an SMTP response message before actually closing the connection.
27885 With the exception of the &`acl-drop`& case, the default message can be
27886 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
27887 &%drop%& verb in another ACL, it is the message from the other ACL that is
27891 .section "Finding an ACL to use" "SECID195"
27892 .cindex "&ACL;" "finding which to use"
27893 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
27894 you can use different ACLs in different circumstances. For example,
27896 acl_smtp_rcpt = ${if ={25}{$interface_port} \
27897 {acl_check_rcpt} {acl_check_rcpt_submit} }
27899 In the default configuration file there are some example settings for
27900 providing an RFC 4409 message submission service on port 587 and a
27901 non-standard &"smtps"& service on port 465. You can use a string
27902 expansion like this to choose an ACL for MUAs on these ports which is
27903 more appropriate for this purpose than the default ACL on port 25.
27905 The expanded string does not have to be the name of an ACL in the
27906 configuration file; there are other possibilities. Having expanded the
27907 string, Exim searches for an ACL as follows:
27910 If the string begins with a slash, Exim uses it as a file name, and reads its
27911 contents as an ACL. The lines are processed in the same way as lines in the
27912 Exim configuration file. In particular, continuation lines are supported, blank
27913 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
27914 If the file does not exist or cannot be read, an error occurs (typically
27915 causing a temporary failure of whatever caused the ACL to be run). For example:
27917 acl_smtp_data = /etc/acls/\
27918 ${lookup{$sender_host_address}lsearch\
27919 {/etc/acllist}{$value}{default}}
27921 This looks up an ACL file to use on the basis of the host's IP address, falling
27922 back to a default if the lookup fails. If an ACL is successfully read from a
27923 file, it is retained in memory for the duration of the Exim process, so that it
27924 can be re-used without having to re-read the file.
27926 If the string does not start with a slash, and does not contain any spaces,
27927 Exim searches the ACL section of the configuration for an ACL whose name
27928 matches the string.
27930 If no named ACL is found, or if the string contains spaces, Exim parses
27931 the string as an inline ACL. This can save typing in cases where you just
27932 want to have something like
27934 acl_smtp_vrfy = accept
27936 in order to allow free use of the VRFY command. Such a string may contain
27937 newlines; it is processed in the same way as an ACL that is read from a file.
27943 .section "ACL return codes" "SECID196"
27944 .cindex "&ACL;" "return codes"
27945 Except for the QUIT ACL, which does not affect the SMTP return code (see
27946 section &<<SECTQUITACL>>& above), the result of running an ACL is either
27947 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
27948 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
27949 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
27950 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
27951 This also causes a 4&'xx'& return code.
27953 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
27954 &"deny"&, because there is no mechanism for passing temporary errors to the
27955 submitters of non-SMTP messages.
27958 ACLs that are relevant to message reception may also return &"discard"&. This
27959 has the effect of &"accept"&, but causes either the entire message or an
27960 individual recipient address to be discarded. In other words, it is a
27961 blackholing facility. Use it with care.
27963 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
27964 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
27965 RCPT ACL is to discard just the one recipient address. If there are no
27966 recipients left when the message's data is received, the DATA ACL is not
27967 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
27968 remaining recipients. The &"discard"& return is not permitted for the
27969 &%acl_smtp_predata%& ACL.
27972 .cindex "&[local_scan()]& function" "when all recipients discarded"
27973 The &[local_scan()]& function is always run, even if there are no remaining
27974 recipients; it may create new recipients.
27978 .section "Unset ACL options" "SECID197"
27979 .cindex "&ACL;" "unset options"
27980 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
27981 all the same. &*Note*&: These defaults apply only when the relevant ACL is
27982 not defined at all. For any defined ACL, the default action when control
27983 reaches the end of the ACL statements is &"deny"&.
27985 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
27986 these two are ACLs that are used only for their side effects. They cannot be
27987 used to accept or reject anything.
27989 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
27990 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
27991 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
27992 when the ACL is not defined is &"accept"&.
27994 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
27995 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
27996 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
27997 messages over an SMTP connection. For an example, see the ACL in the default
27998 configuration file.
28003 .section "Data for message ACLs" "SECID198"
28004 .cindex "&ACL;" "data for message ACL"
28006 .vindex &$local_part$&
28007 .vindex &$sender_address$&
28008 .vindex &$sender_host_address$&
28009 .vindex &$smtp_command$&
28010 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
28011 that contain information about the host and the message's sender (for example,
28012 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
28013 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
28014 &$local_part$& are set from the argument address. The entire SMTP command
28015 is available in &$smtp_command$&.
28017 When an ACL for the AUTH parameter of MAIL is running, the variables that
28018 contain information about the host are set, but &$sender_address$& is not yet
28019 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
28022 .vindex "&$message_size$&"
28023 The &$message_size$& variable is set to the value of the SIZE parameter on
28024 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
28025 that parameter is not given. The value is updated to the true message size by
28026 the time the final DATA ACL is run (after the message data has been
28029 .vindex "&$rcpt_count$&"
28030 .vindex "&$recipients_count$&"
28031 The &$rcpt_count$& variable increases by one for each RCPT command received.
28032 The &$recipients_count$& variable increases by one each time a RCPT command is
28033 accepted, so while an ACL for RCPT is being processed, it contains the number
28034 of previously accepted recipients. At DATA time (for both the DATA ACLs),
28035 &$rcpt_count$& contains the total number of RCPT commands, and
28036 &$recipients_count$& contains the total number of accepted recipients.
28042 .section "Data for non-message ACLs" "SECTdatfornon"
28043 .cindex "&ACL;" "data for non-message ACL"
28044 .vindex &$smtp_command_argument$&
28045 .vindex &$smtp_command$&
28046 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
28047 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
28048 and the entire SMTP command is available in &$smtp_command$&.
28049 These variables can be tested using a &%condition%& condition. For example,
28050 here is an ACL for use with AUTH, which insists that either the session is
28051 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
28052 does not permit authentication methods that use cleartext passwords on
28053 unencrypted connections.
28056 accept encrypted = *
28057 accept condition = ${if eq{${uc:$smtp_command_argument}}\
28059 deny message = TLS encryption or CRAM-MD5 required
28061 (Another way of applying this restriction is to arrange for the authenticators
28062 that use cleartext passwords not to be advertised when the connection is not
28063 encrypted. You can use the generic &%server_advertise_condition%& authenticator
28064 option to do this.)
28068 .section "Format of an ACL" "SECID199"
28069 .cindex "&ACL;" "format of"
28070 .cindex "&ACL;" "verbs, definition of"
28071 An individual ACL consists of a number of statements. Each statement starts
28072 with a verb, optionally followed by a number of conditions and &"modifiers"&.
28073 Modifiers can change the way the verb operates, define error and log messages,
28074 set variables, insert delays, and vary the processing of accepted messages.
28076 If all the conditions are met, the verb is obeyed. The same condition may be
28077 used (with different arguments) more than once in the same statement. This
28078 provides a means of specifying an &"and"& conjunction between conditions. For
28081 deny dnslists = list1.example
28082 dnslists = list2.example
28084 If there are no conditions, the verb is always obeyed. Exim stops evaluating
28085 the conditions and modifiers when it reaches a condition that fails. What
28086 happens then depends on the verb (and in one case, on a special modifier). Not
28087 all the conditions make sense at every testing point. For example, you cannot
28088 test a sender address in the ACL that is run for a VRFY command.
28091 .section "ACL verbs" "SECID200"
28092 The ACL verbs are as follows:
28095 .cindex "&%accept%& ACL verb"
28096 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
28097 of the conditions are not met, what happens depends on whether &%endpass%&
28098 appears among the conditions (for syntax see below). If the failing condition
28099 is before &%endpass%&, control is passed to the next ACL statement; if it is
28100 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
28101 check a RCPT command:
28103 accept domains = +local_domains
28107 If the recipient domain does not match the &%domains%& condition, control
28108 passes to the next statement. If it does match, the recipient is verified, and
28109 the command is accepted if verification succeeds. However, if verification
28110 fails, the ACL yields &"deny"&, because the failing condition is after
28113 The &%endpass%& feature has turned out to be confusing to many people, so its
28114 use is not recommended nowadays. It is always possible to rewrite an ACL so
28115 that &%endpass%& is not needed, and it is no longer used in the default
28118 .cindex "&%message%& ACL modifier" "with &%accept%&"
28119 If a &%message%& modifier appears on an &%accept%& statement, its action
28120 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
28121 (when an &%accept%& verb either accepts or passes control to the next
28122 statement), &%message%& can be used to vary the message that is sent when an
28123 SMTP command is accepted. For example, in a RCPT ACL you could have:
28125 &`accept `&<&'some conditions'&>
28126 &` message = OK, I will allow you through today`&
28128 You can specify an SMTP response code, optionally followed by an &"extended
28129 response code"& at the start of the message, but the first digit must be the
28130 same as would be sent by default, which is 2 for an &%accept%& verb.
28132 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
28133 an error message that is used when access is denied. This behaviour is retained
28134 for backward compatibility, but current &"best practice"& is to avoid the use
28139 .cindex "&%defer%& ACL verb"
28140 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
28141 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
28142 &%defer%& is the same as &%deny%&, because there is no way of sending a
28143 temporary error. For a RCPT command, &%defer%& is much the same as using a
28144 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
28145 be used in any ACL, and even for a recipient it might be a simpler approach.
28149 .cindex "&%deny%& ACL verb"
28150 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
28151 the conditions are not met, control is passed to the next ACL statement. For
28154 deny dnslists = blackholes.mail-abuse.org
28156 rejects commands from hosts that are on a DNS black list.
28160 .cindex "&%discard%& ACL verb"
28161 &%discard%&: This verb behaves like &%accept%&, except that it returns
28162 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
28163 that are concerned with receiving messages. When all the conditions are true,
28164 the sending entity receives a &"success"& response. However, &%discard%& causes
28165 recipients to be discarded. If it is used in an ACL for RCPT, just the one
28166 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
28167 message's recipients are discarded. Recipients that are discarded before DATA
28168 do not appear in the log line when the &%received_recipients%& log selector is set.
28170 If the &%log_message%& modifier is set when &%discard%& operates,
28171 its contents are added to the line that is automatically written to the log.
28172 The &%message%& modifier operates exactly as it does for &%accept%&.
28176 .cindex "&%drop%& ACL verb"
28177 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
28178 forcibly closed after the 5&'xx'& error message has been sent. For example:
28180 drop message = I don't take more than 20 RCPTs
28181 condition = ${if > {$rcpt_count}{20}}
28183 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
28184 The connection is always dropped after sending a 550 response.
28187 .cindex "&%require%& ACL verb"
28188 &%require%&: If all the conditions are met, control is passed to the next ACL
28189 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
28190 example, when checking a RCPT command,
28192 require message = Sender did not verify
28195 passes control to subsequent statements only if the message's sender can be
28196 verified. Otherwise, it rejects the command. Note the positioning of the
28197 &%message%& modifier, before the &%verify%& condition. The reason for this is
28198 discussed in section &<<SECTcondmodproc>>&.
28201 .cindex "&%warn%& ACL verb"
28202 &%warn%&: If all the conditions are true, a line specified by the
28203 &%log_message%& modifier is written to Exim's main log. Control always passes
28204 to the next ACL statement. If any condition is false, the log line is not
28205 written. If an identical log line is requested several times in the same
28206 message, only one copy is actually written to the log. If you want to force
28207 duplicates to be written, use the &%logwrite%& modifier instead.
28209 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
28210 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
28211 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
28212 first failing condition. There is more about adding header lines in section
28213 &<<SECTaddheadacl>>&.
28215 If any condition on a &%warn%& statement cannot be completed (that is, there is
28216 some sort of defer), the log line specified by &%log_message%& is not written.
28217 This does not include the case of a forced failure from a lookup, which
28218 is considered to be a successful completion. After a defer, no further
28219 conditions or modifiers in the &%warn%& statement are processed. The incident
28220 is logged, and the ACL continues to be processed, from the next statement
28224 .vindex "&$acl_verify_message$&"
28225 When one of the &%warn%& conditions is an address verification that fails, the
28226 text of the verification failure message is in &$acl_verify_message$&. If you
28227 want this logged, you must set it up explicitly. For example:
28229 warn !verify = sender
28230 log_message = sender verify failed: $acl_verify_message
28234 At the end of each ACL there is an implicit unconditional &%deny%&.
28236 As you can see from the examples above, the conditions and modifiers are
28237 written one to a line, with the first one on the same line as the verb, and
28238 subsequent ones on following lines. If you have a very long condition, you can
28239 continue it onto several physical lines by the usual backslash continuation
28240 mechanism. It is conventional to align the conditions vertically.
28244 .section "ACL variables" "SECTaclvariables"
28245 .cindex "&ACL;" "variables"
28246 There are some special variables that can be set during ACL processing. They
28247 can be used to pass information between different ACLs, different invocations
28248 of the same ACL in the same SMTP connection, and between ACLs and the routers,
28249 transports, and filters that are used to deliver a message. The names of these
28250 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
28251 an underscore, but the remainder of the name can be any sequence of
28252 alphanumeric characters and underscores that you choose. There is no limit on
28253 the number of ACL variables. The two sets act as follows:
28255 The values of those variables whose names begin with &$acl_c$& persist
28256 throughout an SMTP connection. They are never reset. Thus, a value that is set
28257 while receiving one message is still available when receiving the next message
28258 on the same SMTP connection.
28260 The values of those variables whose names begin with &$acl_m$& persist only
28261 while a message is being received. They are reset afterwards. They are also
28262 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
28265 When a message is accepted, the current values of all the ACL variables are
28266 preserved with the message and are subsequently made available at delivery
28267 time. The ACL variables are set by a modifier called &%set%&. For example:
28269 accept hosts = whatever
28270 set acl_m4 = some value
28271 accept authenticated = *
28272 set acl_c_auth = yes
28274 &*Note*&: A leading dollar sign is not used when naming a variable that is to
28275 be set. If you want to set a variable without taking any action, you can use a
28276 &%warn%& verb without any other modifiers or conditions.
28278 .oindex &%strict_acl_vars%&
28279 What happens if a syntactically valid but undefined ACL variable is
28280 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
28281 false (the default), an empty string is substituted; if it is true, an
28282 error is generated.
28284 Versions of Exim before 4.64 have a limited set of numbered variables, but
28285 their names are compatible, so there is no problem with upgrading.
28288 .section "Condition and modifier processing" "SECTcondmodproc"
28289 .cindex "&ACL;" "conditions; processing"
28290 .cindex "&ACL;" "modifiers; processing"
28291 An exclamation mark preceding a condition negates its result. For example:
28293 deny domains = *.dom.example
28294 !verify = recipient
28296 causes the ACL to return &"deny"& if the recipient domain ends in
28297 &'dom.example'& and the recipient address cannot be verified. Sometimes
28298 negation can be used on the right-hand side of a condition. For example, these
28299 two statements are equivalent:
28301 deny hosts = !192.168.3.4
28302 deny !hosts = 192.168.3.4
28304 However, for many conditions (&%verify%& being a good example), only left-hand
28305 side negation of the whole condition is possible.
28307 The arguments of conditions and modifiers are expanded. A forced failure
28308 of an expansion causes a condition to be ignored, that is, it behaves as if the
28309 condition is true. Consider these two statements:
28311 accept senders = ${lookup{$host_name}lsearch\
28312 {/some/file}{$value}fail}
28313 accept senders = ${lookup{$host_name}lsearch\
28314 {/some/file}{$value}{}}
28316 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
28317 the returned list is searched, but if the lookup fails the behaviour is
28318 different in the two cases. The &%fail%& in the first statement causes the
28319 condition to be ignored, leaving no further conditions. The &%accept%& verb
28320 therefore succeeds. The second statement, however, generates an empty list when
28321 the lookup fails. No sender can match an empty list, so the condition fails,
28322 and therefore the &%accept%& also fails.
28324 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
28325 specify actions that are taken as the conditions for a statement are checked;
28326 others specify text for messages that are used when access is denied or a
28327 warning is generated. The &%control%& modifier affects the way an incoming
28328 message is handled.
28330 The positioning of the modifiers in an ACL statement is important, because the
28331 processing of a verb ceases as soon as its outcome is known. Only those
28332 modifiers that have already been encountered will take effect. For example,
28333 consider this use of the &%message%& modifier:
28335 require message = Can't verify sender
28337 message = Can't verify recipient
28339 message = This message cannot be used
28341 If sender verification fails, Exim knows that the result of the statement is
28342 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
28343 so its text is used as the error message. If sender verification succeeds, but
28344 recipient verification fails, the second message is used. If recipient
28345 verification succeeds, the third message becomes &"current"&, but is never used
28346 because there are no more conditions to cause failure.
28348 For the &%deny%& verb, on the other hand, it is always the last &%message%&
28349 modifier that is used, because all the conditions must be true for rejection to
28350 happen. Specifying more than one &%message%& modifier does not make sense, and
28351 the message can even be specified after all the conditions. For example:
28354 !senders = *@my.domain.example
28355 message = Invalid sender from client host
28357 The &"deny"& result does not happen until the end of the statement is reached,
28358 by which time Exim has set up the message.
28362 .section "ACL modifiers" "SECTACLmodi"
28363 .cindex "&ACL;" "modifiers; list of"
28364 The ACL modifiers are as follows:
28367 .vitem &*add_header*&&~=&~<&'text'&>
28368 This modifier specifies one or more header lines that are to be added to an
28369 incoming message, assuming, of course, that the message is ultimately
28370 accepted. For details, see section &<<SECTaddheadacl>>&.
28372 .vitem &*continue*&&~=&~<&'text'&>
28373 .cindex "&%continue%& ACL modifier"
28374 .cindex "database" "updating in ACL"
28375 This modifier does nothing of itself, and processing of the ACL always
28376 continues with the next condition or modifier. The value of &%continue%& is in
28377 the side effects of expanding its argument. Typically this could be used to
28378 update a database. It is really just a syntactic tidiness, to avoid having to
28379 write rather ugly lines like this:
28381 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
28383 Instead, all you need is
28385 &`continue = `&<&'some expansion'&>
28388 .vitem &*control*&&~=&~<&'text'&>
28389 .cindex "&%control%& ACL modifier"
28390 This modifier affects the subsequent processing of the SMTP connection or of an
28391 incoming message that is accepted. The effect of the first type of control
28392 lasts for the duration of the connection, whereas the effect of the second type
28393 lasts only until the current message has been received. The message-specific
28394 controls always apply to the whole message, not to individual recipients,
28395 even if the &%control%& modifier appears in a RCPT ACL.
28397 As there are now quite a few controls that can be applied, they are described
28398 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
28399 in several different ways. For example:
28401 . ==== As this is a nested list, any displays it contains must be indented
28402 . ==== as otherwise they are too far to the left. That comment applies only
28403 . ==== when xmlto and fop are used; formatting with sdop gets it right either
28407 It can be at the end of an &%accept%& statement:
28409 accept ...some conditions
28410 control = queue_only
28412 In this case, the control is applied when this statement yields &"accept"&, in
28413 other words, when the conditions are all true.
28416 It can be in the middle of an &%accept%& statement:
28418 accept ...some conditions...
28419 control = queue_only
28420 ...some more conditions...
28422 If the first set of conditions are true, the control is applied, even if the
28423 statement does not accept because one of the second set of conditions is false.
28424 In this case, some subsequent statement must yield &"accept"& for the control
28428 It can be used with &%warn%& to apply the control, leaving the
28429 decision about accepting or denying to a subsequent verb. For
28432 warn ...some conditions...
28436 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
28437 &%logwrite%&, so it does not add anything to the message and does not write a
28441 If you want to apply a control unconditionally, you can use it with a
28442 &%require%& verb. For example:
28444 require control = no_multiline_responses
28448 .vitem &*delay*&&~=&~<&'time'&>
28449 .cindex "&%delay%& ACL modifier"
28451 This modifier may appear in any ACL except notquit. It causes Exim to wait for
28452 the time interval before proceeding. However, when testing Exim using the
28453 &%-bh%& option, the delay is not actually imposed (an appropriate message is
28454 output instead). The time is given in the usual Exim notation, and the delay
28455 happens as soon as the modifier is processed. In an SMTP session, pending
28456 output is flushed before the delay is imposed.
28458 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
28461 deny ...some conditions...
28464 The delay happens if all the conditions are true, before the statement returns
28465 &"deny"&. Compare this with:
28468 ...some conditions...
28470 which waits for 30s before processing the conditions. The &%delay%& modifier
28471 can also be used with &%warn%& and together with &%control%&:
28473 warn ...some conditions...
28479 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
28480 responses to several commands are no longer buffered and sent in one packet (as
28481 they would normally be) because all output is flushed before imposing the
28482 delay. This optimization is disabled so that a number of small delays do not
28483 appear to the client as one large aggregated delay that might provoke an
28484 unwanted timeout. You can, however, disable output flushing for &%delay%& by
28485 using a &%control%& modifier to set &%no_delay_flush%&.
28489 .cindex "&%endpass%& ACL modifier"
28490 This modifier, which has no argument, is recognized only in &%accept%& and
28491 &%discard%& statements. It marks the boundary between the conditions whose
28492 failure causes control to pass to the next statement, and the conditions whose
28493 failure causes the ACL to return &"deny"&. This concept has proved to be
28494 confusing to some people, so the use of &%endpass%& is no longer recommended as
28495 &"best practice"&. See the description of &%accept%& above for more details.
28498 .vitem &*log_message*&&~=&~<&'text'&>
28499 .cindex "&%log_message%& ACL modifier"
28500 This modifier sets up a message that is used as part of the log message if the
28501 ACL denies access or a &%warn%& statement's conditions are true. For example:
28503 require log_message = wrong cipher suite $tls_in_cipher
28504 encrypted = DES-CBC3-SHA
28506 &%log_message%& is also used when recipients are discarded by &%discard%&. For
28509 &`discard `&<&'some conditions'&>
28510 &` log_message = Discarded $local_part@$domain because...`&
28512 When access is denied, &%log_message%& adds to any underlying error message
28513 that may exist because of a condition failure. For example, while verifying a
28514 recipient address, a &':fail:'& redirection might have already set up a
28517 The message may be defined before the conditions to which it applies, because
28518 the string expansion does not happen until Exim decides that access is to be
28519 denied. This means that any variables that are set by the condition are
28520 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
28521 variables are set after a DNS black list lookup succeeds. If the expansion of
28522 &%log_message%& fails, or if the result is an empty string, the modifier is
28525 .vindex "&$acl_verify_message$&"
28526 If you want to use a &%warn%& statement to log the result of an address
28527 verification, you can use &$acl_verify_message$& to include the verification
28530 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
28531 the start of the logged message. If the same warning log message is requested
28532 more than once while receiving a single email message, only one copy is
28533 actually logged. If you want to log multiple copies, use &%logwrite%& instead
28534 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
28535 is logged for a successful &%warn%& statement.
28537 If &%log_message%& is not present and there is no underlying error message (for
28538 example, from the failure of address verification), but &%message%& is present,
28539 the &%message%& text is used for logging rejections. However, if any text for
28540 logging contains newlines, only the first line is logged. In the absence of
28541 both &%log_message%& and &%message%&, a default built-in message is used for
28542 logging rejections.
28545 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
28546 .cindex "&%log_reject_target%& ACL modifier"
28547 .cindex "logging in ACL" "specifying which log"
28548 This modifier makes it possible to specify which logs are used for messages
28549 about ACL rejections. Its argument is a colon-separated list of words that can
28550 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
28551 may be empty, in which case a rejection is not logged at all. For example, this
28552 ACL fragment writes no logging information when access is denied:
28554 &`deny `&<&'some conditions'&>
28555 &` log_reject_target =`&
28557 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
28558 permanent and temporary rejections. Its effect lasts for the rest of the
28562 .vitem &*logwrite*&&~=&~<&'text'&>
28563 .cindex "&%logwrite%& ACL modifier"
28564 .cindex "logging in ACL" "immediate"
28565 This modifier writes a message to a log file as soon as it is encountered when
28566 processing an ACL. (Compare &%log_message%&, which, except in the case of
28567 &%warn%& and &%discard%&, is used only if the ACL statement denies
28568 access.) The &%logwrite%& modifier can be used to log special incidents in
28571 &`accept `&<&'some special conditions'&>
28572 &` control = freeze`&
28573 &` logwrite = froze message because ...`&
28575 By default, the message is written to the main log. However, it may begin
28576 with a colon, followed by a comma-separated list of log names, and then
28577 another colon, to specify exactly which logs are to be written. For
28580 logwrite = :main,reject: text for main and reject logs
28581 logwrite = :panic: text for panic log only
28585 .vitem &*message*&&~=&~<&'text'&>
28586 .cindex "&%message%& ACL modifier"
28587 This modifier sets up a text string that is expanded and used as a response
28588 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
28589 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
28590 there is some complication if &%endpass%& is involved; see the description of
28591 &%accept%& for details.)
28593 The expansion of the message happens at the time Exim decides that the ACL is
28594 to end, not at the time it processes &%message%&. If the expansion fails, or
28595 generates an empty string, the modifier is ignored. Here is an example where
28596 &%message%& must be specified first, because the ACL ends with a rejection if
28597 the &%hosts%& condition fails:
28599 require message = Host not recognized
28602 (Once a condition has failed, no further conditions or modifiers are
28605 .cindex "SMTP" "error codes"
28606 .oindex "&%smtp_banner%&
28607 For ACLs that are triggered by SMTP commands, the message is returned as part
28608 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
28609 is meaningful only for SMTP, as no message is returned when a non-SMTP message
28610 is accepted. In the case of the connect ACL, accepting with a message modifier
28611 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
28612 accept message may not contain more than one line (otherwise it will be
28613 truncated at the first newline and a panic logged), and it cannot affect the
28616 When SMTP is involved, the message may begin with an overriding response code,
28617 consisting of three digits optionally followed by an &"extended response code"&
28618 of the form &'n.n.n'&, each code being followed by a space. For example:
28620 deny message = 599 1.2.3 Host not welcome
28621 hosts = 192.168.34.0/24
28623 The first digit of the supplied response code must be the same as would be sent
28624 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
28625 access, but for the predata ACL, note that the default success code is 354, not
28628 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
28629 the message modifier cannot override the 221 response code.
28631 The text in a &%message%& modifier is literal; any quotes are taken as
28632 literals, but because the string is expanded, backslash escapes are processed
28633 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
28636 .vindex "&$acl_verify_message$&"
28637 For ACLs that are called by an &%acl =%& ACL condition, the message is
28638 stored in &$acl_verify_message$&, from which the calling ACL may use it.
28640 If &%message%& is used on a statement that verifies an address, the message
28641 specified overrides any message that is generated by the verification process.
28642 However, the original message is available in the variable
28643 &$acl_verify_message$&, so you can incorporate it into your message if you
28644 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
28645 routers to be passed back as part of the SMTP response, you should either not
28646 use a &%message%& modifier, or make use of &$acl_verify_message$&.
28648 For compatibility with previous releases of Exim, a &%message%& modifier that
28649 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
28650 modifier, but this usage is now deprecated. However, &%message%& acts only when
28651 all the conditions are true, wherever it appears in an ACL command, whereas
28652 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
28653 &%warn%& in an ACL that is not concerned with receiving a message, it has no
28658 .vitem &*queue*&&~=&~<&'text'&>
28659 This modifier specifies the use of a named queue for spool files
28661 It can only be used before the message is received (i.e. not in
28663 This could be used, for example, for known high-volume burst sources
28664 of traffic, or for quarantine of messages.
28665 Separate queue-runner processes will be needed for named queues.
28666 If the text after expansion is empty, the default queue is used.
28670 .vitem &*remove_header*&&~=&~<&'text'&>
28671 This modifier specifies one or more header names in a colon-separated list
28672 that are to be removed from an incoming message, assuming, of course, that
28673 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
28676 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
28677 .cindex "&%set%& ACL modifier"
28678 This modifier puts a value into one of the ACL variables (see section
28679 &<<SECTaclvariables>>&).
28682 .vitem &*udpsend*&&~=&~<&'parameters'&>
28683 This modifier sends a UDP packet, for purposes such as statistics
28684 collection or behaviour monitoring. The parameters are expanded, and
28685 the result of the expansion must be a colon-separated list consisting
28686 of a destination server, port number, and the packet contents. The
28687 server can be specified as a host name or IPv4 or IPv6 address. The
28688 separator can be changed with the usual angle bracket syntax. For
28689 example, you might want to collect information on which hosts connect
28692 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
28693 $tod_zulu $sender_host_address
28700 .section "Use of the control modifier" "SECTcontrols"
28701 .cindex "&%control%& ACL modifier"
28702 The &%control%& modifier supports the following settings:
28705 .vitem &*control&~=&~allow_auth_unadvertised*&
28706 This modifier allows a client host to use the SMTP AUTH command even when it
28707 has not been advertised in response to EHLO. Furthermore, because there are
28708 apparently some really broken clients that do this, Exim will accept AUTH after
28709 HELO (rather than EHLO) when this control is set. It should be used only if you
28710 really need it, and you should limit its use to those broken clients that do
28711 not work without it. For example:
28713 warn hosts = 192.168.34.25
28714 control = allow_auth_unadvertised
28716 Normally, when an Exim server receives an AUTH command, it checks the name of
28717 the authentication mechanism that is given in the command to ensure that it
28718 matches an advertised mechanism. When this control is set, the check that a
28719 mechanism has been advertised is bypassed. Any configured mechanism can be used
28720 by the client. This control is permitted only in the connection and HELO ACLs.
28723 .vitem &*control&~=&~caseful_local_part*& &&&
28724 &*control&~=&~caselower_local_part*&
28725 .cindex "&ACL;" "case of local part in"
28726 .cindex "case of local parts"
28727 .vindex "&$local_part$&"
28728 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
28729 (that is, during RCPT processing). By default, the contents of &$local_part$&
28730 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
28731 any uppercase letters in the original local part are restored in &$local_part$&
28732 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
28735 These controls affect only the current recipient. Moreover, they apply only to
28736 local part handling that takes place directly in the ACL (for example, as a key
28737 in lookups). If a test to verify the recipient is obeyed, the case-related
28738 handling of the local part during the verification is controlled by the router
28739 configuration (see the &%caseful_local_part%& generic router option).
28741 This facility could be used, for example, to add a spam score to local parts
28742 containing upper case letters. For example, using &$acl_m4$& to accumulate the
28745 warn control = caseful_local_part
28746 set acl_m4 = ${eval:\
28748 ${if match{$local_part}{[A-Z]}{1}{0}}\
28750 control = caselower_local_part
28752 Notice that we put back the lower cased version afterwards, assuming that
28753 is what is wanted for subsequent tests.
28756 .vitem &*control&~=&~cutthrough_delivery*&
28757 .cindex "&ACL;" "cutthrough routing"
28758 .cindex "cutthrough" "requesting"
28759 This option requests delivery be attempted while the item is being received.
28761 The option is usable in the RCPT ACL.
28762 If enabled for a message received via smtp and routed to an smtp transport,
28763 and only one transport, interface, destination host and port combination
28764 is used for all recipients of the message,
28765 then the delivery connection is made while the receiving connection is open
28766 and data is copied from one to the other.
28768 An attempt to set this option for any recipient but the first
28769 for a mail will be quietly ignored.
28770 If a recipient-verify callout
28772 connection is subsequently
28773 requested in the same ACL it is held open and used for
28774 any subsequent recipients and the data,
28775 otherwise one is made after the initial RCPT ACL completes.
28777 Note that routers are used in verify mode,
28778 and cannot depend on content of received headers.
28779 Note also that headers cannot be
28780 modified by any of the post-data ACLs (DATA, MIME and DKIM).
28781 Headers may be modified by routers (subject to the above) and transports.
28783 All the usual ACLs are called; if one results in the message being
28784 rejected, all effort spent in delivery (including the costs on
28785 the ultimate destination) will be wasted.
28786 Note that in the case of data-time ACLs this includes the entire
28789 Cutthrough delivery is not supported via transport-filters or when DKIM signing
28790 of outgoing messages is done, because it sends data to the ultimate destination
28791 before the entire message has been received from the source.
28792 It is not supported for messages received with the SMTP PRDR option in use.
28794 Should the ultimate destination system positively accept or reject the mail,
28795 a corresponding indication is given to the source system and nothing is queued.
28796 If there is a temporary error the item is queued for later delivery in the
28797 usual fashion. If the item is successfully delivered in cutthrough mode
28798 the delivery log lines are tagged with ">>" rather than "=>" and appear
28799 before the acceptance "<=" line.
28801 Delivery in this mode avoids the generation of a bounce mail to a
28803 sender when the destination system is doing content-scan based rejection.
28806 .vitem &*control&~=&~debug/*&<&'options'&>
28807 .cindex "&ACL;" "enabling debug logging"
28808 .cindex "debugging" "enabling from an ACL"
28809 This control turns on debug logging, almost as though Exim had been invoked
28810 with &`-d`&, with the output going to a new logfile, by default called
28811 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
28812 may access any variables already defined. The logging may be adjusted with
28813 the &'opts'& option, which takes the same values as the &`-d`& command-line
28816 Logging may be stopped, and the file removed, with the &'kill'& option.
28818 Some examples (which depend on variables that don't exist in all
28822 control = debug/tag=.$sender_host_address
28823 control = debug/opts=+expand+acl
28824 control = debug/tag=.$message_exim_id/opts=+expand
28825 control = debug/kill
28829 .vitem &*control&~=&~dkim_disable_verify*&
28830 .cindex "disable DKIM verify"
28831 .cindex "DKIM" "disable verify"
28832 This control turns off DKIM verification processing entirely. For details on
28833 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
28836 .vitem &*control&~=&~dscp/*&<&'value'&>
28837 .cindex "&ACL;" "setting DSCP value"
28838 .cindex "DSCP" "inbound"
28839 This option causes the DSCP value associated with the socket for the inbound
28840 connection to be adjusted to a given value, given as one of a number of fixed
28841 strings or to numeric value.
28842 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
28843 Common values include &`throughput`&, &`mincost`&, and on newer systems
28844 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
28846 The outbound packets from Exim will be marked with this value in the header
28847 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
28848 that these values will have any effect, not be stripped by networking
28849 equipment, or do much of anything without cooperation with your Network
28850 Engineer and those of all network operators between the source and destination.
28853 .vitem &*control&~=&~enforce_sync*& &&&
28854 &*control&~=&~no_enforce_sync*&
28855 .cindex "SMTP" "synchronization checking"
28856 .cindex "synchronization checking in SMTP"
28857 These controls make it possible to be selective about when SMTP synchronization
28858 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
28859 state of the switch (it is true by default). See the description of this option
28860 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
28862 The effect of these two controls lasts for the remainder of the SMTP
28863 connection. They can appear in any ACL except the one for the non-SMTP
28864 messages. The most straightforward place to put them is in the ACL defined by
28865 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
28866 before the first synchronization check. The expected use is to turn off the
28867 synchronization checks for badly-behaved hosts that you nevertheless need to
28871 .vitem &*control&~=&~fakedefer/*&<&'message'&>
28872 .cindex "fake defer"
28873 .cindex "defer, fake"
28874 This control works in exactly the same way as &%fakereject%& (described below)
28875 except that it causes an SMTP 450 response after the message data instead of a
28876 550 response. You must take care when using &%fakedefer%& because it causes the
28877 messages to be duplicated when the sender retries. Therefore, you should not
28878 use &%fakedefer%& if the message is to be delivered normally.
28880 .vitem &*control&~=&~fakereject/*&<&'message'&>
28881 .cindex "fake rejection"
28882 .cindex "rejection, fake"
28883 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
28884 words, only when an SMTP message is being received. If Exim accepts the
28885 message, instead the final 250 response, a 550 rejection message is sent.
28886 However, Exim proceeds to deliver the message as normal. The control applies
28887 only to the current message, not to any subsequent ones that may be received in
28888 the same SMTP connection.
28890 The text for the 550 response is taken from the &%control%& modifier. If no
28891 message is supplied, the following is used:
28893 550-Your message has been rejected but is being
28894 550-kept for evaluation.
28895 550-If it was a legitimate message, it may still be
28896 550 delivered to the target recipient(s).
28898 This facility should be used with extreme caution.
28900 .vitem &*control&~=&~freeze*&
28901 .cindex "frozen messages" "forcing in ACL"
28902 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28903 other words, only when a message is being received. If the message is accepted,
28904 it is placed on Exim's queue and frozen. The control applies only to the
28905 current message, not to any subsequent ones that may be received in the same
28908 This modifier can optionally be followed by &`/no_tell`&. If the global option
28909 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
28910 is told about the freezing), provided all the &*control=freeze*& modifiers that
28911 are obeyed for the current message have the &`/no_tell`& option.
28913 .vitem &*control&~=&~no_delay_flush*&
28914 .cindex "SMTP" "output flushing, disabling for delay"
28915 Exim normally flushes SMTP output before implementing a delay in an ACL, to
28916 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28917 use. This control, as long as it is encountered before the &%delay%& modifier,
28918 disables such output flushing.
28920 .vitem &*control&~=&~no_callout_flush*&
28921 .cindex "SMTP" "output flushing, disabling for callout"
28922 Exim normally flushes SMTP output before performing a callout in an ACL, to
28923 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28924 use. This control, as long as it is encountered before the &%verify%& condition
28925 that causes the callout, disables such output flushing.
28927 .vitem &*control&~=&~no_mbox_unspool*&
28928 This control is available when Exim is compiled with the content scanning
28929 extension. Content scanning may require a copy of the current message, or parts
28930 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
28931 or spam scanner. Normally, such copies are deleted when they are no longer
28932 needed. If this control is set, the copies are not deleted. The control applies
28933 only to the current message, not to any subsequent ones that may be received in
28934 the same SMTP connection. It is provided for debugging purposes and is unlikely
28935 to be useful in production.
28937 .vitem &*control&~=&~no_multiline_responses*&
28938 .cindex "multiline responses, suppressing"
28939 This control is permitted for any ACL except the one for non-SMTP messages.
28940 It seems that there are broken clients in use that cannot handle multiline
28941 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
28943 If this control is set, multiline SMTP responses from ACL rejections are
28944 suppressed. One way of doing this would have been to put out these responses as
28945 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
28946 (&"use multiline responses for more"& it says &-- ha!), and some of the
28947 responses might get close to that. So this facility, which is after all only a
28948 sop to broken clients, is implemented by doing two very easy things:
28951 Extra information that is normally output as part of a rejection caused by
28952 sender verification failure is omitted. Only the final line (typically &"sender
28953 verification failed"&) is sent.
28955 If a &%message%& modifier supplies a multiline response, only the first
28959 The setting of the switch can, of course, be made conditional on the
28960 calling host. Its effect lasts until the end of the SMTP connection.
28962 .vitem &*control&~=&~no_pipelining*&
28963 .cindex "PIPELINING" "suppressing advertising"
28964 This control turns off the advertising of the PIPELINING extension to SMTP in
28965 the current session. To be useful, it must be obeyed before Exim sends its
28966 response to an EHLO command. Therefore, it should normally appear in an ACL
28967 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
28968 &%pipelining_advertise_hosts%&.
28970 .vitem &*control&~=&~queue_only*&
28971 .oindex "&%queue_only%&"
28972 .cindex "queueing incoming messages"
28973 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28974 other words, only when a message is being received. If the message is accepted,
28975 it is placed on Exim's queue and left there for delivery by a subsequent queue
28976 runner. No immediate delivery process is started. In other words, it has the
28977 effect as the &%queue_only%& global option. However, the control applies only
28978 to the current message, not to any subsequent ones that may be received in the
28979 same SMTP connection.
28981 .vitem &*control&~=&~submission/*&<&'options'&>
28982 .cindex "message" "submission"
28983 .cindex "submission mode"
28984 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
28985 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
28986 the current message is a submission from a local MUA. In this case, Exim
28987 operates in &"submission mode"&, and applies certain fixups to the message if
28988 necessary. For example, it adds a &'Date:'& header line if one is not present.
28989 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
28990 late (the message has already been created).
28992 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
28993 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
28994 submission mode; the available options for this control are described there.
28995 The control applies only to the current message, not to any subsequent ones
28996 that may be received in the same SMTP connection.
28998 .vitem &*control&~=&~suppress_local_fixups*&
28999 .cindex "submission fixups, suppressing"
29000 This control applies to locally submitted (non TCP/IP) messages, and is the
29001 complement of &`control = submission`&. It disables the fixups that are
29002 normally applied to locally-submitted messages. Specifically:
29005 Any &'Sender:'& header line is left alone (in this respect, it is a
29006 dynamic version of &%local_sender_retain%&).
29008 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
29010 There is no check that &'From:'& corresponds to the actual sender.
29013 This control may be useful when a remotely-originated message is accepted,
29014 passed to some scanning program, and then re-submitted for delivery. It can be
29015 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29016 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
29019 &*Note:*& This control applies only to the current message, not to any others
29020 that are being submitted at the same time using &%-bs%& or &%-bS%&.
29022 .vitem &*control&~=&~utf8_downconvert*&
29023 This control enables conversion of UTF-8 in message addresses
29025 For details see &<<SECTi18nMTA>>&.
29029 .section "Summary of message fixup control" "SECTsummesfix"
29030 All four possibilities for message fixups can be specified:
29033 Locally submitted, fixups applied: the default.
29035 Locally submitted, no fixups applied: use
29036 &`control = suppress_local_fixups`&.
29038 Remotely submitted, no fixups applied: the default.
29040 Remotely submitted, fixups applied: use &`control = submission`&.
29045 .section "Adding header lines in ACLs" "SECTaddheadacl"
29046 .cindex "header lines" "adding in an ACL"
29047 .cindex "header lines" "position of added lines"
29048 .cindex "&%add_header%& ACL modifier"
29049 The &%add_header%& modifier can be used to add one or more extra header lines
29050 to an incoming message, as in this example:
29052 warn dnslists = sbl.spamhaus.org : \
29053 dialup.mail-abuse.org
29054 add_header = X-blacklisted-at: $dnslist_domain
29056 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29057 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29058 receiving a message). The message must ultimately be accepted for
29059 &%add_header%& to have any significant effect. You can use &%add_header%& with
29060 any ACL verb, including &%deny%& (though this is potentially useful only in a
29063 Headers will not be added to the message if the modifier is used in
29064 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29066 Leading and trailing newlines are removed from
29067 the data for the &%add_header%& modifier; if it then
29068 contains one or more newlines that
29069 are not followed by a space or a tab, it is assumed to contain multiple header
29070 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
29071 front of any line that is not a valid header line.
29073 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29074 They are added to the message before processing the DATA and MIME ACLs.
29075 However, if an identical header line is requested more than once, only one copy
29076 is actually added to the message. Further header lines may be accumulated
29077 during the DATA and MIME ACLs, after which they are added to the message, again
29078 with duplicates suppressed. Thus, it is possible to add two identical header
29079 lines to an SMTP message, but only if one is added before DATA and one after.
29080 In the case of non-SMTP messages, new headers are accumulated during the
29081 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
29082 message is rejected after DATA or by the non-SMTP ACL, all added header lines
29083 are included in the entry that is written to the reject log.
29085 .cindex "header lines" "added; visibility of"
29086 Header lines are not visible in string expansions
29088 until they are added to the
29089 message. It follows that header lines defined in the MAIL, RCPT, and predata
29090 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
29091 header lines that are added by the DATA or MIME ACLs are not visible in those
29092 ACLs. Because of this restriction, you cannot use header lines as a way of
29093 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
29094 this, you can use ACL variables, as described in section
29095 &<<SECTaclvariables>>&.
29097 The list of headers yet to be added is given by the &%$headers_added%& variable.
29099 The &%add_header%& modifier acts immediately as it is encountered during the
29100 processing of an ACL. Notice the difference between these two cases:
29102 &`accept add_header = ADDED: some text`&
29103 &` `&<&'some condition'&>
29105 &`accept `&<&'some condition'&>
29106 &` add_header = ADDED: some text`&
29108 In the first case, the header line is always added, whether or not the
29109 condition is true. In the second case, the header line is added only if the
29110 condition is true. Multiple occurrences of &%add_header%& may occur in the same
29111 ACL statement. All those that are encountered before a condition fails are
29114 .cindex "&%warn%& ACL verb"
29115 For compatibility with previous versions of Exim, a &%message%& modifier for a
29116 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
29117 effect only if all the conditions are true, even if it appears before some of
29118 them. Furthermore, only the last occurrence of &%message%& is honoured. This
29119 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
29120 are present on a &%warn%& verb, both are processed according to their
29123 By default, new header lines are added to a message at the end of the existing
29124 header lines. However, you can specify that any particular header line should
29125 be added right at the start (before all the &'Received:'& lines), immediately
29126 after the first block of &'Received:'& lines, or immediately before any line
29127 that is not a &'Received:'& or &'Resent-something:'& header.
29129 This is done by specifying &":at_start:"&, &":after_received:"&, or
29130 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
29131 header line, respectively. (Header text cannot start with a colon, as there has
29132 to be a header name first.) For example:
29134 warn add_header = \
29135 :after_received:X-My-Header: something or other...
29137 If more than one header line is supplied in a single &%add_header%& modifier,
29138 each one is treated independently and can therefore be placed differently. If
29139 you add more than one line at the start, or after the Received: block, they end
29140 up in reverse order.
29142 &*Warning*&: This facility currently applies only to header lines that are
29143 added in an ACL. It does NOT work for header lines that are added in a
29144 system filter or in a router or transport.
29148 .section "Removing header lines in ACLs" "SECTremoveheadacl"
29149 .cindex "header lines" "removing in an ACL"
29150 .cindex "header lines" "position of removed lines"
29151 .cindex "&%remove_header%& ACL modifier"
29152 The &%remove_header%& modifier can be used to remove one or more header lines
29153 from an incoming message, as in this example:
29155 warn message = Remove internal headers
29156 remove_header = x-route-mail1 : x-route-mail2
29158 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29159 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29160 receiving a message). The message must ultimately be accepted for
29161 &%remove_header%& to have any significant effect. You can use &%remove_header%&
29162 with any ACL verb, including &%deny%&, though this is really not useful for
29163 any verb that doesn't result in a delivered message.
29165 Headers will not be removed from the message if the modifier is used in
29166 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29168 More than one header can be removed at the same time by using a colon separated
29169 list of header names. The header matching is case insensitive. Wildcards are
29170 not permitted, nor is list expansion performed, so you cannot use hostlists to
29171 create a list of headers, however both connection and message variable expansion
29172 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
29174 warn hosts = +internal_hosts
29175 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
29176 warn message = Remove internal headers
29177 remove_header = $acl_c_ihdrs
29179 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29180 They are removed from the message before processing the DATA and MIME ACLs.
29181 There is no harm in attempting to remove the same header twice nor is removing
29182 a non-existent header. Further header lines to be removed may be accumulated
29183 during the DATA and MIME ACLs, after which they are removed from the message,
29184 if present. In the case of non-SMTP messages, headers to be removed are
29185 accumulated during the non-SMTP ACLs, and are removed from the message after
29186 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
29187 ACL, there really is no effect because there is no logging of what headers
29188 would have been removed.
29190 .cindex "header lines" "removed; visibility of"
29191 Header lines are not visible in string expansions until the DATA phase when it
29192 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
29193 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
29194 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
29195 this restriction, you cannot use header lines as a way of controlling data
29196 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
29197 you should instead use ACL variables, as described in section
29198 &<<SECTaclvariables>>&.
29200 The &%remove_header%& modifier acts immediately as it is encountered during the
29201 processing of an ACL. Notice the difference between these two cases:
29203 &`accept remove_header = X-Internal`&
29204 &` `&<&'some condition'&>
29206 &`accept `&<&'some condition'&>
29207 &` remove_header = X-Internal`&
29209 In the first case, the header line is always removed, whether or not the
29210 condition is true. In the second case, the header line is removed only if the
29211 condition is true. Multiple occurrences of &%remove_header%& may occur in the
29212 same ACL statement. All those that are encountered before a condition fails
29215 &*Warning*&: This facility currently applies only to header lines that are
29216 present during ACL processing. It does NOT remove header lines that are added
29217 in a system filter or in a router or transport.
29222 .section "ACL conditions" "SECTaclconditions"
29223 .cindex "&ACL;" "conditions; list of"
29224 Some of the conditions listed in this section are available only when Exim is
29225 compiled with the content-scanning extension. They are included here briefly
29226 for completeness. More detailed descriptions can be found in the discussion on
29227 content scanning in chapter &<<CHAPexiscan>>&.
29229 Not all conditions are relevant in all circumstances. For example, testing
29230 senders and recipients does not make sense in an ACL that is being run as the
29231 result of the arrival of an ETRN command, and checks on message headers can be
29232 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
29233 can use the same condition (with different parameters) more than once in the
29234 same ACL statement. This provides a way of specifying an &"and"& conjunction.
29235 The conditions are as follows:
29239 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
29240 .cindex "&ACL;" "nested"
29241 .cindex "&ACL;" "indirect"
29242 .cindex "&ACL;" "arguments"
29243 .cindex "&%acl%& ACL condition"
29244 The possible values of the argument are the same as for the
29245 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
29246 &"accept"& the condition is true; if it returns &"deny"& the condition is
29247 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
29248 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
29249 condition false. This means that further processing of the &%warn%& verb
29250 ceases, but processing of the ACL continues.
29252 If the argument is a named ACL, up to nine space-separated optional values
29253 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
29254 and $acl_narg is set to the count of values.
29255 Previous values of these variables are restored after the call returns.
29256 The name and values are expanded separately.
29257 Note that spaces in complex expansions which are used as arguments
29258 will act as argument separators.
29260 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
29261 the connection is dropped. If it returns &"discard"&, the verb must be
29262 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
29263 conditions are tested.
29265 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
29266 loops. This condition allows you to use different ACLs in different
29267 circumstances. For example, different ACLs can be used to handle RCPT commands
29268 for different local users or different local domains.
29270 .vitem &*authenticated&~=&~*&<&'string&~list'&>
29271 .cindex "&%authenticated%& ACL condition"
29272 .cindex "authentication" "ACL checking"
29273 .cindex "&ACL;" "testing for authentication"
29274 If the SMTP connection is not authenticated, the condition is false. Otherwise,
29275 the name of the authenticator is tested against the list. To test for
29276 authentication by any authenticator, you can set
29281 .vitem &*condition&~=&~*&<&'string'&>
29282 .cindex "&%condition%& ACL condition"
29283 .cindex "customizing" "ACL condition"
29284 .cindex "&ACL;" "customized test"
29285 .cindex "&ACL;" "testing, customized"
29286 This feature allows you to make up custom conditions. If the result of
29287 expanding the string is an empty string, the number zero, or one of the strings
29288 &"no"& or &"false"&, the condition is false. If the result is any non-zero
29289 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
29290 any other value, some error is assumed to have occurred, and the ACL returns
29291 &"defer"&. However, if the expansion is forced to fail, the condition is
29292 ignored. The effect is to treat it as true, whether it is positive or
29295 .vitem &*decode&~=&~*&<&'location'&>
29296 .cindex "&%decode%& ACL condition"
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 decoded into a file.
29300 If all goes well, the condition is true. It is false only if there are
29301 problems such as a syntax error or a memory shortage. For more details, see
29302 chapter &<<CHAPexiscan>>&.
29304 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
29305 .cindex "&%dnslists%& ACL condition"
29306 .cindex "DNS list" "in ACL"
29307 .cindex "black list (DNS)"
29308 .cindex "&ACL;" "testing a DNS list"
29309 This condition checks for entries in DNS black lists. These are also known as
29310 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
29311 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
29312 different variants of this condition to describe briefly here. See sections
29313 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
29315 .vitem &*domains&~=&~*&<&'domain&~list'&>
29316 .cindex "&%domains%& ACL condition"
29317 .cindex "domain" "ACL checking"
29318 .cindex "&ACL;" "testing a recipient domain"
29319 .vindex "&$domain_data$&"
29320 This condition is relevant only after a RCPT command. It checks that the domain
29321 of the recipient address is in the domain list. If percent-hack processing is
29322 enabled, it is done before this test is done. If the check succeeds with a
29323 lookup, the result of the lookup is placed in &$domain_data$& until the next
29326 &*Note carefully*& (because many people seem to fall foul of this): you cannot
29327 use &%domains%& in a DATA ACL.
29330 .vitem &*encrypted&~=&~*&<&'string&~list'&>
29331 .cindex "&%encrypted%& ACL condition"
29332 .cindex "encryption" "checking in an ACL"
29333 .cindex "&ACL;" "testing for encryption"
29334 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
29335 name of the cipher suite in use is tested against the list. To test for
29336 encryption without testing for any specific cipher suite(s), set
29342 .vitem &*hosts&~=&~*&<&'host&~list'&>
29343 .cindex "&%hosts%& ACL condition"
29344 .cindex "host" "ACL checking"
29345 .cindex "&ACL;" "testing the client host"
29346 This condition tests that the calling host matches the host list. If you have
29347 name lookups or wildcarded host names and IP addresses in the same host list,
29348 you should normally put the IP addresses first. For example, you could have:
29350 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
29352 The lookup in this example uses the host name for its key. This is implied by
29353 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
29354 and it wouldn't matter which way round you had these two items.)
29356 The reason for the problem with host names lies in the left-to-right way that
29357 Exim processes lists. It can test IP addresses without doing any DNS lookups,
29358 but when it reaches an item that requires a host name, it fails if it cannot
29359 find a host name to compare with the pattern. If the above list is given in the
29360 opposite order, the &%accept%& statement fails for a host whose name cannot be
29361 found, even if its IP address is 10.9.8.7.
29363 If you really do want to do the name check first, and still recognize the IP
29364 address even if the name lookup fails, you can rewrite the ACL like this:
29366 accept hosts = dbm;/etc/friendly/hosts
29367 accept hosts = 10.9.8.7
29369 The default action on failing to find the host name is to assume that the host
29370 is not in the list, so the first &%accept%& statement fails. The second
29371 statement can then check the IP address.
29373 .vindex "&$host_data$&"
29374 If a &%hosts%& condition is satisfied by means of a lookup, the result
29375 of the lookup is made available in the &$host_data$& variable. This
29376 allows you, for example, to set up a statement like this:
29378 deny hosts = net-lsearch;/some/file
29379 message = $host_data
29381 which gives a custom error message for each denied host.
29383 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
29384 .cindex "&%local_parts%& ACL condition"
29385 .cindex "local part" "ACL checking"
29386 .cindex "&ACL;" "testing a local part"
29387 .vindex "&$local_part_data$&"
29388 This condition is relevant only after a RCPT command. It checks that the local
29389 part of the recipient address is in the list. If percent-hack processing is
29390 enabled, it is done before this test. If the check succeeds with a lookup, the
29391 result of the lookup is placed in &$local_part_data$&, which remains set until
29392 the next &%local_parts%& test.
29394 .vitem &*malware&~=&~*&<&'option'&>
29395 .cindex "&%malware%& ACL condition"
29396 .cindex "&ACL;" "virus scanning"
29397 .cindex "&ACL;" "scanning for viruses"
29398 This condition is available only when Exim is compiled with the
29399 content-scanning extension. It causes the incoming message to be scanned for
29400 viruses. For details, see chapter &<<CHAPexiscan>>&.
29402 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29403 .cindex "&%mime_regex%& ACL condition"
29404 .cindex "&ACL;" "testing by regex matching"
29405 This condition is available only when Exim is compiled with the
29406 content-scanning extension, and it is allowed only in the ACL defined by
29407 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
29408 with any of the regular expressions. For details, see chapter
29411 .vitem &*ratelimit&~=&~*&<&'parameters'&>
29412 .cindex "rate limiting"
29413 This condition can be used to limit the rate at which a user or host submits
29414 messages. Details are given in section &<<SECTratelimiting>>&.
29416 .vitem &*recipients&~=&~*&<&'address&~list'&>
29417 .cindex "&%recipients%& ACL condition"
29418 .cindex "recipient" "ACL checking"
29419 .cindex "&ACL;" "testing a recipient"
29420 This condition is relevant only after a RCPT command. It checks the entire
29421 recipient address against a list of recipients.
29423 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29424 .cindex "&%regex%& ACL condition"
29425 .cindex "&ACL;" "testing by regex matching"
29426 This condition is available only when Exim is compiled with the
29427 content-scanning extension, and is available only in the DATA, MIME, and
29428 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
29429 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
29431 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
29432 .cindex "&%sender_domains%& ACL condition"
29433 .cindex "sender" "ACL checking"
29434 .cindex "&ACL;" "testing a sender domain"
29435 .vindex "&$domain$&"
29436 .vindex "&$sender_address_domain$&"
29437 This condition tests the domain of the sender of the message against the given
29438 domain list. &*Note*&: The domain of the sender address is in
29439 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
29440 of this condition. This is an exception to the general rule for testing domain
29441 lists. It is done this way so that, if this condition is used in an ACL for a
29442 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
29443 influence the sender checking.
29445 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29446 relaying, because sender addresses are easily, and commonly, forged.
29448 .vitem &*senders&~=&~*&<&'address&~list'&>
29449 .cindex "&%senders%& ACL condition"
29450 .cindex "sender" "ACL checking"
29451 .cindex "&ACL;" "testing a sender"
29452 This condition tests the sender of the message against the given list. To test
29453 for a bounce message, which has an empty sender, set
29457 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29458 relaying, because sender addresses are easily, and commonly, forged.
29460 .vitem &*spam&~=&~*&<&'username'&>
29461 .cindex "&%spam%& ACL condition"
29462 .cindex "&ACL;" "scanning for spam"
29463 This condition is available only when Exim is compiled with the
29464 content-scanning extension. It causes the incoming message to be scanned by
29465 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
29467 .vitem &*verify&~=&~certificate*&
29468 .cindex "&%verify%& ACL condition"
29469 .cindex "TLS" "client certificate verification"
29470 .cindex "certificate" "verification of client"
29471 .cindex "&ACL;" "certificate verification"
29472 .cindex "&ACL;" "testing a TLS certificate"
29473 This condition is true in an SMTP session if the session is encrypted, and a
29474 certificate was received from the client, and the certificate was verified. The
29475 server requests a certificate only if the client matches &%tls_verify_hosts%&
29476 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
29478 .vitem &*verify&~=&~csa*&
29479 .cindex "CSA verification"
29480 This condition checks whether the sending host (the client) is authorized to
29481 send email. Details of how this works are given in section
29482 &<<SECTverifyCSA>>&.
29484 .vitem &*verify&~=&~header_names_ascii*&
29485 .cindex "&%verify%& ACL condition"
29486 .cindex "&ACL;" "verifying header names only ASCII"
29487 .cindex "header lines" "verifying header names only ASCII"
29488 .cindex "verifying" "header names only ASCII"
29489 This condition is relevant only in an ACL that is run after a message has been
29490 received, that is, in an ACL specified by &%acl_smtp_data%& or
29491 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
29492 there are no non-ASCII characters, also excluding control characters. The
29493 allowable characters are decimal ASCII values 33 through 126.
29495 Exim itself will handle headers with non-ASCII characters, but it can cause
29496 problems for downstream applications, so this option will allow their
29497 detection and rejection in the DATA ACL's.
29499 .vitem &*verify&~=&~header_sender/*&<&'options'&>
29500 .cindex "&%verify%& ACL condition"
29501 .cindex "&ACL;" "verifying sender in the header"
29502 .cindex "header lines" "verifying the sender in"
29503 .cindex "sender" "verifying in header"
29504 .cindex "verifying" "sender in header"
29505 This condition is relevant only in an ACL that is run after a message has been
29506 received, that is, in an ACL specified by &%acl_smtp_data%& or
29507 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
29508 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
29509 is loosely thought of as a &"sender"& address (hence the name of the test).
29510 However, an address that appears in one of these headers need not be an address
29511 that accepts bounce messages; only sender addresses in envelopes are required
29512 to accept bounces. Therefore, if you use the callout option on this check, you
29513 might want to arrange for a non-empty address in the MAIL command.
29515 Details of address verification and the options are given later, starting at
29516 section &<<SECTaddressverification>>& (callouts are described in section
29517 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
29518 condition to restrict it to bounce messages only:
29521 message = A valid sender header is required for bounces
29522 !verify = header_sender
29525 .vitem &*verify&~=&~header_syntax*&
29526 .cindex "&%verify%& ACL condition"
29527 .cindex "&ACL;" "verifying header syntax"
29528 .cindex "header lines" "verifying syntax"
29529 .cindex "verifying" "header syntax"
29530 This condition is relevant only in an ACL that is run after a message has been
29531 received, that is, in an ACL specified by &%acl_smtp_data%& or
29532 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
29533 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
29534 and &'Bcc:'&), returning true if there are no problems.
29535 Unqualified addresses (local parts without domains) are
29536 permitted only in locally generated messages and from hosts that match
29537 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
29540 Note that this condition is a syntax check only. However, a common spamming
29541 ploy used to be to send syntactically invalid headers such as
29545 and this condition can be used to reject such messages, though they are not as
29546 common as they used to be.
29548 .vitem &*verify&~=&~helo*&
29549 .cindex "&%verify%& ACL condition"
29550 .cindex "&ACL;" "verifying HELO/EHLO"
29551 .cindex "HELO" "verifying"
29552 .cindex "EHLO" "verifying"
29553 .cindex "verifying" "EHLO"
29554 .cindex "verifying" "HELO"
29555 This condition is true if a HELO or EHLO command has been received from the
29556 client host, and its contents have been verified. If there has been no previous
29557 attempt to verify the HELO/EHLO contents, it is carried out when this
29558 condition is encountered. See the description of the &%helo_verify_hosts%& and
29559 &%helo_try_verify_hosts%& options for details of how to request verification
29560 independently of this condition.
29562 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
29563 option), this condition is always true.
29566 .vitem &*verify&~=&~not_blind*&
29567 .cindex "verifying" "not blind"
29568 .cindex "bcc recipients, verifying none"
29569 This condition checks that there are no blind (bcc) recipients in the message.
29570 Every envelope recipient must appear either in a &'To:'& header line or in a
29571 &'Cc:'& header line for this condition to be true. Local parts are checked
29572 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
29573 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
29574 used only in a DATA or non-SMTP ACL.
29576 There are, of course, many legitimate messages that make use of blind (bcc)
29577 recipients. This check should not be used on its own for blocking messages.
29580 .vitem &*verify&~=&~recipient/*&<&'options'&>
29581 .cindex "&%verify%& ACL condition"
29582 .cindex "&ACL;" "verifying recipient"
29583 .cindex "recipient" "verifying"
29584 .cindex "verifying" "recipient"
29585 .vindex "&$address_data$&"
29586 This condition is relevant only after a RCPT command. It verifies the current
29587 recipient. Details of address verification are given later, starting at section
29588 &<<SECTaddressverification>>&. After a recipient has been verified, the value
29589 of &$address_data$& is the last value that was set while routing the address.
29590 This applies even if the verification fails. When an address that is being
29591 verified is redirected to a single address, verification continues with the new
29592 address, and in that case, the subsequent value of &$address_data$& is the
29593 value for the child address.
29595 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
29596 .cindex "&%verify%& ACL condition"
29597 .cindex "&ACL;" "verifying host reverse lookup"
29598 .cindex "host" "verifying reverse lookup"
29599 This condition ensures that a verified host name has been looked up from the IP
29600 address of the client host. (This may have happened already if the host name
29601 was needed for checking a host list, or if the host matched &%host_lookup%&.)
29602 Verification ensures that the host name obtained from a reverse DNS lookup, or
29603 one of its aliases, does, when it is itself looked up in the DNS, yield the
29604 original IP address.
29606 There is one possible option, &`defer_ok`&. If this is present and a
29607 DNS operation returns a temporary error, the verify condition succeeds.
29609 If this condition is used for a locally generated message (that is, when there
29610 is no client host involved), it always succeeds.
29612 .vitem &*verify&~=&~sender/*&<&'options'&>
29613 .cindex "&%verify%& ACL condition"
29614 .cindex "&ACL;" "verifying sender"
29615 .cindex "sender" "verifying"
29616 .cindex "verifying" "sender"
29617 This condition is relevant only after a MAIL or RCPT command, or after a
29618 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
29619 the message's sender is empty (that is, this is a bounce message), the
29620 condition is true. Otherwise, the sender address is verified.
29622 .vindex "&$address_data$&"
29623 .vindex "&$sender_address_data$&"
29624 If there is data in the &$address_data$& variable at the end of routing, its
29625 value is placed in &$sender_address_data$& at the end of verification. This
29626 value can be used in subsequent conditions and modifiers in the same ACL
29627 statement. It does not persist after the end of the current statement. If you
29628 want to preserve the value for longer, you can save it in an ACL variable.
29630 Details of verification are given later, starting at section
29631 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
29632 to avoid doing it more than once per message.
29634 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
29635 .cindex "&%verify%& ACL condition"
29636 This is a variation of the previous option, in which a modified address is
29637 verified as a sender.
29642 .section "Using DNS lists" "SECTmorednslists"
29643 .cindex "DNS list" "in ACL"
29644 .cindex "black list (DNS)"
29645 .cindex "&ACL;" "testing a DNS list"
29646 In its simplest form, the &%dnslists%& condition tests whether the calling host
29647 is on at least one of a number of DNS lists by looking up the inverted IP
29648 address in one or more DNS domains. (Note that DNS list domains are not mail
29649 domains, so the &`+`& syntax for named lists doesn't work - it is used for
29650 special options instead.) For example, if the calling host's IP
29651 address is 192.168.62.43, and the ACL statement is
29653 deny dnslists = blackholes.mail-abuse.org : \
29654 dialups.mail-abuse.org
29656 the following records are looked up:
29658 43.62.168.192.blackholes.mail-abuse.org
29659 43.62.168.192.dialups.mail-abuse.org
29661 As soon as Exim finds an existing DNS record, processing of the list stops.
29662 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
29663 to test that a host is on more than one list (an &"and"& conjunction), you can
29664 use two separate conditions:
29666 deny dnslists = blackholes.mail-abuse.org
29667 dnslists = dialups.mail-abuse.org
29669 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
29670 behaves as if the host does not match the list item, that is, as if the DNS
29671 record does not exist. If there are further items in the DNS list, they are
29674 This is usually the required action when &%dnslists%& is used with &%deny%&
29675 (which is the most common usage), because it prevents a DNS failure from
29676 blocking mail. However, you can change this behaviour by putting one of the
29677 following special items in the list:
29679 &`+include_unknown `& behave as if the item is on the list
29680 &`+exclude_unknown `& behave as if the item is not on the list (default)
29681 &`+defer_unknown `& give a temporary error
29683 .cindex "&`+include_unknown`&"
29684 .cindex "&`+exclude_unknown`&"
29685 .cindex "&`+defer_unknown`&"
29686 Each of these applies to any subsequent items on the list. For example:
29688 deny dnslists = +defer_unknown : foo.bar.example
29690 Testing the list of domains stops as soon as a match is found. If you want to
29691 warn for one list and block for another, you can use two different statements:
29693 deny dnslists = blackholes.mail-abuse.org
29694 warn message = X-Warn: sending host is on dialups list
29695 dnslists = dialups.mail-abuse.org
29697 .cindex cacheing "of dns lookup"
29699 DNS list lookups are cached by Exim for the duration of the SMTP session
29700 (but limited by the DNS return TTL value),
29701 so a lookup based on the IP address is done at most once for any incoming
29702 connection (assuming long-enough TTL).
29703 Exim does not share information between multiple incoming
29704 connections (but your local name server cache should be active).
29708 .section "Specifying the IP address for a DNS list lookup" "SECID201"
29709 .cindex "DNS list" "keyed by explicit IP address"
29710 By default, the IP address that is used in a DNS list lookup is the IP address
29711 of the calling host. However, you can specify another IP address by listing it
29712 after the domain name, introduced by a slash. For example:
29714 deny dnslists = black.list.tld/192.168.1.2
29716 This feature is not very helpful with explicit IP addresses; it is intended for
29717 use with IP addresses that are looked up, for example, the IP addresses of the
29718 MX hosts or nameservers of an email sender address. For an example, see section
29719 &<<SECTmulkeyfor>>& below.
29724 .section "DNS lists keyed on domain names" "SECID202"
29725 .cindex "DNS list" "keyed by domain name"
29726 There are some lists that are keyed on domain names rather than inverted IP
29727 addresses (see for example the &'domain based zones'& link at
29728 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
29729 with these lists. You can change the name that is looked up in a DNS list by
29730 listing it after the domain name, introduced by a slash. For example,
29732 deny message = Sender's domain is listed at $dnslist_domain
29733 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
29735 This particular example is useful only in ACLs that are obeyed after the
29736 RCPT or DATA commands, when a sender address is available. If (for
29737 example) the message's sender is &'user@tld.example'& the name that is looked
29738 up by this example is
29740 tld.example.dsn.rfc-ignorant.org
29742 A single &%dnslists%& condition can contain entries for both names and IP
29743 addresses. For example:
29745 deny dnslists = sbl.spamhaus.org : \
29746 dsn.rfc-ignorant.org/$sender_address_domain
29748 The first item checks the sending host's IP address; the second checks a domain
29749 name. The whole condition is true if either of the DNS lookups succeeds.
29754 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
29755 .cindex "DNS list" "multiple keys for"
29756 The syntax described above for looking up explicitly-defined values (either
29757 names or IP addresses) in a DNS blacklist is a simplification. After the domain
29758 name for the DNS list, what follows the slash can in fact be a list of items.
29759 As with all lists in Exim, the default separator is a colon. However, because
29760 this is a sublist within the list of DNS blacklist domains, it is necessary
29761 either to double the separators like this:
29763 dnslists = black.list.tld/name.1::name.2
29765 or to change the separator character, like this:
29767 dnslists = black.list.tld/<;name.1;name.2
29769 If an item in the list is an IP address, it is inverted before the DNS
29770 blacklist domain is appended. If it is not an IP address, no inversion
29771 occurs. Consider this condition:
29773 dnslists = black.list.tld/<;192.168.1.2;a.domain
29775 The DNS lookups that occur are:
29777 2.1.168.192.black.list.tld
29778 a.domain.black.list.tld
29780 Once a DNS record has been found (that matches a specific IP return
29781 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
29782 are done. If there is a temporary DNS error, the rest of the sublist of domains
29783 or IP addresses is tried. A temporary error for the whole dnslists item occurs
29784 only if no other DNS lookup in this sublist succeeds. In other words, a
29785 successful lookup for any of the items in the sublist overrides a temporary
29786 error for a previous item.
29788 The ability to supply a list of items after the slash is in some sense just a
29789 syntactic convenience. These two examples have the same effect:
29791 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
29792 dnslists = black.list.tld/a.domain::b.domain
29794 However, when the data for the list is obtained from a lookup, the second form
29795 is usually much more convenient. Consider this example:
29797 deny message = The mail servers for the domain \
29798 $sender_address_domain \
29799 are listed at $dnslist_domain ($dnslist_value); \
29801 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
29802 ${lookup dnsdb {>|mxh=\
29803 $sender_address_domain} }} }
29805 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
29806 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
29807 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
29808 of expanding the condition might be something like this:
29810 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
29812 Thus, this example checks whether or not the IP addresses of the sender
29813 domain's mail servers are on the Spamhaus black list.
29815 The key that was used for a successful DNS list lookup is put into the variable
29816 &$dnslist_matched$& (see section &<<SECID204>>&).
29821 .section "Data returned by DNS lists" "SECID203"
29822 .cindex "DNS list" "data returned from"
29823 DNS lists are constructed using address records in the DNS. The original RBL
29824 just used the address 127.0.0.1 on the right hand side of each record, but the
29825 RBL+ list and some other lists use a number of values with different meanings.
29826 The values used on the RBL+ list are:
29830 127.1.0.3 DUL and RBL
29832 127.1.0.5 RSS and RBL
29833 127.1.0.6 RSS and DUL
29834 127.1.0.7 RSS and DUL and RBL
29836 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
29837 different values. Some DNS lists may return more than one address record;
29838 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
29841 .section "Variables set from DNS lists" "SECID204"
29842 .cindex "expansion" "variables, set from DNS list"
29843 .cindex "DNS list" "variables set from"
29844 .vindex "&$dnslist_domain$&"
29845 .vindex "&$dnslist_matched$&"
29846 .vindex "&$dnslist_text$&"
29847 .vindex "&$dnslist_value$&"
29848 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
29849 the name of the overall domain that matched (for example,
29850 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
29851 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
29852 the DNS record. When the key is an IP address, it is not reversed in
29853 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
29854 cases, for example:
29856 deny dnslists = spamhaus.example
29858 the key is also available in another variable (in this case,
29859 &$sender_host_address$&). In more complicated cases, however, this is not true.
29860 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
29861 might generate a dnslists lookup like this:
29863 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
29865 If this condition succeeds, the value in &$dnslist_matched$& might be
29866 &`192.168.6.7`& (for example).
29868 If more than one address record is returned by the DNS lookup, all the IP
29869 addresses are included in &$dnslist_value$&, separated by commas and spaces.
29870 The variable &$dnslist_text$& contains the contents of any associated TXT
29871 record. For lists such as RBL+ the TXT record for a merged entry is often not
29872 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
29875 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
29876 &-- although these appear before the condition in the ACL, they are not
29877 expanded until after it has failed. For example:
29879 deny hosts = !+local_networks
29880 message = $sender_host_address is listed \
29882 dnslists = rbl-plus.mail-abuse.example
29887 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
29888 .cindex "DNS list" "matching specific returned data"
29889 You can add an equals sign and an IP address after a &%dnslists%& domain name
29890 in order to restrict its action to DNS records with a matching right hand side.
29893 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
29895 rejects only those hosts that yield 127.0.0.2. Without this additional data,
29896 any address record is considered to be a match. For the moment, we assume
29897 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
29898 describes how multiple records are handled.
29900 More than one IP address may be given for checking, using a comma as a
29901 separator. These are alternatives &-- if any one of them matches, the
29902 &%dnslists%& condition is true. For example:
29904 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29906 If you want to specify a constraining address list and also specify names or IP
29907 addresses to be looked up, the constraining address list must be specified
29908 first. For example:
29910 deny dnslists = dsn.rfc-ignorant.org\
29911 =127.0.0.2/$sender_address_domain
29914 If the character &`&&`& is used instead of &`=`&, the comparison for each
29915 listed IP address is done by a bitwise &"and"& instead of by an equality test.
29916 In other words, the listed addresses are used as bit masks. The comparison is
29917 true if all the bits in the mask are present in the address that is being
29918 tested. For example:
29920 dnslists = a.b.c&0.0.0.3
29922 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
29923 want to test whether one bit or another bit is present (as opposed to both
29924 being present), you must use multiple values. For example:
29926 dnslists = a.b.c&0.0.0.1,0.0.0.2
29928 matches if the final component of the address is an odd number or two times
29933 .section "Negated DNS matching conditions" "SECID205"
29934 You can supply a negative list of IP addresses as part of a &%dnslists%&
29937 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29939 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29940 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
29942 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
29944 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29945 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
29946 words, the result of the test is inverted if an exclamation mark appears before
29947 the &`=`& (or the &`&&`&) sign.
29949 &*Note*&: This kind of negation is not the same as negation in a domain,
29950 host, or address list (which is why the syntax is different).
29952 If you are using just one list, the negation syntax does not gain you much. The
29953 previous example is precisely equivalent to
29955 deny dnslists = a.b.c
29956 !dnslists = a.b.c=127.0.0.2,127.0.0.3
29958 However, if you are using multiple lists, the negation syntax is clearer.
29959 Consider this example:
29961 deny dnslists = sbl.spamhaus.org : \
29963 dnsbl.njabl.org!=127.0.0.3 : \
29966 Using only positive lists, this would have to be:
29968 deny dnslists = sbl.spamhaus.org : \
29970 deny dnslists = dnsbl.njabl.org
29971 !dnslists = dnsbl.njabl.org=127.0.0.3
29972 deny dnslists = relays.ordb.org
29974 which is less clear, and harder to maintain.
29979 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
29980 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
29981 thereby providing more than one IP address. When an item in a &%dnslists%& list
29982 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
29983 the match to specific results from the DNS lookup, there are two ways in which
29984 the checking can be handled. For example, consider the condition:
29986 dnslists = a.b.c=127.0.0.1
29988 What happens if the DNS lookup for the incoming IP address yields both
29989 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
29990 condition true because at least one given value was found, or is it false
29991 because at least one of the found values was not listed? And how does this
29992 affect negated conditions? Both possibilities are provided for with the help of
29993 additional separators &`==`& and &`=&&`&.
29996 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
29997 IP addresses matches one of the listed addresses. For the example above, the
29998 condition is true because 127.0.0.1 matches.
30000 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
30001 looked up IP addresses matches one of the listed addresses. If the condition is
30004 dnslists = a.b.c==127.0.0.1
30006 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30007 false because 127.0.0.2 is not listed. You would need to have:
30009 dnslists = a.b.c==127.0.0.1,127.0.0.2
30011 for the condition to be true.
30014 When &`!`& is used to negate IP address matching, it inverts the result, giving
30015 the precise opposite of the behaviour above. Thus:
30017 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
30018 addresses matches one of the listed addresses. Consider:
30020 dnslists = a.b.c!&0.0.0.1
30022 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30023 false because 127.0.0.1 matches.
30025 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
30026 looked up IP address that does not match. Consider:
30028 dnslists = a.b.c!=&0.0.0.1
30030 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30031 true, because 127.0.0.2 does not match. You would need to have:
30033 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
30035 for the condition to be false.
30037 When the DNS lookup yields only a single IP address, there is no difference
30038 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
30043 .section "Detailed information from merged DNS lists" "SECTmordetinf"
30044 .cindex "DNS list" "information from merged"
30045 When the facility for restricting the matching IP values in a DNS list is used,
30046 the text from the TXT record that is set in &$dnslist_text$& may not reflect
30047 the true reason for rejection. This happens when lists are merged and the IP
30048 address in the A record is used to distinguish them; unfortunately there is
30049 only one TXT record. One way round this is not to use merged lists, but that
30050 can be inefficient because it requires multiple DNS lookups where one would do
30051 in the vast majority of cases when the host of interest is not on any of the
30054 A less inefficient way of solving this problem is available. If
30055 two domain names, comma-separated, are given, the second is used first to
30056 do an initial check, making use of any IP value restrictions that are set.
30057 If there is a match, the first domain is used, without any IP value
30058 restrictions, to get the TXT record. As a byproduct of this, there is also
30059 a check that the IP being tested is indeed on the first list. The first
30060 domain is the one that is put in &$dnslist_domain$&. For example:
30063 rejected because $sender_host_address is blacklisted \
30064 at $dnslist_domain\n$dnslist_text
30066 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
30067 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30069 For the first blacklist item, this starts by doing a lookup in
30070 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
30071 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
30072 value, and as long as something is found, it looks for the corresponding TXT
30073 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
30074 The second blacklist item is processed similarly.
30076 If you are interested in more than one merged list, the same list must be
30077 given several times, but because the results of the DNS lookups are cached,
30078 the DNS calls themselves are not repeated. For example:
30080 reject dnslists = \
30081 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
30082 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
30083 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
30084 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30086 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
30087 values matches (or if no record is found), this is the only lookup that is
30088 done. Only if there is a match is one of the more specific lists consulted.
30092 .section "DNS lists and IPv6" "SECTmorednslistslast"
30093 .cindex "IPv6" "DNS black lists"
30094 .cindex "DNS list" "IPv6 usage"
30095 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
30096 nibble by nibble. For example, if the calling host's IP address is
30097 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
30099 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
30100 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
30102 (split over two lines here to fit on the page). Unfortunately, some of the DNS
30103 lists contain wildcard records, intended for IPv4, that interact badly with
30104 IPv6. For example, the DNS entry
30106 *.3.some.list.example. A 127.0.0.1
30108 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
30109 Unfortunately, it also matches the entire 3::/4 IPv6 network.
30111 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
30112 &%condition%& condition, as in this example:
30114 deny condition = ${if isip4{$sender_host_address}}
30115 dnslists = some.list.example
30118 If an explicit key is being used for a DNS lookup and it may be an IPv6
30119 address you should specify alternate list separators for both the outer
30120 (DNS list name) list and inner (lookup keys) list:
30122 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
30125 .section "Rate limiting incoming messages" "SECTratelimiting"
30126 .cindex "rate limiting" "client sending"
30127 .cindex "limiting client sending rates"
30128 .oindex "&%smtp_ratelimit_*%&"
30129 The &%ratelimit%& ACL condition can be used to measure and control the rate at
30130 which clients can send email. This is more powerful than the
30131 &%smtp_ratelimit_*%& options, because those options control the rate of
30132 commands in a single SMTP session only, whereas the &%ratelimit%& condition
30133 works across all connections (concurrent and sequential) from the same client
30134 host. The syntax of the &%ratelimit%& condition is:
30136 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
30138 If the average client sending rate is less than &'m'& messages per time
30139 period &'p'& then the condition is false; otherwise it is true.
30141 As a side-effect, the &%ratelimit%& condition sets the expansion variable
30142 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
30143 configured value of &'m'&, and &$sender_rate_period$& to the configured value
30146 The parameter &'p'& is the smoothing time constant, in the form of an Exim
30147 time interval, for example, &`8h`& for eight hours. A larger time constant
30148 means that it takes Exim longer to forget a client's past behaviour. The
30149 parameter &'m'& is the maximum number of messages that a client is permitted to
30150 send in each time interval. It also specifies the number of messages permitted
30151 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
30152 constant, you can allow a client to send more messages in a burst without
30153 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
30154 both small, messages must be sent at an even rate.
30156 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
30157 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
30158 when deploying the &%ratelimit%& ACL condition. The script prints usage
30159 instructions when it is run with no arguments.
30161 The key is used to look up the data for calculating the client's average
30162 sending rate. This data is stored in Exim's spool directory, alongside the
30163 retry and other hints databases. The default key is &$sender_host_address$&,
30164 which means Exim computes the sending rate of each client host IP address.
30165 By changing the key you can change how Exim identifies clients for the purpose
30166 of ratelimiting. For example, to limit the sending rate of each authenticated
30167 user, independent of the computer they are sending from, set the key to
30168 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
30169 example, &$authenticated_id$& is only meaningful if the client has
30170 authenticated (which you can check with the &%authenticated%& ACL condition).
30172 The lookup key does not have to identify clients: If you want to limit the
30173 rate at which a recipient receives messages, you can use the key
30174 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
30177 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
30178 specifies what Exim measures the rate of, for example messages or recipients
30179 or bytes. You can adjust the measurement using the &%unique=%& and/or
30180 &%count=%& options. You can also control when Exim updates the recorded rate
30181 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
30182 separated by a slash, like the other parameters. They may appear in any order.
30184 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
30185 any options that alter the meaning of the stored data. The limit &'m'& is not
30186 stored, so you can alter the configured maximum rate and Exim will still
30187 remember clients' past behaviour. If you change the &%per_*%& mode or add or
30188 remove the &%unique=%& option, the lookup key changes so Exim will forget past
30189 behaviour. The lookup key is not affected by changes to the update mode and
30190 the &%count=%& option.
30193 .section "Ratelimit options for what is being measured" "ratoptmea"
30194 .cindex "rate limiting" "per_* options"
30195 The &%per_conn%& option limits the client's connection rate. It is not
30196 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
30197 &%acl_not_smtp_start%& ACLs.
30199 The &%per_mail%& option limits the client's rate of sending messages. This is
30200 the default if none of the &%per_*%& options is specified. It can be used in
30201 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
30202 &%acl_smtp_data%&, or &%acl_not_smtp%&.
30204 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
30205 the same ACLs as the &%per_mail%& option, though it is best to use this option
30206 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
30207 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
30208 in its MAIL command, which may be inaccurate or completely missing. You can
30209 follow the limit &'m'& in the configuration with K, M, or G to specify limits
30210 in kilobytes, megabytes, or gigabytes, respectively.
30212 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
30213 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
30214 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
30215 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
30216 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
30217 in either case the rate limiting engine will see a message with many
30218 recipients as a large high-speed burst.
30220 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
30221 number of different recipients that the client has sent messages to in the
30222 last time period. That is, if the client repeatedly sends messages to the same
30223 recipient, its measured rate is not increased. This option can only be used in
30226 The &%per_cmd%& option causes Exim to recompute the rate every time the
30227 condition is processed. This can be used to limit the rate of any SMTP
30228 command. If it is used in multiple ACLs it can limit the aggregate rate of
30229 multiple different commands.
30231 The &%count=%& option can be used to alter how much Exim adds to the client's
30232 measured rate. For example, the &%per_byte%& option is equivalent to
30233 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
30234 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
30235 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
30237 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
30240 .section "Ratelimit update modes" "ratoptupd"
30241 .cindex "rate limiting" "reading data without updating"
30242 You can specify one of three options with the &%ratelimit%& condition to
30243 control when its database is updated. This section describes the &%readonly%&
30244 mode, and the next section describes the &%strict%& and &%leaky%& modes.
30246 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
30247 previously-computed rate to check against the limit.
30249 For example, you can test the client's sending rate and deny it access (when
30250 it is too fast) in the connect ACL. If the client passes this check then it
30251 can go on to send a message, in which case its recorded rate will be updated
30252 in the MAIL ACL. Subsequent connections from the same client will check this
30256 deny ratelimit = 100 / 5m / readonly
30257 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
30258 (max $sender_rate_limit)
30261 warn ratelimit = 100 / 5m / strict
30262 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
30263 (max $sender_rate_limit)
30266 If Exim encounters multiple &%ratelimit%& conditions with the same key when
30267 processing a message then it may increase the client's measured rate more than
30268 it should. For example, this will happen if you check the &%per_rcpt%& option
30269 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
30270 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
30271 multiple update problems by using the &%readonly%& option on later ratelimit
30274 The &%per_*%& options described above do not make sense in some ACLs. If you
30275 use a &%per_*%& option in an ACL where it is not normally permitted then the
30276 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
30277 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
30278 next section) so you must specify the &%readonly%& option explicitly.
30281 .section "Ratelimit options for handling fast clients" "ratoptfast"
30282 .cindex "rate limiting" "strict and leaky modes"
30283 If a client's average rate is greater than the maximum, the rate limiting
30284 engine can react in two possible ways, depending on the presence of the
30285 &%strict%& or &%leaky%& update modes. This is independent of the other
30286 counter-measures (such as rejecting the message) that may be specified by the
30289 The &%leaky%& (default) option means that the client's recorded rate is not
30290 updated if it is above the limit. The effect of this is that Exim measures the
30291 client's average rate of successfully sent email, which cannot be greater than
30292 the maximum allowed. If the client is over the limit it may suffer some
30293 counter-measures (as specified in the ACL), but it will still be able to send
30294 email at the configured maximum rate, whatever the rate of its attempts. This
30295 is generally the better choice if you have clients that retry automatically.
30296 For example, it does not prevent a sender with an over-aggressive retry rate
30297 from getting any email through.
30299 The &%strict%& option means that the client's recorded rate is always
30300 updated. The effect of this is that Exim measures the client's average rate
30301 of attempts to send email, which can be much higher than the maximum it is
30302 actually allowed. If the client is over the limit it may be subjected to
30303 counter-measures by the ACL. It must slow down and allow sufficient time to
30304 pass that its computed rate falls below the maximum before it can send email
30305 again. The time (the number of smoothing periods) it must wait and not
30306 attempt to send mail can be calculated with this formula:
30308 ln(peakrate/maxrate)
30312 .section "Limiting the rate of different events" "ratoptuniq"
30313 .cindex "rate limiting" "counting unique events"
30314 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
30315 rate of different events. For example, the &%per_addr%& option uses this
30316 mechanism to count the number of different recipients that the client has
30317 sent messages to in the last time period; it is equivalent to
30318 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
30319 measure the rate that a client uses different sender addresses with the
30320 options &`per_mail/unique=$sender_address`&.
30322 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
30323 has seen for that key. The whole set is thrown away when it is older than the
30324 rate smoothing period &'p'&, so each different event is counted at most once
30325 per period. In the &%leaky%& update mode, an event that causes the client to
30326 go over the limit is not added to the set, in the same way that the client's
30327 recorded rate is not updated in the same situation.
30329 When you combine the &%unique=%& and &%readonly%& options, the specific
30330 &%unique=%& value is ignored, and Exim just retrieves the client's stored
30333 The &%unique=%& mechanism needs more space in the ratelimit database than the
30334 other &%ratelimit%& options in order to store the event set. The number of
30335 unique values is potentially as large as the rate limit, so the extra space
30336 required increases with larger limits.
30338 The uniqueification is not perfect: there is a small probability that Exim
30339 will think a new event has happened before. If the sender's rate is less than
30340 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
30341 the measured rate can go above the limit, in which case Exim may under-count
30342 events by a significant margin. Fortunately, if the rate is high enough (2.7
30343 times the limit) that the false positive rate goes above 9%, then Exim will
30344 throw away the over-full event set before the measured rate falls below the
30345 limit. Therefore the only harm should be that exceptionally high sending rates
30346 are logged incorrectly; any countermeasures you configure will be as effective
30350 .section "Using rate limiting" "useratlim"
30351 Exim's other ACL facilities are used to define what counter-measures are taken
30352 when the rate limit is exceeded. This might be anything from logging a warning
30353 (for example, while measuring existing sending rates in order to define
30354 policy), through time delays to slow down fast senders, up to rejecting the
30355 message. For example:
30357 # Log all senders' rates
30358 warn ratelimit = 0 / 1h / strict
30359 log_message = Sender rate $sender_rate / $sender_rate_period
30361 # Slow down fast senders; note the need to truncate $sender_rate
30362 # at the decimal point.
30363 warn ratelimit = 100 / 1h / per_rcpt / strict
30364 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
30365 $sender_rate_limit }s
30367 # Keep authenticated users under control
30368 deny authenticated = *
30369 ratelimit = 100 / 1d / strict / $authenticated_id
30371 # System-wide rate limit
30372 defer message = Sorry, too busy. Try again later.
30373 ratelimit = 10 / 1s / $primary_hostname
30375 # Restrict incoming rate from each host, with a default
30376 # set using a macro and special cases looked up in a table.
30377 defer message = Sender rate exceeds $sender_rate_limit \
30378 messages per $sender_rate_period
30379 ratelimit = ${lookup {$sender_host_address} \
30380 cdb {DB/ratelimits.cdb} \
30381 {$value} {RATELIMIT} }
30383 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
30384 especially with the &%per_rcpt%& option, you may suffer from a performance
30385 bottleneck caused by locking on the ratelimit hints database. Apart from
30386 making your ACLs less complicated, you can reduce the problem by using a
30387 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
30388 this means that Exim will lose its hints data after a reboot (including retry
30389 hints, the callout cache, and ratelimit data).
30393 .section "Address verification" "SECTaddressverification"
30394 .cindex "verifying address" "options for"
30395 .cindex "policy control" "address verification"
30396 Several of the &%verify%& conditions described in section
30397 &<<SECTaclconditions>>& cause addresses to be verified. Section
30398 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
30399 The verification conditions can be followed by options that modify the
30400 verification process. The options are separated from the keyword and from each
30401 other by slashes, and some of them contain parameters. For example:
30403 verify = sender/callout
30404 verify = recipient/defer_ok/callout=10s,defer_ok
30406 The first stage of address verification, which always happens, is to run the
30407 address through the routers, in &"verify mode"&. Routers can detect the
30408 difference between verification and routing for delivery, and their actions can
30409 be varied by a number of generic options such as &%verify%& and &%verify_only%&
30410 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
30411 The available options are as follows:
30414 If the &%callout%& option is specified, successful routing to one or more
30415 remote hosts is followed by a &"callout"& to those hosts as an additional
30416 check. Callouts and their sub-options are discussed in the next section.
30418 If there is a defer error while doing verification routing, the ACL
30419 normally returns &"defer"&. However, if you include &%defer_ok%& in the
30420 options, the condition is forced to be true instead. Note that this is a main
30421 verification option as well as a suboption for callouts.
30423 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
30424 discusses the reporting of sender address verification failures.
30426 The &%success_on_redirect%& option causes verification always to succeed
30427 immediately after a successful redirection. By default, if a redirection
30428 generates just one address, that address is also verified. See further
30429 discussion in section &<<SECTredirwhilveri>>&.
30432 .cindex "verifying address" "differentiating failures"
30433 .vindex "&$recipient_verify_failure$&"
30434 .vindex "&$sender_verify_failure$&"
30435 .vindex "&$acl_verify_message$&"
30436 After an address verification failure, &$acl_verify_message$& contains the
30437 error message that is associated with the failure. It can be preserved by
30440 warn !verify = sender
30441 set acl_m0 = $acl_verify_message
30443 If you are writing your own custom rejection message or log message when
30444 denying access, you can use this variable to include information about the
30445 verification failure.
30447 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
30448 appropriate) contains one of the following words:
30451 &%qualify%&: The address was unqualified (no domain), and the message
30452 was neither local nor came from an exempted host.
30454 &%route%&: Routing failed.
30456 &%mail%&: Routing succeeded, and a callout was attempted; rejection
30457 occurred at or before the MAIL command (that is, on initial
30458 connection, HELO, or MAIL).
30460 &%recipient%&: The RCPT command in a callout was rejected.
30462 &%postmaster%&: The postmaster check in a callout was rejected.
30465 The main use of these variables is expected to be to distinguish between
30466 rejections of MAIL and rejections of RCPT in callouts.
30471 .section "Callout verification" "SECTcallver"
30472 .cindex "verifying address" "by callout"
30473 .cindex "callout" "verification"
30474 .cindex "SMTP" "callout verification"
30475 For non-local addresses, routing verifies the domain, but is unable to do any
30476 checking of the local part. There are situations where some means of verifying
30477 the local part is desirable. One way this can be done is to make an SMTP
30478 &'callback'& to a delivery host for the sender address or a &'callforward'& to
30479 a subsequent host for a recipient address, to see if the host accepts the
30480 address. We use the term &'callout'& to cover both cases. Note that for a
30481 sender address, the callback is not to the client host that is trying to
30482 deliver the message, but to one of the hosts that accepts incoming mail for the
30485 Exim does not do callouts by default. If you want them to happen, you must
30486 request them by setting appropriate options on the &%verify%& condition, as
30487 described below. This facility should be used with care, because it can add a
30488 lot of resource usage to the cost of verifying an address. However, Exim does
30489 cache the results of callouts, which helps to reduce the cost. Details of
30490 caching are in section &<<SECTcallvercache>>&.
30492 Recipient callouts are usually used only between hosts that are controlled by
30493 the same administration. For example, a corporate gateway host could use
30494 callouts to check for valid recipients on an internal mailserver. A successful
30495 callout does not guarantee that a real delivery to the address would succeed;
30496 on the other hand, a failing callout does guarantee that a delivery would fail.
30498 If the &%callout%& option is present on a condition that verifies an address, a
30499 second stage of verification occurs if the address is successfully routed to
30500 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
30501 &(manualroute)& router, where the router specifies the hosts. However, if a
30502 router that does not set up hosts routes to an &(smtp)& transport with a
30503 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
30504 &%hosts_override%& set, its hosts are always used, whether or not the router
30505 supplies a host list.
30506 Callouts are only supported on &(smtp)& transports.
30508 The port that is used is taken from the transport, if it is specified and is a
30509 remote transport. (For routers that do verification only, no transport need be
30510 specified.) Otherwise, the default SMTP port is used. If a remote transport
30511 specifies an outgoing interface, this is used; otherwise the interface is not
30512 specified. Likewise, the text that is used for the HELO command is taken from
30513 the transport's &%helo_data%& option; if there is no transport, the value of
30514 &$smtp_active_hostname$& is used.
30516 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
30517 test whether a bounce message could be delivered to the sender address. The
30518 following SMTP commands are sent:
30520 &`HELO `&<&'local host name'&>
30522 &`RCPT TO:`&<&'the address to be tested'&>
30525 LHLO is used instead of HELO if the transport's &%protocol%& option is
30528 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
30531 A recipient callout check is similar. By default, it also uses an empty address
30532 for the sender. This default is chosen because most hosts do not make use of
30533 the sender address when verifying a recipient. Using the same address means
30534 that a single cache entry can be used for each recipient. Some sites, however,
30535 do make use of the sender address when verifying. These are catered for by the
30536 &%use_sender%& and &%use_postmaster%& options, described in the next section.
30538 If the response to the RCPT command is a 2&'xx'& code, the verification
30539 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
30540 Exim tries the next host, if any. If there is a problem with all the remote
30541 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
30542 &%callout%& option is given, in which case the condition is forced to succeed.
30544 .cindex "SMTP" "output flushing, disabling for callout"
30545 A callout may take a little time. For this reason, Exim normally flushes SMTP
30546 output before performing a callout in an ACL, to avoid unexpected timeouts in
30547 clients when the SMTP PIPELINING extension is in use. The flushing can be
30548 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
30553 .section "Additional parameters for callouts" "CALLaddparcall"
30554 .cindex "callout" "additional parameters for"
30555 The &%callout%& option can be followed by an equals sign and a number of
30556 optional parameters, separated by commas. For example:
30558 verify = recipient/callout=10s,defer_ok
30560 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
30561 separate verify options, is retained for backwards compatibility, but is now
30562 deprecated. The additional parameters for &%callout%& are as follows:
30566 .vitem <&'a&~time&~interval'&>
30567 .cindex "callout" "timeout, specifying"
30568 This specifies the timeout that applies for the callout attempt to each host.
30571 verify = sender/callout=5s
30573 The default is 30 seconds. The timeout is used for each response from the
30574 remote host. It is also used for the initial connection, unless overridden by
30575 the &%connect%& parameter.
30578 .vitem &*connect&~=&~*&<&'time&~interval'&>
30579 .cindex "callout" "connection timeout, specifying"
30580 This parameter makes it possible to set a different (usually smaller) timeout
30581 for making the SMTP connection. For example:
30583 verify = sender/callout=5s,connect=1s
30585 If not specified, this timeout defaults to the general timeout value.
30587 .vitem &*defer_ok*&
30588 .cindex "callout" "defer, action on"
30589 When this parameter is present, failure to contact any host, or any other kind
30590 of temporary error, is treated as success by the ACL. However, the cache is not
30591 updated in this circumstance.
30593 .vitem &*fullpostmaster*&
30594 .cindex "callout" "full postmaster check"
30595 This operates like the &%postmaster%& option (see below), but if the check for
30596 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
30597 accordance with the specification in RFC 2821. The RFC states that the
30598 unqualified address &'postmaster'& should be accepted.
30601 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
30602 .cindex "callout" "sender when verifying header"
30603 When verifying addresses in header lines using the &%header_sender%&
30604 verification option, Exim behaves by default as if the addresses are envelope
30605 sender addresses from a message. Callout verification therefore tests to see
30606 whether a bounce message could be delivered, by using an empty address in the
30607 MAIL command. However, it is arguable that these addresses might never be used
30608 as envelope senders, and could therefore justifiably reject bounce messages
30609 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
30610 address to use in the MAIL command. For example:
30612 require verify = header_sender/callout=mailfrom=abcd@x.y.z
30614 This parameter is available only for the &%header_sender%& verification option.
30617 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
30618 .cindex "callout" "overall timeout, specifying"
30619 This parameter sets an overall timeout for performing a callout verification.
30622 verify = sender/callout=5s,maxwait=30s
30624 This timeout defaults to four times the callout timeout for individual SMTP
30625 commands. The overall timeout applies when there is more than one host that can
30626 be tried. The timeout is checked before trying the next host. This prevents
30627 very long delays if there are a large number of hosts and all are timing out
30628 (for example, when network connections are timing out).
30631 .vitem &*no_cache*&
30632 .cindex "callout" "cache, suppressing"
30633 .cindex "caching callout, suppressing"
30634 When this parameter is given, the callout cache is neither read nor updated.
30636 .vitem &*postmaster*&
30637 .cindex "callout" "postmaster; checking"
30638 When this parameter is set, a successful callout check is followed by a similar
30639 check for the local part &'postmaster'& at the same domain. If this address is
30640 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
30641 the postmaster check is recorded in a cache record; if it is a failure, this is
30642 used to fail subsequent callouts for the domain without a connection being
30643 made, until the cache record expires.
30645 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
30646 The postmaster check uses an empty sender in the MAIL command by default.
30647 You can use this parameter to do a postmaster check using a different address.
30650 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
30652 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
30653 one overrides. The &%postmaster%& parameter is equivalent to this example:
30655 require verify = sender/callout=postmaster_mailfrom=
30657 &*Warning*&: The caching arrangements for postmaster checking do not take
30658 account of the sender address. It is assumed that either the empty address or
30659 a fixed non-empty address will be used. All that Exim remembers is that the
30660 postmaster check for the domain succeeded or failed.
30664 .cindex "callout" "&""random""& check"
30665 When this parameter is set, before doing the normal callout check, Exim does a
30666 check for a &"random"& local part at the same domain. The local part is not
30667 really random &-- it is defined by the expansion of the option
30668 &%callout_random_local_part%&, which defaults to
30670 $primary_hostname-$tod_epoch-testing
30672 The idea here is to try to determine whether the remote host accepts all local
30673 parts without checking. If it does, there is no point in doing callouts for
30674 specific local parts. If the &"random"& check succeeds, the result is saved in
30675 a cache record, and used to force the current and subsequent callout checks to
30676 succeed without a connection being made, until the cache record expires.
30678 .vitem &*use_postmaster*&
30679 .cindex "callout" "sender for recipient check"
30680 This parameter applies to recipient callouts only. For example:
30682 deny !verify = recipient/callout=use_postmaster
30684 .vindex "&$qualify_domain$&"
30685 It causes a non-empty postmaster address to be used in the MAIL command when
30686 performing the callout for the recipient, and also for a &"random"& check if
30687 that is configured. The local part of the address is &`postmaster`& and the
30688 domain is the contents of &$qualify_domain$&.
30690 .vitem &*use_sender*&
30691 This option applies to recipient callouts only. For example:
30693 require verify = recipient/callout=use_sender
30695 It causes the message's actual sender address to be used in the MAIL
30696 command when performing the callout, instead of an empty address. There is no
30697 need to use this option unless you know that the called hosts make use of the
30698 sender when checking recipients. If used indiscriminately, it reduces the
30699 usefulness of callout caching.
30702 If you use any of the parameters that set a non-empty sender for the MAIL
30703 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
30704 &%use_sender%&), you should think about possible loops. Recipient checking is
30705 usually done between two hosts that are under the same management, and the host
30706 that receives the callouts is not normally configured to do callouts itself.
30707 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
30708 these circumstances.
30710 However, if you use a non-empty sender address for a callout to an arbitrary
30711 host, there is the likelihood that the remote host will itself initiate a
30712 callout check back to your host. As it is checking what appears to be a message
30713 sender, it is likely to use an empty address in MAIL, thus avoiding a
30714 callout loop. However, to be on the safe side it would be best to set up your
30715 own ACLs so that they do not do sender verification checks when the recipient
30716 is the address you use for header sender or postmaster callout checking.
30718 Another issue to think about when using non-empty senders for callouts is
30719 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
30720 by the sender/recipient combination; thus, for any given recipient, many more
30721 actual callouts are performed than when an empty sender or postmaster is used.
30726 .section "Callout caching" "SECTcallvercache"
30727 .cindex "hints database" "callout cache"
30728 .cindex "callout" "cache, description of"
30729 .cindex "caching" "callout"
30730 Exim caches the results of callouts in order to reduce the amount of resources
30731 used, unless you specify the &%no_cache%& parameter with the &%callout%&
30732 option. A hints database called &"callout"& is used for the cache. Two
30733 different record types are used: one records the result of a callout check for
30734 a specific address, and the other records information that applies to the
30735 entire domain (for example, that it accepts the local part &'postmaster'&).
30737 When an original callout fails, a detailed SMTP error message is given about
30738 the failure. However, for subsequent failures use the cache data, this message
30741 The expiry times for negative and positive address cache records are
30742 independent, and can be set by the global options &%callout_negative_expire%&
30743 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
30745 If a host gives a negative response to an SMTP connection, or rejects any
30746 commands up to and including
30750 (but not including the MAIL command with a non-empty address),
30751 any callout attempt is bound to fail. Exim remembers such failures in a
30752 domain cache record, which it uses to fail callouts for the domain without
30753 making new connections, until the domain record times out. There are two
30754 separate expiry times for domain cache records:
30755 &%callout_domain_negative_expire%& (default 3h) and
30756 &%callout_domain_positive_expire%& (default 7d).
30758 Domain records expire when the negative expiry time is reached if callouts
30759 cannot be made for the domain, or if the postmaster check failed.
30760 Otherwise, they expire when the positive expiry time is reached. This
30761 ensures that, for example, a host that stops accepting &"random"& local parts
30762 will eventually be noticed.
30764 The callout caching mechanism is based on the domain of the address that is
30765 being tested. If the domain routes to several hosts, it is assumed that their
30766 behaviour will be the same.
30770 .section "Sender address verification reporting" "SECTsenaddver"
30771 .cindex "verifying" "suppressing error details"
30772 See section &<<SECTaddressverification>>& for a general discussion of
30773 verification. When sender verification fails in an ACL, the details of the
30774 failure are given as additional output lines before the 550 response to the
30775 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
30778 MAIL FROM:<xyz@abc.example>
30780 RCPT TO:<pqr@def.example>
30781 550-Verification failed for <xyz@abc.example>
30782 550-Called: 192.168.34.43
30783 550-Sent: RCPT TO:<xyz@abc.example>
30784 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
30785 550 Sender verification failed
30787 If more than one RCPT command fails in the same way, the details are given
30788 only for the first of them. However, some administrators do not want to send
30789 out this much information. You can suppress the details by adding
30790 &`/no_details`& to the ACL statement that requests sender verification. For
30793 verify = sender/no_details
30796 .section "Redirection while verifying" "SECTredirwhilveri"
30797 .cindex "verifying" "redirection while"
30798 .cindex "address redirection" "while verifying"
30799 A dilemma arises when a local address is redirected by aliasing or forwarding
30800 during verification: should the generated addresses themselves be verified,
30801 or should the successful expansion of the original address be enough to verify
30802 it? By default, Exim takes the following pragmatic approach:
30805 When an incoming address is redirected to just one child address, verification
30806 continues with the child address, and if that fails to verify, the original
30807 verification also fails.
30809 When an incoming address is redirected to more than one child address,
30810 verification does not continue. A success result is returned.
30813 This seems the most reasonable behaviour for the common use of aliasing as a
30814 way of redirecting different local parts to the same mailbox. It means, for
30815 example, that a pair of alias entries of the form
30818 aw123: :fail: Gone away, no forwarding address
30820 work as expected, with both local parts causing verification failure. When a
30821 redirection generates more than one address, the behaviour is more like a
30822 mailing list, where the existence of the alias itself is sufficient for
30823 verification to succeed.
30825 It is possible, however, to change the default behaviour so that all successful
30826 redirections count as successful verifications, however many new addresses are
30827 generated. This is specified by the &%success_on_redirect%& verification
30828 option. For example:
30830 require verify = recipient/success_on_redirect/callout=10s
30832 In this example, verification succeeds if a router generates a new address, and
30833 the callout does not occur, because no address was routed to a remote host.
30835 When verification is being tested via the &%-bv%& option, the treatment of
30836 redirections is as just described, unless the &%-v%& or any debugging option is
30837 also specified. In that case, full verification is done for every generated
30838 address and a report is output for each of them.
30842 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
30843 .cindex "CSA" "verifying"
30844 Client SMTP Authorization is a system that allows a site to advertise
30845 which machines are and are not permitted to send email. This is done by placing
30846 special SRV records in the DNS; these are looked up using the client's HELO
30847 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
30848 Authorization checks in Exim are performed by the ACL condition:
30852 This fails if the client is not authorized. If there is a DNS problem, or if no
30853 valid CSA SRV record is found, or if the client is authorized, the condition
30854 succeeds. These three cases can be distinguished using the expansion variable
30855 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
30856 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
30857 be likely to cause problems for legitimate email.
30859 The error messages produced by the CSA code include slightly more
30860 detail. If &$csa_status$& is &"defer"&, this may be because of problems
30861 looking up the CSA SRV record, or problems looking up the CSA target
30862 address record. There are four reasons for &$csa_status$& being &"fail"&:
30865 The client's host name is explicitly not authorized.
30867 The client's IP address does not match any of the CSA target IP addresses.
30869 The client's host name is authorized but it has no valid target IP addresses
30870 (for example, the target's addresses are IPv6 and the client is using IPv4).
30872 The client's host name has no CSA SRV record but a parent domain has asserted
30873 that all subdomains must be explicitly authorized.
30876 The &%csa%& verification condition can take an argument which is the domain to
30877 use for the DNS query. The default is:
30879 verify = csa/$sender_helo_name
30881 This implementation includes an extension to CSA. If the query domain
30882 is an address literal such as [192.0.2.95], or if it is a bare IP
30883 address, Exim searches for CSA SRV records in the reverse DNS as if
30884 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
30887 verify = csa/$sender_host_address
30889 In fact, this is the check that Exim performs if the client does not say HELO.
30890 This extension can be turned off by setting the main configuration option
30891 &%dns_csa_use_reverse%& to be false.
30893 If a CSA SRV record is not found for the domain itself, a search
30894 is performed through its parent domains for a record which might be
30895 making assertions about subdomains. The maximum depth of this search is limited
30896 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
30897 default. Exim does not look for CSA SRV records in a top level domain, so the
30898 default settings handle HELO domains as long as seven
30899 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
30900 of legitimate HELO domains.
30902 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
30903 direct SRV lookups, this is not sufficient because of the extra parent domain
30904 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
30905 addresses into lookups in the reverse DNS space. The result of a successful
30908 ${lookup dnsdb {csa=$sender_helo_name}}
30910 has two space-separated fields: an authorization code and a target host name.
30911 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
30912 authorization required but absent, or &"?"& for unknown.
30917 .section "Bounce address tag validation" "SECTverifyPRVS"
30918 .cindex "BATV, verifying"
30919 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
30920 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
30921 Genuine incoming bounce messages should therefore always be addressed to
30922 recipients that have a valid tag. This scheme is a way of detecting unwanted
30923 bounce messages caused by sender address forgeries (often called &"collateral
30924 spam"&), because the recipients of such messages do not include valid tags.
30926 There are two expansion items to help with the implementation of the BATV
30927 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
30928 the original envelope sender address by using a simple key to add a hash of the
30929 address and some time-based randomizing information. The &%prvs%& expansion
30930 item creates a signed address, and the &%prvscheck%& expansion item checks one.
30931 The syntax of these expansion items is described in section
30932 &<<SECTexpansionitems>>&.
30934 As an example, suppose the secret per-address keys are stored in an MySQL
30935 database. A query to look up the key for an address could be defined as a macro
30938 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
30939 WHERE sender='${quote_mysql:$prvscheck_address}'\
30942 Suppose also that the senders who make use of BATV are defined by an address
30943 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
30946 # Bounces: drop unsigned addresses for BATV senders
30947 deny message = This address does not send an unsigned reverse path
30949 recipients = +batv_senders
30951 # Bounces: In case of prvs-signed address, check signature.
30952 deny message = Invalid reverse path signature.
30954 condition = ${prvscheck {$local_part@$domain}\
30955 {PRVSCHECK_SQL}{1}}
30956 !condition = $prvscheck_result
30958 The first statement rejects recipients for bounce messages that are addressed
30959 to plain BATV sender addresses, because it is known that BATV senders do not
30960 send out messages with plain sender addresses. The second statement rejects
30961 recipients that are prvs-signed, but with invalid signatures (either because
30962 the key is wrong, or the signature has timed out).
30964 A non-prvs-signed address is not rejected by the second statement, because the
30965 &%prvscheck%& expansion yields an empty string if its first argument is not a
30966 prvs-signed address, thus causing the &%condition%& condition to be false. If
30967 the first argument is a syntactically valid prvs-signed address, the yield is
30968 the third string (in this case &"1"&), whether or not the cryptographic and
30969 timeout checks succeed. The &$prvscheck_result$& variable contains the result
30970 of the checks (empty for failure, &"1"& for success).
30972 There is one more issue you must consider when implementing prvs-signing:
30973 you have to ensure that the routers accept prvs-signed addresses and
30974 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
30975 router to remove the signature with a configuration along these lines:
30979 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
30981 This works because, if the third argument of &%prvscheck%& is empty, the result
30982 of the expansion of a prvs-signed address is the decoded value of the original
30983 address. This router should probably be the first of your routers that handles
30986 To create BATV-signed addresses in the first place, a transport of this form
30989 external_smtp_batv:
30991 return_path = ${prvs {$return_path} \
30992 {${lookup mysql{SELECT \
30993 secret FROM batv_prvs WHERE \
30994 sender='${quote_mysql:$sender_address}'} \
30997 If no key can be found for the existing return path, no signing takes place.
31001 .section "Using an ACL to control relaying" "SECTrelaycontrol"
31002 .cindex "&ACL;" "relay control"
31003 .cindex "relaying" "control by ACL"
31004 .cindex "policy control" "relay control"
31005 An MTA is said to &'relay'& a message if it receives it from some host and
31006 delivers it directly to another host as a result of a remote address contained
31007 within it. Redirecting a local address via an alias or forward file and then
31008 passing the message on to another host is not relaying,
31009 .cindex "&""percent hack""&"
31010 but a redirection as a result of the &"percent hack"& is.
31012 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
31013 A host which is acting as a gateway or an MX backup is concerned with incoming
31014 relaying from arbitrary hosts to a specific set of domains. On the other hand,
31015 a host which is acting as a smart host for a number of clients is concerned
31016 with outgoing relaying from those clients to the Internet at large. Often the
31017 same host is fulfilling both functions,
31019 . as illustrated in the diagram below,
31021 but in principle these two kinds of relaying are entirely independent. What is
31022 not wanted is the transmission of mail from arbitrary remote hosts through your
31023 system to arbitrary domains.
31026 You can implement relay control by means of suitable statements in the ACL that
31027 runs for each RCPT command. For convenience, it is often easiest to use
31028 Exim's named list facility to define the domains and hosts involved. For
31029 example, suppose you want to do the following:
31032 Deliver a number of domains to mailboxes on the local host (or process them
31033 locally in some other way). Let's say these are &'my.dom1.example'& and
31034 &'my.dom2.example'&.
31036 Relay mail for a number of other domains for which you are the secondary MX.
31037 These might be &'friend1.example'& and &'friend2.example'&.
31039 Relay mail from the hosts on your local LAN, to whatever domains are involved.
31040 Suppose your LAN is 192.168.45.0/24.
31044 In the main part of the configuration, you put the following definitions:
31046 domainlist local_domains = my.dom1.example : my.dom2.example
31047 domainlist relay_to_domains = friend1.example : friend2.example
31048 hostlist relay_from_hosts = 192.168.45.0/24
31050 Now you can use these definitions in the ACL that is run for every RCPT
31054 accept domains = +local_domains : +relay_to_domains
31055 accept hosts = +relay_from_hosts
31057 The first statement accepts any RCPT command that contains an address in
31058 the local or relay domains. For any other domain, control passes to the second
31059 statement, which accepts the command only if it comes from one of the relay
31060 hosts. In practice, you will probably want to make your ACL more sophisticated
31061 than this, for example, by including sender and recipient verification. The
31062 default configuration includes a more comprehensive example, which is described
31063 in chapter &<<CHAPdefconfil>>&.
31067 .section "Checking a relay configuration" "SECTcheralcon"
31068 .cindex "relaying" "checking control of"
31069 You can check the relay characteristics of your configuration in the same way
31070 that you can test any ACL behaviour for an incoming SMTP connection, by using
31071 the &%-bh%& option to run a fake SMTP session with which you interact.
31076 . ////////////////////////////////////////////////////////////////////////////
31077 . ////////////////////////////////////////////////////////////////////////////
31079 .chapter "Content scanning at ACL time" "CHAPexiscan"
31080 .scindex IIDcosca "content scanning" "at ACL time"
31081 The extension of Exim to include content scanning at ACL time, formerly known
31082 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
31083 was integrated into the main source for Exim release 4.50, and Tom continues to
31084 maintain it. Most of the wording of this chapter is taken from Tom's
31087 It is also possible to scan the content of messages at other times. The
31088 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
31089 scanning after all the ACLs have run. A transport filter can be used to scan
31090 messages at delivery time (see the &%transport_filter%& option, described in
31091 chapter &<<CHAPtransportgeneric>>&).
31093 If you want to include the ACL-time content-scanning features when you compile
31094 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
31095 &_Local/Makefile_&. When you do that, the Exim binary is built with:
31098 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
31099 for all MIME parts for SMTP and non-SMTP messages, respectively.
31101 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
31102 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
31103 run at the end of message reception (the &%acl_smtp_data%& ACL).
31105 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
31106 of messages, or parts of messages, for debugging purposes.
31108 Additional expansion variables that are set in the new ACL and by the new
31111 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
31114 Content-scanning is continually evolving, and new features are still being
31115 added. While such features are still unstable and liable to incompatible
31116 changes, they are made available in Exim by setting options whose names begin
31117 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
31118 this manual. You can find out about them by reading the file called
31119 &_doc/experimental.txt_&.
31121 All the content-scanning facilities work on a MBOX copy of the message that is
31122 temporarily created in a file called:
31124 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
31126 The &_.eml_& extension is a friendly hint to virus scanners that they can
31127 expect an MBOX-like structure inside that file. The file is created when the
31128 first content scanning facility is called. Subsequent calls to content
31129 scanning conditions open the same file again. The directory is recursively
31130 removed when the &%acl_smtp_data%& ACL has finished running, unless
31132 control = no_mbox_unspool
31134 has been encountered. When the MIME ACL decodes files, they are put into the
31135 same directory by default.
31139 .section "Scanning for viruses" "SECTscanvirus"
31140 .cindex "virus scanning"
31141 .cindex "content scanning" "for viruses"
31142 .cindex "content scanning" "the &%malware%& condition"
31143 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
31144 It supports a &"generic"& interface to scanners called via the shell, and
31145 specialized interfaces for &"daemon"& type virus scanners, which are resident
31146 in memory and thus are much faster.
31148 A timeout of 2 minutes is applied to a scanner call (by default);
31149 if it expires then a defer action is taken.
31151 .oindex "&%av_scanner%&"
31152 You can set the &%av_scanner%& option in the main part of the configuration
31153 to specify which scanner to use, together with any additional options that
31154 are needed. The basic syntax is as follows:
31156 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
31158 If you do not set &%av_scanner%&, it defaults to
31160 av_scanner = sophie:/var/run/sophie
31162 If the value of &%av_scanner%& starts with a dollar character, it is expanded
31164 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
31165 The following scanner types are supported in this release:
31169 .cindex "virus scanners" "avast"
31170 This is the scanner daemon of Avast. It has been tested with Avast Core
31171 Security (currently at version 1.1.7).
31172 You can get a trial version at &url(http://www.avast.com) or for Linux
31173 at &url(http://www.avast.com/linux-server-antivirus).
31174 This scanner type takes one option,
31175 which can be either a full path to a UNIX socket,
31176 or host and port specifiers separated by white space.
31177 The host may be a name or an IP address; the port is either a
31178 single number or a pair of numbers with a dash between.
31179 Any further options are given, on separate lines,
31180 to the daemon as options before the main scan command.
31183 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
31184 av_scanner = avast:192.168.2.22 5036
31186 If you omit the argument, the default path
31187 &_/var/run/avast/scan.sock_&
31189 If you use a remote host,
31190 you need to make Exim's spool directory available to it,
31191 as the scanner is passed a file path, not file contents.
31192 For information about available commands and their options you may use
31194 $ socat UNIX:/var/run/avast/scan.sock STDIO:
31201 .vitem &%aveserver%&
31202 .cindex "virus scanners" "Kaspersky"
31203 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
31204 at &url(http://www.kaspersky.com). This scanner type takes one option,
31205 which is the path to the daemon's UNIX socket. The default is shown in this
31208 av_scanner = aveserver:/var/run/aveserver
31213 .cindex "virus scanners" "clamd"
31214 This daemon-type scanner is GPL and free. You can get it at
31215 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
31216 unpack MIME containers, so it used to be recommended to unpack MIME attachments
31217 in the MIME ACL. This is no longer believed to be necessary.
31219 The options are a list of server specifiers, which may be
31220 a UNIX socket specification,
31221 a TCP socket specification,
31222 or a (global) option.
31224 A socket specification consists of a space-separated list.
31225 For a Unix socket the first element is a full path for the socket,
31226 for a TCP socket the first element is the IP address
31227 and the second a port number,
31228 Any further elements are per-server (non-global) options.
31229 These per-server options are supported:
31231 retry=<timespec> Retry on connect fail
31234 The &`retry`& option specifies a time after which a single retry for
31235 a failed connect is made. The default is to not retry.
31237 If a Unix socket file is specified, only one server is supported.
31241 av_scanner = clamd:/opt/clamd/socket
31242 av_scanner = clamd:192.0.2.3 1234
31243 av_scanner = clamd:192.0.2.3 1234:local
31244 av_scanner = clamd:192.0.2.3 1234 retry=10s
31245 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
31247 If the value of av_scanner points to a UNIX socket file or contains the
31249 option, then the ClamAV interface will pass a filename containing the data
31250 to be scanned, which will should normally result in less I/O happening and be
31251 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
31252 Exim does not assume that there is a common filesystem with the remote host.
31253 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
31254 you be running a version of ClamAV prior to 0.95.
31256 The final example shows that multiple TCP targets can be specified. Exim will
31257 randomly use one for each incoming email (i.e. it load balances them). Note
31258 that only TCP targets may be used if specifying a list of scanners; a UNIX
31259 socket cannot be mixed in with TCP targets. If one of the servers becomes
31260 unavailable, Exim will try the remaining one(s) until it finds one that works.
31261 When a clamd server becomes unreachable, Exim will log a message. Exim does
31262 not keep track of scanner state between multiple messages, and the scanner
31263 selection is random, so the message will get logged in the mainlog for each
31264 email that the down scanner gets chosen first (message wrapped to be readable):
31266 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
31267 clamd: connection to localhost, port 3310 failed
31268 (Connection refused)
31271 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
31272 contributing the code for this scanner.
31275 .cindex "virus scanners" "command line interface"
31276 This is the keyword for the generic command line scanner interface. It can be
31277 used to attach virus scanners that are invoked from the shell. This scanner
31278 type takes 3 mandatory options:
31281 The full path and name of the scanner binary, with all command line options,
31282 and a placeholder (&`%s`&) for the directory to scan.
31285 A regular expression to match against the STDOUT and STDERR output of the
31286 virus scanner. If the expression matches, a virus was found. You must make
31287 absolutely sure that this expression matches on &"virus found"&. This is called
31288 the &"trigger"& expression.
31291 Another regular expression, containing exactly one pair of parentheses, to
31292 match the name of the virus found in the scanners output. This is called the
31293 &"name"& expression.
31296 For example, Sophos Sweep reports a virus on a line like this:
31298 Virus 'W32/Magistr-B' found in file ./those.bat
31300 For the trigger expression, we can match the phrase &"found in file"&. For the
31301 name expression, we want to extract the W32/Magistr-B string, so we can match
31302 for the single quotes left and right of it. Altogether, this makes the
31303 configuration setting:
31305 av_scanner = cmdline:\
31306 /path/to/sweep -ss -all -rec -archive %s:\
31307 found in file:'(.+)'
31310 .cindex "virus scanners" "DrWeb"
31311 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
31313 either a full path to a UNIX socket,
31314 or host and port specifiers separated by white space.
31315 The host may be a name or an IP address; the port is either a
31316 single number or a pair of numbers with a dash between.
31319 av_scanner = drweb:/var/run/drwebd.sock
31320 av_scanner = drweb:192.168.2.20 31337
31322 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
31323 is used. Thanks to Alex Miller for contributing the code for this scanner.
31326 .cindex "virus scanners" "f-protd"
31327 The f-protd scanner is accessed via HTTP over TCP.
31328 One argument is taken, being a space-separated hostname and port number
31332 av_scanner = f-protd:localhost 10200-10204
31334 If you omit the argument, the default values show above are used.
31337 .cindex "virus scanners" "F-Secure"
31338 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
31339 argument which is the path to a UNIX socket. For example:
31341 av_scanner = fsecure:/path/to/.fsav
31343 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
31344 Thelmen for contributing the code for this scanner.
31346 .vitem &%kavdaemon%&
31347 .cindex "virus scanners" "Kaspersky"
31348 This is the scanner daemon of Kaspersky Version 4. This version of the
31349 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
31350 scanner type takes one option, which is the path to the daemon's UNIX socket.
31353 av_scanner = kavdaemon:/opt/AVP/AvpCtl
31355 The default path is &_/var/run/AvpCtl_&.
31358 .cindex "virus scanners" "mksd"
31359 This is a daemon type scanner that is aimed mainly at Polish users, though some
31360 parts of documentation are now available in English. You can get it at
31361 &url(http://linux.mks.com.pl/). The only option for this scanner type is
31362 the maximum number of processes used simultaneously to scan the attachments,
31363 provided that mksd has
31364 been run with at least the same number of child processes. For example:
31366 av_scanner = mksd:2
31368 You can safely omit this option (the default value is 1).
31371 .cindex "virus scanners" "simple socket-connected"
31372 This is a general-purpose way of talking to simple scanner daemons
31373 running on the local machine.
31374 There are four options:
31375 an address (which may be an IP address and port, or the path of a Unix socket),
31376 a commandline to send (may include a single %s which will be replaced with
31377 the path to the mail file to be scanned),
31378 an RE to trigger on from the returned data,
31379 an RE to extract malware_name from the returned data.
31382 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
31384 Default for the socket specifier is &_/tmp/malware.sock_&.
31385 Default for the commandline is &_%s\n_&.
31386 Both regular-expressions are required.
31389 .cindex "virus scanners" "Sophos and Sophie"
31390 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
31391 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
31392 for this scanner type is the path to the UNIX socket that Sophie uses for
31393 client communication. For example:
31395 av_scanner = sophie:/tmp/sophie
31397 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
31401 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
31402 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
31405 The &%av_scanner%& option is expanded each time &%malware%& is called. This
31406 makes it possible to use different scanners. See further below for an example.
31407 The &%malware%& condition caches its results, so when you use it multiple times
31408 for the same message, the actual scanning process is only carried out once.
31409 However, using expandable items in &%av_scanner%& disables this caching, in
31410 which case each use of the &%malware%& condition causes a new scan of the
31413 The &%malware%& condition takes a right-hand argument that is expanded before
31414 use and taken as a list, slash-separated by default.
31415 The first element can then be one of
31418 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
31419 The condition succeeds if a virus was found, and fail otherwise. This is the
31422 &"false"& or &"0"& or an empty string, in which case no scanning is done and
31423 the condition fails immediately.
31425 A regular expression, in which case the message is scanned for viruses. The
31426 condition succeeds if a virus is found and its name matches the regular
31427 expression. This allows you to take special actions on certain types of virus.
31428 Note that &"/"& characters in the RE must be doubled due to the list-processing,
31429 unless the separator is changed (in the usual way).
31432 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
31433 messages even if there is a problem with the virus scanner.
31434 Otherwise, such a problem causes the ACL to defer.
31436 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
31437 specify a non-default timeout. The default is two minutes.
31440 malware = * / defer_ok / tmo=10s
31442 A timeout causes the ACL to defer.
31444 .vindex "&$callout_address$&"
31445 When a connection is made to the scanner the expansion variable &$callout_address$&
31446 is set to record the actual address used.
31448 .vindex "&$malware_name$&"
31449 When a virus is found, the condition sets up an expansion variable called
31450 &$malware_name$& that contains the name of the virus. You can use it in a
31451 &%message%& modifier that specifies the error returned to the sender, and/or in
31454 Beware the interaction of Exim's &%message_size_limit%& with any size limits
31455 imposed by your anti-virus scanner.
31457 Here is a very simple scanning example:
31459 deny message = This message contains malware ($malware_name)
31462 The next example accepts messages when there is a problem with the scanner:
31464 deny message = This message contains malware ($malware_name)
31465 malware = */defer_ok
31467 The next example shows how to use an ACL variable to scan with both sophie and
31468 aveserver. It assumes you have set:
31470 av_scanner = $acl_m0
31472 in the main Exim configuration.
31474 deny message = This message contains malware ($malware_name)
31475 set acl_m0 = sophie
31478 deny message = This message contains malware ($malware_name)
31479 set acl_m0 = aveserver
31484 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
31485 .cindex "content scanning" "for spam"
31486 .cindex "spam scanning"
31487 .cindex "SpamAssassin"
31489 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
31490 score and a report for the message.
31491 Support is also provided for Rspamd.
31493 For more information about installation and configuration of SpamAssassin or
31494 Rspamd refer to their respective websites at
31495 &url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
31497 SpamAssassin can be installed with CPAN by running:
31499 perl -MCPAN -e 'install Mail::SpamAssassin'
31501 SpamAssassin has its own set of configuration files. Please review its
31502 documentation to see how you can tweak it. The default installation should work
31505 .oindex "&%spamd_address%&"
31506 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
31507 intend to use an instance running on the local host you do not need to set
31508 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
31509 you must set the &%spamd_address%& option in the global part of the Exim
31510 configuration as follows (example):
31512 spamd_address = 192.168.99.45 387
31515 To use Rspamd (which by default listens on all local addresses
31517 you should add &%variant=rspamd%& after the address/port pair, for example:
31519 spamd_address = 127.0.0.1 11333 variant=rspamd
31522 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
31523 sockets. If you want to us these, supply &%spamd_address%& with an absolute
31524 file name instead of an address/port pair:
31526 spamd_address = /var/run/spamd_socket
31528 You can have multiple &%spamd%& servers to improve scalability. These can
31529 reside on other hardware reachable over the network. To specify multiple
31530 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
31531 option, separated with colons (the separator can be changed in the usual way):
31533 spamd_address = 192.168.2.10 783 : \
31534 192.168.2.11 783 : \
31537 Up to 32 &%spamd%& servers are supported.
31538 When a server fails to respond to the connection attempt, all other
31539 servers are tried until one succeeds. If no server responds, the &%spam%&
31542 Unix and TCP socket specifications may be mixed in any order.
31543 Each element of the list is a list itself, space-separated by default
31544 and changeable in the usual way.
31546 For TCP socket specifications a host name or IP (v4 or v6, but
31547 subject to list-separator quoting rules) address can be used,
31548 and the port can be one or a dash-separated pair.
31549 In the latter case, the range is tried in strict order.
31551 Elements after the first for Unix sockets, or second for TCP socket,
31553 The supported options are:
31555 pri=<priority> Selection priority
31556 weight=<value> Selection bias
31557 time=<start>-<end> Use only between these times of day
31558 retry=<timespec> Retry on connect fail
31559 tmo=<timespec> Connection time limit
31560 variant=rspamd Use Rspamd rather than SpamAssassin protocol
31563 The &`pri`& option specifies a priority for the server within the list,
31564 higher values being tried first.
31565 The default priority is 1.
31567 The &`weight`& option specifies a selection bias.
31568 Within a priority set
31569 servers are queried in a random fashion, weighted by this value.
31570 The default value for selection bias is 1.
31572 Time specifications for the &`time`& option are <hour>.<minute>.<second>
31573 in the local time zone; each element being one or more digits.
31574 Either the seconds or both minutes and seconds, plus the leading &`.`&
31575 characters, may be omitted and will be taken as zero.
31577 Timeout specifications for the &`retry`& and &`tmo`& options
31578 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
31580 The &`tmo`& option specifies an overall timeout for communication.
31581 The default value is two minutes.
31583 The &`retry`& option specifies a time after which a single retry for
31584 a failed connect is made.
31585 The default is to not retry.
31587 The &%spamd_address%& variable is expanded before use if it starts with
31588 a dollar sign. In this case, the expansion may return a string that is
31589 used as the list so that multiple spamd servers can be the result of an
31592 .vindex "&$callout_address$&"
31593 When a connection is made to the server the expansion variable &$callout_address$&
31594 is set to record the actual address used.
31596 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
31597 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
31599 deny message = This message was classified as SPAM
31602 The right-hand side of the &%spam%& condition specifies a name. This is
31603 relevant if you have set up multiple SpamAssassin profiles. If you do not want
31604 to scan using a specific profile, but rather use the SpamAssassin system-wide
31605 default profile, you can scan for an unknown name, or simply use &"nobody"&.
31606 Rspamd does not use this setting. However, you must put something on the
31609 The name allows you to use per-domain or per-user antispam profiles in
31610 principle, but this is not straightforward in practice, because a message may
31611 have multiple recipients, not necessarily all in the same domain. Because the
31612 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
31613 read the contents of the message, the variables &$local_part$& and &$domain$&
31615 Careful enforcement of single-recipient messages
31616 (e.g. by responding with defer in the recipient ACL for all recipients
31618 or the use of PRDR,
31619 .cindex "PRDR" "use for per-user SpamAssassin profiles"
31620 are needed to use this feature.
31622 The right-hand side of the &%spam%& condition is expanded before being used, so
31623 you can put lookups or conditions there. When the right-hand side evaluates to
31624 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
31627 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
31628 large ones may cause significant performance degradation. As most spam messages
31629 are quite small, it is recommended that you do not scan the big ones. For
31632 deny message = This message was classified as SPAM
31633 condition = ${if < {$message_size}{10K}}
31637 The &%spam%& condition returns true if the threshold specified in the user's
31638 SpamAssassin profile has been matched or exceeded. If you want to use the
31639 &%spam%& condition for its side effects (see the variables below), you can make
31640 it always return &"true"& by appending &`:true`& to the username.
31642 .cindex "spam scanning" "returned variables"
31643 When the &%spam%& condition is run, it sets up a number of expansion
31645 Except for &$spam_report$&,
31646 these variables are saved with the received message so are
31647 available for use at delivery time.
31650 .vitem &$spam_score$&
31651 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
31652 for inclusion in log or reject messages.
31654 .vitem &$spam_score_int$&
31655 The spam score of the message, multiplied by ten, as an integer value. For
31656 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
31657 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
31658 The integer value is useful for numeric comparisons in conditions.
31660 .vitem &$spam_bar$&
31661 A string consisting of a number of &"+"& or &"-"& characters, representing the
31662 integer part of the spam score value. A spam score of 4.4 would have a
31663 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
31664 headers, since MUAs can match on such strings. The maximum length of the
31665 spam bar is 50 characters.
31667 .vitem &$spam_report$&
31668 A multiline text table, containing the full SpamAssassin report for the
31669 message. Useful for inclusion in headers or reject messages.
31670 This variable is only usable in a DATA-time ACL.
31672 .vitem &$spam_action$&
31673 For SpamAssassin either 'reject' or 'no action' depending on the
31674 spam score versus threshold.
31675 For Rspamd, the recommended action.
31679 The &%spam%& condition caches its results unless expansion in
31680 spamd_address was used. If you call it again with the same user name, it
31681 does not scan again, but rather returns the same values as before.
31683 The &%spam%& condition returns DEFER if there is any error while running
31684 the message through SpamAssassin or if the expansion of spamd_address
31685 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
31686 statement block), append &`/defer_ok`& to the right-hand side of the
31687 spam condition, like this:
31689 deny message = This message was classified as SPAM
31690 spam = joe/defer_ok
31692 This causes messages to be accepted even if there is a problem with &%spamd%&.
31694 Here is a longer, commented example of the use of the &%spam%&
31697 # put headers in all messages (no matter if spam or not)
31698 warn spam = nobody:true
31699 add_header = X-Spam-Score: $spam_score ($spam_bar)
31700 add_header = X-Spam-Report: $spam_report
31702 # add second subject line with *SPAM* marker when message
31703 # is over threshold
31705 add_header = Subject: *SPAM* $h_Subject:
31707 # reject spam at high scores (> 12)
31708 deny message = This message scored $spam_score spam points.
31710 condition = ${if >{$spam_score_int}{120}{1}{0}}
31715 .section "Scanning MIME parts" "SECTscanmimepart"
31716 .cindex "content scanning" "MIME parts"
31717 .cindex "MIME content scanning"
31718 .oindex "&%acl_smtp_mime%&"
31719 .oindex "&%acl_not_smtp_mime%&"
31720 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
31721 each MIME part of an SMTP message, including multipart types, in the sequence
31722 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
31723 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
31724 options may both refer to the same ACL if you want the same processing in both
31727 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
31728 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
31729 the case of a non-SMTP message. However, a MIME ACL is called only if the
31730 message contains a &'Content-Type:'& header line. When a call to a MIME
31731 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
31732 result code is sent to the client. In the case of an SMTP message, the
31733 &%acl_smtp_data%& ACL is not called when this happens.
31735 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
31736 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
31737 condition to match against the raw MIME part. You can also use the
31738 &%mime_regex%& condition to match against the decoded MIME part (see section
31739 &<<SECTscanregex>>&).
31741 At the start of a MIME ACL, a number of variables are set from the header
31742 information for the relevant MIME part. These are described below. The contents
31743 of the MIME part are not by default decoded into a disk file except for MIME
31744 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
31745 part into a disk file, you can use the &%decode%& condition. The general
31748 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
31750 The right hand side is expanded before use. After expansion,
31754 &"0"& or &"false"&, in which case no decoding is done.
31756 The string &"default"&. In that case, the file is put in the temporary
31757 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
31758 a sequential file name consisting of the message id and a sequence number. The
31759 full path and name is available in &$mime_decoded_filename$& after decoding.
31761 A full path name starting with a slash. If the full name is an existing
31762 directory, it is used as a replacement for the default directory. The filename
31763 is then sequentially assigned. If the path does not exist, it is used as
31764 the full path and file name.
31766 If the string does not start with a slash, it is used as the
31767 filename, and the default path is then used.
31769 The &%decode%& condition normally succeeds. It is only false for syntax
31770 errors or unusual circumstances such as memory shortages. You can easily decode
31771 a file with its original, proposed filename using
31773 decode = $mime_filename
31775 However, you should keep in mind that &$mime_filename$& might contain
31776 anything. If you place files outside of the default path, they are not
31777 automatically unlinked.
31779 For RFC822 attachments (these are messages attached to messages, with a
31780 content-type of &"message/rfc822"&), the ACL is called again in the same manner
31781 as for the primary message, only that the &$mime_is_rfc822$& expansion
31782 variable is set (see below). Attached messages are always decoded to disk
31783 before being checked, and the files are unlinked once the check is done.
31785 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
31786 used to match regular expressions against raw and decoded MIME parts,
31787 respectively. They are described in section &<<SECTscanregex>>&.
31789 .cindex "MIME content scanning" "returned variables"
31790 The following list describes all expansion variables that are
31791 available in the MIME ACL:
31794 .vitem &$mime_boundary$&
31795 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
31796 have a boundary string, which is stored in this variable. If the current part
31797 has no boundary parameter in the &'Content-Type:'& header, this variable
31798 contains the empty string.
31800 .vitem &$mime_charset$&
31801 This variable contains the character set identifier, if one was found in the
31802 &'Content-Type:'& header. Examples for charset identifiers are:
31808 Please note that this value is not normalized, so you should do matches
31809 case-insensitively.
31811 .vitem &$mime_content_description$&
31812 This variable contains the normalized content of the &'Content-Description:'&
31813 header. It can contain a human-readable description of the parts content. Some
31814 implementations repeat the filename for attachments here, but they are usually
31815 only used for display purposes.
31817 .vitem &$mime_content_disposition$&
31818 This variable contains the normalized content of the &'Content-Disposition:'&
31819 header. You can expect strings like &"attachment"& or &"inline"& here.
31821 .vitem &$mime_content_id$&
31822 This variable contains the normalized content of the &'Content-ID:'& header.
31823 This is a unique ID that can be used to reference a part from another part.
31825 .vitem &$mime_content_size$&
31826 This variable is set only after the &%decode%& modifier (see above) has been
31827 successfully run. It contains the size of the decoded part in kilobytes. The
31828 size is always rounded up to full kilobytes, so only a completely empty part
31829 has a &$mime_content_size$& of zero.
31831 .vitem &$mime_content_transfer_encoding$&
31832 This variable contains the normalized content of the
31833 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
31834 type. Typical values are &"base64"& and &"quoted-printable"&.
31836 .vitem &$mime_content_type$&
31837 If the MIME part has a &'Content-Type:'& header, this variable contains its
31838 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
31839 are some examples of popular MIME types, as they may appear in this variable:
31843 application/octet-stream
31847 If the MIME part has no &'Content-Type:'& header, this variable contains the
31850 .vitem &$mime_decoded_filename$&
31851 This variable is set only after the &%decode%& modifier (see above) has been
31852 successfully run. It contains the full path and file name of the file
31853 containing the decoded data.
31858 .vitem &$mime_filename$&
31859 This is perhaps the most important of the MIME variables. It contains a
31860 proposed filename for an attachment, if one was found in either the
31861 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
31864 decoded, but no additional sanity checks are done.
31866 found, this variable contains the empty string.
31868 .vitem &$mime_is_coverletter$&
31869 This variable attempts to differentiate the &"cover letter"& of an e-mail from
31870 attached data. It can be used to clamp down on flashy or unnecessarily encoded
31871 content in the cover letter, while not restricting attachments at all.
31873 The variable contains 1 (true) for a MIME part believed to be part of the
31874 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
31878 The outermost MIME part of a message is always a cover letter.
31881 If a multipart/alternative or multipart/related MIME part is a cover letter,
31882 so are all MIME subparts within that multipart.
31885 If any other multipart is a cover letter, the first subpart is a cover letter,
31886 and the rest are attachments.
31889 All parts contained within an attachment multipart are attachments.
31892 As an example, the following will ban &"HTML mail"& (including that sent with
31893 alternative plain text), while allowing HTML files to be attached. HTML
31894 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
31896 deny message = HTML mail is not accepted here
31897 !condition = $mime_is_rfc822
31898 condition = $mime_is_coverletter
31899 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
31901 .vitem &$mime_is_multipart$&
31902 This variable has the value 1 (true) when the current part has the main type
31903 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
31904 Since multipart entities only serve as containers for other parts, you may not
31905 want to carry out specific actions on them.
31907 .vitem &$mime_is_rfc822$&
31908 This variable has the value 1 (true) if the current part is not a part of the
31909 checked message itself, but part of an attached message. Attached message
31910 decoding is fully recursive.
31912 .vitem &$mime_part_count$&
31913 This variable is a counter that is raised for each processed MIME part. It
31914 starts at zero for the very first part (which is usually a multipart). The
31915 counter is per-message, so it is reset when processing RFC822 attachments (see
31916 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
31917 complete, so you can use it in the DATA ACL to determine the number of MIME
31918 parts of a message. For non-MIME messages, this variable contains the value -1.
31923 .section "Scanning with regular expressions" "SECTscanregex"
31924 .cindex "content scanning" "with regular expressions"
31925 .cindex "regular expressions" "content scanning with"
31926 You can specify your own custom regular expression matches on the full body of
31927 the message, or on individual MIME parts.
31929 The &%regex%& condition takes one or more regular expressions as arguments and
31930 matches them against the full message (when called in the DATA ACL) or a raw
31931 MIME part (when called in the MIME ACL). The &%regex%& condition matches
31932 linewise, with a maximum line length of 32K characters. That means you cannot
31933 have multiline matches with the &%regex%& condition.
31935 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
31936 to 32K of decoded content (the whole content at once, not linewise). If the
31937 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
31938 is decoded automatically when &%mime_regex%& is executed (using default path
31939 and filename values). If the decoded data is larger than 32K, only the first
31940 32K characters are checked.
31942 The regular expressions are passed as a colon-separated list. To include a
31943 literal colon, you must double it. Since the whole right-hand side string is
31944 expanded before being used, you must also escape dollar signs and backslashes
31945 with more backslashes, or use the &`\N`& facility to disable expansion.
31946 Here is a simple example that contains two regular expressions:
31948 deny message = contains blacklisted regex ($regex_match_string)
31949 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
31951 The conditions returns true if any one of the regular expressions matches. The
31952 &$regex_match_string$& expansion variable is then set up and contains the
31953 matching regular expression.
31954 The expansion variables &$regex1$& &$regex2$& etc
31955 are set to any substrings captured by the regular expression.
31957 &*Warning*&: With large messages, these conditions can be fairly
31965 . ////////////////////////////////////////////////////////////////////////////
31966 . ////////////////////////////////////////////////////////////////////////////
31968 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
31969 "Local scan function"
31970 .scindex IIDlosca "&[local_scan()]& function" "description of"
31971 .cindex "customizing" "input scan using C function"
31972 .cindex "policy control" "by local scan function"
31973 In these days of email worms, viruses, and ever-increasing spam, some sites
31974 want to apply a lot of checking to messages before accepting them.
31976 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
31977 passing messages to external virus and spam scanning software. You can also do
31978 a certain amount in Exim itself through string expansions and the &%condition%&
31979 condition in the ACL that runs after the SMTP DATA command or the ACL for
31980 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
31982 To allow for further customization to a site's own requirements, there is the
31983 possibility of linking Exim with a private message scanning function, written
31984 in C. If you want to run code that is written in something other than C, you
31985 can of course use a little C stub to call it.
31987 The local scan function is run once for every incoming message, at the point
31988 when Exim is just about to accept the message.
31989 It can therefore be used to control non-SMTP messages from local processes as
31990 well as messages arriving via SMTP.
31992 Exim applies a timeout to calls of the local scan function, and there is an
31993 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
31994 Zero means &"no timeout"&.
31995 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
31996 before calling the local scan function, so that the most common types of crash
31997 are caught. If the timeout is exceeded or one of those signals is caught, the
31998 incoming message is rejected with a temporary error if it is an SMTP message.
31999 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
32000 code. The incident is logged on the main and reject logs.
32004 .section "Building Exim to use a local scan function" "SECID207"
32005 .cindex "&[local_scan()]& function" "building Exim to use"
32006 To make use of the local scan function feature, you must tell Exim where your
32007 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
32008 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
32009 directory, so you might set
32011 LOCAL_SCAN_SOURCE=Local/local_scan.c
32013 for example. The function must be called &[local_scan()]&. It is called by
32014 Exim after it has received a message, when the success return code is about to
32015 be sent. This is after all the ACLs have been run. The return code from your
32016 function controls whether the message is actually accepted or not. There is a
32017 commented template function (that just accepts the message) in the file
32018 _src/local_scan.c_.
32020 If you want to make use of Exim's run time configuration file to set options
32021 for your &[local_scan()]& function, you must also set
32023 LOCAL_SCAN_HAS_OPTIONS=yes
32025 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
32030 .section "API for local_scan()" "SECTapiforloc"
32031 .cindex "&[local_scan()]& function" "API description"
32032 You must include this line near the start of your code:
32034 #include "local_scan.h"
32036 This header file defines a number of variables and other values, and the
32037 prototype for the function itself. Exim is coded to use unsigned char values
32038 almost exclusively, and one of the things this header defines is a shorthand
32039 for &`unsigned char`& called &`uschar`&.
32040 It also contains the following macro definitions, to simplify casting character
32041 strings and pointers to character strings:
32043 #define CS (char *)
32044 #define CCS (const char *)
32045 #define CSS (char **)
32046 #define US (unsigned char *)
32047 #define CUS (const unsigned char *)
32048 #define USS (unsigned char **)
32050 The function prototype for &[local_scan()]& is:
32052 extern int local_scan(int fd, uschar **return_text);
32054 The arguments are as follows:
32057 &%fd%& is a file descriptor for the file that contains the body of the message
32058 (the -D file). The file is open for reading and writing, but updating it is not
32059 recommended. &*Warning*&: You must &'not'& close this file descriptor.
32061 The descriptor is positioned at character 19 of the file, which is the first
32062 character of the body itself, because the first 19 characters are the message
32063 id followed by &`-D`& and a newline. If you rewind the file, you should use the
32064 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
32065 case this changes in some future version.
32067 &%return_text%& is an address which you can use to return a pointer to a text
32068 string at the end of the function. The value it points to on entry is NULL.
32071 The function must return an &%int%& value which is one of the following macros:
32074 .vitem &`LOCAL_SCAN_ACCEPT`&
32075 .vindex "&$local_scan_data$&"
32076 The message is accepted. If you pass back a string of text, it is saved with
32077 the message, and made available in the variable &$local_scan_data$&. No
32078 newlines are permitted (if there are any, they are turned into spaces) and the
32079 maximum length of text is 1000 characters.
32081 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
32082 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32083 queued without immediate delivery, and is frozen.
32085 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
32086 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32087 queued without immediate delivery.
32089 .vitem &`LOCAL_SCAN_REJECT`&
32090 The message is rejected; the returned text is used as an error message which is
32091 passed back to the sender and which is also logged. Newlines are permitted &--
32092 they cause a multiline response for SMTP rejections, but are converted to
32093 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
32096 .vitem &`LOCAL_SCAN_TEMPREJECT`&
32097 The message is temporarily rejected; the returned text is used as an error
32098 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
32101 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
32102 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
32103 message is not written to the reject log. It has the effect of unsetting the
32104 &%rejected_header%& log selector for just this rejection. If
32105 &%rejected_header%& is already unset (see the discussion of the
32106 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
32107 same as LOCAL_SCAN_REJECT.
32109 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
32110 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
32111 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
32114 If the message is not being received by interactive SMTP, rejections are
32115 reported by writing to &%stderr%& or by sending an email, as configured by the
32116 &%-oe%& command line options.
32120 .section "Configuration options for local_scan()" "SECTconoptloc"
32121 .cindex "&[local_scan()]& function" "configuration options"
32122 It is possible to have option settings in the main configuration file
32123 that set values in static variables in the &[local_scan()]& module. If you
32124 want to do this, you must have the line
32126 LOCAL_SCAN_HAS_OPTIONS=yes
32128 in your &_Local/Makefile_& when you build Exim. (This line is in
32129 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
32130 file, you must define static variables to hold the option values, and a table
32133 The table must be a vector called &%local_scan_options%&, of type
32134 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
32135 and a pointer to the variable that holds the value. The entries must appear in
32136 alphabetical order. Following &%local_scan_options%& you must also define a
32137 variable called &%local_scan_options_count%& that contains the number of
32138 entries in the table. Here is a short example, showing two kinds of option:
32140 static int my_integer_option = 42;
32141 static uschar *my_string_option = US"a default string";
32143 optionlist local_scan_options[] = {
32144 { "my_integer", opt_int, &my_integer_option },
32145 { "my_string", opt_stringptr, &my_string_option }
32148 int local_scan_options_count =
32149 sizeof(local_scan_options)/sizeof(optionlist);
32151 The values of the variables can now be changed from Exim's runtime
32152 configuration file by including a local scan section as in this example:
32156 my_string = some string of text...
32158 The available types of option data are as follows:
32161 .vitem &*opt_bool*&
32162 This specifies a boolean (true/false) option. The address should point to a
32163 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
32164 that are defined as &"1"& and &"0"&, respectively. If you want to detect
32165 whether such a variable has been set at all, you can initialize it to
32166 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
32169 .vitem &*opt_fixed*&
32170 This specifies a fixed point number, such as is used for load averages.
32171 The address should point to a variable of type &`int`&. The value is stored
32172 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
32175 This specifies an integer; the address should point to a variable of type
32176 &`int`&. The value may be specified in any of the integer formats accepted by
32179 .vitem &*opt_mkint*&
32180 This is the same as &%opt_int%&, except that when such a value is output in a
32181 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
32182 printed with the suffix K or M.
32184 .vitem &*opt_octint*&
32185 This also specifies an integer, but the value is always interpreted as an
32186 octal integer, whether or not it starts with the digit zero, and it is
32187 always output in octal.
32189 .vitem &*opt_stringptr*&
32190 This specifies a string value; the address must be a pointer to a
32191 variable that points to a string (for example, of type &`uschar *`&).
32193 .vitem &*opt_time*&
32194 This specifies a time interval value. The address must point to a variable of
32195 type &`int`&. The value that is placed there is a number of seconds.
32198 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
32199 out the values of all the &[local_scan()]& options.
32203 .section "Available Exim variables" "SECID208"
32204 .cindex "&[local_scan()]& function" "available Exim variables"
32205 The header &_local_scan.h_& gives you access to a number of C variables. These
32206 are the only ones that are guaranteed to be maintained from release to release.
32207 Note, however, that you can obtain the value of any Exim expansion variable,
32208 including &$recipients$&, by calling &'expand_string()'&. The exported
32209 C variables are as follows:
32212 .vitem &*int&~body_linecount*&
32213 This variable contains the number of lines in the message's body.
32215 .vitem &*int&~body_zerocount*&
32216 This variable contains the number of binary zero bytes in the message's body.
32218 .vitem &*unsigned&~int&~debug_selector*&
32219 This variable is set to zero when no debugging is taking place. Otherwise, it
32220 is a bitmap of debugging selectors. Two bits are identified for use in
32221 &[local_scan()]&; they are defined as macros:
32224 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
32225 testing option that is not privileged &-- any caller may set it. All the
32226 other selector bits can be set only by admin users.
32229 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
32230 by the &`+local_scan`& debug selector. It is not included in the default set
32234 Thus, to write to the debugging output only when &`+local_scan`& has been
32235 selected, you should use code like this:
32237 if ((debug_selector & D_local_scan) != 0)
32238 debug_printf("xxx", ...);
32240 .vitem &*uschar&~*expand_string_message*&
32241 After a failing call to &'expand_string()'& (returned value NULL), the
32242 variable &%expand_string_message%& contains the error message, zero-terminated.
32244 .vitem &*header_line&~*header_list*&
32245 A pointer to a chain of header lines. The &%header_line%& structure is
32248 .vitem &*header_line&~*header_last*&
32249 A pointer to the last of the header lines.
32251 .vitem &*uschar&~*headers_charset*&
32252 The value of the &%headers_charset%& configuration option.
32254 .vitem &*BOOL&~host_checking*&
32255 This variable is TRUE during a host checking session that is initiated by the
32256 &%-bh%& command line option.
32258 .vitem &*uschar&~*interface_address*&
32259 The IP address of the interface that received the message, as a string. This
32260 is NULL for locally submitted messages.
32262 .vitem &*int&~interface_port*&
32263 The port on which this message was received. When testing with the &%-bh%&
32264 command line option, the value of this variable is -1 unless a port has been
32265 specified via the &%-oMi%& option.
32267 .vitem &*uschar&~*message_id*&
32268 This variable contains Exim's message id for the incoming message (the value of
32269 &$message_exim_id$&) as a zero-terminated string.
32271 .vitem &*uschar&~*received_protocol*&
32272 The name of the protocol by which the message was received.
32274 .vitem &*int&~recipients_count*&
32275 The number of accepted recipients.
32277 .vitem &*recipient_item&~*recipients_list*&
32278 .cindex "recipient" "adding in local scan"
32279 .cindex "recipient" "removing in local scan"
32280 The list of accepted recipients, held in a vector of length
32281 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
32282 can add additional recipients by calling &'receive_add_recipient()'& (see
32283 below). You can delete recipients by removing them from the vector and
32284 adjusting the value in &%recipients_count%&. In particular, by setting
32285 &%recipients_count%& to zero you remove all recipients. If you then return the
32286 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
32287 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
32288 and then call &'receive_add_recipient()'& as often as needed.
32290 .vitem &*uschar&~*sender_address*&
32291 The envelope sender address. For bounce messages this is the empty string.
32293 .vitem &*uschar&~*sender_host_address*&
32294 The IP address of the sending host, as a string. This is NULL for
32295 locally-submitted messages.
32297 .vitem &*uschar&~*sender_host_authenticated*&
32298 The name of the authentication mechanism that was used, or NULL if the message
32299 was not received over an authenticated SMTP connection.
32301 .vitem &*uschar&~*sender_host_name*&
32302 The name of the sending host, if known.
32304 .vitem &*int&~sender_host_port*&
32305 The port on the sending host.
32307 .vitem &*BOOL&~smtp_input*&
32308 This variable is TRUE for all SMTP input, including BSMTP.
32310 .vitem &*BOOL&~smtp_batched_input*&
32311 This variable is TRUE for BSMTP input.
32313 .vitem &*int&~store_pool*&
32314 The contents of this variable control which pool of memory is used for new
32315 requests. See section &<<SECTmemhanloc>>& for details.
32319 .section "Structure of header lines" "SECID209"
32320 The &%header_line%& structure contains the members listed below.
32321 You can add additional header lines by calling the &'header_add()'& function
32322 (see below). You can cause header lines to be ignored (deleted) by setting
32327 .vitem &*struct&~header_line&~*next*&
32328 A pointer to the next header line, or NULL for the last line.
32330 .vitem &*int&~type*&
32331 A code identifying certain headers that Exim recognizes. The codes are printing
32332 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
32333 Notice in particular that any header line whose type is * is not transmitted
32334 with the message. This flagging is used for header lines that have been
32335 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
32336 lines.) Effectively, * means &"deleted"&.
32338 .vitem &*int&~slen*&
32339 The number of characters in the header line, including the terminating and any
32342 .vitem &*uschar&~*text*&
32343 A pointer to the text of the header. It always ends with a newline, followed by
32344 a zero byte. Internal newlines are preserved.
32349 .section "Structure of recipient items" "SECID210"
32350 The &%recipient_item%& structure contains these members:
32353 .vitem &*uschar&~*address*&
32354 This is a pointer to the recipient address as it was received.
32356 .vitem &*int&~pno*&
32357 This is used in later Exim processing when top level addresses are created by
32358 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
32359 and must always contain -1 at this stage.
32361 .vitem &*uschar&~*errors_to*&
32362 If this value is not NULL, bounce messages caused by failing to deliver to the
32363 recipient are sent to the address it contains. In other words, it overrides the
32364 envelope sender for this one recipient. (Compare the &%errors_to%& generic
32365 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
32366 an unqualified address, Exim qualifies it using the domain from
32367 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
32368 is NULL for all recipients.
32373 .section "Available Exim functions" "SECID211"
32374 .cindex "&[local_scan()]& function" "available Exim functions"
32375 The header &_local_scan.h_& gives you access to a number of Exim functions.
32376 These are the only ones that are guaranteed to be maintained from release to
32380 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
32381 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
32383 This function creates a child process that runs the command specified by
32384 &%argv%&. The environment for the process is specified by &%envp%&, which can
32385 be NULL if no environment variables are to be passed. A new umask is supplied
32386 for the process in &%newumask%&.
32388 Pipes to the standard input and output of the new process are set up
32389 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
32390 standard error is cloned to the standard output. If there are any file
32391 descriptors &"in the way"& in the new process, they are closed. If the final
32392 argument is TRUE, the new process is made into a process group leader.
32394 The function returns the pid of the new process, or -1 if things go wrong.
32396 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
32397 This function waits for a child process to terminate, or for a timeout (in
32398 seconds) to expire. A timeout value of zero means wait as long as it takes. The
32399 return value is as follows:
32404 The process terminated by a normal exit and the value is the process
32410 The process was terminated by a signal and the value is the negation of the
32416 The process timed out.
32420 The was some other error in wait(); &%errno%& is still set.
32423 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
32424 This function provide you with a means of submitting a new message to
32425 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
32426 want, but this packages it all up for you.) The function creates a pipe,
32427 forks a subprocess that is running
32429 exim -t -oem -oi -f <>
32431 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
32432 that is connected to the standard input. The yield of the function is the PID
32433 of the subprocess. You can then write a message to the file descriptor, with
32434 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
32436 When you have finished, call &'child_close()'& to wait for the process to
32437 finish and to collect its ending status. A timeout value of zero is usually
32438 fine in this circumstance. Unless you have made a mistake with the recipient
32439 addresses, you should get a return code of zero.
32442 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
32443 *sender_authentication)*&
32444 This function is a more sophisticated version of &'child_open()'&. The command
32447 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
32449 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
32452 .vitem &*void&~debug_printf(char&~*,&~...)*&
32453 This is Exim's debugging function, with arguments as for &'(printf()'&. The
32454 output is written to the standard error stream. If no debugging is selected,
32455 calls to &'debug_printf()'& have no effect. Normally, you should make calls
32456 conditional on the &`local_scan`& debug selector by coding like this:
32458 if ((debug_selector & D_local_scan) != 0)
32459 debug_printf("xxx", ...);
32462 .vitem &*uschar&~*expand_string(uschar&~*string)*&
32463 This is an interface to Exim's string expansion code. The return value is the
32464 expanded string, or NULL if there was an expansion failure.
32465 The C variable &%expand_string_message%& contains an error message after an
32466 expansion failure. If expansion does not change the string, the return value is
32467 the pointer to the input string. Otherwise, the return value points to a new
32468 block of memory that was obtained by a call to &'store_get()'&. See section
32469 &<<SECTmemhanloc>>& below for a discussion of memory handling.
32471 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
32472 This function allows you to an add additional header line at the end of the
32473 existing ones. The first argument is the type, and should normally be a space
32474 character. The second argument is a format string and any number of
32475 substitution arguments as for &[sprintf()]&. You may include internal newlines
32476 if you want, and you must ensure that the string ends with a newline.
32478 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
32479 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
32480 This function adds a new header line at a specified point in the header
32481 chain. The header itself is specified as for &'header_add()'&.
32483 If &%name%& is NULL, the new header is added at the end of the chain if
32484 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
32485 NULL, the header lines are searched for the first non-deleted header that
32486 matches the name. If one is found, the new header is added before it if
32487 &%after%& is false. If &%after%& is true, the new header is added after the
32488 found header and any adjacent subsequent ones with the same name (even if
32489 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
32490 option controls where the header is added. If it is true, addition is at the
32491 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
32492 headers, or at the top if there are no &'Received:'& headers, you could use
32494 header_add_at_position(TRUE, US"Received", TRUE,
32495 ' ', "X-xxx: ...");
32497 Normally, there is always at least one non-deleted &'Received:'& header, but
32498 there may not be if &%received_header_text%& expands to an empty string.
32501 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
32502 This function removes header lines. If &%occurrence%& is zero or negative, all
32503 occurrences of the header are removed. If occurrence is greater than zero, that
32504 particular instance of the header is removed. If no header(s) can be found that
32505 match the specification, the function does nothing.
32508 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
32509 int&~length,&~BOOL&~notdel)*&"
32510 This function tests whether the given header has the given name. It is not just
32511 a string comparison, because white space is permitted between the name and the
32512 colon. If the &%notdel%& argument is true, a false return is forced for all
32513 &"deleted"& headers; otherwise they are not treated specially. For example:
32515 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
32517 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
32518 .cindex "base64 encoding" "functions for &[local_scan()]& use"
32519 This function base64-encodes a string, which is passed by address and length.
32520 The text may contain bytes of any value, including zero. The result is passed
32521 back in dynamic memory that is obtained by calling &'store_get()'&. It is
32524 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
32525 This function decodes a base64-encoded string. Its arguments are a
32526 zero-terminated base64-encoded string and the address of a variable that is set
32527 to point to the result, which is in dynamic memory. The length of the decoded
32528 string is the yield of the function. If the input is invalid base64 data, the
32529 yield is -1. A zero byte is added to the end of the output string to make it
32530 easy to interpret as a C string (assuming it contains no zeros of its own). The
32531 added zero byte is not included in the returned count.
32533 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
32534 This function checks for a match in a domain list. Domains are always
32535 matched caselessly. The return value is one of the following:
32537 &`OK `& match succeeded
32538 &`FAIL `& match failed
32539 &`DEFER `& match deferred
32541 DEFER is usually caused by some kind of lookup defer, such as the
32542 inability to contact a database.
32544 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
32546 This function checks for a match in a local part list. The third argument
32547 controls case-sensitivity. The return values are as for
32548 &'lss_match_domain()'&.
32550 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
32552 This function checks for a match in an address list. The third argument
32553 controls the case-sensitivity of the local part match. The domain is always
32554 matched caselessly. The return values are as for &'lss_match_domain()'&.
32556 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
32558 This function checks for a match in a host list. The most common usage is
32561 lss_match_host(sender_host_name, sender_host_address, ...)
32563 .vindex "&$sender_host_address$&"
32564 An empty address field matches an empty item in the host list. If the host name
32565 is NULL, the name corresponding to &$sender_host_address$& is automatically
32566 looked up if a host name is required to match an item in the list. The return
32567 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
32568 returns ERROR in the case when it had to look up a host name, but the lookup
32571 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
32573 This function writes to Exim's log files. The first argument should be zero (it
32574 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
32575 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
32576 them. It specifies to which log or logs the message is written. The remaining
32577 arguments are a format and relevant insertion arguments. The string should not
32578 contain any newlines, not even at the end.
32581 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
32582 This function adds an additional recipient to the message. The first argument
32583 is the recipient address. If it is unqualified (has no domain), it is qualified
32584 with the &%qualify_recipient%& domain. The second argument must always be -1.
32586 This function does not allow you to specify a private &%errors_to%& address (as
32587 described with the structure of &%recipient_item%& above), because it pre-dates
32588 the addition of that field to the structure. However, it is easy to add such a
32589 value afterwards. For example:
32591 receive_add_recipient(US"monitor@mydom.example", -1);
32592 recipients_list[recipients_count-1].errors_to =
32593 US"postmaster@mydom.example";
32596 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
32597 This is a convenience function to remove a named recipient from the list of
32598 recipients. It returns true if a recipient was removed, and false if no
32599 matching recipient could be found. The argument must be a complete email
32606 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
32607 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
32608 This function decodes strings that are encoded according to RFC 2047. Typically
32609 these are the contents of header lines. First, each &"encoded word"& is decoded
32610 from the Q or B encoding into a byte-string. Then, if provided with the name of
32611 a charset encoding, and if the &[iconv()]& function is available, an attempt is
32612 made to translate the result to the named character set. If this fails, the
32613 binary string is returned with an error message.
32615 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
32616 maximum MIME word length is enforced. The third argument is the target
32617 encoding, or NULL if no translation is wanted.
32619 .cindex "binary zero" "in RFC 2047 decoding"
32620 .cindex "RFC 2047" "binary zero in"
32621 If a binary zero is encountered in the decoded string, it is replaced by the
32622 contents of the &%zeroval%& argument. For use with Exim headers, the value must
32623 not be 0 because header lines are handled as zero-terminated strings.
32625 The function returns the result of processing the string, zero-terminated; if
32626 &%lenptr%& is not NULL, the length of the result is set in the variable to
32627 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
32629 If an error is encountered, the function returns NULL and uses the &%error%&
32630 argument to return an error message. The variable pointed to by &%error%& is
32631 set to NULL if there is no error; it may be set non-NULL even when the function
32632 returns a non-NULL value if decoding was successful, but there was a problem
32636 .vitem &*int&~smtp_fflush(void)*&
32637 This function is used in conjunction with &'smtp_printf()'&, as described
32640 .vitem &*void&~smtp_printf(char&~*,&~...)*&
32641 The arguments of this function are like &[printf()]&; it writes to the SMTP
32642 output stream. You should use this function only when there is an SMTP output
32643 stream, that is, when the incoming message is being received via interactive
32644 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
32645 is FALSE. If you want to test for an incoming message from another host (as
32646 opposed to a local process that used the &%-bs%& command line option), you can
32647 test the value of &%sender_host_address%&, which is non-NULL when a remote host
32650 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
32651 output function, so it can be used for all forms of SMTP connection.
32653 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
32654 must start with an appropriate response code: 550 if you are going to return
32655 LOCAL_SCAN_REJECT, 451 if you are going to return
32656 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
32657 initial lines of a multi-line response, the code must be followed by a hyphen
32658 to indicate that the line is not the final response line. You must also ensure
32659 that the lines you write terminate with CRLF. For example:
32661 smtp_printf("550-this is some extra info\r\n");
32662 return LOCAL_SCAN_REJECT;
32664 Note that you can also create multi-line responses by including newlines in
32665 the data returned via the &%return_text%& argument. The added value of using
32666 &'smtp_printf()'& is that, for instance, you could introduce delays between
32667 multiple output lines.
32669 The &'smtp_printf()'& function does not return any error indication, because it
32670 does not automatically flush pending output, and therefore does not test
32671 the state of the stream. (In the main code of Exim, flushing and error
32672 detection is done when Exim is ready for the next SMTP input command.) If
32673 you want to flush the output and check for an error (for example, the
32674 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
32675 arguments. It flushes the output stream, and returns a non-zero value if there
32678 .vitem &*void&~*store_get(int)*&
32679 This function accesses Exim's internal store (memory) manager. It gets a new
32680 chunk of memory whose size is given by the argument. Exim bombs out if it ever
32681 runs out of memory. See the next section for a discussion of memory handling.
32683 .vitem &*void&~*store_get_perm(int)*&
32684 This function is like &'store_get()'&, but it always gets memory from the
32685 permanent pool. See the next section for a discussion of memory handling.
32687 .vitem &*uschar&~*string_copy(uschar&~*string)*&
32690 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
32693 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
32694 These three functions create strings using Exim's dynamic memory facilities.
32695 The first makes a copy of an entire string. The second copies up to a maximum
32696 number of characters, indicated by the second argument. The third uses a format
32697 and insertion arguments to create a new string. In each case, the result is a
32698 pointer to a new string in the current memory pool. See the next section for
32704 .section "More about Exim's memory handling" "SECTmemhanloc"
32705 .cindex "&[local_scan()]& function" "memory handling"
32706 No function is provided for freeing memory, because that is never needed.
32707 The dynamic memory that Exim uses when receiving a message is automatically
32708 recycled if another message is received by the same process (this applies only
32709 to incoming SMTP connections &-- other input methods can supply only one
32710 message at a time). After receiving the last message, a reception process
32713 Because it is recycled, the normal dynamic memory cannot be used for holding
32714 data that must be preserved over a number of incoming messages on the same SMTP
32715 connection. However, Exim in fact uses two pools of dynamic memory; the second
32716 one is not recycled, and can be used for this purpose.
32718 If you want to allocate memory that remains available for subsequent messages
32719 in the same SMTP connection, you should set
32721 store_pool = POOL_PERM
32723 before calling the function that does the allocation. There is no need to
32724 restore the value if you do not need to; however, if you do want to revert to
32725 the normal pool, you can either restore the previous value of &%store_pool%& or
32726 set it explicitly to POOL_MAIN.
32728 The pool setting applies to all functions that get dynamic memory, including
32729 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
32730 There is also a convenience function called &'store_get_perm()'& that gets a
32731 block of memory from the permanent pool while preserving the value of
32738 . ////////////////////////////////////////////////////////////////////////////
32739 . ////////////////////////////////////////////////////////////////////////////
32741 .chapter "System-wide message filtering" "CHAPsystemfilter"
32742 .scindex IIDsysfil1 "filter" "system filter"
32743 .scindex IIDsysfil2 "filtering all mail"
32744 .scindex IIDsysfil3 "system filter"
32745 The previous chapters (on ACLs and the local scan function) describe checks
32746 that can be applied to messages before they are accepted by a host. There is
32747 also a mechanism for checking messages once they have been received, but before
32748 they are delivered. This is called the &'system filter'&.
32750 The system filter operates in a similar manner to users' filter files, but it
32751 is run just once per message (however many recipients the message has).
32752 It should not normally be used as a substitute for routing, because &%deliver%&
32753 commands in a system router provide new envelope recipient addresses.
32754 The system filter must be an Exim filter. It cannot be a Sieve filter.
32756 The system filter is run at the start of a delivery attempt, before any routing
32757 is done. If a message fails to be completely delivered at the first attempt,
32758 the system filter is run again at the start of every retry.
32759 If you want your filter to do something only once per message, you can make use
32760 of the &%first_delivery%& condition in an &%if%& command in the filter to
32761 prevent it happening on retries.
32763 .vindex "&$domain$&"
32764 .vindex "&$local_part$&"
32765 &*Warning*&: Because the system filter runs just once, variables that are
32766 specific to individual recipient addresses, such as &$local_part$& and
32767 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
32768 you want to run a centrally-specified filter for each recipient address
32769 independently, you can do so by setting up a suitable &(redirect)& router, as
32770 described in section &<<SECTperaddfil>>& below.
32773 .section "Specifying a system filter" "SECID212"
32774 .cindex "uid (user id)" "system filter"
32775 .cindex "gid (group id)" "system filter"
32776 The name of the file that contains the system filter must be specified by
32777 setting &%system_filter%&. If you want the filter to run under a uid and gid
32778 other than root, you must also set &%system_filter_user%& and
32779 &%system_filter_group%& as appropriate. For example:
32781 system_filter = /etc/mail/exim.filter
32782 system_filter_user = exim
32784 If a system filter generates any deliveries directly to files or pipes (via the
32785 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
32786 specified by setting &%system_filter_file_transport%& and
32787 &%system_filter_pipe_transport%&, respectively. Similarly,
32788 &%system_filter_reply_transport%& must be set to handle any messages generated
32789 by the &%reply%& command.
32792 .section "Testing a system filter" "SECID213"
32793 You can run simple tests of a system filter in the same way as for a user
32794 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
32795 are permitted only in system filters are recognized.
32797 If you want to test the combined effect of a system filter and a user filter,
32798 you can use both &%-bF%& and &%-bf%& on the same command line.
32802 .section "Contents of a system filter" "SECID214"
32803 The language used to specify system filters is the same as for users' filter
32804 files. It is described in the separate end-user document &'Exim's interface to
32805 mail filtering'&. However, there are some additional features that are
32806 available only in system filters; these are described in subsequent sections.
32807 If they are encountered in a user's filter file or when testing with &%-bf%&,
32810 .cindex "frozen messages" "manual thaw; testing in filter"
32811 There are two special conditions which, though available in users' filter
32812 files, are designed for use in system filters. The condition &%first_delivery%&
32813 is true only for the first attempt at delivering a message, and
32814 &%manually_thawed%& is true only if the message has been frozen, and
32815 subsequently thawed by an admin user. An explicit forced delivery counts as a
32816 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
32818 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
32819 specify an &"unseen"& (non-significant) delivery, and that delivery does not
32820 succeed, it will not be tried again.
32821 If you want Exim to retry an unseen delivery until it succeeds, you should
32822 arrange to set it up every time the filter runs.
32824 When a system filter finishes running, the values of the variables &$n0$& &--
32825 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
32826 users' filter files. Thus a system filter can, for example, set up &"scores"&
32827 to which users' filter files can refer.
32831 .section "Additional variable for system filters" "SECID215"
32832 .vindex "&$recipients$&"
32833 The expansion variable &$recipients$&, containing a list of all the recipients
32834 of the message (separated by commas and white space), is available in system
32835 filters. It is not available in users' filters for privacy reasons.
32839 .section "Defer, freeze, and fail commands for system filters" "SECID216"
32840 .cindex "freezing messages"
32841 .cindex "message" "freezing"
32842 .cindex "message" "forced failure"
32843 .cindex "&%fail%&" "in system filter"
32844 .cindex "&%freeze%& in system filter"
32845 .cindex "&%defer%& in system filter"
32846 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
32847 always available in system filters, but are not normally enabled in users'
32848 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
32849 for the &(redirect)& router.) These commands can optionally be followed by the
32850 word &%text%& and a string containing an error message, for example:
32852 fail text "this message looks like spam to me"
32854 The keyword &%text%& is optional if the next character is a double quote.
32856 The &%defer%& command defers delivery of the original recipients of the
32857 message. The &%fail%& command causes all the original recipients to be failed,
32858 and a bounce message to be created. The &%freeze%& command suspends all
32859 delivery attempts for the original recipients. In all cases, any new deliveries
32860 that are specified by the filter are attempted as normal after the filter has
32863 The &%freeze%& command is ignored if the message has been manually unfrozen and
32864 not manually frozen since. This means that automatic freezing by a system
32865 filter can be used as a way of checking out suspicious messages. If a message
32866 is found to be all right, manually unfreezing it allows it to be delivered.
32868 .cindex "log" "&%fail%& command log line"
32869 .cindex "&%fail%&" "log line; reducing"
32870 The text given with a fail command is used as part of the bounce message as
32871 well as being written to the log. If the message is quite long, this can fill
32872 up a lot of log space when such failures are common. To reduce the size of the
32873 log message, Exim interprets the text in a special way if it starts with the
32874 two characters &`<<`& and contains &`>>`& later. The text between these two
32875 strings is written to the log, and the rest of the text is used in the bounce
32876 message. For example:
32878 fail "<<filter test 1>>Your message is rejected \
32879 because it contains attachments that we are \
32880 not prepared to receive."
32883 .cindex "loop" "caused by &%fail%&"
32884 Take great care with the &%fail%& command when basing the decision to fail on
32885 the contents of the message, because the bounce message will of course include
32886 the contents of the original message and will therefore trigger the &%fail%&
32887 command again (causing a mail loop) unless steps are taken to prevent this.
32888 Testing the &%error_message%& condition is one way to prevent this. You could
32891 if $message_body contains "this is spam" and not error_message
32892 then fail text "spam is not wanted here" endif
32894 though of course that might let through unwanted bounce messages. The
32895 alternative is clever checking of the body and/or headers to detect bounces
32896 generated by the filter.
32898 The interpretation of a system filter file ceases after a
32900 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
32901 set up earlier in the filter file are honoured, so you can use a sequence such
32907 to send a specified message when the system filter is freezing (or deferring or
32908 failing) a message. The normal deliveries for the message do not, of course,
32913 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
32914 .cindex "header lines" "adding; in system filter"
32915 .cindex "header lines" "removing; in system filter"
32916 .cindex "filter" "header lines; adding/removing"
32917 Two filter commands that are available only in system filters are:
32919 headers add <string>
32920 headers remove <string>
32922 The argument for the &%headers add%& is a string that is expanded and then
32923 added to the end of the message's headers. It is the responsibility of the
32924 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
32925 space is ignored, and if the string is otherwise empty, or if the expansion is
32926 forced to fail, the command has no effect.
32928 You can use &"\n"& within the string, followed by white space, to specify
32929 continued header lines. More than one header may be added in one command by
32930 including &"\n"& within the string without any following white space. For
32933 headers add "X-header-1: ....\n \
32934 continuation of X-header-1 ...\n\
32937 Note that the header line continuation white space after the first newline must
32938 be placed before the backslash that continues the input string, because white
32939 space after input continuations is ignored.
32941 The argument for &%headers remove%& is a colon-separated list of header names.
32942 This command applies only to those headers that are stored with the message;
32943 those that are added at delivery time (such as &'Envelope-To:'& and
32944 &'Return-Path:'&) cannot be removed by this means. If there is more than one
32945 header with the same name, they are all removed.
32947 The &%headers%& command in a system filter makes an immediate change to the set
32948 of header lines that was received with the message (with possible additions
32949 from ACL processing). Subsequent commands in the system filter operate on the
32950 modified set, which also forms the basis for subsequent message delivery.
32951 Unless further modified during routing or transporting, this set of headers is
32952 used for all recipients of the message.
32954 During routing and transporting, the variables that refer to the contents of
32955 header lines refer only to those lines that are in this set. Thus, header lines
32956 that are added by a system filter are visible to users' filter files and to all
32957 routers and transports. This contrasts with the manipulation of header lines by
32958 routers and transports, which is not immediate, but which instead is saved up
32959 until the message is actually being written (see section
32960 &<<SECTheadersaddrem>>&).
32962 If the message is not delivered at the first attempt, header lines that were
32963 added by the system filter are stored with the message, and so are still
32964 present at the next delivery attempt. Header lines that were removed are still
32965 present, but marked &"deleted"& so that they are not transported with the
32966 message. For this reason, it is usual to make the &%headers%& command
32967 conditional on &%first_delivery%& so that the set of header lines is not
32968 modified more than once.
32970 Because header modification in a system filter acts immediately, you have to
32971 use an indirect approach if you want to modify the contents of a header line.
32974 headers add "Old-Subject: $h_subject:"
32975 headers remove "Subject"
32976 headers add "Subject: new subject (was: $h_old-subject:)"
32977 headers remove "Old-Subject"
32982 .section "Setting an errors address in a system filter" "SECID217"
32983 .cindex "envelope sender"
32984 In a system filter, if a &%deliver%& command is followed by
32986 errors_to <some address>
32988 in order to change the envelope sender (and hence the error reporting) for that
32989 delivery, any address may be specified. (In a user filter, only the current
32990 user's address can be set.) For example, if some mail is being monitored, you
32993 unseen deliver monitor@spying.example errors_to root@local.example
32995 to take a copy which would not be sent back to the normal error reporting
32996 address if its delivery failed.
33000 .section "Per-address filtering" "SECTperaddfil"
33001 .vindex "&$domain$&"
33002 .vindex "&$local_part$&"
33003 In contrast to the system filter, which is run just once per message for each
33004 delivery attempt, it is also possible to set up a system-wide filtering
33005 operation that runs once for each recipient address. In this case, variables
33006 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
33007 filter file could be made dependent on them. This is an example of a router
33008 which implements such a filter:
33013 domains = +local_domains
33014 file = /central/filters/$local_part
33019 The filter is run in a separate process under its own uid. Therefore, either
33020 &%check_local_user%& must be set (as above), in which case the filter is run as
33021 the local user, or the &%user%& option must be used to specify which user to
33022 use. If both are set, &%user%& overrides.
33024 Care should be taken to ensure that none of the commands in the filter file
33025 specify a significant delivery if the message is to go on to be delivered to
33026 its intended recipient. The router will not then claim to have dealt with the
33027 address, so it will be passed on to subsequent routers to be delivered in the
33029 .ecindex IIDsysfil1
33030 .ecindex IIDsysfil2
33031 .ecindex IIDsysfil3
33038 . ////////////////////////////////////////////////////////////////////////////
33039 . ////////////////////////////////////////////////////////////////////////////
33041 .chapter "Message processing" "CHAPmsgproc"
33042 .scindex IIDmesproc "message" "general processing"
33043 Exim performs various transformations on the sender and recipient addresses of
33044 all messages that it handles, and also on the messages' header lines. Some of
33045 these are optional and configurable, while others always take place. All of
33046 this processing, except rewriting as a result of routing, and the addition or
33047 removal of header lines while delivering, happens when a message is received,
33048 before it is placed on Exim's queue.
33050 Some of the automatic processing takes place by default only for
33051 &"locally-originated"& messages. This adjective is used to describe messages
33052 that are not received over TCP/IP, but instead are passed to an Exim process on
33053 its standard input. This includes the interactive &"local SMTP"& case that is
33054 set up by the &%-bs%& command line option.
33056 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
33057 or ::1) are not considered to be locally-originated. Exim does not treat the
33058 loopback interface specially in any way.
33060 If you want the loopback interface to be treated specially, you must ensure
33061 that there are appropriate entries in your ACLs.
33066 .section "Submission mode for non-local messages" "SECTsubmodnon"
33067 .cindex "message" "submission"
33068 .cindex "submission mode"
33069 Processing that happens automatically for locally-originated messages (unless
33070 &%suppress_local_fixups%& is set) can also be requested for messages that are
33071 received over TCP/IP. The term &"submission mode"& is used to describe this
33072 state. Submission mode is set by the modifier
33074 control = submission
33076 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
33077 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
33078 a local submission, and is normally used when the source of the message is
33079 known to be an MUA running on a client host (as opposed to an MTA). For
33080 example, to set submission mode for messages originating on the IPv4 loopback
33081 interface, you could include the following in the MAIL ACL:
33083 warn hosts = 127.0.0.1
33084 control = submission
33086 .cindex "&%sender_retain%& submission option"
33087 There are some options that can be used when setting submission mode. A slash
33088 is used to separate options. For example:
33090 control = submission/sender_retain
33092 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
33093 true and &%local_from_check%& false for the current incoming message. The first
33094 of these allows an existing &'Sender:'& header in the message to remain, and
33095 the second suppresses the check to ensure that &'From:'& matches the
33096 authenticated sender. With this setting, Exim still fixes up messages by adding
33097 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
33098 attempt to check sender authenticity in header lines.
33100 When &%sender_retain%& is not set, a submission mode setting may specify a
33101 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
33104 control = submission/domain=some.domain
33106 The domain may be empty. How this value is used is described in sections
33107 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
33108 that allows you to specify the user's full name for inclusion in a created
33109 &'Sender:'& or &'From:'& header line. For example:
33111 accept authenticated = *
33112 control = submission/domain=wonderland.example/\
33113 name=${lookup {$authenticated_id} \
33114 lsearch {/etc/exim/namelist}}
33116 Because the name may contain any characters, including slashes, the &%name%&
33117 option must be given last. The remainder of the string is used as the name. For
33118 the example above, if &_/etc/exim/namelist_& contains:
33120 bigegg: Humpty Dumpty
33122 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
33125 Sender: Humpty Dumpty <bigegg@wonderland.example>
33127 .cindex "return path" "in submission mode"
33128 By default, submission mode forces the return path to the same address as is
33129 used to create the &'Sender:'& header. However, if &%sender_retain%& is
33130 specified, the return path is also left unchanged.
33132 &*Note*&: The changes caused by submission mode take effect after the predata
33133 ACL. This means that any sender checks performed before the fix-ups use the
33134 untrusted sender address specified by the user, not the trusted sender address
33135 specified by submission mode. Although this might be slightly unexpected, it
33136 does mean that you can configure ACL checks to spot that a user is trying to
33137 spoof another's address.
33139 .section "Line endings" "SECTlineendings"
33140 .cindex "line endings"
33141 .cindex "carriage return"
33143 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
33144 linefeed) is the line ending for messages transmitted over the Internet using
33145 SMTP over TCP/IP. However, within individual operating systems, different
33146 conventions are used. For example, Unix-like systems use just LF, but others
33147 use CRLF or just CR.
33149 Exim was designed for Unix-like systems, and internally, it stores messages
33150 using the system's convention of a single LF as a line terminator. When
33151 receiving a message, all line endings are translated to this standard format.
33152 Originally, it was thought that programs that passed messages directly to an
33153 MTA within an operating system would use that system's convention. Experience
33154 has shown that this is not the case; for example, there are Unix applications
33155 that use CRLF in this circumstance. For this reason, and for compatibility with
33156 other MTAs, the way Exim handles line endings for all messages is now as
33160 LF not preceded by CR is treated as a line ending.
33162 CR is treated as a line ending; if it is immediately followed by LF, the LF
33165 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
33166 nor a local message in the state where a line containing only a dot is a
33169 If a bare CR is encountered within a header line, an extra space is added after
33170 the line terminator so as not to end the header line. The reasoning behind this
33171 is that bare CRs in header lines are most likely either to be mistakes, or
33172 people trying to play silly games.
33174 If the first header line received in a message ends with CRLF, a subsequent
33175 bare LF in a header line is treated in the same way as a bare CR in a header
33183 .section "Unqualified addresses" "SECID218"
33184 .cindex "unqualified addresses"
33185 .cindex "address" "qualification"
33186 By default, Exim expects every envelope address it receives from an external
33187 host to be fully qualified. Unqualified addresses cause negative responses to
33188 SMTP commands. However, because SMTP is used as a means of transporting
33189 messages from MUAs running on personal workstations, there is sometimes a
33190 requirement to accept unqualified addresses from specific hosts or IP networks.
33192 Exim has two options that separately control which hosts may send unqualified
33193 sender or recipient addresses in SMTP commands, namely
33194 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
33195 cases, if an unqualified address is accepted, it is qualified by adding the
33196 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
33198 .oindex "&%qualify_domain%&"
33199 .oindex "&%qualify_recipient%&"
33200 Unqualified addresses in header lines are automatically qualified for messages
33201 that are locally originated, unless the &%-bnq%& option is given on the command
33202 line. For messages received over SMTP, unqualified addresses in header lines
33203 are qualified only if unqualified addresses are permitted in SMTP commands. In
33204 other words, such qualification is also controlled by
33205 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
33210 .section "The UUCP From line" "SECID219"
33211 .cindex "&""From""& line"
33212 .cindex "UUCP" "&""From""& line"
33213 .cindex "sender" "address"
33214 .oindex "&%uucp_from_pattern%&"
33215 .oindex "&%uucp_from_sender%&"
33216 .cindex "envelope sender"
33217 .cindex "Sendmail compatibility" "&""From""& line"
33218 Messages that have come from UUCP (and some other applications) often begin
33219 with a line containing the envelope sender and a timestamp, following the word
33220 &"From"&. Examples of two common formats are:
33222 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
33223 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
33225 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
33226 Exim recognizes such lines at the start of messages that are submitted to it
33227 via the command line (that is, on the standard input). It does not recognize
33228 such lines in incoming SMTP messages, unless the sending host matches
33229 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
33230 and &%ignore_fromline_local%& is set. The recognition is controlled by a
33231 regular expression that is defined by the &%uucp_from_pattern%& option, whose
33232 default value matches the two common cases shown above and puts the address
33233 that follows &"From"& into &$1$&.
33235 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
33236 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
33237 a trusted user, the message's sender address is constructed by expanding the
33238 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
33239 then parsed as an RFC 2822 address. If there is no domain, the local part is
33240 qualified with &%qualify_domain%& unless it is the empty string. However, if
33241 the command line &%-f%& option is used, it overrides the &"From"& line.
33243 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
33244 sender address is not changed. This is also the case for incoming SMTP messages
33245 that are permitted to contain &"From"& lines.
33247 Only one &"From"& line is recognized. If there is more than one, the second is
33248 treated as a data line that starts the body of the message, as it is not valid
33249 as a header line. This also happens if a &"From"& line is present in an
33250 incoming SMTP message from a source that is not permitted to send them.
33254 .section "Resent- header lines" "SECID220"
33255 .cindex "&%Resent-%& header lines"
33256 RFC 2822 makes provision for sets of header lines starting with the string
33257 &`Resent-`& to be added to a message when it is resent by the original
33258 recipient to somebody else. These headers are &'Resent-Date:'&,
33259 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
33260 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
33263 &'Resent fields are strictly informational. They MUST NOT be used in the normal
33264 processing of replies or other such automatic actions on messages.'&
33267 This leaves things a bit vague as far as other processing actions such as
33268 address rewriting are concerned. Exim treats &%Resent-%& header lines as
33272 A &'Resent-From:'& line that just contains the login id of the submitting user
33273 is automatically rewritten in the same way as &'From:'& (see below).
33275 If there's a rewriting rule for a particular header line, it is also applied to
33276 &%Resent-%& header lines of the same type. For example, a rule that rewrites
33277 &'From:'& also rewrites &'Resent-From:'&.
33279 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
33282 For a locally-submitted message,
33283 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
33284 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
33285 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
33286 included in log lines in this case.
33288 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
33289 &%Resent-%& header lines are present.
33295 .section "The Auto-Submitted: header line" "SECID221"
33296 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
33297 includes the header line:
33299 Auto-Submitted: auto-replied
33302 .section "The Bcc: header line" "SECID222"
33303 .cindex "&'Bcc:'& header line"
33304 If Exim is called with the &%-t%& option, to take recipient addresses from a
33305 message's header, it removes any &'Bcc:'& header line that may exist (after
33306 extracting its addresses). If &%-t%& is not present on the command line, any
33307 existing &'Bcc:'& is not removed.
33310 .section "The Date: header line" "SECID223"
33311 .cindex "&'Date:'& header line"
33312 If a locally-generated or submission-mode message has no &'Date:'& header line,
33313 Exim adds one, using the current date and time, unless the
33314 &%suppress_local_fixups%& control has been specified.
33316 .section "The Delivery-date: header line" "SECID224"
33317 .cindex "&'Delivery-date:'& header line"
33318 .oindex "&%delivery_date_remove%&"
33319 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
33320 set. Exim can be configured to add them to the final delivery of messages. (See
33321 the generic &%delivery_date_add%& transport option.) They should not be present
33322 in messages in transit. If the &%delivery_date_remove%& configuration option is
33323 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
33327 .section "The Envelope-to: header line" "SECID225"
33328 .cindex "&'Envelope-to:'& header line"
33329 .oindex "&%envelope_to_remove%&"
33330 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
33331 Exim can be configured to add them to the final delivery of messages. (See the
33332 generic &%envelope_to_add%& transport option.) They should not be present in
33333 messages in transit. If the &%envelope_to_remove%& configuration option is set
33334 (the default), Exim removes &'Envelope-to:'& header lines from incoming
33338 .section "The From: header line" "SECTthefrohea"
33339 .cindex "&'From:'& header line"
33340 .cindex "Sendmail compatibility" "&""From""& line"
33341 .cindex "message" "submission"
33342 .cindex "submission mode"
33343 If a submission-mode message does not contain a &'From:'& header line, Exim
33344 adds one if either of the following conditions is true:
33347 The envelope sender address is not empty (that is, this is not a bounce
33348 message). The added header line copies the envelope sender address.
33350 .vindex "&$authenticated_id$&"
33351 The SMTP session is authenticated and &$authenticated_id$& is not empty.
33353 .vindex "&$qualify_domain$&"
33354 If no domain is specified by the submission control, the local part is
33355 &$authenticated_id$& and the domain is &$qualify_domain$&.
33357 If a non-empty domain is specified by the submission control, the local
33358 part is &$authenticated_id$&, and the domain is the specified domain.
33360 If an empty domain is specified by the submission control,
33361 &$authenticated_id$& is assumed to be the complete address.
33365 A non-empty envelope sender takes precedence.
33367 If a locally-generated incoming message does not contain a &'From:'& header
33368 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
33369 containing the sender's address. The calling user's login name and full name
33370 are used to construct the address, as described in section &<<SECTconstr>>&.
33371 They are obtained from the password data by calling &[getpwuid()]& (but see the
33372 &%unknown_login%& configuration option). The address is qualified with
33373 &%qualify_domain%&.
33375 For compatibility with Sendmail, if an incoming, non-SMTP message has a
33376 &'From:'& header line containing just the unqualified login name of the calling
33377 user, this is replaced by an address containing the user's login name and full
33378 name as described in section &<<SECTconstr>>&.
33381 .section "The Message-ID: header line" "SECID226"
33382 .cindex "&'Message-ID:'& header line"
33383 .cindex "message" "submission"
33384 .oindex "&%message_id_header_text%&"
33385 If a locally-generated or submission-mode incoming message does not contain a
33386 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
33387 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
33388 to the message. If there are any &'Resent-:'& headers in the message, it
33389 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
33390 message id, preceded by the letter E to ensure it starts with a letter, and
33391 followed by @ and the primary host name. Additional information can be included
33392 in this header line by setting the &%message_id_header_text%& and/or
33393 &%message_id_header_domain%& options.
33396 .section "The Received: header line" "SECID227"
33397 .cindex "&'Received:'& header line"
33398 A &'Received:'& header line is added at the start of every message. The
33399 contents are defined by the &%received_header_text%& configuration option, and
33400 Exim automatically adds a semicolon and a timestamp to the configured string.
33402 The &'Received:'& header is generated as soon as the message's header lines
33403 have been received. At this stage, the timestamp in the &'Received:'& header
33404 line is the time that the message started to be received. This is the value
33405 that is seen by the DATA ACL and by the &[local_scan()]& function.
33407 Once a message is accepted, the timestamp in the &'Received:'& header line is
33408 changed to the time of acceptance, which is (apart from a small delay while the
33409 -H spool file is written) the earliest time at which delivery could start.
33412 .section "The References: header line" "SECID228"
33413 .cindex "&'References:'& header line"
33414 Messages created by the &(autoreply)& transport include a &'References:'&
33415 header line. This is constructed according to the rules that are described in
33416 section 3.64 of RFC 2822 (which states that replies should contain such a
33417 header line), and section 3.14 of RFC 3834 (which states that automatic
33418 responses are not different in this respect). However, because some mail
33419 processing software does not cope well with very long header lines, no more
33420 than 12 message IDs are copied from the &'References:'& header line in the
33421 incoming message. If there are more than 12, the first one and then the final
33422 11 are copied, before adding the message ID of the incoming message.
33426 .section "The Return-path: header line" "SECID229"
33427 .cindex "&'Return-path:'& header line"
33428 .oindex "&%return_path_remove%&"
33429 &'Return-path:'& header lines are defined as something an MTA may insert when
33430 it does the final delivery of messages. (See the generic &%return_path_add%&
33431 transport option.) Therefore, they should not be present in messages in
33432 transit. If the &%return_path_remove%& configuration option is set (the
33433 default), Exim removes &'Return-path:'& header lines from incoming messages.
33437 .section "The Sender: header line" "SECTthesenhea"
33438 .cindex "&'Sender:'& header line"
33439 .cindex "message" "submission"
33440 For a locally-originated message from an untrusted user, Exim may remove an
33441 existing &'Sender:'& header line, and it may add a new one. You can modify
33442 these actions by setting the &%local_sender_retain%& option true, the
33443 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
33446 When a local message is received from an untrusted user and
33447 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
33448 control has not been set, a check is made to see if the address given in the
33449 &'From:'& header line is the correct (local) sender of the message. The address
33450 that is expected has the login name as the local part and the value of
33451 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
33452 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
33453 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
33454 line is added to the message.
33456 If you set &%local_from_check%& false, this checking does not occur. However,
33457 the removal of an existing &'Sender:'& line still happens, unless you also set
33458 &%local_sender_retain%& to be true. It is not possible to set both of these
33459 options true at the same time.
33461 .cindex "submission mode"
33462 By default, no processing of &'Sender:'& header lines is done for messages
33463 received over TCP/IP or for messages submitted by trusted users. However, when
33464 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
33465 not specified on the submission control, the following processing takes place:
33467 .vindex "&$authenticated_id$&"
33468 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
33469 authenticated, and &$authenticated_id$& is not empty, a sender address is
33470 created as follows:
33473 .vindex "&$qualify_domain$&"
33474 If no domain is specified by the submission control, the local part is
33475 &$authenticated_id$& and the domain is &$qualify_domain$&.
33477 If a non-empty domain is specified by the submission control, the local part
33478 is &$authenticated_id$&, and the domain is the specified domain.
33480 If an empty domain is specified by the submission control,
33481 &$authenticated_id$& is assumed to be the complete address.
33484 This address is compared with the address in the &'From:'& header line. If they
33485 are different, a &'Sender:'& header line containing the created address is
33486 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
33487 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
33489 .cindex "return path" "created from &'Sender:'&"
33490 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
33491 the message (the envelope sender address) is changed to be the same address,
33492 except in the case of submission mode when &%sender_retain%& is specified.
33496 .section "Adding and removing header lines in routers and transports" &&&
33497 "SECTheadersaddrem"
33498 .cindex "header lines" "adding; in router or transport"
33499 .cindex "header lines" "removing; in router or transport"
33500 When a message is delivered, the addition and removal of header lines can be
33501 specified in a system filter, or on any of the routers and transports that
33502 process the message. Section &<<SECTaddremheasys>>& contains details about
33503 modifying headers in a system filter. Header lines can also be added in an ACL
33504 as a message is received (see section &<<SECTaddheadacl>>&).
33506 In contrast to what happens in a system filter, header modifications that are
33507 specified on routers and transports apply only to the particular recipient
33508 addresses that are being processed by those routers and transports. These
33509 changes do not actually take place until a copy of the message is being
33510 transported. Therefore, they do not affect the basic set of header lines, and
33511 they do not affect the values of the variables that refer to header lines.
33513 &*Note*&: In particular, this means that any expansions in the configuration of
33514 the transport cannot refer to the modified header lines, because such
33515 expansions all occur before the message is actually transported.
33517 For both routers and transports, the argument of a &%headers_add%&
33518 option must be in the form of one or more RFC 2822 header lines, separated by
33519 newlines (coded as &"\n"&). For example:
33521 headers_add = X-added-header: added by $primary_hostname\n\
33522 X-added-second: another added header line
33524 Exim does not check the syntax of these added header lines.
33526 Multiple &%headers_add%& options for a single router or transport can be
33527 specified; the values will append to a single list of header lines.
33528 Each header-line is separately expanded.
33530 The argument of a &%headers_remove%& option must consist of a colon-separated
33531 list of header names. This is confusing, because header names themselves are
33532 often terminated by colons. In this case, the colons are the list separators,
33533 not part of the names. For example:
33535 headers_remove = return-receipt-to:acknowledge-to
33538 Multiple &%headers_remove%& options for a single router or transport can be
33539 specified; the arguments will append to a single header-names list.
33540 Each item is separately expanded.
33541 Note that colons in complex expansions which are used to
33542 form all or part of a &%headers_remove%& list
33543 will act as list separators.
33545 When &%headers_add%& or &%headers_remove%& is specified on a router,
33546 items are expanded at routing time,
33547 and then associated with all addresses that are
33548 accepted by that router, and also with any new addresses that it generates. If
33549 an address passes through several routers as a result of aliasing or
33550 forwarding, the changes are cumulative.
33552 .oindex "&%unseen%&"
33553 However, this does not apply to multiple routers that result from the use of
33554 the &%unseen%& option. Any header modifications that were specified by the
33555 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
33557 Addresses that end up with different &%headers_add%& or &%headers_remove%&
33558 settings cannot be delivered together in a batch, so a transport is always
33559 dealing with a set of addresses that have the same header-processing
33562 The transport starts by writing the original set of header lines that arrived
33563 with the message, possibly modified by the system filter. As it writes out
33564 these lines, it consults the list of header names that were attached to the
33565 recipient address(es) by &%headers_remove%& options in routers, and it also
33566 consults the transport's own &%headers_remove%& option. Header lines whose
33567 names are on either of these lists are not written out. If there are multiple
33568 instances of any listed header, they are all skipped.
33570 After the remaining original header lines have been written, new header
33571 lines that were specified by routers' &%headers_add%& options are written, in
33572 the order in which they were attached to the address. These are followed by any
33573 header lines specified by the transport's &%headers_add%& option.
33575 This way of handling header line modifications in routers and transports has
33576 the following consequences:
33579 The original set of header lines, possibly modified by the system filter,
33580 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
33581 to it, at all times.
33583 Header lines that are added by a router's
33584 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
33585 expansion syntax in subsequent routers or the transport.
33587 Conversely, header lines that are specified for removal by &%headers_remove%&
33588 in a router remain visible to subsequent routers and the transport.
33590 Headers added to an address by &%headers_add%& in a router cannot be removed by
33591 a later router or by a transport.
33593 An added header can refer to the contents of an original header that is to be
33594 removed, even it has the same name as the added header. For example:
33596 headers_remove = subject
33597 headers_add = Subject: new subject (was: $h_subject:)
33601 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
33602 for a &(redirect)& router that has the &%one_time%& option set.
33608 .section "Constructed addresses" "SECTconstr"
33609 .cindex "address" "constructed"
33610 .cindex "constructed address"
33611 When Exim constructs a sender address for a locally-generated message, it uses
33614 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
33618 Zaphod Beeblebrox <zaphod@end.univ.example>
33620 The user name is obtained from the &%-F%& command line option if set, or
33621 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
33622 &"gecos"& field from the password entry. If the &"gecos"& field contains an
33623 ampersand character, this is replaced by the login name with the first letter
33624 upper cased, as is conventional in a number of operating systems. See the
33625 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
33626 The &%unknown_username%& option can be used to specify user names in cases when
33627 there is no password file entry.
33630 In all cases, the user name is made to conform to RFC 2822 by quoting all or
33631 parts of it if necessary. In addition, if it contains any non-printing
33632 characters, it is encoded as described in RFC 2047, which defines a way of
33633 including non-ASCII characters in header lines. The value of the
33634 &%headers_charset%& option specifies the name of the encoding that is used (the
33635 characters are assumed to be in this encoding). The setting of
33636 &%print_topbitchars%& controls whether characters with the top bit set (that
33637 is, with codes greater than 127) count as printing characters or not.
33641 .section "Case of local parts" "SECID230"
33642 .cindex "case of local parts"
33643 .cindex "local part" "case of"
33644 RFC 2822 states that the case of letters in the local parts of addresses cannot
33645 be assumed to be non-significant. Exim preserves the case of local parts of
33646 addresses, but by default it uses a lower-cased form when it is routing,
33647 because on most Unix systems, usernames are in lower case and case-insensitive
33648 routing is required. However, any particular router can be made to use the
33649 original case for local parts by setting the &%caseful_local_part%& generic
33652 .cindex "mixed-case login names"
33653 If you must have mixed-case user names on your system, the best way to proceed,
33654 assuming you want case-independent handling of incoming email, is to set up
33655 your first router to convert incoming local parts in your domains to the
33656 correct case by means of a file lookup. For example:
33660 domains = +local_domains
33661 data = ${lookup{$local_part}cdb\
33662 {/etc/usercased.cdb}{$value}fail}\
33665 For this router, the local part is forced to lower case by the default action
33666 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
33667 up a new local part in the correct case. If you then set &%caseful_local_part%&
33668 on any subsequent routers which process your domains, they will operate on
33669 local parts with the correct case in a case-sensitive manner.
33673 .section "Dots in local parts" "SECID231"
33674 .cindex "dot" "in local part"
33675 .cindex "local part" "dots in"
33676 RFC 2822 forbids empty components in local parts. That is, an unquoted local
33677 part may not begin or end with a dot, nor have two consecutive dots in the
33678 middle. However, it seems that many MTAs do not enforce this, so Exim permits
33679 empty components for compatibility.
33683 .section "Rewriting addresses" "SECID232"
33684 .cindex "rewriting" "addresses"
33685 Rewriting of sender and recipient addresses, and addresses in headers, can
33686 happen automatically, or as the result of configuration options, as described
33687 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
33688 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
33690 Automatic rewriting includes qualification, as mentioned above. The other case
33691 in which it can happen is when an incomplete non-local domain is given. The
33692 routing process may cause this to be expanded into the full domain name. For
33693 example, a header such as
33697 might get rewritten as
33699 To: hare@teaparty.wonderland.fict.example
33701 Rewriting as a result of routing is the one kind of message processing that
33702 does not happen at input time, as it cannot be done until the address has
33705 Strictly, one should not do &'any'& deliveries of a message until all its
33706 addresses have been routed, in case any of the headers get changed as a
33707 result of routing. However, doing this in practice would hold up many
33708 deliveries for unreasonable amounts of time, just because one address could not
33709 immediately be routed. Exim therefore does not delay other deliveries when
33710 routing of one or more addresses is deferred.
33711 .ecindex IIDmesproc
33715 . ////////////////////////////////////////////////////////////////////////////
33716 . ////////////////////////////////////////////////////////////////////////////
33718 .chapter "SMTP processing" "CHAPSMTP"
33719 .scindex IIDsmtpproc1 "SMTP" "processing details"
33720 .scindex IIDsmtpproc2 "LMTP" "processing details"
33721 Exim supports a number of different ways of using the SMTP protocol, and its
33722 LMTP variant, which is an interactive protocol for transferring messages into a
33723 closed mail store application. This chapter contains details of how SMTP is
33724 processed. For incoming mail, the following are available:
33727 SMTP over TCP/IP (Exim daemon or &'inetd'&);
33729 SMTP over the standard input and output (the &%-bs%& option);
33731 Batched SMTP on the standard input (the &%-bS%& option).
33734 For mail delivery, the following are available:
33737 SMTP over TCP/IP (the &(smtp)& transport);
33739 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
33742 LMTP over a pipe to a process running in the local host (the &(lmtp)&
33745 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
33746 the &%use_bsmtp%& option set).
33749 &'Batched SMTP'& is the name for a process in which batches of messages are
33750 stored in or read from files (or pipes), in a format in which SMTP commands are
33751 used to contain the envelope information.
33755 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
33756 .cindex "SMTP" "outgoing over TCP/IP"
33757 .cindex "outgoing SMTP over TCP/IP"
33758 .cindex "LMTP" "over TCP/IP"
33759 .cindex "outgoing LMTP over TCP/IP"
33762 .cindex "SIZE option on MAIL command"
33763 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
33764 The &%protocol%& option selects which protocol is to be used, but the actual
33765 processing is the same in both cases.
33767 If, in response to its EHLO command, Exim is told that the SIZE
33768 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
33769 command. The value of <&'n'&> is the message size plus the value of the
33770 &%size_addition%& option (default 1024) to allow for additions to the message
33771 such as per-transport header lines, or changes made in a
33772 .cindex "transport" "filter"
33773 .cindex "filter" "transport filter"
33774 transport filter. If &%size_addition%& is set negative, the use of SIZE is
33777 If the remote server advertises support for PIPELINING, Exim uses the
33778 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
33779 required for the transaction.
33781 If the remote server advertises support for the STARTTLS command, and Exim
33782 was built to support TLS encryption, it tries to start a TLS session unless the
33783 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
33784 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
33785 is called for verification.
33787 If the remote server advertises support for the AUTH command, Exim scans
33788 the authenticators configuration for any suitable client settings, as described
33789 in chapter &<<CHAPSMTPAUTH>>&.
33791 .cindex "carriage return"
33793 Responses from the remote host are supposed to be terminated by CR followed by
33794 LF. However, there are known to be hosts that do not send CR characters, so in
33795 order to be able to interwork with such hosts, Exim treats LF on its own as a
33798 If a message contains a number of different addresses, all those with the same
33799 characteristics (for example, the same envelope sender) that resolve to the
33800 same set of hosts, in the same order, are sent in a single SMTP transaction,
33801 even if they are for different domains, unless there are more than the setting
33802 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
33803 they are split into groups containing no more than &%max_rcpt%&s addresses
33804 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
33805 in parallel sessions. The order of hosts with identical MX values is not
33806 significant when checking whether addresses can be batched in this way.
33808 When the &(smtp)& transport suffers a temporary failure that is not
33809 message-related, Exim updates its transport-specific database, which contains
33810 records indexed by host name that remember which messages are waiting for each
33811 particular host. It also updates the retry database with new retry times.
33813 .cindex "hints database" "retry keys"
33814 Exim's retry hints are based on host name plus IP address, so if one address of
33815 a multi-homed host is broken, it will soon be skipped most of the time.
33816 See the next section for more detail about error handling.
33818 .cindex "SMTP" "passed connection"
33819 .cindex "SMTP" "batching over TCP/IP"
33820 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
33821 looks in the hints database for the transport to see if there are any queued
33822 messages waiting for the host to which it is connected. If it finds one, it
33823 creates a new Exim process using the &%-MC%& option (which can only be used by
33824 a process running as root or the Exim user) and passes the TCP/IP socket to it
33825 so that it can deliver another message using the same socket. The new process
33826 does only those deliveries that are routed to the connected host, and may in
33827 turn pass the socket on to a third process, and so on.
33829 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
33830 limit the number of messages sent down a single TCP/IP connection.
33832 .cindex "asterisk" "after IP address"
33833 The second and subsequent messages delivered down an existing connection are
33834 identified in the main log by the addition of an asterisk after the closing
33835 square bracket of the IP address.
33840 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
33841 .cindex "error" "in outgoing SMTP"
33842 .cindex "SMTP" "errors in outgoing"
33843 .cindex "host" "error"
33844 Three different kinds of error are recognized for outgoing SMTP: host errors,
33845 message errors, and recipient errors.
33848 .vitem "&*Host errors*&"
33849 A host error is not associated with a particular message or with a
33850 particular recipient of a message. The host errors are:
33853 Connection refused or timed out,
33855 Any error response code on connection,
33857 Any error response code to EHLO or HELO,
33859 Loss of connection at any time, except after &"."&,
33861 I/O errors at any time,
33863 Timeouts during the session, other than in response to MAIL, RCPT or
33864 the &"."& at the end of the data.
33867 For a host error, a permanent error response on connection, or in response to
33868 EHLO, causes all addresses routed to the host to be failed. Any other host
33869 error causes all addresses to be deferred, and retry data to be created for the
33870 host. It is not tried again, for any message, until its retry time arrives. If
33871 the current set of addresses are not all delivered in this run (to some
33872 alternative host), the message is added to the list of those waiting for this
33873 host, so if it is still undelivered when a subsequent successful delivery is
33874 made to the host, it will be sent down the same SMTP connection.
33876 .vitem "&*Message errors*&"
33877 .cindex "message" "error"
33878 A message error is associated with a particular message when sent to a
33879 particular host, but not with a particular recipient of the message. The
33880 message errors are:
33883 Any error response code to MAIL, DATA, or the &"."& that terminates
33886 Timeout after MAIL,
33888 Timeout or loss of connection after the &"."& that terminates the data. A
33889 timeout after the DATA command itself is treated as a host error, as is loss of
33890 connection at any other time.
33893 For a message error, a permanent error response (5&'xx'&) causes all addresses
33894 to be failed, and a delivery error report to be returned to the sender. A
33895 temporary error response (4&'xx'&), or one of the timeouts, causes all
33896 addresses to be deferred. Retry data is not created for the host, but instead,
33897 a retry record for the combination of host plus message id is created. The
33898 message is not added to the list of those waiting for this host. This ensures
33899 that the failing message will not be sent to this host again until the retry
33900 time arrives. However, other messages that are routed to the host are not
33901 affected, so if it is some property of the message that is causing the error,
33902 it will not stop the delivery of other mail.
33904 If the remote host specified support for the SIZE parameter in its response
33905 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
33906 over-large message will cause a message error because the error arrives as a
33909 .vitem "&*Recipient errors*&"
33910 .cindex "recipient" "error"
33911 A recipient error is associated with a particular recipient of a message. The
33912 recipient errors are:
33915 Any error response to RCPT,
33917 Timeout after RCPT.
33920 For a recipient error, a permanent error response (5&'xx'&) causes the
33921 recipient address to be failed, and a bounce message to be returned to the
33922 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
33923 address to be deferred, and routing retry data to be created for it. This is
33924 used to delay processing of the address in subsequent queue runs, until its
33925 routing retry time arrives. This applies to all messages, but because it
33926 operates only in queue runs, one attempt will be made to deliver a new message
33927 to the failing address before the delay starts to operate. This ensures that,
33928 if the failure is really related to the message rather than the recipient
33929 (&"message too big for this recipient"& is a possible example), other messages
33930 have a chance of getting delivered. If a delivery to the address does succeed,
33931 the retry information gets cleared, so all stuck messages get tried again, and
33932 the retry clock is reset.
33934 The message is not added to the list of those waiting for this host. Use of the
33935 host for other messages is unaffected, and except in the case of a timeout,
33936 other recipients are processed independently, and may be successfully delivered
33937 in the current SMTP session. After a timeout it is of course impossible to
33938 proceed with the session, so all addresses get deferred. However, those other
33939 than the one that failed do not suffer any subsequent retry delays. Therefore,
33940 if one recipient is causing trouble, the others have a chance of getting
33941 through when a subsequent delivery attempt occurs before the failing
33942 recipient's retry time.
33945 In all cases, if there are other hosts (or IP addresses) available for the
33946 current set of addresses (for example, from multiple MX records), they are
33947 tried in this run for any undelivered addresses, subject of course to their
33948 own retry data. In other words, recipient error retry data does not take effect
33949 until the next delivery attempt.
33951 Some hosts have been observed to give temporary error responses to every
33952 MAIL command at certain times (&"insufficient space"& has been seen). It
33953 would be nice if such circumstances could be recognized, and defer data for the
33954 host itself created, but this is not possible within the current Exim design.
33955 What actually happens is that retry data for every (host, message) combination
33958 The reason that timeouts after MAIL and RCPT are treated specially is that
33959 these can sometimes arise as a result of the remote host's verification
33960 procedures. Exim makes this assumption, and treats them as if a temporary error
33961 response had been received. A timeout after &"."& is treated specially because
33962 it is known that some broken implementations fail to recognize the end of the
33963 message if the last character of the last line is a binary zero. Thus, it is
33964 helpful to treat this case as a message error.
33966 Timeouts at other times are treated as host errors, assuming a problem with the
33967 host, or the connection to it. If a timeout after MAIL, RCPT,
33968 or &"."& is really a connection problem, the assumption is that at the next try
33969 the timeout is likely to occur at some other point in the dialogue, causing it
33970 then to be treated as a host error.
33972 There is experimental evidence that some MTAs drop the connection after the
33973 terminating &"."& if they do not like the contents of the message for some
33974 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
33975 should be given. That is why Exim treats this case as a message rather than a
33976 host error, in order not to delay other messages to the same host.
33981 .section "Incoming SMTP messages over TCP/IP" "SECID233"
33982 .cindex "SMTP" "incoming over TCP/IP"
33983 .cindex "incoming SMTP over TCP/IP"
33986 Incoming SMTP messages can be accepted in one of two ways: by running a
33987 listening daemon, or by using &'inetd'&. In the latter case, the entry in
33988 &_/etc/inetd.conf_& should be like this:
33990 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
33992 Exim distinguishes between this case and the case of a locally running user
33993 agent using the &%-bs%& option by checking whether or not the standard input is
33994 a socket. When it is, either the port must be privileged (less than 1024), or
33995 the caller must be root or the Exim user. If any other user passes a socket
33996 with an unprivileged port number, Exim prints a message on the standard error
33997 stream and exits with an error code.
33999 By default, Exim does not make a log entry when a remote host connects or
34000 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
34001 unexpected. It can be made to write such log entries by setting the
34002 &%smtp_connection%& log selector.
34004 .cindex "carriage return"
34006 Commands from the remote host are supposed to be terminated by CR followed by
34007 LF. However, there are known to be hosts that do not send CR characters. In
34008 order to be able to interwork with such hosts, Exim treats LF on its own as a
34010 Furthermore, because common code is used for receiving messages from all
34011 sources, a CR on its own is also interpreted as a line terminator. However, the
34012 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
34014 .cindex "EHLO" "invalid data"
34015 .cindex "HELO" "invalid data"
34016 One area that sometimes gives rise to problems concerns the EHLO or
34017 HELO commands. Some clients send syntactically invalid versions of these
34018 commands, which Exim rejects by default. (This is nothing to do with verifying
34019 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
34020 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
34021 match the broken hosts that send invalid commands.
34023 .cindex "SIZE option on MAIL command"
34024 .cindex "MAIL" "SIZE option"
34025 The amount of disk space available is checked whenever SIZE is received on
34026 a MAIL command, independently of whether &%message_size_limit%& or
34027 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
34028 false. A temporary error is given if there is not enough space. If
34029 &%check_spool_space%& is set, the check is for that amount of space plus the
34030 value given with SIZE, that is, it checks that the addition of the incoming
34031 message will not reduce the space below the threshold.
34033 When a message is successfully received, Exim includes the local message id in
34034 its response to the final &"."& that terminates the data. If the remote host
34035 logs this text it can help with tracing what has happened to a message.
34037 The Exim daemon can limit the number of simultaneous incoming connections it is
34038 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
34039 number of simultaneous incoming connections from a single remote host (see the
34040 &%smtp_accept_max_per_host%& option). Additional connection attempts are
34041 rejected using the SMTP temporary error code 421.
34043 The Exim daemon does not rely on the SIGCHLD signal to detect when a
34044 subprocess has finished, as this can get lost at busy times. Instead, it looks
34045 for completed subprocesses every time it wakes up. Provided there are other
34046 things happening (new incoming calls, starts of queue runs), completed
34047 processes will be noticed and tidied away. On very quiet systems you may
34048 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
34049 it will be noticed when the daemon next wakes up.
34051 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
34052 and can also be set up to reject SMTP calls from non-reserved hosts at times of
34053 high system load &-- for details see the &%smtp_accept_reserve%&,
34054 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
34055 applies in both the daemon and &'inetd'& cases.
34057 Exim normally starts a delivery process for each message received, though this
34058 can be varied by means of the &%-odq%& command line option and the
34059 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
34060 number of simultaneously running delivery processes started in this way from
34061 SMTP input can be limited by the &%smtp_accept_queue%& and
34062 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
34063 subsequently received messages are just put on the input queue without starting
34064 a delivery process.
34066 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
34067 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
34068 started up from the &'inetd'& daemon, because in that case each connection is
34069 handled by an entirely independent Exim process. Control by load average is,
34070 however, available with &'inetd'&.
34072 Exim can be configured to verify addresses in incoming SMTP commands as they
34073 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
34074 to rewrite addresses at this time &-- before any syntax checking is done. See
34075 section &<<SECTrewriteS>>&.
34077 Exim can also be configured to limit the rate at which a client host submits
34078 MAIL and RCPT commands in a single SMTP session. See the
34079 &%smtp_ratelimit_hosts%& option.
34083 .section "Unrecognized SMTP commands" "SECID234"
34084 .cindex "SMTP" "unrecognized commands"
34085 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
34086 commands during a single SMTP connection, it drops the connection after sending
34087 the error response to the last command. The default value for
34088 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
34089 abuse that subvert web servers into making connections to SMTP ports; in these
34090 circumstances, a number of non-SMTP lines are sent first.
34093 .section "Syntax and protocol errors in SMTP commands" "SECID235"
34094 .cindex "SMTP" "syntax errors"
34095 .cindex "SMTP" "protocol errors"
34096 A syntax error is detected if an SMTP command is recognized, but there is
34097 something syntactically wrong with its data, for example, a malformed email
34098 address in a RCPT command. Protocol errors include invalid command
34099 sequencing such as RCPT before MAIL. If Exim receives more than
34100 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
34101 drops the connection after sending the error response to the last command. The
34102 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
34103 broken clients that loop sending bad commands (yes, it has been seen).
34107 .section "Use of non-mail SMTP commands" "SECID236"
34108 .cindex "SMTP" "non-mail commands"
34109 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
34110 DATA. Exim counts such commands, and drops the connection if there are too
34111 many of them in a single SMTP session. This action catches some
34112 denial-of-service attempts and things like repeated failing AUTHs, or a mad
34113 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
34114 defines what &"too many"& means. Its default value is 10.
34116 When a new message is expected, one occurrence of RSET is not counted. This
34117 allows a client to send one RSET between messages (this is not necessary,
34118 but some clients do it). Exim also allows one uncounted occurrence of HELO
34119 or EHLO, and one occurrence of STARTTLS between messages. After
34120 starting up a TLS session, another EHLO is expected, and so it too is not
34123 The first occurrence of AUTH in a connection, or immediately following
34124 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
34125 RCPT, DATA, and QUIT are counted.
34127 You can control which hosts are subject to the limit set by
34128 &%smtp_accept_max_nonmail%& by setting
34129 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
34130 the limit apply to all hosts. This option means that you can exclude any
34131 specific badly-behaved hosts that you have to live with.
34136 .section "The VRFY and EXPN commands" "SECID237"
34137 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
34138 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
34139 appropriate) in order to decide whether the command should be accepted or not.
34141 .cindex "VRFY" "processing"
34142 When no ACL is defined for VRFY, or if it rejects without
34143 setting an explicit response code, the command is accepted
34144 (with a 252 SMTP response code)
34145 in order to support awkward clients that do a VRFY before every RCPT.
34146 When VRFY is accepted, it runs exactly the same code as when Exim is
34147 called with the &%-bv%& option, and returns 250/451/550
34148 SMTP response codes.
34150 .cindex "EXPN" "processing"
34151 If no ACL for EXPN is defined, the command is rejected.
34152 When EXPN is accepted, a single-level expansion of the address is done.
34153 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
34154 than a verification (the &%-bv%& option). If an unqualified local part is given
34155 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
34156 of VRFY and EXPN commands are logged on the main and reject logs, and
34157 VRFY verification failures are logged on the main log for consistency with
34162 .section "The ETRN command" "SECTETRN"
34163 .cindex "ETRN" "processing"
34164 RFC 1985 describes an SMTP command called ETRN that is designed to
34165 overcome the security problems of the TURN command (which has fallen into
34166 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
34167 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
34168 should be accepted or not. If no ACL is defined, the command is rejected.
34170 The ETRN command is concerned with &"releasing"& messages that are awaiting
34171 delivery to certain hosts. As Exim does not organize its message queue by host,
34172 the only form of ETRN that is supported by default is the one where the
34173 text starts with the &"#"& prefix, in which case the remainder of the text is
34174 specific to the SMTP server. A valid ETRN command causes a run of Exim with
34175 the &%-R%& option to happen, with the remainder of the ETRN text as its
34176 argument. For example,
34184 which causes a delivery attempt on all messages with undelivered addresses
34185 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
34186 default), Exim prevents the simultaneous execution of more than one queue run
34187 for the same argument string as a result of an ETRN command. This stops
34188 a misbehaving client from starting more than one queue runner at once.
34190 .cindex "hints database" "ETRN serialization"
34191 Exim implements the serialization by means of a hints database in which a
34192 record is written whenever a process is started by ETRN, and deleted when
34193 the process completes. However, Exim does not keep the SMTP session waiting for
34194 the ETRN process to complete. Once ETRN is accepted, the client is sent
34195 a &"success"& return code. Obviously there is scope for hints records to get
34196 left lying around if there is a system or program crash. To guard against this,
34197 Exim ignores any records that are more than six hours old.
34199 .oindex "&%smtp_etrn_command%&"
34200 For more control over what ETRN does, the &%smtp_etrn_command%& option can
34201 used. This specifies a command that is run whenever ETRN is received,
34202 whatever the form of its argument. For
34205 smtp_etrn_command = /etc/etrn_command $domain \
34206 $sender_host_address
34208 .vindex "&$domain$&"
34209 The string is split up into arguments which are independently expanded. The
34210 expansion variable &$domain$& is set to the argument of the ETRN command,
34211 and no syntax checking is done on the contents of this argument. Exim does not
34212 wait for the command to complete, so its status code is not checked. Exim runs
34213 under its own uid and gid when receiving incoming SMTP, so it is not possible
34214 for it to change them before running the command.
34218 .section "Incoming local SMTP" "SECID238"
34219 .cindex "SMTP" "local incoming"
34220 Some user agents use SMTP to pass messages to their local MTA using the
34221 standard input and output, as opposed to passing the envelope on the command
34222 line and writing the message to the standard input. This is supported by the
34223 &%-bs%& option. This form of SMTP is handled in the same way as incoming
34224 messages over TCP/IP (including the use of ACLs), except that the envelope
34225 sender given in a MAIL command is ignored unless the caller is trusted. In
34226 an ACL you can detect this form of SMTP input by testing for an empty host
34227 identification. It is common to have this as the first line in the ACL that
34228 runs for RCPT commands:
34232 This accepts SMTP messages from local processes without doing any other tests.
34236 .section "Outgoing batched SMTP" "SECTbatchSMTP"
34237 .cindex "SMTP" "batched outgoing"
34238 .cindex "batched SMTP output"
34239 Both the &(appendfile)& and &(pipe)& transports can be used for handling
34240 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
34241 be output in BSMTP format. No SMTP responses are possible for this form of
34242 delivery. All it is doing is using SMTP commands as a way of transmitting the
34243 envelope along with the message.
34245 The message is written to the file or pipe preceded by the SMTP commands
34246 MAIL and RCPT, and followed by a line containing a single dot. Lines in
34247 the message that start with a dot have an extra dot added. The SMTP command
34248 HELO is not normally used. If it is required, the &%message_prefix%& option
34249 can be used to specify it.
34251 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
34252 one recipient address at a time by default. However, you can arrange for them
34253 to handle several addresses at once by setting the &%batch_max%& option. When
34254 this is done for BSMTP, messages may contain multiple RCPT commands. See
34255 chapter &<<CHAPbatching>>& for more details.
34258 When one or more addresses are routed to a BSMTP transport by a router that
34259 sets up a host list, the name of the first host on the list is available to the
34260 transport in the variable &$host$&. Here is an example of such a transport and
34265 driver = manualroute
34266 transport = smtp_appendfile
34267 route_list = domain.example batch.host.example
34271 driver = appendfile
34272 directory = /var/bsmtp/$host
34277 This causes messages addressed to &'domain.example'& to be written in BSMTP
34278 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
34279 message (unless there are more than 1000 recipients).
34283 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
34284 .cindex "SMTP" "batched incoming"
34285 .cindex "batched SMTP input"
34286 The &%-bS%& command line option causes Exim to accept one or more messages by
34287 reading SMTP on the standard input, but to generate no responses. If the caller
34288 is trusted, the senders in the MAIL commands are believed; otherwise the
34289 sender is always the caller of Exim. Unqualified senders and receivers are not
34290 rejected (there seems little point) but instead just get qualified. HELO
34291 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
34292 as NOOP; QUIT quits.
34294 Minimal policy checking is done for BSMTP input. Only the non-SMTP
34295 ACL is run in the same way as for non-SMTP local input.
34297 If an error is detected while reading a message, including a missing &"."& at
34298 the end, Exim gives up immediately. It writes details of the error to the
34299 standard output in a stylized way that the calling program should be able to
34300 make some use of automatically, for example:
34302 554 Unexpected end of file
34303 Transaction started in line 10
34304 Error detected in line 14
34306 It writes a more verbose version, for human consumption, to the standard error
34309 An error was detected while processing a file of BSMTP input.
34310 The error message was:
34312 501 '>' missing at end of address
34314 The SMTP transaction started in line 10.
34315 The error was detected in line 12.
34316 The SMTP command at fault was:
34318 rcpt to:<malformed@in.com.plete
34320 1 previous message was successfully processed.
34321 The rest of the batch was abandoned.
34323 The return code from Exim is zero only if there were no errors. It is 1 if some
34324 messages were accepted before an error was detected, and 2 if no messages were
34326 .ecindex IIDsmtpproc1
34327 .ecindex IIDsmtpproc2
34331 . ////////////////////////////////////////////////////////////////////////////
34332 . ////////////////////////////////////////////////////////////////////////////
34334 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
34335 "Customizing messages"
34336 When a message fails to be delivered, or remains on the queue for more than a
34337 configured amount of time, Exim sends a message to the original sender, or
34338 to an alternative configured address. The text of these messages is built into
34339 the code of Exim, but it is possible to change it, either by adding a single
34340 string, or by replacing each of the paragraphs by text supplied in a file.
34342 The &'From:'& and &'To:'& header lines are automatically generated; you can
34343 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
34344 option. Exim also adds the line
34346 Auto-Submitted: auto-generated
34348 to all warning and bounce messages,
34351 .section "Customizing bounce messages" "SECID239"
34352 .cindex "customizing" "bounce message"
34353 .cindex "bounce message" "customizing"
34354 If &%bounce_message_text%& is set, its contents are included in the default
34355 message immediately after &"This message was created automatically by mail
34356 delivery software."& The string is not expanded. It is not used if
34357 &%bounce_message_file%& is set.
34359 When &%bounce_message_file%& is set, it must point to a template file for
34360 constructing error messages. The file consists of a series of text items,
34361 separated by lines consisting of exactly four asterisks. If the file cannot be
34362 opened, default text is used and a message is written to the main and panic
34363 logs. If any text item in the file is empty, default text is used for that
34366 .vindex "&$bounce_recipient$&"
34367 .vindex "&$bounce_return_size_limit$&"
34368 Each item of text that is read from the file is expanded, and there are two
34369 expansion variables which can be of use here: &$bounce_recipient$& is set to
34370 the recipient of an error message while it is being created, and
34371 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
34372 option, rounded to a whole number.
34374 The items must appear in the file in the following order:
34377 The first item is included in the headers, and should include at least a
34378 &'Subject:'& header. Exim does not check the syntax of these headers.
34380 The second item forms the start of the error message. After it, Exim lists the
34381 failing addresses with their error messages.
34383 The third item is used to introduce any text from pipe transports that is to be
34384 returned to the sender. It is omitted if there is no such text.
34386 The fourth, fifth and sixth items will be ignored and may be empty.
34387 The fields exist for back-compatibility
34390 The default state (&%bounce_message_file%& unset) is equivalent to the
34391 following file, in which the sixth item is empty. The &'Subject:'& and some
34392 other lines have been split in order to fit them on the page:
34394 Subject: Mail delivery failed
34395 ${if eq{$sender_address}{$bounce_recipient}
34396 {: returning message to sender}}
34398 This message was created automatically by mail delivery software.
34400 A message ${if eq{$sender_address}{$bounce_recipient}
34401 {that you sent }{sent by
34405 }}could not be delivered to all of its recipients.
34406 This is a permanent error. The following address(es) failed:
34408 The following text was generated during the delivery attempt(s):
34410 ------ This is a copy of the message, including all the headers.
34413 ------ The body of the message is $message_size characters long;
34415 ------ $bounce_return_size_limit or so are included here.
34418 .section "Customizing warning messages" "SECTcustwarn"
34419 .cindex "customizing" "warning message"
34420 .cindex "warning of delay" "customizing the message"
34421 The option &%warn_message_file%& can be pointed at a template file for use when
34422 warnings about message delays are created. In this case there are only three
34426 The first item is included in the headers, and should include at least a
34427 &'Subject:'& header. Exim does not check the syntax of these headers.
34429 The second item forms the start of the warning message. After it, Exim lists
34430 the delayed addresses.
34432 The third item then ends the message.
34435 The default state is equivalent to the following file, except that some lines
34436 have been split here, in order to fit them on the page:
34438 Subject: Warning: message $message_exim_id delayed
34439 $warn_message_delay
34441 This message was created automatically by mail delivery software.
34443 A message ${if eq{$sender_address}{$warn_message_recipients}
34444 {that you sent }{sent by
34448 }}has not been delivered to all of its recipients after
34449 more than $warn_message_delay on the queue on $primary_hostname.
34451 The message identifier is: $message_exim_id
34452 The subject of the message is: $h_subject
34453 The date of the message is: $h_date
34455 The following address(es) have not yet been delivered:
34457 No action is required on your part. Delivery attempts will
34458 continue for some time, and this warning may be repeated at
34459 intervals if the message remains undelivered. Eventually the
34460 mail delivery software will give up, and when that happens,
34461 the message will be returned to you.
34463 .vindex "&$warn_message_delay$&"
34464 .vindex "&$warn_message_recipients$&"
34465 However, in the default state the subject and date lines are omitted if no
34466 appropriate headers exist. During the expansion of this file,
34467 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
34468 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
34469 of recipients for the warning message. There may be more than one if there are
34470 multiple addresses with different &%errors_to%& settings on the routers that
34476 . ////////////////////////////////////////////////////////////////////////////
34477 . ////////////////////////////////////////////////////////////////////////////
34479 .chapter "Some common configuration settings" "CHAPcomconreq"
34480 This chapter discusses some configuration settings that seem to be fairly
34481 common. More examples and discussion can be found in the Exim book.
34485 .section "Sending mail to a smart host" "SECID240"
34486 .cindex "smart host" "example router"
34487 If you want to send all mail for non-local domains to a &"smart host"&, you
34488 should replace the default &(dnslookup)& router with a router which does the
34489 routing explicitly:
34491 send_to_smart_host:
34492 driver = manualroute
34493 route_list = !+local_domains smart.host.name
34494 transport = remote_smtp
34496 You can use the smart host's IP address instead of the name if you wish.
34497 If you are using Exim only to submit messages to a smart host, and not for
34498 receiving incoming messages, you can arrange for it to do the submission
34499 synchronously by setting the &%mua_wrapper%& option (see chapter
34500 &<<CHAPnonqueueing>>&).
34505 .section "Using Exim to handle mailing lists" "SECTmailinglists"
34506 .cindex "mailing lists"
34507 Exim can be used to run simple mailing lists, but for large and/or complicated
34508 requirements, the use of additional specialized mailing list software such as
34509 Majordomo or Mailman is recommended.
34511 The &(redirect)& router can be used to handle mailing lists where each list
34512 is maintained in a separate file, which can therefore be managed by an
34513 independent manager. The &%domains%& router option can be used to run these
34514 lists in a separate domain from normal mail. For example:
34518 domains = lists.example
34519 file = /usr/lists/$local_part
34522 errors_to = $local_part-request@lists.example
34525 This router is skipped for domains other than &'lists.example'&. For addresses
34526 in that domain, it looks for a file that matches the local part. If there is no
34527 such file, the router declines, but because &%no_more%& is set, no subsequent
34528 routers are tried, and so the whole delivery fails.
34530 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
34531 expanded into a file name or a pipe delivery, which is usually inappropriate in
34534 .oindex "&%errors_to%&"
34535 The &%errors_to%& option specifies that any delivery errors caused by addresses
34536 taken from a mailing list are to be sent to the given address rather than the
34537 original sender of the message. However, before acting on this, Exim verifies
34538 the error address, and ignores it if verification fails.
34540 For example, using the configuration above, mail sent to
34541 &'dicts@lists.example'& is passed on to those addresses contained in
34542 &_/usr/lists/dicts_&, with error reports directed to
34543 &'dicts-request@lists.example'&, provided that this address can be verified.
34544 There could be a file called &_/usr/lists/dicts-request_& containing
34545 the address(es) of this particular list's manager(s), but other approaches,
34546 such as setting up an earlier router (possibly using the &%local_part_prefix%&
34547 or &%local_part_suffix%& options) to handle addresses of the form
34548 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
34552 .section "Syntax errors in mailing lists" "SECID241"
34553 .cindex "mailing lists" "syntax errors in"
34554 If an entry in redirection data contains a syntax error, Exim normally defers
34555 delivery of the original address. That means that a syntax error in a mailing
34556 list holds up all deliveries to the list. This may not be appropriate when a
34557 list is being maintained automatically from data supplied by users, and the
34558 addresses are not rigorously checked.
34560 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
34561 entries that fail to parse, noting the incident in the log. If in addition
34562 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
34563 whenever a broken address is skipped. It is usually appropriate to set
34564 &%syntax_errors_to%& to the same address as &%errors_to%&.
34568 .section "Re-expansion of mailing lists" "SECID242"
34569 .cindex "mailing lists" "re-expansion of"
34570 Exim remembers every individual address to which a message has been delivered,
34571 in order to avoid duplication, but it normally stores only the original
34572 recipient addresses with a message. If all the deliveries to a mailing list
34573 cannot be done at the first attempt, the mailing list is re-expanded when the
34574 delivery is next tried. This means that alterations to the list are taken into
34575 account at each delivery attempt, so addresses that have been added to
34576 the list since the message arrived will therefore receive a copy of the
34577 message, even though it pre-dates their subscription.
34579 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
34580 on the &(redirect)& router. If this is done, any addresses generated by the
34581 router that fail to deliver at the first attempt are added to the message as
34582 &"top level"& addresses, and the parent address that generated them is marked
34583 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
34584 subsequent delivery attempts. The disadvantage of this is that if any of the
34585 failing addresses are incorrect, correcting them in the file has no effect on
34586 pre-existing messages.
34588 The original top-level address is remembered with each of the generated
34589 addresses, and is output in any log messages. However, any intermediate parent
34590 addresses are not recorded. This makes a difference to the log only if the
34591 &%all_parents%& selector is set, but for mailing lists there is normally only
34592 one level of expansion anyway.
34596 .section "Closed mailing lists" "SECID243"
34597 .cindex "mailing lists" "closed"
34598 The examples so far have assumed open mailing lists, to which anybody may
34599 send mail. It is also possible to set up closed lists, where mail is accepted
34600 from specified senders only. This is done by making use of the generic
34601 &%senders%& option to restrict the router that handles the list.
34603 The following example uses the same file as a list of recipients and as a list
34604 of permitted senders. It requires three routers:
34608 domains = lists.example
34609 local_part_suffix = -request
34610 file = /usr/lists/$local_part$local_part_suffix
34615 domains = lists.example
34616 senders = ${if exists {/usr/lists/$local_part}\
34617 {lsearch;/usr/lists/$local_part}{*}}
34618 file = /usr/lists/$local_part
34621 errors_to = $local_part-request@lists.example
34626 domains = lists.example
34628 data = :fail: $local_part@lists.example is a closed mailing list
34630 All three routers have the same &%domains%& setting, so for any other domains,
34631 they are all skipped. The first router runs only if the local part ends in
34632 &%-request%&. It handles messages to the list manager(s) by means of an open
34635 The second router runs only if the &%senders%& precondition is satisfied. It
34636 checks for the existence of a list that corresponds to the local part, and then
34637 checks that the sender is on the list by means of a linear search. It is
34638 necessary to check for the existence of the file before trying to search it,
34639 because otherwise Exim thinks there is a configuration error. If the file does
34640 not exist, the expansion of &%senders%& is *, which matches all senders. This
34641 means that the router runs, but because there is no list, declines, and
34642 &%no_more%& ensures that no further routers are run. The address fails with an
34643 &"unrouteable address"& error.
34645 The third router runs only if the second router is skipped, which happens when
34646 a mailing list exists, but the sender is not on it. This router forcibly fails
34647 the address, giving a suitable error message.
34652 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
34654 .cindex "Variable Envelope Return Paths"
34655 .cindex "envelope sender"
34656 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
34657 are a way of helping mailing list administrators discover which subscription
34658 address is the cause of a particular delivery failure. The idea is to encode
34659 the original recipient address in the outgoing envelope sender address, so that
34660 if the message is forwarded by another host and then subsequently bounces, the
34661 original recipient can be extracted from the recipient address of the bounce.
34663 .oindex &%errors_to%&
34664 .oindex &%return_path%&
34665 Envelope sender addresses can be modified by Exim using two different
34666 facilities: the &%errors_to%& option on a router (as shown in previous mailing
34667 list examples), or the &%return_path%& option on a transport. The second of
34668 these is effective only if the message is successfully delivered to another
34669 host; it is not used for errors detected on the local host (see the description
34670 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
34671 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
34677 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34678 {$1-request+$local_part=$domain@your.dom.example}fail}
34680 This has the effect of rewriting the return path (envelope sender) on outgoing
34681 SMTP messages, if the local part of the original return path ends in
34682 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
34683 local part and domain of the recipient into the return path. Suppose, for
34684 example, that a message whose return path has been set to
34685 &'somelist-request@your.dom.example'& is sent to
34686 &'subscriber@other.dom.example'&. In the transport, the return path is
34689 somelist-request+subscriber=other.dom.example@your.dom.example
34691 .vindex "&$local_part$&"
34692 For this to work, you must tell Exim to send multiple copies of messages that
34693 have more than one recipient, so that each copy has just one recipient. This is
34694 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
34695 might be sent to several different recipients in the same domain, in which case
34696 &$local_part$& is not available in the transport, because it is not unique.
34698 Unless your host is doing nothing but mailing list deliveries, you should
34699 probably use a separate transport for the VERP deliveries, so as not to use
34700 extra resources in making one-per-recipient copies for other deliveries. This
34701 can easily be done by expanding the &%transport%& option in the router:
34705 domains = ! +local_domains
34707 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34708 {verp_smtp}{remote_smtp}}
34711 If you want to change the return path using &%errors_to%& in a router instead
34712 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
34713 routers that handle mailing list addresses. This will ensure that all delivery
34714 errors, including those detected on the local host, are sent to the VERP
34717 On a host that does no local deliveries and has no manual routing, only the
34718 &(dnslookup)& router needs to be changed. A special transport is not needed for
34719 SMTP deliveries. Every mailing list recipient has its own return path value,
34720 and so Exim must hand them to the transport one at a time. Here is an example
34721 of a &(dnslookup)& router that implements VERP:
34725 domains = ! +local_domains
34726 transport = remote_smtp
34728 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
34729 {$1-request+$local_part=$domain@your.dom.example}fail}
34732 Before you start sending out messages with VERPed return paths, you must also
34733 configure Exim to accept the bounce messages that come back to those paths.
34734 Typically this is done by setting a &%local_part_suffix%& option for a
34735 router, and using this to route the messages to wherever you want to handle
34738 The overhead incurred in using VERP depends very much on the size of the
34739 message, the number of recipient addresses that resolve to the same remote
34740 host, and the speed of the connection over which the message is being sent. If
34741 a lot of addresses resolve to the same host and the connection is slow, sending
34742 a separate copy of the message for each address may take substantially longer
34743 than sending a single copy with many recipients (for which VERP cannot be
34751 .section "Virtual domains" "SECTvirtualdomains"
34752 .cindex "virtual domains"
34753 .cindex "domain" "virtual"
34754 The phrase &'virtual domain'& is unfortunately used with two rather different
34758 A domain for which there are no real mailboxes; all valid local parts are
34759 aliases for other email addresses. Common examples are organizational
34760 top-level domains and &"vanity"& domains.
34762 One of a number of independent domains that are all handled by the same host,
34763 with mailboxes on that host, but where the mailbox owners do not necessarily
34764 have login accounts on that host.
34767 The first usage is probably more common, and does seem more &"virtual"& than
34768 the second. This kind of domain can be handled in Exim with a straightforward
34769 aliasing router. One approach is to create a separate alias file for each
34770 virtual domain. Exim can test for the existence of the alias file to determine
34771 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
34772 to a router of this form:
34776 domains = dsearch;/etc/mail/virtual
34777 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
34780 The &%domains%& option specifies that the router is to be skipped, unless there
34781 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
34782 domain that is being processed. When the router runs, it looks up the local
34783 part in the file to find a new address (or list of addresses). The &%no_more%&
34784 setting ensures that if the lookup fails (leading to &%data%& being an empty
34785 string), Exim gives up on the address without trying any subsequent routers.
34787 This one router can handle all the virtual domains because the alias file names
34788 follow a fixed pattern. Permissions can be arranged so that appropriate people
34789 can edit the different alias files. A successful aliasing operation results in
34790 a new envelope recipient address, which is then routed from scratch.
34792 The other kind of &"virtual"& domain can also be handled in a straightforward
34793 way. One approach is to create a file for each domain containing a list of
34794 valid local parts, and use it in a router like this:
34798 domains = dsearch;/etc/mail/domains
34799 local_parts = lsearch;/etc/mail/domains/$domain
34800 transport = my_mailboxes
34802 The address is accepted if there is a file for the domain, and the local part
34803 can be found in the file. The &%domains%& option is used to check for the
34804 file's existence because &%domains%& is tested before the &%local_parts%&
34805 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
34806 because that option is tested after &%local_parts%&. The transport is as
34810 driver = appendfile
34811 file = /var/mail/$domain/$local_part
34814 This uses a directory of mailboxes for each domain. The &%user%& setting is
34815 required, to specify which uid is to be used for writing to the mailboxes.
34817 The configuration shown here is just one example of how you might support this
34818 requirement. There are many other ways this kind of configuration can be set
34819 up, for example, by using a database instead of separate files to hold all the
34820 information about the domains.
34824 .section "Multiple user mailboxes" "SECTmulbox"
34825 .cindex "multiple mailboxes"
34826 .cindex "mailbox" "multiple"
34827 .cindex "local part" "prefix"
34828 .cindex "local part" "suffix"
34829 Heavy email users often want to operate with multiple mailboxes, into which
34830 incoming mail is automatically sorted. A popular way of handling this is to
34831 allow users to use multiple sender addresses, so that replies can easily be
34832 identified. Users are permitted to add prefixes or suffixes to their local
34833 parts for this purpose. The wildcard facility of the generic router options
34834 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
34835 example, consider this router:
34840 file = $home/.forward
34841 local_part_suffix = -*
34842 local_part_suffix_optional
34845 .vindex "&$local_part_suffix$&"
34846 It runs a user's &_.forward_& file for all local parts of the form
34847 &'username-*'&. Within the filter file the user can distinguish different
34848 cases by testing the variable &$local_part_suffix$&. For example:
34850 if $local_part_suffix contains -special then
34851 save /home/$local_part/Mail/special
34854 If the filter file does not exist, or does not deal with such addresses, they
34855 fall through to subsequent routers, and, assuming no subsequent use of the
34856 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
34857 control over which suffixes are valid.
34859 Alternatively, a suffix can be used to trigger the use of a different
34860 &_.forward_& file &-- which is the way a similar facility is implemented in
34866 file = $home/.forward$local_part_suffix
34867 local_part_suffix = -*
34868 local_part_suffix_optional
34871 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
34872 example, &_.forward-special_& is used. Once again, if the appropriate file
34873 does not exist, or does not deal with the address, it is passed on to
34874 subsequent routers, which could, if required, look for an unqualified
34875 &_.forward_& file to use as a default.
34879 .section "Simplified vacation processing" "SECID244"
34880 .cindex "vacation processing"
34881 The traditional way of running the &'vacation'& program is for a user to set up
34882 a pipe command in a &_.forward_& file
34883 (see section &<<SECTspecitredli>>& for syntax details).
34884 This is prone to error by inexperienced users. There are two features of Exim
34885 that can be used to make this process simpler for users:
34888 A local part prefix such as &"vacation-"& can be specified on a router which
34889 can cause the message to be delivered directly to the &'vacation'& program, or
34890 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
34891 &_.forward_& file are then much simpler. For example:
34893 spqr, vacation-spqr
34896 The &%require_files%& generic router option can be used to trigger a
34897 vacation delivery by checking for the existence of a certain file in the
34898 user's home directory. The &%unseen%& generic option should also be used, to
34899 ensure that the original delivery also proceeds. In this case, all the user has
34900 to do is to create a file called, say, &_.vacation_&, containing a vacation
34904 Another advantage of both these methods is that they both work even when the
34905 use of arbitrary pipes by users is locked out.
34909 .section "Taking copies of mail" "SECID245"
34910 .cindex "message" "copying every"
34911 Some installations have policies that require archive copies of all messages to
34912 be made. A single copy of each message can easily be taken by an appropriate
34913 command in a system filter, which could, for example, use a different file for
34914 each day's messages.
34916 There is also a shadow transport mechanism that can be used to take copies of
34917 messages that are successfully delivered by local transports, one copy per
34918 delivery. This could be used, &'inter alia'&, to implement automatic
34919 notification of delivery by sites that insist on doing such things.
34923 .section "Intermittently connected hosts" "SECID246"
34924 .cindex "intermittently connected hosts"
34925 It has become quite common (because it is cheaper) for hosts to connect to the
34926 Internet periodically rather than remain connected all the time. The normal
34927 arrangement is that mail for such hosts accumulates on a system that is
34928 permanently connected.
34930 Exim was designed for use on permanently connected hosts, and so it is not
34931 particularly well-suited to use in an intermittently connected environment.
34932 Nevertheless there are some features that can be used.
34935 .section "Exim on the upstream server host" "SECID247"
34936 It is tempting to arrange for incoming mail for the intermittently connected
34937 host to remain on Exim's queue until the client connects. However, this
34938 approach does not scale very well. Two different kinds of waiting message are
34939 being mixed up in the same queue &-- those that cannot be delivered because of
34940 some temporary problem, and those that are waiting for their destination host
34941 to connect. This makes it hard to manage the queue, as well as wasting
34942 resources, because each queue runner scans the entire queue.
34944 A better approach is to separate off those messages that are waiting for an
34945 intermittently connected host. This can be done by delivering these messages
34946 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
34947 format, from where they are transmitted by other software when their
34948 destination connects. This makes it easy to collect all the mail for one host
34949 in a single directory, and to apply local timeout rules on a per-message basis
34952 On a very small scale, leaving the mail on Exim's queue can be made to work. If
34953 you are doing this, you should configure Exim with a long retry period for the
34954 intermittent host. For example:
34956 cheshire.wonderland.fict.example * F,5d,24h
34958 This stops a lot of failed delivery attempts from occurring, but Exim remembers
34959 which messages it has queued up for that host. Once the intermittent host comes
34960 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
34961 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
34962 causes all the queued up messages to be delivered, often down a single SMTP
34963 connection. While the host remains connected, any new messages get delivered
34966 If the connecting hosts do not have fixed IP addresses, that is, if a host is
34967 issued with a different IP address each time it connects, Exim's retry
34968 mechanisms on the holding host get confused, because the IP address is normally
34969 used as part of the key string for holding retry information. This can be
34970 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
34971 Since this has disadvantages for permanently connected hosts, it is best to
34972 arrange a separate transport for the intermittently connected ones.
34976 .section "Exim on the intermittently connected client host" "SECID248"
34977 The value of &%smtp_accept_queue_per_connection%& should probably be
34978 increased, or even set to zero (that is, disabled) on the intermittently
34979 connected host, so that all incoming messages down a single connection get
34980 delivered immediately.
34982 .cindex "SMTP" "passed connection"
34983 .cindex "SMTP" "multiple deliveries"
34984 .cindex "multiple SMTP deliveries"
34985 Mail waiting to be sent from an intermittently connected host will probably
34986 not have been routed, because without a connection DNS lookups are not
34987 possible. This means that if a normal queue run is done at connection time,
34988 each message is likely to be sent in a separate SMTP session. This can be
34989 avoided by starting the queue run with a command line option beginning with
34990 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
34991 first pass, routing is done but no deliveries take place. The second pass is a
34992 normal queue run; since all the messages have been previously routed, those
34993 destined for the same host are likely to get sent as multiple deliveries in a
34994 single SMTP connection.
34998 . ////////////////////////////////////////////////////////////////////////////
34999 . ////////////////////////////////////////////////////////////////////////////
35001 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
35002 "Exim as a non-queueing client"
35003 .cindex "client, non-queueing"
35004 .cindex "smart host" "suppressing queueing"
35005 On a personal computer, it is a common requirement for all
35006 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
35007 configured to operate that way, for all the popular operating systems.
35008 However, there are some MUAs for Unix-like systems that cannot be so
35009 configured: they submit messages using the command line interface of
35010 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
35013 If the personal computer runs continuously, there is no problem, because it can
35014 run a conventional MTA that handles delivery to the smart host, and deal with
35015 any delays via its queueing mechanism. However, if the computer does not run
35016 continuously or runs different operating systems at different times, queueing
35017 email is not desirable.
35019 There is therefore a requirement for something that can provide the
35020 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
35021 any queueing or retrying facilities. Furthermore, the delivery to the smart
35022 host should be synchronous, so that if it fails, the sending MUA is immediately
35023 informed. In other words, we want something that extends an MUA that submits
35024 to a local MTA via the command line so that it behaves like one that submits
35025 to a remote smart host using TCP/SMTP.
35027 There are a number of applications (for example, there is one called &'ssmtp'&)
35028 that do this job. However, people have found them to be lacking in various
35029 ways. For instance, you might want to allow aliasing and forwarding to be done
35030 before sending a message to the smart host.
35032 Exim already had the necessary infrastructure for doing this job. Just a few
35033 tweaks were needed to make it behave as required, though it is somewhat of an
35034 overkill to use a fully-featured MTA for this purpose.
35036 .oindex "&%mua_wrapper%&"
35037 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
35038 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
35039 assumes that it is being used to &"wrap"& a command-line MUA in the manner
35040 just described. As well as setting &%mua_wrapper%&, you also need to provide a
35041 compatible router and transport configuration. Typically there will be just one
35042 router and one transport, sending everything to a smart host.
35044 When run in MUA wrapping mode, the behaviour of Exim changes in the
35048 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
35049 In other words, the only way to submit messages is via the command line.
35051 Each message is synchronously delivered as soon as it is received (&%-odi%& is
35052 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
35053 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
35054 does not finish until the delivery attempt is complete. If the delivery is
35055 successful, a zero return code is given.
35057 Address redirection is permitted, but the final routing for all addresses must
35058 be to the same remote transport, and to the same list of hosts. Furthermore,
35059 the return address (envelope sender) must be the same for all recipients, as
35060 must any added or deleted header lines. In other words, it must be possible to
35061 deliver the message in a single SMTP transaction, however many recipients there
35064 If these conditions are not met, or if routing any address results in a
35065 failure or defer status, or if Exim is unable to deliver all the recipients
35066 successfully to one of the smart hosts, delivery of the entire message fails.
35068 Because no queueing is allowed, all failures are treated as permanent; there
35069 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
35070 smart host. Furthermore, because only a single yes/no response can be given to
35071 the caller, it is not possible to deliver to some recipients and not others. If
35072 there is an error (temporary or permanent) for any recipient, all are failed.
35074 If more than one smart host is listed, Exim will try another host after a
35075 connection failure or a timeout, in the normal way. However, if this kind of
35076 failure happens for all the hosts, the delivery fails.
35078 When delivery fails, an error message is written to the standard error stream
35079 (as well as to Exim's log), and Exim exits to the caller with a return code
35080 value 1. The message is expunged from Exim's spool files. No bounce messages
35081 are ever generated.
35083 No retry data is maintained, and any retry rules are ignored.
35085 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
35086 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
35087 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
35090 The overall effect is that Exim makes a single synchronous attempt to deliver
35091 the message, failing if there is any kind of problem. Because no local
35092 deliveries are done and no daemon can be run, Exim does not need root
35093 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
35094 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
35095 the advantages and disadvantages of running without root privilege.
35100 . ////////////////////////////////////////////////////////////////////////////
35101 . ////////////////////////////////////////////////////////////////////////////
35103 .chapter "Log files" "CHAPlog"
35104 .scindex IIDloggen "log" "general description"
35105 .cindex "log" "types of"
35106 Exim writes three different logs, referred to as the main log, the reject log,
35111 The main log records the arrival of each message and each delivery in a single
35112 line in each case. The format is as compact as possible, in an attempt to keep
35113 down the size of log files. Two-character flag sequences make it easy to pick
35114 out these lines. A number of other events are recorded in the main log. Some of
35115 them are optional, in which case the &%log_selector%& option controls whether
35116 they are included or not. A Perl script called &'eximstats'&, which does simple
35117 analysis of main log files, is provided in the Exim distribution (see section
35118 &<<SECTmailstat>>&).
35120 .cindex "reject log"
35121 The reject log records information from messages that are rejected as a result
35122 of a configuration option (that is, for policy reasons).
35123 The first line of each rejection is a copy of the line that is also written to
35124 the main log. Then, if the message's header has been read at the time the log
35125 is written, its contents are written to this log. Only the original header
35126 lines are available; header lines added by ACLs are not logged. You can use the
35127 reject log to check that your policy controls are working correctly; on a busy
35128 host this may be easier than scanning the main log for rejection messages. You
35129 can suppress the writing of the reject log by setting &%write_rejectlog%&
35132 .cindex "panic log"
35133 .cindex "system log"
35134 When certain serious errors occur, Exim writes entries to its panic log. If the
35135 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
35136 are usually written to the main log as well, but can get lost amid the mass of
35137 other entries. The panic log should be empty under normal circumstances. It is
35138 therefore a good idea to check it (or to have a &'cron'& script check it)
35139 regularly, in order to become aware of any problems. When Exim cannot open its
35140 panic log, it tries as a last resort to write to the system log (syslog). This
35141 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
35142 message itself is written at priority LOG_CRIT.
35145 Every log line starts with a timestamp, in the format shown in the following
35146 example. Note that many of the examples shown in this chapter are line-wrapped.
35147 In the log file, this would be all on one line:
35149 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
35152 By default, the timestamps are in the local timezone. There are two
35153 ways of changing this:
35156 You can set the &%timezone%& option to a different time zone; in particular, if
35161 the timestamps will be in UTC (aka GMT).
35163 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
35166 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
35170 .cindex "log" "process ids in"
35171 .cindex "pid (process id)" "in log lines"
35172 Exim does not include its process id in log lines by default, but you can
35173 request that it does so by specifying the &`pid`& log selector (see section
35174 &<<SECTlogselector>>&). When this is set, the process id is output, in square
35175 brackets, immediately after the time and date.
35180 .section "Where the logs are written" "SECTwhelogwri"
35181 .cindex "log" "destination"
35182 .cindex "log" "to file"
35183 .cindex "log" "to syslog"
35185 The logs may be written to local files, or to syslog, or both. However, it
35186 should be noted that many syslog implementations use UDP as a transport, and
35187 are therefore unreliable in the sense that messages are not guaranteed to
35188 arrive at the loghost, nor is the ordering of messages necessarily maintained.
35189 It has also been reported that on large log files (tens of megabytes) you may
35190 need to tweak syslog to prevent it syncing the file with each write &-- on
35191 Linux this has been seen to make syslog take 90% plus of CPU time.
35193 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
35194 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
35195 configuration. This latter string is expanded, so it can contain, for example,
35196 references to the host name:
35198 log_file_path = /var/log/$primary_hostname/exim_%slog
35200 It is generally advisable, however, to set the string in &_Local/Makefile_&
35201 rather than at run time, because then the setting is available right from the
35202 start of Exim's execution. Otherwise, if there's something it wants to log
35203 before it has read the configuration file (for example, an error in the
35204 configuration file) it will not use the path you want, and may not be able to
35207 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
35208 list, currently limited to at most two items. This is one option where the
35209 facility for changing a list separator may not be used. The list must always be
35210 colon-separated. If an item in the list is &"syslog"& then syslog is used;
35211 otherwise the item must either be an absolute path, containing &`%s`& at the
35212 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
35213 implying the use of a default path.
35215 When Exim encounters an empty item in the list, it searches the list defined by
35216 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
35217 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
35218 mean &"use the path specified at build time"&. It no such item exists, log
35219 files are written in the &_log_& subdirectory of the spool directory. This is
35220 equivalent to the setting:
35222 log_file_path = $spool_directory/log/%slog
35224 If you do not specify anything at build time or run time,
35225 or if you unset the option at run time (i.e. &`log_file_path = `&),
35226 that is where the logs are written.
35228 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
35229 are in use &-- see section &<<SECTdatlogfil>>& below.
35231 Here are some examples of possible settings:
35233 &`LOG_FILE_PATH=syslog `& syslog only
35234 &`LOG_FILE_PATH=:syslog `& syslog and default path
35235 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
35236 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
35238 If there are more than two paths in the list, the first is used and a panic
35243 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
35244 .cindex "log" "cycling local files"
35245 .cindex "cycling logs"
35246 .cindex "&'exicyclog'&"
35247 .cindex "log" "local files; writing to"
35248 Some operating systems provide centralized and standardized methods for cycling
35249 log files. For those that do not, a utility script called &'exicyclog'& is
35250 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
35251 main and reject logs each time it is called. The maximum number of old logs to
35252 keep can be set. It is suggested this script is run as a daily &'cron'& job.
35254 An Exim delivery process opens the main log when it first needs to write to it,
35255 and it keeps the file open in case subsequent entries are required &-- for
35256 example, if a number of different deliveries are being done for the same
35257 message. However, remote SMTP deliveries can take a long time, and this means
35258 that the file may be kept open long after it is renamed if &'exicyclog'& or
35259 something similar is being used to rename log files on a regular basis. To
35260 ensure that a switch of log files is noticed as soon as possible, Exim calls
35261 &[stat()]& on the main log's name before reusing an open file, and if the file
35262 does not exist, or its inode has changed, the old file is closed and Exim
35263 tries to open the main log from scratch. Thus, an old log file may remain open
35264 for quite some time, but no Exim processes should write to it once it has been
35269 .section "Datestamped log files" "SECTdatlogfil"
35270 .cindex "log" "datestamped files"
35271 Instead of cycling the main and reject log files by renaming them
35272 periodically, some sites like to use files whose names contain a datestamp,
35273 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
35274 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
35275 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
35276 point where the datestamp is required. For example:
35278 log_file_path = /var/spool/exim/log/%slog-%D
35279 log_file_path = /var/log/exim-%s-%D.log
35280 log_file_path = /var/spool/exim/log/%D-%slog
35281 log_file_path = /var/log/exim/%s.%M
35283 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
35284 examples of names generated by the above examples:
35286 /var/spool/exim/log/mainlog-20021225
35287 /var/log/exim-reject-20021225.log
35288 /var/spool/exim/log/20021225-mainlog
35289 /var/log/exim/main.200212
35291 When this form of log file is specified, Exim automatically switches to new
35292 files at midnight. It does not make any attempt to compress old logs; you
35293 will need to write your own script if you require this. You should not
35294 run &'exicyclog'& with this form of logging.
35296 The location of the panic log is also determined by &%log_file_path%&, but it
35297 is not datestamped, because rotation of the panic log does not make sense.
35298 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
35299 the string. In addition, if it immediately follows a slash, a following
35300 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
35301 character is removed. Thus, the four examples above would give these panic
35304 /var/spool/exim/log/paniclog
35305 /var/log/exim-panic.log
35306 /var/spool/exim/log/paniclog
35307 /var/log/exim/panic
35311 .section "Logging to syslog" "SECID249"
35312 .cindex "log" "syslog; writing to"
35313 The use of syslog does not change what Exim logs or the format of its messages,
35314 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
35315 Exim's log lines are omitted when these lines are sent to syslog. Apart from
35316 that, the same strings are written to syslog as to log files. The syslog
35317 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
35318 by default, but you can change these by setting the &%syslog_facility%& and
35319 &%syslog_processname%& options, respectively. If Exim was compiled with
35320 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
35321 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
35322 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
35323 the time and host name to each line.
35324 The three log streams are mapped onto syslog priorities as follows:
35327 &'mainlog'& is mapped to LOG_INFO
35329 &'rejectlog'& is mapped to LOG_NOTICE
35331 &'paniclog'& is mapped to LOG_ALERT
35334 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
35335 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
35336 these are routed by syslog to the same place. You can suppress this duplication
35337 by setting &%syslog_duplication%& false.
35339 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
35340 entries contain multiple lines when headers are included. To cope with both
35341 these cases, entries written to syslog are split into separate &[syslog()]&
35342 calls at each internal newline, and also after a maximum of
35343 870 data characters. (This allows for a total syslog line length of 1024, when
35344 additions such as timestamps are added.) If you are running a syslog
35345 replacement that can handle lines longer than the 1024 characters allowed by
35346 RFC 3164, you should set
35348 SYSLOG_LONG_LINES=yes
35350 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
35351 lines, but it still splits at internal newlines in &'reject'& log entries.
35353 To make it easy to re-assemble split lines later, each component of a split
35354 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
35355 where <&'n'&> is the component number and <&'m'&> is the total number of
35356 components in the entry. The / delimiter is used when the line was split
35357 because it was too long; if it was split because of an internal newline, the \
35358 delimiter is used. For example, supposing the length limit to be 50 instead of
35359 870, the following would be the result of a typical rejection message to
35360 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
35361 name, and pid as added by syslog:
35363 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
35364 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
35365 [3/5] when scanning for sender: missing or malformed lo
35366 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
35369 The same error might cause the following lines to be written to &"rejectlog"&
35372 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
35373 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
35374 [3/18] er when scanning for sender: missing or malformed
35375 [4/18] local part in "<>" (envelope sender is <ph10@cam
35377 [6\18] Recipients: ph10@some.domain.cam.example
35378 [7\18] P Received: from [127.0.0.1] (ident=ph10)
35379 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
35380 [9\18] id 16RdAL-0006pc-00
35381 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
35382 [11\18] 09:43 +0100
35384 [13\18] Subject: this is a test header
35385 [18\18] X-something: this is another header
35386 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
35389 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
35391 Log lines that are neither too long nor contain newlines are written to syslog
35392 without modification.
35394 If only syslog is being used, the Exim monitor is unable to provide a log tail
35395 display, unless syslog is routing &'mainlog'& to a file on the local host and
35396 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
35401 .section "Log line flags" "SECID250"
35402 One line is written to the main log for each message received, and for each
35403 successful, unsuccessful, and delayed delivery. These lines can readily be
35404 picked out by the distinctive two-character flags that immediately follow the
35405 timestamp. The flags are:
35407 &`<=`& message arrival
35408 &`=>`& normal message delivery
35409 &`->`& additional address in same delivery
35410 &`>>`& cutthrough message delivery
35411 &`*>`& delivery suppressed by &%-N%&
35412 &`**`& delivery failed; address bounced
35413 &`==`& delivery deferred; temporary problem
35417 .section "Logging message reception" "SECID251"
35418 .cindex "log" "reception line"
35419 The format of the single-line entry in the main log that is written for every
35420 message received is shown in the basic example below, which is split over
35421 several lines in order to fit it on the page:
35423 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
35424 H=mailer.fict.example [192.168.123.123] U=exim
35425 P=smtp S=5678 id=<incoming message id>
35427 The address immediately following &"<="& is the envelope sender address. A
35428 bounce message is shown with the sender address &"<>"&, and if it is locally
35429 generated, this is followed by an item of the form
35433 which is a reference to the message that caused the bounce to be sent.
35437 For messages from other hosts, the H and U fields identify the remote host and
35438 record the RFC 1413 identity of the user that sent the message, if one was
35439 received. The number given in square brackets is the IP address of the sending
35440 host. If there is a single, unparenthesized host name in the H field, as
35441 above, it has been verified to correspond to the IP address (see the
35442 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
35443 by the remote host in the SMTP HELO or EHLO command, and has not been
35444 verified. If verification yields a different name to that given for HELO or
35445 EHLO, the verified name appears first, followed by the HELO or EHLO
35446 name in parentheses.
35448 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
35449 without brackets, in the HELO or EHLO command, leading to entries in
35450 the log containing text like these examples:
35452 H=(10.21.32.43) [192.168.8.34]
35453 H=([10.21.32.43]) [192.168.8.34]
35455 This can be confusing. Only the final address in square brackets can be relied
35458 For locally generated messages (that is, messages not received over TCP/IP),
35459 the H field is omitted, and the U field contains the login name of the caller
35462 .cindex "authentication" "logging"
35463 .cindex "AUTH" "logging"
35464 For all messages, the P field specifies the protocol used to receive the
35465 message. This is the value that is stored in &$received_protocol$&. In the case
35466 of incoming SMTP messages, the value indicates whether or not any SMTP
35467 extensions (ESMTP), encryption, or authentication were used. If the SMTP
35468 session was encrypted, there is an additional X field that records the cipher
35469 suite that was used.
35471 .cindex log protocol
35472 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
35473 hosts that have authenticated themselves using the SMTP AUTH command. The first
35474 value is used when the SMTP connection was encrypted (&"secure"&). In this case
35475 there is an additional item A= followed by the name of the authenticator that
35476 was used. If an authenticated identification was set up by the authenticator's
35477 &%server_set_id%& option, this is logged too, separated by a colon from the
35478 authenticator name.
35480 .cindex "size" "of message"
35481 The id field records the existing message id, if present. The size of the
35482 received message is given by the S field. When the message is delivered,
35483 headers may be removed or added, so that the size of delivered copies of the
35484 message may not correspond with this value (and indeed may be different to each
35487 The &%log_selector%& option can be used to request the logging of additional
35488 data when a message is received. See section &<<SECTlogselector>>& below.
35492 .section "Logging deliveries" "SECID252"
35493 .cindex "log" "delivery line"
35494 The format of the single-line entry in the main log that is written for every
35495 delivery is shown in one of the examples below, for local and remote
35496 deliveries, respectively. Each example has been split into multiple lines in order
35497 to fit it on the page:
35499 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
35500 <marv@hitch.fict.example> R=localuser T=local_delivery
35501 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
35502 monk@holistic.fict.example R=dnslookup T=remote_smtp
35503 H=holistic.fict.example [192.168.234.234]
35505 For ordinary local deliveries, the original address is given in angle brackets
35506 after the final delivery address, which might be a pipe or a file. If
35507 intermediate address(es) exist between the original and the final address, the
35508 last of these is given in parentheses after the final address. The R and T
35509 fields record the router and transport that were used to process the address.
35511 If SMTP AUTH was used for the delivery there is an additional item A=
35512 followed by the name of the authenticator that was used.
35513 If an authenticated identification was set up by the authenticator's &%client_set_id%&
35514 option, this is logged too, separated by a colon from the authenticator name.
35516 If a shadow transport was run after a successful local delivery, the log line
35517 for the successful delivery has an item added on the end, of the form
35519 &`ST=<`&&'shadow transport name'&&`>`&
35521 If the shadow transport did not succeed, the error message is put in
35522 parentheses afterwards.
35524 .cindex "asterisk" "after IP address"
35525 When more than one address is included in a single delivery (for example, two
35526 SMTP RCPT commands in one transaction) the second and subsequent addresses are
35527 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
35528 down a single SMTP connection, an asterisk follows the IP address in the log
35529 lines for the second and subsequent messages.
35531 .cindex "delivery" "cutthrough; logging"
35532 .cindex "cutthrough" "logging"
35533 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
35534 line precedes the reception line, since cutthrough waits for a possible
35535 rejection from the destination in case it can reject the sourced item.
35537 The generation of a reply message by a filter file gets logged as a
35538 &"delivery"& to the addressee, preceded by &">"&.
35540 The &%log_selector%& option can be used to request the logging of additional
35541 data when a message is delivered. See section &<<SECTlogselector>>& below.
35544 .section "Discarded deliveries" "SECID253"
35545 .cindex "discarded messages"
35546 .cindex "message" "discarded"
35547 .cindex "delivery" "discarded; logging"
35548 When a message is discarded as a result of the command &"seen finish"& being
35549 obeyed in a filter file which generates no deliveries, a log entry of the form
35551 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
35552 <low.club@bridge.example> R=userforward
35554 is written, to record why no deliveries are logged. When a message is discarded
35555 because it is aliased to &":blackhole:"& the log line is like this:
35557 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
35558 <hole@nowhere.example> R=blackhole_router
35562 .section "Deferred deliveries" "SECID254"
35563 When a delivery is deferred, a line of the following form is logged:
35565 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
35566 R=dnslookup T=smtp defer (146): Connection refused
35568 In the case of remote deliveries, the error is the one that was given for the
35569 last IP address that was tried. Details of individual SMTP failures are also
35570 written to the log, so the above line would be preceded by something like
35572 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
35573 mail1.endrest.example [192.168.239.239]: Connection refused
35575 When a deferred address is skipped because its retry time has not been reached,
35576 a message is written to the log, but this can be suppressed by setting an
35577 appropriate value in &%log_selector%&.
35581 .section "Delivery failures" "SECID255"
35582 .cindex "delivery" "failure; logging"
35583 If a delivery fails because an address cannot be routed, a line of the
35584 following form is logged:
35586 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
35587 <jim@trek99.example>: unknown mail domain
35589 If a delivery fails at transport time, the router and transport are shown, and
35590 the response from the remote host is included, as in this example:
35592 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
35593 R=dnslookup T=remote_smtp: SMTP error from remote mailer
35594 after pipelined RCPT TO:<ace400@pb.example>: host
35595 pbmail3.py.example [192.168.63.111]: 553 5.3.0
35596 <ace400@pb.example>...Addressee unknown
35598 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
35599 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
35600 disabling PIPELINING. The log lines for all forms of delivery failure are
35601 flagged with &`**`&.
35605 .section "Fake deliveries" "SECID256"
35606 .cindex "delivery" "fake; logging"
35607 If a delivery does not actually take place because the &%-N%& option has been
35608 used to suppress it, a normal delivery line is written to the log, except that
35609 &"=>"& is replaced by &"*>"&.
35613 .section "Completion" "SECID257"
35616 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
35618 is written to the main log when a message is about to be removed from the spool
35619 at the end of its processing.
35624 .section "Summary of Fields in Log Lines" "SECID258"
35625 .cindex "log" "summary of fields"
35626 A summary of the field identifiers that are used in log lines is shown in
35627 the following table:
35629 &`A `& authenticator name (and optional id and sender)
35630 &`C `& SMTP confirmation on delivery
35631 &` `& command list for &"no mail in SMTP session"&
35632 &`CV `& certificate verification status
35633 &`D `& duration of &"no mail in SMTP session"&
35634 &`DN `& distinguished name from peer certificate
35635 &`DS `& DNSSEC secured lookups
35636 &`DT `& on &`=>`& lines: time taken for a delivery
35637 &`F `& sender address (on delivery lines)
35638 &`H `& host name and IP address
35639 &`I `& local interface used
35640 &`K `& CHUNKING extension used
35641 &`id `& message id for incoming message
35642 &`P `& on &`<=`& lines: protocol used
35643 &` `& on &`=>`& and &`**`& lines: return path
35644 &`PRDR`& PRDR extension used
35645 &`PRX `& on &'<='& and &`=>`& lines: proxy address
35646 &`Q `& alternate queue name
35647 &`QT `& on &`=>`& lines: time spent on queue so far
35648 &` `& on &"Completed"& lines: time spent on queue
35649 &`R `& on &`<=`& lines: reference for local bounce
35650 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
35651 &`S `& size of message in bytes
35652 &`SNI `& server name indication from TLS client hello
35653 &`ST `& shadow transport name
35654 &`T `& on &`<=`& lines: message subject (topic)
35655 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
35656 &`U `& local user or RFC 1413 identity
35657 &`X `& TLS cipher suite
35661 .section "Other log entries" "SECID259"
35662 Various other types of log entry are written from time to time. Most should be
35663 self-explanatory. Among the more common are:
35666 .cindex "retry" "time not reached"
35667 &'retry time not reached'&&~&~An address previously suffered a temporary error
35668 during routing or local delivery, and the time to retry has not yet arrived.
35669 This message is not written to an individual message log file unless it happens
35670 during the first delivery attempt.
35672 &'retry time not reached for any host'&&~&~An address previously suffered
35673 temporary errors during remote delivery, and the retry time has not yet arrived
35674 for any of the hosts to which it is routed.
35676 .cindex "spool directory" "file locked"
35677 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
35678 some other Exim process is already working on the message. This can be quite
35679 common if queue running processes are started at frequent intervals. The
35680 &'exiwhat'& utility script can be used to find out what Exim processes are
35683 .cindex "error" "ignored"
35684 &'error ignored'&&~&~There are several circumstances that give rise to this
35687 Exim failed to deliver a bounce message whose age was greater than
35688 &%ignore_bounce_errors_after%&. The bounce was discarded.
35690 A filter file set up a delivery using the &"noerror"& option, and the delivery
35691 failed. The delivery was discarded.
35693 A delivery set up by a router configured with
35694 . ==== As this is a nested list, any displays it contains must be indented
35695 . ==== as otherwise they are too far to the left.
35699 failed. The delivery was discarded.
35707 .section "Reducing or increasing what is logged" "SECTlogselector"
35708 .cindex "log" "selectors"
35709 By setting the &%log_selector%& global option, you can disable some of Exim's
35710 default logging, or you can request additional logging. The value of
35711 &%log_selector%& is made up of names preceded by plus or minus characters. For
35714 log_selector = +arguments -retry_defer
35716 The list of optional log items is in the following table, with the default
35717 selection marked by asterisks:
35719 &` 8bitmime `& received 8BITMIME status
35720 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
35721 &` address_rewrite `& address rewriting
35722 &` all_parents `& all parents in => lines
35723 &` arguments `& command line arguments
35724 &`*connection_reject `& connection rejections
35725 &`*delay_delivery `& immediate delivery delayed
35726 &` deliver_time `& time taken to perform delivery
35727 &` delivery_size `& add &`S=`&&'nnn'& to => lines
35728 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
35729 &` dnssec `& DNSSEC secured lookups
35730 &`*etrn `& ETRN commands
35731 &`*host_lookup_failed `& as it says
35732 &` ident_timeout `& timeout for ident connection
35733 &` incoming_interface `& local interface on <= and => lines
35734 &` incoming_port `& remote port on <= lines
35735 &`*lost_incoming_connection `& as it says (includes timeouts)
35736 &` outgoing_interface `& local interface on => lines
35737 &` outgoing_port `& add remote port to => lines
35738 &`*queue_run `& start and end queue runs
35739 &` queue_time `& time on queue for one recipient
35740 &` queue_time_overall `& time on queue for whole message
35741 &` pid `& Exim process id
35742 &` proxy `& proxy address on <= and => lines
35743 &` received_recipients `& recipients on <= lines
35744 &` received_sender `& sender on <= lines
35745 &`*rejected_header `& header contents on reject log
35746 &`*retry_defer `& &"retry time not reached"&
35747 &` return_path_on_delivery `& put return path on => and ** lines
35748 &` sender_on_delivery `& add sender to => lines
35749 &`*sender_verify_fail `& sender verification failures
35750 &`*size_reject `& rejection because too big
35751 &`*skip_delivery `& delivery skipped in a queue run
35752 &`*smtp_confirmation `& SMTP confirmation on => lines
35753 &` smtp_connection `& incoming SMTP connections
35754 &` smtp_incomplete_transaction`& incomplete SMTP transactions
35755 &` smtp_mailauth `& AUTH argument to MAIL commands
35756 &` smtp_no_mail `& session with no MAIL commands
35757 &` smtp_protocol_error `& SMTP protocol errors
35758 &` smtp_syntax_error `& SMTP syntax errors
35759 &` subject `& contents of &'Subject:'& on <= lines
35760 &`*tls_certificate_verified `& certificate verification status
35761 &`*tls_cipher `& TLS cipher suite on <= and => lines
35762 &` tls_peerdn `& TLS peer DN on <= and => lines
35763 &` tls_sni `& TLS SNI on <= lines
35764 &` unknown_in_list `& DNS lookup failed in list match
35766 &` all `& all of the above
35768 See also the &%slow_lookup_log%& main configuration option,
35769 section &<<SECID99>>&
35771 More details on each of these items follows:
35775 .cindex "log" "8BITMIME"
35776 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
35777 which may help in tracking down interoperability issues with ancient MTAs
35778 that are not 8bit clean. This is added to the &"<="& line, tagged with
35779 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
35780 &`7BIT`& and &`8BITMIME`& respectively.
35782 .cindex "&%warn%& ACL verb" "log when skipping"
35783 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
35784 its conditions cannot be evaluated, a log line to this effect is written if
35785 this log selector is set.
35787 .cindex "log" "rewriting"
35788 .cindex "rewriting" "logging"
35789 &%address_rewrite%&: This applies both to global rewrites and per-transport
35790 rewrites, but not to rewrites in filters run as an unprivileged user (because
35791 such users cannot access the log).
35793 .cindex "log" "full parentage"
35794 &%all_parents%&: Normally only the original and final addresses are logged on
35795 delivery lines; with this selector, intermediate parents are given in
35796 parentheses between them.
35798 .cindex "log" "Exim arguments"
35799 .cindex "Exim arguments, logging"
35800 &%arguments%&: This causes Exim to write the arguments with which it was called
35801 to the main log, preceded by the current working directory. This is a debugging
35802 feature, added to make it easier to find out how certain MUAs call
35803 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
35804 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
35805 that are empty or that contain white space are quoted. Non-printing characters
35806 are shown as escape sequences. This facility cannot log unrecognized arguments,
35807 because the arguments are checked before the configuration file is read. The
35808 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
35809 between the caller and Exim.
35811 .cindex "log" "connection rejections"
35812 &%connection_reject%&: A log entry is written whenever an incoming SMTP
35813 connection is rejected, for whatever reason.
35815 .cindex "log" "delayed delivery"
35816 .cindex "delayed delivery, logging"
35817 &%delay_delivery%&: A log entry is written whenever a delivery process is not
35818 started for an incoming message because the load is too high or too many
35819 messages were received on one connection. Logging does not occur if no delivery
35820 process is started because &%queue_only%& is set or &%-odq%& was used.
35822 .cindex "log" "delivery duration"
35823 &%deliver_time%&: For each delivery, the amount of real time it has taken to
35824 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
35826 .cindex "log" "message size on delivery"
35827 .cindex "size" "of message"
35828 &%delivery_size%&: For each delivery, the size of message delivered is added to
35829 the &"=>"& line, tagged with S=.
35831 .cindex "log" "dnslist defer"
35832 .cindex "DNS list" "logging defer"
35833 .cindex "black list (DNS)"
35834 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
35835 DNS black list suffers a temporary error.
35838 .cindex dnssec logging
35839 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
35840 dns lookups gave secure results a tag of DS is added.
35841 For acceptance this covers the reverse and forward lookups for host name verification.
35842 It does not cover helo-name verification.
35843 For delivery this covers the SRV, MX, A and/or AAAA lookups.
35845 .cindex "log" "ETRN commands"
35846 .cindex "ETRN" "logging"
35847 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
35848 is run to determine whether or not it is actually accepted. An invalid ETRN
35849 command, or one received within a message transaction is not logged by this
35850 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
35852 .cindex "log" "host lookup failure"
35853 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
35854 any addresses, or when a lookup of an IP address fails to find a host name, a
35855 log line is written. This logging does not apply to direct DNS lookups when
35856 routing email addresses, but it does apply to &"byname"& lookups.
35858 .cindex "log" "ident timeout"
35859 .cindex "RFC 1413" "logging timeout"
35860 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
35861 client's ident port times out.
35863 .cindex "log" "incoming interface"
35864 .cindex "log" "local interface"
35865 .cindex "log" "local address and port"
35866 .cindex "TCP/IP" "logging local address and port"
35867 .cindex "interface" "logging"
35868 &%incoming_interface%&: The interface on which a message was received is added
35869 to the &"<="& line as an IP address in square brackets, tagged by I= and
35870 followed by a colon and the port number. The local interface and port are also
35871 added to other SMTP log lines, for example &"SMTP connection from"&, to
35872 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
35873 The latter can be disabled by turning off the &%outgoing_interface%& option.
35875 .cindex log "incoming proxy address"
35876 .cindex proxy "logging proxy address"
35877 .cindex "TCP/IP" "logging proxy address"
35878 &%proxy%&: The internal (closest to the system running Exim) IP address
35879 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
35880 on a proxied connection
35881 or the &"=>"& line for a message delivered on a proxied connection..
35882 See &<<SECTproxyInbound>>& for more information.
35884 .cindex "log" "incoming remote port"
35885 .cindex "port" "logging remote"
35886 .cindex "TCP/IP" "logging incoming remote port"
35887 .vindex "&$sender_fullhost$&"
35888 .vindex "&$sender_rcvhost$&"
35889 &%incoming_port%&: The remote port number from which a message was received is
35890 added to log entries and &'Received:'& header lines, following the IP address
35891 in square brackets, and separated from it by a colon. This is implemented by
35892 changing the value that is put in the &$sender_fullhost$& and
35893 &$sender_rcvhost$& variables. Recording the remote port number has become more
35894 important with the widening use of NAT (see RFC 2505).
35896 .cindex "log" "dropped connection"
35897 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
35898 connection is unexpectedly dropped.
35900 .cindex "log" "outgoing interface"
35901 .cindex "log" "local interface"
35902 .cindex "log" "local address and port"
35903 .cindex "TCP/IP" "logging local address and port"
35904 .cindex "interface" "logging"
35905 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
35906 interface on which a message was sent is added to delivery lines as an I= tag
35907 followed by IP address in square brackets. You can disable this by turning
35908 off the &%outgoing_interface%& option.
35910 .cindex "log" "outgoing remote port"
35911 .cindex "port" "logging outgoint remote"
35912 .cindex "TCP/IP" "logging ougtoing remote port"
35913 &%outgoing_port%&: The remote port number is added to delivery log lines (those
35914 containing => tags) following the IP address.
35915 The local port is also added if &%incoming_interface%& and
35916 &%outgoing_interface%& are both enabled.
35917 This option is not included in the default setting, because for most ordinary
35918 configurations, the remote port number is always 25 (the SMTP port), and the
35919 local port is a random ephemeral port.
35921 .cindex "log" "process ids in"
35922 .cindex "pid (process id)" "in log lines"
35923 &%pid%&: The current process id is added to every log line, in square brackets,
35924 immediately after the time and date.
35926 .cindex "log" "queue run"
35927 .cindex "queue runner" "logging"
35928 &%queue_run%&: The start and end of every queue run are logged.
35930 .cindex "log" "queue time"
35931 &%queue_time%&: The amount of time the message has been in the queue on the
35932 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
35933 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
35934 includes reception time as well as the delivery time for the current address.
35935 This means that it may be longer than the difference between the arrival and
35936 delivery log line times, because the arrival log line is not written until the
35937 message has been successfully received.
35939 &%queue_time_overall%&: The amount of time the message has been in the queue on
35940 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
35941 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
35942 message, so it includes reception time as well as the total delivery time.
35944 .cindex "log" "recipients"
35945 &%received_recipients%&: The recipients of a message are listed in the main log
35946 as soon as the message is received. The list appears at the end of the log line
35947 that is written when a message is received, preceded by the word &"for"&. The
35948 addresses are listed after they have been qualified, but before any rewriting
35950 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
35953 .cindex "log" "sender reception"
35954 &%received_sender%&: The unrewritten original sender of a message is added to
35955 the end of the log line that records the message's arrival, after the word
35956 &"from"& (before the recipients if &%received_recipients%& is also set).
35958 .cindex "log" "header lines for rejection"
35959 &%rejected_header%&: If a message's header has been received at the time a
35960 rejection is written to the reject log, the complete header is added to the
35961 log. Header logging can be turned off individually for messages that are
35962 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
35964 .cindex "log" "retry defer"
35965 &%retry_defer%&: A log line is written if a delivery is deferred because a
35966 retry time has not yet been reached. However, this &"retry time not reached"&
35967 message is always omitted from individual message logs after the first delivery
35970 .cindex "log" "return path"
35971 &%return_path_on_delivery%&: The return path that is being transmitted with
35972 the message is included in delivery and bounce lines, using the tag P=.
35973 This is omitted if no delivery actually happens, for example, if routing fails,
35974 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
35976 .cindex "log" "sender on delivery"
35977 &%sender_on_delivery%&: The message's sender address is added to every delivery
35978 and bounce line, tagged by F= (for &"from"&).
35979 This is the original sender that was received with the message; it is not
35980 necessarily the same as the outgoing return path.
35982 .cindex "log" "sender verify failure"
35983 &%sender_verify_fail%&: If this selector is unset, the separate log line that
35984 gives details of a sender verification failure is not written. Log lines for
35985 the rejection of SMTP commands contain just &"sender verify failed"&, so some
35988 .cindex "log" "size rejection"
35989 &%size_reject%&: A log line is written whenever a message is rejected because
35992 .cindex "log" "frozen messages; skipped"
35993 .cindex "frozen messages" "logging skipping"
35994 &%skip_delivery%&: A log line is written whenever a message is skipped during a
35995 queue run because it is frozen or because another process is already delivering
35997 .cindex "&""spool file is locked""&"
35998 The message that is written is &"spool file is locked"&.
36000 .cindex "log" "smtp confirmation"
36001 .cindex "SMTP" "logging confirmation"
36002 .cindex "LMTP" "logging confirmation"
36003 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
36004 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
36005 A number of MTAs (including Exim) return an identifying string in this
36008 .cindex "log" "SMTP connections"
36009 .cindex "SMTP" "logging connections"
36010 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
36011 established or closed, unless the connection is from a host that matches
36012 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
36013 only when the closure is unexpected.) This applies to connections from local
36014 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
36015 dropped in the middle of a message, a log line is always written, whether or
36016 not this selector is set, but otherwise nothing is written at the start and end
36017 of connections unless this selector is enabled.
36019 For TCP/IP connections to an Exim daemon, the current number of connections is
36020 included in the log message for each new connection, but note that the count is
36021 reset if the daemon is restarted.
36022 Also, because connections are closed (and the closure is logged) in
36023 subprocesses, the count may not include connections that have been closed but
36024 whose termination the daemon has not yet noticed. Thus, while it is possible to
36025 match up the opening and closing of connections in the log, the value of the
36026 logged counts may not be entirely accurate.
36028 .cindex "log" "SMTP transaction; incomplete"
36029 .cindex "SMTP" "logging incomplete transactions"
36030 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
36031 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
36032 and the message sender plus any accepted recipients are included in the log
36033 line. This can provide evidence of dictionary attacks.
36035 .cindex "log" "non-MAIL SMTP sessions"
36036 .cindex "MAIL" "logging session without"
36037 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
36038 connection terminates without having issued a MAIL command. This includes both
36039 the case when the connection is dropped, and the case when QUIT is used. It
36040 does not include cases where the connection is rejected right at the start (by
36041 an ACL, or because there are too many connections, or whatever). These cases
36042 already have their own log lines.
36044 The log line that is written contains the identity of the client in the usual
36045 way, followed by D= and a time, which records the duration of the connection.
36046 If the connection was authenticated, this fact is logged exactly as it is for
36047 an incoming message, with an A= item. If the connection was encrypted, CV=,
36048 DN=, and X= items may appear as they do for an incoming message, controlled by
36049 the same logging options.
36051 Finally, if any SMTP commands were issued during the connection, a C= item
36052 is added to the line, listing the commands that were used. For example,
36056 shows that the client issued QUIT straight after EHLO. If there were fewer
36057 than 20 commands, they are all listed. If there were more than 20 commands,
36058 the last 20 are listed, preceded by &"..."&. However, with the default
36059 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
36060 have been aborted before 20 non-mail commands are processed.
36062 &%smtp_mailauth%&: A third subfield with the authenticated sender,
36063 colon-separated, is appended to the A= item for a message arrival or delivery
36064 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
36065 was accepted or used.
36067 .cindex "log" "SMTP protocol error"
36068 .cindex "SMTP" "logging protocol error"
36069 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
36070 encountered. Exim does not have perfect detection of all protocol errors
36071 because of transmission delays and the use of pipelining. If PIPELINING has
36072 been advertised to a client, an Exim server assumes that the client will use
36073 it, and therefore it does not count &"expected"& errors (for example, RCPT
36074 received after rejecting MAIL) as protocol errors.
36076 .cindex "SMTP" "logging syntax errors"
36077 .cindex "SMTP" "syntax errors; logging"
36078 .cindex "SMTP" "unknown command; logging"
36079 .cindex "log" "unknown SMTP command"
36080 .cindex "log" "SMTP syntax error"
36081 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
36082 encountered. An unrecognized command is treated as a syntax error. For an
36083 external connection, the host identity is given; for an internal connection
36084 using &%-bs%& the sender identification (normally the calling user) is given.
36086 .cindex "log" "subject"
36087 .cindex "subject, logging"
36088 &%subject%&: The subject of the message is added to the arrival log line,
36089 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
36090 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
36091 specifies whether characters with values greater than 127 should be logged
36092 unchanged, or whether they should be rendered as escape sequences.
36094 .cindex "log" "certificate verification"
36095 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
36096 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
36097 verified, and &`CV=no`& if not.
36099 .cindex "log" "TLS cipher"
36100 .cindex "TLS" "logging cipher"
36101 &%tls_cipher%&: When a message is sent or received over an encrypted
36102 connection, the cipher suite used is added to the log line, preceded by X=.
36104 .cindex "log" "TLS peer DN"
36105 .cindex "TLS" "logging peer DN"
36106 &%tls_peerdn%&: When a message is sent or received over an encrypted
36107 connection, and a certificate is supplied by the remote host, the peer DN is
36108 added to the log line, preceded by DN=.
36110 .cindex "log" "TLS SNI"
36111 .cindex "TLS" "logging SNI"
36112 &%tls_sni%&: When a message is received over an encrypted connection, and
36113 the remote host provided the Server Name Indication extension, the SNI is
36114 added to the log line, preceded by SNI=.
36116 .cindex "log" "DNS failure in list"
36117 &%unknown_in_list%&: This setting causes a log entry to be written when the
36118 result of a list match is failure because a DNS lookup failed.
36122 .section "Message log" "SECID260"
36123 .cindex "message" "log file for"
36124 .cindex "log" "message log; description of"
36125 .cindex "&_msglog_& directory"
36126 .oindex "&%preserve_message_logs%&"
36127 In addition to the general log files, Exim writes a log file for each message
36128 that it handles. The names of these per-message logs are the message ids, and
36129 they are kept in the &_msglog_& sub-directory of the spool directory. Each
36130 message log contains copies of the log lines that apply to the message. This
36131 makes it easier to inspect the status of an individual message without having
36132 to search the main log. A message log is deleted when processing of the message
36133 is complete, unless &%preserve_message_logs%& is set, but this should be used
36134 only with great care because they can fill up your disk very quickly.
36136 On a heavily loaded system, it may be desirable to disable the use of
36137 per-message logs, in order to reduce disk I/O. This can be done by setting the
36138 &%message_logs%& option false.
36144 . ////////////////////////////////////////////////////////////////////////////
36145 . ////////////////////////////////////////////////////////////////////////////
36147 .chapter "Exim utilities" "CHAPutils"
36148 .scindex IIDutils "utilities"
36149 A number of utility scripts and programs are supplied with Exim and are
36150 described in this chapter. There is also the Exim Monitor, which is covered in
36151 the next chapter. The utilities described here are:
36153 .itable none 0 0 3 7* left 15* left 40* left
36154 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
36155 "list what Exim processes are doing"
36156 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
36157 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
36158 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
36159 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
36161 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
36162 .irow &<<SECTmailstat>>& &'eximstats'& &&&
36163 "extract statistics from the log"
36164 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
36165 "check address acceptance from given IP"
36166 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
36167 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
36168 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
36169 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
36170 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
36171 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
36174 Another utility that might be of use to sites with many MTAs is Tom Kistner's
36175 &'exilog'&. It provides log visualizations across multiple Exim servers. See
36176 &url(http://duncanthrax.net/exilog/) for details.
36181 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
36182 .cindex "&'exiwhat'&"
36183 .cindex "process, querying"
36185 On operating systems that can restart a system call after receiving a signal
36186 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
36187 a line describing what it is doing to the file &_exim-process.info_& in the
36188 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
36189 processes it can find, having first emptied the file. It then waits for one
36190 second to allow the Exim processes to react before displaying the results. In
36191 order to run &'exiwhat'& successfully you have to have sufficient privilege to
36192 send the signal to the Exim processes, so it is normally run as root.
36194 &*Warning*&: This is not an efficient process. It is intended for occasional
36195 use by system administrators. It is not sensible, for example, to set up a
36196 script that sends SIGUSR1 signals to Exim processes at short intervals.
36199 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
36200 varies in different operating systems. Not only are different options used,
36201 but the format of the output is different. For this reason, there are some
36202 system configuration options that configure exactly how &'exiwhat'& works. If
36203 it doesn't seem to be working for you, check the following compile-time
36206 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
36207 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
36208 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
36209 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
36211 An example of typical output from &'exiwhat'& is
36213 164 daemon: -q1h, listening on port 25
36214 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
36215 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
36216 [10.19.42.42] (editor@ref.example)
36217 10592 handling incoming call from [192.168.243.242]
36218 10628 accepting a local non-SMTP message
36220 The first number in the output line is the process number. The third line has
36221 been split here, in order to fit it on the page.
36225 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
36226 .cindex "&'exiqgrep'&"
36227 .cindex "queue" "grepping"
36228 This utility is a Perl script contributed by Matt Hubbard. It runs
36232 or (in case &*-a*& switch is specified)
36236 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
36237 contain alternate exim configuration the queue management might be using.
36239 to obtain a queue listing, and then greps the output to select messages
36240 that match given criteria. The following selection options are available:
36243 .vitem &*-f*&&~<&'regex'&>
36244 Match the sender address using a case-insensitive search. The field that is
36245 tested is enclosed in angle brackets, so you can test for bounce messages with
36249 .vitem &*-r*&&~<&'regex'&>
36250 Match a recipient address using a case-insensitive search. The field that is
36251 tested is not enclosed in angle brackets.
36253 .vitem &*-s*&&~<&'regex'&>
36254 Match against the size field.
36256 .vitem &*-y*&&~<&'seconds'&>
36257 Match messages that are younger than the given time.
36259 .vitem &*-o*&&~<&'seconds'&>
36260 Match messages that are older than the given time.
36263 Match only frozen messages.
36266 Match only non-frozen messages.
36269 The following options control the format of the output:
36273 Display only the count of matching messages.
36276 Long format &-- display the full message information as output by Exim. This is
36280 Display message ids only.
36283 Brief format &-- one line per message.
36286 Display messages in reverse order.
36289 Include delivered recipients in queue listing.
36292 There is one more option, &%-h%&, which outputs a list of options.
36296 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
36297 .cindex "&'exiqsumm'&"
36298 .cindex "queue" "summary"
36299 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
36300 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
36301 running a command such as
36303 exim -bp | exiqsumm
36305 The output consists of one line for each domain that has messages waiting for
36306 it, as in the following example:
36308 3 2322 74m 66m msn.com.example
36310 Each line lists the number of pending deliveries for a domain, their total
36311 volume, and the length of time that the oldest and the newest messages have
36312 been waiting. Note that the number of pending deliveries is greater than the
36313 number of messages when messages have more than one recipient.
36315 A summary line is output at the end. By default the output is sorted on the
36316 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
36317 the output to be sorted by oldest message and by count of messages,
36318 respectively. There are also three options that split the messages for each
36319 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
36320 separates frozen messages, and &%-s%& separates messages according to their
36323 The output of &'exim -bp'& contains the original addresses in the message, so
36324 this also applies to the output from &'exiqsumm'&. No domains from addresses
36325 generated by aliasing or forwarding are included (unless the &%one_time%&
36326 option of the &(redirect)& router has been used to convert them into &"top
36327 level"& addresses).
36332 .section "Extracting specific information from the log (exigrep)" &&&
36334 .cindex "&'exigrep'&"
36335 .cindex "log" "extracts; grepping for"
36336 The &'exigrep'& utility is a Perl script that searches one or more main log
36337 files for entries that match a given pattern. When it finds a match, it
36338 extracts all the log entries for the relevant message, not just those that
36339 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
36340 given message, or all mail for a given user, or for a given host, for example.
36341 The input files can be in Exim log format or syslog format.
36342 If a matching log line is not associated with a specific message, it is
36343 included in &'exigrep'&'s output without any additional lines. The usage is:
36345 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
36347 If no log file names are given on the command line, the standard input is read.
36349 The &%-t%& argument specifies a number of seconds. It adds an additional
36350 condition for message selection. Messages that are complete are shown only if
36351 they spent more than <&'n'&> seconds on the queue.
36353 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
36354 makes it case-sensitive. This may give a performance improvement when searching
36355 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
36356 option; with &%-I%& they do not. In both cases it is possible to change the
36357 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
36359 The &%-l%& option means &"literal"&, that is, treat all characters in the
36360 pattern as standing for themselves. Otherwise the pattern must be a Perl
36361 regular expression.
36363 The &%-v%& option inverts the matching condition. That is, a line is selected
36364 if it does &'not'& match the pattern.
36366 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
36367 that are generated as a result/response to a message that &'exigrep'& matched
36371 user_a sends a message to user_b, which generates a bounce back to user_b. If
36372 &'exigrep'& is used to search for &"user_a"&, only the first message will be
36373 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
36374 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
36375 when searching for &"user_a"& will show both messages since the bounce is
36376 &"related"& to or a &"result"& of the first message that was found by the
36379 If the location of a &'zcat'& command is known from the definition of
36380 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
36381 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
36382 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
36383 autodetection of some well known compression extensions.
36386 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
36387 .cindex "&'exipick'&"
36388 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
36389 lists messages from the queue according to a variety of criteria. For details
36390 of &'exipick'&'s facilities, visit the web page at
36391 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
36392 the &%--help%& option.
36395 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
36396 .cindex "log" "cycling local files"
36397 .cindex "cycling logs"
36398 .cindex "&'exicyclog'&"
36399 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
36400 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
36401 you are using log files with datestamps in their names (see section
36402 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
36403 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
36404 There are two command line options for &'exicyclog'&:
36406 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
36407 default that is set when Exim is built. The default default is 10.
36409 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
36410 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
36411 overriding the script's default, which is to find the setting from Exim's
36415 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
36416 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
36417 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
36418 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
36419 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
36420 logs are handled similarly.
36422 If the limit is greater than 99, the script uses 3-digit numbers such as
36423 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
36424 to one that is greater, or &'vice versa'&, you will have to fix the names of
36425 any existing log files.
36427 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
36428 the end are deleted. All files with numbers greater than 01 are compressed,
36429 using a compression command which is configured by the COMPRESS_COMMAND
36430 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
36431 root &%crontab%& entry of the form
36433 1 0 * * * su exim -c /usr/exim/bin/exicyclog
36435 assuming you have used the name &"exim"& for the Exim user. You can run
36436 &'exicyclog'& as root if you wish, but there is no need.
36440 .section "Mail statistics (eximstats)" "SECTmailstat"
36441 .cindex "statistics"
36442 .cindex "&'eximstats'&"
36443 A Perl script called &'eximstats'& is provided for extracting statistical
36444 information from log files. The output is either plain text, or HTML.
36445 Exim log files are also supported by the &'Lire'& system produced by the
36446 LogReport Foundation &url(http://www.logreport.org).
36448 The &'eximstats'& script has been hacked about quite a bit over time. The
36449 latest version is the result of some extensive revision by Steve Campbell. A
36450 lot of information is given by default, but there are options for suppressing
36451 various parts of it. Following any options, the arguments to the script are a
36452 list of files, which should be main log files. For example:
36454 eximstats -nr /var/spool/exim/log/mainlog.01
36456 By default, &'eximstats'& extracts information about the number and volume of
36457 messages received from or delivered to various hosts. The information is sorted
36458 both by message count and by volume, and the top fifty hosts in each category
36459 are listed on the standard output. Similar information, based on email
36460 addresses or domains instead of hosts can be requested by means of various
36461 options. For messages delivered and received locally, similar statistics are
36462 also produced per user.
36464 The output also includes total counts and statistics about delivery errors, and
36465 histograms showing the number of messages received and deliveries made in each
36466 hour of the day. A delivery with more than one address in its envelope (for
36467 example, an SMTP transaction with more than one RCPT command) is counted
36468 as a single delivery by &'eximstats'&.
36470 Though normally more deliveries than receipts are reported (as messages may
36471 have multiple recipients), it is possible for &'eximstats'& to report more
36472 messages received than delivered, even though the queue is empty at the start
36473 and end of the period in question. If an incoming message contains no valid
36474 recipients, no deliveries are recorded for it. A bounce message is handled as
36475 an entirely separate message.
36477 &'eximstats'& always outputs a grand total summary giving the volume and number
36478 of messages received and deliveries made, and the number of hosts involved in
36479 each case. It also outputs the number of messages that were delayed (that is,
36480 not completely delivered at the first attempt), and the number that had at
36481 least one address that failed.
36483 The remainder of the output is in sections that can be independently disabled
36484 or modified by various options. It consists of a summary of deliveries by
36485 transport, histograms of messages received and delivered per time interval
36486 (default per hour), information about the time messages spent on the queue,
36487 a list of relayed messages, lists of the top fifty sending hosts, local
36488 senders, destination hosts, and destination local users by count and by volume,
36489 and a list of delivery errors that occurred.
36491 The relay information lists messages that were actually relayed, that is, they
36492 came from a remote host and were directly delivered to some other remote host,
36493 without being processed (for example, for aliasing or forwarding) locally.
36495 There are quite a few options for &'eximstats'& to control exactly what it
36496 outputs. These are documented in the Perl script itself, and can be extracted
36497 by running the command &(perldoc)& on the script. For example:
36499 perldoc /usr/exim/bin/eximstats
36502 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
36503 .cindex "&'exim_checkaccess'&"
36504 .cindex "policy control" "checking access"
36505 .cindex "checking access"
36506 The &%-bh%& command line argument allows you to run a fake SMTP session with
36507 debugging output, in order to check what Exim is doing when it is applying
36508 policy controls to incoming SMTP mail. However, not everybody is sufficiently
36509 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
36510 sometimes you just want to answer the question &"Does this address have
36511 access?"& without bothering with any further details.
36513 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
36514 two arguments, an IP address and an email address:
36516 exim_checkaccess 10.9.8.7 A.User@a.domain.example
36518 The utility runs a call to Exim with the &%-bh%& option, to test whether the
36519 given email address would be accepted in a RCPT command in a TCP/IP
36520 connection from the host with the given IP address. The output of the utility
36521 is either the word &"accepted"&, or the SMTP error response, for example:
36524 550 Relay not permitted
36526 When running this test, the utility uses &`<>`& as the envelope sender address
36527 for the MAIL command, but you can change this by providing additional
36528 options. These are passed directly to the Exim command. For example, to specify
36529 that the test is to be run with the sender address &'himself@there.example'&
36532 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
36533 -f himself@there.example
36535 Note that these additional Exim command line items must be given after the two
36536 mandatory arguments.
36538 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
36539 while running its checks. You can run checks that include callouts by using
36540 &%-bhc%&, but this is not yet available in a &"packaged"& form.
36544 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
36545 .cindex "DBM" "building dbm files"
36546 .cindex "building DBM files"
36547 .cindex "&'exim_dbmbuild'&"
36548 .cindex "lower casing"
36549 .cindex "binary zero" "in lookup key"
36550 The &'exim_dbmbuild'& program reads an input file containing keys and data in
36551 the format used by the &(lsearch)& lookup (see section
36552 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
36553 names as keys and the remainder of the information as data. The lower-casing
36554 can be prevented by calling the program with the &%-nolc%& option.
36556 A terminating zero is included as part of the key string. This is expected by
36557 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
36558 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
36559 strings or the data strings. The &(dbmnz)& lookup type can be used with such
36562 The program requires two arguments: the name of the input file (which can be a
36563 single hyphen to indicate the standard input), and the name of the output file.
36564 It creates the output under a temporary name, and then renames it if all went
36568 If the native DB interface is in use (USE_DB is set in a compile-time
36569 configuration file &-- this is common in free versions of Unix) the two file
36570 names must be different, because in this mode the Berkeley DB functions create
36571 a single output file using exactly the name given. For example,
36573 exim_dbmbuild /etc/aliases /etc/aliases.db
36575 reads the system alias file and creates a DBM version of it in
36576 &_/etc/aliases.db_&.
36578 In systems that use the &'ndbm'& routines (mostly proprietary versions of
36579 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
36580 environment, the suffixes are added to the second argument of
36581 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
36582 when the Berkeley functions are used in compatibility mode (though this is not
36583 recommended), because in that case it adds a &_.db_& suffix to the file name.
36585 If a duplicate key is encountered, the program outputs a warning, and when it
36586 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
36587 option is used. By default, only the first of a set of duplicates is used &--
36588 this makes it compatible with &(lsearch)& lookups. There is an option
36589 &%-lastdup%& which causes it to use the data for the last duplicate instead.
36590 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
36591 &%stderr%&. For other errors, where it doesn't actually make a new file, the
36597 .section "Finding individual retry times (exinext)" "SECTfinindret"
36598 .cindex "retry" "times"
36599 .cindex "&'exinext'&"
36600 A utility called &'exinext'& (mostly a Perl script) provides the ability to
36601 fish specific information out of the retry database. Given a mail domain (or a
36602 complete address), it looks up the hosts for that domain, and outputs any retry
36603 information for the hosts or for the domain. At present, the retry information
36604 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
36605 output. For example:
36607 $ exinext piglet@milne.fict.example
36608 kanga.milne.example:192.168.8.1 error 146: Connection refused
36609 first failed: 21-Feb-1996 14:57:34
36610 last tried: 21-Feb-1996 14:57:34
36611 next try at: 21-Feb-1996 15:02:34
36612 roo.milne.example:192.168.8.3 error 146: Connection refused
36613 first failed: 20-Jan-1996 13:12:08
36614 last tried: 21-Feb-1996 11:42:03
36615 next try at: 21-Feb-1996 19:42:03
36616 past final cutoff time
36618 You can also give &'exinext'& a local part, without a domain, and it
36619 will give any retry information for that local part in your default domain.
36620 A message id can be used to obtain retry information pertaining to a specific
36621 message. This exists only when an attempt to deliver a message to a remote host
36622 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
36623 &'exinext'& is not particularly efficient, but then it is not expected to be
36626 The &'exinext'& utility calls Exim to find out information such as the location
36627 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
36628 passed on to the &'exim'& commands. The first specifies an alternate Exim
36629 configuration file, and the second sets macros for use within the configuration
36630 file. These features are mainly to help in testing, but might also be useful in
36631 environments where more than one configuration file is in use.
36635 .section "Hints database maintenance" "SECThindatmai"
36636 .cindex "hints database" "maintenance"
36637 .cindex "maintaining Exim's hints database"
36638 Three utility programs are provided for maintaining the DBM files that Exim
36639 uses to contain its delivery hint information. Each program requires two
36640 arguments. The first specifies the name of Exim's spool directory, and the
36641 second is the name of the database it is to operate on. These are as follows:
36644 &'retry'&: the database of retry information
36646 &'wait-'&<&'transport name'&>: databases of information about messages waiting
36649 &'callout'&: the callout cache
36651 &'ratelimit'&: the data for implementing the ratelimit ACL condition
36653 &'misc'&: other hints data
36656 The &'misc'& database is used for
36659 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
36661 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
36662 &(smtp)& transport)
36664 Limiting the concurrency of specific transports (when &%max_parallel%& is set
36670 .section "exim_dumpdb" "SECID261"
36671 .cindex "&'exim_dumpdb'&"
36672 The entire contents of a database are written to the standard output by the
36673 &'exim_dumpdb'& program, which has no options or arguments other than the
36674 spool and database names. For example, to dump the retry database:
36676 exim_dumpdb /var/spool/exim retry
36678 Two lines of output are produced for each entry:
36680 T:mail.ref.example:192.168.242.242 146 77 Connection refused
36681 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
36683 The first item on the first line is the key of the record. It starts with one
36684 of the letters R, or T, depending on whether it refers to a routing or
36685 transport retry. For a local delivery, the next part is the local address; for
36686 a remote delivery it is the name of the remote host, followed by its failing IP
36687 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
36688 transport). If the remote port is not the standard one (port 25), it is added
36689 to the IP address. Then there follows an error code, an additional error code,
36690 and a textual description of the error.
36692 The three times on the second line are the time of first failure, the time of
36693 the last delivery attempt, and the computed time for the next attempt. The line
36694 ends with an asterisk if the cutoff time for the last retry rule has been
36697 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
36698 consists of a host name followed by a list of ids for messages that are or were
36699 waiting to be delivered to that host. If there are a very large number for any
36700 one host, continuation records, with a sequence number added to the host name,
36701 may be seen. The data in these records is often out of date, because a message
36702 may be routed to several alternative hosts, and Exim makes no effort to keep
36707 .section "exim_tidydb" "SECID262"
36708 .cindex "&'exim_tidydb'&"
36709 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
36710 database. If run with no options, it removes all records that are more than 30
36711 days old. The age is calculated from the date and time that the record was last
36712 updated. Note that, in the case of the retry database, it is &'not'& the time
36713 since the first delivery failure. Information about a host that has been down
36714 for more than 30 days will remain in the database, provided that the record is
36715 updated sufficiently often.
36717 The cutoff date can be altered by means of the &%-t%& option, which must be
36718 followed by a time. For example, to remove all records older than a week from
36719 the retry database:
36721 exim_tidydb -t 7d /var/spool/exim retry
36723 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
36724 message ids. In the former these appear as data in records keyed by host &--
36725 they were messages that were waiting for that host &-- and in the latter they
36726 are the keys for retry information for messages that have suffered certain
36727 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
36728 message ids in database records are those of messages that are still on the
36729 queue. Message ids for messages that no longer exist are removed from
36730 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
36731 For the &'retry'& database, records whose keys are non-existent message ids are
36732 removed. The &'exim_tidydb'& utility outputs comments on the standard output
36733 whenever it removes information from the database.
36735 Certain records are automatically removed by Exim when they are no longer
36736 needed, but others are not. For example, if all the MX hosts for a domain are
36737 down, a retry record is created for each one. If the primary MX host comes back
36738 first, its record is removed when Exim successfully delivers to it, but the
36739 records for the others remain because Exim has not tried to use those hosts.
36741 It is important, therefore, to run &'exim_tidydb'& periodically on all the
36742 hints databases. You should do this at a quiet time of day, because it requires
36743 a database to be locked (and therefore inaccessible to Exim) while it does its
36744 work. Removing records from a DBM file does not normally make the file smaller,
36745 but all the common DBM libraries are able to re-use the space that is released.
36746 After an initial phase of increasing in size, the databases normally reach a
36747 point at which they no longer get any bigger, as long as they are regularly
36750 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
36751 databases is likely to keep on increasing.
36756 .section "exim_fixdb" "SECID263"
36757 .cindex "&'exim_fixdb'&"
36758 The &'exim_fixdb'& program is a utility for interactively modifying databases.
36759 Its main use is for testing Exim, but it might also be occasionally useful for
36760 getting round problems in a live system. It has no options, and its interface
36761 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
36762 key of a database record can then be entered, and the data for that record is
36765 If &"d"& is typed at the next prompt, the entire record is deleted. For all
36766 except the &'retry'& database, that is the only operation that can be carried
36767 out. For the &'retry'& database, each field is output preceded by a number, and
36768 data for individual fields can be changed by typing the field number followed
36769 by new data, for example:
36773 resets the time of the next delivery attempt. Time values are given as a
36774 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
36775 used as optional separators.
36780 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
36781 .cindex "mailbox" "maintenance"
36782 .cindex "&'exim_lock'&"
36783 .cindex "locking mailboxes"
36784 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
36785 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
36786 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
36787 a user agent while investigating a problem. The utility requires the name of
36788 the file as its first argument. If the locking is successful, the second
36789 argument is run as a command (using C's &[system()]& function); if there is no
36790 second argument, the value of the SHELL environment variable is used; if this
36791 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
36792 is unlocked and the utility ends. The following options are available:
36796 Use &[fcntl()]& locking on the open mailbox.
36799 Use &[flock()]& locking on the open mailbox, provided the operating system
36802 .vitem &%-interval%&
36803 This must be followed by a number, which is a number of seconds; it sets the
36804 interval to sleep between retries (default 3).
36806 .vitem &%-lockfile%&
36807 Create a lock file before opening the mailbox.
36810 Lock the mailbox using MBX rules.
36813 Suppress verification output.
36815 .vitem &%-retries%&
36816 This must be followed by a number; it sets the number of times to try to get
36817 the lock (default 10).
36819 .vitem &%-restore_time%&
36820 This option causes &%exim_lock%& to restore the modified and read times to the
36821 locked file before exiting. This allows you to access a locked mailbox (for
36822 example, to take a backup copy) without disturbing the times that the user
36825 .vitem &%-timeout%&
36826 This must be followed by a number, which is a number of seconds; it sets a
36827 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
36828 default), a non-blocking call is used.
36831 Generate verbose output.
36834 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
36835 default is to create a lock file and also to use &[fcntl()]& locking on the
36836 mailbox, which is the same as Exim's default. The use of &%-flock%& or
36837 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
36838 requires that the directory containing the file be writeable. Locking by lock
36839 file does not last for ever; Exim assumes that a lock file is expired if it is
36840 more than 30 minutes old.
36842 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
36843 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
36844 to be taken out on the open mailbox, and an exclusive lock on the file
36845 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
36846 number of the mailbox file. When the locking is released, if an exclusive lock
36847 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
36849 The default output contains verification of the locking that takes place. The
36850 &%-v%& option causes some additional information to be given. The &%-q%& option
36851 suppresses all output except error messages.
36855 exim_lock /var/spool/mail/spqr
36857 runs an interactive shell while the file is locked, whereas
36859 &`exim_lock -q /var/spool/mail/spqr <<End`&
36860 <&'some commands'&>
36863 runs a specific non-interactive sequence of commands while the file is locked,
36864 suppressing all verification output. A single command can be run by a command
36867 exim_lock -q /var/spool/mail/spqr \
36868 "cp /var/spool/mail/spqr /some/where"
36870 Note that if a command is supplied, it must be entirely contained within the
36871 second argument &-- hence the quotes.
36875 . ////////////////////////////////////////////////////////////////////////////
36876 . ////////////////////////////////////////////////////////////////////////////
36878 .chapter "The Exim monitor" "CHAPeximon"
36879 .scindex IIDeximon "Exim monitor" "description"
36880 .cindex "X-windows"
36881 .cindex "&'eximon'&"
36882 .cindex "Local/eximon.conf"
36883 .cindex "&_exim_monitor/EDITME_&"
36884 The Exim monitor is an application which displays in an X window information
36885 about the state of Exim's queue and what Exim is doing. An admin user can
36886 perform certain operations on messages from this GUI interface; however all
36887 such facilities are also available from the command line, and indeed, the
36888 monitor itself makes use of the command line to perform any actions requested.
36892 .section "Running the monitor" "SECID264"
36893 The monitor is started by running the script called &'eximon'&. This is a shell
36894 script that sets up a number of environment variables, and then runs the
36895 binary called &_eximon.bin_&. The default appearance of the monitor window can
36896 be changed by editing the &_Local/eximon.conf_& file created by editing
36897 &_exim_monitor/EDITME_&. Comments in that file describe what the various
36898 parameters are for.
36900 The parameters that get built into the &'eximon'& script can be overridden for
36901 a particular invocation by setting up environment variables of the same names,
36902 preceded by &`EXIMON_`&. For example, a shell command such as
36904 EXIMON_LOG_DEPTH=400 eximon
36906 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
36907 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
36908 overrides the Exim log file configuration. This makes it possible to have
36909 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
36910 syslog messages are routed to a file on the local host.
36912 X resources can be used to change the appearance of the window in the normal
36913 way. For example, a resource setting of the form
36915 Eximon*background: gray94
36917 changes the colour of the background to light grey rather than white. The
36918 stripcharts are drawn with both the data lines and the reference lines in
36919 black. This means that the reference lines are not visible when on top of the
36920 data. However, their colour can be changed by setting a resource called
36921 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
36922 For example, if your X server is running Unix, you could set up lighter
36923 reference lines in the stripcharts by obeying
36926 Eximon*highlight: gray
36929 .cindex "admin user"
36930 In order to see the contents of messages on the queue, and to operate on them,
36931 &'eximon'& must either be run as root or by an admin user.
36933 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
36934 contain X11 resource parameters interpreted by the X11 library. In addition,
36935 if the first parameter starts with the string "gdb" then it is removed and the
36936 binary is invoked under gdb (the parameter is used as the gdb command-name, so
36937 versioned variants of gdb can be invoked).
36939 The monitor's window is divided into three parts. The first contains one or
36940 more stripcharts and two action buttons, the second contains a &"tail"& of the
36941 main log file, and the third is a display of the queue of messages awaiting
36942 delivery, with two more action buttons. The following sections describe these
36943 different parts of the display.
36948 .section "The stripcharts" "SECID265"
36949 .cindex "stripchart"
36950 The first stripchart is always a count of messages on the queue. Its name can
36951 be configured by setting QUEUE_STRIPCHART_NAME in the
36952 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
36953 configuration script by regular expression matches on log file entries, making
36954 it possible to display, for example, counts of messages delivered to certain
36955 hosts or using certain transports. The supplied defaults display counts of
36956 received and delivered messages, and of local and SMTP deliveries. The default
36957 period between stripchart updates is one minute; this can be adjusted by a
36958 parameter in the &_Local/eximon.conf_& file.
36960 The stripchart displays rescale themselves automatically as the value they are
36961 displaying changes. There are always 10 horizontal lines in each chart; the
36962 title string indicates the value of each division when it is greater than one.
36963 For example, &"x2"& means that each division represents a value of 2.
36965 It is also possible to have a stripchart which shows the percentage fullness of
36966 a particular disk partition, which is useful when local deliveries are confined
36967 to a single partition.
36969 .cindex "&%statvfs%& function"
36970 This relies on the availability of the &[statvfs()]& function or equivalent in
36971 the operating system. Most, but not all versions of Unix that support Exim have
36972 this. For this particular stripchart, the top of the chart always represents
36973 100%, and the scale is given as &"x10%"&. This chart is configured by setting
36974 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
36975 &_Local/eximon.conf_& file.
36980 .section "Main action buttons" "SECID266"
36981 .cindex "size" "of monitor window"
36982 .cindex "Exim monitor" "window size"
36983 .cindex "window size"
36984 Below the stripcharts there is an action button for quitting the monitor. Next
36985 to this is another button marked &"Size"&. They are placed here so that
36986 shrinking the window to its default minimum size leaves just the queue count
36987 stripchart and these two buttons visible. Pressing the &"Size"& button causes
36988 the window to expand to its maximum size, unless it is already at the maximum,
36989 in which case it is reduced to its minimum.
36991 When expanding to the maximum, if the window cannot be fully seen where it
36992 currently is, it is moved back to where it was the last time it was at full
36993 size. When it is expanding from its minimum size, the old position is
36994 remembered, and next time it is reduced to the minimum it is moved back there.
36996 The idea is that you can keep a reduced window just showing one or two
36997 stripcharts at a convenient place on your screen, easily expand it to show
36998 the full window when required, and just as easily put it back to what it was.
36999 The idea is copied from what the &'twm'& window manager does for its
37000 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
37001 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
37003 Normally, the monitor starts up with the window at its full size, but it can be
37004 built so that it starts up with the window at its smallest size, by setting
37005 START_SMALL=yes in &_Local/eximon.conf_&.
37009 .section "The log display" "SECID267"
37010 .cindex "log" "tail of; in monitor"
37011 The second section of the window is an area in which a display of the tail of
37012 the main log is maintained.
37013 To save space on the screen, the timestamp on each log line is shortened by
37014 removing the date and, if &%log_timezone%& is set, the timezone.
37015 The log tail is not available when the only destination for logging data is
37016 syslog, unless the syslog lines are routed to a local file whose name is passed
37017 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
37019 The log sub-window has a scroll bar at its lefthand side which can be used to
37020 move back to look at earlier text, and the up and down arrow keys also have a
37021 scrolling effect. The amount of log that is kept depends on the setting of
37022 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
37023 to use. When this is full, the earlier 50% of data is discarded &-- this is
37024 much more efficient than throwing it away line by line. The sub-window also has
37025 a horizontal scroll bar for accessing the ends of long log lines. This is the
37026 only means of horizontal scrolling; the right and left arrow keys are not
37027 available. Text can be cut from this part of the window using the mouse in the
37028 normal way. The size of this subwindow is controlled by parameters in the
37029 configuration file &_Local/eximon.conf_&.
37031 Searches of the text in the log window can be carried out by means of the ^R
37032 and ^S keystrokes, which default to a reverse and a forward search,
37033 respectively. The search covers only the text that is displayed in the window.
37034 It cannot go further back up the log.
37036 The point from which the search starts is indicated by a caret marker. This is
37037 normally at the end of the text in the window, but can be positioned explicitly
37038 by pointing and clicking with the left mouse button, and is moved automatically
37039 by a successful search. If new text arrives in the window when it is scrolled
37040 back, the caret remains where it is, but if the window is not scrolled back,
37041 the caret is moved to the end of the new text.
37043 Pressing ^R or ^S pops up a window into which the search text can be typed.
37044 There are buttons for selecting forward or reverse searching, for carrying out
37045 the search, and for cancelling. If the &"Search"& button is pressed, the search
37046 happens and the window remains so that further searches can be done. If the
37047 &"Return"& key is pressed, a single search is done and the window is closed. If
37048 ^C is typed the search is cancelled.
37050 The searching facility is implemented using the facilities of the Athena text
37051 widget. By default this pops up a window containing both &"search"& and
37052 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
37053 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
37054 However, the linkers in BSDI and HP-UX seem unable to handle an externally
37055 provided version of &%TextPop%& when the remaining parts of the text widget
37056 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
37057 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
37058 on these systems, at the expense of having unwanted items in the search popup
37063 .section "The queue display" "SECID268"
37064 .cindex "queue" "display in monitor"
37065 The bottom section of the monitor window contains a list of all messages that
37066 are on the queue, which includes those currently being received or delivered,
37067 as well as those awaiting delivery. The size of this subwindow is controlled by
37068 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
37069 at which it is updated is controlled by another parameter in the same file &--
37070 the default is 5 minutes, since queue scans can be quite expensive. However,
37071 there is an &"Update"& action button just above the display which can be used
37072 to force an update of the queue display at any time.
37074 When a host is down for some time, a lot of pending mail can build up for it,
37075 and this can make it hard to deal with other messages on the queue. To help
37076 with this situation there is a button next to &"Update"& called &"Hide"&. If
37077 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
37078 type anything in here and press &"Return"&, the text is added to a chain of
37079 such texts, and if every undelivered address in a message matches at least one
37080 of the texts, the message is not displayed.
37082 If there is an address that does not match any of the texts, all the addresses
37083 are displayed as normal. The matching happens on the ends of addresses so, for
37084 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
37085 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
37086 has been set up, a button called &"Unhide"& is displayed. If pressed, it
37087 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
37088 a hide request is automatically cancelled after one hour.
37090 While the dialogue box is displayed, you can't press any buttons or do anything
37091 else to the monitor window. For this reason, if you want to cut text from the
37092 queue display to use in the dialogue box, you have to do the cutting before
37093 pressing the &"Hide"& button.
37095 The queue display contains, for each unhidden queued message, the length of
37096 time it has been on the queue, the size of the message, the message id, the
37097 message sender, and the first undelivered recipient, all on one line. If it is
37098 a bounce message, the sender is shown as &"<>"&. If there is more than one
37099 recipient to which the message has not yet been delivered, subsequent ones are
37100 listed on additional lines, up to a maximum configured number, following which
37101 an ellipsis is displayed. Recipients that have already received the message are
37104 .cindex "frozen messages" "display"
37105 If a message is frozen, an asterisk is displayed at the left-hand side.
37107 The queue display has a vertical scroll bar, and can also be scrolled by means
37108 of the arrow keys. Text can be cut from it using the mouse in the normal way.
37109 The text searching facilities, as described above for the log window, are also
37110 available, but the caret is always moved to the end of the text when the queue
37111 display is updated.
37115 .section "The queue menu" "SECID269"
37116 .cindex "queue" "menu in monitor"
37117 If the &%shift%& key is held down and the left button is clicked when the mouse
37118 pointer is over the text for any message, an action menu pops up, and the first
37119 line of the queue display for the message is highlighted. This does not affect
37122 If you want to use some other event for popping up the menu, you can set the
37123 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
37124 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
37125 value set in this parameter is a standard X event description. For example, to
37126 run eximon using &%ctrl%& rather than &%shift%& you could use
37128 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
37130 The title of the menu is the message id, and it contains entries which act as
37134 &'message log'&: The contents of the message log for the message are displayed
37135 in a new text window.
37137 &'headers'&: Information from the spool file that contains the envelope
37138 information and headers is displayed in a new text window. See chapter
37139 &<<CHAPspool>>& for a description of the format of spool files.
37141 &'body'&: The contents of the spool file containing the body of the message are
37142 displayed in a new text window. There is a default limit of 20,000 bytes to the
37143 amount of data displayed. This can be changed by setting the BODY_MAX
37144 option at compile time, or the EXIMON_BODY_MAX option at run time.
37146 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
37147 delivery of the message. This causes an automatic thaw if the message is
37148 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
37149 a new text window. The delivery is run in a separate process, to avoid holding
37150 up the monitor while the delivery proceeds.
37152 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
37153 that the message be frozen.
37155 .cindex "thawing messages"
37156 .cindex "unfreezing messages"
37157 .cindex "frozen messages" "thawing"
37158 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
37159 that the message be thawed.
37161 .cindex "delivery" "forcing failure"
37162 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
37163 that Exim gives up trying to deliver the message. A bounce message is generated
37164 for any remaining undelivered addresses.
37166 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
37167 that the message be deleted from the system without generating a bounce
37170 &'add recipient'&: A dialog box is displayed into which a recipient address can
37171 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
37172 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
37173 Otherwise it must be entered as a fully qualified address. Pressing RETURN
37174 causes a call to Exim to be made using the &%-Mar%& option to request that an
37175 additional recipient be added to the message, unless the entry box is empty, in
37176 which case no action is taken.
37178 &'mark delivered'&: A dialog box is displayed into which a recipient address
37179 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
37180 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
37181 Otherwise it must be entered as a fully qualified address. Pressing RETURN
37182 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
37183 recipient address as already delivered, unless the entry box is empty, in which
37184 case no action is taken.
37186 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
37187 mark all recipient addresses as already delivered.
37189 &'edit sender'&: A dialog box is displayed initialized with the current
37190 sender's address. Pressing RETURN causes a call to Exim to be made using the
37191 &%-Mes%& option to replace the sender address, unless the entry box is empty,
37192 in which case no action is taken. If you want to set an empty sender (as in
37193 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
37194 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
37195 the address is qualified with that domain.
37198 When a delivery is forced, a window showing the &%-v%& output is displayed. In
37199 other cases when a call to Exim is made, if there is any output from Exim (in
37200 particular, if the command fails) a window containing the command and the
37201 output is displayed. Otherwise, the results of the action are normally apparent
37202 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
37203 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
37204 if no output is generated.
37206 The queue display is automatically updated for actions such as freezing and
37207 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
37208 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
37209 force an update of the display after one of these actions.
37211 In any text window that is displayed as result of a menu action, the normal
37212 cut-and-paste facility is available, and searching can be carried out using ^R
37213 and ^S, as described above for the log tail window.
37220 . ////////////////////////////////////////////////////////////////////////////
37221 . ////////////////////////////////////////////////////////////////////////////
37223 .chapter "Security considerations" "CHAPsecurity"
37224 .scindex IIDsecurcon "security" "discussion of"
37225 This chapter discusses a number of issues concerned with security, some of
37226 which are also covered in other parts of this manual.
37228 For reasons that this author does not understand, some people have promoted
37229 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
37230 existence of this chapter in the documentation. However, the intent of the
37231 chapter is simply to describe the way Exim works in relation to certain
37232 security concerns, not to make any specific claims about the effectiveness of
37233 its security as compared with other MTAs.
37235 What follows is a description of the way Exim is supposed to be. Best efforts
37236 have been made to try to ensure that the code agrees with the theory, but an
37237 absence of bugs can never be guaranteed. Any that are reported will get fixed
37238 as soon as possible.
37241 .section "Building a more &""hardened""& Exim" "SECID286"
37242 .cindex "security" "build-time features"
37243 There are a number of build-time options that can be set in &_Local/Makefile_&
37244 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
37245 Exim administrator who does not have the root password, or by someone who has
37246 penetrated the Exim (but not the root) account. These options are as follows:
37249 ALT_CONFIG_PREFIX can be set to a string that is required to match the
37250 start of any file names used with the &%-C%& option. When it is set, these file
37251 names are also not allowed to contain the sequence &"/../"&. (However, if the
37252 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
37253 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
37254 default setting for &%ALT_CONFIG_PREFIX%&.
37256 If the permitted configuration files are confined to a directory to
37257 which only root has access, this guards against someone who has broken
37258 into the Exim account from running a privileged Exim with an arbitrary
37259 configuration file, and using it to break into other accounts.
37262 If a non-trusted configuration file (i.e. not the default configuration file
37263 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
37264 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
37265 the next item), then root privilege is retained only if the caller of Exim is
37266 root. This locks out the possibility of testing a configuration using &%-C%&
37267 right through message reception and delivery, even if the caller is root. The
37268 reception works, but by that time, Exim is running as the Exim user, so when
37269 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
37270 privilege to be lost. However, root can test reception and delivery using two
37274 The WHITELIST_D_MACROS build option declares some macros to be safe to override
37275 with &%-D%& if the real uid is one of root, the Exim run-time user or the
37276 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
37277 requiring the run-time value supplied to &%-D%& to match a regex that errs on
37278 the restrictive side. Requiring build-time selection of safe macros is onerous
37279 but this option is intended solely as a transition mechanism to permit
37280 previously-working configurations to continue to work after release 4.73.
37282 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
37285 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
37286 never to be used for any deliveries. This is like the &%never_users%& runtime
37287 option, but it cannot be overridden; the runtime option adds additional users
37288 to the list. The default setting is &"root"&; this prevents a non-root user who
37289 is permitted to modify the runtime file from using Exim as a way to get root.
37294 .section "Root privilege" "SECID270"
37296 .cindex "root privilege"
37297 The Exim binary is normally setuid to root, which means that it gains root
37298 privilege (runs as root) when it starts execution. In some special cases (for
37299 example, when the daemon is not in use and there are no local deliveries), it
37300 may be possible to run Exim setuid to some user other than root. This is
37301 discussed in the next section. However, in most installations, root privilege
37302 is required for two things:
37305 To set up a socket connected to the standard SMTP port (25) when initialising
37306 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
37309 To be able to change uid and gid in order to read users' &_.forward_& files and
37310 perform local deliveries as the receiving user or as specified in the
37314 It is not necessary to be root to do any of the other things Exim does, such as
37315 receiving messages and delivering them externally over SMTP, and it is
37316 obviously more secure if Exim does not run as root except when necessary.
37317 For this reason, a user and group for Exim to use must be defined in
37318 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
37319 group"&. Their values can be changed by the run time configuration, though this
37320 is not recommended. Often a user called &'exim'& is used, but some sites use
37321 &'mail'& or another user name altogether.
37323 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
37324 abdication; the process cannot regain root afterwards. Prior to release 4.00,
37325 &[seteuid()]& was used in some circumstances, but this is no longer the case.
37327 After a new Exim process has interpreted its command line options, it changes
37328 uid and gid in the following cases:
37333 If the &%-C%& option is used to specify an alternate configuration file, or if
37334 the &%-D%& option is used to define macro values for the configuration, and the
37335 calling process is not running as root, the uid and gid are changed to those of
37336 the calling process.
37337 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
37338 option may not be used at all.
37339 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
37340 can be supplied if the calling process is running as root, the Exim run-time
37341 user or CONFIGURE_OWNER, if defined.
37346 If the expansion test option (&%-be%&) or one of the filter testing options
37347 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
37350 If the process is not a daemon process or a queue runner process or a delivery
37351 process or a process for testing address routing (started with &%-bt%&), the
37352 uid and gid are changed to the Exim user and group. This means that Exim always
37353 runs under its own uid and gid when receiving messages. This also applies when
37354 testing address verification
37357 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
37360 For a daemon, queue runner, delivery, or address testing process, the uid
37361 remains as root at this stage, but the gid is changed to the Exim group.
37364 The processes that initially retain root privilege behave as follows:
37367 A daemon process changes the gid to the Exim group and the uid to the Exim
37368 user after setting up one or more listening sockets. The &[initgroups()]&
37369 function is called, so that if the Exim user is in any additional groups, they
37370 will be used during message reception.
37372 A queue runner process retains root privilege throughout its execution. Its
37373 job is to fork a controlled sequence of delivery processes.
37375 A delivery process retains root privilege throughout most of its execution,
37376 but any actual deliveries (that is, the transports themselves) are run in
37377 subprocesses which always change to a non-root uid and gid. For local
37378 deliveries this is typically the uid and gid of the owner of the mailbox; for
37379 remote deliveries, the Exim uid and gid are used. Once all the delivery
37380 subprocesses have been run, a delivery process changes to the Exim uid and gid
37381 while doing post-delivery tidying up such as updating the retry database and
37382 generating bounce and warning messages.
37384 While the recipient addresses in a message are being routed, the delivery
37385 process runs as root. However, if a user's filter file has to be processed,
37386 this is done in a subprocess that runs under the individual user's uid and
37387 gid. A system filter is run as root unless &%system_filter_user%& is set.
37389 A process that is testing addresses (the &%-bt%& option) runs as root so that
37390 the routing is done in the same environment as a message delivery.
37396 .section "Running Exim without privilege" "SECTrunexiwitpri"
37397 .cindex "privilege, running without"
37398 .cindex "unprivileged running"
37399 .cindex "root privilege" "running without"
37400 Some installations like to run Exim in an unprivileged state for more of its
37401 operation, for added security. Support for this mode of operation is provided
37402 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
37403 gid are changed to the Exim user and group at the start of a delivery process
37404 (and also queue runner and address testing processes). This means that address
37405 routing is no longer run as root, and the deliveries themselves cannot change
37409 .cindex "daemon" "restarting"
37410 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
37411 that the daemon can still be started in the usual way, and it can respond
37412 correctly to SIGHUP because the re-invocation regains root privilege.
37414 An alternative approach is to make Exim setuid to the Exim user and also setgid
37415 to the Exim group. If you do this, the daemon must be started from a root
37416 process. (Calling Exim from a root process makes it behave in the way it does
37417 when it is setuid root.) However, the daemon cannot restart itself after a
37418 SIGHUP signal because it cannot regain privilege.
37420 It is still useful to set &%deliver_drop_privilege%& in this case, because it
37421 stops Exim from trying to re-invoke itself to do a delivery after a message has
37422 been received. Such a re-invocation is a waste of resources because it has no
37425 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
37426 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
37427 to the Exim user seems a clean approach, but there is one complication:
37429 In this style of operation, Exim is running with the real uid and gid set to
37430 those of the calling process, and the effective uid/gid set to Exim's values.
37431 Ideally, any association with the calling process' uid/gid should be dropped,
37432 that is, the real uid/gid should be reset to the effective values so as to
37433 discard any privileges that the caller may have. While some operating systems
37434 have a function that permits this action for a non-root effective uid, quite a
37435 number of them do not. Because of this lack of standardization, Exim does not
37436 address this problem at this time.
37438 For this reason, the recommended approach for &"mostly unprivileged"& running
37439 is to keep the Exim binary setuid to root, and to set
37440 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
37441 be used in the most straightforward way.
37443 If you configure Exim not to run delivery processes as root, there are a
37444 number of restrictions on what you can do:
37447 You can deliver only as the Exim user/group. You should explicitly use the
37448 &%user%& and &%group%& options to override routers or local transports that
37449 normally deliver as the recipient. This makes sure that configurations that
37450 work in this mode function the same way in normal mode. Any implicit or
37451 explicit specification of another user causes an error.
37453 Use of &_.forward_& files is severely restricted, such that it is usually
37454 not worthwhile to include them in the configuration.
37456 Users who wish to use &_.forward_& would have to make their home directory and
37457 the file itself accessible to the Exim user. Pipe and append-to-file entries,
37458 and their equivalents in Exim filters, cannot be used. While they could be
37459 enabled in the Exim user's name, that would be insecure and not very useful.
37461 Unless the local user mailboxes are all owned by the Exim user (possible in
37462 some POP3 or IMAP-only environments):
37465 They must be owned by the Exim group and be writeable by that group. This
37466 implies you must set &%mode%& in the appendfile configuration, as well as the
37467 mode of the mailbox files themselves.
37469 You must set &%no_check_owner%&, since most or all of the files will not be
37470 owned by the Exim user.
37472 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
37473 on a newly created mailbox when unprivileged. This also implies that new
37474 mailboxes need to be created manually.
37479 These restrictions severely restrict what can be done in local deliveries.
37480 However, there are no restrictions on remote deliveries. If you are running a
37481 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
37482 gives more security at essentially no cost.
37484 If you are using the &%mua_wrapper%& facility (see chapter
37485 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
37490 .section "Delivering to local files" "SECID271"
37491 Full details of the checks applied by &(appendfile)& before it writes to a file
37492 are given in chapter &<<CHAPappendfile>>&.
37496 .section "Running local commands" "SECTsecconslocalcmds"
37497 .cindex "security" "local commands"
37498 .cindex "security" "command injection attacks"
37499 There are a number of ways in which an administrator can configure Exim to run
37500 commands based upon received, untrustworthy, data. Further, in some
37501 configurations a user who can control a &_.forward_& file can also arrange to
37502 run commands. Configuration to check includes, but is not limited to:
37505 Use of &%use_shell%& in the pipe transport: various forms of shell command
37506 injection may be possible with this option present. It is dangerous and should
37507 be used only with considerable caution. Consider constraints which whitelist
37508 allowed characters in a variable which is to be used in a pipe transport that
37509 has &%use_shell%& enabled.
37511 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
37512 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
37513 &_.forward_& files in a redirect router. If Exim is running on a central mail
37514 hub to which ordinary users do not have shell access, but home directories are
37515 NFS mounted (for instance) then administrators should review the list of these
37516 forbid options available, and should bear in mind that the options that may
37517 need forbidding can change as new features are added between releases.
37519 The &%${run...}%& expansion item does not use a shell by default, but
37520 administrators can configure use of &_/bin/sh_& as part of the command.
37521 Such invocations should be viewed with prejudicial suspicion.
37523 Administrators who use embedded Perl are advised to explore how Perl's
37524 taint checking might apply to their usage.
37526 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
37527 administrators are well advised to view its use with suspicion, in case (for
37528 instance) it allows a local-part to contain embedded Exim directives.
37530 Use of &%${match_local_part...}%& and friends becomes more dangerous if
37531 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
37532 each can reference arbitrary lists and files, rather than just being a list
37534 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
37535 real-world security vulnerabilities caused by its use with untrustworthy data
37536 injected in, for SQL injection attacks.
37537 Consider the use of the &%inlisti%& expansion condition instead.
37543 .section "Trust in configuration data" "SECTsecconfdata"
37544 .cindex "security" "data sources"
37545 .cindex "security" "regular expressions"
37546 .cindex "regular expressions" "security"
37547 .cindex "PCRE" "security"
37548 If configuration data for Exim can come from untrustworthy sources, there
37549 are some issues to be aware of:
37552 Use of &%${expand...}%& may provide a path for shell injection attacks.
37554 Letting untrusted data provide a regular expression is unwise.
37556 Using &%${match...}%& to apply a fixed regular expression against untrusted
37557 data may result in pathological behaviour within PCRE. Be aware of what
37558 "backtracking" means and consider options for being more strict with a regular
37559 expression. Avenues to explore include limiting what can match (avoiding &`.`&
37560 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
37561 possessive quantifiers or just not using regular expressions against untrusted
37564 It can be important to correctly use &%${quote:...}%&,
37565 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
37566 items to ensure that data is correctly constructed.
37568 Some lookups might return multiple results, even though normal usage is only
37569 expected to yield one result.
37575 .section "IPv4 source routing" "SECID272"
37576 .cindex "source routing" "in IP packets"
37577 .cindex "IP source routing"
37578 Many operating systems suppress IP source-routed packets in the kernel, but
37579 some cannot be made to do this, so Exim does its own check. It logs incoming
37580 IPv4 source-routed TCP calls, and then drops them. Things are all different in
37581 IPv6. No special checking is currently done.
37585 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
37586 Support for these SMTP commands is disabled by default. If required, they can
37587 be enabled by defining suitable ACLs.
37592 .section "Privileged users" "SECID274"
37593 .cindex "trusted users"
37594 .cindex "admin user"
37595 .cindex "privileged user"
37596 .cindex "user" "trusted"
37597 .cindex "user" "admin"
37598 Exim recognizes two sets of users with special privileges. Trusted users are
37599 able to submit new messages to Exim locally, but supply their own sender
37600 addresses and information about a sending host. For other users submitting
37601 local messages, Exim sets up the sender address from the uid, and doesn't
37602 permit a remote host to be specified.
37605 However, an untrusted user is permitted to use the &%-f%& command line option
37606 in the special form &%-f <>%& to indicate that a delivery failure for the
37607 message should not cause an error report. This affects the message's envelope,
37608 but it does not affect the &'Sender:'& header. Untrusted users may also be
37609 permitted to use specific forms of address with the &%-f%& option by setting
37610 the &%untrusted_set_sender%& option.
37612 Trusted users are used to run processes that receive mail messages from some
37613 other mail domain and pass them on to Exim for delivery either locally, or over
37614 the Internet. Exim trusts a caller that is running as root, as the Exim user,
37615 as any user listed in the &%trusted_users%& configuration option, or under any
37616 group listed in the &%trusted_groups%& option.
37618 Admin users are permitted to do things to the messages on Exim's queue. They
37619 can freeze or thaw messages, cause them to be returned to their senders, remove
37620 them entirely, or modify them in various ways. In addition, admin users can run
37621 the Exim monitor and see all the information it is capable of providing, which
37622 includes the contents of files on the spool.
37626 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
37627 delivery of messages on its queue is restricted to admin users. This
37628 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
37629 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
37630 queue is also restricted to admin users. This restriction can be relaxed by
37631 setting &%no_queue_list_requires_admin%&.
37633 Exim recognizes an admin user if the calling process is running as root or as
37634 the Exim user or if any of the groups associated with the calling process is
37635 the Exim group. It is not necessary actually to be running under the Exim
37636 group. However, if admin users who are not root or the Exim user are to access
37637 the contents of files on the spool via the Exim monitor (which runs
37638 unprivileged), Exim must be built to allow group read access to its spool
37643 .section "Spool files" "SECID275"
37644 .cindex "spool directory" "files"
37645 Exim's spool directory and everything it contains is owned by the Exim user and
37646 set to the Exim group. The mode for spool files is defined in the
37647 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
37648 any user who is a member of the Exim group can access these files.
37652 .section "Use of argv[0]" "SECID276"
37653 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
37654 of specific strings, Exim assumes certain options. For example, calling Exim
37655 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
37656 to calling it with the option &%-bS%&. There are no security implications in
37661 .section "Use of %f formatting" "SECID277"
37662 The only use made of &"%f"& by Exim is in formatting load average values. These
37663 are actually stored in integer variables as 1000 times the load average.
37664 Consequently, their range is limited and so therefore is the length of the
37669 .section "Embedded Exim path" "SECID278"
37670 Exim uses its own path name, which is embedded in the code, only when it needs
37671 to re-exec in order to regain root privilege. Therefore, it is not root when it
37672 does so. If some bug allowed the path to get overwritten, it would lead to an
37673 arbitrary program's being run as exim, not as root.
37677 .section "Dynamic module directory" "SECTdynmoddir"
37678 Any dynamically loadable modules must be installed into the directory
37679 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
37683 .section "Use of sprintf()" "SECID279"
37684 .cindex "&[sprintf()]&"
37685 A large number of occurrences of &"sprintf"& in the code are actually calls to
37686 &'string_sprintf()'&, a function that returns the result in malloc'd store.
37687 The intermediate formatting is done into a large fixed buffer by a function
37688 that runs through the format string itself, and checks the length of each
37689 conversion before performing it, thus preventing buffer overruns.
37691 The remaining uses of &[sprintf()]& happen in controlled circumstances where
37692 the output buffer is known to be sufficiently long to contain the converted
37697 .section "Use of debug_printf() and log_write()" "SECID280"
37698 Arbitrary strings are passed to both these functions, but they do their
37699 formatting by calling the function &'string_vformat()'&, which runs through
37700 the format string itself, and checks the length of each conversion.
37704 .section "Use of strcat() and strcpy()" "SECID281"
37705 These are used only in cases where the output buffer is known to be large
37706 enough to hold the result.
37707 .ecindex IIDsecurcon
37712 . ////////////////////////////////////////////////////////////////////////////
37713 . ////////////////////////////////////////////////////////////////////////////
37715 .chapter "Format of spool files" "CHAPspool"
37716 .scindex IIDforspo1 "format" "spool files"
37717 .scindex IIDforspo2 "spool directory" "format of files"
37718 .scindex IIDforspo3 "spool files" "format of"
37719 .cindex "spool files" "editing"
37720 A message on Exim's queue consists of two files, whose names are the message id
37721 followed by -D and -H, respectively. The data portion of the message is kept in
37722 the -D file on its own. The message's envelope, status, and headers are all
37723 kept in the -H file, whose format is described in this chapter. Each of these
37724 two files contains the final component of its own name as its first line. This
37725 is insurance against disk crashes where the directory is lost but the files
37726 themselves are recoverable.
37728 Some people are tempted into editing -D files in order to modify messages. You
37729 need to be extremely careful if you do this; it is not recommended and you are
37730 on your own if you do it. Here are some of the pitfalls:
37733 You must ensure that Exim does not try to deliver the message while you are
37734 fiddling with it. The safest way is to take out a write lock on the -D file,
37735 which is what Exim itself does, using &[fcntl()]&. If you update the file in
37736 place, the lock will be retained. If you write a new file and rename it, the
37737 lock will be lost at the instant of rename.
37739 .vindex "&$body_linecount$&"
37740 If you change the number of lines in the file, the value of
37741 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
37742 present, this value is not used by Exim, but there is no guarantee that this
37743 will always be the case.
37745 If the message is in MIME format, you must take care not to break it.
37747 If the message is cryptographically signed, any change will invalidate the
37750 All in all, modifying -D files is fraught with danger.
37752 Files whose names end with -J may also be seen in the &_input_& directory (or
37753 its subdirectories when &%split_spool_directory%& is set). These are journal
37754 files, used to record addresses to which the message has been delivered during
37755 the course of a delivery attempt. If there are still undelivered recipients at
37756 the end, the -H file is updated, and the -J file is deleted. If, however, there
37757 is some kind of crash (for example, a power outage) before this happens, the -J
37758 file remains in existence. When Exim next processes the message, it notices the
37759 -J file and uses it to update the -H file before starting the next delivery
37762 .section "Format of the -H file" "SECID282"
37763 .cindex "uid (user id)" "in spool file"
37764 .cindex "gid (group id)" "in spool file"
37765 The second line of the -H file contains the login name for the uid of the
37766 process that called Exim to read the message, followed by the numerical uid and
37767 gid. For a locally generated message, this is normally the user who sent the
37768 message. For a message received over TCP/IP via the daemon, it is
37769 normally the Exim user.
37771 The third line of the file contains the address of the message's sender as
37772 transmitted in the envelope, contained in angle brackets. The sender address is
37773 empty for bounce messages. For incoming SMTP mail, the sender address is given
37774 in the MAIL command. For locally generated mail, the sender address is
37775 created by Exim from the login name of the current user and the configured
37776 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
37777 leading &"From&~"& line if the caller is trusted, or if the supplied address is
37778 &"<>"& or an address that matches &%untrusted_set_senders%&.
37780 The fourth line contains two numbers. The first is the time that the message
37781 was received, in the conventional Unix form &-- the number of seconds since the
37782 start of the epoch. The second number is a count of the number of messages
37783 warning of delayed delivery that have been sent to the sender.
37785 There follow a number of lines starting with a hyphen. These can appear in any
37786 order, and are omitted when not relevant:
37789 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
37790 This item is obsolete, and is not generated from Exim release 4.61 onwards;
37791 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
37792 recognized, to provide backward compatibility. In the old format, a line of
37793 this form is present for every ACL variable that is not empty. The number
37794 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
37795 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
37796 the data string for the variable. The string itself starts at the beginning of
37797 the next line, and is followed by a newline character. It may contain internal
37800 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
37801 A line of this form is present for every ACL connection variable that is
37802 defined. Note that there is a space between &%-aclc%& and the rest of the name.
37803 The length is the length of the data string for the variable. The string itself
37804 starts at the beginning of the next line, and is followed by a newline
37805 character. It may contain internal newlines.
37807 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
37808 A line of this form is present for every ACL message variable that is defined.
37809 Note that there is a space between &%-aclm%& and the rest of the name. The
37810 length is the length of the data string for the variable. The string itself
37811 starts at the beginning of the next line, and is followed by a newline
37812 character. It may contain internal newlines.
37814 .vitem "&%-active_hostname%&&~<&'hostname'&>"
37815 This is present if, when the message was received over SMTP, the value of
37816 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
37818 .vitem &%-allow_unqualified_recipient%&
37819 This is present if unqualified recipient addresses are permitted in header
37820 lines (to stop such addresses from being qualified if rewriting occurs at
37821 transport time). Local messages that were input using &%-bnq%& and remote
37822 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
37824 .vitem &%-allow_unqualified_sender%&
37825 This is present if unqualified sender addresses are permitted in header lines
37826 (to stop such addresses from being qualified if rewriting occurs at transport
37827 time). Local messages that were input using &%-bnq%& and remote messages from
37828 hosts that match &%sender_unqualified_hosts%& set this flag.
37830 .vitem "&%-auth_id%&&~<&'text'&>"
37831 The id information for a message received on an authenticated SMTP connection
37832 &-- the value of the &$authenticated_id$& variable.
37834 .vitem "&%-auth_sender%&&~<&'address'&>"
37835 The address of an authenticated sender &-- the value of the
37836 &$authenticated_sender$& variable.
37838 .vitem "&%-body_linecount%&&~<&'number'&>"
37839 This records the number of lines in the body of the message, and is always
37842 .vitem "&%-body_zerocount%&&~<&'number'&>"
37843 This records the number of binary zero bytes in the body of the message, and is
37844 present if the number is greater than zero.
37846 .vitem &%-deliver_firsttime%&
37847 This is written when a new message is first added to the spool. When the spool
37848 file is updated after a deferral, it is omitted.
37850 .vitem "&%-frozen%&&~<&'time'&>"
37851 .cindex "frozen messages" "spool data"
37852 The message is frozen, and the freezing happened at <&'time'&>.
37854 .vitem "&%-helo_name%&&~<&'text'&>"
37855 This records the host name as specified by a remote host in a HELO or EHLO
37858 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
37859 This records the IP address of the host from which the message was received and
37860 the remote port number that was used. It is omitted for locally generated
37863 .vitem "&%-host_auth%&&~<&'text'&>"
37864 If the message was received on an authenticated SMTP connection, this records
37865 the name of the authenticator &-- the value of the
37866 &$sender_host_authenticated$& variable.
37868 .vitem &%-host_lookup_failed%&
37869 This is present if an attempt to look up the sending host's name from its IP
37870 address failed. It corresponds to the &$host_lookup_failed$& variable.
37872 .vitem "&%-host_name%&&~<&'text'&>"
37873 .cindex "reverse DNS lookup"
37874 .cindex "DNS" "reverse lookup"
37875 This records the name of the remote host from which the message was received,
37876 if the host name was looked up from the IP address when the message was being
37877 received. It is not present if no reverse lookup was done.
37879 .vitem "&%-ident%&&~<&'text'&>"
37880 For locally submitted messages, this records the login of the originating user,
37881 unless it was a trusted user and the &%-oMt%& option was used to specify an
37882 ident value. For messages received over TCP/IP, this records the ident string
37883 supplied by the remote host, if any.
37885 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
37886 This records the IP address of the local interface and the port number through
37887 which a message was received from a remote host. It is omitted for locally
37888 generated messages.
37891 The message is from a local sender.
37893 .vitem &%-localerror%&
37894 The message is a locally-generated bounce message.
37896 .vitem "&%-local_scan%&&~<&'string'&>"
37897 This records the data string that was returned by the &[local_scan()]& function
37898 when the message was received &-- the value of the &$local_scan_data$&
37899 variable. It is omitted if no data was returned.
37901 .vitem &%-manual_thaw%&
37902 The message was frozen but has been thawed manually, that is, by an explicit
37903 Exim command rather than via the auto-thaw process.
37906 A testing delivery process was started using the &%-N%& option to suppress any
37907 actual deliveries, but delivery was deferred. At any further delivery attempts,
37910 .vitem &%-received_protocol%&
37911 This records the value of the &$received_protocol$& variable, which contains
37912 the name of the protocol by which the message was received.
37914 .vitem &%-sender_set_untrusted%&
37915 The envelope sender of this message was set by an untrusted local caller (used
37916 to ensure that the caller is displayed in queue listings).
37918 .vitem "&%-spam_score_int%&&~<&'number'&>"
37919 If a message was scanned by SpamAssassin, this is present. It records the value
37920 of &$spam_score_int$&.
37922 .vitem &%-tls_certificate_verified%&
37923 A TLS certificate was received from the client that sent this message, and the
37924 certificate was verified by the server.
37926 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
37927 When the message was received over an encrypted connection, this records the
37928 name of the cipher suite that was used.
37930 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
37931 When the message was received over an encrypted connection, and a certificate
37932 was received from the client, this records the Distinguished Name from that
37936 Following the options there is a list of those addresses to which the message
37937 is not to be delivered. This set of addresses is initialized from the command
37938 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
37939 is set; otherwise it starts out empty. Whenever a successful delivery is made,
37940 the address is added to this set. The addresses are kept internally as a
37941 balanced binary tree, and it is a representation of that tree which is written
37942 to the spool file. If an address is expanded via an alias or forward file, the
37943 original address is added to the tree when deliveries to all its child
37944 addresses are complete.
37946 If the tree is empty, there is a single line in the spool file containing just
37947 the text &"XX"&. Otherwise, each line consists of two letters, which are either
37948 Y or N, followed by an address. The address is the value for the node of the
37949 tree, and the letters indicate whether the node has a left branch and/or a
37950 right branch attached to it, respectively. If branches exist, they immediately
37951 follow. Here is an example of a three-node tree:
37953 YY darcy@austen.fict.example
37954 NN alice@wonderland.fict.example
37955 NN editor@thesaurus.ref.example
37957 After the non-recipients tree, there is a list of the message's recipients.
37958 This is a simple list, preceded by a count. It includes all the original
37959 recipients of the message, including those to whom the message has already been
37960 delivered. In the simplest case, the list contains one address per line. For
37964 editor@thesaurus.ref.example
37965 darcy@austen.fict.example
37967 alice@wonderland.fict.example
37969 However, when a child address has been added to the top-level addresses as a
37970 result of the use of the &%one_time%& option on a &(redirect)& router, each
37971 line is of the following form:
37973 <&'top-level address'&> <&'errors_to address'&> &&&
37974 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
37976 The 01 flag bit indicates the presence of the three other fields that follow
37977 the top-level address. Other bits may be used in future to support additional
37978 fields. The <&'parent number'&> is the offset in the recipients list of the
37979 original parent of the &"one time"& address. The first two fields are the
37980 envelope sender that is associated with this address and its length. If the
37981 length is zero, there is no special envelope sender (there are then two space
37982 characters in the line). A non-empty field can arise from a &(redirect)& router
37983 that has an &%errors_to%& setting.
37986 A blank line separates the envelope and status information from the headers
37987 which follow. A header may occupy several lines of the file, and to save effort
37988 when reading it in, each header is preceded by a number and an identifying
37989 character. The number is the number of characters in the header, including any
37990 embedded newlines and the terminating newline. The character is one of the
37994 .row <&'blank'&> "header in which Exim has no special interest"
37995 .row &`B`& "&'Bcc:'& header"
37996 .row &`C`& "&'Cc:'& header"
37997 .row &`F`& "&'From:'& header"
37998 .row &`I`& "&'Message-id:'& header"
37999 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
38000 .row &`R`& "&'Reply-To:'& header"
38001 .row &`S`& "&'Sender:'& header"
38002 .row &`T`& "&'To:'& header"
38003 .row &`*`& "replaced or deleted header"
38006 Deleted or replaced (rewritten) headers remain in the spool file for debugging
38007 purposes. They are not transmitted when the message is delivered. Here is a
38008 typical set of headers:
38010 111P Received: by hobbit.fict.example with local (Exim 4.00)
38011 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
38012 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
38013 038* X-rewrote-sender: bb@hobbit.fict.example
38014 042* From: Bilbo Baggins <bb@hobbit.fict.example>
38015 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
38016 099* To: alice@wonderland.fict.example, rdo@foundation,
38017 darcy@austen.fict.example, editor@thesaurus.ref.example
38018 104T To: alice@wonderland.fict.example, rdo@foundation.example,
38019 darcy@austen.fict.example, editor@thesaurus.ref.example
38020 038 Date: Fri, 11 May 2001 10:28:59 +0100
38022 The asterisked headers indicate that the envelope sender, &'From:'& header, and
38023 &'To:'& header have been rewritten, the last one because routing expanded the
38024 unqualified domain &'foundation'&.
38025 .ecindex IIDforspo1
38026 .ecindex IIDforspo2
38027 .ecindex IIDforspo3
38029 . ////////////////////////////////////////////////////////////////////////////
38030 . ////////////////////////////////////////////////////////////////////////////
38032 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
38036 DKIM is a mechanism by which messages sent by some entity can be provably
38037 linked to a domain which that entity controls. It permits reputation to
38038 be tracked on a per-domain basis, rather than merely upon source IP address.
38039 DKIM is documented in RFC 4871.
38041 DKIM support is compiled into Exim by default if TLS support is present.
38042 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
38044 Exim's DKIM implementation allows to
38046 Sign outgoing messages: This function is implemented in the SMTP transport.
38047 It can co-exist with all other Exim features
38048 (including transport filters)
38049 except cutthrough delivery.
38051 Verify signatures in incoming messages: This is implemented by an additional
38052 ACL (acl_smtp_dkim), which can be called several times per message, with
38053 different signature contexts.
38056 In typical Exim style, the verification implementation does not include any
38057 default "policy". Instead it enables you to build your own policy using
38058 Exim's standard controls.
38060 Please note that verification of DKIM signatures in incoming mail is turned
38061 on by default for logging purposes. For each signature in incoming email,
38062 exim will log a line displaying the most important signature details, and the
38063 signature status. Here is an example (with line-breaks added for clarity):
38065 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
38066 d=facebookmail.com s=q1-2009b
38067 c=relaxed/relaxed a=rsa-sha1
38068 i=@facebookmail.com t=1252484542 [verification succeeded]
38070 You might want to turn off DKIM verification processing entirely for internal
38071 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
38072 control modifier. This should typically be done in the RCPT ACL, at points
38073 where you accept mail from relay sources (internal hosts or authenticated
38077 .section "Signing outgoing messages" "SECDKIMSIGN"
38078 .cindex "DKIM" "signing"
38080 Signing is implemented by setting private options on the SMTP transport.
38081 These options take (expandable) strings as arguments.
38083 .option dkim_domain smtp string&!! unset
38085 The domain you want to sign with. The result of this expanded
38086 option is put into the &%$dkim_domain%& expansion variable.
38088 .option dkim_selector smtp string&!! unset
38090 This sets the key selector string. You can use the &%$dkim_domain%& expansion
38091 variable to look up a matching selector. The result is put in the expansion
38092 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
38093 option along with &%$dkim_domain%&.
38095 .option dkim_private_key smtp string&!! unset
38097 This sets the private key to use. You can use the &%$dkim_domain%& and
38098 &%$dkim_selector%& expansion variables to determine the private key to use.
38099 The result can either
38101 be a valid RSA private key in ASCII armor, including line breaks.
38103 start with a slash, in which case it is treated as a file that contains
38106 be "0", "false" or the empty string, in which case the message will not
38107 be signed. This case will not result in an error, even if &%dkim_strict%&
38111 .option dkim_canon smtp string&!! unset
38113 This option sets the canonicalization method used when signing a message.
38114 The DKIM RFC currently supports two methods: "simple" and "relaxed".
38115 The option defaults to "relaxed" when unset. Note: the current implementation
38116 only supports using the same canonicalization method for both headers and body.
38118 .option dkim_strict smtp string&!! unset
38120 This option defines how Exim behaves when signing a message that
38121 should be signed fails for some reason. When the expansion evaluates to
38122 either "1" or "true", Exim will defer. Otherwise Exim will send the message
38123 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
38126 .option dkim_sign_headers smtp string&!! unset
38128 When set, this option must expand to (or be specified as) a colon-separated
38129 list of header names. Headers with these names will be included in the message
38130 signature. When unspecified, the header names recommended in RFC4871 will be
38134 .section "Verifying DKIM signatures in incoming mail" "SECID514"
38135 .cindex "DKIM" "verification"
38137 Verification of DKIM signatures in SMTP incoming email is implemented via the
38138 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
38139 syntactically(!) correct signature in the incoming message.
38140 A missing ACL definition defaults to accept.
38141 If any ACL call does not accept, the message is not accepted.
38142 If a cutthrough delivery was in progress for the message it is
38143 summarily dropped (having wasted the transmission effort).
38145 To evaluate the signature in the ACL a large number of expansion variables
38146 containing the signature status and its details are set up during the
38147 runtime of the ACL.
38149 Calling the ACL only for existing signatures is not sufficient to build
38150 more advanced policies. For that reason, the global option
38151 &%dkim_verify_signers%&, and a global expansion variable
38152 &%$dkim_signers%& exist.
38154 The global option &%dkim_verify_signers%& can be set to a colon-separated
38155 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
38156 called. It is expanded when the message has been received. At this point,
38157 the expansion variable &%$dkim_signers%& already contains a colon-separated
38158 list of signer domains and identities for the message. When
38159 &%dkim_verify_signers%& is not specified in the main configuration,
38162 dkim_verify_signers = $dkim_signers
38164 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
38165 DKIM signature in the message. Current DKIM verifiers may want to explicitly
38166 call the ACL for known domains or identities. This would be achieved as follows:
38168 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
38170 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
38171 and "ebay.com", plus all domains and identities that have signatures in the message.
38172 You can also be more creative in constructing your policy. For example:
38174 dkim_verify_signers = $sender_address_domain:$dkim_signers
38177 If a domain or identity is listed several times in the (expanded) value of
38178 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
38181 Inside the &%acl_smtp_dkim%&, the following expansion variables are
38182 available (from most to least important):
38186 .vitem &%$dkim_cur_signer%&
38187 The signer that is being evaluated in this ACL run. This can be a domain or
38188 an identity. This is one of the list items from the expanded main option
38189 &%dkim_verify_signers%& (see above).
38190 .vitem &%$dkim_verify_status%&
38191 A string describing the general status of the signature. One of
38193 &%none%&: There is no signature in the message for the current domain or
38194 identity (as reflected by &%$dkim_cur_signer%&).
38196 &%invalid%&: The signature could not be verified due to a processing error.
38197 More detail is available in &%$dkim_verify_reason%&.
38199 &%fail%&: Verification of the signature failed. More detail is
38200 available in &%$dkim_verify_reason%&.
38202 &%pass%&: The signature passed verification. It is valid.
38204 .vitem &%$dkim_verify_reason%&
38205 A string giving a little bit more detail when &%$dkim_verify_status%& is either
38206 "fail" or "invalid". One of
38208 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
38209 key for the domain could not be retrieved. This may be a temporary problem.
38211 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
38212 record for the domain is syntactically invalid.
38214 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
38215 body hash does not match the one specified in the signature header. This
38216 means that the message body was modified in transit.
38218 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
38219 could not be verified. This may mean that headers were modified,
38220 re-written or otherwise changed in a way which is incompatible with
38221 DKIM verification. It may of course also mean that the signature is forged.
38223 .vitem &%$dkim_domain%&
38224 The signing domain. IMPORTANT: This variable is only populated if there is
38225 an actual signature in the message for the current domain or identity (as
38226 reflected by &%$dkim_cur_signer%&).
38227 .vitem &%$dkim_identity%&
38228 The signing identity, if present. IMPORTANT: This variable is only populated
38229 if there is an actual signature in the message for the current domain or
38230 identity (as reflected by &%$dkim_cur_signer%&).
38231 .vitem &%$dkim_selector%&
38232 The key record selector string.
38233 .vitem &%$dkim_algo%&
38234 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
38235 .vitem &%$dkim_canon_body%&
38236 The body canonicalization method. One of 'relaxed' or 'simple'.
38237 .vitem &%dkim_canon_headers%&
38238 The header canonicalization method. One of 'relaxed' or 'simple'.
38239 .vitem &%$dkim_copiedheaders%&
38240 A transcript of headers and their values which are included in the signature
38241 (copied from the 'z=' tag of the signature).
38242 .vitem &%$dkim_bodylength%&
38243 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
38244 limit was set by the signer, "9999999999999" is returned. This makes sure
38245 that this variable always expands to an integer value.
38246 .vitem &%$dkim_created%&
38247 UNIX timestamp reflecting the date and time when the signature was created.
38248 When this was not specified by the signer, "0" is returned.
38249 .vitem &%$dkim_expires%&
38250 UNIX timestamp reflecting the date and time when the signer wants the
38251 signature to be treated as "expired". When this was not specified by the
38252 signer, "9999999999999" is returned. This makes it possible to do useful
38253 integer size comparisons against this value.
38254 .vitem &%$dkim_headernames%&
38255 A colon-separated list of names of headers included in the signature.
38256 .vitem &%$dkim_key_testing%&
38257 "1" if the key record has the "testing" flag set, "0" if not.
38258 .vitem &%$dkim_key_nosubdomains%&
38259 "1" if the key record forbids subdomaining, "0" otherwise.
38260 .vitem &%$dkim_key_srvtype%&
38261 Service type (tag s=) from the key record. Defaults to "*" if not specified
38263 .vitem &%$dkim_key_granularity%&
38264 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
38266 .vitem &%$dkim_key_notes%&
38267 Notes from the key record (tag n=).
38268 .vitem &%$dkim_key_length%&
38269 Number of bits in the key.
38272 In addition, two ACL conditions are provided:
38275 .vitem &%dkim_signers%&
38276 ACL condition that checks a colon-separated list of domains or identities
38277 for a match against the domain or identity that the ACL is currently verifying
38278 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
38279 verb to a group of domains or identities. For example:
38282 # Warn when Mail purportedly from GMail has no signature at all
38283 warn log_message = GMail sender without DKIM signature
38284 sender_domains = gmail.com
38285 dkim_signers = gmail.com
38289 .vitem &%dkim_status%&
38290 ACL condition that checks a colon-separated list of possible DKIM verification
38291 results against the actual result of verification. This is typically used
38292 to restrict an ACL verb to a list of verification outcomes, for example:
38295 deny message = Mail from Paypal with invalid/missing signature
38296 sender_domains = paypal.com:paypal.de
38297 dkim_signers = paypal.com:paypal.de
38298 dkim_status = none:invalid:fail
38301 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
38302 see the documentation of the &%$dkim_verify_status%& expansion variable above
38303 for more information of what they mean.
38306 . ////////////////////////////////////////////////////////////////////////////
38307 . ////////////////////////////////////////////////////////////////////////////
38309 .chapter "Proxies" "CHAPproxies" &&&
38311 .cindex "proxy support"
38312 .cindex "proxy" "access via"
38314 A proxy is an intermediate system through which communication is passed.
38315 Proxies may provide a security, availability or load-distribution function.
38318 .section "Inbound proxies" SECTproxyInbound
38319 .cindex proxy inbound
38320 .cindex proxy "server side"
38321 .cindex proxy "Proxy protocol"
38322 .cindex "Proxy protocol" proxy
38324 Exim has support for receiving inbound SMTP connections via a proxy
38325 that uses &"Proxy Protocol"& to speak to it.
38326 To include this support, include &"SUPPORT_PROXY=yes"&
38329 It was built on specifications from:
38330 http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
38331 That URL was revised in May 2014 to version 2 spec:
38332 http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
38334 The purpose of this facility is so that an application load balancer,
38335 such as HAProxy, can sit in front of several Exim servers
38336 to distribute load.
38337 Exim uses the local protocol communication with the proxy to obtain
38338 the remote SMTP system IP address and port information.
38339 There is no logging if a host passes or
38340 fails Proxy Protocol negotiation, but it can easily be determined and
38341 recorded in an ACL (example is below).
38343 Use of a proxy is enabled by setting the &%hosts_proxy%&
38344 main configuration option to a hostlist; connections from these
38345 hosts will use Proxy Protocol.
38348 The following expansion variables are usable
38349 (&"internal"& and &"external"& here refer to the interfaces
38352 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
38353 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
38354 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
38355 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
38356 &'proxy_session '& boolean: SMTP connection via proxy
38358 If &$proxy_session$& is set but &$proxy_external_address$& is empty
38359 there was a protocol error.
38362 Since the real connections are all coming from the proxy, and the
38363 per host connection tracking is done before Proxy Protocol is
38364 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
38365 handle all of the parallel volume you expect per inbound proxy.
38366 With the option set so high, you lose the ability
38367 to protect your server from many connections from one IP.
38368 In order to prevent your server from overload, you
38369 need to add a per connection ratelimit to your connect ACL.
38370 A possible solution is:
38372 # Set max number of connections per host
38374 # Or do some kind of IP lookup in a flat file or database
38375 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
38377 defer message = Too many connections from this IP right now
38378 ratelimit = LIMIT / 5s / per_conn / strict
38383 .section "Outbound proxies" SECTproxySOCKS
38384 .cindex proxy outbound
38385 .cindex proxy "client side"
38386 .cindex proxy SOCKS
38387 .cindex SOCKS proxy
38388 Exim has support for sending outbound SMTP via a proxy
38389 using a protocol called SOCKS5 (defined by RFC1928).
38390 The support can be optionally included by defining SUPPORT_SOCKS=yes in
38393 Use of a proxy is enabled by setting the &%socks_proxy%& option
38394 on an smtp transport.
38395 The option value is expanded and should then be a list
38396 (colon-separated by default) of proxy specifiers.
38397 Each proxy specifier is a list
38398 (space-separated by default) where the initial element
38399 is an IP address and any subsequent elements are options.
38401 Options are a string <name>=<value>.
38402 The list of options is in the following table:
38404 &'auth '& authentication method
38405 &'name '& authentication username
38406 &'pass '& authentication password
38408 &'tmo '& connection timeout
38410 &'weight '& selection bias
38413 More details on each of these options follows:
38416 .cindex authentication "to proxy"
38417 .cindex proxy authentication
38418 &%auth%&: Either &"none"& (default) or &"name"&.
38419 Using &"name"& selects username/password authentication per RFC 1929
38420 for access to the proxy.
38421 Default is &"none"&.
38423 &%name%&: sets the username for the &"name"& authentication method.
38426 &%pass%&: sets the password for the &"name"& authentication method.
38429 &%port%&: the TCP port number to use for the connection to the proxy.
38432 &%tmo%&: sets a connection timeout in seconds for this proxy.
38435 &%pri%&: specifies a priority for the proxy within the list,
38436 higher values being tried first.
38437 The default priority is 1.
38439 &%weight%&: specifies a selection bias.
38440 Within a priority set servers are queried in a random fashion,
38441 weighted by this value.
38442 The default value for selection bias is 1.
38445 Proxies from the list are tried according to their priority
38446 and weight settings until one responds. The timeout for the
38447 overall connection applies to the set of proxied attempts.
38449 .section Logging SECTproxyLog
38450 To log the (local) IP of a proxy in the incoming or delivery logline,
38451 add &"+proxy"& to the &%log_selector%& option.
38452 This will add a component tagged with &"PRX="& to the line.
38454 . ////////////////////////////////////////////////////////////////////////////
38455 . ////////////////////////////////////////////////////////////////////////////
38457 .chapter "Internationalisation" "CHAPi18n" &&&
38458 "Internationalisation""
38459 .cindex internationalisation "email address"
38462 .cindex UTF-8 "mail name handling"
38464 Exim has support for Internationalised mail names.
38465 To include this it must be built with SUPPORT_I18N and the libidn library.
38466 Standards supported are RFCs 2060, 5890, 6530 and 6533.
38468 .section "MTA operations" SECTi18nMTA
38469 .cindex SMTPUTF8 "ESMTP option"
38470 The main configuration option &%smtputf8_advertise_hosts%& specifies
38471 a host list. If this matches the sending host and
38472 accept_8bitmime is true (the default) then the ESMTP option
38473 SMTPUTF8 will be advertised.
38475 If the sender specifies the SMTPUTF8 option on a MAIL command
38476 international handling for the message is enabled and
38477 the expansion variable &$message_smtputf8$& will have value TRUE.
38479 The option &%allow_utf8_domains%& is set to true for this
38480 message. All DNS lookups are converted to a-label form
38481 whatever the setting of &%allow_utf8_domains%&
38482 when Exim is built with SUPPORT_I18N.
38484 Both localparts and domain are maintained as the original
38485 UTF-8 form internally; any comparison or regular-expression use will
38486 require appropriate care. Filenames created, eg. by
38487 the appendfile transport, will have UTF-8 names.
38489 HELO names sent by the smtp transport will have any UTF-8
38490 components expanded to a-label form,
38491 and any certificate name checks will be done using the a-label
38494 .cindex log protocol
38495 .cindex SMTPUTF8 logging
38496 Log lines and Received-by: header lines will acquire a "utf8"
38497 prefix on the protocol element, eg. utf8esmtp.
38499 The following expansion operators can be used:
38501 ${utf8_domain_to_alabel:str}
38502 ${utf8_domain_from_alabel:str}
38503 ${utf8_localpart_to_alabel:str}
38504 ${utf8_localpart_from_alabel:str}
38507 ACLs may use the following modifier:
38509 control = utf8_downconvert
38510 control = utf8_downconvert/<value>
38512 This sets a flag requiring that addresses are converted to
38513 a-label form before smtp delivery, for use in a
38514 Message Submission Agent context.
38515 If a value is appended it may be:
38517 &`1 `& (default) mandatory downconversion
38518 &`0 `& no downconversion
38519 &`-1 `& if SMTPUTF8 not supported by destination host
38522 If mua_wrapper is set, the utf8_downconvert control
38523 is initially set to -1.
38526 There is no explicit support for VRFY and EXPN.
38527 Configurations supporting these should inspect
38528 &$smtp_command_argument$& for an SMTPUTF8 argument.
38530 There is no support for LMTP on Unix sockets.
38531 Using the "lmtp" protocol option on an smtp transport,
38532 for LMTP over TCP, should work as expected.
38534 There is no support for DSN unitext handling,
38535 and no provision for converting logging from or to UTF-8.
38539 .section "MDA operations" SECTi18nMDA
38540 To aid in constructing names suitable for IMAP folders
38541 the following expansion operator can be used:
38543 ${imapfolder {<string>} {<sep>} {<specials>}}
38546 The string is converted from the charset specified by
38547 the "headers charset" command (in a filter file)
38548 or &%headers_charset%& main configuration option (otherwise),
38550 modified UTF-7 encoding specified by RFC 2060,
38551 with the following exception: All occurences of <sep>
38552 (which has to be a single character)
38553 are replaced with periods ("."), and all periods and slashes that are not
38554 <sep> and are not in the <specials> string are BASE64 encoded.
38556 The third argument can be omitted, defaulting to an empty string.
38557 The second argument can be omitted, defaulting to "/".
38559 This is the encoding used by Courier for Maildir names on disk, and followed
38560 by many other IMAP servers.
38564 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
38565 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
38566 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
38569 Note that the source charset setting is vital, and also that characters
38570 must be representable in UTF-16.
38573 . ////////////////////////////////////////////////////////////////////////////
38574 . ////////////////////////////////////////////////////////////////////////////
38576 .chapter "Events" "CHAPevents" &&&
38580 The events mechanism in Exim can be used to intercept processing at a number
38581 of points. It was originally invented to giave a way to do customised logging
38582 actions (for example, to a database) but can also be used to modify some
38583 processing actions.
38585 Most installations will never need to use Events.
38586 The support can be left out of a build by defining DISABLE_EVENT=yes
38587 in &_Local/Makefile_&.
38589 There are two major classes of events: main and transport.
38590 The main configuration option &%event_action%& controls reception events;
38591 a transport option &%event_action%& controls delivery events.
38593 Both options are a string which is expanded when the event fires.
38594 An example might look like:
38595 .cindex logging custom
38597 event_action = ${if eq {msg:delivery}{$event_name} \
38598 {${lookup pgsql {SELECT * FROM record_Delivery( \
38599 '${quote_pgsql:$sender_address_domain}',\
38600 '${quote_pgsql:${lc:$sender_address_local_part}}', \
38601 '${quote_pgsql:$domain}', \
38602 '${quote_pgsql:${lc:$local_part}}', \
38603 '${quote_pgsql:$host_address}', \
38604 '${quote_pgsql:${lc:$host}}', \
38605 '${quote_pgsql:$message_exim_id}')}} \
38609 Events have names which correspond to the point in process at which they fire.
38610 The name is placed in the variable &$event_name$& and the event action
38611 expansion must check this, as it will be called for every possible event type.
38613 The current list of events is:
38615 &`msg:complete after main `& per message
38616 &`msg:delivery after transport `& per recipient
38617 &`msg:rcpt:host:defer after transport `& per recipient per host
38618 &`msg:rcpt:defer after transport `& per recipient
38619 &`msg:host:defer after transport `& per attempt
38620 &`msg:fail:delivery after main `& per recipient
38621 &`msg:fail:internal after main `& per recipient
38622 &`tcp:connect before transport `& per connection
38623 &`tcp:close after transport `& per connection
38624 &`tls:cert before both `& per certificate in verification chain
38625 &`smtp:connect after transport `& per connection
38627 New event types may be added in future.
38629 The event name is a colon-separated list, defining the type of
38630 event in a tree of possibilities. It may be used as a list
38631 or just matched on as a whole. There will be no spaces in the name.
38633 The second column in the table above describes whether the event fires
38634 before or after the action is associates with. Those which fire before
38635 can be used to affect that action (more on this below).
38637 An additional variable, &$event_data$&, is filled with information varying
38638 with the event type:
38640 &`msg:delivery `& smtp confirmation mssage
38641 &`msg:rcpt:host:defer `& error string
38642 &`msg:rcpt:defer `& error string
38643 &`msg:host:defer `& error string
38644 &`tls:cert `& verification chain depth
38645 &`smtp:connect `& smtp banner
38648 The :defer events populate one extra variable: &$event_defer_errno$&.
38650 For complex operations an ACL expansion can be used in &%event_action%&
38651 however due to the multiple contextx that Exim operates in during
38652 the course of its processing:
38654 variables set in transport events will not be visible outside that
38657 acl_m variables in a server context are lost on a new connection,
38658 and after smtp helo/ehlo/mail/starttls/rset commands
38660 Using an ACL expansion with the logwrite modifier can be
38661 a useful way of writing to the main log.
38663 The expansion of the event_action option should normally
38664 return an empty string. Should it return anything else the
38665 following will be forced:
38667 &`msg:delivery `& (ignored)
38668 &`msg:host:defer `& (ignored)
38669 &`msg:fail:delivery`& (ignored)
38670 &`tcp:connect `& do not connect
38671 &`tcp:close `& (ignored)
38672 &`tls:cert `& refuse verification
38673 &`smtp:connect `& close connection
38675 No other use is made of the result string.
38677 For a tcp:connect event, if the connection is being made to a proxy
38678 then the address and port variables will be that of the proxy and not
38681 For tls:cert events, if GnuTLS is in use this will trigger only per
38682 chain element received on the connection.
38683 For OpenSSL it will trigger for every chain element including those
38686 . ////////////////////////////////////////////////////////////////////////////
38687 . ////////////////////////////////////////////////////////////////////////////
38689 .chapter "Adding new drivers or lookup types" "CHID13" &&&
38690 "Adding drivers or lookups"
38691 .cindex "adding drivers"
38692 .cindex "new drivers, adding"
38693 .cindex "drivers" "adding new"
38694 The following actions have to be taken in order to add a new router, transport,
38695 authenticator, or lookup type to Exim:
38698 Choose a name for the driver or lookup type that does not conflict with any
38699 existing name; I will use &"newdriver"& in what follows.
38701 Add to &_src/EDITME_& the line:
38703 <&'type'&>&`_NEWDRIVER=yes`&
38705 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
38706 code is not to be included in the binary by default, comment this line out. You
38707 should also add any relevant comments about the driver or lookup type.
38709 Add to &_src/config.h.defaults_& the line:
38711 #define <type>_NEWDRIVER
38714 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
38715 and create a table entry as is done for all the other drivers and lookup types.
38717 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
38718 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
38719 Add your &`NEWDRIVER`& to that list.
38720 As long as the dynamic module would be named &_newdriver.so_&, you can use the
38721 simple form that most lookups have.
38723 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
38724 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
38725 driver or lookup type and add it to the definition of OBJ.
38727 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
38730 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
38731 as for other drivers and lookups.
38734 Then all you need to do is write the code! A good way to start is to make a
38735 proforma by copying an existing module of the same type, globally changing all
38736 occurrences of the name, and cutting out most of the code. Note that any
38737 options you create must be listed in alphabetical order, because the tables are
38738 searched using a binary chop procedure.
38740 There is a &_README_& file in each of the sub-directories of &_src_& describing
38741 the interface that is expected.
38746 . ////////////////////////////////////////////////////////////////////////////
38747 . ////////////////////////////////////////////////////////////////////////////
38749 . /////////////////////////////////////////////////////////////////////////////
38750 . These lines are processing instructions for the Simple DocBook Processor that
38751 . Philip Hazel has developed as a less cumbersome way of making PostScript and
38752 . PDFs than using xmlto and fop. They will be ignored by all other XML
38754 . /////////////////////////////////////////////////////////////////////////////
38759 foot_right_recto="&chaptertitle;"
38760 foot_right_verso="&chaptertitle;"
38764 .makeindex "Options index" "option"
38765 .makeindex "Variables index" "variable"
38766 .makeindex "Concept index" "concept"
38769 . /////////////////////////////////////////////////////////////////////////////
38770 . /////////////////////////////////////////////////////////////////////////////